Serverside SNI support in libpq

From c8aea86957ad12b7e48a32370eb2c565c20a2205 Mon Sep 17 00:00:00 2001
From: Daniel Gustafsson <dgustafsson@postgresql.org>
Date: Mon, 4 Nov 2024 13:52:23 +0100
Subject: [PATCH v2] Serverside SNI support for libpq

Experimental support for serverside SNI support in libpq, a new config
file $datadir/pg_hosts.conf is used for configuring which certicate and
key should be used for which hostname. A new GUC, ssl_snimode, is added
which controls how the hostname TLS extension is handled. The possible
values are off, default and strict:

  - off: pg_hosts.conf is not parsed and the hostname TLS extension is
    not inspected at all. The normal SSL GUCs for certificates and keys
	are used.
  - default: pg_hosts.conf is loaded as well as the normal GUCs. If no
    match for the TLS extension hostname is found in pg_hosts the cert
	and key from the postgresql.conf GUCs is used as the default (used
	as a wildcard host).
  - strict: only pg_hosts.conf is loaded and the TLS extension hostname
    MUST be passed and MUST have a match in the configuration, else the
	connection is refused.

CRL file(s) are applied from postgresql.conf to all configured hostnames.

Reviewed-by: Cary Huang <cary.huang@highgo.ca>
Reviewed-by: Jacob Champion <jacob.champion@enterprisedb.com>
Discussion: https://postgr.es/m/1C81CD0D-407E-44F9-833A-DD0331C202E5@yesql.se
---
 doc/src/sgml/config.sgml                      |  62 ++++
 doc/src/sgml/runtime.sgml                     |  50 +++
 src/backend/Makefile                          |   1 +
 src/backend/libpq/be-secure-common.c          | 201 ++++++++++-
 src/backend/libpq/be-secure-openssl.c         | 315 ++++++++++++++++--
 src/backend/libpq/be-secure.c                 |   8 +-
 src/backend/libpq/meson.build                 |   1 +
 src/backend/libpq/pg_hosts.conf.sample        |   5 +
 src/backend/utils/misc/guc.c                  |  26 ++
 src/backend/utils/misc/guc_tables.c           |  31 ++
 src/backend/utils/misc/postgresql.conf.sample |   1 +
 src/bin/initdb/initdb.c                       |  16 +-
 src/include/libpq/hba.h                       |  19 ++
 src/include/libpq/libpq-be.h                  |   3 +-
 src/include/libpq/libpq.h                     |  11 +-
 src/include/utils/guc.h                       |   1 +
 src/test/ssl/meson.build                      |   1 +
 src/test/ssl/t/004_sni.pl                     |  92 +++++
 src/tools/pgindent/typedefs.list              |   2 +
 19 files changed, 798 insertions(+), 48 deletions(-)
 create mode 100644 src/backend/libpq/pg_hosts.conf.sample
 create mode 100644 src/test/ssl/t/004_sni.pl

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index e0c8325a39..1cecaccee7 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1652,6 +1652,68 @@ include_dir 'conf.d'
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry id="guc-ssl-snimode" xreflabel="ssl_snimode">
+      <term><varname>ssl_snimode</varname> (<type>enum</type>)
+      <indexterm>
+       <primary><varname>ssl_snimode</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        This parameter determines if the server will inspect the <acronym>SNI</acronym> TLS extension
+        when establishing the connection, and how it should be interpreted.
+        Valid values are currently: <literal>off</literal>, <literal>default</literal> and <literal>strict</literal>.
+       </para>
+       <para>
+        <variablelist>
+         <varlistentry id="guc-ssl-snimode-off">
+          <term><literal>off</literal></term>
+          <listitem>
+           <para>
+            SNI is not enabled and no configuration from
+            <filename>pg_hosts.conf</filename> is loaded.  Configuration of SSL
+            for all connections is done with <xref linkend="guc-ssl-cert-file"/>,
+            <xref linkend="guc-ssl-key-file"/> and <xref linkend="guc-ssl-ca-file"/>.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry id="guc-ssl-snimode-default">
+          <term><literal>default</literal></term>
+          <listitem>
+           <para>
+            SNI is enabled and hostname configuration is loaded from
+            <filename>pg_hosts.conf</filename>. <xref linkend="guc-ssl-cert-file"/>,
+            <xref linkend="guc-ssl-key-file"/> and <xref linkend="guc-ssl-ca-file"/>
+            are loaded as the default configuration.  Any connection specifying
+            <xref linkend="libpq-connect-sslsni"/> to <literal>1</literal>
+            a hostname which is missing in <filename>pg_hosts.conf</filename>
+            will be attempted using the default configuration. If the hostname
+            matches an entry from <filename>pg_hosts.conf</filename>, then the
+            configuration from that entry will be used for setting up the
+            connection.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry id="guc-ssl-snimode-strict">
+          <term><literal>strict</literal></term>
+          <listitem>
+           <para>
+            SNI is enabled and all connections are required to set <xref
+            linkend="libpq-connect-sslsni"/> to <literal>1</literal> and
+            specify a hostname matching an entry in
+            <filename>pg_hosts.conf</filename>. Any connection without <xref
+            linkend="libpq-connect-sslsni"/> or with a hostname missing from
+            <filename>pg_hosts.conf</filename> will be rejected.
+           </para>
+          </listitem>
+         </varlistentry>
+        </variablelist>
+       </para>
+      </listitem>
+     </varlistentry>
     </variablelist>
     </sect2>
    </sect1>
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index 94135e9d5e..0ac79ae28d 100644
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -2444,6 +2444,12 @@ pg_dumpall -p 5432 | psql -d postgres -p 5433
       <entry>client certificate must not be on this list</entry>
      </row>
 
+     <row>
+      <entry><filename>$PGDATA/pg_hosts.conf</filename></entry>
+      <entry>SNI configuration</entry>
+      <entry>defines which certificates to use for which server hostname</entry>
+     </row>
+
     </tbody>
    </tgroup>
   </table>
@@ -2571,6 +2577,50 @@ openssl x509 -req -in server.csr -text -days 365 \
    </para>
   </sect2>
 
+  <sect2 id="ssl-sni">
+   <title>SNI Configuration</title>
+
+   <para>
+    <productname>PostgreSQL</productname> can be configured for
+    <acronym>SNI</acronym> using the <filename>pg_hosts.conf</filename>
+    configuration file. <productname>PostgreSQL</productname> inspects the TLS
+    hostname extension in the SSL connection handshake, and selects the right
+    SSL certificate, key and CA certificate to use for the connection.
+   </para>
+
+   <para>
+    SNI configuration is defined in the hosts configuration file, which is
+    named <filename>pg_hosts.conf</filename> and is stored in the clusters
+    data directory.  The hosts configuration file contains lines of the general
+    forms:
+<synopsis>
+<replaceable>hostname</replaceable> <replaceable>SSL_certificate</replaceable> <replaceable>SSL_key</replaceable> <replaceable>SSL_CA_certificate</replaceable> <replaceable>SSL_passphrase_cmd</replaceable> <replaceable>SSL_passphrase_cmd_reload</replaceable>
+<replaceable>include</replaceable> <replaceable>file</replaceable>
+<replaceable>include_if_exists</replaceable> <replaceable>file</replaceable>
+<replaceable>include_dir</replaceable> <replaceable>directory</replaceable>
+</synopsis>
+    Comments, whitespace and line continuations are handled in the same way as
+    in <filename>pg_hba.conf</filename>.  <replaceable>hostname</replaceable>
+    is matched against the hostname TLS extension in the SSL handshake.
+    <replaceable>SSL_certificate</replaceable>,
+    <replaceable>SSL_key</replaceable>,
+    <replaceable>SSL_CA_certificate</replaceable>,
+    <replaceable>SSL_passphrase_cmd</replaceable>, and
+    <replaceable>SSL_passphrase_cmd_reload</replaceable>
+    are treated like
+    <xref linkend="guc-ssl-cert-file"/>,
+    <xref linkend="guc-ssl-key-file"/>,
+    <xref linkend="guc-ssl-ca-file"/>,
+    <xref linkend="guc-ssl-passphrase-command"/>, and
+    <xref linkend="guc-ssl-passphrase-command-supports-reload"/> respectively.
+    All fields except <replaceable>SSL_passphrase_cmd</replaceable> and
+    <replaceable>SSL_passphrase_cmd_reload</replaceable> are required. If
+    <replaceable>SSL_passphrase_cmd</replaceable> is defined but not
+    <replaceable>SSL_passphrase_cmd_reload</replaceable> then the default
+    value for <replaceable>SSL_passphrase_cmd_reload</replaceable> is
+    <literal>off</literal>.
+   </para>
+  </sect2>
  </sect1>
 
  <sect1 id="gssapi-enc">
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 84302cc6da..bc8accbde0 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -186,6 +186,7 @@ endif
 	$(MAKE) -C utils install-data
 	$(INSTALL_DATA) $(srcdir)/libpq/pg_hba.conf.sample '$(DESTDIR)$(datadir)/pg_hba.conf.sample'
 	$(INSTALL_DATA) $(srcdir)/libpq/pg_ident.conf.sample '$(DESTDIR)$(datadir)/pg_ident.conf.sample'
+	$(INSTALL_DATA) $(srcdir)/libpq/pg_hosts.conf.sample '$(DESTDIR)$(datadir)/pg_hosts.conf.sample'
 	$(INSTALL_DATA) $(srcdir)/utils/misc/postgresql.conf.sample '$(DESTDIR)$(datadir)/postgresql.conf.sample'
 
 ifeq ($(with_llvm), yes)
diff --git a/src/backend/libpq/be-secure-common.c b/src/backend/libpq/be-secure-common.c
index 0cb201acb1..7c900edd45 100644
--- a/src/backend/libpq/be-secure-common.c
+++ b/src/backend/libpq/be-secure-common.c
@@ -24,8 +24,13 @@
 
 #include "common/percentrepl.h"
 #include "common/string.h"
+#include "libpq/hba.h"
 #include "libpq/libpq.h"
 #include "storage/fd.h"
+#include "utils/guc.h"
+#include "utils/memutils.h"
+
+static HostsLine *parse_hosts_line(TokenizedAuthLine *tok_line, int elevel);
 
 /*
  * Run ssl_passphrase_command
@@ -37,19 +42,20 @@
  * value is the length of the actual result.
  */
 int
-run_ssl_passphrase_command(const char *prompt, bool is_server_start, char *buf, int size)
+run_ssl_passphrase_command(const char *prompt, bool is_server_start, char *buf, int size, void *userdata)
 {
 	int			loglevel = is_server_start ? ERROR : LOG;
 	char	   *command;
 	FILE	   *fh;
 	int			pclose_rc;
 	size_t		len = 0;
+	char	   *cmd = (char *) userdata;
 
 	Assert(prompt);
 	Assert(size > 0);
 	buf[0] = '\0';
 
-	command = replace_percent_placeholders(ssl_passphrase_command, "ssl_passphrase_command", "p", prompt);
+	command = replace_percent_placeholders(cmd, "ssl_passphrase_command", "p", prompt);
 
 	fh = OpenPipeStream(command, "r");
 	if (fh == NULL)
@@ -175,3 +181,194 @@ check_ssl_key_file_permissions(const char *ssl_key_file, bool isServerStart)
 
 	return true;
 }
+
+/*
+ * parse_hosts_line
+ *
+ * Parses a loaded line from the pg_hosts.conf configuration and pulls out the
+ * hostname, certificate, key and CA parts in order to build an SNI config in
+ * the TLS backend. Validation of the parsed values is left for the TLS backend
+ * to implement.
+ */
+static HostsLine *
+parse_hosts_line(TokenizedAuthLine *tok_line, int elevel)
+{
+	HostsLine  *parsedline;
+	List	   *tokens;
+	ListCell   *field;
+	AuthToken  *token;
+
+	parsedline = palloc0(sizeof(HostsLine));
+	parsedline->sourcefile = pstrdup(tok_line->file_name);
+	parsedline->linenumber = tok_line->line_num;
+	parsedline->rawline = pstrdup(tok_line->raw_line);
+
+	/* Initialize optional fields */
+	parsedline->ssl_passphrase_cmd = NULL;
+	parsedline->ssl_passphrase_reload = false;
+
+	/* Hostname */
+	field = list_head(tok_line->fields);
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->hostname = pstrdup(token->string);
+
+	/* SSL Certificate (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_cert = pstrdup(token->string);
+
+	/* SSL key (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_key = pstrdup(token->string);
+
+	/* SSL CA (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_ca = pstrdup(token->string);
+
+	/* SSL Passphrase Command (optional) */
+	field = lnext(tok_line->fields, field);
+	if (field)
+	{
+		tokens = lfirst(field);
+		token = linitial(tokens);
+		parsedline->ssl_passphrase_cmd = pstrdup(token->string);
+
+		/*
+		 * SSL Passphrase Command support reload (optional). This field is
+		 * only supported if there was a passphrase command parsed first, so
+		 * nest it under the previous token.
+		 */
+		field = lnext(tok_line->fields, field);
+		if (field)
+		{
+			tokens = lfirst(field);
+			token = linitial(tokens);
+
+			if (token->string[0] == '1'
+				|| pg_strcasecmp(token->string, "true") == 0
+				|| pg_strcasecmp(token->string, "on") == 0)
+				parsedline->ssl_passphrase_reload = true;
+			else if (token->string[0] == '0'
+					 || pg_strcasecmp(token->string, "false") == 0
+					 || pg_strcasecmp(token->string, "off") == 0)
+				parsedline->ssl_passphrase_reload = false;
+			else
+				ereport(elevel,
+						errcode(ERRCODE_CONFIG_FILE_ERROR),
+						errmsg("incorrect syntax for boolean value SSL_passphrase_cmd_reload"),
+						errcontext("line %d of configuration file \"%s\"",
+								   tok_line->line_num, tok_line->file_name));
+		}
+	}
+
+	return parsedline;
+}
+
+/*
+ * load_hosts
+ *
+ * Reads pg_hosts.conf and passes back a List of parsed lines, or NIL in case
+ * of errors.
+ */
+List *
+load_hosts(void)
+{
+	FILE	   *file;
+	ListCell   *line;
+	List	   *hosts_lines = NIL;
+	List	   *parsed_lines = NIL;
+	HostsLine  *newline;
+	bool		ok = true;
+	MemoryContext oldcxt;
+	MemoryContext hostcxt;
+
+	file = open_auth_file(HostsFileName, LOG, 0, NULL);
+	if (file == NULL)
+	{
+		/* An error has already been logged so no need to add one here. */
+		return NIL;
+	}
+
+	tokenize_auth_file(HostsFileName, file, &hosts_lines, LOG, 0);
+
+	hostcxt = AllocSetContextCreate(PostmasterContext,
+									"hosts file parser context",
+									ALLOCSET_SMALL_SIZES);
+	oldcxt = MemoryContextSwitchTo(hostcxt);
+
+	foreach(line, hosts_lines)
+	{
+		TokenizedAuthLine *tok_line = (TokenizedAuthLine *) lfirst(line);
+
+		if (tok_line->err_msg != NULL)
+		{
+			ok = false;
+			continue;
+		}
+
+		if ((newline = parse_hosts_line(tok_line, LOG)) == NULL)
+		{
+			ok = false;
+			continue;
+		}
+
+		parsed_lines = lappend(parsed_lines, newline);
+	}
+
+	free_auth_file(file, 0);
+	MemoryContextSwitchTo(oldcxt);
+
+	/*
+	 * If we didn't find any SNI configuration then that's not an error since
+	 * the pg_hosts file is additive to the default SSL configuration.
+	 */
+	if (ok && parsed_lines == NIL)
+	{
+		ereport(DEBUG1,
+				errmsg("no SNI configuration added from configuration file  \"%s\"",
+					   HostsFileName));
+		MemoryContextDelete(hostcxt);
+		return NIL;
+	}
+
+	if (!ok)
+	{
+		MemoryContextDelete(hostcxt);
+		return NIL;
+	}
+
+	return parsed_lines;
+}
diff --git a/src/backend/libpq/be-secure-openssl.c b/src/backend/libpq/be-secure-openssl.c
index 91a86d62a3..5acfdeb625 100644
--- a/src/backend/libpq/be-secure-openssl.c
+++ b/src/backend/libpq/be-secure-openssl.c
@@ -51,9 +51,18 @@
 #endif
 #include <openssl/x509v3.h>
 
+typedef struct HostContext
+{
+	const char *hostname;
+	const char *ssl_passphrase;
+	SSL_CTX    *context;
+	bool		default_host;
+	bool		ssl_loaded_verify_locations;
+	bool		ssl_passphrase_support_reload;
+} HostContext;
 
 /* default init hook can be overridden by a shared library */
-static void default_openssl_tls_init(SSL_CTX *context, bool isServerStart);
+static void default_openssl_tls_init(SSL_CTX *context, bool isServerStart, HostsLine *hosts);
 openssl_tls_init_hook_typ openssl_tls_init_hook = default_openssl_tls_init;
 
 static int	port_bio_read(BIO *h, char *buf, int size);
@@ -73,6 +82,7 @@ static int	alpn_cb(SSL *ssl,
 					const unsigned char *in,
 					unsigned int inlen,
 					void *userdata);
+static int	sni_servername_cb(SSL *ssl, int *al, void *arg);
 static bool initialize_dh(SSL_CTX *context, bool isServerStart);
 static bool initialize_ecdh(SSL_CTX *context, bool isServerStart);
 static const char *SSLerrmessageExt(unsigned long ecode, const char *replacement);
@@ -80,12 +90,16 @@ static const char *SSLerrmessage(unsigned long ecode);
 
 static char *X509_NAME_to_cstring(X509_NAME *name);
 
+static List *contexts = NIL;
 static SSL_CTX *SSL_context = NULL;
+static HostContext *Host_context = NULL;
 static bool dummy_ssl_passwd_cb_called = false;
 static bool ssl_is_server_start;
 
 static int	ssl_protocol_version_to_openssl(int v);
 static const char *ssl_protocol_version_to_string(int v);
+static SSL_CTX *ssl_init_context(bool isServerStart, HostsLine *host);
+static void free_contexts(void);
 
 /* for passing data back from verify_cb() */
 static const char *cert_errdetail;
@@ -96,11 +110,155 @@ static const char *cert_errdetail;
 
 int
 be_tls_init(bool isServerStart)
+{
+	SSL_CTX    *ctx;
+	List	   *sni_hosts = NIL;
+
+	/*
+	 * If there are contexts loaded when we init they should be released. This
+	 * should only be possible when reloading, but to keep any subtle bugs at
+	 * arms length we check unconditionally with an assert for non-production
+	 * builds.
+	 */
+	if (contexts != NIL)
+	{
+		Assert(isServerStart == false);
+		free_contexts();
+	}
+
+	/*
+	 * When ssl_snimode is off or default we load the certificate and key
+	 * specified in postgresql.conf and set that as the default host.
+	 */
+	if (ssl_snimode == SSL_SNIMODE_OFF || ssl_snimode == SSL_SNIMODE_DEFAULT)
+	{
+		HostContext *host_context;
+		HostsLine	line;
+
+		line.ssl_cert = ssl_cert_file;
+		line.ssl_key = ssl_key_file;
+		line.ssl_ca = ssl_ca_file;
+		line.ssl_passphrase_cmd = ssl_passphrase_command;
+		line.ssl_passphrase_reload = ssl_passphrase_command_supports_reload;
+
+		ctx = ssl_init_context(isServerStart, &line);
+		if (ctx == NULL)
+		{
+			ereport(isServerStart ? FATAL : LOG,
+					(errcode(ERRCODE_CONFIG_FILE_ERROR),
+					 errmsg("could not load default certificate")));
+			return -1;
+		}
+
+		host_context = palloc0(sizeof(HostContext));
+
+		host_context->hostname = pstrdup("*");
+		host_context->context = ctx;
+		host_context->default_host = true;
+
+		/*
+		 * Set flag to remember whether CA store has been loaded into
+		 * SSL_context.
+		 */
+		if (ssl_ca_file[0])
+			host_context->ssl_loaded_verify_locations = true;
+
+		/*
+		 * The contexts list is not used in ssl_snimode off but we add the
+		 * entry there anyways for consistency with the other modes.
+		 */
+		contexts = lappend(contexts, host_context);
+
+		/*
+		 * Install the default certificate which for ssl_snimode default can
+		 * be overridden in the callback if a hostname match is found.
+		 */
+		SSL_context = ctx;
+		Host_context = host_context;
+	}
+
+	/*
+	 * In default or strict ssl_snimode we load all certificates/keys which
+	 * are configured in pg_hosts.conf. In strict mode it is considered a
+	 * fatal error in case there are no configured entries.
+	 */
+	if (ssl_snimode == SSL_SNIMODE_STRICT || ssl_snimode == SSL_SNIMODE_DEFAULT)
+	{
+		ListCell   *line;
+
+		/*
+		 * Load pg_hosts.conf and parse each row, returning the set of hosts
+		 * as a list.
+		 */
+		sni_hosts = load_hosts();
+
+		/*
+		 * In strict ssl_snimode there needs to be a working pg_hosts file,
+		 */
+		if (sni_hosts == NIL && ssl_snimode == SSL_SNIMODE_STRICT)
+		{
+			ereport(isServerStart ? FATAL : LOG,
+					errcode(ERRCODE_CONFIG_FILE_ERROR),
+					errmsg("could not load pg_hosts.conf file"));
+			return -1;
+		}
+
+		foreach(line, sni_hosts)
+		{
+			HostContext *host_context;
+			HostsLine  *host = lfirst(line);
+
+			SSL_context = ssl_init_context(isServerStart, host);
+			if (SSL_context == NULL)
+			{
+				ereport(isServerStart ? FATAL : LOG,
+						errcode(ERRCODE_CONFIG_FILE_ERROR),
+						errmsg("unable to load certificate from pg_hosts.conf file"));
+				return -1;
+			}
+
+			host_context = palloc(sizeof(HostContext));
+			host_context->hostname = pstrdup(host->hostname);
+			host_context->context = SSL_context;
+			host_context->default_host = false;
+			if (host->ssl_passphrase_cmd != NULL)
+				host_context->ssl_passphrase = pstrdup(host->ssl_passphrase_cmd);
+			host_context->ssl_passphrase_support_reload = host->ssl_passphrase_reload;
+
+			/*
+			 * Set flag to remember whether CA store has been loaded into
+			 * SSL_context.
+			 */
+			if (host->ssl_ca)
+				host_context->ssl_loaded_verify_locations = true;
+
+			contexts = lappend(contexts, host_context);
+		}
+	}
+
+	/* Make sure we have at least one certificate loaded */
+	if (list_length(contexts) < 1)
+	{
+		ereport(isServerStart ? FATAL : LOG,
+				(errcode(ERRCODE_CONFIG_FILE_ERROR),
+				 errmsg("no SSL contexts loaded")));
+		return -1;
+	}
+
+	return 0;
+}
+
+static SSL_CTX *
+ssl_init_context(bool isServerStart, HostsLine *host_line)
 {
 	SSL_CTX    *context;
 	int			ssl_ver_min = -1;
 	int			ssl_ver_max = -1;
 
+	const char *ctx_ssl_cert_file = host_line->ssl_cert;
+	const char *ctx_ssl_key_file = host_line->ssl_key;
+	const char *ctx_ssl_ca_file = host_line->ssl_ca;
+
 	/*
 	 * Create a new SSL context into which we'll load all the configuration
 	 * settings.  If we fail partway through, we can avoid memory leakage by
@@ -126,10 +284,17 @@ be_tls_init(bool isServerStart)
 	 */
 	SSL_CTX_set_mode(context, SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER);
 
+	/*
+	 * Install SNI TLS extension callback in case the server is configured to
+	 * validate hostnames.
+	 */
+	if (ssl_snimode != SSL_SNIMODE_OFF)
+		SSL_CTX_set_tlsext_servername_callback(context, sni_servername_cb);
+
 	/*
 	 * Call init hook (usually to set password callback)
 	 */
-	(*openssl_tls_init_hook) (context, isServerStart);
+	(*openssl_tls_init_hook) (context, isServerStart, host_line);
 
 	/* used by the callback */
 	ssl_is_server_start = isServerStart;
@@ -137,16 +302,16 @@ be_tls_init(bool isServerStart)
 	/*
 	 * Load and verify server's certificate and private key
 	 */
-	if (SSL_CTX_use_certificate_chain_file(context, ssl_cert_file) != 1)
+	if (SSL_CTX_use_certificate_chain_file(context, ctx_ssl_cert_file) != 1)
 	{
 		ereport(isServerStart ? FATAL : LOG,
 				(errcode(ERRCODE_CONFIG_FILE_ERROR),
 				 errmsg("could not load server certificate file \"%s\": %s",
-						ssl_cert_file, SSLerrmessage(ERR_get_error()))));
+						ctx_ssl_cert_file, SSLerrmessage(ERR_get_error()))));
 		goto error;
 	}
 
-	if (!check_ssl_key_file_permissions(ssl_key_file, isServerStart))
+	if (!check_ssl_key_file_permissions(ctx_ssl_key_file, isServerStart))
 		goto error;
 
 	/*
@@ -155,19 +320,19 @@ be_tls_init(bool isServerStart)
 	dummy_ssl_passwd_cb_called = false;
 
 	if (SSL_CTX_use_PrivateKey_file(context,
-									ssl_key_file,
+									ctx_ssl_key_file,
 									SSL_FILETYPE_PEM) != 1)
 	{
 		if (dummy_ssl_passwd_cb_called)
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("private key file \"%s\" cannot be reloaded because it requires a passphrase",
-							ssl_key_file)));
+							ctx_ssl_key_file)));
 		else
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("could not load private key file \"%s\": %s",
-							ssl_key_file, SSLerrmessage(ERR_get_error()))));
+							ctx_ssl_key_file, SSLerrmessage(ERR_get_error()))));
 		goto error;
 	}
 
@@ -319,17 +484,17 @@ be_tls_init(bool isServerStart)
 	/*
 	 * Load CA store, so we can verify client certificates if needed.
 	 */
-	if (ssl_ca_file[0])
+	if (ctx_ssl_ca_file[0])
 	{
 		STACK_OF(X509_NAME) * root_cert_list;
 
-		if (SSL_CTX_load_verify_locations(context, ssl_ca_file, NULL) != 1 ||
-			(root_cert_list = SSL_load_client_CA_file(ssl_ca_file)) == NULL)
+		if (SSL_CTX_load_verify_locations(context, ctx_ssl_ca_file, NULL) != 1 ||
+			(root_cert_list = SSL_load_client_CA_file(ctx_ssl_ca_file)) == NULL)
 		{
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("could not load root certificate file \"%s\": %s",
-							ssl_ca_file, SSLerrmessage(ERR_get_error()))));
+							ctx_ssl_ca_file, SSLerrmessage(ERR_get_error()))));
 			goto error;
 		}
 
@@ -401,38 +566,29 @@ be_tls_init(bool isServerStart)
 		}
 	}
 
-	/*
-	 * Success!  Replace any existing SSL_context.
-	 */
-	if (SSL_context)
-		SSL_CTX_free(SSL_context);
-
-	SSL_context = context;
-
-	/*
-	 * Set flag to remember whether CA store has been loaded into SSL_context.
-	 */
-	if (ssl_ca_file[0])
-		ssl_loaded_verify_locations = true;
-	else
-		ssl_loaded_verify_locations = false;
-
-	return 0;
+	return context;
 
 	/* Clean up by releasing working context. */
 error:
 	if (context)
 		SSL_CTX_free(context);
-	return -1;
+	return NULL;
 }
 
 void
 be_tls_destroy(void)
 {
-	if (SSL_context)
-		SSL_CTX_free(SSL_context);
+	ListCell   *cell;
+
+	foreach(cell, contexts)
+	{
+		HostContext *host_context = lfirst(cell);
+
+		SSL_CTX_free(host_context->context);
+		pfree(host_context);
+	}
+
 	SSL_context = NULL;
-	ssl_loaded_verify_locations = false;
 }
 
 int
@@ -1132,7 +1288,7 @@ ssl_external_passwd_cb(char *buf, int size, int rwflag, void *userdata)
 
 	Assert(rwflag == 0);
 
-	return run_ssl_passphrase_command(prompt, ssl_is_server_start, buf, size);
+	return run_ssl_passphrase_command(prompt, ssl_is_server_start, buf, size, userdata);
 }
 
 /*
@@ -1369,6 +1525,60 @@ alpn_cb(SSL *ssl,
 	}
 }
 
+static int
+sni_servername_cb(SSL *ssl, int *al, void *arg)
+{
+	const char *tlsext_hostname;
+	ListCell   *cell;
+	HostContext *host_context;
+
+	Assert(ssl_snimode != SSL_SNIMODE_OFF);
+
+	tlsext_hostname = SSL_get_servername(ssl, TLSEXT_NAMETYPE_host_name);
+
+	if (!tlsext_hostname)
+	{
+		if (ssl_snimode == SSL_SNIMODE_STRICT)
+		{
+			ereport(COMMERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg("no hostname provided in callback")));
+			return SSL_TLSEXT_ERR_ALERT_FATAL;
+		}
+		else
+			return SSL_TLSEXT_ERR_OK;
+	}
+
+	foreach(cell, contexts)
+	{
+		host_context = lfirst(cell);
+
+		if (strcmp(host_context->hostname, tlsext_hostname) == 0)
+		{
+			Host_context = host_context;
+			SSL_context = host_context->context;
+			SSL_set_SSL_CTX(ssl, SSL_context);
+			return SSL_TLSEXT_ERR_OK;
+		}
+	}
+
+	if (ssl_snimode == SSL_SNIMODE_STRICT)
+	{
+		ereport(COMMERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg("no matching pg_hosts entry found for hostname: \"%s\"",
+						tlsext_hostname)));
+		return SSL_TLSEXT_ERR_ALERT_FATAL;
+	}
+
+	/*
+	 * In ssl_snimode "default" we can return without doing anything since we
+	 * already installed the context for the default host when parsing the
+	 * hosts file.
+	 */
+	Assert(SSL_context);
+	return SSL_TLSEXT_ERR_OK;
+}
 
 /*
  * Set DH parameters for generating ephemeral DH keys.  The
@@ -1578,6 +1788,12 @@ be_tls_get_peer_serial(Port *port, char *ptr, size_t len)
 		ptr[0] = '\0';
 }
 
+bool
+be_tls_loaded_verify_locations(void)
+{
+	return Host_context->ssl_loaded_verify_locations;
+}
+
 char *
 be_tls_get_certificate_hash(Port *port, size_t *len)
 {
@@ -1771,17 +1987,23 @@ ssl_protocol_version_to_string(int v)
 
 
 static void
-default_openssl_tls_init(SSL_CTX *context, bool isServerStart)
+default_openssl_tls_init(SSL_CTX *context, bool isServerStart, HostsLine *host)
 {
 	if (isServerStart)
 	{
-		if (ssl_passphrase_command[0])
+		if (host->ssl_passphrase_cmd != NULL)
+		{
 			SSL_CTX_set_default_passwd_cb(context, ssl_external_passwd_cb);
+			SSL_CTX_set_default_passwd_cb_userdata(context, host->ssl_passphrase_cmd);
+		}
 	}
 	else
 	{
-		if (ssl_passphrase_command[0] && ssl_passphrase_command_supports_reload)
+		if (host->ssl_passphrase_cmd != NULL && host->ssl_passphrase_reload)
+		{
 			SSL_CTX_set_default_passwd_cb(context, ssl_external_passwd_cb);
+			SSL_CTX_set_default_passwd_cb_userdata(context, host->ssl_passphrase_cmd);
+		}
 		else
 
 			/*
@@ -1793,3 +2015,22 @@ default_openssl_tls_init(SSL_CTX *context, bool isServerStart)
 			SSL_CTX_set_default_passwd_cb(context, dummy_ssl_passwd_cb);
 	}
 }
+
+static void
+free_contexts(void)
+{
+	if (contexts == NIL)
+		return;
+
+	foreach_ptr(HostContext, host, contexts)
+	{
+		if (host->hostname)
+			pfree(unconstify(char *, host->hostname));
+		if (host->ssl_passphrase)
+			pfree(unconstify(char *, host->ssl_passphrase));
+		SSL_CTX_free(host->context);
+	}
+
+	list_free_deep(contexts);
+	contexts = NIL;
+}
diff --git a/src/backend/libpq/be-secure.c b/src/backend/libpq/be-secure.c
index 2139f81f24..ad3066b63c 100644
--- a/src/backend/libpq/be-secure.c
+++ b/src/backend/libpq/be-secure.c
@@ -43,10 +43,6 @@ char	   *ssl_dh_params_file;
 char	   *ssl_passphrase_command;
 bool		ssl_passphrase_command_supports_reload;
 
-#ifdef USE_SSL
-bool		ssl_loaded_verify_locations = false;
-#endif
-
 /* GUC variable controlling SSL cipher list */
 char	   *SSLCipherSuites = NULL;
 char	   *SSLCipherList = NULL;
@@ -60,6 +56,8 @@ bool		SSLPreferServerCiphers;
 int			ssl_min_protocol_version = PG_TLS1_2_VERSION;
 int			ssl_max_protocol_version = PG_TLS_ANY;
 
+int			ssl_snimode = SSL_SNIMODE_DEFAULT;
+
 /* ------------------------------------------------------------ */
 /*			 Procedures common to all secure sessions			*/
 /* ------------------------------------------------------------ */
@@ -99,7 +97,7 @@ bool
 secure_loaded_verify_locations(void)
 {
 #ifdef USE_SSL
-	return ssl_loaded_verify_locations;
+	return be_tls_loaded_verify_locations();
 #else
 	return false;
 #endif
diff --git a/src/backend/libpq/meson.build b/src/backend/libpq/meson.build
index 7c65314512..1c6269262c 100644
--- a/src/backend/libpq/meson.build
+++ b/src/backend/libpq/meson.build
@@ -30,5 +30,6 @@ endif
 install_data(
   'pg_hba.conf.sample',
   'pg_ident.conf.sample',
+  'pg_hosts.conf.sample',
   install_dir: dir_data,
 )
diff --git a/src/backend/libpq/pg_hosts.conf.sample b/src/backend/libpq/pg_hosts.conf.sample
new file mode 100644
index 0000000000..608210686e
--- /dev/null
+++ b/src/backend/libpq/pg_hosts.conf.sample
@@ -0,0 +1,5 @@
+# PostgreSQL SNI Hostname mappings
+# ================================
+
+# HOSTNAME       SSL CERTIFICATE             SSL KEY
+
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index c10c0844ab..b3e1cf0b25 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -55,6 +55,7 @@
 #define CONFIG_FILENAME "postgresql.conf"
 #define HBA_FILENAME	"pg_hba.conf"
 #define IDENT_FILENAME	"pg_ident.conf"
+#define HOSTS_FILENAME	"pg_hosts.conf"
 
 #ifdef EXEC_BACKEND
 #define CONFIG_EXEC_PARAMS "global/config_exec_params"
@@ -1968,6 +1969,31 @@ SelectConfigFiles(const char *userDoption, const char *progname)
 	}
 	SetConfigOption("ident_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
 
+	/*
+	 * Likewise for pg_hosts.conf
+	 */
+	if (HostsFileName)
+	{
+		fname = make_absolute_path(HostsFileName);
+		fname_is_malloced = true;
+	}
+	else if (configdir)
+	{
+		fname = guc_malloc(FATAL,
+						   strlen(configdir) + strlen(HOSTS_FILENAME) + 2);
+		sprintf(fname, "%s/%s", configdir, HOSTS_FILENAME);
+		fname_is_malloced = false;
+	}
+	else
+	{
+		write_stderr("%s does not know where to find the \"hosts\" configuration file.\n"
+					 "This can be specified as \"hosts_file\" in \"%s\", "
+					 "or by the -D invocation option, or by the "
+					 "PGDATA environment variable.\n",
+					 progname, ConfigFileName);
+	}
+	SetConfigOption("hosts_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
+
 	if (fname_is_malloced)
 		free(fname);
 	else
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index 8cf1afbad2..dca5a15f5c 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -474,6 +474,13 @@ static const struct config_enum_entry wal_compression_options[] = {
 	{NULL, 0, false}
 };
 
+static const struct config_enum_entry ssl_snimode_options[] = {
+	{"off", SSL_SNIMODE_OFF, false},
+	{"default", SSL_SNIMODE_DEFAULT, false},
+	{"strict", SSL_SNIMODE_STRICT, false},
+	{NULL, 0, false}
+};
+
 /*
  * Options for enum values stored in other modules
  */
@@ -538,6 +545,7 @@ char	   *cluster_name = "";
 char	   *ConfigFileName;
 char	   *HbaFileName;
 char	   *IdentFileName;
+char	   *HostsFileName;
 char	   *external_pid_file;
 
 char	   *application_name;
@@ -4562,6 +4570,17 @@ struct config_string ConfigureNamesString[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"hosts_file", PGC_POSTMASTER, FILE_LOCATIONS,
+			gettext_noop("Sets the server's \"hosts\" configuration file."),
+			NULL,
+			GUC_SUPERUSER_ONLY
+		},
+		&HostsFileName,
+		NULL,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"external_pid_file", PGC_POSTMASTER, FILE_LOCATIONS,
 			gettext_noop("Writes the postmaster PID to the specified file."),
@@ -5204,6 +5223,18 @@ struct config_enum ConfigureNamesEnum[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"ssl_snimode", PGC_SIGHUP, CONN_AUTH_SSL,
+			gettext_noop("Sets the SNI mode to use."),
+			NULL,
+			GUC_SUPERUSER_ONLY,
+		},
+		&ssl_snimode,
+		SSL_SNIMODE_DEFAULT,
+		ssl_snimode_options,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"recovery_init_sync_method", PGC_SIGHUP, ERROR_HANDLING_OPTIONS,
 			gettext_noop("Sets the method for synchronizing the data directory before crash recovery."),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index a2ac7575ca..902c4eccef 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -120,6 +120,7 @@
 #ssl_dh_params_file = ''
 #ssl_passphrase_command = ''
 #ssl_passphrase_command_supports_reload = off
+#ssl_snimode = default
 
 
 #------------------------------------------------------------------------------
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 9a91830783..984763da08 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -176,6 +176,7 @@ static int	encodingid;
 static char *bki_file;
 static char *hba_file;
 static char *ident_file;
+static char *hosts_file;
 static char *conf_file;
 static char *dictionary_file;
 static char *info_schema_file;
@@ -1512,6 +1513,14 @@ setup_config(void)
 
 	snprintf(path, sizeof(path), "%s/pg_ident.conf", pg_data);
 
+	writefile(path, conflines);
+	if (chmod(path, pg_file_create_mode) != 0)
+		pg_fatal("could not change permissions of \"%s\": %m", path);
+
+	/* pg_hosts.conf */
+	conflines = readfile(hosts_file);
+	snprintf(path, sizeof(path), "%s/pg_hosts.conf", pg_data);
+
 	writefile(path, conflines);
 	if (chmod(path, pg_file_create_mode) != 0)
 		pg_fatal("could not change permissions of \"%s\": %m", path);
@@ -2771,6 +2780,7 @@ setup_data_file_paths(void)
 	set_input(&bki_file, "postgres.bki");
 	set_input(&hba_file, "pg_hba.conf.sample");
 	set_input(&ident_file, "pg_ident.conf.sample");
+	set_input(&hosts_file, "pg_hosts.conf.sample");
 	set_input(&conf_file, "postgresql.conf.sample");
 	set_input(&dictionary_file, "snowball_create.sql");
 	set_input(&info_schema_file, "information_schema.sql");
@@ -2786,12 +2796,13 @@ setup_data_file_paths(void)
 				"PGDATA=%s\nshare_path=%s\nPGPATH=%s\n"
 				"POSTGRES_SUPERUSERNAME=%s\nPOSTGRES_BKI=%s\n"
 				"POSTGRESQL_CONF_SAMPLE=%s\n"
-				"PG_HBA_SAMPLE=%s\nPG_IDENT_SAMPLE=%s\n",
+				"PG_HBA_SAMPLE=%s\nPG_IDENT_SAMPLE=%s\n"
+				"PG_HOSTS_SAMPLE=%s\n",
 				PG_VERSION,
 				pg_data, share_path, bin_path,
 				username, bki_file,
 				conf_file,
-				hba_file, ident_file);
+				hba_file, ident_file, hosts_file);
 		if (show_setting)
 			exit(0);
 	}
@@ -2799,6 +2810,7 @@ setup_data_file_paths(void)
 	check_input(bki_file);
 	check_input(hba_file);
 	check_input(ident_file);
+	check_input(hosts_file);
 	check_input(conf_file);
 	check_input(dictionary_file);
 	check_input(info_schema_file);
diff --git a/src/include/libpq/hba.h b/src/include/libpq/hba.h
index 8ea837ae82..d1eb750368 100644
--- a/src/include/libpq/hba.h
+++ b/src/include/libpq/hba.h
@@ -146,6 +146,25 @@ typedef struct IdentLine
 	AuthToken  *pg_user;
 } IdentLine;
 
+typedef struct HostsLine
+{
+	int			linenumber;
+
+	char	   *sourcefile;
+	char	   *rawline;
+
+	/* Required fields */
+	bool		default_host;
+	char	   *hostname;
+	char	   *ssl_key;
+	char	   *ssl_cert;
+	char	   *ssl_ca;
+
+	/* Optional fields */
+	char	   *ssl_passphrase_cmd;
+	bool		ssl_passphrase_reload;
+} HostsLine;
+
 /*
  * TokenizedAuthLine represents one line lexed from an authentication
  * configuration file.  Each item in the "fields" list is a sub-list of
diff --git a/src/include/libpq/libpq-be.h b/src/include/libpq/libpq-be.h
index 9109b2c334..cf0e87a28c 100644
--- a/src/include/libpq/libpq-be.h
+++ b/src/include/libpq/libpq-be.h
@@ -314,6 +314,7 @@ extern const char *be_tls_get_cipher(Port *port);
 extern void be_tls_get_peer_subject_name(Port *port, char *ptr, size_t len);
 extern void be_tls_get_peer_issuer_name(Port *port, char *ptr, size_t len);
 extern void be_tls_get_peer_serial(Port *port, char *ptr, size_t len);
+extern bool be_tls_loaded_verify_locations(void);
 
 /*
  * Get the server certificate hash for SCRAM channel binding type
@@ -326,7 +327,7 @@ extern char *be_tls_get_certificate_hash(Port *port, size_t *len);
 
 /* init hook for SSL, the default sets the password callback if appropriate */
 #ifdef USE_OPENSSL
-typedef void (*openssl_tls_init_hook_typ) (SSL_CTX *context, bool isServerStart);
+typedef void (*openssl_tls_init_hook_typ) (SSL_CTX *context, bool isServerStart, HostsLine *host);
 extern PGDLLIMPORT openssl_tls_init_hook_typ openssl_tls_init_hook;
 #endif
 
diff --git a/src/include/libpq/libpq.h b/src/include/libpq/libpq.h
index 07e5b12536..98da8b61eb 100644
--- a/src/include/libpq/libpq.h
+++ b/src/include/libpq/libpq.h
@@ -107,6 +107,7 @@ extern PGDLLIMPORT char *ssl_crl_dir;
 extern PGDLLIMPORT char *ssl_key_file;
 extern PGDLLIMPORT int ssl_min_protocol_version;
 extern PGDLLIMPORT int ssl_max_protocol_version;
+extern PGDLLIMPORT int ssl_snimode;
 extern PGDLLIMPORT char *ssl_passphrase_command;
 extern PGDLLIMPORT bool ssl_passphrase_command_supports_reload;
 extern PGDLLIMPORT char *ssl_dh_params_file;
@@ -134,12 +135,20 @@ enum ssl_protocol_versions
 	PG_TLS1_3_VERSION,
 };
 
+enum ssl_snimode
+{
+	SSL_SNIMODE_OFF = 0,
+	SSL_SNIMODE_DEFAULT,
+	SSL_SNIMODE_STRICT
+};
+
 /*
  * prototypes for functions in be-secure-common.c
  */
 extern int	run_ssl_passphrase_command(const char *prompt, bool is_server_start,
-									   char *buf, int size);
+									   char *buf, int size, void *userdata);
 extern bool check_ssl_key_file_permissions(const char *ssl_key_file,
 										   bool isServerStart);
+extern List *load_hosts(void);
 
 #endif							/* LIBPQ_H */
diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index 840b0fe57f..4c33ba7ca4 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -284,6 +284,7 @@ extern PGDLLIMPORT char *cluster_name;
 extern PGDLLIMPORT char *ConfigFileName;
 extern PGDLLIMPORT char *HbaFileName;
 extern PGDLLIMPORT char *IdentFileName;
+extern PGDLLIMPORT char *HostsFileName;
 extern PGDLLIMPORT char *external_pid_file;
 
 extern PGDLLIMPORT char *application_name;
diff --git a/src/test/ssl/meson.build b/src/test/ssl/meson.build
index b3c5503f79..55f5887d9c 100644
--- a/src/test/ssl/meson.build
+++ b/src/test/ssl/meson.build
@@ -13,6 +13,7 @@ tests += {
       't/001_ssltests.pl',
       't/002_scram.pl',
       't/003_sslinfo.pl',
+      't/004_sni.pl',
     ],
   },
 }
diff --git a/src/test/ssl/t/004_sni.pl b/src/test/ssl/t/004_sni.pl
new file mode 100644
index 0000000000..d2efcd850c
--- /dev/null
+++ b/src/test/ssl/t/004_sni.pl
@@ -0,0 +1,92 @@
+
+# Copyright (c) 2024, PostgreSQL Global Development Group
+
+use strict;
+use warnings FATAL => 'all';
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+use FindBin;
+use lib $FindBin::RealBin;
+
+use SSL::Server;
+
+# This is the hostname used to connect to the server. This cannot be a
+# hostname, because the server certificate is always for the domain
+# postgresql-ssl-regression.test.
+my $SERVERHOSTADDR = '127.0.0.1';
+# This is the pattern to use in pg_hba.conf to match incoming connections.
+my $SERVERHOSTCIDR = '127.0.0.1/32';
+
+if ($ENV{with_ssl} ne 'openssl')
+{
+	plan skip_all => 'OpenSSL not supported by this build';
+}
+
+if (!$ENV{PG_TEST_EXTRA} || $ENV{PG_TEST_EXTRA} !~ /\bssl\b/)
+{
+	plan skip_all =>
+	  'Potentially unsafe test SSL not enabled in PG_TEST_EXTRA';
+}
+
+my $ssl_server = SSL::Server->new();
+
+my $node = PostgreSQL::Test::Cluster->new('primary');
+$node->init;
+
+# PGHOST is enforced here to set up the node, subsequent connections
+# will use a dedicated connection string.
+$ENV{PGHOST} = $node->host;
+$ENV{PGPORT} = $node->port;
+$node->start;
+
+$ssl_server->configure_test_server_for_ssl($node, $SERVERHOSTADDR,
+	$SERVERHOSTCIDR, 'trust');
+
+$ssl_server->switch_server_cert($node, certfile => 'server-cn-only');
+
+my $connstr =
+  "dbname=trustdb hostaddr=$SERVERHOSTADDR host=localhost sslsni=1";
+
+$node->append_conf('postgresql.conf', "ssl_snimode=default");
+$node->reload;
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf', "localhost server.crt server.key root.crt");
+$node->append_conf('postgresql.conf', "ssl_snimode=strict");
+$node->reload;
+
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require",
+	expected_stderr => qr/unexpected eof/);
+
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf', "localhost server-cn-only.crt server-cn-only.key root_ca.crt");
+$node->reload;
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf', 'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo wrongpassword" no');
+my $result = $node->restart(fail_ok => 1);
+is($result, 0, 'restart fails with password-protected key when using the wrong passphrase command');
+
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf', 'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo secret1" no');
+$result = $node->restart(fail_ok => 1);
+is($result, 1, 'restart succeeds with password-protected key when using the correct passphrase command');
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+
+done_testing();
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 2d4c870423..15ccf4cf46 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -1158,6 +1158,8 @@ HeapTupleHeader
 HeapTupleHeaderData
 HeapTupleTableSlot
 HistControl
+HostContext
+HostsLine
 HotStandbyState
 I32
 ICU_Convert_Func
-- 
2.39.3 (Apple Git-146)

From 2033491062b359cd62df4ec1560947ae21f0868c Mon Sep 17 00:00:00 2001
From: Daniel Gustafsson <dgustafsson@postgresql.org>
Date: Mon, 4 Nov 2024 13:52:23 +0100
Subject: [PATCH v3] Serverside SNI support for libpq

Experimental support for serverside SNI support in libpq, a new config
file $datadir/pg_hosts.conf is used for configuring which certicate and
key should be used for which hostname. A new GUC, ssl_snimode, is added
which controls how the hostname TLS extension is handled. The possible
values are off, default and strict:

  - off: pg_hosts.conf is not parsed and the hostname TLS extension is
    not inspected at all. The normal SSL GUCs for certificates and keys
	are used.
  - default: pg_hosts.conf is loaded as well as the normal GUCs. If no
    match for the TLS extension hostname is found in pg_hosts the cert
	and key from the postgresql.conf GUCs is used as the default (used
	as a wildcard host).
  - strict: only pg_hosts.conf is loaded and the TLS extension hostname
    MUST be passed and MUST have a match in the configuration, else the
	connection is refused.

CRL file(s) are applied from postgresql.conf to all configured hostnames.

Reviewed-by: Cary Huang <cary.huang@highgo.ca>
Reviewed-by: Jacob Champion <jacob.champion@enterprisedb.com>
Discussion: https://postgr.es/m/1C81CD0D-407E-44F9-833A-DD0331C202E5@yesql.se
---
 doc/src/sgml/config.sgml                      |  62 ++++
 doc/src/sgml/runtime.sgml                     |  50 +++
 src/backend/Makefile                          |   1 +
 src/backend/libpq/be-secure-common.c          | 203 ++++++++++-
 src/backend/libpq/be-secure-openssl.c         | 315 ++++++++++++++++--
 src/backend/libpq/be-secure.c                 |   8 +-
 src/backend/libpq/meson.build                 |   1 +
 src/backend/libpq/pg_hosts.conf.sample        |   5 +
 src/backend/utils/misc/guc.c                  |  26 ++
 src/backend/utils/misc/guc_tables.c           |  31 ++
 src/backend/utils/misc/postgresql.conf.sample |   1 +
 src/bin/initdb/initdb.c                       |  16 +-
 src/include/libpq/hba.h                       |  19 ++
 src/include/libpq/libpq-be.h                  |   3 +-
 src/include/libpq/libpq.h                     |  11 +-
 src/include/utils/guc.h                       |   1 +
 src/test/ssl/meson.build                      |   1 +
 src/test/ssl/t/004_sni.pl                     | 135 ++++++++
 src/tools/pgindent/typedefs.list              |   2 +
 19 files changed, 843 insertions(+), 48 deletions(-)
 create mode 100644 src/backend/libpq/pg_hosts.conf.sample
 create mode 100644 src/test/ssl/t/004_sni.pl

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index e0c8325a39..1cecaccee7 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1652,6 +1652,68 @@ include_dir 'conf.d'
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry id="guc-ssl-snimode" xreflabel="ssl_snimode">
+      <term><varname>ssl_snimode</varname> (<type>enum</type>)
+      <indexterm>
+       <primary><varname>ssl_snimode</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        This parameter determines if the server will inspect the <acronym>SNI</acronym> TLS extension
+        when establishing the connection, and how it should be interpreted.
+        Valid values are currently: <literal>off</literal>, <literal>default</literal> and <literal>strict</literal>.
+       </para>
+       <para>
+        <variablelist>
+         <varlistentry id="guc-ssl-snimode-off">
+          <term><literal>off</literal></term>
+          <listitem>
+           <para>
+            SNI is not enabled and no configuration from
+            <filename>pg_hosts.conf</filename> is loaded.  Configuration of SSL
+            for all connections is done with <xref linkend="guc-ssl-cert-file"/>,
+            <xref linkend="guc-ssl-key-file"/> and <xref linkend="guc-ssl-ca-file"/>.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry id="guc-ssl-snimode-default">
+          <term><literal>default</literal></term>
+          <listitem>
+           <para>
+            SNI is enabled and hostname configuration is loaded from
+            <filename>pg_hosts.conf</filename>. <xref linkend="guc-ssl-cert-file"/>,
+            <xref linkend="guc-ssl-key-file"/> and <xref linkend="guc-ssl-ca-file"/>
+            are loaded as the default configuration.  Any connection specifying
+            <xref linkend="libpq-connect-sslsni"/> to <literal>1</literal>
+            a hostname which is missing in <filename>pg_hosts.conf</filename>
+            will be attempted using the default configuration. If the hostname
+            matches an entry from <filename>pg_hosts.conf</filename>, then the
+            configuration from that entry will be used for setting up the
+            connection.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry id="guc-ssl-snimode-strict">
+          <term><literal>strict</literal></term>
+          <listitem>
+           <para>
+            SNI is enabled and all connections are required to set <xref
+            linkend="libpq-connect-sslsni"/> to <literal>1</literal> and
+            specify a hostname matching an entry in
+            <filename>pg_hosts.conf</filename>. Any connection without <xref
+            linkend="libpq-connect-sslsni"/> or with a hostname missing from
+            <filename>pg_hosts.conf</filename> will be rejected.
+           </para>
+          </listitem>
+         </varlistentry>
+        </variablelist>
+       </para>
+      </listitem>
+     </varlistentry>
     </variablelist>
     </sect2>
    </sect1>
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index 94135e9d5e..0ac79ae28d 100644
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -2444,6 +2444,12 @@ pg_dumpall -p 5432 | psql -d postgres -p 5433
       <entry>client certificate must not be on this list</entry>
      </row>
 
+     <row>
+      <entry><filename>$PGDATA/pg_hosts.conf</filename></entry>
+      <entry>SNI configuration</entry>
+      <entry>defines which certificates to use for which server hostname</entry>
+     </row>
+
     </tbody>
    </tgroup>
   </table>
@@ -2571,6 +2577,50 @@ openssl x509 -req -in server.csr -text -days 365 \
    </para>
   </sect2>
 
+  <sect2 id="ssl-sni">
+   <title>SNI Configuration</title>
+
+   <para>
+    <productname>PostgreSQL</productname> can be configured for
+    <acronym>SNI</acronym> using the <filename>pg_hosts.conf</filename>
+    configuration file. <productname>PostgreSQL</productname> inspects the TLS
+    hostname extension in the SSL connection handshake, and selects the right
+    SSL certificate, key and CA certificate to use for the connection.
+   </para>
+
+   <para>
+    SNI configuration is defined in the hosts configuration file, which is
+    named <filename>pg_hosts.conf</filename> and is stored in the clusters
+    data directory.  The hosts configuration file contains lines of the general
+    forms:
+<synopsis>
+<replaceable>hostname</replaceable> <replaceable>SSL_certificate</replaceable> <replaceable>SSL_key</replaceable> <replaceable>SSL_CA_certificate</replaceable> <replaceable>SSL_passphrase_cmd</replaceable> <replaceable>SSL_passphrase_cmd_reload</replaceable>
+<replaceable>include</replaceable> <replaceable>file</replaceable>
+<replaceable>include_if_exists</replaceable> <replaceable>file</replaceable>
+<replaceable>include_dir</replaceable> <replaceable>directory</replaceable>
+</synopsis>
+    Comments, whitespace and line continuations are handled in the same way as
+    in <filename>pg_hba.conf</filename>.  <replaceable>hostname</replaceable>
+    is matched against the hostname TLS extension in the SSL handshake.
+    <replaceable>SSL_certificate</replaceable>,
+    <replaceable>SSL_key</replaceable>,
+    <replaceable>SSL_CA_certificate</replaceable>,
+    <replaceable>SSL_passphrase_cmd</replaceable>, and
+    <replaceable>SSL_passphrase_cmd_reload</replaceable>
+    are treated like
+    <xref linkend="guc-ssl-cert-file"/>,
+    <xref linkend="guc-ssl-key-file"/>,
+    <xref linkend="guc-ssl-ca-file"/>,
+    <xref linkend="guc-ssl-passphrase-command"/>, and
+    <xref linkend="guc-ssl-passphrase-command-supports-reload"/> respectively.
+    All fields except <replaceable>SSL_passphrase_cmd</replaceable> and
+    <replaceable>SSL_passphrase_cmd_reload</replaceable> are required. If
+    <replaceable>SSL_passphrase_cmd</replaceable> is defined but not
+    <replaceable>SSL_passphrase_cmd_reload</replaceable> then the default
+    value for <replaceable>SSL_passphrase_cmd_reload</replaceable> is
+    <literal>off</literal>.
+   </para>
+  </sect2>
  </sect1>
 
  <sect1 id="gssapi-enc">
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 84302cc6da..bc8accbde0 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -186,6 +186,7 @@ endif
 	$(MAKE) -C utils install-data
 	$(INSTALL_DATA) $(srcdir)/libpq/pg_hba.conf.sample '$(DESTDIR)$(datadir)/pg_hba.conf.sample'
 	$(INSTALL_DATA) $(srcdir)/libpq/pg_ident.conf.sample '$(DESTDIR)$(datadir)/pg_ident.conf.sample'
+	$(INSTALL_DATA) $(srcdir)/libpq/pg_hosts.conf.sample '$(DESTDIR)$(datadir)/pg_hosts.conf.sample'
 	$(INSTALL_DATA) $(srcdir)/utils/misc/postgresql.conf.sample '$(DESTDIR)$(datadir)/postgresql.conf.sample'
 
 ifeq ($(with_llvm), yes)
diff --git a/src/backend/libpq/be-secure-common.c b/src/backend/libpq/be-secure-common.c
index 0cb201acb1..e483ca7944 100644
--- a/src/backend/libpq/be-secure-common.c
+++ b/src/backend/libpq/be-secure-common.c
@@ -24,8 +24,13 @@
 
 #include "common/percentrepl.h"
 #include "common/string.h"
+#include "libpq/hba.h"
 #include "libpq/libpq.h"
 #include "storage/fd.h"
+#include "utils/guc.h"
+#include "utils/memutils.h"
+
+static HostsLine *parse_hosts_line(TokenizedAuthLine *tok_line, int elevel);
 
 /*
  * Run ssl_passphrase_command
@@ -37,19 +42,20 @@
  * value is the length of the actual result.
  */
 int
-run_ssl_passphrase_command(const char *prompt, bool is_server_start, char *buf, int size)
+run_ssl_passphrase_command(const char *prompt, bool is_server_start, char *buf, int size, void *userdata)
 {
 	int			loglevel = is_server_start ? ERROR : LOG;
 	char	   *command;
 	FILE	   *fh;
 	int			pclose_rc;
 	size_t		len = 0;
+	char	   *cmd = (char *) userdata;
 
 	Assert(prompt);
 	Assert(size > 0);
 	buf[0] = '\0';
 
-	command = replace_percent_placeholders(ssl_passphrase_command, "ssl_passphrase_command", "p", prompt);
+	command = replace_percent_placeholders(cmd, "ssl_passphrase_command", "p", prompt);
 
 	fh = OpenPipeStream(command, "r");
 	if (fh == NULL)
@@ -175,3 +181,196 @@ check_ssl_key_file_permissions(const char *ssl_key_file, bool isServerStart)
 
 	return true;
 }
+
+/*
+ * parse_hosts_line
+ *
+ * Parses a loaded line from the pg_hosts.conf configuration and pulls out the
+ * hostname, certificate, key and CA parts in order to build an SNI config in
+ * the TLS backend. Validation of the parsed values is left for the TLS backend
+ * to implement.
+ */
+static HostsLine *
+parse_hosts_line(TokenizedAuthLine *tok_line, int elevel)
+{
+	HostsLine  *parsedline;
+	List	   *tokens;
+	ListCell   *field;
+	AuthToken  *token;
+
+	parsedline = palloc0(sizeof(HostsLine));
+	parsedline->sourcefile = pstrdup(tok_line->file_name);
+	parsedline->linenumber = tok_line->line_num;
+	parsedline->rawline = pstrdup(tok_line->raw_line);
+
+	/* Initialize optional fields */
+	parsedline->ssl_passphrase_cmd = NULL;
+	parsedline->ssl_passphrase_reload = false;
+
+	/* Hostname */
+	field = list_head(tok_line->fields);
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->hostname = pstrdup(token->string);
+
+	/* SSL Certificate (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_cert = pstrdup(token->string);
+
+	/* SSL key (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_key = pstrdup(token->string);
+
+	/* SSL CA (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_ca = pstrdup(token->string);
+
+	/* SSL Passphrase Command (optional) */
+	field = lnext(tok_line->fields, field);
+	if (field)
+	{
+		tokens = lfirst(field);
+		token = linitial(tokens);
+		parsedline->ssl_passphrase_cmd = pstrdup(token->string);
+
+		/*
+		 * SSL Passphrase Command support reload (optional). This field is
+		 * only supported if there was a passphrase command parsed first, so
+		 * nest it under the previous token.
+		 */
+		field = lnext(tok_line->fields, field);
+		if (field)
+		{
+			tokens = lfirst(field);
+			token = linitial(tokens);
+
+			if (token->string[0] == '1'
+				|| pg_strcasecmp(token->string, "true") == 0
+				|| pg_strcasecmp(token->string, "on") == 0
+				|| pg_strcasecmp(token->string, "yes") == 0)
+				parsedline->ssl_passphrase_reload = true;
+			else if (token->string[0] == '0'
+					 || pg_strcasecmp(token->string, "false") == 0
+					 || pg_strcasecmp(token->string, "off") == 0
+					 || pg_strcasecmp(token->string, "no") == 0)
+				parsedline->ssl_passphrase_reload = false;
+			else
+				ereport(elevel,
+						errcode(ERRCODE_CONFIG_FILE_ERROR),
+						errmsg("incorrect syntax for boolean value SSL_passphrase_cmd_reload"),
+						errcontext("line %d of configuration file \"%s\"",
+								   tok_line->line_num, tok_line->file_name));
+		}
+	}
+
+	return parsedline;
+}
+
+/*
+ * load_hosts
+ *
+ * Reads pg_hosts.conf and passes back a List of parsed lines, or NIL in case
+ * of errors.
+ */
+List *
+load_hosts(void)
+{
+	FILE	   *file;
+	ListCell   *line;
+	List	   *hosts_lines = NIL;
+	List	   *parsed_lines = NIL;
+	HostsLine  *newline;
+	bool		ok = true;
+	MemoryContext oldcxt;
+	MemoryContext hostcxt;
+
+	file = open_auth_file(HostsFileName, LOG, 0, NULL);
+	if (file == NULL)
+	{
+		/* An error has already been logged so no need to add one here. */
+		return NIL;
+	}
+
+	tokenize_auth_file(HostsFileName, file, &hosts_lines, LOG, 0);
+
+	hostcxt = AllocSetContextCreate(PostmasterContext,
+									"hosts file parser context",
+									ALLOCSET_SMALL_SIZES);
+	oldcxt = MemoryContextSwitchTo(hostcxt);
+
+	foreach(line, hosts_lines)
+	{
+		TokenizedAuthLine *tok_line = (TokenizedAuthLine *) lfirst(line);
+
+		if (tok_line->err_msg != NULL)
+		{
+			ok = false;
+			continue;
+		}
+
+		if ((newline = parse_hosts_line(tok_line, LOG)) == NULL)
+		{
+			ok = false;
+			continue;
+		}
+
+		parsed_lines = lappend(parsed_lines, newline);
+	}
+
+	free_auth_file(file, 0);
+	MemoryContextSwitchTo(oldcxt);
+
+	/*
+	 * If we didn't find any SNI configuration then that's not an error since
+	 * the pg_hosts file is additive to the default SSL configuration.
+	 */
+	if (ok && parsed_lines == NIL)
+	{
+		ereport(DEBUG1,
+				errmsg("no SNI configuration added from configuration file  \"%s\"",
+					   HostsFileName));
+		MemoryContextDelete(hostcxt);
+		return NIL;
+	}
+
+	if (!ok)
+	{
+		MemoryContextDelete(hostcxt);
+		return NIL;
+	}
+
+	return parsed_lines;
+}
diff --git a/src/backend/libpq/be-secure-openssl.c b/src/backend/libpq/be-secure-openssl.c
index 91a86d62a3..5acfdeb625 100644
--- a/src/backend/libpq/be-secure-openssl.c
+++ b/src/backend/libpq/be-secure-openssl.c
@@ -51,9 +51,18 @@
 #endif
 #include <openssl/x509v3.h>
 
+typedef struct HostContext
+{
+	const char *hostname;
+	const char *ssl_passphrase;
+	SSL_CTX    *context;
+	bool		default_host;
+	bool		ssl_loaded_verify_locations;
+	bool		ssl_passphrase_support_reload;
+} HostContext;
 
 /* default init hook can be overridden by a shared library */
-static void default_openssl_tls_init(SSL_CTX *context, bool isServerStart);
+static void default_openssl_tls_init(SSL_CTX *context, bool isServerStart, HostsLine *hosts);
 openssl_tls_init_hook_typ openssl_tls_init_hook = default_openssl_tls_init;
 
 static int	port_bio_read(BIO *h, char *buf, int size);
@@ -73,6 +82,7 @@ static int	alpn_cb(SSL *ssl,
 					const unsigned char *in,
 					unsigned int inlen,
 					void *userdata);
+static int	sni_servername_cb(SSL *ssl, int *al, void *arg);
 static bool initialize_dh(SSL_CTX *context, bool isServerStart);
 static bool initialize_ecdh(SSL_CTX *context, bool isServerStart);
 static const char *SSLerrmessageExt(unsigned long ecode, const char *replacement);
@@ -80,12 +90,16 @@ static const char *SSLerrmessage(unsigned long ecode);
 
 static char *X509_NAME_to_cstring(X509_NAME *name);
 
+static List *contexts = NIL;
 static SSL_CTX *SSL_context = NULL;
+static HostContext *Host_context = NULL;
 static bool dummy_ssl_passwd_cb_called = false;
 static bool ssl_is_server_start;
 
 static int	ssl_protocol_version_to_openssl(int v);
 static const char *ssl_protocol_version_to_string(int v);
+static SSL_CTX *ssl_init_context(bool isServerStart, HostsLine *host);
+static void free_contexts(void);
 
 /* for passing data back from verify_cb() */
 static const char *cert_errdetail;
@@ -96,11 +110,155 @@ static const char *cert_errdetail;
 
 int
 be_tls_init(bool isServerStart)
+{
+	SSL_CTX    *ctx;
+	List	   *sni_hosts = NIL;
+
+	/*
+	 * If there are contexts loaded when we init they should be released. This
+	 * should only be possible when reloading, but to keep any subtle bugs at
+	 * arms length we check unconditionally with an assert for non-production
+	 * builds.
+	 */
+	if (contexts != NIL)
+	{
+		Assert(isServerStart == false);
+		free_contexts();
+	}
+
+	/*
+	 * When ssl_snimode is off or default we load the certificate and key
+	 * specified in postgresql.conf and set that as the default host.
+	 */
+	if (ssl_snimode == SSL_SNIMODE_OFF || ssl_snimode == SSL_SNIMODE_DEFAULT)
+	{
+		HostContext *host_context;
+		HostsLine	line;
+
+		line.ssl_cert = ssl_cert_file;
+		line.ssl_key = ssl_key_file;
+		line.ssl_ca = ssl_ca_file;
+		line.ssl_passphrase_cmd = ssl_passphrase_command;
+		line.ssl_passphrase_reload = ssl_passphrase_command_supports_reload;
+
+		ctx = ssl_init_context(isServerStart, &line);
+		if (ctx == NULL)
+		{
+			ereport(isServerStart ? FATAL : LOG,
+					(errcode(ERRCODE_CONFIG_FILE_ERROR),
+					 errmsg("could not load default certificate")));
+			return -1;
+		}
+
+		host_context = palloc0(sizeof(HostContext));
+
+		host_context->hostname = pstrdup("*");
+		host_context->context = ctx;
+		host_context->default_host = true;
+
+		/*
+		 * Set flag to remember whether CA store has been loaded into
+		 * SSL_context.
+		 */
+		if (ssl_ca_file[0])
+			host_context->ssl_loaded_verify_locations = true;
+
+		/*
+		 * The contexts list is not used in ssl_snimode off but we add the
+		 * entry there anyways for consistency with the other modes.
+		 */
+		contexts = lappend(contexts, host_context);
+
+		/*
+		 * Install the default certificate which for ssl_snimode default can
+		 * be overridden in the callback if a hostname match is found.
+		 */
+		SSL_context = ctx;
+		Host_context = host_context;
+	}
+
+	/*
+	 * In default or strict ssl_snimode we load all certificates/keys which
+	 * are configured in pg_hosts.conf. In strict mode it is considered a
+	 * fatal error in case there are no configured entries.
+	 */
+	if (ssl_snimode == SSL_SNIMODE_STRICT || ssl_snimode == SSL_SNIMODE_DEFAULT)
+	{
+		ListCell   *line;
+
+		/*
+		 * Load pg_hosts.conf and parse each row, returning the set of hosts
+		 * as a list.
+		 */
+		sni_hosts = load_hosts();
+
+		/*
+		 * In strict ssl_snimode there needs to be a working pg_hosts file,
+		 */
+		if (sni_hosts == NIL && ssl_snimode == SSL_SNIMODE_STRICT)
+		{
+			ereport(isServerStart ? FATAL : LOG,
+					errcode(ERRCODE_CONFIG_FILE_ERROR),
+					errmsg("could not load pg_hosts.conf file"));
+			return -1;
+		}
+
+		foreach(line, sni_hosts)
+		{
+			HostContext *host_context;
+			HostsLine  *host = lfirst(line);
+
+			SSL_context = ssl_init_context(isServerStart, host);
+			if (SSL_context == NULL)
+			{
+				ereport(isServerStart ? FATAL : LOG,
+						errcode(ERRCODE_CONFIG_FILE_ERROR),
+						errmsg("unable to load certificate from pg_hosts.conf file"));
+				return -1;
+			}
+
+			host_context = palloc(sizeof(HostContext));
+			host_context->hostname = pstrdup(host->hostname);
+			host_context->context = SSL_context;
+			host_context->default_host = false;
+			if (host->ssl_passphrase_cmd != NULL)
+				host_context->ssl_passphrase = pstrdup(host->ssl_passphrase_cmd);
+			host_context->ssl_passphrase_support_reload = host->ssl_passphrase_reload;
+
+			/*
+			 * Set flag to remember whether CA store has been loaded into
+			 * SSL_context.
+			 */
+			if (host->ssl_ca)
+				host_context->ssl_loaded_verify_locations = true;
+
+			contexts = lappend(contexts, host_context);
+		}
+	}
+
+	/* Make sure we have at least one certificate loaded */
+	if (list_length(contexts) < 1)
+	{
+		ereport(isServerStart ? FATAL : LOG,
+				(errcode(ERRCODE_CONFIG_FILE_ERROR),
+				 errmsg("no SSL contexts loaded")));
+		return -1;
+	}
+
+	return 0;
+}
+
+static SSL_CTX *
+ssl_init_context(bool isServerStart, HostsLine *host_line)
 {
 	SSL_CTX    *context;
 	int			ssl_ver_min = -1;
 	int			ssl_ver_max = -1;
 
+	const char *ctx_ssl_cert_file = host_line->ssl_cert;
+	const char *ctx_ssl_key_file = host_line->ssl_key;
+	const char *ctx_ssl_ca_file = host_line->ssl_ca;
+
 	/*
 	 * Create a new SSL context into which we'll load all the configuration
 	 * settings.  If we fail partway through, we can avoid memory leakage by
@@ -126,10 +284,17 @@ be_tls_init(bool isServerStart)
 	 */
 	SSL_CTX_set_mode(context, SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER);
 
+	/*
+	 * Install SNI TLS extension callback in case the server is configured to
+	 * validate hostnames.
+	 */
+	if (ssl_snimode != SSL_SNIMODE_OFF)
+		SSL_CTX_set_tlsext_servername_callback(context, sni_servername_cb);
+
 	/*
 	 * Call init hook (usually to set password callback)
 	 */
-	(*openssl_tls_init_hook) (context, isServerStart);
+	(*openssl_tls_init_hook) (context, isServerStart, host_line);
 
 	/* used by the callback */
 	ssl_is_server_start = isServerStart;
@@ -137,16 +302,16 @@ be_tls_init(bool isServerStart)
 	/*
 	 * Load and verify server's certificate and private key
 	 */
-	if (SSL_CTX_use_certificate_chain_file(context, ssl_cert_file) != 1)
+	if (SSL_CTX_use_certificate_chain_file(context, ctx_ssl_cert_file) != 1)
 	{
 		ereport(isServerStart ? FATAL : LOG,
 				(errcode(ERRCODE_CONFIG_FILE_ERROR),
 				 errmsg("could not load server certificate file \"%s\": %s",
-						ssl_cert_file, SSLerrmessage(ERR_get_error()))));
+						ctx_ssl_cert_file, SSLerrmessage(ERR_get_error()))));
 		goto error;
 	}
 
-	if (!check_ssl_key_file_permissions(ssl_key_file, isServerStart))
+	if (!check_ssl_key_file_permissions(ctx_ssl_key_file, isServerStart))
 		goto error;
 
 	/*
@@ -155,19 +320,19 @@ be_tls_init(bool isServerStart)
 	dummy_ssl_passwd_cb_called = false;
 
 	if (SSL_CTX_use_PrivateKey_file(context,
-									ssl_key_file,
+									ctx_ssl_key_file,
 									SSL_FILETYPE_PEM) != 1)
 	{
 		if (dummy_ssl_passwd_cb_called)
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("private key file \"%s\" cannot be reloaded because it requires a passphrase",
-							ssl_key_file)));
+							ctx_ssl_key_file)));
 		else
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("could not load private key file \"%s\": %s",
-							ssl_key_file, SSLerrmessage(ERR_get_error()))));
+							ctx_ssl_key_file, SSLerrmessage(ERR_get_error()))));
 		goto error;
 	}
 
@@ -319,17 +484,17 @@ be_tls_init(bool isServerStart)
 	/*
 	 * Load CA store, so we can verify client certificates if needed.
 	 */
-	if (ssl_ca_file[0])
+	if (ctx_ssl_ca_file[0])
 	{
 		STACK_OF(X509_NAME) * root_cert_list;
 
-		if (SSL_CTX_load_verify_locations(context, ssl_ca_file, NULL) != 1 ||
-			(root_cert_list = SSL_load_client_CA_file(ssl_ca_file)) == NULL)
+		if (SSL_CTX_load_verify_locations(context, ctx_ssl_ca_file, NULL) != 1 ||
+			(root_cert_list = SSL_load_client_CA_file(ctx_ssl_ca_file)) == NULL)
 		{
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("could not load root certificate file \"%s\": %s",
-							ssl_ca_file, SSLerrmessage(ERR_get_error()))));
+							ctx_ssl_ca_file, SSLerrmessage(ERR_get_error()))));
 			goto error;
 		}
 
@@ -401,38 +566,29 @@ be_tls_init(bool isServerStart)
 		}
 	}
 
-	/*
-	 * Success!  Replace any existing SSL_context.
-	 */
-	if (SSL_context)
-		SSL_CTX_free(SSL_context);
-
-	SSL_context = context;
-
-	/*
-	 * Set flag to remember whether CA store has been loaded into SSL_context.
-	 */
-	if (ssl_ca_file[0])
-		ssl_loaded_verify_locations = true;
-	else
-		ssl_loaded_verify_locations = false;
-
-	return 0;
+	return context;
 
 	/* Clean up by releasing working context. */
 error:
 	if (context)
 		SSL_CTX_free(context);
-	return -1;
+	return NULL;
 }
 
 void
 be_tls_destroy(void)
 {
-	if (SSL_context)
-		SSL_CTX_free(SSL_context);
+	ListCell   *cell;
+
+	foreach(cell, contexts)
+	{
+		HostContext *host_context = lfirst(cell);
+
+		SSL_CTX_free(host_context->context);
+		pfree(host_context);
+	}
+
 	SSL_context = NULL;
-	ssl_loaded_verify_locations = false;
 }
 
 int
@@ -1132,7 +1288,7 @@ ssl_external_passwd_cb(char *buf, int size, int rwflag, void *userdata)
 
 	Assert(rwflag == 0);
 
-	return run_ssl_passphrase_command(prompt, ssl_is_server_start, buf, size);
+	return run_ssl_passphrase_command(prompt, ssl_is_server_start, buf, size, userdata);
 }
 
 /*
@@ -1369,6 +1525,60 @@ alpn_cb(SSL *ssl,
 	}
 }
 
+static int
+sni_servername_cb(SSL *ssl, int *al, void *arg)
+{
+	const char *tlsext_hostname;
+	ListCell   *cell;
+	HostContext *host_context;
+
+	Assert(ssl_snimode != SSL_SNIMODE_OFF);
+
+	tlsext_hostname = SSL_get_servername(ssl, TLSEXT_NAMETYPE_host_name);
+
+	if (!tlsext_hostname)
+	{
+		if (ssl_snimode == SSL_SNIMODE_STRICT)
+		{
+			ereport(COMMERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg("no hostname provided in callback")));
+			return SSL_TLSEXT_ERR_ALERT_FATAL;
+		}
+		else
+			return SSL_TLSEXT_ERR_OK;
+	}
+
+	foreach(cell, contexts)
+	{
+		host_context = lfirst(cell);
+
+		if (strcmp(host_context->hostname, tlsext_hostname) == 0)
+		{
+			Host_context = host_context;
+			SSL_context = host_context->context;
+			SSL_set_SSL_CTX(ssl, SSL_context);
+			return SSL_TLSEXT_ERR_OK;
+		}
+	}
+
+	if (ssl_snimode == SSL_SNIMODE_STRICT)
+	{
+		ereport(COMMERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg("no matching pg_hosts entry found for hostname: \"%s\"",
+						tlsext_hostname)));
+		return SSL_TLSEXT_ERR_ALERT_FATAL;
+	}
+
+	/*
+	 * In ssl_snimode "default" we can return without doing anything since we
+	 * already installed the context for the default host when parsing the
+	 * hosts file.
+	 */
+	Assert(SSL_context);
+	return SSL_TLSEXT_ERR_OK;
+}
 
 /*
  * Set DH parameters for generating ephemeral DH keys.  The
@@ -1578,6 +1788,12 @@ be_tls_get_peer_serial(Port *port, char *ptr, size_t len)
 		ptr[0] = '\0';
 }
 
+bool
+be_tls_loaded_verify_locations(void)
+{
+	return Host_context->ssl_loaded_verify_locations;
+}
+
 char *
 be_tls_get_certificate_hash(Port *port, size_t *len)
 {
@@ -1771,17 +1987,23 @@ ssl_protocol_version_to_string(int v)
 
 
 static void
-default_openssl_tls_init(SSL_CTX *context, bool isServerStart)
+default_openssl_tls_init(SSL_CTX *context, bool isServerStart, HostsLine *host)
 {
 	if (isServerStart)
 	{
-		if (ssl_passphrase_command[0])
+		if (host->ssl_passphrase_cmd != NULL)
+		{
 			SSL_CTX_set_default_passwd_cb(context, ssl_external_passwd_cb);
+			SSL_CTX_set_default_passwd_cb_userdata(context, host->ssl_passphrase_cmd);
+		}
 	}
 	else
 	{
-		if (ssl_passphrase_command[0] && ssl_passphrase_command_supports_reload)
+		if (host->ssl_passphrase_cmd != NULL && host->ssl_passphrase_reload)
+		{
 			SSL_CTX_set_default_passwd_cb(context, ssl_external_passwd_cb);
+			SSL_CTX_set_default_passwd_cb_userdata(context, host->ssl_passphrase_cmd);
+		}
 		else
 
 			/*
@@ -1793,3 +2015,22 @@ default_openssl_tls_init(SSL_CTX *context, bool isServerStart)
 			SSL_CTX_set_default_passwd_cb(context, dummy_ssl_passwd_cb);
 	}
 }
+
+static void
+free_contexts(void)
+{
+	if (contexts == NIL)
+		return;
+
+	foreach_ptr(HostContext, host, contexts)
+	{
+		if (host->hostname)
+			pfree(unconstify(char *, host->hostname));
+		if (host->ssl_passphrase)
+			pfree(unconstify(char *, host->ssl_passphrase));
+		SSL_CTX_free(host->context);
+	}
+
+	list_free_deep(contexts);
+	contexts = NIL;
+}
diff --git a/src/backend/libpq/be-secure.c b/src/backend/libpq/be-secure.c
index 2139f81f24..ad3066b63c 100644
--- a/src/backend/libpq/be-secure.c
+++ b/src/backend/libpq/be-secure.c
@@ -43,10 +43,6 @@ char	   *ssl_dh_params_file;
 char	   *ssl_passphrase_command;
 bool		ssl_passphrase_command_supports_reload;
 
-#ifdef USE_SSL
-bool		ssl_loaded_verify_locations = false;
-#endif
-
 /* GUC variable controlling SSL cipher list */
 char	   *SSLCipherSuites = NULL;
 char	   *SSLCipherList = NULL;
@@ -60,6 +56,8 @@ bool		SSLPreferServerCiphers;
 int			ssl_min_protocol_version = PG_TLS1_2_VERSION;
 int			ssl_max_protocol_version = PG_TLS_ANY;
 
+int			ssl_snimode = SSL_SNIMODE_DEFAULT;
+
 /* ------------------------------------------------------------ */
 /*			 Procedures common to all secure sessions			*/
 /* ------------------------------------------------------------ */
@@ -99,7 +97,7 @@ bool
 secure_loaded_verify_locations(void)
 {
 #ifdef USE_SSL
-	return ssl_loaded_verify_locations;
+	return be_tls_loaded_verify_locations();
 #else
 	return false;
 #endif
diff --git a/src/backend/libpq/meson.build b/src/backend/libpq/meson.build
index 7c65314512..1c6269262c 100644
--- a/src/backend/libpq/meson.build
+++ b/src/backend/libpq/meson.build
@@ -30,5 +30,6 @@ endif
 install_data(
   'pg_hba.conf.sample',
   'pg_ident.conf.sample',
+  'pg_hosts.conf.sample',
   install_dir: dir_data,
 )
diff --git a/src/backend/libpq/pg_hosts.conf.sample b/src/backend/libpq/pg_hosts.conf.sample
new file mode 100644
index 0000000000..608210686e
--- /dev/null
+++ b/src/backend/libpq/pg_hosts.conf.sample
@@ -0,0 +1,5 @@
+# PostgreSQL SNI Hostname mappings
+# ================================
+
+# HOSTNAME       SSL CERTIFICATE             SSL KEY
+
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index c10c0844ab..b3e1cf0b25 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -55,6 +55,7 @@
 #define CONFIG_FILENAME "postgresql.conf"
 #define HBA_FILENAME	"pg_hba.conf"
 #define IDENT_FILENAME	"pg_ident.conf"
+#define HOSTS_FILENAME	"pg_hosts.conf"
 
 #ifdef EXEC_BACKEND
 #define CONFIG_EXEC_PARAMS "global/config_exec_params"
@@ -1968,6 +1969,31 @@ SelectConfigFiles(const char *userDoption, const char *progname)
 	}
 	SetConfigOption("ident_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
 
+	/*
+	 * Likewise for pg_hosts.conf
+	 */
+	if (HostsFileName)
+	{
+		fname = make_absolute_path(HostsFileName);
+		fname_is_malloced = true;
+	}
+	else if (configdir)
+	{
+		fname = guc_malloc(FATAL,
+						   strlen(configdir) + strlen(HOSTS_FILENAME) + 2);
+		sprintf(fname, "%s/%s", configdir, HOSTS_FILENAME);
+		fname_is_malloced = false;
+	}
+	else
+	{
+		write_stderr("%s does not know where to find the \"hosts\" configuration file.\n"
+					 "This can be specified as \"hosts_file\" in \"%s\", "
+					 "or by the -D invocation option, or by the "
+					 "PGDATA environment variable.\n",
+					 progname, ConfigFileName);
+	}
+	SetConfigOption("hosts_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
+
 	if (fname_is_malloced)
 		free(fname);
 	else
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index 8cf1afbad2..dca5a15f5c 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -474,6 +474,13 @@ static const struct config_enum_entry wal_compression_options[] = {
 	{NULL, 0, false}
 };
 
+static const struct config_enum_entry ssl_snimode_options[] = {
+	{"off", SSL_SNIMODE_OFF, false},
+	{"default", SSL_SNIMODE_DEFAULT, false},
+	{"strict", SSL_SNIMODE_STRICT, false},
+	{NULL, 0, false}
+};
+
 /*
  * Options for enum values stored in other modules
  */
@@ -538,6 +545,7 @@ char	   *cluster_name = "";
 char	   *ConfigFileName;
 char	   *HbaFileName;
 char	   *IdentFileName;
+char	   *HostsFileName;
 char	   *external_pid_file;
 
 char	   *application_name;
@@ -4562,6 +4570,17 @@ struct config_string ConfigureNamesString[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"hosts_file", PGC_POSTMASTER, FILE_LOCATIONS,
+			gettext_noop("Sets the server's \"hosts\" configuration file."),
+			NULL,
+			GUC_SUPERUSER_ONLY
+		},
+		&HostsFileName,
+		NULL,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"external_pid_file", PGC_POSTMASTER, FILE_LOCATIONS,
 			gettext_noop("Writes the postmaster PID to the specified file."),
@@ -5204,6 +5223,18 @@ struct config_enum ConfigureNamesEnum[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"ssl_snimode", PGC_SIGHUP, CONN_AUTH_SSL,
+			gettext_noop("Sets the SNI mode to use."),
+			NULL,
+			GUC_SUPERUSER_ONLY,
+		},
+		&ssl_snimode,
+		SSL_SNIMODE_DEFAULT,
+		ssl_snimode_options,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"recovery_init_sync_method", PGC_SIGHUP, ERROR_HANDLING_OPTIONS,
 			gettext_noop("Sets the method for synchronizing the data directory before crash recovery."),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index a2ac7575ca..902c4eccef 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -120,6 +120,7 @@
 #ssl_dh_params_file = ''
 #ssl_passphrase_command = ''
 #ssl_passphrase_command_supports_reload = off
+#ssl_snimode = default
 
 
 #------------------------------------------------------------------------------
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 9a91830783..984763da08 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -176,6 +176,7 @@ static int	encodingid;
 static char *bki_file;
 static char *hba_file;
 static char *ident_file;
+static char *hosts_file;
 static char *conf_file;
 static char *dictionary_file;
 static char *info_schema_file;
@@ -1512,6 +1513,14 @@ setup_config(void)
 
 	snprintf(path, sizeof(path), "%s/pg_ident.conf", pg_data);
 
+	writefile(path, conflines);
+	if (chmod(path, pg_file_create_mode) != 0)
+		pg_fatal("could not change permissions of \"%s\": %m", path);
+
+	/* pg_hosts.conf */
+	conflines = readfile(hosts_file);
+	snprintf(path, sizeof(path), "%s/pg_hosts.conf", pg_data);
+
 	writefile(path, conflines);
 	if (chmod(path, pg_file_create_mode) != 0)
 		pg_fatal("could not change permissions of \"%s\": %m", path);
@@ -2771,6 +2780,7 @@ setup_data_file_paths(void)
 	set_input(&bki_file, "postgres.bki");
 	set_input(&hba_file, "pg_hba.conf.sample");
 	set_input(&ident_file, "pg_ident.conf.sample");
+	set_input(&hosts_file, "pg_hosts.conf.sample");
 	set_input(&conf_file, "postgresql.conf.sample");
 	set_input(&dictionary_file, "snowball_create.sql");
 	set_input(&info_schema_file, "information_schema.sql");
@@ -2786,12 +2796,13 @@ setup_data_file_paths(void)
 				"PGDATA=%s\nshare_path=%s\nPGPATH=%s\n"
 				"POSTGRES_SUPERUSERNAME=%s\nPOSTGRES_BKI=%s\n"
 				"POSTGRESQL_CONF_SAMPLE=%s\n"
-				"PG_HBA_SAMPLE=%s\nPG_IDENT_SAMPLE=%s\n",
+				"PG_HBA_SAMPLE=%s\nPG_IDENT_SAMPLE=%s\n"
+				"PG_HOSTS_SAMPLE=%s\n",
 				PG_VERSION,
 				pg_data, share_path, bin_path,
 				username, bki_file,
 				conf_file,
-				hba_file, ident_file);
+				hba_file, ident_file, hosts_file);
 		if (show_setting)
 			exit(0);
 	}
@@ -2799,6 +2810,7 @@ setup_data_file_paths(void)
 	check_input(bki_file);
 	check_input(hba_file);
 	check_input(ident_file);
+	check_input(hosts_file);
 	check_input(conf_file);
 	check_input(dictionary_file);
 	check_input(info_schema_file);
diff --git a/src/include/libpq/hba.h b/src/include/libpq/hba.h
index 8ea837ae82..d1eb750368 100644
--- a/src/include/libpq/hba.h
+++ b/src/include/libpq/hba.h
@@ -146,6 +146,25 @@ typedef struct IdentLine
 	AuthToken  *pg_user;
 } IdentLine;
 
+typedef struct HostsLine
+{
+	int			linenumber;
+
+	char	   *sourcefile;
+	char	   *rawline;
+
+	/* Required fields */
+	bool		default_host;
+	char	   *hostname;
+	char	   *ssl_key;
+	char	   *ssl_cert;
+	char	   *ssl_ca;
+
+	/* Optional fields */
+	char	   *ssl_passphrase_cmd;
+	bool		ssl_passphrase_reload;
+} HostsLine;
+
 /*
  * TokenizedAuthLine represents one line lexed from an authentication
  * configuration file.  Each item in the "fields" list is a sub-list of
diff --git a/src/include/libpq/libpq-be.h b/src/include/libpq/libpq-be.h
index 9109b2c334..cf0e87a28c 100644
--- a/src/include/libpq/libpq-be.h
+++ b/src/include/libpq/libpq-be.h
@@ -314,6 +314,7 @@ extern const char *be_tls_get_cipher(Port *port);
 extern void be_tls_get_peer_subject_name(Port *port, char *ptr, size_t len);
 extern void be_tls_get_peer_issuer_name(Port *port, char *ptr, size_t len);
 extern void be_tls_get_peer_serial(Port *port, char *ptr, size_t len);
+extern bool be_tls_loaded_verify_locations(void);
 
 /*
  * Get the server certificate hash for SCRAM channel binding type
@@ -326,7 +327,7 @@ extern char *be_tls_get_certificate_hash(Port *port, size_t *len);
 
 /* init hook for SSL, the default sets the password callback if appropriate */
 #ifdef USE_OPENSSL
-typedef void (*openssl_tls_init_hook_typ) (SSL_CTX *context, bool isServerStart);
+typedef void (*openssl_tls_init_hook_typ) (SSL_CTX *context, bool isServerStart, HostsLine *host);
 extern PGDLLIMPORT openssl_tls_init_hook_typ openssl_tls_init_hook;
 #endif
 
diff --git a/src/include/libpq/libpq.h b/src/include/libpq/libpq.h
index 07e5b12536..98da8b61eb 100644
--- a/src/include/libpq/libpq.h
+++ b/src/include/libpq/libpq.h
@@ -107,6 +107,7 @@ extern PGDLLIMPORT char *ssl_crl_dir;
 extern PGDLLIMPORT char *ssl_key_file;
 extern PGDLLIMPORT int ssl_min_protocol_version;
 extern PGDLLIMPORT int ssl_max_protocol_version;
+extern PGDLLIMPORT int ssl_snimode;
 extern PGDLLIMPORT char *ssl_passphrase_command;
 extern PGDLLIMPORT bool ssl_passphrase_command_supports_reload;
 extern PGDLLIMPORT char *ssl_dh_params_file;
@@ -134,12 +135,20 @@ enum ssl_protocol_versions
 	PG_TLS1_3_VERSION,
 };
 
+enum ssl_snimode
+{
+	SSL_SNIMODE_OFF = 0,
+	SSL_SNIMODE_DEFAULT,
+	SSL_SNIMODE_STRICT
+};
+
 /*
  * prototypes for functions in be-secure-common.c
  */
 extern int	run_ssl_passphrase_command(const char *prompt, bool is_server_start,
-									   char *buf, int size);
+									   char *buf, int size, void *userdata);
 extern bool check_ssl_key_file_permissions(const char *ssl_key_file,
 										   bool isServerStart);
+extern List *load_hosts(void);
 
 #endif							/* LIBPQ_H */
diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index 840b0fe57f..4c33ba7ca4 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -284,6 +284,7 @@ extern PGDLLIMPORT char *cluster_name;
 extern PGDLLIMPORT char *ConfigFileName;
 extern PGDLLIMPORT char *HbaFileName;
 extern PGDLLIMPORT char *IdentFileName;
+extern PGDLLIMPORT char *HostsFileName;
 extern PGDLLIMPORT char *external_pid_file;
 
 extern PGDLLIMPORT char *application_name;
diff --git a/src/test/ssl/meson.build b/src/test/ssl/meson.build
index b3c5503f79..55f5887d9c 100644
--- a/src/test/ssl/meson.build
+++ b/src/test/ssl/meson.build
@@ -13,6 +13,7 @@ tests += {
       't/001_ssltests.pl',
       't/002_scram.pl',
       't/003_sslinfo.pl',
+      't/004_sni.pl',
     ],
   },
 }
diff --git a/src/test/ssl/t/004_sni.pl b/src/test/ssl/t/004_sni.pl
new file mode 100644
index 0000000000..1e7e397080
--- /dev/null
+++ b/src/test/ssl/t/004_sni.pl
@@ -0,0 +1,135 @@
+
+# Copyright (c) 2024, PostgreSQL Global Development Group
+
+use strict;
+use warnings FATAL => 'all';
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+use FindBin;
+use lib $FindBin::RealBin;
+
+use SSL::Server;
+
+# This is the hostname used to connect to the server. This cannot be a
+# hostname, because the server certificate is always for the domain
+# postgresql-ssl-regression.test.
+my $SERVERHOSTADDR = '127.0.0.1';
+# This is the pattern to use in pg_hba.conf to match incoming connections.
+my $SERVERHOSTCIDR = '127.0.0.1/32';
+
+if ($ENV{with_ssl} ne 'openssl')
+{
+	plan skip_all => 'OpenSSL not supported by this build';
+}
+
+if (!$ENV{PG_TEST_EXTRA} || $ENV{PG_TEST_EXTRA} !~ /\bssl\b/)
+{
+	plan skip_all =>
+	  'Potentially unsafe test SSL not enabled in PG_TEST_EXTRA';
+}
+
+my $ssl_server = SSL::Server->new();
+
+my $node = PostgreSQL::Test::Cluster->new('primary');
+$node->init;
+
+# PGHOST is enforced here to set up the node, subsequent connections
+# will use a dedicated connection string.
+$ENV{PGHOST} = $node->host;
+$ENV{PGPORT} = $node->port;
+$node->start;
+
+$ssl_server->configure_test_server_for_ssl($node, $SERVERHOSTADDR,
+	$SERVERHOSTCIDR, 'trust');
+
+$ssl_server->switch_server_cert($node, certfile => 'server-cn-only');
+
+my $connstr =
+  "dbname=trustdb hostaddr=$SERVERHOSTADDR host=localhost sslsni=1";
+
+$node->append_conf('postgresql.conf', "ssl_snimode=default");
+$node->reload;
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf', "localhost server.crt server.key root.crt");
+$node->append_conf('postgresql.conf', "ssl_snimode=strict");
+$node->reload;
+
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require",
+	expected_stderr => qr/unexpected eof/);
+
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf', "localhost server-cn-only.crt server-cn-only.key root_ca.crt");
+$node->reload;
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf', 'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo wrongpassword" on');
+my $result = $node->restart(fail_ok => 1);
+is($result, 0, 'restart fails with password-protected key when using the wrong passphrase command');
+
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf', 'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo secret1" on');
+$result = $node->restart(fail_ok => 1);
+is($result, 1, 'restart succeeds with password-protected key when using the correct passphrase command');
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+
+$node->reload;
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"1 connect with correct server CA cert file sslmode=require");
+
+# Stress testing during patch debugging and review, unlikely to be merged in
+# this state.
+for (my $i = 0; $i < 100; $i++)
+{
+	if (int(rand(10)) < 3)
+	{
+		ok(unlink($node->data_dir . '/pg_hosts.conf'));
+		$node->append_conf('pg_hosts.conf', 'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo secret1" on');
+	}
+	$node->append_conf('pg_hosts.conf', 'localhost_' . $i . ' server-cn-only.crt server-password.key root+client_ca.crt "echo secret1" on');
+	$node->reload;
+	$node->reload;
+	$node->connect_ok(
+		"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+		"connect with correct server CA cert file sslmode=require during reload loop");
+}
+$node->append_conf('pg_hosts.conf', 'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo secret1" on');
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require after reload loop");
+
+# Test reloading a passphrase protected key without reloading support in the
+# passphrase hook. Connecting after restart should succeed but not after the
+# following reload.
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf', 'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo secret1" off');
+$result = $node->restart(fail_ok => 1);
+is($result, 1, 'restart succeeds with password-protected key when using the correct passphrase command');
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+
+$node->reload;
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect fails since the passphrase protected key cannot be reloaded",
+	expected_stderr => qr/unexpected eof/);
+
+done_testing();
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 2d4c870423..15ccf4cf46 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -1158,6 +1158,8 @@ HeapTupleHeader
 HeapTupleHeaderData
 HeapTupleTableSlot
 HistControl
+HostContext
+HostsLine
 HotStandbyState
 I32
 ICU_Convert_Func
-- 
2.39.3 (Apple Git-146)

From ed0a6b24a686b85077643dc8d3617957782eac11 Mon Sep 17 00:00:00 2001
From: Daniel Gustafsson <dgustafsson@postgresql.org>
Date: Mon, 4 Nov 2024 13:52:23 +0100
Subject: [PATCH v5] Serverside SNI support for libpq

Experimental support for serverside SNI support in libpq, a new config
file $datadir/pg_hosts.conf is used for configuring which certicate and
key should be used for which hostname. A new GUC, ssl_snimode, is added
which controls how the hostname TLS extension is handled. The possible
values are off, default and strict:

  - off: pg_hosts.conf is not parsed and the hostname TLS extension is
    not inspected at all. The normal SSL GUCs for certificates and keys
	are used.
  - default: pg_hosts.conf is loaded as well as the normal GUCs. If no
    match for the TLS extension hostname is found in pg_hosts the cert
	and key from the postgresql.conf GUCs is used as the default (used
	as a wildcard host).
  - strict: only pg_hosts.conf is loaded and the TLS extension hostname
    MUST be passed and MUST have a match in the configuration, else the
	connection is refused.

CRL file(s) are applied from postgresql.conf to all configured hostnames.

Reviewed-by: Cary Huang <cary.huang@highgo.ca>
Reviewed-by: Jacob Champion <jacob.champion@enterprisedb.com>
Discussion: https://postgr.es/m/1C81CD0D-407E-44F9-833A-DD0331C202E5@yesql.se
---
 doc/src/sgml/config.sgml                      |  62 ++++
 doc/src/sgml/runtime.sgml                     |  57 ++++
 src/backend/Makefile                          |   1 +
 src/backend/libpq/be-secure-common.c          | 203 +++++++++++-
 src/backend/libpq/be-secure-openssl.c         | 307 +++++++++++++++---
 src/backend/libpq/be-secure.c                 |   8 +-
 src/backend/libpq/meson.build                 |   1 +
 src/backend/libpq/pg_hosts.conf.sample        |   5 +
 src/backend/utils/misc/guc.c                  |  26 ++
 src/backend/utils/misc/guc_tables.c           |  31 ++
 src/backend/utils/misc/postgresql.conf.sample |   3 +
 src/bin/initdb/initdb.c                       |  16 +-
 src/include/libpq/hba.h                       |  19 ++
 src/include/libpq/libpq-be.h                  |   3 +-
 src/include/libpq/libpq.h                     |  11 +-
 src/include/utils/guc.h                       |   1 +
 .../ssl_passphrase_func.c                     |   4 +-
 src/test/ssl/meson.build                      |   1 +
 src/test/ssl/t/004_sni.pl                     | 128 ++++++++
 src/tools/pgindent/typedefs.list              |   2 +
 20 files changed, 839 insertions(+), 50 deletions(-)
 create mode 100644 src/backend/libpq/pg_hosts.conf.sample
 create mode 100644 src/test/ssl/t/004_sni.pl

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 9eedcf6f0f4..a10a1a24890 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1652,6 +1652,68 @@ include_dir 'conf.d'
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry id="guc-ssl-snimode" xreflabel="ssl_snimode">
+      <term><varname>ssl_snimode</varname> (<type>enum</type>)
+      <indexterm>
+       <primary><varname>ssl_snimode</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        This parameter determines if the server will inspect the <acronym>SNI</acronym> TLS extension
+        when establishing the connection, and how it should be interpreted.
+        Valid values are currently: <literal>off</literal>, <literal>default</literal> and <literal>strict</literal>.
+       </para>
+       <para>
+        <variablelist>
+         <varlistentry id="guc-ssl-snimode-off">
+          <term><literal>off</literal></term>
+          <listitem>
+           <para>
+            SNI is not enabled and no configuration from
+            <filename>pg_hosts.conf</filename> is loaded.  Configuration of SSL
+            for all connections is done with <xref linkend="guc-ssl-cert-file"/>,
+            <xref linkend="guc-ssl-key-file"/> and <xref linkend="guc-ssl-ca-file"/>.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry id="guc-ssl-snimode-default">
+          <term><literal>default</literal></term>
+          <listitem>
+           <para>
+            SNI is enabled and hostname configuration is loaded from
+            <filename>pg_hosts.conf</filename>. <xref linkend="guc-ssl-cert-file"/>,
+            <xref linkend="guc-ssl-key-file"/> and <xref linkend="guc-ssl-ca-file"/>
+            are loaded as the default configuration.  Connections specifying
+            <xref linkend="libpq-connect-sslsni"/> to <literal>1</literal>
+            will be attempted using the default configuration if the hostname
+            is missing in <filename>pg_hosts.conf</filename>.  If the hostname
+            matches an entry from <filename>pg_hosts.conf</filename>, then the
+            configuration from that entry will be used for setting up the
+            connection.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry id="guc-ssl-snimode-strict">
+          <term><literal>strict</literal></term>
+          <listitem>
+           <para>
+            SNI is enabled and all connections are required to set <xref
+            linkend="libpq-connect-sslsni"/> to <literal>1</literal> and
+            specify a hostname matching an entry in
+            <filename>pg_hosts.conf</filename>. Any connection without <xref
+            linkend="libpq-connect-sslsni"/> or with a hostname missing from
+            <filename>pg_hosts.conf</filename> will be rejected.
+           </para>
+          </listitem>
+         </varlistentry>
+        </variablelist>
+       </para>
+      </listitem>
+     </varlistentry>
     </variablelist>
     </sect2>
    </sect1>
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index 59f39e89924..57dfe972100 100644
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -2444,6 +2444,12 @@ pg_dumpall -p 5432 | psql -d postgres -p 5433
       <entry>client certificate must not be on this list</entry>
      </row>
 
+     <row>
+      <entry><filename>$PGDATA/pg_hosts.conf</filename></entry>
+      <entry>SNI configuration</entry>
+      <entry>defines which certificates to use for which server hostname</entry>
+     </row>
+
     </tbody>
    </tgroup>
   </table>
@@ -2571,6 +2577,57 @@ openssl x509 -req -in server.csr -text -days 365 \
    </para>
   </sect2>
 
+  <sect2 id="ssl-sni">
+   <title>SNI Configuration</title>
+
+   <para>
+    <productname>PostgreSQL</productname> can be configured for
+    <acronym>SNI</acronym> using the <filename>pg_hosts.conf</filename>
+    configuration file. <productname>PostgreSQL</productname> inspects the TLS
+    hostname extension in the SSL connection handshake, and selects the right
+    TLS certificate, key and CA certificate to use for the connection.
+   </para>
+
+   <para>
+    SNI configuration is defined in the hosts configuration file,
+    <filename>pg_hosts.conf</filename>, which is stored in the clusters
+    data directory.  The hosts configuration file contains lines of the general
+    forms:
+<synopsis>
+<replaceable>hostname</replaceable> <replaceable>SSL_certificate</replaceable> <replaceable>SSL_key</replaceable> <replaceable>SSL_CA_certificate</replaceable> <replaceable>SSL_passphrase_cmd</replaceable> <replaceable>SSL_passphrase_cmd_reload</replaceable>
+<replaceable>include</replaceable> <replaceable>file</replaceable>
+<replaceable>include_if_exists</replaceable> <replaceable>file</replaceable>
+<replaceable>include_dir</replaceable> <replaceable>directory</replaceable>
+</synopsis>
+    Comments, whitespace and line continuations are handled in the same way as
+    in <filename>pg_hba.conf</filename>.  <replaceable>hostname</replaceable>
+    is matched against the hostname TLS extension in the SSL handshake.
+    <replaceable>SSL_certificate</replaceable>,
+    <replaceable>SSL_key</replaceable>,
+    <replaceable>SSL_CA_certificate</replaceable>,
+    <replaceable>SSL_passphrase_cmd</replaceable>, and
+    <replaceable>SSL_passphrase_cmd_reload</replaceable>
+    are treated like
+    <xref linkend="guc-ssl-cert-file"/>,
+    <xref linkend="guc-ssl-key-file"/>,
+    <xref linkend="guc-ssl-ca-file"/>,
+    <xref linkend="guc-ssl-passphrase-command"/>, and
+    <xref linkend="guc-ssl-passphrase-command-supports-reload"/> respectively.
+    All fields except <replaceable>SSL_passphrase_cmd</replaceable> and
+    <replaceable>SSL_passphrase_cmd_reload</replaceable> are required. If
+    <replaceable>SSL_passphrase_cmd</replaceable> is defined but not
+    <replaceable>SSL_passphrase_cmd_reload</replaceable> then the default
+    value for <replaceable>SSL_passphrase_cmd_reload</replaceable> is
+    <literal>off</literal>.
+   </para>
+   <para>
+     It is currently not possible to set different <literal>clientname</literal>
+     values for the different certificates.  Any <literal>clientname</literal>
+     setting in <filename>pg_hba.conf</filename> will be applied during
+     authentication regardless of which set of certificates have been loaded
+     via an SNI enabled connection.
+   </para>
+  </sect2>
  </sect1>
 
  <sect1 id="gssapi-enc">
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 42d4a28e5aa..96adabf9581 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -186,6 +186,7 @@ endif
 	$(MAKE) -C utils install-data
 	$(INSTALL_DATA) $(srcdir)/libpq/pg_hba.conf.sample '$(DESTDIR)$(datadir)/pg_hba.conf.sample'
 	$(INSTALL_DATA) $(srcdir)/libpq/pg_ident.conf.sample '$(DESTDIR)$(datadir)/pg_ident.conf.sample'
+	$(INSTALL_DATA) $(srcdir)/libpq/pg_hosts.conf.sample '$(DESTDIR)$(datadir)/pg_hosts.conf.sample'
 	$(INSTALL_DATA) $(srcdir)/utils/misc/postgresql.conf.sample '$(DESTDIR)$(datadir)/postgresql.conf.sample'
 
 ifeq ($(with_llvm), yes)
diff --git a/src/backend/libpq/be-secure-common.c b/src/backend/libpq/be-secure-common.c
index e8b837d1fa7..67a50c7b24c 100644
--- a/src/backend/libpq/be-secure-common.c
+++ b/src/backend/libpq/be-secure-common.c
@@ -24,8 +24,13 @@
 
 #include "common/percentrepl.h"
 #include "common/string.h"
+#include "libpq/hba.h"
 #include "libpq/libpq.h"
 #include "storage/fd.h"
+#include "utils/guc.h"
+#include "utils/memutils.h"
+
+static HostsLine *parse_hosts_line(TokenizedAuthLine *tok_line, int elevel);
 
 /*
  * Run ssl_passphrase_command
@@ -37,19 +42,20 @@
  * value is the length of the actual result.
  */
 int
-run_ssl_passphrase_command(const char *prompt, bool is_server_start, char *buf, int size)
+run_ssl_passphrase_command(const char *prompt, bool is_server_start, char *buf, int size, void *userdata)
 {
 	int			loglevel = is_server_start ? ERROR : LOG;
 	char	   *command;
 	FILE	   *fh;
 	int			pclose_rc;
 	size_t		len = 0;
+	char	   *cmd = (char *) userdata;
 
 	Assert(prompt);
 	Assert(size > 0);
 	buf[0] = '\0';
 
-	command = replace_percent_placeholders(ssl_passphrase_command, "ssl_passphrase_command", "p", prompt);
+	command = replace_percent_placeholders(cmd, "ssl_passphrase_command", "p", prompt);
 
 	fh = OpenPipeStream(command, "r");
 	if (fh == NULL)
@@ -175,3 +181,196 @@ check_ssl_key_file_permissions(const char *ssl_key_file, bool isServerStart)
 
 	return true;
 }
+
+/*
+ * parse_hosts_line
+ *
+ * Parses a loaded line from the pg_hosts.conf configuration and pulls out the
+ * hostname, certificate, key and CA parts in order to build an SNI config in
+ * the TLS backend. Validation of the parsed values is left for the TLS backend
+ * to implement.
+ */
+static HostsLine *
+parse_hosts_line(TokenizedAuthLine *tok_line, int elevel)
+{
+	HostsLine  *parsedline;
+	List	   *tokens;
+	ListCell   *field;
+	AuthToken  *token;
+
+	parsedline = palloc0(sizeof(HostsLine));
+	parsedline->sourcefile = pstrdup(tok_line->file_name);
+	parsedline->linenumber = tok_line->line_num;
+	parsedline->rawline = pstrdup(tok_line->raw_line);
+
+	/* Initialize optional fields */
+	parsedline->ssl_passphrase_cmd = NULL;
+	parsedline->ssl_passphrase_reload = false;
+
+	/* Hostname */
+	field = list_head(tok_line->fields);
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->hostname = pstrdup(token->string);
+
+	/* SSL Certificate (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_cert = pstrdup(token->string);
+
+	/* SSL key (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_key = pstrdup(token->string);
+
+	/* SSL CA (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_ca = pstrdup(token->string);
+
+	/* SSL Passphrase Command (optional) */
+	field = lnext(tok_line->fields, field);
+	if (field)
+	{
+		tokens = lfirst(field);
+		token = linitial(tokens);
+		parsedline->ssl_passphrase_cmd = pstrdup(token->string);
+
+		/*
+		 * SSL Passphrase Command support reload (optional). This field is
+		 * only supported if there was a passphrase command parsed first, so
+		 * nest it under the previous token.
+		 */
+		field = lnext(tok_line->fields, field);
+		if (field)
+		{
+			tokens = lfirst(field);
+			token = linitial(tokens);
+
+			if (token->string[0] == '1'
+				|| pg_strcasecmp(token->string, "true") == 0
+				|| pg_strcasecmp(token->string, "on") == 0
+				|| pg_strcasecmp(token->string, "yes") == 0)
+				parsedline->ssl_passphrase_reload = true;
+			else if (token->string[0] == '0'
+					 || pg_strcasecmp(token->string, "false") == 0
+					 || pg_strcasecmp(token->string, "off") == 0
+					 || pg_strcasecmp(token->string, "no") == 0)
+				parsedline->ssl_passphrase_reload = false;
+			else
+				ereport(elevel,
+						errcode(ERRCODE_CONFIG_FILE_ERROR),
+						errmsg("incorrect syntax for boolean value SSL_passphrase_cmd_reload"),
+						errcontext("line %d of configuration file \"%s\"",
+								   tok_line->line_num, tok_line->file_name));
+		}
+	}
+
+	return parsedline;
+}
+
+/*
+ * load_hosts
+ *
+ * Reads pg_hosts.conf and passes back a List of parsed lines, or NIL in case
+ * of errors.
+ */
+List *
+load_hosts(void)
+{
+	FILE	   *file;
+	ListCell   *line;
+	List	   *hosts_lines = NIL;
+	List	   *parsed_lines = NIL;
+	HostsLine  *newline;
+	bool		ok = true;
+	MemoryContext oldcxt;
+	MemoryContext hostcxt;
+
+	file = open_auth_file(HostsFileName, LOG, 0, NULL);
+	if (file == NULL)
+	{
+		/* An error has already been logged so no need to add one here */
+		return NIL;
+	}
+
+	tokenize_auth_file(HostsFileName, file, &hosts_lines, LOG, 0);
+
+	hostcxt = AllocSetContextCreate(PostmasterContext,
+									"hosts file parser context",
+									ALLOCSET_SMALL_SIZES);
+	oldcxt = MemoryContextSwitchTo(hostcxt);
+
+	foreach(line, hosts_lines)
+	{
+		TokenizedAuthLine *tok_line = (TokenizedAuthLine *) lfirst(line);
+
+		if (tok_line->err_msg != NULL)
+		{
+			ok = false;
+			continue;
+		}
+
+		if ((newline = parse_hosts_line(tok_line, LOG)) == NULL)
+		{
+			ok = false;
+			continue;
+		}
+
+		parsed_lines = lappend(parsed_lines, newline);
+	}
+
+	free_auth_file(file, 0);
+	MemoryContextSwitchTo(oldcxt);
+
+	/*
+	 * If we didn't find any SNI configuration then that's not an error since
+	 * the pg_hosts file is additive to the default SSL configuration.
+	 */
+	if (ok && parsed_lines == NIL)
+	{
+		ereport(DEBUG1,
+				errmsg("no SNI configuration added from configuration file  \"%s\"",
+					   HostsFileName));
+		MemoryContextDelete(hostcxt);
+		return NIL;
+	}
+
+	if (!ok)
+	{
+		MemoryContextDelete(hostcxt);
+		return NIL;
+	}
+
+	return parsed_lines;
+}
diff --git a/src/backend/libpq/be-secure-openssl.c b/src/backend/libpq/be-secure-openssl.c
index 64ff3ce3d6a..bb3e724a190 100644
--- a/src/backend/libpq/be-secure-openssl.c
+++ b/src/backend/libpq/be-secure-openssl.c
@@ -51,9 +51,18 @@
 #endif
 #include <openssl/x509v3.h>
 
+typedef struct HostContext
+{
+	const char *hostname;
+	const char *ssl_passphrase;
+	SSL_CTX    *context;
+	bool		default_host;
+	bool		ssl_loaded_verify_locations;
+	bool		ssl_passphrase_support_reload;
+} HostContext;
 
 /* default init hook can be overridden by a shared library */
-static void default_openssl_tls_init(SSL_CTX *context, bool isServerStart);
+static void default_openssl_tls_init(SSL_CTX *context, bool isServerStart, HostsLine *hosts);
 openssl_tls_init_hook_typ openssl_tls_init_hook = default_openssl_tls_init;
 
 static int	port_bio_read(BIO *h, char *buf, int size);
@@ -73,6 +82,7 @@ static int	alpn_cb(SSL *ssl,
 					const unsigned char *in,
 					unsigned int inlen,
 					void *userdata);
+static int	sni_servername_cb(SSL *ssl, int *al, void *arg);
 static bool initialize_dh(SSL_CTX *context, bool isServerStart);
 static bool initialize_ecdh(SSL_CTX *context, bool isServerStart);
 static const char *SSLerrmessageExt(unsigned long ecode, const char *replacement);
@@ -80,12 +90,16 @@ static const char *SSLerrmessage(unsigned long ecode);
 
 static char *X509_NAME_to_cstring(X509_NAME *name);
 
+static List *contexts = NIL;
 static SSL_CTX *SSL_context = NULL;
+static HostContext *Host_context = NULL;
 static bool dummy_ssl_passwd_cb_called = false;
 static bool ssl_is_server_start;
 
 static int	ssl_protocol_version_to_openssl(int v);
 static const char *ssl_protocol_version_to_string(int v);
+static SSL_CTX *ssl_init_context(bool isServerStart, HostsLine *host);
+static void free_contexts(void);
 
 /* for passing data back from verify_cb() */
 static const char *cert_errdetail;
@@ -96,11 +110,147 @@ static const char *cert_errdetail;
 
 int
 be_tls_init(bool isServerStart)
+{
+	SSL_CTX    *ctx;
+	List	   *sni_hosts = NIL;
+
+	/*
+	 * If there are contexts loaded when we init they should be released.
+	 */
+	if (contexts != NIL)
+		free_contexts();
+
+	/*
+	 * When ssl_snimode is off or default we load the SSL configuration
+	 * specified in postgresql.conf and set that as the default host.
+	 */
+	if (ssl_snimode == SSL_SNIMODE_OFF || ssl_snimode == SSL_SNIMODE_DEFAULT)
+	{
+		HostContext *host_context;
+		HostsLine	line;
+
+		line.ssl_cert = ssl_cert_file;
+		line.ssl_key = ssl_key_file;
+		line.ssl_ca = ssl_ca_file;
+		line.ssl_passphrase_cmd = ssl_passphrase_command;
+		line.ssl_passphrase_reload = ssl_passphrase_command_supports_reload;
+
+		ctx = ssl_init_context(isServerStart, &line);
+		if (ctx == NULL)
+		{
+			ereport(isServerStart ? FATAL : LOG,
+					(errcode(ERRCODE_CONFIG_FILE_ERROR),
+					 errmsg("could not load default certificate")));
+			return -1;
+		}
+
+		host_context = palloc0(sizeof(HostContext));
+
+		host_context->hostname = pstrdup("*");
+		host_context->context = ctx;
+		host_context->default_host = true;
+
+		/*
+		 * Set flag to remember whether CA store has been loaded into
+		 * SSL_context.
+		 */
+		if (ssl_ca_file[0])
+			host_context->ssl_loaded_verify_locations = true;
+
+		/*
+		 * The contexts list is not used in ssl_snimode off but we add the
+		 * entry there anyways for consistency with the other modes.
+		 */
+		contexts = lappend(contexts, host_context);
+
+		/*
+		 * Install the default certificate which for ssl_snimode default can
+		 * be overridden in the callback if a hostname match is found.
+		 */
+		SSL_context = ctx;
+		Host_context = host_context;
+	}
+
+	/*
+	 * In default or strict ssl_snimode we load all certificates/keys which
+	 * are configured in pg_hosts.conf. In strict mode it is considered a
+	 * fatal error in case there are no configured entries.
+	 */
+	if (ssl_snimode == SSL_SNIMODE_STRICT || ssl_snimode == SSL_SNIMODE_DEFAULT)
+	{
+		ListCell   *line;
+
+		/*
+		 * Load pg_hosts.conf and parse each row, returning the set of hosts
+		 * as a list.
+		 */
+		sni_hosts = load_hosts();
+
+		/* In strict ssl_snimode there needs to be a working pg_hosts file */
+		if (sni_hosts == NIL && ssl_snimode == SSL_SNIMODE_STRICT)
+		{
+			ereport(isServerStart ? FATAL : LOG,
+					errcode(ERRCODE_CONFIG_FILE_ERROR),
+					errmsg("could not load %s", "pg_hosts.conf"));
+			return -1;
+		}
+
+		foreach(line, sni_hosts)
+		{
+			HostContext *host_context;
+			HostsLine  *host = lfirst(line);
+
+			SSL_context = ssl_init_context(isServerStart, host);
+			if (SSL_context == NULL)
+			{
+				ereport(isServerStart ? FATAL : LOG,
+						errcode(ERRCODE_CONFIG_FILE_ERROR),
+						errmsg("unable to load certificate from pg_hosts.conf file"));
+				return -1;
+			}
+
+			host_context = palloc0(sizeof(HostContext));
+			host_context->hostname = pstrdup(host->hostname);
+			host_context->context = SSL_context;
+			host_context->default_host = false;
+			if (host->ssl_passphrase_cmd != NULL)
+				host_context->ssl_passphrase = pstrdup(host->ssl_passphrase_cmd);
+			host_context->ssl_passphrase_support_reload = host->ssl_passphrase_reload;
+
+			/*
+			 * Set flag to remember whether CA store has been loaded into this
+			 * SSL_context.
+			 */
+			if (host->ssl_ca)
+				host_context->ssl_loaded_verify_locations = true;
+
+			contexts = lappend(contexts, host_context);
+		}
+	}
+
+	/* Make sure we have at least one certificate loaded */
+	if (list_length(contexts) < 1)
+	{
+		ereport(isServerStart ? FATAL : LOG,
+				(errcode(ERRCODE_CONFIG_FILE_ERROR),
+				 errmsg("no SSL contexts loaded")));
+		return -1;
+	}
+
+	return 0;
+}
+
+static SSL_CTX *
+ssl_init_context(bool isServerStart, HostsLine *host_line)
 {
 	SSL_CTX    *context;
 	int			ssl_ver_min = -1;
 	int			ssl_ver_max = -1;
 
+	const char *ctx_ssl_cert_file = host_line->ssl_cert;
+	const char *ctx_ssl_key_file = host_line->ssl_key;
+	const char *ctx_ssl_ca_file = host_line->ssl_ca;
+
 	/*
 	 * Create a new SSL context into which we'll load all the configuration
 	 * settings.  If we fail partway through, we can avoid memory leakage by
@@ -126,10 +276,17 @@ be_tls_init(bool isServerStart)
 	 */
 	SSL_CTX_set_mode(context, SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER);
 
+	/*
+	 * Install SNI TLS extension callback in case the server is configured to
+	 * validate hostnames.
+	 */
+	if (ssl_snimode != SSL_SNIMODE_OFF)
+		SSL_CTX_set_tlsext_servername_callback(context, sni_servername_cb);
+
 	/*
 	 * Call init hook (usually to set password callback)
 	 */
-	(*openssl_tls_init_hook) (context, isServerStart);
+	(*openssl_tls_init_hook) (context, isServerStart, host_line);
 
 	/* used by the callback */
 	ssl_is_server_start = isServerStart;
@@ -137,16 +294,16 @@ be_tls_init(bool isServerStart)
 	/*
 	 * Load and verify server's certificate and private key
 	 */
-	if (SSL_CTX_use_certificate_chain_file(context, ssl_cert_file) != 1)
+	if (SSL_CTX_use_certificate_chain_file(context, ctx_ssl_cert_file) != 1)
 	{
 		ereport(isServerStart ? FATAL : LOG,
 				(errcode(ERRCODE_CONFIG_FILE_ERROR),
 				 errmsg("could not load server certificate file \"%s\": %s",
-						ssl_cert_file, SSLerrmessage(ERR_get_error()))));
+						ctx_ssl_cert_file, SSLerrmessage(ERR_get_error()))));
 		goto error;
 	}
 
-	if (!check_ssl_key_file_permissions(ssl_key_file, isServerStart))
+	if (!check_ssl_key_file_permissions(ctx_ssl_key_file, isServerStart))
 		goto error;
 
 	/*
@@ -155,19 +312,19 @@ be_tls_init(bool isServerStart)
 	dummy_ssl_passwd_cb_called = false;
 
 	if (SSL_CTX_use_PrivateKey_file(context,
-									ssl_key_file,
+									ctx_ssl_key_file,
 									SSL_FILETYPE_PEM) != 1)
 	{
 		if (dummy_ssl_passwd_cb_called)
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("private key file \"%s\" cannot be reloaded because it requires a passphrase",
-							ssl_key_file)));
+							ctx_ssl_key_file)));
 		else
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("could not load private key file \"%s\": %s",
-							ssl_key_file, SSLerrmessage(ERR_get_error()))));
+							ctx_ssl_key_file, SSLerrmessage(ERR_get_error()))));
 		goto error;
 	}
 
@@ -319,17 +476,17 @@ be_tls_init(bool isServerStart)
 	/*
 	 * Load CA store, so we can verify client certificates if needed.
 	 */
-	if (ssl_ca_file[0])
+	if (ctx_ssl_ca_file[0])
 	{
 		STACK_OF(X509_NAME) * root_cert_list;
 
-		if (SSL_CTX_load_verify_locations(context, ssl_ca_file, NULL) != 1 ||
-			(root_cert_list = SSL_load_client_CA_file(ssl_ca_file)) == NULL)
+		if (SSL_CTX_load_verify_locations(context, ctx_ssl_ca_file, NULL) != 1 ||
+			(root_cert_list = SSL_load_client_CA_file(ctx_ssl_ca_file)) == NULL)
 		{
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("could not load root certificate file \"%s\": %s",
-							ssl_ca_file, SSLerrmessage(ERR_get_error()))));
+							ctx_ssl_ca_file, SSLerrmessage(ERR_get_error()))));
 			goto error;
 		}
 
@@ -401,38 +558,29 @@ be_tls_init(bool isServerStart)
 		}
 	}
 
-	/*
-	 * Success!  Replace any existing SSL_context.
-	 */
-	if (SSL_context)
-		SSL_CTX_free(SSL_context);
-
-	SSL_context = context;
-
-	/*
-	 * Set flag to remember whether CA store has been loaded into SSL_context.
-	 */
-	if (ssl_ca_file[0])
-		ssl_loaded_verify_locations = true;
-	else
-		ssl_loaded_verify_locations = false;
-
-	return 0;
+	return context;
 
 	/* Clean up by releasing working context. */
 error:
 	if (context)
 		SSL_CTX_free(context);
-	return -1;
+	return NULL;
 }
 
 void
 be_tls_destroy(void)
 {
-	if (SSL_context)
-		SSL_CTX_free(SSL_context);
+	ListCell   *cell;
+
+	foreach(cell, contexts)
+	{
+		HostContext *host_context = lfirst(cell);
+
+		SSL_CTX_free(host_context->context);
+		pfree(host_context);
+	}
+
 	SSL_context = NULL;
-	ssl_loaded_verify_locations = false;
 }
 
 int
@@ -1132,7 +1280,7 @@ ssl_external_passwd_cb(char *buf, int size, int rwflag, void *userdata)
 
 	Assert(rwflag == 0);
 
-	return run_ssl_passphrase_command(prompt, ssl_is_server_start, buf, size);
+	return run_ssl_passphrase_command(prompt, ssl_is_server_start, buf, size, userdata);
 }
 
 /*
@@ -1369,6 +1517,60 @@ alpn_cb(SSL *ssl,
 	}
 }
 
+static int
+sni_servername_cb(SSL *ssl, int *al, void *arg)
+{
+	const char *tlsext_hostname;
+	ListCell   *cell;
+	HostContext *host_context;
+
+	Assert(ssl_snimode != SSL_SNIMODE_OFF);
+
+	tlsext_hostname = SSL_get_servername(ssl, TLSEXT_NAMETYPE_host_name);
+
+	if (!tlsext_hostname)
+	{
+		if (ssl_snimode == SSL_SNIMODE_STRICT)
+		{
+			ereport(COMMERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg("no hostname provided in callback")));
+			return SSL_TLSEXT_ERR_ALERT_FATAL;
+		}
+		else
+			return SSL_TLSEXT_ERR_OK;
+	}
+
+	foreach(cell, contexts)
+	{
+		host_context = lfirst(cell);
+
+		if (strcmp(host_context->hostname, tlsext_hostname) == 0)
+		{
+			Host_context = host_context;
+			SSL_context = host_context->context;
+			SSL_set_SSL_CTX(ssl, SSL_context);
+			return SSL_TLSEXT_ERR_OK;
+		}
+	}
+
+	if (ssl_snimode == SSL_SNIMODE_STRICT)
+	{
+		ereport(COMMERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg("no matching pg_hosts entry found for hostname: \"%s\"",
+						tlsext_hostname)));
+		return SSL_TLSEXT_ERR_ALERT_FATAL;
+	}
+
+	/*
+	 * In ssl_snimode "default" we can return without doing anything since we
+	 * already installed the context for the default host when parsing the
+	 * hosts file.
+	 */
+	Assert(SSL_context);
+	return SSL_TLSEXT_ERR_OK;
+}
 
 /*
  * Set DH parameters for generating ephemeral DH keys.  The
@@ -1578,6 +1780,12 @@ be_tls_get_peer_serial(Port *port, char *ptr, size_t len)
 		ptr[0] = '\0';
 }
 
+bool
+be_tls_loaded_verify_locations(void)
+{
+	return Host_context->ssl_loaded_verify_locations;
+}
+
 char *
 be_tls_get_certificate_hash(Port *port, size_t *len)
 {
@@ -1771,17 +1979,23 @@ ssl_protocol_version_to_string(int v)
 
 
 static void
-default_openssl_tls_init(SSL_CTX *context, bool isServerStart)
+default_openssl_tls_init(SSL_CTX *context, bool isServerStart, HostsLine *host)
 {
 	if (isServerStart)
 	{
-		if (ssl_passphrase_command[0])
+		if (host->ssl_passphrase_cmd != NULL)
+		{
 			SSL_CTX_set_default_passwd_cb(context, ssl_external_passwd_cb);
+			SSL_CTX_set_default_passwd_cb_userdata(context, host->ssl_passphrase_cmd);
+		}
 	}
 	else
 	{
-		if (ssl_passphrase_command[0] && ssl_passphrase_command_supports_reload)
+		if (host->ssl_passphrase_cmd != NULL && host->ssl_passphrase_reload)
+		{
 			SSL_CTX_set_default_passwd_cb(context, ssl_external_passwd_cb);
+			SSL_CTX_set_default_passwd_cb_userdata(context, host->ssl_passphrase_cmd);
+		}
 		else
 
 			/*
@@ -1793,3 +2007,22 @@ default_openssl_tls_init(SSL_CTX *context, bool isServerStart)
 			SSL_CTX_set_default_passwd_cb(context, dummy_ssl_passwd_cb);
 	}
 }
+
+static void
+free_contexts(void)
+{
+	if (contexts == NIL)
+		return;
+
+	foreach_ptr(HostContext, host, contexts)
+	{
+		if (host->hostname)
+			pfree(unconstify(char *, host->hostname));
+		if (host->ssl_passphrase)
+			pfree(unconstify(char *, host->ssl_passphrase));
+		SSL_CTX_free(host->context);
+	}
+
+	list_free_deep(contexts);
+	contexts = NIL;
+}
diff --git a/src/backend/libpq/be-secure.c b/src/backend/libpq/be-secure.c
index 91576f94285..b10e8f995ac 100644
--- a/src/backend/libpq/be-secure.c
+++ b/src/backend/libpq/be-secure.c
@@ -43,10 +43,6 @@ char	   *ssl_dh_params_file;
 char	   *ssl_passphrase_command;
 bool		ssl_passphrase_command_supports_reload;
 
-#ifdef USE_SSL
-bool		ssl_loaded_verify_locations = false;
-#endif
-
 /* GUC variable controlling SSL cipher list */
 char	   *SSLCipherSuites = NULL;
 char	   *SSLCipherList = NULL;
@@ -60,6 +56,8 @@ bool		SSLPreferServerCiphers;
 int			ssl_min_protocol_version = PG_TLS1_2_VERSION;
 int			ssl_max_protocol_version = PG_TLS_ANY;
 
+int			ssl_snimode = SSL_SNIMODE_DEFAULT;
+
 /* ------------------------------------------------------------ */
 /*			 Procedures common to all secure sessions			*/
 /* ------------------------------------------------------------ */
@@ -99,7 +97,7 @@ bool
 secure_loaded_verify_locations(void)
 {
 #ifdef USE_SSL
-	return ssl_loaded_verify_locations;
+	return be_tls_loaded_verify_locations();
 #else
 	return false;
 #endif
diff --git a/src/backend/libpq/meson.build b/src/backend/libpq/meson.build
index 0f0421037e4..aed5ec16af2 100644
--- a/src/backend/libpq/meson.build
+++ b/src/backend/libpq/meson.build
@@ -30,5 +30,6 @@ endif
 install_data(
   'pg_hba.conf.sample',
   'pg_ident.conf.sample',
+  'pg_hosts.conf.sample',
   install_dir: dir_data,
 )
diff --git a/src/backend/libpq/pg_hosts.conf.sample b/src/backend/libpq/pg_hosts.conf.sample
new file mode 100644
index 00000000000..608210686e1
--- /dev/null
+++ b/src/backend/libpq/pg_hosts.conf.sample
@@ -0,0 +1,5 @@
+# PostgreSQL SNI Hostname mappings
+# ================================
+
+# HOSTNAME       SSL CERTIFICATE             SSL KEY
+
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 12192445218..1a3e5011b35 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -55,6 +55,7 @@
 #define CONFIG_FILENAME "postgresql.conf"
 #define HBA_FILENAME	"pg_hba.conf"
 #define IDENT_FILENAME	"pg_ident.conf"
+#define HOSTS_FILENAME	"pg_hosts.conf"
 
 #ifdef EXEC_BACKEND
 #define CONFIG_EXEC_PARAMS "global/config_exec_params"
@@ -1968,6 +1969,31 @@ SelectConfigFiles(const char *userDoption, const char *progname)
 	}
 	SetConfigOption("ident_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
 
+	/*
+	 * Likewise for pg_hosts.conf
+	 */
+	if (HostsFileName)
+	{
+		fname = make_absolute_path(HostsFileName);
+		fname_is_malloced = true;
+	}
+	else if (configdir)
+	{
+		fname = guc_malloc(FATAL,
+						   strlen(configdir) + strlen(HOSTS_FILENAME) + 2);
+		sprintf(fname, "%s/%s", configdir, HOSTS_FILENAME);
+		fname_is_malloced = false;
+	}
+	else
+	{
+		write_stderr("%s does not know where to find the \"hosts\" configuration file.\n"
+					 "This can be specified as \"hosts_file\" in \"%s\", "
+					 "or by the -D invocation option, or by the "
+					 "PGDATA environment variable.\n",
+					 progname, ConfigFileName);
+	}
+	SetConfigOption("hosts_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
+
 	if (fname_is_malloced)
 		free(fname);
 	else
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index 3cde94a1759..002e12fe1e4 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -474,6 +474,13 @@ static const struct config_enum_entry wal_compression_options[] = {
 	{NULL, 0, false}
 };
 
+static const struct config_enum_entry ssl_snimode_options[] = {
+	{"off", SSL_SNIMODE_OFF, false},
+	{"default", SSL_SNIMODE_DEFAULT, false},
+	{"strict", SSL_SNIMODE_STRICT, false},
+	{NULL, 0, false}
+};
+
 /*
  * Options for enum values stored in other modules
  */
@@ -538,6 +545,7 @@ char	   *cluster_name = "";
 char	   *ConfigFileName;
 char	   *HbaFileName;
 char	   *IdentFileName;
+char	   *HostsFileName;
 char	   *external_pid_file;
 
 char	   *application_name;
@@ -4622,6 +4630,17 @@ struct config_string ConfigureNamesString[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"hosts_file", PGC_POSTMASTER, FILE_LOCATIONS,
+			gettext_noop("Sets the server's \"hosts\" configuration file."),
+			NULL,
+			GUC_SUPERUSER_ONLY
+		},
+		&HostsFileName,
+		NULL,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"external_pid_file", PGC_POSTMASTER, FILE_LOCATIONS,
 			gettext_noop("Writes the postmaster PID to the specified file."),
@@ -5264,6 +5283,18 @@ struct config_enum ConfigureNamesEnum[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"ssl_snimode", PGC_SIGHUP, CONN_AUTH_SSL,
+			gettext_noop("Sets the SNI mode to use."),
+			NULL,
+			GUC_SUPERUSER_ONLY,
+		},
+		&ssl_snimode,
+		SSL_SNIMODE_DEFAULT,
+		ssl_snimode_options,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"recovery_init_sync_method", PGC_SIGHUP, ERROR_HANDLING_OPTIONS,
 			gettext_noop("Sets the method for synchronizing the data directory before crash recovery."),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 415f253096c..dec30a53a35 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -45,6 +45,8 @@
 					# (change requires restart)
 #ident_file = 'ConfigDir/pg_ident.conf'	# ident configuration file
 					# (change requires restart)
+#hosts_file = 'ConfigDir/pg_hosts.conf' # hosts configuration file
+					# (change requires restart)
 
 # If external_pid_file is not explicitly set, no extra PID file is written.
 #external_pid_file = ''			# write an extra PID file
@@ -120,6 +122,7 @@
 #ssl_dh_params_file = ''
 #ssl_passphrase_command = ''
 #ssl_passphrase_command_supports_reload = off
+#ssl_snimode = default
 
 
 #------------------------------------------------------------------------------
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 21a0fe3ecd9..a6e680f7b44 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -176,6 +176,7 @@ static int	encodingid;
 static char *bki_file;
 static char *hba_file;
 static char *ident_file;
+static char *hosts_file;
 static char *conf_file;
 static char *dictionary_file;
 static char *info_schema_file;
@@ -1542,6 +1543,14 @@ setup_config(void)
 
 	snprintf(path, sizeof(path), "%s/pg_ident.conf", pg_data);
 
+	writefile(path, conflines);
+	if (chmod(path, pg_file_create_mode) != 0)
+		pg_fatal("could not change permissions of \"%s\": %m", path);
+
+	/* pg_hosts.conf */
+	conflines = readfile(hosts_file);
+	snprintf(path, sizeof(path), "%s/pg_hosts.conf", pg_data);
+
 	writefile(path, conflines);
 	if (chmod(path, pg_file_create_mode) != 0)
 		pg_fatal("could not change permissions of \"%s\": %m", path);
@@ -2805,6 +2814,7 @@ setup_data_file_paths(void)
 	set_input(&bki_file, "postgres.bki");
 	set_input(&hba_file, "pg_hba.conf.sample");
 	set_input(&ident_file, "pg_ident.conf.sample");
+	set_input(&hosts_file, "pg_hosts.conf.sample");
 	set_input(&conf_file, "postgresql.conf.sample");
 	set_input(&dictionary_file, "snowball_create.sql");
 	set_input(&info_schema_file, "information_schema.sql");
@@ -2820,12 +2830,13 @@ setup_data_file_paths(void)
 				"PGDATA=%s\nshare_path=%s\nPGPATH=%s\n"
 				"POSTGRES_SUPERUSERNAME=%s\nPOSTGRES_BKI=%s\n"
 				"POSTGRESQL_CONF_SAMPLE=%s\n"
-				"PG_HBA_SAMPLE=%s\nPG_IDENT_SAMPLE=%s\n",
+				"PG_HBA_SAMPLE=%s\nPG_IDENT_SAMPLE=%s\n"
+				"PG_HOSTS_SAMPLE=%s\n",
 				PG_VERSION,
 				pg_data, share_path, bin_path,
 				username, bki_file,
 				conf_file,
-				hba_file, ident_file);
+				hba_file, ident_file, hosts_file);
 		if (show_setting)
 			exit(0);
 	}
@@ -2833,6 +2844,7 @@ setup_data_file_paths(void)
 	check_input(bki_file);
 	check_input(hba_file);
 	check_input(ident_file);
+	check_input(hosts_file);
 	check_input(conf_file);
 	check_input(dictionary_file);
 	check_input(info_schema_file);
diff --git a/src/include/libpq/hba.h b/src/include/libpq/hba.h
index b20d0051f7d..a1ea3cf3e8c 100644
--- a/src/include/libpq/hba.h
+++ b/src/include/libpq/hba.h
@@ -146,6 +146,25 @@ typedef struct IdentLine
 	AuthToken  *pg_user;
 } IdentLine;
 
+typedef struct HostsLine
+{
+	int			linenumber;
+
+	char	   *sourcefile;
+	char	   *rawline;
+
+	/* Required fields */
+	bool		default_host;
+	char	   *hostname;
+	char	   *ssl_key;
+	char	   *ssl_cert;
+	char	   *ssl_ca;
+
+	/* Optional fields */
+	char	   *ssl_passphrase_cmd;
+	bool		ssl_passphrase_reload;
+} HostsLine;
+
 /*
  * TokenizedAuthLine represents one line lexed from an authentication
  * configuration file.  Each item in the "fields" list is a sub-list of
diff --git a/src/include/libpq/libpq-be.h b/src/include/libpq/libpq-be.h
index 7fe92b15477..a5f07aff046 100644
--- a/src/include/libpq/libpq-be.h
+++ b/src/include/libpq/libpq-be.h
@@ -323,6 +323,7 @@ extern const char *be_tls_get_cipher(Port *port);
 extern void be_tls_get_peer_subject_name(Port *port, char *ptr, size_t len);
 extern void be_tls_get_peer_issuer_name(Port *port, char *ptr, size_t len);
 extern void be_tls_get_peer_serial(Port *port, char *ptr, size_t len);
+extern bool be_tls_loaded_verify_locations(void);
 
 /*
  * Get the server certificate hash for SCRAM channel binding type
@@ -335,7 +336,7 @@ extern char *be_tls_get_certificate_hash(Port *port, size_t *len);
 
 /* init hook for SSL, the default sets the password callback if appropriate */
 #ifdef USE_OPENSSL
-typedef void (*openssl_tls_init_hook_typ) (SSL_CTX *context, bool isServerStart);
+typedef void (*openssl_tls_init_hook_typ) (SSL_CTX *context, bool isServerStart, HostsLine *host);
 extern PGDLLIMPORT openssl_tls_init_hook_typ openssl_tls_init_hook;
 #endif
 
diff --git a/src/include/libpq/libpq.h b/src/include/libpq/libpq.h
index 8defcb6de19..6d9332cbe22 100644
--- a/src/include/libpq/libpq.h
+++ b/src/include/libpq/libpq.h
@@ -107,6 +107,7 @@ extern PGDLLIMPORT char *ssl_crl_dir;
 extern PGDLLIMPORT char *ssl_key_file;
 extern PGDLLIMPORT int ssl_min_protocol_version;
 extern PGDLLIMPORT int ssl_max_protocol_version;
+extern PGDLLIMPORT int ssl_snimode;
 extern PGDLLIMPORT char *ssl_passphrase_command;
 extern PGDLLIMPORT bool ssl_passphrase_command_supports_reload;
 extern PGDLLIMPORT char *ssl_dh_params_file;
@@ -134,12 +135,20 @@ enum ssl_protocol_versions
 	PG_TLS1_3_VERSION,
 };
 
+enum ssl_snimode
+{
+	SSL_SNIMODE_OFF = 0,
+	SSL_SNIMODE_DEFAULT,
+	SSL_SNIMODE_STRICT
+};
+
 /*
  * prototypes for functions in be-secure-common.c
  */
 extern int	run_ssl_passphrase_command(const char *prompt, bool is_server_start,
-									   char *buf, int size);
+									   char *buf, int size, void *userdata);
 extern bool check_ssl_key_file_permissions(const char *ssl_key_file,
 										   bool isServerStart);
+extern List *load_hosts(void);
 
 #endif							/* LIBPQ_H */
diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index 1233e07d7da..37cb3ecb5ae 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -288,6 +288,7 @@ extern PGDLLIMPORT char *cluster_name;
 extern PGDLLIMPORT char *ConfigFileName;
 extern PGDLLIMPORT char *HbaFileName;
 extern PGDLLIMPORT char *IdentFileName;
+extern PGDLLIMPORT char *HostsFileName;
 extern PGDLLIMPORT char *external_pid_file;
 
 extern PGDLLIMPORT char *application_name;
diff --git a/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c b/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
index d5992149821..a85d85735cf 100644
--- a/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
+++ b/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
@@ -26,7 +26,7 @@ static char *ssl_passphrase = NULL;
 static int	rot13_passphrase(char *buf, int size, int rwflag, void *userdata);
 
 /* hook function to set the callback */
-static void set_rot13(SSL_CTX *context, bool isServerStart);
+static void set_rot13(SSL_CTX *context, bool isServerStart, HostsLine *host);
 
 /*
  * Module load callback
@@ -53,7 +53,7 @@ _PG_init(void)
 }
 
 static void
-set_rot13(SSL_CTX *context, bool isServerStart)
+set_rot13(SSL_CTX *context, bool isServerStart, HostsLine *host)
 {
 	/* warn if the user has set ssl_passphrase_command */
 	if (ssl_passphrase_command[0])
diff --git a/src/test/ssl/meson.build b/src/test/ssl/meson.build
index cf8b2b9303a..7a2a5b8ca8c 100644
--- a/src/test/ssl/meson.build
+++ b/src/test/ssl/meson.build
@@ -13,6 +13,7 @@ tests += {
       't/001_ssltests.pl',
       't/002_scram.pl',
       't/003_sslinfo.pl',
+      't/004_sni.pl',
     ],
   },
 }
diff --git a/src/test/ssl/t/004_sni.pl b/src/test/ssl/t/004_sni.pl
new file mode 100644
index 00000000000..0542c59ebcb
--- /dev/null
+++ b/src/test/ssl/t/004_sni.pl
@@ -0,0 +1,128 @@
+
+# Copyright (c) 2024, PostgreSQL Global Development Group
+
+use strict;
+use warnings FATAL => 'all';
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+use FindBin;
+use lib $FindBin::RealBin;
+
+use SSL::Server;
+
+# This is the hostname used to connect to the server. This cannot be a
+# hostname, because the server certificate is always for the domain
+# postgresql-ssl-regression.test.
+my $SERVERHOSTADDR = '127.0.0.1';
+# This is the pattern to use in pg_hba.conf to match incoming connections.
+my $SERVERHOSTCIDR = '127.0.0.1/32';
+
+if ($ENV{with_ssl} ne 'openssl')
+{
+	plan skip_all => 'OpenSSL not supported by this build';
+}
+
+if (!$ENV{PG_TEST_EXTRA} || $ENV{PG_TEST_EXTRA} !~ /\bssl\b/)
+{
+	plan skip_all =>
+	  'Potentially unsafe test SSL not enabled in PG_TEST_EXTRA';
+}
+
+my $ssl_server = SSL::Server->new();
+
+my $node = PostgreSQL::Test::Cluster->new('primary');
+$node->init;
+
+# PGHOST is enforced here to set up the node, subsequent connections
+# will use a dedicated connection string.
+$ENV{PGHOST} = $node->host;
+$ENV{PGPORT} = $node->port;
+$node->start;
+
+$ssl_server->configure_test_server_for_ssl($node, $SERVERHOSTADDR,
+	$SERVERHOSTCIDR, 'trust');
+
+$ssl_server->switch_server_cert($node, certfile => 'server-cn-only');
+
+my $connstr =
+  "dbname=trustdb hostaddr=$SERVERHOSTADDR host=localhost sslsni=1";
+
+$node->append_conf('postgresql.conf', "ssl_snimode=default");
+$node->reload;
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	"localhost server.crt server.key root.crt");
+$node->append_conf('postgresql.conf', "ssl_snimode=strict");
+$node->reload;
+
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require",
+	expected_stderr => qr/unexpected eof/);
+
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	"localhost server-cn-only.crt server-cn-only.key root_ca.crt");
+$node->reload;
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo wrongpassword" on'
+);
+my $result = $node->restart(fail_ok => 1);
+is($result, 0,
+	'restart fails with password-protected key when using the wrong passphrase command'
+);
+
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo secret1" on'
+);
+$result = $node->restart(fail_ok => 1);
+is($result, 1,
+	'restart succeeds with password-protected key when using the correct passphrase command'
+);
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+
+$node->reload;
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"1 connect with correct server CA cert file sslmode=require");
+
+# Test reloading a passphrase protected key without reloading support in the
+# passphrase hook. Connecting after restart should succeed but not after the
+# following reload.
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo secret1" off'
+);
+$result = $node->restart(fail_ok => 1);
+is($result, 1,
+	'restart succeeds with password-protected key when using the correct passphrase command'
+);
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+
+$node->reload;
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect fails since the passphrase protected key cannot be reloaded",
+	expected_stderr => qr/unexpected eof/);
+
+done_testing();
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index fb39c915d76..4410bb24d53 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -1165,6 +1165,8 @@ HeapTupleHeader
 HeapTupleHeaderData
 HeapTupleTableSlot
 HistControl
+HostContext
+HostsLine
 HotStandbyState
 I32
 ICU_Convert_Func
-- 
2.39.3 (Apple Git-146)

diff --git a/src/test/ssl/t/004_sni.pl b/src/test/ssl/t/004_sni.pl
index 0542c59ebcb..e183a953ede 100644
--- a/src/test/ssl/t/004_sni.pl
+++ b/src/test/ssl/t/004_sni.pl
@@ -57,6 +57,32 @@ $node->connect_ok(
 	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
 	"connect with correct server CA cert file sslmode=require");
 
+# This is added only for comparison with the same test case below.
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"connect fails with fallback hostname, without intermediate",
+	expected_stderr => qr/certificate verify failed/);
+
+# example.org serves the server cert and its intermediate CA.
+$node->append_conf('pg_hosts.conf',
+	"example.org server-cn-only+server_ca.crt server-cn-only.key root_ca.crt"
+);
+$node->reload;
+
+$node->connect_ok(
+	"$connstr host=example.org sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"connect with configured hostname, serving intermediate server CA");
+
+# Why does this test fail?
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"connect still fails with fallback hostname, without intermediate",
+	expected_stderr => qr/certificate verify failed/);
+
+$node->connect_ok(
+	"$connstr host=localhost sslrootcert=ssl/root+server_ca.crt sslmode=verify-ca",
+	"connect with fallback hostname, intermediate included");
+
 ok(unlink($node->data_dir . '/pg_hosts.conf'));
 $node->append_conf('pg_hosts.conf',
 	"localhost server.crt server.key root.crt");

From ee5508fa4a2b114a6493d60d923b6586250713c5 Mon Sep 17 00:00:00 2001
From: Daniel Gustafsson <dgustafsson@postgresql.org>
Date: Thu, 27 Feb 2025 14:03:31 +0100
Subject: [PATCH v6] Serverside SNI support for libpq

Experimental support for serverside SNI support in libpq, a new config
file $datadir/pg_hosts.conf is used for configuring which certicate and
key should be used for which hostname. A new GUC, ssl_snimode, is added
which controls how the hostname TLS extension is handled. The possible
values are off, default and strict:

  - off: pg_hosts.conf is not parsed and the hostname TLS extension is
    not inspected at all. The normal SSL GUCs for certificates and keys
	are used.
  - default: pg_hosts.conf is loaded as well as the normal GUCs. If no
    match for the TLS extension hostname is found in pg_hosts the cert
	and key from the postgresql.conf GUCs is used as the default (used
	as a wildcard host).
  - strict: only pg_hosts.conf is loaded and the TLS extension hostname
    MUST be passed and MUST have a match in the configuration, else the
	connection is refused.

CRL file(s) are applied from postgresql.conf to all configured hostnames.

Reviewed-by: Cary Huang <cary.huang@highgo.ca>
Reviewed-by: Jacob Champion <jacob.champion@enterprisedb.com>
Discussion: https://postgr.es/m/1C81CD0D-407E-44F9-833A-DD0331C202E5@yesql.se
---
 doc/src/sgml/config.sgml                      |  66 ++++
 doc/src/sgml/runtime.sgml                     |  67 ++++
 src/backend/Makefile                          |   1 +
 src/backend/libpq/be-secure-common.c          | 203 +++++++++-
 src/backend/libpq/be-secure-openssl.c         | 356 ++++++++++++++++--
 src/backend/libpq/be-secure.c                 |   8 +-
 src/backend/libpq/meson.build                 |   1 +
 src/backend/libpq/pg_hosts.conf.sample        |   4 +
 src/backend/utils/misc/guc.c                  |  26 ++
 src/backend/utils/misc/guc_tables.c           |  31 ++
 src/backend/utils/misc/postgresql.conf.sample |   3 +
 src/bin/initdb/initdb.c                       |  16 +-
 src/include/libpq/hba.h                       |  19 +
 src/include/libpq/libpq-be.h                  |   3 +-
 src/include/libpq/libpq.h                     |  11 +-
 src/include/utils/guc.h                       |   1 +
 .../ssl_passphrase_func.c                     |   4 +-
 src/test/ssl/meson.build                      |   1 +
 src/test/ssl/t/004_sni.pl                     | 164 ++++++++
 src/tools/pgindent/typedefs.list              |   2 +
 20 files changed, 937 insertions(+), 50 deletions(-)
 create mode 100644 src/backend/libpq/pg_hosts.conf.sample
 create mode 100644 src/test/ssl/t/004_sni.pl

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index e55700f35b8..61f3178df82 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1678,6 +1678,72 @@ include_dir 'conf.d'
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry id="guc-ssl-snimode" xreflabel="ssl_snimode">
+      <term><varname>ssl_snimode</varname> (<type>enum</type>)
+      <indexterm>
+       <primary><varname>ssl_snimode</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        This parameter determines if the server will inspect the <acronym>SNI</acronym> TLS extension
+        when establishing the connection, and how it should be interpreted.
+        Valid values are currently: <literal>off</literal>, <literal>default</literal> and <literal>strict</literal>.
+       </para>
+       <para>
+        <variablelist>
+         <varlistentry id="guc-ssl-snimode-off">
+          <term><literal>off</literal></term>
+          <listitem>
+           <para>
+            SNI is not enabled and no configuration from
+            <filename>pg_hosts.conf</filename> is loaded.  Configuration of SSL
+            for all connections is done with <xref linkend="guc-ssl-cert-file"/>,
+            <xref linkend="guc-ssl-key-file"/> and <xref linkend="guc-ssl-ca-file"/>.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry id="guc-ssl-snimode-default">
+          <term><literal>default</literal></term>
+          <listitem>
+           <para>
+            SNI is enabled and hostname configuration is loaded from
+            <filename>pg_hosts.conf</filename>. <xref linkend="guc-ssl-cert-file"/>,
+            <xref linkend="guc-ssl-key-file"/> and <xref linkend="guc-ssl-ca-file"/>
+            are loaded as the default configuration.  Connections specifying
+            <xref linkend="libpq-connect-sslsni"/> to <literal>1</literal>
+            will be attempted using the default configuration if the hostname
+            is missing in <filename>pg_hosts.conf</filename>.  If the hostname
+            matches an entry from <filename>pg_hosts.conf</filename>, then the
+            configuration from that entry will be used for setting up the
+            connection.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry id="guc-ssl-snimode-strict">
+          <term><literal>strict</literal></term>
+          <listitem>
+           <para>
+            SNI is enabled and all connections are required to set <xref
+            linkend="libpq-connect-sslsni"/> to <literal>1</literal> and
+            specify a hostname matching an entry in
+            <filename>pg_hosts.conf</filename>. Any connection without <xref
+            linkend="libpq-connect-sslsni"/> or with a hostname missing from
+            <filename>pg_hosts.conf</filename> will be rejected.
+            <xref linkend="guc-ssl-cert-file"/>,
+            <xref linkend="guc-ssl-key-file"/> and <xref linkend="guc-ssl-ca-file"/>
+            are loaded in order to drive the handshake until the appropriate
+            configuration has been selected.
+           </para>
+          </listitem>
+         </varlistentry>
+        </variablelist>
+       </para>
+      </listitem>
+     </varlistentry>
     </variablelist>
     </sect2>
    </sect1>
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index 59f39e89924..1e8f06ba2ce 100644
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -2444,6 +2444,12 @@ pg_dumpall -p 5432 | psql -d postgres -p 5433
       <entry>client certificate must not be on this list</entry>
      </row>
 
+     <row>
+      <entry><filename>$PGDATA/pg_hosts.conf</filename></entry>
+      <entry>SNI configuration</entry>
+      <entry>defines which certificates to use for which server hostname</entry>
+     </row>
+
     </tbody>
    </tgroup>
   </table>
@@ -2571,6 +2577,67 @@ openssl x509 -req -in server.csr -text -days 365 \
    </para>
   </sect2>
 
+  <sect2 id="ssl-sni">
+   <title>SNI Configuration</title>
+
+   <para>
+    <productname>PostgreSQL</productname> can be configured for
+    <acronym>SNI</acronym> using the <filename>pg_hosts.conf</filename>
+    configuration file. <productname>PostgreSQL</productname> inspects the TLS
+    hostname extension in the SSL connection handshake, and selects the right
+    TLS certificate, key and CA certificate to use for the connection.
+   </para>
+
+   <para>
+    SNI configuration is defined in the hosts configuration file,
+    <filename>pg_hosts.conf</filename>, which is stored in the clusters
+    data directory.  The hosts configuration file contains lines of the general
+    forms:
+<synopsis>
+<replaceable>hostname</replaceable> <replaceable>SSL_certificate</replaceable> <replaceable>SSL_key</replaceable> <replaceable>SSL_CA_certificate</replaceable> <replaceable>SSL_passphrase_cmd</replaceable> <replaceable>SSL_passphrase_cmd_reload</replaceable>
+<replaceable>include</replaceable> <replaceable>file</replaceable>
+<replaceable>include_if_exists</replaceable> <replaceable>file</replaceable>
+<replaceable>include_dir</replaceable> <replaceable>directory</replaceable>
+</synopsis>
+    Comments, whitespace and line continuations are handled in the same way as
+    in <filename>pg_hba.conf</filename>.  <replaceable>hostname</replaceable>
+    is matched against the hostname TLS extension in the SSL handshake.
+    <replaceable>SSL_certificate</replaceable>,
+    <replaceable>SSL_key</replaceable>,
+    <replaceable>SSL_CA_certificate</replaceable>,
+    <replaceable>SSL_passphrase_cmd</replaceable>, and
+    <replaceable>SSL_passphrase_cmd_reload</replaceable>
+    are treated like
+    <xref linkend="guc-ssl-cert-file"/>,
+    <xref linkend="guc-ssl-key-file"/>,
+    <xref linkend="guc-ssl-ca-file"/>,
+    <xref linkend="guc-ssl-passphrase-command"/>, and
+    <xref linkend="guc-ssl-passphrase-command-supports-reload"/> respectively.
+    All fields except <replaceable>SSL_passphrase_cmd</replaceable> and
+    <replaceable>SSL_passphrase_cmd_reload</replaceable> are required. If
+    <replaceable>SSL_passphrase_cmd</replaceable> is defined but not
+    <replaceable>SSL_passphrase_cmd_reload</replaceable> then the default
+    value for <replaceable>SSL_passphrase_cmd_reload</replaceable> is
+    <literal>off</literal>.
+   </para>
+   <para>
+    The SSL configuration from <filename>postgresql.conf</filename> is used
+    in order to set up the TLS handshake such that the hostname extension can
+    be inspected.  When <xref linkend="guc-ssl-snimode"/> is set to
+    <literal>default</literal> this configuration will be the defualt fallback
+    if no matching hostname is found in <filename>pg_hosts.conf</filename>.  If
+    <xref linkend="guc-ssl-snimode"/> is set to <literal>strict</literal> it
+    will only be used to for the handshake until the hostname is inspected, it
+    will not be used for the connection.
+   </para>
+   <para>
+    It is currently not possible to set different <literal>clientname</literal>
+    values for the different certificates.  Any <literal>clientname</literal>
+    setting in <filename>pg_hba.conf</filename> will be applied during
+    authentication regardless of which set of certificates have been loaded
+    via an SNI enabled connection.
+   </para>
+  </sect2>
  </sect1>
 
  <sect1 id="gssapi-enc">
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 42d4a28e5aa..96adabf9581 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -186,6 +186,7 @@ endif
 	$(MAKE) -C utils install-data
 	$(INSTALL_DATA) $(srcdir)/libpq/pg_hba.conf.sample '$(DESTDIR)$(datadir)/pg_hba.conf.sample'
 	$(INSTALL_DATA) $(srcdir)/libpq/pg_ident.conf.sample '$(DESTDIR)$(datadir)/pg_ident.conf.sample'
+	$(INSTALL_DATA) $(srcdir)/libpq/pg_hosts.conf.sample '$(DESTDIR)$(datadir)/pg_hosts.conf.sample'
 	$(INSTALL_DATA) $(srcdir)/utils/misc/postgresql.conf.sample '$(DESTDIR)$(datadir)/postgresql.conf.sample'
 
 ifeq ($(with_llvm), yes)
diff --git a/src/backend/libpq/be-secure-common.c b/src/backend/libpq/be-secure-common.c
index e8b837d1fa7..67a50c7b24c 100644
--- a/src/backend/libpq/be-secure-common.c
+++ b/src/backend/libpq/be-secure-common.c
@@ -24,8 +24,13 @@
 
 #include "common/percentrepl.h"
 #include "common/string.h"
+#include "libpq/hba.h"
 #include "libpq/libpq.h"
 #include "storage/fd.h"
+#include "utils/guc.h"
+#include "utils/memutils.h"
+
+static HostsLine *parse_hosts_line(TokenizedAuthLine *tok_line, int elevel);
 
 /*
  * Run ssl_passphrase_command
@@ -37,19 +42,20 @@
  * value is the length of the actual result.
  */
 int
-run_ssl_passphrase_command(const char *prompt, bool is_server_start, char *buf, int size)
+run_ssl_passphrase_command(const char *prompt, bool is_server_start, char *buf, int size, void *userdata)
 {
 	int			loglevel = is_server_start ? ERROR : LOG;
 	char	   *command;
 	FILE	   *fh;
 	int			pclose_rc;
 	size_t		len = 0;
+	char	   *cmd = (char *) userdata;
 
 	Assert(prompt);
 	Assert(size > 0);
 	buf[0] = '\0';
 
-	command = replace_percent_placeholders(ssl_passphrase_command, "ssl_passphrase_command", "p", prompt);
+	command = replace_percent_placeholders(cmd, "ssl_passphrase_command", "p", prompt);
 
 	fh = OpenPipeStream(command, "r");
 	if (fh == NULL)
@@ -175,3 +181,196 @@ check_ssl_key_file_permissions(const char *ssl_key_file, bool isServerStart)
 
 	return true;
 }
+
+/*
+ * parse_hosts_line
+ *
+ * Parses a loaded line from the pg_hosts.conf configuration and pulls out the
+ * hostname, certificate, key and CA parts in order to build an SNI config in
+ * the TLS backend. Validation of the parsed values is left for the TLS backend
+ * to implement.
+ */
+static HostsLine *
+parse_hosts_line(TokenizedAuthLine *tok_line, int elevel)
+{
+	HostsLine  *parsedline;
+	List	   *tokens;
+	ListCell   *field;
+	AuthToken  *token;
+
+	parsedline = palloc0(sizeof(HostsLine));
+	parsedline->sourcefile = pstrdup(tok_line->file_name);
+	parsedline->linenumber = tok_line->line_num;
+	parsedline->rawline = pstrdup(tok_line->raw_line);
+
+	/* Initialize optional fields */
+	parsedline->ssl_passphrase_cmd = NULL;
+	parsedline->ssl_passphrase_reload = false;
+
+	/* Hostname */
+	field = list_head(tok_line->fields);
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->hostname = pstrdup(token->string);
+
+	/* SSL Certificate (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_cert = pstrdup(token->string);
+
+	/* SSL key (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_key = pstrdup(token->string);
+
+	/* SSL CA (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_ca = pstrdup(token->string);
+
+	/* SSL Passphrase Command (optional) */
+	field = lnext(tok_line->fields, field);
+	if (field)
+	{
+		tokens = lfirst(field);
+		token = linitial(tokens);
+		parsedline->ssl_passphrase_cmd = pstrdup(token->string);
+
+		/*
+		 * SSL Passphrase Command support reload (optional). This field is
+		 * only supported if there was a passphrase command parsed first, so
+		 * nest it under the previous token.
+		 */
+		field = lnext(tok_line->fields, field);
+		if (field)
+		{
+			tokens = lfirst(field);
+			token = linitial(tokens);
+
+			if (token->string[0] == '1'
+				|| pg_strcasecmp(token->string, "true") == 0
+				|| pg_strcasecmp(token->string, "on") == 0
+				|| pg_strcasecmp(token->string, "yes") == 0)
+				parsedline->ssl_passphrase_reload = true;
+			else if (token->string[0] == '0'
+					 || pg_strcasecmp(token->string, "false") == 0
+					 || pg_strcasecmp(token->string, "off") == 0
+					 || pg_strcasecmp(token->string, "no") == 0)
+				parsedline->ssl_passphrase_reload = false;
+			else
+				ereport(elevel,
+						errcode(ERRCODE_CONFIG_FILE_ERROR),
+						errmsg("incorrect syntax for boolean value SSL_passphrase_cmd_reload"),
+						errcontext("line %d of configuration file \"%s\"",
+								   tok_line->line_num, tok_line->file_name));
+		}
+	}
+
+	return parsedline;
+}
+
+/*
+ * load_hosts
+ *
+ * Reads pg_hosts.conf and passes back a List of parsed lines, or NIL in case
+ * of errors.
+ */
+List *
+load_hosts(void)
+{
+	FILE	   *file;
+	ListCell   *line;
+	List	   *hosts_lines = NIL;
+	List	   *parsed_lines = NIL;
+	HostsLine  *newline;
+	bool		ok = true;
+	MemoryContext oldcxt;
+	MemoryContext hostcxt;
+
+	file = open_auth_file(HostsFileName, LOG, 0, NULL);
+	if (file == NULL)
+	{
+		/* An error has already been logged so no need to add one here */
+		return NIL;
+	}
+
+	tokenize_auth_file(HostsFileName, file, &hosts_lines, LOG, 0);
+
+	hostcxt = AllocSetContextCreate(PostmasterContext,
+									"hosts file parser context",
+									ALLOCSET_SMALL_SIZES);
+	oldcxt = MemoryContextSwitchTo(hostcxt);
+
+	foreach(line, hosts_lines)
+	{
+		TokenizedAuthLine *tok_line = (TokenizedAuthLine *) lfirst(line);
+
+		if (tok_line->err_msg != NULL)
+		{
+			ok = false;
+			continue;
+		}
+
+		if ((newline = parse_hosts_line(tok_line, LOG)) == NULL)
+		{
+			ok = false;
+			continue;
+		}
+
+		parsed_lines = lappend(parsed_lines, newline);
+	}
+
+	free_auth_file(file, 0);
+	MemoryContextSwitchTo(oldcxt);
+
+	/*
+	 * If we didn't find any SNI configuration then that's not an error since
+	 * the pg_hosts file is additive to the default SSL configuration.
+	 */
+	if (ok && parsed_lines == NIL)
+	{
+		ereport(DEBUG1,
+				errmsg("no SNI configuration added from configuration file  \"%s\"",
+					   HostsFileName));
+		MemoryContextDelete(hostcxt);
+		return NIL;
+	}
+
+	if (!ok)
+	{
+		MemoryContextDelete(hostcxt);
+		return NIL;
+	}
+
+	return parsed_lines;
+}
diff --git a/src/backend/libpq/be-secure-openssl.c b/src/backend/libpq/be-secure-openssl.c
index 64ff3ce3d6a..29544efa667 100644
--- a/src/backend/libpq/be-secure-openssl.c
+++ b/src/backend/libpq/be-secure-openssl.c
@@ -51,9 +51,18 @@
 #endif
 #include <openssl/x509v3.h>
 
+typedef struct HostContext
+{
+	const char *hostname;
+	const char *ssl_passphrase;
+	SSL_CTX    *context;
+	bool		default_host;
+	bool		ssl_loaded_verify_locations;
+	bool		ssl_passphrase_support_reload;
+} HostContext;
 
 /* default init hook can be overridden by a shared library */
-static void default_openssl_tls_init(SSL_CTX *context, bool isServerStart);
+static void default_openssl_tls_init(SSL_CTX *context, bool isServerStart, HostsLine *hosts);
 openssl_tls_init_hook_typ openssl_tls_init_hook = default_openssl_tls_init;
 
 static int	port_bio_read(BIO *h, char *buf, int size);
@@ -73,6 +82,7 @@ static int	alpn_cb(SSL *ssl,
 					const unsigned char *in,
 					unsigned int inlen,
 					void *userdata);
+static int	sni_servername_cb(SSL *ssl, int *al, void *arg);
 static bool initialize_dh(SSL_CTX *context, bool isServerStart);
 static bool initialize_ecdh(SSL_CTX *context, bool isServerStart);
 static const char *SSLerrmessageExt(unsigned long ecode, const char *replacement);
@@ -80,12 +90,17 @@ static const char *SSLerrmessage(unsigned long ecode);
 
 static char *X509_NAME_to_cstring(X509_NAME *name);
 
+static List *contexts = NIL;
 static SSL_CTX *SSL_context = NULL;
+static HostContext *Default_context = NULL;
+static HostContext *Host_context = NULL;
 static bool dummy_ssl_passwd_cb_called = false;
 static bool ssl_is_server_start;
 
 static int	ssl_protocol_version_to_openssl(int v);
 static const char *ssl_protocol_version_to_string(int v);
+static SSL_CTX *ssl_init_context(bool isServerStart, HostsLine *host);
+static void free_contexts(void);
 
 /* for passing data back from verify_cb() */
 static const char *cert_errdetail;
@@ -96,11 +111,160 @@ static const char *cert_errdetail;
 
 int
 be_tls_init(bool isServerStart)
+{
+	SSL_CTX    *ctx;
+	List	   *sni_hosts = NIL;
+	HostsLine	line;
+
+	/*
+	 * If there are contexts loaded when we init they must be released.
+	 */
+	if (contexts != NIL)
+	{
+		free_contexts();
+		Host_context = NULL;
+		SSL_context = NULL;
+		Default_context = NULL;
+	}
+
+	/*
+	 * Load the default configuration from postgresql.conf such that we have a
+	 * context to either be used for the entire connection, or drive the
+	 * handshake until the SNI callback replace it with a configuration from
+	 * the pg_hosts.conf file.
+	 */
+	line.ssl_cert = ssl_cert_file;
+	line.ssl_key = ssl_key_file;
+	line.ssl_ca = ssl_ca_file;
+	line.ssl_passphrase_cmd = ssl_passphrase_command;
+	line.ssl_passphrase_reload = ssl_passphrase_command_supports_reload;
+
+	ctx = ssl_init_context(isServerStart, &line);
+	if (ctx == NULL)
+	{
+		ereport(isServerStart ? FATAL : LOG,
+				(errcode(ERRCODE_CONFIG_FILE_ERROR),
+				 errmsg("could not load default certificate")));
+		return -1;
+	}
+
+	Default_context = palloc0(sizeof(HostContext));
+	Default_context->hostname = pstrdup("*");
+	Default_context->context = ctx;
+	Default_context->default_host = true;
+
+	/*
+	 * Set flag to remember whether CA store has been loaded into SSL_context.
+	 */
+	if (ssl_ca_file[0])
+		Default_context->ssl_loaded_verify_locations = true;
+
+	/*
+	 * While the default context isn't matched against when searching for host
+	 * contexts we still add it to the list to ensure that cleanup code can
+	 * iterate over a single structure to clean up everything.
+	 */
+	contexts = lappend(contexts, Default_context);
+
+	/*
+	 * Install the default context to use as the initial context for the
+	 * connection.  This might be replaced in the SNI callback if there is a
+	 * host/snimode match, but we need something to drive the hand- shake till
+	 * then.
+	 */
+	Host_context = Default_context;
+	SSL_context = Host_context->context;
+
+	/*
+	 * In default or strict ssl_snimode we load all certificates/keys which
+	 * are configured in pg_hosts.conf.  In strict mode it is considered a
+	 * fatal error in case there are no configured entries.
+	 */
+	if (ssl_snimode == SSL_SNIMODE_STRICT || ssl_snimode == SSL_SNIMODE_DEFAULT)
+	{
+		ListCell   *line;
+
+		/*
+		 * Load pg_hosts.conf and parse each row, returning the set of hosts
+		 * as a list.
+		 */
+		sni_hosts = load_hosts();
+
+		/*
+		 * In strict ssl_snimode there needs to be at least one configured
+		 * host in the pg_hosts file since the default fallback context isn't
+		 * allowed to connect with.
+		 */
+		if (sni_hosts == NIL && ssl_snimode == SSL_SNIMODE_STRICT)
+		{
+			ereport(isServerStart ? FATAL : LOG,
+					errcode(ERRCODE_CONFIG_FILE_ERROR),
+					errmsg("could not load %s", "pg_hosts.conf"));
+			return -1;
+		}
+
+		foreach(line, sni_hosts)
+		{
+			HostContext *host_context;
+			HostsLine  *host = lfirst(line);
+			static SSL_CTX *tmp_context = NULL;
+
+			tmp_context = ssl_init_context(isServerStart, host);
+			if (tmp_context == NULL)
+			{
+				ereport(isServerStart ? FATAL : LOG,
+						errcode(ERRCODE_CONFIG_FILE_ERROR),
+						errmsg("unable to load certificate from pg_hosts.conf file"));
+				return -1;
+			}
+
+			/*
+			 * The parsing logic has already verified that the hostname exist
+			 * so we need not check that.  The passphrase command fields are
+			 * however optional so we need to check whether those were set.
+			 */
+			host_context = palloc0(sizeof(HostContext));
+			host_context->hostname = pstrdup(host->hostname);
+			host_context->context = tmp_context;
+			host_context->default_host = false;
+			if (host->ssl_passphrase_cmd != NULL)
+				host_context->ssl_passphrase = pstrdup(host->ssl_passphrase_cmd);
+			host_context->ssl_passphrase_support_reload = host->ssl_passphrase_reload;
+
+			/*
+			 * Set flag to remember whether CA store has been loaded into this
+			 * SSL_context.
+			 */
+			if (host->ssl_ca)
+				host_context->ssl_loaded_verify_locations = true;
+
+			contexts = lappend(contexts, host_context);
+		}
+	}
+
+	/* Make sure we have at least one certificate loaded */
+	if (list_length(contexts) < 1)
+	{
+		ereport(isServerStart ? FATAL : LOG,
+				(errcode(ERRCODE_CONFIG_FILE_ERROR),
+				 errmsg("no SSL contexts loaded")));
+		return -1;
+	}
+
+	return 0;
+}
+
+static SSL_CTX *
+ssl_init_context(bool isServerStart, HostsLine *host_line)
 {
 	SSL_CTX    *context;
 	int			ssl_ver_min = -1;
 	int			ssl_ver_max = -1;
 
+	const char *ctx_ssl_cert_file = host_line->ssl_cert;
+	const char *ctx_ssl_key_file = host_line->ssl_key;
+	const char *ctx_ssl_ca_file = host_line->ssl_ca;
+
 	/*
 	 * Create a new SSL context into which we'll load all the configuration
 	 * settings.  If we fail partway through, we can avoid memory leakage by
@@ -126,10 +290,17 @@ be_tls_init(bool isServerStart)
 	 */
 	SSL_CTX_set_mode(context, SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER);
 
+	/*
+	 * Install SNI TLS extension callback in case the server is configured to
+	 * validate hostnames.
+	 */
+	if (ssl_snimode != SSL_SNIMODE_OFF)
+		SSL_CTX_set_tlsext_servername_callback(context, sni_servername_cb);
+
 	/*
 	 * Call init hook (usually to set password callback)
 	 */
-	(*openssl_tls_init_hook) (context, isServerStart);
+	(*openssl_tls_init_hook) (context, isServerStart, host_line);
 
 	/* used by the callback */
 	ssl_is_server_start = isServerStart;
@@ -137,16 +308,16 @@ be_tls_init(bool isServerStart)
 	/*
 	 * Load and verify server's certificate and private key
 	 */
-	if (SSL_CTX_use_certificate_chain_file(context, ssl_cert_file) != 1)
+	if (SSL_CTX_use_certificate_chain_file(context, ctx_ssl_cert_file) != 1)
 	{
 		ereport(isServerStart ? FATAL : LOG,
 				(errcode(ERRCODE_CONFIG_FILE_ERROR),
 				 errmsg("could not load server certificate file \"%s\": %s",
-						ssl_cert_file, SSLerrmessage(ERR_get_error()))));
+						ctx_ssl_cert_file, SSLerrmessage(ERR_get_error()))));
 		goto error;
 	}
 
-	if (!check_ssl_key_file_permissions(ssl_key_file, isServerStart))
+	if (!check_ssl_key_file_permissions(ctx_ssl_key_file, isServerStart))
 		goto error;
 
 	/*
@@ -155,19 +326,19 @@ be_tls_init(bool isServerStart)
 	dummy_ssl_passwd_cb_called = false;
 
 	if (SSL_CTX_use_PrivateKey_file(context,
-									ssl_key_file,
+									ctx_ssl_key_file,
 									SSL_FILETYPE_PEM) != 1)
 	{
 		if (dummy_ssl_passwd_cb_called)
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("private key file \"%s\" cannot be reloaded because it requires a passphrase",
-							ssl_key_file)));
+							ctx_ssl_key_file)));
 		else
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("could not load private key file \"%s\": %s",
-							ssl_key_file, SSLerrmessage(ERR_get_error()))));
+							ctx_ssl_key_file, SSLerrmessage(ERR_get_error()))));
 		goto error;
 	}
 
@@ -319,17 +490,17 @@ be_tls_init(bool isServerStart)
 	/*
 	 * Load CA store, so we can verify client certificates if needed.
 	 */
-	if (ssl_ca_file[0])
+	if (ctx_ssl_ca_file[0])
 	{
 		STACK_OF(X509_NAME) * root_cert_list;
 
-		if (SSL_CTX_load_verify_locations(context, ssl_ca_file, NULL) != 1 ||
-			(root_cert_list = SSL_load_client_CA_file(ssl_ca_file)) == NULL)
+		if (SSL_CTX_load_verify_locations(context, ctx_ssl_ca_file, NULL) != 1 ||
+			(root_cert_list = SSL_load_client_CA_file(ctx_ssl_ca_file)) == NULL)
 		{
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("could not load root certificate file \"%s\": %s",
-							ssl_ca_file, SSLerrmessage(ERR_get_error()))));
+							ctx_ssl_ca_file, SSLerrmessage(ERR_get_error()))));
 			goto error;
 		}
 
@@ -401,38 +572,29 @@ be_tls_init(bool isServerStart)
 		}
 	}
 
-	/*
-	 * Success!  Replace any existing SSL_context.
-	 */
-	if (SSL_context)
-		SSL_CTX_free(SSL_context);
-
-	SSL_context = context;
-
-	/*
-	 * Set flag to remember whether CA store has been loaded into SSL_context.
-	 */
-	if (ssl_ca_file[0])
-		ssl_loaded_verify_locations = true;
-	else
-		ssl_loaded_verify_locations = false;
-
-	return 0;
+	return context;
 
 	/* Clean up by releasing working context. */
 error:
 	if (context)
 		SSL_CTX_free(context);
-	return -1;
+	return NULL;
 }
 
 void
 be_tls_destroy(void)
 {
-	if (SSL_context)
-		SSL_CTX_free(SSL_context);
+	ListCell   *cell;
+
+	foreach(cell, contexts)
+	{
+		HostContext *host_context = lfirst(cell);
+
+		SSL_CTX_free(host_context->context);
+		pfree(host_context);
+	}
+
 	SSL_context = NULL;
-	ssl_loaded_verify_locations = false;
 }
 
 int
@@ -759,6 +921,9 @@ be_tls_close(Port *port)
 		pfree(port->peer_dn);
 		port->peer_dn = NULL;
 	}
+
+	Host_context = NULL;
+	SSL_context = NULL;
 }
 
 ssize_t
@@ -1132,7 +1297,7 @@ ssl_external_passwd_cb(char *buf, int size, int rwflag, void *userdata)
 
 	Assert(rwflag == 0);
 
-	return run_ssl_passphrase_command(prompt, ssl_is_server_start, buf, size);
+	return run_ssl_passphrase_command(prompt, ssl_is_server_start, buf, size, userdata);
 }
 
 /*
@@ -1369,6 +1534,88 @@ alpn_cb(SSL *ssl,
 	}
 }
 
+static int
+sni_servername_cb(SSL *ssl, int *al, void *arg)
+{
+	const char *tlsext_hostname;
+
+	/*
+	 * Executing this callback when SNI is turned off indicates a programmer
+	 * error or something worse.
+	 */
+	Assert(ssl_snimode != SSL_SNIMODE_OFF);
+
+	tlsext_hostname = SSL_get_servername(ssl, TLSEXT_NAMETYPE_host_name);
+
+	/*
+	 * If there is no hostname set in the TLS extension, we have two options.
+	 * For ssl_snimode strict we error out since we cannot match a host config
+	 * for the connection.  For the default mode we fall back on the default
+	 * hostname configuration.
+	 */
+	if (!tlsext_hostname)
+	{
+		if (ssl_snimode == SSL_SNIMODE_STRICT)
+		{
+			ereport(COMMERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg("no hostname provided in callback")));
+			return SSL_TLSEXT_ERR_ALERT_FATAL;
+		}
+		else
+		{
+			Host_context = Default_context;
+			SSL_context = Host_context->context;
+			SSL_set_SSL_CTX(ssl, SSL_context);
+			return SSL_TLSEXT_ERR_OK;
+		}
+	}
+
+	/*
+	 * We have a requested hostname from the client, match against all entries
+	 * in the pg_hosts configuration to find a match.
+	 */
+	foreach_ptr(HostContext, host, contexts)
+	{
+		/*
+		 * For strict mode we will never want the default host so we can skip
+		 * past it immediately.
+		 */
+		if (ssl_snimode == SSL_SNIMODE_STRICT && host->default_host)
+			continue;
+
+		if (strcmp(host->hostname, tlsext_hostname) == 0)
+		{
+			Host_context = host;
+			SSL_context = host->context;
+			SSL_set_SSL_CTX(ssl, SSL_context);
+			return SSL_TLSEXT_ERR_OK;
+		}
+	}
+
+	/*
+	 * In ssl_snimode "strict" it's an error if there was no match for the
+	 * hostname in the TLS extension.  Terminate the connection.
+	 */
+	if (ssl_snimode == SSL_SNIMODE_STRICT)
+	{
+		ereport(COMMERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg("no matching pg_hosts entry found for hostname: \"%s\"",
+						tlsext_hostname)));
+		return SSL_TLSEXT_ERR_ALERT_FATAL;
+	}
+
+	/*
+	 * In ssl_snimode "default" we fall back on the default host configured in
+	 * postgresql.conf when no match is found in pg_hosts.conf.
+	 */
+	Host_context = Default_context;
+	SSL_context = Host_context->context;
+	SSL_set_SSL_CTX(ssl, SSL_context);
+	Assert(SSL_context);
+	return SSL_TLSEXT_ERR_OK;
+}
 
 /*
  * Set DH parameters for generating ephemeral DH keys.  The
@@ -1578,6 +1825,12 @@ be_tls_get_peer_serial(Port *port, char *ptr, size_t len)
 		ptr[0] = '\0';
 }
 
+bool
+be_tls_loaded_verify_locations(void)
+{
+	return Host_context->ssl_loaded_verify_locations;
+}
+
 char *
 be_tls_get_certificate_hash(Port *port, size_t *len)
 {
@@ -1771,17 +2024,23 @@ ssl_protocol_version_to_string(int v)
 
 
 static void
-default_openssl_tls_init(SSL_CTX *context, bool isServerStart)
+default_openssl_tls_init(SSL_CTX *context, bool isServerStart, HostsLine *host)
 {
 	if (isServerStart)
 	{
-		if (ssl_passphrase_command[0])
+		if (host->ssl_passphrase_cmd != NULL)
+		{
 			SSL_CTX_set_default_passwd_cb(context, ssl_external_passwd_cb);
+			SSL_CTX_set_default_passwd_cb_userdata(context, host->ssl_passphrase_cmd);
+		}
 	}
 	else
 	{
-		if (ssl_passphrase_command[0] && ssl_passphrase_command_supports_reload)
+		if (host->ssl_passphrase_cmd != NULL && host->ssl_passphrase_reload)
+		{
 			SSL_CTX_set_default_passwd_cb(context, ssl_external_passwd_cb);
+			SSL_CTX_set_default_passwd_cb_userdata(context, host->ssl_passphrase_cmd);
+		}
 		else
 
 			/*
@@ -1793,3 +2052,26 @@ default_openssl_tls_init(SSL_CTX *context, bool isServerStart)
 			SSL_CTX_set_default_passwd_cb(context, dummy_ssl_passwd_cb);
 	}
 }
+
+/*
+ * Cleanup function for when hostname configuration is reloaded from the
+ * pg_hosts.conf file, at that point we Must discard all existing contexts.
+ */
+static void
+free_contexts(void)
+{
+	if (contexts == NIL)
+		return;
+
+	foreach_ptr(HostContext, host, contexts)
+	{
+		if (host->hostname)
+			pfree(unconstify(char *, host->hostname));
+		if (host->ssl_passphrase)
+			pfree(unconstify(char *, host->ssl_passphrase));
+		SSL_CTX_free(host->context);
+	}
+
+	list_free_deep(contexts);
+	contexts = NIL;
+}
diff --git a/src/backend/libpq/be-secure.c b/src/backend/libpq/be-secure.c
index 91576f94285..b10e8f995ac 100644
--- a/src/backend/libpq/be-secure.c
+++ b/src/backend/libpq/be-secure.c
@@ -43,10 +43,6 @@ char	   *ssl_dh_params_file;
 char	   *ssl_passphrase_command;
 bool		ssl_passphrase_command_supports_reload;
 
-#ifdef USE_SSL
-bool		ssl_loaded_verify_locations = false;
-#endif
-
 /* GUC variable controlling SSL cipher list */
 char	   *SSLCipherSuites = NULL;
 char	   *SSLCipherList = NULL;
@@ -60,6 +56,8 @@ bool		SSLPreferServerCiphers;
 int			ssl_min_protocol_version = PG_TLS1_2_VERSION;
 int			ssl_max_protocol_version = PG_TLS_ANY;
 
+int			ssl_snimode = SSL_SNIMODE_DEFAULT;
+
 /* ------------------------------------------------------------ */
 /*			 Procedures common to all secure sessions			*/
 /* ------------------------------------------------------------ */
@@ -99,7 +97,7 @@ bool
 secure_loaded_verify_locations(void)
 {
 #ifdef USE_SSL
-	return ssl_loaded_verify_locations;
+	return be_tls_loaded_verify_locations();
 #else
 	return false;
 #endif
diff --git a/src/backend/libpq/meson.build b/src/backend/libpq/meson.build
index 31aa2faae1e..4f6ec13bc74 100644
--- a/src/backend/libpq/meson.build
+++ b/src/backend/libpq/meson.build
@@ -31,5 +31,6 @@ endif
 install_data(
   'pg_hba.conf.sample',
   'pg_ident.conf.sample',
+  'pg_hosts.conf.sample',
   install_dir: dir_data,
 )
diff --git a/src/backend/libpq/pg_hosts.conf.sample b/src/backend/libpq/pg_hosts.conf.sample
new file mode 100644
index 00000000000..5a47f9cae7d
--- /dev/null
+++ b/src/backend/libpq/pg_hosts.conf.sample
@@ -0,0 +1,4 @@
+# PostgreSQL SNI Hostname mappings
+# ================================
+
+# HOSTNAME       SSL CERTIFICATE             SSL KEY
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 12192445218..1a3e5011b35 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -55,6 +55,7 @@
 #define CONFIG_FILENAME "postgresql.conf"
 #define HBA_FILENAME	"pg_hba.conf"
 #define IDENT_FILENAME	"pg_ident.conf"
+#define HOSTS_FILENAME	"pg_hosts.conf"
 
 #ifdef EXEC_BACKEND
 #define CONFIG_EXEC_PARAMS "global/config_exec_params"
@@ -1968,6 +1969,31 @@ SelectConfigFiles(const char *userDoption, const char *progname)
 	}
 	SetConfigOption("ident_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
 
+	/*
+	 * Likewise for pg_hosts.conf
+	 */
+	if (HostsFileName)
+	{
+		fname = make_absolute_path(HostsFileName);
+		fname_is_malloced = true;
+	}
+	else if (configdir)
+	{
+		fname = guc_malloc(FATAL,
+						   strlen(configdir) + strlen(HOSTS_FILENAME) + 2);
+		sprintf(fname, "%s/%s", configdir, HOSTS_FILENAME);
+		fname_is_malloced = false;
+	}
+	else
+	{
+		write_stderr("%s does not know where to find the \"hosts\" configuration file.\n"
+					 "This can be specified as \"hosts_file\" in \"%s\", "
+					 "or by the -D invocation option, or by the "
+					 "PGDATA environment variable.\n",
+					 progname, ConfigFileName);
+	}
+	SetConfigOption("hosts_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
+
 	if (fname_is_malloced)
 		free(fname);
 	else
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index ad25cbb39c5..b7e868b128e 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -476,6 +476,13 @@ static const struct config_enum_entry wal_compression_options[] = {
 	{NULL, 0, false}
 };
 
+static const struct config_enum_entry ssl_snimode_options[] = {
+	{"off", SSL_SNIMODE_OFF, false},
+	{"default", SSL_SNIMODE_DEFAULT, false},
+	{"strict", SSL_SNIMODE_STRICT, false},
+	{NULL, 0, false}
+};
+
 /*
  * Options for enum values stored in other modules
  */
@@ -540,6 +547,7 @@ char	   *cluster_name = "";
 char	   *ConfigFileName;
 char	   *HbaFileName;
 char	   *IdentFileName;
+char	   *HostsFileName;
 char	   *external_pid_file;
 
 char	   *application_name;
@@ -4624,6 +4632,17 @@ struct config_string ConfigureNamesString[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"hosts_file", PGC_POSTMASTER, FILE_LOCATIONS,
+			gettext_noop("Sets the server's \"hosts\" configuration file."),
+			NULL,
+			GUC_SUPERUSER_ONLY
+		},
+		&HostsFileName,
+		NULL,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"external_pid_file", PGC_POSTMASTER, FILE_LOCATIONS,
 			gettext_noop("Writes the postmaster PID to the specified file."),
@@ -5277,6 +5296,18 @@ struct config_enum ConfigureNamesEnum[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"ssl_snimode", PGC_SIGHUP, CONN_AUTH_SSL,
+			gettext_noop("Sets the SNI mode to use."),
+			NULL,
+			GUC_SUPERUSER_ONLY,
+		},
+		&ssl_snimode,
+		SSL_SNIMODE_DEFAULT,
+		ssl_snimode_options,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"recovery_init_sync_method", PGC_SIGHUP, ERROR_HANDLING_OPTIONS,
 			gettext_noop("Sets the method for synchronizing the data directory before crash recovery."),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 5362ff80519..a20a5ba5d75 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -45,6 +45,8 @@
 					# (change requires restart)
 #ident_file = 'ConfigDir/pg_ident.conf'	# ident configuration file
 					# (change requires restart)
+#hosts_file = 'ConfigDir/pg_hosts.conf' # hosts configuration file
+					# (change requires restart)
 
 # If external_pid_file is not explicitly set, no extra PID file is written.
 #external_pid_file = ''			# write an extra PID file
@@ -120,6 +122,7 @@
 #ssl_dh_params_file = ''
 #ssl_passphrase_command = ''
 #ssl_passphrase_command_supports_reload = off
+#ssl_snimode = default
 
 # OAuth
 #oauth_validator_libraries = ''	# comma-separated list of trusted validator modules
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 21a0fe3ecd9..a6e680f7b44 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -176,6 +176,7 @@ static int	encodingid;
 static char *bki_file;
 static char *hba_file;
 static char *ident_file;
+static char *hosts_file;
 static char *conf_file;
 static char *dictionary_file;
 static char *info_schema_file;
@@ -1542,6 +1543,14 @@ setup_config(void)
 
 	snprintf(path, sizeof(path), "%s/pg_ident.conf", pg_data);
 
+	writefile(path, conflines);
+	if (chmod(path, pg_file_create_mode) != 0)
+		pg_fatal("could not change permissions of \"%s\": %m", path);
+
+	/* pg_hosts.conf */
+	conflines = readfile(hosts_file);
+	snprintf(path, sizeof(path), "%s/pg_hosts.conf", pg_data);
+
 	writefile(path, conflines);
 	if (chmod(path, pg_file_create_mode) != 0)
 		pg_fatal("could not change permissions of \"%s\": %m", path);
@@ -2805,6 +2814,7 @@ setup_data_file_paths(void)
 	set_input(&bki_file, "postgres.bki");
 	set_input(&hba_file, "pg_hba.conf.sample");
 	set_input(&ident_file, "pg_ident.conf.sample");
+	set_input(&hosts_file, "pg_hosts.conf.sample");
 	set_input(&conf_file, "postgresql.conf.sample");
 	set_input(&dictionary_file, "snowball_create.sql");
 	set_input(&info_schema_file, "information_schema.sql");
@@ -2820,12 +2830,13 @@ setup_data_file_paths(void)
 				"PGDATA=%s\nshare_path=%s\nPGPATH=%s\n"
 				"POSTGRES_SUPERUSERNAME=%s\nPOSTGRES_BKI=%s\n"
 				"POSTGRESQL_CONF_SAMPLE=%s\n"
-				"PG_HBA_SAMPLE=%s\nPG_IDENT_SAMPLE=%s\n",
+				"PG_HBA_SAMPLE=%s\nPG_IDENT_SAMPLE=%s\n"
+				"PG_HOSTS_SAMPLE=%s\n",
 				PG_VERSION,
 				pg_data, share_path, bin_path,
 				username, bki_file,
 				conf_file,
-				hba_file, ident_file);
+				hba_file, ident_file, hosts_file);
 		if (show_setting)
 			exit(0);
 	}
@@ -2833,6 +2844,7 @@ setup_data_file_paths(void)
 	check_input(bki_file);
 	check_input(hba_file);
 	check_input(ident_file);
+	check_input(hosts_file);
 	check_input(conf_file);
 	check_input(dictionary_file);
 	check_input(info_schema_file);
diff --git a/src/include/libpq/hba.h b/src/include/libpq/hba.h
index 3657f182db3..3d8e33533b8 100644
--- a/src/include/libpq/hba.h
+++ b/src/include/libpq/hba.h
@@ -151,6 +151,25 @@ typedef struct IdentLine
 	AuthToken  *pg_user;
 } IdentLine;
 
+typedef struct HostsLine
+{
+	int			linenumber;
+
+	char	   *sourcefile;
+	char	   *rawline;
+
+	/* Required fields */
+	bool		default_host;
+	char	   *hostname;
+	char	   *ssl_key;
+	char	   *ssl_cert;
+	char	   *ssl_ca;
+
+	/* Optional fields */
+	char	   *ssl_passphrase_cmd;
+	bool		ssl_passphrase_reload;
+} HostsLine;
+
 /*
  * TokenizedAuthLine represents one line lexed from an authentication
  * configuration file.  Each item in the "fields" list is a sub-list of
diff --git a/src/include/libpq/libpq-be.h b/src/include/libpq/libpq-be.h
index 7fe92b15477..a5f07aff046 100644
--- a/src/include/libpq/libpq-be.h
+++ b/src/include/libpq/libpq-be.h
@@ -323,6 +323,7 @@ extern const char *be_tls_get_cipher(Port *port);
 extern void be_tls_get_peer_subject_name(Port *port, char *ptr, size_t len);
 extern void be_tls_get_peer_issuer_name(Port *port, char *ptr, size_t len);
 extern void be_tls_get_peer_serial(Port *port, char *ptr, size_t len);
+extern bool be_tls_loaded_verify_locations(void);
 
 /*
  * Get the server certificate hash for SCRAM channel binding type
@@ -335,7 +336,7 @@ extern char *be_tls_get_certificate_hash(Port *port, size_t *len);
 
 /* init hook for SSL, the default sets the password callback if appropriate */
 #ifdef USE_OPENSSL
-typedef void (*openssl_tls_init_hook_typ) (SSL_CTX *context, bool isServerStart);
+typedef void (*openssl_tls_init_hook_typ) (SSL_CTX *context, bool isServerStart, HostsLine *host);
 extern PGDLLIMPORT openssl_tls_init_hook_typ openssl_tls_init_hook;
 #endif
 
diff --git a/src/include/libpq/libpq.h b/src/include/libpq/libpq.h
index aeb66ca40cf..5feed0eb0a4 100644
--- a/src/include/libpq/libpq.h
+++ b/src/include/libpq/libpq.h
@@ -107,6 +107,7 @@ extern PGDLLIMPORT char *ssl_crl_dir;
 extern PGDLLIMPORT char *ssl_key_file;
 extern PGDLLIMPORT int ssl_min_protocol_version;
 extern PGDLLIMPORT int ssl_max_protocol_version;
+extern PGDLLIMPORT int ssl_snimode;
 extern PGDLLIMPORT char *ssl_passphrase_command;
 extern PGDLLIMPORT bool ssl_passphrase_command_supports_reload;
 extern PGDLLIMPORT char *ssl_dh_params_file;
@@ -134,12 +135,20 @@ enum ssl_protocol_versions
 	PG_TLS1_3_VERSION,
 };
 
+enum ssl_snimode
+{
+	SSL_SNIMODE_OFF = 0,
+	SSL_SNIMODE_DEFAULT,
+	SSL_SNIMODE_STRICT
+};
+
 /*
  * prototypes for functions in be-secure-common.c
  */
 extern int	run_ssl_passphrase_command(const char *prompt, bool is_server_start,
-									   char *buf, int size);
+									   char *buf, int size, void *userdata);
 extern bool check_ssl_key_file_permissions(const char *ssl_key_file,
 										   bool isServerStart);
+extern List *load_hosts(void);
 
 #endif							/* LIBPQ_H */
diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index 1233e07d7da..37cb3ecb5ae 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -288,6 +288,7 @@ extern PGDLLIMPORT char *cluster_name;
 extern PGDLLIMPORT char *ConfigFileName;
 extern PGDLLIMPORT char *HbaFileName;
 extern PGDLLIMPORT char *IdentFileName;
+extern PGDLLIMPORT char *HostsFileName;
 extern PGDLLIMPORT char *external_pid_file;
 
 extern PGDLLIMPORT char *application_name;
diff --git a/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c b/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
index d5992149821..a85d85735cf 100644
--- a/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
+++ b/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
@@ -26,7 +26,7 @@ static char *ssl_passphrase = NULL;
 static int	rot13_passphrase(char *buf, int size, int rwflag, void *userdata);
 
 /* hook function to set the callback */
-static void set_rot13(SSL_CTX *context, bool isServerStart);
+static void set_rot13(SSL_CTX *context, bool isServerStart, HostsLine *host);
 
 /*
  * Module load callback
@@ -53,7 +53,7 @@ _PG_init(void)
 }
 
 static void
-set_rot13(SSL_CTX *context, bool isServerStart)
+set_rot13(SSL_CTX *context, bool isServerStart, HostsLine *host)
 {
 	/* warn if the user has set ssl_passphrase_command */
 	if (ssl_passphrase_command[0])
diff --git a/src/test/ssl/meson.build b/src/test/ssl/meson.build
index cf8b2b9303a..7a2a5b8ca8c 100644
--- a/src/test/ssl/meson.build
+++ b/src/test/ssl/meson.build
@@ -13,6 +13,7 @@ tests += {
       't/001_ssltests.pl',
       't/002_scram.pl',
       't/003_sslinfo.pl',
+      't/004_sni.pl',
     ],
   },
 }
diff --git a/src/test/ssl/t/004_sni.pl b/src/test/ssl/t/004_sni.pl
new file mode 100644
index 00000000000..f0ce048273a
--- /dev/null
+++ b/src/test/ssl/t/004_sni.pl
@@ -0,0 +1,164 @@
+
+# Copyright (c) 2024, PostgreSQL Global Development Group
+
+use strict;
+use warnings FATAL => 'all';
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+use FindBin;
+use lib $FindBin::RealBin;
+
+use SSL::Server;
+
+# This is the hostname used to connect to the server. This cannot be a
+# hostname, because the server certificate is always for the domain
+# postgresql-ssl-regression.test.
+my $SERVERHOSTADDR = '127.0.0.1';
+# This is the pattern to use in pg_hba.conf to match incoming connections.
+my $SERVERHOSTCIDR = '127.0.0.1/32';
+
+if ($ENV{with_ssl} ne 'openssl')
+{
+	plan skip_all => 'OpenSSL not supported by this build';
+}
+
+if (!$ENV{PG_TEST_EXTRA} || $ENV{PG_TEST_EXTRA} !~ /\bssl\b/)
+{
+	plan skip_all =>
+	  'Potentially unsafe test SSL not enabled in PG_TEST_EXTRA';
+}
+
+my $ssl_server = SSL::Server->new();
+
+my $node = PostgreSQL::Test::Cluster->new('primary');
+$node->init;
+
+# PGHOST is enforced here to set up the node, subsequent connections
+# will use a dedicated connection string.
+$ENV{PGHOST} = $node->host;
+$ENV{PGPORT} = $node->port;
+$node->start;
+
+$ssl_server->configure_test_server_for_ssl($node, $SERVERHOSTADDR,
+	$SERVERHOSTCIDR, 'trust');
+
+$ssl_server->switch_server_cert($node, certfile => 'server-cn-only');
+
+my $connstr =
+  "user=ssltestuser dbname=trustdb hostaddr=$SERVERHOSTADDR host=localhost sslsni=1";
+
+$node->append_conf('postgresql.conf', "ssl_snimode=default");
+$node->reload;
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"connect fails with fallback hostname, without intermediate",
+	expected_stderr => qr/certificate verify failed/);
+
+# example.org serves the server cert and its intermediate CA.
+$node->append_conf('pg_hosts.conf',
+	"example.org server-cn-only+server_ca.crt server-cn-only.key root_ca.crt"
+);
+$node->reload;
+
+$node->connect_ok(
+	"$connstr host=example.org sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"connect with configured hostname, serving intermediate server CA");
+
+$node->connect_fails(
+	"$connstr sslrootcert=invalid sslmode=verify-ca",
+	"connect without server root cert sslmode=verify-ca",
+	expected_stderr => qr/root certificate file "invalid" does not exist/);
+
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"connect still fails with fallback hostname, without intermediate",
+	expected_stderr => qr/certificate verify failed/);
+
+$node->connect_ok(
+	"$connstr host=localhost sslrootcert=ssl/root+server_ca.crt sslmode=verify-ca",
+	"connect with fallback hostname, intermediate included");
+
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	"localhost server-cn-only.crt server-cn-only.key root_ca.crt");
+$node->append_conf('postgresql.conf', "ssl_snimode=strict");
+$node->reload;
+
+$node->connect_fails(
+	"$connstr host=example.org sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with missing hostconfig and snimode=struct",
+	expected_stderr => qr/tlsv1 unrecognized name/);
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require sslsni=1",
+	"connect with correct server CA cert file sslmode=require");
+
+# Attempts at connecting without SNI when the server is using strict mode should
+# result in connection failure.
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require sslsni=0",
+	"connect with correct server CA cert file without SNI for strict mode",
+	expected_stderr => qr/tlsv1 unrecognized name/);
+
+# Reconfigure with broken configuration for the key passphrase, the server
+# should not start up
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo wrongpassword" on'
+);
+my $result = $node->restart(fail_ok => 1);
+is($result, 0,
+	'restart fails with password-protected key when using the wrong passphrase command'
+);
+
+# Reconfigure again but with the correct passphrase set
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo secret1" on'
+);
+$result = $node->restart(fail_ok => 1);
+is($result, 1,
+	'restart succeeds with password-protected key when using the correct passphrase command'
+);
+
+# Make sure connecting works, and try to stress the reload logic by issuing
+# subsequent reloads
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+$node->reload;
+$node->reload;
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"1 connect with correct server CA cert file sslmode=require");
+
+# Test reloading a passphrase protected key without reloading support in the
+# passphrase hook. Connecting after restart should succeed but not after the
+# following reload.
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo secret1" off'
+);
+$result = $node->restart(fail_ok => 1);
+is($result, 1,
+	'restart succeeds with password-protected key when using the correct passphrase command'
+);
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+
+$node->reload;
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect fails since the passphrase protected key cannot be reloaded",
+	expected_stderr => qr/tlsv1 unrecognized name/);
+
+done_testing();
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index cfbab589d61..96c91831feb 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -1168,6 +1168,8 @@ HeapTupleHeader
 HeapTupleHeaderData
 HeapTupleTableSlot
 HistControl
+HostContext
+HostsLine
 HotStandbyState
 I32
 ICU_Convert_Func
-- 
2.39.3 (Apple Git-146)

commit a4d9cbf4d1228dcc17f2961b7811321a50e74617
Author: Jacob Champion <jacob.champion@enterprisedb.com>
Date:   Tue Mar 4 13:17:12 2025 -0800

    Tests

diff --git a/src/test/ssl/t/004_sni.pl b/src/test/ssl/t/004_sni.pl
index f0ce048273a..72e64c6c00d 100644
--- a/src/test/ssl/t/004_sni.pl
+++ b/src/test/ssl/t/004_sni.pl
@@ -33,6 +33,11 @@ if (!$ENV{PG_TEST_EXTRA} || $ENV{PG_TEST_EXTRA} !~ /\bssl\b/)
 
 my $ssl_server = SSL::Server->new();
 
+sub sslkey
+{
+	return $ssl_server->sslkey(@_);
+}
+
 my $node = PostgreSQL::Test::Cluster->new('primary');
 $node->init;
 
@@ -161,4 +166,57 @@ $node->connect_fails(
 	"connect fails since the passphrase protected key cannot be reloaded",
 	expected_stderr => qr/tlsv1 unrecognized name/);
 
+# Test client CAs.
+
+$connstr =
+  "user=ssltestuser dbname=certdb hostaddr=$SERVERHOSTADDR sslmode=require sslsni=1";
+
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+# example.org has an unconfigured CA.
+$node->append_conf('pg_hosts.conf', 'example.org server-cn-only.crt server-cn-only.key ""');
+# example.com uses the client CA.
+$node->append_conf('pg_hosts.conf', 'example.com server-cn-only.crt server-cn-only.key root+client_ca.crt');
+# example.net uses the server CA (which is wrong).
+$node->append_conf('pg_hosts.conf', 'example.net server-cn-only.crt server-cn-only.key root+server_ca.crt');
+$node->reload;
+
+my @cases = ( "", "root+client_ca", "root+server_ca" );
+foreach my $default_ca (@cases)
+{
+	# The default CA should, ideally, not matter for the purposes of these
+	# tests, since we connect to the other hosts explicitly.
+	$ssl_server->switch_server_cert(
+		$node,
+		certfile => 'server-cn-only',
+		cafile => $default_ca);
+
+	# example.org is unconfigured and should fail.
+	$node->connect_fails(
+		"$connstr host=example.org sslcertmode=require sslcert=ssl/client.crt " . sslkey('client.key'),
+		"example.org, $default_ca: connect with sslcert, no client CA configured",
+		expected_stderr => qr/client certificates can only be checked if a root certificate store is available/);
+
+	# example.com is configured and should require a valid client cert.
+	$node->connect_fails(
+		"$connstr host=example.com sslcertmode=disable",
+		"example.com, $default_ca: connect fails if no client certificate sent",
+		expected_stderr => qr/connection requires a valid client certificate/);
+
+	$node->connect_ok(
+		"$connstr host=example.com sslcertmode=require sslcert=ssl/client.crt " . sslkey('client.key'),
+		"example.com, $default_ca: connect with sslcert, client certificate sent");
+
+	# example.net is configured and should require a client cert, but will
+	# always fail verification.
+	$node->connect_fails(
+		"$connstr host=example.net sslcertmode=disable",
+		"example.net, $default_ca: connect fails if no client certificate sent",
+		expected_stderr => qr/connection requires a valid client certificate/);
+
+	$node->connect_fails(
+		"$connstr host=example.net sslcertmode=require sslcert=ssl/client.crt " . sslkey('client.key'),
+		"example.net, $default_ca: connect with sslcert, client certificate sent",
+		expected_stderr => qr/unknown ca/);
+}
+
 done_testing();
diff --git a/src/test/ssl/t/SSL/Backend/OpenSSL.pm b/src/test/ssl/t/SSL/Backend/OpenSSL.pm
index e044318531f..bdcce84003e 100644
--- a/src/test/ssl/t/SSL/Backend/OpenSSL.pm
+++ b/src/test/ssl/t/SSL/Backend/OpenSSL.pm
@@ -71,6 +71,7 @@ sub init
 	chmod(0600, glob "$pgdata/server-*.key")
 	  or die "failed to change permissions on server keys: $!";
 	_copy_files("ssl/root+client_ca.crt", $pgdata);
+	_copy_files("ssl/root+server_ca.crt", $pgdata);
 	_copy_files("ssl/root_ca.crt", $pgdata);
 	_copy_files("ssl/root+client.crl", $pgdata);
 	mkdir("$pgdata/root+client-crldir")
@@ -145,7 +146,8 @@ following parameters are supported:
 =item cafile => B<value>
 
 The CA certificate file to use for the C<ssl_ca_file> GUC. If omitted it will
-default to 'root+client_ca.crt'.
+default to 'root+client_ca.crt'. If empty, no C<ssl_ca_file> configuration
+parameter will be set.
 
 =item certfile => B<value>
 
@@ -180,10 +182,11 @@ sub set_server_cert
 	  unless defined $params->{keyfile};
 
 	my $sslconf =
-		"ssl_ca_file='$params->{cafile}.crt'\n"
-	  . "ssl_cert_file='$params->{certfile}.crt'\n"
+		"ssl_cert_file='$params->{certfile}.crt'\n"
 	  . "ssl_key_file='$params->{keyfile}.key'\n"
 	  . "ssl_crl_file='$params->{crlfile}'\n";
+	$sslconf .= "ssl_ca_file='$params->{cafile}.crt'\n"
+	  if $params->{cafile} ne "";
 	$sslconf .= "ssl_crl_dir='$params->{crldir}'\n"
 	  if defined $params->{crldir};
 

From 42c1c44ebec355d48755d7821782d49a15568c77 Mon Sep 17 00:00:00 2001
From: Daniel Gustafsson <dgustafsson@postgresql.org>
Date: Mon, 2 Jun 2025 10:25:08 +0200
Subject: [PATCH v8] Serverside SNI support for libpq

Experimental support for serverside SNI support in libpq, a new config
file $datadir/pg_hosts.conf is used for configuring which certicate and
key should be used for which hostname. A new GUC, ssl_snimode, is added
which controls how the hostname TLS extension is handled. The possible
values are off, default and strict:

  - off: pg_hosts.conf is not parsed and the hostname TLS extension is
    not inspected at all. The normal SSL GUCs for certificates and keys
    are used.
  - default: pg_hosts.conf is loaded as well as the normal GUCs. If no
    match for the TLS extension hostname is found in pg_hosts the cert
    and key from the postgresql.conf GUCs is used as the default (used
    as a wildcard host).
  - strict: only pg_hosts.conf is loaded and the TLS extension hostname
    MUST be passed and MUST have a match in the configuration, else the
    connection is refused.

CRL file(s) are applied from postgresql.conf to all configured hostnames.

Reviewed-by: Cary Huang <cary.huang@highgo.ca>
Reviewed-by: Jacob Champion <jacob.champion@enterprisedb.com>
Discussion: https://postgr.es/m/1C81CD0D-407E-44F9-833A-DD0331C202E5@yesql.se
---
 doc/src/sgml/config.sgml                      |  66 ++++
 doc/src/sgml/runtime.sgml                     |  67 ++++
 src/backend/Makefile                          |   1 +
 src/backend/libpq/be-secure-common.c          | 203 +++++++++-
 src/backend/libpq/be-secure-openssl.c         | 356 ++++++++++++++++--
 src/backend/libpq/be-secure.c                 |   8 +-
 src/backend/libpq/meson.build                 |   1 +
 src/backend/libpq/pg_hosts.conf.sample        |   4 +
 src/backend/utils/misc/guc.c                  |  26 ++
 src/backend/utils/misc/guc_tables.c           |  31 ++
 src/backend/utils/misc/postgresql.conf.sample |   3 +
 src/bin/initdb/initdb.c                       |  16 +-
 src/include/libpq/hba.h                       |  19 +
 src/include/libpq/libpq-be.h                  |   3 +-
 src/include/libpq/libpq.h                     |  11 +-
 src/include/utils/guc.h                       |   1 +
 .../ssl_passphrase_func.c                     |   4 +-
 src/test/perl/PostgreSQL/Test/Cluster.pm      |  35 ++
 src/test/ssl/meson.build                      |   1 +
 src/test/ssl/t/001_ssltests.pl                |  29 +-
 src/test/ssl/t/004_sni.pl                     | 175 +++++++++
 src/test/ssl/t/SSL/Server.pm                  |   8 +
 src/tools/pgindent/typedefs.list              |   2 +
 23 files changed, 1007 insertions(+), 63 deletions(-)
 create mode 100644 src/backend/libpq/pg_hosts.conf.sample
 create mode 100644 src/test/ssl/t/004_sni.pl

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 0a4b3e55ba5..17ba6538de6 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1694,6 +1694,72 @@ include_dir 'conf.d'
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry id="guc-ssl-snimode" xreflabel="ssl_snimode">
+      <term><varname>ssl_snimode</varname> (<type>enum</type>)
+      <indexterm>
+       <primary><varname>ssl_snimode</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        This parameter determines if the server will inspect the <acronym>SNI</acronym> TLS extension
+        when establishing the connection, and how it should be interpreted.
+        Valid values are currently: <literal>off</literal>, <literal>default</literal> and <literal>strict</literal>.
+       </para>
+       <para>
+        <variablelist>
+         <varlistentry id="guc-ssl-snimode-off">
+          <term><literal>off</literal></term>
+          <listitem>
+           <para>
+            SNI is not enabled and no configuration from
+            <filename>pg_hosts.conf</filename> is loaded.  Configuration of SSL
+            for all connections is done with <xref linkend="guc-ssl-cert-file"/>,
+            <xref linkend="guc-ssl-key-file"/> and <xref linkend="guc-ssl-ca-file"/>.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry id="guc-ssl-snimode-default">
+          <term><literal>default</literal></term>
+          <listitem>
+           <para>
+            SNI is enabled and hostname configuration is loaded from
+            <filename>pg_hosts.conf</filename>. <xref linkend="guc-ssl-cert-file"/>,
+            <xref linkend="guc-ssl-key-file"/> and <xref linkend="guc-ssl-ca-file"/>
+            are loaded as the default configuration.  Connections specifying
+            <xref linkend="libpq-connect-sslsni"/> to <literal>1</literal>
+            will be attempted using the default configuration if the hostname
+            is missing in <filename>pg_hosts.conf</filename>.  If the hostname
+            matches an entry from <filename>pg_hosts.conf</filename>, then the
+            configuration from that entry will be used for setting up the
+            connection.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry id="guc-ssl-snimode-strict">
+          <term><literal>strict</literal></term>
+          <listitem>
+           <para>
+            SNI is enabled and all connections are required to set <xref
+            linkend="libpq-connect-sslsni"/> to <literal>1</literal> and
+            specify a hostname matching an entry in
+            <filename>pg_hosts.conf</filename>. Any connection without <xref
+            linkend="libpq-connect-sslsni"/> or with a hostname missing from
+            <filename>pg_hosts.conf</filename> will be rejected.
+            <xref linkend="guc-ssl-cert-file"/>,
+            <xref linkend="guc-ssl-key-file"/> and <xref linkend="guc-ssl-ca-file"/>
+            are loaded in order to drive the handshake until the appropriate
+            configuration has been selected.
+           </para>
+          </listitem>
+         </varlistentry>
+        </variablelist>
+       </para>
+      </listitem>
+     </varlistentry>
     </variablelist>
     </sect2>
    </sect1>
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index 0c60bafac63..fa6fe07adc0 100644
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -2445,6 +2445,12 @@ pg_dumpall -p 5432 | psql -d postgres -p 5433
       <entry>client certificate must not be on this list</entry>
      </row>
 
+     <row>
+      <entry><filename>$PGDATA/pg_hosts.conf</filename></entry>
+      <entry>SNI configuration</entry>
+      <entry>defines which certificates to use for which server hostname</entry>
+     </row>
+
     </tbody>
    </tgroup>
   </table>
@@ -2572,6 +2578,67 @@ openssl x509 -req -in server.csr -text -days 365 \
    </para>
   </sect2>
 
+  <sect2 id="ssl-sni">
+   <title>SNI Configuration</title>
+
+   <para>
+    <productname>PostgreSQL</productname> can be configured for
+    <acronym>SNI</acronym> using the <filename>pg_hosts.conf</filename>
+    configuration file. <productname>PostgreSQL</productname> inspects the TLS
+    hostname extension in the SSL connection handshake, and selects the right
+    TLS certificate, key and CA certificate to use for the connection.
+   </para>
+
+   <para>
+    SNI configuration is defined in the hosts configuration file,
+    <filename>pg_hosts.conf</filename>, which is stored in the clusters
+    data directory.  The hosts configuration file contains lines of the general
+    forms:
+<synopsis>
+<replaceable>hostname</replaceable> <replaceable>SSL_certificate</replaceable> <replaceable>SSL_key</replaceable> <replaceable>SSL_CA_certificate</replaceable> <replaceable>SSL_passphrase_cmd</replaceable> <replaceable>SSL_passphrase_cmd_reload</replaceable>
+<replaceable>include</replaceable> <replaceable>file</replaceable>
+<replaceable>include_if_exists</replaceable> <replaceable>file</replaceable>
+<replaceable>include_dir</replaceable> <replaceable>directory</replaceable>
+</synopsis>
+    Comments, whitespace and line continuations are handled in the same way as
+    in <filename>pg_hba.conf</filename>.  <replaceable>hostname</replaceable>
+    is matched against the hostname TLS extension in the SSL handshake.
+    <replaceable>SSL_certificate</replaceable>,
+    <replaceable>SSL_key</replaceable>,
+    <replaceable>SSL_CA_certificate</replaceable>,
+    <replaceable>SSL_passphrase_cmd</replaceable>, and
+    <replaceable>SSL_passphrase_cmd_reload</replaceable>
+    are treated like
+    <xref linkend="guc-ssl-cert-file"/>,
+    <xref linkend="guc-ssl-key-file"/>,
+    <xref linkend="guc-ssl-ca-file"/>,
+    <xref linkend="guc-ssl-passphrase-command"/>, and
+    <xref linkend="guc-ssl-passphrase-command-supports-reload"/> respectively.
+    All fields except <replaceable>SSL_passphrase_cmd</replaceable> and
+    <replaceable>SSL_passphrase_cmd_reload</replaceable> are required. If
+    <replaceable>SSL_passphrase_cmd</replaceable> is defined but not
+    <replaceable>SSL_passphrase_cmd_reload</replaceable> then the default
+    value for <replaceable>SSL_passphrase_cmd_reload</replaceable> is
+    <literal>off</literal>.
+   </para>
+   <para>
+    The SSL configuration from <filename>postgresql.conf</filename> is used
+    in order to set up the TLS handshake such that the hostname extension can
+    be inspected.  When <xref linkend="guc-ssl-snimode"/> is set to
+    <literal>default</literal> this configuration will be the defualt fallback
+    if no matching hostname is found in <filename>pg_hosts.conf</filename>.  If
+    <xref linkend="guc-ssl-snimode"/> is set to <literal>strict</literal> it
+    will only be used to for the handshake until the hostname is inspected, it
+    will not be used for the connection.
+   </para>
+   <para>
+    It is currently not possible to set different <literal>clientname</literal>
+    values for the different certificates.  Any <literal>clientname</literal>
+    setting in <filename>pg_hba.conf</filename> will be applied during
+    authentication regardless of which set of certificates have been loaded
+    via an SNI enabled connection.
+   </para>
+  </sect2>
  </sect1>
 
  <sect1 id="gssapi-enc">
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 7344c8c7f5c..2d1691c7950 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -187,6 +187,7 @@ endif
 	$(MAKE) -C utils install-data
 	$(INSTALL_DATA) $(srcdir)/libpq/pg_hba.conf.sample '$(DESTDIR)$(datadir)/pg_hba.conf.sample'
 	$(INSTALL_DATA) $(srcdir)/libpq/pg_ident.conf.sample '$(DESTDIR)$(datadir)/pg_ident.conf.sample'
+	$(INSTALL_DATA) $(srcdir)/libpq/pg_hosts.conf.sample '$(DESTDIR)$(datadir)/pg_hosts.conf.sample'
 	$(INSTALL_DATA) $(srcdir)/utils/misc/postgresql.conf.sample '$(DESTDIR)$(datadir)/postgresql.conf.sample'
 
 ifeq ($(with_llvm), yes)
diff --git a/src/backend/libpq/be-secure-common.c b/src/backend/libpq/be-secure-common.c
index e8b837d1fa7..67a50c7b24c 100644
--- a/src/backend/libpq/be-secure-common.c
+++ b/src/backend/libpq/be-secure-common.c
@@ -24,8 +24,13 @@
 
 #include "common/percentrepl.h"
 #include "common/string.h"
+#include "libpq/hba.h"
 #include "libpq/libpq.h"
 #include "storage/fd.h"
+#include "utils/guc.h"
+#include "utils/memutils.h"
+
+static HostsLine *parse_hosts_line(TokenizedAuthLine *tok_line, int elevel);
 
 /*
  * Run ssl_passphrase_command
@@ -37,19 +42,20 @@
  * value is the length of the actual result.
  */
 int
-run_ssl_passphrase_command(const char *prompt, bool is_server_start, char *buf, int size)
+run_ssl_passphrase_command(const char *prompt, bool is_server_start, char *buf, int size, void *userdata)
 {
 	int			loglevel = is_server_start ? ERROR : LOG;
 	char	   *command;
 	FILE	   *fh;
 	int			pclose_rc;
 	size_t		len = 0;
+	char	   *cmd = (char *) userdata;
 
 	Assert(prompt);
 	Assert(size > 0);
 	buf[0] = '\0';
 
-	command = replace_percent_placeholders(ssl_passphrase_command, "ssl_passphrase_command", "p", prompt);
+	command = replace_percent_placeholders(cmd, "ssl_passphrase_command", "p", prompt);
 
 	fh = OpenPipeStream(command, "r");
 	if (fh == NULL)
@@ -175,3 +181,196 @@ check_ssl_key_file_permissions(const char *ssl_key_file, bool isServerStart)
 
 	return true;
 }
+
+/*
+ * parse_hosts_line
+ *
+ * Parses a loaded line from the pg_hosts.conf configuration and pulls out the
+ * hostname, certificate, key and CA parts in order to build an SNI config in
+ * the TLS backend. Validation of the parsed values is left for the TLS backend
+ * to implement.
+ */
+static HostsLine *
+parse_hosts_line(TokenizedAuthLine *tok_line, int elevel)
+{
+	HostsLine  *parsedline;
+	List	   *tokens;
+	ListCell   *field;
+	AuthToken  *token;
+
+	parsedline = palloc0(sizeof(HostsLine));
+	parsedline->sourcefile = pstrdup(tok_line->file_name);
+	parsedline->linenumber = tok_line->line_num;
+	parsedline->rawline = pstrdup(tok_line->raw_line);
+
+	/* Initialize optional fields */
+	parsedline->ssl_passphrase_cmd = NULL;
+	parsedline->ssl_passphrase_reload = false;
+
+	/* Hostname */
+	field = list_head(tok_line->fields);
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->hostname = pstrdup(token->string);
+
+	/* SSL Certificate (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_cert = pstrdup(token->string);
+
+	/* SSL key (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_key = pstrdup(token->string);
+
+	/* SSL CA (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_ca = pstrdup(token->string);
+
+	/* SSL Passphrase Command (optional) */
+	field = lnext(tok_line->fields, field);
+	if (field)
+	{
+		tokens = lfirst(field);
+		token = linitial(tokens);
+		parsedline->ssl_passphrase_cmd = pstrdup(token->string);
+
+		/*
+		 * SSL Passphrase Command support reload (optional). This field is
+		 * only supported if there was a passphrase command parsed first, so
+		 * nest it under the previous token.
+		 */
+		field = lnext(tok_line->fields, field);
+		if (field)
+		{
+			tokens = lfirst(field);
+			token = linitial(tokens);
+
+			if (token->string[0] == '1'
+				|| pg_strcasecmp(token->string, "true") == 0
+				|| pg_strcasecmp(token->string, "on") == 0
+				|| pg_strcasecmp(token->string, "yes") == 0)
+				parsedline->ssl_passphrase_reload = true;
+			else if (token->string[0] == '0'
+					 || pg_strcasecmp(token->string, "false") == 0
+					 || pg_strcasecmp(token->string, "off") == 0
+					 || pg_strcasecmp(token->string, "no") == 0)
+				parsedline->ssl_passphrase_reload = false;
+			else
+				ereport(elevel,
+						errcode(ERRCODE_CONFIG_FILE_ERROR),
+						errmsg("incorrect syntax for boolean value SSL_passphrase_cmd_reload"),
+						errcontext("line %d of configuration file \"%s\"",
+								   tok_line->line_num, tok_line->file_name));
+		}
+	}
+
+	return parsedline;
+}
+
+/*
+ * load_hosts
+ *
+ * Reads pg_hosts.conf and passes back a List of parsed lines, or NIL in case
+ * of errors.
+ */
+List *
+load_hosts(void)
+{
+	FILE	   *file;
+	ListCell   *line;
+	List	   *hosts_lines = NIL;
+	List	   *parsed_lines = NIL;
+	HostsLine  *newline;
+	bool		ok = true;
+	MemoryContext oldcxt;
+	MemoryContext hostcxt;
+
+	file = open_auth_file(HostsFileName, LOG, 0, NULL);
+	if (file == NULL)
+	{
+		/* An error has already been logged so no need to add one here */
+		return NIL;
+	}
+
+	tokenize_auth_file(HostsFileName, file, &hosts_lines, LOG, 0);
+
+	hostcxt = AllocSetContextCreate(PostmasterContext,
+									"hosts file parser context",
+									ALLOCSET_SMALL_SIZES);
+	oldcxt = MemoryContextSwitchTo(hostcxt);
+
+	foreach(line, hosts_lines)
+	{
+		TokenizedAuthLine *tok_line = (TokenizedAuthLine *) lfirst(line);
+
+		if (tok_line->err_msg != NULL)
+		{
+			ok = false;
+			continue;
+		}
+
+		if ((newline = parse_hosts_line(tok_line, LOG)) == NULL)
+		{
+			ok = false;
+			continue;
+		}
+
+		parsed_lines = lappend(parsed_lines, newline);
+	}
+
+	free_auth_file(file, 0);
+	MemoryContextSwitchTo(oldcxt);
+
+	/*
+	 * If we didn't find any SNI configuration then that's not an error since
+	 * the pg_hosts file is additive to the default SSL configuration.
+	 */
+	if (ok && parsed_lines == NIL)
+	{
+		ereport(DEBUG1,
+				errmsg("no SNI configuration added from configuration file  \"%s\"",
+					   HostsFileName));
+		MemoryContextDelete(hostcxt);
+		return NIL;
+	}
+
+	if (!ok)
+	{
+		MemoryContextDelete(hostcxt);
+		return NIL;
+	}
+
+	return parsed_lines;
+}
diff --git a/src/backend/libpq/be-secure-openssl.c b/src/backend/libpq/be-secure-openssl.c
index c8b63ef8249..14ff1d78c40 100644
--- a/src/backend/libpq/be-secure-openssl.c
+++ b/src/backend/libpq/be-secure-openssl.c
@@ -51,9 +51,18 @@
 #endif
 #include <openssl/x509v3.h>
 
+typedef struct HostContext
+{
+	const char *hostname;
+	const char *ssl_passphrase;
+	SSL_CTX    *context;
+	bool		default_host;
+	bool		ssl_loaded_verify_locations;
+	bool		ssl_passphrase_support_reload;
+} HostContext;
 
 /* default init hook can be overridden by a shared library */
-static void default_openssl_tls_init(SSL_CTX *context, bool isServerStart);
+static void default_openssl_tls_init(SSL_CTX *context, bool isServerStart, HostsLine *hosts);
 openssl_tls_init_hook_typ openssl_tls_init_hook = default_openssl_tls_init;
 
 static int	port_bio_read(BIO *h, char *buf, int size);
@@ -73,6 +82,7 @@ static int	alpn_cb(SSL *ssl,
 					const unsigned char *in,
 					unsigned int inlen,
 					void *userdata);
+static int	sni_servername_cb(SSL *ssl, int *al, void *arg);
 static bool initialize_dh(SSL_CTX *context, bool isServerStart);
 static bool initialize_ecdh(SSL_CTX *context, bool isServerStart);
 static const char *SSLerrmessageExt(unsigned long ecode, const char *replacement);
@@ -80,12 +90,17 @@ static const char *SSLerrmessage(unsigned long ecode);
 
 static char *X509_NAME_to_cstring(X509_NAME *name);
 
+static List *contexts = NIL;
 static SSL_CTX *SSL_context = NULL;
+static HostContext *Default_context = NULL;
+static HostContext *Host_context = NULL;
 static bool dummy_ssl_passwd_cb_called = false;
 static bool ssl_is_server_start;
 
 static int	ssl_protocol_version_to_openssl(int v);
 static const char *ssl_protocol_version_to_string(int v);
+static SSL_CTX *ssl_init_context(bool isServerStart, HostsLine *host);
+static void free_contexts(void);
 
 /* for passing data back from verify_cb() */
 static const char *cert_errdetail;
@@ -96,11 +111,160 @@ static const char *cert_errdetail;
 
 int
 be_tls_init(bool isServerStart)
+{
+	SSL_CTX    *ctx;
+	List	   *sni_hosts = NIL;
+	HostsLine	line;
+
+	/*
+	 * If there are contexts loaded when we init they must be released.
+	 */
+	if (contexts != NIL)
+	{
+		free_contexts();
+		Host_context = NULL;
+		SSL_context = NULL;
+		Default_context = NULL;
+	}
+
+	/*
+	 * Load the default configuration from postgresql.conf such that we have a
+	 * context to either be used for the entire connection, or drive the
+	 * handshake until the SNI callback replace it with a configuration from
+	 * the pg_hosts.conf file.
+	 */
+	line.ssl_cert = ssl_cert_file;
+	line.ssl_key = ssl_key_file;
+	line.ssl_ca = ssl_ca_file;
+	line.ssl_passphrase_cmd = ssl_passphrase_command;
+	line.ssl_passphrase_reload = ssl_passphrase_command_supports_reload;
+
+	ctx = ssl_init_context(isServerStart, &line);
+	if (ctx == NULL)
+	{
+		ereport(isServerStart ? FATAL : LOG,
+				(errcode(ERRCODE_CONFIG_FILE_ERROR),
+				 errmsg("could not load default certificate")));
+		return -1;
+	}
+
+	Default_context = palloc0(sizeof(HostContext));
+	Default_context->hostname = pstrdup("*");
+	Default_context->context = ctx;
+	Default_context->default_host = true;
+
+	/*
+	 * Set flag to remember whether CA store has been loaded into SSL_context.
+	 */
+	if (ssl_ca_file[0])
+		Default_context->ssl_loaded_verify_locations = true;
+
+	/*
+	 * While the default context isn't matched against when searching for host
+	 * contexts we still add it to the list to ensure that cleanup code can
+	 * iterate over a single structure to clean up everything.
+	 */
+	contexts = lappend(contexts, Default_context);
+
+	/*
+	 * Install the default context to use as the initial context for the
+	 * connection.  This might be replaced in the SNI callback if there is a
+	 * host/snimode match, but we need something to drive the hand- shake till
+	 * then.
+	 */
+	Host_context = Default_context;
+	SSL_context = Host_context->context;
+
+	/*
+	 * In default or strict ssl_snimode we load all certificates/keys which
+	 * are configured in pg_hosts.conf.  In strict mode it is considered a
+	 * fatal error in case there are no configured entries.
+	 */
+	if (ssl_snimode == SSL_SNIMODE_STRICT || ssl_snimode == SSL_SNIMODE_DEFAULT)
+	{
+		ListCell   *line;
+
+		/*
+		 * Load pg_hosts.conf and parse each row, returning the set of hosts
+		 * as a list.
+		 */
+		sni_hosts = load_hosts();
+
+		/*
+		 * In strict ssl_snimode there needs to be at least one configured
+		 * host in the pg_hosts file since the default fallback context isn't
+		 * allowed to connect with.
+		 */
+		if (sni_hosts == NIL && ssl_snimode == SSL_SNIMODE_STRICT)
+		{
+			ereport(isServerStart ? FATAL : LOG,
+					errcode(ERRCODE_CONFIG_FILE_ERROR),
+					errmsg("could not load %s", "pg_hosts.conf"));
+			return -1;
+		}
+
+		foreach(line, sni_hosts)
+		{
+			HostContext *host_context;
+			HostsLine  *host = lfirst(line);
+			static SSL_CTX *tmp_context = NULL;
+
+			tmp_context = ssl_init_context(isServerStart, host);
+			if (tmp_context == NULL)
+			{
+				ereport(isServerStart ? FATAL : LOG,
+						errcode(ERRCODE_CONFIG_FILE_ERROR),
+						errmsg("unable to load certificate from pg_hosts.conf file"));
+				return -1;
+			}
+
+			/*
+			 * The parsing logic has already verified that the hostname exist
+			 * so we need not check that.  The passphrase command fields are
+			 * however optional so we need to check whether those were set.
+			 */
+			host_context = palloc0(sizeof(HostContext));
+			host_context->hostname = pstrdup(host->hostname);
+			host_context->context = tmp_context;
+			host_context->default_host = false;
+			if (host->ssl_passphrase_cmd != NULL)
+				host_context->ssl_passphrase = pstrdup(host->ssl_passphrase_cmd);
+			host_context->ssl_passphrase_support_reload = host->ssl_passphrase_reload;
+
+			/*
+			 * Set flag to remember whether CA store has been loaded into this
+			 * SSL_context.
+			 */
+			if (host->ssl_ca)
+				host_context->ssl_loaded_verify_locations = true;
+
+			contexts = lappend(contexts, host_context);
+		}
+	}
+
+	/* Make sure we have at least one certificate loaded */
+	if (list_length(contexts) < 1)
+	{
+		ereport(isServerStart ? FATAL : LOG,
+				(errcode(ERRCODE_CONFIG_FILE_ERROR),
+				 errmsg("no SSL contexts loaded")));
+		return -1;
+	}
+
+	return 0;
+}
+
+static SSL_CTX *
+ssl_init_context(bool isServerStart, HostsLine *host_line)
 {
 	SSL_CTX    *context;
 	int			ssl_ver_min = -1;
 	int			ssl_ver_max = -1;
 
+	const char *ctx_ssl_cert_file = host_line->ssl_cert;
+	const char *ctx_ssl_key_file = host_line->ssl_key;
+	const char *ctx_ssl_ca_file = host_line->ssl_ca;
+
 	/*
 	 * Create a new SSL context into which we'll load all the configuration
 	 * settings.  If we fail partway through, we can avoid memory leakage by
@@ -126,10 +290,17 @@ be_tls_init(bool isServerStart)
 	 */
 	SSL_CTX_set_mode(context, SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER);
 
+	/*
+	 * Install SNI TLS extension callback in case the server is configured to
+	 * validate hostnames.
+	 */
+	if (ssl_snimode != SSL_SNIMODE_OFF)
+		SSL_CTX_set_tlsext_servername_callback(context, sni_servername_cb);
+
 	/*
 	 * Call init hook (usually to set password callback)
 	 */
-	(*openssl_tls_init_hook) (context, isServerStart);
+	(*openssl_tls_init_hook) (context, isServerStart, host_line);
 
 	/* used by the callback */
 	ssl_is_server_start = isServerStart;
@@ -137,16 +308,16 @@ be_tls_init(bool isServerStart)
 	/*
 	 * Load and verify server's certificate and private key
 	 */
-	if (SSL_CTX_use_certificate_chain_file(context, ssl_cert_file) != 1)
+	if (SSL_CTX_use_certificate_chain_file(context, ctx_ssl_cert_file) != 1)
 	{
 		ereport(isServerStart ? FATAL : LOG,
 				(errcode(ERRCODE_CONFIG_FILE_ERROR),
 				 errmsg("could not load server certificate file \"%s\": %s",
-						ssl_cert_file, SSLerrmessage(ERR_get_error()))));
+						ctx_ssl_cert_file, SSLerrmessage(ERR_get_error()))));
 		goto error;
 	}
 
-	if (!check_ssl_key_file_permissions(ssl_key_file, isServerStart))
+	if (!check_ssl_key_file_permissions(ctx_ssl_key_file, isServerStart))
 		goto error;
 
 	/*
@@ -155,19 +326,19 @@ be_tls_init(bool isServerStart)
 	dummy_ssl_passwd_cb_called = false;
 
 	if (SSL_CTX_use_PrivateKey_file(context,
-									ssl_key_file,
+									ctx_ssl_key_file,
 									SSL_FILETYPE_PEM) != 1)
 	{
 		if (dummy_ssl_passwd_cb_called)
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("private key file \"%s\" cannot be reloaded because it requires a passphrase",
-							ssl_key_file)));
+							ctx_ssl_key_file)));
 		else
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("could not load private key file \"%s\": %s",
-							ssl_key_file, SSLerrmessage(ERR_get_error()))));
+							ctx_ssl_key_file, SSLerrmessage(ERR_get_error()))));
 		goto error;
 	}
 
@@ -319,17 +490,17 @@ be_tls_init(bool isServerStart)
 	/*
 	 * Load CA store, so we can verify client certificates if needed.
 	 */
-	if (ssl_ca_file[0])
+	if (ctx_ssl_ca_file[0])
 	{
 		STACK_OF(X509_NAME) * root_cert_list;
 
-		if (SSL_CTX_load_verify_locations(context, ssl_ca_file, NULL) != 1 ||
-			(root_cert_list = SSL_load_client_CA_file(ssl_ca_file)) == NULL)
+		if (SSL_CTX_load_verify_locations(context, ctx_ssl_ca_file, NULL) != 1 ||
+			(root_cert_list = SSL_load_client_CA_file(ctx_ssl_ca_file)) == NULL)
 		{
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("could not load root certificate file \"%s\": %s",
-							ssl_ca_file, SSLerrmessage(ERR_get_error()))));
+							ctx_ssl_ca_file, SSLerrmessage(ERR_get_error()))));
 			goto error;
 		}
 
@@ -401,38 +572,29 @@ be_tls_init(bool isServerStart)
 		}
 	}
 
-	/*
-	 * Success!  Replace any existing SSL_context.
-	 */
-	if (SSL_context)
-		SSL_CTX_free(SSL_context);
-
-	SSL_context = context;
-
-	/*
-	 * Set flag to remember whether CA store has been loaded into SSL_context.
-	 */
-	if (ssl_ca_file[0])
-		ssl_loaded_verify_locations = true;
-	else
-		ssl_loaded_verify_locations = false;
-
-	return 0;
+	return context;
 
 	/* Clean up by releasing working context. */
 error:
 	if (context)
 		SSL_CTX_free(context);
-	return -1;
+	return NULL;
 }
 
 void
 be_tls_destroy(void)
 {
-	if (SSL_context)
-		SSL_CTX_free(SSL_context);
+	ListCell   *cell;
+
+	foreach(cell, contexts)
+	{
+		HostContext *host_context = lfirst(cell);
+
+		SSL_CTX_free(host_context->context);
+		pfree(host_context);
+	}
+
 	SSL_context = NULL;
-	ssl_loaded_verify_locations = false;
 }
 
 int
@@ -759,6 +921,9 @@ be_tls_close(Port *port)
 		pfree(port->peer_dn);
 		port->peer_dn = NULL;
 	}
+
+	Host_context = NULL;
+	SSL_context = NULL;
 }
 
 ssize_t
@@ -1132,7 +1297,7 @@ ssl_external_passwd_cb(char *buf, int size, int rwflag, void *userdata)
 
 	Assert(rwflag == 0);
 
-	return run_ssl_passphrase_command(prompt, ssl_is_server_start, buf, size);
+	return run_ssl_passphrase_command(prompt, ssl_is_server_start, buf, size, userdata);
 }
 
 /*
@@ -1369,6 +1534,88 @@ alpn_cb(SSL *ssl,
 	}
 }
 
+static int
+sni_servername_cb(SSL *ssl, int *al, void *arg)
+{
+	const char *tlsext_hostname;
+
+	/*
+	 * Executing this callback when SNI is turned off indicates a programmer
+	 * error or something worse.
+	 */
+	Assert(ssl_snimode != SSL_SNIMODE_OFF);
+
+	tlsext_hostname = SSL_get_servername(ssl, TLSEXT_NAMETYPE_host_name);
+
+	/*
+	 * If there is no hostname set in the TLS extension, we have two options.
+	 * For ssl_snimode strict we error out since we cannot match a host config
+	 * for the connection.  For the default mode we fall back on the default
+	 * hostname configuration.
+	 */
+	if (!tlsext_hostname)
+	{
+		if (ssl_snimode == SSL_SNIMODE_STRICT)
+		{
+			ereport(COMMERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg("no hostname provided in callback")));
+			return SSL_TLSEXT_ERR_ALERT_FATAL;
+		}
+		else
+		{
+			Host_context = Default_context;
+			SSL_context = Host_context->context;
+			SSL_set_SSL_CTX(ssl, SSL_context);
+			return SSL_TLSEXT_ERR_OK;
+		}
+	}
+
+	/*
+	 * We have a requested hostname from the client, match against all entries
+	 * in the pg_hosts configuration to find a match.
+	 */
+	foreach_ptr(HostContext, host, contexts)
+	{
+		/*
+		 * For strict mode we will never want the default host so we can skip
+		 * past it immediately.
+		 */
+		if (ssl_snimode == SSL_SNIMODE_STRICT && host->default_host)
+			continue;
+
+		if (strcmp(host->hostname, tlsext_hostname) == 0)
+		{
+			Host_context = host;
+			SSL_context = host->context;
+			SSL_set_SSL_CTX(ssl, SSL_context);
+			return SSL_TLSEXT_ERR_OK;
+		}
+	}
+
+	/*
+	 * In ssl_snimode "strict" it's an error if there was no match for the
+	 * hostname in the TLS extension.  Terminate the connection.
+	 */
+	if (ssl_snimode == SSL_SNIMODE_STRICT)
+	{
+		ereport(COMMERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg("no matching pg_hosts entry found for hostname: \"%s\"",
+						tlsext_hostname)));
+		return SSL_TLSEXT_ERR_ALERT_FATAL;
+	}
+
+	/*
+	 * In ssl_snimode "default" we fall back on the default host configured in
+	 * postgresql.conf when no match is found in pg_hosts.conf.
+	 */
+	Host_context = Default_context;
+	SSL_context = Host_context->context;
+	SSL_set_SSL_CTX(ssl, SSL_context);
+	Assert(SSL_context);
+	return SSL_TLSEXT_ERR_OK;
+}
 
 /*
  * Set DH parameters for generating ephemeral DH keys.  The
@@ -1578,6 +1825,12 @@ be_tls_get_peer_serial(Port *port, char *ptr, size_t len)
 		ptr[0] = '\0';
 }
 
+bool
+be_tls_loaded_verify_locations(void)
+{
+	return Host_context->ssl_loaded_verify_locations;
+}
+
 char *
 be_tls_get_certificate_hash(Port *port, size_t *len)
 {
@@ -1771,17 +2024,23 @@ ssl_protocol_version_to_string(int v)
 
 
 static void
-default_openssl_tls_init(SSL_CTX *context, bool isServerStart)
+default_openssl_tls_init(SSL_CTX *context, bool isServerStart, HostsLine *host)
 {
 	if (isServerStart)
 	{
-		if (ssl_passphrase_command[0])
+		if (host->ssl_passphrase_cmd != NULL)
+		{
 			SSL_CTX_set_default_passwd_cb(context, ssl_external_passwd_cb);
+			SSL_CTX_set_default_passwd_cb_userdata(context, host->ssl_passphrase_cmd);
+		}
 	}
 	else
 	{
-		if (ssl_passphrase_command[0] && ssl_passphrase_command_supports_reload)
+		if (host->ssl_passphrase_cmd != NULL && host->ssl_passphrase_reload)
+		{
 			SSL_CTX_set_default_passwd_cb(context, ssl_external_passwd_cb);
+			SSL_CTX_set_default_passwd_cb_userdata(context, host->ssl_passphrase_cmd);
+		}
 		else
 
 			/*
@@ -1793,3 +2052,26 @@ default_openssl_tls_init(SSL_CTX *context, bool isServerStart)
 			SSL_CTX_set_default_passwd_cb(context, dummy_ssl_passwd_cb);
 	}
 }
+
+/*
+ * Cleanup function for when hostname configuration is reloaded from the
+ * pg_hosts.conf file, at that point we Must discard all existing contexts.
+ */
+static void
+free_contexts(void)
+{
+	if (contexts == NIL)
+		return;
+
+	foreach_ptr(HostContext, host, contexts)
+	{
+		if (host->hostname)
+			pfree(unconstify(char *, host->hostname));
+		if (host->ssl_passphrase)
+			pfree(unconstify(char *, host->ssl_passphrase));
+		SSL_CTX_free(host->context);
+	}
+
+	list_free_deep(contexts);
+	contexts = NIL;
+}
diff --git a/src/backend/libpq/be-secure.c b/src/backend/libpq/be-secure.c
index d723e74e813..1431f92e332 100644
--- a/src/backend/libpq/be-secure.c
+++ b/src/backend/libpq/be-secure.c
@@ -43,10 +43,6 @@ char	   *ssl_dh_params_file;
 char	   *ssl_passphrase_command;
 bool		ssl_passphrase_command_supports_reload;
 
-#ifdef USE_SSL
-bool		ssl_loaded_verify_locations = false;
-#endif
-
 /* GUC variable controlling SSL cipher list */
 char	   *SSLCipherSuites = NULL;
 char	   *SSLCipherList = NULL;
@@ -60,6 +56,8 @@ bool		SSLPreferServerCiphers;
 int			ssl_min_protocol_version = PG_TLS1_2_VERSION;
 int			ssl_max_protocol_version = PG_TLS_ANY;
 
+int			ssl_snimode = SSL_SNIMODE_DEFAULT;
+
 /* ------------------------------------------------------------ */
 /*			 Procedures common to all secure sessions			*/
 /* ------------------------------------------------------------ */
@@ -99,7 +97,7 @@ bool
 secure_loaded_verify_locations(void)
 {
 #ifdef USE_SSL
-	return ssl_loaded_verify_locations;
+	return be_tls_loaded_verify_locations();
 #else
 	return false;
 #endif
diff --git a/src/backend/libpq/meson.build b/src/backend/libpq/meson.build
index 31aa2faae1e..4f6ec13bc74 100644
--- a/src/backend/libpq/meson.build
+++ b/src/backend/libpq/meson.build
@@ -31,5 +31,6 @@ endif
 install_data(
   'pg_hba.conf.sample',
   'pg_ident.conf.sample',
+  'pg_hosts.conf.sample',
   install_dir: dir_data,
 )
diff --git a/src/backend/libpq/pg_hosts.conf.sample b/src/backend/libpq/pg_hosts.conf.sample
new file mode 100644
index 00000000000..5a47f9cae7d
--- /dev/null
+++ b/src/backend/libpq/pg_hosts.conf.sample
@@ -0,0 +1,4 @@
+# PostgreSQL SNI Hostname mappings
+# ================================
+
+# HOSTNAME       SSL CERTIFICATE             SSL KEY
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 46fdefebe35..ed670822ea3 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -55,6 +55,7 @@
 #define CONFIG_FILENAME "postgresql.conf"
 #define HBA_FILENAME	"pg_hba.conf"
 #define IDENT_FILENAME	"pg_ident.conf"
+#define HOSTS_FILENAME	"pg_hosts.conf"
 
 #ifdef EXEC_BACKEND
 #define CONFIG_EXEC_PARAMS "global/config_exec_params"
@@ -1968,6 +1969,31 @@ SelectConfigFiles(const char *userDoption, const char *progname)
 	}
 	SetConfigOption("ident_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
 
+	/*
+	 * Likewise for pg_hosts.conf
+	 */
+	if (HostsFileName)
+	{
+		fname = make_absolute_path(HostsFileName);
+		fname_is_malloced = true;
+	}
+	else if (configdir)
+	{
+		fname = guc_malloc(FATAL,
+						   strlen(configdir) + strlen(HOSTS_FILENAME) + 2);
+		sprintf(fname, "%s/%s", configdir, HOSTS_FILENAME);
+		fname_is_malloced = false;
+	}
+	else
+	{
+		write_stderr("%s does not know where to find the \"hosts\" configuration file.\n"
+					 "This can be specified as \"hosts_file\" in \"%s\", "
+					 "or by the -D invocation option, or by the "
+					 "PGDATA environment variable.\n",
+					 progname, ConfigFileName);
+	}
+	SetConfigOption("hosts_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
+
 	if (fname_is_malloced)
 		free(fname);
 	else
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index f137129209f..3339e829314 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -491,6 +491,13 @@ static const struct config_enum_entry file_copy_method_options[] = {
 	{NULL, 0, false}
 };
 
+static const struct config_enum_entry ssl_snimode_options[] = {
+	{"off", SSL_SNIMODE_OFF, false},
+	{"default", SSL_SNIMODE_DEFAULT, false},
+	{"strict", SSL_SNIMODE_STRICT, false},
+	{NULL, 0, false}
+};
+
 /*
  * Options for enum values stored in other modules
  */
@@ -555,6 +562,7 @@ char	   *cluster_name = "";
 char	   *ConfigFileName;
 char	   *HbaFileName;
 char	   *IdentFileName;
+char	   *HostsFileName;
 char	   *external_pid_file;
 
 char	   *application_name;
@@ -4787,6 +4795,17 @@ struct config_string ConfigureNamesString[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"hosts_file", PGC_POSTMASTER, FILE_LOCATIONS,
+			gettext_noop("Sets the server's \"hosts\" configuration file."),
+			NULL,
+			GUC_SUPERUSER_ONLY
+		},
+		&HostsFileName,
+		NULL,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"external_pid_file", PGC_POSTMASTER, FILE_LOCATIONS,
 			gettext_noop("Writes the postmaster PID to the specified file."),
@@ -5457,6 +5476,18 @@ struct config_enum ConfigureNamesEnum[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"ssl_snimode", PGC_SIGHUP, CONN_AUTH_SSL,
+			gettext_noop("Sets the SNI mode to use."),
+			NULL,
+			GUC_SUPERUSER_ONLY,
+		},
+		&ssl_snimode,
+		SSL_SNIMODE_DEFAULT,
+		ssl_snimode_options,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"recovery_init_sync_method", PGC_SIGHUP, ERROR_HANDLING_OPTIONS,
 			gettext_noop("Sets the method for synchronizing the data directory before crash recovery."),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index a9d8293474a..57b1be3c38f 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -45,6 +45,8 @@
 					# (change requires restart)
 #ident_file = 'ConfigDir/pg_ident.conf'	# ident configuration file
 					# (change requires restart)
+#hosts_file = 'ConfigDir/pg_hosts.conf' # hosts configuration file
+					# (change requires restart)
 
 # If external_pid_file is not explicitly set, no extra PID file is written.
 #external_pid_file = ''			# write an extra PID file
@@ -121,6 +123,7 @@
 #ssl_dh_params_file = ''
 #ssl_passphrase_command = ''
 #ssl_passphrase_command_supports_reload = off
+#ssl_snimode = default
 
 
 #------------------------------------------------------------------------------
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 92fe2f531f7..087cea4fffc 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -177,6 +177,7 @@ static int	encodingid;
 static char *bki_file;
 static char *hba_file;
 static char *ident_file;
+static char *hosts_file;
 static char *conf_file;
 static char *dictionary_file;
 static char *info_schema_file;
@@ -1530,6 +1531,14 @@ setup_config(void)
 
 	snprintf(path, sizeof(path), "%s/pg_ident.conf", pg_data);
 
+	writefile(path, conflines);
+	if (chmod(path, pg_file_create_mode) != 0)
+		pg_fatal("could not change permissions of \"%s\": %m", path);
+
+	/* pg_hosts.conf */
+	conflines = readfile(hosts_file);
+	snprintf(path, sizeof(path), "%s/pg_hosts.conf", pg_data);
+
 	writefile(path, conflines);
 	if (chmod(path, pg_file_create_mode) != 0)
 		pg_fatal("could not change permissions of \"%s\": %m", path);
@@ -2791,6 +2800,7 @@ setup_data_file_paths(void)
 	set_input(&bki_file, "postgres.bki");
 	set_input(&hba_file, "pg_hba.conf.sample");
 	set_input(&ident_file, "pg_ident.conf.sample");
+	set_input(&hosts_file, "pg_hosts.conf.sample");
 	set_input(&conf_file, "postgresql.conf.sample");
 	set_input(&dictionary_file, "snowball_create.sql");
 	set_input(&info_schema_file, "information_schema.sql");
@@ -2806,12 +2816,13 @@ setup_data_file_paths(void)
 				"PGDATA=%s\nshare_path=%s\nPGPATH=%s\n"
 				"POSTGRES_SUPERUSERNAME=%s\nPOSTGRES_BKI=%s\n"
 				"POSTGRESQL_CONF_SAMPLE=%s\n"
-				"PG_HBA_SAMPLE=%s\nPG_IDENT_SAMPLE=%s\n",
+				"PG_HBA_SAMPLE=%s\nPG_IDENT_SAMPLE=%s\n"
+				"PG_HOSTS_SAMPLE=%s\n",
 				PG_VERSION,
 				pg_data, share_path, bin_path,
 				username, bki_file,
 				conf_file,
-				hba_file, ident_file);
+				hba_file, ident_file, hosts_file);
 		if (show_setting)
 			exit(0);
 	}
@@ -2819,6 +2830,7 @@ setup_data_file_paths(void)
 	check_input(bki_file);
 	check_input(hba_file);
 	check_input(ident_file);
+	check_input(hosts_file);
 	check_input(conf_file);
 	check_input(dictionary_file);
 	check_input(info_schema_file);
diff --git a/src/include/libpq/hba.h b/src/include/libpq/hba.h
index 3657f182db3..3d8e33533b8 100644
--- a/src/include/libpq/hba.h
+++ b/src/include/libpq/hba.h
@@ -151,6 +151,25 @@ typedef struct IdentLine
 	AuthToken  *pg_user;
 } IdentLine;
 
+typedef struct HostsLine
+{
+	int			linenumber;
+
+	char	   *sourcefile;
+	char	   *rawline;
+
+	/* Required fields */
+	bool		default_host;
+	char	   *hostname;
+	char	   *ssl_key;
+	char	   *ssl_cert;
+	char	   *ssl_ca;
+
+	/* Optional fields */
+	char	   *ssl_passphrase_cmd;
+	bool		ssl_passphrase_reload;
+} HostsLine;
+
 /*
  * TokenizedAuthLine represents one line lexed from an authentication
  * configuration file.  Each item in the "fields" list is a sub-list of
diff --git a/src/include/libpq/libpq-be.h b/src/include/libpq/libpq-be.h
index d6e671a6382..e1631cb7b5c 100644
--- a/src/include/libpq/libpq-be.h
+++ b/src/include/libpq/libpq-be.h
@@ -320,6 +320,7 @@ extern const char *be_tls_get_cipher(Port *port);
 extern void be_tls_get_peer_subject_name(Port *port, char *ptr, size_t len);
 extern void be_tls_get_peer_issuer_name(Port *port, char *ptr, size_t len);
 extern void be_tls_get_peer_serial(Port *port, char *ptr, size_t len);
+extern bool be_tls_loaded_verify_locations(void);
 
 /*
  * Get the server certificate hash for SCRAM channel binding type
@@ -332,7 +333,7 @@ extern char *be_tls_get_certificate_hash(Port *port, size_t *len);
 
 /* init hook for SSL, the default sets the password callback if appropriate */
 #ifdef USE_OPENSSL
-typedef void (*openssl_tls_init_hook_typ) (SSL_CTX *context, bool isServerStart);
+typedef void (*openssl_tls_init_hook_typ) (SSL_CTX *context, bool isServerStart, HostsLine *host);
 extern PGDLLIMPORT openssl_tls_init_hook_typ openssl_tls_init_hook;
 #endif
 
diff --git a/src/include/libpq/libpq.h b/src/include/libpq/libpq.h
index aeb66ca40cf..5feed0eb0a4 100644
--- a/src/include/libpq/libpq.h
+++ b/src/include/libpq/libpq.h
@@ -107,6 +107,7 @@ extern PGDLLIMPORT char *ssl_crl_dir;
 extern PGDLLIMPORT char *ssl_key_file;
 extern PGDLLIMPORT int ssl_min_protocol_version;
 extern PGDLLIMPORT int ssl_max_protocol_version;
+extern PGDLLIMPORT int ssl_snimode;
 extern PGDLLIMPORT char *ssl_passphrase_command;
 extern PGDLLIMPORT bool ssl_passphrase_command_supports_reload;
 extern PGDLLIMPORT char *ssl_dh_params_file;
@@ -134,12 +135,20 @@ enum ssl_protocol_versions
 	PG_TLS1_3_VERSION,
 };
 
+enum ssl_snimode
+{
+	SSL_SNIMODE_OFF = 0,
+	SSL_SNIMODE_DEFAULT,
+	SSL_SNIMODE_STRICT
+};
+
 /*
  * prototypes for functions in be-secure-common.c
  */
 extern int	run_ssl_passphrase_command(const char *prompt, bool is_server_start,
-									   char *buf, int size);
+									   char *buf, int size, void *userdata);
 extern bool check_ssl_key_file_permissions(const char *ssl_key_file,
 										   bool isServerStart);
+extern List *load_hosts(void);
 
 #endif							/* LIBPQ_H */
diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index f619100467d..025e7e95e90 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -288,6 +288,7 @@ extern PGDLLIMPORT char *cluster_name;
 extern PGDLLIMPORT char *ConfigFileName;
 extern PGDLLIMPORT char *HbaFileName;
 extern PGDLLIMPORT char *IdentFileName;
+extern PGDLLIMPORT char *HostsFileName;
 extern PGDLLIMPORT char *external_pid_file;
 
 extern PGDLLIMPORT char *application_name;
diff --git a/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c b/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
index d5992149821..a85d85735cf 100644
--- a/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
+++ b/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
@@ -26,7 +26,7 @@ static char *ssl_passphrase = NULL;
 static int	rot13_passphrase(char *buf, int size, int rwflag, void *userdata);
 
 /* hook function to set the callback */
-static void set_rot13(SSL_CTX *context, bool isServerStart);
+static void set_rot13(SSL_CTX *context, bool isServerStart, HostsLine *host);
 
 /*
  * Module load callback
@@ -53,7 +53,7 @@ _PG_init(void)
 }
 
 static void
-set_rot13(SSL_CTX *context, bool isServerStart)
+set_rot13(SSL_CTX *context, bool isServerStart, HostsLine *host)
 {
 	/* warn if the user has set ssl_passphrase_command */
 	if (ssl_passphrase_command[0])
diff --git a/src/test/perl/PostgreSQL/Test/Cluster.pm b/src/test/perl/PostgreSQL/Test/Cluster.pm
index 35413f14019..a46ac325045 100644
--- a/src/test/perl/PostgreSQL/Test/Cluster.pm
+++ b/src/test/perl/PostgreSQL/Test/Cluster.pm
@@ -1302,6 +1302,27 @@ Wrapper for pg_ctl restart.
 With optional extra param fail_ok => 1, returns 0 for failure
 instead of bailing out.
 
+=over
+
+=item fail_ok => 1
+
+By default, failure terminates the entire F<prove> invocation.  If given,
+instead return 0 for failure instead of bailing out.
+
+=item log_unlike => B<pattern>
+
+When defined, the logfile is inspected for the presence of the fragment by
+matching the specified pattern. If the pattern matches agsinst the logfile a
+test failure will be logged.
+
+=item log_like => B<pattern>
+
+When defined, the logfile is inspected for the presence of the fragment by
+matching the pattern. If the pattern doesn't match a test failure will be
+logged.
+
+=back
+
 =cut
 
 sub restart
@@ -1314,6 +1335,8 @@ sub restart
 
 	print "### Restarting node \"$name\"\n";
 
+	my $log_location = -s $self->logfile;
+
 	# -w is now the default but having it here does no harm and helps
 	# compatibility with older versions.
 	$ret = PostgreSQL::Test::Utils::system_log(
@@ -1322,6 +1345,18 @@ sub restart
 		'--log' => $self->logfile,
 		'restart');
 
+	# Check for expected and/or unexpected log fragments if the caller
+	# specified such checks in the params
+	if (defined $params{log_unlike} || defined $params{log_like})
+	{
+		my $log =
+		  PostgreSQL::Test::Utils::slurp_file($self->logfile, $log_location);
+		unlike($log, $params{log_unlike}, "unexpected fragment found in log")
+			if defined $params{log_unlike};
+		like($log, $params{log_like}, "expected fragment not found in log")
+			if defined $params{log_like};
+	}
+
 	if ($ret != 0)
 	{
 		print "# pg_ctl restart failed; see logfile for details: "
diff --git a/src/test/ssl/meson.build b/src/test/ssl/meson.build
index d8e0fb518e0..e5a9402cd9c 100644
--- a/src/test/ssl/meson.build
+++ b/src/test/ssl/meson.build
@@ -13,6 +13,7 @@ tests += {
       't/001_ssltests.pl',
       't/002_scram.pl',
       't/003_sslinfo.pl',
+      't/004_sni.pl',
     ],
   },
 }
diff --git a/src/test/ssl/t/001_ssltests.pl b/src/test/ssl/t/001_ssltests.pl
index b2eb18d3e81..0f0f64b6c7c 100644
--- a/src/test/ssl/t/001_ssltests.pl
+++ b/src/test/ssl/t/001_ssltests.pl
@@ -51,8 +51,15 @@ my $SERVERHOSTCIDR = '127.0.0.1/32';
 my $supports_sslcertmode_require =
   check_pg_config("#define HAVE_SSL_CTX_SET_CERT_CB 1");
 
-# Allocation of base connection string shared among multiple tests.
-my $common_connstr;
+# Set of default settings for SSL parameters in connection string.  This
+# makes the tests protected against any defaults the environment may have
+# in ~/.postgresql/.
+my $default_ssl_connstr =
+  "sslkey=invalid sslcert=invalid sslrootcert=invalid sslcrl=invalid sslcrldir=invalid";
+
+# Base connection string shared among multiple tests.
+my $common_connstr =
+  "$default_ssl_connstr user=ssltestuser dbname=trustdb hostaddr=$SERVERHOSTADDR host=common-name.pg-ssltest.test";
 
 #### Set up the server.
 
@@ -85,7 +92,7 @@ switch_server_cert(
 	passphrase_cmd => 'echo wrongpassword',
 	restart => 'no');
 
-$result = $node->restart(fail_ok => 1);
+$result = $node->restart(fail_ok => 1, log_like => qr/could not load private key file/);
 is($result, 0,
 	'restart fails with password-protected key file with wrong password');
 
@@ -95,11 +102,16 @@ switch_server_cert(
 	cafile => 'root+client_ca',
 	keyfile => 'server-password',
 	passphrase_cmd => 'echo secret1',
+	passphrase_cmd_reload => 'yes',
 	restart => 'no');
 
-$result = $node->restart(fail_ok => 1);
+$result = $node->restart(fail_ok => 1, log_unlike => qr/could not load private key file/);
 is($result, 1, 'restart succeeds with password-protected key file');
 
+$node->connect_ok(
+	"$common_connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+
 # Test compatibility of SSL protocols.
 # TLSv1.1 is lower than TLSv1.2, so it won't work.
 $node->append_conf(
@@ -139,15 +151,6 @@ note "running client tests";
 
 switch_server_cert($node, certfile => 'server-cn-only');
 
-# Set of default settings for SSL parameters in connection string.  This
-# makes the tests protected against any defaults the environment may have
-# in ~/.postgresql/.
-my $default_ssl_connstr =
-  "sslkey=invalid sslcert=invalid sslrootcert=invalid sslcrl=invalid sslcrldir=invalid";
-
-$common_connstr =
-  "$default_ssl_connstr user=ssltestuser dbname=trustdb hostaddr=$SERVERHOSTADDR host=common-name.pg-ssltest.test";
-
 SKIP:
 {
 	skip "Keylogging is not supported with LibreSSL", 5 if $libressl;
diff --git a/src/test/ssl/t/004_sni.pl b/src/test/ssl/t/004_sni.pl
new file mode 100644
index 00000000000..b3b2821a2bd
--- /dev/null
+++ b/src/test/ssl/t/004_sni.pl
@@ -0,0 +1,175 @@
+
+# Copyright (c) 2024, PostgreSQL Global Development Group
+
+use strict;
+use warnings FATAL => 'all';
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+use FindBin;
+use lib $FindBin::RealBin;
+
+use SSL::Server;
+
+# This is the hostname used to connect to the server. This cannot be a
+# hostname, because the server certificate is always for the domain
+# postgresql-ssl-regression.test.
+my $SERVERHOSTADDR = '127.0.0.1';
+# This is the pattern to use in pg_hba.conf to match incoming connections.
+my $SERVERHOSTCIDR = '127.0.0.1/32';
+
+if ($ENV{with_ssl} ne 'openssl')
+{
+	plan skip_all => 'OpenSSL not supported by this build';
+}
+
+if (!$ENV{PG_TEST_EXTRA} || $ENV{PG_TEST_EXTRA} !~ /\bssl\b/)
+{
+	plan skip_all =>
+	  'Potentially unsafe test SSL not enabled in PG_TEST_EXTRA';
+}
+
+my $ssl_server = SSL::Server->new();
+
+my $node = PostgreSQL::Test::Cluster->new('primary');
+$node->init;
+
+# PGHOST is enforced here to set up the node, subsequent connections
+# will use a dedicated connection string.
+$ENV{PGHOST} = $node->host;
+$ENV{PGPORT} = $node->port;
+$node->start;
+
+$ssl_server->configure_test_server_for_ssl($node, $SERVERHOSTADDR,
+	$SERVERHOSTCIDR, 'trust');
+
+$ssl_server->switch_server_cert($node, certfile => 'server-cn-only');
+
+my $connstr =
+  "user=ssltestuser dbname=trustdb hostaddr=$SERVERHOSTADDR host=localhost sslsni=1";
+
+$node->append_conf('postgresql.conf', "ssl_snimode=default");
+$node->reload;
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"connect fails with fallback hostname, without intermediate",
+	expected_stderr => qr/certificate verify failed/);
+
+# example.org serves the server cert and its intermediate CA.
+$node->append_conf('pg_hosts.conf',
+	"example.org server-cn-only+server_ca.crt server-cn-only.key root_ca.crt"
+);
+$node->reload;
+
+$node->connect_ok(
+	"$connstr host=example.org sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"connect with configured hostname, serving intermediate server CA");
+
+$node->connect_fails(
+	"$connstr sslrootcert=invalid sslmode=verify-ca",
+	"connect without server root cert sslmode=verify-ca",
+	expected_stderr => qr/root certificate file "invalid" does not exist/);
+
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"connect still fails with fallback hostname, without intermediate",
+	expected_stderr => qr/certificate verify failed/);
+
+$node->connect_ok(
+	"$connstr host=localhost sslrootcert=ssl/root+server_ca.crt sslmode=verify-ca",
+	"connect with fallback hostname, intermediate included");
+
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	"localhost server-cn-only.crt server-cn-only.key root_ca.crt");
+$node->append_conf('postgresql.conf', "ssl_snimode=strict");
+$node->reload;
+
+$node->connect_fails(
+	"$connstr host=example.org sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with missing hostconfig and snimode=strict",
+	expected_stderr => qr/tlsv1 unrecognized name/);
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require sslsni=1",
+	"connect with correct server CA cert file sslmode=require");
+
+# Attempts at connecting without SNI when the server is using strict mode should
+# result in connection failure.
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require sslsni=0",
+	"connect with correct server CA cert file without SNI for strict mode",
+	expected_stderr => qr/tlsv1 unrecognized name/);
+
+# Reconfigure with broken configuration for the key passphrase, the server
+# should not start up
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo wrongpassword" on'
+);
+my $result = $node->restart(fail_ok => 1);
+is($result, 0,
+	'restart fails with password-protected key when using the wrong passphrase command'
+);
+
+# Reconfigure again but with the correct passphrase set
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo secret1" on'
+);
+$result = $node->restart(fail_ok => 1);
+is($result, 1,
+	'restart succeeds with password-protected key when using the correct passphrase command'
+);
+
+# Make sure connecting works, and try to stress the reload logic by issuing
+# subsequent reloads
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+$node->reload;
+$node->reload;
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"1 connect with correct server CA cert file sslmode=require");
+$node->reload;
+$node->reload;
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"1 connect with correct server CA cert file sslmode=require");
+
+# Test reloading a passphrase protected key without reloading support in the
+# passphrase hook. Connecting after restart should succeed but not after the
+# following reload.
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo secret1" off'
+);
+$result = $node->restart(fail_ok => 1);
+is($result, 1,
+	'restart succeeds with password-protected key when using the correct passphrase command'
+);
+SKIP:
+{
+	# Passphrase reloads must be enabled on Windows to succeed even without a
+	# restart
+	skip "Passphrase command reload required on Windows", 1 if ($windows_os);
+
+	$node->connect_ok(
+		"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+		"connect with correct server CA cert file sslmode=require");
+}
+
+$node->reload;
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect fails since the passphrase protected key cannot be reloaded");
+
+done_testing();
diff --git a/src/test/ssl/t/SSL/Server.pm b/src/test/ssl/t/SSL/Server.pm
index efbd0dafaf6..31e50c8722f 100644
--- a/src/test/ssl/t/SSL/Server.pm
+++ b/src/test/ssl/t/SSL/Server.pm
@@ -296,6 +296,11 @@ The CRL directory to use. Implementation is SSL backend specific.
 The passphrase command to use. If not set, an empty passphrase command will
 be set.
 
+=item passphrase_cmd_reload => B<value>
+
+Whether or not to allow passphrase command reloading. If set the passphrase
+command will set to allow reloading.
+
 =item restart => B<value>
 
 If set to 'no', the server won't be restarted after updating the settings.
@@ -327,6 +332,9 @@ sub switch_server_cert
 		"ssl_passphrase_command='" . $params{passphrase_cmd} . "'")
 	  if defined $params{passphrase_cmd};
 
+	$node->append_conf('sslconfig.conf', 'ssl_passphrase_command_supports_reload=on')
+	  if defined $params{passphrase_cmd_reload};
+
 	return if (defined($params{restart}) && $params{restart} eq 'no');
 
 	$node->restart;
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index a13e8162890..5b61b9a1d4d 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -1202,6 +1202,8 @@ HeapTupleHeader
 HeapTupleHeaderData
 HeapTupleTableSlot
 HistControl
+HostContext
+HostsLine
 HotStandbyState
 I32
 ICU_Convert_Func
-- 
2.39.3 (Apple Git-146)

From 542ffd45c914597821f258e4b838371e03abc32e Mon Sep 17 00:00:00 2001
From: Daniel Gustafsson <dgustafsson@postgresql.org>
Date: Mon, 2 Jun 2025 10:25:08 +0200
Subject: [PATCH v9] Serverside SNI support for libpq

Experimental support for serverside SNI support in libpq, a new config
file $datadir/pg_hosts.conf is used for configuring which certicate and
key should be used for which hostname. A new GUC, ssl_snimode, is added
which controls how the hostname TLS extension is handled. The possible
values are off, default and strict:

  - off: pg_hosts.conf is not parsed and the hostname TLS extension is
    not inspected at all. The normal SSL GUCs for certificates and keys
    are used.
  - default: pg_hosts.conf is loaded as well as the normal GUCs. If no
    match for the TLS extension hostname is found in pg_hosts the cert
    and key from the postgresql.conf GUCs is used as the default (used
    as a wildcard host).
  - strict: only pg_hosts.conf is loaded and the TLS extension hostname
    MUST be passed and MUST have a match in the configuration, else the
    connection is refused.

CRL file(s) are applied from postgresql.conf to all configured hostnames.

Author: Daniel Gustafsson <daniel@yesql.se>
Reviewed-by: Cary Huang <cary.huang@highgo.ca>
Reviewed-by: Jacob Champion <jacob.champion@enterprisedb.com>
Discussion: https://postgr.es/m/1C81CD0D-407E-44F9-833A-DD0331C202E5@yesql.se
---
 doc/src/sgml/config.sgml                      |  66 +++
 doc/src/sgml/runtime.sgml                     |  67 +++
 src/backend/Makefile                          |   1 +
 src/backend/libpq/be-secure-common.c          | 204 +++++++++-
 src/backend/libpq/be-secure-openssl.c         | 382 ++++++++++++++++--
 src/backend/libpq/be-secure.c                 |   8 +-
 src/backend/libpq/meson.build                 |   1 +
 src/backend/libpq/pg_hosts.conf.sample        |   4 +
 src/backend/utils/misc/guc.c                  |  31 ++
 src/backend/utils/misc/guc_parameters.dat     |  15 +
 src/backend/utils/misc/guc_tables.c           |   8 +
 src/backend/utils/misc/postgresql.conf.sample |   3 +
 src/bin/initdb/initdb.c                       |  15 +-
 src/include/libpq/hba.h                       |  19 +
 src/include/libpq/libpq-be.h                  |   3 +-
 src/include/libpq/libpq.h                     |  11 +-
 src/include/utils/guc.h                       |   1 +
 .../ssl_passphrase_func.c                     |   4 +-
 src/test/perl/PostgreSQL/Test/Cluster.pm      |  35 ++
 src/test/ssl/meson.build                      |   1 +
 src/test/ssl/t/004_sni.pl                     | 175 ++++++++
 src/tools/pgindent/typedefs.list              |   2 +
 22 files changed, 1005 insertions(+), 51 deletions(-)
 create mode 100644 src/backend/libpq/pg_hosts.conf.sample
 create mode 100644 src/test/ssl/t/004_sni.pl

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 683f7c36f46..ed6d42a1561 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1694,6 +1694,72 @@ include_dir 'conf.d'
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry id="guc-ssl-snimode" xreflabel="ssl_snimode">
+      <term><varname>ssl_snimode</varname> (<type>enum</type>)
+      <indexterm>
+       <primary><varname>ssl_snimode</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        This parameter determines if the server will inspect the <acronym>SNI</acronym> TLS extension
+        when establishing the connection, and how it should be interpreted.
+        Valid values are currently: <literal>off</literal>, <literal>default</literal> and <literal>strict</literal>.
+       </para>
+       <para>
+        <variablelist>
+         <varlistentry id="guc-ssl-snimode-off">
+          <term><literal>off</literal></term>
+          <listitem>
+           <para>
+            SNI is not enabled and no configuration from
+            <filename>pg_hosts.conf</filename> is loaded.  Configuration of SSL
+            for all connections is done with <xref linkend="guc-ssl-cert-file"/>,
+            <xref linkend="guc-ssl-key-file"/> and <xref linkend="guc-ssl-ca-file"/>.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry id="guc-ssl-snimode-default">
+          <term><literal>default</literal></term>
+          <listitem>
+           <para>
+            SNI is enabled and hostname configuration is loaded from
+            <filename>pg_hosts.conf</filename>. <xref linkend="guc-ssl-cert-file"/>,
+            <xref linkend="guc-ssl-key-file"/> and <xref linkend="guc-ssl-ca-file"/>
+            are loaded as the default configuration.  Connections specifying
+            <xref linkend="libpq-connect-sslsni"/> to <literal>1</literal>
+            will be attempted using the default configuration if the hostname
+            is missing in <filename>pg_hosts.conf</filename>.  If the hostname
+            matches an entry from <filename>pg_hosts.conf</filename>, then the
+            configuration from that entry will be used for setting up the
+            connection.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry id="guc-ssl-snimode-strict">
+          <term><literal>strict</literal></term>
+          <listitem>
+           <para>
+            SNI is enabled and all connections are required to set <xref
+            linkend="libpq-connect-sslsni"/> to <literal>1</literal> and
+            specify a hostname matching an entry in
+            <filename>pg_hosts.conf</filename>. Any connection without <xref
+            linkend="libpq-connect-sslsni"/> or with a hostname missing from
+            <filename>pg_hosts.conf</filename> will be rejected.
+            <xref linkend="guc-ssl-cert-file"/>,
+            <xref linkend="guc-ssl-key-file"/> and <xref linkend="guc-ssl-ca-file"/>
+            are loaded in order to drive the handshake until the appropriate
+            configuration has been selected.
+           </para>
+          </listitem>
+         </varlistentry>
+        </variablelist>
+       </para>
+      </listitem>
+     </varlistentry>
     </variablelist>
     </sect2>
    </sect1>
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index 0c60bafac63..2693dcb81ad 100644
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -2445,6 +2445,12 @@ pg_dumpall -p 5432 | psql -d postgres -p 5433
       <entry>client certificate must not be on this list</entry>
      </row>
 
+     <row>
+      <entry><filename>$PGDATA/pg_hosts.conf</filename></entry>
+      <entry>SNI configuration</entry>
+      <entry>defines which certificates to use for which server hostname</entry>
+     </row>
+
     </tbody>
    </tgroup>
   </table>
@@ -2572,6 +2578,67 @@ openssl x509 -req -in server.csr -text -days 365 \
    </para>
   </sect2>
 
+  <sect2 id="ssl-sni">
+   <title>SNI Configuration</title>
+
+   <para>
+    <productname>PostgreSQL</productname> can be configured for
+    <acronym>SNI</acronym> using the <filename>pg_hosts.conf</filename>
+    configuration file. <productname>PostgreSQL</productname> inspects the TLS
+    hostname extension in the SSL connection handshake, and selects the right
+    TLS certificate, key and CA certificate to use for the connection.
+   </para>
+
+   <para>
+    SNI configuration is defined in the hosts configuration file,
+    <filename>pg_hosts.conf</filename>, which is stored in the clusters
+    data directory.  The hosts configuration file contains lines of the general
+    forms:
+<synopsis>
+<replaceable>hostname</replaceable> <replaceable>SSL_certificate</replaceable> <replaceable>SSL_key</replaceable> <replaceable>SSL_CA_certificate</replaceable> <replaceable>SSL_passphrase_cmd</replaceable> <replaceable>SSL_passphrase_cmd_reload</replaceable>
+<replaceable>include</replaceable> <replaceable>file</replaceable>
+<replaceable>include_if_exists</replaceable> <replaceable>file</replaceable>
+<replaceable>include_dir</replaceable> <replaceable>directory</replaceable>
+</synopsis>
+    Comments, whitespace and line continuations are handled in the same way as
+    in <filename>pg_hba.conf</filename>.  <replaceable>hostname</replaceable>
+    is matched against the hostname TLS extension in the SSL handshake.
+    <replaceable>SSL_certificate</replaceable>,
+    <replaceable>SSL_key</replaceable>,
+    <replaceable>SSL_CA_certificate</replaceable>,
+    <replaceable>SSL_passphrase_cmd</replaceable>, and
+    <replaceable>SSL_passphrase_cmd_reload</replaceable>
+    are treated like
+    <xref linkend="guc-ssl-cert-file"/>,
+    <xref linkend="guc-ssl-key-file"/>,
+    <xref linkend="guc-ssl-ca-file"/>,
+    <xref linkend="guc-ssl-passphrase-command"/>, and
+    <xref linkend="guc-ssl-passphrase-command-supports-reload"/> respectively.
+    All fields except <replaceable>SSL_passphrase_cmd</replaceable> and
+    <replaceable>SSL_passphrase_cmd_reload</replaceable> are required. If
+    <replaceable>SSL_passphrase_cmd</replaceable> is defined but not
+    <replaceable>SSL_passphrase_cmd_reload</replaceable> then the default
+    value for <replaceable>SSL_passphrase_cmd_reload</replaceable> is
+    <literal>off</literal>.
+   </para>
+   <para>
+    The SSL configuration from <filename>postgresql.conf</filename> is used
+    in order to set up the TLS handshake such that the hostname extension can
+    be inspected.  When <xref linkend="guc-ssl-snimode"/> is set to
+    <literal>default</literal> this configuration will be the default fallback
+    if no matching hostname is found in <filename>pg_hosts.conf</filename>.  If
+    <xref linkend="guc-ssl-snimode"/> is set to <literal>strict</literal> it
+    will only be used to for the handshake until the hostname is inspected, it
+    will not be used for the connection.
+   </para>
+   <para>
+    It is currently not possible to set different <literal>clientname</literal>
+    values for the different certificates.  Any <literal>clientname</literal>
+    setting in <filename>pg_hba.conf</filename> will be applied during
+    authentication regardless of which set of certificates have been loaded
+    via an SNI enabled connection.
+   </para>
+  </sect2>
  </sect1>
 
  <sect1 id="gssapi-enc">
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 7344c8c7f5c..2d1691c7950 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -187,6 +187,7 @@ endif
 	$(MAKE) -C utils install-data
 	$(INSTALL_DATA) $(srcdir)/libpq/pg_hba.conf.sample '$(DESTDIR)$(datadir)/pg_hba.conf.sample'
 	$(INSTALL_DATA) $(srcdir)/libpq/pg_ident.conf.sample '$(DESTDIR)$(datadir)/pg_ident.conf.sample'
+	$(INSTALL_DATA) $(srcdir)/libpq/pg_hosts.conf.sample '$(DESTDIR)$(datadir)/pg_hosts.conf.sample'
 	$(INSTALL_DATA) $(srcdir)/utils/misc/postgresql.conf.sample '$(DESTDIR)$(datadir)/postgresql.conf.sample'
 
 ifeq ($(with_llvm), yes)
diff --git a/src/backend/libpq/be-secure-common.c b/src/backend/libpq/be-secure-common.c
index e8b837d1fa7..2d9baff92b5 100644
--- a/src/backend/libpq/be-secure-common.c
+++ b/src/backend/libpq/be-secure-common.c
@@ -24,32 +24,40 @@
 
 #include "common/percentrepl.h"
 #include "common/string.h"
+#include "libpq/hba.h"
 #include "libpq/libpq.h"
 #include "storage/fd.h"
+#include "utils/guc.h"
+#include "utils/memutils.h"
+
+static HostsLine *parse_hosts_line(TokenizedAuthLine *tok_line, int elevel);
 
 /*
  * Run ssl_passphrase_command
  *
  * prompt will be substituted for %p.  is_server_start determines the loglevel
- * of error messages.
+ * of error messages from executing the command, the loglevel for failures in
+ * param substitution will be ERROR regardless of is_server_start.  The actual
+ * command used depends on the configuration for the current host.
  *
  * The result will be put in buffer buf, which is of size size.  The return
  * value is the length of the actual result.
  */
 int
-run_ssl_passphrase_command(const char *prompt, bool is_server_start, char *buf, int size)
+run_ssl_passphrase_command(const char *prompt, bool is_server_start, char *buf, int size, void *userdata)
 {
 	int			loglevel = is_server_start ? ERROR : LOG;
 	char	   *command;
 	FILE	   *fh;
 	int			pclose_rc;
 	size_t		len = 0;
+	char	   *cmd = (char *) userdata;
 
 	Assert(prompt);
 	Assert(size > 0);
 	buf[0] = '\0';
 
-	command = replace_percent_placeholders(ssl_passphrase_command, "ssl_passphrase_command", "p", prompt);
+	command = replace_percent_placeholders(cmd, "ssl_passphrase_command", "p", prompt);
 
 	fh = OpenPipeStream(command, "r");
 	if (fh == NULL)
@@ -175,3 +183,193 @@ check_ssl_key_file_permissions(const char *ssl_key_file, bool isServerStart)
 
 	return true;
 }
+
+/*
+ * parse_hosts_line
+ *
+ * Parses a loaded line from the pg_hosts.conf configuration and pulls out the
+ * hostname, certificate, key and CA parts in order to build an SNI config in
+ * the TLS backend. Validation of the parsed values is left for the TLS backend
+ * to implement.
+ */
+static HostsLine *
+parse_hosts_line(TokenizedAuthLine *tok_line, int elevel)
+{
+	HostsLine  *parsedline;
+	List	   *tokens;
+	ListCell   *field;
+	AuthToken  *token;
+
+	parsedline = palloc0(sizeof(HostsLine));
+	parsedline->sourcefile = pstrdup(tok_line->file_name);
+	parsedline->linenumber = tok_line->line_num;
+	parsedline->rawline = pstrdup(tok_line->raw_line);
+
+	/* Initialize optional fields */
+	parsedline->ssl_passphrase_cmd = NULL;
+	parsedline->ssl_passphrase_reload = false;
+
+	/* Hostname */
+	field = list_head(tok_line->fields);
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->hostname = pstrdup(token->string);
+
+	/* SSL Certificate (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_cert = pstrdup(token->string);
+
+	/* SSL key (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_key = pstrdup(token->string);
+
+	/* SSL CA (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_ca = pstrdup(token->string);
+
+	/* SSL Passphrase Command (optional) */
+	field = lnext(tok_line->fields, field);
+	if (field)
+	{
+		tokens = lfirst(field);
+		token = linitial(tokens);
+		parsedline->ssl_passphrase_cmd = pstrdup(token->string);
+
+		/*
+		 * SSL Passphrase Command support reload (optional). This field is
+		 * only supported if there was a passphrase command parsed first, so
+		 * nest it under the previous token.
+		 */
+		field = lnext(tok_line->fields, field);
+		if (field)
+		{
+			tokens = lfirst(field);
+			token = linitial(tokens);
+
+			if (token->string[0] == '1'
+				|| pg_strcasecmp(token->string, "true") == 0
+				|| pg_strcasecmp(token->string, "on") == 0
+				|| pg_strcasecmp(token->string, "yes") == 0)
+				parsedline->ssl_passphrase_reload = true;
+			else if (token->string[0] == '0'
+					 || pg_strcasecmp(token->string, "false") == 0
+					 || pg_strcasecmp(token->string, "off") == 0
+					 || pg_strcasecmp(token->string, "no") == 0)
+				parsedline->ssl_passphrase_reload = false;
+			else
+			{
+				ereport(elevel,
+						errcode(ERRCODE_CONFIG_FILE_ERROR),
+						errmsg("incorrect syntax for boolean value SSL_passphrase_cmd_reload"),
+						errcontext("line %d of configuration file \"%s\"",
+								   tok_line->line_num, tok_line->file_name));
+				return NULL;
+			}
+		}
+	}
+
+	return parsedline;
+}
+
+/*
+ * load_hosts
+ *
+ * Reads pg_hosts.conf and passes back a List of parsed lines, or NIL in case
+ * of errors.
+ */
+List *
+load_hosts(void)
+{
+	FILE	   *file;
+	ListCell   *line;
+	List	   *hosts_lines = NIL;
+	List	   *parsed_lines = NIL;
+	HostsLine  *newline;
+	bool		ok = true;
+
+	/*
+	 * This is not an auth file per se, but it is using the same file format
+	 * as the pg_hba and pg_ident files and thus the same code infrastructure.
+	 * A future TODO might be to rename the supporting code with a more
+	 * generic name?
+	 */
+	file = open_auth_file(HostsFileName, LOG, 0, NULL);
+	if (file == NULL)
+	{
+		/* An error has already been logged so no need to add one here */
+		return NIL;
+	}
+
+	tokenize_auth_file(HostsFileName, file, &hosts_lines, LOG, 0);
+
+	foreach(line, hosts_lines)
+	{
+		TokenizedAuthLine *tok_line = (TokenizedAuthLine *) lfirst(line);
+
+		if (tok_line->err_msg != NULL)
+		{
+			ok = false;
+			continue;
+		}
+
+		if ((newline = parse_hosts_line(tok_line, LOG)) == NULL)
+		{
+			ok = false;
+			continue;
+		}
+
+		parsed_lines = lappend(parsed_lines, newline);
+	}
+
+	free_auth_file(file, 0);
+
+	/*
+	 * If we didn't find any SNI configuration then that's not an error since
+	 * the pg_hosts file is additive to the default SSL configuration.
+	 */
+	if (ok && parsed_lines == NIL)
+	{
+		ereport(DEBUG1,
+				errmsg("SNI configuration not found in configuration file  \"%s\"",
+					   HostsFileName));
+		return NIL;
+	}
+
+	if (!ok)
+		return NIL;
+
+	return parsed_lines;
+}
diff --git a/src/backend/libpq/be-secure-openssl.c b/src/backend/libpq/be-secure-openssl.c
index c8b63ef8249..ea3ba012b86 100644
--- a/src/backend/libpq/be-secure-openssl.c
+++ b/src/backend/libpq/be-secure-openssl.c
@@ -51,9 +51,17 @@
 #endif
 #include <openssl/x509v3.h>
 
+typedef struct HostContext
+{
+	const char *hostname;
+	const char *ssl_passphrase;
+	SSL_CTX    *context;
+	bool		default_host;
+	bool		ssl_loaded_verify_locations;
+} HostContext;
 
 /* default init hook can be overridden by a shared library */
-static void default_openssl_tls_init(SSL_CTX *context, bool isServerStart);
+static void default_openssl_tls_init(SSL_CTX *context, bool isServerStart, HostsLine *hosts);
 openssl_tls_init_hook_typ openssl_tls_init_hook = default_openssl_tls_init;
 
 static int	port_bio_read(BIO *h, char *buf, int size);
@@ -73,6 +81,7 @@ static int	alpn_cb(SSL *ssl,
 					const unsigned char *in,
 					unsigned int inlen,
 					void *userdata);
+static int	sni_servername_cb(SSL *ssl, int *al, void *arg);
 static bool initialize_dh(SSL_CTX *context, bool isServerStart);
 static bool initialize_ecdh(SSL_CTX *context, bool isServerStart);
 static const char *SSLerrmessageExt(unsigned long ecode, const char *replacement);
@@ -80,12 +89,17 @@ static const char *SSLerrmessage(unsigned long ecode);
 
 static char *X509_NAME_to_cstring(X509_NAME *name);
 
+static List *contexts = NIL;
 static SSL_CTX *SSL_context = NULL;
+static HostContext *Default_context = NULL;
+static HostContext *Host_context = NULL;
 static bool dummy_ssl_passwd_cb_called = false;
 static bool ssl_is_server_start;
 
 static int	ssl_protocol_version_to_openssl(int v);
 static const char *ssl_protocol_version_to_string(int v);
+static SSL_CTX *ssl_init_context(bool isServerStart, HostsLine *host);
+static void free_contexts(void);
 
 /* for passing data back from verify_cb() */
 static const char *cert_errdetail;
@@ -96,11 +110,173 @@ static const char *cert_errdetail;
 
 int
 be_tls_init(bool isServerStart)
+{
+	SSL_CTX    *ctx;
+	List	   *sni_hosts = NIL;
+	HostsLine	line;
+
+	/*
+	 * If there are contexts loaded when we init they must be released. This
+	 * should only be possible during configuration reloads and not when the
+	 * server is starting up.
+	 */
+	if (contexts != NIL)
+	{
+		Assert(!isServerStart);
+		free_contexts();
+		Host_context = NULL;
+		SSL_context = NULL;
+		Default_context = NULL;
+	}
+
+	/*
+	 * Load the default configuration from postgresql.conf such that we have a
+	 * context to either be used for the entire connection, or drive the
+	 * handshake until the SNI callback replace it with a configuration from
+	 * the pg_hosts.conf file.
+	 */
+	line.ssl_cert = ssl_cert_file;
+	line.ssl_key = ssl_key_file;
+	line.ssl_ca = ssl_ca_file;
+	line.ssl_passphrase_cmd = ssl_passphrase_command;
+	line.ssl_passphrase_reload = ssl_passphrase_command_supports_reload;
+
+	ctx = ssl_init_context(isServerStart, &line);
+	if (ctx == NULL)
+	{
+		ereport(isServerStart ? FATAL : LOG,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("could not load default certificate"));
+		return -1;
+	}
+
+	Default_context = palloc0(sizeof(HostContext));
+	Default_context->hostname = pstrdup("*");
+	Default_context->context = ctx;
+	Default_context->default_host = true;
+
+	/*
+	 * Set flag to remember whether CA store has been loaded into SSL_context.
+	 */
+	if (ssl_ca_file[0])
+		Default_context->ssl_loaded_verify_locations = true;
+
+	/*
+	 * While the default context isn't matched against when searching for host
+	 * contexts we still add it to the list to ensure that cleanup code can
+	 * iterate over a single structure to clean up everything.
+	 */
+	contexts = lappend(contexts, Default_context);
+
+	/*
+	 * Install the default context to use as the initial context for the
+	 * connection.  This might be replaced in the SNI callback if there is a
+	 * host/snimode match, but we need something to drive the hand- shake till
+	 * then.
+	 */
+	Host_context = Default_context;
+	SSL_context = Host_context->context;
+
+	/*
+	 * In default or strict ssl_snimode we load all certificates/keys which
+	 * are configured in pg_hosts.conf.  In strict mode it is considered a
+	 * fatal error in case there are no configured entries.
+	 */
+	if (ssl_snimode == SSL_SNIMODE_STRICT || ssl_snimode == SSL_SNIMODE_DEFAULT)
+	{
+		ListCell   *line;
+		MemoryContext oldcxt;
+		MemoryContext hostcxt;
+
+		hostcxt = AllocSetContextCreate(CurrentMemoryContext,
+										"hosts file parser context",
+										ALLOCSET_SMALL_SIZES);
+
+		/*
+		 * Load pg_hosts.conf and parse each row, returning the set of hosts
+		 * as a list.  Make sure to allocate the parsed rows in a temporary
+		 * memory context such that we can avoid memory leaks.
+		 */
+		oldcxt = MemoryContextSwitchTo(hostcxt);
+		sni_hosts = load_hosts();
+		MemoryContextSwitchTo(oldcxt);
+
+		/*
+		 * In strict ssl_snimode there needs to be at least one configured
+		 * host in the pg_hosts file since the default fallback context isn't
+		 * allowed to connect with.
+		 */
+		if (sni_hosts == NIL && ssl_snimode == SSL_SNIMODE_STRICT)
+		{
+			MemoryContextDelete(hostcxt);
+			ereport(isServerStart ? FATAL : LOG,
+					errcode(ERRCODE_CONFIG_FILE_ERROR),
+					errmsg("could not load %s", "pg_hosts.conf"));
+			return -1;
+		}
+
+		foreach(line, sni_hosts)
+		{
+			HostContext *host_context;
+			HostsLine  *host = lfirst(line);
+			static SSL_CTX *tmp_context = NULL;
+
+			tmp_context = ssl_init_context(isServerStart, host);
+			if (tmp_context == NULL)
+			{
+				MemoryContextDelete(hostcxt);
+				ereport(isServerStart ? FATAL : LOG,
+						errcode(ERRCODE_CONFIG_FILE_ERROR),
+						errmsg("unable to load certificate from pg_hosts.conf file"));
+				return -1;
+			}
+
+			/*
+			 * The parsing logic has already verified that the hostname exist
+			 * so we need not check that.  The passphrase command fields are
+			 * however optional so we need to check whether those were set.
+			 */
+			host_context = palloc0(sizeof(HostContext));
+			host_context->hostname = pstrdup(host->hostname);
+			host_context->context = tmp_context;
+			host_context->default_host = false;
+
+			/*
+			 * Set flag to remember whether CA store has been loaded into this
+			 * SSL_context.
+			 */
+			if (host->ssl_ca)
+				host_context->ssl_loaded_verify_locations = true;
+
+			contexts = lappend(contexts, host_context);
+		}
+
+		MemoryContextDelete(hostcxt);
+	}
+
+	/* Make sure we have at least one certificate loaded */
+	if (list_length(contexts) < 1)
+	{
+		ereport(isServerStart ? FATAL : LOG,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("no SSL contexts loaded"));
+		return -1;
+	}
+
+	return 0;
+}
+
+static SSL_CTX *
+ssl_init_context(bool isServerStart, HostsLine *host_line)
 {
 	SSL_CTX    *context;
 	int			ssl_ver_min = -1;
 	int			ssl_ver_max = -1;
 
+	const char *ctx_ssl_cert_file = host_line->ssl_cert;
+	const char *ctx_ssl_key_file = host_line->ssl_key;
+	const char *ctx_ssl_ca_file = host_line->ssl_ca;
+
 	/*
 	 * Create a new SSL context into which we'll load all the configuration
 	 * settings.  If we fail partway through, we can avoid memory leakage by
@@ -126,10 +302,17 @@ be_tls_init(bool isServerStart)
 	 */
 	SSL_CTX_set_mode(context, SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER);
 
+	/*
+	 * Install SNI TLS extension callback in case the server is configured to
+	 * validate hostnames.
+	 */
+	if (ssl_snimode != SSL_SNIMODE_OFF)
+		SSL_CTX_set_tlsext_servername_callback(context, sni_servername_cb);
+
 	/*
 	 * Call init hook (usually to set password callback)
 	 */
-	(*openssl_tls_init_hook) (context, isServerStart);
+	(*openssl_tls_init_hook) (context, isServerStart, host_line);
 
 	/* used by the callback */
 	ssl_is_server_start = isServerStart;
@@ -137,16 +320,16 @@ be_tls_init(bool isServerStart)
 	/*
 	 * Load and verify server's certificate and private key
 	 */
-	if (SSL_CTX_use_certificate_chain_file(context, ssl_cert_file) != 1)
+	if (SSL_CTX_use_certificate_chain_file(context, ctx_ssl_cert_file) != 1)
 	{
 		ereport(isServerStart ? FATAL : LOG,
 				(errcode(ERRCODE_CONFIG_FILE_ERROR),
 				 errmsg("could not load server certificate file \"%s\": %s",
-						ssl_cert_file, SSLerrmessage(ERR_get_error()))));
+						ctx_ssl_cert_file, SSLerrmessage(ERR_get_error()))));
 		goto error;
 	}
 
-	if (!check_ssl_key_file_permissions(ssl_key_file, isServerStart))
+	if (!check_ssl_key_file_permissions(ctx_ssl_key_file, isServerStart))
 		goto error;
 
 	/*
@@ -155,19 +338,19 @@ be_tls_init(bool isServerStart)
 	dummy_ssl_passwd_cb_called = false;
 
 	if (SSL_CTX_use_PrivateKey_file(context,
-									ssl_key_file,
+									ctx_ssl_key_file,
 									SSL_FILETYPE_PEM) != 1)
 	{
 		if (dummy_ssl_passwd_cb_called)
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("private key file \"%s\" cannot be reloaded because it requires a passphrase",
-							ssl_key_file)));
+							ctx_ssl_key_file)));
 		else
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("could not load private key file \"%s\": %s",
-							ssl_key_file, SSLerrmessage(ERR_get_error()))));
+							ctx_ssl_key_file, SSLerrmessage(ERR_get_error()))));
 		goto error;
 	}
 
@@ -319,17 +502,17 @@ be_tls_init(bool isServerStart)
 	/*
 	 * Load CA store, so we can verify client certificates if needed.
 	 */
-	if (ssl_ca_file[0])
+	if (ctx_ssl_ca_file[0])
 	{
 		STACK_OF(X509_NAME) * root_cert_list;
 
-		if (SSL_CTX_load_verify_locations(context, ssl_ca_file, NULL) != 1 ||
-			(root_cert_list = SSL_load_client_CA_file(ssl_ca_file)) == NULL)
+		if (SSL_CTX_load_verify_locations(context, ctx_ssl_ca_file, NULL) != 1 ||
+			(root_cert_list = SSL_load_client_CA_file(ctx_ssl_ca_file)) == NULL)
 		{
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("could not load root certificate file \"%s\": %s",
-							ssl_ca_file, SSLerrmessage(ERR_get_error()))));
+							ctx_ssl_ca_file, SSLerrmessage(ERR_get_error()))));
 			goto error;
 		}
 
@@ -401,38 +584,29 @@ be_tls_init(bool isServerStart)
 		}
 	}
 
-	/*
-	 * Success!  Replace any existing SSL_context.
-	 */
-	if (SSL_context)
-		SSL_CTX_free(SSL_context);
-
-	SSL_context = context;
-
-	/*
-	 * Set flag to remember whether CA store has been loaded into SSL_context.
-	 */
-	if (ssl_ca_file[0])
-		ssl_loaded_verify_locations = true;
-	else
-		ssl_loaded_verify_locations = false;
-
-	return 0;
+	return context;
 
 	/* Clean up by releasing working context. */
 error:
 	if (context)
 		SSL_CTX_free(context);
-	return -1;
+	return NULL;
 }
 
 void
 be_tls_destroy(void)
 {
-	if (SSL_context)
-		SSL_CTX_free(SSL_context);
+	ListCell   *cell;
+
+	foreach(cell, contexts)
+	{
+		HostContext *host_context = lfirst(cell);
+
+		SSL_CTX_free(host_context->context);
+		pfree(host_context);
+	}
+
 	SSL_context = NULL;
-	ssl_loaded_verify_locations = false;
 }
 
 int
@@ -759,6 +933,9 @@ be_tls_close(Port *port)
 		pfree(port->peer_dn);
 		port->peer_dn = NULL;
 	}
+
+	Host_context = NULL;
+	SSL_context = NULL;
 }
 
 ssize_t
@@ -1132,7 +1309,7 @@ ssl_external_passwd_cb(char *buf, int size, int rwflag, void *userdata)
 
 	Assert(rwflag == 0);
 
-	return run_ssl_passphrase_command(prompt, ssl_is_server_start, buf, size);
+	return run_ssl_passphrase_command(prompt, ssl_is_server_start, buf, size, userdata);
 }
 
 /*
@@ -1369,6 +1546,104 @@ alpn_cb(SSL *ssl,
 	}
 }
 
+/*
+ * sni_servername_cb
+ *
+ * Callback executed by OpenSSL during handshake in case the server has been
+ * configured to validate hostnames.  Depending on the SNI mode we either
+ * require a perfect match, or we allow to fallback to a default configuration.
+ * Returning SSL_TLSEXT_ERR_ALERT_FATAL to OpenSSL will immediately terminate
+ * the handshake.
+ */
+static int
+sni_servername_cb(SSL *ssl, int *al, void *arg)
+{
+	const char *tlsext_hostname;
+
+	/*
+	 * Executing this callback when SNI is turned off indicates a programmer
+	 * error or something worse.  Throw an assertion to catch during testing
+	 * but also ensure to terminate the connection in non-assert builds, even
+	 * though this should never happen, just to be on the safe side.
+	 */
+	if (ssl_snimode == SSL_SNIMODE_OFF)
+	{
+		Assert(false);
+		return SSL_TLSEXT_ERR_ALERT_FATAL;
+	}
+
+	tlsext_hostname = SSL_get_servername(ssl, TLSEXT_NAMETYPE_host_name);
+
+	/*
+	 * If there is no hostname set in the TLS extension, we have two options.
+	 * For ssl_snimode strict we error out since we cannot match a host config
+	 * for the connection.  For the default mode we fall back on the default
+	 * hostname configuration.
+	 */
+	if (!tlsext_hostname)
+	{
+		if (ssl_snimode == SSL_SNIMODE_STRICT)
+		{
+			ereport(COMMERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg("no hostname provided in callback")));
+			return SSL_TLSEXT_ERR_ALERT_FATAL;
+		}
+		else
+		{
+			Host_context = Default_context;
+			SSL_context = Host_context->context;
+			SSL_set_SSL_CTX(ssl, SSL_context);
+			return SSL_TLSEXT_ERR_OK;
+		}
+	}
+
+	/*
+	 * We have a requested hostname from the client, match against all entries
+	 * in the pg_hosts configuration to find a match.
+	 */
+	foreach_ptr(HostContext, host, contexts)
+	{
+		/*
+		 * For strict mode we will never want the default host so we can skip
+		 * past it immediately.
+		 */
+		if (ssl_snimode == SSL_SNIMODE_STRICT && host->default_host)
+			continue;
+
+		if (strcmp(host->hostname, tlsext_hostname) == 0)
+		{
+			Host_context = host;
+			SSL_context = host->context;
+			SSL_set_SSL_CTX(ssl, SSL_context);
+			return SSL_TLSEXT_ERR_OK;
+		}
+	}
+
+	/*
+	 * At this point we know that the requested hostname isn't configured in
+	 * the pg_hosts file.  In ssl_snimode "strict" it's an error if there was
+	 * no match for the hostname in the TLS extension so terminate the
+	 * connection.
+	 */
+	if (ssl_snimode == SSL_SNIMODE_STRICT)
+	{
+		ereport(COMMERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg("no matching pg_hosts entry found for hostname: \"%s\"",
+						tlsext_hostname)));
+		return SSL_TLSEXT_ERR_ALERT_FATAL;
+	}
+
+	/*
+	 * In ssl_snimode "default" we fall back on the default host configured in
+	 * postgresql.conf when no match is found in pg_hosts.conf.
+	 */
+	Host_context = Default_context;
+	SSL_context = Host_context->context;
+	SSL_set_SSL_CTX(ssl, SSL_context);
+	return SSL_TLSEXT_ERR_OK;
+}
 
 /*
  * Set DH parameters for generating ephemeral DH keys.  The
@@ -1578,6 +1853,12 @@ be_tls_get_peer_serial(Port *port, char *ptr, size_t len)
 		ptr[0] = '\0';
 }
 
+bool
+be_tls_loaded_verify_locations(void)
+{
+	return Host_context->ssl_loaded_verify_locations;
+}
+
 char *
 be_tls_get_certificate_hash(Port *port, size_t *len)
 {
@@ -1771,17 +2052,23 @@ ssl_protocol_version_to_string(int v)
 
 
 static void
-default_openssl_tls_init(SSL_CTX *context, bool isServerStart)
+default_openssl_tls_init(SSL_CTX *context, bool isServerStart, HostsLine *host)
 {
 	if (isServerStart)
 	{
-		if (ssl_passphrase_command[0])
+		if (host->ssl_passphrase_cmd != NULL)
+		{
 			SSL_CTX_set_default_passwd_cb(context, ssl_external_passwd_cb);
+			SSL_CTX_set_default_passwd_cb_userdata(context, host->ssl_passphrase_cmd);
+		}
 	}
 	else
 	{
-		if (ssl_passphrase_command[0] && ssl_passphrase_command_supports_reload)
+		if (host->ssl_passphrase_cmd != NULL && host->ssl_passphrase_reload)
+		{
 			SSL_CTX_set_default_passwd_cb(context, ssl_external_passwd_cb);
+			SSL_CTX_set_default_passwd_cb_userdata(context, host->ssl_passphrase_cmd);
+		}
 		else
 
 			/*
@@ -1793,3 +2080,24 @@ default_openssl_tls_init(SSL_CTX *context, bool isServerStart)
 			SSL_CTX_set_default_passwd_cb(context, dummy_ssl_passwd_cb);
 	}
 }
+
+/*
+ * Cleanup function for when hostname configuration is reloaded from the
+ * pg_hosts.conf file, at that point we Must discard all existing contexts.
+ */
+static void
+free_contexts(void)
+{
+	if (contexts == NIL)
+		return;
+
+	foreach_ptr(HostContext, host, contexts)
+	{
+		if (host->hostname)
+			pfree(unconstify(char *, host->hostname));
+		SSL_CTX_free(host->context);
+	}
+
+	list_free_deep(contexts);
+	contexts = NIL;
+}
diff --git a/src/backend/libpq/be-secure.c b/src/backend/libpq/be-secure.c
index d723e74e813..1431f92e332 100644
--- a/src/backend/libpq/be-secure.c
+++ b/src/backend/libpq/be-secure.c
@@ -43,10 +43,6 @@ char	   *ssl_dh_params_file;
 char	   *ssl_passphrase_command;
 bool		ssl_passphrase_command_supports_reload;
 
-#ifdef USE_SSL
-bool		ssl_loaded_verify_locations = false;
-#endif
-
 /* GUC variable controlling SSL cipher list */
 char	   *SSLCipherSuites = NULL;
 char	   *SSLCipherList = NULL;
@@ -60,6 +56,8 @@ bool		SSLPreferServerCiphers;
 int			ssl_min_protocol_version = PG_TLS1_2_VERSION;
 int			ssl_max_protocol_version = PG_TLS_ANY;
 
+int			ssl_snimode = SSL_SNIMODE_DEFAULT;
+
 /* ------------------------------------------------------------ */
 /*			 Procedures common to all secure sessions			*/
 /* ------------------------------------------------------------ */
@@ -99,7 +97,7 @@ bool
 secure_loaded_verify_locations(void)
 {
 #ifdef USE_SSL
-	return ssl_loaded_verify_locations;
+	return be_tls_loaded_verify_locations();
 #else
 	return false;
 #endif
diff --git a/src/backend/libpq/meson.build b/src/backend/libpq/meson.build
index 31aa2faae1e..4f6ec13bc74 100644
--- a/src/backend/libpq/meson.build
+++ b/src/backend/libpq/meson.build
@@ -31,5 +31,6 @@ endif
 install_data(
   'pg_hba.conf.sample',
   'pg_ident.conf.sample',
+  'pg_hosts.conf.sample',
   install_dir: dir_data,
 )
diff --git a/src/backend/libpq/pg_hosts.conf.sample b/src/backend/libpq/pg_hosts.conf.sample
new file mode 100644
index 00000000000..5a47f9cae7d
--- /dev/null
+++ b/src/backend/libpq/pg_hosts.conf.sample
@@ -0,0 +1,4 @@
+# PostgreSQL SNI Hostname mappings
+# ================================
+
+# HOSTNAME       SSL CERTIFICATE             SSL KEY
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 679846da42c..ec92c0739b3 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -56,6 +56,7 @@
 #define CONFIG_FILENAME "postgresql.conf"
 #define HBA_FILENAME	"pg_hba.conf"
 #define IDENT_FILENAME	"pg_ident.conf"
+#define HOSTS_FILENAME	"pg_hosts.conf"
 
 #ifdef EXEC_BACKEND
 #define CONFIG_EXEC_PARAMS "global/config_exec_params"
@@ -1838,6 +1839,36 @@ SelectConfigFiles(const char *userDoption, const char *progname)
 	}
 	SetConfigOption("ident_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
 
+	if (fname_is_malloced)
+		free(fname);
+	else
+		guc_free(fname);
+
+	/*
+	 * Likewise for pg_hosts.conf.
+	 */
+	if (HostsFileName)
+	{
+		fname = make_absolute_path(HostsFileName);
+		fname_is_malloced = true;
+	}
+	else if (configdir)
+	{
+		fname = guc_malloc(FATAL,
+						   strlen(configdir) + strlen(HOSTS_FILENAME) + 2);
+		sprintf(fname, "%s/%s", configdir, HOSTS_FILENAME);
+		fname_is_malloced = false;
+	}
+	else
+	{
+		write_stderr("%s does not know where to find the \"hosts\" configuration file.\n"
+					 "This can be specified as \"hosts_file\" in \"%s\", "
+					 "or by the -D invocation option, or by the "
+					 "PGDATA environment variable.\n",
+					 progname, ConfigFileName);
+	}
+	SetConfigOption("hosts_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
+
 	if (fname_is_malloced)
 		free(fname);
 	else
diff --git a/src/backend/utils/misc/guc_parameters.dat b/src/backend/utils/misc/guc_parameters.dat
index 1128167c025..186ac634dae 100644
--- a/src/backend/utils/misc/guc_parameters.dat
+++ b/src/backend/utils/misc/guc_parameters.dat
@@ -1160,6 +1160,13 @@
   boot_val => 'NULL',
 },
 
+{ name => 'hosts_file', type => 'string', context => 'PGC_POSTMASTER', group => 'FILE_LOCATIONS',
+  short_desc => 'Sets the server\'s "hosts" configuration file.',
+  flags => 'GUC_SUPERUSER_ONLY',
+  variable => 'HostsFileName',
+  boot_val => 'NULL',
+},
+
 { name => 'hot_standby', type => 'bool', context => 'PGC_POSTMASTER', group => 'REPLICATION_STANDBY',
   short_desc => 'Allows connections and queries during recovery.',
   variable => 'EnableHotStandby',
@@ -2735,6 +2742,14 @@
   max => '0',
 },
 
+{ name => 'ssl_snimode', type => 'enum', context => 'PGC_SIGHUP', group => 'CONN_AUTH_SSL',
+  short_desc => 'Sets the SNI mode to use for the server.',
+  flags => 'GUC_SUPERUSER_ONLY',
+  variable => 'ssl_snimode',
+  boot_val => 'SSL_SNIMODE_DEFAULT',
+  options => 'ssl_snimode_options',
+},
+
 { name => 'ssl_tls13_ciphers', type => 'string', context => 'PGC_SIGHUP', group => 'CONN_AUTH_SSL',
   short_desc => 'Sets the list of allowed TLSv1.3 cipher suites.',
   long_desc => 'An empty string means use the default cipher suites.',
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index 0209b2067a2..d429c658054 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -491,6 +491,13 @@ static const struct config_enum_entry file_copy_method_options[] = {
 	{NULL, 0, false}
 };
 
+static const struct config_enum_entry ssl_snimode_options[] = {
+	{"off", SSL_SNIMODE_OFF, false},
+	{"default", SSL_SNIMODE_DEFAULT, false},
+	{"strict", SSL_SNIMODE_STRICT, false},
+	{NULL, 0, false}
+};
+
 /*
  * Options for enum values stored in other modules
  */
@@ -556,6 +563,7 @@ char	   *cluster_name = "";
 char	   *ConfigFileName;
 char	   *HbaFileName;
 char	   *IdentFileName;
+char	   *HostsFileName;
 char	   *external_pid_file;
 
 char	   *application_name;
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index f62b61967ef..5828516c4e3 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -45,6 +45,8 @@
 					# (change requires restart)
 #ident_file = 'ConfigDir/pg_ident.conf'	# ident configuration file
 					# (change requires restart)
+#hosts_file = 'ConfigDir/pg_hosts.conf' # hosts configuration file
+					# (change requires restart)
 
 # If external_pid_file is not explicitly set, no extra PID file is written.
 #external_pid_file = ''			# write an extra PID file
@@ -121,6 +123,7 @@
 #ssl_dh_params_file = ''
 #ssl_passphrase_command = ''
 #ssl_passphrase_command_supports_reload = off
+#ssl_snimode = default
 
 
 #------------------------------------------------------------------------------
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 92fe2f531f7..c953f24a58d 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -177,6 +177,7 @@ static int	encodingid;
 static char *bki_file;
 static char *hba_file;
 static char *ident_file;
+static char *hosts_file;
 static char *conf_file;
 static char *dictionary_file;
 static char *info_schema_file;
@@ -1530,6 +1531,14 @@ setup_config(void)
 
 	snprintf(path, sizeof(path), "%s/pg_ident.conf", pg_data);
 
+	writefile(path, conflines);
+	if (chmod(path, pg_file_create_mode) != 0)
+		pg_fatal("could not change permissions of \"%s\": %m", path);
+
+	/* pg_hosts.conf */
+	conflines = readfile(hosts_file);
+	snprintf(path, sizeof(path), "%s/pg_hosts.conf", pg_data);
+
 	writefile(path, conflines);
 	if (chmod(path, pg_file_create_mode) != 0)
 		pg_fatal("could not change permissions of \"%s\": %m", path);
@@ -2791,6 +2800,7 @@ setup_data_file_paths(void)
 	set_input(&bki_file, "postgres.bki");
 	set_input(&hba_file, "pg_hba.conf.sample");
 	set_input(&ident_file, "pg_ident.conf.sample");
+	set_input(&hosts_file, "pg_hosts.conf.sample");
 	set_input(&conf_file, "postgresql.conf.sample");
 	set_input(&dictionary_file, "snowball_create.sql");
 	set_input(&info_schema_file, "information_schema.sql");
@@ -2806,12 +2816,12 @@ setup_data_file_paths(void)
 				"PGDATA=%s\nshare_path=%s\nPGPATH=%s\n"
 				"POSTGRES_SUPERUSERNAME=%s\nPOSTGRES_BKI=%s\n"
 				"POSTGRESQL_CONF_SAMPLE=%s\n"
-				"PG_HBA_SAMPLE=%s\nPG_IDENT_SAMPLE=%s\n",
+				"PG_HBA_SAMPLE=%s\nPG_IDENT_SAMPLE=%s\nPG_HOSTS_SAMPLE=%s\n",
 				PG_VERSION,
 				pg_data, share_path, bin_path,
 				username, bki_file,
 				conf_file,
-				hba_file, ident_file);
+				hba_file, ident_file, hosts_file);
 		if (show_setting)
 			exit(0);
 	}
@@ -2819,6 +2829,7 @@ setup_data_file_paths(void)
 	check_input(bki_file);
 	check_input(hba_file);
 	check_input(ident_file);
+	check_input(hosts_file);
 	check_input(conf_file);
 	check_input(dictionary_file);
 	check_input(info_schema_file);
diff --git a/src/include/libpq/hba.h b/src/include/libpq/hba.h
index e3748d3c8c9..c96818549cc 100644
--- a/src/include/libpq/hba.h
+++ b/src/include/libpq/hba.h
@@ -151,6 +151,25 @@ typedef struct IdentLine
 	AuthToken  *pg_user;
 } IdentLine;
 
+typedef struct HostsLine
+{
+	int			linenumber;
+
+	char	   *sourcefile;
+	char	   *rawline;
+
+	/* Required fields */
+	bool		default_host;
+	char	   *hostname;
+	char	   *ssl_key;
+	char	   *ssl_cert;
+	char	   *ssl_ca;
+
+	/* Optional fields */
+	char	   *ssl_passphrase_cmd;
+	bool		ssl_passphrase_reload;
+} HostsLine;
+
 /*
  * TokenizedAuthLine represents one line lexed from an authentication
  * configuration file.  Each item in the "fields" list is a sub-list of
diff --git a/src/include/libpq/libpq-be.h b/src/include/libpq/libpq-be.h
index d6e671a6382..e1631cb7b5c 100644
--- a/src/include/libpq/libpq-be.h
+++ b/src/include/libpq/libpq-be.h
@@ -320,6 +320,7 @@ extern const char *be_tls_get_cipher(Port *port);
 extern void be_tls_get_peer_subject_name(Port *port, char *ptr, size_t len);
 extern void be_tls_get_peer_issuer_name(Port *port, char *ptr, size_t len);
 extern void be_tls_get_peer_serial(Port *port, char *ptr, size_t len);
+extern bool be_tls_loaded_verify_locations(void);
 
 /*
  * Get the server certificate hash for SCRAM channel binding type
@@ -332,7 +333,7 @@ extern char *be_tls_get_certificate_hash(Port *port, size_t *len);
 
 /* init hook for SSL, the default sets the password callback if appropriate */
 #ifdef USE_OPENSSL
-typedef void (*openssl_tls_init_hook_typ) (SSL_CTX *context, bool isServerStart);
+typedef void (*openssl_tls_init_hook_typ) (SSL_CTX *context, bool isServerStart, HostsLine *host);
 extern PGDLLIMPORT openssl_tls_init_hook_typ openssl_tls_init_hook;
 #endif
 
diff --git a/src/include/libpq/libpq.h b/src/include/libpq/libpq.h
index 5af005ad779..fe2d431291a 100644
--- a/src/include/libpq/libpq.h
+++ b/src/include/libpq/libpq.h
@@ -107,6 +107,7 @@ extern PGDLLIMPORT char *ssl_crl_dir;
 extern PGDLLIMPORT char *ssl_key_file;
 extern PGDLLIMPORT int ssl_min_protocol_version;
 extern PGDLLIMPORT int ssl_max_protocol_version;
+extern PGDLLIMPORT int ssl_snimode;
 extern PGDLLIMPORT char *ssl_passphrase_command;
 extern PGDLLIMPORT bool ssl_passphrase_command_supports_reload;
 extern PGDLLIMPORT char *ssl_dh_params_file;
@@ -152,12 +153,20 @@ enum ssl_protocol_versions
 	PG_TLS1_3_VERSION,
 };
 
+enum ssl_snimode
+{
+	SSL_SNIMODE_OFF = 0,
+	SSL_SNIMODE_DEFAULT,
+	SSL_SNIMODE_STRICT
+};
+
 /*
  * prototypes for functions in be-secure-common.c
  */
 extern int	run_ssl_passphrase_command(const char *prompt, bool is_server_start,
-									   char *buf, int size);
+									   char *buf, int size, void *userdata);
 extern bool check_ssl_key_file_permissions(const char *ssl_key_file,
 										   bool isServerStart);
+extern List *load_hosts(void);
 
 #endif							/* LIBPQ_H */
diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index f21ec37da89..8f08a38b789 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -312,6 +312,7 @@ extern PGDLLIMPORT char *cluster_name;
 extern PGDLLIMPORT char *ConfigFileName;
 extern PGDLLIMPORT char *HbaFileName;
 extern PGDLLIMPORT char *IdentFileName;
+extern PGDLLIMPORT char *HostsFileName;
 extern PGDLLIMPORT char *external_pid_file;
 
 extern PGDLLIMPORT char *application_name;
diff --git a/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c b/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
index d5992149821..a85d85735cf 100644
--- a/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
+++ b/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
@@ -26,7 +26,7 @@ static char *ssl_passphrase = NULL;
 static int	rot13_passphrase(char *buf, int size, int rwflag, void *userdata);
 
 /* hook function to set the callback */
-static void set_rot13(SSL_CTX *context, bool isServerStart);
+static void set_rot13(SSL_CTX *context, bool isServerStart, HostsLine *host);
 
 /*
  * Module load callback
@@ -53,7 +53,7 @@ _PG_init(void)
 }
 
 static void
-set_rot13(SSL_CTX *context, bool isServerStart)
+set_rot13(SSL_CTX *context, bool isServerStart, HostsLine *host)
 {
 	/* warn if the user has set ssl_passphrase_command */
 	if (ssl_passphrase_command[0])
diff --git a/src/test/perl/PostgreSQL/Test/Cluster.pm b/src/test/perl/PostgreSQL/Test/Cluster.pm
index 35413f14019..a46ac325045 100644
--- a/src/test/perl/PostgreSQL/Test/Cluster.pm
+++ b/src/test/perl/PostgreSQL/Test/Cluster.pm
@@ -1302,6 +1302,27 @@ Wrapper for pg_ctl restart.
 With optional extra param fail_ok => 1, returns 0 for failure
 instead of bailing out.
 
+=over
+
+=item fail_ok => 1
+
+By default, failure terminates the entire F<prove> invocation.  If given,
+instead return 0 for failure instead of bailing out.
+
+=item log_unlike => B<pattern>
+
+When defined, the logfile is inspected for the presence of the fragment by
+matching the specified pattern. If the pattern matches agsinst the logfile a
+test failure will be logged.
+
+=item log_like => B<pattern>
+
+When defined, the logfile is inspected for the presence of the fragment by
+matching the pattern. If the pattern doesn't match a test failure will be
+logged.
+
+=back
+
 =cut
 
 sub restart
@@ -1314,6 +1335,8 @@ sub restart
 
 	print "### Restarting node \"$name\"\n";
 
+	my $log_location = -s $self->logfile;
+
 	# -w is now the default but having it here does no harm and helps
 	# compatibility with older versions.
 	$ret = PostgreSQL::Test::Utils::system_log(
@@ -1322,6 +1345,18 @@ sub restart
 		'--log' => $self->logfile,
 		'restart');
 
+	# Check for expected and/or unexpected log fragments if the caller
+	# specified such checks in the params
+	if (defined $params{log_unlike} || defined $params{log_like})
+	{
+		my $log =
+		  PostgreSQL::Test::Utils::slurp_file($self->logfile, $log_location);
+		unlike($log, $params{log_unlike}, "unexpected fragment found in log")
+			if defined $params{log_unlike};
+		like($log, $params{log_like}, "expected fragment not found in log")
+			if defined $params{log_like};
+	}
+
 	if ($ret != 0)
 	{
 		print "# pg_ctl restart failed; see logfile for details: "
diff --git a/src/test/ssl/meson.build b/src/test/ssl/meson.build
index d8e0fb518e0..e5a9402cd9c 100644
--- a/src/test/ssl/meson.build
+++ b/src/test/ssl/meson.build
@@ -13,6 +13,7 @@ tests += {
       't/001_ssltests.pl',
       't/002_scram.pl',
       't/003_sslinfo.pl',
+      't/004_sni.pl',
     ],
   },
 }
diff --git a/src/test/ssl/t/004_sni.pl b/src/test/ssl/t/004_sni.pl
new file mode 100644
index 00000000000..b3b2821a2bd
--- /dev/null
+++ b/src/test/ssl/t/004_sni.pl
@@ -0,0 +1,175 @@
+
+# Copyright (c) 2024, PostgreSQL Global Development Group
+
+use strict;
+use warnings FATAL => 'all';
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+use FindBin;
+use lib $FindBin::RealBin;
+
+use SSL::Server;
+
+# This is the hostname used to connect to the server. This cannot be a
+# hostname, because the server certificate is always for the domain
+# postgresql-ssl-regression.test.
+my $SERVERHOSTADDR = '127.0.0.1';
+# This is the pattern to use in pg_hba.conf to match incoming connections.
+my $SERVERHOSTCIDR = '127.0.0.1/32';
+
+if ($ENV{with_ssl} ne 'openssl')
+{
+	plan skip_all => 'OpenSSL not supported by this build';
+}
+
+if (!$ENV{PG_TEST_EXTRA} || $ENV{PG_TEST_EXTRA} !~ /\bssl\b/)
+{
+	plan skip_all =>
+	  'Potentially unsafe test SSL not enabled in PG_TEST_EXTRA';
+}
+
+my $ssl_server = SSL::Server->new();
+
+my $node = PostgreSQL::Test::Cluster->new('primary');
+$node->init;
+
+# PGHOST is enforced here to set up the node, subsequent connections
+# will use a dedicated connection string.
+$ENV{PGHOST} = $node->host;
+$ENV{PGPORT} = $node->port;
+$node->start;
+
+$ssl_server->configure_test_server_for_ssl($node, $SERVERHOSTADDR,
+	$SERVERHOSTCIDR, 'trust');
+
+$ssl_server->switch_server_cert($node, certfile => 'server-cn-only');
+
+my $connstr =
+  "user=ssltestuser dbname=trustdb hostaddr=$SERVERHOSTADDR host=localhost sslsni=1";
+
+$node->append_conf('postgresql.conf', "ssl_snimode=default");
+$node->reload;
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"connect fails with fallback hostname, without intermediate",
+	expected_stderr => qr/certificate verify failed/);
+
+# example.org serves the server cert and its intermediate CA.
+$node->append_conf('pg_hosts.conf',
+	"example.org server-cn-only+server_ca.crt server-cn-only.key root_ca.crt"
+);
+$node->reload;
+
+$node->connect_ok(
+	"$connstr host=example.org sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"connect with configured hostname, serving intermediate server CA");
+
+$node->connect_fails(
+	"$connstr sslrootcert=invalid sslmode=verify-ca",
+	"connect without server root cert sslmode=verify-ca",
+	expected_stderr => qr/root certificate file "invalid" does not exist/);
+
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"connect still fails with fallback hostname, without intermediate",
+	expected_stderr => qr/certificate verify failed/);
+
+$node->connect_ok(
+	"$connstr host=localhost sslrootcert=ssl/root+server_ca.crt sslmode=verify-ca",
+	"connect with fallback hostname, intermediate included");
+
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	"localhost server-cn-only.crt server-cn-only.key root_ca.crt");
+$node->append_conf('postgresql.conf', "ssl_snimode=strict");
+$node->reload;
+
+$node->connect_fails(
+	"$connstr host=example.org sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with missing hostconfig and snimode=strict",
+	expected_stderr => qr/tlsv1 unrecognized name/);
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require sslsni=1",
+	"connect with correct server CA cert file sslmode=require");
+
+# Attempts at connecting without SNI when the server is using strict mode should
+# result in connection failure.
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require sslsni=0",
+	"connect with correct server CA cert file without SNI for strict mode",
+	expected_stderr => qr/tlsv1 unrecognized name/);
+
+# Reconfigure with broken configuration for the key passphrase, the server
+# should not start up
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo wrongpassword" on'
+);
+my $result = $node->restart(fail_ok => 1);
+is($result, 0,
+	'restart fails with password-protected key when using the wrong passphrase command'
+);
+
+# Reconfigure again but with the correct passphrase set
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo secret1" on'
+);
+$result = $node->restart(fail_ok => 1);
+is($result, 1,
+	'restart succeeds with password-protected key when using the correct passphrase command'
+);
+
+# Make sure connecting works, and try to stress the reload logic by issuing
+# subsequent reloads
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+$node->reload;
+$node->reload;
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"1 connect with correct server CA cert file sslmode=require");
+$node->reload;
+$node->reload;
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"1 connect with correct server CA cert file sslmode=require");
+
+# Test reloading a passphrase protected key without reloading support in the
+# passphrase hook. Connecting after restart should succeed but not after the
+# following reload.
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo secret1" off'
+);
+$result = $node->restart(fail_ok => 1);
+is($result, 1,
+	'restart succeeds with password-protected key when using the correct passphrase command'
+);
+SKIP:
+{
+	# Passphrase reloads must be enabled on Windows to succeed even without a
+	# restart
+	skip "Passphrase command reload required on Windows", 1 if ($windows_os);
+
+	$node->connect_ok(
+		"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+		"connect with correct server CA cert file sslmode=require");
+}
+
+$node->reload;
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect fails since the passphrase protected key cannot be reloaded");
+
+done_testing();
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 432509277c9..fc66acb2f12 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -1206,6 +1206,8 @@ HeapTupleHeader
 HeapTupleHeaderData
 HeapTupleTableSlot
 HistControl
+HostContext
+HostsLine
 HotStandbyState
 I32
 ICU_Convert_Func
-- 
2.39.3 (Apple Git-146)

From 11984e057105c89d7f02f8f0be2a736ababee1f1 Mon Sep 17 00:00:00 2001
From: Daniel Gustafsson <dgustafsson@postgresql.org>
Date: Mon, 24 Nov 2025 15:52:27 +0100
Subject: [PATCH v10] Serverside SNI support for libpq

Experimental support for serverside SNI support in libpq, a new config
file $datadir/pg_hosts.conf is used for configuring which certicate and
key should be used for which hostname. A new GUC, ssl_snimode, is added
which controls how the hostname TLS extension is handled. The possible
values are off, default and strict:

  - off: pg_hosts.conf is not parsed and the hostname TLS extension is
    not inspected at all. The normal SSL GUCs for certificates and keys
    are used.
  - default: pg_hosts.conf is loaded as well as the normal GUCs. If no
    match for the TLS extension hostname is found in pg_hosts the cert
    and key from the postgresql.conf GUCs is used as the default (used
    as a wildcard host).
  - strict: only pg_hosts.conf is loaded and the TLS extension hostname
    MUST be passed and MUST have a match in the configuration, else the
    connection is refused.

CRL file(s) are applied from postgresql.conf to all configured hostnames.

Author: Daniel Gustafsson <daniel@yesql.se>
Reviewed-by: Cary Huang <cary.huang@highgo.ca>
Reviewed-by: Jacob Champion <jacob.champion@enterprisedb.com>
Discussion: https://postgr.es/m/1C81CD0D-407E-44F9-833A-DD0331C202E5@yesql.se
---
 doc/src/sgml/config.sgml                      |  66 +++
 doc/src/sgml/runtime.sgml                     |  67 +++
 src/backend/Makefile                          |   1 +
 src/backend/libpq/be-secure-common.c          | 204 ++++++++-
 src/backend/libpq/be-secure-openssl.c         | 430 ++++++++++++++++--
 src/backend/libpq/be-secure.c                 |   8 +-
 src/backend/libpq/meson.build                 |   1 +
 src/backend/libpq/pg_hosts.conf.sample        |   4 +
 src/backend/utils/misc/guc.c                  |  31 ++
 src/backend/utils/misc/guc_parameters.dat     |  15 +
 src/backend/utils/misc/guc_tables.c           |   8 +
 src/backend/utils/misc/postgresql.conf.sample |   3 +
 src/bin/initdb/initdb.c                       |  15 +-
 src/include/libpq/hba.h                       |  19 +
 src/include/libpq/libpq-be.h                  |   3 +-
 src/include/libpq/libpq.h                     |  11 +-
 src/include/utils/guc.h                       |   1 +
 .../ssl_passphrase_func.c                     |   4 +-
 src/test/perl/PostgreSQL/Test/Cluster.pm      |  35 ++
 src/test/ssl/meson.build                      |   1 +
 src/test/ssl/t/004_sni.pl                     | 237 ++++++++++
 src/test/ssl/t/SSL/Backend/OpenSSL.pm         |  16 +-
 src/tools/pgindent/typedefs.list              |   2 +
 23 files changed, 1120 insertions(+), 62 deletions(-)
 create mode 100644 src/backend/libpq/pg_hosts.conf.sample
 create mode 100644 src/test/ssl/t/004_sni.pl

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 023b3f03ba9..8bca363d542 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1694,6 +1694,72 @@ include_dir 'conf.d'
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry id="guc-ssl-snimode" xreflabel="ssl_snimode">
+      <term><varname>ssl_snimode</varname> (<type>enum</type>)
+      <indexterm>
+       <primary><varname>ssl_snimode</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        This parameter determines if the server will inspect the <acronym>SNI</acronym> TLS extension
+        when establishing the connection, and how it should be interpreted.
+        Valid values are currently: <literal>off</literal>, <literal>default</literal> and <literal>strict</literal>.
+       </para>
+       <para>
+        <variablelist>
+         <varlistentry id="guc-ssl-snimode-off">
+          <term><literal>off</literal></term>
+          <listitem>
+           <para>
+            SNI is not enabled and no configuration from
+            <filename>pg_hosts.conf</filename> is loaded.  Configuration of SSL
+            for all connections is done with <xref linkend="guc-ssl-cert-file"/>,
+            <xref linkend="guc-ssl-key-file"/> and <xref linkend="guc-ssl-ca-file"/>.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry id="guc-ssl-snimode-default">
+          <term><literal>default</literal></term>
+          <listitem>
+           <para>
+            SNI is enabled and hostname configuration is loaded from
+            <filename>pg_hosts.conf</filename>. <xref linkend="guc-ssl-cert-file"/>,
+            <xref linkend="guc-ssl-key-file"/> and <xref linkend="guc-ssl-ca-file"/>
+            are loaded as the default configuration.  Connections specifying
+            <xref linkend="libpq-connect-sslsni"/> to <literal>1</literal>
+            will be attempted using the default configuration if the hostname
+            is missing in <filename>pg_hosts.conf</filename>.  If the hostname
+            matches an entry from <filename>pg_hosts.conf</filename>, then the
+            configuration from that entry will be used for setting up the
+            connection.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry id="guc-ssl-snimode-strict">
+          <term><literal>strict</literal></term>
+          <listitem>
+           <para>
+            SNI is enabled and all connections are required to set <xref
+            linkend="libpq-connect-sslsni"/> to <literal>1</literal> and
+            specify a hostname matching an entry in
+            <filename>pg_hosts.conf</filename>. Any connection without <xref
+            linkend="libpq-connect-sslsni"/> or with a hostname missing from
+            <filename>pg_hosts.conf</filename> will be rejected.
+            <xref linkend="guc-ssl-cert-file"/>,
+            <xref linkend="guc-ssl-key-file"/> and <xref linkend="guc-ssl-ca-file"/>
+            are loaded in order to drive the handshake until the appropriate
+            configuration has been selected.
+           </para>
+          </listitem>
+         </varlistentry>
+        </variablelist>
+       </para>
+      </listitem>
+     </varlistentry>
     </variablelist>
     </sect2>
    </sect1>
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index 0c60bafac63..2693dcb81ad 100644
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -2445,6 +2445,12 @@ pg_dumpall -p 5432 | psql -d postgres -p 5433
       <entry>client certificate must not be on this list</entry>
      </row>
 
+     <row>
+      <entry><filename>$PGDATA/pg_hosts.conf</filename></entry>
+      <entry>SNI configuration</entry>
+      <entry>defines which certificates to use for which server hostname</entry>
+     </row>
+
     </tbody>
    </tgroup>
   </table>
@@ -2572,6 +2578,67 @@ openssl x509 -req -in server.csr -text -days 365 \
    </para>
   </sect2>
 
+  <sect2 id="ssl-sni">
+   <title>SNI Configuration</title>
+
+   <para>
+    <productname>PostgreSQL</productname> can be configured for
+    <acronym>SNI</acronym> using the <filename>pg_hosts.conf</filename>
+    configuration file. <productname>PostgreSQL</productname> inspects the TLS
+    hostname extension in the SSL connection handshake, and selects the right
+    TLS certificate, key and CA certificate to use for the connection.
+   </para>
+
+   <para>
+    SNI configuration is defined in the hosts configuration file,
+    <filename>pg_hosts.conf</filename>, which is stored in the clusters
+    data directory.  The hosts configuration file contains lines of the general
+    forms:
+<synopsis>
+<replaceable>hostname</replaceable> <replaceable>SSL_certificate</replaceable> <replaceable>SSL_key</replaceable> <replaceable>SSL_CA_certificate</replaceable> <replaceable>SSL_passphrase_cmd</replaceable> <replaceable>SSL_passphrase_cmd_reload</replaceable>
+<replaceable>include</replaceable> <replaceable>file</replaceable>
+<replaceable>include_if_exists</replaceable> <replaceable>file</replaceable>
+<replaceable>include_dir</replaceable> <replaceable>directory</replaceable>
+</synopsis>
+    Comments, whitespace and line continuations are handled in the same way as
+    in <filename>pg_hba.conf</filename>.  <replaceable>hostname</replaceable>
+    is matched against the hostname TLS extension in the SSL handshake.
+    <replaceable>SSL_certificate</replaceable>,
+    <replaceable>SSL_key</replaceable>,
+    <replaceable>SSL_CA_certificate</replaceable>,
+    <replaceable>SSL_passphrase_cmd</replaceable>, and
+    <replaceable>SSL_passphrase_cmd_reload</replaceable>
+    are treated like
+    <xref linkend="guc-ssl-cert-file"/>,
+    <xref linkend="guc-ssl-key-file"/>,
+    <xref linkend="guc-ssl-ca-file"/>,
+    <xref linkend="guc-ssl-passphrase-command"/>, and
+    <xref linkend="guc-ssl-passphrase-command-supports-reload"/> respectively.
+    All fields except <replaceable>SSL_passphrase_cmd</replaceable> and
+    <replaceable>SSL_passphrase_cmd_reload</replaceable> are required. If
+    <replaceable>SSL_passphrase_cmd</replaceable> is defined but not
+    <replaceable>SSL_passphrase_cmd_reload</replaceable> then the default
+    value for <replaceable>SSL_passphrase_cmd_reload</replaceable> is
+    <literal>off</literal>.
+   </para>
+   <para>
+    The SSL configuration from <filename>postgresql.conf</filename> is used
+    in order to set up the TLS handshake such that the hostname extension can
+    be inspected.  When <xref linkend="guc-ssl-snimode"/> is set to
+    <literal>default</literal> this configuration will be the default fallback
+    if no matching hostname is found in <filename>pg_hosts.conf</filename>.  If
+    <xref linkend="guc-ssl-snimode"/> is set to <literal>strict</literal> it
+    will only be used to for the handshake until the hostname is inspected, it
+    will not be used for the connection.
+   </para>
+   <para>
+    It is currently not possible to set different <literal>clientname</literal>
+    values for the different certificates.  Any <literal>clientname</literal>
+    setting in <filename>pg_hba.conf</filename> will be applied during
+    authentication regardless of which set of certificates have been loaded
+    via an SNI enabled connection.
+   </para>
+  </sect2>
  </sect1>
 
  <sect1 id="gssapi-enc">
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 7344c8c7f5c..2d1691c7950 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -187,6 +187,7 @@ endif
 	$(MAKE) -C utils install-data
 	$(INSTALL_DATA) $(srcdir)/libpq/pg_hba.conf.sample '$(DESTDIR)$(datadir)/pg_hba.conf.sample'
 	$(INSTALL_DATA) $(srcdir)/libpq/pg_ident.conf.sample '$(DESTDIR)$(datadir)/pg_ident.conf.sample'
+	$(INSTALL_DATA) $(srcdir)/libpq/pg_hosts.conf.sample '$(DESTDIR)$(datadir)/pg_hosts.conf.sample'
 	$(INSTALL_DATA) $(srcdir)/utils/misc/postgresql.conf.sample '$(DESTDIR)$(datadir)/postgresql.conf.sample'
 
 ifeq ($(with_llvm), yes)
diff --git a/src/backend/libpq/be-secure-common.c b/src/backend/libpq/be-secure-common.c
index e8b837d1fa7..2d9baff92b5 100644
--- a/src/backend/libpq/be-secure-common.c
+++ b/src/backend/libpq/be-secure-common.c
@@ -24,32 +24,40 @@
 
 #include "common/percentrepl.h"
 #include "common/string.h"
+#include "libpq/hba.h"
 #include "libpq/libpq.h"
 #include "storage/fd.h"
+#include "utils/guc.h"
+#include "utils/memutils.h"
+
+static HostsLine *parse_hosts_line(TokenizedAuthLine *tok_line, int elevel);
 
 /*
  * Run ssl_passphrase_command
  *
  * prompt will be substituted for %p.  is_server_start determines the loglevel
- * of error messages.
+ * of error messages from executing the command, the loglevel for failures in
+ * param substitution will be ERROR regardless of is_server_start.  The actual
+ * command used depends on the configuration for the current host.
  *
  * The result will be put in buffer buf, which is of size size.  The return
  * value is the length of the actual result.
  */
 int
-run_ssl_passphrase_command(const char *prompt, bool is_server_start, char *buf, int size)
+run_ssl_passphrase_command(const char *prompt, bool is_server_start, char *buf, int size, void *userdata)
 {
 	int			loglevel = is_server_start ? ERROR : LOG;
 	char	   *command;
 	FILE	   *fh;
 	int			pclose_rc;
 	size_t		len = 0;
+	char	   *cmd = (char *) userdata;
 
 	Assert(prompt);
 	Assert(size > 0);
 	buf[0] = '\0';
 
-	command = replace_percent_placeholders(ssl_passphrase_command, "ssl_passphrase_command", "p", prompt);
+	command = replace_percent_placeholders(cmd, "ssl_passphrase_command", "p", prompt);
 
 	fh = OpenPipeStream(command, "r");
 	if (fh == NULL)
@@ -175,3 +183,193 @@ check_ssl_key_file_permissions(const char *ssl_key_file, bool isServerStart)
 
 	return true;
 }
+
+/*
+ * parse_hosts_line
+ *
+ * Parses a loaded line from the pg_hosts.conf configuration and pulls out the
+ * hostname, certificate, key and CA parts in order to build an SNI config in
+ * the TLS backend. Validation of the parsed values is left for the TLS backend
+ * to implement.
+ */
+static HostsLine *
+parse_hosts_line(TokenizedAuthLine *tok_line, int elevel)
+{
+	HostsLine  *parsedline;
+	List	   *tokens;
+	ListCell   *field;
+	AuthToken  *token;
+
+	parsedline = palloc0(sizeof(HostsLine));
+	parsedline->sourcefile = pstrdup(tok_line->file_name);
+	parsedline->linenumber = tok_line->line_num;
+	parsedline->rawline = pstrdup(tok_line->raw_line);
+
+	/* Initialize optional fields */
+	parsedline->ssl_passphrase_cmd = NULL;
+	parsedline->ssl_passphrase_reload = false;
+
+	/* Hostname */
+	field = list_head(tok_line->fields);
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->hostname = pstrdup(token->string);
+
+	/* SSL Certificate (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_cert = pstrdup(token->string);
+
+	/* SSL key (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_key = pstrdup(token->string);
+
+	/* SSL CA (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_ca = pstrdup(token->string);
+
+	/* SSL Passphrase Command (optional) */
+	field = lnext(tok_line->fields, field);
+	if (field)
+	{
+		tokens = lfirst(field);
+		token = linitial(tokens);
+		parsedline->ssl_passphrase_cmd = pstrdup(token->string);
+
+		/*
+		 * SSL Passphrase Command support reload (optional). This field is
+		 * only supported if there was a passphrase command parsed first, so
+		 * nest it under the previous token.
+		 */
+		field = lnext(tok_line->fields, field);
+		if (field)
+		{
+			tokens = lfirst(field);
+			token = linitial(tokens);
+
+			if (token->string[0] == '1'
+				|| pg_strcasecmp(token->string, "true") == 0
+				|| pg_strcasecmp(token->string, "on") == 0
+				|| pg_strcasecmp(token->string, "yes") == 0)
+				parsedline->ssl_passphrase_reload = true;
+			else if (token->string[0] == '0'
+					 || pg_strcasecmp(token->string, "false") == 0
+					 || pg_strcasecmp(token->string, "off") == 0
+					 || pg_strcasecmp(token->string, "no") == 0)
+				parsedline->ssl_passphrase_reload = false;
+			else
+			{
+				ereport(elevel,
+						errcode(ERRCODE_CONFIG_FILE_ERROR),
+						errmsg("incorrect syntax for boolean value SSL_passphrase_cmd_reload"),
+						errcontext("line %d of configuration file \"%s\"",
+								   tok_line->line_num, tok_line->file_name));
+				return NULL;
+			}
+		}
+	}
+
+	return parsedline;
+}
+
+/*
+ * load_hosts
+ *
+ * Reads pg_hosts.conf and passes back a List of parsed lines, or NIL in case
+ * of errors.
+ */
+List *
+load_hosts(void)
+{
+	FILE	   *file;
+	ListCell   *line;
+	List	   *hosts_lines = NIL;
+	List	   *parsed_lines = NIL;
+	HostsLine  *newline;
+	bool		ok = true;
+
+	/*
+	 * This is not an auth file per se, but it is using the same file format
+	 * as the pg_hba and pg_ident files and thus the same code infrastructure.
+	 * A future TODO might be to rename the supporting code with a more
+	 * generic name?
+	 */
+	file = open_auth_file(HostsFileName, LOG, 0, NULL);
+	if (file == NULL)
+	{
+		/* An error has already been logged so no need to add one here */
+		return NIL;
+	}
+
+	tokenize_auth_file(HostsFileName, file, &hosts_lines, LOG, 0);
+
+	foreach(line, hosts_lines)
+	{
+		TokenizedAuthLine *tok_line = (TokenizedAuthLine *) lfirst(line);
+
+		if (tok_line->err_msg != NULL)
+		{
+			ok = false;
+			continue;
+		}
+
+		if ((newline = parse_hosts_line(tok_line, LOG)) == NULL)
+		{
+			ok = false;
+			continue;
+		}
+
+		parsed_lines = lappend(parsed_lines, newline);
+	}
+
+	free_auth_file(file, 0);
+
+	/*
+	 * If we didn't find any SNI configuration then that's not an error since
+	 * the pg_hosts file is additive to the default SSL configuration.
+	 */
+	if (ok && parsed_lines == NIL)
+	{
+		ereport(DEBUG1,
+				errmsg("SNI configuration not found in configuration file  \"%s\"",
+					   HostsFileName));
+		return NIL;
+	}
+
+	if (!ok)
+		return NIL;
+
+	return parsed_lines;
+}
diff --git a/src/backend/libpq/be-secure-openssl.c b/src/backend/libpq/be-secure-openssl.c
index 37f4d97f209..38134ec87de 100644
--- a/src/backend/libpq/be-secure-openssl.c
+++ b/src/backend/libpq/be-secure-openssl.c
@@ -51,9 +51,17 @@
 #endif
 #include <openssl/x509v3.h>
 
+typedef struct HostContext
+{
+	const char *hostname;
+	const char *ssl_passphrase;
+	SSL_CTX    *context;
+	bool		default_host;
+	bool		ssl_loaded_verify_locations;
+} HostContext;
 
 /* default init hook can be overridden by a shared library */
-static void default_openssl_tls_init(SSL_CTX *context, bool isServerStart);
+static void default_openssl_tls_init(SSL_CTX *context, bool isServerStart, HostsLine *hosts);
 openssl_tls_init_hook_typ openssl_tls_init_hook = default_openssl_tls_init;
 
 static int	port_bio_read(BIO *h, char *buf, int size);
@@ -73,6 +81,7 @@ static int	alpn_cb(SSL *ssl,
 					const unsigned char *in,
 					unsigned int inlen,
 					void *userdata);
+static int	sni_servername_cb(SSL *ssl, int *al, void *arg);
 static bool initialize_dh(SSL_CTX *context, bool isServerStart);
 static bool initialize_ecdh(SSL_CTX *context, bool isServerStart);
 static const char *SSLerrmessageExt(unsigned long ecode, const char *replacement);
@@ -80,12 +89,17 @@ static const char *SSLerrmessage(unsigned long ecode);
 
 static char *X509_NAME_to_cstring(X509_NAME *name);
 
+static List *contexts = NIL;
 static SSL_CTX *SSL_context = NULL;
+static HostContext *Default_context = NULL;
+static HostContext *Host_context = NULL;
 static bool dummy_ssl_passwd_cb_called = false;
 static bool ssl_is_server_start;
 
 static int	ssl_protocol_version_to_openssl(int v);
 static const char *ssl_protocol_version_to_string(int v);
+static SSL_CTX *ssl_init_context(bool isServerStart, HostsLine *host);
+static void free_contexts(void);
 
 struct CallbackErr
 {
@@ -102,11 +116,174 @@ struct CallbackErr
 
 int
 be_tls_init(bool isServerStart)
+{
+	SSL_CTX    *ctx;
+	List	   *sni_hosts = NIL;
+	HostsLine	line;
+
+	/*
+	 * If there are contexts loaded when we init they must be released. This
+	 * should only be possible during configuration reloads and not when the
+	 * server is starting up.
+	 */
+	if (contexts != NIL)
+	{
+		Assert(!isServerStart);
+		free_contexts();
+		Host_context = NULL;
+		SSL_context = NULL;
+		Default_context = NULL;
+	}
+
+	/*
+	 * Load the default configuration from postgresql.conf such that we have a
+	 * context to either be used for the entire connection, or drive the
+	 * handshake until the SNI callback replace it with a configuration from
+	 * the pg_hosts.conf file.
+	 */
+	memset(&line, 0, sizeof(line));
+	line.ssl_cert = ssl_cert_file;
+	line.ssl_key = ssl_key_file;
+	line.ssl_ca = ssl_ca_file;
+	line.ssl_passphrase_cmd = ssl_passphrase_command;
+	line.ssl_passphrase_reload = ssl_passphrase_command_supports_reload;
+
+	ctx = ssl_init_context(isServerStart, &line);
+	if (ctx == NULL)
+	{
+		ereport(isServerStart ? FATAL : LOG,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("could not load default certificate"));
+		return -1;
+	}
+
+	Default_context = palloc0(sizeof(HostContext));
+	Default_context->hostname = pstrdup("*");
+	Default_context->context = ctx;
+	Default_context->default_host = true;
+
+	/*
+	 * Set flag to remember whether CA store has been loaded into SSL_context.
+	 */
+	if (ssl_ca_file[0])
+		Default_context->ssl_loaded_verify_locations = true;
+
+	/*
+	 * While the default context isn't matched against when searching for host
+	 * contexts we still add it to the list to ensure that cleanup code can
+	 * iterate over a single structure to clean up everything.
+	 */
+	contexts = lappend(contexts, Default_context);
+
+	/*
+	 * Install the default context to use as the initial context for the
+	 * connection.  This might be replaced in the SNI callback if there is a
+	 * host/snimode match, but we need something to drive the hand- shake till
+	 * then.
+	 */
+	Host_context = Default_context;
+	SSL_context = Host_context->context;
+
+	/*
+	 * In default or strict ssl_snimode we load all certificates/keys which
+	 * are configured in pg_hosts.conf.  In strict mode it is considered a
+	 * fatal error in case there are no configured entries.
+	 */
+	if (ssl_snimode == SSL_SNIMODE_STRICT || ssl_snimode == SSL_SNIMODE_DEFAULT)
+	{
+		ListCell   *line;
+		MemoryContext oldcxt;
+		MemoryContext hostcxt;
+
+		hostcxt = AllocSetContextCreate(CurrentMemoryContext,
+										"hosts file parser context",
+										ALLOCSET_SMALL_SIZES);
+
+		/*
+		 * Load pg_hosts.conf and parse each row, returning the set of hosts
+		 * as a list.  Make sure to allocate the parsed rows in a temporary
+		 * memory context such that we can avoid memory leaks.
+		 */
+		oldcxt = MemoryContextSwitchTo(hostcxt);
+		sni_hosts = load_hosts();
+		MemoryContextSwitchTo(oldcxt);
+
+		/*
+		 * In strict ssl_snimode there needs to be at least one configured
+		 * host in the pg_hosts file since the default fallback context isn't
+		 * allowed to connect with.
+		 */
+		if (sni_hosts == NIL && ssl_snimode == SSL_SNIMODE_STRICT)
+		{
+			MemoryContextDelete(hostcxt);
+			ereport(isServerStart ? FATAL : LOG,
+					errcode(ERRCODE_CONFIG_FILE_ERROR),
+					errmsg("could not load %s", "pg_hosts.conf"),
+					errhint("In strict ssl_snimode there need to be at least one entry in pg_hosts.conf."));
+			return -1;
+		}
+
+		foreach(line, sni_hosts)
+		{
+			HostContext *host_context;
+			HostsLine  *host = lfirst(line);
+			static SSL_CTX *tmp_context = NULL;
+
+			tmp_context = ssl_init_context(isServerStart, host);
+			if (tmp_context == NULL)
+			{
+				MemoryContextDelete(hostcxt);
+				ereport(isServerStart ? FATAL : LOG,
+						errcode(ERRCODE_CONFIG_FILE_ERROR),
+						errmsg("unable to load certificate from pg_hosts.conf file"));
+				return -1;
+			}
+
+			/*
+			 * The parsing logic has already verified that the hostname exist
+			 * so we need not check that.
+			 */
+			host_context = palloc0(sizeof(HostContext));
+			host_context->hostname = pstrdup(host->hostname);
+			host_context->context = tmp_context;
+			host_context->default_host = false;
+
+			/*
+			 * Set flag to remember whether CA store has been loaded into this
+			 * SSL_context.
+			 */
+			if (host->ssl_ca && host->ssl_ca[0] != '\0')
+				host_context->ssl_loaded_verify_locations = true;
+
+			contexts = lappend(contexts, host_context);
+		}
+
+		MemoryContextDelete(hostcxt);
+	}
+
+	/* Make sure we have at least one certificate loaded */
+	if (list_length(contexts) < 1)
+	{
+		ereport(isServerStart ? FATAL : LOG,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("no SSL contexts loaded"));
+		return -1;
+	}
+
+	return 0;
+}
+
+static SSL_CTX *
+ssl_init_context(bool isServerStart, HostsLine *host_line)
 {
 	SSL_CTX    *context;
 	int			ssl_ver_min = -1;
 	int			ssl_ver_max = -1;
 
+	const char *ctx_ssl_cert_file = host_line->ssl_cert;
+	const char *ctx_ssl_key_file = host_line->ssl_key;
+	const char *ctx_ssl_ca_file = host_line->ssl_ca;
+
 	/*
 	 * Create a new SSL context into which we'll load all the configuration
 	 * settings.  If we fail partway through, we can avoid memory leakage by
@@ -132,10 +309,17 @@ be_tls_init(bool isServerStart)
 	 */
 	SSL_CTX_set_mode(context, SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER);
 
+	/*
+	 * Install SNI TLS extension callback in case the server is configured to
+	 * validate hostnames.
+	 */
+	if (ssl_snimode != SSL_SNIMODE_OFF)
+		SSL_CTX_set_tlsext_servername_callback(context, sni_servername_cb);
+
 	/*
 	 * Call init hook (usually to set password callback)
 	 */
-	(*openssl_tls_init_hook) (context, isServerStart);
+	(*openssl_tls_init_hook) (context, isServerStart, host_line);
 
 	/* used by the callback */
 	ssl_is_server_start = isServerStart;
@@ -143,16 +327,16 @@ be_tls_init(bool isServerStart)
 	/*
 	 * Load and verify server's certificate and private key
 	 */
-	if (SSL_CTX_use_certificate_chain_file(context, ssl_cert_file) != 1)
+	if (SSL_CTX_use_certificate_chain_file(context, ctx_ssl_cert_file) != 1)
 	{
 		ereport(isServerStart ? FATAL : LOG,
 				(errcode(ERRCODE_CONFIG_FILE_ERROR),
 				 errmsg("could not load server certificate file \"%s\": %s",
-						ssl_cert_file, SSLerrmessage(ERR_get_error()))));
+						ctx_ssl_cert_file, SSLerrmessage(ERR_get_error()))));
 		goto error;
 	}
 
-	if (!check_ssl_key_file_permissions(ssl_key_file, isServerStart))
+	if (!check_ssl_key_file_permissions(ctx_ssl_key_file, isServerStart))
 		goto error;
 
 	/*
@@ -161,19 +345,19 @@ be_tls_init(bool isServerStart)
 	dummy_ssl_passwd_cb_called = false;
 
 	if (SSL_CTX_use_PrivateKey_file(context,
-									ssl_key_file,
+									ctx_ssl_key_file,
 									SSL_FILETYPE_PEM) != 1)
 	{
 		if (dummy_ssl_passwd_cb_called)
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("private key file \"%s\" cannot be reloaded because it requires a passphrase",
-							ssl_key_file)));
+							ctx_ssl_key_file)));
 		else
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("could not load private key file \"%s\": %s",
-							ssl_key_file, SSLerrmessage(ERR_get_error()))));
+							ctx_ssl_key_file, SSLerrmessage(ERR_get_error()))));
 		goto error;
 	}
 
@@ -325,17 +509,17 @@ be_tls_init(bool isServerStart)
 	/*
 	 * Load CA store, so we can verify client certificates if needed.
 	 */
-	if (ssl_ca_file[0])
+	if (ctx_ssl_ca_file[0])
 	{
 		STACK_OF(X509_NAME) * root_cert_list;
 
-		if (SSL_CTX_load_verify_locations(context, ssl_ca_file, NULL) != 1 ||
-			(root_cert_list = SSL_load_client_CA_file(ssl_ca_file)) == NULL)
+		if (SSL_CTX_load_verify_locations(context, ctx_ssl_ca_file, NULL) != 1 ||
+			(root_cert_list = SSL_load_client_CA_file(ctx_ssl_ca_file)) == NULL)
 		{
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("could not load root certificate file \"%s\": %s",
-							ssl_ca_file, SSLerrmessage(ERR_get_error()))));
+							ctx_ssl_ca_file, SSLerrmessage(ERR_get_error()))));
 			goto error;
 		}
 
@@ -348,16 +532,20 @@ be_tls_init(bool isServerStart)
 		 */
 		SSL_CTX_set_client_CA_list(context, root_cert_list);
 
-		/*
-		 * Always ask for SSL client cert, but don't fail if it's not
-		 * presented.  We might fail such connections later, depending on what
-		 * we find in pg_hba.conf.
-		 */
+	}
+
+	/*
+	 * If we have a CA store, or SNI is enabled, always ask for SSL client
+	 * cert, but don't fail if it's not presented.  We might fail such
+	 * connections later, depending on what we find in pg_hba.conf. The reason
+	 * for enabling in the case of SNI even if there is no CA is that another
+	 * context might have a CA, so the callback must be installed in order for
+	 * that context.
+	 */
+	if (ctx_ssl_ca_file[0] || ssl_snimode != SSL_SNIMODE_OFF)
 		SSL_CTX_set_verify(context,
-						   (SSL_VERIFY_PEER |
-							SSL_VERIFY_CLIENT_ONCE),
+						   (SSL_VERIFY_PEER | SSL_VERIFY_CLIENT_ONCE),
 						   verify_cb);
-	}
 
 	/*----------
 	 * Load the Certificate Revocation List (CRL).
@@ -407,38 +595,29 @@ be_tls_init(bool isServerStart)
 		}
 	}
 
-	/*
-	 * Success!  Replace any existing SSL_context.
-	 */
-	if (SSL_context)
-		SSL_CTX_free(SSL_context);
-
-	SSL_context = context;
-
-	/*
-	 * Set flag to remember whether CA store has been loaded into SSL_context.
-	 */
-	if (ssl_ca_file[0])
-		ssl_loaded_verify_locations = true;
-	else
-		ssl_loaded_verify_locations = false;
-
-	return 0;
+	return context;
 
 	/* Clean up by releasing working context. */
 error:
 	if (context)
 		SSL_CTX_free(context);
-	return -1;
+	return NULL;
 }
 
 void
 be_tls_destroy(void)
 {
-	if (SSL_context)
-		SSL_CTX_free(SSL_context);
+	ListCell   *cell;
+
+	foreach(cell, contexts)
+	{
+		HostContext *host_context = lfirst(cell);
+
+		SSL_CTX_free(host_context->context);
+		pfree(host_context);
+	}
+
 	SSL_context = NULL;
-	ssl_loaded_verify_locations = false;
 }
 
 int
@@ -771,6 +950,9 @@ be_tls_close(Port *port)
 		pfree(port->peer_dn);
 		port->peer_dn = NULL;
 	}
+
+	Host_context = NULL;
+	SSL_context = NULL;
 }
 
 ssize_t
@@ -1144,7 +1326,7 @@ ssl_external_passwd_cb(char *buf, int size, int rwflag, void *userdata)
 
 	Assert(rwflag == 0);
 
-	return run_ssl_passphrase_command(prompt, ssl_is_server_start, buf, size);
+	return run_ssl_passphrase_command(prompt, ssl_is_server_start, buf, size, userdata);
 }
 
 /*
@@ -1390,6 +1572,131 @@ alpn_cb(SSL *ssl,
 	}
 }
 
+/*
+ * sni_servername_cb
+ *
+ * Callback executed by OpenSSL during handshake in case the server has been
+ * configured to validate hostnames.  Depending on the SNI mode we either
+ * require a perfect match, or we allow to fallback to a default configuration.
+ * Returning SSL_TLSEXT_ERR_ALERT_FATAL to OpenSSL will immediately terminate
+ * the handshake.
+ */
+static int
+sni_servername_cb(SSL *ssl, int *al, void *arg)
+{
+	const char *tlsext_hostname;
+
+	/*
+	 * Executing this callback when SNI is turned off indicates a programmer
+	 * error or something worse.  Throw an assertion to catch during testing
+	 * but also ensure to terminate the connection in non-assert builds, even
+	 * though this should never happen, just to be on the safe side.
+	 */
+	if (ssl_snimode == SSL_SNIMODE_OFF)
+	{
+		Assert(false);
+		return SSL_TLSEXT_ERR_ALERT_FATAL;
+	}
+
+	tlsext_hostname = SSL_get_servername(ssl, TLSEXT_NAMETYPE_host_name);
+
+	/*
+	 * If there is no hostname set in the TLS extension, we have two options.
+	 * For ssl_snimode strict we error out since we cannot match a host config
+	 * for the connection.  For the default mode we fall back on the default
+	 * hostname configuration.
+	 */
+	if (!tlsext_hostname)
+	{
+		if (ssl_snimode == SSL_SNIMODE_STRICT)
+		{
+			/*
+			 * The error message for a missing server_name should, according
+			 * to RFC 8446, be missing_extension. This isn't entirely ideal
+			 * since the user won't be able to tell which extension the server
+			 * considered missing.  Sending unrecognized_name would be a more
+			 * helpful error, but for now we stick to the RFC.
+			 */
+			*al = SSL_AD_MISSING_EXTENSION;
+
+			ereport(COMMERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg("no hostname provided in callback")));
+			return SSL_TLSEXT_ERR_ALERT_FATAL;
+		}
+		else
+		{
+			Host_context = Default_context;
+			SSL_context = Host_context->context;
+			if (SSL_set_SSL_CTX(ssl, SSL_context) == NULL)
+			{
+				ereport(COMMERROR,
+						errcode(ERRCODE_PROTOCOL_VIOLATION),
+						errmsg("failed to switch to default SSL context"));
+				return SSL_TLSEXT_ERR_ALERT_FATAL;
+			}
+			return SSL_TLSEXT_ERR_OK;
+		}
+	}
+
+	/*
+	 * We have a requested hostname from the client, match against all entries
+	 * in the pg_hosts configuration to find a match.
+	 */
+	foreach_ptr(HostContext, host, contexts)
+	{
+		/*
+		 * For strict mode we will never want the default host so we can skip
+		 * past it immediately.
+		 */
+		if (ssl_snimode == SSL_SNIMODE_STRICT && host->default_host)
+			continue;
+
+		if (strcmp(host->hostname, tlsext_hostname) == 0)
+		{
+			Host_context = host;
+			SSL_context = host->context;
+			if (SSL_set_SSL_CTX(ssl, SSL_context) == NULL)
+			{
+				ereport(COMMERROR,
+						errcode(ERRCODE_PROTOCOL_VIOLATION),
+						errmsg("failed to switch SSL context for SNI host"));
+				return SSL_TLSEXT_ERR_ALERT_FATAL;
+			}
+			return SSL_TLSEXT_ERR_OK;
+		}
+	}
+
+	/*
+	 * At this point we know that the requested hostname isn't configured in
+	 * the pg_hosts file.  In ssl_snimode "strict" it's an error if there was
+	 * no match for the hostname in the TLS extension so terminate the
+	 * connection.
+	 */
+	if (ssl_snimode == SSL_SNIMODE_STRICT)
+	{
+		ereport(COMMERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg("no matching pg_hosts entry found for hostname: \"%s\"",
+						tlsext_hostname)));
+		return SSL_TLSEXT_ERR_ALERT_FATAL;
+	}
+
+	/*
+	 * In ssl_snimode "default" we fall back on the default host configured in
+	 * postgresql.conf when no match is found in pg_hosts.conf.
+	 */
+	Host_context = Default_context;
+	SSL_context = Host_context->context;
+	if (SSL_set_SSL_CTX(ssl, SSL_context) == NULL)
+	{
+		ereport(COMMERROR,
+				errcode(ERRCODE_PROTOCOL_VIOLATION),
+				errmsg("failed to switch to default SSL context"));
+		return SSL_TLSEXT_ERR_ALERT_FATAL;
+	}
+	return SSL_TLSEXT_ERR_OK;
+}
 
 /*
  * Set DH parameters for generating ephemeral DH keys.  The
@@ -1599,6 +1906,12 @@ be_tls_get_peer_serial(Port *port, char *ptr, size_t len)
 		ptr[0] = '\0';
 }
 
+bool
+be_tls_loaded_verify_locations(void)
+{
+	return Host_context->ssl_loaded_verify_locations;
+}
+
 char *
 be_tls_get_certificate_hash(Port *port, size_t *len)
 {
@@ -1792,17 +2105,23 @@ ssl_protocol_version_to_string(int v)
 
 
 static void
-default_openssl_tls_init(SSL_CTX *context, bool isServerStart)
+default_openssl_tls_init(SSL_CTX *context, bool isServerStart, HostsLine *host)
 {
 	if (isServerStart)
 	{
-		if (ssl_passphrase_command[0])
+		if (host->ssl_passphrase_cmd != NULL)
+		{
 			SSL_CTX_set_default_passwd_cb(context, ssl_external_passwd_cb);
+			SSL_CTX_set_default_passwd_cb_userdata(context, host->ssl_passphrase_cmd);
+		}
 	}
 	else
 	{
-		if (ssl_passphrase_command[0] && ssl_passphrase_command_supports_reload)
+		if (host->ssl_passphrase_cmd != NULL && host->ssl_passphrase_reload)
+		{
 			SSL_CTX_set_default_passwd_cb(context, ssl_external_passwd_cb);
+			SSL_CTX_set_default_passwd_cb_userdata(context, host->ssl_passphrase_cmd);
+		}
 		else
 
 			/*
@@ -1814,3 +2133,24 @@ default_openssl_tls_init(SSL_CTX *context, bool isServerStart)
 			SSL_CTX_set_default_passwd_cb(context, dummy_ssl_passwd_cb);
 	}
 }
+
+/*
+ * Cleanup function for when hostname configuration is reloaded from the
+ * pg_hosts.conf file, at that point we Must discard all existing contexts.
+ */
+static void
+free_contexts(void)
+{
+	if (contexts == NIL)
+		return;
+
+	foreach_ptr(HostContext, host, contexts)
+	{
+		if (host->hostname)
+			pfree(unconstify(char *, host->hostname));
+		SSL_CTX_free(host->context);
+	}
+
+	list_free_deep(contexts);
+	contexts = NIL;
+}
diff --git a/src/backend/libpq/be-secure.c b/src/backend/libpq/be-secure.c
index d723e74e813..1431f92e332 100644
--- a/src/backend/libpq/be-secure.c
+++ b/src/backend/libpq/be-secure.c
@@ -43,10 +43,6 @@ char	   *ssl_dh_params_file;
 char	   *ssl_passphrase_command;
 bool		ssl_passphrase_command_supports_reload;
 
-#ifdef USE_SSL
-bool		ssl_loaded_verify_locations = false;
-#endif
-
 /* GUC variable controlling SSL cipher list */
 char	   *SSLCipherSuites = NULL;
 char	   *SSLCipherList = NULL;
@@ -60,6 +56,8 @@ bool		SSLPreferServerCiphers;
 int			ssl_min_protocol_version = PG_TLS1_2_VERSION;
 int			ssl_max_protocol_version = PG_TLS_ANY;
 
+int			ssl_snimode = SSL_SNIMODE_DEFAULT;
+
 /* ------------------------------------------------------------ */
 /*			 Procedures common to all secure sessions			*/
 /* ------------------------------------------------------------ */
@@ -99,7 +97,7 @@ bool
 secure_loaded_verify_locations(void)
 {
 #ifdef USE_SSL
-	return ssl_loaded_verify_locations;
+	return be_tls_loaded_verify_locations();
 #else
 	return false;
 #endif
diff --git a/src/backend/libpq/meson.build b/src/backend/libpq/meson.build
index 31aa2faae1e..4f6ec13bc74 100644
--- a/src/backend/libpq/meson.build
+++ b/src/backend/libpq/meson.build
@@ -31,5 +31,6 @@ endif
 install_data(
   'pg_hba.conf.sample',
   'pg_ident.conf.sample',
+  'pg_hosts.conf.sample',
   install_dir: dir_data,
 )
diff --git a/src/backend/libpq/pg_hosts.conf.sample b/src/backend/libpq/pg_hosts.conf.sample
new file mode 100644
index 00000000000..5a47f9cae7d
--- /dev/null
+++ b/src/backend/libpq/pg_hosts.conf.sample
@@ -0,0 +1,4 @@
+# PostgreSQL SNI Hostname mappings
+# ================================
+
+# HOSTNAME       SSL CERTIFICATE             SSL KEY
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index c6484aea087..f35a15b48df 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -56,6 +56,7 @@
 #define CONFIG_FILENAME "postgresql.conf"
 #define HBA_FILENAME	"pg_hba.conf"
 #define IDENT_FILENAME	"pg_ident.conf"
+#define HOSTS_FILENAME	"pg_hosts.conf"
 
 #ifdef EXEC_BACKEND
 #define CONFIG_EXEC_PARAMS "global/config_exec_params"
@@ -1838,6 +1839,36 @@ SelectConfigFiles(const char *userDoption, const char *progname)
 	}
 	SetConfigOption("ident_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
 
+	if (fname_is_malloced)
+		free(fname);
+	else
+		guc_free(fname);
+
+	/*
+	 * Likewise for pg_hosts.conf.
+	 */
+	if (HostsFileName)
+	{
+		fname = make_absolute_path(HostsFileName);
+		fname_is_malloced = true;
+	}
+	else if (configdir)
+	{
+		fname = guc_malloc(FATAL,
+						   strlen(configdir) + strlen(HOSTS_FILENAME) + 2);
+		sprintf(fname, "%s/%s", configdir, HOSTS_FILENAME);
+		fname_is_malloced = false;
+	}
+	else
+	{
+		write_stderr("%s does not know where to find the \"hosts\" configuration file.\n"
+					 "This can be specified as \"hosts_file\" in \"%s\", "
+					 "or by the -D invocation option, or by the "
+					 "PGDATA environment variable.\n",
+					 progname, ConfigFileName);
+	}
+	SetConfigOption("hosts_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
+
 	if (fname_is_malloced)
 		free(fname);
 	else
diff --git a/src/backend/utils/misc/guc_parameters.dat b/src/backend/utils/misc/guc_parameters.dat
index 1128167c025..186ac634dae 100644
--- a/src/backend/utils/misc/guc_parameters.dat
+++ b/src/backend/utils/misc/guc_parameters.dat
@@ -1160,6 +1160,13 @@
   boot_val => 'NULL',
 },
 
+{ name => 'hosts_file', type => 'string', context => 'PGC_POSTMASTER', group => 'FILE_LOCATIONS',
+  short_desc => 'Sets the server\'s "hosts" configuration file.',
+  flags => 'GUC_SUPERUSER_ONLY',
+  variable => 'HostsFileName',
+  boot_val => 'NULL',
+},
+
 { name => 'hot_standby', type => 'bool', context => 'PGC_POSTMASTER', group => 'REPLICATION_STANDBY',
   short_desc => 'Allows connections and queries during recovery.',
   variable => 'EnableHotStandby',
@@ -2735,6 +2742,14 @@
   max => '0',
 },
 
+{ name => 'ssl_snimode', type => 'enum', context => 'PGC_SIGHUP', group => 'CONN_AUTH_SSL',
+  short_desc => 'Sets the SNI mode to use for the server.',
+  flags => 'GUC_SUPERUSER_ONLY',
+  variable => 'ssl_snimode',
+  boot_val => 'SSL_SNIMODE_DEFAULT',
+  options => 'ssl_snimode_options',
+},
+
 { name => 'ssl_tls13_ciphers', type => 'string', context => 'PGC_SIGHUP', group => 'CONN_AUTH_SSL',
   short_desc => 'Sets the list of allowed TLSv1.3 cipher suites.',
   long_desc => 'An empty string means use the default cipher suites.',
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index 0209b2067a2..d429c658054 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -491,6 +491,13 @@ static const struct config_enum_entry file_copy_method_options[] = {
 	{NULL, 0, false}
 };
 
+static const struct config_enum_entry ssl_snimode_options[] = {
+	{"off", SSL_SNIMODE_OFF, false},
+	{"default", SSL_SNIMODE_DEFAULT, false},
+	{"strict", SSL_SNIMODE_STRICT, false},
+	{NULL, 0, false}
+};
+
 /*
  * Options for enum values stored in other modules
  */
@@ -556,6 +563,7 @@ char	   *cluster_name = "";
 char	   *ConfigFileName;
 char	   *HbaFileName;
 char	   *IdentFileName;
+char	   *HostsFileName;
 char	   *external_pid_file;
 
 char	   *application_name;
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index dc9e2255f8a..4d0722e7bd7 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -45,6 +45,8 @@
                                         # (change requires restart)
 #ident_file = 'ConfigDir/pg_ident.conf' # ident configuration file
                                         # (change requires restart)
+#hosts_file = 'ConfigDir/pg_hosts.conf' # hosts configuration file
+                                        # (change requires restart)
 
 # If external_pid_file is not explicitly set, no extra PID file is written.
 #external_pid_file = ''                 # write an extra PID file
@@ -121,6 +123,7 @@
 #ssl_dh_params_file = ''
 #ssl_passphrase_command = ''
 #ssl_passphrase_command_supports_reload = off
+#ssl_snimode = default
 
 
 #------------------------------------------------------------------------------
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 92fe2f531f7..c953f24a58d 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -177,6 +177,7 @@ static int	encodingid;
 static char *bki_file;
 static char *hba_file;
 static char *ident_file;
+static char *hosts_file;
 static char *conf_file;
 static char *dictionary_file;
 static char *info_schema_file;
@@ -1530,6 +1531,14 @@ setup_config(void)
 
 	snprintf(path, sizeof(path), "%s/pg_ident.conf", pg_data);
 
+	writefile(path, conflines);
+	if (chmod(path, pg_file_create_mode) != 0)
+		pg_fatal("could not change permissions of \"%s\": %m", path);
+
+	/* pg_hosts.conf */
+	conflines = readfile(hosts_file);
+	snprintf(path, sizeof(path), "%s/pg_hosts.conf", pg_data);
+
 	writefile(path, conflines);
 	if (chmod(path, pg_file_create_mode) != 0)
 		pg_fatal("could not change permissions of \"%s\": %m", path);
@@ -2791,6 +2800,7 @@ setup_data_file_paths(void)
 	set_input(&bki_file, "postgres.bki");
 	set_input(&hba_file, "pg_hba.conf.sample");
 	set_input(&ident_file, "pg_ident.conf.sample");
+	set_input(&hosts_file, "pg_hosts.conf.sample");
 	set_input(&conf_file, "postgresql.conf.sample");
 	set_input(&dictionary_file, "snowball_create.sql");
 	set_input(&info_schema_file, "information_schema.sql");
@@ -2806,12 +2816,12 @@ setup_data_file_paths(void)
 				"PGDATA=%s\nshare_path=%s\nPGPATH=%s\n"
 				"POSTGRES_SUPERUSERNAME=%s\nPOSTGRES_BKI=%s\n"
 				"POSTGRESQL_CONF_SAMPLE=%s\n"
-				"PG_HBA_SAMPLE=%s\nPG_IDENT_SAMPLE=%s\n",
+				"PG_HBA_SAMPLE=%s\nPG_IDENT_SAMPLE=%s\nPG_HOSTS_SAMPLE=%s\n",
 				PG_VERSION,
 				pg_data, share_path, bin_path,
 				username, bki_file,
 				conf_file,
-				hba_file, ident_file);
+				hba_file, ident_file, hosts_file);
 		if (show_setting)
 			exit(0);
 	}
@@ -2819,6 +2829,7 @@ setup_data_file_paths(void)
 	check_input(bki_file);
 	check_input(hba_file);
 	check_input(ident_file);
+	check_input(hosts_file);
 	check_input(conf_file);
 	check_input(dictionary_file);
 	check_input(info_schema_file);
diff --git a/src/include/libpq/hba.h b/src/include/libpq/hba.h
index e3748d3c8c9..c96818549cc 100644
--- a/src/include/libpq/hba.h
+++ b/src/include/libpq/hba.h
@@ -151,6 +151,25 @@ typedef struct IdentLine
 	AuthToken  *pg_user;
 } IdentLine;
 
+typedef struct HostsLine
+{
+	int			linenumber;
+
+	char	   *sourcefile;
+	char	   *rawline;
+
+	/* Required fields */
+	bool		default_host;
+	char	   *hostname;
+	char	   *ssl_key;
+	char	   *ssl_cert;
+	char	   *ssl_ca;
+
+	/* Optional fields */
+	char	   *ssl_passphrase_cmd;
+	bool		ssl_passphrase_reload;
+} HostsLine;
+
 /*
  * TokenizedAuthLine represents one line lexed from an authentication
  * configuration file.  Each item in the "fields" list is a sub-list of
diff --git a/src/include/libpq/libpq-be.h b/src/include/libpq/libpq-be.h
index d6e671a6382..e1631cb7b5c 100644
--- a/src/include/libpq/libpq-be.h
+++ b/src/include/libpq/libpq-be.h
@@ -320,6 +320,7 @@ extern const char *be_tls_get_cipher(Port *port);
 extern void be_tls_get_peer_subject_name(Port *port, char *ptr, size_t len);
 extern void be_tls_get_peer_issuer_name(Port *port, char *ptr, size_t len);
 extern void be_tls_get_peer_serial(Port *port, char *ptr, size_t len);
+extern bool be_tls_loaded_verify_locations(void);
 
 /*
  * Get the server certificate hash for SCRAM channel binding type
@@ -332,7 +333,7 @@ extern char *be_tls_get_certificate_hash(Port *port, size_t *len);
 
 /* init hook for SSL, the default sets the password callback if appropriate */
 #ifdef USE_OPENSSL
-typedef void (*openssl_tls_init_hook_typ) (SSL_CTX *context, bool isServerStart);
+typedef void (*openssl_tls_init_hook_typ) (SSL_CTX *context, bool isServerStart, HostsLine *host);
 extern PGDLLIMPORT openssl_tls_init_hook_typ openssl_tls_init_hook;
 #endif
 
diff --git a/src/include/libpq/libpq.h b/src/include/libpq/libpq.h
index 5af005ad779..fe2d431291a 100644
--- a/src/include/libpq/libpq.h
+++ b/src/include/libpq/libpq.h
@@ -107,6 +107,7 @@ extern PGDLLIMPORT char *ssl_crl_dir;
 extern PGDLLIMPORT char *ssl_key_file;
 extern PGDLLIMPORT int ssl_min_protocol_version;
 extern PGDLLIMPORT int ssl_max_protocol_version;
+extern PGDLLIMPORT int ssl_snimode;
 extern PGDLLIMPORT char *ssl_passphrase_command;
 extern PGDLLIMPORT bool ssl_passphrase_command_supports_reload;
 extern PGDLLIMPORT char *ssl_dh_params_file;
@@ -152,12 +153,20 @@ enum ssl_protocol_versions
 	PG_TLS1_3_VERSION,
 };
 
+enum ssl_snimode
+{
+	SSL_SNIMODE_OFF = 0,
+	SSL_SNIMODE_DEFAULT,
+	SSL_SNIMODE_STRICT
+};
+
 /*
  * prototypes for functions in be-secure-common.c
  */
 extern int	run_ssl_passphrase_command(const char *prompt, bool is_server_start,
-									   char *buf, int size);
+									   char *buf, int size, void *userdata);
 extern bool check_ssl_key_file_permissions(const char *ssl_key_file,
 										   bool isServerStart);
+extern List *load_hosts(void);
 
 #endif							/* LIBPQ_H */
diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index f21ec37da89..8f08a38b789 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -312,6 +312,7 @@ extern PGDLLIMPORT char *cluster_name;
 extern PGDLLIMPORT char *ConfigFileName;
 extern PGDLLIMPORT char *HbaFileName;
 extern PGDLLIMPORT char *IdentFileName;
+extern PGDLLIMPORT char *HostsFileName;
 extern PGDLLIMPORT char *external_pid_file;
 
 extern PGDLLIMPORT char *application_name;
diff --git a/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c b/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
index d5992149821..a85d85735cf 100644
--- a/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
+++ b/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
@@ -26,7 +26,7 @@ static char *ssl_passphrase = NULL;
 static int	rot13_passphrase(char *buf, int size, int rwflag, void *userdata);
 
 /* hook function to set the callback */
-static void set_rot13(SSL_CTX *context, bool isServerStart);
+static void set_rot13(SSL_CTX *context, bool isServerStart, HostsLine *host);
 
 /*
  * Module load callback
@@ -53,7 +53,7 @@ _PG_init(void)
 }
 
 static void
-set_rot13(SSL_CTX *context, bool isServerStart)
+set_rot13(SSL_CTX *context, bool isServerStart, HostsLine *host)
 {
 	/* warn if the user has set ssl_passphrase_command */
 	if (ssl_passphrase_command[0])
diff --git a/src/test/perl/PostgreSQL/Test/Cluster.pm b/src/test/perl/PostgreSQL/Test/Cluster.pm
index 35413f14019..a46ac325045 100644
--- a/src/test/perl/PostgreSQL/Test/Cluster.pm
+++ b/src/test/perl/PostgreSQL/Test/Cluster.pm
@@ -1302,6 +1302,27 @@ Wrapper for pg_ctl restart.
 With optional extra param fail_ok => 1, returns 0 for failure
 instead of bailing out.
 
+=over
+
+=item fail_ok => 1
+
+By default, failure terminates the entire F<prove> invocation.  If given,
+instead return 0 for failure instead of bailing out.
+
+=item log_unlike => B<pattern>
+
+When defined, the logfile is inspected for the presence of the fragment by
+matching the specified pattern. If the pattern matches agsinst the logfile a
+test failure will be logged.
+
+=item log_like => B<pattern>
+
+When defined, the logfile is inspected for the presence of the fragment by
+matching the pattern. If the pattern doesn't match a test failure will be
+logged.
+
+=back
+
 =cut
 
 sub restart
@@ -1314,6 +1335,8 @@ sub restart
 
 	print "### Restarting node \"$name\"\n";
 
+	my $log_location = -s $self->logfile;
+
 	# -w is now the default but having it here does no harm and helps
 	# compatibility with older versions.
 	$ret = PostgreSQL::Test::Utils::system_log(
@@ -1322,6 +1345,18 @@ sub restart
 		'--log' => $self->logfile,
 		'restart');
 
+	# Check for expected and/or unexpected log fragments if the caller
+	# specified such checks in the params
+	if (defined $params{log_unlike} || defined $params{log_like})
+	{
+		my $log =
+		  PostgreSQL::Test::Utils::slurp_file($self->logfile, $log_location);
+		unlike($log, $params{log_unlike}, "unexpected fragment found in log")
+			if defined $params{log_unlike};
+		like($log, $params{log_like}, "expected fragment not found in log")
+			if defined $params{log_like};
+	}
+
 	if ($ret != 0)
 	{
 		print "# pg_ctl restart failed; see logfile for details: "
diff --git a/src/test/ssl/meson.build b/src/test/ssl/meson.build
index d8e0fb518e0..e5a9402cd9c 100644
--- a/src/test/ssl/meson.build
+++ b/src/test/ssl/meson.build
@@ -13,6 +13,7 @@ tests += {
       't/001_ssltests.pl',
       't/002_scram.pl',
       't/003_sslinfo.pl',
+      't/004_sni.pl',
     ],
   },
 }
diff --git a/src/test/ssl/t/004_sni.pl b/src/test/ssl/t/004_sni.pl
new file mode 100644
index 00000000000..90d7560ad11
--- /dev/null
+++ b/src/test/ssl/t/004_sni.pl
@@ -0,0 +1,237 @@
+
+# Copyright (c) 2024, PostgreSQL Global Development Group
+
+use strict;
+use warnings FATAL => 'all';
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+use FindBin;
+use lib $FindBin::RealBin;
+
+use SSL::Server;
+
+# This is the hostname used to connect to the server. This cannot be a
+# hostname, because the server certificate is always for the domain
+# postgresql-ssl-regression.test.
+my $SERVERHOSTADDR = '127.0.0.1';
+# This is the pattern to use in pg_hba.conf to match incoming connections.
+my $SERVERHOSTCIDR = '127.0.0.1/32';
+
+if ($ENV{with_ssl} ne 'openssl')
+{
+	plan skip_all => 'OpenSSL not supported by this build';
+}
+
+if (!$ENV{PG_TEST_EXTRA} || $ENV{PG_TEST_EXTRA} !~ /\bssl\b/)
+{
+	plan skip_all =>
+	  'Potentially unsafe test SSL not enabled in PG_TEST_EXTRA';
+}
+
+my $ssl_server = SSL::Server->new();
+
+my $node = PostgreSQL::Test::Cluster->new('primary');
+$node->init;
+
+# PGHOST is enforced here to set up the node, subsequent connections
+# will use a dedicated connection string.
+$ENV{PGHOST} = $node->host;
+$ENV{PGPORT} = $node->port;
+$node->start;
+
+$ssl_server->configure_test_server_for_ssl($node, $SERVERHOSTADDR,
+	$SERVERHOSTCIDR, 'trust');
+
+$ssl_server->switch_server_cert($node, certfile => 'server-cn-only');
+
+my $connstr =
+  "user=ssltestuser dbname=trustdb hostaddr=$SERVERHOSTADDR host=localhost sslsni=1";
+
+$node->append_conf('postgresql.conf', "ssl_snimode=default");
+$node->reload;
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"connect fails with fallback hostname, without intermediate",
+	expected_stderr => qr/certificate verify failed/);
+
+# example.org serves the server cert and its intermediate CA.
+$node->append_conf('pg_hosts.conf',
+	"example.org server-cn-only+server_ca.crt server-cn-only.key root_ca.crt"
+);
+$node->reload;
+
+$node->connect_ok(
+	"$connstr host=example.org sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"connect with configured hostname, serving intermediate server CA");
+
+$node->connect_fails(
+	"$connstr sslrootcert=invalid sslmode=verify-ca",
+	"connect without server root cert sslmode=verify-ca",
+	expected_stderr => qr/root certificate file "invalid" does not exist/);
+
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"connect still fails with fallback hostname, without intermediate",
+	expected_stderr => qr/certificate verify failed/);
+
+$node->connect_ok(
+	"$connstr host=localhost sslrootcert=ssl/root+server_ca.crt sslmode=verify-ca",
+	"connect with fallback hostname, intermediate included");
+
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	"localhost server-cn-only.crt server-cn-only.key root_ca.crt");
+$node->append_conf('postgresql.conf', "ssl_snimode=strict");
+$node->reload;
+
+$node->connect_fails(
+	"$connstr host=example.org sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with missing hostconfig and snimode=strict",
+	expected_stderr => qr/tlsv1 unrecognized name/);
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require sslsni=1",
+	"connect with correct server CA cert file sslmode=require");
+
+# Attempts at connecting without SNI when the server is using strict mode should
+# result in connection failure.
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require sslsni=0",
+	"connect with correct server CA cert file without SNI for strict mode",
+	expected_stderr => qr/tlsv13 alert missing extension/);
+
+# Reconfigure with broken configuration for the key passphrase, the server
+# should not start up
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo wrongpassword" on'
+);
+my $result = $node->restart(fail_ok => 1);
+is($result, 0,
+	'restart fails with password-protected key when using the wrong passphrase command'
+);
+
+# Reconfigure again but with the correct passphrase set
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo secret1" on'
+);
+$result = $node->restart(fail_ok => 1);
+is($result, 1,
+	'restart succeeds with password-protected key when using the correct passphrase command'
+);
+
+# Make sure connecting works, and try to stress the reload logic by issuing
+# subsequent reloads
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+$node->reload;
+$node->reload;
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file after reloads");
+$node->reload;
+$node->reload;
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file after more reloads");
+
+# Test reloading a passphrase protected key without reloading support in the
+# passphrase hook. Connecting after restart should succeed but not after the
+# following reload.
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo secret1" off'
+);
+$result = $node->restart(fail_ok => 1);
+is($result, 1,
+	'restart succeeds with password-protected key when using the correct passphrase command'
+);
+SKIP:
+{
+	# Passphrase reloads must be enabled on Windows to succeed even without a
+	# restart
+	skip "Passphrase command reload required on Windows", 1 if ($windows_os);
+
+	$node->connect_ok(
+		"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+		"connect with correct server CA cert file sslmode=require");
+}
+
+$node->reload;
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect fails since the passphrase protected key cannot be reloaded");
+
+# Test client CAs by connecting to hosts in pg_hosts.conf while at the same
+# time swapping out default contexts containing different CA configurations.
+
+# pg_hosts configuration
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+# example.org has an unconfigured CA.
+$node->append_conf('pg_hosts.conf',
+	'example.org server-cn-only.crt server-cn-only.key ""');
+# example.com uses the client CA.
+$node->append_conf('pg_hosts.conf',
+	'example.com server-cn-only.crt server-cn-only.key root+client_ca.crt');
+# example.net uses the server CA (which is wrong).
+$node->append_conf('pg_hosts.conf',
+	'example.net server-cn-only.crt server-cn-only.key root+server_ca.crt');
+$node->reload;
+
+$connstr =
+  "user=ssltestuser dbname=certdb hostaddr=$SERVERHOSTADDR sslmode=require sslsni=1";
+
+foreach my $default_ca ("", "root+client_ca", "root+server_ca")
+{
+	# The default CA should, not matter for the purposes of these tests, since
+	# we connect to the other hosts explicitly. Test with various default CA
+	# settings to ensure it's isolated from the actual connections.
+	$ssl_server->switch_server_cert(
+		$node,
+		certfile => 'server-cn-only',
+		cafile => $default_ca);
+
+	# example.org is unconfigured and should fail.
+	$node->connect_fails(
+		"$connstr host=example.org sslcertmode=require sslcert=ssl/client.crt "
+		  . $ssl_server->sslkey('client.key'),
+		"host: 'example.org', ca: '$default_ca': connect with sslcert, no client CA configured",
+		expected_stderr => qr/certificate verify failed/);
+
+	# example.com is configured and should require a valid client cert.
+	$node->connect_fails(
+		"$connstr host=example.com sslcertmode=disable",
+		"host: 'example.com', ca: '$default_ca': connect fails if no client certificate sent",
+		expected_stderr => qr/certificate verify failed/);
+
+	$node->connect_ok(
+		"$connstr host=example.com sslrootcert=ssl/root+server_ca.crt sslcertmode=require sslcert=ssl/client.crt "
+		  . $ssl_server->sslkey('client.key'),
+		"host: 'example.com', ca: '$default_ca': connect with sslcert, client certificate sent"
+	);
+
+	# example.net is configured and should require a client cert, but will
+	# always fail verification.
+	$node->connect_fails(
+		"$connstr host=example.net sslcertmode=disable",
+		"host: 'example.net', ca: '$default_ca': connect fails if no client certificate sent",
+		expected_stderr => qr/certificate verify failed/);
+
+	$node->connect_fails(
+		"$connstr host=example.net sslcertmode=require sslcert=ssl/client.crt "
+		  . $ssl_server->sslkey('client.key'),
+		"host: 'example.net', ca: '$default_ca': connect with sslcert, client certificate sent",
+		expected_stderr => qr/certificate verify failed/);
+}
+
+done_testing();
diff --git a/src/test/ssl/t/SSL/Backend/OpenSSL.pm b/src/test/ssl/t/SSL/Backend/OpenSSL.pm
index 4159addb700..6ea5b64dc28 100644
--- a/src/test/ssl/t/SSL/Backend/OpenSSL.pm
+++ b/src/test/ssl/t/SSL/Backend/OpenSSL.pm
@@ -72,6 +72,7 @@ sub init
 	chmod(0600, glob "$pgdata/server-*.key")
 	  or die "failed to change permissions on server keys: $!";
 	_copy_files("ssl/root+client_ca.crt", $pgdata);
+	_copy_files("ssl/root+server_ca.crt", $pgdata);
 	_copy_files("ssl/root_ca.crt", $pgdata);
 	_copy_files("ssl/root+client.crl", $pgdata);
 	mkdir("$pgdata/root+client-crldir")
@@ -146,7 +147,8 @@ following parameters are supported:
 =item cafile => B<value>
 
 The CA certificate file to use for the C<ssl_ca_file> GUC. If omitted it will
-default to 'root+client_ca.crt'.
+default to 'root+client_ca.crt'. If empty, no C<ssl_ca_file> configuration
+parameter will be set.
 
 =item certfile => B<value>
 
@@ -181,10 +183,18 @@ sub set_server_cert
 	  unless defined $params->{keyfile};
 
 	my $sslconf =
-		"ssl_ca_file='$params->{cafile}.crt'\n"
-	  . "ssl_cert_file='$params->{certfile}.crt'\n"
+		"ssl_cert_file='$params->{certfile}.crt'\n"
 	  . "ssl_key_file='$params->{keyfile}.key'\n"
 	  . "ssl_crl_file='$params->{crlfile}'\n";
+	if ($params->{cafile} ne "")
+	{
+		$sslconf .= "ssl_ca_file='$params->{cafile}.crt'\n"
+	}
+	else
+	{
+		$sslconf .= "ssl_ca_file=''\n"
+	}
+
 	$sslconf .= "ssl_crl_dir='$params->{crldir}'\n"
 	  if defined $params->{crldir};
 
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 57a8f0366a5..bd80880c453 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -1206,6 +1206,8 @@ HeapTupleHeader
 HeapTupleHeaderData
 HeapTupleTableSlot
 HistControl
+HostContext
+HostsLine
 HotStandbyState
 I32
 ICU_Convert_Func
-- 
2.39.3 (Apple Git-146)

From dee74be3d7d00363a444e6c56d60d3daa5abdda8 Mon Sep 17 00:00:00 2001
From: Daniel Gustafsson <dgustafsson@postgresql.org>
Date: Tue, 25 Nov 2025 15:33:18 +0100
Subject: [PATCH v11] Serverside SNI support for libpq

Support for SNI was added to clientside libpq in 5c55dc8b4733 with the
sslsni parameter, but there was no support for utilizing it serverside.
This adds support for serverside SNI such that certficate/key handling
is available per host.  A new config file, $datadir/pg_hosts.conf, is
used for configuring which certificate and key should be used for which
hostname.  A new GUC, ssl_snimode, is used to control how the hostname
TLS extension is handled.  The possible values are off (which is used
as the new backwards compatible default), default and strict:

  - off: pg_hosts.conf is not parsed and the hostname TLS extension is
    not inspected at all.  SSL GUCs for certificates and keys are used.
  - default: pg_hosts.conf is loaded as well as the normal GUCs. If no
    match for the TLS extension hostname is found in pg_hosts the cert
    and key from the postgresql.conf GUCs is used as the default (used
    as a wildcard host).
  - strict: only pg_hosts.conf is loaded and the TLS extension hostname
    MUST be passed and MUST have a match in the configuration, else the
    connection is refused.

CRL file(s) are applied from postgresql.conf to all configured hostnames.

Author: Daniel Gustafsson <daniel@yesql.se>
Reviewed-by: Jacob Champion <jacob.champion@enterprisedb.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Reviewed-by: Cary Huang <cary.huang@highgo.ca>
Discussion: https://postgr.es/m/1C81CD0D-407E-44F9-833A-DD0331C202E5@yesql.se
---
 doc/src/sgml/config.sgml                      |  66 +++
 doc/src/sgml/runtime.sgml                     |  67 +++
 src/backend/Makefile                          |   1 +
 src/backend/libpq/be-secure-common.c          | 223 ++++++++-
 src/backend/libpq/be-secure-openssl.c         | 451 ++++++++++++++++--
 src/backend/libpq/be-secure.c                 |   8 +-
 src/backend/libpq/meson.build                 |   1 +
 src/backend/libpq/pg_hosts.conf.sample        |   4 +
 src/backend/utils/misc/guc.c                  |  31 ++
 src/backend/utils/misc/guc_parameters.dat     |  15 +
 src/backend/utils/misc/guc_tables.c           |   8 +
 src/backend/utils/misc/postgresql.conf.sample |   3 +
 src/bin/initdb/initdb.c                       |  15 +-
 src/include/libpq/hba.h                       |  19 +
 src/include/libpq/libpq-be.h                  |   3 +-
 src/include/libpq/libpq.h                     |  11 +-
 src/include/utils/guc.h                       |   1 +
 .../ssl_passphrase_func.c                     |   4 +-
 src/test/perl/PostgreSQL/Test/Cluster.pm      |  35 ++
 src/test/ssl/meson.build                      |   1 +
 src/test/ssl/t/004_sni.pl                     | 237 +++++++++
 src/test/ssl/t/SSL/Backend/OpenSSL.pm         |  16 +-
 src/tools/pgindent/typedefs.list              |   2 +
 23 files changed, 1160 insertions(+), 62 deletions(-)
 create mode 100644 src/backend/libpq/pg_hosts.conf.sample
 create mode 100644 src/test/ssl/t/004_sni.pl

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 023b3f03ba9..8bca363d542 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1694,6 +1694,72 @@ include_dir 'conf.d'
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry id="guc-ssl-snimode" xreflabel="ssl_snimode">
+      <term><varname>ssl_snimode</varname> (<type>enum</type>)
+      <indexterm>
+       <primary><varname>ssl_snimode</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        This parameter determines if the server will inspect the <acronym>SNI</acronym> TLS extension
+        when establishing the connection, and how it should be interpreted.
+        Valid values are currently: <literal>off</literal>, <literal>default</literal> and <literal>strict</literal>.
+       </para>
+       <para>
+        <variablelist>
+         <varlistentry id="guc-ssl-snimode-off">
+          <term><literal>off</literal></term>
+          <listitem>
+           <para>
+            SNI is not enabled and no configuration from
+            <filename>pg_hosts.conf</filename> is loaded.  Configuration of SSL
+            for all connections is done with <xref linkend="guc-ssl-cert-file"/>,
+            <xref linkend="guc-ssl-key-file"/> and <xref linkend="guc-ssl-ca-file"/>.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry id="guc-ssl-snimode-default">
+          <term><literal>default</literal></term>
+          <listitem>
+           <para>
+            SNI is enabled and hostname configuration is loaded from
+            <filename>pg_hosts.conf</filename>. <xref linkend="guc-ssl-cert-file"/>,
+            <xref linkend="guc-ssl-key-file"/> and <xref linkend="guc-ssl-ca-file"/>
+            are loaded as the default configuration.  Connections specifying
+            <xref linkend="libpq-connect-sslsni"/> to <literal>1</literal>
+            will be attempted using the default configuration if the hostname
+            is missing in <filename>pg_hosts.conf</filename>.  If the hostname
+            matches an entry from <filename>pg_hosts.conf</filename>, then the
+            configuration from that entry will be used for setting up the
+            connection.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry id="guc-ssl-snimode-strict">
+          <term><literal>strict</literal></term>
+          <listitem>
+           <para>
+            SNI is enabled and all connections are required to set <xref
+            linkend="libpq-connect-sslsni"/> to <literal>1</literal> and
+            specify a hostname matching an entry in
+            <filename>pg_hosts.conf</filename>. Any connection without <xref
+            linkend="libpq-connect-sslsni"/> or with a hostname missing from
+            <filename>pg_hosts.conf</filename> will be rejected.
+            <xref linkend="guc-ssl-cert-file"/>,
+            <xref linkend="guc-ssl-key-file"/> and <xref linkend="guc-ssl-ca-file"/>
+            are loaded in order to drive the handshake until the appropriate
+            configuration has been selected.
+           </para>
+          </listitem>
+         </varlistentry>
+        </variablelist>
+       </para>
+      </listitem>
+     </varlistentry>
     </variablelist>
     </sect2>
    </sect1>
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index 0c60bafac63..687aa86f68a 100644
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -2445,6 +2445,12 @@ pg_dumpall -p 5432 | psql -d postgres -p 5433
       <entry>client certificate must not be on this list</entry>
      </row>
 
+     <row>
+      <entry><filename>$PGDATA/pg_hosts.conf</filename></entry>
+      <entry>SNI configuration</entry>
+      <entry>defines which certificates to use for which server hostname</entry>
+     </row>
+
     </tbody>
    </tgroup>
   </table>
@@ -2572,6 +2578,67 @@ openssl x509 -req -in server.csr -text -days 365 \
    </para>
   </sect2>
 
+  <sect2 id="ssl-sni">
+   <title>SNI Configuration</title>
+
+   <para>
+    <productname>PostgreSQL</productname> can be configured for
+    <acronym>SNI</acronym> using the <filename>pg_hosts.conf</filename>
+    configuration file. <productname>PostgreSQL</productname> inspects the TLS
+    hostname extension in the SSL connection handshake, and selects the right
+    TLS certificate, key and CA certificate to use for the connection.
+   </para>
+
+   <para>
+    SNI configuration is defined in the hosts configuration file,
+    <filename>pg_hosts.conf</filename>, which is stored in the cluster's
+    data directory.  The hosts configuration file contains lines of the general
+    forms:
+<synopsis>
+<replaceable>hostname</replaceable> <replaceable>SSL_certificate</replaceable> <replaceable>SSL_key</replaceable> <replaceable>SSL_CA_certificate</replaceable> <replaceable>SSL_passphrase_cmd</replaceable> <replaceable>SSL_passphrase_cmd_reload</replaceable>
+<replaceable>include</replaceable> <replaceable>file</replaceable>
+<replaceable>include_if_exists</replaceable> <replaceable>file</replaceable>
+<replaceable>include_dir</replaceable> <replaceable>directory</replaceable>
+</synopsis>
+    Comments, whitespace and line continuations are handled in the same way as
+    in <filename>pg_hba.conf</filename>.  <replaceable>hostname</replaceable>
+    is matched against the hostname TLS extension in the SSL handshake.
+    <replaceable>SSL_certificate</replaceable>,
+    <replaceable>SSL_key</replaceable>,
+    <replaceable>SSL_CA_certificate</replaceable>,
+    <replaceable>SSL_passphrase_cmd</replaceable>, and
+    <replaceable>SSL_passphrase_cmd_reload</replaceable>
+    are treated like
+    <xref linkend="guc-ssl-cert-file"/>,
+    <xref linkend="guc-ssl-key-file"/>,
+    <xref linkend="guc-ssl-ca-file"/>,
+    <xref linkend="guc-ssl-passphrase-command"/>, and
+    <xref linkend="guc-ssl-passphrase-command-supports-reload"/> respectively.
+    All fields except <replaceable>SSL_passphrase_cmd</replaceable> and
+    <replaceable>SSL_passphrase_cmd_reload</replaceable> are required. If
+    <replaceable>SSL_passphrase_cmd</replaceable> is defined but not
+    <replaceable>SSL_passphrase_cmd_reload</replaceable> then the default
+    value for <replaceable>SSL_passphrase_cmd_reload</replaceable> is
+    <literal>off</literal>.
+   </para>
+   <para>
+    The SSL configuration from <filename>postgresql.conf</filename> is used
+    in order to set up the TLS handshake such that the hostname extension can
+    be inspected.  When <xref linkend="guc-ssl-snimode"/> is set to
+    <literal>default</literal> this configuration will be the default fallback
+    if no matching hostname is found in <filename>pg_hosts.conf</filename>.  If
+    <xref linkend="guc-ssl-snimode"/> is set to <literal>strict</literal> it
+    will only be used for the handshake until the hostname is inspected, it
+    will not be used for the connection.
+   </para>
+   <para>
+    It is currently not possible to set different <literal>clientname</literal>
+    values for the different certificates.  Any <literal>clientname</literal>
+    setting in <filename>pg_hba.conf</filename> will be applied during
+    authentication regardless of which set of certificates have been loaded
+    via an SNI enabled connection.
+   </para>
+  </sect2>
  </sect1>
 
  <sect1 id="gssapi-enc">
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 7344c8c7f5c..2d1691c7950 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -187,6 +187,7 @@ endif
 	$(MAKE) -C utils install-data
 	$(INSTALL_DATA) $(srcdir)/libpq/pg_hba.conf.sample '$(DESTDIR)$(datadir)/pg_hba.conf.sample'
 	$(INSTALL_DATA) $(srcdir)/libpq/pg_ident.conf.sample '$(DESTDIR)$(datadir)/pg_ident.conf.sample'
+	$(INSTALL_DATA) $(srcdir)/libpq/pg_hosts.conf.sample '$(DESTDIR)$(datadir)/pg_hosts.conf.sample'
 	$(INSTALL_DATA) $(srcdir)/utils/misc/postgresql.conf.sample '$(DESTDIR)$(datadir)/postgresql.conf.sample'
 
 ifeq ($(with_llvm), yes)
diff --git a/src/backend/libpq/be-secure-common.c b/src/backend/libpq/be-secure-common.c
index e8b837d1fa7..8d5a0c1ba2c 100644
--- a/src/backend/libpq/be-secure-common.c
+++ b/src/backend/libpq/be-secure-common.c
@@ -24,32 +24,40 @@
 
 #include "common/percentrepl.h"
 #include "common/string.h"
+#include "libpq/hba.h"
 #include "libpq/libpq.h"
 #include "storage/fd.h"
+#include "utils/guc.h"
+#include "utils/memutils.h"
+
+static HostsLine *parse_hosts_line(TokenizedAuthLine *tok_line, int elevel);
 
 /*
  * Run ssl_passphrase_command
  *
  * prompt will be substituted for %p.  is_server_start determines the loglevel
- * of error messages.
+ * of error messages from executing the command, the loglevel for failures in
+ * param substitution will be ERROR regardless of is_server_start.  The actual
+ * command used depends on the configuration for the current host.
  *
  * The result will be put in buffer buf, which is of size size.  The return
  * value is the length of the actual result.
  */
 int
-run_ssl_passphrase_command(const char *prompt, bool is_server_start, char *buf, int size)
+run_ssl_passphrase_command(const char *prompt, bool is_server_start, char *buf, int size, void *userdata)
 {
 	int			loglevel = is_server_start ? ERROR : LOG;
 	char	   *command;
 	FILE	   *fh;
 	int			pclose_rc;
 	size_t		len = 0;
+	const char *cmd = (const char *) userdata;
 
 	Assert(prompt);
 	Assert(size > 0);
 	buf[0] = '\0';
 
-	command = replace_percent_placeholders(ssl_passphrase_command, "ssl_passphrase_command", "p", prompt);
+	command = replace_percent_placeholders(cmd, "ssl_passphrase_command", "p", prompt);
 
 	fh = OpenPipeStream(command, "r");
 	if (fh == NULL)
@@ -175,3 +183,212 @@ check_ssl_key_file_permissions(const char *ssl_key_file, bool isServerStart)
 
 	return true;
 }
+
+/*
+ * parse_hosts_line
+ *
+ * Parses a loaded line from the pg_hosts.conf configuration and pulls out the
+ * hostname, certificate, key and CA parts in order to build an SNI config in
+ * the TLS backend. Validation of the parsed values is left for the TLS backend
+ * to implement.
+ */
+static HostsLine *
+parse_hosts_line(TokenizedAuthLine *tok_line, int elevel)
+{
+	HostsLine  *parsedline;
+	List	   *tokens;
+	ListCell   *field;
+	AuthToken  *token;
+
+	parsedline = palloc0(sizeof(HostsLine));
+	parsedline->sourcefile = pstrdup(tok_line->file_name);
+	parsedline->linenumber = tok_line->line_num;
+	parsedline->rawline = pstrdup(tok_line->raw_line);
+
+	/* Initialize optional fields */
+	parsedline->ssl_passphrase_cmd = NULL;
+	parsedline->ssl_passphrase_reload = false;
+
+	/* Hostname */
+	field = list_head(tok_line->fields);
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->hostname = pstrdup(token->string);
+	if (strcmp(parsedline->hostname, "*") == 0)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("wildcard hostname not allowed in hosts configuration"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+
+	/* SSL Certificate (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_cert = pstrdup(token->string);
+
+	/* SSL key (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_key = pstrdup(token->string);
+
+	/* SSL CA (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_ca = pstrdup(token->string);
+
+	/* SSL Passphrase Command (optional) */
+	field = lnext(tok_line->fields, field);
+	if (field)
+	{
+		tokens = lfirst(field);
+		token = linitial(tokens);
+		parsedline->ssl_passphrase_cmd = pstrdup(token->string);
+
+		/*
+		 * SSL Passphrase Command support reload (optional). This field is
+		 * only supported if there was a passphrase command parsed first, so
+		 * nest it under the previous token.
+		 */
+		field = lnext(tok_line->fields, field);
+		if (field)
+		{
+			tokens = lfirst(field);
+			token = linitial(tokens);
+
+			if (token->string[0] == '1'
+				|| pg_strcasecmp(token->string, "true") == 0
+				|| pg_strcasecmp(token->string, "on") == 0
+				|| pg_strcasecmp(token->string, "yes") == 0)
+				parsedline->ssl_passphrase_reload = true;
+			else if (token->string[0] == '0'
+					 || pg_strcasecmp(token->string, "false") == 0
+					 || pg_strcasecmp(token->string, "off") == 0
+					 || pg_strcasecmp(token->string, "no") == 0)
+				parsedline->ssl_passphrase_reload = false;
+			else
+			{
+				ereport(elevel,
+						errcode(ERRCODE_CONFIG_FILE_ERROR),
+						errmsg("incorrect syntax for boolean value SSL_passphrase_cmd_reload"),
+						errcontext("line %d of configuration file \"%s\"",
+								   tok_line->line_num, tok_line->file_name));
+				return NULL;
+			}
+		}
+	}
+
+	return parsedline;
+}
+
+/*
+ * load_hosts
+ *
+ * Reads and parses the pg_hosts.conf configuration file and passes back a List
+ * of HostLine elements containing the parsed lines, or NIL in case of an empty
+ * file.  The list is returned in the hosts_lines parameter. If loading the
+ * file was successful, true is returned, else false.  or an empty file.  This
+ * function is intended to be executed within a temporary memory context which
+ * can be discarded to free memory allocated during the processing of the file.
+ */
+bool
+load_hosts(List **hosts)
+{
+	FILE	   *file;
+	ListCell   *line;
+	List	   *hosts_lines = NIL;
+	List	   *parsed_lines = NIL;
+	HostsLine  *newline;
+	bool		ok = true;
+
+	if (hosts)
+		*hosts = NIL;
+
+	/*
+	 * This is not an auth file per se, but it is using the same file format
+	 * as the pg_hba and pg_ident files and thus the same code infrastructure.
+	 * A future TODO might be to rename the supporting code with a more
+	 * generic name?
+	 */
+	file = open_auth_file(HostsFileName, LOG, 0, NULL);
+	if (file == NULL)
+	{
+		/* An error has already been logged so no need to add one here */
+		return false;
+	}
+
+	tokenize_auth_file(HostsFileName, file, &hosts_lines, LOG, 0);
+
+	foreach(line, hosts_lines)
+	{
+		TokenizedAuthLine *tok_line = (TokenizedAuthLine *) lfirst(line);
+
+		if (tok_line->err_msg != NULL)
+		{
+			ok = false;
+			continue;
+		}
+
+		if ((newline = parse_hosts_line(tok_line, LOG)) == NULL)
+		{
+			ok = false;
+			continue;
+		}
+
+		parsed_lines = lappend(parsed_lines, newline);
+	}
+
+	free_auth_file(file, 0);
+
+	/*
+	 * If we didn't find any SNI configuration then that might not be an error
+	 * since the pg_hosts file is additive to the default SSL configuration in
+	 * some ssl_sni settings.
+	 */
+	if (ok && parsed_lines == NIL)
+	{
+		ereport(DEBUG1,
+				errmsg("SNI configuration not found in configuration file  \"%s\"",
+					   HostsFileName));
+	}
+
+	if (!ok)
+		return false;
+
+	if (hosts)
+		*hosts = parsed_lines;
+
+	return true;
+}
diff --git a/src/backend/libpq/be-secure-openssl.c b/src/backend/libpq/be-secure-openssl.c
index 37f4d97f209..ac3984bc275 100644
--- a/src/backend/libpq/be-secure-openssl.c
+++ b/src/backend/libpq/be-secure-openssl.c
@@ -51,9 +51,17 @@
 #endif
 #include <openssl/x509v3.h>
 
+typedef struct HostContext
+{
+	const char *hostname;
+	const char *ssl_passphrase;
+	SSL_CTX    *context;
+	bool		default_host;
+	bool		ssl_loaded_verify_locations;
+} HostContext;
 
 /* default init hook can be overridden by a shared library */
-static void default_openssl_tls_init(SSL_CTX *context, bool isServerStart);
+static void default_openssl_tls_init(SSL_CTX *context, bool isServerStart, HostsLine *hosts);
 openssl_tls_init_hook_typ openssl_tls_init_hook = default_openssl_tls_init;
 
 static int	port_bio_read(BIO *h, char *buf, int size);
@@ -73,6 +81,7 @@ static int	alpn_cb(SSL *ssl,
 					const unsigned char *in,
 					unsigned int inlen,
 					void *userdata);
+static int	sni_servername_cb(SSL *ssl, int *al, void *arg);
 static bool initialize_dh(SSL_CTX *context, bool isServerStart);
 static bool initialize_ecdh(SSL_CTX *context, bool isServerStart);
 static const char *SSLerrmessageExt(unsigned long ecode, const char *replacement);
@@ -80,12 +89,17 @@ static const char *SSLerrmessage(unsigned long ecode);
 
 static char *X509_NAME_to_cstring(X509_NAME *name);
 
+static List *contexts = NIL;
 static SSL_CTX *SSL_context = NULL;
+static HostContext *Default_context = NULL;
+static HostContext *Host_context = NULL;
 static bool dummy_ssl_passwd_cb_called = false;
 static bool ssl_is_server_start;
 
 static int	ssl_protocol_version_to_openssl(int v);
 static const char *ssl_protocol_version_to_string(int v);
+static SSL_CTX *ssl_init_context(bool isServerStart, HostsLine *host);
+static void free_contexts(void);
 
 struct CallbackErr
 {
@@ -102,11 +116,195 @@ struct CallbackErr
 
 int
 be_tls_init(bool isServerStart)
+{
+	SSL_CTX    *ctx;
+	List	   *sni_hosts = NIL;
+	HostsLine	line;
+	bool		res;
+
+	/*
+	 * If there are contexts loaded when we init they must be released. This
+	 * should only be possible during configuration reloads and not when the
+	 * server is starting up.
+	 */
+	if (contexts != NIL)
+	{
+		Assert(!isServerStart);
+		free_contexts();
+		Host_context = NULL;
+		SSL_context = NULL;
+		Default_context = NULL;
+	}
+
+	/*
+	 * Load the default configuration from postgresql.conf such that we have a
+	 * context to either be used for the entire connection, or drive the
+	 * handshake until the SNI callback replace it with a configuration from
+	 * the pg_hosts.conf file.
+	 */
+	memset(&line, 0, sizeof(line));
+	line.ssl_cert = ssl_cert_file;
+	line.ssl_key = ssl_key_file;
+	line.ssl_ca = ssl_ca_file;
+	line.ssl_passphrase_cmd = ssl_passphrase_command;
+	line.ssl_passphrase_reload = ssl_passphrase_command_supports_reload;
+
+	ctx = ssl_init_context(isServerStart, &line);
+	if (ctx == NULL)
+	{
+		ereport(isServerStart ? FATAL : LOG,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("could not load default certificate"));
+		return -1;
+	}
+
+	Default_context = palloc0(sizeof(HostContext));
+	Default_context->hostname = pstrdup("*");
+	Default_context->context = ctx;
+	Default_context->default_host = true;
+
+	/*
+	 * Set flag to remember whether CA store has been loaded into SSL_context.
+	 */
+	if (ssl_ca_file[0])
+		Default_context->ssl_loaded_verify_locations = true;
+
+	/*
+	 * While the default context isn't matched against when searching for host
+	 * contexts we still add it to the list to ensure that cleanup code can
+	 * iterate over a single structure to clean up everything.
+	 */
+	contexts = lappend(contexts, Default_context);
+
+	/*
+	 * Install the default context to use as the initial context for the
+	 * connection.  This might be replaced in the SNI callback if there is a
+	 * host/snimode match, but we need something to drive the hand- shake till
+	 * then.
+	 */
+	Host_context = Default_context;
+	SSL_context = Host_context->context;
+
+	/*
+	 * In default or strict ssl_snimode we load all certificates/keys which
+	 * are configured in pg_hosts.conf.  In strict mode it is considered a
+	 * fatal error in case there are no configured entries.
+	 */
+	if (ssl_snimode == SSL_SNIMODE_STRICT || ssl_snimode == SSL_SNIMODE_DEFAULT)
+	{
+		ListCell   *line;
+		MemoryContext oldcxt;
+		MemoryContext hostcxt;
+
+		hostcxt = AllocSetContextCreate(CurrentMemoryContext,
+										"hosts file parser context",
+										ALLOCSET_SMALL_SIZES);
+
+		/*
+		 * Load pg_hosts.conf and parse each row, returning the set of hosts
+		 * as a list.  Make sure to allocate the parsed rows in a temporary
+		 * memory context such that we can avoid memory leaks.
+		 */
+		oldcxt = MemoryContextSwitchTo(hostcxt);
+		res = load_hosts(&sni_hosts);
+		MemoryContextSwitchTo(oldcxt);
+
+		/*
+		 * If loading failed, then make sure to error out regardless. It's not
+		 * really an error to not have a hosts file in non-strict modes but if
+		 * there is one and it fails to load properly, then silently pressing
+		 * on seems worse than raising an error.
+		 */
+		if (!res)
+		{
+			MemoryContextDelete(hostcxt);
+			ereport(isServerStart ? FATAL : LOG,
+					errcode(ERRCODE_CONFIG_FILE_ERROR),
+					errmsg("could not load %s", "pg_hosts.conf"));
+			return -1;
+		}
+
+		/*
+		 * In strict ssl_snimode there needs to be at least one configured
+		 * host in the pg_hosts file since the default fallback context isn't
+		 * allowed to connect with.
+		 */
+		if (sni_hosts == NIL && ssl_snimode == SSL_SNIMODE_STRICT)
+		{
+			MemoryContextDelete(hostcxt);
+			ereport(isServerStart ? FATAL : LOG,
+					errcode(ERRCODE_CONFIG_FILE_ERROR),
+					errmsg("could not load %s", "pg_hosts.conf"),
+					errhint("In strict ssl_snimode there need to be at least one entry in pg_hosts.conf."));
+			return -1;
+		}
+
+		/*
+		 * Loading and parsing the hosts file was successful, create contexts
+		 * for each host entry and add to the the list of host to be checked
+		 * during login.
+		 */
+		foreach(line, sni_hosts)
+		{
+			HostContext *host_context;
+			HostsLine  *host = lfirst(line);
+			static SSL_CTX *tmp_context = NULL;
+
+			tmp_context = ssl_init_context(isServerStart, host);
+			if (tmp_context == NULL)
+			{
+				MemoryContextDelete(hostcxt);
+				ereport(isServerStart ? FATAL : LOG,
+						errcode(ERRCODE_CONFIG_FILE_ERROR),
+						errmsg("unable to load certificate from pg_hosts.conf file"));
+				return -1;
+			}
+
+			/*
+			 * The parsing logic has already verified that the hostname exist
+			 * so we need not check that.
+			 */
+			host_context = palloc0(sizeof(HostContext));
+			host_context->hostname = pstrdup(host->hostname);
+			host_context->context = tmp_context;
+			host_context->default_host = false;
+
+			/*
+			 * Set flag to remember whether CA store has been loaded into this
+			 * SSL_context.
+			 */
+			if (host->ssl_ca && host->ssl_ca[0] != '\0')
+				host_context->ssl_loaded_verify_locations = true;
+
+			contexts = lappend(contexts, host_context);
+		}
+
+		MemoryContextDelete(hostcxt);
+	}
+
+	/* Make sure we have at least one certificate loaded */
+	if (list_length(contexts) < 1)
+	{
+		ereport(isServerStart ? FATAL : LOG,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("no SSL contexts loaded"));
+		return -1;
+	}
+
+	return 0;
+}
+
+static SSL_CTX *
+ssl_init_context(bool isServerStart, HostsLine *host_line)
 {
 	SSL_CTX    *context;
 	int			ssl_ver_min = -1;
 	int			ssl_ver_max = -1;
 
+	const char *ctx_ssl_cert_file = host_line->ssl_cert;
+	const char *ctx_ssl_key_file = host_line->ssl_key;
+	const char *ctx_ssl_ca_file = host_line->ssl_ca;
+
 	/*
 	 * Create a new SSL context into which we'll load all the configuration
 	 * settings.  If we fail partway through, we can avoid memory leakage by
@@ -132,10 +330,17 @@ be_tls_init(bool isServerStart)
 	 */
 	SSL_CTX_set_mode(context, SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER);
 
+	/*
+	 * Install SNI TLS extension callback in case the server is configured to
+	 * validate hostnames.
+	 */
+	if (ssl_snimode != SSL_SNIMODE_OFF)
+		SSL_CTX_set_tlsext_servername_callback(context, sni_servername_cb);
+
 	/*
 	 * Call init hook (usually to set password callback)
 	 */
-	(*openssl_tls_init_hook) (context, isServerStart);
+	(*openssl_tls_init_hook) (context, isServerStart, host_line);
 
 	/* used by the callback */
 	ssl_is_server_start = isServerStart;
@@ -143,16 +348,16 @@ be_tls_init(bool isServerStart)
 	/*
 	 * Load and verify server's certificate and private key
 	 */
-	if (SSL_CTX_use_certificate_chain_file(context, ssl_cert_file) != 1)
+	if (SSL_CTX_use_certificate_chain_file(context, ctx_ssl_cert_file) != 1)
 	{
 		ereport(isServerStart ? FATAL : LOG,
 				(errcode(ERRCODE_CONFIG_FILE_ERROR),
 				 errmsg("could not load server certificate file \"%s\": %s",
-						ssl_cert_file, SSLerrmessage(ERR_get_error()))));
+						ctx_ssl_cert_file, SSLerrmessage(ERR_get_error()))));
 		goto error;
 	}
 
-	if (!check_ssl_key_file_permissions(ssl_key_file, isServerStart))
+	if (!check_ssl_key_file_permissions(ctx_ssl_key_file, isServerStart))
 		goto error;
 
 	/*
@@ -161,19 +366,19 @@ be_tls_init(bool isServerStart)
 	dummy_ssl_passwd_cb_called = false;
 
 	if (SSL_CTX_use_PrivateKey_file(context,
-									ssl_key_file,
+									ctx_ssl_key_file,
 									SSL_FILETYPE_PEM) != 1)
 	{
 		if (dummy_ssl_passwd_cb_called)
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("private key file \"%s\" cannot be reloaded because it requires a passphrase",
-							ssl_key_file)));
+							ctx_ssl_key_file)));
 		else
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("could not load private key file \"%s\": %s",
-							ssl_key_file, SSLerrmessage(ERR_get_error()))));
+							ctx_ssl_key_file, SSLerrmessage(ERR_get_error()))));
 		goto error;
 	}
 
@@ -325,17 +530,17 @@ be_tls_init(bool isServerStart)
 	/*
 	 * Load CA store, so we can verify client certificates if needed.
 	 */
-	if (ssl_ca_file[0])
+	if (ctx_ssl_ca_file[0])
 	{
 		STACK_OF(X509_NAME) * root_cert_list;
 
-		if (SSL_CTX_load_verify_locations(context, ssl_ca_file, NULL) != 1 ||
-			(root_cert_list = SSL_load_client_CA_file(ssl_ca_file)) == NULL)
+		if (SSL_CTX_load_verify_locations(context, ctx_ssl_ca_file, NULL) != 1 ||
+			(root_cert_list = SSL_load_client_CA_file(ctx_ssl_ca_file)) == NULL)
 		{
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("could not load root certificate file \"%s\": %s",
-							ssl_ca_file, SSLerrmessage(ERR_get_error()))));
+							ctx_ssl_ca_file, SSLerrmessage(ERR_get_error()))));
 			goto error;
 		}
 
@@ -348,16 +553,20 @@ be_tls_init(bool isServerStart)
 		 */
 		SSL_CTX_set_client_CA_list(context, root_cert_list);
 
-		/*
-		 * Always ask for SSL client cert, but don't fail if it's not
-		 * presented.  We might fail such connections later, depending on what
-		 * we find in pg_hba.conf.
-		 */
+	}
+
+	/*
+	 * If we have a CA store, or SNI is enabled, always ask for SSL client
+	 * cert, but don't fail if it's not presented.  We might fail such
+	 * connections later, depending on what we find in pg_hba.conf. The reason
+	 * for enabling in the case of SNI even if there is no CA is that another
+	 * context might have a CA, so the callback must be installed in order for
+	 * that context.
+	 */
+	if (ctx_ssl_ca_file[0] || ssl_snimode != SSL_SNIMODE_OFF)
 		SSL_CTX_set_verify(context,
-						   (SSL_VERIFY_PEER |
-							SSL_VERIFY_CLIENT_ONCE),
+						   (SSL_VERIFY_PEER | SSL_VERIFY_CLIENT_ONCE),
 						   verify_cb);
-	}
 
 	/*----------
 	 * Load the Certificate Revocation List (CRL).
@@ -407,38 +616,29 @@ be_tls_init(bool isServerStart)
 		}
 	}
 
-	/*
-	 * Success!  Replace any existing SSL_context.
-	 */
-	if (SSL_context)
-		SSL_CTX_free(SSL_context);
-
-	SSL_context = context;
-
-	/*
-	 * Set flag to remember whether CA store has been loaded into SSL_context.
-	 */
-	if (ssl_ca_file[0])
-		ssl_loaded_verify_locations = true;
-	else
-		ssl_loaded_verify_locations = false;
-
-	return 0;
+	return context;
 
 	/* Clean up by releasing working context. */
 error:
 	if (context)
 		SSL_CTX_free(context);
-	return -1;
+	return NULL;
 }
 
 void
 be_tls_destroy(void)
 {
-	if (SSL_context)
-		SSL_CTX_free(SSL_context);
+	ListCell   *cell;
+
+	foreach(cell, contexts)
+	{
+		HostContext *host_context = lfirst(cell);
+
+		SSL_CTX_free(host_context->context);
+		pfree(host_context);
+	}
+
 	SSL_context = NULL;
-	ssl_loaded_verify_locations = false;
 }
 
 int
@@ -771,6 +971,9 @@ be_tls_close(Port *port)
 		pfree(port->peer_dn);
 		port->peer_dn = NULL;
 	}
+
+	Host_context = NULL;
+	SSL_context = NULL;
 }
 
 ssize_t
@@ -1144,7 +1347,7 @@ ssl_external_passwd_cb(char *buf, int size, int rwflag, void *userdata)
 
 	Assert(rwflag == 0);
 
-	return run_ssl_passphrase_command(prompt, ssl_is_server_start, buf, size);
+	return run_ssl_passphrase_command(prompt, ssl_is_server_start, buf, size, userdata);
 }
 
 /*
@@ -1390,6 +1593,131 @@ alpn_cb(SSL *ssl,
 	}
 }
 
+/*
+ * sni_servername_cb
+ *
+ * Callback executed by OpenSSL during handshake in case the server has been
+ * configured to validate hostnames.  Depending on the SNI mode we either
+ * require a perfect match, or we allow to fallback to a default configuration.
+ * Returning SSL_TLSEXT_ERR_ALERT_FATAL to OpenSSL will immediately terminate
+ * the handshake.
+ */
+static int
+sni_servername_cb(SSL *ssl, int *al, void *arg)
+{
+	const char *tlsext_hostname;
+
+	/*
+	 * Executing this callback when SNI is turned off indicates a programmer
+	 * error or something worse.  Throw an assertion to catch during testing
+	 * but also ensure to terminate the connection in non-assert builds, even
+	 * though this should never happen, just to be on the safe side.
+	 */
+	if (ssl_snimode == SSL_SNIMODE_OFF)
+	{
+		Assert(false);
+		return SSL_TLSEXT_ERR_ALERT_FATAL;
+	}
+
+	tlsext_hostname = SSL_get_servername(ssl, TLSEXT_NAMETYPE_host_name);
+
+	/*
+	 * If there is no hostname set in the TLS extension, we have two options.
+	 * For ssl_snimode strict we error out since we cannot match a host config
+	 * for the connection.  For the default mode we fall back on the default
+	 * hostname configuration.
+	 */
+	if (!tlsext_hostname)
+	{
+		if (ssl_snimode == SSL_SNIMODE_STRICT)
+		{
+			/*
+			 * The error message for a missing server_name should, according
+			 * to RFC 8446, be missing_extension. This isn't entirely ideal
+			 * since the user won't be able to tell which extension the server
+			 * considered missing.  Sending unrecognized_name would be a more
+			 * helpful error, but for now we stick to the RFC.
+			 */
+			*al = SSL_AD_MISSING_EXTENSION;
+
+			ereport(COMMERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg("no hostname provided in callback")));
+			return SSL_TLSEXT_ERR_ALERT_FATAL;
+		}
+		else
+		{
+			Host_context = Default_context;
+			SSL_context = Host_context->context;
+			if (SSL_set_SSL_CTX(ssl, SSL_context) == NULL)
+			{
+				ereport(COMMERROR,
+						errcode(ERRCODE_PROTOCOL_VIOLATION),
+						errmsg("failed to switch to default SSL context"));
+				return SSL_TLSEXT_ERR_ALERT_FATAL;
+			}
+			return SSL_TLSEXT_ERR_OK;
+		}
+	}
+
+	/*
+	 * We have a requested hostname from the client, match against all entries
+	 * in the pg_hosts configuration to find a match.
+	 */
+	foreach_ptr(HostContext, host, contexts)
+	{
+		/*
+		 * For strict mode we will never want the default host so we can skip
+		 * past it immediately.
+		 */
+		if (ssl_snimode == SSL_SNIMODE_STRICT && host->default_host)
+			continue;
+
+		if (strcmp(host->hostname, tlsext_hostname) == 0)
+		{
+			Host_context = host;
+			SSL_context = host->context;
+			if (SSL_set_SSL_CTX(ssl, SSL_context) == NULL)
+			{
+				ereport(COMMERROR,
+						errcode(ERRCODE_PROTOCOL_VIOLATION),
+						errmsg("failed to switch SSL context for SNI host"));
+				return SSL_TLSEXT_ERR_ALERT_FATAL;
+			}
+			return SSL_TLSEXT_ERR_OK;
+		}
+	}
+
+	/*
+	 * At this point we know that the requested hostname isn't configured in
+	 * the pg_hosts file.  In ssl_snimode "strict" it's an error if there was
+	 * no match for the hostname in the TLS extension so terminate the
+	 * connection.
+	 */
+	if (ssl_snimode == SSL_SNIMODE_STRICT)
+	{
+		ereport(COMMERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg("no matching pg_hosts entry found for hostname: \"%s\"",
+						tlsext_hostname)));
+		return SSL_TLSEXT_ERR_ALERT_FATAL;
+	}
+
+	/*
+	 * In ssl_snimode "default" we fall back on the default host configured in
+	 * postgresql.conf when no match is found in pg_hosts.conf.
+	 */
+	Host_context = Default_context;
+	SSL_context = Host_context->context;
+	if (SSL_set_SSL_CTX(ssl, SSL_context) == NULL)
+	{
+		ereport(COMMERROR,
+				errcode(ERRCODE_PROTOCOL_VIOLATION),
+				errmsg("failed to switch to default SSL context"));
+		return SSL_TLSEXT_ERR_ALERT_FATAL;
+	}
+	return SSL_TLSEXT_ERR_OK;
+}
 
 /*
  * Set DH parameters for generating ephemeral DH keys.  The
@@ -1599,6 +1927,12 @@ be_tls_get_peer_serial(Port *port, char *ptr, size_t len)
 		ptr[0] = '\0';
 }
 
+bool
+be_tls_loaded_verify_locations(void)
+{
+	return Host_context->ssl_loaded_verify_locations;
+}
+
 char *
 be_tls_get_certificate_hash(Port *port, size_t *len)
 {
@@ -1792,17 +2126,23 @@ ssl_protocol_version_to_string(int v)
 
 
 static void
-default_openssl_tls_init(SSL_CTX *context, bool isServerStart)
+default_openssl_tls_init(SSL_CTX *context, bool isServerStart, HostsLine *host)
 {
 	if (isServerStart)
 	{
-		if (ssl_passphrase_command[0])
+		if (host->ssl_passphrase_cmd != NULL)
+		{
 			SSL_CTX_set_default_passwd_cb(context, ssl_external_passwd_cb);
+			SSL_CTX_set_default_passwd_cb_userdata(context, host->ssl_passphrase_cmd);
+		}
 	}
 	else
 	{
-		if (ssl_passphrase_command[0] && ssl_passphrase_command_supports_reload)
+		if (host->ssl_passphrase_cmd != NULL && host->ssl_passphrase_reload)
+		{
 			SSL_CTX_set_default_passwd_cb(context, ssl_external_passwd_cb);
+			SSL_CTX_set_default_passwd_cb_userdata(context, host->ssl_passphrase_cmd);
+		}
 		else
 
 			/*
@@ -1814,3 +2154,24 @@ default_openssl_tls_init(SSL_CTX *context, bool isServerStart)
 			SSL_CTX_set_default_passwd_cb(context, dummy_ssl_passwd_cb);
 	}
 }
+
+/*
+ * Cleanup function for when hostname configuration is reloaded from the
+ * pg_hosts.conf file, at that point we Must discard all existing contexts.
+ */
+static void
+free_contexts(void)
+{
+	if (contexts == NIL)
+		return;
+
+	foreach_ptr(HostContext, host, contexts)
+	{
+		if (host->hostname)
+			pfree(unconstify(char *, host->hostname));
+		SSL_CTX_free(host->context);
+	}
+
+	list_free_deep(contexts);
+	contexts = NIL;
+}
diff --git a/src/backend/libpq/be-secure.c b/src/backend/libpq/be-secure.c
index d723e74e813..f6c1422b555 100644
--- a/src/backend/libpq/be-secure.c
+++ b/src/backend/libpq/be-secure.c
@@ -43,10 +43,6 @@ char	   *ssl_dh_params_file;
 char	   *ssl_passphrase_command;
 bool		ssl_passphrase_command_supports_reload;
 
-#ifdef USE_SSL
-bool		ssl_loaded_verify_locations = false;
-#endif
-
 /* GUC variable controlling SSL cipher list */
 char	   *SSLCipherSuites = NULL;
 char	   *SSLCipherList = NULL;
@@ -60,6 +56,8 @@ bool		SSLPreferServerCiphers;
 int			ssl_min_protocol_version = PG_TLS1_2_VERSION;
 int			ssl_max_protocol_version = PG_TLS_ANY;
 
+int			ssl_snimode = SSL_SNIMODE_OFF;
+
 /* ------------------------------------------------------------ */
 /*			 Procedures common to all secure sessions			*/
 /* ------------------------------------------------------------ */
@@ -99,7 +97,7 @@ bool
 secure_loaded_verify_locations(void)
 {
 #ifdef USE_SSL
-	return ssl_loaded_verify_locations;
+	return be_tls_loaded_verify_locations();
 #else
 	return false;
 #endif
diff --git a/src/backend/libpq/meson.build b/src/backend/libpq/meson.build
index 31aa2faae1e..4f6ec13bc74 100644
--- a/src/backend/libpq/meson.build
+++ b/src/backend/libpq/meson.build
@@ -31,5 +31,6 @@ endif
 install_data(
   'pg_hba.conf.sample',
   'pg_ident.conf.sample',
+  'pg_hosts.conf.sample',
   install_dir: dir_data,
 )
diff --git a/src/backend/libpq/pg_hosts.conf.sample b/src/backend/libpq/pg_hosts.conf.sample
new file mode 100644
index 00000000000..5a47f9cae7d
--- /dev/null
+++ b/src/backend/libpq/pg_hosts.conf.sample
@@ -0,0 +1,4 @@
+# PostgreSQL SNI Hostname mappings
+# ================================
+
+# HOSTNAME       SSL CERTIFICATE             SSL KEY
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index c6484aea087..f35a15b48df 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -56,6 +56,7 @@
 #define CONFIG_FILENAME "postgresql.conf"
 #define HBA_FILENAME	"pg_hba.conf"
 #define IDENT_FILENAME	"pg_ident.conf"
+#define HOSTS_FILENAME	"pg_hosts.conf"
 
 #ifdef EXEC_BACKEND
 #define CONFIG_EXEC_PARAMS "global/config_exec_params"
@@ -1838,6 +1839,36 @@ SelectConfigFiles(const char *userDoption, const char *progname)
 	}
 	SetConfigOption("ident_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
 
+	if (fname_is_malloced)
+		free(fname);
+	else
+		guc_free(fname);
+
+	/*
+	 * Likewise for pg_hosts.conf.
+	 */
+	if (HostsFileName)
+	{
+		fname = make_absolute_path(HostsFileName);
+		fname_is_malloced = true;
+	}
+	else if (configdir)
+	{
+		fname = guc_malloc(FATAL,
+						   strlen(configdir) + strlen(HOSTS_FILENAME) + 2);
+		sprintf(fname, "%s/%s", configdir, HOSTS_FILENAME);
+		fname_is_malloced = false;
+	}
+	else
+	{
+		write_stderr("%s does not know where to find the \"hosts\" configuration file.\n"
+					 "This can be specified as \"hosts_file\" in \"%s\", "
+					 "or by the -D invocation option, or by the "
+					 "PGDATA environment variable.\n",
+					 progname, ConfigFileName);
+	}
+	SetConfigOption("hosts_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
+
 	if (fname_is_malloced)
 		free(fname);
 	else
diff --git a/src/backend/utils/misc/guc_parameters.dat b/src/backend/utils/misc/guc_parameters.dat
index 1128167c025..a895067f7ad 100644
--- a/src/backend/utils/misc/guc_parameters.dat
+++ b/src/backend/utils/misc/guc_parameters.dat
@@ -1160,6 +1160,13 @@
   boot_val => 'NULL',
 },
 
+{ name => 'hosts_file', type => 'string', context => 'PGC_POSTMASTER', group => 'FILE_LOCATIONS',
+  short_desc => 'Sets the server\'s "hosts" configuration file.',
+  flags => 'GUC_SUPERUSER_ONLY',
+  variable => 'HostsFileName',
+  boot_val => 'NULL',
+},
+
 { name => 'hot_standby', type => 'bool', context => 'PGC_POSTMASTER', group => 'REPLICATION_STANDBY',
   short_desc => 'Allows connections and queries during recovery.',
   variable => 'EnableHotStandby',
@@ -2735,6 +2742,14 @@
   max => '0',
 },
 
+{ name => 'ssl_snimode', type => 'enum', context => 'PGC_SIGHUP', group => 'CONN_AUTH_SSL',
+  short_desc => 'Sets the SNI mode to use for the server.',
+  flags => 'GUC_SUPERUSER_ONLY',
+  variable => 'ssl_snimode',
+  boot_val => 'SSL_SNIMODE_OFF',
+  options => 'ssl_snimode_options',
+},
+
 { name => 'ssl_tls13_ciphers', type => 'string', context => 'PGC_SIGHUP', group => 'CONN_AUTH_SSL',
   short_desc => 'Sets the list of allowed TLSv1.3 cipher suites.',
   long_desc => 'An empty string means use the default cipher suites.',
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index 0209b2067a2..d429c658054 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -491,6 +491,13 @@ static const struct config_enum_entry file_copy_method_options[] = {
 	{NULL, 0, false}
 };
 
+static const struct config_enum_entry ssl_snimode_options[] = {
+	{"off", SSL_SNIMODE_OFF, false},
+	{"default", SSL_SNIMODE_DEFAULT, false},
+	{"strict", SSL_SNIMODE_STRICT, false},
+	{NULL, 0, false}
+};
+
 /*
  * Options for enum values stored in other modules
  */
@@ -556,6 +563,7 @@ char	   *cluster_name = "";
 char	   *ConfigFileName;
 char	   *HbaFileName;
 char	   *IdentFileName;
+char	   *HostsFileName;
 char	   *external_pid_file;
 
 char	   *application_name;
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index dc9e2255f8a..c5ff8302201 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -45,6 +45,8 @@
                                         # (change requires restart)
 #ident_file = 'ConfigDir/pg_ident.conf' # ident configuration file
                                         # (change requires restart)
+#hosts_file = 'ConfigDir/pg_hosts.conf' # hosts configuration file
+                                        # (change requires restart)
 
 # If external_pid_file is not explicitly set, no extra PID file is written.
 #external_pid_file = ''                 # write an extra PID file
@@ -121,6 +123,7 @@
 #ssl_dh_params_file = ''
 #ssl_passphrase_command = ''
 #ssl_passphrase_command_supports_reload = off
+#ssl_snimode = off
 
 
 #------------------------------------------------------------------------------
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 92fe2f531f7..c953f24a58d 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -177,6 +177,7 @@ static int	encodingid;
 static char *bki_file;
 static char *hba_file;
 static char *ident_file;
+static char *hosts_file;
 static char *conf_file;
 static char *dictionary_file;
 static char *info_schema_file;
@@ -1530,6 +1531,14 @@ setup_config(void)
 
 	snprintf(path, sizeof(path), "%s/pg_ident.conf", pg_data);
 
+	writefile(path, conflines);
+	if (chmod(path, pg_file_create_mode) != 0)
+		pg_fatal("could not change permissions of \"%s\": %m", path);
+
+	/* pg_hosts.conf */
+	conflines = readfile(hosts_file);
+	snprintf(path, sizeof(path), "%s/pg_hosts.conf", pg_data);
+
 	writefile(path, conflines);
 	if (chmod(path, pg_file_create_mode) != 0)
 		pg_fatal("could not change permissions of \"%s\": %m", path);
@@ -2791,6 +2800,7 @@ setup_data_file_paths(void)
 	set_input(&bki_file, "postgres.bki");
 	set_input(&hba_file, "pg_hba.conf.sample");
 	set_input(&ident_file, "pg_ident.conf.sample");
+	set_input(&hosts_file, "pg_hosts.conf.sample");
 	set_input(&conf_file, "postgresql.conf.sample");
 	set_input(&dictionary_file, "snowball_create.sql");
 	set_input(&info_schema_file, "information_schema.sql");
@@ -2806,12 +2816,12 @@ setup_data_file_paths(void)
 				"PGDATA=%s\nshare_path=%s\nPGPATH=%s\n"
 				"POSTGRES_SUPERUSERNAME=%s\nPOSTGRES_BKI=%s\n"
 				"POSTGRESQL_CONF_SAMPLE=%s\n"
-				"PG_HBA_SAMPLE=%s\nPG_IDENT_SAMPLE=%s\n",
+				"PG_HBA_SAMPLE=%s\nPG_IDENT_SAMPLE=%s\nPG_HOSTS_SAMPLE=%s\n",
 				PG_VERSION,
 				pg_data, share_path, bin_path,
 				username, bki_file,
 				conf_file,
-				hba_file, ident_file);
+				hba_file, ident_file, hosts_file);
 		if (show_setting)
 			exit(0);
 	}
@@ -2819,6 +2829,7 @@ setup_data_file_paths(void)
 	check_input(bki_file);
 	check_input(hba_file);
 	check_input(ident_file);
+	check_input(hosts_file);
 	check_input(conf_file);
 	check_input(dictionary_file);
 	check_input(info_schema_file);
diff --git a/src/include/libpq/hba.h b/src/include/libpq/hba.h
index e3748d3c8c9..c96818549cc 100644
--- a/src/include/libpq/hba.h
+++ b/src/include/libpq/hba.h
@@ -151,6 +151,25 @@ typedef struct IdentLine
 	AuthToken  *pg_user;
 } IdentLine;
 
+typedef struct HostsLine
+{
+	int			linenumber;
+
+	char	   *sourcefile;
+	char	   *rawline;
+
+	/* Required fields */
+	bool		default_host;
+	char	   *hostname;
+	char	   *ssl_key;
+	char	   *ssl_cert;
+	char	   *ssl_ca;
+
+	/* Optional fields */
+	char	   *ssl_passphrase_cmd;
+	bool		ssl_passphrase_reload;
+} HostsLine;
+
 /*
  * TokenizedAuthLine represents one line lexed from an authentication
  * configuration file.  Each item in the "fields" list is a sub-list of
diff --git a/src/include/libpq/libpq-be.h b/src/include/libpq/libpq-be.h
index d6e671a6382..e1631cb7b5c 100644
--- a/src/include/libpq/libpq-be.h
+++ b/src/include/libpq/libpq-be.h
@@ -320,6 +320,7 @@ extern const char *be_tls_get_cipher(Port *port);
 extern void be_tls_get_peer_subject_name(Port *port, char *ptr, size_t len);
 extern void be_tls_get_peer_issuer_name(Port *port, char *ptr, size_t len);
 extern void be_tls_get_peer_serial(Port *port, char *ptr, size_t len);
+extern bool be_tls_loaded_verify_locations(void);
 
 /*
  * Get the server certificate hash for SCRAM channel binding type
@@ -332,7 +333,7 @@ extern char *be_tls_get_certificate_hash(Port *port, size_t *len);
 
 /* init hook for SSL, the default sets the password callback if appropriate */
 #ifdef USE_OPENSSL
-typedef void (*openssl_tls_init_hook_typ) (SSL_CTX *context, bool isServerStart);
+typedef void (*openssl_tls_init_hook_typ) (SSL_CTX *context, bool isServerStart, HostsLine *host);
 extern PGDLLIMPORT openssl_tls_init_hook_typ openssl_tls_init_hook;
 #endif
 
diff --git a/src/include/libpq/libpq.h b/src/include/libpq/libpq.h
index 5af005ad779..54d8ee8a2aa 100644
--- a/src/include/libpq/libpq.h
+++ b/src/include/libpq/libpq.h
@@ -107,6 +107,7 @@ extern PGDLLIMPORT char *ssl_crl_dir;
 extern PGDLLIMPORT char *ssl_key_file;
 extern PGDLLIMPORT int ssl_min_protocol_version;
 extern PGDLLIMPORT int ssl_max_protocol_version;
+extern PGDLLIMPORT int ssl_snimode;
 extern PGDLLIMPORT char *ssl_passphrase_command;
 extern PGDLLIMPORT bool ssl_passphrase_command_supports_reload;
 extern PGDLLIMPORT char *ssl_dh_params_file;
@@ -152,12 +153,20 @@ enum ssl_protocol_versions
 	PG_TLS1_3_VERSION,
 };
 
+enum ssl_snimode
+{
+	SSL_SNIMODE_OFF = 0,
+	SSL_SNIMODE_DEFAULT,
+	SSL_SNIMODE_STRICT
+};
+
 /*
  * prototypes for functions in be-secure-common.c
  */
 extern int	run_ssl_passphrase_command(const char *prompt, bool is_server_start,
-									   char *buf, int size);
+									   char *buf, int size, void *userdata);
 extern bool check_ssl_key_file_permissions(const char *ssl_key_file,
 										   bool isServerStart);
+extern bool load_hosts(List **hosts);
 
 #endif							/* LIBPQ_H */
diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index f21ec37da89..8f08a38b789 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -312,6 +312,7 @@ extern PGDLLIMPORT char *cluster_name;
 extern PGDLLIMPORT char *ConfigFileName;
 extern PGDLLIMPORT char *HbaFileName;
 extern PGDLLIMPORT char *IdentFileName;
+extern PGDLLIMPORT char *HostsFileName;
 extern PGDLLIMPORT char *external_pid_file;
 
 extern PGDLLIMPORT char *application_name;
diff --git a/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c b/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
index d5992149821..a85d85735cf 100644
--- a/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
+++ b/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
@@ -26,7 +26,7 @@ static char *ssl_passphrase = NULL;
 static int	rot13_passphrase(char *buf, int size, int rwflag, void *userdata);
 
 /* hook function to set the callback */
-static void set_rot13(SSL_CTX *context, bool isServerStart);
+static void set_rot13(SSL_CTX *context, bool isServerStart, HostsLine *host);
 
 /*
  * Module load callback
@@ -53,7 +53,7 @@ _PG_init(void)
 }
 
 static void
-set_rot13(SSL_CTX *context, bool isServerStart)
+set_rot13(SSL_CTX *context, bool isServerStart, HostsLine *host)
 {
 	/* warn if the user has set ssl_passphrase_command */
 	if (ssl_passphrase_command[0])
diff --git a/src/test/perl/PostgreSQL/Test/Cluster.pm b/src/test/perl/PostgreSQL/Test/Cluster.pm
index 35413f14019..55e0f04d4f5 100644
--- a/src/test/perl/PostgreSQL/Test/Cluster.pm
+++ b/src/test/perl/PostgreSQL/Test/Cluster.pm
@@ -1302,6 +1302,27 @@ Wrapper for pg_ctl restart.
 With optional extra param fail_ok => 1, returns 0 for failure
 instead of bailing out.
 
+=over
+
+=item fail_ok => 1
+
+By default, failure terminates the entire F<prove> invocation.  If given,
+instead return 0 for failure instead of bailing out.
+
+=item log_unlike => B<pattern>
+
+When defined, the logfile is inspected for the presence of the fragment by
+matching the specified pattern. If the pattern matches against the logfile a
+test failure will be logged.
+
+=item log_like => B<pattern>
+
+When defined, the logfile is inspected for the presence of the fragment by
+matching the pattern. If the pattern doesn't match a test failure will be
+logged.
+
+=back
+
 =cut
 
 sub restart
@@ -1314,6 +1335,8 @@ sub restart
 
 	print "### Restarting node \"$name\"\n";
 
+	my $log_location = -s $self->logfile;
+
 	# -w is now the default but having it here does no harm and helps
 	# compatibility with older versions.
 	$ret = PostgreSQL::Test::Utils::system_log(
@@ -1322,6 +1345,18 @@ sub restart
 		'--log' => $self->logfile,
 		'restart');
 
+	# Check for expected and/or unexpected log fragments if the caller
+	# specified such checks in the params
+	if (defined $params{log_unlike} || defined $params{log_like})
+	{
+		my $log =
+		  PostgreSQL::Test::Utils::slurp_file($self->logfile, $log_location);
+		unlike($log, $params{log_unlike}, "unexpected fragment found in log")
+			if defined $params{log_unlike};
+		like($log, $params{log_like}, "expected fragment not found in log")
+			if defined $params{log_like};
+	}
+
 	if ($ret != 0)
 	{
 		print "# pg_ctl restart failed; see logfile for details: "
diff --git a/src/test/ssl/meson.build b/src/test/ssl/meson.build
index d8e0fb518e0..e5a9402cd9c 100644
--- a/src/test/ssl/meson.build
+++ b/src/test/ssl/meson.build
@@ -13,6 +13,7 @@ tests += {
       't/001_ssltests.pl',
       't/002_scram.pl',
       't/003_sslinfo.pl',
+      't/004_sni.pl',
     ],
   },
 }
diff --git a/src/test/ssl/t/004_sni.pl b/src/test/ssl/t/004_sni.pl
new file mode 100644
index 00000000000..90d7560ad11
--- /dev/null
+++ b/src/test/ssl/t/004_sni.pl
@@ -0,0 +1,237 @@
+
+# Copyright (c) 2024, PostgreSQL Global Development Group
+
+use strict;
+use warnings FATAL => 'all';
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+use FindBin;
+use lib $FindBin::RealBin;
+
+use SSL::Server;
+
+# This is the hostname used to connect to the server. This cannot be a
+# hostname, because the server certificate is always for the domain
+# postgresql-ssl-regression.test.
+my $SERVERHOSTADDR = '127.0.0.1';
+# This is the pattern to use in pg_hba.conf to match incoming connections.
+my $SERVERHOSTCIDR = '127.0.0.1/32';
+
+if ($ENV{with_ssl} ne 'openssl')
+{
+	plan skip_all => 'OpenSSL not supported by this build';
+}
+
+if (!$ENV{PG_TEST_EXTRA} || $ENV{PG_TEST_EXTRA} !~ /\bssl\b/)
+{
+	plan skip_all =>
+	  'Potentially unsafe test SSL not enabled in PG_TEST_EXTRA';
+}
+
+my $ssl_server = SSL::Server->new();
+
+my $node = PostgreSQL::Test::Cluster->new('primary');
+$node->init;
+
+# PGHOST is enforced here to set up the node, subsequent connections
+# will use a dedicated connection string.
+$ENV{PGHOST} = $node->host;
+$ENV{PGPORT} = $node->port;
+$node->start;
+
+$ssl_server->configure_test_server_for_ssl($node, $SERVERHOSTADDR,
+	$SERVERHOSTCIDR, 'trust');
+
+$ssl_server->switch_server_cert($node, certfile => 'server-cn-only');
+
+my $connstr =
+  "user=ssltestuser dbname=trustdb hostaddr=$SERVERHOSTADDR host=localhost sslsni=1";
+
+$node->append_conf('postgresql.conf', "ssl_snimode=default");
+$node->reload;
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"connect fails with fallback hostname, without intermediate",
+	expected_stderr => qr/certificate verify failed/);
+
+# example.org serves the server cert and its intermediate CA.
+$node->append_conf('pg_hosts.conf',
+	"example.org server-cn-only+server_ca.crt server-cn-only.key root_ca.crt"
+);
+$node->reload;
+
+$node->connect_ok(
+	"$connstr host=example.org sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"connect with configured hostname, serving intermediate server CA");
+
+$node->connect_fails(
+	"$connstr sslrootcert=invalid sslmode=verify-ca",
+	"connect without server root cert sslmode=verify-ca",
+	expected_stderr => qr/root certificate file "invalid" does not exist/);
+
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"connect still fails with fallback hostname, without intermediate",
+	expected_stderr => qr/certificate verify failed/);
+
+$node->connect_ok(
+	"$connstr host=localhost sslrootcert=ssl/root+server_ca.crt sslmode=verify-ca",
+	"connect with fallback hostname, intermediate included");
+
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	"localhost server-cn-only.crt server-cn-only.key root_ca.crt");
+$node->append_conf('postgresql.conf', "ssl_snimode=strict");
+$node->reload;
+
+$node->connect_fails(
+	"$connstr host=example.org sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with missing hostconfig and snimode=strict",
+	expected_stderr => qr/tlsv1 unrecognized name/);
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require sslsni=1",
+	"connect with correct server CA cert file sslmode=require");
+
+# Attempts at connecting without SNI when the server is using strict mode should
+# result in connection failure.
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require sslsni=0",
+	"connect with correct server CA cert file without SNI for strict mode",
+	expected_stderr => qr/tlsv13 alert missing extension/);
+
+# Reconfigure with broken configuration for the key passphrase, the server
+# should not start up
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo wrongpassword" on'
+);
+my $result = $node->restart(fail_ok => 1);
+is($result, 0,
+	'restart fails with password-protected key when using the wrong passphrase command'
+);
+
+# Reconfigure again but with the correct passphrase set
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo secret1" on'
+);
+$result = $node->restart(fail_ok => 1);
+is($result, 1,
+	'restart succeeds with password-protected key when using the correct passphrase command'
+);
+
+# Make sure connecting works, and try to stress the reload logic by issuing
+# subsequent reloads
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+$node->reload;
+$node->reload;
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file after reloads");
+$node->reload;
+$node->reload;
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file after more reloads");
+
+# Test reloading a passphrase protected key without reloading support in the
+# passphrase hook. Connecting after restart should succeed but not after the
+# following reload.
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo secret1" off'
+);
+$result = $node->restart(fail_ok => 1);
+is($result, 1,
+	'restart succeeds with password-protected key when using the correct passphrase command'
+);
+SKIP:
+{
+	# Passphrase reloads must be enabled on Windows to succeed even without a
+	# restart
+	skip "Passphrase command reload required on Windows", 1 if ($windows_os);
+
+	$node->connect_ok(
+		"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+		"connect with correct server CA cert file sslmode=require");
+}
+
+$node->reload;
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect fails since the passphrase protected key cannot be reloaded");
+
+# Test client CAs by connecting to hosts in pg_hosts.conf while at the same
+# time swapping out default contexts containing different CA configurations.
+
+# pg_hosts configuration
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+# example.org has an unconfigured CA.
+$node->append_conf('pg_hosts.conf',
+	'example.org server-cn-only.crt server-cn-only.key ""');
+# example.com uses the client CA.
+$node->append_conf('pg_hosts.conf',
+	'example.com server-cn-only.crt server-cn-only.key root+client_ca.crt');
+# example.net uses the server CA (which is wrong).
+$node->append_conf('pg_hosts.conf',
+	'example.net server-cn-only.crt server-cn-only.key root+server_ca.crt');
+$node->reload;
+
+$connstr =
+  "user=ssltestuser dbname=certdb hostaddr=$SERVERHOSTADDR sslmode=require sslsni=1";
+
+foreach my $default_ca ("", "root+client_ca", "root+server_ca")
+{
+	# The default CA should, not matter for the purposes of these tests, since
+	# we connect to the other hosts explicitly. Test with various default CA
+	# settings to ensure it's isolated from the actual connections.
+	$ssl_server->switch_server_cert(
+		$node,
+		certfile => 'server-cn-only',
+		cafile => $default_ca);
+
+	# example.org is unconfigured and should fail.
+	$node->connect_fails(
+		"$connstr host=example.org sslcertmode=require sslcert=ssl/client.crt "
+		  . $ssl_server->sslkey('client.key'),
+		"host: 'example.org', ca: '$default_ca': connect with sslcert, no client CA configured",
+		expected_stderr => qr/certificate verify failed/);
+
+	# example.com is configured and should require a valid client cert.
+	$node->connect_fails(
+		"$connstr host=example.com sslcertmode=disable",
+		"host: 'example.com', ca: '$default_ca': connect fails if no client certificate sent",
+		expected_stderr => qr/certificate verify failed/);
+
+	$node->connect_ok(
+		"$connstr host=example.com sslrootcert=ssl/root+server_ca.crt sslcertmode=require sslcert=ssl/client.crt "
+		  . $ssl_server->sslkey('client.key'),
+		"host: 'example.com', ca: '$default_ca': connect with sslcert, client certificate sent"
+	);
+
+	# example.net is configured and should require a client cert, but will
+	# always fail verification.
+	$node->connect_fails(
+		"$connstr host=example.net sslcertmode=disable",
+		"host: 'example.net', ca: '$default_ca': connect fails if no client certificate sent",
+		expected_stderr => qr/certificate verify failed/);
+
+	$node->connect_fails(
+		"$connstr host=example.net sslcertmode=require sslcert=ssl/client.crt "
+		  . $ssl_server->sslkey('client.key'),
+		"host: 'example.net', ca: '$default_ca': connect with sslcert, client certificate sent",
+		expected_stderr => qr/certificate verify failed/);
+}
+
+done_testing();
diff --git a/src/test/ssl/t/SSL/Backend/OpenSSL.pm b/src/test/ssl/t/SSL/Backend/OpenSSL.pm
index 4159addb700..bbd3bed6c86 100644
--- a/src/test/ssl/t/SSL/Backend/OpenSSL.pm
+++ b/src/test/ssl/t/SSL/Backend/OpenSSL.pm
@@ -72,6 +72,7 @@ sub init
 	chmod(0600, glob "$pgdata/server-*.key")
 	  or die "failed to change permissions on server keys: $!";
 	_copy_files("ssl/root+client_ca.crt", $pgdata);
+	_copy_files("ssl/root+server_ca.crt", $pgdata);
 	_copy_files("ssl/root_ca.crt", $pgdata);
 	_copy_files("ssl/root+client.crl", $pgdata);
 	mkdir("$pgdata/root+client-crldir")
@@ -146,7 +147,8 @@ following parameters are supported:
 =item cafile => B<value>
 
 The CA certificate file to use for the C<ssl_ca_file> GUC. If omitted it will
-default to 'root+client_ca.crt'.
+default to 'root+client_ca.crt'. If empty, no C<ssl_ca_file> configuration
+parameter will be set.
 
 =item certfile => B<value>
 
@@ -181,10 +183,18 @@ sub set_server_cert
 	  unless defined $params->{keyfile};
 
 	my $sslconf =
-		"ssl_ca_file='$params->{cafile}.crt'\n"
-	  . "ssl_cert_file='$params->{certfile}.crt'\n"
+		"ssl_cert_file='$params->{certfile}.crt'\n"
 	  . "ssl_key_file='$params->{keyfile}.key'\n"
 	  . "ssl_crl_file='$params->{crlfile}'\n";
+	if ($params->{cafile} ne "")
+	{
+		$sslconf .= "ssl_ca_file='$params->{cafile}.crt'\n";
+	}
+	else
+	{
+		$sslconf .= "ssl_ca_file=''\n";
+	}
+
 	$sslconf .= "ssl_crl_dir='$params->{crldir}'\n"
 	  if defined $params->{crldir};
 
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 57a8f0366a5..bd80880c453 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -1206,6 +1206,8 @@ HeapTupleHeader
 HeapTupleHeaderData
 HeapTupleTableSlot
 HistControl
+HostContext
+HostsLine
 HotStandbyState
 I32
 ICU_Convert_Func
-- 
2.39.3 (Apple Git-146)

From d3eecf4ec13de48e8729c92670560ce79a15b6d1 Mon Sep 17 00:00:00 2001
From: Daniel Gustafsson <dgustafsson@postgresql.org>
Date: Wed, 26 Nov 2025 15:30:56 +0100
Subject: [PATCH v12] Serverside SNI support for libpq

Support for SNI was added to clientside libpq in 5c55dc8b4733 with the
sslsni parameter, but there was no support for utilizing it serverside.
This adds support for serverside SNI such that certificate/key handling
is available per host.  A new config file, $datadir/pg_hosts.conf, is
used for configuring which certificate and key should be used for which
hostname.  A new GUC, ssl_snimode, is used to control how the hostname
TLS extension is handled.  The possible values are off (which is used
as the new backwards compatible default), default and strict:

  - off: pg_hosts.conf is not parsed and the hostname TLS extension is
    not inspected at all.  SSL GUCs for certificates and keys are used.
  - default: pg_hosts.conf is loaded as well as the normal GUCs. If no
    match for the TLS extension hostname is found in pg_hosts the cert
    and key from the postgresql.conf GUCs is used as the default (used
    as a wildcard host).
  - strict: only pg_hosts.conf is loaded and the TLS extension hostname
    MUST be passed and MUST have a match in the configuration, else the
    connection is refused.

CRL file(s) are applied from postgresql.conf to all configured hostnames.

Author: Daniel Gustafsson <daniel@yesql.se>
Reviewed-by: Jacob Champion <jacob.champion@enterprisedb.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Reviewed-by: Dewei Dai <daidewei1970@163.com>
Reviewed-by: Cary Huang <cary.huang@highgo.ca>
Discussion: https://postgr.es/m/1C81CD0D-407E-44F9-833A-DD0331C202E5@yesql.se
---
 doc/src/sgml/config.sgml                      |  66 +++
 doc/src/sgml/runtime.sgml                     |  67 +++
 src/backend/Makefile                          |   2 +
 src/backend/libpq/be-secure-common.c          | 223 ++++++++-
 src/backend/libpq/be-secure-openssl.c         | 443 ++++++++++++++++--
 src/backend/libpq/be-secure.c                 |   8 +-
 src/backend/libpq/meson.build                 |   1 +
 src/backend/libpq/pg_hosts.conf.sample        |   4 +
 src/backend/utils/misc/guc.c                  |  31 ++
 src/backend/utils/misc/guc_parameters.dat     |  15 +
 src/backend/utils/misc/guc_tables.c           |   8 +
 src/backend/utils/misc/postgresql.conf.sample |   3 +
 src/bin/initdb/initdb.c                       |  15 +-
 src/include/libpq/hba.h                       |  19 +
 src/include/libpq/libpq-be.h                  |   3 +-
 src/include/libpq/libpq.h                     |  11 +-
 src/include/utils/guc.h                       |   1 +
 .../ssl_passphrase_func.c                     |   4 +-
 src/test/perl/PostgreSQL/Test/Cluster.pm      |  35 ++
 src/test/ssl/meson.build                      |   1 +
 src/test/ssl/t/004_sni.pl                     | 237 ++++++++++
 src/test/ssl/t/SSL/Backend/OpenSSL.pm         |  16 +-
 src/tools/pgindent/typedefs.list              |   2 +
 23 files changed, 1152 insertions(+), 63 deletions(-)
 create mode 100644 src/backend/libpq/pg_hosts.conf.sample
 create mode 100644 src/test/ssl/t/004_sni.pl

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 737b90736bf..acae1601d39 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1700,6 +1700,72 @@ include_dir 'conf.d'
        </para>
       </listitem>
      </varlistentry>
+
+     <varlistentry id="guc-ssl-snimode" xreflabel="ssl_snimode">
+      <term><varname>ssl_snimode</varname> (<type>enum</type>)
+      <indexterm>
+       <primary><varname>ssl_snimode</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        This parameter determines if the server will inspect the <acronym>SNI</acronym> TLS extension
+        when establishing the connection, and how it should be interpreted.
+        Valid values are currently: <literal>off</literal>, <literal>default</literal> and <literal>strict</literal>.
+       </para>
+       <para>
+        <variablelist>
+         <varlistentry id="guc-ssl-snimode-off">
+          <term><literal>off</literal></term>
+          <listitem>
+           <para>
+            SNI is not enabled and no configuration from
+            <filename>pg_hosts.conf</filename> is loaded.  Configuration of SSL
+            for all connections is done with <xref linkend="guc-ssl-cert-file"/>,
+            <xref linkend="guc-ssl-key-file"/> and <xref linkend="guc-ssl-ca-file"/>.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry id="guc-ssl-snimode-default">
+          <term><literal>default</literal></term>
+          <listitem>
+           <para>
+            SNI is enabled and hostname configuration is loaded from
+            <filename>pg_hosts.conf</filename>. <xref linkend="guc-ssl-cert-file"/>,
+            <xref linkend="guc-ssl-key-file"/> and <xref linkend="guc-ssl-ca-file"/>
+            are loaded as the default configuration.  Connections specifying
+            <xref linkend="libpq-connect-sslsni"/> to <literal>1</literal>
+            will be attempted using the default configuration if the hostname
+            is missing in <filename>pg_hosts.conf</filename>.  If the hostname
+            matches an entry from <filename>pg_hosts.conf</filename>, then the
+            configuration from that entry will be used for setting up the
+            connection.
+           </para>
+          </listitem>
+         </varlistentry>
+
+         <varlistentry id="guc-ssl-snimode-strict">
+          <term><literal>strict</literal></term>
+          <listitem>
+           <para>
+            SNI is enabled and all connections are required to set <xref
+            linkend="libpq-connect-sslsni"/> to <literal>1</literal> and
+            specify a hostname matching an entry in
+            <filename>pg_hosts.conf</filename>. Any connection without <xref
+            linkend="libpq-connect-sslsni"/> or with a hostname missing from
+            <filename>pg_hosts.conf</filename> will be rejected.
+            <xref linkend="guc-ssl-cert-file"/>,
+            <xref linkend="guc-ssl-key-file"/> and <xref linkend="guc-ssl-ca-file"/>
+            are loaded in order to drive the handshake until the appropriate
+            configuration has been selected.
+           </para>
+          </listitem>
+         </varlistentry>
+        </variablelist>
+       </para>
+      </listitem>
+     </varlistentry>
     </variablelist>
     </sect2>
    </sect1>
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index 0c60bafac63..687aa86f68a 100644
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -2445,6 +2445,12 @@ pg_dumpall -p 5432 | psql -d postgres -p 5433
       <entry>client certificate must not be on this list</entry>
      </row>
 
+     <row>
+      <entry><filename>$PGDATA/pg_hosts.conf</filename></entry>
+      <entry>SNI configuration</entry>
+      <entry>defines which certificates to use for which server hostname</entry>
+     </row>
+
     </tbody>
    </tgroup>
   </table>
@@ -2572,6 +2578,67 @@ openssl x509 -req -in server.csr -text -days 365 \
    </para>
   </sect2>
 
+  <sect2 id="ssl-sni">
+   <title>SNI Configuration</title>
+
+   <para>
+    <productname>PostgreSQL</productname> can be configured for
+    <acronym>SNI</acronym> using the <filename>pg_hosts.conf</filename>
+    configuration file. <productname>PostgreSQL</productname> inspects the TLS
+    hostname extension in the SSL connection handshake, and selects the right
+    TLS certificate, key and CA certificate to use for the connection.
+   </para>
+
+   <para>
+    SNI configuration is defined in the hosts configuration file,
+    <filename>pg_hosts.conf</filename>, which is stored in the cluster's
+    data directory.  The hosts configuration file contains lines of the general
+    forms:
+<synopsis>
+<replaceable>hostname</replaceable> <replaceable>SSL_certificate</replaceable> <replaceable>SSL_key</replaceable> <replaceable>SSL_CA_certificate</replaceable> <replaceable>SSL_passphrase_cmd</replaceable> <replaceable>SSL_passphrase_cmd_reload</replaceable>
+<replaceable>include</replaceable> <replaceable>file</replaceable>
+<replaceable>include_if_exists</replaceable> <replaceable>file</replaceable>
+<replaceable>include_dir</replaceable> <replaceable>directory</replaceable>
+</synopsis>
+    Comments, whitespace and line continuations are handled in the same way as
+    in <filename>pg_hba.conf</filename>.  <replaceable>hostname</replaceable>
+    is matched against the hostname TLS extension in the SSL handshake.
+    <replaceable>SSL_certificate</replaceable>,
+    <replaceable>SSL_key</replaceable>,
+    <replaceable>SSL_CA_certificate</replaceable>,
+    <replaceable>SSL_passphrase_cmd</replaceable>, and
+    <replaceable>SSL_passphrase_cmd_reload</replaceable>
+    are treated like
+    <xref linkend="guc-ssl-cert-file"/>,
+    <xref linkend="guc-ssl-key-file"/>,
+    <xref linkend="guc-ssl-ca-file"/>,
+    <xref linkend="guc-ssl-passphrase-command"/>, and
+    <xref linkend="guc-ssl-passphrase-command-supports-reload"/> respectively.
+    All fields except <replaceable>SSL_passphrase_cmd</replaceable> and
+    <replaceable>SSL_passphrase_cmd_reload</replaceable> are required. If
+    <replaceable>SSL_passphrase_cmd</replaceable> is defined but not
+    <replaceable>SSL_passphrase_cmd_reload</replaceable> then the default
+    value for <replaceable>SSL_passphrase_cmd_reload</replaceable> is
+    <literal>off</literal>.
+   </para>
+   <para>
+    The SSL configuration from <filename>postgresql.conf</filename> is used
+    in order to set up the TLS handshake such that the hostname extension can
+    be inspected.  When <xref linkend="guc-ssl-snimode"/> is set to
+    <literal>default</literal> this configuration will be the default fallback
+    if no matching hostname is found in <filename>pg_hosts.conf</filename>.  If
+    <xref linkend="guc-ssl-snimode"/> is set to <literal>strict</literal> it
+    will only be used for the handshake until the hostname is inspected, it
+    will not be used for the connection.
+   </para>
+   <para>
+    It is currently not possible to set different <literal>clientname</literal>
+    values for the different certificates.  Any <literal>clientname</literal>
+    setting in <filename>pg_hba.conf</filename> will be applied during
+    authentication regardless of which set of certificates have been loaded
+    via an SNI enabled connection.
+   </para>
+  </sect2>
  </sect1>
 
  <sect1 id="gssapi-enc">
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 7344c8c7f5c..529126eebeb 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -187,6 +187,7 @@ endif
 	$(MAKE) -C utils install-data
 	$(INSTALL_DATA) $(srcdir)/libpq/pg_hba.conf.sample '$(DESTDIR)$(datadir)/pg_hba.conf.sample'
 	$(INSTALL_DATA) $(srcdir)/libpq/pg_ident.conf.sample '$(DESTDIR)$(datadir)/pg_ident.conf.sample'
+	$(INSTALL_DATA) $(srcdir)/libpq/pg_hosts.conf.sample '$(DESTDIR)$(datadir)/pg_hosts.conf.sample'
 	$(INSTALL_DATA) $(srcdir)/utils/misc/postgresql.conf.sample '$(DESTDIR)$(datadir)/postgresql.conf.sample'
 
 ifeq ($(with_llvm), yes)
@@ -246,6 +247,7 @@ endif
 	$(MAKE) -C utils uninstall-data
 	rm -f '$(DESTDIR)$(datadir)/pg_hba.conf.sample' \
 	      '$(DESTDIR)$(datadir)/pg_ident.conf.sample' \
+	      '$(DESTDIR)$(datadir)/pg_hosts.conf.sample' \
 	      '$(DESTDIR)$(datadir)/postgresql.conf.sample'
 ifeq ($(with_llvm), yes)
 	$(call uninstall_llvm_module,postgres)
diff --git a/src/backend/libpq/be-secure-common.c b/src/backend/libpq/be-secure-common.c
index e8b837d1fa7..8d5a0c1ba2c 100644
--- a/src/backend/libpq/be-secure-common.c
+++ b/src/backend/libpq/be-secure-common.c
@@ -24,32 +24,40 @@
 
 #include "common/percentrepl.h"
 #include "common/string.h"
+#include "libpq/hba.h"
 #include "libpq/libpq.h"
 #include "storage/fd.h"
+#include "utils/guc.h"
+#include "utils/memutils.h"
+
+static HostsLine *parse_hosts_line(TokenizedAuthLine *tok_line, int elevel);
 
 /*
  * Run ssl_passphrase_command
  *
  * prompt will be substituted for %p.  is_server_start determines the loglevel
- * of error messages.
+ * of error messages from executing the command, the loglevel for failures in
+ * param substitution will be ERROR regardless of is_server_start.  The actual
+ * command used depends on the configuration for the current host.
  *
  * The result will be put in buffer buf, which is of size size.  The return
  * value is the length of the actual result.
  */
 int
-run_ssl_passphrase_command(const char *prompt, bool is_server_start, char *buf, int size)
+run_ssl_passphrase_command(const char *prompt, bool is_server_start, char *buf, int size, void *userdata)
 {
 	int			loglevel = is_server_start ? ERROR : LOG;
 	char	   *command;
 	FILE	   *fh;
 	int			pclose_rc;
 	size_t		len = 0;
+	const char *cmd = (const char *) userdata;
 
 	Assert(prompt);
 	Assert(size > 0);
 	buf[0] = '\0';
 
-	command = replace_percent_placeholders(ssl_passphrase_command, "ssl_passphrase_command", "p", prompt);
+	command = replace_percent_placeholders(cmd, "ssl_passphrase_command", "p", prompt);
 
 	fh = OpenPipeStream(command, "r");
 	if (fh == NULL)
@@ -175,3 +183,212 @@ check_ssl_key_file_permissions(const char *ssl_key_file, bool isServerStart)
 
 	return true;
 }
+
+/*
+ * parse_hosts_line
+ *
+ * Parses a loaded line from the pg_hosts.conf configuration and pulls out the
+ * hostname, certificate, key and CA parts in order to build an SNI config in
+ * the TLS backend. Validation of the parsed values is left for the TLS backend
+ * to implement.
+ */
+static HostsLine *
+parse_hosts_line(TokenizedAuthLine *tok_line, int elevel)
+{
+	HostsLine  *parsedline;
+	List	   *tokens;
+	ListCell   *field;
+	AuthToken  *token;
+
+	parsedline = palloc0(sizeof(HostsLine));
+	parsedline->sourcefile = pstrdup(tok_line->file_name);
+	parsedline->linenumber = tok_line->line_num;
+	parsedline->rawline = pstrdup(tok_line->raw_line);
+
+	/* Initialize optional fields */
+	parsedline->ssl_passphrase_cmd = NULL;
+	parsedline->ssl_passphrase_reload = false;
+
+	/* Hostname */
+	field = list_head(tok_line->fields);
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->hostname = pstrdup(token->string);
+	if (strcmp(parsedline->hostname, "*") == 0)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("wildcard hostname not allowed in hosts configuration"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+
+	/* SSL Certificate (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_cert = pstrdup(token->string);
+
+	/* SSL key (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_key = pstrdup(token->string);
+
+	/* SSL CA (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_ca = pstrdup(token->string);
+
+	/* SSL Passphrase Command (optional) */
+	field = lnext(tok_line->fields, field);
+	if (field)
+	{
+		tokens = lfirst(field);
+		token = linitial(tokens);
+		parsedline->ssl_passphrase_cmd = pstrdup(token->string);
+
+		/*
+		 * SSL Passphrase Command support reload (optional). This field is
+		 * only supported if there was a passphrase command parsed first, so
+		 * nest it under the previous token.
+		 */
+		field = lnext(tok_line->fields, field);
+		if (field)
+		{
+			tokens = lfirst(field);
+			token = linitial(tokens);
+
+			if (token->string[0] == '1'
+				|| pg_strcasecmp(token->string, "true") == 0
+				|| pg_strcasecmp(token->string, "on") == 0
+				|| pg_strcasecmp(token->string, "yes") == 0)
+				parsedline->ssl_passphrase_reload = true;
+			else if (token->string[0] == '0'
+					 || pg_strcasecmp(token->string, "false") == 0
+					 || pg_strcasecmp(token->string, "off") == 0
+					 || pg_strcasecmp(token->string, "no") == 0)
+				parsedline->ssl_passphrase_reload = false;
+			else
+			{
+				ereport(elevel,
+						errcode(ERRCODE_CONFIG_FILE_ERROR),
+						errmsg("incorrect syntax for boolean value SSL_passphrase_cmd_reload"),
+						errcontext("line %d of configuration file \"%s\"",
+								   tok_line->line_num, tok_line->file_name));
+				return NULL;
+			}
+		}
+	}
+
+	return parsedline;
+}
+
+/*
+ * load_hosts
+ *
+ * Reads and parses the pg_hosts.conf configuration file and passes back a List
+ * of HostLine elements containing the parsed lines, or NIL in case of an empty
+ * file.  The list is returned in the hosts_lines parameter. If loading the
+ * file was successful, true is returned, else false.  or an empty file.  This
+ * function is intended to be executed within a temporary memory context which
+ * can be discarded to free memory allocated during the processing of the file.
+ */
+bool
+load_hosts(List **hosts)
+{
+	FILE	   *file;
+	ListCell   *line;
+	List	   *hosts_lines = NIL;
+	List	   *parsed_lines = NIL;
+	HostsLine  *newline;
+	bool		ok = true;
+
+	if (hosts)
+		*hosts = NIL;
+
+	/*
+	 * This is not an auth file per se, but it is using the same file format
+	 * as the pg_hba and pg_ident files and thus the same code infrastructure.
+	 * A future TODO might be to rename the supporting code with a more
+	 * generic name?
+	 */
+	file = open_auth_file(HostsFileName, LOG, 0, NULL);
+	if (file == NULL)
+	{
+		/* An error has already been logged so no need to add one here */
+		return false;
+	}
+
+	tokenize_auth_file(HostsFileName, file, &hosts_lines, LOG, 0);
+
+	foreach(line, hosts_lines)
+	{
+		TokenizedAuthLine *tok_line = (TokenizedAuthLine *) lfirst(line);
+
+		if (tok_line->err_msg != NULL)
+		{
+			ok = false;
+			continue;
+		}
+
+		if ((newline = parse_hosts_line(tok_line, LOG)) == NULL)
+		{
+			ok = false;
+			continue;
+		}
+
+		parsed_lines = lappend(parsed_lines, newline);
+	}
+
+	free_auth_file(file, 0);
+
+	/*
+	 * If we didn't find any SNI configuration then that might not be an error
+	 * since the pg_hosts file is additive to the default SSL configuration in
+	 * some ssl_sni settings.
+	 */
+	if (ok && parsed_lines == NIL)
+	{
+		ereport(DEBUG1,
+				errmsg("SNI configuration not found in configuration file  \"%s\"",
+					   HostsFileName));
+	}
+
+	if (!ok)
+		return false;
+
+	if (hosts)
+		*hosts = parsed_lines;
+
+	return true;
+}
diff --git a/src/backend/libpq/be-secure-openssl.c b/src/backend/libpq/be-secure-openssl.c
index 37f4d97f209..678d1587e44 100644
--- a/src/backend/libpq/be-secure-openssl.c
+++ b/src/backend/libpq/be-secure-openssl.c
@@ -51,9 +51,17 @@
 #endif
 #include <openssl/x509v3.h>
 
+typedef struct HostContext
+{
+	const char *hostname;
+	const char *ssl_passphrase;
+	SSL_CTX    *context;
+	bool		default_host;
+	bool		ssl_loaded_verify_locations;
+} HostContext;
 
 /* default init hook can be overridden by a shared library */
-static void default_openssl_tls_init(SSL_CTX *context, bool isServerStart);
+static void default_openssl_tls_init(SSL_CTX *context, bool isServerStart, HostsLine *hosts);
 openssl_tls_init_hook_typ openssl_tls_init_hook = default_openssl_tls_init;
 
 static int	port_bio_read(BIO *h, char *buf, int size);
@@ -73,6 +81,7 @@ static int	alpn_cb(SSL *ssl,
 					const unsigned char *in,
 					unsigned int inlen,
 					void *userdata);
+static int	sni_servername_cb(SSL *ssl, int *al, void *arg);
 static bool initialize_dh(SSL_CTX *context, bool isServerStart);
 static bool initialize_ecdh(SSL_CTX *context, bool isServerStart);
 static const char *SSLerrmessageExt(unsigned long ecode, const char *replacement);
@@ -80,12 +89,17 @@ static const char *SSLerrmessage(unsigned long ecode);
 
 static char *X509_NAME_to_cstring(X509_NAME *name);
 
+static List *contexts = NIL;
 static SSL_CTX *SSL_context = NULL;
+static HostContext *Default_context = NULL;
+static HostContext *Host_context = NULL;
 static bool dummy_ssl_passwd_cb_called = false;
 static bool ssl_is_server_start;
 
 static int	ssl_protocol_version_to_openssl(int v);
 static const char *ssl_protocol_version_to_string(int v);
+static SSL_CTX *ssl_init_context(bool isServerStart, HostsLine *host);
+static void free_contexts(void);
 
 struct CallbackErr
 {
@@ -102,11 +116,195 @@ struct CallbackErr
 
 int
 be_tls_init(bool isServerStart)
+{
+	SSL_CTX    *ctx;
+	List	   *sni_hosts = NIL;
+	HostsLine	line;
+	bool		res;
+
+	/*
+	 * If there are contexts loaded when we init they must be released. This
+	 * should only be possible during configuration reloads and not when the
+	 * server is starting up.
+	 */
+	if (contexts != NIL)
+	{
+		Assert(!isServerStart);
+		free_contexts();
+		Host_context = NULL;
+		SSL_context = NULL;
+		Default_context = NULL;
+	}
+
+	/*
+	 * Load the default configuration from postgresql.conf such that we have a
+	 * context to either be used for the entire connection, or drive the
+	 * handshake until the SNI callback replace it with a configuration from
+	 * the pg_hosts.conf file.
+	 */
+	memset(&line, 0, sizeof(line));
+	line.ssl_cert = ssl_cert_file;
+	line.ssl_key = ssl_key_file;
+	line.ssl_ca = ssl_ca_file;
+	line.ssl_passphrase_cmd = ssl_passphrase_command;
+	line.ssl_passphrase_reload = ssl_passphrase_command_supports_reload;
+
+	ctx = ssl_init_context(isServerStart, &line);
+	if (ctx == NULL)
+	{
+		ereport(isServerStart ? FATAL : LOG,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("could not load default certificate"));
+		return -1;
+	}
+
+	Default_context = palloc0(sizeof(HostContext));
+	Default_context->hostname = pstrdup("*");
+	Default_context->context = ctx;
+	Default_context->default_host = true;
+
+	/*
+	 * Set flag to remember whether CA store has been loaded into SSL_context.
+	 */
+	if (ssl_ca_file[0])
+		Default_context->ssl_loaded_verify_locations = true;
+
+	/*
+	 * While the default context isn't matched against when searching for host
+	 * contexts we still add it to the list to ensure that cleanup code can
+	 * iterate over a single structure to clean up everything.
+	 */
+	contexts = lappend(contexts, Default_context);
+
+	/*
+	 * Install the default context to use as the initial context for the
+	 * connection.  This might be replaced in the SNI callback if there is a
+	 * host/snimode match, but we need something to drive the handshake till
+	 * then.
+	 */
+	Host_context = Default_context;
+	SSL_context = Host_context->context;
+
+	/*
+	 * In default or strict ssl_snimode we load all certificates/keys which
+	 * are configured in pg_hosts.conf.  In strict mode it is considered a
+	 * fatal error in case there are no configured entries.
+	 */
+	if (ssl_snimode == SSL_SNIMODE_STRICT || ssl_snimode == SSL_SNIMODE_DEFAULT)
+	{
+		ListCell   *line;
+		MemoryContext oldcxt;
+		MemoryContext hostcxt;
+
+		hostcxt = AllocSetContextCreate(CurrentMemoryContext,
+										"hosts file parser context",
+										ALLOCSET_SMALL_SIZES);
+
+		/*
+		 * Load pg_hosts.conf and parse each row, returning the set of hosts
+		 * as a list.  Make sure to allocate the parsed rows in a temporary
+		 * memory context such that we can avoid memory leaks.
+		 */
+		oldcxt = MemoryContextSwitchTo(hostcxt);
+		res = load_hosts(&sni_hosts);
+		MemoryContextSwitchTo(oldcxt);
+
+		/*
+		 * If loading failed, then make sure to error out regardless. It's not
+		 * really an error to not have a hosts file in non-strict modes but if
+		 * there is one and it fails to load properly, then silently pressing
+		 * on seems worse than raising an error.
+		 */
+		if (!res)
+		{
+			MemoryContextDelete(hostcxt);
+			ereport(isServerStart ? FATAL : LOG,
+					errcode(ERRCODE_CONFIG_FILE_ERROR),
+					errmsg("could not load %s", "pg_hosts.conf"));
+			return -1;
+		}
+
+		/*
+		 * In strict ssl_snimode there needs to be at least one configured
+		 * host in the pg_hosts file since the default fallback context isn't
+		 * allowed to connect with.
+		 */
+		if (sni_hosts == NIL && ssl_snimode == SSL_SNIMODE_STRICT)
+		{
+			MemoryContextDelete(hostcxt);
+			ereport(isServerStart ? FATAL : LOG,
+					errcode(ERRCODE_CONFIG_FILE_ERROR),
+					errmsg("could not load %s", "pg_hosts.conf"),
+					errhint("In strict ssl_snimode there needs to be at least one entry in pg_hosts.conf."));
+			return -1;
+		}
+
+		/*
+		 * Loading and parsing the hosts file was successful, create contexts
+		 * for each host entry and add to the the list of host to be checked
+		 * during login.
+		 */
+		foreach(line, sni_hosts)
+		{
+			HostContext *host_context;
+			HostsLine  *host = lfirst(line);
+			static SSL_CTX *tmp_context = NULL;
+
+			tmp_context = ssl_init_context(isServerStart, host);
+			if (tmp_context == NULL)
+			{
+				MemoryContextDelete(hostcxt);
+				ereport(isServerStart ? FATAL : LOG,
+						errcode(ERRCODE_CONFIG_FILE_ERROR),
+						errmsg("unable to load certificate from pg_hosts.conf file"));
+				return -1;
+			}
+
+			/*
+			 * The parsing logic has already verified that the hostname exist
+			 * so we need not check that.
+			 */
+			host_context = palloc0(sizeof(HostContext));
+			host_context->hostname = pstrdup(host->hostname);
+			host_context->context = tmp_context;
+			host_context->default_host = false;
+
+			/*
+			 * Set flag to remember whether CA store has been loaded into this
+			 * SSL_context.
+			 */
+			if (host->ssl_ca && host->ssl_ca[0] != '\0')
+				host_context->ssl_loaded_verify_locations = true;
+
+			contexts = lappend(contexts, host_context);
+		}
+
+		MemoryContextDelete(hostcxt);
+	}
+
+	/* Make sure we have at least one certificate loaded */
+	if (list_length(contexts) < 1)
+	{
+		ereport(isServerStart ? FATAL : LOG,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("no SSL contexts loaded"));
+		return -1;
+	}
+
+	return 0;
+}
+
+static SSL_CTX *
+ssl_init_context(bool isServerStart, HostsLine *host_line)
 {
 	SSL_CTX    *context;
 	int			ssl_ver_min = -1;
 	int			ssl_ver_max = -1;
 
+	const char *ctx_ssl_cert_file = host_line->ssl_cert;
+	const char *ctx_ssl_key_file = host_line->ssl_key;
+	const char *ctx_ssl_ca_file = host_line->ssl_ca;
+
 	/*
 	 * Create a new SSL context into which we'll load all the configuration
 	 * settings.  If we fail partway through, we can avoid memory leakage by
@@ -132,10 +330,17 @@ be_tls_init(bool isServerStart)
 	 */
 	SSL_CTX_set_mode(context, SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER);
 
+	/*
+	 * Install SNI TLS extension callback in case the server is configured to
+	 * validate hostnames.
+	 */
+	if (ssl_snimode != SSL_SNIMODE_OFF)
+		SSL_CTX_set_tlsext_servername_callback(context, sni_servername_cb);
+
 	/*
 	 * Call init hook (usually to set password callback)
 	 */
-	(*openssl_tls_init_hook) (context, isServerStart);
+	(*openssl_tls_init_hook) (context, isServerStart, host_line);
 
 	/* used by the callback */
 	ssl_is_server_start = isServerStart;
@@ -143,16 +348,16 @@ be_tls_init(bool isServerStart)
 	/*
 	 * Load and verify server's certificate and private key
 	 */
-	if (SSL_CTX_use_certificate_chain_file(context, ssl_cert_file) != 1)
+	if (SSL_CTX_use_certificate_chain_file(context, ctx_ssl_cert_file) != 1)
 	{
 		ereport(isServerStart ? FATAL : LOG,
 				(errcode(ERRCODE_CONFIG_FILE_ERROR),
 				 errmsg("could not load server certificate file \"%s\": %s",
-						ssl_cert_file, SSLerrmessage(ERR_get_error()))));
+						ctx_ssl_cert_file, SSLerrmessage(ERR_get_error()))));
 		goto error;
 	}
 
-	if (!check_ssl_key_file_permissions(ssl_key_file, isServerStart))
+	if (!check_ssl_key_file_permissions(ctx_ssl_key_file, isServerStart))
 		goto error;
 
 	/*
@@ -161,19 +366,19 @@ be_tls_init(bool isServerStart)
 	dummy_ssl_passwd_cb_called = false;
 
 	if (SSL_CTX_use_PrivateKey_file(context,
-									ssl_key_file,
+									ctx_ssl_key_file,
 									SSL_FILETYPE_PEM) != 1)
 	{
 		if (dummy_ssl_passwd_cb_called)
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("private key file \"%s\" cannot be reloaded because it requires a passphrase",
-							ssl_key_file)));
+							ctx_ssl_key_file)));
 		else
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("could not load private key file \"%s\": %s",
-							ssl_key_file, SSLerrmessage(ERR_get_error()))));
+							ctx_ssl_key_file, SSLerrmessage(ERR_get_error()))));
 		goto error;
 	}
 
@@ -325,17 +530,17 @@ be_tls_init(bool isServerStart)
 	/*
 	 * Load CA store, so we can verify client certificates if needed.
 	 */
-	if (ssl_ca_file[0])
+	if (ctx_ssl_ca_file[0])
 	{
 		STACK_OF(X509_NAME) * root_cert_list;
 
-		if (SSL_CTX_load_verify_locations(context, ssl_ca_file, NULL) != 1 ||
-			(root_cert_list = SSL_load_client_CA_file(ssl_ca_file)) == NULL)
+		if (SSL_CTX_load_verify_locations(context, ctx_ssl_ca_file, NULL) != 1 ||
+			(root_cert_list = SSL_load_client_CA_file(ctx_ssl_ca_file)) == NULL)
 		{
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("could not load root certificate file \"%s\": %s",
-							ssl_ca_file, SSLerrmessage(ERR_get_error()))));
+							ctx_ssl_ca_file, SSLerrmessage(ERR_get_error()))));
 			goto error;
 		}
 
@@ -348,16 +553,20 @@ be_tls_init(bool isServerStart)
 		 */
 		SSL_CTX_set_client_CA_list(context, root_cert_list);
 
-		/*
-		 * Always ask for SSL client cert, but don't fail if it's not
-		 * presented.  We might fail such connections later, depending on what
-		 * we find in pg_hba.conf.
-		 */
+	}
+
+	/*
+	 * If we have a CA store, or SNI is enabled, always ask for SSL client
+	 * cert, but don't fail if it's not presented.  We might fail such
+	 * connections later, depending on what we find in pg_hba.conf. The reason
+	 * for enabling in the case of SNI even if there is no CA is that another
+	 * context might have a CA, so the callback must be installed in order for
+	 * that context.
+	 */
+	if (ctx_ssl_ca_file[0] || ssl_snimode != SSL_SNIMODE_OFF)
 		SSL_CTX_set_verify(context,
-						   (SSL_VERIFY_PEER |
-							SSL_VERIFY_CLIENT_ONCE),
+						   (SSL_VERIFY_PEER | SSL_VERIFY_CLIENT_ONCE),
 						   verify_cb);
-	}
 
 	/*----------
 	 * Load the Certificate Revocation List (CRL).
@@ -407,38 +616,19 @@ be_tls_init(bool isServerStart)
 		}
 	}
 
-	/*
-	 * Success!  Replace any existing SSL_context.
-	 */
-	if (SSL_context)
-		SSL_CTX_free(SSL_context);
-
-	SSL_context = context;
-
-	/*
-	 * Set flag to remember whether CA store has been loaded into SSL_context.
-	 */
-	if (ssl_ca_file[0])
-		ssl_loaded_verify_locations = true;
-	else
-		ssl_loaded_verify_locations = false;
-
-	return 0;
+	return context;
 
 	/* Clean up by releasing working context. */
 error:
 	if (context)
 		SSL_CTX_free(context);
-	return -1;
+	return NULL;
 }
 
 void
 be_tls_destroy(void)
 {
-	if (SSL_context)
-		SSL_CTX_free(SSL_context);
-	SSL_context = NULL;
-	ssl_loaded_verify_locations = false;
+	free_contexts();
 }
 
 int
@@ -771,6 +961,9 @@ be_tls_close(Port *port)
 		pfree(port->peer_dn);
 		port->peer_dn = NULL;
 	}
+
+	Host_context = NULL;
+	SSL_context = NULL;
 }
 
 ssize_t
@@ -1144,7 +1337,7 @@ ssl_external_passwd_cb(char *buf, int size, int rwflag, void *userdata)
 
 	Assert(rwflag == 0);
 
-	return run_ssl_passphrase_command(prompt, ssl_is_server_start, buf, size);
+	return run_ssl_passphrase_command(prompt, ssl_is_server_start, buf, size, userdata);
 }
 
 /*
@@ -1390,6 +1583,131 @@ alpn_cb(SSL *ssl,
 	}
 }
 
+/*
+ * sni_servername_cb
+ *
+ * Callback executed by OpenSSL during handshake in case the server has been
+ * configured to validate hostnames.  Depending on the SNI mode we either
+ * require a perfect match, or we allow to fallback to a default configuration.
+ * Returning SSL_TLSEXT_ERR_ALERT_FATAL to OpenSSL will immediately terminate
+ * the handshake.
+ */
+static int
+sni_servername_cb(SSL *ssl, int *al, void *arg)
+{
+	const char *tlsext_hostname;
+
+	/*
+	 * Executing this callback when SNI is turned off indicates a programmer
+	 * error or something worse.  Throw an assertion to catch during testing
+	 * but also ensure to terminate the connection in non-assert builds, even
+	 * though this should never happen, just to be on the safe side.
+	 */
+	if (ssl_snimode == SSL_SNIMODE_OFF)
+	{
+		Assert(false);
+		return SSL_TLSEXT_ERR_ALERT_FATAL;
+	}
+
+	tlsext_hostname = SSL_get_servername(ssl, TLSEXT_NAMETYPE_host_name);
+
+	/*
+	 * If there is no hostname set in the TLS extension, we have two options.
+	 * For ssl_snimode strict we error out since we cannot match a host config
+	 * for the connection.  For the default mode we fall back on the default
+	 * hostname configuration.
+	 */
+	if (!tlsext_hostname)
+	{
+		if (ssl_snimode == SSL_SNIMODE_STRICT)
+		{
+			/*
+			 * The error message for a missing server_name should, according
+			 * to RFC 8446, be missing_extension. This isn't entirely ideal
+			 * since the user won't be able to tell which extension the server
+			 * considered missing.  Sending unrecognized_name would be a more
+			 * helpful error, but for now we stick to the RFC.
+			 */
+			*al = SSL_AD_MISSING_EXTENSION;
+
+			ereport(COMMERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg("no hostname provided in callback")));
+			return SSL_TLSEXT_ERR_ALERT_FATAL;
+		}
+		else
+		{
+			Host_context = Default_context;
+			SSL_context = Host_context->context;
+			if (SSL_set_SSL_CTX(ssl, SSL_context) == NULL)
+			{
+				ereport(COMMERROR,
+						errcode(ERRCODE_PROTOCOL_VIOLATION),
+						errmsg("failed to switch to default SSL context"));
+				return SSL_TLSEXT_ERR_ALERT_FATAL;
+			}
+			return SSL_TLSEXT_ERR_OK;
+		}
+	}
+
+	/*
+	 * We have a requested hostname from the client, match against all entries
+	 * in the pg_hosts configuration to find a match.
+	 */
+	foreach_ptr(HostContext, host, contexts)
+	{
+		/*
+		 * For strict mode we will never want the default host so we can skip
+		 * past it immediately.
+		 */
+		if (ssl_snimode == SSL_SNIMODE_STRICT && host->default_host)
+			continue;
+
+		if (strcmp(host->hostname, tlsext_hostname) == 0)
+		{
+			Host_context = host;
+			SSL_context = host->context;
+			if (SSL_set_SSL_CTX(ssl, SSL_context) == NULL)
+			{
+				ereport(COMMERROR,
+						errcode(ERRCODE_PROTOCOL_VIOLATION),
+						errmsg("failed to switch SSL context for SNI host"));
+				return SSL_TLSEXT_ERR_ALERT_FATAL;
+			}
+			return SSL_TLSEXT_ERR_OK;
+		}
+	}
+
+	/*
+	 * At this point we know that the requested hostname isn't configured in
+	 * the pg_hosts file.  In ssl_snimode "strict" it's an error if there was
+	 * no match for the hostname in the TLS extension so terminate the
+	 * connection.
+	 */
+	if (ssl_snimode == SSL_SNIMODE_STRICT)
+	{
+		ereport(COMMERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg("no matching pg_hosts entry found for hostname: \"%s\"",
+						tlsext_hostname)));
+		return SSL_TLSEXT_ERR_ALERT_FATAL;
+	}
+
+	/*
+	 * In ssl_snimode "default" we fall back on the default host configured in
+	 * postgresql.conf when no match is found in pg_hosts.conf.
+	 */
+	Host_context = Default_context;
+	SSL_context = Host_context->context;
+	if (SSL_set_SSL_CTX(ssl, SSL_context) == NULL)
+	{
+		ereport(COMMERROR,
+				errcode(ERRCODE_PROTOCOL_VIOLATION),
+				errmsg("failed to switch to default SSL context"));
+		return SSL_TLSEXT_ERR_ALERT_FATAL;
+	}
+	return SSL_TLSEXT_ERR_OK;
+}
 
 /*
  * Set DH parameters for generating ephemeral DH keys.  The
@@ -1599,6 +1917,12 @@ be_tls_get_peer_serial(Port *port, char *ptr, size_t len)
 		ptr[0] = '\0';
 }
 
+bool
+be_tls_loaded_verify_locations(void)
+{
+	return Host_context->ssl_loaded_verify_locations;
+}
+
 char *
 be_tls_get_certificate_hash(Port *port, size_t *len)
 {
@@ -1792,17 +2116,23 @@ ssl_protocol_version_to_string(int v)
 
 
 static void
-default_openssl_tls_init(SSL_CTX *context, bool isServerStart)
+default_openssl_tls_init(SSL_CTX *context, bool isServerStart, HostsLine *host)
 {
 	if (isServerStart)
 	{
-		if (ssl_passphrase_command[0])
+		if (host->ssl_passphrase_cmd != NULL)
+		{
 			SSL_CTX_set_default_passwd_cb(context, ssl_external_passwd_cb);
+			SSL_CTX_set_default_passwd_cb_userdata(context, host->ssl_passphrase_cmd);
+		}
 	}
 	else
 	{
-		if (ssl_passphrase_command[0] && ssl_passphrase_command_supports_reload)
+		if (host->ssl_passphrase_cmd != NULL && host->ssl_passphrase_reload)
+		{
 			SSL_CTX_set_default_passwd_cb(context, ssl_external_passwd_cb);
+			SSL_CTX_set_default_passwd_cb_userdata(context, host->ssl_passphrase_cmd);
+		}
 		else
 
 			/*
@@ -1814,3 +2144,24 @@ default_openssl_tls_init(SSL_CTX *context, bool isServerStart)
 			SSL_CTX_set_default_passwd_cb(context, dummy_ssl_passwd_cb);
 	}
 }
+
+/*
+ * Cleanup function for when hostname configuration is reloaded from the
+ * pg_hosts.conf file, at that point we Must discard all existing contexts.
+ */
+static void
+free_contexts(void)
+{
+	if (contexts == NIL)
+		return;
+
+	foreach_ptr(HostContext, host, contexts)
+	{
+		if (host->hostname)
+			pfree(unconstify(char *, host->hostname));
+		SSL_CTX_free(host->context);
+	}
+
+	list_free_deep(contexts);
+	contexts = NIL;
+}
diff --git a/src/backend/libpq/be-secure.c b/src/backend/libpq/be-secure.c
index d723e74e813..f6c1422b555 100644
--- a/src/backend/libpq/be-secure.c
+++ b/src/backend/libpq/be-secure.c
@@ -43,10 +43,6 @@ char	   *ssl_dh_params_file;
 char	   *ssl_passphrase_command;
 bool		ssl_passphrase_command_supports_reload;
 
-#ifdef USE_SSL
-bool		ssl_loaded_verify_locations = false;
-#endif
-
 /* GUC variable controlling SSL cipher list */
 char	   *SSLCipherSuites = NULL;
 char	   *SSLCipherList = NULL;
@@ -60,6 +56,8 @@ bool		SSLPreferServerCiphers;
 int			ssl_min_protocol_version = PG_TLS1_2_VERSION;
 int			ssl_max_protocol_version = PG_TLS_ANY;
 
+int			ssl_snimode = SSL_SNIMODE_OFF;
+
 /* ------------------------------------------------------------ */
 /*			 Procedures common to all secure sessions			*/
 /* ------------------------------------------------------------ */
@@ -99,7 +97,7 @@ bool
 secure_loaded_verify_locations(void)
 {
 #ifdef USE_SSL
-	return ssl_loaded_verify_locations;
+	return be_tls_loaded_verify_locations();
 #else
 	return false;
 #endif
diff --git a/src/backend/libpq/meson.build b/src/backend/libpq/meson.build
index 31aa2faae1e..4f6ec13bc74 100644
--- a/src/backend/libpq/meson.build
+++ b/src/backend/libpq/meson.build
@@ -31,5 +31,6 @@ endif
 install_data(
   'pg_hba.conf.sample',
   'pg_ident.conf.sample',
+  'pg_hosts.conf.sample',
   install_dir: dir_data,
 )
diff --git a/src/backend/libpq/pg_hosts.conf.sample b/src/backend/libpq/pg_hosts.conf.sample
new file mode 100644
index 00000000000..5a47f9cae7d
--- /dev/null
+++ b/src/backend/libpq/pg_hosts.conf.sample
@@ -0,0 +1,4 @@
+# PostgreSQL SNI Hostname mappings
+# ================================
+
+# HOSTNAME       SSL CERTIFICATE             SSL KEY
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index c6484aea087..f35a15b48df 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -56,6 +56,7 @@
 #define CONFIG_FILENAME "postgresql.conf"
 #define HBA_FILENAME	"pg_hba.conf"
 #define IDENT_FILENAME	"pg_ident.conf"
+#define HOSTS_FILENAME	"pg_hosts.conf"
 
 #ifdef EXEC_BACKEND
 #define CONFIG_EXEC_PARAMS "global/config_exec_params"
@@ -1838,6 +1839,36 @@ SelectConfigFiles(const char *userDoption, const char *progname)
 	}
 	SetConfigOption("ident_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
 
+	if (fname_is_malloced)
+		free(fname);
+	else
+		guc_free(fname);
+
+	/*
+	 * Likewise for pg_hosts.conf.
+	 */
+	if (HostsFileName)
+	{
+		fname = make_absolute_path(HostsFileName);
+		fname_is_malloced = true;
+	}
+	else if (configdir)
+	{
+		fname = guc_malloc(FATAL,
+						   strlen(configdir) + strlen(HOSTS_FILENAME) + 2);
+		sprintf(fname, "%s/%s", configdir, HOSTS_FILENAME);
+		fname_is_malloced = false;
+	}
+	else
+	{
+		write_stderr("%s does not know where to find the \"hosts\" configuration file.\n"
+					 "This can be specified as \"hosts_file\" in \"%s\", "
+					 "or by the -D invocation option, or by the "
+					 "PGDATA environment variable.\n",
+					 progname, ConfigFileName);
+	}
+	SetConfigOption("hosts_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
+
 	if (fname_is_malloced)
 		free(fname);
 	else
diff --git a/src/backend/utils/misc/guc_parameters.dat b/src/backend/utils/misc/guc_parameters.dat
index 3b9d8349078..30cde4ee800 100644
--- a/src/backend/utils/misc/guc_parameters.dat
+++ b/src/backend/utils/misc/guc_parameters.dat
@@ -1167,6 +1167,13 @@
   boot_val => 'NULL',
 },
 
+{ name => 'hosts_file', type => 'string', context => 'PGC_POSTMASTER', group => 'FILE_LOCATIONS',
+  short_desc => 'Sets the server\'s "hosts" configuration file.',
+  flags => 'GUC_SUPERUSER_ONLY',
+  variable => 'HostsFileName',
+  boot_val => 'NULL',
+},
+
 { name => 'hot_standby', type => 'bool', context => 'PGC_POSTMASTER', group => 'REPLICATION_STANDBY',
   short_desc => 'Allows connections and queries during recovery.',
   variable => 'EnableHotStandby',
@@ -2742,6 +2749,14 @@
   max => '0',
 },
 
+{ name => 'ssl_snimode', type => 'enum', context => 'PGC_SIGHUP', group => 'CONN_AUTH_SSL',
+  short_desc => 'Sets the SNI mode to use for the server.',
+  flags => 'GUC_SUPERUSER_ONLY',
+  variable => 'ssl_snimode',
+  boot_val => 'SSL_SNIMODE_OFF',
+  options => 'ssl_snimode_options',
+},
+
 { name => 'ssl_tls13_ciphers', type => 'string', context => 'PGC_SIGHUP', group => 'CONN_AUTH_SSL',
   short_desc => 'Sets the list of allowed TLSv1.3 cipher suites.',
   long_desc => 'An empty string means use the default cipher suites.',
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index f87b558c2c6..cd2074d54e1 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -491,6 +491,13 @@ static const struct config_enum_entry file_copy_method_options[] = {
 	{NULL, 0, false}
 };
 
+static const struct config_enum_entry ssl_snimode_options[] = {
+	{"off", SSL_SNIMODE_OFF, false},
+	{"default", SSL_SNIMODE_DEFAULT, false},
+	{"strict", SSL_SNIMODE_STRICT, false},
+	{NULL, 0, false}
+};
+
 /*
  * Options for enum values stored in other modules
  */
@@ -556,6 +563,7 @@ char	   *cluster_name = "";
 char	   *ConfigFileName;
 char	   *HbaFileName;
 char	   *IdentFileName;
+char	   *HostsFileName;
 char	   *external_pid_file;
 
 char	   *application_name;
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index dc9e2255f8a..c5ff8302201 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -45,6 +45,8 @@
                                         # (change requires restart)
 #ident_file = 'ConfigDir/pg_ident.conf' # ident configuration file
                                         # (change requires restart)
+#hosts_file = 'ConfigDir/pg_hosts.conf' # hosts configuration file
+                                        # (change requires restart)
 
 # If external_pid_file is not explicitly set, no extra PID file is written.
 #external_pid_file = ''                 # write an extra PID file
@@ -121,6 +123,7 @@
 #ssl_dh_params_file = ''
 #ssl_passphrase_command = ''
 #ssl_passphrase_command_supports_reload = off
+#ssl_snimode = off
 
 
 #------------------------------------------------------------------------------
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 92fe2f531f7..c953f24a58d 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -177,6 +177,7 @@ static int	encodingid;
 static char *bki_file;
 static char *hba_file;
 static char *ident_file;
+static char *hosts_file;
 static char *conf_file;
 static char *dictionary_file;
 static char *info_schema_file;
@@ -1530,6 +1531,14 @@ setup_config(void)
 
 	snprintf(path, sizeof(path), "%s/pg_ident.conf", pg_data);
 
+	writefile(path, conflines);
+	if (chmod(path, pg_file_create_mode) != 0)
+		pg_fatal("could not change permissions of \"%s\": %m", path);
+
+	/* pg_hosts.conf */
+	conflines = readfile(hosts_file);
+	snprintf(path, sizeof(path), "%s/pg_hosts.conf", pg_data);
+
 	writefile(path, conflines);
 	if (chmod(path, pg_file_create_mode) != 0)
 		pg_fatal("could not change permissions of \"%s\": %m", path);
@@ -2791,6 +2800,7 @@ setup_data_file_paths(void)
 	set_input(&bki_file, "postgres.bki");
 	set_input(&hba_file, "pg_hba.conf.sample");
 	set_input(&ident_file, "pg_ident.conf.sample");
+	set_input(&hosts_file, "pg_hosts.conf.sample");
 	set_input(&conf_file, "postgresql.conf.sample");
 	set_input(&dictionary_file, "snowball_create.sql");
 	set_input(&info_schema_file, "information_schema.sql");
@@ -2806,12 +2816,12 @@ setup_data_file_paths(void)
 				"PGDATA=%s\nshare_path=%s\nPGPATH=%s\n"
 				"POSTGRES_SUPERUSERNAME=%s\nPOSTGRES_BKI=%s\n"
 				"POSTGRESQL_CONF_SAMPLE=%s\n"
-				"PG_HBA_SAMPLE=%s\nPG_IDENT_SAMPLE=%s\n",
+				"PG_HBA_SAMPLE=%s\nPG_IDENT_SAMPLE=%s\nPG_HOSTS_SAMPLE=%s\n",
 				PG_VERSION,
 				pg_data, share_path, bin_path,
 				username, bki_file,
 				conf_file,
-				hba_file, ident_file);
+				hba_file, ident_file, hosts_file);
 		if (show_setting)
 			exit(0);
 	}
@@ -2819,6 +2829,7 @@ setup_data_file_paths(void)
 	check_input(bki_file);
 	check_input(hba_file);
 	check_input(ident_file);
+	check_input(hosts_file);
 	check_input(conf_file);
 	check_input(dictionary_file);
 	check_input(info_schema_file);
diff --git a/src/include/libpq/hba.h b/src/include/libpq/hba.h
index e3748d3c8c9..c96818549cc 100644
--- a/src/include/libpq/hba.h
+++ b/src/include/libpq/hba.h
@@ -151,6 +151,25 @@ typedef struct IdentLine
 	AuthToken  *pg_user;
 } IdentLine;
 
+typedef struct HostsLine
+{
+	int			linenumber;
+
+	char	   *sourcefile;
+	char	   *rawline;
+
+	/* Required fields */
+	bool		default_host;
+	char	   *hostname;
+	char	   *ssl_key;
+	char	   *ssl_cert;
+	char	   *ssl_ca;
+
+	/* Optional fields */
+	char	   *ssl_passphrase_cmd;
+	bool		ssl_passphrase_reload;
+} HostsLine;
+
 /*
  * TokenizedAuthLine represents one line lexed from an authentication
  * configuration file.  Each item in the "fields" list is a sub-list of
diff --git a/src/include/libpq/libpq-be.h b/src/include/libpq/libpq-be.h
index d6e671a6382..e1631cb7b5c 100644
--- a/src/include/libpq/libpq-be.h
+++ b/src/include/libpq/libpq-be.h
@@ -320,6 +320,7 @@ extern const char *be_tls_get_cipher(Port *port);
 extern void be_tls_get_peer_subject_name(Port *port, char *ptr, size_t len);
 extern void be_tls_get_peer_issuer_name(Port *port, char *ptr, size_t len);
 extern void be_tls_get_peer_serial(Port *port, char *ptr, size_t len);
+extern bool be_tls_loaded_verify_locations(void);
 
 /*
  * Get the server certificate hash for SCRAM channel binding type
@@ -332,7 +333,7 @@ extern char *be_tls_get_certificate_hash(Port *port, size_t *len);
 
 /* init hook for SSL, the default sets the password callback if appropriate */
 #ifdef USE_OPENSSL
-typedef void (*openssl_tls_init_hook_typ) (SSL_CTX *context, bool isServerStart);
+typedef void (*openssl_tls_init_hook_typ) (SSL_CTX *context, bool isServerStart, HostsLine *host);
 extern PGDLLIMPORT openssl_tls_init_hook_typ openssl_tls_init_hook;
 #endif
 
diff --git a/src/include/libpq/libpq.h b/src/include/libpq/libpq.h
index 5af005ad779..54d8ee8a2aa 100644
--- a/src/include/libpq/libpq.h
+++ b/src/include/libpq/libpq.h
@@ -107,6 +107,7 @@ extern PGDLLIMPORT char *ssl_crl_dir;
 extern PGDLLIMPORT char *ssl_key_file;
 extern PGDLLIMPORT int ssl_min_protocol_version;
 extern PGDLLIMPORT int ssl_max_protocol_version;
+extern PGDLLIMPORT int ssl_snimode;
 extern PGDLLIMPORT char *ssl_passphrase_command;
 extern PGDLLIMPORT bool ssl_passphrase_command_supports_reload;
 extern PGDLLIMPORT char *ssl_dh_params_file;
@@ -152,12 +153,20 @@ enum ssl_protocol_versions
 	PG_TLS1_3_VERSION,
 };
 
+enum ssl_snimode
+{
+	SSL_SNIMODE_OFF = 0,
+	SSL_SNIMODE_DEFAULT,
+	SSL_SNIMODE_STRICT
+};
+
 /*
  * prototypes for functions in be-secure-common.c
  */
 extern int	run_ssl_passphrase_command(const char *prompt, bool is_server_start,
-									   char *buf, int size);
+									   char *buf, int size, void *userdata);
 extern bool check_ssl_key_file_permissions(const char *ssl_key_file,
 										   bool isServerStart);
+extern bool load_hosts(List **hosts);
 
 #endif							/* LIBPQ_H */
diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index f21ec37da89..8f08a38b789 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -312,6 +312,7 @@ extern PGDLLIMPORT char *cluster_name;
 extern PGDLLIMPORT char *ConfigFileName;
 extern PGDLLIMPORT char *HbaFileName;
 extern PGDLLIMPORT char *IdentFileName;
+extern PGDLLIMPORT char *HostsFileName;
 extern PGDLLIMPORT char *external_pid_file;
 
 extern PGDLLIMPORT char *application_name;
diff --git a/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c b/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
index d5992149821..a85d85735cf 100644
--- a/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
+++ b/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
@@ -26,7 +26,7 @@ static char *ssl_passphrase = NULL;
 static int	rot13_passphrase(char *buf, int size, int rwflag, void *userdata);
 
 /* hook function to set the callback */
-static void set_rot13(SSL_CTX *context, bool isServerStart);
+static void set_rot13(SSL_CTX *context, bool isServerStart, HostsLine *host);
 
 /*
  * Module load callback
@@ -53,7 +53,7 @@ _PG_init(void)
 }
 
 static void
-set_rot13(SSL_CTX *context, bool isServerStart)
+set_rot13(SSL_CTX *context, bool isServerStart, HostsLine *host)
 {
 	/* warn if the user has set ssl_passphrase_command */
 	if (ssl_passphrase_command[0])
diff --git a/src/test/perl/PostgreSQL/Test/Cluster.pm b/src/test/perl/PostgreSQL/Test/Cluster.pm
index 35413f14019..55e0f04d4f5 100644
--- a/src/test/perl/PostgreSQL/Test/Cluster.pm
+++ b/src/test/perl/PostgreSQL/Test/Cluster.pm
@@ -1302,6 +1302,27 @@ Wrapper for pg_ctl restart.
 With optional extra param fail_ok => 1, returns 0 for failure
 instead of bailing out.
 
+=over
+
+=item fail_ok => 1
+
+By default, failure terminates the entire F<prove> invocation.  If given,
+instead return 0 for failure instead of bailing out.
+
+=item log_unlike => B<pattern>
+
+When defined, the logfile is inspected for the presence of the fragment by
+matching the specified pattern. If the pattern matches against the logfile a
+test failure will be logged.
+
+=item log_like => B<pattern>
+
+When defined, the logfile is inspected for the presence of the fragment by
+matching the pattern. If the pattern doesn't match a test failure will be
+logged.
+
+=back
+
 =cut
 
 sub restart
@@ -1314,6 +1335,8 @@ sub restart
 
 	print "### Restarting node \"$name\"\n";
 
+	my $log_location = -s $self->logfile;
+
 	# -w is now the default but having it here does no harm and helps
 	# compatibility with older versions.
 	$ret = PostgreSQL::Test::Utils::system_log(
@@ -1322,6 +1345,18 @@ sub restart
 		'--log' => $self->logfile,
 		'restart');
 
+	# Check for expected and/or unexpected log fragments if the caller
+	# specified such checks in the params
+	if (defined $params{log_unlike} || defined $params{log_like})
+	{
+		my $log =
+		  PostgreSQL::Test::Utils::slurp_file($self->logfile, $log_location);
+		unlike($log, $params{log_unlike}, "unexpected fragment found in log")
+			if defined $params{log_unlike};
+		like($log, $params{log_like}, "expected fragment not found in log")
+			if defined $params{log_like};
+	}
+
 	if ($ret != 0)
 	{
 		print "# pg_ctl restart failed; see logfile for details: "
diff --git a/src/test/ssl/meson.build b/src/test/ssl/meson.build
index d8e0fb518e0..e5a9402cd9c 100644
--- a/src/test/ssl/meson.build
+++ b/src/test/ssl/meson.build
@@ -13,6 +13,7 @@ tests += {
       't/001_ssltests.pl',
       't/002_scram.pl',
       't/003_sslinfo.pl',
+      't/004_sni.pl',
     ],
   },
 }
diff --git a/src/test/ssl/t/004_sni.pl b/src/test/ssl/t/004_sni.pl
new file mode 100644
index 00000000000..90d7560ad11
--- /dev/null
+++ b/src/test/ssl/t/004_sni.pl
@@ -0,0 +1,237 @@
+
+# Copyright (c) 2024, PostgreSQL Global Development Group
+
+use strict;
+use warnings FATAL => 'all';
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+use FindBin;
+use lib $FindBin::RealBin;
+
+use SSL::Server;
+
+# This is the hostname used to connect to the server. This cannot be a
+# hostname, because the server certificate is always for the domain
+# postgresql-ssl-regression.test.
+my $SERVERHOSTADDR = '127.0.0.1';
+# This is the pattern to use in pg_hba.conf to match incoming connections.
+my $SERVERHOSTCIDR = '127.0.0.1/32';
+
+if ($ENV{with_ssl} ne 'openssl')
+{
+	plan skip_all => 'OpenSSL not supported by this build';
+}
+
+if (!$ENV{PG_TEST_EXTRA} || $ENV{PG_TEST_EXTRA} !~ /\bssl\b/)
+{
+	plan skip_all =>
+	  'Potentially unsafe test SSL not enabled in PG_TEST_EXTRA';
+}
+
+my $ssl_server = SSL::Server->new();
+
+my $node = PostgreSQL::Test::Cluster->new('primary');
+$node->init;
+
+# PGHOST is enforced here to set up the node, subsequent connections
+# will use a dedicated connection string.
+$ENV{PGHOST} = $node->host;
+$ENV{PGPORT} = $node->port;
+$node->start;
+
+$ssl_server->configure_test_server_for_ssl($node, $SERVERHOSTADDR,
+	$SERVERHOSTCIDR, 'trust');
+
+$ssl_server->switch_server_cert($node, certfile => 'server-cn-only');
+
+my $connstr =
+  "user=ssltestuser dbname=trustdb hostaddr=$SERVERHOSTADDR host=localhost sslsni=1";
+
+$node->append_conf('postgresql.conf', "ssl_snimode=default");
+$node->reload;
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"connect fails with fallback hostname, without intermediate",
+	expected_stderr => qr/certificate verify failed/);
+
+# example.org serves the server cert and its intermediate CA.
+$node->append_conf('pg_hosts.conf',
+	"example.org server-cn-only+server_ca.crt server-cn-only.key root_ca.crt"
+);
+$node->reload;
+
+$node->connect_ok(
+	"$connstr host=example.org sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"connect with configured hostname, serving intermediate server CA");
+
+$node->connect_fails(
+	"$connstr sslrootcert=invalid sslmode=verify-ca",
+	"connect without server root cert sslmode=verify-ca",
+	expected_stderr => qr/root certificate file "invalid" does not exist/);
+
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"connect still fails with fallback hostname, without intermediate",
+	expected_stderr => qr/certificate verify failed/);
+
+$node->connect_ok(
+	"$connstr host=localhost sslrootcert=ssl/root+server_ca.crt sslmode=verify-ca",
+	"connect with fallback hostname, intermediate included");
+
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	"localhost server-cn-only.crt server-cn-only.key root_ca.crt");
+$node->append_conf('postgresql.conf', "ssl_snimode=strict");
+$node->reload;
+
+$node->connect_fails(
+	"$connstr host=example.org sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with missing hostconfig and snimode=strict",
+	expected_stderr => qr/tlsv1 unrecognized name/);
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require sslsni=1",
+	"connect with correct server CA cert file sslmode=require");
+
+# Attempts at connecting without SNI when the server is using strict mode should
+# result in connection failure.
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require sslsni=0",
+	"connect with correct server CA cert file without SNI for strict mode",
+	expected_stderr => qr/tlsv13 alert missing extension/);
+
+# Reconfigure with broken configuration for the key passphrase, the server
+# should not start up
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo wrongpassword" on'
+);
+my $result = $node->restart(fail_ok => 1);
+is($result, 0,
+	'restart fails with password-protected key when using the wrong passphrase command'
+);
+
+# Reconfigure again but with the correct passphrase set
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo secret1" on'
+);
+$result = $node->restart(fail_ok => 1);
+is($result, 1,
+	'restart succeeds with password-protected key when using the correct passphrase command'
+);
+
+# Make sure connecting works, and try to stress the reload logic by issuing
+# subsequent reloads
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file sslmode=require");
+$node->reload;
+$node->reload;
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file after reloads");
+$node->reload;
+$node->reload;
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect with correct server CA cert file after more reloads");
+
+# Test reloading a passphrase protected key without reloading support in the
+# passphrase hook. Connecting after restart should succeed but not after the
+# following reload.
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo secret1" off'
+);
+$result = $node->restart(fail_ok => 1);
+is($result, 1,
+	'restart succeeds with password-protected key when using the correct passphrase command'
+);
+SKIP:
+{
+	# Passphrase reloads must be enabled on Windows to succeed even without a
+	# restart
+	skip "Passphrase command reload required on Windows", 1 if ($windows_os);
+
+	$node->connect_ok(
+		"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+		"connect with correct server CA cert file sslmode=require");
+}
+
+$node->reload;
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"connect fails since the passphrase protected key cannot be reloaded");
+
+# Test client CAs by connecting to hosts in pg_hosts.conf while at the same
+# time swapping out default contexts containing different CA configurations.
+
+# pg_hosts configuration
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+# example.org has an unconfigured CA.
+$node->append_conf('pg_hosts.conf',
+	'example.org server-cn-only.crt server-cn-only.key ""');
+# example.com uses the client CA.
+$node->append_conf('pg_hosts.conf',
+	'example.com server-cn-only.crt server-cn-only.key root+client_ca.crt');
+# example.net uses the server CA (which is wrong).
+$node->append_conf('pg_hosts.conf',
+	'example.net server-cn-only.crt server-cn-only.key root+server_ca.crt');
+$node->reload;
+
+$connstr =
+  "user=ssltestuser dbname=certdb hostaddr=$SERVERHOSTADDR sslmode=require sslsni=1";
+
+foreach my $default_ca ("", "root+client_ca", "root+server_ca")
+{
+	# The default CA should, not matter for the purposes of these tests, since
+	# we connect to the other hosts explicitly. Test with various default CA
+	# settings to ensure it's isolated from the actual connections.
+	$ssl_server->switch_server_cert(
+		$node,
+		certfile => 'server-cn-only',
+		cafile => $default_ca);
+
+	# example.org is unconfigured and should fail.
+	$node->connect_fails(
+		"$connstr host=example.org sslcertmode=require sslcert=ssl/client.crt "
+		  . $ssl_server->sslkey('client.key'),
+		"host: 'example.org', ca: '$default_ca': connect with sslcert, no client CA configured",
+		expected_stderr => qr/certificate verify failed/);
+
+	# example.com is configured and should require a valid client cert.
+	$node->connect_fails(
+		"$connstr host=example.com sslcertmode=disable",
+		"host: 'example.com', ca: '$default_ca': connect fails if no client certificate sent",
+		expected_stderr => qr/certificate verify failed/);
+
+	$node->connect_ok(
+		"$connstr host=example.com sslrootcert=ssl/root+server_ca.crt sslcertmode=require sslcert=ssl/client.crt "
+		  . $ssl_server->sslkey('client.key'),
+		"host: 'example.com', ca: '$default_ca': connect with sslcert, client certificate sent"
+	);
+
+	# example.net is configured and should require a client cert, but will
+	# always fail verification.
+	$node->connect_fails(
+		"$connstr host=example.net sslcertmode=disable",
+		"host: 'example.net', ca: '$default_ca': connect fails if no client certificate sent",
+		expected_stderr => qr/certificate verify failed/);
+
+	$node->connect_fails(
+		"$connstr host=example.net sslcertmode=require sslcert=ssl/client.crt "
+		  . $ssl_server->sslkey('client.key'),
+		"host: 'example.net', ca: '$default_ca': connect with sslcert, client certificate sent",
+		expected_stderr => qr/certificate verify failed/);
+}
+
+done_testing();
diff --git a/src/test/ssl/t/SSL/Backend/OpenSSL.pm b/src/test/ssl/t/SSL/Backend/OpenSSL.pm
index 4159addb700..bbd3bed6c86 100644
--- a/src/test/ssl/t/SSL/Backend/OpenSSL.pm
+++ b/src/test/ssl/t/SSL/Backend/OpenSSL.pm
@@ -72,6 +72,7 @@ sub init
 	chmod(0600, glob "$pgdata/server-*.key")
 	  or die "failed to change permissions on server keys: $!";
 	_copy_files("ssl/root+client_ca.crt", $pgdata);
+	_copy_files("ssl/root+server_ca.crt", $pgdata);
 	_copy_files("ssl/root_ca.crt", $pgdata);
 	_copy_files("ssl/root+client.crl", $pgdata);
 	mkdir("$pgdata/root+client-crldir")
@@ -146,7 +147,8 @@ following parameters are supported:
 =item cafile => B<value>
 
 The CA certificate file to use for the C<ssl_ca_file> GUC. If omitted it will
-default to 'root+client_ca.crt'.
+default to 'root+client_ca.crt'. If empty, no C<ssl_ca_file> configuration
+parameter will be set.
 
 =item certfile => B<value>
 
@@ -181,10 +183,18 @@ sub set_server_cert
 	  unless defined $params->{keyfile};
 
 	my $sslconf =
-		"ssl_ca_file='$params->{cafile}.crt'\n"
-	  . "ssl_cert_file='$params->{certfile}.crt'\n"
+		"ssl_cert_file='$params->{certfile}.crt'\n"
 	  . "ssl_key_file='$params->{keyfile}.key'\n"
 	  . "ssl_crl_file='$params->{crlfile}'\n";
+	if ($params->{cafile} ne "")
+	{
+		$sslconf .= "ssl_ca_file='$params->{cafile}.crt'\n";
+	}
+	else
+	{
+		$sslconf .= "ssl_ca_file=''\n";
+	}
+
 	$sslconf .= "ssl_crl_dir='$params->{crldir}'\n"
 	  if defined $params->{crldir};
 
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index dfcd619bfee..9c580db6b7d 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -1208,6 +1208,8 @@ HeapTupleHeader
 HeapTupleHeaderData
 HeapTupleTableSlot
 HistControl
+HostContext
+HostsLine
 HotStandbyState
 I32
 ICU_Convert_Func
-- 
2.39.3 (Apple Git-146)

From 915e41e110dad5dd9c99e7bbcb629a829d3474b0 Mon Sep 17 00:00:00 2001
From: Daniel Gustafsson <dgustafsson@postgresql.org>
Date: Thu, 11 Dec 2025 18:38:00 +0100
Subject: [PATCH v13] Serverside SNI support for libpq

Support for SNI was added to clientside libpq in 5c55dc8b4733 with the
sslsni parameter, but there was no support for utilizing it serverside.
This adds support for serverside SNI such that certificate/key handling
is available per host.  A new config file, $datadir/pg_hosts.conf, is
used for configuring which certificate and key should be used for which
hostname.  If pg_hosts.conf is non-empty it will take precedence over
the regular SSL GUCs, if it is empty or missing the regular GUCs will
be used just as before this commit with no hostname specific handling.

Host configuration can either be for a literal hostname to match, non-
SNI connections using the no_sni keyword or a default fallback matching
all connections.  By omitting no_sni and the fallback a strict mode
can be achieved where only connections using sslsni=1 and a specified
hostname are allowed.

CRL file(s) are applied from postgresql.conf to all configured hostnames.

Author: Daniel Gustafsson <daniel@yesql.se>
Reviewed-by: Jacob Champion <jacob.champion@enterprisedb.com>
Reviewed-by: Chao Li <li.evan.chao@gmail.com>
Reviewed-by: Dewei Dai <daidewei1970@163.com>
Reviewed-by: Cary Huang <cary.huang@highgo.ca>
Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Discussion: https://postgr.es/m/1C81CD0D-407E-44F9-833A-DD0331C202E5@yesql.se
---
 doc/src/sgml/runtime.sgml                     | 118 +++++
 src/backend/Makefile                          |   2 +
 src/backend/libpq/be-secure-common.c          | 198 ++++++++-
 src/backend/libpq/be-secure-openssl.c         | 415 ++++++++++++++++--
 src/backend/libpq/be-secure.c                 |   6 +-
 src/backend/libpq/meson.build                 |   1 +
 src/backend/libpq/pg_hosts.conf.sample        |   4 +
 src/backend/utils/misc/guc.c                  |  31 ++
 src/backend/utils/misc/guc_parameters.dat     |   7 +
 src/backend/utils/misc/guc_tables.c           |   1 +
 src/backend/utils/misc/postgresql.conf.sample |   2 +
 src/bin/initdb/initdb.c                       |  15 +-
 src/include/libpq/hba.h                       |  27 ++
 src/include/libpq/libpq-be.h                  |   3 +-
 src/include/libpq/libpq.h                     |   3 +-
 src/include/utils/guc.h                       |   1 +
 .../ssl_passphrase_func.c                     |   4 +-
 src/test/perl/PostgreSQL/Test/Cluster.pm      |  35 ++
 src/test/ssl/meson.build                      |   1 +
 src/test/ssl/t/001_ssltests.pl                |   6 +-
 src/test/ssl/t/004_sni.pl                     | 289 ++++++++++++
 src/test/ssl/t/SSL/Backend/OpenSSL.pm         |  16 +-
 src/tools/pgindent/typedefs.list              |   3 +
 23 files changed, 1120 insertions(+), 68 deletions(-)
 create mode 100644 src/backend/libpq/pg_hosts.conf.sample
 create mode 100644 src/test/ssl/t/004_sni.pl

diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index 0c60bafac63..ca0a114da76 100644
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -2445,6 +2445,12 @@ pg_dumpall -p 5432 | psql -d postgres -p 5433
       <entry>client certificate must not be on this list</entry>
      </row>
 
+     <row>
+      <entry><filename>$PGDATA/pg_hosts.conf</filename></entry>
+      <entry>SNI configuration</entry>
+      <entry>defines which certificates to use for which server hostname</entry>
+     </row>
+
     </tbody>
    </tgroup>
   </table>
@@ -2572,6 +2578,118 @@ openssl x509 -req -in server.csr -text -days 365 \
    </para>
   </sect2>
 
+  <sect2 id="ssl-sni">
+   <title>SNI Configuration</title>
+
+   <para>
+    <productname>PostgreSQL</productname> can be configured for Server Name
+    Indication, <acronym>SNI</acronym>, using the <filename>pg_hosts.conf</filename>
+    configuration file. <productname>PostgreSQL</productname> inspects the TLS
+    hostname extension in the SSL connection handshake, and selects the right
+    TLS certificate, key and CA certificate to use for the connection based on
+    the hosts which are defined in <filename>pg_hosts.conf</filename>.
+   </para>
+
+   <para>
+    SNI configuration is defined in the hosts configuration file,
+    <filename>pg_hosts.conf</filename>, which is stored in the cluster's
+    data directory.  The hosts configuration file contains lines of the general
+    forms:
+<synopsis>
+<replaceable>hostname</replaceable> <replaceable>SSL_certificate</replaceable> <replaceable>SSL_key</replaceable> <replaceable>SSL_CA_certificate</replaceable> <replaceable>SSL_passphrase_cmd</replaceable> <replaceable>SSL_passphrase_cmd_reload</replaceable>
+<replaceable>include</replaceable> <replaceable>file</replaceable>
+<replaceable>include_if_exists</replaceable> <replaceable>file</replaceable>
+<replaceable>include_dir</replaceable> <replaceable>directory</replaceable>
+</synopsis>
+    Comments, whitespace and line continuations are handled in the same way as
+    in <filename>pg_hba.conf</filename>.  <replaceable>hostname</replaceable>
+    is matched against the hostname TLS extension in the SSL handshake.
+    <replaceable>SSL_certificate</replaceable>,
+    <replaceable>SSL_key</replaceable>,
+    <replaceable>SSL_CA_certificate</replaceable>,
+    <replaceable>SSL_passphrase_cmd</replaceable>, and
+    <replaceable>SSL_passphrase_cmd_reload</replaceable>
+    are treated like
+    <xref linkend="guc-ssl-cert-file"/>,
+    <xref linkend="guc-ssl-key-file"/>,
+    <xref linkend="guc-ssl-ca-file"/>,
+    <xref linkend="guc-ssl-passphrase-command"/>, and
+    <xref linkend="guc-ssl-passphrase-command-supports-reload"/> respectively.
+    All fields except <replaceable>SSL_CA_certificate</replaceable>,
+    <replaceable>SSL_passphrase_cmd</replaceable> and
+    <replaceable>SSL_passphrase_cmd_reload</replaceable> are required. If
+    <replaceable>SSL_passphrase_cmd</replaceable> is defined but not
+    <replaceable>SSL_passphrase_cmd_reload</replaceable> then the default
+    value for <replaceable>SSL_passphrase_cmd_reload</replaceable> is
+    <literal>off</literal>.
+   </para>
+
+   <para>
+    <replaceable>hostname</replaceable> should either be set to the literal
+    hostname for the connection, <literal>no_sni</literal> or <literal>*</literal>.
+    <xref linkend="hostname-values"/> contain details on how these values are
+    used.
+    <table id="hostname-values">
+     <title>Hostname setting values</title>
+     <tgroup cols="3">
+      <thead>
+       <row>
+        <entry>Host Entry</entry>
+        <entry>sslsni</entry>
+        <entry>Description</entry>
+       </row>
+      </thead>
+
+      <tbody>
+       <row>
+        <entry><literal>*</literal></entry>
+        <entry>Not required</entry>
+        <entry>Default host, matches all connections</entry>
+       </row>
+
+       <row>
+        <entry><literal>no_sni</literal></entry>
+        <entry>Not allowed</entry>
+        <entry>
+         Certificate and key to use for connection with no <literal>sslsni</literal> defined.
+        </entry>
+       </row>
+
+       <row>
+        <entry><replaceable>hostname</replaceable></entry>
+        <entry>Required</entry>
+        <entry>
+         Certificate and key to use for connections to the host specified in the
+         connection.
+        </entry>
+       </row>
+      </tbody>
+
+     </tgroup>
+    </table>
+   </para>
+
+   <para>
+    If <filename>pg_hosts.conf</filename> is empty, or missing, then the SSL
+    configuration in <filename>postgresql.conf</filename> will be used for all
+    connections. If <filename>pg_hosts.conf</filename> is non-empty then it
+    will take precedence over certificate and key settings in
+    <filename>postgresql.conf</filename>.
+   </para>
+
+   <para>
+    It is currently not possible to set different <literal>clientname</literal>
+    values for the different certificates.  Any <literal>clientname</literal>
+    setting in <filename>pg_hba.conf</filename> will be applied during
+    authentication regardless of which set of certificates have been loaded
+    via an SNI enabled connection.
+   </para>
+
+   <para>
+    The CRL configuration in <filename>postgresql.conf</filename> is applied
+    on all connections regardless of if they use SNI or not.
+   </para>
+  </sect2>
  </sect1>
 
  <sect1 id="gssapi-enc">
diff --git a/src/backend/Makefile b/src/backend/Makefile
index 7344c8c7f5c..529126eebeb 100644
--- a/src/backend/Makefile
+++ b/src/backend/Makefile
@@ -187,6 +187,7 @@ endif
 	$(MAKE) -C utils install-data
 	$(INSTALL_DATA) $(srcdir)/libpq/pg_hba.conf.sample '$(DESTDIR)$(datadir)/pg_hba.conf.sample'
 	$(INSTALL_DATA) $(srcdir)/libpq/pg_ident.conf.sample '$(DESTDIR)$(datadir)/pg_ident.conf.sample'
+	$(INSTALL_DATA) $(srcdir)/libpq/pg_hosts.conf.sample '$(DESTDIR)$(datadir)/pg_hosts.conf.sample'
 	$(INSTALL_DATA) $(srcdir)/utils/misc/postgresql.conf.sample '$(DESTDIR)$(datadir)/postgresql.conf.sample'
 
 ifeq ($(with_llvm), yes)
@@ -246,6 +247,7 @@ endif
 	$(MAKE) -C utils uninstall-data
 	rm -f '$(DESTDIR)$(datadir)/pg_hba.conf.sample' \
 	      '$(DESTDIR)$(datadir)/pg_ident.conf.sample' \
+	      '$(DESTDIR)$(datadir)/pg_hosts.conf.sample' \
 	      '$(DESTDIR)$(datadir)/postgresql.conf.sample'
 ifeq ($(with_llvm), yes)
 	$(call uninstall_llvm_module,postgres)
diff --git a/src/backend/libpq/be-secure-common.c b/src/backend/libpq/be-secure-common.c
index e8b837d1fa7..be703a87636 100644
--- a/src/backend/libpq/be-secure-common.c
+++ b/src/backend/libpq/be-secure-common.c
@@ -24,32 +24,40 @@
 
 #include "common/percentrepl.h"
 #include "common/string.h"
+#include "libpq/hba.h"
 #include "libpq/libpq.h"
 #include "storage/fd.h"
+#include "utils/guc.h"
+#include "utils/memutils.h"
+
+static HostsLine *parse_hosts_line(TokenizedAuthLine *tok_line, int elevel);
 
 /*
  * Run ssl_passphrase_command
  *
  * prompt will be substituted for %p.  is_server_start determines the loglevel
- * of error messages.
+ * of error messages from executing the command, the loglevel for failures in
+ * param substitution will be ERROR regardless of is_server_start.  The actual
+ * command used depends on the configuration for the current host.
  *
  * The result will be put in buffer buf, which is of size size.  The return
  * value is the length of the actual result.
  */
 int
-run_ssl_passphrase_command(const char *prompt, bool is_server_start, char *buf, int size)
+run_ssl_passphrase_command(const char *prompt, bool is_server_start, char *buf, int size, void *userdata)
 {
 	int			loglevel = is_server_start ? ERROR : LOG;
 	char	   *command;
 	FILE	   *fh;
 	int			pclose_rc;
 	size_t		len = 0;
+	const char *cmd = (const char *) userdata;
 
 	Assert(prompt);
 	Assert(size > 0);
 	buf[0] = '\0';
 
-	command = replace_percent_placeholders(ssl_passphrase_command, "ssl_passphrase_command", "p", prompt);
+	command = replace_percent_placeholders(cmd, "ssl_passphrase_command", "p", prompt);
 
 	fh = OpenPipeStream(command, "r");
 	if (fh == NULL)
@@ -175,3 +183,187 @@ check_ssl_key_file_permissions(const char *ssl_key_file, bool isServerStart)
 
 	return true;
 }
+
+/*
+ * parse_hosts_line
+ *
+ * Parses a loaded line from the pg_hosts.conf configuration and pulls out the
+ * hostname, certificate, key and CA parts in order to build an SNI config in
+ * the TLS backend. Validation of the parsed values is left for the TLS backend
+ * to implement.
+ */
+static HostsLine *
+parse_hosts_line(TokenizedAuthLine *tok_line, int elevel)
+{
+	HostsLine  *parsedline;
+	List	   *tokens;
+	ListCell   *field;
+	AuthToken  *token;
+
+	parsedline = palloc0(sizeof(HostsLine));
+	parsedline->sourcefile = pstrdup(tok_line->file_name);
+	parsedline->linenumber = tok_line->line_num;
+	parsedline->rawline = pstrdup(tok_line->raw_line);
+
+	/* Initialize optional fields */
+	parsedline->ssl_passphrase_cmd = NULL;
+	parsedline->ssl_passphrase_reload = false;
+
+	/* Hostname */
+	field = list_head(tok_line->fields);
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->hostname = pstrdup(token->string);
+
+	/* SSL Certificate (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_cert = pstrdup(token->string);
+
+	/* SSL key (Required) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+	{
+		ereport(elevel,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("missing entry at end of line"),
+				errcontext("line %d of configuration file \"%s\"",
+						   tok_line->line_num, tok_line->file_name));
+		return NULL;
+	}
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_key = pstrdup(token->string);
+
+	/* SSL CA (optional) */
+	field = lnext(tok_line->fields, field);
+	if (!field)
+		return parsedline;
+	tokens = lfirst(field);
+	token = linitial(tokens);
+	parsedline->ssl_ca = pstrdup(token->string);
+
+	/* SSL Passphrase Command (optional) */
+	field = lnext(tok_line->fields, field);
+	if (field)
+	{
+		tokens = lfirst(field);
+		token = linitial(tokens);
+		parsedline->ssl_passphrase_cmd = pstrdup(token->string);
+
+		/*
+		 * SSL Passphrase Command support reload (optional). This field is
+		 * only supported if there was a passphrase command parsed first, so
+		 * nest it under the previous token.
+		 */
+		field = lnext(tok_line->fields, field);
+		if (field)
+		{
+			tokens = lfirst(field);
+			token = linitial(tokens);
+
+			if (token->string[0] == '1'
+				|| pg_strcasecmp(token->string, "true") == 0
+				|| pg_strcasecmp(token->string, "on") == 0
+				|| pg_strcasecmp(token->string, "yes") == 0)
+				parsedline->ssl_passphrase_reload = true;
+			else if (token->string[0] == '0'
+					 || pg_strcasecmp(token->string, "false") == 0
+					 || pg_strcasecmp(token->string, "off") == 0
+					 || pg_strcasecmp(token->string, "no") == 0)
+				parsedline->ssl_passphrase_reload = false;
+			else
+			{
+				ereport(elevel,
+						errcode(ERRCODE_CONFIG_FILE_ERROR),
+						errmsg("incorrect syntax for boolean value SSL_passphrase_cmd_reload"),
+						errcontext("line %d of configuration file \"%s\"",
+								   tok_line->line_num, tok_line->file_name));
+				return NULL;
+			}
+		}
+	}
+
+	return parsedline;
+}
+
+/*
+ * load_hosts
+ *
+ * Reads and parses the pg_hosts.conf configuration file and passes back a List
+ * of HostLine elements containing the parsed lines, or NIL in case of an empty
+ * file.  The list is returned in the hosts_lines parameter. If loading the
+ * file was successful, true is returned, else false.  This function is
+ * intended to be executed within a temporary memory context which can be
+ * discarded to free memory allocated during the processing of the file.
+ */
+int
+load_hosts(List **hosts, char **err_msg)
+{
+	FILE	   *file;
+	ListCell   *line;
+	List	   *hosts_lines = NIL;
+	List	   *parsed_lines = NIL;
+	HostsLine  *newline;
+	bool		ok = true;
+
+	/*
+	 * If we cannot return results then error out immediately. This implies
+	 * API misuse or a similar kind of programmer error.
+	 */
+	if (!hosts)
+		return HOSTSFILE_LOAD_FAILED;
+	*hosts = NIL;
+
+	/*
+	 * This is not an auth file per se, but it is using the same file format
+	 * as the pg_hba and pg_ident files and thus the same code infrastructure.
+	 * A future TODO might be to rename the supporting code with a more
+	 * generic name?
+	 */
+	file = open_auth_file(HostsFileName, LOG, 0, err_msg);
+	if (file == NULL)
+	{
+		if (errno == ENOENT)
+			return HOSTSFILE_MISSING;
+
+		return HOSTSFILE_LOAD_FAILED;
+	}
+
+	tokenize_auth_file(HostsFileName, file, &hosts_lines, LOG, 0);
+
+	foreach(line, hosts_lines)
+	{
+		TokenizedAuthLine *tok_line = (TokenizedAuthLine *) lfirst(line);
+
+		if ((tok_line->err_msg != NULL) ||
+			((newline = parse_hosts_line(tok_line, LOG)) == NULL))
+		{
+			ok = false;
+			continue;
+		}
+
+		parsed_lines = lappend(parsed_lines, newline);
+	}
+
+	free_auth_file(file, 0);
+	*hosts = parsed_lines;
+
+	if (!ok)
+		return HOSTSFILE_LOAD_FAILED;
+
+	if (parsed_lines == NIL)
+		return HOSTSFILE_EMPTY;
+
+	return HOSTSFILE_LOAD_OK;
+}
diff --git a/src/backend/libpq/be-secure-openssl.c b/src/backend/libpq/be-secure-openssl.c
index 37f4d97f209..004a93e4a89 100644
--- a/src/backend/libpq/be-secure-openssl.c
+++ b/src/backend/libpq/be-secure-openssl.c
@@ -51,9 +51,15 @@
 #endif
 #include <openssl/x509v3.h>
 
+typedef struct HostContext
+{
+	const char *hostname;
+	SSL_CTX    *context;
+	bool		ssl_loaded_verify_locations;
+} HostContext;
 
 /* default init hook can be overridden by a shared library */
-static void default_openssl_tls_init(SSL_CTX *context, bool isServerStart);
+static void default_openssl_tls_init(SSL_CTX *context, bool isServerStart, HostsLine *hosts);
 openssl_tls_init_hook_typ openssl_tls_init_hook = default_openssl_tls_init;
 
 static int	port_bio_read(BIO *h, char *buf, int size);
@@ -73,6 +79,7 @@ static int	alpn_cb(SSL *ssl,
 					const unsigned char *in,
 					unsigned int inlen,
 					void *userdata);
+static int	sni_servername_cb(SSL *ssl, int *al, void *arg);
 static bool initialize_dh(SSL_CTX *context, bool isServerStart);
 static bool initialize_ecdh(SSL_CTX *context, bool isServerStart);
 static const char *SSLerrmessageExt(unsigned long ecode, const char *replacement);
@@ -80,12 +87,26 @@ static const char *SSLerrmessage(unsigned long ecode);
 
 static char *X509_NAME_to_cstring(X509_NAME *name);
 
+/* List of SSL contexts for hostname defined connections */
+static List *sni_contexts = NIL;
+
+/* The default SSL context to use as fallback in case no hostname matches */
+static HostContext *default_context = NULL;
+
+/* The SSL context to use for connections without SNI */
+static HostContext *no_sni_context = NULL;
+
+/* The currently active context */
 static SSL_CTX *SSL_context = NULL;
+static HostContext *Host_context = NULL;
+
 static bool dummy_ssl_passwd_cb_called = false;
 static bool ssl_is_server_start;
 
 static int	ssl_protocol_version_to_openssl(int v);
 static const char *ssl_protocol_version_to_string(int v);
+static SSL_CTX *ssl_init_context(bool isServerStart, HostsLine *host);
+static void free_contexts(void);
 
 struct CallbackErr
 {
@@ -102,11 +123,181 @@ struct CallbackErr
 
 int
 be_tls_init(bool isServerStart)
+{
+	List	   *pg_hosts = NIL;
+	ListCell   *line;
+	MemoryContext oldcxt;
+	MemoryContext host_memcxt;
+	char	   *err_msg;
+	int			res;
+
+	/*
+	 * If there are contexts loaded when we init they must be released. This
+	 * should only be possible during configuration reloads and not when the
+	 * server is starting up.
+	 */
+	if (sni_contexts != NIL || default_context || no_sni_context)
+	{
+		Assert(!isServerStart);
+		free_contexts();
+		Host_context = NULL;
+		SSL_context = NULL;
+	}
+
+	/*
+	 * Attempt to load, and parse, TLS configuration from the pg_hosts.conf
+	 * file with the set of hosts returned as a list.  If there are hosts
+	 * configured there they take precedence over the postgresql.conf config.
+	 * Make sure to allocate the parsed rows in a temporary memory context so
+	 * that we can avoid memory leaks from the parsing process.
+	 */
+	host_memcxt = AllocSetContextCreate(CurrentMemoryContext,
+										"hosts file parser context",
+										ALLOCSET_SMALL_SIZES);
+	oldcxt = MemoryContextSwitchTo(host_memcxt);
+	res = load_hosts(&pg_hosts, &err_msg);
+	MemoryContextSwitchTo(oldcxt);
+
+	/*
+	 * pg_hosts.conf is not required to contain configuration, but if it does
+	 * we error out in case it fails to load rather than continue to try the
+	 * postgresql.conf configuration to avoid silently falling back on an
+	 * undesired configuration.
+	 */
+	if (res == HOSTSFILE_LOAD_FAILED)
+	{
+		ereport(isServerStart ? FATAL : LOG,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("could not load \"%s\": %s", "pg_hosts.conf",
+					   err_msg ? err_msg : "unknown error"));
+		MemoryContextDelete(host_memcxt);
+		return -1;
+	}
+
+	/*
+	 * Loading and parsing the hosts file was successful, create contexts for
+	 * each host entry and add to the list of hosts to be checked during
+	 * login.
+	 */
+	else if (res == HOSTSFILE_LOAD_OK)
+	{
+		foreach(line, pg_hosts)
+		{
+			HostContext *host_context;
+			HostsLine  *host = lfirst(line);
+			SSL_CTX    *tmp_context = NULL;
+
+			tmp_context = ssl_init_context(isServerStart, host);
+			if (tmp_context == NULL)
+			{
+				ereport(isServerStart ? FATAL : LOG,
+						errcode(ERRCODE_CONFIG_FILE_ERROR),
+						errmsg("unable to load SSL config from \"%s\" line %i",
+							   host->sourcefile, host->linenumber));
+				free_contexts();
+				MemoryContextDelete(host_memcxt);
+				return -1;
+			}
+
+			host_context = palloc0(sizeof(HostContext));
+			host_context->context = tmp_context;
+
+			/* Set flag to remember whether CA store has been loaded */
+			if (host->ssl_ca && host->ssl_ca[0] != '\0')
+				host_context->ssl_loaded_verify_locations = true;
+
+			/*
+			 * The hostname in the context is NULL in case it is the default
+			 * host, or a context to use for non-SNI connections.
+			 */
+			if (strcmp(host->hostname, "*") == 0)
+				default_context = host_context;
+			else if (strcmp(host->hostname, "no_sni") == 0)
+				no_sni_context = host_context;
+			else
+			{
+				host_context->hostname = pstrdup(host->hostname);
+				sni_contexts = lappend(sni_contexts, host_context);
+			}
+
+			/*
+			 * There needs to be an installed context to drive the handshake
+			 * until the SNI callback switches over to the expected one, for
+			 * now just set it to the first one we see.
+			 */
+			if (!Host_context)
+				Host_context = host_context;
+		}
+
+		MemoryContextDelete(host_memcxt);
+	}
+
+	/*
+	 * If the pg_hosts.conf file doesn't exist, or is empty, then load the
+	 * config from postgresql.conf.
+	 */
+	else if (res == HOSTSFILE_EMPTY || res == HOSTSFILE_MISSING)
+	{
+		HostsLine	pgconf;
+		SSL_CTX    *tmp_context = NULL;
+
+		memset(&pgconf, 0, sizeof(pgconf));
+		pgconf.ssl_cert = ssl_cert_file;
+		pgconf.ssl_key = ssl_key_file;
+		pgconf.ssl_ca = ssl_ca_file;
+		pgconf.ssl_passphrase_cmd = ssl_passphrase_command;
+		pgconf.ssl_passphrase_reload = ssl_passphrase_command_supports_reload;
+
+		tmp_context = ssl_init_context(isServerStart, &pgconf);
+		if (tmp_context == NULL)
+		{
+			ereport(isServerStart ? FATAL : LOG,
+					errcode(ERRCODE_CONFIG_FILE_ERROR),
+					errmsg("could not load SSL configuration from \"%s\"",
+						   "postgresql.conf"));
+			return -1;
+		}
+
+		/*
+		 * If postgresql.conf is used to configure SSL then by definition it
+		 * will be the default context as we don't have per-host config.  We
+		 * can also set it as the Host_context since it will be used for all
+		 * connections.
+		 */
+		default_context = palloc0(sizeof(HostContext));
+		default_context->context = tmp_context;
+		Host_context = default_context;
+
+		/* Set flag to remember whether CA store has been loaded */
+		if (ssl_ca_file[0])
+			default_context->ssl_loaded_verify_locations = true;
+	}
+
+	/* Make sure we have at least one certificate loaded */
+	if (sni_contexts == NIL && !default_context && !no_sni_context)
+	{
+		ereport(isServerStart ? FATAL : LOG,
+				errcode(ERRCODE_CONFIG_FILE_ERROR),
+				errmsg("no SSL contexts loaded"));
+		return -1;
+	}
+
+	SSL_context = Host_context->context;
+
+	return 0;
+}
+
+static SSL_CTX *
+ssl_init_context(bool isServerStart, HostsLine *host_line)
 {
 	SSL_CTX    *context;
 	int			ssl_ver_min = -1;
 	int			ssl_ver_max = -1;
 
+	const char *ctx_ssl_cert_file = host_line->ssl_cert;
+	const char *ctx_ssl_key_file = host_line->ssl_key;
+	const char *ctx_ssl_ca_file = host_line->ssl_ca;
+
 	/*
 	 * Create a new SSL context into which we'll load all the configuration
 	 * settings.  If we fail partway through, we can avoid memory leakage by
@@ -132,10 +323,16 @@ be_tls_init(bool isServerStart)
 	 */
 	SSL_CTX_set_mode(context, SSL_MODE_ACCEPT_MOVING_WRITE_BUFFER);
 
+	/*
+	 * Install SNI TLS extension callback in order to validate hostnames in
+	 * case we have at least one context configured with a host name.
+	 */
+	SSL_CTX_set_tlsext_servername_callback(context, sni_servername_cb);
+
 	/*
 	 * Call init hook (usually to set password callback)
 	 */
-	(*openssl_tls_init_hook) (context, isServerStart);
+	(*openssl_tls_init_hook) (context, isServerStart, host_line);
 
 	/* used by the callback */
 	ssl_is_server_start = isServerStart;
@@ -143,16 +340,16 @@ be_tls_init(bool isServerStart)
 	/*
 	 * Load and verify server's certificate and private key
 	 */
-	if (SSL_CTX_use_certificate_chain_file(context, ssl_cert_file) != 1)
+	if (SSL_CTX_use_certificate_chain_file(context, ctx_ssl_cert_file) != 1)
 	{
 		ereport(isServerStart ? FATAL : LOG,
 				(errcode(ERRCODE_CONFIG_FILE_ERROR),
 				 errmsg("could not load server certificate file \"%s\": %s",
-						ssl_cert_file, SSLerrmessage(ERR_get_error()))));
+						ctx_ssl_cert_file, SSLerrmessage(ERR_get_error()))));
 		goto error;
 	}
 
-	if (!check_ssl_key_file_permissions(ssl_key_file, isServerStart))
+	if (!check_ssl_key_file_permissions(ctx_ssl_key_file, isServerStart))
 		goto error;
 
 	/*
@@ -161,19 +358,19 @@ be_tls_init(bool isServerStart)
 	dummy_ssl_passwd_cb_called = false;
 
 	if (SSL_CTX_use_PrivateKey_file(context,
-									ssl_key_file,
+									ctx_ssl_key_file,
 									SSL_FILETYPE_PEM) != 1)
 	{
 		if (dummy_ssl_passwd_cb_called)
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("private key file \"%s\" cannot be reloaded because it requires a passphrase",
-							ssl_key_file)));
+							ctx_ssl_key_file)));
 		else
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("could not load private key file \"%s\": %s",
-							ssl_key_file, SSLerrmessage(ERR_get_error()))));
+							ctx_ssl_key_file, SSLerrmessage(ERR_get_error()))));
 		goto error;
 	}
 
@@ -325,17 +522,17 @@ be_tls_init(bool isServerStart)
 	/*
 	 * Load CA store, so we can verify client certificates if needed.
 	 */
-	if (ssl_ca_file[0])
+	if (ctx_ssl_ca_file && ctx_ssl_ca_file[0])
 	{
 		STACK_OF(X509_NAME) * root_cert_list;
 
-		if (SSL_CTX_load_verify_locations(context, ssl_ca_file, NULL) != 1 ||
-			(root_cert_list = SSL_load_client_CA_file(ssl_ca_file)) == NULL)
+		if (SSL_CTX_load_verify_locations(context, ctx_ssl_ca_file, NULL) != 1 ||
+			(root_cert_list = SSL_load_client_CA_file(ctx_ssl_ca_file)) == NULL)
 		{
 			ereport(isServerStart ? FATAL : LOG,
 					(errcode(ERRCODE_CONFIG_FILE_ERROR),
 					 errmsg("could not load root certificate file \"%s\": %s",
-							ssl_ca_file, SSLerrmessage(ERR_get_error()))));
+							ctx_ssl_ca_file, SSLerrmessage(ERR_get_error()))));
 			goto error;
 		}
 
@@ -347,18 +544,17 @@ be_tls_init(bool isServerStart)
 		 * free it when no longer needed.
 		 */
 		SSL_CTX_set_client_CA_list(context, root_cert_list);
-
-		/*
-		 * Always ask for SSL client cert, but don't fail if it's not
-		 * presented.  We might fail such connections later, depending on what
-		 * we find in pg_hba.conf.
-		 */
-		SSL_CTX_set_verify(context,
-						   (SSL_VERIFY_PEER |
-							SSL_VERIFY_CLIENT_ONCE),
-						   verify_cb);
 	}
 
+	/*
+	 * Always ask for SSL client cert, but don't fail if it's not presented.
+	 * We might fail such connections later, depending on what we find in
+	 * pg_hba.conf.
+	 */
+	SSL_CTX_set_verify(context,
+					   (SSL_VERIFY_PEER | SSL_VERIFY_CLIENT_ONCE),
+					   verify_cb);
+
 	/*----------
 	 * Load the Certificate Revocation List (CRL).
 	 * http://searchsecurity.techtarget.com/sDefinition/0,,sid14_gci803160,00.html
@@ -407,38 +603,19 @@ be_tls_init(bool isServerStart)
 		}
 	}
 
-	/*
-	 * Success!  Replace any existing SSL_context.
-	 */
-	if (SSL_context)
-		SSL_CTX_free(SSL_context);
-
-	SSL_context = context;
-
-	/*
-	 * Set flag to remember whether CA store has been loaded into SSL_context.
-	 */
-	if (ssl_ca_file[0])
-		ssl_loaded_verify_locations = true;
-	else
-		ssl_loaded_verify_locations = false;
-
-	return 0;
+	return context;
 
 	/* Clean up by releasing working context. */
 error:
 	if (context)
 		SSL_CTX_free(context);
-	return -1;
+	return NULL;
 }
 
 void
 be_tls_destroy(void)
 {
-	if (SSL_context)
-		SSL_CTX_free(SSL_context);
-	SSL_context = NULL;
-	ssl_loaded_verify_locations = false;
+	free_contexts();
 }
 
 int
@@ -771,6 +948,9 @@ be_tls_close(Port *port)
 		pfree(port->peer_dn);
 		port->peer_dn = NULL;
 	}
+
+	Host_context = NULL;
+	SSL_context = NULL;
 }
 
 ssize_t
@@ -1144,7 +1324,7 @@ ssl_external_passwd_cb(char *buf, int size, int rwflag, void *userdata)
 
 	Assert(rwflag == 0);
 
-	return run_ssl_passphrase_command(prompt, ssl_is_server_start, buf, size);
+	return run_ssl_passphrase_command(prompt, ssl_is_server_start, buf, size, userdata);
 }
 
 /*
@@ -1390,6 +1570,92 @@ alpn_cb(SSL *ssl,
 	}
 }
 
+/*
+ * sni_servername_cb
+ *
+ * Callback executed by OpenSSL during handshake in case the server has been
+ * configured to validate hostnames.  Returning SSL_TLSEXT_ERR_ALERT_FATAL to
+ * OpenSSL will immediately terminate the handshake.
+ */
+static int
+sni_servername_cb(SSL *ssl, int *al, void *arg)
+{
+	const char *tlsext_hostname;
+	HostContext *install_context = NULL;
+
+	tlsext_hostname = SSL_get_servername(ssl, TLSEXT_NAMETYPE_host_name);
+
+	/*
+	 * If there is no hostname set in the TLS extension, we have two options:
+	 * i) there is a HostContext defined for non-SNI connections, in that case
+	 * we switch to that; ii) there is no non-SNI config and we error out as
+	 * there is no context to switch to.
+	 */
+	if (!tlsext_hostname)
+	{
+		if (no_sni_context)
+			install_context = no_sni_context;
+		else if (default_context)
+			install_context = default_context;
+		else
+		{
+			/*
+			 * The error message for a missing server_name should, according
+			 * to RFC 8446, be missing_extension. This isn't entirely ideal
+			 * since the user won't be able to tell which extension the server
+			 * considered missing.  Sending unrecognized_name would be a more
+			 * helpful error, but for now we stick to the RFC.
+			 */
+			*al = SSL_AD_MISSING_EXTENSION;
+
+			ereport(COMMERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg("no hostname provided in callback")));
+			return SSL_TLSEXT_ERR_ALERT_FATAL;
+		}
+	}
+	else
+	{
+		/*
+		 * We have a requested hostname from the client, match against all
+		 * entries in the pg_hosts configuration and attempt to find a match.
+		 */
+		foreach_ptr(HostContext, host, sni_contexts)
+		{
+			if (strcmp(host->hostname, tlsext_hostname) == 0)
+			{
+				install_context = host;
+				break;
+			}
+		}
+
+		/*
+		 * If no host specific match was found, and there is a default config,
+		 * then fall back to using that.
+		 */
+		if (!install_context && default_context)
+			install_context = default_context;
+	}
+
+	/*
+	 * If we reach here without a context chosen as the session context then
+	 * fail the handshake and terminate the connection.
+	 */
+	if (install_context == NULL)
+		return SSL_TLSEXT_ERR_ALERT_FATAL;
+
+	Host_context = install_context;
+	SSL_context = install_context->context;
+	if (SSL_set_SSL_CTX(ssl, SSL_context) == NULL)
+	{
+		ereport(COMMERROR,
+				errcode(ERRCODE_PROTOCOL_VIOLATION),
+				errmsg("failed to switch to SSL context for host"));
+		return SSL_TLSEXT_ERR_ALERT_FATAL;
+	}
+
+	return SSL_TLSEXT_ERR_OK;
+}
 
 /*
  * Set DH parameters for generating ephemeral DH keys.  The
@@ -1599,6 +1865,14 @@ be_tls_get_peer_serial(Port *port, char *ptr, size_t len)
 		ptr[0] = '\0';
 }
 
+bool
+be_tls_loaded_verify_locations(void)
+{
+	if (!Host_context)
+		return false;
+	return Host_context->ssl_loaded_verify_locations;
+}
+
 char *
 be_tls_get_certificate_hash(Port *port, size_t *len)
 {
@@ -1792,17 +2066,23 @@ ssl_protocol_version_to_string(int v)
 
 
 static void
-default_openssl_tls_init(SSL_CTX *context, bool isServerStart)
+default_openssl_tls_init(SSL_CTX *context, bool isServerStart, HostsLine *host)
 {
 	if (isServerStart)
 	{
-		if (ssl_passphrase_command[0])
+		if (host->ssl_passphrase_cmd != NULL)
+		{
 			SSL_CTX_set_default_passwd_cb(context, ssl_external_passwd_cb);
+			SSL_CTX_set_default_passwd_cb_userdata(context, host->ssl_passphrase_cmd);
+		}
 	}
 	else
 	{
-		if (ssl_passphrase_command[0] && ssl_passphrase_command_supports_reload)
+		if (host->ssl_passphrase_cmd != NULL && host->ssl_passphrase_reload)
+		{
 			SSL_CTX_set_default_passwd_cb(context, ssl_external_passwd_cb);
+			SSL_CTX_set_default_passwd_cb_userdata(context, host->ssl_passphrase_cmd);
+		}
 		else
 
 			/*
@@ -1814,3 +2094,42 @@ default_openssl_tls_init(SSL_CTX *context, bool isServerStart)
 			SSL_CTX_set_default_passwd_cb(context, dummy_ssl_passwd_cb);
 	}
 }
+
+/*
+ * Cleanup function for when hostname configuration is reloaded from the
+ * pg_hosts.conf file, at that point we must discard all existing contexts.
+ */
+static void
+free_contexts(void)
+{
+	if (sni_contexts != NIL)
+	{
+		foreach_ptr(HostContext, host, sni_contexts)
+		{
+			if (host->hostname)
+				pfree(unconstify(char *, host->hostname));
+			SSL_CTX_free(host->context);
+		}
+
+		list_free_deep(sni_contexts);
+		sni_contexts = NIL;
+	}
+
+	/*
+	 * The hostname need not be freed for the no_sni and default contexts
+	 * since they by definition are not connected to a hostname and thus have
+	 * none allocated.
+	 */
+	if (no_sni_context)
+	{
+		SSL_CTX_free(no_sni_context->context);
+		pfree(no_sni_context);
+		no_sni_context = NULL;
+	}
+	if (default_context)
+	{
+		SSL_CTX_free(default_context->context);
+		pfree(default_context);
+		default_context = NULL;
+	}
+}
diff --git a/src/backend/libpq/be-secure.c b/src/backend/libpq/be-secure.c
index d723e74e813..2e6be47887c 100644
--- a/src/backend/libpq/be-secure.c
+++ b/src/backend/libpq/be-secure.c
@@ -43,10 +43,6 @@ char	   *ssl_dh_params_file;
 char	   *ssl_passphrase_command;
 bool		ssl_passphrase_command_supports_reload;
 
-#ifdef USE_SSL
-bool		ssl_loaded_verify_locations = false;
-#endif
-
 /* GUC variable controlling SSL cipher list */
 char	   *SSLCipherSuites = NULL;
 char	   *SSLCipherList = NULL;
@@ -99,7 +95,7 @@ bool
 secure_loaded_verify_locations(void)
 {
 #ifdef USE_SSL
-	return ssl_loaded_verify_locations;
+	return be_tls_loaded_verify_locations();
 #else
 	return false;
 #endif
diff --git a/src/backend/libpq/meson.build b/src/backend/libpq/meson.build
index 31aa2faae1e..4f6ec13bc74 100644
--- a/src/backend/libpq/meson.build
+++ b/src/backend/libpq/meson.build
@@ -31,5 +31,6 @@ endif
 install_data(
   'pg_hba.conf.sample',
   'pg_ident.conf.sample',
+  'pg_hosts.conf.sample',
   install_dir: dir_data,
 )
diff --git a/src/backend/libpq/pg_hosts.conf.sample b/src/backend/libpq/pg_hosts.conf.sample
new file mode 100644
index 00000000000..a31c49b01f7
--- /dev/null
+++ b/src/backend/libpq/pg_hosts.conf.sample
@@ -0,0 +1,4 @@
+# PostgreSQL SNI Hostname mappings
+# ================================
+
+# HOSTNAME       SSL CERTIFICATE             SSL KEY     SSL CA       PASSPHRASE COMMAND         PASSPHRASE COMMAND RELOAD
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 935c235e1b3..2e30e564715 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -56,6 +56,7 @@
 #define CONFIG_FILENAME "postgresql.conf"
 #define HBA_FILENAME	"pg_hba.conf"
 #define IDENT_FILENAME	"pg_ident.conf"
+#define HOSTS_FILENAME	"pg_hosts.conf"
 
 #ifdef EXEC_BACKEND
 #define CONFIG_EXEC_PARAMS "global/config_exec_params"
@@ -1838,6 +1839,36 @@ SelectConfigFiles(const char *userDoption, const char *progname)
 	}
 	SetConfigOption("ident_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
 
+	if (fname_is_malloced)
+		free(fname);
+	else
+		guc_free(fname);
+
+	/*
+	 * Likewise for pg_hosts.conf.
+	 */
+	if (HostsFileName)
+	{
+		fname = make_absolute_path(HostsFileName);
+		fname_is_malloced = true;
+	}
+	else if (configdir)
+	{
+		fname = guc_malloc(FATAL,
+						   strlen(configdir) + strlen(HOSTS_FILENAME) + 2);
+		sprintf(fname, "%s/%s", configdir, HOSTS_FILENAME);
+		fname_is_malloced = false;
+	}
+	else
+	{
+		write_stderr("%s does not know where to find the \"hosts\" configuration file.\n"
+					 "This can be specified as \"hosts_file\" in \"%s\", "
+					 "or by the -D invocation option, or by the "
+					 "PGDATA environment variable.\n",
+					 progname, ConfigFileName);
+	}
+	SetConfigOption("hosts_file", fname, PGC_POSTMASTER, PGC_S_OVERRIDE);
+
 	if (fname_is_malloced)
 		free(fname);
 	else
diff --git a/src/backend/utils/misc/guc_parameters.dat b/src/backend/utils/misc/guc_parameters.dat
index 3b9d8349078..4ce670e8347 100644
--- a/src/backend/utils/misc/guc_parameters.dat
+++ b/src/backend/utils/misc/guc_parameters.dat
@@ -1167,6 +1167,13 @@
   boot_val => 'NULL',
 },
 
+{ name => 'hosts_file', type => 'string', context => 'PGC_POSTMASTER', group => 'FILE_LOCATIONS',
+  short_desc => 'Sets the server\'s "hosts" configuration file.',
+  flags => 'GUC_SUPERUSER_ONLY',
+  variable => 'HostsFileName',
+  boot_val => 'NULL',
+},
+
 { name => 'hot_standby', type => 'bool', context => 'PGC_POSTMASTER', group => 'REPLICATION_STANDBY',
   short_desc => 'Allows connections and queries during recovery.',
   variable => 'EnableHotStandby',
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index f87b558c2c6..1d26628f879 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -556,6 +556,7 @@ char	   *cluster_name = "";
 char	   *ConfigFileName;
 char	   *HbaFileName;
 char	   *IdentFileName;
+char	   *HostsFileName;
 char	   *external_pid_file;
 
 char	   *application_name;
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index dc9e2255f8a..1f360110564 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -45,6 +45,8 @@
                                         # (change requires restart)
 #ident_file = 'ConfigDir/pg_ident.conf' # ident configuration file
                                         # (change requires restart)
+#hosts_file = 'ConfigDir/pg_hosts.conf' # hosts configuration file
+                                        # (change requires restart)
 
 # If external_pid_file is not explicitly set, no extra PID file is written.
 #external_pid_file = ''                 # write an extra PID file
diff --git a/src/bin/initdb/initdb.c b/src/bin/initdb/initdb.c
index 92fe2f531f7..c953f24a58d 100644
--- a/src/bin/initdb/initdb.c
+++ b/src/bin/initdb/initdb.c
@@ -177,6 +177,7 @@ static int	encodingid;
 static char *bki_file;
 static char *hba_file;
 static char *ident_file;
+static char *hosts_file;
 static char *conf_file;
 static char *dictionary_file;
 static char *info_schema_file;
@@ -1530,6 +1531,14 @@ setup_config(void)
 
 	snprintf(path, sizeof(path), "%s/pg_ident.conf", pg_data);
 
+	writefile(path, conflines);
+	if (chmod(path, pg_file_create_mode) != 0)
+		pg_fatal("could not change permissions of \"%s\": %m", path);
+
+	/* pg_hosts.conf */
+	conflines = readfile(hosts_file);
+	snprintf(path, sizeof(path), "%s/pg_hosts.conf", pg_data);
+
 	writefile(path, conflines);
 	if (chmod(path, pg_file_create_mode) != 0)
 		pg_fatal("could not change permissions of \"%s\": %m", path);
@@ -2791,6 +2800,7 @@ setup_data_file_paths(void)
 	set_input(&bki_file, "postgres.bki");
 	set_input(&hba_file, "pg_hba.conf.sample");
 	set_input(&ident_file, "pg_ident.conf.sample");
+	set_input(&hosts_file, "pg_hosts.conf.sample");
 	set_input(&conf_file, "postgresql.conf.sample");
 	set_input(&dictionary_file, "snowball_create.sql");
 	set_input(&info_schema_file, "information_schema.sql");
@@ -2806,12 +2816,12 @@ setup_data_file_paths(void)
 				"PGDATA=%s\nshare_path=%s\nPGPATH=%s\n"
 				"POSTGRES_SUPERUSERNAME=%s\nPOSTGRES_BKI=%s\n"
 				"POSTGRESQL_CONF_SAMPLE=%s\n"
-				"PG_HBA_SAMPLE=%s\nPG_IDENT_SAMPLE=%s\n",
+				"PG_HBA_SAMPLE=%s\nPG_IDENT_SAMPLE=%s\nPG_HOSTS_SAMPLE=%s\n",
 				PG_VERSION,
 				pg_data, share_path, bin_path,
 				username, bki_file,
 				conf_file,
-				hba_file, ident_file);
+				hba_file, ident_file, hosts_file);
 		if (show_setting)
 			exit(0);
 	}
@@ -2819,6 +2829,7 @@ setup_data_file_paths(void)
 	check_input(bki_file);
 	check_input(hba_file);
 	check_input(ident_file);
+	check_input(hosts_file);
 	check_input(conf_file);
 	check_input(dictionary_file);
 	check_input(info_schema_file);
diff --git a/src/include/libpq/hba.h b/src/include/libpq/hba.h
index 7b93ba4a709..38713381255 100644
--- a/src/include/libpq/hba.h
+++ b/src/include/libpq/hba.h
@@ -151,6 +151,33 @@ typedef struct IdentLine
 	AuthToken  *pg_user;
 } IdentLine;
 
+typedef struct HostsLine
+{
+	int			linenumber;
+
+	char	   *sourcefile;
+	char	   *rawline;
+
+	/* Required fields */
+	bool		default_host;
+	char	   *hostname;
+	char	   *ssl_key;
+	char	   *ssl_cert;
+	char	   *ssl_ca;
+
+	/* Optional fields */
+	char	   *ssl_passphrase_cmd;
+	bool		ssl_passphrase_reload;
+} HostsLine;
+
+typedef enum HostsFileLoad
+{
+	HOSTSFILE_LOAD_OK = 0,
+	HOSTSFILE_LOAD_FAILED,
+	HOSTSFILE_EMPTY,
+	HOSTSFILE_MISSING,
+} HostsFileLoadResult;
+
 /*
  * TokenizedAuthLine represents one line lexed from an authentication
  * configuration file.  Each item in the "fields" list is a sub-list of
diff --git a/src/include/libpq/libpq-be.h b/src/include/libpq/libpq-be.h
index d6e671a6382..e1631cb7b5c 100644
--- a/src/include/libpq/libpq-be.h
+++ b/src/include/libpq/libpq-be.h
@@ -320,6 +320,7 @@ extern const char *be_tls_get_cipher(Port *port);
 extern void be_tls_get_peer_subject_name(Port *port, char *ptr, size_t len);
 extern void be_tls_get_peer_issuer_name(Port *port, char *ptr, size_t len);
 extern void be_tls_get_peer_serial(Port *port, char *ptr, size_t len);
+extern bool be_tls_loaded_verify_locations(void);
 
 /*
  * Get the server certificate hash for SCRAM channel binding type
@@ -332,7 +333,7 @@ extern char *be_tls_get_certificate_hash(Port *port, size_t *len);
 
 /* init hook for SSL, the default sets the password callback if appropriate */
 #ifdef USE_OPENSSL
-typedef void (*openssl_tls_init_hook_typ) (SSL_CTX *context, bool isServerStart);
+typedef void (*openssl_tls_init_hook_typ) (SSL_CTX *context, bool isServerStart, HostsLine *host);
 extern PGDLLIMPORT openssl_tls_init_hook_typ openssl_tls_init_hook;
 #endif
 
diff --git a/src/include/libpq/libpq.h b/src/include/libpq/libpq.h
index 5af005ad779..b9b2c8bd5af 100644
--- a/src/include/libpq/libpq.h
+++ b/src/include/libpq/libpq.h
@@ -156,8 +156,9 @@ enum ssl_protocol_versions
  * prototypes for functions in be-secure-common.c
  */
 extern int	run_ssl_passphrase_command(const char *prompt, bool is_server_start,
-									   char *buf, int size);
+									   char *buf, int size, void *userdata);
 extern bool check_ssl_key_file_permissions(const char *ssl_key_file,
 										   bool isServerStart);
+extern int	load_hosts(List **hosts, char **err_msg);
 
 #endif							/* LIBPQ_H */
diff --git a/src/include/utils/guc.h b/src/include/utils/guc.h
index f21ec37da89..8f08a38b789 100644
--- a/src/include/utils/guc.h
+++ b/src/include/utils/guc.h
@@ -312,6 +312,7 @@ extern PGDLLIMPORT char *cluster_name;
 extern PGDLLIMPORT char *ConfigFileName;
 extern PGDLLIMPORT char *HbaFileName;
 extern PGDLLIMPORT char *IdentFileName;
+extern PGDLLIMPORT char *HostsFileName;
 extern PGDLLIMPORT char *external_pid_file;
 
 extern PGDLLIMPORT char *application_name;
diff --git a/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c b/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
index d5992149821..a85d85735cf 100644
--- a/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
+++ b/src/test/modules/ssl_passphrase_callback/ssl_passphrase_func.c
@@ -26,7 +26,7 @@ static char *ssl_passphrase = NULL;
 static int	rot13_passphrase(char *buf, int size, int rwflag, void *userdata);
 
 /* hook function to set the callback */
-static void set_rot13(SSL_CTX *context, bool isServerStart);
+static void set_rot13(SSL_CTX *context, bool isServerStart, HostsLine *host);
 
 /*
  * Module load callback
@@ -53,7 +53,7 @@ _PG_init(void)
 }
 
 static void
-set_rot13(SSL_CTX *context, bool isServerStart)
+set_rot13(SSL_CTX *context, bool isServerStart, HostsLine *host)
 {
 	/* warn if the user has set ssl_passphrase_command */
 	if (ssl_passphrase_command[0])
diff --git a/src/test/perl/PostgreSQL/Test/Cluster.pm b/src/test/perl/PostgreSQL/Test/Cluster.pm
index 295988b8b87..11f9280b341 100644
--- a/src/test/perl/PostgreSQL/Test/Cluster.pm
+++ b/src/test/perl/PostgreSQL/Test/Cluster.pm
@@ -1302,6 +1302,27 @@ Wrapper for pg_ctl restart.
 With optional extra param fail_ok => 1, returns 0 for failure
 instead of bailing out.
 
+=over
+
+=item fail_ok => 1
+
+By default, failure terminates the entire F<prove> invocation.  If given,
+instead return 0 for failure instead of bailing out.
+
+=item log_unlike => B<pattern>
+
+When defined, the logfile is inspected for the presence of the fragment by
+matching the specified pattern. If the pattern matches against the logfile a
+test failure will be logged.
+
+=item log_like => B<pattern>
+
+When defined, the logfile is inspected for the presence of the fragment by
+matching the pattern. If the pattern doesn't match a test failure will be
+logged.
+
+=back
+
 =cut
 
 sub restart
@@ -1314,6 +1335,8 @@ sub restart
 
 	print "### Restarting node \"$name\"\n";
 
+	my $log_location = -s $self->logfile;
+
 	# -w is now the default but having it here does no harm and helps
 	# compatibility with older versions.
 	$ret = PostgreSQL::Test::Utils::system_log(
@@ -1322,6 +1345,18 @@ sub restart
 		'--log' => $self->logfile,
 		'restart');
 
+	# Check for expected and/or unexpected log fragments if the caller
+	# specified such checks in the params
+	if (defined $params{log_unlike} || defined $params{log_like})
+	{
+		my $log =
+		  PostgreSQL::Test::Utils::slurp_file($self->logfile, $log_location);
+		unlike($log, $params{log_unlike}, "unexpected fragment found in log")
+			if defined $params{log_unlike};
+		like($log, $params{log_like}, "expected fragment not found in log")
+			if defined $params{log_like};
+	}
+
 	if ($ret != 0)
 	{
 		print "# pg_ctl restart failed; see logfile for details: "
diff --git a/src/test/ssl/meson.build b/src/test/ssl/meson.build
index d8e0fb518e0..e5a9402cd9c 100644
--- a/src/test/ssl/meson.build
+++ b/src/test/ssl/meson.build
@@ -13,6 +13,7 @@ tests += {
       't/001_ssltests.pl',
       't/002_scram.pl',
       't/003_sslinfo.pl',
+      't/004_sni.pl',
     ],
   },
 }
diff --git a/src/test/ssl/t/001_ssltests.pl b/src/test/ssl/t/001_ssltests.pl
index fc7c35ef879..15ca0a0e8c2 100644
--- a/src/test/ssl/t/001_ssltests.pl
+++ b/src/test/ssl/t/001_ssltests.pl
@@ -380,11 +380,11 @@ switch_server_cert($node, certfile => 'server-ip-cn-only');
 $common_connstr =
   "$default_ssl_connstr user=ssltestuser dbname=trustdb sslrootcert=ssl/root+server_ca.crt hostaddr=$SERVERHOSTADDR sslmode=verify-full";
 
-$node->connect_ok("$common_connstr host=192.0.2.1",
+$node->connect_ok("$common_connstr host=192.0.2.1 sslsni=0",
 	"IP address in the Common Name");
 
 $node->connect_fails(
-	"$common_connstr host=192.000.002.001",
+	"$common_connstr host=192.000.002.001 sslsni=0",
 	"mismatch between host name and server certificate IP address",
 	expected_stderr =>
 	  qr/\Qserver certificate for "192.0.2.1" does not match host name "192.000.002.001"\E/
@@ -394,7 +394,7 @@ $node->connect_fails(
 # long-standing behavior.)
 switch_server_cert($node, certfile => 'server-ip-in-dnsname');
 
-$node->connect_ok("$common_connstr host=192.0.2.1",
+$node->connect_ok("$common_connstr host=192.0.2.1 sslsni=0",
 	"IP address in a dNSName");
 
 # Test Subject Alternative Names.
diff --git a/src/test/ssl/t/004_sni.pl b/src/test/ssl/t/004_sni.pl
new file mode 100644
index 00000000000..2dd70e7afee
--- /dev/null
+++ b/src/test/ssl/t/004_sni.pl
@@ -0,0 +1,289 @@
+
+# Copyright (c) 2024, PostgreSQL Global Development Group
+
+use strict;
+use warnings FATAL => 'all';
+
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+use FindBin;
+use lib $FindBin::RealBin;
+
+use SSL::Server;
+
+# This is the hostaddr used to connect to the server. This cannot be a
+# hostname, because the server certificate is always for the domain
+# postgresql-ssl-regression.test.
+my $SERVERHOSTADDR = '127.0.0.1';
+# This is the pattern to use in pg_hba.conf to match incoming connections.
+my $SERVERHOSTCIDR = '127.0.0.1/32';
+
+if ($ENV{with_ssl} ne 'openssl')
+{
+	plan skip_all => 'OpenSSL not supported by this build';
+}
+
+if (!$ENV{PG_TEST_EXTRA} || $ENV{PG_TEST_EXTRA} !~ /\bssl\b/)
+{
+	plan skip_all =>
+	  'Potentially unsafe test SSL not enabled in PG_TEST_EXTRA';
+}
+
+my $ssl_server = SSL::Server->new();
+
+my $node = PostgreSQL::Test::Cluster->new('primary');
+$node->init;
+
+# PGHOST is enforced here to set up the node, subsequent connections
+# will use a dedicated connection string.
+$ENV{PGHOST} = $node->host;
+$ENV{PGPORT} = $node->port;
+$node->start;
+
+$ssl_server->configure_test_server_for_ssl($node, $SERVERHOSTADDR,
+	$SERVERHOSTCIDR, 'trust');
+
+$ssl_server->switch_server_cert($node, certfile => 'server-cn-only');
+
+my $connstr =
+  "user=ssltestuser dbname=trustdb hostaddr=$SERVERHOSTADDR sslsni=1";
+
+##############################################################################
+# postgresql.conf
+##############################################################################
+
+# Connect without any hosts configured in pg_hosts.conf, thus using the cert
+# and key in postgresql.conf. pg_hosts.conf exists at this point but is empty
+# apart from the comments stemming from the sample.
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"pg.conf: connect with correct server CA cert file sslmode=require");
+
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"pg.conf: connect fails without intermediate for sslmode=verify-ca",
+	expected_stderr => qr/certificate verify failed/);
+
+# Remove pg_hosts.conf and reload to make sure a missing file is treated like
+# an empty file.
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->reload;
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"pg.conf: connect after deleting pg_hosts.conf");
+
+##############################################################################
+# pg_hosts.conf
+##############################################################################
+
+# Replicate the postgresql.conf configuration into pg_hosts.conf and retry the
+# same tests as above.
+$node->append_conf('pg_hosts.conf',
+	"* server-cn-only.crt server-cn-only.key");
+$node->reload;
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"pg_hosts.conf: connect to default, with correct server CA cert file sslmode=require"
+);
+
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"pg_hosts.conf: connect to default, fail without intermediate for sslmode=verify-ca",
+	expected_stderr => qr/certificate verify failed/);
+
+# Add host entry for example.org which serves the server cert and its
+# intermediate CA.  The previously existing default host still exists without
+# a CA.
+$node->append_conf('pg_hosts.conf',
+	"example.org server-cn-only+server_ca.crt server-cn-only.key root_ca.crt"
+);
+$node->reload;
+
+$node->connect_ok(
+	"$connstr host=example.org sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"pg_hosts.conf: connect to example.org and verify server CA");
+
+$node->connect_fails(
+	"$connstr host=example.org sslrootcert=invalid sslmode=verify-ca",
+	"pg_hosts.conf: connect to example.org but without server root cert, sslmode=verify-ca",
+	expected_stderr => qr/root certificate file "invalid" does not exist/);
+
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root_ca.crt sslmode=verify-ca",
+	"pg_hosts.conf: connect to default and fail to verify CA",
+	expected_stderr => qr/certificate verify failed/);
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require",
+	"pg_hosts.conf: connect to default with sslmode=require");
+
+# Modify pg_hosts.conf to no longer have the default host entry.
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	"example.org server-cn-only+server_ca.crt server-cn-only.key root_ca.crt"
+);
+$node->reload;
+
+# Connecting without a hostname as well as with a hostname which isn't in the
+# pg_hosts configuration should fail.
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require sslsni=0",
+	"pg_hosts.conf: connect to default with sslmode=require",
+	expected_stderr => qr/missing extension/);
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require host=example.com",
+	"pg_hosts.conf: connect to default with sslmode=require",
+	expected_stderr => qr/unrecognized name/);
+
+# Reconfigure with broken configuration for the key passphrase, the server
+# should not start up
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo wrongpassword" on'
+);
+my $result = $node->restart(fail_ok => 1);
+is($result, 0,
+	'pg_hosts.conf: restart fails with password-protected key when using the wrong passphrase command'
+);
+
+# Reconfigure again but with the correct passphrase set
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo secret1" on'
+);
+$result = $node->restart(fail_ok => 1);
+is($result, 1,
+	'pg_hosts.conf: restart succeeds with password-protected key when using the correct passphrase command'
+);
+
+# Make sure connecting works, and try to stress the reload logic by issuing
+# subsequent reloads
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require host=localhost",
+	"pg_hosts.conf: connect with correct server CA cert file sslmode=require"
+);
+$node->reload;
+$node->reload;
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require host=localhost",
+	"pg_hosts.conf: connect with correct server CA cert file after reloads");
+$node->reload;
+$node->reload;
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require host=localhost",
+	"pg_hosts.conf: connect with correct server CA cert file after more reloads"
+);
+
+# Test reloading a passphrase protected key without reloading support in the
+# passphrase hook. Connecting after restart should succeed but not after the
+# following reload.
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	'localhost server-cn-only.crt server-password.key root+client_ca.crt "echo secret1" off'
+);
+$result = $node->restart(fail_ok => 1);
+is($result, 1,
+	'pg_hosts.conf: restart succeeds with password-protected key when using the correct passphrase command'
+);
+SKIP:
+{
+	# Passphrase reloads must be enabled on Windows to succeed even without a
+	# restart
+	skip "Passphrase command reload required on Windows", 1 if ($windows_os);
+
+	$node->connect_ok(
+		"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require host=localhost",
+		"pg_hosts.conf: connect with correct server CA cert file sslmode=require"
+	);
+}
+
+$node->reload;
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require host=localhost",
+	"pg_hosts.conf: connect fails since the passphrase protected key cannot be reloaded"
+);
+
+# Configure with only non-SNI connections allowed
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+$node->append_conf('pg_hosts.conf',
+	"no_sni server-cn-only.crt server-cn-only.key");
+$node->reload;
+
+$node->connect_ok(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require sslsni=0",
+	"pg_hosts.conf: only non-SNI connections allowed");
+
+$node->connect_fails(
+	"$connstr sslrootcert=ssl/root+server_ca.crt sslmode=require host=example.org",
+	"pg_hosts.conf: only non-SNI connections allowed, connecting with SNI",
+	expected_stderr => qr/unrecognized name/);
+
+# Test client CAs by connecting to hosts in pg_hosts.conf while at the same
+# time swapping out default contexts containing different CA configurations.
+
+# pg_hosts configuration
+ok(unlink($node->data_dir . '/pg_hosts.conf'));
+# example.org has an unconfigured CA.
+$node->append_conf('pg_hosts.conf',
+	'example.org server-cn-only.crt server-cn-only.key ""');
+# example.com uses the client CA.
+$node->append_conf('pg_hosts.conf',
+	'example.com server-cn-only.crt server-cn-only.key root+client_ca.crt');
+# example.net uses the server CA (which is wrong).
+$node->append_conf('pg_hosts.conf',
+	'example.net server-cn-only.crt server-cn-only.key root+server_ca.crt');
+$node->reload;
+
+$connstr =
+  "user=ssltestuser dbname=certdb hostaddr=$SERVERHOSTADDR sslmode=require sslsni=1";
+
+foreach my $default_ca ("", "root+client_ca", "root+server_ca")
+{
+	# The default CA should, not matter for the purposes of these tests, since
+	# we connect to the other hosts explicitly. Test with various default CA
+	# settings to ensure it's isolated from the actual connections.
+	$ssl_server->switch_server_cert(
+		$node,
+		certfile => 'server-cn-only',
+		cafile => $default_ca);
+
+	# example.org is unconfigured and should fail.
+	$node->connect_fails(
+		"$connstr host=example.org sslcertmode=require sslcert=ssl/client.crt "
+		  . $ssl_server->sslkey('client.key'),
+		"host: 'example.org', ca: '$default_ca': connect with sslcert, no client CA configured",
+		expected_stderr => qr/unknown ca/);
+
+	# example.com is configured and should require a valid client cert.
+	$node->connect_fails(
+		"$connstr host=example.com sslcertmode=disable",
+		"host: 'example.com', ca: '$default_ca': connect fails if no client certificate sent",
+		expected_stderr => qr/connection requires a valid client certificate/
+	);
+
+	$node->connect_ok(
+		"$connstr host=example.com sslrootcert=ssl/root+server_ca.crt sslcertmode=require sslcert=ssl/client.crt "
+		  . $ssl_server->sslkey('client.key'),
+		"host: 'example.com', ca: '$default_ca': connect with sslcert, client certificate sent"
+	);
+
+	# example.net is configured and should require a client cert, but will
+	# always fail verification.
+	$node->connect_fails(
+		"$connstr host=example.net sslcertmode=disable",
+		"host: 'example.net', ca: '$default_ca': connect fails if no client certificate sent",
+		expected_stderr => qr/connection requires a valid client certificate/
+	);
+
+	$node->connect_fails(
+		"$connstr host=example.net sslcertmode=require sslcert=ssl/client.crt "
+		  . $ssl_server->sslkey('client.key'),
+		"host: 'example.net', ca: '$default_ca': connect with sslcert, client certificate sent",
+		expected_stderr => qr/unknown ca/);
+}
+
+done_testing();
diff --git a/src/test/ssl/t/SSL/Backend/OpenSSL.pm b/src/test/ssl/t/SSL/Backend/OpenSSL.pm
index 4159addb700..bbd3bed6c86 100644
--- a/src/test/ssl/t/SSL/Backend/OpenSSL.pm
+++ b/src/test/ssl/t/SSL/Backend/OpenSSL.pm
@@ -72,6 +72,7 @@ sub init
 	chmod(0600, glob "$pgdata/server-*.key")
 	  or die "failed to change permissions on server keys: $!";
 	_copy_files("ssl/root+client_ca.crt", $pgdata);
+	_copy_files("ssl/root+server_ca.crt", $pgdata);
 	_copy_files("ssl/root_ca.crt", $pgdata);
 	_copy_files("ssl/root+client.crl", $pgdata);
 	mkdir("$pgdata/root+client-crldir")
@@ -146,7 +147,8 @@ following parameters are supported:
 =item cafile => B<value>
 
 The CA certificate file to use for the C<ssl_ca_file> GUC. If omitted it will
-default to 'root+client_ca.crt'.
+default to 'root+client_ca.crt'. If empty, no C<ssl_ca_file> configuration
+parameter will be set.
 
 =item certfile => B<value>
 
@@ -181,10 +183,18 @@ sub set_server_cert
 	  unless defined $params->{keyfile};
 
 	my $sslconf =
-		"ssl_ca_file='$params->{cafile}.crt'\n"
-	  . "ssl_cert_file='$params->{certfile}.crt'\n"
+		"ssl_cert_file='$params->{certfile}.crt'\n"
 	  . "ssl_key_file='$params->{keyfile}.key'\n"
 	  . "ssl_crl_file='$params->{crlfile}'\n";
+	if ($params->{cafile} ne "")
+	{
+		$sslconf .= "ssl_ca_file='$params->{cafile}.crt'\n";
+	}
+	else
+	{
+		$sslconf .= "ssl_ca_file=''\n";
+	}
+
 	$sslconf .= "ssl_crl_dir='$params->{crldir}'\n"
 	  if defined $params->{crldir};
 
diff --git a/src/tools/pgindent/typedefs.list b/src/tools/pgindent/typedefs.list
index 9dd65b10254..43bd1ac3f99 100644
--- a/src/tools/pgindent/typedefs.list
+++ b/src/tools/pgindent/typedefs.list
@@ -1209,6 +1209,9 @@ HeapTupleHeader
 HeapTupleHeaderData
 HeapTupleTableSlot
 HistControl
+HostContext
+HostsFileLoadResult
+HostsLine
 HotStandbyState
 I32
 ICU_Convert_Func
-- 
2.39.3 (Apple Git-146)