POC: Carefully exposing information without authentication
Started by Greg Sabino Mullane8 months ago9 messages
Proposal: Allow a carefully curated selection of information to be shown
without authentication.
A common task for an HA system or a load balancer is to quickly determine
which of your Postgres clusters is the primary, and which are the replicas.
The canonical way to do this is to log in to each server with a valid
username and password, and then run pg_is_in_recovery().
That's a lot of work to determine if a server is a replica or not, and it
struck me that this true/false information about a running cluster is not
super-sensitive information. In other words, would it really be wrong if
there was a way to advertise that information without having to log in? I
toyed with the idea of Postgres maintaining some sort of signal file, but
then I realized that we already have a process, listening on a known port,
that has that information available to us.
Thus, this POC (proof of concept), which lets the postmaster scan for
incoming requests and quickly handle them *before* doing forking and
authenticating. We scan for a simple trigger string, and immediately return
the information to the client.
It also occured to me that since we are going to need to provide a
non-Postgres-protocol special trigger string, and we might as well do
something like "GET /info" to allow existing programs to treat Postgres as
a mini http server. To that end, we end
up with something like this:
$ psql -p 5432 -tc 'select pg_is_in_recovery()'
t
$ curl http://localhost:5432/foobar
curl: (52) Empty reply from server
$ curl http://localhost:5432/info
RECOVERY: 1
To accomplish this, we have boolean GUC flags (defaulting to false) that
control which information is exposed. For the example above, the
expose_recovery boolean has been set to true. If any of these GUCs are
true, we take a slight detour right after we accept() but before we
actually fork. We use recv with the MSG_PEEK flag to take a quick scan of
the incoming data, and use strncmp to see if it matches. If it does, we
send() some information and move on without forking. If it doesn't, we
simply move on as if we were never there, and proceed to the next step of
forking a new backend to start the authentication process.
There are three pieces of information that can be exposed with this patch.
There may be more in the future, but these are all simple, global, and not
(IMO) security leaks. The GUCs are expose_recovery, expose_sysid, and
expose_version. Each one adds a line to the output in a KEY: VALUE format
for the GET /info endpoint. The raw value is output for the direct
endpoints:
* GET /replica
* GET /sysid
* GET /version
The expose_recovery GUC uses RecoveryInProgress() to return a 1 or a 0.
This is returned by the GET /replica endpoint.
The expose_sysid GUC returns GetSystemIdentifier(). Since this can be
thought of as a fingerprint for the server, it's a nice way for external
programs to determine if the cluster is the same one it saw last time, or
for leader/replica matching.
The purpose of the expose_version GUC is to output PG_VERSION_NUM. This
will allow external tools - particularly security scanners - to know the
exact version of Postgres that is running. While some may consider this
privileged information, tools are already taking advantage of our debug
loophole to make an educated guess about the version. See my old post about
this:
https://www.endpointdev.com/blog/2010/05/finding-postgresql-version-without/
Note that this guess by security scanners is sometimes wrong, or only able
to cover a range of versions. Thus, we should give them the correct answer,
rather than providing a dubious one via some trickery.
Here's some example output with all three enabled:
$ psql -c 'alter system set expose_recovery=on'
$ psql -c 'alter system set expose_version=on'
$ psql -c 'alter system set expose_sysid=on'
$ psql -c 'select pg_reload_conf()'
$ curl http://localhost:5432/version
180000
$ curl http://localhost:5432/info
RECOVERY: 1
SYSID: 7504513530771111839
VERSION: 180000
But wait! We can do more. For the recovery, we don't even need a string
that spells out "RECOVERY:", we only need to know if the server is in
recovery or not. In short, a boolean. Patroni does this in its API with a
call of HEAD /replica. It returns a different HTTP code if the server is a
replica (200) or not a replica (503). We can do the same thing! What's
more, we can do it in a way that will allow existing calls to simply point
to the postgres server instead of a Patroni process, and get the same
result back, but faster. Here's an example of what that looks like:
## Calling Patroni
$ curl -s -w "%{http_code}" -o /dev/null -I http://localhost:8008/replica
200
## Calling Postgres directly
$ curl -s -w "%{http_code}" -o /dev/null -I http://localhost:5432/replica
200
Here's a simple Python program showing how easy it is to grab this
information:
import socket
try:
with socket.create_connection(('localhost', 5432), timeout=1) as s:
s.sendall(b'GET /sysid')
print(s.recv(200).split(b'\r\n\r\n',1)[1].decode())
except Exception as e:
print(f"Error: {e}")
That's the basic idea: proof of concept patch is attached. Additional
things to do:
* handling socket quirks (esp. Win32)
* docs (once details are hashed out)
* moving things around (everything is in one function right now for reading
ease)
Cheers,
Greg
--
Crunchy Data - https://www.crunchydata.com
Enterprise Postgres Software Products & Tech Support
Attachments:
0001-Allow-specific-information-to-be-output-directly-by-Postgres.patchapplication/octet-stream; name=0001-Allow-specific-information-to-be-output-directly-by-Postgres.patchDownload
From fd58612f74a308aed3f0d3caf79250c0bfce2068 Mon Sep 17 00:00:00 2001
From: Greg Sabino Mullane <greg@turnstep.com>
Date: Tue, 27 May 2025 07:30:07 -0400
Subject: [PATCH] Allow specific information to be output directly by Postgres.
---
src/backend/postmaster/postmaster.c | 196 +++++++++++++++++-
src/backend/utils/misc/guc_tables.c | 27 +++
src/backend/utils/misc/postgresql.conf.sample | 8 +
src/include/postmaster/postmaster.h | 4 +
src/test/postmaster/t/004_exposed.pl | 105 ++++++++++
5 files changed, 339 insertions(+), 1 deletion(-)
create mode 100644 src/test/postmaster/t/004_exposed.pl
diff --git a/src/backend/postmaster/postmaster.c b/src/backend/postmaster/postmaster.c
index 490f7ce..5818f63 100644
--- a/src/backend/postmaster/postmaster.c
+++ b/src/backend/postmaster/postmaster.c
@@ -92,6 +92,7 @@
#include "access/xlog.h"
#include "access/xlog_internal.h"
#include "access/xlogrecovery.h"
+#include "access/xlogutils.h"
#include "common/file_perm.h"
#include "common/pg_prng.h"
#include "lib/ilist.h"
@@ -197,6 +198,9 @@ btmask_contains(BackendTypeMask mask, BackendType t)
}
+int total_expose = 0;
+
+
BackgroundWorker *MyBgworkerEntry = NULL;
/* The socket number we are listening for connections on */
@@ -247,6 +251,10 @@ char *bonjour_name;
bool restart_after_crash = true;
bool remove_temp_files_after_crash = true;
+bool expose_recovery = false;
+bool expose_sysid = false;
+bool expose_version = false;
+
/*
* When terminating child processes after fatal errors, like a crash of a
* child process, we normally send SIGQUIT -- and most other comments in this
@@ -453,6 +461,8 @@ static void StartSysLogger(void);
static void StartAutovacuumWorker(void);
static bool StartBackgroundWorker(RegisteredBgWorker *rw);
static void InitPostmasterDeathWatchHandle(void);
+static bool ExposeInformation(int fd);
+
#ifdef WIN32
#define WNOHANG 0 /* ignored, so any integer value will do */
@@ -1699,7 +1709,13 @@ ServerLoop(void)
ClientSocket s;
if (AcceptConnection(events[i].fd, &s) == STATUS_OK)
- BackendStartup(&s);
+ {
+ if ((expose_recovery || expose_sysid || expose_version)
+ && ExposeInformation(s.sock))
+ total_expose++;
+ else
+ BackendStartup(&s);
+ }
/* We no longer need the open socket in this process */
if (s.sock != PGINVALID_SOCKET)
@@ -4616,3 +4632,181 @@ InitPostmasterDeathWatchHandle(void)
GetLastError())));
#endif /* WIN32 */
}
+
+
+static
+bool
+ExposeInformation(int fd)
+{
+
+/*
+ * ExposeInformation
+ *
+ *
+ * Handle early socket probe before full backend startup.
+ * Responds to small set of predefined endpoints (e.g. GET /info)
+ *
+ * Requires at least one "expose_" GUC to be true.
+ *
+ * Returns true if endpoint is recognized.
+ * Caller is responsible for closing the socket.
+ */
+
+#define EXPOSE_MIN_QUERY 9 /* Shortest possible line: "Get /info" */
+#define EXPOSE_MAX_QUERY 16 /* Longest possible GET line */
+
+/* What information is being returned */
+ typedef enum
+ {
+ EXPOSE_NOTHING,
+ EXPOSE_HEAD_REPLICA,
+ EXPOSE_GET_ALL,
+ EXPOSE_GET_REPLICA,
+ EXPOSE_GET_SYSID,
+ EXPOSE_GET_VERSION,
+ } ReturnType;
+
+ typedef struct
+ {
+ const char *endpoint;
+ const bool *require;
+ ReturnType type;
+ } endpoint_action;
+
+ static endpoint_action endpoint_actions[] =
+ {
+ {
+ "HEAD /replica", &expose_recovery, EXPOSE_HEAD_REPLICA
+ },
+ {
+ "GET /replica", &expose_recovery, EXPOSE_GET_REPLICA
+ },
+ {
+ "GET /sysid", &expose_sysid, EXPOSE_GET_SYSID
+ },
+ {
+ "GET /version", &expose_version, EXPOSE_GET_VERSION
+ },
+ {
+ "GET /info", NULL, EXPOSE_GET_ALL
+ }
+ };
+
+ ssize_t n;
+ char buf[EXPOSE_MAX_QUERY + 1];
+ int type;
+
+ Assert(expose_recovery || expose_sysid || expose_version);
+
+ do
+ {
+ n = recv(fd, buf, EXPOSE_MAX_QUERY, MSG_PEEK);
+ } while (n < 0 && errno == EINTR);
+
+ /*
+ * Leave as soon as possible if not chance we are interested. We also
+ * simply return false for n == -1
+ */
+ if (n < EXPOSE_MIN_QUERY)
+ return false;
+
+ buf[n] = '\0';
+
+ type = EXPOSE_NOTHING;
+ for (int i = 0; i < lengthof(endpoint_actions); i++)
+ {
+ if (
+ strncmp(buf, endpoint_actions[i].endpoint, strlen(endpoint_actions[i].endpoint)) == 0
+ &&
+ (endpoint_actions[i].require == NULL
+ ||
+ *(endpoint_actions[i].require)
+ ))
+ {
+ type = endpoint_actions[i].type;
+ break;
+ }
+ }
+
+ if (type == EXPOSE_NOTHING)
+ return false;
+
+ {
+ static const char http_version[] = "HTTP/1.1";
+ static const char http_type[] = "Content-Type: text/plain";
+ static const char *http_conn = "Connection: close";
+ static const char http_len[] = "Content-Length";
+
+ StringInfoData msg;
+
+ if (type == EXPOSE_HEAD_REPLICA)
+ {
+ /*
+ * Caller only cares about the HTTP response code, so no content
+ * needed
+ */
+
+ initStringInfoExt(&msg, 64);
+
+ appendStringInfo(&msg,
+ "%s %s\r\n"
+ "%s\r\n"
+ "%s\r\n\r\n",
+ http_version,
+ (RecoveryInProgress() ? "200 OK" : "503 Service Unavailable"),
+ http_type,
+ http_conn
+ );
+ }
+ else
+ {
+ StringInfoData content;
+
+ initStringInfoExt(&content, 64);
+
+ if (expose_recovery && (type == EXPOSE_GET_ALL || type == EXPOSE_GET_REPLICA))
+ appendStringInfo(&content, "%s%d\r\n",
+ type == EXPOSE_GET_ALL ? "RECOVERY: " : "",
+ RecoveryInProgress() ? 1 : 0);
+ if (expose_sysid && (type == EXPOSE_GET_ALL || type == EXPOSE_GET_SYSID))
+ appendStringInfo(&content, "%s%lu\r\n",
+ type == EXPOSE_GET_ALL ? "SYSID: " : "",
+ GetSystemIdentifier());
+ if (expose_version && (type == EXPOSE_GET_ALL || type == EXPOSE_GET_VERSION))
+ appendStringInfo(&content, "%s%d\r\n",
+ type == EXPOSE_GET_ALL ? "VERSION: " : "",
+ PG_VERSION_NUM);
+
+ initStringInfoExt(&msg, 256);
+
+ appendStringInfo(&msg,
+ "%s 200 OK\r\n"
+ "%s\r\n"
+ "%s: %d\r\n"
+ "%s\r\n\r\n"
+ "%s",
+ http_version,
+ http_type,
+ http_len, content.len,
+ http_conn,
+ content.data
+ );
+
+ pfree(content.data);
+ }
+
+ do
+ {
+ n = send(fd, msg.data, msg.len, 0);
+ } while (n < 0 && errno == EINTR);
+
+ pfree(msg.data);
+
+ if (n < 0)
+ elog(DEBUG1, "could not send to client: %m");
+
+ return true;
+
+ }
+
+}
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index 2f8cbd8..38bea71 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -1701,6 +1701,33 @@ struct config_bool ConfigureNamesBool[] =
true,
NULL, NULL, NULL
},
+ {
+ {"expose_recovery", PGC_SIGHUP, CLIENT_CONN_STATEMENT,
+ gettext_noop("Exposes if the server is in recovery without a login."),
+ NULL
+ },
+ &expose_recovery,
+ false,
+ NULL, NULL, NULL
+ },
+ {
+ {"expose_sysid", PGC_SIGHUP, CLIENT_CONN_STATEMENT,
+ gettext_noop("Exposes the system identifier without a login."),
+ NULL
+ },
+ &expose_sysid,
+ false,
+ NULL, NULL, NULL
+ },
+ {
+ {"expose_version", PGC_SIGHUP, CLIENT_CONN_STATEMENT,
+ gettext_noop("Exposes the version without a login."),
+ NULL
+ },
+ &expose_version,
+ false,
+ NULL, NULL, NULL
+ },
{
{"array_nulls", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
gettext_noop("Enables input of NULL elements in arrays."),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 87ce76b..a16d372 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -91,6 +91,14 @@
# disconnection while running queries;
# 0 for never
+
+# - Expose information -
+
+#expose_recovery = off
+#expose_sysid = off
+#expose_version = off
+
+
# - Authentication -
#authentication_timeout = 1min # 1s-600s
diff --git a/src/include/postmaster/postmaster.h b/src/include/postmaster/postmaster.h
index 92497cd..15662ce 100644
--- a/src/include/postmaster/postmaster.h
+++ b/src/include/postmaster/postmaster.h
@@ -70,6 +70,10 @@ extern PGDLLIMPORT bool restart_after_crash;
extern PGDLLIMPORT bool remove_temp_files_after_crash;
extern PGDLLIMPORT bool send_abort_for_crash;
extern PGDLLIMPORT bool send_abort_for_kill;
+extern PGDLLIMPORT bool expose_recovery;
+extern PGDLLIMPORT bool expose_sysid;
+extern PGDLLIMPORT bool expose_version;
+
#ifdef WIN32
extern PGDLLIMPORT HANDLE PostmasterHandle;
diff --git a/src/test/postmaster/t/004_exposed.pl b/src/test/postmaster/t/004_exposed.pl
new file mode 100644
index 0000000..97cc6b1
--- /dev/null
+++ b/src/test/postmaster/t/004_exposed.pl
@@ -0,0 +1,105 @@
+
+# Copyright (c) 2025, PostgreSQL Global Development Group
+
+# Test pre-fork HTTP endpoint information
+
+use strict;
+use warnings FATAL => 'all';
+use PostgreSQL::Test::Cluster;
+use Test::More;
+
+my $node = PostgreSQL::Test::Cluster->new('primary');
+$node->init();
+$node->start;
+
+SKIP:
+{
+ skip "this test requires working raw_connect()"
+ unless $node->raw_connect_works();
+
+ my ($endpoint, $sock, $reply);
+
+ $endpoint = 'GET /info';
+ $sock = $node->raw_connect();
+ $sock->send($endpoint);
+ $sock->recv($reply, 200);
+ is($reply, '', "nothing is returned by $endpoint");
+ $sock->close();
+
+ $endpoint = 'HEAD /replica';
+ $sock = $node->raw_connect();
+ $sock->send($endpoint);
+ $sock->recv($reply, 200);
+ is($reply, '', "nothing is returned by $endpoint");
+
+ $endpoint = 'GET /replica';
+ $sock = $node->raw_connect();
+ $sock->send($endpoint);
+ $sock->recv($reply, 200);
+ is($reply, '', "nothing is returned by $endpoint");
+ $sock->close();
+
+ $node->append_conf('postgresql.conf', "expose_recovery = on");
+ $node->reload();
+
+ $sock = $node->raw_connect();
+ $sock->send($endpoint);
+ $sock->recv($reply, 200);
+ like($reply, qr[\r\n0\b], "recovery information is returned by $endpoint");
+ $sock->close();
+
+ $endpoint = 'GET /sysid';
+ $sock = $node->raw_connect();
+ $sock->send($endpoint);
+ $sock->recv($reply, 200);
+ is($reply, '', "nothing is returned by $endpoint");
+ $sock->close();
+
+ $node->append_conf('postgresql.conf', "expose_sysid = on");
+ $node->reload();
+
+ $sock = $node->raw_connect();
+ $sock->send($endpoint);
+ $sock->recv($reply, 200);
+ like($reply, qr[\r\n\d{10}], "system identifier is returned by $endpoint");
+ $sock->close();
+
+ $endpoint = 'GET /version';
+ $sock = $node->raw_connect();
+ $sock->send($endpoint);
+ $sock->recv($reply, 200);
+ is($reply, '', "nothing is returned by $endpoint");
+ $sock->close();
+
+ $node->append_conf('postgresql.conf', "expose_version = on");
+ $node->reload();
+
+ $sock = $node->raw_connect();
+ $sock->send($endpoint);
+ $sock->recv($reply, 200);
+ like($reply, qr[\r\n\d{6}\b], "version number is returned by $endpoint");
+ $sock->close();
+
+
+ $endpoint = 'GET /info';
+ $sock = $node->raw_connect();
+ $sock->send($endpoint);
+ $sock->recv($reply, 200);
+ like($reply, qr[RECOVERY: 0\b], "recovery is returned by $endpoint");
+ like($reply, qr[SYSID: \d{10}], "sysid is returned by $endpoint");
+ like($reply, qr[VERSION: \d{6}\b], "version number is returned by $endpoint");
+ $sock->close();
+
+ $endpoint = 'HEAD /replica';
+ $sock = $node->raw_connect();
+ $sock->send($endpoint);
+ $sock->recv($reply, 200);
+ like($reply, qr[503 Service Unavailable], "503 returned by $endpoint");
+ $sock->close();
+
+ ## Not working yet:
+ ## $node->backup('testbackup1');
+
+}
+
+done_testing();
--
2.30.2
Re: POC: Carefully exposing information without authentication
Greg Sabino Mullane <htamfids@gmail.com> wrote:
Proposal: Allow a carefully curated selection of information to be shown without authentication.
A common task for an HA system or a load balancer is to quickly determine which of your Postgres clusters is the primary, and which are the
replicas. The canonical way to do this is to log in to each server with a valid username and password, and then run pg_is_in_recovery().
That's a lot of work to determine if a server is a replica or not, and it struck me that this true/false information about a running cluster is not
super-sensitive information. In other words, would it really be wrong if there was a way to advertise that information without having to log in?
I toyed with the idea of Postgres maintaining some sort of signal file, but then I realized that we already have a process, listening on a known
port, that has that information available to us.Thus, this POC (proof of concept), which lets the postmaster scan for incoming requests and quickly handle them *before* doing forking and
authenticating. We scan for a simple trigger string, and immediately return the information to the client.
Why is it important not to fork? My understanding is that pg_is_ready also
tries to start a regular connection, i.e. forks a new backend. I think this
functionality would fit into libpq. (I've got no strong opinion on the amount
of information to be revealed this way. In any case, a GUC to enable the
feature only if the DBA wants it makes sense.)
--
Antonin Houska
Web: https://www.cybertec-postgresql.com
Re: POC: Carefully exposing information without authentication
On Fri, May 30, 2025 at 11:02 AM Antonin Houska <ah@cybertec.at> wrote:
Why is it important not to fork?
Good question. Forking is expensive, and there is also a lot of
housekeeping associated with it that is simply not needed here. We want
this to be lightweight, and simple. No need to fork if we are just going to
do a few strncmp() calls and a send(). However, I'm not highly opposed to
fork-first, as I understand that we want to not slow down postmaster. My
testing showed a barely measurable impact, but I will defer to whatever
decision the elder Postgres gods decide on.
My understanding is that pg_is_ready also tries to start a regular
connection, i.e. forks a new backend.
Yep. I consider pg_isready a spiritual cousin to this feature, but it's not
something that can really do what this does.
Cheers,
Greg
--
Crunchy Data - https://www.crunchydata.com
Enterprise Postgres Software Products & Tech Support
Re: POC: Carefully exposing information without authentication
Greg Sabino Mullane <htamfids@gmail.com> writes:
Good question. Forking is expensive, and there is also a lot of
housekeeping associated with it that is simply not needed here. We want
this to be lightweight, and simple. No need to fork if we are just going to
do a few strncmp() calls and a send().
send() can block. I think calling it in the postmaster is a
nonstarter. For comparison, we make an effort to not do any
communication with incoming clients until after forking a child
to do the communication. The one exception is if we have to
report fork failure --- but we don't make any strong guarantees
about that report succeeding. (IIRC, we put the port into nonblock
mode and try only once.) That's probably not a behavior you want
to adopt for non-edge-case usages.
Another point is that you'll recall that there's a lot of
interest in switching to a threaded model. The argument that
"fork is too expensive" may not have a long shelf life.
I'm not taking a position on whether $SUBJECT is a good idea
in the first place.
regards, tom lane
Re: POC: Carefully exposing information without authentication
On Fri, May 30, 2025 at 9:34 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
I think calling it in the postmaster is a nonstarter.
Thanks for the feedback. Please find attached version two, which moves the
code to the very start of BackendInitialize in
tcop/backend_startup.c. If we handle the request, we simply proc_exit and
avoid all the other backend startup stuff. So still a big win. I also made
a first rough pass at the documentation.
Cheers,
Greg
--
Crunchy Data - https://www.crunchydata.com
Enterprise Postgres Software Products & Tech Support
Attachments:
0002-Allow-specific-information-to-be-output-directly-by-Postgres.patchapplication/octet-stream; name=0002-Allow-specific-information-to-be-output-directly-by-Postgres.patchDownload
From dab6ea7fd21aafbf5f87b163903e54f129f45e0b Mon Sep 17 00:00:00 2001
From: Greg Sabino Mullane <greg@turnstep.com>
Date: Sat, 31 May 2025 00:38:26 -0400
Subject: [PATCH] Allow specific information to be output directly by Postgres.
---
doc/src/sgml/config.sgml | 78 +++++++
src/backend/tcop/backend_startup.c | 191 ++++++++++++++++++
src/backend/utils/misc/guc_tables.c | 27 +++
src/backend/utils/misc/postgresql.conf.sample | 8 +
src/include/postmaster/postmaster.h | 4 +
5 files changed, 308 insertions(+)
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index f4a0191c55b..5774d78740f 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1077,6 +1077,84 @@ include_dir 'conf.d'
</variablelist>
</sect2>
+ <sect2 id="runtime-config-expose-settings">
+ <title>Expose Settings</title>
+
+ <variablelist>
+
+ <varlistentry id="guc-expose-recovery" xreflabel="expose_recovery">
+ <term><varname>expose_recovery</varname> (<type>boolean</type>)
+ <indexterm>
+ <primary><varname>expose_recovery</varname> configuration parameter</primary>
+ </indexterm>
+ </term>
+ <listitem>
+ <para>
+ Enables reporting if the server is in recovery mode without requiring
+ an authenticated login. Clients can send the string <literal>GET /replica</literal>
+ and will receive a 1 or 0. This is equivalent to logging in and running
+ <literal>SELECT pg_is_in_recovery()</literal>. A client can also send the
+ string <literal>HEAD /replica</literal> which will solely return an HTTP literal:
+ <literal>200</literal> if the server is in recovery, <literal>503</literal> if not.
+ (This allows a drop-in replacement to the same Patroni functionality)
+ Finally, a client can issue <literal>GET /info</literal> and receive the string
+ <literal>RECOVERY: </literal> followed by a 1 or 0.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="guc-expose-sysid" xreflabel="expose_sysid">
+ <term><varname>expose_sysid</varname> (<type>boolean</type>)
+ <indexterm>
+ <primary><varname>expose_sysid</varname> configuration parameter</primary>
+ </indexterm>
+ </term>
+ <listitem>
+ <para>
+ Enables reporting the system identifier of the cluster without requiring
+ an authenticated login. Clients can send the string <literal>GET /sysid</literal>
+ and will receive the numeric system identifier. This is a unique number generated
+ by each cluster when initdb is run.
+ </para>
+ <para>
+ A client can issue <literal>GET /info</literal> and receive the string
+ <literal>SYSID: </literal> followed by the numeric system identifier.
+ </para>
+ <para>
+ This feature is useful for determining if the server is the same server as previously
+ encountered. Note than primary and replica servers will share the same system
+ identifier.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="guc-expose-version" xreflabel="expose_version">
+ <term><varname>expose_version</varname> (<type>boolean</type>)
+ <indexterm>
+ <primary><varname>expose_version</varname> configuration parameter</primary>
+ </indexterm>
+ </term>
+ <listitem>
+ <para>
+ Enables reporting the numeric version of the Postgres cluster without requiring
+ an authenticated login. Clients can send the string <literal>GET /version</literal>
+ and will receive an integer representing the version.
+ </para>
+ <para>
+ A client can issue <literal>GET /info</literal> and receive the string
+ <literal>VERSION: </literal> followed by the numeric version.
+ </para>
+ <para>
+ This is particularly useful for non-Postgres systems (esp. security scanners) that
+ need a way to easily determine the version of Postgres in use without requiring
+ a Postgres client - or without needing any knowledge of the Postgres protocol at all.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ </variablelist>
+ </sect2>
+
<sect2 id="runtime-config-connection-authentication">
<title>Authentication</title>
diff --git a/src/backend/tcop/backend_startup.c b/src/backend/tcop/backend_startup.c
index a7d1fec981f..ce8a5087ec6 100644
--- a/src/backend/tcop/backend_startup.c
+++ b/src/backend/tcop/backend_startup.c
@@ -46,6 +46,10 @@
bool Trace_connection_negotiation = false;
uint32 log_connections = 0;
char *log_connections_string = NULL;
+bool expose_recovery = false;
+bool expose_sysid = false;
+bool expose_version = false;
+
/* Other globals */
@@ -65,6 +69,7 @@ static void SendNegotiateProtocolVersion(List *unrecognized_protocol_options);
static void process_startup_packet_die(SIGNAL_ARGS);
static void StartupPacketTimeoutHandler(void);
static bool validate_log_connections_options(List *elemlist, uint32 *flags);
+static bool ExposeInformation(pgsocket fd);
/*
* Entry point for a new backend process.
@@ -148,6 +153,15 @@ BackendInitialize(ClientSocket *client_sock, CAC_state cac)
StringInfoData ps_data;
MemoryContext oldcontext;
+ /*
+ * Possibly scan for a simple GET / HEAD request. If this is detected and
+ * handled, we are done and can immediately exit
+ */
+ if ((expose_recovery || expose_sysid || expose_version)
+ && ExposeInformation(client_sock->sock))
+ proc_exit(0);
+ /* Should we do exit(0) here, despite the warnings in ipc.c? */
+
/* Tell fd.c about the long-lived FD associated with the client_sock */
ReserveExternalFD();
@@ -1113,3 +1127,180 @@ assign_log_connections(const char *newval, void *extra)
{
log_connections = *((int *) extra);
}
+
+
+static
+bool
+ExposeInformation(pgsocket fd)
+{
+
+/*
+ * ExposeInformation
+ *
+ *
+ * Handle early socket probe before full backend startup.
+ * Responds to small set of predefined endpoints (e.g. GET /info)
+ *
+ * Requires at least one "expose_" GUC to be true.
+ *
+ * Returns true if endpoint is recognized.
+ */
+
+#define EXPOSE_MIN_QUERY 9 /* Shortest possible line: "Get /info" */
+#define EXPOSE_MAX_QUERY 16 /* Longest possible GET line */
+
+/* What information is being returned */
+ typedef enum
+ {
+ EXPOSE_NOTHING,
+ EXPOSE_HEAD_REPLICA,
+ EXPOSE_GET_ALL,
+ EXPOSE_GET_REPLICA,
+ EXPOSE_GET_SYSID,
+ EXPOSE_GET_VERSION,
+ } ReturnType;
+
+ typedef struct
+ {
+ const char *endpoint;
+ const bool *require;
+ ReturnType type;
+ } endpoint_action;
+
+ static endpoint_action endpoint_actions[] =
+ {
+ {
+ "HEAD /replica", &expose_recovery, EXPOSE_HEAD_REPLICA
+ },
+ {
+ "GET /replica", &expose_recovery, EXPOSE_GET_REPLICA
+ },
+ {
+ "GET /sysid", &expose_sysid, EXPOSE_GET_SYSID
+ },
+ {
+ "GET /version", &expose_version, EXPOSE_GET_VERSION
+ },
+ {
+ "GET /info", NULL, EXPOSE_GET_ALL
+ }
+ };
+
+ ssize_t n;
+ char buf[EXPOSE_MAX_QUERY + 1];
+ int type;
+
+ Assert(expose_recovery || expose_sysid || expose_version);
+
+ do
+ {
+ n = recv(fd, buf, EXPOSE_MAX_QUERY, MSG_PEEK);
+ } while (n < 0 && errno == EINTR);
+
+ /*
+ * Leave as soon as possible if not chance we are interested. We also
+ * simply return false for n == -1
+ */
+ if (n < EXPOSE_MIN_QUERY)
+ return false;
+
+ buf[n] = '\0';
+
+ type = EXPOSE_NOTHING;
+ for (int i = 0; i < lengthof(endpoint_actions); i++)
+ {
+ if (
+ strncmp(buf, endpoint_actions[i].endpoint, strlen(endpoint_actions[i].endpoint)) == 0
+ &&
+ (endpoint_actions[i].require == NULL
+ ||
+ *(endpoint_actions[i].require)
+ ))
+ {
+ type = endpoint_actions[i].type;
+ break;
+ }
+ }
+
+ if (type == EXPOSE_NOTHING)
+ return false;
+
+ {
+ static const char http_version[] = "HTTP/1.1";
+ static const char http_type[] = "Content-Type: text/plain";
+ static const char *http_conn = "Connection: close";
+ static const char http_len[] = "Content-Length";
+
+ StringInfoData msg;
+
+ if (type == EXPOSE_HEAD_REPLICA)
+ {
+ /*
+ * Caller only cares about the HTTP response code, so no content
+ * needed
+ */
+
+ initStringInfoExt(&msg, 64);
+
+ appendStringInfo(&msg,
+ "%s %s\r\n"
+ "%s\r\n"
+ "%s\r\n\r\n",
+ http_version,
+ (RecoveryInProgress() ? "200 OK" : "503 Service Unavailable"),
+ http_type,
+ http_conn
+ );
+ }
+ else
+ {
+ StringInfoData content;
+
+ initStringInfoExt(&content, 64);
+
+ if (expose_recovery && (type == EXPOSE_GET_ALL || type == EXPOSE_GET_REPLICA))
+ appendStringInfo(&content, "%s%d\r\n",
+ type == EXPOSE_GET_ALL ? "RECOVERY: " : "",
+ RecoveryInProgress() ? 1 : 0);
+ if (expose_sysid && (type == EXPOSE_GET_ALL || type == EXPOSE_GET_SYSID))
+ appendStringInfo(&content, "%s%lu\r\n",
+ type == EXPOSE_GET_ALL ? "SYSID: " : "",
+ GetSystemIdentifier());
+ if (expose_version && (type == EXPOSE_GET_ALL || type == EXPOSE_GET_VERSION))
+ appendStringInfo(&content, "%s%d\r\n",
+ type == EXPOSE_GET_ALL ? "VERSION: " : "",
+ PG_VERSION_NUM);
+
+ initStringInfoExt(&msg, 256);
+
+ appendStringInfo(&msg,
+ "%s 200 OK\r\n"
+ "%s\r\n"
+ "%s: %d\r\n"
+ "%s\r\n\r\n"
+ "%s",
+ http_version,
+ http_type,
+ http_len, content.len,
+ http_conn,
+ content.data
+ );
+
+ pfree(content.data);
+ }
+
+ do
+ {
+ n = send(fd, msg.data, msg.len, 0);
+ } while (n < 0 && errno == EINTR);
+
+ pfree(msg.data);
+
+ if (n < 0)
+ elog(DEBUG1, "could not send to client: %m");
+
+ return true;
+
+ }
+
+}
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index 2f8cbd86759..38bea719011 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -1701,6 +1701,33 @@ struct config_bool ConfigureNamesBool[] =
true,
NULL, NULL, NULL
},
+ {
+ {"expose_recovery", PGC_SIGHUP, CLIENT_CONN_STATEMENT,
+ gettext_noop("Exposes if the server is in recovery without a login."),
+ NULL
+ },
+ &expose_recovery,
+ false,
+ NULL, NULL, NULL
+ },
+ {
+ {"expose_sysid", PGC_SIGHUP, CLIENT_CONN_STATEMENT,
+ gettext_noop("Exposes the system identifier without a login."),
+ NULL
+ },
+ &expose_sysid,
+ false,
+ NULL, NULL, NULL
+ },
+ {
+ {"expose_version", PGC_SIGHUP, CLIENT_CONN_STATEMENT,
+ gettext_noop("Exposes the version without a login."),
+ NULL
+ },
+ &expose_version,
+ false,
+ NULL, NULL, NULL
+ },
{
{"array_nulls", PGC_USERSET, COMPAT_OPTIONS_PREVIOUS,
gettext_noop("Enables input of NULL elements in arrays."),
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 87ce76b18f4..a16d3726824 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -91,6 +91,14 @@
# disconnection while running queries;
# 0 for never
+
+# - Expose information -
+
+#expose_recovery = off
+#expose_sysid = off
+#expose_version = off
+
+
# - Authentication -
#authentication_timeout = 1min # 1s-600s
diff --git a/src/include/postmaster/postmaster.h b/src/include/postmaster/postmaster.h
index 92497cd6a0f..15662ce0059 100644
--- a/src/include/postmaster/postmaster.h
+++ b/src/include/postmaster/postmaster.h
@@ -70,6 +70,10 @@ extern PGDLLIMPORT bool restart_after_crash;
extern PGDLLIMPORT bool remove_temp_files_after_crash;
extern PGDLLIMPORT bool send_abort_for_crash;
extern PGDLLIMPORT bool send_abort_for_kill;
+extern PGDLLIMPORT bool expose_recovery;
+extern PGDLLIMPORT bool expose_sysid;
+extern PGDLLIMPORT bool expose_version;
+
#ifdef WIN32
extern PGDLLIMPORT HANDLE PostmasterHandle;
--
2.30.2
Re: POC: Carefully exposing information without authentication
Please find attached version 3, rebased for PG 19 and now featuring some
tests.
Cheers,
Greg
Attachments:
0003-Allow-specific-information-to-be-output-directly-by-Postgres.patchapplication/octet-stream; name=0003-Allow-specific-information-to-be-output-directly-by-Postgres.patchDownload
From 424d55f3a3164dabcfb8cdf9fe6cd8b7d339b9d5 Mon Sep 17 00:00:00 2001
From: Greg Sabino Mullane <greg@turnstep.com>
Date: Sat, 31 May 2025 00:38:26 -0400
Subject: [PATCH] Allow specific information to be output directly by Postgres.
---
doc/src/sgml/config.sgml | 78 +++++++
src/backend/tcop/backend_startup.c | 191 ++++++++++++++++++
src/backend/utils/misc/guc_parameters.dat | 18 ++
src/backend/utils/misc/postgresql.conf.sample | 8 +
src/include/postmaster/postmaster.h | 4 +
src/test/modules/test_misc/meson.build | 1 +
src/test/modules/test_misc/t/009_expose.pl | 91 ++++++++++++++++++++++
7 files changed, 391 insertions(+)
create mode 100644 src/test/modules/test_misc/t/009_expose.pl
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index e9b420f3ddb..a3d4b388856 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1077,6 +1077,84 @@ include_dir 'conf.d'
</variablelist>
</sect2>
+ <sect2 id="runtime-config-expose-settings">
+ <title>Expose Settings</title>
+
+ <variablelist>
+
+ <varlistentry id="guc-expose-recovery" xreflabel="expose_recovery">
+ <term><varname>expose_recovery</varname> (<type>boolean</type>)
+ <indexterm>
+ <primary><varname>expose_recovery</varname> configuration parameter</primary>
+ </indexterm>
+ </term>
+ <listitem>
+ <para>
+ Enables reporting if the server is in recovery mode without requiring
+ an authenticated login. Clients can send the string <literal>GET /replica</literal>
+ and will receive a 1 or 0. This is equivalent to logging in and running
+ <literal>SELECT pg_is_in_recovery()</literal>. A client can also send the
+ string <literal>HEAD /replica</literal> which will solely return an HTTP literal:
+ <literal>200</literal> if the server is in recovery, <literal>503</literal> if not.
+ (This allows a drop-in replacement to the same Patroni functionality)
+ Finally, a client can issue <literal>GET /info</literal> and receive the string
+ <literal>RECOVERY: </literal> followed by a 1 or 0.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="guc-expose-sysid" xreflabel="expose_sysid">
+ <term><varname>expose_sysid</varname> (<type>boolean</type>)
+ <indexterm>
+ <primary><varname>expose_sysid</varname> configuration parameter</primary>
+ </indexterm>
+ </term>
+ <listitem>
+ <para>
+ Enables reporting the system identifier of the cluster without requiring
+ an authenticated login. Clients can send the string <literal>GET /sysid</literal>
+ and will receive the numeric system identifier. This is a unique number generated
+ by each cluster when initdb is run.
+ </para>
+ <para>
+ A client can issue <literal>GET /info</literal> and receive the string
+ <literal>SYSID: </literal> followed by the numeric system identifier.
+ </para>
+ <para>
+ This feature is useful for determining if the server is the same server as previously
+ encountered. Note than primary and replica servers will share the same system
+ identifier.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="guc-expose-version" xreflabel="expose_version">
+ <term><varname>expose_version</varname> (<type>boolean</type>)
+ <indexterm>
+ <primary><varname>expose_version</varname> configuration parameter</primary>
+ </indexterm>
+ </term>
+ <listitem>
+ <para>
+ Enables reporting the numeric version of the Postgres cluster without requiring
+ an authenticated login. Clients can send the string <literal>GET /version</literal>
+ and will receive an integer representing the version.
+ </para>
+ <para>
+ A client can issue <literal>GET /info</literal> and receive the string
+ <literal>VERSION: </literal> followed by the numeric version.
+ </para>
+ <para>
+ This is particularly useful for non-Postgres systems (esp. security scanners) that
+ need a way to easily determine the version of Postgres in use without requiring
+ a Postgres client - or without needing any knowledge of the Postgres protocol at all.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ </variablelist>
+ </sect2>
+
<sect2 id="runtime-config-connection-authentication">
<title>Authentication</title>
diff --git a/src/backend/tcop/backend_startup.c b/src/backend/tcop/backend_startup.c
index 14d5fc0b196..c69a0727693 100644
--- a/src/backend/tcop/backend_startup.c
+++ b/src/backend/tcop/backend_startup.c
@@ -46,6 +46,10 @@
bool Trace_connection_negotiation = false;
uint32 log_connections = 0;
char *log_connections_string = NULL;
+bool expose_recovery = false;
+bool expose_sysid = false;
+bool expose_version = false;
+
/* Other globals */
@@ -65,6 +69,7 @@ static void SendNegotiateProtocolVersion(List *unrecognized_protocol_options);
static void process_startup_packet_die(SIGNAL_ARGS);
static void StartupPacketTimeoutHandler(void);
static bool validate_log_connections_options(List *elemlist, uint32 *flags);
+static bool ExposeInformation(pgsocket fd);
/*
* Entry point for a new backend process.
@@ -148,6 +153,15 @@ BackendInitialize(ClientSocket *client_sock, CAC_state cac)
StringInfoData ps_data;
MemoryContext oldcontext;
+ /*
+ * Scan for a simple GET / HEAD request. If this is detected and
+ * handled, we are done and can immediately exit
+ */
+ if ((expose_recovery || expose_sysid || expose_version)
+ && ExposeInformation(client_sock->sock))
+ proc_exit(0);
+ /* Should we do exit(0) here, despite the warnings in ipc.c? */
+
/* Tell fd.c about the long-lived FD associated with the client_sock */
ReserveExternalFD();
@@ -1126,3 +1140,180 @@ assign_log_connections(const char *newval, void *extra)
{
log_connections = *((int *) extra);
}
+
+
+static
+bool
+ExposeInformation(pgsocket fd)
+{
+
+/*
+ * ExposeInformation
+ *
+ *
+ * Handle early socket probe before full backend startup.
+ * Responds to small set of predefined endpoints (e.g. GET /info)
+ *
+ * Requires at least one "expose_" GUC to be true.
+ *
+ * Returns true if any endpoint is recognized.
+ */
+
+#define EXPOSE_MIN_QUERY 9 /* Shortest possible line: "Get /info" */
+#define EXPOSE_MAX_QUERY 16 /* Longest possible GET line */
+
+/* What information is being returned */
+ typedef enum
+ {
+ EXPOSE_NOTHING,
+ EXPOSE_HEAD_REPLICA,
+ EXPOSE_GET_ALL,
+ EXPOSE_GET_REPLICA,
+ EXPOSE_GET_SYSID,
+ EXPOSE_GET_VERSION,
+ } ReturnType;
+
+ typedef struct
+ {
+ const char *endpoint;
+ const bool *require;
+ ReturnType type;
+ } endpoint_action;
+
+ static endpoint_action endpoint_actions[] =
+ {
+ {
+ "HEAD /replica", &expose_recovery, EXPOSE_HEAD_REPLICA
+ },
+ {
+ "GET /replica", &expose_recovery, EXPOSE_GET_REPLICA
+ },
+ {
+ "GET /sysid", &expose_sysid, EXPOSE_GET_SYSID
+ },
+ {
+ "GET /version", &expose_version, EXPOSE_GET_VERSION
+ },
+ {
+ "GET /info", NULL, EXPOSE_GET_ALL
+ }
+ };
+
+ ssize_t n;
+ char buf[EXPOSE_MAX_QUERY + 1];
+ int type;
+
+ Assert(expose_recovery || expose_sysid || expose_version);
+
+ do
+ {
+ n = recv(fd, buf, EXPOSE_MAX_QUERY, MSG_PEEK);
+ } while (n < 0 && errno == EINTR);
+
+ /*
+ * Leave as soon as possible if no chance we are interested. We also
+ * simply return false for n == -1
+ */
+ if (n < EXPOSE_MIN_QUERY)
+ return false;
+
+ buf[n] = '\0';
+
+ type = EXPOSE_NOTHING;
+ for (int i = 0; i < lengthof(endpoint_actions); i++)
+ {
+ if (
+ strncmp(buf, endpoint_actions[i].endpoint, strlen(endpoint_actions[i].endpoint)) == 0
+ &&
+ (endpoint_actions[i].require == NULL
+ ||
+ *(endpoint_actions[i].require)
+ ))
+ {
+ type = endpoint_actions[i].type;
+ break;
+ }
+ }
+
+ if (type == EXPOSE_NOTHING)
+ return false;
+
+ {
+ static const char http_version[] = "HTTP/1.1";
+ static const char http_type[] = "Content-Type: text/plain";
+ static const char *http_conn = "Connection: close";
+ static const char http_len[] = "Content-Length";
+
+ StringInfoData msg;
+
+ if (type == EXPOSE_HEAD_REPLICA)
+ {
+ /*
+ * Caller only cares about the HTTP response code, so no content
+ * needed
+ */
+
+ initStringInfoExt(&msg, 64);
+
+ appendStringInfo(&msg,
+ "%s %s\r\n"
+ "%s\r\n"
+ "%s\r\n\r\n",
+ http_version,
+ (RecoveryInProgress() ? "200 OK" : "503 Service Unavailable"),
+ http_type,
+ http_conn
+ );
+ }
+ else
+ {
+ StringInfoData content;
+
+ initStringInfoExt(&content, 64);
+
+ if (expose_recovery && (type == EXPOSE_GET_ALL || type == EXPOSE_GET_REPLICA))
+ appendStringInfo(&content, "%s%d\r\n",
+ type == EXPOSE_GET_ALL ? "RECOVERY: " : "",
+ RecoveryInProgress() ? 1 : 0);
+ if (expose_sysid && (type == EXPOSE_GET_ALL || type == EXPOSE_GET_SYSID))
+ appendStringInfo(&content, "%s%lu\r\n",
+ type == EXPOSE_GET_ALL ? "SYSID: " : "",
+ GetSystemIdentifier());
+ if (expose_version && (type == EXPOSE_GET_ALL || type == EXPOSE_GET_VERSION))
+ appendStringInfo(&content, "%s%d\r\n",
+ type == EXPOSE_GET_ALL ? "VERSION: " : "",
+ PG_VERSION_NUM);
+
+ initStringInfoExt(&msg, 256);
+
+ appendStringInfo(&msg,
+ "%s 200 OK\r\n"
+ "%s\r\n"
+ "%s: %d\r\n"
+ "%s\r\n\r\n"
+ "%s",
+ http_version,
+ http_type,
+ http_len, content.len,
+ http_conn,
+ content.data
+ );
+
+ pfree(content.data);
+ }
+
+ do
+ {
+ n = send(fd, msg.data, msg.len, 0);
+ } while (n < 0 && errno == EINTR);
+
+ pfree(msg.data);
+
+ if (n < 0)
+ elog(DEBUG1, "could not send to client: %m");
+
+ return true;
+
+ }
+
+}
diff --git a/src/backend/utils/misc/guc_parameters.dat b/src/backend/utils/misc/guc_parameters.dat
index 6bc6be13d2a..3accf6bec9f 100644
--- a/src/backend/utils/misc/guc_parameters.dat
+++ b/src/backend/utils/misc/guc_parameters.dat
@@ -637,6 +637,24 @@
boot_val => 'true',
},
+{ name => 'expose_recovery', type => 'bool', context => 'PGC_SIGHUP', group => 'CLIENT_CONN_STATEMENT',
+ short_desc => 'Exposes if the server is in recovery mode without a login.',
+ variable => 'expose_recovery',
+ boot_val => 'false',
+},
+
+{ name => 'expose_sysid', type => 'bool', context => 'PGC_SIGHUP', group => 'CLIENT_CONN_STATEMENT',
+ short_desc => 'Exposes the system identifier without a login.',
+ variable => 'expose_sysid',
+ boot_val => 'false',
+},
+
+{ name => 'expose_version', type => 'bool', context => 'PGC_SIGHUP', group => 'CLIENT_CONN_STATEMENT',
+ short_desc => 'Exposes the server version without a login.',
+ variable => 'expose_version',
+ boot_val => 'false',
+},
+
{ name => 'array_nulls', type => 'bool', context => 'PGC_USERSET', group => 'COMPAT_OPTIONS_PREVIOUS',
short_desc => 'Enables input of NULL elements in arrays.',
long_desc => 'When turned on, unquoted NULL in an array input value means a null value; otherwise it is taken literally.',
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index c36fcb9ab61..8e8be2cf3af 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -91,6 +91,14 @@
# disconnection while running queries;
# 0 for never
+
+# - Expose information -
+
+#expose_recovery = off
+#expose_sysid = off
+#expose_version = off
+
+
# - Authentication -
#authentication_timeout = 1min # 1s-600s
diff --git a/src/include/postmaster/postmaster.h b/src/include/postmaster/postmaster.h
index 753871071ac..ee1ca2fca36 100644
--- a/src/include/postmaster/postmaster.h
+++ b/src/include/postmaster/postmaster.h
@@ -70,6 +70,10 @@ extern PGDLLIMPORT bool restart_after_crash;
extern PGDLLIMPORT bool remove_temp_files_after_crash;
extern PGDLLIMPORT bool send_abort_for_crash;
extern PGDLLIMPORT bool send_abort_for_kill;
+extern PGDLLIMPORT bool expose_recovery;
+extern PGDLLIMPORT bool expose_sysid;
+extern PGDLLIMPORT bool expose_version;
+
#ifdef WIN32
extern PGDLLIMPORT HANDLE PostmasterHandle;
diff --git a/src/test/modules/test_misc/meson.build b/src/test/modules/test_misc/meson.build
index 6b1e730bf46..6fe8ac4a9d1 100644
--- a/src/test/modules/test_misc/meson.build
+++ b/src/test/modules/test_misc/meson.build
@@ -17,6 +17,7 @@ tests += {
't/006_signal_autovacuum.pl',
't/007_catcache_inval.pl',
't/008_replslot_single_user.pl',
+ 't/009_expose.pl',
],
},
}
diff --git a/src/test/modules/test_misc/t/009_expose.pl b/src/test/modules/test_misc/t/009_expose.pl
new file mode 100644
index 00000000000..f9363d0bc04
--- /dev/null
+++ b/src/test/modules/test_misc/t/009_expose.pl
@@ -0,0 +1,91 @@
+# Copyright (c) 2025, PostgreSQL Global Development Group
+
+# Test gathering information before authentication via expose_* variables
+
+# Force use of TCP/IP - call before the 'use'
+INIT{ $PostgreSQL::Test::Utils::use_unix_sockets = 0; }
+
+use strict;
+use warnings;
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+use LWP::UserAgent;
+
+my $node = PostgreSQL::Test::Cluster->new('node1');
+# Setting as logical here simply to avoid wal_level minimal so we can restart as a replica
+$node->init(allows_streaming => "logical");
+$node->start;
+
+my $server_version = $node->safe_psql('postgres', 'show server_version_num');
+my $bindir = $node->config_data('--bindir');
+my $datadir = $node->data_dir;
+my $cdata = qx{$bindir/pg_controldata -D $datadir 2>&1};
+my ($sysid) = $cdata =~ /Database system identifier:\s+(\d+)/;
+
+my $port = $node->port;
+my $URI="http://localhost:$port";
+my $ua = LWP::UserAgent->new(timeout => 2);
+
+my ($response, $code, $content);
+
+$response = $ua->get("$URI/info");
+$code = $response->code;
+is ($code, 500, "GET /info returns HTTP code 500 when nothing is listening");
+
+$response = $ua->head("$URI/replica");
+$code = $response->code;
+is ($code, 500, "HEAD /replica returns HTTP code 500 when nothing is listening");
+
+$node->append_conf('postgresql.conf', 'expose_recovery=on');
+$node->reload();
+
+$response = $ua->get("$URI/replica");
+$code = $response->code;
+is ($code, 200, "GET /replica returns HTTP code 200 when expose_recovery is on (primary)");
+is ($response->content, "0\r\n", "GET /replica returns '0' when expose_recovery is on (primary)");
+
+$response = $ua->head("$URI/replica");
+$code = $response->code;
+is ($code, 503, "HEAD /info returns HTTP code 503 when expose_recovery is on (primary)");
+
+$response = $ua->get("$URI/info");
+$code = $response->code;
+is ($code, 200, "GET /info returns HTTP code 200 when expose_recovery is on");
+is ($response->content, "RECOVERY: 0\r\n", "GET /info returns 'RECOVERY:0' when expose_recovery is on (primary)");
+
+$node->append_conf('postgresql.conf', 'expose_version=on');
+$node->append_conf('postgresql.conf', 'expose_sysid=on');
+$node->reload();
+
+$response = $ua->get("$URI/info");
+$content = $response->content;
+like ($content, qr/RECOVERY: 0/, "GET /info returns 'RECOVERY: 0' when expose_recovery is on (primary)");
+like ($content, qr/VERSION: $server_version/, "GET /info returns 'VERSION: $server_version' when expose_version is on");
+like ($content, qr/SYSID: $sysid/, "GET /info returns correct SYSID when expose_sysid is on");
+
+$response = $ua->get("$URI/sysid");
+$content = $response->content;
+is ($content, "$sysid\r\n", "GET /sysid returns correct value when expose_sysid is on");
+
+$response = $ua->get("$URI/version");
+$content = $response->content;
+is ($content, "$server_version\r\n", "GET /version returns correct value when expose_version is on");
+
+$node->set_standby_mode();
+$node->restart();
+
+$response = $ua->get("$URI/replica");
+$code = $response->code;
+is ($code, 200, "GET /replica returns HTTP code 200 when expose_recovery is on (replica)");
+is ($response->content, "1\r\n", "GET /replica returns '0' when expose_recovery is on (replica)");
+
+$response = $ua->head("$URI/replica");
+$code = $response->code;
+is ($code, 200, "HEAD /info returns HTTP code 200 when expose_recovery is on (replica)");
+
+$response = $ua->get("$URI/info");
+$content = $response->content;
+like ($content, qr/RECOVERY: 1/, "GET /info returns 'RECOVERY: 1' when expose_recovery is on (replica)");
+
+done_testing();
--
2.30.2
Re: POC: Carefully exposing information without authentication
Version 4 attached, rebased to account for new tests, plus a new
instra-test check to make sure LWP::UserAgent is available before running.
Cheers,
Greg
Attachments:
0004-Allow-specific-information-to-be-output-directly-by-Postgres.patchapplication/octet-stream; name=0004-Allow-specific-information-to-be-output-directly-by-Postgres.patchDownload
From d72be5518e7cc4750ef4986dd25677e764c9b27b Mon Sep 17 00:00:00 2001
From: Greg Sabino Mullane <greg@turnstep.com>
Date: Sat, 31 May 2025 00:38:26 -0400
Subject: [PATCH] Allow specific information to be output directly by Postgres.
---
doc/src/sgml/config.sgml | 78 +++++++
src/backend/tcop/backend_startup.c | 191 ++++++++++++++++++
src/backend/utils/misc/guc_parameters.dat | 18 ++
src/backend/utils/misc/postgresql.conf.sample | 8 +
src/include/postmaster/postmaster.h | 4 +
src/test/modules/test_misc/meson.build | 1 +
src/test/modules/test_misc/t/010_expose.pl | 91 +++++++++
7 files changed, 391 insertions(+)
create mode 100644 src/test/modules/test_misc/t/010_expose.pl
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 0a2a8b49fdb..f2002a0607c 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -1077,6 +1077,84 @@ include_dir 'conf.d'
</variablelist>
</sect2>
+ <sect2 id="runtime-config-expose-settings">
+ <title>Expose Settings</title>
+
+ <variablelist>
+
+ <varlistentry id="guc-expose-recovery" xreflabel="expose_recovery">
+ <term><varname>expose_recovery</varname> (<type>boolean</type>)
+ <indexterm>
+ <primary><varname>expose_recovery</varname> configuration parameter</primary>
+ </indexterm>
+ </term>
+ <listitem>
+ <para>
+ Enables reporting if the server is in recovery mode without requiring
+ an authenticated login. Clients can send the string <literal>GET /replica</literal>
+ and will receive a 1 or 0. This is equivalent to logging in and running
+ <literal>SELECT pg_is_in_recovery()</literal>. A client can also send the
+ string <literal>HEAD /replica</literal> which will solely return an HTTP literal:
+ <literal>200</literal> if the server is in recovery, <literal>503</literal> if not.
+ (This allows a drop-in replacement to the same Patroni functionality)
+ Finally, a client can issue <literal>GET /info</literal> and receive the string
+ <literal>RECOVERY: </literal> followed by a 1 or 0.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="guc-expose-sysid" xreflabel="expose_sysid">
+ <term><varname>expose_sysid</varname> (<type>boolean</type>)
+ <indexterm>
+ <primary><varname>expose_sysid</varname> configuration parameter</primary>
+ </indexterm>
+ </term>
+ <listitem>
+ <para>
+ Enables reporting the system identifier of the cluster without requiring
+ an authenticated login. Clients can send the string <literal>GET /sysid</literal>
+ and will receive the numeric system identifier. This is a unique number generated
+ by each cluster when initdb is run.
+ </para>
+ <para>
+ A client can issue <literal>GET /info</literal> and receive the string
+ <literal>SYSID: </literal> followed by the numeric system identifier.
+ </para>
+ <para>
+ This feature is useful for determining if the server is the same server as previously
+ encountered. Note than primary and replica servers will share the same system
+ identifier.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="guc-expose-version" xreflabel="expose_version">
+ <term><varname>expose_version</varname> (<type>boolean</type>)
+ <indexterm>
+ <primary><varname>expose_version</varname> configuration parameter</primary>
+ </indexterm>
+ </term>
+ <listitem>
+ <para>
+ Enables reporting the numeric version of the Postgres cluster without requiring
+ an authenticated login. Clients can send the string <literal>GET /version</literal>
+ and will receive an integer representing the version.
+ </para>
+ <para>
+ A client can issue <literal>GET /info</literal> and receive the string
+ <literal>VERSION: </literal> followed by the numeric version.
+ </para>
+ <para>
+ This is particularly useful for non-Postgres systems (esp. security scanners) that
+ need a way to easily determine the version of Postgres in use without requiring
+ a Postgres client - or without needing any knowledge of the Postgres protocol at all.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ </variablelist>
+ </sect2>
+
<sect2 id="runtime-config-connection-authentication">
<title>Authentication</title>
diff --git a/src/backend/tcop/backend_startup.c b/src/backend/tcop/backend_startup.c
index 14d5fc0b196..b5d96d88307 100644
--- a/src/backend/tcop/backend_startup.c
+++ b/src/backend/tcop/backend_startup.c
@@ -46,6 +46,10 @@
bool Trace_connection_negotiation = false;
uint32 log_connections = 0;
char *log_connections_string = NULL;
+bool expose_recovery = false;
+bool expose_sysid = false;
+bool expose_version = false;
+
/* Other globals */
@@ -65,6 +69,7 @@ static void SendNegotiateProtocolVersion(List *unrecognized_protocol_options);
static void process_startup_packet_die(SIGNAL_ARGS);
static void StartupPacketTimeoutHandler(void);
static bool validate_log_connections_options(List *elemlist, uint32 *flags);
+static bool ExposeInformation(pgsocket fd);
/*
* Entry point for a new backend process.
@@ -148,6 +153,15 @@ BackendInitialize(ClientSocket *client_sock, CAC_state cac)
StringInfoData ps_data;
MemoryContext oldcontext;
+ /*
+ * Scan for a simple GET / HEAD request. If this is detected and
+ * handled, we are done and can immediately exit
+ */
+ if ((expose_recovery || expose_sysid || expose_version)
+ && ExposeInformation(client_sock->sock))
+ proc_exit(0);
+ /* Should we do exit(0) here, despite the warnings in ipc.c? */
+
/* Tell fd.c about the long-lived FD associated with the client_sock */
ReserveExternalFD();
@@ -1126,3 +1140,180 @@ assign_log_connections(const char *newval, void *extra)
{
log_connections = *((int *) extra);
}
+
+
+static
+bool
+ExposeInformation(pgsocket fd)
+{
+
+/*
+ * ExposeInformation
+ *
+ *
+ * Handle early socket probe before full backend startup.
+ * Responds to small set of predefined endpoints (e.g. GET /info)
+ *
+ * Requires at least one "expose_" GUC to be true.
+ *
+ * Returns true if any endpoint is recognized.
+ */
+
+#define EXPOSE_MIN_QUERY 9 /* Shortest possible line: "Get /info" */
+#define EXPOSE_MAX_QUERY 16 /* Longest possible GET line */
+
+/* What information is being returned */
+ typedef enum
+ {
+ EXPOSE_NOTHING,
+ EXPOSE_HEAD_REPLICA,
+ EXPOSE_GET_ALL,
+ EXPOSE_GET_REPLICA,
+ EXPOSE_GET_SYSID,
+ EXPOSE_GET_VERSION,
+ } ReturnType;
+
+ typedef struct
+ {
+ const char *endpoint;
+ const bool *require;
+ ReturnType type;
+ } endpoint_action;
+
+ static endpoint_action endpoint_actions[] =
+ {
+ {
+ "HEAD /replica", &expose_recovery, EXPOSE_HEAD_REPLICA
+ },
+ {
+ "GET /replica", &expose_recovery, EXPOSE_GET_REPLICA
+ },
+ {
+ "GET /sysid", &expose_sysid, EXPOSE_GET_SYSID
+ },
+ {
+ "GET /version", &expose_version, EXPOSE_GET_VERSION
+ },
+ {
+ "GET /info", NULL, EXPOSE_GET_ALL
+ }
+ };
+
+ ssize_t n;
+ char buf[EXPOSE_MAX_QUERY + 1];
+ int type;
+
+ Assert(expose_recovery || expose_sysid || expose_version);
+
+ do
+ {
+ n = recv(fd, buf, EXPOSE_MAX_QUERY, MSG_PEEK);
+ } while (n < 0 && errno == EINTR);
+
+ /*
+ * Leave as soon as possible if no chance we are interested. We also
+ * simply return false for n == -1
+ */
+ if (n < EXPOSE_MIN_QUERY)
+ return false;
+
+ buf[n] = '\0';
+
+ type = EXPOSE_NOTHING;
+ for (int i = 0; i < lengthof(endpoint_actions); i++)
+ {
+ if (
+ strncmp(buf, endpoint_actions[i].endpoint, strlen(endpoint_actions[i].endpoint)) == 0
+ &&
+ (endpoint_actions[i].require == NULL
+ ||
+ *(endpoint_actions[i].require)
+ ))
+ {
+ type = endpoint_actions[i].type;
+ break;
+ }
+ }
+
+ if (type == EXPOSE_NOTHING)
+ return false;
+
+ {
+ static const char http_version[] = "HTTP/1.1";
+ static const char http_type[] = "Content-Type: text/plain";
+ static const char *http_conn = "Connection: close";
+ static const char http_len[] = "Content-Length";
+
+ StringInfoData msg;
+
+ if (type == EXPOSE_HEAD_REPLICA)
+ {
+ /*
+ * Caller only cares about the HTTP response code, so no content
+ * needed
+ */
+
+ initStringInfoExt(&msg, 64);
+
+ appendStringInfo(&msg,
+ "%s %s\r\n"
+ "%s\r\n"
+ "%s\r\n\r\n",
+ http_version,
+ (RecoveryInProgress() ? "200 OK" : "503 Service Unavailable"),
+ http_type,
+ http_conn
+ );
+ }
+ else
+ {
+ StringInfoData content;
+
+ initStringInfoExt(&content, 64);
+
+ if (expose_recovery && (type == EXPOSE_GET_ALL || type == EXPOSE_GET_REPLICA))
+ appendStringInfo(&content, "%s%d\r\n",
+ type == EXPOSE_GET_ALL ? "RECOVERY: " : "",
+ RecoveryInProgress() ? 1 : 0);
+ if (expose_sysid && (type == EXPOSE_GET_ALL || type == EXPOSE_GET_SYSID))
+ appendStringInfo(&content, "%s%lu\r\n",
+ type == EXPOSE_GET_ALL ? "SYSID: " : "",
+ GetSystemIdentifier());
+ if (expose_version && (type == EXPOSE_GET_ALL || type == EXPOSE_GET_VERSION))
+ appendStringInfo(&content, "%s%d\r\n",
+ type == EXPOSE_GET_ALL ? "VERSION: " : "",
+ PG_VERSION_NUM);
+
+ initStringInfoExt(&msg, 256);
+
+ appendStringInfo(&msg,
+ "%s 200 OK\r\n"
+ "%s\r\n"
+ "%s: %d\r\n"
+ "%s\r\n\r\n"
+ "%s",
+ http_version,
+ http_type,
+ http_len, content.len,
+ http_conn,
+ content.data
+ );
+
+ pfree(content.data);
+ }
+
+ do
+ {
+ n = send(fd, msg.data, msg.len, 0);
+ } while (n < 0 && errno == EINTR);
+
+ pfree(msg.data);
+
+ if (n < 0)
+ elog(DEBUG1, "could not send to client: %m");
+
+ return true;
+
+ }
+
+}
diff --git a/src/backend/utils/misc/guc_parameters.dat b/src/backend/utils/misc/guc_parameters.dat
index d6fc8333850..86292b6708e 100644
--- a/src/backend/utils/misc/guc_parameters.dat
+++ b/src/backend/utils/misc/guc_parameters.dat
@@ -644,6 +644,24 @@
boot_val => 'true',
},
+{ name => 'expose_recovery', type => 'bool', context => 'PGC_SIGHUP', group => 'CLIENT_CONN_STATEMENT',
+ short_desc => 'Exposes if the server is in recovery mode without a login.',
+ variable => 'expose_recovery',
+ boot_val => 'false',
+},
+
+{ name => 'expose_sysid', type => 'bool', context => 'PGC_SIGHUP', group => 'CLIENT_CONN_STATEMENT',
+ short_desc => 'Exposes the system identifier without a login.',
+ variable => 'expose_sysid',
+ boot_val => 'false',
+},
+
+{ name => 'expose_version', type => 'bool', context => 'PGC_SIGHUP', group => 'CLIENT_CONN_STATEMENT',
+ short_desc => 'Exposes the server version without a login.',
+ variable => 'expose_version',
+ boot_val => 'false',
+},
+
{ name => 'array_nulls', type => 'bool', context => 'PGC_USERSET', group => 'COMPAT_OPTIONS_PREVIOUS',
short_desc => 'Enables input of NULL elements in arrays.',
long_desc => 'When turned on, unquoted NULL in an array input value means a null value; otherwise it is taken literally.',
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index f62b61967ef..19437471c80 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -91,6 +91,14 @@
# disconnection while running queries;
# 0 for never
+
+# - Expose information -
+
+#expose_recovery = off
+#expose_sysid = off
+#expose_version = off
+
+
# - Authentication -
#authentication_timeout = 1min # 1s-600s
diff --git a/src/include/postmaster/postmaster.h b/src/include/postmaster/postmaster.h
index 753871071ac..ee1ca2fca36 100644
--- a/src/include/postmaster/postmaster.h
+++ b/src/include/postmaster/postmaster.h
@@ -70,6 +70,10 @@ extern PGDLLIMPORT bool restart_after_crash;
extern PGDLLIMPORT bool remove_temp_files_after_crash;
extern PGDLLIMPORT bool send_abort_for_crash;
extern PGDLLIMPORT bool send_abort_for_kill;
+extern PGDLLIMPORT bool expose_recovery;
+extern PGDLLIMPORT bool expose_sysid;
+extern PGDLLIMPORT bool expose_version;
+
#ifdef WIN32
extern PGDLLIMPORT HANDLE PostmasterHandle;
diff --git a/src/test/modules/test_misc/meson.build b/src/test/modules/test_misc/meson.build
index f258bf1ccd9..726bd93908f 100644
--- a/src/test/modules/test_misc/meson.build
+++ b/src/test/modules/test_misc/meson.build
@@ -18,6 +18,7 @@ tests += {
't/007_catcache_inval.pl',
't/008_replslot_single_user.pl',
't/009_log_temp_files.pl',
+ 't/010_expose.pl',
],
},
}
diff --git a/src/test/modules/test_misc/t/010_expose.pl b/src/test/modules/test_misc/t/010_expose.pl
new file mode 100644
index 00000000000..f9363d0bc04
--- /dev/null
+++ b/src/test/modules/test_misc/t/010_expose.pl
@@ -0,0 +1,97 @@
+# Copyright (c) 2025, PostgreSQL Global Development Group
+
+# Test gathering information before authentication via expose_* variables
+
+# Force use of TCP/IP - call before the 'use'
+INIT{ $PostgreSQL::Test::Utils::use_unix_sockets = 0; }
+
+use strict;
+use warnings;
+use PostgreSQL::Test::Cluster;
+use PostgreSQL::Test::Utils;
+use Test::More;
+
+eval {
+ require LWP::UserAgent;
+};
+if ($@) {
+ plan skip_all => 'LWP::UserAgent is needed to run this test';
+}
+
+my $node = PostgreSQL::Test::Cluster->new('node1');
+# Setting as logical here simply to avoid wal_level minimal so we can restart as a replica
+$node->init(allows_streaming => "logical");
+$node->start;
+
+my $server_version = $node->safe_psql('postgres', 'show server_version_num');
+my $bindir = $node->config_data('--bindir');
+my $datadir = $node->data_dir;
+my $cdata = qx{$bindir/pg_controldata -D $datadir 2>&1};
+my ($sysid) = $cdata =~ /Database system identifier:\s+(\d+)/;
+
+my $port = $node->port;
+my $URI="http://localhost:$port";
+my $ua = LWP::UserAgent->new(timeout => 2);
+
+my ($response, $code, $content);
+
+$response = $ua->get("$URI/info");
+$code = $response->code;
+is ($code, 500, "GET /info returns HTTP code 500 when nothing is listening");
+
+$response = $ua->head("$URI/replica");
+$code = $response->code;
+is ($code, 500, "HEAD /replica returns HTTP code 500 when nothing is listening");
+
+$node->append_conf('postgresql.conf', 'expose_recovery=on');
+$node->reload();
+
+$response = $ua->get("$URI/replica");
+$code = $response->code;
+is ($code, 200, "GET /replica returns HTTP code 200 when expose_recovery is on (primary)");
+is ($response->content, "0\r\n", "GET /replica returns '0' when expose_recovery is on (primary)");
+
+$response = $ua->head("$URI/replica");
+$code = $response->code;
+is ($code, 503, "HEAD /info returns HTTP code 503 when expose_recovery is on (primary)");
+
+$response = $ua->get("$URI/info");
+$code = $response->code;
+is ($code, 200, "GET /info returns HTTP code 200 when expose_recovery is on");
+is ($response->content, "RECOVERY: 0\r\n", "GET /info returns 'RECOVERY:0' when expose_recovery is on (primary)");
+
+$node->append_conf('postgresql.conf', 'expose_version=on');
+$node->append_conf('postgresql.conf', 'expose_sysid=on');
+$node->reload();
+
+$response = $ua->get("$URI/info");
+$content = $response->content;
+like ($content, qr/RECOVERY: 0/, "GET /info returns 'RECOVERY: 0' when expose_recovery is on (primary)");
+like ($content, qr/VERSION: $server_version/, "GET /info returns 'VERSION: $server_version' when expose_version is on");
+like ($content, qr/SYSID: $sysid/, "GET /info returns correct SYSID when expose_sysid is on");
+
+$response = $ua->get("$URI/sysid");
+$content = $response->content;
+is ($content, "$sysid\r\n", "GET /sysid returns correct value when expose_sysid is on");
+
+$response = $ua->get("$URI/version");
+$content = $response->content;
+is ($content, "$server_version\r\n", "GET /version returns correct value when expose_version is on");
+
+$node->set_standby_mode();
+$node->restart();
+
+$response = $ua->get("$URI/replica");
+$code = $response->code;
+is ($code, 200, "GET /replica returns HTTP code 200 when expose_recovery is on (replica)");
+is ($response->content, "1\r\n", "GET /replica returns '0' when expose_recovery is on (replica)");
+
+$response = $ua->head("$URI/replica");
+$code = $response->code;
+is ($code, 200, "HEAD /info returns HTTP code 200 when expose_recovery is on (replica)");
+
+$response = $ua->get("$URI/info");
+$content = $response->content;
+like ($content, qr/RECOVERY: 1/, "GET /info returns 'RECOVERY: 1' when expose_recovery is on (replica)");
+
+done_testing();
--
2.47.3
Re: POC: Carefully exposing information without authentication
Greg Sabino Mullane <htamfids@gmail.com> wrote:
Version 4 attached, rebased to account for new tests, plus a new instra-test
check to make sure LWP::UserAgent is available before running.
I'm still not sure it's necessary to handle the problem at socket level. I
imagine it can be implemented this way:
1. Add a new field to the PGconn structure, indicating that the client is only
requesting the server status information, and adjust pg_isready so it sets
this option.
2. Adjust libpq frontend (pqBuildStartupPacket3) so it adds the corresponding
option to the startup packet.
3. On server, if ProcessStartupPacket() sees that option, call ereport(FATAL)
with a specific error code, and let the appropriate GUCs control the contents
of the error message. pg_isready would then just print out the message.
I haven't tried to write any code, so it's possible that I'm missing
something.
Regarding configuration, I'd prefer a single GUC. The value can be a
comma-separated list of keywords, each representing particular piece of
information to be exposed.
--
Antonin Houska
Web: https://www.cybertec-postgresql.com
Re: POC: Carefully exposing information without authentication
On Fri, Jan 9, 2026 at 8:56 AM Antonin Houska <ah@cybertec.at> wrote:
1. Add a new field to the PGconn structure
This kind of defeats one of the major strengths of this patch, which is
allowing systems that don't speak the protocol to get at this information.
Regarding configuration, I'd prefer a single GUC. The value can be a
comma-separated list of keywords, each representing particular piece of
information to be exposed.
Yes, I could see some advantages to that, although I still like the
simplicity of separate boolean values. I've no strong feelings either way.
Let's see if others weigh in.
Thanks for looking over this patch!
Cheers,
Greg