[BUG/PATCH] backend crashes during authentication if data/global/pg_pwd is empty
Hi,
on Solaris 9 with PostgreSQL 7.4:
when you
- 'initdb' a fresh database,
- _don't_ set a password for user 'postgres',
- convert the 'trust' lines in data/pg_hba.conf to 'md5' or 'password'
and then try to connect as user 'postgres', the backend crashes in
backend/libpq/hba.c:372:
368 static int
369 user_group_bsearch_cmp(const void *user, const void *list)
370 {
371 /* first node is line number */
372 char *user2 = lfirst(lnext(*(List **) list));
due to 'list' being NULL, which might mean that 'user_sorted' was never
allocated, due to user_length being zero for an missing or empty
global/pg_pwd:
916 /* create sorted lines for binary searching */
917 user_length = length(user_lines);
918 if (user_length)
919 {
920 int i = 0;
921
922 user_sorted = palloc(user_length * sizeof(List *));
I know this is looks like a case of "don't do it, then", but since it's a
backend crash, I would suggest the following fix:
--- postgresql-7.4.orig/src/backend/libpq/hba.c 2003-10-25 05:48:46.000001000 +0200
+++ postgresql-7.4/src/backend/libpq/hba.c 2003-12-05 15:21:54.000003000 +0100
@@ -62,7 +62,7 @@
static List **user_sorted = NULL; /* sorted user list, for bsearch() */
static List **group_sorted = NULL; /* sorted group list, for
* bsearch() */
-static int user_length;
+static int user_length = 0;
static int group_length; static List *tokenize_file(FILE *file);
@@ -395,6 +395,10 @@
List **
get_user_line(const char *user)
{
+ /* fail if there is nothing to search in */
+ if ((user_sorted == NULL) || (user_length == 0))
+ return NULL;
+
return (List **) bsearch((void *) user,
(void *) user_sorted,
user_length,The initialization of user_length might not be necessary.
Best wishes, Mike
PS: This might be related to
http://archives.postgresql.org/pgsql-admin/2003-03/msg00413.php
--
Life is like a fire. DI Michael Wildpaner
Flames which the passer-by forgets. Ph.D. Student
Ashes which the wind scatters.
A man lived. -- Omar Khayyam
Michael Wildpaner <mike@rainbow.studorg.tuwien.ac.at> writes:
+ /* fail if there is nothing to search in */ + if ((user_sorted == NULL) || (user_length == 0)) + return NULL;
Hm, Solaris' bsearch() fails on empty input? How bizarre.
Easily worked around though --- thanks for the report!
I suspect we'd better put a defense in get_group_line as well.
It looks like there are no other places at risk in the backend.
regards, tom lane
Hm, Solaris' bsearch() fails on empty input? How bizarre.
I was skeptical but apparently this is a known bug ...
googling turned up a couple of references, eg
http://www.opencm.org/pipermail/opencm-dev/2002-July/001077.html
regards, tom lane
Hi,
On Fri, 5 Dec 2003, Tom Lane wrote:
Hm, Solaris' bsearch() fails on empty input? How bizarre.
I was skeptical but apparently this is a known bug ...
googling turned up a couple of references, eg
http://www.opencm.org/pipermail/opencm-dev/2002-July/001077.html
in defense of Solaris' bsearch it should be said that it only breaks if
one passes NULL as the array base, a decidedly undefined (and unfriendly)
case. Passing an array with zero elements works as advertised. Btw, the
same happens on IRIX.
Best wishes, Mike
PS: A little program to demonstrate this: array with elements, empty
array, NULL pointer as base:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
char strings[][4] = { "abc", "efg", "hij", "klm" };
typedef int (*cmp_t)(const void*, const void*);
int main(int argc, char**argv) {
char *s, *term = "hij";
s = bsearch(term, strings, sizeof(strings)/sizeof(char[4]),
sizeof(char*), (cmp_t) strcmp);
fprintf(stderr, "1: %s\n", (s != NULL) ? s : "<not found>");
s = bsearch(term, strings, 0, sizeof(char*), (cmp_t) strcmp);
fprintf(stderr, "2: %s\n", (s != NULL) ? s : "<not found>");
s = bsearch(term, NULL, 0, sizeof(char*), (cmp_t) strcmp);
fprintf(stderr, "3: %s\n", (s != NULL) ? s : "<not found>");
return 0;
}
Results:
$ ./a.out # Solaris 9
1: hij
2: <not found>
Segmentation Fault (core dumped)
$ ./a.out # IRIX 6.5
1: hij
2: <not found>
Segmentation fault (core dumped)
$ ./a.out # Linux with glibc 2.2.5
1: hij
2: <not found>
3: <not found>
$ ./a.out # OpenBSD 3.2
1: hij
2: <not found>
3: <not found>
--
Life is like a fire. DI Michael Wildpaner
Flames which the passer-by forgets. Ph.D. Student
Ashes which the wind scatters.
A man lived. -- Omar Khayyam