[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

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