Empty search_path in Autovacuum and non-psql/pgbench clients.

This makes the client programs behave as documented regardless of the
connect-time search_path and regardless of user-created objects.  Today,
a malicious user with CREATE permission on a search_path schema can take
control of certain of these clients' queries and invoke arbitrary SQL
functions under the client identity, often a superuser.  This is
exploitable in the default configuration, where all users have CREATE
privilege on schema "public".

This changes behavior of user-defined code stored in the database, like
pg_index.indexprs and pg_extension_config_dump().  If they reach code
bearing unqualified names, "does not exist" or "no schema has been
selected to create in" errors might appear.  Users may fix such errors
by schema-qualifying affected names.  After upgrading, consider watching
server logs for these errors.

The --table arguments of src/bin/scripts clients have been lax; for
example, "vacuumdb -Zt pg_am\;CHECKPOINT" performed a checkpoint.  That
now fails, but for now, "vacuumdb -Zt 'pg_am(amname);CHECKPOINT'" still
performs a checkpoint.

Back-patch to 9.3 (all supported versions).

Reviewed by Tom Lane, though this fix strategy was not his first choice.
Reported by Arseniy Sharoglazov.

Security: CVE-2018-1058

1 files changed, 9 insertions, 0 deletions

diff --git a/src/tools/findoidjoins/findoidjoins.c b/src/tools/findoidjoins/findoidjoins.c
index 7ea53b87899..82ef113e92f 100644
--- a/src/tools/findoidjoins/findoidjoins.c
+++ b/src/tools/findoidjoins/findoidjoins.c
@@ -9,6 +9,7 @@
 
 #include "catalog/pg_class.h"
 
+#include "fe_utils/connect.h"
 #include "libpq-fe.h"
 #include "pqexpbuffer.h"
 
@@ -46,6 +47,14 @@ main(int argc, char **argv)
 		exit(EXIT_FAILURE);
 	}
 
+	res = PQexec(conn, ALWAYS_SECURE_SEARCH_PATH_SQL);
+	if (!res || PQresultStatus(res) != PGRES_TUPLES_OK)
+	{
+		fprintf(stderr, "sql error:  %s\n", PQerrorMessage(conn));
+		exit(EXIT_FAILURE);
+	}
+	PQclear(res);
+
 	/* Get a list of relations that have OIDs */
 
 	printfPQExpBuffer(&sql, "%s",