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, 6 insertions, 3 deletions

diff --git a/src/bin/scripts/vacuumdb.c b/src/bin/scripts/vacuumdb.c
index eac5bfe5671..25567777070 100644
--- a/src/bin/scripts/vacuumdb.c
+++ b/src/bin/scripts/vacuumdb.c
@@ -266,7 +266,7 @@ vacuum_one_database(const char *dbname, bool full, bool verbose, bool and_analyz
 	initPQExpBuffer(&sql);
 
 	conn = connectDatabase(dbname, host, port, username, prompt_password,
-						   progname, false);
+						   progname, echo, false);
 
 	if (analyze_only)
 	{
@@ -319,7 +319,10 @@ vacuum_one_database(const char *dbname, bool full, bool verbose, bool and_analyz
 		}
 	}
 	if (table)
-		appendPQExpBuffer(&sql, " %s", table);
+	{
+		appendPQExpBufferChar(&sql, ' ');
+		appendQualifiedRelation(&sql, table, conn, progname, echo);
+	}
 	appendPQExpBufferStr(&sql, ";");
 
 	if (analyze_in_stages)
@@ -386,7 +389,7 @@ vacuum_all_databases(bool full, bool verbose, bool and_analyze, bool analyze_onl
 	int			stage;
 
 	conn = connectMaintenanceDatabase(maintenance_db, host, port,
-									  username, prompt_password, progname);
+									  username, prompt_password, progname, echo);
 	result = executeQuery(conn, "SELECT datname FROM pg_database WHERE datallowconn ORDER BY 1;", progname, echo);
 	PQfinish(conn);