Make standard maintenance operations (including VACUUM, ANALYZE, REINDEX,

and CLUSTER) execute as the table owner rather than the calling user, using
the same privilege-switching mechanism already used for SECURITY DEFINER
functions.  The purpose of this change is to ensure that user-defined
functions used in index definitions cannot acquire the privileges of a
superuser account that is performing routine maintenance.  While a function
used in an index is supposed to be IMMUTABLE and thus not able to do anything
very interesting, there are several easy ways around that restriction; and
even if we could plug them all, there would remain a risk of reading sensitive
information and broadcasting it through a covert channel such as CPU usage.

To prevent bypassing this security measure, execution of SET SESSION
AUTHORIZATION and SET ROLE is now forbidden within a SECURITY DEFINER context.

Thanks to Itagaki Takahiro for reporting this vulnerability.

Security: CVE-2007-6600

1 files changed, 17 insertions, 1 deletions

diff --git a/src/backend/commands/variable.c b/src/backend/commands/variable.c
index b1d970b9ab0..2639a033f38 100644
--- a/src/backend/commands/variable.c
+++ b/src/backend/commands/variable.c
@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/variable.c,v 1.105.4.3 2006/02/12 22:33:14 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/variable.c,v 1.105.4.4 2008/01/03 21:25:00 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -656,6 +656,22 @@ assign_session_authorization(const char *value, bool doit, GucSource source)
 		/* not a saved ID, so look it up */
 		HeapTuple	userTup;
 
+		if (InSecurityDefinerContext())
+		{
+			/*
+			 * Disallow SET SESSION AUTHORIZATION inside a security definer
+			 * context.  We need to do this because when we exit the context,
+			 * GUC won't be notified, leaving things out of sync.  Note that
+			 * this test is positioned so that restoring a previously saved
+			 * setting isn't prevented.
+			 */
+			if (source >= PGC_S_INTERACTIVE)
+				ereport(ERROR,
+						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+						 errmsg("cannot set session authorization within security-definer function")));
+			return NULL;
+		}
+
 		if (!IsTransactionState())
 		{
 			/*