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

doc/src/sgml/ref/set_role.sgml

@@ -1,5 +1,5 @@
 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/set_role.sgml,v 1.4 2007/01/31 23:26:04 momjian Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/set_role.sgml,v 1.5 2008/01/03 21:23:15 tgl Exp $
 PostgreSQL documentation
 -->
 
@@ -31,7 +31,7 @@ RESET ROLE
 
   <para>
    This command sets the current user
-   identifier of the current SQL-session context to be <replaceable
+   identifier of the current SQL session to be <replaceable
    class="parameter">rolename</replaceable>.  The role name can be
    written as either an identifier or a string literal.
    After <command>SET ROLE</>, permissions checking for SQL commands
@@ -89,6 +89,11 @@ RESET ROLE
    roles with <command>SET ROLE</> does not change the set of roles
    allowed to a later <command>SET ROLE</>.
   </para>
+
+  <para>
+   <command>SET ROLE</> cannot be used within a
+   <literal>SECURITY DEFINER</> function.
+  </para>
  </refsect1>
 
  <refsect1>

doc/src/sgml/ref/set_session_auth.sgml

@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/set_session_auth.sgml,v 1.16 2007/01/31 23:26:04 momjian Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/ref/set_session_auth.sgml,v 1.17 2008/01/03 21:23:15 tgl Exp $ -->
 <refentry id="SQL-SET-SESSION-AUTHORIZATION">
  <refmeta>
   <refentrytitle id="sql-set-session-authorization-title">SET SESSION AUTHORIZATION</refentrytitle>
@@ -27,7 +27,7 @@ RESET SESSION AUTHORIZATION
 
   <para>
    This command sets the session user identifier and the current user
-   identifier of the current SQL-session context to be <replaceable
+   identifier of the current SQL session to be <replaceable
    class="parameter">username</replaceable>.  The user name can be
    written as either an identifier or a string literal.  Using this
    command, it is possible, for example, to temporarily become an
@@ -38,7 +38,7 @@ RESET SESSION AUTHORIZATION
    The session user identifier is initially set to be the (possibly
    authenticated) user name provided by the client.  The current user
    identifier is normally equal to the session user identifier, but
-   might change temporarily in the context of <quote>setuid</quote>
+   might change temporarily in the context of <literal>SECURITY DEFINER</>
    functions and similar mechanisms; it can also be changed by
    <xref linkend="sql-set-role" endterm="sql-set-role-title">.
    The current user identifier is relevant for permission checking.
@@ -64,6 +64,15 @@ RESET SESSION AUTHORIZATION
   </para>
  </refsect1>
 
+ <refsect1>
+  <title>Notes</title>
+
+  <para>
+   <command>SET SESSION AUTHORIZATION</> cannot be used within a
+   <literal>SECURITY DEFINER</> function.
+  </para>
+ </refsect1>
+
  <refsect1>
   <title>Examples</title>
 

doc/src/sgml/ref/show.sgml

@@ -1,5 +1,5 @@
 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/show.sgml,v 1.44 2007/09/26 22:36:30 tgl Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/show.sgml,v 1.45 2008/01/03 21:23:15 tgl Exp $
 PostgreSQL documentation
 -->
 
@@ -104,8 +104,7 @@ SHOW ALL
         <term><literal>IS_SUPERUSER</literal></term>
         <listitem>
          <para>
-          True if the current session authorization identifier has
+          True if the current role has superuser privileges.
-          superuser privileges.
          </para>
         </listitem>
        </varlistentry>

src/backend/access/transam/xact.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.255 2008/01/01 19:45:48 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.256 2008/01/03 21:23:15 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -123,7 +123,8 @@ typedef struct TransactionStateData
 	MemoryContext curTransactionContext;		/* my xact-lifetime context */
 	ResourceOwner curTransactionOwner;	/* my query resources */
 	List	   *childXids;		/* subcommitted child XIDs */
-	Oid			currentUser;	/* subxact start current_user */
+	Oid			prevUser;		/* previous CurrentUserId setting */
+	bool		prevSecDefCxt;	/* previous SecurityDefinerContext setting */
 	bool		prevXactReadOnly;		/* entry-time xact r/o state */
 	struct TransactionStateData *parent;		/* back link to parent */
 } TransactionStateData;
@@ -148,7 +149,8 @@ static TransactionStateData TopTransactionStateData = {
 	NULL,						/* cur transaction context */
 	NULL,						/* cur transaction resource owner */
 	NIL,						/* subcommitted child Xids */
-	0,							/* entry-time current userid */
+	InvalidOid,					/* previous CurrentUserId setting */
+	false,						/* previous SecurityDefinerContext setting */
 	false,						/* entry-time xact r/o state */
 	NULL						/* link to parent state block */
 };
@@ -1490,19 +1492,15 @@ StartTransaction(void)
 
 	/*
 	 * initialize current transaction state fields
+	 *
+	 * note: prevXactReadOnly is not used at the outermost level
 	 */
 	s->nestingLevel = 1;
 	s->gucNestLevel = 1;
 	s->childXids = NIL;
-
+	GetUserIdAndContext(&s->prevUser, &s->prevSecDefCxt);
-	/*
+	/* SecurityDefinerContext should never be set outside a transaction */
-	 * You might expect to see "s->currentUser = GetUserId();" here, but you
+	Assert(!s->prevSecDefCxt);
-	 * won't because it doesn't work during startup; the userid isn't set yet
-	 * during a backend's first transaction start.  We only use the
-	 * currentUser field in sub-transaction state structs.
-	 *
-	 * prevXactReadOnly is also valid only in sub-transactions.
-	 */
 
 	/*
 	 * initialize other subsystems for new transaction
@@ -1963,17 +1961,16 @@ AbortTransaction(void)
 	s->state = TRANS_ABORT;
 
 	/*
-	 * Reset user id which might have been changed transiently.  We cannot use
+	 * Reset user ID which might have been changed transiently.  We need this
-	 * s->currentUser, since it may not be set yet; instead rely on internal
+	 * to clean up in case control escaped out of a SECURITY DEFINER function
-	 * state of miscinit.c.
+	 * or other local change of CurrentUserId; therefore, the prior value
+	 * of SecurityDefinerContext also needs to be restored.
 	 *
-	 * (Note: it is not necessary to restore session authorization here
+	 * (Note: it is not necessary to restore session authorization or role
-	 * because that can only be changed via GUC, and GUC will take care of
+	 * settings here because those can only be changed via GUC, and GUC will
-	 * rolling it back if need be.	However, an error within a SECURITY
+	 * take care of rolling them back if need be.)
-	 * DEFINER function could send control here with the wrong current
-	 * userid.)
 	 */
-	AtAbort_UserId();
+	SetUserIdAndContext(s->prevUser, s->prevSecDefCxt);
 
 	/*
 	 * do abort processing
@@ -3806,6 +3803,12 @@ AbortSubTransaction(void)
 
 	s->state = TRANS_ABORT;
 
+	/*
+	 * Reset user ID which might have been changed transiently.  (See notes
+	 * in AbortTransaction.)
+	 */
+	SetUserIdAndContext(s->prevUser, s->prevSecDefCxt);
+
 	/*
 	 * We can skip all this stuff if the subxact failed before creating a
 	 * ResourceOwner...
@@ -3858,20 +3861,6 @@ AbortSubTransaction(void)
 		AtEOSubXact_PgStat(false, s->nestingLevel);
 	}
 
-	/*
-	 * Reset user id which might have been changed transiently.  Here we want
-	 * to restore to the userid that was current at subxact entry. (As in
-	 * AbortTransaction, we need not worry about the session userid.)
-	 *
-	 * Must do this after AtEOXact_GUC to handle the case where we entered the
-	 * subxact inside a SECURITY DEFINER function (hence current and session
-	 * userids were different) and then session auth was changed inside the
-	 * subxact.  GUC will reset both current and session userids to the
-	 * entry-time session userid.  This is right in every other scenario so it
-	 * seems simplest to let GUC do that and fix it here.
-	 */
-	SetUserId(s->currentUser);
-
 	/*
 	 * Restore the upper transaction's read-only state, too.  This should be
 	 * redundant with GUC's cleanup but we may as well do it for consistency
@@ -3926,13 +3915,6 @@ PushTransaction(void)
 {
 	TransactionState p = CurrentTransactionState;
 	TransactionState s;
-	Oid			currentUser;
-
-	/*
-	 * At present, GetUserId cannot fail, but let's not assume that.  Get the
-	 * ID before entering the critical code sequence.
-	 */
-	currentUser = GetUserId();
 
 	/*
 	 * We keep subtransaction state nodes in TopTransactionContext.
@@ -3966,7 +3948,7 @@ PushTransaction(void)
 	s->savepointLevel = p->savepointLevel;
 	s->state = TRANS_DEFAULT;
 	s->blockState = TBLOCK_SUBBEGIN;
-	s->currentUser = currentUser;
+	GetUserIdAndContext(&s->prevUser, &s->prevSecDefCxt);
 	s->prevXactReadOnly = XactReadOnly;
 
 	CurrentTransactionState = s;

src/backend/catalog/index.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/catalog/index.c,v 1.289 2008/01/01 19:45:48 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/catalog/index.c,v 1.290 2008/01/03 21:23:15 tgl Exp $
  *
  *
  * INTERFACE ROUTINES
@@ -1339,6 +1339,8 @@ index_build(Relation heapRelation,
 {
 	RegProcedure procedure;
 	IndexBuildResult *stats;
+	Oid			save_userid;
+	bool		save_secdefcxt;
 
 	/*
 	 * sanity checks
@@ -1349,6 +1351,13 @@ index_build(Relation heapRelation,
 	procedure = indexRelation->rd_am->ambuild;
 	Assert(RegProcedureIsValid(procedure));
 
+	/*
+	 * Switch to the table owner's userid, so that any index functions are
+	 * run as that user.
+	 */
+	GetUserIdAndContext(&save_userid, &save_secdefcxt);
+	SetUserIdAndContext(heapRelation->rd_rel->relowner, true);
+
 	/*
 	 * Call the access method's build procedure
 	 */
@@ -1359,6 +1368,9 @@ index_build(Relation heapRelation,
 										 PointerGetDatum(indexInfo)));
 	Assert(PointerIsValid(stats));
 
+	/* Restore userid */
+	SetUserIdAndContext(save_userid, save_secdefcxt);
+
 	/*
 	 * If we found any potentially broken HOT chains, mark the index as not
 	 * being usable until the current transaction is below the event horizon.
@@ -1857,6 +1869,8 @@ validate_index(Oid heapId, Oid indexId, Snapshot snapshot)
 	IndexInfo  *indexInfo;
 	IndexVacuumInfo ivinfo;
 	v_i_state	state;
+	Oid			save_userid;
+	bool		save_secdefcxt;
 
 	/* Open and lock the parent heap relation */
 	heapRelation = heap_open(heapId, ShareUpdateExclusiveLock);
@@ -1873,6 +1887,13 @@ validate_index(Oid heapId, Oid indexId, Snapshot snapshot)
 	/* mark build is concurrent just for consistency */
 	indexInfo->ii_Concurrent = true;
 
+	/*
+	 * Switch to the table owner's userid, so that any index functions are
+	 * run as that user.
+	 */
+	GetUserIdAndContext(&save_userid, &save_secdefcxt);
+	SetUserIdAndContext(heapRelation->rd_rel->relowner, true);
+
 	/*
 	 * Scan the index and gather up all the TIDs into a tuplesort object.
 	 */
@@ -1910,6 +1931,9 @@ validate_index(Oid heapId, Oid indexId, Snapshot snapshot)
 		 "validate_index found %.0f heap tuples, %.0f index tuples; inserted %.0f missing tuples",
 		 state.htups, state.itups, state.tups_inserted);
 
+	/* Restore userid */
+	SetUserIdAndContext(save_userid, save_secdefcxt);
+
 	/* Close rels, but keep locks */
 	index_close(indexRelation, NoLock);
 	heap_close(heapRelation, NoLock);

src/backend/commands/analyze.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/analyze.c,v 1.113 2008/01/01 19:45:48 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/analyze.c,v 1.114 2008/01/03 21:23:15 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -119,6 +119,8 @@ analyze_rel(Oid relid, VacuumStmt *vacstmt,
 	HeapTuple  *rows;
 	PGRUsage	ru0;
 	TimestampTz starttime = 0;
+	Oid			save_userid;
+	bool		save_secdefcxt;
 
 	if (vacstmt->verbose)
 		elevel = INFO;
@@ -202,6 +204,18 @@ analyze_rel(Oid relid, VacuumStmt *vacstmt,
 		return;
 	}
 
+	ereport(elevel,
+			(errmsg("analyzing \"%s.%s\"",
+					get_namespace_name(RelationGetNamespace(onerel)),
+					RelationGetRelationName(onerel))));
+
+	/*
+	 * Switch to the table owner's userid, so that any index functions are
+	 * run as that user.
+	 */
+	GetUserIdAndContext(&save_userid, &save_secdefcxt);
+	SetUserIdAndContext(onerel->rd_rel->relowner, true);
+
 	/* let others know what I'm doing */
 	LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
 	MyProc->vacuumFlags |= PROC_IN_ANALYZE;
@@ -215,11 +229,6 @@ analyze_rel(Oid relid, VacuumStmt *vacstmt,
 			starttime = GetCurrentTimestamp();
 	}
 
-	ereport(elevel,
-			(errmsg("analyzing \"%s.%s\"",
-					get_namespace_name(RelationGetNamespace(onerel)),
-					RelationGetRelationName(onerel))));
-
 	/*
 	 * Determine which columns to analyze
 	 *
@@ -344,9 +353,7 @@ analyze_rel(Oid relid, VacuumStmt *vacstmt,
 								  onerel->rd_rel->relisshared,
 								  0, 0);
 
-		vac_close_indexes(nindexes, Irel, AccessShareLock);
+		goto cleanup;
-		relation_close(onerel, ShareUpdateExclusiveLock);
-		return;
 	}
 
 	/*
@@ -466,6 +473,9 @@ analyze_rel(Oid relid, VacuumStmt *vacstmt,
 							  totalrows, totaldeadrows);
 	}
 
+	/* We skip to here if there were no analyzable columns */
+cleanup:
+
 	/* Done with indexes */
 	vac_close_indexes(nindexes, Irel, NoLock);
 
@@ -498,6 +508,9 @@ analyze_rel(Oid relid, VacuumStmt *vacstmt,
 	LWLockAcquire(ProcArrayLock, LW_EXCLUSIVE);
 	MyProc->vacuumFlags &= ~PROC_IN_ANALYZE;
 	LWLockRelease(ProcArrayLock);
+
+	/* Restore userid */
+	SetUserIdAndContext(save_userid, save_secdefcxt);
 }
 
 /*

src/backend/commands/schemacmds.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/schemacmds.c,v 1.48 2008/01/01 19:45:49 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/schemacmds.c,v 1.49 2008/01/03 21:23:15 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -48,9 +48,10 @@ CreateSchemaCommand(CreateSchemaStmt *stmt, const char *queryString)
 	ListCell   *parsetree_item;
 	Oid			owner_uid;
 	Oid			saved_uid;
+	bool		saved_secdefcxt;
 	AclResult	aclresult;
 
-	saved_uid = GetUserId();
+	GetUserIdAndContext(&saved_uid, &saved_secdefcxt);
 
 	/*
 	 * Who is supposed to own the new schema?
@@ -86,11 +87,11 @@ CreateSchemaCommand(CreateSchemaStmt *stmt, const char *queryString)
 	 * temporarily set the current user so that the object(s) will be created
 	 * with the correct ownership.
 	 *
-	 * (The setting will revert to session user on error or at the end of this
+	 * (The setting will be restored at the end of this routine, or in case
-	 * routine.)
+	 * of error, transaction abort will clean things up.)
 	 */
 	if (saved_uid != owner_uid)
-		SetUserId(owner_uid);
+		SetUserIdAndContext(owner_uid, true);
 
 	/* Create the schema's namespace */
 	namespaceId = NamespaceCreate(schemaName, owner_uid);
@@ -142,7 +143,7 @@ CreateSchemaCommand(CreateSchemaStmt *stmt, const char *queryString)
 	PopOverrideSearchPath();
 
 	/* Reset current user */
-	SetUserId(saved_uid);
+	SetUserIdAndContext(saved_uid, saved_secdefcxt);
 }
 
 

src/backend/commands/vacuum.c

@@ -13,7 +13,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.362 2008/01/01 19:45:49 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.363 2008/01/03 21:23:15 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -971,6 +971,8 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, char expected_relkind)
 	Relation	onerel;
 	LockRelId	onerelid;
 	Oid			toast_relid;
+	Oid			save_userid;
+	bool		save_secdefcxt;
 
 	/* Begin a transaction for vacuuming this relation */
 	StartTransactionCommand();
@@ -1100,6 +1102,14 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, char expected_relkind)
 	 */
 	toast_relid = onerel->rd_rel->reltoastrelid;
 
+	/*
+	 * Switch to the table owner's userid, so that any index functions are
+	 * run as that user.  (This is unnecessary, but harmless, for lazy
+	 * VACUUM.)
+	 */
+	GetUserIdAndContext(&save_userid, &save_secdefcxt);
+	SetUserIdAndContext(onerel->rd_rel->relowner, true);
+
 	/*
 	 * Do the actual work --- either FULL or "lazy" vacuum
 	 */
@@ -1108,6 +1118,9 @@ vacuum_rel(Oid relid, VacuumStmt *vacstmt, char expected_relkind)
 	else
 		lazy_vacuum_rel(onerel, vacstmt, vac_strategy);
 
+	/* Restore userid */
+	SetUserIdAndContext(save_userid, save_secdefcxt);
+
 	/* all done with this class, but hold lock until commit */
 	relation_close(onerel, NoLock);
 

src/backend/commands/variable.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/commands/variable.c,v 1.124 2008/01/01 19:45:49 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/commands/variable.c,v 1.125 2008/01/03 21:23:15 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -717,6 +717,21 @@ assign_session_authorization(const char *value, bool doit, GucSource source)
 		/* not a saved ID, so look it up */
 		HeapTuple	roleTup;
 
+		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.
+			 */
+			ereport(GUC_complaint_elevel(source),
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("cannot set session authorization within security-definer function")));
+			return NULL;
+		}
+
 		if (!IsTransactionState())
 		{
 			/*
@@ -823,6 +838,24 @@ assign_role(const char *value, bool doit, GucSource source)
 		}
 	}
 
+	if (roleid == InvalidOid && InSecurityDefinerContext())
+	{
+		/*
+		 * Disallow SET ROLE 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 arranged so
+		 * that restoring a previously saved setting isn't prevented.
+		 *
+		 * XXX it would be nice to allow this case in future, with the
+		 * behavior being that the SET ROLE's effects end when the security
+		 * definer context is exited.
+		 */
+		ereport(GUC_complaint_elevel(source),
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("cannot set role within security-definer function")));
+		return NULL;
+	}
+
 	if (roleid == InvalidOid &&
 		strcmp(actual_rolename, "none") != 0)
 	{

src/backend/utils/adt/ri_triggers.c

@@ -15,7 +15,7 @@
  *
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  *
- * $PostgreSQL: pgsql/src/backend/utils/adt/ri_triggers.c,v 1.100 2008/01/01 19:45:52 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/adt/ri_triggers.c,v 1.101 2008/01/03 21:23:15 tgl Exp $
  *
  * ----------
  */
@@ -3173,7 +3173,8 @@ ri_PlanCheck(const char *querystr, int nargs, Oid *argtypes,
 {
 	SPIPlanPtr	qplan;
 	Relation	query_rel;
-	Oid			save_uid;
+	Oid			save_userid;
+	bool		save_secdefcxt;
 
 	/*
 	 * The query is always run against the FK table except when this is an
@@ -3187,8 +3188,8 @@ ri_PlanCheck(const char *querystr, int nargs, Oid *argtypes,
 		query_rel = fk_rel;
 
 	/* Switch to proper UID to perform check as */
-	save_uid = GetUserId();
+	GetUserIdAndContext(&save_userid, &save_secdefcxt);
-	SetUserId(RelationGetForm(query_rel)->relowner);
+	SetUserIdAndContext(RelationGetForm(query_rel)->relowner, true);
 
 	/* Create the plan */
 	qplan = SPI_prepare(querystr, nargs, argtypes);
@@ -3197,7 +3198,7 @@ ri_PlanCheck(const char *querystr, int nargs, Oid *argtypes,
 		elog(ERROR, "SPI_prepare returned %d for %s", SPI_result, querystr);
 
 	/* Restore UID */
-	SetUserId(save_uid);
+	SetUserIdAndContext(save_userid, save_secdefcxt);
 
 	/* Save the plan if requested */
 	if (cache_plan)
@@ -3226,7 +3227,8 @@ ri_PerformCheck(RI_QueryKey *qkey, SPIPlanPtr qplan,
 	Snapshot	crosscheck_snapshot;
 	int			limit;
 	int			spi_result;
-	Oid			save_uid;
+	Oid			save_userid;
+	bool		save_secdefcxt;
 	Datum		vals[RI_MAX_NUMKEYS * 2];
 	char		nulls[RI_MAX_NUMKEYS * 2];
 
@@ -3304,8 +3306,8 @@ ri_PerformCheck(RI_QueryKey *qkey, SPIPlanPtr qplan,
 	limit = (expect_OK == SPI_OK_SELECT) ? 1 : 0;
 
 	/* Switch to proper UID to perform check as */
-	save_uid = GetUserId();
+	GetUserIdAndContext(&save_userid, &save_secdefcxt);
-	SetUserId(RelationGetForm(query_rel)->relowner);
+	SetUserIdAndContext(RelationGetForm(query_rel)->relowner, true);
 
 	/* Finally we can run the query. */
 	spi_result = SPI_execute_snapshot(qplan,
@@ -3314,7 +3316,7 @@ ri_PerformCheck(RI_QueryKey *qkey, SPIPlanPtr qplan,
 									  false, false, limit);
 
 	/* Restore UID */
-	SetUserId(save_uid);
+	SetUserIdAndContext(save_userid, save_secdefcxt);
 
 	/* Check result */
 	if (spi_result < 0)

src/backend/utils/fmgr/fmgr.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/fmgr/fmgr.c,v 1.112 2008/01/01 19:45:53 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/fmgr/fmgr.c,v 1.113 2008/01/03 21:23:15 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -864,6 +864,7 @@ fmgr_security_definer(PG_FUNCTION_ARGS)
 	struct fmgr_security_definer_cache *volatile fcache;
 	FmgrInfo   *save_flinfo;
 	Oid			save_userid;
+	bool		save_secdefcxt;
 	volatile int save_nestlevel;
 
 	if (!fcinfo->flinfo->fn_extra)
@@ -908,46 +909,50 @@ fmgr_security_definer(PG_FUNCTION_ARGS)
 	else
 		fcache = fcinfo->flinfo->fn_extra;
 
-	save_flinfo = fcinfo->flinfo;
+	/* GetUserIdAndContext is cheap enough that no harm in a wasted call */
-	/* GetUserId is cheap enough that no harm in a wasted call */
+	GetUserIdAndContext(&save_userid, &save_secdefcxt);
-	save_userid = GetUserId();
 	if (fcache->proconfig)		/* Need a new GUC nesting level */
 		save_nestlevel = NewGUCNestLevel();
 	else
 		save_nestlevel = 0;		/* keep compiler quiet */
 
+	if (OidIsValid(fcache->userid))
+		SetUserIdAndContext(fcache->userid, true);
+
+	if (fcache->proconfig)
+	{
+		ProcessGUCArray(fcache->proconfig,
+						(superuser() ? PGC_SUSET : PGC_USERSET),
+						PGC_S_SESSION,
+						GUC_ACTION_SAVE);
+	}
+
+	/*
+	 * We don't need to restore GUC or userid settings on error, because the
+	 * ensuing xact or subxact abort will do that.  The PG_TRY block is only
+	 * needed to clean up the flinfo link.
+	 */
+	save_flinfo = fcinfo->flinfo;
+
 	PG_TRY();
 	{
 		fcinfo->flinfo = &fcache->flinfo;
 
-		if (OidIsValid(fcache->userid))
-			SetUserId(fcache->userid);
-
-		if (fcache->proconfig)
-		{
-			ProcessGUCArray(fcache->proconfig,
-							(superuser() ? PGC_SUSET : PGC_USERSET),
-							PGC_S_SESSION,
-							GUC_ACTION_SAVE);
-		}
-
 		result = FunctionCallInvoke(fcinfo);
 	}
 	PG_CATCH();
 	{
 		fcinfo->flinfo = save_flinfo;
-		/* We don't need to restore GUC settings, outer xact abort will */
-		if (OidIsValid(fcache->userid))
-			SetUserId(save_userid);
 		PG_RE_THROW();
 	}
 	PG_END_TRY();
 
 	fcinfo->flinfo = save_flinfo;
+
 	if (fcache->proconfig)
 		AtEOXact_GUC(true, save_nestlevel);
 	if (OidIsValid(fcache->userid))
-		SetUserId(save_userid);
+		SetUserIdAndContext(save_userid, save_secdefcxt);
 
 	return result;
 }

src/backend/utils/init/miscinit.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/init/miscinit.c,v 1.165 2008/01/01 19:45:53 momjian Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/init/miscinit.c,v 1.166 2008/01/03 21:23:15 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -264,13 +264,15 @@ make_absolute_path(const char *path)
  * OuterUserId is the current user ID in effect at the "outer level" (outside
  * any transaction or function).  This is initially the same as SessionUserId,
  * but can be changed by SET ROLE to any role that SessionUserId is a
- * member of.  We store this mainly so that AtAbort_UserId knows what to
+ * member of.  (XXX rename to something like CurrentRoleId?)
- * reset CurrentUserId to.
  *
  * CurrentUserId is the current effective user ID; this is the one to use
  * for all normal permissions-checking purposes.  At outer level this will
  * be the same as OuterUserId, but it changes during calls to SECURITY
  * DEFINER functions, as well as locally in some specialized commands.
+ *
+ * SecurityDefinerContext is TRUE if we are within a SECURITY DEFINER function
+ * or another context that temporarily changes CurrentUserId.
  * ----------------------------------------------------------------
  */
 static Oid	AuthenticatedUserId = InvalidOid;
@@ -282,12 +284,16 @@ static Oid	CurrentUserId = InvalidOid;
 static bool AuthenticatedUserIsSuperuser = false;
 static bool SessionUserIsSuperuser = false;
 
+static bool SecurityDefinerContext = false;
+
 /* We also remember if a SET ROLE is currently active */
 static bool SetRoleIsActive = false;
 
 
 /*
- * GetUserId/SetUserId - get/set the current effective user ID.
+ * GetUserId - get the current effective user ID.
+ *
+ * Note: there's no SetUserId() anymore; use SetUserIdAndContext().
  */
 Oid
 GetUserId(void)
@@ -297,14 +303,6 @@ GetUserId(void)
 }
 
 
-void
-SetUserId(Oid userid)
-{
-	AssertArg(OidIsValid(userid));
-	CurrentUserId = userid;
-}
-
-
 /*
  * GetOuterUserId/SetOuterUserId - get/set the outer-level user ID.
  */
@@ -319,6 +317,7 @@ GetOuterUserId(void)
 static void
 SetOuterUserId(Oid userid)
 {
+	AssertState(!SecurityDefinerContext);
 	AssertArg(OidIsValid(userid));
 	OuterUserId = userid;
 
@@ -341,6 +340,7 @@ GetSessionUserId(void)
 static void
 SetSessionUserId(Oid userid, bool is_superuser)
 {
+	AssertState(!SecurityDefinerContext);
 	AssertArg(OidIsValid(userid));
 	SessionUserId = userid;
 	SessionUserIsSuperuser = is_superuser;
@@ -352,6 +352,44 @@ SetSessionUserId(Oid userid, bool is_superuser)
 }
 
 
+/*
+ * GetUserIdAndContext/SetUserIdAndContext - get/set the current user ID
+ * and the SecurityDefinerContext flag.
+ *
+ * Unlike GetUserId, GetUserIdAndContext does *not* Assert that the current
+ * value of CurrentUserId is valid; nor does SetUserIdAndContext require
+ * the new value to be valid.  In fact, these routines had better not
+ * ever throw any kind of error.  This is because they are used by
+ * StartTransaction and AbortTransaction to save/restore the settings,
+ * and during the first transaction within a backend, the value to be saved
+ * and perhaps restored is indeed invalid.  We have to be able to get
+ * through AbortTransaction without asserting in case InitPostgres fails.
+ */
+void
+GetUserIdAndContext(Oid *userid, bool *sec_def_context)
+{
+	*userid = CurrentUserId;
+	*sec_def_context = SecurityDefinerContext;
+}
+
+void
+SetUserIdAndContext(Oid userid, bool sec_def_context)
+{
+	CurrentUserId = userid;
+	SecurityDefinerContext = sec_def_context;
+}
+
+
+/*
+ * InSecurityDefinerContext - are we inside a SECURITY DEFINER context?
+ */
+bool
+InSecurityDefinerContext(void)
+{
+	return SecurityDefinerContext;
+}
+
+
 /*
  * Initialize user identity during normal backend startup
  */
@@ -479,21 +517,6 @@ InitializeSessionUserIdStandalone(void)
 }
 
 
-/*
- * Reset effective userid during AbortTransaction
- *
- * This is essentially SetUserId(GetOuterUserId()), but without the Asserts.
- * The reason is that if a backend's InitPostgres transaction fails (eg,
- * because an invalid user name was given), we have to be able to get through
- * AbortTransaction without asserting.
- */
-void
-AtAbort_UserId(void)
-{
-	CurrentUserId = OuterUserId;
-}
-
-
 /*
  * Change session auth ID while running
  *

src/include/miscadmin.h

@@ -13,7 +13,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/miscadmin.h,v 1.198 2008/01/01 19:45:56 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/miscadmin.h,v 1.199 2008/01/03 21:23:15 tgl Exp $
  *
  * NOTES
  *	  some of the information in this file should be moved to other files.
@@ -234,12 +234,13 @@ extern void SetDatabasePath(const char *path);
 
 extern char *GetUserNameFromId(Oid roleid);
 extern Oid	GetUserId(void);
-extern void SetUserId(Oid userid);
 extern Oid	GetOuterUserId(void);
 extern Oid	GetSessionUserId(void);
+extern void GetUserIdAndContext(Oid *userid, bool *sec_def_context);
+extern void SetUserIdAndContext(Oid userid, bool sec_def_context);
+extern bool InSecurityDefinerContext(void);
 extern void InitializeSessionUserId(const char *rolename);
 extern void InitializeSessionUserIdStandalone(void);
-extern void AtAbort_UserId(void);
 extern void SetSessionAuthorization(Oid userid, bool is_superuser);
 extern Oid	GetCurrentRoleId(void);
 extern void SetCurrentRoleId(Oid roleid, bool is_superuser);