Avoid repeated name lookups during table and index DDL.

If the name lookups come to different conclusions due to concurrent
activity, we might perform some parts of the DDL on a different table
than other parts.  At least in the case of CREATE INDEX, this can be
used to cause the permissions checks to be performed against a
different table than the index creation, allowing for a privilege
escalation attack.

This changes the calling convention for DefineIndex, CreateTrigger,
transformIndexStmt, transformAlterTableStmt, CheckIndexCompatible
(in 9.2 and newer), and AlterTable (in 9.1 and older).  In addition,
CheckRelationOwnership is removed in 9.2 and newer and the calling
convention is changed in older branches.  A field has also been added
to the Constraint node (FkConstraint in 8.4).  Third-party code calling
these functions or using the Constraint node will require updating.

Report by Andres Freund.  Patch by Robert Haas and Andres Freund,
reviewed by Tom Lane.

Security: CVE-2014-0062

1 files changed, 21 insertions, 5 deletions

diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
index 89ff89a6ba8..a042588a1af 100644
--- a/src/backend/commands/trigger.c
+++ b/src/backend/commands/trigger.c
@@ -69,6 +69,13 @@ static void AfterTriggerSaveEvent(ResultRelInfo *relinfo, int event,
 /*
  * Create a trigger.  Returns the OID of the created trigger.
  *
+ * relOid, if nonzero, is the relation on which the trigger should be
+ * created.  If zero, the name provided in the statement will be looked up.
+ *
+ * refRelOid, if nonzero, is the relation to which the constraint trigger
+ * refers.  If zero, the constraint relation name provided in the statement
+ * will be looked up as needed.
+ *
  * constraintOid, if nonzero, says that this trigger is being created
  * internally to implement that constraint.  A suitable pg_depend entry will
  * be made to link the trigger to that constraint.	constraintOid is zero when
@@ -83,7 +90,8 @@ static void AfterTriggerSaveEvent(ResultRelInfo *relinfo, int event,
  * but a foreign-key constraint.  This is a kluge for backwards compatibility.
  */
 Oid
-CreateTrigger(CreateTrigStmt *stmt, Oid constraintOid, bool checkPermissions)
+CreateTrigger(CreateTrigStmt *stmt, Oid relOid, Oid refRelOid,
+			  Oid constraintOid, bool checkPermissions)
 {
 	int16		tgtype;
 	int2vector *tgattr;
@@ -107,7 +115,10 @@ CreateTrigger(CreateTrigStmt *stmt, Oid constraintOid, bool checkPermissions)
 	ObjectAddress myself,
 				referenced;
 
-	rel = heap_openrv(stmt->relation, AccessExclusiveLock);
+	if (OidIsValid(relOid))
+		rel = heap_open(relOid, AccessExclusiveLock);
+	else
+		rel = heap_openrv(stmt->relation, AccessExclusiveLock);
 
 	if (rel->rd_rel->relkind != RELKIND_RELATION)
 		ereport(ERROR,
@@ -121,8 +132,13 @@ CreateTrigger(CreateTrigStmt *stmt, Oid constraintOid, bool checkPermissions)
 				 errmsg("permission denied: \"%s\" is a system catalog",
 						RelationGetRelationName(rel))));
 
-	if (stmt->isconstraint && stmt->constrrel != NULL)
-		constrrelid = RangeVarGetRelid(stmt->constrrel, false);
+	if (stmt->isconstraint)
+	{
+		if (OidIsValid(refRelOid))
+			constrrelid = refRelOid;
+		else if (stmt->constrrel != NULL)
+			constrrelid = RangeVarGetRelid(stmt->constrrel, false);
+	}
 
 	/* permission checks */
 	if (checkPermissions)
@@ -261,7 +277,7 @@ CreateTrigger(CreateTrigStmt *stmt, Oid constraintOid, bool checkPermissions)
 			ereport(ERROR,
 					(errcode(ERRCODE_DUPLICATE_OBJECT),
 				  errmsg("trigger \"%s\" for relation \"%s\" already exists",
-						 trigname, stmt->relation->relname)));
+						 trigname, RelationGetRelationName(rel))));
 	}
 	systable_endscan(tgscan);