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, 23 insertions, 5 deletions

diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
index 86449a641cc..fa74bd2cf10 100644
--- a/src/backend/commands/trigger.c
+++ b/src/backend/commands/trigger.c
@@ -43,6 +43,7 @@
 #include "pgstat.h"
 #include "rewrite/rewriteManip.h"
 #include "storage/bufmgr.h"
+#include "storage/lmgr.h"
 #include "tcop/utility.h"
 #include "utils/acl.h"
 #include "utils/builtins.h"
@@ -96,6 +97,13 @@ static void AfterTriggerSaveEvent(EState *estate, ResultRelInfo *relinfo,
  * queryString is the source text of the CREATE TRIGGER command.
  * This must be supplied if a whenClause is specified, else it can be NULL.
  *
+ * 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
@@ -118,7 +126,7 @@ static void AfterTriggerSaveEvent(EState *estate, ResultRelInfo *relinfo,
  */
 Oid
 CreateTrigger(CreateTrigStmt *stmt, const char *queryString,
-			  Oid constraintOid, Oid indexOid,
+			  Oid relOid, Oid refRelOid, Oid constraintOid, Oid indexOid,
 			  bool isInternal)
 {
 	int16		tgtype;
@@ -147,7 +155,10 @@ CreateTrigger(CreateTrigStmt *stmt, const char *queryString,
 	ObjectAddress myself,
 				referenced;
 
-	rel = heap_openrv(stmt->relation, AccessExclusiveLock);
+	if (OidIsValid(relOid))
+		rel = heap_open(relOid, AccessExclusiveLock);
+	else
+		rel = heap_openrv(stmt->relation, AccessExclusiveLock);
 
 	/*
 	 * Triggers must be on tables or views, and there are additional
@@ -196,7 +207,7 @@ CreateTrigger(CreateTrigStmt *stmt, const char *queryString,
 				 errmsg("permission denied: \"%s\" is a system catalog",
 						RelationGetRelationName(rel))));
 
-	if (stmt->isconstraint && stmt->constrrel != NULL)
+	if (stmt->isconstraint)
 	{
 		/*
 		 * We must take a lock on the target relation to protect against
@@ -205,7 +216,14 @@ CreateTrigger(CreateTrigStmt *stmt, const char *queryString,
 		 * might end up creating a pg_constraint entry referencing a
 		 * nonexistent table.
 		 */
-		constrrelid = RangeVarGetRelid(stmt->constrrel, AccessShareLock, false);
+		if (OidIsValid(refRelOid))
+		{
+			LockRelationOid(refRelOid, AccessShareLock);
+			constrrelid = refRelOid;
+		}
+		else if (stmt->constrrel != NULL)
+			constrrelid = RangeVarGetRelid(stmt->constrrel, AccessShareLock,
+										   false);
 	}
 
 	/* permission checks */
@@ -501,7 +519,7 @@ CreateTrigger(CreateTrigStmt *stmt, const char *queryString,
 				ereport(ERROR,
 						(errcode(ERRCODE_DUPLICATE_OBJECT),
 				  errmsg("trigger \"%s\" for relation \"%s\" already exists",
-						 trigname, stmt->relation->relname)));
+						 trigname, RelationGetRelationName(rel))));
 		}
 		systable_endscan(tgscan);
 	}