Repair insufficiently careful type checking for SQL-language functions:

we should check that the function code returns the claimed result datatype
every time we parse the function for execution.  Formerly, for simple
scalar result types we assumed the creation-time check was sufficient, but
this fails if the function selects from a table that's been redefined since
then, and even more obviously fails if check_function_bodies had been OFF.

This is a significant security hole: not only can one trivially crash the
backend, but with appropriate misuse of pass-by-reference datatypes it is
possible to read out arbitrary locations in the server process's memory,
which could allow retrieving database content the user should not be able
to see.  Our thanks to Jeff Trout for the initial report.

Security: CVE-2007-0555

src/backend/catalog/pg_proc.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/catalog/pg_proc.c,v 1.94 2002/09/18 21:35:20 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/catalog/pg_proc.c,v 1.94.2.1 2007/02/02 00:04:16 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -33,7 +33,6 @@
 #include "utils/syscache.h"
 
 
-static void checkretval(Oid rettype, char fn_typtype, List *queryTreeList);
 Datum		fmgr_internal_validator(PG_FUNCTION_ARGS);
 Datum		fmgr_c_validator(PG_FUNCTION_ARGS);
 Datum		fmgr_sql_validator(PG_FUNCTION_ARGS);
@@ -294,15 +293,15 @@ ProcedureCreate(const char *procedureName,
 }
 
 /*
- * checkretval() -- check return value of a list of sql parse trees.
+ * check_sql_fn_retval() -- check return value of a list of sql parse trees.
  *
  * The return value of a sql function is the value returned by
  * the final query in the function.  We do some ad-hoc define-time
  * type checking here to be sure that the user is returning the
  * type he claims.
  */
-static void
-checkretval(Oid rettype, char fn_typtype, List *queryTreeList)
+void
+check_sql_fn_retval(Oid rettype, char fn_typtype, List *queryTreeList)
 {
 	Query	   *parse;
 	int			cmd;
@@ -592,7 +591,7 @@ fmgr_sql_validator(PG_FUNCTION_ARGS)
 	prosrc = DatumGetCString(DirectFunctionCall1(textout, tmp));
 
 	querytree_list = pg_parse_and_rewrite(prosrc, proc->proargtypes, proc->pronargs);
-	checkretval(proc->prorettype, functyptype, querytree_list);
+	check_sql_fn_retval(proc->prorettype, functyptype, querytree_list);
 
 	ReleaseSysCache(tuple);
 

src/backend/executor/functions.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/executor/functions.c,v 1.57.2.1 2003/06/12 17:29:37 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/executor/functions.c,v 1.57.2.2 2007/02/02 00:04:16 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -24,6 +24,7 @@
 #include "tcop/tcopprot.h"
 #include "tcop/utility.h"
 #include "utils/builtins.h"
+#include "utils/lsyscache.h"
 #include "utils/syscache.h"
 
 
@@ -53,7 +54,7 @@ typedef struct local_es
 
 typedef struct
 {
-	int			typlen;			/* length of the return type */
+	int16		typlen;			/* length of the return type */
 	bool		typbyval;		/* true if return type is pass by value */
 	bool		returnsTuple;	/* true if return type is a tuple */
 	bool		shutdown_reg;	/* true if registered shutdown callback */
@@ -71,7 +72,8 @@ typedef SQLFunctionCache *SQLFunctionCachePtr;
 
 /* non-export function prototypes */
 static execution_state *init_execution_state(char *src,
-					 Oid *argOidVect, int nargs);
+					 Oid *argOidVect, int nargs,
+					 Oid rettype);
 static void init_sql_fcache(FmgrInfo *finfo);
 static void postquel_start(execution_state *es);
 static TupleTableSlot *postquel_getnext(execution_state *es);
@@ -84,7 +86,8 @@ static void ShutdownSQLFunction(Datum arg);
 
 
 static execution_state *
-init_execution_state(char *src, Oid *argOidVect, int nargs)
+init_execution_state(char *src, Oid *argOidVect, int nargs,
+					 Oid rettype)
 {
 	execution_state *firstes;
 	execution_state *preves;
@@ -93,6 +96,14 @@ init_execution_state(char *src, Oid *argOidVect, int nargs)
 
 	queryTree_list = pg_parse_and_rewrite(src, argOidVect, nargs);
 
+	/*
+	 * Check that the function returns the type it claims to.  Although
+	 * this was already done when the function was defined,
+	 * we have to recheck because database objects used in the function's
+	 * queries might have changed type.
+	 */
+	check_sql_fn_retval(rettype, get_typtype(rettype), queryTree_list);
+
 	firstes = NULL;
 	preves = NULL;
 
@@ -150,6 +161,7 @@ static void
 init_sql_fcache(FmgrInfo *finfo)
 {
 	Oid			foid = finfo->fn_oid;
+	Oid			rettype;
 	HeapTuple	procedureTuple;
 	HeapTuple	typeTuple;
 	Form_pg_proc procedureStruct;
@@ -176,12 +188,14 @@ init_sql_fcache(FmgrInfo *finfo)
 	/*
 	 * get the return type from the procedure tuple
 	 */
+	rettype = procedureStruct->prorettype;
+
 	typeTuple = SearchSysCache(TYPEOID,
-						   ObjectIdGetDatum(procedureStruct->prorettype),
+							   ObjectIdGetDatum(rettype),
 							   0, 0, 0);
 	if (!HeapTupleIsValid(typeTuple))
 		elog(ERROR, "init_sql_fcache: Cache lookup failed for type %u",
-			 procedureStruct->prorettype);
+			 rettype);
 
 	typeStruct = (Form_pg_type) GETSTRUCT(typeTuple);
 
@@ -194,7 +208,7 @@ init_sql_fcache(FmgrInfo *finfo)
 	fcache->typlen = typeStruct->typlen;
 
 	if (typeStruct->typtype != 'c' &&
-		procedureStruct->prorettype != RECORDOID)
+		rettype != RECORDOID)
 	{
 		/* The return type is not a composite type, so just use byval */
 		fcache->typbyval = typeStruct->typbyval;
@@ -243,7 +257,7 @@ init_sql_fcache(FmgrInfo *finfo)
 			 foid);
 	src = DatumGetCString(DirectFunctionCall1(textout, tmp));
 
-	fcache->func_state = init_execution_state(src, argOidVect, nargs);
+	fcache->func_state = init_execution_state(src, argOidVect, nargs, rettype);
 
 	pfree(src);
 

src/include/catalog/pg_proc.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: pg_proc.h,v 1.275.2.3 2006/11/28 19:19:25 tgl Exp $
+ * $Id: pg_proc.h,v 1.275.2.4 2007/02/02 00:04:16 tgl Exp $
  *
  * NOTES
  *	  The script catalog/genbki.sh reads this file and generates .bki
@@ -3150,4 +3150,7 @@ extern Oid ProcedureCreate(const char *procedureName,
 				int parameterCount,
 				const Oid *parameterTypes);
 
+extern void check_sql_fn_retval(Oid rettype, char fn_typtype,
+					List *queryTreeList);
+
 #endif   /* PG_PROC_H */