Ensure cached plans are correctly marked as dependent on role.

If a CTE, subquery, sublink, security invoker view, or coercion
projection references a table with row-level security policies, we
neglected to mark the plan as potentially dependent on which role
is executing it.  This could lead to later executions in the same
session returning or hiding rows that should have been hidden or
returned instead.

Reported-by: Wolfgang Walther
Reviewed-by: Noah Misch
Security: CVE-2024-10976
Backpatch-through: 12

Author: nathan-bossart

src/backend/executor/functions.c

@@ -1972,6 +1972,12 @@ check_sql_fn_retval(List *queryTreeLists,
 		rtr->rtindex = 1;
 		newquery->jointree = makeFromExpr(list_make1(rtr), NULL);
 
+		/*
+		 * Make sure the new query is marked as having row security if the
+		 * original one does.
+		 */
+		newquery->hasRowSecurity = parse->hasRowSecurity;
+
 		/* Replace original query in the correct element of the query list */
 		lfirst(parse_cell) = newquery;
 	}

src/backend/rewrite/rewriteHandler.c

@@ -58,6 +58,12 @@ typedef struct acquireLocksOnSubLinks_context
 	bool		for_execute;	/* AcquireRewriteLocks' forExecute param */
 } acquireLocksOnSubLinks_context;
 
+typedef struct fireRIRonSubLink_context
+{
+	List	   *activeRIRs;
+	bool		hasRowSecurity;
+} fireRIRonSubLink_context;
+
 static bool acquireLocksOnSubLinks(Node *node,
 								   acquireLocksOnSubLinks_context *context);
 static Query *rewriteRuleAction(Query *parsetree,
@@ -1839,6 +1845,12 @@ ApplyRetrieveRule(Query *parsetree,
 	 */
 	rule_action = fireRIRrules(rule_action, activeRIRs);
 
+	/*
+	 * Make sure the query is marked as having row security if the view query
+	 * does.
+	 */
+	parsetree->hasRowSecurity |= rule_action->hasRowSecurity;
+
 	/*
 	 * Now, plug the view query in as a subselect, converting the relation's
 	 * original RTE to a subquery RTE.
@@ -1952,7 +1964,7 @@ markQueryForLocking(Query *qry, Node *jtnode,
  * the SubLink's subselect link with the possibly-rewritten subquery.
  */
 static bool
-fireRIRonSubLink(Node *node, List *activeRIRs)
+fireRIRonSubLink(Node *node, fireRIRonSubLink_context *context)
 {
 	if (node == NULL)
 		return false;
@@ -1962,7 +1974,13 @@ fireRIRonSubLink(Node *node, List *activeRIRs)
 
 		/* Do what we came for */
 		sub->subselect = (Node *) fireRIRrules((Query *) sub->subselect,
-											   activeRIRs);
+											   context->activeRIRs);
+
+		/*
+		 * Remember if any of the sublinks have row security.
+		 */
+		context->hasRowSecurity |= ((Query *) sub->subselect)->hasRowSecurity;
+
 		/* Fall through to process lefthand args of SubLink */
 	}
 
@@ -1971,7 +1989,7 @@ fireRIRonSubLink(Node *node, List *activeRIRs)
 	 * subselects of subselects for us.
 	 */
 	return expression_tree_walker(node, fireRIRonSubLink,
-								  (void *) activeRIRs);
+								  (void *) context);
 }
 
 
@@ -2032,6 +2050,13 @@ fireRIRrules(Query *parsetree, List *activeRIRs)
 		if (rte->rtekind == RTE_SUBQUERY)
 		{
 			rte->subquery = fireRIRrules(rte->subquery, activeRIRs);
+
+			/*
+			 * While we are here, make sure the query is marked as having row
+			 * security if any of its subqueries do.
+			 */
+			parsetree->hasRowSecurity |= rte->subquery->hasRowSecurity;
+
 			continue;
 		}
 
@@ -2145,16 +2170,35 @@ fireRIRrules(Query *parsetree, List *activeRIRs)
 
 		cte->ctequery = (Node *)
 			fireRIRrules((Query *) cte->ctequery, activeRIRs);
+
+		/*
+		 * While we are here, make sure the query is marked as having row
+		 * security if any of its CTEs do.
+		 */
+		parsetree->hasRowSecurity |= ((Query *) cte->ctequery)->hasRowSecurity;
 	}
 
 	/*
 	 * Recurse into sublink subqueries, too.  But we already did the ones in
 	 * the rtable and cteList.
 	 */
 	if (parsetree->hasSubLinks)
-		query_tree_walker(parsetree, fireRIRonSubLink, (void *) activeRIRs,
+	{
+		fireRIRonSubLink_context context;
+
+		context.activeRIRs = activeRIRs;
+		context.hasRowSecurity = false;
+
+		query_tree_walker(parsetree, fireRIRonSubLink, (void *) &context,
 						  QTW_IGNORE_RC_SUBQUERIES);
 
+		/*
+		 * Make sure the query is marked as having row security if any of its
+		 * sublinks do.
+		 */
+		parsetree->hasRowSecurity |= context.hasRowSecurity;
+	}
+
 	/*
 	 * Apply any row-level security policies.  We do this last because it
 	 * requires special recursion detection if the new quals have sublink
@@ -2193,6 +2237,7 @@ fireRIRrules(Query *parsetree, List *activeRIRs)
 			if (hasSubLinks)
 			{
 				acquireLocksOnSubLinks_context context;
+				fireRIRonSubLink_context fire_context;
 
 				/*
 				 * Recursively process the new quals, checking for infinite
@@ -2223,11 +2268,21 @@ fireRIRrules(Query *parsetree, List *activeRIRs)
 				 * Now that we have the locks on anything added by
 				 * get_row_security_policies, fire any RIR rules for them.
 				 */
+				fire_context.activeRIRs = activeRIRs;
+				fire_context.hasRowSecurity = false;
+
 				expression_tree_walker((Node *) securityQuals,
-									   fireRIRonSubLink, (void *) activeRIRs);
+									   fireRIRonSubLink, (void *) &fire_context);
 
 				expression_tree_walker((Node *) withCheckOptions,
-									   fireRIRonSubLink, (void *) activeRIRs);
+									   fireRIRonSubLink, (void *) &fire_context);
+
+				/*
+				 * We can ignore the value of fire_context.hasRowSecurity
+				 * since we only reach this code in cases where hasRowSecurity
+				 * is already true.
+				 */
+				Assert(hasRowSecurity);
 
 				activeRIRs = list_delete_last(activeRIRs);
 			}

src/test/regress/expected/rowsecurity.out

@@ -4556,8 +4556,108 @@ execute q;
 --------------+---
 (0 rows)
 
+-- make sure RLS dependencies in CTEs are handled
+reset role;
+create or replace function rls_f() returns setof rls_t
+  stable language sql
+  as $$ with cte as (select * from rls_t) select * from cte $$;
+prepare r as select current_user, * from rls_f();
+set role regress_rls_alice;
+execute r;
+   current_user    |        c         
+-------------------+------------------
+ regress_rls_alice | invisible to bob
+(1 row)
+
+set role regress_rls_bob;
+execute r;
+ current_user | c 
+--------------+---
+(0 rows)
+
+-- make sure RLS dependencies in subqueries are handled
+reset role;
+create or replace function rls_f() returns setof rls_t
+  stable language sql
+  as $$ select * from (select * from rls_t) _ $$;
+prepare s as select current_user, * from rls_f();
+set role regress_rls_alice;
+execute s;
+   current_user    |        c         
+-------------------+------------------
+ regress_rls_alice | invisible to bob
+(1 row)
+
+set role regress_rls_bob;
+execute s;
+ current_user | c 
+--------------+---
+(0 rows)
+
+-- make sure RLS dependencies in sublinks are handled
+reset role;
+create or replace function rls_f() returns setof rls_t
+  stable language sql
+  as $$ select exists(select * from rls_t)::text $$;
+prepare t as select current_user, * from rls_f();
+set role regress_rls_alice;
+execute t;
+   current_user    |  c   
+-------------------+------
+ regress_rls_alice | true
+(1 row)
+
+set role regress_rls_bob;
+execute t;
+  current_user   |   c   
+-----------------+-------
+ regress_rls_bob | false
+(1 row)
+
+-- make sure RLS dependencies are handled when coercion projections are inserted
+reset role;
+create or replace function rls_f() returns setof rls_t
+  stable language sql
+  as $$ select * from (select array_agg(c) as cs from rls_t) _ group by cs $$;
+prepare u as select current_user, * from rls_f();
+set role regress_rls_alice;
+execute u;
+   current_user    |          c           
+-------------------+----------------------
+ regress_rls_alice | {"invisible to bob"}
+(1 row)
+
+set role regress_rls_bob;
+execute u;
+  current_user   | c 
+-----------------+---
+ regress_rls_bob | 
+(1 row)
+
+-- make sure RLS dependencies in security invoker views are handled
+reset role;
+create view rls_v with (security_invoker) as select * from rls_t;
+grant select on rls_v to regress_rls_alice, regress_rls_bob;
+create or replace function rls_f() returns setof rls_t
+  stable language sql
+  as $$ select * from rls_v $$;
+prepare v as select current_user, * from rls_f();
+set role regress_rls_alice;
+execute v;
+   current_user    |        c         
+-------------------+------------------
+ regress_rls_alice | invisible to bob
+(1 row)
+
+set role regress_rls_bob;
+execute v;
+ current_user | c 
+--------------+---
+(0 rows)
+
 RESET ROLE;
 DROP FUNCTION rls_f();
+DROP VIEW rls_v;
 DROP TABLE rls_t;
 --
 -- Clean up objects

src/test/regress/sql/rowsecurity.sql

@@ -2217,8 +2217,66 @@ execute q;
 set role regress_rls_bob;
 execute q;
 
+-- make sure RLS dependencies in CTEs are handled
+reset role;
+create or replace function rls_f() returns setof rls_t
+  stable language sql
+  as $$ with cte as (select * from rls_t) select * from cte $$;
+prepare r as select current_user, * from rls_f();
+set role regress_rls_alice;
+execute r;
+set role regress_rls_bob;
+execute r;
+
+-- make sure RLS dependencies in subqueries are handled
+reset role;
+create or replace function rls_f() returns setof rls_t
+  stable language sql
+  as $$ select * from (select * from rls_t) _ $$;
+prepare s as select current_user, * from rls_f();
+set role regress_rls_alice;
+execute s;
+set role regress_rls_bob;
+execute s;
+
+-- make sure RLS dependencies in sublinks are handled
+reset role;
+create or replace function rls_f() returns setof rls_t
+  stable language sql
+  as $$ select exists(select * from rls_t)::text $$;
+prepare t as select current_user, * from rls_f();
+set role regress_rls_alice;
+execute t;
+set role regress_rls_bob;
+execute t;
+
+-- make sure RLS dependencies are handled when coercion projections are inserted
+reset role;
+create or replace function rls_f() returns setof rls_t
+  stable language sql
+  as $$ select * from (select array_agg(c) as cs from rls_t) _ group by cs $$;
+prepare u as select current_user, * from rls_f();
+set role regress_rls_alice;
+execute u;
+set role regress_rls_bob;
+execute u;
+
+-- make sure RLS dependencies in security invoker views are handled
+reset role;
+create view rls_v with (security_invoker) as select * from rls_t;
+grant select on rls_v to regress_rls_alice, regress_rls_bob;
+create or replace function rls_f() returns setof rls_t
+  stable language sql
+  as $$ select * from rls_v $$;
+prepare v as select current_user, * from rls_f();
+set role regress_rls_alice;
+execute v;
+set role regress_rls_bob;
+execute v;
+
 RESET ROLE;
 DROP FUNCTION rls_f();
+DROP VIEW rls_v;
 DROP TABLE rls_t;
 
 --

src/tools/pgindent/typedefs.list

@@ -3473,6 +3473,7 @@ fill_string_relopt
 finalize_primnode_context
 find_dependent_phvs_context
 find_expr_references_context
+fireRIRonSubLink_context
 fix_join_expr_context
 fix_scan_expr_context
 fix_upper_expr_context