Fix security checks for selectivity estimation functions with RLS.

In commit e2d4ef8, security checks were added to prevent
user-supplied operators from running over data from pg_statistic
unless the user has table or column privileges on the table, or the
operator is leakproof. For a table with RLS, however, checking for
table or column privileges is insufficient, since that does not
guarantee that the user has permission to view all of the column's
data.

Fix this by also checking for securityQuals on the RTE, and insisting
that the operator be leakproof if there are any. Thus the
leakproofness check will only be skipped if there are no securityQuals
and the user has table or column privileges on the table -- i.e., only
if we know that the user has access to all the data in the column.

Back-patch to 9.5 where RLS was added.

Dean Rasheed, reviewed by Jonathan Katz and Stephen Frost.

Security: CVE-2019-10130

Author: deanrasheed

src/backend/utils/adt/selfuncs.c

@@ -4597,9 +4597,13 @@ examine_variable(PlannerInfo *root, Node *node, int varRelid,
 								 * For simplicity, we insist on the whole
 								 * table being selectable, rather than trying
 								 * to identify which column(s) the index
-								 * depends on.
+								 * depends on.  Also require all rows to be
+								 * selectable --- there must be no
+								 * securityQuals from security barrier views
+								 * or RLS policies.
 								 */
 								vardata->acl_ok =
+									rte->securityQuals == NIL &&
 									(pg_class_aclcheck(rte->relid, GetUserId(),
 													   ACL_SELECT) == ACLCHECK_OK);
 							}
@@ -4663,12 +4667,17 @@ examine_simple_variable(PlannerInfo *root, Var *var,
 
 		if (HeapTupleIsValid(vardata->statsTuple))
 		{
-			/* check if user has permission to read this column */
+			/*
+			 * Check if user has permission to read this column.  We require
+			 * all rows to be accessible, so there must be no securityQuals
+			 * from security barrier views or RLS policies.
+			 */
 			vardata->acl_ok =
-				(pg_class_aclcheck(rte->relid, GetUserId(),
-								   ACL_SELECT) == ACLCHECK_OK) ||
-				(pg_attribute_aclcheck(rte->relid, var->varattno, GetUserId(),
-									   ACL_SELECT) == ACLCHECK_OK);
+				rte->securityQuals == NIL &&
+				((pg_class_aclcheck(rte->relid, GetUserId(),
+									ACL_SELECT) == ACLCHECK_OK) ||
+				 (pg_attribute_aclcheck(rte->relid, var->varattno, GetUserId(),
+										ACL_SELECT) == ACLCHECK_OK));
 		}
 		else
 		{

src/test/regress/expected/rowsecurity.out

@@ -3937,6 +3937,27 @@ RESET SESSION AUTHORIZATION;
 DROP VIEW rls_view;
 DROP TABLE rls_tbl;
 DROP TABLE ref_tbl;
+-- Leaky operator test
+CREATE TABLE rls_tbl (a int);
+INSERT INTO rls_tbl SELECT x/10 FROM generate_series(1, 100) x;
+ANALYZE rls_tbl;
+ALTER TABLE rls_tbl ENABLE ROW LEVEL SECURITY;
+GRANT SELECT ON rls_tbl TO regress_rls_alice;
+SET SESSION AUTHORIZATION regress_rls_alice;
+CREATE FUNCTION op_leak(int, int) RETURNS bool
+    AS 'BEGIN RAISE NOTICE ''op_leak => %, %'', $1, $2; RETURN $1 < $2; END'
+    LANGUAGE plpgsql;
+CREATE OPERATOR <<< (procedure = op_leak, leftarg = int, rightarg = int,
+                     restrict = scalarltsel);
+SELECT * FROM rls_tbl WHERE a <<< 1000;
+ a 
+---
+(0 rows)
+
+DROP OPERATOR <<< (int, int);
+DROP FUNCTION op_leak(int, int);
+RESET SESSION AUTHORIZATION;
+DROP TABLE rls_tbl;
 --
 -- Clean up objects
 --

src/test/regress/sql/rowsecurity.sql

@@ -1790,6 +1790,26 @@ DROP VIEW rls_view;
 DROP TABLE rls_tbl;
 DROP TABLE ref_tbl;
 
+-- Leaky operator test
+CREATE TABLE rls_tbl (a int);
+INSERT INTO rls_tbl SELECT x/10 FROM generate_series(1, 100) x;
+ANALYZE rls_tbl;
+
+ALTER TABLE rls_tbl ENABLE ROW LEVEL SECURITY;
+GRANT SELECT ON rls_tbl TO regress_rls_alice;
+
+SET SESSION AUTHORIZATION regress_rls_alice;
+CREATE FUNCTION op_leak(int, int) RETURNS bool
+    AS 'BEGIN RAISE NOTICE ''op_leak => %, %'', $1, $2; RETURN $1 < $2; END'
+    LANGUAGE plpgsql;
+CREATE OPERATOR <<< (procedure = op_leak, leftarg = int, rightarg = int,
+                     restrict = scalarltsel);
+SELECT * FROM rls_tbl WHERE a <<< 1000;
+DROP OPERATOR <<< (int, int);
+DROP FUNCTION op_leak(int, int);
+RESET SESSION AUTHORIZATION;
+DROP TABLE rls_tbl;
+
 --
 -- Clean up objects
 --