RLS refactoring

This refactors rewrite/rowsecurity.c to simplify the handling of the
default deny case (reducing the number of places where we check for and
add the default deny policy from three to one) by splitting up the
retrival of the policies from the application of them.

This also allowed us to do away with the policy_id field.  A policy_name
field was added for WithCheckOption policies and is used in error
reporting, when available.

Patch by Dean Rasheed, with various mostly cosmetic changes by me.

Back-patch to 9.5 where RLS was introduced to avoid unnecessary
differences, since we're still in alpha, per discussion with Robert.

Author: sfrost

src/backend/commands/policy.c

@@ -186,9 +186,6 @@ policy_role_list_to_array(List *roles, int *num_roles)
 /*
  * Load row security policy from the catalog, and store it in
  * the relation's relcache entry.
- *
- * We will always set up some kind of policy here.  If no explicit policies
- * are found then an implicit default-deny policy is created.
  */
 void
 RelationBuildRowSecurity(Relation relation)
@@ -246,7 +243,6 @@ RelationBuildRowSecurity(Relation relation)
 			char	   *with_check_value;
 			Expr	   *with_check_qual;
 			char	   *policy_name_value;
-			Oid			policy_id;
 			bool		isnull;
 			RowSecurityPolicy *policy;
 
@@ -298,14 +294,11 @@ RelationBuildRowSecurity(Relation relation)
 			else
 				with_check_qual = NULL;
 
-			policy_id = HeapTupleGetOid(tuple);
-
 			/* Now copy everything into the cache context */
 			MemoryContextSwitchTo(rscxt);
 
 			policy = palloc0(sizeof(RowSecurityPolicy));
 			policy->policy_name = pstrdup(policy_name_value);
-			policy->policy_id = policy_id;
 			policy->polcmd = cmd_value;
 			policy->roles = DatumGetArrayTypePCopy(roles_datum);
 			policy->qual = copyObject(qual_expr);
@@ -326,40 +319,6 @@ RelationBuildRowSecurity(Relation relation)
 
 		systable_endscan(sscan);
 		heap_close(catalog, AccessShareLock);
-
-		/*
-		 * Check if no policies were added
-		 *
-		 * If no policies exist in pg_policy for this relation, then we need
-		 * to create a single default-deny policy.  We use InvalidOid for the
-		 * Oid to indicate that this is the default-deny policy (we may decide
-		 * to ignore the default policy if an extension adds policies).
-		 */
-		if (rsdesc->policies == NIL)
-		{
-			RowSecurityPolicy *policy;
-			Datum		role;
-
-			MemoryContextSwitchTo(rscxt);
-
-			role = ObjectIdGetDatum(ACL_ID_PUBLIC);
-
-			policy = palloc0(sizeof(RowSecurityPolicy));
-			policy->policy_name = pstrdup("default-deny policy");
-			policy->policy_id = InvalidOid;
-			policy->polcmd = '*';
-			policy->roles = construct_array(&role, 1, OIDOID, sizeof(Oid), true,
-											'i');
-			policy->qual = (Expr *) makeConst(BOOLOID, -1, InvalidOid,
-										   sizeof(bool), BoolGetDatum(false),
-											  false, true);
-			policy->with_check_qual = copyObject(policy->qual);
-			policy->hassublinks = false;
-
-			rsdesc->policies = lcons(policy, rsdesc->policies);
-
-			MemoryContextSwitchTo(oldcxt);
-		}
 	}
 	PG_CATCH();
 	{

src/backend/executor/execMain.c

@@ -1815,14 +1815,26 @@ ExecWithCheckOptions(WCOKind kind, ResultRelInfo *resultRelInfo,
 					break;
 				case WCO_RLS_INSERT_CHECK:
 				case WCO_RLS_UPDATE_CHECK:
-					ereport(ERROR,
-							(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+					if (wco->polname != NULL)
+						ereport(ERROR,
+								(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+							 errmsg("new row violates row level security policy \"%s\" for \"%s\"",
+									wco->polname, wco->relname)));
+					else
+						ereport(ERROR,
+								(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 							 errmsg("new row violates row level security policy for \"%s\"",
 									wco->relname)));
 					break;
 				case WCO_RLS_CONFLICT_CHECK:
-					ereport(ERROR,
-							(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+					if (wco->polname != NULL)
+						ereport(ERROR,
+								(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+							 errmsg("new row violates row level security policy \"%s\" (USING expression) for \"%s\"",
+									wco->polname, wco->relname)));
+					else
+						ereport(ERROR,
+								(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
 							 errmsg("new row violates row level security policy (USING expression) for \"%s\"",
 									wco->relname)));
 					break;

src/backend/nodes/copyfuncs.c

@@ -2168,6 +2168,7 @@ _copyWithCheckOption(const WithCheckOption *from)
 
 	COPY_SCALAR_FIELD(kind);
 	COPY_STRING_FIELD(relname);
+	COPY_STRING_FIELD(polname);
 	COPY_NODE_FIELD(qual);
 	COPY_SCALAR_FIELD(cascaded);
 

src/backend/nodes/equalfuncs.c

@@ -2455,6 +2455,7 @@ _equalWithCheckOption(const WithCheckOption *a, const WithCheckOption *b)
 {
 	COMPARE_SCALAR_FIELD(kind);
 	COMPARE_STRING_FIELD(relname);
+	COMPARE_STRING_FIELD(polname);
 	COMPARE_NODE_FIELD(qual);
 	COMPARE_SCALAR_FIELD(cascaded);
 

src/backend/nodes/outfuncs.c

@@ -2403,6 +2403,7 @@ _outWithCheckOption(StringInfo str, const WithCheckOption *node)
 
 	WRITE_ENUM_FIELD(kind, WCOKind);
 	WRITE_STRING_FIELD(relname);
+	WRITE_STRING_FIELD(polname);
 	WRITE_NODE_FIELD(qual);
 	WRITE_BOOL_FIELD(cascaded);
 }

src/backend/nodes/readfuncs.c

@@ -270,6 +270,7 @@ _readWithCheckOption(void)
 
 	READ_ENUM_FIELD(kind, WCOKind);
 	READ_STRING_FIELD(relname);
+	READ_STRING_FIELD(polname);
 	READ_NODE_FIELD(qual);
 	READ_BOOL_FIELD(cascaded);
 

src/backend/rewrite/rewriteHandler.c

@@ -1786,8 +1786,8 @@ fireRIRrules(Query *parsetree, List *activeRIRs, bool forUpdatePushedDown)
 		/*
 		 * Fetch any new security quals that must be applied to this RTE.
 		 */
-		get_row_security_policies(parsetree, parsetree->commandType, rte,
-								  rt_index, &securityQuals, &withCheckOptions,
+		get_row_security_policies(parsetree, rte, rt_index,
+								  &securityQuals, &withCheckOptions,
 								  &hasRowSecurity, &hasSubLinks);
 
 		if (securityQuals != NIL || withCheckOptions != NIL)
@@ -3026,6 +3026,7 @@ rewriteTargetView(Query *parsetree, Relation view)
 			wco = makeNode(WithCheckOption);
 			wco->kind = WCO_VIEW_CHECK;
 			wco->relname = pstrdup(RelationGetRelationName(view));
+			wco->polname = NULL;
 			wco->qual = NULL;
 			wco->cascaded = cascaded;