Add a security_barrier option for views.

When a view is marked as a security barrier, it will not be pulled up
into the containing query, and no quals will be pushed down into it,
so that no function or operator chosen by the user can be applied to
rows not exposed by the view.  Views not configured with this
option cannot provide robust row-level security, but will perform far
better.

Patch by KaiGai Kohei; original problem report by Heikki Linnakangas
(in October 2009!).  Review (in earlier versions) by Noah Misch and
others.  Design advice by Tom Lane and myself.  Further review and
cleanup by me.

13 files changed, 125 insertions, 29 deletions

diff --git a/src/backend/access/common/reloptions.c b/src/backend/access/common/reloptions.c
index 100172fa4ac..7220e0e0ce9 100644
--- a/src/backend/access/common/reloptions.c
+++ b/src/backend/access/common/reloptions.c
@@ -67,6 +67,14 @@ static relopt_bool boolRelOpts[] =
 		},
 		true
 	},
+	{
+		{
+			"security_barrier",
+			"View acts as a row security barrier",
+			RELOPT_KIND_VIEW
+		},
+		false
+	},
 	/* list terminator */
 	{{NULL}}
 };
@@ -781,6 +789,7 @@ extractRelOptions(HeapTuple tuple, TupleDesc tupdesc, Oid amoptions)
 	{
 		case RELKIND_RELATION:
 		case RELKIND_TOASTVALUE:
+		case RELKIND_VIEW:
 		case RELKIND_UNCATALOGED:
 			options = heap_reloptions(classForm->relkind, datum, false);
 			break;
@@ -1139,7 +1148,9 @@ default_reloptions(Datum reloptions, bool validate, relopt_kind kind)
 		{"autovacuum_vacuum_scale_factor", RELOPT_TYPE_REAL,
 		offsetof(StdRdOptions, autovacuum) +offsetof(AutoVacOpts, vacuum_scale_factor)},
 		{"autovacuum_analyze_scale_factor", RELOPT_TYPE_REAL,
-		offsetof(StdRdOptions, autovacuum) +offsetof(AutoVacOpts, analyze_scale_factor)}
+		offsetof(StdRdOptions, autovacuum) +offsetof(AutoVacOpts, analyze_scale_factor)},
+		{"security_barrier", RELOPT_TYPE_BOOL,
+		offsetof(StdRdOptions, security_barrier)},
 	};
 
 	options = parseRelOptions(reloptions, validate, kind, &numoptions);
@@ -1159,7 +1170,7 @@ default_reloptions(Datum reloptions, bool validate, relopt_kind kind)
 }
 
 /*
- * Parse options for heaps and toast tables.
+ * Parse options for heaps, views and toast tables.
  */
 bytea *
 heap_reloptions(char relkind, Datum reloptions, bool validate)
@@ -1181,6 +1192,8 @@ heap_reloptions(char relkind, Datum reloptions, bool validate)
 			return (bytea *) rdopts;
 		case RELKIND_RELATION:
 			return default_reloptions(reloptions, validate, RELOPT_KIND_HEAP);
+		case RELKIND_VIEW:
+			return default_reloptions(reloptions, validate, RELOPT_KIND_VIEW);
 		default:
 			/* other relkinds are not supported */
 			return NULL;
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 8473c9e7f44..4953def029b 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -366,7 +366,9 @@ static void ATExecDropCluster(Relation rel, LOCKMODE lockmode);
 static void ATPrepSetTableSpace(AlteredTableInfo *tab, Relation rel,
 					char *tablespacename, LOCKMODE lockmode);
 static void ATExecSetTableSpace(Oid tableOid, Oid newTableSpace, LOCKMODE lockmode);
-static void ATExecSetRelOptions(Relation rel, List *defList, bool isReset, LOCKMODE lockmode);
+static void ATExecSetRelOptions(Relation rel, List *defList,
+								AlterTableType operation,
+								LOCKMODE lockmode);
 static void ATExecEnableDisableTrigger(Relation rel, char *trigname,
 					   char fires_when, bool skip_system, LOCKMODE lockmode);
 static void ATExecEnableDisableRule(Relation rel, char *rulename,
@@ -2866,6 +2868,7 @@ AlterTableGetLockLevel(List *cmds)
 			case AT_DropCluster:
 			case AT_SetRelOptions:
 			case AT_ResetRelOptions:
+			case AT_ReplaceRelOptions:
 			case AT_SetOptions:
 			case AT_ResetOptions:
 			case AT_SetStorage:
@@ -3094,8 +3097,9 @@ ATPrepCmd(List **wqueue, Relation rel, AlterTableCmd *cmd,
 			pass = AT_PASS_MISC;	/* doesn't actually matter */
 			break;
 		case AT_SetRelOptions:	/* SET (...) */
-		case AT_ResetRelOptions:		/* RESET (...) */
-			ATSimplePermissions(rel, ATT_TABLE | ATT_INDEX);
+		case AT_ResetRelOptions:	/* RESET (...) */
+		case AT_ReplaceRelOptions:	/* reset them all, then set just these */
+			ATSimplePermissions(rel, ATT_TABLE | ATT_INDEX | ATT_VIEW);
 			/* This command never recurses */
 			/* No command-specific prep needed */
 			pass = AT_PASS_MISC;
@@ -3338,12 +3342,10 @@ ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
 			 */
 			break;
 		case AT_SetRelOptions:	/* SET (...) */
-			ATExecSetRelOptions(rel, (List *) cmd->def, false, lockmode);
-			break;
 		case AT_ResetRelOptions:		/* RESET (...) */
-			ATExecSetRelOptions(rel, (List *) cmd->def, true, lockmode);
+		case AT_ReplaceRelOptions:		/* replace entire option list */
+			ATExecSetRelOptions(rel, (List *) cmd->def, cmd->subtype, lockmode);
 			break;
-
 		case AT_EnableTrig:		/* ENABLE TRIGGER name */
 			ATExecEnableDisableTrigger(rel, cmd->name,
 								   TRIGGER_FIRES_ON_ORIGIN, false, lockmode);
@@ -8271,10 +8273,11 @@ ATPrepSetTableSpace(AlteredTableInfo *tab, Relation rel, char *tablespacename, L
 }
 
 /*
- * ALTER TABLE/INDEX SET (...) or RESET (...)
+ * Set, reset, or replace reloptions.
  */
 static void
-ATExecSetRelOptions(Relation rel, List *defList, bool isReset, LOCKMODE lockmode)
+ATExecSetRelOptions(Relation rel, List *defList, AlterTableType operation,
+					LOCKMODE lockmode)
 {
 	Oid			relid;
 	Relation	pgclass;
@@ -8288,28 +8291,44 @@ ATExecSetRelOptions(Relation rel, List *defList, bool isReset, LOCKMODE lockmode
 	bool		repl_repl[Natts_pg_class];
 	static char *validnsps[] = HEAP_RELOPT_NAMESPACES;
 
-	if (defList == NIL)
+	if (defList == NIL && operation != AT_ReplaceRelOptions)
 		return;					/* nothing to do */
 
 	pgclass = heap_open(RelationRelationId, RowExclusiveLock);
 
-	/* Get the old reloptions */
+	/* Fetch heap tuple */
 	relid = RelationGetRelid(rel);
 	tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(relid));
 	if (!HeapTupleIsValid(tuple))
 		elog(ERROR, "cache lookup failed for relation %u", relid);
 
-	datum = SysCacheGetAttr(RELOID, tuple, Anum_pg_class_reloptions, &isnull);
+	if (operation == AT_ReplaceRelOptions)
+	{
+		/*
+		 * If we're supposed to replace the reloptions list, we just pretend
+		 * there were none before.
+		 */
+		datum = (Datum) 0;
+		isnull = true;
+	}
+	else
+	{
+		/* Get the old reloptions */
+		datum = SysCacheGetAttr(RELOID, tuple, Anum_pg_class_reloptions,
+								&isnull);
+	}
 
 	/* Generate new proposed reloptions (text array) */
 	newOptions = transformRelOptions(isnull ? (Datum) 0 : datum,
-								   defList, NULL, validnsps, false, isReset);
+								   defList, NULL, validnsps, false,
+								   operation == AT_ResetRelOptions);
 
 	/* Validate */
 	switch (rel->rd_rel->relkind)
 	{
 		case RELKIND_RELATION:
 		case RELKIND_TOASTVALUE:
+		case RELKIND_VIEW:
 			(void) heap_reloptions(rel->rd_rel->relkind, newOptions, true);
 			break;
 		case RELKIND_INDEX:
@@ -8357,15 +8376,30 @@ ATExecSetRelOptions(Relation rel, List *defList, bool isReset, LOCKMODE lockmode
 
 		toastrel = heap_open(toastid, lockmode);
 
-		/* Get the old reloptions */
+		/* Fetch heap tuple */
 		tuple = SearchSysCache1(RELOID, ObjectIdGetDatum(toastid));
 		if (!HeapTupleIsValid(tuple))
 			elog(ERROR, "cache lookup failed for relation %u", toastid);
 
-		datum = SysCacheGetAttr(RELOID, tuple, Anum_pg_class_reloptions, &isnull);
+		if (operation == AT_ReplaceRelOptions)
+		{
+			/*
+			 * If we're supposed to replace the reloptions list, we just
+			 * pretend there were none before.
+			 */
+			datum = (Datum) 0;
+			isnull = true;
+		}
+		else
+		{
+			/* Get the old reloptions */
+			datum = SysCacheGetAttr(RELOID, tuple, Anum_pg_class_reloptions,
+									&isnull);
+		}
 
 		newOptions = transformRelOptions(isnull ? (Datum) 0 : datum,
-								defList, "toast", validnsps, false, isReset);
+								defList, "toast", validnsps, false,
+								operation == AT_ResetRelOptions);
 
 		(void) heap_reloptions(RELKIND_TOASTVALUE, newOptions, true);
 
diff --git a/src/backend/commands/view.c b/src/backend/commands/view.c
index b2381996586..3edcd33eaf4 100644
--- a/src/backend/commands/view.c
+++ b/src/backend/commands/view.c
@@ -32,6 +32,7 @@
 #include "utils/builtins.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
+#include "utils/syscache.h"
 
 
 static void checkViewTupleDesc(TupleDesc newdesc, TupleDesc olddesc);
@@ -98,7 +99,7 @@ isViewOnTempTable_walker(Node *node, void *context)
  */
 static Oid
 DefineVirtualRelation(const RangeVar *relation, List *tlist, bool replace,
-					  Oid namespaceId)
+					  Oid namespaceId, List *options)
 {
 	Oid			viewOid;
 	CreateStmt *createStmt = makeNode(CreateStmt);
@@ -166,6 +167,8 @@ DefineVirtualRelation(const RangeVar *relation, List *tlist, bool replace,
 	{
 		Relation	rel;
 		TupleDesc	descriptor;
+		List	   *atcmds = NIL;
+		AlterTableCmd *atcmd;
 
 		/*
 		 * Yes.  Get exclusive lock on the existing view ...
@@ -204,20 +207,26 @@ DefineVirtualRelation(const RangeVar *relation, List *tlist, bool replace,
 		checkViewTupleDesc(descriptor, rel->rd_att);
 
 		/*
+		 * The new options list replaces the existing options list, even
+		 * if it's empty.
+		 */
+		atcmd = makeNode(AlterTableCmd);
+		atcmd->subtype = AT_ReplaceRelOptions;
+		atcmd->def = (Node *) options;
+		atcmds = lappend(atcmds, atcmd);
+
+		/*
 		 * If new attributes have been added, we must add pg_attribute entries
 		 * for them.  It is convenient (although overkill) to use the ALTER
 		 * TABLE ADD COLUMN infrastructure for this.
 		 */
 		if (list_length(attrList) > rel->rd_att->natts)
 		{
-			List	   *atcmds = NIL;
 			ListCell   *c;
 			int			skip = rel->rd_att->natts;
 
 			foreach(c, attrList)
 			{
-				AlterTableCmd *atcmd;
-
 				if (skip > 0)
 				{
 					skip--;
@@ -228,9 +237,11 @@ DefineVirtualRelation(const RangeVar *relation, List *tlist, bool replace,
 				atcmd->def = (Node *) lfirst(c);
 				atcmds = lappend(atcmds, atcmd);
 			}
-			AlterTableInternal(viewOid, atcmds, true);
 		}
 
+		/* OK, let's do it. */
+		AlterTableInternal(viewOid, atcmds, true);
+
 		/*
 		 * Seems okay, so return the OID of the pre-existing view.
 		 */
@@ -250,7 +261,8 @@ DefineVirtualRelation(const RangeVar *relation, List *tlist, bool replace,
 		createStmt->tableElts = attrList;
 		createStmt->inhRelations = NIL;
 		createStmt->constraints = NIL;
-		createStmt->options = list_make1(defWithOids(false));
+		createStmt->options = options;
+		createStmt->options = lappend(options, defWithOids(false));
 		createStmt->oncommit = ONCOMMIT_NOOP;
 		createStmt->tablespacename = NULL;
 		createStmt->if_not_exists = false;
@@ -513,7 +525,7 @@ DefineView(ViewStmt *stmt, const char *queryString)
 	 * aborted.
 	 */
 	viewOid = DefineVirtualRelation(view, viewParse->targetList,
-									stmt->replace, namespaceId);
+									stmt->replace, namespaceId, stmt->options);
 
 	/*
 	 * The relation we have just created is not visible to any other commands
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 7178b529a2e..dd2dd25ed1b 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -1965,6 +1965,7 @@ _copyRangeTblEntry(const RangeTblEntry *from)
 	COPY_SCALAR_FIELD(relid);
 	COPY_SCALAR_FIELD(relkind);
 	COPY_NODE_FIELD(subquery);
+	COPY_SCALAR_FIELD(security_barrier);
 	COPY_SCALAR_FIELD(jointype);
 	COPY_NODE_FIELD(joinaliasvars);
 	COPY_NODE_FIELD(funcexpr);
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 9f7daf4eda2..c2fdb2ba365 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -2228,6 +2228,7 @@ _equalRangeTblEntry(const RangeTblEntry *a, const RangeTblEntry *b)
 	COMPARE_SCALAR_FIELD(relid);
 	COMPARE_SCALAR_FIELD(relkind);
 	COMPARE_NODE_FIELD(subquery);
+	COMPARE_SCALAR_FIELD(security_barrier);
 	COMPARE_SCALAR_FIELD(jointype);
 	COMPARE_NODE_FIELD(joinaliasvars);
 	COMPARE_NODE_FIELD(funcexpr);
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index bef1e78f5a2..cdc2cab55c6 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -2321,6 +2321,7 @@ _outRangeTblEntry(StringInfo str, const RangeTblEntry *node)
 			break;
 		case RTE_SUBQUERY:
 			WRITE_NODE_FIELD(subquery);
+			WRITE_BOOL_FIELD(security_barrier);
 			break;
 		case RTE_JOIN:
 			WRITE_ENUM_FIELD(jointype, JoinType);
diff --git a/src/backend/nodes/readfuncs.c b/src/backend/nodes/readfuncs.c
index 3de20ad93a9..fa9ad164234 100644
--- a/src/backend/nodes/readfuncs.c
+++ b/src/backend/nodes/readfuncs.c
@@ -1192,6 +1192,7 @@ _readRangeTblEntry(void)
 			break;
 		case RTE_SUBQUERY:
 			READ_NODE_FIELD(subquery);
+			READ_BOOL_FIELD(security_barrier);
 			break;
 		case RTE_JOIN:
 			READ_ENUM_FIELD(jointype, JoinType);
diff --git a/src/backend/optimizer/path/allpaths.c b/src/backend/optimizer/path/allpaths.c
index 815b996a131..b3777eae2e4 100644
--- a/src/backend/optimizer/path/allpaths.c
+++ b/src/backend/optimizer/path/allpaths.c
@@ -744,6 +744,11 @@ set_subquery_pathlist(PlannerInfo *root, RelOptInfo *rel,
 	 * pseudoconstant clauses; better to have the gating node above the
 	 * subquery.
 	 *
+	 * Also, if the sub-query has "security_barrier" flag, it means the
+	 * sub-query originated from a view that must enforce row-level security.
+	 * We must not push down quals in order to avoid information leaks, either
+	 * via side-effects or error output.
+	 *
 	 * Non-pushed-down clauses will get evaluated as qpquals of the
 	 * SubqueryScan node.
 	 *
@@ -762,7 +767,16 @@ set_subquery_pathlist(PlannerInfo *root, RelOptInfo *rel,
 			RestrictInfo *rinfo = (RestrictInfo *) lfirst(l);
 			Node	   *clause = (Node *) rinfo->clause;
 
+			/*
+			 * XXX.  You might wonder why we're testing rte->security_barrier
+			 * qual-by-qual here rather than hoisting the test up into the
+			 * surrounding if statement; after all, the answer will be the
+			 * same for all quals.  The answer is that we expect to shortly
+			 * change this logic to allow pushing down some quals that use only
+			 * "leakproof" operators even through a security barrier.
+			 */
 			if (!rinfo->pseudoconstant &&
+				!rte->security_barrier &&
 				qual_is_pushdown_safe(subquery, rti, clause, differentTypes))
 			{
 				/* Push it down */
diff --git a/src/backend/optimizer/prep/prepjointree.c b/src/backend/optimizer/prep/prepjointree.c
index 8bb011b7116..a711c4f646b 100644
--- a/src/backend/optimizer/prep/prepjointree.c
+++ b/src/backend/optimizer/prep/prepjointree.c
@@ -543,6 +543,7 @@ pull_up_subqueries(PlannerInfo *root, Node *jtnode,
 		 */
 		if (rte->rtekind == RTE_SUBQUERY &&
 			is_simple_subquery(rte->subquery) &&
+			!rte->security_barrier &&
 			(containing_appendrel == NULL ||
 			 is_safe_append_member(rte->subquery)))
 			return pull_up_simple_subquery(root, jtnode, rte,
@@ -712,6 +713,7 @@ pull_up_simple_subquery(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte,
 	 * pull_up_subqueries.
 	 */
 	if (is_simple_subquery(subquery) &&
+		!rte->security_barrier &&
 		(containing_appendrel == NULL || is_safe_append_member(subquery)))
 	{
 		/* good to go */
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 7e8f39abdf7..8943c5b7d04 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -7322,26 +7322,28 @@ transaction_mode_list_or_empty:
  *
  *****************************************************************************/
 
-ViewStmt: CREATE OptTemp VIEW qualified_name opt_column_list
+ViewStmt: CREATE OptTemp VIEW qualified_name opt_column_list opt_reloptions
 				AS SelectStmt opt_check_option
 				{
 					ViewStmt *n = makeNode(ViewStmt);
 					n->view = $4;
 					n->view->relpersistence = $2;
 					n->aliases = $5;
-					n->query = $7;
+					n->query = $8;
 					n->replace = false;
+					n->options = $6;
 					$$ = (Node *) n;
 				}
-		| CREATE OR REPLACE OptTemp VIEW qualified_name opt_column_list
+		| CREATE OR REPLACE OptTemp VIEW qualified_name opt_column_list opt_reloptions
 				AS SelectStmt opt_check_option
 				{
 					ViewStmt *n = makeNode(ViewStmt);
 					n->view = $6;
 					n->view->relpersistence = $4;
 					n->aliases = $7;
-					n->query = $9;
+					n->query = $10;
 					n->replace = true;
+					n->options = $8;
 					$$ = (Node *) n;
 				}
 		;
diff --git a/src/backend/rewrite/rewriteHandler.c b/src/backend/rewrite/rewriteHandler.c
index a6f4141dd7b..8448226bfc8 100644
--- a/src/backend/rewrite/rewriteHandler.c
+++ b/src/backend/rewrite/rewriteHandler.c
@@ -1382,6 +1382,7 @@ ApplyRetrieveRule(Query *parsetree,
 
 	rte->rtekind = RTE_SUBQUERY;
 	rte->relid = InvalidOid;
+	rte->security_barrier = RelationIsSecurityView(relation);
 	rte->subquery = rule_action;
 	rte->inh = false;			/* must not be set for a subquery */
 
diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c
index abef8abc382..bb411f9ad1d 100644
--- a/src/backend/utils/adt/selfuncs.c
+++ b/src/backend/utils/adt/selfuncs.c
@@ -4373,6 +4373,19 @@ examine_simple_variable(PlannerInfo *root, Var *var,
 			return;
 
 		/*
+		 * If the sub-query originated from a view with the security_barrier
+		 * attribute, we treat it as a black-box from outside of the view.
+		 * This is probably a harsher restriction than necessary; it's
+		 * certainly OK for the selectivity estimator (which is a C function,
+		 * and therefore omnipotent anyway) to look at the statistics.  But
+		 * many selectivity estimators will happily *invoke the operator
+		 * function* to try to work out a good estimate - and that's not OK.
+		 * So for now, we do this.
+		 */
+		if (rte->security_barrier)
+			return;
+
+		/*
 		 * OK, fetch RelOptInfo for subquery.  Note that we don't change the
 		 * rel returned in vardata, since caller expects it to be a rel of the
 		 * caller's query level.  Because we might already be recursing, we
diff --git a/src/backend/utils/cache/relcache.c b/src/backend/utils/cache/relcache.c
index f9ad75e7f89..cfb48d3ec4c 100644
--- a/src/backend/utils/cache/relcache.c
+++ b/src/backend/utils/cache/relcache.c
@@ -374,6 +374,7 @@ RelationParseRelOptions(Relation relation, HeapTuple tuple)
 		case RELKIND_RELATION:
 		case RELKIND_TOASTVALUE:
 		case RELKIND_INDEX:
+		case RELKIND_VIEW:
 			break;
 		default:
 			return;