Restrict accesses to non-system views and foreign tables during pg_dump.

When pg_dump retrieves the list of database objects and performs the
data dump, there was possibility that objects are replaced with others
of the same name, such as views, and access them. This vulnerability
could result in code execution with superuser privileges during the
pg_dump process.

This issue can arise when dumping data of sequences, foreign
tables (only 13 or later), or tables registered with a WHERE clause in
the extension configuration table.

To address this, pg_dump now utilizes the newly introduced
restrict_nonsystem_relation_kind GUC parameter to restrict the
accesses to non-system views and foreign tables during the dump
process. This new GUC parameter is added to back branches too, but
these changes do not require cluster recreation.

Back-patch to all supported branches.

Reviewed-by: Noah Misch
Security: CVE-2024-7348
Backpatch-through: 12

11 files changed, 211 insertions, 1 deletions

diff --git a/src/backend/foreign/foreign.c b/src/backend/foreign/foreign.c
index f4f35728b40..bb67d9f92b8 100644
--- a/src/backend/foreign/foreign.c
+++ b/src/backend/foreign/foreign.c
@@ -22,6 +22,7 @@
 #include "foreign/foreign.h"
 #include "funcapi.h"
 #include "miscadmin.h"
+#include "tcop/tcopprot.h"
 #include "utils/builtins.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"
@@ -326,6 +327,15 @@ GetFdwRoutine(Oid fdwhandler)
 	Datum		datum;
 	FdwRoutine *routine;
 
+	/* Check if the access to foreign tables is restricted */
+	if (unlikely((restrict_nonsystem_relation_kind & RESTRICT_RELKIND_FOREIGN_TABLE) != 0))
+	{
+		/* there must not be built-in FDW handler  */
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("access to non-system foreign table is restricted")));
+	}
+
 	datum = OidFunctionCall0(fdwhandler);
 	routine = (FdwRoutine *) DatumGetPointer(datum);
 
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 6b64c4a362d..a5c32b91cca 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -41,6 +41,7 @@
 #include "parser/parse_clause.h"
 #include "parser/parsetree.h"
 #include "partitioning/partprune.h"
+#include "tcop/tcopprot.h"
 #include "utils/lsyscache.h"
 
 
@@ -7141,7 +7142,19 @@ make_modifytable(PlannerInfo *root, Plan *subplan,
 
 			if (rte->rtekind == RTE_RELATION &&
 				rte->relkind == RELKIND_FOREIGN_TABLE)
+			{
+				/* Check if the access to foreign tables is restricted */
+				if (unlikely((restrict_nonsystem_relation_kind & RESTRICT_RELKIND_FOREIGN_TABLE) != 0))
+				{
+					/* there must not be built-in foreign tables */
+					Assert(rte->relid >= FirstNormalObjectId);
+					ereport(ERROR,
+							(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+							 errmsg("access to non-system foreign table is restricted")));
+				}
+
 				fdwroutine = GetFdwRoutineByRelId(rte->relid);
+			}
 			else
 				fdwroutine = NULL;
 		}
diff --git a/src/backend/optimizer/util/plancat.c b/src/backend/optimizer/util/plancat.c
index 775955363ef..86655f05dc8 100644
--- a/src/backend/optimizer/util/plancat.c
+++ b/src/backend/optimizer/util/plancat.c
@@ -45,6 +45,7 @@
 #include "rewrite/rewriteManip.h"
 #include "statistics/statistics.h"
 #include "storage/bufmgr.h"
+#include "tcop/tcopprot.h"
 #include "utils/builtins.h"
 #include "utils/lsyscache.h"
 #include "utils/partcache.h"
@@ -528,6 +529,17 @@ get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent,
 	/* Grab foreign-table info using the relcache, while we have it */
 	if (relation->rd_rel->relkind == RELKIND_FOREIGN_TABLE)
 	{
+		/* Check if the access to foreign tables is restricted */
+		if (unlikely((restrict_nonsystem_relation_kind & RESTRICT_RELKIND_FOREIGN_TABLE) != 0))
+		{
+			/* there must not be built-in foreign tables */
+			Assert(RelationGetRelid(relation) >= FirstNormalObjectId);
+
+			ereport(ERROR,
+					(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+					 errmsg("access to non-system foreign table is restricted")));
+		}
+
 		rel->serverid = GetForeignServerIdByRelId(RelationGetRelid(relation));
 		rel->fdwroutine = GetFdwRoutineForRelation(relation, true);
 	}
diff --git a/src/backend/rewrite/rewriteHandler.c b/src/backend/rewrite/rewriteHandler.c
index e1d805d113e..c223a2c50af 100644
--- a/src/backend/rewrite/rewriteHandler.c
+++ b/src/backend/rewrite/rewriteHandler.c
@@ -40,6 +40,7 @@
 #include "rewrite/rewriteManip.h"
 #include "rewrite/rewriteSearchCycle.h"
 #include "rewrite/rowsecurity.h"
+#include "tcop/tcopprot.h"
 #include "utils/builtins.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"
@@ -1729,6 +1730,14 @@ ApplyRetrieveRule(Query *parsetree,
 	if (rule->qual != NULL)
 		elog(ERROR, "cannot handle qualified ON SELECT rule");
 
+	/* Check if the expansion of non-system views are restricted */
+	if (unlikely((restrict_nonsystem_relation_kind & RESTRICT_RELKIND_VIEW) != 0 &&
+				 RelationGetRelid(relation) >= FirstNormalObjectId))
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("access to non-system view \"%s\" is restricted",
+						RelationGetRelationName(relation))));
+
 	if (rt_index == parsetree->resultRelation)
 	{
 		/*
@@ -3212,6 +3221,14 @@ rewriteTargetView(Query *parsetree, Relation view)
 		}
 	}
 
+	/* Check if the expansion of non-system views are restricted */
+	if (unlikely((restrict_nonsystem_relation_kind & RESTRICT_RELKIND_VIEW) != 0 &&
+				 RelationGetRelid(view) >= FirstNormalObjectId))
+		ereport(ERROR,
+				(errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
+				 errmsg("access to non-system view \"%s\" is restricted",
+						RelationGetRelationName(view))));
+
 	/*
 	 * The view must be updatable, else fail.
 	 *
diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 034e0100bf0..7fe14c5402c 100644
--- a/src/backend/tcop/postgres.c
+++ b/src/backend/tcop/postgres.c
@@ -79,6 +79,7 @@
 #include "utils/snapmgr.h"
 #include "utils/timeout.h"
 #include "utils/timestamp.h"
+#include "utils/varlena.h"
 
 /* ----------------
  *		global variables
@@ -103,6 +104,9 @@ int			PostAuthDelay = 0;
 /* Time between checks that the client is still connected. */
 int			client_connection_check_interval = 0;
 
+/* flags for non-system relation kinds to restrict use */
+int			restrict_nonsystem_relation_kind;
+
 /* ----------------
  *		private typedefs etc
  * ----------------
@@ -3667,6 +3671,66 @@ assign_transaction_timeout(int newval, void *extra)
 	}
 }
 
+/*
+ * GUC check_hook for restrict_nonsystem_relation_kind
+ */
+bool
+check_restrict_nonsystem_relation_kind(char **newval, void **extra, GucSource source)
+{
+	char	   *rawstring;
+	List	   *elemlist;
+	ListCell   *l;
+	int			flags = 0;
+
+	/* Need a modifiable copy of string */
+	rawstring = pstrdup(*newval);
+
+	if (!SplitIdentifierString(rawstring, ',', &elemlist))
+	{
+		/* syntax error in list */
+		GUC_check_errdetail("List syntax is invalid.");
+		pfree(rawstring);
+		list_free(elemlist);
+		return false;
+	}
+
+	foreach(l, elemlist)
+	{
+		char	   *tok = (char *) lfirst(l);
+
+		if (pg_strcasecmp(tok, "view") == 0)
+			flags |= RESTRICT_RELKIND_VIEW;
+		else if (pg_strcasecmp(tok, "foreign-table") == 0)
+			flags |= RESTRICT_RELKIND_FOREIGN_TABLE;
+		else
+		{
+			GUC_check_errdetail("Unrecognized key word: \"%s\".", tok);
+			pfree(rawstring);
+			list_free(elemlist);
+			return false;
+		}
+	}
+
+	pfree(rawstring);
+	list_free(elemlist);
+
+	/* Save the flags in *extra, for use by the assign function */
+	*extra = guc_malloc(ERROR, sizeof(int));
+	*((int *) *extra) = flags;
+
+	return true;
+}
+
+/*
+ * GUC assign_hook for restrict_nonsystem_relation_kind
+ */
+void
+assign_restrict_nonsystem_relation_kind(const char *newval, void *extra)
+{
+	int		   *flags = (int *) extra;
+
+	restrict_nonsystem_relation_kind = *flags;
+}
 
 /*
  * set_debug_options --- apply "-d N" command line option
diff --git a/src/backend/utils/misc/guc_tables.c b/src/backend/utils/misc/guc_tables.c
index 6f4188599b1..319f6d7cc02 100644
--- a/src/backend/utils/misc/guc_tables.c
+++ b/src/backend/utils/misc/guc_tables.c
@@ -578,6 +578,7 @@ static char *server_encoding_string;
 static char *server_version_string;
 static int	server_version_num;
 static char *debug_io_direct_string;
+static char *restrict_nonsystem_relation_kind_string;
 
 #ifdef HAVE_SYSLOG
 #define	DEFAULT_SYSLOG_FACILITY LOG_LOCAL0
@@ -4705,6 +4706,17 @@ struct config_string ConfigureNamesString[] =
 		check_synchronized_standby_slots, assign_synchronized_standby_slots, NULL
 	},
 
+	{
+		{"restrict_nonsystem_relation_kind", PGC_USERSET, CLIENT_CONN_STATEMENT,
+			gettext_noop("Sets relation kinds of non-system relation to restrict use"),
+			NULL,
+			GUC_LIST_INPUT | GUC_NOT_IN_SAMPLE
+		},
+		&restrict_nonsystem_relation_kind_string,
+		"",
+		check_restrict_nonsystem_relation_kind, assign_restrict_nonsystem_relation_kind, NULL
+	},
+
 	/* End-of-list marker */
 	{
 		{NULL, 0, 0, NULL, NULL}, NULL, NULL, NULL, NULL, NULL
diff --git a/src/bin/pg_dump/pg_dump.c b/src/bin/pg_dump/pg_dump.c
index 9202a43eb20..9737e1e189f 100644
--- a/src/bin/pg_dump/pg_dump.c
+++ b/src/bin/pg_dump/pg_dump.c
@@ -336,6 +336,7 @@ static bool nonemptyReloptions(const char *reloptions);
 static void appendReloptionsArrayAH(PQExpBuffer buffer, const char *reloptions,
 									const char *prefix, Archive *fout);
 static char *get_synchronized_snapshot(Archive *fout);
+static void set_restrict_relation_kind(Archive *AH, const char *value);
 static void setupDumpWorker(Archive *AH);
 static TableInfo *getRootTableInfo(const TableInfo *tbinfo);
 static bool forcePartitionRootLoad(const TableInfo *tbinfo);
@@ -1294,6 +1295,13 @@ setup_connection(Archive *AH, const char *dumpencoding,
 	}
 
 	/*
+	 * For security reasons, we restrict the expansion of non-system views and
+	 * access to foreign tables during the pg_dump process. This restriction
+	 * is adjusted when dumping foreign table data.
+	 */
+	set_restrict_relation_kind(AH, "view, foreign-table");
+
+	/*
 	 * Initialize prepared-query state to "nothing prepared".  We do this here
 	 * so that a parallel dump worker will have its own state.
 	 */
@@ -2161,6 +2169,10 @@ dumpTableData_copy(Archive *fout, const void *dcontext)
 	 */
 	if (tdinfo->filtercond || tbinfo->relkind == RELKIND_FOREIGN_TABLE)
 	{
+		/* Temporary allows to access to foreign tables to dump data */
+		if (tbinfo->relkind == RELKIND_FOREIGN_TABLE)
+			set_restrict_relation_kind(fout, "view");
+
 		appendPQExpBufferStr(q, "COPY (SELECT ");
 		/* klugery to get rid of parens in column list */
 		if (strlen(column_list) > 2)
@@ -2272,6 +2284,11 @@ dumpTableData_copy(Archive *fout, const void *dcontext)
 					   classname);
 
 	destroyPQExpBuffer(q);
+
+	/* Revert back the setting */
+	if (tbinfo->relkind == RELKIND_FOREIGN_TABLE)
+		set_restrict_relation_kind(fout, "view, foreign-table");
+
 	return 1;
 }
 
@@ -2298,6 +2315,10 @@ dumpTableData_insert(Archive *fout, const void *dcontext)
 	int			rows_per_statement = dopt->dump_inserts;
 	int			rows_this_statement = 0;
 
+	/* Temporary allows to access to foreign tables to dump data */
+	if (tbinfo->relkind == RELKIND_FOREIGN_TABLE)
+		set_restrict_relation_kind(fout, "view");
+
 	/*
 	 * If we're going to emit INSERTs with column names, the most efficient
 	 * way to deal with generated columns is to exclude them entirely.  For
@@ -2537,6 +2558,10 @@ dumpTableData_insert(Archive *fout, const void *dcontext)
 		destroyPQExpBuffer(insertStmt);
 	free(attgenerated);
 
+	/* Revert back the setting */
+	if (tbinfo->relkind == RELKIND_FOREIGN_TABLE)
+		set_restrict_relation_kind(fout, "view, foreign-table");
+
 	return 1;
 }
 
@@ -4711,6 +4736,28 @@ is_superuser(Archive *fout)
 }
 
 /*
+ * Set the given value to restrict_nonsystem_relation_kind value. Since
+ * restrict_nonsystem_relation_kind is introduced in minor version releases,
+ * the setting query is effective only where available.
+ */
+static void
+set_restrict_relation_kind(Archive *AH, const char *value)
+{
+	PQExpBuffer query = createPQExpBuffer();
+	PGresult   *res;
+
+	appendPQExpBuffer(query,
+					  "SELECT set_config(name, '%s', false) "
+					  "FROM pg_settings "
+					  "WHERE name = 'restrict_nonsystem_relation_kind'",
+					  value);
+	res = ExecuteSqlQuery(AH, query->data, PGRES_TUPLES_OK);
+
+	PQclear(res);
+	destroyPQExpBuffer(query);
+}
+
+/*
  * getSubscriptions
  *	  get information about subscriptions
  */
diff --git a/src/include/tcop/tcopprot.h b/src/include/tcop/tcopprot.h
index 643ce9cffab..180d5a2d227 100644
--- a/src/include/tcop/tcopprot.h
+++ b/src/include/tcop/tcopprot.h
@@ -42,6 +42,12 @@ typedef enum
 
 extern PGDLLIMPORT int log_statement;
 
+/* Flags for restrict_nonsystem_relation_kind value */
+#define RESTRICT_RELKIND_VIEW			0x01
+#define RESTRICT_RELKIND_FOREIGN_TABLE	0x02
+
+extern PGDLLIMPORT int restrict_nonsystem_relation_kind;
+
 extern List *pg_parse_query(const char *query_string);
 extern List *pg_rewrite_query(Query *query);
 extern List *pg_analyze_and_rewrite_fixedparams(RawStmt *parsetree,
diff --git a/src/include/utils/guc_hooks.h b/src/include/utils/guc_hooks.h
index 070d3f2a1ad..8fd91af3887 100644
--- a/src/include/utils/guc_hooks.h
+++ b/src/include/utils/guc_hooks.h
@@ -127,6 +127,9 @@ extern void assign_recovery_target_xid(const char *newval, void *extra);
 extern bool check_role(char **newval, void **extra, GucSource source);
 extern void assign_role(const char *newval, void *extra);
 extern const char *show_role(void);
+extern bool check_restrict_nonsystem_relation_kind(char **newval, void **extra,
+												   GucSource source);
+extern void assign_restrict_nonsystem_relation_kind(const char *newval, void *extra);
 extern bool check_search_path(char **newval, void **extra, GucSource source);
 extern void assign_search_path(const char *newval, void *extra);
 extern bool check_serial_buffers(int *newval, void **extra, GucSource source);
diff --git a/src/test/regress/expected/create_view.out b/src/test/regress/expected/create_view.out
index 61825ef7d4e..f3f8c7b5a2f 100644
--- a/src/test/regress/expected/create_view.out
+++ b/src/test/regress/expected/create_view.out
@@ -2202,6 +2202,21 @@ select pg_get_viewdef('tt26v', true);
     FROM ( VALUES (1,2,3)) v(x, y, z);
 (1 row)
 
+-- test restriction on non-system view expansion.
+create table tt27v_tbl (a int);
+create view tt27v as select a from tt27v_tbl;
+set restrict_nonsystem_relation_kind to 'view';
+select a from tt27v where a > 0; -- Error
+ERROR:  access to non-system view "tt27v" is restricted
+insert into tt27v values (1); -- Error
+ERROR:  access to non-system view "tt27v" is restricted
+select viewname from pg_views where viewname = 'tt27v'; -- Ok to access a system view.
+ viewname 
+----------
+ tt27v
+(1 row)
+
+reset restrict_nonsystem_relation_kind;
 -- clean up all the random objects we made above
 DROP SCHEMA temp_view_test CASCADE;
 NOTICE:  drop cascades to 27 other objects
@@ -2233,7 +2248,7 @@ drop cascades to view aliased_view_2
 drop cascades to view aliased_view_3
 drop cascades to view aliased_view_4
 DROP SCHEMA testviewschm2 CASCADE;
-NOTICE:  drop cascades to 77 other objects
+NOTICE:  drop cascades to 79 other objects
 DETAIL:  drop cascades to table t1
 drop cascades to view temporal1
 drop cascades to view temporal2
@@ -2311,3 +2326,5 @@ drop cascades to view tt23v
 drop cascades to view tt24v
 drop cascades to view tt25v
 drop cascades to view tt26v
+drop cascades to table tt27v_tbl
+drop cascades to view tt27v
diff --git a/src/test/regress/sql/create_view.sql b/src/test/regress/sql/create_view.sql
index 8838a40f7ab..3a78be1b0c7 100644
--- a/src/test/regress/sql/create_view.sql
+++ b/src/test/regress/sql/create_view.sql
@@ -813,6 +813,15 @@ select x + y + z as c1,
 from (values(1,2,3)) v(x,y,z);
 select pg_get_viewdef('tt26v', true);
 
+-- test restriction on non-system view expansion.
+create table tt27v_tbl (a int);
+create view tt27v as select a from tt27v_tbl;
+set restrict_nonsystem_relation_kind to 'view';
+select a from tt27v where a > 0; -- Error
+insert into tt27v values (1); -- Error
+select viewname from pg_views where viewname = 'tt27v'; -- Ok to access a system view.
+reset restrict_nonsystem_relation_kind;
+
 -- clean up all the random objects we made above
 DROP SCHEMA temp_view_test CASCADE;
 DROP SCHEMA testviewschm2 CASCADE;