Empty search_path in Autovacuum and non-psql/pgbench clients.

This makes the client programs behave as documented regardless of the
connect-time search_path and regardless of user-created objects.  Today,
a malicious user with CREATE permission on a search_path schema can take
control of certain of these clients' queries and invoke arbitrary SQL
functions under the client identity, often a superuser.  This is
exploitable in the default configuration, where all users have CREATE
privilege on schema "public".

This changes behavior of user-defined code stored in the database, like
pg_index.indexprs and pg_extension_config_dump().  If they reach code
bearing unqualified names, "does not exist" or "no schema has been
selected to create in" errors might appear.  Users may fix such errors
by schema-qualifying affected names.  After upgrading, consider watching
server logs for these errors.

The --table arguments of src/bin/scripts clients have been lax; for
example, "vacuumdb -Zt pg_am\;CHECKPOINT" performed a checkpoint.  That
now fails, but for now, "vacuumdb -Zt 'pg_am(amname);CHECKPOINT'" still
performs a checkpoint.

Back-patch to 9.3 (all supported versions).

Reviewed by Tom Lane, though this fix strategy was not his first choice.
Reported by Arseniy Sharoglazov.

Security: CVE-2018-1058

1 files changed, 7 insertions, 3 deletions

diff --git a/src/bin/scripts/common.h b/src/bin/scripts/common.h
index 691f6c6a02f..4067af34556 100644
--- a/src/bin/scripts/common.h
+++ b/src/bin/scripts/common.h
@@ -30,11 +30,12 @@ extern void handle_help_version_opts(int argc, char *argv[],
 extern PGconn *connectDatabase(const char *dbname, const char *pghost,
 				const char *pgport, const char *pguser,
 				enum trivalue prompt_password, const char *progname,
-				bool fail_ok);
+				bool echo, bool fail_ok);
 
 extern PGconn *connectMaintenanceDatabase(const char *maintenance_db,
-				  const char *pghost, const char *pgport, const char *pguser,
-						enum trivalue prompt_password, const char *progname);
+						   const char *pghost, const char *pgport,
+						   const char *pguser, enum trivalue prompt_password,
+						   const char *progname, bool echo);
 
 extern PGresult *executeQuery(PGconn *conn, const char *query,
 			 const char *progname, bool echo);
@@ -45,6 +46,9 @@ extern void executeCommand(PGconn *conn, const char *query,
 extern bool executeMaintenanceCommand(PGconn *conn, const char *query,
 						  bool echo);
 
+extern void appendQualifiedRelation(PQExpBuffer buf, const char *name,
+						PGconn *conn, const char *progname, bool echo);
+
 extern bool yesno_prompt(const char *question);
 
 extern void setup_cancel_handler(void);