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, 10 insertions, 6 deletions

diff --git a/src/fe_utils/string_utils.c b/src/fe_utils/string_utils.c
index 8c05a80d31d..b47a396af15 100644
--- a/src/fe_utils/string_utils.c
+++ b/src/fe_utils/string_utils.c
@@ -956,8 +956,9 @@ processSQLNamePattern(PGconn *conn, PQExpBuffer buf, const char *pattern,
 	}
 
 	/*
-	 * Now decide what we need to emit.  Note there will be a leading "^(" in
-	 * the patterns in any case.
+	 * Now decide what we need to emit.  We may run under a hostile
+	 * search_path, so qualify EVERY name.  Note there will be a leading "^("
+	 * in the patterns in any case.
 	 */
 	if (namebuf.len > 2)
 	{
@@ -970,15 +971,18 @@ processSQLNamePattern(PGconn *conn, PQExpBuffer buf, const char *pattern,
 			WHEREAND();
 			if (altnamevar)
 			{
-				appendPQExpBuffer(buf, "(%s ~ ", namevar);
+				appendPQExpBuffer(buf,
+								  "(%s OPERATOR(pg_catalog.~) ", namevar);
 				appendStringLiteralConn(buf, namebuf.data, conn);
-				appendPQExpBuffer(buf, "\n        OR %s ~ ", altnamevar);
+				appendPQExpBuffer(buf,
+								  "\n        OR %s OPERATOR(pg_catalog.~) ",
+								  altnamevar);
 				appendStringLiteralConn(buf, namebuf.data, conn);
 				appendPQExpBufferStr(buf, ")\n");
 			}
 			else
 			{
-				appendPQExpBuffer(buf, "%s ~ ", namevar);
+				appendPQExpBuffer(buf, "%s OPERATOR(pg_catalog.~) ", namevar);
 				appendStringLiteralConn(buf, namebuf.data, conn);
 				appendPQExpBufferChar(buf, '\n');
 			}
@@ -994,7 +998,7 @@ processSQLNamePattern(PGconn *conn, PQExpBuffer buf, const char *pattern,
 		if (strcmp(schemabuf.data, "^(.*)$") != 0 && schemavar)
 		{
 			WHEREAND();
-			appendPQExpBuffer(buf, "%s ~ ", schemavar);
+			appendPQExpBuffer(buf, "%s OPERATOR(pg_catalog.~) ", schemavar);
 			appendStringLiteralConn(buf, schemabuf.data, conn);
 			appendPQExpBufferChar(buf, '\n');
 		}