- djm@cvs.openbsd.org 2008/06/10 22:15:23
[PROTOCOL ssh.c serverloop.c]
Add a no-more-sessions@openssh.com global request extension that the
client sends when it knows that it will never request another session
(i.e. when session multiplexing is disabled). This allows a server to
disallow further session requests and terminate the session.
Why would a non-multiplexing client ever issue additional session
requests? It could have been attacked with something like SSH'jack:
http://www.storm.net.nz/projects/7
feedback & ok markus
diff --git a/ssh.c b/ssh.c
index 3bcca53..e3737bb 100644
--- a/ssh.c
+++ b/ssh.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh.c,v 1.313 2008/05/09 14:26:08 djm Exp $ */
+/* $OpenBSD: ssh.c,v 1.314 2008/06/10 22:15:23 djm Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -1151,6 +1151,15 @@
if (!no_shell_flag || (datafellows & SSH_BUG_DUMMYCHAN))
id = ssh_session2_open();
+ /* If we don't expect to open a new session, then disallow it */
+ if (options.control_master == SSHCTL_MASTER_NO) {
+ debug("Requesting no-more-sessions@openssh.com");
+ packet_start(SSH2_MSG_GLOBAL_REQUEST);
+ packet_put_cstring("no-more-sessions@openssh.com");
+ packet_put_char(0);
+ packet_send();
+ }
+
/* Execute a local command */
if (options.local_command != NULL &&
options.permit_local_command)