Expose devices allocated for tun/tap forwarding.

At the client, the device may be obtained from a new %T expansion
for LocalCommand.

At the server, the allocated devices will be listed in a
SSH_TUNNEL variable exposed to the environment of any user sessions
started after the tunnel forwarding was established.

ok markus

1 files changed, 21 insertions, 2 deletions

diff --git a/usr.bin/ssh/serverloop.c b/usr.bin/ssh/serverloop.c
index aeb39328c4d..955656ec81e 100644
--- a/usr.bin/ssh/serverloop.c
+++ b/usr.bin/ssh/serverloop.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: serverloop.c,v 1.198 2017/09/12 06:35:32 djm Exp $ */
+/* $OpenBSD: serverloop.c,v 1.199 2017/10/23 05:08:00 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -95,6 +95,9 @@ static volatile sig_atomic_t received_sigterm = 0;
 /* prototypes */
 static void server_init_dispatch(void);
 
+/* requested tunnel forwarding interface(s), shared with session.c */
+char *tun_fwd_ifnames = NULL;
+
 /*
  * we write to this pipe if a SIGCHLD is caught in order to avoid
  * the race between select() and child_terminated
@@ -512,6 +515,7 @@ server_request_tun(struct ssh *ssh)
 	Channel *c = NULL;
 	int mode, tun;
 	int sock;
+	char *tmp, *ifname = NULL;
 
 	mode = packet_get_int();
 	switch (mode) {
@@ -534,13 +538,28 @@ server_request_tun(struct ssh *ssh)
 			goto done;
 		tun = forced_tun_device;
 	}
-	sock = tun_open(tun, mode);
+	sock = tun_open(tun, mode, &ifname);
 	if (sock < 0)
 		goto done;
+	debug("Tunnel forwarding using interface %s", ifname);
+
 	c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1,
 	    CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
 	c->datagram = 1;
 
+	/*
+	 * Update the list of names exposed to the session
+	 * XXX remove these if the tunnels are closed (won't matter
+	 * much if they are already in the environment though)
+	 */
+	tmp = tun_fwd_ifnames;
+	xasprintf(&tun_fwd_ifnames, "%s%s%s",
+	    tun_fwd_ifnames == NULL ? "" : tun_fwd_ifnames,
+	    tun_fwd_ifnames == NULL ? "" : ",",
+	    ifname);
+	free(tmp);
+	free(ifname);
+
  done:
 	if (c == NULL)
 		packet_send_debug("Failed to open the tunnel device.");