upstream commit

transfer ownership of stdout to the session channel by
dup2'ing /dev/null to fd 1. This allows propagation of remote stdout close to
the local side; reported by David Newall, ok markus@

Upstream-ID: 8d9ac18a11d89e6b0415f0cbf67b928ac67f0e79

1 files changed, 16 insertions, 2 deletions

diff --git a/ssh.c b/ssh.c
index 74056985b..ae468d286 100644
--- a/ssh.c
+++ b/ssh.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh.c,v 1.466 2017/10/23 05:08:00 djm Exp $ */
+/* $OpenBSD: ssh.c,v 1.467 2017/10/25 00:21:37 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -1817,7 +1817,7 @@ ssh_session2_open(struct ssh *ssh)
 static int
 ssh_session2(struct ssh *ssh, struct passwd *pw)
 {
-        int id = -1;
+        int devnull, id = -1;
         char *cp, *tun_fwd_ifname = NULL;
 
         /* XXX should be pre-session */
@@ -1901,6 +1901,20 @@ ssh_session2(struct ssh *ssh, struct passwd *pw)
                 ssh_local_cmd(options.local_command);
 
         /*
+         * stdout is now owned by the session channel; clobber it here
+         * so future channel closes are propagated to the local fd.
+         * NB. this can only happen after LocalCommand has completed,
+         * as it may want to write to stdout.
+         */
+        if ((devnull = open(_PATH_DEVNULL, O_WRONLY)) == -1)
+                error("%s: open %s: %s", __func__,
+                    _PATH_DEVNULL, strerror(errno));
+        if (dup2(devnull, STDOUT_FILENO) < 0)
+                fatal("%s: dup2() stdout failed", __func__);
+        if (devnull > STDERR_FILENO)
+                close(devnull);
+
+        /*
          * If requested and we are not interested in replies to remote
          * forwarding requests, then let ssh continue in the background.
          */