upstream: close stdout/stderr after "ssh -f ..." forking

bz#3137, ok markus

OpenBSD-Commit-ID: e2d83cc4dea1665651a7aa924ad1ed6bcaaab3e2

1 files changed, 21 insertions, 6 deletions

diff --git a/ssh.c b/ssh.c
index 9c6a6278b..6202e3c09 100644
--- a/ssh.c
+++ b/ssh.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh.c,v 1.534 2020/07/31 04:19:37 dtucker Exp $ */
+/* $OpenBSD: ssh.c,v 1.535 2020/09/20 23:31:46 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -1745,12 +1745,25 @@ control_persist_detach(void)
 static void
 fork_postauth(void)
 {
+        int devnull, keep_stderr;
+
         if (need_controlpersist_detach)
                 control_persist_detach();
         debug("forking to background");
         fork_after_authentication_flag = 0;
         if (daemon(1, 1) == -1)
                 fatal("daemon() failed: %.200s", strerror(errno));
+        if ((devnull = open(_PATH_DEVNULL, O_WRONLY)) == -1)
+                error("%s: open %s: %s", __func__,
+                    _PATH_DEVNULL, strerror(errno));
+        else {
+                keep_stderr = log_is_on_stderr() && debug_flag;
+                if (dup2(devnull, STDOUT_FILENO) == -1 ||
+                    (!keep_stderr && dup2(devnull, STDOUT_FILENO) == -1))
+                        fatal("%s: dup2() stdio failed", __func__);
+                if (devnull > STDERR_FILENO)
+                        close(devnull);
+        }
 }
 
 static void
@@ -2149,13 +2162,15 @@ ssh_session2(struct ssh *ssh, struct passwd *pw)
          * as it may want to write to stdout.
          */
         if (!need_controlpersist_detach) {
-                if ((devnull = open(_PATH_DEVNULL, O_WRONLY)) == -1)
+                if ((devnull = open(_PATH_DEVNULL, O_WRONLY)) == -1) {
                         error("%s: open %s: %s", __func__,
                             _PATH_DEVNULL, strerror(errno));
-                if (dup2(devnull, STDOUT_FILENO) == -1)
-                        fatal("%s: dup2() stdout failed", __func__);
-                if (devnull > STDERR_FILENO)
-                        close(devnull);
+                } else {
+                        if (dup2(devnull, STDOUT_FILENO) == -1)
+                                fatal("%s: dup2() stdout failed", __func__);
+                        if (devnull > STDERR_FILENO)
+                                close(devnull);
+                }
         }
 
         /*