upstream: There are lots of place where we want to redirect stdin,

stdout and/or stderr to /dev/null. Factor all these out to a single
stdfd_devnull() function that allows selection of which of these to redirect.
ok markus@

OpenBSD-Commit-ID: 3033ba5a4c47cacfd5def020d42cabc52fad3099

1 files changed, 8 insertions, 40 deletions

diff --git a/ssh.c b/ssh.c
index f34ca0d7..0329e484 100644
--- a/ssh.c
+++ b/ssh.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh.c,v 1.536 2020/09/21 07:29:09 djm Exp $ */
+/* $OpenBSD: ssh.c,v 1.537 2020/10/03 09:22:26 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -1698,7 +1698,6 @@ static void
 control_persist_detach(void)
 {
 	pid_t pid;
-	int devnull, keep_stderr;
 
 	debug("%s: backgrounding master process", __func__);
 
@@ -1725,18 +1724,8 @@ control_persist_detach(void)
 		/* muxclient() doesn't return on success. */
 		fatal("Failed to connect to new control master");
 	}
-	if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) {
-		error("%s: open(\"/dev/null\"): %s", __func__,
-		    strerror(errno));
-	} else {
-		keep_stderr = log_is_on_stderr() && debug_flag;
-		if (dup2(devnull, STDIN_FILENO) == -1 ||
-		    dup2(devnull, STDOUT_FILENO) == -1 ||
-		    (!keep_stderr && dup2(devnull, STDERR_FILENO) == -1))
-			error("%s: dup2: %s", __func__, strerror(errno));
-		if (devnull > STDERR_FILENO)
-			close(devnull);
-	}
+	if (stdfd_devnull(1, 1, !(log_is_on_stderr() && debug_flag)) == -1)
+		error("%s: stdfd_devnull failed", __func__);
 	daemon(1, 1);
 	setproctitle("%s [mux]", options.control_path);
 }
@@ -1745,26 +1734,14 @@ 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, STDIN_FILENO) == -1 ||
-		    dup2(devnull, STDOUT_FILENO) == -1 ||
-		    (!keep_stderr && dup2(devnull, STDOUT_FILENO) == -1))
-			fatal("%s: dup2() stdio failed", __func__);
-		if (devnull > STDERR_FILENO)
-			close(devnull);
-	}
+	if (stdfd_devnull(1, 1, !(log_is_on_stderr() && debug_flag)) == -1)
+		error("%s: stdfd_devnull failed", __func__);
 }
 
 static void
@@ -2075,7 +2052,7 @@ ssh_session2_open(struct ssh *ssh)
 static int
 ssh_session2(struct ssh *ssh, struct passwd *pw)
 {
-	int r, devnull, id = -1;
+	int r, id = -1;
 	char *cp, *tun_fwd_ifname = NULL;
 
 	/* XXX should be pre-session */
@@ -2162,17 +2139,8 @@ ssh_session2(struct ssh *ssh, struct passwd *pw)
 	 * NB. this can only happen after LocalCommand has completed,
 	 * as it may want to write to stdout.
 	 */
-	if (!need_controlpersist_detach) {
-		if ((devnull = open(_PATH_DEVNULL, O_WRONLY)) == -1) {
-			error("%s: open %s: %s", __func__,
-			    _PATH_DEVNULL, strerror(errno));
-		} else {
-			if (dup2(devnull, STDOUT_FILENO) == -1)
-				fatal("%s: dup2() stdout failed", __func__);
-			if (devnull > STDERR_FILENO)
-				close(devnull);
-		}
-	}
+	if (!need_controlpersist_detach && stdfd_devnull(0, 1, 0) == -1)
+		error("%s: stdfd_devnull failed", __func__);
 
 	/*
 	 * If requested and we are not interested in replies to remote