From 5b2f34a74aa6a524cd57e856b23e1b7b25007721 Mon Sep 17 00:00:00 2001
From: "djm@openbsd.org" <djm@openbsd.org>
Date: Fri, 9 Jun 2017 06:47:13 +0000
Subject: [PATCH] upstream commit

return failure rather than fatal() for more cases during
mux negotiations. Causes the session to fall back to a non-mux connection if
they occur. bz#2707 ok dtucker@

Upstream-ID: d2a7892f464d434e1f615334a1c9d0cdb83b29ab
---
 mux.c | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/mux.c b/mux.c
index 2d6639c5c..3dde4da40 100644
--- a/mux.c
+++ b/mux.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: mux.c,v 1.64 2017/01/21 11:32:04 guenther Exp $ */
+/* $OpenBSD: mux.c,v 1.65 2017/06/09 06:47:13 djm Exp $ */
 /*
  * Copyright (c) 2002-2008 Damien Miller <djm@openbsd.org>
  *
@@ -1570,31 +1570,38 @@ mux_client_hello_exchange(int fd)
 {
 	Buffer m;
 	u_int type, ver;
+	int ret = -1;
 
 	buffer_init(&m);
 	buffer_put_int(&m, MUX_MSG_HELLO);
 	buffer_put_int(&m, SSHMUX_VER);
 	/* no extensions */
 
-	if (mux_client_write_packet(fd, &m) != 0)
-		fatal("%s: write packet: %s", __func__, strerror(errno));
+	if (mux_client_write_packet(fd, &m) != 0) {
+		debug("%s: write packet: %s", __func__, strerror(errno));
+		goto out;
+	}
 
 	buffer_clear(&m);
 
 	/* Read their HELLO */
 	if (mux_client_read_packet(fd, &m) != 0) {
-		buffer_free(&m);
-		return -1;
+		debug("%s: read packet failed", __func__);
+		goto out;
 	}
 
 	type = buffer_get_int(&m);
-	if (type != MUX_MSG_HELLO)
-		fatal("%s: expected HELLO (%u) received %u",
+	if (type != MUX_MSG_HELLO) {
+		error("%s: expected HELLO (%u) received %u",
 		    __func__, MUX_MSG_HELLO, type);
+		goto out;
+	}
 	ver = buffer_get_int(&m);
-	if (ver != SSHMUX_VER)
-		fatal("Unsupported multiplexing protocol version %d "
+	if (ver != SSHMUX_VER) {
+		error("Unsupported multiplexing protocol version %d "
 		    "(expected %d)", ver, SSHMUX_VER);
+		goto out;
+	}
 	debug2("%s: master version %u", __func__, ver);
 	/* No extensions are presently defined */
 	while (buffer_len(&m) > 0) {
@@ -1605,8 +1612,11 @@ mux_client_hello_exchange(int fd)
 		free(name);
 		free(value);
 	}
+	/* success */
+	ret = 0;
+ out:
 	buffer_free(&m);
-	return 0;
+	return ret;
 }
 
 static u_int