--- /dev/null
+From ed4ce82dbfa8a3a3c8ea6fa0db113c71e234416c Mon Sep 17 00:00:00 2001
+From: "djm@openbsd.org" <djm@openbsd.org>
+Date: Wed, 13 Jan 2016 23:04:47 +0000
+Subject: [PATCH] upstream commit
+
+eliminate fallback from untrusted X11 forwarding to trusted
+ forwarding when the X server disables the SECURITY extension; Reported by
+ Thomas Hoger; ok deraadt@
+
+Upstream-ID: f76195bd2064615a63ef9674a0e4096b0713f938
+Upstream-Status: Backport
+CVE: CVE-2016-1907
+
+[YOCTO #8935]
+
+Signed-off-by: Armin Kuster <akuster@mvista.com>
+
+---
+ clientloop.c | 114 ++++++++++++++++++++++++++++++++++++-----------------------
+ clientloop.h | 4 +--
+ mux.c | 22 ++++++------
+ ssh.c | 23 +++++-------
+ 4 files changed, 93 insertions(+), 70 deletions(-)
+
+Index: openssh-7.1p2/clientloop.c
+===================================================================
+--- openssh-7.1p2.orig/clientloop.c
++++ openssh-7.1p2/clientloop.c
+@@ -1,4 +1,4 @@
+-/* $OpenBSD: clientloop.c,v 1.276 2015/10/20 03:36:35 mmcc Exp $ */
++/* $OpenBSD: clientloop.c,v 1.279 2016/01/13 23:04:47 djm Exp $ */
+ /*
+ * Author: Tatu Ylonen <ylo@cs.hut.fi>
+ * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
+@@ -288,6 +288,9 @@ client_x11_display_valid(const char *dis
+ {
+ size_t i, dlen;
+
++ if (display == NULL)
++ return 0;
++
+ dlen = strlen(display);
+ for (i = 0; i < dlen; i++) {
+ if (!isalnum((u_char)display[i]) &&
+@@ -301,34 +304,33 @@ client_x11_display_valid(const char *dis
+
+ #define SSH_X11_PROTO "MIT-MAGIC-COOKIE-1"
+ #define X11_TIMEOUT_SLACK 60
+-void
++int
+ client_x11_get_proto(const char *display, const char *xauth_path,
+ u_int trusted, u_int timeout, char **_proto, char **_data)
+ {
+- char cmd[1024];
+- char line[512];
+- char xdisplay[512];
++ char cmd[1024], line[512], xdisplay[512];
++ char xauthfile[PATH_MAX], xauthdir[PATH_MAX];
+ static char proto[512], data[512];
+ FILE *f;
+- int got_data = 0, generated = 0, do_unlink = 0, i;
+- char xauthdir[PATH_MAX] = "", xauthfile[PATH_MAX] = "";
++ int got_data = 0, generated = 0, do_unlink = 0, i, r;
+ struct stat st;
+ u_int now, x11_timeout_real;
+
+ *_proto = proto;
+ *_data = data;
+- proto[0] = data[0] = '\0';
++ proto[0] = data[0] = xauthfile[0] = xauthdir[0] = '\0';
+
+- if (xauth_path == NULL ||(stat(xauth_path, &st) == -1)) {
+- debug("No xauth program.");
+- } else if (!client_x11_display_valid(display)) {
+- logit("DISPLAY '%s' invalid, falling back to fake xauth data",
++ if (!client_x11_display_valid(display)) {
++ logit("DISPLAY \"%s\" invalid; disabling X11 forwarding",
+ display);
+- } else {
+- if (display == NULL) {
+- debug("x11_get_proto: DISPLAY not set");
+- return;
+- }
++ return -1;
++ }
++ if (xauth_path != NULL && stat(xauth_path, &st) == -1) {
++ debug("No xauth program.");
++ xauth_path = NULL;
++ }
++
++ if (xauth_path != NULL) {
+ /*
+ * Handle FamilyLocal case where $DISPLAY does
+ * not match an authorization entry. For this we
+@@ -337,43 +339,60 @@ client_x11_get_proto(const char *display
+ * is not perfect.
+ */
+ if (strncmp(display, "localhost:", 10) == 0) {
+- snprintf(xdisplay, sizeof(xdisplay), "unix:%s",
+- display + 10);
++ if ((r = snprintf(xdisplay, sizeof(xdisplay), "unix:%s",
++ display + 10)) < 0 ||
++ (size_t)r >= sizeof(xdisplay)) {
++ error("%s: display name too long", __func__);
++ return -1;
++ }
+ display = xdisplay;
+ }
+ if (trusted == 0) {
+- mktemp_proto(xauthdir, PATH_MAX);
+ /*
++ * Generate an untrusted X11 auth cookie.
++ *
+ * The authentication cookie should briefly outlive
+ * ssh's willingness to forward X11 connections to
+ * avoid nasty fail-open behaviour in the X server.
+ */
++ mktemp_proto(xauthdir, sizeof(xauthdir));
++ if (mkdtemp(xauthdir) == NULL) {
++ error("%s: mkdtemp: %s",
++ __func__, strerror(errno));
++ return -1;
++ }
++ do_unlink = 1;
++ if ((r = snprintf(xauthfile, sizeof(xauthfile),
++ "%s/xauthfile", xauthdir)) < 0 ||
++ (size_t)r >= sizeof(xauthfile)) {
++ error("%s: xauthfile path too long", __func__);
++ unlink(xauthfile);
++ rmdir(xauthdir);
++ return -1;
++ }
++
+ if (timeout >= UINT_MAX - X11_TIMEOUT_SLACK)
+ x11_timeout_real = UINT_MAX;
+ else
+ x11_timeout_real = timeout + X11_TIMEOUT_SLACK;
+- if (mkdtemp(xauthdir) != NULL) {
+- do_unlink = 1;
+- snprintf(xauthfile, PATH_MAX, "%s/xauthfile",
+- xauthdir);
+- snprintf(cmd, sizeof(cmd),
+- "%s -f %s generate %s " SSH_X11_PROTO
+- " untrusted timeout %u 2>" _PATH_DEVNULL,
+- xauth_path, xauthfile, display,
+- x11_timeout_real);
+- debug2("x11_get_proto: %s", cmd);
+- if (x11_refuse_time == 0) {
+- now = monotime() + 1;
+- if (UINT_MAX - timeout < now)
+- x11_refuse_time = UINT_MAX;
+- else
+- x11_refuse_time = now + timeout;
+- channel_set_x11_refuse_time(
+- x11_refuse_time);
+- }
+- if (system(cmd) == 0)
+- generated = 1;
++ if ((r = snprintf(cmd, sizeof(cmd),
++ "%s -f %s generate %s " SSH_X11_PROTO
++ " untrusted timeout %u 2>" _PATH_DEVNULL,
++ xauth_path, xauthfile, display,
++ x11_timeout_real)) < 0 ||
++ (size_t)r >= sizeof(cmd))
++ fatal("%s: cmd too long", __func__);
++ debug2("%s: %s", __func__, cmd);
++ if (x11_refuse_time == 0) {
++ now = monotime() + 1;
++ if (UINT_MAX - timeout < now)
++ x11_refuse_time = UINT_MAX;
++ else
++ x11_refuse_time = now + timeout;
++ channel_set_x11_refuse_time(x11_refuse_time);
+ }
++ if (system(cmd) == 0)
++ generated = 1;
+ }
+
+ /*
+@@ -395,9 +414,7 @@ client_x11_get_proto(const char *display
+ got_data = 1;
+ if (f)
+ pclose(f);
+- } else
+- error("Warning: untrusted X11 forwarding setup failed: "
+- "xauth key data not generated");
++ }
+ }
+
+ if (do_unlink) {
+@@ -405,6 +422,13 @@ client_x11_get_proto(const char *display
+ rmdir(xauthdir);
+ }
+
++ /* Don't fall back to fake X11 data for untrusted forwarding */
++ if (!trusted && !got_data) {
++ error("Warning: untrusted X11 forwarding setup failed: "
++ "xauth key data not generated");
++ return -1;
++ }
++
+ /*
+ * If we didn't get authentication data, just make up some
+ * data. The forwarding code will check the validity of the
+@@ -427,6 +451,8 @@ client_x11_get_proto(const char *display
+ rnd >>= 8;
+ }
+ }
++
++ return 0;
+ }
+
+ /*
+Index: openssh-7.1p2/clientloop.h
+===================================================================
+--- openssh-7.1p2.orig/clientloop.h
++++ openssh-7.1p2/clientloop.h
+@@ -1,4 +1,4 @@
+-/* $OpenBSD: clientloop.h,v 1.31 2013/06/02 23:36:29 dtucker Exp $ */
++/* $OpenBSD: clientloop.h,v 1.32 2016/01/13 23:04:47 djm Exp $ */
+
+ /*
+ * Author: Tatu Ylonen <ylo@cs.hut.fi>
+@@ -39,7 +39,7 @@
+
+ /* Client side main loop for the interactive session. */
+ int client_loop(int, int, int);
+-void client_x11_get_proto(const char *, const char *, u_int, u_int,
++int client_x11_get_proto(const char *, const char *, u_int, u_int,
+ char **, char **);
+ void client_global_request_reply_fwd(int, u_int32_t, void *);
+ void client_session2_setup(int, int, int, const char *, struct termios *,
+Index: openssh-7.1p2/mux.c
+===================================================================
+--- openssh-7.1p2.orig/mux.c
++++ openssh-7.1p2/mux.c
+@@ -1,4 +1,4 @@
+-/* $OpenBSD: mux.c,v 1.54 2015/08/19 23:18:26 djm Exp $ */
++/* $OpenBSD: mux.c,v 1.58 2016/01/13 23:04:47 djm Exp $ */
+ /*
+ * Copyright (c) 2002-2008 Damien Miller <djm@openbsd.org>
+ *
+@@ -1354,16 +1354,18 @@ mux_session_confirm(int id, int success,
+ char *proto, *data;
+
+ /* Get reasonable local authentication information. */
+- client_x11_get_proto(display, options.xauth_location,
++ if (client_x11_get_proto(display, options.xauth_location,
+ options.forward_x11_trusted, options.forward_x11_timeout,
+- &proto, &data);
+- /* Request forwarding with authentication spoofing. */
+- debug("Requesting X11 forwarding with authentication "
+- "spoofing.");
+- x11_request_forwarding_with_spoofing(id, display, proto,
+- data, 1);
+- client_expect_confirm(id, "X11 forwarding", CONFIRM_WARN);
+- /* XXX exit_on_forward_failure */
++ &proto, &data) == 0) {
++ /* Request forwarding with authentication spoofing. */
++ debug("Requesting X11 forwarding with authentication "
++ "spoofing.");
++ x11_request_forwarding_with_spoofing(id, display, proto,
++ data, 1);
++ /* XXX exit_on_forward_failure */
++ client_expect_confirm(id, "X11 forwarding",
++ CONFIRM_WARN);
++ }
+ }
+
+ if (cctx->want_agent_fwd && options.forward_agent) {
+Index: openssh-7.1p2/ssh.c
+===================================================================
+--- openssh-7.1p2.orig/ssh.c
++++ openssh-7.1p2/ssh.c
+@@ -1,4 +1,4 @@
+-/* $OpenBSD: ssh.c,v 1.420 2015/07/30 00:01:34 djm Exp $ */
++/* $OpenBSD: ssh.c,v 1.433 2016/01/13 23:04:47 djm Exp $ */
+ /*
+ * Author: Tatu Ylonen <ylo@cs.hut.fi>
+ * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
+@@ -1604,6 +1604,7 @@ ssh_session(void)
+ struct winsize ws;
+ char *cp;
+ const char *display;
++ char *proto = NULL, *data = NULL;
+
+ /* Enable compression if requested. */
+ if (options.compression) {
+@@ -1674,13 +1675,9 @@ ssh_session(void)
+ display = getenv("DISPLAY");
+ if (display == NULL && options.forward_x11)
+ debug("X11 forwarding requested but DISPLAY not set");
+- if (options.forward_x11 && display != NULL) {
+- char *proto, *data;
+- /* Get reasonable local authentication information. */
+- client_x11_get_proto(display, options.xauth_location,
+- options.forward_x11_trusted,
+- options.forward_x11_timeout,
+- &proto, &data);
++ if (options.forward_x11 && client_x11_get_proto(display,
++ options.xauth_location, options.forward_x11_trusted,
++ options.forward_x11_timeout, &proto, &data) == 0) {
+ /* Request forwarding with authentication spoofing. */
+ debug("Requesting X11 forwarding with authentication "
+ "spoofing.");
+@@ -1770,6 +1767,7 @@ ssh_session2_setup(int id, int success,
+ extern char **environ;
+ const char *display;
+ int interactive = tty_flag;
++ char *proto = NULL, *data = NULL;
+
+ if (!success)
+ return; /* No need for error message, channels code sens one */
+@@ -1777,12 +1775,9 @@ ssh_session2_setup(int id, int success,
+ display = getenv("DISPLAY");
+ if (display == NULL && options.forward_x11)
+ debug("X11 forwarding requested but DISPLAY not set");
+- if (options.forward_x11 && display != NULL) {
+- char *proto, *data;
+- /* Get reasonable local authentication information. */
+- client_x11_get_proto(display, options.xauth_location,
+- options.forward_x11_trusted,
+- options.forward_x11_timeout, &proto, &data);
++ if (options.forward_x11 && client_x11_get_proto(display,
++ options.xauth_location, options.forward_x11_trusted,
++ options.forward_x11_timeout, &proto, &data) == 0) {
+ /* Request forwarding with authentication spoofing. */
+ debug("Requesting X11 forwarding with authentication "
+ "spoofing.");
