summaryrefslogtreecommitdiff
diff options
context:
space:
mode:
authordjm@openbsd.org <djm@openbsd.org>2016-01-13 23:04:47 +0000
committerDamien Miller <djm@mindrot.org>2016-01-14 10:06:01 +1100
commited4ce82dbfa8a3a3c8ea6fa0db113c71e234416c (patch)
tree008ac3334471370857e32b48893cb6f07d28e987
parent9a728cc918fad67c8a9a71201088b1e150340ba4 (diff)
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
-rw-r--r--clientloop.c114
-rw-r--r--clientloop.h4
-rw-r--r--mux.c22
-rw-r--r--ssh.c23
4 files changed, 93 insertions, 70 deletions
diff --git a/clientloop.c b/clientloop.c
index f5554519..c0386d56 100644
--- a/clientloop.c
+++ b/clientloop.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: clientloop.c,v 1.278 2015/12/26 07:46:03 semarie 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 *display)
{
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 *display)
#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, const char *xauth_path,
* 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, const char *xauth_path,
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, const char *xauth_path,
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, const char *xauth_path,
rnd >>= 8;
}
}
+
+ return 0;
}
/*
diff --git a/clientloop.h b/clientloop.h
index 338d4518..f4d4c69b 100644
--- a/clientloop.h
+++ b/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 *,
diff --git a/mux.c b/mux.c
index f9c3af65..6bf53ebd 100644
--- a/mux.c
+++ b/mux.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: mux.c,v 1.57 2015/12/26 07:46:03 semarie 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, void *arg)
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) {
diff --git a/ssh.c b/ssh.c
index 81704ab3..096c5b5d 100644
--- a/ssh.c
+++ b/ssh.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh.c,v 1.432 2015/12/11 03:20:09 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
@@ -1626,6 +1626,7 @@ ssh_session(void)
struct winsize ws;
char *cp;
const char *display;
+ char *proto = NULL, *data = NULL;
/* Enable compression if requested. */
if (options.compression) {
@@ -1696,13 +1697,9 @@ 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.");
@@ -1792,6 +1789,7 @@ ssh_session2_setup(int id, int success, void *arg)
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 */
@@ -1799,12 +1797,9 @@ ssh_session2_setup(int id, int success, void *arg)
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.");