upstream: Allow ssh_config ForwardX11Timeout=0 to disable the

timeout and allow X11 connections in untrusted mode indefinitely. ok dtucker@

OpenBSD-Commit-ID: ea1ceed3f540b48e5803f933e59a03b20db10c69

2 files changed, 33 insertions, 16 deletions

diff --git a/clientloop.c b/clientloop.c
index ad35cb7ba..8d312cdaa 100644
--- a/clientloop.c
+++ b/clientloop.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: clientloop.c,v 1.317 2018/07/11 18:53:29 markus Exp $ */
+/* $OpenBSD: clientloop.c,v 1.318 2018/09/21 12:46:22 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -279,7 +279,7 @@ client_x11_get_proto(struct ssh *ssh, const char *display,
     const char *xauth_path, u_int trusted, u_int timeout,
     char **_proto, char **_data)
 {
-        char cmd[1024], line[512], xdisplay[512];
+        char *cmd, line[512], xdisplay[512];
         char xauthfile[PATH_MAX], xauthdir[PATH_MAX];
         static char proto[512], data[512];
         FILE *f;
@@ -343,19 +343,30 @@ client_x11_get_proto(struct ssh *ssh, const char *display,
                                 return -1;
                         }
 
-                        if (timeout >= UINT_MAX - X11_TIMEOUT_SLACK)
-                                x11_timeout_real = UINT_MAX;
-                        else
-                                x11_timeout_real = timeout + X11_TIMEOUT_SLACK;
-                        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__);
+                        if (timeout == 0) {
+                                /* auth doesn't time out */
+                                xasprintf(&cmd, "%s -f %s generate %s %s "
+                                    "untrusted 2>%s",
+                                    xauth_path, xauthfile, display,
+                                    SSH_X11_PROTO, _PATH_DEVNULL);
+                        } else {
+                                /* Add some slack to requested expiry */
+                                if (timeout < UINT_MAX - X11_TIMEOUT_SLACK)
+                                        x11_timeout_real = timeout +
+                                            X11_TIMEOUT_SLACK;
+                                else {
+                                        /* Don't overflow on long timeouts */
+                                        x11_timeout_real = UINT_MAX;
+                                }
+                                xasprintf(&cmd, "%s -f %s generate %s %s "
+                                    "untrusted timeout %u 2>%s",
+                                    xauth_path, xauthfile, display,
+                                    SSH_X11_PROTO, x11_timeout_real,
+                                    _PATH_DEVNULL);
+                        }
                         debug2("%s: %s", __func__, cmd);
-                        if (x11_refuse_time == 0) {
+
+                        if (timeout != 0 && x11_refuse_time == 0) {
                                 now = monotime() + 1;
                                 if (UINT_MAX - timeout < now)
                                         x11_refuse_time = UINT_MAX;
@@ -366,6 +377,7 @@ client_x11_get_proto(struct ssh *ssh, const char *display,
                         }
                         if (system(cmd) == 0)
                                 generated = 1;
+                        free(cmd);
                 }
 
                 /*
@@ -374,7 +386,7 @@ client_x11_get_proto(struct ssh *ssh, const char *display,
                  * above.
                  */
                 if (trusted || generated) {
-                        snprintf(cmd, sizeof(cmd),
+                        xasprintf(&cmd,
                             "%s %s%s list %s 2>" _PATH_DEVNULL,
                             xauth_path,
                             generated ? "-f " : "" ,
@@ -387,6 +399,7 @@ client_x11_get_proto(struct ssh *ssh, const char *display,
                                 got_data = 1;
                         if (f)
                                 pclose(f);
+                        free(cmd);
                 }
         }
 
diff --git a/ssh_config.5 b/ssh_config.5
index 2df1165f1..27136dbd6 100644
--- a/ssh_config.5
+++ b/ssh_config.5
@@ -33,7 +33,7 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.\" $OpenBSD: ssh_config.5,v 1.284 2018/09/21 03:11:36 djm Exp $
+.\" $OpenBSD: ssh_config.5,v 1.285 2018/09/21 12:46:22 djm Exp $
 .Dd $Mdocdate: September 21 2018 $
 .Dt SSH_CONFIG 5
 .Os
@@ -686,6 +686,10 @@ section of
 X11 connections received by
 .Xr ssh 1
 after this time will be refused.
+Setting
+.Cm ForwardX11Timeout
+to zero will disable the timeout and permit X11 forwarding for the life
+of the connection.
 The default is to disable untrusted X11 forwarding after twenty minutes has
 elapsed.
 .It Cm ForwardX11Trusted