don't start the ObscureKeystrokeTiming mitigations if there has been

traffic on a X11 forwarding channel recently.

Should fix X11 forwarding performance problems when this setting is
enabled. Patch from Antonio Larrosa via bz3655

diff --git a/usr.bin/ssh/channels.c b/usr.bin/ssh/channels.c
index 15e702c..07e8c08 100644 (file)
--- a/usr.bin/ssh/channels.c
+++ b/usr.bin/ssh/channels.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: channels.c,v 1.439 2024/07/25 22:40:08 djm Exp $ */
+/* $OpenBSD: channels.c,v 1.440 2024/10/13 22:20:06 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -5219,3 +5219,22 @@ x11_request_forwarding_with_spoofing(struct ssh *ssh, int client_session_id,
                fatal_fr(r, "send x11-req");
        free(new_data);
 }
+
+/*
+ * Returns whether an x11 channel was used recently (less than a second ago)
+ */
+int
+x11_channel_used_recently(struct ssh *ssh) {
+       u_int i;
+       Channel *c;
+       time_t lastused = 0;
+
+       for (i = 0; i < ssh->chanctxt->channels_alloc; i++) {
+               c = ssh->chanctxt->channels[i];
+               if (c == NULL || c->ctype == NULL || c->lastused == 0 ||
+                   strcmp(c->ctype, "x11-connection") != 0)
+                       continue;
+               lastused = c->lastused;
+       }
+       return lastused != 0 && monotime() > lastused + 1;
+}

diff --git a/usr.bin/ssh/channels.h b/usr.bin/ssh/channels.h
index 8a4615e..c227320 100644 (file)
--- a/usr.bin/ssh/channels.h
+++ b/usr.bin/ssh/channels.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: channels.h,v 1.157 2024/07/25 22:40:08 djm Exp $ */
+/* $OpenBSD: channels.h,v 1.158 2024/10/13 22:20:06 djm Exp $ */
 
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
@@ -379,6 +379,7 @@ int  x11_connect_display(struct ssh *);
 int     x11_create_display_inet(struct ssh *, int, int, int, u_int *, int **);
 void    x11_request_forwarding_with_spoofing(struct ssh *, int,
            const char *, const char *, const char *, int);
+int      x11_channel_used_recently(struct ssh *ssh);
 
 /* channel close */
 

diff --git a/usr.bin/ssh/clientloop.c b/usr.bin/ssh/clientloop.c
index c5296e3..07c321c 100644 (file)
--- a/usr.bin/ssh/clientloop.c
+++ b/usr.bin/ssh/clientloop.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: clientloop.c,v 1.408 2024/07/01 04:31:17 djm Exp $ */
+/* $OpenBSD: clientloop.c,v 1.409 2024/10/13 22:20:06 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -650,9 +650,10 @@ obfuscate_keystroke_timing(struct ssh *ssh, struct timespec *timeout,
        if (just_started)
                return 1;
 
-       /* Don't arm output fd for poll until the timing interval has elapsed */
+       /* Don't arm output fd for poll until the timing interval has elapsed... */
        if (timespeccmp(&now, &next_interval, <))
-               return 0;
+               /* ...unless there's x11 communicattion happening */
+               return x11_channel_used_recently(ssh);
 
        /* Calculate number of intervals missed since the last check */
        n = (now.tv_sec - next_interval.tv_sec) * 1000LL * 1000 * 1000;