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upstream: trigger keystroke timing obfucation only if the channels 

layer enqueud some data in the last poll() cycle; this avoids triggering the
obfuscatior for non-channels data like ClientAlive probes and also fixes a
related problem were the obfucations would be triggered on fully quiescent
connections.

Based on / tested by naddy@

OpenBSD-Commit-ID: d98f32dc62d7663ff4660e4556e184032a0db123
This commit is contained in:
djm@openbsd.org 2023-09-04 00:08:14 +00:00 committed by Damien Miller
parent b5fd97896b
commit 694150ad92
No known key found for this signature in database
1 changed files with 14 additions and 10 deletions
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24
clientloop.c
View File

@ -1,4 +1,4 @@
/* $OpenBSD: clientloop.c,v 1.395 2023/09/04 00:04:02 djm Exp $ */
/* $OpenBSD: clientloop.c,v 1.396 2023/09/04 00:08:14 djm Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@ -533,7 +533,8 @@ send_chaff(struct ssh *ssh)
* output fd should be polled.
*/
static int
obfuscate_keystroke_timing(struct ssh *ssh, struct timespec *timeout)
obfuscate_keystroke_timing(struct ssh *ssh, struct timespec *timeout,
int channel_did_enqueue)
{
static int active;
static struct timespec next_interval, chaff_until;
@ -558,7 +559,8 @@ obfuscate_keystroke_timing(struct ssh *ssh, struct timespec *timeout)
ssh_packet_have_data_to_write(ssh)) {
/* Stop if the output buffer has more than a few keystrokes */
stop_reason = "output buffer filling";
} else if (active && ssh_packet_have_data_to_write(ssh)) {
} else if (active && channel_did_enqueue &&
ssh_packet_have_data_to_write(ssh)) {
/* Still in active mode and have a keystroke queued. */
had_keystroke = 1;
} else if (active) {
@ -587,7 +589,8 @@ obfuscate_keystroke_timing(struct ssh *ssh, struct timespec *timeout)
* interactively. In this case, start quantising outbound packets to
* fixed time intervals to hide inter-keystroke timing.
*/
if (!active && ssh_packet_interactive_data_to_write(ssh)) {
if (!active && ssh_packet_interactive_data_to_write(ssh) &&
channel_did_enqueue && ssh_packet_have_data_to_write(ssh)) {
debug3_f("starting: interval %d",
options.obscure_keystroke_timing_interval);
just_started = had_keystroke = active = 1;
@ -637,7 +640,7 @@ obfuscate_keystroke_timing(struct ssh *ssh, struct timespec *timeout)
*/
static void
client_wait_until_can_do_something(struct ssh *ssh, struct pollfd **pfdp,
u_int *npfd_allocp, u_int *npfd_activep, int rekeying,
u_int *npfd_allocp, u_int *npfd_activep, int channel_did_enqueue,
int *conn_in_readyp, int *conn_out_readyp)
{
struct timespec timeout;
@ -661,7 +664,7 @@ client_wait_until_can_do_something(struct ssh *ssh, struct pollfd **pfdp,
return;
}
oready = obfuscate_keystroke_timing(ssh, &timeout);
oready = obfuscate_keystroke_timing(ssh, &timeout, channel_did_enqueue);
/* Monitor server connection on reserved pollfd entries */
(*pfdp)[0].fd = connection_in;
@ -680,7 +683,7 @@ client_wait_until_can_do_something(struct ssh *ssh, struct pollfd **pfdp,
ptimeout_deadline_monotime(&timeout, control_persist_exit_time);
if (options.server_alive_interval > 0)
ptimeout_deadline_monotime(&timeout, server_alive_time);
if (options.rekey_interval > 0 && !rekeying) {
if (options.rekey_interval > 0 && !ssh_packet_is_rekeying(ssh)) {
ptimeout_deadline_sec(&timeout,
ssh_packet_get_rekey_timeout(ssh));
}
@ -1402,7 +1405,7 @@ client_loop(struct ssh *ssh, int have_pty, int escape_char_arg,
struct pollfd *pfd = NULL;
u_int npfd_alloc = 0, npfd_active = 0;
double start_time, total_time;
int r, len;
int channel_did_enqueue = 0, r, len;
u_int64_t ibytes, obytes;
int conn_in_ready, conn_out_ready;
@ -1492,6 +1495,7 @@ client_loop(struct ssh *ssh, int have_pty, int escape_char_arg,
/* Main loop of the client for the interactive session mode. */
while (!quit_pending) {
channel_did_enqueue = 0;
/* Process buffered packets sent by the server. */
client_process_buffered_input_packets(ssh);
@ -1513,7 +1517,7 @@ client_loop(struct ssh *ssh, int have_pty, int escape_char_arg,
* enqueue them for sending to the server.
*/
if (ssh_packet_not_very_much_data_to_write(ssh))
channel_output_poll(ssh);
channel_did_enqueue = channel_output_poll(ssh);
/*
* Check if the window size has changed, and buffer a
@ -1529,7 +1533,7 @@ client_loop(struct ssh *ssh, int have_pty, int escape_char_arg,
* available on one of the descriptors).
*/
client_wait_until_can_do_something(ssh, &pfd, &npfd_alloc,
&npfd_active, ssh_packet_is_rekeying(ssh),
&npfd_active, channel_did_enqueue,
&conn_in_ready, &conn_out_ready);
if (quit_pending)