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clientloop.c
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clientloop.c
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/* $OpenBSD: clientloop.c,v 1.408 2024/07/01 04:31:17 djm Exp $ */
/*
* Author: Tatu Ylonen <[email protected]>
* Copyright (c) 1995 Tatu Ylonen <[email protected]>, Espoo, Finland
* All rights reserved
* The main loop for the interactive session (client side).
*
* As far as I am concerned, the code I have written for this software
* can be used freely for any purpose. Any derived versions of this
* software must be clearly marked as such, and if the derived work is
* incompatible with the protocol description in the RFC file, it must be
* called by a name other than "ssh" or "Secure Shell".
*
*
* Copyright (c) 1999 Theo de Raadt. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*
* SSH2 support added by Markus Friedl.
* Copyright (c) 1999, 2000, 2001 Markus Friedl. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "includes.h"
#include <sys/types.h>
#include <sys/ioctl.h>
#ifdef HAVE_SYS_STAT_H
# include <sys/stat.h>
#endif
#ifdef HAVE_SYS_TIME_H
# include <sys/time.h>
#endif
#include <sys/socket.h>
#include <ctype.h>
#include <errno.h>
#ifdef HAVE_PATHS_H
#include <paths.h>
#endif
#ifdef HAVE_POLL_H
#include <poll.h>
#endif
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdarg.h>
#include <termios.h>
#include <pwd.h>
#include <unistd.h>
#include <limits.h>
#include "openbsd-compat/sys-queue.h"
#include "xmalloc.h"
#include "ssh.h"
#include "ssh2.h"
#include "packet.h"
#include "sshbuf.h"
#include "compat.h"
#include "channels.h"
#include "dispatch.h"
#include "sshkey.h"
#include "cipher.h"
#include "kex.h"
#include "myproposal.h"
#include "log.h"
#include "misc.h"
#include "readconf.h"
#include "clientloop.h"
#include "sshconnect.h"
#include "authfd.h"
#include "atomicio.h"
#include "sshpty.h"
#include "match.h"
#include "msg.h"
#include "ssherr.h"
#include "hostfile.h"
/* Permitted RSA signature algorithms for UpdateHostkeys proofs */
#define HOSTKEY_PROOF_RSA_ALGS "rsa-sha2-512,rsa-sha2-256"
/* Uncertainty (in percent) of keystroke timing intervals */
#define SSH_KEYSTROKE_TIMING_FUZZ 10
/* import options */
extern Options options;
/* Control socket */
extern int muxserver_sock; /* XXX use mux_client_cleanup() instead */
/*
* Name of the host we are connecting to. This is the name given on the
* command line, or the Hostname specified for the user-supplied name in a
* configuration file.
*/
extern char *host;
/*
* If this field is not NULL, the ForwardAgent socket is this path and different
* instead of SSH_AUTH_SOCK.
*/
extern char *forward_agent_sock_path;
/*
* Flag to indicate that we have received a window change signal which has
* not yet been processed. This will cause a message indicating the new
* window size to be sent to the server a little later. This is volatile
* because this is updated in a signal handler.
*/
static volatile sig_atomic_t received_window_change_signal = 0;
static volatile sig_atomic_t received_signal = 0;
/* Time when backgrounded control master using ControlPersist should exit */
static time_t control_persist_exit_time = 0;
/* Common data for the client loop code. */
volatile sig_atomic_t quit_pending; /* Set non-zero to quit the loop. */
static int last_was_cr; /* Last character was a newline. */
static int exit_status; /* Used to store the command exit status. */
static int connection_in; /* Connection to server (input). */
static int connection_out; /* Connection to server (output). */
static int need_rekeying; /* Set to non-zero if rekeying is requested. */
static int session_closed; /* In SSH2: login session closed. */
static time_t x11_refuse_time; /* If >0, refuse x11 opens after this time. */
static time_t server_alive_time; /* Time to do server_alive_check */
static int hostkeys_update_complete;
static int session_setup_complete;
static void client_init_dispatch(struct ssh *ssh);
int session_ident = -1;
/* Track escape per proto2 channel */
struct escape_filter_ctx {
int escape_pending;
int escape_char;
};
/* Context for channel confirmation replies */
struct channel_reply_ctx {
const char *request_type;
int id;
enum confirm_action action;
};
/* Global request success/failure callbacks */
/* XXX move to struct ssh? */
struct global_confirm {
TAILQ_ENTRY(global_confirm) entry;
global_confirm_cb *cb;
void *ctx;
int ref_count;
};
TAILQ_HEAD(global_confirms, global_confirm);
static struct global_confirms global_confirms =
TAILQ_HEAD_INITIALIZER(global_confirms);
static void quit_message(const char *fmt, ...)
__attribute__((__format__ (printf, 1, 2)));
static void
quit_message(const char *fmt, ...)
{
char *msg, *fmt2;
va_list args;
xasprintf(&fmt2, "%s\r\n", fmt);
va_start(args, fmt);
xvasprintf(&msg, fmt2, args);
va_end(args);
(void)atomicio(vwrite, STDERR_FILENO, msg, strlen(msg));
free(msg);
free(fmt2);
quit_pending = 1;
}
/*
* Signal handler for the window change signal (SIGWINCH). This just sets a
* flag indicating that the window has changed.
*/
static void
window_change_handler(int sig)
{
received_window_change_signal = 1;
}
/*
* Signal handler for signals that cause the program to terminate. These
* signals must be trapped to restore terminal modes.
*/
static void
signal_handler(int sig)
{
received_signal = sig;
quit_pending = 1;
}
/*
* Sets control_persist_exit_time to the absolute time when the
* backgrounded control master should exit due to expiry of the
* ControlPersist timeout. Sets it to 0 if we are not a backgrounded
* control master process, or if there is no ControlPersist timeout.
*/
static void
set_control_persist_exit_time(struct ssh *ssh)
{
if (muxserver_sock == -1 || !options.control_persist
|| options.control_persist_timeout == 0) {
/* not using a ControlPersist timeout */
control_persist_exit_time = 0;
} else if (channel_still_open(ssh)) {
/* some client connections are still open */
if (control_persist_exit_time > 0)
debug2_f("cancel scheduled exit");
control_persist_exit_time = 0;
} else if (control_persist_exit_time <= 0) {
/* a client connection has recently closed */
control_persist_exit_time = monotime() +
(time_t)options.control_persist_timeout;
debug2_f("schedule exit in %d seconds",
options.control_persist_timeout);
}
/* else we are already counting down to the timeout */
}
#define SSH_X11_VALID_DISPLAY_CHARS ":/.-_"
static int
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]) &&
strchr(SSH_X11_VALID_DISPLAY_CHARS, display[i]) == NULL) {
debug("Invalid character '%c' in DISPLAY", display[i]);
return 0;
}
}
return 1;
}
#define SSH_X11_PROTO "MIT-MAGIC-COOKIE-1"
#define X11_TIMEOUT_SLACK 60
int
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, 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, r;
struct stat st;
u_int now, x11_timeout_real;
*_proto = proto;
*_data = data;
proto[0] = data[0] = xauthfile[0] = xauthdir[0] = '\0';
if (!client_x11_display_valid(display)) {
if (display != NULL)
logit("DISPLAY \"%s\" invalid; disabling X11 forwarding",
display);
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
* just try "xauth list unix:displaynum.screennum".
* XXX: "localhost" match to determine FamilyLocal
* is not perfect.
*/
if (strncmp(display, "localhost:", 10) == 0) {
if ((r = snprintf(xdisplay, sizeof(xdisplay), "unix:%s",
display + 10)) < 0 ||
(size_t)r >= sizeof(xdisplay)) {
error_f("display name too long");
return -1;
}
display = xdisplay;
}
if (trusted == 0) {
/*
* 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_f("mkdtemp: %s", strerror(errno));
return -1;
}
do_unlink = 1;
if ((r = snprintf(xauthfile, sizeof(xauthfile),
"%s/xauthfile", xauthdir)) < 0 ||
(size_t)r >= sizeof(xauthfile)) {
error_f("xauthfile path too long");
rmdir(xauthdir);
return -1;
}
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_f("xauth command: %s", cmd);
if (timeout != 0 && x11_refuse_time == 0) {
now = monotime() + 1;
if (SSH_TIME_T_MAX - timeout < now)
x11_refuse_time = SSH_TIME_T_MAX;
else
x11_refuse_time = now + timeout;
channel_set_x11_refuse_time(ssh,
x11_refuse_time);
}
if (system(cmd) == 0)
generated = 1;
free(cmd);
}
/*
* When in untrusted mode, we read the cookie only if it was
* successfully generated as an untrusted one in the step
* above.
*/
if (trusted || generated) {
xasprintf(&cmd,
"%s %s%s list %s 2>" _PATH_DEVNULL,
xauth_path,
generated ? "-f " : "" ,
generated ? xauthfile : "",
display);
debug2("x11_get_proto: %s", cmd);
f = popen(cmd, "r");
if (f && fgets(line, sizeof(line), f) &&
sscanf(line, "%*s %511s %511s", proto, data) == 2)
got_data = 1;
if (f)
pclose(f);
free(cmd);
}
}
if (do_unlink) {
unlink(xauthfile);
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
* response anyway, and substitute this data. The X11
* server, however, will ignore this fake data and use
* whatever authentication mechanisms it was using otherwise
* for the local connection.
*/
if (!got_data) {
u_int8_t rnd[16];
u_int i;
logit("Warning: No xauth data; "
"using fake authentication data for X11 forwarding.");
strlcpy(proto, SSH_X11_PROTO, sizeof proto);
arc4random_buf(rnd, sizeof(rnd));
for (i = 0; i < sizeof(rnd); i++) {
snprintf(data + 2 * i, sizeof data - 2 * i, "%02x",
rnd[i]);
}
}
return 0;
}
/*
* Checks if the client window has changed, and sends a packet about it to
* the server if so. The actual change is detected elsewhere (by a software
* interrupt on Unix); this just checks the flag and sends a message if
* appropriate.
*/
static void
client_check_window_change(struct ssh *ssh)
{
if (!received_window_change_signal)
return;
received_window_change_signal = 0;
debug2_f("changed");
channel_send_window_changes(ssh);
}
static int
client_global_request_reply(int type, u_int32_t seq, struct ssh *ssh)
{
struct global_confirm *gc;
if ((gc = TAILQ_FIRST(&global_confirms)) == NULL)
return 0;
if (gc->cb != NULL)
gc->cb(ssh, type, seq, gc->ctx);
if (--gc->ref_count <= 0) {
TAILQ_REMOVE(&global_confirms, gc, entry);
freezero(gc, sizeof(*gc));
}
ssh_packet_set_alive_timeouts(ssh, 0);
return 0;
}
static void
schedule_server_alive_check(void)
{
if (options.server_alive_interval > 0)
server_alive_time = monotime() + options.server_alive_interval;
}
static void
server_alive_check(struct ssh *ssh)
{
int r;
if (ssh_packet_inc_alive_timeouts(ssh) > options.server_alive_count_max) {
logit("Timeout, server %s not responding.", host);
cleanup_exit(255);
}
if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 ||
(r = sshpkt_put_u8(ssh, 1)) != 0 || /* boolean: want reply */
(r = sshpkt_send(ssh)) != 0)
fatal_fr(r, "send packet");
/* Insert an empty placeholder to maintain ordering */
client_register_global_confirm(NULL, NULL);
schedule_server_alive_check();
}
/* Try to send a dummy keystroke */
static int
send_chaff(struct ssh *ssh)
{
int r;
if (ssh->kex == NULL || (ssh->kex->flags & KEX_HAS_PING) == 0)
return 0;
/* XXX probabilistically send chaff? */
/*
* a SSH2_MSG_CHANNEL_DATA payload is 9 bytes:
* 4 bytes channel ID + 4 bytes string length + 1 byte string data
* simulate that here.
*/
if ((r = sshpkt_start(ssh, SSH2_MSG_PING)) != 0 ||
(r = sshpkt_put_cstring(ssh, "PING!")) != 0 ||
(r = sshpkt_send(ssh)) != 0)
fatal_fr(r, "send packet");
return 1;
}
/* Sets the next interval to send a keystroke or chaff packet */
static void
set_next_interval(const struct timespec *now, struct timespec *next_interval,
u_int interval_ms, int starting)
{
struct timespec tmp;
long long interval_ns, fuzz_ns;
static long long rate_fuzz;
interval_ns = interval_ms * (1000LL * 1000);
fuzz_ns = (interval_ns * SSH_KEYSTROKE_TIMING_FUZZ) / 100;
/* Center fuzz around requested interval */
if (fuzz_ns > INT_MAX)
fuzz_ns = INT_MAX;
if (fuzz_ns > interval_ns) {
/* Shouldn't happen */
fatal_f("internal error: fuzz %u%% %lldns > interval %lldns",
SSH_KEYSTROKE_TIMING_FUZZ, fuzz_ns, interval_ns);
}
/*
* Randomise the keystroke/chaff intervals in two ways:
* 1. Each interval has some random jitter applied to make the
* interval-to-interval time unpredictable.
* 2. The overall interval rate is also randomly perturbed for each
* chaffing session to make the average rate unpredictable.
*/
if (starting)
rate_fuzz = arc4random_uniform(fuzz_ns);
interval_ns -= fuzz_ns;
interval_ns += arc4random_uniform(fuzz_ns) + rate_fuzz;
tmp.tv_sec = interval_ns / (1000 * 1000 * 1000);
tmp.tv_nsec = interval_ns % (1000 * 1000 * 1000);
timespecadd(now, &tmp, next_interval);
}
/*
* Performs keystroke timing obfuscation. Returns non-zero if the
* output fd should be polled.
*/
static int
obfuscate_keystroke_timing(struct ssh *ssh, struct timespec *timeout,
int channel_did_enqueue)
{
static int active;
static struct timespec next_interval, chaff_until;
struct timespec now, tmp;
int just_started = 0, had_keystroke = 0;
static unsigned long long nchaff;
char *stop_reason = NULL;
long long n;
monotime_ts(&now);
if (options.obscure_keystroke_timing_interval <= 0)
return 1; /* disabled in config */
if (!channel_tty_open(ssh) || quit_pending) {
/* Stop if no channels left of we're waiting for one to close */
stop_reason = "no active channels";
} else if (ssh_packet_is_rekeying(ssh)) {
/* Stop if we're rekeying */
stop_reason = "rekeying started";
} else if (!ssh_packet_interactive_data_to_write(ssh) &&
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 && 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) {
if (timespeccmp(&now, &chaff_until, >=)) {
/* Stop if there have been no keystrokes for a while */
stop_reason = "chaff time expired";
} else if (timespeccmp(&now, &next_interval, >=) &&
!ssh_packet_have_data_to_write(ssh)) {
/* If due to send but have no data, then send chaff */
if (send_chaff(ssh))
nchaff++;
}
}
if (stop_reason != NULL) {
if (active) {
debug3_f("stopping: %s (%llu chaff packets sent)",
stop_reason, nchaff);
active = 0;
}
return 1;
}
/*
* If we're in interactive mode, and only have a small amount
* of outbound data, then we assume that the user is typing
* 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) &&
channel_did_enqueue && ssh_packet_have_data_to_write(ssh)) {
debug3_f("starting: interval ~%dms",
options.obscure_keystroke_timing_interval);
just_started = had_keystroke = active = 1;
nchaff = 0;
set_next_interval(&now, &next_interval,
options.obscure_keystroke_timing_interval, 1);
}
/* Don't hold off if obfuscation inactive */
if (!active)
return 1;
if (had_keystroke) {
/*
* Arrange to send chaff packets for a random interval after
* the last keystroke was sent.
*/
ms_to_timespec(&tmp, SSH_KEYSTROKE_CHAFF_MIN_MS +
arc4random_uniform(SSH_KEYSTROKE_CHAFF_RNG_MS));
timespecadd(&now, &tmp, &chaff_until);
}
ptimeout_deadline_monotime_tsp(timeout, &next_interval);
if (just_started)
return 1;
/* Don't arm output fd for poll until the timing interval has elapsed */
if (timespeccmp(&now, &next_interval, <))
return 0;
/* Calculate number of intervals missed since the last check */
n = (now.tv_sec - next_interval.tv_sec) * 1000LL * 1000 * 1000;
n += now.tv_nsec - next_interval.tv_nsec;
n /= options.obscure_keystroke_timing_interval * 1000LL * 1000;
n = (n < 0) ? 1 : n + 1;
/* Advance to the next interval */
set_next_interval(&now, &next_interval,
options.obscure_keystroke_timing_interval * n, 0);
return 1;
}
/*
* Waits until the client can do something (some data becomes available on
* one of the file descriptors).
*/
static void
client_wait_until_can_do_something(struct ssh *ssh, struct pollfd **pfdp,
u_int *npfd_allocp, u_int *npfd_activep, int channel_did_enqueue,
sigset_t *sigsetp, int *conn_in_readyp, int *conn_out_readyp)
{
struct timespec timeout;
int ret, oready;
u_int p;
*conn_in_readyp = *conn_out_readyp = 0;
/* Prepare channel poll. First two pollfd entries are reserved */
ptimeout_init(&timeout);
channel_prepare_poll(ssh, pfdp, npfd_allocp, npfd_activep, 2, &timeout);
if (*npfd_activep < 2)
fatal_f("bad npfd %u", *npfd_activep); /* shouldn't happen */
/* channel_prepare_poll could have closed the last channel */
if (session_closed && !channel_still_open(ssh) &&
!ssh_packet_have_data_to_write(ssh)) {
/* clear events since we did not call poll() */
for (p = 0; p < *npfd_activep; p++)
(*pfdp)[p].revents = 0;
return;
}
oready = obfuscate_keystroke_timing(ssh, &timeout, channel_did_enqueue);
/* Monitor server connection on reserved pollfd entries */
(*pfdp)[0].fd = connection_in;
(*pfdp)[0].events = POLLIN;
(*pfdp)[1].fd = connection_out;
(*pfdp)[1].events = (oready && ssh_packet_have_data_to_write(ssh)) ?
POLLOUT : 0;
/*
* Wait for something to happen. This will suspend the process until
* some polled descriptor can be read, written, or has some other
* event pending, or a timeout expires.
*/
set_control_persist_exit_time(ssh);
if (control_persist_exit_time > 0)
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 && !ssh_packet_is_rekeying(ssh)) {
ptimeout_deadline_sec(&timeout,
ssh_packet_get_rekey_timeout(ssh));
}
ret = ppoll(*pfdp, *npfd_activep, ptimeout_get_tsp(&timeout), sigsetp);
if (ret == -1) {
/*
* We have to clear the events because we return.
* We have to return, because the mainloop checks for the flags
* set by the signal handlers.
*/
for (p = 0; p < *npfd_activep; p++)
(*pfdp)[p].revents = 0;
if (errno == EINTR)
return;
/* Note: we might still have data in the buffers. */
quit_message("poll: %s", strerror(errno));
return;
}
*conn_in_readyp = (*pfdp)[0].revents != 0;
*conn_out_readyp = (*pfdp)[1].revents != 0;
if (options.server_alive_interval > 0 && !*conn_in_readyp &&
monotime() >= server_alive_time) {
/*
* ServerAlive check is needed. We can't rely on the poll
* timing out since traffic on the client side such as port
* forwards can keep waking it up.
*/
server_alive_check(ssh);
}
}
static void
client_suspend_self(struct sshbuf *bin, struct sshbuf *bout, struct sshbuf *berr)
{
/* Flush stdout and stderr buffers. */
if (sshbuf_len(bout) > 0)
atomicio(vwrite, fileno(stdout), sshbuf_mutable_ptr(bout),
sshbuf_len(bout));
if (sshbuf_len(berr) > 0)
atomicio(vwrite, fileno(stderr), sshbuf_mutable_ptr(berr),
sshbuf_len(berr));
leave_raw_mode(options.request_tty == REQUEST_TTY_FORCE);
sshbuf_reset(bin);
sshbuf_reset(bout);
sshbuf_reset(berr);
/* Send the suspend signal to the program itself. */
kill(getpid(), SIGTSTP);
/* Reset window sizes in case they have changed */
received_window_change_signal = 1;
enter_raw_mode(options.request_tty == REQUEST_TTY_FORCE);
}
static void
client_process_net_input(struct ssh *ssh)
{
int r;
/*
* Read input from the server, and add any such data to the buffer of
* the packet subsystem.
*/
schedule_server_alive_check();
if ((r = ssh_packet_process_read(ssh, connection_in)) == 0)
return; /* success */
if (r == SSH_ERR_SYSTEM_ERROR) {
if (errno == EAGAIN || errno == EINTR || errno == EWOULDBLOCK)
return;
if (errno == EPIPE) {
quit_message("Connection to %s closed by remote host.",
host);
return;
}
}
quit_message("Read from remote host %s: %s", host, ssh_err(r));
}
static void
client_status_confirm(struct ssh *ssh, int type, Channel *c, void *ctx)
{
struct channel_reply_ctx *cr = (struct channel_reply_ctx *)ctx;
char errmsg[256];
int r, tochan;
/*
* If a TTY was explicitly requested, then a failure to allocate
* one is fatal.
*/
if (cr->action == CONFIRM_TTY &&
(options.request_tty == REQUEST_TTY_FORCE ||
options.request_tty == REQUEST_TTY_YES))
cr->action = CONFIRM_CLOSE;
/* XXX suppress on mux _client_ quietmode */
tochan = options.log_level >= SYSLOG_LEVEL_ERROR &&
c->ctl_chan != -1 && c->extended_usage == CHAN_EXTENDED_WRITE;
if (type == SSH2_MSG_CHANNEL_SUCCESS) {
debug2("%s request accepted on channel %d",
cr->request_type, c->self);
} else if (type == SSH2_MSG_CHANNEL_FAILURE) {
if (tochan) {
snprintf(errmsg, sizeof(errmsg),
"%s request failed\r\n", cr->request_type);
} else {
snprintf(errmsg, sizeof(errmsg),
"%s request failed on channel %d",
cr->request_type, c->self);
}
/* If error occurred on primary session channel, then exit */
if (cr->action == CONFIRM_CLOSE && c->self == session_ident)
fatal("%s", errmsg);
/*
* If error occurred on mux client, append to
* their stderr.
*/
if (tochan) {
debug3_f("channel %d: mux request: %s", c->self,
cr->request_type);
if ((r = sshbuf_put(c->extended, errmsg,
strlen(errmsg))) != 0)
fatal_fr(r, "sshbuf_put");
} else
error("%s", errmsg);
if (cr->action == CONFIRM_TTY) {
/*
* If a TTY allocation error occurred, then arrange
* for the correct TTY to leave raw mode.
*/
if (c->self == session_ident)
leave_raw_mode(0);
else
mux_tty_alloc_failed(ssh, c);
} else if (cr->action == CONFIRM_CLOSE) {
chan_read_failed(ssh, c);
chan_write_failed(ssh, c);
}
}
free(cr);
}
static void
client_abandon_status_confirm(struct ssh *ssh, Channel *c, void *ctx)
{
free(ctx);
}
void
client_expect_confirm(struct ssh *ssh, int id, const char *request,
enum confirm_action action)
{
struct channel_reply_ctx *cr = xcalloc(1, sizeof(*cr));
cr->request_type = request;
cr->action = action;
channel_register_status_confirm(ssh, id, client_status_confirm,
client_abandon_status_confirm, cr);
}
void
client_register_global_confirm(global_confirm_cb *cb, void *ctx)
{
struct global_confirm *gc, *last_gc;
/* Coalesce identical callbacks */
last_gc = TAILQ_LAST(&global_confirms, global_confirms);
if (last_gc && last_gc->cb == cb && last_gc->ctx == ctx) {
if (++last_gc->ref_count >= INT_MAX)
fatal_f("last_gc->ref_count = %d",
last_gc->ref_count);
return;
}
gc = xcalloc(1, sizeof(*gc));
gc->cb = cb;
gc->ctx = ctx;
gc->ref_count = 1;
TAILQ_INSERT_TAIL(&global_confirms, gc, entry);
}
/*
* Returns non-zero if the client is able to handle a [email protected]
* hostkey update request.
*/
static int
can_update_hostkeys(void)
{
if (hostkeys_update_complete)
return 0;
if (options.update_hostkeys == SSH_UPDATE_HOSTKEYS_ASK &&
options.batch_mode)
return 0; /* won't ask in batchmode, so don't even try */
if (!options.update_hostkeys || options.num_user_hostfiles <= 0)
return 0;
return 1;
}
static void
client_repledge(void)
{
debug3_f("enter");
/* Might be able to tighten pledge now that session is established */
if (options.control_master || options.control_path != NULL ||
options.forward_x11 || options.fork_after_authentication ||
can_update_hostkeys() ||
(session_ident != -1 && !session_setup_complete)) {
/* Can't tighten */
return;
}
/*
* LocalCommand and UpdateHostkeys have finished, so can get rid of
* filesystem.
*
* XXX protocol allows a server can to change hostkeys during the
* connection at rekey time that could trigger a hostkeys update
* but AFAIK no implementations support this. Could improve by
* forcing known_hosts to be read-only or via unveil(2).
*/
if (options.num_local_forwards != 0 ||
options.num_remote_forwards != 0 ||
options.num_permitted_remote_opens != 0 ||
options.enable_escape_commandline != 0) {
/* rfwd needs inet */
debug("pledge: network");
if (pledge("stdio unix inet dns proc tty", NULL) == -1)
fatal_f("pledge(): %s", strerror(errno));
} else if (options.forward_agent != 0) {
/* agent forwarding needs to open $SSH_AUTH_SOCK at will */
debug("pledge: agent");
if (pledge("stdio unix proc tty", NULL) == -1)
fatal_f("pledge(): %s", strerror(errno));
} else {
debug("pledge: fork");
if (pledge("stdio proc tty", NULL) == -1)
fatal_f("pledge(): %s", strerror(errno));
}
/* XXX further things to do:
*
* - might be able to get rid of proc if we kill ~^Z
* - ssh -N (no session)
* - stdio forwarding
* - sessions without tty
*/
}
static void
process_cmdline(struct ssh *ssh)
{
void (*handler)(int);
char *s, *cmd;
int ok, delete = 0, local = 0, remote = 0, dynamic = 0;
struct Forward fwd;
memset(&fwd, 0, sizeof(fwd));
leave_raw_mode(options.request_tty == REQUEST_TTY_FORCE);
handler = ssh_signal(SIGINT, SIG_IGN);
cmd = s = read_passphrase("\r\nssh> ", RP_ECHO);
if (s == NULL)
goto out;
while (isspace((u_char)*s))
s++;
if (*s == '-')