blob: 78ba6315344baa949132129ad9674fcc781c3503 [file] [log] [blame]
Damien Millerb1cbfa22008-05-19 16:00:08 +10001/* $OpenBSD: mux.c,v 1.1 2008/05/09 14:18:44 djm Exp $ */
2/*
3 * Copyright (c) 2002-2008 Damien Miller <djm@openbsd.org>
4 *
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
8 *
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16 */
17
18/* ssh session multiplexing support */
19
20#include <sys/types.h>
21#include <sys/param.h>
22#include <sys/stat.h>
23#include <sys/socket.h>
24#include <sys/un.h>
25
26#include <errno.h>
27#include <fcntl.h>
28#include <signal.h>
29#include <stdarg.h>
30#include <stddef.h>
31#include <stdlib.h>
32#include <stdio.h>
33#include <string.h>
34#include <unistd.h>
35#include <util.h>
36#include <paths.h>
37
38#include "openbsd-compat/sys-queue.h"
39#include "xmalloc.h"
40#include "log.h"
41#include "ssh.h"
42#include "pathnames.h"
43#include "misc.h"
44#include "match.h"
45#include "buffer.h"
46#include "channels.h"
47#include "msg.h"
48#include "packet.h"
49#include "monitor_fdpass.h"
50#include "sshpty.h"
51#include "key.h"
52#include "readconf.h"
53#include "clientloop.h"
54
55/* from ssh.c */
56extern int tty_flag;
57extern Options options;
58extern int stdin_null_flag;
59extern char *host;
60int subsystem_flag;
61extern Buffer command;
62
63/* fd to control socket */
64int muxserver_sock = -1;
65
66/* Multiplexing control command */
67u_int muxclient_command = 0;
68
69/* Set when signalled. */
70static volatile sig_atomic_t muxclient_terminate = 0;
71
72/* PID of multiplex server */
73static u_int muxserver_pid = 0;
74
75
76/* ** Multiplexing master support */
77
78/* Prepare a mux master to listen on a Unix domain socket. */
79void
80muxserver_listen(void)
81{
82 struct sockaddr_un addr;
83 mode_t old_umask;
84 int addr_len;
85
86 if (options.control_path == NULL ||
87 options.control_master == SSHCTL_MASTER_NO)
88 return;
89
90 debug("setting up multiplex master socket");
91
92 memset(&addr, '\0', sizeof(addr));
93 addr.sun_family = AF_UNIX;
94 addr_len = offsetof(struct sockaddr_un, sun_path) +
95 strlen(options.control_path) + 1;
96
97 if (strlcpy(addr.sun_path, options.control_path,
98 sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
99 fatal("ControlPath too long");
100
101 if ((muxserver_sock = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
102 fatal("%s socket(): %s", __func__, strerror(errno));
103
104 old_umask = umask(0177);
105 if (bind(muxserver_sock, (struct sockaddr *)&addr, addr_len) == -1) {
106 muxserver_sock = -1;
107 if (errno == EINVAL || errno == EADDRINUSE)
108 fatal("ControlSocket %s already exists",
109 options.control_path);
110 else
111 fatal("%s bind(): %s", __func__, strerror(errno));
112 }
113 umask(old_umask);
114
115 if (listen(muxserver_sock, 64) == -1)
116 fatal("%s listen(): %s", __func__, strerror(errno));
117
118 set_nonblock(muxserver_sock);
119}
120
121/* Callback on open confirmation in mux master for a mux client session. */
122static void
123client_extra_session2_setup(int id, void *arg)
124{
125 struct mux_session_confirm_ctx *cctx = arg;
126 const char *display;
127 Channel *c;
128 int i;
129
130 if (cctx == NULL)
131 fatal("%s: cctx == NULL", __func__);
132 if ((c = channel_lookup(id)) == NULL)
133 fatal("%s: no channel for id %d", __func__, id);
134
135 display = getenv("DISPLAY");
136 if (cctx->want_x_fwd && options.forward_x11 && display != NULL) {
137 char *proto, *data;
138 /* Get reasonable local authentication information. */
139 client_x11_get_proto(display, options.xauth_location,
140 options.forward_x11_trusted, &proto, &data);
141 /* Request forwarding with authentication spoofing. */
142 debug("Requesting X11 forwarding with authentication spoofing.");
143 x11_request_forwarding_with_spoofing(id, display, proto, data);
144 /* XXX wait for reply */
145 }
146
147 if (cctx->want_agent_fwd && options.forward_agent) {
148 debug("Requesting authentication agent forwarding.");
149 channel_request_start(id, "auth-agent-req@openssh.com", 0);
150 packet_send();
151 }
152
153 client_session2_setup(id, cctx->want_tty, cctx->want_subsys,
154 cctx->term, &cctx->tio, c->rfd, &cctx->cmd, cctx->env);
155
156 c->open_confirm_ctx = NULL;
157 buffer_free(&cctx->cmd);
158 xfree(cctx->term);
159 if (cctx->env != NULL) {
160 for (i = 0; cctx->env[i] != NULL; i++)
161 xfree(cctx->env[i]);
162 xfree(cctx->env);
163 }
164 xfree(cctx);
165}
166
167/*
168 * Accept a connection on the mux master socket and process the
169 * client's request. Returns flag indicating whether mux master should
170 * begin graceful close.
171 */
172int
173muxserver_accept_control(void)
174{
175 Buffer m;
176 Channel *c;
177 int client_fd, new_fd[3], ver, allowed, window, packetmax;
178 socklen_t addrlen;
179 struct sockaddr_storage addr;
180 struct mux_session_confirm_ctx *cctx;
181 char *cmd;
182 u_int i, j, len, env_len, mux_command, flags;
183 uid_t euid;
184 gid_t egid;
185 int start_close = 0;
186
187 /*
188 * Accept connection on control socket
189 */
190 memset(&addr, 0, sizeof(addr));
191 addrlen = sizeof(addr);
192 if ((client_fd = accept(muxserver_sock,
193 (struct sockaddr*)&addr, &addrlen)) == -1) {
194 error("%s accept: %s", __func__, strerror(errno));
195 return 0;
196 }
197
198 if (getpeereid(client_fd, &euid, &egid) < 0) {
199 error("%s getpeereid failed: %s", __func__, strerror(errno));
200 close(client_fd);
201 return 0;
202 }
203 if ((euid != 0) && (getuid() != euid)) {
204 error("control mode uid mismatch: peer euid %u != uid %u",
205 (u_int) euid, (u_int) getuid());
206 close(client_fd);
207 return 0;
208 }
209
210 /* XXX handle asynchronously */
211 unset_nonblock(client_fd);
212
213 /* Read command */
214 buffer_init(&m);
215 if (ssh_msg_recv(client_fd, &m) == -1) {
216 error("%s: client msg_recv failed", __func__);
217 close(client_fd);
218 buffer_free(&m);
219 return 0;
220 }
221 if ((ver = buffer_get_char(&m)) != SSHMUX_VER) {
222 error("%s: wrong client version %d", __func__, ver);
223 buffer_free(&m);
224 close(client_fd);
225 return 0;
226 }
227
228 allowed = 1;
229 mux_command = buffer_get_int(&m);
230 flags = buffer_get_int(&m);
231
232 buffer_clear(&m);
233
234 switch (mux_command) {
235 case SSHMUX_COMMAND_OPEN:
236 if (options.control_master == SSHCTL_MASTER_ASK ||
237 options.control_master == SSHCTL_MASTER_AUTO_ASK)
238 allowed = ask_permission("Allow shared connection "
239 "to %s? ", host);
240 /* continue below */
241 break;
242 case SSHMUX_COMMAND_TERMINATE:
243 if (options.control_master == SSHCTL_MASTER_ASK ||
244 options.control_master == SSHCTL_MASTER_AUTO_ASK)
245 allowed = ask_permission("Terminate shared connection "
246 "to %s? ", host);
247 if (allowed)
248 start_close = 1;
249 /* FALLTHROUGH */
250 case SSHMUX_COMMAND_ALIVE_CHECK:
251 /* Reply for SSHMUX_COMMAND_TERMINATE and ALIVE_CHECK */
252 buffer_clear(&m);
253 buffer_put_int(&m, allowed);
254 buffer_put_int(&m, getpid());
255 if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) {
256 error("%s: client msg_send failed", __func__);
257 close(client_fd);
258 buffer_free(&m);
259 return start_close;
260 }
261 buffer_free(&m);
262 close(client_fd);
263 return start_close;
264 default:
265 error("Unsupported command %d", mux_command);
266 buffer_free(&m);
267 close(client_fd);
268 return 0;
269 }
270
271 /* Reply for SSHMUX_COMMAND_OPEN */
272 buffer_clear(&m);
273 buffer_put_int(&m, allowed);
274 buffer_put_int(&m, getpid());
275 if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) {
276 error("%s: client msg_send failed", __func__);
277 close(client_fd);
278 buffer_free(&m);
279 return 0;
280 }
281
282 if (!allowed) {
283 error("Refused control connection");
284 close(client_fd);
285 buffer_free(&m);
286 return 0;
287 }
288
289 buffer_clear(&m);
290 if (ssh_msg_recv(client_fd, &m) == -1) {
291 error("%s: client msg_recv failed", __func__);
292 close(client_fd);
293 buffer_free(&m);
294 return 0;
295 }
296 if ((ver = buffer_get_char(&m)) != SSHMUX_VER) {
297 error("%s: wrong client version %d", __func__, ver);
298 buffer_free(&m);
299 close(client_fd);
300 return 0;
301 }
302
303 cctx = xcalloc(1, sizeof(*cctx));
304 cctx->want_tty = (flags & SSHMUX_FLAG_TTY) != 0;
305 cctx->want_subsys = (flags & SSHMUX_FLAG_SUBSYS) != 0;
306 cctx->want_x_fwd = (flags & SSHMUX_FLAG_X11_FWD) != 0;
307 cctx->want_agent_fwd = (flags & SSHMUX_FLAG_AGENT_FWD) != 0;
308 cctx->term = buffer_get_string(&m, &len);
309
310 cmd = buffer_get_string(&m, &len);
311 buffer_init(&cctx->cmd);
312 buffer_append(&cctx->cmd, cmd, strlen(cmd));
313
314 env_len = buffer_get_int(&m);
315 env_len = MIN(env_len, 4096);
316 debug3("%s: receiving %d env vars", __func__, env_len);
317 if (env_len != 0) {
318 cctx->env = xcalloc(env_len + 1, sizeof(*cctx->env));
319 for (i = 0; i < env_len; i++)
320 cctx->env[i] = buffer_get_string(&m, &len);
321 cctx->env[i] = NULL;
322 }
323
324 debug2("%s: accepted tty %d, subsys %d, cmd %s", __func__,
325 cctx->want_tty, cctx->want_subsys, cmd);
326 xfree(cmd);
327
328 /* Gather fds from client */
329 for(i = 0; i < 3; i++) {
330 if ((new_fd[i] = mm_receive_fd(client_fd)) == -1) {
331 error("%s: failed to receive fd %d from slave",
332 __func__, i);
333 for (j = 0; j < i; j++)
334 close(new_fd[j]);
335 for (j = 0; j < env_len; j++)
336 xfree(cctx->env[j]);
337 if (env_len > 0)
338 xfree(cctx->env);
339 xfree(cctx->term);
340 buffer_free(&cctx->cmd);
341 close(client_fd);
342 xfree(cctx);
343 return 0;
344 }
345 }
346
347 debug2("%s: got fds stdin %d, stdout %d, stderr %d", __func__,
348 new_fd[0], new_fd[1], new_fd[2]);
349
350 /* Try to pick up ttymodes from client before it goes raw */
351 if (cctx->want_tty && tcgetattr(new_fd[0], &cctx->tio) == -1)
352 error("%s: tcgetattr: %s", __func__, strerror(errno));
353
354 /* This roundtrip is just for synchronisation of ttymodes */
355 buffer_clear(&m);
356 if (ssh_msg_send(client_fd, SSHMUX_VER, &m) == -1) {
357 error("%s: client msg_send failed", __func__);
358 close(client_fd);
359 close(new_fd[0]);
360 close(new_fd[1]);
361 close(new_fd[2]);
362 buffer_free(&m);
363 xfree(cctx->term);
364 if (env_len != 0) {
365 for (i = 0; i < env_len; i++)
366 xfree(cctx->env[i]);
367 xfree(cctx->env);
368 }
369 return 0;
370 }
371 buffer_free(&m);
372
373 /* enable nonblocking unless tty */
374 if (!isatty(new_fd[0]))
375 set_nonblock(new_fd[0]);
376 if (!isatty(new_fd[1]))
377 set_nonblock(new_fd[1]);
378 if (!isatty(new_fd[2]))
379 set_nonblock(new_fd[2]);
380
381 set_nonblock(client_fd);
382
383 window = CHAN_SES_WINDOW_DEFAULT;
384 packetmax = CHAN_SES_PACKET_DEFAULT;
385 if (cctx->want_tty) {
386 window >>= 1;
387 packetmax >>= 1;
388 }
389
390 c = channel_new("session", SSH_CHANNEL_OPENING,
391 new_fd[0], new_fd[1], new_fd[2], window, packetmax,
392 CHAN_EXTENDED_WRITE, "client-session", /*nonblock*/0);
393
394 /* XXX */
395 c->ctl_fd = client_fd;
396
397 debug3("%s: channel_new: %d", __func__, c->self);
398
399 channel_send_open(c->self);
400 channel_register_open_confirm(c->self,
401 client_extra_session2_setup, cctx);
402 return 0;
403}
404
405/* ** Multiplexing client support */
406
407/* Exit signal handler */
408static void
409control_client_sighandler(int signo)
410{
411 muxclient_terminate = signo;
412}
413
414/*
415 * Relay signal handler - used to pass some signals from mux client to
416 * mux master.
417 */
418static void
419control_client_sigrelay(int signo)
420{
421 int save_errno = errno;
422
423 if (muxserver_pid > 1)
424 kill(muxserver_pid, signo);
425
426 errno = save_errno;
427}
428
429/* Check mux client environment variables before passing them to mux master. */
430static int
431env_permitted(char *env)
432{
433 int i, ret;
434 char name[1024], *cp;
435
436 if ((cp = strchr(env, '=')) == NULL || cp == env)
437 return (0);
438 ret = snprintf(name, sizeof(name), "%.*s", (int)(cp - env), env);
439 if (ret <= 0 || (size_t)ret >= sizeof(name))
440 fatal("env_permitted: name '%.100s...' too long", env);
441
442 for (i = 0; i < options.num_send_env; i++)
443 if (match_pattern(name, options.send_env[i]))
444 return (1);
445
446 return (0);
447}
448
449/* Multiplex client main loop. */
450void
451muxclient(const char *path)
452{
453 struct sockaddr_un addr;
454 int i, r, fd, sock, exitval[2], num_env, addr_len;
455 Buffer m;
456 char *term;
457 extern char **environ;
458 u_int flags;
459
460 if (muxclient_command == 0)
461 muxclient_command = SSHMUX_COMMAND_OPEN;
462
463 switch (options.control_master) {
464 case SSHCTL_MASTER_AUTO:
465 case SSHCTL_MASTER_AUTO_ASK:
466 debug("auto-mux: Trying existing master");
467 /* FALLTHROUGH */
468 case SSHCTL_MASTER_NO:
469 break;
470 default:
471 return;
472 }
473
474 memset(&addr, '\0', sizeof(addr));
475 addr.sun_family = AF_UNIX;
476 addr_len = offsetof(struct sockaddr_un, sun_path) +
477 strlen(path) + 1;
478
479 if (strlcpy(addr.sun_path, path,
480 sizeof(addr.sun_path)) >= sizeof(addr.sun_path))
481 fatal("ControlPath too long");
482
483 if ((sock = socket(PF_UNIX, SOCK_STREAM, 0)) < 0)
484 fatal("%s socket(): %s", __func__, strerror(errno));
485
486 if (connect(sock, (struct sockaddr *)&addr, addr_len) == -1) {
487 if (muxclient_command != SSHMUX_COMMAND_OPEN) {
488 fatal("Control socket connect(%.100s): %s", path,
489 strerror(errno));
490 }
491 if (errno == ENOENT)
492 debug("Control socket \"%.100s\" does not exist", path);
493 else {
494 error("Control socket connect(%.100s): %s", path,
495 strerror(errno));
496 }
497 close(sock);
498 return;
499 }
500
501 if (stdin_null_flag) {
502 if ((fd = open(_PATH_DEVNULL, O_RDONLY)) == -1)
503 fatal("open(/dev/null): %s", strerror(errno));
504 if (dup2(fd, STDIN_FILENO) == -1)
505 fatal("dup2: %s", strerror(errno));
506 if (fd > STDERR_FILENO)
507 close(fd);
508 }
509
510 term = getenv("TERM");
511
512 flags = 0;
513 if (tty_flag)
514 flags |= SSHMUX_FLAG_TTY;
515 if (subsystem_flag)
516 flags |= SSHMUX_FLAG_SUBSYS;
517 if (options.forward_x11)
518 flags |= SSHMUX_FLAG_X11_FWD;
519 if (options.forward_agent)
520 flags |= SSHMUX_FLAG_AGENT_FWD;
521
522 signal(SIGPIPE, SIG_IGN);
523
524 buffer_init(&m);
525
526 /* Send our command to server */
527 buffer_put_int(&m, muxclient_command);
528 buffer_put_int(&m, flags);
529 if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1)
530 fatal("%s: msg_send", __func__);
531 buffer_clear(&m);
532
533 /* Get authorisation status and PID of controlee */
534 if (ssh_msg_recv(sock, &m) == -1)
535 fatal("%s: msg_recv", __func__);
536 if (buffer_get_char(&m) != SSHMUX_VER)
537 fatal("%s: wrong version", __func__);
538 if (buffer_get_int(&m) != 1)
539 fatal("Connection to master denied");
540 muxserver_pid = buffer_get_int(&m);
541
542 buffer_clear(&m);
543
544 switch (muxclient_command) {
545 case SSHMUX_COMMAND_ALIVE_CHECK:
546 fprintf(stderr, "Master running (pid=%d)\r\n",
547 muxserver_pid);
548 exit(0);
549 case SSHMUX_COMMAND_TERMINATE:
550 fprintf(stderr, "Exit request sent.\r\n");
551 exit(0);
552 case SSHMUX_COMMAND_OPEN:
553 /* continue below */
554 break;
555 default:
556 fatal("silly muxclient_command %d", muxclient_command);
557 }
558
559 /* SSHMUX_COMMAND_OPEN */
560 buffer_put_cstring(&m, term ? term : "");
561 buffer_append(&command, "\0", 1);
562 buffer_put_cstring(&m, buffer_ptr(&command));
563
564 if (options.num_send_env == 0 || environ == NULL) {
565 buffer_put_int(&m, 0);
566 } else {
567 /* Pass environment */
568 num_env = 0;
569 for (i = 0; environ[i] != NULL; i++)
570 if (env_permitted(environ[i]))
571 num_env++; /* Count */
572
573 buffer_put_int(&m, num_env);
574
575 for (i = 0; environ[i] != NULL && num_env >= 0; i++)
576 if (env_permitted(environ[i])) {
577 num_env--;
578 buffer_put_cstring(&m, environ[i]);
579 }
580 }
581
582 if (ssh_msg_send(sock, SSHMUX_VER, &m) == -1)
583 fatal("%s: msg_send", __func__);
584
585 if (mm_send_fd(sock, STDIN_FILENO) == -1 ||
586 mm_send_fd(sock, STDOUT_FILENO) == -1 ||
587 mm_send_fd(sock, STDERR_FILENO) == -1)
588 fatal("%s: send fds failed", __func__);
589
590 /* Wait for reply, so master has a chance to gather ttymodes */
591 buffer_clear(&m);
592 if (ssh_msg_recv(sock, &m) == -1)
593 fatal("%s: msg_recv", __func__);
594 if (buffer_get_char(&m) != SSHMUX_VER)
595 fatal("%s: wrong version", __func__);
596 buffer_free(&m);
597
598 signal(SIGHUP, control_client_sighandler);
599 signal(SIGINT, control_client_sighandler);
600 signal(SIGTERM, control_client_sighandler);
601 signal(SIGWINCH, control_client_sigrelay);
602
603 if (tty_flag)
604 enter_raw_mode();
605
606 /*
607 * Stick around until the controlee closes the client_fd.
608 * Before it does, it is expected to write this process' exit
609 * value (one int). This process must read the value and wait for
610 * the closure of the client_fd; if this one closes early, the
611 * multiplex master will terminate early too (possibly losing data).
612 */
613 exitval[0] = 0;
614 for (i = 0; !muxclient_terminate && i < (int)sizeof(exitval);) {
615 r = read(sock, (char *)exitval + i, sizeof(exitval) - i);
616 if (r == 0) {
617 debug2("Received EOF from master");
618 break;
619 }
620 if (r == -1) {
621 if (errno == EINTR)
622 continue;
623 fatal("%s: read %s", __func__, strerror(errno));
624 }
625 i += r;
626 }
627
628 close(sock);
629 leave_raw_mode();
630 if (i > (int)sizeof(int))
631 fatal("%s: master returned too much data (%d > %lu)",
632 __func__, i, sizeof(int));
633 if (muxclient_terminate) {
634 debug2("Exiting on signal %d", muxclient_terminate);
635 exitval[0] = 255;
636 } else if (i < (int)sizeof(int)) {
637 debug2("Control master terminated unexpectedly");
638 exitval[0] = 255;
639 } else
640 debug2("Received exit status from master %d", exitval[0]);
641
642 if (tty_flag && options.log_level != SYSLOG_LEVEL_QUIET)
643 fprintf(stderr, "Shared connection to %s closed.\r\n", host);
644
645 exit(exitval[0]);
646}