1 /* $OpenBSD: serverloop.c,v 1.232 2022/04/20 04:19:11 djm Exp $ */
2 /*
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5 * All rights reserved
6 * Server main loop for handling the interactive session.
7 *
8 * As far as I am concerned, the code I have written for this software
9 * can be used freely for any purpose. Any derived versions of this
10 * software must be clearly marked as such, and if the derived work is
11 * incompatible with the protocol description in the RFC file, it must be
12 * called by a name other than "ssh" or "Secure Shell".
13 *
14 * SSH2 support by Markus Friedl.
15 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions
19 * are met:
20 * 1. Redistributions of source code must retain the above copyright
21 * notice, this list of conditions and the following disclaimer.
22 * 2. Redistributions in binary form must reproduce the above copyright
23 * notice, this list of conditions and the following disclaimer in the
24 * documentation and/or other materials provided with the distribution.
25 *
26 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
27 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
28 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
29 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
30 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
31 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
35 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
36 */
37
38 #include "includes.h"
39
40 #include <sys/types.h>
41 #include <sys/wait.h>
42 #include <sys/socket.h>
43 #ifdef HAVE_SYS_TIME_H
44 # include <sys/time.h>
45 #endif
46
47 #include <netinet/in.h>
48
49 #include <errno.h>
50 #include <fcntl.h>
51 #include <pwd.h>
52 #include <limits.h>
53 #ifdef HAVE_POLL_H
54 #include <poll.h>
55 #endif
56 #include <signal.h>
57 #include <string.h>
58 #include <termios.h>
59 #include <unistd.h>
60 #include <stdarg.h>
61
62 #include "openbsd-compat/sys-queue.h"
63 #include "xmalloc.h"
64 #include "packet.h"
65 #include "sshbuf.h"
66 #include "log.h"
67 #include "misc.h"
68 #include "servconf.h"
69 #include "canohost.h"
70 #include "sshpty.h"
71 #include "channels.h"
72 #include "compat.h"
73 #include "ssh2.h"
74 #include "sshkey.h"
75 #include "cipher.h"
76 #include "kex.h"
77 #include "hostfile.h"
78 #include "auth.h"
79 #include "session.h"
80 #include "dispatch.h"
81 #include "auth-options.h"
82 #include "serverloop.h"
83 #include "ssherr.h"
84
85 extern ServerOptions options;
86
87 /* XXX */
88 extern Authctxt *the_authctxt;
89 extern struct sshauthopt *auth_opts;
90 extern int use_privsep;
91
92 static int no_more_sessions = 0; /* Disallow further sessions. */
93
94 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */
95
96 /* Cleanup on signals (!use_privsep case only) */
97 static volatile sig_atomic_t received_sigterm = 0;
98
99 /* prototypes */
100 static void server_init_dispatch(struct ssh *);
101
102 /* requested tunnel forwarding interface(s), shared with session.c */
103 char *tun_fwd_ifnames = NULL;
104
105 /* returns 1 if bind to specified port by specified user is permitted */
106 static int
bind_permitted(int port,uid_t uid)107 bind_permitted(int port, uid_t uid)
108 {
109 if (use_privsep)
110 return 1; /* allow system to decide */
111 if (port < IPPORT_RESERVED && uid != 0)
112 return 0;
113 return 1;
114 }
115
116 /*ARGSUSED*/
117 static void
sigchld_handler(int sig)118 sigchld_handler(int sig)
119 {
120 child_terminated = 1;
121 }
122
123 /*ARGSUSED*/
124 static void
sigterm_handler(int sig)125 sigterm_handler(int sig)
126 {
127 received_sigterm = sig;
128 }
129
130 static void
client_alive_check(struct ssh * ssh)131 client_alive_check(struct ssh *ssh)
132 {
133 char remote_id[512];
134 int r, channel_id;
135
136 /* timeout, check to see how many we have had */
137 if (options.client_alive_count_max > 0 &&
138 ssh_packet_inc_alive_timeouts(ssh) >
139 options.client_alive_count_max) {
140 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id));
141 logit("Timeout, client not responding from %s", remote_id);
142 cleanup_exit(255);
143 }
144
145 /*
146 * send a bogus global/channel request with "wantreply",
147 * we should get back a failure
148 */
149 if ((channel_id = channel_find_open(ssh)) == -1) {
150 if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 ||
151 (r = sshpkt_put_cstring(ssh, "keepalive@openssh.com"))
152 != 0 ||
153 (r = sshpkt_put_u8(ssh, 1)) != 0) /* boolean: want reply */
154 fatal_fr(r, "compose");
155 } else {
156 channel_request_start(ssh, channel_id,
157 "keepalive@openssh.com", 1);
158 }
159 if ((r = sshpkt_send(ssh)) != 0)
160 fatal_fr(r, "send");
161 }
162
163 /*
164 * Sleep in ppoll() until we can do something.
165 * Optionally, a maximum time can be specified for the duration of
166 * the wait (0 = infinite).
167 */
168 static void
wait_until_can_do_something(struct ssh * ssh,int connection_in,int connection_out,struct pollfd ** pfdp,u_int * npfd_allocp,u_int * npfd_activep,u_int64_t max_time_ms,sigset_t * sigsetp,int * conn_in_readyp,int * conn_out_readyp)169 wait_until_can_do_something(struct ssh *ssh,
170 int connection_in, int connection_out, struct pollfd **pfdp,
171 u_int *npfd_allocp, u_int *npfd_activep, u_int64_t max_time_ms,
172 sigset_t *sigsetp, int *conn_in_readyp, int *conn_out_readyp)
173 {
174 struct timespec ts, *tsp;
175 int ret;
176 time_t minwait_secs = 0;
177 int client_alive_scheduled = 0;
178 u_int p;
179 /* time we last heard from the client OR sent a keepalive */
180 static time_t last_client_time;
181
182 *conn_in_readyp = *conn_out_readyp = 0;
183
184 /* Prepare channel poll. First two pollfd entries are reserved */
185 channel_prepare_poll(ssh, pfdp, npfd_allocp, npfd_activep,
186 2, &minwait_secs);
187 if (*npfd_activep < 2)
188 fatal_f("bad npfd %u", *npfd_activep); /* shouldn't happen */
189
190 /* XXX need proper deadline system for rekey/client alive */
191 if (minwait_secs != 0)
192 max_time_ms = MINIMUM(max_time_ms, (u_int)minwait_secs * 1000);
193
194 /*
195 * if using client_alive, set the max timeout accordingly,
196 * and indicate that this particular timeout was for client
197 * alive by setting the client_alive_scheduled flag.
198 *
199 * this could be randomized somewhat to make traffic
200 * analysis more difficult, but we're not doing it yet.
201 */
202 if (options.client_alive_interval) {
203 uint64_t keepalive_ms =
204 (uint64_t)options.client_alive_interval * 1000;
205
206 if (max_time_ms == 0 || max_time_ms > keepalive_ms) {
207 max_time_ms = keepalive_ms;
208 client_alive_scheduled = 1;
209 }
210 if (last_client_time == 0)
211 last_client_time = monotime();
212 }
213
214 #if 0
215 /* wrong: bad condition XXX */
216 if (channel_not_very_much_buffered_data())
217 #endif
218 /* Monitor client connection on reserved pollfd entries */
219 (*pfdp)[0].fd = connection_in;
220 (*pfdp)[0].events = POLLIN;
221 (*pfdp)[1].fd = connection_out;
222 (*pfdp)[1].events = ssh_packet_have_data_to_write(ssh) ? POLLOUT : 0;
223
224 /*
225 * If child has terminated and there is enough buffer space to read
226 * from it, then read as much as is available and exit.
227 */
228 if (child_terminated && ssh_packet_not_very_much_data_to_write(ssh))
229 if (max_time_ms == 0 || client_alive_scheduled)
230 max_time_ms = 100;
231
232 if (max_time_ms == 0)
233 tsp = NULL;
234 else {
235 ts.tv_sec = max_time_ms / 1000;
236 ts.tv_nsec = 1000000 * (max_time_ms % 1000);
237 tsp = &ts;
238 }
239
240 /* Wait for something to happen, or the timeout to expire. */
241 ret = ppoll(*pfdp, *npfd_activep, tsp, sigsetp);
242
243 if (ret == -1) {
244 for (p = 0; p < *npfd_activep; p++)
245 (*pfdp)[p].revents = 0;
246 if (errno != EINTR)
247 fatal_f("ppoll: %.100s", strerror(errno));
248 return;
249 }
250
251 *conn_in_readyp = (*pfdp)[0].revents != 0;
252 *conn_out_readyp = (*pfdp)[1].revents != 0;
253
254 if (client_alive_scheduled) {
255 time_t now = monotime();
256
257 /*
258 * If the ppoll timed out, or returned for some other reason
259 * but we haven't heard from the client in time, send keepalive.
260 */
261 if (ret == 0 || (last_client_time != 0 && last_client_time +
262 options.client_alive_interval <= now)) {
263 client_alive_check(ssh);
264 last_client_time = now;
265 } else if (*conn_in_readyp)
266 last_client_time = now;
267 }
268 }
269
270 /*
271 * Processes input from the client and the program. Input data is stored
272 * in buffers and processed later.
273 */
274 static int
process_input(struct ssh * ssh,int connection_in)275 process_input(struct ssh *ssh, int connection_in)
276 {
277 int r;
278
279 if ((r = ssh_packet_process_read(ssh, connection_in)) == 0)
280 return 0; /* success */
281 if (r == SSH_ERR_SYSTEM_ERROR) {
282 if (errno == EAGAIN || errno == EINTR || errno == EWOULDBLOCK)
283 return 0;
284 if (errno == EPIPE) {
285 verbose("Connection closed by %.100s port %d",
286 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
287 return -1;
288 }
289 verbose("Read error from remote host %s port %d: %s",
290 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
291 strerror(errno));
292 cleanup_exit(255);
293 }
294 return -1;
295 }
296
297 /*
298 * Sends data from internal buffers to client program stdin.
299 */
300 static void
process_output(struct ssh * ssh,int connection_out)301 process_output(struct ssh *ssh, int connection_out)
302 {
303 int r;
304
305 /* Send any buffered packet data to the client. */
306 if ((r = ssh_packet_write_poll(ssh)) != 0) {
307 sshpkt_fatal(ssh, r, "%s: ssh_packet_write_poll",
308 __func__);
309 }
310 }
311
312 static void
process_buffered_input_packets(struct ssh * ssh)313 process_buffered_input_packets(struct ssh *ssh)
314 {
315 ssh_dispatch_run_fatal(ssh, DISPATCH_NONBLOCK, NULL);
316 }
317
318 static void
collect_children(struct ssh * ssh)319 collect_children(struct ssh *ssh)
320 {
321 pid_t pid;
322 int status;
323
324 if (child_terminated) {
325 debug("Received SIGCHLD.");
326 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
327 (pid == -1 && errno == EINTR))
328 if (pid > 0)
329 session_close_by_pid(ssh, pid, status);
330 child_terminated = 0;
331 }
332 }
333
334 void
server_loop2(struct ssh * ssh,Authctxt * authctxt)335 server_loop2(struct ssh *ssh, Authctxt *authctxt)
336 {
337 struct pollfd *pfd = NULL;
338 u_int npfd_alloc = 0, npfd_active = 0;
339 int r, conn_in_ready, conn_out_ready;
340 u_int connection_in, connection_out;
341 u_int64_t rekey_timeout_ms = 0;
342 sigset_t bsigset, osigset;
343
344 debug("Entering interactive session for SSH2.");
345
346 if (sigemptyset(&bsigset) == -1 || sigaddset(&bsigset, SIGCHLD) == -1)
347 error_f("bsigset setup: %s", strerror(errno));
348 ssh_signal(SIGCHLD, sigchld_handler);
349 child_terminated = 0;
350 connection_in = ssh_packet_get_connection_in(ssh);
351 connection_out = ssh_packet_get_connection_out(ssh);
352
353 if (!use_privsep) {
354 ssh_signal(SIGTERM, sigterm_handler);
355 ssh_signal(SIGINT, sigterm_handler);
356 ssh_signal(SIGQUIT, sigterm_handler);
357 }
358
359 server_init_dispatch(ssh);
360
361 for (;;) {
362 process_buffered_input_packets(ssh);
363
364 if (!ssh_packet_is_rekeying(ssh) &&
365 ssh_packet_not_very_much_data_to_write(ssh))
366 channel_output_poll(ssh);
367 if (options.rekey_interval > 0 &&
368 !ssh_packet_is_rekeying(ssh)) {
369 rekey_timeout_ms = ssh_packet_get_rekey_timeout(ssh) *
370 1000;
371 } else {
372 rekey_timeout_ms = 0;
373 }
374
375 /*
376 * Block SIGCHLD while we check for dead children, then pass
377 * the old signal mask through to ppoll() so that it'll wake
378 * up immediately if a child exits after we've called waitpid().
379 */
380 if (sigprocmask(SIG_BLOCK, &bsigset, &osigset) == -1)
381 error_f("bsigset sigprocmask: %s", strerror(errno));
382 collect_children(ssh);
383 wait_until_can_do_something(ssh, connection_in, connection_out,
384 &pfd, &npfd_alloc, &npfd_active, rekey_timeout_ms, &osigset,
385 &conn_in_ready, &conn_out_ready);
386 if (sigprocmask(SIG_UNBLOCK, &bsigset, &osigset) == -1)
387 error_f("osigset sigprocmask: %s", strerror(errno));
388
389 if (received_sigterm) {
390 logit("Exiting on signal %d", (int)received_sigterm);
391 /* Clean up sessions, utmp, etc. */
392 cleanup_exit(255);
393 }
394
395 channel_after_poll(ssh, pfd, npfd_active);
396 if (conn_in_ready &&
397 process_input(ssh, connection_in) < 0)
398 break;
399 /* A timeout may have triggered rekeying */
400 if ((r = ssh_packet_check_rekey(ssh)) != 0)
401 fatal_fr(r, "cannot start rekeying");
402 if (conn_out_ready)
403 process_output(ssh, connection_out);
404 }
405 collect_children(ssh);
406 free(pfd);
407
408 /* free all channels, no more reads and writes */
409 channel_free_all(ssh);
410
411 /* free remaining sessions, e.g. remove wtmp entries */
412 session_destroy_all(ssh, NULL);
413 }
414
415 static int
server_input_keep_alive(int type,u_int32_t seq,struct ssh * ssh)416 server_input_keep_alive(int type, u_int32_t seq, struct ssh *ssh)
417 {
418 debug("Got %d/%u for keepalive", type, seq);
419 /*
420 * reset timeout, since we got a sane answer from the client.
421 * even if this was generated by something other than
422 * the bogus CHANNEL_REQUEST we send for keepalives.
423 */
424 ssh_packet_set_alive_timeouts(ssh, 0);
425 return 0;
426 }
427
428 static Channel *
server_request_direct_tcpip(struct ssh * ssh,int * reason,const char ** errmsg)429 server_request_direct_tcpip(struct ssh *ssh, int *reason, const char **errmsg)
430 {
431 Channel *c = NULL;
432 char *target = NULL, *originator = NULL;
433 u_int target_port = 0, originator_port = 0;
434 int r;
435
436 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 ||
437 (r = sshpkt_get_u32(ssh, &target_port)) != 0 ||
438 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 ||
439 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 ||
440 (r = sshpkt_get_end(ssh)) != 0)
441 sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
442 if (target_port > 0xFFFF) {
443 error_f("invalid target port");
444 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
445 goto out;
446 }
447 if (originator_port > 0xFFFF) {
448 error_f("invalid originator port");
449 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
450 goto out;
451 }
452
453 debug_f("originator %s port %u, target %s port %u",
454 originator, originator_port, target, target_port);
455
456 /* XXX fine grained permissions */
457 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 &&
458 auth_opts->permit_port_forwarding_flag &&
459 !options.disable_forwarding) {
460 c = channel_connect_to_port(ssh, target, target_port,
461 "direct-tcpip", "direct-tcpip", reason, errmsg);
462 } else {
463 logit("refused local port forward: "
464 "originator %s port %d, target %s port %d",
465 originator, originator_port, target, target_port);
466 if (reason != NULL)
467 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
468 }
469
470 out:
471 free(originator);
472 free(target);
473 return c;
474 }
475
476 static Channel *
server_request_direct_streamlocal(struct ssh * ssh)477 server_request_direct_streamlocal(struct ssh *ssh)
478 {
479 Channel *c = NULL;
480 char *target = NULL, *originator = NULL;
481 u_int originator_port = 0;
482 struct passwd *pw = the_authctxt->pw;
483 int r;
484
485 if (pw == NULL || !the_authctxt->valid)
486 fatal_f("no/invalid user");
487
488 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 ||
489 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 ||
490 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 ||
491 (r = sshpkt_get_end(ssh)) != 0)
492 sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
493 if (originator_port > 0xFFFF) {
494 error_f("invalid originator port");
495 goto out;
496 }
497
498 debug_f("originator %s port %d, target %s",
499 originator, originator_port, target);
500
501 /* XXX fine grained permissions */
502 if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 &&
503 auth_opts->permit_port_forwarding_flag &&
504 !options.disable_forwarding && (pw->pw_uid == 0 || use_privsep)) {
505 c = channel_connect_to_path(ssh, target,
506 "direct-streamlocal@openssh.com", "direct-streamlocal");
507 } else {
508 logit("refused streamlocal port forward: "
509 "originator %s port %d, target %s",
510 originator, originator_port, target);
511 }
512
513 out:
514 free(originator);
515 free(target);
516 return c;
517 }
518
519 static Channel *
server_request_tun(struct ssh * ssh)520 server_request_tun(struct ssh *ssh)
521 {
522 Channel *c = NULL;
523 u_int mode, tun;
524 int r, sock;
525 char *tmp, *ifname = NULL;
526
527 if ((r = sshpkt_get_u32(ssh, &mode)) != 0)
528 sshpkt_fatal(ssh, r, "%s: parse mode", __func__);
529 switch (mode) {
530 case SSH_TUNMODE_POINTOPOINT:
531 case SSH_TUNMODE_ETHERNET:
532 break;
533 default:
534 ssh_packet_send_debug(ssh, "Unsupported tunnel device mode.");
535 return NULL;
536 }
537 if ((options.permit_tun & mode) == 0) {
538 ssh_packet_send_debug(ssh, "Server has rejected tunnel device "
539 "forwarding");
540 return NULL;
541 }
542
543 if ((r = sshpkt_get_u32(ssh, &tun)) != 0)
544 sshpkt_fatal(ssh, r, "%s: parse device", __func__);
545 if (tun > INT_MAX) {
546 debug_f("invalid tun");
547 goto done;
548 }
549 if (auth_opts->force_tun_device != -1) {
550 if (tun != SSH_TUNID_ANY &&
551 auth_opts->force_tun_device != (int)tun)
552 goto done;
553 tun = auth_opts->force_tun_device;
554 }
555 sock = tun_open(tun, mode, &ifname);
556 if (sock < 0)
557 goto done;
558 debug("Tunnel forwarding using interface %s", ifname);
559
560 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1,
561 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
562 c->datagram = 1;
563 #if defined(SSH_TUN_FILTER)
564 if (mode == SSH_TUNMODE_POINTOPOINT)
565 channel_register_filter(ssh, c->self, sys_tun_infilter,
566 sys_tun_outfilter, NULL, NULL);
567 #endif
568
569 /*
570 * Update the list of names exposed to the session
571 * XXX remove these if the tunnels are closed (won't matter
572 * much if they are already in the environment though)
573 */
574 tmp = tun_fwd_ifnames;
575 xasprintf(&tun_fwd_ifnames, "%s%s%s",
576 tun_fwd_ifnames == NULL ? "" : tun_fwd_ifnames,
577 tun_fwd_ifnames == NULL ? "" : ",",
578 ifname);
579 free(tmp);
580 free(ifname);
581
582 done:
583 if (c == NULL)
584 ssh_packet_send_debug(ssh, "Failed to open the tunnel device.");
585 return c;
586 }
587
588 static Channel *
server_request_session(struct ssh * ssh)589 server_request_session(struct ssh *ssh)
590 {
591 Channel *c;
592 int r;
593
594 debug("input_session_request");
595 if ((r = sshpkt_get_end(ssh)) != 0)
596 sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
597
598 if (no_more_sessions) {
599 ssh_packet_disconnect(ssh, "Possible attack: attempt to open a "
600 "session after additional sessions disabled");
601 }
602
603 /*
604 * A server session has no fd to read or write until a
605 * CHANNEL_REQUEST for a shell is made, so we set the type to
606 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all
607 * CHANNEL_REQUEST messages is registered.
608 */
609 c = channel_new(ssh, "session", SSH_CHANNEL_LARVAL,
610 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
611 0, "server-session", 1);
612 if (session_open(the_authctxt, c->self) != 1) {
613 debug("session open failed, free channel %d", c->self);
614 channel_free(ssh, c);
615 return NULL;
616 }
617 channel_register_cleanup(ssh, c->self, session_close_by_channel, 0);
618 return c;
619 }
620
621 static int
server_input_channel_open(int type,u_int32_t seq,struct ssh * ssh)622 server_input_channel_open(int type, u_int32_t seq, struct ssh *ssh)
623 {
624 Channel *c = NULL;
625 char *ctype = NULL;
626 const char *errmsg = NULL;
627 int r, reason = SSH2_OPEN_CONNECT_FAILED;
628 u_int rchan = 0, rmaxpack = 0, rwindow = 0;
629
630 if ((r = sshpkt_get_cstring(ssh, &ctype, NULL)) != 0 ||
631 (r = sshpkt_get_u32(ssh, &rchan)) != 0 ||
632 (r = sshpkt_get_u32(ssh, &rwindow)) != 0 ||
633 (r = sshpkt_get_u32(ssh, &rmaxpack)) != 0)
634 sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
635 debug_f("ctype %s rchan %u win %u max %u",
636 ctype, rchan, rwindow, rmaxpack);
637
638 if (strcmp(ctype, "session") == 0) {
639 c = server_request_session(ssh);
640 } else if (strcmp(ctype, "direct-tcpip") == 0) {
641 c = server_request_direct_tcpip(ssh, &reason, &errmsg);
642 } else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) {
643 c = server_request_direct_streamlocal(ssh);
644 } else if (strcmp(ctype, "tun@openssh.com") == 0) {
645 c = server_request_tun(ssh);
646 }
647 if (c != NULL) {
648 debug_f("confirm %s", ctype);
649 c->remote_id = rchan;
650 c->have_remote_id = 1;
651 c->remote_window = rwindow;
652 c->remote_maxpacket = rmaxpack;
653 if (c->type != SSH_CHANNEL_CONNECTING) {
654 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION)) != 0 ||
655 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
656 (r = sshpkt_put_u32(ssh, c->self)) != 0 ||
657 (r = sshpkt_put_u32(ssh, c->local_window)) != 0 ||
658 (r = sshpkt_put_u32(ssh, c->local_maxpacket)) != 0 ||
659 (r = sshpkt_send(ssh)) != 0) {
660 sshpkt_fatal(ssh, r,
661 "%s: send open confirm", __func__);
662 }
663 }
664 } else {
665 debug_f("failure %s", ctype);
666 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE)) != 0 ||
667 (r = sshpkt_put_u32(ssh, rchan)) != 0 ||
668 (r = sshpkt_put_u32(ssh, reason)) != 0 ||
669 (r = sshpkt_put_cstring(ssh, errmsg ? errmsg : "open failed")) != 0 ||
670 (r = sshpkt_put_cstring(ssh, "")) != 0 ||
671 (r = sshpkt_send(ssh)) != 0) {
672 sshpkt_fatal(ssh, r,
673 "%s: send open failure", __func__);
674 }
675 }
676 free(ctype);
677 return 0;
678 }
679
680 static int
server_input_hostkeys_prove(struct ssh * ssh,struct sshbuf ** respp)681 server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp)
682 {
683 struct sshbuf *resp = NULL;
684 struct sshbuf *sigbuf = NULL;
685 struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL;
686 int r, ndx, success = 0;
687 const u_char *blob;
688 const char *sigalg, *kex_rsa_sigalg = NULL;
689 u_char *sig = 0;
690 size_t blen, slen;
691
692 if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL)
693 fatal_f("sshbuf_new");
694 if (sshkey_type_plain(sshkey_type_from_name(
695 ssh->kex->hostkey_alg)) == KEY_RSA)
696 kex_rsa_sigalg = ssh->kex->hostkey_alg;
697 while (ssh_packet_remaining(ssh) > 0) {
698 sshkey_free(key);
699 key = NULL;
700 if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 ||
701 (r = sshkey_from_blob(blob, blen, &key)) != 0) {
702 error_fr(r, "parse key");
703 goto out;
704 }
705 /*
706 * Better check that this is actually one of our hostkeys
707 * before attempting to sign anything with it.
708 */
709 if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) {
710 error_f("unknown host %s key", sshkey_type(key));
711 goto out;
712 }
713 /*
714 * XXX refactor: make kex->sign just use an index rather
715 * than passing in public and private keys
716 */
717 if ((key_prv = get_hostkey_by_index(ndx)) == NULL &&
718 (key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) {
719 error_f("can't retrieve hostkey %d", ndx);
720 goto out;
721 }
722 sshbuf_reset(sigbuf);
723 free(sig);
724 sig = NULL;
725 /*
726 * For RSA keys, prefer to use the signature type negotiated
727 * during KEX to the default (SHA1).
728 */
729 sigalg = NULL;
730 if (sshkey_type_plain(key->type) == KEY_RSA) {
731 if (kex_rsa_sigalg != NULL)
732 sigalg = kex_rsa_sigalg;
733 else if (ssh->kex->flags & KEX_RSA_SHA2_512_SUPPORTED)
734 sigalg = "rsa-sha2-512";
735 else if (ssh->kex->flags & KEX_RSA_SHA2_256_SUPPORTED)
736 sigalg = "rsa-sha2-256";
737 }
738 debug3_f("sign %s key (index %d) using sigalg %s",
739 sshkey_type(key), ndx, sigalg == NULL ? "default" : sigalg);
740 if ((r = sshbuf_put_cstring(sigbuf,
741 "hostkeys-prove-00@openssh.com")) != 0 ||
742 (r = sshbuf_put_stringb(sigbuf,
743 ssh->kex->session_id)) != 0 ||
744 (r = sshkey_puts(key, sigbuf)) != 0 ||
745 (r = ssh->kex->sign(ssh, key_prv, key_pub, &sig, &slen,
746 sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), sigalg)) != 0 ||
747 (r = sshbuf_put_string(resp, sig, slen)) != 0) {
748 error_fr(r, "assemble signature");
749 goto out;
750 }
751 }
752 /* Success */
753 *respp = resp;
754 resp = NULL; /* don't free it */
755 success = 1;
756 out:
757 free(sig);
758 sshbuf_free(resp);
759 sshbuf_free(sigbuf);
760 sshkey_free(key);
761 return success;
762 }
763
764 static int
server_input_global_request(int type,u_int32_t seq,struct ssh * ssh)765 server_input_global_request(int type, u_int32_t seq, struct ssh *ssh)
766 {
767 char *rtype = NULL;
768 u_char want_reply = 0;
769 int r, success = 0, allocated_listen_port = 0;
770 u_int port = 0;
771 struct sshbuf *resp = NULL;
772 struct passwd *pw = the_authctxt->pw;
773 struct Forward fwd;
774
775 memset(&fwd, 0, sizeof(fwd));
776 if (pw == NULL || !the_authctxt->valid)
777 fatal_f("no/invalid user");
778
779 if ((r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 ||
780 (r = sshpkt_get_u8(ssh, &want_reply)) != 0)
781 sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
782 debug_f("rtype %s want_reply %d", rtype, want_reply);
783
784 /* -R style forwarding */
785 if (strcmp(rtype, "tcpip-forward") == 0) {
786 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 ||
787 (r = sshpkt_get_u32(ssh, &port)) != 0)
788 sshpkt_fatal(ssh, r, "%s: parse tcpip-forward", __func__);
789 debug_f("tcpip-forward listen %s port %u",
790 fwd.listen_host, port);
791 if (port <= INT_MAX)
792 fwd.listen_port = (int)port;
793 /* check permissions */
794 if (port > INT_MAX ||
795 (options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 ||
796 !auth_opts->permit_port_forwarding_flag ||
797 options.disable_forwarding ||
798 (!want_reply && fwd.listen_port == 0) ||
799 (fwd.listen_port != 0 &&
800 !bind_permitted(fwd.listen_port, pw->pw_uid))) {
801 success = 0;
802 ssh_packet_send_debug(ssh, "Server has disabled port forwarding.");
803 } else {
804 /* Start listening on the port */
805 success = channel_setup_remote_fwd_listener(ssh, &fwd,
806 &allocated_listen_port, &options.fwd_opts);
807 }
808 if ((resp = sshbuf_new()) == NULL)
809 fatal_f("sshbuf_new");
810 if (allocated_listen_port != 0 &&
811 (r = sshbuf_put_u32(resp, allocated_listen_port)) != 0)
812 fatal_fr(r, "sshbuf_put_u32");
813 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
814 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 ||
815 (r = sshpkt_get_u32(ssh, &port)) != 0)
816 sshpkt_fatal(ssh, r, "%s: parse cancel-tcpip-forward", __func__);
817
818 debug_f("cancel-tcpip-forward addr %s port %d",
819 fwd.listen_host, port);
820 if (port <= INT_MAX) {
821 fwd.listen_port = (int)port;
822 success = channel_cancel_rport_listener(ssh, &fwd);
823 }
824 } else if (strcmp(rtype, "streamlocal-forward@openssh.com") == 0) {
825 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0)
826 sshpkt_fatal(ssh, r, "%s: parse streamlocal-forward@openssh.com", __func__);
827 debug_f("streamlocal-forward listen path %s",
828 fwd.listen_path);
829
830 /* check permissions */
831 if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0
832 || !auth_opts->permit_port_forwarding_flag ||
833 options.disable_forwarding ||
834 (pw->pw_uid != 0 && !use_privsep)) {
835 success = 0;
836 ssh_packet_send_debug(ssh, "Server has disabled "
837 "streamlocal forwarding.");
838 } else {
839 /* Start listening on the socket */
840 success = channel_setup_remote_fwd_listener(ssh,
841 &fwd, NULL, &options.fwd_opts);
842 }
843 } else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) {
844 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0)
845 sshpkt_fatal(ssh, r, "%s: parse cancel-streamlocal-forward@openssh.com", __func__);
846 debug_f("cancel-streamlocal-forward path %s",
847 fwd.listen_path);
848
849 success = channel_cancel_rport_listener(ssh, &fwd);
850 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) {
851 no_more_sessions = 1;
852 success = 1;
853 } else if (strcmp(rtype, "hostkeys-prove-00@openssh.com") == 0) {
854 success = server_input_hostkeys_prove(ssh, &resp);
855 }
856 /* XXX sshpkt_get_end() */
857 if (want_reply) {
858 if ((r = sshpkt_start(ssh, success ?
859 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE)) != 0 ||
860 (success && resp != NULL && (r = sshpkt_putb(ssh, resp)) != 0) ||
861 (r = sshpkt_send(ssh)) != 0 ||
862 (r = ssh_packet_write_wait(ssh)) != 0)
863 sshpkt_fatal(ssh, r, "%s: send reply", __func__);
864 }
865 free(fwd.listen_host);
866 free(fwd.listen_path);
867 free(rtype);
868 sshbuf_free(resp);
869 return 0;
870 }
871
872 static int
server_input_channel_req(int type,u_int32_t seq,struct ssh * ssh)873 server_input_channel_req(int type, u_int32_t seq, struct ssh *ssh)
874 {
875 Channel *c;
876 int r, success = 0;
877 char *rtype = NULL;
878 u_char want_reply = 0;
879 u_int id = 0;
880
881 if ((r = sshpkt_get_u32(ssh, &id)) != 0 ||
882 (r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 ||
883 (r = sshpkt_get_u8(ssh, &want_reply)) != 0)
884 sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
885
886 debug("server_input_channel_req: channel %u request %s reply %d",
887 id, rtype, want_reply);
888
889 if (id >= INT_MAX || (c = channel_lookup(ssh, (int)id)) == NULL) {
890 ssh_packet_disconnect(ssh, "%s: unknown channel %d",
891 __func__, id);
892 }
893 if (!strcmp(rtype, "eow@openssh.com")) {
894 if ((r = sshpkt_get_end(ssh)) != 0)
895 sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
896 chan_rcvd_eow(ssh, c);
897 } else if ((c->type == SSH_CHANNEL_LARVAL ||
898 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0)
899 success = session_input_channel_req(ssh, c, rtype);
900 if (want_reply && !(c->flags & CHAN_CLOSE_SENT)) {
901 if (!c->have_remote_id)
902 fatal_f("channel %d: no remote_id", c->self);
903 if ((r = sshpkt_start(ssh, success ?
904 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE)) != 0 ||
905 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
906 (r = sshpkt_send(ssh)) != 0)
907 sshpkt_fatal(ssh, r, "%s: send reply", __func__);
908 }
909 free(rtype);
910 return 0;
911 }
912
913 static void
server_init_dispatch(struct ssh * ssh)914 server_init_dispatch(struct ssh *ssh)
915 {
916 debug("server_init_dispatch");
917 ssh_dispatch_init(ssh, &dispatch_protocol_error);
918 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
919 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_DATA, &channel_input_data);
920 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
921 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
922 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
923 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
924 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
925 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
926 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
927 ssh_dispatch_set(ssh, SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
928 /* client_alive */
929 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive);
930 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
931 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
932 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
933 /* rekeying */
934 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
935 }
936