1 /* $OpenBSD: serverloop.c,v 1.240 2024/06/17 08:28:31 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 "ssh2.h"
73 #include "sshkey.h"
74 #include "cipher.h"
75 #include "kex.h"
76 #include "hostfile.h"
77 #include "auth.h"
78 #include "session.h"
79 #include "dispatch.h"
80 #include "auth-options.h"
81 #include "serverloop.h"
82 #include "ssherr.h"
83
84 extern ServerOptions options;
85
86 /* XXX */
87 extern Authctxt *the_authctxt;
88 extern struct sshauthopt *auth_opts;
89
90 static int no_more_sessions = 0; /* Disallow further sessions. */
91
92 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */
93
94 /* prototypes */
95 static void server_init_dispatch(struct ssh *);
96
97 /* requested tunnel forwarding interface(s), shared with session.c */
98 char *tun_fwd_ifnames = NULL;
99
100 static void
sigchld_handler(int sig)101 sigchld_handler(int sig)
102 {
103 child_terminated = 1;
104 }
105
106 static void
client_alive_check(struct ssh * ssh)107 client_alive_check(struct ssh *ssh)
108 {
109 char remote_id[512];
110 int r, channel_id;
111
112 /* timeout, check to see how many we have had */
113 if (options.client_alive_count_max > 0 &&
114 ssh_packet_inc_alive_timeouts(ssh) >
115 options.client_alive_count_max) {
116 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id));
117 logit("Timeout, client not responding from %s", remote_id);
118 cleanup_exit(255);
119 }
120
121 /*
122 * send a bogus global/channel request with "wantreply",
123 * we should get back a failure
124 */
125 if ((channel_id = channel_find_open(ssh)) == -1) {
126 if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 ||
127 (r = sshpkt_put_cstring(ssh, "keepalive@openssh.com"))
128 != 0 ||
129 (r = sshpkt_put_u8(ssh, 1)) != 0) /* boolean: want reply */
130 fatal_fr(r, "compose");
131 } else {
132 channel_request_start(ssh, channel_id,
133 "keepalive@openssh.com", 1);
134 }
135 if ((r = sshpkt_send(ssh)) != 0)
136 fatal_fr(r, "send");
137 }
138
139 /*
140 * Sleep in ppoll() until we can do something.
141 * Optionally, a maximum time can be specified for the duration of
142 * the wait (0 = infinite).
143 */
144 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,sigset_t * sigsetp,int * conn_in_readyp,int * conn_out_readyp)145 wait_until_can_do_something(struct ssh *ssh,
146 int connection_in, int connection_out, struct pollfd **pfdp,
147 u_int *npfd_allocp, u_int *npfd_activep, sigset_t *sigsetp,
148 int *conn_in_readyp, int *conn_out_readyp)
149 {
150 struct timespec timeout;
151 char remote_id[512];
152 int ret;
153 int client_alive_scheduled = 0;
154 u_int p;
155 time_t now;
156 static time_t last_client_time, unused_connection_expiry;
157
158 *conn_in_readyp = *conn_out_readyp = 0;
159
160 /* Prepare channel poll. First two pollfd entries are reserved */
161 ptimeout_init(&timeout);
162 channel_prepare_poll(ssh, pfdp, npfd_allocp, npfd_activep, 2, &timeout);
163 now = monotime();
164 if (*npfd_activep < 2)
165 fatal_f("bad npfd %u", *npfd_activep); /* shouldn't happen */
166 if (options.rekey_interval > 0 && !ssh_packet_is_rekeying(ssh)) {
167 ptimeout_deadline_sec(&timeout,
168 ssh_packet_get_rekey_timeout(ssh));
169 }
170
171 /*
172 * If no channels are open and UnusedConnectionTimeout is set, then
173 * start the clock to terminate the connection.
174 */
175 if (options.unused_connection_timeout != 0) {
176 if (channel_still_open(ssh) || unused_connection_expiry == 0) {
177 unused_connection_expiry = now +
178 options.unused_connection_timeout;
179 }
180 ptimeout_deadline_monotime(&timeout, unused_connection_expiry);
181 }
182
183 /*
184 * if using client_alive, set the max timeout accordingly,
185 * and indicate that this particular timeout was for client
186 * alive by setting the client_alive_scheduled flag.
187 *
188 * this could be randomized somewhat to make traffic
189 * analysis more difficult, but we're not doing it yet.
190 */
191 if (options.client_alive_interval) {
192 /* Time we last heard from the client OR sent a keepalive */
193 if (last_client_time == 0)
194 last_client_time = now;
195 ptimeout_deadline_sec(&timeout, options.client_alive_interval);
196 /* XXX ? deadline_monotime(last_client_time + alive_interval) */
197 client_alive_scheduled = 1;
198 }
199
200 #if 0
201 /* wrong: bad condition XXX */
202 if (channel_not_very_much_buffered_data())
203 #endif
204 /* Monitor client connection on reserved pollfd entries */
205 (*pfdp)[0].fd = connection_in;
206 (*pfdp)[0].events = POLLIN;
207 (*pfdp)[1].fd = connection_out;
208 (*pfdp)[1].events = ssh_packet_have_data_to_write(ssh) ? POLLOUT : 0;
209
210 /*
211 * If child has terminated and there is enough buffer space to read
212 * from it, then read as much as is available and exit.
213 */
214 if (child_terminated && ssh_packet_not_very_much_data_to_write(ssh))
215 ptimeout_deadline_ms(&timeout, 100);
216
217 /* Wait for something to happen, or the timeout to expire. */
218 ret = ppoll(*pfdp, *npfd_activep, ptimeout_get_tsp(&timeout), sigsetp);
219
220 if (ret == -1) {
221 for (p = 0; p < *npfd_activep; p++)
222 (*pfdp)[p].revents = 0;
223 if (errno != EINTR)
224 fatal_f("ppoll: %.100s", strerror(errno));
225 return;
226 }
227
228 *conn_in_readyp = (*pfdp)[0].revents != 0;
229 *conn_out_readyp = (*pfdp)[1].revents != 0;
230
231 now = monotime(); /* need to reset after ppoll() */
232 /* ClientAliveInterval probing */
233 if (client_alive_scheduled) {
234 if (ret == 0 &&
235 now >= last_client_time + options.client_alive_interval) {
236 /* ppoll timed out and we're due to probe */
237 client_alive_check(ssh);
238 last_client_time = now;
239 } else if (ret != 0 && *conn_in_readyp) {
240 /* Data from peer; reset probe timer. */
241 last_client_time = now;
242 }
243 }
244
245 /* UnusedConnectionTimeout handling */
246 if (unused_connection_expiry != 0 &&
247 now > unused_connection_expiry && !channel_still_open(ssh)) {
248 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id));
249 logit("terminating inactive connection from %s", remote_id);
250 cleanup_exit(255);
251 }
252 }
253
254 /*
255 * Processes input from the client and the program. Input data is stored
256 * in buffers and processed later.
257 */
258 static int
process_input(struct ssh * ssh,int connection_in)259 process_input(struct ssh *ssh, int connection_in)
260 {
261 int r;
262
263 if ((r = ssh_packet_process_read(ssh, connection_in)) == 0)
264 return 0; /* success */
265 if (r == SSH_ERR_SYSTEM_ERROR) {
266 if (errno == EAGAIN || errno == EINTR || errno == EWOULDBLOCK)
267 return 0;
268 if (errno == EPIPE) {
269 logit("Connection closed by %.100s port %d",
270 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
271 return -1;
272 }
273 logit("Read error from remote host %s port %d: %s",
274 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
275 strerror(errno));
276 cleanup_exit(255);
277 }
278 return -1;
279 }
280
281 /*
282 * Sends data from internal buffers to client program stdin.
283 */
284 static void
process_output(struct ssh * ssh,int connection_out)285 process_output(struct ssh *ssh, int connection_out)
286 {
287 int r;
288
289 /* Send any buffered packet data to the client. */
290 if ((r = ssh_packet_write_poll(ssh)) != 0) {
291 sshpkt_fatal(ssh, r, "%s: ssh_packet_write_poll",
292 __func__);
293 }
294 }
295
296 static void
process_buffered_input_packets(struct ssh * ssh)297 process_buffered_input_packets(struct ssh *ssh)
298 {
299 ssh_dispatch_run_fatal(ssh, DISPATCH_NONBLOCK, NULL);
300 }
301
302 static void
collect_children(struct ssh * ssh)303 collect_children(struct ssh *ssh)
304 {
305 pid_t pid;
306 int status;
307
308 if (child_terminated) {
309 debug("Received SIGCHLD.");
310 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
311 (pid == -1 && errno == EINTR))
312 if (pid > 0)
313 session_close_by_pid(ssh, pid, status);
314 child_terminated = 0;
315 }
316 }
317
318 void
server_loop2(struct ssh * ssh,Authctxt * authctxt)319 server_loop2(struct ssh *ssh, Authctxt *authctxt)
320 {
321 struct pollfd *pfd = NULL;
322 u_int npfd_alloc = 0, npfd_active = 0;
323 int r, conn_in_ready, conn_out_ready;
324 u_int connection_in, connection_out;
325 sigset_t bsigset, osigset;
326
327 debug("Entering interactive session for SSH2.");
328
329 if (sigemptyset(&bsigset) == -1 || sigaddset(&bsigset, SIGCHLD) == -1)
330 error_f("bsigset setup: %s", strerror(errno));
331 ssh_signal(SIGCHLD, sigchld_handler);
332 child_terminated = 0;
333 connection_in = ssh_packet_get_connection_in(ssh);
334 connection_out = ssh_packet_get_connection_out(ssh);
335
336 server_init_dispatch(ssh);
337
338 for (;;) {
339 process_buffered_input_packets(ssh);
340
341 if (!ssh_packet_is_rekeying(ssh) &&
342 ssh_packet_not_very_much_data_to_write(ssh))
343 channel_output_poll(ssh);
344
345 /*
346 * Block SIGCHLD while we check for dead children, then pass
347 * the old signal mask through to ppoll() so that it'll wake
348 * up immediately if a child exits after we've called waitpid().
349 */
350 if (sigprocmask(SIG_BLOCK, &bsigset, &osigset) == -1)
351 error_f("bsigset sigprocmask: %s", strerror(errno));
352 collect_children(ssh);
353 wait_until_can_do_something(ssh, connection_in, connection_out,
354 &pfd, &npfd_alloc, &npfd_active, &osigset,
355 &conn_in_ready, &conn_out_ready);
356 if (sigprocmask(SIG_SETMASK, &osigset, NULL) == -1)
357 error_f("osigset sigprocmask: %s", strerror(errno));
358
359 channel_after_poll(ssh, pfd, npfd_active);
360 if (conn_in_ready &&
361 process_input(ssh, connection_in) < 0)
362 break;
363 /* A timeout may have triggered rekeying */
364 if ((r = ssh_packet_check_rekey(ssh)) != 0)
365 fatal_fr(r, "cannot start rekeying");
366 if (conn_out_ready)
367 process_output(ssh, connection_out);
368 }
369 collect_children(ssh);
370 free(pfd);
371
372 /* free all channels, no more reads and writes */
373 channel_free_all(ssh);
374
375 /* free remaining sessions, e.g. remove wtmp entries */
376 session_destroy_all(ssh, NULL);
377 }
378
379 static int
server_input_keep_alive(int type,u_int32_t seq,struct ssh * ssh)380 server_input_keep_alive(int type, u_int32_t seq, struct ssh *ssh)
381 {
382 debug("Got %d/%u for keepalive", type, seq);
383 /*
384 * reset timeout, since we got a sane answer from the client.
385 * even if this was generated by something other than
386 * the bogus CHANNEL_REQUEST we send for keepalives.
387 */
388 ssh_packet_set_alive_timeouts(ssh, 0);
389 return 0;
390 }
391
392 static Channel *
server_request_direct_tcpip(struct ssh * ssh,int * reason,const char ** errmsg)393 server_request_direct_tcpip(struct ssh *ssh, int *reason, const char **errmsg)
394 {
395 Channel *c = NULL;
396 char *target = NULL, *originator = NULL;
397 u_int target_port = 0, originator_port = 0;
398 int r;
399
400 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 ||
401 (r = sshpkt_get_u32(ssh, &target_port)) != 0 ||
402 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 ||
403 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 ||
404 (r = sshpkt_get_end(ssh)) != 0)
405 sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
406 if (target_port > 0xFFFF) {
407 error_f("invalid target port");
408 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
409 goto out;
410 }
411 if (originator_port > 0xFFFF) {
412 error_f("invalid originator port");
413 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
414 goto out;
415 }
416
417 debug_f("originator %s port %u, target %s port %u",
418 originator, originator_port, target, target_port);
419
420 /* XXX fine grained permissions */
421 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 &&
422 auth_opts->permit_port_forwarding_flag &&
423 !options.disable_forwarding) {
424 c = channel_connect_to_port(ssh, target, target_port,
425 "direct-tcpip", "direct-tcpip", reason, errmsg);
426 } else {
427 logit("refused local port forward: "
428 "originator %s port %d, target %s port %d",
429 originator, originator_port, target, target_port);
430 if (reason != NULL)
431 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
432 }
433
434 out:
435 free(originator);
436 free(target);
437 return c;
438 }
439
440 static Channel *
server_request_direct_streamlocal(struct ssh * ssh)441 server_request_direct_streamlocal(struct ssh *ssh)
442 {
443 Channel *c = NULL;
444 char *target = NULL, *originator = NULL;
445 u_int originator_port = 0;
446 struct passwd *pw = the_authctxt->pw;
447 int r;
448
449 if (pw == NULL || !the_authctxt->valid)
450 fatal_f("no/invalid user");
451
452 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 ||
453 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 ||
454 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 ||
455 (r = sshpkt_get_end(ssh)) != 0)
456 sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
457 if (originator_port > 0xFFFF) {
458 error_f("invalid originator port");
459 goto out;
460 }
461
462 debug_f("originator %s port %d, target %s",
463 originator, originator_port, target);
464
465 /* XXX fine grained permissions */
466 if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 &&
467 auth_opts->permit_port_forwarding_flag &&
468 !options.disable_forwarding) {
469 c = channel_connect_to_path(ssh, target,
470 "direct-streamlocal@openssh.com", "direct-streamlocal");
471 } else {
472 logit("refused streamlocal port forward: "
473 "originator %s port %d, target %s",
474 originator, originator_port, target);
475 }
476
477 out:
478 free(originator);
479 free(target);
480 return c;
481 }
482
483 static Channel *
server_request_tun(struct ssh * ssh)484 server_request_tun(struct ssh *ssh)
485 {
486 Channel *c = NULL;
487 u_int mode, tun;
488 int r, sock;
489 char *tmp, *ifname = NULL;
490
491 if ((r = sshpkt_get_u32(ssh, &mode)) != 0)
492 sshpkt_fatal(ssh, r, "%s: parse mode", __func__);
493 switch (mode) {
494 case SSH_TUNMODE_POINTOPOINT:
495 case SSH_TUNMODE_ETHERNET:
496 break;
497 default:
498 ssh_packet_send_debug(ssh, "Unsupported tunnel device mode.");
499 return NULL;
500 }
501 if ((options.permit_tun & mode) == 0) {
502 ssh_packet_send_debug(ssh, "Server has rejected tunnel device "
503 "forwarding");
504 return NULL;
505 }
506
507 if ((r = sshpkt_get_u32(ssh, &tun)) != 0)
508 sshpkt_fatal(ssh, r, "%s: parse device", __func__);
509 if (tun > INT_MAX) {
510 debug_f("invalid tun");
511 goto done;
512 }
513 if (auth_opts->force_tun_device != -1) {
514 if (tun != SSH_TUNID_ANY &&
515 auth_opts->force_tun_device != (int)tun)
516 goto done;
517 tun = auth_opts->force_tun_device;
518 }
519 sock = tun_open(tun, mode, &ifname);
520 if (sock < 0)
521 goto done;
522 debug("Tunnel forwarding using interface %s", ifname);
523
524 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1,
525 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
526 c->datagram = 1;
527 #if defined(SSH_TUN_FILTER)
528 if (mode == SSH_TUNMODE_POINTOPOINT)
529 channel_register_filter(ssh, c->self, sys_tun_infilter,
530 sys_tun_outfilter, NULL, NULL);
531 #endif
532
533 /*
534 * Update the list of names exposed to the session
535 * XXX remove these if the tunnels are closed (won't matter
536 * much if they are already in the environment though)
537 */
538 tmp = tun_fwd_ifnames;
539 xasprintf(&tun_fwd_ifnames, "%s%s%s",
540 tun_fwd_ifnames == NULL ? "" : tun_fwd_ifnames,
541 tun_fwd_ifnames == NULL ? "" : ",",
542 ifname);
543 free(tmp);
544 free(ifname);
545
546 done:
547 if (c == NULL)
548 ssh_packet_send_debug(ssh, "Failed to open the tunnel device.");
549 return c;
550 }
551
552 static Channel *
server_request_session(struct ssh * ssh)553 server_request_session(struct ssh *ssh)
554 {
555 Channel *c;
556 int r;
557
558 debug("input_session_request");
559 if ((r = sshpkt_get_end(ssh)) != 0)
560 sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
561
562 if (no_more_sessions) {
563 ssh_packet_disconnect(ssh, "Possible attack: attempt to open a "
564 "session after additional sessions disabled");
565 }
566
567 /*
568 * A server session has no fd to read or write until a
569 * CHANNEL_REQUEST for a shell is made, so we set the type to
570 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all
571 * CHANNEL_REQUEST messages is registered.
572 */
573 c = channel_new(ssh, "session", SSH_CHANNEL_LARVAL,
574 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
575 0, "server-session", 1);
576 if (session_open(the_authctxt, c->self) != 1) {
577 debug("session open failed, free channel %d", c->self);
578 channel_free(ssh, c);
579 return NULL;
580 }
581 channel_register_cleanup(ssh, c->self, session_close_by_channel, 0);
582 return c;
583 }
584
585 static int
server_input_channel_open(int type,u_int32_t seq,struct ssh * ssh)586 server_input_channel_open(int type, u_int32_t seq, struct ssh *ssh)
587 {
588 Channel *c = NULL;
589 char *ctype = NULL;
590 const char *errmsg = NULL;
591 int r, reason = SSH2_OPEN_CONNECT_FAILED;
592 u_int rchan = 0, rmaxpack = 0, rwindow = 0;
593
594 if ((r = sshpkt_get_cstring(ssh, &ctype, NULL)) != 0 ||
595 (r = sshpkt_get_u32(ssh, &rchan)) != 0 ||
596 (r = sshpkt_get_u32(ssh, &rwindow)) != 0 ||
597 (r = sshpkt_get_u32(ssh, &rmaxpack)) != 0)
598 sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
599 debug_f("ctype %s rchan %u win %u max %u",
600 ctype, rchan, rwindow, rmaxpack);
601
602 if (strcmp(ctype, "session") == 0) {
603 c = server_request_session(ssh);
604 } else if (strcmp(ctype, "direct-tcpip") == 0) {
605 c = server_request_direct_tcpip(ssh, &reason, &errmsg);
606 } else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) {
607 c = server_request_direct_streamlocal(ssh);
608 } else if (strcmp(ctype, "tun@openssh.com") == 0) {
609 c = server_request_tun(ssh);
610 }
611 if (c != NULL) {
612 debug_f("confirm %s", ctype);
613 c->remote_id = rchan;
614 c->have_remote_id = 1;
615 c->remote_window = rwindow;
616 c->remote_maxpacket = rmaxpack;
617 if (c->type != SSH_CHANNEL_CONNECTING) {
618 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION)) != 0 ||
619 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
620 (r = sshpkt_put_u32(ssh, c->self)) != 0 ||
621 (r = sshpkt_put_u32(ssh, c->local_window)) != 0 ||
622 (r = sshpkt_put_u32(ssh, c->local_maxpacket)) != 0 ||
623 (r = sshpkt_send(ssh)) != 0) {
624 sshpkt_fatal(ssh, r,
625 "%s: send open confirm", __func__);
626 }
627 }
628 } else {
629 debug_f("failure %s", ctype);
630 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE)) != 0 ||
631 (r = sshpkt_put_u32(ssh, rchan)) != 0 ||
632 (r = sshpkt_put_u32(ssh, reason)) != 0 ||
633 (r = sshpkt_put_cstring(ssh, errmsg ? errmsg : "open failed")) != 0 ||
634 (r = sshpkt_put_cstring(ssh, "")) != 0 ||
635 (r = sshpkt_send(ssh)) != 0) {
636 sshpkt_fatal(ssh, r,
637 "%s: send open failure", __func__);
638 }
639 }
640 free(ctype);
641 return 0;
642 }
643
644 static int
server_input_hostkeys_prove(struct ssh * ssh,struct sshbuf ** respp)645 server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp)
646 {
647 struct sshbuf *resp = NULL;
648 struct sshbuf *sigbuf = NULL;
649 struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL;
650 int r, ndx, success = 0;
651 const u_char *blob;
652 const char *sigalg, *kex_rsa_sigalg = NULL;
653 u_char *sig = 0;
654 size_t blen, slen;
655
656 if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL)
657 fatal_f("sshbuf_new");
658 if (sshkey_type_plain(sshkey_type_from_name(
659 ssh->kex->hostkey_alg)) == KEY_RSA)
660 kex_rsa_sigalg = ssh->kex->hostkey_alg;
661 while (ssh_packet_remaining(ssh) > 0) {
662 sshkey_free(key);
663 key = NULL;
664 if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 ||
665 (r = sshkey_from_blob(blob, blen, &key)) != 0) {
666 error_fr(r, "parse key");
667 goto out;
668 }
669 /*
670 * Better check that this is actually one of our hostkeys
671 * before attempting to sign anything with it.
672 */
673 if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) {
674 error_f("unknown host %s key", sshkey_type(key));
675 goto out;
676 }
677 /*
678 * XXX refactor: make kex->sign just use an index rather
679 * than passing in public and private keys
680 */
681 if ((key_prv = get_hostkey_by_index(ndx)) == NULL &&
682 (key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) {
683 error_f("can't retrieve hostkey %d", ndx);
684 goto out;
685 }
686 sshbuf_reset(sigbuf);
687 free(sig);
688 sig = NULL;
689 /*
690 * For RSA keys, prefer to use the signature type negotiated
691 * during KEX to the default (SHA1).
692 */
693 sigalg = NULL;
694 if (sshkey_type_plain(key->type) == KEY_RSA) {
695 if (kex_rsa_sigalg != NULL)
696 sigalg = kex_rsa_sigalg;
697 else if (ssh->kex->flags & KEX_RSA_SHA2_512_SUPPORTED)
698 sigalg = "rsa-sha2-512";
699 else if (ssh->kex->flags & KEX_RSA_SHA2_256_SUPPORTED)
700 sigalg = "rsa-sha2-256";
701 }
702 debug3_f("sign %s key (index %d) using sigalg %s",
703 sshkey_type(key), ndx, sigalg == NULL ? "default" : sigalg);
704 if ((r = sshbuf_put_cstring(sigbuf,
705 "hostkeys-prove-00@openssh.com")) != 0 ||
706 (r = sshbuf_put_stringb(sigbuf,
707 ssh->kex->session_id)) != 0 ||
708 (r = sshkey_puts(key, sigbuf)) != 0 ||
709 (r = ssh->kex->sign(ssh, key_prv, key_pub, &sig, &slen,
710 sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), sigalg)) != 0 ||
711 (r = sshbuf_put_string(resp, sig, slen)) != 0) {
712 error_fr(r, "assemble signature");
713 goto out;
714 }
715 }
716 /* Success */
717 *respp = resp;
718 resp = NULL; /* don't free it */
719 success = 1;
720 out:
721 free(sig);
722 sshbuf_free(resp);
723 sshbuf_free(sigbuf);
724 sshkey_free(key);
725 return success;
726 }
727
728 static int
server_input_global_request(int type,u_int32_t seq,struct ssh * ssh)729 server_input_global_request(int type, u_int32_t seq, struct ssh *ssh)
730 {
731 char *rtype = NULL;
732 u_char want_reply = 0;
733 int r, success = 0, allocated_listen_port = 0;
734 u_int port = 0;
735 struct sshbuf *resp = NULL;
736 struct passwd *pw = the_authctxt->pw;
737 struct Forward fwd;
738
739 memset(&fwd, 0, sizeof(fwd));
740 if (pw == NULL || !the_authctxt->valid)
741 fatal_f("no/invalid user");
742
743 if ((r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 ||
744 (r = sshpkt_get_u8(ssh, &want_reply)) != 0)
745 sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
746 debug_f("rtype %s want_reply %d", rtype, want_reply);
747
748 /* -R style forwarding */
749 if (strcmp(rtype, "tcpip-forward") == 0) {
750 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 ||
751 (r = sshpkt_get_u32(ssh, &port)) != 0)
752 sshpkt_fatal(ssh, r, "%s: parse tcpip-forward", __func__);
753 debug_f("tcpip-forward listen %s port %u",
754 fwd.listen_host, port);
755 if (port <= INT_MAX)
756 fwd.listen_port = (int)port;
757 /* check permissions */
758 if (port > INT_MAX ||
759 (options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 ||
760 !auth_opts->permit_port_forwarding_flag ||
761 options.disable_forwarding ||
762 (!want_reply && fwd.listen_port == 0)) {
763 success = 0;
764 ssh_packet_send_debug(ssh, "Server has disabled port forwarding.");
765 } else {
766 /* Start listening on the port */
767 success = channel_setup_remote_fwd_listener(ssh, &fwd,
768 &allocated_listen_port, &options.fwd_opts);
769 }
770 if ((resp = sshbuf_new()) == NULL)
771 fatal_f("sshbuf_new");
772 if (allocated_listen_port != 0 &&
773 (r = sshbuf_put_u32(resp, allocated_listen_port)) != 0)
774 fatal_fr(r, "sshbuf_put_u32");
775 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
776 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 ||
777 (r = sshpkt_get_u32(ssh, &port)) != 0)
778 sshpkt_fatal(ssh, r, "%s: parse cancel-tcpip-forward", __func__);
779
780 debug_f("cancel-tcpip-forward addr %s port %d",
781 fwd.listen_host, port);
782 if (port <= INT_MAX) {
783 fwd.listen_port = (int)port;
784 success = channel_cancel_rport_listener(ssh, &fwd);
785 }
786 } else if (strcmp(rtype, "streamlocal-forward@openssh.com") == 0) {
787 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0)
788 sshpkt_fatal(ssh, r, "%s: parse streamlocal-forward@openssh.com", __func__);
789 debug_f("streamlocal-forward listen path %s",
790 fwd.listen_path);
791
792 /* check permissions */
793 if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0
794 || !auth_opts->permit_port_forwarding_flag ||
795 options.disable_forwarding) {
796 success = 0;
797 ssh_packet_send_debug(ssh, "Server has disabled "
798 "streamlocal forwarding.");
799 } else {
800 /* Start listening on the socket */
801 success = channel_setup_remote_fwd_listener(ssh,
802 &fwd, NULL, &options.fwd_opts);
803 }
804 } else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) {
805 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0)
806 sshpkt_fatal(ssh, r, "%s: parse cancel-streamlocal-forward@openssh.com", __func__);
807 debug_f("cancel-streamlocal-forward path %s",
808 fwd.listen_path);
809
810 success = channel_cancel_rport_listener(ssh, &fwd);
811 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) {
812 no_more_sessions = 1;
813 success = 1;
814 } else if (strcmp(rtype, "hostkeys-prove-00@openssh.com") == 0) {
815 success = server_input_hostkeys_prove(ssh, &resp);
816 }
817 /* XXX sshpkt_get_end() */
818 if (want_reply) {
819 if ((r = sshpkt_start(ssh, success ?
820 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE)) != 0 ||
821 (success && resp != NULL && (r = sshpkt_putb(ssh, resp)) != 0) ||
822 (r = sshpkt_send(ssh)) != 0 ||
823 (r = ssh_packet_write_wait(ssh)) != 0)
824 sshpkt_fatal(ssh, r, "%s: send reply", __func__);
825 }
826 free(fwd.listen_host);
827 free(fwd.listen_path);
828 free(rtype);
829 sshbuf_free(resp);
830 return 0;
831 }
832
833 static int
server_input_channel_req(int type,u_int32_t seq,struct ssh * ssh)834 server_input_channel_req(int type, u_int32_t seq, struct ssh *ssh)
835 {
836 Channel *c;
837 int r, success = 0;
838 char *rtype = NULL;
839 u_char want_reply = 0;
840 u_int id = 0;
841
842 if ((r = sshpkt_get_u32(ssh, &id)) != 0 ||
843 (r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 ||
844 (r = sshpkt_get_u8(ssh, &want_reply)) != 0)
845 sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
846
847 debug("server_input_channel_req: channel %u request %s reply %d",
848 id, rtype, want_reply);
849
850 if (id >= INT_MAX || (c = channel_lookup(ssh, (int)id)) == NULL) {
851 ssh_packet_disconnect(ssh, "%s: unknown channel %d",
852 __func__, id);
853 }
854 if (!strcmp(rtype, "eow@openssh.com")) {
855 if ((r = sshpkt_get_end(ssh)) != 0)
856 sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
857 chan_rcvd_eow(ssh, c);
858 } else if ((c->type == SSH_CHANNEL_LARVAL ||
859 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0)
860 success = session_input_channel_req(ssh, c, rtype);
861 if (want_reply && !(c->flags & CHAN_CLOSE_SENT)) {
862 if (!c->have_remote_id)
863 fatal_f("channel %d: no remote_id", c->self);
864 if ((r = sshpkt_start(ssh, success ?
865 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE)) != 0 ||
866 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
867 (r = sshpkt_send(ssh)) != 0)
868 sshpkt_fatal(ssh, r, "%s: send reply", __func__);
869 }
870 free(rtype);
871 return 0;
872 }
873
874 static void
server_init_dispatch(struct ssh * ssh)875 server_init_dispatch(struct ssh *ssh)
876 {
877 debug("server_init_dispatch");
878 ssh_dispatch_init(ssh, &dispatch_protocol_error);
879 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
880 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_DATA, &channel_input_data);
881 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
882 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
883 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
884 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
885 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
886 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
887 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
888 ssh_dispatch_set(ssh, SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
889 /* client_alive */
890 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive);
891 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
892 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
893 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
894 /* rekeying */
895 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
896 }
897