1 /* $NetBSD: serverloop.c,v 1.38 2025/04/09 15:49:32 christos Exp $ */
2 /* $OpenBSD: serverloop.c,v 1.241 2024/11/26 22:01:37 djm Exp $ */
3
4 /*
5 * Author: Tatu Ylonen <ylo@cs.hut.fi>
6 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
7 * All rights reserved
8 * Server main loop for handling the interactive session.
9 *
10 * As far as I am concerned, the code I have written for this software
11 * can be used freely for any purpose. Any derived versions of this
12 * software must be clearly marked as such, and if the derived work is
13 * incompatible with the protocol description in the RFC file, it must be
14 * called by a name other than "ssh" or "Secure Shell".
15 *
16 * SSH2 support by Markus Friedl.
17 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
18 *
19 * Redistribution and use in source and binary forms, with or without
20 * modification, are permitted provided that the following conditions
21 * are met:
22 * 1. Redistributions of source code must retain the above copyright
23 * notice, this list of conditions and the following disclaimer.
24 * 2. Redistributions in binary form must reproduce the above copyright
25 * notice, this list of conditions and the following disclaimer in the
26 * documentation and/or other materials provided with the distribution.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
29 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
30 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
31 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
32 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
33 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
34 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
35 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
36 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
37 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
38 */
39
40 #include "includes.h"
41 __RCSID("$NetBSD: serverloop.c,v 1.38 2025/04/09 15:49:32 christos Exp $");
42
43 #include <sys/param.h> /* MIN MAX */
44 #include <sys/types.h>
45 #include <sys/wait.h>
46 #include <sys/socket.h>
47 #include <sys/time.h>
48 #include <sys/queue.h>
49
50 #include <netinet/in.h>
51
52 #include <errno.h>
53 #include <fcntl.h>
54 #include <pwd.h>
55 #include <limits.h>
56 #include <poll.h>
57 #include <signal.h>
58 #include <string.h>
59 #include <termios.h>
60 #include <unistd.h>
61 #include <stdarg.h>
62
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 static u_long stdin_bytes = 0; /* Number of bytes written to stdin. */
85 static u_long fdout_bytes = 0; /* Number of stdout bytes read from program. */
86
87 extern ServerOptions options;
88
89 /* XXX */
90 extern Authctxt *the_authctxt;
91 extern struct sshauthopt *auth_opts;
92
93 static int no_more_sessions = 0; /* Disallow further sessions. */
94
95 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */
96
97 /* prototypes */
98 static void server_init_dispatch(struct ssh *);
99
100 /* requested tunnel forwarding interface(s), shared with session.c */
101 char *tun_fwd_ifnames = NULL;
102
103 /*
104 * Returns current time in seconds from Jan 1, 1970 with the maximum
105 * available resolution.
106 */
107
108 static double
get_current_time(void)109 get_current_time(void)
110 {
111 struct timeval tv;
112 gettimeofday(&tv, NULL);
113 return (double) tv.tv_sec + (double) tv.tv_usec / 1000000.0;
114 }
115
116 static void
sigchld_handler(int sig)117 sigchld_handler(int sig)
118 {
119 child_terminated = 1;
120 }
121
122 static void
client_alive_check(struct ssh * ssh)123 client_alive_check(struct ssh *ssh)
124 {
125 char remote_id[512];
126 int r, channel_id;
127
128 /* timeout, check to see how many we have had */
129 if (options.client_alive_count_max > 0 &&
130 ssh_packet_inc_alive_timeouts(ssh) >
131 options.client_alive_count_max) {
132 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id));
133 logit("Timeout, client not responding from %s", remote_id);
134 cleanup_exit(255);
135 }
136
137 /*
138 * send a bogus global/channel request with "wantreply",
139 * we should get back a failure
140 */
141 if ((channel_id = channel_find_open(ssh)) == -1) {
142 if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 ||
143 (r = sshpkt_put_cstring(ssh, "keepalive@openssh.com"))
144 != 0 ||
145 (r = sshpkt_put_u8(ssh, 1)) != 0) /* boolean: want reply */
146 fatal_fr(r, "compose");
147 } else {
148 channel_request_start(ssh, channel_id,
149 "keepalive@openssh.com", 1);
150 }
151 if ((r = sshpkt_send(ssh)) != 0)
152 fatal_fr(r, "send");
153 }
154
155 /*
156 * Sleep in ppoll() until we can do something.
157 * Optionally, a maximum time can be specified for the duration of
158 * the wait (0 = infinite).
159 */
160 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)161 wait_until_can_do_something(struct ssh *ssh,
162 int connection_in, int connection_out, struct pollfd **pfdp,
163 u_int *npfd_allocp, u_int *npfd_activep, sigset_t *sigsetp,
164 int *conn_in_readyp, int *conn_out_readyp)
165 {
166 struct timespec timeout;
167 char remote_id[512];
168 int ret;
169 int client_alive_scheduled = 0;
170 u_int p;
171 time_t now;
172 static time_t last_client_time, unused_connection_expiry;
173
174 *conn_in_readyp = *conn_out_readyp = 0;
175
176 /* Prepare channel poll. First two pollfd entries are reserved */
177 ptimeout_init(&timeout);
178 channel_prepare_poll(ssh, pfdp, npfd_allocp, npfd_activep, 2, &timeout);
179 now = monotime();
180 if (*npfd_activep < 2)
181 fatal_f("bad npfd %u", *npfd_activep); /* shouldn't happen */
182 if (options.rekey_interval > 0 && !ssh_packet_is_rekeying(ssh)) {
183 ptimeout_deadline_sec(&timeout,
184 ssh_packet_get_rekey_timeout(ssh));
185 }
186
187 /*
188 * If no channels are open and UnusedConnectionTimeout is set, then
189 * start the clock to terminate the connection.
190 */
191 if (options.unused_connection_timeout != 0) {
192 if (channel_still_open(ssh) || unused_connection_expiry == 0) {
193 unused_connection_expiry = now +
194 options.unused_connection_timeout;
195 }
196 ptimeout_deadline_monotime(&timeout, unused_connection_expiry);
197 }
198
199 /*
200 * if using client_alive, set the max timeout accordingly,
201 * and indicate that this particular timeout was for client
202 * alive by setting the client_alive_scheduled flag.
203 *
204 * this could be randomized somewhat to make traffic
205 * analysis more difficult, but we're not doing it yet.
206 */
207 if (options.client_alive_interval) {
208 /* Time we last heard from the client OR sent a keepalive */
209 if (last_client_time == 0)
210 last_client_time = now;
211 ptimeout_deadline_sec(&timeout, options.client_alive_interval);
212 /* XXX ? deadline_monotime(last_client_time + alive_interval) */
213 client_alive_scheduled = 1;
214 }
215
216 #if 0
217 /* wrong: bad condition XXX */
218 if (channel_not_very_much_buffered_data())
219 #endif
220 /* Monitor client connection on reserved pollfd entries */
221 (*pfdp)[0].fd = connection_in;
222 (*pfdp)[0].events = POLLIN;
223 (*pfdp)[1].fd = connection_out;
224 (*pfdp)[1].events = ssh_packet_have_data_to_write(ssh) ? POLLOUT : 0;
225
226 /*
227 * If child has terminated and there is enough buffer space to read
228 * from it, then read as much as is available and exit.
229 */
230 if (child_terminated && ssh_packet_not_very_much_data_to_write(ssh))
231 ptimeout_deadline_ms(&timeout, 100);
232
233 /* Wait for something to happen, or the timeout to expire. */
234 ret = ppoll(*pfdp, *npfd_activep, ptimeout_get_tsp(&timeout), sigsetp);
235
236 if (ret == -1) {
237 for (p = 0; p < *npfd_activep; p++)
238 (*pfdp)[p].revents = 0;
239 if (errno != EINTR)
240 fatal_f("ppoll: %.100s", strerror(errno));
241 return;
242 }
243
244 *conn_in_readyp = (*pfdp)[0].revents != 0;
245 *conn_out_readyp = (*pfdp)[1].revents != 0;
246
247 now = monotime(); /* need to reset after ppoll() */
248 /* ClientAliveInterval probing */
249 if (client_alive_scheduled) {
250 if (ret == 0 &&
251 now >= last_client_time + options.client_alive_interval) {
252 /* ppoll timed out and we're due to probe */
253 client_alive_check(ssh);
254 last_client_time = now;
255 } else if (ret != 0 && *conn_in_readyp) {
256 /* Data from peer; reset probe timer. */
257 last_client_time = now;
258 }
259 }
260
261 /* UnusedConnectionTimeout handling */
262 if (unused_connection_expiry != 0 &&
263 now > unused_connection_expiry && !channel_still_open(ssh)) {
264 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id));
265 logit("terminating inactive connection from %s", remote_id);
266 cleanup_exit(255);
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)
283 return 0;
284 if (errno == EPIPE) {
285 logit("Connection closed by %.100s port %d",
286 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
287 return -1;
288 }
289 logit("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 double start_time, total_time;
342 sigset_t bsigset, osigset;
343
344 debug("Entering interactive session for SSH2.");
345 start_time = get_current_time();
346
347 if (sigemptyset(&bsigset) == -1 || sigaddset(&bsigset, SIGCHLD) == -1)
348 error_f("bsigset setup: %s", strerror(errno));
349 ssh_signal(SIGCHLD, sigchld_handler);
350 child_terminated = 0;
351 connection_in = ssh_packet_get_connection_in(ssh);
352 connection_out = ssh_packet_get_connection_out(ssh);
353
354 server_init_dispatch(ssh);
355
356 for (;;) {
357 process_buffered_input_packets(ssh);
358
359 if (!ssh_packet_is_rekeying(ssh) &&
360 ssh_packet_not_very_much_data_to_write(ssh))
361 channel_output_poll(ssh);
362
363 /*
364 * Block SIGCHLD while we check for dead children, then pass
365 * the old signal mask through to ppoll() so that it'll wake
366 * up immediately if a child exits after we've called waitpid().
367 */
368 if (sigprocmask(SIG_BLOCK, &bsigset, &osigset) == -1)
369 error_f("bsigset sigprocmask: %s", strerror(errno));
370 collect_children(ssh);
371 wait_until_can_do_something(ssh, connection_in, connection_out,
372 &pfd, &npfd_alloc, &npfd_active, &osigset,
373 &conn_in_ready, &conn_out_ready);
374 if (sigprocmask(SIG_SETMASK, &osigset, NULL) == -1)
375 error_f("osigset sigprocmask: %s", strerror(errno));
376
377 channel_after_poll(ssh, pfd, npfd_active);
378 if (conn_in_ready &&
379 process_input(ssh, connection_in) < 0)
380 break;
381 /* A timeout may have triggered rekeying */
382 if ((r = ssh_packet_check_rekey(ssh)) != 0)
383 fatal_fr(r, "cannot start rekeying");
384 if (conn_out_ready)
385 process_output(ssh, connection_out);
386 }
387 collect_children(ssh);
388 free(pfd);
389
390 /* free all channels, no more reads and writes */
391 channel_free_all(ssh);
392
393 /* free remaining sessions, e.g. remove wtmp entries */
394 session_destroy_all(ssh, NULL);
395 total_time = get_current_time() - start_time;
396 logit("SSH: Server;LType: Throughput;Remote: %s-%d;IN: %lu;OUT: %lu;Duration: %.1f;tPut_in: %.1f;tPut_out: %.1f",
397 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
398 stdin_bytes, fdout_bytes, total_time, stdin_bytes / total_time,
399 fdout_bytes / total_time);
400 }
401
402 static int
server_input_keep_alive(int type,u_int32_t seq,struct ssh * ssh)403 server_input_keep_alive(int type, u_int32_t seq, struct ssh *ssh)
404 {
405 debug("Got %d/%u for keepalive", type, seq);
406 /*
407 * reset timeout, since we got a sane answer from the client.
408 * even if this was generated by something other than
409 * the bogus CHANNEL_REQUEST we send for keepalives.
410 */
411 ssh_packet_set_alive_timeouts(ssh, 0);
412 return 0;
413 }
414
415 static Channel *
server_request_direct_tcpip(struct ssh * ssh,int * reason,const char ** errmsg)416 server_request_direct_tcpip(struct ssh *ssh, int *reason, const char **errmsg)
417 {
418 Channel *c = NULL;
419 char *target = NULL, *originator = NULL;
420 u_int target_port = 0, originator_port = 0;
421 int r;
422
423 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 ||
424 (r = sshpkt_get_u32(ssh, &target_port)) != 0 ||
425 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 ||
426 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 ||
427 (r = sshpkt_get_end(ssh)) != 0)
428 sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
429 if (target_port > 0xFFFF) {
430 error_f("invalid target port");
431 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
432 goto out;
433 }
434 if (originator_port > 0xFFFF) {
435 error_f("invalid originator port");
436 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
437 goto out;
438 }
439
440 debug_f("originator %s port %u, target %s port %u",
441 originator, originator_port, target, target_port);
442
443 /* XXX fine grained permissions */
444 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 &&
445 auth_opts->permit_port_forwarding_flag &&
446 !options.disable_forwarding) {
447 c = channel_connect_to_port(ssh, target, target_port,
448 "direct-tcpip", "direct-tcpip", reason, errmsg);
449 } else {
450 logit("refused local port forward: "
451 "originator %s port %d, target %s port %d",
452 originator, originator_port, target, target_port);
453 if (reason != NULL)
454 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
455 }
456
457 out:
458 free(originator);
459 free(target);
460 return c;
461 }
462
463 static Channel *
server_request_direct_streamlocal(struct ssh * ssh)464 server_request_direct_streamlocal(struct ssh *ssh)
465 {
466 Channel *c = NULL;
467 char *target = NULL, *originator = NULL;
468 u_int originator_port = 0;
469 struct passwd *pw = the_authctxt->pw;
470 int r;
471
472 if (pw == NULL || !the_authctxt->valid)
473 fatal_f("no/invalid user");
474
475 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 ||
476 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 ||
477 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 ||
478 (r = sshpkt_get_end(ssh)) != 0)
479 sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
480 if (originator_port > 0xFFFF) {
481 error_f("invalid originator port");
482 goto out;
483 }
484
485 debug_f("originator %s port %d, target %s",
486 originator, originator_port, target);
487
488 /* XXX fine grained permissions */
489 if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 &&
490 auth_opts->permit_port_forwarding_flag &&
491 !options.disable_forwarding) {
492 c = channel_connect_to_path(ssh, target,
493 "direct-streamlocal@openssh.com", "direct-streamlocal");
494 } else {
495 logit("refused streamlocal port forward: "
496 "originator %s port %d, target %s",
497 originator, originator_port, target);
498 }
499
500 out:
501 free(originator);
502 free(target);
503 return c;
504 }
505
506 static Channel *
server_request_tun(struct ssh * ssh)507 server_request_tun(struct ssh *ssh)
508 {
509 Channel *c = NULL;
510 u_int mode, tun;
511 int r, sock;
512 char *tmp, *ifname = NULL;
513
514 if ((r = sshpkt_get_u32(ssh, &mode)) != 0)
515 sshpkt_fatal(ssh, r, "%s: parse mode", __func__);
516 switch (mode) {
517 case SSH_TUNMODE_POINTOPOINT:
518 case SSH_TUNMODE_ETHERNET:
519 break;
520 default:
521 ssh_packet_send_debug(ssh, "Unsupported tunnel device mode.");
522 return NULL;
523 }
524 if ((options.permit_tun & mode) == 0) {
525 ssh_packet_send_debug(ssh, "Server has rejected tunnel device "
526 "forwarding");
527 return NULL;
528 }
529
530 if ((r = sshpkt_get_u32(ssh, &tun)) != 0)
531 sshpkt_fatal(ssh, r, "%s: parse device", __func__);
532 if (tun > INT_MAX) {
533 debug_f("invalid tun");
534 goto done;
535 }
536 if (auth_opts->force_tun_device != -1) {
537 if (tun != SSH_TUNID_ANY &&
538 auth_opts->force_tun_device != (int)tun)
539 goto done;
540 tun = auth_opts->force_tun_device;
541 }
542 sock = tun_open(tun, mode, &ifname);
543 if (sock < 0)
544 goto done;
545 debug("Tunnel forwarding using interface %s", ifname);
546
547 if (options.hpn_disabled)
548 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1,
549 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
550 else
551 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1,
552 options.hpn_buffer_size, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
553 c->datagram = 1;
554
555 /*
556 * Update the list of names exposed to the session
557 * XXX remove these if the tunnels are closed (won't matter
558 * much if they are already in the environment though)
559 */
560 tmp = tun_fwd_ifnames;
561 xasprintf(&tun_fwd_ifnames, "%s%s%s",
562 tun_fwd_ifnames == NULL ? "" : tun_fwd_ifnames,
563 tun_fwd_ifnames == NULL ? "" : ",",
564 ifname);
565 free(tmp);
566 free(ifname);
567
568 done:
569 if (c == NULL)
570 ssh_packet_send_debug(ssh, "Failed to open the tunnel device.");
571 return c;
572 }
573
574 static Channel *
server_request_session(struct ssh * ssh)575 server_request_session(struct ssh *ssh)
576 {
577 Channel *c;
578 int r;
579
580 debug("input_session_request");
581 if ((r = sshpkt_get_end(ssh)) != 0)
582 sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
583
584 if (no_more_sessions) {
585 ssh_packet_disconnect(ssh, "Possible attack: attempt to open a "
586 "session after additional sessions disabled");
587 }
588
589 /*
590 * A server session has no fd to read or write until a
591 * CHANNEL_REQUEST for a shell is made, so we set the type to
592 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all
593 * CHANNEL_REQUEST messages is registered.
594 */
595 c = channel_new(ssh, "session", SSH_CHANNEL_LARVAL,
596 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
597 0, "server-session", 1);
598 if ((options.tcp_rcv_buf_poll > 0) && (!options.hpn_disabled))
599 c->dynamic_window = 1;
600 if (session_open(the_authctxt, c->self) != 1) {
601 debug("session open failed, free channel %d", c->self);
602 channel_free(ssh, c);
603 return NULL;
604 }
605 channel_register_cleanup(ssh, c->self, session_close_by_channel, 0);
606 return c;
607 }
608
609 static int
server_input_channel_open(int type,u_int32_t seq,struct ssh * ssh)610 server_input_channel_open(int type, u_int32_t seq, struct ssh *ssh)
611 {
612 Channel *c = NULL;
613 char *ctype = NULL;
614 const char *errmsg = NULL;
615 int r, reason = SSH2_OPEN_CONNECT_FAILED;
616 u_int rchan = 0, rmaxpack = 0, rwindow = 0;
617
618 if ((r = sshpkt_get_cstring(ssh, &ctype, NULL)) != 0 ||
619 (r = sshpkt_get_u32(ssh, &rchan)) != 0 ||
620 (r = sshpkt_get_u32(ssh, &rwindow)) != 0 ||
621 (r = sshpkt_get_u32(ssh, &rmaxpack)) != 0)
622 sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
623 debug_f("ctype %s rchan %u win %u max %u",
624 ctype, rchan, rwindow, rmaxpack);
625
626 if (strcmp(ctype, "session") == 0) {
627 c = server_request_session(ssh);
628 } else if (strcmp(ctype, "direct-tcpip") == 0) {
629 c = server_request_direct_tcpip(ssh, &reason, &errmsg);
630 } else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) {
631 c = server_request_direct_streamlocal(ssh);
632 } else if (strcmp(ctype, "tun@openssh.com") == 0) {
633 c = server_request_tun(ssh);
634 }
635 if (c != NULL) {
636 debug_f("confirm %s", ctype);
637 c->remote_id = rchan;
638 c->have_remote_id = 1;
639 c->remote_window = rwindow;
640 c->remote_maxpacket = rmaxpack;
641 if (c->type != SSH_CHANNEL_CONNECTING) {
642 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION)) != 0 ||
643 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
644 (r = sshpkt_put_u32(ssh, c->self)) != 0 ||
645 (r = sshpkt_put_u32(ssh, c->local_window)) != 0 ||
646 (r = sshpkt_put_u32(ssh, c->local_maxpacket)) != 0 ||
647 (r = sshpkt_send(ssh)) != 0) {
648 sshpkt_fatal(ssh, r,
649 "%s: send open confirm", __func__);
650 }
651 }
652 } else {
653 debug_f("failure %s", ctype);
654 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE)) != 0 ||
655 (r = sshpkt_put_u32(ssh, rchan)) != 0 ||
656 (r = sshpkt_put_u32(ssh, reason)) != 0 ||
657 (r = sshpkt_put_cstring(ssh, errmsg ? errmsg : "open failed")) != 0 ||
658 (r = sshpkt_put_cstring(ssh, "")) != 0 ||
659 (r = sshpkt_send(ssh)) != 0) {
660 sshpkt_fatal(ssh, r,
661 "%s: send open failure", __func__);
662 }
663 }
664 free(ctype);
665 return 0;
666 }
667
668 static int
server_input_hostkeys_prove(struct ssh * ssh,struct sshbuf ** respp)669 server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp)
670 {
671 struct sshbuf *resp = NULL;
672 struct sshbuf *sigbuf = NULL;
673 struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL;
674 int r, ndx, success = 0;
675 const u_char *blob;
676 const char *sigalg, *kex_rsa_sigalg = NULL;
677 u_char *sig = 0;
678 size_t blen, slen;
679
680 if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL)
681 fatal_f("sshbuf_new");
682 if (sshkey_type_plain(sshkey_type_from_name(
683 ssh->kex->hostkey_alg)) == KEY_RSA)
684 kex_rsa_sigalg = ssh->kex->hostkey_alg;
685 while (ssh_packet_remaining(ssh) > 0) {
686 sshkey_free(key);
687 key = NULL;
688 if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 ||
689 (r = sshkey_from_blob(blob, blen, &key)) != 0) {
690 error_fr(r, "parse key");
691 goto out;
692 }
693 /*
694 * Better check that this is actually one of our hostkeys
695 * before attempting to sign anything with it.
696 */
697 if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) {
698 error_f("unknown host %s key", sshkey_type(key));
699 goto out;
700 }
701 /*
702 * XXX refactor: make kex->sign just use an index rather
703 * than passing in public and private keys
704 */
705 if ((key_prv = get_hostkey_by_index(ndx)) == NULL &&
706 (key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) {
707 error_f("can't retrieve hostkey %d", ndx);
708 goto out;
709 }
710 sshbuf_reset(sigbuf);
711 free(sig);
712 sig = NULL;
713 /*
714 * For RSA keys, prefer to use the signature type negotiated
715 * during KEX to the default (SHA1).
716 */
717 sigalg = sshkey_ssh_name(key);
718 if (sshkey_type_plain(key->type) == KEY_RSA) {
719 if (kex_rsa_sigalg != NULL)
720 sigalg = kex_rsa_sigalg;
721 else if (ssh->kex->flags & KEX_RSA_SHA2_512_SUPPORTED)
722 sigalg = "rsa-sha2-512";
723 else if (ssh->kex->flags & KEX_RSA_SHA2_256_SUPPORTED)
724 sigalg = "rsa-sha2-256";
725 }
726
727 debug3_f("sign %s key (index %d) using sigalg %s",
728 sshkey_type(key), ndx, sigalg == NULL ? "default" : sigalg);
729 if ((r = sshbuf_put_cstring(sigbuf,
730 "hostkeys-prove-00@openssh.com")) != 0 ||
731 (r = sshbuf_put_stringb(sigbuf,
732 ssh->kex->session_id)) != 0 ||
733 (r = sshkey_puts(key, sigbuf)) != 0 ||
734 (r = ssh->kex->sign(ssh, key_prv, key_pub, &sig, &slen,
735 sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), sigalg)) != 0 ||
736 (r = sshbuf_put_string(resp, sig, slen)) != 0) {
737 error_fr(r, "assemble signature");
738 goto out;
739 }
740 }
741 /* Success */
742 *respp = resp;
743 resp = NULL; /* don't free it */
744 success = 1;
745 out:
746 free(sig);
747 sshbuf_free(resp);
748 sshbuf_free(sigbuf);
749 sshkey_free(key);
750 return success;
751 }
752
753 static int
server_input_global_request(int type,u_int32_t seq,struct ssh * ssh)754 server_input_global_request(int type, u_int32_t seq, struct ssh *ssh)
755 {
756 char *rtype = NULL;
757 u_char want_reply = 0;
758 int r, success = 0, allocated_listen_port = 0;
759 u_int port = 0;
760 struct sshbuf *resp = NULL;
761 struct passwd *pw = the_authctxt->pw;
762 struct Forward fwd;
763
764 memset(&fwd, 0, sizeof(fwd));
765 if (pw == NULL || !the_authctxt->valid)
766 fatal_f("no/invalid user");
767
768 if ((r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 ||
769 (r = sshpkt_get_u8(ssh, &want_reply)) != 0)
770 sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
771 debug_f("rtype %s want_reply %d", rtype, want_reply);
772
773 /* -R style forwarding */
774 if (strcmp(rtype, "tcpip-forward") == 0) {
775 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 ||
776 (r = sshpkt_get_u32(ssh, &port)) != 0)
777 sshpkt_fatal(ssh, r, "%s: parse tcpip-forward", __func__);
778 debug_f("tcpip-forward listen %s port %u",
779 fwd.listen_host, port);
780 if (port <= INT_MAX)
781 fwd.listen_port = (int)port;
782 /* check permissions */
783 if (port > INT_MAX ||
784 (options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 ||
785 !auth_opts->permit_port_forwarding_flag ||
786 options.disable_forwarding ||
787 (!want_reply && fwd.listen_port == 0)) {
788 success = 0;
789 ssh_packet_send_debug(ssh, "Server has disabled port forwarding.");
790 } else {
791 /* Start listening on the port */
792 success = channel_setup_remote_fwd_listener(ssh, &fwd,
793 &allocated_listen_port, &options.fwd_opts);
794 }
795 if ((resp = sshbuf_new()) == NULL)
796 fatal_f("sshbuf_new");
797 if (allocated_listen_port != 0 &&
798 (r = sshbuf_put_u32(resp, allocated_listen_port)) != 0)
799 fatal_fr(r, "sshbuf_put_u32");
800 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
801 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 ||
802 (r = sshpkt_get_u32(ssh, &port)) != 0)
803 sshpkt_fatal(ssh, r, "%s: parse cancel-tcpip-forward", __func__);
804
805 debug_f("cancel-tcpip-forward addr %s port %d",
806 fwd.listen_host, port);
807 if (port <= INT_MAX) {
808 fwd.listen_port = (int)port;
809 success = channel_cancel_rport_listener(ssh, &fwd);
810 }
811 } else if (strcmp(rtype, "streamlocal-forward@openssh.com") == 0) {
812 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0)
813 sshpkt_fatal(ssh, r, "%s: parse streamlocal-forward@openssh.com", __func__);
814 debug_f("streamlocal-forward listen path %s",
815 fwd.listen_path);
816
817 /* check permissions */
818 if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0
819 || !auth_opts->permit_port_forwarding_flag ||
820 options.disable_forwarding) {
821 success = 0;
822 ssh_packet_send_debug(ssh, "Server has disabled "
823 "streamlocal forwarding.");
824 } else {
825 /* Start listening on the socket */
826 success = channel_setup_remote_fwd_listener(ssh,
827 &fwd, NULL, &options.fwd_opts);
828 }
829 } else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) {
830 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0)
831 sshpkt_fatal(ssh, r, "%s: parse cancel-streamlocal-forward@openssh.com", __func__);
832 debug_f("cancel-streamlocal-forward path %s",
833 fwd.listen_path);
834
835 success = channel_cancel_rport_listener(ssh, &fwd);
836 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) {
837 no_more_sessions = 1;
838 success = 1;
839 } else if (strcmp(rtype, "hostkeys-prove-00@openssh.com") == 0) {
840 success = server_input_hostkeys_prove(ssh, &resp);
841 }
842 /* XXX sshpkt_get_end() */
843 if (want_reply) {
844 if ((r = sshpkt_start(ssh, success ?
845 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE)) != 0 ||
846 (success && resp != NULL && (r = sshpkt_putb(ssh, resp)) != 0) ||
847 (r = sshpkt_send(ssh)) != 0 ||
848 (r = ssh_packet_write_wait(ssh)) < 0)
849 sshpkt_fatal(ssh, r, "%s: send reply", __func__);
850 }
851 free(fwd.listen_host);
852 free(fwd.listen_path);
853 free(rtype);
854 sshbuf_free(resp);
855 return 0;
856 }
857
858 static int
server_input_channel_req(int type,u_int32_t seq,struct ssh * ssh)859 server_input_channel_req(int type, u_int32_t seq, struct ssh *ssh)
860 {
861 Channel *c;
862 int r, success = 0;
863 char *rtype = NULL;
864 u_char want_reply = 0;
865 u_int id = 0;
866
867 if ((r = sshpkt_get_u32(ssh, &id)) != 0 ||
868 (r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 ||
869 (r = sshpkt_get_u8(ssh, &want_reply)) != 0)
870 sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
871
872 debug("server_input_channel_req: channel %u request %s reply %d",
873 id, rtype, want_reply);
874
875 if (id >= INT_MAX || (c = channel_lookup(ssh, (int)id)) == NULL) {
876 ssh_packet_disconnect(ssh, "%s: unknown channel %d",
877 __func__, id);
878 }
879 if (!strcmp(rtype, "eow@openssh.com")) {
880 if ((r = sshpkt_get_end(ssh)) != 0)
881 sshpkt_fatal(ssh, r, "%s: parse packet", __func__);
882 chan_rcvd_eow(ssh, c);
883 } else if ((c->type == SSH_CHANNEL_LARVAL ||
884 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0)
885 success = session_input_channel_req(ssh, c, rtype);
886 if (want_reply && !(c->flags & CHAN_CLOSE_SENT)) {
887 if (!c->have_remote_id)
888 fatal_f("channel %d: no remote_id", c->self);
889 if ((r = sshpkt_start(ssh, success ?
890 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE)) != 0 ||
891 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
892 (r = sshpkt_send(ssh)) != 0)
893 sshpkt_fatal(ssh, r, "%s: send reply", __func__);
894 }
895 free(rtype);
896 return 0;
897 }
898
899 static void
server_init_dispatch(struct ssh * ssh)900 server_init_dispatch(struct ssh *ssh)
901 {
902 debug("server_init_dispatch");
903 ssh_dispatch_init(ssh, &dispatch_protocol_error);
904 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
905 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_DATA, &channel_input_data);
906 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
907 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
908 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
909 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
910 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
911 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
912 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
913 ssh_dispatch_set(ssh, SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
914 /* client_alive */
915 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive);
916 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
917 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
918 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
919 /* rekeying */
920 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit);
921 }
922