1 /* $OpenBSD: nchan.c,v 1.76 2024/07/25 22:40:08 djm Exp $ */
2 /*
3 * Copyright (c) 1999, 2000, 2001, 2002 Markus Friedl. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26 #include "includes.h"
27
28 #include <sys/types.h>
29 #include <sys/socket.h>
30
31 #include <errno.h>
32 #include <string.h>
33 #include <stdarg.h>
34
35 #include "openbsd-compat/sys-queue.h"
36 #include "ssh2.h"
37 #include "sshbuf.h"
38 #include "ssherr.h"
39 #include "packet.h"
40 #include "channels.h"
41 #include "compat.h"
42 #include "log.h"
43
44 /*
45 * SSH Protocol 1.5 aka New Channel Protocol
46 * Thanks to Martina, Axel and everyone who left Erlangen, leaving me bored.
47 * Written by Markus Friedl in October 1999
48 *
49 * Protocol versions 1.3 and 1.5 differ in the handshake protocol used for the
50 * tear down of channels:
51 *
52 * 1.3: strict request-ack-protocol:
53 * CLOSE ->
54 * <- CLOSE_CONFIRM
55 *
56 * 1.5: uses variations of:
57 * IEOF ->
58 * <- OCLOSE
59 * <- IEOF
60 * OCLOSE ->
61 * i.e. both sides have to close the channel
62 *
63 * 2.0: the EOF messages are optional
64 *
65 * See the debugging output from 'ssh -v' and 'sshd -d' of
66 * ssh-1.2.27 as an example.
67 *
68 */
69
70 /* functions manipulating channel states */
71 /*
72 * EVENTS update channel input/output states execute ACTIONS
73 */
74 /*
75 * ACTIONS: should never update the channel states
76 */
77 static void chan_send_eof2(struct ssh *, Channel *);
78 static void chan_send_eow2(struct ssh *, Channel *);
79
80 /* helper */
81 static void chan_shutdown_write(struct ssh *, Channel *);
82 static void chan_shutdown_read(struct ssh *, Channel *);
83 static void chan_shutdown_extended_read(struct ssh *, Channel *);
84
85 static const char * const ostates[] = {
86 "open", "drain", "wait_ieof", "closed",
87 };
88 static const char * const istates[] = {
89 "open", "drain", "wait_oclose", "closed",
90 };
91
92 static void
chan_set_istate(Channel * c,u_int next)93 chan_set_istate(Channel *c, u_int next)
94 {
95 if (c->istate > CHAN_INPUT_CLOSED || next > CHAN_INPUT_CLOSED)
96 fatal("chan_set_istate: bad state %d -> %d", c->istate, next);
97 debug2("channel %d: input %s -> %s", c->self, istates[c->istate],
98 istates[next]);
99 c->istate = next;
100 }
101
102 static void
chan_set_ostate(Channel * c,u_int next)103 chan_set_ostate(Channel *c, u_int next)
104 {
105 if (c->ostate > CHAN_OUTPUT_CLOSED || next > CHAN_OUTPUT_CLOSED)
106 fatal("chan_set_ostate: bad state %d -> %d", c->ostate, next);
107 debug2("channel %d: output %s -> %s", c->self, ostates[c->ostate],
108 ostates[next]);
109 c->ostate = next;
110 }
111
112 void
chan_read_failed(struct ssh * ssh,Channel * c)113 chan_read_failed(struct ssh *ssh, Channel *c)
114 {
115 debug2("channel %d: read failed", c->self);
116 switch (c->istate) {
117 case CHAN_INPUT_OPEN:
118 chan_shutdown_read(ssh, c);
119 chan_set_istate(c, CHAN_INPUT_WAIT_DRAIN);
120 break;
121 default:
122 error("channel %d: chan_read_failed for istate %d",
123 c->self, c->istate);
124 break;
125 }
126 }
127
128 void
chan_ibuf_empty(struct ssh * ssh,Channel * c)129 chan_ibuf_empty(struct ssh *ssh, Channel *c)
130 {
131 debug2("channel %d: ibuf empty", c->self);
132 if (sshbuf_len(c->input)) {
133 error("channel %d: chan_ibuf_empty for non empty buffer",
134 c->self);
135 return;
136 }
137 switch (c->istate) {
138 case CHAN_INPUT_WAIT_DRAIN:
139 if (!(c->flags & (CHAN_CLOSE_SENT|CHAN_LOCAL)))
140 chan_send_eof2(ssh, c);
141 chan_set_istate(c, CHAN_INPUT_CLOSED);
142 break;
143 default:
144 error("channel %d: chan_ibuf_empty for istate %d",
145 c->self, c->istate);
146 break;
147 }
148 }
149
150 void
chan_obuf_empty(struct ssh * ssh,Channel * c)151 chan_obuf_empty(struct ssh *ssh, Channel *c)
152 {
153 debug2("channel %d: obuf empty", c->self);
154 if (sshbuf_len(c->output)) {
155 error("channel %d: chan_obuf_empty for non empty buffer",
156 c->self);
157 return;
158 }
159 switch (c->ostate) {
160 case CHAN_OUTPUT_WAIT_DRAIN:
161 chan_shutdown_write(ssh, c);
162 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
163 break;
164 default:
165 error("channel %d: internal error: obuf_empty for ostate %d",
166 c->self, c->ostate);
167 break;
168 }
169 }
170
171 void
chan_rcvd_eow(struct ssh * ssh,Channel * c)172 chan_rcvd_eow(struct ssh *ssh, Channel *c)
173 {
174 debug2("channel %d: rcvd eow", c->self);
175 switch (c->istate) {
176 case CHAN_INPUT_OPEN:
177 chan_shutdown_read(ssh, c);
178 chan_set_istate(c, CHAN_INPUT_CLOSED);
179 break;
180 }
181 }
182
183 static void
chan_send_eof2(struct ssh * ssh,Channel * c)184 chan_send_eof2(struct ssh *ssh, Channel *c)
185 {
186 int r;
187
188 debug2("channel %d: send eof", c->self);
189 switch (c->istate) {
190 case CHAN_INPUT_WAIT_DRAIN:
191 if (!c->have_remote_id)
192 fatal_f("channel %d: no remote_id", c->self);
193 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_EOF)) != 0 ||
194 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
195 (r = sshpkt_send(ssh)) != 0)
196 fatal_fr(r, "send CHANNEL_EOF");
197 c->flags |= CHAN_EOF_SENT;
198 break;
199 default:
200 error("channel %d: cannot send eof for istate %d",
201 c->self, c->istate);
202 break;
203 }
204 }
205
206 static void
chan_send_close2(struct ssh * ssh,Channel * c)207 chan_send_close2(struct ssh *ssh, Channel *c)
208 {
209 int r;
210
211 debug2("channel %d: send_close2", c->self);
212 if (c->ostate != CHAN_OUTPUT_CLOSED ||
213 c->istate != CHAN_INPUT_CLOSED) {
214 error("channel %d: cannot send close for istate/ostate %d/%d",
215 c->self, c->istate, c->ostate);
216 } else if (c->flags & CHAN_CLOSE_SENT) {
217 error("channel %d: already sent close", c->self);
218 } else {
219 if (!c->have_remote_id)
220 fatal_f("channel %d: no remote_id", c->self);
221 debug2("channel %d: send close for remote id %u", c->self,
222 c->remote_id);
223 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_CLOSE)) != 0 ||
224 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
225 (r = sshpkt_send(ssh)) != 0)
226 fatal_fr(r, "send CHANNEL_EOF");
227 c->flags |= CHAN_CLOSE_SENT;
228 }
229 }
230
231 static void
chan_send_eow2(struct ssh * ssh,Channel * c)232 chan_send_eow2(struct ssh *ssh, Channel *c)
233 {
234 int r;
235
236 debug2("channel %d: send eow", c->self);
237 if (c->ostate == CHAN_OUTPUT_CLOSED) {
238 error("channel %d: must not sent eow on closed output",
239 c->self);
240 return;
241 }
242 if (!(ssh->compat & SSH_NEW_OPENSSH))
243 return;
244 if (!c->have_remote_id)
245 fatal_f("channel %d: no remote_id", c->self);
246 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_REQUEST)) != 0 ||
247 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
248 (r = sshpkt_put_cstring(ssh, "eow@openssh.com")) != 0 ||
249 (r = sshpkt_put_u8(ssh, 0)) != 0 ||
250 (r = sshpkt_send(ssh)) != 0)
251 fatal_fr(r, "send CHANNEL_EOF");
252 }
253
254 /* shared */
255
256 void
chan_rcvd_ieof(struct ssh * ssh,Channel * c)257 chan_rcvd_ieof(struct ssh *ssh, Channel *c)
258 {
259 debug2("channel %d: rcvd eof", c->self);
260 c->flags |= CHAN_EOF_RCVD;
261 if (c->ostate == CHAN_OUTPUT_OPEN)
262 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
263 if (c->ostate == CHAN_OUTPUT_WAIT_DRAIN &&
264 sshbuf_len(c->output) == 0 &&
265 !CHANNEL_EFD_OUTPUT_ACTIVE(c))
266 chan_obuf_empty(ssh, c);
267 }
268
269 void
chan_rcvd_oclose(struct ssh * ssh,Channel * c)270 chan_rcvd_oclose(struct ssh *ssh, Channel *c)
271 {
272 debug2("channel %d: rcvd close", c->self);
273 if (!(c->flags & CHAN_LOCAL)) {
274 if (c->flags & CHAN_CLOSE_RCVD)
275 error("channel %d: protocol error: close rcvd twice",
276 c->self);
277 c->flags |= CHAN_CLOSE_RCVD;
278 }
279 if (c->type == SSH_CHANNEL_LARVAL) {
280 /* tear down larval channels immediately */
281 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
282 chan_set_istate(c, CHAN_INPUT_CLOSED);
283 return;
284 }
285 switch (c->ostate) {
286 case CHAN_OUTPUT_OPEN:
287 /*
288 * wait until a data from the channel is consumed if a CLOSE
289 * is received
290 */
291 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
292 break;
293 }
294 switch (c->istate) {
295 case CHAN_INPUT_OPEN:
296 chan_shutdown_read(ssh, c);
297 chan_shutdown_extended_read(ssh, c);
298 chan_set_istate(c, CHAN_INPUT_CLOSED);
299 break;
300 case CHAN_INPUT_WAIT_DRAIN:
301 if (!(c->flags & CHAN_LOCAL))
302 chan_send_eof2(ssh, c);
303 chan_shutdown_extended_read(ssh, c);
304 chan_set_istate(c, CHAN_INPUT_CLOSED);
305 break;
306 }
307 }
308
309 void
chan_write_failed(struct ssh * ssh,Channel * c)310 chan_write_failed(struct ssh *ssh, Channel *c)
311 {
312 debug2("channel %d: write failed", c->self);
313 switch (c->ostate) {
314 case CHAN_OUTPUT_OPEN:
315 case CHAN_OUTPUT_WAIT_DRAIN:
316 chan_shutdown_write(ssh, c);
317 if (strcmp(c->ctype, "session") == 0)
318 chan_send_eow2(ssh, c);
319 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
320 break;
321 default:
322 error("channel %d: chan_write_failed for ostate %d",
323 c->self, c->ostate);
324 break;
325 }
326 }
327
328 void
chan_mark_dead(struct ssh * ssh,Channel * c)329 chan_mark_dead(struct ssh *ssh, Channel *c)
330 {
331 c->type = SSH_CHANNEL_ZOMBIE;
332 }
333
334 int
chan_is_dead(struct ssh * ssh,Channel * c,int do_send)335 chan_is_dead(struct ssh *ssh, Channel *c, int do_send)
336 {
337 if (c->type == SSH_CHANNEL_ZOMBIE) {
338 debug2("channel %d: zombie", c->self);
339 return 1;
340 }
341 if (c->istate != CHAN_INPUT_CLOSED || c->ostate != CHAN_OUTPUT_CLOSED)
342 return 0;
343 if ((ssh->compat & SSH_BUG_EXTEOF) &&
344 c->extended_usage == CHAN_EXTENDED_WRITE &&
345 c->efd != -1 &&
346 sshbuf_len(c->extended) > 0) {
347 debug2("channel %d: active efd: %d len %zu",
348 c->self, c->efd, sshbuf_len(c->extended));
349 return 0;
350 }
351 if (c->flags & CHAN_LOCAL) {
352 debug2("channel %d: is dead (local)", c->self);
353 return 1;
354 }
355 if (!(c->flags & CHAN_CLOSE_SENT)) {
356 if (do_send) {
357 chan_send_close2(ssh, c);
358 } else {
359 /* channel would be dead if we sent a close */
360 if (c->flags & CHAN_CLOSE_RCVD) {
361 debug2("channel %d: almost dead",
362 c->self);
363 return 1;
364 }
365 }
366 }
367 if ((c->flags & CHAN_CLOSE_SENT) &&
368 (c->flags & CHAN_CLOSE_RCVD)) {
369 debug2("channel %d: is dead", c->self);
370 return 1;
371 }
372 return 0;
373 }
374
375 /* helper */
376 static void
chan_shutdown_write(struct ssh * ssh,Channel * c)377 chan_shutdown_write(struct ssh *ssh, Channel *c)
378 {
379 sshbuf_reset(c->output);
380 if (c->type == SSH_CHANNEL_LARVAL)
381 return;
382 /* shutdown failure is allowed if write failed already */
383 debug2_f("channel %d: (i%d o%d sock %d wfd %d efd %d [%s])",
384 c->self, c->istate, c->ostate, c->sock, c->wfd, c->efd,
385 channel_format_extended_usage(c));
386 if (c->sock != -1) {
387 if (shutdown(c->sock, SHUT_WR) == -1) {
388 debug2_f("channel %d: shutdown() failed for "
389 "fd %d [i%d o%d]: %.100s", c->self, c->sock,
390 c->istate, c->ostate, strerror(errno));
391 }
392 } else {
393 if (channel_close_fd(ssh, c, &c->wfd) < 0) {
394 logit_f("channel %d: close() failed for "
395 "fd %d [i%d o%d]: %.100s", c->self, c->wfd,
396 c->istate, c->ostate, strerror(errno));
397 }
398 }
399 }
400
401 static void
chan_shutdown_read(struct ssh * ssh,Channel * c)402 chan_shutdown_read(struct ssh *ssh, Channel *c)
403 {
404 if (c->type == SSH_CHANNEL_LARVAL)
405 return;
406 debug2_f("channel %d: (i%d o%d sock %d wfd %d efd %d [%s])",
407 c->self, c->istate, c->ostate, c->sock, c->rfd, c->efd,
408 channel_format_extended_usage(c));
409 if (c->sock != -1) {
410 /*
411 * shutdown(sock, SHUT_READ) may return ENOTCONN if the
412 * write side has been closed already. (bug on Linux)
413 * HP-UX may return ENOTCONN also.
414 */
415 if (shutdown(c->sock, SHUT_RD) == -1 && errno != ENOTCONN) {
416 error_f("channel %d: shutdown() failed for "
417 "fd %d [i%d o%d]: %.100s", c->self, c->sock,
418 c->istate, c->ostate, strerror(errno));
419 }
420 } else {
421 if (channel_close_fd(ssh, c, &c->rfd) < 0) {
422 logit_f("channel %d: close() failed for "
423 "fd %d [i%d o%d]: %.100s", c->self, c->rfd,
424 c->istate, c->ostate, strerror(errno));
425 }
426 }
427 }
428
429 static void
chan_shutdown_extended_read(struct ssh * ssh,Channel * c)430 chan_shutdown_extended_read(struct ssh *ssh, Channel *c)
431 {
432 if (c->type == SSH_CHANNEL_LARVAL || c->efd == -1)
433 return;
434 if (c->extended_usage != CHAN_EXTENDED_READ &&
435 c->extended_usage != CHAN_EXTENDED_IGNORE)
436 return;
437 debug_f("channel %d: (i%d o%d sock %d wfd %d efd %d [%s])",
438 c->self, c->istate, c->ostate, c->sock, c->rfd, c->efd,
439 channel_format_extended_usage(c));
440 if (channel_close_fd(ssh, c, &c->efd) < 0) {
441 logit_f("channel %d: close() failed for "
442 "extended fd %d [i%d o%d]: %.100s", c->self, c->efd,
443 c->istate, c->ostate, strerror(errno));
444 }
445 }
446