1 /* $OpenBSD: nchan.c,v 1.75 2024/02/01 02:37:33 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 close", 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 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_CLOSE)) != 0 ||
222 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
223 (r = sshpkt_send(ssh)) != 0)
224 fatal_fr(r, "send CHANNEL_EOF");
225 c->flags |= CHAN_CLOSE_SENT;
226 }
227 }
228
229 static void
chan_send_eow2(struct ssh * ssh,Channel * c)230 chan_send_eow2(struct ssh *ssh, Channel *c)
231 {
232 int r;
233
234 debug2("channel %d: send eow", c->self);
235 if (c->ostate == CHAN_OUTPUT_CLOSED) {
236 error("channel %d: must not sent eow on closed output",
237 c->self);
238 return;
239 }
240 if (!(ssh->compat & SSH_NEW_OPENSSH))
241 return;
242 if (!c->have_remote_id)
243 fatal_f("channel %d: no remote_id", c->self);
244 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_REQUEST)) != 0 ||
245 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
246 (r = sshpkt_put_cstring(ssh, "eow@openssh.com")) != 0 ||
247 (r = sshpkt_put_u8(ssh, 0)) != 0 ||
248 (r = sshpkt_send(ssh)) != 0)
249 fatal_fr(r, "send CHANNEL_EOF");
250 }
251
252 /* shared */
253
254 void
chan_rcvd_ieof(struct ssh * ssh,Channel * c)255 chan_rcvd_ieof(struct ssh *ssh, Channel *c)
256 {
257 debug2("channel %d: rcvd eof", c->self);
258 c->flags |= CHAN_EOF_RCVD;
259 if (c->ostate == CHAN_OUTPUT_OPEN)
260 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
261 if (c->ostate == CHAN_OUTPUT_WAIT_DRAIN &&
262 sshbuf_len(c->output) == 0 &&
263 !CHANNEL_EFD_OUTPUT_ACTIVE(c))
264 chan_obuf_empty(ssh, c);
265 }
266
267 void
chan_rcvd_oclose(struct ssh * ssh,Channel * c)268 chan_rcvd_oclose(struct ssh *ssh, Channel *c)
269 {
270 debug2("channel %d: rcvd close", c->self);
271 if (!(c->flags & CHAN_LOCAL)) {
272 if (c->flags & CHAN_CLOSE_RCVD)
273 error("channel %d: protocol error: close rcvd twice",
274 c->self);
275 c->flags |= CHAN_CLOSE_RCVD;
276 }
277 if (c->type == SSH_CHANNEL_LARVAL) {
278 /* tear down larval channels immediately */
279 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
280 chan_set_istate(c, CHAN_INPUT_CLOSED);
281 return;
282 }
283 switch (c->ostate) {
284 case CHAN_OUTPUT_OPEN:
285 /*
286 * wait until a data from the channel is consumed if a CLOSE
287 * is received
288 */
289 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
290 break;
291 }
292 switch (c->istate) {
293 case CHAN_INPUT_OPEN:
294 chan_shutdown_read(ssh, c);
295 chan_shutdown_extended_read(ssh, c);
296 chan_set_istate(c, CHAN_INPUT_CLOSED);
297 break;
298 case CHAN_INPUT_WAIT_DRAIN:
299 if (!(c->flags & CHAN_LOCAL))
300 chan_send_eof2(ssh, c);
301 chan_shutdown_extended_read(ssh, c);
302 chan_set_istate(c, CHAN_INPUT_CLOSED);
303 break;
304 }
305 }
306
307 void
chan_write_failed(struct ssh * ssh,Channel * c)308 chan_write_failed(struct ssh *ssh, Channel *c)
309 {
310 debug2("channel %d: write failed", c->self);
311 switch (c->ostate) {
312 case CHAN_OUTPUT_OPEN:
313 case CHAN_OUTPUT_WAIT_DRAIN:
314 chan_shutdown_write(ssh, c);
315 if (strcmp(c->ctype, "session") == 0)
316 chan_send_eow2(ssh, c);
317 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
318 break;
319 default:
320 error("channel %d: chan_write_failed for ostate %d",
321 c->self, c->ostate);
322 break;
323 }
324 }
325
326 void
chan_mark_dead(struct ssh * ssh,Channel * c)327 chan_mark_dead(struct ssh *ssh, Channel *c)
328 {
329 c->type = SSH_CHANNEL_ZOMBIE;
330 }
331
332 int
chan_is_dead(struct ssh * ssh,Channel * c,int do_send)333 chan_is_dead(struct ssh *ssh, Channel *c, int do_send)
334 {
335 if (c->type == SSH_CHANNEL_ZOMBIE) {
336 debug2("channel %d: zombie", c->self);
337 return 1;
338 }
339 if (c->istate != CHAN_INPUT_CLOSED || c->ostate != CHAN_OUTPUT_CLOSED)
340 return 0;
341 if ((ssh->compat & SSH_BUG_EXTEOF) &&
342 c->extended_usage == CHAN_EXTENDED_WRITE &&
343 c->efd != -1 &&
344 sshbuf_len(c->extended) > 0) {
345 debug2("channel %d: active efd: %d len %zu",
346 c->self, c->efd, sshbuf_len(c->extended));
347 return 0;
348 }
349 if (c->flags & CHAN_LOCAL) {
350 debug2("channel %d: is dead (local)", c->self);
351 return 1;
352 }
353 if (!(c->flags & CHAN_CLOSE_SENT)) {
354 if (do_send) {
355 chan_send_close2(ssh, c);
356 } else {
357 /* channel would be dead if we sent a close */
358 if (c->flags & CHAN_CLOSE_RCVD) {
359 debug2("channel %d: almost dead",
360 c->self);
361 return 1;
362 }
363 }
364 }
365 if ((c->flags & CHAN_CLOSE_SENT) &&
366 (c->flags & CHAN_CLOSE_RCVD)) {
367 debug2("channel %d: is dead", c->self);
368 return 1;
369 }
370 return 0;
371 }
372
373 /* helper */
374 static void
chan_shutdown_write(struct ssh * ssh,Channel * c)375 chan_shutdown_write(struct ssh *ssh, Channel *c)
376 {
377 sshbuf_reset(c->output);
378 if (c->type == SSH_CHANNEL_LARVAL)
379 return;
380 /* shutdown failure is allowed if write failed already */
381 debug2_f("channel %d: (i%d o%d sock %d wfd %d efd %d [%s])",
382 c->self, c->istate, c->ostate, c->sock, c->wfd, c->efd,
383 channel_format_extended_usage(c));
384 if (c->sock != -1) {
385 if (shutdown(c->sock, SHUT_WR) == -1) {
386 debug2_f("channel %d: shutdown() failed for "
387 "fd %d [i%d o%d]: %.100s", c->self, c->sock,
388 c->istate, c->ostate, strerror(errno));
389 }
390 } else {
391 if (channel_close_fd(ssh, c, &c->wfd) < 0) {
392 logit_f("channel %d: close() failed for "
393 "fd %d [i%d o%d]: %.100s", c->self, c->wfd,
394 c->istate, c->ostate, strerror(errno));
395 }
396 }
397 }
398
399 static void
chan_shutdown_read(struct ssh * ssh,Channel * c)400 chan_shutdown_read(struct ssh *ssh, Channel *c)
401 {
402 if (c->type == SSH_CHANNEL_LARVAL)
403 return;
404 debug2_f("channel %d: (i%d o%d sock %d wfd %d efd %d [%s])",
405 c->self, c->istate, c->ostate, c->sock, c->rfd, c->efd,
406 channel_format_extended_usage(c));
407 if (c->sock != -1) {
408 /*
409 * shutdown(sock, SHUT_READ) may return ENOTCONN if the
410 * write side has been closed already. (bug on Linux)
411 * HP-UX may return ENOTCONN also.
412 */
413 if (shutdown(c->sock, SHUT_RD) == -1 && errno != ENOTCONN) {
414 error_f("channel %d: shutdown() failed for "
415 "fd %d [i%d o%d]: %.100s", c->self, c->sock,
416 c->istate, c->ostate, strerror(errno));
417 }
418 } else {
419 if (channel_close_fd(ssh, c, &c->rfd) < 0) {
420 logit_f("channel %d: close() failed for "
421 "fd %d [i%d o%d]: %.100s", c->self, c->rfd,
422 c->istate, c->ostate, strerror(errno));
423 }
424 }
425 }
426
427 static void
chan_shutdown_extended_read(struct ssh * ssh,Channel * c)428 chan_shutdown_extended_read(struct ssh *ssh, Channel *c)
429 {
430 if (c->type == SSH_CHANNEL_LARVAL || c->efd == -1)
431 return;
432 if (c->extended_usage != CHAN_EXTENDED_READ &&
433 c->extended_usage != CHAN_EXTENDED_IGNORE)
434 return;
435 debug_f("channel %d: (i%d o%d sock %d wfd %d efd %d [%s])",
436 c->self, c->istate, c->ostate, c->sock, c->rfd, c->efd,
437 channel_format_extended_usage(c));
438 if (channel_close_fd(ssh, c, &c->efd) < 0) {
439 logit_f("channel %d: close() failed for "
440 "extended fd %d [i%d o%d]: %.100s", c->self, c->efd,
441 c->istate, c->ostate, strerror(errno));
442 }
443 }
444