1 /* $OpenBSD: nchan.c,v 1.70 2019/06/28 13:35:04 deraadt 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 *ostates[] = { "open", "drain", "wait_ieof", "closed" };
86 static const char *istates[] = { "open", "drain", "wait_oclose", "closed" };
87
88 static void
chan_set_istate(Channel * c,u_int next)89 chan_set_istate(Channel *c, u_int next)
90 {
91 if (c->istate > CHAN_INPUT_CLOSED || next > CHAN_INPUT_CLOSED)
92 fatal("chan_set_istate: bad state %d -> %d", c->istate, next);
93 debug2("channel %d: input %s -> %s", c->self, istates[c->istate],
94 istates[next]);
95 c->istate = next;
96 }
97
98 static void
chan_set_ostate(Channel * c,u_int next)99 chan_set_ostate(Channel *c, u_int next)
100 {
101 if (c->ostate > CHAN_OUTPUT_CLOSED || next > CHAN_OUTPUT_CLOSED)
102 fatal("chan_set_ostate: bad state %d -> %d", c->ostate, next);
103 debug2("channel %d: output %s -> %s", c->self, ostates[c->ostate],
104 ostates[next]);
105 c->ostate = next;
106 }
107
108 void
chan_read_failed(struct ssh * ssh,Channel * c)109 chan_read_failed(struct ssh *ssh, Channel *c)
110 {
111 debug2("channel %d: read failed", c->self);
112 switch (c->istate) {
113 case CHAN_INPUT_OPEN:
114 chan_shutdown_read(ssh, c);
115 chan_set_istate(c, CHAN_INPUT_WAIT_DRAIN);
116 break;
117 default:
118 error("channel %d: chan_read_failed for istate %d",
119 c->self, c->istate);
120 break;
121 }
122 }
123
124 void
chan_ibuf_empty(struct ssh * ssh,Channel * c)125 chan_ibuf_empty(struct ssh *ssh, Channel *c)
126 {
127 debug2("channel %d: ibuf empty", c->self);
128 if (sshbuf_len(c->input)) {
129 error("channel %d: chan_ibuf_empty for non empty buffer",
130 c->self);
131 return;
132 }
133 switch (c->istate) {
134 case CHAN_INPUT_WAIT_DRAIN:
135 if (!(c->flags & (CHAN_CLOSE_SENT|CHAN_LOCAL)))
136 chan_send_eof2(ssh, c);
137 chan_set_istate(c, CHAN_INPUT_CLOSED);
138 break;
139 default:
140 error("channel %d: chan_ibuf_empty for istate %d",
141 c->self, c->istate);
142 break;
143 }
144 }
145
146 void
chan_obuf_empty(struct ssh * ssh,Channel * c)147 chan_obuf_empty(struct ssh *ssh, Channel *c)
148 {
149 debug2("channel %d: obuf empty", c->self);
150 if (sshbuf_len(c->output)) {
151 error("channel %d: chan_obuf_empty for non empty buffer",
152 c->self);
153 return;
154 }
155 switch (c->ostate) {
156 case CHAN_OUTPUT_WAIT_DRAIN:
157 chan_shutdown_write(ssh, c);
158 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
159 break;
160 default:
161 error("channel %d: internal error: obuf_empty for ostate %d",
162 c->self, c->ostate);
163 break;
164 }
165 }
166
167 void
chan_rcvd_eow(struct ssh * ssh,Channel * c)168 chan_rcvd_eow(struct ssh *ssh, Channel *c)
169 {
170 debug2("channel %d: rcvd eow", c->self);
171 switch (c->istate) {
172 case CHAN_INPUT_OPEN:
173 chan_shutdown_read(ssh, c);
174 chan_set_istate(c, CHAN_INPUT_CLOSED);
175 break;
176 }
177 }
178
179 static void
chan_send_eof2(struct ssh * ssh,Channel * c)180 chan_send_eof2(struct ssh *ssh, Channel *c)
181 {
182 int r;
183
184 debug2("channel %d: send eof", c->self);
185 switch (c->istate) {
186 case CHAN_INPUT_WAIT_DRAIN:
187 if (!c->have_remote_id)
188 fatal("%s: channel %d: no remote_id",
189 __func__, c->self);
190 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_EOF)) != 0 ||
191 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
192 (r = sshpkt_send(ssh)) != 0)
193 fatal("%s: send CHANNEL_EOF: %s", __func__, ssh_err(r));
194 c->flags |= CHAN_EOF_SENT;
195 break;
196 default:
197 error("channel %d: cannot send eof for istate %d",
198 c->self, c->istate);
199 break;
200 }
201 }
202
203 static void
chan_send_close2(struct ssh * ssh,Channel * c)204 chan_send_close2(struct ssh *ssh, Channel *c)
205 {
206 int r;
207
208 debug2("channel %d: send close", c->self);
209 if (c->ostate != CHAN_OUTPUT_CLOSED ||
210 c->istate != CHAN_INPUT_CLOSED) {
211 error("channel %d: cannot send close for istate/ostate %d/%d",
212 c->self, c->istate, c->ostate);
213 } else if (c->flags & CHAN_CLOSE_SENT) {
214 error("channel %d: already sent close", c->self);
215 } else {
216 if (!c->have_remote_id)
217 fatal("%s: channel %d: no remote_id",
218 __func__, c->self);
219 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_CLOSE)) != 0 ||
220 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
221 (r = sshpkt_send(ssh)) != 0)
222 fatal("%s: send CHANNEL_EOF: %s", __func__, ssh_err(r));
223 c->flags |= CHAN_CLOSE_SENT;
224 }
225 }
226
227 static void
chan_send_eow2(struct ssh * ssh,Channel * c)228 chan_send_eow2(struct ssh *ssh, Channel *c)
229 {
230 int r;
231
232 debug2("channel %d: send eow", c->self);
233 if (c->ostate == CHAN_OUTPUT_CLOSED) {
234 error("channel %d: must not sent eow on closed output",
235 c->self);
236 return;
237 }
238 if (!(datafellows & SSH_NEW_OPENSSH))
239 return;
240 if (!c->have_remote_id)
241 fatal("%s: channel %d: no remote_id", __func__, c->self);
242 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_REQUEST)) != 0 ||
243 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
244 (r = sshpkt_put_cstring(ssh, "eow@openssh.com")) != 0 ||
245 (r = sshpkt_put_u8(ssh, 0)) != 0 ||
246 (r = sshpkt_send(ssh)) != 0)
247 fatal("%s: send CHANNEL_EOF: %s", __func__, ssh_err(r));
248 }
249
250 /* shared */
251
252 void
chan_rcvd_ieof(struct ssh * ssh,Channel * c)253 chan_rcvd_ieof(struct ssh *ssh, Channel *c)
254 {
255 debug2("channel %d: rcvd eof", c->self);
256 c->flags |= CHAN_EOF_RCVD;
257 if (c->ostate == CHAN_OUTPUT_OPEN)
258 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
259 if (c->ostate == CHAN_OUTPUT_WAIT_DRAIN &&
260 sshbuf_len(c->output) == 0 &&
261 !CHANNEL_EFD_OUTPUT_ACTIVE(c))
262 chan_obuf_empty(ssh, c);
263 }
264
265 void
chan_rcvd_oclose(struct ssh * ssh,Channel * c)266 chan_rcvd_oclose(struct ssh *ssh, Channel *c)
267 {
268 debug2("channel %d: rcvd close", c->self);
269 if (!(c->flags & CHAN_LOCAL)) {
270 if (c->flags & CHAN_CLOSE_RCVD)
271 error("channel %d: protocol error: close rcvd twice",
272 c->self);
273 c->flags |= CHAN_CLOSE_RCVD;
274 }
275 if (c->type == SSH_CHANNEL_LARVAL) {
276 /* tear down larval channels immediately */
277 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
278 chan_set_istate(c, CHAN_INPUT_CLOSED);
279 return;
280 }
281 switch (c->ostate) {
282 case CHAN_OUTPUT_OPEN:
283 /*
284 * wait until a data from the channel is consumed if a CLOSE
285 * is received
286 */
287 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
288 break;
289 }
290 switch (c->istate) {
291 case CHAN_INPUT_OPEN:
292 chan_shutdown_read(ssh, c);
293 chan_shutdown_extended_read(ssh, c);
294 chan_set_istate(c, CHAN_INPUT_CLOSED);
295 break;
296 case CHAN_INPUT_WAIT_DRAIN:
297 if (!(c->flags & CHAN_LOCAL))
298 chan_send_eof2(ssh, c);
299 chan_shutdown_extended_read(ssh, c);
300 chan_set_istate(c, CHAN_INPUT_CLOSED);
301 break;
302 }
303 }
304
305 void
chan_write_failed(struct ssh * ssh,Channel * c)306 chan_write_failed(struct ssh *ssh, Channel *c)
307 {
308 debug2("channel %d: write failed", c->self);
309 switch (c->ostate) {
310 case CHAN_OUTPUT_OPEN:
311 case CHAN_OUTPUT_WAIT_DRAIN:
312 chan_shutdown_write(ssh, c);
313 if (strcmp(c->ctype, "session") == 0)
314 chan_send_eow2(ssh, c);
315 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
316 break;
317 default:
318 error("channel %d: chan_write_failed for ostate %d",
319 c->self, c->ostate);
320 break;
321 }
322 }
323
324 void
chan_mark_dead(struct ssh * ssh,Channel * c)325 chan_mark_dead(struct ssh *ssh, Channel *c)
326 {
327 c->type = SSH_CHANNEL_ZOMBIE;
328 }
329
330 int
chan_is_dead(struct ssh * ssh,Channel * c,int do_send)331 chan_is_dead(struct ssh *ssh, Channel *c, int do_send)
332 {
333 if (c->type == SSH_CHANNEL_ZOMBIE) {
334 debug2("channel %d: zombie", c->self);
335 return 1;
336 }
337 if (c->istate != CHAN_INPUT_CLOSED || c->ostate != CHAN_OUTPUT_CLOSED)
338 return 0;
339 if ((datafellows & SSH_BUG_EXTEOF) &&
340 c->extended_usage == CHAN_EXTENDED_WRITE &&
341 c->efd != -1 &&
342 sshbuf_len(c->extended) > 0) {
343 debug2("channel %d: active efd: %d len %zu",
344 c->self, c->efd, sshbuf_len(c->extended));
345 return 0;
346 }
347 if (c->flags & CHAN_LOCAL) {
348 debug2("channel %d: is dead (local)", c->self);
349 return 1;
350 }
351 if (!(c->flags & CHAN_CLOSE_SENT)) {
352 if (do_send) {
353 chan_send_close2(ssh, c);
354 } else {
355 /* channel would be dead if we sent a close */
356 if (c->flags & CHAN_CLOSE_RCVD) {
357 debug2("channel %d: almost dead",
358 c->self);
359 return 1;
360 }
361 }
362 }
363 if ((c->flags & CHAN_CLOSE_SENT) &&
364 (c->flags & CHAN_CLOSE_RCVD)) {
365 debug2("channel %d: is dead", c->self);
366 return 1;
367 }
368 return 0;
369 }
370
371 /* helper */
372 static void
chan_shutdown_write(struct ssh * ssh,Channel * c)373 chan_shutdown_write(struct ssh *ssh, Channel *c)
374 {
375 sshbuf_reset(c->output);
376 if (c->type == SSH_CHANNEL_LARVAL)
377 return;
378 /* shutdown failure is allowed if write failed already */
379 debug2("channel %d: %s (i%d o%d sock %d wfd %d efd %d [%s])",
380 c->self, __func__, c->istate, c->ostate, c->sock, c->wfd, c->efd,
381 channel_format_extended_usage(c));
382 if (c->sock != -1) {
383 if (shutdown(c->sock, SHUT_WR) == -1) {
384 debug2("channel %d: %s: shutdown() failed for "
385 "fd %d [i%d o%d]: %.100s", c->self, __func__,
386 c->sock, c->istate, c->ostate,
387 strerror(errno));
388 }
389 } else {
390 if (channel_close_fd(ssh, &c->wfd) < 0) {
391 logit("channel %d: %s: close() failed for "
392 "fd %d [i%d o%d]: %.100s",
393 c->self, __func__, c->wfd, c->istate, c->ostate,
394 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("channel %d: %s (i%d o%d sock %d wfd %d efd %d [%s])",
405 c->self, __func__, 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("channel %d: %s: shutdown() failed for "
415 "fd %d [i%d o%d]: %.100s",
416 c->self, __func__, c->sock, c->istate, c->ostate,
417 strerror(errno));
418 }
419 } else {
420 if (channel_close_fd(ssh, &c->rfd) < 0) {
421 logit("channel %d: %s: close() failed for "
422 "fd %d [i%d o%d]: %.100s",
423 c->self, __func__, c->rfd, c->istate, c->ostate,
424 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 debug2("channel %d: %s (i%d o%d sock %d wfd %d efd %d [%s])",
438 c->self, __func__, c->istate, c->ostate, c->sock, c->rfd, c->efd,
439 channel_format_extended_usage(c));
440 if (channel_close_fd(ssh, &c->efd) < 0) {
441 logit("channel %d: %s: close() failed for "
442 "extended fd %d [i%d o%d]: %.100s",
443 c->self, __func__, c->efd, c->istate, c->ostate,
444 strerror(errno));
445 }
446 }
447