xref: /openssh-portable/nchan.c (revision 4d28fa78)
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