xref: /freebsd/crypto/openssh/nchan.c (revision 5ca8e32633c4ffbbcd6762e5888b6a4ba0708c6c) 
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
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
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
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
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
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
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
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
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
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
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
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
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
327 chan_mark_dead(struct ssh *ssh, Channel *c)
328 {
329 	c->type = SSH_CHANNEL_ZOMBIE;
330 }
331 
332 int
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
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
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
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