nchan.c revision 1.41 
1/*
2 * Copyright (c) 1999, 2000, 2001 Markus Friedl.  All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23 */
24
25#include "includes.h"
26RCSID("$OpenBSD: nchan.c,v 1.41 2002/01/14 13:41:13 markus Exp $");
27
28#include "ssh1.h"
29#include "ssh2.h"
30#include "buffer.h"
31#include "packet.h"
32#include "channels.h"
33#include "compat.h"
34#include "log.h"
35
36/*
37 * SSH Protocol 1.5 aka New Channel Protocol
38 * Thanks to Martina, Axel and everyone who left Erlangen, leaving me bored.
39 * Written by Markus Friedl in October 1999
40 *
41 * Protocol versions 1.3 and 1.5 differ in the handshake protocol used for the
42 * tear down of channels:
43 *
44 * 1.3:	strict request-ack-protocol:
45 * 	CLOSE	->
46 * 		<-  CLOSE_CONFIRM
47 *
48 * 1.5:	uses variations of:
49 * 	IEOF	->
50 * 		<-  OCLOSE
51 * 		<-  IEOF
52 * 	OCLOSE	->
53 * 	i.e. both sides have to close the channel
54 *
55 * 2.0: the EOF messages are optional
56 *
57 * See the debugging output from 'ssh -v' and 'sshd -d' of
58 * ssh-1.2.27 as an example.
59 *
60 */
61
62/* functions manipulating channel states */
63/*
64 * EVENTS update channel input/output states execute ACTIONS
65 */
66/* events concerning the INPUT from socket for channel (istate) */
67chan_event_fn *chan_rcvd_oclose			= NULL;
68chan_event_fn *chan_read_failed			= NULL;
69chan_event_fn *chan_ibuf_empty			= NULL;
70/* events concerning the OUTPUT from channel for socket (ostate) */
71chan_event_fn *chan_rcvd_ieof			= NULL;
72chan_event_fn *chan_write_failed		= NULL;
73chan_event_fn *chan_obuf_empty			= NULL;
74/*
75 * ACTIONS: should never update the channel states
76 */
77static void	chan_send_ieof1(Channel *);
78static void	chan_send_oclose1(Channel *);
79static void	chan_send_close2(Channel *);
80static void	chan_send_eof2(Channel *);
81
82/* helper */
83static void	chan_shutdown_write(Channel *);
84static void	chan_shutdown_read(Channel *);
85
86static char *ostates[] = { "open", "drain", "wait_ieof", "closed" };
87static char *istates[] = { "open", "drain", "wait_oclose", "closed" };
88
89static void
90chan_set_istate(Channel *c, u_int next)
91{
92	if (c->istate > CHAN_INPUT_CLOSED || next > CHAN_INPUT_CLOSED)
93		fatal("chan_set_istate: bad state %d -> %d", c->istate, next);
94	debug("channel %d: input %s -> %s", c->self, istates[c->istate],
95	    istates[next]);
96	c->istate = next;
97}
98static void
99chan_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	debug("channel %d: output %s -> %s", c->self, ostates[c->ostate],
104	    ostates[next]);
105	c->ostate = next;
106}
107
108/*
109 * SSH1 specific implementation of event functions
110 */
111
112static void
113chan_rcvd_oclose1(Channel *c)
114{
115	debug("channel %d: rcvd oclose", c->self);
116	switch (c->istate) {
117	case CHAN_INPUT_WAIT_OCLOSE:
118		chan_set_istate(c, CHAN_INPUT_CLOSED);
119		break;
120	case CHAN_INPUT_OPEN:
121		chan_shutdown_read(c);
122		chan_send_ieof1(c);
123		chan_set_istate(c, CHAN_INPUT_CLOSED);
124		break;
125	case CHAN_INPUT_WAIT_DRAIN:
126		/* both local read_failed and remote write_failed  */
127		chan_send_ieof1(c);
128		chan_set_istate(c, CHAN_INPUT_CLOSED);
129		break;
130	default:
131		error("channel %d: protocol error: rcvd_oclose for istate %d",
132		    c->self, c->istate);
133		return;
134	}
135}
136static void
137chan_read_failed_12(Channel *c)
138{
139	debug("channel %d: read failed", c->self);
140	switch (c->istate) {
141	case CHAN_INPUT_OPEN:
142		chan_shutdown_read(c);
143		chan_set_istate(c, CHAN_INPUT_WAIT_DRAIN);
144		break;
145	default:
146		error("channel %d: chan_read_failed for istate %d",
147		    c->self, c->istate);
148		break;
149	}
150}
151static void
152chan_ibuf_empty1(Channel *c)
153{
154	debug("channel %d: ibuf empty", c->self);
155	if (buffer_len(&c->input)) {
156		error("channel %d: chan_ibuf_empty for non empty buffer",
157		    c->self);
158		return;
159	}
160	switch (c->istate) {
161	case CHAN_INPUT_WAIT_DRAIN:
162		if (compat20) {
163			if (!(c->flags & CHAN_CLOSE_SENT))
164				chan_send_eof2(c);
165			chan_set_istate(c, CHAN_INPUT_CLOSED);
166		} else {
167			chan_send_ieof1(c);
168			chan_set_istate(c, CHAN_INPUT_WAIT_OCLOSE);
169		}
170		break;
171	default:
172		error("channel %d: chan_ibuf_empty for istate %d",
173		    c->self, c->istate);
174		break;
175	}
176}
177static void
178chan_rcvd_ieof1(Channel *c)
179{
180	debug("channel %d: rcvd ieof", c->self);
181	switch (c->ostate) {
182	case CHAN_OUTPUT_OPEN:
183		chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
184		break;
185	case CHAN_OUTPUT_WAIT_IEOF:
186		chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
187		break;
188	default:
189		error("channel %d: protocol error: rcvd_ieof for ostate %d",
190		    c->self, c->ostate);
191		break;
192	}
193}
194static void
195chan_write_failed1(Channel *c)
196{
197	debug("channel %d: write failed", c->self);
198	switch (c->ostate) {
199	case CHAN_OUTPUT_OPEN:
200		chan_shutdown_write(c);
201		chan_send_oclose1(c);
202		chan_set_ostate(c, CHAN_OUTPUT_WAIT_IEOF);
203		break;
204	case CHAN_OUTPUT_WAIT_DRAIN:
205		chan_shutdown_write(c);
206		chan_send_oclose1(c);
207		chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
208		break;
209	default:
210		error("channel %d: chan_write_failed for ostate %d",
211		    c->self, c->ostate);
212		break;
213	}
214}
215static void
216chan_obuf_empty1(Channel *c)
217{
218	debug("channel %d: obuf empty", c->self);
219	if (buffer_len(&c->output)) {
220		error("channel %d: chan_obuf_empty for non empty buffer",
221		    c->self);
222		return;
223	}
224	switch (c->ostate) {
225	case CHAN_OUTPUT_WAIT_DRAIN:
226		chan_shutdown_write(c);
227		if (!compat20)
228			chan_send_oclose1(c);
229		chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
230		break;
231	default:
232		error("channel %d: internal error: obuf_empty for ostate %d",
233		    c->self, c->ostate);
234		break;
235	}
236}
237static void
238chan_send_ieof1(Channel *c)
239{
240	debug("channel %d: send ieof", c->self);
241	switch (c->istate) {
242	case CHAN_INPUT_OPEN:
243	case CHAN_INPUT_WAIT_DRAIN:
244		packet_start(SSH_MSG_CHANNEL_INPUT_EOF);
245		packet_put_int(c->remote_id);
246		packet_send();
247		break;
248	default:
249		error("channel %d: cannot send ieof for istate %d",
250		    c->self, c->istate);
251		break;
252	}
253}
254static void
255chan_send_oclose1(Channel *c)
256{
257	debug("channel %d: send oclose", c->self);
258	switch (c->ostate) {
259	case CHAN_OUTPUT_OPEN:
260	case CHAN_OUTPUT_WAIT_DRAIN:
261		buffer_clear(&c->output);
262		packet_start(SSH_MSG_CHANNEL_OUTPUT_CLOSE);
263		packet_put_int(c->remote_id);
264		packet_send();
265		break;
266	default:
267		error("channel %d: cannot send oclose for ostate %d",
268		    c->self, c->ostate);
269		break;
270	}
271}
272
273/*
274 * the same for SSH2
275 */
276static void
277chan_rcvd_close2(Channel *c)
278{
279	debug("channel %d: rcvd close", c->self);
280	if (c->flags & CHAN_CLOSE_RCVD)
281		error("channel %d: protocol error: close rcvd twice", c->self);
282	c->flags |= CHAN_CLOSE_RCVD;
283	if (c->type == SSH_CHANNEL_LARVAL) {
284		/* tear down larval channels immediately */
285		chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
286		chan_set_istate(c, CHAN_INPUT_CLOSED);
287		return;
288	}
289	switch (c->ostate) {
290	case CHAN_OUTPUT_OPEN:
291		/*
292		 * wait until a data from the channel is consumed if a CLOSE
293		 * is received
294		 */
295		chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
296		break;
297	}
298	switch (c->istate) {
299	case CHAN_INPUT_OPEN:
300		chan_shutdown_read(c);
301		chan_set_istate(c, CHAN_INPUT_CLOSED);
302		break;
303	case CHAN_INPUT_WAIT_DRAIN:
304		chan_send_eof2(c);
305		chan_set_istate(c, CHAN_INPUT_CLOSED);
306		break;
307	}
308}
309static void
310chan_ibuf_empty2(Channel *c)
311{
312	chan_ibuf_empty1(c);
313}
314static void
315chan_rcvd_eof2(Channel *c)
316{
317	debug("channel %d: rcvd eof", c->self);
318	if (c->ostate == CHAN_OUTPUT_OPEN)
319		chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
320}
321static void
322chan_write_failed2(Channel *c)
323{
324	debug("channel %d: write failed", c->self);
325	switch (c->ostate) {
326	case CHAN_OUTPUT_OPEN:
327	case CHAN_OUTPUT_WAIT_DRAIN:
328		chan_shutdown_write(c);
329		chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
330		break;
331	default:
332		error("channel %d: chan_write_failed for ostate %d",
333		    c->self, c->ostate);
334		break;
335	}
336}
337static void
338chan_obuf_empty2(Channel *c)
339{
340	chan_obuf_empty1(c);
341}
342static void
343chan_send_eof2(Channel *c)
344{
345	debug("channel %d: send eof", c->self);
346	switch (c->istate) {
347	case CHAN_INPUT_WAIT_DRAIN:
348		packet_start(SSH2_MSG_CHANNEL_EOF);
349		packet_put_int(c->remote_id);
350		packet_send();
351		break;
352	default:
353		error("channel %d: cannot send eof for istate %d",
354		    c->self, c->istate);
355		break;
356	}
357}
358static void
359chan_send_close2(Channel *c)
360{
361	debug("channel %d: send close", c->self);
362	if (c->ostate != CHAN_OUTPUT_CLOSED ||
363	    c->istate != CHAN_INPUT_CLOSED) {
364		error("channel %d: cannot send close for istate/ostate %d/%d",
365		    c->self, c->istate, c->ostate);
366	} else if (c->flags & CHAN_CLOSE_SENT) {
367		error("channel %d: already sent close", c->self);
368	} else {
369		packet_start(SSH2_MSG_CHANNEL_CLOSE);
370		packet_put_int(c->remote_id);
371		packet_send();
372		c->flags |= CHAN_CLOSE_SENT;
373	}
374}
375
376/* shared */
377
378void
379chan_mark_dead(Channel *c)
380{
381	c->type = SSH_CHANNEL_ZOMBIE;
382}
383
384int
385chan_is_dead(Channel *c, int send)
386{
387	if (c->type == SSH_CHANNEL_ZOMBIE) {
388		debug("channel %d: zombie", c->self);
389		return 1;
390	}
391	if (c->istate != CHAN_INPUT_CLOSED || c->ostate != CHAN_OUTPUT_CLOSED)
392		return 0;
393	if (!compat20) {
394		debug("channel %d: is dead", c->self);
395		return 1;
396	}
397	/*
398	 * we have to delay the close message if the efd (for stderr) is
399	 * still active
400	 */
401	if (((c->extended_usage != CHAN_EXTENDED_IGNORE) &&
402	    buffer_len(&c->extended) > 0)
403#if 0
404	    || ((c->extended_usage == CHAN_EXTENDED_READ) &&
405	    c->efd != -1)
406#endif
407	    ) {
408		debug2("channel %d: active efd: %d len %d type %s",
409		    c->self, c->efd, buffer_len(&c->extended),
410		    c->extended_usage==CHAN_EXTENDED_READ ?
411		    "read": "write");
412	} else {
413		if (!(c->flags & CHAN_CLOSE_SENT)) {
414			if (send) {
415				chan_send_close2(c);
416			} else {
417				/* channel would be dead if we sent a close */
418				if (c->flags & CHAN_CLOSE_RCVD) {
419					debug("channel %d: almost dead",
420					    c->self);
421					return 1;
422				}
423			}
424		}
425		if ((c->flags & CHAN_CLOSE_SENT) &&
426		    (c->flags & CHAN_CLOSE_RCVD)) {
427			debug("channel %d: is dead", c->self);
428			return 1;
429		}
430	}
431	return 0;
432}
433
434void
435chan_init_iostates(Channel *c)
436{
437	c->ostate = CHAN_OUTPUT_OPEN;
438	c->istate = CHAN_INPUT_OPEN;
439	c->flags = 0;
440}
441
442/* init */
443void
444chan_init(void)
445{
446	if (compat20) {
447		chan_rcvd_oclose		= chan_rcvd_close2;
448		chan_read_failed		= chan_read_failed_12;
449		chan_ibuf_empty			= chan_ibuf_empty2;
450
451		chan_rcvd_ieof			= chan_rcvd_eof2;
452		chan_write_failed		= chan_write_failed2;
453		chan_obuf_empty			= chan_obuf_empty2;
454	} else {
455		chan_rcvd_oclose		= chan_rcvd_oclose1;
456		chan_read_failed		= chan_read_failed_12;
457		chan_ibuf_empty			= chan_ibuf_empty1;
458
459		chan_rcvd_ieof			= chan_rcvd_ieof1;
460		chan_write_failed		= chan_write_failed1;
461		chan_obuf_empty			= chan_obuf_empty1;
462	}
463}
464
465/* helper */
466static void
467chan_shutdown_write(Channel *c)
468{
469	buffer_clear(&c->output);
470	if (compat20 && c->type == SSH_CHANNEL_LARVAL)
471		return;
472	/* shutdown failure is allowed if write failed already */
473	debug("channel %d: close_write", c->self);
474	if (c->sock != -1) {
475		if (shutdown(c->sock, SHUT_WR) < 0)
476			debug("channel %d: chan_shutdown_write: "
477			    "shutdown() failed for fd%d: %.100s",
478			    c->self, c->sock, strerror(errno));
479	} else {
480		if (channel_close_fd(&c->wfd) < 0)
481			log("channel %d: chan_shutdown_write: "
482			    "close() failed for fd%d: %.100s",
483			    c->self, c->wfd, strerror(errno));
484	}
485}
486static void
487chan_shutdown_read(Channel *c)
488{
489	if (compat20 && c->type == SSH_CHANNEL_LARVAL)
490		return;
491	debug("channel %d: close_read", c->self);
492	if (c->sock != -1) {
493		if (shutdown(c->sock, SHUT_RD) < 0)
494			error("channel %d: chan_shutdown_read: "
495			    "shutdown() failed for fd%d [i%d o%d]: %.100s",
496			    c->self, c->sock, c->istate, c->ostate,
497			    strerror(errno));
498	} else {
499		if (channel_close_fd(&c->rfd) < 0)
500			log("channel %d: chan_shutdown_read: "
501			    "close() failed for fd%d: %.100s",
502			    c->self, c->rfd, strerror(errno));
503	}
504}
505