nchan.c revision 92555 
1/*
2 * Copyright (c) 1999, 2000, 2001, 2002 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 1.44 2002/01/21 23:27:10 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/*
67 * ACTIONS: should never update the channel states
68 */
69static void	chan_send_ieof1(Channel *);
70static void	chan_send_oclose1(Channel *);
71static void	chan_send_close2(Channel *);
72static void	chan_send_eof2(Channel *);
73
74/* helper */
75static void	chan_shutdown_write(Channel *);
76static void	chan_shutdown_read(Channel *);
77
78static char *ostates[] = { "open", "drain", "wait_ieof", "closed" };
79static char *istates[] = { "open", "drain", "wait_oclose", "closed" };
80
81static void
82chan_set_istate(Channel *c, u_int next)
83{
84	if (c->istate > CHAN_INPUT_CLOSED || next > CHAN_INPUT_CLOSED)
85		fatal("chan_set_istate: bad state %d -> %d", c->istate, next);
86	debug("channel %d: input %s -> %s", c->self, istates[c->istate],
87	    istates[next]);
88	c->istate = next;
89}
90static void
91chan_set_ostate(Channel *c, u_int next)
92{
93	if (c->ostate > CHAN_OUTPUT_CLOSED || next > CHAN_OUTPUT_CLOSED)
94		fatal("chan_set_ostate: bad state %d -> %d", c->ostate, next);
95	debug("channel %d: output %s -> %s", c->self, ostates[c->ostate],
96	    ostates[next]);
97	c->ostate = next;
98}
99
100/*
101 * SSH1 specific implementation of event functions
102 */
103
104static void
105chan_rcvd_oclose1(Channel *c)
106{
107	debug("channel %d: rcvd oclose", c->self);
108	switch (c->istate) {
109	case CHAN_INPUT_WAIT_OCLOSE:
110		chan_set_istate(c, CHAN_INPUT_CLOSED);
111		break;
112	case CHAN_INPUT_OPEN:
113		chan_shutdown_read(c);
114		chan_send_ieof1(c);
115		chan_set_istate(c, CHAN_INPUT_CLOSED);
116		break;
117	case CHAN_INPUT_WAIT_DRAIN:
118		/* both local read_failed and remote write_failed  */
119		chan_send_ieof1(c);
120		chan_set_istate(c, CHAN_INPUT_CLOSED);
121		break;
122	default:
123		error("channel %d: protocol error: rcvd_oclose for istate %d",
124		    c->self, c->istate);
125		return;
126	}
127}
128void
129chan_read_failed(Channel *c)
130{
131	debug("channel %d: read failed", c->self);
132	switch (c->istate) {
133	case CHAN_INPUT_OPEN:
134		chan_shutdown_read(c);
135		chan_set_istate(c, CHAN_INPUT_WAIT_DRAIN);
136		break;
137	default:
138		error("channel %d: chan_read_failed for istate %d",
139		    c->self, c->istate);
140		break;
141	}
142}
143void
144chan_ibuf_empty(Channel *c)
145{
146	debug("channel %d: ibuf empty", c->self);
147	if (buffer_len(&c->input)) {
148		error("channel %d: chan_ibuf_empty for non empty buffer",
149		    c->self);
150		return;
151	}
152	switch (c->istate) {
153	case CHAN_INPUT_WAIT_DRAIN:
154		if (compat20) {
155			if (!(c->flags & CHAN_CLOSE_SENT))
156				chan_send_eof2(c);
157			chan_set_istate(c, CHAN_INPUT_CLOSED);
158		} else {
159			chan_send_ieof1(c);
160			chan_set_istate(c, CHAN_INPUT_WAIT_OCLOSE);
161		}
162		break;
163	default:
164		error("channel %d: chan_ibuf_empty for istate %d",
165		    c->self, c->istate);
166		break;
167	}
168}
169static void
170chan_rcvd_ieof1(Channel *c)
171{
172	debug("channel %d: rcvd ieof", c->self);
173	switch (c->ostate) {
174	case CHAN_OUTPUT_OPEN:
175		chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
176		break;
177	case CHAN_OUTPUT_WAIT_IEOF:
178		chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
179		break;
180	default:
181		error("channel %d: protocol error: rcvd_ieof for ostate %d",
182		    c->self, c->ostate);
183		break;
184	}
185}
186static void
187chan_write_failed1(Channel *c)
188{
189	debug("channel %d: write failed", c->self);
190	switch (c->ostate) {
191	case CHAN_OUTPUT_OPEN:
192		chan_shutdown_write(c);
193		chan_send_oclose1(c);
194		chan_set_ostate(c, CHAN_OUTPUT_WAIT_IEOF);
195		break;
196	case CHAN_OUTPUT_WAIT_DRAIN:
197		chan_shutdown_write(c);
198		chan_send_oclose1(c);
199		chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
200		break;
201	default:
202		error("channel %d: chan_write_failed for ostate %d",
203		    c->self, c->ostate);
204		break;
205	}
206}
207void
208chan_obuf_empty(Channel *c)
209{
210	debug("channel %d: obuf empty", c->self);
211	if (buffer_len(&c->output)) {
212		error("channel %d: chan_obuf_empty for non empty buffer",
213		    c->self);
214		return;
215	}
216	switch (c->ostate) {
217	case CHAN_OUTPUT_WAIT_DRAIN:
218		chan_shutdown_write(c);
219		if (!compat20)
220			chan_send_oclose1(c);
221		chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
222		break;
223	default:
224		error("channel %d: internal error: obuf_empty for ostate %d",
225		    c->self, c->ostate);
226		break;
227	}
228}
229static void
230chan_send_ieof1(Channel *c)
231{
232	debug("channel %d: send ieof", c->self);
233	switch (c->istate) {
234	case CHAN_INPUT_OPEN:
235	case CHAN_INPUT_WAIT_DRAIN:
236		packet_start(SSH_MSG_CHANNEL_INPUT_EOF);
237		packet_put_int(c->remote_id);
238		packet_send();
239		break;
240	default:
241		error("channel %d: cannot send ieof for istate %d",
242		    c->self, c->istate);
243		break;
244	}
245}
246static void
247chan_send_oclose1(Channel *c)
248{
249	debug("channel %d: send oclose", c->self);
250	switch (c->ostate) {
251	case CHAN_OUTPUT_OPEN:
252	case CHAN_OUTPUT_WAIT_DRAIN:
253		buffer_clear(&c->output);
254		packet_start(SSH_MSG_CHANNEL_OUTPUT_CLOSE);
255		packet_put_int(c->remote_id);
256		packet_send();
257		break;
258	default:
259		error("channel %d: cannot send oclose for ostate %d",
260		    c->self, c->ostate);
261		break;
262	}
263}
264
265/*
266 * the same for SSH2
267 */
268static void
269chan_rcvd_close2(Channel *c)
270{
271	debug("channel %d: rcvd close", c->self);
272	if (c->flags & CHAN_CLOSE_RCVD)
273		error("channel %d: protocol error: close rcvd twice", c->self);
274	c->flags |= CHAN_CLOSE_RCVD;
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(c);
293		chan_set_istate(c, CHAN_INPUT_CLOSED);
294		break;
295	case CHAN_INPUT_WAIT_DRAIN:
296		chan_send_eof2(c);
297		chan_set_istate(c, CHAN_INPUT_CLOSED);
298		break;
299	}
300}
301static void
302chan_rcvd_eof2(Channel *c)
303{
304	debug("channel %d: rcvd eof", c->self);
305	if (c->ostate == CHAN_OUTPUT_OPEN)
306		chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
307}
308static void
309chan_write_failed2(Channel *c)
310{
311	debug("channel %d: write failed", c->self);
312	switch (c->ostate) {
313	case CHAN_OUTPUT_OPEN:
314	case CHAN_OUTPUT_WAIT_DRAIN:
315		chan_shutdown_write(c);
316		chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
317		break;
318	default:
319		error("channel %d: chan_write_failed for ostate %d",
320		    c->self, c->ostate);
321		break;
322	}
323}
324static void
325chan_send_eof2(Channel *c)
326{
327	debug("channel %d: send eof", c->self);
328	switch (c->istate) {
329	case CHAN_INPUT_WAIT_DRAIN:
330		packet_start(SSH2_MSG_CHANNEL_EOF);
331		packet_put_int(c->remote_id);
332		packet_send();
333		break;
334	default:
335		error("channel %d: cannot send eof for istate %d",
336		    c->self, c->istate);
337		break;
338	}
339}
340static void
341chan_send_close2(Channel *c)
342{
343	debug("channel %d: send close", c->self);
344	if (c->ostate != CHAN_OUTPUT_CLOSED ||
345	    c->istate != CHAN_INPUT_CLOSED) {
346		error("channel %d: cannot send close for istate/ostate %d/%d",
347		    c->self, c->istate, c->ostate);
348	} else if (c->flags & CHAN_CLOSE_SENT) {
349		error("channel %d: already sent close", c->self);
350	} else {
351		packet_start(SSH2_MSG_CHANNEL_CLOSE);
352		packet_put_int(c->remote_id);
353		packet_send();
354		c->flags |= CHAN_CLOSE_SENT;
355	}
356}
357
358/* shared */
359
360void
361chan_rcvd_ieof(Channel *c)
362{
363	if (compat20)
364		chan_rcvd_eof2(c);
365	else
366		chan_rcvd_ieof1(c);
367	if (c->ostate == CHAN_OUTPUT_WAIT_DRAIN &&
368	    buffer_len(&c->output) == 0)
369		chan_obuf_empty(c);
370}
371void
372chan_rcvd_oclose(Channel *c)
373{
374	if (compat20)
375		chan_rcvd_close2(c);
376	else
377		chan_rcvd_oclose1(c);
378}
379void
380chan_write_failed(Channel *c)
381{
382	if (compat20)
383		chan_write_failed2(c);
384	else
385		chan_write_failed1(c);
386}
387
388void
389chan_mark_dead(Channel *c)
390{
391	c->type = SSH_CHANNEL_ZOMBIE;
392}
393
394int
395chan_is_dead(Channel *c, int send)
396{
397	if (c->type == SSH_CHANNEL_ZOMBIE) {
398		debug("channel %d: zombie", c->self);
399		return 1;
400	}
401	if (c->istate != CHAN_INPUT_CLOSED || c->ostate != CHAN_OUTPUT_CLOSED)
402		return 0;
403	if (!compat20) {
404		debug("channel %d: is dead", c->self);
405		return 1;
406	}
407	/*
408	 * we have to delay the close message if the efd (for stderr) is
409	 * still active
410	 */
411	if (((c->extended_usage != CHAN_EXTENDED_IGNORE) &&
412	    buffer_len(&c->extended) > 0)
413#if 0
414	    || ((c->extended_usage == CHAN_EXTENDED_READ) &&
415	    c->efd != -1)
416#endif
417	    ) {
418		debug2("channel %d: active efd: %d len %d type %s",
419		    c->self, c->efd, buffer_len(&c->extended),
420		    c->extended_usage==CHAN_EXTENDED_READ ?
421		    "read": "write");
422	} else {
423		if (!(c->flags & CHAN_CLOSE_SENT)) {
424			if (send) {
425				chan_send_close2(c);
426			} else {
427				/* channel would be dead if we sent a close */
428				if (c->flags & CHAN_CLOSE_RCVD) {
429					debug("channel %d: almost dead",
430					    c->self);
431					return 1;
432				}
433			}
434		}
435		if ((c->flags & CHAN_CLOSE_SENT) &&
436		    (c->flags & CHAN_CLOSE_RCVD)) {
437			debug("channel %d: is dead", c->self);
438			return 1;
439		}
440	}
441	return 0;
442}
443
444/* helper */
445static void
446chan_shutdown_write(Channel *c)
447{
448	buffer_clear(&c->output);
449	if (compat20 && c->type == SSH_CHANNEL_LARVAL)
450		return;
451	/* shutdown failure is allowed if write failed already */
452	debug("channel %d: close_write", c->self);
453	if (c->sock != -1) {
454		if (shutdown(c->sock, SHUT_WR) < 0)
455			debug("channel %d: chan_shutdown_write: "
456			    "shutdown() failed for fd%d: %.100s",
457			    c->self, c->sock, strerror(errno));
458	} else {
459		if (channel_close_fd(&c->wfd) < 0)
460			log("channel %d: chan_shutdown_write: "
461			    "close() failed for fd%d: %.100s",
462			    c->self, c->wfd, strerror(errno));
463	}
464}
465static void
466chan_shutdown_read(Channel *c)
467{
468	if (compat20 && c->type == SSH_CHANNEL_LARVAL)
469		return;
470	debug("channel %d: close_read", c->self);
471	if (c->sock != -1) {
472		if (shutdown(c->sock, SHUT_RD) < 0)
473			error("channel %d: chan_shutdown_read: "
474			    "shutdown() failed for fd%d [i%d o%d]: %.100s",
475			    c->self, c->sock, c->istate, c->ostate,
476			    strerror(errno));
477	} else {
478		if (channel_close_fd(&c->rfd) < 0)
479			log("channel %d: chan_shutdown_read: "
480			    "close() failed for fd%d: %.100s",
481			    c->self, c->rfd, strerror(errno));
482	}
483}
484