1/* $OpenBSD: nchan.c,v 1.69 2018/10/04 07:47:35 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 */
77static void	chan_send_eof2(struct ssh *, Channel *);
78static void	chan_send_eow2(struct ssh *, Channel *);
79
80/* helper */
81static void	chan_shutdown_write(struct ssh *, Channel *);
82static void	chan_shutdown_read(struct ssh *, Channel *);
83static void	chan_shutdown_extended_read(struct ssh *, Channel *);
84
85static const char *ostates[] = { "open", "drain", "wait_ieof", "closed" };
86static const char *istates[] = { "open", "drain", "wait_oclose", "closed" };
87
88static void
89chan_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
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	debug2("channel %d: output %s -> %s", c->self, ostates[c->ostate],
104	    ostates[next]);
105	c->ostate = next;
106}
107
108void
109chan_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
124void
125chan_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
146void
147chan_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
167void
168chan_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
179static void
180chan_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
203static void
204chan_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
227static void
228chan_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
252void
253chan_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
265void
266chan_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
305void
306chan_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
324void
325chan_mark_dead(struct ssh *ssh, Channel *c)
326{
327	c->type = SSH_CHANNEL_ZOMBIE;
328}
329
330int
331chan_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 */
372static void
373chan_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) < 0) {
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
399static void
400chan_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) < 0 && 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
429static void
430chan_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