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 <sys/types.h>
27#include <sys/socket.h>
28#include <sys/queue.h>
29
30#include <errno.h>
31#include <string.h>
32#include <stdarg.h>
33
34#include "ssh2.h"
35#include "sshbuf.h"
36#include "ssherr.h"
37#include "packet.h"
38#include "channels.h"
39#include "compat.h"
40#include "log.h"
41
42/*
43 * SSH Protocol 1.5 aka New Channel Protocol
44 * Thanks to Martina, Axel and everyone who left Erlangen, leaving me bored.
45 * Written by Markus Friedl in October 1999
46 *
47 * Protocol versions 1.3 and 1.5 differ in the handshake protocol used for the
48 * tear down of channels:
49 *
50 * 1.3:	strict request-ack-protocol:
51 *	CLOSE	->
52 *		<-  CLOSE_CONFIRM
53 *
54 * 1.5:	uses variations of:
55 *	IEOF	->
56 *		<-  OCLOSE
57 *		<-  IEOF
58 *	OCLOSE	->
59 *	i.e. both sides have to close the channel
60 *
61 * 2.0: the EOF messages are optional
62 *
63 * See the debugging output from 'ssh -v' and 'sshd -d' of
64 * ssh-1.2.27 as an example.
65 *
66 */
67
68/* functions manipulating channel states */
69/*
70 * EVENTS update channel input/output states execute ACTIONS
71 */
72/*
73 * ACTIONS: should never update the channel states
74 */
75static void	chan_send_eof2(struct ssh *, Channel *);
76static void	chan_send_eow2(struct ssh *, Channel *);
77
78/* helper */
79static void	chan_shutdown_write(struct ssh *, Channel *);
80static void	chan_shutdown_read(struct ssh *, Channel *);
81static void	chan_shutdown_extended_read(struct ssh *, Channel *);
82
83static const char * const ostates[] = {
84	"open", "drain", "wait_ieof", "closed",
85};
86static const char * const istates[] = {
87	"open", "drain", "wait_oclose", "closed",
88};
89
90static void
91chan_set_istate(Channel *c, u_int next)
92{
93	if (c->istate > CHAN_INPUT_CLOSED || next > CHAN_INPUT_CLOSED)
94		fatal("chan_set_istate: bad state %d -> %d", c->istate, next);
95	debug2("channel %d: input %s -> %s", c->self, istates[c->istate],
96	    istates[next]);
97	c->istate = next;
98}
99
100static void
101chan_set_ostate(Channel *c, u_int next)
102{
103	if (c->ostate > CHAN_OUTPUT_CLOSED || next > CHAN_OUTPUT_CLOSED)
104		fatal("chan_set_ostate: bad state %d -> %d", c->ostate, next);
105	debug2("channel %d: output %s -> %s", c->self, ostates[c->ostate],
106	    ostates[next]);
107	c->ostate = next;
108}
109
110void
111chan_read_failed(struct ssh *ssh, Channel *c)
112{
113	debug2("channel %d: read failed", c->self);
114	switch (c->istate) {
115	case CHAN_INPUT_OPEN:
116		chan_shutdown_read(ssh, c);
117		chan_set_istate(c, CHAN_INPUT_WAIT_DRAIN);
118		break;
119	default:
120		error("channel %d: chan_read_failed for istate %d",
121		    c->self, c->istate);
122		break;
123	}
124}
125
126void
127chan_ibuf_empty(struct ssh *ssh, Channel *c)
128{
129	debug2("channel %d: ibuf empty", c->self);
130	if (sshbuf_len(c->input)) {
131		error("channel %d: chan_ibuf_empty for non empty buffer",
132		    c->self);
133		return;
134	}
135	switch (c->istate) {
136	case CHAN_INPUT_WAIT_DRAIN:
137		if (!(c->flags & (CHAN_CLOSE_SENT|CHAN_LOCAL)))
138			chan_send_eof2(ssh, c);
139		chan_set_istate(c, CHAN_INPUT_CLOSED);
140		break;
141	default:
142		error("channel %d: chan_ibuf_empty for istate %d",
143		    c->self, c->istate);
144		break;
145	}
146}
147
148void
149chan_obuf_empty(struct ssh *ssh, Channel *c)
150{
151	debug2("channel %d: obuf empty", c->self);
152	if (sshbuf_len(c->output)) {
153		error("channel %d: chan_obuf_empty for non empty buffer",
154		    c->self);
155		return;
156	}
157	switch (c->ostate) {
158	case CHAN_OUTPUT_WAIT_DRAIN:
159		chan_shutdown_write(ssh, c);
160		chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
161		break;
162	default:
163		error("channel %d: internal error: obuf_empty for ostate %d",
164		    c->self, c->ostate);
165		break;
166	}
167}
168
169void
170chan_rcvd_eow(struct ssh *ssh, Channel *c)
171{
172	debug2("channel %d: rcvd eow", c->self);
173	switch (c->istate) {
174	case CHAN_INPUT_OPEN:
175		chan_shutdown_read(ssh, c);
176		chan_set_istate(c, CHAN_INPUT_CLOSED);
177		break;
178	}
179}
180
181static void
182chan_send_eof2(struct ssh *ssh, Channel *c)
183{
184	int r;
185
186	debug2("channel %d: send eof", c->self);
187	switch (c->istate) {
188	case CHAN_INPUT_WAIT_DRAIN:
189		if (!c->have_remote_id)
190			fatal_f("channel %d: no remote_id", c->self);
191		if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_EOF)) != 0 ||
192		    (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
193		    (r = sshpkt_send(ssh)) != 0)
194			fatal_fr(r, "send CHANNEL_EOF");
195		c->flags |= CHAN_EOF_SENT;
196		break;
197	default:
198		error("channel %d: cannot send eof for istate %d",
199		    c->self, c->istate);
200		break;
201	}
202}
203
204static void
205chan_send_close2(struct ssh *ssh, Channel *c)
206{
207	int r;
208
209	debug2("channel %d: send close", c->self);
210	if (c->ostate != CHAN_OUTPUT_CLOSED ||
211	    c->istate != CHAN_INPUT_CLOSED) {
212		error("channel %d: cannot send close for istate/ostate %d/%d",
213		    c->self, c->istate, c->ostate);
214	} else if (c->flags & CHAN_CLOSE_SENT) {
215		error("channel %d: already sent close", c->self);
216	} else {
217		if (!c->have_remote_id)
218			fatal_f("channel %d: no remote_id", 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_fr(r, "send CHANNEL_EOF");
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 (!(ssh->compat & SSH_NEW_OPENSSH))
239		return;
240	if (!c->have_remote_id)
241		fatal_f("channel %d: no remote_id", 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_fr(r, "send CHANNEL_EOF");
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 ((ssh->compat & 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_f("channel %d: (i%d o%d sock %d wfd %d efd %d [%s])",
380	    c->self, 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_f("channel %d: shutdown() failed for "
385			    "fd %d [i%d o%d]: %.100s", c->self, c->sock,
386			    c->istate, c->ostate, strerror(errno));
387		}
388	} else {
389		if (channel_close_fd(ssh, c, &c->wfd) < 0) {
390			logit_f("channel %d: close() failed for "
391			    "fd %d [i%d o%d]: %.100s", c->self, c->wfd,
392			    c->istate, c->ostate, strerror(errno));
393		}
394	}
395}
396
397static void
398chan_shutdown_read(struct ssh *ssh, Channel *c)
399{
400	if (c->type == SSH_CHANNEL_LARVAL)
401		return;
402	debug2_f("channel %d: (i%d o%d sock %d wfd %d efd %d [%s])",
403	    c->self, c->istate, c->ostate, c->sock, c->rfd, c->efd,
404	    channel_format_extended_usage(c));
405	if (c->sock != -1) {
406		if (shutdown(c->sock, SHUT_RD) == -1) {
407			error_f("channel %d: shutdown() failed for "
408			    "fd %d [i%d o%d]: %.100s", c->self, c->sock,
409			    c->istate, c->ostate, strerror(errno));
410		}
411	} else {
412		if (channel_close_fd(ssh, c, &c->rfd) < 0) {
413			logit_f("channel %d: close() failed for "
414			    "fd %d [i%d o%d]: %.100s", c->self, c->rfd,
415			    c->istate, c->ostate, strerror(errno));
416		}
417	}
418}
419
420static void
421chan_shutdown_extended_read(struct ssh *ssh, Channel *c)
422{
423	if (c->type == SSH_CHANNEL_LARVAL || c->efd == -1)
424		return;
425	if (c->extended_usage != CHAN_EXTENDED_READ &&
426	    c->extended_usage != CHAN_EXTENDED_IGNORE)
427		return;
428	debug_f("channel %d: (i%d o%d sock %d wfd %d efd %d [%s])",
429	    c->self, c->istate, c->ostate, c->sock, c->rfd, c->efd,
430	    channel_format_extended_usage(c));
431	if (channel_close_fd(ssh, c, &c->efd) < 0) {
432		logit_f("channel %d: close() failed for "
433		    "extended fd %d [i%d o%d]: %.100s", c->self, c->efd,
434		    c->istate, c->ostate, strerror(errno));
435	}
436}
437