xref: /openssh-portable/channels.c (revision d5ba1c03)
1 /* $OpenBSD: channels.c,v 1.396 2020/02/26 13:40:09 jsg Exp $ */
2 /*
3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5  *                    All rights reserved
6  * This file contains functions for generic socket connection forwarding.
7  * There is also code for initiating connection forwarding for X11 connections,
8  * arbitrary tcp/ip connections, and the authentication agent connection.
9  *
10  * As far as I am concerned, the code I have written for this software
11  * can be used freely for any purpose.  Any derived versions of this
12  * software must be clearly marked as such, and if the derived work is
13  * incompatible with the protocol description in the RFC file, it must be
14  * called by a name other than "ssh" or "Secure Shell".
15  *
16  * SSH2 support added by Markus Friedl.
17  * Copyright (c) 1999, 2000, 2001, 2002 Markus Friedl.  All rights reserved.
18  * Copyright (c) 1999 Dug Song.  All rights reserved.
19  * Copyright (c) 1999 Theo de Raadt.  All rights reserved.
20  *
21  * Redistribution and use in source and binary forms, with or without
22  * modification, are permitted provided that the following conditions
23  * are met:
24  * 1. Redistributions of source code must retain the above copyright
25  *    notice, this list of conditions and the following disclaimer.
26  * 2. Redistributions in binary form must reproduce the above copyright
27  *    notice, this list of conditions and the following disclaimer in the
28  *    documentation and/or other materials provided with the distribution.
29  *
30  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
31  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
32  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
33  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
34  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
35  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
36  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
37  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
38  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
39  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
40  */
41 
42 #include "includes.h"
43 
44 #include <sys/types.h>
45 #include <sys/stat.h>
46 #include <sys/ioctl.h>
47 #include <sys/un.h>
48 #include <sys/socket.h>
49 #ifdef HAVE_SYS_TIME_H
50 # include <sys/time.h>
51 #endif
52 
53 #include <netinet/in.h>
54 #include <arpa/inet.h>
55 
56 #include <errno.h>
57 #include <fcntl.h>
58 #include <limits.h>
59 #include <netdb.h>
60 #include <stdarg.h>
61 #ifdef HAVE_STDINT_H
62 # include <stdint.h>
63 #endif
64 #include <stdio.h>
65 #include <stdlib.h>
66 #include <string.h>
67 #include <termios.h>
68 #include <unistd.h>
69 
70 #include "openbsd-compat/sys-queue.h"
71 #include "xmalloc.h"
72 #include "ssh.h"
73 #include "ssh2.h"
74 #include "ssherr.h"
75 #include "sshbuf.h"
76 #include "packet.h"
77 #include "log.h"
78 #include "misc.h"
79 #include "channels.h"
80 #include "compat.h"
81 #include "canohost.h"
82 #include "sshkey.h"
83 #include "authfd.h"
84 #include "pathnames.h"
85 #include "match.h"
86 
87 /* -- agent forwarding */
88 #define	NUM_SOCKS	10
89 
90 /* -- tcp forwarding */
91 /* special-case port number meaning allow any port */
92 #define FWD_PERMIT_ANY_PORT	0
93 
94 /* special-case wildcard meaning allow any host */
95 #define FWD_PERMIT_ANY_HOST	"*"
96 
97 /* -- X11 forwarding */
98 /* Maximum number of fake X11 displays to try. */
99 #define MAX_DISPLAYS  1000
100 
101 /* Per-channel callback for pre/post select() actions */
102 typedef void chan_fn(struct ssh *, Channel *c,
103     fd_set *readset, fd_set *writeset);
104 
105 /*
106  * Data structure for storing which hosts are permitted for forward requests.
107  * The local sides of any remote forwards are stored in this array to prevent
108  * a corrupt remote server from accessing arbitrary TCP/IP ports on our local
109  * network (which might be behind a firewall).
110  */
111 /* XXX: streamlocal wants a path instead of host:port */
112 /*      Overload host_to_connect; we could just make this match Forward */
113 /*	XXX - can we use listen_host instead of listen_path? */
114 struct permission {
115 	char *host_to_connect;		/* Connect to 'host'. */
116 	int port_to_connect;		/* Connect to 'port'. */
117 	char *listen_host;		/* Remote side should listen address. */
118 	char *listen_path;		/* Remote side should listen path. */
119 	int listen_port;		/* Remote side should listen port. */
120 	Channel *downstream;		/* Downstream mux*/
121 };
122 
123 /*
124  * Stores the forwarding permission state for a single direction (local or
125  * remote).
126  */
127 struct permission_set {
128 	/*
129 	 * List of all local permitted host/port pairs to allow for the
130 	 * user.
131 	 */
132 	u_int num_permitted_user;
133 	struct permission *permitted_user;
134 
135 	/*
136 	 * List of all permitted host/port pairs to allow for the admin.
137 	 */
138 	u_int num_permitted_admin;
139 	struct permission *permitted_admin;
140 
141 	/*
142 	 * If this is true, all opens/listens are permitted.  This is the
143 	 * case on the server on which we have to trust the client anyway,
144 	 * and the user could do anything after logging in.
145 	 */
146 	int all_permitted;
147 };
148 
149 /* Master structure for channels state */
150 struct ssh_channels {
151 	/*
152 	 * Pointer to an array containing all allocated channels.  The array
153 	 * is dynamically extended as needed.
154 	 */
155 	Channel **channels;
156 
157 	/*
158 	 * Size of the channel array.  All slots of the array must always be
159 	 * initialized (at least the type field); unused slots set to NULL
160 	 */
161 	u_int channels_alloc;
162 
163 	/*
164 	 * Maximum file descriptor value used in any of the channels.  This is
165 	 * updated in channel_new.
166 	 */
167 	int channel_max_fd;
168 
169 	/*
170 	 * 'channel_pre*' are called just before select() to add any bits
171 	 * relevant to channels in the select bitmasks.
172 	 *
173 	 * 'channel_post*': perform any appropriate operations for
174 	 * channels which have events pending.
175 	 */
176 	chan_fn **channel_pre;
177 	chan_fn **channel_post;
178 
179 	/* -- tcp forwarding */
180 	struct permission_set local_perms;
181 	struct permission_set remote_perms;
182 
183 	/* -- X11 forwarding */
184 
185 	/* Saved X11 local (client) display. */
186 	char *x11_saved_display;
187 
188 	/* Saved X11 authentication protocol name. */
189 	char *x11_saved_proto;
190 
191 	/* Saved X11 authentication data.  This is the real data. */
192 	char *x11_saved_data;
193 	u_int x11_saved_data_len;
194 
195 	/* Deadline after which all X11 connections are refused */
196 	u_int x11_refuse_time;
197 
198 	/*
199 	 * Fake X11 authentication data.  This is what the server will be
200 	 * sending us; we should replace any occurrences of this by the
201 	 * real data.
202 	 */
203 	u_char *x11_fake_data;
204 	u_int x11_fake_data_len;
205 
206 	/* AF_UNSPEC or AF_INET or AF_INET6 */
207 	int IPv4or6;
208 };
209 
210 /* helper */
211 static void port_open_helper(struct ssh *ssh, Channel *c, char *rtype);
212 static const char *channel_rfwd_bind_host(const char *listen_host);
213 
214 /* non-blocking connect helpers */
215 static int connect_next(struct channel_connect *);
216 static void channel_connect_ctx_free(struct channel_connect *);
217 static Channel *rdynamic_connect_prepare(struct ssh *, char *, char *);
218 static int rdynamic_connect_finish(struct ssh *, Channel *);
219 
220 /* Setup helper */
221 static void channel_handler_init(struct ssh_channels *sc);
222 
223 /* -- channel core */
224 
225 void
226 channel_init_channels(struct ssh *ssh)
227 {
228 	struct ssh_channels *sc;
229 
230 	if ((sc = calloc(1, sizeof(*sc))) == NULL)
231 		fatal("%s: allocation failed", __func__);
232 	sc->channels_alloc = 10;
233 	sc->channels = xcalloc(sc->channels_alloc, sizeof(*sc->channels));
234 	sc->IPv4or6 = AF_UNSPEC;
235 	channel_handler_init(sc);
236 
237 	ssh->chanctxt = sc;
238 }
239 
240 Channel *
241 channel_by_id(struct ssh *ssh, int id)
242 {
243 	Channel *c;
244 
245 	if (id < 0 || (u_int)id >= ssh->chanctxt->channels_alloc) {
246 		logit("%s: %d: bad id", __func__, id);
247 		return NULL;
248 	}
249 	c = ssh->chanctxt->channels[id];
250 	if (c == NULL) {
251 		logit("%s: %d: bad id: channel free", __func__, id);
252 		return NULL;
253 	}
254 	return c;
255 }
256 
257 Channel *
258 channel_by_remote_id(struct ssh *ssh, u_int remote_id)
259 {
260 	Channel *c;
261 	u_int i;
262 
263 	for (i = 0; i < ssh->chanctxt->channels_alloc; i++) {
264 		c = ssh->chanctxt->channels[i];
265 		if (c != NULL && c->have_remote_id && c->remote_id == remote_id)
266 			return c;
267 	}
268 	return NULL;
269 }
270 
271 /*
272  * Returns the channel if it is allowed to receive protocol messages.
273  * Private channels, like listening sockets, may not receive messages.
274  */
275 Channel *
276 channel_lookup(struct ssh *ssh, int id)
277 {
278 	Channel *c;
279 
280 	if ((c = channel_by_id(ssh, id)) == NULL)
281 		return NULL;
282 
283 	switch (c->type) {
284 	case SSH_CHANNEL_X11_OPEN:
285 	case SSH_CHANNEL_LARVAL:
286 	case SSH_CHANNEL_CONNECTING:
287 	case SSH_CHANNEL_DYNAMIC:
288 	case SSH_CHANNEL_RDYNAMIC_OPEN:
289 	case SSH_CHANNEL_RDYNAMIC_FINISH:
290 	case SSH_CHANNEL_OPENING:
291 	case SSH_CHANNEL_OPEN:
292 	case SSH_CHANNEL_ABANDONED:
293 	case SSH_CHANNEL_MUX_PROXY:
294 		return c;
295 	}
296 	logit("Non-public channel %d, type %d.", id, c->type);
297 	return NULL;
298 }
299 
300 /*
301  * Register filedescriptors for a channel, used when allocating a channel or
302  * when the channel consumer/producer is ready, e.g. shell exec'd
303  */
304 static void
305 channel_register_fds(struct ssh *ssh, Channel *c, int rfd, int wfd, int efd,
306     int extusage, int nonblock, int is_tty)
307 {
308 	struct ssh_channels *sc = ssh->chanctxt;
309 
310 	/* Update the maximum file descriptor value. */
311 	sc->channel_max_fd = MAXIMUM(sc->channel_max_fd, rfd);
312 	sc->channel_max_fd = MAXIMUM(sc->channel_max_fd, wfd);
313 	sc->channel_max_fd = MAXIMUM(sc->channel_max_fd, efd);
314 
315 	if (rfd != -1)
316 		fcntl(rfd, F_SETFD, FD_CLOEXEC);
317 	if (wfd != -1 && wfd != rfd)
318 		fcntl(wfd, F_SETFD, FD_CLOEXEC);
319 	if (efd != -1 && efd != rfd && efd != wfd)
320 		fcntl(efd, F_SETFD, FD_CLOEXEC);
321 
322 	c->rfd = rfd;
323 	c->wfd = wfd;
324 	c->sock = (rfd == wfd) ? rfd : -1;
325 	c->efd = efd;
326 	c->extended_usage = extusage;
327 
328 	if ((c->isatty = is_tty) != 0)
329 		debug2("channel %d: rfd %d isatty", c->self, c->rfd);
330 #ifdef _AIX
331 	/* XXX: Later AIX versions can't push as much data to tty */
332 	c->wfd_isatty = is_tty || isatty(c->wfd);
333 #endif
334 
335 	/* enable nonblocking mode */
336 	if (nonblock) {
337 		if (rfd != -1)
338 			set_nonblock(rfd);
339 		if (wfd != -1)
340 			set_nonblock(wfd);
341 		if (efd != -1)
342 			set_nonblock(efd);
343 	}
344 }
345 
346 /*
347  * Allocate a new channel object and set its type and socket. This will cause
348  * remote_name to be freed.
349  */
350 Channel *
351 channel_new(struct ssh *ssh, char *ctype, int type, int rfd, int wfd, int efd,
352     u_int window, u_int maxpack, int extusage, char *remote_name, int nonblock)
353 {
354 	struct ssh_channels *sc = ssh->chanctxt;
355 	u_int i, found;
356 	Channel *c;
357 
358 	/* Try to find a free slot where to put the new channel. */
359 	for (i = 0; i < sc->channels_alloc; i++) {
360 		if (sc->channels[i] == NULL) {
361 			/* Found a free slot. */
362 			found = i;
363 			break;
364 		}
365 	}
366 	if (i >= sc->channels_alloc) {
367 		/*
368 		 * There are no free slots. Take last+1 slot and expand
369 		 * the array.
370 		 */
371 		found = sc->channels_alloc;
372 		if (sc->channels_alloc > CHANNELS_MAX_CHANNELS)
373 			fatal("%s: internal error: channels_alloc %d too big",
374 			    __func__, sc->channels_alloc);
375 		sc->channels = xrecallocarray(sc->channels, sc->channels_alloc,
376 		    sc->channels_alloc + 10, sizeof(*sc->channels));
377 		sc->channels_alloc += 10;
378 		debug2("channel: expanding %d", sc->channels_alloc);
379 	}
380 	/* Initialize and return new channel. */
381 	c = sc->channels[found] = xcalloc(1, sizeof(Channel));
382 	if ((c->input = sshbuf_new()) == NULL ||
383 	    (c->output = sshbuf_new()) == NULL ||
384 	    (c->extended = sshbuf_new()) == NULL)
385 		fatal("%s: sshbuf_new failed", __func__);
386 	c->ostate = CHAN_OUTPUT_OPEN;
387 	c->istate = CHAN_INPUT_OPEN;
388 	channel_register_fds(ssh, c, rfd, wfd, efd, extusage, nonblock, 0);
389 	c->self = found;
390 	c->type = type;
391 	c->ctype = ctype;
392 	c->local_window = window;
393 	c->local_window_max = window;
394 	c->local_maxpacket = maxpack;
395 	c->remote_name = xstrdup(remote_name);
396 	c->ctl_chan = -1;
397 	c->delayed = 1;		/* prevent call to channel_post handler */
398 	TAILQ_INIT(&c->status_confirms);
399 	debug("channel %d: new [%s]", found, remote_name);
400 	return c;
401 }
402 
403 static void
404 channel_find_maxfd(struct ssh_channels *sc)
405 {
406 	u_int i;
407 	int max = 0;
408 	Channel *c;
409 
410 	for (i = 0; i < sc->channels_alloc; i++) {
411 		c = sc->channels[i];
412 		if (c != NULL) {
413 			max = MAXIMUM(max, c->rfd);
414 			max = MAXIMUM(max, c->wfd);
415 			max = MAXIMUM(max, c->efd);
416 		}
417 	}
418 	sc->channel_max_fd = max;
419 }
420 
421 int
422 channel_close_fd(struct ssh *ssh, int *fdp)
423 {
424 	struct ssh_channels *sc = ssh->chanctxt;
425 	int ret = 0, fd = *fdp;
426 
427 	if (fd != -1) {
428 		ret = close(fd);
429 		*fdp = -1;
430 		if (fd == sc->channel_max_fd)
431 			channel_find_maxfd(sc);
432 	}
433 	return ret;
434 }
435 
436 /* Close all channel fd/socket. */
437 static void
438 channel_close_fds(struct ssh *ssh, Channel *c)
439 {
440 	int sock = c->sock, rfd = c->rfd, wfd = c->wfd, efd = c->efd;
441 
442 	channel_close_fd(ssh, &c->sock);
443 	if (rfd != sock)
444 		channel_close_fd(ssh, &c->rfd);
445 	if (wfd != sock && wfd != rfd)
446 		channel_close_fd(ssh, &c->wfd);
447 	if (efd != sock && efd != rfd && efd != wfd)
448 		channel_close_fd(ssh, &c->efd);
449 }
450 
451 static void
452 fwd_perm_clear(struct permission *perm)
453 {
454 	free(perm->host_to_connect);
455 	free(perm->listen_host);
456 	free(perm->listen_path);
457 	bzero(perm, sizeof(*perm));
458 }
459 
460 /* Returns an printable name for the specified forwarding permission list */
461 static const char *
462 fwd_ident(int who, int where)
463 {
464 	if (who == FORWARD_ADM) {
465 		if (where == FORWARD_LOCAL)
466 			return "admin local";
467 		else if (where == FORWARD_REMOTE)
468 			return "admin remote";
469 	} else if (who == FORWARD_USER) {
470 		if (where == FORWARD_LOCAL)
471 			return "user local";
472 		else if (where == FORWARD_REMOTE)
473 			return "user remote";
474 	}
475 	fatal("Unknown forward permission list %d/%d", who, where);
476 }
477 
478 /* Returns the forwarding permission list for the specified direction */
479 static struct permission_set *
480 permission_set_get(struct ssh *ssh, int where)
481 {
482 	struct ssh_channels *sc = ssh->chanctxt;
483 
484 	switch (where) {
485 	case FORWARD_LOCAL:
486 		return &sc->local_perms;
487 		break;
488 	case FORWARD_REMOTE:
489 		return &sc->remote_perms;
490 		break;
491 	default:
492 		fatal("%s: invalid forwarding direction %d", __func__, where);
493 	}
494 }
495 
496 /* Returns pointers to the specified forwarding list and its element count */
497 static void
498 permission_set_get_array(struct ssh *ssh, int who, int where,
499     struct permission ***permpp, u_int **npermpp)
500 {
501 	struct permission_set *pset = permission_set_get(ssh, where);
502 
503 	switch (who) {
504 	case FORWARD_USER:
505 		*permpp = &pset->permitted_user;
506 		*npermpp = &pset->num_permitted_user;
507 		break;
508 	case FORWARD_ADM:
509 		*permpp = &pset->permitted_admin;
510 		*npermpp = &pset->num_permitted_admin;
511 		break;
512 	default:
513 		fatal("%s: invalid forwarding client %d", __func__, who);
514 	}
515 }
516 
517 /* Adds an entry to the spcified forwarding list */
518 static int
519 permission_set_add(struct ssh *ssh, int who, int where,
520     const char *host_to_connect, int port_to_connect,
521     const char *listen_host, const char *listen_path, int listen_port,
522     Channel *downstream)
523 {
524 	struct permission **permp;
525 	u_int n, *npermp;
526 
527 	permission_set_get_array(ssh, who, where, &permp, &npermp);
528 
529 	if (*npermp >= INT_MAX)
530 		fatal("%s: %s overflow", __func__, fwd_ident(who, where));
531 
532 	*permp = xrecallocarray(*permp, *npermp, *npermp + 1, sizeof(**permp));
533 	n = (*npermp)++;
534 #define MAYBE_DUP(s) ((s == NULL) ? NULL : xstrdup(s))
535 	(*permp)[n].host_to_connect = MAYBE_DUP(host_to_connect);
536 	(*permp)[n].port_to_connect = port_to_connect;
537 	(*permp)[n].listen_host = MAYBE_DUP(listen_host);
538 	(*permp)[n].listen_path = MAYBE_DUP(listen_path);
539 	(*permp)[n].listen_port = listen_port;
540 	(*permp)[n].downstream = downstream;
541 #undef MAYBE_DUP
542 	return (int)n;
543 }
544 
545 static void
546 mux_remove_remote_forwardings(struct ssh *ssh, Channel *c)
547 {
548 	struct ssh_channels *sc = ssh->chanctxt;
549 	struct permission_set *pset = &sc->local_perms;
550 	struct permission *perm;
551 	int r;
552 	u_int i;
553 
554 	for (i = 0; i < pset->num_permitted_user; i++) {
555 		perm = &pset->permitted_user[i];
556 		if (perm->downstream != c)
557 			continue;
558 
559 		/* cancel on the server, since mux client is gone */
560 		debug("channel %d: cleanup remote forward for %s:%u",
561 		    c->self, perm->listen_host, perm->listen_port);
562 		if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 ||
563 		    (r = sshpkt_put_cstring(ssh,
564 		    "cancel-tcpip-forward")) != 0 ||
565 		    (r = sshpkt_put_u8(ssh, 0)) != 0 ||
566 		    (r = sshpkt_put_cstring(ssh,
567 		    channel_rfwd_bind_host(perm->listen_host))) != 0 ||
568 		    (r = sshpkt_put_u32(ssh, perm->listen_port)) != 0 ||
569 		    (r = sshpkt_send(ssh)) != 0) {
570 			fatal("%s: channel %i: %s", __func__,
571 			    c->self, ssh_err(r));
572 		}
573 		fwd_perm_clear(perm); /* unregister */
574 	}
575 }
576 
577 /* Free the channel and close its fd/socket. */
578 void
579 channel_free(struct ssh *ssh, Channel *c)
580 {
581 	struct ssh_channels *sc = ssh->chanctxt;
582 	char *s;
583 	u_int i, n;
584 	Channel *other;
585 	struct channel_confirm *cc;
586 
587 	for (n = 0, i = 0; i < sc->channels_alloc; i++) {
588 		if ((other = sc->channels[i]) == NULL)
589 			continue;
590 		n++;
591 		/* detach from mux client and prepare for closing */
592 		if (c->type == SSH_CHANNEL_MUX_CLIENT &&
593 		    other->type == SSH_CHANNEL_MUX_PROXY &&
594 		    other->mux_ctx == c) {
595 			other->mux_ctx = NULL;
596 			other->type = SSH_CHANNEL_OPEN;
597 			other->istate = CHAN_INPUT_CLOSED;
598 			other->ostate = CHAN_OUTPUT_CLOSED;
599 		}
600 	}
601 	debug("channel %d: free: %s, nchannels %u", c->self,
602 	    c->remote_name ? c->remote_name : "???", n);
603 
604 	if (c->type == SSH_CHANNEL_MUX_CLIENT)
605 		mux_remove_remote_forwardings(ssh, c);
606 
607 	if (log_level_get() >= SYSLOG_LEVEL_DEBUG3) {
608 		s = channel_open_message(ssh);
609 		debug3("channel %d: status: %s", c->self, s);
610 		free(s);
611 	}
612 
613 	channel_close_fds(ssh, c);
614 	sshbuf_free(c->input);
615 	sshbuf_free(c->output);
616 	sshbuf_free(c->extended);
617 	c->input = c->output = c->extended = NULL;
618 	free(c->remote_name);
619 	c->remote_name = NULL;
620 	free(c->path);
621 	c->path = NULL;
622 	free(c->listening_addr);
623 	c->listening_addr = NULL;
624 	while ((cc = TAILQ_FIRST(&c->status_confirms)) != NULL) {
625 		if (cc->abandon_cb != NULL)
626 			cc->abandon_cb(ssh, c, cc->ctx);
627 		TAILQ_REMOVE(&c->status_confirms, cc, entry);
628 		freezero(cc, sizeof(*cc));
629 	}
630 	if (c->filter_cleanup != NULL && c->filter_ctx != NULL)
631 		c->filter_cleanup(ssh, c->self, c->filter_ctx);
632 	sc->channels[c->self] = NULL;
633 	freezero(c, sizeof(*c));
634 }
635 
636 void
637 channel_free_all(struct ssh *ssh)
638 {
639 	u_int i;
640 	struct ssh_channels *sc = ssh->chanctxt;
641 
642 	for (i = 0; i < sc->channels_alloc; i++)
643 		if (sc->channels[i] != NULL)
644 			channel_free(ssh, sc->channels[i]);
645 
646 	free(sc->channels);
647 	sc->channels = NULL;
648 	sc->channels_alloc = 0;
649 	sc->channel_max_fd = 0;
650 
651 	free(sc->x11_saved_display);
652 	sc->x11_saved_display = NULL;
653 
654 	free(sc->x11_saved_proto);
655 	sc->x11_saved_proto = NULL;
656 
657 	free(sc->x11_saved_data);
658 	sc->x11_saved_data = NULL;
659 	sc->x11_saved_data_len = 0;
660 
661 	free(sc->x11_fake_data);
662 	sc->x11_fake_data = NULL;
663 	sc->x11_fake_data_len = 0;
664 }
665 
666 /*
667  * Closes the sockets/fds of all channels.  This is used to close extra file
668  * descriptors after a fork.
669  */
670 void
671 channel_close_all(struct ssh *ssh)
672 {
673 	u_int i;
674 
675 	for (i = 0; i < ssh->chanctxt->channels_alloc; i++)
676 		if (ssh->chanctxt->channels[i] != NULL)
677 			channel_close_fds(ssh, ssh->chanctxt->channels[i]);
678 }
679 
680 /*
681  * Stop listening to channels.
682  */
683 void
684 channel_stop_listening(struct ssh *ssh)
685 {
686 	u_int i;
687 	Channel *c;
688 
689 	for (i = 0; i < ssh->chanctxt->channels_alloc; i++) {
690 		c = ssh->chanctxt->channels[i];
691 		if (c != NULL) {
692 			switch (c->type) {
693 			case SSH_CHANNEL_AUTH_SOCKET:
694 			case SSH_CHANNEL_PORT_LISTENER:
695 			case SSH_CHANNEL_RPORT_LISTENER:
696 			case SSH_CHANNEL_X11_LISTENER:
697 			case SSH_CHANNEL_UNIX_LISTENER:
698 			case SSH_CHANNEL_RUNIX_LISTENER:
699 				channel_close_fd(ssh, &c->sock);
700 				channel_free(ssh, c);
701 				break;
702 			}
703 		}
704 	}
705 }
706 
707 /*
708  * Returns true if no channel has too much buffered data, and false if one or
709  * more channel is overfull.
710  */
711 int
712 channel_not_very_much_buffered_data(struct ssh *ssh)
713 {
714 	u_int i;
715 	u_int maxsize = ssh_packet_get_maxsize(ssh);
716 	Channel *c;
717 
718 	for (i = 0; i < ssh->chanctxt->channels_alloc; i++) {
719 		c = ssh->chanctxt->channels[i];
720 		if (c == NULL || c->type != SSH_CHANNEL_OPEN)
721 			continue;
722 		if (sshbuf_len(c->output) > maxsize) {
723 			debug2("channel %d: big output buffer %zu > %u",
724 			    c->self, sshbuf_len(c->output), maxsize);
725 			return 0;
726 		}
727 	}
728 	return 1;
729 }
730 
731 /* Returns true if any channel is still open. */
732 int
733 channel_still_open(struct ssh *ssh)
734 {
735 	u_int i;
736 	Channel *c;
737 
738 	for (i = 0; i < ssh->chanctxt->channels_alloc; i++) {
739 		c = ssh->chanctxt->channels[i];
740 		if (c == NULL)
741 			continue;
742 		switch (c->type) {
743 		case SSH_CHANNEL_X11_LISTENER:
744 		case SSH_CHANNEL_PORT_LISTENER:
745 		case SSH_CHANNEL_RPORT_LISTENER:
746 		case SSH_CHANNEL_MUX_LISTENER:
747 		case SSH_CHANNEL_CLOSED:
748 		case SSH_CHANNEL_AUTH_SOCKET:
749 		case SSH_CHANNEL_DYNAMIC:
750 		case SSH_CHANNEL_RDYNAMIC_OPEN:
751 		case SSH_CHANNEL_CONNECTING:
752 		case SSH_CHANNEL_ZOMBIE:
753 		case SSH_CHANNEL_ABANDONED:
754 		case SSH_CHANNEL_UNIX_LISTENER:
755 		case SSH_CHANNEL_RUNIX_LISTENER:
756 			continue;
757 		case SSH_CHANNEL_LARVAL:
758 			continue;
759 		case SSH_CHANNEL_OPENING:
760 		case SSH_CHANNEL_OPEN:
761 		case SSH_CHANNEL_RDYNAMIC_FINISH:
762 		case SSH_CHANNEL_X11_OPEN:
763 		case SSH_CHANNEL_MUX_CLIENT:
764 		case SSH_CHANNEL_MUX_PROXY:
765 			return 1;
766 		default:
767 			fatal("%s: bad channel type %d", __func__, c->type);
768 			/* NOTREACHED */
769 		}
770 	}
771 	return 0;
772 }
773 
774 /* Returns the id of an open channel suitable for keepaliving */
775 int
776 channel_find_open(struct ssh *ssh)
777 {
778 	u_int i;
779 	Channel *c;
780 
781 	for (i = 0; i < ssh->chanctxt->channels_alloc; i++) {
782 		c = ssh->chanctxt->channels[i];
783 		if (c == NULL || !c->have_remote_id)
784 			continue;
785 		switch (c->type) {
786 		case SSH_CHANNEL_CLOSED:
787 		case SSH_CHANNEL_DYNAMIC:
788 		case SSH_CHANNEL_RDYNAMIC_OPEN:
789 		case SSH_CHANNEL_RDYNAMIC_FINISH:
790 		case SSH_CHANNEL_X11_LISTENER:
791 		case SSH_CHANNEL_PORT_LISTENER:
792 		case SSH_CHANNEL_RPORT_LISTENER:
793 		case SSH_CHANNEL_MUX_LISTENER:
794 		case SSH_CHANNEL_MUX_CLIENT:
795 		case SSH_CHANNEL_MUX_PROXY:
796 		case SSH_CHANNEL_OPENING:
797 		case SSH_CHANNEL_CONNECTING:
798 		case SSH_CHANNEL_ZOMBIE:
799 		case SSH_CHANNEL_ABANDONED:
800 		case SSH_CHANNEL_UNIX_LISTENER:
801 		case SSH_CHANNEL_RUNIX_LISTENER:
802 			continue;
803 		case SSH_CHANNEL_LARVAL:
804 		case SSH_CHANNEL_AUTH_SOCKET:
805 		case SSH_CHANNEL_OPEN:
806 		case SSH_CHANNEL_X11_OPEN:
807 			return i;
808 		default:
809 			fatal("%s: bad channel type %d", __func__, c->type);
810 			/* NOTREACHED */
811 		}
812 	}
813 	return -1;
814 }
815 
816 /* Returns the state of the channel's extended usage flag */
817 const char *
818 channel_format_extended_usage(const Channel *c)
819 {
820 	if (c->efd == -1)
821 		return "closed";
822 
823 	switch (c->extended_usage) {
824 	case CHAN_EXTENDED_WRITE:
825 		return "write";
826 	case CHAN_EXTENDED_READ:
827 		return "read";
828 	case CHAN_EXTENDED_IGNORE:
829 		return "ignore";
830 	default:
831 		return "UNKNOWN";
832 	}
833 }
834 
835 static char *
836 channel_format_status(const Channel *c)
837 {
838 	char *ret = NULL;
839 
840 	xasprintf(&ret, "t%d %s%u i%u/%zu o%u/%zu e[%s]/%zu "
841 	    "fd %d/%d/%d sock %d cc %d",
842 	    c->type,
843 	    c->have_remote_id ? "r" : "nr", c->remote_id,
844 	    c->istate, sshbuf_len(c->input),
845 	    c->ostate, sshbuf_len(c->output),
846 	    channel_format_extended_usage(c), sshbuf_len(c->extended),
847 	    c->rfd, c->wfd, c->efd, c->sock, c->ctl_chan);
848 	return ret;
849 }
850 
851 /*
852  * Returns a message describing the currently open forwarded connections,
853  * suitable for sending to the client.  The message contains crlf pairs for
854  * newlines.
855  */
856 char *
857 channel_open_message(struct ssh *ssh)
858 {
859 	struct sshbuf *buf;
860 	Channel *c;
861 	u_int i;
862 	int r;
863 	char *cp, *ret;
864 
865 	if ((buf = sshbuf_new()) == NULL)
866 		fatal("%s: sshbuf_new", __func__);
867 	if ((r = sshbuf_putf(buf,
868 	    "The following connections are open:\r\n")) != 0)
869 		fatal("%s: sshbuf_putf: %s", __func__, ssh_err(r));
870 	for (i = 0; i < ssh->chanctxt->channels_alloc; i++) {
871 		c = ssh->chanctxt->channels[i];
872 		if (c == NULL)
873 			continue;
874 		switch (c->type) {
875 		case SSH_CHANNEL_X11_LISTENER:
876 		case SSH_CHANNEL_PORT_LISTENER:
877 		case SSH_CHANNEL_RPORT_LISTENER:
878 		case SSH_CHANNEL_CLOSED:
879 		case SSH_CHANNEL_AUTH_SOCKET:
880 		case SSH_CHANNEL_ZOMBIE:
881 		case SSH_CHANNEL_ABANDONED:
882 		case SSH_CHANNEL_MUX_LISTENER:
883 		case SSH_CHANNEL_UNIX_LISTENER:
884 		case SSH_CHANNEL_RUNIX_LISTENER:
885 			continue;
886 		case SSH_CHANNEL_LARVAL:
887 		case SSH_CHANNEL_OPENING:
888 		case SSH_CHANNEL_CONNECTING:
889 		case SSH_CHANNEL_DYNAMIC:
890 		case SSH_CHANNEL_RDYNAMIC_OPEN:
891 		case SSH_CHANNEL_RDYNAMIC_FINISH:
892 		case SSH_CHANNEL_OPEN:
893 		case SSH_CHANNEL_X11_OPEN:
894 		case SSH_CHANNEL_MUX_PROXY:
895 		case SSH_CHANNEL_MUX_CLIENT:
896 			cp = channel_format_status(c);
897 			if ((r = sshbuf_putf(buf, "  #%d %.300s (%s)\r\n",
898 			    c->self, c->remote_name, cp)) != 0) {
899 				free(cp);
900 				fatal("%s: sshbuf_putf: %s",
901 				    __func__, ssh_err(r));
902 			}
903 			free(cp);
904 			continue;
905 		default:
906 			fatal("%s: bad channel type %d", __func__, c->type);
907 			/* NOTREACHED */
908 		}
909 	}
910 	if ((ret = sshbuf_dup_string(buf)) == NULL)
911 		fatal("%s: sshbuf_dup_string", __func__);
912 	sshbuf_free(buf);
913 	return ret;
914 }
915 
916 static void
917 open_preamble(struct ssh *ssh, const char *where, Channel *c, const char *type)
918 {
919 	int r;
920 
921 	if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN)) != 0 ||
922 	    (r = sshpkt_put_cstring(ssh, type)) != 0 ||
923 	    (r = sshpkt_put_u32(ssh, c->self)) != 0 ||
924 	    (r = sshpkt_put_u32(ssh, c->local_window)) != 0 ||
925 	    (r = sshpkt_put_u32(ssh, c->local_maxpacket)) != 0) {
926 		fatal("%s: channel %i: open: %s", where, c->self, ssh_err(r));
927 	}
928 }
929 
930 void
931 channel_send_open(struct ssh *ssh, int id)
932 {
933 	Channel *c = channel_lookup(ssh, id);
934 	int r;
935 
936 	if (c == NULL) {
937 		logit("channel_send_open: %d: bad id", id);
938 		return;
939 	}
940 	debug2("channel %d: send open", id);
941 	open_preamble(ssh, __func__, c, c->ctype);
942 	if ((r = sshpkt_send(ssh)) != 0)
943 		fatal("%s: channel %i: %s", __func__, c->self, ssh_err(r));
944 }
945 
946 void
947 channel_request_start(struct ssh *ssh, int id, char *service, int wantconfirm)
948 {
949 	Channel *c = channel_lookup(ssh, id);
950 	int r;
951 
952 	if (c == NULL) {
953 		logit("%s: %d: unknown channel id", __func__, id);
954 		return;
955 	}
956 	if (!c->have_remote_id)
957 		fatal(":%s: channel %d: no remote id", __func__, c->self);
958 
959 	debug2("channel %d: request %s confirm %d", id, service, wantconfirm);
960 	if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_REQUEST)) != 0 ||
961 	    (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
962 	    (r = sshpkt_put_cstring(ssh, service)) != 0 ||
963 	    (r = sshpkt_put_u8(ssh, wantconfirm)) != 0) {
964 		fatal("%s: channel %i: %s", __func__, c->self, ssh_err(r));
965 	}
966 }
967 
968 void
969 channel_register_status_confirm(struct ssh *ssh, int id,
970     channel_confirm_cb *cb, channel_confirm_abandon_cb *abandon_cb, void *ctx)
971 {
972 	struct channel_confirm *cc;
973 	Channel *c;
974 
975 	if ((c = channel_lookup(ssh, id)) == NULL)
976 		fatal("%s: %d: bad id", __func__, id);
977 
978 	cc = xcalloc(1, sizeof(*cc));
979 	cc->cb = cb;
980 	cc->abandon_cb = abandon_cb;
981 	cc->ctx = ctx;
982 	TAILQ_INSERT_TAIL(&c->status_confirms, cc, entry);
983 }
984 
985 void
986 channel_register_open_confirm(struct ssh *ssh, int id,
987     channel_open_fn *fn, void *ctx)
988 {
989 	Channel *c = channel_lookup(ssh, id);
990 
991 	if (c == NULL) {
992 		logit("%s: %d: bad id", __func__, id);
993 		return;
994 	}
995 	c->open_confirm = fn;
996 	c->open_confirm_ctx = ctx;
997 }
998 
999 void
1000 channel_register_cleanup(struct ssh *ssh, int id,
1001     channel_callback_fn *fn, int do_close)
1002 {
1003 	Channel *c = channel_by_id(ssh, id);
1004 
1005 	if (c == NULL) {
1006 		logit("%s: %d: bad id", __func__, id);
1007 		return;
1008 	}
1009 	c->detach_user = fn;
1010 	c->detach_close = do_close;
1011 }
1012 
1013 void
1014 channel_cancel_cleanup(struct ssh *ssh, int id)
1015 {
1016 	Channel *c = channel_by_id(ssh, id);
1017 
1018 	if (c == NULL) {
1019 		logit("%s: %d: bad id", __func__, id);
1020 		return;
1021 	}
1022 	c->detach_user = NULL;
1023 	c->detach_close = 0;
1024 }
1025 
1026 void
1027 channel_register_filter(struct ssh *ssh, int id, channel_infilter_fn *ifn,
1028     channel_outfilter_fn *ofn, channel_filter_cleanup_fn *cfn, void *ctx)
1029 {
1030 	Channel *c = channel_lookup(ssh, id);
1031 
1032 	if (c == NULL) {
1033 		logit("%s: %d: bad id", __func__, id);
1034 		return;
1035 	}
1036 	c->input_filter = ifn;
1037 	c->output_filter = ofn;
1038 	c->filter_ctx = ctx;
1039 	c->filter_cleanup = cfn;
1040 }
1041 
1042 void
1043 channel_set_fds(struct ssh *ssh, int id, int rfd, int wfd, int efd,
1044     int extusage, int nonblock, int is_tty, u_int window_max)
1045 {
1046 	Channel *c = channel_lookup(ssh, id);
1047 	int r;
1048 
1049 	if (c == NULL || c->type != SSH_CHANNEL_LARVAL)
1050 		fatal("channel_activate for non-larval channel %d.", id);
1051 	if (!c->have_remote_id)
1052 		fatal(":%s: channel %d: no remote id", __func__, c->self);
1053 
1054 	channel_register_fds(ssh, c, rfd, wfd, efd, extusage, nonblock, is_tty);
1055 	c->type = SSH_CHANNEL_OPEN;
1056 	c->local_window = c->local_window_max = window_max;
1057 
1058 	if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_WINDOW_ADJUST)) != 0 ||
1059 	    (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
1060 	    (r = sshpkt_put_u32(ssh, c->local_window)) != 0 ||
1061 	    (r = sshpkt_send(ssh)) != 0)
1062 		fatal("%s: channel %i: %s", __func__, c->self, ssh_err(r));
1063 }
1064 
1065 static void
1066 channel_pre_listener(struct ssh *ssh, Channel *c,
1067     fd_set *readset, fd_set *writeset)
1068 {
1069 	FD_SET(c->sock, readset);
1070 }
1071 
1072 static void
1073 channel_pre_connecting(struct ssh *ssh, Channel *c,
1074     fd_set *readset, fd_set *writeset)
1075 {
1076 	debug3("channel %d: waiting for connection", c->self);
1077 	FD_SET(c->sock, writeset);
1078 }
1079 
1080 static void
1081 channel_pre_open(struct ssh *ssh, Channel *c,
1082     fd_set *readset, fd_set *writeset)
1083 {
1084 	if (c->istate == CHAN_INPUT_OPEN &&
1085 	    c->remote_window > 0 &&
1086 	    sshbuf_len(c->input) < c->remote_window &&
1087 	    sshbuf_check_reserve(c->input, CHAN_RBUF) == 0)
1088 		FD_SET(c->rfd, readset);
1089 	if (c->ostate == CHAN_OUTPUT_OPEN ||
1090 	    c->ostate == CHAN_OUTPUT_WAIT_DRAIN) {
1091 		if (sshbuf_len(c->output) > 0) {
1092 			FD_SET(c->wfd, writeset);
1093 		} else if (c->ostate == CHAN_OUTPUT_WAIT_DRAIN) {
1094 			if (CHANNEL_EFD_OUTPUT_ACTIVE(c))
1095 				debug2("channel %d: "
1096 				    "obuf_empty delayed efd %d/(%zu)", c->self,
1097 				    c->efd, sshbuf_len(c->extended));
1098 			else
1099 				chan_obuf_empty(ssh, c);
1100 		}
1101 	}
1102 	/** XXX check close conditions, too */
1103 	if (c->efd != -1 && !(c->istate == CHAN_INPUT_CLOSED &&
1104 	    c->ostate == CHAN_OUTPUT_CLOSED)) {
1105 		if (c->extended_usage == CHAN_EXTENDED_WRITE &&
1106 		    sshbuf_len(c->extended) > 0)
1107 			FD_SET(c->efd, writeset);
1108 		else if (c->efd != -1 && !(c->flags & CHAN_EOF_SENT) &&
1109 		    (c->extended_usage == CHAN_EXTENDED_READ ||
1110 		    c->extended_usage == CHAN_EXTENDED_IGNORE) &&
1111 		    sshbuf_len(c->extended) < c->remote_window)
1112 			FD_SET(c->efd, readset);
1113 	}
1114 	/* XXX: What about efd? races? */
1115 }
1116 
1117 /*
1118  * This is a special state for X11 authentication spoofing.  An opened X11
1119  * connection (when authentication spoofing is being done) remains in this
1120  * state until the first packet has been completely read.  The authentication
1121  * data in that packet is then substituted by the real data if it matches the
1122  * fake data, and the channel is put into normal mode.
1123  * XXX All this happens at the client side.
1124  * Returns: 0 = need more data, -1 = wrong cookie, 1 = ok
1125  */
1126 static int
1127 x11_open_helper(struct ssh *ssh, struct sshbuf *b)
1128 {
1129 	struct ssh_channels *sc = ssh->chanctxt;
1130 	u_char *ucp;
1131 	u_int proto_len, data_len;
1132 
1133 	/* Is this being called after the refusal deadline? */
1134 	if (sc->x11_refuse_time != 0 &&
1135 	    (u_int)monotime() >= sc->x11_refuse_time) {
1136 		verbose("Rejected X11 connection after ForwardX11Timeout "
1137 		    "expired");
1138 		return -1;
1139 	}
1140 
1141 	/* Check if the fixed size part of the packet is in buffer. */
1142 	if (sshbuf_len(b) < 12)
1143 		return 0;
1144 
1145 	/* Parse the lengths of variable-length fields. */
1146 	ucp = sshbuf_mutable_ptr(b);
1147 	if (ucp[0] == 0x42) {	/* Byte order MSB first. */
1148 		proto_len = 256 * ucp[6] + ucp[7];
1149 		data_len = 256 * ucp[8] + ucp[9];
1150 	} else if (ucp[0] == 0x6c) {	/* Byte order LSB first. */
1151 		proto_len = ucp[6] + 256 * ucp[7];
1152 		data_len = ucp[8] + 256 * ucp[9];
1153 	} else {
1154 		debug2("Initial X11 packet contains bad byte order byte: 0x%x",
1155 		    ucp[0]);
1156 		return -1;
1157 	}
1158 
1159 	/* Check if the whole packet is in buffer. */
1160 	if (sshbuf_len(b) <
1161 	    12 + ((proto_len + 3) & ~3) + ((data_len + 3) & ~3))
1162 		return 0;
1163 
1164 	/* Check if authentication protocol matches. */
1165 	if (proto_len != strlen(sc->x11_saved_proto) ||
1166 	    memcmp(ucp + 12, sc->x11_saved_proto, proto_len) != 0) {
1167 		debug2("X11 connection uses different authentication protocol.");
1168 		return -1;
1169 	}
1170 	/* Check if authentication data matches our fake data. */
1171 	if (data_len != sc->x11_fake_data_len ||
1172 	    timingsafe_bcmp(ucp + 12 + ((proto_len + 3) & ~3),
1173 		sc->x11_fake_data, sc->x11_fake_data_len) != 0) {
1174 		debug2("X11 auth data does not match fake data.");
1175 		return -1;
1176 	}
1177 	/* Check fake data length */
1178 	if (sc->x11_fake_data_len != sc->x11_saved_data_len) {
1179 		error("X11 fake_data_len %d != saved_data_len %d",
1180 		    sc->x11_fake_data_len, sc->x11_saved_data_len);
1181 		return -1;
1182 	}
1183 	/*
1184 	 * Received authentication protocol and data match
1185 	 * our fake data. Substitute the fake data with real
1186 	 * data.
1187 	 */
1188 	memcpy(ucp + 12 + ((proto_len + 3) & ~3),
1189 	    sc->x11_saved_data, sc->x11_saved_data_len);
1190 	return 1;
1191 }
1192 
1193 static void
1194 channel_pre_x11_open(struct ssh *ssh, Channel *c,
1195     fd_set *readset, fd_set *writeset)
1196 {
1197 	int ret = x11_open_helper(ssh, c->output);
1198 
1199 	/* c->force_drain = 1; */
1200 
1201 	if (ret == 1) {
1202 		c->type = SSH_CHANNEL_OPEN;
1203 		channel_pre_open(ssh, c, readset, writeset);
1204 	} else if (ret == -1) {
1205 		logit("X11 connection rejected because of wrong authentication.");
1206 		debug2("X11 rejected %d i%d/o%d",
1207 		    c->self, c->istate, c->ostate);
1208 		chan_read_failed(ssh, c);
1209 		sshbuf_reset(c->input);
1210 		chan_ibuf_empty(ssh, c);
1211 		sshbuf_reset(c->output);
1212 		chan_write_failed(ssh, c);
1213 		debug2("X11 closed %d i%d/o%d", c->self, c->istate, c->ostate);
1214 	}
1215 }
1216 
1217 static void
1218 channel_pre_mux_client(struct ssh *ssh,
1219     Channel *c, fd_set *readset, fd_set *writeset)
1220 {
1221 	if (c->istate == CHAN_INPUT_OPEN && !c->mux_pause &&
1222 	    sshbuf_check_reserve(c->input, CHAN_RBUF) == 0)
1223 		FD_SET(c->rfd, readset);
1224 	if (c->istate == CHAN_INPUT_WAIT_DRAIN) {
1225 		/* clear buffer immediately (discard any partial packet) */
1226 		sshbuf_reset(c->input);
1227 		chan_ibuf_empty(ssh, c);
1228 		/* Start output drain. XXX just kill chan? */
1229 		chan_rcvd_oclose(ssh, c);
1230 	}
1231 	if (c->ostate == CHAN_OUTPUT_OPEN ||
1232 	    c->ostate == CHAN_OUTPUT_WAIT_DRAIN) {
1233 		if (sshbuf_len(c->output) > 0)
1234 			FD_SET(c->wfd, writeset);
1235 		else if (c->ostate == CHAN_OUTPUT_WAIT_DRAIN)
1236 			chan_obuf_empty(ssh, c);
1237 	}
1238 }
1239 
1240 /* try to decode a socks4 header */
1241 static int
1242 channel_decode_socks4(Channel *c, struct sshbuf *input, struct sshbuf *output)
1243 {
1244 	const u_char *p;
1245 	char *host;
1246 	u_int len, have, i, found, need;
1247 	char username[256];
1248 	struct {
1249 		u_int8_t version;
1250 		u_int8_t command;
1251 		u_int16_t dest_port;
1252 		struct in_addr dest_addr;
1253 	} s4_req, s4_rsp;
1254 	int r;
1255 
1256 	debug2("channel %d: decode socks4", c->self);
1257 
1258 	have = sshbuf_len(input);
1259 	len = sizeof(s4_req);
1260 	if (have < len)
1261 		return 0;
1262 	p = sshbuf_ptr(input);
1263 
1264 	need = 1;
1265 	/* SOCKS4A uses an invalid IP address 0.0.0.x */
1266 	if (p[4] == 0 && p[5] == 0 && p[6] == 0 && p[7] != 0) {
1267 		debug2("channel %d: socks4a request", c->self);
1268 		/* ... and needs an extra string (the hostname) */
1269 		need = 2;
1270 	}
1271 	/* Check for terminating NUL on the string(s) */
1272 	for (found = 0, i = len; i < have; i++) {
1273 		if (p[i] == '\0') {
1274 			found++;
1275 			if (found == need)
1276 				break;
1277 		}
1278 		if (i > 1024) {
1279 			/* the peer is probably sending garbage */
1280 			debug("channel %d: decode socks4: too long",
1281 			    c->self);
1282 			return -1;
1283 		}
1284 	}
1285 	if (found < need)
1286 		return 0;
1287 	if ((r = sshbuf_get(input, &s4_req.version, 1)) != 0 ||
1288 	    (r = sshbuf_get(input, &s4_req.command, 1)) != 0 ||
1289 	    (r = sshbuf_get(input, &s4_req.dest_port, 2)) != 0 ||
1290 	    (r = sshbuf_get(input, &s4_req.dest_addr, 4)) != 0) {
1291 		debug("channels %d: decode socks4: %s", c->self, ssh_err(r));
1292 		return -1;
1293 	}
1294 	have = sshbuf_len(input);
1295 	p = sshbuf_ptr(input);
1296 	if (memchr(p, '\0', have) == NULL) {
1297 		error("channel %d: decode socks4: user not nul terminated",
1298 		    c->self);
1299 		return -1;
1300 	}
1301 	len = strlen(p);
1302 	debug2("channel %d: decode socks4: user %s/%d", c->self, p, len);
1303 	len++; /* trailing '\0' */
1304 	strlcpy(username, p, sizeof(username));
1305 	if ((r = sshbuf_consume(input, len)) != 0) {
1306 		fatal("%s: channel %d: consume: %s", __func__,
1307 		    c->self, ssh_err(r));
1308 	}
1309 	free(c->path);
1310 	c->path = NULL;
1311 	if (need == 1) {			/* SOCKS4: one string */
1312 		host = inet_ntoa(s4_req.dest_addr);
1313 		c->path = xstrdup(host);
1314 	} else {				/* SOCKS4A: two strings */
1315 		have = sshbuf_len(input);
1316 		p = sshbuf_ptr(input);
1317 		if (memchr(p, '\0', have) == NULL) {
1318 			error("channel %d: decode socks4a: host not nul "
1319 			    "terminated", c->self);
1320 			return -1;
1321 		}
1322 		len = strlen(p);
1323 		debug2("channel %d: decode socks4a: host %s/%d",
1324 		    c->self, p, len);
1325 		len++;				/* trailing '\0' */
1326 		if (len > NI_MAXHOST) {
1327 			error("channel %d: hostname \"%.100s\" too long",
1328 			    c->self, p);
1329 			return -1;
1330 		}
1331 		c->path = xstrdup(p);
1332 		if ((r = sshbuf_consume(input, len)) != 0) {
1333 			fatal("%s: channel %d: consume: %s", __func__,
1334 			    c->self, ssh_err(r));
1335 		}
1336 	}
1337 	c->host_port = ntohs(s4_req.dest_port);
1338 
1339 	debug2("channel %d: dynamic request: socks4 host %s port %u command %u",
1340 	    c->self, c->path, c->host_port, s4_req.command);
1341 
1342 	if (s4_req.command != 1) {
1343 		debug("channel %d: cannot handle: %s cn %d",
1344 		    c->self, need == 1 ? "SOCKS4" : "SOCKS4A", s4_req.command);
1345 		return -1;
1346 	}
1347 	s4_rsp.version = 0;			/* vn: 0 for reply */
1348 	s4_rsp.command = 90;			/* cd: req granted */
1349 	s4_rsp.dest_port = 0;			/* ignored */
1350 	s4_rsp.dest_addr.s_addr = INADDR_ANY;	/* ignored */
1351 	if ((r = sshbuf_put(output, &s4_rsp, sizeof(s4_rsp))) != 0) {
1352 		fatal("%s: channel %d: append reply: %s", __func__,
1353 		    c->self, ssh_err(r));
1354 	}
1355 	return 1;
1356 }
1357 
1358 /* try to decode a socks5 header */
1359 #define SSH_SOCKS5_AUTHDONE	0x1000
1360 #define SSH_SOCKS5_NOAUTH	0x00
1361 #define SSH_SOCKS5_IPV4		0x01
1362 #define SSH_SOCKS5_DOMAIN	0x03
1363 #define SSH_SOCKS5_IPV6		0x04
1364 #define SSH_SOCKS5_CONNECT	0x01
1365 #define SSH_SOCKS5_SUCCESS	0x00
1366 
1367 static int
1368 channel_decode_socks5(Channel *c, struct sshbuf *input, struct sshbuf *output)
1369 {
1370 	/* XXX use get/put_u8 instead of trusting struct padding */
1371 	struct {
1372 		u_int8_t version;
1373 		u_int8_t command;
1374 		u_int8_t reserved;
1375 		u_int8_t atyp;
1376 	} s5_req, s5_rsp;
1377 	u_int16_t dest_port;
1378 	char dest_addr[255+1], ntop[INET6_ADDRSTRLEN];
1379 	const u_char *p;
1380 	u_int have, need, i, found, nmethods, addrlen, af;
1381 	int r;
1382 
1383 	debug2("channel %d: decode socks5", c->self);
1384 	p = sshbuf_ptr(input);
1385 	if (p[0] != 0x05)
1386 		return -1;
1387 	have = sshbuf_len(input);
1388 	if (!(c->flags & SSH_SOCKS5_AUTHDONE)) {
1389 		/* format: ver | nmethods | methods */
1390 		if (have < 2)
1391 			return 0;
1392 		nmethods = p[1];
1393 		if (have < nmethods + 2)
1394 			return 0;
1395 		/* look for method: "NO AUTHENTICATION REQUIRED" */
1396 		for (found = 0, i = 2; i < nmethods + 2; i++) {
1397 			if (p[i] == SSH_SOCKS5_NOAUTH) {
1398 				found = 1;
1399 				break;
1400 			}
1401 		}
1402 		if (!found) {
1403 			debug("channel %d: method SSH_SOCKS5_NOAUTH not found",
1404 			    c->self);
1405 			return -1;
1406 		}
1407 		if ((r = sshbuf_consume(input, nmethods + 2)) != 0) {
1408 			fatal("%s: channel %d: consume: %s", __func__,
1409 			    c->self, ssh_err(r));
1410 		}
1411 		/* version, method */
1412 		if ((r = sshbuf_put_u8(output, 0x05)) != 0 ||
1413 		    (r = sshbuf_put_u8(output, SSH_SOCKS5_NOAUTH)) != 0) {
1414 			fatal("%s: channel %d: append reply: %s", __func__,
1415 			    c->self, ssh_err(r));
1416 		}
1417 		c->flags |= SSH_SOCKS5_AUTHDONE;
1418 		debug2("channel %d: socks5 auth done", c->self);
1419 		return 0;				/* need more */
1420 	}
1421 	debug2("channel %d: socks5 post auth", c->self);
1422 	if (have < sizeof(s5_req)+1)
1423 		return 0;			/* need more */
1424 	memcpy(&s5_req, p, sizeof(s5_req));
1425 	if (s5_req.version != 0x05 ||
1426 	    s5_req.command != SSH_SOCKS5_CONNECT ||
1427 	    s5_req.reserved != 0x00) {
1428 		debug2("channel %d: only socks5 connect supported", c->self);
1429 		return -1;
1430 	}
1431 	switch (s5_req.atyp){
1432 	case SSH_SOCKS5_IPV4:
1433 		addrlen = 4;
1434 		af = AF_INET;
1435 		break;
1436 	case SSH_SOCKS5_DOMAIN:
1437 		addrlen = p[sizeof(s5_req)];
1438 		af = -1;
1439 		break;
1440 	case SSH_SOCKS5_IPV6:
1441 		addrlen = 16;
1442 		af = AF_INET6;
1443 		break;
1444 	default:
1445 		debug2("channel %d: bad socks5 atyp %d", c->self, s5_req.atyp);
1446 		return -1;
1447 	}
1448 	need = sizeof(s5_req) + addrlen + 2;
1449 	if (s5_req.atyp == SSH_SOCKS5_DOMAIN)
1450 		need++;
1451 	if (have < need)
1452 		return 0;
1453 	if ((r = sshbuf_consume(input, sizeof(s5_req))) != 0) {
1454 		fatal("%s: channel %d: consume: %s", __func__,
1455 		    c->self, ssh_err(r));
1456 	}
1457 	if (s5_req.atyp == SSH_SOCKS5_DOMAIN) {
1458 		/* host string length */
1459 		if ((r = sshbuf_consume(input, 1)) != 0) {
1460 			fatal("%s: channel %d: consume: %s", __func__,
1461 			    c->self, ssh_err(r));
1462 		}
1463 	}
1464 	if ((r = sshbuf_get(input, &dest_addr, addrlen)) != 0 ||
1465 	    (r = sshbuf_get(input, &dest_port, 2)) != 0) {
1466 		debug("channel %d: parse addr/port: %s", c->self, ssh_err(r));
1467 		return -1;
1468 	}
1469 	dest_addr[addrlen] = '\0';
1470 	free(c->path);
1471 	c->path = NULL;
1472 	if (s5_req.atyp == SSH_SOCKS5_DOMAIN) {
1473 		if (addrlen >= NI_MAXHOST) {
1474 			error("channel %d: dynamic request: socks5 hostname "
1475 			    "\"%.100s\" too long", c->self, dest_addr);
1476 			return -1;
1477 		}
1478 		c->path = xstrdup(dest_addr);
1479 	} else {
1480 		if (inet_ntop(af, dest_addr, ntop, sizeof(ntop)) == NULL)
1481 			return -1;
1482 		c->path = xstrdup(ntop);
1483 	}
1484 	c->host_port = ntohs(dest_port);
1485 
1486 	debug2("channel %d: dynamic request: socks5 host %s port %u command %u",
1487 	    c->self, c->path, c->host_port, s5_req.command);
1488 
1489 	s5_rsp.version = 0x05;
1490 	s5_rsp.command = SSH_SOCKS5_SUCCESS;
1491 	s5_rsp.reserved = 0;			/* ignored */
1492 	s5_rsp.atyp = SSH_SOCKS5_IPV4;
1493 	dest_port = 0;				/* ignored */
1494 
1495 	if ((r = sshbuf_put(output, &s5_rsp, sizeof(s5_rsp))) != 0 ||
1496 	    (r = sshbuf_put_u32(output, ntohl(INADDR_ANY))) != 0 ||
1497 	    (r = sshbuf_put(output, &dest_port, sizeof(dest_port))) != 0)
1498 		fatal("%s: channel %d: append reply: %s", __func__,
1499 		    c->self, ssh_err(r));
1500 	return 1;
1501 }
1502 
1503 Channel *
1504 channel_connect_stdio_fwd(struct ssh *ssh,
1505     const char *host_to_connect, u_short port_to_connect, int in, int out)
1506 {
1507 	Channel *c;
1508 
1509 	debug("%s %s:%d", __func__, host_to_connect, port_to_connect);
1510 
1511 	c = channel_new(ssh, "stdio-forward", SSH_CHANNEL_OPENING, in, out,
1512 	    -1, CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT,
1513 	    0, "stdio-forward", /*nonblock*/0);
1514 
1515 	c->path = xstrdup(host_to_connect);
1516 	c->host_port = port_to_connect;
1517 	c->listening_port = 0;
1518 	c->force_drain = 1;
1519 
1520 	channel_register_fds(ssh, c, in, out, -1, 0, 1, 0);
1521 	port_open_helper(ssh, c, "direct-tcpip");
1522 
1523 	return c;
1524 }
1525 
1526 /* dynamic port forwarding */
1527 static void
1528 channel_pre_dynamic(struct ssh *ssh, Channel *c,
1529     fd_set *readset, fd_set *writeset)
1530 {
1531 	const u_char *p;
1532 	u_int have;
1533 	int ret;
1534 
1535 	have = sshbuf_len(c->input);
1536 	debug2("channel %d: pre_dynamic: have %d", c->self, have);
1537 	/* sshbuf_dump(c->input, stderr); */
1538 	/* check if the fixed size part of the packet is in buffer. */
1539 	if (have < 3) {
1540 		/* need more */
1541 		FD_SET(c->sock, readset);
1542 		return;
1543 	}
1544 	/* try to guess the protocol */
1545 	p = sshbuf_ptr(c->input);
1546 	/* XXX sshbuf_peek_u8? */
1547 	switch (p[0]) {
1548 	case 0x04:
1549 		ret = channel_decode_socks4(c, c->input, c->output);
1550 		break;
1551 	case 0x05:
1552 		ret = channel_decode_socks5(c, c->input, c->output);
1553 		break;
1554 	default:
1555 		ret = -1;
1556 		break;
1557 	}
1558 	if (ret < 0) {
1559 		chan_mark_dead(ssh, c);
1560 	} else if (ret == 0) {
1561 		debug2("channel %d: pre_dynamic: need more", c->self);
1562 		/* need more */
1563 		FD_SET(c->sock, readset);
1564 		if (sshbuf_len(c->output))
1565 			FD_SET(c->sock, writeset);
1566 	} else {
1567 		/* switch to the next state */
1568 		c->type = SSH_CHANNEL_OPENING;
1569 		port_open_helper(ssh, c, "direct-tcpip");
1570 	}
1571 }
1572 
1573 /* simulate read-error */
1574 static void
1575 rdynamic_close(struct ssh *ssh, Channel *c)
1576 {
1577 	c->type = SSH_CHANNEL_OPEN;
1578 	chan_read_failed(ssh, c);
1579 	sshbuf_reset(c->input);
1580 	chan_ibuf_empty(ssh, c);
1581 	sshbuf_reset(c->output);
1582 	chan_write_failed(ssh, c);
1583 }
1584 
1585 /* reverse dynamic port forwarding */
1586 static void
1587 channel_before_prepare_select_rdynamic(struct ssh *ssh, Channel *c)
1588 {
1589 	const u_char *p;
1590 	u_int have, len;
1591 	int r, ret;
1592 
1593 	have = sshbuf_len(c->output);
1594 	debug2("channel %d: pre_rdynamic: have %d", c->self, have);
1595 	/* sshbuf_dump(c->output, stderr); */
1596 	/* EOF received */
1597 	if (c->flags & CHAN_EOF_RCVD) {
1598 		if ((r = sshbuf_consume(c->output, have)) != 0) {
1599 			fatal("%s: channel %d: consume: %s",
1600 			    __func__, c->self, ssh_err(r));
1601 		}
1602 		rdynamic_close(ssh, c);
1603 		return;
1604 	}
1605 	/* check if the fixed size part of the packet is in buffer. */
1606 	if (have < 3)
1607 		return;
1608 	/* try to guess the protocol */
1609 	p = sshbuf_ptr(c->output);
1610 	switch (p[0]) {
1611 	case 0x04:
1612 		/* switch input/output for reverse forwarding */
1613 		ret = channel_decode_socks4(c, c->output, c->input);
1614 		break;
1615 	case 0x05:
1616 		ret = channel_decode_socks5(c, c->output, c->input);
1617 		break;
1618 	default:
1619 		ret = -1;
1620 		break;
1621 	}
1622 	if (ret < 0) {
1623 		rdynamic_close(ssh, c);
1624 	} else if (ret == 0) {
1625 		debug2("channel %d: pre_rdynamic: need more", c->self);
1626 		/* send socks request to peer */
1627 		len = sshbuf_len(c->input);
1628 		if (len > 0 && len < c->remote_window) {
1629 			if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_DATA)) != 0 ||
1630 			    (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
1631 			    (r = sshpkt_put_stringb(ssh, c->input)) != 0 ||
1632 			    (r = sshpkt_send(ssh)) != 0) {
1633 				fatal("%s: channel %i: rdynamic: %s", __func__,
1634 				    c->self, ssh_err(r));
1635 			}
1636 			if ((r = sshbuf_consume(c->input, len)) != 0) {
1637 				fatal("%s: channel %d: consume: %s",
1638 				    __func__, c->self, ssh_err(r));
1639 			}
1640 			c->remote_window -= len;
1641 		}
1642 	} else if (rdynamic_connect_finish(ssh, c) < 0) {
1643 		/* the connect failed */
1644 		rdynamic_close(ssh, c);
1645 	}
1646 }
1647 
1648 /* This is our fake X11 server socket. */
1649 static void
1650 channel_post_x11_listener(struct ssh *ssh, Channel *c,
1651     fd_set *readset, fd_set *writeset)
1652 {
1653 	Channel *nc;
1654 	struct sockaddr_storage addr;
1655 	int r, newsock, oerrno, remote_port;
1656 	socklen_t addrlen;
1657 	char buf[16384], *remote_ipaddr;
1658 
1659 	if (!FD_ISSET(c->sock, readset))
1660 		return;
1661 
1662 	debug("X11 connection requested.");
1663 	addrlen = sizeof(addr);
1664 	newsock = accept(c->sock, (struct sockaddr *)&addr, &addrlen);
1665 	if (c->single_connection) {
1666 		oerrno = errno;
1667 		debug2("single_connection: closing X11 listener.");
1668 		channel_close_fd(ssh, &c->sock);
1669 		chan_mark_dead(ssh, c);
1670 		errno = oerrno;
1671 	}
1672 	if (newsock == -1) {
1673 		if (errno != EINTR && errno != EWOULDBLOCK &&
1674 		    errno != ECONNABORTED)
1675 			error("accept: %.100s", strerror(errno));
1676 		if (errno == EMFILE || errno == ENFILE)
1677 			c->notbefore = monotime() + 1;
1678 		return;
1679 	}
1680 	set_nodelay(newsock);
1681 	remote_ipaddr = get_peer_ipaddr(newsock);
1682 	remote_port = get_peer_port(newsock);
1683 	snprintf(buf, sizeof buf, "X11 connection from %.200s port %d",
1684 	    remote_ipaddr, remote_port);
1685 
1686 	nc = channel_new(ssh, "accepted x11 socket",
1687 	    SSH_CHANNEL_OPENING, newsock, newsock, -1,
1688 	    c->local_window_max, c->local_maxpacket, 0, buf, 1);
1689 	open_preamble(ssh, __func__, nc, "x11");
1690 	if ((r = sshpkt_put_cstring(ssh, remote_ipaddr)) != 0 ||
1691 	    (r = sshpkt_put_u32(ssh, remote_port)) != 0) {
1692 		fatal("%s: channel %i: reply %s", __func__,
1693 		    c->self, ssh_err(r));
1694 	}
1695 	if ((r = sshpkt_send(ssh)) != 0)
1696 		fatal("%s: channel %i: send %s", __func__, c->self, ssh_err(r));
1697 	free(remote_ipaddr);
1698 }
1699 
1700 static void
1701 port_open_helper(struct ssh *ssh, Channel *c, char *rtype)
1702 {
1703 	char *local_ipaddr = get_local_ipaddr(c->sock);
1704 	int local_port = c->sock == -1 ? 65536 : get_local_port(c->sock);
1705 	char *remote_ipaddr = get_peer_ipaddr(c->sock);
1706 	int remote_port = get_peer_port(c->sock);
1707 	int r;
1708 
1709 	if (remote_port == -1) {
1710 		/* Fake addr/port to appease peers that validate it (Tectia) */
1711 		free(remote_ipaddr);
1712 		remote_ipaddr = xstrdup("127.0.0.1");
1713 		remote_port = 65535;
1714 	}
1715 
1716 	free(c->remote_name);
1717 	xasprintf(&c->remote_name,
1718 	    "%s: listening port %d for %.100s port %d, "
1719 	    "connect from %.200s port %d to %.100s port %d",
1720 	    rtype, c->listening_port, c->path, c->host_port,
1721 	    remote_ipaddr, remote_port, local_ipaddr, local_port);
1722 
1723 	open_preamble(ssh, __func__, c, rtype);
1724 	if (strcmp(rtype, "direct-tcpip") == 0) {
1725 		/* target host, port */
1726 		if ((r = sshpkt_put_cstring(ssh, c->path)) != 0 ||
1727 		    (r = sshpkt_put_u32(ssh, c->host_port)) != 0) {
1728 			fatal("%s: channel %i: reply %s", __func__,
1729 			    c->self, ssh_err(r));
1730 		}
1731 	} else if (strcmp(rtype, "direct-streamlocal@openssh.com") == 0) {
1732 		/* target path */
1733 		if ((r = sshpkt_put_cstring(ssh, c->path)) != 0) {
1734 			fatal("%s: channel %i: reply %s", __func__,
1735 			    c->self, ssh_err(r));
1736 		}
1737 	} else if (strcmp(rtype, "forwarded-streamlocal@openssh.com") == 0) {
1738 		/* listen path */
1739 		if ((r = sshpkt_put_cstring(ssh, c->path)) != 0) {
1740 			fatal("%s: channel %i: reply %s", __func__,
1741 			    c->self, ssh_err(r));
1742 		}
1743 	} else {
1744 		/* listen address, port */
1745 		if ((r = sshpkt_put_cstring(ssh, c->path)) != 0 ||
1746 		    (r = sshpkt_put_u32(ssh, local_port)) != 0) {
1747 			fatal("%s: channel %i: reply %s", __func__,
1748 			    c->self, ssh_err(r));
1749 		}
1750 	}
1751 	if (strcmp(rtype, "forwarded-streamlocal@openssh.com") == 0) {
1752 		/* reserved for future owner/mode info */
1753 		if ((r = sshpkt_put_cstring(ssh, "")) != 0) {
1754 			fatal("%s: channel %i: reply %s", __func__,
1755 			    c->self, ssh_err(r));
1756 		}
1757 	} else {
1758 		/* originator host and port */
1759 		if ((r = sshpkt_put_cstring(ssh, remote_ipaddr)) != 0 ||
1760 		    (r = sshpkt_put_u32(ssh, (u_int)remote_port)) != 0) {
1761 			fatal("%s: channel %i: reply %s", __func__,
1762 			    c->self, ssh_err(r));
1763 		}
1764 	}
1765 	if ((r = sshpkt_send(ssh)) != 0)
1766 		fatal("%s: channel %i: send %s", __func__, c->self, ssh_err(r));
1767 	free(remote_ipaddr);
1768 	free(local_ipaddr);
1769 }
1770 
1771 void
1772 channel_set_x11_refuse_time(struct ssh *ssh, u_int refuse_time)
1773 {
1774 	ssh->chanctxt->x11_refuse_time = refuse_time;
1775 }
1776 
1777 /*
1778  * This socket is listening for connections to a forwarded TCP/IP port.
1779  */
1780 static void
1781 channel_post_port_listener(struct ssh *ssh, Channel *c,
1782     fd_set *readset, fd_set *writeset)
1783 {
1784 	Channel *nc;
1785 	struct sockaddr_storage addr;
1786 	int newsock, nextstate;
1787 	socklen_t addrlen;
1788 	char *rtype;
1789 
1790 	if (!FD_ISSET(c->sock, readset))
1791 		return;
1792 
1793 	debug("Connection to port %d forwarding to %.100s port %d requested.",
1794 	    c->listening_port, c->path, c->host_port);
1795 
1796 	if (c->type == SSH_CHANNEL_RPORT_LISTENER) {
1797 		nextstate = SSH_CHANNEL_OPENING;
1798 		rtype = "forwarded-tcpip";
1799 	} else if (c->type == SSH_CHANNEL_RUNIX_LISTENER) {
1800 		nextstate = SSH_CHANNEL_OPENING;
1801 		rtype = "forwarded-streamlocal@openssh.com";
1802 	} else if (c->host_port == PORT_STREAMLOCAL) {
1803 		nextstate = SSH_CHANNEL_OPENING;
1804 		rtype = "direct-streamlocal@openssh.com";
1805 	} else if (c->host_port == 0) {
1806 		nextstate = SSH_CHANNEL_DYNAMIC;
1807 		rtype = "dynamic-tcpip";
1808 	} else {
1809 		nextstate = SSH_CHANNEL_OPENING;
1810 		rtype = "direct-tcpip";
1811 	}
1812 
1813 	addrlen = sizeof(addr);
1814 	newsock = accept(c->sock, (struct sockaddr *)&addr, &addrlen);
1815 	if (newsock == -1) {
1816 		if (errno != EINTR && errno != EWOULDBLOCK &&
1817 		    errno != ECONNABORTED)
1818 			error("accept: %.100s", strerror(errno));
1819 		if (errno == EMFILE || errno == ENFILE)
1820 			c->notbefore = monotime() + 1;
1821 		return;
1822 	}
1823 	if (c->host_port != PORT_STREAMLOCAL)
1824 		set_nodelay(newsock);
1825 	nc = channel_new(ssh, rtype, nextstate, newsock, newsock, -1,
1826 	    c->local_window_max, c->local_maxpacket, 0, rtype, 1);
1827 	nc->listening_port = c->listening_port;
1828 	nc->host_port = c->host_port;
1829 	if (c->path != NULL)
1830 		nc->path = xstrdup(c->path);
1831 
1832 	if (nextstate != SSH_CHANNEL_DYNAMIC)
1833 		port_open_helper(ssh, nc, rtype);
1834 }
1835 
1836 /*
1837  * This is the authentication agent socket listening for connections from
1838  * clients.
1839  */
1840 static void
1841 channel_post_auth_listener(struct ssh *ssh, Channel *c,
1842     fd_set *readset, fd_set *writeset)
1843 {
1844 	Channel *nc;
1845 	int r, newsock;
1846 	struct sockaddr_storage addr;
1847 	socklen_t addrlen;
1848 
1849 	if (!FD_ISSET(c->sock, readset))
1850 		return;
1851 
1852 	addrlen = sizeof(addr);
1853 	newsock = accept(c->sock, (struct sockaddr *)&addr, &addrlen);
1854 	if (newsock == -1) {
1855 		error("accept from auth socket: %.100s", strerror(errno));
1856 		if (errno == EMFILE || errno == ENFILE)
1857 			c->notbefore = monotime() + 1;
1858 		return;
1859 	}
1860 	nc = channel_new(ssh, "accepted auth socket",
1861 	    SSH_CHANNEL_OPENING, newsock, newsock, -1,
1862 	    c->local_window_max, c->local_maxpacket,
1863 	    0, "accepted auth socket", 1);
1864 	open_preamble(ssh, __func__, nc, "auth-agent@openssh.com");
1865 	if ((r = sshpkt_send(ssh)) != 0)
1866 		fatal("%s: channel %i: %s", __func__, c->self, ssh_err(r));
1867 }
1868 
1869 static void
1870 channel_post_connecting(struct ssh *ssh, Channel *c,
1871     fd_set *readset, fd_set *writeset)
1872 {
1873 	int err = 0, sock, isopen, r;
1874 	socklen_t sz = sizeof(err);
1875 
1876 	if (!FD_ISSET(c->sock, writeset))
1877 		return;
1878 	if (!c->have_remote_id)
1879 		fatal(":%s: channel %d: no remote id", __func__, c->self);
1880 	/* for rdynamic the OPEN_CONFIRMATION has been sent already */
1881 	isopen = (c->type == SSH_CHANNEL_RDYNAMIC_FINISH);
1882 	if (getsockopt(c->sock, SOL_SOCKET, SO_ERROR, &err, &sz) == -1) {
1883 		err = errno;
1884 		error("getsockopt SO_ERROR failed");
1885 	}
1886 	if (err == 0) {
1887 		debug("channel %d: connected to %s port %d",
1888 		    c->self, c->connect_ctx.host, c->connect_ctx.port);
1889 		channel_connect_ctx_free(&c->connect_ctx);
1890 		c->type = SSH_CHANNEL_OPEN;
1891 		if (isopen) {
1892 			/* no message necessary */
1893 		} else {
1894 			if ((r = sshpkt_start(ssh,
1895 			    SSH2_MSG_CHANNEL_OPEN_CONFIRMATION)) != 0 ||
1896 			    (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
1897 			    (r = sshpkt_put_u32(ssh, c->self)) != 0 ||
1898 			    (r = sshpkt_put_u32(ssh, c->local_window)) != 0 ||
1899 			    (r = sshpkt_put_u32(ssh, c->local_maxpacket))
1900 			    != 0)
1901 				fatal("%s: channel %i: confirm: %s", __func__,
1902 				    c->self, ssh_err(r));
1903 			if ((r = sshpkt_send(ssh)) != 0)
1904 				fatal("%s: channel %i: %s", __func__, c->self,
1905 				    ssh_err(r));
1906 		}
1907 	} else {
1908 		debug("channel %d: connection failed: %s",
1909 		    c->self, strerror(err));
1910 		/* Try next address, if any */
1911 		if ((sock = connect_next(&c->connect_ctx)) > 0) {
1912 			close(c->sock);
1913 			c->sock = c->rfd = c->wfd = sock;
1914 			channel_find_maxfd(ssh->chanctxt);
1915 			return;
1916 		}
1917 		/* Exhausted all addresses */
1918 		error("connect_to %.100s port %d: failed.",
1919 		    c->connect_ctx.host, c->connect_ctx.port);
1920 		channel_connect_ctx_free(&c->connect_ctx);
1921 		if (isopen) {
1922 			rdynamic_close(ssh, c);
1923 		} else {
1924 			if ((r = sshpkt_start(ssh,
1925 			    SSH2_MSG_CHANNEL_OPEN_FAILURE)) != 0 ||
1926 			    (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
1927 			    (r = sshpkt_put_u32(ssh,
1928 			    SSH2_OPEN_CONNECT_FAILED)) != 0 ||
1929 			    (r = sshpkt_put_cstring(ssh, strerror(err))) != 0 ||
1930 			    (r = sshpkt_put_cstring(ssh, "")) != 0) {
1931 				fatal("%s: channel %i: failure: %s", __func__,
1932 				    c->self, ssh_err(r));
1933 			}
1934 			if ((r = sshpkt_send(ssh)) != 0)
1935 				fatal("%s: channel %i: %s", __func__, c->self,
1936 				    ssh_err(r));
1937 			chan_mark_dead(ssh, c);
1938 		}
1939 	}
1940 }
1941 
1942 static int
1943 channel_handle_rfd(struct ssh *ssh, Channel *c,
1944     fd_set *readset, fd_set *writeset)
1945 {
1946 	char buf[CHAN_RBUF];
1947 	ssize_t len;
1948 	int r, force;
1949 
1950 	force = c->isatty && c->detach_close && c->istate != CHAN_INPUT_CLOSED;
1951 
1952 	if (c->rfd == -1 || (!force && !FD_ISSET(c->rfd, readset)))
1953 		return 1;
1954 
1955 	errno = 0;
1956 	len = read(c->rfd, buf, sizeof(buf));
1957 	if (len == -1 && (errno == EINTR ||
1958 	    ((errno == EAGAIN || errno == EWOULDBLOCK) && !force)))
1959 		return 1;
1960 #ifndef PTY_ZEROREAD
1961  	if (len <= 0) {
1962 #else
1963 	if ((!c->isatty && len <= 0) ||
1964 	    (c->isatty && (len < 0 || (len == 0 && errno != 0)))) {
1965 #endif
1966 		debug2("channel %d: read<=0 rfd %d len %zd",
1967 		    c->self, c->rfd, len);
1968 		if (c->type != SSH_CHANNEL_OPEN) {
1969 			debug2("channel %d: not open", c->self);
1970 			chan_mark_dead(ssh, c);
1971 			return -1;
1972 		} else {
1973 			chan_read_failed(ssh, c);
1974 		}
1975 		return -1;
1976 	}
1977 	if (c->input_filter != NULL) {
1978 		if (c->input_filter(ssh, c, buf, len) == -1) {
1979 			debug2("channel %d: filter stops", c->self);
1980 			chan_read_failed(ssh, c);
1981 		}
1982 	} else if (c->datagram) {
1983 		if ((r = sshbuf_put_string(c->input, buf, len)) != 0)
1984 			fatal("%s: channel %d: put datagram: %s", __func__,
1985 			    c->self, ssh_err(r));
1986 	} else if ((r = sshbuf_put(c->input, buf, len)) != 0) {
1987 		fatal("%s: channel %d: put data: %s", __func__,
1988 		    c->self, ssh_err(r));
1989 	}
1990 	return 1;
1991 }
1992 
1993 static int
1994 channel_handle_wfd(struct ssh *ssh, Channel *c,
1995    fd_set *readset, fd_set *writeset)
1996 {
1997 	struct termios tio;
1998 	u_char *data = NULL, *buf; /* XXX const; need filter API change */
1999 	size_t dlen, olen = 0;
2000 	int r, len;
2001 
2002 	if (c->wfd == -1 || !FD_ISSET(c->wfd, writeset) ||
2003 	    sshbuf_len(c->output) == 0)
2004 		return 1;
2005 
2006 	/* Send buffered output data to the socket. */
2007 	olen = sshbuf_len(c->output);
2008 	if (c->output_filter != NULL) {
2009 		if ((buf = c->output_filter(ssh, c, &data, &dlen)) == NULL) {
2010 			debug2("channel %d: filter stops", c->self);
2011 			if (c->type != SSH_CHANNEL_OPEN)
2012 				chan_mark_dead(ssh, c);
2013 			else
2014 				chan_write_failed(ssh, c);
2015 			return -1;
2016 		}
2017 	} else if (c->datagram) {
2018 		if ((r = sshbuf_get_string(c->output, &data, &dlen)) != 0)
2019 			fatal("%s: channel %d: get datagram: %s", __func__,
2020 			    c->self, ssh_err(r));
2021 		buf = data;
2022 	} else {
2023 		buf = data = sshbuf_mutable_ptr(c->output);
2024 		dlen = sshbuf_len(c->output);
2025 	}
2026 
2027 	if (c->datagram) {
2028 		/* ignore truncated writes, datagrams might get lost */
2029 		len = write(c->wfd, buf, dlen);
2030 		free(data);
2031 		if (len == -1 && (errno == EINTR || errno == EAGAIN ||
2032 		    errno == EWOULDBLOCK))
2033 			return 1;
2034 		if (len <= 0)
2035 			goto write_fail;
2036 		goto out;
2037 	}
2038 
2039 #ifdef _AIX
2040 	/* XXX: Later AIX versions can't push as much data to tty */
2041 	if (c->wfd_isatty)
2042 		dlen = MIN(dlen, 8*1024);
2043 #endif
2044 
2045 	len = write(c->wfd, buf, dlen);
2046 	if (len == -1 &&
2047 	    (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK))
2048 		return 1;
2049 	if (len <= 0) {
2050  write_fail:
2051 		if (c->type != SSH_CHANNEL_OPEN) {
2052 			debug2("channel %d: not open", c->self);
2053 			chan_mark_dead(ssh, c);
2054 			return -1;
2055 		} else {
2056 			chan_write_failed(ssh, c);
2057 		}
2058 		return -1;
2059 	}
2060 #ifndef BROKEN_TCGETATTR_ICANON
2061 	if (c->isatty && dlen >= 1 && buf[0] != '\r') {
2062 		if (tcgetattr(c->wfd, &tio) == 0 &&
2063 		    !(tio.c_lflag & ECHO) && (tio.c_lflag & ICANON)) {
2064 			/*
2065 			 * Simulate echo to reduce the impact of
2066 			 * traffic analysis. We need to match the
2067 			 * size of a SSH2_MSG_CHANNEL_DATA message
2068 			 * (4 byte channel id + buf)
2069 			 */
2070 			if ((r = sshpkt_msg_ignore(ssh, 4+len)) != 0 ||
2071 			    (r = sshpkt_send(ssh)) != 0)
2072 				fatal("%s: channel %d: ignore: %s",
2073 				    __func__, c->self, ssh_err(r));
2074 		}
2075 	}
2076 #endif /* BROKEN_TCGETATTR_ICANON */
2077 	if ((r = sshbuf_consume(c->output, len)) != 0) {
2078 		fatal("%s: channel %d: consume: %s",
2079 		    __func__, c->self, ssh_err(r));
2080 	}
2081  out:
2082 	c->local_consumed += olen - sshbuf_len(c->output);
2083 
2084 	return 1;
2085 }
2086 
2087 static int
2088 channel_handle_efd_write(struct ssh *ssh, Channel *c,
2089     fd_set *readset, fd_set *writeset)
2090 {
2091 	int r;
2092 	ssize_t len;
2093 
2094 	if (!FD_ISSET(c->efd, writeset) || sshbuf_len(c->extended) == 0)
2095 		return 1;
2096 
2097 	len = write(c->efd, sshbuf_ptr(c->extended),
2098 	    sshbuf_len(c->extended));
2099 	debug2("channel %d: written %zd to efd %d", c->self, len, c->efd);
2100 	if (len == -1 && (errno == EINTR || errno == EAGAIN ||
2101 	    errno == EWOULDBLOCK))
2102 		return 1;
2103 	if (len <= 0) {
2104 		debug2("channel %d: closing write-efd %d", c->self, c->efd);
2105 		channel_close_fd(ssh, &c->efd);
2106 	} else {
2107 		if ((r = sshbuf_consume(c->extended, len)) != 0) {
2108 			fatal("%s: channel %d: consume: %s",
2109 			    __func__, c->self, ssh_err(r));
2110 		}
2111 		c->local_consumed += len;
2112 	}
2113 	return 1;
2114 }
2115 
2116 static int
2117 channel_handle_efd_read(struct ssh *ssh, Channel *c,
2118     fd_set *readset, fd_set *writeset)
2119 {
2120 	char buf[CHAN_RBUF];
2121 	ssize_t len;
2122 	int r, force;
2123 
2124 	force = c->isatty && c->detach_close && c->istate != CHAN_INPUT_CLOSED;
2125 
2126 	if (c->efd == -1 || (!force && !FD_ISSET(c->efd, readset)))
2127 		return 1;
2128 
2129 	len = read(c->efd, buf, sizeof(buf));
2130 	debug2("channel %d: read %zd from efd %d", c->self, len, c->efd);
2131 	if (len == -1 && (errno == EINTR || ((errno == EAGAIN ||
2132 	    errno == EWOULDBLOCK) && !force)))
2133 		return 1;
2134 	if (len <= 0) {
2135 		debug2("channel %d: closing read-efd %d",
2136 		    c->self, c->efd);
2137 		channel_close_fd(ssh, &c->efd);
2138 	} else {
2139 		if (c->extended_usage == CHAN_EXTENDED_IGNORE) {
2140 			debug3("channel %d: discard efd",
2141 			    c->self);
2142 		} else if ((r = sshbuf_put(c->extended, buf, len)) != 0) {
2143 			fatal("%s: channel %d: append: %s",
2144 			    __func__, c->self, ssh_err(r));
2145 		}
2146 	}
2147 	return 1;
2148 }
2149 
2150 static int
2151 channel_handle_efd(struct ssh *ssh, Channel *c,
2152     fd_set *readset, fd_set *writeset)
2153 {
2154 	if (c->efd == -1)
2155 		return 1;
2156 
2157 	/** XXX handle drain efd, too */
2158 
2159 	if (c->extended_usage == CHAN_EXTENDED_WRITE)
2160 		return channel_handle_efd_write(ssh, c, readset, writeset);
2161 	else if (c->extended_usage == CHAN_EXTENDED_READ ||
2162 	    c->extended_usage == CHAN_EXTENDED_IGNORE)
2163 		return channel_handle_efd_read(ssh, c, readset, writeset);
2164 
2165 	return 1;
2166 }
2167 
2168 static int
2169 channel_check_window(struct ssh *ssh, Channel *c)
2170 {
2171 	int r;
2172 
2173 	if (c->type == SSH_CHANNEL_OPEN &&
2174 	    !(c->flags & (CHAN_CLOSE_SENT|CHAN_CLOSE_RCVD)) &&
2175 	    ((c->local_window_max - c->local_window >
2176 	    c->local_maxpacket*3) ||
2177 	    c->local_window < c->local_window_max/2) &&
2178 	    c->local_consumed > 0) {
2179 		if (!c->have_remote_id)
2180 			fatal(":%s: channel %d: no remote id",
2181 			    __func__, c->self);
2182 		if ((r = sshpkt_start(ssh,
2183 		    SSH2_MSG_CHANNEL_WINDOW_ADJUST)) != 0 ||
2184 		    (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
2185 		    (r = sshpkt_put_u32(ssh, c->local_consumed)) != 0 ||
2186 		    (r = sshpkt_send(ssh)) != 0) {
2187 			fatal("%s: channel %i: %s", __func__,
2188 			    c->self, ssh_err(r));
2189 		}
2190 		debug2("channel %d: window %d sent adjust %d",
2191 		    c->self, c->local_window,
2192 		    c->local_consumed);
2193 		c->local_window += c->local_consumed;
2194 		c->local_consumed = 0;
2195 	}
2196 	return 1;
2197 }
2198 
2199 static void
2200 channel_post_open(struct ssh *ssh, Channel *c,
2201     fd_set *readset, fd_set *writeset)
2202 {
2203 	channel_handle_rfd(ssh, c, readset, writeset);
2204 	channel_handle_wfd(ssh, c, readset, writeset);
2205 	channel_handle_efd(ssh, c, readset, writeset);
2206 	channel_check_window(ssh, c);
2207 }
2208 
2209 static u_int
2210 read_mux(struct ssh *ssh, Channel *c, u_int need)
2211 {
2212 	char buf[CHAN_RBUF];
2213 	ssize_t len;
2214 	u_int rlen;
2215 	int r;
2216 
2217 	if (sshbuf_len(c->input) < need) {
2218 		rlen = need - sshbuf_len(c->input);
2219 		len = read(c->rfd, buf, MINIMUM(rlen, CHAN_RBUF));
2220 		if (len == -1 && (errno == EINTR || errno == EAGAIN))
2221 			return sshbuf_len(c->input);
2222 		if (len <= 0) {
2223 			debug2("channel %d: ctl read<=0 rfd %d len %zd",
2224 			    c->self, c->rfd, len);
2225 			chan_read_failed(ssh, c);
2226 			return 0;
2227 		} else if ((r = sshbuf_put(c->input, buf, len)) != 0) {
2228 			fatal("%s: channel %d: append: %s",
2229 			    __func__, c->self, ssh_err(r));
2230 		}
2231 	}
2232 	return sshbuf_len(c->input);
2233 }
2234 
2235 static void
2236 channel_post_mux_client_read(struct ssh *ssh, Channel *c,
2237     fd_set *readset, fd_set *writeset)
2238 {
2239 	u_int need;
2240 
2241 	if (c->rfd == -1 || !FD_ISSET(c->rfd, readset))
2242 		return;
2243 	if (c->istate != CHAN_INPUT_OPEN && c->istate != CHAN_INPUT_WAIT_DRAIN)
2244 		return;
2245 	if (c->mux_pause)
2246 		return;
2247 
2248 	/*
2249 	 * Don't not read past the precise end of packets to
2250 	 * avoid disrupting fd passing.
2251 	 */
2252 	if (read_mux(ssh, c, 4) < 4) /* read header */
2253 		return;
2254 	/* XXX sshbuf_peek_u32 */
2255 	need = PEEK_U32(sshbuf_ptr(c->input));
2256 #define CHANNEL_MUX_MAX_PACKET	(256 * 1024)
2257 	if (need > CHANNEL_MUX_MAX_PACKET) {
2258 		debug2("channel %d: packet too big %u > %u",
2259 		    c->self, CHANNEL_MUX_MAX_PACKET, need);
2260 		chan_rcvd_oclose(ssh, c);
2261 		return;
2262 	}
2263 	if (read_mux(ssh, c, need + 4) < need + 4) /* read body */
2264 		return;
2265 	if (c->mux_rcb(ssh, c) != 0) {
2266 		debug("channel %d: mux_rcb failed", c->self);
2267 		chan_mark_dead(ssh, c);
2268 		return;
2269 	}
2270 }
2271 
2272 static void
2273 channel_post_mux_client_write(struct ssh *ssh, Channel *c,
2274     fd_set *readset, fd_set *writeset)
2275 {
2276 	ssize_t len;
2277 	int r;
2278 
2279 	if (c->wfd == -1 || !FD_ISSET(c->wfd, writeset) ||
2280 	    sshbuf_len(c->output) == 0)
2281 		return;
2282 
2283 	len = write(c->wfd, sshbuf_ptr(c->output), sshbuf_len(c->output));
2284 	if (len == -1 && (errno == EINTR || errno == EAGAIN))
2285 		return;
2286 	if (len <= 0) {
2287 		chan_mark_dead(ssh, c);
2288 		return;
2289 	}
2290 	if ((r = sshbuf_consume(c->output, len)) != 0)
2291 		fatal("%s: channel %d: consume: %s", __func__,
2292 		    c->self, ssh_err(r));
2293 }
2294 
2295 static void
2296 channel_post_mux_client(struct ssh *ssh, Channel *c,
2297     fd_set *readset, fd_set *writeset)
2298 {
2299 	channel_post_mux_client_read(ssh, c, readset, writeset);
2300 	channel_post_mux_client_write(ssh, c, readset, writeset);
2301 }
2302 
2303 static void
2304 channel_post_mux_listener(struct ssh *ssh, Channel *c,
2305     fd_set *readset, fd_set *writeset)
2306 {
2307 	Channel *nc;
2308 	struct sockaddr_storage addr;
2309 	socklen_t addrlen;
2310 	int newsock;
2311 	uid_t euid;
2312 	gid_t egid;
2313 
2314 	if (!FD_ISSET(c->sock, readset))
2315 		return;
2316 
2317 	debug("multiplexing control connection");
2318 
2319 	/*
2320 	 * Accept connection on control socket
2321 	 */
2322 	memset(&addr, 0, sizeof(addr));
2323 	addrlen = sizeof(addr);
2324 	if ((newsock = accept(c->sock, (struct sockaddr*)&addr,
2325 	    &addrlen)) == -1) {
2326 		error("%s accept: %s", __func__, strerror(errno));
2327 		if (errno == EMFILE || errno == ENFILE)
2328 			c->notbefore = monotime() + 1;
2329 		return;
2330 	}
2331 
2332 	if (getpeereid(newsock, &euid, &egid) == -1) {
2333 		error("%s getpeereid failed: %s", __func__,
2334 		    strerror(errno));
2335 		close(newsock);
2336 		return;
2337 	}
2338 	if ((euid != 0) && (getuid() != euid)) {
2339 		error("multiplex uid mismatch: peer euid %u != uid %u",
2340 		    (u_int)euid, (u_int)getuid());
2341 		close(newsock);
2342 		return;
2343 	}
2344 	nc = channel_new(ssh, "multiplex client", SSH_CHANNEL_MUX_CLIENT,
2345 	    newsock, newsock, -1, c->local_window_max,
2346 	    c->local_maxpacket, 0, "mux-control", 1);
2347 	nc->mux_rcb = c->mux_rcb;
2348 	debug3("%s: new mux channel %d fd %d", __func__, nc->self, nc->sock);
2349 	/* establish state */
2350 	nc->mux_rcb(ssh, nc);
2351 	/* mux state transitions must not elicit protocol messages */
2352 	nc->flags |= CHAN_LOCAL;
2353 }
2354 
2355 static void
2356 channel_handler_init(struct ssh_channels *sc)
2357 {
2358 	chan_fn **pre, **post;
2359 
2360 	if ((pre = calloc(SSH_CHANNEL_MAX_TYPE, sizeof(*pre))) == NULL ||
2361 	   (post = calloc(SSH_CHANNEL_MAX_TYPE, sizeof(*post))) == NULL)
2362 		fatal("%s: allocation failed", __func__);
2363 
2364 	pre[SSH_CHANNEL_OPEN] =			&channel_pre_open;
2365 	pre[SSH_CHANNEL_X11_OPEN] =		&channel_pre_x11_open;
2366 	pre[SSH_CHANNEL_PORT_LISTENER] =	&channel_pre_listener;
2367 	pre[SSH_CHANNEL_RPORT_LISTENER] =	&channel_pre_listener;
2368 	pre[SSH_CHANNEL_UNIX_LISTENER] =	&channel_pre_listener;
2369 	pre[SSH_CHANNEL_RUNIX_LISTENER] =	&channel_pre_listener;
2370 	pre[SSH_CHANNEL_X11_LISTENER] =		&channel_pre_listener;
2371 	pre[SSH_CHANNEL_AUTH_SOCKET] =		&channel_pre_listener;
2372 	pre[SSH_CHANNEL_CONNECTING] =		&channel_pre_connecting;
2373 	pre[SSH_CHANNEL_DYNAMIC] =		&channel_pre_dynamic;
2374 	pre[SSH_CHANNEL_RDYNAMIC_FINISH] =	&channel_pre_connecting;
2375 	pre[SSH_CHANNEL_MUX_LISTENER] =		&channel_pre_listener;
2376 	pre[SSH_CHANNEL_MUX_CLIENT] =		&channel_pre_mux_client;
2377 
2378 	post[SSH_CHANNEL_OPEN] =		&channel_post_open;
2379 	post[SSH_CHANNEL_PORT_LISTENER] =	&channel_post_port_listener;
2380 	post[SSH_CHANNEL_RPORT_LISTENER] =	&channel_post_port_listener;
2381 	post[SSH_CHANNEL_UNIX_LISTENER] =	&channel_post_port_listener;
2382 	post[SSH_CHANNEL_RUNIX_LISTENER] =	&channel_post_port_listener;
2383 	post[SSH_CHANNEL_X11_LISTENER] =	&channel_post_x11_listener;
2384 	post[SSH_CHANNEL_AUTH_SOCKET] =		&channel_post_auth_listener;
2385 	post[SSH_CHANNEL_CONNECTING] =		&channel_post_connecting;
2386 	post[SSH_CHANNEL_DYNAMIC] =		&channel_post_open;
2387 	post[SSH_CHANNEL_RDYNAMIC_FINISH] =	&channel_post_connecting;
2388 	post[SSH_CHANNEL_MUX_LISTENER] =	&channel_post_mux_listener;
2389 	post[SSH_CHANNEL_MUX_CLIENT] =		&channel_post_mux_client;
2390 
2391 	sc->channel_pre = pre;
2392 	sc->channel_post = post;
2393 }
2394 
2395 /* gc dead channels */
2396 static void
2397 channel_garbage_collect(struct ssh *ssh, Channel *c)
2398 {
2399 	if (c == NULL)
2400 		return;
2401 	if (c->detach_user != NULL) {
2402 		if (!chan_is_dead(ssh, c, c->detach_close))
2403 			return;
2404 
2405 		debug2("channel %d: gc: notify user", c->self);
2406 		c->detach_user(ssh, c->self, NULL);
2407 		/* if we still have a callback */
2408 		if (c->detach_user != NULL)
2409 			return;
2410 		debug2("channel %d: gc: user detached", c->self);
2411 	}
2412 	if (!chan_is_dead(ssh, c, 1))
2413 		return;
2414 	debug2("channel %d: garbage collecting", c->self);
2415 	channel_free(ssh, c);
2416 }
2417 
2418 enum channel_table { CHAN_PRE, CHAN_POST };
2419 
2420 static void
2421 channel_handler(struct ssh *ssh, int table,
2422     fd_set *readset, fd_set *writeset, time_t *unpause_secs)
2423 {
2424 	struct ssh_channels *sc = ssh->chanctxt;
2425 	chan_fn **ftab = table == CHAN_PRE ? sc->channel_pre : sc->channel_post;
2426 	u_int i, oalloc;
2427 	Channel *c;
2428 	time_t now;
2429 
2430 	now = monotime();
2431 	if (unpause_secs != NULL)
2432 		*unpause_secs = 0;
2433 	for (i = 0, oalloc = sc->channels_alloc; i < oalloc; i++) {
2434 		c = sc->channels[i];
2435 		if (c == NULL)
2436 			continue;
2437 		if (c->delayed) {
2438 			if (table == CHAN_PRE)
2439 				c->delayed = 0;
2440 			else
2441 				continue;
2442 		}
2443 		if (ftab[c->type] != NULL) {
2444 			/*
2445 			 * Run handlers that are not paused.
2446 			 */
2447 			if (c->notbefore <= now)
2448 				(*ftab[c->type])(ssh, c, readset, writeset);
2449 			else if (unpause_secs != NULL) {
2450 				/*
2451 				 * Collect the time that the earliest
2452 				 * channel comes off pause.
2453 				 */
2454 				debug3("%s: chan %d: skip for %d more seconds",
2455 				    __func__, c->self,
2456 				    (int)(c->notbefore - now));
2457 				if (*unpause_secs == 0 ||
2458 				    (c->notbefore - now) < *unpause_secs)
2459 					*unpause_secs = c->notbefore - now;
2460 			}
2461 		}
2462 		channel_garbage_collect(ssh, c);
2463 	}
2464 	if (unpause_secs != NULL && *unpause_secs != 0)
2465 		debug3("%s: first channel unpauses in %d seconds",
2466 		    __func__, (int)*unpause_secs);
2467 }
2468 
2469 /*
2470  * Create sockets before allocating the select bitmasks.
2471  * This is necessary for things that need to happen after reading
2472  * the network-input but before channel_prepare_select().
2473  */
2474 static void
2475 channel_before_prepare_select(struct ssh *ssh)
2476 {
2477 	struct ssh_channels *sc = ssh->chanctxt;
2478 	Channel *c;
2479 	u_int i, oalloc;
2480 
2481 	for (i = 0, oalloc = sc->channels_alloc; i < oalloc; i++) {
2482 		c = sc->channels[i];
2483 		if (c == NULL)
2484 			continue;
2485 		if (c->type == SSH_CHANNEL_RDYNAMIC_OPEN)
2486 			channel_before_prepare_select_rdynamic(ssh, c);
2487 	}
2488 }
2489 
2490 /*
2491  * Allocate/update select bitmasks and add any bits relevant to channels in
2492  * select bitmasks.
2493  */
2494 void
2495 channel_prepare_select(struct ssh *ssh, fd_set **readsetp, fd_set **writesetp,
2496     int *maxfdp, u_int *nallocp, time_t *minwait_secs)
2497 {
2498 	u_int n, sz, nfdset;
2499 
2500 	channel_before_prepare_select(ssh); /* might update channel_max_fd */
2501 
2502 	n = MAXIMUM(*maxfdp, ssh->chanctxt->channel_max_fd);
2503 
2504 	nfdset = howmany(n+1, NFDBITS);
2505 	/* Explicitly test here, because xrealloc isn't always called */
2506 	if (nfdset && SIZE_MAX / nfdset < sizeof(fd_mask))
2507 		fatal("channel_prepare_select: max_fd (%d) is too large", n);
2508 	sz = nfdset * sizeof(fd_mask);
2509 
2510 	/* perhaps check sz < nalloc/2 and shrink? */
2511 	if (*readsetp == NULL || sz > *nallocp) {
2512 		*readsetp = xreallocarray(*readsetp, nfdset, sizeof(fd_mask));
2513 		*writesetp = xreallocarray(*writesetp, nfdset, sizeof(fd_mask));
2514 		*nallocp = sz;
2515 	}
2516 	*maxfdp = n;
2517 	memset(*readsetp, 0, sz);
2518 	memset(*writesetp, 0, sz);
2519 
2520 	if (!ssh_packet_is_rekeying(ssh))
2521 		channel_handler(ssh, CHAN_PRE, *readsetp, *writesetp,
2522 		    minwait_secs);
2523 }
2524 
2525 /*
2526  * After select, perform any appropriate operations for channels which have
2527  * events pending.
2528  */
2529 void
2530 channel_after_select(struct ssh *ssh, fd_set *readset, fd_set *writeset)
2531 {
2532 	channel_handler(ssh, CHAN_POST, readset, writeset, NULL);
2533 }
2534 
2535 /*
2536  * Enqueue data for channels with open or draining c->input.
2537  */
2538 static void
2539 channel_output_poll_input_open(struct ssh *ssh, Channel *c)
2540 {
2541 	size_t len, plen;
2542 	const u_char *pkt;
2543 	int r;
2544 
2545 	if ((len = sshbuf_len(c->input)) == 0) {
2546 		if (c->istate == CHAN_INPUT_WAIT_DRAIN) {
2547 			/*
2548 			 * input-buffer is empty and read-socket shutdown:
2549 			 * tell peer, that we will not send more data:
2550 			 * send IEOF.
2551 			 * hack for extended data: delay EOF if EFD still
2552 			 * in use.
2553 			 */
2554 			if (CHANNEL_EFD_INPUT_ACTIVE(c))
2555 				debug2("channel %d: "
2556 				    "ibuf_empty delayed efd %d/(%zu)",
2557 				    c->self, c->efd, sshbuf_len(c->extended));
2558 			else
2559 				chan_ibuf_empty(ssh, c);
2560 		}
2561 		return;
2562 	}
2563 
2564 	if (!c->have_remote_id)
2565 		fatal(":%s: channel %d: no remote id", __func__, c->self);
2566 
2567 	if (c->datagram) {
2568 		/* Check datagram will fit; drop if not */
2569 		if ((r = sshbuf_get_string_direct(c->input, &pkt, &plen)) != 0)
2570 			fatal("%s: channel %d: get datagram: %s", __func__,
2571 			    c->self, ssh_err(r));
2572 		/*
2573 		 * XXX this does tail-drop on the datagram queue which is
2574 		 * usually suboptimal compared to head-drop. Better to have
2575 		 * backpressure at read time? (i.e. read + discard)
2576 		 */
2577 		if (plen > c->remote_window || plen > c->remote_maxpacket) {
2578 			debug("channel %d: datagram too big", c->self);
2579 			return;
2580 		}
2581 		/* Enqueue it */
2582 		if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_DATA)) != 0 ||
2583 		    (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
2584 		    (r = sshpkt_put_string(ssh, pkt, plen)) != 0 ||
2585 		    (r = sshpkt_send(ssh)) != 0) {
2586 			fatal("%s: channel %i: datagram: %s", __func__,
2587 			    c->self, ssh_err(r));
2588 		}
2589 		c->remote_window -= plen;
2590 		return;
2591 	}
2592 
2593 	/* Enqueue packet for buffered data. */
2594 	if (len > c->remote_window)
2595 		len = c->remote_window;
2596 	if (len > c->remote_maxpacket)
2597 		len = c->remote_maxpacket;
2598 	if (len == 0)
2599 		return;
2600 	if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_DATA)) != 0 ||
2601 	    (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
2602 	    (r = sshpkt_put_string(ssh, sshbuf_ptr(c->input), len)) != 0 ||
2603 	    (r = sshpkt_send(ssh)) != 0) {
2604 		fatal("%s: channel %i: data: %s", __func__,
2605 		    c->self, ssh_err(r));
2606 	}
2607 	if ((r = sshbuf_consume(c->input, len)) != 0)
2608 		fatal("%s: channel %i: consume: %s", __func__,
2609 		    c->self, ssh_err(r));
2610 	c->remote_window -= len;
2611 }
2612 
2613 /*
2614  * Enqueue data for channels with open c->extended in read mode.
2615  */
2616 static void
2617 channel_output_poll_extended_read(struct ssh *ssh, Channel *c)
2618 {
2619 	size_t len;
2620 	int r;
2621 
2622 	if ((len = sshbuf_len(c->extended)) == 0)
2623 		return;
2624 
2625 	debug2("channel %d: rwin %u elen %zu euse %d", c->self,
2626 	    c->remote_window, sshbuf_len(c->extended), c->extended_usage);
2627 	if (len > c->remote_window)
2628 		len = c->remote_window;
2629 	if (len > c->remote_maxpacket)
2630 		len = c->remote_maxpacket;
2631 	if (len == 0)
2632 		return;
2633 	if (!c->have_remote_id)
2634 		fatal(":%s: channel %d: no remote id", __func__, c->self);
2635 	if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_EXTENDED_DATA)) != 0 ||
2636 	    (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
2637 	    (r = sshpkt_put_u32(ssh, SSH2_EXTENDED_DATA_STDERR)) != 0 ||
2638 	    (r = sshpkt_put_string(ssh, sshbuf_ptr(c->extended), len)) != 0 ||
2639 	    (r = sshpkt_send(ssh)) != 0) {
2640 		fatal("%s: channel %i: data: %s", __func__,
2641 		    c->self, ssh_err(r));
2642 	}
2643 	if ((r = sshbuf_consume(c->extended, len)) != 0)
2644 		fatal("%s: channel %i: consume: %s", __func__,
2645 		    c->self, ssh_err(r));
2646 	c->remote_window -= len;
2647 	debug2("channel %d: sent ext data %zu", c->self, len);
2648 }
2649 
2650 /* If there is data to send to the connection, enqueue some of it now. */
2651 void
2652 channel_output_poll(struct ssh *ssh)
2653 {
2654 	struct ssh_channels *sc = ssh->chanctxt;
2655 	Channel *c;
2656 	u_int i;
2657 
2658 	for (i = 0; i < sc->channels_alloc; i++) {
2659 		c = sc->channels[i];
2660 		if (c == NULL)
2661 			continue;
2662 
2663 		/*
2664 		 * We are only interested in channels that can have buffered
2665 		 * incoming data.
2666 		 */
2667 		if (c->type != SSH_CHANNEL_OPEN)
2668 			continue;
2669 		if ((c->flags & (CHAN_CLOSE_SENT|CHAN_CLOSE_RCVD))) {
2670 			/* XXX is this true? */
2671 			debug3("channel %d: will not send data after close",
2672 			    c->self);
2673 			continue;
2674 		}
2675 
2676 		/* Get the amount of buffered data for this channel. */
2677 		if (c->istate == CHAN_INPUT_OPEN ||
2678 		    c->istate == CHAN_INPUT_WAIT_DRAIN)
2679 			channel_output_poll_input_open(ssh, c);
2680 		/* Send extended data, i.e. stderr */
2681 		if (!(c->flags & CHAN_EOF_SENT) &&
2682 		    c->extended_usage == CHAN_EXTENDED_READ)
2683 			channel_output_poll_extended_read(ssh, c);
2684 	}
2685 }
2686 
2687 /* -- mux proxy support  */
2688 
2689 /*
2690  * When multiplexing channel messages for mux clients we have to deal
2691  * with downstream messages from the mux client and upstream messages
2692  * from the ssh server:
2693  * 1) Handling downstream messages is straightforward and happens
2694  *    in channel_proxy_downstream():
2695  *    - We forward all messages (mostly) unmodified to the server.
2696  *    - However, in order to route messages from upstream to the correct
2697  *      downstream client, we have to replace the channel IDs used by the
2698  *      mux clients with a unique channel ID because the mux clients might
2699  *      use conflicting channel IDs.
2700  *    - so we inspect and change both SSH2_MSG_CHANNEL_OPEN and
2701  *      SSH2_MSG_CHANNEL_OPEN_CONFIRMATION messages, create a local
2702  *      SSH_CHANNEL_MUX_PROXY channel and replace the mux clients ID
2703  *      with the newly allocated channel ID.
2704  * 2) Upstream messages are received by matching SSH_CHANNEL_MUX_PROXY
2705  *    channels and processed by channel_proxy_upstream(). The local channel ID
2706  *    is then translated back to the original mux client ID.
2707  * 3) In both cases we need to keep track of matching SSH2_MSG_CHANNEL_CLOSE
2708  *    messages so we can clean up SSH_CHANNEL_MUX_PROXY channels.
2709  * 4) The SSH_CHANNEL_MUX_PROXY channels also need to closed when the
2710  *    downstream mux client are removed.
2711  * 5) Handling SSH2_MSG_CHANNEL_OPEN messages from the upstream server
2712  *    requires more work, because they are not addressed to a specific
2713  *    channel. E.g. client_request_forwarded_tcpip() needs to figure
2714  *    out whether the request is addressed to the local client or a
2715  *    specific downstream client based on the listen-address/port.
2716  * 6) Agent and X11-Forwarding have a similar problem and are currently
2717  *    not supported as the matching session/channel cannot be identified
2718  *    easily.
2719  */
2720 
2721 /*
2722  * receive packets from downstream mux clients:
2723  * channel callback fired on read from mux client, creates
2724  * SSH_CHANNEL_MUX_PROXY channels and translates channel IDs
2725  * on channel creation.
2726  */
2727 int
2728 channel_proxy_downstream(struct ssh *ssh, Channel *downstream)
2729 {
2730 	Channel *c = NULL;
2731 	struct sshbuf *original = NULL, *modified = NULL;
2732 	const u_char *cp;
2733 	char *ctype = NULL, *listen_host = NULL;
2734 	u_char type;
2735 	size_t have;
2736 	int ret = -1, r;
2737 	u_int id, remote_id, listen_port;
2738 
2739 	/* sshbuf_dump(downstream->input, stderr); */
2740 	if ((r = sshbuf_get_string_direct(downstream->input, &cp, &have))
2741 	    != 0) {
2742 		error("%s: malformed message: %s", __func__, ssh_err(r));
2743 		return -1;
2744 	}
2745 	if (have < 2) {
2746 		error("%s: short message", __func__);
2747 		return -1;
2748 	}
2749 	type = cp[1];
2750 	/* skip padlen + type */
2751 	cp += 2;
2752 	have -= 2;
2753 	if (ssh_packet_log_type(type))
2754 		debug3("%s: channel %u: down->up: type %u", __func__,
2755 		    downstream->self, type);
2756 
2757 	switch (type) {
2758 	case SSH2_MSG_CHANNEL_OPEN:
2759 		if ((original = sshbuf_from(cp, have)) == NULL ||
2760 		    (modified = sshbuf_new()) == NULL) {
2761 			error("%s: alloc", __func__);
2762 			goto out;
2763 		}
2764 		if ((r = sshbuf_get_cstring(original, &ctype, NULL)) != 0 ||
2765 		    (r = sshbuf_get_u32(original, &id)) != 0) {
2766 			error("%s: parse error %s", __func__, ssh_err(r));
2767 			goto out;
2768 		}
2769 		c = channel_new(ssh, "mux proxy", SSH_CHANNEL_MUX_PROXY,
2770 		   -1, -1, -1, 0, 0, 0, ctype, 1);
2771 		c->mux_ctx = downstream;	/* point to mux client */
2772 		c->mux_downstream_id = id;	/* original downstream id */
2773 		if ((r = sshbuf_put_cstring(modified, ctype)) != 0 ||
2774 		    (r = sshbuf_put_u32(modified, c->self)) != 0 ||
2775 		    (r = sshbuf_putb(modified, original)) != 0) {
2776 			error("%s: compose error %s", __func__, ssh_err(r));
2777 			channel_free(ssh, c);
2778 			goto out;
2779 		}
2780 		break;
2781 	case SSH2_MSG_CHANNEL_OPEN_CONFIRMATION:
2782 		/*
2783 		 * Almost the same as SSH2_MSG_CHANNEL_OPEN, except then we
2784 		 * need to parse 'remote_id' instead of 'ctype'.
2785 		 */
2786 		if ((original = sshbuf_from(cp, have)) == NULL ||
2787 		    (modified = sshbuf_new()) == NULL) {
2788 			error("%s: alloc", __func__);
2789 			goto out;
2790 		}
2791 		if ((r = sshbuf_get_u32(original, &remote_id)) != 0 ||
2792 		    (r = sshbuf_get_u32(original, &id)) != 0) {
2793 			error("%s: parse error %s", __func__, ssh_err(r));
2794 			goto out;
2795 		}
2796 		c = channel_new(ssh, "mux proxy", SSH_CHANNEL_MUX_PROXY,
2797 		   -1, -1, -1, 0, 0, 0, "mux-down-connect", 1);
2798 		c->mux_ctx = downstream;	/* point to mux client */
2799 		c->mux_downstream_id = id;
2800 		c->remote_id = remote_id;
2801 		c->have_remote_id = 1;
2802 		if ((r = sshbuf_put_u32(modified, remote_id)) != 0 ||
2803 		    (r = sshbuf_put_u32(modified, c->self)) != 0 ||
2804 		    (r = sshbuf_putb(modified, original)) != 0) {
2805 			error("%s: compose error %s", __func__, ssh_err(r));
2806 			channel_free(ssh, c);
2807 			goto out;
2808 		}
2809 		break;
2810 	case SSH2_MSG_GLOBAL_REQUEST:
2811 		if ((original = sshbuf_from(cp, have)) == NULL) {
2812 			error("%s: alloc", __func__);
2813 			goto out;
2814 		}
2815 		if ((r = sshbuf_get_cstring(original, &ctype, NULL)) != 0) {
2816 			error("%s: parse error %s", __func__, ssh_err(r));
2817 			goto out;
2818 		}
2819 		if (strcmp(ctype, "tcpip-forward") != 0) {
2820 			error("%s: unsupported request %s", __func__, ctype);
2821 			goto out;
2822 		}
2823 		if ((r = sshbuf_get_u8(original, NULL)) != 0 ||
2824 		    (r = sshbuf_get_cstring(original, &listen_host, NULL)) != 0 ||
2825 		    (r = sshbuf_get_u32(original, &listen_port)) != 0) {
2826 			error("%s: parse error %s", __func__, ssh_err(r));
2827 			goto out;
2828 		}
2829 		if (listen_port > 65535) {
2830 			error("%s: tcpip-forward for %s: bad port %u",
2831 			    __func__, listen_host, listen_port);
2832 			goto out;
2833 		}
2834 		/* Record that connection to this host/port is permitted. */
2835 		permission_set_add(ssh, FORWARD_USER, FORWARD_LOCAL, "<mux>", -1,
2836 		    listen_host, NULL, (int)listen_port, downstream);
2837 		listen_host = NULL;
2838 		break;
2839 	case SSH2_MSG_CHANNEL_CLOSE:
2840 		if (have < 4)
2841 			break;
2842 		remote_id = PEEK_U32(cp);
2843 		if ((c = channel_by_remote_id(