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      1 /*
      2  * Copyright (c) 1999, 2000, 2001, 2002 Markus Friedl.  All rights reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions
      6  * are met:
      7  * 1. Redistributions of source code must retain the above copyright
      8  *    notice, this list of conditions and the following disclaimer.
      9  * 2. Redistributions in binary form must reproduce the above copyright
     10  *    notice, this list of conditions and the following disclaimer in the
     11  *    documentation and/or other materials provided with the distribution.
     12  *
     13  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     14  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     15  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     16  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     17  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     18  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     19  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     20  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     21  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     22  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     23  */
     24 
     25 #include "includes.h"
     26 RCSID("$OpenBSD: nchan.c,v 1.47 2002/06/19 00:27:55 deraadt Exp $");
     27 
     28 #pragma ident	"%Z%%M%	%I%	%E% SMI"
     29 
     30 #include "ssh1.h"
     31 #include "ssh2.h"
     32 #include "buffer.h"
     33 #include "packet.h"
     34 #include "channels.h"
     35 #include "compat.h"
     36 #include "log.h"
     37 
     38 /*
     39  * SSH Protocol 1.5 aka New Channel Protocol
     40  * Thanks to Martina, Axel and everyone who left Erlangen, leaving me bored.
     41  * Written by Markus Friedl in October 1999
     42  *
     43  * Protocol versions 1.3 and 1.5 differ in the handshake protocol used for the
     44  * tear down of channels:
     45  *
     46  * 1.3:	strict request-ack-protocol:
     47  * 	CLOSE	->
     48  * 		<-  CLOSE_CONFIRM
     49  *
     50  * 1.5:	uses variations of:
     51  * 	IEOF	->
     52  * 		<-  OCLOSE
     53  * 		<-  IEOF
     54  * 	OCLOSE	->
     55  * 	i.e. both sides have to close the channel
     56  *
     57  * 2.0: the EOF messages are optional
     58  *
     59  * See the debugging output from 'ssh -v' and 'sshd -d' of
     60  * ssh-1.2.27 as an example.
     61  *
     62  */
     63 
     64 /* functions manipulating channel states */
     65 /*
     66  * EVENTS update channel input/output states execute ACTIONS
     67  */
     68 /*
     69  * ACTIONS: should never update the channel states
     70  */
     71 static void	chan_send_ieof1(Channel *);
     72 static void	chan_send_oclose1(Channel *);
     73 static void	chan_send_close2(Channel *);
     74 static void	chan_send_eof2(Channel *);
     75 
     76 /* helper */
     77 static void	chan_shutdown_write(Channel *);
     78 static void	chan_shutdown_read(Channel *);
     79 
     80 static char *ostates[] = { "open", "drain", "wait_ieof", "closed" };
     81 static char *istates[] = { "open", "drain", "wait_oclose", "closed" };
     82 
     83 static void
     84 chan_set_istate(Channel *c, u_int next)
     85 {
     86 	if (c->istate > CHAN_INPUT_CLOSED || next > CHAN_INPUT_CLOSED)
     87 		fatal("chan_set_istate: bad state %d -> %d", c->istate, next);
     88 	debug("channel %d: input %s -> %s", c->self, istates[c->istate],
     89 	    istates[next]);
     90 	c->istate = next;
     91 }
     92 static void
     93 chan_set_ostate(Channel *c, u_int next)
     94 {
     95 	if (c->ostate > CHAN_OUTPUT_CLOSED || next > CHAN_OUTPUT_CLOSED)
     96 		fatal("chan_set_ostate: bad state %d -> %d", c->ostate, next);
     97 	debug("channel %d: output %s -> %s", c->self, ostates[c->ostate],
     98 	    ostates[next]);
     99 	c->ostate = next;
    100 }
    101 
    102 /*
    103  * SSH1 specific implementation of event functions
    104  */
    105 
    106 static void
    107 chan_rcvd_oclose1(Channel *c)
    108 {
    109 	debug("channel %d: rcvd oclose", c->self);
    110 	switch (c->istate) {
    111 	case CHAN_INPUT_WAIT_OCLOSE:
    112 		chan_set_istate(c, CHAN_INPUT_CLOSED);
    113 		break;
    114 	case CHAN_INPUT_OPEN:
    115 		chan_shutdown_read(c);
    116 		chan_send_ieof1(c);
    117 		chan_set_istate(c, CHAN_INPUT_CLOSED);
    118 		break;
    119 	case CHAN_INPUT_WAIT_DRAIN:
    120 		/* both local read_failed and remote write_failed  */
    121 		chan_send_ieof1(c);
    122 		chan_set_istate(c, CHAN_INPUT_CLOSED);
    123 		break;
    124 	default:
    125 		error("channel %d: protocol error: rcvd_oclose for istate %d",
    126 		    c->self, c->istate);
    127 		return;
    128 	}
    129 }
    130 void
    131 chan_read_failed(Channel *c)
    132 {
    133 	debug("channel %d: read failed", c->self);
    134 	switch (c->istate) {
    135 	case CHAN_INPUT_OPEN:
    136 		chan_shutdown_read(c);
    137 		chan_set_istate(c, CHAN_INPUT_WAIT_DRAIN);
    138 		break;
    139 	default:
    140 		error("channel %d: chan_read_failed for istate %d",
    141 		    c->self, c->istate);
    142 		break;
    143 	}
    144 }
    145 void
    146 chan_ibuf_empty(Channel *c)
    147 {
    148 	debug("channel %d: ibuf empty", c->self);
    149 	if (buffer_len(&c->input)) {
    150 		error("channel %d: chan_ibuf_empty for non empty buffer",
    151 		    c->self);
    152 		return;
    153 	}
    154 	switch (c->istate) {
    155 	case CHAN_INPUT_WAIT_DRAIN:
    156 		if (compat20) {
    157 			if (!(c->flags & CHAN_CLOSE_SENT))
    158 				chan_send_eof2(c);
    159 			chan_set_istate(c, CHAN_INPUT_CLOSED);
    160 		} else {
    161 			chan_send_ieof1(c);
    162 			chan_set_istate(c, CHAN_INPUT_WAIT_OCLOSE);
    163 		}
    164 		break;
    165 	default:
    166 		error("channel %d: chan_ibuf_empty for istate %d",
    167 		    c->self, c->istate);
    168 		break;
    169 	}
    170 }
    171 static void
    172 chan_rcvd_ieof1(Channel *c)
    173 {
    174 	debug("channel %d: rcvd ieof", c->self);
    175 	switch (c->ostate) {
    176 	case CHAN_OUTPUT_OPEN:
    177 		chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
    178 		break;
    179 	case CHAN_OUTPUT_WAIT_IEOF:
    180 		chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
    181 		break;
    182 	default:
    183 		error("channel %d: protocol error: rcvd_ieof for ostate %d",
    184 		    c->self, c->ostate);
    185 		break;
    186 	}
    187 }
    188 static void
    189 chan_write_failed1(Channel *c)
    190 {
    191 	debug("channel %d: write failed", c->self);
    192 	switch (c->ostate) {
    193 	case CHAN_OUTPUT_OPEN:
    194 		chan_shutdown_write(c);
    195 		chan_send_oclose1(c);
    196 		chan_set_ostate(c, CHAN_OUTPUT_WAIT_IEOF);
    197 		break;
    198 	case CHAN_OUTPUT_WAIT_DRAIN:
    199 		chan_shutdown_write(c);
    200 		chan_send_oclose1(c);
    201 		chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
    202 		break;
    203 	default:
    204 		error("channel %d: chan_write_failed for ostate %d",
    205 		    c->self, c->ostate);
    206 		break;
    207 	}
    208 }
    209 void
    210 chan_obuf_empty(Channel *c)
    211 {
    212 	debug("channel %d: obuf empty", c->self);
    213 	if (buffer_len(&c->output)) {
    214 		error("channel %d: chan_obuf_empty for non empty buffer",
    215 		    c->self);
    216 		return;
    217 	}
    218 	switch (c->ostate) {
    219 	case CHAN_OUTPUT_WAIT_DRAIN:
    220 		chan_shutdown_write(c);
    221 		if (!compat20)
    222 			chan_send_oclose1(c);
    223 		chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
    224 		break;
    225 	default:
    226 		error("channel %d: internal error: obuf_empty for ostate %d",
    227 		    c->self, c->ostate);
    228 		break;
    229 	}
    230 }
    231 static void
    232 chan_send_ieof1(Channel *c)
    233 {
    234 	debug("channel %d: send ieof", c->self);
    235 	switch (c->istate) {
    236 	case CHAN_INPUT_OPEN:
    237 	case CHAN_INPUT_WAIT_DRAIN:
    238 		packet_start(SSH_MSG_CHANNEL_INPUT_EOF);
    239 		packet_put_int(c->remote_id);
    240 		packet_send();
    241 		break;
    242 	default:
    243 		error("channel %d: cannot send ieof for istate %d",
    244 		    c->self, c->istate);
    245 		break;
    246 	}
    247 }
    248 static void
    249 chan_send_oclose1(Channel *c)
    250 {
    251 	debug("channel %d: send oclose", c->self);
    252 	switch (c->ostate) {
    253 	case CHAN_OUTPUT_OPEN:
    254 	case CHAN_OUTPUT_WAIT_DRAIN:
    255 		buffer_clear(&c->output);
    256 		packet_start(SSH_MSG_CHANNEL_OUTPUT_CLOSE);
    257 		packet_put_int(c->remote_id);
    258 		packet_send();
    259 		break;
    260 	default:
    261 		error("channel %d: cannot send oclose for ostate %d",
    262 		    c->self, c->ostate);
    263 		break;
    264 	}
    265 }
    266 
    267 /*
    268  * the same for SSH2
    269  */
    270 static void
    271 chan_rcvd_close2(Channel *c)
    272 {
    273 	debug("channel %d: rcvd close", c->self);
    274 	if (c->flags & CHAN_CLOSE_RCVD)
    275 		error("channel %d: protocol error: close rcvd twice", c->self);
    276 	c->flags |= CHAN_CLOSE_RCVD;
    277 	if (c->type == SSH_CHANNEL_LARVAL) {
    278 		/* tear down larval channels immediately */
    279 		chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
    280 		chan_set_istate(c, CHAN_INPUT_CLOSED);
    281 		return;
    282 	}
    283 	switch (c->ostate) {
    284 	case CHAN_OUTPUT_OPEN:
    285 		/*
    286 		 * wait until a data from the channel is consumed if a CLOSE
    287 		 * is received
    288 		 */
    289 		chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
    290 		break;
    291 	}
    292 	switch (c->istate) {
    293 	case CHAN_INPUT_OPEN:
    294 		chan_shutdown_read(c);
    295 		chan_set_istate(c, CHAN_INPUT_CLOSED);
    296 		break;
    297 	case CHAN_INPUT_WAIT_DRAIN:
    298 		chan_send_eof2(c);
    299 		chan_set_istate(c, CHAN_INPUT_CLOSED);
    300 		break;
    301 	}
    302 }
    303 static void
    304 chan_rcvd_eof2(Channel *c)
    305 {
    306 	debug("channel %d: rcvd eof", c->self);
    307 	c->flags |= CHAN_EOF_RCVD;
    308 	if (c->ostate == CHAN_OUTPUT_OPEN)
    309 		chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
    310 }
    311 static void
    312 chan_write_failed2(Channel *c)
    313 {
    314 	debug("channel %d: write failed", c->self);
    315 	switch (c->ostate) {
    316 	case CHAN_OUTPUT_OPEN:
    317 	case CHAN_OUTPUT_WAIT_DRAIN:
    318 		chan_shutdown_write(c);
    319 		chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
    320 		break;
    321 	default:
    322 		error("channel %d: chan_write_failed for ostate %d",
    323 		    c->self, c->ostate);
    324 		break;
    325 	}
    326 }
    327 static void
    328 chan_send_eof2(Channel *c)
    329 {
    330 	debug("channel %d: send eof", c->self);
    331 	switch (c->istate) {
    332 	case CHAN_INPUT_WAIT_DRAIN:
    333 		packet_start(SSH2_MSG_CHANNEL_EOF);
    334 		packet_put_int(c->remote_id);
    335 		packet_send();
    336 		c->flags |= CHAN_EOF_SENT;
    337 		break;
    338 	default:
    339 		error("channel %d: cannot send eof for istate %d",
    340 		    c->self, c->istate);
    341 		break;
    342 	}
    343 }
    344 static void
    345 chan_send_close2(Channel *c)
    346 {
    347 	debug("channel %d: send close", c->self);
    348 	if (c->ostate != CHAN_OUTPUT_CLOSED ||
    349 	    c->istate != CHAN_INPUT_CLOSED) {
    350 		error("channel %d: cannot send close for istate/ostate %d/%d",
    351 		    c->self, c->istate, c->ostate);
    352 	} else if (c->flags & CHAN_CLOSE_SENT) {
    353 		error("channel %d: already sent close", c->self);
    354 	} else {
    355 		packet_start(SSH2_MSG_CHANNEL_CLOSE);
    356 		packet_put_int(c->remote_id);
    357 		packet_send();
    358 		c->flags |= CHAN_CLOSE_SENT;
    359 	}
    360 }
    361 
    362 /* shared */
    363 
    364 void
    365 chan_rcvd_ieof(Channel *c)
    366 {
    367 	if (compat20)
    368 		chan_rcvd_eof2(c);
    369 	else
    370 		chan_rcvd_ieof1(c);
    371 	if (c->ostate == CHAN_OUTPUT_WAIT_DRAIN &&
    372 	    buffer_len(&c->output) == 0 &&
    373 	    !CHANNEL_EFD_OUTPUT_ACTIVE(c))
    374 		chan_obuf_empty(c);
    375 }
    376 void
    377 chan_rcvd_oclose(Channel *c)
    378 {
    379 	if (compat20)
    380 		chan_rcvd_close2(c);
    381 	else
    382 		chan_rcvd_oclose1(c);
    383 }
    384 void
    385 chan_write_failed(Channel *c)
    386 {
    387 	if (compat20)
    388 		chan_write_failed2(c);
    389 	else
    390 		chan_write_failed1(c);
    391 }
    392 
    393 void
    394 chan_mark_dead(Channel *c)
    395 {
    396 	c->type = SSH_CHANNEL_ZOMBIE;
    397 }
    398 
    399 int
    400 chan_is_dead(Channel *c, int send)
    401 {
    402 	if (c->type == SSH_CHANNEL_ZOMBIE) {
    403 		debug("channel %d: zombie", c->self);
    404 		return 1;
    405 	}
    406 	if (c->istate != CHAN_INPUT_CLOSED || c->ostate != CHAN_OUTPUT_CLOSED)
    407 		return 0;
    408 	if (!compat20) {
    409 		debug("channel %d: is dead", c->self);
    410 		return 1;
    411 	}
    412 	if ((datafellows & SSH_BUG_EXTEOF) &&
    413 	    c->extended_usage == CHAN_EXTENDED_WRITE &&
    414 	    c->efd != -1 &&
    415 	    buffer_len(&c->extended) > 0) {
    416 		debug2("channel %d: active efd: %d len %d",
    417 		    c->self, c->efd, buffer_len(&c->extended));
    418 		return 0;
    419 	}
    420 	if (!(c->flags & CHAN_CLOSE_SENT)) {
    421 		if (send) {
    422 			chan_send_close2(c);
    423 		} else {
    424 			/* channel would be dead if we sent a close */
    425 			if (c->flags & CHAN_CLOSE_RCVD) {
    426 				debug("channel %d: almost dead",
    427 				    c->self);
    428 				return 1;
    429 			}
    430 		}
    431 	}
    432 	if ((c->flags & CHAN_CLOSE_SENT) &&
    433 	    (c->flags & CHAN_CLOSE_RCVD)) {
    434 		debug("channel %d: is dead", c->self);
    435 		return 1;
    436 	}
    437 	return 0;
    438 }
    439 
    440 /* helper */
    441 static void
    442 chan_shutdown_write(Channel *c)
    443 {
    444 	buffer_clear(&c->output);
    445 	if (compat20 && c->type == SSH_CHANNEL_LARVAL)
    446 		return;
    447 	/* shutdown failure is allowed if write failed already */
    448 	debug("channel %d: close_write", c->self);
    449 	if (c->sock != -1) {
    450 		if (shutdown(c->sock, SHUT_WR) < 0)
    451 			debug("channel %d: chan_shutdown_write: "
    452 			    "shutdown() failed for fd%d: %.100s",
    453 			    c->self, c->sock, strerror(errno));
    454 	} else {
    455 		if (channel_close_fd(&c->wfd) < 0)
    456 			log("channel %d: chan_shutdown_write: "
    457 			    "close() failed for fd%d: %.100s",
    458 			    c->self, c->wfd, strerror(errno));
    459 	}
    460 }
    461 static void
    462 chan_shutdown_read(Channel *c)
    463 {
    464 	if (compat20 && c->type == SSH_CHANNEL_LARVAL)
    465 		return;
    466 	debug("channel %d: close_read", c->self);
    467 	if (c->sock != -1) {
    468 		/*
    469 		 * shutdown(sock, SHUT_READ) may return ENOTCONN if the
    470 		 * write side has been closed already. (bug on Linux)
    471 		 * HP-UX may return ENOTCONN also.
    472 		 */
    473 		if (shutdown(c->sock, SHUT_RD) < 0
    474 		    && errno != ENOTCONN)
    475 			error("channel %d: chan_shutdown_read: "
    476 			    "shutdown() failed for fd%d [i%d o%d]: %.100s",
    477 			    c->self, c->sock, c->istate, c->ostate,
    478 			    strerror(errno));
    479 	} else {
    480 		if (channel_close_fd(&c->rfd) < 0)
    481 			log("channel %d: chan_shutdown_read: "
    482 			    "close() failed for fd%d: %.100s",
    483 			    c->self, c->rfd, strerror(errno));
    484 	}
    485 }
    486