crypto/openssh/nchan.c

   1 /* $OpenBSD: nchan.c,v 1.67 2017/09/12 06:35:32 djm Exp $ */
   2 /*
   3  * Copyright (c) 1999, 2000, 2001, 2002 Markus Friedl.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  15  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  16  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  17  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  18  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  19  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  20  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  21  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  23  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #include "includes.h"
  27
  28 #include <sys/types.h>
  29 #include <sys/socket.h>
  30
  31 #include <errno.h>
  32 #include <string.h>
  33 #include <stdarg.h>
  34
  35 #include "openbsd-compat/sys-queue.h"
  36 #include "ssh2.h"
  37 #include "sshbuf.h"
  38 #include "ssherr.h"
  39 #include "packet.h"
  40 #include "channels.h"
  41 #include "compat.h"
  42 #include "log.h"
  43
  44 /*
  45  * SSH Protocol 1.5 aka New Channel Protocol
  46  * Thanks to Martina, Axel and everyone who left Erlangen, leaving me bored.
  47  * Written by Markus Friedl in October 1999
  48  *
  49  * Protocol versions 1.3 and 1.5 differ in the handshake protocol used for the
  50  * tear down of channels:
  51  *
  52  * 1.3: strict request-ack-protocol:
  53  *      CLOSE   ->
  54  *              <-  CLOSE_CONFIRM
  55  *
  56  * 1.5: uses variations of:
  57  *      IEOF    ->
  58  *              <-  OCLOSE
  59  *              <-  IEOF
  60  *      OCLOSE  ->
  61  *      i.e. both sides have to close the channel
  62  *
  63  * 2.0: the EOF messages are optional
  64  *
  65  * See the debugging output from 'ssh -v' and 'sshd -d' of
  66  * ssh-1.2.27 as an example.
  67  *
  68  */
  69
  70 /* functions manipulating channel states */
  71 /*
  72  * EVENTS update channel input/output states execute ACTIONS
  73  */
  74 /*
  75  * ACTIONS: should never update the channel states
  76  */
  77 static void     chan_send_eof2(struct ssh *, Channel *);
  78 static void     chan_send_eow2(struct ssh *, Channel *);
  79
  80 /* helper */
  81 static void     chan_shutdown_write(struct ssh *, Channel *);
  82 static void     chan_shutdown_read(struct ssh *, Channel *);
  83
  84 static const char *ostates[] = { "open", "drain", "wait_ieof", "closed" };
  85 static const char *istates[] = { "open", "drain", "wait_oclose", "closed" };
  86
  87 static void
  88 chan_set_istate(Channel *c, u_int next)
  89 {
  90         if (c->istate > CHAN_INPUT_CLOSED || next > CHAN_INPUT_CLOSED)
  91                 fatal("chan_set_istate: bad state %d -> %d", c->istate, next);
  92         debug2("channel %d: input %s -> %s", c->self, istates[c->istate],
  93             istates[next]);
  94         c->istate = next;
  95 }
  96
  97 static void
  98 chan_set_ostate(Channel *c, u_int next)
  99 {
 100         if (c->ostate > CHAN_OUTPUT_CLOSED || next > CHAN_OUTPUT_CLOSED)
 101                 fatal("chan_set_ostate: bad state %d -> %d", c->ostate, next);
 102         debug2("channel %d: output %s -> %s", c->self, ostates[c->ostate],
 103             ostates[next]);
 104         c->ostate = next;
 105 }
 106
 107 void
 108 chan_read_failed(struct ssh *ssh, Channel *c)
 109 {
 110         debug2("channel %d: read failed", c->self);
 111         switch (c->istate) {
 112         case CHAN_INPUT_OPEN:
 113                 chan_shutdown_read(ssh, c);
 114                 chan_set_istate(c, CHAN_INPUT_WAIT_DRAIN);
 115                 break;
 116         default:
 117                 error("channel %d: chan_read_failed for istate %d",
 118                     c->self, c->istate);
 119                 break;
 120         }
 121 }
 122
 123 void
 124 chan_ibuf_empty(struct ssh *ssh, Channel *c)
 125 {
 126         debug2("channel %d: ibuf empty", c->self);
 127         if (sshbuf_len(c->input)) {
 128                 error("channel %d: chan_ibuf_empty for non empty buffer",
 129                     c->self);
 130                 return;
 131         }
 132         switch (c->istate) {
 133         case CHAN_INPUT_WAIT_DRAIN:
 134                 if (!(c->flags & (CHAN_CLOSE_SENT|CHAN_LOCAL)))
 135                         chan_send_eof2(ssh, c);
 136                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 137                 break;
 138         default:
 139                 error("channel %d: chan_ibuf_empty for istate %d",
 140                     c->self, c->istate);
 141                 break;
 142         }
 143 }
 144
 145 void
 146 chan_obuf_empty(struct ssh *ssh, Channel *c)
 147 {
 148         debug2("channel %d: obuf empty", c->self);
 149         if (sshbuf_len(c->output)) {
 150                 error("channel %d: chan_obuf_empty for non empty buffer",
 151                     c->self);
 152                 return;
 153         }
 154         switch (c->ostate) {
 155         case CHAN_OUTPUT_WAIT_DRAIN:
 156                 chan_shutdown_write(ssh, c);
 157                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 158                 break;
 159         default:
 160                 error("channel %d: internal error: obuf_empty for ostate %d",
 161                     c->self, c->ostate);
 162                 break;
 163         }
 164 }
 165
 166 void
 167 chan_rcvd_eow(struct ssh *ssh, Channel *c)
 168 {
 169         debug2("channel %d: rcvd eow", c->self);
 170         switch (c->istate) {
 171         case CHAN_INPUT_OPEN:
 172                 chan_shutdown_read(ssh, c);
 173                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 174                 break;
 175         }
 176 }
 177
 178 static void
 179 chan_send_eof2(struct ssh *ssh, Channel *c)
 180 {
 181         int r;
 182
 183         debug2("channel %d: send eof", c->self);
 184         switch (c->istate) {
 185         case CHAN_INPUT_WAIT_DRAIN:
 186                 if (!c->have_remote_id)
 187                         fatal("%s: channel %d: no remote_id",
 188                             __func__, c->self);
 189                 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_EOF)) != 0 ||
 190                     (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
 191                     (r = sshpkt_send(ssh)) != 0)
 192                         fatal("%s: send CHANNEL_EOF: %s", __func__, ssh_err(r));
 193                 c->flags |= CHAN_EOF_SENT;
 194                 break;
 195         default:
 196                 error("channel %d: cannot send eof for istate %d",
 197                     c->self, c->istate);
 198                 break;
 199         }
 200 }
 201
 202 static void
 203 chan_send_close2(struct ssh *ssh, Channel *c)
 204 {
 205         int r;
 206
 207         debug2("channel %d: send close", c->self);
 208         if (c->ostate != CHAN_OUTPUT_CLOSED ||
 209             c->istate != CHAN_INPUT_CLOSED) {
 210                 error("channel %d: cannot send close for istate/ostate %d/%d",
 211                     c->self, c->istate, c->ostate);
 212         } else if (c->flags & CHAN_CLOSE_SENT) {
 213                 error("channel %d: already sent close", c->self);
 214         } else {
 215                 if (!c->have_remote_id)
 216                         fatal("%s: channel %d: no remote_id",
 217                             __func__, c->self);
 218                 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_CLOSE)) != 0 ||
 219                     (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
 220                     (r = sshpkt_send(ssh)) != 0)
 221                         fatal("%s: send CHANNEL_EOF: %s", __func__, ssh_err(r));
 222                 c->flags |= CHAN_CLOSE_SENT;
 223         }
 224 }
 225
 226 static void
 227 chan_send_eow2(struct ssh *ssh, Channel *c)
 228 {
 229         int r;
 230
 231         debug2("channel %d: send eow", c->self);
 232         if (c->ostate == CHAN_OUTPUT_CLOSED) {
 233                 error("channel %d: must not sent eow on closed output",
 234                     c->self);
 235                 return;
 236         }
 237         if (!(datafellows & SSH_NEW_OPENSSH))
 238                 return;
 239         if (!c->have_remote_id)
 240                 fatal("%s: channel %d: no remote_id", __func__, c->self);
 241         if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_REQUEST)) != 0 ||
 242             (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
 243             (r = sshpkt_put_cstring(ssh, "eow@openssh.com")) != 0 ||
 244             (r = sshpkt_put_u8(ssh, 0)) != 0 ||
 245             (r = sshpkt_send(ssh)) != 0)
 246                 fatal("%s: send CHANNEL_EOF: %s", __func__, ssh_err(r));
 247 }
 248
 249 /* shared */
 250
 251 void
 252 chan_rcvd_ieof(struct ssh *ssh, Channel *c)
 253 {
 254         debug2("channel %d: rcvd eof", c->self);
 255         c->flags |= CHAN_EOF_RCVD;
 256         if (c->ostate == CHAN_OUTPUT_OPEN)
 257                 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
 258         if (c->ostate == CHAN_OUTPUT_WAIT_DRAIN &&
 259             sshbuf_len(c->output) == 0 &&
 260             !CHANNEL_EFD_OUTPUT_ACTIVE(c))
 261                 chan_obuf_empty(ssh, c);
 262 }
 263
 264 void
 265 chan_rcvd_oclose(struct ssh *ssh, Channel *c)
 266 {
 267         debug2("channel %d: rcvd close", c->self);
 268         if (!(c->flags & CHAN_LOCAL)) {
 269                 if (c->flags & CHAN_CLOSE_RCVD)
 270                         error("channel %d: protocol error: close rcvd twice",
 271                             c->self);
 272                 c->flags |= CHAN_CLOSE_RCVD;
 273         }
 274         if (c->type == SSH_CHANNEL_LARVAL) {
 275                 /* tear down larval channels immediately */
 276                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 277                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 278                 return;
 279         }
 280         switch (c->ostate) {
 281         case CHAN_OUTPUT_OPEN:
 282                 /*
 283                  * wait until a data from the channel is consumed if a CLOSE
 284                  * is received
 285                  */
 286                 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
 287                 break;
 288         }
 289         switch (c->istate) {
 290         case CHAN_INPUT_OPEN:
 291                 chan_shutdown_read(ssh, c);
 292                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 293                 break;
 294         case CHAN_INPUT_WAIT_DRAIN:
 295                 if (!(c->flags & CHAN_LOCAL))
 296                         chan_send_eof2(ssh, c);
 297                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 298                 break;
 299         }
 300 }
 301
 302 void
 303 chan_write_failed(struct ssh *ssh, Channel *c)
 304 {
 305         debug2("channel %d: write failed", c->self);
 306         switch (c->ostate) {
 307         case CHAN_OUTPUT_OPEN:
 308         case CHAN_OUTPUT_WAIT_DRAIN:
 309                 chan_shutdown_write(ssh, c);
 310                 if (strcmp(c->ctype, "session") == 0)
 311                         chan_send_eow2(ssh, c);
 312                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 313                 break;
 314         default:
 315                 error("channel %d: chan_write_failed for ostate %d",
 316                     c->self, c->ostate);
 317                 break;
 318         }
 319 }
 320
 321 void
 322 chan_mark_dead(struct ssh *ssh, Channel *c)
 323 {
 324         c->type = SSH_CHANNEL_ZOMBIE;
 325 }
 326
 327 int
 328 chan_is_dead(struct ssh *ssh, Channel *c, int do_send)
 329 {
 330         if (c->type == SSH_CHANNEL_ZOMBIE) {
 331                 debug2("channel %d: zombie", c->self);
 332                 return 1;
 333         }
 334         if (c->istate != CHAN_INPUT_CLOSED || c->ostate != CHAN_OUTPUT_CLOSED)
 335                 return 0;
 336         if ((datafellows & SSH_BUG_EXTEOF) &&
 337             c->extended_usage == CHAN_EXTENDED_WRITE &&
 338             c->efd != -1 &&
 339             sshbuf_len(c->extended) > 0) {
 340                 debug2("channel %d: active efd: %d len %zu",
 341                     c->self, c->efd, sshbuf_len(c->extended));
 342                 return 0;
 343         }
 344         if (c->flags & CHAN_LOCAL) {
 345                 debug2("channel %d: is dead (local)", c->self);
 346                 return 1;
 347         }
 348         if (!(c->flags & CHAN_CLOSE_SENT)) {
 349                 if (do_send) {
 350                         chan_send_close2(ssh, c);
 351                 } else {
 352                         /* channel would be dead if we sent a close */
 353                         if (c->flags & CHAN_CLOSE_RCVD) {
 354                                 debug2("channel %d: almost dead",
 355                                     c->self);
 356                                 return 1;
 357                         }
 358                 }
 359         }
 360         if ((c->flags & CHAN_CLOSE_SENT) &&
 361             (c->flags & CHAN_CLOSE_RCVD)) {
 362                 debug2("channel %d: is dead", c->self);
 363                 return 1;
 364         }
 365         return 0;
 366 }
 367
 368 /* helper */
 369 static void
 370 chan_shutdown_write(struct ssh *ssh, Channel *c)
 371 {
 372         sshbuf_reset(c->output);
 373         if (c->type == SSH_CHANNEL_LARVAL)
 374                 return;
 375         /* shutdown failure is allowed if write failed already */
 376         debug2("channel %d: close_write", c->self);
 377         if (c->sock != -1) {
 378                 if (shutdown(c->sock, SHUT_WR) < 0)
 379                         debug2("channel %d: chan_shutdown_write: "
 380                             "shutdown() failed for fd %d: %.100s",
 381                             c->self, c->sock, strerror(errno));
 382         } else {
 383                 if (channel_close_fd(ssh, &c->wfd) < 0)
 384                         logit("channel %d: chan_shutdown_write: "
 385                             "close() failed for fd %d: %.100s",
 386                             c->self, c->wfd, strerror(errno));
 387         }
 388 }
 389
 390 static void
 391 chan_shutdown_read(struct ssh *ssh, Channel *c)
 392 {
 393         if (c->type == SSH_CHANNEL_LARVAL)
 394                 return;
 395         debug2("channel %d: close_read", c->self);
 396         if (c->sock != -1) {
 397                 /*
 398                  * shutdown(sock, SHUT_READ) may return ENOTCONN if the
 399                  * write side has been closed already. (bug on Linux)
 400                  * HP-UX may return ENOTCONN also.
 401                  */
 402                 if (shutdown(c->sock, SHUT_RD) < 0
 403                     && errno != ENOTCONN)
 404                         error("channel %d: chan_shutdown_read: "
 405                             "shutdown() failed for fd %d [i%d o%d]: %.100s",
 406                             c->self, c->sock, c->istate, c->ostate,
 407                             strerror(errno));
 408         } else {
 409                 if (channel_close_fd(ssh, &c->rfd) < 0)
 410                         logit("channel %d: chan_shutdown_read: "
 411                             "close() failed for fd %d: %.100s",
 412                             c->self, c->rfd, strerror(errno));
 413         }
 414 }