nchan.c

   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 1.51 2004/07/11 17:48:47 deraadt Exp $");
  27
  28 #include "ssh1.h"
  29 #include "ssh2.h"
  30 #include "buffer.h"
  31 #include "packet.h"
  32 #include "channels.h"
  33 #include "compat.h"
  34 #include "log.h"
  35
  36 /*
  37  * SSH Protocol 1.5 aka New Channel Protocol
  38  * Thanks to Martina, Axel and everyone who left Erlangen, leaving me bored.
  39  * Written by Markus Friedl in October 1999
  40  *
  41  * Protocol versions 1.3 and 1.5 differ in the handshake protocol used for the
  42  * tear down of channels:
  43  *
  44  * 1.3: strict request-ack-protocol:
  45  *      CLOSE   ->
  46  *              <-  CLOSE_CONFIRM
  47  *
  48  * 1.5: uses variations of:
  49  *      IEOF    ->
  50  *              <-  OCLOSE
  51  *              <-  IEOF
  52  *      OCLOSE  ->
  53  *      i.e. both sides have to close the channel
  54  *
  55  * 2.0: the EOF messages are optional
  56  *
  57  * See the debugging output from 'ssh -v' and 'sshd -d' of
  58  * ssh-1.2.27 as an example.
  59  *
  60  */
  61
  62 /* functions manipulating channel states */
  63 /*
  64  * EVENTS update channel input/output states execute ACTIONS
  65  */
  66 /*
  67  * ACTIONS: should never update the channel states
  68  */
  69 static void     chan_send_ieof1(Channel *);
  70 static void     chan_send_oclose1(Channel *);
  71 static void     chan_send_close2(Channel *);
  72 static void     chan_send_eof2(Channel *);
  73
  74 /* helper */
  75 static void     chan_shutdown_write(Channel *);
  76 static void     chan_shutdown_read(Channel *);
  77
  78 static char *ostates[] = { "open", "drain", "wait_ieof", "closed" };
  79 static char *istates[] = { "open", "drain", "wait_oclose", "closed" };
  80
  81 static void
  82 chan_set_istate(Channel *c, u_int next)
  83 {
  84         if (c->istate > CHAN_INPUT_CLOSED || next > CHAN_INPUT_CLOSED)
  85                 fatal("chan_set_istate: bad state %d -> %d", c->istate, next);
  86         debug2("channel %d: input %s -> %s", c->self, istates[c->istate],
  87             istates[next]);
  88         c->istate = next;
  89 }
  90 static void
  91 chan_set_ostate(Channel *c, u_int next)
  92 {
  93         if (c->ostate > CHAN_OUTPUT_CLOSED || next > CHAN_OUTPUT_CLOSED)
  94                 fatal("chan_set_ostate: bad state %d -> %d", c->ostate, next);
  95         debug2("channel %d: output %s -> %s", c->self, ostates[c->ostate],
  96             ostates[next]);
  97         c->ostate = next;
  98 }
  99
 100 /*
 101  * SSH1 specific implementation of event functions
 102  */
 103
 104 static void
 105 chan_rcvd_oclose1(Channel *c)
 106 {
 107         debug2("channel %d: rcvd oclose", c->self);
 108         switch (c->istate) {
 109         case CHAN_INPUT_WAIT_OCLOSE:
 110                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 111                 break;
 112         case CHAN_INPUT_OPEN:
 113                 chan_shutdown_read(c);
 114                 chan_send_ieof1(c);
 115                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 116                 break;
 117         case CHAN_INPUT_WAIT_DRAIN:
 118                 /* both local read_failed and remote write_failed  */
 119                 chan_send_ieof1(c);
 120                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 121                 break;
 122         default:
 123                 error("channel %d: protocol error: rcvd_oclose for istate %d",
 124                     c->self, c->istate);
 125                 return;
 126         }
 127 }
 128 void
 129 chan_read_failed(Channel *c)
 130 {
 131         debug2("channel %d: read failed", c->self);
 132         switch (c->istate) {
 133         case CHAN_INPUT_OPEN:
 134                 chan_shutdown_read(c);
 135                 chan_set_istate(c, CHAN_INPUT_WAIT_DRAIN);
 136                 break;
 137         default:
 138                 error("channel %d: chan_read_failed for istate %d",
 139                     c->self, c->istate);
 140                 break;
 141         }
 142 }
 143 void
 144 chan_ibuf_empty(Channel *c)
 145 {
 146         debug2("channel %d: ibuf empty", c->self);
 147         if (buffer_len(&c->input)) {
 148                 error("channel %d: chan_ibuf_empty for non empty buffer",
 149                     c->self);
 150                 return;
 151         }
 152         switch (c->istate) {
 153         case CHAN_INPUT_WAIT_DRAIN:
 154                 if (compat20) {
 155                         if (!(c->flags & CHAN_CLOSE_SENT))
 156                                 chan_send_eof2(c);
 157                         chan_set_istate(c, CHAN_INPUT_CLOSED);
 158                 } else {
 159                         chan_send_ieof1(c);
 160                         chan_set_istate(c, CHAN_INPUT_WAIT_OCLOSE);
 161                 }
 162                 break;
 163         default:
 164                 error("channel %d: chan_ibuf_empty for istate %d",
 165                     c->self, c->istate);
 166                 break;
 167         }
 168 }
 169 static void
 170 chan_rcvd_ieof1(Channel *c)
 171 {
 172         debug2("channel %d: rcvd ieof", c->self);
 173         switch (c->ostate) {
 174         case CHAN_OUTPUT_OPEN:
 175                 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
 176                 break;
 177         case CHAN_OUTPUT_WAIT_IEOF:
 178                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 179                 break;
 180         default:
 181                 error("channel %d: protocol error: rcvd_ieof for ostate %d",
 182                     c->self, c->ostate);
 183                 break;
 184         }
 185 }
 186 static void
 187 chan_write_failed1(Channel *c)
 188 {
 189         debug2("channel %d: write failed", c->self);
 190         switch (c->ostate) {
 191         case CHAN_OUTPUT_OPEN:
 192                 chan_shutdown_write(c);
 193                 chan_send_oclose1(c);
 194                 chan_set_ostate(c, CHAN_OUTPUT_WAIT_IEOF);
 195                 break;
 196         case CHAN_OUTPUT_WAIT_DRAIN:
 197                 chan_shutdown_write(c);
 198                 chan_send_oclose1(c);
 199                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 200                 break;
 201         default:
 202                 error("channel %d: chan_write_failed for ostate %d",
 203                     c->self, c->ostate);
 204                 break;
 205         }
 206 }
 207 void
 208 chan_obuf_empty(Channel *c)
 209 {
 210         debug2("channel %d: obuf empty", c->self);
 211         if (buffer_len(&c->output)) {
 212                 error("channel %d: chan_obuf_empty for non empty buffer",
 213                     c->self);
 214                 return;
 215         }
 216         switch (c->ostate) {
 217         case CHAN_OUTPUT_WAIT_DRAIN:
 218                 chan_shutdown_write(c);
 219                 if (!compat20)
 220                         chan_send_oclose1(c);
 221                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 222                 break;
 223         default:
 224                 error("channel %d: internal error: obuf_empty for ostate %d",
 225                     c->self, c->ostate);
 226                 break;
 227         }
 228 }
 229 static void
 230 chan_send_ieof1(Channel *c)
 231 {
 232         debug2("channel %d: send ieof", c->self);
 233         switch (c->istate) {
 234         case CHAN_INPUT_OPEN:
 235         case CHAN_INPUT_WAIT_DRAIN:
 236                 packet_start(SSH_MSG_CHANNEL_INPUT_EOF);
 237                 packet_put_int(c->remote_id);
 238                 packet_send();
 239                 break;
 240         default:
 241                 error("channel %d: cannot send ieof for istate %d",
 242                     c->self, c->istate);
 243                 break;
 244         }
 245 }
 246 static void
 247 chan_send_oclose1(Channel *c)
 248 {
 249         debug2("channel %d: send oclose", c->self);
 250         switch (c->ostate) {
 251         case CHAN_OUTPUT_OPEN:
 252         case CHAN_OUTPUT_WAIT_DRAIN:
 253                 buffer_clear(&c->output);
 254                 packet_start(SSH_MSG_CHANNEL_OUTPUT_CLOSE);
 255                 packet_put_int(c->remote_id);
 256                 packet_send();
 257                 break;
 258         default:
 259                 error("channel %d: cannot send oclose for ostate %d",
 260                     c->self, c->ostate);
 261                 break;
 262         }
 263 }
 264
 265 /*
 266  * the same for SSH2
 267  */
 268 static void
 269 chan_rcvd_close2(Channel *c)
 270 {
 271         debug2("channel %d: rcvd close", c->self);
 272         if (c->flags & CHAN_CLOSE_RCVD)
 273                 error("channel %d: protocol error: close rcvd twice", c->self);
 274         c->flags |= CHAN_CLOSE_RCVD;
 275         if (c->type == SSH_CHANNEL_LARVAL) {
 276                 /* tear down larval channels immediately */
 277                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 278                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 279                 return;
 280         }
 281         switch (c->ostate) {
 282         case CHAN_OUTPUT_OPEN:
 283                 /*
 284                  * wait until a data from the channel is consumed if a CLOSE
 285                  * is received
 286                  */
 287                 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
 288                 break;
 289         }
 290         switch (c->istate) {
 291         case CHAN_INPUT_OPEN:
 292                 chan_shutdown_read(c);
 293                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 294                 break;
 295         case CHAN_INPUT_WAIT_DRAIN:
 296                 chan_send_eof2(c);
 297                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 298                 break;
 299         }
 300 }
 301 static void
 302 chan_rcvd_eof2(Channel *c)
 303 {
 304         debug2("channel %d: rcvd eof", c->self);
 305         c->flags |= CHAN_EOF_RCVD;
 306         if (c->ostate == CHAN_OUTPUT_OPEN)
 307                 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
 308 }
 309 static void
 310 chan_write_failed2(Channel *c)
 311 {
 312         debug2("channel %d: write failed", c->self);
 313         switch (c->ostate) {
 314         case CHAN_OUTPUT_OPEN:
 315         case CHAN_OUTPUT_WAIT_DRAIN:
 316                 chan_shutdown_write(c);
 317                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 318                 break;
 319         default:
 320                 error("channel %d: chan_write_failed for ostate %d",
 321                     c->self, c->ostate);
 322                 break;
 323         }
 324 }
 325 static void
 326 chan_send_eof2(Channel *c)
 327 {
 328         debug2("channel %d: send eof", c->self);
 329         switch (c->istate) {
 330         case CHAN_INPUT_WAIT_DRAIN:
 331                 packet_start(SSH2_MSG_CHANNEL_EOF);
 332                 packet_put_int(c->remote_id);
 333                 packet_send();
 334                 c->flags |= CHAN_EOF_SENT;
 335                 break;
 336         default:
 337                 error("channel %d: cannot send eof for istate %d",
 338                     c->self, c->istate);
 339                 break;
 340         }
 341 }
 342 static void
 343 chan_send_close2(Channel *c)
 344 {
 345         debug2("channel %d: send close", c->self);
 346         if (c->ostate != CHAN_OUTPUT_CLOSED ||
 347             c->istate != CHAN_INPUT_CLOSED) {
 348                 error("channel %d: cannot send close for istate/ostate %d/%d",
 349                     c->self, c->istate, c->ostate);
 350         } else if (c->flags & CHAN_CLOSE_SENT) {
 351                 error("channel %d: already sent close", c->self);
 352         } else {
 353                 packet_start(SSH2_MSG_CHANNEL_CLOSE);
 354                 packet_put_int(c->remote_id);
 355                 packet_send();
 356                 c->flags |= CHAN_CLOSE_SENT;
 357         }
 358 }
 359
 360 /* shared */
 361
 362 void
 363 chan_rcvd_ieof(Channel *c)
 364 {
 365         if (compat20)
 366                 chan_rcvd_eof2(c);
 367         else
 368                 chan_rcvd_ieof1(c);
 369         if (c->ostate == CHAN_OUTPUT_WAIT_DRAIN &&
 370             buffer_len(&c->output) == 0 &&
 371             !CHANNEL_EFD_OUTPUT_ACTIVE(c))
 372                 chan_obuf_empty(c);
 373 }
 374 void
 375 chan_rcvd_oclose(Channel *c)
 376 {
 377         if (compat20)
 378                 chan_rcvd_close2(c);
 379         else
 380                 chan_rcvd_oclose1(c);
 381 }
 382 void
 383 chan_write_failed(Channel *c)
 384 {
 385         if (compat20)
 386                 chan_write_failed2(c);
 387         else
 388                 chan_write_failed1(c);
 389 }
 390
 391 void
 392 chan_mark_dead(Channel *c)
 393 {
 394         c->type = SSH_CHANNEL_ZOMBIE;
 395 }
 396
 397 int
 398 chan_is_dead(Channel *c, int do_send)
 399 {
 400         if (c->type == SSH_CHANNEL_ZOMBIE) {
 401                 debug2("channel %d: zombie", c->self);
 402                 return 1;
 403         }
 404         if (c->istate != CHAN_INPUT_CLOSED || c->ostate != CHAN_OUTPUT_CLOSED)
 405                 return 0;
 406         if (!compat20) {
 407                 debug2("channel %d: is dead", c->self);
 408                 return 1;
 409         }
 410         if ((datafellows & SSH_BUG_EXTEOF) &&
 411             c->extended_usage == CHAN_EXTENDED_WRITE &&
 412             c->efd != -1 &&
 413             buffer_len(&c->extended) > 0) {
 414                 debug2("channel %d: active efd: %d len %d",
 415                     c->self, c->efd, buffer_len(&c->extended));
 416                 return 0;
 417         }
 418         if (!(c->flags & CHAN_CLOSE_SENT)) {
 419                 if (do_send) {
 420                         chan_send_close2(c);
 421                 } else {
 422                         /* channel would be dead if we sent a close */
 423                         if (c->flags & CHAN_CLOSE_RCVD) {
 424                                 debug2("channel %d: almost dead",
 425                                     c->self);
 426                                 return 1;
 427                         }
 428                 }
 429         }
 430         if ((c->flags & CHAN_CLOSE_SENT) &&
 431             (c->flags & CHAN_CLOSE_RCVD)) {
 432                 debug2("channel %d: is dead", c->self);
 433                 return 1;
 434         }
 435         return 0;
 436 }
 437
 438 /* helper */
 439 static void
 440 chan_shutdown_write(Channel *c)
 441 {
 442         buffer_clear(&c->output);
 443         if (compat20 && c->type == SSH_CHANNEL_LARVAL)
 444                 return;
 445         /* shutdown failure is allowed if write failed already */
 446         debug2("channel %d: close_write", c->self);
 447         if (c->sock != -1) {
 448                 if (shutdown(c->sock, SHUT_WR) < 0)
 449                         debug2("channel %d: chan_shutdown_write: "
 450                             "shutdown() failed for fd%d: %.100s",
 451                             c->self, c->sock, strerror(errno));
 452         } else {
 453                 if (channel_close_fd(&c->wfd) < 0)
 454                         logit("channel %d: chan_shutdown_write: "
 455                             "close() failed for fd%d: %.100s",
 456                             c->self, c->wfd, strerror(errno));
 457         }
 458 }
 459 static void
 460 chan_shutdown_read(Channel *c)
 461 {
 462         if (compat20 && c->type == SSH_CHANNEL_LARVAL)
 463                 return;
 464         debug2("channel %d: close_read", c->self);
 465         if (c->sock != -1) {
 466                 /*
 467                  * shutdown(sock, SHUT_READ) may return ENOTCONN if the
 468                  * write side has been closed already. (bug on Linux)
 469                  * HP-UX may return ENOTCONN also.
 470                  */
 471                 if (shutdown(c->sock, SHUT_RD) < 0
 472                     && errno != ENOTCONN)
 473                         error("channel %d: chan_shutdown_read: "
 474                             "shutdown() failed for fd%d [i%d o%d]: %.100s",
 475                             c->self, c->sock, c->istate, c->ostate,
 476                             strerror(errno));
 477         } else {
 478                 if (channel_close_fd(&c->rfd) < 0)
 479                         logit("channel %d: chan_shutdown_read: "
 480                             "close() failed for fd%d: %.100s",
 481                             c->self, c->rfd, strerror(errno));
 482         }
 483 }