nchan.c

   1 /* $OpenBSD: nchan.c,v 1.57 2006/08/03 03:34:42 deraadt 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 "ssh1.h"
  36 #include "ssh2.h"
  37 #include "buffer.h"
  38 #include "packet.h"
  39 #include "channels.h"
  40 #include "compat.h"
  41 #include "log.h"
  42
  43 /*
  44  * SSH Protocol 1.5 aka New Channel Protocol
  45  * Thanks to Martina, Axel and everyone who left Erlangen, leaving me bored.
  46  * Written by Markus Friedl in October 1999
  47  *
  48  * Protocol versions 1.3 and 1.5 differ in the handshake protocol used for the
  49  * tear down of channels:
  50  *
  51  * 1.3: strict request-ack-protocol:
  52  *      CLOSE   ->
  53  *              <-  CLOSE_CONFIRM
  54  *
  55  * 1.5: uses variations of:
  56  *      IEOF    ->
  57  *              <-  OCLOSE
  58  *              <-  IEOF
  59  *      OCLOSE  ->
  60  *      i.e. both sides have to close the channel
  61  *
  62  * 2.0: the EOF messages are optional
  63  *
  64  * See the debugging output from 'ssh -v' and 'sshd -d' of
  65  * ssh-1.2.27 as an example.
  66  *
  67  */
  68
  69 /* functions manipulating channel states */
  70 /*
  71  * EVENTS update channel input/output states execute ACTIONS
  72  */
  73 /*
  74  * ACTIONS: should never update the channel states
  75  */
  76 static void     chan_send_ieof1(Channel *);
  77 static void     chan_send_oclose1(Channel *);
  78 static void     chan_send_close2(Channel *);
  79 static void     chan_send_eof2(Channel *);
  80
  81 /* helper */
  82 static void     chan_shutdown_write(Channel *);
  83 static void     chan_shutdown_read(Channel *);
  84
  85 static char *ostates[] = { "open", "drain", "wait_ieof", "closed" };
  86 static char *istates[] = { "open", "drain", "wait_oclose", "closed" };
  87
  88 static void
  89 chan_set_istate(Channel *c, u_int next)
  90 {
  91         if (c->istate > CHAN_INPUT_CLOSED || next > CHAN_INPUT_CLOSED)
  92                 fatal("chan_set_istate: bad state %d -> %d", c->istate, next);
  93         debug2("channel %d: input %s -> %s", c->self, istates[c->istate],
  94             istates[next]);
  95         c->istate = next;
  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 /*
 108  * SSH1 specific implementation of event functions
 109  */
 110
 111 static void
 112 chan_rcvd_oclose1(Channel *c)
 113 {
 114         debug2("channel %d: rcvd oclose", c->self);
 115         switch (c->istate) {
 116         case CHAN_INPUT_WAIT_OCLOSE:
 117                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 118                 break;
 119         case CHAN_INPUT_OPEN:
 120                 chan_shutdown_read(c);
 121                 chan_send_ieof1(c);
 122                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 123                 break;
 124         case CHAN_INPUT_WAIT_DRAIN:
 125                 /* both local read_failed and remote write_failed  */
 126                 chan_send_ieof1(c);
 127                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 128                 break;
 129         default:
 130                 error("channel %d: protocol error: rcvd_oclose for istate %d",
 131                     c->self, c->istate);
 132                 return;
 133         }
 134 }
 135 void
 136 chan_read_failed(Channel *c)
 137 {
 138         debug2("channel %d: read failed", c->self);
 139         switch (c->istate) {
 140         case CHAN_INPUT_OPEN:
 141                 chan_shutdown_read(c);
 142                 chan_set_istate(c, CHAN_INPUT_WAIT_DRAIN);
 143                 break;
 144         default:
 145                 error("channel %d: chan_read_failed for istate %d",
 146                     c->self, c->istate);
 147                 break;
 148         }
 149 }
 150 void
 151 chan_ibuf_empty(Channel *c)
 152 {
 153         debug2("channel %d: ibuf empty", c->self);
 154         if (buffer_len(&c->input)) {
 155                 error("channel %d: chan_ibuf_empty for non empty buffer",
 156                     c->self);
 157                 return;
 158         }
 159         switch (c->istate) {
 160         case CHAN_INPUT_WAIT_DRAIN:
 161                 if (compat20) {
 162                         if (!(c->flags & CHAN_CLOSE_SENT))
 163                                 chan_send_eof2(c);
 164                         chan_set_istate(c, CHAN_INPUT_CLOSED);
 165                 } else {
 166                         chan_send_ieof1(c);
 167                         chan_set_istate(c, CHAN_INPUT_WAIT_OCLOSE);
 168                 }
 169                 break;
 170         default:
 171                 error("channel %d: chan_ibuf_empty for istate %d",
 172                     c->self, c->istate);
 173                 break;
 174         }
 175 }
 176 static void
 177 chan_rcvd_ieof1(Channel *c)
 178 {
 179         debug2("channel %d: rcvd ieof", c->self);
 180         switch (c->ostate) {
 181         case CHAN_OUTPUT_OPEN:
 182                 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
 183                 break;
 184         case CHAN_OUTPUT_WAIT_IEOF:
 185                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 186                 break;
 187         default:
 188                 error("channel %d: protocol error: rcvd_ieof for ostate %d",
 189                     c->self, c->ostate);
 190                 break;
 191         }
 192 }
 193 static void
 194 chan_write_failed1(Channel *c)
 195 {
 196         debug2("channel %d: write failed", c->self);
 197         switch (c->ostate) {
 198         case CHAN_OUTPUT_OPEN:
 199                 chan_shutdown_write(c);
 200                 chan_send_oclose1(c);
 201                 chan_set_ostate(c, CHAN_OUTPUT_WAIT_IEOF);
 202                 break;
 203         case CHAN_OUTPUT_WAIT_DRAIN:
 204                 chan_shutdown_write(c);
 205                 chan_send_oclose1(c);
 206                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 207                 break;
 208         default:
 209                 error("channel %d: chan_write_failed for ostate %d",
 210                     c->self, c->ostate);
 211                 break;
 212         }
 213 }
 214 void
 215 chan_obuf_empty(Channel *c)
 216 {
 217         debug2("channel %d: obuf empty", c->self);
 218         if (buffer_len(&c->output)) {
 219                 error("channel %d: chan_obuf_empty for non empty buffer",
 220                     c->self);
 221                 return;
 222         }
 223         switch (c->ostate) {
 224         case CHAN_OUTPUT_WAIT_DRAIN:
 225                 chan_shutdown_write(c);
 226                 if (!compat20)
 227                         chan_send_oclose1(c);
 228                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 229                 break;
 230         default:
 231                 error("channel %d: internal error: obuf_empty for ostate %d",
 232                     c->self, c->ostate);
 233                 break;
 234         }
 235 }
 236 static void
 237 chan_send_ieof1(Channel *c)
 238 {
 239         debug2("channel %d: send ieof", c->self);
 240         switch (c->istate) {
 241         case CHAN_INPUT_OPEN:
 242         case CHAN_INPUT_WAIT_DRAIN:
 243                 packet_start(SSH_MSG_CHANNEL_INPUT_EOF);
 244                 packet_put_int(c->remote_id);
 245                 packet_send();
 246                 break;
 247         default:
 248                 error("channel %d: cannot send ieof for istate %d",
 249                     c->self, c->istate);
 250                 break;
 251         }
 252 }
 253 static void
 254 chan_send_oclose1(Channel *c)
 255 {
 256         debug2("channel %d: send oclose", c->self);
 257         switch (c->ostate) {
 258         case CHAN_OUTPUT_OPEN:
 259         case CHAN_OUTPUT_WAIT_DRAIN:
 260                 buffer_clear(&c->output);
 261                 packet_start(SSH_MSG_CHANNEL_OUTPUT_CLOSE);
 262                 packet_put_int(c->remote_id);
 263                 packet_send();
 264                 break;
 265         default:
 266                 error("channel %d: cannot send oclose for ostate %d",
 267                     c->self, c->ostate);
 268                 break;
 269         }
 270 }
 271
 272 /*
 273  * the same for SSH2
 274  */
 275 static void
 276 chan_rcvd_close2(Channel *c)
 277 {
 278         debug2("channel %d: rcvd close", c->self);
 279         if (c->flags & CHAN_CLOSE_RCVD)
 280                 error("channel %d: protocol error: close rcvd twice", c->self);
 281         c->flags |= CHAN_CLOSE_RCVD;
 282         if (c->type == SSH_CHANNEL_LARVAL) {
 283                 /* tear down larval channels immediately */
 284                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 285                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 286                 return;
 287         }
 288         switch (c->ostate) {
 289         case CHAN_OUTPUT_OPEN:
 290                 /*
 291                  * wait until a data from the channel is consumed if a CLOSE
 292                  * is received
 293                  */
 294                 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
 295                 break;
 296         }
 297         switch (c->istate) {
 298         case CHAN_INPUT_OPEN:
 299                 chan_shutdown_read(c);
 300                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 301                 break;
 302         case CHAN_INPUT_WAIT_DRAIN:
 303                 chan_send_eof2(c);
 304                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 305                 break;
 306         }
 307 }
 308 static void
 309 chan_rcvd_eof2(Channel *c)
 310 {
 311         debug2("channel %d: rcvd eof", c->self);
 312         c->flags |= CHAN_EOF_RCVD;
 313         if (c->ostate == CHAN_OUTPUT_OPEN)
 314                 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
 315 }
 316 static void
 317 chan_write_failed2(Channel *c)
 318 {
 319         debug2("channel %d: write failed", c->self);
 320         switch (c->ostate) {
 321         case CHAN_OUTPUT_OPEN:
 322         case CHAN_OUTPUT_WAIT_DRAIN:
 323                 chan_shutdown_write(c);
 324                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 325                 break;
 326         default:
 327                 error("channel %d: chan_write_failed for ostate %d",
 328                     c->self, c->ostate);
 329                 break;
 330         }
 331 }
 332 static void
 333 chan_send_eof2(Channel *c)
 334 {
 335         debug2("channel %d: send eof", c->self);
 336         switch (c->istate) {
 337         case CHAN_INPUT_WAIT_DRAIN:
 338                 packet_start(SSH2_MSG_CHANNEL_EOF);
 339                 packet_put_int(c->remote_id);
 340                 packet_send();
 341                 c->flags |= CHAN_EOF_SENT;
 342                 break;
 343         default:
 344                 error("channel %d: cannot send eof for istate %d",
 345                     c->self, c->istate);
 346                 break;
 347         }
 348 }
 349 static void
 350 chan_send_close2(Channel *c)
 351 {
 352         debug2("channel %d: send close", c->self);
 353         if (c->ostate != CHAN_OUTPUT_CLOSED ||
 354             c->istate != CHAN_INPUT_CLOSED) {
 355                 error("channel %d: cannot send close for istate/ostate %d/%d",
 356                     c->self, c->istate, c->ostate);
 357         } else if (c->flags & CHAN_CLOSE_SENT) {
 358                 error("channel %d: already sent close", c->self);
 359         } else {
 360                 packet_start(SSH2_MSG_CHANNEL_CLOSE);
 361                 packet_put_int(c->remote_id);
 362                 packet_send();
 363                 c->flags |= CHAN_CLOSE_SENT;
 364         }
 365 }
 366
 367 /* shared */
 368
 369 void
 370 chan_rcvd_ieof(Channel *c)
 371 {
 372         if (compat20)
 373                 chan_rcvd_eof2(c);
 374         else
 375                 chan_rcvd_ieof1(c);
 376         if (c->ostate == CHAN_OUTPUT_WAIT_DRAIN &&
 377             buffer_len(&c->output) == 0 &&
 378             !CHANNEL_EFD_OUTPUT_ACTIVE(c))
 379                 chan_obuf_empty(c);
 380 }
 381 void
 382 chan_rcvd_oclose(Channel *c)
 383 {
 384         if (compat20)
 385                 chan_rcvd_close2(c);
 386         else
 387                 chan_rcvd_oclose1(c);
 388 }
 389 void
 390 chan_write_failed(Channel *c)
 391 {
 392         if (compat20)
 393                 chan_write_failed2(c);
 394         else
 395                 chan_write_failed1(c);
 396 }
 397
 398 void
 399 chan_mark_dead(Channel *c)
 400 {
 401         c->type = SSH_CHANNEL_ZOMBIE;
 402 }
 403
 404 int
 405 chan_is_dead(Channel *c, int do_send)
 406 {
 407         if (c->type == SSH_CHANNEL_ZOMBIE) {
 408                 debug2("channel %d: zombie", c->self);
 409                 return 1;
 410         }
 411         if (c->istate != CHAN_INPUT_CLOSED || c->ostate != CHAN_OUTPUT_CLOSED)
 412                 return 0;
 413         if (!compat20) {
 414                 debug2("channel %d: is dead", c->self);
 415                 return 1;
 416         }
 417         if ((datafellows & SSH_BUG_EXTEOF) &&
 418             c->extended_usage == CHAN_EXTENDED_WRITE &&
 419             c->efd != -1 &&
 420             buffer_len(&c->extended) > 0) {
 421                 debug2("channel %d: active efd: %d len %d",
 422                     c->self, c->efd, buffer_len(&c->extended));
 423                 return 0;
 424         }
 425         if (!(c->flags & CHAN_CLOSE_SENT)) {
 426                 if (do_send) {
 427                         chan_send_close2(c);
 428                 } else {
 429                         /* channel would be dead if we sent a close */
 430                         if (c->flags & CHAN_CLOSE_RCVD) {
 431                                 debug2("channel %d: almost dead",
 432                                     c->self);
 433                                 return 1;
 434                         }
 435                 }
 436         }
 437         if ((c->flags & CHAN_CLOSE_SENT) &&
 438             (c->flags & CHAN_CLOSE_RCVD)) {
 439                 debug2("channel %d: is dead", c->self);
 440                 return 1;
 441         }
 442         return 0;
 443 }
 444
 445 /* helper */
 446 static void
 447 chan_shutdown_write(Channel *c)
 448 {
 449         buffer_clear(&c->output);
 450         if (compat20 && c->type == SSH_CHANNEL_LARVAL)
 451                 return;
 452         /* shutdown failure is allowed if write failed already */
 453         debug2("channel %d: close_write", c->self);
 454         if (c->sock != -1) {
 455                 if (shutdown(c->sock, SHUT_WR) < 0)
 456                         debug2("channel %d: chan_shutdown_write: "
 457                             "shutdown() failed for fd%d: %.100s",
 458                             c->self, c->sock, strerror(errno));
 459         } else {
 460                 if (channel_close_fd(&c->wfd) < 0)
 461                         logit("channel %d: chan_shutdown_write: "
 462                             "close() failed for fd%d: %.100s",
 463                             c->self, c->wfd, strerror(errno));
 464         }
 465 }
 466 static void
 467 chan_shutdown_read(Channel *c)
 468 {
 469         if (compat20 && c->type == SSH_CHANNEL_LARVAL)
 470                 return;
 471         debug2("channel %d: close_read", c->self);
 472         if (c->sock != -1) {
 473                 /*
 474                  * shutdown(sock, SHUT_READ) may return ENOTCONN if the
 475                  * write side has been closed already. (bug on Linux)
 476                  * HP-UX may return ENOTCONN also.
 477                  */
 478                 if (shutdown(c->sock, SHUT_RD) < 0
 479                     && errno != ENOTCONN)
 480                         error("channel %d: chan_shutdown_read: "
 481                             "shutdown() failed for fd%d [i%d o%d]: %.100s",
 482                             c->self, c->sock, c->istate, c->ostate,
 483                             strerror(errno));
 484         } else {
 485                 if (channel_close_fd(&c->rfd) < 0)
 486                         logit("channel %d: chan_shutdown_read: "
 487                             "close() failed for fd%d: %.100s",
 488                             c->self, c->rfd, strerror(errno));
 489         }
 490 }