nchan.c

   1 /* $OpenBSD: nchan.c,v 1.55 2006/07/11 20:07:25 stevesk 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
  33 #include "ssh1.h"
  34 #include "ssh2.h"
  35 #include "buffer.h"
  36 #include "packet.h"
  37 #include "channels.h"
  38 #include "compat.h"
  39 #include "log.h"
  40
  41 /*
  42  * SSH Protocol 1.5 aka New Channel Protocol
  43  * Thanks to Martina, Axel and everyone who left Erlangen, leaving me bored.
  44  * Written by Markus Friedl in October 1999
  45  *
  46  * Protocol versions 1.3 and 1.5 differ in the handshake protocol used for the
  47  * tear down of channels:
  48  *
  49  * 1.3: strict request-ack-protocol:
  50  *      CLOSE   ->
  51  *              <-  CLOSE_CONFIRM
  52  *
  53  * 1.5: uses variations of:
  54  *      IEOF    ->
  55  *              <-  OCLOSE
  56  *              <-  IEOF
  57  *      OCLOSE  ->
  58  *      i.e. both sides have to close the channel
  59  *
  60  * 2.0: the EOF messages are optional
  61  *
  62  * See the debugging output from 'ssh -v' and 'sshd -d' of
  63  * ssh-1.2.27 as an example.
  64  *
  65  */
  66
  67 /* functions manipulating channel states */
  68 /*
  69  * EVENTS update channel input/output states execute ACTIONS
  70  */
  71 /*
  72  * ACTIONS: should never update the channel states
  73  */
  74 static void     chan_send_ieof1(Channel *);
  75 static void     chan_send_oclose1(Channel *);
  76 static void     chan_send_close2(Channel *);
  77 static void     chan_send_eof2(Channel *);
  78
  79 /* helper */
  80 static void     chan_shutdown_write(Channel *);
  81 static void     chan_shutdown_read(Channel *);
  82
  83 static char *ostates[] = { "open", "drain", "wait_ieof", "closed" };
  84 static char *istates[] = { "open", "drain", "wait_oclose", "closed" };
  85
  86 static void
  87 chan_set_istate(Channel *c, u_int next)
  88 {
  89         if (c->istate > CHAN_INPUT_CLOSED || next > CHAN_INPUT_CLOSED)
  90                 fatal("chan_set_istate: bad state %d -> %d", c->istate, next);
  91         debug2("channel %d: input %s -> %s", c->self, istates[c->istate],
  92             istates[next]);
  93         c->istate = next;
  94 }
  95 static void
  96 chan_set_ostate(Channel *c, u_int next)
  97 {
  98         if (c->ostate > CHAN_OUTPUT_CLOSED || next > CHAN_OUTPUT_CLOSED)
  99                 fatal("chan_set_ostate: bad state %d -> %d", c->ostate, next);
 100         debug2("channel %d: output %s -> %s", c->self, ostates[c->ostate],
 101             ostates[next]);
 102         c->ostate = next;
 103 }
 104
 105 /*
 106  * SSH1 specific implementation of event functions
 107  */
 108
 109 static void
 110 chan_rcvd_oclose1(Channel *c)
 111 {
 112         debug2("channel %d: rcvd oclose", c->self);
 113         switch (c->istate) {
 114         case CHAN_INPUT_WAIT_OCLOSE:
 115                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 116                 break;
 117         case CHAN_INPUT_OPEN:
 118                 chan_shutdown_read(c);
 119                 chan_send_ieof1(c);
 120                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 121                 break;
 122         case CHAN_INPUT_WAIT_DRAIN:
 123                 /* both local read_failed and remote write_failed  */
 124                 chan_send_ieof1(c);
 125                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 126                 break;
 127         default:
 128                 error("channel %d: protocol error: rcvd_oclose for istate %d",
 129                     c->self, c->istate);
 130                 return;
 131         }
 132 }
 133 void
 134 chan_read_failed(Channel *c)
 135 {
 136         debug2("channel %d: read failed", c->self);
 137         switch (c->istate) {
 138         case CHAN_INPUT_OPEN:
 139                 chan_shutdown_read(c);
 140                 chan_set_istate(c, CHAN_INPUT_WAIT_DRAIN);
 141                 break;
 142         default:
 143                 error("channel %d: chan_read_failed for istate %d",
 144                     c->self, c->istate);
 145                 break;
 146         }
 147 }
 148 void
 149 chan_ibuf_empty(Channel *c)
 150 {
 151         debug2("channel %d: ibuf empty", c->self);
 152         if (buffer_len(&c->input)) {
 153                 error("channel %d: chan_ibuf_empty for non empty buffer",
 154                     c->self);
 155                 return;
 156         }
 157         switch (c->istate) {
 158         case CHAN_INPUT_WAIT_DRAIN:
 159                 if (compat20) {
 160                         if (!(c->flags & CHAN_CLOSE_SENT))
 161                                 chan_send_eof2(c);
 162                         chan_set_istate(c, CHAN_INPUT_CLOSED);
 163                 } else {
 164                         chan_send_ieof1(c);
 165                         chan_set_istate(c, CHAN_INPUT_WAIT_OCLOSE);
 166                 }
 167                 break;
 168         default:
 169                 error("channel %d: chan_ibuf_empty for istate %d",
 170                     c->self, c->istate);
 171                 break;
 172         }
 173 }
 174 static void
 175 chan_rcvd_ieof1(Channel *c)
 176 {
 177         debug2("channel %d: rcvd ieof", c->self);
 178         switch (c->ostate) {
 179         case CHAN_OUTPUT_OPEN:
 180                 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
 181                 break;
 182         case CHAN_OUTPUT_WAIT_IEOF:
 183                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 184                 break;
 185         default:
 186                 error("channel %d: protocol error: rcvd_ieof for ostate %d",
 187                     c->self, c->ostate);
 188                 break;
 189         }
 190 }
 191 static void
 192 chan_write_failed1(Channel *c)
 193 {
 194         debug2("channel %d: write failed", c->self);
 195         switch (c->ostate) {
 196         case CHAN_OUTPUT_OPEN:
 197                 chan_shutdown_write(c);
 198                 chan_send_oclose1(c);
 199                 chan_set_ostate(c, CHAN_OUTPUT_WAIT_IEOF);
 200                 break;
 201         case CHAN_OUTPUT_WAIT_DRAIN:
 202                 chan_shutdown_write(c);
 203                 chan_send_oclose1(c);
 204                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 205                 break;
 206         default:
 207                 error("channel %d: chan_write_failed for ostate %d",
 208                     c->self, c->ostate);
 209                 break;
 210         }
 211 }
 212 void
 213 chan_obuf_empty(Channel *c)
 214 {
 215         debug2("channel %d: obuf empty", c->self);
 216         if (buffer_len(&c->output)) {
 217                 error("channel %d: chan_obuf_empty for non empty buffer",
 218                     c->self);
 219                 return;
 220         }
 221         switch (c->ostate) {
 222         case CHAN_OUTPUT_WAIT_DRAIN:
 223                 chan_shutdown_write(c);
 224                 if (!compat20)
 225                         chan_send_oclose1(c);
 226                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 227                 break;
 228         default:
 229                 error("channel %d: internal error: obuf_empty for ostate %d",
 230                     c->self, c->ostate);
 231                 break;
 232         }
 233 }
 234 static void
 235 chan_send_ieof1(Channel *c)
 236 {
 237         debug2("channel %d: send ieof", c->self);
 238         switch (c->istate) {
 239         case CHAN_INPUT_OPEN:
 240         case CHAN_INPUT_WAIT_DRAIN:
 241                 packet_start(SSH_MSG_CHANNEL_INPUT_EOF);
 242                 packet_put_int(c->remote_id);
 243                 packet_send();
 244                 break;
 245         default:
 246                 error("channel %d: cannot send ieof for istate %d",
 247                     c->self, c->istate);
 248                 break;
 249         }
 250 }
 251 static void
 252 chan_send_oclose1(Channel *c)
 253 {
 254         debug2("channel %d: send oclose", c->self);
 255         switch (c->ostate) {
 256         case CHAN_OUTPUT_OPEN:
 257         case CHAN_OUTPUT_WAIT_DRAIN:
 258                 buffer_clear(&c->output);
 259                 packet_start(SSH_MSG_CHANNEL_OUTPUT_CLOSE);
 260                 packet_put_int(c->remote_id);
 261                 packet_send();
 262                 break;
 263         default:
 264                 error("channel %d: cannot send oclose for ostate %d",
 265                     c->self, c->ostate);
 266                 break;
 267         }
 268 }
 269
 270 /*
 271  * the same for SSH2
 272  */
 273 static void
 274 chan_rcvd_close2(Channel *c)
 275 {
 276         debug2("channel %d: rcvd close", c->self);
 277         if (c->flags & CHAN_CLOSE_RCVD)
 278                 error("channel %d: protocol error: close rcvd twice", c->self);
 279         c->flags |= CHAN_CLOSE_RCVD;
 280         if (c->type == SSH_CHANNEL_LARVAL) {
 281                 /* tear down larval channels immediately */
 282                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 283                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 284                 return;
 285         }
 286         switch (c->ostate) {
 287         case CHAN_OUTPUT_OPEN:
 288                 /*
 289                  * wait until a data from the channel is consumed if a CLOSE
 290                  * is received
 291                  */
 292                 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
 293                 break;
 294         }
 295         switch (c->istate) {
 296         case CHAN_INPUT_OPEN:
 297                 chan_shutdown_read(c);
 298                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 299                 break;
 300         case CHAN_INPUT_WAIT_DRAIN:
 301                 chan_send_eof2(c);
 302                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 303                 break;
 304         }
 305 }
 306 static void
 307 chan_rcvd_eof2(Channel *c)
 308 {
 309         debug2("channel %d: rcvd eof", c->self);
 310         c->flags |= CHAN_EOF_RCVD;
 311         if (c->ostate == CHAN_OUTPUT_OPEN)
 312                 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
 313 }
 314 static void
 315 chan_write_failed2(Channel *c)
 316 {
 317         debug2("channel %d: write failed", c->self);
 318         switch (c->ostate) {
 319         case CHAN_OUTPUT_OPEN:
 320         case CHAN_OUTPUT_WAIT_DRAIN:
 321                 chan_shutdown_write(c);
 322                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 323                 break;
 324         default:
 325                 error("channel %d: chan_write_failed for ostate %d",
 326                     c->self, c->ostate);
 327                 break;
 328         }
 329 }
 330 static void
 331 chan_send_eof2(Channel *c)
 332 {
 333         debug2("channel %d: send eof", c->self);
 334         switch (c->istate) {
 335         case CHAN_INPUT_WAIT_DRAIN:
 336                 packet_start(SSH2_MSG_CHANNEL_EOF);
 337                 packet_put_int(c->remote_id);
 338                 packet_send();
 339                 c->flags |= CHAN_EOF_SENT;
 340                 break;
 341         default:
 342                 error("channel %d: cannot send eof for istate %d",
 343                     c->self, c->istate);
 344                 break;
 345         }
 346 }
 347 static void
 348 chan_send_close2(Channel *c)
 349 {
 350         debug2("channel %d: send close", c->self);
 351         if (c->ostate != CHAN_OUTPUT_CLOSED ||
 352             c->istate != CHAN_INPUT_CLOSED) {
 353                 error("channel %d: cannot send close for istate/ostate %d/%d",
 354                     c->self, c->istate, c->ostate);
 355         } else if (c->flags & CHAN_CLOSE_SENT) {
 356                 error("channel %d: already sent close", c->self);
 357         } else {
 358                 packet_start(SSH2_MSG_CHANNEL_CLOSE);
 359                 packet_put_int(c->remote_id);
 360                 packet_send();
 361                 c->flags |= CHAN_CLOSE_SENT;
 362         }
 363 }
 364
 365 /* shared */
 366
 367 void
 368 chan_rcvd_ieof(Channel *c)
 369 {
 370         if (compat20)
 371                 chan_rcvd_eof2(c);
 372         else
 373                 chan_rcvd_ieof1(c);
 374         if (c->ostate == CHAN_OUTPUT_WAIT_DRAIN &&
 375             buffer_len(&c->output) == 0 &&
 376             !CHANNEL_EFD_OUTPUT_ACTIVE(c))
 377                 chan_obuf_empty(c);
 378 }
 379 void
 380 chan_rcvd_oclose(Channel *c)
 381 {
 382         if (compat20)
 383                 chan_rcvd_close2(c);
 384         else
 385                 chan_rcvd_oclose1(c);
 386 }
 387 void
 388 chan_write_failed(Channel *c)
 389 {
 390         if (compat20)
 391                 chan_write_failed2(c);
 392         else
 393                 chan_write_failed1(c);
 394 }
 395
 396 void
 397 chan_mark_dead(Channel *c)
 398 {
 399         c->type = SSH_CHANNEL_ZOMBIE;
 400 }
 401
 402 int
 403 chan_is_dead(Channel *c, int do_send)
 404 {
 405         if (c->type == SSH_CHANNEL_ZOMBIE) {
 406                 debug2("channel %d: zombie", c->self);
 407                 return 1;
 408         }
 409         if (c->istate != CHAN_INPUT_CLOSED || c->ostate != CHAN_OUTPUT_CLOSED)
 410                 return 0;
 411         if (!compat20) {
 412                 debug2("channel %d: is dead", c->self);
 413                 return 1;
 414         }
 415         if ((datafellows & SSH_BUG_EXTEOF) &&
 416             c->extended_usage == CHAN_EXTENDED_WRITE &&
 417             c->efd != -1 &&
 418             buffer_len(&c->extended) > 0) {
 419                 debug2("channel %d: active efd: %d len %d",
 420                     c->self, c->efd, buffer_len(&c->extended));
 421                 return 0;
 422         }
 423         if (!(c->flags & CHAN_CLOSE_SENT)) {
 424                 if (do_send) {
 425                         chan_send_close2(c);
 426                 } else {
 427                         /* channel would be dead if we sent a close */
 428                         if (c->flags & CHAN_CLOSE_RCVD) {
 429                                 debug2("channel %d: almost dead",
 430                                     c->self);
 431                                 return 1;
 432                         }
 433                 }
 434         }
 435         if ((c->flags & CHAN_CLOSE_SENT) &&
 436             (c->flags & CHAN_CLOSE_RCVD)) {
 437                 debug2("channel %d: is dead", c->self);
 438                 return 1;
 439         }
 440         return 0;
 441 }
 442
 443 /* helper */
 444 static void
 445 chan_shutdown_write(Channel *c)
 446 {
 447         buffer_clear(&c->output);
 448         if (compat20 && c->type == SSH_CHANNEL_LARVAL)
 449                 return;
 450         /* shutdown failure is allowed if write failed already */
 451         debug2("channel %d: close_write", c->self);
 452         if (c->sock != -1) {
 453                 if (shutdown(c->sock, SHUT_WR) < 0)
 454                         debug2("channel %d: chan_shutdown_write: "
 455                             "shutdown() failed for fd%d: %.100s",
 456                             c->self, c->sock, strerror(errno));
 457         } else {
 458                 if (channel_close_fd(&c->wfd) < 0)
 459                         logit("channel %d: chan_shutdown_write: "
 460                             "close() failed for fd%d: %.100s",
 461                             c->self, c->wfd, strerror(errno));
 462         }
 463 }
 464 static void
 465 chan_shutdown_read(Channel *c)
 466 {
 467         if (compat20 && c->type == SSH_CHANNEL_LARVAL)
 468                 return;
 469         debug2("channel %d: close_read", c->self);
 470         if (c->sock != -1) {
 471                 /*
 472                  * shutdown(sock, SHUT_READ) may return ENOTCONN if the
 473                  * write side has been closed already. (bug on Linux)
 474                  * HP-UX may return ENOTCONN also.
 475                  */
 476                 if (shutdown(c->sock, SHUT_RD) < 0
 477                     && errno != ENOTCONN)
 478                         error("channel %d: chan_shutdown_read: "
 479                             "shutdown() failed for fd%d [i%d o%d]: %.100s",
 480                             c->self, c->sock, c->istate, c->ostate,
 481                             strerror(errno));
 482         } else {
 483                 if (channel_close_fd(&c->rfd) < 0)
 484                         logit("channel %d: chan_shutdown_read: "
 485                             "close() failed for fd%d: %.100s",
 486                             c->self, c->rfd, strerror(errno));
 487         }
 488 }