nchan.c

   1 /* $OpenBSD: nchan.c,v 1.54 2006/07/08 21:47:12 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 "ssh1.h"
  32 #include "ssh2.h"
  33 #include "buffer.h"
  34 #include "packet.h"
  35 #include "channels.h"
  36 #include "compat.h"
  37 #include "log.h"
  38
  39 /*
  40  * SSH Protocol 1.5 aka New Channel Protocol
  41  * Thanks to Martina, Axel and everyone who left Erlangen, leaving me bored.
  42  * Written by Markus Friedl in October 1999
  43  *
  44  * Protocol versions 1.3 and 1.5 differ in the handshake protocol used for the
  45  * tear down of channels:
  46  *
  47  * 1.3: strict request-ack-protocol:
  48  *      CLOSE   ->
  49  *              <-  CLOSE_CONFIRM
  50  *
  51  * 1.5: uses variations of:
  52  *      IEOF    ->
  53  *              <-  OCLOSE
  54  *              <-  IEOF
  55  *      OCLOSE  ->
  56  *      i.e. both sides have to close the channel
  57  *
  58  * 2.0: the EOF messages are optional
  59  *
  60  * See the debugging output from 'ssh -v' and 'sshd -d' of
  61  * ssh-1.2.27 as an example.
  62  *
  63  */
  64
  65 /* functions manipulating channel states */
  66 /*
  67  * EVENTS update channel input/output states execute ACTIONS
  68  */
  69 /*
  70  * ACTIONS: should never update the channel states
  71  */
  72 static void     chan_send_ieof1(Channel *);
  73 static void     chan_send_oclose1(Channel *);
  74 static void     chan_send_close2(Channel *);
  75 static void     chan_send_eof2(Channel *);
  76
  77 /* helper */
  78 static void     chan_shutdown_write(Channel *);
  79 static void     chan_shutdown_read(Channel *);
  80
  81 static char *ostates[] = { "open", "drain", "wait_ieof", "closed" };
  82 static char *istates[] = { "open", "drain", "wait_oclose", "closed" };
  83
  84 static void
  85 chan_set_istate(Channel *c, u_int next)
  86 {
  87         if (c->istate > CHAN_INPUT_CLOSED || next > CHAN_INPUT_CLOSED)
  88                 fatal("chan_set_istate: bad state %d -> %d", c->istate, next);
  89         debug2("channel %d: input %s -> %s", c->self, istates[c->istate],
  90             istates[next]);
  91         c->istate = next;
  92 }
  93 static void
  94 chan_set_ostate(Channel *c, u_int next)
  95 {
  96         if (c->ostate > CHAN_OUTPUT_CLOSED || next > CHAN_OUTPUT_CLOSED)
  97                 fatal("chan_set_ostate: bad state %d -> %d", c->ostate, next);
  98         debug2("channel %d: output %s -> %s", c->self, ostates[c->ostate],
  99             ostates[next]);
 100         c->ostate = next;
 101 }
 102
 103 /*
 104  * SSH1 specific implementation of event functions
 105  */
 106
 107 static void
 108 chan_rcvd_oclose1(Channel *c)
 109 {
 110         debug2("channel %d: rcvd oclose", c->self);
 111         switch (c->istate) {
 112         case CHAN_INPUT_WAIT_OCLOSE:
 113                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 114                 break;
 115         case CHAN_INPUT_OPEN:
 116                 chan_shutdown_read(c);
 117                 chan_send_ieof1(c);
 118                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 119                 break;
 120         case CHAN_INPUT_WAIT_DRAIN:
 121                 /* both local read_failed and remote write_failed  */
 122                 chan_send_ieof1(c);
 123                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 124                 break;
 125         default:
 126                 error("channel %d: protocol error: rcvd_oclose for istate %d",
 127                     c->self, c->istate);
 128                 return;
 129         }
 130 }
 131 void
 132 chan_read_failed(Channel *c)
 133 {
 134         debug2("channel %d: read failed", c->self);
 135         switch (c->istate) {
 136         case CHAN_INPUT_OPEN:
 137                 chan_shutdown_read(c);
 138                 chan_set_istate(c, CHAN_INPUT_WAIT_DRAIN);
 139                 break;
 140         default:
 141                 error("channel %d: chan_read_failed for istate %d",
 142                     c->self, c->istate);
 143                 break;
 144         }
 145 }
 146 void
 147 chan_ibuf_empty(Channel *c)
 148 {
 149         debug2("channel %d: ibuf empty", c->self);
 150         if (buffer_len(&c->input)) {
 151                 error("channel %d: chan_ibuf_empty for non empty buffer",
 152                     c->self);
 153                 return;
 154         }
 155         switch (c->istate) {
 156         case CHAN_INPUT_WAIT_DRAIN:
 157                 if (compat20) {
 158                         if (!(c->flags & CHAN_CLOSE_SENT))
 159                                 chan_send_eof2(c);
 160                         chan_set_istate(c, CHAN_INPUT_CLOSED);
 161                 } else {
 162                         chan_send_ieof1(c);
 163                         chan_set_istate(c, CHAN_INPUT_WAIT_OCLOSE);
 164                 }
 165                 break;
 166         default:
 167                 error("channel %d: chan_ibuf_empty for istate %d",
 168                     c->self, c->istate);
 169                 break;
 170         }
 171 }
 172 static void
 173 chan_rcvd_ieof1(Channel *c)
 174 {
 175         debug2("channel %d: rcvd ieof", c->self);
 176         switch (c->ostate) {
 177         case CHAN_OUTPUT_OPEN:
 178                 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
 179                 break;
 180         case CHAN_OUTPUT_WAIT_IEOF:
 181                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 182                 break;
 183         default:
 184                 error("channel %d: protocol error: rcvd_ieof for ostate %d",
 185                     c->self, c->ostate);
 186                 break;
 187         }
 188 }
 189 static void
 190 chan_write_failed1(Channel *c)
 191 {
 192         debug2("channel %d: write failed", c->self);
 193         switch (c->ostate) {
 194         case CHAN_OUTPUT_OPEN:
 195                 chan_shutdown_write(c);
 196                 chan_send_oclose1(c);
 197                 chan_set_ostate(c, CHAN_OUTPUT_WAIT_IEOF);
 198                 break;
 199         case CHAN_OUTPUT_WAIT_DRAIN:
 200                 chan_shutdown_write(c);
 201                 chan_send_oclose1(c);
 202                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 203                 break;
 204         default:
 205                 error("channel %d: chan_write_failed for ostate %d",
 206                     c->self, c->ostate);
 207                 break;
 208         }
 209 }
 210 void
 211 chan_obuf_empty(Channel *c)
 212 {
 213         debug2("channel %d: obuf empty", c->self);
 214         if (buffer_len(&c->output)) {
 215                 error("channel %d: chan_obuf_empty for non empty buffer",
 216                     c->self);
 217                 return;
 218         }
 219         switch (c->ostate) {
 220         case CHAN_OUTPUT_WAIT_DRAIN:
 221                 chan_shutdown_write(c);
 222                 if (!compat20)
 223                         chan_send_oclose1(c);
 224                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 225                 break;
 226         default:
 227                 error("channel %d: internal error: obuf_empty for ostate %d",
 228                     c->self, c->ostate);
 229                 break;
 230         }
 231 }
 232 static void
 233 chan_send_ieof1(Channel *c)
 234 {
 235         debug2("channel %d: send ieof", c->self);
 236         switch (c->istate) {
 237         case CHAN_INPUT_OPEN:
 238         case CHAN_INPUT_WAIT_DRAIN:
 239                 packet_start(SSH_MSG_CHANNEL_INPUT_EOF);
 240                 packet_put_int(c->remote_id);
 241                 packet_send();
 242                 break;
 243         default:
 244                 error("channel %d: cannot send ieof for istate %d",
 245                     c->self, c->istate);
 246                 break;
 247         }
 248 }
 249 static void
 250 chan_send_oclose1(Channel *c)
 251 {
 252         debug2("channel %d: send oclose", c->self);
 253         switch (c->ostate) {
 254         case CHAN_OUTPUT_OPEN:
 255         case CHAN_OUTPUT_WAIT_DRAIN:
 256                 buffer_clear(&c->output);
 257                 packet_start(SSH_MSG_CHANNEL_OUTPUT_CLOSE);
 258                 packet_put_int(c->remote_id);
 259                 packet_send();
 260                 break;
 261         default:
 262                 error("channel %d: cannot send oclose for ostate %d",
 263                     c->self, c->ostate);
 264                 break;
 265         }
 266 }
 267
 268 /*
 269  * the same for SSH2
 270  */
 271 static void
 272 chan_rcvd_close2(Channel *c)
 273 {
 274         debug2("channel %d: rcvd close", c->self);
 275         if (c->flags & CHAN_CLOSE_RCVD)
 276                 error("channel %d: protocol error: close rcvd twice", c->self);
 277         c->flags |= CHAN_CLOSE_RCVD;
 278         if (c->type == SSH_CHANNEL_LARVAL) {
 279                 /* tear down larval channels immediately */
 280                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 281                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 282                 return;
 283         }
 284         switch (c->ostate) {
 285         case CHAN_OUTPUT_OPEN:
 286                 /*
 287                  * wait until a data from the channel is consumed if a CLOSE
 288                  * is received
 289                  */
 290                 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
 291                 break;
 292         }
 293         switch (c->istate) {
 294         case CHAN_INPUT_OPEN:
 295                 chan_shutdown_read(c);
 296                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 297                 break;
 298         case CHAN_INPUT_WAIT_DRAIN:
 299                 chan_send_eof2(c);
 300                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 301                 break;
 302         }
 303 }
 304 static void
 305 chan_rcvd_eof2(Channel *c)
 306 {
 307         debug2("channel %d: rcvd eof", c->self);
 308         c->flags |= CHAN_EOF_RCVD;
 309         if (c->ostate == CHAN_OUTPUT_OPEN)
 310                 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
 311 }
 312 static void
 313 chan_write_failed2(Channel *c)
 314 {
 315         debug2("channel %d: write failed", c->self);
 316         switch (c->ostate) {
 317         case CHAN_OUTPUT_OPEN:
 318         case CHAN_OUTPUT_WAIT_DRAIN:
 319                 chan_shutdown_write(c);
 320                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 321                 break;
 322         default:
 323                 error("channel %d: chan_write_failed for ostate %d",
 324                     c->self, c->ostate);
 325                 break;
 326         }
 327 }
 328 static void
 329 chan_send_eof2(Channel *c)
 330 {
 331         debug2("channel %d: send eof", c->self);
 332         switch (c->istate) {
 333         case CHAN_INPUT_WAIT_DRAIN:
 334                 packet_start(SSH2_MSG_CHANNEL_EOF);
 335                 packet_put_int(c->remote_id);
 336                 packet_send();
 337                 c->flags |= CHAN_EOF_SENT;
 338                 break;
 339         default:
 340                 error("channel %d: cannot send eof for istate %d",
 341                     c->self, c->istate);
 342                 break;
 343         }
 344 }
 345 static void
 346 chan_send_close2(Channel *c)
 347 {
 348         debug2("channel %d: send close", c->self);
 349         if (c->ostate != CHAN_OUTPUT_CLOSED ||
 350             c->istate != CHAN_INPUT_CLOSED) {
 351                 error("channel %d: cannot send close for istate/ostate %d/%d",
 352                     c->self, c->istate, c->ostate);
 353         } else if (c->flags & CHAN_CLOSE_SENT) {
 354                 error("channel %d: already sent close", c->self);
 355         } else {
 356                 packet_start(SSH2_MSG_CHANNEL_CLOSE);
 357                 packet_put_int(c->remote_id);
 358                 packet_send();
 359                 c->flags |= CHAN_CLOSE_SENT;
 360         }
 361 }
 362
 363 /* shared */
 364
 365 void
 366 chan_rcvd_ieof(Channel *c)
 367 {
 368         if (compat20)
 369                 chan_rcvd_eof2(c);
 370         else
 371                 chan_rcvd_ieof1(c);
 372         if (c->ostate == CHAN_OUTPUT_WAIT_DRAIN &&
 373             buffer_len(&c->output) == 0 &&
 374             !CHANNEL_EFD_OUTPUT_ACTIVE(c))
 375                 chan_obuf_empty(c);
 376 }
 377 void
 378 chan_rcvd_oclose(Channel *c)
 379 {
 380         if (compat20)
 381                 chan_rcvd_close2(c);
 382         else
 383                 chan_rcvd_oclose1(c);
 384 }
 385 void
 386 chan_write_failed(Channel *c)
 387 {
 388         if (compat20)
 389                 chan_write_failed2(c);
 390         else
 391                 chan_write_failed1(c);
 392 }
 393
 394 void
 395 chan_mark_dead(Channel *c)
 396 {
 397         c->type = SSH_CHANNEL_ZOMBIE;
 398 }
 399
 400 int
 401 chan_is_dead(Channel *c, int do_send)
 402 {
 403         if (c->type == SSH_CHANNEL_ZOMBIE) {
 404                 debug2("channel %d: zombie", c->self);
 405                 return 1;
 406         }
 407         if (c->istate != CHAN_INPUT_CLOSED || c->ostate != CHAN_OUTPUT_CLOSED)
 408                 return 0;
 409         if (!compat20) {
 410                 debug2("channel %d: is dead", c->self);
 411                 return 1;
 412         }
 413         if ((datafellows & SSH_BUG_EXTEOF) &&
 414             c->extended_usage == CHAN_EXTENDED_WRITE &&
 415             c->efd != -1 &&
 416             buffer_len(&c->extended) > 0) {
 417                 debug2("channel %d: active efd: %d len %d",
 418                     c->self, c->efd, buffer_len(&c->extended));
 419                 return 0;
 420         }
 421         if (!(c->flags & CHAN_CLOSE_SENT)) {
 422                 if (do_send) {
 423                         chan_send_close2(c);
 424                 } else {
 425                         /* channel would be dead if we sent a close */
 426                         if (c->flags & CHAN_CLOSE_RCVD) {
 427                                 debug2("channel %d: almost dead",
 428                                     c->self);
 429                                 return 1;
 430                         }
 431                 }
 432         }
 433         if ((c->flags & CHAN_CLOSE_SENT) &&
 434             (c->flags & CHAN_CLOSE_RCVD)) {
 435                 debug2("channel %d: is dead", c->self);
 436                 return 1;
 437         }
 438         return 0;
 439 }
 440
 441 /* helper */
 442 static void
 443 chan_shutdown_write(Channel *c)
 444 {
 445         buffer_clear(&c->output);
 446         if (compat20 && c->type == SSH_CHANNEL_LARVAL)
 447                 return;
 448         /* shutdown failure is allowed if write failed already */
 449         debug2("channel %d: close_write", c->self);
 450         if (c->sock != -1) {
 451                 if (shutdown(c->sock, SHUT_WR) < 0)
 452                         debug2("channel %d: chan_shutdown_write: "
 453                             "shutdown() failed for fd%d: %.100s",
 454                             c->self, c->sock, strerror(errno));
 455         } else {
 456                 if (channel_close_fd(&c->wfd) < 0)
 457                         logit("channel %d: chan_shutdown_write: "
 458                             "close() failed for fd%d: %.100s",
 459                             c->self, c->wfd, strerror(errno));
 460         }
 461 }
 462 static void
 463 chan_shutdown_read(Channel *c)
 464 {
 465         if (compat20 && c->type == SSH_CHANNEL_LARVAL)
 466                 return;
 467         debug2("channel %d: close_read", c->self);
 468         if (c->sock != -1) {
 469                 /*
 470                  * shutdown(sock, SHUT_READ) may return ENOTCONN if the
 471                  * write side has been closed already. (bug on Linux)
 472                  * HP-UX may return ENOTCONN also.
 473                  */
 474                 if (shutdown(c->sock, SHUT_RD) < 0
 475                     && errno != ENOTCONN)
 476                         error("channel %d: chan_shutdown_read: "
 477                             "shutdown() failed for fd%d [i%d o%d]: %.100s",
 478                             c->self, c->sock, c->istate, c->ostate,
 479                             strerror(errno));
 480         } else {
 481                 if (channel_close_fd(&c->rfd) < 0)
 482                         logit("channel %d: chan_shutdown_read: "
 483                             "close() failed for fd%d: %.100s",
 484                             c->self, c->rfd, strerror(errno));
 485         }
 486 }