nchan.c

   1 /* $OpenBSD: nchan.c,v 1.75 2024/02/01 02:37:33 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 static void     chan_shutdown_extended_read(struct ssh *, Channel *);
  84
  85 static const char * const ostates[] = {
  86         "open", "drain", "wait_ieof", "closed",
  87 };
  88 static const char * const istates[] = {
  89         "open", "drain", "wait_oclose", "closed",
  90 };
  91
  92 static void
  93 chan_set_istate(Channel *c, u_int next)
  94 {
  95         if (c->istate > CHAN_INPUT_CLOSED || next > CHAN_INPUT_CLOSED)
  96                 fatal("chan_set_istate: bad state %d -> %d", c->istate, next);
  97         debug2("channel %d: input %s -> %s", c->self, istates[c->istate],
  98             istates[next]);
  99         c->istate = next;
 100 }
 101
 102 static void
 103 chan_set_ostate(Channel *c, u_int next)
 104 {
 105         if (c->ostate > CHAN_OUTPUT_CLOSED || next > CHAN_OUTPUT_CLOSED)
 106                 fatal("chan_set_ostate: bad state %d -> %d", c->ostate, next);
 107         debug2("channel %d: output %s -> %s", c->self, ostates[c->ostate],
 108             ostates[next]);
 109         c->ostate = next;
 110 }
 111
 112 void
 113 chan_read_failed(struct ssh *ssh, Channel *c)
 114 {
 115         debug2("channel %d: read failed", c->self);
 116         switch (c->istate) {
 117         case CHAN_INPUT_OPEN:
 118                 chan_shutdown_read(ssh, c);
 119                 chan_set_istate(c, CHAN_INPUT_WAIT_DRAIN);
 120                 break;
 121         default:
 122                 error("channel %d: chan_read_failed for istate %d",
 123                     c->self, c->istate);
 124                 break;
 125         }
 126 }
 127
 128 void
 129 chan_ibuf_empty(struct ssh *ssh, Channel *c)
 130 {
 131         debug2("channel %d: ibuf empty", c->self);
 132         if (sshbuf_len(c->input)) {
 133                 error("channel %d: chan_ibuf_empty for non empty buffer",
 134                     c->self);
 135                 return;
 136         }
 137         switch (c->istate) {
 138         case CHAN_INPUT_WAIT_DRAIN:
 139                 if (!(c->flags & (CHAN_CLOSE_SENT|CHAN_LOCAL)))
 140                         chan_send_eof2(ssh, c);
 141                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 142                 break;
 143         default:
 144                 error("channel %d: chan_ibuf_empty for istate %d",
 145                     c->self, c->istate);
 146                 break;
 147         }
 148 }
 149
 150 void
 151 chan_obuf_empty(struct ssh *ssh, Channel *c)
 152 {
 153         debug2("channel %d: obuf empty", c->self);
 154         if (sshbuf_len(c->output)) {
 155                 error("channel %d: chan_obuf_empty for non empty buffer",
 156                     c->self);
 157                 return;
 158         }
 159         switch (c->ostate) {
 160         case CHAN_OUTPUT_WAIT_DRAIN:
 161                 chan_shutdown_write(ssh, c);
 162                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 163                 break;
 164         default:
 165                 error("channel %d: internal error: obuf_empty for ostate %d",
 166                     c->self, c->ostate);
 167                 break;
 168         }
 169 }
 170
 171 void
 172 chan_rcvd_eow(struct ssh *ssh, Channel *c)
 173 {
 174         debug2("channel %d: rcvd eow", c->self);
 175         switch (c->istate) {
 176         case CHAN_INPUT_OPEN:
 177                 chan_shutdown_read(ssh, c);
 178                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 179                 break;
 180         }
 181 }
 182
 183 static void
 184 chan_send_eof2(struct ssh *ssh, Channel *c)
 185 {
 186         int r;
 187
 188         debug2("channel %d: send eof", c->self);
 189         switch (c->istate) {
 190         case CHAN_INPUT_WAIT_DRAIN:
 191                 if (!c->have_remote_id)
 192                         fatal_f("channel %d: no remote_id", c->self);
 193                 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_EOF)) != 0 ||
 194                     (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
 195                     (r = sshpkt_send(ssh)) != 0)
 196                         fatal_fr(r, "send CHANNEL_EOF");
 197                 c->flags |= CHAN_EOF_SENT;
 198                 break;
 199         default:
 200                 error("channel %d: cannot send eof for istate %d",
 201                     c->self, c->istate);
 202                 break;
 203         }
 204 }
 205
 206 static void
 207 chan_send_close2(struct ssh *ssh, Channel *c)
 208 {
 209         int r;
 210
 211         debug2("channel %d: send close", c->self);
 212         if (c->ostate != CHAN_OUTPUT_CLOSED ||
 213             c->istate != CHAN_INPUT_CLOSED) {
 214                 error("channel %d: cannot send close for istate/ostate %d/%d",
 215                     c->self, c->istate, c->ostate);
 216         } else if (c->flags & CHAN_CLOSE_SENT) {
 217                 error("channel %d: already sent close", c->self);
 218         } else {
 219                 if (!c->have_remote_id)
 220                         fatal_f("channel %d: no remote_id", c->self);
 221                 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_CLOSE)) != 0 ||
 222                     (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
 223                     (r = sshpkt_send(ssh)) != 0)
 224                         fatal_fr(r, "send CHANNEL_EOF");
 225                 c->flags |= CHAN_CLOSE_SENT;
 226         }
 227 }
 228
 229 static void
 230 chan_send_eow2(struct ssh *ssh, Channel *c)
 231 {
 232         int r;
 233
 234         debug2("channel %d: send eow", c->self);
 235         if (c->ostate == CHAN_OUTPUT_CLOSED) {
 236                 error("channel %d: must not sent eow on closed output",
 237                     c->self);
 238                 return;
 239         }
 240         if (!(ssh->compat & SSH_NEW_OPENSSH))
 241                 return;
 242         if (!c->have_remote_id)
 243                 fatal_f("channel %d: no remote_id", c->self);
 244         if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_REQUEST)) != 0 ||
 245             (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 ||
 246             (r = sshpkt_put_cstring(ssh, "eow@openssh.com")) != 0 ||
 247             (r = sshpkt_put_u8(ssh, 0)) != 0 ||
 248             (r = sshpkt_send(ssh)) != 0)
 249                 fatal_fr(r, "send CHANNEL_EOF");
 250 }
 251
 252 /* shared */
 253
 254 void
 255 chan_rcvd_ieof(struct ssh *ssh, Channel *c)
 256 {
 257         debug2("channel %d: rcvd eof", c->self);
 258         c->flags |= CHAN_EOF_RCVD;
 259         if (c->ostate == CHAN_OUTPUT_OPEN)
 260                 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
 261         if (c->ostate == CHAN_OUTPUT_WAIT_DRAIN &&
 262             sshbuf_len(c->output) == 0 &&
 263             !CHANNEL_EFD_OUTPUT_ACTIVE(c))
 264                 chan_obuf_empty(ssh, c);
 265 }
 266
 267 void
 268 chan_rcvd_oclose(struct ssh *ssh, Channel *c)
 269 {
 270         debug2("channel %d: rcvd close", c->self);
 271         if (!(c->flags & CHAN_LOCAL)) {
 272                 if (c->flags & CHAN_CLOSE_RCVD)
 273                         error("channel %d: protocol error: close rcvd twice",
 274                             c->self);
 275                 c->flags |= CHAN_CLOSE_RCVD;
 276         }
 277         if (c->type == SSH_CHANNEL_LARVAL) {
 278                 /* tear down larval channels immediately */
 279                 chan_set_ostate(c, CHAN_OUTPUT_CLOSED);
 280                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 281                 return;
 282         }
 283         switch (c->ostate) {
 284         case CHAN_OUTPUT_OPEN:
 285                 /*
 286                  * wait until a data from the channel is consumed if a CLOSE
 287                  * is received
 288                  */
 289                 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN);
 290                 break;
 291         }
 292         switch (c->istate) {
 293         case CHAN_INPUT_OPEN:
 294                 chan_shutdown_read(ssh, c);
 295                 chan_shutdown_extended_read(ssh, c);
 296                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 297                 break;
 298         case CHAN_INPUT_WAIT_DRAIN:
 299                 if (!(c->flags & CHAN_LOCAL))
 300                         chan_send_eof2(ssh, c);
 301                 chan_shutdown_extended_read(ssh, c);
 302                 chan_set_istate(c, CHAN_INPUT_CLOSED);
 303                 break;
 304         }
 305 }
 306
 307 void
 308 chan_write_failed(struct ssh *ssh, Channel *c)
 309 {
 310         debug2("channel %d: write failed", c->self);
 311         switch (c->ostate) {
 312         case CHAN_OUTPUT_OPEN:
 313         case CHAN_OUTPUT_WAIT_DRAIN:
 314                 chan_shutdown_write(ssh, c);
 315                 if (strcmp(c->ctype, "session") == 0)
 316                         chan_send_eow2(ssh, 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
 326 void
 327 chan_mark_dead(struct ssh *ssh, Channel *c)
 328 {
 329         c->type = SSH_CHANNEL_ZOMBIE;
 330 }
 331
 332 int
 333 chan_is_dead(struct ssh *ssh, Channel *c, int do_send)
 334 {
 335         if (c->type == SSH_CHANNEL_ZOMBIE) {
 336                 debug2("channel %d: zombie", c->self);
 337                 return 1;
 338         }
 339         if (c->istate != CHAN_INPUT_CLOSED || c->ostate != CHAN_OUTPUT_CLOSED)
 340                 return 0;
 341         if ((ssh->compat & SSH_BUG_EXTEOF) &&
 342             c->extended_usage == CHAN_EXTENDED_WRITE &&
 343             c->efd != -1 &&
 344             sshbuf_len(c->extended) > 0) {
 345                 debug2("channel %d: active efd: %d len %zu",
 346                     c->self, c->efd, sshbuf_len(c->extended));
 347                 return 0;
 348         }
 349         if (c->flags & CHAN_LOCAL) {
 350                 debug2("channel %d: is dead (local)", c->self);
 351                 return 1;
 352         }
 353         if (!(c->flags & CHAN_CLOSE_SENT)) {
 354                 if (do_send) {
 355                         chan_send_close2(ssh, c);
 356                 } else {
 357                         /* channel would be dead if we sent a close */
 358                         if (c->flags & CHAN_CLOSE_RCVD) {
 359                                 debug2("channel %d: almost dead",
 360                                     c->self);
 361                                 return 1;
 362                         }
 363                 }
 364         }
 365         if ((c->flags & CHAN_CLOSE_SENT) &&
 366             (c->flags & CHAN_CLOSE_RCVD)) {
 367                 debug2("channel %d: is dead", c->self);
 368                 return 1;
 369         }
 370         return 0;
 371 }
 372
 373 /* helper */
 374 static void
 375 chan_shutdown_write(struct ssh *ssh, Channel *c)
 376 {
 377         sshbuf_reset(c->output);
 378         if (c->type == SSH_CHANNEL_LARVAL)
 379                 return;
 380         /* shutdown failure is allowed if write failed already */
 381         debug2_f("channel %d: (i%d o%d sock %d wfd %d efd %d [%s])",
 382             c->self, c->istate, c->ostate, c->sock, c->wfd, c->efd,
 383             channel_format_extended_usage(c));
 384         if (c->sock != -1) {
 385                 if (shutdown(c->sock, SHUT_WR) == -1) {
 386                         debug2_f("channel %d: shutdown() failed for "
 387                             "fd %d [i%d o%d]: %.100s", c->self, c->sock,
 388                             c->istate, c->ostate, strerror(errno));
 389                 }
 390         } else {
 391                 if (channel_close_fd(ssh, c, &c->wfd) < 0) {
 392                         logit_f("channel %d: close() failed for "
 393                             "fd %d [i%d o%d]: %.100s", c->self, c->wfd,
 394                             c->istate, c->ostate, strerror(errno));
 395                 }
 396         }
 397 }
 398
 399 static void
 400 chan_shutdown_read(struct ssh *ssh, Channel *c)
 401 {
 402         if (c->type == SSH_CHANNEL_LARVAL)
 403                 return;
 404         debug2_f("channel %d: (i%d o%d sock %d wfd %d efd %d [%s])",
 405             c->self, c->istate, c->ostate, c->sock, c->rfd, c->efd,
 406             channel_format_extended_usage(c));
 407         if (c->sock != -1) {
 408                 /*
 409                  * shutdown(sock, SHUT_READ) may return ENOTCONN if the
 410                  * write side has been closed already. (bug on Linux)
 411                  * HP-UX may return ENOTCONN also.
 412                  */
 413                 if (shutdown(c->sock, SHUT_RD) == -1 && errno != ENOTCONN) {
 414                         error_f("channel %d: shutdown() failed for "
 415                             "fd %d [i%d o%d]: %.100s", c->self, c->sock,
 416                             c->istate, c->ostate, strerror(errno));
 417                 }
 418         } else {
 419                 if (channel_close_fd(ssh, c, &c->rfd) < 0) {
 420                         logit_f("channel %d: close() failed for "
 421                             "fd %d [i%d o%d]: %.100s", c->self, c->rfd,
 422                             c->istate, c->ostate, strerror(errno));
 423                 }
 424         }
 425 }
 426
 427 static void
 428 chan_shutdown_extended_read(struct ssh *ssh, Channel *c)
 429 {
 430         if (c->type == SSH_CHANNEL_LARVAL || c->efd == -1)
 431                 return;
 432         if (c->extended_usage != CHAN_EXTENDED_READ &&
 433             c->extended_usage != CHAN_EXTENDED_IGNORE)
 434                 return;
 435         debug_f("channel %d: (i%d o%d sock %d wfd %d efd %d [%s])",
 436             c->self, c->istate, c->ostate, c->sock, c->rfd, c->efd,
 437             channel_format_extended_usage(c));
 438         if (channel_close_fd(ssh, c, &c->efd) < 0) {
 439                 logit_f("channel %d: close() failed for "
 440                     "extended fd %d [i%d o%d]: %.100s", c->self, c->efd,
 441                     c->istate, c->ostate, strerror(errno));
 442         }
 443 }