1 /* $OpenBSD: nchan.c,v 1.73 2021/05/19 01:24:05 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 *ostates[] = { "open", "drain", "wait_ieof", "closed" }; 86 static const 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 98 static void 99 chan_set_ostate(Channel *c, u_int next) 100 { 101 if (c->ostate > CHAN_OUTPUT_CLOSED || next > CHAN_OUTPUT_CLOSED) 102 fatal("chan_set_ostate: bad state %d -> %d", c->ostate, next); 103 debug2("channel %d: output %s -> %s", c->self, ostates[c->ostate], 104 ostates[next]); 105 c->ostate = next; 106 } 107 108 void 109 chan_read_failed(struct ssh *ssh, Channel *c) 110 { 111 debug2("channel %d: read failed", c->self); 112 switch (c->istate) { 113 case CHAN_INPUT_OPEN: 114 chan_shutdown_read(ssh, c); 115 chan_set_istate(c, CHAN_INPUT_WAIT_DRAIN); 116 break; 117 default: 118 error("channel %d: chan_read_failed for istate %d", 119 c->self, c->istate); 120 break; 121 } 122 } 123 124 void 125 chan_ibuf_empty(struct ssh *ssh, Channel *c) 126 { 127 debug2("channel %d: ibuf empty", c->self); 128 if (sshbuf_len(c->input)) { 129 error("channel %d: chan_ibuf_empty for non empty buffer", 130 c->self); 131 return; 132 } 133 switch (c->istate) { 134 case CHAN_INPUT_WAIT_DRAIN: 135 if (!(c->flags & (CHAN_CLOSE_SENT|CHAN_LOCAL))) 136 chan_send_eof2(ssh, c); 137 chan_set_istate(c, CHAN_INPUT_CLOSED); 138 break; 139 default: 140 error("channel %d: chan_ibuf_empty for istate %d", 141 c->self, c->istate); 142 break; 143 } 144 } 145 146 void 147 chan_obuf_empty(struct ssh *ssh, Channel *c) 148 { 149 debug2("channel %d: obuf empty", c->self); 150 if (sshbuf_len(c->output)) { 151 error("channel %d: chan_obuf_empty for non empty buffer", 152 c->self); 153 return; 154 } 155 switch (c->ostate) { 156 case CHAN_OUTPUT_WAIT_DRAIN: 157 chan_shutdown_write(ssh, c); 158 chan_set_ostate(c, CHAN_OUTPUT_CLOSED); 159 break; 160 default: 161 error("channel %d: internal error: obuf_empty for ostate %d", 162 c->self, c->ostate); 163 break; 164 } 165 } 166 167 void 168 chan_rcvd_eow(struct ssh *ssh, Channel *c) 169 { 170 debug2("channel %d: rcvd eow", c->self); 171 switch (c->istate) { 172 case CHAN_INPUT_OPEN: 173 chan_shutdown_read(ssh, c); 174 chan_set_istate(c, CHAN_INPUT_CLOSED); 175 break; 176 } 177 } 178 179 static void 180 chan_send_eof2(struct ssh *ssh, Channel *c) 181 { 182 int r; 183 184 debug2("channel %d: send eof", c->self); 185 switch (c->istate) { 186 case CHAN_INPUT_WAIT_DRAIN: 187 if (!c->have_remote_id) 188 fatal_f("channel %d: no remote_id", c->self); 189 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_EOF)) != 0 || 190 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 191 (r = sshpkt_send(ssh)) != 0) 192 fatal_fr(r, "send CHANNEL_EOF"); 193 c->flags |= CHAN_EOF_SENT; 194 break; 195 default: 196 error("channel %d: cannot send eof for istate %d", 197 c->self, c->istate); 198 break; 199 } 200 } 201 202 static void 203 chan_send_close2(struct ssh *ssh, Channel *c) 204 { 205 int r; 206 207 debug2("channel %d: send close", c->self); 208 if (c->ostate != CHAN_OUTPUT_CLOSED || 209 c->istate != CHAN_INPUT_CLOSED) { 210 error("channel %d: cannot send close for istate/ostate %d/%d", 211 c->self, c->istate, c->ostate); 212 } else if (c->flags & CHAN_CLOSE_SENT) { 213 error("channel %d: already sent close", c->self); 214 } else { 215 if (!c->have_remote_id) 216 fatal_f("channel %d: no remote_id", c->self); 217 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_CLOSE)) != 0 || 218 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 219 (r = sshpkt_send(ssh)) != 0) 220 fatal_fr(r, "send CHANNEL_EOF"); 221 c->flags |= CHAN_CLOSE_SENT; 222 } 223 } 224 225 static void 226 chan_send_eow2(struct ssh *ssh, Channel *c) 227 { 228 int r; 229 230 debug2("channel %d: send eow", c->self); 231 if (c->ostate == CHAN_OUTPUT_CLOSED) { 232 error("channel %d: must not sent eow on closed output", 233 c->self); 234 return; 235 } 236 if (!(ssh->compat & SSH_NEW_OPENSSH)) 237 return; 238 if (!c->have_remote_id) 239 fatal_f("channel %d: no remote_id", c->self); 240 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_REQUEST)) != 0 || 241 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 242 (r = sshpkt_put_cstring(ssh, "eow@openssh.com")) != 0 || 243 (r = sshpkt_put_u8(ssh, 0)) != 0 || 244 (r = sshpkt_send(ssh)) != 0) 245 fatal_fr(r, "send CHANNEL_EOF"); 246 } 247 248 /* shared */ 249 250 void 251 chan_rcvd_ieof(struct ssh *ssh, Channel *c) 252 { 253 debug2("channel %d: rcvd eof", c->self); 254 c->flags |= CHAN_EOF_RCVD; 255 if (c->ostate == CHAN_OUTPUT_OPEN) 256 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN); 257 if (c->ostate == CHAN_OUTPUT_WAIT_DRAIN && 258 sshbuf_len(c->output) == 0 && 259 !CHANNEL_EFD_OUTPUT_ACTIVE(c)) 260 chan_obuf_empty(ssh, c); 261 } 262 263 void 264 chan_rcvd_oclose(struct ssh *ssh, Channel *c) 265 { 266 debug2("channel %d: rcvd close", c->self); 267 if (!(c->flags & CHAN_LOCAL)) { 268 if (c->flags & CHAN_CLOSE_RCVD) 269 error("channel %d: protocol error: close rcvd twice", 270 c->self); 271 c->flags |= CHAN_CLOSE_RCVD; 272 } 273 if (c->type == SSH_CHANNEL_LARVAL) { 274 /* tear down larval channels immediately */ 275 chan_set_ostate(c, CHAN_OUTPUT_CLOSED); 276 chan_set_istate(c, CHAN_INPUT_CLOSED); 277 return; 278 } 279 switch (c->ostate) { 280 case CHAN_OUTPUT_OPEN: 281 /* 282 * wait until a data from the channel is consumed if a CLOSE 283 * is received 284 */ 285 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN); 286 break; 287 } 288 switch (c->istate) { 289 case CHAN_INPUT_OPEN: 290 chan_shutdown_read(ssh, c); 291 chan_shutdown_extended_read(ssh, c); 292 chan_set_istate(c, CHAN_INPUT_CLOSED); 293 break; 294 case CHAN_INPUT_WAIT_DRAIN: 295 if (!(c->flags & CHAN_LOCAL)) 296 chan_send_eof2(ssh, c); 297 chan_shutdown_extended_read(ssh, c); 298 chan_set_istate(c, CHAN_INPUT_CLOSED); 299 break; 300 } 301 } 302 303 void 304 chan_write_failed(struct ssh *ssh, Channel *c) 305 { 306 debug2("channel %d: write failed", c->self); 307 switch (c->ostate) { 308 case CHAN_OUTPUT_OPEN: 309 case CHAN_OUTPUT_WAIT_DRAIN: 310 chan_shutdown_write(ssh, c); 311 if (strcmp(c->ctype, "session") == 0) 312 chan_send_eow2(ssh, c); 313 chan_set_ostate(c, CHAN_OUTPUT_CLOSED); 314 break; 315 default: 316 error("channel %d: chan_write_failed for ostate %d", 317 c->self, c->ostate); 318 break; 319 } 320 } 321 322 void 323 chan_mark_dead(struct ssh *ssh, Channel *c) 324 { 325 c->type = SSH_CHANNEL_ZOMBIE; 326 } 327 328 int 329 chan_is_dead(struct ssh *ssh, Channel *c, int do_send) 330 { 331 if (c->type == SSH_CHANNEL_ZOMBIE) { 332 debug2("channel %d: zombie", c->self); 333 return 1; 334 } 335 if (c->istate != CHAN_INPUT_CLOSED || c->ostate != CHAN_OUTPUT_CLOSED) 336 return 0; 337 if ((ssh->compat & SSH_BUG_EXTEOF) && 338 c->extended_usage == CHAN_EXTENDED_WRITE && 339 c->efd != -1 && 340 sshbuf_len(c->extended) > 0) { 341 debug2("channel %d: active efd: %d len %zu", 342 c->self, c->efd, sshbuf_len(c->extended)); 343 return 0; 344 } 345 if (c->flags & CHAN_LOCAL) { 346 debug2("channel %d: is dead (local)", c->self); 347 return 1; 348 } 349 if (!(c->flags & CHAN_CLOSE_SENT)) { 350 if (do_send) { 351 chan_send_close2(ssh, c); 352 } else { 353 /* channel would be dead if we sent a close */ 354 if (c->flags & CHAN_CLOSE_RCVD) { 355 debug2("channel %d: almost dead", 356 c->self); 357 return 1; 358 } 359 } 360 } 361 if ((c->flags & CHAN_CLOSE_SENT) && 362 (c->flags & CHAN_CLOSE_RCVD)) { 363 debug2("channel %d: is dead", c->self); 364 return 1; 365 } 366 return 0; 367 } 368 369 /* helper */ 370 static void 371 chan_shutdown_write(struct ssh *ssh, Channel *c) 372 { 373 sshbuf_reset(c->output); 374 if (c->type == SSH_CHANNEL_LARVAL) 375 return; 376 /* shutdown failure is allowed if write failed already */ 377 debug2_f("channel %d: (i%d o%d sock %d wfd %d efd %d [%s])", 378 c->self, c->istate, c->ostate, c->sock, c->wfd, c->efd, 379 channel_format_extended_usage(c)); 380 if (c->sock != -1) { 381 if (shutdown(c->sock, SHUT_WR) == -1) { 382 debug2_f("channel %d: shutdown() failed for " 383 "fd %d [i%d o%d]: %.100s", c->self, c->sock, 384 c->istate, c->ostate, strerror(errno)); 385 } 386 } else { 387 if (channel_close_fd(ssh, c, &c->wfd) < 0) { 388 logit_f("channel %d: close() failed for " 389 "fd %d [i%d o%d]: %.100s", c->self, c->wfd, 390 c->istate, c->ostate, strerror(errno)); 391 } 392 } 393 } 394 395 static void 396 chan_shutdown_read(struct ssh *ssh, Channel *c) 397 { 398 if (c->type == SSH_CHANNEL_LARVAL) 399 return; 400 debug2_f("channel %d: (i%d o%d sock %d wfd %d efd %d [%s])", 401 c->self, c->istate, c->ostate, c->sock, c->rfd, c->efd, 402 channel_format_extended_usage(c)); 403 if (c->sock != -1) { 404 /* 405 * shutdown(sock, SHUT_READ) may return ENOTCONN if the 406 * write side has been closed already. (bug on Linux) 407 * HP-UX may return ENOTCONN also. 408 */ 409 if (shutdown(c->sock, SHUT_RD) == -1 && errno != ENOTCONN) { 410 error_f("channel %d: shutdown() failed for " 411 "fd %d [i%d o%d]: %.100s", c->self, c->sock, 412 c->istate, c->ostate, strerror(errno)); 413 } 414 } else { 415 if (channel_close_fd(ssh, c, &c->rfd) < 0) { 416 logit_f("channel %d: close() failed for " 417 "fd %d [i%d o%d]: %.100s", c->self, c->rfd, 418 c->istate, c->ostate, strerror(errno)); 419 } 420 } 421 } 422 423 static void 424 chan_shutdown_extended_read(struct ssh *ssh, Channel *c) 425 { 426 if (c->type == SSH_CHANNEL_LARVAL || c->efd == -1) 427 return; 428 if (c->extended_usage != CHAN_EXTENDED_READ && 429 c->extended_usage != CHAN_EXTENDED_IGNORE) 430 return; 431 debug_f("channel %d: (i%d o%d sock %d wfd %d efd %d [%s])", 432 c->self, c->istate, c->ostate, c->sock, c->rfd, c->efd, 433 channel_format_extended_usage(c)); 434 if (channel_close_fd(ssh, c, &c->efd) < 0) { 435 logit_f("channel %d: close() failed for " 436 "extended fd %d [i%d o%d]: %.100s", c->self, c->efd, 437 c->istate, c->ostate, strerror(errno)); 438 } 439 } 440