1 /* $OpenBSD: nchan.c,v 1.76 2024/07/25 22:40:08 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 <sys/types.h> 27 #include <sys/socket.h> 28 #include <sys/queue.h> 29 30 #include <errno.h> 31 #include <string.h> 32 #include <stdarg.h> 33 34 #include "ssh2.h" 35 #include "sshbuf.h" 36 #include "ssherr.h" 37 #include "packet.h" 38 #include "channels.h" 39 #include "compat.h" 40 #include "log.h" 41 42 /* 43 * SSH Protocol 1.5 aka New Channel Protocol 44 * Thanks to Martina, Axel and everyone who left Erlangen, leaving me bored. 45 * Written by Markus Friedl in October 1999 46 * 47 * Protocol versions 1.3 and 1.5 differ in the handshake protocol used for the 48 * tear down of channels: 49 * 50 * 1.3: strict request-ack-protocol: 51 * CLOSE -> 52 * <- CLOSE_CONFIRM 53 * 54 * 1.5: uses variations of: 55 * IEOF -> 56 * <- OCLOSE 57 * <- IEOF 58 * OCLOSE -> 59 * i.e. both sides have to close the channel 60 * 61 * 2.0: the EOF messages are optional 62 * 63 * See the debugging output from 'ssh -v' and 'sshd -d' of 64 * ssh-1.2.27 as an example. 65 * 66 */ 67 68 /* functions manipulating channel states */ 69 /* 70 * EVENTS update channel input/output states execute ACTIONS 71 */ 72 /* 73 * ACTIONS: should never update the channel states 74 */ 75 static void chan_send_eof2(struct ssh *, Channel *); 76 static void chan_send_eow2(struct ssh *, Channel *); 77 78 /* helper */ 79 static void chan_shutdown_write(struct ssh *, Channel *); 80 static void chan_shutdown_read(struct ssh *, Channel *); 81 static void chan_shutdown_extended_read(struct ssh *, Channel *); 82 83 static const char * const ostates[] = { 84 "open", "drain", "wait_ieof", "closed", 85 }; 86 static const char * const istates[] = { 87 "open", "drain", "wait_oclose", "closed", 88 }; 89 90 static void 91 chan_set_istate(Channel *c, u_int next) 92 { 93 if (c->istate > CHAN_INPUT_CLOSED || next > CHAN_INPUT_CLOSED) 94 fatal("chan_set_istate: bad state %d -> %d", c->istate, next); 95 debug2("channel %d: input %s -> %s", c->self, istates[c->istate], 96 istates[next]); 97 c->istate = next; 98 } 99 100 static void 101 chan_set_ostate(Channel *c, u_int next) 102 { 103 if (c->ostate > CHAN_OUTPUT_CLOSED || next > CHAN_OUTPUT_CLOSED) 104 fatal("chan_set_ostate: bad state %d -> %d", c->ostate, next); 105 debug2("channel %d: output %s -> %s", c->self, ostates[c->ostate], 106 ostates[next]); 107 c->ostate = next; 108 } 109 110 void 111 chan_read_failed(struct ssh *ssh, Channel *c) 112 { 113 debug2("channel %d: read failed", c->self); 114 switch (c->istate) { 115 case CHAN_INPUT_OPEN: 116 chan_shutdown_read(ssh, c); 117 chan_set_istate(c, CHAN_INPUT_WAIT_DRAIN); 118 break; 119 default: 120 error("channel %d: chan_read_failed for istate %d", 121 c->self, c->istate); 122 break; 123 } 124 } 125 126 void 127 chan_ibuf_empty(struct ssh *ssh, Channel *c) 128 { 129 debug2("channel %d: ibuf empty", c->self); 130 if (sshbuf_len(c->input)) { 131 error("channel %d: chan_ibuf_empty for non empty buffer", 132 c->self); 133 return; 134 } 135 switch (c->istate) { 136 case CHAN_INPUT_WAIT_DRAIN: 137 if (!(c->flags & (CHAN_CLOSE_SENT|CHAN_LOCAL))) 138 chan_send_eof2(ssh, c); 139 chan_set_istate(c, CHAN_INPUT_CLOSED); 140 break; 141 default: 142 error("channel %d: chan_ibuf_empty for istate %d", 143 c->self, c->istate); 144 break; 145 } 146 } 147 148 void 149 chan_obuf_empty(struct ssh *ssh, Channel *c) 150 { 151 debug2("channel %d: obuf empty", c->self); 152 if (sshbuf_len(c->output)) { 153 error("channel %d: chan_obuf_empty for non empty buffer", 154 c->self); 155 return; 156 } 157 switch (c->ostate) { 158 case CHAN_OUTPUT_WAIT_DRAIN: 159 chan_shutdown_write(ssh, c); 160 chan_set_ostate(c, CHAN_OUTPUT_CLOSED); 161 break; 162 default: 163 error("channel %d: internal error: obuf_empty for ostate %d", 164 c->self, c->ostate); 165 break; 166 } 167 } 168 169 void 170 chan_rcvd_eow(struct ssh *ssh, Channel *c) 171 { 172 debug2("channel %d: rcvd eow", c->self); 173 switch (c->istate) { 174 case CHAN_INPUT_OPEN: 175 chan_shutdown_read(ssh, c); 176 chan_set_istate(c, CHAN_INPUT_CLOSED); 177 break; 178 } 179 } 180 181 static void 182 chan_send_eof2(struct ssh *ssh, Channel *c) 183 { 184 int r; 185 186 debug2("channel %d: send eof", c->self); 187 switch (c->istate) { 188 case CHAN_INPUT_WAIT_DRAIN: 189 if (!c->have_remote_id) 190 fatal_f("channel %d: no remote_id", c->self); 191 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_EOF)) != 0 || 192 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 193 (r = sshpkt_send(ssh)) != 0) 194 fatal_fr(r, "send CHANNEL_EOF"); 195 c->flags |= CHAN_EOF_SENT; 196 break; 197 default: 198 error("channel %d: cannot send eof for istate %d", 199 c->self, c->istate); 200 break; 201 } 202 } 203 204 static void 205 chan_send_close2(struct ssh *ssh, Channel *c) 206 { 207 int r; 208 209 debug2("channel %d: send_close2", c->self); 210 if (c->ostate != CHAN_OUTPUT_CLOSED || 211 c->istate != CHAN_INPUT_CLOSED) { 212 error("channel %d: cannot send close for istate/ostate %d/%d", 213 c->self, c->istate, c->ostate); 214 } else if (c->flags & CHAN_CLOSE_SENT) { 215 error("channel %d: already sent close", c->self); 216 } else { 217 if (!c->have_remote_id) 218 fatal_f("channel %d: no remote_id", c->self); 219 debug2("channel %d: send close for remote id %u", c->self, 220 c->remote_id); 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 if (shutdown(c->sock, SHUT_RD) == -1) { 409 error_f("channel %d: shutdown() failed for " 410 "fd %d [i%d o%d]: %.100s", c->self, c->sock, 411 c->istate, c->ostate, strerror(errno)); 412 } 413 } else { 414 if (channel_close_fd(ssh, c, &c->rfd) < 0) { 415 logit_f("channel %d: close() failed for " 416 "fd %d [i%d o%d]: %.100s", c->self, c->rfd, 417 c->istate, c->ostate, strerror(errno)); 418 } 419 } 420 } 421 422 static void 423 chan_shutdown_extended_read(struct ssh *ssh, Channel *c) 424 { 425 if (c->type == SSH_CHANNEL_LARVAL || c->efd == -1) 426 return; 427 if (c->extended_usage != CHAN_EXTENDED_READ && 428 c->extended_usage != CHAN_EXTENDED_IGNORE) 429 return; 430 debug_f("channel %d: (i%d o%d sock %d wfd %d efd %d [%s])", 431 c->self, c->istate, c->ostate, c->sock, c->rfd, c->efd, 432 channel_format_extended_usage(c)); 433 if (channel_close_fd(ssh, c, &c->efd) < 0) { 434 logit_f("channel %d: close() failed for " 435 "extended fd %d [i%d o%d]: %.100s", c->self, c->efd, 436 c->istate, c->ostate, strerror(errno)); 437 } 438 } 439