1 /* $OpenBSD: nchan.c,v 1.67 2017/09/12 06:35:32 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 82 static const char *ostates[] = { "open", "drain", "wait_ieof", "closed" }; 83 static const char *istates[] = { "open", "drain", "wait_oclose", "closed" }; 84 85 static void 86 chan_set_istate(Channel *c, u_int next) 87 { 88 if (c->istate > CHAN_INPUT_CLOSED || next > CHAN_INPUT_CLOSED) 89 fatal("chan_set_istate: bad state %d -> %d", c->istate, next); 90 debug2("channel %d: input %s -> %s", c->self, istates[c->istate], 91 istates[next]); 92 c->istate = next; 93 } 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 void 106 chan_read_failed(struct ssh *ssh, Channel *c) 107 { 108 debug2("channel %d: read failed", c->self); 109 switch (c->istate) { 110 case CHAN_INPUT_OPEN: 111 chan_shutdown_read(ssh, c); 112 chan_set_istate(c, CHAN_INPUT_WAIT_DRAIN); 113 break; 114 default: 115 error("channel %d: chan_read_failed for istate %d", 116 c->self, c->istate); 117 break; 118 } 119 } 120 121 void 122 chan_ibuf_empty(struct ssh *ssh, Channel *c) 123 { 124 debug2("channel %d: ibuf empty", c->self); 125 if (sshbuf_len(c->input)) { 126 error("channel %d: chan_ibuf_empty for non empty buffer", 127 c->self); 128 return; 129 } 130 switch (c->istate) { 131 case CHAN_INPUT_WAIT_DRAIN: 132 if (!(c->flags & (CHAN_CLOSE_SENT|CHAN_LOCAL))) 133 chan_send_eof2(ssh, c); 134 chan_set_istate(c, CHAN_INPUT_CLOSED); 135 break; 136 default: 137 error("channel %d: chan_ibuf_empty for istate %d", 138 c->self, c->istate); 139 break; 140 } 141 } 142 143 void 144 chan_obuf_empty(struct ssh *ssh, Channel *c) 145 { 146 debug2("channel %d: obuf empty", c->self); 147 if (sshbuf_len(c->output)) { 148 error("channel %d: chan_obuf_empty for non empty buffer", 149 c->self); 150 return; 151 } 152 switch (c->ostate) { 153 case CHAN_OUTPUT_WAIT_DRAIN: 154 chan_shutdown_write(ssh, c); 155 chan_set_ostate(c, CHAN_OUTPUT_CLOSED); 156 break; 157 default: 158 error("channel %d: internal error: obuf_empty for ostate %d", 159 c->self, c->ostate); 160 break; 161 } 162 } 163 164 void 165 chan_rcvd_eow(struct ssh *ssh, Channel *c) 166 { 167 debug2("channel %d: rcvd eow", c->self); 168 switch (c->istate) { 169 case CHAN_INPUT_OPEN: 170 chan_shutdown_read(ssh, c); 171 chan_set_istate(c, CHAN_INPUT_CLOSED); 172 break; 173 } 174 } 175 176 static void 177 chan_send_eof2(struct ssh *ssh, Channel *c) 178 { 179 int r; 180 181 debug2("channel %d: send eof", c->self); 182 switch (c->istate) { 183 case CHAN_INPUT_WAIT_DRAIN: 184 if (!c->have_remote_id) 185 fatal("%s: channel %d: no remote_id", 186 __func__, c->self); 187 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_EOF)) != 0 || 188 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 189 (r = sshpkt_send(ssh)) != 0) 190 fatal("%s: send CHANNEL_EOF: %s", __func__, ssh_err(r)); 191 c->flags |= CHAN_EOF_SENT; 192 break; 193 default: 194 error("channel %d: cannot send eof for istate %d", 195 c->self, c->istate); 196 break; 197 } 198 } 199 200 static void 201 chan_send_close2(struct ssh *ssh, Channel *c) 202 { 203 int r; 204 205 debug2("channel %d: send close", c->self); 206 if (c->ostate != CHAN_OUTPUT_CLOSED || 207 c->istate != CHAN_INPUT_CLOSED) { 208 error("channel %d: cannot send close for istate/ostate %d/%d", 209 c->self, c->istate, c->ostate); 210 } else if (c->flags & CHAN_CLOSE_SENT) { 211 error("channel %d: already sent close", c->self); 212 } else { 213 if (!c->have_remote_id) 214 fatal("%s: channel %d: no remote_id", 215 __func__, c->self); 216 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_CLOSE)) != 0 || 217 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 218 (r = sshpkt_send(ssh)) != 0) 219 fatal("%s: send CHANNEL_EOF: %s", __func__, ssh_err(r)); 220 c->flags |= CHAN_CLOSE_SENT; 221 } 222 } 223 224 static void 225 chan_send_eow2(struct ssh *ssh, Channel *c) 226 { 227 int r; 228 229 debug2("channel %d: send eow", c->self); 230 if (c->ostate == CHAN_OUTPUT_CLOSED) { 231 error("channel %d: must not sent eow on closed output", 232 c->self); 233 return; 234 } 235 if (!(datafellows & SSH_NEW_OPENSSH)) 236 return; 237 if (!c->have_remote_id) 238 fatal("%s: channel %d: no remote_id", __func__, c->self); 239 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_REQUEST)) != 0 || 240 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 241 (r = sshpkt_put_cstring(ssh, "eow@openssh.com")) != 0 || 242 (r = sshpkt_put_u8(ssh, 0)) != 0 || 243 (r = sshpkt_send(ssh)) != 0) 244 fatal("%s: send CHANNEL_EOF: %s", __func__, ssh_err(r)); 245 } 246 247 /* shared */ 248 249 void 250 chan_rcvd_ieof(struct ssh *ssh, Channel *c) 251 { 252 debug2("channel %d: rcvd eof", c->self); 253 c->flags |= CHAN_EOF_RCVD; 254 if (c->ostate == CHAN_OUTPUT_OPEN) 255 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN); 256 if (c->ostate == CHAN_OUTPUT_WAIT_DRAIN && 257 sshbuf_len(c->output) == 0 && 258 !CHANNEL_EFD_OUTPUT_ACTIVE(c)) 259 chan_obuf_empty(ssh, c); 260 } 261 262 void 263 chan_rcvd_oclose(struct ssh *ssh, Channel *c) 264 { 265 debug2("channel %d: rcvd close", c->self); 266 if (!(c->flags & CHAN_LOCAL)) { 267 if (c->flags & CHAN_CLOSE_RCVD) 268 error("channel %d: protocol error: close rcvd twice", 269 c->self); 270 c->flags |= CHAN_CLOSE_RCVD; 271 } 272 if (c->type == SSH_CHANNEL_LARVAL) { 273 /* tear down larval channels immediately */ 274 chan_set_ostate(c, CHAN_OUTPUT_CLOSED); 275 chan_set_istate(c, CHAN_INPUT_CLOSED); 276 return; 277 } 278 switch (c->ostate) { 279 case CHAN_OUTPUT_OPEN: 280 /* 281 * wait until a data from the channel is consumed if a CLOSE 282 * is received 283 */ 284 chan_set_ostate(c, CHAN_OUTPUT_WAIT_DRAIN); 285 break; 286 } 287 switch (c->istate) { 288 case CHAN_INPUT_OPEN: 289 chan_shutdown_read(ssh, c); 290 chan_set_istate(c, CHAN_INPUT_CLOSED); 291 break; 292 case CHAN_INPUT_WAIT_DRAIN: 293 if (!(c->flags & CHAN_LOCAL)) 294 chan_send_eof2(ssh, c); 295 chan_set_istate(c, CHAN_INPUT_CLOSED); 296 break; 297 } 298 } 299 300 void 301 chan_write_failed(struct ssh *ssh, Channel *c) 302 { 303 debug2("channel %d: write failed", c->self); 304 switch (c->ostate) { 305 case CHAN_OUTPUT_OPEN: 306 case CHAN_OUTPUT_WAIT_DRAIN: 307 chan_shutdown_write(ssh, c); 308 if (strcmp(c->ctype, "session") == 0) 309 chan_send_eow2(ssh, c); 310 chan_set_ostate(c, CHAN_OUTPUT_CLOSED); 311 break; 312 default: 313 error("channel %d: chan_write_failed for ostate %d", 314 c->self, c->ostate); 315 break; 316 } 317 } 318 319 void 320 chan_mark_dead(struct ssh *ssh, Channel *c) 321 { 322 c->type = SSH_CHANNEL_ZOMBIE; 323 } 324 325 int 326 chan_is_dead(struct ssh *ssh, Channel *c, int do_send) 327 { 328 if (c->type == SSH_CHANNEL_ZOMBIE) { 329 debug2("channel %d: zombie", c->self); 330 return 1; 331 } 332 if (c->istate != CHAN_INPUT_CLOSED || c->ostate != CHAN_OUTPUT_CLOSED) 333 return 0; 334 if ((datafellows & SSH_BUG_EXTEOF) && 335 c->extended_usage == CHAN_EXTENDED_WRITE && 336 c->efd != -1 && 337 sshbuf_len(c->extended) > 0) { 338 debug2("channel %d: active efd: %d len %zu", 339 c->self, c->efd, sshbuf_len(c->extended)); 340 return 0; 341 } 342 if (c->flags & CHAN_LOCAL) { 343 debug2("channel %d: is dead (local)", c->self); 344 return 1; 345 } 346 if (!(c->flags & CHAN_CLOSE_SENT)) { 347 if (do_send) { 348 chan_send_close2(ssh, c); 349 } else { 350 /* channel would be dead if we sent a close */ 351 if (c->flags & CHAN_CLOSE_RCVD) { 352 debug2("channel %d: almost dead", 353 c->self); 354 return 1; 355 } 356 } 357 } 358 if ((c->flags & CHAN_CLOSE_SENT) && 359 (c->flags & CHAN_CLOSE_RCVD)) { 360 debug2("channel %d: is dead", c->self); 361 return 1; 362 } 363 return 0; 364 } 365 366 /* helper */ 367 static void 368 chan_shutdown_write(struct ssh *ssh, Channel *c) 369 { 370 sshbuf_reset(c->output); 371 if (c->type == SSH_CHANNEL_LARVAL) 372 return; 373 /* shutdown failure is allowed if write failed already */ 374 debug2("channel %d: close_write", c->self); 375 if (c->sock != -1) { 376 if (shutdown(c->sock, SHUT_WR) < 0) 377 debug2("channel %d: chan_shutdown_write: " 378 "shutdown() failed for fd %d: %.100s", 379 c->self, c->sock, strerror(errno)); 380 } else { 381 if (channel_close_fd(ssh, &c->wfd) < 0) 382 logit("channel %d: chan_shutdown_write: " 383 "close() failed for fd %d: %.100s", 384 c->self, c->wfd, strerror(errno)); 385 } 386 } 387 388 static void 389 chan_shutdown_read(struct ssh *ssh, Channel *c) 390 { 391 if (c->type == SSH_CHANNEL_LARVAL) 392 return; 393 debug2("channel %d: close_read", c->self); 394 if (c->sock != -1) { 395 if (shutdown(c->sock, SHUT_RD) < 0) 396 error("channel %d: chan_shutdown_read: " 397 "shutdown() failed for fd %d [i%d o%d]: %.100s", 398 c->self, c->sock, c->istate, c->ostate, 399 strerror(errno)); 400 } else { 401 if (channel_close_fd(ssh, &c->rfd) < 0) 402 logit("channel %d: chan_shutdown_read: " 403 "close() failed for fd %d: %.100s", 404 c->self, c->rfd, strerror(errno)); 405 } 406 } 407