1 /* $OpenBSD: serverloop.c,v 1.222 2020/01/30 07:21:38 djm Exp $ */ 2 /* 3 * Author: Tatu Ylonen <ylo@cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 5 * All rights reserved 6 * Server main loop for handling the interactive session. 7 * 8 * As far as I am concerned, the code I have written for this software 9 * can be used freely for any purpose. Any derived versions of this 10 * software must be clearly marked as such, and if the derived work is 11 * incompatible with the protocol description in the RFC file, it must be 12 * called by a name other than "ssh" or "Secure Shell". 13 * 14 * SSH2 support by Markus Friedl. 15 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. 16 * 17 * Redistribution and use in source and binary forms, with or without 18 * modification, are permitted provided that the following conditions 19 * are met: 20 * 1. Redistributions of source code must retain the above copyright 21 * notice, this list of conditions and the following disclaimer. 22 * 2. Redistributions in binary form must reproduce the above copyright 23 * notice, this list of conditions and the following disclaimer in the 24 * documentation and/or other materials provided with the distribution. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 27 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 28 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 29 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 30 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 31 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 35 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 36 */ 37 38 #include "includes.h" 39 40 #include <sys/types.h> 41 #include <sys/wait.h> 42 #include <sys/socket.h> 43 #ifdef HAVE_SYS_TIME_H 44 # include <sys/time.h> 45 #endif 46 47 #include <netinet/in.h> 48 49 #include <errno.h> 50 #include <fcntl.h> 51 #include <pwd.h> 52 #include <limits.h> 53 #include <signal.h> 54 #include <string.h> 55 #include <termios.h> 56 #include <unistd.h> 57 #include <stdarg.h> 58 59 #include "openbsd-compat/sys-queue.h" 60 #include "xmalloc.h" 61 #include "packet.h" 62 #include "sshbuf.h" 63 #include "log.h" 64 #include "misc.h" 65 #include "servconf.h" 66 #include "canohost.h" 67 #include "sshpty.h" 68 #include "channels.h" 69 #include "compat.h" 70 #include "ssh2.h" 71 #include "sshkey.h" 72 #include "cipher.h" 73 #include "kex.h" 74 #include "hostfile.h" 75 #include "auth.h" 76 #include "session.h" 77 #include "dispatch.h" 78 #include "auth-options.h" 79 #include "serverloop.h" 80 #include "ssherr.h" 81 82 extern ServerOptions options; 83 84 /* XXX */ 85 extern Authctxt *the_authctxt; 86 extern struct sshauthopt *auth_opts; 87 extern int use_privsep; 88 89 static int no_more_sessions = 0; /* Disallow further sessions. */ 90 91 /* 92 * This SIGCHLD kludge is used to detect when the child exits. The server 93 * will exit after that, as soon as forwarded connections have terminated. 94 */ 95 96 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */ 97 98 /* Cleanup on signals (!use_privsep case only) */ 99 static volatile sig_atomic_t received_sigterm = 0; 100 101 /* prototypes */ 102 static void server_init_dispatch(struct ssh *); 103 104 /* requested tunnel forwarding interface(s), shared with session.c */ 105 char *tun_fwd_ifnames = NULL; 106 107 /* returns 1 if bind to specified port by specified user is permitted */ 108 static int 109 bind_permitted(int port, uid_t uid) 110 { 111 if (use_privsep) 112 return 1; /* allow system to decide */ 113 if (port < IPPORT_RESERVED && uid != 0) 114 return 0; 115 return 1; 116 } 117 118 /* 119 * we write to this pipe if a SIGCHLD is caught in order to avoid 120 * the race between select() and child_terminated 121 */ 122 static int notify_pipe[2]; 123 static void 124 notify_setup(void) 125 { 126 if (pipe(notify_pipe) == -1) { 127 error("pipe(notify_pipe) failed %s", strerror(errno)); 128 } else if ((fcntl(notify_pipe[0], F_SETFD, FD_CLOEXEC) == -1) || 129 (fcntl(notify_pipe[1], F_SETFD, FD_CLOEXEC) == -1)) { 130 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno)); 131 close(notify_pipe[0]); 132 close(notify_pipe[1]); 133 } else { 134 set_nonblock(notify_pipe[0]); 135 set_nonblock(notify_pipe[1]); 136 return; 137 } 138 notify_pipe[0] = -1; /* read end */ 139 notify_pipe[1] = -1; /* write end */ 140 } 141 static void 142 notify_parent(void) 143 { 144 if (notify_pipe[1] != -1) 145 (void)write(notify_pipe[1], "", 1); 146 } 147 static void 148 notify_prepare(fd_set *readset) 149 { 150 if (notify_pipe[0] != -1) 151 FD_SET(notify_pipe[0], readset); 152 } 153 static void 154 notify_done(fd_set *readset) 155 { 156 char c; 157 158 if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset)) 159 while (read(notify_pipe[0], &c, 1) != -1) 160 debug2("%s: reading", __func__); 161 } 162 163 /*ARGSUSED*/ 164 static void 165 sigchld_handler(int sig) 166 { 167 int save_errno = errno; 168 child_terminated = 1; 169 notify_parent(); 170 errno = save_errno; 171 } 172 173 /*ARGSUSED*/ 174 static void 175 sigterm_handler(int sig) 176 { 177 received_sigterm = sig; 178 } 179 180 static void 181 client_alive_check(struct ssh *ssh) 182 { 183 char remote_id[512]; 184 int r, channel_id; 185 186 /* timeout, check to see how many we have had */ 187 if (options.client_alive_count_max > 0 && 188 ssh_packet_inc_alive_timeouts(ssh) > 189 options.client_alive_count_max) { 190 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id)); 191 logit("Timeout, client not responding from %s", remote_id); 192 cleanup_exit(255); 193 } 194 195 /* 196 * send a bogus global/channel request with "wantreply", 197 * we should get back a failure 198 */ 199 if ((channel_id = channel_find_open(ssh)) == -1) { 200 if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 || 201 (r = sshpkt_put_cstring(ssh, "keepalive@openssh.com")) 202 != 0 || 203 (r = sshpkt_put_u8(ssh, 1)) != 0) /* boolean: want reply */ 204 fatal("%s: %s", __func__, ssh_err(r)); 205 } else { 206 channel_request_start(ssh, channel_id, 207 "keepalive@openssh.com", 1); 208 } 209 if ((r = sshpkt_send(ssh)) != 0) 210 fatal("%s: %s", __func__, ssh_err(r)); 211 } 212 213 /* 214 * Sleep in select() until we can do something. This will initialize the 215 * select masks. Upon return, the masks will indicate which descriptors 216 * have data or can accept data. Optionally, a maximum time can be specified 217 * for the duration of the wait (0 = infinite). 218 */ 219 static void 220 wait_until_can_do_something(struct ssh *ssh, 221 int connection_in, int connection_out, 222 fd_set **readsetp, fd_set **writesetp, int *maxfdp, 223 u_int *nallocp, u_int64_t max_time_ms) 224 { 225 struct timeval tv, *tvp; 226 int ret; 227 time_t minwait_secs = 0; 228 int client_alive_scheduled = 0; 229 /* time we last heard from the client OR sent a keepalive */ 230 static time_t last_client_time; 231 232 /* Allocate and update select() masks for channel descriptors. */ 233 channel_prepare_select(ssh, readsetp, writesetp, maxfdp, 234 nallocp, &minwait_secs); 235 236 /* XXX need proper deadline system for rekey/client alive */ 237 if (minwait_secs != 0) 238 max_time_ms = MINIMUM(max_time_ms, (u_int)minwait_secs * 1000); 239 240 /* 241 * if using client_alive, set the max timeout accordingly, 242 * and indicate that this particular timeout was for client 243 * alive by setting the client_alive_scheduled flag. 244 * 245 * this could be randomized somewhat to make traffic 246 * analysis more difficult, but we're not doing it yet. 247 */ 248 if (options.client_alive_interval) { 249 uint64_t keepalive_ms = 250 (uint64_t)options.client_alive_interval * 1000; 251 252 if (max_time_ms == 0 || max_time_ms > keepalive_ms) { 253 max_time_ms = keepalive_ms; 254 client_alive_scheduled = 1; 255 } 256 } 257 258 #if 0 259 /* wrong: bad condition XXX */ 260 if (channel_not_very_much_buffered_data()) 261 #endif 262 FD_SET(connection_in, *readsetp); 263 notify_prepare(*readsetp); 264 265 /* 266 * If we have buffered packet data going to the client, mark that 267 * descriptor. 268 */ 269 if (ssh_packet_have_data_to_write(ssh)) 270 FD_SET(connection_out, *writesetp); 271 272 /* 273 * If child has terminated and there is enough buffer space to read 274 * from it, then read as much as is available and exit. 275 */ 276 if (child_terminated && ssh_packet_not_very_much_data_to_write(ssh)) 277 if (max_time_ms == 0 || client_alive_scheduled) 278 max_time_ms = 100; 279 280 if (max_time_ms == 0) 281 tvp = NULL; 282 else { 283 tv.tv_sec = max_time_ms / 1000; 284 tv.tv_usec = 1000 * (max_time_ms % 1000); 285 tvp = &tv; 286 } 287 288 /* Wait for something to happen, or the timeout to expire. */ 289 ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp); 290 291 if (ret == -1) { 292 memset(*readsetp, 0, *nallocp); 293 memset(*writesetp, 0, *nallocp); 294 if (errno != EINTR) 295 error("select: %.100s", strerror(errno)); 296 } else if (client_alive_scheduled) { 297 time_t now = monotime(); 298 299 /* 300 * If the select timed out, or returned for some other reason 301 * but we haven't heard from the client in time, send keepalive. 302 */ 303 if (ret == 0 || (last_client_time != 0 && last_client_time + 304 options.client_alive_interval <= now)) { 305 client_alive_check(ssh); 306 last_client_time = now; 307 } else if (FD_ISSET(connection_in, *readsetp)) { 308 last_client_time = now; 309 } 310 } 311 312 notify_done(*readsetp); 313 } 314 315 /* 316 * Processes input from the client and the program. Input data is stored 317 * in buffers and processed later. 318 */ 319 static int 320 process_input(struct ssh *ssh, fd_set *readset, int connection_in) 321 { 322 int r, len; 323 char buf[16384]; 324 325 /* Read and buffer any input data from the client. */ 326 if (FD_ISSET(connection_in, readset)) { 327 len = read(connection_in, buf, sizeof(buf)); 328 if (len == 0) { 329 verbose("Connection closed by %.100s port %d", 330 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 331 return -1; 332 } else if (len == -1) { 333 if (errno != EINTR && errno != EAGAIN && 334 errno != EWOULDBLOCK) { 335 verbose("Read error from remote host " 336 "%.100s port %d: %.100s", 337 ssh_remote_ipaddr(ssh), 338 ssh_remote_port(ssh), strerror(errno)); 339 cleanup_exit(255); 340 } 341 } else { 342 /* Buffer any received data. */ 343 if ((r = ssh_packet_process_incoming(ssh, buf, len)) 344 != 0) 345 fatal("%s: ssh_packet_process_incoming: %s", 346 __func__, ssh_err(r)); 347 } 348 } 349 return 0; 350 } 351 352 /* 353 * Sends data from internal buffers to client program stdin. 354 */ 355 static void 356 process_output(struct ssh *ssh, fd_set *writeset, int connection_out) 357 { 358 int r; 359 360 /* Send any buffered packet data to the client. */ 361 if (FD_ISSET(connection_out, writeset)) { 362 if ((r = ssh_packet_write_poll(ssh)) != 0) { 363 sshpkt_fatal(ssh, r, "%s: ssh_packet_write_poll", 364 __func__); 365 } 366 } 367 } 368 369 static void 370 process_buffered_input_packets(struct ssh *ssh) 371 { 372 ssh_dispatch_run_fatal(ssh, DISPATCH_NONBLOCK, NULL); 373 } 374 375 static void 376 collect_children(struct ssh *ssh) 377 { 378 pid_t pid; 379 sigset_t oset, nset; 380 int status; 381 382 /* block SIGCHLD while we check for dead children */ 383 sigemptyset(&nset); 384 sigaddset(&nset, SIGCHLD); 385 sigprocmask(SIG_BLOCK, &nset, &oset); 386 if (child_terminated) { 387 debug("Received SIGCHLD."); 388 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 389 (pid == -1 && errno == EINTR)) 390 if (pid > 0) 391 session_close_by_pid(ssh, pid, status); 392 child_terminated = 0; 393 } 394 sigprocmask(SIG_SETMASK, &oset, NULL); 395 } 396 397 void 398 server_loop2(struct ssh *ssh, Authctxt *authctxt) 399 { 400 fd_set *readset = NULL, *writeset = NULL; 401 int max_fd; 402 u_int nalloc = 0, connection_in, connection_out; 403 u_int64_t rekey_timeout_ms = 0; 404 405 debug("Entering interactive session for SSH2."); 406 407 ssh_signal(SIGCHLD, sigchld_handler); 408 child_terminated = 0; 409 connection_in = ssh_packet_get_connection_in(ssh); 410 connection_out = ssh_packet_get_connection_out(ssh); 411 412 if (!use_privsep) { 413 ssh_signal(SIGTERM, sigterm_handler); 414 ssh_signal(SIGINT, sigterm_handler); 415 ssh_signal(SIGQUIT, sigterm_handler); 416 } 417 418 notify_setup(); 419 420 max_fd = MAXIMUM(connection_in, connection_out); 421 max_fd = MAXIMUM(max_fd, notify_pipe[0]); 422 423 server_init_dispatch(ssh); 424 425 for (;;) { 426 process_buffered_input_packets(ssh); 427 428 if (!ssh_packet_is_rekeying(ssh) && 429 ssh_packet_not_very_much_data_to_write(ssh)) 430 channel_output_poll(ssh); 431 if (options.rekey_interval > 0 && 432 !ssh_packet_is_rekeying(ssh)) { 433 rekey_timeout_ms = ssh_packet_get_rekey_timeout(ssh) * 434 1000; 435 } else { 436 rekey_timeout_ms = 0; 437 } 438 439 wait_until_can_do_something(ssh, connection_in, connection_out, 440 &readset, &writeset, &max_fd, &nalloc, rekey_timeout_ms); 441 442 if (received_sigterm) { 443 logit("Exiting on signal %d", (int)received_sigterm); 444 /* Clean up sessions, utmp, etc. */ 445 cleanup_exit(255); 446 } 447 448 collect_children(ssh); 449 if (!ssh_packet_is_rekeying(ssh)) 450 channel_after_select(ssh, readset, writeset); 451 if (process_input(ssh, readset, connection_in) < 0) 452 break; 453 process_output(ssh, writeset, connection_out); 454 } 455 collect_children(ssh); 456 457 free(readset); 458 free(writeset); 459 460 /* free all channels, no more reads and writes */ 461 channel_free_all(ssh); 462 463 /* free remaining sessions, e.g. remove wtmp entries */ 464 session_destroy_all(ssh, NULL); 465 } 466 467 static int 468 server_input_keep_alive(int type, u_int32_t seq, struct ssh *ssh) 469 { 470 debug("Got %d/%u for keepalive", type, seq); 471 /* 472 * reset timeout, since we got a sane answer from the client. 473 * even if this was generated by something other than 474 * the bogus CHANNEL_REQUEST we send for keepalives. 475 */ 476 ssh_packet_set_alive_timeouts(ssh, 0); 477 return 0; 478 } 479 480 static Channel * 481 server_request_direct_tcpip(struct ssh *ssh, int *reason, const char **errmsg) 482 { 483 Channel *c = NULL; 484 char *target = NULL, *originator = NULL; 485 u_int target_port = 0, originator_port = 0; 486 int r; 487 488 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 489 (r = sshpkt_get_u32(ssh, &target_port)) != 0 || 490 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 491 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 492 (r = sshpkt_get_end(ssh)) != 0) 493 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 494 if (target_port > 0xFFFF) { 495 error("%s: invalid target port", __func__); 496 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 497 goto out; 498 } 499 if (originator_port > 0xFFFF) { 500 error("%s: invalid originator port", __func__); 501 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 502 goto out; 503 } 504 505 debug("%s: originator %s port %u, target %s port %u", __func__, 506 originator, originator_port, target, target_port); 507 508 /* XXX fine grained permissions */ 509 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 && 510 auth_opts->permit_port_forwarding_flag && 511 !options.disable_forwarding) { 512 c = channel_connect_to_port(ssh, target, target_port, 513 "direct-tcpip", "direct-tcpip", reason, errmsg); 514 } else { 515 logit("refused local port forward: " 516 "originator %s port %d, target %s port %d", 517 originator, originator_port, target, target_port); 518 if (reason != NULL) 519 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 520 } 521 522 out: 523 free(originator); 524 free(target); 525 return c; 526 } 527 528 static Channel * 529 server_request_direct_streamlocal(struct ssh *ssh) 530 { 531 Channel *c = NULL; 532 char *target = NULL, *originator = NULL; 533 u_int originator_port = 0; 534 struct passwd *pw = the_authctxt->pw; 535 int r; 536 537 if (pw == NULL || !the_authctxt->valid) 538 fatal("%s: no/invalid user", __func__); 539 540 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 541 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 542 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 543 (r = sshpkt_get_end(ssh)) != 0) 544 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 545 if (originator_port > 0xFFFF) { 546 error("%s: invalid originator port", __func__); 547 goto out; 548 } 549 550 debug("%s: originator %s port %d, target %s", __func__, 551 originator, originator_port, target); 552 553 /* XXX fine grained permissions */ 554 if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 && 555 auth_opts->permit_port_forwarding_flag && 556 !options.disable_forwarding && (pw->pw_uid == 0 || use_privsep)) { 557 c = channel_connect_to_path(ssh, target, 558 "direct-streamlocal@openssh.com", "direct-streamlocal"); 559 } else { 560 logit("refused streamlocal port forward: " 561 "originator %s port %d, target %s", 562 originator, originator_port, target); 563 } 564 565 out: 566 free(originator); 567 free(target); 568 return c; 569 } 570 571 static Channel * 572 server_request_tun(struct ssh *ssh) 573 { 574 Channel *c = NULL; 575 u_int mode, tun; 576 int r, sock; 577 char *tmp, *ifname = NULL; 578 579 if ((r = sshpkt_get_u32(ssh, &mode)) != 0) 580 sshpkt_fatal(ssh, r, "%s: parse mode", __func__); 581 switch (mode) { 582 case SSH_TUNMODE_POINTOPOINT: 583 case SSH_TUNMODE_ETHERNET: 584 break; 585 default: 586 ssh_packet_send_debug(ssh, "Unsupported tunnel device mode."); 587 return NULL; 588 } 589 if ((options.permit_tun & mode) == 0) { 590 ssh_packet_send_debug(ssh, "Server has rejected tunnel device " 591 "forwarding"); 592 return NULL; 593 } 594 595 if ((r = sshpkt_get_u32(ssh, &tun)) != 0) 596 sshpkt_fatal(ssh, r, "%s: parse device", __func__); 597 if (tun > INT_MAX) { 598 debug("%s: invalid tun", __func__); 599 goto done; 600 } 601 if (auth_opts->force_tun_device != -1) { 602 if (tun != SSH_TUNID_ANY && 603 auth_opts->force_tun_device != (int)tun) 604 goto done; 605 tun = auth_opts->force_tun_device; 606 } 607 sock = tun_open(tun, mode, &ifname); 608 if (sock < 0) 609 goto done; 610 debug("Tunnel forwarding using interface %s", ifname); 611 612 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1, 613 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 614 c->datagram = 1; 615 #if defined(SSH_TUN_FILTER) 616 if (mode == SSH_TUNMODE_POINTOPOINT) 617 channel_register_filter(ssh, c->self, sys_tun_infilter, 618 sys_tun_outfilter, NULL, NULL); 619 #endif 620 621 /* 622 * Update the list of names exposed to the session 623 * XXX remove these if the tunnels are closed (won't matter 624 * much if they are already in the environment though) 625 */ 626 tmp = tun_fwd_ifnames; 627 xasprintf(&tun_fwd_ifnames, "%s%s%s", 628 tun_fwd_ifnames == NULL ? "" : tun_fwd_ifnames, 629 tun_fwd_ifnames == NULL ? "" : ",", 630 ifname); 631 free(tmp); 632 free(ifname); 633 634 done: 635 if (c == NULL) 636 ssh_packet_send_debug(ssh, "Failed to open the tunnel device."); 637 return c; 638 } 639 640 static Channel * 641 server_request_session(struct ssh *ssh) 642 { 643 Channel *c; 644 int r; 645 646 debug("input_session_request"); 647 if ((r = sshpkt_get_end(ssh)) != 0) 648 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 649 650 if (no_more_sessions) { 651 ssh_packet_disconnect(ssh, "Possible attack: attempt to open a " 652 "session after additional sessions disabled"); 653 } 654 655 /* 656 * A server session has no fd to read or write until a 657 * CHANNEL_REQUEST for a shell is made, so we set the type to 658 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all 659 * CHANNEL_REQUEST messages is registered. 660 */ 661 c = channel_new(ssh, "session", SSH_CHANNEL_LARVAL, 662 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, 663 0, "server-session", 1); 664 if (session_open(the_authctxt, c->self) != 1) { 665 debug("session open failed, free channel %d", c->self); 666 channel_free(ssh, c); 667 return NULL; 668 } 669 channel_register_cleanup(ssh, c->self, session_close_by_channel, 0); 670 return c; 671 } 672 673 static int 674 server_input_channel_open(int type, u_int32_t seq, struct ssh *ssh) 675 { 676 Channel *c = NULL; 677 char *ctype = NULL; 678 const char *errmsg = NULL; 679 int r, reason = SSH2_OPEN_CONNECT_FAILED; 680 u_int rchan = 0, rmaxpack = 0, rwindow = 0; 681 682 if ((r = sshpkt_get_cstring(ssh, &ctype, NULL)) != 0 || 683 (r = sshpkt_get_u32(ssh, &rchan)) != 0 || 684 (r = sshpkt_get_u32(ssh, &rwindow)) != 0 || 685 (r = sshpkt_get_u32(ssh, &rmaxpack)) != 0) 686 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 687 debug("%s: ctype %s rchan %u win %u max %u", __func__, 688 ctype, rchan, rwindow, rmaxpack); 689 690 if (strcmp(ctype, "session") == 0) { 691 c = server_request_session(ssh); 692 } else if (strcmp(ctype, "direct-tcpip") == 0) { 693 c = server_request_direct_tcpip(ssh, &reason, &errmsg); 694 } else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) { 695 c = server_request_direct_streamlocal(ssh); 696 } else if (strcmp(ctype, "tun@openssh.com") == 0) { 697 c = server_request_tun(ssh); 698 } 699 if (c != NULL) { 700 debug("%s: confirm %s", __func__, ctype); 701 c->remote_id = rchan; 702 c->have_remote_id = 1; 703 c->remote_window = rwindow; 704 c->remote_maxpacket = rmaxpack; 705 if (c->type != SSH_CHANNEL_CONNECTING) { 706 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION)) != 0 || 707 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 708 (r = sshpkt_put_u32(ssh, c->self)) != 0 || 709 (r = sshpkt_put_u32(ssh, c->local_window)) != 0 || 710 (r = sshpkt_put_u32(ssh, c->local_maxpacket)) != 0 || 711 (r = sshpkt_send(ssh)) != 0) { 712 sshpkt_fatal(ssh, r, 713 "%s: send open confirm", __func__); 714 } 715 } 716 } else { 717 debug("%s: failure %s", __func__, ctype); 718 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE)) != 0 || 719 (r = sshpkt_put_u32(ssh, rchan)) != 0 || 720 (r = sshpkt_put_u32(ssh, reason)) != 0 || 721 (r = sshpkt_put_cstring(ssh, errmsg ? errmsg : "open failed")) != 0 || 722 (r = sshpkt_put_cstring(ssh, "")) != 0 || 723 (r = sshpkt_send(ssh)) != 0) { 724 sshpkt_fatal(ssh, r, 725 "%s: send open failure", __func__); 726 } 727 } 728 free(ctype); 729 return 0; 730 } 731 732 static int 733 server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp) 734 { 735 struct sshbuf *resp = NULL; 736 struct sshbuf *sigbuf = NULL; 737 struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL; 738 int r, ndx, kexsigtype, use_kexsigtype, success = 0; 739 const u_char *blob; 740 u_char *sig = 0; 741 size_t blen, slen; 742 743 if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL) 744 fatal("%s: sshbuf_new", __func__); 745 746 kexsigtype = sshkey_type_plain( 747 sshkey_type_from_name(ssh->kex->hostkey_alg)); 748 while (ssh_packet_remaining(ssh) > 0) { 749 sshkey_free(key); 750 key = NULL; 751 if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 || 752 (r = sshkey_from_blob(blob, blen, &key)) != 0) { 753 error("%s: couldn't parse key: %s", 754 __func__, ssh_err(r)); 755 goto out; 756 } 757 /* 758 * Better check that this is actually one of our hostkeys 759 * before attempting to sign anything with it. 760 */ 761 if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) { 762 error("%s: unknown host %s key", 763 __func__, sshkey_type(key)); 764 goto out; 765 } 766 /* 767 * XXX refactor: make kex->sign just use an index rather 768 * than passing in public and private keys 769 */ 770 if ((key_prv = get_hostkey_by_index(ndx)) == NULL && 771 (key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) { 772 error("%s: can't retrieve hostkey %d", __func__, ndx); 773 goto out; 774 } 775 sshbuf_reset(sigbuf); 776 free(sig); 777 sig = NULL; 778 /* 779 * For RSA keys, prefer to use the signature type negotiated 780 * during KEX to the default (SHA1). 781 */ 782 use_kexsigtype = kexsigtype == KEY_RSA && 783 sshkey_type_plain(key->type) == KEY_RSA; 784 if ((r = sshbuf_put_cstring(sigbuf, 785 "hostkeys-prove-00@openssh.com")) != 0 || 786 (r = sshbuf_put_string(sigbuf, 787 ssh->kex->session_id, ssh->kex->session_id_len)) != 0 || 788 (r = sshkey_puts(key, sigbuf)) != 0 || 789 (r = ssh->kex->sign(ssh, key_prv, key_pub, &sig, &slen, 790 sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), 791 use_kexsigtype ? ssh->kex->hostkey_alg : NULL)) != 0 || 792 (r = sshbuf_put_string(resp, sig, slen)) != 0) { 793 error("%s: couldn't prepare signature: %s", 794 __func__, ssh_err(r)); 795 goto out; 796 } 797 } 798 /* Success */ 799 *respp = resp; 800 resp = NULL; /* don't free it */ 801 success = 1; 802 out: 803 free(sig); 804 sshbuf_free(resp); 805 sshbuf_free(sigbuf); 806 sshkey_free(key); 807 return success; 808 } 809 810 static int 811 server_input_global_request(int type, u_int32_t seq, struct ssh *ssh) 812 { 813 char *rtype = NULL; 814 u_char want_reply = 0; 815 int r, success = 0, allocated_listen_port = 0; 816 u_int port = 0; 817 struct sshbuf *resp = NULL; 818 struct passwd *pw = the_authctxt->pw; 819 struct Forward fwd; 820 821 memset(&fwd, 0, sizeof(fwd)); 822 if (pw == NULL || !the_authctxt->valid) 823 fatal("%s: no/invalid user", __func__); 824 825 if ((r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 826 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 827 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 828 debug("%s: rtype %s want_reply %d", __func__, rtype, want_reply); 829 830 /* -R style forwarding */ 831 if (strcmp(rtype, "tcpip-forward") == 0) { 832 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 833 (r = sshpkt_get_u32(ssh, &port)) != 0) 834 sshpkt_fatal(ssh, r, "%s: parse tcpip-forward", __func__); 835 debug("%s: tcpip-forward listen %s port %u", __func__, 836 fwd.listen_host, port); 837 if (port <= INT_MAX) 838 fwd.listen_port = (int)port; 839 /* check permissions */ 840 if (port > INT_MAX || 841 (options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 || 842 !auth_opts->permit_port_forwarding_flag || 843 options.disable_forwarding || 844 (!want_reply && fwd.listen_port == 0) || 845 (fwd.listen_port != 0 && 846 !bind_permitted(fwd.listen_port, pw->pw_uid))) { 847 success = 0; 848 ssh_packet_send_debug(ssh, "Server has disabled port forwarding."); 849 } else { 850 /* Start listening on the port */ 851 success = channel_setup_remote_fwd_listener(ssh, &fwd, 852 &allocated_listen_port, &options.fwd_opts); 853 } 854 if ((resp = sshbuf_new()) == NULL) 855 fatal("%s: sshbuf_new", __func__); 856 if (allocated_listen_port != 0 && 857 (r = sshbuf_put_u32(resp, allocated_listen_port)) != 0) 858 fatal("%s: sshbuf_put_u32: %s", __func__, ssh_err(r)); 859 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) { 860 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 861 (r = sshpkt_get_u32(ssh, &port)) != 0) 862 sshpkt_fatal(ssh, r, "%s: parse cancel-tcpip-forward", __func__); 863 864 debug("%s: cancel-tcpip-forward addr %s port %d", __func__, 865 fwd.listen_host, port); 866 if (port <= INT_MAX) { 867 fwd.listen_port = (int)port; 868 success = channel_cancel_rport_listener(ssh, &fwd); 869 } 870 } else if (strcmp(rtype, "streamlocal-forward@openssh.com") == 0) { 871 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 872 sshpkt_fatal(ssh, r, "%s: parse streamlocal-forward@openssh.com", __func__); 873 debug("%s: streamlocal-forward listen path %s", __func__, 874 fwd.listen_path); 875 876 /* check permissions */ 877 if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0 878 || !auth_opts->permit_port_forwarding_flag || 879 options.disable_forwarding || 880 (pw->pw_uid != 0 && !use_privsep)) { 881 success = 0; 882 ssh_packet_send_debug(ssh, "Server has disabled " 883 "streamlocal forwarding."); 884 } else { 885 /* Start listening on the socket */ 886 success = channel_setup_remote_fwd_listener(ssh, 887 &fwd, NULL, &options.fwd_opts); 888 } 889 } else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) { 890 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 891 sshpkt_fatal(ssh, r, "%s: parse cancel-streamlocal-forward@openssh.com", __func__); 892 debug("%s: cancel-streamlocal-forward path %s", __func__, 893 fwd.listen_path); 894 895 success = channel_cancel_rport_listener(ssh, &fwd); 896 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) { 897 no_more_sessions = 1; 898 success = 1; 899 } else if (strcmp(rtype, "hostkeys-prove-00@openssh.com") == 0) { 900 success = server_input_hostkeys_prove(ssh, &resp); 901 } 902 /* XXX sshpkt_get_end() */ 903 if (want_reply) { 904 if ((r = sshpkt_start(ssh, success ? 905 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE)) != 0 || 906 (success && resp != NULL && (r = sshpkt_putb(ssh, resp)) != 0) || 907 (r = sshpkt_send(ssh)) != 0 || 908 (r = ssh_packet_write_wait(ssh)) != 0) 909 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 910 } 911 free(fwd.listen_host); 912 free(fwd.listen_path); 913 free(rtype); 914 sshbuf_free(resp); 915 return 0; 916 } 917 918 static int 919 server_input_channel_req(int type, u_int32_t seq, struct ssh *ssh) 920 { 921 Channel *c; 922 int r, success = 0; 923 char *rtype = NULL; 924 u_char want_reply = 0; 925 u_int id = 0; 926 927 if ((r = sshpkt_get_u32(ssh, &id)) != 0 || 928 (r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 929 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 930 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 931 932 debug("server_input_channel_req: channel %u request %s reply %d", 933 id, rtype, want_reply); 934 935 if (id >= INT_MAX || (c = channel_lookup(ssh, (int)id)) == NULL) { 936 ssh_packet_disconnect(ssh, "%s: unknown channel %d", 937 __func__, id); 938 } 939 if (!strcmp(rtype, "eow@openssh.com")) { 940 if ((r = sshpkt_get_end(ssh)) != 0) 941 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 942 chan_rcvd_eow(ssh, c); 943 } else if ((c->type == SSH_CHANNEL_LARVAL || 944 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0) 945 success = session_input_channel_req(ssh, c, rtype); 946 if (want_reply && !(c->flags & CHAN_CLOSE_SENT)) { 947 if (!c->have_remote_id) 948 fatal("%s: channel %d: no remote_id", 949 __func__, c->self); 950 if ((r = sshpkt_start(ssh, success ? 951 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE)) != 0 || 952 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 953 (r = sshpkt_send(ssh)) != 0) 954 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 955 } 956 free(rtype); 957 return 0; 958 } 959 960 static void 961 server_init_dispatch(struct ssh *ssh) 962 { 963 debug("server_init_dispatch"); 964 ssh_dispatch_init(ssh, &dispatch_protocol_error); 965 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); 966 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_DATA, &channel_input_data); 967 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); 968 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); 969 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); 970 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 971 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 972 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); 973 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); 974 ssh_dispatch_set(ssh, SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); 975 /* client_alive */ 976 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive); 977 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); 978 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); 979 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); 980 /* rekeying */ 981 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit); 982 } 983