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