1 /* $OpenBSD: serverloop.c,v 1.205 2018/03/03 03:15:51 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 <signal.h> 53 #include <string.h> 54 #include <termios.h> 55 #include <unistd.h> 56 #include <stdarg.h> 57 58 #include "openbsd-compat/sys-queue.h" 59 #include "xmalloc.h" 60 #include "packet.h" 61 #include "buffer.h" 62 #include "log.h" 63 #include "misc.h" 64 #include "servconf.h" 65 #include "canohost.h" 66 #include "sshpty.h" 67 #include "channels.h" 68 #include "compat.h" 69 #include "ssh2.h" 70 #include "key.h" 71 #include "cipher.h" 72 #include "kex.h" 73 #include "hostfile.h" 74 #include "auth.h" 75 #include "session.h" 76 #include "dispatch.h" 77 #include "auth-options.h" 78 #include "serverloop.h" 79 #include "ssherr.h" 80 81 extern ServerOptions options; 82 83 /* XXX */ 84 extern Authctxt *the_authctxt; 85 extern struct sshauthopt *auth_opts; 86 extern int use_privsep; 87 88 static int no_more_sessions = 0; /* Disallow further sessions. */ 89 90 /* 91 * This SIGCHLD kludge is used to detect when the child exits. The server 92 * will exit after that, as soon as forwarded connections have terminated. 93 */ 94 95 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */ 96 97 /* Cleanup on signals (!use_privsep case only) */ 98 static volatile sig_atomic_t received_sigterm = 0; 99 100 /* prototypes */ 101 static void server_init_dispatch(void); 102 103 /* requested tunnel forwarding interface(s), shared with session.c */ 104 char *tun_fwd_ifnames = NULL; 105 106 /* 107 * we write to this pipe if a SIGCHLD is caught in order to avoid 108 * the race between select() and child_terminated 109 */ 110 static int notify_pipe[2]; 111 static void 112 notify_setup(void) 113 { 114 if (pipe(notify_pipe) < 0) { 115 error("pipe(notify_pipe) failed %s", strerror(errno)); 116 } else if ((fcntl(notify_pipe[0], F_SETFD, FD_CLOEXEC) == -1) || 117 (fcntl(notify_pipe[1], F_SETFD, FD_CLOEXEC) == -1)) { 118 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno)); 119 close(notify_pipe[0]); 120 close(notify_pipe[1]); 121 } else { 122 set_nonblock(notify_pipe[0]); 123 set_nonblock(notify_pipe[1]); 124 return; 125 } 126 notify_pipe[0] = -1; /* read end */ 127 notify_pipe[1] = -1; /* write end */ 128 } 129 static void 130 notify_parent(void) 131 { 132 if (notify_pipe[1] != -1) 133 (void)write(notify_pipe[1], "", 1); 134 } 135 static void 136 notify_prepare(fd_set *readset) 137 { 138 if (notify_pipe[0] != -1) 139 FD_SET(notify_pipe[0], readset); 140 } 141 static void 142 notify_done(fd_set *readset) 143 { 144 char c; 145 146 if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset)) 147 while (read(notify_pipe[0], &c, 1) != -1) 148 debug2("notify_done: reading"); 149 } 150 151 /*ARGSUSED*/ 152 static void 153 sigchld_handler(int sig) 154 { 155 int save_errno = errno; 156 child_terminated = 1; 157 notify_parent(); 158 errno = save_errno; 159 } 160 161 /*ARGSUSED*/ 162 static void 163 sigterm_handler(int sig) 164 { 165 received_sigterm = sig; 166 } 167 168 static void 169 client_alive_check(struct ssh *ssh) 170 { 171 int channel_id; 172 char remote_id[512]; 173 174 /* timeout, check to see how many we have had */ 175 if (packet_inc_alive_timeouts() > options.client_alive_count_max) { 176 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id)); 177 logit("Timeout, client not responding from %s", remote_id); 178 cleanup_exit(255); 179 } 180 181 /* 182 * send a bogus global/channel request with "wantreply", 183 * we should get back a failure 184 */ 185 if ((channel_id = channel_find_open(ssh)) == -1) { 186 packet_start(SSH2_MSG_GLOBAL_REQUEST); 187 packet_put_cstring("keepalive@openssh.com"); 188 packet_put_char(1); /* boolean: want reply */ 189 } else { 190 channel_request_start(ssh, channel_id, 191 "keepalive@openssh.com", 1); 192 } 193 packet_send(); 194 } 195 196 /* 197 * Sleep in select() until we can do something. This will initialize the 198 * select masks. Upon return, the masks will indicate which descriptors 199 * have data or can accept data. Optionally, a maximum time can be specified 200 * for the duration of the wait (0 = infinite). 201 */ 202 static void 203 wait_until_can_do_something(struct ssh *ssh, 204 int connection_in, int connection_out, 205 fd_set **readsetp, fd_set **writesetp, int *maxfdp, 206 u_int *nallocp, u_int64_t max_time_ms) 207 { 208 struct timeval tv, *tvp; 209 int ret; 210 time_t minwait_secs = 0; 211 int client_alive_scheduled = 0; 212 static time_t last_client_time; 213 214 /* Allocate and update select() masks for channel descriptors. */ 215 channel_prepare_select(ssh, readsetp, writesetp, maxfdp, 216 nallocp, &minwait_secs); 217 218 /* XXX need proper deadline system for rekey/client alive */ 219 if (minwait_secs != 0) 220 max_time_ms = MINIMUM(max_time_ms, (u_int)minwait_secs * 1000); 221 222 /* 223 * if using client_alive, set the max timeout accordingly, 224 * and indicate that this particular timeout was for client 225 * alive by setting the client_alive_scheduled flag. 226 * 227 * this could be randomized somewhat to make traffic 228 * analysis more difficult, but we're not doing it yet. 229 */ 230 if (options.client_alive_interval) { 231 uint64_t keepalive_ms = 232 (uint64_t)options.client_alive_interval * 1000; 233 234 client_alive_scheduled = 1; 235 if (max_time_ms == 0 || max_time_ms > keepalive_ms) 236 max_time_ms = keepalive_ms; 237 } 238 239 #if 0 240 /* wrong: bad condition XXX */ 241 if (channel_not_very_much_buffered_data()) 242 #endif 243 FD_SET(connection_in, *readsetp); 244 notify_prepare(*readsetp); 245 246 /* 247 * If we have buffered packet data going to the client, mark that 248 * descriptor. 249 */ 250 if (packet_have_data_to_write()) 251 FD_SET(connection_out, *writesetp); 252 253 /* 254 * If child has terminated and there is enough buffer space to read 255 * from it, then read as much as is available and exit. 256 */ 257 if (child_terminated && packet_not_very_much_data_to_write()) 258 if (max_time_ms == 0 || client_alive_scheduled) 259 max_time_ms = 100; 260 261 if (max_time_ms == 0) 262 tvp = NULL; 263 else { 264 tv.tv_sec = max_time_ms / 1000; 265 tv.tv_usec = 1000 * (max_time_ms % 1000); 266 tvp = &tv; 267 } 268 269 /* Wait for something to happen, or the timeout to expire. */ 270 ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp); 271 272 if (ret == -1) { 273 memset(*readsetp, 0, *nallocp); 274 memset(*writesetp, 0, *nallocp); 275 if (errno != EINTR) 276 error("select: %.100s", strerror(errno)); 277 } else if (client_alive_scheduled) { 278 time_t now = monotime(); 279 280 if (ret == 0) { /* timeout */ 281 client_alive_check(ssh); 282 } else if (FD_ISSET(connection_in, *readsetp)) { 283 last_client_time = now; 284 } else if (last_client_time != 0 && last_client_time + 285 options.client_alive_interval <= now) { 286 client_alive_check(ssh); 287 last_client_time = now; 288 } 289 } 290 291 notify_done(*readsetp); 292 } 293 294 /* 295 * Processes input from the client and the program. Input data is stored 296 * in buffers and processed later. 297 */ 298 static int 299 process_input(struct ssh *ssh, fd_set *readset, int connection_in) 300 { 301 int len; 302 char buf[16384]; 303 304 /* Read and buffer any input data from the client. */ 305 if (FD_ISSET(connection_in, readset)) { 306 len = read(connection_in, buf, sizeof(buf)); 307 if (len == 0) { 308 verbose("Connection closed by %.100s port %d", 309 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 310 return -1; 311 } else if (len < 0) { 312 if (errno != EINTR && errno != EAGAIN && 313 errno != EWOULDBLOCK) { 314 verbose("Read error from remote host " 315 "%.100s port %d: %.100s", 316 ssh_remote_ipaddr(ssh), 317 ssh_remote_port(ssh), strerror(errno)); 318 cleanup_exit(255); 319 } 320 } else { 321 /* Buffer any received data. */ 322 packet_process_incoming(buf, len); 323 } 324 } 325 return 0; 326 } 327 328 /* 329 * Sends data from internal buffers to client program stdin. 330 */ 331 static void 332 process_output(fd_set *writeset, int connection_out) 333 { 334 /* Send any buffered packet data to the client. */ 335 if (FD_ISSET(connection_out, writeset)) 336 packet_write_poll(); 337 } 338 339 static void 340 process_buffered_input_packets(struct ssh *ssh) 341 { 342 ssh_dispatch_run_fatal(ssh, DISPATCH_NONBLOCK, NULL); 343 } 344 345 static void 346 collect_children(struct ssh *ssh) 347 { 348 pid_t pid; 349 sigset_t oset, nset; 350 int status; 351 352 /* block SIGCHLD while we check for dead children */ 353 sigemptyset(&nset); 354 sigaddset(&nset, SIGCHLD); 355 sigprocmask(SIG_BLOCK, &nset, &oset); 356 if (child_terminated) { 357 debug("Received SIGCHLD."); 358 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 359 (pid < 0 && errno == EINTR)) 360 if (pid > 0) 361 session_close_by_pid(ssh, pid, status); 362 child_terminated = 0; 363 } 364 sigprocmask(SIG_SETMASK, &oset, NULL); 365 } 366 367 void 368 server_loop2(struct ssh *ssh, Authctxt *authctxt) 369 { 370 fd_set *readset = NULL, *writeset = NULL; 371 int max_fd; 372 u_int nalloc = 0, connection_in, connection_out; 373 u_int64_t rekey_timeout_ms = 0; 374 375 debug("Entering interactive session for SSH2."); 376 377 signal(SIGCHLD, sigchld_handler); 378 child_terminated = 0; 379 connection_in = packet_get_connection_in(); 380 connection_out = packet_get_connection_out(); 381 382 if (!use_privsep) { 383 signal(SIGTERM, sigterm_handler); 384 signal(SIGINT, sigterm_handler); 385 signal(SIGQUIT, sigterm_handler); 386 } 387 388 notify_setup(); 389 390 max_fd = MAXIMUM(connection_in, connection_out); 391 max_fd = MAXIMUM(max_fd, notify_pipe[0]); 392 393 server_init_dispatch(); 394 395 for (;;) { 396 process_buffered_input_packets(ssh); 397 398 if (!ssh_packet_is_rekeying(ssh) && 399 packet_not_very_much_data_to_write()) 400 channel_output_poll(ssh); 401 if (options.rekey_interval > 0 && !ssh_packet_is_rekeying(ssh)) 402 rekey_timeout_ms = packet_get_rekey_timeout() * 1000; 403 else 404 rekey_timeout_ms = 0; 405 406 wait_until_can_do_something(ssh, connection_in, connection_out, 407 &readset, &writeset, &max_fd, &nalloc, rekey_timeout_ms); 408 409 if (received_sigterm) { 410 logit("Exiting on signal %d", (int)received_sigterm); 411 /* Clean up sessions, utmp, etc. */ 412 cleanup_exit(255); 413 } 414 415 collect_children(ssh); 416 if (!ssh_packet_is_rekeying(ssh)) 417 channel_after_select(ssh, readset, writeset); 418 if (process_input(ssh, readset, connection_in) < 0) 419 break; 420 process_output(writeset, connection_out); 421 } 422 collect_children(ssh); 423 424 free(readset); 425 free(writeset); 426 427 /* free all channels, no more reads and writes */ 428 channel_free_all(ssh); 429 430 /* free remaining sessions, e.g. remove wtmp entries */ 431 session_destroy_all(ssh, NULL); 432 } 433 434 static int 435 server_input_keep_alive(int type, u_int32_t seq, struct ssh *ssh) 436 { 437 debug("Got %d/%u for keepalive", type, seq); 438 /* 439 * reset timeout, since we got a sane answer from the client. 440 * even if this was generated by something other than 441 * the bogus CHANNEL_REQUEST we send for keepalives. 442 */ 443 packet_set_alive_timeouts(0); 444 return 0; 445 } 446 447 static Channel * 448 server_request_direct_tcpip(struct ssh *ssh, int *reason, const char **errmsg) 449 { 450 Channel *c = NULL; 451 char *target, *originator; 452 u_short target_port, originator_port; 453 454 target = packet_get_string(NULL); 455 target_port = packet_get_int(); 456 originator = packet_get_string(NULL); 457 originator_port = packet_get_int(); 458 packet_check_eom(); 459 460 debug("%s: originator %s port %d, target %s port %d", __func__, 461 originator, originator_port, target, target_port); 462 463 /* XXX fine grained permissions */ 464 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 && 465 auth_opts->permit_port_forwarding_flag && 466 !options.disable_forwarding) { 467 c = channel_connect_to_port(ssh, target, target_port, 468 "direct-tcpip", "direct-tcpip", reason, errmsg); 469 } else { 470 logit("refused local port forward: " 471 "originator %s port %d, target %s port %d", 472 originator, originator_port, target, target_port); 473 if (reason != NULL) 474 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 475 } 476 477 free(originator); 478 free(target); 479 480 return c; 481 } 482 483 static Channel * 484 server_request_direct_streamlocal(struct ssh *ssh) 485 { 486 Channel *c = NULL; 487 char *target, *originator; 488 u_short originator_port; 489 struct passwd *pw = the_authctxt->pw; 490 491 if (pw == NULL || !the_authctxt->valid) 492 fatal("%s: no/invalid user", __func__); 493 494 target = packet_get_string(NULL); 495 originator = packet_get_string(NULL); 496 originator_port = packet_get_int(); 497 packet_check_eom(); 498 499 debug("%s: originator %s port %d, target %s", __func__, 500 originator, originator_port, target); 501 502 /* XXX fine grained permissions */ 503 if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 && 504 auth_opts->permit_port_forwarding_flag && 505 !options.disable_forwarding && (pw->pw_uid == 0 || use_privsep)) { 506 c = channel_connect_to_path(ssh, target, 507 "direct-streamlocal@openssh.com", "direct-streamlocal"); 508 } else { 509 logit("refused streamlocal port forward: " 510 "originator %s port %d, target %s", 511 originator, originator_port, target); 512 } 513 514 free(originator); 515 free(target); 516 517 return c; 518 } 519 520 static Channel * 521 server_request_tun(struct ssh *ssh) 522 { 523 Channel *c = NULL; 524 int mode, tun, sock; 525 char *tmp, *ifname = NULL; 526 527 mode = packet_get_int(); 528 switch (mode) { 529 case SSH_TUNMODE_POINTOPOINT: 530 case SSH_TUNMODE_ETHERNET: 531 break; 532 default: 533 packet_send_debug("Unsupported tunnel device mode."); 534 return NULL; 535 } 536 if ((options.permit_tun & mode) == 0) { 537 packet_send_debug("Server has rejected tunnel device " 538 "forwarding"); 539 return NULL; 540 } 541 542 tun = packet_get_int(); 543 if (auth_opts->force_tun_device != -1) { 544 if (tun != SSH_TUNID_ANY && auth_opts->force_tun_device != tun) 545 goto done; 546 tun = auth_opts->force_tun_device; 547 } 548 sock = tun_open(tun, mode, &ifname); 549 if (sock < 0) 550 goto done; 551 debug("Tunnel forwarding using interface %s", ifname); 552 553 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1, 554 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 555 c->datagram = 1; 556 #if defined(SSH_TUN_FILTER) 557 if (mode == SSH_TUNMODE_POINTOPOINT) 558 channel_register_filter(ssh, c->self, sys_tun_infilter, 559 sys_tun_outfilter, NULL, NULL); 560 #endif 561 562 /* 563 * Update the list of names exposed to the session 564 * XXX remove these if the tunnels are closed (won't matter 565 * much if they are already in the environment though) 566 */ 567 tmp = tun_fwd_ifnames; 568 xasprintf(&tun_fwd_ifnames, "%s%s%s", 569 tun_fwd_ifnames == NULL ? "" : tun_fwd_ifnames, 570 tun_fwd_ifnames == NULL ? "" : ",", 571 ifname); 572 free(tmp); 573 free(ifname); 574 575 done: 576 if (c == NULL) 577 packet_send_debug("Failed to open the tunnel device."); 578 return c; 579 } 580 581 static Channel * 582 server_request_session(struct ssh *ssh) 583 { 584 Channel *c; 585 586 debug("input_session_request"); 587 packet_check_eom(); 588 589 if (no_more_sessions) { 590 packet_disconnect("Possible attack: attempt to open a session " 591 "after additional sessions disabled"); 592 } 593 594 /* 595 * A server session has no fd to read or write until a 596 * CHANNEL_REQUEST for a shell is made, so we set the type to 597 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all 598 * CHANNEL_REQUEST messages is registered. 599 */ 600 c = channel_new(ssh, "session", SSH_CHANNEL_LARVAL, 601 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, 602 0, "server-session", 1); 603 if (session_open(the_authctxt, c->self) != 1) { 604 debug("session open failed, free channel %d", c->self); 605 channel_free(ssh, c); 606 return NULL; 607 } 608 channel_register_cleanup(ssh, c->self, session_close_by_channel, 0); 609 return c; 610 } 611 612 static int 613 server_input_channel_open(int type, u_int32_t seq, struct ssh *ssh) 614 { 615 Channel *c = NULL; 616 char *ctype; 617 const char *errmsg = NULL; 618 int rchan, reason = SSH2_OPEN_CONNECT_FAILED; 619 u_int rmaxpack, rwindow, len; 620 621 ctype = packet_get_string(&len); 622 rchan = packet_get_int(); 623 rwindow = packet_get_int(); 624 rmaxpack = packet_get_int(); 625 626 debug("server_input_channel_open: ctype %s rchan %d win %d max %d", 627 ctype, rchan, rwindow, rmaxpack); 628 629 if (strcmp(ctype, "session") == 0) { 630 c = server_request_session(ssh); 631 } else if (strcmp(ctype, "direct-tcpip") == 0) { 632 c = server_request_direct_tcpip(ssh, &reason, &errmsg); 633 } else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) { 634 c = server_request_direct_streamlocal(ssh); 635 } else if (strcmp(ctype, "tun@openssh.com") == 0) { 636 c = server_request_tun(ssh); 637 } 638 if (c != NULL) { 639 debug("server_input_channel_open: confirm %s", ctype); 640 c->remote_id = rchan; 641 c->have_remote_id = 1; 642 c->remote_window = rwindow; 643 c->remote_maxpacket = rmaxpack; 644 if (c->type != SSH_CHANNEL_CONNECTING) { 645 packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION); 646 packet_put_int(c->remote_id); 647 packet_put_int(c->self); 648 packet_put_int(c->local_window); 649 packet_put_int(c->local_maxpacket); 650 packet_send(); 651 } 652 } else { 653 debug("server_input_channel_open: failure %s", ctype); 654 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE); 655 packet_put_int(rchan); 656 packet_put_int(reason); 657 packet_put_cstring(errmsg ? errmsg : "open failed"); 658 packet_put_cstring(""); 659 packet_send(); 660 } 661 free(ctype); 662 return 0; 663 } 664 665 static int 666 server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp) 667 { 668 struct sshbuf *resp = NULL; 669 struct sshbuf *sigbuf = NULL; 670 struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL; 671 int r, ndx, kexsigtype, use_kexsigtype, success = 0; 672 const u_char *blob; 673 u_char *sig = 0; 674 size_t blen, slen; 675 676 if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL) 677 fatal("%s: sshbuf_new", __func__); 678 679 kexsigtype = sshkey_type_plain( 680 sshkey_type_from_name(ssh->kex->hostkey_alg)); 681 while (ssh_packet_remaining(ssh) > 0) { 682 sshkey_free(key); 683 key = NULL; 684 if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 || 685 (r = sshkey_from_blob(blob, blen, &key)) != 0) { 686 error("%s: couldn't parse key: %s", 687 __func__, ssh_err(r)); 688 goto out; 689 } 690 /* 691 * Better check that this is actually one of our hostkeys 692 * before attempting to sign anything with it. 693 */ 694 if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) { 695 error("%s: unknown host %s key", 696 __func__, sshkey_type(key)); 697 goto out; 698 } 699 /* 700 * XXX refactor: make kex->sign just use an index rather 701 * than passing in public and private keys 702 */ 703 if ((key_prv = get_hostkey_by_index(ndx)) == NULL && 704 (key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) { 705 error("%s: can't retrieve hostkey %d", __func__, ndx); 706 goto out; 707 } 708 sshbuf_reset(sigbuf); 709 free(sig); 710 sig = NULL; 711 /* 712 * For RSA keys, prefer to use the signature type negotiated 713 * during KEX to the default (SHA1). 714 */ 715 use_kexsigtype = kexsigtype == KEY_RSA && 716 sshkey_type_plain(key->type) == KEY_RSA; 717 if ((r = sshbuf_put_cstring(sigbuf, 718 "hostkeys-prove-00@openssh.com")) != 0 || 719 (r = sshbuf_put_string(sigbuf, 720 ssh->kex->session_id, ssh->kex->session_id_len)) != 0 || 721 (r = sshkey_puts(key, sigbuf)) != 0 || 722 (r = ssh->kex->sign(key_prv, key_pub, &sig, &slen, 723 sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), 724 use_kexsigtype ? ssh->kex->hostkey_alg : NULL, 0)) != 0 || 725 (r = sshbuf_put_string(resp, sig, slen)) != 0) { 726 error("%s: couldn't prepare signature: %s", 727 __func__, ssh_err(r)); 728 goto out; 729 } 730 } 731 /* Success */ 732 *respp = resp; 733 resp = NULL; /* don't free it */ 734 success = 1; 735 out: 736 free(sig); 737 sshbuf_free(resp); 738 sshbuf_free(sigbuf); 739 sshkey_free(key); 740 return success; 741 } 742 743 static int 744 server_input_global_request(int type, u_int32_t seq, struct ssh *ssh) 745 { 746 char *rtype; 747 int want_reply; 748 int r, success = 0, allocated_listen_port = 0; 749 struct sshbuf *resp = NULL; 750 struct passwd *pw = the_authctxt->pw; 751 752 if (pw == NULL || !the_authctxt->valid) 753 fatal("server_input_global_request: no/invalid user"); 754 755 rtype = packet_get_string(NULL); 756 want_reply = packet_get_char(); 757 debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply); 758 759 /* -R style forwarding */ 760 if (strcmp(rtype, "tcpip-forward") == 0) { 761 struct Forward fwd; 762 763 memset(&fwd, 0, sizeof(fwd)); 764 fwd.listen_host = packet_get_string(NULL); 765 fwd.listen_port = (u_short)packet_get_int(); 766 debug("server_input_global_request: tcpip-forward listen %s port %d", 767 fwd.listen_host, fwd.listen_port); 768 769 /* check permissions */ 770 if ((options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 || 771 !auth_opts->permit_port_forwarding_flag || 772 options.disable_forwarding || 773 (!want_reply && fwd.listen_port == 0) || 774 (fwd.listen_port != 0 && 775 !bind_permitted(fwd.listen_port, pw->pw_uid))) { 776 success = 0; 777 packet_send_debug("Server has disabled port forwarding."); 778 } else { 779 /* Start listening on the port */ 780 success = channel_setup_remote_fwd_listener(ssh, &fwd, 781 &allocated_listen_port, &options.fwd_opts); 782 } 783 free(fwd.listen_host); 784 if ((resp = sshbuf_new()) == NULL) 785 fatal("%s: sshbuf_new", __func__); 786 if (allocated_listen_port != 0 && 787 (r = sshbuf_put_u32(resp, allocated_listen_port)) != 0) 788 fatal("%s: sshbuf_put_u32: %s", __func__, ssh_err(r)); 789 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) { 790 struct Forward fwd; 791 792 memset(&fwd, 0, sizeof(fwd)); 793 fwd.listen_host = packet_get_string(NULL); 794 fwd.listen_port = (u_short)packet_get_int(); 795 debug("%s: cancel-tcpip-forward addr %s port %d", __func__, 796 fwd.listen_host, fwd.listen_port); 797 798 success = channel_cancel_rport_listener(ssh, &fwd); 799 free(fwd.listen_host); 800 } else if (strcmp(rtype, "streamlocal-forward@openssh.com") == 0) { 801 struct Forward fwd; 802 803 memset(&fwd, 0, sizeof(fwd)); 804 fwd.listen_path = packet_get_string(NULL); 805 debug("server_input_global_request: streamlocal-forward listen path %s", 806 fwd.listen_path); 807 808 /* check permissions */ 809 if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0 810 || !auth_opts->permit_port_forwarding_flag || 811 options.disable_forwarding || 812 (pw->pw_uid != 0 && !use_privsep)) { 813 success = 0; 814 packet_send_debug("Server has disabled " 815 "streamlocal forwarding."); 816 } else { 817 /* Start listening on the socket */ 818 success = channel_setup_remote_fwd_listener(ssh, 819 &fwd, NULL, &options.fwd_opts); 820 } 821 free(fwd.listen_path); 822 } else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) { 823 struct Forward fwd; 824 825 memset(&fwd, 0, sizeof(fwd)); 826 fwd.listen_path = packet_get_string(NULL); 827 debug("%s: cancel-streamlocal-forward path %s", __func__, 828 fwd.listen_path); 829 830 success = channel_cancel_rport_listener(ssh, &fwd); 831 free(fwd.listen_path); 832 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) { 833 no_more_sessions = 1; 834 success = 1; 835 } else if (strcmp(rtype, "hostkeys-prove-00@openssh.com") == 0) { 836 success = server_input_hostkeys_prove(ssh, &resp); 837 } 838 if (want_reply) { 839 packet_start(success ? 840 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE); 841 if (success && resp != NULL) 842 ssh_packet_put_raw(ssh, sshbuf_ptr(resp), 843 sshbuf_len(resp)); 844 packet_send(); 845 packet_write_wait(); 846 } 847 free(rtype); 848 sshbuf_free(resp); 849 return 0; 850 } 851 852 static int 853 server_input_channel_req(int type, u_int32_t seq, struct ssh *ssh) 854 { 855 Channel *c; 856 int id, reply, success = 0; 857 char *rtype; 858 859 id = packet_get_int(); 860 rtype = packet_get_string(NULL); 861 reply = packet_get_char(); 862 863 debug("server_input_channel_req: channel %d request %s reply %d", 864 id, rtype, reply); 865 866 if ((c = channel_lookup(ssh, id)) == NULL) 867 packet_disconnect("server_input_channel_req: " 868 "unknown channel %d", id); 869 if (!strcmp(rtype, "eow@openssh.com")) { 870 packet_check_eom(); 871 chan_rcvd_eow(ssh, c); 872 } else if ((c->type == SSH_CHANNEL_LARVAL || 873 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0) 874 success = session_input_channel_req(ssh, c, rtype); 875 if (reply && !(c->flags & CHAN_CLOSE_SENT)) { 876 if (!c->have_remote_id) 877 fatal("%s: channel %d: no remote_id", 878 __func__, c->self); 879 packet_start(success ? 880 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE); 881 packet_put_int(c->remote_id); 882 packet_send(); 883 } 884 free(rtype); 885 return 0; 886 } 887 888 static void 889 server_init_dispatch(void) 890 { 891 debug("server_init_dispatch"); 892 dispatch_init(&dispatch_protocol_error); 893 dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); 894 dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data); 895 dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); 896 dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); 897 dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); 898 dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 899 dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 900 dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); 901 dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); 902 dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); 903 /* client_alive */ 904 dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive); 905 dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); 906 dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); 907 dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); 908 /* rekeying */ 909 dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit); 910 } 911