1 /* $OpenBSD: serverloop.c,v 1.215 2019/03/27 09:29:14 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) < 0) { 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 (ssh_packet_inc_alive_timeouts(ssh) > 188 options.client_alive_count_max) { 189 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id)); 190 logit("Timeout, client not responding from %s", remote_id); 191 cleanup_exit(255); 192 } 193 194 /* 195 * send a bogus global/channel request with "wantreply", 196 * we should get back a failure 197 */ 198 if ((channel_id = channel_find_open(ssh)) == -1) { 199 if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 || 200 (r = sshpkt_put_cstring(ssh, "keepalive@openssh.com")) 201 != 0 || 202 (r = sshpkt_put_u8(ssh, 1)) != 0) /* boolean: want reply */ 203 fatal("%s: %s", __func__, ssh_err(r)); 204 } else { 205 channel_request_start(ssh, channel_id, 206 "keepalive@openssh.com", 1); 207 } 208 if ((r = sshpkt_send(ssh)) != 0) 209 fatal("%s: %s", __func__, ssh_err(r)); 210 } 211 212 /* 213 * Sleep in select() until we can do something. This will initialize the 214 * select masks. Upon return, the masks will indicate which descriptors 215 * have data or can accept data. Optionally, a maximum time can be specified 216 * for the duration of the wait (0 = infinite). 217 */ 218 static void 219 wait_until_can_do_something(struct ssh *ssh, 220 int connection_in, int connection_out, 221 fd_set **readsetp, fd_set **writesetp, int *maxfdp, 222 u_int *nallocp, u_int64_t max_time_ms) 223 { 224 struct timeval tv, *tvp; 225 int ret; 226 time_t minwait_secs = 0; 227 int client_alive_scheduled = 0; 228 /* time we last heard from the client OR sent a keepalive */ 229 static time_t last_client_time; 230 231 /* Allocate and update select() masks for channel descriptors. */ 232 channel_prepare_select(ssh, readsetp, writesetp, maxfdp, 233 nallocp, &minwait_secs); 234 235 /* XXX need proper deadline system for rekey/client alive */ 236 if (minwait_secs != 0) 237 max_time_ms = MINIMUM(max_time_ms, (u_int)minwait_secs * 1000); 238 239 /* 240 * if using client_alive, set the max timeout accordingly, 241 * and indicate that this particular timeout was for client 242 * alive by setting the client_alive_scheduled flag. 243 * 244 * this could be randomized somewhat to make traffic 245 * analysis more difficult, but we're not doing it yet. 246 */ 247 if (options.client_alive_interval) { 248 uint64_t keepalive_ms = 249 (uint64_t)options.client_alive_interval * 1000; 250 251 if (max_time_ms == 0 || max_time_ms > keepalive_ms) { 252 max_time_ms = keepalive_ms; 253 client_alive_scheduled = 1; 254 } 255 } 256 257 #if 0 258 /* wrong: bad condition XXX */ 259 if (channel_not_very_much_buffered_data()) 260 #endif 261 FD_SET(connection_in, *readsetp); 262 notify_prepare(*readsetp); 263 264 /* 265 * If we have buffered packet data going to the client, mark that 266 * descriptor. 267 */ 268 if (ssh_packet_have_data_to_write(ssh)) 269 FD_SET(connection_out, *writesetp); 270 271 /* 272 * If child has terminated and there is enough buffer space to read 273 * from it, then read as much as is available and exit. 274 */ 275 if (child_terminated && ssh_packet_not_very_much_data_to_write(ssh)) 276 if (max_time_ms == 0 || client_alive_scheduled) 277 max_time_ms = 100; 278 279 if (max_time_ms == 0) 280 tvp = NULL; 281 else { 282 tv.tv_sec = max_time_ms / 1000; 283 tv.tv_usec = 1000 * (max_time_ms % 1000); 284 tvp = &tv; 285 } 286 287 /* Wait for something to happen, or the timeout to expire. */ 288 ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp); 289 290 if (ret == -1) { 291 memset(*readsetp, 0, *nallocp); 292 memset(*writesetp, 0, *nallocp); 293 if (errno != EINTR) 294 error("select: %.100s", strerror(errno)); 295 } else if (client_alive_scheduled) { 296 time_t now = monotime(); 297 298 /* 299 * If the select timed out, or returned for some other reason 300 * but we haven't heard from the client in time, send keepalive. 301 */ 302 if (ret == 0 || (last_client_time != 0 && last_client_time + 303 options.client_alive_interval <= now)) { 304 client_alive_check(ssh); 305 last_client_time = now; 306 } else if (FD_ISSET(connection_in, *readsetp)) { 307 last_client_time = now; 308 } 309 } 310 311 notify_done(*readsetp); 312 } 313 314 /* 315 * Processes input from the client and the program. Input data is stored 316 * in buffers and processed later. 317 */ 318 static int 319 process_input(struct ssh *ssh, fd_set *readset, int connection_in) 320 { 321 int r, len; 322 char buf[16384]; 323 324 /* Read and buffer any input data from the client. */ 325 if (FD_ISSET(connection_in, readset)) { 326 len = read(connection_in, buf, sizeof(buf)); 327 if (len == 0) { 328 verbose("Connection closed by %.100s port %d", 329 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 330 return -1; 331 } else if (len < 0) { 332 if (errno != EINTR && errno != EAGAIN && 333 errno != EWOULDBLOCK) { 334 verbose("Read error from remote host " 335 "%.100s port %d: %.100s", 336 ssh_remote_ipaddr(ssh), 337 ssh_remote_port(ssh), strerror(errno)); 338 cleanup_exit(255); 339 } 340 } else { 341 /* Buffer any received data. */ 342 if ((r = ssh_packet_process_incoming(ssh, buf, len)) 343 != 0) 344 fatal("%s: ssh_packet_process_incoming: %s", 345 __func__, ssh_err(r)); 346 } 347 } 348 return 0; 349 } 350 351 /* 352 * Sends data from internal buffers to client program stdin. 353 */ 354 static void 355 process_output(struct ssh *ssh, fd_set *writeset, int connection_out) 356 { 357 int r; 358 359 /* Send any buffered packet data to the client. */ 360 if (FD_ISSET(connection_out, writeset)) { 361 if ((r = ssh_packet_write_poll(ssh)) != 0) 362 fatal("%s: ssh_packet_write_poll: %s", 363 __func__, ssh_err(r)); 364 } 365 } 366 367 static void 368 process_buffered_input_packets(struct ssh *ssh) 369 { 370 ssh_dispatch_run_fatal(ssh, DISPATCH_NONBLOCK, NULL); 371 } 372 373 static void 374 collect_children(struct ssh *ssh) 375 { 376 pid_t pid; 377 sigset_t oset, nset; 378 int status; 379 380 /* block SIGCHLD while we check for dead children */ 381 sigemptyset(&nset); 382 sigaddset(&nset, SIGCHLD); 383 sigprocmask(SIG_BLOCK, &nset, &oset); 384 if (child_terminated) { 385 debug("Received SIGCHLD."); 386 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 387 (pid < 0 && errno == EINTR)) 388 if (pid > 0) 389 session_close_by_pid(ssh, pid, status); 390 child_terminated = 0; 391 } 392 sigprocmask(SIG_SETMASK, &oset, NULL); 393 } 394 395 void 396 server_loop2(struct ssh *ssh, Authctxt *authctxt) 397 { 398 fd_set *readset = NULL, *writeset = NULL; 399 int max_fd; 400 u_int nalloc = 0, connection_in, connection_out; 401 u_int64_t rekey_timeout_ms = 0; 402 403 debug("Entering interactive session for SSH2."); 404 405 signal(SIGCHLD, sigchld_handler); 406 child_terminated = 0; 407 connection_in = ssh_packet_get_connection_in(ssh); 408 connection_out = ssh_packet_get_connection_out(ssh); 409 410 if (!use_privsep) { 411 signal(SIGTERM, sigterm_handler); 412 signal(SIGINT, sigterm_handler); 413 signal(SIGQUIT, sigterm_handler); 414 } 415 416 notify_setup(); 417 418 max_fd = MAXIMUM(connection_in, connection_out); 419 max_fd = MAXIMUM(max_fd, notify_pipe[0]); 420 421 server_init_dispatch(ssh); 422 423 for (;;) { 424 process_buffered_input_packets(ssh); 425 426 if (!ssh_packet_is_rekeying(ssh) && 427 ssh_packet_not_very_much_data_to_write(ssh)) 428 channel_output_poll(ssh); 429 if (options.rekey_interval > 0 && 430 !ssh_packet_is_rekeying(ssh)) { 431 rekey_timeout_ms = ssh_packet_get_rekey_timeout(ssh) * 432 1000; 433 } else { 434 rekey_timeout_ms = 0; 435 } 436 437 wait_until_can_do_something(ssh, connection_in, connection_out, 438 &readset, &writeset, &max_fd, &nalloc, rekey_timeout_ms); 439 440 if (received_sigterm) { 441 logit("Exiting on signal %d", (int)received_sigterm); 442 /* Clean up sessions, utmp, etc. */ 443 cleanup_exit(255); 444 } 445 446 collect_children(ssh); 447 if (!ssh_packet_is_rekeying(ssh)) 448 channel_after_select(ssh, readset, writeset); 449 if (process_input(ssh, readset, connection_in) < 0) 450 break; 451 process_output(ssh, writeset, connection_out); 452 } 453 collect_children(ssh); 454 455 free(readset); 456 free(writeset); 457 458 /* free all channels, no more reads and writes */ 459 channel_free_all(ssh); 460 461 /* free remaining sessions, e.g. remove wtmp entries */ 462 session_destroy_all(ssh, NULL); 463 } 464 465 static int 466 server_input_keep_alive(int type, u_int32_t seq, struct ssh *ssh) 467 { 468 debug("Got %d/%u for keepalive", type, seq); 469 /* 470 * reset timeout, since we got a sane answer from the client. 471 * even if this was generated by something other than 472 * the bogus CHANNEL_REQUEST we send for keepalives. 473 */ 474 ssh_packet_set_alive_timeouts(ssh, 0); 475 return 0; 476 } 477 478 static Channel * 479 server_request_direct_tcpip(struct ssh *ssh, int *reason, const char **errmsg) 480 { 481 Channel *c = NULL; 482 char *target = NULL, *originator = NULL; 483 u_int target_port = 0, originator_port = 0; 484 int r; 485 486 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 487 (r = sshpkt_get_u32(ssh, &target_port)) != 0 || 488 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 489 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 490 (r = sshpkt_get_end(ssh)) != 0) 491 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 492 if (target_port > 0xFFFF) { 493 error("%s: invalid target port", __func__); 494 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 495 goto out; 496 } 497 if (originator_port > 0xFFFF) { 498 error("%s: invalid originator port", __func__); 499 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 500 goto out; 501 } 502 503 debug("%s: originator %s port %u, target %s port %u", __func__, 504 originator, originator_port, target, target_port); 505 506 /* XXX fine grained permissions */ 507 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 && 508 auth_opts->permit_port_forwarding_flag && 509 !options.disable_forwarding) { 510 c = channel_connect_to_port(ssh, target, target_port, 511 "direct-tcpip", "direct-tcpip", reason, errmsg); 512 } else { 513 logit("refused local port forward: " 514 "originator %s port %d, target %s port %d", 515 originator, originator_port, target, target_port); 516 if (reason != NULL) 517 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 518 } 519 520 out: 521 free(originator); 522 free(target); 523 return c; 524 } 525 526 static Channel * 527 server_request_direct_streamlocal(struct ssh *ssh) 528 { 529 Channel *c = NULL; 530 char *target = NULL, *originator = NULL; 531 u_int originator_port = 0; 532 struct passwd *pw = the_authctxt->pw; 533 int r; 534 535 if (pw == NULL || !the_authctxt->valid) 536 fatal("%s: no/invalid user", __func__); 537 538 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 539 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 540 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 541 (r = sshpkt_get_end(ssh)) != 0) 542 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 543 if (originator_port > 0xFFFF) { 544 error("%s: invalid originator port", __func__); 545 goto out; 546 } 547 548 debug("%s: originator %s port %d, target %s", __func__, 549 originator, originator_port, target); 550 551 /* XXX fine grained permissions */ 552 if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 && 553 auth_opts->permit_port_forwarding_flag && 554 !options.disable_forwarding && (pw->pw_uid == 0 || use_privsep)) { 555 c = channel_connect_to_path(ssh, target, 556 "direct-streamlocal@openssh.com", "direct-streamlocal"); 557 } else { 558 logit("refused streamlocal port forward: " 559 "originator %s port %d, target %s", 560 originator, originator_port, target); 561 } 562 563 out: 564 free(originator); 565 free(target); 566 return c; 567 } 568 569 static Channel * 570 server_request_tun(struct ssh *ssh) 571 { 572 Channel *c = NULL; 573 u_int mode, tun; 574 int r, sock; 575 char *tmp, *ifname = NULL; 576 577 if ((r = sshpkt_get_u32(ssh, &mode)) != 0) 578 sshpkt_fatal(ssh, r, "%s: parse mode", __func__); 579 switch (mode) { 580 case SSH_TUNMODE_POINTOPOINT: 581 case SSH_TUNMODE_ETHERNET: 582 break; 583 default: 584 ssh_packet_send_debug(ssh, "Unsupported tunnel device mode."); 585 return NULL; 586 } 587 if ((options.permit_tun & mode) == 0) { 588 ssh_packet_send_debug(ssh, "Server has rejected tunnel device " 589 "forwarding"); 590 return NULL; 591 } 592 593 if ((r = sshpkt_get_u32(ssh, &tun)) != 0) 594 sshpkt_fatal(ssh, r, "%s: parse device", __func__); 595 if (tun > INT_MAX) { 596 debug("%s: invalid tun", __func__); 597 goto done; 598 } 599 if (auth_opts->force_tun_device != -1) { 600 if (tun != SSH_TUNID_ANY && 601 auth_opts->force_tun_device != (int)tun) 602 goto done; 603 tun = auth_opts->force_tun_device; 604 } 605 sock = tun_open(tun, mode, &ifname); 606 if (sock < 0) 607 goto done; 608 debug("Tunnel forwarding using interface %s", ifname); 609 610 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1, 611 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 612 c->datagram = 1; 613 #if defined(SSH_TUN_FILTER) 614 if (mode == SSH_TUNMODE_POINTOPOINT) 615 channel_register_filter(ssh, c->self, sys_tun_infilter, 616 sys_tun_outfilter, NULL, NULL); 617 #endif 618 619 /* 620 * Update the list of names exposed to the session 621 * XXX remove these if the tunnels are closed (won't matter 622 * much if they are already in the environment though) 623 */ 624 tmp = tun_fwd_ifnames; 625 xasprintf(&tun_fwd_ifnames, "%s%s%s", 626 tun_fwd_ifnames == NULL ? "" : tun_fwd_ifnames, 627 tun_fwd_ifnames == NULL ? "" : ",", 628 ifname); 629 free(tmp); 630 free(ifname); 631 632 done: 633 if (c == NULL) 634 ssh_packet_send_debug(ssh, "Failed to open the tunnel device."); 635 return c; 636 } 637 638 static Channel * 639 server_request_session(struct ssh *ssh) 640 { 641 Channel *c; 642 int r; 643 644 debug("input_session_request"); 645 if ((r = sshpkt_get_end(ssh)) != 0) 646 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 647 648 if (no_more_sessions) { 649 ssh_packet_disconnect(ssh, "Possible attack: attempt to open a " 650 "session after additional sessions disabled"); 651 } 652 653 /* 654 * A server session has no fd to read or write until a 655 * CHANNEL_REQUEST for a shell is made, so we set the type to 656 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all 657 * CHANNEL_REQUEST messages is registered. 658 */ 659 c = channel_new(ssh, "session", SSH_CHANNEL_LARVAL, 660 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, 661 0, "server-session", 1); 662 if (session_open(the_authctxt, c->self) != 1) { 663 debug("session open failed, free channel %d", c->self); 664 channel_free(ssh, c); 665 return NULL; 666 } 667 channel_register_cleanup(ssh, c->self, session_close_by_channel, 0); 668 return c; 669 } 670 671 static int 672 server_input_channel_open(int type, u_int32_t seq, struct ssh *ssh) 673 { 674 Channel *c = NULL; 675 char *ctype = NULL; 676 const char *errmsg = NULL; 677 int r, reason = SSH2_OPEN_CONNECT_FAILED; 678 u_int rchan = 0, rmaxpack = 0, rwindow = 0; 679 680 if ((r = sshpkt_get_cstring(ssh, &ctype, NULL)) != 0 || 681 (r = sshpkt_get_u32(ssh, &rchan)) != 0 || 682 (r = sshpkt_get_u32(ssh, &rwindow)) != 0 || 683 (r = sshpkt_get_u32(ssh, &rmaxpack)) != 0) 684 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 685 debug("%s: ctype %s rchan %u win %u max %u", __func__, 686 ctype, rchan, rwindow, rmaxpack); 687 688 if (rchan > INT_MAX) { 689 error("%s: invalid remote channel ID", __func__); 690 } else 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 = (int)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