1 /* $OpenBSD: serverloop.c,v 1.232 2022/04/20 04:19:11 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 #ifdef HAVE_POLL_H 54 #include <poll.h> 55 #endif 56 #include <signal.h> 57 #include <string.h> 58 #include <termios.h> 59 #include <unistd.h> 60 #include <stdarg.h> 61 62 #include "openbsd-compat/sys-queue.h" 63 #include "xmalloc.h" 64 #include "packet.h" 65 #include "sshbuf.h" 66 #include "log.h" 67 #include "misc.h" 68 #include "servconf.h" 69 #include "canohost.h" 70 #include "sshpty.h" 71 #include "channels.h" 72 #include "compat.h" 73 #include "ssh2.h" 74 #include "sshkey.h" 75 #include "cipher.h" 76 #include "kex.h" 77 #include "hostfile.h" 78 #include "auth.h" 79 #include "session.h" 80 #include "dispatch.h" 81 #include "auth-options.h" 82 #include "serverloop.h" 83 #include "ssherr.h" 84 85 extern ServerOptions options; 86 87 /* XXX */ 88 extern Authctxt *the_authctxt; 89 extern struct sshauthopt *auth_opts; 90 extern int use_privsep; 91 92 static int no_more_sessions = 0; /* Disallow further sessions. */ 93 94 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */ 95 96 /* Cleanup on signals (!use_privsep case only) */ 97 static volatile sig_atomic_t received_sigterm = 0; 98 99 /* prototypes */ 100 static void server_init_dispatch(struct ssh *); 101 102 /* requested tunnel forwarding interface(s), shared with session.c */ 103 char *tun_fwd_ifnames = NULL; 104 105 /* returns 1 if bind to specified port by specified user is permitted */ 106 static int 107 bind_permitted(int port, uid_t uid) 108 { 109 if (use_privsep) 110 return 1; /* allow system to decide */ 111 if (port < IPPORT_RESERVED && uid != 0) 112 return 0; 113 return 1; 114 } 115 116 /*ARGSUSED*/ 117 static void 118 sigchld_handler(int sig) 119 { 120 child_terminated = 1; 121 } 122 123 /*ARGSUSED*/ 124 static void 125 sigterm_handler(int sig) 126 { 127 received_sigterm = sig; 128 } 129 130 static void 131 client_alive_check(struct ssh *ssh) 132 { 133 char remote_id[512]; 134 int r, channel_id; 135 136 /* timeout, check to see how many we have had */ 137 if (options.client_alive_count_max > 0 && 138 ssh_packet_inc_alive_timeouts(ssh) > 139 options.client_alive_count_max) { 140 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id)); 141 logit("Timeout, client not responding from %s", remote_id); 142 cleanup_exit(255); 143 } 144 145 /* 146 * send a bogus global/channel request with "wantreply", 147 * we should get back a failure 148 */ 149 if ((channel_id = channel_find_open(ssh)) == -1) { 150 if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 || 151 (r = sshpkt_put_cstring(ssh, "keepalive@openssh.com")) 152 != 0 || 153 (r = sshpkt_put_u8(ssh, 1)) != 0) /* boolean: want reply */ 154 fatal_fr(r, "compose"); 155 } else { 156 channel_request_start(ssh, channel_id, 157 "keepalive@openssh.com", 1); 158 } 159 if ((r = sshpkt_send(ssh)) != 0) 160 fatal_fr(r, "send"); 161 } 162 163 /* 164 * Sleep in ppoll() until we can do something. 165 * Optionally, a maximum time can be specified for the duration of 166 * the wait (0 = infinite). 167 */ 168 static void 169 wait_until_can_do_something(struct ssh *ssh, 170 int connection_in, int connection_out, struct pollfd **pfdp, 171 u_int *npfd_allocp, u_int *npfd_activep, u_int64_t max_time_ms, 172 sigset_t *sigsetp, int *conn_in_readyp, int *conn_out_readyp) 173 { 174 struct timespec ts, *tsp; 175 int ret; 176 time_t minwait_secs = 0; 177 int client_alive_scheduled = 0; 178 u_int p; 179 /* time we last heard from the client OR sent a keepalive */ 180 static time_t last_client_time; 181 182 *conn_in_readyp = *conn_out_readyp = 0; 183 184 /* Prepare channel poll. First two pollfd entries are reserved */ 185 channel_prepare_poll(ssh, pfdp, npfd_allocp, npfd_activep, 186 2, &minwait_secs); 187 if (*npfd_activep < 2) 188 fatal_f("bad npfd %u", *npfd_activep); /* shouldn't happen */ 189 190 /* XXX need proper deadline system for rekey/client alive */ 191 if (minwait_secs != 0) 192 max_time_ms = MINIMUM(max_time_ms, (u_int)minwait_secs * 1000); 193 194 /* 195 * if using client_alive, set the max timeout accordingly, 196 * and indicate that this particular timeout was for client 197 * alive by setting the client_alive_scheduled flag. 198 * 199 * this could be randomized somewhat to make traffic 200 * analysis more difficult, but we're not doing it yet. 201 */ 202 if (options.client_alive_interval) { 203 uint64_t keepalive_ms = 204 (uint64_t)options.client_alive_interval * 1000; 205 206 if (max_time_ms == 0 || max_time_ms > keepalive_ms) { 207 max_time_ms = keepalive_ms; 208 client_alive_scheduled = 1; 209 } 210 if (last_client_time == 0) 211 last_client_time = monotime(); 212 } 213 214 #if 0 215 /* wrong: bad condition XXX */ 216 if (channel_not_very_much_buffered_data()) 217 #endif 218 /* Monitor client connection on reserved pollfd entries */ 219 (*pfdp)[0].fd = connection_in; 220 (*pfdp)[0].events = POLLIN; 221 (*pfdp)[1].fd = connection_out; 222 (*pfdp)[1].events = ssh_packet_have_data_to_write(ssh) ? POLLOUT : 0; 223 224 /* 225 * If child has terminated and there is enough buffer space to read 226 * from it, then read as much as is available and exit. 227 */ 228 if (child_terminated && ssh_packet_not_very_much_data_to_write(ssh)) 229 if (max_time_ms == 0 || client_alive_scheduled) 230 max_time_ms = 100; 231 232 if (max_time_ms == 0) 233 tsp = NULL; 234 else { 235 ts.tv_sec = max_time_ms / 1000; 236 ts.tv_nsec = 1000000 * (max_time_ms % 1000); 237 tsp = &ts; 238 } 239 240 /* Wait for something to happen, or the timeout to expire. */ 241 ret = ppoll(*pfdp, *npfd_activep, tsp, sigsetp); 242 243 if (ret == -1) { 244 for (p = 0; p < *npfd_activep; p++) 245 (*pfdp)[p].revents = 0; 246 if (errno != EINTR) 247 fatal_f("ppoll: %.100s", strerror(errno)); 248 return; 249 } 250 251 *conn_in_readyp = (*pfdp)[0].revents != 0; 252 *conn_out_readyp = (*pfdp)[1].revents != 0; 253 254 if (client_alive_scheduled) { 255 time_t now = monotime(); 256 257 /* 258 * If the ppoll timed out, or returned for some other reason 259 * but we haven't heard from the client in time, send keepalive. 260 */ 261 if (ret == 0 || (last_client_time != 0 && last_client_time + 262 options.client_alive_interval <= now)) { 263 client_alive_check(ssh); 264 last_client_time = now; 265 } else if (*conn_in_readyp) 266 last_client_time = now; 267 } 268 } 269 270 /* 271 * Processes input from the client and the program. Input data is stored 272 * in buffers and processed later. 273 */ 274 static int 275 process_input(struct ssh *ssh, int connection_in) 276 { 277 int r; 278 279 if ((r = ssh_packet_process_read(ssh, connection_in)) == 0) 280 return 0; /* success */ 281 if (r == SSH_ERR_SYSTEM_ERROR) { 282 if (errno == EAGAIN || errno == EINTR || errno == EWOULDBLOCK) 283 return 0; 284 if (errno == EPIPE) { 285 verbose("Connection closed by %.100s port %d", 286 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 287 return -1; 288 } 289 verbose("Read error from remote host %s port %d: %s", 290 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), 291 strerror(errno)); 292 cleanup_exit(255); 293 } 294 return -1; 295 } 296 297 /* 298 * Sends data from internal buffers to client program stdin. 299 */ 300 static void 301 process_output(struct ssh *ssh, int connection_out) 302 { 303 int r; 304 305 /* Send any buffered packet data to the client. */ 306 if ((r = ssh_packet_write_poll(ssh)) != 0) { 307 sshpkt_fatal(ssh, r, "%s: ssh_packet_write_poll", 308 __func__); 309 } 310 } 311 312 static void 313 process_buffered_input_packets(struct ssh *ssh) 314 { 315 ssh_dispatch_run_fatal(ssh, DISPATCH_NONBLOCK, NULL); 316 } 317 318 static void 319 collect_children(struct ssh *ssh) 320 { 321 pid_t pid; 322 int status; 323 324 if (child_terminated) { 325 debug("Received SIGCHLD."); 326 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 327 (pid == -1 && errno == EINTR)) 328 if (pid > 0) 329 session_close_by_pid(ssh, pid, status); 330 child_terminated = 0; 331 } 332 } 333 334 void 335 server_loop2(struct ssh *ssh, Authctxt *authctxt) 336 { 337 struct pollfd *pfd = NULL; 338 u_int npfd_alloc = 0, npfd_active = 0; 339 int r, conn_in_ready, conn_out_ready; 340 u_int connection_in, connection_out; 341 u_int64_t rekey_timeout_ms = 0; 342 sigset_t bsigset, osigset; 343 344 debug("Entering interactive session for SSH2."); 345 346 if (sigemptyset(&bsigset) == -1 || sigaddset(&bsigset, SIGCHLD) == -1) 347 error_f("bsigset setup: %s", strerror(errno)); 348 ssh_signal(SIGCHLD, sigchld_handler); 349 child_terminated = 0; 350 connection_in = ssh_packet_get_connection_in(ssh); 351 connection_out = ssh_packet_get_connection_out(ssh); 352 353 if (!use_privsep) { 354 ssh_signal(SIGTERM, sigterm_handler); 355 ssh_signal(SIGINT, sigterm_handler); 356 ssh_signal(SIGQUIT, sigterm_handler); 357 } 358 359 server_init_dispatch(ssh); 360 361 for (;;) { 362 process_buffered_input_packets(ssh); 363 364 if (!ssh_packet_is_rekeying(ssh) && 365 ssh_packet_not_very_much_data_to_write(ssh)) 366 channel_output_poll(ssh); 367 if (options.rekey_interval > 0 && 368 !ssh_packet_is_rekeying(ssh)) { 369 rekey_timeout_ms = ssh_packet_get_rekey_timeout(ssh) * 370 1000; 371 } else { 372 rekey_timeout_ms = 0; 373 } 374 375 /* 376 * Block SIGCHLD while we check for dead children, then pass 377 * the old signal mask through to ppoll() so that it'll wake 378 * up immediately if a child exits after we've called waitpid(). 379 */ 380 if (sigprocmask(SIG_BLOCK, &bsigset, &osigset) == -1) 381 error_f("bsigset sigprocmask: %s", strerror(errno)); 382 collect_children(ssh); 383 wait_until_can_do_something(ssh, connection_in, connection_out, 384 &pfd, &npfd_alloc, &npfd_active, rekey_timeout_ms, &osigset, 385 &conn_in_ready, &conn_out_ready); 386 if (sigprocmask(SIG_UNBLOCK, &bsigset, &osigset) == -1) 387 error_f("osigset sigprocmask: %s", strerror(errno)); 388 389 if (received_sigterm) { 390 logit("Exiting on signal %d", (int)received_sigterm); 391 /* Clean up sessions, utmp, etc. */ 392 cleanup_exit(255); 393 } 394 395 channel_after_poll(ssh, pfd, npfd_active); 396 if (conn_in_ready && 397 process_input(ssh, connection_in) < 0) 398 break; 399 /* A timeout may have triggered rekeying */ 400 if ((r = ssh_packet_check_rekey(ssh)) != 0) 401 fatal_fr(r, "cannot start rekeying"); 402 if (conn_out_ready) 403 process_output(ssh, connection_out); 404 } 405 collect_children(ssh); 406 free(pfd); 407 408 /* free all channels, no more reads and writes */ 409 channel_free_all(ssh); 410 411 /* free remaining sessions, e.g. remove wtmp entries */ 412 session_destroy_all(ssh, NULL); 413 } 414 415 static int 416 server_input_keep_alive(int type, u_int32_t seq, struct ssh *ssh) 417 { 418 debug("Got %d/%u for keepalive", type, seq); 419 /* 420 * reset timeout, since we got a sane answer from the client. 421 * even if this was generated by something other than 422 * the bogus CHANNEL_REQUEST we send for keepalives. 423 */ 424 ssh_packet_set_alive_timeouts(ssh, 0); 425 return 0; 426 } 427 428 static Channel * 429 server_request_direct_tcpip(struct ssh *ssh, int *reason, const char **errmsg) 430 { 431 Channel *c = NULL; 432 char *target = NULL, *originator = NULL; 433 u_int target_port = 0, originator_port = 0; 434 int r; 435 436 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 437 (r = sshpkt_get_u32(ssh, &target_port)) != 0 || 438 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 439 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 440 (r = sshpkt_get_end(ssh)) != 0) 441 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 442 if (target_port > 0xFFFF) { 443 error_f("invalid target port"); 444 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 445 goto out; 446 } 447 if (originator_port > 0xFFFF) { 448 error_f("invalid originator port"); 449 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 450 goto out; 451 } 452 453 debug_f("originator %s port %u, target %s port %u", 454 originator, originator_port, target, target_port); 455 456 /* XXX fine grained permissions */ 457 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 && 458 auth_opts->permit_port_forwarding_flag && 459 !options.disable_forwarding) { 460 c = channel_connect_to_port(ssh, target, target_port, 461 "direct-tcpip", "direct-tcpip", reason, errmsg); 462 } else { 463 logit("refused local port forward: " 464 "originator %s port %d, target %s port %d", 465 originator, originator_port, target, target_port); 466 if (reason != NULL) 467 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 468 } 469 470 out: 471 free(originator); 472 free(target); 473 return c; 474 } 475 476 static Channel * 477 server_request_direct_streamlocal(struct ssh *ssh) 478 { 479 Channel *c = NULL; 480 char *target = NULL, *originator = NULL; 481 u_int originator_port = 0; 482 struct passwd *pw = the_authctxt->pw; 483 int r; 484 485 if (pw == NULL || !the_authctxt->valid) 486 fatal_f("no/invalid user"); 487 488 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 489 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 490 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 491 (r = sshpkt_get_end(ssh)) != 0) 492 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 493 if (originator_port > 0xFFFF) { 494 error_f("invalid originator port"); 495 goto out; 496 } 497 498 debug_f("originator %s port %d, target %s", 499 originator, originator_port, target); 500 501 /* XXX fine grained permissions */ 502 if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 && 503 auth_opts->permit_port_forwarding_flag && 504 !options.disable_forwarding && (pw->pw_uid == 0 || use_privsep)) { 505 c = channel_connect_to_path(ssh, target, 506 "direct-streamlocal@openssh.com", "direct-streamlocal"); 507 } else { 508 logit("refused streamlocal port forward: " 509 "originator %s port %d, target %s", 510 originator, originator_port, target); 511 } 512 513 out: 514 free(originator); 515 free(target); 516 return c; 517 } 518 519 static Channel * 520 server_request_tun(struct ssh *ssh) 521 { 522 Channel *c = NULL; 523 u_int mode, tun; 524 int r, sock; 525 char *tmp, *ifname = NULL; 526 527 if ((r = sshpkt_get_u32(ssh, &mode)) != 0) 528 sshpkt_fatal(ssh, r, "%s: parse mode", __func__); 529 switch (mode) { 530 case SSH_TUNMODE_POINTOPOINT: 531 case SSH_TUNMODE_ETHERNET: 532 break; 533 default: 534 ssh_packet_send_debug(ssh, "Unsupported tunnel device mode."); 535 return NULL; 536 } 537 if ((options.permit_tun & mode) == 0) { 538 ssh_packet_send_debug(ssh, "Server has rejected tunnel device " 539 "forwarding"); 540 return NULL; 541 } 542 543 if ((r = sshpkt_get_u32(ssh, &tun)) != 0) 544 sshpkt_fatal(ssh, r, "%s: parse device", __func__); 545 if (tun > INT_MAX) { 546 debug_f("invalid tun"); 547 goto done; 548 } 549 if (auth_opts->force_tun_device != -1) { 550 if (tun != SSH_TUNID_ANY && 551 auth_opts->force_tun_device != (int)tun) 552 goto done; 553 tun = auth_opts->force_tun_device; 554 } 555 sock = tun_open(tun, mode, &ifname); 556 if (sock < 0) 557 goto done; 558 debug("Tunnel forwarding using interface %s", ifname); 559 560 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1, 561 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 562 c->datagram = 1; 563 #if defined(SSH_TUN_FILTER) 564 if (mode == SSH_TUNMODE_POINTOPOINT) 565 channel_register_filter(ssh, c->self, sys_tun_infilter, 566 sys_tun_outfilter, NULL, NULL); 567 #endif 568 569 /* 570 * Update the list of names exposed to the session 571 * XXX remove these if the tunnels are closed (won't matter 572 * much if they are already in the environment though) 573 */ 574 tmp = tun_fwd_ifnames; 575 xasprintf(&tun_fwd_ifnames, "%s%s%s", 576 tun_fwd_ifnames == NULL ? "" : tun_fwd_ifnames, 577 tun_fwd_ifnames == NULL ? "" : ",", 578 ifname); 579 free(tmp); 580 free(ifname); 581 582 done: 583 if (c == NULL) 584 ssh_packet_send_debug(ssh, "Failed to open the tunnel device."); 585 return c; 586 } 587 588 static Channel * 589 server_request_session(struct ssh *ssh) 590 { 591 Channel *c; 592 int r; 593 594 debug("input_session_request"); 595 if ((r = sshpkt_get_end(ssh)) != 0) 596 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 597 598 if (no_more_sessions) { 599 ssh_packet_disconnect(ssh, "Possible attack: attempt to open a " 600 "session after additional sessions disabled"); 601 } 602 603 /* 604 * A server session has no fd to read or write until a 605 * CHANNEL_REQUEST for a shell is made, so we set the type to 606 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all 607 * CHANNEL_REQUEST messages is registered. 608 */ 609 c = channel_new(ssh, "session", SSH_CHANNEL_LARVAL, 610 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, 611 0, "server-session", 1); 612 if (session_open(the_authctxt, c->self) != 1) { 613 debug("session open failed, free channel %d", c->self); 614 channel_free(ssh, c); 615 return NULL; 616 } 617 channel_register_cleanup(ssh, c->self, session_close_by_channel, 0); 618 return c; 619 } 620 621 static int 622 server_input_channel_open(int type, u_int32_t seq, struct ssh *ssh) 623 { 624 Channel *c = NULL; 625 char *ctype = NULL; 626 const char *errmsg = NULL; 627 int r, reason = SSH2_OPEN_CONNECT_FAILED; 628 u_int rchan = 0, rmaxpack = 0, rwindow = 0; 629 630 if ((r = sshpkt_get_cstring(ssh, &ctype, NULL)) != 0 || 631 (r = sshpkt_get_u32(ssh, &rchan)) != 0 || 632 (r = sshpkt_get_u32(ssh, &rwindow)) != 0 || 633 (r = sshpkt_get_u32(ssh, &rmaxpack)) != 0) 634 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 635 debug_f("ctype %s rchan %u win %u max %u", 636 ctype, rchan, rwindow, rmaxpack); 637 638 if (strcmp(ctype, "session") == 0) { 639 c = server_request_session(ssh); 640 } else if (strcmp(ctype, "direct-tcpip") == 0) { 641 c = server_request_direct_tcpip(ssh, &reason, &errmsg); 642 } else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) { 643 c = server_request_direct_streamlocal(ssh); 644 } else if (strcmp(ctype, "tun@openssh.com") == 0) { 645 c = server_request_tun(ssh); 646 } 647 if (c != NULL) { 648 debug_f("confirm %s", ctype); 649 c->remote_id = rchan; 650 c->have_remote_id = 1; 651 c->remote_window = rwindow; 652 c->remote_maxpacket = rmaxpack; 653 if (c->type != SSH_CHANNEL_CONNECTING) { 654 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION)) != 0 || 655 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 656 (r = sshpkt_put_u32(ssh, c->self)) != 0 || 657 (r = sshpkt_put_u32(ssh, c->local_window)) != 0 || 658 (r = sshpkt_put_u32(ssh, c->local_maxpacket)) != 0 || 659 (r = sshpkt_send(ssh)) != 0) { 660 sshpkt_fatal(ssh, r, 661 "%s: send open confirm", __func__); 662 } 663 } 664 } else { 665 debug_f("failure %s", ctype); 666 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE)) != 0 || 667 (r = sshpkt_put_u32(ssh, rchan)) != 0 || 668 (r = sshpkt_put_u32(ssh, reason)) != 0 || 669 (r = sshpkt_put_cstring(ssh, errmsg ? errmsg : "open failed")) != 0 || 670 (r = sshpkt_put_cstring(ssh, "")) != 0 || 671 (r = sshpkt_send(ssh)) != 0) { 672 sshpkt_fatal(ssh, r, 673 "%s: send open failure", __func__); 674 } 675 } 676 free(ctype); 677 return 0; 678 } 679 680 static int 681 server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp) 682 { 683 struct sshbuf *resp = NULL; 684 struct sshbuf *sigbuf = NULL; 685 struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL; 686 int r, ndx, success = 0; 687 const u_char *blob; 688 const char *sigalg, *kex_rsa_sigalg = NULL; 689 u_char *sig = 0; 690 size_t blen, slen; 691 692 if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL) 693 fatal_f("sshbuf_new"); 694 if (sshkey_type_plain(sshkey_type_from_name( 695 ssh->kex->hostkey_alg)) == KEY_RSA) 696 kex_rsa_sigalg = ssh->kex->hostkey_alg; 697 while (ssh_packet_remaining(ssh) > 0) { 698 sshkey_free(key); 699 key = NULL; 700 if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 || 701 (r = sshkey_from_blob(blob, blen, &key)) != 0) { 702 error_fr(r, "parse key"); 703 goto out; 704 } 705 /* 706 * Better check that this is actually one of our hostkeys 707 * before attempting to sign anything with it. 708 */ 709 if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) { 710 error_f("unknown host %s key", sshkey_type(key)); 711 goto out; 712 } 713 /* 714 * XXX refactor: make kex->sign just use an index rather 715 * than passing in public and private keys 716 */ 717 if ((key_prv = get_hostkey_by_index(ndx)) == NULL && 718 (key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) { 719 error_f("can't retrieve hostkey %d", ndx); 720 goto out; 721 } 722 sshbuf_reset(sigbuf); 723 free(sig); 724 sig = NULL; 725 /* 726 * For RSA keys, prefer to use the signature type negotiated 727 * during KEX to the default (SHA1). 728 */ 729 sigalg = NULL; 730 if (sshkey_type_plain(key->type) == KEY_RSA) { 731 if (kex_rsa_sigalg != NULL) 732 sigalg = kex_rsa_sigalg; 733 else if (ssh->kex->flags & KEX_RSA_SHA2_512_SUPPORTED) 734 sigalg = "rsa-sha2-512"; 735 else if (ssh->kex->flags & KEX_RSA_SHA2_256_SUPPORTED) 736 sigalg = "rsa-sha2-256"; 737 } 738 debug3_f("sign %s key (index %d) using sigalg %s", 739 sshkey_type(key), ndx, sigalg == NULL ? "default" : sigalg); 740 if ((r = sshbuf_put_cstring(sigbuf, 741 "hostkeys-prove-00@openssh.com")) != 0 || 742 (r = sshbuf_put_stringb(sigbuf, 743 ssh->kex->session_id)) != 0 || 744 (r = sshkey_puts(key, sigbuf)) != 0 || 745 (r = ssh->kex->sign(ssh, key_prv, key_pub, &sig, &slen, 746 sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), sigalg)) != 0 || 747 (r = sshbuf_put_string(resp, sig, slen)) != 0) { 748 error_fr(r, "assemble signature"); 749 goto out; 750 } 751 } 752 /* Success */ 753 *respp = resp; 754 resp = NULL; /* don't free it */ 755 success = 1; 756 out: 757 free(sig); 758 sshbuf_free(resp); 759 sshbuf_free(sigbuf); 760 sshkey_free(key); 761 return success; 762 } 763 764 static int 765 server_input_global_request(int type, u_int32_t seq, struct ssh *ssh) 766 { 767 char *rtype = NULL; 768 u_char want_reply = 0; 769 int r, success = 0, allocated_listen_port = 0; 770 u_int port = 0; 771 struct sshbuf *resp = NULL; 772 struct passwd *pw = the_authctxt->pw; 773 struct Forward fwd; 774 775 memset(&fwd, 0, sizeof(fwd)); 776 if (pw == NULL || !the_authctxt->valid) 777 fatal_f("no/invalid user"); 778 779 if ((r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 780 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 781 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 782 debug_f("rtype %s want_reply %d", rtype, want_reply); 783 784 /* -R style forwarding */ 785 if (strcmp(rtype, "tcpip-forward") == 0) { 786 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 787 (r = sshpkt_get_u32(ssh, &port)) != 0) 788 sshpkt_fatal(ssh, r, "%s: parse tcpip-forward", __func__); 789 debug_f("tcpip-forward listen %s port %u", 790 fwd.listen_host, port); 791 if (port <= INT_MAX) 792 fwd.listen_port = (int)port; 793 /* check permissions */ 794 if (port > INT_MAX || 795 (options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 || 796 !auth_opts->permit_port_forwarding_flag || 797 options.disable_forwarding || 798 (!want_reply && fwd.listen_port == 0) || 799 (fwd.listen_port != 0 && 800 !bind_permitted(fwd.listen_port, pw->pw_uid))) { 801 success = 0; 802 ssh_packet_send_debug(ssh, "Server has disabled port forwarding."); 803 } else { 804 /* Start listening on the port */ 805 success = channel_setup_remote_fwd_listener(ssh, &fwd, 806 &allocated_listen_port, &options.fwd_opts); 807 } 808 if ((resp = sshbuf_new()) == NULL) 809 fatal_f("sshbuf_new"); 810 if (allocated_listen_port != 0 && 811 (r = sshbuf_put_u32(resp, allocated_listen_port)) != 0) 812 fatal_fr(r, "sshbuf_put_u32"); 813 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) { 814 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 815 (r = sshpkt_get_u32(ssh, &port)) != 0) 816 sshpkt_fatal(ssh, r, "%s: parse cancel-tcpip-forward", __func__); 817 818 debug_f("cancel-tcpip-forward addr %s port %d", 819 fwd.listen_host, port); 820 if (port <= INT_MAX) { 821 fwd.listen_port = (int)port; 822 success = channel_cancel_rport_listener(ssh, &fwd); 823 } 824 } else if (strcmp(rtype, "streamlocal-forward@openssh.com") == 0) { 825 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 826 sshpkt_fatal(ssh, r, "%s: parse streamlocal-forward@openssh.com", __func__); 827 debug_f("streamlocal-forward listen path %s", 828 fwd.listen_path); 829 830 /* check permissions */ 831 if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0 832 || !auth_opts->permit_port_forwarding_flag || 833 options.disable_forwarding || 834 (pw->pw_uid != 0 && !use_privsep)) { 835 success = 0; 836 ssh_packet_send_debug(ssh, "Server has disabled " 837 "streamlocal forwarding."); 838 } else { 839 /* Start listening on the socket */ 840 success = channel_setup_remote_fwd_listener(ssh, 841 &fwd, NULL, &options.fwd_opts); 842 } 843 } else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) { 844 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 845 sshpkt_fatal(ssh, r, "%s: parse cancel-streamlocal-forward@openssh.com", __func__); 846 debug_f("cancel-streamlocal-forward path %s", 847 fwd.listen_path); 848 849 success = channel_cancel_rport_listener(ssh, &fwd); 850 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) { 851 no_more_sessions = 1; 852 success = 1; 853 } else if (strcmp(rtype, "hostkeys-prove-00@openssh.com") == 0) { 854 success = server_input_hostkeys_prove(ssh, &resp); 855 } 856 /* XXX sshpkt_get_end() */ 857 if (want_reply) { 858 if ((r = sshpkt_start(ssh, success ? 859 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE)) != 0 || 860 (success && resp != NULL && (r = sshpkt_putb(ssh, resp)) != 0) || 861 (r = sshpkt_send(ssh)) != 0 || 862 (r = ssh_packet_write_wait(ssh)) != 0) 863 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 864 } 865 free(fwd.listen_host); 866 free(fwd.listen_path); 867 free(rtype); 868 sshbuf_free(resp); 869 return 0; 870 } 871 872 static int 873 server_input_channel_req(int type, u_int32_t seq, struct ssh *ssh) 874 { 875 Channel *c; 876 int r, success = 0; 877 char *rtype = NULL; 878 u_char want_reply = 0; 879 u_int id = 0; 880 881 if ((r = sshpkt_get_u32(ssh, &id)) != 0 || 882 (r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 883 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 884 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 885 886 debug("server_input_channel_req: channel %u request %s reply %d", 887 id, rtype, want_reply); 888 889 if (id >= INT_MAX || (c = channel_lookup(ssh, (int)id)) == NULL) { 890 ssh_packet_disconnect(ssh, "%s: unknown channel %d", 891 __func__, id); 892 } 893 if (!strcmp(rtype, "eow@openssh.com")) { 894 if ((r = sshpkt_get_end(ssh)) != 0) 895 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 896 chan_rcvd_eow(ssh, c); 897 } else if ((c->type == SSH_CHANNEL_LARVAL || 898 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0) 899 success = session_input_channel_req(ssh, c, rtype); 900 if (want_reply && !(c->flags & CHAN_CLOSE_SENT)) { 901 if (!c->have_remote_id) 902 fatal_f("channel %d: no remote_id", c->self); 903 if ((r = sshpkt_start(ssh, success ? 904 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE)) != 0 || 905 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 906 (r = sshpkt_send(ssh)) != 0) 907 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 908 } 909 free(rtype); 910 return 0; 911 } 912 913 static void 914 server_init_dispatch(struct ssh *ssh) 915 { 916 debug("server_init_dispatch"); 917 ssh_dispatch_init(ssh, &dispatch_protocol_error); 918 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); 919 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_DATA, &channel_input_data); 920 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); 921 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); 922 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); 923 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 924 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 925 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); 926 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); 927 ssh_dispatch_set(ssh, SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); 928 /* client_alive */ 929 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive); 930 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); 931 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); 932 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); 933 /* rekeying */ 934 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit); 935 } 936