1 /* $OpenBSD: serverloop.c,v 1.236 2023/03/08 04:43:12 guenther 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 "ssh2.h" 73 #include "sshkey.h" 74 #include "cipher.h" 75 #include "kex.h" 76 #include "hostfile.h" 77 #include "auth.h" 78 #include "session.h" 79 #include "dispatch.h" 80 #include "auth-options.h" 81 #include "serverloop.h" 82 #include "ssherr.h" 83 84 extern ServerOptions options; 85 86 /* XXX */ 87 extern Authctxt *the_authctxt; 88 extern struct sshauthopt *auth_opts; 89 extern int use_privsep; 90 91 static int no_more_sessions = 0; /* Disallow further sessions. */ 92 93 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */ 94 95 /* Cleanup on signals (!use_privsep case only) */ 96 static volatile sig_atomic_t received_sigterm = 0; 97 98 /* prototypes */ 99 static void server_init_dispatch(struct ssh *); 100 101 /* requested tunnel forwarding interface(s), shared with session.c */ 102 char *tun_fwd_ifnames = NULL; 103 104 /* returns 1 if bind to specified port by specified user is permitted */ 105 static int 106 bind_permitted(int port, uid_t uid) 107 { 108 if (use_privsep) 109 return 1; /* allow system to decide */ 110 if (port < IPPORT_RESERVED && uid != 0) 111 return 0; 112 return 1; 113 } 114 115 static void 116 sigchld_handler(int sig) 117 { 118 child_terminated = 1; 119 } 120 121 static void 122 sigterm_handler(int sig) 123 { 124 received_sigterm = sig; 125 } 126 127 static void 128 client_alive_check(struct ssh *ssh) 129 { 130 char remote_id[512]; 131 int r, channel_id; 132 133 /* timeout, check to see how many we have had */ 134 if (options.client_alive_count_max > 0 && 135 ssh_packet_inc_alive_timeouts(ssh) > 136 options.client_alive_count_max) { 137 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id)); 138 logit("Timeout, client not responding from %s", remote_id); 139 cleanup_exit(255); 140 } 141 142 /* 143 * send a bogus global/channel request with "wantreply", 144 * we should get back a failure 145 */ 146 if ((channel_id = channel_find_open(ssh)) == -1) { 147 if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 || 148 (r = sshpkt_put_cstring(ssh, "keepalive@openssh.com")) 149 != 0 || 150 (r = sshpkt_put_u8(ssh, 1)) != 0) /* boolean: want reply */ 151 fatal_fr(r, "compose"); 152 } else { 153 channel_request_start(ssh, channel_id, 154 "keepalive@openssh.com", 1); 155 } 156 if ((r = sshpkt_send(ssh)) != 0) 157 fatal_fr(r, "send"); 158 } 159 160 /* 161 * Sleep in ppoll() until we can do something. 162 * Optionally, a maximum time can be specified for the duration of 163 * the wait (0 = infinite). 164 */ 165 static void 166 wait_until_can_do_something(struct ssh *ssh, 167 int connection_in, int connection_out, struct pollfd **pfdp, 168 u_int *npfd_allocp, u_int *npfd_activep, sigset_t *sigsetp, 169 int *conn_in_readyp, int *conn_out_readyp) 170 { 171 struct timespec timeout; 172 char remote_id[512]; 173 int ret; 174 int client_alive_scheduled = 0; 175 u_int p; 176 time_t now; 177 static time_t last_client_time, unused_connection_expiry; 178 179 *conn_in_readyp = *conn_out_readyp = 0; 180 181 /* Prepare channel poll. First two pollfd entries are reserved */ 182 ptimeout_init(&timeout); 183 channel_prepare_poll(ssh, pfdp, npfd_allocp, npfd_activep, 2, &timeout); 184 now = monotime(); 185 if (*npfd_activep < 2) 186 fatal_f("bad npfd %u", *npfd_activep); /* shouldn't happen */ 187 if (options.rekey_interval > 0 && !ssh_packet_is_rekeying(ssh)) { 188 ptimeout_deadline_sec(&timeout, 189 ssh_packet_get_rekey_timeout(ssh)); 190 } 191 192 /* 193 * If no channels are open and UnusedConnectionTimeout is set, then 194 * start the clock to terminate the connection. 195 */ 196 if (options.unused_connection_timeout != 0) { 197 if (channel_still_open(ssh) || unused_connection_expiry == 0) { 198 unused_connection_expiry = now + 199 options.unused_connection_timeout; 200 } 201 ptimeout_deadline_monotime(&timeout, unused_connection_expiry); 202 } 203 204 /* 205 * if using client_alive, set the max timeout accordingly, 206 * and indicate that this particular timeout was for client 207 * alive by setting the client_alive_scheduled flag. 208 * 209 * this could be randomized somewhat to make traffic 210 * analysis more difficult, but we're not doing it yet. 211 */ 212 if (options.client_alive_interval) { 213 /* Time we last heard from the client OR sent a keepalive */ 214 if (last_client_time == 0) 215 last_client_time = now; 216 ptimeout_deadline_sec(&timeout, options.client_alive_interval); 217 /* XXX ? deadline_monotime(last_client_time + alive_interval) */ 218 client_alive_scheduled = 1; 219 } 220 221 #if 0 222 /* wrong: bad condition XXX */ 223 if (channel_not_very_much_buffered_data()) 224 #endif 225 /* Monitor client connection on reserved pollfd entries */ 226 (*pfdp)[0].fd = connection_in; 227 (*pfdp)[0].events = POLLIN; 228 (*pfdp)[1].fd = connection_out; 229 (*pfdp)[1].events = ssh_packet_have_data_to_write(ssh) ? POLLOUT : 0; 230 231 /* 232 * If child has terminated and there is enough buffer space to read 233 * from it, then read as much as is available and exit. 234 */ 235 if (child_terminated && ssh_packet_not_very_much_data_to_write(ssh)) 236 ptimeout_deadline_ms(&timeout, 100); 237 238 /* Wait for something to happen, or the timeout to expire. */ 239 ret = ppoll(*pfdp, *npfd_activep, ptimeout_get_tsp(&timeout), sigsetp); 240 241 if (ret == -1) { 242 for (p = 0; p < *npfd_activep; p++) 243 (*pfdp)[p].revents = 0; 244 if (errno != EINTR) 245 fatal_f("ppoll: %.100s", strerror(errno)); 246 return; 247 } 248 249 *conn_in_readyp = (*pfdp)[0].revents != 0; 250 *conn_out_readyp = (*pfdp)[1].revents != 0; 251 252 now = monotime(); /* need to reset after ppoll() */ 253 /* ClientAliveInterval probing */ 254 if (client_alive_scheduled) { 255 if (ret == 0 && 256 now > last_client_time + options.client_alive_interval) { 257 /* ppoll timed out and we're due to probe */ 258 client_alive_check(ssh); 259 last_client_time = now; 260 } else if (ret != 0 && *conn_in_readyp) { 261 /* Data from peer; reset probe timer. */ 262 last_client_time = now; 263 } 264 } 265 266 /* UnusedConnectionTimeout handling */ 267 if (unused_connection_expiry != 0 && 268 now > unused_connection_expiry && !channel_still_open(ssh)) { 269 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id)); 270 logit("terminating inactive connection from %s", remote_id); 271 cleanup_exit(255); 272 } 273 } 274 275 /* 276 * Processes input from the client and the program. Input data is stored 277 * in buffers and processed later. 278 */ 279 static int 280 process_input(struct ssh *ssh, int connection_in) 281 { 282 int r; 283 284 if ((r = ssh_packet_process_read(ssh, connection_in)) == 0) 285 return 0; /* success */ 286 if (r == SSH_ERR_SYSTEM_ERROR) { 287 if (errno == EAGAIN || errno == EINTR || errno == EWOULDBLOCK) 288 return 0; 289 if (errno == EPIPE) { 290 verbose("Connection closed by %.100s port %d", 291 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 292 return -1; 293 } 294 verbose("Read error from remote host %s port %d: %s", 295 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), 296 strerror(errno)); 297 cleanup_exit(255); 298 } 299 return -1; 300 } 301 302 /* 303 * Sends data from internal buffers to client program stdin. 304 */ 305 static void 306 process_output(struct ssh *ssh, int connection_out) 307 { 308 int r; 309 310 /* Send any buffered packet data to the client. */ 311 if ((r = ssh_packet_write_poll(ssh)) != 0) { 312 sshpkt_fatal(ssh, r, "%s: ssh_packet_write_poll", 313 __func__); 314 } 315 } 316 317 static void 318 process_buffered_input_packets(struct ssh *ssh) 319 { 320 ssh_dispatch_run_fatal(ssh, DISPATCH_NONBLOCK, NULL); 321 } 322 323 static void 324 collect_children(struct ssh *ssh) 325 { 326 pid_t pid; 327 int status; 328 329 if (child_terminated) { 330 debug("Received SIGCHLD."); 331 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 332 (pid == -1 && errno == EINTR)) 333 if (pid > 0) 334 session_close_by_pid(ssh, pid, status); 335 child_terminated = 0; 336 } 337 } 338 339 void 340 server_loop2(struct ssh *ssh, Authctxt *authctxt) 341 { 342 struct pollfd *pfd = NULL; 343 u_int npfd_alloc = 0, npfd_active = 0; 344 int r, conn_in_ready, conn_out_ready; 345 u_int connection_in, connection_out; 346 sigset_t bsigset, osigset; 347 348 debug("Entering interactive session for SSH2."); 349 350 if (sigemptyset(&bsigset) == -1 || sigaddset(&bsigset, SIGCHLD) == -1) 351 error_f("bsigset setup: %s", strerror(errno)); 352 ssh_signal(SIGCHLD, sigchld_handler); 353 child_terminated = 0; 354 connection_in = ssh_packet_get_connection_in(ssh); 355 connection_out = ssh_packet_get_connection_out(ssh); 356 357 if (!use_privsep) { 358 ssh_signal(SIGTERM, sigterm_handler); 359 ssh_signal(SIGINT, sigterm_handler); 360 ssh_signal(SIGQUIT, sigterm_handler); 361 } 362 363 server_init_dispatch(ssh); 364 365 for (;;) { 366 process_buffered_input_packets(ssh); 367 368 if (!ssh_packet_is_rekeying(ssh) && 369 ssh_packet_not_very_much_data_to_write(ssh)) 370 channel_output_poll(ssh); 371 372 /* 373 * Block SIGCHLD while we check for dead children, then pass 374 * the old signal mask through to ppoll() so that it'll wake 375 * up immediately if a child exits after we've called waitpid(). 376 */ 377 if (sigprocmask(SIG_BLOCK, &bsigset, &osigset) == -1) 378 error_f("bsigset sigprocmask: %s", strerror(errno)); 379 collect_children(ssh); 380 wait_until_can_do_something(ssh, connection_in, connection_out, 381 &pfd, &npfd_alloc, &npfd_active, &osigset, 382 &conn_in_ready, &conn_out_ready); 383 if (sigprocmask(SIG_UNBLOCK, &bsigset, &osigset) == -1) 384 error_f("osigset sigprocmask: %s", strerror(errno)); 385 386 if (received_sigterm) { 387 logit("Exiting on signal %d", (int)received_sigterm); 388 /* Clean up sessions, utmp, etc. */ 389 cleanup_exit(255); 390 } 391 392 channel_after_poll(ssh, pfd, npfd_active); 393 if (conn_in_ready && 394 process_input(ssh, connection_in) < 0) 395 break; 396 /* A timeout may have triggered rekeying */ 397 if ((r = ssh_packet_check_rekey(ssh)) != 0) 398 fatal_fr(r, "cannot start rekeying"); 399 if (conn_out_ready) 400 process_output(ssh, connection_out); 401 } 402 collect_children(ssh); 403 free(pfd); 404 405 /* free all channels, no more reads and writes */ 406 channel_free_all(ssh); 407 408 /* free remaining sessions, e.g. remove wtmp entries */ 409 session_destroy_all(ssh, NULL); 410 } 411 412 static int 413 server_input_keep_alive(int type, u_int32_t seq, struct ssh *ssh) 414 { 415 debug("Got %d/%u for keepalive", type, seq); 416 /* 417 * reset timeout, since we got a sane answer from the client. 418 * even if this was generated by something other than 419 * the bogus CHANNEL_REQUEST we send for keepalives. 420 */ 421 ssh_packet_set_alive_timeouts(ssh, 0); 422 return 0; 423 } 424 425 static Channel * 426 server_request_direct_tcpip(struct ssh *ssh, int *reason, const char **errmsg) 427 { 428 Channel *c = NULL; 429 char *target = NULL, *originator = NULL; 430 u_int target_port = 0, originator_port = 0; 431 int r; 432 433 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 434 (r = sshpkt_get_u32(ssh, &target_port)) != 0 || 435 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 436 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 437 (r = sshpkt_get_end(ssh)) != 0) 438 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 439 if (target_port > 0xFFFF) { 440 error_f("invalid target port"); 441 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 442 goto out; 443 } 444 if (originator_port > 0xFFFF) { 445 error_f("invalid originator port"); 446 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 447 goto out; 448 } 449 450 debug_f("originator %s port %u, target %s port %u", 451 originator, originator_port, target, target_port); 452 453 /* XXX fine grained permissions */ 454 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 && 455 auth_opts->permit_port_forwarding_flag && 456 !options.disable_forwarding) { 457 c = channel_connect_to_port(ssh, target, target_port, 458 "direct-tcpip", "direct-tcpip", reason, errmsg); 459 } else { 460 logit("refused local port forward: " 461 "originator %s port %d, target %s port %d", 462 originator, originator_port, target, target_port); 463 if (reason != NULL) 464 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 465 } 466 467 out: 468 free(originator); 469 free(target); 470 return c; 471 } 472 473 static Channel * 474 server_request_direct_streamlocal(struct ssh *ssh) 475 { 476 Channel *c = NULL; 477 char *target = NULL, *originator = NULL; 478 u_int originator_port = 0; 479 struct passwd *pw = the_authctxt->pw; 480 int r; 481 482 if (pw == NULL || !the_authctxt->valid) 483 fatal_f("no/invalid user"); 484 485 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 486 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 487 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 488 (r = sshpkt_get_end(ssh)) != 0) 489 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 490 if (originator_port > 0xFFFF) { 491 error_f("invalid originator port"); 492 goto out; 493 } 494 495 debug_f("originator %s port %d, target %s", 496 originator, originator_port, target); 497 498 /* XXX fine grained permissions */ 499 if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 && 500 auth_opts->permit_port_forwarding_flag && 501 !options.disable_forwarding && (pw->pw_uid == 0 || use_privsep)) { 502 c = channel_connect_to_path(ssh, target, 503 "direct-streamlocal@openssh.com", "direct-streamlocal"); 504 } else { 505 logit("refused streamlocal port forward: " 506 "originator %s port %d, target %s", 507 originator, originator_port, target); 508 } 509 510 out: 511 free(originator); 512 free(target); 513 return c; 514 } 515 516 static Channel * 517 server_request_tun(struct ssh *ssh) 518 { 519 Channel *c = NULL; 520 u_int mode, tun; 521 int r, sock; 522 char *tmp, *ifname = NULL; 523 524 if ((r = sshpkt_get_u32(ssh, &mode)) != 0) 525 sshpkt_fatal(ssh, r, "%s: parse mode", __func__); 526 switch (mode) { 527 case SSH_TUNMODE_POINTOPOINT: 528 case SSH_TUNMODE_ETHERNET: 529 break; 530 default: 531 ssh_packet_send_debug(ssh, "Unsupported tunnel device mode."); 532 return NULL; 533 } 534 if ((options.permit_tun & mode) == 0) { 535 ssh_packet_send_debug(ssh, "Server has rejected tunnel device " 536 "forwarding"); 537 return NULL; 538 } 539 540 if ((r = sshpkt_get_u32(ssh, &tun)) != 0) 541 sshpkt_fatal(ssh, r, "%s: parse device", __func__); 542 if (tun > INT_MAX) { 543 debug_f("invalid tun"); 544 goto done; 545 } 546 if (auth_opts->force_tun_device != -1) { 547 if (tun != SSH_TUNID_ANY && 548 auth_opts->force_tun_device != (int)tun) 549 goto done; 550 tun = auth_opts->force_tun_device; 551 } 552 sock = tun_open(tun, mode, &ifname); 553 if (sock < 0) 554 goto done; 555 debug("Tunnel forwarding using interface %s", ifname); 556 557 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1, 558 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 559 c->datagram = 1; 560 #if defined(SSH_TUN_FILTER) 561 if (mode == SSH_TUNMODE_POINTOPOINT) 562 channel_register_filter(ssh, c->self, sys_tun_infilter, 563 sys_tun_outfilter, NULL, NULL); 564 #endif 565 566 /* 567 * Update the list of names exposed to the session 568 * XXX remove these if the tunnels are closed (won't matter 569 * much if they are already in the environment though) 570 */ 571 tmp = tun_fwd_ifnames; 572 xasprintf(&tun_fwd_ifnames, "%s%s%s", 573 tun_fwd_ifnames == NULL ? "" : tun_fwd_ifnames, 574 tun_fwd_ifnames == NULL ? "" : ",", 575 ifname); 576 free(tmp); 577 free(ifname); 578 579 done: 580 if (c == NULL) 581 ssh_packet_send_debug(ssh, "Failed to open the tunnel device."); 582 return c; 583 } 584 585 static Channel * 586 server_request_session(struct ssh *ssh) 587 { 588 Channel *c; 589 int r; 590 591 debug("input_session_request"); 592 if ((r = sshpkt_get_end(ssh)) != 0) 593 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 594 595 if (no_more_sessions) { 596 ssh_packet_disconnect(ssh, "Possible attack: attempt to open a " 597 "session after additional sessions disabled"); 598 } 599 600 /* 601 * A server session has no fd to read or write until a 602 * CHANNEL_REQUEST for a shell is made, so we set the type to 603 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all 604 * CHANNEL_REQUEST messages is registered. 605 */ 606 c = channel_new(ssh, "session", SSH_CHANNEL_LARVAL, 607 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, 608 0, "server-session", 1); 609 if (session_open(the_authctxt, c->self) != 1) { 610 debug("session open failed, free channel %d", c->self); 611 channel_free(ssh, c); 612 return NULL; 613 } 614 channel_register_cleanup(ssh, c->self, session_close_by_channel, 0); 615 return c; 616 } 617 618 static int 619 server_input_channel_open(int type, u_int32_t seq, struct ssh *ssh) 620 { 621 Channel *c = NULL; 622 char *ctype = NULL; 623 const char *errmsg = NULL; 624 int r, reason = SSH2_OPEN_CONNECT_FAILED; 625 u_int rchan = 0, rmaxpack = 0, rwindow = 0; 626 627 if ((r = sshpkt_get_cstring(ssh, &ctype, NULL)) != 0 || 628 (r = sshpkt_get_u32(ssh, &rchan)) != 0 || 629 (r = sshpkt_get_u32(ssh, &rwindow)) != 0 || 630 (r = sshpkt_get_u32(ssh, &rmaxpack)) != 0) 631 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 632 debug_f("ctype %s rchan %u win %u max %u", 633 ctype, rchan, rwindow, rmaxpack); 634 635 if (strcmp(ctype, "session") == 0) { 636 c = server_request_session(ssh); 637 } else if (strcmp(ctype, "direct-tcpip") == 0) { 638 c = server_request_direct_tcpip(ssh, &reason, &errmsg); 639 } else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) { 640 c = server_request_direct_streamlocal(ssh); 641 } else if (strcmp(ctype, "tun@openssh.com") == 0) { 642 c = server_request_tun(ssh); 643 } 644 if (c != NULL) { 645 debug_f("confirm %s", ctype); 646 c->remote_id = rchan; 647 c->have_remote_id = 1; 648 c->remote_window = rwindow; 649 c->remote_maxpacket = rmaxpack; 650 if (c->type != SSH_CHANNEL_CONNECTING) { 651 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION)) != 0 || 652 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 653 (r = sshpkt_put_u32(ssh, c->self)) != 0 || 654 (r = sshpkt_put_u32(ssh, c->local_window)) != 0 || 655 (r = sshpkt_put_u32(ssh, c->local_maxpacket)) != 0 || 656 (r = sshpkt_send(ssh)) != 0) { 657 sshpkt_fatal(ssh, r, 658 "%s: send open confirm", __func__); 659 } 660 } 661 } else { 662 debug_f("failure %s", ctype); 663 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE)) != 0 || 664 (r = sshpkt_put_u32(ssh, rchan)) != 0 || 665 (r = sshpkt_put_u32(ssh, reason)) != 0 || 666 (r = sshpkt_put_cstring(ssh, errmsg ? errmsg : "open failed")) != 0 || 667 (r = sshpkt_put_cstring(ssh, "")) != 0 || 668 (r = sshpkt_send(ssh)) != 0) { 669 sshpkt_fatal(ssh, r, 670 "%s: send open failure", __func__); 671 } 672 } 673 free(ctype); 674 return 0; 675 } 676 677 static int 678 server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp) 679 { 680 struct sshbuf *resp = NULL; 681 struct sshbuf *sigbuf = NULL; 682 struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL; 683 int r, ndx, success = 0; 684 const u_char *blob; 685 const char *sigalg, *kex_rsa_sigalg = NULL; 686 u_char *sig = 0; 687 size_t blen, slen; 688 689 if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL) 690 fatal_f("sshbuf_new"); 691 if (sshkey_type_plain(sshkey_type_from_name( 692 ssh->kex->hostkey_alg)) == KEY_RSA) 693 kex_rsa_sigalg = ssh->kex->hostkey_alg; 694 while (ssh_packet_remaining(ssh) > 0) { 695 sshkey_free(key); 696 key = NULL; 697 if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 || 698 (r = sshkey_from_blob(blob, blen, &key)) != 0) { 699 error_fr(r, "parse key"); 700 goto out; 701 } 702 /* 703 * Better check that this is actually one of our hostkeys 704 * before attempting to sign anything with it. 705 */ 706 if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) { 707 error_f("unknown host %s key", sshkey_type(key)); 708 goto out; 709 } 710 /* 711 * XXX refactor: make kex->sign just use an index rather 712 * than passing in public and private keys 713 */ 714 if ((key_prv = get_hostkey_by_index(ndx)) == NULL && 715 (key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) { 716 error_f("can't retrieve hostkey %d", ndx); 717 goto out; 718 } 719 sshbuf_reset(sigbuf); 720 free(sig); 721 sig = NULL; 722 /* 723 * For RSA keys, prefer to use the signature type negotiated 724 * during KEX to the default (SHA1). 725 */ 726 sigalg = NULL; 727 if (sshkey_type_plain(key->type) == KEY_RSA) { 728 if (kex_rsa_sigalg != NULL) 729 sigalg = kex_rsa_sigalg; 730 else if (ssh->kex->flags & KEX_RSA_SHA2_512_SUPPORTED) 731 sigalg = "rsa-sha2-512"; 732 else if (ssh->kex->flags & KEX_RSA_SHA2_256_SUPPORTED) 733 sigalg = "rsa-sha2-256"; 734 } 735 debug3_f("sign %s key (index %d) using sigalg %s", 736 sshkey_type(key), ndx, sigalg == NULL ? "default" : sigalg); 737 if ((r = sshbuf_put_cstring(sigbuf, 738 "hostkeys-prove-00@openssh.com")) != 0 || 739 (r = sshbuf_put_stringb(sigbuf, 740 ssh->kex->session_id)) != 0 || 741 (r = sshkey_puts(key, sigbuf)) != 0 || 742 (r = ssh->kex->sign(ssh, key_prv, key_pub, &sig, &slen, 743 sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), sigalg)) != 0 || 744 (r = sshbuf_put_string(resp, sig, slen)) != 0) { 745 error_fr(r, "assemble signature"); 746 goto out; 747 } 748 } 749 /* Success */ 750 *respp = resp; 751 resp = NULL; /* don't free it */ 752 success = 1; 753 out: 754 free(sig); 755 sshbuf_free(resp); 756 sshbuf_free(sigbuf); 757 sshkey_free(key); 758 return success; 759 } 760 761 static int 762 server_input_global_request(int type, u_int32_t seq, struct ssh *ssh) 763 { 764 char *rtype = NULL; 765 u_char want_reply = 0; 766 int r, success = 0, allocated_listen_port = 0; 767 u_int port = 0; 768 struct sshbuf *resp = NULL; 769 struct passwd *pw = the_authctxt->pw; 770 struct Forward fwd; 771 772 memset(&fwd, 0, sizeof(fwd)); 773 if (pw == NULL || !the_authctxt->valid) 774 fatal_f("no/invalid user"); 775 776 if ((r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 777 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 778 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 779 debug_f("rtype %s want_reply %d", rtype, want_reply); 780 781 /* -R style forwarding */ 782 if (strcmp(rtype, "tcpip-forward") == 0) { 783 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 784 (r = sshpkt_get_u32(ssh, &port)) != 0) 785 sshpkt_fatal(ssh, r, "%s: parse tcpip-forward", __func__); 786 debug_f("tcpip-forward listen %s port %u", 787 fwd.listen_host, port); 788 if (port <= INT_MAX) 789 fwd.listen_port = (int)port; 790 /* check permissions */ 791 if (port > INT_MAX || 792 (options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 || 793 !auth_opts->permit_port_forwarding_flag || 794 options.disable_forwarding || 795 (!want_reply && fwd.listen_port == 0) || 796 (fwd.listen_port != 0 && 797 !bind_permitted(fwd.listen_port, pw->pw_uid))) { 798 success = 0; 799 ssh_packet_send_debug(ssh, "Server has disabled port forwarding."); 800 } else { 801 /* Start listening on the port */ 802 success = channel_setup_remote_fwd_listener(ssh, &fwd, 803 &allocated_listen_port, &options.fwd_opts); 804 } 805 if ((resp = sshbuf_new()) == NULL) 806 fatal_f("sshbuf_new"); 807 if (allocated_listen_port != 0 && 808 (r = sshbuf_put_u32(resp, allocated_listen_port)) != 0) 809 fatal_fr(r, "sshbuf_put_u32"); 810 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) { 811 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 812 (r = sshpkt_get_u32(ssh, &port)) != 0) 813 sshpkt_fatal(ssh, r, "%s: parse cancel-tcpip-forward", __func__); 814 815 debug_f("cancel-tcpip-forward addr %s port %d", 816 fwd.listen_host, port); 817 if (port <= INT_MAX) { 818 fwd.listen_port = (int)port; 819 success = channel_cancel_rport_listener(ssh, &fwd); 820 } 821 } else if (strcmp(rtype, "streamlocal-forward@openssh.com") == 0) { 822 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 823 sshpkt_fatal(ssh, r, "%s: parse streamlocal-forward@openssh.com", __func__); 824 debug_f("streamlocal-forward listen path %s", 825 fwd.listen_path); 826 827 /* check permissions */ 828 if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0 829 || !auth_opts->permit_port_forwarding_flag || 830 options.disable_forwarding || 831 (pw->pw_uid != 0 && !use_privsep)) { 832 success = 0; 833 ssh_packet_send_debug(ssh, "Server has disabled " 834 "streamlocal forwarding."); 835 } else { 836 /* Start listening on the socket */ 837 success = channel_setup_remote_fwd_listener(ssh, 838 &fwd, NULL, &options.fwd_opts); 839 } 840 } else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) { 841 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 842 sshpkt_fatal(ssh, r, "%s: parse cancel-streamlocal-forward@openssh.com", __func__); 843 debug_f("cancel-streamlocal-forward path %s", 844 fwd.listen_path); 845 846 success = channel_cancel_rport_listener(ssh, &fwd); 847 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) { 848 no_more_sessions = 1; 849 success = 1; 850 } else if (strcmp(rtype, "hostkeys-prove-00@openssh.com") == 0) { 851 success = server_input_hostkeys_prove(ssh, &resp); 852 } 853 /* XXX sshpkt_get_end() */ 854 if (want_reply) { 855 if ((r = sshpkt_start(ssh, success ? 856 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE)) != 0 || 857 (success && resp != NULL && (r = sshpkt_putb(ssh, resp)) != 0) || 858 (r = sshpkt_send(ssh)) != 0 || 859 (r = ssh_packet_write_wait(ssh)) != 0) 860 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 861 } 862 free(fwd.listen_host); 863 free(fwd.listen_path); 864 free(rtype); 865 sshbuf_free(resp); 866 return 0; 867 } 868 869 static int 870 server_input_channel_req(int type, u_int32_t seq, struct ssh *ssh) 871 { 872 Channel *c; 873 int r, success = 0; 874 char *rtype = NULL; 875 u_char want_reply = 0; 876 u_int id = 0; 877 878 if ((r = sshpkt_get_u32(ssh, &id)) != 0 || 879 (r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 880 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 881 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 882 883 debug("server_input_channel_req: channel %u request %s reply %d", 884 id, rtype, want_reply); 885 886 if (id >= INT_MAX || (c = channel_lookup(ssh, (int)id)) == NULL) { 887 ssh_packet_disconnect(ssh, "%s: unknown channel %d", 888 __func__, id); 889 } 890 if (!strcmp(rtype, "eow@openssh.com")) { 891 if ((r = sshpkt_get_end(ssh)) != 0) 892 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 893 chan_rcvd_eow(ssh, c); 894 } else if ((c->type == SSH_CHANNEL_LARVAL || 895 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0) 896 success = session_input_channel_req(ssh, c, rtype); 897 if (want_reply && !(c->flags & CHAN_CLOSE_SENT)) { 898 if (!c->have_remote_id) 899 fatal_f("channel %d: no remote_id", c->self); 900 if ((r = sshpkt_start(ssh, success ? 901 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE)) != 0 || 902 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 903 (r = sshpkt_send(ssh)) != 0) 904 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 905 } 906 free(rtype); 907 return 0; 908 } 909 910 static void 911 server_init_dispatch(struct ssh *ssh) 912 { 913 debug("server_init_dispatch"); 914 ssh_dispatch_init(ssh, &dispatch_protocol_error); 915 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); 916 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_DATA, &channel_input_data); 917 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); 918 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); 919 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); 920 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 921 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 922 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); 923 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); 924 ssh_dispatch_set(ssh, SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); 925 /* client_alive */ 926 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive); 927 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); 928 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); 929 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); 930 /* rekeying */ 931 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit); 932 } 933