1 /* $OpenBSD: serverloop.c,v 1.234 2023/01/17 09:44:48 djm Exp $ */ 2 /* 3 * Author: Tatu Ylonen <ylo@cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 5 * All rights reserved 6 * Server main loop for handling the interactive session. 7 * 8 * As far as I am concerned, the code I have written for this software 9 * can be used freely for any purpose. Any derived versions of this 10 * software must be clearly marked as such, and if the derived work is 11 * incompatible with the protocol description in the RFC file, it must be 12 * called by a name other than "ssh" or "Secure Shell". 13 * 14 * SSH2 support by Markus Friedl. 15 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. 16 * 17 * Redistribution and use in source and binary forms, with or without 18 * modification, are permitted provided that the following conditions 19 * are met: 20 * 1. Redistributions of source code must retain the above copyright 21 * notice, this list of conditions and the following disclaimer. 22 * 2. Redistributions in binary form must reproduce the above copyright 23 * notice, this list of conditions and the following disclaimer in the 24 * documentation and/or other materials provided with the distribution. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 27 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 28 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 29 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 30 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 31 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 35 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 36 */ 37 38 #include <sys/types.h> 39 #include <sys/wait.h> 40 #include <sys/socket.h> 41 #include <sys/time.h> 42 #include <sys/queue.h> 43 44 #include <netinet/in.h> 45 46 #include <errno.h> 47 #include <fcntl.h> 48 #include <pwd.h> 49 #include <limits.h> 50 #include <poll.h> 51 #include <signal.h> 52 #include <string.h> 53 #include <termios.h> 54 #include <unistd.h> 55 #include <stdarg.h> 56 57 #include "xmalloc.h" 58 #include "packet.h" 59 #include "sshbuf.h" 60 #include "log.h" 61 #include "misc.h" 62 #include "servconf.h" 63 #include "canohost.h" 64 #include "sshpty.h" 65 #include "channels.h" 66 #include "compat.h" 67 #include "ssh2.h" 68 #include "sshkey.h" 69 #include "cipher.h" 70 #include "kex.h" 71 #include "hostfile.h" 72 #include "auth.h" 73 #include "session.h" 74 #include "dispatch.h" 75 #include "auth-options.h" 76 #include "serverloop.h" 77 #include "ssherr.h" 78 79 extern ServerOptions options; 80 81 /* XXX */ 82 extern Authctxt *the_authctxt; 83 extern struct sshauthopt *auth_opts; 84 extern int use_privsep; 85 86 static int no_more_sessions = 0; /* Disallow further sessions. */ 87 88 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */ 89 90 /* Cleanup on signals (!use_privsep case only) */ 91 static volatile sig_atomic_t received_sigterm = 0; 92 93 /* prototypes */ 94 static void server_init_dispatch(struct ssh *); 95 96 /* requested tunnel forwarding interface(s), shared with session.c */ 97 char *tun_fwd_ifnames = NULL; 98 99 /* returns 1 if bind to specified port by specified user is permitted */ 100 static int 101 bind_permitted(int port, uid_t uid) 102 { 103 if (use_privsep) 104 return 1; /* allow system to decide */ 105 if (port < IPPORT_RESERVED && uid != 0) 106 return 0; 107 return 1; 108 } 109 110 /*ARGSUSED*/ 111 static void 112 sigchld_handler(int sig) 113 { 114 child_terminated = 1; 115 } 116 117 /*ARGSUSED*/ 118 static void 119 sigterm_handler(int sig) 120 { 121 received_sigterm = sig; 122 } 123 124 static void 125 client_alive_check(struct ssh *ssh) 126 { 127 char remote_id[512]; 128 int r, channel_id; 129 130 /* timeout, check to see how many we have had */ 131 if (options.client_alive_count_max > 0 && 132 ssh_packet_inc_alive_timeouts(ssh) > 133 options.client_alive_count_max) { 134 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id)); 135 logit("Timeout, client not responding from %s", remote_id); 136 cleanup_exit(255); 137 } 138 139 /* 140 * send a bogus global/channel request with "wantreply", 141 * we should get back a failure 142 */ 143 if ((channel_id = channel_find_open(ssh)) == -1) { 144 if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 || 145 (r = sshpkt_put_cstring(ssh, "keepalive@openssh.com")) 146 != 0 || 147 (r = sshpkt_put_u8(ssh, 1)) != 0) /* boolean: want reply */ 148 fatal_fr(r, "compose"); 149 } else { 150 channel_request_start(ssh, channel_id, 151 "keepalive@openssh.com", 1); 152 } 153 if ((r = sshpkt_send(ssh)) != 0) 154 fatal_fr(r, "send"); 155 } 156 157 /* 158 * Sleep in ppoll() until we can do something. 159 * Optionally, a maximum time can be specified for the duration of 160 * the wait (0 = infinite). 161 */ 162 static void 163 wait_until_can_do_something(struct ssh *ssh, 164 int connection_in, int connection_out, struct pollfd **pfdp, 165 u_int *npfd_allocp, u_int *npfd_activep, sigset_t *sigsetp, 166 int *conn_in_readyp, int *conn_out_readyp) 167 { 168 struct timespec timeout; 169 char remote_id[512]; 170 int ret; 171 int client_alive_scheduled = 0; 172 u_int p; 173 time_t now; 174 static time_t last_client_time, unused_connection_expiry; 175 176 *conn_in_readyp = *conn_out_readyp = 0; 177 178 /* Prepare channel poll. First two pollfd entries are reserved */ 179 ptimeout_init(&timeout); 180 channel_prepare_poll(ssh, pfdp, npfd_allocp, npfd_activep, 2, &timeout); 181 now = monotime(); 182 if (*npfd_activep < 2) 183 fatal_f("bad npfd %u", *npfd_activep); /* shouldn't happen */ 184 if (options.rekey_interval > 0 && !ssh_packet_is_rekeying(ssh)) { 185 ptimeout_deadline_sec(&timeout, 186 ssh_packet_get_rekey_timeout(ssh)); 187 } 188 189 /* 190 * If no channels are open and UnusedConnectionTimeout is set, then 191 * start the clock to terminate the connection. 192 */ 193 if (options.unused_connection_timeout != 0) { 194 if (channel_still_open(ssh) || unused_connection_expiry == 0) { 195 unused_connection_expiry = now + 196 options.unused_connection_timeout; 197 } 198 ptimeout_deadline_monotime(&timeout, unused_connection_expiry); 199 } 200 201 /* 202 * if using client_alive, set the max timeout accordingly, 203 * and indicate that this particular timeout was for client 204 * alive by setting the client_alive_scheduled flag. 205 * 206 * this could be randomized somewhat to make traffic 207 * analysis more difficult, but we're not doing it yet. 208 */ 209 if (options.client_alive_interval) { 210 /* Time we last heard from the client OR sent a keepalive */ 211 if (last_client_time == 0) 212 last_client_time = now; 213 ptimeout_deadline_sec(&timeout, options.client_alive_interval); 214 /* XXX ? deadline_monotime(last_client_time + alive_interval) */ 215 client_alive_scheduled = 1; 216 } 217 218 #if 0 219 /* wrong: bad condition XXX */ 220 if (channel_not_very_much_buffered_data()) 221 #endif 222 /* Monitor client connection on reserved pollfd entries */ 223 (*pfdp)[0].fd = connection_in; 224 (*pfdp)[0].events = POLLIN; 225 (*pfdp)[1].fd = connection_out; 226 (*pfdp)[1].events = ssh_packet_have_data_to_write(ssh) ? POLLOUT : 0; 227 228 /* 229 * If child has terminated and there is enough buffer space to read 230 * from it, then read as much as is available and exit. 231 */ 232 if (child_terminated && ssh_packet_not_very_much_data_to_write(ssh)) 233 ptimeout_deadline_ms(&timeout, 100); 234 235 /* Wait for something to happen, or the timeout to expire. */ 236 ret = ppoll(*pfdp, *npfd_activep, ptimeout_get_tsp(&timeout), sigsetp); 237 238 if (ret == -1) { 239 for (p = 0; p < *npfd_activep; p++) 240 (*pfdp)[p].revents = 0; 241 if (errno != EINTR) 242 fatal_f("ppoll: %.100s", strerror(errno)); 243 return; 244 } 245 246 *conn_in_readyp = (*pfdp)[0].revents != 0; 247 *conn_out_readyp = (*pfdp)[1].revents != 0; 248 249 now = monotime(); /* need to reset after ppoll() */ 250 /* ClientAliveInterval probing */ 251 if (client_alive_scheduled) { 252 if (ret == 0 && 253 now > last_client_time + options.client_alive_interval) { 254 /* ppoll timed out and we're due to probe */ 255 client_alive_check(ssh); 256 last_client_time = now; 257 } else if (ret != 0 && *conn_in_readyp) { 258 /* Data from peer; reset probe timer. */ 259 last_client_time = now; 260 } 261 } 262 263 /* UnusedConnectionTimeout handling */ 264 if (unused_connection_expiry != 0 && 265 now > unused_connection_expiry && !channel_still_open(ssh)) { 266 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id)); 267 logit("terminating inactive connection from %s", remote_id); 268 cleanup_exit(255); 269 } 270 } 271 272 /* 273 * Processes input from the client and the program. Input data is stored 274 * in buffers and processed later. 275 */ 276 static int 277 process_input(struct ssh *ssh, int connection_in) 278 { 279 int r; 280 281 if ((r = ssh_packet_process_read(ssh, connection_in)) == 0) 282 return 0; /* success */ 283 if (r == SSH_ERR_SYSTEM_ERROR) { 284 if (errno == EAGAIN || errno == EINTR) 285 return 0; 286 if (errno == EPIPE) { 287 verbose("Connection closed by %.100s port %d", 288 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 289 return -1; 290 } 291 verbose("Read error from remote host %s port %d: %s", 292 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), 293 strerror(errno)); 294 cleanup_exit(255); 295 } 296 return -1; 297 } 298 299 /* 300 * Sends data from internal buffers to client program stdin. 301 */ 302 static void 303 process_output(struct ssh *ssh, int connection_out) 304 { 305 int r; 306 307 /* Send any buffered packet data to the client. */ 308 if ((r = ssh_packet_write_poll(ssh)) != 0) { 309 sshpkt_fatal(ssh, r, "%s: ssh_packet_write_poll", 310 __func__); 311 } 312 } 313 314 static void 315 process_buffered_input_packets(struct ssh *ssh) 316 { 317 ssh_dispatch_run_fatal(ssh, DISPATCH_NONBLOCK, NULL); 318 } 319 320 static void 321 collect_children(struct ssh *ssh) 322 { 323 pid_t pid; 324 int status; 325 326 if (child_terminated) { 327 debug("Received SIGCHLD."); 328 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 329 (pid == -1 && errno == EINTR)) 330 if (pid > 0) 331 session_close_by_pid(ssh, pid, status); 332 child_terminated = 0; 333 } 334 } 335 336 void 337 server_loop2(struct ssh *ssh, Authctxt *authctxt) 338 { 339 struct pollfd *pfd = NULL; 340 u_int npfd_alloc = 0, npfd_active = 0; 341 int r, conn_in_ready, conn_out_ready; 342 u_int connection_in, connection_out; 343 sigset_t bsigset, osigset; 344 345 debug("Entering interactive session for SSH2."); 346 347 if (sigemptyset(&bsigset) == -1 || sigaddset(&bsigset, SIGCHLD) == -1) 348 error_f("bsigset setup: %s", strerror(errno)); 349 ssh_signal(SIGCHLD, sigchld_handler); 350 child_terminated = 0; 351 connection_in = ssh_packet_get_connection_in(ssh); 352 connection_out = ssh_packet_get_connection_out(ssh); 353 354 if (!use_privsep) { 355 ssh_signal(SIGTERM, sigterm_handler); 356 ssh_signal(SIGINT, sigterm_handler); 357 ssh_signal(SIGQUIT, sigterm_handler); 358 } 359 360 server_init_dispatch(ssh); 361 362 for (;;) { 363 process_buffered_input_packets(ssh); 364 365 if (!ssh_packet_is_rekeying(ssh) && 366 ssh_packet_not_very_much_data_to_write(ssh)) 367 channel_output_poll(ssh); 368 369 /* 370 * Block SIGCHLD while we check for dead children, then pass 371 * the old signal mask through to ppoll() so that it'll wake 372 * up immediately if a child exits after we've called waitpid(). 373 */ 374 if (sigprocmask(SIG_BLOCK, &bsigset, &osigset) == -1) 375 error_f("bsigset sigprocmask: %s", strerror(errno)); 376 collect_children(ssh); 377 wait_until_can_do_something(ssh, connection_in, connection_out, 378 &pfd, &npfd_alloc, &npfd_active, &osigset, 379 &conn_in_ready, &conn_out_ready); 380 if (sigprocmask(SIG_UNBLOCK, &bsigset, &osigset) == -1) 381 error_f("osigset sigprocmask: %s", strerror(errno)); 382 383 if (received_sigterm) { 384 logit("Exiting on signal %d", (int)received_sigterm); 385 /* Clean up sessions, utmp, etc. */ 386 cleanup_exit(255); 387 } 388 389 channel_after_poll(ssh, pfd, npfd_active); 390 if (conn_in_ready && 391 process_input(ssh, connection_in) < 0) 392 break; 393 /* A timeout may have triggered rekeying */ 394 if ((r = ssh_packet_check_rekey(ssh)) != 0) 395 fatal_fr(r, "cannot start rekeying"); 396 if (conn_out_ready) 397 process_output(ssh, connection_out); 398 } 399 collect_children(ssh); 400 free(pfd); 401 402 /* free all channels, no more reads and writes */ 403 channel_free_all(ssh); 404 405 /* free remaining sessions, e.g. remove wtmp entries */ 406 session_destroy_all(ssh, NULL); 407 } 408 409 static int 410 server_input_keep_alive(int type, u_int32_t seq, struct ssh *ssh) 411 { 412 debug("Got %d/%u for keepalive", type, seq); 413 /* 414 * reset timeout, since we got a sane answer from the client. 415 * even if this was generated by something other than 416 * the bogus CHANNEL_REQUEST we send for keepalives. 417 */ 418 ssh_packet_set_alive_timeouts(ssh, 0); 419 return 0; 420 } 421 422 static Channel * 423 server_request_direct_tcpip(struct ssh *ssh, int *reason, const char **errmsg) 424 { 425 Channel *c = NULL; 426 char *target = NULL, *originator = NULL; 427 u_int target_port = 0, originator_port = 0; 428 int r; 429 430 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 431 (r = sshpkt_get_u32(ssh, &target_port)) != 0 || 432 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 433 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 434 (r = sshpkt_get_end(ssh)) != 0) 435 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 436 if (target_port > 0xFFFF) { 437 error_f("invalid target port"); 438 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 439 goto out; 440 } 441 if (originator_port > 0xFFFF) { 442 error_f("invalid originator port"); 443 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 444 goto out; 445 } 446 447 debug_f("originator %s port %u, target %s port %u", 448 originator, originator_port, target, target_port); 449 450 /* XXX fine grained permissions */ 451 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 && 452 auth_opts->permit_port_forwarding_flag && 453 !options.disable_forwarding) { 454 c = channel_connect_to_port(ssh, target, target_port, 455 "direct-tcpip", "direct-tcpip", reason, errmsg); 456 } else { 457 logit("refused local port forward: " 458 "originator %s port %d, target %s port %d", 459 originator, originator_port, target, target_port); 460 if (reason != NULL) 461 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 462 } 463 464 out: 465 free(originator); 466 free(target); 467 return c; 468 } 469 470 static Channel * 471 server_request_direct_streamlocal(struct ssh *ssh) 472 { 473 Channel *c = NULL; 474 char *target = NULL, *originator = NULL; 475 u_int originator_port = 0; 476 struct passwd *pw = the_authctxt->pw; 477 int r; 478 479 if (pw == NULL || !the_authctxt->valid) 480 fatal_f("no/invalid user"); 481 482 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 483 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 484 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 485 (r = sshpkt_get_end(ssh)) != 0) 486 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 487 if (originator_port > 0xFFFF) { 488 error_f("invalid originator port"); 489 goto out; 490 } 491 492 debug_f("originator %s port %d, target %s", 493 originator, originator_port, target); 494 495 /* XXX fine grained permissions */ 496 if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 && 497 auth_opts->permit_port_forwarding_flag && 498 !options.disable_forwarding && (pw->pw_uid == 0 || use_privsep)) { 499 c = channel_connect_to_path(ssh, target, 500 "direct-streamlocal@openssh.com", "direct-streamlocal"); 501 } else { 502 logit("refused streamlocal port forward: " 503 "originator %s port %d, target %s", 504 originator, originator_port, target); 505 } 506 507 out: 508 free(originator); 509 free(target); 510 return c; 511 } 512 513 static Channel * 514 server_request_tun(struct ssh *ssh) 515 { 516 Channel *c = NULL; 517 u_int mode, tun; 518 int r, sock; 519 char *tmp, *ifname = NULL; 520 521 if ((r = sshpkt_get_u32(ssh, &mode)) != 0) 522 sshpkt_fatal(ssh, r, "%s: parse mode", __func__); 523 switch (mode) { 524 case SSH_TUNMODE_POINTOPOINT: 525 case SSH_TUNMODE_ETHERNET: 526 break; 527 default: 528 ssh_packet_send_debug(ssh, "Unsupported tunnel device mode."); 529 return NULL; 530 } 531 if ((options.permit_tun & mode) == 0) { 532 ssh_packet_send_debug(ssh, "Server has rejected tunnel device " 533 "forwarding"); 534 return NULL; 535 } 536 537 if ((r = sshpkt_get_u32(ssh, &tun)) != 0) 538 sshpkt_fatal(ssh, r, "%s: parse device", __func__); 539 if (tun > INT_MAX) { 540 debug_f("invalid tun"); 541 goto done; 542 } 543 if (auth_opts->force_tun_device != -1) { 544 if (tun != SSH_TUNID_ANY && 545 auth_opts->force_tun_device != (int)tun) 546 goto done; 547 tun = auth_opts->force_tun_device; 548 } 549 sock = tun_open(tun, mode, &ifname); 550 if (sock < 0) 551 goto done; 552 debug("Tunnel forwarding using interface %s", ifname); 553 554 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1, 555 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 556 c->datagram = 1; 557 558 /* 559 * Update the list of names exposed to the session 560 * XXX remove these if the tunnels are closed (won't matter 561 * much if they are already in the environment though) 562 */ 563 tmp = tun_fwd_ifnames; 564 xasprintf(&tun_fwd_ifnames, "%s%s%s", 565 tun_fwd_ifnames == NULL ? "" : tun_fwd_ifnames, 566 tun_fwd_ifnames == NULL ? "" : ",", 567 ifname); 568 free(tmp); 569 free(ifname); 570 571 done: 572 if (c == NULL) 573 ssh_packet_send_debug(ssh, "Failed to open the tunnel device."); 574 return c; 575 } 576 577 static Channel * 578 server_request_session(struct ssh *ssh) 579 { 580 Channel *c; 581 int r; 582 583 debug("input_session_request"); 584 if ((r = sshpkt_get_end(ssh)) != 0) 585 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 586 587 if (no_more_sessions) { 588 ssh_packet_disconnect(ssh, "Possible attack: attempt to open a " 589 "session after additional sessions disabled"); 590 } 591 592 /* 593 * A server session has no fd to read or write until a 594 * CHANNEL_REQUEST for a shell is made, so we set the type to 595 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all 596 * CHANNEL_REQUEST messages is registered. 597 */ 598 c = channel_new(ssh, "session", SSH_CHANNEL_LARVAL, 599 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, 600 0, "server-session", 1); 601 if (session_open(the_authctxt, c->self) != 1) { 602 debug("session open failed, free channel %d", c->self); 603 channel_free(ssh, c); 604 return NULL; 605 } 606 channel_register_cleanup(ssh, c->self, session_close_by_channel, 0); 607 return c; 608 } 609 610 static int 611 server_input_channel_open(int type, u_int32_t seq, struct ssh *ssh) 612 { 613 Channel *c = NULL; 614 char *ctype = NULL; 615 const char *errmsg = NULL; 616 int r, reason = SSH2_OPEN_CONNECT_FAILED; 617 u_int rchan = 0, rmaxpack = 0, rwindow = 0; 618 619 if ((r = sshpkt_get_cstring(ssh, &ctype, NULL)) != 0 || 620 (r = sshpkt_get_u32(ssh, &rchan)) != 0 || 621 (r = sshpkt_get_u32(ssh, &rwindow)) != 0 || 622 (r = sshpkt_get_u32(ssh, &rmaxpack)) != 0) 623 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 624 debug_f("ctype %s rchan %u win %u max %u", 625 ctype, rchan, rwindow, rmaxpack); 626 627 if (strcmp(ctype, "session") == 0) { 628 c = server_request_session(ssh); 629 } else if (strcmp(ctype, "direct-tcpip") == 0) { 630 c = server_request_direct_tcpip(ssh, &reason, &errmsg); 631 } else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) { 632 c = server_request_direct_streamlocal(ssh); 633 } else if (strcmp(ctype, "tun@openssh.com") == 0) { 634 c = server_request_tun(ssh); 635 } 636 if (c != NULL) { 637 debug_f("confirm %s", ctype); 638 c->remote_id = rchan; 639 c->have_remote_id = 1; 640 c->remote_window = rwindow; 641 c->remote_maxpacket = rmaxpack; 642 if (c->type != SSH_CHANNEL_CONNECTING) { 643 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION)) != 0 || 644 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 645 (r = sshpkt_put_u32(ssh, c->self)) != 0 || 646 (r = sshpkt_put_u32(ssh, c->local_window)) != 0 || 647 (r = sshpkt_put_u32(ssh, c->local_maxpacket)) != 0 || 648 (r = sshpkt_send(ssh)) != 0) { 649 sshpkt_fatal(ssh, r, 650 "%s: send open confirm", __func__); 651 } 652 } 653 } else { 654 debug_f("failure %s", ctype); 655 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE)) != 0 || 656 (r = sshpkt_put_u32(ssh, rchan)) != 0 || 657 (r = sshpkt_put_u32(ssh, reason)) != 0 || 658 (r = sshpkt_put_cstring(ssh, errmsg ? errmsg : "open failed")) != 0 || 659 (r = sshpkt_put_cstring(ssh, "")) != 0 || 660 (r = sshpkt_send(ssh)) != 0) { 661 sshpkt_fatal(ssh, r, 662 "%s: send open failure", __func__); 663 } 664 } 665 free(ctype); 666 return 0; 667 } 668 669 static int 670 server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp) 671 { 672 struct sshbuf *resp = NULL; 673 struct sshbuf *sigbuf = NULL; 674 struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL; 675 int r, ndx, success = 0; 676 const u_char *blob; 677 const char *sigalg, *kex_rsa_sigalg = NULL; 678 u_char *sig = 0; 679 size_t blen, slen; 680 681 if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL) 682 fatal_f("sshbuf_new"); 683 if (sshkey_type_plain(sshkey_type_from_name( 684 ssh->kex->hostkey_alg)) == KEY_RSA) 685 kex_rsa_sigalg = ssh->kex->hostkey_alg; 686 while (ssh_packet_remaining(ssh) > 0) { 687 sshkey_free(key); 688 key = NULL; 689 if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 || 690 (r = sshkey_from_blob(blob, blen, &key)) != 0) { 691 error_fr(r, "parse key"); 692 goto out; 693 } 694 /* 695 * Better check that this is actually one of our hostkeys 696 * before attempting to sign anything with it. 697 */ 698 if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) { 699 error_f("unknown host %s key", sshkey_type(key)); 700 goto out; 701 } 702 /* 703 * XXX refactor: make kex->sign just use an index rather 704 * than passing in public and private keys 705 */ 706 if ((key_prv = get_hostkey_by_index(ndx)) == NULL && 707 (key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) { 708 error_f("can't retrieve hostkey %d", ndx); 709 goto out; 710 } 711 sshbuf_reset(sigbuf); 712 free(sig); 713 sig = NULL; 714 /* 715 * For RSA keys, prefer to use the signature type negotiated 716 * during KEX to the default (SHA1). 717 */ 718 sigalg = NULL; 719 if (sshkey_type_plain(key->type) == KEY_RSA) { 720 if (kex_rsa_sigalg != NULL) 721 sigalg = kex_rsa_sigalg; 722 else if (ssh->kex->flags & KEX_RSA_SHA2_512_SUPPORTED) 723 sigalg = "rsa-sha2-512"; 724 else if (ssh->kex->flags & KEX_RSA_SHA2_256_SUPPORTED) 725 sigalg = "rsa-sha2-256"; 726 } 727 debug3_f("sign %s key (index %d) using sigalg %s", 728 sshkey_type(key), ndx, sigalg == NULL ? "default" : sigalg); 729 if ((r = sshbuf_put_cstring(sigbuf, 730 "hostkeys-prove-00@openssh.com")) != 0 || 731 (r = sshbuf_put_stringb(sigbuf, 732 ssh->kex->session_id)) != 0 || 733 (r = sshkey_puts(key, sigbuf)) != 0 || 734 (r = ssh->kex->sign(ssh, key_prv, key_pub, &sig, &slen, 735 sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), sigalg)) != 0 || 736 (r = sshbuf_put_string(resp, sig, slen)) != 0) { 737 error_fr(r, "assemble signature"); 738 goto out; 739 } 740 } 741 /* Success */ 742 *respp = resp; 743 resp = NULL; /* don't free it */ 744 success = 1; 745 out: 746 free(sig); 747 sshbuf_free(resp); 748 sshbuf_free(sigbuf); 749 sshkey_free(key); 750 return success; 751 } 752 753 static int 754 server_input_global_request(int type, u_int32_t seq, struct ssh *ssh) 755 { 756 char *rtype = NULL; 757 u_char want_reply = 0; 758 int r, success = 0, allocated_listen_port = 0; 759 u_int port = 0; 760 struct sshbuf *resp = NULL; 761 struct passwd *pw = the_authctxt->pw; 762 struct Forward fwd; 763 764 memset(&fwd, 0, sizeof(fwd)); 765 if (pw == NULL || !the_authctxt->valid) 766 fatal_f("no/invalid user"); 767 768 if ((r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 769 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 770 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 771 debug_f("rtype %s want_reply %d", rtype, want_reply); 772 773 /* -R style forwarding */ 774 if (strcmp(rtype, "tcpip-forward") == 0) { 775 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 776 (r = sshpkt_get_u32(ssh, &port)) != 0) 777 sshpkt_fatal(ssh, r, "%s: parse tcpip-forward", __func__); 778 debug_f("tcpip-forward listen %s port %u", 779 fwd.listen_host, port); 780 if (port <= INT_MAX) 781 fwd.listen_port = (int)port; 782 /* check permissions */ 783 if (port > INT_MAX || 784 (options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 || 785 !auth_opts->permit_port_forwarding_flag || 786 options.disable_forwarding || 787 (!want_reply && fwd.listen_port == 0) || 788 (fwd.listen_port != 0 && 789 !bind_permitted(fwd.listen_port, pw->pw_uid))) { 790 success = 0; 791 ssh_packet_send_debug(ssh, "Server has disabled port forwarding."); 792 } else { 793 /* Start listening on the port */ 794 success = channel_setup_remote_fwd_listener(ssh, &fwd, 795 &allocated_listen_port, &options.fwd_opts); 796 } 797 if ((resp = sshbuf_new()) == NULL) 798 fatal_f("sshbuf_new"); 799 if (allocated_listen_port != 0 && 800 (r = sshbuf_put_u32(resp, allocated_listen_port)) != 0) 801 fatal_fr(r, "sshbuf_put_u32"); 802 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) { 803 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 804 (r = sshpkt_get_u32(ssh, &port)) != 0) 805 sshpkt_fatal(ssh, r, "%s: parse cancel-tcpip-forward", __func__); 806 807 debug_f("cancel-tcpip-forward addr %s port %d", 808 fwd.listen_host, port); 809 if (port <= INT_MAX) { 810 fwd.listen_port = (int)port; 811 success = channel_cancel_rport_listener(ssh, &fwd); 812 } 813 } else if (strcmp(rtype, "streamlocal-forward@openssh.com") == 0) { 814 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 815 sshpkt_fatal(ssh, r, "%s: parse streamlocal-forward@openssh.com", __func__); 816 debug_f("streamlocal-forward listen path %s", 817 fwd.listen_path); 818 819 /* check permissions */ 820 if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0 821 || !auth_opts->permit_port_forwarding_flag || 822 options.disable_forwarding || 823 (pw->pw_uid != 0 && !use_privsep)) { 824 success = 0; 825 ssh_packet_send_debug(ssh, "Server has disabled " 826 "streamlocal forwarding."); 827 } else { 828 /* Start listening on the socket */ 829 success = channel_setup_remote_fwd_listener(ssh, 830 &fwd, NULL, &options.fwd_opts); 831 } 832 } else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) { 833 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 834 sshpkt_fatal(ssh, r, "%s: parse cancel-streamlocal-forward@openssh.com", __func__); 835 debug_f("cancel-streamlocal-forward path %s", 836 fwd.listen_path); 837 838 success = channel_cancel_rport_listener(ssh, &fwd); 839 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) { 840 no_more_sessions = 1; 841 success = 1; 842 } else if (strcmp(rtype, "hostkeys-prove-00@openssh.com") == 0) { 843 success = server_input_hostkeys_prove(ssh, &resp); 844 } 845 /* XXX sshpkt_get_end() */ 846 if (want_reply) { 847 if ((r = sshpkt_start(ssh, success ? 848 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE)) != 0 || 849 (success && resp != NULL && (r = sshpkt_putb(ssh, resp)) != 0) || 850 (r = sshpkt_send(ssh)) != 0 || 851 (r = ssh_packet_write_wait(ssh)) != 0) 852 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 853 } 854 free(fwd.listen_host); 855 free(fwd.listen_path); 856 free(rtype); 857 sshbuf_free(resp); 858 return 0; 859 } 860 861 static int 862 server_input_channel_req(int type, u_int32_t seq, struct ssh *ssh) 863 { 864 Channel *c; 865 int r, success = 0; 866 char *rtype = NULL; 867 u_char want_reply = 0; 868 u_int id = 0; 869 870 if ((r = sshpkt_get_u32(ssh, &id)) != 0 || 871 (r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 872 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 873 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 874 875 debug("server_input_channel_req: channel %u request %s reply %d", 876 id, rtype, want_reply); 877 878 if (id >= INT_MAX || (c = channel_lookup(ssh, (int)id)) == NULL) { 879 ssh_packet_disconnect(ssh, "%s: unknown channel %d", 880 __func__, id); 881 } 882 if (!strcmp(rtype, "eow@openssh.com")) { 883 if ((r = sshpkt_get_end(ssh)) != 0) 884 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 885 chan_rcvd_eow(ssh, c); 886 } else if ((c->type == SSH_CHANNEL_LARVAL || 887 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0) 888 success = session_input_channel_req(ssh, c, rtype); 889 if (want_reply && !(c->flags & CHAN_CLOSE_SENT)) { 890 if (!c->have_remote_id) 891 fatal_f("channel %d: no remote_id", c->self); 892 if ((r = sshpkt_start(ssh, success ? 893 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE)) != 0 || 894 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 895 (r = sshpkt_send(ssh)) != 0) 896 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 897 } 898 free(rtype); 899 return 0; 900 } 901 902 static void 903 server_init_dispatch(struct ssh *ssh) 904 { 905 debug("server_init_dispatch"); 906 ssh_dispatch_init(ssh, &dispatch_protocol_error); 907 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); 908 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_DATA, &channel_input_data); 909 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); 910 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); 911 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); 912 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 913 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 914 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); 915 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); 916 ssh_dispatch_set(ssh, SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); 917 /* client_alive */ 918 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive); 919 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); 920 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); 921 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); 922 /* rekeying */ 923 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit); 924 } 925