1 /* $NetBSD: serverloop.c,v 1.35 2023/10/25 20:19:57 christos Exp $ */ 2 /* $OpenBSD: serverloop.c,v 1.237 2023/08/21 04:59:54 djm Exp $ */ 3 4 /* 5 * Author: Tatu Ylonen <ylo@cs.hut.fi> 6 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 7 * All rights reserved 8 * Server main loop for handling the interactive session. 9 * 10 * As far as I am concerned, the code I have written for this software 11 * can be used freely for any purpose. Any derived versions of this 12 * software must be clearly marked as such, and if the derived work is 13 * incompatible with the protocol description in the RFC file, it must be 14 * called by a name other than "ssh" or "Secure Shell". 15 * 16 * SSH2 support by Markus Friedl. 17 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. 18 * 19 * Redistribution and use in source and binary forms, with or without 20 * modification, are permitted provided that the following conditions 21 * are met: 22 * 1. Redistributions of source code must retain the above copyright 23 * notice, this list of conditions and the following disclaimer. 24 * 2. Redistributions in binary form must reproduce the above copyright 25 * notice, this list of conditions and the following disclaimer in the 26 * documentation and/or other materials provided with the distribution. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 29 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 30 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 31 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 32 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 33 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 34 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 35 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 36 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 37 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 38 */ 39 40 #include "includes.h" 41 __RCSID("$NetBSD: serverloop.c,v 1.35 2023/10/25 20:19:57 christos Exp $"); 42 43 #include <sys/param.h> /* MIN MAX */ 44 #include <sys/types.h> 45 #include <sys/wait.h> 46 #include <sys/socket.h> 47 #include <sys/time.h> 48 #include <sys/queue.h> 49 50 #include <netinet/in.h> 51 52 #include <errno.h> 53 #include <fcntl.h> 54 #include <pwd.h> 55 #include <limits.h> 56 #include <poll.h> 57 #include <signal.h> 58 #include <string.h> 59 #include <termios.h> 60 #include <unistd.h> 61 #include <stdarg.h> 62 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 static u_long stdin_bytes = 0; /* Number of bytes written to stdin. */ 85 static u_long fdout_bytes = 0; /* Number of stdout bytes read from program. */ 86 87 extern ServerOptions options; 88 89 /* XXX */ 90 extern Authctxt *the_authctxt; 91 extern struct sshauthopt *auth_opts; 92 extern int use_privsep; 93 94 static int no_more_sessions = 0; /* Disallow further sessions. */ 95 96 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */ 97 98 /* Cleanup on signals (!use_privsep case only) */ 99 static volatile sig_atomic_t received_sigterm = 0; 100 101 /* prototypes */ 102 static void server_init_dispatch(struct ssh *); 103 104 /* requested tunnel forwarding interface(s), shared with session.c */ 105 char *tun_fwd_ifnames = NULL; 106 107 /* returns 1 if bind to specified port by specified user is permitted */ 108 static int 109 bind_permitted(int port, uid_t uid) 110 { 111 if (use_privsep) 112 return 1; /* allow system to decide */ 113 if (port < IPPORT_RESERVED && uid != 0) 114 return 0; 115 return 1; 116 } 117 118 /* 119 * Returns current time in seconds from Jan 1, 1970 with the maximum 120 * available resolution. 121 */ 122 123 static double 124 get_current_time(void) 125 { 126 struct timeval tv; 127 gettimeofday(&tv, NULL); 128 return (double) tv.tv_sec + (double) tv.tv_usec / 1000000.0; 129 } 130 131 /*ARGSUSED*/ 132 static void 133 sigchld_handler(int sig) 134 { 135 child_terminated = 1; 136 } 137 138 static void 139 sigterm_handler(int sig) 140 { 141 received_sigterm = sig; 142 } 143 144 static void 145 client_alive_check(struct ssh *ssh) 146 { 147 char remote_id[512]; 148 int r, channel_id; 149 150 /* timeout, check to see how many we have had */ 151 if (options.client_alive_count_max > 0 && 152 ssh_packet_inc_alive_timeouts(ssh) > 153 options.client_alive_count_max) { 154 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id)); 155 logit("Timeout, client not responding from %s", remote_id); 156 cleanup_exit(255); 157 } 158 159 /* 160 * send a bogus global/channel request with "wantreply", 161 * we should get back a failure 162 */ 163 if ((channel_id = channel_find_open(ssh)) == -1) { 164 if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 || 165 (r = sshpkt_put_cstring(ssh, "keepalive@openssh.com")) 166 != 0 || 167 (r = sshpkt_put_u8(ssh, 1)) != 0) /* boolean: want reply */ 168 fatal_fr(r, "compose"); 169 } else { 170 channel_request_start(ssh, channel_id, 171 "keepalive@openssh.com", 1); 172 } 173 if ((r = sshpkt_send(ssh)) != 0) 174 fatal_fr(r, "send"); 175 } 176 177 /* 178 * Sleep in ppoll() until we can do something. 179 * Optionally, a maximum time can be specified for the duration of 180 * the wait (0 = infinite). 181 */ 182 static void 183 wait_until_can_do_something(struct ssh *ssh, 184 int connection_in, int connection_out, struct pollfd **pfdp, 185 u_int *npfd_allocp, u_int *npfd_activep, sigset_t *sigsetp, 186 int *conn_in_readyp, int *conn_out_readyp) 187 { 188 struct timespec timeout; 189 char remote_id[512]; 190 int ret; 191 int client_alive_scheduled = 0; 192 u_int p; 193 time_t now; 194 static time_t last_client_time, unused_connection_expiry; 195 196 *conn_in_readyp = *conn_out_readyp = 0; 197 198 /* Prepare channel poll. First two pollfd entries are reserved */ 199 ptimeout_init(&timeout); 200 channel_prepare_poll(ssh, pfdp, npfd_allocp, npfd_activep, 2, &timeout); 201 now = monotime(); 202 if (*npfd_activep < 2) 203 fatal_f("bad npfd %u", *npfd_activep); /* shouldn't happen */ 204 if (options.rekey_interval > 0 && !ssh_packet_is_rekeying(ssh)) { 205 ptimeout_deadline_sec(&timeout, 206 ssh_packet_get_rekey_timeout(ssh)); 207 } 208 209 /* 210 * If no channels are open and UnusedConnectionTimeout is set, then 211 * start the clock to terminate the connection. 212 */ 213 if (options.unused_connection_timeout != 0) { 214 if (channel_still_open(ssh) || unused_connection_expiry == 0) { 215 unused_connection_expiry = now + 216 options.unused_connection_timeout; 217 } 218 ptimeout_deadline_monotime(&timeout, unused_connection_expiry); 219 } 220 221 /* 222 * if using client_alive, set the max timeout accordingly, 223 * and indicate that this particular timeout was for client 224 * alive by setting the client_alive_scheduled flag. 225 * 226 * this could be randomized somewhat to make traffic 227 * analysis more difficult, but we're not doing it yet. 228 */ 229 if (options.client_alive_interval) { 230 /* Time we last heard from the client OR sent a keepalive */ 231 if (last_client_time == 0) 232 last_client_time = now; 233 ptimeout_deadline_sec(&timeout, options.client_alive_interval); 234 /* XXX ? deadline_monotime(last_client_time + alive_interval) */ 235 client_alive_scheduled = 1; 236 } 237 238 #if 0 239 /* wrong: bad condition XXX */ 240 if (channel_not_very_much_buffered_data()) 241 #endif 242 /* Monitor client connection on reserved pollfd entries */ 243 (*pfdp)[0].fd = connection_in; 244 (*pfdp)[0].events = POLLIN; 245 (*pfdp)[1].fd = connection_out; 246 (*pfdp)[1].events = ssh_packet_have_data_to_write(ssh) ? POLLOUT : 0; 247 248 /* 249 * If child has terminated and there is enough buffer space to read 250 * from it, then read as much as is available and exit. 251 */ 252 if (child_terminated && ssh_packet_not_very_much_data_to_write(ssh)) 253 ptimeout_deadline_ms(&timeout, 100); 254 255 /* Wait for something to happen, or the timeout to expire. */ 256 ret = ppoll(*pfdp, *npfd_activep, ptimeout_get_tsp(&timeout), sigsetp); 257 258 if (ret == -1) { 259 for (p = 0; p < *npfd_activep; p++) 260 (*pfdp)[p].revents = 0; 261 if (errno != EINTR) 262 fatal_f("ppoll: %.100s", strerror(errno)); 263 return; 264 } 265 266 *conn_in_readyp = (*pfdp)[0].revents != 0; 267 *conn_out_readyp = (*pfdp)[1].revents != 0; 268 269 now = monotime(); /* need to reset after ppoll() */ 270 /* ClientAliveInterval probing */ 271 if (client_alive_scheduled) { 272 if (ret == 0 && 273 now >= last_client_time + options.client_alive_interval) { 274 /* ppoll timed out and we're due to probe */ 275 client_alive_check(ssh); 276 last_client_time = now; 277 } else if (ret != 0 && *conn_in_readyp) { 278 /* Data from peer; reset probe timer. */ 279 last_client_time = now; 280 } 281 } 282 283 /* UnusedConnectionTimeout handling */ 284 if (unused_connection_expiry != 0 && 285 now > unused_connection_expiry && !channel_still_open(ssh)) { 286 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id)); 287 logit("terminating inactive connection from %s", remote_id); 288 cleanup_exit(255); 289 } 290 } 291 292 /* 293 * Processes input from the client and the program. Input data is stored 294 * in buffers and processed later. 295 */ 296 static int 297 process_input(struct ssh *ssh, int connection_in) 298 { 299 int r; 300 301 if ((r = ssh_packet_process_read(ssh, connection_in)) == 0) 302 return 0; /* success */ 303 if (r == SSH_ERR_SYSTEM_ERROR) { 304 if (errno == EAGAIN || errno == EINTR) 305 return 0; 306 if (errno == EPIPE) { 307 verbose("Connection closed by %.100s port %d", 308 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 309 return -1; 310 } 311 verbose("Read error from remote host %s port %d: %s", 312 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), 313 strerror(errno)); 314 cleanup_exit(254); 315 } 316 return -1; 317 } 318 319 /* 320 * Sends data from internal buffers to client program stdin. 321 */ 322 static void 323 process_output(struct ssh *ssh, int connection_out) 324 { 325 int r; 326 327 /* Send any buffered packet data to the client. */ 328 if ((r = ssh_packet_write_poll(ssh)) < 0) { 329 sshpkt_fatal(ssh, r, "%s: ssh_packet_write_poll", 330 __func__); 331 } 332 } 333 334 static void 335 process_buffered_input_packets(struct ssh *ssh) 336 { 337 ssh_dispatch_run_fatal(ssh, DISPATCH_NONBLOCK, NULL); 338 } 339 340 static void 341 collect_children(struct ssh *ssh) 342 { 343 pid_t pid; 344 int status; 345 346 if (child_terminated) { 347 debug("Received SIGCHLD."); 348 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 349 (pid == -1 && errno == EINTR)) 350 if (pid > 0) 351 session_close_by_pid(ssh, pid, status); 352 child_terminated = 0; 353 } 354 } 355 356 void 357 server_loop2(struct ssh *ssh, Authctxt *authctxt) 358 { 359 struct pollfd *pfd = NULL; 360 u_int npfd_alloc = 0, npfd_active = 0; 361 int r, conn_in_ready, conn_out_ready; 362 u_int connection_in, connection_out; 363 double start_time, total_time; 364 sigset_t bsigset, osigset; 365 366 debug("Entering interactive session for SSH2."); 367 start_time = get_current_time(); 368 369 if (sigemptyset(&bsigset) == -1 || sigaddset(&bsigset, SIGCHLD) == -1) 370 error_f("bsigset setup: %s", strerror(errno)); 371 ssh_signal(SIGCHLD, sigchld_handler); 372 child_terminated = 0; 373 connection_in = ssh_packet_get_connection_in(ssh); 374 connection_out = ssh_packet_get_connection_out(ssh); 375 376 if (!use_privsep) { 377 ssh_signal(SIGTERM, sigterm_handler); 378 ssh_signal(SIGINT, sigterm_handler); 379 ssh_signal(SIGQUIT, sigterm_handler); 380 } 381 382 server_init_dispatch(ssh); 383 384 for (;;) { 385 process_buffered_input_packets(ssh); 386 387 if (!ssh_packet_is_rekeying(ssh) && 388 ssh_packet_not_very_much_data_to_write(ssh)) 389 channel_output_poll(ssh); 390 391 /* 392 * Block SIGCHLD while we check for dead children, then pass 393 * the old signal mask through to ppoll() so that it'll wake 394 * up immediately if a child exits after we've called waitpid(). 395 */ 396 if (sigprocmask(SIG_BLOCK, &bsigset, &osigset) == -1) 397 error_f("bsigset sigprocmask: %s", strerror(errno)); 398 collect_children(ssh); 399 wait_until_can_do_something(ssh, connection_in, connection_out, 400 &pfd, &npfd_alloc, &npfd_active, &osigset, 401 &conn_in_ready, &conn_out_ready); 402 if (sigprocmask(SIG_UNBLOCK, &bsigset, &osigset) == -1) 403 error_f("osigset sigprocmask: %s", strerror(errno)); 404 405 if (received_sigterm) { 406 logit("Exiting on signal %d", (int)received_sigterm); 407 /* Clean up sessions, utmp, etc. */ 408 cleanup_exit(254); 409 } 410 411 channel_after_poll(ssh, pfd, npfd_active); 412 if (conn_in_ready && 413 process_input(ssh, connection_in) < 0) 414 break; 415 /* A timeout may have triggered rekeying */ 416 if ((r = ssh_packet_check_rekey(ssh)) != 0) 417 fatal_fr(r, "cannot start rekeying"); 418 if (conn_out_ready) 419 process_output(ssh, connection_out); 420 } 421 collect_children(ssh); 422 free(pfd); 423 424 /* free all channels, no more reads and writes */ 425 channel_free_all(ssh); 426 427 /* free remaining sessions, e.g. remove wtmp entries */ 428 session_destroy_all(ssh, NULL); 429 total_time = get_current_time() - start_time; 430 logit("SSH: Server;LType: Throughput;Remote: %s-%d;IN: %lu;OUT: %lu;Duration: %.1f;tPut_in: %.1f;tPut_out: %.1f", 431 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), 432 stdin_bytes, fdout_bytes, total_time, stdin_bytes / total_time, 433 fdout_bytes / total_time); 434 } 435 436 static int 437 server_input_keep_alive(int type, u_int32_t seq, struct ssh *ssh) 438 { 439 debug("Got %d/%u for keepalive", type, seq); 440 /* 441 * reset timeout, since we got a sane answer from the client. 442 * even if this was generated by something other than 443 * the bogus CHANNEL_REQUEST we send for keepalives. 444 */ 445 ssh_packet_set_alive_timeouts(ssh, 0); 446 return 0; 447 } 448 449 static Channel * 450 server_request_direct_tcpip(struct ssh *ssh, int *reason, const char **errmsg) 451 { 452 Channel *c = NULL; 453 char *target = NULL, *originator = NULL; 454 u_int target_port = 0, originator_port = 0; 455 int r; 456 457 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 458 (r = sshpkt_get_u32(ssh, &target_port)) != 0 || 459 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 460 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 461 (r = sshpkt_get_end(ssh)) != 0) 462 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 463 if (target_port > 0xFFFF) { 464 error_f("invalid target port"); 465 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 466 goto out; 467 } 468 if (originator_port > 0xFFFF) { 469 error_f("invalid originator port"); 470 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 471 goto out; 472 } 473 474 debug_f("originator %s port %u, target %s port %u", 475 originator, originator_port, target, target_port); 476 477 /* XXX fine grained permissions */ 478 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 && 479 auth_opts->permit_port_forwarding_flag && 480 !options.disable_forwarding) { 481 c = channel_connect_to_port(ssh, target, target_port, 482 "direct-tcpip", "direct-tcpip", reason, errmsg); 483 } else { 484 logit("refused local port forward: " 485 "originator %s port %d, target %s port %d", 486 originator, originator_port, target, target_port); 487 if (reason != NULL) 488 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 489 } 490 491 out: 492 free(originator); 493 free(target); 494 return c; 495 } 496 497 static Channel * 498 server_request_direct_streamlocal(struct ssh *ssh) 499 { 500 Channel *c = NULL; 501 char *target = NULL, *originator = NULL; 502 u_int originator_port = 0; 503 struct passwd *pw = the_authctxt->pw; 504 int r; 505 506 if (pw == NULL || !the_authctxt->valid) 507 fatal_f("no/invalid user"); 508 509 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 510 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 511 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 512 (r = sshpkt_get_end(ssh)) != 0) 513 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 514 if (originator_port > 0xFFFF) { 515 error_f("invalid originator port"); 516 goto out; 517 } 518 519 debug_f("originator %s port %d, target %s", 520 originator, originator_port, target); 521 522 /* XXX fine grained permissions */ 523 if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 && 524 auth_opts->permit_port_forwarding_flag && 525 !options.disable_forwarding && (pw->pw_uid == 0 || use_privsep)) { 526 c = channel_connect_to_path(ssh, target, 527 "direct-streamlocal@openssh.com", "direct-streamlocal"); 528 } else { 529 logit("refused streamlocal port forward: " 530 "originator %s port %d, target %s", 531 originator, originator_port, target); 532 } 533 534 out: 535 free(originator); 536 free(target); 537 return c; 538 } 539 540 static Channel * 541 server_request_tun(struct ssh *ssh) 542 { 543 Channel *c = NULL; 544 u_int mode, tun; 545 int r, sock; 546 char *tmp, *ifname = NULL; 547 548 if ((r = sshpkt_get_u32(ssh, &mode)) != 0) 549 sshpkt_fatal(ssh, r, "%s: parse mode", __func__); 550 switch (mode) { 551 case SSH_TUNMODE_POINTOPOINT: 552 case SSH_TUNMODE_ETHERNET: 553 break; 554 default: 555 ssh_packet_send_debug(ssh, "Unsupported tunnel device mode."); 556 return NULL; 557 } 558 if ((options.permit_tun & mode) == 0) { 559 ssh_packet_send_debug(ssh, "Server has rejected tunnel device " 560 "forwarding"); 561 return NULL; 562 } 563 564 if ((r = sshpkt_get_u32(ssh, &tun)) != 0) 565 sshpkt_fatal(ssh, r, "%s: parse device", __func__); 566 if (tun > INT_MAX) { 567 debug_f("invalid tun"); 568 goto done; 569 } 570 if (auth_opts->force_tun_device != -1) { 571 if (tun != SSH_TUNID_ANY && 572 auth_opts->force_tun_device != (int)tun) 573 goto done; 574 tun = auth_opts->force_tun_device; 575 } 576 sock = tun_open(tun, mode, &ifname); 577 if (sock < 0) 578 goto done; 579 debug("Tunnel forwarding using interface %s", ifname); 580 581 if (options.hpn_disabled) 582 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1, 583 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 584 else 585 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1, 586 options.hpn_buffer_size, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 587 c->datagram = 1; 588 589 /* 590 * Update the list of names exposed to the session 591 * XXX remove these if the tunnels are closed (won't matter 592 * much if they are already in the environment though) 593 */ 594 tmp = tun_fwd_ifnames; 595 xasprintf(&tun_fwd_ifnames, "%s%s%s", 596 tun_fwd_ifnames == NULL ? "" : tun_fwd_ifnames, 597 tun_fwd_ifnames == NULL ? "" : ",", 598 ifname); 599 free(tmp); 600 free(ifname); 601 602 done: 603 if (c == NULL) 604 ssh_packet_send_debug(ssh, "Failed to open the tunnel device."); 605 return c; 606 } 607 608 static Channel * 609 server_request_session(struct ssh *ssh) 610 { 611 Channel *c; 612 int r; 613 614 debug("input_session_request"); 615 if ((r = sshpkt_get_end(ssh)) != 0) 616 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 617 618 if (no_more_sessions) { 619 ssh_packet_disconnect(ssh, "Possible attack: attempt to open a " 620 "session after additional sessions disabled"); 621 } 622 623 /* 624 * A server session has no fd to read or write until a 625 * CHANNEL_REQUEST for a shell is made, so we set the type to 626 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all 627 * CHANNEL_REQUEST messages is registered. 628 */ 629 c = channel_new(ssh, "session", SSH_CHANNEL_LARVAL, 630 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, 631 0, "server-session", 1); 632 if ((options.tcp_rcv_buf_poll > 0) && (!options.hpn_disabled)) 633 c->dynamic_window = 1; 634 if (session_open(the_authctxt, c->self) != 1) { 635 debug("session open failed, free channel %d", c->self); 636 channel_free(ssh, c); 637 return NULL; 638 } 639 channel_register_cleanup(ssh, c->self, session_close_by_channel, 0); 640 return c; 641 } 642 643 static int 644 server_input_channel_open(int type, u_int32_t seq, struct ssh *ssh) 645 { 646 Channel *c = NULL; 647 char *ctype = NULL; 648 const char *errmsg = NULL; 649 int r, reason = SSH2_OPEN_CONNECT_FAILED; 650 u_int rchan = 0, rmaxpack = 0, rwindow = 0; 651 652 if ((r = sshpkt_get_cstring(ssh, &ctype, NULL)) != 0 || 653 (r = sshpkt_get_u32(ssh, &rchan)) != 0 || 654 (r = sshpkt_get_u32(ssh, &rwindow)) != 0 || 655 (r = sshpkt_get_u32(ssh, &rmaxpack)) != 0) 656 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 657 debug_f("ctype %s rchan %u win %u max %u", 658 ctype, rchan, rwindow, rmaxpack); 659 660 if (strcmp(ctype, "session") == 0) { 661 c = server_request_session(ssh); 662 } else if (strcmp(ctype, "direct-tcpip") == 0) { 663 c = server_request_direct_tcpip(ssh, &reason, &errmsg); 664 } else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) { 665 c = server_request_direct_streamlocal(ssh); 666 } else if (strcmp(ctype, "tun@openssh.com") == 0) { 667 c = server_request_tun(ssh); 668 } 669 if (c != NULL) { 670 debug_f("confirm %s", ctype); 671 c->remote_id = rchan; 672 c->have_remote_id = 1; 673 c->remote_window = rwindow; 674 c->remote_maxpacket = rmaxpack; 675 if (c->type != SSH_CHANNEL_CONNECTING) { 676 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION)) != 0 || 677 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 678 (r = sshpkt_put_u32(ssh, c->self)) != 0 || 679 (r = sshpkt_put_u32(ssh, c->local_window)) != 0 || 680 (r = sshpkt_put_u32(ssh, c->local_maxpacket)) != 0 || 681 (r = sshpkt_send(ssh)) != 0) { 682 sshpkt_fatal(ssh, r, 683 "%s: send open confirm", __func__); 684 } 685 } 686 } else { 687 debug_f("failure %s", ctype); 688 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE)) != 0 || 689 (r = sshpkt_put_u32(ssh, rchan)) != 0 || 690 (r = sshpkt_put_u32(ssh, reason)) != 0 || 691 (r = sshpkt_put_cstring(ssh, errmsg ? errmsg : "open failed")) != 0 || 692 (r = sshpkt_put_cstring(ssh, "")) != 0 || 693 (r = sshpkt_send(ssh)) != 0) { 694 sshpkt_fatal(ssh, r, 695 "%s: send open failure", __func__); 696 } 697 } 698 free(ctype); 699 return 0; 700 } 701 702 static int 703 server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp) 704 { 705 struct sshbuf *resp = NULL; 706 struct sshbuf *sigbuf = NULL; 707 struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL; 708 int r, ndx, success = 0; 709 const u_char *blob; 710 const char *sigalg, *kex_rsa_sigalg = NULL; 711 u_char *sig = 0; 712 size_t blen, slen; 713 714 if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL) 715 fatal_f("sshbuf_new"); 716 if (sshkey_type_plain(sshkey_type_from_name( 717 ssh->kex->hostkey_alg)) == KEY_RSA) 718 kex_rsa_sigalg = ssh->kex->hostkey_alg; 719 while (ssh_packet_remaining(ssh) > 0) { 720 sshkey_free(key); 721 key = NULL; 722 if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 || 723 (r = sshkey_from_blob(blob, blen, &key)) != 0) { 724 error_fr(r, "parse key"); 725 goto out; 726 } 727 /* 728 * Better check that this is actually one of our hostkeys 729 * before attempting to sign anything with it. 730 */ 731 if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) { 732 error_f("unknown host %s key", sshkey_type(key)); 733 goto out; 734 } 735 /* 736 * XXX refactor: make kex->sign just use an index rather 737 * than passing in public and private keys 738 */ 739 if ((key_prv = get_hostkey_by_index(ndx)) == NULL && 740 (key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) { 741 error_f("can't retrieve hostkey %d", ndx); 742 goto out; 743 } 744 sshbuf_reset(sigbuf); 745 free(sig); 746 sig = NULL; 747 /* 748 * For RSA keys, prefer to use the signature type negotiated 749 * during KEX to the default (SHA1). 750 */ 751 sigalg = NULL; 752 if (sshkey_type_plain(key->type) == KEY_RSA) { 753 if (kex_rsa_sigalg != NULL) 754 sigalg = kex_rsa_sigalg; 755 else if (ssh->kex->flags & KEX_RSA_SHA2_512_SUPPORTED) 756 sigalg = "rsa-sha2-512"; 757 else if (ssh->kex->flags & KEX_RSA_SHA2_256_SUPPORTED) 758 sigalg = "rsa-sha2-256"; 759 } 760 debug3_f("sign %s key (index %d) using sigalg %s", 761 sshkey_type(key), ndx, sigalg == NULL ? "default" : sigalg); 762 if ((r = sshbuf_put_cstring(sigbuf, 763 "hostkeys-prove-00@openssh.com")) != 0 || 764 (r = sshbuf_put_stringb(sigbuf, 765 ssh->kex->session_id)) != 0 || 766 (r = sshkey_puts(key, sigbuf)) != 0 || 767 (r = ssh->kex->sign(ssh, key_prv, key_pub, &sig, &slen, 768 sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), sigalg)) != 0 || 769 (r = sshbuf_put_string(resp, sig, slen)) != 0) { 770 error_fr(r, "assemble signature"); 771 goto out; 772 } 773 } 774 /* Success */ 775 *respp = resp; 776 resp = NULL; /* don't free it */ 777 success = 1; 778 out: 779 free(sig); 780 sshbuf_free(resp); 781 sshbuf_free(sigbuf); 782 sshkey_free(key); 783 return success; 784 } 785 786 static int 787 server_input_global_request(int type, u_int32_t seq, struct ssh *ssh) 788 { 789 char *rtype = NULL; 790 u_char want_reply = 0; 791 int r, success = 0, allocated_listen_port = 0; 792 u_int port = 0; 793 struct sshbuf *resp = NULL; 794 struct passwd *pw = the_authctxt->pw; 795 struct Forward fwd; 796 797 memset(&fwd, 0, sizeof(fwd)); 798 if (pw == NULL || !the_authctxt->valid) 799 fatal_f("no/invalid user"); 800 801 if ((r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 802 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 803 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 804 debug_f("rtype %s want_reply %d", rtype, want_reply); 805 806 /* -R style forwarding */ 807 if (strcmp(rtype, "tcpip-forward") == 0) { 808 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 809 (r = sshpkt_get_u32(ssh, &port)) != 0) 810 sshpkt_fatal(ssh, r, "%s: parse tcpip-forward", __func__); 811 debug_f("tcpip-forward listen %s port %u", 812 fwd.listen_host, port); 813 if (port <= INT_MAX) 814 fwd.listen_port = (int)port; 815 /* check permissions */ 816 if (port > INT_MAX || 817 (options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 || 818 !auth_opts->permit_port_forwarding_flag || 819 options.disable_forwarding || 820 (!want_reply && fwd.listen_port == 0) || 821 (fwd.listen_port != 0 && 822 !bind_permitted(fwd.listen_port, pw->pw_uid))) { 823 success = 0; 824 ssh_packet_send_debug(ssh, "Server has disabled port forwarding."); 825 } else { 826 /* Start listening on the port */ 827 success = channel_setup_remote_fwd_listener(ssh, &fwd, 828 &allocated_listen_port, &options.fwd_opts); 829 } 830 if ((resp = sshbuf_new()) == NULL) 831 fatal_f("sshbuf_new"); 832 if (allocated_listen_port != 0 && 833 (r = sshbuf_put_u32(resp, allocated_listen_port)) != 0) 834 fatal_fr(r, "sshbuf_put_u32"); 835 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) { 836 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 837 (r = sshpkt_get_u32(ssh, &port)) != 0) 838 sshpkt_fatal(ssh, r, "%s: parse cancel-tcpip-forward", __func__); 839 840 debug_f("cancel-tcpip-forward addr %s port %d", 841 fwd.listen_host, port); 842 if (port <= INT_MAX) { 843 fwd.listen_port = (int)port; 844 success = channel_cancel_rport_listener(ssh, &fwd); 845 } 846 } else if (strcmp(rtype, "streamlocal-forward@openssh.com") == 0) { 847 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 848 sshpkt_fatal(ssh, r, "%s: parse streamlocal-forward@openssh.com", __func__); 849 debug_f("streamlocal-forward listen path %s", 850 fwd.listen_path); 851 852 /* check permissions */ 853 if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0 854 || !auth_opts->permit_port_forwarding_flag || 855 options.disable_forwarding || 856 (pw->pw_uid != 0 && !use_privsep)) { 857 success = 0; 858 ssh_packet_send_debug(ssh, "Server has disabled " 859 "streamlocal forwarding."); 860 } else { 861 /* Start listening on the socket */ 862 success = channel_setup_remote_fwd_listener(ssh, 863 &fwd, NULL, &options.fwd_opts); 864 } 865 } else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) { 866 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 867 sshpkt_fatal(ssh, r, "%s: parse cancel-streamlocal-forward@openssh.com", __func__); 868 debug_f("cancel-streamlocal-forward path %s", 869 fwd.listen_path); 870 871 success = channel_cancel_rport_listener(ssh, &fwd); 872 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) { 873 no_more_sessions = 1; 874 success = 1; 875 } else if (strcmp(rtype, "hostkeys-prove-00@openssh.com") == 0) { 876 success = server_input_hostkeys_prove(ssh, &resp); 877 } 878 /* XXX sshpkt_get_end() */ 879 if (want_reply) { 880 if ((r = sshpkt_start(ssh, success ? 881 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE)) != 0 || 882 (success && resp != NULL && (r = sshpkt_putb(ssh, resp)) != 0) || 883 (r = sshpkt_send(ssh)) != 0 || 884 (r = ssh_packet_write_wait(ssh)) < 0) 885 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 886 } 887 free(fwd.listen_host); 888 free(fwd.listen_path); 889 free(rtype); 890 sshbuf_free(resp); 891 return 0; 892 } 893 894 static int 895 server_input_channel_req(int type, u_int32_t seq, struct ssh *ssh) 896 { 897 Channel *c; 898 int r, success = 0; 899 char *rtype = NULL; 900 u_char want_reply = 0; 901 u_int id = 0; 902 903 if ((r = sshpkt_get_u32(ssh, &id)) != 0 || 904 (r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 905 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 906 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 907 908 debug("server_input_channel_req: channel %u request %s reply %d", 909 id, rtype, want_reply); 910 911 if (id >= INT_MAX || (c = channel_lookup(ssh, (int)id)) == NULL) { 912 ssh_packet_disconnect(ssh, "%s: unknown channel %d", 913 __func__, id); 914 } 915 if (!strcmp(rtype, "eow@openssh.com")) { 916 if ((r = sshpkt_get_end(ssh)) != 0) 917 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 918 chan_rcvd_eow(ssh, c); 919 } else if ((c->type == SSH_CHANNEL_LARVAL || 920 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0) 921 success = session_input_channel_req(ssh, c, rtype); 922 if (want_reply && !(c->flags & CHAN_CLOSE_SENT)) { 923 if (!c->have_remote_id) 924 fatal_f("channel %d: no remote_id", c->self); 925 if ((r = sshpkt_start(ssh, success ? 926 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE)) != 0 || 927 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 928 (r = sshpkt_send(ssh)) != 0) 929 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 930 } 931 free(rtype); 932 return 0; 933 } 934 935 static void 936 server_init_dispatch(struct ssh *ssh) 937 { 938 debug("server_init_dispatch"); 939 ssh_dispatch_init(ssh, &dispatch_protocol_error); 940 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); 941 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_DATA, &channel_input_data); 942 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); 943 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); 944 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); 945 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 946 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 947 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); 948 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); 949 ssh_dispatch_set(ssh, SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); 950 /* client_alive */ 951 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive); 952 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); 953 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); 954 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); 955 /* rekeying */ 956 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit); 957 } 958