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