1 /* $OpenBSD: serverloop.c,v 1.241 2024/11/26 22:01:37 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 "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 84 static int no_more_sessions = 0; /* Disallow further sessions. */ 85 86 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */ 87 88 /* prototypes */ 89 static void server_init_dispatch(struct ssh *); 90 91 /* requested tunnel forwarding interface(s), shared with session.c */ 92 char *tun_fwd_ifnames = NULL; 93 94 static void 95 sigchld_handler(int sig) 96 { 97 child_terminated = 1; 98 } 99 100 static void 101 client_alive_check(struct ssh *ssh) 102 { 103 char remote_id[512]; 104 int r, channel_id; 105 106 /* timeout, check to see how many we have had */ 107 if (options.client_alive_count_max > 0 && 108 ssh_packet_inc_alive_timeouts(ssh) > 109 options.client_alive_count_max) { 110 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id)); 111 logit("Timeout, client not responding from %s", remote_id); 112 cleanup_exit(255); 113 } 114 115 /* 116 * send a bogus global/channel request with "wantreply", 117 * we should get back a failure 118 */ 119 if ((channel_id = channel_find_open(ssh)) == -1) { 120 if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 || 121 (r = sshpkt_put_cstring(ssh, "keepalive@openssh.com")) 122 != 0 || 123 (r = sshpkt_put_u8(ssh, 1)) != 0) /* boolean: want reply */ 124 fatal_fr(r, "compose"); 125 } else { 126 channel_request_start(ssh, channel_id, 127 "keepalive@openssh.com", 1); 128 } 129 if ((r = sshpkt_send(ssh)) != 0) 130 fatal_fr(r, "send"); 131 } 132 133 /* 134 * Sleep in ppoll() until we can do something. 135 * Optionally, a maximum time can be specified for the duration of 136 * the wait (0 = infinite). 137 */ 138 static void 139 wait_until_can_do_something(struct ssh *ssh, 140 int connection_in, int connection_out, struct pollfd **pfdp, 141 u_int *npfd_allocp, u_int *npfd_activep, sigset_t *sigsetp, 142 int *conn_in_readyp, int *conn_out_readyp) 143 { 144 struct timespec timeout; 145 char remote_id[512]; 146 int ret; 147 int client_alive_scheduled = 0; 148 u_int p; 149 time_t now; 150 static time_t last_client_time, unused_connection_expiry; 151 152 *conn_in_readyp = *conn_out_readyp = 0; 153 154 /* Prepare channel poll. First two pollfd entries are reserved */ 155 ptimeout_init(&timeout); 156 channel_prepare_poll(ssh, pfdp, npfd_allocp, npfd_activep, 2, &timeout); 157 now = monotime(); 158 if (*npfd_activep < 2) 159 fatal_f("bad npfd %u", *npfd_activep); /* shouldn't happen */ 160 if (options.rekey_interval > 0 && !ssh_packet_is_rekeying(ssh)) { 161 ptimeout_deadline_sec(&timeout, 162 ssh_packet_get_rekey_timeout(ssh)); 163 } 164 165 /* 166 * If no channels are open and UnusedConnectionTimeout is set, then 167 * start the clock to terminate the connection. 168 */ 169 if (options.unused_connection_timeout != 0) { 170 if (channel_still_open(ssh) || unused_connection_expiry == 0) { 171 unused_connection_expiry = now + 172 options.unused_connection_timeout; 173 } 174 ptimeout_deadline_monotime(&timeout, unused_connection_expiry); 175 } 176 177 /* 178 * if using client_alive, set the max timeout accordingly, 179 * and indicate that this particular timeout was for client 180 * alive by setting the client_alive_scheduled flag. 181 * 182 * this could be randomized somewhat to make traffic 183 * analysis more difficult, but we're not doing it yet. 184 */ 185 if (options.client_alive_interval) { 186 /* Time we last heard from the client OR sent a keepalive */ 187 if (last_client_time == 0) 188 last_client_time = now; 189 ptimeout_deadline_sec(&timeout, options.client_alive_interval); 190 /* XXX ? deadline_monotime(last_client_time + alive_interval) */ 191 client_alive_scheduled = 1; 192 } 193 194 #if 0 195 /* wrong: bad condition XXX */ 196 if (channel_not_very_much_buffered_data()) 197 #endif 198 /* Monitor client connection on reserved pollfd entries */ 199 (*pfdp)[0].fd = connection_in; 200 (*pfdp)[0].events = POLLIN; 201 (*pfdp)[1].fd = connection_out; 202 (*pfdp)[1].events = ssh_packet_have_data_to_write(ssh) ? POLLOUT : 0; 203 204 /* 205 * If child has terminated and there is enough buffer space to read 206 * from it, then read as much as is available and exit. 207 */ 208 if (child_terminated && ssh_packet_not_very_much_data_to_write(ssh)) 209 ptimeout_deadline_ms(&timeout, 100); 210 211 /* Wait for something to happen, or the timeout to expire. */ 212 ret = ppoll(*pfdp, *npfd_activep, ptimeout_get_tsp(&timeout), sigsetp); 213 214 if (ret == -1) { 215 for (p = 0; p < *npfd_activep; p++) 216 (*pfdp)[p].revents = 0; 217 if (errno != EINTR) 218 fatal_f("ppoll: %.100s", strerror(errno)); 219 return; 220 } 221 222 *conn_in_readyp = (*pfdp)[0].revents != 0; 223 *conn_out_readyp = (*pfdp)[1].revents != 0; 224 225 now = monotime(); /* need to reset after ppoll() */ 226 /* ClientAliveInterval probing */ 227 if (client_alive_scheduled) { 228 if (ret == 0 && 229 now >= last_client_time + options.client_alive_interval) { 230 /* ppoll timed out and we're due to probe */ 231 client_alive_check(ssh); 232 last_client_time = now; 233 } else if (ret != 0 && *conn_in_readyp) { 234 /* Data from peer; reset probe timer. */ 235 last_client_time = now; 236 } 237 } 238 239 /* UnusedConnectionTimeout handling */ 240 if (unused_connection_expiry != 0 && 241 now > unused_connection_expiry && !channel_still_open(ssh)) { 242 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id)); 243 logit("terminating inactive connection from %s", remote_id); 244 cleanup_exit(255); 245 } 246 } 247 248 /* 249 * Processes input from the client and the program. Input data is stored 250 * in buffers and processed later. 251 */ 252 static int 253 process_input(struct ssh *ssh, int connection_in) 254 { 255 int r; 256 257 if ((r = ssh_packet_process_read(ssh, connection_in)) == 0) 258 return 0; /* success */ 259 if (r == SSH_ERR_SYSTEM_ERROR) { 260 if (errno == EAGAIN || errno == EINTR) 261 return 0; 262 if (errno == EPIPE) { 263 logit("Connection closed by %.100s port %d", 264 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 265 return -1; 266 } 267 logit("Read error from remote host %s port %d: %s", 268 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), 269 strerror(errno)); 270 cleanup_exit(255); 271 } 272 return -1; 273 } 274 275 /* 276 * Sends data from internal buffers to client program stdin. 277 */ 278 static void 279 process_output(struct ssh *ssh, int connection_out) 280 { 281 int r; 282 283 /* Send any buffered packet data to the client. */ 284 if ((r = ssh_packet_write_poll(ssh)) != 0) { 285 sshpkt_fatal(ssh, r, "%s: ssh_packet_write_poll", 286 __func__); 287 } 288 } 289 290 static void 291 process_buffered_input_packets(struct ssh *ssh) 292 { 293 ssh_dispatch_run_fatal(ssh, DISPATCH_NONBLOCK, NULL); 294 } 295 296 static void 297 collect_children(struct ssh *ssh) 298 { 299 pid_t pid; 300 int status; 301 302 if (child_terminated) { 303 debug("Received SIGCHLD."); 304 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 305 (pid == -1 && errno == EINTR)) 306 if (pid > 0) 307 session_close_by_pid(ssh, pid, status); 308 child_terminated = 0; 309 } 310 } 311 312 void 313 server_loop2(struct ssh *ssh, Authctxt *authctxt) 314 { 315 struct pollfd *pfd = NULL; 316 u_int npfd_alloc = 0, npfd_active = 0; 317 int r, conn_in_ready, conn_out_ready; 318 u_int connection_in, connection_out; 319 sigset_t bsigset, osigset; 320 321 debug("Entering interactive session for SSH2."); 322 323 if (sigemptyset(&bsigset) == -1 || sigaddset(&bsigset, SIGCHLD) == -1) 324 error_f("bsigset setup: %s", strerror(errno)); 325 ssh_signal(SIGCHLD, sigchld_handler); 326 child_terminated = 0; 327 connection_in = ssh_packet_get_connection_in(ssh); 328 connection_out = ssh_packet_get_connection_out(ssh); 329 330 server_init_dispatch(ssh); 331 332 for (;;) { 333 process_buffered_input_packets(ssh); 334 335 if (!ssh_packet_is_rekeying(ssh) && 336 ssh_packet_not_very_much_data_to_write(ssh)) 337 channel_output_poll(ssh); 338 339 /* 340 * Block SIGCHLD while we check for dead children, then pass 341 * the old signal mask through to ppoll() so that it'll wake 342 * up immediately if a child exits after we've called waitpid(). 343 */ 344 if (sigprocmask(SIG_BLOCK, &bsigset, &osigset) == -1) 345 error_f("bsigset sigprocmask: %s", strerror(errno)); 346 collect_children(ssh); 347 wait_until_can_do_something(ssh, connection_in, connection_out, 348 &pfd, &npfd_alloc, &npfd_active, &osigset, 349 &conn_in_ready, &conn_out_ready); 350 if (sigprocmask(SIG_SETMASK, &osigset, NULL) == -1) 351 error_f("osigset sigprocmask: %s", strerror(errno)); 352 353 channel_after_poll(ssh, pfd, npfd_active); 354 if (conn_in_ready && 355 process_input(ssh, connection_in) < 0) 356 break; 357 /* A timeout may have triggered rekeying */ 358 if ((r = ssh_packet_check_rekey(ssh)) != 0) 359 fatal_fr(r, "cannot start rekeying"); 360 if (conn_out_ready) 361 process_output(ssh, connection_out); 362 } 363 collect_children(ssh); 364 free(pfd); 365 366 /* free all channels, no more reads and writes */ 367 channel_free_all(ssh); 368 369 /* free remaining sessions, e.g. remove wtmp entries */ 370 session_destroy_all(ssh, NULL); 371 } 372 373 static int 374 server_input_keep_alive(int type, u_int32_t seq, struct ssh *ssh) 375 { 376 debug("Got %d/%u for keepalive", type, seq); 377 /* 378 * reset timeout, since we got a sane answer from the client. 379 * even if this was generated by something other than 380 * the bogus CHANNEL_REQUEST we send for keepalives. 381 */ 382 ssh_packet_set_alive_timeouts(ssh, 0); 383 return 0; 384 } 385 386 static Channel * 387 server_request_direct_tcpip(struct ssh *ssh, int *reason, const char **errmsg) 388 { 389 Channel *c = NULL; 390 char *target = NULL, *originator = NULL; 391 u_int target_port = 0, originator_port = 0; 392 int r; 393 394 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 395 (r = sshpkt_get_u32(ssh, &target_port)) != 0 || 396 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 397 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 398 (r = sshpkt_get_end(ssh)) != 0) 399 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 400 if (target_port > 0xFFFF) { 401 error_f("invalid target port"); 402 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 403 goto out; 404 } 405 if (originator_port > 0xFFFF) { 406 error_f("invalid originator port"); 407 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 408 goto out; 409 } 410 411 debug_f("originator %s port %u, target %s port %u", 412 originator, originator_port, target, target_port); 413 414 /* XXX fine grained permissions */ 415 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 && 416 auth_opts->permit_port_forwarding_flag && 417 !options.disable_forwarding) { 418 c = channel_connect_to_port(ssh, target, target_port, 419 "direct-tcpip", "direct-tcpip", reason, errmsg); 420 } else { 421 logit("refused local port forward: " 422 "originator %s port %d, target %s port %d", 423 originator, originator_port, target, target_port); 424 if (reason != NULL) 425 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 426 } 427 428 out: 429 free(originator); 430 free(target); 431 return c; 432 } 433 434 static Channel * 435 server_request_direct_streamlocal(struct ssh *ssh) 436 { 437 Channel *c = NULL; 438 char *target = NULL, *originator = NULL; 439 u_int originator_port = 0; 440 struct passwd *pw = the_authctxt->pw; 441 int r; 442 443 if (pw == NULL || !the_authctxt->valid) 444 fatal_f("no/invalid user"); 445 446 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 447 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 448 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 449 (r = sshpkt_get_end(ssh)) != 0) 450 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 451 if (originator_port > 0xFFFF) { 452 error_f("invalid originator port"); 453 goto out; 454 } 455 456 debug_f("originator %s port %d, target %s", 457 originator, originator_port, target); 458 459 /* XXX fine grained permissions */ 460 if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 && 461 auth_opts->permit_port_forwarding_flag && 462 !options.disable_forwarding) { 463 c = channel_connect_to_path(ssh, target, 464 "direct-streamlocal@openssh.com", "direct-streamlocal"); 465 } else { 466 logit("refused streamlocal port forward: " 467 "originator %s port %d, target %s", 468 originator, originator_port, target); 469 } 470 471 out: 472 free(originator); 473 free(target); 474 return c; 475 } 476 477 static Channel * 478 server_request_tun(struct ssh *ssh) 479 { 480 Channel *c = NULL; 481 u_int mode, tun; 482 int r, sock; 483 char *tmp, *ifname = NULL; 484 485 if ((r = sshpkt_get_u32(ssh, &mode)) != 0) 486 sshpkt_fatal(ssh, r, "%s: parse mode", __func__); 487 switch (mode) { 488 case SSH_TUNMODE_POINTOPOINT: 489 case SSH_TUNMODE_ETHERNET: 490 break; 491 default: 492 ssh_packet_send_debug(ssh, "Unsupported tunnel device mode."); 493 return NULL; 494 } 495 if ((options.permit_tun & mode) == 0) { 496 ssh_packet_send_debug(ssh, "Server has rejected tunnel device " 497 "forwarding"); 498 return NULL; 499 } 500 501 if ((r = sshpkt_get_u32(ssh, &tun)) != 0) 502 sshpkt_fatal(ssh, r, "%s: parse device", __func__); 503 if (tun > INT_MAX) { 504 debug_f("invalid tun"); 505 goto done; 506 } 507 if (auth_opts->force_tun_device != -1) { 508 if (tun != SSH_TUNID_ANY && 509 auth_opts->force_tun_device != (int)tun) 510 goto done; 511 tun = auth_opts->force_tun_device; 512 } 513 sock = tun_open(tun, mode, &ifname); 514 if (sock < 0) 515 goto done; 516 debug("Tunnel forwarding using interface %s", ifname); 517 518 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1, 519 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 520 c->datagram = 1; 521 522 /* 523 * Update the list of names exposed to the session 524 * XXX remove these if the tunnels are closed (won't matter 525 * much if they are already in the environment though) 526 */ 527 tmp = tun_fwd_ifnames; 528 xasprintf(&tun_fwd_ifnames, "%s%s%s", 529 tun_fwd_ifnames == NULL ? "" : tun_fwd_ifnames, 530 tun_fwd_ifnames == NULL ? "" : ",", 531 ifname); 532 free(tmp); 533 free(ifname); 534 535 done: 536 if (c == NULL) 537 ssh_packet_send_debug(ssh, "Failed to open the tunnel device."); 538 return c; 539 } 540 541 static Channel * 542 server_request_session(struct ssh *ssh) 543 { 544 Channel *c; 545 int r; 546 547 debug("input_session_request"); 548 if ((r = sshpkt_get_end(ssh)) != 0) 549 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 550 551 if (no_more_sessions) { 552 ssh_packet_disconnect(ssh, "Possible attack: attempt to open a " 553 "session after additional sessions disabled"); 554 } 555 556 /* 557 * A server session has no fd to read or write until a 558 * CHANNEL_REQUEST for a shell is made, so we set the type to 559 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all 560 * CHANNEL_REQUEST messages is registered. 561 */ 562 c = channel_new(ssh, "session", SSH_CHANNEL_LARVAL, 563 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, 564 0, "server-session", 1); 565 if (session_open(the_authctxt, c->self) != 1) { 566 debug("session open failed, free channel %d", c->self); 567 channel_free(ssh, c); 568 return NULL; 569 } 570 channel_register_cleanup(ssh, c->self, session_close_by_channel, 0); 571 return c; 572 } 573 574 static int 575 server_input_channel_open(int type, u_int32_t seq, struct ssh *ssh) 576 { 577 Channel *c = NULL; 578 char *ctype = NULL; 579 const char *errmsg = NULL; 580 int r, reason = SSH2_OPEN_CONNECT_FAILED; 581 u_int rchan = 0, rmaxpack = 0, rwindow = 0; 582 583 if ((r = sshpkt_get_cstring(ssh, &ctype, NULL)) != 0 || 584 (r = sshpkt_get_u32(ssh, &rchan)) != 0 || 585 (r = sshpkt_get_u32(ssh, &rwindow)) != 0 || 586 (r = sshpkt_get_u32(ssh, &rmaxpack)) != 0) 587 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 588 debug_f("ctype %s rchan %u win %u max %u", 589 ctype, rchan, rwindow, rmaxpack); 590 591 if (strcmp(ctype, "session") == 0) { 592 c = server_request_session(ssh); 593 } else if (strcmp(ctype, "direct-tcpip") == 0) { 594 c = server_request_direct_tcpip(ssh, &reason, &errmsg); 595 } else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) { 596 c = server_request_direct_streamlocal(ssh); 597 } else if (strcmp(ctype, "tun@openssh.com") == 0) { 598 c = server_request_tun(ssh); 599 } 600 if (c != NULL) { 601 debug_f("confirm %s", ctype); 602 c->remote_id = rchan; 603 c->have_remote_id = 1; 604 c->remote_window = rwindow; 605 c->remote_maxpacket = rmaxpack; 606 if (c->type != SSH_CHANNEL_CONNECTING) { 607 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION)) != 0 || 608 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 609 (r = sshpkt_put_u32(ssh, c->self)) != 0 || 610 (r = sshpkt_put_u32(ssh, c->local_window)) != 0 || 611 (r = sshpkt_put_u32(ssh, c->local_maxpacket)) != 0 || 612 (r = sshpkt_send(ssh)) != 0) { 613 sshpkt_fatal(ssh, r, 614 "%s: send open confirm", __func__); 615 } 616 } 617 } else { 618 debug_f("failure %s", ctype); 619 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE)) != 0 || 620 (r = sshpkt_put_u32(ssh, rchan)) != 0 || 621 (r = sshpkt_put_u32(ssh, reason)) != 0 || 622 (r = sshpkt_put_cstring(ssh, errmsg ? errmsg : "open failed")) != 0 || 623 (r = sshpkt_put_cstring(ssh, "")) != 0 || 624 (r = sshpkt_send(ssh)) != 0) { 625 sshpkt_fatal(ssh, r, 626 "%s: send open failure", __func__); 627 } 628 } 629 free(ctype); 630 return 0; 631 } 632 633 static int 634 server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp) 635 { 636 struct sshbuf *resp = NULL; 637 struct sshbuf *sigbuf = NULL; 638 struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL; 639 int r, ndx, success = 0; 640 const u_char *blob; 641 const char *sigalg, *kex_rsa_sigalg = NULL; 642 u_char *sig = 0; 643 size_t blen, slen; 644 645 if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL) 646 fatal_f("sshbuf_new"); 647 if (sshkey_type_plain(sshkey_type_from_name( 648 ssh->kex->hostkey_alg)) == KEY_RSA) 649 kex_rsa_sigalg = ssh->kex->hostkey_alg; 650 while (ssh_packet_remaining(ssh) > 0) { 651 sshkey_free(key); 652 key = NULL; 653 if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 || 654 (r = sshkey_from_blob(blob, blen, &key)) != 0) { 655 error_fr(r, "parse key"); 656 goto out; 657 } 658 /* 659 * Better check that this is actually one of our hostkeys 660 * before attempting to sign anything with it. 661 */ 662 if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) { 663 error_f("unknown host %s key", sshkey_type(key)); 664 goto out; 665 } 666 /* 667 * XXX refactor: make kex->sign just use an index rather 668 * than passing in public and private keys 669 */ 670 if ((key_prv = get_hostkey_by_index(ndx)) == NULL && 671 (key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) { 672 error_f("can't retrieve hostkey %d", ndx); 673 goto out; 674 } 675 sshbuf_reset(sigbuf); 676 free(sig); 677 sig = NULL; 678 /* 679 * For RSA keys, prefer to use the signature type negotiated 680 * during KEX to the default (SHA1). 681 */ 682 sigalg = sshkey_ssh_name(key); 683 if (sshkey_type_plain(key->type) == KEY_RSA) { 684 if (kex_rsa_sigalg != NULL) 685 sigalg = kex_rsa_sigalg; 686 else if (ssh->kex->flags & KEX_RSA_SHA2_512_SUPPORTED) 687 sigalg = "rsa-sha2-512"; 688 else if (ssh->kex->flags & KEX_RSA_SHA2_256_SUPPORTED) 689 sigalg = "rsa-sha2-256"; 690 } 691 692 debug3_f("sign %s key (index %d) using sigalg %s", 693 sshkey_type(key), ndx, sigalg == NULL ? "default" : sigalg); 694 if ((r = sshbuf_put_cstring(sigbuf, 695 "hostkeys-prove-00@openssh.com")) != 0 || 696 (r = sshbuf_put_stringb(sigbuf, 697 ssh->kex->session_id)) != 0 || 698 (r = sshkey_puts(key, sigbuf)) != 0 || 699 (r = ssh->kex->sign(ssh, key_prv, key_pub, &sig, &slen, 700 sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), sigalg)) != 0 || 701 (r = sshbuf_put_string(resp, sig, slen)) != 0) { 702 error_fr(r, "assemble signature"); 703 goto out; 704 } 705 } 706 /* Success */ 707 *respp = resp; 708 resp = NULL; /* don't free it */ 709 success = 1; 710 out: 711 free(sig); 712 sshbuf_free(resp); 713 sshbuf_free(sigbuf); 714 sshkey_free(key); 715 return success; 716 } 717 718 static int 719 server_input_global_request(int type, u_int32_t seq, struct ssh *ssh) 720 { 721 char *rtype = NULL; 722 u_char want_reply = 0; 723 int r, success = 0, allocated_listen_port = 0; 724 u_int port = 0; 725 struct sshbuf *resp = NULL; 726 struct passwd *pw = the_authctxt->pw; 727 struct Forward fwd; 728 729 memset(&fwd, 0, sizeof(fwd)); 730 if (pw == NULL || !the_authctxt->valid) 731 fatal_f("no/invalid user"); 732 733 if ((r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 734 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 735 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 736 debug_f("rtype %s want_reply %d", rtype, want_reply); 737 738 /* -R style forwarding */ 739 if (strcmp(rtype, "tcpip-forward") == 0) { 740 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 741 (r = sshpkt_get_u32(ssh, &port)) != 0) 742 sshpkt_fatal(ssh, r, "%s: parse tcpip-forward", __func__); 743 debug_f("tcpip-forward listen %s port %u", 744 fwd.listen_host, port); 745 if (port <= INT_MAX) 746 fwd.listen_port = (int)port; 747 /* check permissions */ 748 if (port > INT_MAX || 749 (options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 || 750 !auth_opts->permit_port_forwarding_flag || 751 options.disable_forwarding || 752 (!want_reply && fwd.listen_port == 0)) { 753 success = 0; 754 ssh_packet_send_debug(ssh, "Server has disabled port forwarding."); 755 } else { 756 /* Start listening on the port */ 757 success = channel_setup_remote_fwd_listener(ssh, &fwd, 758 &allocated_listen_port, &options.fwd_opts); 759 } 760 if ((resp = sshbuf_new()) == NULL) 761 fatal_f("sshbuf_new"); 762 if (allocated_listen_port != 0 && 763 (r = sshbuf_put_u32(resp, allocated_listen_port)) != 0) 764 fatal_fr(r, "sshbuf_put_u32"); 765 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) { 766 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 767 (r = sshpkt_get_u32(ssh, &port)) != 0) 768 sshpkt_fatal(ssh, r, "%s: parse cancel-tcpip-forward", __func__); 769 770 debug_f("cancel-tcpip-forward addr %s port %d", 771 fwd.listen_host, port); 772 if (port <= INT_MAX) { 773 fwd.listen_port = (int)port; 774 success = channel_cancel_rport_listener(ssh, &fwd); 775 } 776 } else if (strcmp(rtype, "streamlocal-forward@openssh.com") == 0) { 777 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 778 sshpkt_fatal(ssh, r, "%s: parse streamlocal-forward@openssh.com", __func__); 779 debug_f("streamlocal-forward listen path %s", 780 fwd.listen_path); 781 782 /* check permissions */ 783 if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0 784 || !auth_opts->permit_port_forwarding_flag || 785 options.disable_forwarding) { 786 success = 0; 787 ssh_packet_send_debug(ssh, "Server has disabled " 788 "streamlocal forwarding."); 789 } else { 790 /* Start listening on the socket */ 791 success = channel_setup_remote_fwd_listener(ssh, 792 &fwd, NULL, &options.fwd_opts); 793 } 794 } else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) { 795 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 796 sshpkt_fatal(ssh, r, "%s: parse cancel-streamlocal-forward@openssh.com", __func__); 797 debug_f("cancel-streamlocal-forward path %s", 798 fwd.listen_path); 799 800 success = channel_cancel_rport_listener(ssh, &fwd); 801 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) { 802 no_more_sessions = 1; 803 success = 1; 804 } else if (strcmp(rtype, "hostkeys-prove-00@openssh.com") == 0) { 805 success = server_input_hostkeys_prove(ssh, &resp); 806 } 807 /* XXX sshpkt_get_end() */ 808 if (want_reply) { 809 if ((r = sshpkt_start(ssh, success ? 810 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE)) != 0 || 811 (success && resp != NULL && (r = sshpkt_putb(ssh, resp)) != 0) || 812 (r = sshpkt_send(ssh)) != 0 || 813 (r = ssh_packet_write_wait(ssh)) != 0) 814 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 815 } 816 free(fwd.listen_host); 817 free(fwd.listen_path); 818 free(rtype); 819 sshbuf_free(resp); 820 return 0; 821 } 822 823 static int 824 server_input_channel_req(int type, u_int32_t seq, struct ssh *ssh) 825 { 826 Channel *c; 827 int r, success = 0; 828 char *rtype = NULL; 829 u_char want_reply = 0; 830 u_int id = 0; 831 832 if ((r = sshpkt_get_u32(ssh, &id)) != 0 || 833 (r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 834 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 835 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 836 837 debug("server_input_channel_req: channel %u request %s reply %d", 838 id, rtype, want_reply); 839 840 if (id >= INT_MAX || (c = channel_lookup(ssh, (int)id)) == NULL) { 841 ssh_packet_disconnect(ssh, "%s: unknown channel %d", 842 __func__, id); 843 } 844 if (!strcmp(rtype, "eow@openssh.com")) { 845 if ((r = sshpkt_get_end(ssh)) != 0) 846 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 847 chan_rcvd_eow(ssh, c); 848 } else if ((c->type == SSH_CHANNEL_LARVAL || 849 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0) 850 success = session_input_channel_req(ssh, c, rtype); 851 if (want_reply && !(c->flags & CHAN_CLOSE_SENT)) { 852 if (!c->have_remote_id) 853 fatal_f("channel %d: no remote_id", c->self); 854 if ((r = sshpkt_start(ssh, success ? 855 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE)) != 0 || 856 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 857 (r = sshpkt_send(ssh)) != 0) 858 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 859 } 860 free(rtype); 861 return 0; 862 } 863 864 static void 865 server_init_dispatch(struct ssh *ssh) 866 { 867 debug("server_init_dispatch"); 868 ssh_dispatch_init(ssh, &dispatch_protocol_error); 869 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); 870 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_DATA, &channel_input_data); 871 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); 872 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); 873 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); 874 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 875 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 876 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); 877 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); 878 ssh_dispatch_set(ssh, SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); 879 /* client_alive */ 880 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive); 881 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); 882 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); 883 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); 884 /* rekeying */ 885 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit); 886 } 887