1 /* $NetBSD: serverloop.c,v 1.36 2024/07/08 22:33:44 christos Exp $ */ 2 /* $OpenBSD: serverloop.c,v 1.240 2024/06/17 08:28:31 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 1.36 2024/07/08 22:33:44 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 93 static int no_more_sessions = 0; /* Disallow further sessions. */ 94 95 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */ 96 97 /* prototypes */ 98 static void server_init_dispatch(struct ssh *); 99 100 /* requested tunnel forwarding interface(s), shared with session.c */ 101 char *tun_fwd_ifnames = NULL; 102 103 /* 104 * Returns current time in seconds from Jan 1, 1970 with the maximum 105 * available resolution. 106 */ 107 108 static double 109 get_current_time(void) 110 { 111 struct timeval tv; 112 gettimeofday(&tv, NULL); 113 return (double) tv.tv_sec + (double) tv.tv_usec / 1000000.0; 114 } 115 116 static void 117 sigchld_handler(int sig) 118 { 119 child_terminated = 1; 120 } 121 122 static void 123 client_alive_check(struct ssh *ssh) 124 { 125 char remote_id[512]; 126 int r, channel_id; 127 128 /* timeout, check to see how many we have had */ 129 if (options.client_alive_count_max > 0 && 130 ssh_packet_inc_alive_timeouts(ssh) > 131 options.client_alive_count_max) { 132 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id)); 133 logit("Timeout, client not responding from %s", remote_id); 134 cleanup_exit(255); 135 } 136 137 /* 138 * send a bogus global/channel request with "wantreply", 139 * we should get back a failure 140 */ 141 if ((channel_id = channel_find_open(ssh)) == -1) { 142 if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 || 143 (r = sshpkt_put_cstring(ssh, "keepalive@openssh.com")) 144 != 0 || 145 (r = sshpkt_put_u8(ssh, 1)) != 0) /* boolean: want reply */ 146 fatal_fr(r, "compose"); 147 } else { 148 channel_request_start(ssh, channel_id, 149 "keepalive@openssh.com", 1); 150 } 151 if ((r = sshpkt_send(ssh)) != 0) 152 fatal_fr(r, "send"); 153 } 154 155 /* 156 * Sleep in ppoll() until we can do something. 157 * Optionally, a maximum time can be specified for the duration of 158 * the wait (0 = infinite). 159 */ 160 static void 161 wait_until_can_do_something(struct ssh *ssh, 162 int connection_in, int connection_out, struct pollfd **pfdp, 163 u_int *npfd_allocp, u_int *npfd_activep, sigset_t *sigsetp, 164 int *conn_in_readyp, int *conn_out_readyp) 165 { 166 struct timespec timeout; 167 char remote_id[512]; 168 int ret; 169 int client_alive_scheduled = 0; 170 u_int p; 171 time_t now; 172 static time_t last_client_time, unused_connection_expiry; 173 174 *conn_in_readyp = *conn_out_readyp = 0; 175 176 /* Prepare channel poll. First two pollfd entries are reserved */ 177 ptimeout_init(&timeout); 178 channel_prepare_poll(ssh, pfdp, npfd_allocp, npfd_activep, 2, &timeout); 179 now = monotime(); 180 if (*npfd_activep < 2) 181 fatal_f("bad npfd %u", *npfd_activep); /* shouldn't happen */ 182 if (options.rekey_interval > 0 && !ssh_packet_is_rekeying(ssh)) { 183 ptimeout_deadline_sec(&timeout, 184 ssh_packet_get_rekey_timeout(ssh)); 185 } 186 187 /* 188 * If no channels are open and UnusedConnectionTimeout is set, then 189 * start the clock to terminate the connection. 190 */ 191 if (options.unused_connection_timeout != 0) { 192 if (channel_still_open(ssh) || unused_connection_expiry == 0) { 193 unused_connection_expiry = now + 194 options.unused_connection_timeout; 195 } 196 ptimeout_deadline_monotime(&timeout, unused_connection_expiry); 197 } 198 199 /* 200 * if using client_alive, set the max timeout accordingly, 201 * and indicate that this particular timeout was for client 202 * alive by setting the client_alive_scheduled flag. 203 * 204 * this could be randomized somewhat to make traffic 205 * analysis more difficult, but we're not doing it yet. 206 */ 207 if (options.client_alive_interval) { 208 /* Time we last heard from the client OR sent a keepalive */ 209 if (last_client_time == 0) 210 last_client_time = now; 211 ptimeout_deadline_sec(&timeout, options.client_alive_interval); 212 /* XXX ? deadline_monotime(last_client_time + alive_interval) */ 213 client_alive_scheduled = 1; 214 } 215 216 #if 0 217 /* wrong: bad condition XXX */ 218 if (channel_not_very_much_buffered_data()) 219 #endif 220 /* Monitor client connection on reserved pollfd entries */ 221 (*pfdp)[0].fd = connection_in; 222 (*pfdp)[0].events = POLLIN; 223 (*pfdp)[1].fd = connection_out; 224 (*pfdp)[1].events = ssh_packet_have_data_to_write(ssh) ? POLLOUT : 0; 225 226 /* 227 * If child has terminated and there is enough buffer space to read 228 * from it, then read as much as is available and exit. 229 */ 230 if (child_terminated && ssh_packet_not_very_much_data_to_write(ssh)) 231 ptimeout_deadline_ms(&timeout, 100); 232 233 /* Wait for something to happen, or the timeout to expire. */ 234 ret = ppoll(*pfdp, *npfd_activep, ptimeout_get_tsp(&timeout), sigsetp); 235 236 if (ret == -1) { 237 for (p = 0; p < *npfd_activep; p++) 238 (*pfdp)[p].revents = 0; 239 if (errno != EINTR) 240 fatal_f("ppoll: %.100s", strerror(errno)); 241 return; 242 } 243 244 *conn_in_readyp = (*pfdp)[0].revents != 0; 245 *conn_out_readyp = (*pfdp)[1].revents != 0; 246 247 now = monotime(); /* need to reset after ppoll() */ 248 /* ClientAliveInterval probing */ 249 if (client_alive_scheduled) { 250 if (ret == 0 && 251 now >= last_client_time + options.client_alive_interval) { 252 /* ppoll timed out and we're due to probe */ 253 client_alive_check(ssh); 254 last_client_time = now; 255 } else if (ret != 0 && *conn_in_readyp) { 256 /* Data from peer; reset probe timer. */ 257 last_client_time = now; 258 } 259 } 260 261 /* UnusedConnectionTimeout handling */ 262 if (unused_connection_expiry != 0 && 263 now > unused_connection_expiry && !channel_still_open(ssh)) { 264 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id)); 265 logit("terminating inactive connection from %s", remote_id); 266 cleanup_exit(255); 267 } 268 } 269 270 /* 271 * Processes input from the client and the program. Input data is stored 272 * in buffers and processed later. 273 */ 274 static int 275 process_input(struct ssh *ssh, int connection_in) 276 { 277 int r; 278 279 if ((r = ssh_packet_process_read(ssh, connection_in)) == 0) 280 return 0; /* success */ 281 if (r == SSH_ERR_SYSTEM_ERROR) { 282 if (errno == EAGAIN || errno == EINTR) 283 return 0; 284 if (errno == EPIPE) { 285 logit("Connection closed by %.100s port %d", 286 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 287 return -1; 288 } 289 logit("Read error from remote host %s port %d: %s", 290 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), 291 strerror(errno)); 292 cleanup_exit(254); 293 } 294 return -1; 295 } 296 297 /* 298 * Sends data from internal buffers to client program stdin. 299 */ 300 static void 301 process_output(struct ssh *ssh, int connection_out) 302 { 303 int r; 304 305 /* Send any buffered packet data to the client. */ 306 if ((r = ssh_packet_write_poll(ssh)) < 0) { 307 sshpkt_fatal(ssh, r, "%s: ssh_packet_write_poll", 308 __func__); 309 } 310 } 311 312 static void 313 process_buffered_input_packets(struct ssh *ssh) 314 { 315 ssh_dispatch_run_fatal(ssh, DISPATCH_NONBLOCK, NULL); 316 } 317 318 static void 319 collect_children(struct ssh *ssh) 320 { 321 pid_t pid; 322 int status; 323 324 if (child_terminated) { 325 debug("Received SIGCHLD."); 326 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 327 (pid == -1 && errno == EINTR)) 328 if (pid > 0) 329 session_close_by_pid(ssh, pid, status); 330 child_terminated = 0; 331 } 332 } 333 334 void 335 server_loop2(struct ssh *ssh, Authctxt *authctxt) 336 { 337 struct pollfd *pfd = NULL; 338 u_int npfd_alloc = 0, npfd_active = 0; 339 int r, conn_in_ready, conn_out_ready; 340 u_int connection_in, connection_out; 341 double start_time, total_time; 342 sigset_t bsigset, osigset; 343 344 debug("Entering interactive session for SSH2."); 345 start_time = get_current_time(); 346 347 if (sigemptyset(&bsigset) == -1 || sigaddset(&bsigset, SIGCHLD) == -1) 348 error_f("bsigset setup: %s", strerror(errno)); 349 ssh_signal(SIGCHLD, sigchld_handler); 350 child_terminated = 0; 351 connection_in = ssh_packet_get_connection_in(ssh); 352 connection_out = ssh_packet_get_connection_out(ssh); 353 354 server_init_dispatch(ssh); 355 356 for (;;) { 357 process_buffered_input_packets(ssh); 358 359 if (!ssh_packet_is_rekeying(ssh) && 360 ssh_packet_not_very_much_data_to_write(ssh)) 361 channel_output_poll(ssh); 362 363 /* 364 * Block SIGCHLD while we check for dead children, then pass 365 * the old signal mask through to ppoll() so that it'll wake 366 * up immediately if a child exits after we've called waitpid(). 367 */ 368 if (sigprocmask(SIG_BLOCK, &bsigset, &osigset) == -1) 369 error_f("bsigset sigprocmask: %s", strerror(errno)); 370 collect_children(ssh); 371 wait_until_can_do_something(ssh, connection_in, connection_out, 372 &pfd, &npfd_alloc, &npfd_active, &osigset, 373 &conn_in_ready, &conn_out_ready); 374 if (sigprocmask(SIG_SETMASK, &osigset, NULL) == -1) 375 error_f("osigset sigprocmask: %s", strerror(errno)); 376 377 channel_after_poll(ssh, pfd, npfd_active); 378 if (conn_in_ready && 379 process_input(ssh, connection_in) < 0) 380 break; 381 /* A timeout may have triggered rekeying */ 382 if ((r = ssh_packet_check_rekey(ssh)) != 0) 383 fatal_fr(r, "cannot start rekeying"); 384 if (conn_out_ready) 385 process_output(ssh, connection_out); 386 } 387 collect_children(ssh); 388 free(pfd); 389 390 /* free all channels, no more reads and writes */ 391 channel_free_all(ssh); 392 393 /* free remaining sessions, e.g. remove wtmp entries */ 394 session_destroy_all(ssh, NULL); 395 total_time = get_current_time() - start_time; 396 logit("SSH: Server;LType: Throughput;Remote: %s-%d;IN: %lu;OUT: %lu;Duration: %.1f;tPut_in: %.1f;tPut_out: %.1f", 397 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), 398 stdin_bytes, fdout_bytes, total_time, stdin_bytes / total_time, 399 fdout_bytes / total_time); 400 } 401 402 static int 403 server_input_keep_alive(int type, u_int32_t seq, struct ssh *ssh) 404 { 405 debug("Got %d/%u for keepalive", type, seq); 406 /* 407 * reset timeout, since we got a sane answer from the client. 408 * even if this was generated by something other than 409 * the bogus CHANNEL_REQUEST we send for keepalives. 410 */ 411 ssh_packet_set_alive_timeouts(ssh, 0); 412 return 0; 413 } 414 415 static Channel * 416 server_request_direct_tcpip(struct ssh *ssh, int *reason, const char **errmsg) 417 { 418 Channel *c = NULL; 419 char *target = NULL, *originator = NULL; 420 u_int target_port = 0, originator_port = 0; 421 int r; 422 423 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 424 (r = sshpkt_get_u32(ssh, &target_port)) != 0 || 425 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 426 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 427 (r = sshpkt_get_end(ssh)) != 0) 428 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 429 if (target_port > 0xFFFF) { 430 error_f("invalid target port"); 431 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 432 goto out; 433 } 434 if (originator_port > 0xFFFF) { 435 error_f("invalid originator port"); 436 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 437 goto out; 438 } 439 440 debug_f("originator %s port %u, target %s port %u", 441 originator, originator_port, target, target_port); 442 443 /* XXX fine grained permissions */ 444 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 && 445 auth_opts->permit_port_forwarding_flag && 446 !options.disable_forwarding) { 447 c = channel_connect_to_port(ssh, target, target_port, 448 "direct-tcpip", "direct-tcpip", reason, errmsg); 449 } else { 450 logit("refused local port forward: " 451 "originator %s port %d, target %s port %d", 452 originator, originator_port, target, target_port); 453 if (reason != NULL) 454 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 455 } 456 457 out: 458 free(originator); 459 free(target); 460 return c; 461 } 462 463 static Channel * 464 server_request_direct_streamlocal(struct ssh *ssh) 465 { 466 Channel *c = NULL; 467 char *target = NULL, *originator = NULL; 468 u_int originator_port = 0; 469 struct passwd *pw = the_authctxt->pw; 470 int r; 471 472 if (pw == NULL || !the_authctxt->valid) 473 fatal_f("no/invalid user"); 474 475 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 476 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 477 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 478 (r = sshpkt_get_end(ssh)) != 0) 479 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 480 if (originator_port > 0xFFFF) { 481 error_f("invalid originator port"); 482 goto out; 483 } 484 485 debug_f("originator %s port %d, target %s", 486 originator, originator_port, target); 487 488 /* XXX fine grained permissions */ 489 if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 && 490 auth_opts->permit_port_forwarding_flag && 491 !options.disable_forwarding) { 492 c = channel_connect_to_path(ssh, target, 493 "direct-streamlocal@openssh.com", "direct-streamlocal"); 494 } else { 495 logit("refused streamlocal port forward: " 496 "originator %s port %d, target %s", 497 originator, originator_port, target); 498 } 499 500 out: 501 free(originator); 502 free(target); 503 return c; 504 } 505 506 static Channel * 507 server_request_tun(struct ssh *ssh) 508 { 509 Channel *c = NULL; 510 u_int mode, tun; 511 int r, sock; 512 char *tmp, *ifname = NULL; 513 514 if ((r = sshpkt_get_u32(ssh, &mode)) != 0) 515 sshpkt_fatal(ssh, r, "%s: parse mode", __func__); 516 switch (mode) { 517 case SSH_TUNMODE_POINTOPOINT: 518 case SSH_TUNMODE_ETHERNET: 519 break; 520 default: 521 ssh_packet_send_debug(ssh, "Unsupported tunnel device mode."); 522 return NULL; 523 } 524 if ((options.permit_tun & mode) == 0) { 525 ssh_packet_send_debug(ssh, "Server has rejected tunnel device " 526 "forwarding"); 527 return NULL; 528 } 529 530 if ((r = sshpkt_get_u32(ssh, &tun)) != 0) 531 sshpkt_fatal(ssh, r, "%s: parse device", __func__); 532 if (tun > INT_MAX) { 533 debug_f("invalid tun"); 534 goto done; 535 } 536 if (auth_opts->force_tun_device != -1) { 537 if (tun != SSH_TUNID_ANY && 538 auth_opts->force_tun_device != (int)tun) 539 goto done; 540 tun = auth_opts->force_tun_device; 541 } 542 sock = tun_open(tun, mode, &ifname); 543 if (sock < 0) 544 goto done; 545 debug("Tunnel forwarding using interface %s", ifname); 546 547 if (options.hpn_disabled) 548 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1, 549 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 550 else 551 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1, 552 options.hpn_buffer_size, 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 ((options.tcp_rcv_buf_poll > 0) && (!options.hpn_disabled)) 599 c->dynamic_window = 1; 600 if (session_open(the_authctxt, c->self) != 1) { 601 debug("session open failed, free channel %d", c->self); 602 channel_free(ssh, c); 603 return NULL; 604 } 605 channel_register_cleanup(ssh, c->self, session_close_by_channel, 0); 606 return c; 607 } 608 609 static int 610 server_input_channel_open(int type, u_int32_t seq, struct ssh *ssh) 611 { 612 Channel *c = NULL; 613 char *ctype = NULL; 614 const char *errmsg = NULL; 615 int r, reason = SSH2_OPEN_CONNECT_FAILED; 616 u_int rchan = 0, rmaxpack = 0, rwindow = 0; 617 618 if ((r = sshpkt_get_cstring(ssh, &ctype, NULL)) != 0 || 619 (r = sshpkt_get_u32(ssh, &rchan)) != 0 || 620 (r = sshpkt_get_u32(ssh, &rwindow)) != 0 || 621 (r = sshpkt_get_u32(ssh, &rmaxpack)) != 0) 622 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 623 debug_f("ctype %s rchan %u win %u max %u", 624 ctype, rchan, rwindow, rmaxpack); 625 626 if (strcmp(ctype, "session") == 0) { 627 c = server_request_session(ssh); 628 } else if (strcmp(ctype, "direct-tcpip") == 0) { 629 c = server_request_direct_tcpip(ssh, &reason, &errmsg); 630 } else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) { 631 c = server_request_direct_streamlocal(ssh); 632 } else if (strcmp(ctype, "tun@openssh.com") == 0) { 633 c = server_request_tun(ssh); 634 } 635 if (c != NULL) { 636 debug_f("confirm %s", ctype); 637 c->remote_id = rchan; 638 c->have_remote_id = 1; 639 c->remote_window = rwindow; 640 c->remote_maxpacket = rmaxpack; 641 if (c->type != SSH_CHANNEL_CONNECTING) { 642 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION)) != 0 || 643 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 644 (r = sshpkt_put_u32(ssh, c->self)) != 0 || 645 (r = sshpkt_put_u32(ssh, c->local_window)) != 0 || 646 (r = sshpkt_put_u32(ssh, c->local_maxpacket)) != 0 || 647 (r = sshpkt_send(ssh)) != 0) { 648 sshpkt_fatal(ssh, r, 649 "%s: send open confirm", __func__); 650 } 651 } 652 } else { 653 debug_f("failure %s", ctype); 654 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE)) != 0 || 655 (r = sshpkt_put_u32(ssh, rchan)) != 0 || 656 (r = sshpkt_put_u32(ssh, reason)) != 0 || 657 (r = sshpkt_put_cstring(ssh, errmsg ? errmsg : "open failed")) != 0 || 658 (r = sshpkt_put_cstring(ssh, "")) != 0 || 659 (r = sshpkt_send(ssh)) != 0) { 660 sshpkt_fatal(ssh, r, 661 "%s: send open failure", __func__); 662 } 663 } 664 free(ctype); 665 return 0; 666 } 667 668 static int 669 server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp) 670 { 671 struct sshbuf *resp = NULL; 672 struct sshbuf *sigbuf = NULL; 673 struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL; 674 int r, ndx, success = 0; 675 const u_char *blob; 676 const char *sigalg, *kex_rsa_sigalg = NULL; 677 u_char *sig = 0; 678 size_t blen, slen; 679 680 if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL) 681 fatal_f("sshbuf_new"); 682 if (sshkey_type_plain(sshkey_type_from_name( 683 ssh->kex->hostkey_alg)) == KEY_RSA) 684 kex_rsa_sigalg = ssh->kex->hostkey_alg; 685 while (ssh_packet_remaining(ssh) > 0) { 686 sshkey_free(key); 687 key = NULL; 688 if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 || 689 (r = sshkey_from_blob(blob, blen, &key)) != 0) { 690 error_fr(r, "parse key"); 691 goto out; 692 } 693 /* 694 * Better check that this is actually one of our hostkeys 695 * before attempting to sign anything with it. 696 */ 697 if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) { 698 error_f("unknown host %s key", sshkey_type(key)); 699 goto out; 700 } 701 /* 702 * XXX refactor: make kex->sign just use an index rather 703 * than passing in public and private keys 704 */ 705 if ((key_prv = get_hostkey_by_index(ndx)) == NULL && 706 (key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) { 707 error_f("can't retrieve hostkey %d", ndx); 708 goto out; 709 } 710 sshbuf_reset(sigbuf); 711 free(sig); 712 sig = NULL; 713 /* 714 * For RSA keys, prefer to use the signature type negotiated 715 * during KEX to the default (SHA1). 716 */ 717 sigalg = NULL; 718 if (sshkey_type_plain(key->type) == KEY_RSA) { 719 if (kex_rsa_sigalg != NULL) 720 sigalg = kex_rsa_sigalg; 721 else if (ssh->kex->flags & KEX_RSA_SHA2_512_SUPPORTED) 722 sigalg = "rsa-sha2-512"; 723 else if (ssh->kex->flags & KEX_RSA_SHA2_256_SUPPORTED) 724 sigalg = "rsa-sha2-256"; 725 } 726 debug3_f("sign %s key (index %d) using sigalg %s", 727 sshkey_type(key), ndx, sigalg == NULL ? "default" : sigalg); 728 if ((r = sshbuf_put_cstring(sigbuf, 729 "hostkeys-prove-00@openssh.com")) != 0 || 730 (r = sshbuf_put_stringb(sigbuf, 731 ssh->kex->session_id)) != 0 || 732 (r = sshkey_puts(key, sigbuf)) != 0 || 733 (r = ssh->kex->sign(ssh, key_prv, key_pub, &sig, &slen, 734 sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), sigalg)) != 0 || 735 (r = sshbuf_put_string(resp, sig, slen)) != 0) { 736 error_fr(r, "assemble signature"); 737 goto out; 738 } 739 } 740 /* Success */ 741 *respp = resp; 742 resp = NULL; /* don't free it */ 743 success = 1; 744 out: 745 free(sig); 746 sshbuf_free(resp); 747 sshbuf_free(sigbuf); 748 sshkey_free(key); 749 return success; 750 } 751 752 static int 753 server_input_global_request(int type, u_int32_t seq, struct ssh *ssh) 754 { 755 char *rtype = NULL; 756 u_char want_reply = 0; 757 int r, success = 0, allocated_listen_port = 0; 758 u_int port = 0; 759 struct sshbuf *resp = NULL; 760 struct passwd *pw = the_authctxt->pw; 761 struct Forward fwd; 762 763 memset(&fwd, 0, sizeof(fwd)); 764 if (pw == NULL || !the_authctxt->valid) 765 fatal_f("no/invalid user"); 766 767 if ((r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 768 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 769 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 770 debug_f("rtype %s want_reply %d", rtype, want_reply); 771 772 /* -R style forwarding */ 773 if (strcmp(rtype, "tcpip-forward") == 0) { 774 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 775 (r = sshpkt_get_u32(ssh, &port)) != 0) 776 sshpkt_fatal(ssh, r, "%s: parse tcpip-forward", __func__); 777 debug_f("tcpip-forward listen %s port %u", 778 fwd.listen_host, port); 779 if (port <= INT_MAX) 780 fwd.listen_port = (int)port; 781 /* check permissions */ 782 if (port > INT_MAX || 783 (options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 || 784 !auth_opts->permit_port_forwarding_flag || 785 options.disable_forwarding || 786 (!want_reply && fwd.listen_port == 0)) { 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 success = 0; 821 ssh_packet_send_debug(ssh, "Server has disabled " 822 "streamlocal forwarding."); 823 } else { 824 /* Start listening on the socket */ 825 success = channel_setup_remote_fwd_listener(ssh, 826 &fwd, NULL, &options.fwd_opts); 827 } 828 } else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) { 829 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 830 sshpkt_fatal(ssh, r, "%s: parse cancel-streamlocal-forward@openssh.com", __func__); 831 debug_f("cancel-streamlocal-forward path %s", 832 fwd.listen_path); 833 834 success = channel_cancel_rport_listener(ssh, &fwd); 835 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) { 836 no_more_sessions = 1; 837 success = 1; 838 } else if (strcmp(rtype, "hostkeys-prove-00@openssh.com") == 0) { 839 success = server_input_hostkeys_prove(ssh, &resp); 840 } 841 /* XXX sshpkt_get_end() */ 842 if (want_reply) { 843 if ((r = sshpkt_start(ssh, success ? 844 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE)) != 0 || 845 (success && resp != NULL && (r = sshpkt_putb(ssh, resp)) != 0) || 846 (r = sshpkt_send(ssh)) != 0 || 847 (r = ssh_packet_write_wait(ssh)) < 0) 848 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 849 } 850 free(fwd.listen_host); 851 free(fwd.listen_path); 852 free(rtype); 853 sshbuf_free(resp); 854 return 0; 855 } 856 857 static int 858 server_input_channel_req(int type, u_int32_t seq, struct ssh *ssh) 859 { 860 Channel *c; 861 int r, success = 0; 862 char *rtype = NULL; 863 u_char want_reply = 0; 864 u_int id = 0; 865 866 if ((r = sshpkt_get_u32(ssh, &id)) != 0 || 867 (r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 868 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 869 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 870 871 debug("server_input_channel_req: channel %u request %s reply %d", 872 id, rtype, want_reply); 873 874 if (id >= INT_MAX || (c = channel_lookup(ssh, (int)id)) == NULL) { 875 ssh_packet_disconnect(ssh, "%s: unknown channel %d", 876 __func__, id); 877 } 878 if (!strcmp(rtype, "eow@openssh.com")) { 879 if ((r = sshpkt_get_end(ssh)) != 0) 880 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 881 chan_rcvd_eow(ssh, c); 882 } else if ((c->type == SSH_CHANNEL_LARVAL || 883 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0) 884 success = session_input_channel_req(ssh, c, rtype); 885 if (want_reply && !(c->flags & CHAN_CLOSE_SENT)) { 886 if (!c->have_remote_id) 887 fatal_f("channel %d: no remote_id", c->self); 888 if ((r = sshpkt_start(ssh, success ? 889 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE)) != 0 || 890 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 891 (r = sshpkt_send(ssh)) != 0) 892 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 893 } 894 free(rtype); 895 return 0; 896 } 897 898 static void 899 server_init_dispatch(struct ssh *ssh) 900 { 901 debug("server_init_dispatch"); 902 ssh_dispatch_init(ssh, &dispatch_protocol_error); 903 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); 904 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_DATA, &channel_input_data); 905 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); 906 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); 907 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); 908 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 909 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 910 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); 911 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); 912 ssh_dispatch_set(ssh, SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); 913 /* client_alive */ 914 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive); 915 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); 916 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); 917 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); 918 /* rekeying */ 919 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit); 920 } 921