1 /* $NetBSD: serverloop.c,v 1.28 2020/12/04 18:42:50 christos Exp $ */ 2 /* $OpenBSD: serverloop.c,v 1.223 2020/07/03 06:29:57 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 1.28 2020/12/04 18:42:50 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 <signal.h> 57 #include <string.h> 58 #include <termios.h> 59 #include <unistd.h> 60 #include <stdarg.h> 61 62 #include "xmalloc.h" 63 #include "packet.h" 64 #include "sshbuf.h" 65 #include "log.h" 66 #include "misc.h" 67 #include "servconf.h" 68 #include "canohost.h" 69 #include "sshpty.h" 70 #include "channels.h" 71 #include "compat.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 /* 97 * This SIGCHLD kludge is used to detect when the child exits. The server 98 * will exit after that, as soon as forwarded connections have terminated. 99 */ 100 101 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */ 102 103 /* Cleanup on signals (!use_privsep case only) */ 104 static volatile sig_atomic_t received_sigterm = 0; 105 106 /* prototypes */ 107 static void server_init_dispatch(struct ssh *); 108 109 /* requested tunnel forwarding interface(s), shared with session.c */ 110 char *tun_fwd_ifnames = NULL; 111 112 /* returns 1 if bind to specified port by specified user is permitted */ 113 static int 114 bind_permitted(int port, uid_t uid) 115 { 116 if (use_privsep) 117 return 1; /* allow system to decide */ 118 if (port < IPPORT_RESERVED && uid != 0) 119 return 0; 120 return 1; 121 } 122 123 /* 124 * Returns current time in seconds from Jan 1, 1970 with the maximum 125 * available resolution. 126 */ 127 128 static double 129 get_current_time(void) 130 { 131 struct timeval tv; 132 gettimeofday(&tv, NULL); 133 return (double) tv.tv_sec + (double) tv.tv_usec / 1000000.0; 134 } 135 136 /* 137 * we write to this pipe if a SIGCHLD is caught in order to avoid 138 * the race between select() and child_terminated 139 */ 140 static int notify_pipe[2]; 141 static void 142 notify_setup(void) 143 { 144 if (pipe(notify_pipe) == -1) { 145 error("pipe(notify_pipe) failed %s", strerror(errno)); 146 } else if ((fcntl(notify_pipe[0], F_SETFD, FD_CLOEXEC) == -1) || 147 (fcntl(notify_pipe[1], F_SETFD, FD_CLOEXEC) == -1)) { 148 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno)); 149 close(notify_pipe[0]); 150 close(notify_pipe[1]); 151 } else { 152 set_nonblock(notify_pipe[0]); 153 set_nonblock(notify_pipe[1]); 154 return; 155 } 156 notify_pipe[0] = -1; /* read end */ 157 notify_pipe[1] = -1; /* write end */ 158 } 159 static void 160 notify_parent(void) 161 { 162 if (notify_pipe[1] != -1) 163 (void)write(notify_pipe[1], "", 1); 164 } 165 static void 166 notify_prepare(fd_set *readset) 167 { 168 if (notify_pipe[0] != -1) 169 FD_SET(notify_pipe[0], readset); 170 } 171 static void 172 notify_done(fd_set *readset) 173 { 174 char c; 175 176 if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset)) 177 while (read(notify_pipe[0], &c, 1) != -1) 178 debug2("%s: reading", __func__); 179 } 180 181 /*ARGSUSED*/ 182 static void 183 sigchld_handler(int sig) 184 { 185 int save_errno = errno; 186 child_terminated = 1; 187 notify_parent(); 188 errno = save_errno; 189 } 190 191 /*ARGSUSED*/ 192 static void 193 sigterm_handler(int sig) 194 { 195 received_sigterm = sig; 196 } 197 198 static void 199 client_alive_check(struct ssh *ssh) 200 { 201 char remote_id[512]; 202 int r, channel_id; 203 204 /* timeout, check to see how many we have had */ 205 if (options.client_alive_count_max > 0 && 206 ssh_packet_inc_alive_timeouts(ssh) > 207 options.client_alive_count_max) { 208 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id)); 209 logit("Timeout, client not responding from %s", remote_id); 210 cleanup_exit(255); 211 } 212 213 /* 214 * send a bogus global/channel request with "wantreply", 215 * we should get back a failure 216 */ 217 if ((channel_id = channel_find_open(ssh)) == -1) { 218 if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 || 219 (r = sshpkt_put_cstring(ssh, "keepalive@openssh.com")) 220 != 0 || 221 (r = sshpkt_put_u8(ssh, 1)) != 0) /* boolean: want reply */ 222 fatal("%s: %s", __func__, ssh_err(r)); 223 } else { 224 channel_request_start(ssh, channel_id, 225 "keepalive@openssh.com", 1); 226 } 227 if ((r = sshpkt_send(ssh)) != 0) 228 fatal("%s: %s", __func__, ssh_err(r)); 229 } 230 231 /* 232 * Sleep in select() until we can do something. This will initialize the 233 * select masks. Upon return, the masks will indicate which descriptors 234 * have data or can accept data. Optionally, a maximum time can be specified 235 * for the duration of the wait (0 = infinite). 236 */ 237 static void 238 wait_until_can_do_something(struct ssh *ssh, 239 int connection_in, int connection_out, 240 fd_set **readsetp, fd_set **writesetp, int *maxfdp, 241 u_int *nallocp, u_int64_t max_time_ms) 242 { 243 struct timeval tv, *tvp; 244 int ret; 245 time_t minwait_secs = 0; 246 int client_alive_scheduled = 0; 247 /* time we last heard from the client OR sent a keepalive */ 248 static time_t last_client_time; 249 250 /* Allocate and update select() masks for channel descriptors. */ 251 channel_prepare_select(ssh, readsetp, writesetp, maxfdp, 252 nallocp, &minwait_secs); 253 254 /* XXX need proper deadline system for rekey/client alive */ 255 if (minwait_secs != 0) 256 max_time_ms = MINIMUM(max_time_ms, (u_int)minwait_secs * 1000); 257 258 /* 259 * if using client_alive, set the max timeout accordingly, 260 * and indicate that this particular timeout was for client 261 * alive by setting the client_alive_scheduled flag. 262 * 263 * this could be randomized somewhat to make traffic 264 * analysis more difficult, but we're not doing it yet. 265 */ 266 if (options.client_alive_interval) { 267 uint64_t keepalive_ms = 268 (uint64_t)options.client_alive_interval * 1000; 269 270 if (max_time_ms == 0 || max_time_ms > keepalive_ms) { 271 max_time_ms = keepalive_ms; 272 client_alive_scheduled = 1; 273 } 274 if (last_client_time == 0) 275 last_client_time = monotime(); 276 } 277 278 #if 0 279 /* wrong: bad condition XXX */ 280 if (channel_not_very_much_buffered_data()) 281 #endif 282 FD_SET(connection_in, *readsetp); 283 notify_prepare(*readsetp); 284 285 /* 286 * If we have buffered packet data going to the client, mark that 287 * descriptor. 288 */ 289 if (ssh_packet_have_data_to_write(ssh)) 290 FD_SET(connection_out, *writesetp); 291 292 /* 293 * If child has terminated and there is enough buffer space to read 294 * from it, then read as much as is available and exit. 295 */ 296 if (child_terminated && ssh_packet_not_very_much_data_to_write(ssh)) 297 if (max_time_ms == 0 || client_alive_scheduled) 298 max_time_ms = 100; 299 300 if (max_time_ms == 0) 301 tvp = NULL; 302 else { 303 tv.tv_sec = max_time_ms / 1000; 304 tv.tv_usec = 1000 * (max_time_ms % 1000); 305 tvp = &tv; 306 } 307 308 /* Wait for something to happen, or the timeout to expire. */ 309 ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp); 310 311 if (ret == -1) { 312 memset(*readsetp, 0, *nallocp); 313 memset(*writesetp, 0, *nallocp); 314 if (errno != EINTR) 315 error("select: %.100s", strerror(errno)); 316 } else if (client_alive_scheduled) { 317 time_t now = monotime(); 318 319 /* 320 * If the select timed out, or returned for some other reason 321 * but we haven't heard from the client in time, send keepalive. 322 */ 323 if (ret == 0 || (last_client_time != 0 && last_client_time + 324 options.client_alive_interval <= now)) { 325 client_alive_check(ssh); 326 last_client_time = now; 327 } else if (FD_ISSET(connection_in, *readsetp)) { 328 last_client_time = now; 329 } 330 } 331 332 notify_done(*readsetp); 333 } 334 335 /* 336 * Processes input from the client and the program. Input data is stored 337 * in buffers and processed later. 338 */ 339 static int 340 process_input(struct ssh *ssh, fd_set *readset, int connection_in) 341 { 342 int r, len; 343 char buf[16384]; 344 345 /* Read and buffer any input data from the client. */ 346 if (FD_ISSET(connection_in, readset)) { 347 len = read(connection_in, buf, sizeof(buf)); 348 if (len == 0) { 349 verbose("Connection closed by %.100s port %d", 350 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 351 return -1; 352 } else if (len == -1) { 353 if (errno != EINTR && errno != EAGAIN) { 354 verbose("Read error from remote host " 355 "%.100s port %d: %.100s", 356 ssh_remote_ipaddr(ssh), 357 ssh_remote_port(ssh), strerror(errno)); 358 cleanup_exit(254); 359 } 360 } else { 361 /* Buffer any received data. */ 362 if ((r = ssh_packet_process_incoming(ssh, buf, len)) 363 != 0) 364 fatal("%s: ssh_packet_process_incoming: %s", 365 __func__, ssh_err(r)); 366 } 367 } 368 return 0; 369 } 370 371 /* 372 * Sends data from internal buffers to client program stdin. 373 */ 374 static void 375 process_output(struct ssh *ssh, fd_set *writeset, int connection_out) 376 { 377 int r; 378 379 /* Send any buffered packet data to the client. */ 380 if (FD_ISSET(connection_out, writeset)) { 381 if ((r = ssh_packet_write_poll(ssh)) < 0) 382 sshpkt_fatal(ssh, r, "%s: ssh_packet_write_poll", 383 __func__); 384 } 385 } 386 387 static void 388 process_buffered_input_packets(struct ssh *ssh) 389 { 390 ssh_dispatch_run_fatal(ssh, DISPATCH_NONBLOCK, NULL); 391 } 392 393 static void 394 collect_children(struct ssh *ssh) 395 { 396 pid_t pid; 397 sigset_t oset, nset; 398 int status; 399 400 /* block SIGCHLD while we check for dead children */ 401 sigemptyset(&nset); 402 sigaddset(&nset, SIGCHLD); 403 sigprocmask(SIG_BLOCK, &nset, &oset); 404 if (child_terminated) { 405 debug("Received SIGCHLD."); 406 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 407 (pid == -1 && errno == EINTR)) 408 if (pid > 0) 409 session_close_by_pid(ssh, pid, status); 410 child_terminated = 0; 411 } 412 sigprocmask(SIG_SETMASK, &oset, NULL); 413 } 414 415 void 416 server_loop2(struct ssh *ssh, Authctxt *authctxt) 417 { 418 fd_set *readset = NULL, *writeset = NULL; 419 int max_fd; 420 u_int nalloc = 0, connection_in, connection_out; 421 u_int64_t rekey_timeout_ms = 0; 422 double start_time, total_time; 423 424 debug("Entering interactive session for SSH2."); 425 start_time = get_current_time(); 426 427 ssh_signal(SIGCHLD, sigchld_handler); 428 child_terminated = 0; 429 connection_in = ssh_packet_get_connection_in(ssh); 430 connection_out = ssh_packet_get_connection_out(ssh); 431 432 if (!use_privsep) { 433 ssh_signal(SIGTERM, sigterm_handler); 434 ssh_signal(SIGINT, sigterm_handler); 435 ssh_signal(SIGQUIT, sigterm_handler); 436 } 437 438 notify_setup(); 439 440 max_fd = MAXIMUM(connection_in, connection_out); 441 max_fd = MAXIMUM(max_fd, notify_pipe[0]); 442 443 server_init_dispatch(ssh); 444 445 for (;;) { 446 process_buffered_input_packets(ssh); 447 448 if (!ssh_packet_is_rekeying(ssh) && 449 ssh_packet_not_very_much_data_to_write(ssh)) 450 channel_output_poll(ssh); 451 if (options.rekey_interval > 0 && 452 !ssh_packet_is_rekeying(ssh)) { 453 rekey_timeout_ms = ssh_packet_get_rekey_timeout(ssh) * 454 1000; 455 } else { 456 rekey_timeout_ms = 0; 457 } 458 459 wait_until_can_do_something(ssh, connection_in, connection_out, 460 &readset, &writeset, &max_fd, &nalloc, rekey_timeout_ms); 461 462 if (received_sigterm) { 463 logit("Exiting on signal %d", (int)received_sigterm); 464 /* Clean up sessions, utmp, etc. */ 465 cleanup_exit(254); 466 } 467 468 collect_children(ssh); 469 if (!ssh_packet_is_rekeying(ssh)) 470 channel_after_select(ssh, readset, writeset); 471 if (process_input(ssh, readset, connection_in) < 0) 472 break; 473 process_output(ssh, writeset, connection_out); 474 } 475 collect_children(ssh); 476 477 free(readset); 478 free(writeset); 479 480 /* free all channels, no more reads and writes */ 481 channel_free_all(ssh); 482 483 /* free remaining sessions, e.g. remove wtmp entries */ 484 session_destroy_all(ssh, NULL); 485 total_time = get_current_time() - start_time; 486 logit("SSH: Server;LType: Throughput;Remote: %s-%d;IN: %lu;OUT: %lu;Duration: %.1f;tPut_in: %.1f;tPut_out: %.1f", 487 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), 488 stdin_bytes, fdout_bytes, total_time, stdin_bytes / total_time, 489 fdout_bytes / total_time); 490 } 491 492 static int 493 server_input_keep_alive(int type, u_int32_t seq, struct ssh *ssh) 494 { 495 debug("Got %d/%u for keepalive", type, seq); 496 /* 497 * reset timeout, since we got a sane answer from the client. 498 * even if this was generated by something other than 499 * the bogus CHANNEL_REQUEST we send for keepalives. 500 */ 501 ssh_packet_set_alive_timeouts(ssh, 0); 502 return 0; 503 } 504 505 static Channel * 506 server_request_direct_tcpip(struct ssh *ssh, int *reason, const char **errmsg) 507 { 508 Channel *c = NULL; 509 char *target = NULL, *originator = NULL; 510 u_int target_port = 0, originator_port = 0; 511 int r; 512 513 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 514 (r = sshpkt_get_u32(ssh, &target_port)) != 0 || 515 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 516 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 517 (r = sshpkt_get_end(ssh)) != 0) 518 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 519 if (target_port > 0xFFFF) { 520 error("%s: invalid target port", __func__); 521 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 522 goto out; 523 } 524 if (originator_port > 0xFFFF) { 525 error("%s: invalid originator port", __func__); 526 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 527 goto out; 528 } 529 530 debug("%s: originator %s port %u, target %s port %u", __func__, 531 originator, originator_port, target, target_port); 532 533 /* XXX fine grained permissions */ 534 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 && 535 auth_opts->permit_port_forwarding_flag && 536 !options.disable_forwarding) { 537 c = channel_connect_to_port(ssh, target, target_port, 538 "direct-tcpip", "direct-tcpip", reason, errmsg); 539 } else { 540 logit("refused local port forward: " 541 "originator %s port %d, target %s port %d", 542 originator, originator_port, target, target_port); 543 if (reason != NULL) 544 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 545 } 546 547 out: 548 free(originator); 549 free(target); 550 return c; 551 } 552 553 static Channel * 554 server_request_direct_streamlocal(struct ssh *ssh) 555 { 556 Channel *c = NULL; 557 char *target = NULL, *originator = NULL; 558 u_int originator_port = 0; 559 struct passwd *pw = the_authctxt->pw; 560 int r; 561 562 if (pw == NULL || !the_authctxt->valid) 563 fatal("%s: no/invalid user", __func__); 564 565 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 566 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 567 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 568 (r = sshpkt_get_end(ssh)) != 0) 569 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 570 if (originator_port > 0xFFFF) { 571 error("%s: invalid originator port", __func__); 572 goto out; 573 } 574 575 debug("%s: originator %s port %d, target %s", __func__, 576 originator, originator_port, target); 577 578 /* XXX fine grained permissions */ 579 if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 && 580 auth_opts->permit_port_forwarding_flag && 581 !options.disable_forwarding && (pw->pw_uid == 0 || use_privsep)) { 582 c = channel_connect_to_path(ssh, target, 583 "direct-streamlocal@openssh.com", "direct-streamlocal"); 584 } else { 585 logit("refused streamlocal port forward: " 586 "originator %s port %d, target %s", 587 originator, originator_port, target); 588 } 589 590 out: 591 free(originator); 592 free(target); 593 return c; 594 } 595 596 static Channel * 597 server_request_tun(struct ssh *ssh) 598 { 599 Channel *c = NULL; 600 u_int mode, tun; 601 int r, sock; 602 char *tmp, *ifname = NULL; 603 604 if ((r = sshpkt_get_u32(ssh, &mode)) != 0) 605 sshpkt_fatal(ssh, r, "%s: parse mode", __func__); 606 switch (mode) { 607 case SSH_TUNMODE_POINTOPOINT: 608 case SSH_TUNMODE_ETHERNET: 609 break; 610 default: 611 ssh_packet_send_debug(ssh, "Unsupported tunnel device mode."); 612 return NULL; 613 } 614 if ((options.permit_tun & mode) == 0) { 615 ssh_packet_send_debug(ssh, "Server has rejected tunnel device " 616 "forwarding"); 617 return NULL; 618 } 619 620 if ((r = sshpkt_get_u32(ssh, &tun)) != 0) 621 sshpkt_fatal(ssh, r, "%s: parse device", __func__); 622 if (tun > INT_MAX) { 623 debug("%s: invalid tun", __func__); 624 goto done; 625 } 626 if (auth_opts->force_tun_device != -1) { 627 if (tun != SSH_TUNID_ANY && 628 auth_opts->force_tun_device != (int)tun) 629 goto done; 630 tun = auth_opts->force_tun_device; 631 } 632 sock = tun_open(tun, mode, &ifname); 633 if (sock < 0) 634 goto done; 635 debug("Tunnel forwarding using interface %s", ifname); 636 637 if (options.hpn_disabled) 638 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1, 639 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 640 else 641 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1, 642 options.hpn_buffer_size, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 643 c->datagram = 1; 644 645 /* 646 * Update the list of names exposed to the session 647 * XXX remove these if the tunnels are closed (won't matter 648 * much if they are already in the environment though) 649 */ 650 tmp = tun_fwd_ifnames; 651 xasprintf(&tun_fwd_ifnames, "%s%s%s", 652 tun_fwd_ifnames == NULL ? "" : tun_fwd_ifnames, 653 tun_fwd_ifnames == NULL ? "" : ",", 654 ifname); 655 free(tmp); 656 free(ifname); 657 658 done: 659 if (c == NULL) 660 ssh_packet_send_debug(ssh, "Failed to open the tunnel device."); 661 return c; 662 } 663 664 static Channel * 665 server_request_session(struct ssh *ssh) 666 { 667 Channel *c; 668 int r; 669 670 debug("input_session_request"); 671 if ((r = sshpkt_get_end(ssh)) != 0) 672 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 673 674 if (no_more_sessions) { 675 ssh_packet_disconnect(ssh, "Possible attack: attempt to open a " 676 "session after additional sessions disabled"); 677 } 678 679 /* 680 * A server session has no fd to read or write until a 681 * CHANNEL_REQUEST for a shell is made, so we set the type to 682 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all 683 * CHANNEL_REQUEST messages is registered. 684 */ 685 c = channel_new(ssh, "session", SSH_CHANNEL_LARVAL, 686 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, 687 0, "server-session", 1); 688 if ((options.tcp_rcv_buf_poll > 0) && (!options.hpn_disabled)) 689 c->dynamic_window = 1; 690 if (session_open(the_authctxt, c->self) != 1) { 691 debug("session open failed, free channel %d", c->self); 692 channel_free(ssh, c); 693 return NULL; 694 } 695 channel_register_cleanup(ssh, c->self, session_close_by_channel, 0); 696 return c; 697 } 698 699 static int 700 server_input_channel_open(int type, u_int32_t seq, struct ssh *ssh) 701 { 702 Channel *c = NULL; 703 char *ctype = NULL; 704 const char *errmsg = NULL; 705 int r, reason = SSH2_OPEN_CONNECT_FAILED; 706 u_int rchan = 0, rmaxpack = 0, rwindow = 0; 707 708 if ((r = sshpkt_get_cstring(ssh, &ctype, NULL)) != 0 || 709 (r = sshpkt_get_u32(ssh, &rchan)) != 0 || 710 (r = sshpkt_get_u32(ssh, &rwindow)) != 0 || 711 (r = sshpkt_get_u32(ssh, &rmaxpack)) != 0) 712 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 713 debug("%s: ctype %s rchan %u win %u max %u", __func__, 714 ctype, rchan, rwindow, rmaxpack); 715 716 if (strcmp(ctype, "session") == 0) { 717 c = server_request_session(ssh); 718 } else if (strcmp(ctype, "direct-tcpip") == 0) { 719 c = server_request_direct_tcpip(ssh, &reason, &errmsg); 720 } else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) { 721 c = server_request_direct_streamlocal(ssh); 722 } else if (strcmp(ctype, "tun@openssh.com") == 0) { 723 c = server_request_tun(ssh); 724 } 725 if (c != NULL) { 726 debug("%s: confirm %s", __func__, ctype); 727 c->remote_id = rchan; 728 c->have_remote_id = 1; 729 c->remote_window = rwindow; 730 c->remote_maxpacket = rmaxpack; 731 if (c->type != SSH_CHANNEL_CONNECTING) { 732 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION)) != 0 || 733 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 734 (r = sshpkt_put_u32(ssh, c->self)) != 0 || 735 (r = sshpkt_put_u32(ssh, c->local_window)) != 0 || 736 (r = sshpkt_put_u32(ssh, c->local_maxpacket)) != 0 || 737 (r = sshpkt_send(ssh)) != 0) { 738 sshpkt_fatal(ssh, r, 739 "%s: send open confirm", __func__); 740 } 741 } 742 } else { 743 debug("%s: failure %s", __func__, ctype); 744 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE)) != 0 || 745 (r = sshpkt_put_u32(ssh, rchan)) != 0 || 746 (r = sshpkt_put_u32(ssh, reason)) != 0 || 747 (r = sshpkt_put_cstring(ssh, errmsg ? errmsg : "open failed")) != 0 || 748 (r = sshpkt_put_cstring(ssh, "")) != 0 || 749 (r = sshpkt_send(ssh)) != 0) { 750 sshpkt_fatal(ssh, r, 751 "%s: send open failure", __func__); 752 } 753 } 754 free(ctype); 755 return 0; 756 } 757 758 static int 759 server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp) 760 { 761 struct sshbuf *resp = NULL; 762 struct sshbuf *sigbuf = NULL; 763 struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL; 764 int r, ndx, kexsigtype, use_kexsigtype, success = 0; 765 const u_char *blob; 766 u_char *sig = 0; 767 size_t blen, slen; 768 769 if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL) 770 fatal("%s: sshbuf_new", __func__); 771 772 kexsigtype = sshkey_type_plain( 773 sshkey_type_from_name(ssh->kex->hostkey_alg)); 774 while (ssh_packet_remaining(ssh) > 0) { 775 sshkey_free(key); 776 key = NULL; 777 if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 || 778 (r = sshkey_from_blob(blob, blen, &key)) != 0) { 779 error("%s: couldn't parse key: %s", 780 __func__, ssh_err(r)); 781 goto out; 782 } 783 /* 784 * Better check that this is actually one of our hostkeys 785 * before attempting to sign anything with it. 786 */ 787 if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) { 788 error("%s: unknown host %s key", 789 __func__, sshkey_type(key)); 790 goto out; 791 } 792 /* 793 * XXX refactor: make kex->sign just use an index rather 794 * than passing in public and private keys 795 */ 796 if ((key_prv = get_hostkey_by_index(ndx)) == NULL && 797 (key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) { 798 error("%s: can't retrieve hostkey %d", __func__, ndx); 799 goto out; 800 } 801 sshbuf_reset(sigbuf); 802 free(sig); 803 sig = NULL; 804 /* 805 * For RSA keys, prefer to use the signature type negotiated 806 * during KEX to the default (SHA1). 807 */ 808 use_kexsigtype = kexsigtype == KEY_RSA && 809 sshkey_type_plain(key->type) == KEY_RSA; 810 if ((r = sshbuf_put_cstring(sigbuf, 811 "hostkeys-prove-00@openssh.com")) != 0 || 812 (r = sshbuf_put_string(sigbuf, 813 ssh->kex->session_id, ssh->kex->session_id_len)) != 0 || 814 (r = sshkey_puts(key, sigbuf)) != 0 || 815 (r = ssh->kex->sign(ssh, key_prv, key_pub, &sig, &slen, 816 sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), 817 use_kexsigtype ? ssh->kex->hostkey_alg : NULL)) != 0 || 818 (r = sshbuf_put_string(resp, sig, slen)) != 0) { 819 error("%s: couldn't prepare signature: %s", 820 __func__, ssh_err(r)); 821 goto out; 822 } 823 } 824 /* Success */ 825 *respp = resp; 826 resp = NULL; /* don't free it */ 827 success = 1; 828 out: 829 free(sig); 830 sshbuf_free(resp); 831 sshbuf_free(sigbuf); 832 sshkey_free(key); 833 return success; 834 } 835 836 static int 837 server_input_global_request(int type, u_int32_t seq, struct ssh *ssh) 838 { 839 char *rtype = NULL; 840 u_char want_reply = 0; 841 int r, success = 0, allocated_listen_port = 0; 842 u_int port = 0; 843 struct sshbuf *resp = NULL; 844 struct passwd *pw = the_authctxt->pw; 845 struct Forward fwd; 846 847 memset(&fwd, 0, sizeof(fwd)); 848 if (pw == NULL || !the_authctxt->valid) 849 fatal("%s: no/invalid user", __func__); 850 851 if ((r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 852 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 853 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 854 debug("%s: rtype %s want_reply %d", __func__, rtype, want_reply); 855 856 /* -R style forwarding */ 857 if (strcmp(rtype, "tcpip-forward") == 0) { 858 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 859 (r = sshpkt_get_u32(ssh, &port)) != 0) 860 sshpkt_fatal(ssh, r, "%s: parse tcpip-forward", __func__); 861 debug("%s: tcpip-forward listen %s port %u", __func__, 862 fwd.listen_host, port); 863 if (port <= INT_MAX) 864 fwd.listen_port = (int)port; 865 /* check permissions */ 866 if (port > INT_MAX || 867 (options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 || 868 !auth_opts->permit_port_forwarding_flag || 869 options.disable_forwarding || 870 (!want_reply && fwd.listen_port == 0) || 871 (fwd.listen_port != 0 && 872 !bind_permitted(fwd.listen_port, pw->pw_uid))) { 873 success = 0; 874 ssh_packet_send_debug(ssh, "Server has disabled port forwarding."); 875 } else { 876 /* Start listening on the port */ 877 success = channel_setup_remote_fwd_listener(ssh, &fwd, 878 &allocated_listen_port, &options.fwd_opts); 879 } 880 if ((resp = sshbuf_new()) == NULL) 881 fatal("%s: sshbuf_new", __func__); 882 if (allocated_listen_port != 0 && 883 (r = sshbuf_put_u32(resp, allocated_listen_port)) != 0) 884 fatal("%s: sshbuf_put_u32: %s", __func__, ssh_err(r)); 885 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) { 886 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 887 (r = sshpkt_get_u32(ssh, &port)) != 0) 888 sshpkt_fatal(ssh, r, "%s: parse cancel-tcpip-forward", __func__); 889 890 debug("%s: cancel-tcpip-forward addr %s port %d", __func__, 891 fwd.listen_host, port); 892 if (port <= INT_MAX) { 893 fwd.listen_port = (int)port; 894 success = channel_cancel_rport_listener(ssh, &fwd); 895 } 896 } else if (strcmp(rtype, "streamlocal-forward@openssh.com") == 0) { 897 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 898 sshpkt_fatal(ssh, r, "%s: parse streamlocal-forward@openssh.com", __func__); 899 debug("%s: streamlocal-forward listen path %s", __func__, 900 fwd.listen_path); 901 902 /* check permissions */ 903 if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0 904 || !auth_opts->permit_port_forwarding_flag || 905 options.disable_forwarding || 906 (pw->pw_uid != 0 && !use_privsep)) { 907 success = 0; 908 ssh_packet_send_debug(ssh, "Server has disabled " 909 "streamlocal forwarding."); 910 } else { 911 /* Start listening on the socket */ 912 success = channel_setup_remote_fwd_listener(ssh, 913 &fwd, NULL, &options.fwd_opts); 914 } 915 } else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) { 916 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 917 sshpkt_fatal(ssh, r, "%s: parse cancel-streamlocal-forward@openssh.com", __func__); 918 debug("%s: cancel-streamlocal-forward path %s", __func__, 919 fwd.listen_path); 920 921 success = channel_cancel_rport_listener(ssh, &fwd); 922 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) { 923 no_more_sessions = 1; 924 success = 1; 925 } else if (strcmp(rtype, "hostkeys-prove-00@openssh.com") == 0) { 926 success = server_input_hostkeys_prove(ssh, &resp); 927 } 928 /* XXX sshpkt_get_end() */ 929 if (want_reply) { 930 if ((r = sshpkt_start(ssh, success ? 931 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE)) != 0 || 932 (success && resp != NULL && (r = sshpkt_putb(ssh, resp)) != 0) || 933 (r = sshpkt_send(ssh)) != 0 || 934 (r = ssh_packet_write_wait(ssh)) < 0) 935 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 936 } 937 free(fwd.listen_host); 938 free(fwd.listen_path); 939 free(rtype); 940 sshbuf_free(resp); 941 return 0; 942 } 943 944 static int 945 server_input_channel_req(int type, u_int32_t seq, struct ssh *ssh) 946 { 947 Channel *c; 948 int r, success = 0; 949 char *rtype = NULL; 950 u_char want_reply = 0; 951 u_int id = 0; 952 953 if ((r = sshpkt_get_u32(ssh, &id)) != 0 || 954 (r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 955 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 956 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 957 958 debug("server_input_channel_req: channel %u request %s reply %d", 959 id, rtype, want_reply); 960 961 if (id >= INT_MAX || (c = channel_lookup(ssh, (int)id)) == NULL) { 962 ssh_packet_disconnect(ssh, "%s: unknown channel %d", 963 __func__, id); 964 } 965 if (!strcmp(rtype, "eow@openssh.com")) { 966 if ((r = sshpkt_get_end(ssh)) != 0) 967 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 968 chan_rcvd_eow(ssh, c); 969 } else if ((c->type == SSH_CHANNEL_LARVAL || 970 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0) 971 success = session_input_channel_req(ssh, c, rtype); 972 if (want_reply && !(c->flags & CHAN_CLOSE_SENT)) { 973 if (!c->have_remote_id) 974 fatal("%s: channel %d: no remote_id", 975 __func__, c->self); 976 if ((r = sshpkt_start(ssh, success ? 977 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE)) != 0 || 978 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 979 (r = sshpkt_send(ssh)) != 0) 980 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 981 } 982 free(rtype); 983 return 0; 984 } 985 986 static void 987 server_init_dispatch(struct ssh *ssh) 988 { 989 debug("server_init_dispatch"); 990 ssh_dispatch_init(ssh, &dispatch_protocol_error); 991 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); 992 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_DATA, &channel_input_data); 993 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); 994 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); 995 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); 996 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 997 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 998 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); 999 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); 1000 ssh_dispatch_set(ssh, SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); 1001 /* client_alive */ 1002 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive); 1003 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); 1004 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); 1005 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); 1006 /* rekeying */ 1007 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit); 1008 } 1009