1 /* $NetBSD: serverloop.c,v 1.27 2020/02/27 00:24:40 christos Exp $ */ 2 /* $OpenBSD: serverloop.c,v 1.222 2020/01/30 07:21:38 djm Exp $ */ 3 /* 4 * Author: Tatu Ylonen <ylo@cs.hut.fi> 5 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 6 * All rights reserved 7 * Server main loop for handling the interactive session. 8 * 9 * As far as I am concerned, the code I have written for this software 10 * can be used freely for any purpose. Any derived versions of this 11 * software must be clearly marked as such, and if the derived work is 12 * incompatible with the protocol description in the RFC file, it must be 13 * called by a name other than "ssh" or "Secure Shell". 14 * 15 * SSH2 support by Markus Friedl. 16 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. 17 * 18 * Redistribution and use in source and binary forms, with or without 19 * modification, are permitted provided that the following conditions 20 * are met: 21 * 1. Redistributions of source code must retain the above copyright 22 * notice, this list of conditions and the following disclaimer. 23 * 2. Redistributions in binary form must reproduce the above copyright 24 * notice, this list of conditions and the following disclaimer in the 25 * documentation and/or other materials provided with the distribution. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 28 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 29 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 30 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 31 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 32 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 33 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 34 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 35 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 36 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 37 */ 38 39 #include "includes.h" 40 __RCSID("$NetBSD: serverloop.c,v 1.27 2020/02/27 00:24:40 christos Exp $"); 41 42 #include <sys/param.h> /* MIN MAX */ 43 #include <sys/types.h> 44 #include <sys/wait.h> 45 #include <sys/socket.h> 46 #include <sys/time.h> 47 #include <sys/queue.h> 48 49 #include <netinet/in.h> 50 51 #include <errno.h> 52 #include <fcntl.h> 53 #include <pwd.h> 54 #include <limits.h> 55 #include <signal.h> 56 #include <string.h> 57 #include <termios.h> 58 #include <unistd.h> 59 #include <stdarg.h> 60 61 #include "xmalloc.h" 62 #include "packet.h" 63 #include "sshbuf.h" 64 #include "log.h" 65 #include "misc.h" 66 #include "servconf.h" 67 #include "canohost.h" 68 #include "sshpty.h" 69 #include "channels.h" 70 #include "compat.h" 71 #include "ssh2.h" 72 #include "sshkey.h" 73 #include "cipher.h" 74 #include "kex.h" 75 #include "hostfile.h" 76 #include "auth.h" 77 #include "session.h" 78 #include "dispatch.h" 79 #include "auth-options.h" 80 #include "serverloop.h" 81 #include "ssherr.h" 82 83 static u_long stdin_bytes = 0; /* Number of bytes written to stdin. */ 84 static u_long fdout_bytes = 0; /* Number of stdout bytes read from program. */ 85 86 extern ServerOptions options; 87 88 /* XXX */ 89 extern Authctxt *the_authctxt; 90 extern struct sshauthopt *auth_opts; 91 extern int use_privsep; 92 93 static int no_more_sessions = 0; /* Disallow further sessions. */ 94 95 /* 96 * This SIGCHLD kludge is used to detect when the child exits. The server 97 * will exit after that, as soon as forwarded connections have terminated. 98 */ 99 100 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */ 101 102 /* Cleanup on signals (!use_privsep case only) */ 103 static volatile sig_atomic_t received_sigterm = 0; 104 105 /* prototypes */ 106 static void server_init_dispatch(struct ssh *); 107 108 /* requested tunnel forwarding interface(s), shared with session.c */ 109 char *tun_fwd_ifnames = NULL; 110 111 /* returns 1 if bind to specified port by specified user is permitted */ 112 static int 113 bind_permitted(int port, uid_t uid) 114 { 115 if (use_privsep) 116 return 1; /* allow system to decide */ 117 if (port < IPPORT_RESERVED && uid != 0) 118 return 0; 119 return 1; 120 } 121 122 /* 123 * Returns current time in seconds from Jan 1, 1970 with the maximum 124 * available resolution. 125 */ 126 127 static double 128 get_current_time(void) 129 { 130 struct timeval tv; 131 gettimeofday(&tv, NULL); 132 return (double) tv.tv_sec + (double) tv.tv_usec / 1000000.0; 133 } 134 135 /* 136 * we write to this pipe if a SIGCHLD is caught in order to avoid 137 * the race between select() and child_terminated 138 */ 139 static int notify_pipe[2]; 140 static void 141 notify_setup(void) 142 { 143 if (pipe(notify_pipe) == -1) { 144 error("pipe(notify_pipe) failed %s", strerror(errno)); 145 } else if ((fcntl(notify_pipe[0], F_SETFD, FD_CLOEXEC) == -1) || 146 (fcntl(notify_pipe[1], F_SETFD, FD_CLOEXEC) == -1)) { 147 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno)); 148 close(notify_pipe[0]); 149 close(notify_pipe[1]); 150 } else { 151 set_nonblock(notify_pipe[0]); 152 set_nonblock(notify_pipe[1]); 153 return; 154 } 155 notify_pipe[0] = -1; /* read end */ 156 notify_pipe[1] = -1; /* write end */ 157 } 158 static void 159 notify_parent(void) 160 { 161 if (notify_pipe[1] != -1) 162 (void)write(notify_pipe[1], "", 1); 163 } 164 static void 165 notify_prepare(fd_set *readset) 166 { 167 if (notify_pipe[0] != -1) 168 FD_SET(notify_pipe[0], readset); 169 } 170 static void 171 notify_done(fd_set *readset) 172 { 173 char c; 174 175 if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset)) 176 while (read(notify_pipe[0], &c, 1) != -1) 177 debug2("%s: reading", __func__); 178 } 179 180 /*ARGSUSED*/ 181 static void 182 sigchld_handler(int sig) 183 { 184 int save_errno = errno; 185 child_terminated = 1; 186 notify_parent(); 187 errno = save_errno; 188 } 189 190 /*ARGSUSED*/ 191 static void 192 sigterm_handler(int sig) 193 { 194 received_sigterm = sig; 195 } 196 197 static void 198 client_alive_check(struct ssh *ssh) 199 { 200 char remote_id[512]; 201 int r, channel_id; 202 203 /* timeout, check to see how many we have had */ 204 if (options.client_alive_count_max > 0 && 205 ssh_packet_inc_alive_timeouts(ssh) > 206 options.client_alive_count_max) { 207 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id)); 208 logit("Timeout, client not responding from %s", remote_id); 209 cleanup_exit(255); 210 } 211 212 /* 213 * send a bogus global/channel request with "wantreply", 214 * we should get back a failure 215 */ 216 if ((channel_id = channel_find_open(ssh)) == -1) { 217 if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 || 218 (r = sshpkt_put_cstring(ssh, "keepalive@openssh.com")) 219 != 0 || 220 (r = sshpkt_put_u8(ssh, 1)) != 0) /* boolean: want reply */ 221 fatal("%s: %s", __func__, ssh_err(r)); 222 } else { 223 channel_request_start(ssh, channel_id, 224 "keepalive@openssh.com", 1); 225 } 226 if ((r = sshpkt_send(ssh)) != 0) 227 fatal("%s: %s", __func__, ssh_err(r)); 228 } 229 230 /* 231 * Sleep in select() until we can do something. This will initialize the 232 * select masks. Upon return, the masks will indicate which descriptors 233 * have data or can accept data. Optionally, a maximum time can be specified 234 * for the duration of the wait (0 = infinite). 235 */ 236 static void 237 wait_until_can_do_something(struct ssh *ssh, 238 int connection_in, int connection_out, 239 fd_set **readsetp, fd_set **writesetp, int *maxfdp, 240 u_int *nallocp, u_int64_t max_time_ms) 241 { 242 struct timeval tv, *tvp; 243 int ret; 244 time_t minwait_secs = 0; 245 int client_alive_scheduled = 0; 246 /* time we last heard from the client OR sent a keepalive */ 247 static time_t last_client_time; 248 249 /* Allocate and update select() masks for channel descriptors. */ 250 channel_prepare_select(ssh, readsetp, writesetp, maxfdp, 251 nallocp, &minwait_secs); 252 253 /* XXX need proper deadline system for rekey/client alive */ 254 if (minwait_secs != 0) 255 max_time_ms = MINIMUM(max_time_ms, (u_int)minwait_secs * 1000); 256 257 /* 258 * if using client_alive, set the max timeout accordingly, 259 * and indicate that this particular timeout was for client 260 * alive by setting the client_alive_scheduled flag. 261 * 262 * this could be randomized somewhat to make traffic 263 * analysis more difficult, but we're not doing it yet. 264 */ 265 if (options.client_alive_interval) { 266 uint64_t keepalive_ms = 267 (uint64_t)options.client_alive_interval * 1000; 268 269 if (max_time_ms == 0 || max_time_ms > keepalive_ms) { 270 max_time_ms = keepalive_ms; 271 client_alive_scheduled = 1; 272 } 273 } 274 275 #if 0 276 /* wrong: bad condition XXX */ 277 if (channel_not_very_much_buffered_data()) 278 #endif 279 FD_SET(connection_in, *readsetp); 280 notify_prepare(*readsetp); 281 282 /* 283 * If we have buffered packet data going to the client, mark that 284 * descriptor. 285 */ 286 if (ssh_packet_have_data_to_write(ssh)) 287 FD_SET(connection_out, *writesetp); 288 289 /* 290 * If child has terminated and there is enough buffer space to read 291 * from it, then read as much as is available and exit. 292 */ 293 if (child_terminated && ssh_packet_not_very_much_data_to_write(ssh)) 294 if (max_time_ms == 0 || client_alive_scheduled) 295 max_time_ms = 100; 296 297 if (max_time_ms == 0) 298 tvp = NULL; 299 else { 300 tv.tv_sec = max_time_ms / 1000; 301 tv.tv_usec = 1000 * (max_time_ms % 1000); 302 tvp = &tv; 303 } 304 305 /* Wait for something to happen, or the timeout to expire. */ 306 ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp); 307 308 if (ret == -1) { 309 memset(*readsetp, 0, *nallocp); 310 memset(*writesetp, 0, *nallocp); 311 if (errno != EINTR) 312 error("select: %.100s", strerror(errno)); 313 } else if (client_alive_scheduled) { 314 time_t now = monotime(); 315 316 /* 317 * If the select timed out, or returned for some other reason 318 * but we haven't heard from the client in time, send keepalive. 319 */ 320 if (ret == 0 || (last_client_time != 0 && last_client_time + 321 options.client_alive_interval <= now)) { 322 client_alive_check(ssh); 323 last_client_time = now; 324 } else if (FD_ISSET(connection_in, *readsetp)) { 325 last_client_time = now; 326 } 327 } 328 329 notify_done(*readsetp); 330 } 331 332 /* 333 * Processes input from the client and the program. Input data is stored 334 * in buffers and processed later. 335 */ 336 static int 337 process_input(struct ssh *ssh, fd_set *readset, int connection_in) 338 { 339 int r, len; 340 char buf[16384]; 341 342 /* Read and buffer any input data from the client. */ 343 if (FD_ISSET(connection_in, readset)) { 344 len = read(connection_in, buf, sizeof(buf)); 345 if (len == 0) { 346 verbose("Connection closed by %.100s port %d", 347 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 348 return -1; 349 } else if (len == -1) { 350 if (errno != EINTR && errno != EAGAIN) { 351 verbose("Read error from remote host " 352 "%.100s port %d: %.100s", 353 ssh_remote_ipaddr(ssh), 354 ssh_remote_port(ssh), strerror(errno)); 355 cleanup_exit(254); 356 } 357 } else { 358 /* Buffer any received data. */ 359 if ((r = ssh_packet_process_incoming(ssh, buf, len)) 360 != 0) 361 fatal("%s: ssh_packet_process_incoming: %s", 362 __func__, ssh_err(r)); 363 } 364 } 365 return 0; 366 } 367 368 /* 369 * Sends data from internal buffers to client program stdin. 370 */ 371 static void 372 process_output(struct ssh *ssh, fd_set *writeset, int connection_out) 373 { 374 int r; 375 376 /* Send any buffered packet data to the client. */ 377 if (FD_ISSET(connection_out, writeset)) { 378 if ((r = ssh_packet_write_poll(ssh)) < 0) 379 sshpkt_fatal(ssh, r, "%s: ssh_packet_write_poll", 380 __func__); 381 } 382 } 383 384 static void 385 process_buffered_input_packets(struct ssh *ssh) 386 { 387 ssh_dispatch_run_fatal(ssh, DISPATCH_NONBLOCK, NULL); 388 } 389 390 static void 391 collect_children(struct ssh *ssh) 392 { 393 pid_t pid; 394 sigset_t oset, nset; 395 int status; 396 397 /* block SIGCHLD while we check for dead children */ 398 sigemptyset(&nset); 399 sigaddset(&nset, SIGCHLD); 400 sigprocmask(SIG_BLOCK, &nset, &oset); 401 if (child_terminated) { 402 debug("Received SIGCHLD."); 403 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 404 (pid == -1 && errno == EINTR)) 405 if (pid > 0) 406 session_close_by_pid(ssh, pid, status); 407 child_terminated = 0; 408 } 409 sigprocmask(SIG_SETMASK, &oset, NULL); 410 } 411 412 void 413 server_loop2(struct ssh *ssh, Authctxt *authctxt) 414 { 415 fd_set *readset = NULL, *writeset = NULL; 416 int max_fd; 417 u_int nalloc = 0, connection_in, connection_out; 418 u_int64_t rekey_timeout_ms = 0; 419 double start_time, total_time; 420 421 debug("Entering interactive session for SSH2."); 422 start_time = get_current_time(); 423 424 ssh_signal(SIGCHLD, sigchld_handler); 425 child_terminated = 0; 426 connection_in = ssh_packet_get_connection_in(ssh); 427 connection_out = ssh_packet_get_connection_out(ssh); 428 429 if (!use_privsep) { 430 ssh_signal(SIGTERM, sigterm_handler); 431 ssh_signal(SIGINT, sigterm_handler); 432 ssh_signal(SIGQUIT, sigterm_handler); 433 } 434 435 notify_setup(); 436 437 max_fd = MAXIMUM(connection_in, connection_out); 438 max_fd = MAXIMUM(max_fd, notify_pipe[0]); 439 440 server_init_dispatch(ssh); 441 442 for (;;) { 443 process_buffered_input_packets(ssh); 444 445 if (!ssh_packet_is_rekeying(ssh) && 446 ssh_packet_not_very_much_data_to_write(ssh)) 447 channel_output_poll(ssh); 448 if (options.rekey_interval > 0 && 449 !ssh_packet_is_rekeying(ssh)) { 450 rekey_timeout_ms = ssh_packet_get_rekey_timeout(ssh) * 451 1000; 452 } else { 453 rekey_timeout_ms = 0; 454 } 455 456 wait_until_can_do_something(ssh, connection_in, connection_out, 457 &readset, &writeset, &max_fd, &nalloc, rekey_timeout_ms); 458 459 if (received_sigterm) { 460 logit("Exiting on signal %d", (int)received_sigterm); 461 /* Clean up sessions, utmp, etc. */ 462 cleanup_exit(254); 463 } 464 465 collect_children(ssh); 466 if (!ssh_packet_is_rekeying(ssh)) 467 channel_after_select(ssh, readset, writeset); 468 if (process_input(ssh, readset, connection_in) < 0) 469 break; 470 process_output(ssh, writeset, connection_out); 471 } 472 collect_children(ssh); 473 474 free(readset); 475 free(writeset); 476 477 /* free all channels, no more reads and writes */ 478 channel_free_all(ssh); 479 480 /* free remaining sessions, e.g. remove wtmp entries */ 481 session_destroy_all(ssh, NULL); 482 total_time = get_current_time() - start_time; 483 logit("SSH: Server;LType: Throughput;Remote: %s-%d;IN: %lu;OUT: %lu;Duration: %.1f;tPut_in: %.1f;tPut_out: %.1f", 484 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), 485 stdin_bytes, fdout_bytes, total_time, stdin_bytes / total_time, 486 fdout_bytes / total_time); 487 } 488 489 static int 490 server_input_keep_alive(int type, u_int32_t seq, struct ssh *ssh) 491 { 492 debug("Got %d/%u for keepalive", type, seq); 493 /* 494 * reset timeout, since we got a sane answer from the client. 495 * even if this was generated by something other than 496 * the bogus CHANNEL_REQUEST we send for keepalives. 497 */ 498 ssh_packet_set_alive_timeouts(ssh, 0); 499 return 0; 500 } 501 502 static Channel * 503 server_request_direct_tcpip(struct ssh *ssh, int *reason, const char **errmsg) 504 { 505 Channel *c = NULL; 506 char *target = NULL, *originator = NULL; 507 u_int target_port = 0, originator_port = 0; 508 int r; 509 510 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 511 (r = sshpkt_get_u32(ssh, &target_port)) != 0 || 512 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 513 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 514 (r = sshpkt_get_end(ssh)) != 0) 515 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 516 if (target_port > 0xFFFF) { 517 error("%s: invalid target port", __func__); 518 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 519 goto out; 520 } 521 if (originator_port > 0xFFFF) { 522 error("%s: invalid originator port", __func__); 523 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 524 goto out; 525 } 526 527 debug("%s: originator %s port %u, target %s port %u", __func__, 528 originator, originator_port, target, target_port); 529 530 /* XXX fine grained permissions */ 531 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 && 532 auth_opts->permit_port_forwarding_flag && 533 !options.disable_forwarding) { 534 c = channel_connect_to_port(ssh, target, target_port, 535 "direct-tcpip", "direct-tcpip", reason, errmsg); 536 } else { 537 logit("refused local port forward: " 538 "originator %s port %d, target %s port %d", 539 originator, originator_port, target, target_port); 540 if (reason != NULL) 541 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 542 } 543 544 out: 545 free(originator); 546 free(target); 547 return c; 548 } 549 550 static Channel * 551 server_request_direct_streamlocal(struct ssh *ssh) 552 { 553 Channel *c = NULL; 554 char *target = NULL, *originator = NULL; 555 u_int originator_port = 0; 556 struct passwd *pw = the_authctxt->pw; 557 int r; 558 559 if (pw == NULL || !the_authctxt->valid) 560 fatal("%s: no/invalid user", __func__); 561 562 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 563 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 564 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 565 (r = sshpkt_get_end(ssh)) != 0) 566 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 567 if (originator_port > 0xFFFF) { 568 error("%s: invalid originator port", __func__); 569 goto out; 570 } 571 572 debug("%s: originator %s port %d, target %s", __func__, 573 originator, originator_port, target); 574 575 /* XXX fine grained permissions */ 576 if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 && 577 auth_opts->permit_port_forwarding_flag && 578 !options.disable_forwarding && (pw->pw_uid == 0 || use_privsep)) { 579 c = channel_connect_to_path(ssh, target, 580 "direct-streamlocal@openssh.com", "direct-streamlocal"); 581 } else { 582 logit("refused streamlocal port forward: " 583 "originator %s port %d, target %s", 584 originator, originator_port, target); 585 } 586 587 out: 588 free(originator); 589 free(target); 590 return c; 591 } 592 593 static Channel * 594 server_request_tun(struct ssh *ssh) 595 { 596 Channel *c = NULL; 597 u_int mode, tun; 598 int r, sock; 599 char *tmp, *ifname = NULL; 600 601 if ((r = sshpkt_get_u32(ssh, &mode)) != 0) 602 sshpkt_fatal(ssh, r, "%s: parse mode", __func__); 603 switch (mode) { 604 case SSH_TUNMODE_POINTOPOINT: 605 case SSH_TUNMODE_ETHERNET: 606 break; 607 default: 608 ssh_packet_send_debug(ssh, "Unsupported tunnel device mode."); 609 return NULL; 610 } 611 if ((options.permit_tun & mode) == 0) { 612 ssh_packet_send_debug(ssh, "Server has rejected tunnel device " 613 "forwarding"); 614 return NULL; 615 } 616 617 if ((r = sshpkt_get_u32(ssh, &tun)) != 0) 618 sshpkt_fatal(ssh, r, "%s: parse device", __func__); 619 if (tun > INT_MAX) { 620 debug("%s: invalid tun", __func__); 621 goto done; 622 } 623 if (auth_opts->force_tun_device != -1) { 624 if (tun != SSH_TUNID_ANY && 625 auth_opts->force_tun_device != (int)tun) 626 goto done; 627 tun = auth_opts->force_tun_device; 628 } 629 sock = tun_open(tun, mode, &ifname); 630 if (sock < 0) 631 goto done; 632 debug("Tunnel forwarding using interface %s", ifname); 633 634 if (options.hpn_disabled) 635 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1, 636 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 637 else 638 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1, 639 options.hpn_buffer_size, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 640 c->datagram = 1; 641 642 /* 643 * Update the list of names exposed to the session 644 * XXX remove these if the tunnels are closed (won't matter 645 * much if they are already in the environment though) 646 */ 647 tmp = tun_fwd_ifnames; 648 xasprintf(&tun_fwd_ifnames, "%s%s%s", 649 tun_fwd_ifnames == NULL ? "" : tun_fwd_ifnames, 650 tun_fwd_ifnames == NULL ? "" : ",", 651 ifname); 652 free(tmp); 653 free(ifname); 654 655 done: 656 if (c == NULL) 657 ssh_packet_send_debug(ssh, "Failed to open the tunnel device."); 658 return c; 659 } 660 661 static Channel * 662 server_request_session(struct ssh *ssh) 663 { 664 Channel *c; 665 int r; 666 667 debug("input_session_request"); 668 if ((r = sshpkt_get_end(ssh)) != 0) 669 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 670 671 if (no_more_sessions) { 672 ssh_packet_disconnect(ssh, "Possible attack: attempt to open a " 673 "session after additional sessions disabled"); 674 } 675 676 /* 677 * A server session has no fd to read or write until a 678 * CHANNEL_REQUEST for a shell is made, so we set the type to 679 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all 680 * CHANNEL_REQUEST messages is registered. 681 */ 682 c = channel_new(ssh, "session", SSH_CHANNEL_LARVAL, 683 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, 684 0, "server-session", 1); 685 if ((options.tcp_rcv_buf_poll > 0) && (!options.hpn_disabled)) 686 c->dynamic_window = 1; 687 if (session_open(the_authctxt, c->self) != 1) { 688 debug("session open failed, free channel %d", c->self); 689 channel_free(ssh, c); 690 return NULL; 691 } 692 channel_register_cleanup(ssh, c->self, session_close_by_channel, 0); 693 return c; 694 } 695 696 static int 697 server_input_channel_open(int type, u_int32_t seq, struct ssh *ssh) 698 { 699 Channel *c = NULL; 700 char *ctype = NULL; 701 const char *errmsg = NULL; 702 int r, reason = SSH2_OPEN_CONNECT_FAILED; 703 u_int rchan = 0, rmaxpack = 0, rwindow = 0; 704 705 if ((r = sshpkt_get_cstring(ssh, &ctype, NULL)) != 0 || 706 (r = sshpkt_get_u32(ssh, &rchan)) != 0 || 707 (r = sshpkt_get_u32(ssh, &rwindow)) != 0 || 708 (r = sshpkt_get_u32(ssh, &rmaxpack)) != 0) 709 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 710 debug("%s: ctype %s rchan %u win %u max %u", __func__, 711 ctype, rchan, rwindow, rmaxpack); 712 713 if (strcmp(ctype, "session") == 0) { 714 c = server_request_session(ssh); 715 } else if (strcmp(ctype, "direct-tcpip") == 0) { 716 c = server_request_direct_tcpip(ssh, &reason, &errmsg); 717 } else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) { 718 c = server_request_direct_streamlocal(ssh); 719 } else if (strcmp(ctype, "tun@openssh.com") == 0) { 720 c = server_request_tun(ssh); 721 } 722 if (c != NULL) { 723 debug("%s: confirm %s", __func__, ctype); 724 c->remote_id = rchan; 725 c->have_remote_id = 1; 726 c->remote_window = rwindow; 727 c->remote_maxpacket = rmaxpack; 728 if (c->type != SSH_CHANNEL_CONNECTING) { 729 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION)) != 0 || 730 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 731 (r = sshpkt_put_u32(ssh, c->self)) != 0 || 732 (r = sshpkt_put_u32(ssh, c->local_window)) != 0 || 733 (r = sshpkt_put_u32(ssh, c->local_maxpacket)) != 0 || 734 (r = sshpkt_send(ssh)) != 0) { 735 sshpkt_fatal(ssh, r, 736 "%s: send open confirm", __func__); 737 } 738 } 739 } else { 740 debug("%s: failure %s", __func__, ctype); 741 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE)) != 0 || 742 (r = sshpkt_put_u32(ssh, rchan)) != 0 || 743 (r = sshpkt_put_u32(ssh, reason)) != 0 || 744 (r = sshpkt_put_cstring(ssh, errmsg ? errmsg : "open failed")) != 0 || 745 (r = sshpkt_put_cstring(ssh, "")) != 0 || 746 (r = sshpkt_send(ssh)) != 0) { 747 sshpkt_fatal(ssh, r, 748 "%s: send open failure", __func__); 749 } 750 } 751 free(ctype); 752 return 0; 753 } 754 755 static int 756 server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp) 757 { 758 struct sshbuf *resp = NULL; 759 struct sshbuf *sigbuf = NULL; 760 struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL; 761 int r, ndx, kexsigtype, use_kexsigtype, success = 0; 762 const u_char *blob; 763 u_char *sig = 0; 764 size_t blen, slen; 765 766 if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL) 767 fatal("%s: sshbuf_new", __func__); 768 769 kexsigtype = sshkey_type_plain( 770 sshkey_type_from_name(ssh->kex->hostkey_alg)); 771 while (ssh_packet_remaining(ssh) > 0) { 772 sshkey_free(key); 773 key = NULL; 774 if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 || 775 (r = sshkey_from_blob(blob, blen, &key)) != 0) { 776 error("%s: couldn't parse key: %s", 777 __func__, ssh_err(r)); 778 goto out; 779 } 780 /* 781 * Better check that this is actually one of our hostkeys 782 * before attempting to sign anything with it. 783 */ 784 if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) { 785 error("%s: unknown host %s key", 786 __func__, sshkey_type(key)); 787 goto out; 788 } 789 /* 790 * XXX refactor: make kex->sign just use an index rather 791 * than passing in public and private keys 792 */ 793 if ((key_prv = get_hostkey_by_index(ndx)) == NULL && 794 (key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) { 795 error("%s: can't retrieve hostkey %d", __func__, ndx); 796 goto out; 797 } 798 sshbuf_reset(sigbuf); 799 free(sig); 800 sig = NULL; 801 /* 802 * For RSA keys, prefer to use the signature type negotiated 803 * during KEX to the default (SHA1). 804 */ 805 use_kexsigtype = kexsigtype == KEY_RSA && 806 sshkey_type_plain(key->type) == KEY_RSA; 807 if ((r = sshbuf_put_cstring(sigbuf, 808 "hostkeys-prove-00@openssh.com")) != 0 || 809 (r = sshbuf_put_string(sigbuf, 810 ssh->kex->session_id, ssh->kex->session_id_len)) != 0 || 811 (r = sshkey_puts(key, sigbuf)) != 0 || 812 (r = ssh->kex->sign(ssh, key_prv, key_pub, &sig, &slen, 813 sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), 814 use_kexsigtype ? ssh->kex->hostkey_alg : NULL)) != 0 || 815 (r = sshbuf_put_string(resp, sig, slen)) != 0) { 816 error("%s: couldn't prepare signature: %s", 817 __func__, ssh_err(r)); 818 goto out; 819 } 820 } 821 /* Success */ 822 *respp = resp; 823 resp = NULL; /* don't free it */ 824 success = 1; 825 out: 826 free(sig); 827 sshbuf_free(resp); 828 sshbuf_free(sigbuf); 829 sshkey_free(key); 830 return success; 831 } 832 833 static int 834 server_input_global_request(int type, u_int32_t seq, struct ssh *ssh) 835 { 836 char *rtype = NULL; 837 u_char want_reply = 0; 838 int r, success = 0, allocated_listen_port = 0; 839 u_int port = 0; 840 struct sshbuf *resp = NULL; 841 struct passwd *pw = the_authctxt->pw; 842 struct Forward fwd; 843 844 memset(&fwd, 0, sizeof(fwd)); 845 if (pw == NULL || !the_authctxt->valid) 846 fatal("%s: no/invalid user", __func__); 847 848 if ((r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 849 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 850 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 851 debug("%s: rtype %s want_reply %d", __func__, rtype, want_reply); 852 853 /* -R style forwarding */ 854 if (strcmp(rtype, "tcpip-forward") == 0) { 855 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 856 (r = sshpkt_get_u32(ssh, &port)) != 0) 857 sshpkt_fatal(ssh, r, "%s: parse tcpip-forward", __func__); 858 debug("%s: tcpip-forward listen %s port %u", __func__, 859 fwd.listen_host, port); 860 if (port <= INT_MAX) 861 fwd.listen_port = (int)port; 862 /* check permissions */ 863 if (port > INT_MAX || 864 (options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 || 865 !auth_opts->permit_port_forwarding_flag || 866 options.disable_forwarding || 867 (!want_reply && fwd.listen_port == 0) || 868 (fwd.listen_port != 0 && 869 !bind_permitted(fwd.listen_port, pw->pw_uid))) { 870 success = 0; 871 ssh_packet_send_debug(ssh, "Server has disabled port forwarding."); 872 } else { 873 /* Start listening on the port */ 874 success = channel_setup_remote_fwd_listener(ssh, &fwd, 875 &allocated_listen_port, &options.fwd_opts); 876 } 877 if ((resp = sshbuf_new()) == NULL) 878 fatal("%s: sshbuf_new", __func__); 879 if (allocated_listen_port != 0 && 880 (r = sshbuf_put_u32(resp, allocated_listen_port)) != 0) 881 fatal("%s: sshbuf_put_u32: %s", __func__, ssh_err(r)); 882 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) { 883 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 884 (r = sshpkt_get_u32(ssh, &port)) != 0) 885 sshpkt_fatal(ssh, r, "%s: parse cancel-tcpip-forward", __func__); 886 887 debug("%s: cancel-tcpip-forward addr %s port %d", __func__, 888 fwd.listen_host, port); 889 if (port <= INT_MAX) { 890 fwd.listen_port = (int)port; 891 success = channel_cancel_rport_listener(ssh, &fwd); 892 } 893 } else if (strcmp(rtype, "streamlocal-forward@openssh.com") == 0) { 894 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 895 sshpkt_fatal(ssh, r, "%s: parse streamlocal-forward@openssh.com", __func__); 896 debug("%s: streamlocal-forward listen path %s", __func__, 897 fwd.listen_path); 898 899 /* check permissions */ 900 if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0 901 || !auth_opts->permit_port_forwarding_flag || 902 options.disable_forwarding || 903 (pw->pw_uid != 0 && !use_privsep)) { 904 success = 0; 905 ssh_packet_send_debug(ssh, "Server has disabled " 906 "streamlocal forwarding."); 907 } else { 908 /* Start listening on the socket */ 909 success = channel_setup_remote_fwd_listener(ssh, 910 &fwd, NULL, &options.fwd_opts); 911 } 912 } else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) { 913 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 914 sshpkt_fatal(ssh, r, "%s: parse cancel-streamlocal-forward@openssh.com", __func__); 915 debug("%s: cancel-streamlocal-forward path %s", __func__, 916 fwd.listen_path); 917 918 success = channel_cancel_rport_listener(ssh, &fwd); 919 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) { 920 no_more_sessions = 1; 921 success = 1; 922 } else if (strcmp(rtype, "hostkeys-prove-00@openssh.com") == 0) { 923 success = server_input_hostkeys_prove(ssh, &resp); 924 } 925 /* XXX sshpkt_get_end() */ 926 if (want_reply) { 927 if ((r = sshpkt_start(ssh, success ? 928 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE)) != 0 || 929 (success && resp != NULL && (r = sshpkt_putb(ssh, resp)) != 0) || 930 (r = sshpkt_send(ssh)) != 0 || 931 (r = ssh_packet_write_wait(ssh)) < 0) 932 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 933 } 934 free(fwd.listen_host); 935 free(fwd.listen_path); 936 free(rtype); 937 sshbuf_free(resp); 938 return 0; 939 } 940 941 static int 942 server_input_channel_req(int type, u_int32_t seq, struct ssh *ssh) 943 { 944 Channel *c; 945 int r, success = 0; 946 char *rtype = NULL; 947 u_char want_reply = 0; 948 u_int id = 0; 949 950 if ((r = sshpkt_get_u32(ssh, &id)) != 0 || 951 (r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 952 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 953 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 954 955 debug("server_input_channel_req: channel %u request %s reply %d", 956 id, rtype, want_reply); 957 958 if (id >= INT_MAX || (c = channel_lookup(ssh, (int)id)) == NULL) { 959 ssh_packet_disconnect(ssh, "%s: unknown channel %d", 960 __func__, id); 961 } 962 if (!strcmp(rtype, "eow@openssh.com")) { 963 if ((r = sshpkt_get_end(ssh)) != 0) 964 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 965 chan_rcvd_eow(ssh, c); 966 } else if ((c->type == SSH_CHANNEL_LARVAL || 967 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0) 968 success = session_input_channel_req(ssh, c, rtype); 969 if (want_reply && !(c->flags & CHAN_CLOSE_SENT)) { 970 if (!c->have_remote_id) 971 fatal("%s: channel %d: no remote_id", 972 __func__, c->self); 973 if ((r = sshpkt_start(ssh, success ? 974 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE)) != 0 || 975 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 976 (r = sshpkt_send(ssh)) != 0) 977 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 978 } 979 free(rtype); 980 return 0; 981 } 982 983 static void 984 server_init_dispatch(struct ssh *ssh) 985 { 986 debug("server_init_dispatch"); 987 ssh_dispatch_init(ssh, &dispatch_protocol_error); 988 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); 989 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_DATA, &channel_input_data); 990 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); 991 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); 992 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); 993 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 994 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 995 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); 996 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); 997 ssh_dispatch_set(ssh, SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); 998 /* client_alive */ 999 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive); 1000 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); 1001 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); 1002 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); 1003 /* rekeying */ 1004 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit); 1005 } 1006