1 /* $NetBSD: serverloop.c,v 1.31 2021/09/02 11:26:18 christos Exp $ */ 2 /* $OpenBSD: serverloop.c,v 1.228 2021/07/16 09:00:23 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 1.31 2021/09/02 11:26:18 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 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */ 97 98 /* Cleanup on signals (!use_privsep case only) */ 99 static volatile sig_atomic_t received_sigterm = 0; 100 101 /* prototypes */ 102 static void server_init_dispatch(struct ssh *); 103 104 /* requested tunnel forwarding interface(s), shared with session.c */ 105 char *tun_fwd_ifnames = NULL; 106 107 /* returns 1 if bind to specified port by specified user is permitted */ 108 static int 109 bind_permitted(int port, uid_t uid) 110 { 111 if (use_privsep) 112 return 1; /* allow system to decide */ 113 if (port < IPPORT_RESERVED && uid != 0) 114 return 0; 115 return 1; 116 } 117 118 /* 119 * Returns current time in seconds from Jan 1, 1970 with the maximum 120 * available resolution. 121 */ 122 123 static double 124 get_current_time(void) 125 { 126 struct timeval tv; 127 gettimeofday(&tv, NULL); 128 return (double) tv.tv_sec + (double) tv.tv_usec / 1000000.0; 129 } 130 131 /*ARGSUSED*/ 132 static void 133 sigchld_handler(int sig) 134 { 135 child_terminated = 1; 136 } 137 138 /*ARGSUSED*/ 139 static void 140 sigterm_handler(int sig) 141 { 142 received_sigterm = sig; 143 } 144 145 static void 146 client_alive_check(struct ssh *ssh) 147 { 148 char remote_id[512]; 149 int r, channel_id; 150 151 /* timeout, check to see how many we have had */ 152 if (options.client_alive_count_max > 0 && 153 ssh_packet_inc_alive_timeouts(ssh) > 154 options.client_alive_count_max) { 155 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id)); 156 logit("Timeout, client not responding from %s", remote_id); 157 cleanup_exit(255); 158 } 159 160 /* 161 * send a bogus global/channel request with "wantreply", 162 * we should get back a failure 163 */ 164 if ((channel_id = channel_find_open(ssh)) == -1) { 165 if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 || 166 (r = sshpkt_put_cstring(ssh, "keepalive@openssh.com")) 167 != 0 || 168 (r = sshpkt_put_u8(ssh, 1)) != 0) /* boolean: want reply */ 169 fatal_fr(r, "compose"); 170 } else { 171 channel_request_start(ssh, channel_id, 172 "keepalive@openssh.com", 1); 173 } 174 if ((r = sshpkt_send(ssh)) != 0) 175 fatal_fr(r, "send"); 176 } 177 178 /* 179 * Sleep in pselect() until we can do something. This will initialize the 180 * pselect masks. Upon return, the masks will indicate which descriptors 181 * have data or can accept data. Optionally, a maximum time can be specified 182 * for the duration of the wait (0 = infinite). 183 */ 184 static void 185 wait_until_can_do_something(struct ssh *ssh, 186 int connection_in, int connection_out, 187 fd_set **readsetp, fd_set **writesetp, int *maxfdp, 188 u_int *nallocp, u_int64_t max_time_ms, sigset_t *sigsetp) 189 { 190 struct timespec ts, *tsp; 191 int ret; 192 time_t minwait_secs = 0; 193 int client_alive_scheduled = 0; 194 /* time we last heard from the client OR sent a keepalive */ 195 static time_t last_client_time; 196 197 /* Allocate and update pselect() masks for channel descriptors. */ 198 channel_prepare_select(ssh, readsetp, writesetp, maxfdp, 199 nallocp, &minwait_secs); 200 201 /* XXX need proper deadline system for rekey/client alive */ 202 if (minwait_secs != 0) 203 max_time_ms = MINIMUM(max_time_ms, (u_int)minwait_secs * 1000); 204 205 /* 206 * if using client_alive, set the max timeout accordingly, 207 * and indicate that this particular timeout was for client 208 * alive by setting the client_alive_scheduled flag. 209 * 210 * this could be randomized somewhat to make traffic 211 * analysis more difficult, but we're not doing it yet. 212 */ 213 if (options.client_alive_interval) { 214 uint64_t keepalive_ms = 215 (uint64_t)options.client_alive_interval * 1000; 216 217 if (max_time_ms == 0 || max_time_ms > keepalive_ms) { 218 max_time_ms = keepalive_ms; 219 client_alive_scheduled = 1; 220 } 221 if (last_client_time == 0) 222 last_client_time = monotime(); 223 } 224 225 #if 0 226 /* wrong: bad condition XXX */ 227 if (channel_not_very_much_buffered_data()) 228 #endif 229 FD_SET(connection_in, *readsetp); 230 231 /* 232 * If we have buffered packet data going to the client, mark that 233 * descriptor. 234 */ 235 if (ssh_packet_have_data_to_write(ssh)) 236 FD_SET(connection_out, *writesetp); 237 238 /* 239 * If child has terminated and there is enough buffer space to read 240 * from it, then read as much as is available and exit. 241 */ 242 if (child_terminated && ssh_packet_not_very_much_data_to_write(ssh)) 243 if (max_time_ms == 0 || client_alive_scheduled) 244 max_time_ms = 100; 245 246 if (max_time_ms == 0) 247 tsp = NULL; 248 else { 249 ts.tv_sec = max_time_ms / 1000; 250 ts.tv_nsec = 1000000 * (max_time_ms % 1000); 251 tsp = &ts; 252 } 253 254 /* Wait for something to happen, or the timeout to expire. */ 255 ret = pselect((*maxfdp)+1, *readsetp, *writesetp, NULL, tsp, sigsetp); 256 257 if (ret == -1) { 258 memset(*readsetp, 0, *nallocp); 259 memset(*writesetp, 0, *nallocp); 260 if (errno != EINTR) 261 error("pselect: %.100s", strerror(errno)); 262 } else if (client_alive_scheduled) { 263 time_t now = monotime(); 264 265 /* 266 * If the pselect timed out, or returned for some other reason 267 * but we haven't heard from the client in time, send keepalive. 268 */ 269 if (ret == 0 || (last_client_time != 0 && last_client_time + 270 options.client_alive_interval <= now)) { 271 client_alive_check(ssh); 272 last_client_time = now; 273 } else if (FD_ISSET(connection_in, *readsetp)) { 274 last_client_time = now; 275 } 276 } 277 } 278 279 /* 280 * Processes input from the client and the program. Input data is stored 281 * in buffers and processed later. 282 */ 283 static int 284 process_input(struct ssh *ssh, fd_set *readset, int connection_in) 285 { 286 int r, len; 287 char buf[16384]; 288 289 /* Read and buffer any input data from the client. */ 290 if (FD_ISSET(connection_in, readset)) { 291 len = read(connection_in, buf, sizeof(buf)); 292 if (len == 0) { 293 verbose("Connection closed by %.100s port %d", 294 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 295 return -1; 296 } else if (len == -1) { 297 if (errno == EINTR || errno == EAGAIN) 298 return 0; 299 verbose("Read error from remote host %s port %d: %s", 300 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), 301 strerror(errno)); 302 cleanup_exit(254); 303 } 304 /* Buffer any received data. */ 305 if ((r = ssh_packet_process_incoming(ssh, buf, len)) != 0) 306 fatal_fr(r, "ssh_packet_process_incoming"); 307 } 308 return 0; 309 } 310 311 /* 312 * Sends data from internal buffers to client program stdin. 313 */ 314 static void 315 process_output(struct ssh *ssh, fd_set *writeset, int connection_out) 316 { 317 int r; 318 319 /* Send any buffered packet data to the client. */ 320 if (FD_ISSET(connection_out, writeset)) { 321 if ((r = ssh_packet_write_poll(ssh)) < 0) 322 sshpkt_fatal(ssh, r, "%s: ssh_packet_write_poll", 323 __func__); 324 } 325 } 326 327 static void 328 process_buffered_input_packets(struct ssh *ssh) 329 { 330 ssh_dispatch_run_fatal(ssh, DISPATCH_NONBLOCK, NULL); 331 } 332 333 static void 334 collect_children(struct ssh *ssh) 335 { 336 pid_t pid; 337 int status; 338 339 if (child_terminated) { 340 debug("Received SIGCHLD."); 341 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 342 (pid == -1 && errno == EINTR)) 343 if (pid > 0) 344 session_close_by_pid(ssh, pid, status); 345 child_terminated = 0; 346 } 347 } 348 349 void 350 server_loop2(struct ssh *ssh, Authctxt *authctxt) 351 { 352 fd_set *readset = NULL, *writeset = NULL; 353 int r, max_fd; 354 u_int nalloc = 0, connection_in, connection_out; 355 u_int64_t rekey_timeout_ms = 0; 356 double start_time, total_time; 357 sigset_t bsigset, osigset; 358 359 debug("Entering interactive session for SSH2."); 360 start_time = get_current_time(); 361 362 if (sigemptyset(&bsigset) == -1 || sigaddset(&bsigset, SIGCHLD) == -1) 363 error_f("bsigset setup: %s", strerror(errno)); 364 ssh_signal(SIGCHLD, sigchld_handler); 365 child_terminated = 0; 366 connection_in = ssh_packet_get_connection_in(ssh); 367 connection_out = ssh_packet_get_connection_out(ssh); 368 369 if (!use_privsep) { 370 ssh_signal(SIGTERM, sigterm_handler); 371 ssh_signal(SIGINT, sigterm_handler); 372 ssh_signal(SIGQUIT, sigterm_handler); 373 } 374 375 max_fd = MAXIMUM(connection_in, connection_out); 376 377 server_init_dispatch(ssh); 378 379 for (;;) { 380 process_buffered_input_packets(ssh); 381 382 if (!ssh_packet_is_rekeying(ssh) && 383 ssh_packet_not_very_much_data_to_write(ssh)) 384 channel_output_poll(ssh); 385 if (options.rekey_interval > 0 && 386 !ssh_packet_is_rekeying(ssh)) { 387 rekey_timeout_ms = ssh_packet_get_rekey_timeout(ssh) * 388 1000; 389 } else { 390 rekey_timeout_ms = 0; 391 } 392 393 /* 394 * Block SIGCHLD while we check for dead children, then pass 395 * the old signal mask through to pselect() so that it'll wake 396 * up immediately if a child exits after we've called waitpid(). 397 */ 398 if (sigprocmask(SIG_BLOCK, &bsigset, &osigset) == -1) 399 error_f("bsigset sigprocmask: %s", strerror(errno)); 400 collect_children(ssh); 401 wait_until_can_do_something(ssh, connection_in, connection_out, 402 &readset, &writeset, &max_fd, &nalloc, rekey_timeout_ms, 403 &osigset); 404 if (sigprocmask(SIG_UNBLOCK, &bsigset, &osigset) == -1) 405 error_f("osigset sigprocmask: %s", strerror(errno)); 406 407 if (received_sigterm) { 408 logit("Exiting on signal %d", (int)received_sigterm); 409 /* Clean up sessions, utmp, etc. */ 410 cleanup_exit(254); 411 } 412 413 if (!ssh_packet_is_rekeying(ssh)) 414 channel_after_select(ssh, readset, writeset); 415 if (process_input(ssh, readset, connection_in) < 0) 416 break; 417 /* A timeout may have triggered rekeying */ 418 if ((r = ssh_packet_check_rekey(ssh)) != 0) 419 fatal_fr(r, "cannot start rekeying"); 420 process_output(ssh, writeset, connection_out); 421 } 422 collect_children(ssh); 423 424 free(readset); 425 free(writeset); 426 427 /* free all channels, no more reads and writes */ 428 channel_free_all(ssh); 429 430 /* free remaining sessions, e.g. remove wtmp entries */ 431 session_destroy_all(ssh, NULL); 432 total_time = get_current_time() - start_time; 433 logit("SSH: Server;LType: Throughput;Remote: %s-%d;IN: %lu;OUT: %lu;Duration: %.1f;tPut_in: %.1f;tPut_out: %.1f", 434 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), 435 stdin_bytes, fdout_bytes, total_time, stdin_bytes / total_time, 436 fdout_bytes / total_time); 437 } 438 439 static int 440 server_input_keep_alive(int type, u_int32_t seq, struct ssh *ssh) 441 { 442 debug("Got %d/%u for keepalive", type, seq); 443 /* 444 * reset timeout, since we got a sane answer from the client. 445 * even if this was generated by something other than 446 * the bogus CHANNEL_REQUEST we send for keepalives. 447 */ 448 ssh_packet_set_alive_timeouts(ssh, 0); 449 return 0; 450 } 451 452 static Channel * 453 server_request_direct_tcpip(struct ssh *ssh, int *reason, const char **errmsg) 454 { 455 Channel *c = NULL; 456 char *target = NULL, *originator = NULL; 457 u_int target_port = 0, originator_port = 0; 458 int r; 459 460 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 461 (r = sshpkt_get_u32(ssh, &target_port)) != 0 || 462 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 463 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 464 (r = sshpkt_get_end(ssh)) != 0) 465 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 466 if (target_port > 0xFFFF) { 467 error_f("invalid target port"); 468 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 469 goto out; 470 } 471 if (originator_port > 0xFFFF) { 472 error_f("invalid originator port"); 473 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 474 goto out; 475 } 476 477 debug_f("originator %s port %u, target %s port %u", 478 originator, originator_port, target, target_port); 479 480 /* XXX fine grained permissions */ 481 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 && 482 auth_opts->permit_port_forwarding_flag && 483 !options.disable_forwarding) { 484 c = channel_connect_to_port(ssh, target, target_port, 485 "direct-tcpip", "direct-tcpip", reason, errmsg); 486 } else { 487 logit("refused local port forward: " 488 "originator %s port %d, target %s port %d", 489 originator, originator_port, target, target_port); 490 if (reason != NULL) 491 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 492 } 493 494 out: 495 free(originator); 496 free(target); 497 return c; 498 } 499 500 static Channel * 501 server_request_direct_streamlocal(struct ssh *ssh) 502 { 503 Channel *c = NULL; 504 char *target = NULL, *originator = NULL; 505 u_int originator_port = 0; 506 struct passwd *pw = the_authctxt->pw; 507 int r; 508 509 if (pw == NULL || !the_authctxt->valid) 510 fatal_f("no/invalid user"); 511 512 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 513 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 514 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 515 (r = sshpkt_get_end(ssh)) != 0) 516 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 517 if (originator_port > 0xFFFF) { 518 error_f("invalid originator port"); 519 goto out; 520 } 521 522 debug_f("originator %s port %d, target %s", 523 originator, originator_port, target); 524 525 /* XXX fine grained permissions */ 526 if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 && 527 auth_opts->permit_port_forwarding_flag && 528 !options.disable_forwarding && (pw->pw_uid == 0 || use_privsep)) { 529 c = channel_connect_to_path(ssh, target, 530 "direct-streamlocal@openssh.com", "direct-streamlocal"); 531 } else { 532 logit("refused streamlocal port forward: " 533 "originator %s port %d, target %s", 534 originator, originator_port, target); 535 } 536 537 out: 538 free(originator); 539 free(target); 540 return c; 541 } 542 543 static Channel * 544 server_request_tun(struct ssh *ssh) 545 { 546 Channel *c = NULL; 547 u_int mode, tun; 548 int r, sock; 549 char *tmp, *ifname = NULL; 550 551 if ((r = sshpkt_get_u32(ssh, &mode)) != 0) 552 sshpkt_fatal(ssh, r, "%s: parse mode", __func__); 553 switch (mode) { 554 case SSH_TUNMODE_POINTOPOINT: 555 case SSH_TUNMODE_ETHERNET: 556 break; 557 default: 558 ssh_packet_send_debug(ssh, "Unsupported tunnel device mode."); 559 return NULL; 560 } 561 if ((options.permit_tun & mode) == 0) { 562 ssh_packet_send_debug(ssh, "Server has rejected tunnel device " 563 "forwarding"); 564 return NULL; 565 } 566 567 if ((r = sshpkt_get_u32(ssh, &tun)) != 0) 568 sshpkt_fatal(ssh, r, "%s: parse device", __func__); 569 if (tun > INT_MAX) { 570 debug_f("invalid tun"); 571 goto done; 572 } 573 if (auth_opts->force_tun_device != -1) { 574 if (tun != SSH_TUNID_ANY && 575 auth_opts->force_tun_device != (int)tun) 576 goto done; 577 tun = auth_opts->force_tun_device; 578 } 579 sock = tun_open(tun, mode, &ifname); 580 if (sock < 0) 581 goto done; 582 debug("Tunnel forwarding using interface %s", ifname); 583 584 if (options.hpn_disabled) 585 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1, 586 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 587 else 588 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1, 589 options.hpn_buffer_size, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 590 c->datagram = 1; 591 592 /* 593 * Update the list of names exposed to the session 594 * XXX remove these if the tunnels are closed (won't matter 595 * much if they are already in the environment though) 596 */ 597 tmp = tun_fwd_ifnames; 598 xasprintf(&tun_fwd_ifnames, "%s%s%s", 599 tun_fwd_ifnames == NULL ? "" : tun_fwd_ifnames, 600 tun_fwd_ifnames == NULL ? "" : ",", 601 ifname); 602 free(tmp); 603 free(ifname); 604 605 done: 606 if (c == NULL) 607 ssh_packet_send_debug(ssh, "Failed to open the tunnel device."); 608 return c; 609 } 610 611 static Channel * 612 server_request_session(struct ssh *ssh) 613 { 614 Channel *c; 615 int r; 616 617 debug("input_session_request"); 618 if ((r = sshpkt_get_end(ssh)) != 0) 619 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 620 621 if (no_more_sessions) { 622 ssh_packet_disconnect(ssh, "Possible attack: attempt to open a " 623 "session after additional sessions disabled"); 624 } 625 626 /* 627 * A server session has no fd to read or write until a 628 * CHANNEL_REQUEST for a shell is made, so we set the type to 629 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all 630 * CHANNEL_REQUEST messages is registered. 631 */ 632 c = channel_new(ssh, "session", SSH_CHANNEL_LARVAL, 633 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, 634 0, "server-session", 1); 635 if ((options.tcp_rcv_buf_poll > 0) && (!options.hpn_disabled)) 636 c->dynamic_window = 1; 637 if (session_open(the_authctxt, c->self) != 1) { 638 debug("session open failed, free channel %d", c->self); 639 channel_free(ssh, c); 640 return NULL; 641 } 642 channel_register_cleanup(ssh, c->self, session_close_by_channel, 0); 643 return c; 644 } 645 646 static int 647 server_input_channel_open(int type, u_int32_t seq, struct ssh *ssh) 648 { 649 Channel *c = NULL; 650 char *ctype = NULL; 651 const char *errmsg = NULL; 652 int r, reason = SSH2_OPEN_CONNECT_FAILED; 653 u_int rchan = 0, rmaxpack = 0, rwindow = 0; 654 655 if ((r = sshpkt_get_cstring(ssh, &ctype, NULL)) != 0 || 656 (r = sshpkt_get_u32(ssh, &rchan)) != 0 || 657 (r = sshpkt_get_u32(ssh, &rwindow)) != 0 || 658 (r = sshpkt_get_u32(ssh, &rmaxpack)) != 0) 659 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 660 debug_f("ctype %s rchan %u win %u max %u", 661 ctype, rchan, rwindow, rmaxpack); 662 663 if (strcmp(ctype, "session") == 0) { 664 c = server_request_session(ssh); 665 } else if (strcmp(ctype, "direct-tcpip") == 0) { 666 c = server_request_direct_tcpip(ssh, &reason, &errmsg); 667 } else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) { 668 c = server_request_direct_streamlocal(ssh); 669 } else if (strcmp(ctype, "tun@openssh.com") == 0) { 670 c = server_request_tun(ssh); 671 } 672 if (c != NULL) { 673 debug_f("confirm %s", ctype); 674 c->remote_id = rchan; 675 c->have_remote_id = 1; 676 c->remote_window = rwindow; 677 c->remote_maxpacket = rmaxpack; 678 if (c->type != SSH_CHANNEL_CONNECTING) { 679 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION)) != 0 || 680 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 681 (r = sshpkt_put_u32(ssh, c->self)) != 0 || 682 (r = sshpkt_put_u32(ssh, c->local_window)) != 0 || 683 (r = sshpkt_put_u32(ssh, c->local_maxpacket)) != 0 || 684 (r = sshpkt_send(ssh)) != 0) { 685 sshpkt_fatal(ssh, r, 686 "%s: send open confirm", __func__); 687 } 688 } 689 } else { 690 debug_f("failure %s", ctype); 691 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE)) != 0 || 692 (r = sshpkt_put_u32(ssh, rchan)) != 0 || 693 (r = sshpkt_put_u32(ssh, reason)) != 0 || 694 (r = sshpkt_put_cstring(ssh, errmsg ? errmsg : "open failed")) != 0 || 695 (r = sshpkt_put_cstring(ssh, "")) != 0 || 696 (r = sshpkt_send(ssh)) != 0) { 697 sshpkt_fatal(ssh, r, 698 "%s: send open failure", __func__); 699 } 700 } 701 free(ctype); 702 return 0; 703 } 704 705 static int 706 server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp) 707 { 708 struct sshbuf *resp = NULL; 709 struct sshbuf *sigbuf = NULL; 710 struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL; 711 int r, ndx, kexsigtype, use_kexsigtype, success = 0; 712 const u_char *blob; 713 u_char *sig = 0; 714 size_t blen, slen; 715 716 if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL) 717 fatal_f("sshbuf_new"); 718 719 kexsigtype = sshkey_type_plain( 720 sshkey_type_from_name(ssh->kex->hostkey_alg)); 721 while (ssh_packet_remaining(ssh) > 0) { 722 sshkey_free(key); 723 key = NULL; 724 if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 || 725 (r = sshkey_from_blob(blob, blen, &key)) != 0) { 726 error_fr(r, "parse key"); 727 goto out; 728 } 729 /* 730 * Better check that this is actually one of our hostkeys 731 * before attempting to sign anything with it. 732 */ 733 if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) { 734 error_f("unknown host %s key", sshkey_type(key)); 735 goto out; 736 } 737 /* 738 * XXX refactor: make kex->sign just use an index rather 739 * than passing in public and private keys 740 */ 741 if ((key_prv = get_hostkey_by_index(ndx)) == NULL && 742 (key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) { 743 error_f("can't retrieve hostkey %d", ndx); 744 goto out; 745 } 746 sshbuf_reset(sigbuf); 747 free(sig); 748 sig = NULL; 749 /* 750 * For RSA keys, prefer to use the signature type negotiated 751 * during KEX to the default (SHA1). 752 */ 753 use_kexsigtype = kexsigtype == KEY_RSA && 754 sshkey_type_plain(key->type) == KEY_RSA; 755 if ((r = sshbuf_put_cstring(sigbuf, 756 "hostkeys-prove-00@openssh.com")) != 0 || 757 (r = sshbuf_put_stringb(sigbuf, 758 ssh->kex->session_id)) != 0 || 759 (r = sshkey_puts(key, sigbuf)) != 0 || 760 (r = ssh->kex->sign(ssh, key_prv, key_pub, &sig, &slen, 761 sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), 762 use_kexsigtype ? ssh->kex->hostkey_alg : NULL)) != 0 || 763 (r = sshbuf_put_string(resp, sig, slen)) != 0) { 764 error_fr(r, "assemble signature"); 765 goto out; 766 } 767 } 768 /* Success */ 769 *respp = resp; 770 resp = NULL; /* don't free it */ 771 success = 1; 772 out: 773 free(sig); 774 sshbuf_free(resp); 775 sshbuf_free(sigbuf); 776 sshkey_free(key); 777 return success; 778 } 779 780 static int 781 server_input_global_request(int type, u_int32_t seq, struct ssh *ssh) 782 { 783 char *rtype = NULL; 784 u_char want_reply = 0; 785 int r, success = 0, allocated_listen_port = 0; 786 u_int port = 0; 787 struct sshbuf *resp = NULL; 788 struct passwd *pw = the_authctxt->pw; 789 struct Forward fwd; 790 791 memset(&fwd, 0, sizeof(fwd)); 792 if (pw == NULL || !the_authctxt->valid) 793 fatal_f("no/invalid user"); 794 795 if ((r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 796 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 797 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 798 debug_f("rtype %s want_reply %d", rtype, want_reply); 799 800 /* -R style forwarding */ 801 if (strcmp(rtype, "tcpip-forward") == 0) { 802 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 803 (r = sshpkt_get_u32(ssh, &port)) != 0) 804 sshpkt_fatal(ssh, r, "%s: parse tcpip-forward", __func__); 805 debug_f("tcpip-forward listen %s port %u", 806 fwd.listen_host, port); 807 if (port <= INT_MAX) 808 fwd.listen_port = (int)port; 809 /* check permissions */ 810 if (port > INT_MAX || 811 (options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 || 812 !auth_opts->permit_port_forwarding_flag || 813 options.disable_forwarding || 814 (!want_reply && fwd.listen_port == 0) || 815 (fwd.listen_port != 0 && 816 !bind_permitted(fwd.listen_port, pw->pw_uid))) { 817 success = 0; 818 ssh_packet_send_debug(ssh, "Server has disabled port forwarding."); 819 } else { 820 /* Start listening on the port */ 821 success = channel_setup_remote_fwd_listener(ssh, &fwd, 822 &allocated_listen_port, &options.fwd_opts); 823 } 824 if ((resp = sshbuf_new()) == NULL) 825 fatal_f("sshbuf_new"); 826 if (allocated_listen_port != 0 && 827 (r = sshbuf_put_u32(resp, allocated_listen_port)) != 0) 828 fatal_fr(r, "sshbuf_put_u32"); 829 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) { 830 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 831 (r = sshpkt_get_u32(ssh, &port)) != 0) 832 sshpkt_fatal(ssh, r, "%s: parse cancel-tcpip-forward", __func__); 833 834 debug_f("cancel-tcpip-forward addr %s port %d", 835 fwd.listen_host, port); 836 if (port <= INT_MAX) { 837 fwd.listen_port = (int)port; 838 success = channel_cancel_rport_listener(ssh, &fwd); 839 } 840 } else if (strcmp(rtype, "streamlocal-forward@openssh.com") == 0) { 841 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 842 sshpkt_fatal(ssh, r, "%s: parse streamlocal-forward@openssh.com", __func__); 843 debug_f("streamlocal-forward listen path %s", 844 fwd.listen_path); 845 846 /* check permissions */ 847 if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0 848 || !auth_opts->permit_port_forwarding_flag || 849 options.disable_forwarding || 850 (pw->pw_uid != 0 && !use_privsep)) { 851 success = 0; 852 ssh_packet_send_debug(ssh, "Server has disabled " 853 "streamlocal forwarding."); 854 } else { 855 /* Start listening on the socket */ 856 success = channel_setup_remote_fwd_listener(ssh, 857 &fwd, NULL, &options.fwd_opts); 858 } 859 } else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) { 860 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 861 sshpkt_fatal(ssh, r, "%s: parse cancel-streamlocal-forward@openssh.com", __func__); 862 debug_f("cancel-streamlocal-forward path %s", 863 fwd.listen_path); 864 865 success = channel_cancel_rport_listener(ssh, &fwd); 866 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) { 867 no_more_sessions = 1; 868 success = 1; 869 } else if (strcmp(rtype, "hostkeys-prove-00@openssh.com") == 0) { 870 success = server_input_hostkeys_prove(ssh, &resp); 871 } 872 /* XXX sshpkt_get_end() */ 873 if (want_reply) { 874 if ((r = sshpkt_start(ssh, success ? 875 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE)) != 0 || 876 (success && resp != NULL && (r = sshpkt_putb(ssh, resp)) != 0) || 877 (r = sshpkt_send(ssh)) != 0 || 878 (r = ssh_packet_write_wait(ssh)) < 0) 879 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 880 } 881 free(fwd.listen_host); 882 free(fwd.listen_path); 883 free(rtype); 884 sshbuf_free(resp); 885 return 0; 886 } 887 888 static int 889 server_input_channel_req(int type, u_int32_t seq, struct ssh *ssh) 890 { 891 Channel *c; 892 int r, success = 0; 893 char *rtype = NULL; 894 u_char want_reply = 0; 895 u_int id = 0; 896 897 if ((r = sshpkt_get_u32(ssh, &id)) != 0 || 898 (r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 899 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 900 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 901 902 debug("server_input_channel_req: channel %u request %s reply %d", 903 id, rtype, want_reply); 904 905 if (id >= INT_MAX || (c = channel_lookup(ssh, (int)id)) == NULL) { 906 ssh_packet_disconnect(ssh, "%s: unknown channel %d", 907 __func__, id); 908 } 909 if (!strcmp(rtype, "eow@openssh.com")) { 910 if ((r = sshpkt_get_end(ssh)) != 0) 911 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 912 chan_rcvd_eow(ssh, c); 913 } else if ((c->type == SSH_CHANNEL_LARVAL || 914 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0) 915 success = session_input_channel_req(ssh, c, rtype); 916 if (want_reply && !(c->flags & CHAN_CLOSE_SENT)) { 917 if (!c->have_remote_id) 918 fatal_f("channel %d: no remote_id", c->self); 919 if ((r = sshpkt_start(ssh, success ? 920 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE)) != 0 || 921 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 922 (r = sshpkt_send(ssh)) != 0) 923 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 924 } 925 free(rtype); 926 return 0; 927 } 928 929 static void 930 server_init_dispatch(struct ssh *ssh) 931 { 932 debug("server_init_dispatch"); 933 ssh_dispatch_init(ssh, &dispatch_protocol_error); 934 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); 935 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_DATA, &channel_input_data); 936 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); 937 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); 938 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); 939 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 940 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 941 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); 942 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); 943 ssh_dispatch_set(ssh, SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); 944 /* client_alive */ 945 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive); 946 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); 947 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); 948 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); 949 /* rekeying */ 950 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit); 951 } 952