1 /* $OpenBSD: sshd.c,v 1.514 2018/08/13 02:41:05 djm Exp $ */ 2 /* 3 * Author: Tatu Ylonen <ylo@cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 5 * All rights reserved 6 * This program is the ssh daemon. It listens for connections from clients, 7 * and performs authentication, executes use commands or shell, and forwards 8 * information to/from the application to the user client over an encrypted 9 * connection. This can also handle forwarding of X11, TCP/IP, and 10 * authentication agent connections. 11 * 12 * As far as I am concerned, the code I have written for this software 13 * can be used freely for any purpose. Any derived versions of this 14 * software must be clearly marked as such, and if the derived work is 15 * incompatible with the protocol description in the RFC file, it must be 16 * called by a name other than "ssh" or "Secure Shell". 17 * 18 * SSH2 implementation: 19 * Privilege Separation: 20 * 21 * Copyright (c) 2000, 2001, 2002 Markus Friedl. All rights reserved. 22 * Copyright (c) 2002 Niels Provos. All rights reserved. 23 * 24 * Redistribution and use in source and binary forms, with or without 25 * modification, are permitted provided that the following conditions 26 * are met: 27 * 1. Redistributions of source code must retain the above copyright 28 * notice, this list of conditions and the following disclaimer. 29 * 2. Redistributions in binary form must reproduce the above copyright 30 * notice, this list of conditions and the following disclaimer in the 31 * documentation and/or other materials provided with the distribution. 32 * 33 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 34 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 35 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 36 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 37 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 38 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 39 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 40 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 41 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 42 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 43 */ 44 45 #include "includes.h" 46 __RCSID("$FreeBSD$"); 47 48 #include <sys/types.h> 49 #include <sys/ioctl.h> 50 #include <sys/mman.h> 51 #include <sys/socket.h> 52 #ifdef HAVE_SYS_STAT_H 53 # include <sys/stat.h> 54 #endif 55 #ifdef HAVE_SYS_TIME_H 56 # include <sys/time.h> 57 #endif 58 #include "openbsd-compat/sys-tree.h" 59 #include "openbsd-compat/sys-queue.h" 60 #include <sys/wait.h> 61 62 #include <errno.h> 63 #include <fcntl.h> 64 #include <netdb.h> 65 #ifdef HAVE_PATHS_H 66 #include <paths.h> 67 #endif 68 #include <grp.h> 69 #include <pwd.h> 70 #include <signal.h> 71 #include <stdarg.h> 72 #include <stdio.h> 73 #include <stdlib.h> 74 #include <string.h> 75 #include <unistd.h> 76 #include <limits.h> 77 78 #ifdef WITH_OPENSSL 79 #include <openssl/dh.h> 80 #include <openssl/bn.h> 81 #include <openssl/rand.h> 82 #include "openbsd-compat/openssl-compat.h" 83 #endif 84 85 #ifdef HAVE_SECUREWARE 86 #include <sys/security.h> 87 #include <prot.h> 88 #endif 89 90 #ifdef __FreeBSD__ 91 #include <resolv.h> 92 #if defined(GSSAPI) && defined(HAVE_GSSAPI_GSSAPI_H) 93 #include <gssapi/gssapi.h> 94 #elif defined(GSSAPI) && defined(HAVE_GSSAPI_H) 95 #include <gssapi.h> 96 #endif 97 #endif 98 99 #include "xmalloc.h" 100 #include "ssh.h" 101 #include "ssh2.h" 102 #include "sshpty.h" 103 #include "packet.h" 104 #include "log.h" 105 #include "sshbuf.h" 106 #include "misc.h" 107 #include "match.h" 108 #include "servconf.h" 109 #include "uidswap.h" 110 #include "compat.h" 111 #include "cipher.h" 112 #include "digest.h" 113 #include "sshkey.h" 114 #include "kex.h" 115 #include "myproposal.h" 116 #include "authfile.h" 117 #include "pathnames.h" 118 #include "atomicio.h" 119 #include "canohost.h" 120 #include "hostfile.h" 121 #include "auth.h" 122 #include "authfd.h" 123 #include "msg.h" 124 #include "dispatch.h" 125 #include "channels.h" 126 #include "session.h" 127 #include "monitor.h" 128 #ifdef GSSAPI 129 #include "ssh-gss.h" 130 #endif 131 #include "monitor_wrap.h" 132 #include "ssh-sandbox.h" 133 #include "auth-options.h" 134 #include "version.h" 135 #include "ssherr.h" 136 #include "blacklist_client.h" 137 138 #ifdef LIBWRAP 139 #include <tcpd.h> 140 #include <syslog.h> 141 int allow_severity; 142 int deny_severity; 143 #endif /* LIBWRAP */ 144 145 /* Re-exec fds */ 146 #define REEXEC_DEVCRYPTO_RESERVED_FD (STDERR_FILENO + 1) 147 #define REEXEC_STARTUP_PIPE_FD (STDERR_FILENO + 2) 148 #define REEXEC_CONFIG_PASS_FD (STDERR_FILENO + 3) 149 #define REEXEC_MIN_FREE_FD (STDERR_FILENO + 4) 150 151 extern char *__progname; 152 153 /* Server configuration options. */ 154 ServerOptions options; 155 156 /* Name of the server configuration file. */ 157 char *config_file_name = _PATH_SERVER_CONFIG_FILE; 158 159 /* 160 * Debug mode flag. This can be set on the command line. If debug 161 * mode is enabled, extra debugging output will be sent to the system 162 * log, the daemon will not go to background, and will exit after processing 163 * the first connection. 164 */ 165 int debug_flag = 0; 166 167 /* 168 * Indicating that the daemon should only test the configuration and keys. 169 * If test_flag > 1 ("-T" flag), then sshd will also dump the effective 170 * configuration, optionally using connection information provided by the 171 * "-C" flag. 172 */ 173 int test_flag = 0; 174 175 /* Flag indicating that the daemon is being started from inetd. */ 176 int inetd_flag = 0; 177 178 /* Flag indicating that sshd should not detach and become a daemon. */ 179 int no_daemon_flag = 0; 180 181 /* debug goes to stderr unless inetd_flag is set */ 182 int log_stderr = 0; 183 184 /* Saved arguments to main(). */ 185 char **saved_argv; 186 int saved_argc; 187 188 /* re-exec */ 189 int rexeced_flag = 0; 190 int rexec_flag = 1; 191 int rexec_argc = 0; 192 char **rexec_argv; 193 194 /* 195 * The sockets that the server is listening; this is used in the SIGHUP 196 * signal handler. 197 */ 198 #define MAX_LISTEN_SOCKS 16 199 int listen_socks[MAX_LISTEN_SOCKS]; 200 int num_listen_socks = 0; 201 202 /* 203 * the client's version string, passed by sshd2 in compat mode. if != NULL, 204 * sshd will skip the version-number exchange 205 */ 206 char *client_version_string = NULL; 207 char *server_version_string = NULL; 208 209 /* Daemon's agent connection */ 210 int auth_sock = -1; 211 int have_agent = 0; 212 213 /* 214 * Any really sensitive data in the application is contained in this 215 * structure. The idea is that this structure could be locked into memory so 216 * that the pages do not get written into swap. However, there are some 217 * problems. The private key contains BIGNUMs, and we do not (in principle) 218 * have access to the internals of them, and locking just the structure is 219 * not very useful. Currently, memory locking is not implemented. 220 */ 221 struct { 222 struct sshkey **host_keys; /* all private host keys */ 223 struct sshkey **host_pubkeys; /* all public host keys */ 224 struct sshkey **host_certificates; /* all public host certificates */ 225 int have_ssh2_key; 226 } sensitive_data; 227 228 /* This is set to true when a signal is received. */ 229 static volatile sig_atomic_t received_sighup = 0; 230 static volatile sig_atomic_t received_sigterm = 0; 231 232 /* session identifier, used by RSA-auth */ 233 u_char session_id[16]; 234 235 /* same for ssh2 */ 236 u_char *session_id2 = NULL; 237 u_int session_id2_len = 0; 238 239 /* record remote hostname or ip */ 240 u_int utmp_len = HOST_NAME_MAX+1; 241 242 /* options.max_startup sized array of fd ints */ 243 int *startup_pipes = NULL; 244 int startup_pipe; /* in child */ 245 246 /* variables used for privilege separation */ 247 int use_privsep = -1; 248 struct monitor *pmonitor = NULL; 249 int privsep_is_preauth = 1; 250 static int privsep_chroot = 1; 251 252 /* global authentication context */ 253 Authctxt *the_authctxt = NULL; 254 255 /* global key/cert auth options. XXX move to permanent ssh->authctxt? */ 256 struct sshauthopt *auth_opts = NULL; 257 258 /* sshd_config buffer */ 259 struct sshbuf *cfg; 260 261 /* message to be displayed after login */ 262 struct sshbuf *loginmsg; 263 264 /* Unprivileged user */ 265 struct passwd *privsep_pw = NULL; 266 267 /* Prototypes for various functions defined later in this file. */ 268 void destroy_sensitive_data(void); 269 void demote_sensitive_data(void); 270 static void do_ssh2_kex(void); 271 272 /* 273 * Close all listening sockets 274 */ 275 static void 276 close_listen_socks(void) 277 { 278 int i; 279 280 for (i = 0; i < num_listen_socks; i++) 281 close(listen_socks[i]); 282 num_listen_socks = -1; 283 } 284 285 static void 286 close_startup_pipes(void) 287 { 288 int i; 289 290 if (startup_pipes) 291 for (i = 0; i < options.max_startups; i++) 292 if (startup_pipes[i] != -1) 293 close(startup_pipes[i]); 294 } 295 296 /* 297 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP; 298 * the effect is to reread the configuration file (and to regenerate 299 * the server key). 300 */ 301 302 /*ARGSUSED*/ 303 static void 304 sighup_handler(int sig) 305 { 306 int save_errno = errno; 307 308 received_sighup = 1; 309 errno = save_errno; 310 } 311 312 /* 313 * Called from the main program after receiving SIGHUP. 314 * Restarts the server. 315 */ 316 static void 317 sighup_restart(void) 318 { 319 logit("Received SIGHUP; restarting."); 320 if (options.pid_file != NULL) 321 unlink(options.pid_file); 322 platform_pre_restart(); 323 close_listen_socks(); 324 close_startup_pipes(); 325 alarm(0); /* alarm timer persists across exec */ 326 signal(SIGHUP, SIG_IGN); /* will be restored after exec */ 327 execv(saved_argv[0], saved_argv); 328 logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], 329 strerror(errno)); 330 exit(1); 331 } 332 333 /* 334 * Generic signal handler for terminating signals in the master daemon. 335 */ 336 /*ARGSUSED*/ 337 static void 338 sigterm_handler(int sig) 339 { 340 received_sigterm = sig; 341 } 342 343 /* 344 * SIGCHLD handler. This is called whenever a child dies. This will then 345 * reap any zombies left by exited children. 346 */ 347 /*ARGSUSED*/ 348 static void 349 main_sigchld_handler(int sig) 350 { 351 int save_errno = errno; 352 pid_t pid; 353 int status; 354 355 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 356 (pid < 0 && errno == EINTR)) 357 ; 358 errno = save_errno; 359 } 360 361 /* 362 * Signal handler for the alarm after the login grace period has expired. 363 */ 364 /*ARGSUSED*/ 365 static void 366 grace_alarm_handler(int sig) 367 { 368 if (use_privsep && pmonitor != NULL && pmonitor->m_pid > 0) 369 kill(pmonitor->m_pid, SIGALRM); 370 371 /* 372 * Try to kill any processes that we have spawned, E.g. authorized 373 * keys command helpers. 374 */ 375 if (getpgid(0) == getpid()) { 376 signal(SIGTERM, SIG_IGN); 377 kill(0, SIGTERM); 378 } 379 380 BLACKLIST_NOTIFY(BLACKLIST_AUTH_FAIL, "ssh"); 381 382 /* Log error and exit. */ 383 sigdie("Timeout before authentication for %s port %d", 384 ssh_remote_ipaddr(active_state), ssh_remote_port(active_state)); 385 } 386 387 static void 388 sshd_exchange_identification(struct ssh *ssh, int sock_in, int sock_out) 389 { 390 u_int i; 391 int remote_major, remote_minor; 392 char *s; 393 char buf[256]; /* Must not be larger than remote_version. */ 394 char remote_version[256]; /* Must be at least as big as buf. */ 395 396 xasprintf(&server_version_string, "SSH-%d.%d-%.100s%s%s\r\n", 397 PROTOCOL_MAJOR_2, PROTOCOL_MINOR_2, SSH_VERSION, 398 *options.version_addendum == '\0' ? "" : " ", 399 options.version_addendum); 400 401 /* Send our protocol version identification. */ 402 if (atomicio(vwrite, sock_out, server_version_string, 403 strlen(server_version_string)) 404 != strlen(server_version_string)) { 405 logit("Could not write ident string to %s port %d", 406 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 407 cleanup_exit(255); 408 } 409 410 /* Read other sides version identification. */ 411 memset(buf, 0, sizeof(buf)); 412 for (i = 0; i < sizeof(buf) - 1; i++) { 413 if (atomicio(read, sock_in, &buf[i], 1) != 1) { 414 logit("Did not receive identification string " 415 "from %s port %d", 416 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 417 cleanup_exit(255); 418 } 419 if (buf[i] == '\r') { 420 buf[i] = 0; 421 /* Kludge for F-Secure Macintosh < 1.0.2 */ 422 if (i == 12 && 423 strncmp(buf, "SSH-1.5-W1.0", 12) == 0) 424 break; 425 continue; 426 } 427 if (buf[i] == '\n') { 428 buf[i] = 0; 429 break; 430 } 431 } 432 buf[sizeof(buf) - 1] = 0; 433 client_version_string = xstrdup(buf); 434 435 /* 436 * Check that the versions match. In future this might accept 437 * several versions and set appropriate flags to handle them. 438 */ 439 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n", 440 &remote_major, &remote_minor, remote_version) != 3) { 441 s = "Protocol mismatch.\n"; 442 (void) atomicio(vwrite, sock_out, s, strlen(s)); 443 logit("Bad protocol version identification '%.100s' " 444 "from %s port %d", client_version_string, 445 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 446 close(sock_in); 447 close(sock_out); 448 cleanup_exit(255); 449 } 450 debug("Client protocol version %d.%d; client software version %.100s", 451 remote_major, remote_minor, remote_version); 452 453 ssh->compat = compat_datafellows(remote_version); 454 455 if ((ssh->compat & SSH_BUG_PROBE) != 0) { 456 logit("probed from %s port %d with %s. Don't panic.", 457 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), 458 client_version_string); 459 cleanup_exit(255); 460 } 461 if ((ssh->compat & SSH_BUG_SCANNER) != 0) { 462 logit("scanned from %s port %d with %s. Don't panic.", 463 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), 464 client_version_string); 465 cleanup_exit(255); 466 } 467 if ((ssh->compat & SSH_BUG_RSASIGMD5) != 0) { 468 logit("Client version \"%.100s\" uses unsafe RSA signature " 469 "scheme; disabling use of RSA keys", remote_version); 470 } 471 472 chop(server_version_string); 473 debug("Local version string %.200s", server_version_string); 474 475 if (remote_major != 2 && 476 !(remote_major == 1 && remote_minor == 99)) { 477 s = "Protocol major versions differ.\n"; 478 (void) atomicio(vwrite, sock_out, s, strlen(s)); 479 close(sock_in); 480 close(sock_out); 481 logit("Protocol major versions differ for %s port %d: " 482 "%.200s vs. %.200s", 483 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), 484 server_version_string, client_version_string); 485 cleanup_exit(255); 486 } 487 } 488 489 /* Destroy the host and server keys. They will no longer be needed. */ 490 void 491 destroy_sensitive_data(void) 492 { 493 u_int i; 494 495 for (i = 0; i < options.num_host_key_files; i++) { 496 if (sensitive_data.host_keys[i]) { 497 sshkey_free(sensitive_data.host_keys[i]); 498 sensitive_data.host_keys[i] = NULL; 499 } 500 if (sensitive_data.host_certificates[i]) { 501 sshkey_free(sensitive_data.host_certificates[i]); 502 sensitive_data.host_certificates[i] = NULL; 503 } 504 } 505 } 506 507 /* Demote private to public keys for network child */ 508 void 509 demote_sensitive_data(void) 510 { 511 struct sshkey *tmp; 512 u_int i; 513 int r; 514 515 for (i = 0; i < options.num_host_key_files; i++) { 516 if (sensitive_data.host_keys[i]) { 517 if ((r = sshkey_from_private( 518 sensitive_data.host_keys[i], &tmp)) != 0) 519 fatal("could not demote host %s key: %s", 520 sshkey_type(sensitive_data.host_keys[i]), 521 ssh_err(r)); 522 sshkey_free(sensitive_data.host_keys[i]); 523 sensitive_data.host_keys[i] = tmp; 524 } 525 /* Certs do not need demotion */ 526 } 527 } 528 529 static void 530 reseed_prngs(void) 531 { 532 u_int32_t rnd[256]; 533 534 #ifdef WITH_OPENSSL 535 RAND_poll(); 536 #endif 537 arc4random_stir(); /* noop on recent arc4random() implementations */ 538 arc4random_buf(rnd, sizeof(rnd)); /* let arc4random notice PID change */ 539 540 #ifdef WITH_OPENSSL 541 RAND_seed(rnd, sizeof(rnd)); 542 /* give libcrypto a chance to notice the PID change */ 543 if ((RAND_bytes((u_char *)rnd, 1)) != 1) 544 fatal("%s: RAND_bytes failed", __func__); 545 #endif 546 547 explicit_bzero(rnd, sizeof(rnd)); 548 } 549 550 static void 551 privsep_preauth_child(void) 552 { 553 gid_t gidset[1]; 554 555 /* Enable challenge-response authentication for privilege separation */ 556 privsep_challenge_enable(); 557 558 #ifdef GSSAPI 559 /* Cache supported mechanism OIDs for later use */ 560 if (options.gss_authentication) 561 ssh_gssapi_prepare_supported_oids(); 562 #endif 563 564 reseed_prngs(); 565 566 /* Demote the private keys to public keys. */ 567 demote_sensitive_data(); 568 569 /* Demote the child */ 570 if (privsep_chroot) { 571 /* Change our root directory */ 572 if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1) 573 fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR, 574 strerror(errno)); 575 if (chdir("/") == -1) 576 fatal("chdir(\"/\"): %s", strerror(errno)); 577 578 /* Drop our privileges */ 579 debug3("privsep user:group %u:%u", (u_int)privsep_pw->pw_uid, 580 (u_int)privsep_pw->pw_gid); 581 gidset[0] = privsep_pw->pw_gid; 582 if (setgroups(1, gidset) < 0) 583 fatal("setgroups: %.100s", strerror(errno)); 584 permanently_set_uid(privsep_pw); 585 } 586 } 587 588 static int 589 privsep_preauth(Authctxt *authctxt) 590 { 591 int status, r; 592 pid_t pid; 593 struct ssh_sandbox *box = NULL; 594 595 /* Set up unprivileged child process to deal with network data */ 596 pmonitor = monitor_init(); 597 /* Store a pointer to the kex for later rekeying */ 598 pmonitor->m_pkex = &active_state->kex; 599 600 if (use_privsep == PRIVSEP_ON) 601 box = ssh_sandbox_init(pmonitor); 602 pid = fork(); 603 if (pid == -1) { 604 fatal("fork of unprivileged child failed"); 605 } else if (pid != 0) { 606 debug2("Network child is on pid %ld", (long)pid); 607 608 pmonitor->m_pid = pid; 609 if (have_agent) { 610 r = ssh_get_authentication_socket(&auth_sock); 611 if (r != 0) { 612 error("Could not get agent socket: %s", 613 ssh_err(r)); 614 have_agent = 0; 615 } 616 } 617 if (box != NULL) 618 ssh_sandbox_parent_preauth(box, pid); 619 monitor_child_preauth(authctxt, pmonitor); 620 621 /* Wait for the child's exit status */ 622 while (waitpid(pid, &status, 0) < 0) { 623 if (errno == EINTR) 624 continue; 625 pmonitor->m_pid = -1; 626 fatal("%s: waitpid: %s", __func__, strerror(errno)); 627 } 628 privsep_is_preauth = 0; 629 pmonitor->m_pid = -1; 630 if (WIFEXITED(status)) { 631 if (WEXITSTATUS(status) != 0) 632 fatal("%s: preauth child exited with status %d", 633 __func__, WEXITSTATUS(status)); 634 } else if (WIFSIGNALED(status)) 635 fatal("%s: preauth child terminated by signal %d", 636 __func__, WTERMSIG(status)); 637 if (box != NULL) 638 ssh_sandbox_parent_finish(box); 639 return 1; 640 } else { 641 /* child */ 642 close(pmonitor->m_sendfd); 643 close(pmonitor->m_log_recvfd); 644 645 /* Arrange for logging to be sent to the monitor */ 646 set_log_handler(mm_log_handler, pmonitor); 647 648 privsep_preauth_child(); 649 setproctitle("%s", "[net]"); 650 if (box != NULL) 651 ssh_sandbox_child(box); 652 653 return 0; 654 } 655 } 656 657 static void 658 privsep_postauth(Authctxt *authctxt) 659 { 660 #ifdef DISABLE_FD_PASSING 661 if (1) { 662 #else 663 if (authctxt->pw->pw_uid == 0) { 664 #endif 665 /* File descriptor passing is broken or root login */ 666 use_privsep = 0; 667 goto skip; 668 } 669 670 /* New socket pair */ 671 monitor_reinit(pmonitor); 672 673 pmonitor->m_pid = fork(); 674 if (pmonitor->m_pid == -1) 675 fatal("fork of unprivileged child failed"); 676 else if (pmonitor->m_pid != 0) { 677 verbose("User child is on pid %ld", (long)pmonitor->m_pid); 678 sshbuf_reset(loginmsg); 679 monitor_clear_keystate(pmonitor); 680 monitor_child_postauth(pmonitor); 681 682 /* NEVERREACHED */ 683 exit(0); 684 } 685 686 /* child */ 687 688 close(pmonitor->m_sendfd); 689 pmonitor->m_sendfd = -1; 690 691 /* Demote the private keys to public keys. */ 692 demote_sensitive_data(); 693 694 reseed_prngs(); 695 696 /* Drop privileges */ 697 do_setusercontext(authctxt->pw); 698 699 skip: 700 /* It is safe now to apply the key state */ 701 monitor_apply_keystate(pmonitor); 702 703 /* 704 * Tell the packet layer that authentication was successful, since 705 * this information is not part of the key state. 706 */ 707 packet_set_authenticated(); 708 } 709 710 static void 711 append_hostkey_type(struct sshbuf *b, const char *s) 712 { 713 int r; 714 715 if (match_pattern_list(s, options.hostkeyalgorithms, 0) != 1) { 716 debug3("%s: %s key not permitted by HostkeyAlgorithms", 717 __func__, s); 718 return; 719 } 720 if ((r = sshbuf_putf(b, "%s%s", sshbuf_len(b) > 0 ? "," : "", s)) != 0) 721 fatal("%s: sshbuf_putf: %s", __func__, ssh_err(r)); 722 } 723 724 static char * 725 list_hostkey_types(void) 726 { 727 struct sshbuf *b; 728 struct sshkey *key; 729 char *ret; 730 u_int i; 731 732 if ((b = sshbuf_new()) == NULL) 733 fatal("%s: sshbuf_new failed", __func__); 734 for (i = 0; i < options.num_host_key_files; i++) { 735 key = sensitive_data.host_keys[i]; 736 if (key == NULL) 737 key = sensitive_data.host_pubkeys[i]; 738 if (key == NULL) 739 continue; 740 switch (key->type) { 741 case KEY_RSA: 742 /* for RSA we also support SHA2 signatures */ 743 append_hostkey_type(b, "rsa-sha2-512"); 744 append_hostkey_type(b, "rsa-sha2-256"); 745 /* FALLTHROUGH */ 746 case KEY_DSA: 747 case KEY_ECDSA: 748 case KEY_ED25519: 749 case KEY_XMSS: 750 append_hostkey_type(b, sshkey_ssh_name(key)); 751 break; 752 } 753 /* If the private key has a cert peer, then list that too */ 754 key = sensitive_data.host_certificates[i]; 755 if (key == NULL) 756 continue; 757 switch (key->type) { 758 case KEY_RSA_CERT: 759 /* for RSA we also support SHA2 signatures */ 760 append_hostkey_type(b, 761 "rsa-sha2-512-cert-v01@openssh.com"); 762 append_hostkey_type(b, 763 "rsa-sha2-256-cert-v01@openssh.com"); 764 /* FALLTHROUGH */ 765 case KEY_DSA_CERT: 766 case KEY_ECDSA_CERT: 767 case KEY_ED25519_CERT: 768 case KEY_XMSS_CERT: 769 append_hostkey_type(b, sshkey_ssh_name(key)); 770 break; 771 } 772 } 773 if ((ret = sshbuf_dup_string(b)) == NULL) 774 fatal("%s: sshbuf_dup_string failed", __func__); 775 sshbuf_free(b); 776 debug("%s: %s", __func__, ret); 777 return ret; 778 } 779 780 static struct sshkey * 781 get_hostkey_by_type(int type, int nid, int need_private, struct ssh *ssh) 782 { 783 u_int i; 784 struct sshkey *key; 785 786 for (i = 0; i < options.num_host_key_files; i++) { 787 switch (type) { 788 case KEY_RSA_CERT: 789 case KEY_DSA_CERT: 790 case KEY_ECDSA_CERT: 791 case KEY_ED25519_CERT: 792 case KEY_XMSS_CERT: 793 key = sensitive_data.host_certificates[i]; 794 break; 795 default: 796 key = sensitive_data.host_keys[i]; 797 if (key == NULL && !need_private) 798 key = sensitive_data.host_pubkeys[i]; 799 break; 800 } 801 if (key != NULL && key->type == type && 802 (key->type != KEY_ECDSA || key->ecdsa_nid == nid)) 803 return need_private ? 804 sensitive_data.host_keys[i] : key; 805 } 806 return NULL; 807 } 808 809 struct sshkey * 810 get_hostkey_public_by_type(int type, int nid, struct ssh *ssh) 811 { 812 return get_hostkey_by_type(type, nid, 0, ssh); 813 } 814 815 struct sshkey * 816 get_hostkey_private_by_type(int type, int nid, struct ssh *ssh) 817 { 818 return get_hostkey_by_type(type, nid, 1, ssh); 819 } 820 821 struct sshkey * 822 get_hostkey_by_index(int ind) 823 { 824 if (ind < 0 || (u_int)ind >= options.num_host_key_files) 825 return (NULL); 826 return (sensitive_data.host_keys[ind]); 827 } 828 829 struct sshkey * 830 get_hostkey_public_by_index(int ind, struct ssh *ssh) 831 { 832 if (ind < 0 || (u_int)ind >= options.num_host_key_files) 833 return (NULL); 834 return (sensitive_data.host_pubkeys[ind]); 835 } 836 837 int 838 get_hostkey_index(struct sshkey *key, int compare, struct ssh *ssh) 839 { 840 u_int i; 841 842 for (i = 0; i < options.num_host_key_files; i++) { 843 if (sshkey_is_cert(key)) { 844 if (key == sensitive_data.host_certificates[i] || 845 (compare && sensitive_data.host_certificates[i] && 846 sshkey_equal(key, 847 sensitive_data.host_certificates[i]))) 848 return (i); 849 } else { 850 if (key == sensitive_data.host_keys[i] || 851 (compare && sensitive_data.host_keys[i] && 852 sshkey_equal(key, sensitive_data.host_keys[i]))) 853 return (i); 854 if (key == sensitive_data.host_pubkeys[i] || 855 (compare && sensitive_data.host_pubkeys[i] && 856 sshkey_equal(key, sensitive_data.host_pubkeys[i]))) 857 return (i); 858 } 859 } 860 return (-1); 861 } 862 863 /* Inform the client of all hostkeys */ 864 static void 865 notify_hostkeys(struct ssh *ssh) 866 { 867 struct sshbuf *buf; 868 struct sshkey *key; 869 u_int i, nkeys; 870 int r; 871 char *fp; 872 873 /* Some clients cannot cope with the hostkeys message, skip those. */ 874 if (datafellows & SSH_BUG_HOSTKEYS) 875 return; 876 877 if ((buf = sshbuf_new()) == NULL) 878 fatal("%s: sshbuf_new", __func__); 879 for (i = nkeys = 0; i < options.num_host_key_files; i++) { 880 key = get_hostkey_public_by_index(i, ssh); 881 if (key == NULL || key->type == KEY_UNSPEC || 882 sshkey_is_cert(key)) 883 continue; 884 fp = sshkey_fingerprint(key, options.fingerprint_hash, 885 SSH_FP_DEFAULT); 886 debug3("%s: key %d: %s %s", __func__, i, 887 sshkey_ssh_name(key), fp); 888 free(fp); 889 if (nkeys == 0) { 890 packet_start(SSH2_MSG_GLOBAL_REQUEST); 891 packet_put_cstring("hostkeys-00@openssh.com"); 892 packet_put_char(0); /* want-reply */ 893 } 894 sshbuf_reset(buf); 895 if ((r = sshkey_putb(key, buf)) != 0) 896 fatal("%s: couldn't put hostkey %d: %s", 897 __func__, i, ssh_err(r)); 898 packet_put_string(sshbuf_ptr(buf), sshbuf_len(buf)); 899 nkeys++; 900 } 901 debug3("%s: sent %u hostkeys", __func__, nkeys); 902 if (nkeys == 0) 903 fatal("%s: no hostkeys", __func__); 904 packet_send(); 905 sshbuf_free(buf); 906 } 907 908 /* 909 * returns 1 if connection should be dropped, 0 otherwise. 910 * dropping starts at connection #max_startups_begin with a probability 911 * of (max_startups_rate/100). the probability increases linearly until 912 * all connections are dropped for startups > max_startups 913 */ 914 static int 915 drop_connection(int startups) 916 { 917 int p, r; 918 919 if (startups < options.max_startups_begin) 920 return 0; 921 if (startups >= options.max_startups) 922 return 1; 923 if (options.max_startups_rate == 100) 924 return 1; 925 926 p = 100 - options.max_startups_rate; 927 p *= startups - options.max_startups_begin; 928 p /= options.max_startups - options.max_startups_begin; 929 p += options.max_startups_rate; 930 r = arc4random_uniform(100); 931 932 debug("drop_connection: p %d, r %d", p, r); 933 return (r < p) ? 1 : 0; 934 } 935 936 static void 937 usage(void) 938 { 939 if (options.version_addendum && *options.version_addendum != '\0') 940 fprintf(stderr, "%s %s, %s\n", 941 SSH_RELEASE, 942 options.version_addendum, OPENSSL_VERSION_STRING); 943 else 944 fprintf(stderr, "%s, %s\n", 945 SSH_RELEASE, OPENSSL_VERSION_STRING); 946 fprintf(stderr, 947 "usage: sshd [-46DdeiqTt] [-C connection_spec] [-c host_cert_file]\n" 948 " [-E log_file] [-f config_file] [-g login_grace_time]\n" 949 " [-h host_key_file] [-o option] [-p port] [-u len]\n" 950 ); 951 exit(1); 952 } 953 954 static void 955 send_rexec_state(int fd, struct sshbuf *conf) 956 { 957 struct sshbuf *m; 958 int r; 959 960 debug3("%s: entering fd = %d config len %zu", __func__, fd, 961 sshbuf_len(conf)); 962 963 /* 964 * Protocol from reexec master to child: 965 * string configuration 966 * string rngseed (only if OpenSSL is not self-seeded) 967 */ 968 if ((m = sshbuf_new()) == NULL) 969 fatal("%s: sshbuf_new failed", __func__); 970 if ((r = sshbuf_put_stringb(m, conf)) != 0) 971 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 972 973 #if defined(WITH_OPENSSL) && !defined(OPENSSL_PRNG_ONLY) 974 rexec_send_rng_seed(m); 975 #endif 976 977 if (ssh_msg_send(fd, 0, m) == -1) 978 fatal("%s: ssh_msg_send failed", __func__); 979 980 sshbuf_free(m); 981 982 debug3("%s: done", __func__); 983 } 984 985 static void 986 recv_rexec_state(int fd, struct sshbuf *conf) 987 { 988 struct sshbuf *m; 989 u_char *cp, ver; 990 size_t len; 991 int r; 992 993 debug3("%s: entering fd = %d", __func__, fd); 994 995 if ((m = sshbuf_new()) == NULL) 996 fatal("%s: sshbuf_new failed", __func__); 997 if (ssh_msg_recv(fd, m) == -1) 998 fatal("%s: ssh_msg_recv failed", __func__); 999 if ((r = sshbuf_get_u8(m, &ver)) != 0) 1000 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 1001 if (ver != 0) 1002 fatal("%s: rexec version mismatch", __func__); 1003 if ((r = sshbuf_get_string(m, &cp, &len)) != 0) 1004 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 1005 if (conf != NULL && (r = sshbuf_put(conf, cp, len))) 1006 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 1007 #if defined(WITH_OPENSSL) && !defined(OPENSSL_PRNG_ONLY) 1008 rexec_recv_rng_seed(m); 1009 #endif 1010 1011 free(cp); 1012 sshbuf_free(m); 1013 1014 debug3("%s: done", __func__); 1015 } 1016 1017 /* Accept a connection from inetd */ 1018 static void 1019 server_accept_inetd(int *sock_in, int *sock_out) 1020 { 1021 int fd; 1022 1023 startup_pipe = -1; 1024 if (rexeced_flag) { 1025 close(REEXEC_CONFIG_PASS_FD); 1026 *sock_in = *sock_out = dup(STDIN_FILENO); 1027 if (!debug_flag) { 1028 startup_pipe = dup(REEXEC_STARTUP_PIPE_FD); 1029 close(REEXEC_STARTUP_PIPE_FD); 1030 } 1031 } else { 1032 *sock_in = dup(STDIN_FILENO); 1033 *sock_out = dup(STDOUT_FILENO); 1034 } 1035 /* 1036 * We intentionally do not close the descriptors 0, 1, and 2 1037 * as our code for setting the descriptors won't work if 1038 * ttyfd happens to be one of those. 1039 */ 1040 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) { 1041 dup2(fd, STDIN_FILENO); 1042 dup2(fd, STDOUT_FILENO); 1043 if (!log_stderr) 1044 dup2(fd, STDERR_FILENO); 1045 if (fd > (log_stderr ? STDERR_FILENO : STDOUT_FILENO)) 1046 close(fd); 1047 } 1048 debug("inetd sockets after dupping: %d, %d", *sock_in, *sock_out); 1049 } 1050 1051 /* 1052 * Listen for TCP connections 1053 */ 1054 static void 1055 listen_on_addrs(struct listenaddr *la) 1056 { 1057 int ret, listen_sock; 1058 struct addrinfo *ai; 1059 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 1060 int socksize; 1061 socklen_t len; 1062 1063 for (ai = la->addrs; ai; ai = ai->ai_next) { 1064 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 1065 continue; 1066 if (num_listen_socks >= MAX_LISTEN_SOCKS) 1067 fatal("Too many listen sockets. " 1068 "Enlarge MAX_LISTEN_SOCKS"); 1069 if ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen, 1070 ntop, sizeof(ntop), strport, sizeof(strport), 1071 NI_NUMERICHOST|NI_NUMERICSERV)) != 0) { 1072 error("getnameinfo failed: %.100s", 1073 ssh_gai_strerror(ret)); 1074 continue; 1075 } 1076 /* Create socket for listening. */ 1077 listen_sock = socket(ai->ai_family, ai->ai_socktype, 1078 ai->ai_protocol); 1079 if (listen_sock < 0) { 1080 /* kernel may not support ipv6 */ 1081 verbose("socket: %.100s", strerror(errno)); 1082 continue; 1083 } 1084 if (set_nonblock(listen_sock) == -1) { 1085 close(listen_sock); 1086 continue; 1087 } 1088 if (fcntl(listen_sock, F_SETFD, FD_CLOEXEC) == -1) { 1089 verbose("socket: CLOEXEC: %s", strerror(errno)); 1090 close(listen_sock); 1091 continue; 1092 } 1093 /* Socket options */ 1094 set_reuseaddr(listen_sock); 1095 if (la->rdomain != NULL && 1096 set_rdomain(listen_sock, la->rdomain) == -1) { 1097 close(listen_sock); 1098 continue; 1099 } 1100 1101 /* Only communicate in IPv6 over AF_INET6 sockets. */ 1102 if (ai->ai_family == AF_INET6) 1103 sock_set_v6only(listen_sock); 1104 1105 debug("Bind to port %s on %s.", strport, ntop); 1106 1107 len = sizeof(socksize); 1108 getsockopt(listen_sock, SOL_SOCKET, SO_RCVBUF, &socksize, &len); 1109 debug("Server TCP RWIN socket size: %d", socksize); 1110 1111 /* Bind the socket to the desired port. */ 1112 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) { 1113 error("Bind to port %s on %s failed: %.200s.", 1114 strport, ntop, strerror(errno)); 1115 close(listen_sock); 1116 continue; 1117 } 1118 listen_socks[num_listen_socks] = listen_sock; 1119 num_listen_socks++; 1120 1121 /* Start listening on the port. */ 1122 if (listen(listen_sock, SSH_LISTEN_BACKLOG) < 0) 1123 fatal("listen on [%s]:%s: %.100s", 1124 ntop, strport, strerror(errno)); 1125 logit("Server listening on %s port %s%s%s.", 1126 ntop, strport, 1127 la->rdomain == NULL ? "" : " rdomain ", 1128 la->rdomain == NULL ? "" : la->rdomain); 1129 } 1130 } 1131 1132 static void 1133 server_listen(void) 1134 { 1135 u_int i; 1136 1137 for (i = 0; i < options.num_listen_addrs; i++) { 1138 listen_on_addrs(&options.listen_addrs[i]); 1139 freeaddrinfo(options.listen_addrs[i].addrs); 1140 free(options.listen_addrs[i].rdomain); 1141 memset(&options.listen_addrs[i], 0, 1142 sizeof(options.listen_addrs[i])); 1143 } 1144 free(options.listen_addrs); 1145 options.listen_addrs = NULL; 1146 options.num_listen_addrs = 0; 1147 1148 if (!num_listen_socks) 1149 fatal("Cannot bind any address."); 1150 } 1151 1152 /* 1153 * The main TCP accept loop. Note that, for the non-debug case, returns 1154 * from this function are in a forked subprocess. 1155 */ 1156 static void 1157 server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s) 1158 { 1159 fd_set *fdset; 1160 int i, j, ret, maxfd; 1161 int startups = 0; 1162 int startup_p[2] = { -1 , -1 }; 1163 struct sockaddr_storage from; 1164 socklen_t fromlen; 1165 pid_t pid; 1166 u_char rnd[256]; 1167 1168 /* setup fd set for accept */ 1169 fdset = NULL; 1170 maxfd = 0; 1171 for (i = 0; i < num_listen_socks; i++) 1172 if (listen_socks[i] > maxfd) 1173 maxfd = listen_socks[i]; 1174 /* pipes connected to unauthenticated childs */ 1175 startup_pipes = xcalloc(options.max_startups, sizeof(int)); 1176 for (i = 0; i < options.max_startups; i++) 1177 startup_pipes[i] = -1; 1178 1179 /* 1180 * Stay listening for connections until the system crashes or 1181 * the daemon is killed with a signal. 1182 */ 1183 for (;;) { 1184 if (received_sighup) 1185 sighup_restart(); 1186 free(fdset); 1187 fdset = xcalloc(howmany(maxfd + 1, NFDBITS), 1188 sizeof(fd_mask)); 1189 1190 for (i = 0; i < num_listen_socks; i++) 1191 FD_SET(listen_socks[i], fdset); 1192 for (i = 0; i < options.max_startups; i++) 1193 if (startup_pipes[i] != -1) 1194 FD_SET(startup_pipes[i], fdset); 1195 1196 /* Wait in select until there is a connection. */ 1197 ret = select(maxfd+1, fdset, NULL, NULL, NULL); 1198 if (ret < 0 && errno != EINTR) 1199 error("select: %.100s", strerror(errno)); 1200 if (received_sigterm) { 1201 logit("Received signal %d; terminating.", 1202 (int) received_sigterm); 1203 close_listen_socks(); 1204 if (options.pid_file != NULL) 1205 unlink(options.pid_file); 1206 exit(received_sigterm == SIGTERM ? 0 : 255); 1207 } 1208 if (ret < 0) 1209 continue; 1210 1211 for (i = 0; i < options.max_startups; i++) 1212 if (startup_pipes[i] != -1 && 1213 FD_ISSET(startup_pipes[i], fdset)) { 1214 /* 1215 * the read end of the pipe is ready 1216 * if the child has closed the pipe 1217 * after successful authentication 1218 * or if the child has died 1219 */ 1220 close(startup_pipes[i]); 1221 startup_pipes[i] = -1; 1222 startups--; 1223 } 1224 for (i = 0; i < num_listen_socks; i++) { 1225 if (!FD_ISSET(listen_socks[i], fdset)) 1226 continue; 1227 fromlen = sizeof(from); 1228 *newsock = accept(listen_socks[i], 1229 (struct sockaddr *)&from, &fromlen); 1230 if (*newsock < 0) { 1231 if (errno != EINTR && errno != EWOULDBLOCK && 1232 errno != ECONNABORTED && errno != EAGAIN) 1233 error("accept: %.100s", 1234 strerror(errno)); 1235 if (errno == EMFILE || errno == ENFILE) 1236 usleep(100 * 1000); 1237 continue; 1238 } 1239 if (unset_nonblock(*newsock) == -1) { 1240 close(*newsock); 1241 continue; 1242 } 1243 if (drop_connection(startups) == 1) { 1244 char *laddr = get_local_ipaddr(*newsock); 1245 char *raddr = get_peer_ipaddr(*newsock); 1246 1247 verbose("drop connection #%d from [%s]:%d " 1248 "on [%s]:%d past MaxStartups", startups, 1249 raddr, get_peer_port(*newsock), 1250 laddr, get_local_port(*newsock)); 1251 free(laddr); 1252 free(raddr); 1253 close(*newsock); 1254 continue; 1255 } 1256 if (pipe(startup_p) == -1) { 1257 close(*newsock); 1258 continue; 1259 } 1260 1261 if (rexec_flag && socketpair(AF_UNIX, 1262 SOCK_STREAM, 0, config_s) == -1) { 1263 error("reexec socketpair: %s", 1264 strerror(errno)); 1265 close(*newsock); 1266 close(startup_p[0]); 1267 close(startup_p[1]); 1268 continue; 1269 } 1270 1271 for (j = 0; j < options.max_startups; j++) 1272 if (startup_pipes[j] == -1) { 1273 startup_pipes[j] = startup_p[0]; 1274 if (maxfd < startup_p[0]) 1275 maxfd = startup_p[0]; 1276 startups++; 1277 break; 1278 } 1279 1280 /* 1281 * Got connection. Fork a child to handle it, unless 1282 * we are in debugging mode. 1283 */ 1284 if (debug_flag) { 1285 /* 1286 * In debugging mode. Close the listening 1287 * socket, and start processing the 1288 * connection without forking. 1289 */ 1290 debug("Server will not fork when running in debugging mode."); 1291 close_listen_socks(); 1292 *sock_in = *newsock; 1293 *sock_out = *newsock; 1294 close(startup_p[0]); 1295 close(startup_p[1]); 1296 startup_pipe = -1; 1297 pid = getpid(); 1298 if (rexec_flag) { 1299 send_rexec_state(config_s[0], cfg); 1300 close(config_s[0]); 1301 } 1302 break; 1303 } 1304 1305 /* 1306 * Normal production daemon. Fork, and have 1307 * the child process the connection. The 1308 * parent continues listening. 1309 */ 1310 platform_pre_fork(); 1311 if ((pid = fork()) == 0) { 1312 /* 1313 * Child. Close the listening and 1314 * max_startup sockets. Start using 1315 * the accepted socket. Reinitialize 1316 * logging (since our pid has changed). 1317 * We break out of the loop to handle 1318 * the connection. 1319 */ 1320 platform_post_fork_child(); 1321 startup_pipe = startup_p[1]; 1322 close_startup_pipes(); 1323 close_listen_socks(); 1324 *sock_in = *newsock; 1325 *sock_out = *newsock; 1326 log_init(__progname, 1327 options.log_level, 1328 options.log_facility, 1329 log_stderr); 1330 if (rexec_flag) 1331 close(config_s[0]); 1332 break; 1333 } 1334 1335 /* Parent. Stay in the loop. */ 1336 platform_post_fork_parent(pid); 1337 if (pid < 0) 1338 error("fork: %.100s", strerror(errno)); 1339 else 1340 debug("Forked child %ld.", (long)pid); 1341 1342 close(startup_p[1]); 1343 1344 if (rexec_flag) { 1345 send_rexec_state(config_s[0], cfg); 1346 close(config_s[0]); 1347 close(config_s[1]); 1348 } 1349 close(*newsock); 1350 1351 /* 1352 * Ensure that our random state differs 1353 * from that of the child 1354 */ 1355 arc4random_stir(); 1356 arc4random_buf(rnd, sizeof(rnd)); 1357 #ifdef WITH_OPENSSL 1358 RAND_seed(rnd, sizeof(rnd)); 1359 if ((RAND_bytes((u_char *)rnd, 1)) != 1) 1360 fatal("%s: RAND_bytes failed", __func__); 1361 #endif 1362 explicit_bzero(rnd, sizeof(rnd)); 1363 } 1364 1365 /* child process check (or debug mode) */ 1366 if (num_listen_socks < 0) 1367 break; 1368 } 1369 } 1370 1371 /* 1372 * If IP options are supported, make sure there are none (log and 1373 * return an error if any are found). Basically we are worried about 1374 * source routing; it can be used to pretend you are somebody 1375 * (ip-address) you are not. That itself may be "almost acceptable" 1376 * under certain circumstances, but rhosts authentication is useless 1377 * if source routing is accepted. Notice also that if we just dropped 1378 * source routing here, the other side could use IP spoofing to do 1379 * rest of the interaction and could still bypass security. So we 1380 * exit here if we detect any IP options. 1381 */ 1382 static void 1383 check_ip_options(struct ssh *ssh) 1384 { 1385 #ifdef IP_OPTIONS 1386 int sock_in = ssh_packet_get_connection_in(ssh); 1387 struct sockaddr_storage from; 1388 u_char opts[200]; 1389 socklen_t i, option_size = sizeof(opts), fromlen = sizeof(from); 1390 char text[sizeof(opts) * 3 + 1]; 1391 1392 memset(&from, 0, sizeof(from)); 1393 if (getpeername(sock_in, (struct sockaddr *)&from, 1394 &fromlen) < 0) 1395 return; 1396 if (from.ss_family != AF_INET) 1397 return; 1398 /* XXX IPv6 options? */ 1399 1400 if (getsockopt(sock_in, IPPROTO_IP, IP_OPTIONS, opts, 1401 &option_size) >= 0 && option_size != 0) { 1402 text[0] = '\0'; 1403 for (i = 0; i < option_size; i++) 1404 snprintf(text + i*3, sizeof(text) - i*3, 1405 " %2.2x", opts[i]); 1406 fatal("Connection from %.100s port %d with IP opts: %.800s", 1407 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), text); 1408 } 1409 return; 1410 #endif /* IP_OPTIONS */ 1411 } 1412 1413 /* Set the routing domain for this process */ 1414 static void 1415 set_process_rdomain(struct ssh *ssh, const char *name) 1416 { 1417 #if defined(HAVE_SYS_SET_PROCESS_RDOMAIN) 1418 if (name == NULL) 1419 return; /* default */ 1420 1421 if (strcmp(name, "%D") == 0) { 1422 /* "expands" to routing domain of connection */ 1423 if ((name = ssh_packet_rdomain_in(ssh)) == NULL) 1424 return; 1425 } 1426 /* NB. We don't pass 'ssh' to sys_set_process_rdomain() */ 1427 return sys_set_process_rdomain(name); 1428 #elif defined(__OpenBSD__) 1429 int rtable, ortable = getrtable(); 1430 const char *errstr; 1431 1432 if (name == NULL) 1433 return; /* default */ 1434 1435 if (strcmp(name, "%D") == 0) { 1436 /* "expands" to routing domain of connection */ 1437 if ((name = ssh_packet_rdomain_in(ssh)) == NULL) 1438 return; 1439 } 1440 1441 rtable = (int)strtonum(name, 0, 255, &errstr); 1442 if (errstr != NULL) /* Shouldn't happen */ 1443 fatal("Invalid routing domain \"%s\": %s", name, errstr); 1444 if (rtable != ortable && setrtable(rtable) != 0) 1445 fatal("Unable to set routing domain %d: %s", 1446 rtable, strerror(errno)); 1447 debug("%s: set routing domain %d (was %d)", __func__, rtable, ortable); 1448 #else /* defined(__OpenBSD__) */ 1449 fatal("Unable to set routing domain: not supported in this platform"); 1450 #endif 1451 } 1452 1453 static void 1454 accumulate_host_timing_secret(struct sshbuf *server_cfg, 1455 const struct sshkey *key) 1456 { 1457 static struct ssh_digest_ctx *ctx; 1458 u_char *hash; 1459 size_t len; 1460 struct sshbuf *buf; 1461 int r; 1462 1463 if (ctx == NULL && (ctx = ssh_digest_start(SSH_DIGEST_SHA512)) == NULL) 1464 fatal("%s: ssh_digest_start", __func__); 1465 if (key == NULL) { /* finalize */ 1466 /* add server config in case we are using agent for host keys */ 1467 if (ssh_digest_update(ctx, sshbuf_ptr(server_cfg), 1468 sshbuf_len(server_cfg)) != 0) 1469 fatal("%s: ssh_digest_update", __func__); 1470 len = ssh_digest_bytes(SSH_DIGEST_SHA512); 1471 hash = xmalloc(len); 1472 if (ssh_digest_final(ctx, hash, len) != 0) 1473 fatal("%s: ssh_digest_final", __func__); 1474 options.timing_secret = PEEK_U64(hash); 1475 freezero(hash, len); 1476 ssh_digest_free(ctx); 1477 ctx = NULL; 1478 return; 1479 } 1480 if ((buf = sshbuf_new()) == NULL) 1481 fatal("%s could not allocate buffer", __func__); 1482 if ((r = sshkey_private_serialize(key, buf)) != 0) 1483 fatal("sshkey_private_serialize: %s", ssh_err(r)); 1484 if (ssh_digest_update(ctx, sshbuf_ptr(buf), sshbuf_len(buf)) != 0) 1485 fatal("%s: ssh_digest_update", __func__); 1486 sshbuf_reset(buf); 1487 sshbuf_free(buf); 1488 } 1489 1490 /* 1491 * Main program for the daemon. 1492 */ 1493 int 1494 main(int ac, char **av) 1495 { 1496 struct ssh *ssh = NULL; 1497 extern char *optarg; 1498 extern int optind; 1499 int r, opt, on = 1, already_daemon, remote_port; 1500 int sock_in = -1, sock_out = -1, newsock = -1; 1501 const char *remote_ip, *rdomain; 1502 char *fp, *line, *laddr, *logfile = NULL; 1503 int config_s[2] = { -1 , -1 }; 1504 u_int i, j; 1505 u_int64_t ibytes, obytes; 1506 mode_t new_umask; 1507 struct sshkey *key; 1508 struct sshkey *pubkey; 1509 int keytype; 1510 Authctxt *authctxt; 1511 struct connection_info *connection_info = NULL; 1512 1513 ssh_malloc_init(); /* must be called before any mallocs */ 1514 1515 #ifdef HAVE_SECUREWARE 1516 (void)set_auth_parameters(ac, av); 1517 #endif 1518 __progname = ssh_get_progname(av[0]); 1519 1520 /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */ 1521 saved_argc = ac; 1522 rexec_argc = ac; 1523 saved_argv = xcalloc(ac + 1, sizeof(*saved_argv)); 1524 for (i = 0; (int)i < ac; i++) 1525 saved_argv[i] = xstrdup(av[i]); 1526 saved_argv[i] = NULL; 1527 1528 #ifndef HAVE_SETPROCTITLE 1529 /* Prepare for later setproctitle emulation */ 1530 compat_init_setproctitle(ac, av); 1531 av = saved_argv; 1532 #endif 1533 1534 if (geteuid() == 0 && setgroups(0, NULL) == -1) 1535 debug("setgroups(): %.200s", strerror(errno)); 1536 1537 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */ 1538 sanitise_stdfd(); 1539 1540 /* Initialize configuration options to their default values. */ 1541 initialize_server_options(&options); 1542 1543 /* Parse command-line arguments. */ 1544 while ((opt = getopt(ac, av, 1545 "C:E:b:c:f:g:h:k:o:p:u:46DQRTdeiqrt")) != -1) { 1546 switch (opt) { 1547 case '4': 1548 options.address_family = AF_INET; 1549 break; 1550 case '6': 1551 options.address_family = AF_INET6; 1552 break; 1553 case 'f': 1554 config_file_name = optarg; 1555 break; 1556 case 'c': 1557 servconf_add_hostcert("[command-line]", 0, 1558 &options, optarg); 1559 break; 1560 case 'd': 1561 if (debug_flag == 0) { 1562 debug_flag = 1; 1563 options.log_level = SYSLOG_LEVEL_DEBUG1; 1564 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) 1565 options.log_level++; 1566 break; 1567 case 'D': 1568 no_daemon_flag = 1; 1569 break; 1570 case 'E': 1571 logfile = optarg; 1572 /* FALLTHROUGH */ 1573 case 'e': 1574 log_stderr = 1; 1575 break; 1576 case 'i': 1577 inetd_flag = 1; 1578 break; 1579 case 'r': 1580 rexec_flag = 0; 1581 break; 1582 case 'R': 1583 rexeced_flag = 1; 1584 inetd_flag = 1; 1585 break; 1586 case 'Q': 1587 /* ignored */ 1588 break; 1589 case 'q': 1590 options.log_level = SYSLOG_LEVEL_QUIET; 1591 break; 1592 case 'b': 1593 /* protocol 1, ignored */ 1594 break; 1595 case 'p': 1596 options.ports_from_cmdline = 1; 1597 if (options.num_ports >= MAX_PORTS) { 1598 fprintf(stderr, "too many ports.\n"); 1599 exit(1); 1600 } 1601 options.ports[options.num_ports++] = a2port(optarg); 1602 if (options.ports[options.num_ports-1] <= 0) { 1603 fprintf(stderr, "Bad port number.\n"); 1604 exit(1); 1605 } 1606 break; 1607 case 'g': 1608 if ((options.login_grace_time = convtime(optarg)) == -1) { 1609 fprintf(stderr, "Invalid login grace time.\n"); 1610 exit(1); 1611 } 1612 break; 1613 case 'k': 1614 /* protocol 1, ignored */ 1615 break; 1616 case 'h': 1617 servconf_add_hostkey("[command-line]", 0, 1618 &options, optarg); 1619 break; 1620 case 't': 1621 test_flag = 1; 1622 break; 1623 case 'T': 1624 test_flag = 2; 1625 break; 1626 case 'C': 1627 connection_info = get_connection_info(0, 0); 1628 if (parse_server_match_testspec(connection_info, 1629 optarg) == -1) 1630 exit(1); 1631 break; 1632 case 'u': 1633 utmp_len = (u_int)strtonum(optarg, 0, HOST_NAME_MAX+1+1, NULL); 1634 if (utmp_len > HOST_NAME_MAX+1) { 1635 fprintf(stderr, "Invalid utmp length.\n"); 1636 exit(1); 1637 } 1638 break; 1639 case 'o': 1640 line = xstrdup(optarg); 1641 if (process_server_config_line(&options, line, 1642 "command-line", 0, NULL, NULL) != 0) 1643 exit(1); 1644 free(line); 1645 break; 1646 case '?': 1647 default: 1648 usage(); 1649 break; 1650 } 1651 } 1652 if (rexeced_flag || inetd_flag) 1653 rexec_flag = 0; 1654 if (!test_flag && (rexec_flag && (av[0] == NULL || *av[0] != '/'))) 1655 fatal("sshd re-exec requires execution with an absolute path"); 1656 if (rexeced_flag) 1657 closefrom(REEXEC_MIN_FREE_FD); 1658 else 1659 closefrom(REEXEC_DEVCRYPTO_RESERVED_FD); 1660 1661 #ifdef WITH_OPENSSL 1662 OpenSSL_add_all_algorithms(); 1663 #endif 1664 1665 /* If requested, redirect the logs to the specified logfile. */ 1666 if (logfile != NULL) 1667 log_redirect_stderr_to(logfile); 1668 /* 1669 * Force logging to stderr until we have loaded the private host 1670 * key (unless started from inetd) 1671 */ 1672 log_init(__progname, 1673 options.log_level == SYSLOG_LEVEL_NOT_SET ? 1674 SYSLOG_LEVEL_INFO : options.log_level, 1675 options.log_facility == SYSLOG_FACILITY_NOT_SET ? 1676 SYSLOG_FACILITY_AUTH : options.log_facility, 1677 log_stderr || !inetd_flag); 1678 1679 /* 1680 * Unset KRB5CCNAME, otherwise the user's session may inherit it from 1681 * root's environment 1682 */ 1683 if (getenv("KRB5CCNAME") != NULL) 1684 (void) unsetenv("KRB5CCNAME"); 1685 1686 sensitive_data.have_ssh2_key = 0; 1687 1688 /* 1689 * If we're not doing an extended test do not silently ignore connection 1690 * test params. 1691 */ 1692 if (test_flag < 2 && connection_info != NULL) 1693 fatal("Config test connection parameter (-C) provided without " 1694 "test mode (-T)"); 1695 1696 /* Fetch our configuration */ 1697 if ((cfg = sshbuf_new()) == NULL) 1698 fatal("%s: sshbuf_new failed", __func__); 1699 if (rexeced_flag) 1700 recv_rexec_state(REEXEC_CONFIG_PASS_FD, cfg); 1701 else if (strcasecmp(config_file_name, "none") != 0) 1702 load_server_config(config_file_name, cfg); 1703 1704 parse_server_config(&options, rexeced_flag ? "rexec" : config_file_name, 1705 cfg, NULL); 1706 1707 seed_rng(); 1708 1709 /* Fill in default values for those options not explicitly set. */ 1710 fill_default_server_options(&options); 1711 1712 /* challenge-response is implemented via keyboard interactive */ 1713 if (options.challenge_response_authentication) 1714 options.kbd_interactive_authentication = 1; 1715 1716 /* Check that options are sensible */ 1717 if (options.authorized_keys_command_user == NULL && 1718 (options.authorized_keys_command != NULL && 1719 strcasecmp(options.authorized_keys_command, "none") != 0)) 1720 fatal("AuthorizedKeysCommand set without " 1721 "AuthorizedKeysCommandUser"); 1722 if (options.authorized_principals_command_user == NULL && 1723 (options.authorized_principals_command != NULL && 1724 strcasecmp(options.authorized_principals_command, "none") != 0)) 1725 fatal("AuthorizedPrincipalsCommand set without " 1726 "AuthorizedPrincipalsCommandUser"); 1727 1728 /* 1729 * Check whether there is any path through configured auth methods. 1730 * Unfortunately it is not possible to verify this generally before 1731 * daemonisation in the presence of Match block, but this catches 1732 * and warns for trivial misconfigurations that could break login. 1733 */ 1734 if (options.num_auth_methods != 0) { 1735 for (i = 0; i < options.num_auth_methods; i++) { 1736 if (auth2_methods_valid(options.auth_methods[i], 1737 1) == 0) 1738 break; 1739 } 1740 if (i >= options.num_auth_methods) 1741 fatal("AuthenticationMethods cannot be satisfied by " 1742 "enabled authentication methods"); 1743 } 1744 1745 /* Check that there are no remaining arguments. */ 1746 if (optind < ac) { 1747 fprintf(stderr, "Extra argument %s.\n", av[optind]); 1748 exit(1); 1749 } 1750 1751 debug("sshd version %s, %s", SSH_VERSION, 1752 #ifdef WITH_OPENSSL 1753 SSLeay_version(SSLEAY_VERSION) 1754 #else 1755 "without OpenSSL" 1756 #endif 1757 ); 1758 1759 /* Store privilege separation user for later use if required. */ 1760 privsep_chroot = use_privsep && (getuid() == 0 || geteuid() == 0); 1761 if ((privsep_pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) { 1762 if (privsep_chroot || options.kerberos_authentication) 1763 fatal("Privilege separation user %s does not exist", 1764 SSH_PRIVSEP_USER); 1765 } else { 1766 privsep_pw = pwcopy(privsep_pw); 1767 freezero(privsep_pw->pw_passwd, strlen(privsep_pw->pw_passwd)); 1768 privsep_pw->pw_passwd = xstrdup("*"); 1769 } 1770 endpwent(); 1771 1772 /* load host keys */ 1773 sensitive_data.host_keys = xcalloc(options.num_host_key_files, 1774 sizeof(struct sshkey *)); 1775 sensitive_data.host_pubkeys = xcalloc(options.num_host_key_files, 1776 sizeof(struct sshkey *)); 1777 1778 if (options.host_key_agent) { 1779 if (strcmp(options.host_key_agent, SSH_AUTHSOCKET_ENV_NAME)) 1780 setenv(SSH_AUTHSOCKET_ENV_NAME, 1781 options.host_key_agent, 1); 1782 if ((r = ssh_get_authentication_socket(NULL)) == 0) 1783 have_agent = 1; 1784 else 1785 error("Could not connect to agent \"%s\": %s", 1786 options.host_key_agent, ssh_err(r)); 1787 } 1788 1789 for (i = 0; i < options.num_host_key_files; i++) { 1790 if (options.host_key_files[i] == NULL) 1791 continue; 1792 if ((r = sshkey_load_private(options.host_key_files[i], "", 1793 &key, NULL)) != 0 && r != SSH_ERR_SYSTEM_ERROR) 1794 error("Error loading host key \"%s\": %s", 1795 options.host_key_files[i], ssh_err(r)); 1796 if ((r = sshkey_load_public(options.host_key_files[i], 1797 &pubkey, NULL)) != 0 && r != SSH_ERR_SYSTEM_ERROR) 1798 error("Error loading host key \"%s\": %s", 1799 options.host_key_files[i], ssh_err(r)); 1800 if (pubkey == NULL && key != NULL) 1801 if ((r = sshkey_from_private(key, &pubkey)) != 0) 1802 fatal("Could not demote key: \"%s\": %s", 1803 options.host_key_files[i], ssh_err(r)); 1804 sensitive_data.host_keys[i] = key; 1805 sensitive_data.host_pubkeys[i] = pubkey; 1806 1807 if (key == NULL && pubkey != NULL && have_agent) { 1808 debug("will rely on agent for hostkey %s", 1809 options.host_key_files[i]); 1810 keytype = pubkey->type; 1811 } else if (key != NULL) { 1812 keytype = key->type; 1813 accumulate_host_timing_secret(cfg, key); 1814 } else { 1815 error("Could not load host key: %s", 1816 options.host_key_files[i]); 1817 sensitive_data.host_keys[i] = NULL; 1818 sensitive_data.host_pubkeys[i] = NULL; 1819 continue; 1820 } 1821 1822 switch (keytype) { 1823 case KEY_RSA: 1824 case KEY_DSA: 1825 case KEY_ECDSA: 1826 case KEY_ED25519: 1827 case KEY_XMSS: 1828 if (have_agent || key != NULL) 1829 sensitive_data.have_ssh2_key = 1; 1830 break; 1831 } 1832 if ((fp = sshkey_fingerprint(pubkey, options.fingerprint_hash, 1833 SSH_FP_DEFAULT)) == NULL) 1834 fatal("sshkey_fingerprint failed"); 1835 debug("%s host key #%d: %s %s", 1836 key ? "private" : "agent", i, sshkey_ssh_name(pubkey), fp); 1837 free(fp); 1838 } 1839 accumulate_host_timing_secret(cfg, NULL); 1840 if (!sensitive_data.have_ssh2_key) { 1841 logit("sshd: no hostkeys available -- exiting."); 1842 exit(1); 1843 } 1844 1845 /* 1846 * Load certificates. They are stored in an array at identical 1847 * indices to the public keys that they relate to. 1848 */ 1849 sensitive_data.host_certificates = xcalloc(options.num_host_key_files, 1850 sizeof(struct sshkey *)); 1851 for (i = 0; i < options.num_host_key_files; i++) 1852 sensitive_data.host_certificates[i] = NULL; 1853 1854 for (i = 0; i < options.num_host_cert_files; i++) { 1855 if (options.host_cert_files[i] == NULL) 1856 continue; 1857 if ((r = sshkey_load_public(options.host_cert_files[i], 1858 &key, NULL)) != 0) { 1859 error("Could not load host certificate \"%s\": %s", 1860 options.host_cert_files[i], ssh_err(r)); 1861 continue; 1862 } 1863 if (!sshkey_is_cert(key)) { 1864 error("Certificate file is not a certificate: %s", 1865 options.host_cert_files[i]); 1866 sshkey_free(key); 1867 continue; 1868 } 1869 /* Find matching private key */ 1870 for (j = 0; j < options.num_host_key_files; j++) { 1871 if (sshkey_equal_public(key, 1872 sensitive_data.host_keys[j])) { 1873 sensitive_data.host_certificates[j] = key; 1874 break; 1875 } 1876 } 1877 if (j >= options.num_host_key_files) { 1878 error("No matching private key for certificate: %s", 1879 options.host_cert_files[i]); 1880 sshkey_free(key); 1881 continue; 1882 } 1883 sensitive_data.host_certificates[j] = key; 1884 debug("host certificate: #%u type %d %s", j, key->type, 1885 sshkey_type(key)); 1886 } 1887 1888 if (privsep_chroot) { 1889 struct stat st; 1890 1891 if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) || 1892 (S_ISDIR(st.st_mode) == 0)) 1893 fatal("Missing privilege separation directory: %s", 1894 _PATH_PRIVSEP_CHROOT_DIR); 1895 1896 #ifdef HAVE_CYGWIN 1897 if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) && 1898 (st.st_uid != getuid () || 1899 (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)) 1900 #else 1901 if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0) 1902 #endif 1903 fatal("%s must be owned by root and not group or " 1904 "world-writable.", _PATH_PRIVSEP_CHROOT_DIR); 1905 } 1906 1907 if (test_flag > 1) { 1908 /* 1909 * If no connection info was provided by -C then use 1910 * use a blank one that will cause no predicate to match. 1911 */ 1912 if (connection_info == NULL) 1913 connection_info = get_connection_info(0, 0); 1914 parse_server_match_config(&options, connection_info); 1915 dump_config(&options); 1916 } 1917 1918 /* Configuration looks good, so exit if in test mode. */ 1919 if (test_flag) 1920 exit(0); 1921 1922 /* 1923 * Clear out any supplemental groups we may have inherited. This 1924 * prevents inadvertent creation of files with bad modes (in the 1925 * portable version at least, it's certainly possible for PAM 1926 * to create a file, and we can't control the code in every 1927 * module which might be used). 1928 */ 1929 if (setgroups(0, NULL) < 0) 1930 debug("setgroups() failed: %.200s", strerror(errno)); 1931 1932 if (rexec_flag) { 1933 if (rexec_argc < 0) 1934 fatal("rexec_argc %d < 0", rexec_argc); 1935 rexec_argv = xcalloc(rexec_argc + 2, sizeof(char *)); 1936 for (i = 0; i < (u_int)rexec_argc; i++) { 1937 debug("rexec_argv[%d]='%s'", i, saved_argv[i]); 1938 rexec_argv[i] = saved_argv[i]; 1939 } 1940 rexec_argv[rexec_argc] = "-R"; 1941 rexec_argv[rexec_argc + 1] = NULL; 1942 } 1943 1944 /* Ensure that umask disallows at least group and world write */ 1945 new_umask = umask(0077) | 0022; 1946 (void) umask(new_umask); 1947 1948 /* Initialize the log (it is reinitialized below in case we forked). */ 1949 if (debug_flag && (!inetd_flag || rexeced_flag)) 1950 log_stderr = 1; 1951 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1952 1953 /* 1954 * If not in debugging mode, not started from inetd and not already 1955 * daemonized (eg re-exec via SIGHUP), disconnect from the controlling 1956 * terminal, and fork. The original process exits. 1957 */ 1958 already_daemon = daemonized(); 1959 if (!(debug_flag || inetd_flag || no_daemon_flag || already_daemon)) { 1960 1961 if (daemon(0, 0) < 0) 1962 fatal("daemon() failed: %.200s", strerror(errno)); 1963 1964 disconnect_controlling_tty(); 1965 } 1966 /* Reinitialize the log (because of the fork above). */ 1967 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1968 1969 /* Avoid killing the process in high-pressure swapping environments. */ 1970 if (!inetd_flag && madvise(NULL, 0, MADV_PROTECT) != 0) 1971 debug("madvise(): %.200s", strerror(errno)); 1972 1973 /* Chdir to the root directory so that the current disk can be 1974 unmounted if desired. */ 1975 if (chdir("/") == -1) 1976 error("chdir(\"/\"): %s", strerror(errno)); 1977 1978 /* ignore SIGPIPE */ 1979 signal(SIGPIPE, SIG_IGN); 1980 1981 /* Get a connection, either from inetd or a listening TCP socket */ 1982 if (inetd_flag) { 1983 server_accept_inetd(&sock_in, &sock_out); 1984 } else { 1985 platform_pre_listen(); 1986 server_listen(); 1987 1988 signal(SIGHUP, sighup_handler); 1989 signal(SIGCHLD, main_sigchld_handler); 1990 signal(SIGTERM, sigterm_handler); 1991 signal(SIGQUIT, sigterm_handler); 1992 1993 /* 1994 * Write out the pid file after the sigterm handler 1995 * is setup and the listen sockets are bound 1996 */ 1997 if (options.pid_file != NULL && !debug_flag) { 1998 FILE *f = fopen(options.pid_file, "w"); 1999 2000 if (f == NULL) { 2001 error("Couldn't create pid file \"%s\": %s", 2002 options.pid_file, strerror(errno)); 2003 } else { 2004 fprintf(f, "%ld\n", (long) getpid()); 2005 fclose(f); 2006 } 2007 } 2008 2009 /* Accept a connection and return in a forked child */ 2010 server_accept_loop(&sock_in, &sock_out, 2011 &newsock, config_s); 2012 } 2013 2014 /* This is the child processing a new connection. */ 2015 setproctitle("%s", "[accepted]"); 2016 2017 /* 2018 * Create a new session and process group since the 4.4BSD 2019 * setlogin() affects the entire process group. We don't 2020 * want the child to be able to affect the parent. 2021 */ 2022 #if !defined(SSHD_ACQUIRES_CTTY) 2023 /* 2024 * If setsid is called, on some platforms sshd will later acquire a 2025 * controlling terminal which will result in "could not set 2026 * controlling tty" errors. 2027 */ 2028 if (!debug_flag && !inetd_flag && setsid() < 0) 2029 error("setsid: %.100s", strerror(errno)); 2030 #endif 2031 2032 if (rexec_flag) { 2033 int fd; 2034 2035 debug("rexec start in %d out %d newsock %d pipe %d sock %d", 2036 sock_in, sock_out, newsock, startup_pipe, config_s[0]); 2037 dup2(newsock, STDIN_FILENO); 2038 dup2(STDIN_FILENO, STDOUT_FILENO); 2039 if (startup_pipe == -1) 2040 close(REEXEC_STARTUP_PIPE_FD); 2041 else if (startup_pipe != REEXEC_STARTUP_PIPE_FD) { 2042 dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD); 2043 close(startup_pipe); 2044 startup_pipe = REEXEC_STARTUP_PIPE_FD; 2045 } 2046 2047 dup2(config_s[1], REEXEC_CONFIG_PASS_FD); 2048 close(config_s[1]); 2049 2050 execv(rexec_argv[0], rexec_argv); 2051 2052 /* Reexec has failed, fall back and continue */ 2053 error("rexec of %s failed: %s", rexec_argv[0], strerror(errno)); 2054 recv_rexec_state(REEXEC_CONFIG_PASS_FD, NULL); 2055 log_init(__progname, options.log_level, 2056 options.log_facility, log_stderr); 2057 2058 /* Clean up fds */ 2059 close(REEXEC_CONFIG_PASS_FD); 2060 newsock = sock_out = sock_in = dup(STDIN_FILENO); 2061 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) { 2062 dup2(fd, STDIN_FILENO); 2063 dup2(fd, STDOUT_FILENO); 2064 if (fd > STDERR_FILENO) 2065 close(fd); 2066 } 2067 debug("rexec cleanup in %d out %d newsock %d pipe %d sock %d", 2068 sock_in, sock_out, newsock, startup_pipe, config_s[0]); 2069 } 2070 2071 /* Executed child processes don't need these. */ 2072 fcntl(sock_out, F_SETFD, FD_CLOEXEC); 2073 fcntl(sock_in, F_SETFD, FD_CLOEXEC); 2074 2075 /* 2076 * Disable the key regeneration alarm. We will not regenerate the 2077 * key since we are no longer in a position to give it to anyone. We 2078 * will not restart on SIGHUP since it no longer makes sense. 2079 */ 2080 alarm(0); 2081 signal(SIGALRM, SIG_DFL); 2082 signal(SIGHUP, SIG_DFL); 2083 signal(SIGTERM, SIG_DFL); 2084 signal(SIGQUIT, SIG_DFL); 2085 signal(SIGCHLD, SIG_DFL); 2086 signal(SIGINT, SIG_DFL); 2087 2088 #ifdef __FreeBSD__ 2089 /* 2090 * Initialize the resolver. This may not happen automatically 2091 * before privsep chroot(). 2092 */ 2093 if ((_res.options & RES_INIT) == 0) { 2094 debug("res_init()"); 2095 res_init(); 2096 } 2097 #ifdef GSSAPI 2098 /* 2099 * Force GSS-API to parse its configuration and load any 2100 * mechanism plugins. 2101 */ 2102 { 2103 gss_OID_set mechs; 2104 OM_uint32 minor_status; 2105 gss_indicate_mechs(&minor_status, &mechs); 2106 gss_release_oid_set(&minor_status, &mechs); 2107 } 2108 #endif 2109 #endif 2110 2111 /* 2112 * Register our connection. This turns encryption off because we do 2113 * not have a key. 2114 */ 2115 packet_set_connection(sock_in, sock_out); 2116 packet_set_server(); 2117 ssh = active_state; /* XXX */ 2118 2119 check_ip_options(ssh); 2120 2121 /* Prepare the channels layer */ 2122 channel_init_channels(ssh); 2123 channel_set_af(ssh, options.address_family); 2124 process_permitopen(ssh, &options); 2125 2126 /* Set SO_KEEPALIVE if requested. */ 2127 if (options.tcp_keep_alive && packet_connection_is_on_socket() && 2128 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) < 0) 2129 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 2130 2131 if ((remote_port = ssh_remote_port(ssh)) < 0) { 2132 debug("ssh_remote_port failed"); 2133 cleanup_exit(255); 2134 } 2135 2136 if (options.routing_domain != NULL) 2137 set_process_rdomain(ssh, options.routing_domain); 2138 2139 /* 2140 * The rest of the code depends on the fact that 2141 * ssh_remote_ipaddr() caches the remote ip, even if 2142 * the socket goes away. 2143 */ 2144 remote_ip = ssh_remote_ipaddr(ssh); 2145 2146 #ifdef HAVE_LOGIN_CAP 2147 /* Also caches remote hostname for sandboxed child. */ 2148 auth_get_canonical_hostname(ssh, options.use_dns); 2149 #endif 2150 2151 #ifdef SSH_AUDIT_EVENTS 2152 audit_connection_from(remote_ip, remote_port); 2153 #endif 2154 #ifdef LIBWRAP 2155 allow_severity = options.log_facility|LOG_INFO; 2156 deny_severity = options.log_facility|LOG_WARNING; 2157 /* Check whether logins are denied from this host. */ 2158 if (packet_connection_is_on_socket()) { 2159 struct request_info req; 2160 2161 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0); 2162 fromhost(&req); 2163 2164 if (!hosts_access(&req)) { 2165 debug("Connection refused by tcp wrapper"); 2166 refuse(&req); 2167 /* NOTREACHED */ 2168 fatal("libwrap refuse returns"); 2169 } 2170 } 2171 #endif /* LIBWRAP */ 2172 2173 rdomain = ssh_packet_rdomain_in(ssh); 2174 2175 /* Log the connection. */ 2176 laddr = get_local_ipaddr(sock_in); 2177 verbose("Connection from %s port %d on %s port %d%s%s%s", 2178 remote_ip, remote_port, laddr, ssh_local_port(ssh), 2179 rdomain == NULL ? "" : " rdomain \"", 2180 rdomain == NULL ? "" : rdomain, 2181 rdomain == NULL ? "" : "\""); 2182 free(laddr); 2183 2184 /* 2185 * We don't want to listen forever unless the other side 2186 * successfully authenticates itself. So we set up an alarm which is 2187 * cleared after successful authentication. A limit of zero 2188 * indicates no limit. Note that we don't set the alarm in debugging 2189 * mode; it is just annoying to have the server exit just when you 2190 * are about to discover the bug. 2191 */ 2192 signal(SIGALRM, grace_alarm_handler); 2193 if (!debug_flag) 2194 alarm(options.login_grace_time); 2195 2196 sshd_exchange_identification(ssh, sock_in, sock_out); 2197 packet_set_nonblocking(); 2198 2199 /* allocate authentication context */ 2200 authctxt = xcalloc(1, sizeof(*authctxt)); 2201 2202 authctxt->loginmsg = loginmsg; 2203 2204 /* XXX global for cleanup, access from other modules */ 2205 the_authctxt = authctxt; 2206 2207 /* Set default key authentication options */ 2208 if ((auth_opts = sshauthopt_new_with_keys_defaults()) == NULL) 2209 fatal("allocation failed"); 2210 2211 /* prepare buffer to collect messages to display to user after login */ 2212 if ((loginmsg = sshbuf_new()) == NULL) 2213 fatal("%s: sshbuf_new failed", __func__); 2214 auth_debug_reset(); 2215 2216 BLACKLIST_INIT(); 2217 2218 if (use_privsep) { 2219 if (privsep_preauth(authctxt) == 1) 2220 goto authenticated; 2221 } else if (have_agent) { 2222 if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) { 2223 error("Unable to get agent socket: %s", ssh_err(r)); 2224 have_agent = 0; 2225 } 2226 } 2227 2228 /* perform the key exchange */ 2229 /* authenticate user and start session */ 2230 do_ssh2_kex(); 2231 do_authentication2(authctxt); 2232 2233 /* 2234 * If we use privilege separation, the unprivileged child transfers 2235 * the current keystate and exits 2236 */ 2237 if (use_privsep) { 2238 mm_send_keystate(pmonitor); 2239 packet_clear_keys(); 2240 exit(0); 2241 } 2242 2243 authenticated: 2244 /* 2245 * Cancel the alarm we set to limit the time taken for 2246 * authentication. 2247 */ 2248 alarm(0); 2249 signal(SIGALRM, SIG_DFL); 2250 authctxt->authenticated = 1; 2251 if (startup_pipe != -1) { 2252 close(startup_pipe); 2253 startup_pipe = -1; 2254 } 2255 2256 #ifdef SSH_AUDIT_EVENTS 2257 audit_event(SSH_AUTH_SUCCESS); 2258 #endif 2259 2260 #ifdef GSSAPI 2261 if (options.gss_authentication) { 2262 temporarily_use_uid(authctxt->pw); 2263 ssh_gssapi_storecreds(); 2264 restore_uid(); 2265 } 2266 #endif 2267 #ifdef USE_PAM 2268 if (options.use_pam) { 2269 do_pam_setcred(1); 2270 do_pam_session(ssh); 2271 } 2272 #endif 2273 2274 /* 2275 * In privilege separation, we fork another child and prepare 2276 * file descriptor passing. 2277 */ 2278 if (use_privsep) { 2279 privsep_postauth(authctxt); 2280 /* the monitor process [priv] will not return */ 2281 } 2282 2283 packet_set_timeout(options.client_alive_interval, 2284 options.client_alive_count_max); 2285 2286 /* Try to send all our hostkeys to the client */ 2287 notify_hostkeys(ssh); 2288 2289 /* Start session. */ 2290 do_authenticated(ssh, authctxt); 2291 2292 /* The connection has been terminated. */ 2293 packet_get_bytes(&ibytes, &obytes); 2294 verbose("Transferred: sent %llu, received %llu bytes", 2295 (unsigned long long)obytes, (unsigned long long)ibytes); 2296 2297 verbose("Closing connection to %.500s port %d", remote_ip, remote_port); 2298 2299 #ifdef USE_PAM 2300 if (options.use_pam) 2301 finish_pam(); 2302 #endif /* USE_PAM */ 2303 2304 #ifdef SSH_AUDIT_EVENTS 2305 PRIVSEP(audit_event(SSH_CONNECTION_CLOSE)); 2306 #endif 2307 2308 packet_close(); 2309 2310 if (use_privsep) 2311 mm_terminate(); 2312 2313 exit(0); 2314 } 2315 2316 int 2317 sshd_hostkey_sign(struct sshkey *privkey, struct sshkey *pubkey, 2318 u_char **signature, size_t *slenp, const u_char *data, size_t dlen, 2319 const char *alg, u_int flag) 2320 { 2321 int r; 2322 2323 if (privkey) { 2324 if (PRIVSEP(sshkey_sign(privkey, signature, slenp, data, dlen, 2325 alg, datafellows)) < 0) 2326 fatal("%s: key_sign failed", __func__); 2327 } else if (use_privsep) { 2328 if (mm_sshkey_sign(pubkey, signature, slenp, data, dlen, 2329 alg, datafellows) < 0) 2330 fatal("%s: pubkey_sign failed", __func__); 2331 } else { 2332 if ((r = ssh_agent_sign(auth_sock, pubkey, signature, slenp, 2333 data, dlen, alg, datafellows)) != 0) 2334 fatal("%s: ssh_agent_sign failed: %s", 2335 __func__, ssh_err(r)); 2336 } 2337 return 0; 2338 } 2339 2340 /* SSH2 key exchange */ 2341 static void 2342 do_ssh2_kex(void) 2343 { 2344 char *myproposal[PROPOSAL_MAX] = { KEX_SERVER }; 2345 struct kex *kex; 2346 int r; 2347 2348 myproposal[PROPOSAL_KEX_ALGS] = compat_kex_proposal( 2349 options.kex_algorithms); 2350 myproposal[PROPOSAL_ENC_ALGS_CTOS] = compat_cipher_proposal( 2351 options.ciphers); 2352 myproposal[PROPOSAL_ENC_ALGS_STOC] = compat_cipher_proposal( 2353 options.ciphers); 2354 myproposal[PROPOSAL_MAC_ALGS_CTOS] = 2355 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs; 2356 2357 if (options.compression == COMP_NONE) { 2358 myproposal[PROPOSAL_COMP_ALGS_CTOS] = 2359 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none"; 2360 } 2361 2362 if (options.rekey_limit || options.rekey_interval) 2363 packet_set_rekey_limits(options.rekey_limit, 2364 options.rekey_interval); 2365 2366 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = compat_pkalg_proposal( 2367 list_hostkey_types()); 2368 2369 /* start key exchange */ 2370 if ((r = kex_setup(active_state, myproposal)) != 0) 2371 fatal("kex_setup: %s", ssh_err(r)); 2372 kex = active_state->kex; 2373 #ifdef WITH_OPENSSL 2374 kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server; 2375 kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server; 2376 kex->kex[KEX_DH_GRP14_SHA256] = kexdh_server; 2377 kex->kex[KEX_DH_GRP16_SHA512] = kexdh_server; 2378 kex->kex[KEX_DH_GRP18_SHA512] = kexdh_server; 2379 kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 2380 kex->kex[KEX_DH_GEX_SHA256] = kexgex_server; 2381 # ifdef OPENSSL_HAS_ECC 2382 kex->kex[KEX_ECDH_SHA2] = kexecdh_server; 2383 # endif 2384 #endif 2385 kex->kex[KEX_C25519_SHA256] = kexc25519_server; 2386 kex->server = 1; 2387 kex->client_version_string=client_version_string; 2388 kex->server_version_string=server_version_string; 2389 kex->load_host_public_key=&get_hostkey_public_by_type; 2390 kex->load_host_private_key=&get_hostkey_private_by_type; 2391 kex->host_key_index=&get_hostkey_index; 2392 kex->sign = sshd_hostkey_sign; 2393 2394 ssh_dispatch_run_fatal(active_state, DISPATCH_BLOCK, &kex->done); 2395 2396 session_id2 = kex->session_id; 2397 session_id2_len = kex->session_id_len; 2398 2399 #ifdef DEBUG_KEXDH 2400 /* send 1st encrypted/maced/compressed message */ 2401 packet_start(SSH2_MSG_IGNORE); 2402 packet_put_cstring("markus"); 2403 packet_send(); 2404 packet_write_wait(); 2405 #endif 2406 debug("KEX done"); 2407 } 2408 2409 /* server specific fatal cleanup */ 2410 void 2411 cleanup_exit(int i) 2412 { 2413 struct ssh *ssh = active_state; /* XXX */ 2414 2415 if (the_authctxt) { 2416 do_cleanup(ssh, the_authctxt); 2417 if (use_privsep && privsep_is_preauth && 2418 pmonitor != NULL && pmonitor->m_pid > 1) { 2419 debug("Killing privsep child %d", pmonitor->m_pid); 2420 if (kill(pmonitor->m_pid, SIGKILL) != 0 && 2421 errno != ESRCH) 2422 error("%s: kill(%d): %s", __func__, 2423 pmonitor->m_pid, strerror(errno)); 2424 } 2425 } 2426 #ifdef SSH_AUDIT_EVENTS 2427 /* done after do_cleanup so it can cancel the PAM auth 'thread' */ 2428 if (!use_privsep || mm_is_monitor()) 2429 audit_event(SSH_CONNECTION_ABANDON); 2430 #endif 2431 _exit(i); 2432 } 2433