1 /* $OpenBSD: sshd.c,v 1.578 2021/07/19 02:21:50 dtucker 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 "sk-api.h" 137 #include "srclimit.h" 138 #include "dh.h" 139 #include "blacklist_client.h" 140 141 #ifdef LIBWRAP 142 #include <tcpd.h> 143 #include <syslog.h> 144 extern int allow_severity; 145 extern int deny_severity; 146 #endif /* LIBWRAP */ 147 148 /* Re-exec fds */ 149 #define REEXEC_DEVCRYPTO_RESERVED_FD (STDERR_FILENO + 1) 150 #define REEXEC_STARTUP_PIPE_FD (STDERR_FILENO + 2) 151 #define REEXEC_CONFIG_PASS_FD (STDERR_FILENO + 3) 152 #define REEXEC_MIN_FREE_FD (STDERR_FILENO + 4) 153 154 extern char *__progname; 155 156 /* Server configuration options. */ 157 ServerOptions options; 158 159 /* Name of the server configuration file. */ 160 char *config_file_name = _PATH_SERVER_CONFIG_FILE; 161 162 /* 163 * Debug mode flag. This can be set on the command line. If debug 164 * mode is enabled, extra debugging output will be sent to the system 165 * log, the daemon will not go to background, and will exit after processing 166 * the first connection. 167 */ 168 int debug_flag = 0; 169 170 /* 171 * Indicating that the daemon should only test the configuration and keys. 172 * If test_flag > 1 ("-T" flag), then sshd will also dump the effective 173 * configuration, optionally using connection information provided by the 174 * "-C" flag. 175 */ 176 static int test_flag = 0; 177 178 /* Flag indicating that the daemon is being started from inetd. */ 179 static int inetd_flag = 0; 180 181 /* Flag indicating that sshd should not detach and become a daemon. */ 182 static int no_daemon_flag = 0; 183 184 /* debug goes to stderr unless inetd_flag is set */ 185 static int log_stderr = 0; 186 187 /* Saved arguments to main(). */ 188 static char **saved_argv; 189 static int saved_argc; 190 191 /* re-exec */ 192 static int rexeced_flag = 0; 193 static int rexec_flag = 1; 194 static int rexec_argc = 0; 195 static char **rexec_argv; 196 197 /* 198 * The sockets that the server is listening; this is used in the SIGHUP 199 * signal handler. 200 */ 201 #define MAX_LISTEN_SOCKS 16 202 static int listen_socks[MAX_LISTEN_SOCKS]; 203 static int num_listen_socks = 0; 204 205 /* Daemon's agent connection */ 206 int auth_sock = -1; 207 static int have_agent = 0; 208 209 /* 210 * Any really sensitive data in the application is contained in this 211 * structure. The idea is that this structure could be locked into memory so 212 * that the pages do not get written into swap. However, there are some 213 * problems. The private key contains BIGNUMs, and we do not (in principle) 214 * have access to the internals of them, and locking just the structure is 215 * not very useful. Currently, memory locking is not implemented. 216 */ 217 struct { 218 struct sshkey **host_keys; /* all private host keys */ 219 struct sshkey **host_pubkeys; /* all public host keys */ 220 struct sshkey **host_certificates; /* all public host certificates */ 221 int have_ssh2_key; 222 } sensitive_data; 223 224 /* This is set to true when a signal is received. */ 225 static volatile sig_atomic_t received_sighup = 0; 226 static volatile sig_atomic_t received_sigterm = 0; 227 228 /* record remote hostname or ip */ 229 u_int utmp_len = HOST_NAME_MAX+1; 230 231 /* 232 * startup_pipes/flags are used for tracking children of the listening sshd 233 * process early in their lifespans. This tracking is needed for three things: 234 * 235 * 1) Implementing the MaxStartups limit of concurrent unauthenticated 236 * connections. 237 * 2) Avoiding a race condition for SIGHUP processing, where child processes 238 * may have listen_socks open that could collide with main listener process 239 * after it restarts. 240 * 3) Ensuring that rexec'd sshd processes have received their initial state 241 * from the parent listen process before handling SIGHUP. 242 * 243 * Child processes signal that they have completed closure of the listen_socks 244 * and (if applicable) received their rexec state by sending a char over their 245 * sock. Child processes signal that authentication has completed by closing 246 * the sock (or by exiting). 247 */ 248 static int *startup_pipes = NULL; 249 static int *startup_flags = NULL; /* Indicates child closed listener */ 250 static int startup_pipe = -1; /* in child */ 251 252 /* variables used for privilege separation */ 253 int use_privsep = -1; 254 struct monitor *pmonitor = NULL; 255 int privsep_is_preauth = 1; 256 static int privsep_chroot = 1; 257 258 /* global connection state and authentication contexts */ 259 Authctxt *the_authctxt = NULL; 260 struct ssh *the_active_state; 261 262 /* global key/cert auth options. XXX move to permanent ssh->authctxt? */ 263 struct sshauthopt *auth_opts = NULL; 264 265 /* sshd_config buffer */ 266 struct sshbuf *cfg; 267 268 /* Included files from the configuration file */ 269 struct include_list includes = TAILQ_HEAD_INITIALIZER(includes); 270 271 /* message to be displayed after login */ 272 struct sshbuf *loginmsg; 273 274 /* Unprivileged user */ 275 struct passwd *privsep_pw = NULL; 276 277 /* Prototypes for various functions defined later in this file. */ 278 void destroy_sensitive_data(void); 279 void demote_sensitive_data(void); 280 static void do_ssh2_kex(struct ssh *); 281 282 static char *listener_proctitle; 283 284 /* 285 * Close all listening sockets 286 */ 287 static void 288 close_listen_socks(void) 289 { 290 int i; 291 292 for (i = 0; i < num_listen_socks; i++) 293 close(listen_socks[i]); 294 num_listen_socks = -1; 295 } 296 297 static void 298 close_startup_pipes(void) 299 { 300 int i; 301 302 if (startup_pipes) 303 for (i = 0; i < options.max_startups; i++) 304 if (startup_pipes[i] != -1) 305 close(startup_pipes[i]); 306 } 307 308 /* 309 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP; 310 * the effect is to reread the configuration file (and to regenerate 311 * the server key). 312 */ 313 314 /*ARGSUSED*/ 315 static void 316 sighup_handler(int sig) 317 { 318 received_sighup = 1; 319 } 320 321 /* 322 * Called from the main program after receiving SIGHUP. 323 * Restarts the server. 324 */ 325 static void 326 sighup_restart(void) 327 { 328 logit("Received SIGHUP; restarting."); 329 if (options.pid_file != NULL) 330 unlink(options.pid_file); 331 platform_pre_restart(); 332 close_listen_socks(); 333 close_startup_pipes(); 334 ssh_signal(SIGHUP, SIG_IGN); /* will be restored after exec */ 335 execv(saved_argv[0], saved_argv); 336 logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], 337 strerror(errno)); 338 exit(1); 339 } 340 341 /* 342 * Generic signal handler for terminating signals in the master daemon. 343 */ 344 /*ARGSUSED*/ 345 static void 346 sigterm_handler(int sig) 347 { 348 received_sigterm = sig; 349 } 350 351 /* 352 * SIGCHLD handler. This is called whenever a child dies. This will then 353 * reap any zombies left by exited children. 354 */ 355 /*ARGSUSED*/ 356 static void 357 main_sigchld_handler(int sig) 358 { 359 int save_errno = errno; 360 pid_t pid; 361 int status; 362 363 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 364 (pid == -1 && errno == EINTR)) 365 ; 366 errno = save_errno; 367 } 368 369 /* 370 * Signal handler for the alarm after the login grace period has expired. 371 */ 372 /*ARGSUSED*/ 373 static void 374 grace_alarm_handler(int sig) 375 { 376 if (use_privsep && pmonitor != NULL && pmonitor->m_pid > 0) 377 kill(pmonitor->m_pid, SIGALRM); 378 379 /* 380 * Try to kill any processes that we have spawned, E.g. authorized 381 * keys command helpers. 382 */ 383 if (getpgid(0) == getpid()) { 384 ssh_signal(SIGTERM, SIG_IGN); 385 kill(0, SIGTERM); 386 } 387 388 BLACKLIST_NOTIFY(the_active_state, BLACKLIST_AUTH_FAIL, "ssh"); 389 390 /* Log error and exit. */ 391 if (use_privsep && pmonitor != NULL && pmonitor->m_pid <= 0) 392 cleanup_exit(255); /* don't log in privsep child */ 393 else { 394 sigdie("Timeout before authentication for %s port %d", 395 ssh_remote_ipaddr(the_active_state), 396 ssh_remote_port(the_active_state)); 397 } 398 } 399 400 /* Destroy the host and server keys. They will no longer be needed. */ 401 void 402 destroy_sensitive_data(void) 403 { 404 u_int i; 405 406 for (i = 0; i < options.num_host_key_files; i++) { 407 if (sensitive_data.host_keys[i]) { 408 sshkey_free(sensitive_data.host_keys[i]); 409 sensitive_data.host_keys[i] = NULL; 410 } 411 if (sensitive_data.host_certificates[i]) { 412 sshkey_free(sensitive_data.host_certificates[i]); 413 sensitive_data.host_certificates[i] = NULL; 414 } 415 } 416 } 417 418 /* Demote private to public keys for network child */ 419 void 420 demote_sensitive_data(void) 421 { 422 struct sshkey *tmp; 423 u_int i; 424 int r; 425 426 for (i = 0; i < options.num_host_key_files; i++) { 427 if (sensitive_data.host_keys[i]) { 428 if ((r = sshkey_from_private( 429 sensitive_data.host_keys[i], &tmp)) != 0) 430 fatal_r(r, "could not demote host %s key", 431 sshkey_type(sensitive_data.host_keys[i])); 432 sshkey_free(sensitive_data.host_keys[i]); 433 sensitive_data.host_keys[i] = tmp; 434 } 435 /* Certs do not need demotion */ 436 } 437 } 438 439 static void 440 reseed_prngs(void) 441 { 442 u_int32_t rnd[256]; 443 444 #ifdef WITH_OPENSSL 445 RAND_poll(); 446 #endif 447 arc4random_stir(); /* noop on recent arc4random() implementations */ 448 arc4random_buf(rnd, sizeof(rnd)); /* let arc4random notice PID change */ 449 450 #ifdef WITH_OPENSSL 451 RAND_seed(rnd, sizeof(rnd)); 452 /* give libcrypto a chance to notice the PID change */ 453 if ((RAND_bytes((u_char *)rnd, 1)) != 1) 454 fatal("%s: RAND_bytes failed", __func__); 455 #endif 456 457 explicit_bzero(rnd, sizeof(rnd)); 458 } 459 460 static void 461 privsep_preauth_child(void) 462 { 463 gid_t gidset[1]; 464 465 /* Enable challenge-response authentication for privilege separation */ 466 privsep_challenge_enable(); 467 468 #ifdef GSSAPI 469 /* Cache supported mechanism OIDs for later use */ 470 ssh_gssapi_prepare_supported_oids(); 471 #endif 472 473 reseed_prngs(); 474 475 /* Demote the private keys to public keys. */ 476 demote_sensitive_data(); 477 478 /* Demote the child */ 479 if (privsep_chroot) { 480 /* Change our root directory */ 481 if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1) 482 fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR, 483 strerror(errno)); 484 if (chdir("/") == -1) 485 fatal("chdir(\"/\"): %s", strerror(errno)); 486 487 /* Drop our privileges */ 488 debug3("privsep user:group %u:%u", (u_int)privsep_pw->pw_uid, 489 (u_int)privsep_pw->pw_gid); 490 gidset[0] = privsep_pw->pw_gid; 491 if (setgroups(1, gidset) == -1) 492 fatal("setgroups: %.100s", strerror(errno)); 493 permanently_set_uid(privsep_pw); 494 } 495 } 496 497 static int 498 privsep_preauth(struct ssh *ssh) 499 { 500 int status, r; 501 pid_t pid; 502 struct ssh_sandbox *box = NULL; 503 504 /* Set up unprivileged child process to deal with network data */ 505 pmonitor = monitor_init(); 506 /* Store a pointer to the kex for later rekeying */ 507 pmonitor->m_pkex = &ssh->kex; 508 509 if (use_privsep == PRIVSEP_ON) 510 box = ssh_sandbox_init(pmonitor); 511 pid = fork(); 512 if (pid == -1) { 513 fatal("fork of unprivileged child failed"); 514 } else if (pid != 0) { 515 debug2("Network child is on pid %ld", (long)pid); 516 517 pmonitor->m_pid = pid; 518 if (have_agent) { 519 r = ssh_get_authentication_socket(&auth_sock); 520 if (r != 0) { 521 error_r(r, "Could not get agent socket"); 522 have_agent = 0; 523 } 524 } 525 if (box != NULL) 526 ssh_sandbox_parent_preauth(box, pid); 527 monitor_child_preauth(ssh, pmonitor); 528 529 /* Wait for the child's exit status */ 530 while (waitpid(pid, &status, 0) == -1) { 531 if (errno == EINTR) 532 continue; 533 pmonitor->m_pid = -1; 534 fatal_f("waitpid: %s", strerror(errno)); 535 } 536 privsep_is_preauth = 0; 537 pmonitor->m_pid = -1; 538 if (WIFEXITED(status)) { 539 if (WEXITSTATUS(status) != 0) 540 fatal_f("preauth child exited with status %d", 541 WEXITSTATUS(status)); 542 } else if (WIFSIGNALED(status)) 543 fatal_f("preauth child terminated by signal %d", 544 WTERMSIG(status)); 545 if (box != NULL) 546 ssh_sandbox_parent_finish(box); 547 return 1; 548 } else { 549 /* child */ 550 close(pmonitor->m_sendfd); 551 close(pmonitor->m_log_recvfd); 552 553 /* Arrange for logging to be sent to the monitor */ 554 set_log_handler(mm_log_handler, pmonitor); 555 556 privsep_preauth_child(); 557 setproctitle("%s", "[net]"); 558 if (box != NULL) 559 ssh_sandbox_child(box); 560 561 return 0; 562 } 563 } 564 565 static void 566 privsep_postauth(struct ssh *ssh, Authctxt *authctxt) 567 { 568 #ifdef DISABLE_FD_PASSING 569 if (1) { 570 #else 571 if (authctxt->pw->pw_uid == 0) { 572 #endif 573 /* File descriptor passing is broken or root login */ 574 use_privsep = 0; 575 goto skip; 576 } 577 578 /* New socket pair */ 579 monitor_reinit(pmonitor); 580 581 pmonitor->m_pid = fork(); 582 if (pmonitor->m_pid == -1) 583 fatal("fork of unprivileged child failed"); 584 else if (pmonitor->m_pid != 0) { 585 verbose("User child is on pid %ld", (long)pmonitor->m_pid); 586 sshbuf_reset(loginmsg); 587 monitor_clear_keystate(ssh, pmonitor); 588 monitor_child_postauth(ssh, pmonitor); 589 590 /* NEVERREACHED */ 591 exit(0); 592 } 593 594 /* child */ 595 596 close(pmonitor->m_sendfd); 597 pmonitor->m_sendfd = -1; 598 599 /* Demote the private keys to public keys. */ 600 demote_sensitive_data(); 601 602 reseed_prngs(); 603 604 /* Drop privileges */ 605 do_setusercontext(authctxt->pw); 606 607 skip: 608 /* It is safe now to apply the key state */ 609 monitor_apply_keystate(ssh, pmonitor); 610 611 /* 612 * Tell the packet layer that authentication was successful, since 613 * this information is not part of the key state. 614 */ 615 ssh_packet_set_authenticated(ssh); 616 } 617 618 static void 619 append_hostkey_type(struct sshbuf *b, const char *s) 620 { 621 int r; 622 623 if (match_pattern_list(s, options.hostkeyalgorithms, 0) != 1) { 624 debug3_f("%s key not permitted by HostkeyAlgorithms", s); 625 return; 626 } 627 if ((r = sshbuf_putf(b, "%s%s", sshbuf_len(b) > 0 ? "," : "", s)) != 0) 628 fatal_fr(r, "sshbuf_putf"); 629 } 630 631 static char * 632 list_hostkey_types(void) 633 { 634 struct sshbuf *b; 635 struct sshkey *key; 636 char *ret; 637 u_int i; 638 639 if ((b = sshbuf_new()) == NULL) 640 fatal_f("sshbuf_new failed"); 641 for (i = 0; i < options.num_host_key_files; i++) { 642 key = sensitive_data.host_keys[i]; 643 if (key == NULL) 644 key = sensitive_data.host_pubkeys[i]; 645 if (key == NULL) 646 continue; 647 switch (key->type) { 648 case KEY_RSA: 649 /* for RSA we also support SHA2 signatures */ 650 append_hostkey_type(b, "rsa-sha2-512"); 651 append_hostkey_type(b, "rsa-sha2-256"); 652 /* FALLTHROUGH */ 653 case KEY_DSA: 654 case KEY_ECDSA: 655 case KEY_ED25519: 656 case KEY_ECDSA_SK: 657 case KEY_ED25519_SK: 658 case KEY_XMSS: 659 append_hostkey_type(b, sshkey_ssh_name(key)); 660 break; 661 } 662 /* If the private key has a cert peer, then list that too */ 663 key = sensitive_data.host_certificates[i]; 664 if (key == NULL) 665 continue; 666 switch (key->type) { 667 case KEY_RSA_CERT: 668 /* for RSA we also support SHA2 signatures */ 669 append_hostkey_type(b, 670 "rsa-sha2-512-cert-v01@openssh.com"); 671 append_hostkey_type(b, 672 "rsa-sha2-256-cert-v01@openssh.com"); 673 /* FALLTHROUGH */ 674 case KEY_DSA_CERT: 675 case KEY_ECDSA_CERT: 676 case KEY_ED25519_CERT: 677 case KEY_ECDSA_SK_CERT: 678 case KEY_ED25519_SK_CERT: 679 case KEY_XMSS_CERT: 680 append_hostkey_type(b, sshkey_ssh_name(key)); 681 break; 682 } 683 } 684 if ((ret = sshbuf_dup_string(b)) == NULL) 685 fatal_f("sshbuf_dup_string failed"); 686 sshbuf_free(b); 687 debug_f("%s", ret); 688 return ret; 689 } 690 691 static struct sshkey * 692 get_hostkey_by_type(int type, int nid, int need_private, struct ssh *ssh) 693 { 694 u_int i; 695 struct sshkey *key; 696 697 for (i = 0; i < options.num_host_key_files; i++) { 698 switch (type) { 699 case KEY_RSA_CERT: 700 case KEY_DSA_CERT: 701 case KEY_ECDSA_CERT: 702 case KEY_ED25519_CERT: 703 case KEY_ECDSA_SK_CERT: 704 case KEY_ED25519_SK_CERT: 705 case KEY_XMSS_CERT: 706 key = sensitive_data.host_certificates[i]; 707 break; 708 default: 709 key = sensitive_data.host_keys[i]; 710 if (key == NULL && !need_private) 711 key = sensitive_data.host_pubkeys[i]; 712 break; 713 } 714 if (key == NULL || key->type != type) 715 continue; 716 switch (type) { 717 case KEY_ECDSA: 718 case KEY_ECDSA_SK: 719 case KEY_ECDSA_CERT: 720 case KEY_ECDSA_SK_CERT: 721 if (key->ecdsa_nid != nid) 722 continue; 723 /* FALLTHROUGH */ 724 default: 725 return need_private ? 726 sensitive_data.host_keys[i] : key; 727 } 728 } 729 return NULL; 730 } 731 732 struct sshkey * 733 get_hostkey_public_by_type(int type, int nid, struct ssh *ssh) 734 { 735 return get_hostkey_by_type(type, nid, 0, ssh); 736 } 737 738 struct sshkey * 739 get_hostkey_private_by_type(int type, int nid, struct ssh *ssh) 740 { 741 return get_hostkey_by_type(type, nid, 1, ssh); 742 } 743 744 struct sshkey * 745 get_hostkey_by_index(int ind) 746 { 747 if (ind < 0 || (u_int)ind >= options.num_host_key_files) 748 return (NULL); 749 return (sensitive_data.host_keys[ind]); 750 } 751 752 struct sshkey * 753 get_hostkey_public_by_index(int ind, struct ssh *ssh) 754 { 755 if (ind < 0 || (u_int)ind >= options.num_host_key_files) 756 return (NULL); 757 return (sensitive_data.host_pubkeys[ind]); 758 } 759 760 int 761 get_hostkey_index(struct sshkey *key, int compare, struct ssh *ssh) 762 { 763 u_int i; 764 765 for (i = 0; i < options.num_host_key_files; i++) { 766 if (sshkey_is_cert(key)) { 767 if (key == sensitive_data.host_certificates[i] || 768 (compare && sensitive_data.host_certificates[i] && 769 sshkey_equal(key, 770 sensitive_data.host_certificates[i]))) 771 return (i); 772 } else { 773 if (key == sensitive_data.host_keys[i] || 774 (compare && sensitive_data.host_keys[i] && 775 sshkey_equal(key, sensitive_data.host_keys[i]))) 776 return (i); 777 if (key == sensitive_data.host_pubkeys[i] || 778 (compare && sensitive_data.host_pubkeys[i] && 779 sshkey_equal(key, sensitive_data.host_pubkeys[i]))) 780 return (i); 781 } 782 } 783 return (-1); 784 } 785 786 /* Inform the client of all hostkeys */ 787 static void 788 notify_hostkeys(struct ssh *ssh) 789 { 790 struct sshbuf *buf; 791 struct sshkey *key; 792 u_int i, nkeys; 793 int r; 794 char *fp; 795 796 /* Some clients cannot cope with the hostkeys message, skip those. */ 797 if (ssh->compat & SSH_BUG_HOSTKEYS) 798 return; 799 800 if ((buf = sshbuf_new()) == NULL) 801 fatal_f("sshbuf_new"); 802 for (i = nkeys = 0; i < options.num_host_key_files; i++) { 803 key = get_hostkey_public_by_index(i, ssh); 804 if (key == NULL || key->type == KEY_UNSPEC || 805 sshkey_is_cert(key)) 806 continue; 807 fp = sshkey_fingerprint(key, options.fingerprint_hash, 808 SSH_FP_DEFAULT); 809 debug3_f("key %d: %s %s", i, sshkey_ssh_name(key), fp); 810 free(fp); 811 if (nkeys == 0) { 812 /* 813 * Start building the request when we find the 814 * first usable key. 815 */ 816 if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 || 817 (r = sshpkt_put_cstring(ssh, "hostkeys-00@openssh.com")) != 0 || 818 (r = sshpkt_put_u8(ssh, 0)) != 0) /* want reply */ 819 sshpkt_fatal(ssh, r, "%s: start request", __func__); 820 } 821 /* Append the key to the request */ 822 sshbuf_reset(buf); 823 if ((r = sshkey_putb(key, buf)) != 0) 824 fatal_fr(r, "couldn't put hostkey %d", i); 825 if ((r = sshpkt_put_stringb(ssh, buf)) != 0) 826 sshpkt_fatal(ssh, r, "%s: append key", __func__); 827 nkeys++; 828 } 829 debug3_f("sent %u hostkeys", nkeys); 830 if (nkeys == 0) 831 fatal_f("no hostkeys"); 832 if ((r = sshpkt_send(ssh)) != 0) 833 sshpkt_fatal(ssh, r, "%s: send", __func__); 834 sshbuf_free(buf); 835 } 836 837 /* 838 * returns 1 if connection should be dropped, 0 otherwise. 839 * dropping starts at connection #max_startups_begin with a probability 840 * of (max_startups_rate/100). the probability increases linearly until 841 * all connections are dropped for startups > max_startups 842 */ 843 static int 844 should_drop_connection(int startups) 845 { 846 int p, r; 847 848 if (startups < options.max_startups_begin) 849 return 0; 850 if (startups >= options.max_startups) 851 return 1; 852 if (options.max_startups_rate == 100) 853 return 1; 854 855 p = 100 - options.max_startups_rate; 856 p *= startups - options.max_startups_begin; 857 p /= options.max_startups - options.max_startups_begin; 858 p += options.max_startups_rate; 859 r = arc4random_uniform(100); 860 861 debug_f("p %d, r %d", p, r); 862 return (r < p) ? 1 : 0; 863 } 864 865 /* 866 * Check whether connection should be accepted by MaxStartups. 867 * Returns 0 if the connection is accepted. If the connection is refused, 868 * returns 1 and attempts to send notification to client. 869 * Logs when the MaxStartups condition is entered or exited, and periodically 870 * while in that state. 871 */ 872 static int 873 drop_connection(int sock, int startups, int notify_pipe) 874 { 875 char *laddr, *raddr; 876 const char msg[] = "Exceeded MaxStartups\r\n"; 877 static time_t last_drop, first_drop; 878 static u_int ndropped; 879 LogLevel drop_level = SYSLOG_LEVEL_VERBOSE; 880 time_t now; 881 882 now = monotime(); 883 if (!should_drop_connection(startups) && 884 srclimit_check_allow(sock, notify_pipe) == 1) { 885 if (last_drop != 0 && 886 startups < options.max_startups_begin - 1) { 887 /* XXX maybe need better hysteresis here */ 888 logit("exited MaxStartups throttling after %s, " 889 "%u connections dropped", 890 fmt_timeframe(now - first_drop), ndropped); 891 last_drop = 0; 892 } 893 return 0; 894 } 895 896 #define SSHD_MAXSTARTUPS_LOG_INTERVAL (5 * 60) 897 if (last_drop == 0) { 898 error("beginning MaxStartups throttling"); 899 drop_level = SYSLOG_LEVEL_INFO; 900 first_drop = now; 901 ndropped = 0; 902 } else if (last_drop + SSHD_MAXSTARTUPS_LOG_INTERVAL < now) { 903 /* Periodic logs */ 904 error("in MaxStartups throttling for %s, " 905 "%u connections dropped", 906 fmt_timeframe(now - first_drop), ndropped + 1); 907 drop_level = SYSLOG_LEVEL_INFO; 908 } 909 last_drop = now; 910 ndropped++; 911 912 laddr = get_local_ipaddr(sock); 913 raddr = get_peer_ipaddr(sock); 914 do_log2(drop_level, "drop connection #%d from [%s]:%d on [%s]:%d " 915 "past MaxStartups", startups, raddr, get_peer_port(sock), 916 laddr, get_local_port(sock)); 917 free(laddr); 918 free(raddr); 919 /* best-effort notification to client */ 920 (void)write(sock, msg, sizeof(msg) - 1); 921 return 1; 922 } 923 924 static void 925 usage(void) 926 { 927 if (options.version_addendum && *options.version_addendum != '\0') 928 fprintf(stderr, "%s %s, %s\n", 929 SSH_RELEASE, 930 options.version_addendum, OPENSSL_VERSION_STRING); 931 else 932 fprintf(stderr, "%s, %s\n", 933 SSH_RELEASE, OPENSSL_VERSION_STRING); 934 fprintf(stderr, 935 "usage: sshd [-46DdeiqTt] [-C connection_spec] [-c host_cert_file]\n" 936 " [-E log_file] [-f config_file] [-g login_grace_time]\n" 937 " [-h host_key_file] [-o option] [-p port] [-u len]\n" 938 ); 939 exit(1); 940 } 941 942 static void 943 send_rexec_state(int fd, struct sshbuf *conf) 944 { 945 struct sshbuf *m = NULL, *inc = NULL; 946 struct include_item *item = NULL; 947 int r; 948 949 debug3_f("entering fd = %d config len %zu", fd, 950 sshbuf_len(conf)); 951 952 if ((m = sshbuf_new()) == NULL || (inc = sshbuf_new()) == NULL) 953 fatal_f("sshbuf_new failed"); 954 955 /* pack includes into a string */ 956 TAILQ_FOREACH(item, &includes, entry) { 957 if ((r = sshbuf_put_cstring(inc, item->selector)) != 0 || 958 (r = sshbuf_put_cstring(inc, item->filename)) != 0 || 959 (r = sshbuf_put_stringb(inc, item->contents)) != 0) 960 fatal_fr(r, "compose includes"); 961 } 962 963 /* 964 * Protocol from reexec master to child: 965 * string configuration 966 * string included_files[] { 967 * string selector 968 * string filename 969 * string contents 970 * } 971 * string rng_seed (if required) 972 */ 973 if ((r = sshbuf_put_stringb(m, conf)) != 0 || 974 (r = sshbuf_put_stringb(m, inc)) != 0) 975 fatal_fr(r, "compose config"); 976 #if defined(WITH_OPENSSL) && !defined(OPENSSL_PRNG_ONLY) 977 rexec_send_rng_seed(m); 978 #endif 979 if (ssh_msg_send(fd, 0, m) == -1) 980 error_f("ssh_msg_send failed"); 981 982 sshbuf_free(m); 983 sshbuf_free(inc); 984 985 debug3_f("done"); 986 } 987 988 static void 989 recv_rexec_state(int fd, struct sshbuf *conf) 990 { 991 struct sshbuf *m, *inc; 992 u_char *cp, ver; 993 size_t len; 994 int r; 995 struct include_item *item; 996 997 debug3_f("entering fd = %d", fd); 998 999 if ((m = sshbuf_new()) == NULL || (inc = sshbuf_new()) == NULL) 1000 fatal_f("sshbuf_new failed"); 1001 if (ssh_msg_recv(fd, m) == -1) 1002 fatal_f("ssh_msg_recv failed"); 1003 if ((r = sshbuf_get_u8(m, &ver)) != 0) 1004 fatal_fr(r, "parse version"); 1005 if (ver != 0) 1006 fatal_f("rexec version mismatch"); 1007 if ((r = sshbuf_get_string(m, &cp, &len)) != 0 || 1008 (r = sshbuf_get_stringb(m, inc)) != 0) 1009 fatal_fr(r, "parse config"); 1010 1011 #if defined(WITH_OPENSSL) && !defined(OPENSSL_PRNG_ONLY) 1012 rexec_recv_rng_seed(m); 1013 #endif 1014 1015 if (conf != NULL && (r = sshbuf_put(conf, cp, len))) 1016 fatal_fr(r, "sshbuf_put"); 1017 1018 while (sshbuf_len(inc) != 0) { 1019 item = xcalloc(1, sizeof(*item)); 1020 if ((item->contents = sshbuf_new()) == NULL) 1021 fatal_f("sshbuf_new failed"); 1022 if ((r = sshbuf_get_cstring(inc, &item->selector, NULL)) != 0 || 1023 (r = sshbuf_get_cstring(inc, &item->filename, NULL)) != 0 || 1024 (r = sshbuf_get_stringb(inc, item->contents)) != 0) 1025 fatal_fr(r, "parse includes"); 1026 TAILQ_INSERT_TAIL(&includes, item, entry); 1027 } 1028 1029 free(cp); 1030 sshbuf_free(m); 1031 1032 debug3_f("done"); 1033 } 1034 1035 /* Accept a connection from inetd */ 1036 static void 1037 server_accept_inetd(int *sock_in, int *sock_out) 1038 { 1039 if (rexeced_flag) { 1040 close(REEXEC_CONFIG_PASS_FD); 1041 *sock_in = *sock_out = dup(STDIN_FILENO); 1042 } else { 1043 *sock_in = dup(STDIN_FILENO); 1044 *sock_out = dup(STDOUT_FILENO); 1045 } 1046 /* 1047 * We intentionally do not close the descriptors 0, 1, and 2 1048 * as our code for setting the descriptors won't work if 1049 * ttyfd happens to be one of those. 1050 */ 1051 if (stdfd_devnull(1, 1, !log_stderr) == -1) 1052 error_f("stdfd_devnull failed"); 1053 debug("inetd sockets after dupping: %d, %d", *sock_in, *sock_out); 1054 } 1055 1056 /* 1057 * Listen for TCP connections 1058 */ 1059 static void 1060 listen_on_addrs(struct listenaddr *la) 1061 { 1062 int ret, listen_sock; 1063 struct addrinfo *ai; 1064 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 1065 1066 for (ai = la->addrs; ai; ai = ai->ai_next) { 1067 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 1068 continue; 1069 if (num_listen_socks >= MAX_LISTEN_SOCKS) 1070 fatal("Too many listen sockets. " 1071 "Enlarge MAX_LISTEN_SOCKS"); 1072 if ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen, 1073 ntop, sizeof(ntop), strport, sizeof(strport), 1074 NI_NUMERICHOST|NI_NUMERICSERV)) != 0) { 1075 error("getnameinfo failed: %.100s", 1076 ssh_gai_strerror(ret)); 1077 continue; 1078 } 1079 /* Create socket for listening. */ 1080 listen_sock = socket(ai->ai_family, ai->ai_socktype, 1081 ai->ai_protocol); 1082 if (listen_sock == -1) { 1083 /* kernel may not support ipv6 */ 1084 verbose("socket: %.100s", strerror(errno)); 1085 continue; 1086 } 1087 if (set_nonblock(listen_sock) == -1) { 1088 close(listen_sock); 1089 continue; 1090 } 1091 if (fcntl(listen_sock, F_SETFD, FD_CLOEXEC) == -1) { 1092 verbose("socket: CLOEXEC: %s", strerror(errno)); 1093 close(listen_sock); 1094 continue; 1095 } 1096 /* Socket options */ 1097 set_reuseaddr(listen_sock); 1098 if (la->rdomain != NULL && 1099 set_rdomain(listen_sock, la->rdomain) == -1) { 1100 close(listen_sock); 1101 continue; 1102 } 1103 1104 /* Only communicate in IPv6 over AF_INET6 sockets. */ 1105 if (ai->ai_family == AF_INET6) 1106 sock_set_v6only(listen_sock); 1107 1108 debug("Bind to port %s on %s.", strport, ntop); 1109 1110 /* Bind the socket to the desired port. */ 1111 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) == -1) { 1112 error("Bind to port %s on %s failed: %.200s.", 1113 strport, ntop, strerror(errno)); 1114 close(listen_sock); 1115 continue; 1116 } 1117 listen_socks[num_listen_socks] = listen_sock; 1118 num_listen_socks++; 1119 1120 /* Start listening on the port. */ 1121 if (listen(listen_sock, SSH_LISTEN_BACKLOG) == -1) 1122 fatal("listen on [%s]:%s: %.100s", 1123 ntop, strport, strerror(errno)); 1124 logit("Server listening on %s port %s%s%s.", 1125 ntop, strport, 1126 la->rdomain == NULL ? "" : " rdomain ", 1127 la->rdomain == NULL ? "" : la->rdomain); 1128 } 1129 } 1130 1131 static void 1132 server_listen(void) 1133 { 1134 u_int i; 1135 1136 /* Initialise per-source limit tracking. */ 1137 srclimit_init(options.max_startups, options.per_source_max_startups, 1138 options.per_source_masklen_ipv4, options.per_source_masklen_ipv6); 1139 1140 for (i = 0; i < options.num_listen_addrs; i++) { 1141 listen_on_addrs(&options.listen_addrs[i]); 1142 freeaddrinfo(options.listen_addrs[i].addrs); 1143 free(options.listen_addrs[i].rdomain); 1144 memset(&options.listen_addrs[i], 0, 1145 sizeof(options.listen_addrs[i])); 1146 } 1147 free(options.listen_addrs); 1148 options.listen_addrs = NULL; 1149 options.num_listen_addrs = 0; 1150 1151 if (!num_listen_socks) 1152 fatal("Cannot bind any address."); 1153 } 1154 1155 /* 1156 * The main TCP accept loop. Note that, for the non-debug case, returns 1157 * from this function are in a forked subprocess. 1158 */ 1159 static void 1160 server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s) 1161 { 1162 fd_set *fdset; 1163 int i, j, ret, maxfd; 1164 int ostartups = -1, startups = 0, listening = 0, lameduck = 0; 1165 int startup_p[2] = { -1 , -1 }; 1166 char c = 0; 1167 struct sockaddr_storage from; 1168 socklen_t fromlen; 1169 pid_t pid; 1170 u_char rnd[256]; 1171 sigset_t nsigset, osigset; 1172 #ifdef LIBWRAP 1173 struct request_info req; 1174 1175 request_init(&req, RQ_DAEMON, __progname, 0); 1176 #endif 1177 1178 /* setup fd set for accept */ 1179 fdset = NULL; 1180 maxfd = 0; 1181 for (i = 0; i < num_listen_socks; i++) 1182 if (listen_socks[i] > maxfd) 1183 maxfd = listen_socks[i]; 1184 /* pipes connected to unauthenticated child sshd processes */ 1185 startup_pipes = xcalloc(options.max_startups, sizeof(int)); 1186 startup_flags = xcalloc(options.max_startups, sizeof(int)); 1187 for (i = 0; i < options.max_startups; i++) 1188 startup_pipes[i] = -1; 1189 1190 /* 1191 * Prepare signal mask that we use to block signals that might set 1192 * received_sigterm or received_sighup, so that we are guaranteed 1193 * to immediately wake up the pselect if a signal is received after 1194 * the flag is checked. 1195 */ 1196 sigemptyset(&nsigset); 1197 sigaddset(&nsigset, SIGHUP); 1198 sigaddset(&nsigset, SIGCHLD); 1199 sigaddset(&nsigset, SIGTERM); 1200 sigaddset(&nsigset, SIGQUIT); 1201 1202 /* 1203 * Stay listening for connections until the system crashes or 1204 * the daemon is killed with a signal. 1205 */ 1206 for (;;) { 1207 sigprocmask(SIG_BLOCK, &nsigset, &osigset); 1208 if (received_sigterm) { 1209 logit("Received signal %d; terminating.", 1210 (int) received_sigterm); 1211 close_listen_socks(); 1212 if (options.pid_file != NULL) 1213 unlink(options.pid_file); 1214 exit(received_sigterm == SIGTERM ? 0 : 255); 1215 } 1216 if (ostartups != startups) { 1217 setproctitle("%s [listener] %d of %d-%d startups", 1218 listener_proctitle, startups, 1219 options.max_startups_begin, options.max_startups); 1220 ostartups = startups; 1221 } 1222 if (received_sighup) { 1223 if (!lameduck) { 1224 debug("Received SIGHUP; waiting for children"); 1225 close_listen_socks(); 1226 lameduck = 1; 1227 } 1228 if (listening <= 0) { 1229 sigprocmask(SIG_SETMASK, &osigset, NULL); 1230 sighup_restart(); 1231 } 1232 } 1233 free(fdset); 1234 fdset = xcalloc(howmany(maxfd + 1, NFDBITS), 1235 sizeof(fd_mask)); 1236 1237 for (i = 0; i < num_listen_socks; i++) 1238 FD_SET(listen_socks[i], fdset); 1239 for (i = 0; i < options.max_startups; i++) 1240 if (startup_pipes[i] != -1) 1241 FD_SET(startup_pipes[i], fdset); 1242 1243 /* Wait until a connection arrives or a child exits. */ 1244 ret = pselect(maxfd+1, fdset, NULL, NULL, NULL, &osigset); 1245 if (ret == -1 && errno != EINTR) 1246 error("pselect: %.100s", strerror(errno)); 1247 sigprocmask(SIG_SETMASK, &osigset, NULL); 1248 if (ret == -1) 1249 continue; 1250 1251 for (i = 0; i < options.max_startups; i++) { 1252 if (startup_pipes[i] == -1 || 1253 !FD_ISSET(startup_pipes[i], fdset)) 1254 continue; 1255 switch (read(startup_pipes[i], &c, sizeof(c))) { 1256 case -1: 1257 if (errno == EINTR || errno == EAGAIN) 1258 continue; 1259 if (errno != EPIPE) { 1260 error_f("startup pipe %d (fd=%d): " 1261 "read %s", i, startup_pipes[i], 1262 strerror(errno)); 1263 } 1264 /* FALLTHROUGH */ 1265 case 0: 1266 /* child exited or completed auth */ 1267 close(startup_pipes[i]); 1268 srclimit_done(startup_pipes[i]); 1269 startup_pipes[i] = -1; 1270 startups--; 1271 if (startup_flags[i]) 1272 listening--; 1273 break; 1274 case 1: 1275 /* child has finished preliminaries */ 1276 if (startup_flags[i]) { 1277 listening--; 1278 startup_flags[i] = 0; 1279 } 1280 break; 1281 } 1282 } 1283 for (i = 0; i < num_listen_socks; i++) { 1284 if (!FD_ISSET(listen_socks[i], fdset)) 1285 continue; 1286 fromlen = sizeof(from); 1287 *newsock = accept(listen_socks[i], 1288 (struct sockaddr *)&from, &fromlen); 1289 if (*newsock == -1) { 1290 if (errno != EINTR && errno != EWOULDBLOCK && 1291 errno != ECONNABORTED && errno != EAGAIN) 1292 error("accept: %.100s", 1293 strerror(errno)); 1294 if (errno == EMFILE || errno == ENFILE) 1295 usleep(100 * 1000); 1296 continue; 1297 } 1298 #ifdef LIBWRAP 1299 /* Check whether logins are denied from this host. */ 1300 request_set(&req, RQ_FILE, *newsock, 1301 RQ_CLIENT_NAME, "", RQ_CLIENT_ADDR, "", 0); 1302 sock_host(&req); 1303 if (!hosts_access(&req)) { 1304 const struct linger l = { .l_onoff = 1, 1305 .l_linger = 0 }; 1306 1307 (void )setsockopt(*newsock, SOL_SOCKET, 1308 SO_LINGER, &l, sizeof(l)); 1309 (void )close(*newsock); 1310 /* 1311 * Mimic message from libwrap's refuse() 1312 * exactly. sshguard, and supposedly lots 1313 * of custom made scripts rely on it. 1314 */ 1315 syslog(deny_severity, 1316 "refused connect from %s (%s)", 1317 eval_client(&req), 1318 eval_hostaddr(req.client)); 1319 debug("Connection refused by tcp wrapper"); 1320 continue; 1321 } 1322 #endif /* LIBWRAP */ 1323 if (unset_nonblock(*newsock) == -1 || 1324 pipe(startup_p) == -1) 1325 continue; 1326 if (drop_connection(*newsock, startups, startup_p[0])) { 1327 close(*newsock); 1328 close(startup_p[0]); 1329 close(startup_p[1]); 1330 continue; 1331 } 1332 1333 if (rexec_flag && socketpair(AF_UNIX, 1334 SOCK_STREAM, 0, config_s) == -1) { 1335 error("reexec socketpair: %s", 1336 strerror(errno)); 1337 close(*newsock); 1338 close(startup_p[0]); 1339 close(startup_p[1]); 1340 continue; 1341 } 1342 1343 for (j = 0; j < options.max_startups; j++) 1344 if (startup_pipes[j] == -1) { 1345 startup_pipes[j] = startup_p[0]; 1346 if (maxfd < startup_p[0]) 1347 maxfd = startup_p[0]; 1348 startups++; 1349 startup_flags[j] = 1; 1350 break; 1351 } 1352 1353 /* 1354 * Got connection. Fork a child to handle it, unless 1355 * we are in debugging mode. 1356 */ 1357 if (debug_flag) { 1358 /* 1359 * In debugging mode. Close the listening 1360 * socket, and start processing the 1361 * connection without forking. 1362 */ 1363 debug("Server will not fork when running in debugging mode."); 1364 close_listen_socks(); 1365 *sock_in = *newsock; 1366 *sock_out = *newsock; 1367 close(startup_p[0]); 1368 close(startup_p[1]); 1369 startup_pipe = -1; 1370 pid = getpid(); 1371 if (rexec_flag) { 1372 send_rexec_state(config_s[0], cfg); 1373 close(config_s[0]); 1374 } 1375 return; 1376 } 1377 1378 /* 1379 * Normal production daemon. Fork, and have 1380 * the child process the connection. The 1381 * parent continues listening. 1382 */ 1383 platform_pre_fork(); 1384 listening++; 1385 if ((pid = fork()) == 0) { 1386 /* 1387 * Child. Close the listening and 1388 * max_startup sockets. Start using 1389 * the accepted socket. Reinitialize 1390 * logging (since our pid has changed). 1391 * We return from this function to handle 1392 * the connection. 1393 */ 1394 platform_post_fork_child(); 1395 startup_pipe = startup_p[1]; 1396 close_startup_pipes(); 1397 close_listen_socks(); 1398 *sock_in = *newsock; 1399 *sock_out = *newsock; 1400 log_init(__progname, 1401 options.log_level, 1402 options.log_facility, 1403 log_stderr); 1404 if (rexec_flag) 1405 close(config_s[0]); 1406 else { 1407 /* 1408 * Signal parent that the preliminaries 1409 * for this child are complete. For the 1410 * re-exec case, this happens after the 1411 * child has received the rexec state 1412 * from the server. 1413 */ 1414 (void)atomicio(vwrite, startup_pipe, 1415 "\0", 1); 1416 } 1417 return; 1418 } 1419 1420 /* Parent. Stay in the loop. */ 1421 platform_post_fork_parent(pid); 1422 if (pid == -1) 1423 error("fork: %.100s", strerror(errno)); 1424 else 1425 debug("Forked child %ld.", (long)pid); 1426 1427 close(startup_p[1]); 1428 1429 if (rexec_flag) { 1430 close(config_s[1]); 1431 send_rexec_state(config_s[0], cfg); 1432 close(config_s[0]); 1433 } 1434 close(*newsock); 1435 1436 /* 1437 * Ensure that our random state differs 1438 * from that of the child 1439 */ 1440 arc4random_stir(); 1441 arc4random_buf(rnd, sizeof(rnd)); 1442 #ifdef WITH_OPENSSL 1443 RAND_seed(rnd, sizeof(rnd)); 1444 if ((RAND_bytes((u_char *)rnd, 1)) != 1) 1445 fatal("%s: RAND_bytes failed", __func__); 1446 #endif 1447 explicit_bzero(rnd, sizeof(rnd)); 1448 } 1449 } 1450 } 1451 1452 /* 1453 * If IP options are supported, make sure there are none (log and 1454 * return an error if any are found). Basically we are worried about 1455 * source routing; it can be used to pretend you are somebody 1456 * (ip-address) you are not. That itself may be "almost acceptable" 1457 * under certain circumstances, but rhosts authentication is useless 1458 * if source routing is accepted. Notice also that if we just dropped 1459 * source routing here, the other side could use IP spoofing to do 1460 * rest of the interaction and could still bypass security. So we 1461 * exit here if we detect any IP options. 1462 */ 1463 static void 1464 check_ip_options(struct ssh *ssh) 1465 { 1466 #ifdef IP_OPTIONS 1467 int sock_in = ssh_packet_get_connection_in(ssh); 1468 struct sockaddr_storage from; 1469 u_char opts[200]; 1470 socklen_t i, option_size = sizeof(opts), fromlen = sizeof(from); 1471 char text[sizeof(opts) * 3 + 1]; 1472 1473 memset(&from, 0, sizeof(from)); 1474 if (getpeername(sock_in, (struct sockaddr *)&from, 1475 &fromlen) == -1) 1476 return; 1477 if (from.ss_family != AF_INET) 1478 return; 1479 /* XXX IPv6 options? */ 1480 1481 if (getsockopt(sock_in, IPPROTO_IP, IP_OPTIONS, opts, 1482 &option_size) >= 0 && option_size != 0) { 1483 text[0] = '\0'; 1484 for (i = 0; i < option_size; i++) 1485 snprintf(text + i*3, sizeof(text) - i*3, 1486 " %2.2x", opts[i]); 1487 fatal("Connection from %.100s port %d with IP opts: %.800s", 1488 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), text); 1489 } 1490 return; 1491 #endif /* IP_OPTIONS */ 1492 } 1493 1494 /* Set the routing domain for this process */ 1495 static void 1496 set_process_rdomain(struct ssh *ssh, const char *name) 1497 { 1498 #if defined(HAVE_SYS_SET_PROCESS_RDOMAIN) 1499 if (name == NULL) 1500 return; /* default */ 1501 1502 if (strcmp(name, "%D") == 0) { 1503 /* "expands" to routing domain of connection */ 1504 if ((name = ssh_packet_rdomain_in(ssh)) == NULL) 1505 return; 1506 } 1507 /* NB. We don't pass 'ssh' to sys_set_process_rdomain() */ 1508 return sys_set_process_rdomain(name); 1509 #elif defined(__OpenBSD__) 1510 int rtable, ortable = getrtable(); 1511 const char *errstr; 1512 1513 if (name == NULL) 1514 return; /* default */ 1515 1516 if (strcmp(name, "%D") == 0) { 1517 /* "expands" to routing domain of connection */ 1518 if ((name = ssh_packet_rdomain_in(ssh)) == NULL) 1519 return; 1520 } 1521 1522 rtable = (int)strtonum(name, 0, 255, &errstr); 1523 if (errstr != NULL) /* Shouldn't happen */ 1524 fatal("Invalid routing domain \"%s\": %s", name, errstr); 1525 if (rtable != ortable && setrtable(rtable) != 0) 1526 fatal("Unable to set routing domain %d: %s", 1527 rtable, strerror(errno)); 1528 debug_f("set routing domain %d (was %d)", rtable, ortable); 1529 #else /* defined(__OpenBSD__) */ 1530 fatal("Unable to set routing domain: not supported in this platform"); 1531 #endif 1532 } 1533 1534 static void 1535 accumulate_host_timing_secret(struct sshbuf *server_cfg, 1536 struct sshkey *key) 1537 { 1538 static struct ssh_digest_ctx *ctx; 1539 u_char *hash; 1540 size_t len; 1541 struct sshbuf *buf; 1542 int r; 1543 1544 if (ctx == NULL && (ctx = ssh_digest_start(SSH_DIGEST_SHA512)) == NULL) 1545 fatal_f("ssh_digest_start"); 1546 if (key == NULL) { /* finalize */ 1547 /* add server config in case we are using agent for host keys */ 1548 if (ssh_digest_update(ctx, sshbuf_ptr(server_cfg), 1549 sshbuf_len(server_cfg)) != 0) 1550 fatal_f("ssh_digest_update"); 1551 len = ssh_digest_bytes(SSH_DIGEST_SHA512); 1552 hash = xmalloc(len); 1553 if (ssh_digest_final(ctx, hash, len) != 0) 1554 fatal_f("ssh_digest_final"); 1555 options.timing_secret = PEEK_U64(hash); 1556 freezero(hash, len); 1557 ssh_digest_free(ctx); 1558 ctx = NULL; 1559 return; 1560 } 1561 if ((buf = sshbuf_new()) == NULL) 1562 fatal_f("could not allocate buffer"); 1563 if ((r = sshkey_private_serialize(key, buf)) != 0) 1564 fatal_fr(r, "decode key"); 1565 if (ssh_digest_update(ctx, sshbuf_ptr(buf), sshbuf_len(buf)) != 0) 1566 fatal_f("ssh_digest_update"); 1567 sshbuf_reset(buf); 1568 sshbuf_free(buf); 1569 } 1570 1571 static char * 1572 prepare_proctitle(int ac, char **av) 1573 { 1574 char *ret = NULL; 1575 int i; 1576 1577 for (i = 0; i < ac; i++) 1578 xextendf(&ret, " ", "%s", av[i]); 1579 return ret; 1580 } 1581 1582 /* 1583 * Main program for the daemon. 1584 */ 1585 int 1586 main(int ac, char **av) 1587 { 1588 struct ssh *ssh = NULL; 1589 extern char *optarg; 1590 extern int optind; 1591 int r, opt, on = 1, already_daemon, remote_port; 1592 int sock_in = -1, sock_out = -1, newsock = -1; 1593 const char *remote_ip, *rdomain; 1594 char *fp, *line, *laddr, *logfile = NULL; 1595 int config_s[2] = { -1 , -1 }; 1596 u_int i, j; 1597 u_int64_t ibytes, obytes; 1598 mode_t new_umask; 1599 struct sshkey *key; 1600 struct sshkey *pubkey; 1601 int keytype; 1602 Authctxt *authctxt; 1603 struct connection_info *connection_info = NULL; 1604 1605 #ifdef HAVE_SECUREWARE 1606 (void)set_auth_parameters(ac, av); 1607 #endif 1608 __progname = ssh_get_progname(av[0]); 1609 1610 /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */ 1611 saved_argc = ac; 1612 rexec_argc = ac; 1613 saved_argv = xcalloc(ac + 1, sizeof(*saved_argv)); 1614 for (i = 0; (int)i < ac; i++) 1615 saved_argv[i] = xstrdup(av[i]); 1616 saved_argv[i] = NULL; 1617 1618 #ifndef HAVE_SETPROCTITLE 1619 /* Prepare for later setproctitle emulation */ 1620 compat_init_setproctitle(ac, av); 1621 av = saved_argv; 1622 #endif 1623 1624 if (geteuid() == 0 && setgroups(0, NULL) == -1) 1625 debug("setgroups(): %.200s", strerror(errno)); 1626 1627 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */ 1628 sanitise_stdfd(); 1629 1630 seed_rng(); 1631 1632 /* Initialize configuration options to their default values. */ 1633 initialize_server_options(&options); 1634 1635 /* Parse command-line arguments. */ 1636 while ((opt = getopt(ac, av, 1637 "C:E:b:c:f:g:h:k:o:p:u:46DQRTdeiqrt")) != -1) { 1638 switch (opt) { 1639 case '4': 1640 options.address_family = AF_INET; 1641 break; 1642 case '6': 1643 options.address_family = AF_INET6; 1644 break; 1645 case 'f': 1646 config_file_name = optarg; 1647 break; 1648 case 'c': 1649 servconf_add_hostcert("[command-line]", 0, 1650 &options, optarg); 1651 break; 1652 case 'd': 1653 if (debug_flag == 0) { 1654 debug_flag = 1; 1655 options.log_level = SYSLOG_LEVEL_DEBUG1; 1656 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) 1657 options.log_level++; 1658 break; 1659 case 'D': 1660 no_daemon_flag = 1; 1661 break; 1662 case 'E': 1663 logfile = optarg; 1664 /* FALLTHROUGH */ 1665 case 'e': 1666 log_stderr = 1; 1667 break; 1668 case 'i': 1669 inetd_flag = 1; 1670 break; 1671 case 'r': 1672 rexec_flag = 0; 1673 break; 1674 case 'R': 1675 rexeced_flag = 1; 1676 inetd_flag = 1; 1677 break; 1678 case 'Q': 1679 /* ignored */ 1680 break; 1681 case 'q': 1682 options.log_level = SYSLOG_LEVEL_QUIET; 1683 break; 1684 case 'b': 1685 /* protocol 1, ignored */ 1686 break; 1687 case 'p': 1688 options.ports_from_cmdline = 1; 1689 if (options.num_ports >= MAX_PORTS) { 1690 fprintf(stderr, "too many ports.\n"); 1691 exit(1); 1692 } 1693 options.ports[options.num_ports++] = a2port(optarg); 1694 if (options.ports[options.num_ports-1] <= 0) { 1695 fprintf(stderr, "Bad port number.\n"); 1696 exit(1); 1697 } 1698 break; 1699 case 'g': 1700 if ((options.login_grace_time = convtime(optarg)) == -1) { 1701 fprintf(stderr, "Invalid login grace time.\n"); 1702 exit(1); 1703 } 1704 break; 1705 case 'k': 1706 /* protocol 1, ignored */ 1707 break; 1708 case 'h': 1709 servconf_add_hostkey("[command-line]", 0, 1710 &options, optarg, 1); 1711 break; 1712 case 't': 1713 test_flag = 1; 1714 break; 1715 case 'T': 1716 test_flag = 2; 1717 break; 1718 case 'C': 1719 connection_info = get_connection_info(ssh, 0, 0); 1720 if (parse_server_match_testspec(connection_info, 1721 optarg) == -1) 1722 exit(1); 1723 break; 1724 case 'u': 1725 utmp_len = (u_int)strtonum(optarg, 0, HOST_NAME_MAX+1+1, NULL); 1726 if (utmp_len > HOST_NAME_MAX+1) { 1727 fprintf(stderr, "Invalid utmp length.\n"); 1728 exit(1); 1729 } 1730 break; 1731 case 'o': 1732 line = xstrdup(optarg); 1733 if (process_server_config_line(&options, line, 1734 "command-line", 0, NULL, NULL, &includes) != 0) 1735 exit(1); 1736 free(line); 1737 break; 1738 case '?': 1739 default: 1740 usage(); 1741 break; 1742 } 1743 } 1744 if (rexeced_flag || inetd_flag) 1745 rexec_flag = 0; 1746 if (!test_flag && rexec_flag && !path_absolute(av[0])) 1747 fatal("sshd re-exec requires execution with an absolute path"); 1748 if (rexeced_flag) 1749 closefrom(REEXEC_MIN_FREE_FD); 1750 else 1751 closefrom(REEXEC_DEVCRYPTO_RESERVED_FD); 1752 1753 /* If requested, redirect the logs to the specified logfile. */ 1754 if (logfile != NULL) 1755 log_redirect_stderr_to(logfile); 1756 /* 1757 * Force logging to stderr until we have loaded the private host 1758 * key (unless started from inetd) 1759 */ 1760 log_init(__progname, 1761 options.log_level == SYSLOG_LEVEL_NOT_SET ? 1762 SYSLOG_LEVEL_INFO : options.log_level, 1763 options.log_facility == SYSLOG_FACILITY_NOT_SET ? 1764 SYSLOG_FACILITY_AUTH : options.log_facility, 1765 log_stderr || !inetd_flag || debug_flag); 1766 1767 /* 1768 * Unset KRB5CCNAME, otherwise the user's session may inherit it from 1769 * root's environment 1770 */ 1771 if (getenv("KRB5CCNAME") != NULL) 1772 (void) unsetenv("KRB5CCNAME"); 1773 1774 sensitive_data.have_ssh2_key = 0; 1775 1776 /* 1777 * If we're not doing an extended test do not silently ignore connection 1778 * test params. 1779 */ 1780 if (test_flag < 2 && connection_info != NULL) 1781 fatal("Config test connection parameter (-C) provided without " 1782 "test mode (-T)"); 1783 1784 /* Fetch our configuration */ 1785 if ((cfg = sshbuf_new()) == NULL) 1786 fatal_f("sshbuf_new failed"); 1787 if (rexeced_flag) { 1788 setproctitle("%s", "[rexeced]"); 1789 recv_rexec_state(REEXEC_CONFIG_PASS_FD, cfg); 1790 if (!debug_flag) { 1791 startup_pipe = dup(REEXEC_STARTUP_PIPE_FD); 1792 close(REEXEC_STARTUP_PIPE_FD); 1793 /* 1794 * Signal parent that this child is at a point where 1795 * they can go away if they have a SIGHUP pending. 1796 */ 1797 (void)atomicio(vwrite, startup_pipe, "\0", 1); 1798 } 1799 } else if (strcasecmp(config_file_name, "none") != 0) 1800 load_server_config(config_file_name, cfg); 1801 1802 parse_server_config(&options, rexeced_flag ? "rexec" : config_file_name, 1803 cfg, &includes, NULL); 1804 1805 #ifdef WITH_OPENSSL 1806 if (options.moduli_file != NULL) 1807 dh_set_moduli_file(options.moduli_file); 1808 #endif 1809 1810 /* Fill in default values for those options not explicitly set. */ 1811 fill_default_server_options(&options); 1812 1813 /* Check that options are sensible */ 1814 if (options.authorized_keys_command_user == NULL && 1815 (options.authorized_keys_command != NULL && 1816 strcasecmp(options.authorized_keys_command, "none") != 0)) 1817 fatal("AuthorizedKeysCommand set without " 1818 "AuthorizedKeysCommandUser"); 1819 if (options.authorized_principals_command_user == NULL && 1820 (options.authorized_principals_command != NULL && 1821 strcasecmp(options.authorized_principals_command, "none") != 0)) 1822 fatal("AuthorizedPrincipalsCommand set without " 1823 "AuthorizedPrincipalsCommandUser"); 1824 1825 /* 1826 * Check whether there is any path through configured auth methods. 1827 * Unfortunately it is not possible to verify this generally before 1828 * daemonisation in the presence of Match block, but this catches 1829 * and warns for trivial misconfigurations that could break login. 1830 */ 1831 if (options.num_auth_methods != 0) { 1832 for (i = 0; i < options.num_auth_methods; i++) { 1833 if (auth2_methods_valid(options.auth_methods[i], 1834 1) == 0) 1835 break; 1836 } 1837 if (i >= options.num_auth_methods) 1838 fatal("AuthenticationMethods cannot be satisfied by " 1839 "enabled authentication methods"); 1840 } 1841 1842 /* Check that there are no remaining arguments. */ 1843 if (optind < ac) { 1844 fprintf(stderr, "Extra argument %s.\n", av[optind]); 1845 exit(1); 1846 } 1847 1848 debug("sshd version %s, %s", SSH_VERSION, SSH_OPENSSL_VERSION); 1849 1850 /* Store privilege separation user for later use if required. */ 1851 privsep_chroot = use_privsep && (getuid() == 0 || geteuid() == 0); 1852 if ((privsep_pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) { 1853 if (privsep_chroot || options.kerberos_authentication) 1854 fatal("Privilege separation user %s does not exist", 1855 SSH_PRIVSEP_USER); 1856 } else { 1857 privsep_pw = pwcopy(privsep_pw); 1858 freezero(privsep_pw->pw_passwd, strlen(privsep_pw->pw_passwd)); 1859 privsep_pw->pw_passwd = xstrdup("*"); 1860 } 1861 endpwent(); 1862 1863 /* load host keys */ 1864 sensitive_data.host_keys = xcalloc(options.num_host_key_files, 1865 sizeof(struct sshkey *)); 1866 sensitive_data.host_pubkeys = xcalloc(options.num_host_key_files, 1867 sizeof(struct sshkey *)); 1868 1869 if (options.host_key_agent) { 1870 if (strcmp(options.host_key_agent, SSH_AUTHSOCKET_ENV_NAME)) 1871 setenv(SSH_AUTHSOCKET_ENV_NAME, 1872 options.host_key_agent, 1); 1873 if ((r = ssh_get_authentication_socket(NULL)) == 0) 1874 have_agent = 1; 1875 else 1876 error_r(r, "Could not connect to agent \"%s\"", 1877 options.host_key_agent); 1878 } 1879 1880 for (i = 0; i < options.num_host_key_files; i++) { 1881 int ll = options.host_key_file_userprovided[i] ? 1882 SYSLOG_LEVEL_ERROR : SYSLOG_LEVEL_DEBUG1; 1883 1884 if (options.host_key_files[i] == NULL) 1885 continue; 1886 if ((r = sshkey_load_private(options.host_key_files[i], "", 1887 &key, NULL)) != 0 && r != SSH_ERR_SYSTEM_ERROR) 1888 do_log2_r(r, ll, "Unable to load host key \"%s\"", 1889 options.host_key_files[i]); 1890 if (sshkey_is_sk(key) && 1891 key->sk_flags & SSH_SK_USER_PRESENCE_REQD) { 1892 debug("host key %s requires user presence, ignoring", 1893 options.host_key_files[i]); 1894 key->sk_flags &= ~SSH_SK_USER_PRESENCE_REQD; 1895 } 1896 if (r == 0 && key != NULL && 1897 (r = sshkey_shield_private(key)) != 0) { 1898 do_log2_r(r, ll, "Unable to shield host key \"%s\"", 1899 options.host_key_files[i]); 1900 sshkey_free(key); 1901 key = NULL; 1902 } 1903 if ((r = sshkey_load_public(options.host_key_files[i], 1904 &pubkey, NULL)) != 0 && r != SSH_ERR_SYSTEM_ERROR) 1905 do_log2_r(r, ll, "Unable to load host key \"%s\"", 1906 options.host_key_files[i]); 1907 if (pubkey != NULL && key != NULL) { 1908 if (!sshkey_equal(pubkey, key)) { 1909 error("Public key for %s does not match " 1910 "private key", options.host_key_files[i]); 1911 sshkey_free(pubkey); 1912 pubkey = NULL; 1913 } 1914 } 1915 if (pubkey == NULL && key != NULL) { 1916 if ((r = sshkey_from_private(key, &pubkey)) != 0) 1917 fatal_r(r, "Could not demote key: \"%s\"", 1918 options.host_key_files[i]); 1919 } 1920 sensitive_data.host_keys[i] = key; 1921 sensitive_data.host_pubkeys[i] = pubkey; 1922 1923 if (key == NULL && pubkey != NULL && have_agent) { 1924 debug("will rely on agent for hostkey %s", 1925 options.host_key_files[i]); 1926 keytype = pubkey->type; 1927 } else if (key != NULL) { 1928 keytype = key->type; 1929 accumulate_host_timing_secret(cfg, key); 1930 } else { 1931 do_log2(ll, "Unable to load host key: %s", 1932 options.host_key_files[i]); 1933 sensitive_data.host_keys[i] = NULL; 1934 sensitive_data.host_pubkeys[i] = NULL; 1935 continue; 1936 } 1937 1938 switch (keytype) { 1939 case KEY_RSA: 1940 case KEY_DSA: 1941 case KEY_ECDSA: 1942 case KEY_ED25519: 1943 case KEY_ECDSA_SK: 1944 case KEY_ED25519_SK: 1945 case KEY_XMSS: 1946 if (have_agent || key != NULL) 1947 sensitive_data.have_ssh2_key = 1; 1948 break; 1949 } 1950 if ((fp = sshkey_fingerprint(pubkey, options.fingerprint_hash, 1951 SSH_FP_DEFAULT)) == NULL) 1952 fatal("sshkey_fingerprint failed"); 1953 debug("%s host key #%d: %s %s", 1954 key ? "private" : "agent", i, sshkey_ssh_name(pubkey), fp); 1955 free(fp); 1956 } 1957 accumulate_host_timing_secret(cfg, NULL); 1958 if (!sensitive_data.have_ssh2_key) { 1959 logit("sshd: no hostkeys available -- exiting."); 1960 exit(1); 1961 } 1962 1963 /* 1964 * Load certificates. They are stored in an array at identical 1965 * indices to the public keys that they relate to. 1966 */ 1967 sensitive_data.host_certificates = xcalloc(options.num_host_key_files, 1968 sizeof(struct sshkey *)); 1969 for (i = 0; i < options.num_host_key_files; i++) 1970 sensitive_data.host_certificates[i] = NULL; 1971 1972 for (i = 0; i < options.num_host_cert_files; i++) { 1973 if (options.host_cert_files[i] == NULL) 1974 continue; 1975 if ((r = sshkey_load_public(options.host_cert_files[i], 1976 &key, NULL)) != 0) { 1977 error_r(r, "Could not load host certificate \"%s\"", 1978 options.host_cert_files[i]); 1979 continue; 1980 } 1981 if (!sshkey_is_cert(key)) { 1982 error("Certificate file is not a certificate: %s", 1983 options.host_cert_files[i]); 1984 sshkey_free(key); 1985 continue; 1986 } 1987 /* Find matching private key */ 1988 for (j = 0; j < options.num_host_key_files; j++) { 1989 if (sshkey_equal_public(key, 1990 sensitive_data.host_pubkeys[j])) { 1991 sensitive_data.host_certificates[j] = key; 1992 break; 1993 } 1994 } 1995 if (j >= options.num_host_key_files) { 1996 error("No matching private key for certificate: %s", 1997 options.host_cert_files[i]); 1998 sshkey_free(key); 1999 continue; 2000 } 2001 sensitive_data.host_certificates[j] = key; 2002 debug("host certificate: #%u type %d %s", j, key->type, 2003 sshkey_type(key)); 2004 } 2005 2006 if (privsep_chroot) { 2007 struct stat st; 2008 2009 if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) || 2010 (S_ISDIR(st.st_mode) == 0)) 2011 fatal("Missing privilege separation directory: %s", 2012 _PATH_PRIVSEP_CHROOT_DIR); 2013 2014 #ifdef HAVE_CYGWIN 2015 if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) && 2016 (st.st_uid != getuid () || 2017 (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)) 2018 #else 2019 if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0) 2020 #endif 2021 fatal("%s must be owned by root and not group or " 2022 "world-writable.", _PATH_PRIVSEP_CHROOT_DIR); 2023 } 2024 2025 if (test_flag > 1) { 2026 /* 2027 * If no connection info was provided by -C then use 2028 * use a blank one that will cause no predicate to match. 2029 */ 2030 if (connection_info == NULL) 2031 connection_info = get_connection_info(ssh, 0, 0); 2032 connection_info->test = 1; 2033 parse_server_match_config(&options, &includes, connection_info); 2034 dump_config(&options); 2035 } 2036 2037 /* Configuration looks good, so exit if in test mode. */ 2038 if (test_flag) 2039 exit(0); 2040 2041 /* 2042 * Clear out any supplemental groups we may have inherited. This 2043 * prevents inadvertent creation of files with bad modes (in the 2044 * portable version at least, it's certainly possible for PAM 2045 * to create a file, and we can't control the code in every 2046 * module which might be used). 2047 */ 2048 if (setgroups(0, NULL) < 0) 2049 debug("setgroups() failed: %.200s", strerror(errno)); 2050 2051 if (rexec_flag) { 2052 if (rexec_argc < 0) 2053 fatal("rexec_argc %d < 0", rexec_argc); 2054 rexec_argv = xcalloc(rexec_argc + 2, sizeof(char *)); 2055 for (i = 0; i < (u_int)rexec_argc; i++) { 2056 debug("rexec_argv[%d]='%s'", i, saved_argv[i]); 2057 rexec_argv[i] = saved_argv[i]; 2058 } 2059 rexec_argv[rexec_argc] = "-R"; 2060 rexec_argv[rexec_argc + 1] = NULL; 2061 } 2062 listener_proctitle = prepare_proctitle(ac, av); 2063 2064 /* Ensure that umask disallows at least group and world write */ 2065 new_umask = umask(0077) | 0022; 2066 (void) umask(new_umask); 2067 2068 /* Initialize the log (it is reinitialized below in case we forked). */ 2069 if (debug_flag && (!inetd_flag || rexeced_flag)) 2070 log_stderr = 1; 2071 log_init(__progname, options.log_level, 2072 options.log_facility, log_stderr); 2073 for (i = 0; i < options.num_log_verbose; i++) 2074 log_verbose_add(options.log_verbose[i]); 2075 2076 /* 2077 * If not in debugging mode, not started from inetd and not already 2078 * daemonized (eg re-exec via SIGHUP), disconnect from the controlling 2079 * terminal, and fork. The original process exits. 2080 */ 2081 already_daemon = daemonized(); 2082 if (!(debug_flag || inetd_flag || no_daemon_flag || already_daemon)) { 2083 2084 if (daemon(0, 0) == -1) 2085 fatal("daemon() failed: %.200s", strerror(errno)); 2086 2087 disconnect_controlling_tty(); 2088 } 2089 /* Reinitialize the log (because of the fork above). */ 2090 log_init(__progname, options.log_level, options.log_facility, log_stderr); 2091 2092 #ifdef LIBWRAP 2093 /* 2094 * We log refusals ourselves. However, libwrap will report 2095 * syntax errors in hosts.allow via syslog(3). 2096 */ 2097 allow_severity = options.log_facility|LOG_INFO; 2098 deny_severity = options.log_facility|LOG_WARNING; 2099 #endif 2100 /* Avoid killing the process in high-pressure swapping environments. */ 2101 if (!inetd_flag && madvise(NULL, 0, MADV_PROTECT) != 0) 2102 debug("madvise(): %.200s", strerror(errno)); 2103 2104 /* 2105 * Chdir to the root directory so that the current disk can be 2106 * unmounted if desired. 2107 */ 2108 if (chdir("/") == -1) 2109 error("chdir(\"/\"): %s", strerror(errno)); 2110 2111 /* ignore SIGPIPE */ 2112 ssh_signal(SIGPIPE, SIG_IGN); 2113 2114 /* Get a connection, either from inetd or a listening TCP socket */ 2115 if (inetd_flag) { 2116 server_accept_inetd(&sock_in, &sock_out); 2117 } else { 2118 platform_pre_listen(); 2119 server_listen(); 2120 2121 ssh_signal(SIGHUP, sighup_handler); 2122 ssh_signal(SIGCHLD, main_sigchld_handler); 2123 ssh_signal(SIGTERM, sigterm_handler); 2124 ssh_signal(SIGQUIT, sigterm_handler); 2125 2126 /* 2127 * Write out the pid file after the sigterm handler 2128 * is setup and the listen sockets are bound 2129 */ 2130 if (options.pid_file != NULL && !debug_flag) { 2131 FILE *f = fopen(options.pid_file, "w"); 2132 2133 if (f == NULL) { 2134 error("Couldn't create pid file \"%s\": %s", 2135 options.pid_file, strerror(errno)); 2136 } else { 2137 fprintf(f, "%ld\n", (long) getpid()); 2138 fclose(f); 2139 } 2140 } 2141 2142 /* Accept a connection and return in a forked child */ 2143 server_accept_loop(&sock_in, &sock_out, 2144 &newsock, config_s); 2145 } 2146 2147 /* This is the child processing a new connection. */ 2148 setproctitle("%s", "[accepted]"); 2149 2150 /* 2151 * Create a new session and process group since the 4.4BSD 2152 * setlogin() affects the entire process group. We don't 2153 * want the child to be able to affect the parent. 2154 */ 2155 #if !defined(SSHD_ACQUIRES_CTTY) 2156 /* 2157 * If setsid is called, on some platforms sshd will later acquire a 2158 * controlling terminal which will result in "could not set 2159 * controlling tty" errors. 2160 */ 2161 if (!debug_flag && !inetd_flag && setsid() == -1) 2162 error("setsid: %.100s", strerror(errno)); 2163 #endif 2164 2165 if (rexec_flag) { 2166 debug("rexec start in %d out %d newsock %d pipe %d sock %d", 2167 sock_in, sock_out, newsock, startup_pipe, config_s[0]); 2168 dup2(newsock, STDIN_FILENO); 2169 dup2(STDIN_FILENO, STDOUT_FILENO); 2170 if (startup_pipe == -1) 2171 close(REEXEC_STARTUP_PIPE_FD); 2172 else if (startup_pipe != REEXEC_STARTUP_PIPE_FD) { 2173 dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD); 2174 close(startup_pipe); 2175 startup_pipe = REEXEC_STARTUP_PIPE_FD; 2176 } 2177 2178 dup2(config_s[1], REEXEC_CONFIG_PASS_FD); 2179 close(config_s[1]); 2180 2181 ssh_signal(SIGHUP, SIG_IGN); /* avoid reset to SIG_DFL */ 2182 execv(rexec_argv[0], rexec_argv); 2183 2184 /* Reexec has failed, fall back and continue */ 2185 error("rexec of %s failed: %s", rexec_argv[0], strerror(errno)); 2186 recv_rexec_state(REEXEC_CONFIG_PASS_FD, NULL); 2187 log_init(__progname, options.log_level, 2188 options.log_facility, log_stderr); 2189 2190 /* Clean up fds */ 2191 close(REEXEC_CONFIG_PASS_FD); 2192 newsock = sock_out = sock_in = dup(STDIN_FILENO); 2193 if (stdfd_devnull(1, 1, 0) == -1) 2194 error_f("stdfd_devnull failed"); 2195 debug("rexec cleanup in %d out %d newsock %d pipe %d sock %d", 2196 sock_in, sock_out, newsock, startup_pipe, config_s[0]); 2197 } 2198 2199 /* Executed child processes don't need these. */ 2200 fcntl(sock_out, F_SETFD, FD_CLOEXEC); 2201 fcntl(sock_in, F_SETFD, FD_CLOEXEC); 2202 2203 /* We will not restart on SIGHUP since it no longer makes sense. */ 2204 ssh_signal(SIGALRM, SIG_DFL); 2205 ssh_signal(SIGHUP, SIG_DFL); 2206 ssh_signal(SIGTERM, SIG_DFL); 2207 ssh_signal(SIGQUIT, SIG_DFL); 2208 ssh_signal(SIGCHLD, SIG_DFL); 2209 ssh_signal(SIGINT, SIG_DFL); 2210 2211 #ifdef __FreeBSD__ 2212 /* 2213 * Initialize the resolver. This may not happen automatically 2214 * before privsep chroot(). 2215 */ 2216 if ((_res.options & RES_INIT) == 0) { 2217 debug("res_init()"); 2218 res_init(); 2219 } 2220 #ifdef GSSAPI 2221 /* 2222 * Force GSS-API to parse its configuration and load any 2223 * mechanism plugins. 2224 */ 2225 { 2226 gss_OID_set mechs; 2227 OM_uint32 minor_status; 2228 gss_indicate_mechs(&minor_status, &mechs); 2229 gss_release_oid_set(&minor_status, &mechs); 2230 } 2231 #endif 2232 #endif 2233 2234 /* 2235 * Register our connection. This turns encryption off because we do 2236 * not have a key. 2237 */ 2238 if ((ssh = ssh_packet_set_connection(NULL, sock_in, sock_out)) == NULL) 2239 fatal("Unable to create connection"); 2240 the_active_state = ssh; 2241 ssh_packet_set_server(ssh); 2242 2243 check_ip_options(ssh); 2244 2245 /* Prepare the channels layer */ 2246 channel_init_channels(ssh); 2247 channel_set_af(ssh, options.address_family); 2248 process_permitopen(ssh, &options); 2249 2250 /* Set SO_KEEPALIVE if requested. */ 2251 if (options.tcp_keep_alive && ssh_packet_connection_is_on_socket(ssh) && 2252 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) == -1) 2253 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 2254 2255 if ((remote_port = ssh_remote_port(ssh)) < 0) { 2256 debug("ssh_remote_port failed"); 2257 cleanup_exit(255); 2258 } 2259 2260 if (options.routing_domain != NULL) 2261 set_process_rdomain(ssh, options.routing_domain); 2262 2263 /* 2264 * The rest of the code depends on the fact that 2265 * ssh_remote_ipaddr() caches the remote ip, even if 2266 * the socket goes away. 2267 */ 2268 remote_ip = ssh_remote_ipaddr(ssh); 2269 2270 #ifdef HAVE_LOGIN_CAP 2271 /* Also caches remote hostname for sandboxed child. */ 2272 auth_get_canonical_hostname(ssh, options.use_dns); 2273 #endif 2274 2275 #ifdef SSH_AUDIT_EVENTS 2276 audit_connection_from(remote_ip, remote_port); 2277 #endif 2278 2279 rdomain = ssh_packet_rdomain_in(ssh); 2280 2281 /* Log the connection. */ 2282 laddr = get_local_ipaddr(sock_in); 2283 verbose("Connection from %s port %d on %s port %d%s%s%s", 2284 remote_ip, remote_port, laddr, ssh_local_port(ssh), 2285 rdomain == NULL ? "" : " rdomain \"", 2286 rdomain == NULL ? "" : rdomain, 2287 rdomain == NULL ? "" : "\""); 2288 free(laddr); 2289 2290 /* 2291 * We don't want to listen forever unless the other side 2292 * successfully authenticates itself. So we set up an alarm which is 2293 * cleared after successful authentication. A limit of zero 2294 * indicates no limit. Note that we don't set the alarm in debugging 2295 * mode; it is just annoying to have the server exit just when you 2296 * are about to discover the bug. 2297 */ 2298 ssh_signal(SIGALRM, grace_alarm_handler); 2299 if (!debug_flag) 2300 alarm(options.login_grace_time); 2301 2302 if ((r = kex_exchange_identification(ssh, -1, 2303 options.version_addendum)) != 0) 2304 sshpkt_fatal(ssh, r, "banner exchange"); 2305 2306 ssh_packet_set_nonblocking(ssh); 2307 2308 /* allocate authentication context */ 2309 authctxt = xcalloc(1, sizeof(*authctxt)); 2310 ssh->authctxt = authctxt; 2311 2312 authctxt->loginmsg = loginmsg; 2313 2314 /* XXX global for cleanup, access from other modules */ 2315 the_authctxt = authctxt; 2316 2317 /* Set default key authentication options */ 2318 if ((auth_opts = sshauthopt_new_with_keys_defaults()) == NULL) 2319 fatal("allocation failed"); 2320 2321 /* prepare buffer to collect messages to display to user after login */ 2322 if ((loginmsg = sshbuf_new()) == NULL) 2323 fatal_f("sshbuf_new failed"); 2324 auth_debug_reset(); 2325 2326 BLACKLIST_INIT(); 2327 2328 if (use_privsep) { 2329 if (privsep_preauth(ssh) == 1) 2330 goto authenticated; 2331 } else if (have_agent) { 2332 if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) { 2333 error_r(r, "Unable to get agent socket"); 2334 have_agent = 0; 2335 } 2336 } 2337 2338 /* perform the key exchange */ 2339 /* authenticate user and start session */ 2340 do_ssh2_kex(ssh); 2341 do_authentication2(ssh); 2342 2343 /* 2344 * If we use privilege separation, the unprivileged child transfers 2345 * the current keystate and exits 2346 */ 2347 if (use_privsep) { 2348 mm_send_keystate(ssh, pmonitor); 2349 ssh_packet_clear_keys(ssh); 2350 exit(0); 2351 } 2352 2353 authenticated: 2354 /* 2355 * Cancel the alarm we set to limit the time taken for 2356 * authentication. 2357 */ 2358 alarm(0); 2359 ssh_signal(SIGALRM, SIG_DFL); 2360 authctxt->authenticated = 1; 2361 if (startup_pipe != -1) { 2362 close(startup_pipe); 2363 startup_pipe = -1; 2364 } 2365 2366 #ifdef SSH_AUDIT_EVENTS 2367 audit_event(ssh, SSH_AUTH_SUCCESS); 2368 #endif 2369 2370 #ifdef GSSAPI 2371 if (options.gss_authentication) { 2372 temporarily_use_uid(authctxt->pw); 2373 ssh_gssapi_storecreds(); 2374 restore_uid(); 2375 } 2376 #endif 2377 #ifdef USE_PAM 2378 if (options.use_pam) { 2379 do_pam_setcred(1); 2380 do_pam_session(ssh); 2381 } 2382 #endif 2383 2384 /* 2385 * In privilege separation, we fork another child and prepare 2386 * file descriptor passing. 2387 */ 2388 if (use_privsep) { 2389 privsep_postauth(ssh, authctxt); 2390 /* the monitor process [priv] will not return */ 2391 } 2392 2393 ssh_packet_set_timeout(ssh, options.client_alive_interval, 2394 options.client_alive_count_max); 2395 2396 /* Try to send all our hostkeys to the client */ 2397 notify_hostkeys(ssh); 2398 2399 /* Start session. */ 2400 do_authenticated(ssh, authctxt); 2401 2402 /* The connection has been terminated. */ 2403 ssh_packet_get_bytes(ssh, &ibytes, &obytes); 2404 verbose("Transferred: sent %llu, received %llu bytes", 2405 (unsigned long long)obytes, (unsigned long long)ibytes); 2406 2407 verbose("Closing connection to %.500s port %d", remote_ip, remote_port); 2408 2409 #ifdef USE_PAM 2410 if (options.use_pam) 2411 finish_pam(); 2412 #endif /* USE_PAM */ 2413 2414 #ifdef SSH_AUDIT_EVENTS 2415 PRIVSEP(audit_event(ssh, SSH_CONNECTION_CLOSE)); 2416 #endif 2417 2418 ssh_packet_close(ssh); 2419 2420 if (use_privsep) 2421 mm_terminate(); 2422 2423 exit(0); 2424 } 2425 2426 int 2427 sshd_hostkey_sign(struct ssh *ssh, struct sshkey *privkey, 2428 struct sshkey *pubkey, u_char **signature, size_t *slenp, 2429 const u_char *data, size_t dlen, const char *alg) 2430 { 2431 int r; 2432 2433 if (use_privsep) { 2434 if (privkey) { 2435 if (mm_sshkey_sign(ssh, privkey, signature, slenp, 2436 data, dlen, alg, options.sk_provider, NULL, 2437 ssh->compat) < 0) 2438 fatal_f("privkey sign failed"); 2439 } else { 2440 if (mm_sshkey_sign(ssh, pubkey, signature, slenp, 2441 data, dlen, alg, options.sk_provider, NULL, 2442 ssh->compat) < 0) 2443 fatal_f("pubkey sign failed"); 2444 } 2445 } else { 2446 if (privkey) { 2447 if (sshkey_sign(privkey, signature, slenp, data, dlen, 2448 alg, options.sk_provider, NULL, ssh->compat) < 0) 2449 fatal_f("privkey sign failed"); 2450 } else { 2451 if ((r = ssh_agent_sign(auth_sock, pubkey, 2452 signature, slenp, data, dlen, alg, 2453 ssh->compat)) != 0) { 2454 fatal_fr(r, "agent sign failed"); 2455 } 2456 } 2457 } 2458 return 0; 2459 } 2460 2461 /* SSH2 key exchange */ 2462 static void 2463 do_ssh2_kex(struct ssh *ssh) 2464 { 2465 char *myproposal[PROPOSAL_MAX] = { KEX_SERVER }; 2466 struct kex *kex; 2467 int r; 2468 2469 myproposal[PROPOSAL_KEX_ALGS] = compat_kex_proposal(ssh, 2470 options.kex_algorithms); 2471 myproposal[PROPOSAL_ENC_ALGS_CTOS] = compat_cipher_proposal(ssh, 2472 options.ciphers); 2473 myproposal[PROPOSAL_ENC_ALGS_STOC] = compat_cipher_proposal(ssh, 2474 options.ciphers); 2475 myproposal[PROPOSAL_MAC_ALGS_CTOS] = 2476 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs; 2477 2478 if (options.compression == COMP_NONE) { 2479 myproposal[PROPOSAL_COMP_ALGS_CTOS] = 2480 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none"; 2481 } 2482 2483 if (options.rekey_limit || options.rekey_interval) 2484 ssh_packet_set_rekey_limits(ssh, options.rekey_limit, 2485 options.rekey_interval); 2486 2487 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = compat_pkalg_proposal( 2488 ssh, list_hostkey_types()); 2489 2490 /* start key exchange */ 2491 if ((r = kex_setup(ssh, myproposal)) != 0) 2492 fatal_r(r, "kex_setup"); 2493 kex = ssh->kex; 2494 #ifdef WITH_OPENSSL 2495 kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server; 2496 kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server; 2497 kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server; 2498 kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server; 2499 kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server; 2500 kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 2501 kex->kex[KEX_DH_GEX_SHA256] = kexgex_server; 2502 # ifdef OPENSSL_HAS_ECC 2503 kex->kex[KEX_ECDH_SHA2] = kex_gen_server; 2504 # endif 2505 #endif 2506 kex->kex[KEX_C25519_SHA256] = kex_gen_server; 2507 kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_server; 2508 kex->load_host_public_key=&get_hostkey_public_by_type; 2509 kex->load_host_private_key=&get_hostkey_private_by_type; 2510 kex->host_key_index=&get_hostkey_index; 2511 kex->sign = sshd_hostkey_sign; 2512 2513 ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &kex->done); 2514 2515 #ifdef DEBUG_KEXDH 2516 /* send 1st encrypted/maced/compressed message */ 2517 if ((r = sshpkt_start(ssh, SSH2_MSG_IGNORE)) != 0 || 2518 (r = sshpkt_put_cstring(ssh, "markus")) != 0 || 2519 (r = sshpkt_send(ssh)) != 0 || 2520 (r = ssh_packet_write_wait(ssh)) != 0) 2521 fatal_fr(r, "send test"); 2522 #endif 2523 debug("KEX done"); 2524 } 2525 2526 /* server specific fatal cleanup */ 2527 void 2528 cleanup_exit(int i) 2529 { 2530 if (the_active_state != NULL && the_authctxt != NULL) { 2531 do_cleanup(the_active_state, the_authctxt); 2532 if (use_privsep && privsep_is_preauth && 2533 pmonitor != NULL && pmonitor->m_pid > 1) { 2534 debug("Killing privsep child %d", pmonitor->m_pid); 2535 if (kill(pmonitor->m_pid, SIGKILL) != 0 && 2536 errno != ESRCH) { 2537 error_f("kill(%d): %s", pmonitor->m_pid, 2538 strerror(errno)); 2539 } 2540 } 2541 } 2542 #ifdef SSH_AUDIT_EVENTS 2543 /* done after do_cleanup so it can cancel the PAM auth 'thread' */ 2544 if (the_active_state != NULL && (!use_privsep || mm_is_monitor())) 2545 audit_event(the_active_state, SSH_CONNECTION_ABANDON); 2546 #endif 2547 _exit(i); 2548 } 2549