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 47 #include <sys/types.h> 48 #include <sys/ioctl.h> 49 #include <sys/socket.h> 50 #ifdef HAVE_SYS_STAT_H 51 # include <sys/stat.h> 52 #endif 53 #ifdef HAVE_SYS_TIME_H 54 # include <sys/time.h> 55 #endif 56 #include "openbsd-compat/sys-tree.h" 57 #include "openbsd-compat/sys-queue.h" 58 #include <sys/wait.h> 59 60 #include <errno.h> 61 #include <fcntl.h> 62 #include <netdb.h> 63 #ifdef HAVE_PATHS_H 64 #include <paths.h> 65 #endif 66 #include <grp.h> 67 #include <pwd.h> 68 #include <signal.h> 69 #include <stdarg.h> 70 #include <stdio.h> 71 #include <stdlib.h> 72 #include <string.h> 73 #include <unistd.h> 74 #include <limits.h> 75 76 #ifdef WITH_OPENSSL 77 #include <openssl/dh.h> 78 #include <openssl/bn.h> 79 #include <openssl/rand.h> 80 #include "openbsd-compat/openssl-compat.h" 81 #endif 82 83 #ifdef HAVE_SECUREWARE 84 #include <sys/security.h> 85 #include <prot.h> 86 #endif 87 88 #include "xmalloc.h" 89 #include "ssh.h" 90 #include "ssh2.h" 91 #include "sshpty.h" 92 #include "packet.h" 93 #include "log.h" 94 #include "sshbuf.h" 95 #include "misc.h" 96 #include "match.h" 97 #include "servconf.h" 98 #include "uidswap.h" 99 #include "compat.h" 100 #include "cipher.h" 101 #include "digest.h" 102 #include "sshkey.h" 103 #include "kex.h" 104 #include "myproposal.h" 105 #include "authfile.h" 106 #include "pathnames.h" 107 #include "atomicio.h" 108 #include "canohost.h" 109 #include "hostfile.h" 110 #include "auth.h" 111 #include "authfd.h" 112 #include "msg.h" 113 #include "dispatch.h" 114 #include "channels.h" 115 #include "session.h" 116 #include "monitor.h" 117 #ifdef GSSAPI 118 #include "ssh-gss.h" 119 #endif 120 #include "monitor_wrap.h" 121 #include "ssh-sandbox.h" 122 #include "auth-options.h" 123 #include "version.h" 124 #include "ssherr.h" 125 #include "sk-api.h" 126 #include "srclimit.h" 127 #include "dh.h" 128 129 /* Re-exec fds */ 130 #define REEXEC_DEVCRYPTO_RESERVED_FD (STDERR_FILENO + 1) 131 #define REEXEC_STARTUP_PIPE_FD (STDERR_FILENO + 2) 132 #define REEXEC_CONFIG_PASS_FD (STDERR_FILENO + 3) 133 #define REEXEC_MIN_FREE_FD (STDERR_FILENO + 4) 134 135 extern char *__progname; 136 137 /* Server configuration options. */ 138 ServerOptions options; 139 140 /* Name of the server configuration file. */ 141 char *config_file_name = _PATH_SERVER_CONFIG_FILE; 142 143 /* 144 * Debug mode flag. This can be set on the command line. If debug 145 * mode is enabled, extra debugging output will be sent to the system 146 * log, the daemon will not go to background, and will exit after processing 147 * the first connection. 148 */ 149 int debug_flag = 0; 150 151 /* 152 * Indicating that the daemon should only test the configuration and keys. 153 * If test_flag > 1 ("-T" flag), then sshd will also dump the effective 154 * configuration, optionally using connection information provided by the 155 * "-C" flag. 156 */ 157 static int test_flag = 0; 158 159 /* Flag indicating that the daemon is being started from inetd. */ 160 static int inetd_flag = 0; 161 162 /* Flag indicating that sshd should not detach and become a daemon. */ 163 static int no_daemon_flag = 0; 164 165 /* debug goes to stderr unless inetd_flag is set */ 166 static int log_stderr = 0; 167 168 /* Saved arguments to main(). */ 169 static char **saved_argv; 170 static int saved_argc; 171 172 /* re-exec */ 173 static int rexeced_flag = 0; 174 static int rexec_flag = 1; 175 static int rexec_argc = 0; 176 static char **rexec_argv; 177 178 /* 179 * The sockets that the server is listening; this is used in the SIGHUP 180 * signal handler. 181 */ 182 #define MAX_LISTEN_SOCKS 16 183 static int listen_socks[MAX_LISTEN_SOCKS]; 184 static int num_listen_socks = 0; 185 186 /* Daemon's agent connection */ 187 int auth_sock = -1; 188 static int have_agent = 0; 189 190 /* 191 * Any really sensitive data in the application is contained in this 192 * structure. The idea is that this structure could be locked into memory so 193 * that the pages do not get written into swap. However, there are some 194 * problems. The private key contains BIGNUMs, and we do not (in principle) 195 * have access to the internals of them, and locking just the structure is 196 * not very useful. Currently, memory locking is not implemented. 197 */ 198 struct { 199 struct sshkey **host_keys; /* all private host keys */ 200 struct sshkey **host_pubkeys; /* all public host keys */ 201 struct sshkey **host_certificates; /* all public host certificates */ 202 int have_ssh2_key; 203 } sensitive_data; 204 205 /* This is set to true when a signal is received. */ 206 static volatile sig_atomic_t received_sighup = 0; 207 static volatile sig_atomic_t received_sigterm = 0; 208 209 /* record remote hostname or ip */ 210 u_int utmp_len = HOST_NAME_MAX+1; 211 212 /* 213 * startup_pipes/flags are used for tracking children of the listening sshd 214 * process early in their lifespans. This tracking is needed for three things: 215 * 216 * 1) Implementing the MaxStartups limit of concurrent unauthenticated 217 * connections. 218 * 2) Avoiding a race condition for SIGHUP processing, where child processes 219 * may have listen_socks open that could collide with main listener process 220 * after it restarts. 221 * 3) Ensuring that rexec'd sshd processes have received their initial state 222 * from the parent listen process before handling SIGHUP. 223 * 224 * Child processes signal that they have completed closure of the listen_socks 225 * and (if applicable) received their rexec state by sending a char over their 226 * sock. Child processes signal that authentication has completed by closing 227 * the sock (or by exiting). 228 */ 229 static int *startup_pipes = NULL; 230 static int *startup_flags = NULL; /* Indicates child closed listener */ 231 static int startup_pipe = -1; /* in child */ 232 233 /* variables used for privilege separation */ 234 int use_privsep = -1; 235 struct monitor *pmonitor = NULL; 236 int privsep_is_preauth = 1; 237 static int privsep_chroot = 1; 238 239 /* global connection state and authentication contexts */ 240 Authctxt *the_authctxt = NULL; 241 struct ssh *the_active_state; 242 243 /* global key/cert auth options. XXX move to permanent ssh->authctxt? */ 244 struct sshauthopt *auth_opts = NULL; 245 246 /* sshd_config buffer */ 247 struct sshbuf *cfg; 248 249 /* Included files from the configuration file */ 250 struct include_list includes = TAILQ_HEAD_INITIALIZER(includes); 251 252 /* message to be displayed after login */ 253 struct sshbuf *loginmsg; 254 255 /* Unprivileged user */ 256 struct passwd *privsep_pw = NULL; 257 258 /* Prototypes for various functions defined later in this file. */ 259 void destroy_sensitive_data(void); 260 void demote_sensitive_data(void); 261 static void do_ssh2_kex(struct ssh *); 262 263 static char *listener_proctitle; 264 265 /* 266 * Close all listening sockets 267 */ 268 static void 269 close_listen_socks(void) 270 { 271 int i; 272 273 for (i = 0; i < num_listen_socks; i++) 274 close(listen_socks[i]); 275 num_listen_socks = -1; 276 } 277 278 static void 279 close_startup_pipes(void) 280 { 281 int i; 282 283 if (startup_pipes) 284 for (i = 0; i < options.max_startups; i++) 285 if (startup_pipes[i] != -1) 286 close(startup_pipes[i]); 287 } 288 289 /* 290 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP; 291 * the effect is to reread the configuration file (and to regenerate 292 * the server key). 293 */ 294 295 /*ARGSUSED*/ 296 static void 297 sighup_handler(int sig) 298 { 299 received_sighup = 1; 300 } 301 302 /* 303 * Called from the main program after receiving SIGHUP. 304 * Restarts the server. 305 */ 306 static void 307 sighup_restart(void) 308 { 309 logit("Received SIGHUP; restarting."); 310 if (options.pid_file != NULL) 311 unlink(options.pid_file); 312 platform_pre_restart(); 313 close_listen_socks(); 314 close_startup_pipes(); 315 ssh_signal(SIGHUP, SIG_IGN); /* will be restored after exec */ 316 execv(saved_argv[0], saved_argv); 317 logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], 318 strerror(errno)); 319 exit(1); 320 } 321 322 /* 323 * Generic signal handler for terminating signals in the master daemon. 324 */ 325 /*ARGSUSED*/ 326 static void 327 sigterm_handler(int sig) 328 { 329 received_sigterm = sig; 330 } 331 332 /* 333 * SIGCHLD handler. This is called whenever a child dies. This will then 334 * reap any zombies left by exited children. 335 */ 336 /*ARGSUSED*/ 337 static void 338 main_sigchld_handler(int sig) 339 { 340 int save_errno = errno; 341 pid_t pid; 342 int status; 343 344 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 345 (pid == -1 && errno == EINTR)) 346 ; 347 errno = save_errno; 348 } 349 350 /* 351 * Signal handler for the alarm after the login grace period has expired. 352 */ 353 /*ARGSUSED*/ 354 static void 355 grace_alarm_handler(int sig) 356 { 357 if (use_privsep && pmonitor != NULL && pmonitor->m_pid > 0) 358 kill(pmonitor->m_pid, SIGALRM); 359 360 /* 361 * Try to kill any processes that we have spawned, E.g. authorized 362 * keys command helpers. 363 */ 364 if (getpgid(0) == getpid()) { 365 ssh_signal(SIGTERM, SIG_IGN); 366 kill(0, SIGTERM); 367 } 368 369 /* Log error and exit. */ 370 if (use_privsep && pmonitor != NULL && pmonitor->m_pid <= 0) 371 cleanup_exit(255); /* don't log in privsep child */ 372 else { 373 sigdie("Timeout before authentication for %s port %d", 374 ssh_remote_ipaddr(the_active_state), 375 ssh_remote_port(the_active_state)); 376 } 377 } 378 379 /* Destroy the host and server keys. They will no longer be needed. */ 380 void 381 destroy_sensitive_data(void) 382 { 383 u_int i; 384 385 for (i = 0; i < options.num_host_key_files; i++) { 386 if (sensitive_data.host_keys[i]) { 387 sshkey_free(sensitive_data.host_keys[i]); 388 sensitive_data.host_keys[i] = NULL; 389 } 390 if (sensitive_data.host_certificates[i]) { 391 sshkey_free(sensitive_data.host_certificates[i]); 392 sensitive_data.host_certificates[i] = NULL; 393 } 394 } 395 } 396 397 /* Demote private to public keys for network child */ 398 void 399 demote_sensitive_data(void) 400 { 401 struct sshkey *tmp; 402 u_int i; 403 int r; 404 405 for (i = 0; i < options.num_host_key_files; i++) { 406 if (sensitive_data.host_keys[i]) { 407 if ((r = sshkey_from_private( 408 sensitive_data.host_keys[i], &tmp)) != 0) 409 fatal_r(r, "could not demote host %s key", 410 sshkey_type(sensitive_data.host_keys[i])); 411 sshkey_free(sensitive_data.host_keys[i]); 412 sensitive_data.host_keys[i] = tmp; 413 } 414 /* Certs do not need demotion */ 415 } 416 } 417 418 static void 419 reseed_prngs(void) 420 { 421 u_int32_t rnd[256]; 422 423 #ifdef WITH_OPENSSL 424 RAND_poll(); 425 #endif 426 arc4random_stir(); /* noop on recent arc4random() implementations */ 427 arc4random_buf(rnd, sizeof(rnd)); /* let arc4random notice PID change */ 428 429 #ifdef WITH_OPENSSL 430 RAND_seed(rnd, sizeof(rnd)); 431 /* give libcrypto a chance to notice the PID change */ 432 if ((RAND_bytes((u_char *)rnd, 1)) != 1) 433 fatal("%s: RAND_bytes failed", __func__); 434 #endif 435 436 explicit_bzero(rnd, sizeof(rnd)); 437 } 438 439 static void 440 privsep_preauth_child(void) 441 { 442 gid_t gidset[1]; 443 444 /* Enable challenge-response authentication for privilege separation */ 445 privsep_challenge_enable(); 446 447 #ifdef GSSAPI 448 /* Cache supported mechanism OIDs for later use */ 449 ssh_gssapi_prepare_supported_oids(); 450 #endif 451 452 reseed_prngs(); 453 454 /* Demote the private keys to public keys. */ 455 demote_sensitive_data(); 456 457 /* Demote the child */ 458 if (privsep_chroot) { 459 /* Change our root directory */ 460 if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1) 461 fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR, 462 strerror(errno)); 463 if (chdir("/") == -1) 464 fatal("chdir(\"/\"): %s", strerror(errno)); 465 466 /* Drop our privileges */ 467 debug3("privsep user:group %u:%u", (u_int)privsep_pw->pw_uid, 468 (u_int)privsep_pw->pw_gid); 469 gidset[0] = privsep_pw->pw_gid; 470 if (setgroups(1, gidset) == -1) 471 fatal("setgroups: %.100s", strerror(errno)); 472 permanently_set_uid(privsep_pw); 473 } 474 } 475 476 static int 477 privsep_preauth(struct ssh *ssh) 478 { 479 int status, r; 480 pid_t pid; 481 struct ssh_sandbox *box = NULL; 482 483 /* Set up unprivileged child process to deal with network data */ 484 pmonitor = monitor_init(); 485 /* Store a pointer to the kex for later rekeying */ 486 pmonitor->m_pkex = &ssh->kex; 487 488 if (use_privsep == PRIVSEP_ON) 489 box = ssh_sandbox_init(pmonitor); 490 pid = fork(); 491 if (pid == -1) { 492 fatal("fork of unprivileged child failed"); 493 } else if (pid != 0) { 494 debug2("Network child is on pid %ld", (long)pid); 495 496 pmonitor->m_pid = pid; 497 if (have_agent) { 498 r = ssh_get_authentication_socket(&auth_sock); 499 if (r != 0) { 500 error_r(r, "Could not get agent socket"); 501 have_agent = 0; 502 } 503 } 504 if (box != NULL) 505 ssh_sandbox_parent_preauth(box, pid); 506 monitor_child_preauth(ssh, pmonitor); 507 508 /* Wait for the child's exit status */ 509 while (waitpid(pid, &status, 0) == -1) { 510 if (errno == EINTR) 511 continue; 512 pmonitor->m_pid = -1; 513 fatal_f("waitpid: %s", strerror(errno)); 514 } 515 privsep_is_preauth = 0; 516 pmonitor->m_pid = -1; 517 if (WIFEXITED(status)) { 518 if (WEXITSTATUS(status) != 0) 519 fatal_f("preauth child exited with status %d", 520 WEXITSTATUS(status)); 521 } else if (WIFSIGNALED(status)) 522 fatal_f("preauth child terminated by signal %d", 523 WTERMSIG(status)); 524 if (box != NULL) 525 ssh_sandbox_parent_finish(box); 526 return 1; 527 } else { 528 /* child */ 529 close(pmonitor->m_sendfd); 530 close(pmonitor->m_log_recvfd); 531 532 /* Arrange for logging to be sent to the monitor */ 533 set_log_handler(mm_log_handler, pmonitor); 534 535 privsep_preauth_child(); 536 setproctitle("%s", "[net]"); 537 if (box != NULL) 538 ssh_sandbox_child(box); 539 540 return 0; 541 } 542 } 543 544 static void 545 privsep_postauth(struct ssh *ssh, Authctxt *authctxt) 546 { 547 #ifdef DISABLE_FD_PASSING 548 if (1) { 549 #else 550 if (authctxt->pw->pw_uid == 0) { 551 #endif 552 /* File descriptor passing is broken or root login */ 553 use_privsep = 0; 554 goto skip; 555 } 556 557 /* New socket pair */ 558 monitor_reinit(pmonitor); 559 560 pmonitor->m_pid = fork(); 561 if (pmonitor->m_pid == -1) 562 fatal("fork of unprivileged child failed"); 563 else if (pmonitor->m_pid != 0) { 564 verbose("User child is on pid %ld", (long)pmonitor->m_pid); 565 sshbuf_reset(loginmsg); 566 monitor_clear_keystate(ssh, pmonitor); 567 monitor_child_postauth(ssh, pmonitor); 568 569 /* NEVERREACHED */ 570 exit(0); 571 } 572 573 /* child */ 574 575 close(pmonitor->m_sendfd); 576 pmonitor->m_sendfd = -1; 577 578 /* Demote the private keys to public keys. */ 579 demote_sensitive_data(); 580 581 reseed_prngs(); 582 583 /* Drop privileges */ 584 do_setusercontext(authctxt->pw); 585 586 skip: 587 /* It is safe now to apply the key state */ 588 monitor_apply_keystate(ssh, pmonitor); 589 590 /* 591 * Tell the packet layer that authentication was successful, since 592 * this information is not part of the key state. 593 */ 594 ssh_packet_set_authenticated(ssh); 595 } 596 597 static void 598 append_hostkey_type(struct sshbuf *b, const char *s) 599 { 600 int r; 601 602 if (match_pattern_list(s, options.hostkeyalgorithms, 0) != 1) { 603 debug3_f("%s key not permitted by HostkeyAlgorithms", s); 604 return; 605 } 606 if ((r = sshbuf_putf(b, "%s%s", sshbuf_len(b) > 0 ? "," : "", s)) != 0) 607 fatal_fr(r, "sshbuf_putf"); 608 } 609 610 static char * 611 list_hostkey_types(void) 612 { 613 struct sshbuf *b; 614 struct sshkey *key; 615 char *ret; 616 u_int i; 617 618 if ((b = sshbuf_new()) == NULL) 619 fatal_f("sshbuf_new failed"); 620 for (i = 0; i < options.num_host_key_files; i++) { 621 key = sensitive_data.host_keys[i]; 622 if (key == NULL) 623 key = sensitive_data.host_pubkeys[i]; 624 if (key == NULL) 625 continue; 626 switch (key->type) { 627 case KEY_RSA: 628 /* for RSA we also support SHA2 signatures */ 629 append_hostkey_type(b, "rsa-sha2-512"); 630 append_hostkey_type(b, "rsa-sha2-256"); 631 /* FALLTHROUGH */ 632 case KEY_DSA: 633 case KEY_ECDSA: 634 case KEY_ED25519: 635 case KEY_ECDSA_SK: 636 case KEY_ED25519_SK: 637 case KEY_XMSS: 638 append_hostkey_type(b, sshkey_ssh_name(key)); 639 break; 640 } 641 /* If the private key has a cert peer, then list that too */ 642 key = sensitive_data.host_certificates[i]; 643 if (key == NULL) 644 continue; 645 switch (key->type) { 646 case KEY_RSA_CERT: 647 /* for RSA we also support SHA2 signatures */ 648 append_hostkey_type(b, 649 "rsa-sha2-512-cert-v01@openssh.com"); 650 append_hostkey_type(b, 651 "rsa-sha2-256-cert-v01@openssh.com"); 652 /* FALLTHROUGH */ 653 case KEY_DSA_CERT: 654 case KEY_ECDSA_CERT: 655 case KEY_ED25519_CERT: 656 case KEY_ECDSA_SK_CERT: 657 case KEY_ED25519_SK_CERT: 658 case KEY_XMSS_CERT: 659 append_hostkey_type(b, sshkey_ssh_name(key)); 660 break; 661 } 662 } 663 if ((ret = sshbuf_dup_string(b)) == NULL) 664 fatal_f("sshbuf_dup_string failed"); 665 sshbuf_free(b); 666 debug_f("%s", ret); 667 return ret; 668 } 669 670 static struct sshkey * 671 get_hostkey_by_type(int type, int nid, int need_private, struct ssh *ssh) 672 { 673 u_int i; 674 struct sshkey *key; 675 676 for (i = 0; i < options.num_host_key_files; i++) { 677 switch (type) { 678 case KEY_RSA_CERT: 679 case KEY_DSA_CERT: 680 case KEY_ECDSA_CERT: 681 case KEY_ED25519_CERT: 682 case KEY_ECDSA_SK_CERT: 683 case KEY_ED25519_SK_CERT: 684 case KEY_XMSS_CERT: 685 key = sensitive_data.host_certificates[i]; 686 break; 687 default: 688 key = sensitive_data.host_keys[i]; 689 if (key == NULL && !need_private) 690 key = sensitive_data.host_pubkeys[i]; 691 break; 692 } 693 if (key == NULL || key->type != type) 694 continue; 695 switch (type) { 696 case KEY_ECDSA: 697 case KEY_ECDSA_SK: 698 case KEY_ECDSA_CERT: 699 case KEY_ECDSA_SK_CERT: 700 if (key->ecdsa_nid != nid) 701 continue; 702 /* FALLTHROUGH */ 703 default: 704 return need_private ? 705 sensitive_data.host_keys[i] : key; 706 } 707 } 708 return NULL; 709 } 710 711 struct sshkey * 712 get_hostkey_public_by_type(int type, int nid, struct ssh *ssh) 713 { 714 return get_hostkey_by_type(type, nid, 0, ssh); 715 } 716 717 struct sshkey * 718 get_hostkey_private_by_type(int type, int nid, struct ssh *ssh) 719 { 720 return get_hostkey_by_type(type, nid, 1, ssh); 721 } 722 723 struct sshkey * 724 get_hostkey_by_index(int ind) 725 { 726 if (ind < 0 || (u_int)ind >= options.num_host_key_files) 727 return (NULL); 728 return (sensitive_data.host_keys[ind]); 729 } 730 731 struct sshkey * 732 get_hostkey_public_by_index(int ind, struct ssh *ssh) 733 { 734 if (ind < 0 || (u_int)ind >= options.num_host_key_files) 735 return (NULL); 736 return (sensitive_data.host_pubkeys[ind]); 737 } 738 739 int 740 get_hostkey_index(struct sshkey *key, int compare, struct ssh *ssh) 741 { 742 u_int i; 743 744 for (i = 0; i < options.num_host_key_files; i++) { 745 if (sshkey_is_cert(key)) { 746 if (key == sensitive_data.host_certificates[i] || 747 (compare && sensitive_data.host_certificates[i] && 748 sshkey_equal(key, 749 sensitive_data.host_certificates[i]))) 750 return (i); 751 } else { 752 if (key == sensitive_data.host_keys[i] || 753 (compare && sensitive_data.host_keys[i] && 754 sshkey_equal(key, sensitive_data.host_keys[i]))) 755 return (i); 756 if (key == sensitive_data.host_pubkeys[i] || 757 (compare && sensitive_data.host_pubkeys[i] && 758 sshkey_equal(key, sensitive_data.host_pubkeys[i]))) 759 return (i); 760 } 761 } 762 return (-1); 763 } 764 765 /* Inform the client of all hostkeys */ 766 static void 767 notify_hostkeys(struct ssh *ssh) 768 { 769 struct sshbuf *buf; 770 struct sshkey *key; 771 u_int i, nkeys; 772 int r; 773 char *fp; 774 775 /* Some clients cannot cope with the hostkeys message, skip those. */ 776 if (ssh->compat & SSH_BUG_HOSTKEYS) 777 return; 778 779 if ((buf = sshbuf_new()) == NULL) 780 fatal_f("sshbuf_new"); 781 for (i = nkeys = 0; i < options.num_host_key_files; i++) { 782 key = get_hostkey_public_by_index(i, ssh); 783 if (key == NULL || key->type == KEY_UNSPEC || 784 sshkey_is_cert(key)) 785 continue; 786 fp = sshkey_fingerprint(key, options.fingerprint_hash, 787 SSH_FP_DEFAULT); 788 debug3_f("key %d: %s %s", i, sshkey_ssh_name(key), fp); 789 free(fp); 790 if (nkeys == 0) { 791 /* 792 * Start building the request when we find the 793 * first usable key. 794 */ 795 if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 || 796 (r = sshpkt_put_cstring(ssh, "hostkeys-00@openssh.com")) != 0 || 797 (r = sshpkt_put_u8(ssh, 0)) != 0) /* want reply */ 798 sshpkt_fatal(ssh, r, "%s: start request", __func__); 799 } 800 /* Append the key to the request */ 801 sshbuf_reset(buf); 802 if ((r = sshkey_putb(key, buf)) != 0) 803 fatal_fr(r, "couldn't put hostkey %d", i); 804 if ((r = sshpkt_put_stringb(ssh, buf)) != 0) 805 sshpkt_fatal(ssh, r, "%s: append key", __func__); 806 nkeys++; 807 } 808 debug3_f("sent %u hostkeys", nkeys); 809 if (nkeys == 0) 810 fatal_f("no hostkeys"); 811 if ((r = sshpkt_send(ssh)) != 0) 812 sshpkt_fatal(ssh, r, "%s: send", __func__); 813 sshbuf_free(buf); 814 } 815 816 /* 817 * returns 1 if connection should be dropped, 0 otherwise. 818 * dropping starts at connection #max_startups_begin with a probability 819 * of (max_startups_rate/100). the probability increases linearly until 820 * all connections are dropped for startups > max_startups 821 */ 822 static int 823 should_drop_connection(int startups) 824 { 825 int p, r; 826 827 if (startups < options.max_startups_begin) 828 return 0; 829 if (startups >= options.max_startups) 830 return 1; 831 if (options.max_startups_rate == 100) 832 return 1; 833 834 p = 100 - options.max_startups_rate; 835 p *= startups - options.max_startups_begin; 836 p /= options.max_startups - options.max_startups_begin; 837 p += options.max_startups_rate; 838 r = arc4random_uniform(100); 839 840 debug_f("p %d, r %d", p, r); 841 return (r < p) ? 1 : 0; 842 } 843 844 /* 845 * Check whether connection should be accepted by MaxStartups. 846 * Returns 0 if the connection is accepted. If the connection is refused, 847 * returns 1 and attempts to send notification to client. 848 * Logs when the MaxStartups condition is entered or exited, and periodically 849 * while in that state. 850 */ 851 static int 852 drop_connection(int sock, int startups, int notify_pipe) 853 { 854 char *laddr, *raddr; 855 const char msg[] = "Exceeded MaxStartups\r\n"; 856 static time_t last_drop, first_drop; 857 static u_int ndropped; 858 LogLevel drop_level = SYSLOG_LEVEL_VERBOSE; 859 time_t now; 860 861 now = monotime(); 862 if (!should_drop_connection(startups) && 863 srclimit_check_allow(sock, notify_pipe) == 1) { 864 if (last_drop != 0 && 865 startups < options.max_startups_begin - 1) { 866 /* XXX maybe need better hysteresis here */ 867 logit("exited MaxStartups throttling after %s, " 868 "%u connections dropped", 869 fmt_timeframe(now - first_drop), ndropped); 870 last_drop = 0; 871 } 872 return 0; 873 } 874 875 #define SSHD_MAXSTARTUPS_LOG_INTERVAL (5 * 60) 876 if (last_drop == 0) { 877 error("beginning MaxStartups throttling"); 878 drop_level = SYSLOG_LEVEL_INFO; 879 first_drop = now; 880 ndropped = 0; 881 } else if (last_drop + SSHD_MAXSTARTUPS_LOG_INTERVAL < now) { 882 /* Periodic logs */ 883 error("in MaxStartups throttling for %s, " 884 "%u connections dropped", 885 fmt_timeframe(now - first_drop), ndropped + 1); 886 drop_level = SYSLOG_LEVEL_INFO; 887 } 888 last_drop = now; 889 ndropped++; 890 891 laddr = get_local_ipaddr(sock); 892 raddr = get_peer_ipaddr(sock); 893 do_log2(drop_level, "drop connection #%d from [%s]:%d on [%s]:%d " 894 "past MaxStartups", startups, raddr, get_peer_port(sock), 895 laddr, get_local_port(sock)); 896 free(laddr); 897 free(raddr); 898 /* best-effort notification to client */ 899 (void)write(sock, msg, sizeof(msg) - 1); 900 return 1; 901 } 902 903 static void 904 usage(void) 905 { 906 fprintf(stderr, "%s, %s\n", SSH_RELEASE, SSH_OPENSSL_VERSION); 907 fprintf(stderr, 908 "usage: sshd [-46DdeiqTt] [-C connection_spec] [-c host_cert_file]\n" 909 " [-E log_file] [-f config_file] [-g login_grace_time]\n" 910 " [-h host_key_file] [-o option] [-p port] [-u len]\n" 911 ); 912 exit(1); 913 } 914 915 static void 916 send_rexec_state(int fd, struct sshbuf *conf) 917 { 918 struct sshbuf *m = NULL, *inc = NULL; 919 struct include_item *item = NULL; 920 int r; 921 922 debug3_f("entering fd = %d config len %zu", fd, 923 sshbuf_len(conf)); 924 925 if ((m = sshbuf_new()) == NULL || (inc = sshbuf_new()) == NULL) 926 fatal_f("sshbuf_new failed"); 927 928 /* pack includes into a string */ 929 TAILQ_FOREACH(item, &includes, entry) { 930 if ((r = sshbuf_put_cstring(inc, item->selector)) != 0 || 931 (r = sshbuf_put_cstring(inc, item->filename)) != 0 || 932 (r = sshbuf_put_stringb(inc, item->contents)) != 0) 933 fatal_fr(r, "compose includes"); 934 } 935 936 /* 937 * Protocol from reexec master to child: 938 * string configuration 939 * string included_files[] { 940 * string selector 941 * string filename 942 * string contents 943 * } 944 * string rng_seed (if required) 945 */ 946 if ((r = sshbuf_put_stringb(m, conf)) != 0 || 947 (r = sshbuf_put_stringb(m, inc)) != 0) 948 fatal_fr(r, "compose config"); 949 #if defined(WITH_OPENSSL) && !defined(OPENSSL_PRNG_ONLY) 950 rexec_send_rng_seed(m); 951 #endif 952 if (ssh_msg_send(fd, 0, m) == -1) 953 error_f("ssh_msg_send failed"); 954 955 sshbuf_free(m); 956 sshbuf_free(inc); 957 958 debug3_f("done"); 959 } 960 961 static void 962 recv_rexec_state(int fd, struct sshbuf *conf) 963 { 964 struct sshbuf *m, *inc; 965 u_char *cp, ver; 966 size_t len; 967 int r; 968 struct include_item *item; 969 970 debug3_f("entering fd = %d", fd); 971 972 if ((m = sshbuf_new()) == NULL || (inc = sshbuf_new()) == NULL) 973 fatal_f("sshbuf_new failed"); 974 if (ssh_msg_recv(fd, m) == -1) 975 fatal_f("ssh_msg_recv failed"); 976 if ((r = sshbuf_get_u8(m, &ver)) != 0) 977 fatal_fr(r, "parse version"); 978 if (ver != 0) 979 fatal_f("rexec version mismatch"); 980 if ((r = sshbuf_get_string(m, &cp, &len)) != 0 || 981 (r = sshbuf_get_stringb(m, inc)) != 0) 982 fatal_fr(r, "parse config"); 983 984 #if defined(WITH_OPENSSL) && !defined(OPENSSL_PRNG_ONLY) 985 rexec_recv_rng_seed(m); 986 #endif 987 988 if (conf != NULL && (r = sshbuf_put(conf, cp, len))) 989 fatal_fr(r, "sshbuf_put"); 990 991 while (sshbuf_len(inc) != 0) { 992 item = xcalloc(1, sizeof(*item)); 993 if ((item->contents = sshbuf_new()) == NULL) 994 fatal_f("sshbuf_new failed"); 995 if ((r = sshbuf_get_cstring(inc, &item->selector, NULL)) != 0 || 996 (r = sshbuf_get_cstring(inc, &item->filename, NULL)) != 0 || 997 (r = sshbuf_get_stringb(inc, item->contents)) != 0) 998 fatal_fr(r, "parse includes"); 999 TAILQ_INSERT_TAIL(&includes, item, entry); 1000 } 1001 1002 free(cp); 1003 sshbuf_free(m); 1004 1005 debug3_f("done"); 1006 } 1007 1008 /* Accept a connection from inetd */ 1009 static void 1010 server_accept_inetd(int *sock_in, int *sock_out) 1011 { 1012 if (rexeced_flag) { 1013 close(REEXEC_CONFIG_PASS_FD); 1014 *sock_in = *sock_out = dup(STDIN_FILENO); 1015 } else { 1016 *sock_in = dup(STDIN_FILENO); 1017 *sock_out = dup(STDOUT_FILENO); 1018 } 1019 /* 1020 * We intentionally do not close the descriptors 0, 1, and 2 1021 * as our code for setting the descriptors won't work if 1022 * ttyfd happens to be one of those. 1023 */ 1024 if (stdfd_devnull(1, 1, !log_stderr) == -1) 1025 error_f("stdfd_devnull failed"); 1026 debug("inetd sockets after dupping: %d, %d", *sock_in, *sock_out); 1027 } 1028 1029 /* 1030 * Listen for TCP connections 1031 */ 1032 static void 1033 listen_on_addrs(struct listenaddr *la) 1034 { 1035 int ret, listen_sock; 1036 struct addrinfo *ai; 1037 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 1038 1039 for (ai = la->addrs; ai; ai = ai->ai_next) { 1040 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 1041 continue; 1042 if (num_listen_socks >= MAX_LISTEN_SOCKS) 1043 fatal("Too many listen sockets. " 1044 "Enlarge MAX_LISTEN_SOCKS"); 1045 if ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen, 1046 ntop, sizeof(ntop), strport, sizeof(strport), 1047 NI_NUMERICHOST|NI_NUMERICSERV)) != 0) { 1048 error("getnameinfo failed: %.100s", 1049 ssh_gai_strerror(ret)); 1050 continue; 1051 } 1052 /* Create socket for listening. */ 1053 listen_sock = socket(ai->ai_family, ai->ai_socktype, 1054 ai->ai_protocol); 1055 if (listen_sock == -1) { 1056 /* kernel may not support ipv6 */ 1057 verbose("socket: %.100s", strerror(errno)); 1058 continue; 1059 } 1060 if (set_nonblock(listen_sock) == -1) { 1061 close(listen_sock); 1062 continue; 1063 } 1064 if (fcntl(listen_sock, F_SETFD, FD_CLOEXEC) == -1) { 1065 verbose("socket: CLOEXEC: %s", strerror(errno)); 1066 close(listen_sock); 1067 continue; 1068 } 1069 /* Socket options */ 1070 set_reuseaddr(listen_sock); 1071 if (la->rdomain != NULL && 1072 set_rdomain(listen_sock, la->rdomain) == -1) { 1073 close(listen_sock); 1074 continue; 1075 } 1076 1077 /* Only communicate in IPv6 over AF_INET6 sockets. */ 1078 if (ai->ai_family == AF_INET6) 1079 sock_set_v6only(listen_sock); 1080 1081 debug("Bind to port %s on %s.", strport, ntop); 1082 1083 /* Bind the socket to the desired port. */ 1084 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) == -1) { 1085 error("Bind to port %s on %s failed: %.200s.", 1086 strport, ntop, strerror(errno)); 1087 close(listen_sock); 1088 continue; 1089 } 1090 listen_socks[num_listen_socks] = listen_sock; 1091 num_listen_socks++; 1092 1093 /* Start listening on the port. */ 1094 if (listen(listen_sock, SSH_LISTEN_BACKLOG) == -1) 1095 fatal("listen on [%s]:%s: %.100s", 1096 ntop, strport, strerror(errno)); 1097 logit("Server listening on %s port %s%s%s.", 1098 ntop, strport, 1099 la->rdomain == NULL ? "" : " rdomain ", 1100 la->rdomain == NULL ? "" : la->rdomain); 1101 } 1102 } 1103 1104 static void 1105 server_listen(void) 1106 { 1107 u_int i; 1108 1109 /* Initialise per-source limit tracking. */ 1110 srclimit_init(options.max_startups, options.per_source_max_startups, 1111 options.per_source_masklen_ipv4, options.per_source_masklen_ipv6); 1112 1113 for (i = 0; i < options.num_listen_addrs; i++) { 1114 listen_on_addrs(&options.listen_addrs[i]); 1115 freeaddrinfo(options.listen_addrs[i].addrs); 1116 free(options.listen_addrs[i].rdomain); 1117 memset(&options.listen_addrs[i], 0, 1118 sizeof(options.listen_addrs[i])); 1119 } 1120 free(options.listen_addrs); 1121 options.listen_addrs = NULL; 1122 options.num_listen_addrs = 0; 1123 1124 if (!num_listen_socks) 1125 fatal("Cannot bind any address."); 1126 } 1127 1128 /* 1129 * The main TCP accept loop. Note that, for the non-debug case, returns 1130 * from this function are in a forked subprocess. 1131 */ 1132 static void 1133 server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s) 1134 { 1135 fd_set *fdset; 1136 int i, j, ret, maxfd; 1137 int ostartups = -1, startups = 0, listening = 0, lameduck = 0; 1138 int startup_p[2] = { -1 , -1 }; 1139 char c = 0; 1140 struct sockaddr_storage from; 1141 socklen_t fromlen; 1142 pid_t pid; 1143 u_char rnd[256]; 1144 sigset_t nsigset, osigset; 1145 1146 /* setup fd set for accept */ 1147 fdset = NULL; 1148 maxfd = 0; 1149 for (i = 0; i < num_listen_socks; i++) 1150 if (listen_socks[i] > maxfd) 1151 maxfd = listen_socks[i]; 1152 /* pipes connected to unauthenticated child sshd processes */ 1153 startup_pipes = xcalloc(options.max_startups, sizeof(int)); 1154 startup_flags = xcalloc(options.max_startups, sizeof(int)); 1155 for (i = 0; i < options.max_startups; i++) 1156 startup_pipes[i] = -1; 1157 1158 /* 1159 * Prepare signal mask that we use to block signals that might set 1160 * received_sigterm or received_sighup, so that we are guaranteed 1161 * to immediately wake up the pselect if a signal is received after 1162 * the flag is checked. 1163 */ 1164 sigemptyset(&nsigset); 1165 sigaddset(&nsigset, SIGHUP); 1166 sigaddset(&nsigset, SIGCHLD); 1167 sigaddset(&nsigset, SIGTERM); 1168 sigaddset(&nsigset, SIGQUIT); 1169 1170 /* 1171 * Stay listening for connections until the system crashes or 1172 * the daemon is killed with a signal. 1173 */ 1174 for (;;) { 1175 sigprocmask(SIG_BLOCK, &nsigset, &osigset); 1176 if (received_sigterm) { 1177 logit("Received signal %d; terminating.", 1178 (int) received_sigterm); 1179 close_listen_socks(); 1180 if (options.pid_file != NULL) 1181 unlink(options.pid_file); 1182 exit(received_sigterm == SIGTERM ? 0 : 255); 1183 } 1184 if (ostartups != startups) { 1185 setproctitle("%s [listener] %d of %d-%d startups", 1186 listener_proctitle, startups, 1187 options.max_startups_begin, options.max_startups); 1188 ostartups = startups; 1189 } 1190 if (received_sighup) { 1191 if (!lameduck) { 1192 debug("Received SIGHUP; waiting for children"); 1193 close_listen_socks(); 1194 lameduck = 1; 1195 } 1196 if (listening <= 0) { 1197 sigprocmask(SIG_SETMASK, &osigset, NULL); 1198 sighup_restart(); 1199 } 1200 } 1201 free(fdset); 1202 fdset = xcalloc(howmany(maxfd + 1, NFDBITS), 1203 sizeof(fd_mask)); 1204 1205 for (i = 0; i < num_listen_socks; i++) 1206 FD_SET(listen_socks[i], fdset); 1207 for (i = 0; i < options.max_startups; i++) 1208 if (startup_pipes[i] != -1) 1209 FD_SET(startup_pipes[i], fdset); 1210 1211 /* Wait until a connection arrives or a child exits. */ 1212 ret = pselect(maxfd+1, fdset, NULL, NULL, NULL, &osigset); 1213 if (ret == -1 && errno != EINTR) 1214 error("pselect: %.100s", strerror(errno)); 1215 sigprocmask(SIG_SETMASK, &osigset, NULL); 1216 if (ret == -1) 1217 continue; 1218 1219 for (i = 0; i < options.max_startups; i++) { 1220 if (startup_pipes[i] == -1 || 1221 !FD_ISSET(startup_pipes[i], fdset)) 1222 continue; 1223 switch (read(startup_pipes[i], &c, sizeof(c))) { 1224 case -1: 1225 if (errno == EINTR || errno == EAGAIN) 1226 continue; 1227 if (errno != EPIPE) { 1228 error_f("startup pipe %d (fd=%d): " 1229 "read %s", i, startup_pipes[i], 1230 strerror(errno)); 1231 } 1232 /* FALLTHROUGH */ 1233 case 0: 1234 /* child exited or completed auth */ 1235 close(startup_pipes[i]); 1236 srclimit_done(startup_pipes[i]); 1237 startup_pipes[i] = -1; 1238 startups--; 1239 if (startup_flags[i]) 1240 listening--; 1241 break; 1242 case 1: 1243 /* child has finished preliminaries */ 1244 if (startup_flags[i]) { 1245 listening--; 1246 startup_flags[i] = 0; 1247 } 1248 break; 1249 } 1250 } 1251 for (i = 0; i < num_listen_socks; i++) { 1252 if (!FD_ISSET(listen_socks[i], fdset)) 1253 continue; 1254 fromlen = sizeof(from); 1255 *newsock = accept(listen_socks[i], 1256 (struct sockaddr *)&from, &fromlen); 1257 if (*newsock == -1) { 1258 if (errno != EINTR && errno != EWOULDBLOCK && 1259 errno != ECONNABORTED && errno != EAGAIN) 1260 error("accept: %.100s", 1261 strerror(errno)); 1262 if (errno == EMFILE || errno == ENFILE) 1263 usleep(100 * 1000); 1264 continue; 1265 } 1266 if (unset_nonblock(*newsock) == -1 || 1267 pipe(startup_p) == -1) 1268 continue; 1269 if (drop_connection(*newsock, startups, startup_p[0])) { 1270 close(*newsock); 1271 close(startup_p[0]); 1272 close(startup_p[1]); 1273 continue; 1274 } 1275 1276 if (rexec_flag && socketpair(AF_UNIX, 1277 SOCK_STREAM, 0, config_s) == -1) { 1278 error("reexec socketpair: %s", 1279 strerror(errno)); 1280 close(*newsock); 1281 close(startup_p[0]); 1282 close(startup_p[1]); 1283 continue; 1284 } 1285 1286 for (j = 0; j < options.max_startups; j++) 1287 if (startup_pipes[j] == -1) { 1288 startup_pipes[j] = startup_p[0]; 1289 if (maxfd < startup_p[0]) 1290 maxfd = startup_p[0]; 1291 startups++; 1292 startup_flags[j] = 1; 1293 break; 1294 } 1295 1296 /* 1297 * Got connection. Fork a child to handle it, unless 1298 * we are in debugging mode. 1299 */ 1300 if (debug_flag) { 1301 /* 1302 * In debugging mode. Close the listening 1303 * socket, and start processing the 1304 * connection without forking. 1305 */ 1306 debug("Server will not fork when running in debugging mode."); 1307 close_listen_socks(); 1308 *sock_in = *newsock; 1309 *sock_out = *newsock; 1310 close(startup_p[0]); 1311 close(startup_p[1]); 1312 startup_pipe = -1; 1313 pid = getpid(); 1314 if (rexec_flag) { 1315 send_rexec_state(config_s[0], cfg); 1316 close(config_s[0]); 1317 } 1318 return; 1319 } 1320 1321 /* 1322 * Normal production daemon. Fork, and have 1323 * the child process the connection. The 1324 * parent continues listening. 1325 */ 1326 platform_pre_fork(); 1327 listening++; 1328 if ((pid = fork()) == 0) { 1329 /* 1330 * Child. Close the listening and 1331 * max_startup sockets. Start using 1332 * the accepted socket. Reinitialize 1333 * logging (since our pid has changed). 1334 * We return from this function to handle 1335 * the connection. 1336 */ 1337 platform_post_fork_child(); 1338 startup_pipe = startup_p[1]; 1339 close_startup_pipes(); 1340 close_listen_socks(); 1341 *sock_in = *newsock; 1342 *sock_out = *newsock; 1343 log_init(__progname, 1344 options.log_level, 1345 options.log_facility, 1346 log_stderr); 1347 if (rexec_flag) 1348 close(config_s[0]); 1349 else { 1350 /* 1351 * Signal parent that the preliminaries 1352 * for this child are complete. For the 1353 * re-exec case, this happens after the 1354 * child has received the rexec state 1355 * from the server. 1356 */ 1357 (void)atomicio(vwrite, startup_pipe, 1358 "\0", 1); 1359 } 1360 return; 1361 } 1362 1363 /* Parent. Stay in the loop. */ 1364 platform_post_fork_parent(pid); 1365 if (pid == -1) 1366 error("fork: %.100s", strerror(errno)); 1367 else 1368 debug("Forked child %ld.", (long)pid); 1369 1370 close(startup_p[1]); 1371 1372 if (rexec_flag) { 1373 close(config_s[1]); 1374 send_rexec_state(config_s[0], cfg); 1375 close(config_s[0]); 1376 } 1377 close(*newsock); 1378 1379 /* 1380 * Ensure that our random state differs 1381 * from that of the child 1382 */ 1383 arc4random_stir(); 1384 arc4random_buf(rnd, sizeof(rnd)); 1385 #ifdef WITH_OPENSSL 1386 RAND_seed(rnd, sizeof(rnd)); 1387 if ((RAND_bytes((u_char *)rnd, 1)) != 1) 1388 fatal("%s: RAND_bytes failed", __func__); 1389 #endif 1390 explicit_bzero(rnd, sizeof(rnd)); 1391 } 1392 } 1393 } 1394 1395 /* 1396 * If IP options are supported, make sure there are none (log and 1397 * return an error if any are found). Basically we are worried about 1398 * source routing; it can be used to pretend you are somebody 1399 * (ip-address) you are not. That itself may be "almost acceptable" 1400 * under certain circumstances, but rhosts authentication is useless 1401 * if source routing is accepted. Notice also that if we just dropped 1402 * source routing here, the other side could use IP spoofing to do 1403 * rest of the interaction and could still bypass security. So we 1404 * exit here if we detect any IP options. 1405 */ 1406 static void 1407 check_ip_options(struct ssh *ssh) 1408 { 1409 #ifdef IP_OPTIONS 1410 int sock_in = ssh_packet_get_connection_in(ssh); 1411 struct sockaddr_storage from; 1412 u_char opts[200]; 1413 socklen_t i, option_size = sizeof(opts), fromlen = sizeof(from); 1414 char text[sizeof(opts) * 3 + 1]; 1415 1416 memset(&from, 0, sizeof(from)); 1417 if (getpeername(sock_in, (struct sockaddr *)&from, 1418 &fromlen) == -1) 1419 return; 1420 if (from.ss_family != AF_INET) 1421 return; 1422 /* XXX IPv6 options? */ 1423 1424 if (getsockopt(sock_in, IPPROTO_IP, IP_OPTIONS, opts, 1425 &option_size) >= 0 && option_size != 0) { 1426 text[0] = '\0'; 1427 for (i = 0; i < option_size; i++) 1428 snprintf(text + i*3, sizeof(text) - i*3, 1429 " %2.2x", opts[i]); 1430 fatal("Connection from %.100s port %d with IP opts: %.800s", 1431 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), text); 1432 } 1433 return; 1434 #endif /* IP_OPTIONS */ 1435 } 1436 1437 /* Set the routing domain for this process */ 1438 static void 1439 set_process_rdomain(struct ssh *ssh, const char *name) 1440 { 1441 #if defined(HAVE_SYS_SET_PROCESS_RDOMAIN) 1442 if (name == NULL) 1443 return; /* default */ 1444 1445 if (strcmp(name, "%D") == 0) { 1446 /* "expands" to routing domain of connection */ 1447 if ((name = ssh_packet_rdomain_in(ssh)) == NULL) 1448 return; 1449 } 1450 /* NB. We don't pass 'ssh' to sys_set_process_rdomain() */ 1451 return sys_set_process_rdomain(name); 1452 #elif defined(__OpenBSD__) 1453 int rtable, ortable = getrtable(); 1454 const char *errstr; 1455 1456 if (name == NULL) 1457 return; /* default */ 1458 1459 if (strcmp(name, "%D") == 0) { 1460 /* "expands" to routing domain of connection */ 1461 if ((name = ssh_packet_rdomain_in(ssh)) == NULL) 1462 return; 1463 } 1464 1465 rtable = (int)strtonum(name, 0, 255, &errstr); 1466 if (errstr != NULL) /* Shouldn't happen */ 1467 fatal("Invalid routing domain \"%s\": %s", name, errstr); 1468 if (rtable != ortable && setrtable(rtable) != 0) 1469 fatal("Unable to set routing domain %d: %s", 1470 rtable, strerror(errno)); 1471 debug_f("set routing domain %d (was %d)", rtable, ortable); 1472 #else /* defined(__OpenBSD__) */ 1473 fatal("Unable to set routing domain: not supported in this platform"); 1474 #endif 1475 } 1476 1477 static void 1478 accumulate_host_timing_secret(struct sshbuf *server_cfg, 1479 struct sshkey *key) 1480 { 1481 static struct ssh_digest_ctx *ctx; 1482 u_char *hash; 1483 size_t len; 1484 struct sshbuf *buf; 1485 int r; 1486 1487 if (ctx == NULL && (ctx = ssh_digest_start(SSH_DIGEST_SHA512)) == NULL) 1488 fatal_f("ssh_digest_start"); 1489 if (key == NULL) { /* finalize */ 1490 /* add server config in case we are using agent for host keys */ 1491 if (ssh_digest_update(ctx, sshbuf_ptr(server_cfg), 1492 sshbuf_len(server_cfg)) != 0) 1493 fatal_f("ssh_digest_update"); 1494 len = ssh_digest_bytes(SSH_DIGEST_SHA512); 1495 hash = xmalloc(len); 1496 if (ssh_digest_final(ctx, hash, len) != 0) 1497 fatal_f("ssh_digest_final"); 1498 options.timing_secret = PEEK_U64(hash); 1499 freezero(hash, len); 1500 ssh_digest_free(ctx); 1501 ctx = NULL; 1502 return; 1503 } 1504 if ((buf = sshbuf_new()) == NULL) 1505 fatal_f("could not allocate buffer"); 1506 if ((r = sshkey_private_serialize(key, buf)) != 0) 1507 fatal_fr(r, "decode key"); 1508 if (ssh_digest_update(ctx, sshbuf_ptr(buf), sshbuf_len(buf)) != 0) 1509 fatal_f("ssh_digest_update"); 1510 sshbuf_reset(buf); 1511 sshbuf_free(buf); 1512 } 1513 1514 static char * 1515 prepare_proctitle(int ac, char **av) 1516 { 1517 char *ret = NULL; 1518 int i; 1519 1520 for (i = 0; i < ac; i++) 1521 xextendf(&ret, " ", "%s", av[i]); 1522 return ret; 1523 } 1524 1525 /* 1526 * Main program for the daemon. 1527 */ 1528 int 1529 main(int ac, char **av) 1530 { 1531 struct ssh *ssh = NULL; 1532 extern char *optarg; 1533 extern int optind; 1534 int r, opt, on = 1, already_daemon, remote_port; 1535 int sock_in = -1, sock_out = -1, newsock = -1; 1536 const char *remote_ip, *rdomain; 1537 char *fp, *line, *laddr, *logfile = NULL; 1538 int config_s[2] = { -1 , -1 }; 1539 u_int i, j; 1540 u_int64_t ibytes, obytes; 1541 mode_t new_umask; 1542 struct sshkey *key; 1543 struct sshkey *pubkey; 1544 int keytype; 1545 Authctxt *authctxt; 1546 struct connection_info *connection_info = NULL; 1547 1548 #ifdef HAVE_SECUREWARE 1549 (void)set_auth_parameters(ac, av); 1550 #endif 1551 __progname = ssh_get_progname(av[0]); 1552 1553 /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */ 1554 saved_argc = ac; 1555 rexec_argc = ac; 1556 saved_argv = xcalloc(ac + 1, sizeof(*saved_argv)); 1557 for (i = 0; (int)i < ac; i++) 1558 saved_argv[i] = xstrdup(av[i]); 1559 saved_argv[i] = NULL; 1560 1561 #ifndef HAVE_SETPROCTITLE 1562 /* Prepare for later setproctitle emulation */ 1563 compat_init_setproctitle(ac, av); 1564 av = saved_argv; 1565 #endif 1566 1567 if (geteuid() == 0 && setgroups(0, NULL) == -1) 1568 debug("setgroups(): %.200s", strerror(errno)); 1569 1570 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */ 1571 sanitise_stdfd(); 1572 1573 seed_rng(); 1574 1575 /* Initialize configuration options to their default values. */ 1576 initialize_server_options(&options); 1577 1578 /* Parse command-line arguments. */ 1579 while ((opt = getopt(ac, av, 1580 "C:E:b:c:f:g:h:k:o:p:u:46DQRTdeiqrt")) != -1) { 1581 switch (opt) { 1582 case '4': 1583 options.address_family = AF_INET; 1584 break; 1585 case '6': 1586 options.address_family = AF_INET6; 1587 break; 1588 case 'f': 1589 config_file_name = optarg; 1590 break; 1591 case 'c': 1592 servconf_add_hostcert("[command-line]", 0, 1593 &options, optarg); 1594 break; 1595 case 'd': 1596 if (debug_flag == 0) { 1597 debug_flag = 1; 1598 options.log_level = SYSLOG_LEVEL_DEBUG1; 1599 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) 1600 options.log_level++; 1601 break; 1602 case 'D': 1603 no_daemon_flag = 1; 1604 break; 1605 case 'E': 1606 logfile = optarg; 1607 /* FALLTHROUGH */ 1608 case 'e': 1609 log_stderr = 1; 1610 break; 1611 case 'i': 1612 inetd_flag = 1; 1613 break; 1614 case 'r': 1615 rexec_flag = 0; 1616 break; 1617 case 'R': 1618 rexeced_flag = 1; 1619 inetd_flag = 1; 1620 break; 1621 case 'Q': 1622 /* ignored */ 1623 break; 1624 case 'q': 1625 options.log_level = SYSLOG_LEVEL_QUIET; 1626 break; 1627 case 'b': 1628 /* protocol 1, ignored */ 1629 break; 1630 case 'p': 1631 options.ports_from_cmdline = 1; 1632 if (options.num_ports >= MAX_PORTS) { 1633 fprintf(stderr, "too many ports.\n"); 1634 exit(1); 1635 } 1636 options.ports[options.num_ports++] = a2port(optarg); 1637 if (options.ports[options.num_ports-1] <= 0) { 1638 fprintf(stderr, "Bad port number.\n"); 1639 exit(1); 1640 } 1641 break; 1642 case 'g': 1643 if ((options.login_grace_time = convtime(optarg)) == -1) { 1644 fprintf(stderr, "Invalid login grace time.\n"); 1645 exit(1); 1646 } 1647 break; 1648 case 'k': 1649 /* protocol 1, ignored */ 1650 break; 1651 case 'h': 1652 servconf_add_hostkey("[command-line]", 0, 1653 &options, optarg, 1); 1654 break; 1655 case 't': 1656 test_flag = 1; 1657 break; 1658 case 'T': 1659 test_flag = 2; 1660 break; 1661 case 'C': 1662 connection_info = get_connection_info(ssh, 0, 0); 1663 if (parse_server_match_testspec(connection_info, 1664 optarg) == -1) 1665 exit(1); 1666 break; 1667 case 'u': 1668 utmp_len = (u_int)strtonum(optarg, 0, HOST_NAME_MAX+1+1, NULL); 1669 if (utmp_len > HOST_NAME_MAX+1) { 1670 fprintf(stderr, "Invalid utmp length.\n"); 1671 exit(1); 1672 } 1673 break; 1674 case 'o': 1675 line = xstrdup(optarg); 1676 if (process_server_config_line(&options, line, 1677 "command-line", 0, NULL, NULL, &includes) != 0) 1678 exit(1); 1679 free(line); 1680 break; 1681 case '?': 1682 default: 1683 usage(); 1684 break; 1685 } 1686 } 1687 if (rexeced_flag || inetd_flag) 1688 rexec_flag = 0; 1689 if (!test_flag && rexec_flag && !path_absolute(av[0])) 1690 fatal("sshd re-exec requires execution with an absolute path"); 1691 if (rexeced_flag) 1692 closefrom(REEXEC_MIN_FREE_FD); 1693 else 1694 closefrom(REEXEC_DEVCRYPTO_RESERVED_FD); 1695 1696 /* If requested, redirect the logs to the specified logfile. */ 1697 if (logfile != NULL) 1698 log_redirect_stderr_to(logfile); 1699 /* 1700 * Force logging to stderr until we have loaded the private host 1701 * key (unless started from inetd) 1702 */ 1703 log_init(__progname, 1704 options.log_level == SYSLOG_LEVEL_NOT_SET ? 1705 SYSLOG_LEVEL_INFO : options.log_level, 1706 options.log_facility == SYSLOG_FACILITY_NOT_SET ? 1707 SYSLOG_FACILITY_AUTH : options.log_facility, 1708 log_stderr || !inetd_flag || debug_flag); 1709 1710 /* 1711 * Unset KRB5CCNAME, otherwise the user's session may inherit it from 1712 * root's environment 1713 */ 1714 if (getenv("KRB5CCNAME") != NULL) 1715 (void) unsetenv("KRB5CCNAME"); 1716 1717 sensitive_data.have_ssh2_key = 0; 1718 1719 /* 1720 * If we're not doing an extended test do not silently ignore connection 1721 * test params. 1722 */ 1723 if (test_flag < 2 && connection_info != NULL) 1724 fatal("Config test connection parameter (-C) provided without " 1725 "test mode (-T)"); 1726 1727 /* Fetch our configuration */ 1728 if ((cfg = sshbuf_new()) == NULL) 1729 fatal_f("sshbuf_new failed"); 1730 if (rexeced_flag) { 1731 setproctitle("%s", "[rexeced]"); 1732 recv_rexec_state(REEXEC_CONFIG_PASS_FD, cfg); 1733 if (!debug_flag) { 1734 startup_pipe = dup(REEXEC_STARTUP_PIPE_FD); 1735 close(REEXEC_STARTUP_PIPE_FD); 1736 /* 1737 * Signal parent that this child is at a point where 1738 * they can go away if they have a SIGHUP pending. 1739 */ 1740 (void)atomicio(vwrite, startup_pipe, "\0", 1); 1741 } 1742 } else if (strcasecmp(config_file_name, "none") != 0) 1743 load_server_config(config_file_name, cfg); 1744 1745 parse_server_config(&options, rexeced_flag ? "rexec" : config_file_name, 1746 cfg, &includes, NULL); 1747 1748 #ifdef WITH_OPENSSL 1749 if (options.moduli_file != NULL) 1750 dh_set_moduli_file(options.moduli_file); 1751 #endif 1752 1753 /* Fill in default values for those options not explicitly set. */ 1754 fill_default_server_options(&options); 1755 1756 /* Check that options are sensible */ 1757 if (options.authorized_keys_command_user == NULL && 1758 (options.authorized_keys_command != NULL && 1759 strcasecmp(options.authorized_keys_command, "none") != 0)) 1760 fatal("AuthorizedKeysCommand set without " 1761 "AuthorizedKeysCommandUser"); 1762 if (options.authorized_principals_command_user == NULL && 1763 (options.authorized_principals_command != NULL && 1764 strcasecmp(options.authorized_principals_command, "none") != 0)) 1765 fatal("AuthorizedPrincipalsCommand set without " 1766 "AuthorizedPrincipalsCommandUser"); 1767 1768 /* 1769 * Check whether there is any path through configured auth methods. 1770 * Unfortunately it is not possible to verify this generally before 1771 * daemonisation in the presence of Match block, but this catches 1772 * and warns for trivial misconfigurations that could break login. 1773 */ 1774 if (options.num_auth_methods != 0) { 1775 for (i = 0; i < options.num_auth_methods; i++) { 1776 if (auth2_methods_valid(options.auth_methods[i], 1777 1) == 0) 1778 break; 1779 } 1780 if (i >= options.num_auth_methods) 1781 fatal("AuthenticationMethods cannot be satisfied by " 1782 "enabled authentication methods"); 1783 } 1784 1785 /* Check that there are no remaining arguments. */ 1786 if (optind < ac) { 1787 fprintf(stderr, "Extra argument %s.\n", av[optind]); 1788 exit(1); 1789 } 1790 1791 debug("sshd version %s, %s", SSH_VERSION, SSH_OPENSSL_VERSION); 1792 1793 /* Store privilege separation user for later use if required. */ 1794 privsep_chroot = use_privsep && (getuid() == 0 || geteuid() == 0); 1795 if ((privsep_pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) { 1796 if (privsep_chroot || options.kerberos_authentication) 1797 fatal("Privilege separation user %s does not exist", 1798 SSH_PRIVSEP_USER); 1799 } else { 1800 privsep_pw = pwcopy(privsep_pw); 1801 freezero(privsep_pw->pw_passwd, strlen(privsep_pw->pw_passwd)); 1802 privsep_pw->pw_passwd = xstrdup("*"); 1803 } 1804 endpwent(); 1805 1806 /* load host keys */ 1807 sensitive_data.host_keys = xcalloc(options.num_host_key_files, 1808 sizeof(struct sshkey *)); 1809 sensitive_data.host_pubkeys = xcalloc(options.num_host_key_files, 1810 sizeof(struct sshkey *)); 1811 1812 if (options.host_key_agent) { 1813 if (strcmp(options.host_key_agent, SSH_AUTHSOCKET_ENV_NAME)) 1814 setenv(SSH_AUTHSOCKET_ENV_NAME, 1815 options.host_key_agent, 1); 1816 if ((r = ssh_get_authentication_socket(NULL)) == 0) 1817 have_agent = 1; 1818 else 1819 error_r(r, "Could not connect to agent \"%s\"", 1820 options.host_key_agent); 1821 } 1822 1823 for (i = 0; i < options.num_host_key_files; i++) { 1824 int ll = options.host_key_file_userprovided[i] ? 1825 SYSLOG_LEVEL_ERROR : SYSLOG_LEVEL_DEBUG1; 1826 1827 if (options.host_key_files[i] == NULL) 1828 continue; 1829 if ((r = sshkey_load_private(options.host_key_files[i], "", 1830 &key, NULL)) != 0 && r != SSH_ERR_SYSTEM_ERROR) 1831 do_log2_r(r, ll, "Unable to load host key \"%s\"", 1832 options.host_key_files[i]); 1833 if (sshkey_is_sk(key) && 1834 key->sk_flags & SSH_SK_USER_PRESENCE_REQD) { 1835 debug("host key %s requires user presence, ignoring", 1836 options.host_key_files[i]); 1837 key->sk_flags &= ~SSH_SK_USER_PRESENCE_REQD; 1838 } 1839 if (r == 0 && key != NULL && 1840 (r = sshkey_shield_private(key)) != 0) { 1841 do_log2_r(r, ll, "Unable to shield host key \"%s\"", 1842 options.host_key_files[i]); 1843 sshkey_free(key); 1844 key = NULL; 1845 } 1846 if ((r = sshkey_load_public(options.host_key_files[i], 1847 &pubkey, NULL)) != 0 && r != SSH_ERR_SYSTEM_ERROR) 1848 do_log2_r(r, ll, "Unable to load host key \"%s\"", 1849 options.host_key_files[i]); 1850 if (pubkey != NULL && key != NULL) { 1851 if (!sshkey_equal(pubkey, key)) { 1852 error("Public key for %s does not match " 1853 "private key", options.host_key_files[i]); 1854 sshkey_free(pubkey); 1855 pubkey = NULL; 1856 } 1857 } 1858 if (pubkey == NULL && key != NULL) { 1859 if ((r = sshkey_from_private(key, &pubkey)) != 0) 1860 fatal_r(r, "Could not demote key: \"%s\"", 1861 options.host_key_files[i]); 1862 } 1863 sensitive_data.host_keys[i] = key; 1864 sensitive_data.host_pubkeys[i] = pubkey; 1865 1866 if (key == NULL && pubkey != NULL && have_agent) { 1867 debug("will rely on agent for hostkey %s", 1868 options.host_key_files[i]); 1869 keytype = pubkey->type; 1870 } else if (key != NULL) { 1871 keytype = key->type; 1872 accumulate_host_timing_secret(cfg, key); 1873 } else { 1874 do_log2(ll, "Unable to load host key: %s", 1875 options.host_key_files[i]); 1876 sensitive_data.host_keys[i] = NULL; 1877 sensitive_data.host_pubkeys[i] = NULL; 1878 continue; 1879 } 1880 1881 switch (keytype) { 1882 case KEY_RSA: 1883 case KEY_DSA: 1884 case KEY_ECDSA: 1885 case KEY_ED25519: 1886 case KEY_ECDSA_SK: 1887 case KEY_ED25519_SK: 1888 case KEY_XMSS: 1889 if (have_agent || key != NULL) 1890 sensitive_data.have_ssh2_key = 1; 1891 break; 1892 } 1893 if ((fp = sshkey_fingerprint(pubkey, options.fingerprint_hash, 1894 SSH_FP_DEFAULT)) == NULL) 1895 fatal("sshkey_fingerprint failed"); 1896 debug("%s host key #%d: %s %s", 1897 key ? "private" : "agent", i, sshkey_ssh_name(pubkey), fp); 1898 free(fp); 1899 } 1900 accumulate_host_timing_secret(cfg, NULL); 1901 if (!sensitive_data.have_ssh2_key) { 1902 logit("sshd: no hostkeys available -- exiting."); 1903 exit(1); 1904 } 1905 1906 /* 1907 * Load certificates. They are stored in an array at identical 1908 * indices to the public keys that they relate to. 1909 */ 1910 sensitive_data.host_certificates = xcalloc(options.num_host_key_files, 1911 sizeof(struct sshkey *)); 1912 for (i = 0; i < options.num_host_key_files; i++) 1913 sensitive_data.host_certificates[i] = NULL; 1914 1915 for (i = 0; i < options.num_host_cert_files; i++) { 1916 if (options.host_cert_files[i] == NULL) 1917 continue; 1918 if ((r = sshkey_load_public(options.host_cert_files[i], 1919 &key, NULL)) != 0) { 1920 error_r(r, "Could not load host certificate \"%s\"", 1921 options.host_cert_files[i]); 1922 continue; 1923 } 1924 if (!sshkey_is_cert(key)) { 1925 error("Certificate file is not a certificate: %s", 1926 options.host_cert_files[i]); 1927 sshkey_free(key); 1928 continue; 1929 } 1930 /* Find matching private key */ 1931 for (j = 0; j < options.num_host_key_files; j++) { 1932 if (sshkey_equal_public(key, 1933 sensitive_data.host_pubkeys[j])) { 1934 sensitive_data.host_certificates[j] = key; 1935 break; 1936 } 1937 } 1938 if (j >= options.num_host_key_files) { 1939 error("No matching private key for certificate: %s", 1940 options.host_cert_files[i]); 1941 sshkey_free(key); 1942 continue; 1943 } 1944 sensitive_data.host_certificates[j] = key; 1945 debug("host certificate: #%u type %d %s", j, key->type, 1946 sshkey_type(key)); 1947 } 1948 1949 if (privsep_chroot) { 1950 struct stat st; 1951 1952 if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) || 1953 (S_ISDIR(st.st_mode) == 0)) 1954 fatal("Missing privilege separation directory: %s", 1955 _PATH_PRIVSEP_CHROOT_DIR); 1956 1957 #ifdef HAVE_CYGWIN 1958 if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) && 1959 (st.st_uid != getuid () || 1960 (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)) 1961 #else 1962 if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0) 1963 #endif 1964 fatal("%s must be owned by root and not group or " 1965 "world-writable.", _PATH_PRIVSEP_CHROOT_DIR); 1966 } 1967 1968 if (test_flag > 1) { 1969 /* 1970 * If no connection info was provided by -C then use 1971 * use a blank one that will cause no predicate to match. 1972 */ 1973 if (connection_info == NULL) 1974 connection_info = get_connection_info(ssh, 0, 0); 1975 connection_info->test = 1; 1976 parse_server_match_config(&options, &includes, connection_info); 1977 dump_config(&options); 1978 } 1979 1980 /* Configuration looks good, so exit if in test mode. */ 1981 if (test_flag) 1982 exit(0); 1983 1984 /* 1985 * Clear out any supplemental groups we may have inherited. This 1986 * prevents inadvertent creation of files with bad modes (in the 1987 * portable version at least, it's certainly possible for PAM 1988 * to create a file, and we can't control the code in every 1989 * module which might be used). 1990 */ 1991 if (setgroups(0, NULL) < 0) 1992 debug("setgroups() failed: %.200s", strerror(errno)); 1993 1994 if (rexec_flag) { 1995 if (rexec_argc < 0) 1996 fatal("rexec_argc %d < 0", rexec_argc); 1997 rexec_argv = xcalloc(rexec_argc + 2, sizeof(char *)); 1998 for (i = 0; i < (u_int)rexec_argc; i++) { 1999 debug("rexec_argv[%d]='%s'", i, saved_argv[i]); 2000 rexec_argv[i] = saved_argv[i]; 2001 } 2002 rexec_argv[rexec_argc] = "-R"; 2003 rexec_argv[rexec_argc + 1] = NULL; 2004 } 2005 listener_proctitle = prepare_proctitle(ac, av); 2006 2007 /* Ensure that umask disallows at least group and world write */ 2008 new_umask = umask(0077) | 0022; 2009 (void) umask(new_umask); 2010 2011 /* Initialize the log (it is reinitialized below in case we forked). */ 2012 if (debug_flag && (!inetd_flag || rexeced_flag)) 2013 log_stderr = 1; 2014 log_init(__progname, options.log_level, 2015 options.log_facility, log_stderr); 2016 for (i = 0; i < options.num_log_verbose; i++) 2017 log_verbose_add(options.log_verbose[i]); 2018 2019 /* 2020 * If not in debugging mode, not started from inetd and not already 2021 * daemonized (eg re-exec via SIGHUP), disconnect from the controlling 2022 * terminal, and fork. The original process exits. 2023 */ 2024 already_daemon = daemonized(); 2025 if (!(debug_flag || inetd_flag || no_daemon_flag || already_daemon)) { 2026 2027 if (daemon(0, 0) == -1) 2028 fatal("daemon() failed: %.200s", strerror(errno)); 2029 2030 disconnect_controlling_tty(); 2031 } 2032 /* Reinitialize the log (because of the fork above). */ 2033 log_init(__progname, options.log_level, options.log_facility, log_stderr); 2034 2035 /* 2036 * Chdir to the root directory so that the current disk can be 2037 * unmounted if desired. 2038 */ 2039 if (chdir("/") == -1) 2040 error("chdir(\"/\"): %s", strerror(errno)); 2041 2042 /* ignore SIGPIPE */ 2043 ssh_signal(SIGPIPE, SIG_IGN); 2044 2045 /* Get a connection, either from inetd or a listening TCP socket */ 2046 if (inetd_flag) { 2047 server_accept_inetd(&sock_in, &sock_out); 2048 } else { 2049 platform_pre_listen(); 2050 server_listen(); 2051 2052 ssh_signal(SIGHUP, sighup_handler); 2053 ssh_signal(SIGCHLD, main_sigchld_handler); 2054 ssh_signal(SIGTERM, sigterm_handler); 2055 ssh_signal(SIGQUIT, sigterm_handler); 2056 2057 /* 2058 * Write out the pid file after the sigterm handler 2059 * is setup and the listen sockets are bound 2060 */ 2061 if (options.pid_file != NULL && !debug_flag) { 2062 FILE *f = fopen(options.pid_file, "w"); 2063 2064 if (f == NULL) { 2065 error("Couldn't create pid file \"%s\": %s", 2066 options.pid_file, strerror(errno)); 2067 } else { 2068 fprintf(f, "%ld\n", (long) getpid()); 2069 fclose(f); 2070 } 2071 } 2072 2073 /* Accept a connection and return in a forked child */ 2074 server_accept_loop(&sock_in, &sock_out, 2075 &newsock, config_s); 2076 } 2077 2078 /* This is the child processing a new connection. */ 2079 setproctitle("%s", "[accepted]"); 2080 2081 /* 2082 * Create a new session and process group since the 4.4BSD 2083 * setlogin() affects the entire process group. We don't 2084 * want the child to be able to affect the parent. 2085 */ 2086 #if !defined(SSHD_ACQUIRES_CTTY) 2087 /* 2088 * If setsid is called, on some platforms sshd will later acquire a 2089 * controlling terminal which will result in "could not set 2090 * controlling tty" errors. 2091 */ 2092 if (!debug_flag && !inetd_flag && setsid() == -1) 2093 error("setsid: %.100s", strerror(errno)); 2094 #endif 2095 2096 if (rexec_flag) { 2097 debug("rexec start in %d out %d newsock %d pipe %d sock %d", 2098 sock_in, sock_out, newsock, startup_pipe, config_s[0]); 2099 dup2(newsock, STDIN_FILENO); 2100 dup2(STDIN_FILENO, STDOUT_FILENO); 2101 if (startup_pipe == -1) 2102 close(REEXEC_STARTUP_PIPE_FD); 2103 else if (startup_pipe != REEXEC_STARTUP_PIPE_FD) { 2104 dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD); 2105 close(startup_pipe); 2106 startup_pipe = REEXEC_STARTUP_PIPE_FD; 2107 } 2108 2109 dup2(config_s[1], REEXEC_CONFIG_PASS_FD); 2110 close(config_s[1]); 2111 2112 ssh_signal(SIGHUP, SIG_IGN); /* avoid reset to SIG_DFL */ 2113 execv(rexec_argv[0], rexec_argv); 2114 2115 /* Reexec has failed, fall back and continue */ 2116 error("rexec of %s failed: %s", rexec_argv[0], strerror(errno)); 2117 recv_rexec_state(REEXEC_CONFIG_PASS_FD, NULL); 2118 log_init(__progname, options.log_level, 2119 options.log_facility, log_stderr); 2120 2121 /* Clean up fds */ 2122 close(REEXEC_CONFIG_PASS_FD); 2123 newsock = sock_out = sock_in = dup(STDIN_FILENO); 2124 if (stdfd_devnull(1, 1, 0) == -1) 2125 error_f("stdfd_devnull failed"); 2126 debug("rexec cleanup in %d out %d newsock %d pipe %d sock %d", 2127 sock_in, sock_out, newsock, startup_pipe, config_s[0]); 2128 } 2129 2130 /* Executed child processes don't need these. */ 2131 fcntl(sock_out, F_SETFD, FD_CLOEXEC); 2132 fcntl(sock_in, F_SETFD, FD_CLOEXEC); 2133 2134 /* We will not restart on SIGHUP since it no longer makes sense. */ 2135 ssh_signal(SIGALRM, SIG_DFL); 2136 ssh_signal(SIGHUP, SIG_DFL); 2137 ssh_signal(SIGTERM, SIG_DFL); 2138 ssh_signal(SIGQUIT, SIG_DFL); 2139 ssh_signal(SIGCHLD, SIG_DFL); 2140 ssh_signal(SIGINT, SIG_DFL); 2141 2142 /* 2143 * Register our connection. This turns encryption off because we do 2144 * not have a key. 2145 */ 2146 if ((ssh = ssh_packet_set_connection(NULL, sock_in, sock_out)) == NULL) 2147 fatal("Unable to create connection"); 2148 the_active_state = ssh; 2149 ssh_packet_set_server(ssh); 2150 2151 check_ip_options(ssh); 2152 2153 /* Prepare the channels layer */ 2154 channel_init_channels(ssh); 2155 channel_set_af(ssh, options.address_family); 2156 process_permitopen(ssh, &options); 2157 2158 /* Set SO_KEEPALIVE if requested. */ 2159 if (options.tcp_keep_alive && ssh_packet_connection_is_on_socket(ssh) && 2160 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) == -1) 2161 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 2162 2163 if ((remote_port = ssh_remote_port(ssh)) < 0) { 2164 debug("ssh_remote_port failed"); 2165 cleanup_exit(255); 2166 } 2167 2168 if (options.routing_domain != NULL) 2169 set_process_rdomain(ssh, options.routing_domain); 2170 2171 /* 2172 * The rest of the code depends on the fact that 2173 * ssh_remote_ipaddr() caches the remote ip, even if 2174 * the socket goes away. 2175 */ 2176 remote_ip = ssh_remote_ipaddr(ssh); 2177 2178 #ifdef SSH_AUDIT_EVENTS 2179 audit_connection_from(remote_ip, remote_port); 2180 #endif 2181 2182 rdomain = ssh_packet_rdomain_in(ssh); 2183 2184 /* Log the connection. */ 2185 laddr = get_local_ipaddr(sock_in); 2186 verbose("Connection from %s port %d on %s port %d%s%s%s", 2187 remote_ip, remote_port, laddr, ssh_local_port(ssh), 2188 rdomain == NULL ? "" : " rdomain \"", 2189 rdomain == NULL ? "" : rdomain, 2190 rdomain == NULL ? "" : "\""); 2191 free(laddr); 2192 2193 /* 2194 * We don't want to listen forever unless the other side 2195 * successfully authenticates itself. So we set up an alarm which is 2196 * cleared after successful authentication. A limit of zero 2197 * indicates no limit. Note that we don't set the alarm in debugging 2198 * mode; it is just annoying to have the server exit just when you 2199 * are about to discover the bug. 2200 */ 2201 ssh_signal(SIGALRM, grace_alarm_handler); 2202 if (!debug_flag) 2203 alarm(options.login_grace_time); 2204 2205 if ((r = kex_exchange_identification(ssh, -1, 2206 options.version_addendum)) != 0) 2207 sshpkt_fatal(ssh, r, "banner exchange"); 2208 2209 ssh_packet_set_nonblocking(ssh); 2210 2211 /* allocate authentication context */ 2212 authctxt = xcalloc(1, sizeof(*authctxt)); 2213 ssh->authctxt = authctxt; 2214 2215 authctxt->loginmsg = loginmsg; 2216 2217 /* XXX global for cleanup, access from other modules */ 2218 the_authctxt = authctxt; 2219 2220 /* Set default key authentication options */ 2221 if ((auth_opts = sshauthopt_new_with_keys_defaults()) == NULL) 2222 fatal("allocation failed"); 2223 2224 /* prepare buffer to collect messages to display to user after login */ 2225 if ((loginmsg = sshbuf_new()) == NULL) 2226 fatal_f("sshbuf_new failed"); 2227 auth_debug_reset(); 2228 2229 if (use_privsep) { 2230 if (privsep_preauth(ssh) == 1) 2231 goto authenticated; 2232 } else if (have_agent) { 2233 if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) { 2234 error_r(r, "Unable to get agent socket"); 2235 have_agent = 0; 2236 } 2237 } 2238 2239 /* perform the key exchange */ 2240 /* authenticate user and start session */ 2241 do_ssh2_kex(ssh); 2242 do_authentication2(ssh); 2243 2244 /* 2245 * If we use privilege separation, the unprivileged child transfers 2246 * the current keystate and exits 2247 */ 2248 if (use_privsep) { 2249 mm_send_keystate(ssh, pmonitor); 2250 ssh_packet_clear_keys(ssh); 2251 exit(0); 2252 } 2253 2254 authenticated: 2255 /* 2256 * Cancel the alarm we set to limit the time taken for 2257 * authentication. 2258 */ 2259 alarm(0); 2260 ssh_signal(SIGALRM, SIG_DFL); 2261 authctxt->authenticated = 1; 2262 if (startup_pipe != -1) { 2263 close(startup_pipe); 2264 startup_pipe = -1; 2265 } 2266 2267 #ifdef SSH_AUDIT_EVENTS 2268 audit_event(ssh, SSH_AUTH_SUCCESS); 2269 #endif 2270 2271 #ifdef GSSAPI 2272 if (options.gss_authentication) { 2273 temporarily_use_uid(authctxt->pw); 2274 ssh_gssapi_storecreds(); 2275 restore_uid(); 2276 } 2277 #endif 2278 #ifdef USE_PAM 2279 if (options.use_pam) { 2280 do_pam_setcred(1); 2281 do_pam_session(ssh); 2282 } 2283 #endif 2284 2285 /* 2286 * In privilege separation, we fork another child and prepare 2287 * file descriptor passing. 2288 */ 2289 if (use_privsep) { 2290 privsep_postauth(ssh, authctxt); 2291 /* the monitor process [priv] will not return */ 2292 } 2293 2294 ssh_packet_set_timeout(ssh, options.client_alive_interval, 2295 options.client_alive_count_max); 2296 2297 /* Try to send all our hostkeys to the client */ 2298 notify_hostkeys(ssh); 2299 2300 /* Start session. */ 2301 do_authenticated(ssh, authctxt); 2302 2303 /* The connection has been terminated. */ 2304 ssh_packet_get_bytes(ssh, &ibytes, &obytes); 2305 verbose("Transferred: sent %llu, received %llu bytes", 2306 (unsigned long long)obytes, (unsigned long long)ibytes); 2307 2308 verbose("Closing connection to %.500s port %d", remote_ip, remote_port); 2309 2310 #ifdef USE_PAM 2311 if (options.use_pam) 2312 finish_pam(); 2313 #endif /* USE_PAM */ 2314 2315 #ifdef SSH_AUDIT_EVENTS 2316 PRIVSEP(audit_event(ssh, SSH_CONNECTION_CLOSE)); 2317 #endif 2318 2319 ssh_packet_close(ssh); 2320 2321 if (use_privsep) 2322 mm_terminate(); 2323 2324 exit(0); 2325 } 2326 2327 int 2328 sshd_hostkey_sign(struct ssh *ssh, struct sshkey *privkey, 2329 struct sshkey *pubkey, u_char **signature, size_t *slenp, 2330 const u_char *data, size_t dlen, const char *alg) 2331 { 2332 int r; 2333 2334 if (use_privsep) { 2335 if (privkey) { 2336 if (mm_sshkey_sign(ssh, privkey, signature, slenp, 2337 data, dlen, alg, options.sk_provider, NULL, 2338 ssh->compat) < 0) 2339 fatal_f("privkey sign failed"); 2340 } else { 2341 if (mm_sshkey_sign(ssh, pubkey, signature, slenp, 2342 data, dlen, alg, options.sk_provider, NULL, 2343 ssh->compat) < 0) 2344 fatal_f("pubkey sign failed"); 2345 } 2346 } else { 2347 if (privkey) { 2348 if (sshkey_sign(privkey, signature, slenp, data, dlen, 2349 alg, options.sk_provider, NULL, ssh->compat) < 0) 2350 fatal_f("privkey sign failed"); 2351 } else { 2352 if ((r = ssh_agent_sign(auth_sock, pubkey, 2353 signature, slenp, data, dlen, alg, 2354 ssh->compat)) != 0) { 2355 fatal_fr(r, "agent sign failed"); 2356 } 2357 } 2358 } 2359 return 0; 2360 } 2361 2362 /* SSH2 key exchange */ 2363 static void 2364 do_ssh2_kex(struct ssh *ssh) 2365 { 2366 char *myproposal[PROPOSAL_MAX] = { KEX_SERVER }; 2367 struct kex *kex; 2368 int r; 2369 2370 myproposal[PROPOSAL_KEX_ALGS] = compat_kex_proposal(ssh, 2371 options.kex_algorithms); 2372 myproposal[PROPOSAL_ENC_ALGS_CTOS] = compat_cipher_proposal(ssh, 2373 options.ciphers); 2374 myproposal[PROPOSAL_ENC_ALGS_STOC] = compat_cipher_proposal(ssh, 2375 options.ciphers); 2376 myproposal[PROPOSAL_MAC_ALGS_CTOS] = 2377 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs; 2378 2379 if (options.compression == COMP_NONE) { 2380 myproposal[PROPOSAL_COMP_ALGS_CTOS] = 2381 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none"; 2382 } 2383 2384 if (options.rekey_limit || options.rekey_interval) 2385 ssh_packet_set_rekey_limits(ssh, options.rekey_limit, 2386 options.rekey_interval); 2387 2388 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = compat_pkalg_proposal( 2389 ssh, list_hostkey_types()); 2390 2391 /* start key exchange */ 2392 if ((r = kex_setup(ssh, myproposal)) != 0) 2393 fatal_r(r, "kex_setup"); 2394 kex = ssh->kex; 2395 #ifdef WITH_OPENSSL 2396 kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server; 2397 kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server; 2398 kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server; 2399 kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server; 2400 kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server; 2401 kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 2402 kex->kex[KEX_DH_GEX_SHA256] = kexgex_server; 2403 # ifdef OPENSSL_HAS_ECC 2404 kex->kex[KEX_ECDH_SHA2] = kex_gen_server; 2405 # endif 2406 #endif 2407 kex->kex[KEX_C25519_SHA256] = kex_gen_server; 2408 kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_server; 2409 kex->load_host_public_key=&get_hostkey_public_by_type; 2410 kex->load_host_private_key=&get_hostkey_private_by_type; 2411 kex->host_key_index=&get_hostkey_index; 2412 kex->sign = sshd_hostkey_sign; 2413 2414 ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &kex->done); 2415 2416 #ifdef DEBUG_KEXDH 2417 /* send 1st encrypted/maced/compressed message */ 2418 if ((r = sshpkt_start(ssh, SSH2_MSG_IGNORE)) != 0 || 2419 (r = sshpkt_put_cstring(ssh, "markus")) != 0 || 2420 (r = sshpkt_send(ssh)) != 0 || 2421 (r = ssh_packet_write_wait(ssh)) != 0) 2422 fatal_fr(r, "send test"); 2423 #endif 2424 debug("KEX done"); 2425 } 2426 2427 /* server specific fatal cleanup */ 2428 void 2429 cleanup_exit(int i) 2430 { 2431 if (the_active_state != NULL && the_authctxt != NULL) { 2432 do_cleanup(the_active_state, the_authctxt); 2433 if (use_privsep && privsep_is_preauth && 2434 pmonitor != NULL && pmonitor->m_pid > 1) { 2435 debug("Killing privsep child %d", pmonitor->m_pid); 2436 if (kill(pmonitor->m_pid, SIGKILL) != 0 && 2437 errno != ESRCH) { 2438 error_f("kill(%d): %s", pmonitor->m_pid, 2439 strerror(errno)); 2440 } 2441 } 2442 } 2443 #ifdef SSH_AUDIT_EVENTS 2444 /* done after do_cleanup so it can cancel the PAM auth 'thread' */ 2445 if (the_active_state != NULL && (!use_privsep || mm_is_monitor())) 2446 audit_event(the_active_state, SSH_CONNECTION_ABANDON); 2447 #endif 2448 _exit(i); 2449 } 2450