1/* $OpenBSD: sshd.c,v 1.602 2024/01/08 00:34:34 djm Exp $ */ 2/* 3 * Author: Tatu Ylonen <ylo@cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 5 * All rights reserved 6 * This program is the ssh daemon. It listens for connections from clients, 7 * and performs authentication, executes use commands or shell, and forwards 8 * information to/from the application to the user client over an encrypted 9 * connection. This can also handle forwarding of X11, TCP/IP, and 10 * authentication agent connections. 11 * 12 * As far as I am concerned, the code I have written for this software 13 * can be used freely for any purpose. Any derived versions of this 14 * software must be clearly marked as such, and if the derived work is 15 * incompatible with the protocol description in the RFC file, it must be 16 * called by a name other than "ssh" or "Secure Shell". 17 * 18 * SSH2 implementation: 19 * Privilege Separation: 20 * 21 * Copyright (c) 2000, 2001, 2002 Markus Friedl. All rights reserved. 22 * Copyright (c) 2002 Niels Provos. All rights reserved. 23 * 24 * Redistribution and use in source and binary forms, with or without 25 * modification, are permitted provided that the following conditions 26 * are met: 27 * 1. Redistributions of source code must retain the above copyright 28 * notice, this list of conditions and the following disclaimer. 29 * 2. Redistributions in binary form must reproduce the above copyright 30 * notice, this list of conditions and the following disclaimer in the 31 * documentation and/or other materials provided with the distribution. 32 * 33 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 34 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 35 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 36 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 37 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 38 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 39 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 40 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 41 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 42 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 43 */ 44 45#include "includes.h" 46 47#include <sys/types.h> 48#include <sys/ioctl.h> 49#include <sys/mman.h> 50#include <sys/socket.h> 51#ifdef HAVE_SYS_STAT_H 52# include <sys/stat.h> 53#endif 54#ifdef HAVE_SYS_TIME_H 55# include <sys/time.h> 56#endif 57#include "openbsd-compat/sys-tree.h" 58#include "openbsd-compat/sys-queue.h" 59#include <sys/wait.h> 60 61#include <errno.h> 62#include <fcntl.h> 63#include <netdb.h> 64#ifdef HAVE_PATHS_H 65#include <paths.h> 66#endif 67#include <grp.h> 68#ifdef HAVE_POLL_H 69#include <poll.h> 70#endif 71#include <pwd.h> 72#include <signal.h> 73#include <stdarg.h> 74#include <stdio.h> 75#include <stdlib.h> 76#include <string.h> 77#include <unistd.h> 78#include <limits.h> 79 80#ifdef WITH_OPENSSL 81#include <openssl/dh.h> 82#include <openssl/bn.h> 83#include <openssl/rand.h> 84#include "openbsd-compat/openssl-compat.h" 85#endif 86 87#ifdef HAVE_SECUREWARE 88#include <sys/security.h> 89#include <prot.h> 90#endif 91 92#ifdef __FreeBSD__ 93#include <resolv.h> 94#if defined(GSSAPI) && defined(HAVE_GSSAPI_GSSAPI_H) 95#include <gssapi/gssapi.h> 96#elif defined(GSSAPI) && defined(HAVE_GSSAPI_H) 97#include <gssapi.h> 98#endif 99#endif 100 101#include "xmalloc.h" 102#include "ssh.h" 103#include "ssh2.h" 104#include "sshpty.h" 105#include "packet.h" 106#include "log.h" 107#include "sshbuf.h" 108#include "misc.h" 109#include "match.h" 110#include "servconf.h" 111#include "uidswap.h" 112#include "compat.h" 113#include "cipher.h" 114#include "digest.h" 115#include "sshkey.h" 116#include "kex.h" 117#include "authfile.h" 118#include "pathnames.h" 119#include "atomicio.h" 120#include "canohost.h" 121#include "hostfile.h" 122#include "auth.h" 123#include "authfd.h" 124#include "msg.h" 125#include "dispatch.h" 126#include "channels.h" 127#include "session.h" 128#include "monitor.h" 129#ifdef GSSAPI 130#include "ssh-gss.h" 131#endif 132#include "monitor_wrap.h" 133#include "ssh-sandbox.h" 134#include "auth-options.h" 135#include "version.h" 136#include "ssherr.h" 137#include "sk-api.h" 138#include "srclimit.h" 139#include "dh.h" 140#include "blacklist_client.h" 141 142#ifdef LIBWRAP 143#include <tcpd.h> 144#include <syslog.h> 145#endif /* LIBWRAP */ 146 147/* Re-exec fds */ 148#define REEXEC_DEVCRYPTO_RESERVED_FD (STDERR_FILENO + 1) 149#define REEXEC_STARTUP_PIPE_FD (STDERR_FILENO + 2) 150#define REEXEC_CONFIG_PASS_FD (STDERR_FILENO + 3) 151#define REEXEC_MIN_FREE_FD (STDERR_FILENO + 4) 152 153extern char *__progname; 154 155/* Server configuration options. */ 156ServerOptions options; 157 158/* Name of the server configuration file. */ 159char *config_file_name = _PATH_SERVER_CONFIG_FILE; 160 161/* 162 * Debug mode flag. This can be set on the command line. If debug 163 * mode is enabled, extra debugging output will be sent to the system 164 * log, the daemon will not go to background, and will exit after processing 165 * the first connection. 166 */ 167int debug_flag = 0; 168 169/* 170 * Indicating that the daemon should only test the configuration and keys. 171 * If test_flag > 1 ("-T" flag), then sshd will also dump the effective 172 * configuration, optionally using connection information provided by the 173 * "-C" flag. 174 */ 175static int test_flag = 0; 176 177/* Flag indicating that the daemon is being started from inetd. */ 178static int inetd_flag = 0; 179 180/* Flag indicating that sshd should not detach and become a daemon. */ 181static int no_daemon_flag = 0; 182 183/* debug goes to stderr unless inetd_flag is set */ 184static int log_stderr = 0; 185 186/* Saved arguments to main(). */ 187static char **saved_argv; 188static int saved_argc; 189 190/* re-exec */ 191static int rexeced_flag = 0; 192static int rexec_flag = 1; 193static int rexec_argc = 0; 194static char **rexec_argv; 195 196/* 197 * The sockets that the server is listening; this is used in the SIGHUP 198 * signal handler. 199 */ 200#define MAX_LISTEN_SOCKS 16 201static int listen_socks[MAX_LISTEN_SOCKS]; 202static int num_listen_socks = 0; 203 204/* Daemon's agent connection */ 205int auth_sock = -1; 206static int have_agent = 0; 207 208/* 209 * Any really sensitive data in the application is contained in this 210 * structure. The idea is that this structure could be locked into memory so 211 * that the pages do not get written into swap. However, there are some 212 * problems. The private key contains BIGNUMs, and we do not (in principle) 213 * have access to the internals of them, and locking just the structure is 214 * not very useful. Currently, memory locking is not implemented. 215 */ 216struct { 217 struct sshkey **host_keys; /* all private host keys */ 218 struct sshkey **host_pubkeys; /* all public host keys */ 219 struct sshkey **host_certificates; /* all public host certificates */ 220 int have_ssh2_key; 221} sensitive_data; 222 223/* This is set to true when a signal is received. */ 224static volatile sig_atomic_t received_sighup = 0; 225static volatile sig_atomic_t received_sigterm = 0; 226 227/* record remote hostname or ip */ 228u_int utmp_len = HOST_NAME_MAX+1; 229 230/* 231 * startup_pipes/flags are used for tracking children of the listening sshd 232 * process early in their lifespans. This tracking is needed for three things: 233 * 234 * 1) Implementing the MaxStartups limit of concurrent unauthenticated 235 * connections. 236 * 2) Avoiding a race condition for SIGHUP processing, where child processes 237 * may have listen_socks open that could collide with main listener process 238 * after it restarts. 239 * 3) Ensuring that rexec'd sshd processes have received their initial state 240 * from the parent listen process before handling SIGHUP. 241 * 242 * Child processes signal that they have completed closure of the listen_socks 243 * and (if applicable) received their rexec state by sending a char over their 244 * sock. Child processes signal that authentication has completed by closing 245 * the sock (or by exiting). 246 */ 247static int *startup_pipes = NULL; 248static int *startup_flags = NULL; /* Indicates child closed listener */ 249static int startup_pipe = -1; /* in child */ 250 251/* variables used for privilege separation */ 252int use_privsep = -1; 253struct monitor *pmonitor = NULL; 254int privsep_is_preauth = 1; 255static int privsep_chroot = 1; 256 257/* global connection state and authentication contexts */ 258Authctxt *the_authctxt = NULL; 259struct ssh *the_active_state; 260 261/* global key/cert auth options. XXX move to permanent ssh->authctxt? */ 262struct sshauthopt *auth_opts = NULL; 263 264/* sshd_config buffer */ 265struct sshbuf *cfg; 266 267/* Included files from the configuration file */ 268struct include_list includes = TAILQ_HEAD_INITIALIZER(includes); 269 270/* message to be displayed after login */ 271struct sshbuf *loginmsg; 272 273/* Unprivileged user */ 274struct passwd *privsep_pw = NULL; 275 276/* Prototypes for various functions defined later in this file. */ 277void destroy_sensitive_data(void); 278void demote_sensitive_data(void); 279static void do_ssh2_kex(struct ssh *); 280 281static char *listener_proctitle; 282 283/* 284 * Close all listening sockets 285 */ 286static void 287close_listen_socks(void) 288{ 289 int i; 290 291 for (i = 0; i < num_listen_socks; i++) 292 close(listen_socks[i]); 293 num_listen_socks = 0; 294} 295 296static void 297close_startup_pipes(void) 298{ 299 int i; 300 301 if (startup_pipes) 302 for (i = 0; i < options.max_startups; i++) 303 if (startup_pipes[i] != -1) 304 close(startup_pipes[i]); 305} 306 307/* 308 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP; 309 * the effect is to reread the configuration file (and to regenerate 310 * the server key). 311 */ 312 313static void 314sighup_handler(int sig) 315{ 316 received_sighup = 1; 317} 318 319/* 320 * Called from the main program after receiving SIGHUP. 321 * Restarts the server. 322 */ 323static void 324sighup_restart(void) 325{ 326 logit("Received SIGHUP; restarting."); 327 if (options.pid_file != NULL) 328 unlink(options.pid_file); 329 platform_pre_restart(); 330 close_listen_socks(); 331 close_startup_pipes(); 332 ssh_signal(SIGHUP, SIG_IGN); /* will be restored after exec */ 333 execv(saved_argv[0], saved_argv); 334 logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], 335 strerror(errno)); 336 exit(1); 337} 338 339/* 340 * Generic signal handler for terminating signals in the master daemon. 341 */ 342static void 343sigterm_handler(int sig) 344{ 345 received_sigterm = sig; 346} 347 348/* 349 * SIGCHLD handler. This is called whenever a child dies. This will then 350 * reap any zombies left by exited children. 351 */ 352static void 353main_sigchld_handler(int sig) 354{ 355 int save_errno = errno; 356 pid_t pid; 357 int status; 358 359 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 360 (pid == -1 && errno == EINTR)) 361 ; 362 errno = save_errno; 363} 364 365/* 366 * Signal handler for the alarm after the login grace period has expired. 367 */ 368static void 369grace_alarm_handler(int sig) 370{ 371 /* 372 * Try to kill any processes that we have spawned, E.g. authorized 373 * keys command helpers or privsep children. 374 */ 375 if (getpgid(0) == getpid()) { 376 ssh_signal(SIGTERM, SIG_IGN); 377 kill(0, SIGTERM); 378 } 379 380 BLACKLIST_NOTIFY(the_active_state, BLACKLIST_AUTH_FAIL, "ssh"); 381 382 /* Log error and exit. */ 383 sigdie("Timeout before authentication for %s port %d", 384 ssh_remote_ipaddr(the_active_state), 385 ssh_remote_port(the_active_state)); 386} 387 388/* Destroy the host and server keys. They will no longer be needed. */ 389void 390destroy_sensitive_data(void) 391{ 392 u_int i; 393 394 for (i = 0; i < options.num_host_key_files; i++) { 395 if (sensitive_data.host_keys[i]) { 396 sshkey_free(sensitive_data.host_keys[i]); 397 sensitive_data.host_keys[i] = NULL; 398 } 399 if (sensitive_data.host_certificates[i]) { 400 sshkey_free(sensitive_data.host_certificates[i]); 401 sensitive_data.host_certificates[i] = NULL; 402 } 403 } 404} 405 406/* Demote private to public keys for network child */ 407void 408demote_sensitive_data(void) 409{ 410 struct sshkey *tmp; 411 u_int i; 412 int r; 413 414 for (i = 0; i < options.num_host_key_files; i++) { 415 if (sensitive_data.host_keys[i]) { 416 if ((r = sshkey_from_private( 417 sensitive_data.host_keys[i], &tmp)) != 0) 418 fatal_r(r, "could not demote host %s key", 419 sshkey_type(sensitive_data.host_keys[i])); 420 sshkey_free(sensitive_data.host_keys[i]); 421 sensitive_data.host_keys[i] = tmp; 422 } 423 /* Certs do not need demotion */ 424 } 425} 426 427static void 428reseed_prngs(void) 429{ 430 u_int32_t rnd[256]; 431 432#ifdef WITH_OPENSSL 433 RAND_poll(); 434#endif 435 arc4random_stir(); /* noop on recent arc4random() implementations */ 436 arc4random_buf(rnd, sizeof(rnd)); /* let arc4random notice PID change */ 437 438#ifdef WITH_OPENSSL 439 RAND_seed(rnd, sizeof(rnd)); 440 /* give libcrypto a chance to notice the PID change */ 441 if ((RAND_bytes((u_char *)rnd, 1)) != 1) 442 fatal("%s: RAND_bytes failed", __func__); 443#endif 444 445 explicit_bzero(rnd, sizeof(rnd)); 446} 447 448static void 449privsep_preauth_child(void) 450{ 451 gid_t gidset[1]; 452 453 /* Enable challenge-response authentication for privilege separation */ 454 privsep_challenge_enable(); 455 456#ifdef GSSAPI 457 /* Cache supported mechanism OIDs for later use */ 458 ssh_gssapi_prepare_supported_oids(); 459#endif 460 461 reseed_prngs(); 462 463 /* Demote the private keys to public keys. */ 464 demote_sensitive_data(); 465 466 /* Demote the child */ 467 if (privsep_chroot) { 468 /* Change our root directory */ 469 if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1) 470 fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR, 471 strerror(errno)); 472 if (chdir("/") == -1) 473 fatal("chdir(\"/\"): %s", strerror(errno)); 474 475 /* Drop our privileges */ 476 debug3("privsep user:group %u:%u", (u_int)privsep_pw->pw_uid, 477 (u_int)privsep_pw->pw_gid); 478 gidset[0] = privsep_pw->pw_gid; 479 if (setgroups(1, gidset) == -1) 480 fatal("setgroups: %.100s", strerror(errno)); 481 permanently_set_uid(privsep_pw); 482 } 483} 484 485static int 486privsep_preauth(struct ssh *ssh) 487{ 488 int status, r; 489 pid_t pid; 490 struct ssh_sandbox *box = NULL; 491 492 /* Set up unprivileged child process to deal with network data */ 493 pmonitor = monitor_init(); 494 /* Store a pointer to the kex for later rekeying */ 495 pmonitor->m_pkex = &ssh->kex; 496 497 if (use_privsep == PRIVSEP_ON) 498 box = ssh_sandbox_init(pmonitor); 499 pid = fork(); 500 if (pid == -1) { 501 fatal("fork of unprivileged child failed"); 502 } else if (pid != 0) { 503 debug2("Network child is on pid %ld", (long)pid); 504 505 pmonitor->m_pid = pid; 506 if (have_agent) { 507 r = ssh_get_authentication_socket(&auth_sock); 508 if (r != 0) { 509 error_r(r, "Could not get agent socket"); 510 have_agent = 0; 511 } 512 } 513 if (box != NULL) 514 ssh_sandbox_parent_preauth(box, pid); 515 monitor_child_preauth(ssh, pmonitor); 516 517 /* Wait for the child's exit status */ 518 while (waitpid(pid, &status, 0) == -1) { 519 if (errno == EINTR) 520 continue; 521 pmonitor->m_pid = -1; 522 fatal_f("waitpid: %s", strerror(errno)); 523 } 524 privsep_is_preauth = 0; 525 pmonitor->m_pid = -1; 526 if (WIFEXITED(status)) { 527 if (WEXITSTATUS(status) != 0) 528 fatal_f("preauth child exited with status %d", 529 WEXITSTATUS(status)); 530 } else if (WIFSIGNALED(status)) 531 fatal_f("preauth child terminated by signal %d", 532 WTERMSIG(status)); 533 if (box != NULL) 534 ssh_sandbox_parent_finish(box); 535 return 1; 536 } else { 537 /* child */ 538 close(pmonitor->m_sendfd); 539 close(pmonitor->m_log_recvfd); 540 541 /* Arrange for logging to be sent to the monitor */ 542 set_log_handler(mm_log_handler, pmonitor); 543 544 privsep_preauth_child(); 545 setproctitle("%s", "[net]"); 546 if (box != NULL) 547 ssh_sandbox_child(box); 548 549 return 0; 550 } 551} 552 553static void 554privsep_postauth(struct ssh *ssh, Authctxt *authctxt) 555{ 556#ifdef DISABLE_FD_PASSING 557 if (1) { 558#else 559 if (authctxt->pw->pw_uid == 0) { 560#endif 561 /* File descriptor passing is broken or root login */ 562 use_privsep = 0; 563 goto skip; 564 } 565 566 /* New socket pair */ 567 monitor_reinit(pmonitor); 568 569 pmonitor->m_pid = fork(); 570 if (pmonitor->m_pid == -1) 571 fatal("fork of unprivileged child failed"); 572 else if (pmonitor->m_pid != 0) { 573 verbose("User child is on pid %ld", (long)pmonitor->m_pid); 574 sshbuf_reset(loginmsg); 575 monitor_clear_keystate(ssh, pmonitor); 576 monitor_child_postauth(ssh, pmonitor); 577 578 /* NEVERREACHED */ 579 exit(0); 580 } 581 582 /* child */ 583 584 close(pmonitor->m_sendfd); 585 pmonitor->m_sendfd = -1; 586 587 /* Demote the private keys to public keys. */ 588 demote_sensitive_data(); 589 590 reseed_prngs(); 591 592 /* Drop privileges */ 593 do_setusercontext(authctxt->pw); 594 595 skip: 596 /* It is safe now to apply the key state */ 597 monitor_apply_keystate(ssh, pmonitor); 598 599 /* 600 * Tell the packet layer that authentication was successful, since 601 * this information is not part of the key state. 602 */ 603 ssh_packet_set_authenticated(ssh); 604} 605 606static void 607append_hostkey_type(struct sshbuf *b, const char *s) 608{ 609 int r; 610 611 if (match_pattern_list(s, options.hostkeyalgorithms, 0) != 1) { 612 debug3_f("%s key not permitted by HostkeyAlgorithms", s); 613 return; 614 } 615 if ((r = sshbuf_putf(b, "%s%s", sshbuf_len(b) > 0 ? "," : "", s)) != 0) 616 fatal_fr(r, "sshbuf_putf"); 617} 618 619static char * 620list_hostkey_types(void) 621{ 622 struct sshbuf *b; 623 struct sshkey *key; 624 char *ret; 625 u_int i; 626 627 if ((b = sshbuf_new()) == NULL) 628 fatal_f("sshbuf_new failed"); 629 for (i = 0; i < options.num_host_key_files; i++) { 630 key = sensitive_data.host_keys[i]; 631 if (key == NULL) 632 key = sensitive_data.host_pubkeys[i]; 633 if (key == NULL) 634 continue; 635 switch (key->type) { 636 case KEY_RSA: 637 /* for RSA we also support SHA2 signatures */ 638 append_hostkey_type(b, "rsa-sha2-512"); 639 append_hostkey_type(b, "rsa-sha2-256"); 640 /* FALLTHROUGH */ 641 case KEY_DSA: 642 case KEY_ECDSA: 643 case KEY_ED25519: 644 case KEY_ECDSA_SK: 645 case KEY_ED25519_SK: 646 case KEY_XMSS: 647 append_hostkey_type(b, sshkey_ssh_name(key)); 648 break; 649 } 650 /* If the private key has a cert peer, then list that too */ 651 key = sensitive_data.host_certificates[i]; 652 if (key == NULL) 653 continue; 654 switch (key->type) { 655 case KEY_RSA_CERT: 656 /* for RSA we also support SHA2 signatures */ 657 append_hostkey_type(b, 658 "rsa-sha2-512-cert-v01@openssh.com"); 659 append_hostkey_type(b, 660 "rsa-sha2-256-cert-v01@openssh.com"); 661 /* FALLTHROUGH */ 662 case KEY_DSA_CERT: 663 case KEY_ECDSA_CERT: 664 case KEY_ED25519_CERT: 665 case KEY_ECDSA_SK_CERT: 666 case KEY_ED25519_SK_CERT: 667 case KEY_XMSS_CERT: 668 append_hostkey_type(b, sshkey_ssh_name(key)); 669 break; 670 } 671 } 672 if ((ret = sshbuf_dup_string(b)) == NULL) 673 fatal_f("sshbuf_dup_string failed"); 674 sshbuf_free(b); 675 debug_f("%s", ret); 676 return ret; 677} 678 679static struct sshkey * 680get_hostkey_by_type(int type, int nid, int need_private, struct ssh *ssh) 681{ 682 u_int i; 683 struct sshkey *key; 684 685 for (i = 0; i < options.num_host_key_files; i++) { 686 switch (type) { 687 case KEY_RSA_CERT: 688 case KEY_DSA_CERT: 689 case KEY_ECDSA_CERT: 690 case KEY_ED25519_CERT: 691 case KEY_ECDSA_SK_CERT: 692 case KEY_ED25519_SK_CERT: 693 case KEY_XMSS_CERT: 694 key = sensitive_data.host_certificates[i]; 695 break; 696 default: 697 key = sensitive_data.host_keys[i]; 698 if (key == NULL && !need_private) 699 key = sensitive_data.host_pubkeys[i]; 700 break; 701 } 702 if (key == NULL || key->type != type) 703 continue; 704 switch (type) { 705 case KEY_ECDSA: 706 case KEY_ECDSA_SK: 707 case KEY_ECDSA_CERT: 708 case KEY_ECDSA_SK_CERT: 709 if (key->ecdsa_nid != nid) 710 continue; 711 /* FALLTHROUGH */ 712 default: 713 return need_private ? 714 sensitive_data.host_keys[i] : key; 715 } 716 } 717 return NULL; 718} 719 720struct sshkey * 721get_hostkey_public_by_type(int type, int nid, struct ssh *ssh) 722{ 723 return get_hostkey_by_type(type, nid, 0, ssh); 724} 725 726struct sshkey * 727get_hostkey_private_by_type(int type, int nid, struct ssh *ssh) 728{ 729 return get_hostkey_by_type(type, nid, 1, ssh); 730} 731 732struct sshkey * 733get_hostkey_by_index(int ind) 734{ 735 if (ind < 0 || (u_int)ind >= options.num_host_key_files) 736 return (NULL); 737 return (sensitive_data.host_keys[ind]); 738} 739 740struct sshkey * 741get_hostkey_public_by_index(int ind, struct ssh *ssh) 742{ 743 if (ind < 0 || (u_int)ind >= options.num_host_key_files) 744 return (NULL); 745 return (sensitive_data.host_pubkeys[ind]); 746} 747 748int 749get_hostkey_index(struct sshkey *key, int compare, struct ssh *ssh) 750{ 751 u_int i; 752 753 for (i = 0; i < options.num_host_key_files; i++) { 754 if (sshkey_is_cert(key)) { 755 if (key == sensitive_data.host_certificates[i] || 756 (compare && sensitive_data.host_certificates[i] && 757 sshkey_equal(key, 758 sensitive_data.host_certificates[i]))) 759 return (i); 760 } else { 761 if (key == sensitive_data.host_keys[i] || 762 (compare && sensitive_data.host_keys[i] && 763 sshkey_equal(key, sensitive_data.host_keys[i]))) 764 return (i); 765 if (key == sensitive_data.host_pubkeys[i] || 766 (compare && sensitive_data.host_pubkeys[i] && 767 sshkey_equal(key, sensitive_data.host_pubkeys[i]))) 768 return (i); 769 } 770 } 771 return (-1); 772} 773 774/* Inform the client of all hostkeys */ 775static void 776notify_hostkeys(struct ssh *ssh) 777{ 778 struct sshbuf *buf; 779 struct sshkey *key; 780 u_int i, nkeys; 781 int r; 782 char *fp; 783 784 /* Some clients cannot cope with the hostkeys message, skip those. */ 785 if (ssh->compat & SSH_BUG_HOSTKEYS) 786 return; 787 788 if ((buf = sshbuf_new()) == NULL) 789 fatal_f("sshbuf_new"); 790 for (i = nkeys = 0; i < options.num_host_key_files; i++) { 791 key = get_hostkey_public_by_index(i, ssh); 792 if (key == NULL || key->type == KEY_UNSPEC || 793 sshkey_is_cert(key)) 794 continue; 795 fp = sshkey_fingerprint(key, options.fingerprint_hash, 796 SSH_FP_DEFAULT); 797 debug3_f("key %d: %s %s", i, sshkey_ssh_name(key), fp); 798 free(fp); 799 if (nkeys == 0) { 800 /* 801 * Start building the request when we find the 802 * first usable key. 803 */ 804 if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 || 805 (r = sshpkt_put_cstring(ssh, "hostkeys-00@openssh.com")) != 0 || 806 (r = sshpkt_put_u8(ssh, 0)) != 0) /* want reply */ 807 sshpkt_fatal(ssh, r, "%s: start request", __func__); 808 } 809 /* Append the key to the request */ 810 sshbuf_reset(buf); 811 if ((r = sshkey_putb(key, buf)) != 0) 812 fatal_fr(r, "couldn't put hostkey %d", i); 813 if ((r = sshpkt_put_stringb(ssh, buf)) != 0) 814 sshpkt_fatal(ssh, r, "%s: append key", __func__); 815 nkeys++; 816 } 817 debug3_f("sent %u hostkeys", nkeys); 818 if (nkeys == 0) 819 fatal_f("no hostkeys"); 820 if ((r = sshpkt_send(ssh)) != 0) 821 sshpkt_fatal(ssh, r, "%s: send", __func__); 822 sshbuf_free(buf); 823} 824 825/* 826 * returns 1 if connection should be dropped, 0 otherwise. 827 * dropping starts at connection #max_startups_begin with a probability 828 * of (max_startups_rate/100). the probability increases linearly until 829 * all connections are dropped for startups > max_startups 830 */ 831static int 832should_drop_connection(int startups) 833{ 834 int p, r; 835 836 if (startups < options.max_startups_begin) 837 return 0; 838 if (startups >= options.max_startups) 839 return 1; 840 if (options.max_startups_rate == 100) 841 return 1; 842 843 p = 100 - options.max_startups_rate; 844 p *= startups - options.max_startups_begin; 845 p /= options.max_startups - options.max_startups_begin; 846 p += options.max_startups_rate; 847 r = arc4random_uniform(100); 848 849 debug_f("p %d, r %d", p, r); 850 return (r < p) ? 1 : 0; 851} 852 853/* 854 * Check whether connection should be accepted by MaxStartups. 855 * Returns 0 if the connection is accepted. If the connection is refused, 856 * returns 1 and attempts to send notification to client. 857 * Logs when the MaxStartups condition is entered or exited, and periodically 858 * while in that state. 859 */ 860static int 861drop_connection(int sock, int startups, int notify_pipe) 862{ 863 char *laddr, *raddr; 864 const char msg[] = "Exceeded MaxStartups\r\n"; 865 static time_t last_drop, first_drop; 866 static u_int ndropped; 867 LogLevel drop_level = SYSLOG_LEVEL_VERBOSE; 868 time_t now; 869 870 now = monotime(); 871 if (!should_drop_connection(startups) && 872 srclimit_check_allow(sock, notify_pipe) == 1) { 873 if (last_drop != 0 && 874 startups < options.max_startups_begin - 1) { 875 /* XXX maybe need better hysteresis here */ 876 logit("exited MaxStartups throttling after %s, " 877 "%u connections dropped", 878 fmt_timeframe(now - first_drop), ndropped); 879 last_drop = 0; 880 } 881 return 0; 882 } 883 884#define SSHD_MAXSTARTUPS_LOG_INTERVAL (5 * 60) 885 if (last_drop == 0) { 886 error("beginning MaxStartups throttling"); 887 drop_level = SYSLOG_LEVEL_INFO; 888 first_drop = now; 889 ndropped = 0; 890 } else if (last_drop + SSHD_MAXSTARTUPS_LOG_INTERVAL < now) { 891 /* Periodic logs */ 892 error("in MaxStartups throttling for %s, " 893 "%u connections dropped", 894 fmt_timeframe(now - first_drop), ndropped + 1); 895 drop_level = SYSLOG_LEVEL_INFO; 896 } 897 last_drop = now; 898 ndropped++; 899 900 laddr = get_local_ipaddr(sock); 901 raddr = get_peer_ipaddr(sock); 902 do_log2(drop_level, "drop connection #%d from [%s]:%d on [%s]:%d " 903 "past MaxStartups", startups, raddr, get_peer_port(sock), 904 laddr, get_local_port(sock)); 905 free(laddr); 906 free(raddr); 907 /* best-effort notification to client */ 908 (void)write(sock, msg, sizeof(msg) - 1); 909 return 1; 910} 911 912static void 913usage(void) 914{ 915 if (options.version_addendum != NULL && 916 *options.version_addendum != '\0') 917 fprintf(stderr, "%s %s, %s\n", 918 SSH_RELEASE, 919 options.version_addendum, SSH_OPENSSL_VERSION); 920 else 921 fprintf(stderr, "%s, %s\n", 922 SSH_RELEASE, SSH_OPENSSL_VERSION); 923 fprintf(stderr, 924"usage: sshd [-46DdeGiqTtV] [-C connection_spec] [-c host_cert_file]\n" 925" [-E log_file] [-f config_file] [-g login_grace_time]\n" 926" [-h host_key_file] [-o option] [-p port] [-u len]\n" 927 ); 928 exit(1); 929} 930 931static void 932send_rexec_state(int fd, struct sshbuf *conf) 933{ 934 struct sshbuf *m = NULL, *inc = NULL; 935 struct include_item *item = NULL; 936 int r; 937 938 debug3_f("entering fd = %d config len %zu", fd, 939 sshbuf_len(conf)); 940 941 if ((m = sshbuf_new()) == NULL || (inc = sshbuf_new()) == NULL) 942 fatal_f("sshbuf_new failed"); 943 944 /* pack includes into a string */ 945 TAILQ_FOREACH(item, &includes, entry) { 946 if ((r = sshbuf_put_cstring(inc, item->selector)) != 0 || 947 (r = sshbuf_put_cstring(inc, item->filename)) != 0 || 948 (r = sshbuf_put_stringb(inc, item->contents)) != 0) 949 fatal_fr(r, "compose includes"); 950 } 951 952 /* 953 * Protocol from reexec master to child: 954 * string configuration 955 * string included_files[] { 956 * string selector 957 * string filename 958 * string contents 959 * } 960 */ 961 if ((r = sshbuf_put_stringb(m, conf)) != 0 || 962 (r = sshbuf_put_stringb(m, inc)) != 0) 963 fatal_fr(r, "compose config"); 964 if (ssh_msg_send(fd, 0, m) == -1) 965 error_f("ssh_msg_send failed"); 966 967 sshbuf_free(m); 968 sshbuf_free(inc); 969 970 debug3_f("done"); 971} 972 973static void 974recv_rexec_state(int fd, struct sshbuf *conf) 975{ 976 struct sshbuf *m, *inc; 977 u_char *cp, ver; 978 size_t len; 979 int r; 980 struct include_item *item; 981 982 debug3_f("entering fd = %d", fd); 983 984 if ((m = sshbuf_new()) == NULL || (inc = sshbuf_new()) == NULL) 985 fatal_f("sshbuf_new failed"); 986 if (ssh_msg_recv(fd, m) == -1) 987 fatal_f("ssh_msg_recv failed"); 988 if ((r = sshbuf_get_u8(m, &ver)) != 0) 989 fatal_fr(r, "parse version"); 990 if (ver != 0) 991 fatal_f("rexec version mismatch"); 992 if ((r = sshbuf_get_string(m, &cp, &len)) != 0 || 993 (r = sshbuf_get_stringb(m, inc)) != 0) 994 fatal_fr(r, "parse config"); 995 996 if (conf != NULL && (r = sshbuf_put(conf, cp, len))) 997 fatal_fr(r, "sshbuf_put"); 998 999 while (sshbuf_len(inc) != 0) { 1000 item = xcalloc(1, sizeof(*item)); 1001 if ((item->contents = sshbuf_new()) == NULL) 1002 fatal_f("sshbuf_new failed"); 1003 if ((r = sshbuf_get_cstring(inc, &item->selector, NULL)) != 0 || 1004 (r = sshbuf_get_cstring(inc, &item->filename, NULL)) != 0 || 1005 (r = sshbuf_get_stringb(inc, item->contents)) != 0) 1006 fatal_fr(r, "parse includes"); 1007 TAILQ_INSERT_TAIL(&includes, item, entry); 1008 } 1009 1010 free(cp); 1011 sshbuf_free(m); 1012 1013 debug3_f("done"); 1014} 1015 1016/* Accept a connection from inetd */ 1017static void 1018server_accept_inetd(int *sock_in, int *sock_out) 1019{ 1020 if (rexeced_flag) { 1021 close(REEXEC_CONFIG_PASS_FD); 1022 *sock_in = *sock_out = dup(STDIN_FILENO); 1023 } else { 1024 *sock_in = dup(STDIN_FILENO); 1025 *sock_out = dup(STDOUT_FILENO); 1026 } 1027 /* 1028 * We intentionally do not close the descriptors 0, 1, and 2 1029 * as our code for setting the descriptors won't work if 1030 * ttyfd happens to be one of those. 1031 */ 1032 if (stdfd_devnull(1, 1, !log_stderr) == -1) 1033 error_f("stdfd_devnull failed"); 1034 debug("inetd sockets after dupping: %d, %d", *sock_in, *sock_out); 1035} 1036 1037/* 1038 * Listen for TCP connections 1039 */ 1040static void 1041listen_on_addrs(struct listenaddr *la) 1042{ 1043 int ret, listen_sock; 1044 struct addrinfo *ai; 1045 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 1046 1047 for (ai = la->addrs; ai; ai = ai->ai_next) { 1048 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 1049 continue; 1050 if (num_listen_socks >= MAX_LISTEN_SOCKS) 1051 fatal("Too many listen sockets. " 1052 "Enlarge MAX_LISTEN_SOCKS"); 1053 if ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen, 1054 ntop, sizeof(ntop), strport, sizeof(strport), 1055 NI_NUMERICHOST|NI_NUMERICSERV)) != 0) { 1056 error("getnameinfo failed: %.100s", 1057 ssh_gai_strerror(ret)); 1058 continue; 1059 } 1060 /* Create socket for listening. */ 1061 listen_sock = socket(ai->ai_family, ai->ai_socktype, 1062 ai->ai_protocol); 1063 if (listen_sock == -1) { 1064 /* kernel may not support ipv6 */ 1065 verbose("socket: %.100s", strerror(errno)); 1066 continue; 1067 } 1068 if (set_nonblock(listen_sock) == -1) { 1069 close(listen_sock); 1070 continue; 1071 } 1072 if (fcntl(listen_sock, F_SETFD, FD_CLOEXEC) == -1) { 1073 verbose("socket: CLOEXEC: %s", strerror(errno)); 1074 close(listen_sock); 1075 continue; 1076 } 1077 /* Socket options */ 1078 set_reuseaddr(listen_sock); 1079 if (la->rdomain != NULL && 1080 set_rdomain(listen_sock, la->rdomain) == -1) { 1081 close(listen_sock); 1082 continue; 1083 } 1084 1085 /* Only communicate in IPv6 over AF_INET6 sockets. */ 1086 if (ai->ai_family == AF_INET6) 1087 sock_set_v6only(listen_sock); 1088 1089 debug("Bind to port %s on %s.", strport, ntop); 1090 1091 /* Bind the socket to the desired port. */ 1092 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) == -1) { 1093 error("Bind to port %s on %s failed: %.200s.", 1094 strport, ntop, strerror(errno)); 1095 close(listen_sock); 1096 continue; 1097 } 1098 listen_socks[num_listen_socks] = listen_sock; 1099 num_listen_socks++; 1100 1101 /* Start listening on the port. */ 1102 if (listen(listen_sock, SSH_LISTEN_BACKLOG) == -1) 1103 fatal("listen on [%s]:%s: %.100s", 1104 ntop, strport, strerror(errno)); 1105 logit("Server listening on %s port %s%s%s.", 1106 ntop, strport, 1107 la->rdomain == NULL ? "" : " rdomain ", 1108 la->rdomain == NULL ? "" : la->rdomain); 1109 } 1110} 1111 1112static void 1113server_listen(void) 1114{ 1115 u_int i; 1116 1117 /* Initialise per-source limit tracking. */ 1118 srclimit_init(options.max_startups, options.per_source_max_startups, 1119 options.per_source_masklen_ipv4, options.per_source_masklen_ipv6); 1120 1121 for (i = 0; i < options.num_listen_addrs; i++) { 1122 listen_on_addrs(&options.listen_addrs[i]); 1123 freeaddrinfo(options.listen_addrs[i].addrs); 1124 free(options.listen_addrs[i].rdomain); 1125 memset(&options.listen_addrs[i], 0, 1126 sizeof(options.listen_addrs[i])); 1127 } 1128 free(options.listen_addrs); 1129 options.listen_addrs = NULL; 1130 options.num_listen_addrs = 0; 1131 1132 if (!num_listen_socks) 1133 fatal("Cannot bind any address."); 1134} 1135 1136/* 1137 * The main TCP accept loop. Note that, for the non-debug case, returns 1138 * from this function are in a forked subprocess. 1139 */ 1140static void 1141server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s) 1142{ 1143 struct pollfd *pfd = NULL; 1144 int i, j, ret, npfd; 1145 int ostartups = -1, startups = 0, listening = 0, lameduck = 0; 1146 int startup_p[2] = { -1 , -1 }, *startup_pollfd; 1147 char c = 0; 1148 struct sockaddr_storage from; 1149 socklen_t fromlen; 1150 pid_t pid; 1151 u_char rnd[256]; 1152 sigset_t nsigset, osigset; 1153#ifdef LIBWRAP 1154 struct request_info req; 1155 1156 request_init(&req, RQ_DAEMON, __progname, 0); 1157#endif 1158 1159 /* pipes connected to unauthenticated child sshd processes */ 1160 startup_pipes = xcalloc(options.max_startups, sizeof(int)); 1161 startup_flags = xcalloc(options.max_startups, sizeof(int)); 1162 startup_pollfd = xcalloc(options.max_startups, sizeof(int)); 1163 for (i = 0; i < options.max_startups; i++) 1164 startup_pipes[i] = -1; 1165 1166 /* 1167 * Prepare signal mask that we use to block signals that might set 1168 * received_sigterm or received_sighup, so that we are guaranteed 1169 * to immediately wake up the ppoll if a signal is received after 1170 * the flag is checked. 1171 */ 1172 sigemptyset(&nsigset); 1173 sigaddset(&nsigset, SIGHUP); 1174 sigaddset(&nsigset, SIGCHLD); 1175 sigaddset(&nsigset, SIGTERM); 1176 sigaddset(&nsigset, SIGQUIT); 1177 1178 /* sized for worst-case */ 1179 pfd = xcalloc(num_listen_socks + options.max_startups, 1180 sizeof(struct pollfd)); 1181 1182 /* 1183 * Stay listening for connections until the system crashes or 1184 * the daemon is killed with a signal. 1185 */ 1186 for (;;) { 1187 sigprocmask(SIG_BLOCK, &nsigset, &osigset); 1188 if (received_sigterm) { 1189 logit("Received signal %d; terminating.", 1190 (int) received_sigterm); 1191 close_listen_socks(); 1192 if (options.pid_file != NULL) 1193 unlink(options.pid_file); 1194 exit(received_sigterm == SIGTERM ? 0 : 255); 1195 } 1196 if (ostartups != startups) { 1197 setproctitle("%s [listener] %d of %d-%d startups", 1198 listener_proctitle, startups, 1199 options.max_startups_begin, options.max_startups); 1200 ostartups = startups; 1201 } 1202 if (received_sighup) { 1203 if (!lameduck) { 1204 debug("Received SIGHUP; waiting for children"); 1205 close_listen_socks(); 1206 lameduck = 1; 1207 } 1208 if (listening <= 0) { 1209 sigprocmask(SIG_SETMASK, &osigset, NULL); 1210 sighup_restart(); 1211 } 1212 } 1213 1214 for (i = 0; i < num_listen_socks; i++) { 1215 pfd[i].fd = listen_socks[i]; 1216 pfd[i].events = POLLIN; 1217 } 1218 npfd = num_listen_socks; 1219 for (i = 0; i < options.max_startups; i++) { 1220 startup_pollfd[i] = -1; 1221 if (startup_pipes[i] != -1) { 1222 pfd[npfd].fd = startup_pipes[i]; 1223 pfd[npfd].events = POLLIN; 1224 startup_pollfd[i] = npfd++; 1225 } 1226 } 1227 1228 /* Wait until a connection arrives or a child exits. */ 1229 ret = ppoll(pfd, npfd, NULL, &osigset); 1230 if (ret == -1 && errno != EINTR) { 1231 error("ppoll: %.100s", strerror(errno)); 1232 if (errno == EINVAL) 1233 cleanup_exit(1); /* can't recover */ 1234 } 1235 sigprocmask(SIG_SETMASK, &osigset, NULL); 1236 if (ret == -1) 1237 continue; 1238 1239 for (i = 0; i < options.max_startups; i++) { 1240 if (startup_pipes[i] == -1 || 1241 startup_pollfd[i] == -1 || 1242 !(pfd[startup_pollfd[i]].revents & (POLLIN|POLLHUP))) 1243 continue; 1244 switch (read(startup_pipes[i], &c, sizeof(c))) { 1245 case -1: 1246 if (errno == EINTR || errno == EAGAIN) 1247 continue; 1248 if (errno != EPIPE) { 1249 error_f("startup pipe %d (fd=%d): " 1250 "read %s", i, startup_pipes[i], 1251 strerror(errno)); 1252 } 1253 /* FALLTHROUGH */ 1254 case 0: 1255 /* child exited or completed auth */ 1256 close(startup_pipes[i]); 1257 srclimit_done(startup_pipes[i]); 1258 startup_pipes[i] = -1; 1259 startups--; 1260 if (startup_flags[i]) 1261 listening--; 1262 break; 1263 case 1: 1264 /* child has finished preliminaries */ 1265 if (startup_flags[i]) { 1266 listening--; 1267 startup_flags[i] = 0; 1268 } 1269 break; 1270 } 1271 } 1272 for (i = 0; i < num_listen_socks; i++) { 1273 if (!(pfd[i].revents & POLLIN)) 1274 continue; 1275 fromlen = sizeof(from); 1276 *newsock = accept(listen_socks[i], 1277 (struct sockaddr *)&from, &fromlen); 1278 if (*newsock == -1) { 1279 if (errno != EINTR && errno != EWOULDBLOCK && 1280 errno != ECONNABORTED && errno != EAGAIN) 1281 error("accept: %.100s", 1282 strerror(errno)); 1283 if (errno == EMFILE || errno == ENFILE) 1284 usleep(100 * 1000); 1285 continue; 1286 } 1287#ifdef LIBWRAP 1288 /* Check whether logins are denied from this host. */ 1289 request_set(&req, RQ_FILE, *newsock, 1290 RQ_CLIENT_NAME, "", RQ_CLIENT_ADDR, "", 0); 1291 sock_host(&req); 1292 if (!hosts_access(&req)) { 1293 const struct linger l = { .l_onoff = 1, 1294 .l_linger = 0 }; 1295 1296 (void )setsockopt(*newsock, SOL_SOCKET, 1297 SO_LINGER, &l, sizeof(l)); 1298 (void )close(*newsock); 1299 /* 1300 * Mimic message from libwrap's refuse() as 1301 * precisely as we can afford. The authentic 1302 * message prints the IP address and the 1303 * hostname it resolves to in parentheses. If 1304 * the IP address cannot be resolved to a 1305 * hostname, the IP address will be repeated 1306 * in parentheses. As name resolution in the 1307 * main server loop could stall, and logging 1308 * resolved names adds little or no value to 1309 * incident investigation, this implementation 1310 * only repeats the IP address in parentheses. 1311 * This should resemble librwap's refuse() 1312 * closely enough not to break auditing 1313 * software like sshguard or custom scripts. 1314 */ 1315 syslog(LOG_WARNING, 1316 "refused connect from %s (%s)", 1317 eval_hostaddr(req.client), 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 close(*newsock); 1325 continue; 1326 } 1327 if (pipe(startup_p) == -1) { 1328 error_f("pipe(startup_p): %s", strerror(errno)); 1329 close(*newsock); 1330 continue; 1331 } 1332 if (drop_connection(*newsock, startups, startup_p[0])) { 1333 close(*newsock); 1334 close(startup_p[0]); 1335 close(startup_p[1]); 1336 continue; 1337 } 1338 1339 if (rexec_flag && socketpair(AF_UNIX, 1340 SOCK_STREAM, 0, config_s) == -1) { 1341 error("reexec socketpair: %s", 1342 strerror(errno)); 1343 close(*newsock); 1344 close(startup_p[0]); 1345 close(startup_p[1]); 1346 continue; 1347 } 1348 1349 for (j = 0; j < options.max_startups; j++) 1350 if (startup_pipes[j] == -1) { 1351 startup_pipes[j] = startup_p[0]; 1352 startups++; 1353 startup_flags[j] = 1; 1354 break; 1355 } 1356 1357 /* 1358 * Got connection. Fork a child to handle it, unless 1359 * we are in debugging mode. 1360 */ 1361 if (debug_flag) { 1362 /* 1363 * In debugging mode. Close the listening 1364 * socket, and start processing the 1365 * connection without forking. 1366 */ 1367 debug("Server will not fork when running in debugging mode."); 1368 close_listen_socks(); 1369 *sock_in = *newsock; 1370 *sock_out = *newsock; 1371 close(startup_p[0]); 1372 close(startup_p[1]); 1373 startup_pipe = -1; 1374 pid = getpid(); 1375 if (rexec_flag) { 1376 send_rexec_state(config_s[0], cfg); 1377 close(config_s[0]); 1378 } 1379 free(pfd); 1380 return; 1381 } 1382 1383 /* 1384 * Normal production daemon. Fork, and have 1385 * the child process the connection. The 1386 * parent continues listening. 1387 */ 1388 platform_pre_fork(); 1389 listening++; 1390 if ((pid = fork()) == 0) { 1391 /* 1392 * Child. Close the listening and 1393 * max_startup sockets. Start using 1394 * the accepted socket. Reinitialize 1395 * logging (since our pid has changed). 1396 * We return from this function to handle 1397 * the connection. 1398 */ 1399 platform_post_fork_child(); 1400 startup_pipe = startup_p[1]; 1401 close_startup_pipes(); 1402 close_listen_socks(); 1403 *sock_in = *newsock; 1404 *sock_out = *newsock; 1405 log_init(__progname, 1406 options.log_level, 1407 options.log_facility, 1408 log_stderr); 1409 if (rexec_flag) 1410 close(config_s[0]); 1411 else { 1412 /* 1413 * Signal parent that the preliminaries 1414 * for this child are complete. For the 1415 * re-exec case, this happens after the 1416 * child has received the rexec state 1417 * from the server. 1418 */ 1419 (void)atomicio(vwrite, startup_pipe, 1420 "\0", 1); 1421 } 1422 free(pfd); 1423 return; 1424 } 1425 1426 /* Parent. Stay in the loop. */ 1427 platform_post_fork_parent(pid); 1428 if (pid == -1) 1429 error("fork: %.100s", strerror(errno)); 1430 else 1431 debug("Forked child %ld.", (long)pid); 1432 1433 close(startup_p[1]); 1434 1435 if (rexec_flag) { 1436 close(config_s[1]); 1437 send_rexec_state(config_s[0], cfg); 1438 close(config_s[0]); 1439 } 1440 close(*newsock); 1441 1442 /* 1443 * Ensure that our random state differs 1444 * from that of the child 1445 */ 1446 arc4random_stir(); 1447 arc4random_buf(rnd, sizeof(rnd)); 1448#ifdef WITH_OPENSSL 1449 RAND_seed(rnd, sizeof(rnd)); 1450 if ((RAND_bytes((u_char *)rnd, 1)) != 1) 1451 fatal("%s: RAND_bytes failed", __func__); 1452#endif 1453 explicit_bzero(rnd, sizeof(rnd)); 1454 } 1455 } 1456} 1457 1458/* 1459 * If IP options are supported, make sure there are none (log and 1460 * return an error if any are found). Basically we are worried about 1461 * source routing; it can be used to pretend you are somebody 1462 * (ip-address) you are not. That itself may be "almost acceptable" 1463 * under certain circumstances, but rhosts authentication is useless 1464 * if source routing is accepted. Notice also that if we just dropped 1465 * source routing here, the other side could use IP spoofing to do 1466 * rest of the interaction and could still bypass security. So we 1467 * exit here if we detect any IP options. 1468 */ 1469static void 1470check_ip_options(struct ssh *ssh) 1471{ 1472#ifdef IP_OPTIONS 1473 int sock_in = ssh_packet_get_connection_in(ssh); 1474 struct sockaddr_storage from; 1475 u_char opts[200]; 1476 socklen_t i, option_size = sizeof(opts), fromlen = sizeof(from); 1477 char text[sizeof(opts) * 3 + 1]; 1478 1479 memset(&from, 0, sizeof(from)); 1480 if (getpeername(sock_in, (struct sockaddr *)&from, 1481 &fromlen) == -1) 1482 return; 1483 if (from.ss_family != AF_INET) 1484 return; 1485 /* XXX IPv6 options? */ 1486 1487 if (getsockopt(sock_in, IPPROTO_IP, IP_OPTIONS, opts, 1488 &option_size) >= 0 && option_size != 0) { 1489 text[0] = '\0'; 1490 for (i = 0; i < option_size; i++) 1491 snprintf(text + i*3, sizeof(text) - i*3, 1492 " %2.2x", opts[i]); 1493 fatal("Connection from %.100s port %d with IP opts: %.800s", 1494 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), text); 1495 } 1496 return; 1497#endif /* IP_OPTIONS */ 1498} 1499 1500/* Set the routing domain for this process */ 1501static void 1502set_process_rdomain(struct ssh *ssh, const char *name) 1503{ 1504#if defined(HAVE_SYS_SET_PROCESS_RDOMAIN) 1505 if (name == NULL) 1506 return; /* default */ 1507 1508 if (strcmp(name, "%D") == 0) { 1509 /* "expands" to routing domain of connection */ 1510 if ((name = ssh_packet_rdomain_in(ssh)) == NULL) 1511 return; 1512 } 1513 /* NB. We don't pass 'ssh' to sys_set_process_rdomain() */ 1514 return sys_set_process_rdomain(name); 1515#elif defined(__OpenBSD__) 1516 int rtable, ortable = getrtable(); 1517 const char *errstr; 1518 1519 if (name == NULL) 1520 return; /* default */ 1521 1522 if (strcmp(name, "%D") == 0) { 1523 /* "expands" to routing domain of connection */ 1524 if ((name = ssh_packet_rdomain_in(ssh)) == NULL) 1525 return; 1526 } 1527 1528 rtable = (int)strtonum(name, 0, 255, &errstr); 1529 if (errstr != NULL) /* Shouldn't happen */ 1530 fatal("Invalid routing domain \"%s\": %s", name, errstr); 1531 if (rtable != ortable && setrtable(rtable) != 0) 1532 fatal("Unable to set routing domain %d: %s", 1533 rtable, strerror(errno)); 1534 debug_f("set routing domain %d (was %d)", rtable, ortable); 1535#else /* defined(__OpenBSD__) */ 1536 fatal("Unable to set routing domain: not supported in this platform"); 1537#endif 1538} 1539 1540static void 1541accumulate_host_timing_secret(struct sshbuf *server_cfg, 1542 struct sshkey *key) 1543{ 1544 static struct ssh_digest_ctx *ctx; 1545 u_char *hash; 1546 size_t len; 1547 struct sshbuf *buf; 1548 int r; 1549 1550 if (ctx == NULL && (ctx = ssh_digest_start(SSH_DIGEST_SHA512)) == NULL) 1551 fatal_f("ssh_digest_start"); 1552 if (key == NULL) { /* finalize */ 1553 /* add server config in case we are using agent for host keys */ 1554 if (ssh_digest_update(ctx, sshbuf_ptr(server_cfg), 1555 sshbuf_len(server_cfg)) != 0) 1556 fatal_f("ssh_digest_update"); 1557 len = ssh_digest_bytes(SSH_DIGEST_SHA512); 1558 hash = xmalloc(len); 1559 if (ssh_digest_final(ctx, hash, len) != 0) 1560 fatal_f("ssh_digest_final"); 1561 options.timing_secret = PEEK_U64(hash); 1562 freezero(hash, len); 1563 ssh_digest_free(ctx); 1564 ctx = NULL; 1565 return; 1566 } 1567 if ((buf = sshbuf_new()) == NULL) 1568 fatal_f("could not allocate buffer"); 1569 if ((r = sshkey_private_serialize(key, buf)) != 0) 1570 fatal_fr(r, "encode %s key", sshkey_ssh_name(key)); 1571 if (ssh_digest_update(ctx, sshbuf_ptr(buf), sshbuf_len(buf)) != 0) 1572 fatal_f("ssh_digest_update"); 1573 sshbuf_reset(buf); 1574 sshbuf_free(buf); 1575} 1576 1577static char * 1578prepare_proctitle(int ac, char **av) 1579{ 1580 char *ret = NULL; 1581 int i; 1582 1583 for (i = 0; i < ac; i++) 1584 xextendf(&ret, " ", "%s", av[i]); 1585 return ret; 1586} 1587 1588static void 1589print_config(struct ssh *ssh, struct connection_info *connection_info) 1590{ 1591 /* 1592 * If no connection info was provided by -C then use 1593 * use a blank one that will cause no predicate to match. 1594 */ 1595 if (connection_info == NULL) 1596 connection_info = get_connection_info(ssh, 0, 0); 1597 connection_info->test = 1; 1598 parse_server_match_config(&options, &includes, connection_info); 1599 dump_config(&options); 1600 exit(0); 1601} 1602 1603/* 1604 * Main program for the daemon. 1605 */ 1606int 1607main(int ac, char **av) 1608{ 1609 struct ssh *ssh = NULL; 1610 extern char *optarg; 1611 extern int optind; 1612 int r, opt, on = 1, do_dump_cfg = 0, already_daemon, remote_port; 1613 int sock_in = -1, sock_out = -1, newsock = -1; 1614 const char *remote_ip, *rdomain; 1615 char *fp, *line, *laddr, *logfile = NULL; 1616 int config_s[2] = { -1 , -1 }; 1617 u_int i, j; 1618 u_int64_t ibytes, obytes; 1619 mode_t new_umask; 1620 struct sshkey *key; 1621 struct sshkey *pubkey; 1622 int keytype; 1623 Authctxt *authctxt; 1624 struct connection_info *connection_info = NULL; 1625 sigset_t sigmask; 1626 1627#ifdef HAVE_SECUREWARE 1628 (void)set_auth_parameters(ac, av); 1629#endif 1630 __progname = ssh_get_progname(av[0]); 1631 1632 sigemptyset(&sigmask); 1633 sigprocmask(SIG_SETMASK, &sigmask, NULL); 1634 1635 /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */ 1636 saved_argc = ac; 1637 rexec_argc = ac; 1638 saved_argv = xcalloc(ac + 1, sizeof(*saved_argv)); 1639 for (i = 0; (int)i < ac; i++) 1640 saved_argv[i] = xstrdup(av[i]); 1641 saved_argv[i] = NULL; 1642 1643#ifndef HAVE_SETPROCTITLE 1644 /* Prepare for later setproctitle emulation */ 1645 compat_init_setproctitle(ac, av); 1646 av = saved_argv; 1647#endif 1648 1649 if (geteuid() == 0 && setgroups(0, NULL) == -1) 1650 debug("setgroups(): %.200s", strerror(errno)); 1651 1652 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */ 1653 sanitise_stdfd(); 1654 1655 /* Initialize configuration options to their default values. */ 1656 initialize_server_options(&options); 1657 1658 /* Parse command-line arguments. */ 1659 while ((opt = getopt(ac, av, 1660 "C:E:b:c:f:g:h:k:o:p:u:46DGQRTdeiqrtV")) != -1) { 1661 switch (opt) { 1662 case '4': 1663 options.address_family = AF_INET; 1664 break; 1665 case '6': 1666 options.address_family = AF_INET6; 1667 break; 1668 case 'f': 1669 config_file_name = optarg; 1670 break; 1671 case 'c': 1672 servconf_add_hostcert("[command-line]", 0, 1673 &options, optarg); 1674 break; 1675 case 'd': 1676 if (debug_flag == 0) { 1677 debug_flag = 1; 1678 options.log_level = SYSLOG_LEVEL_DEBUG1; 1679 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) 1680 options.log_level++; 1681 break; 1682 case 'D': 1683 no_daemon_flag = 1; 1684 break; 1685 case 'G': 1686 do_dump_cfg = 1; 1687 break; 1688 case 'E': 1689 logfile = optarg; 1690 /* FALLTHROUGH */ 1691 case 'e': 1692 log_stderr = 1; 1693 break; 1694 case 'i': 1695 inetd_flag = 1; 1696 break; 1697 case 'r': 1698 rexec_flag = 0; 1699 break; 1700 case 'R': 1701 rexeced_flag = 1; 1702 inetd_flag = 1; 1703 break; 1704 case 'Q': 1705 /* ignored */ 1706 break; 1707 case 'q': 1708 options.log_level = SYSLOG_LEVEL_QUIET; 1709 break; 1710 case 'b': 1711 /* protocol 1, ignored */ 1712 break; 1713 case 'p': 1714 options.ports_from_cmdline = 1; 1715 if (options.num_ports >= MAX_PORTS) { 1716 fprintf(stderr, "too many ports.\n"); 1717 exit(1); 1718 } 1719 options.ports[options.num_ports++] = a2port(optarg); 1720 if (options.ports[options.num_ports-1] <= 0) { 1721 fprintf(stderr, "Bad port number.\n"); 1722 exit(1); 1723 } 1724 break; 1725 case 'g': 1726 if ((options.login_grace_time = convtime(optarg)) == -1) { 1727 fprintf(stderr, "Invalid login grace time.\n"); 1728 exit(1); 1729 } 1730 break; 1731 case 'k': 1732 /* protocol 1, ignored */ 1733 break; 1734 case 'h': 1735 servconf_add_hostkey("[command-line]", 0, 1736 &options, optarg, 1); 1737 break; 1738 case 't': 1739 test_flag = 1; 1740 break; 1741 case 'T': 1742 test_flag = 2; 1743 break; 1744 case 'C': 1745 connection_info = get_connection_info(ssh, 0, 0); 1746 if (parse_server_match_testspec(connection_info, 1747 optarg) == -1) 1748 exit(1); 1749 break; 1750 case 'u': 1751 utmp_len = (u_int)strtonum(optarg, 0, HOST_NAME_MAX+1+1, NULL); 1752 if (utmp_len > HOST_NAME_MAX+1) { 1753 fprintf(stderr, "Invalid utmp length.\n"); 1754 exit(1); 1755 } 1756 break; 1757 case 'o': 1758 line = xstrdup(optarg); 1759 if (process_server_config_line(&options, line, 1760 "command-line", 0, NULL, NULL, &includes) != 0) 1761 exit(1); 1762 free(line); 1763 break; 1764 case 'V': 1765 fprintf(stderr, "%s, %s\n", 1766 SSH_RELEASE, SSH_OPENSSL_VERSION); 1767 exit(0); 1768 default: 1769 usage(); 1770 break; 1771 } 1772 } 1773 if (rexeced_flag || inetd_flag) 1774 rexec_flag = 0; 1775 if (!test_flag && !do_dump_cfg && rexec_flag && !path_absolute(av[0])) 1776 fatal("sshd re-exec requires execution with an absolute path"); 1777 if (rexeced_flag) 1778 closefrom(REEXEC_MIN_FREE_FD); 1779 else 1780 closefrom(REEXEC_DEVCRYPTO_RESERVED_FD); 1781 1782 seed_rng(); 1783 1784 /* If requested, redirect the logs to the specified logfile. */ 1785 if (logfile != NULL) 1786 log_redirect_stderr_to(logfile); 1787 /* 1788 * Force logging to stderr until we have loaded the private host 1789 * key (unless started from inetd) 1790 */ 1791 log_init(__progname, 1792 options.log_level == SYSLOG_LEVEL_NOT_SET ? 1793 SYSLOG_LEVEL_INFO : options.log_level, 1794 options.log_facility == SYSLOG_FACILITY_NOT_SET ? 1795 SYSLOG_FACILITY_AUTH : options.log_facility, 1796 log_stderr || !inetd_flag || debug_flag); 1797 1798 /* 1799 * Unset KRB5CCNAME, otherwise the user's session may inherit it from 1800 * root's environment 1801 */ 1802 if (getenv("KRB5CCNAME") != NULL) 1803 (void) unsetenv("KRB5CCNAME"); 1804 1805 sensitive_data.have_ssh2_key = 0; 1806 1807 /* 1808 * If we're not doing an extended test do not silently ignore connection 1809 * test params. 1810 */ 1811 if (test_flag < 2 && connection_info != NULL) 1812 fatal("Config test connection parameter (-C) provided without " 1813 "test mode (-T)"); 1814 1815 /* Fetch our configuration */ 1816 if ((cfg = sshbuf_new()) == NULL) 1817 fatal_f("sshbuf_new failed"); 1818 if (rexeced_flag) { 1819 setproctitle("%s", "[rexeced]"); 1820 recv_rexec_state(REEXEC_CONFIG_PASS_FD, cfg); 1821 if (!debug_flag) { 1822 startup_pipe = dup(REEXEC_STARTUP_PIPE_FD); 1823 close(REEXEC_STARTUP_PIPE_FD); 1824 /* 1825 * Signal parent that this child is at a point where 1826 * they can go away if they have a SIGHUP pending. 1827 */ 1828 (void)atomicio(vwrite, startup_pipe, "\0", 1); 1829 } 1830 } else if (strcasecmp(config_file_name, "none") != 0) 1831 load_server_config(config_file_name, cfg); 1832 1833 parse_server_config(&options, rexeced_flag ? "rexec" : config_file_name, 1834 cfg, &includes, NULL, rexeced_flag); 1835 1836#ifdef WITH_OPENSSL 1837 if (options.moduli_file != NULL) 1838 dh_set_moduli_file(options.moduli_file); 1839#endif 1840 1841 /* Fill in default values for those options not explicitly set. */ 1842 fill_default_server_options(&options); 1843 1844 /* Check that options are sensible */ 1845 if (options.authorized_keys_command_user == NULL && 1846 (options.authorized_keys_command != NULL && 1847 strcasecmp(options.authorized_keys_command, "none") != 0)) 1848 fatal("AuthorizedKeysCommand set without " 1849 "AuthorizedKeysCommandUser"); 1850 if (options.authorized_principals_command_user == NULL && 1851 (options.authorized_principals_command != NULL && 1852 strcasecmp(options.authorized_principals_command, "none") != 0)) 1853 fatal("AuthorizedPrincipalsCommand set without " 1854 "AuthorizedPrincipalsCommandUser"); 1855 1856 /* 1857 * Check whether there is any path through configured auth methods. 1858 * Unfortunately it is not possible to verify this generally before 1859 * daemonisation in the presence of Match block, but this catches 1860 * and warns for trivial misconfigurations that could break login. 1861 */ 1862 if (options.num_auth_methods != 0) { 1863 for (i = 0; i < options.num_auth_methods; i++) { 1864 if (auth2_methods_valid(options.auth_methods[i], 1865 1) == 0) 1866 break; 1867 } 1868 if (i >= options.num_auth_methods) 1869 fatal("AuthenticationMethods cannot be satisfied by " 1870 "enabled authentication methods"); 1871 } 1872 1873 /* Check that there are no remaining arguments. */ 1874 if (optind < ac) { 1875 fprintf(stderr, "Extra argument %s.\n", av[optind]); 1876 exit(1); 1877 } 1878 1879 debug("sshd version %s, %s", SSH_VERSION, SSH_OPENSSL_VERSION); 1880 1881 if (do_dump_cfg) 1882 print_config(ssh, connection_info); 1883 1884 /* Store privilege separation user for later use if required. */ 1885 privsep_chroot = use_privsep && (getuid() == 0 || geteuid() == 0); 1886 if ((privsep_pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) { 1887 if (privsep_chroot || options.kerberos_authentication) 1888 fatal("Privilege separation user %s does not exist", 1889 SSH_PRIVSEP_USER); 1890 } else { 1891 privsep_pw = pwcopy(privsep_pw); 1892 freezero(privsep_pw->pw_passwd, strlen(privsep_pw->pw_passwd)); 1893 privsep_pw->pw_passwd = xstrdup("*"); 1894 } 1895 endpwent(); 1896 1897 /* load host keys */ 1898 sensitive_data.host_keys = xcalloc(options.num_host_key_files, 1899 sizeof(struct sshkey *)); 1900 sensitive_data.host_pubkeys = xcalloc(options.num_host_key_files, 1901 sizeof(struct sshkey *)); 1902 1903 if (options.host_key_agent) { 1904 if (strcmp(options.host_key_agent, SSH_AUTHSOCKET_ENV_NAME)) 1905 setenv(SSH_AUTHSOCKET_ENV_NAME, 1906 options.host_key_agent, 1); 1907 if ((r = ssh_get_authentication_socket(NULL)) == 0) 1908 have_agent = 1; 1909 else 1910 error_r(r, "Could not connect to agent \"%s\"", 1911 options.host_key_agent); 1912 } 1913 1914 for (i = 0; i < options.num_host_key_files; i++) { 1915 int ll = options.host_key_file_userprovided[i] ? 1916 SYSLOG_LEVEL_ERROR : SYSLOG_LEVEL_DEBUG1; 1917 1918 if (options.host_key_files[i] == NULL) 1919 continue; 1920 if ((r = sshkey_load_private(options.host_key_files[i], "", 1921 &key, NULL)) != 0 && r != SSH_ERR_SYSTEM_ERROR) 1922 do_log2_r(r, ll, "Unable to load host key \"%s\"", 1923 options.host_key_files[i]); 1924 if (sshkey_is_sk(key) && 1925 key->sk_flags & SSH_SK_USER_PRESENCE_REQD) { 1926 debug("host key %s requires user presence, ignoring", 1927 options.host_key_files[i]); 1928 key->sk_flags &= ~SSH_SK_USER_PRESENCE_REQD; 1929 } 1930 if (r == 0 && key != NULL && 1931 (r = sshkey_shield_private(key)) != 0) { 1932 do_log2_r(r, ll, "Unable to shield host key \"%s\"", 1933 options.host_key_files[i]); 1934 sshkey_free(key); 1935 key = NULL; 1936 } 1937 if ((r = sshkey_load_public(options.host_key_files[i], 1938 &pubkey, NULL)) != 0 && r != SSH_ERR_SYSTEM_ERROR) 1939 do_log2_r(r, ll, "Unable to load host key \"%s\"", 1940 options.host_key_files[i]); 1941 if (pubkey != NULL && key != NULL) { 1942 if (!sshkey_equal(pubkey, key)) { 1943 error("Public key for %s does not match " 1944 "private key", options.host_key_files[i]); 1945 sshkey_free(pubkey); 1946 pubkey = NULL; 1947 } 1948 } 1949 if (pubkey == NULL && key != NULL) { 1950 if ((r = sshkey_from_private(key, &pubkey)) != 0) 1951 fatal_r(r, "Could not demote key: \"%s\"", 1952 options.host_key_files[i]); 1953 } 1954 if (pubkey != NULL && (r = sshkey_check_rsa_length(pubkey, 1955 options.required_rsa_size)) != 0) { 1956 error_fr(r, "Host key %s", options.host_key_files[i]); 1957 sshkey_free(pubkey); 1958 sshkey_free(key); 1959 continue; 1960 } 1961 sensitive_data.host_keys[i] = key; 1962 sensitive_data.host_pubkeys[i] = pubkey; 1963 1964 if (key == NULL && pubkey != NULL && have_agent) { 1965 debug("will rely on agent for hostkey %s", 1966 options.host_key_files[i]); 1967 keytype = pubkey->type; 1968 } else if (key != NULL) { 1969 keytype = key->type; 1970 accumulate_host_timing_secret(cfg, key); 1971 } else { 1972 do_log2(ll, "Unable to load host key: %s", 1973 options.host_key_files[i]); 1974 sensitive_data.host_keys[i] = NULL; 1975 sensitive_data.host_pubkeys[i] = NULL; 1976 continue; 1977 } 1978 1979 switch (keytype) { 1980 case KEY_RSA: 1981 case KEY_DSA: 1982 case KEY_ECDSA: 1983 case KEY_ED25519: 1984 case KEY_ECDSA_SK: 1985 case KEY_ED25519_SK: 1986 case KEY_XMSS: 1987 if (have_agent || key != NULL) 1988 sensitive_data.have_ssh2_key = 1; 1989 break; 1990 } 1991 if ((fp = sshkey_fingerprint(pubkey, options.fingerprint_hash, 1992 SSH_FP_DEFAULT)) == NULL) 1993 fatal("sshkey_fingerprint failed"); 1994 debug("%s host key #%d: %s %s", 1995 key ? "private" : "agent", i, sshkey_ssh_name(pubkey), fp); 1996 free(fp); 1997 } 1998 accumulate_host_timing_secret(cfg, NULL); 1999 if (!sensitive_data.have_ssh2_key) { 2000 logit("sshd: no hostkeys available -- exiting."); 2001 exit(1); 2002 } 2003 2004 /* 2005 * Load certificates. They are stored in an array at identical 2006 * indices to the public keys that they relate to. 2007 */ 2008 sensitive_data.host_certificates = xcalloc(options.num_host_key_files, 2009 sizeof(struct sshkey *)); 2010 for (i = 0; i < options.num_host_key_files; i++) 2011 sensitive_data.host_certificates[i] = NULL; 2012 2013 for (i = 0; i < options.num_host_cert_files; i++) { 2014 if (options.host_cert_files[i] == NULL) 2015 continue; 2016 if ((r = sshkey_load_public(options.host_cert_files[i], 2017 &key, NULL)) != 0) { 2018 error_r(r, "Could not load host certificate \"%s\"", 2019 options.host_cert_files[i]); 2020 continue; 2021 } 2022 if (!sshkey_is_cert(key)) { 2023 error("Certificate file is not a certificate: %s", 2024 options.host_cert_files[i]); 2025 sshkey_free(key); 2026 continue; 2027 } 2028 /* Find matching private key */ 2029 for (j = 0; j < options.num_host_key_files; j++) { 2030 if (sshkey_equal_public(key, 2031 sensitive_data.host_pubkeys[j])) { 2032 sensitive_data.host_certificates[j] = key; 2033 break; 2034 } 2035 } 2036 if (j >= options.num_host_key_files) { 2037 error("No matching private key for certificate: %s", 2038 options.host_cert_files[i]); 2039 sshkey_free(key); 2040 continue; 2041 } 2042 sensitive_data.host_certificates[j] = key; 2043 debug("host certificate: #%u type %d %s", j, key->type, 2044 sshkey_type(key)); 2045 } 2046 2047 if (privsep_chroot) { 2048 struct stat st; 2049 2050 if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) || 2051 (S_ISDIR(st.st_mode) == 0)) 2052 fatal("Missing privilege separation directory: %s", 2053 _PATH_PRIVSEP_CHROOT_DIR); 2054 2055#ifdef HAVE_CYGWIN 2056 if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) && 2057 (st.st_uid != getuid () || 2058 (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)) 2059#else 2060 if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0) 2061#endif 2062 fatal("%s must be owned by root and not group or " 2063 "world-writable.", _PATH_PRIVSEP_CHROOT_DIR); 2064 } 2065 2066 if (test_flag > 1) 2067 print_config(ssh, connection_info); 2068 2069 /* Configuration looks good, so exit if in test mode. */ 2070 if (test_flag) 2071 exit(0); 2072 2073 /* 2074 * Clear out any supplemental groups we may have inherited. This 2075 * prevents inadvertent creation of files with bad modes (in the 2076 * portable version at least, it's certainly possible for PAM 2077 * to create a file, and we can't control the code in every 2078 * module which might be used). 2079 */ 2080 if (setgroups(0, NULL) < 0) 2081 debug("setgroups() failed: %.200s", strerror(errno)); 2082 2083 if (rexec_flag) { 2084 if (rexec_argc < 0) 2085 fatal("rexec_argc %d < 0", rexec_argc); 2086 rexec_argv = xcalloc(rexec_argc + 2, sizeof(char *)); 2087 for (i = 0; i < (u_int)rexec_argc; i++) { 2088 debug("rexec_argv[%d]='%s'", i, saved_argv[i]); 2089 rexec_argv[i] = saved_argv[i]; 2090 } 2091 rexec_argv[rexec_argc] = "-R"; 2092 rexec_argv[rexec_argc + 1] = NULL; 2093 } 2094 listener_proctitle = prepare_proctitle(ac, av); 2095 2096 /* Ensure that umask disallows at least group and world write */ 2097 new_umask = umask(0077) | 0022; 2098 (void) umask(new_umask); 2099 2100 /* Initialize the log (it is reinitialized below in case we forked). */ 2101 if (debug_flag && (!inetd_flag || rexeced_flag)) 2102 log_stderr = 1; 2103 log_init(__progname, options.log_level, 2104 options.log_facility, log_stderr); 2105 for (i = 0; i < options.num_log_verbose; i++) 2106 log_verbose_add(options.log_verbose[i]); 2107 2108 /* 2109 * If not in debugging mode, not started from inetd and not already 2110 * daemonized (eg re-exec via SIGHUP), disconnect from the controlling 2111 * terminal, and fork. The original process exits. 2112 */ 2113 already_daemon = daemonized(); 2114 if (!(debug_flag || inetd_flag || no_daemon_flag || already_daemon)) { 2115 2116 if (daemon(0, 0) == -1) 2117 fatal("daemon() failed: %.200s", strerror(errno)); 2118 2119 disconnect_controlling_tty(); 2120 } 2121 /* Reinitialize the log (because of the fork above). */ 2122 log_init(__progname, options.log_level, options.log_facility, log_stderr); 2123 2124 /* Avoid killing the process in high-pressure swapping environments. */ 2125 if (!inetd_flag && madvise(NULL, 0, MADV_PROTECT) != 0) 2126 debug("madvise(): %.200s", strerror(errno)); 2127 2128 /* 2129 * Chdir to the root directory so that the current disk can be 2130 * unmounted if desired. 2131 */ 2132 if (chdir("/") == -1) 2133 error("chdir(\"/\"): %s", strerror(errno)); 2134 2135 /* ignore SIGPIPE */ 2136 ssh_signal(SIGPIPE, SIG_IGN); 2137 2138 /* Get a connection, either from inetd or a listening TCP socket */ 2139 if (inetd_flag) { 2140 server_accept_inetd(&sock_in, &sock_out); 2141 } else { 2142 platform_pre_listen(); 2143 server_listen(); 2144 2145 ssh_signal(SIGHUP, sighup_handler); 2146 ssh_signal(SIGCHLD, main_sigchld_handler); 2147 ssh_signal(SIGTERM, sigterm_handler); 2148 ssh_signal(SIGQUIT, sigterm_handler); 2149 2150 /* 2151 * Write out the pid file after the sigterm handler 2152 * is setup and the listen sockets are bound 2153 */ 2154 if (options.pid_file != NULL && !debug_flag) { 2155 FILE *f = fopen(options.pid_file, "w"); 2156 2157 if (f == NULL) { 2158 error("Couldn't create pid file \"%s\": %s", 2159 options.pid_file, strerror(errno)); 2160 } else { 2161 fprintf(f, "%ld\n", (long) getpid()); 2162 fclose(f); 2163 } 2164 } 2165 2166 /* Accept a connection and return in a forked child */ 2167 server_accept_loop(&sock_in, &sock_out, 2168 &newsock, config_s); 2169 } 2170 2171 /* This is the child processing a new connection. */ 2172 setproctitle("%s", "[accepted]"); 2173 2174 /* 2175 * Create a new session and process group since the 4.4BSD 2176 * setlogin() affects the entire process group. We don't 2177 * want the child to be able to affect the parent. 2178 */ 2179 if (!debug_flag && !inetd_flag && setsid() == -1) 2180 error("setsid: %.100s", strerror(errno)); 2181 2182 if (rexec_flag) { 2183 debug("rexec start in %d out %d newsock %d pipe %d sock %d", 2184 sock_in, sock_out, newsock, startup_pipe, config_s[0]); 2185 if (dup2(newsock, STDIN_FILENO) == -1) 2186 debug3_f("dup2 stdin: %s", strerror(errno)); 2187 if (dup2(STDIN_FILENO, STDOUT_FILENO) == -1) 2188 debug3_f("dup2 stdout: %s", strerror(errno)); 2189 if (startup_pipe == -1) 2190 close(REEXEC_STARTUP_PIPE_FD); 2191 else if (startup_pipe != REEXEC_STARTUP_PIPE_FD) { 2192 if (dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD) == -1) 2193 debug3_f("dup2 startup_p: %s", strerror(errno)); 2194 close(startup_pipe); 2195 startup_pipe = REEXEC_STARTUP_PIPE_FD; 2196 } 2197 2198 if (dup2(config_s[1], REEXEC_CONFIG_PASS_FD) == -1) 2199 debug3_f("dup2 config_s: %s", strerror(errno)); 2200 close(config_s[1]); 2201 2202 ssh_signal(SIGHUP, SIG_IGN); /* avoid reset to SIG_DFL */ 2203 execv(rexec_argv[0], rexec_argv); 2204 2205 /* Reexec has failed, fall back and continue */ 2206 error("rexec of %s failed: %s", rexec_argv[0], strerror(errno)); 2207 recv_rexec_state(REEXEC_CONFIG_PASS_FD, NULL); 2208 log_init(__progname, options.log_level, 2209 options.log_facility, log_stderr); 2210 2211 /* Clean up fds */ 2212 close(REEXEC_CONFIG_PASS_FD); 2213 newsock = sock_out = sock_in = dup(STDIN_FILENO); 2214 if (stdfd_devnull(1, 1, 0) == -1) 2215 error_f("stdfd_devnull failed"); 2216 debug("rexec cleanup in %d out %d newsock %d pipe %d sock %d", 2217 sock_in, sock_out, newsock, startup_pipe, config_s[0]); 2218 } 2219 2220 /* Executed child processes don't need these. */ 2221 fcntl(sock_out, F_SETFD, FD_CLOEXEC); 2222 fcntl(sock_in, F_SETFD, FD_CLOEXEC); 2223 2224 /* We will not restart on SIGHUP since it no longer makes sense. */ 2225 ssh_signal(SIGALRM, SIG_DFL); 2226 ssh_signal(SIGHUP, SIG_DFL); 2227 ssh_signal(SIGTERM, SIG_DFL); 2228 ssh_signal(SIGQUIT, SIG_DFL); 2229 ssh_signal(SIGCHLD, SIG_DFL); 2230 ssh_signal(SIGINT, SIG_DFL); 2231 2232#ifdef __FreeBSD__ 2233 /* 2234 * Initialize the resolver. This may not happen automatically 2235 * before privsep chroot(). 2236 */ 2237 if ((_res.options & RES_INIT) == 0) { 2238 debug("res_init()"); 2239 res_init(); 2240 } 2241#ifdef GSSAPI 2242 /* 2243 * Force GSS-API to parse its configuration and load any 2244 * mechanism plugins. 2245 */ 2246 { 2247 gss_OID_set mechs; 2248 OM_uint32 minor_status; 2249 gss_indicate_mechs(&minor_status, &mechs); 2250 gss_release_oid_set(&minor_status, &mechs); 2251 } 2252#endif 2253#endif 2254 2255 /* 2256 * Register our connection. This turns encryption off because we do 2257 * not have a key. 2258 */ 2259 if ((ssh = ssh_packet_set_connection(NULL, sock_in, sock_out)) == NULL) 2260 fatal("Unable to create connection"); 2261 the_active_state = ssh; 2262 ssh_packet_set_server(ssh); 2263 2264 check_ip_options(ssh); 2265 2266 /* Prepare the channels layer */ 2267 channel_init_channels(ssh); 2268 channel_set_af(ssh, options.address_family); 2269 process_channel_timeouts(ssh, &options); 2270 process_permitopen(ssh, &options); 2271 2272 /* Set SO_KEEPALIVE if requested. */ 2273 if (options.tcp_keep_alive && ssh_packet_connection_is_on_socket(ssh) && 2274 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) == -1) 2275 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 2276 2277 if ((remote_port = ssh_remote_port(ssh)) < 0) { 2278 debug("ssh_remote_port failed"); 2279 cleanup_exit(255); 2280 } 2281 2282 if (options.routing_domain != NULL) 2283 set_process_rdomain(ssh, options.routing_domain); 2284 2285 /* 2286 * The rest of the code depends on the fact that 2287 * ssh_remote_ipaddr() caches the remote ip, even if 2288 * the socket goes away. 2289 */ 2290 remote_ip = ssh_remote_ipaddr(ssh); 2291 2292#ifdef HAVE_LOGIN_CAP 2293 /* Also caches remote hostname for sandboxed child. */ 2294 auth_get_canonical_hostname(ssh, options.use_dns); 2295#endif 2296 2297#ifdef SSH_AUDIT_EVENTS 2298 audit_connection_from(remote_ip, remote_port); 2299#endif 2300 2301 rdomain = ssh_packet_rdomain_in(ssh); 2302 2303 /* Log the connection. */ 2304 laddr = get_local_ipaddr(sock_in); 2305 verbose("Connection from %s port %d on %s port %d%s%s%s", 2306 remote_ip, remote_port, laddr, ssh_local_port(ssh), 2307 rdomain == NULL ? "" : " rdomain \"", 2308 rdomain == NULL ? "" : rdomain, 2309 rdomain == NULL ? "" : "\""); 2310 free(laddr); 2311 2312 /* 2313 * We don't want to listen forever unless the other side 2314 * successfully authenticates itself. So we set up an alarm which is 2315 * cleared after successful authentication. A limit of zero 2316 * indicates no limit. Note that we don't set the alarm in debugging 2317 * mode; it is just annoying to have the server exit just when you 2318 * are about to discover the bug. 2319 */ 2320 ssh_signal(SIGALRM, grace_alarm_handler); 2321 if (!debug_flag) 2322 alarm(options.login_grace_time); 2323 2324 if ((r = kex_exchange_identification(ssh, -1, 2325 options.version_addendum)) != 0) 2326 sshpkt_fatal(ssh, r, "banner exchange"); 2327 2328 ssh_packet_set_nonblocking(ssh); 2329 2330 /* allocate authentication context */ 2331 authctxt = xcalloc(1, sizeof(*authctxt)); 2332 ssh->authctxt = authctxt; 2333 2334 authctxt->loginmsg = loginmsg; 2335 2336 /* XXX global for cleanup, access from other modules */ 2337 the_authctxt = authctxt; 2338 2339 /* Set default key authentication options */ 2340 if ((auth_opts = sshauthopt_new_with_keys_defaults()) == NULL) 2341 fatal("allocation failed"); 2342 2343 /* prepare buffer to collect messages to display to user after login */ 2344 if ((loginmsg = sshbuf_new()) == NULL) 2345 fatal_f("sshbuf_new failed"); 2346 auth_debug_reset(); 2347 2348 BLACKLIST_INIT(); 2349 2350 if (use_privsep) { 2351 if (privsep_preauth(ssh) == 1) 2352 goto authenticated; 2353 } else if (have_agent) { 2354 if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) { 2355 error_r(r, "Unable to get agent socket"); 2356 have_agent = 0; 2357 } 2358 } 2359 2360 /* perform the key exchange */ 2361 /* authenticate user and start session */ 2362 do_ssh2_kex(ssh); 2363 do_authentication2(ssh); 2364 2365 /* 2366 * If we use privilege separation, the unprivileged child transfers 2367 * the current keystate and exits 2368 */ 2369 if (use_privsep) { 2370 mm_send_keystate(ssh, pmonitor); 2371 ssh_packet_clear_keys(ssh); 2372 exit(0); 2373 } 2374 2375 authenticated: 2376 /* 2377 * Cancel the alarm we set to limit the time taken for 2378 * authentication. 2379 */ 2380 alarm(0); 2381 ssh_signal(SIGALRM, SIG_DFL); 2382 authctxt->authenticated = 1; 2383 if (startup_pipe != -1) { 2384 close(startup_pipe); 2385 startup_pipe = -1; 2386 } 2387 2388#ifdef SSH_AUDIT_EVENTS 2389 audit_event(ssh, SSH_AUTH_SUCCESS); 2390#endif 2391 2392#ifdef GSSAPI 2393 if (options.gss_authentication) { 2394 temporarily_use_uid(authctxt->pw); 2395 ssh_gssapi_storecreds(); 2396 restore_uid(); 2397 } 2398#endif 2399#ifdef USE_PAM 2400 if (options.use_pam) { 2401 do_pam_setcred(1); 2402 do_pam_session(ssh); 2403 } 2404#endif 2405 2406 /* 2407 * In privilege separation, we fork another child and prepare 2408 * file descriptor passing. 2409 */ 2410 if (use_privsep) { 2411 privsep_postauth(ssh, authctxt); 2412 /* the monitor process [priv] will not return */ 2413 } 2414 2415 ssh_packet_set_timeout(ssh, options.client_alive_interval, 2416 options.client_alive_count_max); 2417 2418 /* Try to send all our hostkeys to the client */ 2419 notify_hostkeys(ssh); 2420 2421 /* Start session. */ 2422 do_authenticated(ssh, authctxt); 2423 2424 /* The connection has been terminated. */ 2425 ssh_packet_get_bytes(ssh, &ibytes, &obytes); 2426 verbose("Transferred: sent %llu, received %llu bytes", 2427 (unsigned long long)obytes, (unsigned long long)ibytes); 2428 2429 verbose("Closing connection to %.500s port %d", remote_ip, remote_port); 2430 2431#ifdef USE_PAM 2432 if (options.use_pam) 2433 finish_pam(); 2434#endif /* USE_PAM */ 2435 2436#ifdef SSH_AUDIT_EVENTS 2437 PRIVSEP(audit_event(ssh, SSH_CONNECTION_CLOSE)); 2438#endif 2439 2440 ssh_packet_close(ssh); 2441 2442 if (use_privsep) 2443 mm_terminate(); 2444 2445 exit(0); 2446} 2447 2448int 2449sshd_hostkey_sign(struct ssh *ssh, struct sshkey *privkey, 2450 struct sshkey *pubkey, u_char **signature, size_t *slenp, 2451 const u_char *data, size_t dlen, const char *alg) 2452{ 2453 int r; 2454 2455 if (use_privsep) { 2456 if (privkey) { 2457 if (mm_sshkey_sign(ssh, privkey, signature, slenp, 2458 data, dlen, alg, options.sk_provider, NULL, 2459 ssh->compat) < 0) 2460 fatal_f("privkey sign failed"); 2461 } else { 2462 if (mm_sshkey_sign(ssh, pubkey, signature, slenp, 2463 data, dlen, alg, options.sk_provider, NULL, 2464 ssh->compat) < 0) 2465 fatal_f("pubkey sign failed"); 2466 } 2467 } else { 2468 if (privkey) { 2469 if (sshkey_sign(privkey, signature, slenp, data, dlen, 2470 alg, options.sk_provider, NULL, ssh->compat) < 0) 2471 fatal_f("privkey sign failed"); 2472 } else { 2473 if ((r = ssh_agent_sign(auth_sock, pubkey, 2474 signature, slenp, data, dlen, alg, 2475 ssh->compat)) != 0) { 2476 fatal_fr(r, "agent sign failed"); 2477 } 2478 } 2479 } 2480 return 0; 2481} 2482 2483/* SSH2 key exchange */ 2484static void 2485do_ssh2_kex(struct ssh *ssh) 2486{ 2487 char *hkalgs = NULL, *myproposal[PROPOSAL_MAX]; 2488 const char *compression = NULL; 2489 struct kex *kex; 2490 int r; 2491 2492 if (options.rekey_limit || options.rekey_interval) 2493 ssh_packet_set_rekey_limits(ssh, options.rekey_limit, 2494 options.rekey_interval); 2495 2496 if (options.compression == COMP_NONE) 2497 compression = "none"; 2498 hkalgs = list_hostkey_types(); 2499 2500 kex_proposal_populate_entries(ssh, myproposal, options.kex_algorithms, 2501 options.ciphers, options.macs, compression, hkalgs); 2502 2503 free(hkalgs); 2504 2505 /* start key exchange */ 2506 if ((r = kex_setup(ssh, myproposal)) != 0) 2507 fatal_r(r, "kex_setup"); 2508 kex_set_server_sig_algs(ssh, options.pubkey_accepted_algos); 2509 kex = ssh->kex; 2510 2511#ifdef WITH_OPENSSL 2512 kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server; 2513 kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server; 2514 kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server; 2515 kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server; 2516 kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server; 2517 kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 2518 kex->kex[KEX_DH_GEX_SHA256] = kexgex_server; 2519# ifdef OPENSSL_HAS_ECC 2520 kex->kex[KEX_ECDH_SHA2] = kex_gen_server; 2521# endif 2522#endif 2523 kex->kex[KEX_C25519_SHA256] = kex_gen_server; 2524 kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_server; 2525 kex->load_host_public_key=&get_hostkey_public_by_type; 2526 kex->load_host_private_key=&get_hostkey_private_by_type; 2527 kex->host_key_index=&get_hostkey_index; 2528 kex->sign = sshd_hostkey_sign; 2529 2530 ssh_dispatch_run_fatal(ssh, DISPATCH_BLOCK, &kex->done); 2531 kex_proposal_free_entries(myproposal); 2532 2533#ifdef DEBUG_KEXDH 2534 /* send 1st encrypted/maced/compressed message */ 2535 if ((r = sshpkt_start(ssh, SSH2_MSG_IGNORE)) != 0 || 2536 (r = sshpkt_put_cstring(ssh, "markus")) != 0 || 2537 (r = sshpkt_send(ssh)) != 0 || 2538 (r = ssh_packet_write_wait(ssh)) != 0) 2539 fatal_fr(r, "send test"); 2540#endif 2541 debug("KEX done"); 2542} 2543 2544/* server specific fatal cleanup */ 2545void 2546cleanup_exit(int i) 2547{ 2548 if (the_active_state != NULL && the_authctxt != NULL) { 2549 do_cleanup(the_active_state, the_authctxt); 2550 if (use_privsep && privsep_is_preauth && 2551 pmonitor != NULL && pmonitor->m_pid > 1) { 2552 debug("Killing privsep child %d", pmonitor->m_pid); 2553 if (kill(pmonitor->m_pid, SIGKILL) != 0 && 2554 errno != ESRCH) { 2555 error_f("kill(%d): %s", pmonitor->m_pid, 2556 strerror(errno)); 2557 } 2558 } 2559 } 2560#ifdef SSH_AUDIT_EVENTS 2561 /* done after do_cleanup so it can cancel the PAM auth 'thread' */ 2562 if (the_active_state != NULL && (!use_privsep || mm_is_monitor())) 2563 audit_event(the_active_state, SSH_CONNECTION_ABANDON); 2564#endif 2565 _exit(i); 2566} 2567