1/* $OpenBSD: sshd.c,v 1.444 2015/02/20 22:17:21 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/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 "ssh1.h" 91#include "ssh2.h" 92#include "rsa.h" 93#include "sshpty.h" 94#include "packet.h" 95#include "log.h" 96#include "buffer.h" 97#include "misc.h" 98#include "servconf.h" 99#include "uidswap.h" 100#include "compat.h" 101#include "cipher.h" 102#include "digest.h" 103#include "key.h" 104#include "kex.h" 105#include "myproposal.h" 106#include "authfile.h" 107#include "pathnames.h" 108#include "atomicio.h" 109#include "canohost.h" 110#include "hostfile.h" 111#include "auth.h" 112#include "authfd.h" 113#include "msg.h" 114#include "dispatch.h" 115#include "channels.h" 116#include "session.h" 117#include "monitor_mm.h" 118#include "monitor.h" 119#ifdef GSSAPI 120#include "ssh-gss.h" 121#endif 122#include "monitor_wrap.h" 123#include "roaming.h" 124#include "ssh-sandbox.h" 125#include "version.h" 126#include "ssherr.h" 127 128#ifndef O_NOCTTY 129#define O_NOCTTY 0 130#endif 131 132/* Re-exec fds */ 133#define REEXEC_DEVCRYPTO_RESERVED_FD (STDERR_FILENO + 1) 134#define REEXEC_STARTUP_PIPE_FD (STDERR_FILENO + 2) 135#define REEXEC_CONFIG_PASS_FD (STDERR_FILENO + 3) 136#define REEXEC_MIN_FREE_FD (STDERR_FILENO + 4) 137 138extern char *__progname; 139 140/* Server configuration options. */ 141ServerOptions options; 142 143/* Name of the server configuration file. */ 144char *config_file_name = _PATH_SERVER_CONFIG_FILE; 145 146/* 147 * Debug mode flag. This can be set on the command line. If debug 148 * mode is enabled, extra debugging output will be sent to the system 149 * log, the daemon will not go to background, and will exit after processing 150 * the first connection. 151 */ 152int debug_flag = 0; 153 154/* Flag indicating that the daemon should only test the configuration and keys. */ 155int test_flag = 0; 156 157/* Flag indicating that the daemon is being started from inetd. */ 158int inetd_flag = 0; 159 160/* Flag indicating that sshd should not detach and become a daemon. */ 161int no_daemon_flag = 0; 162 163/* debug goes to stderr unless inetd_flag is set */ 164int log_stderr = 0; 165 166/* Saved arguments to main(). */ 167char **saved_argv; 168int saved_argc; 169 170/* re-exec */ 171int rexeced_flag = 0; 172int rexec_flag = 1; 173int rexec_argc = 0; 174char **rexec_argv; 175 176/* 177 * The sockets that the server is listening; this is used in the SIGHUP 178 * signal handler. 179 */ 180#define MAX_LISTEN_SOCKS 16 181int listen_socks[MAX_LISTEN_SOCKS]; 182int num_listen_socks = 0; 183 184/* 185 * the client's version string, passed by sshd2 in compat mode. if != NULL, 186 * sshd will skip the version-number exchange 187 */ 188char *client_version_string = NULL; 189char *server_version_string = NULL; 190 191/* Daemon's agent connection */ 192int auth_sock = -1; 193int have_agent = 0; 194 195/* 196 * Any really sensitive data in the application is contained in this 197 * structure. The idea is that this structure could be locked into memory so 198 * that the pages do not get written into swap. However, there are some 199 * problems. The private key contains BIGNUMs, and we do not (in principle) 200 * have access to the internals of them, and locking just the structure is 201 * not very useful. Currently, memory locking is not implemented. 202 */ 203struct { 204 Key *server_key; /* ephemeral server key */ 205 Key *ssh1_host_key; /* ssh1 host key */ 206 Key **host_keys; /* all private host keys */ 207 Key **host_pubkeys; /* all public host keys */ 208 Key **host_certificates; /* all public host certificates */ 209 int have_ssh1_key; 210 int have_ssh2_key; 211 u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH]; 212} sensitive_data; 213 214/* 215 * Flag indicating whether the RSA server key needs to be regenerated. 216 * Is set in the SIGALRM handler and cleared when the key is regenerated. 217 */ 218static volatile sig_atomic_t key_do_regen = 0; 219 220/* This is set to true when a signal is received. */ 221static volatile sig_atomic_t received_sighup = 0; 222static volatile sig_atomic_t received_sigterm = 0; 223 224/* session identifier, used by RSA-auth */ 225u_char session_id[16]; 226 227/* same for ssh2 */ 228u_char *session_id2 = NULL; 229u_int session_id2_len = 0; 230 231/* record remote hostname or ip */ 232u_int utmp_len = HOST_NAME_MAX+1; 233 234/* options.max_startup sized array of fd ints */ 235int *startup_pipes = NULL; 236int startup_pipe; /* in child */ 237 238/* variables used for privilege separation */ 239int use_privsep = -1; 240struct monitor *pmonitor = NULL; 241int privsep_is_preauth = 1; 242 243/* global authentication context */ 244Authctxt *the_authctxt = NULL; 245 246/* sshd_config buffer */ 247Buffer cfg; 248 249/* message to be displayed after login */ 250Buffer loginmsg; 251 252/* Unprivileged user */ 253struct passwd *privsep_pw = NULL; 254 255/* Prototypes for various functions defined later in this file. */ 256void destroy_sensitive_data(void); 257void demote_sensitive_data(void); 258 259#ifdef WITH_SSH1 260static void do_ssh1_kex(void); 261#endif 262static void do_ssh2_kex(void); 263 264/* 265 * Close all listening sockets 266 */ 267static void 268close_listen_socks(void) 269{ 270 int i; 271 272 for (i = 0; i < num_listen_socks; i++) 273 close(listen_socks[i]); 274 num_listen_socks = -1; 275} 276 277static void 278close_startup_pipes(void) 279{ 280 int i; 281 282 if (startup_pipes) 283 for (i = 0; i < options.max_startups; i++) 284 if (startup_pipes[i] != -1) 285 close(startup_pipes[i]); 286} 287 288/* 289 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP; 290 * the effect is to reread the configuration file (and to regenerate 291 * the server key). 292 */ 293 294/*ARGSUSED*/ 295static void 296sighup_handler(int sig) 297{ 298 int save_errno = errno; 299 300 received_sighup = 1; 301 signal(SIGHUP, sighup_handler); 302 errno = save_errno; 303} 304 305/* 306 * Called from the main program after receiving SIGHUP. 307 * Restarts the server. 308 */ 309static void 310sighup_restart(void) 311{ 312 logit("Received SIGHUP; restarting."); 313 platform_pre_restart(); 314 close_listen_socks(); 315 close_startup_pipes(); 316 alarm(0); /* alarm timer persists across exec */ 317 signal(SIGHUP, SIG_IGN); /* will be restored after exec */ 318 execv(saved_argv[0], saved_argv); 319 logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], 320 strerror(errno)); 321 exit(1); 322} 323 324/* 325 * Generic signal handler for terminating signals in the master daemon. 326 */ 327/*ARGSUSED*/ 328static void 329sigterm_handler(int sig) 330{ 331 received_sigterm = sig; 332} 333 334/* 335 * SIGCHLD handler. This is called whenever a child dies. This will then 336 * reap any zombies left by exited children. 337 */ 338/*ARGSUSED*/ 339static void 340main_sigchld_handler(int sig) 341{ 342 int save_errno = errno; 343 pid_t pid; 344 int status; 345 346 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 347 (pid < 0 && errno == EINTR)) 348 ; 349 350 signal(SIGCHLD, main_sigchld_handler); 351 errno = save_errno; 352} 353 354/* 355 * Signal handler for the alarm after the login grace period has expired. 356 */ 357/*ARGSUSED*/ 358static void 359grace_alarm_handler(int sig) 360{ 361 if (use_privsep && pmonitor != NULL && pmonitor->m_pid > 0) 362 kill(pmonitor->m_pid, SIGALRM); 363 364 /* 365 * Try to kill any processes that we have spawned, E.g. authorized 366 * keys command helpers. 367 */ 368 if (getpgid(0) == getpid()) { 369 signal(SIGTERM, SIG_IGN); 370 kill(0, SIGTERM); 371 } 372 373 /* Log error and exit. */ 374 sigdie("Timeout before authentication for %s", get_remote_ipaddr()); 375} 376 377/* 378 * Signal handler for the key regeneration alarm. Note that this 379 * alarm only occurs in the daemon waiting for connections, and it does not 380 * do anything with the private key or random state before forking. 381 * Thus there should be no concurrency control/asynchronous execution 382 * problems. 383 */ 384static void 385generate_ephemeral_server_key(void) 386{ 387 verbose("Generating %s%d bit RSA key.", 388 sensitive_data.server_key ? "new " : "", options.server_key_bits); 389 if (sensitive_data.server_key != NULL) 390 key_free(sensitive_data.server_key); 391 sensitive_data.server_key = key_generate(KEY_RSA1, 392 options.server_key_bits); 393 verbose("RSA key generation complete."); 394 395 arc4random_buf(sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); 396} 397 398/*ARGSUSED*/ 399static void 400key_regeneration_alarm(int sig) 401{ 402 int save_errno = errno; 403 404 signal(SIGALRM, SIG_DFL); 405 errno = save_errno; 406 key_do_regen = 1; 407} 408 409static void 410sshd_exchange_identification(int sock_in, int sock_out) 411{ 412 u_int i; 413 int mismatch; 414 int remote_major, remote_minor; 415 int major, minor; 416 char *s, *newline = "\n"; 417 char buf[256]; /* Must not be larger than remote_version. */ 418 char remote_version[256]; /* Must be at least as big as buf. */ 419 420 if ((options.protocol & SSH_PROTO_1) && 421 (options.protocol & SSH_PROTO_2)) { 422 major = PROTOCOL_MAJOR_1; 423 minor = 99; 424 } else if (options.protocol & SSH_PROTO_2) { 425 major = PROTOCOL_MAJOR_2; 426 minor = PROTOCOL_MINOR_2; 427 newline = "\r\n"; 428 } else { 429 major = PROTOCOL_MAJOR_1; 430 minor = PROTOCOL_MINOR_1; 431 } 432 433 xasprintf(&server_version_string, "SSH-%d.%d-%.100s%s%s%s", 434 major, minor, SSH_VERSION, 435 *options.version_addendum == '\0' ? "" : " ", 436 options.version_addendum, newline); 437 438 /* Send our protocol version identification. */ 439 if (roaming_atomicio(vwrite, sock_out, server_version_string, 440 strlen(server_version_string)) 441 != strlen(server_version_string)) { 442 logit("Could not write ident string to %s", get_remote_ipaddr()); 443 cleanup_exit(255); 444 } 445 446 /* Read other sides version identification. */ 447 memset(buf, 0, sizeof(buf)); 448 for (i = 0; i < sizeof(buf) - 1; i++) { 449 if (roaming_atomicio(read, sock_in, &buf[i], 1) != 1) { 450 logit("Did not receive identification string from %s", 451 get_remote_ipaddr()); 452 cleanup_exit(255); 453 } 454 if (buf[i] == '\r') { 455 buf[i] = 0; 456 /* Kludge for F-Secure Macintosh < 1.0.2 */ 457 if (i == 12 && 458 strncmp(buf, "SSH-1.5-W1.0", 12) == 0) 459 break; 460 continue; 461 } 462 if (buf[i] == '\n') { 463 buf[i] = 0; 464 break; 465 } 466 } 467 buf[sizeof(buf) - 1] = 0; 468 client_version_string = xstrdup(buf); 469 470 /* 471 * Check that the versions match. In future this might accept 472 * several versions and set appropriate flags to handle them. 473 */ 474 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n", 475 &remote_major, &remote_minor, remote_version) != 3) { 476 s = "Protocol mismatch.\n"; 477 (void) atomicio(vwrite, sock_out, s, strlen(s)); 478 logit("Bad protocol version identification '%.100s' " 479 "from %s port %d", client_version_string, 480 get_remote_ipaddr(), get_remote_port()); 481 close(sock_in); 482 close(sock_out); 483 cleanup_exit(255); 484 } 485 debug("Client protocol version %d.%d; client software version %.100s", 486 remote_major, remote_minor, remote_version); 487 488 active_state->compat = compat_datafellows(remote_version); 489 490 if ((datafellows & SSH_BUG_PROBE) != 0) { 491 logit("probed from %s with %s. Don't panic.", 492 get_remote_ipaddr(), client_version_string); 493 cleanup_exit(255); 494 } 495 if ((datafellows & SSH_BUG_SCANNER) != 0) { 496 logit("scanned from %s with %s. Don't panic.", 497 get_remote_ipaddr(), client_version_string); 498 cleanup_exit(255); 499 } 500 if ((datafellows & SSH_BUG_RSASIGMD5) != 0) { 501 logit("Client version \"%.100s\" uses unsafe RSA signature " 502 "scheme; disabling use of RSA keys", remote_version); 503 } 504 if ((datafellows & SSH_BUG_DERIVEKEY) != 0) { 505 fatal("Client version \"%.100s\" uses unsafe key agreement; " 506 "refusing connection", remote_version); 507 } 508 509 mismatch = 0; 510 switch (remote_major) { 511 case 1: 512 if (remote_minor == 99) { 513 if (options.protocol & SSH_PROTO_2) 514 enable_compat20(); 515 else 516 mismatch = 1; 517 break; 518 } 519 if (!(options.protocol & SSH_PROTO_1)) { 520 mismatch = 1; 521 break; 522 } 523 if (remote_minor < 3) { 524 packet_disconnect("Your ssh version is too old and " 525 "is no longer supported. Please install a newer version."); 526 } else if (remote_minor == 3) { 527 /* note that this disables agent-forwarding */ 528 enable_compat13(); 529 } 530 break; 531 case 2: 532 if (options.protocol & SSH_PROTO_2) { 533 enable_compat20(); 534 break; 535 } 536 /* FALLTHROUGH */ 537 default: 538 mismatch = 1; 539 break; 540 } 541 chop(server_version_string); 542 debug("Local version string %.200s", server_version_string); 543 544 if (mismatch) { 545 s = "Protocol major versions differ.\n"; 546 (void) atomicio(vwrite, sock_out, s, strlen(s)); 547 close(sock_in); 548 close(sock_out); 549 logit("Protocol major versions differ for %s: %.200s vs. %.200s", 550 get_remote_ipaddr(), 551 server_version_string, client_version_string); 552 cleanup_exit(255); 553 } 554} 555 556/* Destroy the host and server keys. They will no longer be needed. */ 557void 558destroy_sensitive_data(void) 559{ 560 int i; 561 562 if (sensitive_data.server_key) { 563 key_free(sensitive_data.server_key); 564 sensitive_data.server_key = NULL; 565 } 566 for (i = 0; i < options.num_host_key_files; i++) { 567 if (sensitive_data.host_keys[i]) { 568 key_free(sensitive_data.host_keys[i]); 569 sensitive_data.host_keys[i] = NULL; 570 } 571 if (sensitive_data.host_certificates[i]) { 572 key_free(sensitive_data.host_certificates[i]); 573 sensitive_data.host_certificates[i] = NULL; 574 } 575 } 576 sensitive_data.ssh1_host_key = NULL; 577 explicit_bzero(sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); 578} 579 580/* Demote private to public keys for network child */ 581void 582demote_sensitive_data(void) 583{ 584 Key *tmp; 585 int i; 586 587 if (sensitive_data.server_key) { 588 tmp = key_demote(sensitive_data.server_key); 589 key_free(sensitive_data.server_key); 590 sensitive_data.server_key = tmp; 591 } 592 593 for (i = 0; i < options.num_host_key_files; i++) { 594 if (sensitive_data.host_keys[i]) { 595 tmp = key_demote(sensitive_data.host_keys[i]); 596 key_free(sensitive_data.host_keys[i]); 597 sensitive_data.host_keys[i] = tmp; 598 if (tmp->type == KEY_RSA1) 599 sensitive_data.ssh1_host_key = tmp; 600 } 601 /* Certs do not need demotion */ 602 } 603 604 /* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */ 605} 606 607static void 608privsep_preauth_child(void) 609{ 610 u_int32_t rnd[256]; 611 gid_t gidset[1]; 612 613 /* Enable challenge-response authentication for privilege separation */ 614 privsep_challenge_enable(); 615 616#ifdef GSSAPI 617 /* Cache supported mechanism OIDs for later use */ 618 if (options.gss_authentication) 619 ssh_gssapi_prepare_supported_oids(); 620#endif 621 622 arc4random_stir(); 623 arc4random_buf(rnd, sizeof(rnd)); 624#ifdef WITH_OPENSSL 625 RAND_seed(rnd, sizeof(rnd)); 626#endif 627 explicit_bzero(rnd, sizeof(rnd)); 628 629 /* Demote the private keys to public keys. */ 630 demote_sensitive_data(); 631 632 /* Change our root directory */ 633 if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1) 634 fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR, 635 strerror(errno)); 636 if (chdir("/") == -1) 637 fatal("chdir(\"/\"): %s", strerror(errno)); 638 639 /* Drop our privileges */ 640 debug3("privsep user:group %u:%u", (u_int)privsep_pw->pw_uid, 641 (u_int)privsep_pw->pw_gid); 642#if 0 643 /* XXX not ready, too heavy after chroot */ 644 do_setusercontext(privsep_pw); 645#else 646 gidset[0] = privsep_pw->pw_gid; 647 if (setgroups(1, gidset) < 0) 648 fatal("setgroups: %.100s", strerror(errno)); 649 permanently_set_uid(privsep_pw); 650#endif 651} 652 653static int 654privsep_preauth(Authctxt *authctxt) 655{ 656 int status, r; 657 pid_t pid; 658 struct ssh_sandbox *box = NULL; 659 660 /* Set up unprivileged child process to deal with network data */ 661 pmonitor = monitor_init(); 662 /* Store a pointer to the kex for later rekeying */ 663 pmonitor->m_pkex = &active_state->kex; 664 665 if (use_privsep == PRIVSEP_ON) 666 box = ssh_sandbox_init(pmonitor); 667 pid = fork(); 668 if (pid == -1) { 669 fatal("fork of unprivileged child failed"); 670 } else if (pid != 0) { 671 debug2("Network child is on pid %ld", (long)pid); 672 673 pmonitor->m_pid = pid; 674 if (have_agent) { 675 r = ssh_get_authentication_socket(&auth_sock); 676 if (r != 0) { 677 error("Could not get agent socket: %s", 678 ssh_err(r)); 679 have_agent = 0; 680 } 681 } 682 if (box != NULL) 683 ssh_sandbox_parent_preauth(box, pid); 684 monitor_child_preauth(authctxt, pmonitor); 685 686 /* Sync memory */ 687 monitor_sync(pmonitor); 688 689 /* Wait for the child's exit status */ 690 while (waitpid(pid, &status, 0) < 0) { 691 if (errno == EINTR) 692 continue; 693 pmonitor->m_pid = -1; 694 fatal("%s: waitpid: %s", __func__, strerror(errno)); 695 } 696 privsep_is_preauth = 0; 697 pmonitor->m_pid = -1; 698 if (WIFEXITED(status)) { 699 if (WEXITSTATUS(status) != 0) 700 fatal("%s: preauth child exited with status %d", 701 __func__, WEXITSTATUS(status)); 702 } else if (WIFSIGNALED(status)) 703 fatal("%s: preauth child terminated by signal %d", 704 __func__, WTERMSIG(status)); 705 if (box != NULL) 706 ssh_sandbox_parent_finish(box); 707 return 1; 708 } else { 709 /* child */ 710 close(pmonitor->m_sendfd); 711 close(pmonitor->m_log_recvfd); 712 713 /* Arrange for logging to be sent to the monitor */ 714 set_log_handler(mm_log_handler, pmonitor); 715 716 /* Demote the child */ 717 if (getuid() == 0 || geteuid() == 0) 718 privsep_preauth_child(); 719 setproctitle("%s", "[net]"); 720 if (box != NULL) 721 ssh_sandbox_child(box); 722 723 return 0; 724 } 725} 726 727static void 728privsep_postauth(Authctxt *authctxt) 729{ 730 u_int32_t rnd[256]; 731 732#ifdef DISABLE_FD_PASSING 733 if (1) { 734#else 735 if (authctxt->pw->pw_uid == 0 || options.use_login) { 736#endif 737 /* File descriptor passing is broken or root login */ 738 use_privsep = 0; 739 goto skip; 740 } 741 742 /* New socket pair */ 743 monitor_reinit(pmonitor); 744 745 pmonitor->m_pid = fork(); 746 if (pmonitor->m_pid == -1) 747 fatal("fork of unprivileged child failed"); 748 else if (pmonitor->m_pid != 0) { 749 verbose("User child is on pid %ld", (long)pmonitor->m_pid); 750 buffer_clear(&loginmsg); 751 monitor_child_postauth(pmonitor); 752 753 /* NEVERREACHED */ 754 exit(0); 755 } 756 757 /* child */ 758 759 close(pmonitor->m_sendfd); 760 pmonitor->m_sendfd = -1; 761 762 /* Demote the private keys to public keys. */ 763 demote_sensitive_data(); 764 765 arc4random_stir(); 766 arc4random_buf(rnd, sizeof(rnd)); 767#ifdef WITH_OPENSSL 768 RAND_seed(rnd, sizeof(rnd)); 769#endif 770 explicit_bzero(rnd, sizeof(rnd)); 771 772 /* Drop privileges */ 773 do_setusercontext(authctxt->pw); 774 775 skip: 776 /* It is safe now to apply the key state */ 777 monitor_apply_keystate(pmonitor); 778 779 /* 780 * Tell the packet layer that authentication was successful, since 781 * this information is not part of the key state. 782 */ 783 packet_set_authenticated(); 784} 785 786static char * 787list_hostkey_types(void) 788{ 789 Buffer b; 790 const char *p; 791 char *ret; 792 int i; 793 Key *key; 794 795 buffer_init(&b); 796 for (i = 0; i < options.num_host_key_files; i++) { 797 key = sensitive_data.host_keys[i]; 798 if (key == NULL) 799 key = sensitive_data.host_pubkeys[i]; 800 if (key == NULL) 801 continue; 802 switch (key->type) { 803 case KEY_RSA: 804 case KEY_DSA: 805 case KEY_ECDSA: 806 case KEY_ED25519: 807 if (buffer_len(&b) > 0) 808 buffer_append(&b, ",", 1); 809 p = key_ssh_name(key); 810 buffer_append(&b, p, strlen(p)); 811 break; 812 } 813 /* If the private key has a cert peer, then list that too */ 814 key = sensitive_data.host_certificates[i]; 815 if (key == NULL) 816 continue; 817 switch (key->type) { 818 case KEY_RSA_CERT_V00: 819 case KEY_DSA_CERT_V00: 820 case KEY_RSA_CERT: 821 case KEY_DSA_CERT: 822 case KEY_ECDSA_CERT: 823 case KEY_ED25519_CERT: 824 if (buffer_len(&b) > 0) 825 buffer_append(&b, ",", 1); 826 p = key_ssh_name(key); 827 buffer_append(&b, p, strlen(p)); 828 break; 829 } 830 } 831 buffer_append(&b, "\0", 1); 832 ret = xstrdup(buffer_ptr(&b)); 833 buffer_free(&b); 834 debug("list_hostkey_types: %s", ret); 835 return ret; 836} 837 838static Key * 839get_hostkey_by_type(int type, int nid, int need_private, struct ssh *ssh) 840{ 841 int i; 842 Key *key; 843 844 for (i = 0; i < options.num_host_key_files; i++) { 845 switch (type) { 846 case KEY_RSA_CERT_V00: 847 case KEY_DSA_CERT_V00: 848 case KEY_RSA_CERT: 849 case KEY_DSA_CERT: 850 case KEY_ECDSA_CERT: 851 case KEY_ED25519_CERT: 852 key = sensitive_data.host_certificates[i]; 853 break; 854 default: 855 key = sensitive_data.host_keys[i]; 856 if (key == NULL && !need_private) 857 key = sensitive_data.host_pubkeys[i]; 858 break; 859 } 860 if (key != NULL && key->type == type && 861 (key->type != KEY_ECDSA || key->ecdsa_nid == nid)) 862 return need_private ? 863 sensitive_data.host_keys[i] : key; 864 } 865 return NULL; 866} 867 868Key * 869get_hostkey_public_by_type(int type, int nid, struct ssh *ssh) 870{ 871 return get_hostkey_by_type(type, nid, 0, ssh); 872} 873 874Key * 875get_hostkey_private_by_type(int type, int nid, struct ssh *ssh) 876{ 877 return get_hostkey_by_type(type, nid, 1, ssh); 878} 879 880Key * 881get_hostkey_by_index(int ind) 882{ 883 if (ind < 0 || ind >= options.num_host_key_files) 884 return (NULL); 885 return (sensitive_data.host_keys[ind]); 886} 887 888Key * 889get_hostkey_public_by_index(int ind, struct ssh *ssh) 890{ 891 if (ind < 0 || ind >= options.num_host_key_files) 892 return (NULL); 893 return (sensitive_data.host_pubkeys[ind]); 894} 895 896int 897get_hostkey_index(Key *key, int compare, struct ssh *ssh) 898{ 899 int i; 900 901 for (i = 0; i < options.num_host_key_files; i++) { 902 if (key_is_cert(key)) { 903 if (key == sensitive_data.host_certificates[i] || 904 (compare && sensitive_data.host_certificates[i] && 905 sshkey_equal(key, 906 sensitive_data.host_certificates[i]))) 907 return (i); 908 } else { 909 if (key == sensitive_data.host_keys[i] || 910 (compare && sensitive_data.host_keys[i] && 911 sshkey_equal(key, sensitive_data.host_keys[i]))) 912 return (i); 913 if (key == sensitive_data.host_pubkeys[i] || 914 (compare && sensitive_data.host_pubkeys[i] && 915 sshkey_equal(key, sensitive_data.host_pubkeys[i]))) 916 return (i); 917 } 918 } 919 return (-1); 920} 921 922/* Inform the client of all hostkeys */ 923static void 924notify_hostkeys(struct ssh *ssh) 925{ 926 struct sshbuf *buf; 927 struct sshkey *key; 928 int i, nkeys, r; 929 char *fp; 930 931 if ((buf = sshbuf_new()) == NULL) 932 fatal("%s: sshbuf_new", __func__); 933 for (i = nkeys = 0; i < options.num_host_key_files; i++) { 934 key = get_hostkey_public_by_index(i, ssh); 935 if (key == NULL || key->type == KEY_UNSPEC || 936 key->type == KEY_RSA1 || sshkey_is_cert(key)) 937 continue; 938 fp = sshkey_fingerprint(key, options.fingerprint_hash, 939 SSH_FP_DEFAULT); 940 debug3("%s: key %d: %s %s", __func__, i, 941 sshkey_ssh_name(key), fp); 942 free(fp); 943 if (nkeys == 0) { 944 packet_start(SSH2_MSG_GLOBAL_REQUEST); 945 packet_put_cstring("hostkeys-00@openssh.com"); 946 packet_put_char(0); /* want-reply */ 947 } 948 sshbuf_reset(buf); 949 if ((r = sshkey_putb(key, buf)) != 0) 950 fatal("%s: couldn't put hostkey %d: %s", 951 __func__, i, ssh_err(r)); 952 packet_put_string(sshbuf_ptr(buf), sshbuf_len(buf)); 953 nkeys++; 954 } 955 debug3("%s: sent %d hostkeys", __func__, nkeys); 956 if (nkeys == 0) 957 fatal("%s: no hostkeys", __func__); 958 packet_send(); 959 sshbuf_free(buf); 960} 961 962/* 963 * returns 1 if connection should be dropped, 0 otherwise. 964 * dropping starts at connection #max_startups_begin with a probability 965 * of (max_startups_rate/100). the probability increases linearly until 966 * all connections are dropped for startups > max_startups 967 */ 968static int 969drop_connection(int startups) 970{ 971 int p, r; 972 973 if (startups < options.max_startups_begin) 974 return 0; 975 if (startups >= options.max_startups) 976 return 1; 977 if (options.max_startups_rate == 100) 978 return 1; 979 980 p = 100 - options.max_startups_rate; 981 p *= startups - options.max_startups_begin; 982 p /= options.max_startups - options.max_startups_begin; 983 p += options.max_startups_rate; 984 r = arc4random_uniform(100); 985 986 debug("drop_connection: p %d, r %d", p, r); 987 return (r < p) ? 1 : 0; 988} 989 990static void 991usage(void) 992{ 993 fprintf(stderr, "%s, %s\n", 994 SSH_RELEASE, 995#ifdef WITH_OPENSSL 996 SSLeay_version(SSLEAY_VERSION) 997#else 998 "without OpenSSL" 999#endif 1000 ); 1001 fprintf(stderr, 1002"usage: sshd [-46DdeiqTt] [-b bits] [-C connection_spec] [-c host_cert_file]\n" 1003" [-E log_file] [-f config_file] [-g login_grace_time]\n" 1004" [-h host_key_file] [-k key_gen_time] [-o option] [-p port]\n" 1005" [-u len]\n" 1006 ); 1007 exit(1); 1008} 1009 1010static void 1011send_rexec_state(int fd, Buffer *conf) 1012{ 1013 Buffer m; 1014 1015 debug3("%s: entering fd = %d config len %d", __func__, fd, 1016 buffer_len(conf)); 1017 1018 /* 1019 * Protocol from reexec master to child: 1020 * string configuration 1021 * u_int ephemeral_key_follows 1022 * bignum e (only if ephemeral_key_follows == 1) 1023 * bignum n " 1024 * bignum d " 1025 * bignum iqmp " 1026 * bignum p " 1027 * bignum q " 1028 * string rngseed (only if OpenSSL is not self-seeded) 1029 */ 1030 buffer_init(&m); 1031 buffer_put_cstring(&m, buffer_ptr(conf)); 1032 1033#ifdef WITH_SSH1 1034 if (sensitive_data.server_key != NULL && 1035 sensitive_data.server_key->type == KEY_RSA1) { 1036 buffer_put_int(&m, 1); 1037 buffer_put_bignum(&m, sensitive_data.server_key->rsa->e); 1038 buffer_put_bignum(&m, sensitive_data.server_key->rsa->n); 1039 buffer_put_bignum(&m, sensitive_data.server_key->rsa->d); 1040 buffer_put_bignum(&m, sensitive_data.server_key->rsa->iqmp); 1041 buffer_put_bignum(&m, sensitive_data.server_key->rsa->p); 1042 buffer_put_bignum(&m, sensitive_data.server_key->rsa->q); 1043 } else 1044#endif 1045 buffer_put_int(&m, 0); 1046 1047#if defined(WITH_OPENSSL) && !defined(OPENSSL_PRNG_ONLY) 1048 rexec_send_rng_seed(&m); 1049#endif 1050 1051 if (ssh_msg_send(fd, 0, &m) == -1) 1052 fatal("%s: ssh_msg_send failed", __func__); 1053 1054 buffer_free(&m); 1055 1056 debug3("%s: done", __func__); 1057} 1058 1059static void 1060recv_rexec_state(int fd, Buffer *conf) 1061{ 1062 Buffer m; 1063 char *cp; 1064 u_int len; 1065 1066 debug3("%s: entering fd = %d", __func__, fd); 1067 1068 buffer_init(&m); 1069 1070 if (ssh_msg_recv(fd, &m) == -1) 1071 fatal("%s: ssh_msg_recv failed", __func__); 1072 if (buffer_get_char(&m) != 0) 1073 fatal("%s: rexec version mismatch", __func__); 1074 1075 cp = buffer_get_string(&m, &len); 1076 if (conf != NULL) 1077 buffer_append(conf, cp, len + 1); 1078 free(cp); 1079 1080 if (buffer_get_int(&m)) { 1081#ifdef WITH_SSH1 1082 if (sensitive_data.server_key != NULL) 1083 key_free(sensitive_data.server_key); 1084 sensitive_data.server_key = key_new_private(KEY_RSA1); 1085 buffer_get_bignum(&m, sensitive_data.server_key->rsa->e); 1086 buffer_get_bignum(&m, sensitive_data.server_key->rsa->n); 1087 buffer_get_bignum(&m, sensitive_data.server_key->rsa->d); 1088 buffer_get_bignum(&m, sensitive_data.server_key->rsa->iqmp); 1089 buffer_get_bignum(&m, sensitive_data.server_key->rsa->p); 1090 buffer_get_bignum(&m, sensitive_data.server_key->rsa->q); 1091 if (rsa_generate_additional_parameters( 1092 sensitive_data.server_key->rsa) != 0) 1093 fatal("%s: rsa_generate_additional_parameters " 1094 "error", __func__); 1095#else 1096 fatal("ssh1 not supported"); 1097#endif 1098 } 1099 1100#if defined(WITH_OPENSSL) && !defined(OPENSSL_PRNG_ONLY) 1101 rexec_recv_rng_seed(&m); 1102#endif 1103 1104 buffer_free(&m); 1105 1106 debug3("%s: done", __func__); 1107} 1108 1109/* Accept a connection from inetd */ 1110static void 1111server_accept_inetd(int *sock_in, int *sock_out) 1112{ 1113 int fd; 1114 1115 startup_pipe = -1; 1116 if (rexeced_flag) { 1117 close(REEXEC_CONFIG_PASS_FD); 1118 *sock_in = *sock_out = dup(STDIN_FILENO); 1119 if (!debug_flag) { 1120 startup_pipe = dup(REEXEC_STARTUP_PIPE_FD); 1121 close(REEXEC_STARTUP_PIPE_FD); 1122 } 1123 } else { 1124 *sock_in = dup(STDIN_FILENO); 1125 *sock_out = dup(STDOUT_FILENO); 1126 } 1127 /* 1128 * We intentionally do not close the descriptors 0, 1, and 2 1129 * as our code for setting the descriptors won't work if 1130 * ttyfd happens to be one of those. 1131 */ 1132 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) { 1133 dup2(fd, STDIN_FILENO); 1134 dup2(fd, STDOUT_FILENO); 1135 if (!log_stderr) 1136 dup2(fd, STDERR_FILENO); 1137 if (fd > (log_stderr ? STDERR_FILENO : STDOUT_FILENO)) 1138 close(fd); 1139 } 1140 debug("inetd sockets after dupping: %d, %d", *sock_in, *sock_out); 1141} 1142 1143/* 1144 * Listen for TCP connections 1145 */ 1146static void 1147server_listen(void) 1148{ 1149 int ret, listen_sock, on = 1; 1150 struct addrinfo *ai; 1151 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 1152 1153 for (ai = options.listen_addrs; ai; ai = ai->ai_next) { 1154 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 1155 continue; 1156 if (num_listen_socks >= MAX_LISTEN_SOCKS) 1157 fatal("Too many listen sockets. " 1158 "Enlarge MAX_LISTEN_SOCKS"); 1159 if ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen, 1160 ntop, sizeof(ntop), strport, sizeof(strport), 1161 NI_NUMERICHOST|NI_NUMERICSERV)) != 0) { 1162 error("getnameinfo failed: %.100s", 1163 ssh_gai_strerror(ret)); 1164 continue; 1165 } 1166 /* Create socket for listening. */ 1167 listen_sock = socket(ai->ai_family, ai->ai_socktype, 1168 ai->ai_protocol); 1169 if (listen_sock < 0) { 1170 /* kernel may not support ipv6 */ 1171 verbose("socket: %.100s", strerror(errno)); 1172 continue; 1173 } 1174 if (set_nonblock(listen_sock) == -1) { 1175 close(listen_sock); 1176 continue; 1177 } 1178 /* 1179 * Set socket options. 1180 * Allow local port reuse in TIME_WAIT. 1181 */ 1182 if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR, 1183 &on, sizeof(on)) == -1) 1184 error("setsockopt SO_REUSEADDR: %s", strerror(errno)); 1185 1186 /* Only communicate in IPv6 over AF_INET6 sockets. */ 1187 if (ai->ai_family == AF_INET6) 1188 sock_set_v6only(listen_sock); 1189 1190 debug("Bind to port %s on %s.", strport, ntop); 1191 1192 /* Bind the socket to the desired port. */ 1193 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) { 1194 error("Bind to port %s on %s failed: %.200s.", 1195 strport, ntop, strerror(errno)); 1196 close(listen_sock); 1197 continue; 1198 } 1199 listen_socks[num_listen_socks] = listen_sock; 1200 num_listen_socks++; 1201 1202 /* Start listening on the port. */ 1203 if (listen(listen_sock, SSH_LISTEN_BACKLOG) < 0) 1204 fatal("listen on [%s]:%s: %.100s", 1205 ntop, strport, strerror(errno)); 1206 logit("Server listening on %s port %s.", ntop, strport); 1207 } 1208 freeaddrinfo(options.listen_addrs); 1209 1210 if (!num_listen_socks) 1211 fatal("Cannot bind any address."); 1212} 1213 1214/* 1215 * The main TCP accept loop. Note that, for the non-debug case, returns 1216 * from this function are in a forked subprocess. 1217 */ 1218static void 1219server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s) 1220{ 1221 fd_set *fdset; 1222 int i, j, ret, maxfd; 1223 int key_used = 0, startups = 0; 1224 int startup_p[2] = { -1 , -1 }; 1225 struct sockaddr_storage from; 1226 socklen_t fromlen; 1227 pid_t pid; 1228 u_char rnd[256]; 1229 1230 /* setup fd set for accept */ 1231 fdset = NULL; 1232 maxfd = 0; 1233 for (i = 0; i < num_listen_socks; i++) 1234 if (listen_socks[i] > maxfd) 1235 maxfd = listen_socks[i]; 1236 /* pipes connected to unauthenticated childs */ 1237 startup_pipes = xcalloc(options.max_startups, sizeof(int)); 1238 for (i = 0; i < options.max_startups; i++) 1239 startup_pipes[i] = -1; 1240 1241 /* 1242 * Stay listening for connections until the system crashes or 1243 * the daemon is killed with a signal. 1244 */ 1245 for (;;) { 1246 if (received_sighup) 1247 sighup_restart(); 1248 if (fdset != NULL) 1249 free(fdset); 1250 fdset = (fd_set *)xcalloc(howmany(maxfd + 1, NFDBITS), 1251 sizeof(fd_mask)); 1252 1253 for (i = 0; i < num_listen_socks; i++) 1254 FD_SET(listen_socks[i], fdset); 1255 for (i = 0; i < options.max_startups; i++) 1256 if (startup_pipes[i] != -1) 1257 FD_SET(startup_pipes[i], fdset); 1258 1259 /* Wait in select until there is a connection. */ 1260 ret = select(maxfd+1, fdset, NULL, NULL, NULL); 1261 if (ret < 0 && errno != EINTR) 1262 error("select: %.100s", strerror(errno)); 1263 if (received_sigterm) { 1264 logit("Received signal %d; terminating.", 1265 (int) received_sigterm); 1266 close_listen_socks(); 1267 if (options.pid_file != NULL) 1268 unlink(options.pid_file); 1269 exit(received_sigterm == SIGTERM ? 0 : 255); 1270 } 1271 if (key_used && key_do_regen) { 1272 generate_ephemeral_server_key(); 1273 key_used = 0; 1274 key_do_regen = 0; 1275 } 1276 if (ret < 0) 1277 continue; 1278 1279 for (i = 0; i < options.max_startups; i++) 1280 if (startup_pipes[i] != -1 && 1281 FD_ISSET(startup_pipes[i], fdset)) { 1282 /* 1283 * the read end of the pipe is ready 1284 * if the child has closed the pipe 1285 * after successful authentication 1286 * or if the child has died 1287 */ 1288 close(startup_pipes[i]); 1289 startup_pipes[i] = -1; 1290 startups--; 1291 } 1292 for (i = 0; i < num_listen_socks; i++) { 1293 if (!FD_ISSET(listen_socks[i], fdset)) 1294 continue; 1295 fromlen = sizeof(from); 1296 *newsock = accept(listen_socks[i], 1297 (struct sockaddr *)&from, &fromlen); 1298 if (*newsock < 0) { 1299 if (errno != EINTR && errno != EWOULDBLOCK && 1300 errno != ECONNABORTED && errno != EAGAIN) 1301 error("accept: %.100s", 1302 strerror(errno)); 1303 if (errno == EMFILE || errno == ENFILE) 1304 usleep(100 * 1000); 1305 continue; 1306 } 1307 if (unset_nonblock(*newsock) == -1) { 1308 close(*newsock); 1309 continue; 1310 } 1311 if (drop_connection(startups) == 1) { 1312 debug("drop connection #%d", startups); 1313 close(*newsock); 1314 continue; 1315 } 1316 if (pipe(startup_p) == -1) { 1317 close(*newsock); 1318 continue; 1319 } 1320 1321 if (rexec_flag && socketpair(AF_UNIX, 1322 SOCK_STREAM, 0, config_s) == -1) { 1323 error("reexec socketpair: %s", 1324 strerror(errno)); 1325 close(*newsock); 1326 close(startup_p[0]); 1327 close(startup_p[1]); 1328 continue; 1329 } 1330 1331 for (j = 0; j < options.max_startups; j++) 1332 if (startup_pipes[j] == -1) { 1333 startup_pipes[j] = startup_p[0]; 1334 if (maxfd < startup_p[0]) 1335 maxfd = startup_p[0]; 1336 startups++; 1337 break; 1338 } 1339 1340 /* 1341 * Got connection. Fork a child to handle it, unless 1342 * we are in debugging mode. 1343 */ 1344 if (debug_flag) { 1345 /* 1346 * In debugging mode. Close the listening 1347 * socket, and start processing the 1348 * connection without forking. 1349 */ 1350 debug("Server will not fork when running in debugging mode."); 1351 close_listen_socks(); 1352 *sock_in = *newsock; 1353 *sock_out = *newsock; 1354 close(startup_p[0]); 1355 close(startup_p[1]); 1356 startup_pipe = -1; 1357 pid = getpid(); 1358 if (rexec_flag) { 1359 send_rexec_state(config_s[0], 1360 &cfg); 1361 close(config_s[0]); 1362 } 1363 break; 1364 } 1365 1366 /* 1367 * Normal production daemon. Fork, and have 1368 * the child process the connection. The 1369 * parent continues listening. 1370 */ 1371 platform_pre_fork(); 1372 if ((pid = fork()) == 0) { 1373 /* 1374 * Child. Close the listening and 1375 * max_startup sockets. Start using 1376 * the accepted socket. Reinitialize 1377 * logging (since our pid has changed). 1378 * We break out of the loop to handle 1379 * the connection. 1380 */ 1381 platform_post_fork_child(); 1382 startup_pipe = startup_p[1]; 1383 close_startup_pipes(); 1384 close_listen_socks(); 1385 *sock_in = *newsock; 1386 *sock_out = *newsock; 1387 log_init(__progname, 1388 options.log_level, 1389 options.log_facility, 1390 log_stderr); 1391 if (rexec_flag) 1392 close(config_s[0]); 1393 break; 1394 } 1395 1396 /* Parent. Stay in the loop. */ 1397 platform_post_fork_parent(pid); 1398 if (pid < 0) 1399 error("fork: %.100s", strerror(errno)); 1400 else 1401 debug("Forked child %ld.", (long)pid); 1402 1403 close(startup_p[1]); 1404 1405 if (rexec_flag) { 1406 send_rexec_state(config_s[0], &cfg); 1407 close(config_s[0]); 1408 close(config_s[1]); 1409 } 1410 1411 /* 1412 * Mark that the key has been used (it 1413 * was "given" to the child). 1414 */ 1415 if ((options.protocol & SSH_PROTO_1) && 1416 key_used == 0) { 1417 /* Schedule server key regeneration alarm. */ 1418 signal(SIGALRM, key_regeneration_alarm); 1419 alarm(options.key_regeneration_time); 1420 key_used = 1; 1421 } 1422 1423 close(*newsock); 1424 1425 /* 1426 * Ensure that our random state differs 1427 * from that of the child 1428 */ 1429 arc4random_stir(); 1430 arc4random_buf(rnd, sizeof(rnd)); 1431#ifdef WITH_OPENSSL 1432 RAND_seed(rnd, sizeof(rnd)); 1433#endif 1434 explicit_bzero(rnd, sizeof(rnd)); 1435 } 1436 1437 /* child process check (or debug mode) */ 1438 if (num_listen_socks < 0) 1439 break; 1440 } 1441} 1442 1443 1444/* 1445 * Main program for the daemon. 1446 */ 1447int 1448main(int ac, char **av) 1449{ 1450 extern char *optarg; 1451 extern int optind; 1452 int r, opt, i, j, on = 1; 1453 int sock_in = -1, sock_out = -1, newsock = -1; 1454 const char *remote_ip; 1455 int remote_port; 1456 char *fp, *line, *logfile = NULL; 1457 int config_s[2] = { -1 , -1 }; 1458 u_int n; 1459 u_int64_t ibytes, obytes; 1460 mode_t new_umask; 1461 Key *key; 1462 Key *pubkey; 1463 int keytype; 1464 Authctxt *authctxt; 1465 struct connection_info *connection_info = get_connection_info(0, 0); 1466 1467#ifdef HAVE_SECUREWARE 1468 (void)set_auth_parameters(ac, av); 1469#endif 1470 __progname = ssh_get_progname(av[0]); 1471 1472 /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */ 1473 saved_argc = ac; 1474 rexec_argc = ac; 1475 saved_argv = xcalloc(ac + 1, sizeof(*saved_argv)); 1476 for (i = 0; i < ac; i++) 1477 saved_argv[i] = xstrdup(av[i]); 1478 saved_argv[i] = NULL; 1479 1480#ifndef HAVE_SETPROCTITLE 1481 /* Prepare for later setproctitle emulation */ 1482 compat_init_setproctitle(ac, av); 1483 av = saved_argv; 1484#endif 1485 1486 if (geteuid() == 0 && setgroups(0, NULL) == -1) 1487 debug("setgroups(): %.200s", strerror(errno)); 1488 1489 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */ 1490 sanitise_stdfd(); 1491 1492 /* Initialize configuration options to their default values. */ 1493 initialize_server_options(&options); 1494 1495 /* Parse command-line arguments. */ 1496 while ((opt = getopt(ac, av, "f:p:b:k:h:g:u:o:C:dDeE:iqrtQRT46")) != -1) { 1497 switch (opt) { 1498 case '4': 1499 options.address_family = AF_INET; 1500 break; 1501 case '6': 1502 options.address_family = AF_INET6; 1503 break; 1504 case 'f': 1505 config_file_name = optarg; 1506 break; 1507 case 'c': 1508 if (options.num_host_cert_files >= MAX_HOSTCERTS) { 1509 fprintf(stderr, "too many host certificates.\n"); 1510 exit(1); 1511 } 1512 options.host_cert_files[options.num_host_cert_files++] = 1513 derelativise_path(optarg); 1514 break; 1515 case 'd': 1516 if (debug_flag == 0) { 1517 debug_flag = 1; 1518 options.log_level = SYSLOG_LEVEL_DEBUG1; 1519 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) 1520 options.log_level++; 1521 break; 1522 case 'D': 1523 no_daemon_flag = 1; 1524 break; 1525 case 'E': 1526 logfile = xstrdup(optarg); 1527 /* FALLTHROUGH */ 1528 case 'e': 1529 log_stderr = 1; 1530 break; 1531 case 'i': 1532 inetd_flag = 1; 1533 break; 1534 case 'r': 1535 rexec_flag = 0; 1536 break; 1537 case 'R': 1538 rexeced_flag = 1; 1539 inetd_flag = 1; 1540 break; 1541 case 'Q': 1542 /* ignored */ 1543 break; 1544 case 'q': 1545 options.log_level = SYSLOG_LEVEL_QUIET; 1546 break; 1547 case 'b': 1548 options.server_key_bits = (int)strtonum(optarg, 256, 1549 32768, NULL); 1550 break; 1551 case 'p': 1552 options.ports_from_cmdline = 1; 1553 if (options.num_ports >= MAX_PORTS) { 1554 fprintf(stderr, "too many ports.\n"); 1555 exit(1); 1556 } 1557 options.ports[options.num_ports++] = a2port(optarg); 1558 if (options.ports[options.num_ports-1] <= 0) { 1559 fprintf(stderr, "Bad port number.\n"); 1560 exit(1); 1561 } 1562 break; 1563 case 'g': 1564 if ((options.login_grace_time = convtime(optarg)) == -1) { 1565 fprintf(stderr, "Invalid login grace time.\n"); 1566 exit(1); 1567 } 1568 break; 1569 case 'k': 1570 if ((options.key_regeneration_time = convtime(optarg)) == -1) { 1571 fprintf(stderr, "Invalid key regeneration interval.\n"); 1572 exit(1); 1573 } 1574 break; 1575 case 'h': 1576 if (options.num_host_key_files >= MAX_HOSTKEYS) { 1577 fprintf(stderr, "too many host keys.\n"); 1578 exit(1); 1579 } 1580 options.host_key_files[options.num_host_key_files++] = 1581 derelativise_path(optarg); 1582 break; 1583 case 't': 1584 test_flag = 1; 1585 break; 1586 case 'T': 1587 test_flag = 2; 1588 break; 1589 case 'C': 1590 if (parse_server_match_testspec(connection_info, 1591 optarg) == -1) 1592 exit(1); 1593 break; 1594 case 'u': 1595 utmp_len = (u_int)strtonum(optarg, 0, HOST_NAME_MAX+1+1, NULL); 1596 if (utmp_len > HOST_NAME_MAX+1) { 1597 fprintf(stderr, "Invalid utmp length.\n"); 1598 exit(1); 1599 } 1600 break; 1601 case 'o': 1602 line = xstrdup(optarg); 1603 if (process_server_config_line(&options, line, 1604 "command-line", 0, NULL, NULL) != 0) 1605 exit(1); 1606 free(line); 1607 break; 1608 case '?': 1609 default: 1610 usage(); 1611 break; 1612 } 1613 } 1614 if (rexeced_flag || inetd_flag) 1615 rexec_flag = 0; 1616 if (!test_flag && (rexec_flag && (av[0] == NULL || *av[0] != '/'))) 1617 fatal("sshd re-exec requires execution with an absolute path"); 1618 if (rexeced_flag) 1619 closefrom(REEXEC_MIN_FREE_FD); 1620 else 1621 closefrom(REEXEC_DEVCRYPTO_RESERVED_FD); 1622 1623#ifdef WITH_OPENSSL 1624 OpenSSL_add_all_algorithms(); 1625#endif 1626 1627 /* If requested, redirect the logs to the specified logfile. */ 1628 if (logfile != NULL) { 1629 log_redirect_stderr_to(logfile); 1630 free(logfile); 1631 } 1632 /* 1633 * Force logging to stderr until we have loaded the private host 1634 * key (unless started from inetd) 1635 */ 1636 log_init(__progname, 1637 options.log_level == SYSLOG_LEVEL_NOT_SET ? 1638 SYSLOG_LEVEL_INFO : options.log_level, 1639 options.log_facility == SYSLOG_FACILITY_NOT_SET ? 1640 SYSLOG_FACILITY_AUTH : options.log_facility, 1641 log_stderr || !inetd_flag); 1642 1643 /* 1644 * Unset KRB5CCNAME, otherwise the user's session may inherit it from 1645 * root's environment 1646 */ 1647 if (getenv("KRB5CCNAME") != NULL) 1648 (void) unsetenv("KRB5CCNAME"); 1649 1650#ifdef _UNICOS 1651 /* Cray can define user privs drop all privs now! 1652 * Not needed on PRIV_SU systems! 1653 */ 1654 drop_cray_privs(); 1655#endif 1656 1657 sensitive_data.server_key = NULL; 1658 sensitive_data.ssh1_host_key = NULL; 1659 sensitive_data.have_ssh1_key = 0; 1660 sensitive_data.have_ssh2_key = 0; 1661 1662 /* 1663 * If we're doing an extended config test, make sure we have all of 1664 * the parameters we need. If we're not doing an extended test, 1665 * do not silently ignore connection test params. 1666 */ 1667 if (test_flag >= 2 && server_match_spec_complete(connection_info) == 0) 1668 fatal("user, host and addr are all required when testing " 1669 "Match configs"); 1670 if (test_flag < 2 && server_match_spec_complete(connection_info) >= 0) 1671 fatal("Config test connection parameter (-C) provided without " 1672 "test mode (-T)"); 1673 1674 /* Fetch our configuration */ 1675 buffer_init(&cfg); 1676 if (rexeced_flag) 1677 recv_rexec_state(REEXEC_CONFIG_PASS_FD, &cfg); 1678 else 1679 load_server_config(config_file_name, &cfg); 1680 1681 parse_server_config(&options, rexeced_flag ? "rexec" : config_file_name, 1682 &cfg, NULL); 1683 1684 seed_rng(); 1685 1686 /* Fill in default values for those options not explicitly set. */ 1687 fill_default_server_options(&options); 1688 1689 /* challenge-response is implemented via keyboard interactive */ 1690 if (options.challenge_response_authentication) 1691 options.kbd_interactive_authentication = 1; 1692 1693 /* Check that options are sensible */ 1694 if (options.authorized_keys_command_user == NULL && 1695 (options.authorized_keys_command != NULL && 1696 strcasecmp(options.authorized_keys_command, "none") != 0)) 1697 fatal("AuthorizedKeysCommand set without " 1698 "AuthorizedKeysCommandUser"); 1699 1700 /* 1701 * Check whether there is any path through configured auth methods. 1702 * Unfortunately it is not possible to verify this generally before 1703 * daemonisation in the presence of Match block, but this catches 1704 * and warns for trivial misconfigurations that could break login. 1705 */ 1706 if (options.num_auth_methods != 0) { 1707 if ((options.protocol & SSH_PROTO_1)) 1708 fatal("AuthenticationMethods is not supported with " 1709 "SSH protocol 1"); 1710 for (n = 0; n < options.num_auth_methods; n++) { 1711 if (auth2_methods_valid(options.auth_methods[n], 1712 1) == 0) 1713 break; 1714 } 1715 if (n >= options.num_auth_methods) 1716 fatal("AuthenticationMethods cannot be satisfied by " 1717 "enabled authentication methods"); 1718 } 1719 1720 /* set default channel AF */ 1721 channel_set_af(options.address_family); 1722 1723 /* Check that there are no remaining arguments. */ 1724 if (optind < ac) { 1725 fprintf(stderr, "Extra argument %s.\n", av[optind]); 1726 exit(1); 1727 } 1728 1729 debug("sshd version %s, %s", SSH_VERSION, 1730#ifdef WITH_OPENSSL 1731 SSLeay_version(SSLEAY_VERSION) 1732#else 1733 "without OpenSSL" 1734#endif 1735 ); 1736 1737 /* Store privilege separation user for later use if required. */ 1738 if ((privsep_pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) { 1739 if (use_privsep || options.kerberos_authentication) 1740 fatal("Privilege separation user %s does not exist", 1741 SSH_PRIVSEP_USER); 1742 } else { 1743 if (privsep_pw->pw_passwd != NULL) { 1744 explicit_bzero(privsep_pw->pw_passwd, 1745 strlen(privsep_pw->pw_passwd)); 1746 } 1747 privsep_pw = pwcopy(privsep_pw); 1748 if (privsep_pw->pw_passwd != NULL) { 1749 free(privsep_pw->pw_passwd); 1750 } 1751 privsep_pw->pw_passwd = xstrdup("*"); 1752 } 1753#if !defined(ANDROID) 1754 endpwent(); 1755#endif 1756 1757 /* load host keys */ 1758 sensitive_data.host_keys = xcalloc(options.num_host_key_files, 1759 sizeof(Key *)); 1760 sensitive_data.host_pubkeys = xcalloc(options.num_host_key_files, 1761 sizeof(Key *)); 1762 1763 if (options.host_key_agent) { 1764 if (strcmp(options.host_key_agent, SSH_AUTHSOCKET_ENV_NAME)) 1765 setenv(SSH_AUTHSOCKET_ENV_NAME, 1766 options.host_key_agent, 1); 1767 if ((r = ssh_get_authentication_socket(NULL)) == 0) 1768 have_agent = 1; 1769 else 1770 error("Could not connect to agent \"%s\": %s", 1771 options.host_key_agent, ssh_err(r)); 1772 } 1773 1774 for (i = 0; i < options.num_host_key_files; i++) { 1775 if (options.host_key_files[i] == NULL) 1776 continue; 1777 key = key_load_private(options.host_key_files[i], "", NULL); 1778 pubkey = key_load_public(options.host_key_files[i], NULL); 1779 if (pubkey == NULL && key != NULL) 1780 pubkey = key_demote(key); 1781 sensitive_data.host_keys[i] = key; 1782 sensitive_data.host_pubkeys[i] = pubkey; 1783 1784 if (key == NULL && pubkey != NULL && pubkey->type != KEY_RSA1 && 1785 have_agent) { 1786 debug("will rely on agent for hostkey %s", 1787 options.host_key_files[i]); 1788 keytype = pubkey->type; 1789 } else if (key != NULL) { 1790 keytype = key->type; 1791 } else { 1792 error("Could not load host key: %s", 1793 options.host_key_files[i]); 1794 sensitive_data.host_keys[i] = NULL; 1795 sensitive_data.host_pubkeys[i] = NULL; 1796 continue; 1797 } 1798 1799 switch (keytype) { 1800 case KEY_RSA1: 1801 sensitive_data.ssh1_host_key = key; 1802 sensitive_data.have_ssh1_key = 1; 1803 break; 1804 case KEY_RSA: 1805 case KEY_DSA: 1806 case KEY_ECDSA: 1807 case KEY_ED25519: 1808 if (have_agent || key != NULL) 1809 sensitive_data.have_ssh2_key = 1; 1810 break; 1811 } 1812 if ((fp = sshkey_fingerprint(pubkey, options.fingerprint_hash, 1813 SSH_FP_DEFAULT)) == NULL) 1814 fatal("sshkey_fingerprint failed"); 1815 debug("%s host key #%d: %s %s", 1816 key ? "private" : "agent", i, keytype == KEY_RSA1 ? 1817 sshkey_type(pubkey) : sshkey_ssh_name(pubkey), fp); 1818 free(fp); 1819 } 1820 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) { 1821 logit("Disabling protocol version 1. Could not load host key"); 1822 options.protocol &= ~SSH_PROTO_1; 1823 } 1824 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) { 1825 logit("Disabling protocol version 2. Could not load host key"); 1826 options.protocol &= ~SSH_PROTO_2; 1827 } 1828 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) { 1829 logit("sshd: no hostkeys available -- exiting."); 1830 exit(1); 1831 } 1832 1833 /* 1834 * Load certificates. They are stored in an array at identical 1835 * indices to the public keys that they relate to. 1836 */ 1837 sensitive_data.host_certificates = xcalloc(options.num_host_key_files, 1838 sizeof(Key *)); 1839 for (i = 0; i < options.num_host_key_files; i++) 1840 sensitive_data.host_certificates[i] = NULL; 1841 1842 for (i = 0; i < options.num_host_cert_files; i++) { 1843 if (options.host_cert_files[i] == NULL) 1844 continue; 1845 key = key_load_public(options.host_cert_files[i], NULL); 1846 if (key == NULL) { 1847 error("Could not load host certificate: %s", 1848 options.host_cert_files[i]); 1849 continue; 1850 } 1851 if (!key_is_cert(key)) { 1852 error("Certificate file is not a certificate: %s", 1853 options.host_cert_files[i]); 1854 key_free(key); 1855 continue; 1856 } 1857 /* Find matching private key */ 1858 for (j = 0; j < options.num_host_key_files; j++) { 1859 if (key_equal_public(key, 1860 sensitive_data.host_keys[j])) { 1861 sensitive_data.host_certificates[j] = key; 1862 break; 1863 } 1864 } 1865 if (j >= options.num_host_key_files) { 1866 error("No matching private key for certificate: %s", 1867 options.host_cert_files[i]); 1868 key_free(key); 1869 continue; 1870 } 1871 sensitive_data.host_certificates[j] = key; 1872 debug("host certificate: #%d type %d %s", j, key->type, 1873 key_type(key)); 1874 } 1875 1876#ifdef WITH_SSH1 1877 /* Check certain values for sanity. */ 1878 if (options.protocol & SSH_PROTO_1) { 1879 if (options.server_key_bits < 512 || 1880 options.server_key_bits > 32768) { 1881 fprintf(stderr, "Bad server key size.\n"); 1882 exit(1); 1883 } 1884 /* 1885 * Check that server and host key lengths differ sufficiently. This 1886 * is necessary to make double encryption work with rsaref. Oh, I 1887 * hate software patents. I dont know if this can go? Niels 1888 */ 1889 if (options.server_key_bits > 1890 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - 1891 SSH_KEY_BITS_RESERVED && options.server_key_bits < 1892 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + 1893 SSH_KEY_BITS_RESERVED) { 1894 options.server_key_bits = 1895 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + 1896 SSH_KEY_BITS_RESERVED; 1897 debug("Forcing server key to %d bits to make it differ from host key.", 1898 options.server_key_bits); 1899 } 1900 } 1901#endif 1902 1903 if (use_privsep) { 1904 struct stat st; 1905 1906 if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) || 1907 (S_ISDIR(st.st_mode) == 0)) 1908 fatal("Missing privilege separation directory: %s", 1909 _PATH_PRIVSEP_CHROOT_DIR); 1910 1911#ifdef HAVE_CYGWIN 1912 if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) && 1913 (st.st_uid != getuid () || 1914 (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)) 1915#else 1916 if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0) 1917#endif 1918 fatal("%s must be owned by root and not group or " 1919 "world-writable.", _PATH_PRIVSEP_CHROOT_DIR); 1920 } 1921 1922 if (test_flag > 1) { 1923 if (server_match_spec_complete(connection_info) == 1) 1924 parse_server_match_config(&options, connection_info); 1925 dump_config(&options); 1926 } 1927 1928 /* Configuration looks good, so exit if in test mode. */ 1929 if (test_flag) 1930 exit(0); 1931 1932 /* 1933 * Clear out any supplemental groups we may have inherited. This 1934 * prevents inadvertent creation of files with bad modes (in the 1935 * portable version at least, it's certainly possible for PAM 1936 * to create a file, and we can't control the code in every 1937 * module which might be used). 1938 */ 1939 if (setgroups(0, NULL) < 0) 1940 debug("setgroups() failed: %.200s", strerror(errno)); 1941 1942 if (rexec_flag) { 1943 rexec_argv = xcalloc(rexec_argc + 2, sizeof(char *)); 1944 for (i = 0; i < rexec_argc; i++) { 1945 debug("rexec_argv[%d]='%s'", i, saved_argv[i]); 1946 rexec_argv[i] = saved_argv[i]; 1947 } 1948 rexec_argv[rexec_argc] = "-R"; 1949 rexec_argv[rexec_argc + 1] = NULL; 1950 } 1951 1952 /* Ensure that umask disallows at least group and world write */ 1953 new_umask = umask(0077) | 0022; 1954 (void) umask(new_umask); 1955 1956 /* Initialize the log (it is reinitialized below in case we forked). */ 1957 if (debug_flag && (!inetd_flag || rexeced_flag)) 1958 log_stderr = 1; 1959 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1960 1961 /* 1962 * If not in debugging mode, and not started from inetd, disconnect 1963 * from the controlling terminal, and fork. The original process 1964 * exits. 1965 */ 1966 if (!(debug_flag || inetd_flag || no_daemon_flag)) { 1967#ifdef TIOCNOTTY 1968 int fd; 1969#endif /* TIOCNOTTY */ 1970 if (daemon(0, 0) < 0) 1971 fatal("daemon() failed: %.200s", strerror(errno)); 1972 1973 /* Disconnect from the controlling tty. */ 1974#ifdef TIOCNOTTY 1975 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 1976 if (fd >= 0) { 1977 (void) ioctl(fd, TIOCNOTTY, NULL); 1978 close(fd); 1979 } 1980#endif /* TIOCNOTTY */ 1981 } 1982 /* Reinitialize the log (because of the fork above). */ 1983 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1984 1985 /* Chdir to the root directory so that the current disk can be 1986 unmounted if desired. */ 1987 if (chdir("/") == -1) 1988 error("chdir(\"/\"): %s", strerror(errno)); 1989 1990 /* ignore SIGPIPE */ 1991 signal(SIGPIPE, SIG_IGN); 1992 1993 /* Get a connection, either from inetd or a listening TCP socket */ 1994 if (inetd_flag) { 1995 server_accept_inetd(&sock_in, &sock_out); 1996 } else { 1997 platform_pre_listen(); 1998 server_listen(); 1999 2000 if (options.protocol & SSH_PROTO_1) 2001 generate_ephemeral_server_key(); 2002 2003 signal(SIGHUP, sighup_handler); 2004 signal(SIGCHLD, main_sigchld_handler); 2005 signal(SIGTERM, sigterm_handler); 2006 signal(SIGQUIT, sigterm_handler); 2007 2008 /* 2009 * Write out the pid file after the sigterm handler 2010 * is setup and the listen sockets are bound 2011 */ 2012 if (options.pid_file != NULL && !debug_flag) { 2013 FILE *f = fopen(options.pid_file, "w"); 2014 2015 if (f == NULL) { 2016 error("Couldn't create pid file \"%s\": %s", 2017 options.pid_file, strerror(errno)); 2018 } else { 2019 fprintf(f, "%ld\n", (long) getpid()); 2020 fclose(f); 2021 } 2022 } 2023 2024 /* Accept a connection and return in a forked child */ 2025 server_accept_loop(&sock_in, &sock_out, 2026 &newsock, config_s); 2027 } 2028 2029 /* This is the child processing a new connection. */ 2030 setproctitle("%s", "[accepted]"); 2031 2032 /* 2033 * Create a new session and process group since the 4.4BSD 2034 * setlogin() affects the entire process group. We don't 2035 * want the child to be able to affect the parent. 2036 */ 2037#if !defined(SSHD_ACQUIRES_CTTY) 2038 /* 2039 * If setsid is called, on some platforms sshd will later acquire a 2040 * controlling terminal which will result in "could not set 2041 * controlling tty" errors. 2042 */ 2043 if (!debug_flag && !inetd_flag && setsid() < 0) 2044 error("setsid: %.100s", strerror(errno)); 2045#endif 2046 2047 if (rexec_flag) { 2048 int fd; 2049 2050 debug("rexec start in %d out %d newsock %d pipe %d sock %d", 2051 sock_in, sock_out, newsock, startup_pipe, config_s[0]); 2052 dup2(newsock, STDIN_FILENO); 2053 dup2(STDIN_FILENO, STDOUT_FILENO); 2054 if (startup_pipe == -1) 2055 close(REEXEC_STARTUP_PIPE_FD); 2056 else if (startup_pipe != REEXEC_STARTUP_PIPE_FD) { 2057 dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD); 2058 close(startup_pipe); 2059 startup_pipe = REEXEC_STARTUP_PIPE_FD; 2060 } 2061 2062 dup2(config_s[1], REEXEC_CONFIG_PASS_FD); 2063 close(config_s[1]); 2064 2065 execv(rexec_argv[0], rexec_argv); 2066 2067 /* Reexec has failed, fall back and continue */ 2068 error("rexec of %s failed: %s", rexec_argv[0], strerror(errno)); 2069 recv_rexec_state(REEXEC_CONFIG_PASS_FD, NULL); 2070 log_init(__progname, options.log_level, 2071 options.log_facility, log_stderr); 2072 2073 /* Clean up fds */ 2074 close(REEXEC_CONFIG_PASS_FD); 2075 newsock = sock_out = sock_in = dup(STDIN_FILENO); 2076 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) { 2077 dup2(fd, STDIN_FILENO); 2078 dup2(fd, STDOUT_FILENO); 2079 if (fd > STDERR_FILENO) 2080 close(fd); 2081 } 2082 debug("rexec cleanup in %d out %d newsock %d pipe %d sock %d", 2083 sock_in, sock_out, newsock, startup_pipe, config_s[0]); 2084 } 2085 2086 /* Executed child processes don't need these. */ 2087 fcntl(sock_out, F_SETFD, FD_CLOEXEC); 2088 fcntl(sock_in, F_SETFD, FD_CLOEXEC); 2089 2090 /* 2091 * Disable the key regeneration alarm. We will not regenerate the 2092 * key since we are no longer in a position to give it to anyone. We 2093 * will not restart on SIGHUP since it no longer makes sense. 2094 */ 2095 alarm(0); 2096 signal(SIGALRM, SIG_DFL); 2097 signal(SIGHUP, SIG_DFL); 2098 signal(SIGTERM, SIG_DFL); 2099 signal(SIGQUIT, SIG_DFL); 2100 signal(SIGCHLD, SIG_DFL); 2101 signal(SIGINT, SIG_DFL); 2102 2103 /* 2104 * Register our connection. This turns encryption off because we do 2105 * not have a key. 2106 */ 2107 packet_set_connection(sock_in, sock_out); 2108 packet_set_server(); 2109 2110 /* Set SO_KEEPALIVE if requested. */ 2111 if (options.tcp_keep_alive && packet_connection_is_on_socket() && 2112 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) < 0) 2113 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 2114 2115 if ((remote_port = get_remote_port()) < 0) { 2116 debug("get_remote_port failed"); 2117 cleanup_exit(255); 2118 } 2119 2120 /* 2121 * We use get_canonical_hostname with usedns = 0 instead of 2122 * get_remote_ipaddr here so IP options will be checked. 2123 */ 2124 (void) get_canonical_hostname(0); 2125 /* 2126 * The rest of the code depends on the fact that 2127 * get_remote_ipaddr() caches the remote ip, even if 2128 * the socket goes away. 2129 */ 2130 remote_ip = get_remote_ipaddr(); 2131 2132#ifdef SSH_AUDIT_EVENTS 2133 audit_connection_from(remote_ip, remote_port); 2134#endif 2135 2136 /* Log the connection. */ 2137 verbose("Connection from %s port %d on %s port %d", 2138 remote_ip, remote_port, 2139 get_local_ipaddr(sock_in), get_local_port()); 2140 2141 /* 2142 * We don't want to listen forever unless the other side 2143 * successfully authenticates itself. So we set up an alarm which is 2144 * cleared after successful authentication. A limit of zero 2145 * indicates no limit. Note that we don't set the alarm in debugging 2146 * mode; it is just annoying to have the server exit just when you 2147 * are about to discover the bug. 2148 */ 2149 signal(SIGALRM, grace_alarm_handler); 2150 if (!debug_flag) 2151 alarm(options.login_grace_time); 2152 2153 sshd_exchange_identification(sock_in, sock_out); 2154 2155 /* In inetd mode, generate ephemeral key only for proto 1 connections */ 2156 if (!compat20 && inetd_flag && sensitive_data.server_key == NULL) 2157 generate_ephemeral_server_key(); 2158 2159 packet_set_nonblocking(); 2160 2161 /* allocate authentication context */ 2162 authctxt = xcalloc(1, sizeof(*authctxt)); 2163 2164 authctxt->loginmsg = &loginmsg; 2165 2166 /* XXX global for cleanup, access from other modules */ 2167 the_authctxt = authctxt; 2168 2169 /* prepare buffer to collect messages to display to user after login */ 2170 buffer_init(&loginmsg); 2171 auth_debug_reset(); 2172 2173 if (use_privsep) { 2174 if (privsep_preauth(authctxt) == 1) 2175 goto authenticated; 2176 } else if (compat20 && have_agent) { 2177 if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) { 2178 error("Unable to get agent socket: %s", ssh_err(r)); 2179 have_agent = 0; 2180 } 2181 } 2182 2183 /* perform the key exchange */ 2184 /* authenticate user and start session */ 2185 if (compat20) { 2186 do_ssh2_kex(); 2187 do_authentication2(authctxt); 2188 } else { 2189#ifdef WITH_SSH1 2190 do_ssh1_kex(); 2191 do_authentication(authctxt); 2192#else 2193 fatal("ssh1 not supported"); 2194#endif 2195 } 2196 /* 2197 * If we use privilege separation, the unprivileged child transfers 2198 * the current keystate and exits 2199 */ 2200 if (use_privsep) { 2201 mm_send_keystate(pmonitor); 2202 exit(0); 2203 } 2204 2205 authenticated: 2206 /* 2207 * Cancel the alarm we set to limit the time taken for 2208 * authentication. 2209 */ 2210 alarm(0); 2211 signal(SIGALRM, SIG_DFL); 2212 authctxt->authenticated = 1; 2213 if (startup_pipe != -1) { 2214 close(startup_pipe); 2215 startup_pipe = -1; 2216 } 2217 2218#ifdef SSH_AUDIT_EVENTS 2219 audit_event(SSH_AUTH_SUCCESS); 2220#endif 2221 2222#ifdef GSSAPI 2223 if (options.gss_authentication) { 2224 temporarily_use_uid(authctxt->pw); 2225 ssh_gssapi_storecreds(); 2226 restore_uid(); 2227 } 2228#endif 2229#ifdef USE_PAM 2230 if (options.use_pam) { 2231 do_pam_setcred(1); 2232 do_pam_session(); 2233 } 2234#endif 2235 2236 /* 2237 * In privilege separation, we fork another child and prepare 2238 * file descriptor passing. 2239 */ 2240 if (use_privsep) { 2241 privsep_postauth(authctxt); 2242 /* the monitor process [priv] will not return */ 2243 if (!compat20) 2244 destroy_sensitive_data(); 2245 } 2246 2247 packet_set_timeout(options.client_alive_interval, 2248 options.client_alive_count_max); 2249 2250 /* Try to send all our hostkeys to the client */ 2251 if (compat20) 2252 notify_hostkeys(active_state); 2253 2254 /* Start session. */ 2255 do_authenticated(authctxt); 2256 2257 /* The connection has been terminated. */ 2258 packet_get_bytes(&ibytes, &obytes); 2259 verbose("Transferred: sent %llu, received %llu bytes", 2260 (unsigned long long)obytes, (unsigned long long)ibytes); 2261 2262 verbose("Closing connection to %.500s port %d", remote_ip, remote_port); 2263 2264#ifdef USE_PAM 2265 if (options.use_pam) 2266 finish_pam(); 2267#endif /* USE_PAM */ 2268 2269#ifdef SSH_AUDIT_EVENTS 2270 PRIVSEP(audit_event(SSH_CONNECTION_CLOSE)); 2271#endif 2272 2273 packet_close(); 2274 2275 if (use_privsep) 2276 mm_terminate(); 2277 2278 exit(0); 2279} 2280 2281#ifdef WITH_SSH1 2282/* 2283 * Decrypt session_key_int using our private server key and private host key 2284 * (key with larger modulus first). 2285 */ 2286int 2287ssh1_session_key(BIGNUM *session_key_int) 2288{ 2289 int rsafail = 0; 2290 2291 if (BN_cmp(sensitive_data.server_key->rsa->n, 2292 sensitive_data.ssh1_host_key->rsa->n) > 0) { 2293 /* Server key has bigger modulus. */ 2294 if (BN_num_bits(sensitive_data.server_key->rsa->n) < 2295 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + 2296 SSH_KEY_BITS_RESERVED) { 2297 fatal("do_connection: %s: " 2298 "server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d", 2299 get_remote_ipaddr(), 2300 BN_num_bits(sensitive_data.server_key->rsa->n), 2301 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n), 2302 SSH_KEY_BITS_RESERVED); 2303 } 2304 if (rsa_private_decrypt(session_key_int, session_key_int, 2305 sensitive_data.server_key->rsa) != 0) 2306 rsafail++; 2307 if (rsa_private_decrypt(session_key_int, session_key_int, 2308 sensitive_data.ssh1_host_key->rsa) != 0) 2309 rsafail++; 2310 } else { 2311 /* Host key has bigger modulus (or they are equal). */ 2312 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) < 2313 BN_num_bits(sensitive_data.server_key->rsa->n) + 2314 SSH_KEY_BITS_RESERVED) { 2315 fatal("do_connection: %s: " 2316 "host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d", 2317 get_remote_ipaddr(), 2318 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n), 2319 BN_num_bits(sensitive_data.server_key->rsa->n), 2320 SSH_KEY_BITS_RESERVED); 2321 } 2322 if (rsa_private_decrypt(session_key_int, session_key_int, 2323 sensitive_data.ssh1_host_key->rsa) != 0) 2324 rsafail++; 2325 if (rsa_private_decrypt(session_key_int, session_key_int, 2326 sensitive_data.server_key->rsa) != 0) 2327 rsafail++; 2328 } 2329 return (rsafail); 2330} 2331 2332/* 2333 * SSH1 key exchange 2334 */ 2335static void 2336do_ssh1_kex(void) 2337{ 2338 int i, len; 2339 int rsafail = 0; 2340 BIGNUM *session_key_int, *fake_key_int, *real_key_int; 2341 u_char session_key[SSH_SESSION_KEY_LENGTH]; 2342 u_char fake_key_bytes[4096 / 8]; 2343 size_t fake_key_len; 2344 u_char cookie[8]; 2345 u_int cipher_type, auth_mask, protocol_flags; 2346 2347 /* 2348 * Generate check bytes that the client must send back in the user 2349 * packet in order for it to be accepted; this is used to defy ip 2350 * spoofing attacks. Note that this only works against somebody 2351 * doing IP spoofing from a remote machine; any machine on the local 2352 * network can still see outgoing packets and catch the random 2353 * cookie. This only affects rhosts authentication, and this is one 2354 * of the reasons why it is inherently insecure. 2355 */ 2356 arc4random_buf(cookie, sizeof(cookie)); 2357 2358 /* 2359 * Send our public key. We include in the packet 64 bits of random 2360 * data that must be matched in the reply in order to prevent IP 2361 * spoofing. 2362 */ 2363 packet_start(SSH_SMSG_PUBLIC_KEY); 2364 for (i = 0; i < 8; i++) 2365 packet_put_char(cookie[i]); 2366 2367 /* Store our public server RSA key. */ 2368 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n)); 2369 packet_put_bignum(sensitive_data.server_key->rsa->e); 2370 packet_put_bignum(sensitive_data.server_key->rsa->n); 2371 2372 /* Store our public host RSA key. */ 2373 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n)); 2374 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e); 2375 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n); 2376 2377 /* Put protocol flags. */ 2378 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN); 2379 2380 /* Declare which ciphers we support. */ 2381 packet_put_int(cipher_mask_ssh1(0)); 2382 2383 /* Declare supported authentication types. */ 2384 auth_mask = 0; 2385 if (options.rhosts_rsa_authentication) 2386 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA; 2387 if (options.rsa_authentication) 2388 auth_mask |= 1 << SSH_AUTH_RSA; 2389 if (options.challenge_response_authentication == 1) 2390 auth_mask |= 1 << SSH_AUTH_TIS; 2391 if (options.password_authentication) 2392 auth_mask |= 1 << SSH_AUTH_PASSWORD; 2393 packet_put_int(auth_mask); 2394 2395 /* Send the packet and wait for it to be sent. */ 2396 packet_send(); 2397 packet_write_wait(); 2398 2399 debug("Sent %d bit server key and %d bit host key.", 2400 BN_num_bits(sensitive_data.server_key->rsa->n), 2401 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n)); 2402 2403 /* Read clients reply (cipher type and session key). */ 2404 packet_read_expect(SSH_CMSG_SESSION_KEY); 2405 2406 /* Get cipher type and check whether we accept this. */ 2407 cipher_type = packet_get_char(); 2408 2409 if (!(cipher_mask_ssh1(0) & (1 << cipher_type))) 2410 packet_disconnect("Warning: client selects unsupported cipher."); 2411 2412 /* Get check bytes from the packet. These must match those we 2413 sent earlier with the public key packet. */ 2414 for (i = 0; i < 8; i++) 2415 if (cookie[i] != packet_get_char()) 2416 packet_disconnect("IP Spoofing check bytes do not match."); 2417 2418 debug("Encryption type: %.200s", cipher_name(cipher_type)); 2419 2420 /* Get the encrypted integer. */ 2421 if ((real_key_int = BN_new()) == NULL) 2422 fatal("do_ssh1_kex: BN_new failed"); 2423 packet_get_bignum(real_key_int); 2424 2425 protocol_flags = packet_get_int(); 2426 packet_set_protocol_flags(protocol_flags); 2427 packet_check_eom(); 2428 2429 /* Setup a fake key in case RSA decryption fails */ 2430 if ((fake_key_int = BN_new()) == NULL) 2431 fatal("do_ssh1_kex: BN_new failed"); 2432 fake_key_len = BN_num_bytes(real_key_int); 2433 if (fake_key_len > sizeof(fake_key_bytes)) 2434 fake_key_len = sizeof(fake_key_bytes); 2435 arc4random_buf(fake_key_bytes, fake_key_len); 2436 if (BN_bin2bn(fake_key_bytes, fake_key_len, fake_key_int) == NULL) 2437 fatal("do_ssh1_kex: BN_bin2bn failed"); 2438 2439 /* Decrypt real_key_int using host/server keys */ 2440 rsafail = PRIVSEP(ssh1_session_key(real_key_int)); 2441 /* If decryption failed, use the fake key. Else, the real key. */ 2442 if (rsafail) 2443 session_key_int = fake_key_int; 2444 else 2445 session_key_int = real_key_int; 2446 2447 /* 2448 * Extract session key from the decrypted integer. The key is in the 2449 * least significant 256 bits of the integer; the first byte of the 2450 * key is in the highest bits. 2451 */ 2452 (void) BN_mask_bits(session_key_int, sizeof(session_key) * 8); 2453 len = BN_num_bytes(session_key_int); 2454 if (len < 0 || (u_int)len > sizeof(session_key)) { 2455 error("do_ssh1_kex: bad session key len from %s: " 2456 "session_key_int %d > sizeof(session_key) %lu", 2457 get_remote_ipaddr(), len, (u_long)sizeof(session_key)); 2458 rsafail++; 2459 } else { 2460 explicit_bzero(session_key, sizeof(session_key)); 2461 BN_bn2bin(session_key_int, 2462 session_key + sizeof(session_key) - len); 2463 2464 derive_ssh1_session_id( 2465 sensitive_data.ssh1_host_key->rsa->n, 2466 sensitive_data.server_key->rsa->n, 2467 cookie, session_id); 2468 /* 2469 * Xor the first 16 bytes of the session key with the 2470 * session id. 2471 */ 2472 for (i = 0; i < 16; i++) 2473 session_key[i] ^= session_id[i]; 2474 } 2475 2476 /* Destroy the private and public keys. No longer. */ 2477 destroy_sensitive_data(); 2478 2479 if (use_privsep) 2480 mm_ssh1_session_id(session_id); 2481 2482 /* Destroy the decrypted integer. It is no longer needed. */ 2483 BN_clear_free(real_key_int); 2484 BN_clear_free(fake_key_int); 2485 2486 /* Set the session key. From this on all communications will be encrypted. */ 2487 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type); 2488 2489 /* Destroy our copy of the session key. It is no longer needed. */ 2490 explicit_bzero(session_key, sizeof(session_key)); 2491 2492 debug("Received session key; encryption turned on."); 2493 2494 /* Send an acknowledgment packet. Note that this packet is sent encrypted. */ 2495 packet_start(SSH_SMSG_SUCCESS); 2496 packet_send(); 2497 packet_write_wait(); 2498} 2499#endif 2500 2501int 2502sshd_hostkey_sign(Key *privkey, Key *pubkey, u_char **signature, size_t *slen, 2503 const u_char *data, size_t dlen, u_int flag) 2504{ 2505 int r; 2506 u_int xxx_slen, xxx_dlen = dlen; 2507 2508 if (privkey) { 2509 if (PRIVSEP(key_sign(privkey, signature, &xxx_slen, data, xxx_dlen) < 0)) 2510 fatal("%s: key_sign failed", __func__); 2511 if (slen) 2512 *slen = xxx_slen; 2513 } else if (use_privsep) { 2514 if (mm_key_sign(pubkey, signature, &xxx_slen, data, xxx_dlen) < 0) 2515 fatal("%s: pubkey_sign failed", __func__); 2516 if (slen) 2517 *slen = xxx_slen; 2518 } else { 2519 if ((r = ssh_agent_sign(auth_sock, pubkey, signature, slen, 2520 data, dlen, datafellows)) != 0) 2521 fatal("%s: ssh_agent_sign failed: %s", 2522 __func__, ssh_err(r)); 2523 } 2524 return 0; 2525} 2526 2527/* 2528 * SSH2 key exchange: diffie-hellman-group1-sha1 2529 */ 2530static void 2531do_ssh2_kex(void) 2532{ 2533 char *myproposal[PROPOSAL_MAX] = { KEX_SERVER }; 2534 struct kex *kex; 2535 int r; 2536 2537 if (options.ciphers != NULL) { 2538 myproposal[PROPOSAL_ENC_ALGS_CTOS] = 2539 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers; 2540 } 2541 myproposal[PROPOSAL_ENC_ALGS_CTOS] = 2542 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]); 2543 myproposal[PROPOSAL_ENC_ALGS_STOC] = 2544 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]); 2545 2546 if (options.macs != NULL) { 2547 myproposal[PROPOSAL_MAC_ALGS_CTOS] = 2548 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs; 2549 } 2550 if (options.compression == COMP_NONE) { 2551 myproposal[PROPOSAL_COMP_ALGS_CTOS] = 2552 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none"; 2553 } else if (options.compression == COMP_DELAYED) { 2554 myproposal[PROPOSAL_COMP_ALGS_CTOS] = 2555 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none,zlib@openssh.com"; 2556 } 2557 if (options.kex_algorithms != NULL) 2558 myproposal[PROPOSAL_KEX_ALGS] = options.kex_algorithms; 2559 2560 myproposal[PROPOSAL_KEX_ALGS] = compat_kex_proposal( 2561 myproposal[PROPOSAL_KEX_ALGS]); 2562 2563 if (options.rekey_limit || options.rekey_interval) 2564 packet_set_rekey_limits((u_int32_t)options.rekey_limit, 2565 (time_t)options.rekey_interval); 2566 2567 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = compat_pkalg_proposal( 2568 list_hostkey_types()); 2569 2570 /* start key exchange */ 2571 if ((r = kex_setup(active_state, myproposal)) != 0) 2572 fatal("kex_setup: %s", ssh_err(r)); 2573 kex = active_state->kex; 2574#ifdef WITH_OPENSSL 2575 kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server; 2576 kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server; 2577 kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 2578 kex->kex[KEX_DH_GEX_SHA256] = kexgex_server; 2579# ifdef OPENSSL_HAS_ECC 2580 kex->kex[KEX_ECDH_SHA2] = kexecdh_server; 2581# endif 2582#endif 2583 kex->kex[KEX_C25519_SHA256] = kexc25519_server; 2584 kex->server = 1; 2585 kex->client_version_string=client_version_string; 2586 kex->server_version_string=server_version_string; 2587 kex->load_host_public_key=&get_hostkey_public_by_type; 2588 kex->load_host_private_key=&get_hostkey_private_by_type; 2589 kex->host_key_index=&get_hostkey_index; 2590 kex->sign = sshd_hostkey_sign; 2591 2592 dispatch_run(DISPATCH_BLOCK, &kex->done, active_state); 2593 2594 session_id2 = kex->session_id; 2595 session_id2_len = kex->session_id_len; 2596 2597#ifdef DEBUG_KEXDH 2598 /* send 1st encrypted/maced/compressed message */ 2599 packet_start(SSH2_MSG_IGNORE); 2600 packet_put_cstring("markus"); 2601 packet_send(); 2602 packet_write_wait(); 2603#endif 2604 debug("KEX done"); 2605} 2606 2607/* server specific fatal cleanup */ 2608void 2609cleanup_exit(int i) 2610{ 2611 if (the_authctxt) { 2612 do_cleanup(the_authctxt); 2613 if (use_privsep && privsep_is_preauth && 2614 pmonitor != NULL && pmonitor->m_pid > 1) { 2615 debug("Killing privsep child %d", pmonitor->m_pid); 2616 if (kill(pmonitor->m_pid, SIGKILL) != 0 && 2617 errno != ESRCH) 2618 error("%s: kill(%d): %s", __func__, 2619 pmonitor->m_pid, strerror(errno)); 2620 } 2621 } 2622#ifdef SSH_AUDIT_EVENTS 2623 /* done after do_cleanup so it can cancel the PAM auth 'thread' */ 2624 if (!use_privsep || mm_is_monitor()) 2625 audit_event(SSH_CONNECTION_ABANDON); 2626#endif 2627 _exit(i); 2628} 2629