1 /* 2 * Author: Tatu Ylonen <ylo@cs.hut.fi> 3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 4 * All rights reserved 5 * This program is the ssh daemon. It listens for connections from clients, 6 * and performs authentication, executes use commands or shell, and forwards 7 * information to/from the application to the user client over an encrypted 8 * connection. This can also handle forwarding of X11, TCP/IP, and 9 * authentication agent connections. 10 * 11 * As far as I am concerned, the code I have written for this software 12 * can be used freely for any purpose. Any derived versions of this 13 * software must be clearly marked as such, and if the derived work is 14 * incompatible with the protocol description in the RFC file, it must be 15 * called by a name other than "ssh" or "Secure Shell". 16 * 17 * SSH2 implementation: 18 * Privilege Separation: 19 * 20 * Copyright (c) 2000, 2001, 2002 Markus Friedl. All rights reserved. 21 * Copyright (c) 2002 Niels Provos. All rights reserved. 22 * 23 * Redistribution and use in source and binary forms, with or without 24 * modification, are permitted provided that the following conditions 25 * are met: 26 * 1. Redistributions of source code must retain the above copyright 27 * notice, this list of conditions and the following disclaimer. 28 * 2. Redistributions in binary form must reproduce the above copyright 29 * notice, this list of conditions and the following disclaimer in the 30 * documentation and/or other materials provided with the distribution. 31 * 32 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 33 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 34 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 35 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 36 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 37 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 38 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 39 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 40 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 41 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 42 */ 43 44 #include "includes.h" 45 RCSID("$FreeBSD$"); 46 RCSID("$OpenBSD: sshd.c,v 1.286 2004/02/23 12:02:33 markus Exp $"); 47 48 #include <openssl/dh.h> 49 #include <openssl/bn.h> 50 #include <openssl/md5.h> 51 #include <openssl/rand.h> 52 #ifdef HAVE_SECUREWARE 53 #include <sys/security.h> 54 #include <prot.h> 55 #endif 56 57 #ifdef __FreeBSD__ 58 #include <resolv.h> 59 #endif 60 61 #include "ssh.h" 62 #include "ssh1.h" 63 #include "ssh2.h" 64 #include "xmalloc.h" 65 #include "rsa.h" 66 #include "sshpty.h" 67 #include "packet.h" 68 #include "mpaux.h" 69 #include "log.h" 70 #include "servconf.h" 71 #include "uidswap.h" 72 #include "compat.h" 73 #include "buffer.h" 74 #include "cipher.h" 75 #include "kex.h" 76 #include "key.h" 77 #include "dh.h" 78 #include "myproposal.h" 79 #include "authfile.h" 80 #include "pathnames.h" 81 #include "atomicio.h" 82 #include "canohost.h" 83 #include "auth.h" 84 #include "misc.h" 85 #include "dispatch.h" 86 #include "channels.h" 87 #include "session.h" 88 #include "monitor_mm.h" 89 #include "monitor.h" 90 #include "monitor_wrap.h" 91 #include "monitor_fdpass.h" 92 93 #ifdef LIBWRAP 94 #include <tcpd.h> 95 #include <syslog.h> 96 int allow_severity = LOG_INFO; 97 int deny_severity = LOG_WARNING; 98 #endif /* LIBWRAP */ 99 100 #ifndef O_NOCTTY 101 #define O_NOCTTY 0 102 #endif 103 104 #ifdef HAVE___PROGNAME 105 extern char *__progname; 106 #else 107 char *__progname; 108 #endif 109 110 /* Server configuration options. */ 111 ServerOptions options; 112 113 /* Name of the server configuration file. */ 114 char *config_file_name = _PATH_SERVER_CONFIG_FILE; 115 116 /* 117 * Flag indicating whether IPv4 or IPv6. This can be set on the command line. 118 * Default value is AF_UNSPEC means both IPv4 and IPv6. 119 */ 120 int IPv4or6 = AF_UNSPEC; 121 122 /* 123 * Debug mode flag. This can be set on the command line. If debug 124 * mode is enabled, extra debugging output will be sent to the system 125 * log, the daemon will not go to background, and will exit after processing 126 * the first connection. 127 */ 128 int debug_flag = 0; 129 130 /* Flag indicating that the daemon should only test the configuration and keys. */ 131 int test_flag = 0; 132 133 /* Flag indicating that the daemon is being started from inetd. */ 134 int inetd_flag = 0; 135 136 /* Flag indicating that sshd should not detach and become a daemon. */ 137 int no_daemon_flag = 0; 138 139 /* debug goes to stderr unless inetd_flag is set */ 140 int log_stderr = 0; 141 142 /* Saved arguments to main(). */ 143 char **saved_argv; 144 int saved_argc; 145 146 /* 147 * The sockets that the server is listening; this is used in the SIGHUP 148 * signal handler. 149 */ 150 #define MAX_LISTEN_SOCKS 16 151 int listen_socks[MAX_LISTEN_SOCKS]; 152 int num_listen_socks = 0; 153 154 /* 155 * the client's version string, passed by sshd2 in compat mode. if != NULL, 156 * sshd will skip the version-number exchange 157 */ 158 char *client_version_string = NULL; 159 char *server_version_string = NULL; 160 161 /* for rekeying XXX fixme */ 162 Kex *xxx_kex; 163 164 /* 165 * Any really sensitive data in the application is contained in this 166 * structure. The idea is that this structure could be locked into memory so 167 * that the pages do not get written into swap. However, there are some 168 * problems. The private key contains BIGNUMs, and we do not (in principle) 169 * have access to the internals of them, and locking just the structure is 170 * not very useful. Currently, memory locking is not implemented. 171 */ 172 struct { 173 Key *server_key; /* ephemeral server key */ 174 Key *ssh1_host_key; /* ssh1 host key */ 175 Key **host_keys; /* all private host keys */ 176 int have_ssh1_key; 177 int have_ssh2_key; 178 u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH]; 179 } sensitive_data; 180 181 /* 182 * Flag indicating whether the RSA server key needs to be regenerated. 183 * Is set in the SIGALRM handler and cleared when the key is regenerated. 184 */ 185 static volatile sig_atomic_t key_do_regen = 0; 186 187 /* This is set to true when a signal is received. */ 188 static volatile sig_atomic_t received_sighup = 0; 189 static volatile sig_atomic_t received_sigterm = 0; 190 191 /* session identifier, used by RSA-auth */ 192 u_char session_id[16]; 193 194 /* same for ssh2 */ 195 u_char *session_id2 = NULL; 196 u_int session_id2_len = 0; 197 198 /* record remote hostname or ip */ 199 u_int utmp_len = MAXHOSTNAMELEN; 200 201 /* options.max_startup sized array of fd ints */ 202 int *startup_pipes = NULL; 203 int startup_pipe; /* in child */ 204 205 /* variables used for privilege separation */ 206 int use_privsep; 207 struct monitor *pmonitor = NULL; 208 209 /* message to be displayed after login */ 210 Buffer loginmsg; 211 212 /* global authentication context */ 213 Authctxt *the_authctxt = NULL; 214 215 /* Prototypes for various functions defined later in this file. */ 216 void destroy_sensitive_data(void); 217 void demote_sensitive_data(void); 218 219 static void do_ssh1_kex(void); 220 static void do_ssh2_kex(void); 221 222 /* 223 * Close all listening sockets 224 */ 225 static void 226 close_listen_socks(void) 227 { 228 int i; 229 230 for (i = 0; i < num_listen_socks; i++) 231 close(listen_socks[i]); 232 num_listen_socks = -1; 233 } 234 235 static void 236 close_startup_pipes(void) 237 { 238 int i; 239 240 if (startup_pipes) 241 for (i = 0; i < options.max_startups; i++) 242 if (startup_pipes[i] != -1) 243 close(startup_pipes[i]); 244 } 245 246 /* 247 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP; 248 * the effect is to reread the configuration file (and to regenerate 249 * the server key). 250 */ 251 static void 252 sighup_handler(int sig) 253 { 254 int save_errno = errno; 255 256 received_sighup = 1; 257 signal(SIGHUP, sighup_handler); 258 errno = save_errno; 259 } 260 261 /* 262 * Called from the main program after receiving SIGHUP. 263 * Restarts the server. 264 */ 265 static void 266 sighup_restart(void) 267 { 268 logit("Received SIGHUP; restarting."); 269 close_listen_socks(); 270 close_startup_pipes(); 271 execv(saved_argv[0], saved_argv); 272 logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], 273 strerror(errno)); 274 exit(1); 275 } 276 277 /* 278 * Generic signal handler for terminating signals in the master daemon. 279 */ 280 static void 281 sigterm_handler(int sig) 282 { 283 received_sigterm = sig; 284 } 285 286 /* 287 * SIGCHLD handler. This is called whenever a child dies. This will then 288 * reap any zombies left by exited children. 289 */ 290 static void 291 main_sigchld_handler(int sig) 292 { 293 int save_errno = errno; 294 pid_t pid; 295 int status; 296 297 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 298 (pid < 0 && errno == EINTR)) 299 ; 300 301 signal(SIGCHLD, main_sigchld_handler); 302 errno = save_errno; 303 } 304 305 /* 306 * Signal handler for the alarm after the login grace period has expired. 307 */ 308 static void 309 grace_alarm_handler(int sig) 310 { 311 /* XXX no idea how fix this signal handler */ 312 313 if (use_privsep && pmonitor != NULL && pmonitor->m_pid > 0) 314 kill(pmonitor->m_pid, SIGALRM); 315 316 /* Log error and exit. */ 317 fatal("Timeout before authentication for %s", get_remote_ipaddr()); 318 } 319 320 /* 321 * Signal handler for the key regeneration alarm. Note that this 322 * alarm only occurs in the daemon waiting for connections, and it does not 323 * do anything with the private key or random state before forking. 324 * Thus there should be no concurrency control/asynchronous execution 325 * problems. 326 */ 327 static void 328 generate_ephemeral_server_key(void) 329 { 330 u_int32_t rnd = 0; 331 int i; 332 333 verbose("Generating %s%d bit RSA key.", 334 sensitive_data.server_key ? "new " : "", options.server_key_bits); 335 if (sensitive_data.server_key != NULL) 336 key_free(sensitive_data.server_key); 337 sensitive_data.server_key = key_generate(KEY_RSA1, 338 options.server_key_bits); 339 verbose("RSA key generation complete."); 340 341 for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) { 342 if (i % 4 == 0) 343 rnd = arc4random(); 344 sensitive_data.ssh1_cookie[i] = rnd & 0xff; 345 rnd >>= 8; 346 } 347 arc4random_stir(); 348 } 349 350 static void 351 key_regeneration_alarm(int sig) 352 { 353 int save_errno = errno; 354 355 signal(SIGALRM, SIG_DFL); 356 errno = save_errno; 357 key_do_regen = 1; 358 } 359 360 static void 361 sshd_exchange_identification(int sock_in, int sock_out) 362 { 363 int i, mismatch; 364 int remote_major, remote_minor; 365 int major, minor; 366 char *s; 367 char buf[256]; /* Must not be larger than remote_version. */ 368 char remote_version[256]; /* Must be at least as big as buf. */ 369 370 if ((options.protocol & SSH_PROTO_1) && 371 (options.protocol & SSH_PROTO_2)) { 372 major = PROTOCOL_MAJOR_1; 373 minor = 99; 374 } else if (options.protocol & SSH_PROTO_2) { 375 major = PROTOCOL_MAJOR_2; 376 minor = PROTOCOL_MINOR_2; 377 } else { 378 major = PROTOCOL_MAJOR_1; 379 minor = PROTOCOL_MINOR_1; 380 } 381 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION); 382 server_version_string = xstrdup(buf); 383 384 /* Send our protocol version identification. */ 385 if (atomicio(vwrite, sock_out, server_version_string, 386 strlen(server_version_string)) 387 != strlen(server_version_string)) { 388 logit("Could not write ident string to %s", get_remote_ipaddr()); 389 cleanup_exit(255); 390 } 391 392 /* Read other sides version identification. */ 393 memset(buf, 0, sizeof(buf)); 394 for (i = 0; i < sizeof(buf) - 1; i++) { 395 if (atomicio(read, sock_in, &buf[i], 1) != 1) { 396 logit("Did not receive identification string from %s", 397 get_remote_ipaddr()); 398 cleanup_exit(255); 399 } 400 if (buf[i] == '\r') { 401 buf[i] = 0; 402 /* Kludge for F-Secure Macintosh < 1.0.2 */ 403 if (i == 12 && 404 strncmp(buf, "SSH-1.5-W1.0", 12) == 0) 405 break; 406 continue; 407 } 408 if (buf[i] == '\n') { 409 buf[i] = 0; 410 break; 411 } 412 } 413 buf[sizeof(buf) - 1] = 0; 414 client_version_string = xstrdup(buf); 415 416 /* 417 * Check that the versions match. In future this might accept 418 * several versions and set appropriate flags to handle them. 419 */ 420 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n", 421 &remote_major, &remote_minor, remote_version) != 3) { 422 s = "Protocol mismatch.\n"; 423 (void) atomicio(vwrite, sock_out, s, strlen(s)); 424 close(sock_in); 425 close(sock_out); 426 logit("Bad protocol version identification '%.100s' from %s", 427 client_version_string, get_remote_ipaddr()); 428 cleanup_exit(255); 429 } 430 debug("Client protocol version %d.%d; client software version %.100s", 431 remote_major, remote_minor, remote_version); 432 433 compat_datafellows(remote_version); 434 435 if (datafellows & SSH_BUG_PROBE) { 436 logit("probed from %s with %s. Don't panic.", 437 get_remote_ipaddr(), client_version_string); 438 cleanup_exit(255); 439 } 440 441 if (datafellows & SSH_BUG_SCANNER) { 442 logit("scanned from %s with %s. Don't panic.", 443 get_remote_ipaddr(), client_version_string); 444 cleanup_exit(255); 445 } 446 447 mismatch = 0; 448 switch (remote_major) { 449 case 1: 450 if (remote_minor == 99) { 451 if (options.protocol & SSH_PROTO_2) 452 enable_compat20(); 453 else 454 mismatch = 1; 455 break; 456 } 457 if (!(options.protocol & SSH_PROTO_1)) { 458 mismatch = 1; 459 break; 460 } 461 if (remote_minor < 3) { 462 packet_disconnect("Your ssh version is too old and " 463 "is no longer supported. Please install a newer version."); 464 } else if (remote_minor == 3) { 465 /* note that this disables agent-forwarding */ 466 enable_compat13(); 467 } 468 break; 469 case 2: 470 if (options.protocol & SSH_PROTO_2) { 471 enable_compat20(); 472 break; 473 } 474 /* FALLTHROUGH */ 475 default: 476 mismatch = 1; 477 break; 478 } 479 chop(server_version_string); 480 debug("Local version string %.200s", server_version_string); 481 482 if (mismatch) { 483 s = "Protocol major versions differ.\n"; 484 (void) atomicio(vwrite, sock_out, s, strlen(s)); 485 close(sock_in); 486 close(sock_out); 487 logit("Protocol major versions differ for %s: %.200s vs. %.200s", 488 get_remote_ipaddr(), 489 server_version_string, client_version_string); 490 cleanup_exit(255); 491 } 492 } 493 494 /* Destroy the host and server keys. They will no longer be needed. */ 495 void 496 destroy_sensitive_data(void) 497 { 498 int i; 499 500 if (sensitive_data.server_key) { 501 key_free(sensitive_data.server_key); 502 sensitive_data.server_key = NULL; 503 } 504 for (i = 0; i < options.num_host_key_files; i++) { 505 if (sensitive_data.host_keys[i]) { 506 key_free(sensitive_data.host_keys[i]); 507 sensitive_data.host_keys[i] = NULL; 508 } 509 } 510 sensitive_data.ssh1_host_key = NULL; 511 memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH); 512 } 513 514 /* Demote private to public keys for network child */ 515 void 516 demote_sensitive_data(void) 517 { 518 Key *tmp; 519 int i; 520 521 if (sensitive_data.server_key) { 522 tmp = key_demote(sensitive_data.server_key); 523 key_free(sensitive_data.server_key); 524 sensitive_data.server_key = tmp; 525 } 526 527 for (i = 0; i < options.num_host_key_files; i++) { 528 if (sensitive_data.host_keys[i]) { 529 tmp = key_demote(sensitive_data.host_keys[i]); 530 key_free(sensitive_data.host_keys[i]); 531 sensitive_data.host_keys[i] = tmp; 532 if (tmp->type == KEY_RSA1) 533 sensitive_data.ssh1_host_key = tmp; 534 } 535 } 536 537 /* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */ 538 } 539 540 static void 541 privsep_preauth_child(void) 542 { 543 u_int32_t rnd[256]; 544 gid_t gidset[1]; 545 struct passwd *pw; 546 int i; 547 548 /* Enable challenge-response authentication for privilege separation */ 549 privsep_challenge_enable(); 550 551 for (i = 0; i < 256; i++) 552 rnd[i] = arc4random(); 553 RAND_seed(rnd, sizeof(rnd)); 554 555 /* Demote the private keys to public keys. */ 556 demote_sensitive_data(); 557 558 if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) 559 fatal("Privilege separation user %s does not exist", 560 SSH_PRIVSEP_USER); 561 memset(pw->pw_passwd, 0, strlen(pw->pw_passwd)); 562 endpwent(); 563 564 /* Change our root directory */ 565 if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1) 566 fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR, 567 strerror(errno)); 568 if (chdir("/") == -1) 569 fatal("chdir(\"/\"): %s", strerror(errno)); 570 571 /* Drop our privileges */ 572 debug3("privsep user:group %u:%u", (u_int)pw->pw_uid, 573 (u_int)pw->pw_gid); 574 #if 0 575 /* XXX not ready, too heavy after chroot */ 576 do_setusercontext(pw); 577 #else 578 gidset[0] = pw->pw_gid; 579 if (setgroups(1, gidset) < 0) 580 fatal("setgroups: %.100s", strerror(errno)); 581 permanently_set_uid(pw); 582 #endif 583 } 584 585 static int 586 privsep_preauth(Authctxt *authctxt) 587 { 588 int status; 589 pid_t pid; 590 591 /* Set up unprivileged child process to deal with network data */ 592 pmonitor = monitor_init(); 593 /* Store a pointer to the kex for later rekeying */ 594 pmonitor->m_pkex = &xxx_kex; 595 596 pid = fork(); 597 if (pid == -1) { 598 fatal("fork of unprivileged child failed"); 599 } else if (pid != 0) { 600 debug2("Network child is on pid %ld", (long)pid); 601 602 close(pmonitor->m_recvfd); 603 pmonitor->m_pid = pid; 604 monitor_child_preauth(authctxt, pmonitor); 605 close(pmonitor->m_sendfd); 606 607 /* Sync memory */ 608 monitor_sync(pmonitor); 609 610 /* Wait for the child's exit status */ 611 while (waitpid(pid, &status, 0) < 0) 612 if (errno != EINTR) 613 break; 614 return (1); 615 } else { 616 /* child */ 617 618 close(pmonitor->m_sendfd); 619 620 /* Demote the child */ 621 if (getuid() == 0 || geteuid() == 0) 622 privsep_preauth_child(); 623 setproctitle("%s", "[net]"); 624 } 625 return (0); 626 } 627 628 static void 629 privsep_postauth(Authctxt *authctxt) 630 { 631 #ifdef DISABLE_FD_PASSING 632 if (1) { 633 #else 634 if (authctxt->pw->pw_uid == 0 || options.use_login) { 635 #endif 636 /* File descriptor passing is broken or root login */ 637 monitor_apply_keystate(pmonitor); 638 use_privsep = 0; 639 return; 640 } 641 642 /* Authentication complete */ 643 alarm(0); 644 if (startup_pipe != -1) { 645 close(startup_pipe); 646 startup_pipe = -1; 647 } 648 649 /* New socket pair */ 650 monitor_reinit(pmonitor); 651 652 pmonitor->m_pid = fork(); 653 if (pmonitor->m_pid == -1) 654 fatal("fork of unprivileged child failed"); 655 else if (pmonitor->m_pid != 0) { 656 debug2("User child is on pid %ld", (long)pmonitor->m_pid); 657 close(pmonitor->m_recvfd); 658 monitor_child_postauth(pmonitor); 659 660 /* NEVERREACHED */ 661 exit(0); 662 } 663 664 close(pmonitor->m_sendfd); 665 666 /* Demote the private keys to public keys. */ 667 demote_sensitive_data(); 668 669 /* Drop privileges */ 670 do_setusercontext(authctxt->pw); 671 672 /* It is safe now to apply the key state */ 673 monitor_apply_keystate(pmonitor); 674 } 675 676 static char * 677 list_hostkey_types(void) 678 { 679 Buffer b; 680 const char *p; 681 char *ret; 682 int i; 683 684 buffer_init(&b); 685 for (i = 0; i < options.num_host_key_files; i++) { 686 Key *key = sensitive_data.host_keys[i]; 687 if (key == NULL) 688 continue; 689 switch (key->type) { 690 case KEY_RSA: 691 case KEY_DSA: 692 if (buffer_len(&b) > 0) 693 buffer_append(&b, ",", 1); 694 p = key_ssh_name(key); 695 buffer_append(&b, p, strlen(p)); 696 break; 697 } 698 } 699 buffer_append(&b, "\0", 1); 700 ret = xstrdup(buffer_ptr(&b)); 701 buffer_free(&b); 702 debug("list_hostkey_types: %s", ret); 703 return ret; 704 } 705 706 Key * 707 get_hostkey_by_type(int type) 708 { 709 int i; 710 711 for (i = 0; i < options.num_host_key_files; i++) { 712 Key *key = sensitive_data.host_keys[i]; 713 if (key != NULL && key->type == type) 714 return key; 715 } 716 return NULL; 717 } 718 719 Key * 720 get_hostkey_by_index(int ind) 721 { 722 if (ind < 0 || ind >= options.num_host_key_files) 723 return (NULL); 724 return (sensitive_data.host_keys[ind]); 725 } 726 727 int 728 get_hostkey_index(Key *key) 729 { 730 int i; 731 732 for (i = 0; i < options.num_host_key_files; i++) { 733 if (key == sensitive_data.host_keys[i]) 734 return (i); 735 } 736 return (-1); 737 } 738 739 /* 740 * returns 1 if connection should be dropped, 0 otherwise. 741 * dropping starts at connection #max_startups_begin with a probability 742 * of (max_startups_rate/100). the probability increases linearly until 743 * all connections are dropped for startups > max_startups 744 */ 745 static int 746 drop_connection(int startups) 747 { 748 double p, r; 749 750 if (startups < options.max_startups_begin) 751 return 0; 752 if (startups >= options.max_startups) 753 return 1; 754 if (options.max_startups_rate == 100) 755 return 1; 756 757 p = 100 - options.max_startups_rate; 758 p *= startups - options.max_startups_begin; 759 p /= (double) (options.max_startups - options.max_startups_begin); 760 p += options.max_startups_rate; 761 p /= 100.0; 762 r = arc4random() / (double) UINT_MAX; 763 764 debug("drop_connection: p %g, r %g", p, r); 765 return (r < p) ? 1 : 0; 766 } 767 768 static void 769 usage(void) 770 { 771 fprintf(stderr, "%s, %s\n", 772 SSH_VERSION, SSLeay_version(SSLEAY_VERSION)); 773 fprintf(stderr, 774 "usage: sshd [-46Ddeiqt] [-b bits] [-f config_file] [-g login_grace_time]\n" 775 " [-h host_key_file] [-k key_gen_time] [-o option] [-p port] [-u len]\n" 776 ); 777 exit(1); 778 } 779 780 /* 781 * Main program for the daemon. 782 */ 783 int 784 main(int ac, char **av) 785 { 786 extern char *optarg; 787 extern int optind; 788 int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1; 789 pid_t pid; 790 socklen_t fromlen; 791 fd_set *fdset; 792 struct sockaddr_storage from; 793 const char *remote_ip; 794 int remote_port; 795 FILE *f; 796 struct addrinfo *ai; 797 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 798 char *line; 799 int listen_sock, maxfd; 800 int startup_p[2]; 801 int startups = 0; 802 Key *key; 803 Authctxt *authctxt; 804 int ret, key_used = 0; 805 806 #ifdef HAVE_SECUREWARE 807 (void)set_auth_parameters(ac, av); 808 #endif 809 __progname = ssh_get_progname(av[0]); 810 init_rng(); 811 812 /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */ 813 saved_argc = ac; 814 saved_argv = xmalloc(sizeof(*saved_argv) * (ac + 1)); 815 for (i = 0; i < ac; i++) 816 saved_argv[i] = xstrdup(av[i]); 817 saved_argv[i] = NULL; 818 819 #ifndef HAVE_SETPROCTITLE 820 /* Prepare for later setproctitle emulation */ 821 compat_init_setproctitle(ac, av); 822 av = saved_argv; 823 #endif 824 825 if (geteuid() == 0 && setgroups(0, NULL) == -1) 826 debug("setgroups(): %.200s", strerror(errno)); 827 828 /* Initialize configuration options to their default values. */ 829 initialize_server_options(&options); 830 831 /* Parse command-line arguments. */ 832 while ((opt = getopt(ac, av, "f:p:b:k:h:g:u:o:dDeiqtQ46")) != -1) { 833 switch (opt) { 834 case '4': 835 IPv4or6 = AF_INET; 836 break; 837 case '6': 838 IPv4or6 = AF_INET6; 839 break; 840 case 'f': 841 config_file_name = optarg; 842 break; 843 case 'd': 844 if (debug_flag == 0) { 845 debug_flag = 1; 846 options.log_level = SYSLOG_LEVEL_DEBUG1; 847 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) 848 options.log_level++; 849 break; 850 case 'D': 851 no_daemon_flag = 1; 852 break; 853 case 'e': 854 log_stderr = 1; 855 break; 856 case 'i': 857 inetd_flag = 1; 858 break; 859 case 'Q': 860 /* ignored */ 861 break; 862 case 'q': 863 options.log_level = SYSLOG_LEVEL_QUIET; 864 break; 865 case 'b': 866 options.server_key_bits = atoi(optarg); 867 break; 868 case 'p': 869 options.ports_from_cmdline = 1; 870 if (options.num_ports >= MAX_PORTS) { 871 fprintf(stderr, "too many ports.\n"); 872 exit(1); 873 } 874 options.ports[options.num_ports++] = a2port(optarg); 875 if (options.ports[options.num_ports-1] == 0) { 876 fprintf(stderr, "Bad port number.\n"); 877 exit(1); 878 } 879 break; 880 case 'g': 881 if ((options.login_grace_time = convtime(optarg)) == -1) { 882 fprintf(stderr, "Invalid login grace time.\n"); 883 exit(1); 884 } 885 break; 886 case 'k': 887 if ((options.key_regeneration_time = convtime(optarg)) == -1) { 888 fprintf(stderr, "Invalid key regeneration interval.\n"); 889 exit(1); 890 } 891 break; 892 case 'h': 893 if (options.num_host_key_files >= MAX_HOSTKEYS) { 894 fprintf(stderr, "too many host keys.\n"); 895 exit(1); 896 } 897 options.host_key_files[options.num_host_key_files++] = optarg; 898 break; 899 case 't': 900 test_flag = 1; 901 break; 902 case 'u': 903 utmp_len = atoi(optarg); 904 if (utmp_len > MAXHOSTNAMELEN) { 905 fprintf(stderr, "Invalid utmp length.\n"); 906 exit(1); 907 } 908 break; 909 case 'o': 910 line = xstrdup(optarg); 911 if (process_server_config_line(&options, line, 912 "command-line", 0) != 0) 913 exit(1); 914 xfree(line); 915 break; 916 case '?': 917 default: 918 usage(); 919 break; 920 } 921 } 922 SSLeay_add_all_algorithms(); 923 channel_set_af(IPv4or6); 924 925 /* 926 * Force logging to stderr until we have loaded the private host 927 * key (unless started from inetd) 928 */ 929 log_init(__progname, 930 options.log_level == SYSLOG_LEVEL_NOT_SET ? 931 SYSLOG_LEVEL_INFO : options.log_level, 932 options.log_facility == SYSLOG_FACILITY_NOT_SET ? 933 SYSLOG_FACILITY_AUTH : options.log_facility, 934 log_stderr || !inetd_flag); 935 936 #ifdef _AIX 937 /* 938 * Unset KRB5CCNAME, otherwise the user's session may inherit it from 939 * root's environment 940 */ 941 unsetenv("KRB5CCNAME"); 942 #endif /* _AIX */ 943 #ifdef _UNICOS 944 /* Cray can define user privs drop all prives now! 945 * Not needed on PRIV_SU systems! 946 */ 947 drop_cray_privs(); 948 #endif 949 950 seed_rng(); 951 952 /* Read server configuration options from the configuration file. */ 953 read_server_config(&options, config_file_name); 954 955 /* Fill in default values for those options not explicitly set. */ 956 fill_default_server_options(&options); 957 958 /* Check that there are no remaining arguments. */ 959 if (optind < ac) { 960 fprintf(stderr, "Extra argument %s.\n", av[optind]); 961 exit(1); 962 } 963 964 debug("sshd version %.100s", SSH_VERSION); 965 966 /* load private host keys */ 967 sensitive_data.host_keys = xmalloc(options.num_host_key_files * 968 sizeof(Key *)); 969 for (i = 0; i < options.num_host_key_files; i++) 970 sensitive_data.host_keys[i] = NULL; 971 sensitive_data.server_key = NULL; 972 sensitive_data.ssh1_host_key = NULL; 973 sensitive_data.have_ssh1_key = 0; 974 sensitive_data.have_ssh2_key = 0; 975 976 for (i = 0; i < options.num_host_key_files; i++) { 977 key = key_load_private(options.host_key_files[i], "", NULL); 978 sensitive_data.host_keys[i] = key; 979 if (key == NULL) { 980 error("Could not load host key: %s", 981 options.host_key_files[i]); 982 sensitive_data.host_keys[i] = NULL; 983 continue; 984 } 985 switch (key->type) { 986 case KEY_RSA1: 987 sensitive_data.ssh1_host_key = key; 988 sensitive_data.have_ssh1_key = 1; 989 break; 990 case KEY_RSA: 991 case KEY_DSA: 992 sensitive_data.have_ssh2_key = 1; 993 break; 994 } 995 debug("private host key: #%d type %d %s", i, key->type, 996 key_type(key)); 997 } 998 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) { 999 logit("Disabling protocol version 1. Could not load host key"); 1000 options.protocol &= ~SSH_PROTO_1; 1001 } 1002 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) { 1003 logit("Disabling protocol version 2. Could not load host key"); 1004 options.protocol &= ~SSH_PROTO_2; 1005 } 1006 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) { 1007 logit("sshd: no hostkeys available -- exiting."); 1008 exit(1); 1009 } 1010 1011 /* Check certain values for sanity. */ 1012 if (options.protocol & SSH_PROTO_1) { 1013 if (options.server_key_bits < 512 || 1014 options.server_key_bits > 32768) { 1015 fprintf(stderr, "Bad server key size.\n"); 1016 exit(1); 1017 } 1018 /* 1019 * Check that server and host key lengths differ sufficiently. This 1020 * is necessary to make double encryption work with rsaref. Oh, I 1021 * hate software patents. I dont know if this can go? Niels 1022 */ 1023 if (options.server_key_bits > 1024 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - 1025 SSH_KEY_BITS_RESERVED && options.server_key_bits < 1026 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + 1027 SSH_KEY_BITS_RESERVED) { 1028 options.server_key_bits = 1029 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + 1030 SSH_KEY_BITS_RESERVED; 1031 debug("Forcing server key to %d bits to make it differ from host key.", 1032 options.server_key_bits); 1033 } 1034 } 1035 1036 if (use_privsep) { 1037 struct passwd *pw; 1038 struct stat st; 1039 1040 if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) 1041 fatal("Privilege separation user %s does not exist", 1042 SSH_PRIVSEP_USER); 1043 if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) || 1044 (S_ISDIR(st.st_mode) == 0)) 1045 fatal("Missing privilege separation directory: %s", 1046 _PATH_PRIVSEP_CHROOT_DIR); 1047 1048 #ifdef HAVE_CYGWIN 1049 if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) && 1050 (st.st_uid != getuid () || 1051 (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)) 1052 #else 1053 if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0) 1054 #endif 1055 fatal("%s must be owned by root and not group or " 1056 "world-writable.", _PATH_PRIVSEP_CHROOT_DIR); 1057 } 1058 1059 /* Configuration looks good, so exit if in test mode. */ 1060 if (test_flag) 1061 exit(0); 1062 1063 /* 1064 * Clear out any supplemental groups we may have inherited. This 1065 * prevents inadvertent creation of files with bad modes (in the 1066 * portable version at least, it's certainly possible for PAM 1067 * to create a file, and we can't control the code in every 1068 * module which might be used). 1069 */ 1070 if (setgroups(0, NULL) < 0) 1071 debug("setgroups() failed: %.200s", strerror(errno)); 1072 1073 /* Initialize the log (it is reinitialized below in case we forked). */ 1074 if (debug_flag && !inetd_flag) 1075 log_stderr = 1; 1076 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1077 1078 /* 1079 * If not in debugging mode, and not started from inetd, disconnect 1080 * from the controlling terminal, and fork. The original process 1081 * exits. 1082 */ 1083 if (!(debug_flag || inetd_flag || no_daemon_flag)) { 1084 #ifdef TIOCNOTTY 1085 int fd; 1086 #endif /* TIOCNOTTY */ 1087 if (daemon(0, 0) < 0) 1088 fatal("daemon() failed: %.200s", strerror(errno)); 1089 1090 /* Disconnect from the controlling tty. */ 1091 #ifdef TIOCNOTTY 1092 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 1093 if (fd >= 0) { 1094 (void) ioctl(fd, TIOCNOTTY, NULL); 1095 close(fd); 1096 } 1097 #endif /* TIOCNOTTY */ 1098 } 1099 /* Reinitialize the log (because of the fork above). */ 1100 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1101 1102 /* Initialize the random number generator. */ 1103 arc4random_stir(); 1104 1105 /* Chdir to the root directory so that the current disk can be 1106 unmounted if desired. */ 1107 chdir("/"); 1108 1109 /* ignore SIGPIPE */ 1110 signal(SIGPIPE, SIG_IGN); 1111 1112 /* Start listening for a socket, unless started from inetd. */ 1113 if (inetd_flag) { 1114 int s1; 1115 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */ 1116 dup(s1); 1117 sock_in = dup(0); 1118 sock_out = dup(1); 1119 startup_pipe = -1; 1120 /* 1121 * We intentionally do not close the descriptors 0, 1, and 2 1122 * as our code for setting the descriptors won\'t work if 1123 * ttyfd happens to be one of those. 1124 */ 1125 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out); 1126 if (options.protocol & SSH_PROTO_1) 1127 generate_ephemeral_server_key(); 1128 } else { 1129 for (ai = options.listen_addrs; ai; ai = ai->ai_next) { 1130 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 1131 continue; 1132 if (num_listen_socks >= MAX_LISTEN_SOCKS) 1133 fatal("Too many listen sockets. " 1134 "Enlarge MAX_LISTEN_SOCKS"); 1135 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 1136 ntop, sizeof(ntop), strport, sizeof(strport), 1137 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 1138 error("getnameinfo failed"); 1139 continue; 1140 } 1141 /* Create socket for listening. */ 1142 listen_sock = socket(ai->ai_family, ai->ai_socktype, 1143 ai->ai_protocol); 1144 if (listen_sock < 0) { 1145 /* kernel may not support ipv6 */ 1146 verbose("socket: %.100s", strerror(errno)); 1147 continue; 1148 } 1149 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) { 1150 error("listen_sock O_NONBLOCK: %s", strerror(errno)); 1151 close(listen_sock); 1152 continue; 1153 } 1154 /* 1155 * Set socket options. 1156 * Allow local port reuse in TIME_WAIT. 1157 */ 1158 if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR, 1159 &on, sizeof(on)) == -1) 1160 error("setsockopt SO_REUSEADDR: %s", strerror(errno)); 1161 1162 debug("Bind to port %s on %s.", strport, ntop); 1163 1164 /* Bind the socket to the desired port. */ 1165 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) { 1166 if (!ai->ai_next) 1167 error("Bind to port %s on %s failed: %.200s.", 1168 strport, ntop, strerror(errno)); 1169 close(listen_sock); 1170 continue; 1171 } 1172 listen_socks[num_listen_socks] = listen_sock; 1173 num_listen_socks++; 1174 1175 /* Start listening on the port. */ 1176 logit("Server listening on %s port %s.", ntop, strport); 1177 if (listen(listen_sock, SSH_LISTEN_BACKLOG) < 0) 1178 fatal("listen: %.100s", strerror(errno)); 1179 1180 } 1181 freeaddrinfo(options.listen_addrs); 1182 1183 if (!num_listen_socks) 1184 fatal("Cannot bind any address."); 1185 1186 if (options.protocol & SSH_PROTO_1) 1187 generate_ephemeral_server_key(); 1188 1189 /* 1190 * Arrange to restart on SIGHUP. The handler needs 1191 * listen_sock. 1192 */ 1193 signal(SIGHUP, sighup_handler); 1194 1195 signal(SIGTERM, sigterm_handler); 1196 signal(SIGQUIT, sigterm_handler); 1197 1198 /* Arrange SIGCHLD to be caught. */ 1199 signal(SIGCHLD, main_sigchld_handler); 1200 1201 /* Write out the pid file after the sigterm handler is setup */ 1202 if (!debug_flag) { 1203 /* 1204 * Record our pid in /var/run/sshd.pid to make it 1205 * easier to kill the correct sshd. We don't want to 1206 * do this before the bind above because the bind will 1207 * fail if there already is a daemon, and this will 1208 * overwrite any old pid in the file. 1209 */ 1210 f = fopen(options.pid_file, "wb"); 1211 if (f == NULL) { 1212 error("Couldn't create pid file \"%s\": %s", 1213 options.pid_file, strerror(errno)); 1214 } else { 1215 fprintf(f, "%ld\n", (long) getpid()); 1216 fclose(f); 1217 } 1218 } 1219 1220 /* setup fd set for listen */ 1221 fdset = NULL; 1222 maxfd = 0; 1223 for (i = 0; i < num_listen_socks; i++) 1224 if (listen_socks[i] > maxfd) 1225 maxfd = listen_socks[i]; 1226 /* pipes connected to unauthenticated childs */ 1227 startup_pipes = xmalloc(options.max_startups * sizeof(int)); 1228 for (i = 0; i < options.max_startups; i++) 1229 startup_pipes[i] = -1; 1230 1231 /* 1232 * Stay listening for connections until the system crashes or 1233 * the daemon is killed with a signal. 1234 */ 1235 for (;;) { 1236 if (received_sighup) 1237 sighup_restart(); 1238 if (fdset != NULL) 1239 xfree(fdset); 1240 fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask); 1241 fdset = (fd_set *)xmalloc(fdsetsz); 1242 memset(fdset, 0, fdsetsz); 1243 1244 for (i = 0; i < num_listen_socks; i++) 1245 FD_SET(listen_socks[i], fdset); 1246 for (i = 0; i < options.max_startups; i++) 1247 if (startup_pipes[i] != -1) 1248 FD_SET(startup_pipes[i], fdset); 1249 1250 /* Wait in select until there is a connection. */ 1251 ret = select(maxfd+1, fdset, NULL, NULL, NULL); 1252 if (ret < 0 && errno != EINTR) 1253 error("select: %.100s", strerror(errno)); 1254 if (received_sigterm) { 1255 logit("Received signal %d; terminating.", 1256 (int) received_sigterm); 1257 close_listen_socks(); 1258 unlink(options.pid_file); 1259 exit(255); 1260 } 1261 if (key_used && key_do_regen) { 1262 generate_ephemeral_server_key(); 1263 key_used = 0; 1264 key_do_regen = 0; 1265 } 1266 if (ret < 0) 1267 continue; 1268 1269 for (i = 0; i < options.max_startups; i++) 1270 if (startup_pipes[i] != -1 && 1271 FD_ISSET(startup_pipes[i], fdset)) { 1272 /* 1273 * the read end of the pipe is ready 1274 * if the child has closed the pipe 1275 * after successful authentication 1276 * or if the child has died 1277 */ 1278 close(startup_pipes[i]); 1279 startup_pipes[i] = -1; 1280 startups--; 1281 } 1282 for (i = 0; i < num_listen_socks; i++) { 1283 if (!FD_ISSET(listen_socks[i], fdset)) 1284 continue; 1285 fromlen = sizeof(from); 1286 newsock = accept(listen_socks[i], (struct sockaddr *)&from, 1287 &fromlen); 1288 if (newsock < 0) { 1289 if (errno != EINTR && errno != EWOULDBLOCK) 1290 error("accept: %.100s", strerror(errno)); 1291 continue; 1292 } 1293 if (fcntl(newsock, F_SETFL, 0) < 0) { 1294 error("newsock del O_NONBLOCK: %s", strerror(errno)); 1295 close(newsock); 1296 continue; 1297 } 1298 if (drop_connection(startups) == 1) { 1299 debug("drop connection #%d", startups); 1300 close(newsock); 1301 continue; 1302 } 1303 if (pipe(startup_p) == -1) { 1304 close(newsock); 1305 continue; 1306 } 1307 1308 for (j = 0; j < options.max_startups; j++) 1309 if (startup_pipes[j] == -1) { 1310 startup_pipes[j] = startup_p[0]; 1311 if (maxfd < startup_p[0]) 1312 maxfd = startup_p[0]; 1313 startups++; 1314 break; 1315 } 1316 1317 /* 1318 * Got connection. Fork a child to handle it, unless 1319 * we are in debugging mode. 1320 */ 1321 if (debug_flag) { 1322 /* 1323 * In debugging mode. Close the listening 1324 * socket, and start processing the 1325 * connection without forking. 1326 */ 1327 debug("Server will not fork when running in debugging mode."); 1328 close_listen_socks(); 1329 sock_in = newsock; 1330 sock_out = newsock; 1331 startup_pipe = -1; 1332 pid = getpid(); 1333 break; 1334 } else { 1335 /* 1336 * Normal production daemon. Fork, and have 1337 * the child process the connection. The 1338 * parent continues listening. 1339 */ 1340 if ((pid = fork()) == 0) { 1341 /* 1342 * Child. Close the listening and max_startup 1343 * sockets. Start using the accepted socket. 1344 * Reinitialize logging (since our pid has 1345 * changed). We break out of the loop to handle 1346 * the connection. 1347 */ 1348 startup_pipe = startup_p[1]; 1349 close_startup_pipes(); 1350 close_listen_socks(); 1351 sock_in = newsock; 1352 sock_out = newsock; 1353 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1354 break; 1355 } 1356 } 1357 1358 /* Parent. Stay in the loop. */ 1359 if (pid < 0) 1360 error("fork: %.100s", strerror(errno)); 1361 else 1362 debug("Forked child %ld.", (long)pid); 1363 1364 close(startup_p[1]); 1365 1366 /* Mark that the key has been used (it was "given" to the child). */ 1367 if ((options.protocol & SSH_PROTO_1) && 1368 key_used == 0) { 1369 /* Schedule server key regeneration alarm. */ 1370 signal(SIGALRM, key_regeneration_alarm); 1371 alarm(options.key_regeneration_time); 1372 key_used = 1; 1373 } 1374 1375 arc4random_stir(); 1376 1377 /* Close the new socket (the child is now taking care of it). */ 1378 close(newsock); 1379 } 1380 /* child process check (or debug mode) */ 1381 if (num_listen_socks < 0) 1382 break; 1383 } 1384 } 1385 1386 /* This is the child processing a new connection. */ 1387 setproctitle("%s", "[accepted]"); 1388 1389 /* 1390 * Create a new session and process group since the 4.4BSD 1391 * setlogin() affects the entire process group. We don't 1392 * want the child to be able to affect the parent. 1393 */ 1394 #if !defined(SSHD_ACQUIRES_CTTY) 1395 /* 1396 * If setsid is called, on some platforms sshd will later acquire a 1397 * controlling terminal which will result in "could not set 1398 * controlling tty" errors. 1399 */ 1400 if (!debug_flag && !inetd_flag && setsid() < 0) 1401 error("setsid: %.100s", strerror(errno)); 1402 #endif 1403 1404 /* 1405 * Disable the key regeneration alarm. We will not regenerate the 1406 * key since we are no longer in a position to give it to anyone. We 1407 * will not restart on SIGHUP since it no longer makes sense. 1408 */ 1409 alarm(0); 1410 signal(SIGALRM, SIG_DFL); 1411 signal(SIGHUP, SIG_DFL); 1412 signal(SIGTERM, SIG_DFL); 1413 signal(SIGQUIT, SIG_DFL); 1414 signal(SIGCHLD, SIG_DFL); 1415 signal(SIGINT, SIG_DFL); 1416 1417 /* Set SO_KEEPALIVE if requested. */ 1418 if (options.tcp_keep_alive && 1419 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, 1420 sizeof(on)) < 0) 1421 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 1422 1423 #ifdef __FreeBSD__ 1424 /* 1425 * Initialize the resolver. This may not happen automatically 1426 * before privsep chroot(). 1427 */ 1428 if ((_res.options & RES_INIT) == 0) { 1429 debug("res_init()"); 1430 res_init(); 1431 } 1432 #endif 1433 1434 /* 1435 * Register our connection. This turns encryption off because we do 1436 * not have a key. 1437 */ 1438 packet_set_connection(sock_in, sock_out); 1439 1440 remote_port = get_remote_port(); 1441 remote_ip = get_remote_ipaddr(); 1442 1443 #ifdef LIBWRAP 1444 /* Check whether logins are denied from this host. */ 1445 { 1446 struct request_info req; 1447 1448 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0); 1449 fromhost(&req); 1450 1451 if (!hosts_access(&req)) { 1452 debug("Connection refused by tcp wrapper"); 1453 refuse(&req); 1454 /* NOTREACHED */ 1455 fatal("libwrap refuse returns"); 1456 } 1457 } 1458 #endif /* LIBWRAP */ 1459 1460 /* Log the connection. */ 1461 verbose("Connection from %.500s port %d", remote_ip, remote_port); 1462 1463 /* 1464 * We don\'t want to listen forever unless the other side 1465 * successfully authenticates itself. So we set up an alarm which is 1466 * cleared after successful authentication. A limit of zero 1467 * indicates no limit. Note that we don\'t set the alarm in debugging 1468 * mode; it is just annoying to have the server exit just when you 1469 * are about to discover the bug. 1470 */ 1471 signal(SIGALRM, grace_alarm_handler); 1472 if (!debug_flag) 1473 alarm(options.login_grace_time); 1474 1475 sshd_exchange_identification(sock_in, sock_out); 1476 1477 packet_set_nonblocking(); 1478 1479 /* prepare buffers to collect authentication messages */ 1480 buffer_init(&loginmsg); 1481 1482 /* allocate authentication context */ 1483 authctxt = xmalloc(sizeof(*authctxt)); 1484 memset(authctxt, 0, sizeof(*authctxt)); 1485 1486 /* XXX global for cleanup, access from other modules */ 1487 the_authctxt = authctxt; 1488 1489 if (use_privsep) 1490 if (privsep_preauth(authctxt) == 1) 1491 goto authenticated; 1492 1493 /* perform the key exchange */ 1494 /* authenticate user and start session */ 1495 if (compat20) { 1496 do_ssh2_kex(); 1497 do_authentication2(authctxt); 1498 } else { 1499 do_ssh1_kex(); 1500 do_authentication(authctxt); 1501 } 1502 /* 1503 * If we use privilege separation, the unprivileged child transfers 1504 * the current keystate and exits 1505 */ 1506 if (use_privsep) { 1507 mm_send_keystate(pmonitor); 1508 exit(0); 1509 } 1510 1511 authenticated: 1512 /* 1513 * In privilege separation, we fork another child and prepare 1514 * file descriptor passing. 1515 */ 1516 if (use_privsep) { 1517 privsep_postauth(authctxt); 1518 /* the monitor process [priv] will not return */ 1519 if (!compat20) 1520 destroy_sensitive_data(); 1521 } 1522 1523 /* Start session. */ 1524 do_authenticated(authctxt); 1525 1526 /* The connection has been terminated. */ 1527 verbose("Closing connection to %.100s", remote_ip); 1528 1529 #ifdef USE_PAM 1530 if (options.use_pam) 1531 finish_pam(); 1532 #endif /* USE_PAM */ 1533 1534 packet_close(); 1535 1536 if (use_privsep) 1537 mm_terminate(); 1538 1539 exit(0); 1540 } 1541 1542 /* 1543 * Decrypt session_key_int using our private server key and private host key 1544 * (key with larger modulus first). 1545 */ 1546 int 1547 ssh1_session_key(BIGNUM *session_key_int) 1548 { 1549 int rsafail = 0; 1550 1551 if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) { 1552 /* Server key has bigger modulus. */ 1553 if (BN_num_bits(sensitive_data.server_key->rsa->n) < 1554 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) { 1555 fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d", 1556 get_remote_ipaddr(), 1557 BN_num_bits(sensitive_data.server_key->rsa->n), 1558 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n), 1559 SSH_KEY_BITS_RESERVED); 1560 } 1561 if (rsa_private_decrypt(session_key_int, session_key_int, 1562 sensitive_data.server_key->rsa) <= 0) 1563 rsafail++; 1564 if (rsa_private_decrypt(session_key_int, session_key_int, 1565 sensitive_data.ssh1_host_key->rsa) <= 0) 1566 rsafail++; 1567 } else { 1568 /* Host key has bigger modulus (or they are equal). */ 1569 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) < 1570 BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) { 1571 fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d", 1572 get_remote_ipaddr(), 1573 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n), 1574 BN_num_bits(sensitive_data.server_key->rsa->n), 1575 SSH_KEY_BITS_RESERVED); 1576 } 1577 if (rsa_private_decrypt(session_key_int, session_key_int, 1578 sensitive_data.ssh1_host_key->rsa) < 0) 1579 rsafail++; 1580 if (rsa_private_decrypt(session_key_int, session_key_int, 1581 sensitive_data.server_key->rsa) < 0) 1582 rsafail++; 1583 } 1584 return (rsafail); 1585 } 1586 /* 1587 * SSH1 key exchange 1588 */ 1589 static void 1590 do_ssh1_kex(void) 1591 { 1592 int i, len; 1593 int rsafail = 0; 1594 BIGNUM *session_key_int; 1595 u_char session_key[SSH_SESSION_KEY_LENGTH]; 1596 u_char cookie[8]; 1597 u_int cipher_type, auth_mask, protocol_flags; 1598 u_int32_t rnd = 0; 1599 1600 /* 1601 * Generate check bytes that the client must send back in the user 1602 * packet in order for it to be accepted; this is used to defy ip 1603 * spoofing attacks. Note that this only works against somebody 1604 * doing IP spoofing from a remote machine; any machine on the local 1605 * network can still see outgoing packets and catch the random 1606 * cookie. This only affects rhosts authentication, and this is one 1607 * of the reasons why it is inherently insecure. 1608 */ 1609 for (i = 0; i < 8; i++) { 1610 if (i % 4 == 0) 1611 rnd = arc4random(); 1612 cookie[i] = rnd & 0xff; 1613 rnd >>= 8; 1614 } 1615 1616 /* 1617 * Send our public key. We include in the packet 64 bits of random 1618 * data that must be matched in the reply in order to prevent IP 1619 * spoofing. 1620 */ 1621 packet_start(SSH_SMSG_PUBLIC_KEY); 1622 for (i = 0; i < 8; i++) 1623 packet_put_char(cookie[i]); 1624 1625 /* Store our public server RSA key. */ 1626 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n)); 1627 packet_put_bignum(sensitive_data.server_key->rsa->e); 1628 packet_put_bignum(sensitive_data.server_key->rsa->n); 1629 1630 /* Store our public host RSA key. */ 1631 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n)); 1632 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e); 1633 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n); 1634 1635 /* Put protocol flags. */ 1636 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN); 1637 1638 /* Declare which ciphers we support. */ 1639 packet_put_int(cipher_mask_ssh1(0)); 1640 1641 /* Declare supported authentication types. */ 1642 auth_mask = 0; 1643 if (options.rhosts_rsa_authentication) 1644 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA; 1645 if (options.rsa_authentication) 1646 auth_mask |= 1 << SSH_AUTH_RSA; 1647 if (options.challenge_response_authentication == 1) 1648 auth_mask |= 1 << SSH_AUTH_TIS; 1649 if (options.password_authentication) 1650 auth_mask |= 1 << SSH_AUTH_PASSWORD; 1651 packet_put_int(auth_mask); 1652 1653 /* Send the packet and wait for it to be sent. */ 1654 packet_send(); 1655 packet_write_wait(); 1656 1657 debug("Sent %d bit server key and %d bit host key.", 1658 BN_num_bits(sensitive_data.server_key->rsa->n), 1659 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n)); 1660 1661 /* Read clients reply (cipher type and session key). */ 1662 packet_read_expect(SSH_CMSG_SESSION_KEY); 1663 1664 /* Get cipher type and check whether we accept this. */ 1665 cipher_type = packet_get_char(); 1666 1667 if (!(cipher_mask_ssh1(0) & (1 << cipher_type))) 1668 packet_disconnect("Warning: client selects unsupported cipher."); 1669 1670 /* Get check bytes from the packet. These must match those we 1671 sent earlier with the public key packet. */ 1672 for (i = 0; i < 8; i++) 1673 if (cookie[i] != packet_get_char()) 1674 packet_disconnect("IP Spoofing check bytes do not match."); 1675 1676 debug("Encryption type: %.200s", cipher_name(cipher_type)); 1677 1678 /* Get the encrypted integer. */ 1679 if ((session_key_int = BN_new()) == NULL) 1680 fatal("do_ssh1_kex: BN_new failed"); 1681 packet_get_bignum(session_key_int); 1682 1683 protocol_flags = packet_get_int(); 1684 packet_set_protocol_flags(protocol_flags); 1685 packet_check_eom(); 1686 1687 /* Decrypt session_key_int using host/server keys */ 1688 rsafail = PRIVSEP(ssh1_session_key(session_key_int)); 1689 1690 /* 1691 * Extract session key from the decrypted integer. The key is in the 1692 * least significant 256 bits of the integer; the first byte of the 1693 * key is in the highest bits. 1694 */ 1695 if (!rsafail) { 1696 BN_mask_bits(session_key_int, sizeof(session_key) * 8); 1697 len = BN_num_bytes(session_key_int); 1698 if (len < 0 || len > sizeof(session_key)) { 1699 error("do_connection: bad session key len from %s: " 1700 "session_key_int %d > sizeof(session_key) %lu", 1701 get_remote_ipaddr(), len, (u_long)sizeof(session_key)); 1702 rsafail++; 1703 } else { 1704 memset(session_key, 0, sizeof(session_key)); 1705 BN_bn2bin(session_key_int, 1706 session_key + sizeof(session_key) - len); 1707 1708 compute_session_id(session_id, cookie, 1709 sensitive_data.ssh1_host_key->rsa->n, 1710 sensitive_data.server_key->rsa->n); 1711 /* 1712 * Xor the first 16 bytes of the session key with the 1713 * session id. 1714 */ 1715 for (i = 0; i < 16; i++) 1716 session_key[i] ^= session_id[i]; 1717 } 1718 } 1719 if (rsafail) { 1720 int bytes = BN_num_bytes(session_key_int); 1721 u_char *buf = xmalloc(bytes); 1722 MD5_CTX md; 1723 1724 logit("do_connection: generating a fake encryption key"); 1725 BN_bn2bin(session_key_int, buf); 1726 MD5_Init(&md); 1727 MD5_Update(&md, buf, bytes); 1728 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); 1729 MD5_Final(session_key, &md); 1730 MD5_Init(&md); 1731 MD5_Update(&md, session_key, 16); 1732 MD5_Update(&md, buf, bytes); 1733 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); 1734 MD5_Final(session_key + 16, &md); 1735 memset(buf, 0, bytes); 1736 xfree(buf); 1737 for (i = 0; i < 16; i++) 1738 session_id[i] = session_key[i] ^ session_key[i + 16]; 1739 } 1740 /* Destroy the private and public keys. No longer. */ 1741 destroy_sensitive_data(); 1742 1743 if (use_privsep) 1744 mm_ssh1_session_id(session_id); 1745 1746 /* Destroy the decrypted integer. It is no longer needed. */ 1747 BN_clear_free(session_key_int); 1748 1749 /* Set the session key. From this on all communications will be encrypted. */ 1750 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type); 1751 1752 /* Destroy our copy of the session key. It is no longer needed. */ 1753 memset(session_key, 0, sizeof(session_key)); 1754 1755 debug("Received session key; encryption turned on."); 1756 1757 /* Send an acknowledgment packet. Note that this packet is sent encrypted. */ 1758 packet_start(SSH_SMSG_SUCCESS); 1759 packet_send(); 1760 packet_write_wait(); 1761 } 1762 1763 /* 1764 * SSH2 key exchange: diffie-hellman-group1-sha1 1765 */ 1766 static void 1767 do_ssh2_kex(void) 1768 { 1769 Kex *kex; 1770 1771 if (options.ciphers != NULL) { 1772 myproposal[PROPOSAL_ENC_ALGS_CTOS] = 1773 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers; 1774 } 1775 myproposal[PROPOSAL_ENC_ALGS_CTOS] = 1776 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]); 1777 myproposal[PROPOSAL_ENC_ALGS_STOC] = 1778 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]); 1779 1780 if (options.macs != NULL) { 1781 myproposal[PROPOSAL_MAC_ALGS_CTOS] = 1782 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs; 1783 } 1784 if (!options.compression) { 1785 myproposal[PROPOSAL_COMP_ALGS_CTOS] = 1786 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none"; 1787 } 1788 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types(); 1789 1790 /* start key exchange */ 1791 kex = kex_setup(myproposal); 1792 kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server; 1793 kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 1794 kex->server = 1; 1795 kex->client_version_string=client_version_string; 1796 kex->server_version_string=server_version_string; 1797 kex->load_host_key=&get_hostkey_by_type; 1798 kex->host_key_index=&get_hostkey_index; 1799 1800 xxx_kex = kex; 1801 1802 dispatch_run(DISPATCH_BLOCK, &kex->done, kex); 1803 1804 session_id2 = kex->session_id; 1805 session_id2_len = kex->session_id_len; 1806 1807 #ifdef DEBUG_KEXDH 1808 /* send 1st encrypted/maced/compressed message */ 1809 packet_start(SSH2_MSG_IGNORE); 1810 packet_put_cstring("markus"); 1811 packet_send(); 1812 packet_write_wait(); 1813 #endif 1814 debug("KEX done"); 1815 } 1816 1817 /* server specific fatal cleanup */ 1818 void 1819 cleanup_exit(int i) 1820 { 1821 if (the_authctxt) 1822 do_cleanup(the_authctxt); 1823 _exit(i); 1824 } 1825