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("$OpenBSD: sshd.c,v 1.276 2003/08/28 12:54:34 markus Exp $"); 46 RCSID("$FreeBSD$"); 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; 208 209 /* message to be displayed after login */ 210 Buffer loginmsg; 211 212 /* Prototypes for various functions defined later in this file. */ 213 void destroy_sensitive_data(void); 214 void demote_sensitive_data(void); 215 216 static void do_ssh1_kex(void); 217 static void do_ssh2_kex(void); 218 219 /* 220 * Close all listening sockets 221 */ 222 static void 223 close_listen_socks(void) 224 { 225 int i; 226 227 for (i = 0; i < num_listen_socks; i++) 228 close(listen_socks[i]); 229 num_listen_socks = -1; 230 } 231 232 static void 233 close_startup_pipes(void) 234 { 235 int i; 236 237 if (startup_pipes) 238 for (i = 0; i < options.max_startups; i++) 239 if (startup_pipes[i] != -1) 240 close(startup_pipes[i]); 241 } 242 243 /* 244 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP; 245 * the effect is to reread the configuration file (and to regenerate 246 * the server key). 247 */ 248 static void 249 sighup_handler(int sig) 250 { 251 int save_errno = errno; 252 253 received_sighup = 1; 254 signal(SIGHUP, sighup_handler); 255 errno = save_errno; 256 } 257 258 /* 259 * Called from the main program after receiving SIGHUP. 260 * Restarts the server. 261 */ 262 static void 263 sighup_restart(void) 264 { 265 logit("Received SIGHUP; restarting."); 266 close_listen_socks(); 267 close_startup_pipes(); 268 execv(saved_argv[0], saved_argv); 269 logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], 270 strerror(errno)); 271 exit(1); 272 } 273 274 /* 275 * Generic signal handler for terminating signals in the master daemon. 276 */ 277 static void 278 sigterm_handler(int sig) 279 { 280 received_sigterm = sig; 281 } 282 283 /* 284 * SIGCHLD handler. This is called whenever a child dies. This will then 285 * reap any zombies left by exited children. 286 */ 287 static void 288 main_sigchld_handler(int sig) 289 { 290 int save_errno = errno; 291 pid_t pid; 292 int status; 293 294 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 295 (pid < 0 && errno == EINTR)) 296 ; 297 298 signal(SIGCHLD, main_sigchld_handler); 299 errno = save_errno; 300 } 301 302 /* 303 * Signal handler for the alarm after the login grace period has expired. 304 */ 305 static void 306 grace_alarm_handler(int sig) 307 { 308 /* XXX no idea how fix this signal handler */ 309 310 /* Log error and exit. */ 311 fatal("Timeout before authentication for %s", get_remote_ipaddr()); 312 } 313 314 /* 315 * Signal handler for the key regeneration alarm. Note that this 316 * alarm only occurs in the daemon waiting for connections, and it does not 317 * do anything with the private key or random state before forking. 318 * Thus there should be no concurrency control/asynchronous execution 319 * problems. 320 */ 321 static void 322 generate_ephemeral_server_key(void) 323 { 324 u_int32_t rnd = 0; 325 int i; 326 327 verbose("Generating %s%d bit RSA key.", 328 sensitive_data.server_key ? "new " : "", options.server_key_bits); 329 if (sensitive_data.server_key != NULL) 330 key_free(sensitive_data.server_key); 331 sensitive_data.server_key = key_generate(KEY_RSA1, 332 options.server_key_bits); 333 verbose("RSA key generation complete."); 334 335 for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) { 336 if (i % 4 == 0) 337 rnd = arc4random(); 338 sensitive_data.ssh1_cookie[i] = rnd & 0xff; 339 rnd >>= 8; 340 } 341 arc4random_stir(); 342 } 343 344 static void 345 key_regeneration_alarm(int sig) 346 { 347 int save_errno = errno; 348 349 signal(SIGALRM, SIG_DFL); 350 errno = save_errno; 351 key_do_regen = 1; 352 } 353 354 static void 355 sshd_exchange_identification(int sock_in, int sock_out) 356 { 357 int i, mismatch; 358 int remote_major, remote_minor; 359 int major, minor; 360 char *s; 361 char buf[256]; /* Must not be larger than remote_version. */ 362 char remote_version[256]; /* Must be at least as big as buf. */ 363 364 if ((options.protocol & SSH_PROTO_1) && 365 (options.protocol & SSH_PROTO_2)) { 366 major = PROTOCOL_MAJOR_1; 367 minor = 99; 368 } else if (options.protocol & SSH_PROTO_2) { 369 major = PROTOCOL_MAJOR_2; 370 minor = PROTOCOL_MINOR_2; 371 } else { 372 major = PROTOCOL_MAJOR_1; 373 minor = PROTOCOL_MINOR_1; 374 } 375 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION); 376 server_version_string = xstrdup(buf); 377 378 /* Send our protocol version identification. */ 379 if (atomicio(vwrite, sock_out, server_version_string, 380 strlen(server_version_string)) 381 != strlen(server_version_string)) { 382 logit("Could not write ident string to %s", get_remote_ipaddr()); 383 fatal_cleanup(); 384 } 385 386 /* Read other sides version identification. */ 387 memset(buf, 0, sizeof(buf)); 388 for (i = 0; i < sizeof(buf) - 1; i++) { 389 if (atomicio(read, sock_in, &buf[i], 1) != 1) { 390 logit("Did not receive identification string from %s", 391 get_remote_ipaddr()); 392 fatal_cleanup(); 393 } 394 if (buf[i] == '\r') { 395 buf[i] = 0; 396 /* Kludge for F-Secure Macintosh < 1.0.2 */ 397 if (i == 12 && 398 strncmp(buf, "SSH-1.5-W1.0", 12) == 0) 399 break; 400 continue; 401 } 402 if (buf[i] == '\n') { 403 buf[i] = 0; 404 break; 405 } 406 } 407 buf[sizeof(buf) - 1] = 0; 408 client_version_string = xstrdup(buf); 409 410 /* 411 * Check that the versions match. In future this might accept 412 * several versions and set appropriate flags to handle them. 413 */ 414 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n", 415 &remote_major, &remote_minor, remote_version) != 3) { 416 s = "Protocol mismatch.\n"; 417 (void) atomicio(vwrite, sock_out, s, strlen(s)); 418 close(sock_in); 419 close(sock_out); 420 logit("Bad protocol version identification '%.100s' from %s", 421 client_version_string, get_remote_ipaddr()); 422 fatal_cleanup(); 423 } 424 debug("Client protocol version %d.%d; client software version %.100s", 425 remote_major, remote_minor, remote_version); 426 427 compat_datafellows(remote_version); 428 429 if (datafellows & SSH_BUG_PROBE) { 430 logit("probed from %s with %s. Don't panic.", 431 get_remote_ipaddr(), client_version_string); 432 fatal_cleanup(); 433 } 434 435 if (datafellows & SSH_BUG_SCANNER) { 436 logit("scanned from %s with %s. Don't panic.", 437 get_remote_ipaddr(), client_version_string); 438 fatal_cleanup(); 439 } 440 441 mismatch = 0; 442 switch (remote_major) { 443 case 1: 444 if (remote_minor == 99) { 445 if (options.protocol & SSH_PROTO_2) 446 enable_compat20(); 447 else 448 mismatch = 1; 449 break; 450 } 451 if (!(options.protocol & SSH_PROTO_1)) { 452 mismatch = 1; 453 break; 454 } 455 if (remote_minor < 3) { 456 packet_disconnect("Your ssh version is too old and " 457 "is no longer supported. Please install a newer version."); 458 } else if (remote_minor == 3) { 459 /* note that this disables agent-forwarding */ 460 enable_compat13(); 461 } 462 break; 463 case 2: 464 if (options.protocol & SSH_PROTO_2) { 465 enable_compat20(); 466 break; 467 } 468 /* FALLTHROUGH */ 469 default: 470 mismatch = 1; 471 break; 472 } 473 chop(server_version_string); 474 debug("Local version string %.200s", server_version_string); 475 476 if (mismatch) { 477 s = "Protocol major versions differ.\n"; 478 (void) atomicio(vwrite, sock_out, s, strlen(s)); 479 close(sock_in); 480 close(sock_out); 481 logit("Protocol major versions differ for %s: %.200s vs. %.200s", 482 get_remote_ipaddr(), 483 server_version_string, client_version_string); 484 fatal_cleanup(); 485 } 486 } 487 488 /* Destroy the host and server keys. They will no longer be needed. */ 489 void 490 destroy_sensitive_data(void) 491 { 492 int i; 493 494 if (sensitive_data.server_key) { 495 key_free(sensitive_data.server_key); 496 sensitive_data.server_key = NULL; 497 } 498 for (i = 0; i < options.num_host_key_files; i++) { 499 if (sensitive_data.host_keys[i]) { 500 key_free(sensitive_data.host_keys[i]); 501 sensitive_data.host_keys[i] = NULL; 502 } 503 } 504 sensitive_data.ssh1_host_key = NULL; 505 memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH); 506 } 507 508 /* Demote private to public keys for network child */ 509 void 510 demote_sensitive_data(void) 511 { 512 Key *tmp; 513 int i; 514 515 if (sensitive_data.server_key) { 516 tmp = key_demote(sensitive_data.server_key); 517 key_free(sensitive_data.server_key); 518 sensitive_data.server_key = tmp; 519 } 520 521 for (i = 0; i < options.num_host_key_files; i++) { 522 if (sensitive_data.host_keys[i]) { 523 tmp = key_demote(sensitive_data.host_keys[i]); 524 key_free(sensitive_data.host_keys[i]); 525 sensitive_data.host_keys[i] = tmp; 526 if (tmp->type == KEY_RSA1) 527 sensitive_data.ssh1_host_key = tmp; 528 } 529 } 530 531 /* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */ 532 } 533 534 static void 535 privsep_preauth_child(void) 536 { 537 u_int32_t rnd[256]; 538 gid_t gidset[1]; 539 struct passwd *pw; 540 int i; 541 542 /* Enable challenge-response authentication for privilege separation */ 543 privsep_challenge_enable(); 544 545 for (i = 0; i < 256; i++) 546 rnd[i] = arc4random(); 547 RAND_seed(rnd, sizeof(rnd)); 548 549 /* Demote the private keys to public keys. */ 550 demote_sensitive_data(); 551 552 if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) 553 fatal("Privilege separation user %s does not exist", 554 SSH_PRIVSEP_USER); 555 memset(pw->pw_passwd, 0, strlen(pw->pw_passwd)); 556 endpwent(); 557 558 /* Change our root directory */ 559 if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1) 560 fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR, 561 strerror(errno)); 562 if (chdir("/") == -1) 563 fatal("chdir(\"/\"): %s", strerror(errno)); 564 565 /* Drop our privileges */ 566 debug3("privsep user:group %u:%u", (u_int)pw->pw_uid, 567 (u_int)pw->pw_gid); 568 #if 0 569 /* XXX not ready, to heavy after chroot */ 570 do_setusercontext(pw); 571 #else 572 gidset[0] = pw->pw_gid; 573 if (setgroups(1, gidset) < 0) 574 fatal("setgroups: %.100s", strerror(errno)); 575 permanently_set_uid(pw); 576 #endif 577 } 578 579 static Authctxt * 580 privsep_preauth(void) 581 { 582 Authctxt *authctxt = NULL; 583 int status; 584 pid_t pid; 585 586 /* Set up unprivileged child process to deal with network data */ 587 pmonitor = monitor_init(); 588 /* Store a pointer to the kex for later rekeying */ 589 pmonitor->m_pkex = &xxx_kex; 590 591 pid = fork(); 592 if (pid == -1) { 593 fatal("fork of unprivileged child failed"); 594 } else if (pid != 0) { 595 fatal_remove_cleanup((void (*) (void *)) packet_close, NULL); 596 597 debug2("Network child is on pid %ld", (long)pid); 598 599 close(pmonitor->m_recvfd); 600 authctxt = monitor_child_preauth(pmonitor); 601 close(pmonitor->m_sendfd); 602 603 /* Sync memory */ 604 monitor_sync(pmonitor); 605 606 /* Wait for the child's exit status */ 607 while (waitpid(pid, &status, 0) < 0) 608 if (errno != EINTR) 609 break; 610 611 /* Reinstall, since the child has finished */ 612 fatal_add_cleanup((void (*) (void *)) packet_close, NULL); 613 614 return (authctxt); 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 (NULL); 626 } 627 628 static void 629 privsep_postauth(Authctxt *authctxt) 630 { 631 extern Authctxt *x_authctxt; 632 633 /* XXX - Remote port forwarding */ 634 x_authctxt = authctxt; 635 636 #ifdef DISABLE_FD_PASSING 637 if (1) { 638 #else 639 if (authctxt->pw->pw_uid == 0 || options.use_login) { 640 #endif 641 /* File descriptor passing is broken or root login */ 642 monitor_apply_keystate(pmonitor); 643 use_privsep = 0; 644 return; 645 } 646 647 /* Authentication complete */ 648 alarm(0); 649 if (startup_pipe != -1) { 650 close(startup_pipe); 651 startup_pipe = -1; 652 } 653 654 /* New socket pair */ 655 monitor_reinit(pmonitor); 656 657 pmonitor->m_pid = fork(); 658 if (pmonitor->m_pid == -1) 659 fatal("fork of unprivileged child failed"); 660 else if (pmonitor->m_pid != 0) { 661 fatal_remove_cleanup((void (*) (void *)) packet_close, NULL); 662 663 debug2("User child is on pid %ld", (long)pmonitor->m_pid); 664 close(pmonitor->m_recvfd); 665 monitor_child_postauth(pmonitor); 666 667 /* NEVERREACHED */ 668 exit(0); 669 } 670 671 close(pmonitor->m_sendfd); 672 673 /* Demote the private keys to public keys. */ 674 demote_sensitive_data(); 675 676 /* Drop privileges */ 677 do_setusercontext(authctxt->pw); 678 679 /* It is safe now to apply the key state */ 680 monitor_apply_keystate(pmonitor); 681 } 682 683 static char * 684 list_hostkey_types(void) 685 { 686 Buffer b; 687 char *p; 688 int i; 689 690 buffer_init(&b); 691 for (i = 0; i < options.num_host_key_files; i++) { 692 Key *key = sensitive_data.host_keys[i]; 693 if (key == NULL) 694 continue; 695 switch (key->type) { 696 case KEY_RSA: 697 case KEY_DSA: 698 if (buffer_len(&b) > 0) 699 buffer_append(&b, ",", 1); 700 p = key_ssh_name(key); 701 buffer_append(&b, p, strlen(p)); 702 break; 703 } 704 } 705 buffer_append(&b, "\0", 1); 706 p = xstrdup(buffer_ptr(&b)); 707 buffer_free(&b); 708 debug("list_hostkey_types: %s", p); 709 return p; 710 } 711 712 Key * 713 get_hostkey_by_type(int type) 714 { 715 int i; 716 717 for (i = 0; i < options.num_host_key_files; i++) { 718 Key *key = sensitive_data.host_keys[i]; 719 if (key != NULL && key->type == type) 720 return key; 721 } 722 return NULL; 723 } 724 725 Key * 726 get_hostkey_by_index(int ind) 727 { 728 if (ind < 0 || ind >= options.num_host_key_files) 729 return (NULL); 730 return (sensitive_data.host_keys[ind]); 731 } 732 733 int 734 get_hostkey_index(Key *key) 735 { 736 int i; 737 738 for (i = 0; i < options.num_host_key_files; i++) { 739 if (key == sensitive_data.host_keys[i]) 740 return (i); 741 } 742 return (-1); 743 } 744 745 /* 746 * returns 1 if connection should be dropped, 0 otherwise. 747 * dropping starts at connection #max_startups_begin with a probability 748 * of (max_startups_rate/100). the probability increases linearly until 749 * all connections are dropped for startups > max_startups 750 */ 751 static int 752 drop_connection(int startups) 753 { 754 double p, r; 755 756 if (startups < options.max_startups_begin) 757 return 0; 758 if (startups >= options.max_startups) 759 return 1; 760 if (options.max_startups_rate == 100) 761 return 1; 762 763 p = 100 - options.max_startups_rate; 764 p *= startups - options.max_startups_begin; 765 p /= (double) (options.max_startups - options.max_startups_begin); 766 p += options.max_startups_rate; 767 p /= 100.0; 768 r = arc4random() / (double) UINT_MAX; 769 770 debug("drop_connection: p %g, r %g", p, r); 771 return (r < p) ? 1 : 0; 772 } 773 774 static void 775 usage(void) 776 { 777 fprintf(stderr, "sshd version %s\n", SSH_VERSION); 778 fprintf(stderr, "Usage: %s [options]\n", __progname); 779 fprintf(stderr, "Options:\n"); 780 fprintf(stderr, " -f file Configuration file (default %s)\n", _PATH_SERVER_CONFIG_FILE); 781 fprintf(stderr, " -d Debugging mode (multiple -d means more debugging)\n"); 782 fprintf(stderr, " -i Started from inetd\n"); 783 fprintf(stderr, " -D Do not fork into daemon mode\n"); 784 fprintf(stderr, " -t Only test configuration file and keys\n"); 785 fprintf(stderr, " -q Quiet (no logging)\n"); 786 fprintf(stderr, " -p port Listen on the specified port (default: 22)\n"); 787 fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n"); 788 fprintf(stderr, " -g seconds Grace period for authentication (default: 600)\n"); 789 fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n"); 790 fprintf(stderr, " -h file File from which to read host key (default: %s)\n", 791 _PATH_HOST_KEY_FILE); 792 fprintf(stderr, " -u len Maximum hostname length for utmp recording\n"); 793 fprintf(stderr, " -4 Use IPv4 only\n"); 794 fprintf(stderr, " -6 Use IPv6 only\n"); 795 fprintf(stderr, " -o option Process the option as if it was read from a configuration file.\n"); 796 exit(1); 797 } 798 799 /* 800 * Main program for the daemon. 801 */ 802 int 803 main(int ac, char **av) 804 { 805 extern char *optarg; 806 extern int optind; 807 int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1; 808 pid_t pid; 809 socklen_t fromlen; 810 fd_set *fdset; 811 struct sockaddr_storage from; 812 const char *remote_ip; 813 int remote_port; 814 FILE *f; 815 struct addrinfo *ai; 816 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 817 int listen_sock, maxfd; 818 int startup_p[2]; 819 int startups = 0; 820 Authctxt *authctxt; 821 Key *key; 822 int ret, key_used = 0; 823 824 #ifdef HAVE_SECUREWARE 825 (void)set_auth_parameters(ac, av); 826 #endif 827 __progname = ssh_get_progname(av[0]); 828 init_rng(); 829 830 /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */ 831 saved_argc = ac; 832 saved_argv = xmalloc(sizeof(*saved_argv) * (ac + 1)); 833 for (i = 0; i < ac; i++) 834 saved_argv[i] = xstrdup(av[i]); 835 saved_argv[i] = NULL; 836 837 #ifndef HAVE_SETPROCTITLE 838 /* Prepare for later setproctitle emulation */ 839 compat_init_setproctitle(ac, av); 840 av = saved_argv; 841 #endif 842 843 /* Initialize configuration options to their default values. */ 844 initialize_server_options(&options); 845 846 /* Parse command-line arguments. */ 847 while ((opt = getopt(ac, av, "f:p:b:k:h:g:u:o:dDeiqtQ46")) != -1) { 848 switch (opt) { 849 case '4': 850 IPv4or6 = AF_INET; 851 break; 852 case '6': 853 IPv4or6 = AF_INET6; 854 break; 855 case 'f': 856 config_file_name = optarg; 857 break; 858 case 'd': 859 if (debug_flag == 0) { 860 debug_flag = 1; 861 options.log_level = SYSLOG_LEVEL_DEBUG1; 862 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) 863 options.log_level++; 864 break; 865 case 'D': 866 no_daemon_flag = 1; 867 break; 868 case 'e': 869 log_stderr = 1; 870 break; 871 case 'i': 872 inetd_flag = 1; 873 break; 874 case 'Q': 875 /* ignored */ 876 break; 877 case 'q': 878 options.log_level = SYSLOG_LEVEL_QUIET; 879 break; 880 case 'b': 881 options.server_key_bits = atoi(optarg); 882 break; 883 case 'p': 884 options.ports_from_cmdline = 1; 885 if (options.num_ports >= MAX_PORTS) { 886 fprintf(stderr, "too many ports.\n"); 887 exit(1); 888 } 889 options.ports[options.num_ports++] = a2port(optarg); 890 if (options.ports[options.num_ports-1] == 0) { 891 fprintf(stderr, "Bad port number.\n"); 892 exit(1); 893 } 894 break; 895 case 'g': 896 if ((options.login_grace_time = convtime(optarg)) == -1) { 897 fprintf(stderr, "Invalid login grace time.\n"); 898 exit(1); 899 } 900 break; 901 case 'k': 902 if ((options.key_regeneration_time = convtime(optarg)) == -1) { 903 fprintf(stderr, "Invalid key regeneration interval.\n"); 904 exit(1); 905 } 906 break; 907 case 'h': 908 if (options.num_host_key_files >= MAX_HOSTKEYS) { 909 fprintf(stderr, "too many host keys.\n"); 910 exit(1); 911 } 912 options.host_key_files[options.num_host_key_files++] = optarg; 913 break; 914 case 't': 915 test_flag = 1; 916 break; 917 case 'u': 918 utmp_len = atoi(optarg); 919 if (utmp_len > MAXHOSTNAMELEN) { 920 fprintf(stderr, "Invalid utmp length.\n"); 921 exit(1); 922 } 923 break; 924 case 'o': 925 if (process_server_config_line(&options, optarg, 926 "command-line", 0) != 0) 927 exit(1); 928 break; 929 case '?': 930 default: 931 usage(); 932 break; 933 } 934 } 935 SSLeay_add_all_algorithms(); 936 channel_set_af(IPv4or6); 937 938 /* 939 * Force logging to stderr until we have loaded the private host 940 * key (unless started from inetd) 941 */ 942 log_init(__progname, 943 options.log_level == SYSLOG_LEVEL_NOT_SET ? 944 SYSLOG_LEVEL_INFO : options.log_level, 945 options.log_facility == SYSLOG_FACILITY_NOT_SET ? 946 SYSLOG_FACILITY_AUTH : options.log_facility, 947 log_stderr || !inetd_flag); 948 949 #ifdef _UNICOS 950 /* Cray can define user privs drop all prives now! 951 * Not needed on PRIV_SU systems! 952 */ 953 drop_cray_privs(); 954 #endif 955 956 seed_rng(); 957 958 /* Read server configuration options from the configuration file. */ 959 read_server_config(&options, config_file_name); 960 961 /* Fill in default values for those options not explicitly set. */ 962 fill_default_server_options(&options); 963 964 /* Check that there are no remaining arguments. */ 965 if (optind < ac) { 966 fprintf(stderr, "Extra argument %s.\n", av[optind]); 967 exit(1); 968 } 969 970 debug("sshd version %.100s", SSH_VERSION); 971 972 /* load private host keys */ 973 sensitive_data.host_keys = xmalloc(options.num_host_key_files * 974 sizeof(Key *)); 975 for (i = 0; i < options.num_host_key_files; i++) 976 sensitive_data.host_keys[i] = NULL; 977 sensitive_data.server_key = NULL; 978 sensitive_data.ssh1_host_key = NULL; 979 sensitive_data.have_ssh1_key = 0; 980 sensitive_data.have_ssh2_key = 0; 981 982 for (i = 0; i < options.num_host_key_files; i++) { 983 key = key_load_private(options.host_key_files[i], "", NULL); 984 sensitive_data.host_keys[i] = key; 985 if (key == NULL) { 986 error("Could not load host key: %s", 987 options.host_key_files[i]); 988 sensitive_data.host_keys[i] = NULL; 989 continue; 990 } 991 switch (key->type) { 992 case KEY_RSA1: 993 sensitive_data.ssh1_host_key = key; 994 sensitive_data.have_ssh1_key = 1; 995 break; 996 case KEY_RSA: 997 case KEY_DSA: 998 sensitive_data.have_ssh2_key = 1; 999 break; 1000 } 1001 debug("private host key: #%d type %d %s", i, key->type, 1002 key_type(key)); 1003 } 1004 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) { 1005 logit("Disabling protocol version 1. Could not load host key"); 1006 options.protocol &= ~SSH_PROTO_1; 1007 } 1008 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) { 1009 logit("Disabling protocol version 2. Could not load host key"); 1010 options.protocol &= ~SSH_PROTO_2; 1011 } 1012 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) { 1013 logit("sshd: no hostkeys available -- exiting."); 1014 exit(1); 1015 } 1016 1017 /* Check certain values for sanity. */ 1018 if (options.protocol & SSH_PROTO_1) { 1019 if (options.server_key_bits < 512 || 1020 options.server_key_bits > 32768) { 1021 fprintf(stderr, "Bad server key size.\n"); 1022 exit(1); 1023 } 1024 /* 1025 * Check that server and host key lengths differ sufficiently. This 1026 * is necessary to make double encryption work with rsaref. Oh, I 1027 * hate software patents. I dont know if this can go? Niels 1028 */ 1029 if (options.server_key_bits > 1030 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - 1031 SSH_KEY_BITS_RESERVED && options.server_key_bits < 1032 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + 1033 SSH_KEY_BITS_RESERVED) { 1034 options.server_key_bits = 1035 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + 1036 SSH_KEY_BITS_RESERVED; 1037 debug("Forcing server key to %d bits to make it differ from host key.", 1038 options.server_key_bits); 1039 } 1040 } 1041 1042 if (use_privsep) { 1043 struct passwd *pw; 1044 struct stat st; 1045 1046 if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) 1047 fatal("Privilege separation user %s does not exist", 1048 SSH_PRIVSEP_USER); 1049 if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) || 1050 (S_ISDIR(st.st_mode) == 0)) 1051 fatal("Missing privilege separation directory: %s", 1052 _PATH_PRIVSEP_CHROOT_DIR); 1053 1054 #ifdef HAVE_CYGWIN 1055 if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) && 1056 (st.st_uid != getuid () || 1057 (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)) 1058 #else 1059 if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0) 1060 #endif 1061 fatal("%s must be owned by root and not group or " 1062 "world-writable.", _PATH_PRIVSEP_CHROOT_DIR); 1063 } 1064 1065 /* Configuration looks good, so exit if in test mode. */ 1066 if (test_flag) 1067 exit(0); 1068 1069 /* 1070 * Clear out any supplemental groups we may have inherited. This 1071 * prevents inadvertent creation of files with bad modes (in the 1072 * portable version at least, it's certainly possible for PAM 1073 * to create a file, and we can't control the code in every 1074 * module which might be used). 1075 */ 1076 if (setgroups(0, NULL) < 0) 1077 debug("setgroups() failed: %.200s", strerror(errno)); 1078 1079 /* Initialize the log (it is reinitialized below in case we forked). */ 1080 if (debug_flag && !inetd_flag) 1081 log_stderr = 1; 1082 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1083 1084 /* 1085 * If not in debugging mode, and not started from inetd, disconnect 1086 * from the controlling terminal, and fork. The original process 1087 * exits. 1088 */ 1089 if (!(debug_flag || inetd_flag || no_daemon_flag)) { 1090 #ifdef TIOCNOTTY 1091 int fd; 1092 #endif /* TIOCNOTTY */ 1093 if (daemon(0, 0) < 0) 1094 fatal("daemon() failed: %.200s", strerror(errno)); 1095 1096 /* Disconnect from the controlling tty. */ 1097 #ifdef TIOCNOTTY 1098 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 1099 if (fd >= 0) { 1100 (void) ioctl(fd, TIOCNOTTY, NULL); 1101 close(fd); 1102 } 1103 #endif /* TIOCNOTTY */ 1104 } 1105 /* Reinitialize the log (because of the fork above). */ 1106 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1107 1108 /* Initialize the random number generator. */ 1109 arc4random_stir(); 1110 1111 /* Chdir to the root directory so that the current disk can be 1112 unmounted if desired. */ 1113 chdir("/"); 1114 1115 /* ignore SIGPIPE */ 1116 signal(SIGPIPE, SIG_IGN); 1117 1118 /* Start listening for a socket, unless started from inetd. */ 1119 if (inetd_flag) { 1120 int s1; 1121 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */ 1122 dup(s1); 1123 sock_in = dup(0); 1124 sock_out = dup(1); 1125 startup_pipe = -1; 1126 /* 1127 * We intentionally do not close the descriptors 0, 1, and 2 1128 * as our code for setting the descriptors won\'t work if 1129 * ttyfd happens to be one of those. 1130 */ 1131 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out); 1132 if (options.protocol & SSH_PROTO_1) 1133 generate_ephemeral_server_key(); 1134 } else { 1135 for (ai = options.listen_addrs; ai; ai = ai->ai_next) { 1136 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 1137 continue; 1138 if (num_listen_socks >= MAX_LISTEN_SOCKS) 1139 fatal("Too many listen sockets. " 1140 "Enlarge MAX_LISTEN_SOCKS"); 1141 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 1142 ntop, sizeof(ntop), strport, sizeof(strport), 1143 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 1144 error("getnameinfo failed"); 1145 continue; 1146 } 1147 /* Create socket for listening. */ 1148 listen_sock = socket(ai->ai_family, ai->ai_socktype, 1149 ai->ai_protocol); 1150 if (listen_sock < 0) { 1151 /* kernel may not support ipv6 */ 1152 verbose("socket: %.100s", strerror(errno)); 1153 continue; 1154 } 1155 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) { 1156 error("listen_sock O_NONBLOCK: %s", strerror(errno)); 1157 close(listen_sock); 1158 continue; 1159 } 1160 /* 1161 * Set socket options. 1162 * Allow local port reuse in TIME_WAIT. 1163 */ 1164 if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR, 1165 &on, sizeof(on)) == -1) 1166 error("setsockopt SO_REUSEADDR: %s", strerror(errno)); 1167 1168 debug("Bind to port %s on %s.", strport, ntop); 1169 1170 /* Bind the socket to the desired port. */ 1171 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) { 1172 if (!ai->ai_next) 1173 error("Bind to port %s on %s failed: %.200s.", 1174 strport, ntop, strerror(errno)); 1175 close(listen_sock); 1176 continue; 1177 } 1178 listen_socks[num_listen_socks] = listen_sock; 1179 num_listen_socks++; 1180 1181 /* Start listening on the port. */ 1182 logit("Server listening on %s port %s.", ntop, strport); 1183 if (listen(listen_sock, 5) < 0) 1184 fatal("listen: %.100s", strerror(errno)); 1185 1186 } 1187 freeaddrinfo(options.listen_addrs); 1188 1189 if (!num_listen_socks) 1190 fatal("Cannot bind any address."); 1191 1192 if (options.protocol & SSH_PROTO_1) 1193 generate_ephemeral_server_key(); 1194 1195 /* 1196 * Arrange to restart on SIGHUP. The handler needs 1197 * listen_sock. 1198 */ 1199 signal(SIGHUP, sighup_handler); 1200 1201 signal(SIGTERM, sigterm_handler); 1202 signal(SIGQUIT, sigterm_handler); 1203 1204 /* Arrange SIGCHLD to be caught. */ 1205 signal(SIGCHLD, main_sigchld_handler); 1206 1207 /* Write out the pid file after the sigterm handler is setup */ 1208 if (!debug_flag) { 1209 /* 1210 * Record our pid in /var/run/sshd.pid to make it 1211 * easier to kill the correct sshd. We don't want to 1212 * do this before the bind above because the bind will 1213 * fail if there already is a daemon, and this will 1214 * overwrite any old pid in the file. 1215 */ 1216 f = fopen(options.pid_file, "wb"); 1217 if (f == NULL) { 1218 error("Couldn't create pid file \"%s\": %s", 1219 options.pid_file, strerror(errno)); 1220 } else { 1221 fprintf(f, "%ld\n", (long) getpid()); 1222 fclose(f); 1223 } 1224 } 1225 1226 /* setup fd set for listen */ 1227 fdset = NULL; 1228 maxfd = 0; 1229 for (i = 0; i < num_listen_socks; i++) 1230 if (listen_socks[i] > maxfd) 1231 maxfd = listen_socks[i]; 1232 /* pipes connected to unauthenticated childs */ 1233 startup_pipes = xmalloc(options.max_startups * sizeof(int)); 1234 for (i = 0; i < options.max_startups; i++) 1235 startup_pipes[i] = -1; 1236 1237 /* 1238 * Stay listening for connections until the system crashes or 1239 * the daemon is killed with a signal. 1240 */ 1241 for (;;) { 1242 if (received_sighup) 1243 sighup_restart(); 1244 if (fdset != NULL) 1245 xfree(fdset); 1246 fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask); 1247 fdset = (fd_set *)xmalloc(fdsetsz); 1248 memset(fdset, 0, fdsetsz); 1249 1250 for (i = 0; i < num_listen_socks; i++) 1251 FD_SET(listen_socks[i], fdset); 1252 for (i = 0; i < options.max_startups; i++) 1253 if (startup_pipes[i] != -1) 1254 FD_SET(startup_pipes[i], fdset); 1255 1256 /* Wait in select until there is a connection. */ 1257 ret = select(maxfd+1, fdset, NULL, NULL, NULL); 1258 if (ret < 0 && errno != EINTR) 1259 error("select: %.100s", strerror(errno)); 1260 if (received_sigterm) { 1261 logit("Received signal %d; terminating.", 1262 (int) received_sigterm); 1263 close_listen_socks(); 1264 unlink(options.pid_file); 1265 exit(255); 1266 } 1267 if (key_used && key_do_regen) { 1268 generate_ephemeral_server_key(); 1269 key_used = 0; 1270 key_do_regen = 0; 1271 } 1272 if (ret < 0) 1273 continue; 1274 1275 for (i = 0; i < options.max_startups; i++) 1276 if (startup_pipes[i] != -1 && 1277 FD_ISSET(startup_pipes[i], fdset)) { 1278 /* 1279 * the read end of the pipe is ready 1280 * if the child has closed the pipe 1281 * after successful authentication 1282 * or if the child has died 1283 */ 1284 close(startup_pipes[i]); 1285 startup_pipes[i] = -1; 1286 startups--; 1287 } 1288 for (i = 0; i < num_listen_socks; i++) { 1289 if (!FD_ISSET(listen_socks[i], fdset)) 1290 continue; 1291 fromlen = sizeof(from); 1292 newsock = accept(listen_socks[i], (struct sockaddr *)&from, 1293 &fromlen); 1294 if (newsock < 0) { 1295 if (errno != EINTR && errno != EWOULDBLOCK) 1296 error("accept: %.100s", strerror(errno)); 1297 continue; 1298 } 1299 if (fcntl(newsock, F_SETFL, 0) < 0) { 1300 error("newsock del O_NONBLOCK: %s", strerror(errno)); 1301 close(newsock); 1302 continue; 1303 } 1304 if (drop_connection(startups) == 1) { 1305 debug("drop connection #%d", startups); 1306 close(newsock); 1307 continue; 1308 } 1309 if (pipe(startup_p) == -1) { 1310 close(newsock); 1311 continue; 1312 } 1313 1314 for (j = 0; j < options.max_startups; j++) 1315 if (startup_pipes[j] == -1) { 1316 startup_pipes[j] = startup_p[0]; 1317 if (maxfd < startup_p[0]) 1318 maxfd = startup_p[0]; 1319 startups++; 1320 break; 1321 } 1322 1323 /* 1324 * Got connection. Fork a child to handle it, unless 1325 * we are in debugging mode. 1326 */ 1327 if (debug_flag) { 1328 /* 1329 * In debugging mode. Close the listening 1330 * socket, and start processing the 1331 * connection without forking. 1332 */ 1333 debug("Server will not fork when running in debugging mode."); 1334 close_listen_socks(); 1335 sock_in = newsock; 1336 sock_out = newsock; 1337 startup_pipe = -1; 1338 pid = getpid(); 1339 break; 1340 } else { 1341 /* 1342 * Normal production daemon. Fork, and have 1343 * the child process the connection. The 1344 * parent continues listening. 1345 */ 1346 if ((pid = fork()) == 0) { 1347 /* 1348 * Child. Close the listening and max_startup 1349 * sockets. Start using the accepted socket. 1350 * Reinitialize logging (since our pid has 1351 * changed). We break out of the loop to handle 1352 * the connection. 1353 */ 1354 startup_pipe = startup_p[1]; 1355 close_startup_pipes(); 1356 close_listen_socks(); 1357 sock_in = newsock; 1358 sock_out = newsock; 1359 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1360 break; 1361 } 1362 } 1363 1364 /* Parent. Stay in the loop. */ 1365 if (pid < 0) 1366 error("fork: %.100s", strerror(errno)); 1367 else 1368 debug("Forked child %ld.", (long)pid); 1369 1370 close(startup_p[1]); 1371 1372 /* Mark that the key has been used (it was "given" to the child). */ 1373 if ((options.protocol & SSH_PROTO_1) && 1374 key_used == 0) { 1375 /* Schedule server key regeneration alarm. */ 1376 signal(SIGALRM, key_regeneration_alarm); 1377 alarm(options.key_regeneration_time); 1378 key_used = 1; 1379 } 1380 1381 arc4random_stir(); 1382 1383 /* Close the new socket (the child is now taking care of it). */ 1384 close(newsock); 1385 } 1386 /* child process check (or debug mode) */ 1387 if (num_listen_socks < 0) 1388 break; 1389 } 1390 } 1391 1392 /* This is the child processing a new connection. */ 1393 1394 /* 1395 * Create a new session and process group since the 4.4BSD 1396 * setlogin() affects the entire process group. We don't 1397 * want the child to be able to affect the parent. 1398 */ 1399 #if !defined(SSHD_ACQUIRES_CTTY) 1400 /* 1401 * If setsid is called, on some platforms sshd will later acquire a 1402 * controlling terminal which will result in "could not set 1403 * controlling tty" errors. 1404 */ 1405 if (!debug_flag && !inetd_flag && setsid() < 0) 1406 error("setsid: %.100s", strerror(errno)); 1407 #endif 1408 1409 /* 1410 * Disable the key regeneration alarm. We will not regenerate the 1411 * key since we are no longer in a position to give it to anyone. We 1412 * will not restart on SIGHUP since it no longer makes sense. 1413 */ 1414 alarm(0); 1415 signal(SIGALRM, SIG_DFL); 1416 signal(SIGHUP, SIG_DFL); 1417 signal(SIGTERM, SIG_DFL); 1418 signal(SIGQUIT, SIG_DFL); 1419 signal(SIGCHLD, SIG_DFL); 1420 signal(SIGINT, SIG_DFL); 1421 1422 /* Set keepalives if requested. */ 1423 if (options.keepalives && 1424 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, 1425 sizeof(on)) < 0) 1426 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 1427 1428 #ifdef __FreeBSD__ 1429 /* 1430 * Initialize the resolver. This may not happen automatically 1431 * before privsep chroot(). 1432 */ 1433 if ((_res.options & RES_INIT) == 0) { 1434 debug("res_init()"); 1435 res_init(); 1436 } 1437 #endif 1438 1439 /* 1440 * Register our connection. This turns encryption off because we do 1441 * not have a key. 1442 */ 1443 packet_set_connection(sock_in, sock_out); 1444 1445 remote_port = get_remote_port(); 1446 remote_ip = get_remote_ipaddr(); 1447 1448 #ifdef LIBWRAP 1449 /* Check whether logins are denied from this host. */ 1450 { 1451 struct request_info req; 1452 1453 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0); 1454 fromhost(&req); 1455 1456 if (!hosts_access(&req)) { 1457 debug("Connection refused by tcp wrapper"); 1458 refuse(&req); 1459 /* NOTREACHED */ 1460 fatal("libwrap refuse returns"); 1461 } 1462 } 1463 #endif /* LIBWRAP */ 1464 1465 /* Log the connection. */ 1466 verbose("Connection from %.500s port %d", remote_ip, remote_port); 1467 1468 /* 1469 * We don\'t want to listen forever unless the other side 1470 * successfully authenticates itself. So we set up an alarm which is 1471 * cleared after successful authentication. A limit of zero 1472 * indicates no limit. Note that we don\'t set the alarm in debugging 1473 * mode; it is just annoying to have the server exit just when you 1474 * are about to discover the bug. 1475 */ 1476 signal(SIGALRM, grace_alarm_handler); 1477 if (!debug_flag) 1478 alarm(options.login_grace_time); 1479 1480 sshd_exchange_identification(sock_in, sock_out); 1481 1482 packet_set_nonblocking(); 1483 1484 /* prepare buffers to collect authentication messages */ 1485 buffer_init(&loginmsg); 1486 1487 if (use_privsep) 1488 if ((authctxt = privsep_preauth()) != NULL) 1489 goto authenticated; 1490 1491 /* perform the key exchange */ 1492 /* authenticate user and start session */ 1493 if (compat20) { 1494 do_ssh2_kex(); 1495 authctxt = do_authentication2(); 1496 } else { 1497 do_ssh1_kex(); 1498 authctxt = do_authentication(); 1499 } 1500 /* 1501 * If we use privilege separation, the unprivileged child transfers 1502 * the current keystate and exits 1503 */ 1504 if (use_privsep) { 1505 mm_send_keystate(pmonitor); 1506 exit(0); 1507 } 1508 1509 authenticated: 1510 /* 1511 * In privilege separation, we fork another child and prepare 1512 * file descriptor passing. 1513 */ 1514 if (use_privsep) { 1515 privsep_postauth(authctxt); 1516 /* the monitor process [priv] will not return */ 1517 if (!compat20) 1518 destroy_sensitive_data(); 1519 } 1520 1521 /* Perform session preparation. */ 1522 do_authenticated(authctxt); 1523 1524 /* The connection has been terminated. */ 1525 verbose("Closing connection to %.100s", remote_ip); 1526 1527 #ifdef USE_PAM 1528 if (options.use_pam) 1529 finish_pam(); 1530 #endif /* USE_PAM */ 1531 1532 packet_close(); 1533 1534 if (use_privsep) 1535 mm_terminate(); 1536 1537 exit(0); 1538 } 1539 1540 /* 1541 * Decrypt session_key_int using our private server key and private host key 1542 * (key with larger modulus first). 1543 */ 1544 int 1545 ssh1_session_key(BIGNUM *session_key_int) 1546 { 1547 int rsafail = 0; 1548 1549 if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) { 1550 /* Server key has bigger modulus. */ 1551 if (BN_num_bits(sensitive_data.server_key->rsa->n) < 1552 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) { 1553 fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d", 1554 get_remote_ipaddr(), 1555 BN_num_bits(sensitive_data.server_key->rsa->n), 1556 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n), 1557 SSH_KEY_BITS_RESERVED); 1558 } 1559 if (rsa_private_decrypt(session_key_int, session_key_int, 1560 sensitive_data.server_key->rsa) <= 0) 1561 rsafail++; 1562 if (rsa_private_decrypt(session_key_int, session_key_int, 1563 sensitive_data.ssh1_host_key->rsa) <= 0) 1564 rsafail++; 1565 } else { 1566 /* Host key has bigger modulus (or they are equal). */ 1567 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) < 1568 BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) { 1569 fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d", 1570 get_remote_ipaddr(), 1571 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n), 1572 BN_num_bits(sensitive_data.server_key->rsa->n), 1573 SSH_KEY_BITS_RESERVED); 1574 } 1575 if (rsa_private_decrypt(session_key_int, session_key_int, 1576 sensitive_data.ssh1_host_key->rsa) < 0) 1577 rsafail++; 1578 if (rsa_private_decrypt(session_key_int, session_key_int, 1579 sensitive_data.server_key->rsa) < 0) 1580 rsafail++; 1581 } 1582 return (rsafail); 1583 } 1584 /* 1585 * SSH1 key exchange 1586 */ 1587 static void 1588 do_ssh1_kex(void) 1589 { 1590 int i, len; 1591 int rsafail = 0; 1592 BIGNUM *session_key_int; 1593 u_char session_key[SSH_SESSION_KEY_LENGTH]; 1594 u_char cookie[8]; 1595 u_int cipher_type, auth_mask, protocol_flags; 1596 u_int32_t rnd = 0; 1597 1598 /* 1599 * Generate check bytes that the client must send back in the user 1600 * packet in order for it to be accepted; this is used to defy ip 1601 * spoofing attacks. Note that this only works against somebody 1602 * doing IP spoofing from a remote machine; any machine on the local 1603 * network can still see outgoing packets and catch the random 1604 * cookie. This only affects rhosts authentication, and this is one 1605 * of the reasons why it is inherently insecure. 1606 */ 1607 for (i = 0; i < 8; i++) { 1608 if (i % 4 == 0) 1609 rnd = arc4random(); 1610 cookie[i] = rnd & 0xff; 1611 rnd >>= 8; 1612 } 1613 1614 /* 1615 * Send our public key. We include in the packet 64 bits of random 1616 * data that must be matched in the reply in order to prevent IP 1617 * spoofing. 1618 */ 1619 packet_start(SSH_SMSG_PUBLIC_KEY); 1620 for (i = 0; i < 8; i++) 1621 packet_put_char(cookie[i]); 1622 1623 /* Store our public server RSA key. */ 1624 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n)); 1625 packet_put_bignum(sensitive_data.server_key->rsa->e); 1626 packet_put_bignum(sensitive_data.server_key->rsa->n); 1627 1628 /* Store our public host RSA key. */ 1629 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n)); 1630 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e); 1631 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n); 1632 1633 /* Put protocol flags. */ 1634 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN); 1635 1636 /* Declare which ciphers we support. */ 1637 packet_put_int(cipher_mask_ssh1(0)); 1638 1639 /* Declare supported authentication types. */ 1640 auth_mask = 0; 1641 if (options.rhosts_rsa_authentication) 1642 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA; 1643 if (options.rsa_authentication) 1644 auth_mask |= 1 << SSH_AUTH_RSA; 1645 if (options.challenge_response_authentication == 1) 1646 auth_mask |= 1 << SSH_AUTH_TIS; 1647 if (options.password_authentication) 1648 auth_mask |= 1 << SSH_AUTH_PASSWORD; 1649 packet_put_int(auth_mask); 1650 1651 /* Send the packet and wait for it to be sent. */ 1652 packet_send(); 1653 packet_write_wait(); 1654 1655 debug("Sent %d bit server key and %d bit host key.", 1656 BN_num_bits(sensitive_data.server_key->rsa->n), 1657 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n)); 1658 1659 /* Read clients reply (cipher type and session key). */ 1660 packet_read_expect(SSH_CMSG_SESSION_KEY); 1661 1662 /* Get cipher type and check whether we accept this. */ 1663 cipher_type = packet_get_char(); 1664 1665 if (!(cipher_mask_ssh1(0) & (1 << cipher_type))) 1666 packet_disconnect("Warning: client selects unsupported cipher."); 1667 1668 /* Get check bytes from the packet. These must match those we 1669 sent earlier with the public key packet. */ 1670 for (i = 0; i < 8; i++) 1671 if (cookie[i] != packet_get_char()) 1672 packet_disconnect("IP Spoofing check bytes do not match."); 1673 1674 debug("Encryption type: %.200s", cipher_name(cipher_type)); 1675 1676 /* Get the encrypted integer. */ 1677 if ((session_key_int = BN_new()) == NULL) 1678 fatal("do_ssh1_kex: BN_new failed"); 1679 packet_get_bignum(session_key_int); 1680 1681 protocol_flags = packet_get_int(); 1682 packet_set_protocol_flags(protocol_flags); 1683 packet_check_eom(); 1684 1685 /* Decrypt session_key_int using host/server keys */ 1686 rsafail = PRIVSEP(ssh1_session_key(session_key_int)); 1687 1688 /* 1689 * Extract session key from the decrypted integer. The key is in the 1690 * least significant 256 bits of the integer; the first byte of the 1691 * key is in the highest bits. 1692 */ 1693 if (!rsafail) { 1694 BN_mask_bits(session_key_int, sizeof(session_key) * 8); 1695 len = BN_num_bytes(session_key_int); 1696 if (len < 0 || len > sizeof(session_key)) { 1697 error("do_connection: bad session key len from %s: " 1698 "session_key_int %d > sizeof(session_key) %lu", 1699 get_remote_ipaddr(), len, (u_long)sizeof(session_key)); 1700 rsafail++; 1701 } else { 1702 memset(session_key, 0, sizeof(session_key)); 1703 BN_bn2bin(session_key_int, 1704 session_key + sizeof(session_key) - len); 1705 1706 compute_session_id(session_id, cookie, 1707 sensitive_data.ssh1_host_key->rsa->n, 1708 sensitive_data.server_key->rsa->n); 1709 /* 1710 * Xor the first 16 bytes of the session key with the 1711 * session id. 1712 */ 1713 for (i = 0; i < 16; i++) 1714 session_key[i] ^= session_id[i]; 1715 } 1716 } 1717 if (rsafail) { 1718 int bytes = BN_num_bytes(session_key_int); 1719 u_char *buf = xmalloc(bytes); 1720 MD5_CTX md; 1721 1722 logit("do_connection: generating a fake encryption key"); 1723 BN_bn2bin(session_key_int, buf); 1724 MD5_Init(&md); 1725 MD5_Update(&md, buf, bytes); 1726 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); 1727 MD5_Final(session_key, &md); 1728 MD5_Init(&md); 1729 MD5_Update(&md, session_key, 16); 1730 MD5_Update(&md, buf, bytes); 1731 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); 1732 MD5_Final(session_key + 16, &md); 1733 memset(buf, 0, bytes); 1734 xfree(buf); 1735 for (i = 0; i < 16; i++) 1736 session_id[i] = session_key[i] ^ session_key[i + 16]; 1737 } 1738 /* Destroy the private and public keys. No longer. */ 1739 destroy_sensitive_data(); 1740 1741 if (use_privsep) 1742 mm_ssh1_session_id(session_id); 1743 1744 /* Destroy the decrypted integer. It is no longer needed. */ 1745 BN_clear_free(session_key_int); 1746 1747 /* Set the session key. From this on all communications will be encrypted. */ 1748 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type); 1749 1750 /* Destroy our copy of the session key. It is no longer needed. */ 1751 memset(session_key, 0, sizeof(session_key)); 1752 1753 debug("Received session key; encryption turned on."); 1754 1755 /* Send an acknowledgment packet. Note that this packet is sent encrypted. */ 1756 packet_start(SSH_SMSG_SUCCESS); 1757 packet_send(); 1758 packet_write_wait(); 1759 } 1760 1761 /* 1762 * SSH2 key exchange: diffie-hellman-group1-sha1 1763 */ 1764 static void 1765 do_ssh2_kex(void) 1766 { 1767 Kex *kex; 1768 1769 if (options.ciphers != NULL) { 1770 myproposal[PROPOSAL_ENC_ALGS_CTOS] = 1771 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers; 1772 } 1773 myproposal[PROPOSAL_ENC_ALGS_CTOS] = 1774 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]); 1775 myproposal[PROPOSAL_ENC_ALGS_STOC] = 1776 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]); 1777 1778 if (options.macs != NULL) { 1779 myproposal[PROPOSAL_MAC_ALGS_CTOS] = 1780 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs; 1781 } 1782 if (!options.compression) { 1783 myproposal[PROPOSAL_COMP_ALGS_CTOS] = 1784 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none"; 1785 } 1786 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types(); 1787 1788 /* start key exchange */ 1789 kex = kex_setup(myproposal); 1790 kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server; 1791 kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 1792 kex->server = 1; 1793 kex->client_version_string=client_version_string; 1794 kex->server_version_string=server_version_string; 1795 kex->load_host_key=&get_hostkey_by_type; 1796 kex->host_key_index=&get_hostkey_index; 1797 1798 xxx_kex = kex; 1799 1800 dispatch_run(DISPATCH_BLOCK, &kex->done, kex); 1801 1802 session_id2 = kex->session_id; 1803 session_id2_len = kex->session_id_len; 1804 1805 #ifdef DEBUG_KEXDH 1806 /* send 1st encrypted/maced/compressed message */ 1807 packet_start(SSH2_MSG_IGNORE); 1808 packet_put_cstring("markus"); 1809 packet_send(); 1810 packet_write_wait(); 1811 #endif 1812 debug("KEX done"); 1813 } 1814