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 1.263 2003/02/16 17:09:57 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 #ifdef IPV4_DEFAULT 121 int IPv4or6 = AF_INET; 122 #else 123 int IPv4or6 = AF_UNSPEC; 124 #endif 125 126 /* 127 * Debug mode flag. This can be set on the command line. If debug 128 * mode is enabled, extra debugging output will be sent to the system 129 * log, the daemon will not go to background, and will exit after processing 130 * the first connection. 131 */ 132 int debug_flag = 0; 133 134 /* Flag indicating that the daemon should only test the configuration and keys. */ 135 int test_flag = 0; 136 137 /* Flag indicating that the daemon is being started from inetd. */ 138 int inetd_flag = 0; 139 140 /* Flag indicating that sshd should not detach and become a daemon. */ 141 int no_daemon_flag = 0; 142 143 /* debug goes to stderr unless inetd_flag is set */ 144 int log_stderr = 0; 145 146 /* Saved arguments to main(). */ 147 char **saved_argv; 148 int saved_argc; 149 150 /* 151 * The sockets that the server is listening; this is used in the SIGHUP 152 * signal handler. 153 */ 154 #define MAX_LISTEN_SOCKS 16 155 int listen_socks[MAX_LISTEN_SOCKS]; 156 int num_listen_socks = 0; 157 158 /* 159 * the client's version string, passed by sshd2 in compat mode. if != NULL, 160 * sshd will skip the version-number exchange 161 */ 162 char *client_version_string = NULL; 163 char *server_version_string = NULL; 164 165 /* for rekeying XXX fixme */ 166 Kex *xxx_kex; 167 168 /* 169 * Any really sensitive data in the application is contained in this 170 * structure. The idea is that this structure could be locked into memory so 171 * that the pages do not get written into swap. However, there are some 172 * problems. The private key contains BIGNUMs, and we do not (in principle) 173 * have access to the internals of them, and locking just the structure is 174 * not very useful. Currently, memory locking is not implemented. 175 */ 176 struct { 177 Key *server_key; /* ephemeral server key */ 178 Key *ssh1_host_key; /* ssh1 host key */ 179 Key **host_keys; /* all private host keys */ 180 int have_ssh1_key; 181 int have_ssh2_key; 182 u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH]; 183 } sensitive_data; 184 185 /* 186 * Flag indicating whether the RSA server key needs to be regenerated. 187 * Is set in the SIGALRM handler and cleared when the key is regenerated. 188 */ 189 static volatile sig_atomic_t key_do_regen = 0; 190 191 /* This is set to true when a signal is received. */ 192 static volatile sig_atomic_t received_sighup = 0; 193 static volatile sig_atomic_t received_sigterm = 0; 194 195 /* session identifier, used by RSA-auth */ 196 u_char session_id[16]; 197 198 /* same for ssh2 */ 199 u_char *session_id2 = NULL; 200 int session_id2_len = 0; 201 202 /* record remote hostname or ip */ 203 u_int utmp_len = MAXHOSTNAMELEN; 204 205 /* options.max_startup sized array of fd ints */ 206 int *startup_pipes = NULL; 207 int startup_pipe; /* in child */ 208 209 /* variables used for privilege separation */ 210 int use_privsep; 211 struct monitor *pmonitor; 212 213 /* Prototypes for various functions defined later in this file. */ 214 void destroy_sensitive_data(void); 215 void demote_sensitive_data(void); 216 217 static void do_ssh1_kex(void); 218 static void do_ssh2_kex(void); 219 220 /* 221 * Close all listening sockets 222 */ 223 static void 224 close_listen_socks(void) 225 { 226 int i; 227 228 for (i = 0; i < num_listen_socks; i++) 229 close(listen_socks[i]); 230 num_listen_socks = -1; 231 } 232 233 static void 234 close_startup_pipes(void) 235 { 236 int i; 237 238 if (startup_pipes) 239 for (i = 0; i < options.max_startups; i++) 240 if (startup_pipes[i] != -1) 241 close(startup_pipes[i]); 242 } 243 244 /* 245 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP; 246 * the effect is to reread the configuration file (and to regenerate 247 * the server key). 248 */ 249 static void 250 sighup_handler(int sig) 251 { 252 int save_errno = errno; 253 254 received_sighup = 1; 255 signal(SIGHUP, sighup_handler); 256 errno = save_errno; 257 } 258 259 /* 260 * Called from the main program after receiving SIGHUP. 261 * Restarts the server. 262 */ 263 static void 264 sighup_restart(void) 265 { 266 log("Received SIGHUP; restarting."); 267 close_listen_socks(); 268 close_startup_pipes(); 269 execv(saved_argv[0], saved_argv); 270 log("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], 271 strerror(errno)); 272 exit(1); 273 } 274 275 /* 276 * Generic signal handler for terminating signals in the master daemon. 277 */ 278 static void 279 sigterm_handler(int sig) 280 { 281 received_sigterm = sig; 282 } 283 284 /* 285 * SIGCHLD handler. This is called whenever a child dies. This will then 286 * reap any zombies left by exited children. 287 */ 288 static void 289 main_sigchld_handler(int sig) 290 { 291 int save_errno = errno; 292 pid_t pid; 293 int status; 294 295 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 296 (pid < 0 && errno == EINTR)) 297 ; 298 299 signal(SIGCHLD, main_sigchld_handler); 300 errno = save_errno; 301 } 302 303 /* 304 * Signal handler for the alarm after the login grace period has expired. 305 */ 306 static void 307 grace_alarm_handler(int sig) 308 { 309 /* XXX no idea how fix this signal handler */ 310 311 /* Log error and exit. */ 312 fatal("Timeout before authentication for %s", get_remote_ipaddr()); 313 } 314 315 /* 316 * Signal handler for the key regeneration alarm. Note that this 317 * alarm only occurs in the daemon waiting for connections, and it does not 318 * do anything with the private key or random state before forking. 319 * Thus there should be no concurrency control/asynchronous execution 320 * problems. 321 */ 322 static void 323 generate_ephemeral_server_key(void) 324 { 325 u_int32_t rnd = 0; 326 int i; 327 328 verbose("Generating %s%d bit RSA key.", 329 sensitive_data.server_key ? "new " : "", options.server_key_bits); 330 if (sensitive_data.server_key != NULL) 331 key_free(sensitive_data.server_key); 332 sensitive_data.server_key = key_generate(KEY_RSA1, 333 options.server_key_bits); 334 verbose("RSA key generation complete."); 335 336 for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) { 337 if (i % 4 == 0) 338 rnd = arc4random(); 339 sensitive_data.ssh1_cookie[i] = rnd & 0xff; 340 rnd >>= 8; 341 } 342 arc4random_stir(); 343 } 344 345 static void 346 key_regeneration_alarm(int sig) 347 { 348 int save_errno = errno; 349 350 signal(SIGALRM, SIG_DFL); 351 errno = save_errno; 352 key_do_regen = 1; 353 } 354 355 static void 356 sshd_exchange_identification(int sock_in, int sock_out) 357 { 358 int i, mismatch; 359 int remote_major, remote_minor; 360 int major, minor; 361 char *s; 362 char buf[256]; /* Must not be larger than remote_version. */ 363 char remote_version[256]; /* Must be at least as big as buf. */ 364 365 if ((options.protocol & SSH_PROTO_1) && 366 (options.protocol & SSH_PROTO_2)) { 367 major = PROTOCOL_MAJOR_1; 368 minor = 99; 369 } else if (options.protocol & SSH_PROTO_2) { 370 major = PROTOCOL_MAJOR_2; 371 minor = PROTOCOL_MINOR_2; 372 } else { 373 major = PROTOCOL_MAJOR_1; 374 minor = PROTOCOL_MINOR_1; 375 } 376 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION); 377 server_version_string = xstrdup(buf); 378 379 if (client_version_string == NULL) { 380 /* Send our protocol version identification. */ 381 if (atomicio(write, sock_out, server_version_string, 382 strlen(server_version_string)) 383 != strlen(server_version_string)) { 384 log("Could not write ident string to %s", get_remote_ipaddr()); 385 fatal_cleanup(); 386 } 387 388 /* Read other sides version identification. */ 389 memset(buf, 0, sizeof(buf)); 390 for (i = 0; i < sizeof(buf) - 1; i++) { 391 if (atomicio(read, sock_in, &buf[i], 1) != 1) { 392 log("Did not receive identification string from %s", 393 get_remote_ipaddr()); 394 fatal_cleanup(); 395 } 396 if (buf[i] == '\r') { 397 buf[i] = 0; 398 /* Kludge for F-Secure Macintosh < 1.0.2 */ 399 if (i == 12 && 400 strncmp(buf, "SSH-1.5-W1.0", 12) == 0) 401 break; 402 continue; 403 } 404 if (buf[i] == '\n') { 405 buf[i] = 0; 406 break; 407 } 408 } 409 buf[sizeof(buf) - 1] = 0; 410 client_version_string = xstrdup(buf); 411 } 412 413 /* 414 * Check that the versions match. In future this might accept 415 * several versions and set appropriate flags to handle them. 416 */ 417 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n", 418 &remote_major, &remote_minor, remote_version) != 3) { 419 s = "Protocol mismatch.\n"; 420 (void) atomicio(write, sock_out, s, strlen(s)); 421 close(sock_in); 422 close(sock_out); 423 log("Bad protocol version identification '%.100s' from %s", 424 client_version_string, get_remote_ipaddr()); 425 fatal_cleanup(); 426 } 427 debug("Client protocol version %d.%d; client software version %.100s", 428 remote_major, remote_minor, remote_version); 429 430 compat_datafellows(remote_version); 431 432 if (datafellows & SSH_BUG_PROBE) { 433 log("probed from %s with %s. Don't panic.", 434 get_remote_ipaddr(), client_version_string); 435 fatal_cleanup(); 436 } 437 438 if (datafellows & SSH_BUG_SCANNER) { 439 log("scanned from %s with %s. Don't panic.", 440 get_remote_ipaddr(), client_version_string); 441 fatal_cleanup(); 442 } 443 444 mismatch = 0; 445 switch (remote_major) { 446 case 1: 447 if (remote_minor == 99) { 448 if (options.protocol & SSH_PROTO_2) 449 enable_compat20(); 450 else 451 mismatch = 1; 452 break; 453 } 454 if (!(options.protocol & SSH_PROTO_1)) { 455 mismatch = 1; 456 break; 457 } 458 if (remote_minor < 3) { 459 packet_disconnect("Your ssh version is too old and " 460 "is no longer supported. Please install a newer version."); 461 } else if (remote_minor == 3) { 462 /* note that this disables agent-forwarding */ 463 enable_compat13(); 464 } 465 break; 466 case 2: 467 if (options.protocol & SSH_PROTO_2) { 468 enable_compat20(); 469 break; 470 } 471 /* FALLTHROUGH */ 472 default: 473 mismatch = 1; 474 break; 475 } 476 chop(server_version_string); 477 debug("Local version string %.200s", server_version_string); 478 479 if (mismatch) { 480 s = "Protocol major versions differ.\n"; 481 (void) atomicio(write, sock_out, s, strlen(s)); 482 close(sock_in); 483 close(sock_out); 484 log("Protocol major versions differ for %s: %.200s vs. %.200s", 485 get_remote_ipaddr(), 486 server_version_string, client_version_string); 487 fatal_cleanup(); 488 } 489 } 490 491 /* Destroy the host and server keys. They will no longer be needed. */ 492 void 493 destroy_sensitive_data(void) 494 { 495 int i; 496 497 if (sensitive_data.server_key) { 498 key_free(sensitive_data.server_key); 499 sensitive_data.server_key = NULL; 500 } 501 for (i = 0; i < options.num_host_key_files; i++) { 502 if (sensitive_data.host_keys[i]) { 503 key_free(sensitive_data.host_keys[i]); 504 sensitive_data.host_keys[i] = NULL; 505 } 506 } 507 sensitive_data.ssh1_host_key = NULL; 508 memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH); 509 } 510 511 /* Demote private to public keys for network child */ 512 void 513 demote_sensitive_data(void) 514 { 515 Key *tmp; 516 int i; 517 518 if (sensitive_data.server_key) { 519 tmp = key_demote(sensitive_data.server_key); 520 key_free(sensitive_data.server_key); 521 sensitive_data.server_key = tmp; 522 } 523 524 for (i = 0; i < options.num_host_key_files; i++) { 525 if (sensitive_data.host_keys[i]) { 526 tmp = key_demote(sensitive_data.host_keys[i]); 527 key_free(sensitive_data.host_keys[i]); 528 sensitive_data.host_keys[i] = tmp; 529 if (tmp->type == KEY_RSA1) 530 sensitive_data.ssh1_host_key = tmp; 531 } 532 } 533 534 /* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */ 535 } 536 537 static void 538 privsep_preauth_child(void) 539 { 540 u_int32_t rnd[256]; 541 gid_t gidset[1]; 542 struct passwd *pw; 543 int i; 544 545 /* Enable challenge-response authentication for privilege separation */ 546 privsep_challenge_enable(); 547 548 for (i = 0; i < 256; i++) 549 rnd[i] = arc4random(); 550 RAND_seed(rnd, sizeof(rnd)); 551 552 /* Demote the private keys to public keys. */ 553 demote_sensitive_data(); 554 555 if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) 556 fatal("Privilege separation user %s does not exist", 557 SSH_PRIVSEP_USER); 558 memset(pw->pw_passwd, 0, strlen(pw->pw_passwd)); 559 endpwent(); 560 561 /* Change our root directory */ 562 if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1) 563 fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR, 564 strerror(errno)); 565 if (chdir("/") == -1) 566 fatal("chdir(\"/\"): %s", strerror(errno)); 567 568 /* Drop our privileges */ 569 debug3("privsep user:group %u:%u", (u_int)pw->pw_uid, 570 (u_int)pw->pw_gid); 571 #if 0 572 /* XXX not ready, to heavy after chroot */ 573 do_setusercontext(pw); 574 #else 575 gidset[0] = pw->pw_gid; 576 if (setgid(pw->pw_gid) < 0) 577 fatal("setgid failed for %u", pw->pw_gid ); 578 if (setgroups(1, gidset) < 0) 579 fatal("setgroups: %.100s", strerror(errno)); 580 permanently_set_uid(pw); 581 #endif 582 } 583 584 static Authctxt * 585 privsep_preauth(void) 586 { 587 Authctxt *authctxt = NULL; 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 fatal_remove_cleanup((void (*) (void *)) packet_close, NULL); 601 602 debug2("Network child is on pid %ld", (long)pid); 603 604 close(pmonitor->m_recvfd); 605 authctxt = monitor_child_preauth(pmonitor); 606 close(pmonitor->m_sendfd); 607 608 /* Sync memory */ 609 monitor_sync(pmonitor); 610 611 /* Wait for the child's exit status */ 612 while (waitpid(pid, &status, 0) < 0) 613 if (errno != EINTR) 614 break; 615 616 /* Reinstall, since the child has finished */ 617 fatal_add_cleanup((void (*) (void *)) packet_close, NULL); 618 619 return (authctxt); 620 } else { 621 /* child */ 622 623 close(pmonitor->m_sendfd); 624 625 /* Demote the child */ 626 if (getuid() == 0 || geteuid() == 0) 627 privsep_preauth_child(); 628 setproctitle("%s", "[net]"); 629 } 630 return (NULL); 631 } 632 633 static void 634 privsep_postauth(Authctxt *authctxt) 635 { 636 extern Authctxt *x_authctxt; 637 638 /* XXX - Remote port forwarding */ 639 x_authctxt = authctxt; 640 641 #ifdef DISABLE_FD_PASSING 642 if (1) { 643 #else 644 if (authctxt->pw->pw_uid == 0 || options.use_login) { 645 #endif 646 /* File descriptor passing is broken or root login */ 647 monitor_apply_keystate(pmonitor); 648 use_privsep = 0; 649 return; 650 } 651 652 /* Authentication complete */ 653 alarm(0); 654 if (startup_pipe != -1) { 655 close(startup_pipe); 656 startup_pipe = -1; 657 } 658 659 /* New socket pair */ 660 monitor_reinit(pmonitor); 661 662 pmonitor->m_pid = fork(); 663 if (pmonitor->m_pid == -1) 664 fatal("fork of unprivileged child failed"); 665 else if (pmonitor->m_pid != 0) { 666 fatal_remove_cleanup((void (*) (void *)) packet_close, NULL); 667 668 debug2("User child is on pid %ld", (long)pmonitor->m_pid); 669 close(pmonitor->m_recvfd); 670 monitor_child_postauth(pmonitor); 671 672 /* NEVERREACHED */ 673 exit(0); 674 } 675 676 close(pmonitor->m_sendfd); 677 678 /* Demote the private keys to public keys. */ 679 demote_sensitive_data(); 680 681 /* Drop privileges */ 682 do_setusercontext(authctxt->pw); 683 684 /* It is safe now to apply the key state */ 685 monitor_apply_keystate(pmonitor); 686 } 687 688 static char * 689 list_hostkey_types(void) 690 { 691 Buffer b; 692 char *p; 693 int i; 694 695 buffer_init(&b); 696 for (i = 0; i < options.num_host_key_files; i++) { 697 Key *key = sensitive_data.host_keys[i]; 698 if (key == NULL) 699 continue; 700 switch (key->type) { 701 case KEY_RSA: 702 case KEY_DSA: 703 if (buffer_len(&b) > 0) 704 buffer_append(&b, ",", 1); 705 p = key_ssh_name(key); 706 buffer_append(&b, p, strlen(p)); 707 break; 708 } 709 } 710 buffer_append(&b, "\0", 1); 711 p = xstrdup(buffer_ptr(&b)); 712 buffer_free(&b); 713 debug("list_hostkey_types: %s", p); 714 return p; 715 } 716 717 Key * 718 get_hostkey_by_type(int type) 719 { 720 int i; 721 722 for (i = 0; i < options.num_host_key_files; i++) { 723 Key *key = sensitive_data.host_keys[i]; 724 if (key != NULL && key->type == type) 725 return key; 726 } 727 return NULL; 728 } 729 730 Key * 731 get_hostkey_by_index(int ind) 732 { 733 if (ind < 0 || ind >= options.num_host_key_files) 734 return (NULL); 735 return (sensitive_data.host_keys[ind]); 736 } 737 738 int 739 get_hostkey_index(Key *key) 740 { 741 int i; 742 743 for (i = 0; i < options.num_host_key_files; i++) { 744 if (key == sensitive_data.host_keys[i]) 745 return (i); 746 } 747 return (-1); 748 } 749 750 /* 751 * returns 1 if connection should be dropped, 0 otherwise. 752 * dropping starts at connection #max_startups_begin with a probability 753 * of (max_startups_rate/100). the probability increases linearly until 754 * all connections are dropped for startups > max_startups 755 */ 756 static int 757 drop_connection(int startups) 758 { 759 double p, r; 760 761 if (startups < options.max_startups_begin) 762 return 0; 763 if (startups >= options.max_startups) 764 return 1; 765 if (options.max_startups_rate == 100) 766 return 1; 767 768 p = 100 - options.max_startups_rate; 769 p *= startups - options.max_startups_begin; 770 p /= (double) (options.max_startups - options.max_startups_begin); 771 p += options.max_startups_rate; 772 p /= 100.0; 773 r = arc4random() / (double) UINT_MAX; 774 775 debug("drop_connection: p %g, r %g", p, r); 776 return (r < p) ? 1 : 0; 777 } 778 779 static void 780 usage(void) 781 { 782 fprintf(stderr, "sshd version %s\n", SSH_VERSION); 783 fprintf(stderr, "Usage: %s [options]\n", __progname); 784 fprintf(stderr, "Options:\n"); 785 fprintf(stderr, " -f file Configuration file (default %s)\n", _PATH_SERVER_CONFIG_FILE); 786 fprintf(stderr, " -d Debugging mode (multiple -d means more debugging)\n"); 787 fprintf(stderr, " -i Started from inetd\n"); 788 fprintf(stderr, " -D Do not fork into daemon mode\n"); 789 fprintf(stderr, " -t Only test configuration file and keys\n"); 790 fprintf(stderr, " -q Quiet (no logging)\n"); 791 fprintf(stderr, " -p port Listen on the specified port (default: 22)\n"); 792 fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n"); 793 fprintf(stderr, " -g seconds Grace period for authentication (default: 600)\n"); 794 fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n"); 795 fprintf(stderr, " -h file File from which to read host key (default: %s)\n", 796 _PATH_HOST_KEY_FILE); 797 fprintf(stderr, " -u len Maximum hostname length for utmp recording\n"); 798 fprintf(stderr, " -4 Use IPv4 only\n"); 799 fprintf(stderr, " -6 Use IPv6 only\n"); 800 fprintf(stderr, " -o option Process the option as if it was read from a configuration file.\n"); 801 exit(1); 802 } 803 804 /* 805 * Main program for the daemon. 806 */ 807 int 808 main(int ac, char **av) 809 { 810 extern char *optarg; 811 extern int optind; 812 int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1; 813 pid_t pid; 814 socklen_t fromlen; 815 fd_set *fdset; 816 struct sockaddr_storage from; 817 const char *remote_ip; 818 int remote_port; 819 FILE *f; 820 struct addrinfo *ai; 821 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 822 int listen_sock, maxfd; 823 int startup_p[2]; 824 int startups = 0; 825 Authctxt *authctxt; 826 Key *key; 827 int ret, key_used = 0; 828 829 #ifdef HAVE_SECUREWARE 830 (void)set_auth_parameters(ac, av); 831 #endif 832 __progname = get_progname(av[0]); 833 init_rng(); 834 835 /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */ 836 saved_argc = ac; 837 saved_argv = av; 838 saved_argv = xmalloc(sizeof(*saved_argv) * (ac + 1)); 839 for (i = 0; i < ac; i++) 840 saved_argv[i] = xstrdup(av[i]); 841 saved_argv[ac] = NULL; 842 843 #ifndef HAVE_SETPROCTITLE 844 /* Prepare for later setproctitle emulation */ 845 compat_init_setproctitle(ac, av); 846 #endif 847 848 /* Initialize configuration options to their default values. */ 849 initialize_server_options(&options); 850 851 /* Parse command-line arguments. */ 852 while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:o:dDeiqtQ46")) != -1) { 853 switch (opt) { 854 case '4': 855 IPv4or6 = AF_INET; 856 break; 857 case '6': 858 IPv4or6 = AF_INET6; 859 break; 860 case 'f': 861 config_file_name = optarg; 862 break; 863 case 'd': 864 if (0 == debug_flag) { 865 debug_flag = 1; 866 options.log_level = SYSLOG_LEVEL_DEBUG1; 867 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) { 868 options.log_level++; 869 } else { 870 fprintf(stderr, "Too high debugging level.\n"); 871 exit(1); 872 } 873 break; 874 case 'D': 875 no_daemon_flag = 1; 876 break; 877 case 'e': 878 log_stderr = 1; 879 break; 880 case 'i': 881 inetd_flag = 1; 882 break; 883 case 'Q': 884 /* ignored */ 885 break; 886 case 'q': 887 options.log_level = SYSLOG_LEVEL_QUIET; 888 break; 889 case 'b': 890 options.server_key_bits = atoi(optarg); 891 break; 892 case 'p': 893 options.ports_from_cmdline = 1; 894 if (options.num_ports >= MAX_PORTS) { 895 fprintf(stderr, "too many ports.\n"); 896 exit(1); 897 } 898 options.ports[options.num_ports++] = a2port(optarg); 899 if (options.ports[options.num_ports-1] == 0) { 900 fprintf(stderr, "Bad port number.\n"); 901 exit(1); 902 } 903 break; 904 case 'g': 905 if ((options.login_grace_time = convtime(optarg)) == -1) { 906 fprintf(stderr, "Invalid login grace time.\n"); 907 exit(1); 908 } 909 break; 910 case 'k': 911 if ((options.key_regeneration_time = convtime(optarg)) == -1) { 912 fprintf(stderr, "Invalid key regeneration interval.\n"); 913 exit(1); 914 } 915 break; 916 case 'h': 917 if (options.num_host_key_files >= MAX_HOSTKEYS) { 918 fprintf(stderr, "too many host keys.\n"); 919 exit(1); 920 } 921 options.host_key_files[options.num_host_key_files++] = optarg; 922 break; 923 case 'V': 924 client_version_string = optarg; 925 /* only makes sense with inetd_flag, i.e. no listen() */ 926 inetd_flag = 1; 927 break; 928 case 't': 929 test_flag = 1; 930 break; 931 case 'u': 932 utmp_len = atoi(optarg); 933 if (utmp_len > MAXHOSTNAMELEN) { 934 fprintf(stderr, "Invalid utmp length.\n"); 935 exit(1); 936 } 937 break; 938 case 'o': 939 if (process_server_config_line(&options, optarg, 940 "command-line", 0) != 0) 941 exit(1); 942 break; 943 case '?': 944 default: 945 usage(); 946 break; 947 } 948 } 949 SSLeay_add_all_algorithms(); 950 channel_set_af(IPv4or6); 951 952 /* 953 * Force logging to stderr until we have loaded the private host 954 * key (unless started from inetd) 955 */ 956 log_init(__progname, 957 options.log_level == SYSLOG_LEVEL_NOT_SET ? 958 SYSLOG_LEVEL_INFO : options.log_level, 959 options.log_facility == SYSLOG_FACILITY_NOT_SET ? 960 SYSLOG_FACILITY_AUTH : options.log_facility, 961 log_stderr || !inetd_flag); 962 963 #ifdef _UNICOS 964 /* Cray can define user privs drop all prives now! 965 * Not needed on PRIV_SU systems! 966 */ 967 drop_cray_privs(); 968 #endif 969 970 seed_rng(); 971 972 /* Read server configuration options from the configuration file. */ 973 read_server_config(&options, config_file_name); 974 975 /* Fill in default values for those options not explicitly set. */ 976 fill_default_server_options(&options); 977 978 /* Check that there are no remaining arguments. */ 979 if (optind < ac) { 980 fprintf(stderr, "Extra argument %s.\n", av[optind]); 981 exit(1); 982 } 983 984 debug("sshd version %.100s", SSH_VERSION); 985 986 /* load private host keys */ 987 sensitive_data.host_keys = xmalloc(options.num_host_key_files * 988 sizeof(Key *)); 989 for (i = 0; i < options.num_host_key_files; i++) 990 sensitive_data.host_keys[i] = NULL; 991 sensitive_data.server_key = NULL; 992 sensitive_data.ssh1_host_key = NULL; 993 sensitive_data.have_ssh1_key = 0; 994 sensitive_data.have_ssh2_key = 0; 995 996 for (i = 0; i < options.num_host_key_files; i++) { 997 key = key_load_private(options.host_key_files[i], "", NULL); 998 sensitive_data.host_keys[i] = key; 999 if (key == NULL) { 1000 error("Could not load host key: %s", 1001 options.host_key_files[i]); 1002 sensitive_data.host_keys[i] = NULL; 1003 continue; 1004 } 1005 switch (key->type) { 1006 case KEY_RSA1: 1007 sensitive_data.ssh1_host_key = key; 1008 sensitive_data.have_ssh1_key = 1; 1009 break; 1010 case KEY_RSA: 1011 case KEY_DSA: 1012 sensitive_data.have_ssh2_key = 1; 1013 break; 1014 } 1015 debug("private host key: #%d type %d %s", i, key->type, 1016 key_type(key)); 1017 } 1018 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) { 1019 log("Disabling protocol version 1. Could not load host key"); 1020 options.protocol &= ~SSH_PROTO_1; 1021 } 1022 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) { 1023 log("Disabling protocol version 2. Could not load host key"); 1024 options.protocol &= ~SSH_PROTO_2; 1025 } 1026 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) { 1027 log("sshd: no hostkeys available -- exiting."); 1028 exit(1); 1029 } 1030 1031 /* Check certain values for sanity. */ 1032 if (options.protocol & SSH_PROTO_1) { 1033 if (options.server_key_bits < 512 || 1034 options.server_key_bits > 32768) { 1035 fprintf(stderr, "Bad server key size.\n"); 1036 exit(1); 1037 } 1038 /* 1039 * Check that server and host key lengths differ sufficiently. This 1040 * is necessary to make double encryption work with rsaref. Oh, I 1041 * hate software patents. I dont know if this can go? Niels 1042 */ 1043 if (options.server_key_bits > 1044 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - 1045 SSH_KEY_BITS_RESERVED && options.server_key_bits < 1046 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + 1047 SSH_KEY_BITS_RESERVED) { 1048 options.server_key_bits = 1049 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + 1050 SSH_KEY_BITS_RESERVED; 1051 debug("Forcing server key to %d bits to make it differ from host key.", 1052 options.server_key_bits); 1053 } 1054 } 1055 1056 if (use_privsep) { 1057 struct passwd *pw; 1058 struct stat st; 1059 1060 if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) 1061 fatal("Privilege separation user %s does not exist", 1062 SSH_PRIVSEP_USER); 1063 if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) || 1064 (S_ISDIR(st.st_mode) == 0)) 1065 fatal("Missing privilege separation directory: %s", 1066 _PATH_PRIVSEP_CHROOT_DIR); 1067 1068 #ifdef HAVE_CYGWIN 1069 if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) && 1070 (st.st_uid != getuid () || 1071 (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)) 1072 #else 1073 if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0) 1074 #endif 1075 fatal("%s must be owned by root and not group or " 1076 "world-writable.", _PATH_PRIVSEP_CHROOT_DIR); 1077 } 1078 1079 /* Configuration looks good, so exit if in test mode. */ 1080 if (test_flag) 1081 exit(0); 1082 1083 /* 1084 * Clear out any supplemental groups we may have inherited. This 1085 * prevents inadvertent creation of files with bad modes (in the 1086 * portable version at least, it's certainly possible for PAM 1087 * to create a file, and we can't control the code in every 1088 * module which might be used). 1089 */ 1090 if (setgroups(0, NULL) < 0) 1091 debug("setgroups() failed: %.200s", strerror(errno)); 1092 1093 /* Initialize the log (it is reinitialized below in case we forked). */ 1094 if (debug_flag && !inetd_flag) 1095 log_stderr = 1; 1096 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1097 1098 /* 1099 * If not in debugging mode, and not started from inetd, disconnect 1100 * from the controlling terminal, and fork. The original process 1101 * exits. 1102 */ 1103 if (!(debug_flag || inetd_flag || no_daemon_flag)) { 1104 #ifdef TIOCNOTTY 1105 int fd; 1106 #endif /* TIOCNOTTY */ 1107 if (daemon(0, 0) < 0) 1108 fatal("daemon() failed: %.200s", strerror(errno)); 1109 1110 /* Disconnect from the controlling tty. */ 1111 #ifdef TIOCNOTTY 1112 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 1113 if (fd >= 0) { 1114 (void) ioctl(fd, TIOCNOTTY, NULL); 1115 close(fd); 1116 } 1117 #endif /* TIOCNOTTY */ 1118 } 1119 /* Reinitialize the log (because of the fork above). */ 1120 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1121 1122 /* Initialize the random number generator. */ 1123 arc4random_stir(); 1124 1125 /* Chdir to the root directory so that the current disk can be 1126 unmounted if desired. */ 1127 chdir("/"); 1128 1129 /* ignore SIGPIPE */ 1130 signal(SIGPIPE, SIG_IGN); 1131 1132 /* Start listening for a socket, unless started from inetd. */ 1133 if (inetd_flag) { 1134 int s1; 1135 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */ 1136 dup(s1); 1137 sock_in = dup(0); 1138 sock_out = dup(1); 1139 startup_pipe = -1; 1140 /* 1141 * We intentionally do not close the descriptors 0, 1, and 2 1142 * as our code for setting the descriptors won\'t work if 1143 * ttyfd happens to be one of those. 1144 */ 1145 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out); 1146 if (options.protocol & SSH_PROTO_1) 1147 generate_ephemeral_server_key(); 1148 } else { 1149 for (ai = options.listen_addrs; ai; ai = ai->ai_next) { 1150 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 1151 continue; 1152 if (num_listen_socks >= MAX_LISTEN_SOCKS) 1153 fatal("Too many listen sockets. " 1154 "Enlarge MAX_LISTEN_SOCKS"); 1155 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 1156 ntop, sizeof(ntop), strport, sizeof(strport), 1157 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 1158 error("getnameinfo failed"); 1159 continue; 1160 } 1161 /* Create socket for listening. */ 1162 listen_sock = socket(ai->ai_family, SOCK_STREAM, 0); 1163 if (listen_sock < 0) { 1164 /* kernel may not support ipv6 */ 1165 verbose("socket: %.100s", strerror(errno)); 1166 continue; 1167 } 1168 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) { 1169 error("listen_sock O_NONBLOCK: %s", strerror(errno)); 1170 close(listen_sock); 1171 continue; 1172 } 1173 /* 1174 * Set socket options. 1175 * Allow local port reuse in TIME_WAIT. 1176 */ 1177 if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR, 1178 &on, sizeof(on)) == -1) 1179 error("setsockopt SO_REUSEADDR: %s", strerror(errno)); 1180 1181 debug("Bind to port %s on %s.", strport, ntop); 1182 1183 /* Bind the socket to the desired port. */ 1184 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) { 1185 if (!ai->ai_next) 1186 error("Bind to port %s on %s failed: %.200s.", 1187 strport, ntop, strerror(errno)); 1188 close(listen_sock); 1189 continue; 1190 } 1191 listen_socks[num_listen_socks] = listen_sock; 1192 num_listen_socks++; 1193 1194 /* Start listening on the port. */ 1195 log("Server listening on %s port %s.", ntop, strport); 1196 if (listen(listen_sock, 5) < 0) 1197 fatal("listen: %.100s", strerror(errno)); 1198 1199 } 1200 freeaddrinfo(options.listen_addrs); 1201 1202 if (!num_listen_socks) 1203 fatal("Cannot bind any address."); 1204 1205 if (options.protocol & SSH_PROTO_1) 1206 generate_ephemeral_server_key(); 1207 1208 /* 1209 * Arrange to restart on SIGHUP. The handler needs 1210 * listen_sock. 1211 */ 1212 signal(SIGHUP, sighup_handler); 1213 1214 signal(SIGTERM, sigterm_handler); 1215 signal(SIGQUIT, sigterm_handler); 1216 1217 /* Arrange SIGCHLD to be caught. */ 1218 signal(SIGCHLD, main_sigchld_handler); 1219 1220 /* Write out the pid file after the sigterm handler is setup */ 1221 if (!debug_flag) { 1222 /* 1223 * Record our pid in /var/run/sshd.pid to make it 1224 * easier to kill the correct sshd. We don't want to 1225 * do this before the bind above because the bind will 1226 * fail if there already is a daemon, and this will 1227 * overwrite any old pid in the file. 1228 */ 1229 f = fopen(options.pid_file, "wb"); 1230 if (f) { 1231 fprintf(f, "%ld\n", (long) getpid()); 1232 fclose(f); 1233 } 1234 } 1235 1236 /* setup fd set for listen */ 1237 fdset = NULL; 1238 maxfd = 0; 1239 for (i = 0; i < num_listen_socks; i++) 1240 if (listen_socks[i] > maxfd) 1241 maxfd = listen_socks[i]; 1242 /* pipes connected to unauthenticated childs */ 1243 startup_pipes = xmalloc(options.max_startups * sizeof(int)); 1244 for (i = 0; i < options.max_startups; i++) 1245 startup_pipes[i] = -1; 1246 1247 /* 1248 * Stay listening for connections until the system crashes or 1249 * the daemon is killed with a signal. 1250 */ 1251 for (;;) { 1252 if (received_sighup) 1253 sighup_restart(); 1254 if (fdset != NULL) 1255 xfree(fdset); 1256 fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask); 1257 fdset = (fd_set *)xmalloc(fdsetsz); 1258 memset(fdset, 0, fdsetsz); 1259 1260 for (i = 0; i < num_listen_socks; i++) 1261 FD_SET(listen_socks[i], fdset); 1262 for (i = 0; i < options.max_startups; i++) 1263 if (startup_pipes[i] != -1) 1264 FD_SET(startup_pipes[i], fdset); 1265 1266 /* Wait in select until there is a connection. */ 1267 ret = select(maxfd+1, fdset, NULL, NULL, NULL); 1268 if (ret < 0 && errno != EINTR) 1269 error("select: %.100s", strerror(errno)); 1270 if (received_sigterm) { 1271 log("Received signal %d; terminating.", 1272 (int) received_sigterm); 1273 close_listen_socks(); 1274 unlink(options.pid_file); 1275 exit(255); 1276 } 1277 if (key_used && key_do_regen) { 1278 generate_ephemeral_server_key(); 1279 key_used = 0; 1280 key_do_regen = 0; 1281 } 1282 if (ret < 0) 1283 continue; 1284 1285 for (i = 0; i < options.max_startups; i++) 1286 if (startup_pipes[i] != -1 && 1287 FD_ISSET(startup_pipes[i], fdset)) { 1288 /* 1289 * the read end of the pipe is ready 1290 * if the child has closed the pipe 1291 * after successful authentication 1292 * or if the child has died 1293 */ 1294 close(startup_pipes[i]); 1295 startup_pipes[i] = -1; 1296 startups--; 1297 } 1298 for (i = 0; i < num_listen_socks; i++) { 1299 if (!FD_ISSET(listen_socks[i], fdset)) 1300 continue; 1301 fromlen = sizeof(from); 1302 newsock = accept(listen_socks[i], (struct sockaddr *)&from, 1303 &fromlen); 1304 if (newsock < 0) { 1305 if (errno != EINTR && errno != EWOULDBLOCK) 1306 error("accept: %.100s", strerror(errno)); 1307 continue; 1308 } 1309 if (fcntl(newsock, F_SETFL, 0) < 0) { 1310 error("newsock del O_NONBLOCK: %s", strerror(errno)); 1311 close(newsock); 1312 continue; 1313 } 1314 if (drop_connection(startups) == 1) { 1315 debug("drop connection #%d", startups); 1316 close(newsock); 1317 continue; 1318 } 1319 if (pipe(startup_p) == -1) { 1320 close(newsock); 1321 continue; 1322 } 1323 1324 for (j = 0; j < options.max_startups; j++) 1325 if (startup_pipes[j] == -1) { 1326 startup_pipes[j] = startup_p[0]; 1327 if (maxfd < startup_p[0]) 1328 maxfd = startup_p[0]; 1329 startups++; 1330 break; 1331 } 1332 1333 /* 1334 * Got connection. Fork a child to handle it, unless 1335 * we are in debugging mode. 1336 */ 1337 if (debug_flag) { 1338 /* 1339 * In debugging mode. Close the listening 1340 * socket, and start processing the 1341 * connection without forking. 1342 */ 1343 debug("Server will not fork when running in debugging mode."); 1344 close_listen_socks(); 1345 sock_in = newsock; 1346 sock_out = newsock; 1347 startup_pipe = -1; 1348 pid = getpid(); 1349 break; 1350 } else { 1351 /* 1352 * Normal production daemon. Fork, and have 1353 * the child process the connection. The 1354 * parent continues listening. 1355 */ 1356 if ((pid = fork()) == 0) { 1357 /* 1358 * Child. Close the listening and max_startup 1359 * sockets. Start using the accepted socket. 1360 * Reinitialize logging (since our pid has 1361 * changed). We break out of the loop to handle 1362 * the connection. 1363 */ 1364 startup_pipe = startup_p[1]; 1365 close_startup_pipes(); 1366 close_listen_socks(); 1367 sock_in = newsock; 1368 sock_out = newsock; 1369 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1370 break; 1371 } 1372 } 1373 1374 /* Parent. Stay in the loop. */ 1375 if (pid < 0) 1376 error("fork: %.100s", strerror(errno)); 1377 else 1378 debug("Forked child %ld.", (long)pid); 1379 1380 close(startup_p[1]); 1381 1382 /* Mark that the key has been used (it was "given" to the child). */ 1383 if ((options.protocol & SSH_PROTO_1) && 1384 key_used == 0) { 1385 /* Schedule server key regeneration alarm. */ 1386 signal(SIGALRM, key_regeneration_alarm); 1387 alarm(options.key_regeneration_time); 1388 key_used = 1; 1389 } 1390 1391 arc4random_stir(); 1392 1393 /* Close the new socket (the child is now taking care of it). */ 1394 close(newsock); 1395 } 1396 /* child process check (or debug mode) */ 1397 if (num_listen_socks < 0) 1398 break; 1399 } 1400 } 1401 1402 /* This is the child processing a new connection. */ 1403 1404 /* 1405 * Create a new session and process group since the 4.4BSD 1406 * setlogin() affects the entire process group. We don't 1407 * want the child to be able to affect the parent. 1408 */ 1409 #if !defined(STREAMS_PUSH_ACQUIRES_CTTY) 1410 /* 1411 * If setsid is called on Solaris, sshd will acquire the controlling 1412 * terminal while pushing STREAMS modules. This will prevent the 1413 * shell from acquiring it later. 1414 */ 1415 if (!debug_flag && !inetd_flag && setsid() < 0) 1416 error("setsid: %.100s", strerror(errno)); 1417 #endif 1418 1419 /* 1420 * Disable the key regeneration alarm. We will not regenerate the 1421 * key since we are no longer in a position to give it to anyone. We 1422 * will not restart on SIGHUP since it no longer makes sense. 1423 */ 1424 alarm(0); 1425 signal(SIGALRM, SIG_DFL); 1426 signal(SIGHUP, SIG_DFL); 1427 signal(SIGTERM, SIG_DFL); 1428 signal(SIGQUIT, SIG_DFL); 1429 signal(SIGCHLD, SIG_DFL); 1430 signal(SIGINT, SIG_DFL); 1431 1432 /* Set keepalives if requested. */ 1433 if (options.keepalives && 1434 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, 1435 sizeof(on)) < 0) 1436 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 1437 1438 #ifdef __FreeBSD__ 1439 /* 1440 * Initialize the resolver. This may not happen automatically 1441 * before privsep chroot(). 1442 */ 1443 if ((_res.options & RES_INIT) == 0) { 1444 debug("res_init()"); 1445 res_init(); 1446 } 1447 #endif 1448 1449 /* 1450 * Register our connection. This turns encryption off because we do 1451 * not have a key. 1452 */ 1453 packet_set_connection(sock_in, sock_out); 1454 1455 remote_port = get_remote_port(); 1456 remote_ip = get_remote_ipaddr(); 1457 1458 #ifdef LIBWRAP 1459 /* Check whether logins are denied from this host. */ 1460 { 1461 struct request_info req; 1462 1463 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0); 1464 fromhost(&req); 1465 1466 if (!hosts_access(&req)) { 1467 debug("Connection refused by tcp wrapper"); 1468 refuse(&req); 1469 /* NOTREACHED */ 1470 fatal("libwrap refuse returns"); 1471 } 1472 } 1473 #endif /* LIBWRAP */ 1474 1475 /* Log the connection. */ 1476 verbose("Connection from %.500s port %d", remote_ip, remote_port); 1477 1478 /* 1479 * We don\'t want to listen forever unless the other side 1480 * successfully authenticates itself. So we set up an alarm which is 1481 * cleared after successful authentication. A limit of zero 1482 * indicates no limit. Note that we don\'t set the alarm in debugging 1483 * mode; it is just annoying to have the server exit just when you 1484 * are about to discover the bug. 1485 */ 1486 signal(SIGALRM, grace_alarm_handler); 1487 if (!debug_flag) 1488 alarm(options.login_grace_time); 1489 1490 sshd_exchange_identification(sock_in, sock_out); 1491 /* 1492 * Check that the connection comes from a privileged port. 1493 * Rhosts-Authentication only makes sense from privileged 1494 * programs. Of course, if the intruder has root access on his local 1495 * machine, he can connect from any port. So do not use these 1496 * authentication methods from machines that you do not trust. 1497 */ 1498 if (options.rhosts_authentication && 1499 (remote_port >= IPPORT_RESERVED || 1500 remote_port < IPPORT_RESERVED / 2)) { 1501 debug("Rhosts Authentication disabled, " 1502 "originating port %d not trusted.", remote_port); 1503 options.rhosts_authentication = 0; 1504 } 1505 #if defined(KRB4) && !defined(KRB5) 1506 if (!packet_connection_is_ipv4() && 1507 options.kerberos_authentication) { 1508 debug("Kerberos Authentication disabled, only available for IPv4."); 1509 options.kerberos_authentication = 0; 1510 } 1511 #endif /* KRB4 && !KRB5 */ 1512 #ifdef AFS 1513 /* If machine has AFS, set process authentication group. */ 1514 if (k_hasafs()) { 1515 k_setpag(); 1516 k_unlog(); 1517 } 1518 #endif /* AFS */ 1519 1520 packet_set_nonblocking(); 1521 1522 if (use_privsep) 1523 if ((authctxt = privsep_preauth()) != NULL) 1524 goto authenticated; 1525 1526 /* perform the key exchange */ 1527 /* authenticate user and start session */ 1528 if (compat20) { 1529 do_ssh2_kex(); 1530 authctxt = do_authentication2(); 1531 } else { 1532 do_ssh1_kex(); 1533 authctxt = do_authentication(); 1534 } 1535 /* 1536 * If we use privilege separation, the unprivileged child transfers 1537 * the current keystate and exits 1538 */ 1539 if (use_privsep) { 1540 mm_send_keystate(pmonitor); 1541 exit(0); 1542 } 1543 1544 authenticated: 1545 /* 1546 * In privilege separation, we fork another child and prepare 1547 * file descriptor passing. 1548 */ 1549 if (use_privsep) { 1550 privsep_postauth(authctxt); 1551 /* the monitor process [priv] will not return */ 1552 if (!compat20) 1553 destroy_sensitive_data(); 1554 } 1555 1556 /* Perform session preparation. */ 1557 do_authenticated(authctxt); 1558 1559 /* The connection has been terminated. */ 1560 verbose("Closing connection to %.100s", remote_ip); 1561 1562 #ifdef USE_PAM 1563 finish_pam(); 1564 #endif /* USE_PAM */ 1565 1566 packet_close(); 1567 1568 if (use_privsep) 1569 mm_terminate(); 1570 1571 exit(0); 1572 } 1573 1574 /* 1575 * Decrypt session_key_int using our private server key and private host key 1576 * (key with larger modulus first). 1577 */ 1578 int 1579 ssh1_session_key(BIGNUM *session_key_int) 1580 { 1581 int rsafail = 0; 1582 1583 if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) { 1584 /* Server key has bigger modulus. */ 1585 if (BN_num_bits(sensitive_data.server_key->rsa->n) < 1586 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) { 1587 fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d", 1588 get_remote_ipaddr(), 1589 BN_num_bits(sensitive_data.server_key->rsa->n), 1590 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n), 1591 SSH_KEY_BITS_RESERVED); 1592 } 1593 if (rsa_private_decrypt(session_key_int, session_key_int, 1594 sensitive_data.server_key->rsa) <= 0) 1595 rsafail++; 1596 if (rsa_private_decrypt(session_key_int, session_key_int, 1597 sensitive_data.ssh1_host_key->rsa) <= 0) 1598 rsafail++; 1599 } else { 1600 /* Host key has bigger modulus (or they are equal). */ 1601 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) < 1602 BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) { 1603 fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d", 1604 get_remote_ipaddr(), 1605 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n), 1606 BN_num_bits(sensitive_data.server_key->rsa->n), 1607 SSH_KEY_BITS_RESERVED); 1608 } 1609 if (rsa_private_decrypt(session_key_int, session_key_int, 1610 sensitive_data.ssh1_host_key->rsa) < 0) 1611 rsafail++; 1612 if (rsa_private_decrypt(session_key_int, session_key_int, 1613 sensitive_data.server_key->rsa) < 0) 1614 rsafail++; 1615 } 1616 return (rsafail); 1617 } 1618 /* 1619 * SSH1 key exchange 1620 */ 1621 static void 1622 do_ssh1_kex(void) 1623 { 1624 int i, len; 1625 int rsafail = 0; 1626 BIGNUM *session_key_int; 1627 u_char session_key[SSH_SESSION_KEY_LENGTH]; 1628 u_char cookie[8]; 1629 u_int cipher_type, auth_mask, protocol_flags; 1630 u_int32_t rnd = 0; 1631 1632 /* 1633 * Generate check bytes that the client must send back in the user 1634 * packet in order for it to be accepted; this is used to defy ip 1635 * spoofing attacks. Note that this only works against somebody 1636 * doing IP spoofing from a remote machine; any machine on the local 1637 * network can still see outgoing packets and catch the random 1638 * cookie. This only affects rhosts authentication, and this is one 1639 * of the reasons why it is inherently insecure. 1640 */ 1641 for (i = 0; i < 8; i++) { 1642 if (i % 4 == 0) 1643 rnd = arc4random(); 1644 cookie[i] = rnd & 0xff; 1645 rnd >>= 8; 1646 } 1647 1648 /* 1649 * Send our public key. We include in the packet 64 bits of random 1650 * data that must be matched in the reply in order to prevent IP 1651 * spoofing. 1652 */ 1653 packet_start(SSH_SMSG_PUBLIC_KEY); 1654 for (i = 0; i < 8; i++) 1655 packet_put_char(cookie[i]); 1656 1657 /* Store our public server RSA key. */ 1658 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n)); 1659 packet_put_bignum(sensitive_data.server_key->rsa->e); 1660 packet_put_bignum(sensitive_data.server_key->rsa->n); 1661 1662 /* Store our public host RSA key. */ 1663 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n)); 1664 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e); 1665 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n); 1666 1667 /* Put protocol flags. */ 1668 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN); 1669 1670 /* Declare which ciphers we support. */ 1671 packet_put_int(cipher_mask_ssh1(0)); 1672 1673 /* Declare supported authentication types. */ 1674 auth_mask = 0; 1675 if (options.rhosts_authentication) 1676 auth_mask |= 1 << SSH_AUTH_RHOSTS; 1677 if (options.rhosts_rsa_authentication) 1678 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA; 1679 if (options.rsa_authentication) 1680 auth_mask |= 1 << SSH_AUTH_RSA; 1681 #if defined(KRB4) || defined(KRB5) 1682 if (options.kerberos_authentication) 1683 auth_mask |= 1 << SSH_AUTH_KERBEROS; 1684 #endif 1685 #if defined(AFS) || defined(KRB5) 1686 if (options.kerberos_tgt_passing) 1687 auth_mask |= 1 << SSH_PASS_KERBEROS_TGT; 1688 #endif 1689 #ifdef AFS 1690 if (options.afs_token_passing) 1691 auth_mask |= 1 << SSH_PASS_AFS_TOKEN; 1692 #endif 1693 if (options.challenge_response_authentication == 1) 1694 auth_mask |= 1 << SSH_AUTH_TIS; 1695 if (options.password_authentication) 1696 auth_mask |= 1 << SSH_AUTH_PASSWORD; 1697 packet_put_int(auth_mask); 1698 1699 /* Send the packet and wait for it to be sent. */ 1700 packet_send(); 1701 packet_write_wait(); 1702 1703 debug("Sent %d bit server key and %d bit host key.", 1704 BN_num_bits(sensitive_data.server_key->rsa->n), 1705 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n)); 1706 1707 /* Read clients reply (cipher type and session key). */ 1708 packet_read_expect(SSH_CMSG_SESSION_KEY); 1709 1710 /* Get cipher type and check whether we accept this. */ 1711 cipher_type = packet_get_char(); 1712 1713 if (!(cipher_mask_ssh1(0) & (1 << cipher_type))) 1714 packet_disconnect("Warning: client selects unsupported cipher."); 1715 1716 /* Get check bytes from the packet. These must match those we 1717 sent earlier with the public key packet. */ 1718 for (i = 0; i < 8; i++) 1719 if (cookie[i] != packet_get_char()) 1720 packet_disconnect("IP Spoofing check bytes do not match."); 1721 1722 debug("Encryption type: %.200s", cipher_name(cipher_type)); 1723 1724 /* Get the encrypted integer. */ 1725 if ((session_key_int = BN_new()) == NULL) 1726 fatal("do_ssh1_kex: BN_new failed"); 1727 packet_get_bignum(session_key_int); 1728 1729 protocol_flags = packet_get_int(); 1730 packet_set_protocol_flags(protocol_flags); 1731 packet_check_eom(); 1732 1733 /* Decrypt session_key_int using host/server keys */ 1734 rsafail = PRIVSEP(ssh1_session_key(session_key_int)); 1735 1736 /* 1737 * Extract session key from the decrypted integer. The key is in the 1738 * least significant 256 bits of the integer; the first byte of the 1739 * key is in the highest bits. 1740 */ 1741 if (!rsafail) { 1742 BN_mask_bits(session_key_int, sizeof(session_key) * 8); 1743 len = BN_num_bytes(session_key_int); 1744 if (len < 0 || len > sizeof(session_key)) { 1745 error("do_connection: bad session key len from %s: " 1746 "session_key_int %d > sizeof(session_key) %lu", 1747 get_remote_ipaddr(), len, (u_long)sizeof(session_key)); 1748 rsafail++; 1749 } else { 1750 memset(session_key, 0, sizeof(session_key)); 1751 BN_bn2bin(session_key_int, 1752 session_key + sizeof(session_key) - len); 1753 1754 compute_session_id(session_id, cookie, 1755 sensitive_data.ssh1_host_key->rsa->n, 1756 sensitive_data.server_key->rsa->n); 1757 /* 1758 * Xor the first 16 bytes of the session key with the 1759 * session id. 1760 */ 1761 for (i = 0; i < 16; i++) 1762 session_key[i] ^= session_id[i]; 1763 } 1764 } 1765 if (rsafail) { 1766 int bytes = BN_num_bytes(session_key_int); 1767 u_char *buf = xmalloc(bytes); 1768 MD5_CTX md; 1769 1770 log("do_connection: generating a fake encryption key"); 1771 BN_bn2bin(session_key_int, buf); 1772 MD5_Init(&md); 1773 MD5_Update(&md, buf, bytes); 1774 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); 1775 MD5_Final(session_key, &md); 1776 MD5_Init(&md); 1777 MD5_Update(&md, session_key, 16); 1778 MD5_Update(&md, buf, bytes); 1779 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); 1780 MD5_Final(session_key + 16, &md); 1781 memset(buf, 0, bytes); 1782 xfree(buf); 1783 for (i = 0; i < 16; i++) 1784 session_id[i] = session_key[i] ^ session_key[i + 16]; 1785 } 1786 /* Destroy the private and public keys. No longer. */ 1787 destroy_sensitive_data(); 1788 1789 if (use_privsep) 1790 mm_ssh1_session_id(session_id); 1791 1792 /* Destroy the decrypted integer. It is no longer needed. */ 1793 BN_clear_free(session_key_int); 1794 1795 /* Set the session key. From this on all communications will be encrypted. */ 1796 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type); 1797 1798 /* Destroy our copy of the session key. It is no longer needed. */ 1799 memset(session_key, 0, sizeof(session_key)); 1800 1801 debug("Received session key; encryption turned on."); 1802 1803 /* Send an acknowledgment packet. Note that this packet is sent encrypted. */ 1804 packet_start(SSH_SMSG_SUCCESS); 1805 packet_send(); 1806 packet_write_wait(); 1807 } 1808 1809 /* 1810 * SSH2 key exchange: diffie-hellman-group1-sha1 1811 */ 1812 static void 1813 do_ssh2_kex(void) 1814 { 1815 Kex *kex; 1816 1817 if (options.ciphers != NULL) { 1818 myproposal[PROPOSAL_ENC_ALGS_CTOS] = 1819 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers; 1820 } 1821 myproposal[PROPOSAL_ENC_ALGS_CTOS] = 1822 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]); 1823 myproposal[PROPOSAL_ENC_ALGS_STOC] = 1824 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]); 1825 1826 if (options.macs != NULL) { 1827 myproposal[PROPOSAL_MAC_ALGS_CTOS] = 1828 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs; 1829 } 1830 if (!options.compression) { 1831 myproposal[PROPOSAL_COMP_ALGS_CTOS] = 1832 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none"; 1833 } 1834 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types(); 1835 1836 /* start key exchange */ 1837 kex = kex_setup(myproposal); 1838 kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server; 1839 kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 1840 kex->server = 1; 1841 kex->client_version_string=client_version_string; 1842 kex->server_version_string=server_version_string; 1843 kex->load_host_key=&get_hostkey_by_type; 1844 kex->host_key_index=&get_hostkey_index; 1845 1846 xxx_kex = kex; 1847 1848 dispatch_run(DISPATCH_BLOCK, &kex->done, kex); 1849 1850 session_id2 = kex->session_id; 1851 session_id2_len = kex->session_id_len; 1852 1853 #ifdef DEBUG_KEXDH 1854 /* send 1st encrypted/maced/compressed message */ 1855 packet_start(SSH2_MSG_IGNORE); 1856 packet_put_cstring("markus"); 1857 packet_send(); 1858 packet_write_wait(); 1859 #endif 1860 debug("KEX done"); 1861 } 1862