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 47 #include <openssl/dh.h> 48 #include <openssl/bn.h> 49 #include <openssl/md5.h> 50 #include <openssl/rand.h> 51 52 #include "ssh.h" 53 #include "ssh1.h" 54 #include "ssh2.h" 55 #include "xmalloc.h" 56 #include "rsa.h" 57 #include "sshpty.h" 58 #include "packet.h" 59 #include "mpaux.h" 60 #include "log.h" 61 #include "servconf.h" 62 #include "uidswap.h" 63 #include "compat.h" 64 #include "buffer.h" 65 #include "cipher.h" 66 #include "kex.h" 67 #include "key.h" 68 #include "dh.h" 69 #include "myproposal.h" 70 #include "authfile.h" 71 #include "pathnames.h" 72 #include "atomicio.h" 73 #include "canohost.h" 74 #include "auth.h" 75 #include "misc.h" 76 #include "dispatch.h" 77 #include "channels.h" 78 #include "session.h" 79 #include "monitor_mm.h" 80 #include "monitor.h" 81 #include "monitor_wrap.h" 82 #include "monitor_fdpass.h" 83 84 #ifdef LIBWRAP 85 #include <tcpd.h> 86 #include <syslog.h> 87 int allow_severity = LOG_INFO; 88 int deny_severity = LOG_WARNING; 89 #endif /* LIBWRAP */ 90 91 #ifndef O_NOCTTY 92 #define O_NOCTTY 0 93 #endif 94 95 extern char *__progname; 96 97 /* Server configuration options. */ 98 ServerOptions options; 99 100 /* Name of the server configuration file. */ 101 char *config_file_name = _PATH_SERVER_CONFIG_FILE; 102 103 /* 104 * Flag indicating whether IPv4 or IPv6. This can be set on the command line. 105 * Default value is AF_UNSPEC means both IPv4 and IPv6. 106 */ 107 int IPv4or6 = AF_UNSPEC; 108 109 /* 110 * Debug mode flag. This can be set on the command line. If debug 111 * mode is enabled, extra debugging output will be sent to the system 112 * log, the daemon will not go to background, and will exit after processing 113 * the first connection. 114 */ 115 int debug_flag = 0; 116 117 /* Flag indicating that the daemon should only test the configuration and keys. */ 118 int test_flag = 0; 119 120 /* Flag indicating that the daemon is being started from inetd. */ 121 int inetd_flag = 0; 122 123 /* Flag indicating that sshd should not detach and become a daemon. */ 124 int no_daemon_flag = 0; 125 126 /* debug goes to stderr unless inetd_flag is set */ 127 int log_stderr = 0; 128 129 /* Saved arguments to main(). */ 130 char **saved_argv; 131 132 /* 133 * The sockets that the server is listening; this is used in the SIGHUP 134 * signal handler. 135 */ 136 #define MAX_LISTEN_SOCKS 16 137 int listen_socks[MAX_LISTEN_SOCKS]; 138 int num_listen_socks = 0; 139 140 /* 141 * the client's version string, passed by sshd2 in compat mode. if != NULL, 142 * sshd will skip the version-number exchange 143 */ 144 char *client_version_string = NULL; 145 char *server_version_string = NULL; 146 147 /* for rekeying XXX fixme */ 148 Kex *xxx_kex; 149 150 /* 151 * Any really sensitive data in the application is contained in this 152 * structure. The idea is that this structure could be locked into memory so 153 * that the pages do not get written into swap. However, there are some 154 * problems. The private key contains BIGNUMs, and we do not (in principle) 155 * have access to the internals of them, and locking just the structure is 156 * not very useful. Currently, memory locking is not implemented. 157 */ 158 struct { 159 Key *server_key; /* ephemeral server key */ 160 Key *ssh1_host_key; /* ssh1 host key */ 161 Key **host_keys; /* all private host keys */ 162 int have_ssh1_key; 163 int have_ssh2_key; 164 u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH]; 165 } sensitive_data; 166 167 /* 168 * Flag indicating whether the RSA server key needs to be regenerated. 169 * Is set in the SIGALRM handler and cleared when the key is regenerated. 170 */ 171 static volatile sig_atomic_t key_do_regen = 0; 172 173 /* This is set to true when a signal is received. */ 174 static volatile sig_atomic_t received_sighup = 0; 175 static volatile sig_atomic_t received_sigterm = 0; 176 177 /* session identifier, used by RSA-auth */ 178 u_char session_id[16]; 179 180 /* same for ssh2 */ 181 u_char *session_id2 = NULL; 182 u_int session_id2_len = 0; 183 184 /* record remote hostname or ip */ 185 u_int utmp_len = MAXHOSTNAMELEN; 186 187 /* options.max_startup sized array of fd ints */ 188 int *startup_pipes = NULL; 189 int startup_pipe; /* in child */ 190 191 /* variables used for privilege separation */ 192 int use_privsep; 193 struct monitor *pmonitor; 194 195 /* Prototypes for various functions defined later in this file. */ 196 void destroy_sensitive_data(void); 197 void demote_sensitive_data(void); 198 199 static void do_ssh1_kex(void); 200 static void do_ssh2_kex(void); 201 202 /* 203 * Close all listening sockets 204 */ 205 static void 206 close_listen_socks(void) 207 { 208 int i; 209 210 for (i = 0; i < num_listen_socks; i++) 211 close(listen_socks[i]); 212 num_listen_socks = -1; 213 } 214 215 static void 216 close_startup_pipes(void) 217 { 218 int i; 219 220 if (startup_pipes) 221 for (i = 0; i < options.max_startups; i++) 222 if (startup_pipes[i] != -1) 223 close(startup_pipes[i]); 224 } 225 226 /* 227 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP; 228 * the effect is to reread the configuration file (and to regenerate 229 * the server key). 230 */ 231 static void 232 sighup_handler(int sig) 233 { 234 int save_errno = errno; 235 236 received_sighup = 1; 237 signal(SIGHUP, sighup_handler); 238 errno = save_errno; 239 } 240 241 /* 242 * Called from the main program after receiving SIGHUP. 243 * Restarts the server. 244 */ 245 static void 246 sighup_restart(void) 247 { 248 logit("Received SIGHUP; restarting."); 249 close_listen_socks(); 250 close_startup_pipes(); 251 execv(saved_argv[0], saved_argv); 252 logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], 253 strerror(errno)); 254 exit(1); 255 } 256 257 /* 258 * Generic signal handler for terminating signals in the master daemon. 259 */ 260 static void 261 sigterm_handler(int sig) 262 { 263 received_sigterm = sig; 264 } 265 266 /* 267 * SIGCHLD handler. This is called whenever a child dies. This will then 268 * reap any zombies left by exited children. 269 */ 270 static void 271 main_sigchld_handler(int sig) 272 { 273 int save_errno = errno; 274 pid_t pid; 275 int status; 276 277 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 278 (pid < 0 && errno == EINTR)) 279 ; 280 281 signal(SIGCHLD, main_sigchld_handler); 282 errno = save_errno; 283 } 284 285 /* 286 * Signal handler for the alarm after the login grace period has expired. 287 */ 288 static void 289 grace_alarm_handler(int sig) 290 { 291 /* XXX no idea how fix this signal handler */ 292 293 /* Log error and exit. */ 294 fatal("Timeout before authentication for %s", get_remote_ipaddr()); 295 } 296 297 /* 298 * Signal handler for the key regeneration alarm. Note that this 299 * alarm only occurs in the daemon waiting for connections, and it does not 300 * do anything with the private key or random state before forking. 301 * Thus there should be no concurrency control/asynchronous execution 302 * problems. 303 */ 304 static void 305 generate_ephemeral_server_key(void) 306 { 307 u_int32_t rnd = 0; 308 int i; 309 310 verbose("Generating %s%d bit RSA key.", 311 sensitive_data.server_key ? "new " : "", options.server_key_bits); 312 if (sensitive_data.server_key != NULL) 313 key_free(sensitive_data.server_key); 314 sensitive_data.server_key = key_generate(KEY_RSA1, 315 options.server_key_bits); 316 verbose("RSA key generation complete."); 317 318 for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) { 319 if (i % 4 == 0) 320 rnd = arc4random(); 321 sensitive_data.ssh1_cookie[i] = rnd & 0xff; 322 rnd >>= 8; 323 } 324 arc4random_stir(); 325 } 326 327 static void 328 key_regeneration_alarm(int sig) 329 { 330 int save_errno = errno; 331 332 signal(SIGALRM, SIG_DFL); 333 errno = save_errno; 334 key_do_regen = 1; 335 } 336 337 static void 338 sshd_exchange_identification(int sock_in, int sock_out) 339 { 340 int i, mismatch; 341 int remote_major, remote_minor; 342 int major, minor; 343 char *s; 344 char buf[256]; /* Must not be larger than remote_version. */ 345 char remote_version[256]; /* Must be at least as big as buf. */ 346 347 if ((options.protocol & SSH_PROTO_1) && 348 (options.protocol & SSH_PROTO_2)) { 349 major = PROTOCOL_MAJOR_1; 350 minor = 99; 351 } else if (options.protocol & SSH_PROTO_2) { 352 major = PROTOCOL_MAJOR_2; 353 minor = PROTOCOL_MINOR_2; 354 } else { 355 major = PROTOCOL_MAJOR_1; 356 minor = PROTOCOL_MINOR_1; 357 } 358 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION); 359 server_version_string = xstrdup(buf); 360 361 /* Send our protocol version identification. */ 362 if (atomicio(vwrite, sock_out, server_version_string, 363 strlen(server_version_string)) 364 != strlen(server_version_string)) { 365 logit("Could not write ident string to %s", get_remote_ipaddr()); 366 fatal_cleanup(); 367 } 368 369 /* Read other sides version identification. */ 370 memset(buf, 0, sizeof(buf)); 371 for (i = 0; i < sizeof(buf) - 1; i++) { 372 if (atomicio(read, sock_in, &buf[i], 1) != 1) { 373 logit("Did not receive identification string from %s", 374 get_remote_ipaddr()); 375 fatal_cleanup(); 376 } 377 if (buf[i] == '\r') { 378 buf[i] = 0; 379 /* Kludge for F-Secure Macintosh < 1.0.2 */ 380 if (i == 12 && 381 strncmp(buf, "SSH-1.5-W1.0", 12) == 0) 382 break; 383 continue; 384 } 385 if (buf[i] == '\n') { 386 buf[i] = 0; 387 break; 388 } 389 } 390 buf[sizeof(buf) - 1] = 0; 391 client_version_string = xstrdup(buf); 392 393 /* 394 * Check that the versions match. In future this might accept 395 * several versions and set appropriate flags to handle them. 396 */ 397 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n", 398 &remote_major, &remote_minor, remote_version) != 3) { 399 s = "Protocol mismatch.\n"; 400 (void) atomicio(vwrite, sock_out, s, strlen(s)); 401 close(sock_in); 402 close(sock_out); 403 logit("Bad protocol version identification '%.100s' from %s", 404 client_version_string, get_remote_ipaddr()); 405 fatal_cleanup(); 406 } 407 debug("Client protocol version %d.%d; client software version %.100s", 408 remote_major, remote_minor, remote_version); 409 410 compat_datafellows(remote_version); 411 412 if (datafellows & SSH_BUG_PROBE) { 413 logit("probed from %s with %s. Don't panic.", 414 get_remote_ipaddr(), client_version_string); 415 fatal_cleanup(); 416 } 417 418 if (datafellows & SSH_BUG_SCANNER) { 419 logit("scanned from %s with %s. Don't panic.", 420 get_remote_ipaddr(), client_version_string); 421 fatal_cleanup(); 422 } 423 424 mismatch = 0; 425 switch (remote_major) { 426 case 1: 427 if (remote_minor == 99) { 428 if (options.protocol & SSH_PROTO_2) 429 enable_compat20(); 430 else 431 mismatch = 1; 432 break; 433 } 434 if (!(options.protocol & SSH_PROTO_1)) { 435 mismatch = 1; 436 break; 437 } 438 if (remote_minor < 3) { 439 packet_disconnect("Your ssh version is too old and " 440 "is no longer supported. Please install a newer version."); 441 } else if (remote_minor == 3) { 442 /* note that this disables agent-forwarding */ 443 enable_compat13(); 444 } 445 break; 446 case 2: 447 if (options.protocol & SSH_PROTO_2) { 448 enable_compat20(); 449 break; 450 } 451 /* FALLTHROUGH */ 452 default: 453 mismatch = 1; 454 break; 455 } 456 chop(server_version_string); 457 debug("Local version string %.200s", server_version_string); 458 459 if (mismatch) { 460 s = "Protocol major versions differ.\n"; 461 (void) atomicio(vwrite, sock_out, s, strlen(s)); 462 close(sock_in); 463 close(sock_out); 464 logit("Protocol major versions differ for %s: %.200s vs. %.200s", 465 get_remote_ipaddr(), 466 server_version_string, client_version_string); 467 fatal_cleanup(); 468 } 469 } 470 471 /* Destroy the host and server keys. They will no longer be needed. */ 472 void 473 destroy_sensitive_data(void) 474 { 475 int i; 476 477 if (sensitive_data.server_key) { 478 key_free(sensitive_data.server_key); 479 sensitive_data.server_key = NULL; 480 } 481 for (i = 0; i < options.num_host_key_files; i++) { 482 if (sensitive_data.host_keys[i]) { 483 key_free(sensitive_data.host_keys[i]); 484 sensitive_data.host_keys[i] = NULL; 485 } 486 } 487 sensitive_data.ssh1_host_key = NULL; 488 memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH); 489 } 490 491 /* Demote private to public keys for network child */ 492 void 493 demote_sensitive_data(void) 494 { 495 Key *tmp; 496 int i; 497 498 if (sensitive_data.server_key) { 499 tmp = key_demote(sensitive_data.server_key); 500 key_free(sensitive_data.server_key); 501 sensitive_data.server_key = tmp; 502 } 503 504 for (i = 0; i < options.num_host_key_files; i++) { 505 if (sensitive_data.host_keys[i]) { 506 tmp = key_demote(sensitive_data.host_keys[i]); 507 key_free(sensitive_data.host_keys[i]); 508 sensitive_data.host_keys[i] = tmp; 509 if (tmp->type == KEY_RSA1) 510 sensitive_data.ssh1_host_key = tmp; 511 } 512 } 513 514 /* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */ 515 } 516 517 static void 518 privsep_preauth_child(void) 519 { 520 u_int32_t rnd[256]; 521 gid_t gidset[1]; 522 struct passwd *pw; 523 int i; 524 525 /* Enable challenge-response authentication for privilege separation */ 526 privsep_challenge_enable(); 527 528 for (i = 0; i < 256; i++) 529 rnd[i] = arc4random(); 530 RAND_seed(rnd, sizeof(rnd)); 531 532 /* Demote the private keys to public keys. */ 533 demote_sensitive_data(); 534 535 if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) 536 fatal("Privilege separation user %s does not exist", 537 SSH_PRIVSEP_USER); 538 memset(pw->pw_passwd, 0, strlen(pw->pw_passwd)); 539 endpwent(); 540 541 /* Change our root directory */ 542 if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1) 543 fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR, 544 strerror(errno)); 545 if (chdir("/") == -1) 546 fatal("chdir(\"/\"): %s", strerror(errno)); 547 548 /* Drop our privileges */ 549 debug3("privsep user:group %u:%u", (u_int)pw->pw_uid, 550 (u_int)pw->pw_gid); 551 #if 0 552 /* XXX not ready, to heavy after chroot */ 553 do_setusercontext(pw); 554 #else 555 gidset[0] = pw->pw_gid; 556 if (setgroups(1, gidset) < 0) 557 fatal("setgroups: %.100s", strerror(errno)); 558 permanently_set_uid(pw); 559 #endif 560 } 561 562 static Authctxt * 563 privsep_preauth(void) 564 { 565 Authctxt *authctxt = NULL; 566 int status; 567 pid_t pid; 568 569 /* Set up unprivileged child process to deal with network data */ 570 pmonitor = monitor_init(); 571 /* Store a pointer to the kex for later rekeying */ 572 pmonitor->m_pkex = &xxx_kex; 573 574 pid = fork(); 575 if (pid == -1) { 576 fatal("fork of unprivileged child failed"); 577 } else if (pid != 0) { 578 fatal_remove_cleanup((void (*) (void *)) packet_close, NULL); 579 580 debug2("Network child is on pid %ld", (long)pid); 581 582 close(pmonitor->m_recvfd); 583 authctxt = monitor_child_preauth(pmonitor); 584 close(pmonitor->m_sendfd); 585 586 /* Sync memory */ 587 monitor_sync(pmonitor); 588 589 /* Wait for the child's exit status */ 590 while (waitpid(pid, &status, 0) < 0) 591 if (errno != EINTR) 592 break; 593 594 /* Reinstall, since the child has finished */ 595 fatal_add_cleanup((void (*) (void *)) packet_close, NULL); 596 597 return (authctxt); 598 } else { 599 /* child */ 600 601 close(pmonitor->m_sendfd); 602 603 /* Demote the child */ 604 if (getuid() == 0 || geteuid() == 0) 605 privsep_preauth_child(); 606 setproctitle("%s", "[net]"); 607 } 608 return (NULL); 609 } 610 611 static void 612 privsep_postauth(Authctxt *authctxt) 613 { 614 extern Authctxt *x_authctxt; 615 616 /* XXX - Remote port forwarding */ 617 x_authctxt = authctxt; 618 619 if (authctxt->pw->pw_uid == 0 || options.use_login) { 620 /* File descriptor passing is broken or root login */ 621 monitor_apply_keystate(pmonitor); 622 use_privsep = 0; 623 return; 624 } 625 626 /* Authentication complete */ 627 alarm(0); 628 if (startup_pipe != -1) { 629 close(startup_pipe); 630 startup_pipe = -1; 631 } 632 633 /* New socket pair */ 634 monitor_reinit(pmonitor); 635 636 pmonitor->m_pid = fork(); 637 if (pmonitor->m_pid == -1) 638 fatal("fork of unprivileged child failed"); 639 else if (pmonitor->m_pid != 0) { 640 fatal_remove_cleanup((void (*) (void *)) packet_close, NULL); 641 642 debug2("User child is on pid %ld", (long)pmonitor->m_pid); 643 close(pmonitor->m_recvfd); 644 monitor_child_postauth(pmonitor); 645 646 /* NEVERREACHED */ 647 exit(0); 648 } 649 650 close(pmonitor->m_sendfd); 651 652 /* Demote the private keys to public keys. */ 653 demote_sensitive_data(); 654 655 /* Drop privileges */ 656 do_setusercontext(authctxt->pw); 657 658 /* It is safe now to apply the key state */ 659 monitor_apply_keystate(pmonitor); 660 } 661 662 static char * 663 list_hostkey_types(void) 664 { 665 Buffer b; 666 char *p; 667 int i; 668 669 buffer_init(&b); 670 for (i = 0; i < options.num_host_key_files; i++) { 671 Key *key = sensitive_data.host_keys[i]; 672 if (key == NULL) 673 continue; 674 switch (key->type) { 675 case KEY_RSA: 676 case KEY_DSA: 677 if (buffer_len(&b) > 0) 678 buffer_append(&b, ",", 1); 679 p = key_ssh_name(key); 680 buffer_append(&b, p, strlen(p)); 681 break; 682 } 683 } 684 buffer_append(&b, "\0", 1); 685 p = xstrdup(buffer_ptr(&b)); 686 buffer_free(&b); 687 debug("list_hostkey_types: %s", p); 688 return p; 689 } 690 691 Key * 692 get_hostkey_by_type(int type) 693 { 694 int i; 695 696 for (i = 0; i < options.num_host_key_files; i++) { 697 Key *key = sensitive_data.host_keys[i]; 698 if (key != NULL && key->type == type) 699 return key; 700 } 701 return NULL; 702 } 703 704 Key * 705 get_hostkey_by_index(int ind) 706 { 707 if (ind < 0 || ind >= options.num_host_key_files) 708 return (NULL); 709 return (sensitive_data.host_keys[ind]); 710 } 711 712 int 713 get_hostkey_index(Key *key) 714 { 715 int i; 716 717 for (i = 0; i < options.num_host_key_files; i++) { 718 if (key == sensitive_data.host_keys[i]) 719 return (i); 720 } 721 return (-1); 722 } 723 724 /* 725 * returns 1 if connection should be dropped, 0 otherwise. 726 * dropping starts at connection #max_startups_begin with a probability 727 * of (max_startups_rate/100). the probability increases linearly until 728 * all connections are dropped for startups > max_startups 729 */ 730 static int 731 drop_connection(int startups) 732 { 733 double p, r; 734 735 if (startups < options.max_startups_begin) 736 return 0; 737 if (startups >= options.max_startups) 738 return 1; 739 if (options.max_startups_rate == 100) 740 return 1; 741 742 p = 100 - options.max_startups_rate; 743 p *= startups - options.max_startups_begin; 744 p /= (double) (options.max_startups - options.max_startups_begin); 745 p += options.max_startups_rate; 746 p /= 100.0; 747 r = arc4random() / (double) UINT_MAX; 748 749 debug("drop_connection: p %g, r %g", p, r); 750 return (r < p) ? 1 : 0; 751 } 752 753 static void 754 usage(void) 755 { 756 fprintf(stderr, "sshd version %s\n", SSH_VERSION); 757 fprintf(stderr, "Usage: %s [options]\n", __progname); 758 fprintf(stderr, "Options:\n"); 759 fprintf(stderr, " -f file Configuration file (default %s)\n", _PATH_SERVER_CONFIG_FILE); 760 fprintf(stderr, " -d Debugging mode (multiple -d means more debugging)\n"); 761 fprintf(stderr, " -i Started from inetd\n"); 762 fprintf(stderr, " -D Do not fork into daemon mode\n"); 763 fprintf(stderr, " -t Only test configuration file and keys\n"); 764 fprintf(stderr, " -q Quiet (no logging)\n"); 765 fprintf(stderr, " -p port Listen on the specified port (default: 22)\n"); 766 fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n"); 767 fprintf(stderr, " -g seconds Grace period for authentication (default: 600)\n"); 768 fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n"); 769 fprintf(stderr, " -h file File from which to read host key (default: %s)\n", 770 _PATH_HOST_KEY_FILE); 771 fprintf(stderr, " -u len Maximum hostname length for utmp recording\n"); 772 fprintf(stderr, " -4 Use IPv4 only\n"); 773 fprintf(stderr, " -6 Use IPv6 only\n"); 774 fprintf(stderr, " -o option Process the option as if it was read from a configuration file.\n"); 775 exit(1); 776 } 777 778 /* 779 * Main program for the daemon. 780 */ 781 int 782 main(int ac, char **av) 783 { 784 extern char *optarg; 785 extern int optind; 786 int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1; 787 pid_t pid; 788 socklen_t fromlen; 789 fd_set *fdset; 790 struct sockaddr_storage from; 791 const char *remote_ip; 792 int remote_port; 793 FILE *f; 794 struct addrinfo *ai; 795 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 796 int listen_sock, maxfd; 797 int startup_p[2]; 798 int startups = 0; 799 Authctxt *authctxt; 800 Key *key; 801 int ret, key_used = 0; 802 803 /* Save argv. */ 804 saved_argv = av; 805 806 /* Initialize configuration options to their default values. */ 807 initialize_server_options(&options); 808 809 /* Parse command-line arguments. */ 810 while ((opt = getopt(ac, av, "f:p:b:k:h:g:u:o:dDeiqtQ46")) != -1) { 811 switch (opt) { 812 case '4': 813 IPv4or6 = AF_INET; 814 break; 815 case '6': 816 IPv4or6 = AF_INET6; 817 break; 818 case 'f': 819 config_file_name = optarg; 820 break; 821 case 'd': 822 if (debug_flag == 0) { 823 debug_flag = 1; 824 options.log_level = SYSLOG_LEVEL_DEBUG1; 825 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) 826 options.log_level++; 827 break; 828 case 'D': 829 no_daemon_flag = 1; 830 break; 831 case 'e': 832 log_stderr = 1; 833 break; 834 case 'i': 835 inetd_flag = 1; 836 break; 837 case 'Q': 838 /* ignored */ 839 break; 840 case 'q': 841 options.log_level = SYSLOG_LEVEL_QUIET; 842 break; 843 case 'b': 844 options.server_key_bits = atoi(optarg); 845 break; 846 case 'p': 847 options.ports_from_cmdline = 1; 848 if (options.num_ports >= MAX_PORTS) { 849 fprintf(stderr, "too many ports.\n"); 850 exit(1); 851 } 852 options.ports[options.num_ports++] = a2port(optarg); 853 if (options.ports[options.num_ports-1] == 0) { 854 fprintf(stderr, "Bad port number.\n"); 855 exit(1); 856 } 857 break; 858 case 'g': 859 if ((options.login_grace_time = convtime(optarg)) == -1) { 860 fprintf(stderr, "Invalid login grace time.\n"); 861 exit(1); 862 } 863 break; 864 case 'k': 865 if ((options.key_regeneration_time = convtime(optarg)) == -1) { 866 fprintf(stderr, "Invalid key regeneration interval.\n"); 867 exit(1); 868 } 869 break; 870 case 'h': 871 if (options.num_host_key_files >= MAX_HOSTKEYS) { 872 fprintf(stderr, "too many host keys.\n"); 873 exit(1); 874 } 875 options.host_key_files[options.num_host_key_files++] = optarg; 876 break; 877 case 't': 878 test_flag = 1; 879 break; 880 case 'u': 881 utmp_len = atoi(optarg); 882 if (utmp_len > MAXHOSTNAMELEN) { 883 fprintf(stderr, "Invalid utmp length.\n"); 884 exit(1); 885 } 886 break; 887 case 'o': 888 if (process_server_config_line(&options, optarg, 889 "command-line", 0) != 0) 890 exit(1); 891 break; 892 case '?': 893 default: 894 usage(); 895 break; 896 } 897 } 898 SSLeay_add_all_algorithms(); 899 channel_set_af(IPv4or6); 900 901 /* 902 * Force logging to stderr until we have loaded the private host 903 * key (unless started from inetd) 904 */ 905 log_init(__progname, 906 options.log_level == SYSLOG_LEVEL_NOT_SET ? 907 SYSLOG_LEVEL_INFO : options.log_level, 908 options.log_facility == SYSLOG_FACILITY_NOT_SET ? 909 SYSLOG_FACILITY_AUTH : options.log_facility, 910 log_stderr || !inetd_flag); 911 912 /* Read server configuration options from the configuration file. */ 913 read_server_config(&options, config_file_name); 914 915 /* Fill in default values for those options not explicitly set. */ 916 fill_default_server_options(&options); 917 918 /* Check that there are no remaining arguments. */ 919 if (optind < ac) { 920 fprintf(stderr, "Extra argument %s.\n", av[optind]); 921 exit(1); 922 } 923 924 debug("sshd version %.100s", SSH_VERSION); 925 926 /* load private host keys */ 927 sensitive_data.host_keys = xmalloc(options.num_host_key_files * 928 sizeof(Key *)); 929 for (i = 0; i < options.num_host_key_files; i++) 930 sensitive_data.host_keys[i] = NULL; 931 sensitive_data.server_key = NULL; 932 sensitive_data.ssh1_host_key = NULL; 933 sensitive_data.have_ssh1_key = 0; 934 sensitive_data.have_ssh2_key = 0; 935 936 for (i = 0; i < options.num_host_key_files; i++) { 937 key = key_load_private(options.host_key_files[i], "", NULL); 938 sensitive_data.host_keys[i] = key; 939 if (key == NULL) { 940 error("Could not load host key: %s", 941 options.host_key_files[i]); 942 sensitive_data.host_keys[i] = NULL; 943 continue; 944 } 945 switch (key->type) { 946 case KEY_RSA1: 947 sensitive_data.ssh1_host_key = key; 948 sensitive_data.have_ssh1_key = 1; 949 break; 950 case KEY_RSA: 951 case KEY_DSA: 952 sensitive_data.have_ssh2_key = 1; 953 break; 954 } 955 debug("private host key: #%d type %d %s", i, key->type, 956 key_type(key)); 957 } 958 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) { 959 logit("Disabling protocol version 1. Could not load host key"); 960 options.protocol &= ~SSH_PROTO_1; 961 } 962 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) { 963 logit("Disabling protocol version 2. Could not load host key"); 964 options.protocol &= ~SSH_PROTO_2; 965 } 966 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) { 967 logit("sshd: no hostkeys available -- exiting."); 968 exit(1); 969 } 970 971 /* Check certain values for sanity. */ 972 if (options.protocol & SSH_PROTO_1) { 973 if (options.server_key_bits < 512 || 974 options.server_key_bits > 32768) { 975 fprintf(stderr, "Bad server key size.\n"); 976 exit(1); 977 } 978 /* 979 * Check that server and host key lengths differ sufficiently. This 980 * is necessary to make double encryption work with rsaref. Oh, I 981 * hate software patents. I dont know if this can go? Niels 982 */ 983 if (options.server_key_bits > 984 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - 985 SSH_KEY_BITS_RESERVED && options.server_key_bits < 986 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + 987 SSH_KEY_BITS_RESERVED) { 988 options.server_key_bits = 989 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + 990 SSH_KEY_BITS_RESERVED; 991 debug("Forcing server key to %d bits to make it differ from host key.", 992 options.server_key_bits); 993 } 994 } 995 996 if (use_privsep) { 997 struct passwd *pw; 998 struct stat st; 999 1000 if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) 1001 fatal("Privilege separation user %s does not exist", 1002 SSH_PRIVSEP_USER); 1003 if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) || 1004 (S_ISDIR(st.st_mode) == 0)) 1005 fatal("Missing privilege separation directory: %s", 1006 _PATH_PRIVSEP_CHROOT_DIR); 1007 if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0) 1008 fatal("%s must be owned by root and not group or " 1009 "world-writable.", _PATH_PRIVSEP_CHROOT_DIR); 1010 } 1011 1012 /* Configuration looks good, so exit if in test mode. */ 1013 if (test_flag) 1014 exit(0); 1015 1016 /* Initialize the log (it is reinitialized below in case we forked). */ 1017 if (debug_flag && !inetd_flag) 1018 log_stderr = 1; 1019 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1020 1021 /* 1022 * If not in debugging mode, and not started from inetd, disconnect 1023 * from the controlling terminal, and fork. The original process 1024 * exits. 1025 */ 1026 if (!(debug_flag || inetd_flag || no_daemon_flag)) { 1027 #ifdef TIOCNOTTY 1028 int fd; 1029 #endif /* TIOCNOTTY */ 1030 if (daemon(0, 0) < 0) 1031 fatal("daemon() failed: %.200s", strerror(errno)); 1032 1033 /* Disconnect from the controlling tty. */ 1034 #ifdef TIOCNOTTY 1035 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 1036 if (fd >= 0) { 1037 (void) ioctl(fd, TIOCNOTTY, NULL); 1038 close(fd); 1039 } 1040 #endif /* TIOCNOTTY */ 1041 } 1042 /* Reinitialize the log (because of the fork above). */ 1043 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1044 1045 /* Initialize the random number generator. */ 1046 arc4random_stir(); 1047 1048 /* Chdir to the root directory so that the current disk can be 1049 unmounted if desired. */ 1050 chdir("/"); 1051 1052 /* ignore SIGPIPE */ 1053 signal(SIGPIPE, SIG_IGN); 1054 1055 /* Start listening for a socket, unless started from inetd. */ 1056 if (inetd_flag) { 1057 int s1; 1058 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */ 1059 dup(s1); 1060 sock_in = dup(0); 1061 sock_out = dup(1); 1062 startup_pipe = -1; 1063 /* 1064 * We intentionally do not close the descriptors 0, 1, and 2 1065 * as our code for setting the descriptors won\'t work if 1066 * ttyfd happens to be one of those. 1067 */ 1068 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out); 1069 if (options.protocol & SSH_PROTO_1) 1070 generate_ephemeral_server_key(); 1071 } else { 1072 for (ai = options.listen_addrs; ai; ai = ai->ai_next) { 1073 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 1074 continue; 1075 if (num_listen_socks >= MAX_LISTEN_SOCKS) 1076 fatal("Too many listen sockets. " 1077 "Enlarge MAX_LISTEN_SOCKS"); 1078 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 1079 ntop, sizeof(ntop), strport, sizeof(strport), 1080 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 1081 error("getnameinfo failed"); 1082 continue; 1083 } 1084 /* Create socket for listening. */ 1085 listen_sock = socket(ai->ai_family, ai->ai_socktype, 1086 ai->ai_protocol); 1087 if (listen_sock < 0) { 1088 /* kernel may not support ipv6 */ 1089 verbose("socket: %.100s", strerror(errno)); 1090 continue; 1091 } 1092 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) { 1093 error("listen_sock O_NONBLOCK: %s", strerror(errno)); 1094 close(listen_sock); 1095 continue; 1096 } 1097 /* 1098 * Set socket options. 1099 * Allow local port reuse in TIME_WAIT. 1100 */ 1101 if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR, 1102 &on, sizeof(on)) == -1) 1103 error("setsockopt SO_REUSEADDR: %s", strerror(errno)); 1104 1105 debug("Bind to port %s on %s.", strport, ntop); 1106 1107 /* Bind the socket to the desired port. */ 1108 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) { 1109 error("Bind to port %s on %s failed: %.200s.", 1110 strport, ntop, strerror(errno)); 1111 close(listen_sock); 1112 continue; 1113 } 1114 listen_socks[num_listen_socks] = listen_sock; 1115 num_listen_socks++; 1116 1117 /* Start listening on the port. */ 1118 logit("Server listening on %s port %s.", ntop, strport); 1119 if (listen(listen_sock, 5) < 0) 1120 fatal("listen: %.100s", strerror(errno)); 1121 1122 } 1123 freeaddrinfo(options.listen_addrs); 1124 1125 if (!num_listen_socks) 1126 fatal("Cannot bind any address."); 1127 1128 if (options.protocol & SSH_PROTO_1) 1129 generate_ephemeral_server_key(); 1130 1131 /* 1132 * Arrange to restart on SIGHUP. The handler needs 1133 * listen_sock. 1134 */ 1135 signal(SIGHUP, sighup_handler); 1136 1137 signal(SIGTERM, sigterm_handler); 1138 signal(SIGQUIT, sigterm_handler); 1139 1140 /* Arrange SIGCHLD to be caught. */ 1141 signal(SIGCHLD, main_sigchld_handler); 1142 1143 /* Write out the pid file after the sigterm handler is setup */ 1144 if (!debug_flag) { 1145 /* 1146 * Record our pid in /var/run/sshd.pid to make it 1147 * easier to kill the correct sshd. We don't want to 1148 * do this before the bind above because the bind will 1149 * fail if there already is a daemon, and this will 1150 * overwrite any old pid in the file. 1151 */ 1152 f = fopen(options.pid_file, "w"); 1153 if (f == NULL) { 1154 error("Couldn't create pid file \"%s\": %s", 1155 options.pid_file, strerror(errno)); 1156 } else { 1157 fprintf(f, "%ld\n", (long) getpid()); 1158 fclose(f); 1159 } 1160 } 1161 1162 /* setup fd set for listen */ 1163 fdset = NULL; 1164 maxfd = 0; 1165 for (i = 0; i < num_listen_socks; i++) 1166 if (listen_socks[i] > maxfd) 1167 maxfd = listen_socks[i]; 1168 /* pipes connected to unauthenticated childs */ 1169 startup_pipes = xmalloc(options.max_startups * sizeof(int)); 1170 for (i = 0; i < options.max_startups; i++) 1171 startup_pipes[i] = -1; 1172 1173 /* 1174 * Stay listening for connections until the system crashes or 1175 * the daemon is killed with a signal. 1176 */ 1177 for (;;) { 1178 if (received_sighup) 1179 sighup_restart(); 1180 if (fdset != NULL) 1181 xfree(fdset); 1182 fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask); 1183 fdset = (fd_set *)xmalloc(fdsetsz); 1184 memset(fdset, 0, fdsetsz); 1185 1186 for (i = 0; i < num_listen_socks; i++) 1187 FD_SET(listen_socks[i], fdset); 1188 for (i = 0; i < options.max_startups; i++) 1189 if (startup_pipes[i] != -1) 1190 FD_SET(startup_pipes[i], fdset); 1191 1192 /* Wait in select until there is a connection. */ 1193 ret = select(maxfd+1, fdset, NULL, NULL, NULL); 1194 if (ret < 0 && errno != EINTR) 1195 error("select: %.100s", strerror(errno)); 1196 if (received_sigterm) { 1197 logit("Received signal %d; terminating.", 1198 (int) received_sigterm); 1199 close_listen_socks(); 1200 unlink(options.pid_file); 1201 exit(255); 1202 } 1203 if (key_used && key_do_regen) { 1204 generate_ephemeral_server_key(); 1205 key_used = 0; 1206 key_do_regen = 0; 1207 } 1208 if (ret < 0) 1209 continue; 1210 1211 for (i = 0; i < options.max_startups; i++) 1212 if (startup_pipes[i] != -1 && 1213 FD_ISSET(startup_pipes[i], fdset)) { 1214 /* 1215 * the read end of the pipe is ready 1216 * if the child has closed the pipe 1217 * after successful authentication 1218 * or if the child has died 1219 */ 1220 close(startup_pipes[i]); 1221 startup_pipes[i] = -1; 1222 startups--; 1223 } 1224 for (i = 0; i < num_listen_socks; i++) { 1225 if (!FD_ISSET(listen_socks[i], fdset)) 1226 continue; 1227 fromlen = sizeof(from); 1228 newsock = accept(listen_socks[i], (struct sockaddr *)&from, 1229 &fromlen); 1230 if (newsock < 0) { 1231 if (errno != EINTR && errno != EWOULDBLOCK) 1232 error("accept: %.100s", strerror(errno)); 1233 continue; 1234 } 1235 if (fcntl(newsock, F_SETFL, 0) < 0) { 1236 error("newsock del O_NONBLOCK: %s", strerror(errno)); 1237 close(newsock); 1238 continue; 1239 } 1240 if (drop_connection(startups) == 1) { 1241 debug("drop connection #%d", startups); 1242 close(newsock); 1243 continue; 1244 } 1245 if (pipe(startup_p) == -1) { 1246 close(newsock); 1247 continue; 1248 } 1249 1250 for (j = 0; j < options.max_startups; j++) 1251 if (startup_pipes[j] == -1) { 1252 startup_pipes[j] = startup_p[0]; 1253 if (maxfd < startup_p[0]) 1254 maxfd = startup_p[0]; 1255 startups++; 1256 break; 1257 } 1258 1259 /* 1260 * Got connection. Fork a child to handle it, unless 1261 * we are in debugging mode. 1262 */ 1263 if (debug_flag) { 1264 /* 1265 * In debugging mode. Close the listening 1266 * socket, and start processing the 1267 * connection without forking. 1268 */ 1269 debug("Server will not fork when running in debugging mode."); 1270 close_listen_socks(); 1271 sock_in = newsock; 1272 sock_out = newsock; 1273 startup_pipe = -1; 1274 pid = getpid(); 1275 break; 1276 } else { 1277 /* 1278 * Normal production daemon. Fork, and have 1279 * the child process the connection. The 1280 * parent continues listening. 1281 */ 1282 if ((pid = fork()) == 0) { 1283 /* 1284 * Child. Close the listening and max_startup 1285 * sockets. Start using the accepted socket. 1286 * Reinitialize logging (since our pid has 1287 * changed). We break out of the loop to handle 1288 * the connection. 1289 */ 1290 startup_pipe = startup_p[1]; 1291 close_startup_pipes(); 1292 close_listen_socks(); 1293 sock_in = newsock; 1294 sock_out = newsock; 1295 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1296 break; 1297 } 1298 } 1299 1300 /* Parent. Stay in the loop. */ 1301 if (pid < 0) 1302 error("fork: %.100s", strerror(errno)); 1303 else 1304 debug("Forked child %ld.", (long)pid); 1305 1306 close(startup_p[1]); 1307 1308 /* Mark that the key has been used (it was "given" to the child). */ 1309 if ((options.protocol & SSH_PROTO_1) && 1310 key_used == 0) { 1311 /* Schedule server key regeneration alarm. */ 1312 signal(SIGALRM, key_regeneration_alarm); 1313 alarm(options.key_regeneration_time); 1314 key_used = 1; 1315 } 1316 1317 arc4random_stir(); 1318 1319 /* Close the new socket (the child is now taking care of it). */ 1320 close(newsock); 1321 } 1322 /* child process check (or debug mode) */ 1323 if (num_listen_socks < 0) 1324 break; 1325 } 1326 } 1327 1328 /* This is the child processing a new connection. */ 1329 1330 /* 1331 * Create a new session and process group since the 4.4BSD 1332 * setlogin() affects the entire process group. We don't 1333 * want the child to be able to affect the parent. 1334 */ 1335 if (!debug_flag && !inetd_flag && setsid() < 0) 1336 error("setsid: %.100s", strerror(errno)); 1337 1338 /* 1339 * Disable the key regeneration alarm. We will not regenerate the 1340 * key since we are no longer in a position to give it to anyone. We 1341 * will not restart on SIGHUP since it no longer makes sense. 1342 */ 1343 alarm(0); 1344 signal(SIGALRM, SIG_DFL); 1345 signal(SIGHUP, SIG_DFL); 1346 signal(SIGTERM, SIG_DFL); 1347 signal(SIGQUIT, SIG_DFL); 1348 signal(SIGCHLD, SIG_DFL); 1349 1350 /* Set keepalives if requested. */ 1351 if (options.keepalives && 1352 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, 1353 sizeof(on)) < 0) 1354 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 1355 1356 /* 1357 * Register our connection. This turns encryption off because we do 1358 * not have a key. 1359 */ 1360 packet_set_connection(sock_in, sock_out); 1361 1362 remote_port = get_remote_port(); 1363 remote_ip = get_remote_ipaddr(); 1364 1365 #ifdef LIBWRAP 1366 /* Check whether logins are denied from this host. */ 1367 { 1368 struct request_info req; 1369 1370 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0); 1371 fromhost(&req); 1372 1373 if (!hosts_access(&req)) { 1374 debug("Connection refused by tcp wrapper"); 1375 refuse(&req); 1376 /* NOTREACHED */ 1377 fatal("libwrap refuse returns"); 1378 } 1379 } 1380 #endif /* LIBWRAP */ 1381 1382 /* Log the connection. */ 1383 verbose("Connection from %.500s port %d", remote_ip, remote_port); 1384 1385 /* 1386 * We don\'t want to listen forever unless the other side 1387 * successfully authenticates itself. So we set up an alarm which is 1388 * cleared after successful authentication. A limit of zero 1389 * indicates no limit. Note that we don\'t set the alarm in debugging 1390 * mode; it is just annoying to have the server exit just when you 1391 * are about to discover the bug. 1392 */ 1393 signal(SIGALRM, grace_alarm_handler); 1394 if (!debug_flag) 1395 alarm(options.login_grace_time); 1396 1397 sshd_exchange_identification(sock_in, sock_out); 1398 1399 packet_set_nonblocking(); 1400 1401 if (use_privsep) 1402 if ((authctxt = privsep_preauth()) != NULL) 1403 goto authenticated; 1404 1405 /* perform the key exchange */ 1406 /* authenticate user and start session */ 1407 if (compat20) { 1408 do_ssh2_kex(); 1409 authctxt = do_authentication2(); 1410 } else { 1411 do_ssh1_kex(); 1412 authctxt = do_authentication(); 1413 } 1414 /* 1415 * If we use privilege separation, the unprivileged child transfers 1416 * the current keystate and exits 1417 */ 1418 if (use_privsep) { 1419 mm_send_keystate(pmonitor); 1420 exit(0); 1421 } 1422 1423 authenticated: 1424 /* 1425 * In privilege separation, we fork another child and prepare 1426 * file descriptor passing. 1427 */ 1428 if (use_privsep) { 1429 privsep_postauth(authctxt); 1430 /* the monitor process [priv] will not return */ 1431 if (!compat20) 1432 destroy_sensitive_data(); 1433 } 1434 1435 /* Perform session preparation. */ 1436 do_authenticated(authctxt); 1437 1438 /* The connection has been terminated. */ 1439 verbose("Closing connection to %.100s", remote_ip); 1440 packet_close(); 1441 1442 if (use_privsep) 1443 mm_terminate(); 1444 1445 exit(0); 1446 } 1447 1448 /* 1449 * Decrypt session_key_int using our private server key and private host key 1450 * (key with larger modulus first). 1451 */ 1452 int 1453 ssh1_session_key(BIGNUM *session_key_int) 1454 { 1455 int rsafail = 0; 1456 1457 if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) { 1458 /* Server key has bigger modulus. */ 1459 if (BN_num_bits(sensitive_data.server_key->rsa->n) < 1460 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) { 1461 fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d", 1462 get_remote_ipaddr(), 1463 BN_num_bits(sensitive_data.server_key->rsa->n), 1464 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n), 1465 SSH_KEY_BITS_RESERVED); 1466 } 1467 if (rsa_private_decrypt(session_key_int, session_key_int, 1468 sensitive_data.server_key->rsa) <= 0) 1469 rsafail++; 1470 if (rsa_private_decrypt(session_key_int, session_key_int, 1471 sensitive_data.ssh1_host_key->rsa) <= 0) 1472 rsafail++; 1473 } else { 1474 /* Host key has bigger modulus (or they are equal). */ 1475 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) < 1476 BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) { 1477 fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d", 1478 get_remote_ipaddr(), 1479 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n), 1480 BN_num_bits(sensitive_data.server_key->rsa->n), 1481 SSH_KEY_BITS_RESERVED); 1482 } 1483 if (rsa_private_decrypt(session_key_int, session_key_int, 1484 sensitive_data.ssh1_host_key->rsa) < 0) 1485 rsafail++; 1486 if (rsa_private_decrypt(session_key_int, session_key_int, 1487 sensitive_data.server_key->rsa) < 0) 1488 rsafail++; 1489 } 1490 return (rsafail); 1491 } 1492 /* 1493 * SSH1 key exchange 1494 */ 1495 static void 1496 do_ssh1_kex(void) 1497 { 1498 int i, len; 1499 int rsafail = 0; 1500 BIGNUM *session_key_int; 1501 u_char session_key[SSH_SESSION_KEY_LENGTH]; 1502 u_char cookie[8]; 1503 u_int cipher_type, auth_mask, protocol_flags; 1504 u_int32_t rnd = 0; 1505 1506 /* 1507 * Generate check bytes that the client must send back in the user 1508 * packet in order for it to be accepted; this is used to defy ip 1509 * spoofing attacks. Note that this only works against somebody 1510 * doing IP spoofing from a remote machine; any machine on the local 1511 * network can still see outgoing packets and catch the random 1512 * cookie. This only affects rhosts authentication, and this is one 1513 * of the reasons why it is inherently insecure. 1514 */ 1515 for (i = 0; i < 8; i++) { 1516 if (i % 4 == 0) 1517 rnd = arc4random(); 1518 cookie[i] = rnd & 0xff; 1519 rnd >>= 8; 1520 } 1521 1522 /* 1523 * Send our public key. We include in the packet 64 bits of random 1524 * data that must be matched in the reply in order to prevent IP 1525 * spoofing. 1526 */ 1527 packet_start(SSH_SMSG_PUBLIC_KEY); 1528 for (i = 0; i < 8; i++) 1529 packet_put_char(cookie[i]); 1530 1531 /* Store our public server RSA key. */ 1532 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n)); 1533 packet_put_bignum(sensitive_data.server_key->rsa->e); 1534 packet_put_bignum(sensitive_data.server_key->rsa->n); 1535 1536 /* Store our public host RSA key. */ 1537 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n)); 1538 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e); 1539 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n); 1540 1541 /* Put protocol flags. */ 1542 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN); 1543 1544 /* Declare which ciphers we support. */ 1545 packet_put_int(cipher_mask_ssh1(0)); 1546 1547 /* Declare supported authentication types. */ 1548 auth_mask = 0; 1549 if (options.rhosts_rsa_authentication) 1550 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA; 1551 if (options.rsa_authentication) 1552 auth_mask |= 1 << SSH_AUTH_RSA; 1553 if (options.challenge_response_authentication == 1) 1554 auth_mask |= 1 << SSH_AUTH_TIS; 1555 if (options.password_authentication) 1556 auth_mask |= 1 << SSH_AUTH_PASSWORD; 1557 packet_put_int(auth_mask); 1558 1559 /* Send the packet and wait for it to be sent. */ 1560 packet_send(); 1561 packet_write_wait(); 1562 1563 debug("Sent %d bit server key and %d bit host key.", 1564 BN_num_bits(sensitive_data.server_key->rsa->n), 1565 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n)); 1566 1567 /* Read clients reply (cipher type and session key). */ 1568 packet_read_expect(SSH_CMSG_SESSION_KEY); 1569 1570 /* Get cipher type and check whether we accept this. */ 1571 cipher_type = packet_get_char(); 1572 1573 if (!(cipher_mask_ssh1(0) & (1 << cipher_type))) 1574 packet_disconnect("Warning: client selects unsupported cipher."); 1575 1576 /* Get check bytes from the packet. These must match those we 1577 sent earlier with the public key packet. */ 1578 for (i = 0; i < 8; i++) 1579 if (cookie[i] != packet_get_char()) 1580 packet_disconnect("IP Spoofing check bytes do not match."); 1581 1582 debug("Encryption type: %.200s", cipher_name(cipher_type)); 1583 1584 /* Get the encrypted integer. */ 1585 if ((session_key_int = BN_new()) == NULL) 1586 fatal("do_ssh1_kex: BN_new failed"); 1587 packet_get_bignum(session_key_int); 1588 1589 protocol_flags = packet_get_int(); 1590 packet_set_protocol_flags(protocol_flags); 1591 packet_check_eom(); 1592 1593 /* Decrypt session_key_int using host/server keys */ 1594 rsafail = PRIVSEP(ssh1_session_key(session_key_int)); 1595 1596 /* 1597 * Extract session key from the decrypted integer. The key is in the 1598 * least significant 256 bits of the integer; the first byte of the 1599 * key is in the highest bits. 1600 */ 1601 if (!rsafail) { 1602 BN_mask_bits(session_key_int, sizeof(session_key) * 8); 1603 len = BN_num_bytes(session_key_int); 1604 if (len < 0 || len > sizeof(session_key)) { 1605 error("do_connection: bad session key len from %s: " 1606 "session_key_int %d > sizeof(session_key) %lu", 1607 get_remote_ipaddr(), len, (u_long)sizeof(session_key)); 1608 rsafail++; 1609 } else { 1610 memset(session_key, 0, sizeof(session_key)); 1611 BN_bn2bin(session_key_int, 1612 session_key + sizeof(session_key) - len); 1613 1614 compute_session_id(session_id, cookie, 1615 sensitive_data.ssh1_host_key->rsa->n, 1616 sensitive_data.server_key->rsa->n); 1617 /* 1618 * Xor the first 16 bytes of the session key with the 1619 * session id. 1620 */ 1621 for (i = 0; i < 16; i++) 1622 session_key[i] ^= session_id[i]; 1623 } 1624 } 1625 if (rsafail) { 1626 int bytes = BN_num_bytes(session_key_int); 1627 u_char *buf = xmalloc(bytes); 1628 MD5_CTX md; 1629 1630 logit("do_connection: generating a fake encryption key"); 1631 BN_bn2bin(session_key_int, buf); 1632 MD5_Init(&md); 1633 MD5_Update(&md, buf, bytes); 1634 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); 1635 MD5_Final(session_key, &md); 1636 MD5_Init(&md); 1637 MD5_Update(&md, session_key, 16); 1638 MD5_Update(&md, buf, bytes); 1639 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); 1640 MD5_Final(session_key + 16, &md); 1641 memset(buf, 0, bytes); 1642 xfree(buf); 1643 for (i = 0; i < 16; i++) 1644 session_id[i] = session_key[i] ^ session_key[i + 16]; 1645 } 1646 /* Destroy the private and public keys. No longer. */ 1647 destroy_sensitive_data(); 1648 1649 if (use_privsep) 1650 mm_ssh1_session_id(session_id); 1651 1652 /* Destroy the decrypted integer. It is no longer needed. */ 1653 BN_clear_free(session_key_int); 1654 1655 /* Set the session key. From this on all communications will be encrypted. */ 1656 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type); 1657 1658 /* Destroy our copy of the session key. It is no longer needed. */ 1659 memset(session_key, 0, sizeof(session_key)); 1660 1661 debug("Received session key; encryption turned on."); 1662 1663 /* Send an acknowledgment packet. Note that this packet is sent encrypted. */ 1664 packet_start(SSH_SMSG_SUCCESS); 1665 packet_send(); 1666 packet_write_wait(); 1667 } 1668 1669 /* 1670 * SSH2 key exchange: diffie-hellman-group1-sha1 1671 */ 1672 static void 1673 do_ssh2_kex(void) 1674 { 1675 Kex *kex; 1676 1677 if (options.ciphers != NULL) { 1678 myproposal[PROPOSAL_ENC_ALGS_CTOS] = 1679 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers; 1680 } 1681 myproposal[PROPOSAL_ENC_ALGS_CTOS] = 1682 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]); 1683 myproposal[PROPOSAL_ENC_ALGS_STOC] = 1684 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]); 1685 1686 if (options.macs != NULL) { 1687 myproposal[PROPOSAL_MAC_ALGS_CTOS] = 1688 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs; 1689 } 1690 if (!options.compression) { 1691 myproposal[PROPOSAL_COMP_ALGS_CTOS] = 1692 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none"; 1693 } 1694 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types(); 1695 1696 /* start key exchange */ 1697 kex = kex_setup(myproposal); 1698 kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server; 1699 kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 1700 kex->server = 1; 1701 kex->client_version_string=client_version_string; 1702 kex->server_version_string=server_version_string; 1703 kex->load_host_key=&get_hostkey_by_type; 1704 kex->host_key_index=&get_hostkey_index; 1705 1706 xxx_kex = kex; 1707 1708 dispatch_run(DISPATCH_BLOCK, &kex->done, kex); 1709 1710 session_id2 = kex->session_id; 1711 session_id2_len = kex->session_id_len; 1712 1713 #ifdef DEBUG_KEXDH 1714 /* send 1st encrypted/maced/compressed message */ 1715 packet_start(SSH2_MSG_IGNORE); 1716 packet_put_cstring("markus"); 1717 packet_send(); 1718 packet_write_wait(); 1719 #endif 1720 debug("KEX done"); 1721 } 1722