1 /* $OpenBSD: sshd.c,v 1.374 2010/03/07 11:57:13 dtucker Exp $ */ 2 /* 3 * Author: Tatu Ylonen <ylo@cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 5 * All rights reserved 6 * This program is the ssh daemon. It listens for connections from clients, 7 * and performs authentication, executes use commands or shell, and forwards 8 * information to/from the application to the user client over an encrypted 9 * connection. This can also handle forwarding of X11, TCP/IP, and 10 * authentication agent connections. 11 * 12 * As far as I am concerned, the code I have written for this software 13 * can be used freely for any purpose. Any derived versions of this 14 * software must be clearly marked as such, and if the derived work is 15 * incompatible with the protocol description in the RFC file, it must be 16 * called by a name other than "ssh" or "Secure Shell". 17 * 18 * SSH2 implementation: 19 * Privilege Separation: 20 * 21 * Copyright (c) 2000, 2001, 2002 Markus Friedl. All rights reserved. 22 * Copyright (c) 2002 Niels Provos. All rights reserved. 23 * 24 * Redistribution and use in source and binary forms, with or without 25 * modification, are permitted provided that the following conditions 26 * are met: 27 * 1. Redistributions of source code must retain the above copyright 28 * notice, this list of conditions and the following disclaimer. 29 * 2. Redistributions in binary form must reproduce the above copyright 30 * notice, this list of conditions and the following disclaimer in the 31 * documentation and/or other materials provided with the distribution. 32 * 33 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 34 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 35 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 36 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 37 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 38 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 39 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 40 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 41 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 42 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 43 */ 44 45 #include "includes.h" 46 __RCSID("$FreeBSD$"); 47 48 #include <sys/types.h> 49 #include <sys/ioctl.h> 50 #include <sys/mman.h> 51 #include <sys/socket.h> 52 #ifdef HAVE_SYS_STAT_H 53 # include <sys/stat.h> 54 #endif 55 #ifdef HAVE_SYS_TIME_H 56 # include <sys/time.h> 57 #endif 58 #include "openbsd-compat/sys-tree.h" 59 #include "openbsd-compat/sys-queue.h" 60 #include <sys/wait.h> 61 62 #include <errno.h> 63 #include <fcntl.h> 64 #include <netdb.h> 65 #ifdef HAVE_PATHS_H 66 #include <paths.h> 67 #endif 68 #include <grp.h> 69 #include <pwd.h> 70 #include <signal.h> 71 #include <stdarg.h> 72 #include <stdio.h> 73 #include <stdlib.h> 74 #include <string.h> 75 #include <unistd.h> 76 77 #include <openssl/dh.h> 78 #include <openssl/bn.h> 79 #include <openssl/md5.h> 80 #include <openssl/rand.h> 81 #include "openbsd-compat/openssl-compat.h" 82 83 #ifdef HAVE_SECUREWARE 84 #include <sys/security.h> 85 #include <prot.h> 86 #endif 87 88 #ifdef __FreeBSD__ 89 #include <resolv.h> 90 #if defined(GSSAPI) && defined(HAVE_GSSAPI_H) 91 #include <gssapi.h> 92 #elif defined(GSSAPI) && defined(HAVE_GSSAPI_GSSAPI_H) 93 #include <gssapi/gssapi.h> 94 #endif 95 #endif 96 97 #include "xmalloc.h" 98 #include "ssh.h" 99 #include "ssh1.h" 100 #include "ssh2.h" 101 #include "rsa.h" 102 #include "sshpty.h" 103 #include "packet.h" 104 #include "log.h" 105 #include "buffer.h" 106 #include "servconf.h" 107 #include "uidswap.h" 108 #include "compat.h" 109 #include "cipher.h" 110 #include "key.h" 111 #include "kex.h" 112 #include "dh.h" 113 #include "myproposal.h" 114 #include "authfile.h" 115 #include "pathnames.h" 116 #include "atomicio.h" 117 #include "canohost.h" 118 #include "hostfile.h" 119 #include "auth.h" 120 #include "misc.h" 121 #include "msg.h" 122 #include "dispatch.h" 123 #include "channels.h" 124 #include "session.h" 125 #include "monitor_mm.h" 126 #include "monitor.h" 127 #ifdef GSSAPI 128 #include "ssh-gss.h" 129 #endif 130 #include "monitor_wrap.h" 131 #include "roaming.h" 132 #include "version.h" 133 134 #ifdef LIBWRAP 135 #include <tcpd.h> 136 #include <syslog.h> 137 int allow_severity; 138 int deny_severity; 139 #endif /* LIBWRAP */ 140 141 #ifndef O_NOCTTY 142 #define O_NOCTTY 0 143 #endif 144 145 /* Re-exec fds */ 146 #define REEXEC_DEVCRYPTO_RESERVED_FD (STDERR_FILENO + 1) 147 #define REEXEC_STARTUP_PIPE_FD (STDERR_FILENO + 2) 148 #define REEXEC_CONFIG_PASS_FD (STDERR_FILENO + 3) 149 #define REEXEC_MIN_FREE_FD (STDERR_FILENO + 4) 150 151 extern char *__progname; 152 153 /* Server configuration options. */ 154 ServerOptions options; 155 156 /* Name of the server configuration file. */ 157 char *config_file_name = _PATH_SERVER_CONFIG_FILE; 158 159 /* 160 * Debug mode flag. This can be set on the command line. If debug 161 * mode is enabled, extra debugging output will be sent to the system 162 * log, the daemon will not go to background, and will exit after processing 163 * the first connection. 164 */ 165 int debug_flag = 0; 166 167 /* Flag indicating that the daemon should only test the configuration and keys. */ 168 int test_flag = 0; 169 170 /* Flag indicating that the daemon is being started from inetd. */ 171 int inetd_flag = 0; 172 173 /* Flag indicating that sshd should not detach and become a daemon. */ 174 int no_daemon_flag = 0; 175 176 /* debug goes to stderr unless inetd_flag is set */ 177 int log_stderr = 0; 178 179 /* Saved arguments to main(). */ 180 char **saved_argv; 181 int saved_argc; 182 183 /* re-exec */ 184 int rexeced_flag = 0; 185 int rexec_flag = 1; 186 int rexec_argc = 0; 187 char **rexec_argv; 188 189 /* 190 * The sockets that the server is listening; this is used in the SIGHUP 191 * signal handler. 192 */ 193 #define MAX_LISTEN_SOCKS 16 194 int listen_socks[MAX_LISTEN_SOCKS]; 195 int num_listen_socks = 0; 196 197 /* 198 * the client's version string, passed by sshd2 in compat mode. if != NULL, 199 * sshd will skip the version-number exchange 200 */ 201 char *client_version_string = NULL; 202 char *server_version_string = NULL; 203 204 /* for rekeying XXX fixme */ 205 Kex *xxx_kex; 206 207 /* 208 * Any really sensitive data in the application is contained in this 209 * structure. The idea is that this structure could be locked into memory so 210 * that the pages do not get written into swap. However, there are some 211 * problems. The private key contains BIGNUMs, and we do not (in principle) 212 * have access to the internals of them, and locking just the structure is 213 * not very useful. Currently, memory locking is not implemented. 214 */ 215 struct { 216 Key *server_key; /* ephemeral server key */ 217 Key *ssh1_host_key; /* ssh1 host key */ 218 Key **host_keys; /* all private host keys */ 219 Key **host_certificates; /* all public host certificates */ 220 int have_ssh1_key; 221 int have_ssh2_key; 222 u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH]; 223 } sensitive_data; 224 225 /* 226 * Flag indicating whether the RSA server key needs to be regenerated. 227 * Is set in the SIGALRM handler and cleared when the key is regenerated. 228 */ 229 static volatile sig_atomic_t key_do_regen = 0; 230 231 /* This is set to true when a signal is received. */ 232 static volatile sig_atomic_t received_sighup = 0; 233 static volatile sig_atomic_t received_sigterm = 0; 234 235 /* session identifier, used by RSA-auth */ 236 u_char session_id[16]; 237 238 /* same for ssh2 */ 239 u_char *session_id2 = NULL; 240 u_int session_id2_len = 0; 241 242 /* record remote hostname or ip */ 243 u_int utmp_len = MAXHOSTNAMELEN; 244 245 /* options.max_startup sized array of fd ints */ 246 int *startup_pipes = NULL; 247 int startup_pipe; /* in child */ 248 249 /* variables used for privilege separation */ 250 int use_privsep = -1; 251 struct monitor *pmonitor = NULL; 252 253 /* global authentication context */ 254 Authctxt *the_authctxt = NULL; 255 256 /* sshd_config buffer */ 257 Buffer cfg; 258 259 /* message to be displayed after login */ 260 Buffer loginmsg; 261 262 /* Unprivileged user */ 263 struct passwd *privsep_pw = NULL; 264 265 /* Prototypes for various functions defined later in this file. */ 266 void destroy_sensitive_data(void); 267 void demote_sensitive_data(void); 268 269 static void do_ssh1_kex(void); 270 static void do_ssh2_kex(void); 271 272 /* 273 * Close all listening sockets 274 */ 275 static void 276 close_listen_socks(void) 277 { 278 int i; 279 280 for (i = 0; i < num_listen_socks; i++) 281 close(listen_socks[i]); 282 num_listen_socks = -1; 283 } 284 285 static void 286 close_startup_pipes(void) 287 { 288 int i; 289 290 if (startup_pipes) 291 for (i = 0; i < options.max_startups; i++) 292 if (startup_pipes[i] != -1) 293 close(startup_pipes[i]); 294 } 295 296 /* 297 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP; 298 * the effect is to reread the configuration file (and to regenerate 299 * the server key). 300 */ 301 302 /*ARGSUSED*/ 303 static void 304 sighup_handler(int sig) 305 { 306 int save_errno = errno; 307 308 received_sighup = 1; 309 signal(SIGHUP, sighup_handler); 310 errno = save_errno; 311 } 312 313 /* 314 * Called from the main program after receiving SIGHUP. 315 * Restarts the server. 316 */ 317 static void 318 sighup_restart(void) 319 { 320 logit("Received SIGHUP; restarting."); 321 close_listen_socks(); 322 close_startup_pipes(); 323 alarm(0); /* alarm timer persists across exec */ 324 signal(SIGHUP, SIG_IGN); /* will be restored after exec */ 325 execv(saved_argv[0], saved_argv); 326 logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], 327 strerror(errno)); 328 exit(1); 329 } 330 331 /* 332 * Generic signal handler for terminating signals in the master daemon. 333 */ 334 /*ARGSUSED*/ 335 static void 336 sigterm_handler(int sig) 337 { 338 received_sigterm = sig; 339 } 340 341 /* 342 * SIGCHLD handler. This is called whenever a child dies. This will then 343 * reap any zombies left by exited children. 344 */ 345 /*ARGSUSED*/ 346 static void 347 main_sigchld_handler(int sig) 348 { 349 int save_errno = errno; 350 pid_t pid; 351 int status; 352 353 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 354 (pid < 0 && errno == EINTR)) 355 ; 356 357 signal(SIGCHLD, main_sigchld_handler); 358 errno = save_errno; 359 } 360 361 /* 362 * Signal handler for the alarm after the login grace period has expired. 363 */ 364 /*ARGSUSED*/ 365 static void 366 grace_alarm_handler(int sig) 367 { 368 if (use_privsep && pmonitor != NULL && pmonitor->m_pid > 0) 369 kill(pmonitor->m_pid, SIGALRM); 370 371 /* Log error and exit. */ 372 sigdie("Timeout before authentication for %s", get_remote_ipaddr()); 373 } 374 375 /* 376 * Signal handler for the key regeneration alarm. Note that this 377 * alarm only occurs in the daemon waiting for connections, and it does not 378 * do anything with the private key or random state before forking. 379 * Thus there should be no concurrency control/asynchronous execution 380 * problems. 381 */ 382 static void 383 generate_ephemeral_server_key(void) 384 { 385 verbose("Generating %s%d bit RSA key.", 386 sensitive_data.server_key ? "new " : "", options.server_key_bits); 387 if (sensitive_data.server_key != NULL) 388 key_free(sensitive_data.server_key); 389 sensitive_data.server_key = key_generate(KEY_RSA1, 390 options.server_key_bits); 391 verbose("RSA key generation complete."); 392 393 arc4random_buf(sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); 394 arc4random_stir(); 395 } 396 397 /*ARGSUSED*/ 398 static void 399 key_regeneration_alarm(int sig) 400 { 401 int save_errno = errno; 402 403 signal(SIGALRM, SIG_DFL); 404 errno = save_errno; 405 key_do_regen = 1; 406 } 407 408 static void 409 sshd_exchange_identification(int sock_in, int sock_out) 410 { 411 u_int i; 412 int mismatch; 413 int remote_major, remote_minor; 414 int major, minor; 415 char *s, *newline = "\n"; 416 char buf[256]; /* Must not be larger than remote_version. */ 417 char remote_version[256]; /* Must be at least as big as buf. */ 418 419 if ((options.protocol & SSH_PROTO_1) && 420 (options.protocol & SSH_PROTO_2)) { 421 major = PROTOCOL_MAJOR_1; 422 minor = 99; 423 } else if (options.protocol & SSH_PROTO_2) { 424 major = PROTOCOL_MAJOR_2; 425 minor = PROTOCOL_MINOR_2; 426 newline = "\r\n"; 427 } else { 428 major = PROTOCOL_MAJOR_1; 429 minor = PROTOCOL_MINOR_1; 430 } 431 snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s%s", major, minor, 432 SSH_VERSION, newline); 433 server_version_string = xstrdup(buf); 434 435 /* Send our protocol version identification. */ 436 if (roaming_atomicio(vwrite, sock_out, server_version_string, 437 strlen(server_version_string)) 438 != strlen(server_version_string)) { 439 logit("Could not write ident string to %s", get_remote_ipaddr()); 440 cleanup_exit(255); 441 } 442 443 /* Read other sides version identification. */ 444 memset(buf, 0, sizeof(buf)); 445 for (i = 0; i < sizeof(buf) - 1; i++) { 446 if (roaming_atomicio(read, sock_in, &buf[i], 1) != 1) { 447 logit("Did not receive identification string from %s", 448 get_remote_ipaddr()); 449 cleanup_exit(255); 450 } 451 if (buf[i] == '\r') { 452 buf[i] = 0; 453 /* Kludge for F-Secure Macintosh < 1.0.2 */ 454 if (i == 12 && 455 strncmp(buf, "SSH-1.5-W1.0", 12) == 0) 456 break; 457 continue; 458 } 459 if (buf[i] == '\n') { 460 buf[i] = 0; 461 break; 462 } 463 } 464 buf[sizeof(buf) - 1] = 0; 465 client_version_string = xstrdup(buf); 466 467 /* 468 * Check that the versions match. In future this might accept 469 * several versions and set appropriate flags to handle them. 470 */ 471 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n", 472 &remote_major, &remote_minor, remote_version) != 3) { 473 s = "Protocol mismatch.\n"; 474 (void) atomicio(vwrite, sock_out, s, strlen(s)); 475 close(sock_in); 476 close(sock_out); 477 logit("Bad protocol version identification '%.100s' from %s", 478 client_version_string, get_remote_ipaddr()); 479 cleanup_exit(255); 480 } 481 debug("Client protocol version %d.%d; client software version %.100s", 482 remote_major, remote_minor, remote_version); 483 484 compat_datafellows(remote_version); 485 486 if (datafellows & SSH_BUG_PROBE) { 487 logit("probed from %s with %s. Don't panic.", 488 get_remote_ipaddr(), client_version_string); 489 cleanup_exit(255); 490 } 491 492 if (datafellows & SSH_BUG_SCANNER) { 493 logit("scanned from %s with %s. Don't panic.", 494 get_remote_ipaddr(), client_version_string); 495 cleanup_exit(255); 496 } 497 498 mismatch = 0; 499 switch (remote_major) { 500 case 1: 501 if (remote_minor == 99) { 502 if (options.protocol & SSH_PROTO_2) 503 enable_compat20(); 504 else 505 mismatch = 1; 506 break; 507 } 508 if (!(options.protocol & SSH_PROTO_1)) { 509 mismatch = 1; 510 break; 511 } 512 if (remote_minor < 3) { 513 packet_disconnect("Your ssh version is too old and " 514 "is no longer supported. Please install a newer version."); 515 } else if (remote_minor == 3) { 516 /* note that this disables agent-forwarding */ 517 enable_compat13(); 518 } 519 break; 520 case 2: 521 if (options.protocol & SSH_PROTO_2) { 522 enable_compat20(); 523 break; 524 } 525 /* FALLTHROUGH */ 526 default: 527 mismatch = 1; 528 break; 529 } 530 chop(server_version_string); 531 debug("Local version string %.200s", server_version_string); 532 533 if (mismatch) { 534 s = "Protocol major versions differ.\n"; 535 (void) atomicio(vwrite, sock_out, s, strlen(s)); 536 close(sock_in); 537 close(sock_out); 538 logit("Protocol major versions differ for %s: %.200s vs. %.200s", 539 get_remote_ipaddr(), 540 server_version_string, client_version_string); 541 cleanup_exit(255); 542 } 543 } 544 545 /* Destroy the host and server keys. They will no longer be needed. */ 546 void 547 destroy_sensitive_data(void) 548 { 549 int i; 550 551 if (sensitive_data.server_key) { 552 key_free(sensitive_data.server_key); 553 sensitive_data.server_key = NULL; 554 } 555 for (i = 0; i < options.num_host_key_files; i++) { 556 if (sensitive_data.host_keys[i]) { 557 key_free(sensitive_data.host_keys[i]); 558 sensitive_data.host_keys[i] = NULL; 559 } 560 if (sensitive_data.host_certificates[i]) { 561 key_free(sensitive_data.host_certificates[i]); 562 sensitive_data.host_certificates[i] = NULL; 563 } 564 } 565 sensitive_data.ssh1_host_key = NULL; 566 memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH); 567 } 568 569 /* Demote private to public keys for network child */ 570 void 571 demote_sensitive_data(void) 572 { 573 Key *tmp; 574 int i; 575 576 if (sensitive_data.server_key) { 577 tmp = key_demote(sensitive_data.server_key); 578 key_free(sensitive_data.server_key); 579 sensitive_data.server_key = tmp; 580 } 581 582 for (i = 0; i < options.num_host_key_files; i++) { 583 if (sensitive_data.host_keys[i]) { 584 tmp = key_demote(sensitive_data.host_keys[i]); 585 key_free(sensitive_data.host_keys[i]); 586 sensitive_data.host_keys[i] = tmp; 587 if (tmp->type == KEY_RSA1) 588 sensitive_data.ssh1_host_key = tmp; 589 } 590 /* Certs do not need demotion */ 591 } 592 593 /* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */ 594 } 595 596 static void 597 privsep_preauth_child(void) 598 { 599 u_int32_t rnd[256]; 600 gid_t gidset[1]; 601 602 /* Enable challenge-response authentication for privilege separation */ 603 privsep_challenge_enable(); 604 605 arc4random_stir(); 606 arc4random_buf(rnd, sizeof(rnd)); 607 RAND_seed(rnd, sizeof(rnd)); 608 609 /* Demote the private keys to public keys. */ 610 demote_sensitive_data(); 611 612 /* Change our root directory */ 613 if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1) 614 fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR, 615 strerror(errno)); 616 if (chdir("/") == -1) 617 fatal("chdir(\"/\"): %s", strerror(errno)); 618 619 /* Drop our privileges */ 620 debug3("privsep user:group %u:%u", (u_int)privsep_pw->pw_uid, 621 (u_int)privsep_pw->pw_gid); 622 #if 0 623 /* XXX not ready, too heavy after chroot */ 624 do_setusercontext(privsep_pw); 625 #else 626 gidset[0] = privsep_pw->pw_gid; 627 if (setgroups(1, gidset) < 0) 628 fatal("setgroups: %.100s", strerror(errno)); 629 permanently_set_uid(privsep_pw); 630 #endif 631 } 632 633 static int 634 privsep_preauth(Authctxt *authctxt) 635 { 636 int status; 637 pid_t pid; 638 639 /* Set up unprivileged child process to deal with network data */ 640 pmonitor = monitor_init(); 641 /* Store a pointer to the kex for later rekeying */ 642 pmonitor->m_pkex = &xxx_kex; 643 644 pid = fork(); 645 if (pid == -1) { 646 fatal("fork of unprivileged child failed"); 647 } else if (pid != 0) { 648 debug2("Network child is on pid %ld", (long)pid); 649 650 close(pmonitor->m_recvfd); 651 pmonitor->m_pid = pid; 652 monitor_child_preauth(authctxt, pmonitor); 653 close(pmonitor->m_sendfd); 654 655 /* Sync memory */ 656 monitor_sync(pmonitor); 657 658 /* Wait for the child's exit status */ 659 while (waitpid(pid, &status, 0) < 0) 660 if (errno != EINTR) 661 break; 662 return (1); 663 } else { 664 /* child */ 665 666 close(pmonitor->m_sendfd); 667 668 /* Demote the child */ 669 if (getuid() == 0 || geteuid() == 0) 670 privsep_preauth_child(); 671 setproctitle("%s", "[net]"); 672 } 673 return (0); 674 } 675 676 static void 677 privsep_postauth(Authctxt *authctxt) 678 { 679 u_int32_t rnd[256]; 680 681 #ifdef DISABLE_FD_PASSING 682 if (1) { 683 #else 684 if (authctxt->pw->pw_uid == 0 || options.use_login) { 685 #endif 686 /* File descriptor passing is broken or root login */ 687 use_privsep = 0; 688 goto skip; 689 } 690 691 /* New socket pair */ 692 monitor_reinit(pmonitor); 693 694 pmonitor->m_pid = fork(); 695 if (pmonitor->m_pid == -1) 696 fatal("fork of unprivileged child failed"); 697 else if (pmonitor->m_pid != 0) { 698 verbose("User child is on pid %ld", (long)pmonitor->m_pid); 699 close(pmonitor->m_recvfd); 700 buffer_clear(&loginmsg); 701 monitor_child_postauth(pmonitor); 702 703 /* NEVERREACHED */ 704 exit(0); 705 } 706 707 close(pmonitor->m_sendfd); 708 709 /* Demote the private keys to public keys. */ 710 demote_sensitive_data(); 711 712 arc4random_stir(); 713 arc4random_buf(rnd, sizeof(rnd)); 714 RAND_seed(rnd, sizeof(rnd)); 715 716 /* Drop privileges */ 717 do_setusercontext(authctxt->pw); 718 719 skip: 720 /* It is safe now to apply the key state */ 721 monitor_apply_keystate(pmonitor); 722 723 /* 724 * Tell the packet layer that authentication was successful, since 725 * this information is not part of the key state. 726 */ 727 packet_set_authenticated(); 728 } 729 730 static char * 731 list_hostkey_types(void) 732 { 733 Buffer b; 734 const char *p; 735 char *ret; 736 int i; 737 Key *key; 738 739 buffer_init(&b); 740 for (i = 0; i < options.num_host_key_files; i++) { 741 key = sensitive_data.host_keys[i]; 742 if (key == NULL) 743 continue; 744 switch (key->type) { 745 case KEY_RSA: 746 case KEY_DSA: 747 if (buffer_len(&b) > 0) 748 buffer_append(&b, ",", 1); 749 p = key_ssh_name(key); 750 buffer_append(&b, p, strlen(p)); 751 break; 752 } 753 /* If the private key has a cert peer, then list that too */ 754 key = sensitive_data.host_certificates[i]; 755 if (key == NULL) 756 continue; 757 switch (key->type) { 758 case KEY_RSA_CERT: 759 case KEY_DSA_CERT: 760 if (buffer_len(&b) > 0) 761 buffer_append(&b, ",", 1); 762 p = key_ssh_name(key); 763 buffer_append(&b, p, strlen(p)); 764 break; 765 } 766 } 767 buffer_append(&b, "\0", 1); 768 ret = xstrdup(buffer_ptr(&b)); 769 buffer_free(&b); 770 debug("list_hostkey_types: %s", ret); 771 return ret; 772 } 773 774 static Key * 775 get_hostkey_by_type(int type, int need_private) 776 { 777 int i; 778 Key *key; 779 780 for (i = 0; i < options.num_host_key_files; i++) { 781 if (type == KEY_RSA_CERT || type == KEY_DSA_CERT) 782 key = sensitive_data.host_certificates[i]; 783 else 784 key = sensitive_data.host_keys[i]; 785 if (key != NULL && key->type == type) 786 return need_private ? 787 sensitive_data.host_keys[i] : key; 788 } 789 return NULL; 790 } 791 792 Key * 793 get_hostkey_public_by_type(int type) 794 { 795 return get_hostkey_by_type(type, 0); 796 } 797 798 Key * 799 get_hostkey_private_by_type(int type) 800 { 801 return get_hostkey_by_type(type, 1); 802 } 803 804 Key * 805 get_hostkey_by_index(int ind) 806 { 807 if (ind < 0 || ind >= options.num_host_key_files) 808 return (NULL); 809 return (sensitive_data.host_keys[ind]); 810 } 811 812 int 813 get_hostkey_index(Key *key) 814 { 815 int i; 816 817 for (i = 0; i < options.num_host_key_files; i++) { 818 if (key_is_cert(key)) { 819 if (key == sensitive_data.host_certificates[i]) 820 return (i); 821 } else { 822 if (key == sensitive_data.host_keys[i]) 823 return (i); 824 } 825 } 826 return (-1); 827 } 828 829 /* 830 * returns 1 if connection should be dropped, 0 otherwise. 831 * dropping starts at connection #max_startups_begin with a probability 832 * of (max_startups_rate/100). the probability increases linearly until 833 * all connections are dropped for startups > max_startups 834 */ 835 static int 836 drop_connection(int startups) 837 { 838 int p, r; 839 840 if (startups < options.max_startups_begin) 841 return 0; 842 if (startups >= options.max_startups) 843 return 1; 844 if (options.max_startups_rate == 100) 845 return 1; 846 847 p = 100 - options.max_startups_rate; 848 p *= startups - options.max_startups_begin; 849 p /= options.max_startups - options.max_startups_begin; 850 p += options.max_startups_rate; 851 r = arc4random_uniform(100); 852 853 debug("drop_connection: p %d, r %d", p, r); 854 return (r < p) ? 1 : 0; 855 } 856 857 static void 858 usage(void) 859 { 860 fprintf(stderr, "%s, %s\n", 861 SSH_RELEASE, SSLeay_version(SSLEAY_VERSION)); 862 fprintf(stderr, 863 "usage: sshd [-46DdeiqTt] [-b bits] [-C connection_spec] [-c host_cert_file]\n" 864 " [-f config_file] [-g login_grace_time] [-h host_key_file]\n" 865 " [-k key_gen_time] [-o option] [-p port] [-u len]\n" 866 ); 867 exit(1); 868 } 869 870 static void 871 send_rexec_state(int fd, Buffer *conf) 872 { 873 Buffer m; 874 875 debug3("%s: entering fd = %d config len %d", __func__, fd, 876 buffer_len(conf)); 877 878 /* 879 * Protocol from reexec master to child: 880 * string configuration 881 * u_int ephemeral_key_follows 882 * bignum e (only if ephemeral_key_follows == 1) 883 * bignum n " 884 * bignum d " 885 * bignum iqmp " 886 * bignum p " 887 * bignum q " 888 * string rngseed (only if OpenSSL is not self-seeded) 889 */ 890 buffer_init(&m); 891 buffer_put_cstring(&m, buffer_ptr(conf)); 892 893 if (sensitive_data.server_key != NULL && 894 sensitive_data.server_key->type == KEY_RSA1) { 895 buffer_put_int(&m, 1); 896 buffer_put_bignum(&m, sensitive_data.server_key->rsa->e); 897 buffer_put_bignum(&m, sensitive_data.server_key->rsa->n); 898 buffer_put_bignum(&m, sensitive_data.server_key->rsa->d); 899 buffer_put_bignum(&m, sensitive_data.server_key->rsa->iqmp); 900 buffer_put_bignum(&m, sensitive_data.server_key->rsa->p); 901 buffer_put_bignum(&m, sensitive_data.server_key->rsa->q); 902 } else 903 buffer_put_int(&m, 0); 904 905 #ifndef OPENSSL_PRNG_ONLY 906 rexec_send_rng_seed(&m); 907 #endif 908 909 if (ssh_msg_send(fd, 0, &m) == -1) 910 fatal("%s: ssh_msg_send failed", __func__); 911 912 buffer_free(&m); 913 914 debug3("%s: done", __func__); 915 } 916 917 static void 918 recv_rexec_state(int fd, Buffer *conf) 919 { 920 Buffer m; 921 char *cp; 922 u_int len; 923 924 debug3("%s: entering fd = %d", __func__, fd); 925 926 buffer_init(&m); 927 928 if (ssh_msg_recv(fd, &m) == -1) 929 fatal("%s: ssh_msg_recv failed", __func__); 930 if (buffer_get_char(&m) != 0) 931 fatal("%s: rexec version mismatch", __func__); 932 933 cp = buffer_get_string(&m, &len); 934 if (conf != NULL) 935 buffer_append(conf, cp, len + 1); 936 xfree(cp); 937 938 if (buffer_get_int(&m)) { 939 if (sensitive_data.server_key != NULL) 940 key_free(sensitive_data.server_key); 941 sensitive_data.server_key = key_new_private(KEY_RSA1); 942 buffer_get_bignum(&m, sensitive_data.server_key->rsa->e); 943 buffer_get_bignum(&m, sensitive_data.server_key->rsa->n); 944 buffer_get_bignum(&m, sensitive_data.server_key->rsa->d); 945 buffer_get_bignum(&m, sensitive_data.server_key->rsa->iqmp); 946 buffer_get_bignum(&m, sensitive_data.server_key->rsa->p); 947 buffer_get_bignum(&m, sensitive_data.server_key->rsa->q); 948 rsa_generate_additional_parameters( 949 sensitive_data.server_key->rsa); 950 } 951 952 #ifndef OPENSSL_PRNG_ONLY 953 rexec_recv_rng_seed(&m); 954 #endif 955 956 buffer_free(&m); 957 958 debug3("%s: done", __func__); 959 } 960 961 /* Accept a connection from inetd */ 962 static void 963 server_accept_inetd(int *sock_in, int *sock_out) 964 { 965 int fd; 966 967 startup_pipe = -1; 968 if (rexeced_flag) { 969 close(REEXEC_CONFIG_PASS_FD); 970 *sock_in = *sock_out = dup(STDIN_FILENO); 971 if (!debug_flag) { 972 startup_pipe = dup(REEXEC_STARTUP_PIPE_FD); 973 close(REEXEC_STARTUP_PIPE_FD); 974 } 975 } else { 976 *sock_in = dup(STDIN_FILENO); 977 *sock_out = dup(STDOUT_FILENO); 978 } 979 /* 980 * We intentionally do not close the descriptors 0, 1, and 2 981 * as our code for setting the descriptors won't work if 982 * ttyfd happens to be one of those. 983 */ 984 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) { 985 dup2(fd, STDIN_FILENO); 986 dup2(fd, STDOUT_FILENO); 987 if (fd > STDOUT_FILENO) 988 close(fd); 989 } 990 debug("inetd sockets after dupping: %d, %d", *sock_in, *sock_out); 991 } 992 993 /* 994 * Listen for TCP connections 995 */ 996 static void 997 server_listen(void) 998 { 999 int ret, listen_sock, on = 1; 1000 struct addrinfo *ai; 1001 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 1002 1003 for (ai = options.listen_addrs; ai; ai = ai->ai_next) { 1004 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 1005 continue; 1006 if (num_listen_socks >= MAX_LISTEN_SOCKS) 1007 fatal("Too many listen sockets. " 1008 "Enlarge MAX_LISTEN_SOCKS"); 1009 if ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen, 1010 ntop, sizeof(ntop), strport, sizeof(strport), 1011 NI_NUMERICHOST|NI_NUMERICSERV)) != 0) { 1012 error("getnameinfo failed: %.100s", 1013 ssh_gai_strerror(ret)); 1014 continue; 1015 } 1016 /* Create socket for listening. */ 1017 listen_sock = socket(ai->ai_family, ai->ai_socktype, 1018 ai->ai_protocol); 1019 if (listen_sock < 0) { 1020 /* kernel may not support ipv6 */ 1021 verbose("socket: %.100s", strerror(errno)); 1022 continue; 1023 } 1024 if (set_nonblock(listen_sock) == -1) { 1025 close(listen_sock); 1026 continue; 1027 } 1028 /* 1029 * Set socket options. 1030 * Allow local port reuse in TIME_WAIT. 1031 */ 1032 if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR, 1033 &on, sizeof(on)) == -1) 1034 error("setsockopt SO_REUSEADDR: %s", strerror(errno)); 1035 1036 /* Only communicate in IPv6 over AF_INET6 sockets. */ 1037 if (ai->ai_family == AF_INET6) 1038 sock_set_v6only(listen_sock); 1039 1040 debug("Bind to port %s on %s.", strport, ntop); 1041 1042 /* Bind the socket to the desired port. */ 1043 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) { 1044 error("Bind to port %s on %s failed: %.200s.", 1045 strport, ntop, strerror(errno)); 1046 close(listen_sock); 1047 continue; 1048 } 1049 listen_socks[num_listen_socks] = listen_sock; 1050 num_listen_socks++; 1051 1052 /* Start listening on the port. */ 1053 if (listen(listen_sock, SSH_LISTEN_BACKLOG) < 0) 1054 fatal("listen on [%s]:%s: %.100s", 1055 ntop, strport, strerror(errno)); 1056 logit("Server listening on %s port %s.", ntop, strport); 1057 } 1058 freeaddrinfo(options.listen_addrs); 1059 1060 if (!num_listen_socks) 1061 fatal("Cannot bind any address."); 1062 } 1063 1064 /* 1065 * The main TCP accept loop. Note that, for the non-debug case, returns 1066 * from this function are in a forked subprocess. 1067 */ 1068 static void 1069 server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s) 1070 { 1071 fd_set *fdset; 1072 int i, j, ret, maxfd; 1073 int key_used = 0, startups = 0; 1074 int startup_p[2] = { -1 , -1 }; 1075 struct sockaddr_storage from; 1076 socklen_t fromlen; 1077 pid_t pid; 1078 1079 /* setup fd set for accept */ 1080 fdset = NULL; 1081 maxfd = 0; 1082 for (i = 0; i < num_listen_socks; i++) 1083 if (listen_socks[i] > maxfd) 1084 maxfd = listen_socks[i]; 1085 /* pipes connected to unauthenticated childs */ 1086 startup_pipes = xcalloc(options.max_startups, sizeof(int)); 1087 for (i = 0; i < options.max_startups; i++) 1088 startup_pipes[i] = -1; 1089 1090 /* 1091 * Stay listening for connections until the system crashes or 1092 * the daemon is killed with a signal. 1093 */ 1094 for (;;) { 1095 if (received_sighup) 1096 sighup_restart(); 1097 if (fdset != NULL) 1098 xfree(fdset); 1099 fdset = (fd_set *)xcalloc(howmany(maxfd + 1, NFDBITS), 1100 sizeof(fd_mask)); 1101 1102 for (i = 0; i < num_listen_socks; i++) 1103 FD_SET(listen_socks[i], fdset); 1104 for (i = 0; i < options.max_startups; i++) 1105 if (startup_pipes[i] != -1) 1106 FD_SET(startup_pipes[i], fdset); 1107 1108 /* Wait in select until there is a connection. */ 1109 ret = select(maxfd+1, fdset, NULL, NULL, NULL); 1110 if (ret < 0 && errno != EINTR) 1111 error("select: %.100s", strerror(errno)); 1112 if (received_sigterm) { 1113 logit("Received signal %d; terminating.", 1114 (int) received_sigterm); 1115 close_listen_socks(); 1116 unlink(options.pid_file); 1117 exit(255); 1118 } 1119 if (key_used && key_do_regen) { 1120 generate_ephemeral_server_key(); 1121 key_used = 0; 1122 key_do_regen = 0; 1123 } 1124 if (ret < 0) 1125 continue; 1126 1127 for (i = 0; i < options.max_startups; i++) 1128 if (startup_pipes[i] != -1 && 1129 FD_ISSET(startup_pipes[i], fdset)) { 1130 /* 1131 * the read end of the pipe is ready 1132 * if the child has closed the pipe 1133 * after successful authentication 1134 * or if the child has died 1135 */ 1136 close(startup_pipes[i]); 1137 startup_pipes[i] = -1; 1138 startups--; 1139 } 1140 for (i = 0; i < num_listen_socks; i++) { 1141 if (!FD_ISSET(listen_socks[i], fdset)) 1142 continue; 1143 fromlen = sizeof(from); 1144 *newsock = accept(listen_socks[i], 1145 (struct sockaddr *)&from, &fromlen); 1146 if (*newsock < 0) { 1147 if (errno != EINTR && errno != EAGAIN && 1148 errno != EWOULDBLOCK) 1149 error("accept: %.100s", strerror(errno)); 1150 continue; 1151 } 1152 if (unset_nonblock(*newsock) == -1) { 1153 close(*newsock); 1154 continue; 1155 } 1156 if (drop_connection(startups) == 1) { 1157 debug("drop connection #%d", startups); 1158 close(*newsock); 1159 continue; 1160 } 1161 if (pipe(startup_p) == -1) { 1162 close(*newsock); 1163 continue; 1164 } 1165 1166 if (rexec_flag && socketpair(AF_UNIX, 1167 SOCK_STREAM, 0, config_s) == -1) { 1168 error("reexec socketpair: %s", 1169 strerror(errno)); 1170 close(*newsock); 1171 close(startup_p[0]); 1172 close(startup_p[1]); 1173 continue; 1174 } 1175 1176 for (j = 0; j < options.max_startups; j++) 1177 if (startup_pipes[j] == -1) { 1178 startup_pipes[j] = startup_p[0]; 1179 if (maxfd < startup_p[0]) 1180 maxfd = startup_p[0]; 1181 startups++; 1182 break; 1183 } 1184 1185 /* 1186 * Got connection. Fork a child to handle it, unless 1187 * we are in debugging mode. 1188 */ 1189 if (debug_flag) { 1190 /* 1191 * In debugging mode. Close the listening 1192 * socket, and start processing the 1193 * connection without forking. 1194 */ 1195 debug("Server will not fork when running in debugging mode."); 1196 close_listen_socks(); 1197 *sock_in = *newsock; 1198 *sock_out = *newsock; 1199 close(startup_p[0]); 1200 close(startup_p[1]); 1201 startup_pipe = -1; 1202 pid = getpid(); 1203 if (rexec_flag) { 1204 send_rexec_state(config_s[0], 1205 &cfg); 1206 close(config_s[0]); 1207 } 1208 break; 1209 } 1210 1211 /* 1212 * Normal production daemon. Fork, and have 1213 * the child process the connection. The 1214 * parent continues listening. 1215 */ 1216 platform_pre_fork(); 1217 if ((pid = fork()) == 0) { 1218 /* 1219 * Child. Close the listening and 1220 * max_startup sockets. Start using 1221 * the accepted socket. Reinitialize 1222 * logging (since our pid has changed). 1223 * We break out of the loop to handle 1224 * the connection. 1225 */ 1226 platform_post_fork_child(); 1227 startup_pipe = startup_p[1]; 1228 close_startup_pipes(); 1229 close_listen_socks(); 1230 *sock_in = *newsock; 1231 *sock_out = *newsock; 1232 log_init(__progname, 1233 options.log_level, 1234 options.log_facility, 1235 log_stderr); 1236 if (rexec_flag) 1237 close(config_s[0]); 1238 break; 1239 } 1240 1241 /* Parent. Stay in the loop. */ 1242 platform_post_fork_parent(pid); 1243 if (pid < 0) 1244 error("fork: %.100s", strerror(errno)); 1245 else 1246 debug("Forked child %ld.", (long)pid); 1247 1248 close(startup_p[1]); 1249 1250 if (rexec_flag) { 1251 send_rexec_state(config_s[0], &cfg); 1252 close(config_s[0]); 1253 close(config_s[1]); 1254 } 1255 1256 /* 1257 * Mark that the key has been used (it 1258 * was "given" to the child). 1259 */ 1260 if ((options.protocol & SSH_PROTO_1) && 1261 key_used == 0) { 1262 /* Schedule server key regeneration alarm. */ 1263 signal(SIGALRM, key_regeneration_alarm); 1264 alarm(options.key_regeneration_time); 1265 key_used = 1; 1266 } 1267 1268 close(*newsock); 1269 1270 /* 1271 * Ensure that our random state differs 1272 * from that of the child 1273 */ 1274 arc4random_stir(); 1275 } 1276 1277 /* child process check (or debug mode) */ 1278 if (num_listen_socks < 0) 1279 break; 1280 } 1281 } 1282 1283 1284 /* 1285 * Main program for the daemon. 1286 */ 1287 int 1288 main(int ac, char **av) 1289 { 1290 extern char *optarg; 1291 extern int optind; 1292 int opt, i, j, on = 1; 1293 int sock_in = -1, sock_out = -1, newsock = -1; 1294 const char *remote_ip; 1295 char *test_user = NULL, *test_host = NULL, *test_addr = NULL; 1296 int remote_port; 1297 char *line, *p, *cp; 1298 int config_s[2] = { -1 , -1 }; 1299 u_int64_t ibytes, obytes; 1300 mode_t new_umask; 1301 Key *key; 1302 Authctxt *authctxt; 1303 1304 #ifdef HAVE_SECUREWARE 1305 (void)set_auth_parameters(ac, av); 1306 #endif 1307 __progname = ssh_get_progname(av[0]); 1308 init_rng(); 1309 1310 /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */ 1311 saved_argc = ac; 1312 rexec_argc = ac; 1313 saved_argv = xcalloc(ac + 1, sizeof(*saved_argv)); 1314 for (i = 0; i < ac; i++) 1315 saved_argv[i] = xstrdup(av[i]); 1316 saved_argv[i] = NULL; 1317 1318 #ifndef HAVE_SETPROCTITLE 1319 /* Prepare for later setproctitle emulation */ 1320 compat_init_setproctitle(ac, av); 1321 av = saved_argv; 1322 #endif 1323 1324 if (geteuid() == 0 && setgroups(0, NULL) == -1) 1325 debug("setgroups(): %.200s", strerror(errno)); 1326 1327 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */ 1328 sanitise_stdfd(); 1329 1330 /* Initialize configuration options to their default values. */ 1331 initialize_server_options(&options); 1332 1333 /* Parse command-line arguments. */ 1334 while ((opt = getopt(ac, av, "f:p:b:k:h:g:u:o:C:dDeiqrtQRT46")) != -1) { 1335 switch (opt) { 1336 case '4': 1337 options.address_family = AF_INET; 1338 break; 1339 case '6': 1340 options.address_family = AF_INET6; 1341 break; 1342 case 'f': 1343 config_file_name = optarg; 1344 break; 1345 case 'c': 1346 if (options.num_host_cert_files >= MAX_HOSTCERTS) { 1347 fprintf(stderr, "too many host certificates.\n"); 1348 exit(1); 1349 } 1350 options.host_cert_files[options.num_host_cert_files++] = 1351 derelativise_path(optarg); 1352 break; 1353 case 'd': 1354 if (debug_flag == 0) { 1355 debug_flag = 1; 1356 options.log_level = SYSLOG_LEVEL_DEBUG1; 1357 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) 1358 options.log_level++; 1359 break; 1360 case 'D': 1361 no_daemon_flag = 1; 1362 break; 1363 case 'e': 1364 log_stderr = 1; 1365 break; 1366 case 'i': 1367 inetd_flag = 1; 1368 break; 1369 case 'r': 1370 rexec_flag = 0; 1371 break; 1372 case 'R': 1373 rexeced_flag = 1; 1374 inetd_flag = 1; 1375 break; 1376 case 'Q': 1377 /* ignored */ 1378 break; 1379 case 'q': 1380 options.log_level = SYSLOG_LEVEL_QUIET; 1381 break; 1382 case 'b': 1383 options.server_key_bits = (int)strtonum(optarg, 256, 1384 32768, NULL); 1385 break; 1386 case 'p': 1387 options.ports_from_cmdline = 1; 1388 if (options.num_ports >= MAX_PORTS) { 1389 fprintf(stderr, "too many ports.\n"); 1390 exit(1); 1391 } 1392 options.ports[options.num_ports++] = a2port(optarg); 1393 if (options.ports[options.num_ports-1] <= 0) { 1394 fprintf(stderr, "Bad port number.\n"); 1395 exit(1); 1396 } 1397 break; 1398 case 'g': 1399 if ((options.login_grace_time = convtime(optarg)) == -1) { 1400 fprintf(stderr, "Invalid login grace time.\n"); 1401 exit(1); 1402 } 1403 break; 1404 case 'k': 1405 if ((options.key_regeneration_time = convtime(optarg)) == -1) { 1406 fprintf(stderr, "Invalid key regeneration interval.\n"); 1407 exit(1); 1408 } 1409 break; 1410 case 'h': 1411 if (options.num_host_key_files >= MAX_HOSTKEYS) { 1412 fprintf(stderr, "too many host keys.\n"); 1413 exit(1); 1414 } 1415 options.host_key_files[options.num_host_key_files++] = 1416 derelativise_path(optarg); 1417 break; 1418 case 't': 1419 test_flag = 1; 1420 break; 1421 case 'T': 1422 test_flag = 2; 1423 break; 1424 case 'C': 1425 cp = optarg; 1426 while ((p = strsep(&cp, ",")) && *p != '\0') { 1427 if (strncmp(p, "addr=", 5) == 0) 1428 test_addr = xstrdup(p + 5); 1429 else if (strncmp(p, "host=", 5) == 0) 1430 test_host = xstrdup(p + 5); 1431 else if (strncmp(p, "user=", 5) == 0) 1432 test_user = xstrdup(p + 5); 1433 else { 1434 fprintf(stderr, "Invalid test " 1435 "mode specification %s\n", p); 1436 exit(1); 1437 } 1438 } 1439 break; 1440 case 'u': 1441 utmp_len = (u_int)strtonum(optarg, 0, MAXHOSTNAMELEN+1, NULL); 1442 if (utmp_len > MAXHOSTNAMELEN) { 1443 fprintf(stderr, "Invalid utmp length.\n"); 1444 exit(1); 1445 } 1446 break; 1447 case 'o': 1448 line = xstrdup(optarg); 1449 if (process_server_config_line(&options, line, 1450 "command-line", 0, NULL, NULL, NULL, NULL) != 0) 1451 exit(1); 1452 xfree(line); 1453 break; 1454 case '?': 1455 default: 1456 usage(); 1457 break; 1458 } 1459 } 1460 if (rexeced_flag || inetd_flag) 1461 rexec_flag = 0; 1462 if (!test_flag && (rexec_flag && (av[0] == NULL || *av[0] != '/'))) 1463 fatal("sshd re-exec requires execution with an absolute path"); 1464 if (rexeced_flag) 1465 closefrom(REEXEC_MIN_FREE_FD); 1466 else 1467 closefrom(REEXEC_DEVCRYPTO_RESERVED_FD); 1468 1469 SSLeay_add_all_algorithms(); 1470 1471 /* 1472 * Force logging to stderr until we have loaded the private host 1473 * key (unless started from inetd) 1474 */ 1475 log_init(__progname, 1476 options.log_level == SYSLOG_LEVEL_NOT_SET ? 1477 SYSLOG_LEVEL_INFO : options.log_level, 1478 options.log_facility == SYSLOG_FACILITY_NOT_SET ? 1479 SYSLOG_FACILITY_AUTH : options.log_facility, 1480 log_stderr || !inetd_flag); 1481 1482 /* 1483 * Unset KRB5CCNAME, otherwise the user's session may inherit it from 1484 * root's environment 1485 */ 1486 if (getenv("KRB5CCNAME") != NULL) 1487 unsetenv("KRB5CCNAME"); 1488 1489 #ifdef _UNICOS 1490 /* Cray can define user privs drop all privs now! 1491 * Not needed on PRIV_SU systems! 1492 */ 1493 drop_cray_privs(); 1494 #endif 1495 1496 sensitive_data.server_key = NULL; 1497 sensitive_data.ssh1_host_key = NULL; 1498 sensitive_data.have_ssh1_key = 0; 1499 sensitive_data.have_ssh2_key = 0; 1500 1501 /* 1502 * If we're doing an extended config test, make sure we have all of 1503 * the parameters we need. If we're not doing an extended test, 1504 * do not silently ignore connection test params. 1505 */ 1506 if (test_flag >= 2 && 1507 (test_user != NULL || test_host != NULL || test_addr != NULL) 1508 && (test_user == NULL || test_host == NULL || test_addr == NULL)) 1509 fatal("user, host and addr are all required when testing " 1510 "Match configs"); 1511 if (test_flag < 2 && (test_user != NULL || test_host != NULL || 1512 test_addr != NULL)) 1513 fatal("Config test connection parameter (-C) provided without " 1514 "test mode (-T)"); 1515 1516 /* Fetch our configuration */ 1517 buffer_init(&cfg); 1518 if (rexeced_flag) 1519 recv_rexec_state(REEXEC_CONFIG_PASS_FD, &cfg); 1520 else 1521 load_server_config(config_file_name, &cfg); 1522 1523 parse_server_config(&options, rexeced_flag ? "rexec" : config_file_name, 1524 &cfg, NULL, NULL, NULL); 1525 1526 seed_rng(); 1527 1528 /* Fill in default values for those options not explicitly set. */ 1529 fill_default_server_options(&options); 1530 1531 /* challenge-response is implemented via keyboard interactive */ 1532 if (options.challenge_response_authentication) 1533 options.kbd_interactive_authentication = 1; 1534 1535 /* set default channel AF */ 1536 channel_set_af(options.address_family); 1537 1538 /* Check that there are no remaining arguments. */ 1539 if (optind < ac) { 1540 fprintf(stderr, "Extra argument %s.\n", av[optind]); 1541 exit(1); 1542 } 1543 1544 debug("sshd version %.100s", SSH_RELEASE); 1545 1546 /* Store privilege separation user for later use if required. */ 1547 if ((privsep_pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) { 1548 if (use_privsep || options.kerberos_authentication) 1549 fatal("Privilege separation user %s does not exist", 1550 SSH_PRIVSEP_USER); 1551 } else { 1552 memset(privsep_pw->pw_passwd, 0, strlen(privsep_pw->pw_passwd)); 1553 privsep_pw = pwcopy(privsep_pw); 1554 xfree(privsep_pw->pw_passwd); 1555 privsep_pw->pw_passwd = xstrdup("*"); 1556 } 1557 endpwent(); 1558 1559 /* load private host keys */ 1560 sensitive_data.host_keys = xcalloc(options.num_host_key_files, 1561 sizeof(Key *)); 1562 for (i = 0; i < options.num_host_key_files; i++) 1563 sensitive_data.host_keys[i] = NULL; 1564 1565 for (i = 0; i < options.num_host_key_files; i++) { 1566 key = key_load_private(options.host_key_files[i], "", NULL); 1567 sensitive_data.host_keys[i] = key; 1568 if (key == NULL) { 1569 error("Could not load host key: %s", 1570 options.host_key_files[i]); 1571 sensitive_data.host_keys[i] = NULL; 1572 continue; 1573 } 1574 switch (key->type) { 1575 case KEY_RSA1: 1576 sensitive_data.ssh1_host_key = key; 1577 sensitive_data.have_ssh1_key = 1; 1578 break; 1579 case KEY_RSA: 1580 case KEY_DSA: 1581 sensitive_data.have_ssh2_key = 1; 1582 break; 1583 } 1584 debug("private host key: #%d type %d %s", i, key->type, 1585 key_type(key)); 1586 } 1587 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) { 1588 logit("Disabling protocol version 1. Could not load host key"); 1589 options.protocol &= ~SSH_PROTO_1; 1590 } 1591 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) { 1592 logit("Disabling protocol version 2. Could not load host key"); 1593 options.protocol &= ~SSH_PROTO_2; 1594 } 1595 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) { 1596 logit("sshd: no hostkeys available -- exiting."); 1597 exit(1); 1598 } 1599 1600 /* 1601 * Load certificates. They are stored in an array at identical 1602 * indices to the public keys that they relate to. 1603 */ 1604 sensitive_data.host_certificates = xcalloc(options.num_host_key_files, 1605 sizeof(Key *)); 1606 for (i = 0; i < options.num_host_key_files; i++) 1607 sensitive_data.host_certificates[i] = NULL; 1608 1609 for (i = 0; i < options.num_host_cert_files; i++) { 1610 key = key_load_public(options.host_cert_files[i], NULL); 1611 if (key == NULL) { 1612 error("Could not load host certificate: %s", 1613 options.host_cert_files[i]); 1614 continue; 1615 } 1616 if (!key_is_cert(key)) { 1617 error("Certificate file is not a certificate: %s", 1618 options.host_cert_files[i]); 1619 key_free(key); 1620 continue; 1621 } 1622 /* Find matching private key */ 1623 for (j = 0; j < options.num_host_key_files; j++) { 1624 if (key_equal_public(key, 1625 sensitive_data.host_keys[j])) { 1626 sensitive_data.host_certificates[j] = key; 1627 break; 1628 } 1629 } 1630 if (j >= options.num_host_key_files) { 1631 error("No matching private key for certificate: %s", 1632 options.host_cert_files[i]); 1633 key_free(key); 1634 continue; 1635 } 1636 sensitive_data.host_certificates[j] = key; 1637 debug("host certificate: #%d type %d %s", j, key->type, 1638 key_type(key)); 1639 } 1640 /* Check certain values for sanity. */ 1641 if (options.protocol & SSH_PROTO_1) { 1642 if (options.server_key_bits < 512 || 1643 options.server_key_bits > 32768) { 1644 fprintf(stderr, "Bad server key size.\n"); 1645 exit(1); 1646 } 1647 /* 1648 * Check that server and host key lengths differ sufficiently. This 1649 * is necessary to make double encryption work with rsaref. Oh, I 1650 * hate software patents. I dont know if this can go? Niels 1651 */ 1652 if (options.server_key_bits > 1653 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - 1654 SSH_KEY_BITS_RESERVED && options.server_key_bits < 1655 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + 1656 SSH_KEY_BITS_RESERVED) { 1657 options.server_key_bits = 1658 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + 1659 SSH_KEY_BITS_RESERVED; 1660 debug("Forcing server key to %d bits to make it differ from host key.", 1661 options.server_key_bits); 1662 } 1663 } 1664 1665 if (use_privsep) { 1666 struct stat st; 1667 1668 if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) || 1669 (S_ISDIR(st.st_mode) == 0)) 1670 fatal("Missing privilege separation directory: %s", 1671 _PATH_PRIVSEP_CHROOT_DIR); 1672 1673 #ifdef HAVE_CYGWIN 1674 if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) && 1675 (st.st_uid != getuid () || 1676 (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)) 1677 #else 1678 if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0) 1679 #endif 1680 fatal("%s must be owned by root and not group or " 1681 "world-writable.", _PATH_PRIVSEP_CHROOT_DIR); 1682 } 1683 1684 if (test_flag > 1) { 1685 if (test_user != NULL && test_addr != NULL && test_host != NULL) 1686 parse_server_match_config(&options, test_user, 1687 test_host, test_addr); 1688 dump_config(&options); 1689 } 1690 1691 /* Configuration looks good, so exit if in test mode. */ 1692 if (test_flag) 1693 exit(0); 1694 1695 /* 1696 * Clear out any supplemental groups we may have inherited. This 1697 * prevents inadvertent creation of files with bad modes (in the 1698 * portable version at least, it's certainly possible for PAM 1699 * to create a file, and we can't control the code in every 1700 * module which might be used). 1701 */ 1702 if (setgroups(0, NULL) < 0) 1703 debug("setgroups() failed: %.200s", strerror(errno)); 1704 1705 if (rexec_flag) { 1706 rexec_argv = xcalloc(rexec_argc + 2, sizeof(char *)); 1707 for (i = 0; i < rexec_argc; i++) { 1708 debug("rexec_argv[%d]='%s'", i, saved_argv[i]); 1709 rexec_argv[i] = saved_argv[i]; 1710 } 1711 rexec_argv[rexec_argc] = "-R"; 1712 rexec_argv[rexec_argc + 1] = NULL; 1713 } 1714 1715 /* Ensure that umask disallows at least group and world write */ 1716 new_umask = umask(0077) | 0022; 1717 (void) umask(new_umask); 1718 1719 /* Initialize the log (it is reinitialized below in case we forked). */ 1720 if (debug_flag && (!inetd_flag || rexeced_flag)) 1721 log_stderr = 1; 1722 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1723 1724 /* 1725 * If not in debugging mode, and not started from inetd, disconnect 1726 * from the controlling terminal, and fork. The original process 1727 * exits. 1728 */ 1729 if (!(debug_flag || inetd_flag || no_daemon_flag)) { 1730 #ifdef TIOCNOTTY 1731 int fd; 1732 #endif /* TIOCNOTTY */ 1733 if (daemon(0, 0) < 0) 1734 fatal("daemon() failed: %.200s", strerror(errno)); 1735 1736 /* Disconnect from the controlling tty. */ 1737 #ifdef TIOCNOTTY 1738 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 1739 if (fd >= 0) { 1740 (void) ioctl(fd, TIOCNOTTY, NULL); 1741 close(fd); 1742 } 1743 #endif /* TIOCNOTTY */ 1744 } 1745 /* Reinitialize the log (because of the fork above). */ 1746 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1747 1748 /* Avoid killing the process in high-pressure swapping environments. */ 1749 if (!inetd_flag && madvise(NULL, 0, MADV_PROTECT) != 0) 1750 debug("madvise(): %.200s", strerror(errno)); 1751 1752 /* Initialize the random number generator. */ 1753 arc4random_stir(); 1754 1755 /* Chdir to the root directory so that the current disk can be 1756 unmounted if desired. */ 1757 chdir("/"); 1758 1759 /* ignore SIGPIPE */ 1760 signal(SIGPIPE, SIG_IGN); 1761 1762 /* Get a connection, either from inetd or a listening TCP socket */ 1763 if (inetd_flag) { 1764 server_accept_inetd(&sock_in, &sock_out); 1765 } else { 1766 platform_pre_listen(); 1767 server_listen(); 1768 1769 if (options.protocol & SSH_PROTO_1) 1770 generate_ephemeral_server_key(); 1771 1772 signal(SIGHUP, sighup_handler); 1773 signal(SIGCHLD, main_sigchld_handler); 1774 signal(SIGTERM, sigterm_handler); 1775 signal(SIGQUIT, sigterm_handler); 1776 1777 /* 1778 * Write out the pid file after the sigterm handler 1779 * is setup and the listen sockets are bound 1780 */ 1781 if (!debug_flag) { 1782 FILE *f = fopen(options.pid_file, "w"); 1783 1784 if (f == NULL) { 1785 error("Couldn't create pid file \"%s\": %s", 1786 options.pid_file, strerror(errno)); 1787 } else { 1788 fprintf(f, "%ld\n", (long) getpid()); 1789 fclose(f); 1790 } 1791 } 1792 1793 /* Accept a connection and return in a forked child */ 1794 server_accept_loop(&sock_in, &sock_out, 1795 &newsock, config_s); 1796 } 1797 1798 /* This is the child processing a new connection. */ 1799 setproctitle("%s", "[accepted]"); 1800 1801 /* 1802 * Create a new session and process group since the 4.4BSD 1803 * setlogin() affects the entire process group. We don't 1804 * want the child to be able to affect the parent. 1805 */ 1806 #if !defined(SSHD_ACQUIRES_CTTY) 1807 /* 1808 * If setsid is called, on some platforms sshd will later acquire a 1809 * controlling terminal which will result in "could not set 1810 * controlling tty" errors. 1811 */ 1812 if (!debug_flag && !inetd_flag && setsid() < 0) 1813 error("setsid: %.100s", strerror(errno)); 1814 #endif 1815 1816 if (rexec_flag) { 1817 int fd; 1818 1819 debug("rexec start in %d out %d newsock %d pipe %d sock %d", 1820 sock_in, sock_out, newsock, startup_pipe, config_s[0]); 1821 dup2(newsock, STDIN_FILENO); 1822 dup2(STDIN_FILENO, STDOUT_FILENO); 1823 if (startup_pipe == -1) 1824 close(REEXEC_STARTUP_PIPE_FD); 1825 else 1826 dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD); 1827 1828 dup2(config_s[1], REEXEC_CONFIG_PASS_FD); 1829 close(config_s[1]); 1830 if (startup_pipe != -1) 1831 close(startup_pipe); 1832 1833 execv(rexec_argv[0], rexec_argv); 1834 1835 /* Reexec has failed, fall back and continue */ 1836 error("rexec of %s failed: %s", rexec_argv[0], strerror(errno)); 1837 recv_rexec_state(REEXEC_CONFIG_PASS_FD, NULL); 1838 log_init(__progname, options.log_level, 1839 options.log_facility, log_stderr); 1840 1841 /* Clean up fds */ 1842 startup_pipe = REEXEC_STARTUP_PIPE_FD; 1843 close(config_s[1]); 1844 close(REEXEC_CONFIG_PASS_FD); 1845 newsock = sock_out = sock_in = dup(STDIN_FILENO); 1846 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) { 1847 dup2(fd, STDIN_FILENO); 1848 dup2(fd, STDOUT_FILENO); 1849 if (fd > STDERR_FILENO) 1850 close(fd); 1851 } 1852 debug("rexec cleanup in %d out %d newsock %d pipe %d sock %d", 1853 sock_in, sock_out, newsock, startup_pipe, config_s[0]); 1854 } 1855 1856 /* Executed child processes don't need these. */ 1857 fcntl(sock_out, F_SETFD, FD_CLOEXEC); 1858 fcntl(sock_in, F_SETFD, FD_CLOEXEC); 1859 1860 /* 1861 * Disable the key regeneration alarm. We will not regenerate the 1862 * key since we are no longer in a position to give it to anyone. We 1863 * will not restart on SIGHUP since it no longer makes sense. 1864 */ 1865 alarm(0); 1866 signal(SIGALRM, SIG_DFL); 1867 signal(SIGHUP, SIG_DFL); 1868 signal(SIGTERM, SIG_DFL); 1869 signal(SIGQUIT, SIG_DFL); 1870 signal(SIGCHLD, SIG_DFL); 1871 signal(SIGINT, SIG_DFL); 1872 1873 #ifdef __FreeBSD__ 1874 /* 1875 * Initialize the resolver. This may not happen automatically 1876 * before privsep chroot(). 1877 */ 1878 if ((_res.options & RES_INIT) == 0) { 1879 debug("res_init()"); 1880 res_init(); 1881 } 1882 #ifdef GSSAPI 1883 /* 1884 * Force GSS-API to parse its configuration and load any 1885 * mechanism plugins. 1886 */ 1887 { 1888 gss_OID_set mechs; 1889 OM_uint32 minor_status; 1890 gss_indicate_mechs(&minor_status, &mechs); 1891 gss_release_oid_set(&minor_status, &mechs); 1892 } 1893 #endif 1894 #endif 1895 1896 /* 1897 * Register our connection. This turns encryption off because we do 1898 * not have a key. 1899 */ 1900 packet_set_connection(sock_in, sock_out); 1901 packet_set_server(); 1902 1903 /* Set SO_KEEPALIVE if requested. */ 1904 if (options.tcp_keep_alive && packet_connection_is_on_socket() && 1905 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) < 0) 1906 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 1907 1908 if ((remote_port = get_remote_port()) < 0) { 1909 debug("get_remote_port failed"); 1910 cleanup_exit(255); 1911 } 1912 1913 /* 1914 * We use get_canonical_hostname with usedns = 0 instead of 1915 * get_remote_ipaddr here so IP options will be checked. 1916 */ 1917 (void) get_canonical_hostname(0); 1918 /* 1919 * The rest of the code depends on the fact that 1920 * get_remote_ipaddr() caches the remote ip, even if 1921 * the socket goes away. 1922 */ 1923 remote_ip = get_remote_ipaddr(); 1924 1925 #ifdef SSH_AUDIT_EVENTS 1926 audit_connection_from(remote_ip, remote_port); 1927 #endif 1928 #ifdef LIBWRAP 1929 allow_severity = options.log_facility|LOG_INFO; 1930 deny_severity = options.log_facility|LOG_WARNING; 1931 /* Check whether logins are denied from this host. */ 1932 if (packet_connection_is_on_socket()) { 1933 struct request_info req; 1934 1935 request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0); 1936 fromhost(&req); 1937 1938 if (!hosts_access(&req)) { 1939 debug("Connection refused by tcp wrapper"); 1940 refuse(&req); 1941 /* NOTREACHED */ 1942 fatal("libwrap refuse returns"); 1943 } 1944 } 1945 #endif /* LIBWRAP */ 1946 1947 /* Log the connection. */ 1948 verbose("Connection from %.500s port %d", remote_ip, remote_port); 1949 1950 /* 1951 * We don't want to listen forever unless the other side 1952 * successfully authenticates itself. So we set up an alarm which is 1953 * cleared after successful authentication. A limit of zero 1954 * indicates no limit. Note that we don't set the alarm in debugging 1955 * mode; it is just annoying to have the server exit just when you 1956 * are about to discover the bug. 1957 */ 1958 signal(SIGALRM, grace_alarm_handler); 1959 if (!debug_flag) 1960 alarm(options.login_grace_time); 1961 1962 sshd_exchange_identification(sock_in, sock_out); 1963 1964 /* In inetd mode, generate ephemeral key only for proto 1 connections */ 1965 if (!compat20 && inetd_flag && sensitive_data.server_key == NULL) 1966 generate_ephemeral_server_key(); 1967 1968 packet_set_nonblocking(); 1969 1970 /* allocate authentication context */ 1971 authctxt = xcalloc(1, sizeof(*authctxt)); 1972 1973 authctxt->loginmsg = &loginmsg; 1974 1975 /* XXX global for cleanup, access from other modules */ 1976 the_authctxt = authctxt; 1977 1978 /* prepare buffer to collect messages to display to user after login */ 1979 buffer_init(&loginmsg); 1980 auth_debug_reset(); 1981 1982 if (use_privsep) 1983 if (privsep_preauth(authctxt) == 1) 1984 goto authenticated; 1985 1986 /* perform the key exchange */ 1987 /* authenticate user and start session */ 1988 if (compat20) { 1989 do_ssh2_kex(); 1990 do_authentication2(authctxt); 1991 } else { 1992 do_ssh1_kex(); 1993 do_authentication(authctxt); 1994 } 1995 /* 1996 * If we use privilege separation, the unprivileged child transfers 1997 * the current keystate and exits 1998 */ 1999 if (use_privsep) { 2000 mm_send_keystate(pmonitor); 2001 exit(0); 2002 } 2003 2004 authenticated: 2005 /* 2006 * Cancel the alarm we set to limit the time taken for 2007 * authentication. 2008 */ 2009 alarm(0); 2010 signal(SIGALRM, SIG_DFL); 2011 authctxt->authenticated = 1; 2012 if (startup_pipe != -1) { 2013 close(startup_pipe); 2014 startup_pipe = -1; 2015 } 2016 2017 #ifdef SSH_AUDIT_EVENTS 2018 audit_event(SSH_AUTH_SUCCESS); 2019 #endif 2020 2021 #ifdef GSSAPI 2022 if (options.gss_authentication) { 2023 temporarily_use_uid(authctxt->pw); 2024 ssh_gssapi_storecreds(); 2025 restore_uid(); 2026 } 2027 #endif 2028 #ifdef USE_PAM 2029 if (options.use_pam) { 2030 do_pam_setcred(1); 2031 do_pam_session(); 2032 } 2033 #endif 2034 2035 /* 2036 * In privilege separation, we fork another child and prepare 2037 * file descriptor passing. 2038 */ 2039 if (use_privsep) { 2040 privsep_postauth(authctxt); 2041 /* the monitor process [priv] will not return */ 2042 if (!compat20) 2043 destroy_sensitive_data(); 2044 } 2045 2046 packet_set_timeout(options.client_alive_interval, 2047 options.client_alive_count_max); 2048 2049 /* Start session. */ 2050 do_authenticated(authctxt); 2051 2052 /* The connection has been terminated. */ 2053 packet_get_state(MODE_IN, NULL, NULL, NULL, &ibytes); 2054 packet_get_state(MODE_OUT, NULL, NULL, NULL, &obytes); 2055 verbose("Transferred: sent %llu, received %llu bytes", obytes, ibytes); 2056 2057 verbose("Closing connection to %.500s port %d", remote_ip, remote_port); 2058 2059 #ifdef USE_PAM 2060 if (options.use_pam) 2061 finish_pam(); 2062 #endif /* USE_PAM */ 2063 2064 #ifdef SSH_AUDIT_EVENTS 2065 PRIVSEP(audit_event(SSH_CONNECTION_CLOSE)); 2066 #endif 2067 2068 packet_close(); 2069 2070 if (use_privsep) 2071 mm_terminate(); 2072 2073 exit(0); 2074 } 2075 2076 /* 2077 * Decrypt session_key_int using our private server key and private host key 2078 * (key with larger modulus first). 2079 */ 2080 int 2081 ssh1_session_key(BIGNUM *session_key_int) 2082 { 2083 int rsafail = 0; 2084 2085 if (BN_cmp(sensitive_data.server_key->rsa->n, 2086 sensitive_data.ssh1_host_key->rsa->n) > 0) { 2087 /* Server key has bigger modulus. */ 2088 if (BN_num_bits(sensitive_data.server_key->rsa->n) < 2089 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + 2090 SSH_KEY_BITS_RESERVED) { 2091 fatal("do_connection: %s: " 2092 "server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d", 2093 get_remote_ipaddr(), 2094 BN_num_bits(sensitive_data.server_key->rsa->n), 2095 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n), 2096 SSH_KEY_BITS_RESERVED); 2097 } 2098 if (rsa_private_decrypt(session_key_int, session_key_int, 2099 sensitive_data.server_key->rsa) <= 0) 2100 rsafail++; 2101 if (rsa_private_decrypt(session_key_int, session_key_int, 2102 sensitive_data.ssh1_host_key->rsa) <= 0) 2103 rsafail++; 2104 } else { 2105 /* Host key has bigger modulus (or they are equal). */ 2106 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) < 2107 BN_num_bits(sensitive_data.server_key->rsa->n) + 2108 SSH_KEY_BITS_RESERVED) { 2109 fatal("do_connection: %s: " 2110 "host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d", 2111 get_remote_ipaddr(), 2112 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n), 2113 BN_num_bits(sensitive_data.server_key->rsa->n), 2114 SSH_KEY_BITS_RESERVED); 2115 } 2116 if (rsa_private_decrypt(session_key_int, session_key_int, 2117 sensitive_data.ssh1_host_key->rsa) < 0) 2118 rsafail++; 2119 if (rsa_private_decrypt(session_key_int, session_key_int, 2120 sensitive_data.server_key->rsa) < 0) 2121 rsafail++; 2122 } 2123 return (rsafail); 2124 } 2125 /* 2126 * SSH1 key exchange 2127 */ 2128 static void 2129 do_ssh1_kex(void) 2130 { 2131 int i, len; 2132 int rsafail = 0; 2133 BIGNUM *session_key_int; 2134 u_char session_key[SSH_SESSION_KEY_LENGTH]; 2135 u_char cookie[8]; 2136 u_int cipher_type, auth_mask, protocol_flags; 2137 2138 /* 2139 * Generate check bytes that the client must send back in the user 2140 * packet in order for it to be accepted; this is used to defy ip 2141 * spoofing attacks. Note that this only works against somebody 2142 * doing IP spoofing from a remote machine; any machine on the local 2143 * network can still see outgoing packets and catch the random 2144 * cookie. This only affects rhosts authentication, and this is one 2145 * of the reasons why it is inherently insecure. 2146 */ 2147 arc4random_buf(cookie, sizeof(cookie)); 2148 2149 /* 2150 * Send our public key. We include in the packet 64 bits of random 2151 * data that must be matched in the reply in order to prevent IP 2152 * spoofing. 2153 */ 2154 packet_start(SSH_SMSG_PUBLIC_KEY); 2155 for (i = 0; i < 8; i++) 2156 packet_put_char(cookie[i]); 2157 2158 /* Store our public server RSA key. */ 2159 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n)); 2160 packet_put_bignum(sensitive_data.server_key->rsa->e); 2161 packet_put_bignum(sensitive_data.server_key->rsa->n); 2162 2163 /* Store our public host RSA key. */ 2164 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n)); 2165 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e); 2166 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n); 2167 2168 /* Put protocol flags. */ 2169 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN); 2170 2171 /* Declare which ciphers we support. */ 2172 packet_put_int(cipher_mask_ssh1(0)); 2173 2174 /* Declare supported authentication types. */ 2175 auth_mask = 0; 2176 if (options.rhosts_rsa_authentication) 2177 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA; 2178 if (options.rsa_authentication) 2179 auth_mask |= 1 << SSH_AUTH_RSA; 2180 if (options.challenge_response_authentication == 1) 2181 auth_mask |= 1 << SSH_AUTH_TIS; 2182 if (options.password_authentication) 2183 auth_mask |= 1 << SSH_AUTH_PASSWORD; 2184 packet_put_int(auth_mask); 2185 2186 /* Send the packet and wait for it to be sent. */ 2187 packet_send(); 2188 packet_write_wait(); 2189 2190 debug("Sent %d bit server key and %d bit host key.", 2191 BN_num_bits(sensitive_data.server_key->rsa->n), 2192 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n)); 2193 2194 /* Read clients reply (cipher type and session key). */ 2195 packet_read_expect(SSH_CMSG_SESSION_KEY); 2196 2197 /* Get cipher type and check whether we accept this. */ 2198 cipher_type = packet_get_char(); 2199 2200 if (!(cipher_mask_ssh1(0) & (1 << cipher_type))) 2201 packet_disconnect("Warning: client selects unsupported cipher."); 2202 2203 /* Get check bytes from the packet. These must match those we 2204 sent earlier with the public key packet. */ 2205 for (i = 0; i < 8; i++) 2206 if (cookie[i] != packet_get_char()) 2207 packet_disconnect("IP Spoofing check bytes do not match."); 2208 2209 debug("Encryption type: %.200s", cipher_name(cipher_type)); 2210 2211 /* Get the encrypted integer. */ 2212 if ((session_key_int = BN_new()) == NULL) 2213 fatal("do_ssh1_kex: BN_new failed"); 2214 packet_get_bignum(session_key_int); 2215 2216 protocol_flags = packet_get_int(); 2217 packet_set_protocol_flags(protocol_flags); 2218 packet_check_eom(); 2219 2220 /* Decrypt session_key_int using host/server keys */ 2221 rsafail = PRIVSEP(ssh1_session_key(session_key_int)); 2222 2223 /* 2224 * Extract session key from the decrypted integer. The key is in the 2225 * least significant 256 bits of the integer; the first byte of the 2226 * key is in the highest bits. 2227 */ 2228 if (!rsafail) { 2229 (void) BN_mask_bits(session_key_int, sizeof(session_key) * 8); 2230 len = BN_num_bytes(session_key_int); 2231 if (len < 0 || (u_int)len > sizeof(session_key)) { 2232 error("do_ssh1_kex: bad session key len from %s: " 2233 "session_key_int %d > sizeof(session_key) %lu", 2234 get_remote_ipaddr(), len, (u_long)sizeof(session_key)); 2235 rsafail++; 2236 } else { 2237 memset(session_key, 0, sizeof(session_key)); 2238 BN_bn2bin(session_key_int, 2239 session_key + sizeof(session_key) - len); 2240 2241 derive_ssh1_session_id( 2242 sensitive_data.ssh1_host_key->rsa->n, 2243 sensitive_data.server_key->rsa->n, 2244 cookie, session_id); 2245 /* 2246 * Xor the first 16 bytes of the session key with the 2247 * session id. 2248 */ 2249 for (i = 0; i < 16; i++) 2250 session_key[i] ^= session_id[i]; 2251 } 2252 } 2253 if (rsafail) { 2254 int bytes = BN_num_bytes(session_key_int); 2255 u_char *buf = xmalloc(bytes); 2256 MD5_CTX md; 2257 2258 logit("do_connection: generating a fake encryption key"); 2259 BN_bn2bin(session_key_int, buf); 2260 MD5_Init(&md); 2261 MD5_Update(&md, buf, bytes); 2262 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); 2263 MD5_Final(session_key, &md); 2264 MD5_Init(&md); 2265 MD5_Update(&md, session_key, 16); 2266 MD5_Update(&md, buf, bytes); 2267 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); 2268 MD5_Final(session_key + 16, &md); 2269 memset(buf, 0, bytes); 2270 xfree(buf); 2271 for (i = 0; i < 16; i++) 2272 session_id[i] = session_key[i] ^ session_key[i + 16]; 2273 } 2274 /* Destroy the private and public keys. No longer. */ 2275 destroy_sensitive_data(); 2276 2277 if (use_privsep) 2278 mm_ssh1_session_id(session_id); 2279 2280 /* Destroy the decrypted integer. It is no longer needed. */ 2281 BN_clear_free(session_key_int); 2282 2283 /* Set the session key. From this on all communications will be encrypted. */ 2284 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type); 2285 2286 /* Destroy our copy of the session key. It is no longer needed. */ 2287 memset(session_key, 0, sizeof(session_key)); 2288 2289 debug("Received session key; encryption turned on."); 2290 2291 /* Send an acknowledgment packet. Note that this packet is sent encrypted. */ 2292 packet_start(SSH_SMSG_SUCCESS); 2293 packet_send(); 2294 packet_write_wait(); 2295 } 2296 2297 /* 2298 * SSH2 key exchange: diffie-hellman-group1-sha1 2299 */ 2300 static void 2301 do_ssh2_kex(void) 2302 { 2303 Kex *kex; 2304 2305 if (options.ciphers != NULL) { 2306 myproposal[PROPOSAL_ENC_ALGS_CTOS] = 2307 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers; 2308 } 2309 myproposal[PROPOSAL_ENC_ALGS_CTOS] = 2310 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]); 2311 myproposal[PROPOSAL_ENC_ALGS_STOC] = 2312 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]); 2313 2314 if (options.macs != NULL) { 2315 myproposal[PROPOSAL_MAC_ALGS_CTOS] = 2316 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs; 2317 } 2318 if (options.compression == COMP_NONE) { 2319 myproposal[PROPOSAL_COMP_ALGS_CTOS] = 2320 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none"; 2321 } else if (options.compression == COMP_DELAYED) { 2322 myproposal[PROPOSAL_COMP_ALGS_CTOS] = 2323 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none,zlib@openssh.com"; 2324 } 2325 2326 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types(); 2327 2328 /* start key exchange */ 2329 kex = kex_setup(myproposal); 2330 kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server; 2331 kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server; 2332 kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 2333 kex->kex[KEX_DH_GEX_SHA256] = kexgex_server; 2334 kex->server = 1; 2335 kex->client_version_string=client_version_string; 2336 kex->server_version_string=server_version_string; 2337 kex->load_host_public_key=&get_hostkey_public_by_type; 2338 kex->load_host_private_key=&get_hostkey_private_by_type; 2339 kex->host_key_index=&get_hostkey_index; 2340 2341 xxx_kex = kex; 2342 2343 dispatch_run(DISPATCH_BLOCK, &kex->done, kex); 2344 2345 session_id2 = kex->session_id; 2346 session_id2_len = kex->session_id_len; 2347 2348 #ifdef DEBUG_KEXDH 2349 /* send 1st encrypted/maced/compressed message */ 2350 packet_start(SSH2_MSG_IGNORE); 2351 packet_put_cstring("markus"); 2352 packet_send(); 2353 packet_write_wait(); 2354 #endif 2355 debug("KEX done"); 2356 } 2357 2358 /* server specific fatal cleanup */ 2359 void 2360 cleanup_exit(int i) 2361 { 2362 if (the_authctxt) 2363 do_cleanup(the_authctxt); 2364 #ifdef SSH_AUDIT_EVENTS 2365 /* done after do_cleanup so it can cancel the PAM auth 'thread' */ 2366 if (!use_privsep || mm_is_monitor()) 2367 audit_event(SSH_CONNECTION_ABANDON); 2368 #endif 2369 _exit(i); 2370 } 2371