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 * Copyright 2009 Sun Microsystems, Inc. All rights reserved. 45 * Use is subject to license terms. 46 */ 47 48 #include "includes.h" 49 RCSID("$OpenBSD: sshd.c,v 1.260 2002/09/27 10:42:09 mickey Exp $"); 50 51 #include <openssl/dh.h> 52 #include <openssl/bn.h> 53 #include <openssl/md5.h> 54 55 #include <openssl/rand.h> 56 57 #include "ssh.h" 58 #include "ssh1.h" 59 #include "ssh2.h" 60 #include "xmalloc.h" 61 #include "rsa.h" 62 #include "sshpty.h" 63 #include "packet.h" 64 #include "mpaux.h" 65 #include "log.h" 66 #include "servconf.h" 67 #include "uidswap.h" 68 #include "compat.h" 69 #include "buffer.h" 70 #include "cipher.h" 71 #include "kex.h" 72 #include "key.h" 73 #include "dh.h" 74 #include "myproposal.h" 75 #include "authfile.h" 76 #include "pathnames.h" 77 #include "atomicio.h" 78 #include "canohost.h" 79 #include "auth.h" 80 #include "misc.h" 81 #include "dispatch.h" 82 #include "channels.h" 83 #include "session.h" 84 #include "g11n.h" 85 #include "sshlogin.h" 86 #include "xlist.h" 87 #include "engine.h" 88 89 #ifdef HAVE_BSM 90 #include "bsmaudit.h" 91 #endif /* HAVE_BSM */ 92 93 #ifdef ALTPRIVSEP 94 #include "altprivsep.h" 95 #endif /* ALTPRIVSEP */ 96 97 #ifdef HAVE_SOLARIS_CONTRACTS 98 #include <sys/ctfs.h> 99 #include <sys/contract.h> 100 #include <sys/contract/process.h> 101 #include <libcontract.h> 102 #endif /* HAVE_SOLARIS_CONTRACTS */ 103 104 #ifdef GSSAPI 105 #include "ssh-gss.h" 106 #endif /* GSSAPI */ 107 108 #ifdef LIBWRAP 109 #include <tcpd.h> 110 #include <syslog.h> 111 #ifndef lint 112 int allow_severity = LOG_INFO; 113 int deny_severity = LOG_WARNING; 114 #endif /* lint */ 115 #endif /* LIBWRAP */ 116 117 #ifndef O_NOCTTY 118 #define O_NOCTTY 0 119 #endif 120 121 #ifdef HAVE___PROGNAME 122 extern char *__progname; 123 #else 124 char *__progname; 125 #endif 126 127 /* Server configuration options. */ 128 ServerOptions options; 129 130 /* Name of the server configuration file. */ 131 static char *config_file_name = _PATH_SERVER_CONFIG_FILE; 132 133 /* 134 * Flag indicating whether IPv4 or IPv6. This can be set on the command line. 135 * Default value is AF_UNSPEC means both IPv4 and IPv6. 136 */ 137 #ifdef IPV4_DEFAULT 138 int IPv4or6 = AF_INET; 139 #else 140 int IPv4or6 = AF_UNSPEC; 141 #endif 142 143 /* 144 * Debug mode flag. This can be set on the command line. If debug 145 * mode is enabled, extra debugging output will be sent to the system 146 * log, the daemon will not go to background, and will exit after processing 147 * the first connection. 148 */ 149 int debug_flag = 0; 150 151 /* Flag indicating that the daemon should only test the configuration and keys. */ 152 static int test_flag = 0; 153 154 /* Flag indicating that the daemon is being started from inetd. */ 155 static int inetd_flag = 0; 156 157 /* Flag indicating that sshd should not detach and become a daemon. */ 158 static int no_daemon_flag = 0; 159 160 /* debug goes to stderr unless inetd_flag is set */ 161 int log_stderr = 0; 162 163 /* Saved arguments to main(). */ 164 static char **saved_argv; 165 static int saved_argc; 166 167 /* 168 * The sockets that the server is listening; this is used in the SIGHUP 169 * signal handler. 170 */ 171 #define MAX_LISTEN_SOCKS 16 172 static int listen_socks[MAX_LISTEN_SOCKS]; 173 static int num_listen_socks = 0; 174 175 /* 176 * the client's version string, passed by sshd2 in compat mode. if != NULL, 177 * sshd will skip the version-number exchange 178 */ 179 static char *client_version_string = NULL; 180 static char *server_version_string = NULL; 181 182 /* for rekeying XXX fixme */ 183 Kex *xxx_kex; 184 185 /* 186 * Any really sensitive data in the application is contained in this 187 * structure. The idea is that this structure could be locked into memory so 188 * that the pages do not get written into swap. However, there are some 189 * problems. The private key contains BIGNUMs, and we do not (in principle) 190 * have access to the internals of them, and locking just the structure is 191 * not very useful. Currently, memory locking is not implemented. 192 */ 193 static struct { 194 Key *server_key; /* ephemeral server key */ 195 Key *ssh1_host_key; /* ssh1 host key */ 196 Key **host_keys; /* all private host keys */ 197 int have_ssh1_key; 198 int have_ssh2_key; 199 u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH]; 200 } sensitive_data; 201 202 /* 203 * Flag indicating whether the RSA server key needs to be regenerated. 204 * Is set in the SIGALRM handler and cleared when the key is regenerated. 205 */ 206 static volatile sig_atomic_t key_do_regen = 0; 207 208 /* This is set to true when a signal is received. */ 209 static volatile sig_atomic_t received_sighup = 0; 210 static volatile sig_atomic_t received_sigterm = 0; 211 212 /* session identifier, used by RSA-auth */ 213 u_char session_id[16]; 214 215 /* same for ssh2 */ 216 u_char *session_id2 = NULL; 217 int session_id2_len = 0; 218 219 /* record remote hostname or ip */ 220 u_int utmp_len = MAXHOSTNAMELEN; 221 222 /* options.max_startup sized array of fd ints */ 223 static int *startup_pipes = NULL; 224 static int startup_pipe = -1; /* in child */ 225 226 #ifdef GSSAPI 227 static gss_OID_set mechs = GSS_C_NULL_OID_SET; 228 #endif /* GSSAPI */ 229 230 /* Prototypes for various functions defined later in this file. */ 231 void destroy_sensitive_data(void); 232 static void demote_sensitive_data(void); 233 234 static void do_ssh1_kex(void); 235 static void do_ssh2_kex(void); 236 237 /* 238 * Close all listening sockets 239 */ 240 static void 241 close_listen_socks(void) 242 { 243 int i; 244 245 for (i = 0; i < num_listen_socks; i++) 246 (void) close(listen_socks[i]); 247 num_listen_socks = -1; 248 } 249 250 static void 251 close_startup_pipes(void) 252 { 253 int i; 254 255 if (startup_pipes) 256 for (i = 0; i < options.max_startups; i++) 257 if (startup_pipes[i] != -1) 258 (void) close(startup_pipes[i]); 259 } 260 261 /* 262 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP; 263 * the effect is to reread the configuration file (and to regenerate 264 * the server key). 265 */ 266 static void 267 sighup_handler(int sig) 268 { 269 int save_errno = errno; 270 271 received_sighup = 1; 272 (void) signal(SIGHUP, sighup_handler); 273 errno = save_errno; 274 } 275 276 /* 277 * Called from the main program after receiving SIGHUP. 278 * Restarts the server. 279 */ 280 static void 281 sighup_restart(void) 282 { 283 log("Received SIGHUP; restarting."); 284 close_listen_socks(); 285 close_startup_pipes(); 286 (void) execv(saved_argv[0], saved_argv); 287 log("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], 288 strerror(errno)); 289 exit(1); 290 } 291 292 /* 293 * Generic signal handler for terminating signals in the master daemon. 294 */ 295 static void 296 sigterm_handler(int sig) 297 { 298 received_sigterm = sig; 299 } 300 301 /* 302 * SIGCHLD handler. This is called whenever a child dies. This will then 303 * reap any zombies left by exited children. 304 */ 305 static void 306 main_sigchld_handler(int sig) 307 { 308 int save_errno = errno; 309 pid_t pid; 310 int status; 311 312 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 313 (pid < 0 && errno == EINTR)) 314 ; 315 316 (void) signal(SIGCHLD, main_sigchld_handler); 317 errno = save_errno; 318 } 319 320 /* 321 * Signal handler for the alarm after the login grace period has expired. 322 */ 323 static void 324 grace_alarm_handler(int sig) 325 { 326 /* XXX no idea how fix this signal handler */ 327 328 /* Log error and exit. */ 329 fatal("Timeout before authentication for %s", get_remote_ipaddr()); 330 } 331 332 #ifdef HAVE_SOLARIS_CONTRACTS 333 static int contracts_fd = -1; 334 void 335 contracts_pre_fork() 336 { 337 const char *during = "opening process contract template"; 338 339 /* 340 * Failure should not be treated as fatal on the theory that 341 * it's better to start with children in the same contract as 342 * the master listener than not at all. 343 */ 344 345 if (contracts_fd == -1) { 346 if ((contracts_fd = open64(CTFS_ROOT "/process/template", 347 O_RDWR)) == -1) 348 goto cleanup; 349 350 during = "setting sundry contract terms"; 351 if ((errno = ct_pr_tmpl_set_param(contracts_fd, CT_PR_PGRPONLY))) 352 goto cleanup; 353 354 if ((errno = ct_tmpl_set_informative(contracts_fd, CT_PR_EV_HWERR))) 355 goto cleanup; 356 357 if ((errno = ct_pr_tmpl_set_fatal(contracts_fd, CT_PR_EV_HWERR))) 358 goto cleanup; 359 360 if ((errno = ct_tmpl_set_critical(contracts_fd, 0))) 361 goto cleanup; 362 } 363 364 during = "setting active template"; 365 if ((errno = ct_tmpl_activate(contracts_fd))) 366 goto cleanup; 367 368 debug3("Set active contract"); 369 return; 370 371 cleanup: 372 if (contracts_fd != -1) 373 (void) close(contracts_fd); 374 375 contracts_fd = -1; 376 377 if (errno) 378 debug2("Error while trying to set up active contract" 379 " template: %s while %s", strerror(errno), during); 380 } 381 382 void 383 contracts_post_fork_child() 384 { 385 /* Clear active template so fork() creates no new contracts. */ 386 387 if (contracts_fd == -1) 388 return; 389 390 if ((errno = (ct_tmpl_clear(contracts_fd)))) 391 debug2("Error while trying to clear active contract template" 392 " (child): %s", strerror(errno)); 393 else 394 debug3("Cleared active contract template (child)"); 395 396 (void) close(contracts_fd); 397 398 contracts_fd = -1; 399 } 400 401 void 402 contracts_post_fork_parent(int fork_succeeded) 403 { 404 char path[PATH_MAX]; 405 int cfd, n; 406 ct_stathdl_t st; 407 ctid_t latest; 408 409 /* Clear active template, abandon latest contract. */ 410 if (contracts_fd == -1) 411 return; 412 413 if ((errno = ct_tmpl_clear(contracts_fd))) 414 debug2("Error while clearing active contract template: %s", 415 strerror(errno)); 416 else 417 debug3("Cleared active contract template (parent)"); 418 419 if (!fork_succeeded) 420 return; 421 422 if ((cfd = open64(CTFS_ROOT "/process/latest", O_RDONLY)) == -1) { 423 debug2("Error while getting latest contract: %s", 424 strerror(errno)); 425 return; 426 } 427 428 if ((errno = ct_status_read(cfd, CTD_COMMON, &st)) != 0) { 429 debug2("Error while getting latest contract ID: %s", 430 strerror(errno)); 431 (void) close(cfd); 432 return; 433 } 434 435 latest = ct_status_get_id(st); 436 ct_status_free(st); 437 (void) close(cfd); 438 439 n = snprintf(path, PATH_MAX, CTFS_ROOT "/all/%ld/ctl", latest); 440 441 if (n >= PATH_MAX) { 442 debug2("Error while opening the latest contract ctl file: %s", 443 strerror(ENAMETOOLONG)); 444 return; 445 } 446 447 if ((cfd = open64(path, O_WRONLY)) == -1) { 448 debug2("Error while opening the latest contract ctl file: %s", 449 strerror(errno)); 450 return; 451 } 452 453 if ((errno = ct_ctl_abandon(cfd))) 454 debug2("Error while abandoning latest contract: %s", 455 strerror(errno)); 456 else 457 debug3("Abandoned latest contract"); 458 459 (void) close(cfd); 460 } 461 #endif /* HAVE_SOLARIS_CONTRACTS */ 462 463 /* 464 * Signal handler for the key regeneration alarm. Note that this 465 * alarm only occurs in the daemon waiting for connections, and it does not 466 * do anything with the private key or random state before forking. 467 * Thus there should be no concurrency control/asynchronous execution 468 * problems. 469 */ 470 static void 471 generate_ephemeral_server_key(void) 472 { 473 u_int32_t rnd = 0; 474 int i; 475 476 verbose("Generating %s%d bit RSA key.", 477 sensitive_data.server_key ? "new " : "", options.server_key_bits); 478 if (sensitive_data.server_key != NULL) 479 key_free(sensitive_data.server_key); 480 sensitive_data.server_key = key_generate(KEY_RSA1, 481 options.server_key_bits); 482 verbose("RSA key generation complete."); 483 484 for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) { 485 if (i % 4 == 0) 486 rnd = arc4random(); 487 sensitive_data.ssh1_cookie[i] = rnd & 0xff; 488 rnd >>= 8; 489 } 490 arc4random_stir(); 491 } 492 493 static void 494 key_regeneration_alarm(int sig) 495 { 496 int save_errno = errno; 497 498 (void) signal(SIGALRM, SIG_DFL); 499 errno = save_errno; 500 key_do_regen = 1; 501 } 502 503 static void 504 sshd_exchange_identification(int sock_in, int sock_out) 505 { 506 int i, mismatch; 507 int remote_major, remote_minor; 508 int major, minor; 509 char *s; 510 char buf[256]; /* Must not be larger than remote_version. */ 511 char remote_version[256]; /* Must be at least as big as buf. */ 512 513 if ((options.protocol & SSH_PROTO_1) && 514 (options.protocol & SSH_PROTO_2)) { 515 major = PROTOCOL_MAJOR_1; 516 minor = 99; 517 } else if (options.protocol & SSH_PROTO_2) { 518 major = PROTOCOL_MAJOR_2; 519 minor = PROTOCOL_MINOR_2; 520 } else { 521 major = PROTOCOL_MAJOR_1; 522 minor = PROTOCOL_MINOR_1; 523 } 524 (void) snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION); 525 server_version_string = xstrdup(buf); 526 527 if (client_version_string == NULL) { 528 /* Send our protocol version identification. */ 529 if (atomicio(write, sock_out, server_version_string, 530 strlen(server_version_string)) 531 != strlen(server_version_string)) { 532 log("Could not write ident string to %s", get_remote_ipaddr()); 533 fatal_cleanup(); 534 } 535 536 /* Read other sides version identification. */ 537 (void) memset(buf, 0, sizeof(buf)); 538 for (i = 0; i < sizeof(buf) - 1; i++) { 539 if (atomicio(read, sock_in, &buf[i], 1) != 1) { 540 log("Did not receive identification string from %s", 541 get_remote_ipaddr()); 542 fatal_cleanup(); 543 } 544 if (buf[i] == '\r') { 545 buf[i] = 0; 546 /* Kludge for F-Secure Macintosh < 1.0.2 */ 547 if (i == 12 && 548 strncmp(buf, "SSH-1.5-W1.0", 12) == 0) 549 break; 550 continue; 551 } 552 if (buf[i] == '\n') { 553 buf[i] = 0; 554 break; 555 } 556 } 557 buf[sizeof(buf) - 1] = 0; 558 client_version_string = xstrdup(buf); 559 } 560 561 /* 562 * Check that the versions match. In future this might accept 563 * several versions and set appropriate flags to handle them. 564 */ 565 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n", 566 &remote_major, &remote_minor, remote_version) != 3) { 567 s = "Protocol mismatch.\n"; 568 (void) atomicio(write, sock_out, s, strlen(s)); 569 (void) close(sock_in); 570 (void) close(sock_out); 571 log("Bad protocol version identification '%.100s' from %s", 572 client_version_string, get_remote_ipaddr()); 573 fatal_cleanup(); 574 } 575 debug("Client protocol version %d.%d; client software version %.100s", 576 remote_major, remote_minor, remote_version); 577 578 compat_datafellows(remote_version); 579 580 if (datafellows & SSH_BUG_PROBE) { 581 log("probed from %s with %s. Don't panic.", 582 get_remote_ipaddr(), client_version_string); 583 fatal_cleanup(); 584 } 585 586 if (datafellows & SSH_BUG_SCANNER) { 587 log("scanned from %s with %s. Don't panic.", 588 get_remote_ipaddr(), client_version_string); 589 fatal_cleanup(); 590 } 591 592 mismatch = 0; 593 switch (remote_major) { 594 case 1: 595 if (remote_minor == 99) { 596 if (options.protocol & SSH_PROTO_2) 597 enable_compat20(); 598 else 599 mismatch = 1; 600 break; 601 } 602 if (!(options.protocol & SSH_PROTO_1)) { 603 mismatch = 1; 604 break; 605 } 606 if (remote_minor < 3) { 607 packet_disconnect("Your ssh version is too old and " 608 "is no longer supported. Please install a newer version."); 609 } else if (remote_minor == 3) { 610 /* note that this disables agent-forwarding */ 611 enable_compat13(); 612 } 613 break; 614 case 2: 615 if (options.protocol & SSH_PROTO_2) { 616 enable_compat20(); 617 break; 618 } 619 /* FALLTHROUGH */ 620 default: 621 mismatch = 1; 622 break; 623 } 624 chop(server_version_string); 625 debug("Local version string %.200s", server_version_string); 626 627 if (mismatch) { 628 s = "Protocol major versions differ.\n"; 629 (void) atomicio(write, sock_out, s, strlen(s)); 630 (void) close(sock_in); 631 (void) close(sock_out); 632 log("Protocol major versions differ for %s: %.200s vs. %.200s", 633 get_remote_ipaddr(), 634 server_version_string, client_version_string); 635 fatal_cleanup(); 636 } 637 } 638 639 /* Destroy the host and server keys. They will no longer be needed. */ 640 void 641 destroy_sensitive_data(void) 642 { 643 int i; 644 645 if (sensitive_data.server_key) { 646 key_free(sensitive_data.server_key); 647 sensitive_data.server_key = NULL; 648 } 649 for (i = 0; i < options.num_host_key_files; i++) { 650 if (sensitive_data.host_keys[i]) { 651 key_free(sensitive_data.host_keys[i]); 652 sensitive_data.host_keys[i] = NULL; 653 } 654 } 655 sensitive_data.ssh1_host_key = NULL; 656 (void) memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH); 657 } 658 659 /* Demote private to public keys for network child */ 660 static void 661 demote_sensitive_data(void) 662 { 663 Key *tmp; 664 int i; 665 666 if (sensitive_data.server_key) { 667 tmp = key_demote(sensitive_data.server_key); 668 key_free(sensitive_data.server_key); 669 sensitive_data.server_key = tmp; 670 } 671 672 for (i = 0; i < options.num_host_key_files; i++) { 673 if (sensitive_data.host_keys[i]) { 674 tmp = key_demote(sensitive_data.host_keys[i]); 675 key_free(sensitive_data.host_keys[i]); 676 sensitive_data.host_keys[i] = tmp; 677 if (tmp->type == KEY_RSA1) 678 sensitive_data.ssh1_host_key = tmp; 679 } 680 } 681 682 /* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */ 683 } 684 685 static char * 686 list_hostkey_types(void) 687 { 688 Buffer b; 689 char *p; 690 int i; 691 692 buffer_init(&b); 693 for (i = 0; i < options.num_host_key_files; i++) { 694 Key *key = sensitive_data.host_keys[i]; 695 if (key == NULL) 696 continue; 697 switch (key->type) { 698 case KEY_RSA: 699 case KEY_DSA: 700 if (buffer_len(&b) > 0) 701 buffer_append(&b, ",", 1); 702 p = key_ssh_name(key); 703 buffer_append(&b, p, strlen(p)); 704 break; 705 } 706 } 707 buffer_append(&b, "\0", 1); 708 p = xstrdup(buffer_ptr(&b)); 709 buffer_free(&b); 710 debug("list_hostkey_types: %s", p); 711 return p; 712 } 713 714 #ifdef lint 715 static 716 #endif /* lint */ 717 Key * 718 get_hostkey_by_type(int type) 719 { 720 int i; 721 722 for (i = 0; i < options.num_host_key_files; i++) { 723 Key *key = sensitive_data.host_keys[i]; 724 if (key != NULL && key->type == type) 725 return key; 726 } 727 return NULL; 728 } 729 730 #ifdef lint 731 static 732 #endif /* lint */ 733 Key * 734 get_hostkey_by_index(int ind) 735 { 736 if (ind < 0 || ind >= options.num_host_key_files) 737 return (NULL); 738 return (sensitive_data.host_keys[ind]); 739 } 740 741 #ifdef lint 742 static 743 #endif /* lint */ 744 int 745 get_hostkey_index(Key *key) 746 { 747 int i; 748 749 for (i = 0; i < options.num_host_key_files; i++) { 750 if (key == sensitive_data.host_keys[i]) 751 return (i); 752 } 753 return (-1); 754 } 755 756 /* 757 * returns 1 if connection should be dropped, 0 otherwise. 758 * dropping starts at connection #max_startups_begin with a probability 759 * of (max_startups_rate/100). the probability increases linearly until 760 * all connections are dropped for startups > max_startups 761 */ 762 static int 763 drop_connection(int startups) 764 { 765 double p, r; 766 767 if (startups < options.max_startups_begin) 768 return 0; 769 if (startups >= options.max_startups) 770 return 1; 771 if (options.max_startups_rate == 100) 772 return 1; 773 774 p = 100 - options.max_startups_rate; 775 p *= startups - options.max_startups_begin; 776 p /= (double) (options.max_startups - options.max_startups_begin); 777 p += options.max_startups_rate; 778 p /= 100.0; 779 r = arc4random() / (double) UINT_MAX; 780 781 debug("drop_connection: p %g, r %g", p, r); 782 return (r < p) ? 1 : 0; 783 } 784 785 static void 786 usage(void) 787 { 788 (void) fprintf(stderr, gettext("sshd version %s\n"), SSH_VERSION); 789 (void) fprintf(stderr, 790 gettext("Usage: %s [options]\n" 791 "Options:\n" 792 " -f file Configuration file (default %s)\n" 793 " -d Debugging mode (multiple -d means more " 794 "debugging)\n" 795 " -i Started from inetd\n" 796 " -D Do not fork into daemon mode\n" 797 " -t Only test configuration file and keys\n" 798 " -q Quiet (no logging)\n" 799 " -p port Listen on the specified port (default: 22)\n" 800 " -k seconds Regenerate server key every this many seconds " 801 "(default: 3600)\n" 802 " -g seconds Grace period for authentication (default: 600)\n" 803 " -b bits Size of server RSA key (default: 768 bits)\n" 804 " -h file File from which to read host key (default: %s)\n" 805 " -4 Use IPv4 only\n" 806 " -6 Use IPv6 only\n" 807 " -o option Process the option as if it was read from " 808 "a configuration file.\n"), 809 __progname, _PATH_SERVER_CONFIG_FILE, _PATH_HOST_KEY_FILE); 810 exit(1); 811 } 812 813 /* 814 * Main program for the daemon. 815 */ 816 int 817 main(int ac, char **av) 818 { 819 extern char *optarg; 820 extern int optind; 821 int opt, j, i, fdsetsz, sock_in = 0, sock_out = 0, newsock = -1, on = 1; 822 pid_t pid; 823 socklen_t fromlen; 824 fd_set *fdset; 825 struct sockaddr_storage from; 826 const char *remote_ip; 827 int remote_port; 828 FILE *f; 829 struct addrinfo *ai; 830 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 831 int listen_sock, maxfd; 832 int startup_p[2]; 833 int startups = 0; 834 Authctxt *authctxt = NULL; 835 Key *key; 836 int ret, key_used = 0; 837 #ifdef HAVE_BSM 838 au_id_t auid = AU_NOAUDITID; 839 #endif /* HAVE_BSM */ 840 int mpipe; 841 842 __progname = get_progname(av[0]); 843 844 (void) g11n_setlocale(LC_ALL, ""); 845 846 init_rng(); 847 848 /* Save argv. */ 849 saved_argc = ac; 850 saved_argv = av; 851 852 /* Initialize configuration options to their default values. */ 853 initialize_server_options(&options); 854 855 /* Parse command-line arguments. */ 856 while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:o:dDeiqtQ46")) != -1) { 857 switch (opt) { 858 case '4': 859 IPv4or6 = AF_INET; 860 break; 861 case '6': 862 IPv4or6 = AF_INET6; 863 break; 864 case 'f': 865 config_file_name = optarg; 866 break; 867 case 'd': 868 if (0 == debug_flag) { 869 debug_flag = 1; 870 options.log_level = SYSLOG_LEVEL_DEBUG1; 871 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) { 872 options.log_level++; 873 } else { 874 (void) fprintf(stderr, 875 gettext("Debug level too high.\n")); 876 exit(1); 877 } 878 break; 879 case 'D': 880 no_daemon_flag = 1; 881 break; 882 case 'e': 883 log_stderr = 1; 884 break; 885 case 'i': 886 inetd_flag = 1; 887 break; 888 case 'Q': 889 /* ignored */ 890 break; 891 case 'q': 892 options.log_level = SYSLOG_LEVEL_QUIET; 893 break; 894 case 'b': 895 options.server_key_bits = atoi(optarg); 896 break; 897 case 'p': 898 options.ports_from_cmdline = 1; 899 if (options.num_ports >= MAX_PORTS) { 900 (void) fprintf(stderr, gettext("too many ports.\n")); 901 exit(1); 902 } 903 options.ports[options.num_ports++] = a2port(optarg); 904 if (options.ports[options.num_ports-1] == 0) { 905 (void) fprintf(stderr, gettext("Bad port number.\n")); 906 exit(1); 907 } 908 break; 909 case 'g': 910 if ((options.login_grace_time = convtime(optarg)) == -1) { 911 (void) fprintf(stderr, 912 gettext("Invalid login grace time.\n")); 913 exit(1); 914 } 915 break; 916 case 'k': 917 if ((options.key_regeneration_time = convtime(optarg)) == -1) { 918 (void) fprintf(stderr, 919 gettext("Invalid key regeneration " 920 "interval.\n")); 921 exit(1); 922 } 923 break; 924 case 'h': 925 if (options.num_host_key_files >= MAX_HOSTKEYS) { 926 (void) fprintf(stderr, 927 gettext("too many host keys.\n")); 928 exit(1); 929 } 930 options.host_key_files[options.num_host_key_files++] = optarg; 931 break; 932 case 'V': 933 client_version_string = optarg; 934 /* only makes sense with inetd_flag, i.e. no listen() */ 935 inetd_flag = 1; 936 break; 937 case 't': 938 test_flag = 1; 939 break; 940 case 'o': 941 if (process_server_config_line(&options, optarg, 942 "command-line", 0) != 0) 943 exit(1); 944 break; 945 case '?': 946 default: 947 usage(); 948 break; 949 } 950 } 951 952 /* 953 * There is no need to use the PKCS#11 engine in the master SSH process. 954 */ 955 SSLeay_add_all_algorithms(); 956 seed_rng(); 957 channel_set_af(IPv4or6); 958 959 /* 960 * Force logging to stderr until we have loaded the private host 961 * key (unless started from inetd) 962 */ 963 log_init(__progname, 964 options.log_level == SYSLOG_LEVEL_NOT_SET ? 965 SYSLOG_LEVEL_INFO : options.log_level, 966 options.log_facility == SYSLOG_FACILITY_NOT_SET ? 967 SYSLOG_FACILITY_AUTH : options.log_facility, 968 !inetd_flag); 969 970 #ifdef _UNICOS 971 /* Cray can define user privs drop all prives now! 972 * Not needed on PRIV_SU systems! 973 */ 974 drop_cray_privs(); 975 #endif 976 977 /* Read server configuration options from the configuration file. */ 978 read_server_config(&options, config_file_name); 979 980 /* Fill in default values for those options not explicitly set. */ 981 fill_default_server_options(&options); 982 983 utmp_len = options.lookup_client_hostnames ? utmp_len : 0; 984 985 /* Check that there are no remaining arguments. */ 986 if (optind < ac) { 987 (void) fprintf(stderr, gettext("Extra argument %s.\n"), av[optind]); 988 exit(1); 989 } 990 991 debug("sshd version %.100s", SSH_VERSION); 992 993 /* load private host keys */ 994 if (options.num_host_key_files > 0) 995 sensitive_data.host_keys = 996 xmalloc(options.num_host_key_files * sizeof(Key *)); 997 for (i = 0; i < options.num_host_key_files; i++) 998 sensitive_data.host_keys[i] = NULL; 999 sensitive_data.server_key = NULL; 1000 sensitive_data.ssh1_host_key = NULL; 1001 sensitive_data.have_ssh1_key = 0; 1002 sensitive_data.have_ssh2_key = 0; 1003 1004 for (i = 0; i < options.num_host_key_files; i++) { 1005 key = key_load_private(options.host_key_files[i], "", NULL); 1006 sensitive_data.host_keys[i] = key; 1007 if (key == NULL) { 1008 error("Could not load host key: %s", 1009 options.host_key_files[i]); 1010 sensitive_data.host_keys[i] = NULL; 1011 continue; 1012 } 1013 switch (key->type) { 1014 case KEY_RSA1: 1015 sensitive_data.ssh1_host_key = key; 1016 sensitive_data.have_ssh1_key = 1; 1017 break; 1018 case KEY_RSA: 1019 case KEY_DSA: 1020 sensitive_data.have_ssh2_key = 1; 1021 break; 1022 } 1023 debug("private host key: #%d type %d %s", i, key->type, 1024 key_type(key)); 1025 } 1026 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) { 1027 log("Disabling protocol version 1. Could not load host key"); 1028 options.protocol &= ~SSH_PROTO_1; 1029 } 1030 if ((options.protocol & SSH_PROTO_2) && 1031 !sensitive_data.have_ssh2_key) { 1032 #ifdef GSSAPI 1033 if (options.gss_keyex) 1034 ssh_gssapi_server_mechs(&mechs); 1035 1036 if (mechs == GSS_C_NULL_OID_SET) { 1037 log("Disabling protocol version 2. Could not load host" 1038 "key or GSS-API mechanisms"); 1039 options.protocol &= ~SSH_PROTO_2; 1040 } 1041 #else 1042 log("Disabling protocol version 2. Could not load host key"); 1043 options.protocol &= ~SSH_PROTO_2; 1044 #endif /* GSSAPI */ 1045 } 1046 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) { 1047 log("sshd: no hostkeys available -- exiting."); 1048 exit(1); 1049 } 1050 1051 /* Check certain values for sanity. */ 1052 if (options.protocol & SSH_PROTO_1) { 1053 if (options.server_key_bits < 512 || 1054 options.server_key_bits > 32768) { 1055 (void) fprintf(stderr, gettext("Bad server key size.\n")); 1056 exit(1); 1057 } 1058 /* 1059 * Check that server and host key lengths differ sufficiently. This 1060 * is necessary to make double encryption work with rsaref. Oh, I 1061 * hate software patents. I dont know if this can go? Niels 1062 */ 1063 if (options.server_key_bits > 1064 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - 1065 SSH_KEY_BITS_RESERVED && options.server_key_bits < 1066 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + 1067 SSH_KEY_BITS_RESERVED) { 1068 options.server_key_bits = 1069 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + 1070 SSH_KEY_BITS_RESERVED; 1071 debug("Forcing server key to %d bits to make it differ from host key.", 1072 options.server_key_bits); 1073 } 1074 } 1075 1076 /* Configuration looks good, so exit if in test mode. */ 1077 if (test_flag) 1078 exit(0); 1079 1080 /* 1081 * Clear out any supplemental groups we may have inherited. This 1082 * prevents inadvertent creation of files with bad modes (in the 1083 * portable version at least, it's certainly possible for PAM 1084 * to create a file, and we can't control the code in every 1085 * module which might be used). 1086 */ 1087 if (setgroups(0, NULL) < 0) 1088 debug("setgroups() failed: %.200s", strerror(errno)); 1089 1090 /* Initialize the log (it is reinitialized below in case we forked). */ 1091 if (debug_flag && !inetd_flag) 1092 log_stderr = 1; 1093 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1094 1095 /* 1096 * Solaris 9 and systems upgraded from it may have the Ciphers option 1097 * explicitly set to "aes128-cbc,blowfish-cbc,3des-cbc" in the 1098 * sshd_config. Since the default server cipher list completely changed 1099 * since then we rather notify the administator on startup. We do this 1100 * check after log_init() so that the message goes to syslogd and not to 1101 * stderr (unless the server is in the debug mode). Note that since 1102 * Solaris 10 we no longer ship sshd_config with explicit settings for 1103 * Ciphers or MACs. Do not try to augment the cipher list here since 1104 * that might end up in a very confusing situation. 1105 */ 1106 #define OLD_DEFAULT_CIPHERS_LIST "aes128-cbc,blowfish-cbc,3des-cbc" 1107 if (options.ciphers != NULL && 1108 strcmp(options.ciphers, OLD_DEFAULT_CIPHERS_LIST) == 0) { 1109 notice("Old default value \"%s\" for the \"Ciphers\" " 1110 "option found in use. In general it is prudent to let " 1111 "the server choose the defaults unless your environment " 1112 "specifically needs an explicit setting. See " 1113 "sshd_config(4) for more information.", 1114 OLD_DEFAULT_CIPHERS_LIST); 1115 } 1116 1117 #ifdef HAVE_BSM 1118 (void) setauid(&auid); 1119 #endif /* HAVE_BSM */ 1120 1121 /* 1122 * If not in debugging mode, and not started from inetd, disconnect 1123 * from the controlling terminal, and fork. The original process 1124 * exits. 1125 */ 1126 if (!(debug_flag || inetd_flag || no_daemon_flag)) { 1127 #ifdef TIOCNOTTY 1128 int fd; 1129 #endif /* TIOCNOTTY */ 1130 if (daemon(0, 0) < 0) 1131 fatal("daemon() failed: %.200s", strerror(errno)); 1132 1133 /* Disconnect from the controlling tty. */ 1134 #ifdef TIOCNOTTY 1135 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 1136 if (fd >= 0) { 1137 (void) ioctl(fd, TIOCNOTTY, NULL); 1138 (void) close(fd); 1139 } 1140 #endif /* TIOCNOTTY */ 1141 } 1142 /* Reinitialize the log (because of the fork above). */ 1143 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1144 1145 /* Initialize the random number generator. */ 1146 arc4random_stir(); 1147 1148 /* Chdir to the root directory so that the current disk can be 1149 unmounted if desired. */ 1150 (void) chdir("/"); 1151 1152 /* ignore SIGPIPE */ 1153 (void) signal(SIGPIPE, SIG_IGN); 1154 1155 /* Start listening for a socket, unless started from inetd. */ 1156 if (inetd_flag) { 1157 int s1; 1158 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */ 1159 (void) dup(s1); 1160 sock_in = dup(0); 1161 sock_out = dup(1); 1162 startup_pipe = -1; 1163 /* we need this later for setting audit context */ 1164 newsock = sock_in; 1165 /* 1166 * We intentionally do not close the descriptors 0, 1, and 2 1167 * as our code for setting the descriptors won\'t work if 1168 * ttyfd happens to be one of those. 1169 */ 1170 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out); 1171 if (options.protocol & SSH_PROTO_1) 1172 generate_ephemeral_server_key(); 1173 } else { 1174 for (ai = options.listen_addrs; ai; ai = ai->ai_next) { 1175 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 1176 continue; 1177 if (num_listen_socks >= MAX_LISTEN_SOCKS) 1178 fatal("Too many listen sockets. " 1179 "Enlarge MAX_LISTEN_SOCKS"); 1180 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 1181 ntop, sizeof(ntop), strport, sizeof(strport), 1182 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 1183 error("getnameinfo failed"); 1184 continue; 1185 } 1186 /* Create socket for listening. */ 1187 listen_sock = socket(ai->ai_family, SOCK_STREAM, 0); 1188 if (listen_sock < 0) { 1189 /* kernel may not support ipv6 */ 1190 verbose("socket: %.100s", strerror(errno)); 1191 continue; 1192 } 1193 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) { 1194 error("listen_sock O_NONBLOCK: %s", strerror(errno)); 1195 (void) close(listen_sock); 1196 continue; 1197 } 1198 /* 1199 * Set socket options. 1200 * Allow local port reuse in TIME_WAIT. 1201 */ 1202 if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR, 1203 &on, sizeof(on)) == -1) 1204 error("setsockopt SO_REUSEADDR: %s", strerror(errno)); 1205 1206 debug("Bind to port %s on %s.", strport, ntop); 1207 1208 /* Bind the socket to the desired port. */ 1209 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) { 1210 if (!ai->ai_next) 1211 error("Bind to port %s on %s failed: %.200s.", 1212 strport, ntop, strerror(errno)); 1213 (void) close(listen_sock); 1214 continue; 1215 } 1216 listen_socks[num_listen_socks] = listen_sock; 1217 num_listen_socks++; 1218 1219 /* Start listening on the port. */ 1220 log("Server listening on %s port %s.", ntop, strport); 1221 if (listen(listen_sock, 5) < 0) 1222 fatal("listen: %.100s", strerror(errno)); 1223 1224 } 1225 freeaddrinfo(options.listen_addrs); 1226 1227 if (!num_listen_socks) 1228 fatal("Cannot bind any address."); 1229 1230 if (options.protocol & SSH_PROTO_1) 1231 generate_ephemeral_server_key(); 1232 1233 /* 1234 * Arrange to restart on SIGHUP. The handler needs 1235 * listen_sock. 1236 */ 1237 (void) signal(SIGHUP, sighup_handler); 1238 1239 (void) signal(SIGTERM, sigterm_handler); 1240 (void) signal(SIGQUIT, sigterm_handler); 1241 1242 /* Arrange SIGCHLD to be caught. */ 1243 (void) signal(SIGCHLD, main_sigchld_handler); 1244 1245 /* Write out the pid file after the sigterm handler is setup */ 1246 if (!debug_flag) { 1247 /* 1248 * Record our pid in /var/run/sshd.pid to make it 1249 * easier to kill the correct sshd. We don't want to 1250 * do this before the bind above because the bind will 1251 * fail if there already is a daemon, and this will 1252 * overwrite any old pid in the file. 1253 */ 1254 f = fopen(options.pid_file, "wb"); 1255 if (f) { 1256 (void) fprintf(f, "%ld\n", (long) getpid()); 1257 (void) fclose(f); 1258 } 1259 } 1260 1261 /* setup fd set for listen */ 1262 fdset = NULL; 1263 maxfd = 0; 1264 for (i = 0; i < num_listen_socks; i++) 1265 if (listen_socks[i] > maxfd) 1266 maxfd = listen_socks[i]; 1267 /* pipes connected to unauthenticated childs */ 1268 startup_pipes = xmalloc(options.max_startups * sizeof(int)); 1269 for (i = 0; i < options.max_startups; i++) 1270 startup_pipes[i] = -1; 1271 1272 /* 1273 * Stay listening for connections until the system crashes or 1274 * the daemon is killed with a signal. 1275 */ 1276 for (;;) { 1277 if (received_sighup) 1278 sighup_restart(); 1279 if (fdset != NULL) 1280 xfree(fdset); 1281 fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask); 1282 fdset = (fd_set *)xmalloc(fdsetsz); 1283 (void) memset(fdset, 0, fdsetsz); 1284 1285 for (i = 0; i < num_listen_socks; i++) 1286 FD_SET(listen_socks[i], fdset); 1287 for (i = 0; i < options.max_startups; i++) 1288 if (startup_pipes[i] != -1) 1289 FD_SET(startup_pipes[i], fdset); 1290 1291 /* Wait in select until there is a connection. */ 1292 ret = select(maxfd+1, fdset, NULL, NULL, NULL); 1293 if (ret < 0 && errno != EINTR) 1294 error("select: %.100s", strerror(errno)); 1295 if (received_sigterm) { 1296 log("Received signal %d; terminating.", 1297 (int) received_sigterm); 1298 close_listen_socks(); 1299 (void) unlink(options.pid_file); 1300 exit(255); 1301 } 1302 if (key_used && key_do_regen) { 1303 generate_ephemeral_server_key(); 1304 key_used = 0; 1305 key_do_regen = 0; 1306 } 1307 if (ret < 0) 1308 continue; 1309 1310 for (i = 0; i < options.max_startups; i++) 1311 if (startup_pipes[i] != -1 && 1312 FD_ISSET(startup_pipes[i], fdset)) { 1313 /* 1314 * the read end of the pipe is ready 1315 * if the child has closed the pipe 1316 * after successful authentication 1317 * or if the child has died 1318 */ 1319 (void) close(startup_pipes[i]); 1320 startup_pipes[i] = -1; 1321 startups--; 1322 } 1323 for (i = 0; i < num_listen_socks; i++) { 1324 if (!FD_ISSET(listen_socks[i], fdset)) 1325 continue; 1326 fromlen = sizeof(from); 1327 newsock = accept(listen_socks[i], (struct sockaddr *)&from, 1328 &fromlen); 1329 if (newsock < 0) { 1330 if (errno != EINTR && errno != EWOULDBLOCK) 1331 error("accept: %.100s", strerror(errno)); 1332 continue; 1333 } 1334 if (fcntl(newsock, F_SETFL, 0) < 0) { 1335 error("newsock del O_NONBLOCK: %s", strerror(errno)); 1336 (void) close(newsock); 1337 continue; 1338 } 1339 if (drop_connection(startups) == 1) { 1340 debug("drop connection #%d", startups); 1341 (void) close(newsock); 1342 continue; 1343 } 1344 if (pipe(startup_p) == -1) { 1345 (void) close(newsock); 1346 continue; 1347 } 1348 1349 for (j = 0; j < options.max_startups; j++) 1350 if (startup_pipes[j] == -1) { 1351 startup_pipes[j] = startup_p[0]; 1352 if (maxfd < startup_p[0]) 1353 maxfd = startup_p[0]; 1354 startups++; 1355 break; 1356 } 1357 1358 /* 1359 * Got connection. Fork a child to handle it, unless 1360 * we are in debugging mode. 1361 */ 1362 if (debug_flag) { 1363 /* 1364 * In debugging mode. Close the listening 1365 * socket, and start processing the 1366 * connection without forking. 1367 */ 1368 debug("Server will not fork when running in debugging mode."); 1369 close_listen_socks(); 1370 sock_in = newsock; 1371 sock_out = newsock; 1372 startup_pipe = -1; 1373 pid = getpid(); 1374 break; 1375 } else { 1376 /* 1377 * Normal production daemon. Fork, and have 1378 * the child process the connection. The 1379 * parent continues listening. 1380 */ 1381 #ifdef HAVE_SOLARIS_CONTRACTS 1382 /* 1383 * Setup Solaris contract template so 1384 * the child process is in a different 1385 * process contract than the parent; 1386 * prevents established connections from 1387 * being killed when the sshd master 1388 * listener service is stopped. 1389 */ 1390 contracts_pre_fork(); 1391 #endif /* HAVE_SOLARIS_CONTRACTS */ 1392 if ((pid = fork()) == 0) { 1393 /* 1394 * Child. Close the listening and max_startup 1395 * sockets. Start using the accepted socket. 1396 * Reinitialize logging (since our pid has 1397 * changed). We break out of the loop to handle 1398 * the connection. 1399 */ 1400 #ifdef HAVE_SOLARIS_CONTRACTS 1401 contracts_post_fork_child(); 1402 #endif /* HAVE_SOLARIS_CONTRACTS */ 1403 xfree(fdset); 1404 startup_pipe = startup_p[1]; 1405 close_startup_pipes(); 1406 close_listen_socks(); 1407 sock_in = newsock; 1408 sock_out = newsock; 1409 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1410 break; 1411 } 1412 1413 #ifdef HAVE_SOLARIS_CONTRACTS 1414 contracts_post_fork_parent((pid > 0)); 1415 #endif /* HAVE_SOLARIS_CONTRACTS */ 1416 } 1417 1418 /* Parent. Stay in the loop. */ 1419 if (pid < 0) 1420 error("fork: %.100s", strerror(errno)); 1421 else 1422 debug("Forked child %ld.", (long)pid); 1423 1424 (void) close(startup_p[1]); 1425 1426 /* Mark that the key has been used (it was "given" to the child). */ 1427 if ((options.protocol & SSH_PROTO_1) && 1428 key_used == 0) { 1429 /* Schedule server key regeneration alarm. */ 1430 (void) signal(SIGALRM, key_regeneration_alarm); 1431 (void) alarm(options.key_regeneration_time); 1432 key_used = 1; 1433 } 1434 1435 arc4random_stir(); 1436 1437 /* 1438 * Close the accepted socket since the child 1439 * will now take care of the new connection. 1440 */ 1441 (void) close(newsock); 1442 } 1443 /* child process check (or debug mode) */ 1444 if (num_listen_socks < 0) 1445 break; 1446 } 1447 } 1448 1449 /* 1450 * This is the child processing a new connection, the SSH master process 1451 * stays in the ( ; ; ) loop above. 1452 */ 1453 #ifdef HAVE_BSM 1454 audit_sshd_settid(newsock); 1455 #endif 1456 /* 1457 * Create a new session and process group since the 4.4BSD 1458 * setlogin() affects the entire process group. We don't 1459 * want the child to be able to affect the parent. 1460 */ 1461 #if 0 1462 /* XXX: this breaks Solaris */ 1463 if (!debug_flag && !inetd_flag && setsid() < 0) 1464 error("setsid: %.100s", strerror(errno)); 1465 #endif 1466 1467 /* 1468 * Disable the key regeneration alarm. We will not regenerate the 1469 * key since we are no longer in a position to give it to anyone. We 1470 * will not restart on SIGHUP since it no longer makes sense. 1471 */ 1472 (void) alarm(0); 1473 (void) signal(SIGALRM, SIG_DFL); 1474 (void) signal(SIGHUP, SIG_DFL); 1475 (void) signal(SIGTERM, SIG_DFL); 1476 (void) signal(SIGQUIT, SIG_DFL); 1477 (void) signal(SIGCHLD, SIG_DFL); 1478 (void) signal(SIGINT, SIG_DFL); 1479 1480 /* Set keepalives if requested. */ 1481 if (options.keepalives && 1482 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, 1483 sizeof(on)) < 0) 1484 debug2("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 1485 1486 /* 1487 * Register our connection. This turns encryption off because we do 1488 * not have a key. 1489 */ 1490 packet_set_connection(sock_in, sock_out); 1491 1492 remote_port = get_remote_port(); 1493 remote_ip = get_remote_ipaddr(); 1494 1495 #ifdef LIBWRAP 1496 /* Check whether logins are denied from this host. */ 1497 { 1498 struct request_info req; 1499 1500 (void) request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0); 1501 fromhost(&req); 1502 1503 if (!hosts_access(&req)) { 1504 debug("Connection refused by tcp wrapper"); 1505 refuse(&req); 1506 /* NOTREACHED */ 1507 fatal("libwrap refuse returns"); 1508 } 1509 } 1510 #endif /* LIBWRAP */ 1511 1512 /* Log the connection. */ 1513 verbose("Connection from %.500s port %d", remote_ip, remote_port); 1514 1515 /* 1516 * We don\'t want to listen forever unless the other side 1517 * successfully authenticates itself. So we set up an alarm which is 1518 * cleared after successful authentication. A limit of zero 1519 * indicates no limit. Note that we don\'t set the alarm in debugging 1520 * mode; it is just annoying to have the server exit just when you 1521 * are about to discover the bug. 1522 */ 1523 (void) signal(SIGALRM, grace_alarm_handler); 1524 if (!debug_flag) 1525 (void) alarm(options.login_grace_time); 1526 1527 sshd_exchange_identification(sock_in, sock_out); 1528 /* 1529 * Check that the connection comes from a privileged port. 1530 * Rhosts-Authentication only makes sense from privileged 1531 * programs. Of course, if the intruder has root access on his local 1532 * machine, he can connect from any port. So do not use these 1533 * authentication methods from machines that you do not trust. 1534 */ 1535 if (options.rhosts_authentication && 1536 (remote_port >= IPPORT_RESERVED || 1537 remote_port < IPPORT_RESERVED / 2)) { 1538 debug("Rhosts Authentication disabled, " 1539 "originating port %d not trusted.", remote_port); 1540 options.rhosts_authentication = 0; 1541 } 1542 #if defined(KRB4) && !defined(KRB5) 1543 if (!packet_connection_is_ipv4() && 1544 options.kerberos_authentication) { 1545 debug("Kerberos Authentication disabled, only available for IPv4."); 1546 options.kerberos_authentication = 0; 1547 } 1548 #endif /* KRB4 && !KRB5 */ 1549 #ifdef AFS 1550 /* If machine has AFS, set process authentication group. */ 1551 if (k_hasafs()) { 1552 k_setpag(); 1553 k_unlog(); 1554 } 1555 #endif /* AFS */ 1556 1557 packet_set_nonblocking(); 1558 1559 /* 1560 * Start the monitor. That way both processes will have their own 1561 * PKCS#11 sessions. See the PKCS#11 standard for more information on 1562 * fork safety and packet.c for information about forking with the 1563 * engine. 1564 */ 1565 altprivsep_start_and_do_monitor(options.use_openssl_engine, 1566 inetd_flag, newsock, startup_pipe); 1567 1568 /* 1569 * The child is about to start the first key exchange while the monitor 1570 * stays in altprivsep_start_and_do_monitor() function. 1571 */ 1572 (void) pkcs11_engine_load(options.use_openssl_engine); 1573 1574 /* perform the key exchange */ 1575 /* authenticate user and start session */ 1576 if (compat20) { 1577 do_ssh2_kex(); 1578 authctxt = do_authentication2(); 1579 } else { 1580 do_ssh1_kex(); 1581 authctxt = do_authentication(); 1582 } 1583 1584 authenticated: 1585 /* Authentication complete */ 1586 (void) alarm(0); 1587 /* we no longer need an alarm handler */ 1588 (void) signal(SIGALRM, SIG_DFL); 1589 1590 if (startup_pipe != -1) { 1591 (void) close(startup_pipe); 1592 startup_pipe = -1; 1593 } 1594 1595 /* ALTPRIVSEP Child */ 1596 1597 /* 1598 * Drop privileges, access to privileged resources. 1599 * 1600 * Destroy private host keys, if any. 1601 * 1602 * No need to release any GSS credentials -- sshd only acquires 1603 * creds to determine what mechs it can negotiate then releases 1604 * them right away and uses GSS_C_NO_CREDENTIAL to accept 1605 * contexts. 1606 */ 1607 debug2("Unprivileged server process dropping privileges"); 1608 permanently_set_uid(authctxt->pw, options.chroot_directory); 1609 destroy_sensitive_data(); 1610 1611 /* Just another safety check. */ 1612 if (getuid() != authctxt->pw->pw_uid || 1613 geteuid() != authctxt->pw->pw_uid) { 1614 fatal("Failed to set uids to %u.", (u_int)authctxt->pw->pw_uid); 1615 } 1616 1617 ssh_gssapi_server_mechs(NULL); /* release cached mechs list */ 1618 packet_set_server(); 1619 1620 /* now send the authentication context to the monitor */ 1621 altprivsep_send_auth_context(authctxt); 1622 1623 mpipe = altprivsep_get_pipe_fd(); 1624 if (fcntl(mpipe, F_SETFL, O_NONBLOCK) < 0) 1625 error("fcntl O_NONBLOCK: %.100s", strerror(errno)); 1626 1627 #ifdef HAVE_BSM 1628 fatal_remove_cleanup( 1629 (void (*)(void *))audit_failed_login_cleanup, 1630 (void *)authctxt); 1631 #endif /* HAVE_BSM */ 1632 1633 if (compat20) { 1634 debug3("setting handler to forward re-key packets to the monitor"); 1635 dispatch_range(SSH2_MSG_KEXINIT, SSH2_MSG_TRANSPORT_MAX, 1636 &altprivsep_rekey); 1637 } 1638 1639 /* Logged-in session. */ 1640 do_authenticated(authctxt); 1641 1642 /* The connection has been terminated. */ 1643 verbose("Closing connection to %.100s", remote_ip); 1644 1645 packet_close(); 1646 1647 #ifdef USE_PAM 1648 finish_pam(authctxt); 1649 #endif /* USE_PAM */ 1650 1651 return (0); 1652 } 1653 1654 /* 1655 * Decrypt session_key_int using our private server key and private host key 1656 * (key with larger modulus first). 1657 */ 1658 int 1659 ssh1_session_key(BIGNUM *session_key_int) 1660 { 1661 int rsafail = 0; 1662 1663 if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) { 1664 /* Server key has bigger modulus. */ 1665 if (BN_num_bits(sensitive_data.server_key->rsa->n) < 1666 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) { 1667 fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d", 1668 get_remote_ipaddr(), 1669 BN_num_bits(sensitive_data.server_key->rsa->n), 1670 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n), 1671 SSH_KEY_BITS_RESERVED); 1672 } 1673 if (rsa_private_decrypt(session_key_int, session_key_int, 1674 sensitive_data.server_key->rsa) <= 0) 1675 rsafail++; 1676 if (rsa_private_decrypt(session_key_int, session_key_int, 1677 sensitive_data.ssh1_host_key->rsa) <= 0) 1678 rsafail++; 1679 } else { 1680 /* Host key has bigger modulus (or they are equal). */ 1681 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) < 1682 BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) { 1683 fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d", 1684 get_remote_ipaddr(), 1685 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n), 1686 BN_num_bits(sensitive_data.server_key->rsa->n), 1687 SSH_KEY_BITS_RESERVED); 1688 } 1689 if (rsa_private_decrypt(session_key_int, session_key_int, 1690 sensitive_data.ssh1_host_key->rsa) < 0) 1691 rsafail++; 1692 if (rsa_private_decrypt(session_key_int, session_key_int, 1693 sensitive_data.server_key->rsa) < 0) 1694 rsafail++; 1695 } 1696 return (rsafail); 1697 } 1698 /* 1699 * SSH1 key exchange 1700 */ 1701 static void 1702 do_ssh1_kex(void) 1703 { 1704 int i, len; 1705 int rsafail = 0; 1706 BIGNUM *session_key_int; 1707 u_char session_key[SSH_SESSION_KEY_LENGTH]; 1708 u_char cookie[8]; 1709 u_int cipher_type, auth_mask, protocol_flags; 1710 u_int32_t rnd = 0; 1711 1712 /* 1713 * Generate check bytes that the client must send back in the user 1714 * packet in order for it to be accepted; this is used to defy ip 1715 * spoofing attacks. Note that this only works against somebody 1716 * doing IP spoofing from a remote machine; any machine on the local 1717 * network can still see outgoing packets and catch the random 1718 * cookie. This only affects rhosts authentication, and this is one 1719 * of the reasons why it is inherently insecure. 1720 */ 1721 for (i = 0; i < 8; i++) { 1722 if (i % 4 == 0) 1723 rnd = arc4random(); 1724 cookie[i] = rnd & 0xff; 1725 rnd >>= 8; 1726 } 1727 1728 /* 1729 * Send our public key. We include in the packet 64 bits of random 1730 * data that must be matched in the reply in order to prevent IP 1731 * spoofing. 1732 */ 1733 packet_start(SSH_SMSG_PUBLIC_KEY); 1734 for (i = 0; i < 8; i++) 1735 packet_put_char(cookie[i]); 1736 1737 /* Store our public server RSA key. */ 1738 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n)); 1739 packet_put_bignum(sensitive_data.server_key->rsa->e); 1740 packet_put_bignum(sensitive_data.server_key->rsa->n); 1741 1742 /* Store our public host RSA key. */ 1743 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n)); 1744 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e); 1745 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n); 1746 1747 /* Put protocol flags. */ 1748 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN); 1749 1750 /* Declare which ciphers we support. */ 1751 packet_put_int(cipher_mask_ssh1(0)); 1752 1753 /* Declare supported authentication types. */ 1754 auth_mask = 0; 1755 if (options.rhosts_authentication) 1756 auth_mask |= 1 << SSH_AUTH_RHOSTS; 1757 if (options.rhosts_rsa_authentication) 1758 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA; 1759 if (options.rsa_authentication) 1760 auth_mask |= 1 << SSH_AUTH_RSA; 1761 #if defined(KRB4) || defined(KRB5) 1762 if (options.kerberos_authentication) 1763 auth_mask |= 1 << SSH_AUTH_KERBEROS; 1764 #endif 1765 #if defined(AFS) || defined(KRB5) 1766 if (options.kerberos_tgt_passing) 1767 auth_mask |= 1 << SSH_PASS_KERBEROS_TGT; 1768 #endif 1769 #ifdef AFS 1770 if (options.afs_token_passing) 1771 auth_mask |= 1 << SSH_PASS_AFS_TOKEN; 1772 #endif 1773 if (options.challenge_response_authentication == 1) 1774 auth_mask |= 1 << SSH_AUTH_TIS; 1775 if (options.password_authentication) 1776 auth_mask |= 1 << SSH_AUTH_PASSWORD; 1777 packet_put_int(auth_mask); 1778 1779 /* Send the packet and wait for it to be sent. */ 1780 packet_send(); 1781 packet_write_wait(); 1782 1783 debug("Sent %d bit server key and %d bit host key.", 1784 BN_num_bits(sensitive_data.server_key->rsa->n), 1785 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n)); 1786 1787 /* Read clients reply (cipher type and session key). */ 1788 packet_read_expect(SSH_CMSG_SESSION_KEY); 1789 1790 /* Get cipher type and check whether we accept this. */ 1791 cipher_type = packet_get_char(); 1792 1793 if (!(cipher_mask_ssh1(0) & (1 << cipher_type))) { 1794 packet_disconnect("Warning: client selects unsupported cipher."); 1795 } 1796 1797 /* Get check bytes from the packet. These must match those we 1798 sent earlier with the public key packet. */ 1799 for (i = 0; i < 8; i++) { 1800 if (cookie[i] != packet_get_char()) { 1801 packet_disconnect("IP Spoofing check bytes do not match."); 1802 } 1803 } 1804 1805 debug("Encryption type: %.200s", cipher_name(cipher_type)); 1806 1807 /* Get the encrypted integer. */ 1808 if ((session_key_int = BN_new()) == NULL) 1809 fatal("do_ssh1_kex: BN_new failed"); 1810 packet_get_bignum(session_key_int); 1811 1812 protocol_flags = packet_get_int(); 1813 packet_set_protocol_flags(protocol_flags); 1814 packet_check_eom(); 1815 1816 /* Decrypt session_key_int using host/server keys */ 1817 rsafail = ssh1_session_key(session_key_int); 1818 1819 /* 1820 * Extract session key from the decrypted integer. The key is in the 1821 * least significant 256 bits of the integer; the first byte of the 1822 * key is in the highest bits. 1823 */ 1824 if (!rsafail) { 1825 (void) BN_mask_bits(session_key_int, sizeof(session_key) * 8); 1826 len = BN_num_bytes(session_key_int); 1827 if (len < 0 || len > sizeof(session_key)) { 1828 error("do_connection: bad session key len from %s: " 1829 "session_key_int %d > sizeof(session_key) %lu", 1830 get_remote_ipaddr(), len, (u_long)sizeof(session_key)); 1831 rsafail++; 1832 } else { 1833 (void) memset(session_key, 0, sizeof(session_key)); 1834 (void) BN_bn2bin(session_key_int, 1835 session_key + sizeof(session_key) - len); 1836 1837 compute_session_id(session_id, cookie, 1838 sensitive_data.ssh1_host_key->rsa->n, 1839 sensitive_data.server_key->rsa->n); 1840 /* 1841 * Xor the first 16 bytes of the session key with the 1842 * session id. 1843 */ 1844 for (i = 0; i < 16; i++) 1845 session_key[i] ^= session_id[i]; 1846 } 1847 } 1848 if (rsafail) { 1849 int bytes = BN_num_bytes(session_key_int); 1850 u_char *buf = xmalloc(bytes); 1851 MD5_CTX md; 1852 1853 log("do_connection: generating a fake encryption key"); 1854 (void) BN_bn2bin(session_key_int, buf); 1855 MD5_Init(&md); 1856 MD5_Update(&md, buf, bytes); 1857 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); 1858 MD5_Final(session_key, &md); 1859 MD5_Init(&md); 1860 MD5_Update(&md, session_key, 16); 1861 MD5_Update(&md, buf, bytes); 1862 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); 1863 MD5_Final(session_key + 16, &md); 1864 (void) memset(buf, 0, bytes); 1865 xfree(buf); 1866 for (i = 0; i < 16; i++) 1867 session_id[i] = session_key[i] ^ session_key[i + 16]; 1868 } 1869 /* Destroy the private and public keys. No longer. */ 1870 destroy_sensitive_data(); 1871 1872 /* Destroy the decrypted integer. It is no longer needed. */ 1873 BN_clear_free(session_key_int); 1874 1875 /* Set the session key. From this on all communications will be encrypted. */ 1876 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type); 1877 1878 /* Destroy our copy of the session key. It is no longer needed. */ 1879 (void) memset(session_key, 0, sizeof(session_key)); 1880 1881 debug("Received session key; encryption turned on."); 1882 1883 /* Send an acknowledgment packet. Note that this packet is sent encrypted. */ 1884 packet_start(SSH_SMSG_SUCCESS); 1885 packet_send(); 1886 packet_write_wait(); 1887 } 1888 1889 /* 1890 * Prepare for SSH2 key exchange. 1891 */ 1892 Kex * 1893 prepare_for_ssh2_kex(void) 1894 { 1895 Kex *kex; 1896 Kex_hook_func kex_hook = NULL; 1897 char **locales; 1898 static char **myproposal; 1899 1900 myproposal = my_srv_proposal; 1901 1902 if (options.ciphers != NULL) { 1903 myproposal[PROPOSAL_ENC_ALGS_CTOS] = 1904 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers; 1905 } 1906 myproposal[PROPOSAL_ENC_ALGS_CTOS] = 1907 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]); 1908 myproposal[PROPOSAL_ENC_ALGS_STOC] = 1909 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]); 1910 1911 if (options.macs != NULL) { 1912 myproposal[PROPOSAL_MAC_ALGS_CTOS] = 1913 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs; 1914 } 1915 if (!options.compression) { 1916 myproposal[PROPOSAL_COMP_ALGS_CTOS] = 1917 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none"; 1918 } 1919 1920 /* 1921 * Prepare kex algs / hostkey algs (excluding GSS, which is 1922 * handled in the kex hook. 1923 * 1924 * XXX This should probably move to the kex hook as well, where 1925 * all non-constant kex offer material belongs. 1926 */ 1927 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types(); 1928 1929 /* If we have no host key algs we can't offer KEXDH/KEX_DH_GEX */ 1930 if (myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] == NULL || 1931 *myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] == '\0') 1932 myproposal[PROPOSAL_KEX_ALGS] = ""; 1933 1934 if ((locales = g11n_getlocales()) != NULL) { 1935 /* Solaris 9 SSH expects a list of locales */ 1936 if (datafellows & SSH_BUG_LOCALES_NOT_LANGTAGS) 1937 myproposal[PROPOSAL_LANG_STOC] = xjoin(locales, ','); 1938 else 1939 myproposal[PROPOSAL_LANG_STOC] = 1940 g11n_locales2langs(locales); 1941 } 1942 1943 if (locales != NULL) 1944 g11n_freelist(locales); 1945 1946 if ((myproposal[PROPOSAL_LANG_STOC] != NULL) && 1947 (strcmp(myproposal[PROPOSAL_LANG_STOC], "")) != 0) 1948 myproposal[PROPOSAL_LANG_CTOS] = 1949 xstrdup(myproposal[PROPOSAL_LANG_STOC]); 1950 1951 #ifdef GSSAPI 1952 if (options.gss_keyex) 1953 kex_hook = ssh_gssapi_server_kex_hook; 1954 #endif /* GSSAPI */ 1955 1956 kex = kex_setup(NULL, myproposal, kex_hook); 1957 1958 /* 1959 * Note that the my_srv_proposal variable (ie., myproposal) is staticly 1960 * initialized with "" for the language fields; we must not xfree such 1961 * strings. 1962 */ 1963 if (myproposal[PROPOSAL_LANG_STOC] != NULL && 1964 strcmp(myproposal[PROPOSAL_LANG_STOC], "") != 0) 1965 xfree(myproposal[PROPOSAL_LANG_STOC]); 1966 if (myproposal[PROPOSAL_LANG_CTOS] != NULL && 1967 strcmp(myproposal[PROPOSAL_LANG_STOC], "") != 0) 1968 xfree(myproposal[PROPOSAL_LANG_CTOS]); 1969 1970 kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server; 1971 kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 1972 #ifdef GSSAPI 1973 kex->kex[KEX_GSS_GRP1_SHA1] = kexgss_server; 1974 #endif /* GSSAPI */ 1975 kex->server = 1; 1976 kex->client_version_string = client_version_string; 1977 kex->server_version_string = server_version_string; 1978 kex->load_host_key = &get_hostkey_by_type; 1979 kex->host_key_index = &get_hostkey_index; 1980 1981 xxx_kex = kex; 1982 return (kex); 1983 } 1984 1985 /* 1986 * Do SSH2 key exchange. 1987 */ 1988 static void 1989 do_ssh2_kex(void) 1990 { 1991 Kex *kex; 1992 1993 kex = prepare_for_ssh2_kex(); 1994 kex_start(kex); 1995 1996 dispatch_run(DISPATCH_BLOCK, &kex->done, kex); 1997 1998 if (kex->name) { 1999 xfree(kex->name); 2000 kex->name = NULL; 2001 } 2002 session_id2 = kex->session_id; 2003 session_id2_len = kex->session_id_len; 2004 2005 #ifdef DEBUG_KEXDH 2006 /* send 1st encrypted/maced/compressed message */ 2007 packet_start(SSH2_MSG_IGNORE); 2008 packet_put_cstring("markus"); 2009 packet_send(); 2010 packet_write_wait(); 2011 #endif 2012 debug("KEX done"); 2013 } 2014