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 /* sshd_config buffer */ 227 Buffer cfg; 228 229 #ifdef GSSAPI 230 static gss_OID_set mechs = GSS_C_NULL_OID_SET; 231 #endif /* GSSAPI */ 232 233 /* Prototypes for various functions defined later in this file. */ 234 void destroy_sensitive_data(void); 235 static void demote_sensitive_data(void); 236 237 static void do_ssh1_kex(void); 238 static void do_ssh2_kex(void); 239 240 /* 241 * Close all listening sockets 242 */ 243 static void 244 close_listen_socks(void) 245 { 246 int i; 247 248 for (i = 0; i < num_listen_socks; i++) 249 (void) close(listen_socks[i]); 250 num_listen_socks = -1; 251 } 252 253 static void 254 close_startup_pipes(void) 255 { 256 int i; 257 258 if (startup_pipes) 259 for (i = 0; i < options.max_startups; i++) 260 if (startup_pipes[i] != -1) 261 (void) close(startup_pipes[i]); 262 } 263 264 /* 265 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP; 266 * the effect is to reread the configuration file (and to regenerate 267 * the server key). 268 */ 269 static void 270 sighup_handler(int sig) 271 { 272 int save_errno = errno; 273 274 received_sighup = 1; 275 (void) signal(SIGHUP, sighup_handler); 276 errno = save_errno; 277 } 278 279 /* 280 * Called from the main program after receiving SIGHUP. 281 * Restarts the server. 282 */ 283 static void 284 sighup_restart(void) 285 { 286 log("Received SIGHUP; restarting."); 287 close_listen_socks(); 288 close_startup_pipes(); 289 (void) execv(saved_argv[0], saved_argv); 290 log("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], 291 strerror(errno)); 292 exit(1); 293 } 294 295 /* 296 * Generic signal handler for terminating signals in the master daemon. 297 */ 298 static void 299 sigterm_handler(int sig) 300 { 301 received_sigterm = sig; 302 } 303 304 /* 305 * SIGCHLD handler. This is called whenever a child dies. This will then 306 * reap any zombies left by exited children. 307 */ 308 static void 309 main_sigchld_handler(int sig) 310 { 311 int save_errno = errno; 312 pid_t pid; 313 int status; 314 315 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 316 (pid < 0 && errno == EINTR)) 317 ; 318 319 (void) signal(SIGCHLD, main_sigchld_handler); 320 errno = save_errno; 321 } 322 323 /* 324 * Signal handler for the alarm after the login grace period has expired. This 325 * is for the (soon-to-be) unprivileged child only. The monitor gets an event on 326 * the communication pipe and exits as well. 327 */ 328 static void 329 grace_alarm_handler(int sig) 330 { 331 /* Log error and exit. */ 332 fatal("Timeout before authentication for %.200s", get_remote_ipaddr()); 333 } 334 335 #ifdef HAVE_SOLARIS_CONTRACTS 336 static int contracts_fd = -1; 337 void 338 contracts_pre_fork() 339 { 340 const char *during = "opening process contract template"; 341 342 /* 343 * Failure should not be treated as fatal on the theory that 344 * it's better to start with children in the same contract as 345 * the master listener than not at all. 346 */ 347 348 if (contracts_fd == -1) { 349 if ((contracts_fd = open64(CTFS_ROOT "/process/template", 350 O_RDWR)) == -1) 351 goto cleanup; 352 353 during = "setting sundry contract terms"; 354 if ((errno = ct_pr_tmpl_set_param(contracts_fd, CT_PR_PGRPONLY))) 355 goto cleanup; 356 357 if ((errno = ct_tmpl_set_informative(contracts_fd, CT_PR_EV_HWERR))) 358 goto cleanup; 359 360 if ((errno = ct_pr_tmpl_set_fatal(contracts_fd, CT_PR_EV_HWERR))) 361 goto cleanup; 362 363 if ((errno = ct_tmpl_set_critical(contracts_fd, 0))) 364 goto cleanup; 365 } 366 367 during = "setting active template"; 368 if ((errno = ct_tmpl_activate(contracts_fd))) 369 goto cleanup; 370 371 debug3("Set active contract"); 372 return; 373 374 cleanup: 375 if (contracts_fd != -1) 376 (void) close(contracts_fd); 377 378 contracts_fd = -1; 379 380 if (errno) 381 debug2("Error while trying to set up active contract" 382 " template: %s while %s", strerror(errno), during); 383 } 384 385 void 386 contracts_post_fork_child() 387 { 388 /* Clear active template so fork() creates no new contracts. */ 389 390 if (contracts_fd == -1) 391 return; 392 393 if ((errno = (ct_tmpl_clear(contracts_fd)))) 394 debug2("Error while trying to clear active contract template" 395 " (child): %s", strerror(errno)); 396 else 397 debug3("Cleared active contract template (child)"); 398 399 (void) close(contracts_fd); 400 401 contracts_fd = -1; 402 } 403 404 void 405 contracts_post_fork_parent(int fork_succeeded) 406 { 407 char path[PATH_MAX]; 408 int cfd, n; 409 ct_stathdl_t st; 410 ctid_t latest; 411 412 /* Clear active template, abandon latest contract. */ 413 if (contracts_fd == -1) 414 return; 415 416 if ((errno = ct_tmpl_clear(contracts_fd))) 417 debug2("Error while clearing active contract template: %s", 418 strerror(errno)); 419 else 420 debug3("Cleared active contract template (parent)"); 421 422 if (!fork_succeeded) 423 return; 424 425 if ((cfd = open64(CTFS_ROOT "/process/latest", O_RDONLY)) == -1) { 426 debug2("Error while getting latest contract: %s", 427 strerror(errno)); 428 return; 429 } 430 431 if ((errno = ct_status_read(cfd, CTD_COMMON, &st)) != 0) { 432 debug2("Error while getting latest contract ID: %s", 433 strerror(errno)); 434 (void) close(cfd); 435 return; 436 } 437 438 latest = ct_status_get_id(st); 439 ct_status_free(st); 440 (void) close(cfd); 441 442 n = snprintf(path, PATH_MAX, CTFS_ROOT "/all/%ld/ctl", latest); 443 444 if (n >= PATH_MAX) { 445 debug2("Error while opening the latest contract ctl file: %s", 446 strerror(ENAMETOOLONG)); 447 return; 448 } 449 450 if ((cfd = open64(path, O_WRONLY)) == -1) { 451 debug2("Error while opening the latest contract ctl file: %s", 452 strerror(errno)); 453 return; 454 } 455 456 if ((errno = ct_ctl_abandon(cfd))) 457 debug2("Error while abandoning latest contract: %s", 458 strerror(errno)); 459 else 460 debug3("Abandoned latest contract"); 461 462 (void) close(cfd); 463 } 464 #endif /* HAVE_SOLARIS_CONTRACTS */ 465 466 /* 467 * Signal handler for the key regeneration alarm. Note that this 468 * alarm only occurs in the daemon waiting for connections, and it does not 469 * do anything with the private key or random state before forking. 470 * Thus there should be no concurrency control/asynchronous execution 471 * problems. 472 */ 473 static void 474 generate_ephemeral_server_key(void) 475 { 476 u_int32_t rnd = 0; 477 int i; 478 479 verbose("Generating %s%d bit RSA key.", 480 sensitive_data.server_key ? "new " : "", options.server_key_bits); 481 if (sensitive_data.server_key != NULL) 482 key_free(sensitive_data.server_key); 483 sensitive_data.server_key = key_generate(KEY_RSA1, 484 options.server_key_bits); 485 verbose("RSA key generation complete."); 486 487 for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) { 488 if (i % 4 == 0) 489 rnd = arc4random(); 490 sensitive_data.ssh1_cookie[i] = rnd & 0xff; 491 rnd >>= 8; 492 } 493 arc4random_stir(); 494 } 495 496 static void 497 key_regeneration_alarm(int sig) 498 { 499 int save_errno = errno; 500 501 (void) signal(SIGALRM, SIG_DFL); 502 errno = save_errno; 503 key_do_regen = 1; 504 } 505 506 static void 507 sshd_exchange_identification(int sock_in, int sock_out) 508 { 509 int i, mismatch; 510 int remote_major, remote_minor; 511 int major, minor; 512 char *s; 513 char buf[256]; /* Must not be larger than remote_version. */ 514 char remote_version[256]; /* Must be at least as big as buf. */ 515 516 if ((options.protocol & SSH_PROTO_1) && 517 (options.protocol & SSH_PROTO_2)) { 518 major = PROTOCOL_MAJOR_1; 519 minor = 99; 520 } else if (options.protocol & SSH_PROTO_2) { 521 major = PROTOCOL_MAJOR_2; 522 minor = PROTOCOL_MINOR_2; 523 } else { 524 major = PROTOCOL_MAJOR_1; 525 minor = PROTOCOL_MINOR_1; 526 } 527 (void) snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION); 528 server_version_string = xstrdup(buf); 529 530 if (client_version_string == NULL) { 531 /* Send our protocol version identification. */ 532 if (atomicio(write, sock_out, server_version_string, 533 strlen(server_version_string)) 534 != strlen(server_version_string)) { 535 log("Could not write ident string to %s", get_remote_ipaddr()); 536 fatal_cleanup(); 537 } 538 539 /* Read other sides version identification. */ 540 (void) memset(buf, 0, sizeof(buf)); 541 for (i = 0; i < sizeof(buf) - 1; i++) { 542 if (atomicio(read, sock_in, &buf[i], 1) != 1) { 543 log("Did not receive identification string from %s", 544 get_remote_ipaddr()); 545 fatal_cleanup(); 546 } 547 if (buf[i] == '\r') { 548 buf[i] = 0; 549 /* Kludge for F-Secure Macintosh < 1.0.2 */ 550 if (i == 12 && 551 strncmp(buf, "SSH-1.5-W1.0", 12) == 0) 552 break; 553 continue; 554 } 555 if (buf[i] == '\n') { 556 buf[i] = 0; 557 break; 558 } 559 } 560 buf[sizeof(buf) - 1] = 0; 561 client_version_string = xstrdup(buf); 562 } 563 564 /* 565 * Check that the versions match. In future this might accept 566 * several versions and set appropriate flags to handle them. 567 */ 568 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n", 569 &remote_major, &remote_minor, remote_version) != 3) { 570 s = "Protocol mismatch.\n"; 571 (void) atomicio(write, sock_out, s, strlen(s)); 572 (void) close(sock_in); 573 (void) close(sock_out); 574 log("Bad protocol version identification '%.100s' from %s", 575 client_version_string, get_remote_ipaddr()); 576 fatal_cleanup(); 577 } 578 debug("Client protocol version %d.%d; client software version %.100s", 579 remote_major, remote_minor, remote_version); 580 581 compat_datafellows(remote_version); 582 583 if (datafellows & SSH_BUG_PROBE) { 584 log("probed from %s with %s. Don't panic.", 585 get_remote_ipaddr(), client_version_string); 586 fatal_cleanup(); 587 } 588 589 if (datafellows & SSH_BUG_SCANNER) { 590 log("scanned from %s with %s. Don't panic.", 591 get_remote_ipaddr(), client_version_string); 592 fatal_cleanup(); 593 } 594 595 mismatch = 0; 596 switch (remote_major) { 597 case 1: 598 if (remote_minor == 99) { 599 if (options.protocol & SSH_PROTO_2) 600 enable_compat20(); 601 else 602 mismatch = 1; 603 break; 604 } 605 if (!(options.protocol & SSH_PROTO_1)) { 606 mismatch = 1; 607 break; 608 } 609 if (remote_minor < 3) { 610 packet_disconnect("Your ssh version is too old and " 611 "is no longer supported. Please install a newer version."); 612 } else if (remote_minor == 3) { 613 /* note that this disables agent-forwarding */ 614 enable_compat13(); 615 } 616 break; 617 case 2: 618 if (options.protocol & SSH_PROTO_2) { 619 enable_compat20(); 620 break; 621 } 622 /* FALLTHROUGH */ 623 default: 624 mismatch = 1; 625 break; 626 } 627 chop(server_version_string); 628 debug("Local version string %.200s", server_version_string); 629 630 if (mismatch) { 631 s = "Protocol major versions differ.\n"; 632 (void) atomicio(write, sock_out, s, strlen(s)); 633 (void) close(sock_in); 634 (void) close(sock_out); 635 log("Protocol major versions differ for %s: %.200s vs. %.200s", 636 get_remote_ipaddr(), 637 server_version_string, client_version_string); 638 fatal_cleanup(); 639 } 640 } 641 642 /* Destroy the host and server keys. They will no longer be needed. */ 643 void 644 destroy_sensitive_data(void) 645 { 646 int i; 647 648 if (sensitive_data.server_key) { 649 key_free(sensitive_data.server_key); 650 sensitive_data.server_key = NULL; 651 } 652 for (i = 0; i < options.num_host_key_files; i++) { 653 if (sensitive_data.host_keys[i]) { 654 key_free(sensitive_data.host_keys[i]); 655 sensitive_data.host_keys[i] = NULL; 656 } 657 } 658 sensitive_data.ssh1_host_key = NULL; 659 (void) memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH); 660 } 661 662 /* Demote private to public keys for network child */ 663 static void 664 demote_sensitive_data(void) 665 { 666 Key *tmp; 667 int i; 668 669 if (sensitive_data.server_key) { 670 tmp = key_demote(sensitive_data.server_key); 671 key_free(sensitive_data.server_key); 672 sensitive_data.server_key = tmp; 673 } 674 675 for (i = 0; i < options.num_host_key_files; i++) { 676 if (sensitive_data.host_keys[i]) { 677 tmp = key_demote(sensitive_data.host_keys[i]); 678 key_free(sensitive_data.host_keys[i]); 679 sensitive_data.host_keys[i] = tmp; 680 if (tmp->type == KEY_RSA1) 681 sensitive_data.ssh1_host_key = tmp; 682 } 683 } 684 685 /* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */ 686 } 687 688 static char * 689 list_hostkey_types(void) 690 { 691 Buffer b; 692 char *p; 693 int i; 694 695 buffer_init(&b); 696 for (i = 0; i < options.num_host_key_files; i++) { 697 Key *key = sensitive_data.host_keys[i]; 698 if (key == NULL) 699 continue; 700 switch (key->type) { 701 case KEY_RSA: 702 case KEY_DSA: 703 if (buffer_len(&b) > 0) 704 buffer_append(&b, ",", 1); 705 p = key_ssh_name(key); 706 buffer_append(&b, p, strlen(p)); 707 break; 708 } 709 } 710 buffer_append(&b, "\0", 1); 711 p = xstrdup(buffer_ptr(&b)); 712 buffer_free(&b); 713 debug("list_hostkey_types: %s", p); 714 return p; 715 } 716 717 #ifdef lint 718 static 719 #endif /* lint */ 720 Key * 721 get_hostkey_by_type(int type) 722 { 723 int i; 724 725 for (i = 0; i < options.num_host_key_files; i++) { 726 Key *key = sensitive_data.host_keys[i]; 727 if (key != NULL && key->type == type) 728 return key; 729 } 730 return NULL; 731 } 732 733 #ifdef lint 734 static 735 #endif /* lint */ 736 Key * 737 get_hostkey_by_index(int ind) 738 { 739 if (ind < 0 || ind >= options.num_host_key_files) 740 return (NULL); 741 return (sensitive_data.host_keys[ind]); 742 } 743 744 #ifdef lint 745 static 746 #endif /* lint */ 747 int 748 get_hostkey_index(Key *key) 749 { 750 int i; 751 752 for (i = 0; i < options.num_host_key_files; i++) { 753 if (key == sensitive_data.host_keys[i]) 754 return (i); 755 } 756 return (-1); 757 } 758 759 /* 760 * returns 1 if connection should be dropped, 0 otherwise. 761 * dropping starts at connection #max_startups_begin with a probability 762 * of (max_startups_rate/100). the probability increases linearly until 763 * all connections are dropped for startups > max_startups 764 */ 765 static int 766 drop_connection(int startups) 767 { 768 double p, r; 769 770 if (startups < options.max_startups_begin) 771 return 0; 772 if (startups >= options.max_startups) 773 return 1; 774 if (options.max_startups_rate == 100) 775 return 1; 776 777 p = 100 - options.max_startups_rate; 778 p *= startups - options.max_startups_begin; 779 p /= (double) (options.max_startups - options.max_startups_begin); 780 p += options.max_startups_rate; 781 p /= 100.0; 782 r = arc4random() / (double) UINT_MAX; 783 784 debug("drop_connection: p %g, r %g", p, r); 785 return (r < p) ? 1 : 0; 786 } 787 788 static void 789 usage(void) 790 { 791 (void) fprintf(stderr, gettext("sshd version %s\n"), SSH_VERSION); 792 (void) fprintf(stderr, 793 gettext("Usage: %s [options]\n" 794 "Options:\n" 795 " -f file Configuration file (default %s)\n" 796 " -d Debugging mode (multiple -d means more " 797 "debugging)\n" 798 " -i Started from inetd\n" 799 " -D Do not fork into daemon mode\n" 800 " -t Only test configuration file and keys\n" 801 " -q Quiet (no logging)\n" 802 " -p port Listen on the specified port (default: 22)\n" 803 " -k seconds Regenerate server key every this many seconds " 804 "(default: 3600)\n" 805 " -g seconds Grace period for authentication (default: 600)\n" 806 " -b bits Size of server RSA key (default: 768 bits)\n" 807 " -h file File from which to read host key (default: %s)\n" 808 " -4 Use IPv4 only\n" 809 " -6 Use IPv6 only\n" 810 " -o option Process the option as if it was read from " 811 "a configuration file.\n"), 812 __progname, _PATH_SERVER_CONFIG_FILE, _PATH_HOST_KEY_FILE); 813 exit(1); 814 } 815 816 /* 817 * Main program for the daemon. 818 */ 819 int 820 main(int ac, char **av) 821 { 822 extern char *optarg; 823 extern int optind; 824 int opt, j, i, fdsetsz, sock_in = 0, sock_out = 0, newsock = -1, on = 1; 825 pid_t pid; 826 socklen_t fromlen; 827 fd_set *fdset; 828 struct sockaddr_storage from; 829 const char *remote_ip; 830 int remote_port; 831 FILE *f; 832 struct addrinfo *ai; 833 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 834 int listen_sock, maxfd; 835 int startup_p[2]; 836 int startups = 0; 837 Authctxt *authctxt = NULL; 838 Key *key; 839 int ret, key_used = 0; 840 #ifdef HAVE_BSM 841 au_id_t auid = AU_NOAUDITID; 842 #endif /* HAVE_BSM */ 843 int mpipe; 844 845 __progname = get_progname(av[0]); 846 847 (void) g11n_setlocale(LC_ALL, ""); 848 849 init_rng(); 850 851 /* Save argv. */ 852 saved_argc = ac; 853 saved_argv = av; 854 855 /* Initialize configuration options to their default values. */ 856 initialize_server_options(&options); 857 858 /* Parse command-line arguments. */ 859 while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:o:dDeiqtQ46")) != -1) { 860 switch (opt) { 861 case '4': 862 IPv4or6 = AF_INET; 863 break; 864 case '6': 865 IPv4or6 = AF_INET6; 866 break; 867 case 'f': 868 config_file_name = optarg; 869 break; 870 case 'd': 871 if (0 == debug_flag) { 872 debug_flag = 1; 873 options.log_level = SYSLOG_LEVEL_DEBUG1; 874 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) { 875 options.log_level++; 876 } else { 877 (void) fprintf(stderr, 878 gettext("Debug level too high.\n")); 879 exit(1); 880 } 881 break; 882 case 'D': 883 no_daemon_flag = 1; 884 break; 885 case 'e': 886 log_stderr = 1; 887 break; 888 case 'i': 889 inetd_flag = 1; 890 break; 891 case 'Q': 892 /* ignored */ 893 break; 894 case 'q': 895 options.log_level = SYSLOG_LEVEL_QUIET; 896 break; 897 case 'b': 898 options.server_key_bits = atoi(optarg); 899 break; 900 case 'p': 901 options.ports_from_cmdline = 1; 902 if (options.num_ports >= MAX_PORTS) { 903 (void) fprintf(stderr, gettext("too many ports.\n")); 904 exit(1); 905 } 906 options.ports[options.num_ports++] = a2port(optarg); 907 if (options.ports[options.num_ports-1] == 0) { 908 (void) fprintf(stderr, gettext("Bad port number.\n")); 909 exit(1); 910 } 911 break; 912 case 'g': 913 if ((options.login_grace_time = convtime(optarg)) == -1) { 914 (void) fprintf(stderr, 915 gettext("Invalid login grace time.\n")); 916 exit(1); 917 } 918 break; 919 case 'k': 920 if ((options.key_regeneration_time = convtime(optarg)) == -1) { 921 (void) fprintf(stderr, 922 gettext("Invalid key regeneration " 923 "interval.\n")); 924 exit(1); 925 } 926 break; 927 case 'h': 928 if (options.num_host_key_files >= MAX_HOSTKEYS) { 929 (void) fprintf(stderr, 930 gettext("too many host keys.\n")); 931 exit(1); 932 } 933 options.host_key_files[options.num_host_key_files++] = optarg; 934 break; 935 case 'V': 936 client_version_string = optarg; 937 /* only makes sense with inetd_flag, i.e. no listen() */ 938 inetd_flag = 1; 939 break; 940 case 't': 941 test_flag = 1; 942 break; 943 case 'o': 944 if (process_server_config_line(&options, optarg, 945 "command-line", 0, NULL, NULL, NULL, NULL) != 0) 946 exit(1); 947 break; 948 case '?': 949 default: 950 usage(); 951 break; 952 } 953 } 954 955 /* 956 * There is no need to use the PKCS#11 engine in the master SSH process. 957 */ 958 SSLeay_add_all_algorithms(); 959 seed_rng(); 960 channel_set_af(IPv4or6); 961 962 /* 963 * Force logging to stderr until we have loaded the private host 964 * key (unless started from inetd) 965 */ 966 log_init(__progname, 967 options.log_level == SYSLOG_LEVEL_NOT_SET ? 968 SYSLOG_LEVEL_INFO : options.log_level, 969 options.log_facility == SYSLOG_FACILITY_NOT_SET ? 970 SYSLOG_FACILITY_AUTH : options.log_facility, 971 !inetd_flag); 972 973 #ifdef _UNICOS 974 /* Cray can define user privs drop all prives now! 975 * Not needed on PRIV_SU systems! 976 */ 977 drop_cray_privs(); 978 #endif 979 980 /* Fetch our configuration */ 981 buffer_init(&cfg); 982 load_server_config(config_file_name, &cfg); 983 parse_server_config(&options, config_file_name, &cfg, NULL, NULL, NULL); 984 985 /* Fill in default values for those options not explicitly set. */ 986 fill_default_server_options(&options); 987 988 utmp_len = options.lookup_client_hostnames ? utmp_len : 0; 989 990 /* Check that there are no remaining arguments. */ 991 if (optind < ac) { 992 (void) fprintf(stderr, gettext("Extra argument %s.\n"), av[optind]); 993 exit(1); 994 } 995 996 debug("sshd version %.100s", SSH_VERSION); 997 998 /* load private host keys */ 999 if (options.num_host_key_files > 0) 1000 sensitive_data.host_keys = 1001 xmalloc(options.num_host_key_files * sizeof(Key *)); 1002 for (i = 0; i < options.num_host_key_files; i++) 1003 sensitive_data.host_keys[i] = NULL; 1004 sensitive_data.server_key = NULL; 1005 sensitive_data.ssh1_host_key = NULL; 1006 sensitive_data.have_ssh1_key = 0; 1007 sensitive_data.have_ssh2_key = 0; 1008 1009 for (i = 0; i < options.num_host_key_files; i++) { 1010 key = key_load_private(options.host_key_files[i], "", NULL); 1011 sensitive_data.host_keys[i] = key; 1012 if (key == NULL) { 1013 error("Could not load host key: %s", 1014 options.host_key_files[i]); 1015 sensitive_data.host_keys[i] = NULL; 1016 continue; 1017 } 1018 switch (key->type) { 1019 case KEY_RSA1: 1020 sensitive_data.ssh1_host_key = key; 1021 sensitive_data.have_ssh1_key = 1; 1022 break; 1023 case KEY_RSA: 1024 case KEY_DSA: 1025 sensitive_data.have_ssh2_key = 1; 1026 break; 1027 } 1028 debug("private host key: #%d type %d %s", i, key->type, 1029 key_type(key)); 1030 } 1031 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) { 1032 log("Disabling protocol version 1. Could not load host key"); 1033 options.protocol &= ~SSH_PROTO_1; 1034 } 1035 if ((options.protocol & SSH_PROTO_2) && 1036 !sensitive_data.have_ssh2_key) { 1037 #ifdef GSSAPI 1038 if (options.gss_keyex) 1039 ssh_gssapi_server_mechs(&mechs); 1040 1041 if (mechs == GSS_C_NULL_OID_SET) { 1042 log("Disabling protocol version 2. Could not load host" 1043 "key or GSS-API mechanisms"); 1044 options.protocol &= ~SSH_PROTO_2; 1045 } 1046 #else 1047 log("Disabling protocol version 2. Could not load host key"); 1048 options.protocol &= ~SSH_PROTO_2; 1049 #endif /* GSSAPI */ 1050 } 1051 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) { 1052 log("sshd: no hostkeys available -- exiting."); 1053 exit(1); 1054 } 1055 1056 /* Check certain values for sanity. */ 1057 if (options.protocol & SSH_PROTO_1) { 1058 if (options.server_key_bits < 512 || 1059 options.server_key_bits > 32768) { 1060 (void) fprintf(stderr, gettext("Bad server key size.\n")); 1061 exit(1); 1062 } 1063 /* 1064 * Check that server and host key lengths differ sufficiently. This 1065 * is necessary to make double encryption work with rsaref. Oh, I 1066 * hate software patents. I dont know if this can go? Niels 1067 */ 1068 if (options.server_key_bits > 1069 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - 1070 SSH_KEY_BITS_RESERVED && options.server_key_bits < 1071 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + 1072 SSH_KEY_BITS_RESERVED) { 1073 options.server_key_bits = 1074 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + 1075 SSH_KEY_BITS_RESERVED; 1076 debug("Forcing server key to %d bits to make it differ from host key.", 1077 options.server_key_bits); 1078 } 1079 } 1080 1081 /* Configuration looks good, so exit if in test mode. */ 1082 if (test_flag) 1083 exit(0); 1084 1085 /* 1086 * Clear out any supplemental groups we may have inherited. This 1087 * prevents inadvertent creation of files with bad modes (in the 1088 * portable version at least, it's certainly possible for PAM 1089 * to create a file, and we can't control the code in every 1090 * module which might be used). 1091 */ 1092 if (setgroups(0, NULL) < 0) 1093 debug("setgroups() failed: %.200s", strerror(errno)); 1094 1095 /* Initialize the log (it is reinitialized below in case we forked). */ 1096 if (debug_flag && !inetd_flag) 1097 log_stderr = 1; 1098 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1099 1100 /* 1101 * Solaris 9 and systems upgraded from it may have the Ciphers option 1102 * explicitly set to "aes128-cbc,blowfish-cbc,3des-cbc" in the 1103 * sshd_config. Since the default server cipher list completely changed 1104 * since then we rather notify the administator on startup. We do this 1105 * check after log_init() so that the message goes to syslogd and not to 1106 * stderr (unless the server is in the debug mode). Note that since 1107 * Solaris 10 we no longer ship sshd_config with explicit settings for 1108 * Ciphers or MACs. Do not try to augment the cipher list here since 1109 * that might end up in a very confusing situation. 1110 */ 1111 #define OLD_DEFAULT_CIPHERS_LIST "aes128-cbc,blowfish-cbc,3des-cbc" 1112 if (options.ciphers != NULL && 1113 strcmp(options.ciphers, OLD_DEFAULT_CIPHERS_LIST) == 0) { 1114 notice("Old default value \"%s\" for the \"Ciphers\" " 1115 "option found in use. In general it is prudent to let " 1116 "the server choose the defaults unless your environment " 1117 "specifically needs an explicit setting. See " 1118 "sshd_config(4) for more information.", 1119 OLD_DEFAULT_CIPHERS_LIST); 1120 } 1121 1122 #ifdef HAVE_BSM 1123 (void) setauid(&auid); 1124 #endif /* HAVE_BSM */ 1125 1126 /* 1127 * If not in debugging mode, and not started from inetd, disconnect 1128 * from the controlling terminal, and fork. The original process 1129 * exits. 1130 */ 1131 if (!(debug_flag || inetd_flag || no_daemon_flag)) { 1132 #ifdef TIOCNOTTY 1133 int fd; 1134 #endif /* TIOCNOTTY */ 1135 if (daemon(0, 0) < 0) 1136 fatal("daemon() failed: %.200s", strerror(errno)); 1137 1138 /* Disconnect from the controlling tty. */ 1139 #ifdef TIOCNOTTY 1140 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 1141 if (fd >= 0) { 1142 (void) ioctl(fd, TIOCNOTTY, NULL); 1143 (void) close(fd); 1144 } 1145 #endif /* TIOCNOTTY */ 1146 } 1147 /* Reinitialize the log (because of the fork above). */ 1148 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1149 1150 /* Initialize the random number generator. */ 1151 arc4random_stir(); 1152 1153 /* Chdir to the root directory so that the current disk can be 1154 unmounted if desired. */ 1155 (void) chdir("/"); 1156 1157 /* ignore SIGPIPE */ 1158 (void) signal(SIGPIPE, SIG_IGN); 1159 1160 /* Start listening for a socket, unless started from inetd. */ 1161 if (inetd_flag) { 1162 int s1; 1163 s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */ 1164 (void) dup(s1); 1165 sock_in = dup(0); 1166 sock_out = dup(1); 1167 startup_pipe = -1; 1168 /* we need this later for setting audit context */ 1169 newsock = sock_in; 1170 /* 1171 * We intentionally do not close the descriptors 0, 1, and 2 1172 * as our code for setting the descriptors won\'t work if 1173 * ttyfd happens to be one of those. 1174 */ 1175 debug("inetd sockets after dupping: %d, %d", sock_in, sock_out); 1176 if (options.protocol & SSH_PROTO_1) 1177 generate_ephemeral_server_key(); 1178 } else { 1179 for (ai = options.listen_addrs; ai; ai = ai->ai_next) { 1180 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 1181 continue; 1182 if (num_listen_socks >= MAX_LISTEN_SOCKS) 1183 fatal("Too many listen sockets. " 1184 "Enlarge MAX_LISTEN_SOCKS"); 1185 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, 1186 ntop, sizeof(ntop), strport, sizeof(strport), 1187 NI_NUMERICHOST|NI_NUMERICSERV) != 0) { 1188 error("getnameinfo failed"); 1189 continue; 1190 } 1191 /* Create socket for listening. */ 1192 listen_sock = socket(ai->ai_family, SOCK_STREAM, 0); 1193 if (listen_sock < 0) { 1194 /* kernel may not support ipv6 */ 1195 verbose("socket: %.100s", strerror(errno)); 1196 continue; 1197 } 1198 if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) { 1199 error("listen_sock O_NONBLOCK: %s", strerror(errno)); 1200 (void) close(listen_sock); 1201 continue; 1202 } 1203 /* 1204 * Set socket options. 1205 * Allow local port reuse in TIME_WAIT. 1206 */ 1207 if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR, 1208 &on, sizeof(on)) == -1) 1209 error("setsockopt SO_REUSEADDR: %s", strerror(errno)); 1210 1211 debug("Bind to port %s on %s.", strport, ntop); 1212 1213 /* Bind the socket to the desired port. */ 1214 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) { 1215 if (!ai->ai_next) 1216 error("Bind to port %s on %s failed: %.200s.", 1217 strport, ntop, strerror(errno)); 1218 (void) close(listen_sock); 1219 continue; 1220 } 1221 listen_socks[num_listen_socks] = listen_sock; 1222 num_listen_socks++; 1223 1224 /* Start listening on the port. */ 1225 log("Server listening on %s port %s.", ntop, strport); 1226 if (listen(listen_sock, 5) < 0) 1227 fatal("listen: %.100s", strerror(errno)); 1228 1229 } 1230 freeaddrinfo(options.listen_addrs); 1231 1232 if (!num_listen_socks) 1233 fatal("Cannot bind any address."); 1234 1235 if (options.protocol & SSH_PROTO_1) 1236 generate_ephemeral_server_key(); 1237 1238 /* 1239 * Arrange to restart on SIGHUP. The handler needs 1240 * listen_sock. 1241 */ 1242 (void) signal(SIGHUP, sighup_handler); 1243 1244 (void) signal(SIGTERM, sigterm_handler); 1245 (void) signal(SIGQUIT, sigterm_handler); 1246 1247 /* Arrange SIGCHLD to be caught. */ 1248 (void) signal(SIGCHLD, main_sigchld_handler); 1249 1250 /* Write out the pid file after the sigterm handler is setup */ 1251 if (!debug_flag) { 1252 /* 1253 * Record our pid in /var/run/sshd.pid to make it 1254 * easier to kill the correct sshd. We don't want to 1255 * do this before the bind above because the bind will 1256 * fail if there already is a daemon, and this will 1257 * overwrite any old pid in the file. 1258 */ 1259 f = fopen(options.pid_file, "wb"); 1260 if (f) { 1261 (void) fprintf(f, "%ld\n", (long) getpid()); 1262 (void) fclose(f); 1263 } 1264 } 1265 1266 /* setup fd set for listen */ 1267 fdset = NULL; 1268 maxfd = 0; 1269 for (i = 0; i < num_listen_socks; i++) 1270 if (listen_socks[i] > maxfd) 1271 maxfd = listen_socks[i]; 1272 /* pipes connected to unauthenticated childs */ 1273 startup_pipes = xmalloc(options.max_startups * sizeof(int)); 1274 for (i = 0; i < options.max_startups; i++) 1275 startup_pipes[i] = -1; 1276 1277 /* 1278 * Stay listening for connections until the system crashes or 1279 * the daemon is killed with a signal. 1280 */ 1281 for (;;) { 1282 if (received_sighup) 1283 sighup_restart(); 1284 if (fdset != NULL) 1285 xfree(fdset); 1286 fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask); 1287 fdset = (fd_set *)xmalloc(fdsetsz); 1288 (void) memset(fdset, 0, fdsetsz); 1289 1290 for (i = 0; i < num_listen_socks; i++) 1291 FD_SET(listen_socks[i], fdset); 1292 for (i = 0; i < options.max_startups; i++) 1293 if (startup_pipes[i] != -1) 1294 FD_SET(startup_pipes[i], fdset); 1295 1296 /* Wait in select until there is a connection. */ 1297 ret = select(maxfd+1, fdset, NULL, NULL, NULL); 1298 if (ret < 0 && errno != EINTR) 1299 error("select: %.100s", strerror(errno)); 1300 if (received_sigterm) { 1301 log("Received signal %d; terminating.", 1302 (int) received_sigterm); 1303 close_listen_socks(); 1304 (void) unlink(options.pid_file); 1305 exit(255); 1306 } 1307 if (key_used && key_do_regen) { 1308 generate_ephemeral_server_key(); 1309 key_used = 0; 1310 key_do_regen = 0; 1311 } 1312 if (ret < 0) 1313 continue; 1314 1315 for (i = 0; i < options.max_startups; i++) 1316 if (startup_pipes[i] != -1 && 1317 FD_ISSET(startup_pipes[i], fdset)) { 1318 /* 1319 * the read end of the pipe is ready 1320 * if the child has closed the pipe 1321 * after successful authentication 1322 * or if the child has died 1323 */ 1324 (void) close(startup_pipes[i]); 1325 startup_pipes[i] = -1; 1326 startups--; 1327 } 1328 for (i = 0; i < num_listen_socks; i++) { 1329 if (!FD_ISSET(listen_socks[i], fdset)) 1330 continue; 1331 fromlen = sizeof(from); 1332 newsock = accept(listen_socks[i], (struct sockaddr *)&from, 1333 &fromlen); 1334 if (newsock < 0) { 1335 if (errno != EINTR && errno != EWOULDBLOCK) 1336 error("accept: %.100s", strerror(errno)); 1337 continue; 1338 } 1339 if (fcntl(newsock, F_SETFL, 0) < 0) { 1340 error("newsock del O_NONBLOCK: %s", strerror(errno)); 1341 (void) close(newsock); 1342 continue; 1343 } 1344 if (drop_connection(startups) == 1) { 1345 debug("drop connection #%d", startups); 1346 (void) close(newsock); 1347 continue; 1348 } 1349 if (pipe(startup_p) == -1) { 1350 (void) close(newsock); 1351 continue; 1352 } 1353 1354 for (j = 0; j < options.max_startups; j++) 1355 if (startup_pipes[j] == -1) { 1356 startup_pipes[j] = startup_p[0]; 1357 if (maxfd < startup_p[0]) 1358 maxfd = startup_p[0]; 1359 startups++; 1360 break; 1361 } 1362 1363 /* 1364 * Got connection. Fork a child to handle it, unless 1365 * we are in debugging mode. 1366 */ 1367 if (debug_flag) { 1368 /* 1369 * In debugging mode. Close the listening 1370 * socket, and start processing the 1371 * connection without forking. 1372 */ 1373 debug("Server will not fork when running in debugging mode."); 1374 close_listen_socks(); 1375 sock_in = newsock; 1376 sock_out = newsock; 1377 startup_pipe = -1; 1378 pid = getpid(); 1379 break; 1380 } else { 1381 /* 1382 * Normal production daemon. Fork, and have 1383 * the child process the connection. The 1384 * parent continues listening. 1385 */ 1386 #ifdef HAVE_SOLARIS_CONTRACTS 1387 /* 1388 * Setup Solaris contract template so 1389 * the child process is in a different 1390 * process contract than the parent; 1391 * prevents established connections from 1392 * being killed when the sshd master 1393 * listener service is stopped. 1394 */ 1395 contracts_pre_fork(); 1396 #endif /* HAVE_SOLARIS_CONTRACTS */ 1397 if ((pid = fork()) == 0) { 1398 /* 1399 * Child. Close the listening and max_startup 1400 * sockets. Start using the accepted socket. 1401 * Reinitialize logging (since our pid has 1402 * changed). We break out of the loop to handle 1403 * the connection. 1404 */ 1405 #ifdef HAVE_SOLARIS_CONTRACTS 1406 contracts_post_fork_child(); 1407 #endif /* HAVE_SOLARIS_CONTRACTS */ 1408 xfree(fdset); 1409 startup_pipe = startup_p[1]; 1410 close_startup_pipes(); 1411 close_listen_socks(); 1412 sock_in = newsock; 1413 sock_out = newsock; 1414 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1415 break; 1416 } 1417 1418 #ifdef HAVE_SOLARIS_CONTRACTS 1419 contracts_post_fork_parent((pid > 0)); 1420 #endif /* HAVE_SOLARIS_CONTRACTS */ 1421 } 1422 1423 /* Parent. Stay in the loop. */ 1424 if (pid < 0) 1425 error("fork: %.100s", strerror(errno)); 1426 else 1427 debug("Forked child %ld.", (long)pid); 1428 1429 (void) close(startup_p[1]); 1430 1431 /* Mark that the key has been used (it was "given" to the child). */ 1432 if ((options.protocol & SSH_PROTO_1) && 1433 key_used == 0) { 1434 /* Schedule server key regeneration alarm. */ 1435 (void) signal(SIGALRM, key_regeneration_alarm); 1436 (void) alarm(options.key_regeneration_time); 1437 key_used = 1; 1438 } 1439 1440 arc4random_stir(); 1441 1442 /* 1443 * Close the accepted socket since the child 1444 * will now take care of the new connection. 1445 */ 1446 (void) close(newsock); 1447 } 1448 /* child process check (or debug mode) */ 1449 if (num_listen_socks < 0) 1450 break; 1451 } 1452 } 1453 1454 /* 1455 * This is the child processing a new connection, the SSH master process 1456 * stays in the ( ; ; ) loop above. 1457 */ 1458 #ifdef HAVE_BSM 1459 audit_sshd_settid(newsock); 1460 #endif 1461 /* 1462 * Create a new session and process group since the 4.4BSD 1463 * setlogin() affects the entire process group. We don't 1464 * want the child to be able to affect the parent. 1465 */ 1466 #if 0 1467 /* XXX: this breaks Solaris */ 1468 if (!debug_flag && !inetd_flag && setsid() < 0) 1469 error("setsid: %.100s", strerror(errno)); 1470 #endif 1471 1472 /* 1473 * Disable the key regeneration alarm. We will not regenerate the 1474 * key since we are no longer in a position to give it to anyone. We 1475 * will not restart on SIGHUP since it no longer makes sense. 1476 */ 1477 (void) alarm(0); 1478 (void) signal(SIGALRM, SIG_DFL); 1479 (void) signal(SIGHUP, SIG_DFL); 1480 (void) signal(SIGTERM, SIG_DFL); 1481 (void) signal(SIGQUIT, SIG_DFL); 1482 (void) signal(SIGCHLD, SIG_DFL); 1483 (void) signal(SIGINT, SIG_DFL); 1484 1485 /* Set keepalives if requested. */ 1486 if (options.keepalives && 1487 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, 1488 sizeof(on)) < 0) 1489 debug2("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 1490 1491 /* 1492 * Register our connection. This turns encryption off because we do 1493 * not have a key. 1494 */ 1495 packet_set_connection(sock_in, sock_out); 1496 1497 remote_port = get_remote_port(); 1498 remote_ip = get_remote_ipaddr(); 1499 1500 #ifdef LIBWRAP 1501 /* Check whether logins are denied from this host. */ 1502 { 1503 struct request_info req; 1504 1505 (void) request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0); 1506 fromhost(&req); 1507 1508 if (!hosts_access(&req)) { 1509 debug("Connection refused by tcp wrapper"); 1510 refuse(&req); 1511 /* NOTREACHED */ 1512 fatal("libwrap refuse returns"); 1513 } 1514 } 1515 #endif /* LIBWRAP */ 1516 1517 /* Log the connection. */ 1518 verbose("Connection from %.500s port %d", remote_ip, remote_port); 1519 1520 sshd_exchange_identification(sock_in, sock_out); 1521 /* 1522 * Check that the connection comes from a privileged port. 1523 * Rhosts-Authentication only makes sense from privileged 1524 * programs. Of course, if the intruder has root access on his local 1525 * machine, he can connect from any port. So do not use these 1526 * authentication methods from machines that you do not trust. 1527 */ 1528 if (options.rhosts_authentication && 1529 (remote_port >= IPPORT_RESERVED || 1530 remote_port < IPPORT_RESERVED / 2)) { 1531 debug("Rhosts Authentication disabled, " 1532 "originating port %d not trusted.", remote_port); 1533 options.rhosts_authentication = 0; 1534 } 1535 #if defined(KRB4) && !defined(KRB5) 1536 if (!packet_connection_is_ipv4() && 1537 options.kerberos_authentication) { 1538 debug("Kerberos Authentication disabled, only available for IPv4."); 1539 options.kerberos_authentication = 0; 1540 } 1541 #endif /* KRB4 && !KRB5 */ 1542 #ifdef AFS 1543 /* If machine has AFS, set process authentication group. */ 1544 if (k_hasafs()) { 1545 k_setpag(); 1546 k_unlog(); 1547 } 1548 #endif /* AFS */ 1549 1550 packet_set_nonblocking(); 1551 1552 /* 1553 * Start the monitor. That way both processes will have their own 1554 * PKCS#11 sessions. See the PKCS#11 standard for more information on 1555 * fork safety and packet.c for information about forking with the 1556 * engine. 1557 * 1558 * Note that the monitor stays in the function while the child is the 1559 * only one that returns. 1560 */ 1561 altprivsep_start_and_do_monitor(options.use_openssl_engine, 1562 inetd_flag, newsock, startup_pipe); 1563 1564 /* 1565 * We don't want to listen forever unless the other side successfully 1566 * authenticates itself. So we set up an alarm which is cleared after 1567 * successful authentication. A limit of zero indicates no limit. Note 1568 * that we don't set the alarm in debugging mode; it is just annoying to 1569 * have the server exit just when you are about to discover the bug. 1570 */ 1571 (void) signal(SIGALRM, grace_alarm_handler); 1572 if (!debug_flag) 1573 (void) alarm(options.login_grace_time); 1574 1575 /* 1576 * The child is about to start the first key exchange while the monitor 1577 * stays in altprivsep_start_and_do_monitor() function. 1578 */ 1579 (void) pkcs11_engine_load(options.use_openssl_engine); 1580 1581 /* perform the key exchange */ 1582 /* authenticate user and start session */ 1583 if (compat20) { 1584 do_ssh2_kex(); 1585 authctxt = do_authentication2(); 1586 } else { 1587 do_ssh1_kex(); 1588 authctxt = do_authentication(); 1589 } 1590 1591 /* Authentication complete */ 1592 (void) alarm(0); 1593 /* we no longer need an alarm handler */ 1594 (void) signal(SIGALRM, SIG_DFL); 1595 1596 if (startup_pipe != -1) { 1597 (void) close(startup_pipe); 1598 startup_pipe = -1; 1599 } 1600 1601 /* ALTPRIVSEP Child */ 1602 1603 /* 1604 * Drop privileges, access to privileged resources. 1605 * 1606 * Destroy private host keys, if any. 1607 * 1608 * No need to release any GSS credentials -- sshd only acquires 1609 * creds to determine what mechs it can negotiate then releases 1610 * them right away and uses GSS_C_NO_CREDENTIAL to accept 1611 * contexts. 1612 */ 1613 debug2("Unprivileged server process dropping privileges"); 1614 permanently_set_uid(authctxt->pw, options.chroot_directory); 1615 destroy_sensitive_data(); 1616 1617 /* Just another safety check. */ 1618 if (getuid() != authctxt->pw->pw_uid || 1619 geteuid() != authctxt->pw->pw_uid) { 1620 fatal("Failed to set uids to %u.", (u_int)authctxt->pw->pw_uid); 1621 } 1622 1623 ssh_gssapi_server_mechs(NULL); /* release cached mechs list */ 1624 packet_set_server(); 1625 1626 /* now send the authentication context to the monitor */ 1627 altprivsep_send_auth_context(authctxt); 1628 1629 mpipe = altprivsep_get_pipe_fd(); 1630 if (fcntl(mpipe, F_SETFL, O_NONBLOCK) < 0) 1631 error("fcntl O_NONBLOCK: %.100s", strerror(errno)); 1632 1633 #ifdef HAVE_BSM 1634 fatal_remove_cleanup( 1635 (void (*)(void *))audit_failed_login_cleanup, 1636 (void *)authctxt); 1637 #endif /* HAVE_BSM */ 1638 1639 if (compat20) { 1640 debug3("setting handler to forward re-key packets to the monitor"); 1641 dispatch_range(SSH2_MSG_KEXINIT, SSH2_MSG_TRANSPORT_MAX, 1642 &altprivsep_rekey); 1643 } 1644 1645 /* Logged-in session. */ 1646 do_authenticated(authctxt); 1647 1648 /* The connection has been terminated. */ 1649 verbose("Closing connection to %.100s", remote_ip); 1650 1651 packet_close(); 1652 1653 #ifdef USE_PAM 1654 finish_pam(authctxt); 1655 #endif /* USE_PAM */ 1656 1657 return (0); 1658 } 1659 1660 /* 1661 * Decrypt session_key_int using our private server key and private host key 1662 * (key with larger modulus first). 1663 */ 1664 int 1665 ssh1_session_key(BIGNUM *session_key_int) 1666 { 1667 int rsafail = 0; 1668 1669 if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) { 1670 /* Server key has bigger modulus. */ 1671 if (BN_num_bits(sensitive_data.server_key->rsa->n) < 1672 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) { 1673 fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d", 1674 get_remote_ipaddr(), 1675 BN_num_bits(sensitive_data.server_key->rsa->n), 1676 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n), 1677 SSH_KEY_BITS_RESERVED); 1678 } 1679 if (rsa_private_decrypt(session_key_int, session_key_int, 1680 sensitive_data.server_key->rsa) <= 0) 1681 rsafail++; 1682 if (rsa_private_decrypt(session_key_int, session_key_int, 1683 sensitive_data.ssh1_host_key->rsa) <= 0) 1684 rsafail++; 1685 } else { 1686 /* Host key has bigger modulus (or they are equal). */ 1687 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) < 1688 BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) { 1689 fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d", 1690 get_remote_ipaddr(), 1691 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n), 1692 BN_num_bits(sensitive_data.server_key->rsa->n), 1693 SSH_KEY_BITS_RESERVED); 1694 } 1695 if (rsa_private_decrypt(session_key_int, session_key_int, 1696 sensitive_data.ssh1_host_key->rsa) < 0) 1697 rsafail++; 1698 if (rsa_private_decrypt(session_key_int, session_key_int, 1699 sensitive_data.server_key->rsa) < 0) 1700 rsafail++; 1701 } 1702 return (rsafail); 1703 } 1704 /* 1705 * SSH1 key exchange 1706 */ 1707 static void 1708 do_ssh1_kex(void) 1709 { 1710 int i, len; 1711 int rsafail = 0; 1712 BIGNUM *session_key_int; 1713 u_char session_key[SSH_SESSION_KEY_LENGTH]; 1714 u_char cookie[8]; 1715 u_int cipher_type, auth_mask, protocol_flags; 1716 u_int32_t rnd = 0; 1717 1718 /* 1719 * Generate check bytes that the client must send back in the user 1720 * packet in order for it to be accepted; this is used to defy ip 1721 * spoofing attacks. Note that this only works against somebody 1722 * doing IP spoofing from a remote machine; any machine on the local 1723 * network can still see outgoing packets and catch the random 1724 * cookie. This only affects rhosts authentication, and this is one 1725 * of the reasons why it is inherently insecure. 1726 */ 1727 for (i = 0; i < 8; i++) { 1728 if (i % 4 == 0) 1729 rnd = arc4random(); 1730 cookie[i] = rnd & 0xff; 1731 rnd >>= 8; 1732 } 1733 1734 /* 1735 * Send our public key. We include in the packet 64 bits of random 1736 * data that must be matched in the reply in order to prevent IP 1737 * spoofing. 1738 */ 1739 packet_start(SSH_SMSG_PUBLIC_KEY); 1740 for (i = 0; i < 8; i++) 1741 packet_put_char(cookie[i]); 1742 1743 /* Store our public server RSA key. */ 1744 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n)); 1745 packet_put_bignum(sensitive_data.server_key->rsa->e); 1746 packet_put_bignum(sensitive_data.server_key->rsa->n); 1747 1748 /* Store our public host RSA key. */ 1749 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n)); 1750 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e); 1751 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n); 1752 1753 /* Put protocol flags. */ 1754 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN); 1755 1756 /* Declare which ciphers we support. */ 1757 packet_put_int(cipher_mask_ssh1(0)); 1758 1759 /* Declare supported authentication types. */ 1760 auth_mask = 0; 1761 if (options.rhosts_authentication) 1762 auth_mask |= 1 << SSH_AUTH_RHOSTS; 1763 if (options.rhosts_rsa_authentication) 1764 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA; 1765 if (options.rsa_authentication) 1766 auth_mask |= 1 << SSH_AUTH_RSA; 1767 #if defined(KRB4) || defined(KRB5) 1768 if (options.kerberos_authentication) 1769 auth_mask |= 1 << SSH_AUTH_KERBEROS; 1770 #endif 1771 #if defined(AFS) || defined(KRB5) 1772 if (options.kerberos_tgt_passing) 1773 auth_mask |= 1 << SSH_PASS_KERBEROS_TGT; 1774 #endif 1775 #ifdef AFS 1776 if (options.afs_token_passing) 1777 auth_mask |= 1 << SSH_PASS_AFS_TOKEN; 1778 #endif 1779 if (options.challenge_response_authentication == 1) 1780 auth_mask |= 1 << SSH_AUTH_TIS; 1781 if (options.password_authentication) 1782 auth_mask |= 1 << SSH_AUTH_PASSWORD; 1783 packet_put_int(auth_mask); 1784 1785 /* Send the packet and wait for it to be sent. */ 1786 packet_send(); 1787 packet_write_wait(); 1788 1789 debug("Sent %d bit server key and %d bit host key.", 1790 BN_num_bits(sensitive_data.server_key->rsa->n), 1791 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n)); 1792 1793 /* Read clients reply (cipher type and session key). */ 1794 packet_read_expect(SSH_CMSG_SESSION_KEY); 1795 1796 /* Get cipher type and check whether we accept this. */ 1797 cipher_type = packet_get_char(); 1798 1799 if (!(cipher_mask_ssh1(0) & (1 << cipher_type))) { 1800 packet_disconnect("Warning: client selects unsupported cipher."); 1801 } 1802 1803 /* Get check bytes from the packet. These must match those we 1804 sent earlier with the public key packet. */ 1805 for (i = 0; i < 8; i++) { 1806 if (cookie[i] != packet_get_char()) { 1807 packet_disconnect("IP Spoofing check bytes do not match."); 1808 } 1809 } 1810 1811 debug("Encryption type: %.200s", cipher_name(cipher_type)); 1812 1813 /* Get the encrypted integer. */ 1814 if ((session_key_int = BN_new()) == NULL) 1815 fatal("do_ssh1_kex: BN_new failed"); 1816 packet_get_bignum(session_key_int); 1817 1818 protocol_flags = packet_get_int(); 1819 packet_set_protocol_flags(protocol_flags); 1820 packet_check_eom(); 1821 1822 /* Decrypt session_key_int using host/server keys */ 1823 rsafail = ssh1_session_key(session_key_int); 1824 1825 /* 1826 * Extract session key from the decrypted integer. The key is in the 1827 * least significant 256 bits of the integer; the first byte of the 1828 * key is in the highest bits. 1829 */ 1830 if (!rsafail) { 1831 (void) BN_mask_bits(session_key_int, sizeof(session_key) * 8); 1832 len = BN_num_bytes(session_key_int); 1833 if (len < 0 || len > sizeof(session_key)) { 1834 error("do_connection: bad session key len from %s: " 1835 "session_key_int %d > sizeof(session_key) %lu", 1836 get_remote_ipaddr(), len, (u_long)sizeof(session_key)); 1837 rsafail++; 1838 } else { 1839 (void) memset(session_key, 0, sizeof(session_key)); 1840 (void) BN_bn2bin(session_key_int, 1841 session_key + sizeof(session_key) - len); 1842 1843 compute_session_id(session_id, cookie, 1844 sensitive_data.ssh1_host_key->rsa->n, 1845 sensitive_data.server_key->rsa->n); 1846 /* 1847 * Xor the first 16 bytes of the session key with the 1848 * session id. 1849 */ 1850 for (i = 0; i < 16; i++) 1851 session_key[i] ^= session_id[i]; 1852 } 1853 } 1854 if (rsafail) { 1855 int bytes = BN_num_bytes(session_key_int); 1856 u_char *buf = xmalloc(bytes); 1857 MD5_CTX md; 1858 1859 log("do_connection: generating a fake encryption key"); 1860 (void) BN_bn2bin(session_key_int, buf); 1861 MD5_Init(&md); 1862 MD5_Update(&md, buf, bytes); 1863 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); 1864 MD5_Final(session_key, &md); 1865 MD5_Init(&md); 1866 MD5_Update(&md, session_key, 16); 1867 MD5_Update(&md, buf, bytes); 1868 MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); 1869 MD5_Final(session_key + 16, &md); 1870 (void) memset(buf, 0, bytes); 1871 xfree(buf); 1872 for (i = 0; i < 16; i++) 1873 session_id[i] = session_key[i] ^ session_key[i + 16]; 1874 } 1875 /* Destroy the private and public keys. No longer. */ 1876 destroy_sensitive_data(); 1877 1878 /* Destroy the decrypted integer. It is no longer needed. */ 1879 BN_clear_free(session_key_int); 1880 1881 /* Set the session key. From this on all communications will be encrypted. */ 1882 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type); 1883 1884 /* Destroy our copy of the session key. It is no longer needed. */ 1885 (void) memset(session_key, 0, sizeof(session_key)); 1886 1887 debug("Received session key; encryption turned on."); 1888 1889 /* Send an acknowledgment packet. Note that this packet is sent encrypted. */ 1890 packet_start(SSH_SMSG_SUCCESS); 1891 packet_send(); 1892 packet_write_wait(); 1893 } 1894 1895 /* 1896 * Prepare for SSH2 key exchange. 1897 */ 1898 Kex * 1899 prepare_for_ssh2_kex(void) 1900 { 1901 Kex *kex; 1902 Kex_hook_func kex_hook = NULL; 1903 char **locales; 1904 static char **myproposal; 1905 1906 myproposal = my_srv_proposal; 1907 1908 if (options.ciphers != NULL) { 1909 myproposal[PROPOSAL_ENC_ALGS_CTOS] = 1910 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers; 1911 } 1912 myproposal[PROPOSAL_ENC_ALGS_CTOS] = 1913 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]); 1914 myproposal[PROPOSAL_ENC_ALGS_STOC] = 1915 compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]); 1916 1917 if (options.macs != NULL) { 1918 myproposal[PROPOSAL_MAC_ALGS_CTOS] = 1919 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs; 1920 } 1921 if (!options.compression) { 1922 myproposal[PROPOSAL_COMP_ALGS_CTOS] = 1923 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none"; 1924 } 1925 1926 /* 1927 * Prepare kex algs / hostkey algs (excluding GSS, which is 1928 * handled in the kex hook. 1929 * 1930 * XXX This should probably move to the kex hook as well, where 1931 * all non-constant kex offer material belongs. 1932 */ 1933 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types(); 1934 1935 /* If we have no host key algs we can't offer KEXDH/KEX_DH_GEX */ 1936 if (myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] == NULL || 1937 *myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] == '\0') 1938 myproposal[PROPOSAL_KEX_ALGS] = ""; 1939 1940 if ((locales = g11n_getlocales()) != NULL) { 1941 /* Solaris 9 SSH expects a list of locales */ 1942 if (datafellows & SSH_BUG_LOCALES_NOT_LANGTAGS) 1943 myproposal[PROPOSAL_LANG_STOC] = xjoin(locales, ','); 1944 else 1945 myproposal[PROPOSAL_LANG_STOC] = 1946 g11n_locales2langs(locales); 1947 } 1948 1949 if (locales != NULL) 1950 g11n_freelist(locales); 1951 1952 if ((myproposal[PROPOSAL_LANG_STOC] != NULL) && 1953 (strcmp(myproposal[PROPOSAL_LANG_STOC], "")) != 0) 1954 myproposal[PROPOSAL_LANG_CTOS] = 1955 xstrdup(myproposal[PROPOSAL_LANG_STOC]); 1956 1957 #ifdef GSSAPI 1958 if (options.gss_keyex) 1959 kex_hook = ssh_gssapi_server_kex_hook; 1960 #endif /* GSSAPI */ 1961 1962 kex = kex_setup(NULL, myproposal, kex_hook); 1963 1964 /* 1965 * Note that the my_srv_proposal variable (ie., myproposal) is staticly 1966 * initialized with "" for the language fields; we must not xfree such 1967 * strings. 1968 */ 1969 if (myproposal[PROPOSAL_LANG_STOC] != NULL && 1970 strcmp(myproposal[PROPOSAL_LANG_STOC], "") != 0) 1971 xfree(myproposal[PROPOSAL_LANG_STOC]); 1972 if (myproposal[PROPOSAL_LANG_CTOS] != NULL && 1973 strcmp(myproposal[PROPOSAL_LANG_STOC], "") != 0) 1974 xfree(myproposal[PROPOSAL_LANG_CTOS]); 1975 1976 kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server; 1977 kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 1978 #ifdef GSSAPI 1979 kex->kex[KEX_GSS_GRP1_SHA1] = kexgss_server; 1980 #endif /* GSSAPI */ 1981 kex->server = 1; 1982 kex->client_version_string = client_version_string; 1983 kex->server_version_string = server_version_string; 1984 kex->load_host_key = &get_hostkey_by_type; 1985 kex->host_key_index = &get_hostkey_index; 1986 1987 xxx_kex = kex; 1988 return (kex); 1989 } 1990 1991 /* 1992 * Do SSH2 key exchange. 1993 */ 1994 static void 1995 do_ssh2_kex(void) 1996 { 1997 Kex *kex; 1998 1999 kex = prepare_for_ssh2_kex(); 2000 kex_start(kex); 2001 2002 dispatch_run(DISPATCH_BLOCK, &kex->done, kex); 2003 2004 if (kex->name) { 2005 xfree(kex->name); 2006 kex->name = NULL; 2007 } 2008 session_id2 = kex->session_id; 2009 session_id2_len = kex->session_id_len; 2010 2011 #ifdef DEBUG_KEXDH 2012 /* send 1st encrypted/maced/compressed message */ 2013 packet_start(SSH2_MSG_IGNORE); 2014 packet_put_cstring("markus"); 2015 packet_send(); 2016 packet_write_wait(); 2017 #endif 2018 debug("KEX done"); 2019 } 2020