1/* $OpenBSD: sshd.c,v 1.458 2015/08/20 22:32:42 deraadt Exp $ */ 2/* 3 * Author: Tatu Ylonen <ylo@cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 5 * All rights reserved 6 * This program is the ssh daemon. It listens for connections from clients, 7 * and performs authentication, executes use commands or shell, and forwards 8 * information to/from the application to the user client over an encrypted 9 * connection. This can also handle forwarding of X11, TCP/IP, and 10 * authentication agent connections. 11 * 12 * As far as I am concerned, the code I have written for this software 13 * can be used freely for any purpose. Any derived versions of this 14 * software must be clearly marked as such, and if the derived work is 15 * incompatible with the protocol description in the RFC file, it must be 16 * called by a name other than "ssh" or "Secure Shell". 17 * 18 * SSH2 implementation: 19 * Privilege Separation: 20 * 21 * Copyright (c) 2000, 2001, 2002 Markus Friedl. All rights reserved. 22 * Copyright (c) 2002 Niels Provos. All rights reserved. 23 * 24 * Redistribution and use in source and binary forms, with or without 25 * modification, are permitted provided that the following conditions 26 * are met: 27 * 1. Redistributions of source code must retain the above copyright 28 * notice, this list of conditions and the following disclaimer. 29 * 2. Redistributions in binary form must reproduce the above copyright 30 * notice, this list of conditions and the following disclaimer in the 31 * documentation and/or other materials provided with the distribution. 32 * 33 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 34 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 35 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 36 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 37 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 38 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 39 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 40 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 41 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 42 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 43 */ 44 45#include "includes.h" 46 47#include <sys/types.h> 48#include <sys/ioctl.h> 49#include <sys/socket.h> 50#ifdef HAVE_SYS_STAT_H 51# include <sys/stat.h> 52#endif 53#ifdef HAVE_SYS_TIME_H 54# include <sys/time.h> 55#endif 56#include "openbsd-compat/sys-tree.h" 57#include "openbsd-compat/sys-queue.h" 58#include <sys/wait.h> 59 60#include <errno.h> 61#include <fcntl.h> 62#include <netdb.h> 63#ifdef HAVE_PATHS_H 64#include <paths.h> 65#endif 66#include <grp.h> 67#include <pwd.h> 68#include <signal.h> 69#include <stdarg.h> 70#include <stdio.h> 71#include <stdlib.h> 72#include <string.h> 73#include <unistd.h> 74#include <limits.h> 75 76#ifdef WITH_OPENSSL 77#include <openssl/dh.h> 78#include <openssl/bn.h> 79#include <openssl/rand.h> 80#include "openbsd-compat/openssl-compat.h" 81#endif 82 83#ifdef HAVE_SECUREWARE 84#include <sys/security.h> 85#include <prot.h> 86#endif 87 88#include "xmalloc.h" 89#include "ssh.h" 90#include "ssh1.h" 91#include "ssh2.h" 92#include "rsa.h" 93#include "sshpty.h" 94#include "packet.h" 95#include "log.h" 96#include "buffer.h" 97#include "misc.h" 98#include "match.h" 99#include "servconf.h" 100#include "uidswap.h" 101#include "compat.h" 102#include "cipher.h" 103#include "digest.h" 104#include "key.h" 105#include "kex.h" 106#include "myproposal.h" 107#include "authfile.h" 108#include "pathnames.h" 109#include "atomicio.h" 110#include "canohost.h" 111#include "hostfile.h" 112#include "auth.h" 113#include "authfd.h" 114#include "msg.h" 115#include "dispatch.h" 116#include "channels.h" 117#include "session.h" 118#include "monitor_mm.h" 119#include "monitor.h" 120#ifdef GSSAPI 121#include "ssh-gss.h" 122#endif 123#include "monitor_wrap.h" 124#include "roaming.h" 125#include "ssh-sandbox.h" 126#include "version.h" 127#include "ssherr.h" 128 129#ifndef O_NOCTTY 130#define O_NOCTTY 0 131#endif 132 133/* Re-exec fds */ 134#define REEXEC_DEVCRYPTO_RESERVED_FD (STDERR_FILENO + 1) 135#define REEXEC_STARTUP_PIPE_FD (STDERR_FILENO + 2) 136#define REEXEC_CONFIG_PASS_FD (STDERR_FILENO + 3) 137#define REEXEC_MIN_FREE_FD (STDERR_FILENO + 4) 138 139extern char *__progname; 140 141/* Server configuration options. */ 142ServerOptions options; 143 144/* Name of the server configuration file. */ 145char *config_file_name = _PATH_SERVER_CONFIG_FILE; 146 147/* 148 * Debug mode flag. This can be set on the command line. If debug 149 * mode is enabled, extra debugging output will be sent to the system 150 * log, the daemon will not go to background, and will exit after processing 151 * the first connection. 152 */ 153int debug_flag = 0; 154 155/* Flag indicating that the daemon should only test the configuration and keys. */ 156int test_flag = 0; 157 158/* Flag indicating that the daemon is being started from inetd. */ 159int inetd_flag = 0; 160 161/* Flag indicating that sshd should not detach and become a daemon. */ 162int no_daemon_flag = 0; 163 164/* debug goes to stderr unless inetd_flag is set */ 165int log_stderr = 0; 166 167/* Saved arguments to main(). */ 168char **saved_argv; 169int saved_argc; 170 171/* re-exec */ 172int rexeced_flag = 0; 173int rexec_flag = 1; 174int rexec_argc = 0; 175char **rexec_argv; 176 177/* 178 * The sockets that the server is listening; this is used in the SIGHUP 179 * signal handler. 180 */ 181#define MAX_LISTEN_SOCKS 16 182int listen_socks[MAX_LISTEN_SOCKS]; 183int num_listen_socks = 0; 184 185/* 186 * the client's version string, passed by sshd2 in compat mode. if != NULL, 187 * sshd will skip the version-number exchange 188 */ 189char *client_version_string = NULL; 190char *server_version_string = NULL; 191 192/* Daemon's agent connection */ 193int auth_sock = -1; 194int have_agent = 0; 195 196/* 197 * Any really sensitive data in the application is contained in this 198 * structure. The idea is that this structure could be locked into memory so 199 * that the pages do not get written into swap. However, there are some 200 * problems. The private key contains BIGNUMs, and we do not (in principle) 201 * have access to the internals of them, and locking just the structure is 202 * not very useful. Currently, memory locking is not implemented. 203 */ 204struct { 205 Key *server_key; /* ephemeral server key */ 206 Key *ssh1_host_key; /* ssh1 host key */ 207 Key **host_keys; /* all private host keys */ 208 Key **host_pubkeys; /* all public host keys */ 209 Key **host_certificates; /* all public host certificates */ 210 int have_ssh1_key; 211 int have_ssh2_key; 212 u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH]; 213} sensitive_data; 214 215/* 216 * Flag indicating whether the RSA server key needs to be regenerated. 217 * Is set in the SIGALRM handler and cleared when the key is regenerated. 218 */ 219static volatile sig_atomic_t key_do_regen = 0; 220 221/* This is set to true when a signal is received. */ 222static volatile sig_atomic_t received_sighup = 0; 223static volatile sig_atomic_t received_sigterm = 0; 224 225/* session identifier, used by RSA-auth */ 226u_char session_id[16]; 227 228/* same for ssh2 */ 229u_char *session_id2 = NULL; 230u_int session_id2_len = 0; 231 232/* record remote hostname or ip */ 233u_int utmp_len = HOST_NAME_MAX+1; 234 235/* options.max_startup sized array of fd ints */ 236int *startup_pipes = NULL; 237int startup_pipe; /* in child */ 238 239/* variables used for privilege separation */ 240int use_privsep = -1; 241struct monitor *pmonitor = NULL; 242int privsep_is_preauth = 1; 243 244/* global authentication context */ 245Authctxt *the_authctxt = NULL; 246 247/* sshd_config buffer */ 248Buffer cfg; 249 250/* message to be displayed after login */ 251Buffer loginmsg; 252 253/* Unprivileged user */ 254struct passwd *privsep_pw = NULL; 255 256/* Prototypes for various functions defined later in this file. */ 257void destroy_sensitive_data(void); 258void demote_sensitive_data(void); 259 260#ifdef WITH_SSH1 261static void do_ssh1_kex(void); 262#endif 263static void do_ssh2_kex(void); 264 265/* 266 * Close all listening sockets 267 */ 268static void 269close_listen_socks(void) 270{ 271 int i; 272 273 for (i = 0; i < num_listen_socks; i++) 274 close(listen_socks[i]); 275 num_listen_socks = -1; 276} 277 278static void 279close_startup_pipes(void) 280{ 281 int i; 282 283 if (startup_pipes) 284 for (i = 0; i < options.max_startups; i++) 285 if (startup_pipes[i] != -1) 286 close(startup_pipes[i]); 287} 288 289/* 290 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP; 291 * the effect is to reread the configuration file (and to regenerate 292 * the server key). 293 */ 294 295/*ARGSUSED*/ 296static void 297sighup_handler(int sig) 298{ 299 int save_errno = errno; 300 301 received_sighup = 1; 302 signal(SIGHUP, sighup_handler); 303 errno = save_errno; 304} 305 306/* 307 * Called from the main program after receiving SIGHUP. 308 * Restarts the server. 309 */ 310static void 311sighup_restart(void) 312{ 313 logit("Received SIGHUP; restarting."); 314 platform_pre_restart(); 315 close_listen_socks(); 316 close_startup_pipes(); 317 alarm(0); /* alarm timer persists across exec */ 318 signal(SIGHUP, SIG_IGN); /* will be restored after exec */ 319 execv(saved_argv[0], saved_argv); 320 logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], 321 strerror(errno)); 322 exit(1); 323} 324 325/* 326 * Generic signal handler for terminating signals in the master daemon. 327 */ 328/*ARGSUSED*/ 329static void 330sigterm_handler(int sig) 331{ 332 received_sigterm = sig; 333} 334 335/* 336 * SIGCHLD handler. This is called whenever a child dies. This will then 337 * reap any zombies left by exited children. 338 */ 339/*ARGSUSED*/ 340static void 341main_sigchld_handler(int sig) 342{ 343 int save_errno = errno; 344 pid_t pid; 345 int status; 346 347 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 348 (pid < 0 && errno == EINTR)) 349 ; 350 351 signal(SIGCHLD, main_sigchld_handler); 352 errno = save_errno; 353} 354 355/* 356 * Signal handler for the alarm after the login grace period has expired. 357 */ 358/*ARGSUSED*/ 359static void 360grace_alarm_handler(int sig) 361{ 362 if (use_privsep && pmonitor != NULL && pmonitor->m_pid > 0) 363 kill(pmonitor->m_pid, SIGALRM); 364 365 /* 366 * Try to kill any processes that we have spawned, E.g. authorized 367 * keys command helpers. 368 */ 369 if (getpgid(0) == getpid()) { 370 signal(SIGTERM, SIG_IGN); 371 kill(0, SIGTERM); 372 } 373 374 /* Log error and exit. */ 375 sigdie("Timeout before authentication for %s", get_remote_ipaddr()); 376} 377 378/* 379 * Signal handler for the key regeneration alarm. Note that this 380 * alarm only occurs in the daemon waiting for connections, and it does not 381 * do anything with the private key or random state before forking. 382 * Thus there should be no concurrency control/asynchronous execution 383 * problems. 384 */ 385static void 386generate_ephemeral_server_key(void) 387{ 388 verbose("Generating %s%d bit RSA key.", 389 sensitive_data.server_key ? "new " : "", options.server_key_bits); 390 if (sensitive_data.server_key != NULL) 391 key_free(sensitive_data.server_key); 392 sensitive_data.server_key = key_generate(KEY_RSA1, 393 options.server_key_bits); 394 verbose("RSA key generation complete."); 395 396 arc4random_buf(sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); 397} 398 399/*ARGSUSED*/ 400static void 401key_regeneration_alarm(int sig) 402{ 403 int save_errno = errno; 404 405 signal(SIGALRM, SIG_DFL); 406 errno = save_errno; 407 key_do_regen = 1; 408} 409 410static void 411sshd_exchange_identification(int sock_in, int sock_out) 412{ 413 u_int i; 414 int mismatch; 415 int remote_major, remote_minor; 416 int major, minor; 417 char *s, *newline = "\n"; 418 char buf[256]; /* Must not be larger than remote_version. */ 419 char remote_version[256]; /* Must be at least as big as buf. */ 420 421 if ((options.protocol & SSH_PROTO_1) && 422 (options.protocol & SSH_PROTO_2)) { 423 major = PROTOCOL_MAJOR_1; 424 minor = 99; 425 } else if (options.protocol & SSH_PROTO_2) { 426 major = PROTOCOL_MAJOR_2; 427 minor = PROTOCOL_MINOR_2; 428 newline = "\r\n"; 429 } else { 430 major = PROTOCOL_MAJOR_1; 431 minor = PROTOCOL_MINOR_1; 432 } 433 434 xasprintf(&server_version_string, "SSH-%d.%d-%.100s%s%s%s", 435 major, minor, SSH_VERSION, 436 *options.version_addendum == '\0' ? "" : " ", 437 options.version_addendum, newline); 438 439 /* Send our protocol version identification. */ 440 if (roaming_atomicio(vwrite, sock_out, server_version_string, 441 strlen(server_version_string)) 442 != strlen(server_version_string)) { 443 logit("Could not write ident string to %s", get_remote_ipaddr()); 444 cleanup_exit(255); 445 } 446 447 /* Read other sides version identification. */ 448 memset(buf, 0, sizeof(buf)); 449 for (i = 0; i < sizeof(buf) - 1; i++) { 450 if (roaming_atomicio(read, sock_in, &buf[i], 1) != 1) { 451 logit("Did not receive identification string from %s", 452 get_remote_ipaddr()); 453 cleanup_exit(255); 454 } 455 if (buf[i] == '\r') { 456 buf[i] = 0; 457 /* Kludge for F-Secure Macintosh < 1.0.2 */ 458 if (i == 12 && 459 strncmp(buf, "SSH-1.5-W1.0", 12) == 0) 460 break; 461 continue; 462 } 463 if (buf[i] == '\n') { 464 buf[i] = 0; 465 break; 466 } 467 } 468 buf[sizeof(buf) - 1] = 0; 469 client_version_string = xstrdup(buf); 470 471 /* 472 * Check that the versions match. In future this might accept 473 * several versions and set appropriate flags to handle them. 474 */ 475 if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n", 476 &remote_major, &remote_minor, remote_version) != 3) { 477 s = "Protocol mismatch.\n"; 478 (void) atomicio(vwrite, sock_out, s, strlen(s)); 479 logit("Bad protocol version identification '%.100s' " 480 "from %s port %d", client_version_string, 481 get_remote_ipaddr(), get_remote_port()); 482 close(sock_in); 483 close(sock_out); 484 cleanup_exit(255); 485 } 486 debug("Client protocol version %d.%d; client software version %.100s", 487 remote_major, remote_minor, remote_version); 488 489 active_state->compat = compat_datafellows(remote_version); 490 491 if ((datafellows & SSH_BUG_PROBE) != 0) { 492 logit("probed from %s with %s. Don't panic.", 493 get_remote_ipaddr(), client_version_string); 494 cleanup_exit(255); 495 } 496 if ((datafellows & SSH_BUG_SCANNER) != 0) { 497 logit("scanned from %s with %s. Don't panic.", 498 get_remote_ipaddr(), client_version_string); 499 cleanup_exit(255); 500 } 501 if ((datafellows & SSH_BUG_RSASIGMD5) != 0) { 502 logit("Client version \"%.100s\" uses unsafe RSA signature " 503 "scheme; disabling use of RSA keys", remote_version); 504 } 505 if ((datafellows & SSH_BUG_DERIVEKEY) != 0) { 506 fatal("Client version \"%.100s\" uses unsafe key agreement; " 507 "refusing connection", remote_version); 508 } 509 510 mismatch = 0; 511 switch (remote_major) { 512 case 1: 513 if (remote_minor == 99) { 514 if (options.protocol & SSH_PROTO_2) 515 enable_compat20(); 516 else 517 mismatch = 1; 518 break; 519 } 520 if (!(options.protocol & SSH_PROTO_1)) { 521 mismatch = 1; 522 break; 523 } 524 if (remote_minor < 3) { 525 packet_disconnect("Your ssh version is too old and " 526 "is no longer supported. Please install a newer version."); 527 } else if (remote_minor == 3) { 528 /* note that this disables agent-forwarding */ 529 enable_compat13(); 530 } 531 break; 532 case 2: 533 if (options.protocol & SSH_PROTO_2) { 534 enable_compat20(); 535 break; 536 } 537 /* FALLTHROUGH */ 538 default: 539 mismatch = 1; 540 break; 541 } 542 chop(server_version_string); 543 debug("Local version string %.200s", server_version_string); 544 545 if (mismatch) { 546 s = "Protocol major versions differ.\n"; 547 (void) atomicio(vwrite, sock_out, s, strlen(s)); 548 close(sock_in); 549 close(sock_out); 550 logit("Protocol major versions differ for %s: %.200s vs. %.200s", 551 get_remote_ipaddr(), 552 server_version_string, client_version_string); 553 cleanup_exit(255); 554 } 555} 556 557/* Destroy the host and server keys. They will no longer be needed. */ 558void 559destroy_sensitive_data(void) 560{ 561 int i; 562 563 if (sensitive_data.server_key) { 564 key_free(sensitive_data.server_key); 565 sensitive_data.server_key = NULL; 566 } 567 for (i = 0; i < options.num_host_key_files; i++) { 568 if (sensitive_data.host_keys[i]) { 569 key_free(sensitive_data.host_keys[i]); 570 sensitive_data.host_keys[i] = NULL; 571 } 572 if (sensitive_data.host_certificates[i]) { 573 key_free(sensitive_data.host_certificates[i]); 574 sensitive_data.host_certificates[i] = NULL; 575 } 576 } 577 sensitive_data.ssh1_host_key = NULL; 578 explicit_bzero(sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH); 579} 580 581/* Demote private to public keys for network child */ 582void 583demote_sensitive_data(void) 584{ 585 Key *tmp; 586 int i; 587 588 if (sensitive_data.server_key) { 589 tmp = key_demote(sensitive_data.server_key); 590 key_free(sensitive_data.server_key); 591 sensitive_data.server_key = tmp; 592 } 593 594 for (i = 0; i < options.num_host_key_files; i++) { 595 if (sensitive_data.host_keys[i]) { 596 tmp = key_demote(sensitive_data.host_keys[i]); 597 key_free(sensitive_data.host_keys[i]); 598 sensitive_data.host_keys[i] = tmp; 599 if (tmp->type == KEY_RSA1) 600 sensitive_data.ssh1_host_key = tmp; 601 } 602 /* Certs do not need demotion */ 603 } 604 605 /* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */ 606} 607 608static void 609privsep_preauth_child(void) 610{ 611 u_int32_t rnd[256]; 612 gid_t gidset[1]; 613 614 /* Enable challenge-response authentication for privilege separation */ 615 privsep_challenge_enable(); 616 617#ifdef GSSAPI 618 /* Cache supported mechanism OIDs for later use */ 619 if (options.gss_authentication) 620 ssh_gssapi_prepare_supported_oids(); 621#endif 622 623 arc4random_stir(); 624 arc4random_buf(rnd, sizeof(rnd)); 625#ifdef WITH_OPENSSL 626 RAND_seed(rnd, sizeof(rnd)); 627 if ((RAND_bytes((u_char *)rnd, 1)) != 1) 628 fatal("%s: RAND_bytes failed", __func__); 629#endif 630 explicit_bzero(rnd, sizeof(rnd)); 631 632 /* Demote the private keys to public keys. */ 633 demote_sensitive_data(); 634 635 /* Change our root directory */ 636 if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1) 637 fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR, 638 strerror(errno)); 639 if (chdir("/") == -1) 640 fatal("chdir(\"/\"): %s", strerror(errno)); 641 642 /* Drop our privileges */ 643 debug3("privsep user:group %u:%u", (u_int)privsep_pw->pw_uid, 644 (u_int)privsep_pw->pw_gid); 645#if 0 646 /* XXX not ready, too heavy after chroot */ 647 do_setusercontext(privsep_pw); 648#else 649 gidset[0] = privsep_pw->pw_gid; 650 if (setgroups(1, gidset) < 0) 651 fatal("setgroups: %.100s", strerror(errno)); 652 permanently_set_uid(privsep_pw); 653#endif 654} 655 656static int 657privsep_preauth(Authctxt *authctxt) 658{ 659 int status, r; 660 pid_t pid; 661 struct ssh_sandbox *box = NULL; 662 663 /* Set up unprivileged child process to deal with network data */ 664 pmonitor = monitor_init(); 665 /* Store a pointer to the kex for later rekeying */ 666 pmonitor->m_pkex = &active_state->kex; 667 668 if (use_privsep == PRIVSEP_ON) 669 box = ssh_sandbox_init(pmonitor); 670 pid = fork(); 671 if (pid == -1) { 672 fatal("fork of unprivileged child failed"); 673 } else if (pid != 0) { 674 debug2("Network child is on pid %ld", (long)pid); 675 676 pmonitor->m_pid = pid; 677 if (have_agent) { 678 r = ssh_get_authentication_socket(&auth_sock); 679 if (r != 0) { 680 error("Could not get agent socket: %s", 681 ssh_err(r)); 682 have_agent = 0; 683 } 684 } 685 if (box != NULL) 686 ssh_sandbox_parent_preauth(box, pid); 687 monitor_child_preauth(authctxt, pmonitor); 688 689 /* Sync memory */ 690 monitor_sync(pmonitor); 691 692 /* Wait for the child's exit status */ 693 while (waitpid(pid, &status, 0) < 0) { 694 if (errno == EINTR) 695 continue; 696 pmonitor->m_pid = -1; 697 fatal("%s: waitpid: %s", __func__, strerror(errno)); 698 } 699 privsep_is_preauth = 0; 700 pmonitor->m_pid = -1; 701 if (WIFEXITED(status)) { 702 if (WEXITSTATUS(status) != 0) 703 fatal("%s: preauth child exited with status %d", 704 __func__, WEXITSTATUS(status)); 705 } else if (WIFSIGNALED(status)) 706 fatal("%s: preauth child terminated by signal %d", 707 __func__, WTERMSIG(status)); 708 if (box != NULL) 709 ssh_sandbox_parent_finish(box); 710 return 1; 711 } else { 712 /* child */ 713 close(pmonitor->m_sendfd); 714 close(pmonitor->m_log_recvfd); 715 716 /* Arrange for logging to be sent to the monitor */ 717 set_log_handler(mm_log_handler, pmonitor); 718 719 /* Demote the child */ 720 if (getuid() == 0 || geteuid() == 0) 721 privsep_preauth_child(); 722 setproctitle("%s", "[net]"); 723 if (box != NULL) 724 ssh_sandbox_child(box); 725 726 return 0; 727 } 728} 729 730static void 731privsep_postauth(Authctxt *authctxt) 732{ 733 u_int32_t rnd[256]; 734 735#ifdef DISABLE_FD_PASSING 736 if (1) { 737#else 738 if (authctxt->pw->pw_uid == 0 || options.use_login) { 739#endif 740 /* File descriptor passing is broken or root login */ 741 use_privsep = 0; 742 goto skip; 743 } 744 745 /* New socket pair */ 746 monitor_reinit(pmonitor); 747 748 pmonitor->m_pid = fork(); 749 if (pmonitor->m_pid == -1) 750 fatal("fork of unprivileged child failed"); 751 else if (pmonitor->m_pid != 0) { 752 verbose("User child is on pid %ld", (long)pmonitor->m_pid); 753 buffer_clear(&loginmsg); 754 monitor_child_postauth(pmonitor); 755 756 /* NEVERREACHED */ 757 exit(0); 758 } 759 760 /* child */ 761 762 close(pmonitor->m_sendfd); 763 pmonitor->m_sendfd = -1; 764 765 /* Demote the private keys to public keys. */ 766 demote_sensitive_data(); 767 768 arc4random_stir(); 769 arc4random_buf(rnd, sizeof(rnd)); 770#ifdef WITH_OPENSSL 771 RAND_seed(rnd, sizeof(rnd)); 772 if ((RAND_bytes((u_char *)rnd, 1)) != 1) 773 fatal("%s: RAND_bytes failed", __func__); 774#endif 775 explicit_bzero(rnd, sizeof(rnd)); 776 777 /* Drop privileges */ 778 do_setusercontext(authctxt->pw); 779 780 skip: 781 /* It is safe now to apply the key state */ 782 monitor_apply_keystate(pmonitor); 783 784 /* 785 * Tell the packet layer that authentication was successful, since 786 * this information is not part of the key state. 787 */ 788 packet_set_authenticated(); 789} 790 791static char * 792list_hostkey_types(void) 793{ 794 Buffer b; 795 const char *p; 796 char *ret; 797 int i; 798 Key *key; 799 800 buffer_init(&b); 801 for (i = 0; i < options.num_host_key_files; i++) { 802 key = sensitive_data.host_keys[i]; 803 if (key == NULL) 804 key = sensitive_data.host_pubkeys[i]; 805 if (key == NULL || key->type == KEY_RSA1) 806 continue; 807 /* Check that the key is accepted in HostkeyAlgorithms */ 808 if (match_pattern_list(sshkey_ssh_name(key), 809 options.hostkeyalgorithms, 0) != 1) { 810 debug3("%s: %s key not permitted by HostkeyAlgorithms", 811 __func__, sshkey_ssh_name(key)); 812 continue; 813 } 814 switch (key->type) { 815 case KEY_RSA: 816 case KEY_DSA: 817 case KEY_ECDSA: 818 case KEY_ED25519: 819 if (buffer_len(&b) > 0) 820 buffer_append(&b, ",", 1); 821 p = key_ssh_name(key); 822 buffer_append(&b, p, strlen(p)); 823 break; 824 } 825 /* If the private key has a cert peer, then list that too */ 826 key = sensitive_data.host_certificates[i]; 827 if (key == NULL) 828 continue; 829 switch (key->type) { 830 case KEY_RSA_CERT: 831 case KEY_DSA_CERT: 832 case KEY_ECDSA_CERT: 833 case KEY_ED25519_CERT: 834 if (buffer_len(&b) > 0) 835 buffer_append(&b, ",", 1); 836 p = key_ssh_name(key); 837 buffer_append(&b, p, strlen(p)); 838 break; 839 } 840 } 841 buffer_append(&b, "\0", 1); 842 ret = xstrdup(buffer_ptr(&b)); 843 buffer_free(&b); 844 debug("list_hostkey_types: %s", ret); 845 return ret; 846} 847 848static Key * 849get_hostkey_by_type(int type, int nid, int need_private, struct ssh *ssh) 850{ 851 int i; 852 Key *key; 853 854 for (i = 0; i < options.num_host_key_files; i++) { 855 switch (type) { 856 case KEY_RSA_CERT: 857 case KEY_DSA_CERT: 858 case KEY_ECDSA_CERT: 859 case KEY_ED25519_CERT: 860 key = sensitive_data.host_certificates[i]; 861 break; 862 default: 863 key = sensitive_data.host_keys[i]; 864 if (key == NULL && !need_private) 865 key = sensitive_data.host_pubkeys[i]; 866 break; 867 } 868 if (key != NULL && key->type == type && 869 (key->type != KEY_ECDSA || key->ecdsa_nid == nid)) 870 return need_private ? 871 sensitive_data.host_keys[i] : key; 872 } 873 return NULL; 874} 875 876Key * 877get_hostkey_public_by_type(int type, int nid, struct ssh *ssh) 878{ 879 return get_hostkey_by_type(type, nid, 0, ssh); 880} 881 882Key * 883get_hostkey_private_by_type(int type, int nid, struct ssh *ssh) 884{ 885 return get_hostkey_by_type(type, nid, 1, ssh); 886} 887 888Key * 889get_hostkey_by_index(int ind) 890{ 891 if (ind < 0 || ind >= options.num_host_key_files) 892 return (NULL); 893 return (sensitive_data.host_keys[ind]); 894} 895 896Key * 897get_hostkey_public_by_index(int ind, struct ssh *ssh) 898{ 899 if (ind < 0 || ind >= options.num_host_key_files) 900 return (NULL); 901 return (sensitive_data.host_pubkeys[ind]); 902} 903 904int 905get_hostkey_index(Key *key, int compare, struct ssh *ssh) 906{ 907 int i; 908 909 for (i = 0; i < options.num_host_key_files; i++) { 910 if (key_is_cert(key)) { 911 if (key == sensitive_data.host_certificates[i] || 912 (compare && sensitive_data.host_certificates[i] && 913 sshkey_equal(key, 914 sensitive_data.host_certificates[i]))) 915 return (i); 916 } else { 917 if (key == sensitive_data.host_keys[i] || 918 (compare && sensitive_data.host_keys[i] && 919 sshkey_equal(key, sensitive_data.host_keys[i]))) 920 return (i); 921 if (key == sensitive_data.host_pubkeys[i] || 922 (compare && sensitive_data.host_pubkeys[i] && 923 sshkey_equal(key, sensitive_data.host_pubkeys[i]))) 924 return (i); 925 } 926 } 927 return (-1); 928} 929 930/* Inform the client of all hostkeys */ 931static void 932notify_hostkeys(struct ssh *ssh) 933{ 934 struct sshbuf *buf; 935 struct sshkey *key; 936 int i, nkeys, r; 937 char *fp; 938 939 /* Some clients cannot cope with the hostkeys message, skip those. */ 940 if (datafellows & SSH_BUG_HOSTKEYS) 941 return; 942 943 if ((buf = sshbuf_new()) == NULL) 944 fatal("%s: sshbuf_new", __func__); 945 for (i = nkeys = 0; i < options.num_host_key_files; i++) { 946 key = get_hostkey_public_by_index(i, ssh); 947 if (key == NULL || key->type == KEY_UNSPEC || 948 key->type == KEY_RSA1 || sshkey_is_cert(key)) 949 continue; 950 fp = sshkey_fingerprint(key, options.fingerprint_hash, 951 SSH_FP_DEFAULT); 952 debug3("%s: key %d: %s %s", __func__, i, 953 sshkey_ssh_name(key), fp); 954 free(fp); 955 if (nkeys == 0) { 956 packet_start(SSH2_MSG_GLOBAL_REQUEST); 957 packet_put_cstring("hostkeys-00@openssh.com"); 958 packet_put_char(0); /* want-reply */ 959 } 960 sshbuf_reset(buf); 961 if ((r = sshkey_putb(key, buf)) != 0) 962 fatal("%s: couldn't put hostkey %d: %s", 963 __func__, i, ssh_err(r)); 964 packet_put_string(sshbuf_ptr(buf), sshbuf_len(buf)); 965 nkeys++; 966 } 967 debug3("%s: sent %d hostkeys", __func__, nkeys); 968 if (nkeys == 0) 969 fatal("%s: no hostkeys", __func__); 970 packet_send(); 971 sshbuf_free(buf); 972} 973 974/* 975 * returns 1 if connection should be dropped, 0 otherwise. 976 * dropping starts at connection #max_startups_begin with a probability 977 * of (max_startups_rate/100). the probability increases linearly until 978 * all connections are dropped for startups > max_startups 979 */ 980static int 981drop_connection(int startups) 982{ 983 int p, r; 984 985 if (startups < options.max_startups_begin) 986 return 0; 987 if (startups >= options.max_startups) 988 return 1; 989 if (options.max_startups_rate == 100) 990 return 1; 991 992 p = 100 - options.max_startups_rate; 993 p *= startups - options.max_startups_begin; 994 p /= options.max_startups - options.max_startups_begin; 995 p += options.max_startups_rate; 996 r = arc4random_uniform(100); 997 998 debug("drop_connection: p %d, r %d", p, r); 999 return (r < p) ? 1 : 0; 1000} 1001 1002static void 1003usage(void) 1004{ 1005 fprintf(stderr, "%s, %s\n", 1006 SSH_RELEASE, 1007#ifdef WITH_OPENSSL 1008 SSLeay_version(SSLEAY_VERSION) 1009#else 1010 "without OpenSSL" 1011#endif 1012 ); 1013 fprintf(stderr, 1014"usage: sshd [-46DdeiqTt] [-b bits] [-C connection_spec] [-c host_cert_file]\n" 1015" [-E log_file] [-f config_file] [-g login_grace_time]\n" 1016" [-h host_key_file] [-k key_gen_time] [-o option] [-p port]\n" 1017" [-u len]\n" 1018 ); 1019 exit(1); 1020} 1021 1022static void 1023send_rexec_state(int fd, Buffer *conf) 1024{ 1025 Buffer m; 1026 1027 debug3("%s: entering fd = %d config len %d", __func__, fd, 1028 buffer_len(conf)); 1029 1030 /* 1031 * Protocol from reexec master to child: 1032 * string configuration 1033 * u_int ephemeral_key_follows 1034 * bignum e (only if ephemeral_key_follows == 1) 1035 * bignum n " 1036 * bignum d " 1037 * bignum iqmp " 1038 * bignum p " 1039 * bignum q " 1040 * string rngseed (only if OpenSSL is not self-seeded) 1041 */ 1042 buffer_init(&m); 1043 buffer_put_cstring(&m, buffer_ptr(conf)); 1044 1045#ifdef WITH_SSH1 1046 if (sensitive_data.server_key != NULL && 1047 sensitive_data.server_key->type == KEY_RSA1) { 1048 buffer_put_int(&m, 1); 1049 buffer_put_bignum(&m, sensitive_data.server_key->rsa->e); 1050 buffer_put_bignum(&m, sensitive_data.server_key->rsa->n); 1051 buffer_put_bignum(&m, sensitive_data.server_key->rsa->d); 1052 buffer_put_bignum(&m, sensitive_data.server_key->rsa->iqmp); 1053 buffer_put_bignum(&m, sensitive_data.server_key->rsa->p); 1054 buffer_put_bignum(&m, sensitive_data.server_key->rsa->q); 1055 } else 1056#endif 1057 buffer_put_int(&m, 0); 1058 1059#if defined(WITH_OPENSSL) && !defined(OPENSSL_PRNG_ONLY) 1060 rexec_send_rng_seed(&m); 1061#endif 1062 1063 if (ssh_msg_send(fd, 0, &m) == -1) 1064 fatal("%s: ssh_msg_send failed", __func__); 1065 1066 buffer_free(&m); 1067 1068 debug3("%s: done", __func__); 1069} 1070 1071static void 1072recv_rexec_state(int fd, Buffer *conf) 1073{ 1074 Buffer m; 1075 char *cp; 1076 u_int len; 1077 1078 debug3("%s: entering fd = %d", __func__, fd); 1079 1080 buffer_init(&m); 1081 1082 if (ssh_msg_recv(fd, &m) == -1) 1083 fatal("%s: ssh_msg_recv failed", __func__); 1084 if (buffer_get_char(&m) != 0) 1085 fatal("%s: rexec version mismatch", __func__); 1086 1087 cp = buffer_get_string(&m, &len); 1088 if (conf != NULL) 1089 buffer_append(conf, cp, len + 1); 1090 free(cp); 1091 1092 if (buffer_get_int(&m)) { 1093#ifdef WITH_SSH1 1094 if (sensitive_data.server_key != NULL) 1095 key_free(sensitive_data.server_key); 1096 sensitive_data.server_key = key_new_private(KEY_RSA1); 1097 buffer_get_bignum(&m, sensitive_data.server_key->rsa->e); 1098 buffer_get_bignum(&m, sensitive_data.server_key->rsa->n); 1099 buffer_get_bignum(&m, sensitive_data.server_key->rsa->d); 1100 buffer_get_bignum(&m, sensitive_data.server_key->rsa->iqmp); 1101 buffer_get_bignum(&m, sensitive_data.server_key->rsa->p); 1102 buffer_get_bignum(&m, sensitive_data.server_key->rsa->q); 1103 if (rsa_generate_additional_parameters( 1104 sensitive_data.server_key->rsa) != 0) 1105 fatal("%s: rsa_generate_additional_parameters " 1106 "error", __func__); 1107#endif 1108 } 1109 1110#if defined(WITH_OPENSSL) && !defined(OPENSSL_PRNG_ONLY) 1111 rexec_recv_rng_seed(&m); 1112#endif 1113 1114 buffer_free(&m); 1115 1116 debug3("%s: done", __func__); 1117} 1118 1119/* Accept a connection from inetd */ 1120static void 1121server_accept_inetd(int *sock_in, int *sock_out) 1122{ 1123 int fd; 1124 1125 startup_pipe = -1; 1126 if (rexeced_flag) { 1127 close(REEXEC_CONFIG_PASS_FD); 1128 *sock_in = *sock_out = dup(STDIN_FILENO); 1129 if (!debug_flag) { 1130 startup_pipe = dup(REEXEC_STARTUP_PIPE_FD); 1131 close(REEXEC_STARTUP_PIPE_FD); 1132 } 1133 } else { 1134 *sock_in = dup(STDIN_FILENO); 1135 *sock_out = dup(STDOUT_FILENO); 1136 } 1137 /* 1138 * We intentionally do not close the descriptors 0, 1, and 2 1139 * as our code for setting the descriptors won't work if 1140 * ttyfd happens to be one of those. 1141 */ 1142 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) { 1143 dup2(fd, STDIN_FILENO); 1144 dup2(fd, STDOUT_FILENO); 1145 if (!log_stderr) 1146 dup2(fd, STDERR_FILENO); 1147 if (fd > (log_stderr ? STDERR_FILENO : STDOUT_FILENO)) 1148 close(fd); 1149 } 1150 debug("inetd sockets after dupping: %d, %d", *sock_in, *sock_out); 1151} 1152 1153/* 1154 * Listen for TCP connections 1155 */ 1156static void 1157server_listen(void) 1158{ 1159 int ret, listen_sock, on = 1; 1160 struct addrinfo *ai; 1161 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 1162 1163 for (ai = options.listen_addrs; ai; ai = ai->ai_next) { 1164 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 1165 continue; 1166 if (num_listen_socks >= MAX_LISTEN_SOCKS) 1167 fatal("Too many listen sockets. " 1168 "Enlarge MAX_LISTEN_SOCKS"); 1169 if ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen, 1170 ntop, sizeof(ntop), strport, sizeof(strport), 1171 NI_NUMERICHOST|NI_NUMERICSERV)) != 0) { 1172 error("getnameinfo failed: %.100s", 1173 ssh_gai_strerror(ret)); 1174 continue; 1175 } 1176 /* Create socket for listening. */ 1177 listen_sock = socket(ai->ai_family, ai->ai_socktype, 1178 ai->ai_protocol); 1179 if (listen_sock < 0) { 1180 /* kernel may not support ipv6 */ 1181 verbose("socket: %.100s", strerror(errno)); 1182 continue; 1183 } 1184 if (set_nonblock(listen_sock) == -1) { 1185 close(listen_sock); 1186 continue; 1187 } 1188 /* 1189 * Set socket options. 1190 * Allow local port reuse in TIME_WAIT. 1191 */ 1192 if (setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR, 1193 &on, sizeof(on)) == -1) 1194 error("setsockopt SO_REUSEADDR: %s", strerror(errno)); 1195 1196 /* Only communicate in IPv6 over AF_INET6 sockets. */ 1197 if (ai->ai_family == AF_INET6) 1198 sock_set_v6only(listen_sock); 1199 1200 debug("Bind to port %s on %s.", strport, ntop); 1201 1202 /* Bind the socket to the desired port. */ 1203 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) { 1204 error("Bind to port %s on %s failed: %.200s.", 1205 strport, ntop, strerror(errno)); 1206 close(listen_sock); 1207 continue; 1208 } 1209 listen_socks[num_listen_socks] = listen_sock; 1210 num_listen_socks++; 1211 1212 /* Start listening on the port. */ 1213 if (listen(listen_sock, SSH_LISTEN_BACKLOG) < 0) 1214 fatal("listen on [%s]:%s: %.100s", 1215 ntop, strport, strerror(errno)); 1216 logit("Server listening on %s port %s.", ntop, strport); 1217 } 1218 freeaddrinfo(options.listen_addrs); 1219 1220 if (!num_listen_socks) 1221 fatal("Cannot bind any address."); 1222} 1223 1224/* 1225 * The main TCP accept loop. Note that, for the non-debug case, returns 1226 * from this function are in a forked subprocess. 1227 */ 1228static void 1229server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s) 1230{ 1231 fd_set *fdset; 1232 int i, j, ret, maxfd; 1233 int key_used = 0, startups = 0; 1234 int startup_p[2] = { -1 , -1 }; 1235 struct sockaddr_storage from; 1236 socklen_t fromlen; 1237 pid_t pid; 1238 u_char rnd[256]; 1239 1240 /* setup fd set for accept */ 1241 fdset = NULL; 1242 maxfd = 0; 1243 for (i = 0; i < num_listen_socks; i++) 1244 if (listen_socks[i] > maxfd) 1245 maxfd = listen_socks[i]; 1246 /* pipes connected to unauthenticated childs */ 1247 startup_pipes = xcalloc(options.max_startups, sizeof(int)); 1248 for (i = 0; i < options.max_startups; i++) 1249 startup_pipes[i] = -1; 1250 1251 /* 1252 * Stay listening for connections until the system crashes or 1253 * the daemon is killed with a signal. 1254 */ 1255 for (;;) { 1256 if (received_sighup) 1257 sighup_restart(); 1258 if (fdset != NULL) 1259 free(fdset); 1260 fdset = xcalloc(howmany(maxfd + 1, NFDBITS), 1261 sizeof(fd_mask)); 1262 1263 for (i = 0; i < num_listen_socks; i++) 1264 FD_SET(listen_socks[i], fdset); 1265 for (i = 0; i < options.max_startups; i++) 1266 if (startup_pipes[i] != -1) 1267 FD_SET(startup_pipes[i], fdset); 1268 1269 /* Wait in select until there is a connection. */ 1270 ret = select(maxfd+1, fdset, NULL, NULL, NULL); 1271 if (ret < 0 && errno != EINTR) 1272 error("select: %.100s", strerror(errno)); 1273 if (received_sigterm) { 1274 logit("Received signal %d; terminating.", 1275 (int) received_sigterm); 1276 close_listen_socks(); 1277 if (options.pid_file != NULL) 1278 unlink(options.pid_file); 1279 exit(received_sigterm == SIGTERM ? 0 : 255); 1280 } 1281 if (key_used && key_do_regen) { 1282 generate_ephemeral_server_key(); 1283 key_used = 0; 1284 key_do_regen = 0; 1285 } 1286 if (ret < 0) 1287 continue; 1288 1289 for (i = 0; i < options.max_startups; i++) 1290 if (startup_pipes[i] != -1 && 1291 FD_ISSET(startup_pipes[i], fdset)) { 1292 /* 1293 * the read end of the pipe is ready 1294 * if the child has closed the pipe 1295 * after successful authentication 1296 * or if the child has died 1297 */ 1298 close(startup_pipes[i]); 1299 startup_pipes[i] = -1; 1300 startups--; 1301 } 1302 for (i = 0; i < num_listen_socks; i++) { 1303 if (!FD_ISSET(listen_socks[i], fdset)) 1304 continue; 1305 fromlen = sizeof(from); 1306 *newsock = accept(listen_socks[i], 1307 (struct sockaddr *)&from, &fromlen); 1308 if (*newsock < 0) { 1309 if (errno != EINTR && errno != EWOULDBLOCK && 1310 errno != ECONNABORTED && errno != EAGAIN) 1311 error("accept: %.100s", 1312 strerror(errno)); 1313 if (errno == EMFILE || errno == ENFILE) 1314 usleep(100 * 1000); 1315 continue; 1316 } 1317 if (unset_nonblock(*newsock) == -1) { 1318 close(*newsock); 1319 continue; 1320 } 1321 if (drop_connection(startups) == 1) { 1322 debug("drop connection #%d", startups); 1323 close(*newsock); 1324 continue; 1325 } 1326 if (pipe(startup_p) == -1) { 1327 close(*newsock); 1328 continue; 1329 } 1330 1331 if (rexec_flag && socketpair(AF_UNIX, 1332 SOCK_STREAM, 0, config_s) == -1) { 1333 error("reexec socketpair: %s", 1334 strerror(errno)); 1335 close(*newsock); 1336 close(startup_p[0]); 1337 close(startup_p[1]); 1338 continue; 1339 } 1340 1341 for (j = 0; j < options.max_startups; j++) 1342 if (startup_pipes[j] == -1) { 1343 startup_pipes[j] = startup_p[0]; 1344 if (maxfd < startup_p[0]) 1345 maxfd = startup_p[0]; 1346 startups++; 1347 break; 1348 } 1349 1350 /* 1351 * Got connection. Fork a child to handle it, unless 1352 * we are in debugging mode. 1353 */ 1354 if (debug_flag) { 1355 /* 1356 * In debugging mode. Close the listening 1357 * socket, and start processing the 1358 * connection without forking. 1359 */ 1360 debug("Server will not fork when running in debugging mode."); 1361 close_listen_socks(); 1362 *sock_in = *newsock; 1363 *sock_out = *newsock; 1364 close(startup_p[0]); 1365 close(startup_p[1]); 1366 startup_pipe = -1; 1367 pid = getpid(); 1368 if (rexec_flag) { 1369 send_rexec_state(config_s[0], 1370 &cfg); 1371 close(config_s[0]); 1372 } 1373 break; 1374 } 1375 1376 /* 1377 * Normal production daemon. Fork, and have 1378 * the child process the connection. The 1379 * parent continues listening. 1380 */ 1381 platform_pre_fork(); 1382 if ((pid = fork()) == 0) { 1383 /* 1384 * Child. Close the listening and 1385 * max_startup sockets. Start using 1386 * the accepted socket. Reinitialize 1387 * logging (since our pid has changed). 1388 * We break out of the loop to handle 1389 * the connection. 1390 */ 1391 platform_post_fork_child(); 1392 startup_pipe = startup_p[1]; 1393 close_startup_pipes(); 1394 close_listen_socks(); 1395 *sock_in = *newsock; 1396 *sock_out = *newsock; 1397 log_init(__progname, 1398 options.log_level, 1399 options.log_facility, 1400 log_stderr); 1401 if (rexec_flag) 1402 close(config_s[0]); 1403 break; 1404 } 1405 1406 /* Parent. Stay in the loop. */ 1407 platform_post_fork_parent(pid); 1408 if (pid < 0) 1409 error("fork: %.100s", strerror(errno)); 1410 else 1411 debug("Forked child %ld.", (long)pid); 1412 1413 close(startup_p[1]); 1414 1415 if (rexec_flag) { 1416 send_rexec_state(config_s[0], &cfg); 1417 close(config_s[0]); 1418 close(config_s[1]); 1419 } 1420 1421 /* 1422 * Mark that the key has been used (it 1423 * was "given" to the child). 1424 */ 1425 if ((options.protocol & SSH_PROTO_1) && 1426 key_used == 0) { 1427 /* Schedule server key regeneration alarm. */ 1428 signal(SIGALRM, key_regeneration_alarm); 1429 alarm(options.key_regeneration_time); 1430 key_used = 1; 1431 } 1432 1433 close(*newsock); 1434 1435 /* 1436 * Ensure that our random state differs 1437 * from that of the child 1438 */ 1439 arc4random_stir(); 1440 arc4random_buf(rnd, sizeof(rnd)); 1441#ifdef WITH_OPENSSL 1442 RAND_seed(rnd, sizeof(rnd)); 1443 if ((RAND_bytes((u_char *)rnd, 1)) != 1) 1444 fatal("%s: RAND_bytes failed", __func__); 1445#endif 1446 explicit_bzero(rnd, sizeof(rnd)); 1447 } 1448 1449 /* child process check (or debug mode) */ 1450 if (num_listen_socks < 0) 1451 break; 1452 } 1453} 1454 1455 1456/* 1457 * Main program for the daemon. 1458 */ 1459int 1460main(int ac, char **av) 1461{ 1462 extern char *optarg; 1463 extern int optind; 1464 int r, opt, i, j, on = 1; 1465 int sock_in = -1, sock_out = -1, newsock = -1; 1466 const char *remote_ip; 1467 int remote_port; 1468 char *fp, *line, *laddr, *logfile = NULL; 1469 int config_s[2] = { -1 , -1 }; 1470 u_int n; 1471 u_int64_t ibytes, obytes; 1472 mode_t new_umask; 1473 Key *key; 1474 Key *pubkey; 1475 int keytype; 1476 Authctxt *authctxt; 1477 struct connection_info *connection_info = get_connection_info(0, 0); 1478 1479#ifdef HAVE_SECUREWARE 1480 (void)set_auth_parameters(ac, av); 1481#endif 1482 __progname = ssh_get_progname(av[0]); 1483 1484 /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */ 1485 saved_argc = ac; 1486 rexec_argc = ac; 1487 saved_argv = xcalloc(ac + 1, sizeof(*saved_argv)); 1488 for (i = 0; i < ac; i++) 1489 saved_argv[i] = xstrdup(av[i]); 1490 saved_argv[i] = NULL; 1491 1492#ifndef HAVE_SETPROCTITLE 1493 /* Prepare for later setproctitle emulation */ 1494 compat_init_setproctitle(ac, av); 1495 av = saved_argv; 1496#endif 1497 1498 if (geteuid() == 0 && setgroups(0, NULL) == -1) 1499 debug("setgroups(): %.200s", strerror(errno)); 1500 1501 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */ 1502 sanitise_stdfd(); 1503 1504 /* Initialize configuration options to their default values. */ 1505 initialize_server_options(&options); 1506 1507 /* Parse command-line arguments. */ 1508 while ((opt = getopt(ac, av, 1509 "C:E:b:c:f:g:h:k:o:p:u:46DQRTdeiqrt")) != -1) { 1510 switch (opt) { 1511 case '4': 1512 options.address_family = AF_INET; 1513 break; 1514 case '6': 1515 options.address_family = AF_INET6; 1516 break; 1517 case 'f': 1518 config_file_name = optarg; 1519 break; 1520 case 'c': 1521 if (options.num_host_cert_files >= MAX_HOSTCERTS) { 1522 fprintf(stderr, "too many host certificates.\n"); 1523 exit(1); 1524 } 1525 options.host_cert_files[options.num_host_cert_files++] = 1526 derelativise_path(optarg); 1527 break; 1528 case 'd': 1529 if (debug_flag == 0) { 1530 debug_flag = 1; 1531 options.log_level = SYSLOG_LEVEL_DEBUG1; 1532 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) 1533 options.log_level++; 1534 break; 1535 case 'D': 1536 no_daemon_flag = 1; 1537 break; 1538 case 'E': 1539 logfile = xstrdup(optarg); 1540 /* FALLTHROUGH */ 1541 case 'e': 1542 log_stderr = 1; 1543 break; 1544 case 'i': 1545 inetd_flag = 1; 1546 break; 1547 case 'r': 1548 rexec_flag = 0; 1549 break; 1550 case 'R': 1551 rexeced_flag = 1; 1552 inetd_flag = 1; 1553 break; 1554 case 'Q': 1555 /* ignored */ 1556 break; 1557 case 'q': 1558 options.log_level = SYSLOG_LEVEL_QUIET; 1559 break; 1560 case 'b': 1561 options.server_key_bits = (int)strtonum(optarg, 256, 1562 32768, NULL); 1563 break; 1564 case 'p': 1565 options.ports_from_cmdline = 1; 1566 if (options.num_ports >= MAX_PORTS) { 1567 fprintf(stderr, "too many ports.\n"); 1568 exit(1); 1569 } 1570 options.ports[options.num_ports++] = a2port(optarg); 1571 if (options.ports[options.num_ports-1] <= 0) { 1572 fprintf(stderr, "Bad port number.\n"); 1573 exit(1); 1574 } 1575 break; 1576 case 'g': 1577 if ((options.login_grace_time = convtime(optarg)) == -1) { 1578 fprintf(stderr, "Invalid login grace time.\n"); 1579 exit(1); 1580 } 1581 break; 1582 case 'k': 1583 if ((options.key_regeneration_time = convtime(optarg)) == -1) { 1584 fprintf(stderr, "Invalid key regeneration interval.\n"); 1585 exit(1); 1586 } 1587 break; 1588 case 'h': 1589 if (options.num_host_key_files >= MAX_HOSTKEYS) { 1590 fprintf(stderr, "too many host keys.\n"); 1591 exit(1); 1592 } 1593 options.host_key_files[options.num_host_key_files++] = 1594 derelativise_path(optarg); 1595 break; 1596 case 't': 1597 test_flag = 1; 1598 break; 1599 case 'T': 1600 test_flag = 2; 1601 break; 1602 case 'C': 1603 if (parse_server_match_testspec(connection_info, 1604 optarg) == -1) 1605 exit(1); 1606 break; 1607 case 'u': 1608 utmp_len = (u_int)strtonum(optarg, 0, HOST_NAME_MAX+1+1, NULL); 1609 if (utmp_len > HOST_NAME_MAX+1) { 1610 fprintf(stderr, "Invalid utmp length.\n"); 1611 exit(1); 1612 } 1613 break; 1614 case 'o': 1615 line = xstrdup(optarg); 1616 if (process_server_config_line(&options, line, 1617 "command-line", 0, NULL, NULL) != 0) 1618 exit(1); 1619 free(line); 1620 break; 1621 case '?': 1622 default: 1623 usage(); 1624 break; 1625 } 1626 } 1627 if (rexeced_flag || inetd_flag) 1628 rexec_flag = 0; 1629 if (!test_flag && (rexec_flag && (av[0] == NULL || *av[0] != '/'))) 1630 fatal("sshd re-exec requires execution with an absolute path"); 1631 if (rexeced_flag) 1632 closefrom(REEXEC_MIN_FREE_FD); 1633 else 1634 closefrom(REEXEC_DEVCRYPTO_RESERVED_FD); 1635 1636#ifdef WITH_OPENSSL 1637 OpenSSL_add_all_algorithms(); 1638#endif 1639 1640 /* If requested, redirect the logs to the specified logfile. */ 1641 if (logfile != NULL) { 1642 log_redirect_stderr_to(logfile); 1643 free(logfile); 1644 } 1645 /* 1646 * Force logging to stderr until we have loaded the private host 1647 * key (unless started from inetd) 1648 */ 1649 log_init(__progname, 1650 options.log_level == SYSLOG_LEVEL_NOT_SET ? 1651 SYSLOG_LEVEL_INFO : options.log_level, 1652 options.log_facility == SYSLOG_FACILITY_NOT_SET ? 1653 SYSLOG_FACILITY_AUTH : options.log_facility, 1654 log_stderr || !inetd_flag); 1655 1656 /* 1657 * Unset KRB5CCNAME, otherwise the user's session may inherit it from 1658 * root's environment 1659 */ 1660 if (getenv("KRB5CCNAME") != NULL) 1661 (void) unsetenv("KRB5CCNAME"); 1662 1663#ifdef _UNICOS 1664 /* Cray can define user privs drop all privs now! 1665 * Not needed on PRIV_SU systems! 1666 */ 1667 drop_cray_privs(); 1668#endif 1669 1670 sensitive_data.server_key = NULL; 1671 sensitive_data.ssh1_host_key = NULL; 1672 sensitive_data.have_ssh1_key = 0; 1673 sensitive_data.have_ssh2_key = 0; 1674 1675 /* 1676 * If we're doing an extended config test, make sure we have all of 1677 * the parameters we need. If we're not doing an extended test, 1678 * do not silently ignore connection test params. 1679 */ 1680 if (test_flag >= 2 && server_match_spec_complete(connection_info) == 0) 1681 fatal("user, host and addr are all required when testing " 1682 "Match configs"); 1683 if (test_flag < 2 && server_match_spec_complete(connection_info) >= 0) 1684 fatal("Config test connection parameter (-C) provided without " 1685 "test mode (-T)"); 1686 1687 /* Fetch our configuration */ 1688 buffer_init(&cfg); 1689 if (rexeced_flag) 1690 recv_rexec_state(REEXEC_CONFIG_PASS_FD, &cfg); 1691 else if (strcasecmp(config_file_name, "none") != 0) 1692 load_server_config(config_file_name, &cfg); 1693 1694 parse_server_config(&options, rexeced_flag ? "rexec" : config_file_name, 1695 &cfg, NULL); 1696 1697 seed_rng(); 1698 1699 /* Fill in default values for those options not explicitly set. */ 1700 fill_default_server_options(&options); 1701 1702 /* challenge-response is implemented via keyboard interactive */ 1703 if (options.challenge_response_authentication) 1704 options.kbd_interactive_authentication = 1; 1705 1706 /* Check that options are sensible */ 1707 if (options.authorized_keys_command_user == NULL && 1708 (options.authorized_keys_command != NULL && 1709 strcasecmp(options.authorized_keys_command, "none") != 0)) 1710 fatal("AuthorizedKeysCommand set without " 1711 "AuthorizedKeysCommandUser"); 1712 if (options.authorized_principals_command_user == NULL && 1713 (options.authorized_principals_command != NULL && 1714 strcasecmp(options.authorized_principals_command, "none") != 0)) 1715 fatal("AuthorizedPrincipalsCommand set without " 1716 "AuthorizedPrincipalsCommandUser"); 1717 1718 /* 1719 * Check whether there is any path through configured auth methods. 1720 * Unfortunately it is not possible to verify this generally before 1721 * daemonisation in the presence of Match block, but this catches 1722 * and warns for trivial misconfigurations that could break login. 1723 */ 1724 if (options.num_auth_methods != 0) { 1725 if ((options.protocol & SSH_PROTO_1)) 1726 fatal("AuthenticationMethods is not supported with " 1727 "SSH protocol 1"); 1728 for (n = 0; n < options.num_auth_methods; n++) { 1729 if (auth2_methods_valid(options.auth_methods[n], 1730 1) == 0) 1731 break; 1732 } 1733 if (n >= options.num_auth_methods) 1734 fatal("AuthenticationMethods cannot be satisfied by " 1735 "enabled authentication methods"); 1736 } 1737 1738 /* set default channel AF */ 1739 channel_set_af(options.address_family); 1740 1741 /* Check that there are no remaining arguments. */ 1742 if (optind < ac) { 1743 fprintf(stderr, "Extra argument %s.\n", av[optind]); 1744 exit(1); 1745 } 1746 1747 debug("sshd version %s, %s", SSH_VERSION, 1748#ifdef WITH_OPENSSL 1749 SSLeay_version(SSLEAY_VERSION) 1750#else 1751 "without OpenSSL" 1752#endif 1753 ); 1754 1755 /* Store privilege separation user for later use if required. */ 1756 if ((privsep_pw = getpwnam(SSH_PRIVSEP_USER)) == NULL) { 1757 if (use_privsep || options.kerberos_authentication) 1758 fatal("Privilege separation user %s does not exist", 1759 SSH_PRIVSEP_USER); 1760 } else { 1761 if (privsep_pw->pw_passwd != NULL) { 1762 explicit_bzero(privsep_pw->pw_passwd, 1763 strlen(privsep_pw->pw_passwd)); 1764 } 1765 privsep_pw = pwcopy(privsep_pw); 1766 if (privsep_pw->pw_passwd != NULL) { 1767 free(privsep_pw->pw_passwd); 1768 } 1769 privsep_pw->pw_passwd = xstrdup("*"); 1770 } 1771#if !defined(ANDROID) 1772 endpwent(); 1773#endif 1774 1775 /* load host keys */ 1776 sensitive_data.host_keys = xcalloc(options.num_host_key_files, 1777 sizeof(Key *)); 1778 sensitive_data.host_pubkeys = xcalloc(options.num_host_key_files, 1779 sizeof(Key *)); 1780 1781 if (options.host_key_agent) { 1782 if (strcmp(options.host_key_agent, SSH_AUTHSOCKET_ENV_NAME)) 1783 setenv(SSH_AUTHSOCKET_ENV_NAME, 1784 options.host_key_agent, 1); 1785 if ((r = ssh_get_authentication_socket(NULL)) == 0) 1786 have_agent = 1; 1787 else 1788 error("Could not connect to agent \"%s\": %s", 1789 options.host_key_agent, ssh_err(r)); 1790 } 1791 1792 for (i = 0; i < options.num_host_key_files; i++) { 1793 if (options.host_key_files[i] == NULL) 1794 continue; 1795 key = key_load_private(options.host_key_files[i], "", NULL); 1796 pubkey = key_load_public(options.host_key_files[i], NULL); 1797 if (pubkey == NULL && key != NULL) 1798 pubkey = key_demote(key); 1799 sensitive_data.host_keys[i] = key; 1800 sensitive_data.host_pubkeys[i] = pubkey; 1801 1802 if (key == NULL && pubkey != NULL && pubkey->type != KEY_RSA1 && 1803 have_agent) { 1804 debug("will rely on agent for hostkey %s", 1805 options.host_key_files[i]); 1806 keytype = pubkey->type; 1807 } else if (key != NULL) { 1808 keytype = key->type; 1809 } else { 1810 error("Could not load host key: %s", 1811 options.host_key_files[i]); 1812 sensitive_data.host_keys[i] = NULL; 1813 sensitive_data.host_pubkeys[i] = NULL; 1814 continue; 1815 } 1816 1817 switch (keytype) { 1818 case KEY_RSA1: 1819 sensitive_data.ssh1_host_key = key; 1820 sensitive_data.have_ssh1_key = 1; 1821 break; 1822 case KEY_RSA: 1823 case KEY_DSA: 1824 case KEY_ECDSA: 1825 case KEY_ED25519: 1826 if (have_agent || key != NULL) 1827 sensitive_data.have_ssh2_key = 1; 1828 break; 1829 } 1830 if ((fp = sshkey_fingerprint(pubkey, options.fingerprint_hash, 1831 SSH_FP_DEFAULT)) == NULL) 1832 fatal("sshkey_fingerprint failed"); 1833 debug("%s host key #%d: %s %s", 1834 key ? "private" : "agent", i, keytype == KEY_RSA1 ? 1835 sshkey_type(pubkey) : sshkey_ssh_name(pubkey), fp); 1836 free(fp); 1837 } 1838 if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) { 1839 logit("Disabling protocol version 1. Could not load host key"); 1840 options.protocol &= ~SSH_PROTO_1; 1841 } 1842 if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) { 1843 logit("Disabling protocol version 2. Could not load host key"); 1844 options.protocol &= ~SSH_PROTO_2; 1845 } 1846 if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) { 1847 logit("sshd: no hostkeys available -- exiting."); 1848 exit(1); 1849 } 1850 1851 /* 1852 * Load certificates. They are stored in an array at identical 1853 * indices to the public keys that they relate to. 1854 */ 1855 sensitive_data.host_certificates = xcalloc(options.num_host_key_files, 1856 sizeof(Key *)); 1857 for (i = 0; i < options.num_host_key_files; i++) 1858 sensitive_data.host_certificates[i] = NULL; 1859 1860 for (i = 0; i < options.num_host_cert_files; i++) { 1861 if (options.host_cert_files[i] == NULL) 1862 continue; 1863 key = key_load_public(options.host_cert_files[i], NULL); 1864 if (key == NULL) { 1865 error("Could not load host certificate: %s", 1866 options.host_cert_files[i]); 1867 continue; 1868 } 1869 if (!key_is_cert(key)) { 1870 error("Certificate file is not a certificate: %s", 1871 options.host_cert_files[i]); 1872 key_free(key); 1873 continue; 1874 } 1875 /* Find matching private key */ 1876 for (j = 0; j < options.num_host_key_files; j++) { 1877 if (key_equal_public(key, 1878 sensitive_data.host_keys[j])) { 1879 sensitive_data.host_certificates[j] = key; 1880 break; 1881 } 1882 } 1883 if (j >= options.num_host_key_files) { 1884 error("No matching private key for certificate: %s", 1885 options.host_cert_files[i]); 1886 key_free(key); 1887 continue; 1888 } 1889 sensitive_data.host_certificates[j] = key; 1890 debug("host certificate: #%d type %d %s", j, key->type, 1891 key_type(key)); 1892 } 1893 1894#ifdef WITH_SSH1 1895 /* Check certain values for sanity. */ 1896 if (options.protocol & SSH_PROTO_1) { 1897 if (options.server_key_bits < SSH_RSA_MINIMUM_MODULUS_SIZE || 1898 options.server_key_bits > OPENSSL_RSA_MAX_MODULUS_BITS) { 1899 fprintf(stderr, "Bad server key size.\n"); 1900 exit(1); 1901 } 1902 /* 1903 * Check that server and host key lengths differ sufficiently. This 1904 * is necessary to make double encryption work with rsaref. Oh, I 1905 * hate software patents. I dont know if this can go? Niels 1906 */ 1907 if (options.server_key_bits > 1908 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - 1909 SSH_KEY_BITS_RESERVED && options.server_key_bits < 1910 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + 1911 SSH_KEY_BITS_RESERVED) { 1912 options.server_key_bits = 1913 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + 1914 SSH_KEY_BITS_RESERVED; 1915 debug("Forcing server key to %d bits to make it differ from host key.", 1916 options.server_key_bits); 1917 } 1918 } 1919#endif 1920 1921 if (use_privsep) { 1922 struct stat st; 1923 1924 if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &st) == -1) || 1925 (S_ISDIR(st.st_mode) == 0)) 1926 fatal("Missing privilege separation directory: %s", 1927 _PATH_PRIVSEP_CHROOT_DIR); 1928 1929#ifdef HAVE_CYGWIN 1930 if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) && 1931 (st.st_uid != getuid () || 1932 (st.st_mode & (S_IWGRP|S_IWOTH)) != 0)) 1933#else 1934 if (st.st_uid != 0 || (st.st_mode & (S_IWGRP|S_IWOTH)) != 0) 1935#endif 1936 fatal("%s must be owned by root and not group or " 1937 "world-writable.", _PATH_PRIVSEP_CHROOT_DIR); 1938 } 1939 1940 if (test_flag > 1) { 1941 if (server_match_spec_complete(connection_info) == 1) 1942 parse_server_match_config(&options, connection_info); 1943 dump_config(&options); 1944 } 1945 1946 /* Configuration looks good, so exit if in test mode. */ 1947 if (test_flag) 1948 exit(0); 1949 1950 /* 1951 * Clear out any supplemental groups we may have inherited. This 1952 * prevents inadvertent creation of files with bad modes (in the 1953 * portable version at least, it's certainly possible for PAM 1954 * to create a file, and we can't control the code in every 1955 * module which might be used). 1956 */ 1957 if (setgroups(0, NULL) < 0) 1958 debug("setgroups() failed: %.200s", strerror(errno)); 1959 1960 if (rexec_flag) { 1961 rexec_argv = xcalloc(rexec_argc + 2, sizeof(char *)); 1962 for (i = 0; i < rexec_argc; i++) { 1963 debug("rexec_argv[%d]='%s'", i, saved_argv[i]); 1964 rexec_argv[i] = saved_argv[i]; 1965 } 1966 rexec_argv[rexec_argc] = "-R"; 1967 rexec_argv[rexec_argc + 1] = NULL; 1968 } 1969 1970 /* Ensure that umask disallows at least group and world write */ 1971 new_umask = umask(0077) | 0022; 1972 (void) umask(new_umask); 1973 1974 /* Initialize the log (it is reinitialized below in case we forked). */ 1975 if (debug_flag && (!inetd_flag || rexeced_flag)) 1976 log_stderr = 1; 1977 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1978 1979 /* 1980 * If not in debugging mode, and not started from inetd, disconnect 1981 * from the controlling terminal, and fork. The original process 1982 * exits. 1983 */ 1984 if (!(debug_flag || inetd_flag || no_daemon_flag)) { 1985#ifdef TIOCNOTTY 1986 int fd; 1987#endif /* TIOCNOTTY */ 1988 if (daemon(0, 0) < 0) 1989 fatal("daemon() failed: %.200s", strerror(errno)); 1990 1991 /* Disconnect from the controlling tty. */ 1992#ifdef TIOCNOTTY 1993 fd = open(_PATH_TTY, O_RDWR | O_NOCTTY); 1994 if (fd >= 0) { 1995 (void) ioctl(fd, TIOCNOTTY, NULL); 1996 close(fd); 1997 } 1998#endif /* TIOCNOTTY */ 1999 } 2000 /* Reinitialize the log (because of the fork above). */ 2001 log_init(__progname, options.log_level, options.log_facility, log_stderr); 2002 2003 /* Chdir to the root directory so that the current disk can be 2004 unmounted if desired. */ 2005 if (chdir("/") == -1) 2006 error("chdir(\"/\"): %s", strerror(errno)); 2007 2008 /* ignore SIGPIPE */ 2009 signal(SIGPIPE, SIG_IGN); 2010 2011 /* Get a connection, either from inetd or a listening TCP socket */ 2012 if (inetd_flag) { 2013 server_accept_inetd(&sock_in, &sock_out); 2014 } else { 2015 platform_pre_listen(); 2016 server_listen(); 2017 2018 if (options.protocol & SSH_PROTO_1) 2019 generate_ephemeral_server_key(); 2020 2021 signal(SIGHUP, sighup_handler); 2022 signal(SIGCHLD, main_sigchld_handler); 2023 signal(SIGTERM, sigterm_handler); 2024 signal(SIGQUIT, sigterm_handler); 2025 2026 /* 2027 * Write out the pid file after the sigterm handler 2028 * is setup and the listen sockets are bound 2029 */ 2030 if (options.pid_file != NULL && !debug_flag) { 2031 FILE *f = fopen(options.pid_file, "w"); 2032 2033 if (f == NULL) { 2034 error("Couldn't create pid file \"%s\": %s", 2035 options.pid_file, strerror(errno)); 2036 } else { 2037 fprintf(f, "%ld\n", (long) getpid()); 2038 fclose(f); 2039 } 2040 } 2041 2042 /* Accept a connection and return in a forked child */ 2043 server_accept_loop(&sock_in, &sock_out, 2044 &newsock, config_s); 2045 } 2046 2047 /* This is the child processing a new connection. */ 2048 setproctitle("%s", "[accepted]"); 2049 2050 /* 2051 * Create a new session and process group since the 4.4BSD 2052 * setlogin() affects the entire process group. We don't 2053 * want the child to be able to affect the parent. 2054 */ 2055#if !defined(SSHD_ACQUIRES_CTTY) 2056 /* 2057 * If setsid is called, on some platforms sshd will later acquire a 2058 * controlling terminal which will result in "could not set 2059 * controlling tty" errors. 2060 */ 2061 if (!debug_flag && !inetd_flag && setsid() < 0) 2062 error("setsid: %.100s", strerror(errno)); 2063#endif 2064 2065 if (rexec_flag) { 2066 int fd; 2067 2068 debug("rexec start in %d out %d newsock %d pipe %d sock %d", 2069 sock_in, sock_out, newsock, startup_pipe, config_s[0]); 2070 dup2(newsock, STDIN_FILENO); 2071 dup2(STDIN_FILENO, STDOUT_FILENO); 2072 if (startup_pipe == -1) 2073 close(REEXEC_STARTUP_PIPE_FD); 2074 else if (startup_pipe != REEXEC_STARTUP_PIPE_FD) { 2075 dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD); 2076 close(startup_pipe); 2077 startup_pipe = REEXEC_STARTUP_PIPE_FD; 2078 } 2079 2080 dup2(config_s[1], REEXEC_CONFIG_PASS_FD); 2081 close(config_s[1]); 2082 2083 execv(rexec_argv[0], rexec_argv); 2084 2085 /* Reexec has failed, fall back and continue */ 2086 error("rexec of %s failed: %s", rexec_argv[0], strerror(errno)); 2087 recv_rexec_state(REEXEC_CONFIG_PASS_FD, NULL); 2088 log_init(__progname, options.log_level, 2089 options.log_facility, log_stderr); 2090 2091 /* Clean up fds */ 2092 close(REEXEC_CONFIG_PASS_FD); 2093 newsock = sock_out = sock_in = dup(STDIN_FILENO); 2094 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) { 2095 dup2(fd, STDIN_FILENO); 2096 dup2(fd, STDOUT_FILENO); 2097 if (fd > STDERR_FILENO) 2098 close(fd); 2099 } 2100 debug("rexec cleanup in %d out %d newsock %d pipe %d sock %d", 2101 sock_in, sock_out, newsock, startup_pipe, config_s[0]); 2102 } 2103 2104 /* Executed child processes don't need these. */ 2105 fcntl(sock_out, F_SETFD, FD_CLOEXEC); 2106 fcntl(sock_in, F_SETFD, FD_CLOEXEC); 2107 2108 /* 2109 * Disable the key regeneration alarm. We will not regenerate the 2110 * key since we are no longer in a position to give it to anyone. We 2111 * will not restart on SIGHUP since it no longer makes sense. 2112 */ 2113 alarm(0); 2114 signal(SIGALRM, SIG_DFL); 2115 signal(SIGHUP, SIG_DFL); 2116 signal(SIGTERM, SIG_DFL); 2117 signal(SIGQUIT, SIG_DFL); 2118 signal(SIGCHLD, SIG_DFL); 2119 signal(SIGINT, SIG_DFL); 2120 2121 /* 2122 * Register our connection. This turns encryption off because we do 2123 * not have a key. 2124 */ 2125 packet_set_connection(sock_in, sock_out); 2126 packet_set_server(); 2127 2128 /* Set SO_KEEPALIVE if requested. */ 2129 if (options.tcp_keep_alive && packet_connection_is_on_socket() && 2130 setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on, sizeof(on)) < 0) 2131 error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); 2132 2133 if ((remote_port = get_remote_port()) < 0) { 2134 debug("get_remote_port failed"); 2135 cleanup_exit(255); 2136 } 2137 2138 /* 2139 * We use get_canonical_hostname with usedns = 0 instead of 2140 * get_remote_ipaddr here so IP options will be checked. 2141 */ 2142 (void) get_canonical_hostname(0); 2143 /* 2144 * The rest of the code depends on the fact that 2145 * get_remote_ipaddr() caches the remote ip, even if 2146 * the socket goes away. 2147 */ 2148 remote_ip = get_remote_ipaddr(); 2149 2150#ifdef SSH_AUDIT_EVENTS 2151 audit_connection_from(remote_ip, remote_port); 2152#endif 2153 2154 /* Log the connection. */ 2155 laddr = get_local_ipaddr(sock_in); 2156 verbose("Connection from %s port %d on %s port %d", 2157 remote_ip, remote_port, laddr, get_local_port()); 2158 free(laddr); 2159 2160 /* 2161 * We don't want to listen forever unless the other side 2162 * successfully authenticates itself. So we set up an alarm which is 2163 * cleared after successful authentication. A limit of zero 2164 * indicates no limit. Note that we don't set the alarm in debugging 2165 * mode; it is just annoying to have the server exit just when you 2166 * are about to discover the bug. 2167 */ 2168 signal(SIGALRM, grace_alarm_handler); 2169 if (!debug_flag) 2170 alarm(options.login_grace_time); 2171 2172 sshd_exchange_identification(sock_in, sock_out); 2173 2174 /* In inetd mode, generate ephemeral key only for proto 1 connections */ 2175 if (!compat20 && inetd_flag && sensitive_data.server_key == NULL) 2176 generate_ephemeral_server_key(); 2177 2178 packet_set_nonblocking(); 2179 2180 /* allocate authentication context */ 2181 authctxt = xcalloc(1, sizeof(*authctxt)); 2182 2183 authctxt->loginmsg = &loginmsg; 2184 2185 /* XXX global for cleanup, access from other modules */ 2186 the_authctxt = authctxt; 2187 2188 /* prepare buffer to collect messages to display to user after login */ 2189 buffer_init(&loginmsg); 2190 auth_debug_reset(); 2191 2192 if (use_privsep) { 2193 if (privsep_preauth(authctxt) == 1) 2194 goto authenticated; 2195 } else if (compat20 && have_agent) { 2196 if ((r = ssh_get_authentication_socket(&auth_sock)) != 0) { 2197 error("Unable to get agent socket: %s", ssh_err(r)); 2198 have_agent = 0; 2199 } 2200 } 2201 2202 /* perform the key exchange */ 2203 /* authenticate user and start session */ 2204 if (compat20) { 2205 do_ssh2_kex(); 2206 do_authentication2(authctxt); 2207 } else { 2208#ifdef WITH_SSH1 2209 do_ssh1_kex(); 2210 do_authentication(authctxt); 2211#else 2212 fatal("ssh1 not supported"); 2213#endif 2214 } 2215 /* 2216 * If we use privilege separation, the unprivileged child transfers 2217 * the current keystate and exits 2218 */ 2219 if (use_privsep) { 2220 mm_send_keystate(pmonitor); 2221 exit(0); 2222 } 2223 2224 authenticated: 2225 /* 2226 * Cancel the alarm we set to limit the time taken for 2227 * authentication. 2228 */ 2229 alarm(0); 2230 signal(SIGALRM, SIG_DFL); 2231 authctxt->authenticated = 1; 2232 if (startup_pipe != -1) { 2233 close(startup_pipe); 2234 startup_pipe = -1; 2235 } 2236 2237#ifdef SSH_AUDIT_EVENTS 2238 audit_event(SSH_AUTH_SUCCESS); 2239#endif 2240 2241#ifdef GSSAPI 2242 if (options.gss_authentication) { 2243 temporarily_use_uid(authctxt->pw); 2244 ssh_gssapi_storecreds(); 2245 restore_uid(); 2246 } 2247#endif 2248#ifdef USE_PAM 2249 if (options.use_pam) { 2250 do_pam_setcred(1); 2251 do_pam_session(); 2252 } 2253#endif 2254 2255 /* 2256 * In privilege separation, we fork another child and prepare 2257 * file descriptor passing. 2258 */ 2259 if (use_privsep) { 2260 privsep_postauth(authctxt); 2261 /* the monitor process [priv] will not return */ 2262 if (!compat20) 2263 destroy_sensitive_data(); 2264 } 2265 2266 packet_set_timeout(options.client_alive_interval, 2267 options.client_alive_count_max); 2268 2269 /* Try to send all our hostkeys to the client */ 2270 if (compat20) 2271 notify_hostkeys(active_state); 2272 2273 /* Start session. */ 2274 do_authenticated(authctxt); 2275 2276 /* The connection has been terminated. */ 2277 packet_get_bytes(&ibytes, &obytes); 2278 verbose("Transferred: sent %llu, received %llu bytes", 2279 (unsigned long long)obytes, (unsigned long long)ibytes); 2280 2281 verbose("Closing connection to %.500s port %d", remote_ip, remote_port); 2282 2283#ifdef USE_PAM 2284 if (options.use_pam) 2285 finish_pam(); 2286#endif /* USE_PAM */ 2287 2288#ifdef SSH_AUDIT_EVENTS 2289 PRIVSEP(audit_event(SSH_CONNECTION_CLOSE)); 2290#endif 2291 2292 packet_close(); 2293 2294 if (use_privsep) 2295 mm_terminate(); 2296 2297 exit(0); 2298} 2299 2300#ifdef WITH_SSH1 2301/* 2302 * Decrypt session_key_int using our private server key and private host key 2303 * (key with larger modulus first). 2304 */ 2305int 2306ssh1_session_key(BIGNUM *session_key_int) 2307{ 2308 int rsafail = 0; 2309 2310 if (BN_cmp(sensitive_data.server_key->rsa->n, 2311 sensitive_data.ssh1_host_key->rsa->n) > 0) { 2312 /* Server key has bigger modulus. */ 2313 if (BN_num_bits(sensitive_data.server_key->rsa->n) < 2314 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + 2315 SSH_KEY_BITS_RESERVED) { 2316 fatal("do_connection: %s: " 2317 "server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d", 2318 get_remote_ipaddr(), 2319 BN_num_bits(sensitive_data.server_key->rsa->n), 2320 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n), 2321 SSH_KEY_BITS_RESERVED); 2322 } 2323 if (rsa_private_decrypt(session_key_int, session_key_int, 2324 sensitive_data.server_key->rsa) != 0) 2325 rsafail++; 2326 if (rsa_private_decrypt(session_key_int, session_key_int, 2327 sensitive_data.ssh1_host_key->rsa) != 0) 2328 rsafail++; 2329 } else { 2330 /* Host key has bigger modulus (or they are equal). */ 2331 if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) < 2332 BN_num_bits(sensitive_data.server_key->rsa->n) + 2333 SSH_KEY_BITS_RESERVED) { 2334 fatal("do_connection: %s: " 2335 "host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d", 2336 get_remote_ipaddr(), 2337 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n), 2338 BN_num_bits(sensitive_data.server_key->rsa->n), 2339 SSH_KEY_BITS_RESERVED); 2340 } 2341 if (rsa_private_decrypt(session_key_int, session_key_int, 2342 sensitive_data.ssh1_host_key->rsa) != 0) 2343 rsafail++; 2344 if (rsa_private_decrypt(session_key_int, session_key_int, 2345 sensitive_data.server_key->rsa) != 0) 2346 rsafail++; 2347 } 2348 return (rsafail); 2349} 2350 2351/* 2352 * SSH1 key exchange 2353 */ 2354static void 2355do_ssh1_kex(void) 2356{ 2357 int i, len; 2358 int rsafail = 0; 2359 BIGNUM *session_key_int, *fake_key_int, *real_key_int; 2360 u_char session_key[SSH_SESSION_KEY_LENGTH]; 2361 u_char fake_key_bytes[4096 / 8]; 2362 size_t fake_key_len; 2363 u_char cookie[8]; 2364 u_int cipher_type, auth_mask, protocol_flags; 2365 2366 /* 2367 * Generate check bytes that the client must send back in the user 2368 * packet in order for it to be accepted; this is used to defy ip 2369 * spoofing attacks. Note that this only works against somebody 2370 * doing IP spoofing from a remote machine; any machine on the local 2371 * network can still see outgoing packets and catch the random 2372 * cookie. This only affects rhosts authentication, and this is one 2373 * of the reasons why it is inherently insecure. 2374 */ 2375 arc4random_buf(cookie, sizeof(cookie)); 2376 2377 /* 2378 * Send our public key. We include in the packet 64 bits of random 2379 * data that must be matched in the reply in order to prevent IP 2380 * spoofing. 2381 */ 2382 packet_start(SSH_SMSG_PUBLIC_KEY); 2383 for (i = 0; i < 8; i++) 2384 packet_put_char(cookie[i]); 2385 2386 /* Store our public server RSA key. */ 2387 packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n)); 2388 packet_put_bignum(sensitive_data.server_key->rsa->e); 2389 packet_put_bignum(sensitive_data.server_key->rsa->n); 2390 2391 /* Store our public host RSA key. */ 2392 packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n)); 2393 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e); 2394 packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n); 2395 2396 /* Put protocol flags. */ 2397 packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN); 2398 2399 /* Declare which ciphers we support. */ 2400 packet_put_int(cipher_mask_ssh1(0)); 2401 2402 /* Declare supported authentication types. */ 2403 auth_mask = 0; 2404 if (options.rhosts_rsa_authentication) 2405 auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA; 2406 if (options.rsa_authentication) 2407 auth_mask |= 1 << SSH_AUTH_RSA; 2408 if (options.challenge_response_authentication == 1) 2409 auth_mask |= 1 << SSH_AUTH_TIS; 2410 if (options.password_authentication) 2411 auth_mask |= 1 << SSH_AUTH_PASSWORD; 2412 packet_put_int(auth_mask); 2413 2414 /* Send the packet and wait for it to be sent. */ 2415 packet_send(); 2416 packet_write_wait(); 2417 2418 debug("Sent %d bit server key and %d bit host key.", 2419 BN_num_bits(sensitive_data.server_key->rsa->n), 2420 BN_num_bits(sensitive_data.ssh1_host_key->rsa->n)); 2421 2422 /* Read clients reply (cipher type and session key). */ 2423 packet_read_expect(SSH_CMSG_SESSION_KEY); 2424 2425 /* Get cipher type and check whether we accept this. */ 2426 cipher_type = packet_get_char(); 2427 2428 if (!(cipher_mask_ssh1(0) & (1 << cipher_type))) 2429 packet_disconnect("Warning: client selects unsupported cipher."); 2430 2431 /* Get check bytes from the packet. These must match those we 2432 sent earlier with the public key packet. */ 2433 for (i = 0; i < 8; i++) 2434 if (cookie[i] != packet_get_char()) 2435 packet_disconnect("IP Spoofing check bytes do not match."); 2436 2437 debug("Encryption type: %.200s", cipher_name(cipher_type)); 2438 2439 /* Get the encrypted integer. */ 2440 if ((real_key_int = BN_new()) == NULL) 2441 fatal("do_ssh1_kex: BN_new failed"); 2442 packet_get_bignum(real_key_int); 2443 2444 protocol_flags = packet_get_int(); 2445 packet_set_protocol_flags(protocol_flags); 2446 packet_check_eom(); 2447 2448 /* Setup a fake key in case RSA decryption fails */ 2449 if ((fake_key_int = BN_new()) == NULL) 2450 fatal("do_ssh1_kex: BN_new failed"); 2451 fake_key_len = BN_num_bytes(real_key_int); 2452 if (fake_key_len > sizeof(fake_key_bytes)) 2453 fake_key_len = sizeof(fake_key_bytes); 2454 arc4random_buf(fake_key_bytes, fake_key_len); 2455 if (BN_bin2bn(fake_key_bytes, fake_key_len, fake_key_int) == NULL) 2456 fatal("do_ssh1_kex: BN_bin2bn failed"); 2457 2458 /* Decrypt real_key_int using host/server keys */ 2459 rsafail = PRIVSEP(ssh1_session_key(real_key_int)); 2460 /* If decryption failed, use the fake key. Else, the real key. */ 2461 if (rsafail) 2462 session_key_int = fake_key_int; 2463 else 2464 session_key_int = real_key_int; 2465 2466 /* 2467 * Extract session key from the decrypted integer. The key is in the 2468 * least significant 256 bits of the integer; the first byte of the 2469 * key is in the highest bits. 2470 */ 2471 (void) BN_mask_bits(session_key_int, sizeof(session_key) * 8); 2472 len = BN_num_bytes(session_key_int); 2473 if (len < 0 || (u_int)len > sizeof(session_key)) { 2474 error("do_ssh1_kex: bad session key len from %s: " 2475 "session_key_int %d > sizeof(session_key) %lu", 2476 get_remote_ipaddr(), len, (u_long)sizeof(session_key)); 2477 rsafail++; 2478 } else { 2479 explicit_bzero(session_key, sizeof(session_key)); 2480 BN_bn2bin(session_key_int, 2481 session_key + sizeof(session_key) - len); 2482 2483 derive_ssh1_session_id( 2484 sensitive_data.ssh1_host_key->rsa->n, 2485 sensitive_data.server_key->rsa->n, 2486 cookie, session_id); 2487 /* 2488 * Xor the first 16 bytes of the session key with the 2489 * session id. 2490 */ 2491 for (i = 0; i < 16; i++) 2492 session_key[i] ^= session_id[i]; 2493 } 2494 2495 /* Destroy the private and public keys. No longer. */ 2496 destroy_sensitive_data(); 2497 2498 if (use_privsep) 2499 mm_ssh1_session_id(session_id); 2500 2501 /* Destroy the decrypted integer. It is no longer needed. */ 2502 BN_clear_free(real_key_int); 2503 BN_clear_free(fake_key_int); 2504 2505 /* Set the session key. From this on all communications will be encrypted. */ 2506 packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type); 2507 2508 /* Destroy our copy of the session key. It is no longer needed. */ 2509 explicit_bzero(session_key, sizeof(session_key)); 2510 2511 debug("Received session key; encryption turned on."); 2512 2513 /* Send an acknowledgment packet. Note that this packet is sent encrypted. */ 2514 packet_start(SSH_SMSG_SUCCESS); 2515 packet_send(); 2516 packet_write_wait(); 2517} 2518#endif 2519 2520int 2521sshd_hostkey_sign(Key *privkey, Key *pubkey, u_char **signature, size_t *slen, 2522 const u_char *data, size_t dlen, u_int flag) 2523{ 2524 int r; 2525 u_int xxx_slen, xxx_dlen = dlen; 2526 2527 if (privkey) { 2528 if (PRIVSEP(key_sign(privkey, signature, &xxx_slen, data, xxx_dlen) < 0)) 2529 fatal("%s: key_sign failed", __func__); 2530 if (slen) 2531 *slen = xxx_slen; 2532 } else if (use_privsep) { 2533 if (mm_key_sign(pubkey, signature, &xxx_slen, data, xxx_dlen) < 0) 2534 fatal("%s: pubkey_sign failed", __func__); 2535 if (slen) 2536 *slen = xxx_slen; 2537 } else { 2538 if ((r = ssh_agent_sign(auth_sock, pubkey, signature, slen, 2539 data, dlen, datafellows)) != 0) 2540 fatal("%s: ssh_agent_sign failed: %s", 2541 __func__, ssh_err(r)); 2542 } 2543 return 0; 2544} 2545 2546/* SSH2 key exchange */ 2547static void 2548do_ssh2_kex(void) 2549{ 2550 char *myproposal[PROPOSAL_MAX] = { KEX_SERVER }; 2551 struct kex *kex; 2552 int r; 2553 2554 myproposal[PROPOSAL_KEX_ALGS] = compat_kex_proposal( 2555 options.kex_algorithms); 2556 myproposal[PROPOSAL_ENC_ALGS_CTOS] = compat_cipher_proposal( 2557 options.ciphers); 2558 myproposal[PROPOSAL_ENC_ALGS_STOC] = compat_cipher_proposal( 2559 options.ciphers); 2560 myproposal[PROPOSAL_MAC_ALGS_CTOS] = 2561 myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs; 2562 2563 if (options.compression == COMP_NONE) { 2564 myproposal[PROPOSAL_COMP_ALGS_CTOS] = 2565 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none"; 2566 } else if (options.compression == COMP_DELAYED) { 2567 myproposal[PROPOSAL_COMP_ALGS_CTOS] = 2568 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none,zlib@openssh.com"; 2569 } 2570 2571 if (options.rekey_limit || options.rekey_interval) 2572 packet_set_rekey_limits((u_int32_t)options.rekey_limit, 2573 (time_t)options.rekey_interval); 2574 2575 myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = compat_pkalg_proposal( 2576 list_hostkey_types()); 2577 2578 /* start key exchange */ 2579 if ((r = kex_setup(active_state, myproposal)) != 0) 2580 fatal("kex_setup: %s", ssh_err(r)); 2581 kex = active_state->kex; 2582#ifdef WITH_OPENSSL 2583 kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server; 2584 kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server; 2585 kex->kex[KEX_DH_GEX_SHA1] = kexgex_server; 2586 kex->kex[KEX_DH_GEX_SHA256] = kexgex_server; 2587# ifdef OPENSSL_HAS_ECC 2588 kex->kex[KEX_ECDH_SHA2] = kexecdh_server; 2589# endif 2590#endif 2591 kex->kex[KEX_C25519_SHA256] = kexc25519_server; 2592 kex->server = 1; 2593 kex->client_version_string=client_version_string; 2594 kex->server_version_string=server_version_string; 2595 kex->load_host_public_key=&get_hostkey_public_by_type; 2596 kex->load_host_private_key=&get_hostkey_private_by_type; 2597 kex->host_key_index=&get_hostkey_index; 2598 kex->sign = sshd_hostkey_sign; 2599 2600 dispatch_run(DISPATCH_BLOCK, &kex->done, active_state); 2601 2602 session_id2 = kex->session_id; 2603 session_id2_len = kex->session_id_len; 2604 2605#ifdef DEBUG_KEXDH 2606 /* send 1st encrypted/maced/compressed message */ 2607 packet_start(SSH2_MSG_IGNORE); 2608 packet_put_cstring("markus"); 2609 packet_send(); 2610 packet_write_wait(); 2611#endif 2612 debug("KEX done"); 2613} 2614 2615/* server specific fatal cleanup */ 2616void 2617cleanup_exit(int i) 2618{ 2619 if (the_authctxt) { 2620 do_cleanup(the_authctxt); 2621 if (use_privsep && privsep_is_preauth && 2622 pmonitor != NULL && pmonitor->m_pid > 1) { 2623 debug("Killing privsep child %d", pmonitor->m_pid); 2624 if (kill(pmonitor->m_pid, SIGKILL) != 0 && 2625 errno != ESRCH) 2626 error("%s: kill(%d): %s", __func__, 2627 pmonitor->m_pid, strerror(errno)); 2628 } 2629 } 2630#ifdef SSH_AUDIT_EVENTS 2631 /* done after do_cleanup so it can cancel the PAM auth 'thread' */ 2632 if (!use_privsep || mm_is_monitor()) 2633 audit_event(SSH_CONNECTION_ABANDON); 2634#endif 2635 _exit(i); 2636} 2637