1 /* $OpenBSD: sshd.c,v 1.612 2024/09/15 01:11:26 djm Exp $ */ 2 /* 3 * Copyright (c) 2000, 2001, 2002 Markus Friedl. All rights reserved. 4 * Copyright (c) 2002 Niels Provos. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 #include "includes.h" 28 29 #include <sys/types.h> 30 #include <sys/ioctl.h> 31 #include <sys/mman.h> 32 #include <sys/socket.h> 33 #ifdef HAVE_SYS_STAT_H 34 # include <sys/stat.h> 35 #endif 36 #ifdef HAVE_SYS_TIME_H 37 # include <sys/time.h> 38 #endif 39 #include "openbsd-compat/sys-tree.h" 40 #include "openbsd-compat/sys-queue.h" 41 #include <sys/wait.h> 42 43 #include <errno.h> 44 #include <fcntl.h> 45 #include <netdb.h> 46 #ifdef HAVE_PATHS_H 47 #include <paths.h> 48 #endif 49 #include <grp.h> 50 #ifdef HAVE_POLL_H 51 #include <poll.h> 52 #endif 53 #include <pwd.h> 54 #include <signal.h> 55 #include <stdarg.h> 56 #include <stdio.h> 57 #include <stdlib.h> 58 #include <string.h> 59 #include <unistd.h> 60 #include <limits.h> 61 62 #ifdef WITH_OPENSSL 63 #include <openssl/evp.h> 64 #include <openssl/rand.h> 65 #include "openbsd-compat/openssl-compat.h" 66 #endif 67 68 #ifdef HAVE_SECUREWARE 69 #include <sys/security.h> 70 #include <prot.h> 71 #endif 72 73 #ifdef __FreeBSD__ 74 #include <resolv.h> 75 #if defined(GSSAPI) && defined(HAVE_GSSAPI_GSSAPI_H) 76 #include <gssapi/gssapi.h> 77 #elif defined(GSSAPI) && defined(HAVE_GSSAPI_H) 78 #include <gssapi.h> 79 #endif 80 #endif 81 82 #include "xmalloc.h" 83 #include "ssh.h" 84 #include "sshpty.h" 85 #include "log.h" 86 #include "sshbuf.h" 87 #include "misc.h" 88 #include "servconf.h" 89 #include "compat.h" 90 #include "digest.h" 91 #include "sshkey.h" 92 #include "authfile.h" 93 #include "pathnames.h" 94 #include "canohost.h" 95 #include "hostfile.h" 96 #include "auth.h" 97 #include "authfd.h" 98 #include "msg.h" 99 #include "version.h" 100 #include "ssherr.h" 101 #include "sk-api.h" 102 #include "addr.h" 103 #include "srclimit.h" 104 105 #ifdef LIBWRAP 106 #include <tcpd.h> 107 #include <syslog.h> 108 #endif /* LIBWRAP */ 109 110 /* Re-exec fds */ 111 #define REEXEC_DEVCRYPTO_RESERVED_FD (STDERR_FILENO + 1) 112 #define REEXEC_STARTUP_PIPE_FD (STDERR_FILENO + 2) 113 #define REEXEC_CONFIG_PASS_FD (STDERR_FILENO + 3) 114 #define REEXEC_MIN_FREE_FD (STDERR_FILENO + 4) 115 116 extern char *__progname; 117 118 /* Server configuration options. */ 119 ServerOptions options; 120 121 /* 122 * Debug mode flag. This can be set on the command line. If debug 123 * mode is enabled, extra debugging output will be sent to the system 124 * log, the daemon will not go to background, and will exit after processing 125 * the first connection. 126 */ 127 int debug_flag = 0; 128 129 /* Saved arguments to main(). */ 130 static char **saved_argv; 131 static int saved_argc; 132 133 /* 134 * The sockets that the server is listening; this is used in the SIGHUP 135 * signal handler. 136 */ 137 #define MAX_LISTEN_SOCKS 16 138 static int listen_socks[MAX_LISTEN_SOCKS]; 139 static int num_listen_socks = 0; 140 141 /* 142 * Any really sensitive data in the application is contained in this 143 * structure. The idea is that this structure could be locked into memory so 144 * that the pages do not get written into swap. However, there are some 145 * problems. The private key contains BIGNUMs, and we do not (in principle) 146 * have access to the internals of them, and locking just the structure is 147 * not very useful. Currently, memory locking is not implemented. 148 */ 149 struct { 150 struct sshkey **host_keys; /* all private host keys */ 151 struct sshkey **host_pubkeys; /* all public host keys */ 152 struct sshkey **host_certificates; /* all public host certificates */ 153 int have_ssh2_key; 154 } sensitive_data; 155 156 /* This is set to true when a signal is received. */ 157 static volatile sig_atomic_t received_siginfo = 0; 158 static volatile sig_atomic_t received_sigchld = 0; 159 static volatile sig_atomic_t received_sighup = 0; 160 static volatile sig_atomic_t received_sigterm = 0; 161 162 /* record remote hostname or ip */ 163 u_int utmp_len = HOST_NAME_MAX+1; 164 165 /* 166 * The early_child/children array below is used for tracking children of the 167 * listening sshd process early in their lifespans, before they have 168 * completed authentication. This tracking is needed for four things: 169 * 170 * 1) Implementing the MaxStartups limit of concurrent unauthenticated 171 * connections. 172 * 2) Avoiding a race condition for SIGHUP processing, where child processes 173 * may have listen_socks open that could collide with main listener process 174 * after it restarts. 175 * 3) Ensuring that rexec'd sshd processes have received their initial state 176 * from the parent listen process before handling SIGHUP. 177 * 4) Tracking and logging unsuccessful exits from the preauth sshd monitor, 178 * including and especially those for LoginGraceTime timeouts. 179 * 180 * Child processes signal that they have completed closure of the listen_socks 181 * and (if applicable) received their rexec state by sending a char over their 182 * sock. 183 * 184 * Child processes signal that authentication has completed by sending a 185 * second char over the socket before closing it, otherwise the listener will 186 * continue tracking the child (and using up a MaxStartups slot) until the 187 * preauth subprocess exits, whereupon the listener will log its exit status. 188 * preauth processes will exit with a status of EXIT_LOGIN_GRACE to indicate 189 * they did not authenticate before the LoginGraceTime alarm fired. 190 */ 191 struct early_child { 192 int pipefd; 193 int early; /* Indicates child closed listener */ 194 char *id; /* human readable connection identifier */ 195 pid_t pid; 196 struct xaddr addr; 197 int have_addr; 198 int status, have_status; 199 }; 200 static struct early_child *children; 201 static int children_active; 202 static int startup_pipe = -1; /* in child */ 203 204 /* sshd_config buffer */ 205 struct sshbuf *cfg; 206 207 /* Included files from the configuration file */ 208 struct include_list includes = TAILQ_HEAD_INITIALIZER(includes); 209 210 /* message to be displayed after login */ 211 struct sshbuf *loginmsg; 212 213 /* Unprivileged user */ 214 struct passwd *privsep_pw = NULL; 215 216 static char *listener_proctitle; 217 218 /* 219 * Close all listening sockets 220 */ 221 static void 222 close_listen_socks(void) 223 { 224 int i; 225 226 for (i = 0; i < num_listen_socks; i++) 227 close(listen_socks[i]); 228 num_listen_socks = 0; 229 } 230 231 /* Allocate and initialise the children array */ 232 static void 233 child_alloc(void) 234 { 235 int i; 236 237 children = xcalloc(options.max_startups, sizeof(*children)); 238 for (i = 0; i < options.max_startups; i++) { 239 children[i].pipefd = -1; 240 children[i].pid = -1; 241 } 242 } 243 244 /* Register a new connection in the children array; child pid comes later */ 245 static struct early_child * 246 child_register(int pipefd, int sockfd) 247 { 248 int i, lport, rport; 249 char *laddr = NULL, *raddr = NULL; 250 struct early_child *child = NULL; 251 struct sockaddr_storage addr; 252 socklen_t addrlen = sizeof(addr); 253 struct sockaddr *sa = (struct sockaddr *)&addr; 254 255 for (i = 0; i < options.max_startups; i++) { 256 if (children[i].pipefd != -1 || children[i].pid > 0) 257 continue; 258 child = &(children[i]); 259 break; 260 } 261 if (child == NULL) { 262 fatal_f("error: accepted connection when all %d child " 263 " slots full", options.max_startups); 264 } 265 child->pipefd = pipefd; 266 child->early = 1; 267 /* record peer address, if available */ 268 if (getpeername(sockfd, sa, &addrlen) == 0 && 269 addr_sa_to_xaddr(sa, addrlen, &child->addr) == 0) 270 child->have_addr = 1; 271 /* format peer address string for logs */ 272 if ((lport = get_local_port(sockfd)) == 0 || 273 (rport = get_peer_port(sockfd)) == 0) { 274 /* Not a TCP socket */ 275 raddr = get_peer_ipaddr(sockfd); 276 xasprintf(&child->id, "connection from %s", raddr); 277 } else { 278 laddr = get_local_ipaddr(sockfd); 279 raddr = get_peer_ipaddr(sockfd); 280 xasprintf(&child->id, "connection from %s to %s", raddr, laddr); 281 } 282 free(laddr); 283 free(raddr); 284 if (++children_active > options.max_startups) 285 fatal_f("internal error: more children than max_startups"); 286 287 return child; 288 } 289 290 /* 291 * Finally free a child entry. Don't call this directly. 292 */ 293 static void 294 child_finish(struct early_child *child) 295 { 296 if (children_active == 0) 297 fatal_f("internal error: children_active underflow"); 298 if (child->pipefd != -1) 299 close(child->pipefd); 300 free(child->id); 301 memset(child, '\0', sizeof(*child)); 302 child->pipefd = -1; 303 child->pid = -1; 304 children_active--; 305 } 306 307 /* 308 * Close a child's pipe. This will not stop tracking the child immediately 309 * (it will still be tracked for waitpid()) unless force_final is set, or 310 * child has already exited. 311 */ 312 static void 313 child_close(struct early_child *child, int force_final, int quiet) 314 { 315 if (!quiet) 316 debug_f("enter%s", force_final ? " (forcing)" : ""); 317 if (child->pipefd != -1) { 318 close(child->pipefd); 319 child->pipefd = -1; 320 } 321 if (child->pid == -1 || force_final) 322 child_finish(child); 323 } 324 325 /* Record a child exit. Safe to call from signal handlers */ 326 static void 327 child_exit(pid_t pid, int status) 328 { 329 int i; 330 331 if (children == NULL || pid <= 0) 332 return; 333 for (i = 0; i < options.max_startups; i++) { 334 if (children[i].pid == pid) { 335 children[i].have_status = 1; 336 children[i].status = status; 337 break; 338 } 339 } 340 } 341 342 /* 343 * Reap a child entry that has exited, as previously flagged 344 * using child_exit(). 345 * Handles logging of exit condition and will finalise the child if its pipe 346 * had already been closed. 347 */ 348 static void 349 child_reap(struct early_child *child) 350 { 351 LogLevel level = SYSLOG_LEVEL_DEBUG1; 352 int was_crash, penalty_type = SRCLIMIT_PENALTY_NONE; 353 354 /* Log exit information */ 355 if (WIFSIGNALED(child->status)) { 356 /* 357 * Increase logging for signals potentially associated 358 * with serious conditions. 359 */ 360 if ((was_crash = signal_is_crash(WTERMSIG(child->status)))) 361 level = SYSLOG_LEVEL_ERROR; 362 do_log2(level, "session process %ld for %s killed by " 363 "signal %d%s", (long)child->pid, child->id, 364 WTERMSIG(child->status), child->early ? " (early)" : ""); 365 if (was_crash) 366 penalty_type = SRCLIMIT_PENALTY_CRASH; 367 } else if (!WIFEXITED(child->status)) { 368 penalty_type = SRCLIMIT_PENALTY_CRASH; 369 error("session process %ld for %s terminated abnormally, " 370 "status=0x%x%s", (long)child->pid, child->id, child->status, 371 child->early ? " (early)" : ""); 372 } else { 373 /* Normal exit. We care about the status */ 374 switch (WEXITSTATUS(child->status)) { 375 case 0: 376 debug3_f("preauth child %ld for %s completed " 377 "normally %s", (long)child->pid, child->id, 378 child->early ? " (early)" : ""); 379 break; 380 case EXIT_LOGIN_GRACE: 381 penalty_type = SRCLIMIT_PENALTY_GRACE_EXCEEDED; 382 logit("Timeout before authentication for %s, " 383 "pid = %ld%s", child->id, (long)child->pid, 384 child->early ? " (early)" : ""); 385 break; 386 case EXIT_CHILD_CRASH: 387 penalty_type = SRCLIMIT_PENALTY_CRASH; 388 logit("Session process %ld unpriv child crash for %s%s", 389 (long)child->pid, child->id, 390 child->early ? " (early)" : ""); 391 break; 392 case EXIT_AUTH_ATTEMPTED: 393 penalty_type = SRCLIMIT_PENALTY_AUTHFAIL; 394 debug_f("preauth child %ld for %s exited " 395 "after unsuccessful auth attempt %s", 396 (long)child->pid, child->id, 397 child->early ? " (early)" : ""); 398 break; 399 case EXIT_CONFIG_REFUSED: 400 penalty_type = SRCLIMIT_PENALTY_REFUSECONNECTION; 401 debug_f("preauth child %ld for %s prohibited by" 402 "RefuseConnection %s", 403 (long)child->pid, child->id, 404 child->early ? " (early)" : ""); 405 break; 406 default: 407 penalty_type = SRCLIMIT_PENALTY_NOAUTH; 408 debug_f("preauth child %ld for %s exited " 409 "with status %d%s", (long)child->pid, child->id, 410 WEXITSTATUS(child->status), 411 child->early ? " (early)" : ""); 412 break; 413 } 414 } 415 416 if (child->have_addr) 417 srclimit_penalise(&child->addr, penalty_type); 418 419 child->pid = -1; 420 child->have_status = 0; 421 if (child->pipefd == -1) 422 child_finish(child); 423 } 424 425 /* Reap all children that have exited; called after SIGCHLD */ 426 static void 427 child_reap_all_exited(void) 428 { 429 int i; 430 pid_t pid; 431 int status; 432 433 if (children == NULL) 434 return; 435 436 for (;;) { 437 if ((pid = waitpid(-1, &status, WNOHANG)) == 0) 438 break; 439 else if (pid == -1) { 440 if (errno == EINTR || errno == EAGAIN) 441 continue; 442 if (errno != ECHILD) 443 error_f("waitpid: %s", strerror(errno)); 444 break; 445 } 446 child_exit(pid, status); 447 } 448 449 for (i = 0; i < options.max_startups; i++) { 450 if (!children[i].have_status) 451 continue; 452 child_reap(&(children[i])); 453 } 454 } 455 456 static void 457 close_startup_pipes(void) 458 { 459 int i; 460 461 if (children == NULL) 462 return; 463 for (i = 0; i < options.max_startups; i++) { 464 if (children[i].pipefd != -1) 465 child_close(&(children[i]), 1, 1); 466 } 467 } 468 469 /* Called after SIGINFO */ 470 static void 471 show_info(void) 472 { 473 int i; 474 475 /* XXX print listening sockets here too */ 476 if (children == NULL) 477 return; 478 logit("%d active startups", children_active); 479 for (i = 0; i < options.max_startups; i++) { 480 if (children[i].pipefd == -1 && children[i].pid <= 0) 481 continue; 482 logit("child %d: fd=%d pid=%ld %s%s", i, children[i].pipefd, 483 (long)children[i].pid, children[i].id, 484 children[i].early ? " (early)" : ""); 485 } 486 srclimit_penalty_info(); 487 } 488 489 /* 490 * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP; 491 * the effect is to reread the configuration file (and to regenerate 492 * the server key). 493 */ 494 495 static void 496 sighup_handler(int sig) 497 { 498 received_sighup = 1; 499 } 500 501 /* 502 * Called from the main program after receiving SIGHUP. 503 * Restarts the server. 504 */ 505 static void 506 sighup_restart(void) 507 { 508 logit("Received SIGHUP; restarting."); 509 if (options.pid_file != NULL) 510 unlink(options.pid_file); 511 platform_pre_restart(); 512 close_listen_socks(); 513 close_startup_pipes(); 514 ssh_signal(SIGHUP, SIG_IGN); /* will be restored after exec */ 515 execv(saved_argv[0], saved_argv); 516 logit("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], 517 strerror(errno)); 518 exit(1); 519 } 520 521 /* 522 * Generic signal handler for terminating signals in the master daemon. 523 */ 524 static void 525 sigterm_handler(int sig) 526 { 527 received_sigterm = sig; 528 } 529 530 #ifdef SIGINFO 531 static void 532 siginfo_handler(int sig) 533 { 534 received_siginfo = 1; 535 } 536 #endif 537 538 static void 539 main_sigchld_handler(int sig) 540 { 541 received_sigchld = 1; 542 } 543 544 /* 545 * returns 1 if connection should be dropped, 0 otherwise. 546 * dropping starts at connection #max_startups_begin with a probability 547 * of (max_startups_rate/100). the probability increases linearly until 548 * all connections are dropped for startups > max_startups 549 */ 550 static int 551 should_drop_connection(int startups) 552 { 553 int p, r; 554 555 if (startups < options.max_startups_begin) 556 return 0; 557 if (startups >= options.max_startups) 558 return 1; 559 if (options.max_startups_rate == 100) 560 return 1; 561 562 p = 100 - options.max_startups_rate; 563 p *= startups - options.max_startups_begin; 564 p /= options.max_startups - options.max_startups_begin; 565 p += options.max_startups_rate; 566 r = arc4random_uniform(100); 567 568 debug_f("p %d, r %d", p, r); 569 return (r < p) ? 1 : 0; 570 } 571 572 /* 573 * Check whether connection should be accepted by MaxStartups or for penalty. 574 * Returns 0 if the connection is accepted. If the connection is refused, 575 * returns 1 and attempts to send notification to client. 576 * Logs when the MaxStartups condition is entered or exited, and periodically 577 * while in that state. 578 */ 579 static int 580 drop_connection(int sock, int startups, int notify_pipe) 581 { 582 char *laddr, *raddr; 583 const char *reason = NULL, msg[] = "Not allowed at this time\r\n"; 584 static time_t last_drop, first_drop; 585 static u_int ndropped; 586 LogLevel drop_level = SYSLOG_LEVEL_VERBOSE; 587 time_t now; 588 589 if (!srclimit_penalty_check_allow(sock, &reason)) { 590 drop_level = SYSLOG_LEVEL_INFO; 591 goto handle; 592 } 593 594 now = monotime(); 595 if (!should_drop_connection(startups) && 596 srclimit_check_allow(sock, notify_pipe) == 1) { 597 if (last_drop != 0 && 598 startups < options.max_startups_begin - 1) { 599 /* XXX maybe need better hysteresis here */ 600 logit("exited MaxStartups throttling after %s, " 601 "%u connections dropped", 602 fmt_timeframe(now - first_drop), ndropped); 603 last_drop = 0; 604 } 605 return 0; 606 } 607 608 #define SSHD_MAXSTARTUPS_LOG_INTERVAL (5 * 60) 609 if (last_drop == 0) { 610 error("beginning MaxStartups throttling"); 611 drop_level = SYSLOG_LEVEL_INFO; 612 first_drop = now; 613 ndropped = 0; 614 } else if (last_drop + SSHD_MAXSTARTUPS_LOG_INTERVAL < now) { 615 /* Periodic logs */ 616 error("in MaxStartups throttling for %s, " 617 "%u connections dropped", 618 fmt_timeframe(now - first_drop), ndropped + 1); 619 drop_level = SYSLOG_LEVEL_INFO; 620 } 621 last_drop = now; 622 ndropped++; 623 reason = "past Maxstartups"; 624 625 handle: 626 laddr = get_local_ipaddr(sock); 627 raddr = get_peer_ipaddr(sock); 628 do_log2(drop_level, "drop connection #%d from [%s]:%d on [%s]:%d %s", 629 startups, 630 raddr, get_peer_port(sock), 631 laddr, get_local_port(sock), 632 reason); 633 free(laddr); 634 free(raddr); 635 /* best-effort notification to client */ 636 (void)write(sock, msg, sizeof(msg) - 1); 637 return 1; 638 } 639 640 static void 641 usage(void) 642 { 643 if (options.version_addendum != NULL && 644 *options.version_addendum != '\0') 645 fprintf(stderr, "%s %s, %s\n", 646 SSH_RELEASE, 647 options.version_addendum, SSH_OPENSSL_VERSION); 648 else 649 fprintf(stderr, "%s, %s\n", 650 SSH_RELEASE, SSH_OPENSSL_VERSION); 651 fprintf(stderr, 652 "usage: sshd [-46DdeGiqTtV] [-C connection_spec] [-c host_cert_file]\n" 653 " [-E log_file] [-f config_file] [-g login_grace_time]\n" 654 " [-h host_key_file] [-o option] [-p port] [-u len]\n" 655 ); 656 exit(1); 657 } 658 659 static struct sshbuf * 660 pack_hostkeys(void) 661 { 662 struct sshbuf *keybuf = NULL, *hostkeys = NULL; 663 int r; 664 u_int i; 665 666 if ((keybuf = sshbuf_new()) == NULL || 667 (hostkeys = sshbuf_new()) == NULL) 668 fatal_f("sshbuf_new failed"); 669 670 /* pack hostkeys into a string. Empty key slots get empty strings */ 671 for (i = 0; i < options.num_host_key_files; i++) { 672 /* private key */ 673 sshbuf_reset(keybuf); 674 if (sensitive_data.host_keys[i] != NULL && 675 (r = sshkey_private_serialize(sensitive_data.host_keys[i], 676 keybuf)) != 0) 677 fatal_fr(r, "serialize hostkey private"); 678 if ((r = sshbuf_put_stringb(hostkeys, keybuf)) != 0) 679 fatal_fr(r, "compose hostkey private"); 680 /* public key */ 681 if (sensitive_data.host_pubkeys[i] != NULL) { 682 if ((r = sshkey_puts(sensitive_data.host_pubkeys[i], 683 hostkeys)) != 0) 684 fatal_fr(r, "compose hostkey public"); 685 } else { 686 if ((r = sshbuf_put_string(hostkeys, NULL, 0)) != 0) 687 fatal_fr(r, "compose hostkey empty public"); 688 } 689 /* cert */ 690 if (sensitive_data.host_certificates[i] != NULL) { 691 if ((r = sshkey_puts( 692 sensitive_data.host_certificates[i], 693 hostkeys)) != 0) 694 fatal_fr(r, "compose host cert"); 695 } else { 696 if ((r = sshbuf_put_string(hostkeys, NULL, 0)) != 0) 697 fatal_fr(r, "compose host cert empty"); 698 } 699 } 700 701 sshbuf_free(keybuf); 702 return hostkeys; 703 } 704 705 static void 706 send_rexec_state(int fd, struct sshbuf *conf) 707 { 708 struct sshbuf *m = NULL, *inc = NULL, *hostkeys = NULL; 709 struct include_item *item = NULL; 710 int r, sz; 711 712 debug3_f("entering fd = %d config len %zu", fd, 713 sshbuf_len(conf)); 714 715 if ((m = sshbuf_new()) == NULL || 716 (inc = sshbuf_new()) == NULL) 717 fatal_f("sshbuf_new failed"); 718 719 /* pack includes into a string */ 720 TAILQ_FOREACH(item, &includes, entry) { 721 if ((r = sshbuf_put_cstring(inc, item->selector)) != 0 || 722 (r = sshbuf_put_cstring(inc, item->filename)) != 0 || 723 (r = sshbuf_put_stringb(inc, item->contents)) != 0) 724 fatal_fr(r, "compose includes"); 725 } 726 727 hostkeys = pack_hostkeys(); 728 729 /* 730 * Protocol from reexec master to child: 731 * string configuration 732 * uint64 timing_secret 733 * string host_keys[] { 734 * string private_key 735 * string public_key 736 * string certificate 737 * } 738 * string included_files[] { 739 * string selector 740 * string filename 741 * string contents 742 * } 743 */ 744 if ((r = sshbuf_put_stringb(m, conf)) != 0 || 745 (r = sshbuf_put_u64(m, options.timing_secret)) != 0 || 746 (r = sshbuf_put_stringb(m, hostkeys)) != 0 || 747 (r = sshbuf_put_stringb(m, inc)) != 0) 748 fatal_fr(r, "compose config"); 749 750 /* We need to fit the entire message inside the socket send buffer */ 751 sz = ROUNDUP(sshbuf_len(m) + 5, 16*1024); 752 if (setsockopt(fd, SOL_SOCKET, SO_SNDBUF, &sz, sizeof sz) == -1) 753 fatal_f("setsockopt SO_SNDBUF: %s", strerror(errno)); 754 755 if (ssh_msg_send(fd, 0, m) == -1) 756 error_f("ssh_msg_send failed"); 757 758 sshbuf_free(m); 759 sshbuf_free(inc); 760 sshbuf_free(hostkeys); 761 762 debug3_f("done"); 763 } 764 765 /* 766 * Listen for TCP connections 767 */ 768 static void 769 listen_on_addrs(struct listenaddr *la) 770 { 771 int ret, listen_sock; 772 struct addrinfo *ai; 773 char ntop[NI_MAXHOST], strport[NI_MAXSERV]; 774 775 for (ai = la->addrs; ai; ai = ai->ai_next) { 776 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) 777 continue; 778 if (num_listen_socks >= MAX_LISTEN_SOCKS) 779 fatal("Too many listen sockets. " 780 "Enlarge MAX_LISTEN_SOCKS"); 781 if ((ret = getnameinfo(ai->ai_addr, ai->ai_addrlen, 782 ntop, sizeof(ntop), strport, sizeof(strport), 783 NI_NUMERICHOST|NI_NUMERICSERV)) != 0) { 784 error("getnameinfo failed: %.100s", 785 ssh_gai_strerror(ret)); 786 continue; 787 } 788 /* Create socket for listening. */ 789 listen_sock = socket(ai->ai_family, ai->ai_socktype, 790 ai->ai_protocol); 791 if (listen_sock == -1) { 792 /* kernel may not support ipv6 */ 793 verbose("socket: %.100s", strerror(errno)); 794 continue; 795 } 796 if (set_nonblock(listen_sock) == -1) { 797 close(listen_sock); 798 continue; 799 } 800 if (fcntl(listen_sock, F_SETFD, FD_CLOEXEC) == -1) { 801 verbose("socket: CLOEXEC: %s", strerror(errno)); 802 close(listen_sock); 803 continue; 804 } 805 /* Socket options */ 806 set_reuseaddr(listen_sock); 807 if (la->rdomain != NULL && 808 set_rdomain(listen_sock, la->rdomain) == -1) { 809 close(listen_sock); 810 continue; 811 } 812 813 /* Only communicate in IPv6 over AF_INET6 sockets. */ 814 if (ai->ai_family == AF_INET6) 815 sock_set_v6only(listen_sock); 816 817 debug("Bind to port %s on %s.", strport, ntop); 818 819 /* Bind the socket to the desired port. */ 820 if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) == -1) { 821 error("Bind to port %s on %s failed: %.200s.", 822 strport, ntop, strerror(errno)); 823 close(listen_sock); 824 continue; 825 } 826 listen_socks[num_listen_socks] = listen_sock; 827 num_listen_socks++; 828 829 /* Start listening on the port. */ 830 if (listen(listen_sock, SSH_LISTEN_BACKLOG) == -1) 831 fatal("listen on [%s]:%s: %.100s", 832 ntop, strport, strerror(errno)); 833 logit("Server listening on %s port %s%s%s.", 834 ntop, strport, 835 la->rdomain == NULL ? "" : " rdomain ", 836 la->rdomain == NULL ? "" : la->rdomain); 837 } 838 } 839 840 static void 841 server_listen(void) 842 { 843 u_int i; 844 845 /* Initialise per-source limit tracking. */ 846 srclimit_init(options.max_startups, 847 options.per_source_max_startups, 848 options.per_source_masklen_ipv4, 849 options.per_source_masklen_ipv6, 850 &options.per_source_penalty, 851 options.per_source_penalty_exempt); 852 853 for (i = 0; i < options.num_listen_addrs; i++) { 854 listen_on_addrs(&options.listen_addrs[i]); 855 freeaddrinfo(options.listen_addrs[i].addrs); 856 free(options.listen_addrs[i].rdomain); 857 memset(&options.listen_addrs[i], 0, 858 sizeof(options.listen_addrs[i])); 859 } 860 free(options.listen_addrs); 861 options.listen_addrs = NULL; 862 options.num_listen_addrs = 0; 863 864 if (!num_listen_socks) 865 fatal("Cannot bind any address."); 866 } 867 868 /* 869 * The main TCP accept loop. Note that, for the non-debug case, returns 870 * from this function are in a forked subprocess. 871 */ 872 static void 873 server_accept_loop(int *sock_in, int *sock_out, int *newsock, int *config_s, 874 int log_stderr) 875 { 876 struct pollfd *pfd = NULL; 877 int i, ret, npfd; 878 int oactive = -1, listening = 0, lameduck = 0; 879 int startup_p[2] = { -1 , -1 }, *startup_pollfd; 880 char c = 0; 881 struct sockaddr_storage from; 882 struct early_child *child; 883 socklen_t fromlen; 884 u_char rnd[256]; 885 sigset_t nsigset, osigset; 886 #ifdef LIBWRAP 887 struct request_info req; 888 889 request_init(&req, RQ_DAEMON, __progname, 0); 890 #endif 891 892 /* pipes connected to unauthenticated child sshd processes */ 893 child_alloc(); 894 startup_pollfd = xcalloc(options.max_startups, sizeof(int)); 895 896 /* 897 * Prepare signal mask that we use to block signals that might set 898 * received_sigterm/hup/chld/info, so that we are guaranteed 899 * to immediately wake up the ppoll if a signal is received after 900 * the flag is checked. 901 */ 902 sigemptyset(&nsigset); 903 sigaddset(&nsigset, SIGHUP); 904 sigaddset(&nsigset, SIGCHLD); 905 #ifdef SIGINFO 906 sigaddset(&nsigset, SIGINFO); 907 #endif 908 sigaddset(&nsigset, SIGTERM); 909 sigaddset(&nsigset, SIGQUIT); 910 911 /* sized for worst-case */ 912 pfd = xcalloc(num_listen_socks + options.max_startups, 913 sizeof(struct pollfd)); 914 915 /* 916 * Stay listening for connections until the system crashes or 917 * the daemon is killed with a signal. 918 */ 919 for (;;) { 920 sigprocmask(SIG_BLOCK, &nsigset, &osigset); 921 if (received_sigterm) { 922 logit("Received signal %d; terminating.", 923 (int) received_sigterm); 924 close_listen_socks(); 925 if (options.pid_file != NULL) 926 unlink(options.pid_file); 927 exit(received_sigterm == SIGTERM ? 0 : 255); 928 } 929 if (received_sigchld) { 930 child_reap_all_exited(); 931 received_sigchld = 0; 932 } 933 if (received_siginfo) { 934 show_info(); 935 received_siginfo = 0; 936 } 937 if (oactive != children_active) { 938 setproctitle("%s [listener] %d of %d-%d startups", 939 listener_proctitle, children_active, 940 options.max_startups_begin, options.max_startups); 941 oactive = children_active; 942 } 943 if (received_sighup) { 944 if (!lameduck) { 945 debug("Received SIGHUP; waiting for children"); 946 close_listen_socks(); 947 lameduck = 1; 948 } 949 if (listening <= 0) { 950 sigprocmask(SIG_SETMASK, &osigset, NULL); 951 sighup_restart(); 952 } 953 } 954 955 for (i = 0; i < num_listen_socks; i++) { 956 pfd[i].fd = listen_socks[i]; 957 pfd[i].events = POLLIN; 958 } 959 npfd = num_listen_socks; 960 for (i = 0; i < options.max_startups; i++) { 961 startup_pollfd[i] = -1; 962 if (children[i].pipefd != -1) { 963 pfd[npfd].fd = children[i].pipefd; 964 pfd[npfd].events = POLLIN; 965 startup_pollfd[i] = npfd++; 966 } 967 } 968 969 /* Wait until a connection arrives or a child exits. */ 970 ret = ppoll(pfd, npfd, NULL, &osigset); 971 if (ret == -1 && errno != EINTR) { 972 error("ppoll: %.100s", strerror(errno)); 973 if (errno == EINVAL) 974 cleanup_exit(1); /* can't recover */ 975 } 976 sigprocmask(SIG_SETMASK, &osigset, NULL); 977 if (ret == -1) 978 continue; 979 980 for (i = 0; i < options.max_startups; i++) { 981 if (children[i].pipefd == -1 || 982 startup_pollfd[i] == -1 || 983 !(pfd[startup_pollfd[i]].revents & (POLLIN|POLLHUP))) 984 continue; 985 switch (read(children[i].pipefd, &c, sizeof(c))) { 986 case -1: 987 if (errno == EINTR || errno == EAGAIN) 988 continue; 989 if (errno != EPIPE) { 990 error_f("startup pipe %d (fd=%d): " 991 "read %s", i, children[i].pipefd, 992 strerror(errno)); 993 } 994 /* FALLTHROUGH */ 995 case 0: 996 /* child exited preauth */ 997 if (children[i].early) 998 listening--; 999 srclimit_done(children[i].pipefd); 1000 child_close(&(children[i]), 0, 0); 1001 break; 1002 case 1: 1003 if (children[i].early && c == '\0') { 1004 /* child has finished preliminaries */ 1005 listening--; 1006 children[i].early = 0; 1007 debug2_f("child %lu for %s received " 1008 "config", (long)children[i].pid, 1009 children[i].id); 1010 } else if (!children[i].early && c == '\001') { 1011 /* child has completed auth */ 1012 debug2_f("child %lu for %s auth done", 1013 (long)children[i].pid, 1014 children[i].id); 1015 child_close(&(children[i]), 1, 0); 1016 } else { 1017 error_f("unexpected message 0x%02x " 1018 "child %ld for %s in state %d", 1019 (int)c, (long)children[i].pid, 1020 children[i].id, children[i].early); 1021 } 1022 break; 1023 } 1024 } 1025 for (i = 0; i < num_listen_socks; i++) { 1026 if (!(pfd[i].revents & POLLIN)) 1027 continue; 1028 fromlen = sizeof(from); 1029 *newsock = accept(listen_socks[i], 1030 (struct sockaddr *)&from, &fromlen); 1031 if (*newsock == -1) { 1032 if (errno != EINTR && errno != EWOULDBLOCK && 1033 errno != ECONNABORTED && errno != EAGAIN) 1034 error("accept: %.100s", 1035 strerror(errno)); 1036 if (errno == EMFILE || errno == ENFILE) 1037 usleep(100 * 1000); 1038 continue; 1039 } 1040 #ifdef LIBWRAP 1041 /* Check whether logins are denied from this host. */ 1042 request_set(&req, RQ_FILE, *newsock, 1043 RQ_CLIENT_NAME, "", RQ_CLIENT_ADDR, "", 0); 1044 sock_host(&req); 1045 if (!hosts_access(&req)) { 1046 const struct linger l = { .l_onoff = 1, 1047 .l_linger = 0 }; 1048 1049 (void )setsockopt(*newsock, SOL_SOCKET, 1050 SO_LINGER, &l, sizeof(l)); 1051 (void )close(*newsock); 1052 /* 1053 * Mimic message from libwrap's refuse() as 1054 * precisely as we can afford. The authentic 1055 * message prints the IP address and the 1056 * hostname it resolves to in parentheses. If 1057 * the IP address cannot be resolved to a 1058 * hostname, the IP address will be repeated 1059 * in parentheses. As name resolution in the 1060 * main server loop could stall, and logging 1061 * resolved names adds little or no value to 1062 * incident investigation, this implementation 1063 * only repeats the IP address in parentheses. 1064 * This should resemble librwap's refuse() 1065 * closely enough not to break auditing 1066 * software like sshguard or custom scripts. 1067 */ 1068 syslog(LOG_WARNING, 1069 "refused connect from %s (%s)", 1070 eval_hostaddr(req.client), 1071 eval_hostaddr(req.client)); 1072 debug("Connection refused by tcp wrapper"); 1073 continue; 1074 } 1075 #endif /* LIBWRAP */ 1076 if (unset_nonblock(*newsock) == -1) { 1077 close(*newsock); 1078 continue; 1079 } 1080 if (pipe(startup_p) == -1) { 1081 error_f("pipe(startup_p): %s", strerror(errno)); 1082 close(*newsock); 1083 continue; 1084 } 1085 if (drop_connection(*newsock, 1086 children_active, startup_p[0])) { 1087 close(*newsock); 1088 close(startup_p[0]); 1089 close(startup_p[1]); 1090 continue; 1091 } 1092 1093 if (socketpair(AF_UNIX, 1094 SOCK_STREAM, 0, config_s) == -1) { 1095 error("reexec socketpair: %s", 1096 strerror(errno)); 1097 close(*newsock); 1098 close(startup_p[0]); 1099 close(startup_p[1]); 1100 continue; 1101 } 1102 1103 /* 1104 * Got connection. Fork a child to handle it, unless 1105 * we are in debugging mode. 1106 */ 1107 if (debug_flag) { 1108 /* 1109 * In debugging mode. Close the listening 1110 * socket, and start processing the 1111 * connection without forking. 1112 */ 1113 debug("Server will not fork when running in debugging mode."); 1114 close_listen_socks(); 1115 *sock_in = *newsock; 1116 *sock_out = *newsock; 1117 close(startup_p[0]); 1118 close(startup_p[1]); 1119 startup_pipe = -1; 1120 send_rexec_state(config_s[0], cfg); 1121 close(config_s[0]); 1122 free(pfd); 1123 return; 1124 } 1125 1126 /* 1127 * Normal production daemon. Fork, and have 1128 * the child process the connection. The 1129 * parent continues listening. 1130 */ 1131 platform_pre_fork(); 1132 listening++; 1133 child = child_register(startup_p[0], *newsock); 1134 if ((child->pid = fork()) == 0) { 1135 /* 1136 * Child. Close the listening and 1137 * max_startup sockets. Start using 1138 * the accepted socket. Reinitialize 1139 * logging (since our pid has changed). 1140 * We return from this function to handle 1141 * the connection. 1142 */ 1143 platform_post_fork_child(); 1144 startup_pipe = startup_p[1]; 1145 close_startup_pipes(); 1146 close_listen_socks(); 1147 *sock_in = *newsock; 1148 *sock_out = *newsock; 1149 log_init(__progname, 1150 options.log_level, 1151 options.log_facility, 1152 log_stderr); 1153 close(config_s[0]); 1154 free(pfd); 1155 return; 1156 } 1157 1158 /* Parent. Stay in the loop. */ 1159 platform_post_fork_parent(child->pid); 1160 if (child->pid == -1) 1161 error("fork: %.100s", strerror(errno)); 1162 else 1163 debug("Forked child %ld.", (long)child->pid); 1164 1165 close(startup_p[1]); 1166 1167 close(config_s[1]); 1168 send_rexec_state(config_s[0], cfg); 1169 close(config_s[0]); 1170 close(*newsock); 1171 1172 /* 1173 * Ensure that our random state differs 1174 * from that of the child 1175 */ 1176 arc4random_stir(); 1177 arc4random_buf(rnd, sizeof(rnd)); 1178 #ifdef WITH_OPENSSL 1179 RAND_seed(rnd, sizeof(rnd)); 1180 if ((RAND_bytes((u_char *)rnd, 1)) != 1) 1181 fatal("%s: RAND_bytes failed", __func__); 1182 #endif 1183 explicit_bzero(rnd, sizeof(rnd)); 1184 } 1185 } 1186 } 1187 1188 static void 1189 accumulate_host_timing_secret(struct sshbuf *server_cfg, 1190 struct sshkey *key) 1191 { 1192 static struct ssh_digest_ctx *ctx; 1193 u_char *hash; 1194 size_t len; 1195 struct sshbuf *buf; 1196 int r; 1197 1198 if (ctx == NULL && (ctx = ssh_digest_start(SSH_DIGEST_SHA512)) == NULL) 1199 fatal_f("ssh_digest_start"); 1200 if (key == NULL) { /* finalize */ 1201 /* add server config in case we are using agent for host keys */ 1202 if (ssh_digest_update(ctx, sshbuf_ptr(server_cfg), 1203 sshbuf_len(server_cfg)) != 0) 1204 fatal_f("ssh_digest_update"); 1205 len = ssh_digest_bytes(SSH_DIGEST_SHA512); 1206 hash = xmalloc(len); 1207 if (ssh_digest_final(ctx, hash, len) != 0) 1208 fatal_f("ssh_digest_final"); 1209 options.timing_secret = PEEK_U64(hash); 1210 freezero(hash, len); 1211 ssh_digest_free(ctx); 1212 ctx = NULL; 1213 return; 1214 } 1215 if ((buf = sshbuf_new()) == NULL) 1216 fatal_f("could not allocate buffer"); 1217 if ((r = sshkey_private_serialize(key, buf)) != 0) 1218 fatal_fr(r, "encode %s key", sshkey_ssh_name(key)); 1219 if (ssh_digest_update(ctx, sshbuf_ptr(buf), sshbuf_len(buf)) != 0) 1220 fatal_f("ssh_digest_update"); 1221 sshbuf_reset(buf); 1222 sshbuf_free(buf); 1223 } 1224 1225 static char * 1226 prepare_proctitle(int ac, char **av) 1227 { 1228 char *ret = NULL; 1229 int i; 1230 1231 for (i = 0; i < ac; i++) 1232 xextendf(&ret, " ", "%s", av[i]); 1233 return ret; 1234 } 1235 1236 static void 1237 print_config(struct connection_info *connection_info) 1238 { 1239 connection_info->test = 1; 1240 parse_server_match_config(&options, &includes, connection_info); 1241 dump_config(&options); 1242 exit(0); 1243 } 1244 1245 /* 1246 * Main program for the daemon. 1247 */ 1248 int 1249 main(int ac, char **av) 1250 { 1251 extern char *optarg; 1252 extern int optind; 1253 int log_stderr = 0, inetd_flag = 0, test_flag = 0, no_daemon_flag = 0; 1254 char *config_file_name = _PATH_SERVER_CONFIG_FILE; 1255 int r, opt, do_dump_cfg = 0, keytype, already_daemon, have_agent = 0; 1256 int sock_in = -1, sock_out = -1, newsock = -1, rexec_argc = 0; 1257 int devnull, config_s[2] = { -1 , -1 }, have_connection_info = 0; 1258 int need_chroot = 1; 1259 char *fp, *line, *logfile = NULL, **rexec_argv = NULL; 1260 struct stat sb; 1261 u_int i, j; 1262 mode_t new_umask; 1263 struct sshkey *key; 1264 struct sshkey *pubkey; 1265 struct connection_info connection_info; 1266 sigset_t sigmask; 1267 1268 memset(&connection_info, 0, sizeof(connection_info)); 1269 #ifdef HAVE_SECUREWARE 1270 (void)set_auth_parameters(ac, av); 1271 #endif 1272 __progname = ssh_get_progname(av[0]); 1273 1274 sigemptyset(&sigmask); 1275 sigprocmask(SIG_SETMASK, &sigmask, NULL); 1276 1277 /* Save argv. Duplicate so setproctitle emulation doesn't clobber it */ 1278 saved_argc = ac; 1279 rexec_argc = ac; 1280 saved_argv = xcalloc(ac + 1, sizeof(*saved_argv)); 1281 for (i = 0; (int)i < ac; i++) 1282 saved_argv[i] = xstrdup(av[i]); 1283 saved_argv[i] = NULL; 1284 1285 #ifndef HAVE_SETPROCTITLE 1286 /* Prepare for later setproctitle emulation */ 1287 compat_init_setproctitle(ac, av); 1288 av = saved_argv; 1289 #endif 1290 1291 if (geteuid() == 0 && setgroups(0, NULL) == -1) 1292 debug("setgroups(): %.200s", strerror(errno)); 1293 1294 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */ 1295 sanitise_stdfd(); 1296 1297 /* Initialize configuration options to their default values. */ 1298 initialize_server_options(&options); 1299 1300 /* Parse command-line arguments. */ 1301 while ((opt = getopt(ac, av, 1302 "C:E:b:c:f:g:h:k:o:p:u:46DGQRTdeiqrtV")) != -1) { 1303 switch (opt) { 1304 case '4': 1305 options.address_family = AF_INET; 1306 break; 1307 case '6': 1308 options.address_family = AF_INET6; 1309 break; 1310 case 'f': 1311 config_file_name = optarg; 1312 break; 1313 case 'c': 1314 servconf_add_hostcert("[command-line]", 0, 1315 &options, optarg); 1316 break; 1317 case 'd': 1318 if (debug_flag == 0) { 1319 debug_flag = 1; 1320 options.log_level = SYSLOG_LEVEL_DEBUG1; 1321 } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) 1322 options.log_level++; 1323 break; 1324 case 'D': 1325 no_daemon_flag = 1; 1326 break; 1327 case 'G': 1328 do_dump_cfg = 1; 1329 break; 1330 case 'E': 1331 logfile = optarg; 1332 /* FALLTHROUGH */ 1333 case 'e': 1334 log_stderr = 1; 1335 break; 1336 case 'i': 1337 inetd_flag = 1; 1338 break; 1339 case 'r': 1340 logit("-r option is deprecated"); 1341 break; 1342 case 'R': 1343 fatal("-R not supported here"); 1344 break; 1345 case 'Q': 1346 /* ignored */ 1347 break; 1348 case 'q': 1349 options.log_level = SYSLOG_LEVEL_QUIET; 1350 break; 1351 case 'b': 1352 /* protocol 1, ignored */ 1353 break; 1354 case 'p': 1355 options.ports_from_cmdline = 1; 1356 if (options.num_ports >= MAX_PORTS) { 1357 fprintf(stderr, "too many ports.\n"); 1358 exit(1); 1359 } 1360 options.ports[options.num_ports++] = a2port(optarg); 1361 if (options.ports[options.num_ports-1] <= 0) { 1362 fprintf(stderr, "Bad port number.\n"); 1363 exit(1); 1364 } 1365 break; 1366 case 'g': 1367 if ((options.login_grace_time = convtime(optarg)) == -1) { 1368 fprintf(stderr, "Invalid login grace time.\n"); 1369 exit(1); 1370 } 1371 break; 1372 case 'k': 1373 /* protocol 1, ignored */ 1374 break; 1375 case 'h': 1376 servconf_add_hostkey("[command-line]", 0, 1377 &options, optarg, 1); 1378 break; 1379 case 't': 1380 test_flag = 1; 1381 break; 1382 case 'T': 1383 test_flag = 2; 1384 break; 1385 case 'C': 1386 if (parse_server_match_testspec(&connection_info, 1387 optarg) == -1) 1388 exit(1); 1389 have_connection_info = 1; 1390 break; 1391 case 'u': 1392 utmp_len = (u_int)strtonum(optarg, 0, HOST_NAME_MAX+1+1, NULL); 1393 if (utmp_len > HOST_NAME_MAX+1) { 1394 fprintf(stderr, "Invalid utmp length.\n"); 1395 exit(1); 1396 } 1397 break; 1398 case 'o': 1399 line = xstrdup(optarg); 1400 if (process_server_config_line(&options, line, 1401 "command-line", 0, NULL, NULL, &includes) != 0) 1402 exit(1); 1403 free(line); 1404 break; 1405 case 'V': 1406 fprintf(stderr, "%s, %s\n", 1407 SSH_RELEASE, SSH_OPENSSL_VERSION); 1408 exit(0); 1409 default: 1410 usage(); 1411 break; 1412 } 1413 } 1414 if (!test_flag && !inetd_flag && !do_dump_cfg && !path_absolute(av[0])) 1415 fatal("sshd requires execution with an absolute path"); 1416 1417 closefrom(STDERR_FILENO + 1); 1418 1419 /* Reserve fds we'll need later for reexec things */ 1420 if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) 1421 fatal("open %s: %s", _PATH_DEVNULL, strerror(errno)); 1422 while (devnull < REEXEC_MIN_FREE_FD) { 1423 if ((devnull = dup(devnull)) == -1) 1424 fatal("dup %s: %s", _PATH_DEVNULL, strerror(errno)); 1425 } 1426 1427 seed_rng(); 1428 1429 /* If requested, redirect the logs to the specified logfile. */ 1430 if (logfile != NULL) { 1431 char *cp, pid_s[32]; 1432 1433 snprintf(pid_s, sizeof(pid_s), "%ld", (unsigned long)getpid()); 1434 cp = percent_expand(logfile, 1435 "p", pid_s, 1436 "P", "sshd", 1437 (char *)NULL); 1438 log_redirect_stderr_to(cp); 1439 free(cp); 1440 } 1441 1442 /* 1443 * Force logging to stderr until we have loaded the private host 1444 * key (unless started from inetd) 1445 */ 1446 log_init(__progname, 1447 options.log_level == SYSLOG_LEVEL_NOT_SET ? 1448 SYSLOG_LEVEL_INFO : options.log_level, 1449 options.log_facility == SYSLOG_FACILITY_NOT_SET ? 1450 SYSLOG_FACILITY_AUTH : options.log_facility, 1451 log_stderr || !inetd_flag || debug_flag); 1452 1453 /* 1454 * Unset KRB5CCNAME, otherwise the user's session may inherit it from 1455 * root's environment 1456 */ 1457 if (getenv("KRB5CCNAME") != NULL) 1458 (void) unsetenv("KRB5CCNAME"); 1459 1460 sensitive_data.have_ssh2_key = 0; 1461 1462 /* 1463 * If we're not doing an extended test do not silently ignore connection 1464 * test params. 1465 */ 1466 if (test_flag < 2 && have_connection_info) 1467 fatal("Config test connection parameter (-C) provided without " 1468 "test mode (-T)"); 1469 1470 /* Fetch our configuration */ 1471 if ((cfg = sshbuf_new()) == NULL) 1472 fatal("sshbuf_new config failed"); 1473 if (strcasecmp(config_file_name, "none") != 0) 1474 load_server_config(config_file_name, cfg); 1475 1476 parse_server_config(&options, config_file_name, cfg, 1477 &includes, NULL, 0); 1478 1479 /* Fill in default values for those options not explicitly set. */ 1480 fill_default_server_options(&options); 1481 1482 /* Check that options are sensible */ 1483 if (options.authorized_keys_command_user == NULL && 1484 (options.authorized_keys_command != NULL && 1485 strcasecmp(options.authorized_keys_command, "none") != 0)) 1486 fatal("AuthorizedKeysCommand set without " 1487 "AuthorizedKeysCommandUser"); 1488 if (options.authorized_principals_command_user == NULL && 1489 (options.authorized_principals_command != NULL && 1490 strcasecmp(options.authorized_principals_command, "none") != 0)) 1491 fatal("AuthorizedPrincipalsCommand set without " 1492 "AuthorizedPrincipalsCommandUser"); 1493 1494 /* 1495 * Check whether there is any path through configured auth methods. 1496 * Unfortunately it is not possible to verify this generally before 1497 * daemonisation in the presence of Match blocks, but this catches 1498 * and warns for trivial misconfigurations that could break login. 1499 */ 1500 if (options.num_auth_methods != 0) { 1501 for (i = 0; i < options.num_auth_methods; i++) { 1502 if (auth2_methods_valid(options.auth_methods[i], 1503 1) == 0) 1504 break; 1505 } 1506 if (i >= options.num_auth_methods) 1507 fatal("AuthenticationMethods cannot be satisfied by " 1508 "enabled authentication methods"); 1509 } 1510 1511 /* Check that there are no remaining arguments. */ 1512 if (optind < ac) { 1513 fprintf(stderr, "Extra argument %s.\n", av[optind]); 1514 exit(1); 1515 } 1516 1517 debug("sshd version %s, %s", SSH_VERSION, SSH_OPENSSL_VERSION); 1518 1519 if (do_dump_cfg) 1520 print_config(&connection_info); 1521 1522 /* load host keys */ 1523 sensitive_data.host_keys = xcalloc(options.num_host_key_files, 1524 sizeof(struct sshkey *)); 1525 sensitive_data.host_pubkeys = xcalloc(options.num_host_key_files, 1526 sizeof(struct sshkey *)); 1527 1528 if (options.host_key_agent) { 1529 if (strcmp(options.host_key_agent, SSH_AUTHSOCKET_ENV_NAME)) 1530 setenv(SSH_AUTHSOCKET_ENV_NAME, 1531 options.host_key_agent, 1); 1532 if ((r = ssh_get_authentication_socket(NULL)) == 0) 1533 have_agent = 1; 1534 else 1535 error_r(r, "Could not connect to agent \"%s\"", 1536 options.host_key_agent); 1537 } 1538 1539 for (i = 0; i < options.num_host_key_files; i++) { 1540 int ll = options.host_key_file_userprovided[i] ? 1541 SYSLOG_LEVEL_ERROR : SYSLOG_LEVEL_DEBUG1; 1542 1543 if (options.host_key_files[i] == NULL) 1544 continue; 1545 if ((r = sshkey_load_private(options.host_key_files[i], "", 1546 &key, NULL)) != 0 && r != SSH_ERR_SYSTEM_ERROR) 1547 do_log2_r(r, ll, "Unable to load host key \"%s\"", 1548 options.host_key_files[i]); 1549 if (sshkey_is_sk(key) && 1550 key->sk_flags & SSH_SK_USER_PRESENCE_REQD) { 1551 debug("host key %s requires user presence, ignoring", 1552 options.host_key_files[i]); 1553 key->sk_flags &= ~SSH_SK_USER_PRESENCE_REQD; 1554 } 1555 if (r == 0 && key != NULL && 1556 (r = sshkey_shield_private(key)) != 0) { 1557 do_log2_r(r, ll, "Unable to shield host key \"%s\"", 1558 options.host_key_files[i]); 1559 sshkey_free(key); 1560 key = NULL; 1561 } 1562 if ((r = sshkey_load_public(options.host_key_files[i], 1563 &pubkey, NULL)) != 0 && r != SSH_ERR_SYSTEM_ERROR) 1564 do_log2_r(r, ll, "Unable to load host key \"%s\"", 1565 options.host_key_files[i]); 1566 if (pubkey != NULL && key != NULL) { 1567 if (!sshkey_equal(pubkey, key)) { 1568 error("Public key for %s does not match " 1569 "private key", options.host_key_files[i]); 1570 sshkey_free(pubkey); 1571 pubkey = NULL; 1572 } 1573 } 1574 if (pubkey == NULL && key != NULL) { 1575 if ((r = sshkey_from_private(key, &pubkey)) != 0) 1576 fatal_r(r, "Could not demote key: \"%s\"", 1577 options.host_key_files[i]); 1578 } 1579 if (pubkey != NULL && (r = sshkey_check_rsa_length(pubkey, 1580 options.required_rsa_size)) != 0) { 1581 error_fr(r, "Host key %s", options.host_key_files[i]); 1582 sshkey_free(pubkey); 1583 sshkey_free(key); 1584 continue; 1585 } 1586 sensitive_data.host_keys[i] = key; 1587 sensitive_data.host_pubkeys[i] = pubkey; 1588 1589 if (key == NULL && pubkey != NULL && have_agent) { 1590 debug("will rely on agent for hostkey %s", 1591 options.host_key_files[i]); 1592 keytype = pubkey->type; 1593 } else if (key != NULL) { 1594 keytype = key->type; 1595 accumulate_host_timing_secret(cfg, key); 1596 } else { 1597 do_log2(ll, "Unable to load host key: %s", 1598 options.host_key_files[i]); 1599 sensitive_data.host_keys[i] = NULL; 1600 sensitive_data.host_pubkeys[i] = NULL; 1601 continue; 1602 } 1603 1604 switch (keytype) { 1605 case KEY_RSA: 1606 case KEY_DSA: 1607 case KEY_ECDSA: 1608 case KEY_ED25519: 1609 case KEY_ECDSA_SK: 1610 case KEY_ED25519_SK: 1611 case KEY_XMSS: 1612 if (have_agent || key != NULL) 1613 sensitive_data.have_ssh2_key = 1; 1614 break; 1615 } 1616 if ((fp = sshkey_fingerprint(pubkey, options.fingerprint_hash, 1617 SSH_FP_DEFAULT)) == NULL) 1618 fatal("sshkey_fingerprint failed"); 1619 debug("%s host key #%d: %s %s", 1620 key ? "private" : "agent", i, sshkey_ssh_name(pubkey), fp); 1621 free(fp); 1622 } 1623 accumulate_host_timing_secret(cfg, NULL); 1624 if (!sensitive_data.have_ssh2_key) { 1625 logit("sshd: no hostkeys available -- exiting."); 1626 exit(1); 1627 } 1628 1629 /* 1630 * Load certificates. They are stored in an array at identical 1631 * indices to the public keys that they relate to. 1632 */ 1633 sensitive_data.host_certificates = xcalloc(options.num_host_key_files, 1634 sizeof(struct sshkey *)); 1635 for (i = 0; i < options.num_host_key_files; i++) 1636 sensitive_data.host_certificates[i] = NULL; 1637 1638 for (i = 0; i < options.num_host_cert_files; i++) { 1639 if (options.host_cert_files[i] == NULL) 1640 continue; 1641 if ((r = sshkey_load_public(options.host_cert_files[i], 1642 &key, NULL)) != 0) { 1643 error_r(r, "Could not load host certificate \"%s\"", 1644 options.host_cert_files[i]); 1645 continue; 1646 } 1647 if (!sshkey_is_cert(key)) { 1648 error("Certificate file is not a certificate: %s", 1649 options.host_cert_files[i]); 1650 sshkey_free(key); 1651 continue; 1652 } 1653 /* Find matching private key */ 1654 for (j = 0; j < options.num_host_key_files; j++) { 1655 if (sshkey_equal_public(key, 1656 sensitive_data.host_pubkeys[j])) { 1657 sensitive_data.host_certificates[j] = key; 1658 break; 1659 } 1660 } 1661 if (j >= options.num_host_key_files) { 1662 error("No matching private key for certificate: %s", 1663 options.host_cert_files[i]); 1664 sshkey_free(key); 1665 continue; 1666 } 1667 sensitive_data.host_certificates[j] = key; 1668 debug("host certificate: #%u type %d %s", j, key->type, 1669 sshkey_type(key)); 1670 } 1671 1672 /* Ensure privsep directory is correctly configured. */ 1673 need_chroot = ((getuid() == 0 || geteuid() == 0) || 1674 options.kerberos_authentication); 1675 if ((getpwnam(SSH_PRIVSEP_USER)) == NULL && need_chroot) { 1676 fatal("Privilege separation user %s does not exist", 1677 SSH_PRIVSEP_USER); 1678 } 1679 endpwent(); 1680 1681 if (need_chroot) { 1682 if ((stat(_PATH_PRIVSEP_CHROOT_DIR, &sb) == -1) || 1683 (S_ISDIR(sb.st_mode) == 0)) 1684 fatal("Missing privilege separation directory: %s", 1685 _PATH_PRIVSEP_CHROOT_DIR); 1686 #ifdef HAVE_CYGWIN 1687 if (check_ntsec(_PATH_PRIVSEP_CHROOT_DIR) && 1688 (sb.st_uid != getuid () || 1689 (sb.st_mode & (S_IWGRP|S_IWOTH)) != 0)) 1690 #else 1691 if (sb.st_uid != 0 || (sb.st_mode & (S_IWGRP|S_IWOTH)) != 0) 1692 #endif 1693 fatal("%s must be owned by root and not group or " 1694 "world-writable.", _PATH_PRIVSEP_CHROOT_DIR); 1695 } 1696 1697 if (test_flag > 1) 1698 print_config(&connection_info); 1699 1700 /* Configuration looks good, so exit if in test mode. */ 1701 if (test_flag) 1702 exit(0); 1703 1704 /* 1705 * Clear out any supplemental groups we may have inherited. This 1706 * prevents inadvertent creation of files with bad modes (in the 1707 * portable version at least, it's certainly possible for PAM 1708 * to create a file, and we can't control the code in every 1709 * module which might be used). 1710 */ 1711 if (setgroups(0, NULL) < 0) 1712 debug("setgroups() failed: %.200s", strerror(errno)); 1713 1714 /* Prepare arguments for sshd-session */ 1715 if (rexec_argc < 0) 1716 fatal("rexec_argc %d < 0", rexec_argc); 1717 rexec_argv = xcalloc(rexec_argc + 3, sizeof(char *)); 1718 /* Point to the sshd-session binary instead of sshd */ 1719 rexec_argv[0] = options.sshd_session_path; 1720 for (i = 1; i < (u_int)rexec_argc; i++) { 1721 debug("rexec_argv[%d]='%s'", i, saved_argv[i]); 1722 rexec_argv[i] = saved_argv[i]; 1723 } 1724 rexec_argv[rexec_argc++] = "-R"; 1725 rexec_argv[rexec_argc] = NULL; 1726 if (stat(rexec_argv[0], &sb) != 0 || !(sb.st_mode & (S_IXOTH|S_IXUSR))) 1727 fatal("%s does not exist or is not executable", rexec_argv[0]); 1728 debug3("using %s for re-exec", rexec_argv[0]); 1729 1730 listener_proctitle = prepare_proctitle(ac, av); 1731 1732 /* Ensure that umask disallows at least group and world write */ 1733 new_umask = umask(0077) | 0022; 1734 (void) umask(new_umask); 1735 1736 /* Initialize the log (it is reinitialized below in case we forked). */ 1737 if (debug_flag && !inetd_flag) 1738 log_stderr = 1; 1739 log_init(__progname, options.log_level, 1740 options.log_facility, log_stderr); 1741 for (i = 0; i < options.num_log_verbose; i++) 1742 log_verbose_add(options.log_verbose[i]); 1743 1744 /* 1745 * If not in debugging mode, not started from inetd and not already 1746 * daemonized (eg re-exec via SIGHUP), disconnect from the controlling 1747 * terminal, and fork. The original process exits. 1748 */ 1749 already_daemon = daemonized(); 1750 if (!(debug_flag || inetd_flag || no_daemon_flag || already_daemon)) { 1751 1752 if (daemon(0, 0) == -1) 1753 fatal("daemon() failed: %.200s", strerror(errno)); 1754 1755 disconnect_controlling_tty(); 1756 } 1757 /* Reinitialize the log (because of the fork above). */ 1758 log_init(__progname, options.log_level, options.log_facility, log_stderr); 1759 1760 /* Avoid killing the process in high-pressure swapping environments. */ 1761 if (!inetd_flag && madvise(NULL, 0, MADV_PROTECT) != 0) 1762 debug("madvise(): %.200s", strerror(errno)); 1763 1764 /* 1765 * Chdir to the root directory so that the current disk can be 1766 * unmounted if desired. 1767 */ 1768 if (chdir("/") == -1) 1769 error("chdir(\"/\"): %s", strerror(errno)); 1770 1771 /* ignore SIGPIPE */ 1772 ssh_signal(SIGPIPE, SIG_IGN); 1773 1774 /* Get a connection, either from inetd or a listening TCP socket */ 1775 if (inetd_flag) { 1776 /* Send configuration to ancestor sshd-session process */ 1777 if (socketpair(AF_UNIX, SOCK_STREAM, 0, config_s) == -1) 1778 fatal("socketpair: %s", strerror(errno)); 1779 send_rexec_state(config_s[0], cfg); 1780 close(config_s[0]); 1781 } else { 1782 platform_pre_listen(); 1783 server_listen(); 1784 1785 ssh_signal(SIGHUP, sighup_handler); 1786 ssh_signal(SIGCHLD, main_sigchld_handler); 1787 ssh_signal(SIGTERM, sigterm_handler); 1788 ssh_signal(SIGQUIT, sigterm_handler); 1789 #ifdef SIGINFO 1790 ssh_signal(SIGINFO, siginfo_handler); 1791 #endif 1792 1793 platform_post_listen(); 1794 1795 /* 1796 * Write out the pid file after the sigterm handler 1797 * is setup and the listen sockets are bound 1798 */ 1799 if (options.pid_file != NULL && !debug_flag) { 1800 FILE *f = fopen(options.pid_file, "w"); 1801 1802 if (f == NULL) { 1803 error("Couldn't create pid file \"%s\": %s", 1804 options.pid_file, strerror(errno)); 1805 } else { 1806 fprintf(f, "%ld\n", (long) getpid()); 1807 fclose(f); 1808 } 1809 } 1810 1811 /* Accept a connection and return in a forked child */ 1812 server_accept_loop(&sock_in, &sock_out, 1813 &newsock, config_s, log_stderr); 1814 } 1815 1816 /* This is the child processing a new connection. */ 1817 setproctitle("%s", "[accepted]"); 1818 1819 /* 1820 * Create a new session and process group since the 4.4BSD 1821 * setlogin() affects the entire process group. We don't 1822 * want the child to be able to affect the parent. 1823 */ 1824 if (!debug_flag && !inetd_flag && setsid() == -1) 1825 error("setsid: %.100s", strerror(errno)); 1826 1827 debug("rexec start in %d out %d newsock %d pipe %d sock %d/%d", 1828 sock_in, sock_out, newsock, startup_pipe, config_s[0], config_s[1]); 1829 if (!inetd_flag) { 1830 if (dup2(newsock, STDIN_FILENO) == -1) 1831 fatal("dup2 stdin: %s", strerror(errno)); 1832 if (dup2(STDIN_FILENO, STDOUT_FILENO) == -1) 1833 fatal("dup2 stdout: %s", strerror(errno)); 1834 if (newsock > STDOUT_FILENO) 1835 close(newsock); 1836 } 1837 if (config_s[1] != REEXEC_CONFIG_PASS_FD) { 1838 if (dup2(config_s[1], REEXEC_CONFIG_PASS_FD) == -1) 1839 fatal("dup2 config_s: %s", strerror(errno)); 1840 close(config_s[1]); 1841 } 1842 if (startup_pipe == -1) 1843 close(REEXEC_STARTUP_PIPE_FD); 1844 else if (startup_pipe != REEXEC_STARTUP_PIPE_FD) { 1845 if (dup2(startup_pipe, REEXEC_STARTUP_PIPE_FD) == -1) 1846 fatal("dup2 startup_p: %s", strerror(errno)); 1847 close(startup_pipe); 1848 } 1849 log_redirect_stderr_to(NULL); 1850 closefrom(REEXEC_MIN_FREE_FD); 1851 1852 ssh_signal(SIGHUP, SIG_IGN); /* avoid reset to SIG_DFL */ 1853 execv(rexec_argv[0], rexec_argv); 1854 1855 fatal("rexec of %s failed: %s", rexec_argv[0], strerror(errno)); 1856 #ifdef __FreeBSD__ 1857 /* 1858 * Initialize the resolver. This may not happen automatically 1859 * before privsep chroot(). 1860 */ 1861 if ((_res.options & RES_INIT) == 0) { 1862 debug("res_init()"); 1863 res_init(); 1864 } 1865 #ifdef GSSAPI 1866 /* 1867 * Force GSS-API to parse its configuration and load any 1868 * mechanism plugins. 1869 */ 1870 { 1871 gss_OID_set mechs; 1872 OM_uint32 minor_status; 1873 gss_indicate_mechs(&minor_status, &mechs); 1874 gss_release_oid_set(&minor_status, &mechs); 1875 } 1876 #endif 1877 #endif 1878 } 1879 1880 /* server specific fatal cleanup */ 1881 void 1882 cleanup_exit(int i) 1883 { 1884 _exit(i); 1885 } 1886