1 /* $OpenBSD: auth.c,v 1.114 2016/03/07 19:02:43 djm Exp $ */ 2 /* 3 * Copyright (c) 2000 Markus Friedl. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 */ 25 26 #include <sys/types.h> 27 #include <sys/stat.h> 28 #include <sys/socket.h> 29 30 #include <errno.h> 31 #include <fcntl.h> 32 #include <libgen.h> 33 #include <login_cap.h> 34 #include <paths.h> 35 #include <pwd.h> 36 #include <stdarg.h> 37 #include <stdio.h> 38 #include <string.h> 39 #include <unistd.h> 40 #include <limits.h> 41 #include <netdb.h> 42 43 #include "xmalloc.h" 44 #include "match.h" 45 #include "groupaccess.h" 46 #include "log.h" 47 #include "buffer.h" 48 #include "misc.h" 49 #include "servconf.h" 50 #include "key.h" 51 #include "hostfile.h" 52 #include "auth.h" 53 #include "auth-options.h" 54 #include "canohost.h" 55 #include "uidswap.h" 56 #include "packet.h" 57 #ifdef GSSAPI 58 #include "ssh-gss.h" 59 #endif 60 #include "authfile.h" 61 #include "monitor_wrap.h" 62 #include "authfile.h" 63 #include "ssherr.h" 64 #include "compat.h" 65 66 /* import */ 67 extern ServerOptions options; 68 extern int use_privsep; 69 70 /* Debugging messages */ 71 Buffer auth_debug; 72 int auth_debug_init; 73 74 /* 75 * Check if the user is allowed to log in via ssh. If user is listed 76 * in DenyUsers or one of user's groups is listed in DenyGroups, false 77 * will be returned. If AllowUsers isn't empty and user isn't listed 78 * there, or if AllowGroups isn't empty and one of user's groups isn't 79 * listed there, false will be returned. 80 * If the user's shell is not executable, false will be returned. 81 * Otherwise true is returned. 82 */ 83 int 84 allowed_user(struct passwd * pw) 85 { 86 struct ssh *ssh = active_state; /* XXX */ 87 struct stat st; 88 const char *hostname = NULL, *ipaddr = NULL; 89 u_int i; 90 91 /* Shouldn't be called if pw is NULL, but better safe than sorry... */ 92 if (!pw || !pw->pw_name) 93 return 0; 94 95 /* 96 * Deny if shell does not exist or is not executable unless we 97 * are chrooting. 98 */ 99 if (options.chroot_directory == NULL || 100 strcasecmp(options.chroot_directory, "none") == 0) { 101 char *shell = xstrdup((pw->pw_shell[0] == '\0') ? 102 _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */ 103 104 if (stat(shell, &st) != 0) { 105 logit("User %.100s not allowed because shell %.100s " 106 "does not exist", pw->pw_name, shell); 107 free(shell); 108 return 0; 109 } 110 if (S_ISREG(st.st_mode) == 0 || 111 (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { 112 logit("User %.100s not allowed because shell %.100s " 113 "is not executable", pw->pw_name, shell); 114 free(shell); 115 return 0; 116 } 117 free(shell); 118 } 119 120 if (options.num_deny_users > 0 || options.num_allow_users > 0 || 121 options.num_deny_groups > 0 || options.num_allow_groups > 0) { 122 hostname = auth_get_canonical_hostname(ssh, options.use_dns); 123 ipaddr = ssh_remote_ipaddr(ssh); 124 } 125 126 /* Return false if user is listed in DenyUsers */ 127 if (options.num_deny_users > 0) { 128 for (i = 0; i < options.num_deny_users; i++) 129 if (match_user(pw->pw_name, hostname, ipaddr, 130 options.deny_users[i])) { 131 logit("User %.100s from %.100s not allowed " 132 "because listed in DenyUsers", 133 pw->pw_name, hostname); 134 return 0; 135 } 136 } 137 /* Return false if AllowUsers isn't empty and user isn't listed there */ 138 if (options.num_allow_users > 0) { 139 for (i = 0; i < options.num_allow_users; i++) 140 if (match_user(pw->pw_name, hostname, ipaddr, 141 options.allow_users[i])) 142 break; 143 /* i < options.num_allow_users iff we break for loop */ 144 if (i >= options.num_allow_users) { 145 logit("User %.100s from %.100s not allowed because " 146 "not listed in AllowUsers", pw->pw_name, hostname); 147 return 0; 148 } 149 } 150 if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { 151 /* Get the user's group access list (primary and supplementary) */ 152 if (ga_init(pw->pw_name, pw->pw_gid) == 0) { 153 logit("User %.100s from %.100s not allowed because " 154 "not in any group", pw->pw_name, hostname); 155 return 0; 156 } 157 158 /* Return false if one of user's groups is listed in DenyGroups */ 159 if (options.num_deny_groups > 0) 160 if (ga_match(options.deny_groups, 161 options.num_deny_groups)) { 162 ga_free(); 163 logit("User %.100s from %.100s not allowed " 164 "because a group is listed in DenyGroups", 165 pw->pw_name, hostname); 166 return 0; 167 } 168 /* 169 * Return false if AllowGroups isn't empty and one of user's groups 170 * isn't listed there 171 */ 172 if (options.num_allow_groups > 0) 173 if (!ga_match(options.allow_groups, 174 options.num_allow_groups)) { 175 ga_free(); 176 logit("User %.100s from %.100s not allowed " 177 "because none of user's groups are listed " 178 "in AllowGroups", pw->pw_name, hostname); 179 return 0; 180 } 181 ga_free(); 182 } 183 /* We found no reason not to let this user try to log on... */ 184 return 1; 185 } 186 187 void 188 auth_info(Authctxt *authctxt, const char *fmt, ...) 189 { 190 va_list ap; 191 int i; 192 193 free(authctxt->info); 194 authctxt->info = NULL; 195 196 va_start(ap, fmt); 197 i = vasprintf(&authctxt->info, fmt, ap); 198 va_end(ap); 199 200 if (i < 0 || authctxt->info == NULL) 201 fatal("vasprintf failed"); 202 } 203 204 void 205 auth_log(Authctxt *authctxt, int authenticated, int partial, 206 const char *method, const char *submethod) 207 { 208 struct ssh *ssh = active_state; /* XXX */ 209 void (*authlog) (const char *fmt,...) = verbose; 210 char *authmsg; 211 212 if (use_privsep && !mm_is_monitor() && !authctxt->postponed) 213 return; 214 215 /* Raise logging level */ 216 if (authenticated == 1 || 217 !authctxt->valid || 218 authctxt->failures >= options.max_authtries / 2 || 219 strcmp(method, "password") == 0) 220 authlog = logit; 221 222 if (authctxt->postponed) 223 authmsg = "Postponed"; 224 else if (partial) 225 authmsg = "Partial"; 226 else 227 authmsg = authenticated ? "Accepted" : "Failed"; 228 229 authlog("%s %s%s%s for %s%.100s from %.200s port %d %s%s%s", 230 authmsg, 231 method, 232 submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod, 233 authctxt->valid ? "" : "invalid user ", 234 authctxt->user, 235 ssh_remote_ipaddr(ssh), 236 ssh_remote_port(ssh), 237 compat20 ? "ssh2" : "ssh1", 238 authctxt->info != NULL ? ": " : "", 239 authctxt->info != NULL ? authctxt->info : ""); 240 free(authctxt->info); 241 authctxt->info = NULL; 242 } 243 244 void 245 auth_maxtries_exceeded(Authctxt *authctxt) 246 { 247 struct ssh *ssh = active_state; /* XXX */ 248 249 error("maximum authentication attempts exceeded for " 250 "%s%.100s from %.200s port %d %s", 251 authctxt->valid ? "" : "invalid user ", 252 authctxt->user, 253 ssh_remote_ipaddr(ssh), 254 ssh_remote_port(ssh), 255 compat20 ? "ssh2" : "ssh1"); 256 packet_disconnect("Too many authentication failures"); 257 /* NOTREACHED */ 258 } 259 260 /* 261 * Check whether root logins are disallowed. 262 */ 263 int 264 auth_root_allowed(const char *method) 265 { 266 struct ssh *ssh = active_state; /* XXX */ 267 268 switch (options.permit_root_login) { 269 case PERMIT_YES: 270 return 1; 271 case PERMIT_NO_PASSWD: 272 if (strcmp(method, "publickey") == 0 || 273 strcmp(method, "hostbased") == 0 || 274 strcmp(method, "gssapi-with-mic") == 0) 275 return 1; 276 break; 277 case PERMIT_FORCED_ONLY: 278 if (forced_command) { 279 logit("Root login accepted for forced command."); 280 return 1; 281 } 282 break; 283 } 284 logit("ROOT LOGIN REFUSED FROM %.200s port %d", 285 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 286 return 0; 287 } 288 289 290 /* 291 * Given a template and a passwd structure, build a filename 292 * by substituting % tokenised options. Currently, %% becomes '%', 293 * %h becomes the home directory and %u the username. 294 * 295 * This returns a buffer allocated by xmalloc. 296 */ 297 char * 298 expand_authorized_keys(const char *filename, struct passwd *pw) 299 { 300 char *file, ret[PATH_MAX]; 301 int i; 302 303 file = percent_expand(filename, "h", pw->pw_dir, 304 "u", pw->pw_name, (char *)NULL); 305 306 /* 307 * Ensure that filename starts anchored. If not, be backward 308 * compatible and prepend the '%h/' 309 */ 310 if (*file == '/') 311 return (file); 312 313 i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file); 314 if (i < 0 || (size_t)i >= sizeof(ret)) 315 fatal("expand_authorized_keys: path too long"); 316 free(file); 317 return (xstrdup(ret)); 318 } 319 320 char * 321 authorized_principals_file(struct passwd *pw) 322 { 323 if (options.authorized_principals_file == NULL) 324 return NULL; 325 return expand_authorized_keys(options.authorized_principals_file, pw); 326 } 327 328 /* return ok if key exists in sysfile or userfile */ 329 HostStatus 330 check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host, 331 const char *sysfile, const char *userfile) 332 { 333 char *user_hostfile; 334 struct stat st; 335 HostStatus host_status; 336 struct hostkeys *hostkeys; 337 const struct hostkey_entry *found; 338 339 hostkeys = init_hostkeys(); 340 load_hostkeys(hostkeys, host, sysfile); 341 if (userfile != NULL) { 342 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); 343 if (options.strict_modes && 344 (stat(user_hostfile, &st) == 0) && 345 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || 346 (st.st_mode & 022) != 0)) { 347 logit("Authentication refused for %.100s: " 348 "bad owner or modes for %.200s", 349 pw->pw_name, user_hostfile); 350 auth_debug_add("Ignored %.200s: bad ownership or modes", 351 user_hostfile); 352 } else { 353 temporarily_use_uid(pw); 354 load_hostkeys(hostkeys, host, user_hostfile); 355 restore_uid(); 356 } 357 free(user_hostfile); 358 } 359 host_status = check_key_in_hostkeys(hostkeys, key, &found); 360 if (host_status == HOST_REVOKED) 361 error("WARNING: revoked key for %s attempted authentication", 362 found->host); 363 else if (host_status == HOST_OK) 364 debug("%s: key for %s found at %s:%ld", __func__, 365 found->host, found->file, found->line); 366 else 367 debug("%s: key for host %s not found", __func__, host); 368 369 free_hostkeys(hostkeys); 370 371 return host_status; 372 } 373 374 /* 375 * Check a given path for security. This is defined as all components 376 * of the path to the file must be owned by either the owner of 377 * of the file or root and no directories must be group or world writable. 378 * 379 * XXX Should any specific check be done for sym links ? 380 * 381 * Takes a file name, its stat information (preferably from fstat() to 382 * avoid races), the uid of the expected owner, their home directory and an 383 * error buffer plus max size as arguments. 384 * 385 * Returns 0 on success and -1 on failure 386 */ 387 int 388 auth_secure_path(const char *name, struct stat *stp, const char *pw_dir, 389 uid_t uid, char *err, size_t errlen) 390 { 391 char buf[PATH_MAX], homedir[PATH_MAX]; 392 char *cp; 393 int comparehome = 0; 394 struct stat st; 395 396 if (realpath(name, buf) == NULL) { 397 snprintf(err, errlen, "realpath %s failed: %s", name, 398 strerror(errno)); 399 return -1; 400 } 401 if (pw_dir != NULL && realpath(pw_dir, homedir) != NULL) 402 comparehome = 1; 403 404 if (!S_ISREG(stp->st_mode)) { 405 snprintf(err, errlen, "%s is not a regular file", buf); 406 return -1; 407 } 408 if ((stp->st_uid != 0 && stp->st_uid != uid) || 409 (stp->st_mode & 022) != 0) { 410 snprintf(err, errlen, "bad ownership or modes for file %s", 411 buf); 412 return -1; 413 } 414 415 /* for each component of the canonical path, walking upwards */ 416 for (;;) { 417 if ((cp = dirname(buf)) == NULL) { 418 snprintf(err, errlen, "dirname() failed"); 419 return -1; 420 } 421 strlcpy(buf, cp, sizeof(buf)); 422 423 if (stat(buf, &st) < 0 || 424 (st.st_uid != 0 && st.st_uid != uid) || 425 (st.st_mode & 022) != 0) { 426 snprintf(err, errlen, 427 "bad ownership or modes for directory %s", buf); 428 return -1; 429 } 430 431 /* If are past the homedir then we can stop */ 432 if (comparehome && strcmp(homedir, buf) == 0) 433 break; 434 435 /* 436 * dirname should always complete with a "/" path, 437 * but we can be paranoid and check for "." too 438 */ 439 if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0)) 440 break; 441 } 442 return 0; 443 } 444 445 /* 446 * Version of secure_path() that accepts an open file descriptor to 447 * avoid races. 448 * 449 * Returns 0 on success and -1 on failure 450 */ 451 static int 452 secure_filename(FILE *f, const char *file, struct passwd *pw, 453 char *err, size_t errlen) 454 { 455 struct stat st; 456 457 /* check the open file to avoid races */ 458 if (fstat(fileno(f), &st) < 0) { 459 snprintf(err, errlen, "cannot stat file %s: %s", 460 file, strerror(errno)); 461 return -1; 462 } 463 return auth_secure_path(file, &st, pw->pw_dir, pw->pw_uid, err, errlen); 464 } 465 466 static FILE * 467 auth_openfile(const char *file, struct passwd *pw, int strict_modes, 468 int log_missing, char *file_type) 469 { 470 char line[1024]; 471 struct stat st; 472 int fd; 473 FILE *f; 474 475 if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) { 476 if (log_missing || errno != ENOENT) 477 debug("Could not open %s '%s': %s", file_type, file, 478 strerror(errno)); 479 return NULL; 480 } 481 482 if (fstat(fd, &st) < 0) { 483 close(fd); 484 return NULL; 485 } 486 if (!S_ISREG(st.st_mode)) { 487 logit("User %s %s %s is not a regular file", 488 pw->pw_name, file_type, file); 489 close(fd); 490 return NULL; 491 } 492 unset_nonblock(fd); 493 if ((f = fdopen(fd, "r")) == NULL) { 494 close(fd); 495 return NULL; 496 } 497 if (strict_modes && 498 secure_filename(f, file, pw, line, sizeof(line)) != 0) { 499 fclose(f); 500 logit("Authentication refused: %s", line); 501 auth_debug_add("Ignored %s: %s", file_type, line); 502 return NULL; 503 } 504 505 return f; 506 } 507 508 509 FILE * 510 auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes) 511 { 512 return auth_openfile(file, pw, strict_modes, 1, "authorized keys"); 513 } 514 515 FILE * 516 auth_openprincipals(const char *file, struct passwd *pw, int strict_modes) 517 { 518 return auth_openfile(file, pw, strict_modes, 0, 519 "authorized principals"); 520 } 521 522 struct passwd * 523 getpwnamallow(const char *user) 524 { 525 struct ssh *ssh = active_state; /* XXX */ 526 extern login_cap_t *lc; 527 auth_session_t *as; 528 struct passwd *pw; 529 struct connection_info *ci = get_connection_info(1, options.use_dns); 530 531 ci->user = user; 532 parse_server_match_config(&options, ci); 533 534 pw = getpwnam(user); 535 if (pw == NULL) { 536 logit("Invalid user %.100s from %.100s port %d", 537 user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 538 return (NULL); 539 } 540 if (!allowed_user(pw)) 541 return (NULL); 542 if ((lc = login_getclass(pw->pw_class)) == NULL) { 543 debug("unable to get login class: %s", user); 544 return (NULL); 545 } 546 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || 547 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { 548 debug("Approval failure for %s", user); 549 pw = NULL; 550 } 551 if (as != NULL) 552 auth_close(as); 553 if (pw != NULL) 554 return (pwcopy(pw)); 555 return (NULL); 556 } 557 558 /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */ 559 int 560 auth_key_is_revoked(Key *key) 561 { 562 char *fp = NULL; 563 int r; 564 565 if (options.revoked_keys_file == NULL) 566 return 0; 567 if ((fp = sshkey_fingerprint(key, options.fingerprint_hash, 568 SSH_FP_DEFAULT)) == NULL) { 569 r = SSH_ERR_ALLOC_FAIL; 570 error("%s: fingerprint key: %s", __func__, ssh_err(r)); 571 goto out; 572 } 573 574 r = sshkey_check_revoked(key, options.revoked_keys_file); 575 switch (r) { 576 case 0: 577 break; /* not revoked */ 578 case SSH_ERR_KEY_REVOKED: 579 error("Authentication key %s %s revoked by file %s", 580 sshkey_type(key), fp, options.revoked_keys_file); 581 goto out; 582 default: 583 error("Error checking authentication key %s %s in " 584 "revoked keys file %s: %s", sshkey_type(key), fp, 585 options.revoked_keys_file, ssh_err(r)); 586 goto out; 587 } 588 589 /* Success */ 590 r = 0; 591 592 out: 593 free(fp); 594 return r == 0 ? 0 : 1; 595 } 596 597 void 598 auth_debug_add(const char *fmt,...) 599 { 600 char buf[1024]; 601 va_list args; 602 603 if (!auth_debug_init) 604 return; 605 606 va_start(args, fmt); 607 vsnprintf(buf, sizeof(buf), fmt, args); 608 va_end(args); 609 buffer_put_cstring(&auth_debug, buf); 610 } 611 612 void 613 auth_debug_send(void) 614 { 615 char *msg; 616 617 if (!auth_debug_init) 618 return; 619 while (buffer_len(&auth_debug)) { 620 msg = buffer_get_string(&auth_debug, NULL); 621 packet_send_debug("%s", msg); 622 free(msg); 623 } 624 } 625 626 void 627 auth_debug_reset(void) 628 { 629 if (auth_debug_init) 630 buffer_clear(&auth_debug); 631 else { 632 buffer_init(&auth_debug); 633 auth_debug_init = 1; 634 } 635 } 636 637 struct passwd * 638 fakepw(void) 639 { 640 static struct passwd fake; 641 642 memset(&fake, 0, sizeof(fake)); 643 fake.pw_name = "NOUSER"; 644 fake.pw_passwd = 645 "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK"; 646 fake.pw_gecos = "NOUSER"; 647 fake.pw_uid = (uid_t)-1; 648 fake.pw_gid = (gid_t)-1; 649 fake.pw_class = ""; 650 fake.pw_dir = "/nonexist"; 651 fake.pw_shell = "/nonexist"; 652 653 return (&fake); 654 } 655 656 /* 657 * Returns the remote DNS hostname as a string. The returned string must not 658 * be freed. NB. this will usually trigger a DNS query the first time it is 659 * called. 660 * This function does additional checks on the hostname to mitigate some 661 * attacks on legacy rhosts-style authentication. 662 * XXX is RhostsRSAAuthentication vulnerable to these? 663 * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?) 664 */ 665 666 static char * 667 remote_hostname(struct ssh *ssh) 668 { 669 struct sockaddr_storage from; 670 socklen_t fromlen; 671 struct addrinfo hints, *ai, *aitop; 672 char name[NI_MAXHOST], ntop2[NI_MAXHOST]; 673 const char *ntop = ssh_remote_ipaddr(ssh); 674 675 /* Get IP address of client. */ 676 fromlen = sizeof(from); 677 memset(&from, 0, sizeof(from)); 678 if (getpeername(ssh_packet_get_connection_in(ssh), 679 (struct sockaddr *)&from, &fromlen) < 0) { 680 debug("getpeername failed: %.100s", strerror(errno)); 681 return strdup(ntop); 682 } 683 684 debug3("Trying to reverse map address %.100s.", ntop); 685 /* Map the IP address to a host name. */ 686 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), 687 NULL, 0, NI_NAMEREQD) != 0) { 688 /* Host name not found. Use ip address. */ 689 return strdup(ntop); 690 } 691 692 /* 693 * if reverse lookup result looks like a numeric hostname, 694 * someone is trying to trick us by PTR record like following: 695 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5 696 */ 697 memset(&hints, 0, sizeof(hints)); 698 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 699 hints.ai_flags = AI_NUMERICHOST; 700 if (getaddrinfo(name, NULL, &hints, &ai) == 0) { 701 logit("Nasty PTR record \"%s\" is set up for %s, ignoring", 702 name, ntop); 703 freeaddrinfo(ai); 704 return strdup(ntop); 705 } 706 707 /* Names are stored in lowercase. */ 708 lowercase(name); 709 710 /* 711 * Map it back to an IP address and check that the given 712 * address actually is an address of this host. This is 713 * necessary because anyone with access to a name server can 714 * define arbitrary names for an IP address. Mapping from 715 * name to IP address can be trusted better (but can still be 716 * fooled if the intruder has access to the name server of 717 * the domain). 718 */ 719 memset(&hints, 0, sizeof(hints)); 720 hints.ai_family = from.ss_family; 721 hints.ai_socktype = SOCK_STREAM; 722 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { 723 logit("reverse mapping checking getaddrinfo for %.700s " 724 "[%s] failed - POSSIBLE BREAK-IN ATTEMPT!", name, ntop); 725 return strdup(ntop); 726 } 727 /* Look for the address from the list of addresses. */ 728 for (ai = aitop; ai; ai = ai->ai_next) { 729 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, 730 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && 731 (strcmp(ntop, ntop2) == 0)) 732 break; 733 } 734 freeaddrinfo(aitop); 735 /* If we reached the end of the list, the address was not there. */ 736 if (ai == NULL) { 737 /* Address not found for the host name. */ 738 logit("Address %.100s maps to %.600s, but this does not " 739 "map back to the address - POSSIBLE BREAK-IN ATTEMPT!", 740 ntop, name); 741 return strdup(ntop); 742 } 743 return strdup(name); 744 } 745 746 /* 747 * Return the canonical name of the host in the other side of the current 748 * connection. The host name is cached, so it is efficient to call this 749 * several times. 750 */ 751 752 const char * 753 auth_get_canonical_hostname(struct ssh *ssh, int use_dns) 754 { 755 static char *dnsname; 756 757 if (!use_dns) 758 return ssh_remote_ipaddr(ssh); 759 else if (dnsname != NULL) 760 return dnsname; 761 else { 762 dnsname = remote_hostname(ssh); 763 return dnsname; 764 } 765 } 766