1 /* $OpenBSD: auth.c,v 1.124 2017/09/12 06:32:07 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 "includes.h" 27 28 #include <sys/types.h> 29 #include <sys/stat.h> 30 #include <sys/socket.h> 31 32 #include <netinet/in.h> 33 34 #include <errno.h> 35 #include <fcntl.h> 36 #ifdef HAVE_PATHS_H 37 # include <paths.h> 38 #endif 39 #include <pwd.h> 40 #ifdef HAVE_LOGIN_H 41 #include <login.h> 42 #endif 43 #ifdef USE_SHADOW 44 #include <shadow.h> 45 #endif 46 #include <stdarg.h> 47 #include <stdio.h> 48 #include <string.h> 49 #include <unistd.h> 50 #include <limits.h> 51 #include <netdb.h> 52 53 #include "xmalloc.h" 54 #include "match.h" 55 #include "groupaccess.h" 56 #include "log.h" 57 #include "buffer.h" 58 #include "misc.h" 59 #include "servconf.h" 60 #include "key.h" 61 #include "hostfile.h" 62 #include "auth.h" 63 #include "auth-options.h" 64 #include "canohost.h" 65 #include "uidswap.h" 66 #include "packet.h" 67 #include "loginrec.h" 68 #ifdef GSSAPI 69 #include "ssh-gss.h" 70 #endif 71 #include "authfile.h" 72 #include "monitor_wrap.h" 73 #include "authfile.h" 74 #include "ssherr.h" 75 #include "compat.h" 76 77 /* import */ 78 extern ServerOptions options; 79 extern int use_privsep; 80 extern Buffer loginmsg; 81 extern struct passwd *privsep_pw; 82 83 /* Debugging messages */ 84 Buffer auth_debug; 85 int auth_debug_init; 86 87 /* 88 * Check if the user is allowed to log in via ssh. If user is listed 89 * in DenyUsers or one of user's groups is listed in DenyGroups, false 90 * will be returned. If AllowUsers isn't empty and user isn't listed 91 * there, or if AllowGroups isn't empty and one of user's groups isn't 92 * listed there, false will be returned. 93 * If the user's shell is not executable, false will be returned. 94 * Otherwise true is returned. 95 */ 96 int 97 allowed_user(struct passwd * pw) 98 { 99 struct ssh *ssh = active_state; /* XXX */ 100 struct stat st; 101 const char *hostname = NULL, *ipaddr = NULL, *passwd = NULL; 102 u_int i; 103 int r; 104 #ifdef USE_SHADOW 105 struct spwd *spw = NULL; 106 #endif 107 108 /* Shouldn't be called if pw is NULL, but better safe than sorry... */ 109 if (!pw || !pw->pw_name) 110 return 0; 111 112 #ifdef USE_SHADOW 113 if (!options.use_pam) 114 spw = getspnam(pw->pw_name); 115 #ifdef HAS_SHADOW_EXPIRE 116 if (!options.use_pam && spw != NULL && auth_shadow_acctexpired(spw)) 117 return 0; 118 #endif /* HAS_SHADOW_EXPIRE */ 119 #endif /* USE_SHADOW */ 120 121 /* grab passwd field for locked account check */ 122 passwd = pw->pw_passwd; 123 #ifdef USE_SHADOW 124 if (spw != NULL) 125 #ifdef USE_LIBIAF 126 passwd = get_iaf_password(pw); 127 #else 128 passwd = spw->sp_pwdp; 129 #endif /* USE_LIBIAF */ 130 #endif 131 132 /* check for locked account */ 133 if (!options.use_pam && passwd && *passwd) { 134 int locked = 0; 135 136 #ifdef LOCKED_PASSWD_STRING 137 if (strcmp(passwd, LOCKED_PASSWD_STRING) == 0) 138 locked = 1; 139 #endif 140 #ifdef LOCKED_PASSWD_PREFIX 141 if (strncmp(passwd, LOCKED_PASSWD_PREFIX, 142 strlen(LOCKED_PASSWD_PREFIX)) == 0) 143 locked = 1; 144 #endif 145 #ifdef LOCKED_PASSWD_SUBSTR 146 if (strstr(passwd, LOCKED_PASSWD_SUBSTR)) 147 locked = 1; 148 #endif 149 #ifdef USE_LIBIAF 150 free((void *) passwd); 151 #endif /* USE_LIBIAF */ 152 if (locked) { 153 logit("User %.100s not allowed because account is locked", 154 pw->pw_name); 155 return 0; 156 } 157 } 158 159 /* 160 * Deny if shell does not exist or is not executable unless we 161 * are chrooting. 162 */ 163 if (options.chroot_directory == NULL || 164 strcasecmp(options.chroot_directory, "none") == 0) { 165 char *shell = xstrdup((pw->pw_shell[0] == '\0') ? 166 _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */ 167 168 if (stat(shell, &st) != 0) { 169 logit("User %.100s not allowed because shell %.100s " 170 "does not exist", pw->pw_name, shell); 171 free(shell); 172 return 0; 173 } 174 if (S_ISREG(st.st_mode) == 0 || 175 (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { 176 logit("User %.100s not allowed because shell %.100s " 177 "is not executable", pw->pw_name, shell); 178 free(shell); 179 return 0; 180 } 181 free(shell); 182 } 183 184 if (options.num_deny_users > 0 || options.num_allow_users > 0 || 185 options.num_deny_groups > 0 || options.num_allow_groups > 0) { 186 hostname = auth_get_canonical_hostname(ssh, options.use_dns); 187 ipaddr = ssh_remote_ipaddr(ssh); 188 } 189 190 /* Return false if user is listed in DenyUsers */ 191 if (options.num_deny_users > 0) { 192 for (i = 0; i < options.num_deny_users; i++) { 193 r = match_user(pw->pw_name, hostname, ipaddr, 194 options.deny_users[i]); 195 if (r < 0) { 196 fatal("Invalid DenyUsers pattern \"%.100s\"", 197 options.deny_users[i]); 198 } else if (r != 0) { 199 logit("User %.100s from %.100s not allowed " 200 "because listed in DenyUsers", 201 pw->pw_name, hostname); 202 return 0; 203 } 204 } 205 } 206 /* Return false if AllowUsers isn't empty and user isn't listed there */ 207 if (options.num_allow_users > 0) { 208 for (i = 0; i < options.num_allow_users; i++) { 209 r = match_user(pw->pw_name, hostname, ipaddr, 210 options.allow_users[i]); 211 if (r < 0) { 212 fatal("Invalid AllowUsers pattern \"%.100s\"", 213 options.allow_users[i]); 214 } else if (r == 1) 215 break; 216 } 217 /* i < options.num_allow_users iff we break for loop */ 218 if (i >= options.num_allow_users) { 219 logit("User %.100s from %.100s not allowed because " 220 "not listed in AllowUsers", pw->pw_name, hostname); 221 return 0; 222 } 223 } 224 if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { 225 /* Get the user's group access list (primary and supplementary) */ 226 if (ga_init(pw->pw_name, pw->pw_gid) == 0) { 227 logit("User %.100s from %.100s not allowed because " 228 "not in any group", pw->pw_name, hostname); 229 return 0; 230 } 231 232 /* Return false if one of user's groups is listed in DenyGroups */ 233 if (options.num_deny_groups > 0) 234 if (ga_match(options.deny_groups, 235 options.num_deny_groups)) { 236 ga_free(); 237 logit("User %.100s from %.100s not allowed " 238 "because a group is listed in DenyGroups", 239 pw->pw_name, hostname); 240 return 0; 241 } 242 /* 243 * Return false if AllowGroups isn't empty and one of user's groups 244 * isn't listed there 245 */ 246 if (options.num_allow_groups > 0) 247 if (!ga_match(options.allow_groups, 248 options.num_allow_groups)) { 249 ga_free(); 250 logit("User %.100s from %.100s not allowed " 251 "because none of user's groups are listed " 252 "in AllowGroups", pw->pw_name, hostname); 253 return 0; 254 } 255 ga_free(); 256 } 257 258 #ifdef CUSTOM_SYS_AUTH_ALLOWED_USER 259 if (!sys_auth_allowed_user(pw, &loginmsg)) 260 return 0; 261 #endif 262 263 /* We found no reason not to let this user try to log on... */ 264 return 1; 265 } 266 267 /* 268 * Formats any key left in authctxt->auth_method_key for inclusion in 269 * auth_log()'s message. Also includes authxtct->auth_method_info if present. 270 */ 271 static char * 272 format_method_key(Authctxt *authctxt) 273 { 274 const struct sshkey *key = authctxt->auth_method_key; 275 const char *methinfo = authctxt->auth_method_info; 276 char *fp, *ret = NULL; 277 278 if (key == NULL) 279 return NULL; 280 281 if (key_is_cert(key)) { 282 fp = sshkey_fingerprint(key->cert->signature_key, 283 options.fingerprint_hash, SSH_FP_DEFAULT); 284 xasprintf(&ret, "%s ID %s (serial %llu) CA %s %s%s%s", 285 sshkey_type(key), key->cert->key_id, 286 (unsigned long long)key->cert->serial, 287 sshkey_type(key->cert->signature_key), 288 fp == NULL ? "(null)" : fp, 289 methinfo == NULL ? "" : ", ", 290 methinfo == NULL ? "" : methinfo); 291 free(fp); 292 } else { 293 fp = sshkey_fingerprint(key, options.fingerprint_hash, 294 SSH_FP_DEFAULT); 295 xasprintf(&ret, "%s %s%s%s", sshkey_type(key), 296 fp == NULL ? "(null)" : fp, 297 methinfo == NULL ? "" : ", ", 298 methinfo == NULL ? "" : methinfo); 299 free(fp); 300 } 301 return ret; 302 } 303 304 void 305 auth_log(Authctxt *authctxt, int authenticated, int partial, 306 const char *method, const char *submethod) 307 { 308 struct ssh *ssh = active_state; /* XXX */ 309 void (*authlog) (const char *fmt,...) = verbose; 310 const char *authmsg; 311 char *extra = NULL; 312 313 if (use_privsep && !mm_is_monitor() && !authctxt->postponed) 314 return; 315 316 /* Raise logging level */ 317 if (authenticated == 1 || 318 !authctxt->valid || 319 authctxt->failures >= options.max_authtries / 2 || 320 strcmp(method, "password") == 0) 321 authlog = logit; 322 323 if (authctxt->postponed) 324 authmsg = "Postponed"; 325 else if (partial) 326 authmsg = "Partial"; 327 else 328 authmsg = authenticated ? "Accepted" : "Failed"; 329 330 if ((extra = format_method_key(authctxt)) == NULL) { 331 if (authctxt->auth_method_info != NULL) 332 extra = xstrdup(authctxt->auth_method_info); 333 } 334 335 authlog("%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s", 336 authmsg, 337 method, 338 submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod, 339 authctxt->valid ? "" : "invalid user ", 340 authctxt->user, 341 ssh_remote_ipaddr(ssh), 342 ssh_remote_port(ssh), 343 extra != NULL ? ": " : "", 344 extra != NULL ? extra : ""); 345 346 free(extra); 347 348 #ifdef CUSTOM_FAILED_LOGIN 349 if (authenticated == 0 && !authctxt->postponed && 350 (strcmp(method, "password") == 0 || 351 strncmp(method, "keyboard-interactive", 20) == 0 || 352 strcmp(method, "challenge-response") == 0)) 353 record_failed_login(authctxt->user, 354 auth_get_canonical_hostname(ssh, options.use_dns), "ssh"); 355 # ifdef WITH_AIXAUTHENTICATE 356 if (authenticated) 357 sys_auth_record_login(authctxt->user, 358 auth_get_canonical_hostname(ssh, options.use_dns), "ssh", 359 &loginmsg); 360 # endif 361 #endif 362 #ifdef SSH_AUDIT_EVENTS 363 if (authenticated == 0 && !authctxt->postponed) 364 audit_event(audit_classify_auth(method)); 365 #endif 366 } 367 368 369 void 370 auth_maxtries_exceeded(Authctxt *authctxt) 371 { 372 struct ssh *ssh = active_state; /* XXX */ 373 374 error("maximum authentication attempts exceeded for " 375 "%s%.100s from %.200s port %d ssh2", 376 authctxt->valid ? "" : "invalid user ", 377 authctxt->user, 378 ssh_remote_ipaddr(ssh), 379 ssh_remote_port(ssh)); 380 packet_disconnect("Too many authentication failures"); 381 /* NOTREACHED */ 382 } 383 384 /* 385 * Check whether root logins are disallowed. 386 */ 387 int 388 auth_root_allowed(const char *method) 389 { 390 struct ssh *ssh = active_state; /* XXX */ 391 392 switch (options.permit_root_login) { 393 case PERMIT_YES: 394 return 1; 395 case PERMIT_NO_PASSWD: 396 if (strcmp(method, "publickey") == 0 || 397 strcmp(method, "hostbased") == 0 || 398 strcmp(method, "gssapi-with-mic") == 0) 399 return 1; 400 break; 401 case PERMIT_FORCED_ONLY: 402 if (forced_command) { 403 logit("Root login accepted for forced command."); 404 return 1; 405 } 406 break; 407 } 408 logit("ROOT LOGIN REFUSED FROM %.200s port %d", 409 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 410 return 0; 411 } 412 413 414 /* 415 * Given a template and a passwd structure, build a filename 416 * by substituting % tokenised options. Currently, %% becomes '%', 417 * %h becomes the home directory and %u the username. 418 * 419 * This returns a buffer allocated by xmalloc. 420 */ 421 char * 422 expand_authorized_keys(const char *filename, struct passwd *pw) 423 { 424 char *file, ret[PATH_MAX]; 425 int i; 426 427 file = percent_expand(filename, "h", pw->pw_dir, 428 "u", pw->pw_name, (char *)NULL); 429 430 /* 431 * Ensure that filename starts anchored. If not, be backward 432 * compatible and prepend the '%h/' 433 */ 434 if (*file == '/') 435 return (file); 436 437 i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file); 438 if (i < 0 || (size_t)i >= sizeof(ret)) 439 fatal("expand_authorized_keys: path too long"); 440 free(file); 441 return (xstrdup(ret)); 442 } 443 444 char * 445 authorized_principals_file(struct passwd *pw) 446 { 447 if (options.authorized_principals_file == NULL) 448 return NULL; 449 return expand_authorized_keys(options.authorized_principals_file, pw); 450 } 451 452 /* return ok if key exists in sysfile or userfile */ 453 HostStatus 454 check_key_in_hostfiles(struct passwd *pw, struct sshkey *key, const char *host, 455 const char *sysfile, const char *userfile) 456 { 457 char *user_hostfile; 458 struct stat st; 459 HostStatus host_status; 460 struct hostkeys *hostkeys; 461 const struct hostkey_entry *found; 462 463 hostkeys = init_hostkeys(); 464 load_hostkeys(hostkeys, host, sysfile); 465 if (userfile != NULL) { 466 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); 467 if (options.strict_modes && 468 (stat(user_hostfile, &st) == 0) && 469 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || 470 (st.st_mode & 022) != 0)) { 471 logit("Authentication refused for %.100s: " 472 "bad owner or modes for %.200s", 473 pw->pw_name, user_hostfile); 474 auth_debug_add("Ignored %.200s: bad ownership or modes", 475 user_hostfile); 476 } else { 477 temporarily_use_uid(pw); 478 load_hostkeys(hostkeys, host, user_hostfile); 479 restore_uid(); 480 } 481 free(user_hostfile); 482 } 483 host_status = check_key_in_hostkeys(hostkeys, key, &found); 484 if (host_status == HOST_REVOKED) 485 error("WARNING: revoked key for %s attempted authentication", 486 found->host); 487 else if (host_status == HOST_OK) 488 debug("%s: key for %s found at %s:%ld", __func__, 489 found->host, found->file, found->line); 490 else 491 debug("%s: key for host %s not found", __func__, host); 492 493 free_hostkeys(hostkeys); 494 495 return host_status; 496 } 497 498 static FILE * 499 auth_openfile(const char *file, struct passwd *pw, int strict_modes, 500 int log_missing, char *file_type) 501 { 502 char line[1024]; 503 struct stat st; 504 int fd; 505 FILE *f; 506 507 if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) { 508 if (log_missing || errno != ENOENT) 509 debug("Could not open %s '%s': %s", file_type, file, 510 strerror(errno)); 511 return NULL; 512 } 513 514 if (fstat(fd, &st) < 0) { 515 close(fd); 516 return NULL; 517 } 518 if (!S_ISREG(st.st_mode)) { 519 logit("User %s %s %s is not a regular file", 520 pw->pw_name, file_type, file); 521 close(fd); 522 return NULL; 523 } 524 unset_nonblock(fd); 525 if ((f = fdopen(fd, "r")) == NULL) { 526 close(fd); 527 return NULL; 528 } 529 if (strict_modes && 530 safe_path_fd(fileno(f), file, pw, line, sizeof(line)) != 0) { 531 fclose(f); 532 logit("Authentication refused: %s", line); 533 auth_debug_add("Ignored %s: %s", file_type, line); 534 return NULL; 535 } 536 537 return f; 538 } 539 540 541 FILE * 542 auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes) 543 { 544 return auth_openfile(file, pw, strict_modes, 1, "authorized keys"); 545 } 546 547 FILE * 548 auth_openprincipals(const char *file, struct passwd *pw, int strict_modes) 549 { 550 return auth_openfile(file, pw, strict_modes, 0, 551 "authorized principals"); 552 } 553 554 struct passwd * 555 getpwnamallow(const char *user) 556 { 557 struct ssh *ssh = active_state; /* XXX */ 558 #ifdef HAVE_LOGIN_CAP 559 extern login_cap_t *lc; 560 #ifdef BSD_AUTH 561 auth_session_t *as; 562 #endif 563 #endif 564 struct passwd *pw; 565 struct connection_info *ci = get_connection_info(1, options.use_dns); 566 567 ci->user = user; 568 parse_server_match_config(&options, ci); 569 log_change_level(options.log_level); 570 process_permitopen(ssh, &options); 571 572 #if defined(_AIX) && defined(HAVE_SETAUTHDB) 573 aix_setauthdb(user); 574 #endif 575 576 pw = getpwnam(user); 577 578 #if defined(_AIX) && defined(HAVE_SETAUTHDB) 579 aix_restoreauthdb(); 580 #endif 581 #ifdef HAVE_CYGWIN 582 /* 583 * Windows usernames are case-insensitive. To avoid later problems 584 * when trying to match the username, the user is only allowed to 585 * login if the username is given in the same case as stored in the 586 * user database. 587 */ 588 if (pw != NULL && strcmp(user, pw->pw_name) != 0) { 589 logit("Login name %.100s does not match stored username %.100s", 590 user, pw->pw_name); 591 pw = NULL; 592 } 593 #endif 594 if (pw == NULL) { 595 logit("Invalid user %.100s from %.100s port %d", 596 user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 597 #ifdef CUSTOM_FAILED_LOGIN 598 record_failed_login(user, 599 auth_get_canonical_hostname(ssh, options.use_dns), "ssh"); 600 #endif 601 #ifdef SSH_AUDIT_EVENTS 602 audit_event(SSH_INVALID_USER); 603 #endif /* SSH_AUDIT_EVENTS */ 604 return (NULL); 605 } 606 if (!allowed_user(pw)) 607 return (NULL); 608 #ifdef HAVE_LOGIN_CAP 609 if ((lc = login_getclass(pw->pw_class)) == NULL) { 610 debug("unable to get login class: %s", user); 611 return (NULL); 612 } 613 #ifdef BSD_AUTH 614 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || 615 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { 616 debug("Approval failure for %s", user); 617 pw = NULL; 618 } 619 if (as != NULL) 620 auth_close(as); 621 #endif 622 #endif 623 if (pw != NULL) 624 return (pwcopy(pw)); 625 return (NULL); 626 } 627 628 /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */ 629 int 630 auth_key_is_revoked(struct sshkey *key) 631 { 632 char *fp = NULL; 633 int r; 634 635 if (options.revoked_keys_file == NULL) 636 return 0; 637 if ((fp = sshkey_fingerprint(key, options.fingerprint_hash, 638 SSH_FP_DEFAULT)) == NULL) { 639 r = SSH_ERR_ALLOC_FAIL; 640 error("%s: fingerprint key: %s", __func__, ssh_err(r)); 641 goto out; 642 } 643 644 r = sshkey_check_revoked(key, options.revoked_keys_file); 645 switch (r) { 646 case 0: 647 break; /* not revoked */ 648 case SSH_ERR_KEY_REVOKED: 649 error("Authentication key %s %s revoked by file %s", 650 sshkey_type(key), fp, options.revoked_keys_file); 651 goto out; 652 default: 653 error("Error checking authentication key %s %s in " 654 "revoked keys file %s: %s", sshkey_type(key), fp, 655 options.revoked_keys_file, ssh_err(r)); 656 goto out; 657 } 658 659 /* Success */ 660 r = 0; 661 662 out: 663 free(fp); 664 return r == 0 ? 0 : 1; 665 } 666 667 void 668 auth_debug_add(const char *fmt,...) 669 { 670 char buf[1024]; 671 va_list args; 672 673 if (!auth_debug_init) 674 return; 675 676 va_start(args, fmt); 677 vsnprintf(buf, sizeof(buf), fmt, args); 678 va_end(args); 679 buffer_put_cstring(&auth_debug, buf); 680 } 681 682 void 683 auth_debug_send(void) 684 { 685 char *msg; 686 687 if (!auth_debug_init) 688 return; 689 while (buffer_len(&auth_debug)) { 690 msg = buffer_get_string(&auth_debug, NULL); 691 packet_send_debug("%s", msg); 692 free(msg); 693 } 694 } 695 696 void 697 auth_debug_reset(void) 698 { 699 if (auth_debug_init) 700 buffer_clear(&auth_debug); 701 else { 702 buffer_init(&auth_debug); 703 auth_debug_init = 1; 704 } 705 } 706 707 struct passwd * 708 fakepw(void) 709 { 710 static struct passwd fake; 711 712 memset(&fake, 0, sizeof(fake)); 713 fake.pw_name = "NOUSER"; 714 fake.pw_passwd = 715 "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK"; 716 #ifdef HAVE_STRUCT_PASSWD_PW_GECOS 717 fake.pw_gecos = "NOUSER"; 718 #endif 719 fake.pw_uid = privsep_pw == NULL ? (uid_t)-1 : privsep_pw->pw_uid; 720 fake.pw_gid = privsep_pw == NULL ? (gid_t)-1 : privsep_pw->pw_gid; 721 #ifdef HAVE_STRUCT_PASSWD_PW_CLASS 722 fake.pw_class = ""; 723 #endif 724 fake.pw_dir = "/nonexist"; 725 fake.pw_shell = "/nonexist"; 726 727 return (&fake); 728 } 729 730 /* 731 * Returns the remote DNS hostname as a string. The returned string must not 732 * be freed. NB. this will usually trigger a DNS query the first time it is 733 * called. 734 * This function does additional checks on the hostname to mitigate some 735 * attacks on legacy rhosts-style authentication. 736 * XXX is RhostsRSAAuthentication vulnerable to these? 737 * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?) 738 */ 739 740 static char * 741 remote_hostname(struct ssh *ssh) 742 { 743 struct sockaddr_storage from; 744 socklen_t fromlen; 745 struct addrinfo hints, *ai, *aitop; 746 char name[NI_MAXHOST], ntop2[NI_MAXHOST]; 747 const char *ntop = ssh_remote_ipaddr(ssh); 748 749 /* Get IP address of client. */ 750 fromlen = sizeof(from); 751 memset(&from, 0, sizeof(from)); 752 if (getpeername(ssh_packet_get_connection_in(ssh), 753 (struct sockaddr *)&from, &fromlen) < 0) { 754 debug("getpeername failed: %.100s", strerror(errno)); 755 return strdup(ntop); 756 } 757 758 ipv64_normalise_mapped(&from, &fromlen); 759 if (from.ss_family == AF_INET6) 760 fromlen = sizeof(struct sockaddr_in6); 761 762 debug3("Trying to reverse map address %.100s.", ntop); 763 /* Map the IP address to a host name. */ 764 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), 765 NULL, 0, NI_NAMEREQD) != 0) { 766 /* Host name not found. Use ip address. */ 767 return strdup(ntop); 768 } 769 770 /* 771 * if reverse lookup result looks like a numeric hostname, 772 * someone is trying to trick us by PTR record like following: 773 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5 774 */ 775 memset(&hints, 0, sizeof(hints)); 776 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 777 hints.ai_flags = AI_NUMERICHOST; 778 if (getaddrinfo(name, NULL, &hints, &ai) == 0) { 779 logit("Nasty PTR record \"%s\" is set up for %s, ignoring", 780 name, ntop); 781 freeaddrinfo(ai); 782 return strdup(ntop); 783 } 784 785 /* Names are stored in lowercase. */ 786 lowercase(name); 787 788 /* 789 * Map it back to an IP address and check that the given 790 * address actually is an address of this host. This is 791 * necessary because anyone with access to a name server can 792 * define arbitrary names for an IP address. Mapping from 793 * name to IP address can be trusted better (but can still be 794 * fooled if the intruder has access to the name server of 795 * the domain). 796 */ 797 memset(&hints, 0, sizeof(hints)); 798 hints.ai_family = from.ss_family; 799 hints.ai_socktype = SOCK_STREAM; 800 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { 801 logit("reverse mapping checking getaddrinfo for %.700s " 802 "[%s] failed.", name, ntop); 803 return strdup(ntop); 804 } 805 /* Look for the address from the list of addresses. */ 806 for (ai = aitop; ai; ai = ai->ai_next) { 807 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, 808 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && 809 (strcmp(ntop, ntop2) == 0)) 810 break; 811 } 812 freeaddrinfo(aitop); 813 /* If we reached the end of the list, the address was not there. */ 814 if (ai == NULL) { 815 /* Address not found for the host name. */ 816 logit("Address %.100s maps to %.600s, but this does not " 817 "map back to the address.", ntop, name); 818 return strdup(ntop); 819 } 820 return strdup(name); 821 } 822 823 /* 824 * Return the canonical name of the host in the other side of the current 825 * connection. The host name is cached, so it is efficient to call this 826 * several times. 827 */ 828 829 const char * 830 auth_get_canonical_hostname(struct ssh *ssh, int use_dns) 831 { 832 static char *dnsname; 833 834 if (!use_dns) 835 return ssh_remote_ipaddr(ssh); 836 else if (dnsname != NULL) 837 return dnsname; 838 else { 839 dnsname = remote_hostname(ssh); 840 return dnsname; 841 } 842 } 843