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 __RCSID("$FreeBSD$"); 28 29 #include <sys/types.h> 30 #include <sys/stat.h> 31 #include <sys/socket.h> 32 33 #include <netinet/in.h> 34 35 #include <errno.h> 36 #include <fcntl.h> 37 #ifdef HAVE_PATHS_H 38 # include <paths.h> 39 #endif 40 #include <pwd.h> 41 #ifdef HAVE_LOGIN_H 42 #include <login.h> 43 #endif 44 #ifdef USE_SHADOW 45 #include <shadow.h> 46 #endif 47 #include <stdarg.h> 48 #include <stdio.h> 49 #include <string.h> 50 #include <unistd.h> 51 #include <limits.h> 52 #include <netdb.h> 53 54 #include "xmalloc.h" 55 #include "match.h" 56 #include "groupaccess.h" 57 #include "log.h" 58 #include "buffer.h" 59 #include "misc.h" 60 #include "servconf.h" 61 #include "key.h" 62 #include "hostfile.h" 63 #include "auth.h" 64 #include "auth-options.h" 65 #include "canohost.h" 66 #include "uidswap.h" 67 #include "packet.h" 68 #include "loginrec.h" 69 #ifdef GSSAPI 70 #include "ssh-gss.h" 71 #endif 72 #include "authfile.h" 73 #include "monitor_wrap.h" 74 #include "authfile.h" 75 #include "ssherr.h" 76 #include "compat.h" 77 #include "blacklist_client.h" 78 79 /* import */ 80 extern ServerOptions options; 81 extern int use_privsep; 82 extern Buffer loginmsg; 83 extern struct passwd *privsep_pw; 84 85 /* Debugging messages */ 86 Buffer auth_debug; 87 int auth_debug_init; 88 89 /* 90 * Check if the user is allowed to log in via ssh. If user is listed 91 * in DenyUsers or one of user's groups is listed in DenyGroups, false 92 * will be returned. If AllowUsers isn't empty and user isn't listed 93 * there, or if AllowGroups isn't empty and one of user's groups isn't 94 * listed there, false will be returned. 95 * If the user's shell is not executable, false will be returned. 96 * Otherwise true is returned. 97 */ 98 int 99 allowed_user(struct passwd * pw) 100 { 101 struct ssh *ssh = active_state; /* XXX */ 102 struct stat st; 103 const char *hostname = NULL, *ipaddr = NULL, *passwd = NULL; 104 u_int i; 105 int r; 106 #ifdef USE_SHADOW 107 struct spwd *spw = NULL; 108 #endif 109 110 /* Shouldn't be called if pw is NULL, but better safe than sorry... */ 111 if (!pw || !pw->pw_name) 112 return 0; 113 114 #ifdef USE_SHADOW 115 if (!options.use_pam) 116 spw = getspnam(pw->pw_name); 117 #ifdef HAS_SHADOW_EXPIRE 118 if (!options.use_pam && spw != NULL && auth_shadow_acctexpired(spw)) 119 return 0; 120 #endif /* HAS_SHADOW_EXPIRE */ 121 #endif /* USE_SHADOW */ 122 123 /* grab passwd field for locked account check */ 124 passwd = pw->pw_passwd; 125 #ifdef USE_SHADOW 126 if (spw != NULL) 127 #ifdef USE_LIBIAF 128 passwd = get_iaf_password(pw); 129 #else 130 passwd = spw->sp_pwdp; 131 #endif /* USE_LIBIAF */ 132 #endif 133 134 /* check for locked account */ 135 if (!options.use_pam && passwd && *passwd) { 136 int locked = 0; 137 138 #ifdef LOCKED_PASSWD_STRING 139 if (strcmp(passwd, LOCKED_PASSWD_STRING) == 0) 140 locked = 1; 141 #endif 142 #ifdef LOCKED_PASSWD_PREFIX 143 if (strncmp(passwd, LOCKED_PASSWD_PREFIX, 144 strlen(LOCKED_PASSWD_PREFIX)) == 0) 145 locked = 1; 146 #endif 147 #ifdef LOCKED_PASSWD_SUBSTR 148 if (strstr(passwd, LOCKED_PASSWD_SUBSTR)) 149 locked = 1; 150 #endif 151 #ifdef USE_LIBIAF 152 free((void *) passwd); 153 #endif /* USE_LIBIAF */ 154 if (locked) { 155 logit("User %.100s not allowed because account is locked", 156 pw->pw_name); 157 return 0; 158 } 159 } 160 161 /* 162 * Deny if shell does not exist or is not executable unless we 163 * are chrooting. 164 */ 165 if (options.chroot_directory == NULL || 166 strcasecmp(options.chroot_directory, "none") == 0) { 167 char *shell = xstrdup((pw->pw_shell[0] == '\0') ? 168 _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */ 169 170 if (stat(shell, &st) != 0) { 171 logit("User %.100s not allowed because shell %.100s " 172 "does not exist", pw->pw_name, shell); 173 free(shell); 174 return 0; 175 } 176 if (S_ISREG(st.st_mode) == 0 || 177 (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { 178 logit("User %.100s not allowed because shell %.100s " 179 "is not executable", pw->pw_name, shell); 180 free(shell); 181 return 0; 182 } 183 free(shell); 184 } 185 186 if (options.num_deny_users > 0 || options.num_allow_users > 0 || 187 options.num_deny_groups > 0 || options.num_allow_groups > 0) { 188 hostname = auth_get_canonical_hostname(ssh, options.use_dns); 189 ipaddr = ssh_remote_ipaddr(ssh); 190 } 191 192 /* Return false if user is listed in DenyUsers */ 193 if (options.num_deny_users > 0) { 194 for (i = 0; i < options.num_deny_users; i++) { 195 r = match_user(pw->pw_name, hostname, ipaddr, 196 options.deny_users[i]); 197 if (r < 0) { 198 fatal("Invalid DenyUsers pattern \"%.100s\"", 199 options.deny_users[i]); 200 } else if (r != 0) { 201 logit("User %.100s from %.100s not allowed " 202 "because listed in DenyUsers", 203 pw->pw_name, hostname); 204 return 0; 205 } 206 } 207 } 208 /* Return false if AllowUsers isn't empty and user isn't listed there */ 209 if (options.num_allow_users > 0) { 210 for (i = 0; i < options.num_allow_users; i++) { 211 r = match_user(pw->pw_name, hostname, ipaddr, 212 options.allow_users[i]); 213 if (r < 0) { 214 fatal("Invalid AllowUsers pattern \"%.100s\"", 215 options.allow_users[i]); 216 } else if (r == 1) 217 break; 218 } 219 /* i < options.num_allow_users iff we break for loop */ 220 if (i >= options.num_allow_users) { 221 logit("User %.100s from %.100s not allowed because " 222 "not listed in AllowUsers", pw->pw_name, hostname); 223 return 0; 224 } 225 } 226 if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { 227 /* Get the user's group access list (primary and supplementary) */ 228 if (ga_init(pw->pw_name, pw->pw_gid) == 0) { 229 logit("User %.100s from %.100s not allowed because " 230 "not in any group", pw->pw_name, hostname); 231 return 0; 232 } 233 234 /* Return false if one of user's groups is listed in DenyGroups */ 235 if (options.num_deny_groups > 0) 236 if (ga_match(options.deny_groups, 237 options.num_deny_groups)) { 238 ga_free(); 239 logit("User %.100s from %.100s not allowed " 240 "because a group is listed in DenyGroups", 241 pw->pw_name, hostname); 242 return 0; 243 } 244 /* 245 * Return false if AllowGroups isn't empty and one of user's groups 246 * isn't listed there 247 */ 248 if (options.num_allow_groups > 0) 249 if (!ga_match(options.allow_groups, 250 options.num_allow_groups)) { 251 ga_free(); 252 logit("User %.100s from %.100s not allowed " 253 "because none of user's groups are listed " 254 "in AllowGroups", pw->pw_name, hostname); 255 return 0; 256 } 257 ga_free(); 258 } 259 260 #ifdef CUSTOM_SYS_AUTH_ALLOWED_USER 261 if (!sys_auth_allowed_user(pw, &loginmsg)) 262 return 0; 263 #endif 264 265 /* We found no reason not to let this user try to log on... */ 266 return 1; 267 } 268 269 /* 270 * Formats any key left in authctxt->auth_method_key for inclusion in 271 * auth_log()'s message. Also includes authxtct->auth_method_info if present. 272 */ 273 static char * 274 format_method_key(Authctxt *authctxt) 275 { 276 const struct sshkey *key = authctxt->auth_method_key; 277 const char *methinfo = authctxt->auth_method_info; 278 char *fp, *ret = NULL; 279 280 if (key == NULL) 281 return NULL; 282 283 if (key_is_cert(key)) { 284 fp = sshkey_fingerprint(key->cert->signature_key, 285 options.fingerprint_hash, SSH_FP_DEFAULT); 286 xasprintf(&ret, "%s ID %s (serial %llu) CA %s %s%s%s", 287 sshkey_type(key), key->cert->key_id, 288 (unsigned long long)key->cert->serial, 289 sshkey_type(key->cert->signature_key), 290 fp == NULL ? "(null)" : fp, 291 methinfo == NULL ? "" : ", ", 292 methinfo == NULL ? "" : methinfo); 293 free(fp); 294 } else { 295 fp = sshkey_fingerprint(key, options.fingerprint_hash, 296 SSH_FP_DEFAULT); 297 xasprintf(&ret, "%s %s%s%s", sshkey_type(key), 298 fp == NULL ? "(null)" : fp, 299 methinfo == NULL ? "" : ", ", 300 methinfo == NULL ? "" : methinfo); 301 free(fp); 302 } 303 return ret; 304 } 305 306 void 307 auth_log(Authctxt *authctxt, int authenticated, int partial, 308 const char *method, const char *submethod) 309 { 310 struct ssh *ssh = active_state; /* XXX */ 311 void (*authlog) (const char *fmt,...) = verbose; 312 const char *authmsg; 313 char *extra = NULL; 314 315 if (use_privsep && !mm_is_monitor() && !authctxt->postponed) 316 return; 317 318 /* Raise logging level */ 319 if (authenticated == 1 || 320 !authctxt->valid || 321 authctxt->failures >= options.max_authtries / 2 || 322 strcmp(method, "password") == 0) 323 authlog = logit; 324 325 if (authctxt->postponed) 326 authmsg = "Postponed"; 327 else if (partial) 328 authmsg = "Partial"; 329 else { 330 authmsg = authenticated ? "Accepted" : "Failed"; 331 if (authenticated) 332 BLACKLIST_NOTIFY(BLACKLIST_AUTH_OK, "ssh"); 333 } 334 335 if ((extra = format_method_key(authctxt)) == NULL) { 336 if (authctxt->auth_method_info != NULL) 337 extra = xstrdup(authctxt->auth_method_info); 338 } 339 340 authlog("%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s", 341 authmsg, 342 method, 343 submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod, 344 authctxt->valid ? "" : "invalid user ", 345 authctxt->user, 346 ssh_remote_ipaddr(ssh), 347 ssh_remote_port(ssh), 348 extra != NULL ? ": " : "", 349 extra != NULL ? extra : ""); 350 351 free(extra); 352 353 #ifdef CUSTOM_FAILED_LOGIN 354 if (authenticated == 0 && !authctxt->postponed && 355 (strcmp(method, "password") == 0 || 356 strncmp(method, "keyboard-interactive", 20) == 0 || 357 strcmp(method, "challenge-response") == 0)) 358 record_failed_login(authctxt->user, 359 auth_get_canonical_hostname(ssh, options.use_dns), "ssh"); 360 # ifdef WITH_AIXAUTHENTICATE 361 if (authenticated) 362 sys_auth_record_login(authctxt->user, 363 auth_get_canonical_hostname(ssh, options.use_dns), "ssh", 364 &loginmsg); 365 # endif 366 #endif 367 #ifdef SSH_AUDIT_EVENTS 368 if (authenticated == 0 && !authctxt->postponed) 369 audit_event(audit_classify_auth(method)); 370 #endif 371 } 372 373 374 void 375 auth_maxtries_exceeded(Authctxt *authctxt) 376 { 377 struct ssh *ssh = active_state; /* XXX */ 378 379 error("maximum authentication attempts exceeded for " 380 "%s%.100s from %.200s port %d ssh2", 381 authctxt->valid ? "" : "invalid user ", 382 authctxt->user, 383 ssh_remote_ipaddr(ssh), 384 ssh_remote_port(ssh)); 385 packet_disconnect("Too many authentication failures"); 386 /* NOTREACHED */ 387 } 388 389 /* 390 * Check whether root logins are disallowed. 391 */ 392 int 393 auth_root_allowed(const char *method) 394 { 395 struct ssh *ssh = active_state; /* XXX */ 396 397 switch (options.permit_root_login) { 398 case PERMIT_YES: 399 return 1; 400 case PERMIT_NO_PASSWD: 401 if (strcmp(method, "publickey") == 0 || 402 strcmp(method, "hostbased") == 0 || 403 strcmp(method, "gssapi-with-mic") == 0) 404 return 1; 405 break; 406 case PERMIT_FORCED_ONLY: 407 if (forced_command) { 408 logit("Root login accepted for forced command."); 409 return 1; 410 } 411 break; 412 } 413 logit("ROOT LOGIN REFUSED FROM %.200s port %d", 414 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 415 return 0; 416 } 417 418 419 /* 420 * Given a template and a passwd structure, build a filename 421 * by substituting % tokenised options. Currently, %% becomes '%', 422 * %h becomes the home directory and %u the username. 423 * 424 * This returns a buffer allocated by xmalloc. 425 */ 426 char * 427 expand_authorized_keys(const char *filename, struct passwd *pw) 428 { 429 char *file, ret[PATH_MAX]; 430 int i; 431 432 file = percent_expand(filename, "h", pw->pw_dir, 433 "u", pw->pw_name, (char *)NULL); 434 435 /* 436 * Ensure that filename starts anchored. If not, be backward 437 * compatible and prepend the '%h/' 438 */ 439 if (*file == '/') 440 return (file); 441 442 i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file); 443 if (i < 0 || (size_t)i >= sizeof(ret)) 444 fatal("expand_authorized_keys: path too long"); 445 free(file); 446 return (xstrdup(ret)); 447 } 448 449 char * 450 authorized_principals_file(struct passwd *pw) 451 { 452 if (options.authorized_principals_file == NULL) 453 return NULL; 454 return expand_authorized_keys(options.authorized_principals_file, pw); 455 } 456 457 /* return ok if key exists in sysfile or userfile */ 458 HostStatus 459 check_key_in_hostfiles(struct passwd *pw, struct sshkey *key, const char *host, 460 const char *sysfile, const char *userfile) 461 { 462 char *user_hostfile; 463 struct stat st; 464 HostStatus host_status; 465 struct hostkeys *hostkeys; 466 const struct hostkey_entry *found; 467 468 hostkeys = init_hostkeys(); 469 load_hostkeys(hostkeys, host, sysfile); 470 if (userfile != NULL) { 471 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); 472 if (options.strict_modes && 473 (stat(user_hostfile, &st) == 0) && 474 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || 475 (st.st_mode & 022) != 0)) { 476 logit("Authentication refused for %.100s: " 477 "bad owner or modes for %.200s", 478 pw->pw_name, user_hostfile); 479 auth_debug_add("Ignored %.200s: bad ownership or modes", 480 user_hostfile); 481 } else { 482 temporarily_use_uid(pw); 483 load_hostkeys(hostkeys, host, user_hostfile); 484 restore_uid(); 485 } 486 free(user_hostfile); 487 } 488 host_status = check_key_in_hostkeys(hostkeys, key, &found); 489 if (host_status == HOST_REVOKED) 490 error("WARNING: revoked key for %s attempted authentication", 491 found->host); 492 else if (host_status == HOST_OK) 493 debug("%s: key for %s found at %s:%ld", __func__, 494 found->host, found->file, found->line); 495 else 496 debug("%s: key for host %s not found", __func__, host); 497 498 free_hostkeys(hostkeys); 499 500 return host_status; 501 } 502 503 static FILE * 504 auth_openfile(const char *file, struct passwd *pw, int strict_modes, 505 int log_missing, char *file_type) 506 { 507 char line[1024]; 508 struct stat st; 509 int fd; 510 FILE *f; 511 512 if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) { 513 if (log_missing || errno != ENOENT) 514 debug("Could not open %s '%s': %s", file_type, file, 515 strerror(errno)); 516 return NULL; 517 } 518 519 if (fstat(fd, &st) < 0) { 520 close(fd); 521 return NULL; 522 } 523 if (!S_ISREG(st.st_mode)) { 524 logit("User %s %s %s is not a regular file", 525 pw->pw_name, file_type, file); 526 close(fd); 527 return NULL; 528 } 529 unset_nonblock(fd); 530 if ((f = fdopen(fd, "r")) == NULL) { 531 close(fd); 532 return NULL; 533 } 534 if (strict_modes && 535 safe_path_fd(fileno(f), file, pw, line, sizeof(line)) != 0) { 536 fclose(f); 537 logit("Authentication refused: %s", line); 538 auth_debug_add("Ignored %s: %s", file_type, line); 539 return NULL; 540 } 541 542 return f; 543 } 544 545 546 FILE * 547 auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes) 548 { 549 return auth_openfile(file, pw, strict_modes, 1, "authorized keys"); 550 } 551 552 FILE * 553 auth_openprincipals(const char *file, struct passwd *pw, int strict_modes) 554 { 555 return auth_openfile(file, pw, strict_modes, 0, 556 "authorized principals"); 557 } 558 559 struct passwd * 560 getpwnamallow(const char *user) 561 { 562 struct ssh *ssh = active_state; /* XXX */ 563 #ifdef HAVE_LOGIN_CAP 564 extern login_cap_t *lc; 565 #ifdef BSD_AUTH 566 auth_session_t *as; 567 #endif 568 #endif 569 struct passwd *pw; 570 struct connection_info *ci = get_connection_info(1, options.use_dns); 571 572 ci->user = user; 573 parse_server_match_config(&options, ci); 574 log_change_level(options.log_level); 575 process_permitopen(ssh, &options); 576 577 #if defined(_AIX) && defined(HAVE_SETAUTHDB) 578 aix_setauthdb(user); 579 #endif 580 581 pw = getpwnam(user); 582 583 #if defined(_AIX) && defined(HAVE_SETAUTHDB) 584 aix_restoreauthdb(); 585 #endif 586 #ifdef HAVE_CYGWIN 587 /* 588 * Windows usernames are case-insensitive. To avoid later problems 589 * when trying to match the username, the user is only allowed to 590 * login if the username is given in the same case as stored in the 591 * user database. 592 */ 593 if (pw != NULL && strcmp(user, pw->pw_name) != 0) { 594 logit("Login name %.100s does not match stored username %.100s", 595 user, pw->pw_name); 596 pw = NULL; 597 } 598 #endif 599 if (pw == NULL) { 600 BLACKLIST_NOTIFY(BLACKLIST_BAD_USER, user); 601 logit("Invalid user %.100s from %.100s port %d", 602 user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 603 #ifdef CUSTOM_FAILED_LOGIN 604 record_failed_login(user, 605 auth_get_canonical_hostname(ssh, options.use_dns), "ssh"); 606 #endif 607 #ifdef SSH_AUDIT_EVENTS 608 audit_event(SSH_INVALID_USER); 609 #endif /* SSH_AUDIT_EVENTS */ 610 return (NULL); 611 } 612 if (!allowed_user(pw)) 613 return (NULL); 614 #ifdef HAVE_LOGIN_CAP 615 if ((lc = login_getpwclass(pw)) == NULL) { 616 debug("unable to get login class: %s", user); 617 return (NULL); 618 } 619 #ifdef BSD_AUTH 620 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || 621 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { 622 debug("Approval failure for %s", user); 623 pw = NULL; 624 } 625 if (as != NULL) 626 auth_close(as); 627 #endif 628 #endif 629 if (pw != NULL) 630 return (pwcopy(pw)); 631 return (NULL); 632 } 633 634 /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */ 635 int 636 auth_key_is_revoked(struct sshkey *key) 637 { 638 char *fp = NULL; 639 int r; 640 641 if (options.revoked_keys_file == NULL) 642 return 0; 643 if ((fp = sshkey_fingerprint(key, options.fingerprint_hash, 644 SSH_FP_DEFAULT)) == NULL) { 645 r = SSH_ERR_ALLOC_FAIL; 646 error("%s: fingerprint key: %s", __func__, ssh_err(r)); 647 goto out; 648 } 649 650 r = sshkey_check_revoked(key, options.revoked_keys_file); 651 switch (r) { 652 case 0: 653 break; /* not revoked */ 654 case SSH_ERR_KEY_REVOKED: 655 error("Authentication key %s %s revoked by file %s", 656 sshkey_type(key), fp, options.revoked_keys_file); 657 goto out; 658 default: 659 error("Error checking authentication key %s %s in " 660 "revoked keys file %s: %s", sshkey_type(key), fp, 661 options.revoked_keys_file, ssh_err(r)); 662 goto out; 663 } 664 665 /* Success */ 666 r = 0; 667 668 out: 669 free(fp); 670 return r == 0 ? 0 : 1; 671 } 672 673 void 674 auth_debug_add(const char *fmt,...) 675 { 676 char buf[1024]; 677 va_list args; 678 679 if (!auth_debug_init) 680 return; 681 682 va_start(args, fmt); 683 vsnprintf(buf, sizeof(buf), fmt, args); 684 va_end(args); 685 buffer_put_cstring(&auth_debug, buf); 686 } 687 688 void 689 auth_debug_send(void) 690 { 691 char *msg; 692 693 if (!auth_debug_init) 694 return; 695 while (buffer_len(&auth_debug)) { 696 msg = buffer_get_string(&auth_debug, NULL); 697 packet_send_debug("%s", msg); 698 free(msg); 699 } 700 } 701 702 void 703 auth_debug_reset(void) 704 { 705 if (auth_debug_init) 706 buffer_clear(&auth_debug); 707 else { 708 buffer_init(&auth_debug); 709 auth_debug_init = 1; 710 } 711 } 712 713 struct passwd * 714 fakepw(void) 715 { 716 static struct passwd fake; 717 718 memset(&fake, 0, sizeof(fake)); 719 fake.pw_name = "NOUSER"; 720 fake.pw_passwd = 721 "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK"; 722 #ifdef HAVE_STRUCT_PASSWD_PW_GECOS 723 fake.pw_gecos = "NOUSER"; 724 #endif 725 fake.pw_uid = privsep_pw == NULL ? (uid_t)-1 : privsep_pw->pw_uid; 726 fake.pw_gid = privsep_pw == NULL ? (gid_t)-1 : privsep_pw->pw_gid; 727 #ifdef HAVE_STRUCT_PASSWD_PW_CLASS 728 fake.pw_class = ""; 729 #endif 730 fake.pw_dir = "/nonexist"; 731 fake.pw_shell = "/nonexist"; 732 733 return (&fake); 734 } 735 736 /* 737 * Returns the remote DNS hostname as a string. The returned string must not 738 * be freed. NB. this will usually trigger a DNS query the first time it is 739 * called. 740 * This function does additional checks on the hostname to mitigate some 741 * attacks on legacy rhosts-style authentication. 742 * XXX is RhostsRSAAuthentication vulnerable to these? 743 * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?) 744 */ 745 746 static char * 747 remote_hostname(struct ssh *ssh) 748 { 749 struct sockaddr_storage from; 750 socklen_t fromlen; 751 struct addrinfo hints, *ai, *aitop; 752 char name[NI_MAXHOST], ntop2[NI_MAXHOST]; 753 const char *ntop = ssh_remote_ipaddr(ssh); 754 755 /* Get IP address of client. */ 756 fromlen = sizeof(from); 757 memset(&from, 0, sizeof(from)); 758 if (getpeername(ssh_packet_get_connection_in(ssh), 759 (struct sockaddr *)&from, &fromlen) < 0) { 760 debug("getpeername failed: %.100s", strerror(errno)); 761 return strdup(ntop); 762 } 763 764 ipv64_normalise_mapped(&from, &fromlen); 765 if (from.ss_family == AF_INET6) 766 fromlen = sizeof(struct sockaddr_in6); 767 768 debug3("Trying to reverse map address %.100s.", ntop); 769 /* Map the IP address to a host name. */ 770 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), 771 NULL, 0, NI_NAMEREQD) != 0) { 772 /* Host name not found. Use ip address. */ 773 return strdup(ntop); 774 } 775 776 /* 777 * if reverse lookup result looks like a numeric hostname, 778 * someone is trying to trick us by PTR record like following: 779 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5 780 */ 781 memset(&hints, 0, sizeof(hints)); 782 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 783 hints.ai_flags = AI_NUMERICHOST; 784 if (getaddrinfo(name, NULL, &hints, &ai) == 0) { 785 logit("Nasty PTR record \"%s\" is set up for %s, ignoring", 786 name, ntop); 787 freeaddrinfo(ai); 788 return strdup(ntop); 789 } 790 791 /* Names are stored in lowercase. */ 792 lowercase(name); 793 794 /* 795 * Map it back to an IP address and check that the given 796 * address actually is an address of this host. This is 797 * necessary because anyone with access to a name server can 798 * define arbitrary names for an IP address. Mapping from 799 * name to IP address can be trusted better (but can still be 800 * fooled if the intruder has access to the name server of 801 * the domain). 802 */ 803 memset(&hints, 0, sizeof(hints)); 804 hints.ai_family = from.ss_family; 805 hints.ai_socktype = SOCK_STREAM; 806 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { 807 logit("reverse mapping checking getaddrinfo for %.700s " 808 "[%s] failed.", name, ntop); 809 return strdup(ntop); 810 } 811 /* Look for the address from the list of addresses. */ 812 for (ai = aitop; ai; ai = ai->ai_next) { 813 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, 814 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && 815 (strcmp(ntop, ntop2) == 0)) 816 break; 817 } 818 freeaddrinfo(aitop); 819 /* If we reached the end of the list, the address was not there. */ 820 if (ai == NULL) { 821 /* Address not found for the host name. */ 822 logit("Address %.100s maps to %.600s, but this does not " 823 "map back to the address.", ntop, name); 824 return strdup(ntop); 825 } 826 return strdup(name); 827 } 828 829 /* 830 * Return the canonical name of the host in the other side of the current 831 * connection. The host name is cached, so it is efficient to call this 832 * several times. 833 */ 834 835 const char * 836 auth_get_canonical_hostname(struct ssh *ssh, int use_dns) 837 { 838 static char *dnsname; 839 840 if (!use_dns) 841 return ssh_remote_ipaddr(ssh); 842 else if (dnsname != NULL) 843 return dnsname; 844 else { 845 dnsname = remote_hostname(ssh); 846 return dnsname; 847 } 848 } 849