1 /* $OpenBSD: auth.c,v 1.154 2022/02/23 11:17:10 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 #include <sys/wait.h> 33 34 #include <netinet/in.h> 35 36 #include <stdlib.h> 37 #include <errno.h> 38 #include <fcntl.h> 39 #ifdef HAVE_PATHS_H 40 # include <paths.h> 41 #endif 42 #include <pwd.h> 43 #ifdef HAVE_LOGIN_H 44 #include <login.h> 45 #endif 46 #ifdef USE_SHADOW 47 #include <shadow.h> 48 #endif 49 #include <stdarg.h> 50 #include <stdio.h> 51 #include <string.h> 52 #include <unistd.h> 53 #include <limits.h> 54 #include <netdb.h> 55 #include <time.h> 56 57 #include "xmalloc.h" 58 #include "match.h" 59 #include "groupaccess.h" 60 #include "log.h" 61 #include "sshbuf.h" 62 #include "misc.h" 63 #include "servconf.h" 64 #include "sshkey.h" 65 #include "hostfile.h" 66 #include "auth.h" 67 #include "auth-options.h" 68 #include "canohost.h" 69 #include "uidswap.h" 70 #include "packet.h" 71 #include "loginrec.h" 72 #ifdef GSSAPI 73 #include "ssh-gss.h" 74 #endif 75 #include "authfile.h" 76 #include "monitor_wrap.h" 77 #include "ssherr.h" 78 #include "compat.h" 79 #include "channels.h" 80 #include "blacklist_client.h" 81 82 /* import */ 83 extern ServerOptions options; 84 extern struct include_list includes; 85 extern int use_privsep; 86 extern struct sshbuf *loginmsg; 87 extern struct passwd *privsep_pw; 88 extern struct sshauthopt *auth_opts; 89 90 /* Debugging messages */ 91 static struct sshbuf *auth_debug; 92 93 /* 94 * Check if the user is allowed to log in via ssh. If user is listed 95 * in DenyUsers or one of user's groups is listed in DenyGroups, false 96 * will be returned. If AllowUsers isn't empty and user isn't listed 97 * there, or if AllowGroups isn't empty and one of user's groups isn't 98 * listed there, false will be returned. 99 * If the user's shell is not executable, false will be returned. 100 * Otherwise true is returned. 101 */ 102 int 103 allowed_user(struct ssh *ssh, struct passwd * pw) 104 { 105 struct stat st; 106 const char *hostname = NULL, *ipaddr = NULL, *passwd = NULL; 107 u_int i; 108 int r; 109 #ifdef USE_SHADOW 110 struct spwd *spw = NULL; 111 #endif 112 113 /* Shouldn't be called if pw is NULL, but better safe than sorry... */ 114 if (!pw || !pw->pw_name) 115 return 0; 116 117 #ifdef USE_SHADOW 118 if (!options.use_pam) 119 spw = getspnam(pw->pw_name); 120 #ifdef HAS_SHADOW_EXPIRE 121 if (!options.use_pam && spw != NULL && auth_shadow_acctexpired(spw)) 122 return 0; 123 #endif /* HAS_SHADOW_EXPIRE */ 124 #endif /* USE_SHADOW */ 125 126 /* grab passwd field for locked account check */ 127 passwd = pw->pw_passwd; 128 #ifdef USE_SHADOW 129 if (spw != NULL) 130 #ifdef USE_LIBIAF 131 passwd = get_iaf_password(pw); 132 #else 133 passwd = spw->sp_pwdp; 134 #endif /* USE_LIBIAF */ 135 #endif 136 137 /* check for locked account */ 138 if (!options.use_pam && passwd && *passwd) { 139 int locked = 0; 140 141 #ifdef LOCKED_PASSWD_STRING 142 if (strcmp(passwd, LOCKED_PASSWD_STRING) == 0) 143 locked = 1; 144 #endif 145 #ifdef LOCKED_PASSWD_PREFIX 146 if (strncmp(passwd, LOCKED_PASSWD_PREFIX, 147 strlen(LOCKED_PASSWD_PREFIX)) == 0) 148 locked = 1; 149 #endif 150 #ifdef LOCKED_PASSWD_SUBSTR 151 if (strstr(passwd, LOCKED_PASSWD_SUBSTR)) 152 locked = 1; 153 #endif 154 #ifdef USE_LIBIAF 155 free((void *) passwd); 156 #endif /* USE_LIBIAF */ 157 if (locked) { 158 logit("User %.100s not allowed because account is locked", 159 pw->pw_name); 160 return 0; 161 } 162 } 163 164 /* 165 * Deny if shell does not exist or is not executable unless we 166 * are chrooting. 167 */ 168 if (options.chroot_directory == NULL || 169 strcasecmp(options.chroot_directory, "none") == 0) { 170 char *shell = xstrdup((pw->pw_shell[0] == '\0') ? 171 _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */ 172 173 if (stat(shell, &st) == -1) { 174 logit("User %.100s not allowed because shell %.100s " 175 "does not exist", pw->pw_name, shell); 176 free(shell); 177 return 0; 178 } 179 if (S_ISREG(st.st_mode) == 0 || 180 (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { 181 logit("User %.100s not allowed because shell %.100s " 182 "is not executable", pw->pw_name, shell); 183 free(shell); 184 return 0; 185 } 186 free(shell); 187 } 188 189 if (options.num_deny_users > 0 || options.num_allow_users > 0 || 190 options.num_deny_groups > 0 || options.num_allow_groups > 0) { 191 hostname = auth_get_canonical_hostname(ssh, options.use_dns); 192 ipaddr = ssh_remote_ipaddr(ssh); 193 } 194 195 /* Return false if user is listed in DenyUsers */ 196 if (options.num_deny_users > 0) { 197 for (i = 0; i < options.num_deny_users; i++) { 198 r = match_user(pw->pw_name, hostname, ipaddr, 199 options.deny_users[i]); 200 if (r < 0) { 201 fatal("Invalid DenyUsers pattern \"%.100s\"", 202 options.deny_users[i]); 203 } else if (r != 0) { 204 logit("User %.100s from %.100s not allowed " 205 "because listed in DenyUsers", 206 pw->pw_name, hostname); 207 return 0; 208 } 209 } 210 } 211 /* Return false if AllowUsers isn't empty and user isn't listed there */ 212 if (options.num_allow_users > 0) { 213 for (i = 0; i < options.num_allow_users; i++) { 214 r = match_user(pw->pw_name, hostname, ipaddr, 215 options.allow_users[i]); 216 if (r < 0) { 217 fatal("Invalid AllowUsers pattern \"%.100s\"", 218 options.allow_users[i]); 219 } else if (r == 1) 220 break; 221 } 222 /* i < options.num_allow_users iff we break for loop */ 223 if (i >= options.num_allow_users) { 224 logit("User %.100s from %.100s not allowed because " 225 "not listed in AllowUsers", pw->pw_name, hostname); 226 return 0; 227 } 228 } 229 if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { 230 /* Get the user's group access list (primary and supplementary) */ 231 if (ga_init(pw->pw_name, pw->pw_gid) == 0) { 232 logit("User %.100s from %.100s not allowed because " 233 "not in any group", pw->pw_name, hostname); 234 return 0; 235 } 236 237 /* Return false if one of user's groups is listed in DenyGroups */ 238 if (options.num_deny_groups > 0) 239 if (ga_match(options.deny_groups, 240 options.num_deny_groups)) { 241 ga_free(); 242 logit("User %.100s from %.100s not allowed " 243 "because a group is listed in DenyGroups", 244 pw->pw_name, hostname); 245 return 0; 246 } 247 /* 248 * Return false if AllowGroups isn't empty and one of user's groups 249 * isn't listed there 250 */ 251 if (options.num_allow_groups > 0) 252 if (!ga_match(options.allow_groups, 253 options.num_allow_groups)) { 254 ga_free(); 255 logit("User %.100s from %.100s not allowed " 256 "because none of user's groups are listed " 257 "in AllowGroups", pw->pw_name, hostname); 258 return 0; 259 } 260 ga_free(); 261 } 262 263 #ifdef CUSTOM_SYS_AUTH_ALLOWED_USER 264 if (!sys_auth_allowed_user(pw, loginmsg)) 265 return 0; 266 #endif 267 268 /* We found no reason not to let this user try to log on... */ 269 return 1; 270 } 271 272 /* 273 * Formats any key left in authctxt->auth_method_key for inclusion in 274 * auth_log()'s message. Also includes authxtct->auth_method_info if present. 275 */ 276 static char * 277 format_method_key(Authctxt *authctxt) 278 { 279 const struct sshkey *key = authctxt->auth_method_key; 280 const char *methinfo = authctxt->auth_method_info; 281 char *fp, *cafp, *ret = NULL; 282 283 if (key == NULL) 284 return NULL; 285 286 if (sshkey_is_cert(key)) { 287 fp = sshkey_fingerprint(key, 288 options.fingerprint_hash, SSH_FP_DEFAULT); 289 cafp = sshkey_fingerprint(key->cert->signature_key, 290 options.fingerprint_hash, SSH_FP_DEFAULT); 291 xasprintf(&ret, "%s %s ID %s (serial %llu) CA %s %s%s%s", 292 sshkey_type(key), fp == NULL ? "(null)" : fp, 293 key->cert->key_id, 294 (unsigned long long)key->cert->serial, 295 sshkey_type(key->cert->signature_key), 296 cafp == NULL ? "(null)" : cafp, 297 methinfo == NULL ? "" : ", ", 298 methinfo == NULL ? "" : methinfo); 299 free(fp); 300 free(cafp); 301 } else { 302 fp = sshkey_fingerprint(key, options.fingerprint_hash, 303 SSH_FP_DEFAULT); 304 xasprintf(&ret, "%s %s%s%s", sshkey_type(key), 305 fp == NULL ? "(null)" : fp, 306 methinfo == NULL ? "" : ", ", 307 methinfo == NULL ? "" : methinfo); 308 free(fp); 309 } 310 return ret; 311 } 312 313 void 314 auth_log(struct ssh *ssh, int authenticated, int partial, 315 const char *method, const char *submethod) 316 { 317 Authctxt *authctxt = (Authctxt *)ssh->authctxt; 318 int level = SYSLOG_LEVEL_VERBOSE; 319 const char *authmsg; 320 char *extra = NULL; 321 322 if (use_privsep && !mm_is_monitor() && !authctxt->postponed) 323 return; 324 325 /* Raise logging level */ 326 if (authenticated == 1 || 327 !authctxt->valid || 328 authctxt->failures >= options.max_authtries / 2 || 329 strcmp(method, "password") == 0) 330 level = SYSLOG_LEVEL_INFO; 331 332 if (authctxt->postponed) 333 authmsg = "Postponed"; 334 else if (partial) 335 authmsg = "Partial"; 336 else { 337 authmsg = authenticated ? "Accepted" : "Failed"; 338 if (authenticated) 339 BLACKLIST_NOTIFY(ssh, BLACKLIST_AUTH_OK, "ssh"); 340 } 341 342 if ((extra = format_method_key(authctxt)) == NULL) { 343 if (authctxt->auth_method_info != NULL) 344 extra = xstrdup(authctxt->auth_method_info); 345 } 346 347 do_log2(level, "%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s", 348 authmsg, 349 method, 350 submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod, 351 authctxt->valid ? "" : "invalid user ", 352 authctxt->user, 353 ssh_remote_ipaddr(ssh), 354 ssh_remote_port(ssh), 355 extra != NULL ? ": " : "", 356 extra != NULL ? extra : ""); 357 358 free(extra); 359 360 #if defined(CUSTOM_FAILED_LOGIN) || defined(SSH_AUDIT_EVENTS) 361 if (authenticated == 0 && !(authctxt->postponed || partial)) { 362 /* Log failed login attempt */ 363 # ifdef CUSTOM_FAILED_LOGIN 364 if (strcmp(method, "password") == 0 || 365 strncmp(method, "keyboard-interactive", 20) == 0 || 366 strcmp(method, "challenge-response") == 0) 367 record_failed_login(ssh, authctxt->user, 368 auth_get_canonical_hostname(ssh, options.use_dns), "ssh"); 369 # endif 370 # ifdef SSH_AUDIT_EVENTS 371 audit_event(ssh, audit_classify_auth(method)); 372 # endif 373 } 374 #endif 375 #if defined(CUSTOM_FAILED_LOGIN) && defined(WITH_AIXAUTHENTICATE) 376 if (authenticated) 377 sys_auth_record_login(authctxt->user, 378 auth_get_canonical_hostname(ssh, options.use_dns), "ssh", 379 loginmsg); 380 #endif 381 } 382 383 void 384 auth_maxtries_exceeded(struct ssh *ssh) 385 { 386 Authctxt *authctxt = (Authctxt *)ssh->authctxt; 387 388 error("maximum authentication attempts exceeded for " 389 "%s%.100s from %.200s port %d ssh2", 390 authctxt->valid ? "" : "invalid user ", 391 authctxt->user, 392 ssh_remote_ipaddr(ssh), 393 ssh_remote_port(ssh)); 394 ssh_packet_disconnect(ssh, "Too many authentication failures"); 395 /* NOTREACHED */ 396 } 397 398 /* 399 * Check whether root logins are disallowed. 400 */ 401 int 402 auth_root_allowed(struct ssh *ssh, const char *method) 403 { 404 switch (options.permit_root_login) { 405 case PERMIT_YES: 406 return 1; 407 case PERMIT_NO_PASSWD: 408 if (strcmp(method, "publickey") == 0 || 409 strcmp(method, "hostbased") == 0 || 410 strcmp(method, "gssapi-with-mic") == 0) 411 return 1; 412 break; 413 case PERMIT_FORCED_ONLY: 414 if (auth_opts->force_command != NULL) { 415 logit("Root login accepted for forced command."); 416 return 1; 417 } 418 break; 419 } 420 logit("ROOT LOGIN REFUSED FROM %.200s port %d", 421 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 422 return 0; 423 } 424 425 426 /* 427 * Given a template and a passwd structure, build a filename 428 * by substituting % tokenised options. Currently, %% becomes '%', 429 * %h becomes the home directory and %u the username. 430 * 431 * This returns a buffer allocated by xmalloc. 432 */ 433 char * 434 expand_authorized_keys(const char *filename, struct passwd *pw) 435 { 436 char *file, uidstr[32], ret[PATH_MAX]; 437 int i; 438 439 snprintf(uidstr, sizeof(uidstr), "%llu", 440 (unsigned long long)pw->pw_uid); 441 file = percent_expand(filename, "h", pw->pw_dir, 442 "u", pw->pw_name, "U", uidstr, (char *)NULL); 443 444 /* 445 * Ensure that filename starts anchored. If not, be backward 446 * compatible and prepend the '%h/' 447 */ 448 if (path_absolute(file)) 449 return (file); 450 451 i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file); 452 if (i < 0 || (size_t)i >= sizeof(ret)) 453 fatal("expand_authorized_keys: path too long"); 454 free(file); 455 return (xstrdup(ret)); 456 } 457 458 char * 459 authorized_principals_file(struct passwd *pw) 460 { 461 if (options.authorized_principals_file == NULL) 462 return NULL; 463 return expand_authorized_keys(options.authorized_principals_file, pw); 464 } 465 466 /* return ok if key exists in sysfile or userfile */ 467 HostStatus 468 check_key_in_hostfiles(struct passwd *pw, struct sshkey *key, const char *host, 469 const char *sysfile, const char *userfile) 470 { 471 char *user_hostfile; 472 struct stat st; 473 HostStatus host_status; 474 struct hostkeys *hostkeys; 475 const struct hostkey_entry *found; 476 477 hostkeys = init_hostkeys(); 478 load_hostkeys(hostkeys, host, sysfile, 0); 479 if (userfile != NULL) { 480 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); 481 if (options.strict_modes && 482 (stat(user_hostfile, &st) == 0) && 483 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || 484 (st.st_mode & 022) != 0)) { 485 logit("Authentication refused for %.100s: " 486 "bad owner or modes for %.200s", 487 pw->pw_name, user_hostfile); 488 auth_debug_add("Ignored %.200s: bad ownership or modes", 489 user_hostfile); 490 } else { 491 temporarily_use_uid(pw); 492 load_hostkeys(hostkeys, host, user_hostfile, 0); 493 restore_uid(); 494 } 495 free(user_hostfile); 496 } 497 host_status = check_key_in_hostkeys(hostkeys, key, &found); 498 if (host_status == HOST_REVOKED) 499 error("WARNING: revoked key for %s attempted authentication", 500 host); 501 else if (host_status == HOST_OK) 502 debug_f("key for %s found at %s:%ld", 503 found->host, found->file, found->line); 504 else 505 debug_f("key for host %s not found", host); 506 507 free_hostkeys(hostkeys); 508 509 return host_status; 510 } 511 512 static FILE * 513 auth_openfile(const char *file, struct passwd *pw, int strict_modes, 514 int log_missing, char *file_type) 515 { 516 char line[1024]; 517 struct stat st; 518 int fd; 519 FILE *f; 520 521 if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) { 522 if (log_missing || errno != ENOENT) 523 debug("Could not open %s '%s': %s", file_type, file, 524 strerror(errno)); 525 return NULL; 526 } 527 528 if (fstat(fd, &st) == -1) { 529 close(fd); 530 return NULL; 531 } 532 if (!S_ISREG(st.st_mode)) { 533 logit("User %s %s %s is not a regular file", 534 pw->pw_name, file_type, file); 535 close(fd); 536 return NULL; 537 } 538 unset_nonblock(fd); 539 if ((f = fdopen(fd, "r")) == NULL) { 540 close(fd); 541 return NULL; 542 } 543 if (strict_modes && 544 safe_path_fd(fileno(f), file, pw, line, sizeof(line)) != 0) { 545 fclose(f); 546 logit("Authentication refused: %s", line); 547 auth_debug_add("Ignored %s: %s", file_type, line); 548 return NULL; 549 } 550 551 return f; 552 } 553 554 555 FILE * 556 auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes) 557 { 558 return auth_openfile(file, pw, strict_modes, 1, "authorized keys"); 559 } 560 561 FILE * 562 auth_openprincipals(const char *file, struct passwd *pw, int strict_modes) 563 { 564 return auth_openfile(file, pw, strict_modes, 0, 565 "authorized principals"); 566 } 567 568 struct passwd * 569 getpwnamallow(struct ssh *ssh, const char *user) 570 { 571 #ifdef HAVE_LOGIN_CAP 572 extern login_cap_t *lc; 573 #ifdef HAVE_AUTH_HOSTOK 574 const char *from_host, *from_ip; 575 #endif 576 #ifdef BSD_AUTH 577 auth_session_t *as; 578 #endif 579 #endif 580 struct passwd *pw; 581 struct connection_info *ci; 582 u_int i; 583 584 ci = get_connection_info(ssh, 1, options.use_dns); 585 ci->user = user; 586 parse_server_match_config(&options, &includes, ci); 587 log_change_level(options.log_level); 588 log_verbose_reset(); 589 for (i = 0; i < options.num_log_verbose; i++) 590 log_verbose_add(options.log_verbose[i]); 591 process_permitopen(ssh, &options); 592 593 #if defined(_AIX) && defined(HAVE_SETAUTHDB) 594 aix_setauthdb(user); 595 #endif 596 597 pw = getpwnam(user); 598 599 #if defined(_AIX) && defined(HAVE_SETAUTHDB) 600 aix_restoreauthdb(); 601 #endif 602 if (pw == NULL) { 603 BLACKLIST_NOTIFY(ssh, BLACKLIST_BAD_USER, user); 604 logit("Invalid user %.100s from %.100s port %d", 605 user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 606 #ifdef CUSTOM_FAILED_LOGIN 607 record_failed_login(ssh, user, 608 auth_get_canonical_hostname(ssh, options.use_dns), "ssh"); 609 #endif 610 #ifdef SSH_AUDIT_EVENTS 611 audit_event(ssh, SSH_INVALID_USER); 612 #endif /* SSH_AUDIT_EVENTS */ 613 return (NULL); 614 } 615 if (!allowed_user(ssh, pw)) 616 return (NULL); 617 #ifdef HAVE_LOGIN_CAP 618 if ((lc = login_getpwclass(pw)) == NULL) { 619 debug("unable to get login class: %s", user); 620 return (NULL); 621 } 622 #ifdef HAVE_AUTH_HOSTOK 623 from_host = auth_get_canonical_hostname(ssh, options.use_dns); 624 from_ip = ssh_remote_ipaddr(ssh); 625 if (!auth_hostok(lc, from_host, from_ip)) { 626 debug("Denied connection for %.200s from %.200s [%.200s].", 627 pw->pw_name, from_host, from_ip); 628 return (NULL); 629 } 630 #endif /* HAVE_AUTH_HOSTOK */ 631 #ifdef HAVE_AUTH_TIMEOK 632 if (!auth_timeok(lc, time(NULL))) { 633 debug("LOGIN %.200s REFUSED (TIME)", pw->pw_name); 634 return (NULL); 635 } 636 #endif /* HAVE_AUTH_TIMEOK */ 637 #ifdef BSD_AUTH 638 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || 639 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { 640 debug("Approval failure for %s", user); 641 pw = NULL; 642 } 643 if (as != NULL) 644 auth_close(as); 645 #endif 646 #endif 647 if (pw != NULL) 648 return (pwcopy(pw)); 649 return (NULL); 650 } 651 652 /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */ 653 int 654 auth_key_is_revoked(struct sshkey *key) 655 { 656 char *fp = NULL; 657 int r; 658 659 if (options.revoked_keys_file == NULL) 660 return 0; 661 if ((fp = sshkey_fingerprint(key, options.fingerprint_hash, 662 SSH_FP_DEFAULT)) == NULL) { 663 r = SSH_ERR_ALLOC_FAIL; 664 error_fr(r, "fingerprint key"); 665 goto out; 666 } 667 668 r = sshkey_check_revoked(key, options.revoked_keys_file); 669 switch (r) { 670 case 0: 671 break; /* not revoked */ 672 case SSH_ERR_KEY_REVOKED: 673 error("Authentication key %s %s revoked by file %s", 674 sshkey_type(key), fp, options.revoked_keys_file); 675 goto out; 676 default: 677 error_r(r, "Error checking authentication key %s %s in " 678 "revoked keys file %s", sshkey_type(key), fp, 679 options.revoked_keys_file); 680 goto out; 681 } 682 683 /* Success */ 684 r = 0; 685 686 out: 687 free(fp); 688 return r == 0 ? 0 : 1; 689 } 690 691 void 692 auth_debug_add(const char *fmt,...) 693 { 694 char buf[1024]; 695 va_list args; 696 int r; 697 698 if (auth_debug == NULL) 699 return; 700 701 va_start(args, fmt); 702 vsnprintf(buf, sizeof(buf), fmt, args); 703 va_end(args); 704 if ((r = sshbuf_put_cstring(auth_debug, buf)) != 0) 705 fatal_fr(r, "sshbuf_put_cstring"); 706 } 707 708 void 709 auth_debug_send(struct ssh *ssh) 710 { 711 char *msg; 712 int r; 713 714 if (auth_debug == NULL) 715 return; 716 while (sshbuf_len(auth_debug) != 0) { 717 if ((r = sshbuf_get_cstring(auth_debug, &msg, NULL)) != 0) 718 fatal_fr(r, "sshbuf_get_cstring"); 719 ssh_packet_send_debug(ssh, "%s", msg); 720 free(msg); 721 } 722 } 723 724 void 725 auth_debug_reset(void) 726 { 727 if (auth_debug != NULL) 728 sshbuf_reset(auth_debug); 729 else if ((auth_debug = sshbuf_new()) == NULL) 730 fatal_f("sshbuf_new failed"); 731 } 732 733 struct passwd * 734 fakepw(void) 735 { 736 static int done = 0; 737 static struct passwd fake; 738 const char hashchars[] = "./ABCDEFGHIJKLMNOPQRSTUVWXYZ" 739 "abcdefghijklmnopqrstuvwxyz0123456789"; /* from bcrypt.c */ 740 char *cp; 741 742 if (done) 743 return (&fake); 744 745 memset(&fake, 0, sizeof(fake)); 746 fake.pw_name = "NOUSER"; 747 fake.pw_passwd = xstrdup("$2a$10$" 748 "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"); 749 for (cp = fake.pw_passwd + 7; *cp != '\0'; cp++) 750 *cp = hashchars[arc4random_uniform(sizeof(hashchars) - 1)]; 751 #ifdef HAVE_STRUCT_PASSWD_PW_GECOS 752 fake.pw_gecos = "NOUSER"; 753 #endif 754 fake.pw_uid = privsep_pw == NULL ? (uid_t)-1 : privsep_pw->pw_uid; 755 fake.pw_gid = privsep_pw == NULL ? (gid_t)-1 : privsep_pw->pw_gid; 756 #ifdef HAVE_STRUCT_PASSWD_PW_CLASS 757 fake.pw_class = ""; 758 #endif 759 fake.pw_dir = "/nonexist"; 760 fake.pw_shell = "/nonexist"; 761 done = 1; 762 763 return (&fake); 764 } 765 766 /* 767 * Returns the remote DNS hostname as a string. The returned string must not 768 * be freed. NB. this will usually trigger a DNS query the first time it is 769 * called. 770 * This function does additional checks on the hostname to mitigate some 771 * attacks on based on conflation of hostnames and IP addresses. 772 */ 773 774 static char * 775 remote_hostname(struct ssh *ssh) 776 { 777 struct sockaddr_storage from; 778 socklen_t fromlen; 779 struct addrinfo hints, *ai, *aitop; 780 char name[NI_MAXHOST], ntop2[NI_MAXHOST]; 781 const char *ntop = ssh_remote_ipaddr(ssh); 782 783 /* Get IP address of client. */ 784 fromlen = sizeof(from); 785 memset(&from, 0, sizeof(from)); 786 if (getpeername(ssh_packet_get_connection_in(ssh), 787 (struct sockaddr *)&from, &fromlen) == -1) { 788 debug("getpeername failed: %.100s", strerror(errno)); 789 return xstrdup(ntop); 790 } 791 792 ipv64_normalise_mapped(&from, &fromlen); 793 if (from.ss_family == AF_INET6) 794 fromlen = sizeof(struct sockaddr_in6); 795 796 debug3("Trying to reverse map address %.100s.", ntop); 797 /* Map the IP address to a host name. */ 798 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), 799 NULL, 0, NI_NAMEREQD) != 0) { 800 /* Host name not found. Use ip address. */ 801 return xstrdup(ntop); 802 } 803 804 /* 805 * if reverse lookup result looks like a numeric hostname, 806 * someone is trying to trick us by PTR record like following: 807 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5 808 */ 809 memset(&hints, 0, sizeof(hints)); 810 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 811 hints.ai_flags = AI_NUMERICHOST; 812 if (getaddrinfo(name, NULL, &hints, &ai) == 0) { 813 logit("Nasty PTR record \"%s\" is set up for %s, ignoring", 814 name, ntop); 815 freeaddrinfo(ai); 816 return xstrdup(ntop); 817 } 818 819 /* Names are stored in lowercase. */ 820 lowercase(name); 821 822 /* 823 * Map it back to an IP address and check that the given 824 * address actually is an address of this host. This is 825 * necessary because anyone with access to a name server can 826 * define arbitrary names for an IP address. Mapping from 827 * name to IP address can be trusted better (but can still be 828 * fooled if the intruder has access to the name server of 829 * the domain). 830 */ 831 memset(&hints, 0, sizeof(hints)); 832 hints.ai_family = from.ss_family; 833 hints.ai_socktype = SOCK_STREAM; 834 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { 835 logit("reverse mapping checking getaddrinfo for %.700s " 836 "[%s] failed.", name, ntop); 837 return xstrdup(ntop); 838 } 839 /* Look for the address from the list of addresses. */ 840 for (ai = aitop; ai; ai = ai->ai_next) { 841 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, 842 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && 843 (strcmp(ntop, ntop2) == 0)) 844 break; 845 } 846 freeaddrinfo(aitop); 847 /* If we reached the end of the list, the address was not there. */ 848 if (ai == NULL) { 849 /* Address not found for the host name. */ 850 logit("Address %.100s maps to %.600s, but this does not " 851 "map back to the address.", ntop, name); 852 return xstrdup(ntop); 853 } 854 return xstrdup(name); 855 } 856 857 /* 858 * Return the canonical name of the host in the other side of the current 859 * connection. The host name is cached, so it is efficient to call this 860 * several times. 861 */ 862 863 const char * 864 auth_get_canonical_hostname(struct ssh *ssh, int use_dns) 865 { 866 static char *dnsname; 867 868 if (!use_dns) 869 return ssh_remote_ipaddr(ssh); 870 else if (dnsname != NULL) 871 return dnsname; 872 else { 873 dnsname = remote_hostname(ssh); 874 return dnsname; 875 } 876 } 877 878 /* These functions link key/cert options to the auth framework */ 879 880 /* Log sshauthopt options locally and (optionally) for remote transmission */ 881 void 882 auth_log_authopts(const char *loc, const struct sshauthopt *opts, int do_remote) 883 { 884 int do_env = options.permit_user_env && opts->nenv > 0; 885 int do_permitopen = opts->npermitopen > 0 && 886 (options.allow_tcp_forwarding & FORWARD_LOCAL) != 0; 887 int do_permitlisten = opts->npermitlisten > 0 && 888 (options.allow_tcp_forwarding & FORWARD_REMOTE) != 0; 889 size_t i; 890 char msg[1024], buf[64]; 891 892 snprintf(buf, sizeof(buf), "%d", opts->force_tun_device); 893 /* Try to keep this alphabetically sorted */ 894 snprintf(msg, sizeof(msg), "key options:%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s", 895 opts->permit_agent_forwarding_flag ? " agent-forwarding" : "", 896 opts->force_command == NULL ? "" : " command", 897 do_env ? " environment" : "", 898 opts->valid_before == 0 ? "" : "expires", 899 opts->no_require_user_presence ? " no-touch-required" : "", 900 do_permitopen ? " permitopen" : "", 901 do_permitlisten ? " permitlisten" : "", 902 opts->permit_port_forwarding_flag ? " port-forwarding" : "", 903 opts->cert_principals == NULL ? "" : " principals", 904 opts->permit_pty_flag ? " pty" : "", 905 opts->require_verify ? " uv" : "", 906 opts->force_tun_device == -1 ? "" : " tun=", 907 opts->force_tun_device == -1 ? "" : buf, 908 opts->permit_user_rc ? " user-rc" : "", 909 opts->permit_x11_forwarding_flag ? " x11-forwarding" : ""); 910 911 debug("%s: %s", loc, msg); 912 if (do_remote) 913 auth_debug_add("%s: %s", loc, msg); 914 915 if (options.permit_user_env) { 916 for (i = 0; i < opts->nenv; i++) { 917 debug("%s: environment: %s", loc, opts->env[i]); 918 if (do_remote) { 919 auth_debug_add("%s: environment: %s", 920 loc, opts->env[i]); 921 } 922 } 923 } 924 925 /* Go into a little more details for the local logs. */ 926 if (opts->valid_before != 0) { 927 format_absolute_time(opts->valid_before, buf, sizeof(buf)); 928 debug("%s: expires at %s", loc, buf); 929 } 930 if (opts->cert_principals != NULL) { 931 debug("%s: authorized principals: \"%s\"", 932 loc, opts->cert_principals); 933 } 934 if (opts->force_command != NULL) 935 debug("%s: forced command: \"%s\"", loc, opts->force_command); 936 if (do_permitopen) { 937 for (i = 0; i < opts->npermitopen; i++) { 938 debug("%s: permitted open: %s", 939 loc, opts->permitopen[i]); 940 } 941 } 942 if (do_permitlisten) { 943 for (i = 0; i < opts->npermitlisten; i++) { 944 debug("%s: permitted listen: %s", 945 loc, opts->permitlisten[i]); 946 } 947 } 948 } 949 950 /* Activate a new set of key/cert options; merging with what is there. */ 951 int 952 auth_activate_options(struct ssh *ssh, struct sshauthopt *opts) 953 { 954 struct sshauthopt *old = auth_opts; 955 const char *emsg = NULL; 956 957 debug_f("setting new authentication options"); 958 if ((auth_opts = sshauthopt_merge(old, opts, &emsg)) == NULL) { 959 error("Inconsistent authentication options: %s", emsg); 960 return -1; 961 } 962 return 0; 963 } 964 965 /* Disable forwarding, etc for the session */ 966 void 967 auth_restrict_session(struct ssh *ssh) 968 { 969 struct sshauthopt *restricted; 970 971 debug_f("restricting session"); 972 973 /* A blank sshauthopt defaults to permitting nothing */ 974 restricted = sshauthopt_new(); 975 restricted->permit_pty_flag = 1; 976 restricted->restricted = 1; 977 978 if (auth_activate_options(ssh, restricted) != 0) 979 fatal_f("failed to restrict session"); 980 sshauthopt_free(restricted); 981 } 982 983 int 984 auth_authorise_keyopts(struct ssh *ssh, struct passwd *pw, 985 struct sshauthopt *opts, int allow_cert_authority, const char *loc) 986 { 987 const char *remote_ip = ssh_remote_ipaddr(ssh); 988 const char *remote_host = auth_get_canonical_hostname(ssh, 989 options.use_dns); 990 time_t now = time(NULL); 991 char buf[64]; 992 993 /* 994 * Check keys/principals file expiry time. 995 * NB. validity interval in certificate is handled elsewhere. 996 */ 997 if (opts->valid_before && now > 0 && 998 opts->valid_before < (uint64_t)now) { 999 format_absolute_time(opts->valid_before, buf, sizeof(buf)); 1000 debug("%s: entry expired at %s", loc, buf); 1001 auth_debug_add("%s: entry expired at %s", loc, buf); 1002 return -1; 1003 } 1004 /* Consistency checks */ 1005 if (opts->cert_principals != NULL && !opts->cert_authority) { 1006 debug("%s: principals on non-CA key", loc); 1007 auth_debug_add("%s: principals on non-CA key", loc); 1008 /* deny access */ 1009 return -1; 1010 } 1011 /* cert-authority flag isn't valid in authorized_principals files */ 1012 if (!allow_cert_authority && opts->cert_authority) { 1013 debug("%s: cert-authority flag invalid here", loc); 1014 auth_debug_add("%s: cert-authority flag invalid here", loc); 1015 /* deny access */ 1016 return -1; 1017 } 1018 1019 /* Perform from= checks */ 1020 if (opts->required_from_host_keys != NULL) { 1021 switch (match_host_and_ip(remote_host, remote_ip, 1022 opts->required_from_host_keys )) { 1023 case 1: 1024 /* Host name matches. */ 1025 break; 1026 case -1: 1027 default: 1028 debug("%s: invalid from criteria", loc); 1029 auth_debug_add("%s: invalid from criteria", loc); 1030 /* FALLTHROUGH */ 1031 case 0: 1032 logit("%s: Authentication tried for %.100s with " 1033 "correct key but not from a permitted " 1034 "host (host=%.200s, ip=%.200s, required=%.200s).", 1035 loc, pw->pw_name, remote_host, remote_ip, 1036 opts->required_from_host_keys); 1037 auth_debug_add("%s: Your host '%.200s' is not " 1038 "permitted to use this key for login.", 1039 loc, remote_host); 1040 /* deny access */ 1041 return -1; 1042 } 1043 } 1044 /* Check source-address restriction from certificate */ 1045 if (opts->required_from_host_cert != NULL) { 1046 switch (addr_match_cidr_list(remote_ip, 1047 opts->required_from_host_cert)) { 1048 case 1: 1049 /* accepted */ 1050 break; 1051 case -1: 1052 default: 1053 /* invalid */ 1054 error("%s: Certificate source-address invalid", loc); 1055 /* FALLTHROUGH */ 1056 case 0: 1057 logit("%s: Authentication tried for %.100s with valid " 1058 "certificate but not from a permitted source " 1059 "address (%.200s).", loc, pw->pw_name, remote_ip); 1060 auth_debug_add("%s: Your address '%.200s' is not " 1061 "permitted to use this certificate for login.", 1062 loc, remote_ip); 1063 return -1; 1064 } 1065 } 1066 /* 1067 * 1068 * XXX this is spammy. We should report remotely only for keys 1069 * that are successful in actual auth attempts, and not PK_OK 1070 * tests. 1071 */ 1072 auth_log_authopts(loc, opts, 1); 1073 1074 return 0; 1075 } 1076