1 /* $NetBSD: auth.c,v 1.21 2018/04/06 18:58:59 christos Exp $ */ 2 /* $OpenBSD: auth.c,v 1.127 2018/03/12 00:52:01 djm Exp $ */ 3 /* 4 * Copyright (c) 2000 Markus Friedl. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 #include "includes.h" 28 __RCSID("$NetBSD: auth.c,v 1.21 2018/04/06 18:58:59 christos Exp $"); 29 #include <sys/types.h> 30 #include <sys/stat.h> 31 #include <sys/socket.h> 32 #include <sys/wait.h> 33 34 #include <errno.h> 35 #include <fcntl.h> 36 #include <login_cap.h> 37 #include <paths.h> 38 #include <pwd.h> 39 #include <stdarg.h> 40 #include <stdio.h> 41 #include <string.h> 42 #include <unistd.h> 43 #include <limits.h> 44 #include <netdb.h> 45 46 #include "xmalloc.h" 47 #include "match.h" 48 #include "groupaccess.h" 49 #include "log.h" 50 #include "buffer.h" 51 #include "misc.h" 52 #include "servconf.h" 53 #include "key.h" 54 #include "hostfile.h" 55 #include "auth.h" 56 #include "auth-options.h" 57 #include "canohost.h" 58 #include "uidswap.h" 59 #include "packet.h" 60 #ifdef GSSAPI 61 #include "ssh-gss.h" 62 #endif 63 #include "authfile.h" 64 #include "monitor_wrap.h" 65 #include "authfile.h" 66 #include "ssherr.h" 67 #include "compat.h" 68 #include "channels.h" 69 #include "pfilter.h" 70 71 #ifdef HAVE_LOGIN_CAP 72 #include <login_cap.h> 73 #endif 74 75 /* import */ 76 extern ServerOptions options; 77 extern int use_privsep; 78 extern struct sshauthopt *auth_opts; 79 80 /* Debugging messages */ 81 Buffer auth_debug; 82 int auth_debug_init; 83 84 #ifndef HOST_ONLY 85 /* 86 * Check if the user is allowed to log in via ssh. If user is listed 87 * in DenyUsers or one of user's groups is listed in DenyGroups, false 88 * will be returned. If AllowUsers isn't empty and user isn't listed 89 * there, or if AllowGroups isn't empty and one of user's groups isn't 90 * listed there, false will be returned. 91 * If the user's shell is not executable, false will be returned. 92 * Otherwise true is returned. 93 */ 94 int 95 allowed_user(struct passwd * pw) 96 { 97 #ifdef HAVE_LOGIN_CAP 98 extern login_cap_t *lc; 99 int match_name, match_ip; 100 char *cap_hlist, *hp; 101 #endif 102 struct ssh *ssh = active_state; /* XXX */ 103 struct stat st; 104 const char *hostname = NULL, *ipaddr = NULL; 105 int r; 106 u_int i; 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 HAVE_LOGIN_CAP 113 hostname = auth_get_canonical_hostname(ssh, options.use_dns); 114 ipaddr = ssh_remote_ipaddr(ssh); 115 116 lc = login_getclass(pw->pw_class); 117 118 /* 119 * Check the deny list. 120 */ 121 cap_hlist = login_getcapstr(lc, "host.deny", NULL, NULL); 122 if (cap_hlist != NULL) { 123 hp = strtok(cap_hlist, ","); 124 while (hp != NULL) { 125 match_name = match_hostname(hostname, hp); 126 match_ip = match_hostname(ipaddr, hp); 127 /* 128 * Only a positive match here causes a "deny". 129 */ 130 if (match_name > 0 || match_ip > 0) { 131 free(cap_hlist); 132 login_close(lc); 133 return 0; 134 } 135 hp = strtok(NULL, ","); 136 } 137 free(cap_hlist); 138 } 139 140 /* 141 * Check the allow list. If the allow list exists, and the 142 * remote host is not in it, the user is implicitly denied. 143 */ 144 cap_hlist = login_getcapstr(lc, "host.allow", NULL, NULL); 145 if (cap_hlist != NULL) { 146 hp = strtok(cap_hlist, ","); 147 if (hp == NULL) { 148 /* Just in case there's an empty string... */ 149 free(cap_hlist); 150 login_close(lc); 151 return 0; 152 } 153 while (hp != NULL) { 154 match_name = match_hostname(hostname, hp); 155 match_ip = match_hostname(ipaddr, hp); 156 /* 157 * Negative match causes an immediate "deny". 158 * Positive match causes us to break out 159 * of the loop (allowing a fallthrough). 160 */ 161 if (match_name < 0 || match_ip < 0) { 162 free(cap_hlist); 163 login_close(lc); 164 return 0; 165 } 166 if (match_name > 0 || match_ip > 0) 167 break; 168 hp = strtok(NULL, ","); 169 } 170 free(cap_hlist); 171 if (hp == NULL) { 172 login_close(lc); 173 return 0; 174 } 175 } 176 177 login_close(lc); 178 #endif 179 180 #ifdef USE_PAM 181 if (!options.use_pam) { 182 #endif 183 /* 184 * password/account expiration. 185 */ 186 if (pw->pw_change || pw->pw_expire) { 187 struct timeval tv; 188 189 (void)gettimeofday(&tv, (struct timezone *)NULL); 190 if (pw->pw_expire) { 191 if (tv.tv_sec >= pw->pw_expire) { 192 logit("User %.100s not allowed because account has expired", 193 pw->pw_name); 194 return 0; /* expired */ 195 } 196 } 197 #ifdef _PASSWORD_CHGNOW 198 if (pw->pw_change == _PASSWORD_CHGNOW) { 199 logit("User %.100s not allowed because password needs to be changed", 200 pw->pw_name); 201 202 return 0; /* can't force password change (yet) */ 203 } 204 #endif 205 if (pw->pw_change) { 206 if (tv.tv_sec >= pw->pw_change) { 207 logit("User %.100s not allowed because password has expired", 208 pw->pw_name); 209 return 0; /* expired */ 210 } 211 } 212 } 213 #ifdef USE_PAM 214 } 215 #endif 216 217 /* 218 * Deny if shell does not exist or is not executable unless we 219 * are chrooting. 220 */ 221 /* 222 * XXX Should check to see if it is executable by the 223 * XXX requesting user. --thorpej 224 */ 225 if (options.chroot_directory == NULL || 226 strcasecmp(options.chroot_directory, "none") == 0) { 227 char *shell = xstrdup((pw->pw_shell[0] == '\0') ? 228 _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */ 229 230 if (stat(shell, &st) != 0) { 231 logit("User %.100s not allowed because shell %.100s " 232 "does not exist", pw->pw_name, shell); 233 free(shell); 234 return 0; 235 } 236 if (S_ISREG(st.st_mode) == 0 || 237 (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { 238 logit("User %.100s not allowed because shell %.100s " 239 "is not executable", pw->pw_name, shell); 240 free(shell); 241 return 0; 242 } 243 free(shell); 244 } 245 /* 246 * XXX Consider nuking {Allow,Deny}{Users,Groups}. We have the 247 * XXX login_cap(3) mechanism which covers all other types of 248 * XXX logins, too. 249 */ 250 251 if (options.num_deny_users > 0 || options.num_allow_users > 0 || 252 options.num_deny_groups > 0 || options.num_allow_groups > 0) { 253 hostname = auth_get_canonical_hostname(ssh, options.use_dns); 254 ipaddr = ssh_remote_ipaddr(ssh); 255 } 256 257 /* Return false if user is listed in DenyUsers */ 258 if (options.num_deny_users > 0) { 259 for (i = 0; i < options.num_deny_users; i++) { 260 r = match_user(pw->pw_name, hostname, ipaddr, 261 options.deny_users[i]); 262 if (r < 0) { 263 fatal("Invalid DenyUsers pattern \"%.100s\"", 264 options.deny_users[i]); 265 } else if (r != 0) { 266 logit("User %.100s from %.100s not allowed " 267 "because listed in DenyUsers", 268 pw->pw_name, hostname); 269 return 0; 270 } 271 } 272 } 273 /* Return false if AllowUsers isn't empty and user isn't listed there */ 274 if (options.num_allow_users > 0) { 275 for (i = 0; i < options.num_allow_users; i++) { 276 r = match_user(pw->pw_name, hostname, ipaddr, 277 options.allow_users[i]); 278 if (r < 0) { 279 fatal("Invalid AllowUsers pattern \"%.100s\"", 280 options.allow_users[i]); 281 } else if (r == 1) 282 break; 283 } 284 /* i < options.num_allow_users iff we break for loop */ 285 if (i >= options.num_allow_users) { 286 logit("User %.100s from %.100s not allowed because " 287 "not listed in AllowUsers", pw->pw_name, hostname); 288 return 0; 289 } 290 } 291 if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { 292 /* Get the user's group access list (primary and supplementary) */ 293 if (ga_init(pw->pw_name, pw->pw_gid) == 0) { 294 logit("User %.100s from %.100s not allowed because " 295 "not in any group", pw->pw_name, hostname); 296 return 0; 297 } 298 299 /* Return false if one of user's groups is listed in DenyGroups */ 300 if (options.num_deny_groups > 0) 301 if (ga_match(options.deny_groups, 302 options.num_deny_groups)) { 303 ga_free(); 304 logit("User %.100s from %.100s not allowed " 305 "because a group is listed in DenyGroups", 306 pw->pw_name, hostname); 307 return 0; 308 } 309 /* 310 * Return false if AllowGroups isn't empty and one of user's groups 311 * isn't listed there 312 */ 313 if (options.num_allow_groups > 0) 314 if (!ga_match(options.allow_groups, 315 options.num_allow_groups)) { 316 ga_free(); 317 logit("User %.100s from %.100s not allowed " 318 "because none of user's groups are listed " 319 "in AllowGroups", pw->pw_name, hostname); 320 return 0; 321 } 322 ga_free(); 323 } 324 /* We found no reason not to let this user try to log on... */ 325 return 1; 326 } 327 328 /* 329 * Formats any key left in authctxt->auth_method_key for inclusion in 330 * auth_log()'s message. Also includes authxtct->auth_method_info if present. 331 */ 332 static char * 333 format_method_key(Authctxt *authctxt) 334 { 335 const struct sshkey *key = authctxt->auth_method_key; 336 const char *methinfo = authctxt->auth_method_info; 337 char *fp, *ret = NULL; 338 339 if (key == NULL) 340 return NULL; 341 342 if (key_is_cert(key)) { 343 fp = sshkey_fingerprint(key->cert->signature_key, 344 options.fingerprint_hash, SSH_FP_DEFAULT); 345 xasprintf(&ret, "%s ID %s (serial %llu) CA %s %s%s%s", 346 sshkey_type(key), key->cert->key_id, 347 (unsigned long long)key->cert->serial, 348 sshkey_type(key->cert->signature_key), 349 fp == NULL ? "(null)" : fp, 350 methinfo == NULL ? "" : ", ", 351 methinfo == NULL ? "" : methinfo); 352 free(fp); 353 } else { 354 fp = sshkey_fingerprint(key, options.fingerprint_hash, 355 SSH_FP_DEFAULT); 356 xasprintf(&ret, "%s %s%s%s", sshkey_type(key), 357 fp == NULL ? "(null)" : fp, 358 methinfo == NULL ? "" : ", ", 359 methinfo == NULL ? "" : methinfo); 360 free(fp); 361 } 362 return ret; 363 } 364 365 void 366 auth_log(Authctxt *authctxt, int authenticated, int partial, 367 const char *method, const char *submethod) 368 { 369 struct ssh *ssh = active_state; /* XXX */ 370 void (*authlog) (const char *fmt,...) = verbose; 371 const char *authmsg; 372 char *extra = NULL; 373 374 if (use_privsep && !mm_is_monitor() && !authctxt->postponed) 375 return; 376 377 /* Raise logging level */ 378 if (authenticated == 1 || 379 !authctxt->valid || 380 authctxt->failures >= options.max_authtries / 2 || 381 strcmp(method, "password") == 0) 382 authlog = logit; 383 384 if (authctxt->postponed) 385 authmsg = "Postponed"; 386 else if (partial) 387 authmsg = "Partial"; 388 else 389 authmsg = authenticated ? "Accepted" : "Failed"; 390 391 if ((extra = format_method_key(authctxt)) == NULL) { 392 if (authctxt->auth_method_info != NULL) 393 extra = xstrdup(authctxt->auth_method_info); 394 } 395 396 authlog("%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s", 397 authmsg, 398 method, 399 submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod, 400 authctxt->valid ? "" : "invalid user ", 401 authctxt->user, 402 ssh_remote_ipaddr(ssh), 403 ssh_remote_port(ssh), 404 extra != NULL ? ": " : "", 405 extra != NULL ? extra : ""); 406 407 free(extra); 408 if (!authctxt->postponed) 409 pfilter_notify(!authenticated); 410 } 411 412 void 413 auth_maxtries_exceeded(Authctxt *authctxt) 414 { 415 struct ssh *ssh = active_state; /* XXX */ 416 417 error("maximum authentication attempts exceeded for " 418 "%s%.100s from %.200s port %d ssh2", 419 authctxt->valid ? "" : "invalid user ", 420 authctxt->user, 421 ssh_remote_ipaddr(ssh), 422 ssh_remote_port(ssh)); 423 packet_disconnect("Too many authentication failures"); 424 /* NOTREACHED */ 425 } 426 427 /* 428 * Check whether root logins are disallowed. 429 */ 430 int 431 auth_root_allowed(struct ssh *ssh, const char *method) 432 { 433 switch (options.permit_root_login) { 434 case PERMIT_YES: 435 return 1; 436 case PERMIT_NO_PASSWD: 437 if (strcmp(method, "publickey") == 0 || 438 strcmp(method, "hostbased") == 0 || 439 strcmp(method, "gssapi-with-mic") == 0) 440 return 1; 441 break; 442 case PERMIT_FORCED_ONLY: 443 if (auth_opts->force_command != NULL) { 444 logit("Root login accepted for forced command."); 445 return 1; 446 } 447 break; 448 } 449 logit("ROOT LOGIN REFUSED FROM %.200s port %d", 450 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 451 return 0; 452 } 453 454 455 /* 456 * Given a template and a passwd structure, build a filename 457 * by substituting % tokenised options. Currently, %% becomes '%', 458 * %h becomes the home directory and %u the username. 459 * 460 * This returns a buffer allocated by xmalloc. 461 */ 462 char * 463 expand_authorized_keys(const char *filename, struct passwd *pw) 464 { 465 char *file, ret[PATH_MAX]; 466 int i; 467 468 file = percent_expand(filename, "h", pw->pw_dir, 469 "u", pw->pw_name, (char *)NULL); 470 471 /* 472 * Ensure that filename starts anchored. If not, be backward 473 * compatible and prepend the '%h/' 474 */ 475 if (*file == '/') 476 return (file); 477 478 i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file); 479 if (i < 0 || (size_t)i >= sizeof(ret)) 480 fatal("expand_authorized_keys: path too long"); 481 free(file); 482 return (xstrdup(ret)); 483 } 484 485 char * 486 authorized_principals_file(struct passwd *pw) 487 { 488 if (options.authorized_principals_file == NULL) 489 return NULL; 490 return expand_authorized_keys(options.authorized_principals_file, pw); 491 } 492 493 /* return ok if key exists in sysfile or userfile */ 494 HostStatus 495 check_key_in_hostfiles(struct passwd *pw, struct sshkey *key, const char *host, 496 const char *sysfile, const char *userfile) 497 { 498 char *user_hostfile; 499 struct stat st; 500 HostStatus host_status; 501 struct hostkeys *hostkeys; 502 const struct hostkey_entry *found; 503 504 hostkeys = init_hostkeys(); 505 load_hostkeys(hostkeys, host, sysfile); 506 if (userfile != NULL) { 507 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); 508 if (options.strict_modes && 509 (stat(user_hostfile, &st) == 0) && 510 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || 511 (st.st_mode & 022) != 0)) { 512 logit("Authentication refused for %.100s: " 513 "bad owner or modes for %.200s", 514 pw->pw_name, user_hostfile); 515 auth_debug_add("Ignored %.200s: bad ownership or modes", 516 user_hostfile); 517 } else { 518 temporarily_use_uid(pw); 519 load_hostkeys(hostkeys, host, user_hostfile); 520 restore_uid(); 521 } 522 free(user_hostfile); 523 } 524 host_status = check_key_in_hostkeys(hostkeys, key, &found); 525 if (host_status == HOST_REVOKED) 526 error("WARNING: revoked key for %s attempted authentication", 527 found->host); 528 else if (host_status == HOST_OK) 529 debug("%s: key for %s found at %s:%ld", __func__, 530 found->host, found->file, found->line); 531 else 532 debug("%s: key for host %s not found", __func__, host); 533 534 free_hostkeys(hostkeys); 535 536 return host_status; 537 } 538 539 static FILE * 540 auth_openfile(const char *file, struct passwd *pw, int strict_modes, 541 int log_missing, const char *file_type) 542 { 543 char line[1024]; 544 struct stat st; 545 int fd; 546 FILE *f; 547 548 if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) { 549 if (log_missing || errno != ENOENT) 550 debug("Could not open %s '%s': %s", file_type, file, 551 strerror(errno)); 552 return NULL; 553 } 554 555 if (fstat(fd, &st) < 0) { 556 close(fd); 557 return NULL; 558 } 559 if (!S_ISREG(st.st_mode)) { 560 logit("User %s %s %s is not a regular file", 561 pw->pw_name, file_type, file); 562 close(fd); 563 return NULL; 564 } 565 unset_nonblock(fd); 566 if ((f = fdopen(fd, "r")) == NULL) { 567 close(fd); 568 return NULL; 569 } 570 if (strict_modes && 571 safe_path_fd(fileno(f), file, pw, line, sizeof(line)) != 0) { 572 fclose(f); 573 logit("Authentication refused: %s", line); 574 auth_debug_add("Ignored %s: %s", file_type, line); 575 return NULL; 576 } 577 578 return f; 579 } 580 581 582 FILE * 583 auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes) 584 { 585 return auth_openfile(file, pw, strict_modes, 1, "authorized keys"); 586 } 587 588 FILE * 589 auth_openprincipals(const char *file, struct passwd *pw, int strict_modes) 590 { 591 return auth_openfile(file, pw, strict_modes, 0, 592 "authorized principals"); 593 } 594 595 struct passwd * 596 getpwnamallow(const char *user) 597 { 598 #ifdef HAVE_LOGIN_CAP 599 extern login_cap_t *lc; 600 #ifdef BSD_AUTH 601 auth_session_t *as; 602 #endif 603 #endif 604 struct ssh *ssh = active_state; /* XXX */ 605 struct passwd *pw; 606 struct connection_info *ci = get_connection_info(1, options.use_dns); 607 608 ci->user = user; 609 parse_server_match_config(&options, ci); 610 log_change_level(options.log_level); 611 process_permitopen(ssh, &options); 612 613 pw = getpwnam(user); 614 if (pw == NULL) { 615 pfilter_notify(1); 616 logit("Invalid user %.100s from %.100s port %d", 617 user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 618 return (NULL); 619 } 620 if (!allowed_user(pw)) 621 return (NULL); 622 #ifdef HAVE_LOGIN_CAP 623 if ((lc = login_getclass(pw->pw_class)) == NULL) { 624 debug("unable to get login class: %s", user); 625 return (NULL); 626 } 627 #ifdef BSD_AUTH 628 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || 629 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { 630 debug("Approval failure for %s", user); 631 pw = NULL; 632 } 633 if (as != NULL) 634 auth_close(as); 635 #endif 636 #endif 637 if (pw != NULL) 638 return (pwcopy(pw)); 639 return (NULL); 640 } 641 642 /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */ 643 int 644 auth_key_is_revoked(struct sshkey *key) 645 { 646 char *fp = NULL; 647 int r; 648 649 if (options.revoked_keys_file == NULL) 650 return 0; 651 if ((fp = sshkey_fingerprint(key, options.fingerprint_hash, 652 SSH_FP_DEFAULT)) == NULL) { 653 r = SSH_ERR_ALLOC_FAIL; 654 error("%s: fingerprint key: %s", __func__, ssh_err(r)); 655 goto out; 656 } 657 658 r = sshkey_check_revoked(key, options.revoked_keys_file); 659 switch (r) { 660 case 0: 661 break; /* not revoked */ 662 case SSH_ERR_KEY_REVOKED: 663 error("Authentication key %s %s revoked by file %s", 664 sshkey_type(key), fp, options.revoked_keys_file); 665 goto out; 666 default: 667 error("Error checking authentication key %s %s in " 668 "revoked keys file %s: %s", sshkey_type(key), fp, 669 options.revoked_keys_file, ssh_err(r)); 670 goto out; 671 } 672 673 /* Success */ 674 r = 0; 675 676 out: 677 free(fp); 678 return r == 0 ? 0 : 1; 679 } 680 #endif 681 682 void 683 auth_debug_add(const char *fmt,...) 684 { 685 char buf[1024]; 686 va_list args; 687 688 if (!auth_debug_init) 689 return; 690 691 va_start(args, fmt); 692 vsnprintf(buf, sizeof(buf), fmt, args); 693 va_end(args); 694 buffer_put_cstring(&auth_debug, buf); 695 } 696 697 void 698 auth_debug_send(void) 699 { 700 char *msg; 701 702 if (!auth_debug_init) 703 return; 704 while (buffer_len(&auth_debug)) { 705 msg = buffer_get_string(&auth_debug, NULL); 706 packet_send_debug("%s", msg); 707 free(msg); 708 } 709 } 710 711 void 712 auth_debug_reset(void) 713 { 714 if (auth_debug_init) 715 buffer_clear(&auth_debug); 716 else { 717 buffer_init(&auth_debug); 718 auth_debug_init = 1; 719 } 720 } 721 722 struct passwd * 723 fakepw(void) 724 { 725 static struct passwd fake; 726 static char nouser[] = "NOUSER"; 727 static char nonexist[] = "/nonexist"; 728 729 memset(&fake, 0, sizeof(fake)); 730 fake.pw_name = nouser; 731 fake.pw_passwd = __UNCONST( 732 "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK"); 733 fake.pw_gecos = nouser; 734 fake.pw_uid = (uid_t)-1; 735 fake.pw_gid = (gid_t)-1; 736 fake.pw_class = __UNCONST(""); 737 fake.pw_dir = nonexist; 738 fake.pw_shell = nonexist; 739 740 return (&fake); 741 } 742 743 /* 744 * Returns the remote DNS hostname as a string. The returned string must not 745 * be freed. NB. this will usually trigger a DNS query the first time it is 746 * called. 747 * This function does additional checks on the hostname to mitigate some 748 * attacks on legacy rhosts-style authentication. 749 * XXX is RhostsRSAAuthentication vulnerable to these? 750 * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?) 751 */ 752 753 static char * 754 remote_hostname(struct ssh *ssh) 755 { 756 struct sockaddr_storage from; 757 socklen_t fromlen; 758 struct addrinfo hints, *ai, *aitop; 759 char name[NI_MAXHOST], ntop2[NI_MAXHOST]; 760 const char *ntop = ssh_remote_ipaddr(ssh); 761 762 /* Get IP address of client. */ 763 fromlen = sizeof(from); 764 memset(&from, 0, sizeof(from)); 765 if (getpeername(ssh_packet_get_connection_in(ssh), 766 (struct sockaddr *)&from, &fromlen) < 0) { 767 debug("getpeername failed: %.100s", strerror(errno)); 768 return strdup(ntop); 769 } 770 771 debug3("Trying to reverse map address %.100s.", ntop); 772 /* Map the IP address to a host name. */ 773 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), 774 NULL, 0, NI_NAMEREQD) != 0) { 775 /* Host name not found. Use ip address. */ 776 return strdup(ntop); 777 } 778 779 /* 780 * if reverse lookup result looks like a numeric hostname, 781 * someone is trying to trick us by PTR record like following: 782 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5 783 */ 784 memset(&hints, 0, sizeof(hints)); 785 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 786 hints.ai_flags = AI_NUMERICHOST; 787 if (getaddrinfo(name, NULL, &hints, &ai) == 0) { 788 logit("Nasty PTR record \"%s\" is set up for %s, ignoring", 789 name, ntop); 790 freeaddrinfo(ai); 791 return strdup(ntop); 792 } 793 794 /* Names are stored in lowercase. */ 795 lowercase(name); 796 797 /* 798 * Map it back to an IP address and check that the given 799 * address actually is an address of this host. This is 800 * necessary because anyone with access to a name server can 801 * define arbitrary names for an IP address. Mapping from 802 * name to IP address can be trusted better (but can still be 803 * fooled if the intruder has access to the name server of 804 * the domain). 805 */ 806 memset(&hints, 0, sizeof(hints)); 807 hints.ai_family = from.ss_family; 808 hints.ai_socktype = SOCK_STREAM; 809 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { 810 logit("reverse mapping checking getaddrinfo for %.700s " 811 "[%s] failed.", name, ntop); 812 return strdup(ntop); 813 } 814 /* Look for the address from the list of addresses. */ 815 for (ai = aitop; ai; ai = ai->ai_next) { 816 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, 817 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && 818 (strcmp(ntop, ntop2) == 0)) 819 break; 820 } 821 freeaddrinfo(aitop); 822 /* If we reached the end of the list, the address was not there. */ 823 if (ai == NULL) { 824 /* Address not found for the host name. */ 825 logit("Address %.100s maps to %.600s, but this does not " 826 "map back to the address.", ntop, name); 827 return strdup(ntop); 828 } 829 return strdup(name); 830 } 831 832 /* 833 * Return the canonical name of the host in the other side of the current 834 * connection. The host name is cached, so it is efficient to call this 835 * several times. 836 */ 837 838 const char * 839 auth_get_canonical_hostname(struct ssh *ssh, int use_dns) 840 { 841 static char *dnsname; 842 843 if (!use_dns) 844 return ssh_remote_ipaddr(ssh); 845 else if (dnsname != NULL) 846 return dnsname; 847 else { 848 dnsname = remote_hostname(ssh); 849 return dnsname; 850 } 851 } 852 853 /* 854 * Runs command in a subprocess wuth a minimal environment. 855 * Returns pid on success, 0 on failure. 856 * The child stdout and stderr maybe captured, left attached or sent to 857 * /dev/null depending on the contents of flags. 858 * "tag" is prepended to log messages. 859 * NB. "command" is only used for logging; the actual command executed is 860 * av[0]. 861 */ 862 pid_t 863 subprocess(const char *tag, struct passwd *pw, const char *command, 864 int ac, char **av, FILE **child, u_int flags) 865 { 866 FILE *f = NULL; 867 struct stat st; 868 int fd, devnull, p[2], i; 869 pid_t pid; 870 char *cp, errmsg[512]; 871 u_int envsize; 872 char **child_env; 873 874 if (child != NULL) 875 *child = NULL; 876 877 debug3("%s: %s command \"%s\" running as %s (flags 0x%x)", __func__, 878 tag, command, pw->pw_name, flags); 879 880 /* Check consistency */ 881 if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 && 882 (flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) { 883 error("%s: inconsistent flags", __func__); 884 return 0; 885 } 886 if (((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) != (child == NULL)) { 887 error("%s: inconsistent flags/output", __func__); 888 return 0; 889 } 890 891 /* 892 * If executing an explicit binary, then verify the it exists 893 * and appears safe-ish to execute 894 */ 895 if (*av[0] != '/') { 896 error("%s path is not absolute", tag); 897 return 0; 898 } 899 temporarily_use_uid(pw); 900 if (stat(av[0], &st) < 0) { 901 error("Could not stat %s \"%s\": %s", tag, 902 av[0], strerror(errno)); 903 restore_uid(); 904 return 0; 905 } 906 if (safe_path(av[0], &st, NULL, 0, errmsg, sizeof(errmsg)) != 0) { 907 error("Unsafe %s \"%s\": %s", tag, av[0], errmsg); 908 restore_uid(); 909 return 0; 910 } 911 /* Prepare to keep the child's stdout if requested */ 912 if (pipe(p) != 0) { 913 error("%s: pipe: %s", tag, strerror(errno)); 914 restore_uid(); 915 return 0; 916 } 917 restore_uid(); 918 919 switch ((pid = fork())) { 920 case -1: /* error */ 921 error("%s: fork: %s", tag, strerror(errno)); 922 close(p[0]); 923 close(p[1]); 924 return 0; 925 case 0: /* child */ 926 /* Prepare a minimal environment for the child. */ 927 envsize = 5; 928 child_env = xcalloc(sizeof(*child_env), envsize); 929 child_set_env(&child_env, &envsize, "PATH", _PATH_STDPATH); 930 child_set_env(&child_env, &envsize, "USER", pw->pw_name); 931 child_set_env(&child_env, &envsize, "LOGNAME", pw->pw_name); 932 child_set_env(&child_env, &envsize, "HOME", pw->pw_dir); 933 if ((cp = getenv("LANG")) != NULL) 934 child_set_env(&child_env, &envsize, "LANG", cp); 935 936 for (i = 0; i < NSIG; i++) 937 signal(i, SIG_DFL); 938 939 if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) { 940 error("%s: open %s: %s", tag, _PATH_DEVNULL, 941 strerror(errno)); 942 _exit(1); 943 } 944 if (dup2(devnull, STDIN_FILENO) == -1) { 945 error("%s: dup2: %s", tag, strerror(errno)); 946 _exit(1); 947 } 948 949 /* Set up stdout as requested; leave stderr in place for now. */ 950 fd = -1; 951 if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) 952 fd = p[1]; 953 else if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0) 954 fd = devnull; 955 if (fd != -1 && dup2(fd, STDOUT_FILENO) == -1) { 956 error("%s: dup2: %s", tag, strerror(errno)); 957 _exit(1); 958 } 959 closefrom(STDERR_FILENO + 1); 960 961 /* Don't use permanently_set_uid() here to avoid fatal() */ 962 #ifdef __NetBSD__ 963 #define setresgid(a, b, c) setgid(a) 964 #define setresuid(a, b, c) setuid(a) 965 #endif 966 if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0) { 967 error("%s: setresgid %u: %s", tag, (u_int)pw->pw_gid, 968 strerror(errno)); 969 _exit(1); 970 } 971 if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0) { 972 error("%s: setresuid %u: %s", tag, (u_int)pw->pw_uid, 973 strerror(errno)); 974 _exit(1); 975 } 976 /* stdin is pointed to /dev/null at this point */ 977 if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 && 978 dup2(STDIN_FILENO, STDERR_FILENO) == -1) { 979 error("%s: dup2: %s", tag, strerror(errno)); 980 _exit(1); 981 } 982 983 execve(av[0], av, child_env); 984 error("%s exec \"%s\": %s", tag, command, strerror(errno)); 985 _exit(127); 986 default: /* parent */ 987 break; 988 } 989 990 close(p[1]); 991 if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) 992 close(p[0]); 993 else if ((f = fdopen(p[0], "r")) == NULL) { 994 error("%s: fdopen: %s", tag, strerror(errno)); 995 close(p[0]); 996 /* Don't leave zombie child */ 997 kill(pid, SIGTERM); 998 while (waitpid(pid, NULL, 0) == -1 && errno == EINTR) 999 ; 1000 return 0; 1001 } 1002 /* Success */ 1003 debug3("%s: %s pid %ld", __func__, tag, (long)pid); 1004 if (child != NULL) 1005 *child = f; 1006 return pid; 1007 } 1008 1009 /* These functions link key/cert options to the auth framework */ 1010 1011 /* Log sshauthopt options locally and (optionally) for remote transmission */ 1012 void 1013 auth_log_authopts(const char *loc, const struct sshauthopt *opts, int do_remote) 1014 { 1015 int do_env = options.permit_user_env && opts->nenv > 0; 1016 int do_permitopen = opts->npermitopen > 0 && 1017 (options.allow_tcp_forwarding & FORWARD_LOCAL) != 0; 1018 size_t i; 1019 char msg[1024], buf[64]; 1020 1021 snprintf(buf, sizeof(buf), "%d", opts->force_tun_device); 1022 /* Try to keep this alphabetically sorted */ 1023 snprintf(msg, sizeof(msg), "key options:%s%s%s%s%s%s%s%s%s%s%s%s", 1024 opts->permit_agent_forwarding_flag ? " agent-forwarding" : "", 1025 opts->force_command == NULL ? "" : " command", 1026 do_env ? " environment" : "", 1027 opts->valid_before == 0 ? "" : "expires", 1028 do_permitopen ? " permitopen" : "", 1029 opts->permit_port_forwarding_flag ? " port-forwarding" : "", 1030 opts->cert_principals == NULL ? "" : " principals", 1031 opts->permit_pty_flag ? " pty" : "", 1032 opts->force_tun_device == -1 ? "" : " tun=", 1033 opts->force_tun_device == -1 ? "" : buf, 1034 opts->permit_user_rc ? " user-rc" : "", 1035 opts->permit_x11_forwarding_flag ? " x11-forwarding" : ""); 1036 1037 debug("%s: %s", loc, msg); 1038 if (do_remote) 1039 auth_debug_add("%s: %s", loc, msg); 1040 1041 if (options.permit_user_env) { 1042 for (i = 0; i < opts->nenv; i++) { 1043 debug("%s: environment: %s", loc, opts->env[i]); 1044 if (do_remote) { 1045 auth_debug_add("%s: environment: %s", 1046 loc, opts->env[i]); 1047 } 1048 } 1049 } 1050 1051 /* Go into a little more details for the local logs. */ 1052 if (opts->valid_before != 0) { 1053 format_absolute_time(opts->valid_before, buf, sizeof(buf)); 1054 debug("%s: expires at %s", loc, buf); 1055 } 1056 if (opts->cert_principals != NULL) { 1057 debug("%s: authorized principals: \"%s\"", 1058 loc, opts->cert_principals); 1059 } 1060 if (opts->force_command != NULL) 1061 debug("%s: forced command: \"%s\"", loc, opts->force_command); 1062 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0) { 1063 for (i = 0; i < opts->npermitopen; i++) { 1064 debug("%s: permitted open: %s", 1065 loc, opts->permitopen[i]); 1066 } 1067 } 1068 } 1069 1070 #ifndef HOST_ONLY 1071 /* Activate a new set of key/cert options; merging with what is there. */ 1072 int 1073 auth_activate_options(struct ssh *ssh, struct sshauthopt *opts) 1074 { 1075 struct sshauthopt *old = auth_opts; 1076 const char *emsg = NULL; 1077 1078 debug("%s: setting new authentication options", __func__); 1079 if ((auth_opts = sshauthopt_merge(old, opts, &emsg)) == NULL) { 1080 error("Inconsistent authentication options: %s", emsg); 1081 return -1; 1082 } 1083 return 0; 1084 } 1085 1086 /* Disable forwarding, etc for the session */ 1087 void 1088 auth_restrict_session(struct ssh *ssh) 1089 { 1090 struct sshauthopt *restricted; 1091 1092 debug("%s: restricting session", __func__); 1093 1094 /* A blank sshauthopt defaults to permitting nothing */ 1095 restricted = sshauthopt_new(); 1096 restricted->restricted = 1; 1097 1098 if (auth_activate_options(ssh, restricted) != 0) 1099 fatal("%s: failed to restrict session", __func__); 1100 sshauthopt_free(restricted); 1101 } 1102 1103 int 1104 auth_authorise_keyopts(struct ssh *ssh, struct passwd *pw, 1105 struct sshauthopt *opts, int allow_cert_authority, const char *loc) 1106 { 1107 const char *remote_ip = ssh_remote_ipaddr(ssh); 1108 const char *remote_host = auth_get_canonical_hostname(ssh, 1109 options.use_dns); 1110 time_t now = time(NULL); 1111 char buf[64]; 1112 1113 /* 1114 * Check keys/principals file expiry time. 1115 * NB. validity interval in certificate is handled elsewhere. 1116 */ 1117 if (opts->valid_before && now > 0 && 1118 opts->valid_before < (uint64_t)now) { 1119 format_absolute_time(opts->valid_before, buf, sizeof(buf)); 1120 debug("%s: entry expired at %s", loc, buf); 1121 auth_debug_add("%s: entry expired at %s", loc, buf); 1122 return -1; 1123 } 1124 /* Consistency checks */ 1125 if (opts->cert_principals != NULL && !opts->cert_authority) { 1126 debug("%s: principals on non-CA key", loc); 1127 auth_debug_add("%s: principals on non-CA key", loc); 1128 /* deny access */ 1129 return -1; 1130 } 1131 /* cert-authority flag isn't valid in authorized_principals files */ 1132 if (!allow_cert_authority && opts->cert_authority) { 1133 debug("%s: cert-authority flag invalid here", loc); 1134 auth_debug_add("%s: cert-authority flag invalid here", loc); 1135 /* deny access */ 1136 return -1; 1137 } 1138 1139 /* Perform from= checks */ 1140 if (opts->required_from_host_keys != NULL) { 1141 switch (match_host_and_ip(remote_host, remote_ip, 1142 opts->required_from_host_keys )) { 1143 case 1: 1144 /* Host name matches. */ 1145 break; 1146 case -1: 1147 default: 1148 debug("%s: invalid from criteria", loc); 1149 auth_debug_add("%s: invalid from criteria", loc); 1150 /* FALLTHROUGH */ 1151 case 0: 1152 logit("%s: Authentication tried for %.100s with " 1153 "correct key but not from a permitted " 1154 "host (host=%.200s, ip=%.200s, required=%.200s).", 1155 loc, pw->pw_name, remote_host, remote_ip, 1156 opts->required_from_host_keys); 1157 auth_debug_add("%s: Your host '%.200s' is not " 1158 "permitted to use this key for login.", 1159 loc, remote_host); 1160 /* deny access */ 1161 return -1; 1162 } 1163 } 1164 /* Check source-address restriction from certificate */ 1165 if (opts->required_from_host_cert != NULL) { 1166 switch (addr_match_cidr_list(remote_ip, 1167 opts->required_from_host_cert)) { 1168 case 1: 1169 /* accepted */ 1170 break; 1171 case -1: 1172 default: 1173 /* invalid */ 1174 error("%s: Certificate source-address invalid", 1175 loc); 1176 /* FALLTHROUGH */ 1177 case 0: 1178 logit("%s: Authentication tried for %.100s with valid " 1179 "certificate but not from a permitted source " 1180 "address (%.200s).", loc, pw->pw_name, remote_ip); 1181 auth_debug_add("%s: Your address '%.200s' is not " 1182 "permitted to use this certificate for login.", 1183 loc, remote_ip); 1184 return -1; 1185 } 1186 } 1187 /* 1188 * 1189 * XXX this is spammy. We should report remotely only for keys 1190 * that are successful in actual auth attempts, and not PK_OK 1191 * tests. 1192 */ 1193 auth_log_authopts(loc, opts, 1); 1194 1195 return 0; 1196 } 1197 #endif 1198