1 /* $OpenBSD: auth.c,v 1.132 2018/07/11 08:19:35 martijn 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 <errno.h> 37 #include <fcntl.h> 38 #ifdef HAVE_PATHS_H 39 # include <paths.h> 40 #endif 41 #include <pwd.h> 42 #ifdef HAVE_LOGIN_H 43 #include <login.h> 44 #endif 45 #ifdef USE_SHADOW 46 #include <shadow.h> 47 #endif 48 #include <stdarg.h> 49 #include <stdio.h> 50 #include <string.h> 51 #include <unistd.h> 52 #include <limits.h> 53 #include <netdb.h> 54 55 #include "xmalloc.h" 56 #include "match.h" 57 #include "groupaccess.h" 58 #include "log.h" 59 #include "sshbuf.h" 60 #include "misc.h" 61 #include "servconf.h" 62 #include "sshkey.h" 63 #include "hostfile.h" 64 #include "auth.h" 65 #include "auth-options.h" 66 #include "canohost.h" 67 #include "uidswap.h" 68 #include "packet.h" 69 #include "loginrec.h" 70 #ifdef GSSAPI 71 #include "ssh-gss.h" 72 #endif 73 #include "authfile.h" 74 #include "monitor_wrap.h" 75 #include "authfile.h" 76 #include "ssherr.h" 77 #include "compat.h" 78 #include "channels.h" 79 #include "blacklist_client.h" 80 81 /* import */ 82 extern ServerOptions options; 83 extern int use_privsep; 84 extern struct sshbuf *loginmsg; 85 extern struct passwd *privsep_pw; 86 extern struct sshauthopt *auth_opts; 87 88 /* Debugging messages */ 89 static struct sshbuf *auth_debug; 90 91 /* 92 * Check if the user is allowed to log in via ssh. If user is listed 93 * in DenyUsers or one of user's groups is listed in DenyGroups, false 94 * will be returned. If AllowUsers isn't empty and user isn't listed 95 * there, or if AllowGroups isn't empty and one of user's groups isn't 96 * listed there, false will be returned. 97 * If the user's shell is not executable, false will be returned. 98 * Otherwise true is returned. 99 */ 100 int 101 allowed_user(struct passwd * pw) 102 { 103 struct ssh *ssh = active_state; /* XXX */ 104 struct stat st; 105 const char *hostname = NULL, *ipaddr = NULL, *passwd = NULL; 106 u_int i; 107 int r; 108 #ifdef USE_SHADOW 109 struct spwd *spw = NULL; 110 #endif 111 112 /* Shouldn't be called if pw is NULL, but better safe than sorry... */ 113 if (!pw || !pw->pw_name) 114 return 0; 115 116 #ifdef USE_SHADOW 117 if (!options.use_pam) 118 spw = getspnam(pw->pw_name); 119 #ifdef HAS_SHADOW_EXPIRE 120 if (!options.use_pam && spw != NULL && auth_shadow_acctexpired(spw)) 121 return 0; 122 #endif /* HAS_SHADOW_EXPIRE */ 123 #endif /* USE_SHADOW */ 124 125 /* grab passwd field for locked account check */ 126 passwd = pw->pw_passwd; 127 #ifdef USE_SHADOW 128 if (spw != NULL) 129 #ifdef USE_LIBIAF 130 passwd = get_iaf_password(pw); 131 #else 132 passwd = spw->sp_pwdp; 133 #endif /* USE_LIBIAF */ 134 #endif 135 136 /* check for locked account */ 137 if (!options.use_pam && passwd && *passwd) { 138 int locked = 0; 139 140 #ifdef LOCKED_PASSWD_STRING 141 if (strcmp(passwd, LOCKED_PASSWD_STRING) == 0) 142 locked = 1; 143 #endif 144 #ifdef LOCKED_PASSWD_PREFIX 145 if (strncmp(passwd, LOCKED_PASSWD_PREFIX, 146 strlen(LOCKED_PASSWD_PREFIX)) == 0) 147 locked = 1; 148 #endif 149 #ifdef LOCKED_PASSWD_SUBSTR 150 if (strstr(passwd, LOCKED_PASSWD_SUBSTR)) 151 locked = 1; 152 #endif 153 #ifdef USE_LIBIAF 154 free((void *) passwd); 155 #endif /* USE_LIBIAF */ 156 if (locked) { 157 logit("User %.100s not allowed because account is locked", 158 pw->pw_name); 159 return 0; 160 } 161 } 162 163 /* 164 * Deny if shell does not exist or is not executable unless we 165 * are chrooting. 166 */ 167 if (options.chroot_directory == NULL || 168 strcasecmp(options.chroot_directory, "none") == 0) { 169 char *shell = xstrdup((pw->pw_shell[0] == '\0') ? 170 _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */ 171 172 if (stat(shell, &st) != 0) { 173 logit("User %.100s not allowed because shell %.100s " 174 "does not exist", pw->pw_name, shell); 175 free(shell); 176 return 0; 177 } 178 if (S_ISREG(st.st_mode) == 0 || 179 (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { 180 logit("User %.100s not allowed because shell %.100s " 181 "is not executable", pw->pw_name, shell); 182 free(shell); 183 return 0; 184 } 185 free(shell); 186 } 187 188 if (options.num_deny_users > 0 || options.num_allow_users > 0 || 189 options.num_deny_groups > 0 || options.num_allow_groups > 0) { 190 hostname = auth_get_canonical_hostname(ssh, options.use_dns); 191 ipaddr = ssh_remote_ipaddr(ssh); 192 } 193 194 /* Return false if user is listed in DenyUsers */ 195 if (options.num_deny_users > 0) { 196 for (i = 0; i < options.num_deny_users; i++) { 197 r = match_user(pw->pw_name, hostname, ipaddr, 198 options.deny_users[i]); 199 if (r < 0) { 200 fatal("Invalid DenyUsers pattern \"%.100s\"", 201 options.deny_users[i]); 202 } else if (r != 0) { 203 logit("User %.100s from %.100s not allowed " 204 "because listed in DenyUsers", 205 pw->pw_name, hostname); 206 return 0; 207 } 208 } 209 } 210 /* Return false if AllowUsers isn't empty and user isn't listed there */ 211 if (options.num_allow_users > 0) { 212 for (i = 0; i < options.num_allow_users; i++) { 213 r = match_user(pw->pw_name, hostname, ipaddr, 214 options.allow_users[i]); 215 if (r < 0) { 216 fatal("Invalid AllowUsers pattern \"%.100s\"", 217 options.allow_users[i]); 218 } else if (r == 1) 219 break; 220 } 221 /* i < options.num_allow_users iff we break for loop */ 222 if (i >= options.num_allow_users) { 223 logit("User %.100s from %.100s not allowed because " 224 "not listed in AllowUsers", pw->pw_name, hostname); 225 return 0; 226 } 227 } 228 if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { 229 /* Get the user's group access list (primary and supplementary) */ 230 if (ga_init(pw->pw_name, pw->pw_gid) == 0) { 231 logit("User %.100s from %.100s not allowed because " 232 "not in any group", pw->pw_name, hostname); 233 return 0; 234 } 235 236 /* Return false if one of user's groups is listed in DenyGroups */ 237 if (options.num_deny_groups > 0) 238 if (ga_match(options.deny_groups, 239 options.num_deny_groups)) { 240 ga_free(); 241 logit("User %.100s from %.100s not allowed " 242 "because a group is listed in DenyGroups", 243 pw->pw_name, hostname); 244 return 0; 245 } 246 /* 247 * Return false if AllowGroups isn't empty and one of user's groups 248 * isn't listed there 249 */ 250 if (options.num_allow_groups > 0) 251 if (!ga_match(options.allow_groups, 252 options.num_allow_groups)) { 253 ga_free(); 254 logit("User %.100s from %.100s not allowed " 255 "because none of user's groups are listed " 256 "in AllowGroups", pw->pw_name, hostname); 257 return 0; 258 } 259 ga_free(); 260 } 261 262 #ifdef CUSTOM_SYS_AUTH_ALLOWED_USER 263 if (!sys_auth_allowed_user(pw, &loginmsg)) 264 return 0; 265 #endif 266 267 /* We found no reason not to let this user try to log on... */ 268 return 1; 269 } 270 271 /* 272 * Formats any key left in authctxt->auth_method_key for inclusion in 273 * auth_log()'s message. Also includes authxtct->auth_method_info if present. 274 */ 275 static char * 276 format_method_key(Authctxt *authctxt) 277 { 278 const struct sshkey *key = authctxt->auth_method_key; 279 const char *methinfo = authctxt->auth_method_info; 280 char *fp, *ret = NULL; 281 282 if (key == NULL) 283 return NULL; 284 285 if (sshkey_is_cert(key)) { 286 fp = sshkey_fingerprint(key->cert->signature_key, 287 options.fingerprint_hash, SSH_FP_DEFAULT); 288 xasprintf(&ret, "%s ID %s (serial %llu) CA %s %s%s%s", 289 sshkey_type(key), key->cert->key_id, 290 (unsigned long long)key->cert->serial, 291 sshkey_type(key->cert->signature_key), 292 fp == NULL ? "(null)" : fp, 293 methinfo == NULL ? "" : ", ", 294 methinfo == NULL ? "" : methinfo); 295 free(fp); 296 } else { 297 fp = sshkey_fingerprint(key, options.fingerprint_hash, 298 SSH_FP_DEFAULT); 299 xasprintf(&ret, "%s %s%s%s", sshkey_type(key), 300 fp == NULL ? "(null)" : fp, 301 methinfo == NULL ? "" : ", ", 302 methinfo == NULL ? "" : methinfo); 303 free(fp); 304 } 305 return ret; 306 } 307 308 void 309 auth_log(Authctxt *authctxt, int authenticated, int partial, 310 const char *method, const char *submethod) 311 { 312 struct ssh *ssh = active_state; /* XXX */ 313 void (*authlog) (const char *fmt,...) = verbose; 314 const char *authmsg; 315 char *extra = NULL; 316 317 if (use_privsep && !mm_is_monitor() && !authctxt->postponed) 318 return; 319 320 /* Raise logging level */ 321 if (authenticated == 1 || 322 !authctxt->valid || 323 authctxt->failures >= options.max_authtries / 2 || 324 strcmp(method, "password") == 0) 325 authlog = logit; 326 327 if (authctxt->postponed) 328 authmsg = "Postponed"; 329 else if (partial) 330 authmsg = "Partial"; 331 else { 332 authmsg = authenticated ? "Accepted" : "Failed"; 333 if (authenticated) 334 BLACKLIST_NOTIFY(BLACKLIST_AUTH_OK, "ssh"); 335 } 336 337 if ((extra = format_method_key(authctxt)) == NULL) { 338 if (authctxt->auth_method_info != NULL) 339 extra = xstrdup(authctxt->auth_method_info); 340 } 341 342 authlog("%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s", 343 authmsg, 344 method, 345 submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod, 346 authctxt->valid ? "" : "invalid user ", 347 authctxt->user, 348 ssh_remote_ipaddr(ssh), 349 ssh_remote_port(ssh), 350 extra != NULL ? ": " : "", 351 extra != NULL ? extra : ""); 352 353 free(extra); 354 355 #ifdef CUSTOM_FAILED_LOGIN 356 if (authenticated == 0 && !authctxt->postponed && 357 (strcmp(method, "password") == 0 || 358 strncmp(method, "keyboard-interactive", 20) == 0 || 359 strcmp(method, "challenge-response") == 0)) 360 record_failed_login(authctxt->user, 361 auth_get_canonical_hostname(ssh, options.use_dns), "ssh"); 362 # ifdef WITH_AIXAUTHENTICATE 363 if (authenticated) 364 sys_auth_record_login(authctxt->user, 365 auth_get_canonical_hostname(ssh, options.use_dns), "ssh", 366 &loginmsg); 367 # endif 368 #endif 369 #ifdef SSH_AUDIT_EVENTS 370 if (authenticated == 0 && !authctxt->postponed) 371 audit_event(audit_classify_auth(method)); 372 #endif 373 } 374 375 376 void 377 auth_maxtries_exceeded(Authctxt *authctxt) 378 { 379 struct ssh *ssh = active_state; /* XXX */ 380 381 error("maximum authentication attempts exceeded for " 382 "%s%.100s from %.200s port %d ssh2", 383 authctxt->valid ? "" : "invalid user ", 384 authctxt->user, 385 ssh_remote_ipaddr(ssh), 386 ssh_remote_port(ssh)); 387 packet_disconnect("Too many authentication failures"); 388 /* NOTREACHED */ 389 } 390 391 /* 392 * Check whether root logins are disallowed. 393 */ 394 int 395 auth_root_allowed(struct ssh *ssh, const char *method) 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 (auth_opts->force_command != NULL) { 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, uidstr[32], ret[PATH_MAX]; 430 int i; 431 432 snprintf(uidstr, sizeof(uidstr), "%llu", 433 (unsigned long long)pw->pw_uid); 434 file = percent_expand(filename, "h", pw->pw_dir, 435 "u", pw->pw_name, "U", uidstr, (char *)NULL); 436 437 /* 438 * Ensure that filename starts anchored. If not, be backward 439 * compatible and prepend the '%h/' 440 */ 441 if (*file == '/') 442 return (file); 443 444 i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file); 445 if (i < 0 || (size_t)i >= sizeof(ret)) 446 fatal("expand_authorized_keys: path too long"); 447 free(file); 448 return (xstrdup(ret)); 449 } 450 451 char * 452 authorized_principals_file(struct passwd *pw) 453 { 454 if (options.authorized_principals_file == NULL) 455 return NULL; 456 return expand_authorized_keys(options.authorized_principals_file, pw); 457 } 458 459 /* return ok if key exists in sysfile or userfile */ 460 HostStatus 461 check_key_in_hostfiles(struct passwd *pw, struct sshkey *key, const char *host, 462 const char *sysfile, const char *userfile) 463 { 464 char *user_hostfile; 465 struct stat st; 466 HostStatus host_status; 467 struct hostkeys *hostkeys; 468 const struct hostkey_entry *found; 469 470 hostkeys = init_hostkeys(); 471 load_hostkeys(hostkeys, host, sysfile); 472 if (userfile != NULL) { 473 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); 474 if (options.strict_modes && 475 (stat(user_hostfile, &st) == 0) && 476 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || 477 (st.st_mode & 022) != 0)) { 478 logit("Authentication refused for %.100s: " 479 "bad owner or modes for %.200s", 480 pw->pw_name, user_hostfile); 481 auth_debug_add("Ignored %.200s: bad ownership or modes", 482 user_hostfile); 483 } else { 484 temporarily_use_uid(pw); 485 load_hostkeys(hostkeys, host, user_hostfile); 486 restore_uid(); 487 } 488 free(user_hostfile); 489 } 490 host_status = check_key_in_hostkeys(hostkeys, key, &found); 491 if (host_status == HOST_REVOKED) 492 error("WARNING: revoked key for %s attempted authentication", 493 found->host); 494 else if (host_status == HOST_OK) 495 debug("%s: key for %s found at %s:%ld", __func__, 496 found->host, found->file, found->line); 497 else 498 debug("%s: key for host %s not found", __func__, host); 499 500 free_hostkeys(hostkeys); 501 502 return host_status; 503 } 504 505 static FILE * 506 auth_openfile(const char *file, struct passwd *pw, int strict_modes, 507 int log_missing, char *file_type) 508 { 509 char line[1024]; 510 struct stat st; 511 int fd; 512 FILE *f; 513 514 if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) { 515 if (log_missing || errno != ENOENT) 516 debug("Could not open %s '%s': %s", file_type, file, 517 strerror(errno)); 518 return NULL; 519 } 520 521 if (fstat(fd, &st) < 0) { 522 close(fd); 523 return NULL; 524 } 525 if (!S_ISREG(st.st_mode)) { 526 logit("User %s %s %s is not a regular file", 527 pw->pw_name, file_type, file); 528 close(fd); 529 return NULL; 530 } 531 unset_nonblock(fd); 532 if ((f = fdopen(fd, "r")) == NULL) { 533 close(fd); 534 return NULL; 535 } 536 if (strict_modes && 537 safe_path_fd(fileno(f), file, pw, line, sizeof(line)) != 0) { 538 fclose(f); 539 logit("Authentication refused: %s", line); 540 auth_debug_add("Ignored %s: %s", file_type, line); 541 return NULL; 542 } 543 544 return f; 545 } 546 547 548 FILE * 549 auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes) 550 { 551 return auth_openfile(file, pw, strict_modes, 1, "authorized keys"); 552 } 553 554 FILE * 555 auth_openprincipals(const char *file, struct passwd *pw, int strict_modes) 556 { 557 return auth_openfile(file, pw, strict_modes, 0, 558 "authorized principals"); 559 } 560 561 struct passwd * 562 getpwnamallow(const char *user) 563 { 564 struct ssh *ssh = active_state; /* XXX */ 565 #ifdef HAVE_LOGIN_CAP 566 extern login_cap_t *lc; 567 #ifdef BSD_AUTH 568 auth_session_t *as; 569 #endif 570 #endif 571 struct passwd *pw; 572 struct connection_info *ci = get_connection_info(1, options.use_dns); 573 574 ci->user = user; 575 parse_server_match_config(&options, ci); 576 log_change_level(options.log_level); 577 process_permitopen(ssh, &options); 578 579 #if defined(_AIX) && defined(HAVE_SETAUTHDB) 580 aix_setauthdb(user); 581 #endif 582 583 pw = getpwnam(user); 584 585 #if defined(_AIX) && defined(HAVE_SETAUTHDB) 586 aix_restoreauthdb(); 587 #endif 588 #ifdef HAVE_CYGWIN 589 /* 590 * Windows usernames are case-insensitive. To avoid later problems 591 * when trying to match the username, the user is only allowed to 592 * login if the username is given in the same case as stored in the 593 * user database. 594 */ 595 if (pw != NULL && strcmp(user, pw->pw_name) != 0) { 596 logit("Login name %.100s does not match stored username %.100s", 597 user, pw->pw_name); 598 pw = NULL; 599 } 600 #endif 601 if (pw == NULL) { 602 BLACKLIST_NOTIFY(BLACKLIST_BAD_USER, user); 603 logit("Invalid user %.100s from %.100s port %d", 604 user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 605 #ifdef CUSTOM_FAILED_LOGIN 606 record_failed_login(user, 607 auth_get_canonical_hostname(ssh, options.use_dns), "ssh"); 608 #endif 609 #ifdef SSH_AUDIT_EVENTS 610 audit_event(SSH_INVALID_USER); 611 #endif /* SSH_AUDIT_EVENTS */ 612 return (NULL); 613 } 614 if (!allowed_user(pw)) 615 return (NULL); 616 #ifdef HAVE_LOGIN_CAP 617 if ((lc = login_getpwclass(pw)) == NULL) { 618 debug("unable to get login class: %s", user); 619 return (NULL); 620 } 621 #ifdef BSD_AUTH 622 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || 623 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { 624 debug("Approval failure for %s", user); 625 pw = NULL; 626 } 627 if (as != NULL) 628 auth_close(as); 629 #endif 630 #endif 631 if (pw != NULL) 632 return (pwcopy(pw)); 633 return (NULL); 634 } 635 636 /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */ 637 int 638 auth_key_is_revoked(struct sshkey *key) 639 { 640 char *fp = NULL; 641 int r; 642 643 if (options.revoked_keys_file == NULL) 644 return 0; 645 if ((fp = sshkey_fingerprint(key, options.fingerprint_hash, 646 SSH_FP_DEFAULT)) == NULL) { 647 r = SSH_ERR_ALLOC_FAIL; 648 error("%s: fingerprint key: %s", __func__, ssh_err(r)); 649 goto out; 650 } 651 652 r = sshkey_check_revoked(key, options.revoked_keys_file); 653 switch (r) { 654 case 0: 655 break; /* not revoked */ 656 case SSH_ERR_KEY_REVOKED: 657 error("Authentication key %s %s revoked by file %s", 658 sshkey_type(key), fp, options.revoked_keys_file); 659 goto out; 660 default: 661 error("Error checking authentication key %s %s in " 662 "revoked keys file %s: %s", sshkey_type(key), fp, 663 options.revoked_keys_file, ssh_err(r)); 664 goto out; 665 } 666 667 /* Success */ 668 r = 0; 669 670 out: 671 free(fp); 672 return r == 0 ? 0 : 1; 673 } 674 675 void 676 auth_debug_add(const char *fmt,...) 677 { 678 char buf[1024]; 679 va_list args; 680 int r; 681 682 if (auth_debug == NULL) 683 return; 684 685 va_start(args, fmt); 686 vsnprintf(buf, sizeof(buf), fmt, args); 687 va_end(args); 688 if ((r = sshbuf_put_cstring(auth_debug, buf)) != 0) 689 fatal("%s: sshbuf_put_cstring: %s", __func__, ssh_err(r)); 690 } 691 692 void 693 auth_debug_send(void) 694 { 695 struct ssh *ssh = active_state; /* XXX */ 696 char *msg; 697 int r; 698 699 if (auth_debug == NULL) 700 return; 701 while (sshbuf_len(auth_debug) != 0) { 702 if ((r = sshbuf_get_cstring(auth_debug, &msg, NULL)) != 0) 703 fatal("%s: sshbuf_get_cstring: %s", 704 __func__, ssh_err(r)); 705 ssh_packet_send_debug(ssh, "%s", msg); 706 free(msg); 707 } 708 } 709 710 void 711 auth_debug_reset(void) 712 { 713 if (auth_debug != NULL) 714 sshbuf_reset(auth_debug); 715 else if ((auth_debug = sshbuf_new()) == NULL) 716 fatal("%s: sshbuf_new failed", __func__); 717 } 718 719 struct passwd * 720 fakepw(void) 721 { 722 static struct passwd fake; 723 724 memset(&fake, 0, sizeof(fake)); 725 fake.pw_name = "NOUSER"; 726 fake.pw_passwd = 727 "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK"; 728 #ifdef HAVE_STRUCT_PASSWD_PW_GECOS 729 fake.pw_gecos = "NOUSER"; 730 #endif 731 fake.pw_uid = privsep_pw == NULL ? (uid_t)-1 : privsep_pw->pw_uid; 732 fake.pw_gid = privsep_pw == NULL ? (gid_t)-1 : privsep_pw->pw_gid; 733 #ifdef HAVE_STRUCT_PASSWD_PW_CLASS 734 fake.pw_class = ""; 735 #endif 736 fake.pw_dir = "/nonexist"; 737 fake.pw_shell = "/nonexist"; 738 739 return (&fake); 740 } 741 742 /* 743 * Returns the remote DNS hostname as a string. The returned string must not 744 * be freed. NB. this will usually trigger a DNS query the first time it is 745 * called. 746 * This function does additional checks on the hostname to mitigate some 747 * attacks on legacy rhosts-style authentication. 748 * XXX is RhostsRSAAuthentication vulnerable to these? 749 * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?) 750 */ 751 752 static char * 753 remote_hostname(struct ssh *ssh) 754 { 755 struct sockaddr_storage from; 756 socklen_t fromlen; 757 struct addrinfo hints, *ai, *aitop; 758 char name[NI_MAXHOST], ntop2[NI_MAXHOST]; 759 const char *ntop = ssh_remote_ipaddr(ssh); 760 761 /* Get IP address of client. */ 762 fromlen = sizeof(from); 763 memset(&from, 0, sizeof(from)); 764 if (getpeername(ssh_packet_get_connection_in(ssh), 765 (struct sockaddr *)&from, &fromlen) < 0) { 766 debug("getpeername failed: %.100s", strerror(errno)); 767 return strdup(ntop); 768 } 769 770 ipv64_normalise_mapped(&from, &fromlen); 771 if (from.ss_family == AF_INET6) 772 fromlen = sizeof(struct sockaddr_in6); 773 774 debug3("Trying to reverse map address %.100s.", ntop); 775 /* Map the IP address to a host name. */ 776 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), 777 NULL, 0, NI_NAMEREQD) != 0) { 778 /* Host name not found. Use ip address. */ 779 return strdup(ntop); 780 } 781 782 /* 783 * if reverse lookup result looks like a numeric hostname, 784 * someone is trying to trick us by PTR record like following: 785 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5 786 */ 787 memset(&hints, 0, sizeof(hints)); 788 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 789 hints.ai_flags = AI_NUMERICHOST; 790 if (getaddrinfo(name, NULL, &hints, &ai) == 0) { 791 logit("Nasty PTR record \"%s\" is set up for %s, ignoring", 792 name, ntop); 793 freeaddrinfo(ai); 794 return strdup(ntop); 795 } 796 797 /* Names are stored in lowercase. */ 798 lowercase(name); 799 800 /* 801 * Map it back to an IP address and check that the given 802 * address actually is an address of this host. This is 803 * necessary because anyone with access to a name server can 804 * define arbitrary names for an IP address. Mapping from 805 * name to IP address can be trusted better (but can still be 806 * fooled if the intruder has access to the name server of 807 * the domain). 808 */ 809 memset(&hints, 0, sizeof(hints)); 810 hints.ai_family = from.ss_family; 811 hints.ai_socktype = SOCK_STREAM; 812 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { 813 logit("reverse mapping checking getaddrinfo for %.700s " 814 "[%s] failed.", name, ntop); 815 return strdup(ntop); 816 } 817 /* Look for the address from the list of addresses. */ 818 for (ai = aitop; ai; ai = ai->ai_next) { 819 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, 820 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && 821 (strcmp(ntop, ntop2) == 0)) 822 break; 823 } 824 freeaddrinfo(aitop); 825 /* If we reached the end of the list, the address was not there. */ 826 if (ai == NULL) { 827 /* Address not found for the host name. */ 828 logit("Address %.100s maps to %.600s, but this does not " 829 "map back to the address.", ntop, name); 830 return strdup(ntop); 831 } 832 return strdup(name); 833 } 834 835 /* 836 * Return the canonical name of the host in the other side of the current 837 * connection. The host name is cached, so it is efficient to call this 838 * several times. 839 */ 840 841 const char * 842 auth_get_canonical_hostname(struct ssh *ssh, int use_dns) 843 { 844 static char *dnsname; 845 846 if (!use_dns) 847 return ssh_remote_ipaddr(ssh); 848 else if (dnsname != NULL) 849 return dnsname; 850 else { 851 dnsname = remote_hostname(ssh); 852 return dnsname; 853 } 854 } 855 856 /* 857 * Runs command in a subprocess with a minimal environment. 858 * Returns pid on success, 0 on failure. 859 * The child stdout and stderr maybe captured, left attached or sent to 860 * /dev/null depending on the contents of flags. 861 * "tag" is prepended to log messages. 862 * NB. "command" is only used for logging; the actual command executed is 863 * av[0]. 864 */ 865 pid_t 866 subprocess(const char *tag, struct passwd *pw, const char *command, 867 int ac, char **av, FILE **child, u_int flags) 868 { 869 FILE *f = NULL; 870 struct stat st; 871 int fd, devnull, p[2], i; 872 pid_t pid; 873 char *cp, errmsg[512]; 874 u_int envsize; 875 char **child_env; 876 877 if (child != NULL) 878 *child = NULL; 879 880 debug3("%s: %s command \"%s\" running as %s (flags 0x%x)", __func__, 881 tag, command, pw->pw_name, flags); 882 883 /* Check consistency */ 884 if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 && 885 (flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) { 886 error("%s: inconsistent flags", __func__); 887 return 0; 888 } 889 if (((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) != (child == NULL)) { 890 error("%s: inconsistent flags/output", __func__); 891 return 0; 892 } 893 894 /* 895 * If executing an explicit binary, then verify the it exists 896 * and appears safe-ish to execute 897 */ 898 if (*av[0] != '/') { 899 error("%s path is not absolute", tag); 900 return 0; 901 } 902 temporarily_use_uid(pw); 903 if (stat(av[0], &st) < 0) { 904 error("Could not stat %s \"%s\": %s", tag, 905 av[0], strerror(errno)); 906 restore_uid(); 907 return 0; 908 } 909 if (safe_path(av[0], &st, NULL, 0, errmsg, sizeof(errmsg)) != 0) { 910 error("Unsafe %s \"%s\": %s", tag, av[0], errmsg); 911 restore_uid(); 912 return 0; 913 } 914 /* Prepare to keep the child's stdout if requested */ 915 if (pipe(p) != 0) { 916 error("%s: pipe: %s", tag, strerror(errno)); 917 restore_uid(); 918 return 0; 919 } 920 restore_uid(); 921 922 switch ((pid = fork())) { 923 case -1: /* error */ 924 error("%s: fork: %s", tag, strerror(errno)); 925 close(p[0]); 926 close(p[1]); 927 return 0; 928 case 0: /* child */ 929 /* Prepare a minimal environment for the child. */ 930 envsize = 5; 931 child_env = xcalloc(sizeof(*child_env), envsize); 932 child_set_env(&child_env, &envsize, "PATH", _PATH_STDPATH); 933 child_set_env(&child_env, &envsize, "USER", pw->pw_name); 934 child_set_env(&child_env, &envsize, "LOGNAME", pw->pw_name); 935 child_set_env(&child_env, &envsize, "HOME", pw->pw_dir); 936 if ((cp = getenv("LANG")) != NULL) 937 child_set_env(&child_env, &envsize, "LANG", cp); 938 939 for (i = 0; i < NSIG; i++) 940 signal(i, SIG_DFL); 941 942 if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) { 943 error("%s: open %s: %s", tag, _PATH_DEVNULL, 944 strerror(errno)); 945 _exit(1); 946 } 947 if (dup2(devnull, STDIN_FILENO) == -1) { 948 error("%s: dup2: %s", tag, strerror(errno)); 949 _exit(1); 950 } 951 952 /* Set up stdout as requested; leave stderr in place for now. */ 953 fd = -1; 954 if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) 955 fd = p[1]; 956 else if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0) 957 fd = devnull; 958 if (fd != -1 && dup2(fd, STDOUT_FILENO) == -1) { 959 error("%s: dup2: %s", tag, strerror(errno)); 960 _exit(1); 961 } 962 closefrom(STDERR_FILENO + 1); 963 964 /* Don't use permanently_set_uid() here to avoid fatal() */ 965 if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0) { 966 error("%s: setresgid %u: %s", tag, (u_int)pw->pw_gid, 967 strerror(errno)); 968 _exit(1); 969 } 970 if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0) { 971 error("%s: setresuid %u: %s", tag, (u_int)pw->pw_uid, 972 strerror(errno)); 973 _exit(1); 974 } 975 /* stdin is pointed to /dev/null at this point */ 976 if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 && 977 dup2(STDIN_FILENO, STDERR_FILENO) == -1) { 978 error("%s: dup2: %s", tag, strerror(errno)); 979 _exit(1); 980 } 981 982 execve(av[0], av, child_env); 983 error("%s exec \"%s\": %s", tag, command, strerror(errno)); 984 _exit(127); 985 default: /* parent */ 986 break; 987 } 988 989 close(p[1]); 990 if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) 991 close(p[0]); 992 else if ((f = fdopen(p[0], "r")) == NULL) { 993 error("%s: fdopen: %s", tag, strerror(errno)); 994 close(p[0]); 995 /* Don't leave zombie child */ 996 kill(pid, SIGTERM); 997 while (waitpid(pid, NULL, 0) == -1 && errno == EINTR) 998 ; 999 return 0; 1000 } 1001 /* Success */ 1002 debug3("%s: %s pid %ld", __func__, tag, (long)pid); 1003 if (child != NULL) 1004 *child = f; 1005 return pid; 1006 } 1007 1008 /* These functions link key/cert options to the auth framework */ 1009 1010 /* Log sshauthopt options locally and (optionally) for remote transmission */ 1011 void 1012 auth_log_authopts(const char *loc, const struct sshauthopt *opts, int do_remote) 1013 { 1014 int do_env = options.permit_user_env && opts->nenv > 0; 1015 int do_permitopen = opts->npermitopen > 0 && 1016 (options.allow_tcp_forwarding & FORWARD_LOCAL) != 0; 1017 int do_permitlisten = opts->npermitlisten > 0 && 1018 (options.allow_tcp_forwarding & FORWARD_REMOTE) != 0; 1019 size_t i; 1020 char msg[1024], buf[64]; 1021 1022 snprintf(buf, sizeof(buf), "%d", opts->force_tun_device); 1023 /* Try to keep this alphabetically sorted */ 1024 snprintf(msg, sizeof(msg), "key options:%s%s%s%s%s%s%s%s%s%s%s%s%s", 1025 opts->permit_agent_forwarding_flag ? " agent-forwarding" : "", 1026 opts->force_command == NULL ? "" : " command", 1027 do_env ? " environment" : "", 1028 opts->valid_before == 0 ? "" : "expires", 1029 do_permitopen ? " permitopen" : "", 1030 do_permitlisten ? " permitlisten" : "", 1031 opts->permit_port_forwarding_flag ? " port-forwarding" : "", 1032 opts->cert_principals == NULL ? "" : " principals", 1033 opts->permit_pty_flag ? " pty" : "", 1034 opts->force_tun_device == -1 ? "" : " tun=", 1035 opts->force_tun_device == -1 ? "" : buf, 1036 opts->permit_user_rc ? " user-rc" : "", 1037 opts->permit_x11_forwarding_flag ? " x11-forwarding" : ""); 1038 1039 debug("%s: %s", loc, msg); 1040 if (do_remote) 1041 auth_debug_add("%s: %s", loc, msg); 1042 1043 if (options.permit_user_env) { 1044 for (i = 0; i < opts->nenv; i++) { 1045 debug("%s: environment: %s", loc, opts->env[i]); 1046 if (do_remote) { 1047 auth_debug_add("%s: environment: %s", 1048 loc, opts->env[i]); 1049 } 1050 } 1051 } 1052 1053 /* Go into a little more details for the local logs. */ 1054 if (opts->valid_before != 0) { 1055 format_absolute_time(opts->valid_before, buf, sizeof(buf)); 1056 debug("%s: expires at %s", loc, buf); 1057 } 1058 if (opts->cert_principals != NULL) { 1059 debug("%s: authorized principals: \"%s\"", 1060 loc, opts->cert_principals); 1061 } 1062 if (opts->force_command != NULL) 1063 debug("%s: forced command: \"%s\"", loc, opts->force_command); 1064 if (do_permitopen) { 1065 for (i = 0; i < opts->npermitopen; i++) { 1066 debug("%s: permitted open: %s", 1067 loc, opts->permitopen[i]); 1068 } 1069 } 1070 if (do_permitlisten) { 1071 for (i = 0; i < opts->npermitlisten; i++) { 1072 debug("%s: permitted listen: %s", 1073 loc, opts->permitlisten[i]); 1074 } 1075 } 1076 } 1077 1078 /* Activate a new set of key/cert options; merging with what is there. */ 1079 int 1080 auth_activate_options(struct ssh *ssh, struct sshauthopt *opts) 1081 { 1082 struct sshauthopt *old = auth_opts; 1083 const char *emsg = NULL; 1084 1085 debug("%s: setting new authentication options", __func__); 1086 if ((auth_opts = sshauthopt_merge(old, opts, &emsg)) == NULL) { 1087 error("Inconsistent authentication options: %s", emsg); 1088 return -1; 1089 } 1090 return 0; 1091 } 1092 1093 /* Disable forwarding, etc for the session */ 1094 void 1095 auth_restrict_session(struct ssh *ssh) 1096 { 1097 struct sshauthopt *restricted; 1098 1099 debug("%s: restricting session", __func__); 1100 1101 /* A blank sshauthopt defaults to permitting nothing */ 1102 restricted = sshauthopt_new(); 1103 restricted->permit_pty_flag = 1; 1104 restricted->restricted = 1; 1105 1106 if (auth_activate_options(ssh, restricted) != 0) 1107 fatal("%s: failed to restrict session", __func__); 1108 sshauthopt_free(restricted); 1109 } 1110 1111 int 1112 auth_authorise_keyopts(struct ssh *ssh, struct passwd *pw, 1113 struct sshauthopt *opts, int allow_cert_authority, const char *loc) 1114 { 1115 const char *remote_ip = ssh_remote_ipaddr(ssh); 1116 const char *remote_host = auth_get_canonical_hostname(ssh, 1117 options.use_dns); 1118 time_t now = time(NULL); 1119 char buf[64]; 1120 1121 /* 1122 * Check keys/principals file expiry time. 1123 * NB. validity interval in certificate is handled elsewhere. 1124 */ 1125 if (opts->valid_before && now > 0 && 1126 opts->valid_before < (uint64_t)now) { 1127 format_absolute_time(opts->valid_before, buf, sizeof(buf)); 1128 debug("%s: entry expired at %s", loc, buf); 1129 auth_debug_add("%s: entry expired at %s", loc, buf); 1130 return -1; 1131 } 1132 /* Consistency checks */ 1133 if (opts->cert_principals != NULL && !opts->cert_authority) { 1134 debug("%s: principals on non-CA key", loc); 1135 auth_debug_add("%s: principals on non-CA key", loc); 1136 /* deny access */ 1137 return -1; 1138 } 1139 /* cert-authority flag isn't valid in authorized_principals files */ 1140 if (!allow_cert_authority && opts->cert_authority) { 1141 debug("%s: cert-authority flag invalid here", loc); 1142 auth_debug_add("%s: cert-authority flag invalid here", loc); 1143 /* deny access */ 1144 return -1; 1145 } 1146 1147 /* Perform from= checks */ 1148 if (opts->required_from_host_keys != NULL) { 1149 switch (match_host_and_ip(remote_host, remote_ip, 1150 opts->required_from_host_keys )) { 1151 case 1: 1152 /* Host name matches. */ 1153 break; 1154 case -1: 1155 default: 1156 debug("%s: invalid from criteria", loc); 1157 auth_debug_add("%s: invalid from criteria", loc); 1158 /* FALLTHROUGH */ 1159 case 0: 1160 logit("%s: Authentication tried for %.100s with " 1161 "correct key but not from a permitted " 1162 "host (host=%.200s, ip=%.200s, required=%.200s).", 1163 loc, pw->pw_name, remote_host, remote_ip, 1164 opts->required_from_host_keys); 1165 auth_debug_add("%s: Your host '%.200s' is not " 1166 "permitted to use this key for login.", 1167 loc, remote_host); 1168 /* deny access */ 1169 return -1; 1170 } 1171 } 1172 /* Check source-address restriction from certificate */ 1173 if (opts->required_from_host_cert != NULL) { 1174 switch (addr_match_cidr_list(remote_ip, 1175 opts->required_from_host_cert)) { 1176 case 1: 1177 /* accepted */ 1178 break; 1179 case -1: 1180 default: 1181 /* invalid */ 1182 error("%s: Certificate source-address invalid", 1183 loc); 1184 /* FALLTHROUGH */ 1185 case 0: 1186 logit("%s: Authentication tried for %.100s with valid " 1187 "certificate but not from a permitted source " 1188 "address (%.200s).", loc, pw->pw_name, remote_ip); 1189 auth_debug_add("%s: Your address '%.200s' is not " 1190 "permitted to use this certificate for login.", 1191 loc, remote_ip); 1192 return -1; 1193 } 1194 } 1195 /* 1196 * 1197 * XXX this is spammy. We should report remotely only for keys 1198 * that are successful in actual auth attempts, and not PK_OK 1199 * tests. 1200 */ 1201 auth_log_authopts(loc, opts, 1); 1202 1203 return 0; 1204 } 1205