1 /* $OpenBSD: auth.c,v 1.138 2019/01/19 21:41:18 djm Exp $ */ 2 /* 3 * Copyright (c) 2000 Markus Friedl. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 */ 25 26 #include "includes.h" 27 28 #include <sys/types.h> 29 #include <sys/stat.h> 30 #include <sys/socket.h> 31 #include <sys/wait.h> 32 33 #include <netinet/in.h> 34 35 #include <errno.h> 36 #include <fcntl.h> 37 #ifdef HAVE_PATHS_H 38 # include <paths.h> 39 #endif 40 #include <pwd.h> 41 #ifdef HAVE_LOGIN_H 42 #include <login.h> 43 #endif 44 #ifdef USE_SHADOW 45 #include <shadow.h> 46 #endif 47 #include <stdarg.h> 48 #include <stdio.h> 49 #include <string.h> 50 #include <unistd.h> 51 #include <limits.h> 52 #include <netdb.h> 53 #include <time.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 80 /* import */ 81 extern ServerOptions options; 82 extern int use_privsep; 83 extern struct sshbuf *loginmsg; 84 extern struct passwd *privsep_pw; 85 extern struct sshauthopt *auth_opts; 86 87 /* Debugging messages */ 88 static struct sshbuf *auth_debug; 89 90 /* 91 * Check if the user is allowed to log in via ssh. If user is listed 92 * in DenyUsers or one of user's groups is listed in DenyGroups, false 93 * will be returned. If AllowUsers isn't empty and user isn't listed 94 * there, or if AllowGroups isn't empty and one of user's groups isn't 95 * listed there, false will be returned. 96 * If the user's shell is not executable, false will be returned. 97 * Otherwise true is returned. 98 */ 99 int 100 allowed_user(struct ssh *ssh, struct passwd * pw) 101 { 102 struct stat st; 103 const char *hostname = NULL, *ipaddr = NULL, *passwd = NULL; 104 u_int i; 105 int r; 106 #ifdef USE_SHADOW 107 struct spwd *spw = NULL; 108 #endif 109 110 /* Shouldn't be called if pw is NULL, but better safe than sorry... */ 111 if (!pw || !pw->pw_name) 112 return 0; 113 114 #ifdef USE_SHADOW 115 if (!options.use_pam) 116 spw = getspnam(pw->pw_name); 117 #ifdef HAS_SHADOW_EXPIRE 118 if (!options.use_pam && spw != NULL && auth_shadow_acctexpired(spw)) 119 return 0; 120 #endif /* HAS_SHADOW_EXPIRE */ 121 #endif /* USE_SHADOW */ 122 123 /* grab passwd field for locked account check */ 124 passwd = pw->pw_passwd; 125 #ifdef USE_SHADOW 126 if (spw != NULL) 127 #ifdef USE_LIBIAF 128 passwd = get_iaf_password(pw); 129 #else 130 passwd = spw->sp_pwdp; 131 #endif /* USE_LIBIAF */ 132 #endif 133 134 /* check for locked account */ 135 if (!options.use_pam && passwd && *passwd) { 136 int locked = 0; 137 138 #ifdef LOCKED_PASSWD_STRING 139 if (strcmp(passwd, LOCKED_PASSWD_STRING) == 0) 140 locked = 1; 141 #endif 142 #ifdef LOCKED_PASSWD_PREFIX 143 if (strncmp(passwd, LOCKED_PASSWD_PREFIX, 144 strlen(LOCKED_PASSWD_PREFIX)) == 0) 145 locked = 1; 146 #endif 147 #ifdef LOCKED_PASSWD_SUBSTR 148 if (strstr(passwd, LOCKED_PASSWD_SUBSTR)) 149 locked = 1; 150 #endif 151 #ifdef USE_LIBIAF 152 free((void *) passwd); 153 #endif /* USE_LIBIAF */ 154 if (locked) { 155 logit("User %.100s not allowed because account is locked", 156 pw->pw_name); 157 return 0; 158 } 159 } 160 161 /* 162 * Deny if shell does not exist or is not executable unless we 163 * are chrooting. 164 */ 165 if (options.chroot_directory == NULL || 166 strcasecmp(options.chroot_directory, "none") == 0) { 167 char *shell = xstrdup((pw->pw_shell[0] == '\0') ? 168 _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */ 169 170 if (stat(shell, &st) != 0) { 171 logit("User %.100s not allowed because shell %.100s " 172 "does not exist", pw->pw_name, shell); 173 free(shell); 174 return 0; 175 } 176 if (S_ISREG(st.st_mode) == 0 || 177 (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { 178 logit("User %.100s not allowed because shell %.100s " 179 "is not executable", pw->pw_name, shell); 180 free(shell); 181 return 0; 182 } 183 free(shell); 184 } 185 186 if (options.num_deny_users > 0 || options.num_allow_users > 0 || 187 options.num_deny_groups > 0 || options.num_allow_groups > 0) { 188 hostname = auth_get_canonical_hostname(ssh, options.use_dns); 189 ipaddr = ssh_remote_ipaddr(ssh); 190 } 191 192 /* Return false if user is listed in DenyUsers */ 193 if (options.num_deny_users > 0) { 194 for (i = 0; i < options.num_deny_users; i++) { 195 r = match_user(pw->pw_name, hostname, ipaddr, 196 options.deny_users[i]); 197 if (r < 0) { 198 fatal("Invalid DenyUsers pattern \"%.100s\"", 199 options.deny_users[i]); 200 } else if (r != 0) { 201 logit("User %.100s from %.100s not allowed " 202 "because listed in DenyUsers", 203 pw->pw_name, hostname); 204 return 0; 205 } 206 } 207 } 208 /* Return false if AllowUsers isn't empty and user isn't listed there */ 209 if (options.num_allow_users > 0) { 210 for (i = 0; i < options.num_allow_users; i++) { 211 r = match_user(pw->pw_name, hostname, ipaddr, 212 options.allow_users[i]); 213 if (r < 0) { 214 fatal("Invalid AllowUsers pattern \"%.100s\"", 215 options.allow_users[i]); 216 } else if (r == 1) 217 break; 218 } 219 /* i < options.num_allow_users iff we break for loop */ 220 if (i >= options.num_allow_users) { 221 logit("User %.100s from %.100s not allowed because " 222 "not listed in AllowUsers", pw->pw_name, hostname); 223 return 0; 224 } 225 } 226 if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { 227 /* Get the user's group access list (primary and supplementary) */ 228 if (ga_init(pw->pw_name, pw->pw_gid) == 0) { 229 logit("User %.100s from %.100s not allowed because " 230 "not in any group", pw->pw_name, hostname); 231 return 0; 232 } 233 234 /* Return false if one of user's groups is listed in DenyGroups */ 235 if (options.num_deny_groups > 0) 236 if (ga_match(options.deny_groups, 237 options.num_deny_groups)) { 238 ga_free(); 239 logit("User %.100s from %.100s not allowed " 240 "because a group is listed in DenyGroups", 241 pw->pw_name, hostname); 242 return 0; 243 } 244 /* 245 * Return false if AllowGroups isn't empty and one of user's groups 246 * isn't listed there 247 */ 248 if (options.num_allow_groups > 0) 249 if (!ga_match(options.allow_groups, 250 options.num_allow_groups)) { 251 ga_free(); 252 logit("User %.100s from %.100s not allowed " 253 "because none of user's groups are listed " 254 "in AllowGroups", pw->pw_name, hostname); 255 return 0; 256 } 257 ga_free(); 258 } 259 260 #ifdef CUSTOM_SYS_AUTH_ALLOWED_USER 261 if (!sys_auth_allowed_user(pw, loginmsg)) 262 return 0; 263 #endif 264 265 /* We found no reason not to let this user try to log on... */ 266 return 1; 267 } 268 269 /* 270 * Formats any key left in authctxt->auth_method_key for inclusion in 271 * auth_log()'s message. Also includes authxtct->auth_method_info if present. 272 */ 273 static char * 274 format_method_key(Authctxt *authctxt) 275 { 276 const struct sshkey *key = authctxt->auth_method_key; 277 const char *methinfo = authctxt->auth_method_info; 278 char *fp, *cafp, *ret = NULL; 279 280 if (key == NULL) 281 return NULL; 282 283 if (sshkey_is_cert(key)) { 284 fp = sshkey_fingerprint(key, 285 options.fingerprint_hash, SSH_FP_DEFAULT); 286 cafp = sshkey_fingerprint(key->cert->signature_key, 287 options.fingerprint_hash, SSH_FP_DEFAULT); 288 xasprintf(&ret, "%s %s ID %s (serial %llu) CA %s %s%s%s", 289 sshkey_type(key), fp == NULL ? "(null)" : fp, 290 key->cert->key_id, 291 (unsigned long long)key->cert->serial, 292 sshkey_type(key->cert->signature_key), 293 cafp == NULL ? "(null)" : cafp, 294 methinfo == NULL ? "" : ", ", 295 methinfo == NULL ? "" : methinfo); 296 free(fp); 297 free(cafp); 298 } else { 299 fp = sshkey_fingerprint(key, options.fingerprint_hash, 300 SSH_FP_DEFAULT); 301 xasprintf(&ret, "%s %s%s%s", sshkey_type(key), 302 fp == NULL ? "(null)" : fp, 303 methinfo == NULL ? "" : ", ", 304 methinfo == NULL ? "" : methinfo); 305 free(fp); 306 } 307 return ret; 308 } 309 310 void 311 auth_log(struct ssh *ssh, int authenticated, int partial, 312 const char *method, const char *submethod) 313 { 314 Authctxt *authctxt = (Authctxt *)ssh->authctxt; 315 int level = SYSLOG_LEVEL_VERBOSE; 316 const char *authmsg; 317 char *extra = NULL; 318 319 if (use_privsep && !mm_is_monitor() && !authctxt->postponed) 320 return; 321 322 /* Raise logging level */ 323 if (authenticated == 1 || 324 !authctxt->valid || 325 authctxt->failures >= options.max_authtries / 2 || 326 strcmp(method, "password") == 0) 327 level = SYSLOG_LEVEL_INFO; 328 329 if (authctxt->postponed) 330 authmsg = "Postponed"; 331 else if (partial) 332 authmsg = "Partial"; 333 else 334 authmsg = authenticated ? "Accepted" : "Failed"; 335 336 if ((extra = format_method_key(authctxt)) == NULL) { 337 if (authctxt->auth_method_info != NULL) 338 extra = xstrdup(authctxt->auth_method_info); 339 } 340 341 do_log2(level, "%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s", 342 authmsg, 343 method, 344 submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod, 345 authctxt->valid ? "" : "invalid user ", 346 authctxt->user, 347 ssh_remote_ipaddr(ssh), 348 ssh_remote_port(ssh), 349 extra != NULL ? ": " : "", 350 extra != NULL ? extra : ""); 351 352 free(extra); 353 354 #ifdef CUSTOM_FAILED_LOGIN 355 if (authenticated == 0 && !authctxt->postponed && 356 (strcmp(method, "password") == 0 || 357 strncmp(method, "keyboard-interactive", 20) == 0 || 358 strcmp(method, "challenge-response") == 0)) 359 record_failed_login(ssh, authctxt->user, 360 auth_get_canonical_hostname(ssh, options.use_dns), "ssh"); 361 # ifdef WITH_AIXAUTHENTICATE 362 if (authenticated) 363 sys_auth_record_login(authctxt->user, 364 auth_get_canonical_hostname(ssh, options.use_dns), "ssh", 365 loginmsg); 366 # endif 367 #endif 368 #ifdef SSH_AUDIT_EVENTS 369 if (authenticated == 0 && !authctxt->postponed) 370 audit_event(ssh, audit_classify_auth(method)); 371 #endif 372 } 373 374 375 void 376 auth_maxtries_exceeded(struct ssh *ssh) 377 { 378 Authctxt *authctxt = (Authctxt *)ssh->authctxt; 379 380 error("maximum authentication attempts exceeded for " 381 "%s%.100s from %.200s port %d ssh2", 382 authctxt->valid ? "" : "invalid user ", 383 authctxt->user, 384 ssh_remote_ipaddr(ssh), 385 ssh_remote_port(ssh)); 386 ssh_packet_disconnect(ssh, "Too many authentication failures"); 387 /* NOTREACHED */ 388 } 389 390 /* 391 * Check whether root logins are disallowed. 392 */ 393 int 394 auth_root_allowed(struct ssh *ssh, const char *method) 395 { 396 switch (options.permit_root_login) { 397 case PERMIT_YES: 398 return 1; 399 case PERMIT_NO_PASSWD: 400 if (strcmp(method, "publickey") == 0 || 401 strcmp(method, "hostbased") == 0 || 402 strcmp(method, "gssapi-with-mic") == 0) 403 return 1; 404 break; 405 case PERMIT_FORCED_ONLY: 406 if (auth_opts->force_command != NULL) { 407 logit("Root login accepted for forced command."); 408 return 1; 409 } 410 break; 411 } 412 logit("ROOT LOGIN REFUSED FROM %.200s port %d", 413 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 414 return 0; 415 } 416 417 418 /* 419 * Given a template and a passwd structure, build a filename 420 * by substituting % tokenised options. Currently, %% becomes '%', 421 * %h becomes the home directory and %u the username. 422 * 423 * This returns a buffer allocated by xmalloc. 424 */ 425 char * 426 expand_authorized_keys(const char *filename, struct passwd *pw) 427 { 428 char *file, uidstr[32], ret[PATH_MAX]; 429 int i; 430 431 snprintf(uidstr, sizeof(uidstr), "%llu", 432 (unsigned long long)pw->pw_uid); 433 file = percent_expand(filename, "h", pw->pw_dir, 434 "u", pw->pw_name, "U", uidstr, (char *)NULL); 435 436 /* 437 * Ensure that filename starts anchored. If not, be backward 438 * compatible and prepend the '%h/' 439 */ 440 if (path_absolute(file)) 441 return (file); 442 443 i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file); 444 if (i < 0 || (size_t)i >= sizeof(ret)) 445 fatal("expand_authorized_keys: path too long"); 446 free(file); 447 return (xstrdup(ret)); 448 } 449 450 char * 451 authorized_principals_file(struct passwd *pw) 452 { 453 if (options.authorized_principals_file == NULL) 454 return NULL; 455 return expand_authorized_keys(options.authorized_principals_file, pw); 456 } 457 458 /* return ok if key exists in sysfile or userfile */ 459 HostStatus 460 check_key_in_hostfiles(struct passwd *pw, struct sshkey *key, const char *host, 461 const char *sysfile, const char *userfile) 462 { 463 char *user_hostfile; 464 struct stat st; 465 HostStatus host_status; 466 struct hostkeys *hostkeys; 467 const struct hostkey_entry *found; 468 469 hostkeys = init_hostkeys(); 470 load_hostkeys(hostkeys, host, sysfile); 471 if (userfile != NULL) { 472 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); 473 if (options.strict_modes && 474 (stat(user_hostfile, &st) == 0) && 475 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || 476 (st.st_mode & 022) != 0)) { 477 logit("Authentication refused for %.100s: " 478 "bad owner or modes for %.200s", 479 pw->pw_name, user_hostfile); 480 auth_debug_add("Ignored %.200s: bad ownership or modes", 481 user_hostfile); 482 } else { 483 temporarily_use_uid(pw); 484 load_hostkeys(hostkeys, host, user_hostfile); 485 restore_uid(); 486 } 487 free(user_hostfile); 488 } 489 host_status = check_key_in_hostkeys(hostkeys, key, &found); 490 if (host_status == HOST_REVOKED) 491 error("WARNING: revoked key for %s attempted authentication", 492 found->host); 493 else if (host_status == HOST_OK) 494 debug("%s: key for %s found at %s:%ld", __func__, 495 found->host, found->file, found->line); 496 else 497 debug("%s: key for host %s not found", __func__, host); 498 499 free_hostkeys(hostkeys); 500 501 return host_status; 502 } 503 504 static FILE * 505 auth_openfile(const char *file, struct passwd *pw, int strict_modes, 506 int log_missing, char *file_type) 507 { 508 char line[1024]; 509 struct stat st; 510 int fd; 511 FILE *f; 512 513 if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) { 514 if (log_missing || errno != ENOENT) 515 debug("Could not open %s '%s': %s", file_type, file, 516 strerror(errno)); 517 return NULL; 518 } 519 520 if (fstat(fd, &st) < 0) { 521 close(fd); 522 return NULL; 523 } 524 if (!S_ISREG(st.st_mode)) { 525 logit("User %s %s %s is not a regular file", 526 pw->pw_name, file_type, file); 527 close(fd); 528 return NULL; 529 } 530 unset_nonblock(fd); 531 if ((f = fdopen(fd, "r")) == NULL) { 532 close(fd); 533 return NULL; 534 } 535 if (strict_modes && 536 safe_path_fd(fileno(f), file, pw, line, sizeof(line)) != 0) { 537 fclose(f); 538 logit("Authentication refused: %s", line); 539 auth_debug_add("Ignored %s: %s", file_type, line); 540 return NULL; 541 } 542 543 return f; 544 } 545 546 547 FILE * 548 auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes) 549 { 550 return auth_openfile(file, pw, strict_modes, 1, "authorized keys"); 551 } 552 553 FILE * 554 auth_openprincipals(const char *file, struct passwd *pw, int strict_modes) 555 { 556 return auth_openfile(file, pw, strict_modes, 0, 557 "authorized principals"); 558 } 559 560 struct passwd * 561 getpwnamallow(struct ssh *ssh, const char *user) 562 { 563 #ifdef HAVE_LOGIN_CAP 564 extern login_cap_t *lc; 565 #ifdef BSD_AUTH 566 auth_session_t *as; 567 #endif 568 #endif 569 struct passwd *pw; 570 struct connection_info *ci; 571 572 ci = get_connection_info(ssh, 1, options.use_dns); 573 ci->user = user; 574 parse_server_match_config(&options, ci); 575 log_change_level(options.log_level); 576 process_permitopen(ssh, &options); 577 578 #if defined(_AIX) && defined(HAVE_SETAUTHDB) 579 aix_setauthdb(user); 580 #endif 581 582 pw = getpwnam(user); 583 584 #if defined(_AIX) && defined(HAVE_SETAUTHDB) 585 aix_restoreauthdb(); 586 #endif 587 if (pw == NULL) { 588 logit("Invalid user %.100s from %.100s port %d", 589 user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 590 #ifdef CUSTOM_FAILED_LOGIN 591 record_failed_login(ssh, user, 592 auth_get_canonical_hostname(ssh, options.use_dns), "ssh"); 593 #endif 594 #ifdef SSH_AUDIT_EVENTS 595 audit_event(ssh, SSH_INVALID_USER); 596 #endif /* SSH_AUDIT_EVENTS */ 597 return (NULL); 598 } 599 if (!allowed_user(ssh, pw)) 600 return (NULL); 601 #ifdef HAVE_LOGIN_CAP 602 if ((lc = login_getclass(pw->pw_class)) == NULL) { 603 debug("unable to get login class: %s", user); 604 return (NULL); 605 } 606 #ifdef BSD_AUTH 607 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || 608 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { 609 debug("Approval failure for %s", user); 610 pw = NULL; 611 } 612 if (as != NULL) 613 auth_close(as); 614 #endif 615 #endif 616 if (pw != NULL) 617 return (pwcopy(pw)); 618 return (NULL); 619 } 620 621 /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */ 622 int 623 auth_key_is_revoked(struct sshkey *key) 624 { 625 char *fp = NULL; 626 int r; 627 628 if (options.revoked_keys_file == NULL) 629 return 0; 630 if ((fp = sshkey_fingerprint(key, options.fingerprint_hash, 631 SSH_FP_DEFAULT)) == NULL) { 632 r = SSH_ERR_ALLOC_FAIL; 633 error("%s: fingerprint key: %s", __func__, ssh_err(r)); 634 goto out; 635 } 636 637 r = sshkey_check_revoked(key, options.revoked_keys_file); 638 switch (r) { 639 case 0: 640 break; /* not revoked */ 641 case SSH_ERR_KEY_REVOKED: 642 error("Authentication key %s %s revoked by file %s", 643 sshkey_type(key), fp, options.revoked_keys_file); 644 goto out; 645 default: 646 error("Error checking authentication key %s %s in " 647 "revoked keys file %s: %s", sshkey_type(key), fp, 648 options.revoked_keys_file, ssh_err(r)); 649 goto out; 650 } 651 652 /* Success */ 653 r = 0; 654 655 out: 656 free(fp); 657 return r == 0 ? 0 : 1; 658 } 659 660 void 661 auth_debug_add(const char *fmt,...) 662 { 663 char buf[1024]; 664 va_list args; 665 int r; 666 667 if (auth_debug == NULL) 668 return; 669 670 va_start(args, fmt); 671 vsnprintf(buf, sizeof(buf), fmt, args); 672 va_end(args); 673 if ((r = sshbuf_put_cstring(auth_debug, buf)) != 0) 674 fatal("%s: sshbuf_put_cstring: %s", __func__, ssh_err(r)); 675 } 676 677 void 678 auth_debug_send(struct ssh *ssh) 679 { 680 char *msg; 681 int r; 682 683 if (auth_debug == NULL) 684 return; 685 while (sshbuf_len(auth_debug) != 0) { 686 if ((r = sshbuf_get_cstring(auth_debug, &msg, NULL)) != 0) 687 fatal("%s: sshbuf_get_cstring: %s", 688 __func__, ssh_err(r)); 689 ssh_packet_send_debug(ssh, "%s", msg); 690 free(msg); 691 } 692 } 693 694 void 695 auth_debug_reset(void) 696 { 697 if (auth_debug != NULL) 698 sshbuf_reset(auth_debug); 699 else if ((auth_debug = sshbuf_new()) == NULL) 700 fatal("%s: sshbuf_new failed", __func__); 701 } 702 703 struct passwd * 704 fakepw(void) 705 { 706 static struct passwd fake; 707 708 memset(&fake, 0, sizeof(fake)); 709 fake.pw_name = "NOUSER"; 710 fake.pw_passwd = 711 "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK"; 712 #ifdef HAVE_STRUCT_PASSWD_PW_GECOS 713 fake.pw_gecos = "NOUSER"; 714 #endif 715 fake.pw_uid = privsep_pw == NULL ? (uid_t)-1 : privsep_pw->pw_uid; 716 fake.pw_gid = privsep_pw == NULL ? (gid_t)-1 : privsep_pw->pw_gid; 717 #ifdef HAVE_STRUCT_PASSWD_PW_CLASS 718 fake.pw_class = ""; 719 #endif 720 fake.pw_dir = "/nonexist"; 721 fake.pw_shell = "/nonexist"; 722 723 return (&fake); 724 } 725 726 /* 727 * Returns the remote DNS hostname as a string. The returned string must not 728 * be freed. NB. this will usually trigger a DNS query the first time it is 729 * called. 730 * This function does additional checks on the hostname to mitigate some 731 * attacks on legacy rhosts-style authentication. 732 * XXX is RhostsRSAAuthentication vulnerable to these? 733 * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?) 734 */ 735 736 static char * 737 remote_hostname(struct ssh *ssh) 738 { 739 struct sockaddr_storage from; 740 socklen_t fromlen; 741 struct addrinfo hints, *ai, *aitop; 742 char name[NI_MAXHOST], ntop2[NI_MAXHOST]; 743 const char *ntop = ssh_remote_ipaddr(ssh); 744 745 /* Get IP address of client. */ 746 fromlen = sizeof(from); 747 memset(&from, 0, sizeof(from)); 748 if (getpeername(ssh_packet_get_connection_in(ssh), 749 (struct sockaddr *)&from, &fromlen) < 0) { 750 debug("getpeername failed: %.100s", strerror(errno)); 751 return strdup(ntop); 752 } 753 754 ipv64_normalise_mapped(&from, &fromlen); 755 if (from.ss_family == AF_INET6) 756 fromlen = sizeof(struct sockaddr_in6); 757 758 debug3("Trying to reverse map address %.100s.", ntop); 759 /* Map the IP address to a host name. */ 760 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), 761 NULL, 0, NI_NAMEREQD) != 0) { 762 /* Host name not found. Use ip address. */ 763 return strdup(ntop); 764 } 765 766 /* 767 * if reverse lookup result looks like a numeric hostname, 768 * someone is trying to trick us by PTR record like following: 769 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5 770 */ 771 memset(&hints, 0, sizeof(hints)); 772 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 773 hints.ai_flags = AI_NUMERICHOST; 774 if (getaddrinfo(name, NULL, &hints, &ai) == 0) { 775 logit("Nasty PTR record \"%s\" is set up for %s, ignoring", 776 name, ntop); 777 freeaddrinfo(ai); 778 return strdup(ntop); 779 } 780 781 /* Names are stored in lowercase. */ 782 lowercase(name); 783 784 /* 785 * Map it back to an IP address and check that the given 786 * address actually is an address of this host. This is 787 * necessary because anyone with access to a name server can 788 * define arbitrary names for an IP address. Mapping from 789 * name to IP address can be trusted better (but can still be 790 * fooled if the intruder has access to the name server of 791 * the domain). 792 */ 793 memset(&hints, 0, sizeof(hints)); 794 hints.ai_family = from.ss_family; 795 hints.ai_socktype = SOCK_STREAM; 796 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { 797 logit("reverse mapping checking getaddrinfo for %.700s " 798 "[%s] failed.", name, ntop); 799 return strdup(ntop); 800 } 801 /* Look for the address from the list of addresses. */ 802 for (ai = aitop; ai; ai = ai->ai_next) { 803 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, 804 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && 805 (strcmp(ntop, ntop2) == 0)) 806 break; 807 } 808 freeaddrinfo(aitop); 809 /* If we reached the end of the list, the address was not there. */ 810 if (ai == NULL) { 811 /* Address not found for the host name. */ 812 logit("Address %.100s maps to %.600s, but this does not " 813 "map back to the address.", ntop, name); 814 return strdup(ntop); 815 } 816 return strdup(name); 817 } 818 819 /* 820 * Return the canonical name of the host in the other side of the current 821 * connection. The host name is cached, so it is efficient to call this 822 * several times. 823 */ 824 825 const char * 826 auth_get_canonical_hostname(struct ssh *ssh, int use_dns) 827 { 828 static char *dnsname; 829 830 if (!use_dns) 831 return ssh_remote_ipaddr(ssh); 832 else if (dnsname != NULL) 833 return dnsname; 834 else { 835 dnsname = remote_hostname(ssh); 836 return dnsname; 837 } 838 } 839 840 /* 841 * Runs command in a subprocess with a minimal environment. 842 * Returns pid on success, 0 on failure. 843 * The child stdout and stderr maybe captured, left attached or sent to 844 * /dev/null depending on the contents of flags. 845 * "tag" is prepended to log messages. 846 * NB. "command" is only used for logging; the actual command executed is 847 * av[0]. 848 */ 849 pid_t 850 subprocess(const char *tag, struct passwd *pw, const char *command, 851 int ac, char **av, FILE **child, u_int flags) 852 { 853 FILE *f = NULL; 854 struct stat st; 855 int fd, devnull, p[2], i; 856 pid_t pid; 857 char *cp, errmsg[512]; 858 u_int envsize; 859 char **child_env; 860 861 if (child != NULL) 862 *child = NULL; 863 864 debug3("%s: %s command \"%s\" running as %s (flags 0x%x)", __func__, 865 tag, command, pw->pw_name, flags); 866 867 /* Check consistency */ 868 if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 && 869 (flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) { 870 error("%s: inconsistent flags", __func__); 871 return 0; 872 } 873 if (((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) != (child == NULL)) { 874 error("%s: inconsistent flags/output", __func__); 875 return 0; 876 } 877 878 /* 879 * If executing an explicit binary, then verify the it exists 880 * and appears safe-ish to execute 881 */ 882 if (!path_absolute(av[0])) { 883 error("%s path is not absolute", tag); 884 return 0; 885 } 886 temporarily_use_uid(pw); 887 if (stat(av[0], &st) < 0) { 888 error("Could not stat %s \"%s\": %s", tag, 889 av[0], strerror(errno)); 890 restore_uid(); 891 return 0; 892 } 893 if (safe_path(av[0], &st, NULL, 0, errmsg, sizeof(errmsg)) != 0) { 894 error("Unsafe %s \"%s\": %s", tag, av[0], errmsg); 895 restore_uid(); 896 return 0; 897 } 898 /* Prepare to keep the child's stdout if requested */ 899 if (pipe(p) != 0) { 900 error("%s: pipe: %s", tag, strerror(errno)); 901 restore_uid(); 902 return 0; 903 } 904 restore_uid(); 905 906 switch ((pid = fork())) { 907 case -1: /* error */ 908 error("%s: fork: %s", tag, strerror(errno)); 909 close(p[0]); 910 close(p[1]); 911 return 0; 912 case 0: /* child */ 913 /* Prepare a minimal environment for the child. */ 914 envsize = 5; 915 child_env = xcalloc(sizeof(*child_env), envsize); 916 child_set_env(&child_env, &envsize, "PATH", _PATH_STDPATH); 917 child_set_env(&child_env, &envsize, "USER", pw->pw_name); 918 child_set_env(&child_env, &envsize, "LOGNAME", pw->pw_name); 919 child_set_env(&child_env, &envsize, "HOME", pw->pw_dir); 920 if ((cp = getenv("LANG")) != NULL) 921 child_set_env(&child_env, &envsize, "LANG", cp); 922 923 for (i = 0; i < NSIG; i++) 924 signal(i, SIG_DFL); 925 926 if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) { 927 error("%s: open %s: %s", tag, _PATH_DEVNULL, 928 strerror(errno)); 929 _exit(1); 930 } 931 if (dup2(devnull, STDIN_FILENO) == -1) { 932 error("%s: dup2: %s", tag, strerror(errno)); 933 _exit(1); 934 } 935 936 /* Set up stdout as requested; leave stderr in place for now. */ 937 fd = -1; 938 if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) 939 fd = p[1]; 940 else if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0) 941 fd = devnull; 942 if (fd != -1 && dup2(fd, STDOUT_FILENO) == -1) { 943 error("%s: dup2: %s", tag, strerror(errno)); 944 _exit(1); 945 } 946 closefrom(STDERR_FILENO + 1); 947 948 /* Don't use permanently_set_uid() here to avoid fatal() */ 949 if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0) { 950 error("%s: setresgid %u: %s", tag, (u_int)pw->pw_gid, 951 strerror(errno)); 952 _exit(1); 953 } 954 if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0) { 955 error("%s: setresuid %u: %s", tag, (u_int)pw->pw_uid, 956 strerror(errno)); 957 _exit(1); 958 } 959 /* stdin is pointed to /dev/null at this point */ 960 if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 && 961 dup2(STDIN_FILENO, STDERR_FILENO) == -1) { 962 error("%s: dup2: %s", tag, strerror(errno)); 963 _exit(1); 964 } 965 966 execve(av[0], av, child_env); 967 error("%s exec \"%s\": %s", tag, command, strerror(errno)); 968 _exit(127); 969 default: /* parent */ 970 break; 971 } 972 973 close(p[1]); 974 if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) 975 close(p[0]); 976 else if ((f = fdopen(p[0], "r")) == NULL) { 977 error("%s: fdopen: %s", tag, strerror(errno)); 978 close(p[0]); 979 /* Don't leave zombie child */ 980 kill(pid, SIGTERM); 981 while (waitpid(pid, NULL, 0) == -1 && errno == EINTR) 982 ; 983 return 0; 984 } 985 /* Success */ 986 debug3("%s: %s pid %ld", __func__, tag, (long)pid); 987 if (child != NULL) 988 *child = f; 989 return pid; 990 } 991 992 /* These functions link key/cert options to the auth framework */ 993 994 /* Log sshauthopt options locally and (optionally) for remote transmission */ 995 void 996 auth_log_authopts(const char *loc, const struct sshauthopt *opts, int do_remote) 997 { 998 int do_env = options.permit_user_env && opts->nenv > 0; 999 int do_permitopen = opts->npermitopen > 0 && 1000 (options.allow_tcp_forwarding & FORWARD_LOCAL) != 0; 1001 int do_permitlisten = opts->npermitlisten > 0 && 1002 (options.allow_tcp_forwarding & FORWARD_REMOTE) != 0; 1003 size_t i; 1004 char msg[1024], buf[64]; 1005 1006 snprintf(buf, sizeof(buf), "%d", opts->force_tun_device); 1007 /* Try to keep this alphabetically sorted */ 1008 snprintf(msg, sizeof(msg), "key options:%s%s%s%s%s%s%s%s%s%s%s%s%s", 1009 opts->permit_agent_forwarding_flag ? " agent-forwarding" : "", 1010 opts->force_command == NULL ? "" : " command", 1011 do_env ? " environment" : "", 1012 opts->valid_before == 0 ? "" : "expires", 1013 do_permitopen ? " permitopen" : "", 1014 do_permitlisten ? " permitlisten" : "", 1015 opts->permit_port_forwarding_flag ? " port-forwarding" : "", 1016 opts->cert_principals == NULL ? "" : " principals", 1017 opts->permit_pty_flag ? " pty" : "", 1018 opts->force_tun_device == -1 ? "" : " tun=", 1019 opts->force_tun_device == -1 ? "" : buf, 1020 opts->permit_user_rc ? " user-rc" : "", 1021 opts->permit_x11_forwarding_flag ? " x11-forwarding" : ""); 1022 1023 debug("%s: %s", loc, msg); 1024 if (do_remote) 1025 auth_debug_add("%s: %s", loc, msg); 1026 1027 if (options.permit_user_env) { 1028 for (i = 0; i < opts->nenv; i++) { 1029 debug("%s: environment: %s", loc, opts->env[i]); 1030 if (do_remote) { 1031 auth_debug_add("%s: environment: %s", 1032 loc, opts->env[i]); 1033 } 1034 } 1035 } 1036 1037 /* Go into a little more details for the local logs. */ 1038 if (opts->valid_before != 0) { 1039 format_absolute_time(opts->valid_before, buf, sizeof(buf)); 1040 debug("%s: expires at %s", loc, buf); 1041 } 1042 if (opts->cert_principals != NULL) { 1043 debug("%s: authorized principals: \"%s\"", 1044 loc, opts->cert_principals); 1045 } 1046 if (opts->force_command != NULL) 1047 debug("%s: forced command: \"%s\"", loc, opts->force_command); 1048 if (do_permitopen) { 1049 for (i = 0; i < opts->npermitopen; i++) { 1050 debug("%s: permitted open: %s", 1051 loc, opts->permitopen[i]); 1052 } 1053 } 1054 if (do_permitlisten) { 1055 for (i = 0; i < opts->npermitlisten; i++) { 1056 debug("%s: permitted listen: %s", 1057 loc, opts->permitlisten[i]); 1058 } 1059 } 1060 } 1061 1062 /* Activate a new set of key/cert options; merging with what is there. */ 1063 int 1064 auth_activate_options(struct ssh *ssh, struct sshauthopt *opts) 1065 { 1066 struct sshauthopt *old = auth_opts; 1067 const char *emsg = NULL; 1068 1069 debug("%s: setting new authentication options", __func__); 1070 if ((auth_opts = sshauthopt_merge(old, opts, &emsg)) == NULL) { 1071 error("Inconsistent authentication options: %s", emsg); 1072 return -1; 1073 } 1074 return 0; 1075 } 1076 1077 /* Disable forwarding, etc for the session */ 1078 void 1079 auth_restrict_session(struct ssh *ssh) 1080 { 1081 struct sshauthopt *restricted; 1082 1083 debug("%s: restricting session", __func__); 1084 1085 /* A blank sshauthopt defaults to permitting nothing */ 1086 restricted = sshauthopt_new(); 1087 restricted->permit_pty_flag = 1; 1088 restricted->restricted = 1; 1089 1090 if (auth_activate_options(ssh, restricted) != 0) 1091 fatal("%s: failed to restrict session", __func__); 1092 sshauthopt_free(restricted); 1093 } 1094 1095 int 1096 auth_authorise_keyopts(struct ssh *ssh, struct passwd *pw, 1097 struct sshauthopt *opts, int allow_cert_authority, const char *loc) 1098 { 1099 const char *remote_ip = ssh_remote_ipaddr(ssh); 1100 const char *remote_host = auth_get_canonical_hostname(ssh, 1101 options.use_dns); 1102 time_t now = time(NULL); 1103 char buf[64]; 1104 1105 /* 1106 * Check keys/principals file expiry time. 1107 * NB. validity interval in certificate is handled elsewhere. 1108 */ 1109 if (opts->valid_before && now > 0 && 1110 opts->valid_before < (uint64_t)now) { 1111 format_absolute_time(opts->valid_before, buf, sizeof(buf)); 1112 debug("%s: entry expired at %s", loc, buf); 1113 auth_debug_add("%s: entry expired at %s", loc, buf); 1114 return -1; 1115 } 1116 /* Consistency checks */ 1117 if (opts->cert_principals != NULL && !opts->cert_authority) { 1118 debug("%s: principals on non-CA key", loc); 1119 auth_debug_add("%s: principals on non-CA key", loc); 1120 /* deny access */ 1121 return -1; 1122 } 1123 /* cert-authority flag isn't valid in authorized_principals files */ 1124 if (!allow_cert_authority && opts->cert_authority) { 1125 debug("%s: cert-authority flag invalid here", loc); 1126 auth_debug_add("%s: cert-authority flag invalid here", loc); 1127 /* deny access */ 1128 return -1; 1129 } 1130 1131 /* Perform from= checks */ 1132 if (opts->required_from_host_keys != NULL) { 1133 switch (match_host_and_ip(remote_host, remote_ip, 1134 opts->required_from_host_keys )) { 1135 case 1: 1136 /* Host name matches. */ 1137 break; 1138 case -1: 1139 default: 1140 debug("%s: invalid from criteria", loc); 1141 auth_debug_add("%s: invalid from criteria", loc); 1142 /* FALLTHROUGH */ 1143 case 0: 1144 logit("%s: Authentication tried for %.100s with " 1145 "correct key but not from a permitted " 1146 "host (host=%.200s, ip=%.200s, required=%.200s).", 1147 loc, pw->pw_name, remote_host, remote_ip, 1148 opts->required_from_host_keys); 1149 auth_debug_add("%s: Your host '%.200s' is not " 1150 "permitted to use this key for login.", 1151 loc, remote_host); 1152 /* deny access */ 1153 return -1; 1154 } 1155 } 1156 /* Check source-address restriction from certificate */ 1157 if (opts->required_from_host_cert != NULL) { 1158 switch (addr_match_cidr_list(remote_ip, 1159 opts->required_from_host_cert)) { 1160 case 1: 1161 /* accepted */ 1162 break; 1163 case -1: 1164 default: 1165 /* invalid */ 1166 error("%s: Certificate source-address invalid", 1167 loc); 1168 /* FALLTHROUGH */ 1169 case 0: 1170 logit("%s: Authentication tried for %.100s with valid " 1171 "certificate but not from a permitted source " 1172 "address (%.200s).", loc, pw->pw_name, remote_ip); 1173 auth_debug_add("%s: Your address '%.200s' is not " 1174 "permitted to use this certificate for login.", 1175 loc, remote_ip); 1176 return -1; 1177 } 1178 } 1179 /* 1180 * 1181 * XXX this is spammy. We should report remotely only for keys 1182 * that are successful in actual auth attempts, and not PK_OK 1183 * tests. 1184 */ 1185 auth_log_authopts(loc, opts, 1); 1186 1187 return 0; 1188 } 1189