1 /* $OpenBSD: auth.c,v 1.146 2020/01/31 22:42:45 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 <stdlib.h> 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 #include <time.h> 55 56 #include "xmalloc.h" 57 #include "match.h" 58 #include "groupaccess.h" 59 #include "log.h" 60 #include "sshbuf.h" 61 #include "misc.h" 62 #include "servconf.h" 63 #include "sshkey.h" 64 #include "hostfile.h" 65 #include "auth.h" 66 #include "auth-options.h" 67 #include "canohost.h" 68 #include "uidswap.h" 69 #include "packet.h" 70 #include "loginrec.h" 71 #ifdef GSSAPI 72 #include "ssh-gss.h" 73 #endif 74 #include "authfile.h" 75 #include "monitor_wrap.h" 76 #include "ssherr.h" 77 #include "compat.h" 78 #include "channels.h" 79 80 /* import */ 81 extern ServerOptions options; 82 extern struct include_list includes; 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 ssh *ssh, struct passwd * pw) 102 { 103 struct stat st; 104 const char *hostname = NULL, *ipaddr = NULL, *passwd = NULL; 105 u_int i; 106 int r; 107 #ifdef USE_SHADOW 108 struct spwd *spw = NULL; 109 #endif 110 111 /* Shouldn't be called if pw is NULL, but better safe than sorry... */ 112 if (!pw || !pw->pw_name) 113 return 0; 114 115 #ifdef USE_SHADOW 116 if (!options.use_pam) 117 spw = getspnam(pw->pw_name); 118 #ifdef HAS_SHADOW_EXPIRE 119 if (!options.use_pam && spw != NULL && auth_shadow_acctexpired(spw)) 120 return 0; 121 #endif /* HAS_SHADOW_EXPIRE */ 122 #endif /* USE_SHADOW */ 123 124 /* grab passwd field for locked account check */ 125 passwd = pw->pw_passwd; 126 #ifdef USE_SHADOW 127 if (spw != NULL) 128 #ifdef USE_LIBIAF 129 passwd = get_iaf_password(pw); 130 #else 131 passwd = spw->sp_pwdp; 132 #endif /* USE_LIBIAF */ 133 #endif 134 135 /* check for locked account */ 136 if (!options.use_pam && passwd && *passwd) { 137 int locked = 0; 138 139 #ifdef LOCKED_PASSWD_STRING 140 if (strcmp(passwd, LOCKED_PASSWD_STRING) == 0) 141 locked = 1; 142 #endif 143 #ifdef LOCKED_PASSWD_PREFIX 144 if (strncmp(passwd, LOCKED_PASSWD_PREFIX, 145 strlen(LOCKED_PASSWD_PREFIX)) == 0) 146 locked = 1; 147 #endif 148 #ifdef LOCKED_PASSWD_SUBSTR 149 if (strstr(passwd, LOCKED_PASSWD_SUBSTR)) 150 locked = 1; 151 #endif 152 #ifdef USE_LIBIAF 153 free((void *) passwd); 154 #endif /* USE_LIBIAF */ 155 if (locked) { 156 logit("User %.100s not allowed because account is locked", 157 pw->pw_name); 158 return 0; 159 } 160 } 161 162 /* 163 * Deny if shell does not exist or is not executable unless we 164 * are chrooting. 165 */ 166 if (options.chroot_directory == NULL || 167 strcasecmp(options.chroot_directory, "none") == 0) { 168 char *shell = xstrdup((pw->pw_shell[0] == '\0') ? 169 _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */ 170 171 if (stat(shell, &st) == -1) { 172 logit("User %.100s not allowed because shell %.100s " 173 "does not exist", pw->pw_name, shell); 174 free(shell); 175 return 0; 176 } 177 if (S_ISREG(st.st_mode) == 0 || 178 (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { 179 logit("User %.100s not allowed because shell %.100s " 180 "is not executable", pw->pw_name, shell); 181 free(shell); 182 return 0; 183 } 184 free(shell); 185 } 186 187 if (options.num_deny_users > 0 || options.num_allow_users > 0 || 188 options.num_deny_groups > 0 || options.num_allow_groups > 0) { 189 hostname = auth_get_canonical_hostname(ssh, options.use_dns); 190 ipaddr = ssh_remote_ipaddr(ssh); 191 } 192 193 /* Return false if user is listed in DenyUsers */ 194 if (options.num_deny_users > 0) { 195 for (i = 0; i < options.num_deny_users; i++) { 196 r = match_user(pw->pw_name, hostname, ipaddr, 197 options.deny_users[i]); 198 if (r < 0) { 199 fatal("Invalid DenyUsers pattern \"%.100s\"", 200 options.deny_users[i]); 201 } else if (r != 0) { 202 logit("User %.100s from %.100s not allowed " 203 "because listed in DenyUsers", 204 pw->pw_name, hostname); 205 return 0; 206 } 207 } 208 } 209 /* Return false if AllowUsers isn't empty and user isn't listed there */ 210 if (options.num_allow_users > 0) { 211 for (i = 0; i < options.num_allow_users; i++) { 212 r = match_user(pw->pw_name, hostname, ipaddr, 213 options.allow_users[i]); 214 if (r < 0) { 215 fatal("Invalid AllowUsers pattern \"%.100s\"", 216 options.allow_users[i]); 217 } else if (r == 1) 218 break; 219 } 220 /* i < options.num_allow_users iff we break for loop */ 221 if (i >= options.num_allow_users) { 222 logit("User %.100s from %.100s not allowed because " 223 "not listed in AllowUsers", pw->pw_name, hostname); 224 return 0; 225 } 226 } 227 if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { 228 /* Get the user's group access list (primary and supplementary) */ 229 if (ga_init(pw->pw_name, pw->pw_gid) == 0) { 230 logit("User %.100s from %.100s not allowed because " 231 "not in any group", pw->pw_name, hostname); 232 return 0; 233 } 234 235 /* Return false if one of user's groups is listed in DenyGroups */ 236 if (options.num_deny_groups > 0) 237 if (ga_match(options.deny_groups, 238 options.num_deny_groups)) { 239 ga_free(); 240 logit("User %.100s from %.100s not allowed " 241 "because a group is listed in DenyGroups", 242 pw->pw_name, hostname); 243 return 0; 244 } 245 /* 246 * Return false if AllowGroups isn't empty and one of user's groups 247 * isn't listed there 248 */ 249 if (options.num_allow_groups > 0) 250 if (!ga_match(options.allow_groups, 251 options.num_allow_groups)) { 252 ga_free(); 253 logit("User %.100s from %.100s not allowed " 254 "because none of user's groups are listed " 255 "in AllowGroups", pw->pw_name, hostname); 256 return 0; 257 } 258 ga_free(); 259 } 260 261 #ifdef CUSTOM_SYS_AUTH_ALLOWED_USER 262 if (!sys_auth_allowed_user(pw, loginmsg)) 263 return 0; 264 #endif 265 266 /* We found no reason not to let this user try to log on... */ 267 return 1; 268 } 269 270 /* 271 * Formats any key left in authctxt->auth_method_key for inclusion in 272 * auth_log()'s message. Also includes authxtct->auth_method_info if present. 273 */ 274 static char * 275 format_method_key(Authctxt *authctxt) 276 { 277 const struct sshkey *key = authctxt->auth_method_key; 278 const char *methinfo = authctxt->auth_method_info; 279 char *fp, *cafp, *ret = NULL; 280 281 if (key == NULL) 282 return NULL; 283 284 if (sshkey_is_cert(key)) { 285 fp = sshkey_fingerprint(key, 286 options.fingerprint_hash, SSH_FP_DEFAULT); 287 cafp = sshkey_fingerprint(key->cert->signature_key, 288 options.fingerprint_hash, SSH_FP_DEFAULT); 289 xasprintf(&ret, "%s %s ID %s (serial %llu) CA %s %s%s%s", 290 sshkey_type(key), fp == NULL ? "(null)" : fp, 291 key->cert->key_id, 292 (unsigned long long)key->cert->serial, 293 sshkey_type(key->cert->signature_key), 294 cafp == NULL ? "(null)" : cafp, 295 methinfo == NULL ? "" : ", ", 296 methinfo == NULL ? "" : methinfo); 297 free(fp); 298 free(cafp); 299 } else { 300 fp = sshkey_fingerprint(key, options.fingerprint_hash, 301 SSH_FP_DEFAULT); 302 xasprintf(&ret, "%s %s%s%s", sshkey_type(key), 303 fp == NULL ? "(null)" : fp, 304 methinfo == NULL ? "" : ", ", 305 methinfo == NULL ? "" : methinfo); 306 free(fp); 307 } 308 return ret; 309 } 310 311 void 312 auth_log(struct ssh *ssh, int authenticated, int partial, 313 const char *method, const char *submethod) 314 { 315 Authctxt *authctxt = (Authctxt *)ssh->authctxt; 316 int level = SYSLOG_LEVEL_VERBOSE; 317 const char *authmsg; 318 char *extra = NULL; 319 320 if (use_privsep && !mm_is_monitor() && !authctxt->postponed) 321 return; 322 323 /* Raise logging level */ 324 if (authenticated == 1 || 325 !authctxt->valid || 326 authctxt->failures >= options.max_authtries / 2 || 327 strcmp(method, "password") == 0) 328 level = SYSLOG_LEVEL_INFO; 329 330 if (authctxt->postponed) 331 authmsg = "Postponed"; 332 else if (partial) 333 authmsg = "Partial"; 334 else 335 authmsg = authenticated ? "Accepted" : "Failed"; 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 do_log2(level, "%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(ssh, 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(ssh, audit_classify_auth(method)); 372 #endif 373 } 374 375 376 void 377 auth_maxtries_exceeded(struct ssh *ssh) 378 { 379 Authctxt *authctxt = (Authctxt *)ssh->authctxt; 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 ssh_packet_disconnect(ssh, "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 (path_absolute(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 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) == -1) { 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(struct ssh *ssh, const char *user) 563 { 564 #ifdef HAVE_LOGIN_CAP 565 extern login_cap_t *lc; 566 #ifdef BSD_AUTH 567 auth_session_t *as; 568 #endif 569 #endif 570 struct passwd *pw; 571 struct connection_info *ci; 572 573 ci = get_connection_info(ssh, 1, options.use_dns); 574 ci->user = user; 575 parse_server_match_config(&options, &includes, 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 if (pw == NULL) { 589 logit("Invalid user %.100s from %.100s port %d", 590 user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 591 #ifdef CUSTOM_FAILED_LOGIN 592 record_failed_login(ssh, user, 593 auth_get_canonical_hostname(ssh, options.use_dns), "ssh"); 594 #endif 595 #ifdef SSH_AUDIT_EVENTS 596 audit_event(ssh, SSH_INVALID_USER); 597 #endif /* SSH_AUDIT_EVENTS */ 598 return (NULL); 599 } 600 if (!allowed_user(ssh, pw)) 601 return (NULL); 602 #ifdef HAVE_LOGIN_CAP 603 if ((lc = login_getclass(pw->pw_class)) == NULL) { 604 debug("unable to get login class: %s", user); 605 return (NULL); 606 } 607 #ifdef BSD_AUTH 608 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || 609 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { 610 debug("Approval failure for %s", user); 611 pw = NULL; 612 } 613 if (as != NULL) 614 auth_close(as); 615 #endif 616 #endif 617 if (pw != NULL) 618 return (pwcopy(pw)); 619 return (NULL); 620 } 621 622 /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */ 623 int 624 auth_key_is_revoked(struct sshkey *key) 625 { 626 char *fp = NULL; 627 int r; 628 629 if (options.revoked_keys_file == NULL) 630 return 0; 631 if ((fp = sshkey_fingerprint(key, options.fingerprint_hash, 632 SSH_FP_DEFAULT)) == NULL) { 633 r = SSH_ERR_ALLOC_FAIL; 634 error("%s: fingerprint key: %s", __func__, ssh_err(r)); 635 goto out; 636 } 637 638 r = sshkey_check_revoked(key, options.revoked_keys_file); 639 switch (r) { 640 case 0: 641 break; /* not revoked */ 642 case SSH_ERR_KEY_REVOKED: 643 error("Authentication key %s %s revoked by file %s", 644 sshkey_type(key), fp, options.revoked_keys_file); 645 goto out; 646 default: 647 error("Error checking authentication key %s %s in " 648 "revoked keys file %s: %s", sshkey_type(key), fp, 649 options.revoked_keys_file, ssh_err(r)); 650 goto out; 651 } 652 653 /* Success */ 654 r = 0; 655 656 out: 657 free(fp); 658 return r == 0 ? 0 : 1; 659 } 660 661 void 662 auth_debug_add(const char *fmt,...) 663 { 664 char buf[1024]; 665 va_list args; 666 int r; 667 668 if (auth_debug == NULL) 669 return; 670 671 va_start(args, fmt); 672 vsnprintf(buf, sizeof(buf), fmt, args); 673 va_end(args); 674 if ((r = sshbuf_put_cstring(auth_debug, buf)) != 0) 675 fatal("%s: sshbuf_put_cstring: %s", __func__, ssh_err(r)); 676 } 677 678 void 679 auth_debug_send(struct ssh *ssh) 680 { 681 char *msg; 682 int r; 683 684 if (auth_debug == NULL) 685 return; 686 while (sshbuf_len(auth_debug) != 0) { 687 if ((r = sshbuf_get_cstring(auth_debug, &msg, NULL)) != 0) 688 fatal("%s: sshbuf_get_cstring: %s", 689 __func__, ssh_err(r)); 690 ssh_packet_send_debug(ssh, "%s", msg); 691 free(msg); 692 } 693 } 694 695 void 696 auth_debug_reset(void) 697 { 698 if (auth_debug != NULL) 699 sshbuf_reset(auth_debug); 700 else if ((auth_debug = sshbuf_new()) == NULL) 701 fatal("%s: sshbuf_new failed", __func__); 702 } 703 704 struct passwd * 705 fakepw(void) 706 { 707 static struct passwd fake; 708 709 memset(&fake, 0, sizeof(fake)); 710 fake.pw_name = "NOUSER"; 711 fake.pw_passwd = 712 "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK"; 713 #ifdef HAVE_STRUCT_PASSWD_PW_GECOS 714 fake.pw_gecos = "NOUSER"; 715 #endif 716 fake.pw_uid = privsep_pw == NULL ? (uid_t)-1 : privsep_pw->pw_uid; 717 fake.pw_gid = privsep_pw == NULL ? (gid_t)-1 : privsep_pw->pw_gid; 718 #ifdef HAVE_STRUCT_PASSWD_PW_CLASS 719 fake.pw_class = ""; 720 #endif 721 fake.pw_dir = "/nonexist"; 722 fake.pw_shell = "/nonexist"; 723 724 return (&fake); 725 } 726 727 /* 728 * Returns the remote DNS hostname as a string. The returned string must not 729 * be freed. NB. this will usually trigger a DNS query the first time it is 730 * called. 731 * This function does additional checks on the hostname to mitigate some 732 * attacks on legacy rhosts-style authentication. 733 * XXX is RhostsRSAAuthentication vulnerable to these? 734 * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?) 735 */ 736 737 static char * 738 remote_hostname(struct ssh *ssh) 739 { 740 struct sockaddr_storage from; 741 socklen_t fromlen; 742 struct addrinfo hints, *ai, *aitop; 743 char name[NI_MAXHOST], ntop2[NI_MAXHOST]; 744 const char *ntop = ssh_remote_ipaddr(ssh); 745 746 /* Get IP address of client. */ 747 fromlen = sizeof(from); 748 memset(&from, 0, sizeof(from)); 749 if (getpeername(ssh_packet_get_connection_in(ssh), 750 (struct sockaddr *)&from, &fromlen) == -1) { 751 debug("getpeername failed: %.100s", strerror(errno)); 752 return xstrdup(ntop); 753 } 754 755 ipv64_normalise_mapped(&from, &fromlen); 756 if (from.ss_family == AF_INET6) 757 fromlen = sizeof(struct sockaddr_in6); 758 759 debug3("Trying to reverse map address %.100s.", ntop); 760 /* Map the IP address to a host name. */ 761 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), 762 NULL, 0, NI_NAMEREQD) != 0) { 763 /* Host name not found. Use ip address. */ 764 return xstrdup(ntop); 765 } 766 767 /* 768 * if reverse lookup result looks like a numeric hostname, 769 * someone is trying to trick us by PTR record like following: 770 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5 771 */ 772 memset(&hints, 0, sizeof(hints)); 773 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 774 hints.ai_flags = AI_NUMERICHOST; 775 if (getaddrinfo(name, NULL, &hints, &ai) == 0) { 776 logit("Nasty PTR record \"%s\" is set up for %s, ignoring", 777 name, ntop); 778 freeaddrinfo(ai); 779 return xstrdup(ntop); 780 } 781 782 /* Names are stored in lowercase. */ 783 lowercase(name); 784 785 /* 786 * Map it back to an IP address and check that the given 787 * address actually is an address of this host. This is 788 * necessary because anyone with access to a name server can 789 * define arbitrary names for an IP address. Mapping from 790 * name to IP address can be trusted better (but can still be 791 * fooled if the intruder has access to the name server of 792 * the domain). 793 */ 794 memset(&hints, 0, sizeof(hints)); 795 hints.ai_family = from.ss_family; 796 hints.ai_socktype = SOCK_STREAM; 797 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { 798 logit("reverse mapping checking getaddrinfo for %.700s " 799 "[%s] failed.", name, ntop); 800 return xstrdup(ntop); 801 } 802 /* Look for the address from the list of addresses. */ 803 for (ai = aitop; ai; ai = ai->ai_next) { 804 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, 805 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && 806 (strcmp(ntop, ntop2) == 0)) 807 break; 808 } 809 freeaddrinfo(aitop); 810 /* If we reached the end of the list, the address was not there. */ 811 if (ai == NULL) { 812 /* Address not found for the host name. */ 813 logit("Address %.100s maps to %.600s, but this does not " 814 "map back to the address.", ntop, name); 815 return xstrdup(ntop); 816 } 817 return xstrdup(name); 818 } 819 820 /* 821 * Return the canonical name of the host in the other side of the current 822 * connection. The host name is cached, so it is efficient to call this 823 * several times. 824 */ 825 826 const char * 827 auth_get_canonical_hostname(struct ssh *ssh, int use_dns) 828 { 829 static char *dnsname; 830 831 if (!use_dns) 832 return ssh_remote_ipaddr(ssh); 833 else if (dnsname != NULL) 834 return dnsname; 835 else { 836 dnsname = remote_hostname(ssh); 837 return dnsname; 838 } 839 } 840 841 /* 842 * Runs command in a subprocess with a minimal environment. 843 * Returns pid on success, 0 on failure. 844 * The child stdout and stderr maybe captured, left attached or sent to 845 * /dev/null depending on the contents of flags. 846 * "tag" is prepended to log messages. 847 * NB. "command" is only used for logging; the actual command executed is 848 * av[0]. 849 */ 850 pid_t 851 subprocess(const char *tag, struct passwd *pw, const char *command, 852 int ac, char **av, FILE **child, u_int flags) 853 { 854 FILE *f = NULL; 855 struct stat st; 856 int fd, devnull, p[2], i; 857 pid_t pid; 858 char *cp, errmsg[512]; 859 u_int envsize; 860 char **child_env; 861 862 if (child != NULL) 863 *child = NULL; 864 865 debug3("%s: %s command \"%s\" running as %s (flags 0x%x)", __func__, 866 tag, command, pw->pw_name, flags); 867 868 /* Check consistency */ 869 if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 && 870 (flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) { 871 error("%s: inconsistent flags", __func__); 872 return 0; 873 } 874 if (((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) != (child == NULL)) { 875 error("%s: inconsistent flags/output", __func__); 876 return 0; 877 } 878 879 /* 880 * If executing an explicit binary, then verify the it exists 881 * and appears safe-ish to execute 882 */ 883 if (!path_absolute(av[0])) { 884 error("%s path is not absolute", tag); 885 return 0; 886 } 887 temporarily_use_uid(pw); 888 if (stat(av[0], &st) == -1) { 889 error("Could not stat %s \"%s\": %s", tag, 890 av[0], strerror(errno)); 891 restore_uid(); 892 return 0; 893 } 894 if (safe_path(av[0], &st, NULL, 0, errmsg, sizeof(errmsg)) != 0) { 895 error("Unsafe %s \"%s\": %s", tag, av[0], errmsg); 896 restore_uid(); 897 return 0; 898 } 899 /* Prepare to keep the child's stdout if requested */ 900 if (pipe(p) == -1) { 901 error("%s: pipe: %s", tag, strerror(errno)); 902 restore_uid(); 903 return 0; 904 } 905 restore_uid(); 906 907 switch ((pid = fork())) { 908 case -1: /* error */ 909 error("%s: fork: %s", tag, strerror(errno)); 910 close(p[0]); 911 close(p[1]); 912 return 0; 913 case 0: /* child */ 914 /* Prepare a minimal environment for the child. */ 915 envsize = 5; 916 child_env = xcalloc(sizeof(*child_env), envsize); 917 child_set_env(&child_env, &envsize, "PATH", _PATH_STDPATH); 918 child_set_env(&child_env, &envsize, "USER", pw->pw_name); 919 child_set_env(&child_env, &envsize, "LOGNAME", pw->pw_name); 920 child_set_env(&child_env, &envsize, "HOME", pw->pw_dir); 921 if ((cp = getenv("LANG")) != NULL) 922 child_set_env(&child_env, &envsize, "LANG", cp); 923 924 for (i = 0; i < NSIG; i++) 925 ssh_signal(i, SIG_DFL); 926 927 if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) { 928 error("%s: open %s: %s", tag, _PATH_DEVNULL, 929 strerror(errno)); 930 _exit(1); 931 } 932 if (dup2(devnull, STDIN_FILENO) == -1) { 933 error("%s: dup2: %s", tag, strerror(errno)); 934 _exit(1); 935 } 936 937 /* Set up stdout as requested; leave stderr in place for now. */ 938 fd = -1; 939 if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) 940 fd = p[1]; 941 else if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0) 942 fd = devnull; 943 if (fd != -1 && dup2(fd, STDOUT_FILENO) == -1) { 944 error("%s: dup2: %s", tag, strerror(errno)); 945 _exit(1); 946 } 947 closefrom(STDERR_FILENO + 1); 948 949 /* Don't use permanently_set_uid() here to avoid fatal() */ 950 if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) == -1) { 951 error("%s: setresgid %u: %s", tag, (u_int)pw->pw_gid, 952 strerror(errno)); 953 _exit(1); 954 } 955 if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) == -1) { 956 error("%s: setresuid %u: %s", tag, (u_int)pw->pw_uid, 957 strerror(errno)); 958 _exit(1); 959 } 960 /* stdin is pointed to /dev/null at this point */ 961 if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 && 962 dup2(STDIN_FILENO, STDERR_FILENO) == -1) { 963 error("%s: dup2: %s", tag, strerror(errno)); 964 _exit(1); 965 } 966 967 execve(av[0], av, child_env); 968 error("%s exec \"%s\": %s", tag, command, strerror(errno)); 969 _exit(127); 970 default: /* parent */ 971 break; 972 } 973 974 close(p[1]); 975 if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) 976 close(p[0]); 977 else if ((f = fdopen(p[0], "r")) == NULL) { 978 error("%s: fdopen: %s", tag, strerror(errno)); 979 close(p[0]); 980 /* Don't leave zombie child */ 981 kill(pid, SIGTERM); 982 while (waitpid(pid, NULL, 0) == -1 && errno == EINTR) 983 ; 984 return 0; 985 } 986 /* Success */ 987 debug3("%s: %s pid %ld", __func__, tag, (long)pid); 988 if (child != NULL) 989 *child = f; 990 return pid; 991 } 992 993 /* These functions link key/cert options to the auth framework */ 994 995 /* Log sshauthopt options locally and (optionally) for remote transmission */ 996 void 997 auth_log_authopts(const char *loc, const struct sshauthopt *opts, int do_remote) 998 { 999 int do_env = options.permit_user_env && opts->nenv > 0; 1000 int do_permitopen = opts->npermitopen > 0 && 1001 (options.allow_tcp_forwarding & FORWARD_LOCAL) != 0; 1002 int do_permitlisten = opts->npermitlisten > 0 && 1003 (options.allow_tcp_forwarding & FORWARD_REMOTE) != 0; 1004 size_t i; 1005 char msg[1024], buf[64]; 1006 1007 snprintf(buf, sizeof(buf), "%d", opts->force_tun_device); 1008 /* Try to keep this alphabetically sorted */ 1009 snprintf(msg, sizeof(msg), "key options:%s%s%s%s%s%s%s%s%s%s%s%s%s%s", 1010 opts->permit_agent_forwarding_flag ? " agent-forwarding" : "", 1011 opts->force_command == NULL ? "" : " command", 1012 do_env ? " environment" : "", 1013 opts->valid_before == 0 ? "" : "expires", 1014 do_permitopen ? " permitopen" : "", 1015 do_permitlisten ? " permitlisten" : "", 1016 opts->permit_port_forwarding_flag ? " port-forwarding" : "", 1017 opts->cert_principals == NULL ? "" : " principals", 1018 opts->permit_pty_flag ? " pty" : "", 1019 opts->force_tun_device == -1 ? "" : " tun=", 1020 opts->force_tun_device == -1 ? "" : buf, 1021 opts->permit_user_rc ? " user-rc" : "", 1022 opts->permit_x11_forwarding_flag ? " x11-forwarding" : "", 1023 opts->no_require_user_presence ? " no-touch-required" : ""); 1024 1025 debug("%s: %s", loc, msg); 1026 if (do_remote) 1027 auth_debug_add("%s: %s", loc, msg); 1028 1029 if (options.permit_user_env) { 1030 for (i = 0; i < opts->nenv; i++) { 1031 debug("%s: environment: %s", loc, opts->env[i]); 1032 if (do_remote) { 1033 auth_debug_add("%s: environment: %s", 1034 loc, opts->env[i]); 1035 } 1036 } 1037 } 1038 1039 /* Go into a little more details for the local logs. */ 1040 if (opts->valid_before != 0) { 1041 format_absolute_time(opts->valid_before, buf, sizeof(buf)); 1042 debug("%s: expires at %s", loc, buf); 1043 } 1044 if (opts->cert_principals != NULL) { 1045 debug("%s: authorized principals: \"%s\"", 1046 loc, opts->cert_principals); 1047 } 1048 if (opts->force_command != NULL) 1049 debug("%s: forced command: \"%s\"", loc, opts->force_command); 1050 if (do_permitopen) { 1051 for (i = 0; i < opts->npermitopen; i++) { 1052 debug("%s: permitted open: %s", 1053 loc, opts->permitopen[i]); 1054 } 1055 } 1056 if (do_permitlisten) { 1057 for (i = 0; i < opts->npermitlisten; i++) { 1058 debug("%s: permitted listen: %s", 1059 loc, opts->permitlisten[i]); 1060 } 1061 } 1062 } 1063 1064 /* Activate a new set of key/cert options; merging with what is there. */ 1065 int 1066 auth_activate_options(struct ssh *ssh, struct sshauthopt *opts) 1067 { 1068 struct sshauthopt *old = auth_opts; 1069 const char *emsg = NULL; 1070 1071 debug("%s: setting new authentication options", __func__); 1072 if ((auth_opts = sshauthopt_merge(old, opts, &emsg)) == NULL) { 1073 error("Inconsistent authentication options: %s", emsg); 1074 return -1; 1075 } 1076 return 0; 1077 } 1078 1079 /* Disable forwarding, etc for the session */ 1080 void 1081 auth_restrict_session(struct ssh *ssh) 1082 { 1083 struct sshauthopt *restricted; 1084 1085 debug("%s: restricting session", __func__); 1086 1087 /* A blank sshauthopt defaults to permitting nothing */ 1088 restricted = sshauthopt_new(); 1089 restricted->permit_pty_flag = 1; 1090 restricted->restricted = 1; 1091 1092 if (auth_activate_options(ssh, restricted) != 0) 1093 fatal("%s: failed to restrict session", __func__); 1094 sshauthopt_free(restricted); 1095 } 1096 1097 int 1098 auth_authorise_keyopts(struct ssh *ssh, struct passwd *pw, 1099 struct sshauthopt *opts, int allow_cert_authority, const char *loc) 1100 { 1101 const char *remote_ip = ssh_remote_ipaddr(ssh); 1102 const char *remote_host = auth_get_canonical_hostname(ssh, 1103 options.use_dns); 1104 time_t now = time(NULL); 1105 char buf[64]; 1106 1107 /* 1108 * Check keys/principals file expiry time. 1109 * NB. validity interval in certificate is handled elsewhere. 1110 */ 1111 if (opts->valid_before && now > 0 && 1112 opts->valid_before < (uint64_t)now) { 1113 format_absolute_time(opts->valid_before, buf, sizeof(buf)); 1114 debug("%s: entry expired at %s", loc, buf); 1115 auth_debug_add("%s: entry expired at %s", loc, buf); 1116 return -1; 1117 } 1118 /* Consistency checks */ 1119 if (opts->cert_principals != NULL && !opts->cert_authority) { 1120 debug("%s: principals on non-CA key", loc); 1121 auth_debug_add("%s: principals on non-CA key", loc); 1122 /* deny access */ 1123 return -1; 1124 } 1125 /* cert-authority flag isn't valid in authorized_principals files */ 1126 if (!allow_cert_authority && opts->cert_authority) { 1127 debug("%s: cert-authority flag invalid here", loc); 1128 auth_debug_add("%s: cert-authority flag invalid here", loc); 1129 /* deny access */ 1130 return -1; 1131 } 1132 1133 /* Perform from= checks */ 1134 if (opts->required_from_host_keys != NULL) { 1135 switch (match_host_and_ip(remote_host, remote_ip, 1136 opts->required_from_host_keys )) { 1137 case 1: 1138 /* Host name matches. */ 1139 break; 1140 case -1: 1141 default: 1142 debug("%s: invalid from criteria", loc); 1143 auth_debug_add("%s: invalid from criteria", loc); 1144 /* FALLTHROUGH */ 1145 case 0: 1146 logit("%s: Authentication tried for %.100s with " 1147 "correct key but not from a permitted " 1148 "host (host=%.200s, ip=%.200s, required=%.200s).", 1149 loc, pw->pw_name, remote_host, remote_ip, 1150 opts->required_from_host_keys); 1151 auth_debug_add("%s: Your host '%.200s' is not " 1152 "permitted to use this key for login.", 1153 loc, remote_host); 1154 /* deny access */ 1155 return -1; 1156 } 1157 } 1158 /* Check source-address restriction from certificate */ 1159 if (opts->required_from_host_cert != NULL) { 1160 switch (addr_match_cidr_list(remote_ip, 1161 opts->required_from_host_cert)) { 1162 case 1: 1163 /* accepted */ 1164 break; 1165 case -1: 1166 default: 1167 /* invalid */ 1168 error("%s: Certificate source-address invalid", 1169 loc); 1170 /* FALLTHROUGH */ 1171 case 0: 1172 logit("%s: Authentication tried for %.100s with valid " 1173 "certificate but not from a permitted source " 1174 "address (%.200s).", loc, pw->pw_name, remote_ip); 1175 auth_debug_add("%s: Your address '%.200s' is not " 1176 "permitted to use this certificate for login.", 1177 loc, remote_ip); 1178 return -1; 1179 } 1180 } 1181 /* 1182 * 1183 * XXX this is spammy. We should report remotely only for keys 1184 * that are successful in actual auth attempts, and not PK_OK 1185 * tests. 1186 */ 1187 auth_log_authopts(loc, opts, 1); 1188 1189 return 0; 1190 } 1191