1 /* $OpenBSD: auth.c,v 1.153 2021/07/05 00:50:25 dtucker 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 #if defined(CUSTOM_FAILED_LOGIN) || defined(SSH_AUDIT_EVENTS) 356 if (authenticated == 0 && !(authctxt->postponed || partial)) { 357 /* Log failed login attempt */ 358 # ifdef CUSTOM_FAILED_LOGIN 359 if (strcmp(method, "password") == 0 || 360 strncmp(method, "keyboard-interactive", 20) == 0 || 361 strcmp(method, "challenge-response") == 0) 362 record_failed_login(ssh, authctxt->user, 363 auth_get_canonical_hostname(ssh, options.use_dns), "ssh"); 364 # endif 365 # ifdef SSH_AUDIT_EVENTS 366 audit_event(ssh, audit_classify_auth(method)); 367 # endif 368 } 369 #endif 370 #if defined(CUSTOM_FAILED_LOGIN) && defined(WITH_AIXAUTHENTICATE) 371 if (authenticated) 372 sys_auth_record_login(authctxt->user, 373 auth_get_canonical_hostname(ssh, options.use_dns), "ssh", 374 loginmsg); 375 #endif 376 } 377 378 void 379 auth_maxtries_exceeded(struct ssh *ssh) 380 { 381 Authctxt *authctxt = (Authctxt *)ssh->authctxt; 382 383 error("maximum authentication attempts exceeded for " 384 "%s%.100s from %.200s port %d ssh2", 385 authctxt->valid ? "" : "invalid user ", 386 authctxt->user, 387 ssh_remote_ipaddr(ssh), 388 ssh_remote_port(ssh)); 389 ssh_packet_disconnect(ssh, "Too many authentication failures"); 390 /* NOTREACHED */ 391 } 392 393 /* 394 * Check whether root logins are disallowed. 395 */ 396 int 397 auth_root_allowed(struct ssh *ssh, const char *method) 398 { 399 switch (options.permit_root_login) { 400 case PERMIT_YES: 401 return 1; 402 case PERMIT_NO_PASSWD: 403 if (strcmp(method, "publickey") == 0 || 404 strcmp(method, "hostbased") == 0 || 405 strcmp(method, "gssapi-with-mic") == 0) 406 return 1; 407 break; 408 case PERMIT_FORCED_ONLY: 409 if (auth_opts->force_command != NULL) { 410 logit("Root login accepted for forced command."); 411 return 1; 412 } 413 break; 414 } 415 logit("ROOT LOGIN REFUSED FROM %.200s port %d", 416 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 417 return 0; 418 } 419 420 421 /* 422 * Given a template and a passwd structure, build a filename 423 * by substituting % tokenised options. Currently, %% becomes '%', 424 * %h becomes the home directory and %u the username. 425 * 426 * This returns a buffer allocated by xmalloc. 427 */ 428 char * 429 expand_authorized_keys(const char *filename, struct passwd *pw) 430 { 431 char *file, uidstr[32], ret[PATH_MAX]; 432 int i; 433 434 snprintf(uidstr, sizeof(uidstr), "%llu", 435 (unsigned long long)pw->pw_uid); 436 file = percent_expand(filename, "h", pw->pw_dir, 437 "u", pw->pw_name, "U", uidstr, (char *)NULL); 438 439 /* 440 * Ensure that filename starts anchored. If not, be backward 441 * compatible and prepend the '%h/' 442 */ 443 if (path_absolute(file)) 444 return (file); 445 446 i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file); 447 if (i < 0 || (size_t)i >= sizeof(ret)) 448 fatal("expand_authorized_keys: path too long"); 449 free(file); 450 return (xstrdup(ret)); 451 } 452 453 char * 454 authorized_principals_file(struct passwd *pw) 455 { 456 if (options.authorized_principals_file == NULL) 457 return NULL; 458 return expand_authorized_keys(options.authorized_principals_file, pw); 459 } 460 461 /* return ok if key exists in sysfile or userfile */ 462 HostStatus 463 check_key_in_hostfiles(struct passwd *pw, struct sshkey *key, const char *host, 464 const char *sysfile, const char *userfile) 465 { 466 char *user_hostfile; 467 struct stat st; 468 HostStatus host_status; 469 struct hostkeys *hostkeys; 470 const struct hostkey_entry *found; 471 472 hostkeys = init_hostkeys(); 473 load_hostkeys(hostkeys, host, sysfile, 0); 474 if (userfile != NULL) { 475 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); 476 if (options.strict_modes && 477 (stat(user_hostfile, &st) == 0) && 478 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || 479 (st.st_mode & 022) != 0)) { 480 logit("Authentication refused for %.100s: " 481 "bad owner or modes for %.200s", 482 pw->pw_name, user_hostfile); 483 auth_debug_add("Ignored %.200s: bad ownership or modes", 484 user_hostfile); 485 } else { 486 temporarily_use_uid(pw); 487 load_hostkeys(hostkeys, host, user_hostfile, 0); 488 restore_uid(); 489 } 490 free(user_hostfile); 491 } 492 host_status = check_key_in_hostkeys(hostkeys, key, &found); 493 if (host_status == HOST_REVOKED) 494 error("WARNING: revoked key for %s attempted authentication", 495 host); 496 else if (host_status == HOST_OK) 497 debug_f("key for %s found at %s:%ld", 498 found->host, found->file, found->line); 499 else 500 debug_f("key for host %s not found", host); 501 502 free_hostkeys(hostkeys); 503 504 return host_status; 505 } 506 507 static FILE * 508 auth_openfile(const char *file, struct passwd *pw, int strict_modes, 509 int log_missing, char *file_type) 510 { 511 char line[1024]; 512 struct stat st; 513 int fd; 514 FILE *f; 515 516 if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) { 517 if (log_missing || errno != ENOENT) 518 debug("Could not open %s '%s': %s", file_type, file, 519 strerror(errno)); 520 return NULL; 521 } 522 523 if (fstat(fd, &st) == -1) { 524 close(fd); 525 return NULL; 526 } 527 if (!S_ISREG(st.st_mode)) { 528 logit("User %s %s %s is not a regular file", 529 pw->pw_name, file_type, file); 530 close(fd); 531 return NULL; 532 } 533 unset_nonblock(fd); 534 if ((f = fdopen(fd, "r")) == NULL) { 535 close(fd); 536 return NULL; 537 } 538 if (strict_modes && 539 safe_path_fd(fileno(f), file, pw, line, sizeof(line)) != 0) { 540 fclose(f); 541 logit("Authentication refused: %s", line); 542 auth_debug_add("Ignored %s: %s", file_type, line); 543 return NULL; 544 } 545 546 return f; 547 } 548 549 550 FILE * 551 auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes) 552 { 553 return auth_openfile(file, pw, strict_modes, 1, "authorized keys"); 554 } 555 556 FILE * 557 auth_openprincipals(const char *file, struct passwd *pw, int strict_modes) 558 { 559 return auth_openfile(file, pw, strict_modes, 0, 560 "authorized principals"); 561 } 562 563 struct passwd * 564 getpwnamallow(struct ssh *ssh, const char *user) 565 { 566 #ifdef HAVE_LOGIN_CAP 567 extern login_cap_t *lc; 568 #ifdef BSD_AUTH 569 auth_session_t *as; 570 #endif 571 #endif 572 struct passwd *pw; 573 struct connection_info *ci; 574 u_int i; 575 576 ci = get_connection_info(ssh, 1, options.use_dns); 577 ci->user = user; 578 parse_server_match_config(&options, &includes, ci); 579 log_change_level(options.log_level); 580 log_verbose_reset(); 581 for (i = 0; i < options.num_log_verbose; i++) 582 log_verbose_add(options.log_verbose[i]); 583 process_permitopen(ssh, &options); 584 585 #if defined(_AIX) && defined(HAVE_SETAUTHDB) 586 aix_setauthdb(user); 587 #endif 588 589 pw = getpwnam(user); 590 591 #if defined(_AIX) && defined(HAVE_SETAUTHDB) 592 aix_restoreauthdb(); 593 #endif 594 if (pw == NULL) { 595 logit("Invalid user %.100s from %.100s port %d", 596 user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 597 #ifdef CUSTOM_FAILED_LOGIN 598 record_failed_login(ssh, user, 599 auth_get_canonical_hostname(ssh, options.use_dns), "ssh"); 600 #endif 601 #ifdef SSH_AUDIT_EVENTS 602 audit_event(ssh, SSH_INVALID_USER); 603 #endif /* SSH_AUDIT_EVENTS */ 604 return (NULL); 605 } 606 if (!allowed_user(ssh, pw)) 607 return (NULL); 608 #ifdef HAVE_LOGIN_CAP 609 if ((lc = login_getpwclass(pw)) == NULL) { 610 debug("unable to get login class: %s", user); 611 return (NULL); 612 } 613 #ifdef BSD_AUTH 614 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || 615 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { 616 debug("Approval failure for %s", user); 617 pw = NULL; 618 } 619 if (as != NULL) 620 auth_close(as); 621 #endif 622 #endif 623 if (pw != NULL) 624 return (pwcopy(pw)); 625 return (NULL); 626 } 627 628 /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */ 629 int 630 auth_key_is_revoked(struct sshkey *key) 631 { 632 char *fp = NULL; 633 int r; 634 635 if (options.revoked_keys_file == NULL) 636 return 0; 637 if ((fp = sshkey_fingerprint(key, options.fingerprint_hash, 638 SSH_FP_DEFAULT)) == NULL) { 639 r = SSH_ERR_ALLOC_FAIL; 640 error_fr(r, "fingerprint key"); 641 goto out; 642 } 643 644 r = sshkey_check_revoked(key, options.revoked_keys_file); 645 switch (r) { 646 case 0: 647 break; /* not revoked */ 648 case SSH_ERR_KEY_REVOKED: 649 error("Authentication key %s %s revoked by file %s", 650 sshkey_type(key), fp, options.revoked_keys_file); 651 goto out; 652 default: 653 error_r(r, "Error checking authentication key %s %s in " 654 "revoked keys file %s", sshkey_type(key), fp, 655 options.revoked_keys_file); 656 goto out; 657 } 658 659 /* Success */ 660 r = 0; 661 662 out: 663 free(fp); 664 return r == 0 ? 0 : 1; 665 } 666 667 void 668 auth_debug_add(const char *fmt,...) 669 { 670 char buf[1024]; 671 va_list args; 672 int r; 673 674 if (auth_debug == NULL) 675 return; 676 677 va_start(args, fmt); 678 vsnprintf(buf, sizeof(buf), fmt, args); 679 va_end(args); 680 if ((r = sshbuf_put_cstring(auth_debug, buf)) != 0) 681 fatal_fr(r, "sshbuf_put_cstring"); 682 } 683 684 void 685 auth_debug_send(struct ssh *ssh) 686 { 687 char *msg; 688 int r; 689 690 if (auth_debug == NULL) 691 return; 692 while (sshbuf_len(auth_debug) != 0) { 693 if ((r = sshbuf_get_cstring(auth_debug, &msg, NULL)) != 0) 694 fatal_fr(r, "sshbuf_get_cstring"); 695 ssh_packet_send_debug(ssh, "%s", msg); 696 free(msg); 697 } 698 } 699 700 void 701 auth_debug_reset(void) 702 { 703 if (auth_debug != NULL) 704 sshbuf_reset(auth_debug); 705 else if ((auth_debug = sshbuf_new()) == NULL) 706 fatal_f("sshbuf_new failed"); 707 } 708 709 struct passwd * 710 fakepw(void) 711 { 712 static struct passwd fake; 713 714 memset(&fake, 0, sizeof(fake)); 715 fake.pw_name = "NOUSER"; 716 fake.pw_passwd = 717 "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK"; 718 #ifdef HAVE_STRUCT_PASSWD_PW_GECOS 719 fake.pw_gecos = "NOUSER"; 720 #endif 721 fake.pw_uid = privsep_pw == NULL ? (uid_t)-1 : privsep_pw->pw_uid; 722 fake.pw_gid = privsep_pw == NULL ? (gid_t)-1 : privsep_pw->pw_gid; 723 #ifdef HAVE_STRUCT_PASSWD_PW_CLASS 724 fake.pw_class = ""; 725 #endif 726 fake.pw_dir = "/nonexist"; 727 fake.pw_shell = "/nonexist"; 728 729 return (&fake); 730 } 731 732 /* 733 * Returns the remote DNS hostname as a string. The returned string must not 734 * be freed. NB. this will usually trigger a DNS query the first time it is 735 * called. 736 * This function does additional checks on the hostname to mitigate some 737 * attacks on based on conflation of hostnames and IP addresses. 738 */ 739 740 static char * 741 remote_hostname(struct ssh *ssh) 742 { 743 struct sockaddr_storage from; 744 socklen_t fromlen; 745 struct addrinfo hints, *ai, *aitop; 746 char name[NI_MAXHOST], ntop2[NI_MAXHOST]; 747 const char *ntop = ssh_remote_ipaddr(ssh); 748 749 /* Get IP address of client. */ 750 fromlen = sizeof(from); 751 memset(&from, 0, sizeof(from)); 752 if (getpeername(ssh_packet_get_connection_in(ssh), 753 (struct sockaddr *)&from, &fromlen) == -1) { 754 debug("getpeername failed: %.100s", strerror(errno)); 755 return xstrdup(ntop); 756 } 757 758 ipv64_normalise_mapped(&from, &fromlen); 759 if (from.ss_family == AF_INET6) 760 fromlen = sizeof(struct sockaddr_in6); 761 762 debug3("Trying to reverse map address %.100s.", ntop); 763 /* Map the IP address to a host name. */ 764 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), 765 NULL, 0, NI_NAMEREQD) != 0) { 766 /* Host name not found. Use ip address. */ 767 return xstrdup(ntop); 768 } 769 770 /* 771 * if reverse lookup result looks like a numeric hostname, 772 * someone is trying to trick us by PTR record like following: 773 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5 774 */ 775 memset(&hints, 0, sizeof(hints)); 776 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 777 hints.ai_flags = AI_NUMERICHOST; 778 if (getaddrinfo(name, NULL, &hints, &ai) == 0) { 779 logit("Nasty PTR record \"%s\" is set up for %s, ignoring", 780 name, ntop); 781 freeaddrinfo(ai); 782 return xstrdup(ntop); 783 } 784 785 /* Names are stored in lowercase. */ 786 lowercase(name); 787 788 /* 789 * Map it back to an IP address and check that the given 790 * address actually is an address of this host. This is 791 * necessary because anyone with access to a name server can 792 * define arbitrary names for an IP address. Mapping from 793 * name to IP address can be trusted better (but can still be 794 * fooled if the intruder has access to the name server of 795 * the domain). 796 */ 797 memset(&hints, 0, sizeof(hints)); 798 hints.ai_family = from.ss_family; 799 hints.ai_socktype = SOCK_STREAM; 800 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { 801 logit("reverse mapping checking getaddrinfo for %.700s " 802 "[%s] failed.", name, ntop); 803 return xstrdup(ntop); 804 } 805 /* Look for the address from the list of addresses. */ 806 for (ai = aitop; ai; ai = ai->ai_next) { 807 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, 808 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && 809 (strcmp(ntop, ntop2) == 0)) 810 break; 811 } 812 freeaddrinfo(aitop); 813 /* If we reached the end of the list, the address was not there. */ 814 if (ai == NULL) { 815 /* Address not found for the host name. */ 816 logit("Address %.100s maps to %.600s, but this does not " 817 "map back to the address.", ntop, name); 818 return xstrdup(ntop); 819 } 820 return xstrdup(name); 821 } 822 823 /* 824 * Return the canonical name of the host in the other side of the current 825 * connection. The host name is cached, so it is efficient to call this 826 * several times. 827 */ 828 829 const char * 830 auth_get_canonical_hostname(struct ssh *ssh, int use_dns) 831 { 832 static char *dnsname; 833 834 if (!use_dns) 835 return ssh_remote_ipaddr(ssh); 836 else if (dnsname != NULL) 837 return dnsname; 838 else { 839 dnsname = remote_hostname(ssh); 840 return dnsname; 841 } 842 } 843 844 /* These functions link key/cert options to the auth framework */ 845 846 /* Log sshauthopt options locally and (optionally) for remote transmission */ 847 void 848 auth_log_authopts(const char *loc, const struct sshauthopt *opts, int do_remote) 849 { 850 int do_env = options.permit_user_env && opts->nenv > 0; 851 int do_permitopen = opts->npermitopen > 0 && 852 (options.allow_tcp_forwarding & FORWARD_LOCAL) != 0; 853 int do_permitlisten = opts->npermitlisten > 0 && 854 (options.allow_tcp_forwarding & FORWARD_REMOTE) != 0; 855 size_t i; 856 char msg[1024], buf[64]; 857 858 snprintf(buf, sizeof(buf), "%d", opts->force_tun_device); 859 /* Try to keep this alphabetically sorted */ 860 snprintf(msg, sizeof(msg), "key options:%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s", 861 opts->permit_agent_forwarding_flag ? " agent-forwarding" : "", 862 opts->force_command == NULL ? "" : " command", 863 do_env ? " environment" : "", 864 opts->valid_before == 0 ? "" : "expires", 865 opts->no_require_user_presence ? " no-touch-required" : "", 866 do_permitopen ? " permitopen" : "", 867 do_permitlisten ? " permitlisten" : "", 868 opts->permit_port_forwarding_flag ? " port-forwarding" : "", 869 opts->cert_principals == NULL ? "" : " principals", 870 opts->permit_pty_flag ? " pty" : "", 871 opts->require_verify ? " uv" : "", 872 opts->force_tun_device == -1 ? "" : " tun=", 873 opts->force_tun_device == -1 ? "" : buf, 874 opts->permit_user_rc ? " user-rc" : "", 875 opts->permit_x11_forwarding_flag ? " x11-forwarding" : ""); 876 877 debug("%s: %s", loc, msg); 878 if (do_remote) 879 auth_debug_add("%s: %s", loc, msg); 880 881 if (options.permit_user_env) { 882 for (i = 0; i < opts->nenv; i++) { 883 debug("%s: environment: %s", loc, opts->env[i]); 884 if (do_remote) { 885 auth_debug_add("%s: environment: %s", 886 loc, opts->env[i]); 887 } 888 } 889 } 890 891 /* Go into a little more details for the local logs. */ 892 if (opts->valid_before != 0) { 893 format_absolute_time(opts->valid_before, buf, sizeof(buf)); 894 debug("%s: expires at %s", loc, buf); 895 } 896 if (opts->cert_principals != NULL) { 897 debug("%s: authorized principals: \"%s\"", 898 loc, opts->cert_principals); 899 } 900 if (opts->force_command != NULL) 901 debug("%s: forced command: \"%s\"", loc, opts->force_command); 902 if (do_permitopen) { 903 for (i = 0; i < opts->npermitopen; i++) { 904 debug("%s: permitted open: %s", 905 loc, opts->permitopen[i]); 906 } 907 } 908 if (do_permitlisten) { 909 for (i = 0; i < opts->npermitlisten; i++) { 910 debug("%s: permitted listen: %s", 911 loc, opts->permitlisten[i]); 912 } 913 } 914 } 915 916 /* Activate a new set of key/cert options; merging with what is there. */ 917 int 918 auth_activate_options(struct ssh *ssh, struct sshauthopt *opts) 919 { 920 struct sshauthopt *old = auth_opts; 921 const char *emsg = NULL; 922 923 debug_f("setting new authentication options"); 924 if ((auth_opts = sshauthopt_merge(old, opts, &emsg)) == NULL) { 925 error("Inconsistent authentication options: %s", emsg); 926 return -1; 927 } 928 return 0; 929 } 930 931 /* Disable forwarding, etc for the session */ 932 void 933 auth_restrict_session(struct ssh *ssh) 934 { 935 struct sshauthopt *restricted; 936 937 debug_f("restricting session"); 938 939 /* A blank sshauthopt defaults to permitting nothing */ 940 restricted = sshauthopt_new(); 941 restricted->permit_pty_flag = 1; 942 restricted->restricted = 1; 943 944 if (auth_activate_options(ssh, restricted) != 0) 945 fatal_f("failed to restrict session"); 946 sshauthopt_free(restricted); 947 } 948 949 int 950 auth_authorise_keyopts(struct ssh *ssh, struct passwd *pw, 951 struct sshauthopt *opts, int allow_cert_authority, const char *loc) 952 { 953 const char *remote_ip = ssh_remote_ipaddr(ssh); 954 const char *remote_host = auth_get_canonical_hostname(ssh, 955 options.use_dns); 956 time_t now = time(NULL); 957 char buf[64]; 958 959 /* 960 * Check keys/principals file expiry time. 961 * NB. validity interval in certificate is handled elsewhere. 962 */ 963 if (opts->valid_before && now > 0 && 964 opts->valid_before < (uint64_t)now) { 965 format_absolute_time(opts->valid_before, buf, sizeof(buf)); 966 debug("%s: entry expired at %s", loc, buf); 967 auth_debug_add("%s: entry expired at %s", loc, buf); 968 return -1; 969 } 970 /* Consistency checks */ 971 if (opts->cert_principals != NULL && !opts->cert_authority) { 972 debug("%s: principals on non-CA key", loc); 973 auth_debug_add("%s: principals on non-CA key", loc); 974 /* deny access */ 975 return -1; 976 } 977 /* cert-authority flag isn't valid in authorized_principals files */ 978 if (!allow_cert_authority && opts->cert_authority) { 979 debug("%s: cert-authority flag invalid here", loc); 980 auth_debug_add("%s: cert-authority flag invalid here", loc); 981 /* deny access */ 982 return -1; 983 } 984 985 /* Perform from= checks */ 986 if (opts->required_from_host_keys != NULL) { 987 switch (match_host_and_ip(remote_host, remote_ip, 988 opts->required_from_host_keys )) { 989 case 1: 990 /* Host name matches. */ 991 break; 992 case -1: 993 default: 994 debug("%s: invalid from criteria", loc); 995 auth_debug_add("%s: invalid from criteria", loc); 996 /* FALLTHROUGH */ 997 case 0: 998 logit("%s: Authentication tried for %.100s with " 999 "correct key but not from a permitted " 1000 "host (host=%.200s, ip=%.200s, required=%.200s).", 1001 loc, pw->pw_name, remote_host, remote_ip, 1002 opts->required_from_host_keys); 1003 auth_debug_add("%s: Your host '%.200s' is not " 1004 "permitted to use this key for login.", 1005 loc, remote_host); 1006 /* deny access */ 1007 return -1; 1008 } 1009 } 1010 /* Check source-address restriction from certificate */ 1011 if (opts->required_from_host_cert != NULL) { 1012 switch (addr_match_cidr_list(remote_ip, 1013 opts->required_from_host_cert)) { 1014 case 1: 1015 /* accepted */ 1016 break; 1017 case -1: 1018 default: 1019 /* invalid */ 1020 error("%s: Certificate source-address invalid", loc); 1021 /* FALLTHROUGH */ 1022 case 0: 1023 logit("%s: Authentication tried for %.100s with valid " 1024 "certificate but not from a permitted source " 1025 "address (%.200s).", loc, pw->pw_name, remote_ip); 1026 auth_debug_add("%s: Your address '%.200s' is not " 1027 "permitted to use this certificate for login.", 1028 loc, remote_ip); 1029 return -1; 1030 } 1031 } 1032 /* 1033 * 1034 * XXX this is spammy. We should report remotely only for keys 1035 * that are successful in actual auth attempts, and not PK_OK 1036 * tests. 1037 */ 1038 auth_log_authopts(loc, opts, 1); 1039 1040 return 0; 1041 } 1042