1 /* $OpenBSD: auth.c,v 1.159 2022/12/09 00:17:40 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 #include "blacklist_client.h" 80 81 /* import */ 82 extern ServerOptions options; 83 extern struct include_list includes; 84 extern int use_privsep; 85 extern struct sshbuf *loginmsg; 86 extern struct passwd *privsep_pw; 87 extern struct sshauthopt *auth_opts; 88 89 /* Debugging messages */ 90 static struct sshbuf *auth_debug; 91 92 /* 93 * Check if the user is allowed to log in via ssh. If user is listed 94 * in DenyUsers or one of user's groups is listed in DenyGroups, false 95 * will be returned. If AllowUsers isn't empty and user isn't listed 96 * there, or if AllowGroups isn't empty and one of user's groups isn't 97 * listed there, false will be returned. 98 * If the user's shell is not executable, false will be returned. 99 * Otherwise true is returned. 100 */ 101 int 102 allowed_user(struct ssh *ssh, struct passwd * pw) 103 { 104 struct stat st; 105 const char *hostname = NULL, *ipaddr = NULL; 106 u_int i; 107 int r; 108 109 /* Shouldn't be called if pw is NULL, but better safe than sorry... */ 110 if (!pw || !pw->pw_name) 111 return 0; 112 113 if (!options.use_pam && platform_locked_account(pw)) { 114 logit("User %.100s not allowed because account is locked", 115 pw->pw_name); 116 return 0; 117 } 118 119 /* 120 * Deny if shell does not exist or is not executable unless we 121 * are chrooting. 122 */ 123 if (options.chroot_directory == NULL || 124 strcasecmp(options.chroot_directory, "none") == 0) { 125 char *shell = xstrdup((pw->pw_shell[0] == '\0') ? 126 _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */ 127 128 if (stat(shell, &st) == -1) { 129 logit("User %.100s not allowed because shell %.100s " 130 "does not exist", pw->pw_name, shell); 131 free(shell); 132 return 0; 133 } 134 if (S_ISREG(st.st_mode) == 0 || 135 (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { 136 logit("User %.100s not allowed because shell %.100s " 137 "is not executable", pw->pw_name, shell); 138 free(shell); 139 return 0; 140 } 141 free(shell); 142 } 143 144 if (options.num_deny_users > 0 || options.num_allow_users > 0 || 145 options.num_deny_groups > 0 || options.num_allow_groups > 0) { 146 hostname = auth_get_canonical_hostname(ssh, options.use_dns); 147 ipaddr = ssh_remote_ipaddr(ssh); 148 } 149 150 /* Return false if user is listed in DenyUsers */ 151 if (options.num_deny_users > 0) { 152 for (i = 0; i < options.num_deny_users; i++) { 153 r = match_user(pw->pw_name, hostname, ipaddr, 154 options.deny_users[i]); 155 if (r < 0) { 156 fatal("Invalid DenyUsers pattern \"%.100s\"", 157 options.deny_users[i]); 158 } else if (r != 0) { 159 logit("User %.100s from %.100s not allowed " 160 "because listed in DenyUsers", 161 pw->pw_name, hostname); 162 return 0; 163 } 164 } 165 } 166 /* Return false if AllowUsers isn't empty and user isn't listed there */ 167 if (options.num_allow_users > 0) { 168 for (i = 0; i < options.num_allow_users; i++) { 169 r = match_user(pw->pw_name, hostname, ipaddr, 170 options.allow_users[i]); 171 if (r < 0) { 172 fatal("Invalid AllowUsers pattern \"%.100s\"", 173 options.allow_users[i]); 174 } else if (r == 1) 175 break; 176 } 177 /* i < options.num_allow_users iff we break for loop */ 178 if (i >= options.num_allow_users) { 179 logit("User %.100s from %.100s not allowed because " 180 "not listed in AllowUsers", pw->pw_name, hostname); 181 return 0; 182 } 183 } 184 if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { 185 /* Get the user's group access list (primary and supplementary) */ 186 if (ga_init(pw->pw_name, pw->pw_gid) == 0) { 187 logit("User %.100s from %.100s not allowed because " 188 "not in any group", pw->pw_name, hostname); 189 return 0; 190 } 191 192 /* Return false if one of user's groups is listed in DenyGroups */ 193 if (options.num_deny_groups > 0) 194 if (ga_match(options.deny_groups, 195 options.num_deny_groups)) { 196 ga_free(); 197 logit("User %.100s from %.100s not allowed " 198 "because a group is listed in DenyGroups", 199 pw->pw_name, hostname); 200 return 0; 201 } 202 /* 203 * Return false if AllowGroups isn't empty and one of user's groups 204 * isn't listed there 205 */ 206 if (options.num_allow_groups > 0) 207 if (!ga_match(options.allow_groups, 208 options.num_allow_groups)) { 209 ga_free(); 210 logit("User %.100s from %.100s not allowed " 211 "because none of user's groups are listed " 212 "in AllowGroups", pw->pw_name, hostname); 213 return 0; 214 } 215 ga_free(); 216 } 217 218 #ifdef CUSTOM_SYS_AUTH_ALLOWED_USER 219 if (!sys_auth_allowed_user(pw, loginmsg)) 220 return 0; 221 #endif 222 223 /* We found no reason not to let this user try to log on... */ 224 return 1; 225 } 226 227 /* 228 * Formats any key left in authctxt->auth_method_key for inclusion in 229 * auth_log()'s message. Also includes authxtct->auth_method_info if present. 230 */ 231 static char * 232 format_method_key(Authctxt *authctxt) 233 { 234 const struct sshkey *key = authctxt->auth_method_key; 235 const char *methinfo = authctxt->auth_method_info; 236 char *fp, *cafp, *ret = NULL; 237 238 if (key == NULL) 239 return NULL; 240 241 if (sshkey_is_cert(key)) { 242 fp = sshkey_fingerprint(key, 243 options.fingerprint_hash, SSH_FP_DEFAULT); 244 cafp = sshkey_fingerprint(key->cert->signature_key, 245 options.fingerprint_hash, SSH_FP_DEFAULT); 246 xasprintf(&ret, "%s %s ID %s (serial %llu) CA %s %s%s%s", 247 sshkey_type(key), fp == NULL ? "(null)" : fp, 248 key->cert->key_id, 249 (unsigned long long)key->cert->serial, 250 sshkey_type(key->cert->signature_key), 251 cafp == NULL ? "(null)" : cafp, 252 methinfo == NULL ? "" : ", ", 253 methinfo == NULL ? "" : methinfo); 254 free(fp); 255 free(cafp); 256 } else { 257 fp = sshkey_fingerprint(key, options.fingerprint_hash, 258 SSH_FP_DEFAULT); 259 xasprintf(&ret, "%s %s%s%s", sshkey_type(key), 260 fp == NULL ? "(null)" : fp, 261 methinfo == NULL ? "" : ", ", 262 methinfo == NULL ? "" : methinfo); 263 free(fp); 264 } 265 return ret; 266 } 267 268 void 269 auth_log(struct ssh *ssh, int authenticated, int partial, 270 const char *method, const char *submethod) 271 { 272 Authctxt *authctxt = (Authctxt *)ssh->authctxt; 273 int level = SYSLOG_LEVEL_VERBOSE; 274 const char *authmsg; 275 char *extra = NULL; 276 277 if (use_privsep && !mm_is_monitor() && !authctxt->postponed) 278 return; 279 280 /* Raise logging level */ 281 if (authenticated == 1 || 282 !authctxt->valid || 283 authctxt->failures >= options.max_authtries / 2 || 284 strcmp(method, "password") == 0) 285 level = SYSLOG_LEVEL_INFO; 286 287 if (authctxt->postponed) 288 authmsg = "Postponed"; 289 else if (partial) 290 authmsg = "Partial"; 291 else { 292 authmsg = authenticated ? "Accepted" : "Failed"; 293 if (authenticated) 294 BLACKLIST_NOTIFY(ssh, BLACKLIST_AUTH_OK, "ssh"); 295 } 296 297 if ((extra = format_method_key(authctxt)) == NULL) { 298 if (authctxt->auth_method_info != NULL) 299 extra = xstrdup(authctxt->auth_method_info); 300 } 301 302 do_log2(level, "%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s", 303 authmsg, 304 method, 305 submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod, 306 authctxt->valid ? "" : "invalid user ", 307 authctxt->user, 308 ssh_remote_ipaddr(ssh), 309 ssh_remote_port(ssh), 310 extra != NULL ? ": " : "", 311 extra != NULL ? extra : ""); 312 313 free(extra); 314 315 #if defined(CUSTOM_FAILED_LOGIN) || defined(SSH_AUDIT_EVENTS) 316 if (authenticated == 0 && !(authctxt->postponed || partial)) { 317 /* Log failed login attempt */ 318 # ifdef CUSTOM_FAILED_LOGIN 319 if (strcmp(method, "password") == 0 || 320 strncmp(method, "keyboard-interactive", 20) == 0 || 321 strcmp(method, "challenge-response") == 0) 322 record_failed_login(ssh, authctxt->user, 323 auth_get_canonical_hostname(ssh, options.use_dns), "ssh"); 324 # endif 325 # ifdef SSH_AUDIT_EVENTS 326 audit_event(ssh, audit_classify_auth(method)); 327 # endif 328 } 329 #endif 330 #if defined(CUSTOM_FAILED_LOGIN) && defined(WITH_AIXAUTHENTICATE) 331 if (authenticated) 332 sys_auth_record_login(authctxt->user, 333 auth_get_canonical_hostname(ssh, options.use_dns), "ssh", 334 loginmsg); 335 #endif 336 } 337 338 void 339 auth_maxtries_exceeded(struct ssh *ssh) 340 { 341 Authctxt *authctxt = (Authctxt *)ssh->authctxt; 342 343 error("maximum authentication attempts exceeded for " 344 "%s%.100s from %.200s port %d ssh2", 345 authctxt->valid ? "" : "invalid user ", 346 authctxt->user, 347 ssh_remote_ipaddr(ssh), 348 ssh_remote_port(ssh)); 349 ssh_packet_disconnect(ssh, "Too many authentication failures"); 350 /* NOTREACHED */ 351 } 352 353 /* 354 * Check whether root logins are disallowed. 355 */ 356 int 357 auth_root_allowed(struct ssh *ssh, const char *method) 358 { 359 switch (options.permit_root_login) { 360 case PERMIT_YES: 361 return 1; 362 case PERMIT_NO_PASSWD: 363 if (strcmp(method, "publickey") == 0 || 364 strcmp(method, "hostbased") == 0 || 365 strcmp(method, "gssapi-with-mic") == 0) 366 return 1; 367 break; 368 case PERMIT_FORCED_ONLY: 369 if (auth_opts->force_command != NULL) { 370 logit("Root login accepted for forced command."); 371 return 1; 372 } 373 break; 374 } 375 logit("ROOT LOGIN REFUSED FROM %.200s port %d", 376 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 377 return 0; 378 } 379 380 381 /* 382 * Given a template and a passwd structure, build a filename 383 * by substituting % tokenised options. Currently, %% becomes '%', 384 * %h becomes the home directory and %u the username. 385 * 386 * This returns a buffer allocated by xmalloc. 387 */ 388 char * 389 expand_authorized_keys(const char *filename, struct passwd *pw) 390 { 391 char *file, uidstr[32], ret[PATH_MAX]; 392 int i; 393 394 snprintf(uidstr, sizeof(uidstr), "%llu", 395 (unsigned long long)pw->pw_uid); 396 file = percent_expand(filename, "h", pw->pw_dir, 397 "u", pw->pw_name, "U", uidstr, (char *)NULL); 398 399 /* 400 * Ensure that filename starts anchored. If not, be backward 401 * compatible and prepend the '%h/' 402 */ 403 if (path_absolute(file)) 404 return (file); 405 406 i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file); 407 if (i < 0 || (size_t)i >= sizeof(ret)) 408 fatal("expand_authorized_keys: path too long"); 409 free(file); 410 return (xstrdup(ret)); 411 } 412 413 char * 414 authorized_principals_file(struct passwd *pw) 415 { 416 if (options.authorized_principals_file == NULL) 417 return NULL; 418 return expand_authorized_keys(options.authorized_principals_file, pw); 419 } 420 421 /* return ok if key exists in sysfile or userfile */ 422 HostStatus 423 check_key_in_hostfiles(struct passwd *pw, struct sshkey *key, const char *host, 424 const char *sysfile, const char *userfile) 425 { 426 char *user_hostfile; 427 struct stat st; 428 HostStatus host_status; 429 struct hostkeys *hostkeys; 430 const struct hostkey_entry *found; 431 432 hostkeys = init_hostkeys(); 433 load_hostkeys(hostkeys, host, sysfile, 0); 434 if (userfile != NULL) { 435 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); 436 if (options.strict_modes && 437 (stat(user_hostfile, &st) == 0) && 438 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || 439 (st.st_mode & 022) != 0)) { 440 logit("Authentication refused for %.100s: " 441 "bad owner or modes for %.200s", 442 pw->pw_name, user_hostfile); 443 auth_debug_add("Ignored %.200s: bad ownership or modes", 444 user_hostfile); 445 } else { 446 temporarily_use_uid(pw); 447 load_hostkeys(hostkeys, host, user_hostfile, 0); 448 restore_uid(); 449 } 450 free(user_hostfile); 451 } 452 host_status = check_key_in_hostkeys(hostkeys, key, &found); 453 if (host_status == HOST_REVOKED) 454 error("WARNING: revoked key for %s attempted authentication", 455 host); 456 else if (host_status == HOST_OK) 457 debug_f("key for %s found at %s:%ld", 458 found->host, found->file, found->line); 459 else 460 debug_f("key for host %s not found", host); 461 462 free_hostkeys(hostkeys); 463 464 return host_status; 465 } 466 467 struct passwd * 468 getpwnamallow(struct ssh *ssh, const char *user) 469 { 470 #ifdef HAVE_LOGIN_CAP 471 extern login_cap_t *lc; 472 #ifdef HAVE_AUTH_HOSTOK 473 const char *from_host, *from_ip; 474 #endif 475 #ifdef BSD_AUTH 476 auth_session_t *as; 477 #endif 478 #endif 479 struct passwd *pw; 480 struct connection_info *ci; 481 u_int i; 482 483 ci = get_connection_info(ssh, 1, options.use_dns); 484 ci->user = user; 485 parse_server_match_config(&options, &includes, ci); 486 log_change_level(options.log_level); 487 log_verbose_reset(); 488 for (i = 0; i < options.num_log_verbose; i++) 489 log_verbose_add(options.log_verbose[i]); 490 process_permitopen(ssh, &options); 491 492 #if defined(_AIX) && defined(HAVE_SETAUTHDB) 493 aix_setauthdb(user); 494 #endif 495 496 pw = getpwnam(user); 497 498 #if defined(_AIX) && defined(HAVE_SETAUTHDB) 499 aix_restoreauthdb(); 500 #endif 501 if (pw == NULL) { 502 BLACKLIST_NOTIFY(ssh, BLACKLIST_BAD_USER, user); 503 logit("Invalid user %.100s from %.100s port %d", 504 user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 505 #ifdef CUSTOM_FAILED_LOGIN 506 record_failed_login(ssh, user, 507 auth_get_canonical_hostname(ssh, options.use_dns), "ssh"); 508 #endif 509 #ifdef SSH_AUDIT_EVENTS 510 audit_event(ssh, SSH_INVALID_USER); 511 #endif /* SSH_AUDIT_EVENTS */ 512 return (NULL); 513 } 514 if (!allowed_user(ssh, pw)) 515 return (NULL); 516 #ifdef HAVE_LOGIN_CAP 517 if ((lc = login_getpwclass(pw)) == NULL) { 518 debug("unable to get login class: %s", user); 519 return (NULL); 520 } 521 #ifdef HAVE_AUTH_HOSTOK 522 from_host = auth_get_canonical_hostname(ssh, options.use_dns); 523 from_ip = ssh_remote_ipaddr(ssh); 524 if (!auth_hostok(lc, from_host, from_ip)) { 525 debug("Denied connection for %.200s from %.200s [%.200s].", 526 pw->pw_name, from_host, from_ip); 527 return (NULL); 528 } 529 #endif /* HAVE_AUTH_HOSTOK */ 530 #ifdef HAVE_AUTH_TIMEOK 531 if (!auth_timeok(lc, time(NULL))) { 532 debug("LOGIN %.200s REFUSED (TIME)", pw->pw_name); 533 return (NULL); 534 } 535 #endif /* HAVE_AUTH_TIMEOK */ 536 #ifdef BSD_AUTH 537 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || 538 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { 539 debug("Approval failure for %s", user); 540 pw = NULL; 541 } 542 if (as != NULL) 543 auth_close(as); 544 #endif 545 #endif 546 if (pw != NULL) 547 return (pwcopy(pw)); 548 return (NULL); 549 } 550 551 /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */ 552 int 553 auth_key_is_revoked(struct sshkey *key) 554 { 555 char *fp = NULL; 556 int r; 557 558 if (options.revoked_keys_file == NULL) 559 return 0; 560 if ((fp = sshkey_fingerprint(key, options.fingerprint_hash, 561 SSH_FP_DEFAULT)) == NULL) { 562 r = SSH_ERR_ALLOC_FAIL; 563 error_fr(r, "fingerprint key"); 564 goto out; 565 } 566 567 r = sshkey_check_revoked(key, options.revoked_keys_file); 568 switch (r) { 569 case 0: 570 break; /* not revoked */ 571 case SSH_ERR_KEY_REVOKED: 572 error("Authentication key %s %s revoked by file %s", 573 sshkey_type(key), fp, options.revoked_keys_file); 574 goto out; 575 default: 576 error_r(r, "Error checking authentication key %s %s in " 577 "revoked keys file %s", sshkey_type(key), fp, 578 options.revoked_keys_file); 579 goto out; 580 } 581 582 /* Success */ 583 r = 0; 584 585 out: 586 free(fp); 587 return r == 0 ? 0 : 1; 588 } 589 590 void 591 auth_debug_add(const char *fmt,...) 592 { 593 char buf[1024]; 594 va_list args; 595 int r; 596 597 va_start(args, fmt); 598 vsnprintf(buf, sizeof(buf), fmt, args); 599 va_end(args); 600 debug3("%s", buf); 601 if (auth_debug != NULL) 602 if ((r = sshbuf_put_cstring(auth_debug, buf)) != 0) 603 fatal_fr(r, "sshbuf_put_cstring"); 604 } 605 606 void 607 auth_debug_send(struct ssh *ssh) 608 { 609 char *msg; 610 int r; 611 612 if (auth_debug == NULL) 613 return; 614 while (sshbuf_len(auth_debug) != 0) { 615 if ((r = sshbuf_get_cstring(auth_debug, &msg, NULL)) != 0) 616 fatal_fr(r, "sshbuf_get_cstring"); 617 ssh_packet_send_debug(ssh, "%s", msg); 618 free(msg); 619 } 620 } 621 622 void 623 auth_debug_reset(void) 624 { 625 if (auth_debug != NULL) 626 sshbuf_reset(auth_debug); 627 else if ((auth_debug = sshbuf_new()) == NULL) 628 fatal_f("sshbuf_new failed"); 629 } 630 631 struct passwd * 632 fakepw(void) 633 { 634 static int done = 0; 635 static struct passwd fake; 636 const char hashchars[] = "./ABCDEFGHIJKLMNOPQRSTUVWXYZ" 637 "abcdefghijklmnopqrstuvwxyz0123456789"; /* from bcrypt.c */ 638 char *cp; 639 640 if (done) 641 return (&fake); 642 643 memset(&fake, 0, sizeof(fake)); 644 fake.pw_name = "NOUSER"; 645 fake.pw_passwd = xstrdup("$2a$10$" 646 "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"); 647 for (cp = fake.pw_passwd + 7; *cp != '\0'; cp++) 648 *cp = hashchars[arc4random_uniform(sizeof(hashchars) - 1)]; 649 #ifdef HAVE_STRUCT_PASSWD_PW_GECOS 650 fake.pw_gecos = "NOUSER"; 651 #endif 652 fake.pw_uid = privsep_pw == NULL ? (uid_t)-1 : privsep_pw->pw_uid; 653 fake.pw_gid = privsep_pw == NULL ? (gid_t)-1 : privsep_pw->pw_gid; 654 #ifdef HAVE_STRUCT_PASSWD_PW_CLASS 655 fake.pw_class = ""; 656 #endif 657 fake.pw_dir = "/nonexist"; 658 fake.pw_shell = "/nonexist"; 659 done = 1; 660 661 return (&fake); 662 } 663 664 /* 665 * Returns the remote DNS hostname as a string. The returned string must not 666 * be freed. NB. this will usually trigger a DNS query the first time it is 667 * called. 668 * This function does additional checks on the hostname to mitigate some 669 * attacks on based on conflation of hostnames and IP addresses. 670 */ 671 672 static char * 673 remote_hostname(struct ssh *ssh) 674 { 675 struct sockaddr_storage from; 676 socklen_t fromlen; 677 struct addrinfo hints, *ai, *aitop; 678 char name[NI_MAXHOST], ntop2[NI_MAXHOST]; 679 const char *ntop = ssh_remote_ipaddr(ssh); 680 681 /* Get IP address of client. */ 682 fromlen = sizeof(from); 683 memset(&from, 0, sizeof(from)); 684 if (getpeername(ssh_packet_get_connection_in(ssh), 685 (struct sockaddr *)&from, &fromlen) == -1) { 686 debug("getpeername failed: %.100s", strerror(errno)); 687 return xstrdup(ntop); 688 } 689 690 ipv64_normalise_mapped(&from, &fromlen); 691 if (from.ss_family == AF_INET6) 692 fromlen = sizeof(struct sockaddr_in6); 693 694 debug3("Trying to reverse map address %.100s.", ntop); 695 /* Map the IP address to a host name. */ 696 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), 697 NULL, 0, NI_NAMEREQD) != 0) { 698 /* Host name not found. Use ip address. */ 699 return xstrdup(ntop); 700 } 701 702 /* 703 * if reverse lookup result looks like a numeric hostname, 704 * someone is trying to trick us by PTR record like following: 705 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5 706 */ 707 memset(&hints, 0, sizeof(hints)); 708 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 709 hints.ai_flags = AI_NUMERICHOST; 710 if (getaddrinfo(name, NULL, &hints, &ai) == 0) { 711 logit("Nasty PTR record \"%s\" is set up for %s, ignoring", 712 name, ntop); 713 freeaddrinfo(ai); 714 return xstrdup(ntop); 715 } 716 717 /* Names are stored in lowercase. */ 718 lowercase(name); 719 720 /* 721 * Map it back to an IP address and check that the given 722 * address actually is an address of this host. This is 723 * necessary because anyone with access to a name server can 724 * define arbitrary names for an IP address. Mapping from 725 * name to IP address can be trusted better (but can still be 726 * fooled if the intruder has access to the name server of 727 * the domain). 728 */ 729 memset(&hints, 0, sizeof(hints)); 730 hints.ai_family = from.ss_family; 731 hints.ai_socktype = SOCK_STREAM; 732 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { 733 logit("reverse mapping checking getaddrinfo for %.700s " 734 "[%s] failed.", name, ntop); 735 return xstrdup(ntop); 736 } 737 /* Look for the address from the list of addresses. */ 738 for (ai = aitop; ai; ai = ai->ai_next) { 739 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, 740 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && 741 (strcmp(ntop, ntop2) == 0)) 742 break; 743 } 744 freeaddrinfo(aitop); 745 /* If we reached the end of the list, the address was not there. */ 746 if (ai == NULL) { 747 /* Address not found for the host name. */ 748 logit("Address %.100s maps to %.600s, but this does not " 749 "map back to the address.", ntop, name); 750 return xstrdup(ntop); 751 } 752 return xstrdup(name); 753 } 754 755 /* 756 * Return the canonical name of the host in the other side of the current 757 * connection. The host name is cached, so it is efficient to call this 758 * several times. 759 */ 760 761 const char * 762 auth_get_canonical_hostname(struct ssh *ssh, int use_dns) 763 { 764 static char *dnsname; 765 766 if (!use_dns) 767 return ssh_remote_ipaddr(ssh); 768 else if (dnsname != NULL) 769 return dnsname; 770 else { 771 dnsname = remote_hostname(ssh); 772 return dnsname; 773 } 774 } 775 776 /* These functions link key/cert options to the auth framework */ 777 778 /* Log sshauthopt options locally and (optionally) for remote transmission */ 779 void 780 auth_log_authopts(const char *loc, const struct sshauthopt *opts, int do_remote) 781 { 782 int do_env = options.permit_user_env && opts->nenv > 0; 783 int do_permitopen = opts->npermitopen > 0 && 784 (options.allow_tcp_forwarding & FORWARD_LOCAL) != 0; 785 int do_permitlisten = opts->npermitlisten > 0 && 786 (options.allow_tcp_forwarding & FORWARD_REMOTE) != 0; 787 size_t i; 788 char msg[1024], buf[64]; 789 790 snprintf(buf, sizeof(buf), "%d", opts->force_tun_device); 791 /* Try to keep this alphabetically sorted */ 792 snprintf(msg, sizeof(msg), "key options:%s%s%s%s%s%s%s%s%s%s%s%s%s%s%s", 793 opts->permit_agent_forwarding_flag ? " agent-forwarding" : "", 794 opts->force_command == NULL ? "" : " command", 795 do_env ? " environment" : "", 796 opts->valid_before == 0 ? "" : "expires", 797 opts->no_require_user_presence ? " no-touch-required" : "", 798 do_permitopen ? " permitopen" : "", 799 do_permitlisten ? " permitlisten" : "", 800 opts->permit_port_forwarding_flag ? " port-forwarding" : "", 801 opts->cert_principals == NULL ? "" : " principals", 802 opts->permit_pty_flag ? " pty" : "", 803 opts->require_verify ? " uv" : "", 804 opts->force_tun_device == -1 ? "" : " tun=", 805 opts->force_tun_device == -1 ? "" : buf, 806 opts->permit_user_rc ? " user-rc" : "", 807 opts->permit_x11_forwarding_flag ? " x11-forwarding" : ""); 808 809 debug("%s: %s", loc, msg); 810 if (do_remote) 811 auth_debug_add("%s: %s", loc, msg); 812 813 if (options.permit_user_env) { 814 for (i = 0; i < opts->nenv; i++) { 815 debug("%s: environment: %s", loc, opts->env[i]); 816 if (do_remote) { 817 auth_debug_add("%s: environment: %s", 818 loc, opts->env[i]); 819 } 820 } 821 } 822 823 /* Go into a little more details for the local logs. */ 824 if (opts->valid_before != 0) { 825 format_absolute_time(opts->valid_before, buf, sizeof(buf)); 826 debug("%s: expires at %s", loc, buf); 827 } 828 if (opts->cert_principals != NULL) { 829 debug("%s: authorized principals: \"%s\"", 830 loc, opts->cert_principals); 831 } 832 if (opts->force_command != NULL) 833 debug("%s: forced command: \"%s\"", loc, opts->force_command); 834 if (do_permitopen) { 835 for (i = 0; i < opts->npermitopen; i++) { 836 debug("%s: permitted open: %s", 837 loc, opts->permitopen[i]); 838 } 839 } 840 if (do_permitlisten) { 841 for (i = 0; i < opts->npermitlisten; i++) { 842 debug("%s: permitted listen: %s", 843 loc, opts->permitlisten[i]); 844 } 845 } 846 } 847 848 /* Activate a new set of key/cert options; merging with what is there. */ 849 int 850 auth_activate_options(struct ssh *ssh, struct sshauthopt *opts) 851 { 852 struct sshauthopt *old = auth_opts; 853 const char *emsg = NULL; 854 855 debug_f("setting new authentication options"); 856 if ((auth_opts = sshauthopt_merge(old, opts, &emsg)) == NULL) { 857 error("Inconsistent authentication options: %s", emsg); 858 return -1; 859 } 860 return 0; 861 } 862 863 /* Disable forwarding, etc for the session */ 864 void 865 auth_restrict_session(struct ssh *ssh) 866 { 867 struct sshauthopt *restricted; 868 869 debug_f("restricting session"); 870 871 /* A blank sshauthopt defaults to permitting nothing */ 872 if ((restricted = sshauthopt_new()) == NULL) 873 fatal_f("sshauthopt_new failed"); 874 restricted->permit_pty_flag = 1; 875 restricted->restricted = 1; 876 877 if (auth_activate_options(ssh, restricted) != 0) 878 fatal_f("failed to restrict session"); 879 sshauthopt_free(restricted); 880 } 881