1/* $OpenBSD: auth.c,v 1.133 2018/09/12 01:19:12 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__RCSID("$FreeBSD$"); 28 29#include <sys/types.h> 30#include <sys/stat.h> 31#include <sys/socket.h> 32#include <sys/wait.h> 33 34#include <netinet/in.h> 35 36#include <errno.h> 37#include <fcntl.h> 38#ifdef HAVE_PATHS_H 39# include <paths.h> 40#endif 41#include <pwd.h> 42#ifdef HAVE_LOGIN_H 43#include <login.h> 44#endif 45#ifdef USE_SHADOW 46#include <shadow.h> 47#endif 48#include <stdarg.h> 49#include <stdio.h> 50#include <string.h> 51#include <unistd.h> 52#include <limits.h> 53#include <netdb.h> 54 55#include "xmalloc.h" 56#include "match.h" 57#include "groupaccess.h" 58#include "log.h" 59#include "sshbuf.h" 60#include "misc.h" 61#include "servconf.h" 62#include "sshkey.h" 63#include "hostfile.h" 64#include "auth.h" 65#include "auth-options.h" 66#include "canohost.h" 67#include "uidswap.h" 68#include "packet.h" 69#include "loginrec.h" 70#ifdef GSSAPI 71#include "ssh-gss.h" 72#endif 73#include "authfile.h" 74#include "monitor_wrap.h" 75#include "authfile.h" 76#include "ssherr.h" 77#include "compat.h" 78#include "channels.h" 79#include "blacklist_client.h" 80 81/* import */ 82extern ServerOptions options; 83extern int use_privsep; 84extern struct sshbuf *loginmsg; 85extern struct passwd *privsep_pw; 86extern struct sshauthopt *auth_opts; 87 88/* Debugging messages */ 89static 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 */ 100int 101allowed_user(struct passwd * pw) 102{ 103 struct ssh *ssh = active_state; /* XXX */ 104 struct stat st; 105 const char *hostname = NULL, *ipaddr = NULL, *passwd = NULL; 106 u_int i; 107 int r; 108#ifdef USE_SHADOW 109 struct spwd *spw = NULL; 110#endif 111 112 /* Shouldn't be called if pw is NULL, but better safe than sorry... */ 113 if (!pw || !pw->pw_name) 114 return 0; 115 116#ifdef USE_SHADOW 117 if (!options.use_pam) 118 spw = getspnam(pw->pw_name); 119#ifdef HAS_SHADOW_EXPIRE 120 if (!options.use_pam && spw != NULL && auth_shadow_acctexpired(spw)) 121 return 0; 122#endif /* HAS_SHADOW_EXPIRE */ 123#endif /* USE_SHADOW */ 124 125 /* grab passwd field for locked account check */ 126 passwd = pw->pw_passwd; 127#ifdef USE_SHADOW 128 if (spw != NULL) 129#ifdef USE_LIBIAF 130 passwd = get_iaf_password(pw); 131#else 132 passwd = spw->sp_pwdp; 133#endif /* USE_LIBIAF */ 134#endif 135 136 /* check for locked account */ 137 if (!options.use_pam && passwd && *passwd) { 138 int locked = 0; 139 140#ifdef LOCKED_PASSWD_STRING 141 if (strcmp(passwd, LOCKED_PASSWD_STRING) == 0) 142 locked = 1; 143#endif 144#ifdef LOCKED_PASSWD_PREFIX 145 if (strncmp(passwd, LOCKED_PASSWD_PREFIX, 146 strlen(LOCKED_PASSWD_PREFIX)) == 0) 147 locked = 1; 148#endif 149#ifdef LOCKED_PASSWD_SUBSTR 150 if (strstr(passwd, LOCKED_PASSWD_SUBSTR)) 151 locked = 1; 152#endif 153#ifdef USE_LIBIAF 154 free((void *) passwd); 155#endif /* USE_LIBIAF */ 156 if (locked) { 157 logit("User %.100s not allowed because account is locked", 158 pw->pw_name); 159 return 0; 160 } 161 } 162 163 /* 164 * Deny if shell does not exist or is not executable unless we 165 * are chrooting. 166 */ 167 if (options.chroot_directory == NULL || 168 strcasecmp(options.chroot_directory, "none") == 0) { 169 char *shell = xstrdup((pw->pw_shell[0] == '\0') ? 170 _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */ 171 172 if (stat(shell, &st) != 0) { 173 logit("User %.100s not allowed because shell %.100s " 174 "does not exist", pw->pw_name, shell); 175 free(shell); 176 return 0; 177 } 178 if (S_ISREG(st.st_mode) == 0 || 179 (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { 180 logit("User %.100s not allowed because shell %.100s " 181 "is not executable", pw->pw_name, shell); 182 free(shell); 183 return 0; 184 } 185 free(shell); 186 } 187 188 if (options.num_deny_users > 0 || options.num_allow_users > 0 || 189 options.num_deny_groups > 0 || options.num_allow_groups > 0) { 190 hostname = auth_get_canonical_hostname(ssh, options.use_dns); 191 ipaddr = ssh_remote_ipaddr(ssh); 192 } 193 194 /* Return false if user is listed in DenyUsers */ 195 if (options.num_deny_users > 0) { 196 for (i = 0; i < options.num_deny_users; i++) { 197 r = match_user(pw->pw_name, hostname, ipaddr, 198 options.deny_users[i]); 199 if (r < 0) { 200 fatal("Invalid DenyUsers pattern \"%.100s\"", 201 options.deny_users[i]); 202 } else if (r != 0) { 203 logit("User %.100s from %.100s not allowed " 204 "because listed in DenyUsers", 205 pw->pw_name, hostname); 206 return 0; 207 } 208 } 209 } 210 /* Return false if AllowUsers isn't empty and user isn't listed there */ 211 if (options.num_allow_users > 0) { 212 for (i = 0; i < options.num_allow_users; i++) { 213 r = match_user(pw->pw_name, hostname, ipaddr, 214 options.allow_users[i]); 215 if (r < 0) { 216 fatal("Invalid AllowUsers pattern \"%.100s\"", 217 options.allow_users[i]); 218 } else if (r == 1) 219 break; 220 } 221 /* i < options.num_allow_users iff we break for loop */ 222 if (i >= options.num_allow_users) { 223 logit("User %.100s from %.100s not allowed because " 224 "not listed in AllowUsers", pw->pw_name, hostname); 225 return 0; 226 } 227 } 228 if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { 229 /* Get the user's group access list (primary and supplementary) */ 230 if (ga_init(pw->pw_name, pw->pw_gid) == 0) { 231 logit("User %.100s from %.100s not allowed because " 232 "not in any group", pw->pw_name, hostname); 233 return 0; 234 } 235 236 /* Return false if one of user's groups is listed in DenyGroups */ 237 if (options.num_deny_groups > 0) 238 if (ga_match(options.deny_groups, 239 options.num_deny_groups)) { 240 ga_free(); 241 logit("User %.100s from %.100s not allowed " 242 "because a group is listed in DenyGroups", 243 pw->pw_name, hostname); 244 return 0; 245 } 246 /* 247 * Return false if AllowGroups isn't empty and one of user's groups 248 * isn't listed there 249 */ 250 if (options.num_allow_groups > 0) 251 if (!ga_match(options.allow_groups, 252 options.num_allow_groups)) { 253 ga_free(); 254 logit("User %.100s from %.100s not allowed " 255 "because none of user's groups are listed " 256 "in AllowGroups", pw->pw_name, hostname); 257 return 0; 258 } 259 ga_free(); 260 } 261 262#ifdef CUSTOM_SYS_AUTH_ALLOWED_USER 263 if (!sys_auth_allowed_user(pw, &loginmsg)) 264 return 0; 265#endif 266 267 /* We found no reason not to let this user try to log on... */ 268 return 1; 269} 270 271/* 272 * Formats any key left in authctxt->auth_method_key for inclusion in 273 * auth_log()'s message. Also includes authxtct->auth_method_info if present. 274 */ 275static char * 276format_method_key(Authctxt *authctxt) 277{ 278 const struct sshkey *key = authctxt->auth_method_key; 279 const char *methinfo = authctxt->auth_method_info; 280 char *fp, *cafp, *ret = NULL; 281 282 if (key == NULL) 283 return NULL; 284 285 if (sshkey_is_cert(key)) { 286 fp = sshkey_fingerprint(key, 287 options.fingerprint_hash, SSH_FP_DEFAULT); 288 cafp = sshkey_fingerprint(key->cert->signature_key, 289 options.fingerprint_hash, SSH_FP_DEFAULT); 290 xasprintf(&ret, "%s %s ID %s (serial %llu) CA %s %s%s%s", 291 sshkey_type(key), fp == NULL ? "(null)" : fp, 292 key->cert->key_id, 293 (unsigned long long)key->cert->serial, 294 sshkey_type(key->cert->signature_key), 295 cafp == NULL ? "(null)" : cafp, 296 methinfo == NULL ? "" : ", ", 297 methinfo == NULL ? "" : methinfo); 298 free(fp); 299 free(cafp); 300 } else { 301 fp = sshkey_fingerprint(key, options.fingerprint_hash, 302 SSH_FP_DEFAULT); 303 xasprintf(&ret, "%s %s%s%s", sshkey_type(key), 304 fp == NULL ? "(null)" : fp, 305 methinfo == NULL ? "" : ", ", 306 methinfo == NULL ? "" : methinfo); 307 free(fp); 308 } 309 return ret; 310} 311 312void 313auth_log(Authctxt *authctxt, int authenticated, int partial, 314 const char *method, const char *submethod) 315{ 316 struct ssh *ssh = active_state; /* XXX */ 317 int level = SYSLOG_LEVEL_VERBOSE; 318 const char *authmsg; 319 char *extra = NULL; 320 321 if (use_privsep && !mm_is_monitor() && !authctxt->postponed) 322 return; 323 324 /* Raise logging level */ 325 if (authenticated == 1 || 326 !authctxt->valid || 327 authctxt->failures >= options.max_authtries / 2 || 328 strcmp(method, "password") == 0) 329 level = SYSLOG_LEVEL_INFO; 330 331 if (authctxt->postponed) 332 authmsg = "Postponed"; 333 else if (partial) 334 authmsg = "Partial"; 335 else { 336 authmsg = authenticated ? "Accepted" : "Failed"; 337 if (authenticated) 338 BLACKLIST_NOTIFY(BLACKLIST_AUTH_OK, "ssh"); 339 } 340 341 if ((extra = format_method_key(authctxt)) == NULL) { 342 if (authctxt->auth_method_info != NULL) 343 extra = xstrdup(authctxt->auth_method_info); 344 } 345 346 do_log2(level, "%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s", 347 authmsg, 348 method, 349 submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod, 350 authctxt->valid ? "" : "invalid user ", 351 authctxt->user, 352 ssh_remote_ipaddr(ssh), 353 ssh_remote_port(ssh), 354 extra != NULL ? ": " : "", 355 extra != NULL ? extra : ""); 356 357 free(extra); 358 359#ifdef CUSTOM_FAILED_LOGIN 360 if (authenticated == 0 && !authctxt->postponed && 361 (strcmp(method, "password") == 0 || 362 strncmp(method, "keyboard-interactive", 20) == 0 || 363 strcmp(method, "challenge-response") == 0)) 364 record_failed_login(authctxt->user, 365 auth_get_canonical_hostname(ssh, options.use_dns), "ssh"); 366# ifdef WITH_AIXAUTHENTICATE 367 if (authenticated) 368 sys_auth_record_login(authctxt->user, 369 auth_get_canonical_hostname(ssh, options.use_dns), "ssh", 370 &loginmsg); 371# endif 372#endif 373#ifdef SSH_AUDIT_EVENTS 374 if (authenticated == 0 && !authctxt->postponed) 375 audit_event(audit_classify_auth(method)); 376#endif 377} 378 379 380void 381auth_maxtries_exceeded(Authctxt *authctxt) 382{ 383 struct ssh *ssh = active_state; /* XXX */ 384 385 error("maximum authentication attempts exceeded for " 386 "%s%.100s from %.200s port %d ssh2", 387 authctxt->valid ? "" : "invalid user ", 388 authctxt->user, 389 ssh_remote_ipaddr(ssh), 390 ssh_remote_port(ssh)); 391 packet_disconnect("Too many authentication failures"); 392 /* NOTREACHED */ 393} 394 395/* 396 * Check whether root logins are disallowed. 397 */ 398int 399auth_root_allowed(struct ssh *ssh, const char *method) 400{ 401 switch (options.permit_root_login) { 402 case PERMIT_YES: 403 return 1; 404 case PERMIT_NO_PASSWD: 405 if (strcmp(method, "publickey") == 0 || 406 strcmp(method, "hostbased") == 0 || 407 strcmp(method, "gssapi-with-mic") == 0) 408 return 1; 409 break; 410 case PERMIT_FORCED_ONLY: 411 if (auth_opts->force_command != NULL) { 412 logit("Root login accepted for forced command."); 413 return 1; 414 } 415 break; 416 } 417 logit("ROOT LOGIN REFUSED FROM %.200s port %d", 418 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 419 return 0; 420} 421 422 423/* 424 * Given a template and a passwd structure, build a filename 425 * by substituting % tokenised options. Currently, %% becomes '%', 426 * %h becomes the home directory and %u the username. 427 * 428 * This returns a buffer allocated by xmalloc. 429 */ 430char * 431expand_authorized_keys(const char *filename, struct passwd *pw) 432{ 433 char *file, uidstr[32], ret[PATH_MAX]; 434 int i; 435 436 snprintf(uidstr, sizeof(uidstr), "%llu", 437 (unsigned long long)pw->pw_uid); 438 file = percent_expand(filename, "h", pw->pw_dir, 439 "u", pw->pw_name, "U", uidstr, (char *)NULL); 440 441 /* 442 * Ensure that filename starts anchored. If not, be backward 443 * compatible and prepend the '%h/' 444 */ 445 if (*file == '/') 446 return (file); 447 448 i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file); 449 if (i < 0 || (size_t)i >= sizeof(ret)) 450 fatal("expand_authorized_keys: path too long"); 451 free(file); 452 return (xstrdup(ret)); 453} 454 455char * 456authorized_principals_file(struct passwd *pw) 457{ 458 if (options.authorized_principals_file == NULL) 459 return NULL; 460 return expand_authorized_keys(options.authorized_principals_file, pw); 461} 462 463/* return ok if key exists in sysfile or userfile */ 464HostStatus 465check_key_in_hostfiles(struct passwd *pw, struct sshkey *key, const char *host, 466 const char *sysfile, const char *userfile) 467{ 468 char *user_hostfile; 469 struct stat st; 470 HostStatus host_status; 471 struct hostkeys *hostkeys; 472 const struct hostkey_entry *found; 473 474 hostkeys = init_hostkeys(); 475 load_hostkeys(hostkeys, host, sysfile); 476 if (userfile != NULL) { 477 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); 478 if (options.strict_modes && 479 (stat(user_hostfile, &st) == 0) && 480 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || 481 (st.st_mode & 022) != 0)) { 482 logit("Authentication refused for %.100s: " 483 "bad owner or modes for %.200s", 484 pw->pw_name, user_hostfile); 485 auth_debug_add("Ignored %.200s: bad ownership or modes", 486 user_hostfile); 487 } else { 488 temporarily_use_uid(pw); 489 load_hostkeys(hostkeys, host, user_hostfile); 490 restore_uid(); 491 } 492 free(user_hostfile); 493 } 494 host_status = check_key_in_hostkeys(hostkeys, key, &found); 495 if (host_status == HOST_REVOKED) 496 error("WARNING: revoked key for %s attempted authentication", 497 found->host); 498 else if (host_status == HOST_OK) 499 debug("%s: key for %s found at %s:%ld", __func__, 500 found->host, found->file, found->line); 501 else 502 debug("%s: key for host %s not found", __func__, host); 503 504 free_hostkeys(hostkeys); 505 506 return host_status; 507} 508 509static FILE * 510auth_openfile(const char *file, struct passwd *pw, int strict_modes, 511 int log_missing, char *file_type) 512{ 513 char line[1024]; 514 struct stat st; 515 int fd; 516 FILE *f; 517 518 if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) { 519 if (log_missing || errno != ENOENT) 520 debug("Could not open %s '%s': %s", file_type, file, 521 strerror(errno)); 522 return NULL; 523 } 524 525 if (fstat(fd, &st) < 0) { 526 close(fd); 527 return NULL; 528 } 529 if (!S_ISREG(st.st_mode)) { 530 logit("User %s %s %s is not a regular file", 531 pw->pw_name, file_type, file); 532 close(fd); 533 return NULL; 534 } 535 unset_nonblock(fd); 536 if ((f = fdopen(fd, "r")) == NULL) { 537 close(fd); 538 return NULL; 539 } 540 if (strict_modes && 541 safe_path_fd(fileno(f), file, pw, line, sizeof(line)) != 0) { 542 fclose(f); 543 logit("Authentication refused: %s", line); 544 auth_debug_add("Ignored %s: %s", file_type, line); 545 return NULL; 546 } 547 548 return f; 549} 550 551 552FILE * 553auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes) 554{ 555 return auth_openfile(file, pw, strict_modes, 1, "authorized keys"); 556} 557 558FILE * 559auth_openprincipals(const char *file, struct passwd *pw, int strict_modes) 560{ 561 return auth_openfile(file, pw, strict_modes, 0, 562 "authorized principals"); 563} 564 565struct passwd * 566getpwnamallow(const char *user) 567{ 568 struct ssh *ssh = active_state; /* XXX */ 569#ifdef HAVE_LOGIN_CAP 570 extern login_cap_t *lc; 571#ifdef BSD_AUTH 572 auth_session_t *as; 573#endif 574#endif 575 struct passwd *pw; 576 struct connection_info *ci = get_connection_info(1, options.use_dns); 577 578 ci->user = user; 579 parse_server_match_config(&options, ci); 580 log_change_level(options.log_level); 581 process_permitopen(ssh, &options); 582 583#if defined(_AIX) && defined(HAVE_SETAUTHDB) 584 aix_setauthdb(user); 585#endif 586 587 pw = getpwnam(user); 588 589#if defined(_AIX) && defined(HAVE_SETAUTHDB) 590 aix_restoreauthdb(); 591#endif 592#ifdef HAVE_CYGWIN 593 /* 594 * Windows usernames are case-insensitive. To avoid later problems 595 * when trying to match the username, the user is only allowed to 596 * login if the username is given in the same case as stored in the 597 * user database. 598 */ 599 if (pw != NULL && strcmp(user, pw->pw_name) != 0) { 600 logit("Login name %.100s does not match stored username %.100s", 601 user, pw->pw_name); 602 pw = NULL; 603 } 604#endif 605 if (pw == NULL) { 606 BLACKLIST_NOTIFY(BLACKLIST_BAD_USER, user); 607 logit("Invalid user %.100s from %.100s port %d", 608 user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 609#ifdef CUSTOM_FAILED_LOGIN 610 record_failed_login(user, 611 auth_get_canonical_hostname(ssh, options.use_dns), "ssh"); 612#endif 613#ifdef SSH_AUDIT_EVENTS 614 audit_event(SSH_INVALID_USER); 615#endif /* SSH_AUDIT_EVENTS */ 616 return (NULL); 617 } 618 if (!allowed_user(pw)) 619 return (NULL); 620#ifdef HAVE_LOGIN_CAP 621 if ((lc = login_getpwclass(pw)) == NULL) { 622 debug("unable to get login class: %s", user); 623 return (NULL); 624 } 625#ifdef BSD_AUTH 626 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || 627 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { 628 debug("Approval failure for %s", user); 629 pw = NULL; 630 } 631 if (as != NULL) 632 auth_close(as); 633#endif 634#endif 635 if (pw != NULL) 636 return (pwcopy(pw)); 637 return (NULL); 638} 639 640/* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */ 641int 642auth_key_is_revoked(struct sshkey *key) 643{ 644 char *fp = NULL; 645 int r; 646 647 if (options.revoked_keys_file == NULL) 648 return 0; 649 if ((fp = sshkey_fingerprint(key, options.fingerprint_hash, 650 SSH_FP_DEFAULT)) == NULL) { 651 r = SSH_ERR_ALLOC_FAIL; 652 error("%s: fingerprint key: %s", __func__, ssh_err(r)); 653 goto out; 654 } 655 656 r = sshkey_check_revoked(key, options.revoked_keys_file); 657 switch (r) { 658 case 0: 659 break; /* not revoked */ 660 case SSH_ERR_KEY_REVOKED: 661 error("Authentication key %s %s revoked by file %s", 662 sshkey_type(key), fp, options.revoked_keys_file); 663 goto out; 664 default: 665 error("Error checking authentication key %s %s in " 666 "revoked keys file %s: %s", sshkey_type(key), fp, 667 options.revoked_keys_file, ssh_err(r)); 668 goto out; 669 } 670 671 /* Success */ 672 r = 0; 673 674 out: 675 free(fp); 676 return r == 0 ? 0 : 1; 677} 678 679void 680auth_debug_add(const char *fmt,...) 681{ 682 char buf[1024]; 683 va_list args; 684 int r; 685 686 if (auth_debug == NULL) 687 return; 688 689 va_start(args, fmt); 690 vsnprintf(buf, sizeof(buf), fmt, args); 691 va_end(args); 692 if ((r = sshbuf_put_cstring(auth_debug, buf)) != 0) 693 fatal("%s: sshbuf_put_cstring: %s", __func__, ssh_err(r)); 694} 695 696void 697auth_debug_send(void) 698{ 699 struct ssh *ssh = active_state; /* XXX */ 700 char *msg; 701 int r; 702 703 if (auth_debug == NULL) 704 return; 705 while (sshbuf_len(auth_debug) != 0) { 706 if ((r = sshbuf_get_cstring(auth_debug, &msg, NULL)) != 0) 707 fatal("%s: sshbuf_get_cstring: %s", 708 __func__, ssh_err(r)); 709 ssh_packet_send_debug(ssh, "%s", msg); 710 free(msg); 711 } 712} 713 714void 715auth_debug_reset(void) 716{ 717 if (auth_debug != NULL) 718 sshbuf_reset(auth_debug); 719 else if ((auth_debug = sshbuf_new()) == NULL) 720 fatal("%s: sshbuf_new failed", __func__); 721} 722 723struct passwd * 724fakepw(void) 725{ 726 static struct passwd fake; 727 728 memset(&fake, 0, sizeof(fake)); 729 fake.pw_name = "NOUSER"; 730 fake.pw_passwd = 731 "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK"; 732#ifdef HAVE_STRUCT_PASSWD_PW_GECOS 733 fake.pw_gecos = "NOUSER"; 734#endif 735 fake.pw_uid = privsep_pw == NULL ? (uid_t)-1 : privsep_pw->pw_uid; 736 fake.pw_gid = privsep_pw == NULL ? (gid_t)-1 : privsep_pw->pw_gid; 737#ifdef HAVE_STRUCT_PASSWD_PW_CLASS 738 fake.pw_class = ""; 739#endif 740 fake.pw_dir = "/nonexist"; 741 fake.pw_shell = "/nonexist"; 742 743 return (&fake); 744} 745 746/* 747 * Returns the remote DNS hostname as a string. The returned string must not 748 * be freed. NB. this will usually trigger a DNS query the first time it is 749 * called. 750 * This function does additional checks on the hostname to mitigate some 751 * attacks on legacy rhosts-style authentication. 752 * XXX is RhostsRSAAuthentication vulnerable to these? 753 * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?) 754 */ 755 756static char * 757remote_hostname(struct ssh *ssh) 758{ 759 struct sockaddr_storage from; 760 socklen_t fromlen; 761 struct addrinfo hints, *ai, *aitop; 762 char name[NI_MAXHOST], ntop2[NI_MAXHOST]; 763 const char *ntop = ssh_remote_ipaddr(ssh); 764 765 /* Get IP address of client. */ 766 fromlen = sizeof(from); 767 memset(&from, 0, sizeof(from)); 768 if (getpeername(ssh_packet_get_connection_in(ssh), 769 (struct sockaddr *)&from, &fromlen) < 0) { 770 debug("getpeername failed: %.100s", strerror(errno)); 771 return strdup(ntop); 772 } 773 774 ipv64_normalise_mapped(&from, &fromlen); 775 if (from.ss_family == AF_INET6) 776 fromlen = sizeof(struct sockaddr_in6); 777 778 debug3("Trying to reverse map address %.100s.", ntop); 779 /* Map the IP address to a host name. */ 780 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), 781 NULL, 0, NI_NAMEREQD) != 0) { 782 /* Host name not found. Use ip address. */ 783 return strdup(ntop); 784 } 785 786 /* 787 * if reverse lookup result looks like a numeric hostname, 788 * someone is trying to trick us by PTR record like following: 789 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5 790 */ 791 memset(&hints, 0, sizeof(hints)); 792 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 793 hints.ai_flags = AI_NUMERICHOST; 794 if (getaddrinfo(name, NULL, &hints, &ai) == 0) { 795 logit("Nasty PTR record \"%s\" is set up for %s, ignoring", 796 name, ntop); 797 freeaddrinfo(ai); 798 return strdup(ntop); 799 } 800 801 /* Names are stored in lowercase. */ 802 lowercase(name); 803 804 /* 805 * Map it back to an IP address and check that the given 806 * address actually is an address of this host. This is 807 * necessary because anyone with access to a name server can 808 * define arbitrary names for an IP address. Mapping from 809 * name to IP address can be trusted better (but can still be 810 * fooled if the intruder has access to the name server of 811 * the domain). 812 */ 813 memset(&hints, 0, sizeof(hints)); 814 hints.ai_family = from.ss_family; 815 hints.ai_socktype = SOCK_STREAM; 816 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { 817 logit("reverse mapping checking getaddrinfo for %.700s " 818 "[%s] failed.", name, ntop); 819 return strdup(ntop); 820 } 821 /* Look for the address from the list of addresses. */ 822 for (ai = aitop; ai; ai = ai->ai_next) { 823 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, 824 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && 825 (strcmp(ntop, ntop2) == 0)) 826 break; 827 } 828 freeaddrinfo(aitop); 829 /* If we reached the end of the list, the address was not there. */ 830 if (ai == NULL) { 831 /* Address not found for the host name. */ 832 logit("Address %.100s maps to %.600s, but this does not " 833 "map back to the address.", ntop, name); 834 return strdup(ntop); 835 } 836 return strdup(name); 837} 838 839/* 840 * Return the canonical name of the host in the other side of the current 841 * connection. The host name is cached, so it is efficient to call this 842 * several times. 843 */ 844 845const char * 846auth_get_canonical_hostname(struct ssh *ssh, int use_dns) 847{ 848 static char *dnsname; 849 850 if (!use_dns) 851 return ssh_remote_ipaddr(ssh); 852 else if (dnsname != NULL) 853 return dnsname; 854 else { 855 dnsname = remote_hostname(ssh); 856 return dnsname; 857 } 858} 859 860/* 861 * Runs command in a subprocess with a minimal environment. 862 * Returns pid on success, 0 on failure. 863 * The child stdout and stderr maybe captured, left attached or sent to 864 * /dev/null depending on the contents of flags. 865 * "tag" is prepended to log messages. 866 * NB. "command" is only used for logging; the actual command executed is 867 * av[0]. 868 */ 869pid_t 870subprocess(const char *tag, struct passwd *pw, const char *command, 871 int ac, char **av, FILE **child, u_int flags) 872{ 873 FILE *f = NULL; 874 struct stat st; 875 int fd, devnull, p[2], i; 876 pid_t pid; 877 char *cp, errmsg[512]; 878 u_int envsize; 879 char **child_env; 880 881 if (child != NULL) 882 *child = NULL; 883 884 debug3("%s: %s command \"%s\" running as %s (flags 0x%x)", __func__, 885 tag, command, pw->pw_name, flags); 886 887 /* Check consistency */ 888 if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 && 889 (flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) { 890 error("%s: inconsistent flags", __func__); 891 return 0; 892 } 893 if (((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) != (child == NULL)) { 894 error("%s: inconsistent flags/output", __func__); 895 return 0; 896 } 897 898 /* 899 * If executing an explicit binary, then verify the it exists 900 * and appears safe-ish to execute 901 */ 902 if (*av[0] != '/') { 903 error("%s path is not absolute", tag); 904 return 0; 905 } 906 temporarily_use_uid(pw); 907 if (stat(av[0], &st) < 0) { 908 error("Could not stat %s \"%s\": %s", tag, 909 av[0], strerror(errno)); 910 restore_uid(); 911 return 0; 912 } 913 if (safe_path(av[0], &st, NULL, 0, errmsg, sizeof(errmsg)) != 0) { 914 error("Unsafe %s \"%s\": %s", tag, av[0], errmsg); 915 restore_uid(); 916 return 0; 917 } 918 /* Prepare to keep the child's stdout if requested */ 919 if (pipe(p) != 0) { 920 error("%s: pipe: %s", tag, strerror(errno)); 921 restore_uid(); 922 return 0; 923 } 924 restore_uid(); 925 926 switch ((pid = fork())) { 927 case -1: /* error */ 928 error("%s: fork: %s", tag, strerror(errno)); 929 close(p[0]); 930 close(p[1]); 931 return 0; 932 case 0: /* child */ 933 /* Prepare a minimal environment for the child. */ 934 envsize = 5; 935 child_env = xcalloc(sizeof(*child_env), envsize); 936 child_set_env(&child_env, &envsize, "PATH", _PATH_STDPATH); 937 child_set_env(&child_env, &envsize, "USER", pw->pw_name); 938 child_set_env(&child_env, &envsize, "LOGNAME", pw->pw_name); 939 child_set_env(&child_env, &envsize, "HOME", pw->pw_dir); 940 if ((cp = getenv("LANG")) != NULL) 941 child_set_env(&child_env, &envsize, "LANG", cp); 942 943 for (i = 0; i < NSIG; i++) 944 signal(i, SIG_DFL); 945 946 if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) { 947 error("%s: open %s: %s", tag, _PATH_DEVNULL, 948 strerror(errno)); 949 _exit(1); 950 } 951 if (dup2(devnull, STDIN_FILENO) == -1) { 952 error("%s: dup2: %s", tag, strerror(errno)); 953 _exit(1); 954 } 955 956 /* Set up stdout as requested; leave stderr in place for now. */ 957 fd = -1; 958 if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) 959 fd = p[1]; 960 else if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0) 961 fd = devnull; 962 if (fd != -1 && dup2(fd, STDOUT_FILENO) == -1) { 963 error("%s: dup2: %s", tag, strerror(errno)); 964 _exit(1); 965 } 966 closefrom(STDERR_FILENO + 1); 967 968 /* Don't use permanently_set_uid() here to avoid fatal() */ 969 if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0) { 970 error("%s: setresgid %u: %s", tag, (u_int)pw->pw_gid, 971 strerror(errno)); 972 _exit(1); 973 } 974 if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0) { 975 error("%s: setresuid %u: %s", tag, (u_int)pw->pw_uid, 976 strerror(errno)); 977 _exit(1); 978 } 979 /* stdin is pointed to /dev/null at this point */ 980 if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 && 981 dup2(STDIN_FILENO, STDERR_FILENO) == -1) { 982 error("%s: dup2: %s", tag, strerror(errno)); 983 _exit(1); 984 } 985 986 execve(av[0], av, child_env); 987 error("%s exec \"%s\": %s", tag, command, strerror(errno)); 988 _exit(127); 989 default: /* parent */ 990 break; 991 } 992 993 close(p[1]); 994 if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) 995 close(p[0]); 996 else if ((f = fdopen(p[0], "r")) == NULL) { 997 error("%s: fdopen: %s", tag, strerror(errno)); 998 close(p[0]); 999 /* Don't leave zombie child */ 1000 kill(pid, SIGTERM); 1001 while (waitpid(pid, NULL, 0) == -1 && errno == EINTR) 1002 ; 1003 return 0; 1004 } 1005 /* Success */ 1006 debug3("%s: %s pid %ld", __func__, tag, (long)pid); 1007 if (child != NULL) 1008 *child = f; 1009 return pid; 1010} 1011 1012/* These functions link key/cert options to the auth framework */ 1013 1014/* Log sshauthopt options locally and (optionally) for remote transmission */ 1015void 1016auth_log_authopts(const char *loc, const struct sshauthopt *opts, int do_remote) 1017{ 1018 int do_env = options.permit_user_env && opts->nenv > 0; 1019 int do_permitopen = opts->npermitopen > 0 && 1020 (options.allow_tcp_forwarding & FORWARD_LOCAL) != 0; 1021 int do_permitlisten = opts->npermitlisten > 0 && 1022 (options.allow_tcp_forwarding & FORWARD_REMOTE) != 0; 1023 size_t i; 1024 char msg[1024], buf[64]; 1025 1026 snprintf(buf, sizeof(buf), "%d", opts->force_tun_device); 1027 /* Try to keep this alphabetically sorted */ 1028 snprintf(msg, sizeof(msg), "key options:%s%s%s%s%s%s%s%s%s%s%s%s%s", 1029 opts->permit_agent_forwarding_flag ? " agent-forwarding" : "", 1030 opts->force_command == NULL ? "" : " command", 1031 do_env ? " environment" : "", 1032 opts->valid_before == 0 ? "" : "expires", 1033 do_permitopen ? " permitopen" : "", 1034 do_permitlisten ? " permitlisten" : "", 1035 opts->permit_port_forwarding_flag ? " port-forwarding" : "", 1036 opts->cert_principals == NULL ? "" : " principals", 1037 opts->permit_pty_flag ? " pty" : "", 1038 opts->force_tun_device == -1 ? "" : " tun=", 1039 opts->force_tun_device == -1 ? "" : buf, 1040 opts->permit_user_rc ? " user-rc" : "", 1041 opts->permit_x11_forwarding_flag ? " x11-forwarding" : ""); 1042 1043 debug("%s: %s", loc, msg); 1044 if (do_remote) 1045 auth_debug_add("%s: %s", loc, msg); 1046 1047 if (options.permit_user_env) { 1048 for (i = 0; i < opts->nenv; i++) { 1049 debug("%s: environment: %s", loc, opts->env[i]); 1050 if (do_remote) { 1051 auth_debug_add("%s: environment: %s", 1052 loc, opts->env[i]); 1053 } 1054 } 1055 } 1056 1057 /* Go into a little more details for the local logs. */ 1058 if (opts->valid_before != 0) { 1059 format_absolute_time(opts->valid_before, buf, sizeof(buf)); 1060 debug("%s: expires at %s", loc, buf); 1061 } 1062 if (opts->cert_principals != NULL) { 1063 debug("%s: authorized principals: \"%s\"", 1064 loc, opts->cert_principals); 1065 } 1066 if (opts->force_command != NULL) 1067 debug("%s: forced command: \"%s\"", loc, opts->force_command); 1068 if (do_permitopen) { 1069 for (i = 0; i < opts->npermitopen; i++) { 1070 debug("%s: permitted open: %s", 1071 loc, opts->permitopen[i]); 1072 } 1073 } 1074 if (do_permitlisten) { 1075 for (i = 0; i < opts->npermitlisten; i++) { 1076 debug("%s: permitted listen: %s", 1077 loc, opts->permitlisten[i]); 1078 } 1079 } 1080} 1081 1082/* Activate a new set of key/cert options; merging with what is there. */ 1083int 1084auth_activate_options(struct ssh *ssh, struct sshauthopt *opts) 1085{ 1086 struct sshauthopt *old = auth_opts; 1087 const char *emsg = NULL; 1088 1089 debug("%s: setting new authentication options", __func__); 1090 if ((auth_opts = sshauthopt_merge(old, opts, &emsg)) == NULL) { 1091 error("Inconsistent authentication options: %s", emsg); 1092 return -1; 1093 } 1094 return 0; 1095} 1096 1097/* Disable forwarding, etc for the session */ 1098void 1099auth_restrict_session(struct ssh *ssh) 1100{ 1101 struct sshauthopt *restricted; 1102 1103 debug("%s: restricting session", __func__); 1104 1105 /* A blank sshauthopt defaults to permitting nothing */ 1106 restricted = sshauthopt_new(); 1107 restricted->permit_pty_flag = 1; 1108 restricted->restricted = 1; 1109 1110 if (auth_activate_options(ssh, restricted) != 0) 1111 fatal("%s: failed to restrict session", __func__); 1112 sshauthopt_free(restricted); 1113} 1114 1115int 1116auth_authorise_keyopts(struct ssh *ssh, struct passwd *pw, 1117 struct sshauthopt *opts, int allow_cert_authority, const char *loc) 1118{ 1119 const char *remote_ip = ssh_remote_ipaddr(ssh); 1120 const char *remote_host = auth_get_canonical_hostname(ssh, 1121 options.use_dns); 1122 time_t now = time(NULL); 1123 char buf[64]; 1124 1125 /* 1126 * Check keys/principals file expiry time. 1127 * NB. validity interval in certificate is handled elsewhere. 1128 */ 1129 if (opts->valid_before && now > 0 && 1130 opts->valid_before < (uint64_t)now) { 1131 format_absolute_time(opts->valid_before, buf, sizeof(buf)); 1132 debug("%s: entry expired at %s", loc, buf); 1133 auth_debug_add("%s: entry expired at %s", loc, buf); 1134 return -1; 1135 } 1136 /* Consistency checks */ 1137 if (opts->cert_principals != NULL && !opts->cert_authority) { 1138 debug("%s: principals on non-CA key", loc); 1139 auth_debug_add("%s: principals on non-CA key", loc); 1140 /* deny access */ 1141 return -1; 1142 } 1143 /* cert-authority flag isn't valid in authorized_principals files */ 1144 if (!allow_cert_authority && opts->cert_authority) { 1145 debug("%s: cert-authority flag invalid here", loc); 1146 auth_debug_add("%s: cert-authority flag invalid here", loc); 1147 /* deny access */ 1148 return -1; 1149 } 1150 1151 /* Perform from= checks */ 1152 if (opts->required_from_host_keys != NULL) { 1153 switch (match_host_and_ip(remote_host, remote_ip, 1154 opts->required_from_host_keys )) { 1155 case 1: 1156 /* Host name matches. */ 1157 break; 1158 case -1: 1159 default: 1160 debug("%s: invalid from criteria", loc); 1161 auth_debug_add("%s: invalid from criteria", loc); 1162 /* FALLTHROUGH */ 1163 case 0: 1164 logit("%s: Authentication tried for %.100s with " 1165 "correct key but not from a permitted " 1166 "host (host=%.200s, ip=%.200s, required=%.200s).", 1167 loc, pw->pw_name, remote_host, remote_ip, 1168 opts->required_from_host_keys); 1169 auth_debug_add("%s: Your host '%.200s' is not " 1170 "permitted to use this key for login.", 1171 loc, remote_host); 1172 /* deny access */ 1173 return -1; 1174 } 1175 } 1176 /* Check source-address restriction from certificate */ 1177 if (opts->required_from_host_cert != NULL) { 1178 switch (addr_match_cidr_list(remote_ip, 1179 opts->required_from_host_cert)) { 1180 case 1: 1181 /* accepted */ 1182 break; 1183 case -1: 1184 default: 1185 /* invalid */ 1186 error("%s: Certificate source-address invalid", 1187 loc); 1188 /* FALLTHROUGH */ 1189 case 0: 1190 logit("%s: Authentication tried for %.100s with valid " 1191 "certificate but not from a permitted source " 1192 "address (%.200s).", loc, pw->pw_name, remote_ip); 1193 auth_debug_add("%s: Your address '%.200s' is not " 1194 "permitted to use this certificate for login.", 1195 loc, remote_ip); 1196 return -1; 1197 } 1198 } 1199 /* 1200 * 1201 * XXX this is spammy. We should report remotely only for keys 1202 * that are successful in actual auth attempts, and not PK_OK 1203 * tests. 1204 */ 1205 auth_log_authopts(loc, opts, 1); 1206 1207 return 0; 1208} 1209