1 /* 2 * Copyright (c) 2000 Markus Friedl. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 23 */ 24 /* 25 * Copyright 2004 Sun Microsystems, Inc. All rights reserved. 26 * Use is subject to license terms. 27 */ 28 29 #include "includes.h" 30 RCSID("$OpenBSD: auth.c,v 1.45 2002/09/20 18:41:29 stevesk Exp $"); 31 32 #pragma ident "%Z%%M% %I% %E% SMI" 33 34 #ifdef HAVE_LOGIN_H 35 #include <login.h> 36 #endif 37 #if defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) 38 #include <shadow.h> 39 #endif /* defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) */ 40 41 #ifdef HAVE_LIBGEN_H 42 #include <libgen.h> 43 #endif 44 45 #include "xmalloc.h" 46 #include "match.h" 47 #include "groupaccess.h" 48 #include "log.h" 49 #include "servconf.h" 50 #include "auth.h" 51 #include "auth-options.h" 52 #include "canohost.h" 53 #include "buffer.h" 54 #include "bufaux.h" 55 #include "uidswap.h" 56 #include "tildexpand.h" 57 #include "misc.h" 58 #include "bufaux.h" 59 #include "packet.h" 60 61 #ifdef HAVE_BSM 62 #include "bsmaudit.h" 63 #include <bsm/adt.h> 64 #endif /* HAVE_BSM */ 65 66 /* import */ 67 extern ServerOptions options; 68 69 /* Debugging messages */ 70 Buffer auth_debug; 71 int auth_debug_init; 72 73 /* 74 * Check if the user is allowed to log in via ssh. If user is listed 75 * in DenyUsers or one of user's groups is listed in DenyGroups, false 76 * will be returned. If AllowUsers isn't empty and user isn't listed 77 * there, or if AllowGroups isn't empty and one of user's groups isn't 78 * listed there, false will be returned. 79 * If the user's shell is not executable, false will be returned. 80 * Otherwise true is returned. 81 */ 82 int 83 allowed_user(struct passwd * pw) 84 { 85 struct stat st; 86 const char *hostname = NULL, *ipaddr = NULL; 87 char *shell; 88 int i; 89 #ifdef WITH_AIXAUTHENTICATE 90 char *loginmsg; 91 #endif /* WITH_AIXAUTHENTICATE */ 92 #if !defined(USE_PAM) && defined(HAVE_SHADOW_H) && \ 93 !defined(DISABLE_SHADOW) && defined(HAS_SHADOW_EXPIRE) 94 struct spwd *spw; 95 96 /* Shouldn't be called if pw is NULL, but better safe than sorry... */ 97 if (!pw || !pw->pw_name) 98 return 0; 99 100 #define DAY (24L * 60 * 60) /* 1 day in seconds */ 101 spw = getspnam(pw->pw_name); 102 if (spw != NULL) { 103 time_t today = time(NULL) / DAY; 104 debug3("allowed_user: today %d sp_expire %d sp_lstchg %d" 105 " sp_max %d", (int)today, (int)spw->sp_expire, 106 (int)spw->sp_lstchg, (int)spw->sp_max); 107 108 /* 109 * We assume account and password expiration occurs the 110 * day after the day specified. 111 */ 112 if (spw->sp_expire != -1 && today > spw->sp_expire) { 113 log("Account %.100s has expired", pw->pw_name); 114 return 0; 115 } 116 117 if (spw->sp_lstchg == 0) { 118 log("User %.100s password has expired (root forced)", 119 pw->pw_name); 120 return 0; 121 } 122 123 if (spw->sp_max != -1 && 124 today > spw->sp_lstchg + spw->sp_max) { 125 log("User %.100s password has expired (password aged)", 126 pw->pw_name); 127 return 0; 128 } 129 } 130 #else 131 /* Shouldn't be called if pw is NULL, but better safe than sorry... */ 132 if (!pw || !pw->pw_name) 133 return 0; 134 #endif 135 136 /* 137 * Get the shell from the password data. An empty shell field is 138 * legal, and means /bin/sh. 139 */ 140 shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell; 141 142 /* deny if shell does not exists or is not executable */ 143 if (stat(shell, &st) != 0) { 144 log("User %.100s not allowed because shell %.100s does not exist", 145 pw->pw_name, shell); 146 return 0; 147 } 148 if (S_ISREG(st.st_mode) == 0 || 149 (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { 150 log("User %.100s not allowed because shell %.100s is not executable", 151 pw->pw_name, shell); 152 return 0; 153 } 154 155 if (options.num_deny_users > 0 || options.num_allow_users > 0) { 156 hostname = get_canonical_hostname(options.verify_reverse_mapping); 157 ipaddr = get_remote_ipaddr(); 158 } 159 160 /* Return false if user is listed in DenyUsers */ 161 if (options.num_deny_users > 0) { 162 for (i = 0; i < options.num_deny_users; i++) 163 if (match_user(pw->pw_name, hostname, ipaddr, 164 options.deny_users[i])) { 165 log("User %.100s not allowed because listed in DenyUsers", 166 pw->pw_name); 167 return 0; 168 } 169 } 170 /* Return false if AllowUsers isn't empty and user isn't listed there */ 171 if (options.num_allow_users > 0) { 172 for (i = 0; i < options.num_allow_users; i++) 173 if (match_user(pw->pw_name, hostname, ipaddr, 174 options.allow_users[i])) 175 break; 176 /* i < options.num_allow_users iff we break for loop */ 177 if (i >= options.num_allow_users) { 178 log("User %.100s not allowed because not listed in AllowUsers", 179 pw->pw_name); 180 return 0; 181 } 182 } 183 if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { 184 /* Get the user's group access list (primary and supplementary) */ 185 if (ga_init(pw->pw_name, pw->pw_gid) == 0) { 186 log("User %.100s not allowed because not in any group", 187 pw->pw_name); 188 return 0; 189 } 190 191 /* Return false if one of user's groups is listed in DenyGroups */ 192 if (options.num_deny_groups > 0) 193 if (ga_match(options.deny_groups, 194 options.num_deny_groups)) { 195 ga_free(); 196 log("User %.100s not allowed because a group is listed in DenyGroups", 197 pw->pw_name); 198 return 0; 199 } 200 /* 201 * Return false if AllowGroups isn't empty and one of user's groups 202 * isn't listed there 203 */ 204 if (options.num_allow_groups > 0) 205 if (!ga_match(options.allow_groups, 206 options.num_allow_groups)) { 207 ga_free(); 208 log("User %.100s not allowed because none of user's groups are listed in AllowGroups", 209 pw->pw_name); 210 return 0; 211 } 212 ga_free(); 213 } 214 215 #ifdef WITH_AIXAUTHENTICATE 216 if (loginrestrictions(pw->pw_name, S_RLOGIN, NULL, &loginmsg) != 0) { 217 if (loginmsg && *loginmsg) { 218 /* Remove embedded newlines (if any) */ 219 char *p; 220 for (p = loginmsg; *p; p++) { 221 if (*p == '\n') 222 *p = ' '; 223 } 224 /* Remove trailing newline */ 225 *--p = '\0'; 226 log("Login restricted for %s: %.100s", pw->pw_name, loginmsg); 227 } 228 return 0; 229 } 230 #endif /* WITH_AIXAUTHENTICATE */ 231 232 /* We found no reason not to let this user try to log on... */ 233 return 1; 234 } 235 236 Authctxt * 237 authctxt_new(void) 238 { 239 Authctxt *authctxt = xmalloc(sizeof(*authctxt)); 240 memset(authctxt, 0, sizeof(*authctxt)); 241 return authctxt; 242 } 243 244 void 245 auth_log(Authctxt *authctxt, int authenticated, char *method, char *info) 246 { 247 void (*authlog) (const char *fmt,...) = verbose; 248 char *authmsg, *user_str; 249 250 if (authctxt == NULL) 251 fatal("%s: INTERNAL ERROR", __func__); 252 253 /* Raise logging level */ 254 if (authenticated == 1 || !authctxt->valid) 255 authlog = log; 256 else if (authctxt->failures >= AUTH_FAIL_LOG || 257 authctxt->attempt >= options.max_auth_tries_log || 258 authctxt->init_attempt >= options.max_init_auth_tries_log) 259 authlog = notice; 260 261 if (authctxt->method) { 262 authmsg = "Failed"; 263 if (authctxt->method->postponed) 264 authmsg = "Postponed"; /* shouldn't happen */ 265 if (authctxt->method->abandoned) 266 authmsg = "Abandoned"; 267 if (authctxt->method->authenticated) { 268 if (userauth_check_partial_failure(authctxt)) 269 authmsg = "Partially accepted"; 270 else 271 authmsg = "Accepted"; 272 } 273 else 274 authmsg = "Failed"; 275 } 276 else { 277 authmsg = authenticated ? "Accepted" : "Failed"; 278 } 279 280 if (authctxt->user == NULL || *authctxt->user == '\0') 281 user_str = "<implicit>"; 282 else if (!authctxt->valid) 283 user_str = "<invalid username>"; 284 else 285 user_str = authctxt->user; 286 287 authlog("%s %s for %s from %.200s port %d%s", 288 authmsg, 289 (method != NULL) ? method : "<unknown authentication method>", 290 user_str, 291 get_remote_ipaddr(), 292 get_remote_port(), 293 info); 294 295 #ifdef WITH_AIXAUTHENTICATE 296 if (authenticated == 0 && strcmp(method, "password") == 0) 297 loginfailed(authctxt->user, 298 get_canonical_hostname(options.verify_reverse_mapping), 299 "ssh"); 300 #endif /* WITH_AIXAUTHENTICATE */ 301 302 } 303 304 #ifdef HAVE_BSM 305 void 306 audit_failed_login_cleanup(void *ctxt) 307 { 308 Authctxt *authctxt = (Authctxt *)ctxt; 309 adt_session_data_t *ah; 310 311 if (authctxt == NULL) 312 /* Internal error */ 313 audit_sshd_login_failure(&ah, PAM_ABORT); 314 else if (authctxt->pam == NULL && authctxt->pam_retval != PAM_SUCCESS) 315 audit_sshd_login_failure(&ah, authctxt->pam_retval); 316 else if (authctxt->pam == NULL && authctxt->pam_retval == PAM_SUCCESS) 317 audit_sshd_login_failure(&ah, PAM_PERM_DENIED); 318 else if (!authctxt->valid) 319 audit_sshd_login_failure(&ah, PAM_USER_UNKNOWN); 320 else 321 audit_sshd_login_failure(&ah, AUTHPAM_ERROR(authctxt, 322 PAM_PERM_DENIED)); 323 } 324 #endif /* HAVE_BSM */ 325 326 /* 327 * Check whether root logins are disallowed. 328 */ 329 int 330 auth_root_allowed(char *method) 331 { 332 switch (options.permit_root_login) { 333 case PERMIT_YES: 334 return 1; 335 break; 336 case PERMIT_NO_PASSWD: 337 if (strcmp(method, "password") != 0 && 338 strcmp(method, "keyboard-interactive") != 0) 339 return 1; 340 break; 341 case PERMIT_FORCED_ONLY: 342 if (forced_command) { 343 log("Root login accepted for forced command."); 344 return 1; 345 } 346 break; 347 } 348 log("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr()); 349 return 0; 350 } 351 352 353 /* 354 * Given a template and a passwd structure, build a filename 355 * by substituting % tokenised options. Currently, %% becomes '%', 356 * %h becomes the home directory and %u the username. 357 * 358 * This returns a buffer allocated by xmalloc. 359 */ 360 char * 361 expand_filename(const char *filename, struct passwd *pw) 362 { 363 Buffer buffer; 364 char *file; 365 const char *cp; 366 367 if (pw == 0) 368 return NULL; /* shouldn't happen */ 369 /* 370 * Build the filename string in the buffer by making the appropriate 371 * substitutions to the given file name. 372 */ 373 buffer_init(&buffer); 374 for (cp = filename; *cp; cp++) { 375 if (cp[0] == '%' && cp[1] == '%') { 376 buffer_append(&buffer, "%", 1); 377 cp++; 378 continue; 379 } 380 if (cp[0] == '%' && cp[1] == 'h') { 381 buffer_append(&buffer, pw->pw_dir, strlen(pw->pw_dir)); 382 cp++; 383 continue; 384 } 385 if (cp[0] == '%' && cp[1] == 'u') { 386 buffer_append(&buffer, pw->pw_name, 387 strlen(pw->pw_name)); 388 cp++; 389 continue; 390 } 391 buffer_append(&buffer, cp, 1); 392 } 393 buffer_append(&buffer, "\0", 1); 394 395 /* 396 * Ensure that filename starts anchored. If not, be backward 397 * compatible and prepend the '%h/' 398 */ 399 file = xmalloc(MAXPATHLEN); 400 cp = buffer_ptr(&buffer); 401 if (*cp != '/') 402 snprintf(file, MAXPATHLEN, "%s/%s", pw->pw_dir, cp); 403 else 404 strlcpy(file, cp, MAXPATHLEN); 405 406 buffer_free(&buffer); 407 return file; 408 } 409 410 char * 411 authorized_keys_file(struct passwd *pw) 412 { 413 return expand_filename(options.authorized_keys_file, pw); 414 } 415 416 char * 417 authorized_keys_file2(struct passwd *pw) 418 { 419 return expand_filename(options.authorized_keys_file2, pw); 420 } 421 422 /* return ok if key exists in sysfile or userfile */ 423 HostStatus 424 check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host, 425 const char *sysfile, const char *userfile) 426 { 427 Key *found; 428 char *user_hostfile; 429 struct stat st; 430 HostStatus host_status; 431 432 /* Check if we know the host and its host key. */ 433 found = key_new(key->type); 434 host_status = check_host_in_hostfile(sysfile, host, key, found, NULL); 435 436 if (host_status != HOST_OK && userfile != NULL) { 437 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); 438 if (options.strict_modes && 439 (stat(user_hostfile, &st) == 0) && 440 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || 441 (st.st_mode & 022) != 0)) { 442 log("Authentication refused for %.100s: " 443 "bad owner or modes for %.200s", 444 pw->pw_name, user_hostfile); 445 } else { 446 temporarily_use_uid(pw); 447 host_status = check_host_in_hostfile(user_hostfile, 448 host, key, found, NULL); 449 restore_uid(); 450 } 451 xfree(user_hostfile); 452 } 453 key_free(found); 454 455 debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ? 456 "ok" : "not found", host); 457 return host_status; 458 } 459 460 461 /* 462 * Check a given file for security. This is defined as all components 463 * of the path to the file must be owned by either the owner of 464 * of the file or root and no directories must be group or world writable. 465 * 466 * XXX Should any specific check be done for sym links ? 467 * 468 * Takes an open file descriptor, the file name, a uid and and 469 * error buffer plus max size as arguments. 470 * 471 * Returns 0 on success and -1 on failure 472 */ 473 int 474 secure_filename(FILE *f, const char *file, struct passwd *pw, 475 char *err, size_t errlen) 476 { 477 uid_t uid; 478 char buf[MAXPATHLEN], homedir[MAXPATHLEN]; 479 char *cp; 480 struct stat st; 481 482 if (pw == NULL) 483 return 0; 484 485 uid = pw->pw_uid; 486 487 if (realpath(file, buf) == NULL) { 488 snprintf(err, errlen, "realpath %s failed: %s", file, 489 strerror(errno)); 490 return -1; 491 } 492 if (realpath(pw->pw_dir, homedir) == NULL) { 493 snprintf(err, errlen, "realpath %s failed: %s", pw->pw_dir, 494 strerror(errno)); 495 return -1; 496 } 497 498 /* check the open file to avoid races */ 499 if (fstat(fileno(f), &st) < 0 || 500 (st.st_uid != 0 && st.st_uid != uid) || 501 (st.st_mode & 022) != 0) { 502 snprintf(err, errlen, "bad ownership or modes for file %s", 503 buf); 504 return -1; 505 } 506 507 /* for each component of the canonical path, walking upwards */ 508 for (;;) { 509 if ((cp = dirname(buf)) == NULL) { 510 snprintf(err, errlen, "dirname() failed"); 511 return -1; 512 } 513 strlcpy(buf, cp, sizeof(buf)); 514 515 debug3("secure_filename: checking '%s'", buf); 516 if (stat(buf, &st) < 0 || 517 (st.st_uid != 0 && st.st_uid != uid) || 518 (st.st_mode & 022) != 0) { 519 snprintf(err, errlen, 520 "bad ownership or modes for directory %s", buf); 521 return -1; 522 } 523 524 /* If are passed the homedir then we can stop */ 525 if (strcmp(homedir, buf) == 0) { 526 debug3("secure_filename: terminating check at '%s'", 527 buf); 528 break; 529 } 530 /* 531 * dirname should always complete with a "/" path, 532 * but we can be paranoid and check for "." too 533 */ 534 if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0)) 535 break; 536 } 537 return 0; 538 } 539 540 struct passwd * 541 getpwnamallow(const char *user) 542 { 543 #ifdef HAVE_LOGIN_CAP 544 extern login_cap_t *lc; 545 #ifdef BSD_AUTH 546 auth_session_t *as; 547 #endif 548 #endif 549 struct passwd *pw; 550 551 if (user == NULL || *user == '\0') 552 return (NULL); /* implicit user, will be set later */ 553 554 pw = getpwnam(user); 555 if (pw == NULL) { 556 log("Illegal user %.100s from %.100s", 557 user, get_remote_ipaddr()); 558 return (NULL); 559 } 560 if (!allowed_user(pw)) 561 return (NULL); 562 #ifdef HAVE_LOGIN_CAP 563 if ((lc = login_getclass(pw->pw_class)) == NULL) { 564 debug("unable to get login class: %s", user); 565 return (NULL); 566 } 567 #ifdef BSD_AUTH 568 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || 569 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { 570 debug("Approval failure for %s", user); 571 pw = NULL; 572 } 573 if (as != NULL) 574 auth_close(as); 575 #endif 576 #endif 577 if (pw != NULL) 578 return (pwcopy(pw)); 579 return (NULL); 580 } 581 582 void 583 auth_debug_add(const char *fmt,...) 584 { 585 char buf[1024]; 586 va_list args; 587 588 if (!auth_debug_init) 589 return; 590 591 va_start(args, fmt); 592 vsnprintf(buf, sizeof(buf), fmt, args); 593 va_end(args); 594 buffer_put_cstring(&auth_debug, buf); 595 } 596 597 void 598 auth_debug_send(void) 599 { 600 char *msg; 601 602 if (!auth_debug_init) 603 return; 604 while (buffer_len(&auth_debug)) { 605 msg = buffer_get_string(&auth_debug, NULL); 606 packet_send_debug("%s", msg); 607 xfree(msg); 608 } 609 } 610 611 void 612 auth_debug_reset(void) 613 { 614 if (auth_debug_init) 615 buffer_clear(&auth_debug); 616 else { 617 buffer_init(&auth_debug); 618 auth_debug_init = 1; 619 } 620 } 621