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 #include "includes.h" 26 RCSID("$OpenBSD: auth.c,v 1.46 2002/11/04 10:07:53 markus Exp $"); 27 RCSID("$FreeBSD$"); 28 29 #ifdef HAVE_LOGIN_H 30 #include <login.h> 31 #endif 32 #if defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) 33 #include <shadow.h> 34 #endif /* defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) */ 35 36 #ifdef HAVE_LIBGEN_H 37 #include <libgen.h> 38 #endif 39 40 #include "xmalloc.h" 41 #include "match.h" 42 #include "groupaccess.h" 43 #include "log.h" 44 #include "servconf.h" 45 #include "auth.h" 46 #include "auth-options.h" 47 #include "canohost.h" 48 #include "buffer.h" 49 #include "bufaux.h" 50 #include "uidswap.h" 51 #include "tildexpand.h" 52 #include "misc.h" 53 #include "bufaux.h" 54 #include "packet.h" 55 56 /* import */ 57 extern ServerOptions options; 58 59 /* Debugging messages */ 60 Buffer auth_debug; 61 int auth_debug_init; 62 63 /* 64 * Check if the user is allowed to log in via ssh. If user is listed 65 * in DenyUsers or one of user's groups is listed in DenyGroups, false 66 * will be returned. If AllowUsers isn't empty and user isn't listed 67 * there, or if AllowGroups isn't empty and one of user's groups isn't 68 * listed there, false will be returned. 69 * If the user's shell is not executable, false will be returned. 70 * Otherwise true is returned. 71 */ 72 int 73 allowed_user(struct passwd * pw) 74 { 75 struct stat st; 76 const char *hostname = NULL, *ipaddr = NULL; 77 char *shell; 78 int i; 79 #ifdef WITH_AIXAUTHENTICATE 80 char *loginmsg; 81 #endif /* WITH_AIXAUTHENTICATE */ 82 #if !defined(USE_PAM) && defined(HAVE_SHADOW_H) && \ 83 !defined(DISABLE_SHADOW) && defined(HAS_SHADOW_EXPIRE) 84 struct spwd *spw; 85 time_t today; 86 #endif 87 88 /* Shouldn't be called if pw is NULL, but better safe than sorry... */ 89 if (!pw || !pw->pw_name) 90 return 0; 91 92 #if !defined(USE_PAM) && defined(HAVE_SHADOW_H) && \ 93 !defined(DISABLE_SHADOW) && defined(HAS_SHADOW_EXPIRE) 94 #define DAY (24L * 60 * 60) /* 1 day in seconds */ 95 if ((spw = getspnam(pw->pw_name)) != NULL) { 96 today = time(NULL) / DAY; 97 debug3("allowed_user: today %d sp_expire %d sp_lstchg %d" 98 " sp_max %d", (int)today, (int)spw->sp_expire, 99 (int)spw->sp_lstchg, (int)spw->sp_max); 100 101 /* 102 * We assume account and password expiration occurs the 103 * day after the day specified. 104 */ 105 if (spw->sp_expire != -1 && today > spw->sp_expire) { 106 log("Account %.100s has expired", pw->pw_name); 107 return 0; 108 } 109 110 if (spw->sp_lstchg == 0) { 111 log("User %.100s password has expired (root forced)", 112 pw->pw_name); 113 return 0; 114 } 115 116 if (spw->sp_max != -1 && 117 today > spw->sp_lstchg + spw->sp_max) { 118 log("User %.100s password has expired (password aged)", 119 pw->pw_name); 120 return 0; 121 } 122 } 123 #endif 124 125 /* 126 * Get the shell from the password data. An empty shell field is 127 * legal, and means /bin/sh. 128 */ 129 shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell; 130 131 /* deny if shell does not exists or is not executable */ 132 if (stat(shell, &st) != 0) { 133 log("User %.100s not allowed because shell %.100s does not exist", 134 pw->pw_name, shell); 135 return 0; 136 } 137 if (S_ISREG(st.st_mode) == 0 || 138 (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { 139 log("User %.100s not allowed because shell %.100s is not executable", 140 pw->pw_name, shell); 141 return 0; 142 } 143 144 if (options.num_deny_users > 0 || options.num_allow_users > 0) { 145 hostname = get_canonical_hostname(options.verify_reverse_mapping); 146 ipaddr = get_remote_ipaddr(); 147 } 148 149 /* Return false if user is listed in DenyUsers */ 150 if (options.num_deny_users > 0) { 151 for (i = 0; i < options.num_deny_users; i++) 152 if (match_user(pw->pw_name, hostname, ipaddr, 153 options.deny_users[i])) { 154 log("User %.100s not allowed because listed in DenyUsers", 155 pw->pw_name); 156 return 0; 157 } 158 } 159 /* Return false if AllowUsers isn't empty and user isn't listed there */ 160 if (options.num_allow_users > 0) { 161 for (i = 0; i < options.num_allow_users; i++) 162 if (match_user(pw->pw_name, hostname, ipaddr, 163 options.allow_users[i])) 164 break; 165 /* i < options.num_allow_users iff we break for loop */ 166 if (i >= options.num_allow_users) { 167 log("User %.100s not allowed because not listed in AllowUsers", 168 pw->pw_name); 169 return 0; 170 } 171 } 172 if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { 173 /* Get the user's group access list (primary and supplementary) */ 174 if (ga_init(pw->pw_name, pw->pw_gid) == 0) { 175 log("User %.100s not allowed because not in any group", 176 pw->pw_name); 177 return 0; 178 } 179 180 /* Return false if one of user's groups is listed in DenyGroups */ 181 if (options.num_deny_groups > 0) 182 if (ga_match(options.deny_groups, 183 options.num_deny_groups)) { 184 ga_free(); 185 log("User %.100s not allowed because a group is listed in DenyGroups", 186 pw->pw_name); 187 return 0; 188 } 189 /* 190 * Return false if AllowGroups isn't empty and one of user's groups 191 * isn't listed there 192 */ 193 if (options.num_allow_groups > 0) 194 if (!ga_match(options.allow_groups, 195 options.num_allow_groups)) { 196 ga_free(); 197 log("User %.100s not allowed because none of user's groups are listed in AllowGroups", 198 pw->pw_name); 199 return 0; 200 } 201 ga_free(); 202 } 203 204 #ifdef WITH_AIXAUTHENTICATE 205 /* 206 * Don't check loginrestrictions() for root account (use 207 * PermitRootLogin to control logins via ssh), or if running as 208 * non-root user (since loginrestrictions will always fail). 209 */ 210 if ((pw->pw_uid != 0) && (geteuid() == 0) && 211 loginrestrictions(pw->pw_name, S_RLOGIN, NULL, &loginmsg) != 0) { 212 int loginrestrict_errno = errno; 213 214 if (loginmsg && *loginmsg) { 215 /* Remove embedded newlines (if any) */ 216 char *p; 217 for (p = loginmsg; *p; p++) { 218 if (*p == '\n') 219 *p = ' '; 220 } 221 /* Remove trailing newline */ 222 *--p = '\0'; 223 log("Login restricted for %s: %.100s", pw->pw_name, 224 loginmsg); 225 } 226 /* Don't fail if /etc/nologin set */ 227 if (!(loginrestrict_errno == EPERM && 228 stat(_PATH_NOLOGIN, &st) == 0)) 229 return 0; 230 } 231 #endif /* WITH_AIXAUTHENTICATE */ 232 233 /* We found no reason not to let this user try to log on... */ 234 return 1; 235 } 236 237 Authctxt * 238 authctxt_new(void) 239 { 240 Authctxt *authctxt = xmalloc(sizeof(*authctxt)); 241 memset(authctxt, 0, sizeof(*authctxt)); 242 return authctxt; 243 } 244 245 void 246 auth_log(Authctxt *authctxt, int authenticated, char *method, char *info) 247 { 248 void (*authlog) (const char *fmt,...) = verbose; 249 char *authmsg; 250 251 /* Raise logging level */ 252 if (authenticated == 1 || 253 !authctxt->valid || 254 authctxt->failures >= AUTH_FAIL_LOG || 255 strcmp(method, "password") == 0) 256 authlog = log; 257 258 if (authctxt->postponed) 259 authmsg = "Postponed"; 260 else 261 authmsg = authenticated ? "Accepted" : "Failed"; 262 263 authlog("%s %s for %s%.100s from %.200s port %d%s", 264 authmsg, 265 method, 266 authctxt->valid ? "" : "illegal user ", 267 authctxt->user, 268 get_remote_ipaddr(), 269 get_remote_port(), 270 info); 271 272 #ifdef WITH_AIXAUTHENTICATE 273 if (authenticated == 0 && strcmp(method, "password") == 0) 274 loginfailed(authctxt->user, 275 get_canonical_hostname(options.verify_reverse_mapping), 276 "ssh"); 277 #endif /* WITH_AIXAUTHENTICATE */ 278 279 } 280 281 /* 282 * Check whether root logins are disallowed. 283 */ 284 int 285 auth_root_allowed(char *method) 286 { 287 switch (options.permit_root_login) { 288 case PERMIT_YES: 289 return 1; 290 break; 291 case PERMIT_NO_PASSWD: 292 if (strcmp(method, "password") != 0) 293 return 1; 294 break; 295 case PERMIT_FORCED_ONLY: 296 if (forced_command) { 297 log("Root login accepted for forced command."); 298 return 1; 299 } 300 break; 301 } 302 log("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr()); 303 return 0; 304 } 305 306 307 /* 308 * Given a template and a passwd structure, build a filename 309 * by substituting % tokenised options. Currently, %% becomes '%', 310 * %h becomes the home directory and %u the username. 311 * 312 * This returns a buffer allocated by xmalloc. 313 */ 314 char * 315 expand_filename(const char *filename, struct passwd *pw) 316 { 317 Buffer buffer; 318 char *file; 319 const char *cp; 320 321 /* 322 * Build the filename string in the buffer by making the appropriate 323 * substitutions to the given file name. 324 */ 325 buffer_init(&buffer); 326 for (cp = filename; *cp; cp++) { 327 if (cp[0] == '%' && cp[1] == '%') { 328 buffer_append(&buffer, "%", 1); 329 cp++; 330 continue; 331 } 332 if (cp[0] == '%' && cp[1] == 'h') { 333 buffer_append(&buffer, pw->pw_dir, strlen(pw->pw_dir)); 334 cp++; 335 continue; 336 } 337 if (cp[0] == '%' && cp[1] == 'u') { 338 buffer_append(&buffer, pw->pw_name, 339 strlen(pw->pw_name)); 340 cp++; 341 continue; 342 } 343 buffer_append(&buffer, cp, 1); 344 } 345 buffer_append(&buffer, "\0", 1); 346 347 /* 348 * Ensure that filename starts anchored. If not, be backward 349 * compatible and prepend the '%h/' 350 */ 351 file = xmalloc(MAXPATHLEN); 352 cp = buffer_ptr(&buffer); 353 if (*cp != '/') 354 snprintf(file, MAXPATHLEN, "%s/%s", pw->pw_dir, cp); 355 else 356 strlcpy(file, cp, MAXPATHLEN); 357 358 buffer_free(&buffer); 359 return file; 360 } 361 362 char * 363 authorized_keys_file(struct passwd *pw) 364 { 365 return expand_filename(options.authorized_keys_file, pw); 366 } 367 368 char * 369 authorized_keys_file2(struct passwd *pw) 370 { 371 return expand_filename(options.authorized_keys_file2, pw); 372 } 373 374 /* return ok if key exists in sysfile or userfile */ 375 HostStatus 376 check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host, 377 const char *sysfile, const char *userfile) 378 { 379 Key *found; 380 char *user_hostfile; 381 struct stat st; 382 HostStatus host_status; 383 384 /* Check if we know the host and its host key. */ 385 found = key_new(key->type); 386 host_status = check_host_in_hostfile(sysfile, host, key, found, NULL); 387 388 if (host_status != HOST_OK && userfile != NULL) { 389 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); 390 if (options.strict_modes && 391 (stat(user_hostfile, &st) == 0) && 392 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || 393 (st.st_mode & 022) != 0)) { 394 log("Authentication refused for %.100s: " 395 "bad owner or modes for %.200s", 396 pw->pw_name, user_hostfile); 397 } else { 398 temporarily_use_uid(pw); 399 host_status = check_host_in_hostfile(user_hostfile, 400 host, key, found, NULL); 401 restore_uid(); 402 } 403 xfree(user_hostfile); 404 } 405 key_free(found); 406 407 debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ? 408 "ok" : "not found", host); 409 return host_status; 410 } 411 412 413 /* 414 * Check a given file for security. This is defined as all components 415 * of the path to the file must be owned by either the owner of 416 * of the file or root and no directories must be group or world writable. 417 * 418 * XXX Should any specific check be done for sym links ? 419 * 420 * Takes an open file descriptor, the file name, a uid and and 421 * error buffer plus max size as arguments. 422 * 423 * Returns 0 on success and -1 on failure 424 */ 425 int 426 secure_filename(FILE *f, const char *file, struct passwd *pw, 427 char *err, size_t errlen) 428 { 429 uid_t uid = pw->pw_uid; 430 char buf[MAXPATHLEN], homedir[MAXPATHLEN]; 431 char *cp; 432 int comparehome = 0; 433 struct stat st; 434 435 if (realpath(file, buf) == NULL) { 436 snprintf(err, errlen, "realpath %s failed: %s", file, 437 strerror(errno)); 438 return -1; 439 } 440 if (realpath(pw->pw_dir, homedir) != NULL) 441 comparehome = 1; 442 443 /* check the open file to avoid races */ 444 if (fstat(fileno(f), &st) < 0 || 445 (st.st_uid != 0 && st.st_uid != uid) || 446 (st.st_mode & 022) != 0) { 447 snprintf(err, errlen, "bad ownership or modes for file %s", 448 buf); 449 return -1; 450 } 451 452 /* for each component of the canonical path, walking upwards */ 453 for (;;) { 454 if ((cp = dirname(buf)) == NULL) { 455 snprintf(err, errlen, "dirname() failed"); 456 return -1; 457 } 458 strlcpy(buf, cp, sizeof(buf)); 459 460 debug3("secure_filename: checking '%s'", buf); 461 if (stat(buf, &st) < 0 || 462 (st.st_uid != 0 && st.st_uid != uid) || 463 (st.st_mode & 022) != 0) { 464 snprintf(err, errlen, 465 "bad ownership or modes for directory %s", buf); 466 return -1; 467 } 468 469 /* If are passed the homedir then we can stop */ 470 if (comparehome && strcmp(homedir, buf) == 0) { 471 debug3("secure_filename: terminating check at '%s'", 472 buf); 473 break; 474 } 475 /* 476 * dirname should always complete with a "/" path, 477 * but we can be paranoid and check for "." too 478 */ 479 if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0)) 480 break; 481 } 482 return 0; 483 } 484 485 struct passwd * 486 getpwnamallow(const char *user) 487 { 488 #ifdef HAVE_LOGIN_CAP 489 extern login_cap_t *lc; 490 #ifdef BSD_AUTH 491 auth_session_t *as; 492 #endif 493 #endif 494 struct passwd *pw; 495 496 pw = getpwnam(user); 497 if (pw == NULL) { 498 log("Illegal user %.100s from %.100s", 499 user, get_remote_ipaddr()); 500 #ifdef WITH_AIXAUTHENTICATE 501 loginfailed(user, 502 get_canonical_hostname(options.verify_reverse_mapping), 503 "ssh"); 504 #endif 505 return (NULL); 506 } 507 if (!allowed_user(pw)) 508 return (NULL); 509 #ifdef HAVE_LOGIN_CAP 510 if ((lc = login_getpwclass(pw)) == NULL) { 511 debug("unable to get login class: %s", user); 512 return (NULL); 513 } 514 #ifdef BSD_AUTH 515 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || 516 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { 517 debug("Approval failure for %s", user); 518 pw = NULL; 519 } 520 if (as != NULL) 521 auth_close(as); 522 #endif 523 #endif 524 if (pw != NULL) 525 return (pwcopy(pw)); 526 return (NULL); 527 } 528 529 void 530 auth_debug_add(const char *fmt,...) 531 { 532 char buf[1024]; 533 va_list args; 534 535 if (!auth_debug_init) 536 return; 537 538 va_start(args, fmt); 539 vsnprintf(buf, sizeof(buf), fmt, args); 540 va_end(args); 541 buffer_put_cstring(&auth_debug, buf); 542 } 543 544 void 545 auth_debug_send(void) 546 { 547 char *msg; 548 549 if (!auth_debug_init) 550 return; 551 while (buffer_len(&auth_debug)) { 552 msg = buffer_get_string(&auth_debug, NULL); 553 packet_send_debug("%s", msg); 554 xfree(msg); 555 } 556 } 557 558 void 559 auth_debug_reset(void) 560 { 561 if (auth_debug_init) 562 buffer_clear(&auth_debug); 563 else { 564 buffer_init(&auth_debug); 565 auth_debug_init = 1; 566 } 567 } 568