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 1.43 2002/05/17 14:27:55 millert Exp $"); 27 28 #ifdef HAVE_LOGIN_H 29 #include <login.h> 30 #endif 31 #if defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) 32 #include <shadow.h> 33 #endif /* defined(HAVE_SHADOW_H) && !defined(DISABLE_SHADOW) */ 34 35 #ifdef HAVE_LIBGEN_H 36 #include <libgen.h> 37 #endif 38 39 #include "xmalloc.h" 40 #include "match.h" 41 #include "groupaccess.h" 42 #include "log.h" 43 #include "servconf.h" 44 #include "auth.h" 45 #include "auth-options.h" 46 #include "canohost.h" 47 #include "buffer.h" 48 #include "bufaux.h" 49 #include "uidswap.h" 50 #include "tildexpand.h" 51 #include "misc.h" 52 #include "bufaux.h" 53 #include "packet.h" 54 55 /* import */ 56 extern ServerOptions options; 57 58 /* Debugging messages */ 59 Buffer auth_debug; 60 int auth_debug_init; 61 62 /* 63 * Check if the user is allowed to log in via ssh. If user is listed 64 * in DenyUsers or one of user's groups is listed in DenyGroups, false 65 * will be returned. If AllowUsers isn't empty and user isn't listed 66 * there, or if AllowGroups isn't empty and one of user's groups isn't 67 * listed there, false will be returned. 68 * If the user's shell is not executable, false will be returned. 69 * Otherwise true is returned. 70 */ 71 int 72 allowed_user(struct passwd * pw) 73 { 74 struct stat st; 75 const char *hostname = NULL, *ipaddr = NULL; 76 char *shell; 77 int i; 78 #ifdef WITH_AIXAUTHENTICATE 79 char *loginmsg; 80 #endif /* WITH_AIXAUTHENTICATE */ 81 #if !defined(USE_PAM) && defined(HAVE_SHADOW_H) && \ 82 !defined(DISABLE_SHADOW) && defined(HAS_SHADOW_EXPIRE) 83 struct spwd *spw; 84 85 /* Shouldn't be called if pw is NULL, but better safe than sorry... */ 86 if (!pw || !pw->pw_name) 87 return 0; 88 89 #define DAY (24L * 60 * 60) /* 1 day in seconds */ 90 spw = getspnam(pw->pw_name); 91 if (spw != NULL) { 92 time_t today = time(NULL) / DAY; 93 debug3("allowed_user: today %d sp_expire %d sp_lstchg %d" 94 " sp_max %d", (int)today, (int)spw->sp_expire, 95 (int)spw->sp_lstchg, (int)spw->sp_max); 96 97 /* 98 * We assume account and password expiration occurs the 99 * day after the day specified. 100 */ 101 if (spw->sp_expire != -1 && today > spw->sp_expire) { 102 log("Account %.100s has expired", pw->pw_name); 103 return 0; 104 } 105 106 if (spw->sp_lstchg == 0) { 107 log("User %.100s password has expired (root forced)", 108 pw->pw_name); 109 return 0; 110 } 111 112 if (spw->sp_max != -1 && 113 today > spw->sp_lstchg + spw->sp_max) { 114 log("User %.100s password has expired (password aged)", 115 pw->pw_name); 116 return 0; 117 } 118 } 119 #else 120 /* Shouldn't be called if pw is NULL, but better safe than sorry... */ 121 if (!pw || !pw->pw_name) 122 return 0; 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 if (loginrestrictions(pw->pw_name, S_RLOGIN, NULL, &loginmsg) != 0) { 206 if (loginmsg && *loginmsg) { 207 /* Remove embedded newlines (if any) */ 208 char *p; 209 for (p = loginmsg; *p; p++) { 210 if (*p == '\n') 211 *p = ' '; 212 } 213 /* Remove trailing newline */ 214 *--p = '\0'; 215 log("Login restricted for %s: %.100s", pw->pw_name, loginmsg); 216 } 217 return 0; 218 } 219 #endif /* WITH_AIXAUTHENTICATE */ 220 221 /* We found no reason not to let this user try to log on... */ 222 return 1; 223 } 224 225 Authctxt * 226 authctxt_new(void) 227 { 228 Authctxt *authctxt = xmalloc(sizeof(*authctxt)); 229 memset(authctxt, 0, sizeof(*authctxt)); 230 return authctxt; 231 } 232 233 void 234 auth_log(Authctxt *authctxt, int authenticated, char *method, char *info) 235 { 236 void (*authlog) (const char *fmt,...) = verbose; 237 char *authmsg; 238 239 /* Raise logging level */ 240 if (authenticated == 1 || 241 !authctxt->valid || 242 authctxt->failures >= AUTH_FAIL_LOG || 243 strcmp(method, "password") == 0) 244 authlog = log; 245 246 if (authctxt->postponed) 247 authmsg = "Postponed"; 248 else 249 authmsg = authenticated ? "Accepted" : "Failed"; 250 251 authlog("%s %s for %s%.100s from %.200s port %d%s", 252 authmsg, 253 method, 254 authctxt->valid ? "" : "illegal user ", 255 authctxt->user, 256 get_remote_ipaddr(), 257 get_remote_port(), 258 info); 259 } 260 261 /* 262 * Check whether root logins are disallowed. 263 */ 264 int 265 auth_root_allowed(char *method) 266 { 267 switch (options.permit_root_login) { 268 case PERMIT_YES: 269 return 1; 270 break; 271 case PERMIT_NO_PASSWD: 272 if (strcmp(method, "password") != 0) 273 return 1; 274 break; 275 case PERMIT_FORCED_ONLY: 276 if (forced_command) { 277 log("Root login accepted for forced command."); 278 return 1; 279 } 280 break; 281 } 282 log("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr()); 283 return 0; 284 } 285 286 287 /* 288 * Given a template and a passwd structure, build a filename 289 * by substituting % tokenised options. Currently, %% becomes '%', 290 * %h becomes the home directory and %u the username. 291 * 292 * This returns a buffer allocated by xmalloc. 293 */ 294 char * 295 expand_filename(const char *filename, struct passwd *pw) 296 { 297 Buffer buffer; 298 char *file; 299 const char *cp; 300 301 /* 302 * Build the filename string in the buffer by making the appropriate 303 * substitutions to the given file name. 304 */ 305 buffer_init(&buffer); 306 for (cp = filename; *cp; cp++) { 307 if (cp[0] == '%' && cp[1] == '%') { 308 buffer_append(&buffer, "%", 1); 309 cp++; 310 continue; 311 } 312 if (cp[0] == '%' && cp[1] == 'h') { 313 buffer_append(&buffer, pw->pw_dir, strlen(pw->pw_dir)); 314 cp++; 315 continue; 316 } 317 if (cp[0] == '%' && cp[1] == 'u') { 318 buffer_append(&buffer, pw->pw_name, 319 strlen(pw->pw_name)); 320 cp++; 321 continue; 322 } 323 buffer_append(&buffer, cp, 1); 324 } 325 buffer_append(&buffer, "\0", 1); 326 327 /* 328 * Ensure that filename starts anchored. If not, be backward 329 * compatible and prepend the '%h/' 330 */ 331 file = xmalloc(MAXPATHLEN); 332 cp = buffer_ptr(&buffer); 333 if (*cp != '/') 334 snprintf(file, MAXPATHLEN, "%s/%s", pw->pw_dir, cp); 335 else 336 strlcpy(file, cp, MAXPATHLEN); 337 338 buffer_free(&buffer); 339 return file; 340 } 341 342 char * 343 authorized_keys_file(struct passwd *pw) 344 { 345 return expand_filename(options.authorized_keys_file, pw); 346 } 347 348 char * 349 authorized_keys_file2(struct passwd *pw) 350 { 351 return expand_filename(options.authorized_keys_file2, pw); 352 } 353 354 /* return ok if key exists in sysfile or userfile */ 355 HostStatus 356 check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host, 357 const char *sysfile, const char *userfile) 358 { 359 Key *found; 360 char *user_hostfile; 361 struct stat st; 362 HostStatus host_status; 363 364 /* Check if we know the host and its host key. */ 365 found = key_new(key->type); 366 host_status = check_host_in_hostfile(sysfile, host, key, found, NULL); 367 368 if (host_status != HOST_OK && userfile != NULL) { 369 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); 370 if (options.strict_modes && 371 (stat(user_hostfile, &st) == 0) && 372 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || 373 (st.st_mode & 022) != 0)) { 374 log("Authentication refused for %.100s: " 375 "bad owner or modes for %.200s", 376 pw->pw_name, user_hostfile); 377 } else { 378 temporarily_use_uid(pw); 379 host_status = check_host_in_hostfile(user_hostfile, 380 host, key, found, NULL); 381 restore_uid(); 382 } 383 xfree(user_hostfile); 384 } 385 key_free(found); 386 387 debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ? 388 "ok" : "not found", host); 389 return host_status; 390 } 391 392 393 /* 394 * Check a given file for security. This is defined as all components 395 * of the path to the file must either be owned by either the owner of 396 * of the file or root and no directories must be group or world writable. 397 * 398 * XXX Should any specific check be done for sym links ? 399 * 400 * Takes an open file descriptor, the file name, a uid and and 401 * error buffer plus max size as arguments. 402 * 403 * Returns 0 on success and -1 on failure 404 */ 405 int 406 secure_filename(FILE *f, const char *file, struct passwd *pw, 407 char *err, size_t errlen) 408 { 409 uid_t uid = pw->pw_uid; 410 char buf[MAXPATHLEN], homedir[MAXPATHLEN]; 411 char *cp; 412 struct stat st; 413 414 if (realpath(file, buf) == NULL) { 415 snprintf(err, errlen, "realpath %s failed: %s", file, 416 strerror(errno)); 417 return -1; 418 } 419 if (realpath(pw->pw_dir, homedir) == NULL) { 420 snprintf(err, errlen, "realpath %s failed: %s", pw->pw_dir, 421 strerror(errno)); 422 return -1; 423 } 424 425 /* check the open file to avoid races */ 426 if (fstat(fileno(f), &st) < 0 || 427 (st.st_uid != 0 && st.st_uid != uid) || 428 (st.st_mode & 022) != 0) { 429 snprintf(err, errlen, "bad ownership or modes for file %s", 430 buf); 431 return -1; 432 } 433 434 /* for each component of the canonical path, walking upwards */ 435 for (;;) { 436 if ((cp = dirname(buf)) == NULL) { 437 snprintf(err, errlen, "dirname() failed"); 438 return -1; 439 } 440 strlcpy(buf, cp, sizeof(buf)); 441 442 debug3("secure_filename: checking '%s'", buf); 443 if (stat(buf, &st) < 0 || 444 (st.st_uid != 0 && st.st_uid != uid) || 445 (st.st_mode & 022) != 0) { 446 snprintf(err, errlen, 447 "bad ownership or modes for directory %s", buf); 448 return -1; 449 } 450 451 /* If are passed the homedir then we can stop */ 452 if (strcmp(homedir, buf) == 0) { 453 debug3("secure_filename: terminating check at '%s'", 454 buf); 455 break; 456 } 457 /* 458 * dirname should always complete with a "/" path, 459 * but we can be paranoid and check for "." too 460 */ 461 if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0)) 462 break; 463 } 464 return 0; 465 } 466 467 struct passwd * 468 getpwnamallow(const char *user) 469 { 470 #ifdef HAVE_LOGIN_CAP 471 extern login_cap_t *lc; 472 #ifdef BSD_AUTH 473 auth_session_t *as; 474 #endif 475 #endif 476 struct passwd *pw; 477 478 pw = getpwnam(user); 479 if (pw == NULL || !allowed_user(pw)) 480 return (NULL); 481 #ifdef HAVE_LOGIN_CAP 482 if ((lc = login_getclass(pw->pw_class)) == NULL) { 483 debug("unable to get login class: %s", user); 484 return (NULL); 485 } 486 #ifdef BSD_AUTH 487 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || 488 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { 489 debug("Approval failure for %s", user); 490 pw = NULL; 491 } 492 if (as != NULL) 493 auth_close(as); 494 #endif 495 #endif 496 if (pw != NULL) 497 return (pwcopy(pw)); 498 return (NULL); 499 } 500 501 void 502 auth_debug_add(const char *fmt,...) 503 { 504 char buf[1024]; 505 va_list args; 506 507 if (!auth_debug_init) 508 return; 509 510 va_start(args, fmt); 511 vsnprintf(buf, sizeof(buf), fmt, args); 512 va_end(args); 513 buffer_put_cstring(&auth_debug, buf); 514 } 515 516 void 517 auth_debug_send(void) 518 { 519 char *msg; 520 521 if (!auth_debug_init) 522 return; 523 while (buffer_len(&auth_debug)) { 524 msg = buffer_get_string(&auth_debug, NULL); 525 packet_send_debug("%s", msg); 526 xfree(msg); 527 } 528 } 529 530 void 531 auth_debug_reset(void) 532 { 533 if (auth_debug_init) 534 buffer_clear(&auth_debug); 535 else { 536 buffer_init(&auth_debug); 537 auth_debug_init = 1; 538 } 539 } 540