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 1.45 2002/09/20 18:41:29 stevesk 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 86 /* Shouldn't be called if pw is NULL, but better safe than sorry... */ 87 if (!pw || !pw->pw_name) 88 return 0; 89 90 #define DAY (24L * 60 * 60) /* 1 day in seconds */ 91 spw = getspnam(pw->pw_name); 92 if (spw != NULL) { 93 time_t today = time(NULL) / DAY; 94 debug3("allowed_user: today %d sp_expire %d sp_lstchg %d" 95 " sp_max %d", (int)today, (int)spw->sp_expire, 96 (int)spw->sp_lstchg, (int)spw->sp_max); 97 98 /* 99 * We assume account and password expiration occurs the 100 * day after the day specified. 101 */ 102 if (spw->sp_expire != -1 && today > spw->sp_expire) { 103 log("Account %.100s has expired", pw->pw_name); 104 return 0; 105 } 106 107 if (spw->sp_lstchg == 0) { 108 log("User %.100s password has expired (root forced)", 109 pw->pw_name); 110 return 0; 111 } 112 113 if (spw->sp_max != -1 && 114 today > spw->sp_lstchg + spw->sp_max) { 115 log("User %.100s password has expired (password aged)", 116 pw->pw_name); 117 return 0; 118 } 119 } 120 #else 121 /* Shouldn't be called if pw is NULL, but better safe than sorry... */ 122 if (!pw || !pw->pw_name) 123 return 0; 124 #endif 125 126 /* 127 * Get the shell from the password data. An empty shell field is 128 * legal, and means /bin/sh. 129 */ 130 shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell; 131 132 /* deny if shell does not exists or is not executable */ 133 if (stat(shell, &st) != 0) { 134 log("User %.100s not allowed because shell %.100s does not exist", 135 pw->pw_name, shell); 136 return 0; 137 } 138 if (S_ISREG(st.st_mode) == 0 || 139 (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { 140 log("User %.100s not allowed because shell %.100s is not executable", 141 pw->pw_name, shell); 142 return 0; 143 } 144 145 if (options.num_deny_users > 0 || options.num_allow_users > 0) { 146 hostname = get_canonical_hostname(options.verify_reverse_mapping); 147 ipaddr = get_remote_ipaddr(); 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 if (match_user(pw->pw_name, hostname, ipaddr, 154 options.deny_users[i])) { 155 log("User %.100s not allowed because listed in DenyUsers", 156 pw->pw_name); 157 return 0; 158 } 159 } 160 /* Return false if AllowUsers isn't empty and user isn't listed there */ 161 if (options.num_allow_users > 0) { 162 for (i = 0; i < options.num_allow_users; i++) 163 if (match_user(pw->pw_name, hostname, ipaddr, 164 options.allow_users[i])) 165 break; 166 /* i < options.num_allow_users iff we break for loop */ 167 if (i >= options.num_allow_users) { 168 log("User %.100s not allowed because not listed in AllowUsers", 169 pw->pw_name); 170 return 0; 171 } 172 } 173 if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { 174 /* Get the user's group access list (primary and supplementary) */ 175 if (ga_init(pw->pw_name, pw->pw_gid) == 0) { 176 log("User %.100s not allowed because not in any group", 177 pw->pw_name); 178 return 0; 179 } 180 181 /* Return false if one of user's groups is listed in DenyGroups */ 182 if (options.num_deny_groups > 0) 183 if (ga_match(options.deny_groups, 184 options.num_deny_groups)) { 185 ga_free(); 186 log("User %.100s not allowed because a group is listed in DenyGroups", 187 pw->pw_name); 188 return 0; 189 } 190 /* 191 * Return false if AllowGroups isn't empty and one of user's groups 192 * isn't listed there 193 */ 194 if (options.num_allow_groups > 0) 195 if (!ga_match(options.allow_groups, 196 options.num_allow_groups)) { 197 ga_free(); 198 log("User %.100s not allowed because none of user's groups are listed in AllowGroups", 199 pw->pw_name); 200 return 0; 201 } 202 ga_free(); 203 } 204 205 #ifdef WITH_AIXAUTHENTICATE 206 if (loginrestrictions(pw->pw_name, S_RLOGIN, NULL, &loginmsg) != 0) { 207 if (loginmsg && *loginmsg) { 208 /* Remove embedded newlines (if any) */ 209 char *p; 210 for (p = loginmsg; *p; p++) { 211 if (*p == '\n') 212 *p = ' '; 213 } 214 /* Remove trailing newline */ 215 *--p = '\0'; 216 log("Login restricted for %s: %.100s", pw->pw_name, loginmsg); 217 } 218 return 0; 219 } 220 #endif /* WITH_AIXAUTHENTICATE */ 221 222 /* We found no reason not to let this user try to log on... */ 223 return 1; 224 } 225 226 Authctxt * 227 authctxt_new(void) 228 { 229 Authctxt *authctxt = xmalloc(sizeof(*authctxt)); 230 memset(authctxt, 0, sizeof(*authctxt)); 231 return authctxt; 232 } 233 234 void 235 auth_log(Authctxt *authctxt, int authenticated, char *method, char *info) 236 { 237 void (*authlog) (const char *fmt,...) = verbose; 238 char *authmsg; 239 240 /* Raise logging level */ 241 if (authenticated == 1 || 242 !authctxt->valid || 243 authctxt->failures >= AUTH_FAIL_LOG || 244 strcmp(method, "password") == 0) 245 authlog = log; 246 247 if (authctxt->postponed) 248 authmsg = "Postponed"; 249 else 250 authmsg = authenticated ? "Accepted" : "Failed"; 251 252 authlog("%s %s for %s%.100s from %.200s port %d%s", 253 authmsg, 254 method, 255 authctxt->valid ? "" : "illegal user ", 256 authctxt->user, 257 get_remote_ipaddr(), 258 get_remote_port(), 259 info); 260 261 #ifdef WITH_AIXAUTHENTICATE 262 if (authenticated == 0 && strcmp(method, "password") == 0) 263 loginfailed(authctxt->user, 264 get_canonical_hostname(options.verify_reverse_mapping), 265 "ssh"); 266 #endif /* WITH_AIXAUTHENTICATE */ 267 268 } 269 270 /* 271 * Check whether root logins are disallowed. 272 */ 273 int 274 auth_root_allowed(char *method) 275 { 276 switch (options.permit_root_login) { 277 case PERMIT_YES: 278 return 1; 279 break; 280 case PERMIT_NO_PASSWD: 281 if (strcmp(method, "password") != 0) 282 return 1; 283 break; 284 case PERMIT_FORCED_ONLY: 285 if (forced_command) { 286 log("Root login accepted for forced command."); 287 return 1; 288 } 289 break; 290 } 291 log("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr()); 292 return 0; 293 } 294 295 296 /* 297 * Given a template and a passwd structure, build a filename 298 * by substituting % tokenised options. Currently, %% becomes '%', 299 * %h becomes the home directory and %u the username. 300 * 301 * This returns a buffer allocated by xmalloc. 302 */ 303 char * 304 expand_filename(const char *filename, struct passwd *pw) 305 { 306 Buffer buffer; 307 char *file; 308 const char *cp; 309 310 /* 311 * Build the filename string in the buffer by making the appropriate 312 * substitutions to the given file name. 313 */ 314 buffer_init(&buffer); 315 for (cp = filename; *cp; cp++) { 316 if (cp[0] == '%' && cp[1] == '%') { 317 buffer_append(&buffer, "%", 1); 318 cp++; 319 continue; 320 } 321 if (cp[0] == '%' && cp[1] == 'h') { 322 buffer_append(&buffer, pw->pw_dir, strlen(pw->pw_dir)); 323 cp++; 324 continue; 325 } 326 if (cp[0] == '%' && cp[1] == 'u') { 327 buffer_append(&buffer, pw->pw_name, 328 strlen(pw->pw_name)); 329 cp++; 330 continue; 331 } 332 buffer_append(&buffer, cp, 1); 333 } 334 buffer_append(&buffer, "\0", 1); 335 336 /* 337 * Ensure that filename starts anchored. If not, be backward 338 * compatible and prepend the '%h/' 339 */ 340 file = xmalloc(MAXPATHLEN); 341 cp = buffer_ptr(&buffer); 342 if (*cp != '/') 343 snprintf(file, MAXPATHLEN, "%s/%s", pw->pw_dir, cp); 344 else 345 strlcpy(file, cp, MAXPATHLEN); 346 347 buffer_free(&buffer); 348 return file; 349 } 350 351 char * 352 authorized_keys_file(struct passwd *pw) 353 { 354 return expand_filename(options.authorized_keys_file, pw); 355 } 356 357 char * 358 authorized_keys_file2(struct passwd *pw) 359 { 360 return expand_filename(options.authorized_keys_file2, pw); 361 } 362 363 /* return ok if key exists in sysfile or userfile */ 364 HostStatus 365 check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host, 366 const char *sysfile, const char *userfile) 367 { 368 Key *found; 369 char *user_hostfile; 370 struct stat st; 371 HostStatus host_status; 372 373 /* Check if we know the host and its host key. */ 374 found = key_new(key->type); 375 host_status = check_host_in_hostfile(sysfile, host, key, found, NULL); 376 377 if (host_status != HOST_OK && userfile != NULL) { 378 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); 379 if (options.strict_modes && 380 (stat(user_hostfile, &st) == 0) && 381 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || 382 (st.st_mode & 022) != 0)) { 383 log("Authentication refused for %.100s: " 384 "bad owner or modes for %.200s", 385 pw->pw_name, user_hostfile); 386 } else { 387 temporarily_use_uid(pw); 388 host_status = check_host_in_hostfile(user_hostfile, 389 host, key, found, NULL); 390 restore_uid(); 391 } 392 xfree(user_hostfile); 393 } 394 key_free(found); 395 396 debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ? 397 "ok" : "not found", host); 398 return host_status; 399 } 400 401 402 /* 403 * Check a given file for security. This is defined as all components 404 * of the path to the file must be owned by either the owner of 405 * of the file or root and no directories must be group or world writable. 406 * 407 * XXX Should any specific check be done for sym links ? 408 * 409 * Takes an open file descriptor, the file name, a uid and and 410 * error buffer plus max size as arguments. 411 * 412 * Returns 0 on success and -1 on failure 413 */ 414 int 415 secure_filename(FILE *f, const char *file, struct passwd *pw, 416 char *err, size_t errlen) 417 { 418 uid_t uid = pw->pw_uid; 419 char buf[MAXPATHLEN], homedir[MAXPATHLEN]; 420 char *cp; 421 struct stat st; 422 423 if (realpath(file, buf) == NULL) { 424 snprintf(err, errlen, "realpath %s failed: %s", file, 425 strerror(errno)); 426 return -1; 427 } 428 if (realpath(pw->pw_dir, homedir) == NULL) { 429 snprintf(err, errlen, "realpath %s failed: %s", pw->pw_dir, 430 strerror(errno)); 431 return -1; 432 } 433 434 /* check the open file to avoid races */ 435 if (fstat(fileno(f), &st) < 0 || 436 (st.st_uid != 0 && st.st_uid != uid) || 437 (st.st_mode & 022) != 0) { 438 snprintf(err, errlen, "bad ownership or modes for file %s", 439 buf); 440 return -1; 441 } 442 443 /* for each component of the canonical path, walking upwards */ 444 for (;;) { 445 if ((cp = dirname(buf)) == NULL) { 446 snprintf(err, errlen, "dirname() failed"); 447 return -1; 448 } 449 strlcpy(buf, cp, sizeof(buf)); 450 451 debug3("secure_filename: checking '%s'", buf); 452 if (stat(buf, &st) < 0 || 453 (st.st_uid != 0 && st.st_uid != uid) || 454 (st.st_mode & 022) != 0) { 455 snprintf(err, errlen, 456 "bad ownership or modes for directory %s", buf); 457 return -1; 458 } 459 460 /* If are passed the homedir then we can stop */ 461 if (strcmp(homedir, buf) == 0) { 462 debug3("secure_filename: terminating check at '%s'", 463 buf); 464 break; 465 } 466 /* 467 * dirname should always complete with a "/" path, 468 * but we can be paranoid and check for "." too 469 */ 470 if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0)) 471 break; 472 } 473 return 0; 474 } 475 476 struct passwd * 477 getpwnamallow(const char *user) 478 { 479 #ifdef HAVE_LOGIN_CAP 480 extern login_cap_t *lc; 481 #ifdef BSD_AUTH 482 auth_session_t *as; 483 #endif 484 #endif 485 struct passwd *pw; 486 487 pw = getpwnam(user); 488 if (pw == NULL) { 489 log("Illegal user %.100s from %.100s", 490 user, get_remote_ipaddr()); 491 return (NULL); 492 } 493 if (!allowed_user(pw)) 494 return (NULL); 495 #ifdef HAVE_LOGIN_CAP 496 if ((lc = login_getpwclass(pw)) == NULL) { 497 debug("unable to get login class: %s", user); 498 return (NULL); 499 } 500 #ifdef BSD_AUTH 501 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || 502 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { 503 debug("Approval failure for %s", user); 504 pw = NULL; 505 } 506 if (as != NULL) 507 auth_close(as); 508 #endif 509 #endif 510 if (pw != NULL) 511 return (pwcopy(pw)); 512 return (NULL); 513 } 514 515 void 516 auth_debug_add(const char *fmt,...) 517 { 518 char buf[1024]; 519 va_list args; 520 521 if (!auth_debug_init) 522 return; 523 524 va_start(args, fmt); 525 vsnprintf(buf, sizeof(buf), fmt, args); 526 va_end(args); 527 buffer_put_cstring(&auth_debug, buf); 528 } 529 530 void 531 auth_debug_send(void) 532 { 533 char *msg; 534 535 if (!auth_debug_init) 536 return; 537 while (buffer_len(&auth_debug)) { 538 msg = buffer_get_string(&auth_debug, NULL); 539 packet_send_debug("%s", msg); 540 xfree(msg); 541 } 542 } 543 544 void 545 auth_debug_reset(void) 546 { 547 if (auth_debug_init) 548 buffer_clear(&auth_debug); 549 else { 550 buffer_init(&auth_debug); 551 auth_debug_init = 1; 552 } 553 } 554