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 1.51 2003/11/21 11:57:02 djm Exp $"); 27 RCSID("$FreeBSD$"); 28 29 #ifdef HAVE_LOGIN_H 30 #include <login.h> 31 #endif 32 #ifdef USE_SHADOW 33 #include <shadow.h> 34 #endif 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 extern Buffer loginmsg; 59 60 /* Debugging messages */ 61 Buffer auth_debug; 62 int auth_debug_init; 63 64 /* 65 * Check if the user is allowed to log in via ssh. If user is listed 66 * in DenyUsers or one of user's groups is listed in DenyGroups, false 67 * will be returned. If AllowUsers isn't empty and user isn't listed 68 * there, or if AllowGroups isn't empty and one of user's groups isn't 69 * listed there, false will be returned. 70 * If the user's shell is not executable, false will be returned. 71 * Otherwise true is returned. 72 */ 73 int 74 allowed_user(struct passwd * pw) 75 { 76 struct stat st; 77 const char *hostname = NULL, *ipaddr = NULL, *passwd = NULL; 78 char *shell; 79 int i; 80 #ifdef USE_SHADOW 81 struct spwd *spw = NULL; 82 #endif 83 84 /* Shouldn't be called if pw is NULL, but better safe than sorry... */ 85 if (!pw || !pw->pw_name) 86 return 0; 87 88 #ifdef USE_SHADOW 89 if (!options.use_pam) 90 spw = getspnam(pw->pw_name); 91 #ifdef HAS_SHADOW_EXPIRE 92 if (!options.use_pam && spw != NULL && auth_shadow_acctexpired(spw)) 93 return 0; 94 #endif /* HAS_SHADOW_EXPIRE */ 95 #endif /* USE_SHADOW */ 96 97 /* grab passwd field for locked account check */ 98 #ifdef USE_SHADOW 99 if (spw != NULL) 100 passwd = spw->sp_pwdp; 101 #else 102 passwd = pw->pw_passwd; 103 #endif 104 105 /* check for locked account */ 106 if (!options.use_pam && passwd && *passwd) { 107 int locked = 0; 108 109 #ifdef LOCKED_PASSWD_STRING 110 if (strcmp(passwd, LOCKED_PASSWD_STRING) == 0) 111 locked = 1; 112 #endif 113 #ifdef LOCKED_PASSWD_PREFIX 114 if (strncmp(passwd, LOCKED_PASSWD_PREFIX, 115 strlen(LOCKED_PASSWD_PREFIX)) == 0) 116 locked = 1; 117 #endif 118 #ifdef LOCKED_PASSWD_SUBSTR 119 if (strstr(passwd, LOCKED_PASSWD_SUBSTR)) 120 locked = 1; 121 #endif 122 if (locked) { 123 logit("User %.100s not allowed because account is locked", 124 pw->pw_name); 125 return 0; 126 } 127 } 128 129 /* 130 * Get the shell from the password data. An empty shell field is 131 * legal, and means /bin/sh. 132 */ 133 shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell; 134 135 /* deny if shell does not exists or is not executable */ 136 if (stat(shell, &st) != 0) { 137 logit("User %.100s not allowed because shell %.100s does not exist", 138 pw->pw_name, shell); 139 return 0; 140 } 141 if (S_ISREG(st.st_mode) == 0 || 142 (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { 143 logit("User %.100s not allowed because shell %.100s is not executable", 144 pw->pw_name, shell); 145 return 0; 146 } 147 148 if (options.num_deny_users > 0 || options.num_allow_users > 0) { 149 hostname = get_canonical_hostname(options.use_dns); 150 ipaddr = get_remote_ipaddr(); 151 } 152 153 /* Return false if user is listed in DenyUsers */ 154 if (options.num_deny_users > 0) { 155 for (i = 0; i < options.num_deny_users; i++) 156 if (match_user(pw->pw_name, hostname, ipaddr, 157 options.deny_users[i])) { 158 logit("User %.100s not allowed because listed in DenyUsers", 159 pw->pw_name); 160 return 0; 161 } 162 } 163 /* Return false if AllowUsers isn't empty and user isn't listed there */ 164 if (options.num_allow_users > 0) { 165 for (i = 0; i < options.num_allow_users; i++) 166 if (match_user(pw->pw_name, hostname, ipaddr, 167 options.allow_users[i])) 168 break; 169 /* i < options.num_allow_users iff we break for loop */ 170 if (i >= options.num_allow_users) { 171 logit("User %.100s not allowed because not listed in AllowUsers", 172 pw->pw_name); 173 return 0; 174 } 175 } 176 if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { 177 /* Get the user's group access list (primary and supplementary) */ 178 if (ga_init(pw->pw_name, pw->pw_gid) == 0) { 179 logit("User %.100s not allowed because not in any group", 180 pw->pw_name); 181 return 0; 182 } 183 184 /* Return false if one of user's groups is listed in DenyGroups */ 185 if (options.num_deny_groups > 0) 186 if (ga_match(options.deny_groups, 187 options.num_deny_groups)) { 188 ga_free(); 189 logit("User %.100s not allowed because a group is listed in DenyGroups", 190 pw->pw_name); 191 return 0; 192 } 193 /* 194 * Return false if AllowGroups isn't empty and one of user's groups 195 * isn't listed there 196 */ 197 if (options.num_allow_groups > 0) 198 if (!ga_match(options.allow_groups, 199 options.num_allow_groups)) { 200 ga_free(); 201 logit("User %.100s not allowed because none of user's groups are listed in AllowGroups", 202 pw->pw_name); 203 return 0; 204 } 205 ga_free(); 206 } 207 208 #ifdef WITH_AIXAUTHENTICATE 209 /* 210 * Don't check loginrestrictions() for root account (use 211 * PermitRootLogin to control logins via ssh), or if running as 212 * non-root user (since loginrestrictions will always fail). 213 */ 214 if ((pw->pw_uid != 0) && (geteuid() == 0)) { 215 char *msg; 216 217 if (loginrestrictions(pw->pw_name, S_RLOGIN, NULL, &msg) != 0) { 218 int loginrestrict_errno = errno; 219 220 if (msg && *msg) { 221 buffer_append(&loginmsg, msg, strlen(msg)); 222 aix_remove_embedded_newlines(msg); 223 logit("Login restricted for %s: %.100s", 224 pw->pw_name, msg); 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 } 232 #endif /* WITH_AIXAUTHENTICATE */ 233 234 /* We found no reason not to let this user try to log on... */ 235 return 1; 236 } 237 238 void 239 auth_log(Authctxt *authctxt, int authenticated, char *method, char *info) 240 { 241 void (*authlog) (const char *fmt,...) = verbose; 242 char *authmsg; 243 244 /* Raise logging level */ 245 if (authenticated == 1 || 246 !authctxt->valid || 247 authctxt->failures >= AUTH_FAIL_LOG || 248 strcmp(method, "password") == 0) 249 authlog = logit; 250 251 if (authctxt->postponed) 252 authmsg = "Postponed"; 253 else 254 authmsg = authenticated ? "Accepted" : "Failed"; 255 256 authlog("%s %s for %s%.100s from %.200s port %d%s", 257 authmsg, 258 method, 259 authctxt->valid ? "" : "illegal user ", 260 authctxt->user, 261 get_remote_ipaddr(), 262 get_remote_port(), 263 info); 264 265 #ifdef CUSTOM_FAILED_LOGIN 266 if (authenticated == 0 && strcmp(method, "password") == 0) 267 record_failed_login(authctxt->user, "ssh"); 268 #endif 269 } 270 271 /* 272 * Check whether root logins are disallowed. 273 */ 274 int 275 auth_root_allowed(char *method) 276 { 277 switch (options.permit_root_login) { 278 case PERMIT_YES: 279 return 1; 280 break; 281 case PERMIT_NO_PASSWD: 282 if (strcmp(method, "password") != 0) 283 return 1; 284 break; 285 case PERMIT_FORCED_ONLY: 286 if (forced_command) { 287 logit("Root login accepted for forced command."); 288 return 1; 289 } 290 break; 291 } 292 logit("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr()); 293 return 0; 294 } 295 296 297 /* 298 * Given a template and a passwd structure, build a filename 299 * by substituting % tokenised options. Currently, %% becomes '%', 300 * %h becomes the home directory and %u the username. 301 * 302 * This returns a buffer allocated by xmalloc. 303 */ 304 char * 305 expand_filename(const char *filename, struct passwd *pw) 306 { 307 Buffer buffer; 308 char *file; 309 const char *cp; 310 311 /* 312 * Build the filename string in the buffer by making the appropriate 313 * substitutions to the given file name. 314 */ 315 buffer_init(&buffer); 316 for (cp = filename; *cp; cp++) { 317 if (cp[0] == '%' && cp[1] == '%') { 318 buffer_append(&buffer, "%", 1); 319 cp++; 320 continue; 321 } 322 if (cp[0] == '%' && cp[1] == 'h') { 323 buffer_append(&buffer, pw->pw_dir, strlen(pw->pw_dir)); 324 cp++; 325 continue; 326 } 327 if (cp[0] == '%' && cp[1] == 'u') { 328 buffer_append(&buffer, pw->pw_name, 329 strlen(pw->pw_name)); 330 cp++; 331 continue; 332 } 333 buffer_append(&buffer, cp, 1); 334 } 335 buffer_append(&buffer, "\0", 1); 336 337 /* 338 * Ensure that filename starts anchored. If not, be backward 339 * compatible and prepend the '%h/' 340 */ 341 file = xmalloc(MAXPATHLEN); 342 cp = buffer_ptr(&buffer); 343 if (*cp != '/') 344 snprintf(file, MAXPATHLEN, "%s/%s", pw->pw_dir, cp); 345 else 346 strlcpy(file, cp, MAXPATHLEN); 347 348 buffer_free(&buffer); 349 return file; 350 } 351 352 char * 353 authorized_keys_file(struct passwd *pw) 354 { 355 return expand_filename(options.authorized_keys_file, pw); 356 } 357 358 char * 359 authorized_keys_file2(struct passwd *pw) 360 { 361 return expand_filename(options.authorized_keys_file2, pw); 362 } 363 364 /* return ok if key exists in sysfile or userfile */ 365 HostStatus 366 check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host, 367 const char *sysfile, const char *userfile) 368 { 369 Key *found; 370 char *user_hostfile; 371 struct stat st; 372 HostStatus host_status; 373 374 /* Check if we know the host and its host key. */ 375 found = key_new(key->type); 376 host_status = check_host_in_hostfile(sysfile, host, key, found, NULL); 377 378 if (host_status != HOST_OK && userfile != NULL) { 379 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); 380 if (options.strict_modes && 381 (stat(user_hostfile, &st) == 0) && 382 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || 383 (st.st_mode & 022) != 0)) { 384 logit("Authentication refused for %.100s: " 385 "bad owner or modes for %.200s", 386 pw->pw_name, user_hostfile); 387 } else { 388 temporarily_use_uid(pw); 389 host_status = check_host_in_hostfile(user_hostfile, 390 host, key, found, NULL); 391 restore_uid(); 392 } 393 xfree(user_hostfile); 394 } 395 key_free(found); 396 397 debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ? 398 "ok" : "not found", host); 399 return host_status; 400 } 401 402 403 /* 404 * Check a given file for security. This is defined as all components 405 * of the path to the file must be owned by either the owner of 406 * of the file or root and no directories must be group or world writable. 407 * 408 * XXX Should any specific check be done for sym links ? 409 * 410 * Takes an open file descriptor, the file name, a uid and and 411 * error buffer plus max size as arguments. 412 * 413 * Returns 0 on success and -1 on failure 414 */ 415 int 416 secure_filename(FILE *f, const char *file, struct passwd *pw, 417 char *err, size_t errlen) 418 { 419 uid_t uid = pw->pw_uid; 420 char buf[MAXPATHLEN], homedir[MAXPATHLEN]; 421 char *cp; 422 int comparehome = 0; 423 struct stat st; 424 425 if (realpath(file, buf) == NULL) { 426 snprintf(err, errlen, "realpath %s failed: %s", file, 427 strerror(errno)); 428 return -1; 429 } 430 if (realpath(pw->pw_dir, homedir) != NULL) 431 comparehome = 1; 432 433 /* check the open file to avoid races */ 434 if (fstat(fileno(f), &st) < 0 || 435 (st.st_uid != 0 && st.st_uid != uid) || 436 (st.st_mode & 022) != 0) { 437 snprintf(err, errlen, "bad ownership or modes for file %s", 438 buf); 439 return -1; 440 } 441 442 /* for each component of the canonical path, walking upwards */ 443 for (;;) { 444 if ((cp = dirname(buf)) == NULL) { 445 snprintf(err, errlen, "dirname() failed"); 446 return -1; 447 } 448 strlcpy(buf, cp, sizeof(buf)); 449 450 debug3("secure_filename: checking '%s'", buf); 451 if (stat(buf, &st) < 0 || 452 (st.st_uid != 0 && st.st_uid != uid) || 453 (st.st_mode & 022) != 0) { 454 snprintf(err, errlen, 455 "bad ownership or modes for directory %s", buf); 456 return -1; 457 } 458 459 /* If are passed the homedir then we can stop */ 460 if (comparehome && strcmp(homedir, buf) == 0) { 461 debug3("secure_filename: terminating check at '%s'", 462 buf); 463 break; 464 } 465 /* 466 * dirname should always complete with a "/" path, 467 * but we can be paranoid and check for "." too 468 */ 469 if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0)) 470 break; 471 } 472 return 0; 473 } 474 475 struct passwd * 476 getpwnamallow(const char *user) 477 { 478 #ifdef HAVE_LOGIN_CAP 479 extern login_cap_t *lc; 480 #ifdef BSD_AUTH 481 auth_session_t *as; 482 #endif 483 #endif 484 struct passwd *pw; 485 486 pw = getpwnam(user); 487 if (pw == NULL) { 488 logit("Illegal user %.100s from %.100s", 489 user, get_remote_ipaddr()); 490 #ifdef CUSTOM_FAILED_LOGIN 491 record_failed_login(user, "ssh"); 492 #endif 493 return (NULL); 494 } 495 if (!allowed_user(pw)) 496 return (NULL); 497 #ifdef HAVE_LOGIN_CAP 498 if ((lc = login_getpwclass(pw)) == NULL) { 499 debug("unable to get login class: %s", user); 500 return (NULL); 501 } 502 #ifdef BSD_AUTH 503 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || 504 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { 505 debug("Approval failure for %s", user); 506 pw = NULL; 507 } 508 if (as != NULL) 509 auth_close(as); 510 #endif 511 #endif 512 if (pw != NULL) 513 return (pwcopy(pw)); 514 return (NULL); 515 } 516 517 void 518 auth_debug_add(const char *fmt,...) 519 { 520 char buf[1024]; 521 va_list args; 522 523 if (!auth_debug_init) 524 return; 525 526 va_start(args, fmt); 527 vsnprintf(buf, sizeof(buf), fmt, args); 528 va_end(args); 529 buffer_put_cstring(&auth_debug, buf); 530 } 531 532 void 533 auth_debug_send(void) 534 { 535 char *msg; 536 537 if (!auth_debug_init) 538 return; 539 while (buffer_len(&auth_debug)) { 540 msg = buffer_get_string(&auth_debug, NULL); 541 packet_send_debug("%s", msg); 542 xfree(msg); 543 } 544 } 545 546 void 547 auth_debug_reset(void) 548 { 549 if (auth_debug_init) 550 buffer_clear(&auth_debug); 551 else { 552 buffer_init(&auth_debug); 553 auth_debug_init = 1; 554 } 555 } 556 557 struct passwd * 558 fakepw(void) 559 { 560 static struct passwd fake; 561 562 memset(&fake, 0, sizeof(fake)); 563 fake.pw_name = "NOUSER"; 564 fake.pw_passwd = 565 "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK"; 566 fake.pw_gecos = "NOUSER"; 567 fake.pw_uid = -1; 568 fake.pw_gid = -1; 569 #ifdef HAVE_PW_CLASS_IN_PASSWD 570 fake.pw_class = ""; 571 #endif 572 fake.pw_dir = "/nonexist"; 573 fake.pw_shell = "/nonexist"; 574 575 return (&fake); 576 } 577