1 /* $OpenBSD: auth.c,v 1.80 2008/11/04 07:58:09 djm Exp $ */ 2 /* 3 * Copyright (c) 2000 Markus Friedl. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 */ 25 26 #include "includes.h" 27 28 #include <sys/types.h> 29 #include <sys/stat.h> 30 #include <sys/param.h> 31 32 #include <netinet/in.h> 33 34 #include <errno.h> 35 #include <fcntl.h> 36 #ifdef HAVE_PATHS_H 37 # include <paths.h> 38 #endif 39 #include <pwd.h> 40 #ifdef HAVE_LOGIN_H 41 #include <login.h> 42 #endif 43 #ifdef USE_SHADOW 44 #include <shadow.h> 45 #endif 46 #ifdef HAVE_LIBGEN_H 47 #include <libgen.h> 48 #endif 49 #include <stdarg.h> 50 #include <stdio.h> 51 #include <string.h> 52 #include <unistd.h> 53 54 #include "xmalloc.h" 55 #include "match.h" 56 #include "groupaccess.h" 57 #include "log.h" 58 #include "buffer.h" 59 #include "servconf.h" 60 #include "key.h" 61 #include "hostfile.h" 62 #include "auth.h" 63 #include "auth-options.h" 64 #include "canohost.h" 65 #include "uidswap.h" 66 #include "misc.h" 67 #include "packet.h" 68 #include "loginrec.h" 69 #ifdef GSSAPI 70 #include "ssh-gss.h" 71 #endif 72 #include "monitor_wrap.h" 73 74 /* import */ 75 extern ServerOptions options; 76 extern int use_privsep; 77 extern Buffer loginmsg; 78 extern struct passwd *privsep_pw; 79 80 /* Debugging messages */ 81 Buffer auth_debug; 82 int auth_debug_init; 83 84 /* 85 * Check if the user is allowed to log in via ssh. If user is listed 86 * in DenyUsers or one of user's groups is listed in DenyGroups, false 87 * will be returned. If AllowUsers isn't empty and user isn't listed 88 * there, or if AllowGroups isn't empty and one of user's groups isn't 89 * listed there, false will be returned. 90 * If the user's shell is not executable, false will be returned. 91 * Otherwise true is returned. 92 */ 93 int 94 allowed_user(struct passwd * pw) 95 { 96 struct stat st; 97 const char *hostname = NULL, *ipaddr = NULL, *passwd = NULL; 98 char *shell; 99 u_int i; 100 #ifdef USE_SHADOW 101 struct spwd *spw = NULL; 102 #endif 103 104 /* Shouldn't be called if pw is NULL, but better safe than sorry... */ 105 if (!pw || !pw->pw_name) 106 return 0; 107 108 #ifdef USE_SHADOW 109 if (!options.use_pam) 110 spw = getspnam(pw->pw_name); 111 #ifdef HAS_SHADOW_EXPIRE 112 if (!options.use_pam && spw != NULL && auth_shadow_acctexpired(spw)) 113 return 0; 114 #endif /* HAS_SHADOW_EXPIRE */ 115 #endif /* USE_SHADOW */ 116 117 /* grab passwd field for locked account check */ 118 passwd = pw->pw_passwd; 119 #ifdef USE_SHADOW 120 if (spw != NULL) 121 #ifdef USE_LIBIAF 122 passwd = get_iaf_password(pw); 123 #else 124 passwd = spw->sp_pwdp; 125 #endif /* USE_LIBIAF */ 126 #endif 127 128 /* check for locked account */ 129 if (!options.use_pam && passwd && *passwd) { 130 int locked = 0; 131 132 #ifdef LOCKED_PASSWD_STRING 133 if (strcmp(passwd, LOCKED_PASSWD_STRING) == 0) 134 locked = 1; 135 #endif 136 #ifdef LOCKED_PASSWD_PREFIX 137 if (strncmp(passwd, LOCKED_PASSWD_PREFIX, 138 strlen(LOCKED_PASSWD_PREFIX)) == 0) 139 locked = 1; 140 #endif 141 #ifdef LOCKED_PASSWD_SUBSTR 142 if (strstr(passwd, LOCKED_PASSWD_SUBSTR)) 143 locked = 1; 144 #endif 145 #ifdef USE_LIBIAF 146 free(passwd); 147 #endif /* USE_LIBIAF */ 148 if (locked) { 149 logit("User %.100s not allowed because account is locked", 150 pw->pw_name); 151 return 0; 152 } 153 } 154 155 /* 156 * Get the shell from the password data. An empty shell field is 157 * legal, and means /bin/sh. 158 */ 159 shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell; 160 161 /* deny if shell does not exists or is not executable */ 162 if (stat(shell, &st) != 0) { 163 logit("User %.100s not allowed because shell %.100s does not exist", 164 pw->pw_name, shell); 165 return 0; 166 } 167 if (S_ISREG(st.st_mode) == 0 || 168 (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { 169 logit("User %.100s not allowed because shell %.100s is not executable", 170 pw->pw_name, shell); 171 return 0; 172 } 173 174 if (options.num_deny_users > 0 || options.num_allow_users > 0 || 175 options.num_deny_groups > 0 || options.num_allow_groups > 0) { 176 hostname = get_canonical_hostname(options.use_dns); 177 ipaddr = get_remote_ipaddr(); 178 } 179 180 /* Return false if user is listed in DenyUsers */ 181 if (options.num_deny_users > 0) { 182 for (i = 0; i < options.num_deny_users; i++) 183 if (match_user(pw->pw_name, hostname, ipaddr, 184 options.deny_users[i])) { 185 logit("User %.100s from %.100s not allowed " 186 "because listed in DenyUsers", 187 pw->pw_name, hostname); 188 return 0; 189 } 190 } 191 /* Return false if AllowUsers isn't empty and user isn't listed there */ 192 if (options.num_allow_users > 0) { 193 for (i = 0; i < options.num_allow_users; i++) 194 if (match_user(pw->pw_name, hostname, ipaddr, 195 options.allow_users[i])) 196 break; 197 /* i < options.num_allow_users iff we break for loop */ 198 if (i >= options.num_allow_users) { 199 logit("User %.100s from %.100s not allowed because " 200 "not listed in AllowUsers", pw->pw_name, hostname); 201 return 0; 202 } 203 } 204 if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { 205 /* Get the user's group access list (primary and supplementary) */ 206 if (ga_init(pw->pw_name, pw->pw_gid) == 0) { 207 logit("User %.100s from %.100s not allowed because " 208 "not in any group", pw->pw_name, hostname); 209 return 0; 210 } 211 212 /* Return false if one of user's groups is listed in DenyGroups */ 213 if (options.num_deny_groups > 0) 214 if (ga_match(options.deny_groups, 215 options.num_deny_groups)) { 216 ga_free(); 217 logit("User %.100s from %.100s not allowed " 218 "because a group is listed in DenyGroups", 219 pw->pw_name, hostname); 220 return 0; 221 } 222 /* 223 * Return false if AllowGroups isn't empty and one of user's groups 224 * isn't listed there 225 */ 226 if (options.num_allow_groups > 0) 227 if (!ga_match(options.allow_groups, 228 options.num_allow_groups)) { 229 ga_free(); 230 logit("User %.100s from %.100s not allowed " 231 "because none of user's groups are listed " 232 "in AllowGroups", pw->pw_name, hostname); 233 return 0; 234 } 235 ga_free(); 236 } 237 238 #ifdef CUSTOM_SYS_AUTH_ALLOWED_USER 239 if (!sys_auth_allowed_user(pw, &loginmsg)) 240 return 0; 241 #endif 242 243 /* We found no reason not to let this user try to log on... */ 244 return 1; 245 } 246 247 void 248 auth_log(Authctxt *authctxt, int authenticated, char *method, char *info) 249 { 250 void (*authlog) (const char *fmt,...) = verbose; 251 char *authmsg; 252 253 if (use_privsep && !mm_is_monitor() && !authctxt->postponed) 254 return; 255 256 /* Raise logging level */ 257 if (authenticated == 1 || 258 !authctxt->valid || 259 authctxt->failures >= options.max_authtries / 2 || 260 strcmp(method, "password") == 0) 261 authlog = logit; 262 263 if (authctxt->postponed) 264 authmsg = "Postponed"; 265 else 266 authmsg = authenticated ? "Accepted" : "Failed"; 267 268 authlog("%s %s for %s%.100s from %.200s port %d%s", 269 authmsg, 270 method, 271 authctxt->valid ? "" : "invalid user ", 272 authctxt->user, 273 get_remote_ipaddr(), 274 get_remote_port(), 275 info); 276 277 #ifdef CUSTOM_FAILED_LOGIN 278 if (authenticated == 0 && !authctxt->postponed && 279 (strcmp(method, "password") == 0 || 280 strncmp(method, "keyboard-interactive", 20) == 0 || 281 strcmp(method, "challenge-response") == 0)) 282 record_failed_login(authctxt->user, 283 get_canonical_hostname(options.use_dns), "ssh"); 284 # ifdef WITH_AIXAUTHENTICATE 285 if (authenticated) 286 sys_auth_record_login(authctxt->user, 287 get_canonical_hostname(options.use_dns), "ssh", &loginmsg); 288 # endif 289 #endif 290 #ifdef SSH_AUDIT_EVENTS 291 if (authenticated == 0 && !authctxt->postponed) 292 audit_event(audit_classify_auth(method)); 293 #endif 294 } 295 296 /* 297 * Check whether root logins are disallowed. 298 */ 299 int 300 auth_root_allowed(char *method) 301 { 302 switch (options.permit_root_login) { 303 case PERMIT_YES: 304 return 1; 305 case PERMIT_NO_PASSWD: 306 if (strcmp(method, "password") != 0) 307 return 1; 308 break; 309 case PERMIT_FORCED_ONLY: 310 if (forced_command) { 311 logit("Root login accepted for forced command."); 312 return 1; 313 } 314 break; 315 } 316 logit("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr()); 317 return 0; 318 } 319 320 321 /* 322 * Given a template and a passwd structure, build a filename 323 * by substituting % tokenised options. Currently, %% becomes '%', 324 * %h becomes the home directory and %u the username. 325 * 326 * This returns a buffer allocated by xmalloc. 327 */ 328 static char * 329 expand_authorized_keys(const char *filename, struct passwd *pw) 330 { 331 char *file, ret[MAXPATHLEN]; 332 int i; 333 334 file = percent_expand(filename, "h", pw->pw_dir, 335 "u", pw->pw_name, (char *)NULL); 336 337 /* 338 * Ensure that filename starts anchored. If not, be backward 339 * compatible and prepend the '%h/' 340 */ 341 if (*file == '/') 342 return (file); 343 344 i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file); 345 if (i < 0 || (size_t)i >= sizeof(ret)) 346 fatal("expand_authorized_keys: path too long"); 347 xfree(file); 348 return (xstrdup(ret)); 349 } 350 351 char * 352 authorized_keys_file(struct passwd *pw) 353 { 354 return expand_authorized_keys(options.authorized_keys_file, pw); 355 } 356 357 char * 358 authorized_keys_file2(struct passwd *pw) 359 { 360 return expand_authorized_keys(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 logit("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 static 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 int comparehome = 0; 422 struct stat st; 423 424 if (realpath(file, buf) == NULL) { 425 snprintf(err, errlen, "realpath %s failed: %s", file, 426 strerror(errno)); 427 return -1; 428 } 429 if (realpath(pw->pw_dir, homedir) != NULL) 430 comparehome = 1; 431 432 /* check the open file to avoid races */ 433 if (fstat(fileno(f), &st) < 0 || 434 (st.st_uid != 0 && st.st_uid != uid) || 435 (st.st_mode & 022) != 0) { 436 snprintf(err, errlen, "bad ownership or modes for file %s", 437 buf); 438 return -1; 439 } 440 441 /* for each component of the canonical path, walking upwards */ 442 for (;;) { 443 if ((cp = dirname(buf)) == NULL) { 444 snprintf(err, errlen, "dirname() failed"); 445 return -1; 446 } 447 strlcpy(buf, cp, sizeof(buf)); 448 449 debug3("secure_filename: checking '%s'", buf); 450 if (stat(buf, &st) < 0 || 451 (st.st_uid != 0 && st.st_uid != uid) || 452 (st.st_mode & 022) != 0) { 453 snprintf(err, errlen, 454 "bad ownership or modes for directory %s", buf); 455 return -1; 456 } 457 458 /* If are passed the homedir then we can stop */ 459 if (comparehome && strcmp(homedir, buf) == 0) { 460 debug3("secure_filename: terminating check at '%s'", 461 buf); 462 break; 463 } 464 /* 465 * dirname should always complete with a "/" path, 466 * but we can be paranoid and check for "." too 467 */ 468 if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0)) 469 break; 470 } 471 return 0; 472 } 473 474 FILE * 475 auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes) 476 { 477 char line[1024]; 478 struct stat st; 479 int fd; 480 FILE *f; 481 482 /* 483 * Open the file containing the authorized keys 484 * Fail quietly if file does not exist 485 */ 486 if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) 487 return NULL; 488 489 if (fstat(fd, &st) < 0) { 490 close(fd); 491 return NULL; 492 } 493 if (!S_ISREG(st.st_mode)) { 494 logit("User %s authorized keys %s is not a regular file", 495 pw->pw_name, file); 496 close(fd); 497 return NULL; 498 } 499 unset_nonblock(fd); 500 if ((f = fdopen(fd, "r")) == NULL) { 501 close(fd); 502 return NULL; 503 } 504 if (options.strict_modes && 505 secure_filename(f, file, pw, line, sizeof(line)) != 0) { 506 fclose(f); 507 logit("Authentication refused: %s", line); 508 return NULL; 509 } 510 511 return f; 512 } 513 514 struct passwd * 515 getpwnamallow(const char *user) 516 { 517 #ifdef HAVE_LOGIN_CAP 518 extern login_cap_t *lc; 519 #ifdef BSD_AUTH 520 auth_session_t *as; 521 #endif 522 #endif 523 struct passwd *pw; 524 525 parse_server_match_config(&options, user, 526 get_canonical_hostname(options.use_dns), get_remote_ipaddr()); 527 528 pw = getpwnam(user); 529 if (pw == NULL) { 530 logit("Invalid user %.100s from %.100s", 531 user, get_remote_ipaddr()); 532 #ifdef CUSTOM_FAILED_LOGIN 533 record_failed_login(user, 534 get_canonical_hostname(options.use_dns), "ssh"); 535 #endif 536 #ifdef SSH_AUDIT_EVENTS 537 audit_event(SSH_INVALID_USER); 538 #endif /* SSH_AUDIT_EVENTS */ 539 return (NULL); 540 } 541 if (!allowed_user(pw)) 542 return (NULL); 543 #ifdef HAVE_LOGIN_CAP 544 if ((lc = login_getclass(pw->pw_class)) == NULL) { 545 debug("unable to get login class: %s", user); 546 return (NULL); 547 } 548 #ifdef BSD_AUTH 549 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || 550 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { 551 debug("Approval failure for %s", user); 552 pw = NULL; 553 } 554 if (as != NULL) 555 auth_close(as); 556 #endif 557 #endif 558 if (pw != NULL) 559 return (pwcopy(pw)); 560 return (NULL); 561 } 562 563 void 564 auth_debug_add(const char *fmt,...) 565 { 566 char buf[1024]; 567 va_list args; 568 569 if (!auth_debug_init) 570 return; 571 572 va_start(args, fmt); 573 vsnprintf(buf, sizeof(buf), fmt, args); 574 va_end(args); 575 buffer_put_cstring(&auth_debug, buf); 576 } 577 578 void 579 auth_debug_send(void) 580 { 581 char *msg; 582 583 if (!auth_debug_init) 584 return; 585 while (buffer_len(&auth_debug)) { 586 msg = buffer_get_string(&auth_debug, NULL); 587 packet_send_debug("%s", msg); 588 xfree(msg); 589 } 590 } 591 592 void 593 auth_debug_reset(void) 594 { 595 if (auth_debug_init) 596 buffer_clear(&auth_debug); 597 else { 598 buffer_init(&auth_debug); 599 auth_debug_init = 1; 600 } 601 } 602 603 struct passwd * 604 fakepw(void) 605 { 606 static struct passwd fake; 607 608 memset(&fake, 0, sizeof(fake)); 609 fake.pw_name = "NOUSER"; 610 fake.pw_passwd = 611 "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK"; 612 fake.pw_gecos = "NOUSER"; 613 fake.pw_uid = privsep_pw == NULL ? (uid_t)-1 : privsep_pw->pw_uid; 614 fake.pw_gid = privsep_pw == NULL ? (gid_t)-1 : privsep_pw->pw_gid; 615 #ifdef HAVE_PW_CLASS_IN_PASSWD 616 fake.pw_class = ""; 617 #endif 618 fake.pw_dir = "/nonexist"; 619 fake.pw_shell = "/nonexist"; 620 621 return (&fake); 622 } 623