1 /* $NetBSD: auth.c,v 1.2 2009/06/07 22:38:46 christos Exp $ */ 2 /* $OpenBSD: auth.c,v 1.80 2008/11/04 07:58:09 djm Exp $ */ 3 /* 4 * Copyright (c) 2000 Markus Friedl. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 #include "includes.h" 28 __RCSID("$NetBSD: auth.c,v 1.2 2009/06/07 22:38:46 christos Exp $"); 29 #include <sys/types.h> 30 #include <sys/stat.h> 31 #include <sys/param.h> 32 33 #include <errno.h> 34 #include <fcntl.h> 35 #include <libgen.h> 36 #include <login_cap.h> 37 #include <paths.h> 38 #include <pwd.h> 39 #include <stdarg.h> 40 #include <stdio.h> 41 #include <string.h> 42 #include <unistd.h> 43 44 #include "xmalloc.h" 45 #include "match.h" 46 #include "groupaccess.h" 47 #include "log.h" 48 #include "buffer.h" 49 #include "servconf.h" 50 #include "key.h" 51 #include "hostfile.h" 52 #include "auth.h" 53 #include "auth-options.h" 54 #include "canohost.h" 55 #include "uidswap.h" 56 #include "misc.h" 57 #include "packet.h" 58 #ifdef GSSAPI 59 #include "ssh-gss.h" 60 #endif 61 #include "monitor_wrap.h" 62 63 #ifdef HAVE_LOGIN_CAP 64 #include <login_cap.h> 65 #endif 66 67 /* import */ 68 extern ServerOptions options; 69 extern int use_privsep; 70 71 /* Debugging messages */ 72 Buffer auth_debug; 73 int auth_debug_init; 74 75 /* 76 * Check if the user is allowed to log in via ssh. If user is listed 77 * in DenyUsers or one of user's groups is listed in DenyGroups, false 78 * will be returned. If AllowUsers isn't empty and user isn't listed 79 * there, or if AllowGroups isn't empty and one of user's groups isn't 80 * listed there, false will be returned. 81 * If the user's shell is not executable, false will be returned. 82 * Otherwise true is returned. 83 */ 84 int 85 allowed_user(struct passwd * pw) 86 { 87 #ifdef HAVE_LOGIN_CAP 88 extern login_cap_t *lc; 89 int match_name, match_ip; 90 char *cap_hlist, *hp; 91 #endif 92 struct stat st; 93 const char *hostname = NULL, *ipaddr = NULL; 94 char *shell; 95 u_int i; 96 97 /* Shouldn't be called if pw is NULL, but better safe than sorry... */ 98 if (!pw || !pw->pw_name) 99 return 0; 100 101 #ifdef HAVE_LOGIN_CAP 102 hostname = get_canonical_hostname(1); 103 ipaddr = get_remote_ipaddr(); 104 105 lc = login_getclass(pw->pw_class); 106 107 /* 108 * Check the deny list. 109 */ 110 cap_hlist = login_getcapstr(lc, "host.deny", NULL, NULL); 111 if (cap_hlist != NULL) { 112 hp = strtok(cap_hlist, ","); 113 while (hp != NULL) { 114 match_name = match_hostname(hostname, 115 hp, strlen(hp)); 116 match_ip = match_hostname(ipaddr, 117 hp, strlen(hp)); 118 /* 119 * Only a positive match here causes a "deny". 120 */ 121 if (match_name > 0 || match_ip > 0) { 122 free(cap_hlist); 123 login_close(lc); 124 return 0; 125 } 126 hp = strtok(NULL, ","); 127 } 128 free(cap_hlist); 129 } 130 131 /* 132 * Check the allow list. If the allow list exists, and the 133 * remote host is not in it, the user is implicitly denied. 134 */ 135 cap_hlist = login_getcapstr(lc, "host.allow", NULL, NULL); 136 if (cap_hlist != NULL) { 137 hp = strtok(cap_hlist, ","); 138 if (hp == NULL) { 139 /* Just in case there's an empty string... */ 140 free(cap_hlist); 141 login_close(lc); 142 return 0; 143 } 144 while (hp != NULL) { 145 match_name = match_hostname(hostname, 146 hp, strlen(hp)); 147 match_ip = match_hostname(ipaddr, 148 hp, strlen(hp)); 149 /* 150 * Negative match causes an immediate "deny". 151 * Positive match causes us to break out 152 * of the loop (allowing a fallthrough). 153 */ 154 if (match_name < 0 || match_ip < 0) { 155 free(cap_hlist); 156 login_close(lc); 157 return 0; 158 } 159 if (match_name > 0 || match_ip > 0) 160 break; 161 hp = strtok(NULL, ","); 162 } 163 free(cap_hlist); 164 if (hp == NULL) { 165 login_close(lc); 166 return 0; 167 } 168 } 169 170 login_close(lc); 171 #endif 172 173 #ifdef USE_PAM 174 if (!options.use_pam) { 175 #endif 176 /* 177 * password/account expiration. 178 */ 179 if (pw->pw_change || pw->pw_expire) { 180 struct timeval tv; 181 182 (void)gettimeofday(&tv, (struct timezone *)NULL); 183 if (pw->pw_expire) { 184 if (tv.tv_sec >= pw->pw_expire) { 185 logit("User %.100s not allowed because account has expired", 186 pw->pw_name); 187 return 0; /* expired */ 188 } 189 } 190 #ifdef _PASSWORD_CHGNOW 191 if (pw->pw_change == _PASSWORD_CHGNOW) { 192 logit("User %.100s not allowed because password needs to be changed", 193 pw->pw_name); 194 195 return 0; /* can't force password change (yet) */ 196 } 197 #endif 198 if (pw->pw_change) { 199 if (tv.tv_sec >= pw->pw_change) { 200 logit("User %.100s not allowed because password has expired", 201 pw->pw_name); 202 return 0; /* expired */ 203 } 204 } 205 } 206 #ifdef USE_PAM 207 } 208 #endif 209 210 /* 211 * Get the shell from the password data. An empty shell field is 212 * legal, and means /bin/sh. 213 */ 214 shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell; 215 216 /* deny if shell does not exists or is not executable */ 217 /* 218 * XXX Should check to see if it is executable by the 219 * XXX requesting user. --thorpej 220 */ 221 if (stat(shell, &st) != 0) { 222 logit("User %.100s not allowed because shell %.100s does not exist", 223 pw->pw_name, shell); 224 return 0; 225 } 226 if (S_ISREG(st.st_mode) == 0 || 227 (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { 228 logit("User %.100s not allowed because shell %.100s is not executable", 229 pw->pw_name, shell); 230 return 0; 231 } 232 /* 233 * XXX Consider nuking {Allow,Deny}{Users,Groups}. We have the 234 * XXX login_cap(3) mechanism which covers all other types of 235 * XXX logins, too. 236 */ 237 238 if (options.num_deny_users > 0 || options.num_allow_users > 0 || 239 options.num_deny_groups > 0 || options.num_allow_groups > 0) { 240 hostname = get_canonical_hostname(options.use_dns); 241 ipaddr = get_remote_ipaddr(); 242 } 243 244 /* Return false if user is listed in DenyUsers */ 245 if (options.num_deny_users > 0) { 246 for (i = 0; i < options.num_deny_users; i++) 247 if (match_user(pw->pw_name, hostname, ipaddr, 248 options.deny_users[i])) { 249 logit("User %.100s from %.100s not allowed " 250 "because listed in DenyUsers", 251 pw->pw_name, hostname); 252 return 0; 253 } 254 } 255 /* Return false if AllowUsers isn't empty and user isn't listed there */ 256 if (options.num_allow_users > 0) { 257 for (i = 0; i < options.num_allow_users; i++) 258 if (match_user(pw->pw_name, hostname, ipaddr, 259 options.allow_users[i])) 260 break; 261 /* i < options.num_allow_users iff we break for loop */ 262 if (i >= options.num_allow_users) { 263 logit("User %.100s from %.100s not allowed because " 264 "not listed in AllowUsers", pw->pw_name, hostname); 265 return 0; 266 } 267 } 268 if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { 269 /* Get the user's group access list (primary and supplementary) */ 270 if (ga_init(pw->pw_name, pw->pw_gid) == 0) { 271 logit("User %.100s from %.100s not allowed because " 272 "not in any group", pw->pw_name, hostname); 273 return 0; 274 } 275 276 /* Return false if one of user's groups is listed in DenyGroups */ 277 if (options.num_deny_groups > 0) 278 if (ga_match(options.deny_groups, 279 options.num_deny_groups)) { 280 ga_free(); 281 logit("User %.100s from %.100s not allowed " 282 "because a group is listed in DenyGroups", 283 pw->pw_name, hostname); 284 return 0; 285 } 286 /* 287 * Return false if AllowGroups isn't empty and one of user's groups 288 * isn't listed there 289 */ 290 if (options.num_allow_groups > 0) 291 if (!ga_match(options.allow_groups, 292 options.num_allow_groups)) { 293 ga_free(); 294 logit("User %.100s from %.100s not allowed " 295 "because none of user's groups are listed " 296 "in AllowGroups", pw->pw_name, hostname); 297 return 0; 298 } 299 ga_free(); 300 } 301 /* We found no reason not to let this user try to log on... */ 302 return 1; 303 } 304 305 void 306 auth_log(Authctxt *authctxt, int authenticated, char *method, char *info) 307 { 308 void (*authlog) (const char *fmt,...) = verbose; 309 char *authmsg; 310 311 if (use_privsep && !mm_is_monitor() && !authctxt->postponed) 312 return; 313 314 /* Raise logging level */ 315 if (authenticated == 1 || 316 !authctxt->valid || 317 authctxt->failures >= options.max_authtries / 2 || 318 strcmp(method, "password") == 0) 319 authlog = logit; 320 321 if (authctxt->postponed) 322 authmsg = "Postponed"; 323 else 324 authmsg = authenticated ? "Accepted" : "Failed"; 325 326 authlog("%s %s for %s%.100s from %.200s port %d%s", 327 authmsg, 328 method, 329 authctxt->valid ? "" : "invalid user ", 330 authctxt->user, 331 get_remote_ipaddr(), 332 get_remote_port(), 333 info); 334 } 335 336 /* 337 * Check whether root logins are disallowed. 338 */ 339 int 340 auth_root_allowed(char *method) 341 { 342 switch (options.permit_root_login) { 343 case PERMIT_YES: 344 return 1; 345 case PERMIT_NO_PASSWD: 346 if (strcmp(method, "password") != 0) 347 return 1; 348 break; 349 case PERMIT_FORCED_ONLY: 350 if (forced_command) { 351 logit("Root login accepted for forced command."); 352 return 1; 353 } 354 break; 355 } 356 logit("ROOT LOGIN REFUSED FROM %.200s", get_remote_ipaddr()); 357 return 0; 358 } 359 360 361 /* 362 * Given a template and a passwd structure, build a filename 363 * by substituting % tokenised options. Currently, %% becomes '%', 364 * %h becomes the home directory and %u the username. 365 * 366 * This returns a buffer allocated by xmalloc. 367 */ 368 static char * 369 expand_authorized_keys(const char *filename, struct passwd *pw) 370 { 371 char *file, ret[MAXPATHLEN]; 372 int i; 373 374 file = percent_expand(filename, "h", pw->pw_dir, 375 "u", pw->pw_name, (char *)NULL); 376 377 /* 378 * Ensure that filename starts anchored. If not, be backward 379 * compatible and prepend the '%h/' 380 */ 381 if (*file == '/') 382 return (file); 383 384 i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file); 385 if (i < 0 || (size_t)i >= sizeof(ret)) 386 fatal("expand_authorized_keys: path too long"); 387 xfree(file); 388 return (xstrdup(ret)); 389 } 390 391 char * 392 authorized_keys_file(struct passwd *pw) 393 { 394 return expand_authorized_keys(options.authorized_keys_file, pw); 395 } 396 397 char * 398 authorized_keys_file2(struct passwd *pw) 399 { 400 return expand_authorized_keys(options.authorized_keys_file2, pw); 401 } 402 403 /* return ok if key exists in sysfile or userfile */ 404 HostStatus 405 check_key_in_hostfiles(struct passwd *pw, Key *key, const char *host, 406 const char *sysfile, const char *userfile) 407 { 408 Key *found; 409 char *user_hostfile; 410 struct stat st; 411 HostStatus host_status; 412 413 /* Check if we know the host and its host key. */ 414 found = key_new(key->type); 415 host_status = check_host_in_hostfile(sysfile, host, key, found, NULL); 416 417 if (host_status != HOST_OK && userfile != NULL) { 418 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); 419 if (options.strict_modes && 420 (stat(user_hostfile, &st) == 0) && 421 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || 422 (st.st_mode & 022) != 0)) { 423 logit("Authentication refused for %.100s: " 424 "bad owner or modes for %.200s", 425 pw->pw_name, user_hostfile); 426 } else { 427 temporarily_use_uid(pw); 428 host_status = check_host_in_hostfile(user_hostfile, 429 host, key, found, NULL); 430 restore_uid(); 431 } 432 xfree(user_hostfile); 433 } 434 key_free(found); 435 436 debug2("check_key_in_hostfiles: key %s for %s", host_status == HOST_OK ? 437 "ok" : "not found", host); 438 return host_status; 439 } 440 441 442 /* 443 * Check a given file for security. This is defined as all components 444 * of the path to the file must be owned by either the owner of 445 * of the file or root and no directories must be group or world writable. 446 * 447 * XXX Should any specific check be done for sym links ? 448 * 449 * Takes an open file descriptor, the file name, a uid and and 450 * error buffer plus max size as arguments. 451 * 452 * Returns 0 on success and -1 on failure 453 */ 454 static int 455 secure_filename(FILE *f, const char *file, struct passwd *pw, 456 char *err, size_t errlen) 457 { 458 uid_t uid = pw->pw_uid; 459 char buf[MAXPATHLEN], homedir[MAXPATHLEN]; 460 char *cp; 461 int comparehome = 0; 462 struct stat st; 463 464 if (realpath(file, buf) == NULL) { 465 snprintf(err, errlen, "realpath %s failed: %s", file, 466 strerror(errno)); 467 return -1; 468 } 469 if (realpath(pw->pw_dir, homedir) != NULL) 470 comparehome = 1; 471 472 /* check the open file to avoid races */ 473 if (fstat(fileno(f), &st) < 0 || 474 (st.st_uid != 0 && st.st_uid != uid) || 475 (st.st_mode & 022) != 0) { 476 snprintf(err, errlen, "bad ownership or modes for file %s", 477 buf); 478 return -1; 479 } 480 481 /* for each component of the canonical path, walking upwards */ 482 for (;;) { 483 if ((cp = dirname(buf)) == NULL) { 484 snprintf(err, errlen, "dirname() failed"); 485 return -1; 486 } 487 strlcpy(buf, cp, sizeof(buf)); 488 489 debug3("secure_filename: checking '%s'", buf); 490 if (stat(buf, &st) < 0 || 491 (st.st_uid != 0 && st.st_uid != uid) || 492 (st.st_mode & 022) != 0) { 493 snprintf(err, errlen, 494 "bad ownership or modes for directory %s", buf); 495 return -1; 496 } 497 498 /* If are passed the homedir then we can stop */ 499 if (comparehome && strcmp(homedir, buf) == 0) { 500 debug3("secure_filename: terminating check at '%s'", 501 buf); 502 break; 503 } 504 /* 505 * dirname should always complete with a "/" path, 506 * but we can be paranoid and check for "." too 507 */ 508 if ((strcmp("/", buf) == 0) || (strcmp(".", buf) == 0)) 509 break; 510 } 511 return 0; 512 } 513 514 FILE * 515 auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes) 516 { 517 char line[1024]; 518 struct stat st; 519 int fd; 520 FILE *f; 521 522 /* 523 * Open the file containing the authorized keys 524 * Fail quietly if file does not exist 525 */ 526 if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) 527 return NULL; 528 529 if (fstat(fd, &st) < 0) { 530 close(fd); 531 return NULL; 532 } 533 if (!S_ISREG(st.st_mode)) { 534 logit("User %s authorized keys %s is not a regular file", 535 pw->pw_name, file); 536 close(fd); 537 return NULL; 538 } 539 unset_nonblock(fd); 540 if ((f = fdopen(fd, "r")) == NULL) { 541 close(fd); 542 return NULL; 543 } 544 if (options.strict_modes && 545 secure_filename(f, file, pw, line, sizeof(line)) != 0) { 546 fclose(f); 547 logit("Authentication refused: %s", line); 548 return NULL; 549 } 550 551 return f; 552 } 553 554 struct passwd * 555 getpwnamallow(const char *user) 556 { 557 #ifdef HAVE_LOGIN_CAP 558 extern login_cap_t *lc; 559 #ifdef BSD_AUTH 560 auth_session_t *as; 561 #endif 562 #endif 563 struct passwd *pw; 564 565 parse_server_match_config(&options, user, 566 get_canonical_hostname(options.use_dns), get_remote_ipaddr()); 567 568 pw = getpwnam(user); 569 if (pw == NULL) { 570 logit("Invalid user %.100s from %.100s", 571 user, get_remote_ipaddr()); 572 return (NULL); 573 } 574 if (!allowed_user(pw)) 575 return (NULL); 576 #ifdef HAVE_LOGIN_CAP 577 if ((lc = login_getclass(pw->pw_class)) == NULL) { 578 debug("unable to get login class: %s", user); 579 return (NULL); 580 } 581 #ifdef BSD_AUTH 582 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || 583 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { 584 debug("Approval failure for %s", user); 585 pw = NULL; 586 } 587 if (as != NULL) 588 auth_close(as); 589 #endif 590 #endif 591 if (pw != NULL) 592 return (pwcopy(pw)); 593 return (NULL); 594 } 595 596 void 597 auth_debug_add(const char *fmt,...) 598 { 599 char buf[1024]; 600 va_list args; 601 602 if (!auth_debug_init) 603 return; 604 605 va_start(args, fmt); 606 vsnprintf(buf, sizeof(buf), fmt, args); 607 va_end(args); 608 buffer_put_cstring(&auth_debug, buf); 609 } 610 611 void 612 auth_debug_send(void) 613 { 614 char *msg; 615 616 if (!auth_debug_init) 617 return; 618 while (buffer_len(&auth_debug)) { 619 msg = buffer_get_string(&auth_debug, NULL); 620 packet_send_debug("%s", msg); 621 xfree(msg); 622 } 623 } 624 625 void 626 auth_debug_reset(void) 627 { 628 if (auth_debug_init) 629 buffer_clear(&auth_debug); 630 else { 631 buffer_init(&auth_debug); 632 auth_debug_init = 1; 633 } 634 } 635 636 struct passwd * 637 fakepw(void) 638 { 639 static struct passwd fake; 640 641 memset(&fake, 0, sizeof(fake)); 642 fake.pw_name = "NOUSER"; 643 fake.pw_passwd = 644 "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK"; 645 fake.pw_gecos = "NOUSER"; 646 fake.pw_uid = (uid_t)-1; 647 fake.pw_gid = (gid_t)-1; 648 fake.pw_class = ""; 649 fake.pw_dir = "/nonexist"; 650 fake.pw_shell = "/nonexist"; 651 652 return (&fake); 653 } 654