1 /* $OpenBSD: auth.c,v 1.136 2019/01/19 21:31:32 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 <sys/types.h> 27 #include <sys/stat.h> 28 #include <sys/socket.h> 29 #include <sys/wait.h> 30 31 #include <errno.h> 32 #include <fcntl.h> 33 #include <login_cap.h> 34 #include <paths.h> 35 #include <pwd.h> 36 #include <stdarg.h> 37 #include <stdio.h> 38 #include <string.h> 39 #include <unistd.h> 40 #include <limits.h> 41 #include <netdb.h> 42 #include <time.h> 43 44 #include "xmalloc.h" 45 #include "match.h" 46 #include "groupaccess.h" 47 #include "log.h" 48 #include "sshbuf.h" 49 #include "misc.h" 50 #include "servconf.h" 51 #include "sshkey.h" 52 #include "hostfile.h" 53 #include "auth.h" 54 #include "auth-options.h" 55 #include "canohost.h" 56 #include "uidswap.h" 57 #include "packet.h" 58 #ifdef GSSAPI 59 #include "ssh-gss.h" 60 #endif 61 #include "authfile.h" 62 #include "monitor_wrap.h" 63 #include "authfile.h" 64 #include "ssherr.h" 65 #include "compat.h" 66 #include "channels.h" 67 68 #include "opacket.h" /* XXX */ 69 extern struct ssh *active_state; /* XXX */ 70 71 /* import */ 72 extern ServerOptions options; 73 extern int use_privsep; 74 extern struct sshauthopt *auth_opts; 75 76 /* Debugging messages */ 77 static struct sshbuf *auth_debug; 78 79 /* 80 * Check if the user is allowed to log in via ssh. If user is listed 81 * in DenyUsers or one of user's groups is listed in DenyGroups, false 82 * will be returned. If AllowUsers isn't empty and user isn't listed 83 * there, or if AllowGroups isn't empty and one of user's groups isn't 84 * listed there, false will be returned. 85 * If the user's shell is not executable, false will be returned. 86 * Otherwise true is returned. 87 */ 88 int 89 allowed_user(struct passwd * pw) 90 { 91 struct ssh *ssh = active_state; /* XXX */ 92 struct stat st; 93 const char *hostname = NULL, *ipaddr = NULL; 94 int r; 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 /* 102 * Deny if shell does not exist or is not executable unless we 103 * are chrooting. 104 */ 105 if (options.chroot_directory == NULL || 106 strcasecmp(options.chroot_directory, "none") == 0) { 107 char *shell = xstrdup((pw->pw_shell[0] == '\0') ? 108 _PATH_BSHELL : pw->pw_shell); /* empty = /bin/sh */ 109 110 if (stat(shell, &st) != 0) { 111 logit("User %.100s not allowed because shell %.100s " 112 "does not exist", pw->pw_name, shell); 113 free(shell); 114 return 0; 115 } 116 if (S_ISREG(st.st_mode) == 0 || 117 (st.st_mode & (S_IXOTH|S_IXUSR|S_IXGRP)) == 0) { 118 logit("User %.100s not allowed because shell %.100s " 119 "is not executable", pw->pw_name, shell); 120 free(shell); 121 return 0; 122 } 123 free(shell); 124 } 125 126 if (options.num_deny_users > 0 || options.num_allow_users > 0 || 127 options.num_deny_groups > 0 || options.num_allow_groups > 0) { 128 hostname = auth_get_canonical_hostname(ssh, options.use_dns); 129 ipaddr = ssh_remote_ipaddr(ssh); 130 } 131 132 /* Return false if user is listed in DenyUsers */ 133 if (options.num_deny_users > 0) { 134 for (i = 0; i < options.num_deny_users; i++) { 135 r = match_user(pw->pw_name, hostname, ipaddr, 136 options.deny_users[i]); 137 if (r < 0) { 138 fatal("Invalid DenyUsers pattern \"%.100s\"", 139 options.deny_users[i]); 140 } else if (r != 0) { 141 logit("User %.100s from %.100s not allowed " 142 "because listed in DenyUsers", 143 pw->pw_name, hostname); 144 return 0; 145 } 146 } 147 } 148 /* Return false if AllowUsers isn't empty and user isn't listed there */ 149 if (options.num_allow_users > 0) { 150 for (i = 0; i < options.num_allow_users; i++) { 151 r = match_user(pw->pw_name, hostname, ipaddr, 152 options.allow_users[i]); 153 if (r < 0) { 154 fatal("Invalid AllowUsers pattern \"%.100s\"", 155 options.allow_users[i]); 156 } else if (r == 1) 157 break; 158 } 159 /* i < options.num_allow_users iff we break for loop */ 160 if (i >= options.num_allow_users) { 161 logit("User %.100s from %.100s not allowed because " 162 "not listed in AllowUsers", pw->pw_name, hostname); 163 return 0; 164 } 165 } 166 if (options.num_deny_groups > 0 || options.num_allow_groups > 0) { 167 /* Get the user's group access list (primary and supplementary) */ 168 if (ga_init(pw->pw_name, pw->pw_gid) == 0) { 169 logit("User %.100s from %.100s not allowed because " 170 "not in any group", pw->pw_name, hostname); 171 return 0; 172 } 173 174 /* Return false if one of user's groups is listed in DenyGroups */ 175 if (options.num_deny_groups > 0) 176 if (ga_match(options.deny_groups, 177 options.num_deny_groups)) { 178 ga_free(); 179 logit("User %.100s from %.100s not allowed " 180 "because a group is listed in DenyGroups", 181 pw->pw_name, hostname); 182 return 0; 183 } 184 /* 185 * Return false if AllowGroups isn't empty and one of user's groups 186 * isn't listed there 187 */ 188 if (options.num_allow_groups > 0) 189 if (!ga_match(options.allow_groups, 190 options.num_allow_groups)) { 191 ga_free(); 192 logit("User %.100s from %.100s not allowed " 193 "because none of user's groups are listed " 194 "in AllowGroups", pw->pw_name, hostname); 195 return 0; 196 } 197 ga_free(); 198 } 199 /* We found no reason not to let this user try to log on... */ 200 return 1; 201 } 202 203 /* 204 * Formats any key left in authctxt->auth_method_key for inclusion in 205 * auth_log()'s message. Also includes authxtct->auth_method_info if present. 206 */ 207 static char * 208 format_method_key(Authctxt *authctxt) 209 { 210 const struct sshkey *key = authctxt->auth_method_key; 211 const char *methinfo = authctxt->auth_method_info; 212 char *fp, *cafp, *ret = NULL; 213 214 if (key == NULL) 215 return NULL; 216 217 if (sshkey_is_cert(key)) { 218 fp = sshkey_fingerprint(key, 219 options.fingerprint_hash, SSH_FP_DEFAULT); 220 cafp = sshkey_fingerprint(key->cert->signature_key, 221 options.fingerprint_hash, SSH_FP_DEFAULT); 222 xasprintf(&ret, "%s %s ID %s (serial %llu) CA %s %s%s%s", 223 sshkey_type(key), fp == NULL ? "(null)" : fp, 224 key->cert->key_id, 225 (unsigned long long)key->cert->serial, 226 sshkey_type(key->cert->signature_key), 227 cafp == NULL ? "(null)" : cafp, 228 methinfo == NULL ? "" : ", ", 229 methinfo == NULL ? "" : methinfo); 230 free(fp); 231 free(cafp); 232 } else { 233 fp = sshkey_fingerprint(key, options.fingerprint_hash, 234 SSH_FP_DEFAULT); 235 xasprintf(&ret, "%s %s%s%s", sshkey_type(key), 236 fp == NULL ? "(null)" : fp, 237 methinfo == NULL ? "" : ", ", 238 methinfo == NULL ? "" : methinfo); 239 free(fp); 240 } 241 return ret; 242 } 243 244 void 245 auth_log(Authctxt *authctxt, int authenticated, int partial, 246 const char *method, const char *submethod) 247 { 248 struct ssh *ssh = active_state; /* XXX */ 249 int level = SYSLOG_LEVEL_VERBOSE; 250 const char *authmsg; 251 char *extra = NULL; 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 level = SYSLOG_LEVEL_INFO; 262 263 if (authctxt->postponed) 264 authmsg = "Postponed"; 265 else if (partial) 266 authmsg = "Partial"; 267 else 268 authmsg = authenticated ? "Accepted" : "Failed"; 269 270 if ((extra = format_method_key(authctxt)) == NULL) { 271 if (authctxt->auth_method_info != NULL) 272 extra = xstrdup(authctxt->auth_method_info); 273 } 274 275 do_log2(level, "%s %s%s%s for %s%.100s from %.200s port %d ssh2%s%s", 276 authmsg, 277 method, 278 submethod != NULL ? "/" : "", submethod == NULL ? "" : submethod, 279 authctxt->valid ? "" : "invalid user ", 280 authctxt->user, 281 ssh_remote_ipaddr(ssh), 282 ssh_remote_port(ssh), 283 extra != NULL ? ": " : "", 284 extra != NULL ? extra : ""); 285 286 free(extra); 287 } 288 289 void 290 auth_maxtries_exceeded(Authctxt *authctxt) 291 { 292 struct ssh *ssh = active_state; /* XXX */ 293 294 error("maximum authentication attempts exceeded for " 295 "%s%.100s from %.200s port %d ssh2", 296 authctxt->valid ? "" : "invalid user ", 297 authctxt->user, 298 ssh_remote_ipaddr(ssh), 299 ssh_remote_port(ssh)); 300 packet_disconnect("Too many authentication failures"); 301 /* NOTREACHED */ 302 } 303 304 /* 305 * Check whether root logins are disallowed. 306 */ 307 int 308 auth_root_allowed(struct ssh *ssh, const char *method) 309 { 310 switch (options.permit_root_login) { 311 case PERMIT_YES: 312 return 1; 313 case PERMIT_NO_PASSWD: 314 if (strcmp(method, "publickey") == 0 || 315 strcmp(method, "hostbased") == 0 || 316 strcmp(method, "gssapi-with-mic") == 0) 317 return 1; 318 break; 319 case PERMIT_FORCED_ONLY: 320 if (auth_opts->force_command != NULL) { 321 logit("Root login accepted for forced command."); 322 return 1; 323 } 324 break; 325 } 326 logit("ROOT LOGIN REFUSED FROM %.200s port %d", 327 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 328 return 0; 329 } 330 331 332 /* 333 * Given a template and a passwd structure, build a filename 334 * by substituting % tokenised options. Currently, %% becomes '%', 335 * %h becomes the home directory and %u the username. 336 * 337 * This returns a buffer allocated by xmalloc. 338 */ 339 char * 340 expand_authorized_keys(const char *filename, struct passwd *pw) 341 { 342 char *file, uidstr[32], ret[PATH_MAX]; 343 int i; 344 345 snprintf(uidstr, sizeof(uidstr), "%llu", 346 (unsigned long long)pw->pw_uid); 347 file = percent_expand(filename, "h", pw->pw_dir, 348 "u", pw->pw_name, "U", uidstr, (char *)NULL); 349 350 /* 351 * Ensure that filename starts anchored. If not, be backward 352 * compatible and prepend the '%h/' 353 */ 354 if (path_absolute(file)) 355 return (file); 356 357 i = snprintf(ret, sizeof(ret), "%s/%s", pw->pw_dir, file); 358 if (i < 0 || (size_t)i >= sizeof(ret)) 359 fatal("expand_authorized_keys: path too long"); 360 free(file); 361 return (xstrdup(ret)); 362 } 363 364 char * 365 authorized_principals_file(struct passwd *pw) 366 { 367 if (options.authorized_principals_file == NULL) 368 return NULL; 369 return expand_authorized_keys(options.authorized_principals_file, pw); 370 } 371 372 /* return ok if key exists in sysfile or userfile */ 373 HostStatus 374 check_key_in_hostfiles(struct passwd *pw, struct sshkey *key, const char *host, 375 const char *sysfile, const char *userfile) 376 { 377 char *user_hostfile; 378 struct stat st; 379 HostStatus host_status; 380 struct hostkeys *hostkeys; 381 const struct hostkey_entry *found; 382 383 hostkeys = init_hostkeys(); 384 load_hostkeys(hostkeys, host, sysfile); 385 if (userfile != NULL) { 386 user_hostfile = tilde_expand_filename(userfile, pw->pw_uid); 387 if (options.strict_modes && 388 (stat(user_hostfile, &st) == 0) && 389 ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || 390 (st.st_mode & 022) != 0)) { 391 logit("Authentication refused for %.100s: " 392 "bad owner or modes for %.200s", 393 pw->pw_name, user_hostfile); 394 auth_debug_add("Ignored %.200s: bad ownership or modes", 395 user_hostfile); 396 } else { 397 temporarily_use_uid(pw); 398 load_hostkeys(hostkeys, host, user_hostfile); 399 restore_uid(); 400 } 401 free(user_hostfile); 402 } 403 host_status = check_key_in_hostkeys(hostkeys, key, &found); 404 if (host_status == HOST_REVOKED) 405 error("WARNING: revoked key for %s attempted authentication", 406 found->host); 407 else if (host_status == HOST_OK) 408 debug("%s: key for %s found at %s:%ld", __func__, 409 found->host, found->file, found->line); 410 else 411 debug("%s: key for host %s not found", __func__, host); 412 413 free_hostkeys(hostkeys); 414 415 return host_status; 416 } 417 418 static FILE * 419 auth_openfile(const char *file, struct passwd *pw, int strict_modes, 420 int log_missing, char *file_type) 421 { 422 char line[1024]; 423 struct stat st; 424 int fd; 425 FILE *f; 426 427 if ((fd = open(file, O_RDONLY|O_NONBLOCK)) == -1) { 428 if (log_missing || errno != ENOENT) 429 debug("Could not open %s '%s': %s", file_type, file, 430 strerror(errno)); 431 return NULL; 432 } 433 434 if (fstat(fd, &st) < 0) { 435 close(fd); 436 return NULL; 437 } 438 if (!S_ISREG(st.st_mode)) { 439 logit("User %s %s %s is not a regular file", 440 pw->pw_name, file_type, file); 441 close(fd); 442 return NULL; 443 } 444 unset_nonblock(fd); 445 if ((f = fdopen(fd, "r")) == NULL) { 446 close(fd); 447 return NULL; 448 } 449 if (strict_modes && 450 safe_path_fd(fileno(f), file, pw, line, sizeof(line)) != 0) { 451 fclose(f); 452 logit("Authentication refused: %s", line); 453 auth_debug_add("Ignored %s: %s", file_type, line); 454 return NULL; 455 } 456 457 return f; 458 } 459 460 461 FILE * 462 auth_openkeyfile(const char *file, struct passwd *pw, int strict_modes) 463 { 464 return auth_openfile(file, pw, strict_modes, 1, "authorized keys"); 465 } 466 467 FILE * 468 auth_openprincipals(const char *file, struct passwd *pw, int strict_modes) 469 { 470 return auth_openfile(file, pw, strict_modes, 0, 471 "authorized principals"); 472 } 473 474 struct passwd * 475 getpwnamallow(const char *user) 476 { 477 struct ssh *ssh = active_state; /* XXX */ 478 extern login_cap_t *lc; 479 auth_session_t *as; 480 struct passwd *pw; 481 struct connection_info *ci = get_connection_info(1, options.use_dns); 482 483 ci->user = user; 484 parse_server_match_config(&options, ci); 485 log_change_level(options.log_level); 486 process_permitopen(ssh, &options); 487 488 pw = getpwnam(user); 489 if (pw == NULL) { 490 logit("Invalid user %.100s from %.100s port %d", 491 user, ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 492 return (NULL); 493 } 494 if (!allowed_user(pw)) 495 return (NULL); 496 if ((lc = login_getclass(pw->pw_class)) == NULL) { 497 debug("unable to get login class: %s", user); 498 return (NULL); 499 } 500 if ((as = auth_open()) == NULL || auth_setpwd(as, pw) != 0 || 501 auth_approval(as, lc, pw->pw_name, "ssh") <= 0) { 502 debug("Approval failure for %s", user); 503 pw = NULL; 504 } 505 if (as != NULL) 506 auth_close(as); 507 if (pw != NULL) 508 return (pwcopy(pw)); 509 return (NULL); 510 } 511 512 /* Returns 1 if key is revoked by revoked_keys_file, 0 otherwise */ 513 int 514 auth_key_is_revoked(struct sshkey *key) 515 { 516 char *fp = NULL; 517 int r; 518 519 if (options.revoked_keys_file == NULL) 520 return 0; 521 if ((fp = sshkey_fingerprint(key, options.fingerprint_hash, 522 SSH_FP_DEFAULT)) == NULL) { 523 r = SSH_ERR_ALLOC_FAIL; 524 error("%s: fingerprint key: %s", __func__, ssh_err(r)); 525 goto out; 526 } 527 528 r = sshkey_check_revoked(key, options.revoked_keys_file); 529 switch (r) { 530 case 0: 531 break; /* not revoked */ 532 case SSH_ERR_KEY_REVOKED: 533 error("Authentication key %s %s revoked by file %s", 534 sshkey_type(key), fp, options.revoked_keys_file); 535 goto out; 536 default: 537 error("Error checking authentication key %s %s in " 538 "revoked keys file %s: %s", sshkey_type(key), fp, 539 options.revoked_keys_file, ssh_err(r)); 540 goto out; 541 } 542 543 /* Success */ 544 r = 0; 545 546 out: 547 free(fp); 548 return r == 0 ? 0 : 1; 549 } 550 551 void 552 auth_debug_add(const char *fmt,...) 553 { 554 char buf[1024]; 555 va_list args; 556 int r; 557 558 if (auth_debug == NULL) 559 return; 560 561 va_start(args, fmt); 562 vsnprintf(buf, sizeof(buf), fmt, args); 563 va_end(args); 564 if ((r = sshbuf_put_cstring(auth_debug, buf)) != 0) 565 fatal("%s: sshbuf_put_cstring: %s", __func__, ssh_err(r)); 566 } 567 568 void 569 auth_debug_send(void) 570 { 571 struct ssh *ssh = active_state; /* XXX */ 572 char *msg; 573 int r; 574 575 if (auth_debug == NULL) 576 return; 577 while (sshbuf_len(auth_debug) != 0) { 578 if ((r = sshbuf_get_cstring(auth_debug, &msg, NULL)) != 0) 579 fatal("%s: sshbuf_get_cstring: %s", 580 __func__, ssh_err(r)); 581 ssh_packet_send_debug(ssh, "%s", msg); 582 free(msg); 583 } 584 } 585 586 void 587 auth_debug_reset(void) 588 { 589 if (auth_debug != NULL) 590 sshbuf_reset(auth_debug); 591 else if ((auth_debug = sshbuf_new()) == NULL) 592 fatal("%s: sshbuf_new failed", __func__); 593 } 594 595 struct passwd * 596 fakepw(void) 597 { 598 static struct passwd fake; 599 600 memset(&fake, 0, sizeof(fake)); 601 fake.pw_name = "NOUSER"; 602 fake.pw_passwd = 603 "$2a$06$r3.juUaHZDlIbQaO2dS9FuYxL1W9M81R1Tc92PoSNmzvpEqLkLGrK"; 604 fake.pw_gecos = "NOUSER"; 605 fake.pw_uid = (uid_t)-1; 606 fake.pw_gid = (gid_t)-1; 607 fake.pw_class = ""; 608 fake.pw_dir = "/nonexist"; 609 fake.pw_shell = "/nonexist"; 610 611 return (&fake); 612 } 613 614 /* 615 * Returns the remote DNS hostname as a string. The returned string must not 616 * be freed. NB. this will usually trigger a DNS query the first time it is 617 * called. 618 * This function does additional checks on the hostname to mitigate some 619 * attacks on legacy rhosts-style authentication. 620 * XXX is RhostsRSAAuthentication vulnerable to these? 621 * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?) 622 */ 623 624 static char * 625 remote_hostname(struct ssh *ssh) 626 { 627 struct sockaddr_storage from; 628 socklen_t fromlen; 629 struct addrinfo hints, *ai, *aitop; 630 char name[NI_MAXHOST], ntop2[NI_MAXHOST]; 631 const char *ntop = ssh_remote_ipaddr(ssh); 632 633 /* Get IP address of client. */ 634 fromlen = sizeof(from); 635 memset(&from, 0, sizeof(from)); 636 if (getpeername(ssh_packet_get_connection_in(ssh), 637 (struct sockaddr *)&from, &fromlen) < 0) { 638 debug("getpeername failed: %.100s", strerror(errno)); 639 return strdup(ntop); 640 } 641 642 debug3("Trying to reverse map address %.100s.", ntop); 643 /* Map the IP address to a host name. */ 644 if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), 645 NULL, 0, NI_NAMEREQD) != 0) { 646 /* Host name not found. Use ip address. */ 647 return strdup(ntop); 648 } 649 650 /* 651 * if reverse lookup result looks like a numeric hostname, 652 * someone is trying to trick us by PTR record like following: 653 * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5 654 */ 655 memset(&hints, 0, sizeof(hints)); 656 hints.ai_socktype = SOCK_DGRAM; /*dummy*/ 657 hints.ai_flags = AI_NUMERICHOST; 658 if (getaddrinfo(name, NULL, &hints, &ai) == 0) { 659 logit("Nasty PTR record \"%s\" is set up for %s, ignoring", 660 name, ntop); 661 freeaddrinfo(ai); 662 return strdup(ntop); 663 } 664 665 /* Names are stored in lowercase. */ 666 lowercase(name); 667 668 /* 669 * Map it back to an IP address and check that the given 670 * address actually is an address of this host. This is 671 * necessary because anyone with access to a name server can 672 * define arbitrary names for an IP address. Mapping from 673 * name to IP address can be trusted better (but can still be 674 * fooled if the intruder has access to the name server of 675 * the domain). 676 */ 677 memset(&hints, 0, sizeof(hints)); 678 hints.ai_family = from.ss_family; 679 hints.ai_socktype = SOCK_STREAM; 680 if (getaddrinfo(name, NULL, &hints, &aitop) != 0) { 681 logit("reverse mapping checking getaddrinfo for %.700s " 682 "[%s] failed.", name, ntop); 683 return strdup(ntop); 684 } 685 /* Look for the address from the list of addresses. */ 686 for (ai = aitop; ai; ai = ai->ai_next) { 687 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2, 688 sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 && 689 (strcmp(ntop, ntop2) == 0)) 690 break; 691 } 692 freeaddrinfo(aitop); 693 /* If we reached the end of the list, the address was not there. */ 694 if (ai == NULL) { 695 /* Address not found for the host name. */ 696 logit("Address %.100s maps to %.600s, but this does not " 697 "map back to the address.", ntop, name); 698 return strdup(ntop); 699 } 700 return strdup(name); 701 } 702 703 /* 704 * Return the canonical name of the host in the other side of the current 705 * connection. The host name is cached, so it is efficient to call this 706 * several times. 707 */ 708 709 const char * 710 auth_get_canonical_hostname(struct ssh *ssh, int use_dns) 711 { 712 static char *dnsname; 713 714 if (!use_dns) 715 return ssh_remote_ipaddr(ssh); 716 else if (dnsname != NULL) 717 return dnsname; 718 else { 719 dnsname = remote_hostname(ssh); 720 return dnsname; 721 } 722 } 723 724 /* 725 * Runs command in a subprocess with a minimal environment. 726 * Returns pid on success, 0 on failure. 727 * The child stdout and stderr maybe captured, left attached or sent to 728 * /dev/null depending on the contents of flags. 729 * "tag" is prepended to log messages. 730 * NB. "command" is only used for logging; the actual command executed is 731 * av[0]. 732 */ 733 pid_t 734 subprocess(const char *tag, struct passwd *pw, const char *command, 735 int ac, char **av, FILE **child, u_int flags) 736 { 737 FILE *f = NULL; 738 struct stat st; 739 int fd, devnull, p[2], i; 740 pid_t pid; 741 char *cp, errmsg[512]; 742 u_int envsize; 743 char **child_env; 744 745 if (child != NULL) 746 *child = NULL; 747 748 debug3("%s: %s command \"%s\" running as %s (flags 0x%x)", __func__, 749 tag, command, pw->pw_name, flags); 750 751 /* Check consistency */ 752 if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 && 753 (flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) { 754 error("%s: inconsistent flags", __func__); 755 return 0; 756 } 757 if (((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) != (child == NULL)) { 758 error("%s: inconsistent flags/output", __func__); 759 return 0; 760 } 761 762 /* 763 * If executing an explicit binary, then verify the it exists 764 * and appears safe-ish to execute 765 */ 766 if (!path_absolute(av[0])) { 767 error("%s path is not absolute", tag); 768 return 0; 769 } 770 temporarily_use_uid(pw); 771 if (stat(av[0], &st) < 0) { 772 error("Could not stat %s \"%s\": %s", tag, 773 av[0], strerror(errno)); 774 restore_uid(); 775 return 0; 776 } 777 if (safe_path(av[0], &st, NULL, 0, errmsg, sizeof(errmsg)) != 0) { 778 error("Unsafe %s \"%s\": %s", tag, av[0], errmsg); 779 restore_uid(); 780 return 0; 781 } 782 /* Prepare to keep the child's stdout if requested */ 783 if (pipe(p) != 0) { 784 error("%s: pipe: %s", tag, strerror(errno)); 785 restore_uid(); 786 return 0; 787 } 788 restore_uid(); 789 790 switch ((pid = fork())) { 791 case -1: /* error */ 792 error("%s: fork: %s", tag, strerror(errno)); 793 close(p[0]); 794 close(p[1]); 795 return 0; 796 case 0: /* child */ 797 /* Prepare a minimal environment for the child. */ 798 envsize = 5; 799 child_env = xcalloc(sizeof(*child_env), envsize); 800 child_set_env(&child_env, &envsize, "PATH", _PATH_STDPATH); 801 child_set_env(&child_env, &envsize, "USER", pw->pw_name); 802 child_set_env(&child_env, &envsize, "LOGNAME", pw->pw_name); 803 child_set_env(&child_env, &envsize, "HOME", pw->pw_dir); 804 if ((cp = getenv("LANG")) != NULL) 805 child_set_env(&child_env, &envsize, "LANG", cp); 806 807 for (i = 0; i < NSIG; i++) 808 signal(i, SIG_DFL); 809 810 if ((devnull = open(_PATH_DEVNULL, O_RDWR)) == -1) { 811 error("%s: open %s: %s", tag, _PATH_DEVNULL, 812 strerror(errno)); 813 _exit(1); 814 } 815 if (dup2(devnull, STDIN_FILENO) == -1) { 816 error("%s: dup2: %s", tag, strerror(errno)); 817 _exit(1); 818 } 819 820 /* Set up stdout as requested; leave stderr in place for now. */ 821 fd = -1; 822 if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) != 0) 823 fd = p[1]; 824 else if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0) 825 fd = devnull; 826 if (fd != -1 && dup2(fd, STDOUT_FILENO) == -1) { 827 error("%s: dup2: %s", tag, strerror(errno)); 828 _exit(1); 829 } 830 closefrom(STDERR_FILENO + 1); 831 832 /* Don't use permanently_set_uid() here to avoid fatal() */ 833 if (setresgid(pw->pw_gid, pw->pw_gid, pw->pw_gid) != 0) { 834 error("%s: setresgid %u: %s", tag, (u_int)pw->pw_gid, 835 strerror(errno)); 836 _exit(1); 837 } 838 if (setresuid(pw->pw_uid, pw->pw_uid, pw->pw_uid) != 0) { 839 error("%s: setresuid %u: %s", tag, (u_int)pw->pw_uid, 840 strerror(errno)); 841 _exit(1); 842 } 843 /* stdin is pointed to /dev/null at this point */ 844 if ((flags & SSH_SUBPROCESS_STDOUT_DISCARD) != 0 && 845 dup2(STDIN_FILENO, STDERR_FILENO) == -1) { 846 error("%s: dup2: %s", tag, strerror(errno)); 847 _exit(1); 848 } 849 850 execve(av[0], av, child_env); 851 error("%s exec \"%s\": %s", tag, command, strerror(errno)); 852 _exit(127); 853 default: /* parent */ 854 break; 855 } 856 857 close(p[1]); 858 if ((flags & SSH_SUBPROCESS_STDOUT_CAPTURE) == 0) 859 close(p[0]); 860 else if ((f = fdopen(p[0], "r")) == NULL) { 861 error("%s: fdopen: %s", tag, strerror(errno)); 862 close(p[0]); 863 /* Don't leave zombie child */ 864 kill(pid, SIGTERM); 865 while (waitpid(pid, NULL, 0) == -1 && errno == EINTR) 866 ; 867 return 0; 868 } 869 /* Success */ 870 debug3("%s: %s pid %ld", __func__, tag, (long)pid); 871 if (child != NULL) 872 *child = f; 873 return pid; 874 } 875 876 /* These functions link key/cert options to the auth framework */ 877 878 /* Log sshauthopt options locally and (optionally) for remote transmission */ 879 void 880 auth_log_authopts(const char *loc, const struct sshauthopt *opts, int do_remote) 881 { 882 int do_env = options.permit_user_env && opts->nenv > 0; 883 int do_permitopen = opts->npermitopen > 0 && 884 (options.allow_tcp_forwarding & FORWARD_LOCAL) != 0; 885 int do_permitlisten = opts->npermitlisten > 0 && 886 (options.allow_tcp_forwarding & FORWARD_REMOTE) != 0; 887 size_t i; 888 char msg[1024], buf[64]; 889 890 snprintf(buf, sizeof(buf), "%d", opts->force_tun_device); 891 /* Try to keep this alphabetically sorted */ 892 snprintf(msg, sizeof(msg), "key options:%s%s%s%s%s%s%s%s%s%s%s%s%s", 893 opts->permit_agent_forwarding_flag ? " agent-forwarding" : "", 894 opts->force_command == NULL ? "" : " command", 895 do_env ? " environment" : "", 896 opts->valid_before == 0 ? "" : "expires", 897 do_permitopen ? " permitopen" : "", 898 do_permitlisten ? " permitlisten" : "", 899 opts->permit_port_forwarding_flag ? " port-forwarding" : "", 900 opts->cert_principals == NULL ? "" : " principals", 901 opts->permit_pty_flag ? " pty" : "", 902 opts->force_tun_device == -1 ? "" : " tun=", 903 opts->force_tun_device == -1 ? "" : buf, 904 opts->permit_user_rc ? " user-rc" : "", 905 opts->permit_x11_forwarding_flag ? " x11-forwarding" : ""); 906 907 debug("%s: %s", loc, msg); 908 if (do_remote) 909 auth_debug_add("%s: %s", loc, msg); 910 911 if (options.permit_user_env) { 912 for (i = 0; i < opts->nenv; i++) { 913 debug("%s: environment: %s", loc, opts->env[i]); 914 if (do_remote) { 915 auth_debug_add("%s: environment: %s", 916 loc, opts->env[i]); 917 } 918 } 919 } 920 921 /* Go into a little more details for the local logs. */ 922 if (opts->valid_before != 0) { 923 format_absolute_time(opts->valid_before, buf, sizeof(buf)); 924 debug("%s: expires at %s", loc, buf); 925 } 926 if (opts->cert_principals != NULL) { 927 debug("%s: authorized principals: \"%s\"", 928 loc, opts->cert_principals); 929 } 930 if (opts->force_command != NULL) 931 debug("%s: forced command: \"%s\"", loc, opts->force_command); 932 if (do_permitopen) { 933 for (i = 0; i < opts->npermitopen; i++) { 934 debug("%s: permitted open: %s", 935 loc, opts->permitopen[i]); 936 } 937 } 938 if (do_permitlisten) { 939 for (i = 0; i < opts->npermitlisten; i++) { 940 debug("%s: permitted listen: %s", 941 loc, opts->permitlisten[i]); 942 } 943 } 944 } 945 946 /* Activate a new set of key/cert options; merging with what is there. */ 947 int 948 auth_activate_options(struct ssh *ssh, struct sshauthopt *opts) 949 { 950 struct sshauthopt *old = auth_opts; 951 const char *emsg = NULL; 952 953 debug("%s: setting new authentication options", __func__); 954 if ((auth_opts = sshauthopt_merge(old, opts, &emsg)) == NULL) { 955 error("Inconsistent authentication options: %s", emsg); 956 return -1; 957 } 958 return 0; 959 } 960 961 /* Disable forwarding, etc for the session */ 962 void 963 auth_restrict_session(struct ssh *ssh) 964 { 965 struct sshauthopt *restricted; 966 967 debug("%s: restricting session", __func__); 968 969 /* A blank sshauthopt defaults to permitting nothing */ 970 restricted = sshauthopt_new(); 971 restricted->permit_pty_flag = 1; 972 restricted->restricted = 1; 973 974 if (auth_activate_options(ssh, restricted) != 0) 975 fatal("%s: failed to restrict session", __func__); 976 sshauthopt_free(restricted); 977 } 978 979 int 980 auth_authorise_keyopts(struct ssh *ssh, struct passwd *pw, 981 struct sshauthopt *opts, int allow_cert_authority, const char *loc) 982 { 983 const char *remote_ip = ssh_remote_ipaddr(ssh); 984 const char *remote_host = auth_get_canonical_hostname(ssh, 985 options.use_dns); 986 time_t now = time(NULL); 987 char buf[64]; 988 989 /* 990 * Check keys/principals file expiry time. 991 * NB. validity interval in certificate is handled elsewhere. 992 */ 993 if (opts->valid_before && now > 0 && 994 opts->valid_before < (uint64_t)now) { 995 format_absolute_time(opts->valid_before, buf, sizeof(buf)); 996 debug("%s: entry expired at %s", loc, buf); 997 auth_debug_add("%s: entry expired at %s", loc, buf); 998 return -1; 999 } 1000 /* Consistency checks */ 1001 if (opts->cert_principals != NULL && !opts->cert_authority) { 1002 debug("%s: principals on non-CA key", loc); 1003 auth_debug_add("%s: principals on non-CA key", loc); 1004 /* deny access */ 1005 return -1; 1006 } 1007 /* cert-authority flag isn't valid in authorized_principals files */ 1008 if (!allow_cert_authority && opts->cert_authority) { 1009 debug("%s: cert-authority flag invalid here", loc); 1010 auth_debug_add("%s: cert-authority flag invalid here", loc); 1011 /* deny access */ 1012 return -1; 1013 } 1014 1015 /* Perform from= checks */ 1016 if (opts->required_from_host_keys != NULL) { 1017 switch (match_host_and_ip(remote_host, remote_ip, 1018 opts->required_from_host_keys )) { 1019 case 1: 1020 /* Host name matches. */ 1021 break; 1022 case -1: 1023 default: 1024 debug("%s: invalid from criteria", loc); 1025 auth_debug_add("%s: invalid from criteria", loc); 1026 /* FALLTHROUGH */ 1027 case 0: 1028 logit("%s: Authentication tried for %.100s with " 1029 "correct key but not from a permitted " 1030 "host (host=%.200s, ip=%.200s, required=%.200s).", 1031 loc, pw->pw_name, remote_host, remote_ip, 1032 opts->required_from_host_keys); 1033 auth_debug_add("%s: Your host '%.200s' is not " 1034 "permitted to use this key for login.", 1035 loc, remote_host); 1036 /* deny access */ 1037 return -1; 1038 } 1039 } 1040 /* Check source-address restriction from certificate */ 1041 if (opts->required_from_host_cert != NULL) { 1042 switch (addr_match_cidr_list(remote_ip, 1043 opts->required_from_host_cert)) { 1044 case 1: 1045 /* accepted */ 1046 break; 1047 case -1: 1048 default: 1049 /* invalid */ 1050 error("%s: Certificate source-address invalid", 1051 loc); 1052 /* FALLTHROUGH */ 1053 case 0: 1054 logit("%s: Authentication tried for %.100s with valid " 1055 "certificate but not from a permitted source " 1056 "address (%.200s).", loc, pw->pw_name, remote_ip); 1057 auth_debug_add("%s: Your address '%.200s' is not " 1058 "permitted to use this certificate for login.", 1059 loc, remote_ip); 1060 return -1; 1061 } 1062 } 1063 /* 1064 * 1065 * XXX this is spammy. We should report remotely only for keys 1066 * that are successful in actual auth attempts, and not PK_OK 1067 * tests. 1068 */ 1069 auth_log_authopts(loc, opts, 1); 1070 1071 return 0; 1072 } 1073