1 /* $NetBSD: auth2-pubkey.c,v 1.25 2020/02/27 00:24:40 christos Exp $ */ 2 /* $OpenBSD: auth2-pubkey.c,v 1.99 2020/02/06 22:30:54 naddy 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: auth2-pubkey.c,v 1.25 2020/02/27 00:24:40 christos Exp $"); 29 #include <sys/types.h> 30 #include <sys/stat.h> 31 32 #include <stdlib.h> 33 #include <errno.h> 34 #include <fcntl.h> 35 #include <paths.h> 36 #include <pwd.h> 37 #include <signal.h> 38 #include <stdio.h> 39 #include <stdarg.h> 40 #include <string.h> 41 #include <time.h> 42 #include <unistd.h> 43 #include <limits.h> 44 45 #include "xmalloc.h" 46 #include "ssh.h" 47 #include "ssh2.h" 48 #include "packet.h" 49 #include "sshbuf.h" 50 #include "log.h" 51 #include "misc.h" 52 #include "servconf.h" 53 #include "compat.h" 54 #include "sshkey.h" 55 #include "hostfile.h" 56 #include "auth.h" 57 #include "pathnames.h" 58 #include "uidswap.h" 59 #include "auth-options.h" 60 #include "canohost.h" 61 #ifdef GSSAPI 62 #include "ssh-gss.h" 63 #endif 64 #include "monitor_wrap.h" 65 #include "authfile.h" 66 #include "match.h" 67 #include "digest.h" 68 69 #ifdef WITH_LDAP_PUBKEY 70 #include "ldapauth.h" 71 #endif 72 73 #include "ssherr.h" 74 #include "channels.h" /* XXX for session.h */ 75 #include "session.h" /* XXX for child_set_env(); refactor? */ 76 #include "sk-api.h" 77 78 /* import */ 79 extern ServerOptions options; 80 extern u_char *session_id2; 81 extern u_int session_id2_len; 82 83 static char * 84 format_key(const struct sshkey *key) 85 { 86 char *ret, *fp = sshkey_fingerprint(key, 87 options.fingerprint_hash, SSH_FP_DEFAULT); 88 89 xasprintf(&ret, "%s %s", sshkey_type(key), fp); 90 free(fp); 91 return ret; 92 } 93 94 static int 95 userauth_pubkey(struct ssh *ssh) 96 { 97 Authctxt *authctxt = ssh->authctxt; 98 struct passwd *pw = authctxt->pw; 99 struct sshbuf *b = NULL; 100 struct sshkey *key = NULL; 101 char *pkalg = NULL, *userstyle = NULL, *key_s = NULL, *ca_s = NULL; 102 u_char *pkblob = NULL, *sig = NULL, have_sig; 103 size_t blen, slen; 104 int r, pktype; 105 int req_presence = 0, authenticated = 0; 106 struct sshauthopt *authopts = NULL; 107 struct sshkey_sig_details *sig_details = NULL; 108 109 if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0 || 110 (r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 || 111 (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0) 112 fatal("%s: parse request failed: %s", __func__, ssh_err(r)); 113 114 if (log_level_get() >= SYSLOG_LEVEL_DEBUG2) { 115 char *keystring; 116 struct sshbuf *pkbuf; 117 118 if ((pkbuf = sshbuf_from(pkblob, blen)) == NULL) 119 fatal("%s: sshbuf_from failed", __func__); 120 if ((keystring = sshbuf_dtob64_string(pkbuf, 0)) == NULL) 121 fatal("%s: sshbuf_dtob64 failed", __func__); 122 debug2("%s: %s user %s %s public key %s %s", __func__, 123 authctxt->valid ? "valid" : "invalid", authctxt->user, 124 have_sig ? "attempting" : "querying", pkalg, keystring); 125 sshbuf_free(pkbuf); 126 free(keystring); 127 } 128 129 pktype = sshkey_type_from_name(pkalg); 130 if (pktype == KEY_UNSPEC) { 131 /* this is perfectly legal */ 132 verbose("%s: unsupported public key algorithm: %s", 133 __func__, pkalg); 134 goto done; 135 } 136 if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) { 137 error("%s: could not parse key: %s", __func__, ssh_err(r)); 138 goto done; 139 } 140 if (key == NULL) { 141 error("%s: cannot decode key: %s", __func__, pkalg); 142 goto done; 143 } 144 if (key->type != pktype) { 145 error("%s: type mismatch for decoded key " 146 "(received %d, expected %d)", __func__, key->type, pktype); 147 goto done; 148 } 149 if (sshkey_type_plain(key->type) == KEY_RSA && 150 (ssh->compat & SSH_BUG_RSASIGMD5) != 0) { 151 logit("Refusing RSA key because client uses unsafe " 152 "signature scheme"); 153 goto done; 154 } 155 if (auth2_key_already_used(authctxt, key)) { 156 logit("refusing previously-used %s key", sshkey_type(key)); 157 goto done; 158 } 159 if (match_pattern_list(pkalg, options.pubkey_key_types, 0) != 1) { 160 logit("%s: key type %s not in PubkeyAcceptedKeyTypes", 161 __func__, sshkey_ssh_name(key)); 162 goto done; 163 } 164 if ((r = sshkey_check_cert_sigtype(key, 165 options.ca_sign_algorithms)) != 0) { 166 logit("%s: certificate signature algorithm %s: %s", __func__, 167 (key->cert == NULL || key->cert->signature_type == NULL) ? 168 "(null)" : key->cert->signature_type, ssh_err(r)); 169 goto done; 170 } 171 key_s = format_key(key); 172 if (sshkey_is_cert(key)) 173 ca_s = format_key(key->cert->signature_key); 174 175 if (have_sig) { 176 debug3("%s: have %s signature for %s%s%s", 177 __func__, pkalg, key_s, 178 ca_s == NULL ? "" : " CA ", 179 ca_s == NULL ? "" : ca_s); 180 if ((r = sshpkt_get_string(ssh, &sig, &slen)) != 0 || 181 (r = sshpkt_get_end(ssh)) != 0) 182 fatal("%s: %s", __func__, ssh_err(r)); 183 if ((b = sshbuf_new()) == NULL) 184 fatal("%s: sshbuf_new failed", __func__); 185 if (ssh->compat & SSH_OLD_SESSIONID) { 186 if ((r = sshbuf_put(b, session_id2, 187 session_id2_len)) != 0) 188 fatal("%s: sshbuf_put session id: %s", 189 __func__, ssh_err(r)); 190 } else { 191 if ((r = sshbuf_put_string(b, session_id2, 192 session_id2_len)) != 0) 193 fatal("%s: sshbuf_put_string session id: %s", 194 __func__, ssh_err(r)); 195 } 196 if (!authctxt->valid || authctxt->user == NULL) { 197 debug2("%s: disabled because of invalid user", 198 __func__); 199 goto done; 200 } 201 /* reconstruct packet */ 202 xasprintf(&userstyle, "%s%s%s", authctxt->user, 203 authctxt->style ? ":" : "", 204 authctxt->style ? authctxt->style : ""); 205 if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 || 206 (r = sshbuf_put_cstring(b, userstyle)) != 0 || 207 (r = sshbuf_put_cstring(b, authctxt->service)) != 0 || 208 (r = sshbuf_put_cstring(b, "publickey")) != 0 || 209 (r = sshbuf_put_u8(b, have_sig)) != 0 || 210 (r = sshbuf_put_cstring(b, pkalg)) != 0 || 211 (r = sshbuf_put_string(b, pkblob, blen)) != 0) 212 fatal("%s: build packet failed: %s", 213 __func__, ssh_err(r)); 214 #ifdef DEBUG_PK 215 sshbuf_dump(b, stderr); 216 #endif 217 /* test for correct signature */ 218 authenticated = 0; 219 if (PRIVSEP(user_key_allowed(ssh, pw, key, 1, &authopts)) && 220 PRIVSEP(sshkey_verify(key, sig, slen, 221 sshbuf_ptr(b), sshbuf_len(b), 222 (ssh->compat & SSH_BUG_SIGTYPE) == 0 ? pkalg : NULL, 223 ssh->compat, &sig_details)) == 0) { 224 authenticated = 1; 225 } 226 if (authenticated == 1 && sig_details != NULL) { 227 auth2_record_info(authctxt, "signature count = %u", 228 sig_details->sk_counter); 229 debug("%s: sk_counter = %u, sk_flags = 0x%02x", 230 __func__, sig_details->sk_counter, 231 sig_details->sk_flags); 232 req_presence = (options.pubkey_auth_options & 233 PUBKEYAUTH_TOUCH_REQUIRED) || 234 !authopts->no_require_user_presence; 235 if (req_presence && (sig_details->sk_flags & 236 SSH_SK_USER_PRESENCE_REQD) == 0) { 237 error("public key %s signature for %s%s from " 238 "%.128s port %d rejected: user presence " 239 "(authenticator touch) requirement " 240 "not met ", key_s, 241 authctxt->valid ? "" : "invalid user ", 242 authctxt->user, ssh_remote_ipaddr(ssh), 243 ssh_remote_port(ssh)); 244 authenticated = 0; 245 goto done; 246 } 247 } 248 auth2_record_key(authctxt, authenticated, key); 249 } else { 250 debug("%s: test pkalg %s pkblob %s%s%s", 251 __func__, pkalg, key_s, 252 ca_s == NULL ? "" : " CA ", 253 ca_s == NULL ? "" : ca_s); 254 255 if ((r = sshpkt_get_end(ssh)) != 0) 256 fatal("%s: %s", __func__, ssh_err(r)); 257 258 if (!authctxt->valid || authctxt->user == NULL) { 259 debug2("%s: disabled because of invalid user", 260 __func__); 261 goto done; 262 } 263 /* XXX fake reply and always send PK_OK ? */ 264 /* 265 * XXX this allows testing whether a user is allowed 266 * to login: if you happen to have a valid pubkey this 267 * message is sent. the message is NEVER sent at all 268 * if a user is not allowed to login. is this an 269 * issue? -markus 270 */ 271 if (PRIVSEP(user_key_allowed(ssh, pw, key, 0, NULL))) { 272 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_PK_OK)) 273 != 0 || 274 (r = sshpkt_put_cstring(ssh, pkalg)) != 0 || 275 (r = sshpkt_put_string(ssh, pkblob, blen)) != 0 || 276 (r = sshpkt_send(ssh)) != 0 || 277 (r = ssh_packet_write_wait(ssh)) < 0) 278 fatal("%s: %s", __func__, ssh_err(r)); 279 authctxt->postponed = 1; 280 } 281 } 282 done: 283 if (authenticated == 1 && auth_activate_options(ssh, authopts) != 0) { 284 debug("%s: key options inconsistent with existing", __func__); 285 authenticated = 0; 286 } 287 debug2("%s: authenticated %d pkalg %s", __func__, authenticated, pkalg); 288 289 sshbuf_free(b); 290 sshauthopt_free(authopts); 291 sshkey_free(key); 292 free(userstyle); 293 free(pkalg); 294 free(pkblob); 295 free(key_s); 296 free(ca_s); 297 free(sig); 298 sshkey_sig_details_free(sig_details); 299 return authenticated; 300 } 301 302 static int 303 match_principals_option(const char *principal_list, struct sshkey_cert *cert) 304 { 305 char *result; 306 u_int i; 307 308 /* XXX percent_expand() sequences for authorized_principals? */ 309 310 for (i = 0; i < cert->nprincipals; i++) { 311 if ((result = match_list(cert->principals[i], 312 principal_list, NULL)) != NULL) { 313 debug3("matched principal from key options \"%.100s\"", 314 result); 315 free(result); 316 return 1; 317 } 318 } 319 return 0; 320 } 321 322 /* 323 * Process a single authorized_principals format line. Returns 0 and sets 324 * authoptsp is principal is authorised, -1 otherwise. "loc" is used as a 325 * log preamble for file/line information. 326 */ 327 static int 328 check_principals_line(struct ssh *ssh, char *cp, const struct sshkey_cert *cert, 329 const char *loc, struct sshauthopt **authoptsp) 330 { 331 u_int i, found = 0; 332 char *ep, *line_opts; 333 const char *reason = NULL; 334 struct sshauthopt *opts = NULL; 335 336 if (authoptsp != NULL) 337 *authoptsp = NULL; 338 339 /* Trim trailing whitespace. */ 340 ep = cp + strlen(cp) - 1; 341 while (ep > cp && (*ep == '\n' || *ep == ' ' || *ep == '\t')) 342 *ep-- = '\0'; 343 344 /* 345 * If the line has internal whitespace then assume it has 346 * key options. 347 */ 348 line_opts = NULL; 349 if ((ep = strrchr(cp, ' ')) != NULL || 350 (ep = strrchr(cp, '\t')) != NULL) { 351 for (; *ep == ' ' || *ep == '\t'; ep++) 352 ; 353 line_opts = cp; 354 cp = ep; 355 } 356 if ((opts = sshauthopt_parse(line_opts, &reason)) == NULL) { 357 debug("%s: bad principals options: %s", loc, reason); 358 auth_debug_add("%s: bad principals options: %s", loc, reason); 359 return -1; 360 } 361 /* Check principals in cert against those on line */ 362 for (i = 0; i < cert->nprincipals; i++) { 363 if (strcmp(cp, cert->principals[i]) != 0) 364 continue; 365 debug3("%s: matched principal \"%.100s\"", 366 loc, cert->principals[i]); 367 found = 1; 368 } 369 if (found && authoptsp != NULL) { 370 *authoptsp = opts; 371 opts = NULL; 372 } 373 sshauthopt_free(opts); 374 return found ? 0 : -1; 375 } 376 377 static int 378 process_principals(struct ssh *ssh, FILE *f, const char *file, 379 const struct sshkey_cert *cert, struct sshauthopt **authoptsp) 380 { 381 char loc[256], *line = NULL, *cp, *ep; 382 size_t linesize = 0; 383 u_long linenum = 0; 384 u_int found_principal = 0; 385 386 if (authoptsp != NULL) 387 *authoptsp = NULL; 388 389 while (getline(&line, &linesize, f) != -1) { 390 linenum++; 391 /* Always consume entire input */ 392 if (found_principal) 393 continue; 394 395 /* Skip leading whitespace. */ 396 for (cp = line; *cp == ' ' || *cp == '\t'; cp++) 397 ; 398 /* Skip blank and comment lines. */ 399 if ((ep = strchr(cp, '#')) != NULL) 400 *ep = '\0'; 401 if (!*cp || *cp == '\n') 402 continue; 403 404 snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum); 405 if (check_principals_line(ssh, cp, cert, loc, authoptsp) == 0) 406 found_principal = 1; 407 } 408 free(line); 409 return found_principal; 410 } 411 412 /* XXX remove pw args here and elsewhere once ssh->authctxt is guaranteed */ 413 414 static int 415 match_principals_file(struct ssh *ssh, struct passwd *pw, char *file, 416 struct sshkey_cert *cert, struct sshauthopt **authoptsp) 417 { 418 FILE *f; 419 int success; 420 421 if (authoptsp != NULL) 422 *authoptsp = NULL; 423 424 temporarily_use_uid(pw); 425 debug("trying authorized principals file %s", file); 426 if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) { 427 restore_uid(); 428 return 0; 429 } 430 success = process_principals(ssh, f, file, cert, authoptsp); 431 fclose(f); 432 restore_uid(); 433 return success; 434 } 435 436 /* 437 * Checks whether principal is allowed in output of command. 438 * returns 1 if the principal is allowed or 0 otherwise. 439 */ 440 static int 441 match_principals_command(struct ssh *ssh, struct passwd *user_pw, 442 const struct sshkey *key, struct sshauthopt **authoptsp) 443 { 444 struct passwd *runas_pw = NULL; 445 const struct sshkey_cert *cert = key->cert; 446 FILE *f = NULL; 447 int r, ok, found_principal = 0; 448 int i, ac = 0, uid_swapped = 0; 449 pid_t pid; 450 char *tmp, *username = NULL, *command = NULL, **av = NULL; 451 char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL; 452 char serial_s[32], uidstr[32]; 453 void (*osigchld)(int); 454 455 if (authoptsp != NULL) 456 *authoptsp = NULL; 457 if (options.authorized_principals_command == NULL) 458 return 0; 459 if (options.authorized_principals_command_user == NULL) { 460 error("No user for AuthorizedPrincipalsCommand specified, " 461 "skipping"); 462 return 0; 463 } 464 465 /* 466 * NB. all returns later this function should go via "out" to 467 * ensure the original SIGCHLD handler is restored properly. 468 */ 469 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 470 471 /* Prepare and verify the user for the command */ 472 username = percent_expand(options.authorized_principals_command_user, 473 "u", user_pw->pw_name, (char *)NULL); 474 runas_pw = getpwnam(username); 475 if (runas_pw == NULL) { 476 error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s", 477 username, strerror(errno)); 478 goto out; 479 } 480 481 /* Turn the command into an argument vector */ 482 if (argv_split(options.authorized_principals_command, &ac, &av) != 0) { 483 error("AuthorizedPrincipalsCommand \"%s\" contains " 484 "invalid quotes", options.authorized_principals_command); 485 goto out; 486 } 487 if (ac == 0) { 488 error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments", 489 options.authorized_principals_command); 490 goto out; 491 } 492 if ((ca_fp = sshkey_fingerprint(cert->signature_key, 493 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 494 error("%s: sshkey_fingerprint failed", __func__); 495 goto out; 496 } 497 if ((key_fp = sshkey_fingerprint(key, 498 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 499 error("%s: sshkey_fingerprint failed", __func__); 500 goto out; 501 } 502 if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) { 503 error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r)); 504 goto out; 505 } 506 if ((r = sshkey_to_base64(key, &keytext)) != 0) { 507 error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r)); 508 goto out; 509 } 510 snprintf(serial_s, sizeof(serial_s), "%llu", 511 (unsigned long long)cert->serial); 512 snprintf(uidstr, sizeof(uidstr), "%llu", 513 (unsigned long long)user_pw->pw_uid); 514 for (i = 1; i < ac; i++) { 515 tmp = percent_expand(av[i], 516 "U", uidstr, 517 "u", user_pw->pw_name, 518 "h", user_pw->pw_dir, 519 "t", sshkey_ssh_name(key), 520 "T", sshkey_ssh_name(cert->signature_key), 521 "f", key_fp, 522 "F", ca_fp, 523 "k", keytext, 524 "K", catext, 525 "i", cert->key_id, 526 "s", serial_s, 527 (char *)NULL); 528 if (tmp == NULL) 529 fatal("%s: percent_expand failed", __func__); 530 free(av[i]); 531 av[i] = tmp; 532 } 533 /* Prepare a printable command for logs, etc. */ 534 command = argv_assemble(ac, av); 535 536 if ((pid = subprocess("AuthorizedPrincipalsCommand", runas_pw, command, 537 ac, av, &f, 538 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0) 539 goto out; 540 541 uid_swapped = 1; 542 temporarily_use_uid(runas_pw); 543 544 ok = process_principals(ssh, f, "(command)", cert, authoptsp); 545 546 fclose(f); 547 f = NULL; 548 549 if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0) 550 goto out; 551 552 /* Read completed successfully */ 553 found_principal = ok; 554 out: 555 if (f != NULL) 556 fclose(f); 557 ssh_signal(SIGCHLD, osigchld); 558 for (i = 0; i < ac; i++) 559 free(av[i]); 560 free(av); 561 if (uid_swapped) 562 restore_uid(); 563 free(command); 564 free(username); 565 free(ca_fp); 566 free(key_fp); 567 free(catext); 568 free(keytext); 569 return found_principal; 570 } 571 572 /* 573 * Check a single line of an authorized_keys-format file. Returns 0 if key 574 * matches, -1 otherwise. Will return key/cert options via *authoptsp 575 * on success. "loc" is used as file/line location in log messages. 576 */ 577 static int 578 check_authkey_line(struct ssh *ssh, struct passwd *pw, struct sshkey *key, 579 char *cp, const char *loc, struct sshauthopt **authoptsp) 580 { 581 int want_keytype = sshkey_is_cert(key) ? KEY_UNSPEC : key->type; 582 struct sshkey *found = NULL; 583 struct sshauthopt *keyopts = NULL, *certopts = NULL, *finalopts = NULL; 584 char *key_options = NULL, *fp = NULL; 585 const char *reason = NULL; 586 int ret = -1; 587 588 if (authoptsp != NULL) 589 *authoptsp = NULL; 590 591 if ((found = sshkey_new(want_keytype)) == NULL) { 592 debug3("%s: keytype %d failed", __func__, want_keytype); 593 goto out; 594 } 595 596 /* XXX djm: peek at key type in line and skip if unwanted */ 597 598 if (sshkey_read(found, &cp) != 0) { 599 /* no key? check for options */ 600 debug2("%s: check options: '%s'", loc, cp); 601 key_options = cp; 602 if (sshkey_advance_past_options(&cp) != 0) { 603 reason = "invalid key option string"; 604 goto fail_reason; 605 } 606 skip_space(&cp); 607 if (sshkey_read(found, &cp) != 0) { 608 /* still no key? advance to next line*/ 609 debug2("%s: advance: '%s'", loc, cp); 610 goto out; 611 } 612 } 613 /* Parse key options now; we need to know if this is a CA key */ 614 if ((keyopts = sshauthopt_parse(key_options, &reason)) == NULL) { 615 debug("%s: bad key options: %s", loc, reason); 616 auth_debug_add("%s: bad key options: %s", loc, reason); 617 goto out; 618 } 619 /* Ignore keys that don't match or incorrectly marked as CAs */ 620 if (sshkey_is_cert(key)) { 621 /* Certificate; check signature key against CA */ 622 if (!sshkey_equal(found, key->cert->signature_key) || 623 !keyopts->cert_authority) 624 goto out; 625 } else { 626 /* Plain key: check it against key found in file */ 627 if (!sshkey_equal(found, key) || keyopts->cert_authority) 628 goto out; 629 } 630 631 /* We have a candidate key, perform authorisation checks */ 632 if ((fp = sshkey_fingerprint(found, 633 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 634 fatal("%s: fingerprint failed", __func__); 635 636 debug("%s: matching %s found: %s %s", loc, 637 sshkey_is_cert(key) ? "CA" : "key", sshkey_type(found), fp); 638 639 if (auth_authorise_keyopts(ssh, pw, keyopts, 640 sshkey_is_cert(key), loc) != 0) { 641 reason = "Refused by key options"; 642 goto fail_reason; 643 } 644 /* That's all we need for plain keys. */ 645 if (!sshkey_is_cert(key)) { 646 verbose("Accepted key %s %s found at %s", 647 sshkey_type(found), fp, loc); 648 finalopts = keyopts; 649 keyopts = NULL; 650 goto success; 651 } 652 653 /* 654 * Additional authorisation for certificates. 655 */ 656 657 /* Parse and check options present in certificate */ 658 if ((certopts = sshauthopt_from_cert(key)) == NULL) { 659 reason = "Invalid certificate options"; 660 goto fail_reason; 661 } 662 if (auth_authorise_keyopts(ssh, pw, certopts, 0, loc) != 0) { 663 reason = "Refused by certificate options"; 664 goto fail_reason; 665 } 666 if ((finalopts = sshauthopt_merge(keyopts, certopts, &reason)) == NULL) 667 goto fail_reason; 668 669 /* 670 * If the user has specified a list of principals as 671 * a key option, then prefer that list to matching 672 * their username in the certificate principals list. 673 */ 674 if (keyopts->cert_principals != NULL && 675 !match_principals_option(keyopts->cert_principals, key->cert)) { 676 reason = "Certificate does not contain an authorized principal"; 677 goto fail_reason; 678 } 679 if (sshkey_cert_check_authority(key, 0, 0, 680 keyopts->cert_principals == NULL ? pw->pw_name : NULL, &reason) != 0) 681 goto fail_reason; 682 683 verbose("Accepted certificate ID \"%s\" (serial %llu) " 684 "signed by CA %s %s found at %s", 685 key->cert->key_id, 686 (unsigned long long)key->cert->serial, 687 sshkey_type(found), fp, loc); 688 689 success: 690 if (finalopts == NULL) 691 fatal("%s: internal error: missing options", __func__); 692 if (authoptsp != NULL) { 693 *authoptsp = finalopts; 694 finalopts = NULL; 695 } 696 /* success */ 697 ret = 0; 698 goto out; 699 700 fail_reason: 701 error("%s", reason); 702 auth_debug_add("%s", reason); 703 out: 704 free(fp); 705 sshauthopt_free(keyopts); 706 sshauthopt_free(certopts); 707 sshauthopt_free(finalopts); 708 sshkey_free(found); 709 return ret; 710 } 711 712 /* 713 * Checks whether key is allowed in authorized_keys-format file, 714 * returns 1 if the key is allowed or 0 otherwise. 715 */ 716 static int 717 check_authkeys_file(struct ssh *ssh, struct passwd *pw, FILE *f, 718 char *file, struct sshkey *key, struct sshauthopt **authoptsp) 719 { 720 char *cp, *line = NULL, loc[256]; 721 size_t linesize = 0; 722 int found_key = 0; 723 u_long linenum = 0; 724 struct sshauthopt *opts = NULL; 725 #ifdef WITH_LDAP_PUBKEY 726 struct sshkey *found = NULL; 727 ldap_key_t * k; 728 unsigned int i = 0; 729 const char *reason; 730 #endif 731 732 #ifdef WITH_LDAP_PUBKEY 733 found_key = 0; 734 /* allocate a new key type */ 735 found = sshkey_new(key->type); 736 737 /* first check if the options is enabled, then try.. */ 738 if (options.lpk.on) { 739 debug("[LDAP] trying LDAP first uid=%s",pw->pw_name); 740 if (ldap_ismember(&options.lpk, pw->pw_name) > 0) { 741 if ((k = ldap_getuserkey(&options.lpk, pw->pw_name)) != NULL) { 742 /* Skip leading whitespace, empty and comment lines. */ 743 for (i = 0 ; i < k->num ; i++) { 744 /* dont forget if multiple keys to reset options */ 745 char *xoptions = NULL; 746 747 for (cp = (char *)k->keys[i]->bv_val; *cp == ' ' || *cp == '\t'; cp++) 748 ; 749 if (!*cp || *cp == '\n' || *cp == '#') 750 continue; 751 752 if (sshkey_read(found, &cp) != 0) { 753 /* no key? check if there are options for this key */ 754 int quoted = 0; 755 debug2("[LDAP] user_key_allowed: check options: '%s'", cp); 756 xoptions = cp; 757 for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) { 758 if (*cp == '\\' && cp[1] == '"') 759 cp++; /* Skip both */ 760 else if (*cp == '"') 761 quoted = !quoted; 762 } 763 /* Skip remaining whitespace. */ 764 for (; *cp == ' ' || *cp == '\t'; cp++) 765 ; 766 if (sshkey_read(found, &cp) != 0) { 767 debug2("[LDAP] user_key_allowed: advance: '%s'", cp); 768 /* still no key? advance to next line*/ 769 continue; 770 } 771 } 772 if ((opts = sshauthopt_parse(xoptions, &reason)) == NULL) { 773 debug("[LDAP] %s: bad principals options: %s", xoptions, reason); 774 auth_debug_add("[LDAP] %s: bad principals options: %s", xoptions, reason); 775 continue; 776 } 777 778 779 if (sshkey_equal(found, key)) { 780 found_key = 1; 781 debug("[LDAP] matching key found"); 782 char *fp = sshkey_fingerprint(found, SSH_FP_HASH_DEFAULT, SSH_FP_HEX); 783 verbose("[LDAP] Found matching %s key: %s", sshkey_type(found), fp); 784 785 /* restoring memory */ 786 ldap_keys_free(k); 787 free(fp); 788 restore_uid(); 789 sshkey_free(found); 790 return found_key; 791 break; 792 } 793 }/* end of LDAP for() */ 794 } else { 795 logit("[LDAP] no keys found for '%s'!", pw->pw_name); 796 } 797 } else { 798 logit("[LDAP] '%s' is not in '%s'", pw->pw_name, options.lpk.sgroup); 799 } 800 } 801 #endif 802 803 if (authoptsp != NULL) 804 *authoptsp = opts; 805 806 while (getline(&line, &linesize, f) != -1) { 807 linenum++; 808 /* Always consume entire file */ 809 if (found_key) 810 continue; 811 812 /* Skip leading whitespace, empty and comment lines. */ 813 cp = line; 814 skip_space(&cp); 815 if (!*cp || *cp == '\n' || *cp == '#') 816 continue; 817 snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum); 818 if (check_authkey_line(ssh, pw, key, cp, loc, authoptsp) == 0) 819 found_key = 1; 820 } 821 free(line); 822 return found_key; 823 } 824 825 /* Authenticate a certificate key against TrustedUserCAKeys */ 826 static int 827 user_cert_trusted_ca(struct ssh *ssh, struct passwd *pw, struct sshkey *key, 828 struct sshauthopt **authoptsp) 829 { 830 char *ca_fp, *principals_file = NULL; 831 const char *reason; 832 struct sshauthopt *principals_opts = NULL, *cert_opts = NULL; 833 struct sshauthopt *final_opts = NULL; 834 int r, ret = 0, found_principal = 0, use_authorized_principals; 835 836 if (authoptsp != NULL) 837 *authoptsp = NULL; 838 839 if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL) 840 return 0; 841 842 if ((ca_fp = sshkey_fingerprint(key->cert->signature_key, 843 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 844 return 0; 845 846 if ((r = sshkey_in_file(key->cert->signature_key, 847 options.trusted_user_ca_keys, 1, 0)) != 0) { 848 debug2("%s: CA %s %s is not listed in %s: %s", __func__, 849 sshkey_type(key->cert->signature_key), ca_fp, 850 options.trusted_user_ca_keys, ssh_err(r)); 851 goto out; 852 } 853 /* 854 * If AuthorizedPrincipals is in use, then compare the certificate 855 * principals against the names in that file rather than matching 856 * against the username. 857 */ 858 if ((principals_file = authorized_principals_file(pw)) != NULL) { 859 if (match_principals_file(ssh, pw, principals_file, 860 key->cert, &principals_opts)) 861 found_principal = 1; 862 } 863 /* Try querying command if specified */ 864 if (!found_principal && match_principals_command(ssh, pw, key, 865 &principals_opts)) 866 found_principal = 1; 867 /* If principals file or command is specified, then require a match */ 868 use_authorized_principals = principals_file != NULL || 869 options.authorized_principals_command != NULL; 870 if (!found_principal && use_authorized_principals) { 871 reason = "Certificate does not contain an authorized principal"; 872 goto fail_reason; 873 } 874 if (use_authorized_principals && principals_opts == NULL) 875 fatal("%s: internal error: missing principals_opts", __func__); 876 if (sshkey_cert_check_authority(key, 0, 1, 877 use_authorized_principals ? NULL : pw->pw_name, &reason) != 0) 878 goto fail_reason; 879 880 /* Check authority from options in key and from principals file/cmd */ 881 if ((cert_opts = sshauthopt_from_cert(key)) == NULL) { 882 reason = "Invalid certificate options"; 883 goto fail_reason; 884 } 885 if (auth_authorise_keyopts(ssh, pw, cert_opts, 0, "cert") != 0) { 886 reason = "Refused by certificate options"; 887 goto fail_reason; 888 } 889 if (principals_opts == NULL) { 890 final_opts = cert_opts; 891 cert_opts = NULL; 892 } else { 893 if (auth_authorise_keyopts(ssh, pw, principals_opts, 0, 894 "principals") != 0) { 895 reason = "Refused by certificate principals options"; 896 goto fail_reason; 897 } 898 if ((final_opts = sshauthopt_merge(principals_opts, 899 cert_opts, &reason)) == NULL) { 900 fail_reason: 901 error("%s", reason); 902 auth_debug_add("%s", reason); 903 goto out; 904 } 905 } 906 907 /* Success */ 908 verbose("Accepted certificate ID \"%s\" (serial %llu) signed by " 909 "%s CA %s via %s", key->cert->key_id, 910 (unsigned long long)key->cert->serial, 911 sshkey_type(key->cert->signature_key), ca_fp, 912 options.trusted_user_ca_keys); 913 if (authoptsp != NULL) { 914 *authoptsp = final_opts; 915 final_opts = NULL; 916 } 917 ret = 1; 918 out: 919 sshauthopt_free(principals_opts); 920 sshauthopt_free(cert_opts); 921 sshauthopt_free(final_opts); 922 free(principals_file); 923 free(ca_fp); 924 return ret; 925 } 926 927 /* 928 * Checks whether key is allowed in file. 929 * returns 1 if the key is allowed or 0 otherwise. 930 */ 931 static int 932 user_key_allowed2(struct ssh *ssh, struct passwd *pw, struct sshkey *key, 933 char *file, struct sshauthopt **authoptsp) 934 { 935 FILE *f; 936 int found_key = 0; 937 938 if (authoptsp != NULL) 939 *authoptsp = NULL; 940 941 /* Temporarily use the user's uid. */ 942 temporarily_use_uid(pw); 943 944 debug("trying public key file %s", file); 945 if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) { 946 found_key = check_authkeys_file(ssh, pw, f, file, 947 key, authoptsp); 948 fclose(f); 949 } 950 951 restore_uid(); 952 return found_key; 953 } 954 955 /* 956 * Checks whether key is allowed in output of command. 957 * returns 1 if the key is allowed or 0 otherwise. 958 */ 959 static int 960 user_key_command_allowed2(struct ssh *ssh, struct passwd *user_pw, 961 struct sshkey *key, struct sshauthopt **authoptsp) 962 { 963 struct passwd *runas_pw = NULL; 964 FILE *f = NULL; 965 int r, ok, found_key = 0; 966 int i, uid_swapped = 0, ac = 0; 967 pid_t pid; 968 char *username = NULL, *key_fp = NULL, *keytext = NULL; 969 char uidstr[32], *tmp, *command = NULL, **av = NULL; 970 void (*osigchld)(int); 971 972 if (authoptsp != NULL) 973 *authoptsp = NULL; 974 if (options.authorized_keys_command == NULL) 975 return 0; 976 if (options.authorized_keys_command_user == NULL) { 977 error("No user for AuthorizedKeysCommand specified, skipping"); 978 return 0; 979 } 980 981 /* 982 * NB. all returns later this function should go via "out" to 983 * ensure the original SIGCHLD handler is restored properly. 984 */ 985 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 986 987 /* Prepare and verify the user for the command */ 988 username = percent_expand(options.authorized_keys_command_user, 989 "u", user_pw->pw_name, (char *)NULL); 990 runas_pw = getpwnam(username); 991 if (runas_pw == NULL) { 992 error("AuthorizedKeysCommandUser \"%s\" not found: %s", 993 username, strerror(errno)); 994 goto out; 995 } 996 997 /* Prepare AuthorizedKeysCommand */ 998 if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash, 999 SSH_FP_DEFAULT)) == NULL) { 1000 error("%s: sshkey_fingerprint failed", __func__); 1001 goto out; 1002 } 1003 if ((r = sshkey_to_base64(key, &keytext)) != 0) { 1004 error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r)); 1005 goto out; 1006 } 1007 1008 /* Turn the command into an argument vector */ 1009 if (argv_split(options.authorized_keys_command, &ac, &av) != 0) { 1010 error("AuthorizedKeysCommand \"%s\" contains invalid quotes", 1011 command); 1012 goto out; 1013 } 1014 if (ac == 0) { 1015 error("AuthorizedKeysCommand \"%s\" yielded no arguments", 1016 command); 1017 goto out; 1018 } 1019 snprintf(uidstr, sizeof(uidstr), "%llu", 1020 (unsigned long long)user_pw->pw_uid); 1021 for (i = 1; i < ac; i++) { 1022 tmp = percent_expand(av[i], 1023 "U", uidstr, 1024 "u", user_pw->pw_name, 1025 "h", user_pw->pw_dir, 1026 "t", sshkey_ssh_name(key), 1027 "f", key_fp, 1028 "k", keytext, 1029 (char *)NULL); 1030 if (tmp == NULL) 1031 fatal("%s: percent_expand failed", __func__); 1032 free(av[i]); 1033 av[i] = tmp; 1034 } 1035 /* Prepare a printable command for logs, etc. */ 1036 command = argv_assemble(ac, av); 1037 1038 /* 1039 * If AuthorizedKeysCommand was run without arguments 1040 * then fall back to the old behaviour of passing the 1041 * target username as a single argument. 1042 */ 1043 if (ac == 1) { 1044 av = xreallocarray(av, ac + 2, sizeof(*av)); 1045 av[1] = xstrdup(user_pw->pw_name); 1046 av[2] = NULL; 1047 /* Fix up command too, since it is used in log messages */ 1048 free(command); 1049 xasprintf(&command, "%s %s", av[0], av[1]); 1050 } 1051 1052 if ((pid = subprocess("AuthorizedKeysCommand", runas_pw, command, 1053 ac, av, &f, 1054 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0) 1055 goto out; 1056 1057 uid_swapped = 1; 1058 temporarily_use_uid(runas_pw); 1059 1060 ok = check_authkeys_file(ssh, user_pw, f, 1061 options.authorized_keys_command, key, authoptsp); 1062 1063 fclose(f); 1064 f = NULL; 1065 1066 if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0) 1067 goto out; 1068 1069 /* Read completed successfully */ 1070 found_key = ok; 1071 out: 1072 if (f != NULL) 1073 fclose(f); 1074 ssh_signal(SIGCHLD, osigchld); 1075 for (i = 0; i < ac; i++) 1076 free(av[i]); 1077 free(av); 1078 if (uid_swapped) 1079 restore_uid(); 1080 free(command); 1081 free(username); 1082 free(key_fp); 1083 free(keytext); 1084 return found_key; 1085 } 1086 1087 /* 1088 * Check whether key authenticates and authorises the user. 1089 */ 1090 int 1091 user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key, 1092 int auth_attempt, struct sshauthopt **authoptsp) 1093 { 1094 u_int success = 0, i; 1095 char *file; 1096 struct sshauthopt *opts = NULL; 1097 1098 if (authoptsp != NULL) 1099 *authoptsp = NULL; 1100 1101 if (auth_key_is_revoked(key)) 1102 return 0; 1103 if (sshkey_is_cert(key) && 1104 auth_key_is_revoked(key->cert->signature_key)) 1105 return 0; 1106 1107 for (i = 0; !success && i < options.num_authkeys_files; i++) { 1108 if (strcasecmp(options.authorized_keys_files[i], "none") == 0) 1109 continue; 1110 file = expand_authorized_keys( 1111 options.authorized_keys_files[i], pw); 1112 success = user_key_allowed2(ssh, pw, key, file, &opts); 1113 free(file); 1114 if (!success) { 1115 sshauthopt_free(opts); 1116 opts = NULL; 1117 } 1118 } 1119 if (success) 1120 goto out; 1121 1122 if ((success = user_cert_trusted_ca(ssh, pw, key, &opts)) != 0) 1123 goto out; 1124 sshauthopt_free(opts); 1125 opts = NULL; 1126 1127 if ((success = user_key_command_allowed2(ssh, pw, key, &opts)) != 0) 1128 goto out; 1129 sshauthopt_free(opts); 1130 opts = NULL; 1131 1132 out: 1133 if (success && authoptsp != NULL) { 1134 *authoptsp = opts; 1135 opts = NULL; 1136 } 1137 sshauthopt_free(opts); 1138 return success; 1139 } 1140 1141 Authmethod method_pubkey = { 1142 "publickey", 1143 userauth_pubkey, 1144 &options.pubkey_authentication 1145 }; 1146