1 /* $OpenBSD: auth2-pubkey.c,v 1.71 2017/09/07 23:48:09 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 31 #include <errno.h> 32 #include <fcntl.h> 33 #ifdef HAVE_PATHS_H 34 # include <paths.h> 35 #endif 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 "buffer.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 "ssherr.h" 68 #include "channels.h" /* XXX for session.h */ 69 #include "session.h" /* XXX for child_set_env(); refactor? */ 70 71 /* import */ 72 extern ServerOptions options; 73 extern u_char *session_id2; 74 extern u_int session_id2_len; 75 76 static int 77 userauth_pubkey(struct ssh *ssh) 78 { 79 Authctxt *authctxt = ssh->authctxt; 80 struct sshbuf *b; 81 struct sshkey *key = NULL; 82 char *pkalg, *userstyle = NULL, *fp = NULL; 83 u_char *pkblob, *sig, have_sig; 84 size_t blen, slen; 85 int r, pktype; 86 int authenticated = 0; 87 88 if (!authctxt->valid) { 89 debug2("%s: disabled because of invalid user", __func__); 90 return 0; 91 } 92 if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0) 93 fatal("%s: sshpkt_get_u8 failed: %s", __func__, ssh_err(r)); 94 if (ssh->compat & SSH_BUG_PKAUTH) { 95 debug2("%s: SSH_BUG_PKAUTH", __func__); 96 if ((b = sshbuf_new()) == NULL) 97 fatal("%s: sshbuf_new failed", __func__); 98 /* no explicit pkalg given */ 99 /* so we have to extract the pkalg from the pkblob */ 100 /* XXX use sshbuf_from() */ 101 if ((r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0 || 102 (r = sshbuf_put(b, pkblob, blen)) != 0 || 103 (r = sshbuf_get_cstring(b, &pkalg, NULL)) != 0) 104 fatal("%s: failed: %s", __func__, ssh_err(r)); 105 sshbuf_free(b); 106 } else { 107 if ((r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 || 108 (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0) 109 fatal("%s: sshpkt_get_cstring failed: %s", 110 __func__, ssh_err(r)); 111 } 112 pktype = sshkey_type_from_name(pkalg); 113 if (pktype == KEY_UNSPEC) { 114 /* this is perfectly legal */ 115 logit("%s: unsupported public key algorithm: %s", 116 __func__, pkalg); 117 goto done; 118 } 119 if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) { 120 error("%s: could not parse key: %s", __func__, ssh_err(r)); 121 goto done; 122 } 123 if (key == NULL) { 124 error("%s: cannot decode key: %s", __func__, pkalg); 125 goto done; 126 } 127 if (key->type != pktype) { 128 error("%s: type mismatch for decoded key " 129 "(received %d, expected %d)", __func__, key->type, pktype); 130 goto done; 131 } 132 if (sshkey_type_plain(key->type) == KEY_RSA && 133 (ssh->compat & SSH_BUG_RSASIGMD5) != 0) { 134 logit("Refusing RSA key because client uses unsafe " 135 "signature scheme"); 136 goto done; 137 } 138 fp = sshkey_fingerprint(key, options.fingerprint_hash, SSH_FP_DEFAULT); 139 if (auth2_key_already_used(authctxt, key)) { 140 logit("refusing previously-used %s key", sshkey_type(key)); 141 goto done; 142 } 143 if (match_pattern_list(sshkey_ssh_name(key), 144 options.pubkey_key_types, 0) != 1) { 145 logit("%s: key type %s not in PubkeyAcceptedKeyTypes", 146 __func__, sshkey_ssh_name(key)); 147 goto done; 148 } 149 150 if (have_sig) { 151 debug3("%s: have signature for %s %s", 152 __func__, sshkey_type(key), fp); 153 if ((r = sshpkt_get_string(ssh, &sig, &slen)) != 0 || 154 (r = sshpkt_get_end(ssh)) != 0) 155 fatal("%s: %s", __func__, ssh_err(r)); 156 if ((b = sshbuf_new()) == NULL) 157 fatal("%s: sshbuf_new failed", __func__); 158 if (ssh->compat & SSH_OLD_SESSIONID) { 159 if ((r = sshbuf_put(b, session_id2, 160 session_id2_len)) != 0) 161 fatal("%s: sshbuf_put session id: %s", 162 __func__, ssh_err(r)); 163 } else { 164 if ((r = sshbuf_put_string(b, session_id2, 165 session_id2_len)) != 0) 166 fatal("%s: sshbuf_put_string session id: %s", 167 __func__, ssh_err(r)); 168 } 169 /* reconstruct packet */ 170 xasprintf(&userstyle, "%s%s%s", authctxt->user, 171 authctxt->style ? ":" : "", 172 authctxt->style ? authctxt->style : ""); 173 if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 || 174 (r = sshbuf_put_cstring(b, userstyle)) != 0 || 175 (r = sshbuf_put_cstring(b, ssh->compat & SSH_BUG_PKSERVICE ? 176 "ssh-userauth" : authctxt->service)) != 0) 177 fatal("%s: build packet failed: %s", 178 __func__, ssh_err(r)); 179 if (ssh->compat & SSH_BUG_PKAUTH) { 180 if ((r = sshbuf_put_u8(b, have_sig)) != 0) 181 fatal("%s: build packet failed: %s", 182 __func__, ssh_err(r)); 183 } else { 184 if ((r = sshbuf_put_cstring(b, "publickey")) != 0 || 185 (r = sshbuf_put_u8(b, have_sig)) != 0 || 186 (r = sshbuf_put_cstring(b, pkalg) != 0)) 187 fatal("%s: build packet failed: %s", 188 __func__, ssh_err(r)); 189 } 190 if ((r = sshbuf_put_string(b, pkblob, blen)) != 0) 191 fatal("%s: build packet failed: %s", 192 __func__, ssh_err(r)); 193 #ifdef DEBUG_PK 194 sshbuf_dump(b, stderr); 195 #endif 196 197 /* test for correct signature */ 198 authenticated = 0; 199 if (PRIVSEP(user_key_allowed(authctxt->pw, key, 1)) && 200 PRIVSEP(sshkey_verify(key, sig, slen, sshbuf_ptr(b), 201 sshbuf_len(b), ssh->compat)) == 0) { 202 authenticated = 1; 203 } 204 sshbuf_free(b); 205 free(sig); 206 auth2_record_key(authctxt, authenticated, key); 207 } else { 208 debug("%s: test whether pkalg/pkblob are acceptable for %s %s", 209 __func__, sshkey_type(key), fp); 210 if ((r = sshpkt_get_end(ssh)) != 0) 211 fatal("%s: %s", __func__, ssh_err(r)); 212 213 /* XXX fake reply and always send PK_OK ? */ 214 /* 215 * XXX this allows testing whether a user is allowed 216 * to login: if you happen to have a valid pubkey this 217 * message is sent. the message is NEVER sent at all 218 * if a user is not allowed to login. is this an 219 * issue? -markus 220 */ 221 if (PRIVSEP(user_key_allowed(authctxt->pw, key, 0))) { 222 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_PK_OK)) 223 != 0 || 224 (r = sshpkt_put_cstring(ssh, pkalg)) != 0 || 225 (r = sshpkt_put_string(ssh, pkblob, blen)) != 0 || 226 (r = sshpkt_send(ssh)) != 0) 227 fatal("%s: %s", __func__, ssh_err(r)); 228 ssh_packet_write_wait(ssh); 229 authctxt->postponed = 1; 230 } 231 } 232 if (authenticated != 1) 233 auth_clear_options(); 234 done: 235 debug2("%s: authenticated %d pkalg %s", __func__, authenticated, pkalg); 236 sshkey_free(key); 237 free(userstyle); 238 free(pkalg); 239 free(pkblob); 240 free(fp); 241 return authenticated; 242 } 243 244 static int 245 match_principals_option(const char *principal_list, struct sshkey_cert *cert) 246 { 247 char *result; 248 u_int i; 249 250 /* XXX percent_expand() sequences for authorized_principals? */ 251 252 for (i = 0; i < cert->nprincipals; i++) { 253 if ((result = match_list(cert->principals[i], 254 principal_list, NULL)) != NULL) { 255 debug3("matched principal from key options \"%.100s\"", 256 result); 257 free(result); 258 return 1; 259 } 260 } 261 return 0; 262 } 263 264 static int 265 process_principals(FILE *f, const char *file, struct passwd *pw, 266 const struct sshkey_cert *cert) 267 { 268 char line[SSH_MAX_PUBKEY_BYTES], *cp, *ep, *line_opts; 269 u_long linenum = 0; 270 u_int i, found_principal = 0; 271 272 while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) { 273 /* Always consume entire input */ 274 if (found_principal) 275 continue; 276 /* Skip leading whitespace. */ 277 for (cp = line; *cp == ' ' || *cp == '\t'; cp++) 278 ; 279 /* Skip blank and comment lines. */ 280 if ((ep = strchr(cp, '#')) != NULL) 281 *ep = '\0'; 282 if (!*cp || *cp == '\n') 283 continue; 284 /* Trim trailing whitespace. */ 285 ep = cp + strlen(cp) - 1; 286 while (ep > cp && (*ep == '\n' || *ep == ' ' || *ep == '\t')) 287 *ep-- = '\0'; 288 /* 289 * If the line has internal whitespace then assume it has 290 * key options. 291 */ 292 line_opts = NULL; 293 if ((ep = strrchr(cp, ' ')) != NULL || 294 (ep = strrchr(cp, '\t')) != NULL) { 295 for (; *ep == ' ' || *ep == '\t'; ep++) 296 ; 297 line_opts = cp; 298 cp = ep; 299 } 300 for (i = 0; i < cert->nprincipals; i++) { 301 if (strcmp(cp, cert->principals[i]) == 0) { 302 debug3("%s:%lu: matched principal \"%.100s\"", 303 file, linenum, cert->principals[i]); 304 if (auth_parse_options(pw, line_opts, 305 file, linenum) != 1) 306 continue; 307 found_principal = 1; 308 continue; 309 } 310 } 311 } 312 return found_principal; 313 } 314 315 static int 316 match_principals_file(char *file, struct passwd *pw, struct sshkey_cert *cert) 317 { 318 FILE *f; 319 int success; 320 321 temporarily_use_uid(pw); 322 debug("trying authorized principals file %s", file); 323 if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) { 324 restore_uid(); 325 return 0; 326 } 327 success = process_principals(f, file, pw, cert); 328 fclose(f); 329 restore_uid(); 330 return success; 331 } 332 333 /* 334 * Checks whether principal is allowed in output of command. 335 * returns 1 if the principal is allowed or 0 otherwise. 336 */ 337 static int 338 match_principals_command(struct passwd *user_pw, const struct sshkey *key) 339 { 340 const struct sshkey_cert *cert = key->cert; 341 FILE *f = NULL; 342 int r, ok, found_principal = 0; 343 struct passwd *pw; 344 int i, ac = 0, uid_swapped = 0; 345 pid_t pid; 346 char *tmp, *username = NULL, *command = NULL, **av = NULL; 347 char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL; 348 char serial_s[16]; 349 void (*osigchld)(int); 350 351 if (options.authorized_principals_command == NULL) 352 return 0; 353 if (options.authorized_principals_command_user == NULL) { 354 error("No user for AuthorizedPrincipalsCommand specified, " 355 "skipping"); 356 return 0; 357 } 358 359 /* 360 * NB. all returns later this function should go via "out" to 361 * ensure the original SIGCHLD handler is restored properly. 362 */ 363 osigchld = signal(SIGCHLD, SIG_DFL); 364 365 /* Prepare and verify the user for the command */ 366 username = percent_expand(options.authorized_principals_command_user, 367 "u", user_pw->pw_name, (char *)NULL); 368 pw = getpwnam(username); 369 if (pw == NULL) { 370 error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s", 371 username, strerror(errno)); 372 goto out; 373 } 374 375 /* Turn the command into an argument vector */ 376 if (argv_split(options.authorized_principals_command, &ac, &av) != 0) { 377 error("AuthorizedPrincipalsCommand \"%s\" contains " 378 "invalid quotes", command); 379 goto out; 380 } 381 if (ac == 0) { 382 error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments", 383 command); 384 goto out; 385 } 386 if ((ca_fp = sshkey_fingerprint(cert->signature_key, 387 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 388 error("%s: sshkey_fingerprint failed", __func__); 389 goto out; 390 } 391 if ((key_fp = sshkey_fingerprint(key, 392 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 393 error("%s: sshkey_fingerprint failed", __func__); 394 goto out; 395 } 396 if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) { 397 error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r)); 398 goto out; 399 } 400 if ((r = sshkey_to_base64(key, &keytext)) != 0) { 401 error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r)); 402 goto out; 403 } 404 snprintf(serial_s, sizeof(serial_s), "%llu", 405 (unsigned long long)cert->serial); 406 for (i = 1; i < ac; i++) { 407 tmp = percent_expand(av[i], 408 "u", user_pw->pw_name, 409 "h", user_pw->pw_dir, 410 "t", sshkey_ssh_name(key), 411 "T", sshkey_ssh_name(cert->signature_key), 412 "f", key_fp, 413 "F", ca_fp, 414 "k", keytext, 415 "K", catext, 416 "i", cert->key_id, 417 "s", serial_s, 418 (char *)NULL); 419 if (tmp == NULL) 420 fatal("%s: percent_expand failed", __func__); 421 free(av[i]); 422 av[i] = tmp; 423 } 424 /* Prepare a printable command for logs, etc. */ 425 command = argv_assemble(ac, av); 426 427 if ((pid = subprocess("AuthorizedPrincipalsCommand", pw, command, 428 ac, av, &f, 429 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0) 430 goto out; 431 432 uid_swapped = 1; 433 temporarily_use_uid(pw); 434 435 ok = process_principals(f, "(command)", pw, cert); 436 437 fclose(f); 438 f = NULL; 439 440 if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0) 441 goto out; 442 443 /* Read completed successfully */ 444 found_principal = ok; 445 out: 446 if (f != NULL) 447 fclose(f); 448 signal(SIGCHLD, osigchld); 449 for (i = 0; i < ac; i++) 450 free(av[i]); 451 free(av); 452 if (uid_swapped) 453 restore_uid(); 454 free(command); 455 free(username); 456 free(ca_fp); 457 free(key_fp); 458 free(catext); 459 free(keytext); 460 return found_principal; 461 } 462 /* 463 * Checks whether key is allowed in authorized_keys-format file, 464 * returns 1 if the key is allowed or 0 otherwise. 465 */ 466 static int 467 check_authkeys_file(FILE *f, char *file, struct sshkey *key, struct passwd *pw) 468 { 469 char line[SSH_MAX_PUBKEY_BYTES]; 470 int found_key = 0; 471 u_long linenum = 0; 472 struct sshkey *found = NULL; 473 474 while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) { 475 char *cp, *key_options = NULL, *fp = NULL; 476 const char *reason = NULL; 477 478 /* Always consume entire file */ 479 if (found_key) 480 continue; 481 if (found != NULL) 482 sshkey_free(found); 483 found = sshkey_new(sshkey_is_cert(key) ? KEY_UNSPEC : key->type); 484 if (found == NULL) 485 goto done; 486 auth_clear_options(); 487 488 /* Skip leading whitespace, empty and comment lines. */ 489 for (cp = line; *cp == ' ' || *cp == '\t'; cp++) 490 ; 491 if (!*cp || *cp == '\n' || *cp == '#') 492 continue; 493 494 if (sshkey_read(found, &cp) != 0) { 495 /* no key? check if there are options for this key */ 496 int quoted = 0; 497 debug2("user_key_allowed: check options: '%s'", cp); 498 key_options = cp; 499 for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) { 500 if (*cp == '\\' && cp[1] == '"') 501 cp++; /* Skip both */ 502 else if (*cp == '"') 503 quoted = !quoted; 504 } 505 /* Skip remaining whitespace. */ 506 for (; *cp == ' ' || *cp == '\t'; cp++) 507 ; 508 if (sshkey_read(found, &cp) != 0) { 509 debug2("user_key_allowed: advance: '%s'", cp); 510 /* still no key? advance to next line*/ 511 continue; 512 } 513 } 514 if (sshkey_is_cert(key)) { 515 if (!sshkey_equal(found, key->cert->signature_key)) 516 continue; 517 if (auth_parse_options(pw, key_options, file, 518 linenum) != 1) 519 continue; 520 if (!key_is_cert_authority) 521 continue; 522 if ((fp = sshkey_fingerprint(found, 523 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 524 continue; 525 debug("matching CA found: file %s, line %lu, %s %s", 526 file, linenum, sshkey_type(found), fp); 527 /* 528 * If the user has specified a list of principals as 529 * a key option, then prefer that list to matching 530 * their username in the certificate principals list. 531 */ 532 if (authorized_principals != NULL && 533 !match_principals_option(authorized_principals, 534 key->cert)) { 535 reason = "Certificate does not contain an " 536 "authorized principal"; 537 fail_reason: 538 free(fp); 539 error("%s", reason); 540 auth_debug_add("%s", reason); 541 continue; 542 } 543 if (sshkey_cert_check_authority(key, 0, 0, 544 authorized_principals == NULL ? pw->pw_name : NULL, 545 &reason) != 0) 546 goto fail_reason; 547 if (auth_cert_options(key, pw, &reason) != 0) 548 goto fail_reason; 549 verbose("Accepted certificate ID \"%s\" (serial %llu) " 550 "signed by %s CA %s via %s", key->cert->key_id, 551 (unsigned long long)key->cert->serial, 552 sshkey_type(found), fp, file); 553 free(fp); 554 found_key = 1; 555 break; 556 } else if (sshkey_equal(found, key)) { 557 if (auth_parse_options(pw, key_options, file, 558 linenum) != 1) 559 continue; 560 if (key_is_cert_authority) 561 continue; 562 if ((fp = sshkey_fingerprint(found, 563 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 564 continue; 565 debug("matching key found: file %s, line %lu %s %s", 566 file, linenum, sshkey_type(found), fp); 567 free(fp); 568 found_key = 1; 569 continue; 570 } 571 } 572 done: 573 if (found != NULL) 574 sshkey_free(found); 575 if (!found_key) 576 debug2("key not found"); 577 return found_key; 578 } 579 580 /* Authenticate a certificate key against TrustedUserCAKeys */ 581 static int 582 user_cert_trusted_ca(struct passwd *pw, struct sshkey *key) 583 { 584 char *ca_fp, *principals_file = NULL; 585 const char *reason; 586 int r, ret = 0, found_principal = 0, use_authorized_principals; 587 588 if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL) 589 return 0; 590 591 if ((ca_fp = sshkey_fingerprint(key->cert->signature_key, 592 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 593 return 0; 594 595 if ((r = sshkey_in_file(key->cert->signature_key, 596 options.trusted_user_ca_keys, 1, 0)) != 0) { 597 debug2("%s: CA %s %s is not listed in %s: %s", __func__, 598 sshkey_type(key->cert->signature_key), ca_fp, 599 options.trusted_user_ca_keys, ssh_err(r)); 600 goto out; 601 } 602 /* 603 * If AuthorizedPrincipals is in use, then compare the certificate 604 * principals against the names in that file rather than matching 605 * against the username. 606 */ 607 if ((principals_file = authorized_principals_file(pw)) != NULL) { 608 if (match_principals_file(principals_file, pw, key->cert)) 609 found_principal = 1; 610 } 611 /* Try querying command if specified */ 612 if (!found_principal && match_principals_command(pw, key)) 613 found_principal = 1; 614 /* If principals file or command is specified, then require a match */ 615 use_authorized_principals = principals_file != NULL || 616 options.authorized_principals_command != NULL; 617 if (!found_principal && use_authorized_principals) { 618 reason = "Certificate does not contain an authorized principal"; 619 fail_reason: 620 error("%s", reason); 621 auth_debug_add("%s", reason); 622 goto out; 623 } 624 if (sshkey_cert_check_authority(key, 0, 1, 625 use_authorized_principals ? NULL : pw->pw_name, &reason) != 0) 626 goto fail_reason; 627 if (auth_cert_options(key, pw, &reason) != 0) 628 goto fail_reason; 629 630 verbose("Accepted certificate ID \"%s\" (serial %llu) signed by " 631 "%s CA %s via %s", key->cert->key_id, 632 (unsigned long long)key->cert->serial, 633 sshkey_type(key->cert->signature_key), ca_fp, 634 options.trusted_user_ca_keys); 635 ret = 1; 636 637 out: 638 free(principals_file); 639 free(ca_fp); 640 return ret; 641 } 642 643 /* 644 * Checks whether key is allowed in file. 645 * returns 1 if the key is allowed or 0 otherwise. 646 */ 647 static int 648 user_key_allowed2(struct passwd *pw, struct sshkey *key, char *file) 649 { 650 FILE *f; 651 int found_key = 0; 652 653 /* Temporarily use the user's uid. */ 654 temporarily_use_uid(pw); 655 656 debug("trying public key file %s", file); 657 if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) { 658 found_key = check_authkeys_file(f, file, key, pw); 659 fclose(f); 660 } 661 662 restore_uid(); 663 return found_key; 664 } 665 666 /* 667 * Checks whether key is allowed in output of command. 668 * returns 1 if the key is allowed or 0 otherwise. 669 */ 670 static int 671 user_key_command_allowed2(struct passwd *user_pw, struct sshkey *key) 672 { 673 FILE *f = NULL; 674 int r, ok, found_key = 0; 675 struct passwd *pw; 676 int i, uid_swapped = 0, ac = 0; 677 pid_t pid; 678 char *username = NULL, *key_fp = NULL, *keytext = NULL; 679 char *tmp, *command = NULL, **av = NULL; 680 void (*osigchld)(int); 681 682 if (options.authorized_keys_command == NULL) 683 return 0; 684 if (options.authorized_keys_command_user == NULL) { 685 error("No user for AuthorizedKeysCommand specified, skipping"); 686 return 0; 687 } 688 689 /* 690 * NB. all returns later this function should go via "out" to 691 * ensure the original SIGCHLD handler is restored properly. 692 */ 693 osigchld = signal(SIGCHLD, SIG_DFL); 694 695 /* Prepare and verify the user for the command */ 696 username = percent_expand(options.authorized_keys_command_user, 697 "u", user_pw->pw_name, (char *)NULL); 698 pw = getpwnam(username); 699 if (pw == NULL) { 700 error("AuthorizedKeysCommandUser \"%s\" not found: %s", 701 username, strerror(errno)); 702 goto out; 703 } 704 705 /* Prepare AuthorizedKeysCommand */ 706 if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash, 707 SSH_FP_DEFAULT)) == NULL) { 708 error("%s: sshkey_fingerprint failed", __func__); 709 goto out; 710 } 711 if ((r = sshkey_to_base64(key, &keytext)) != 0) { 712 error("%s: sshkey_to_base64 failed: %s", __func__, ssh_err(r)); 713 goto out; 714 } 715 716 /* Turn the command into an argument vector */ 717 if (argv_split(options.authorized_keys_command, &ac, &av) != 0) { 718 error("AuthorizedKeysCommand \"%s\" contains invalid quotes", 719 command); 720 goto out; 721 } 722 if (ac == 0) { 723 error("AuthorizedKeysCommand \"%s\" yielded no arguments", 724 command); 725 goto out; 726 } 727 for (i = 1; i < ac; i++) { 728 tmp = percent_expand(av[i], 729 "u", user_pw->pw_name, 730 "h", user_pw->pw_dir, 731 "t", sshkey_ssh_name(key), 732 "f", key_fp, 733 "k", keytext, 734 (char *)NULL); 735 if (tmp == NULL) 736 fatal("%s: percent_expand failed", __func__); 737 free(av[i]); 738 av[i] = tmp; 739 } 740 /* Prepare a printable command for logs, etc. */ 741 command = argv_assemble(ac, av); 742 743 /* 744 * If AuthorizedKeysCommand was run without arguments 745 * then fall back to the old behaviour of passing the 746 * target username as a single argument. 747 */ 748 if (ac == 1) { 749 av = xreallocarray(av, ac + 2, sizeof(*av)); 750 av[1] = xstrdup(user_pw->pw_name); 751 av[2] = NULL; 752 /* Fix up command too, since it is used in log messages */ 753 free(command); 754 xasprintf(&command, "%s %s", av[0], av[1]); 755 } 756 757 if ((pid = subprocess("AuthorizedKeysCommand", pw, command, 758 ac, av, &f, 759 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD)) == 0) 760 goto out; 761 762 uid_swapped = 1; 763 temporarily_use_uid(pw); 764 765 ok = check_authkeys_file(f, options.authorized_keys_command, key, pw); 766 767 fclose(f); 768 f = NULL; 769 770 if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0) 771 goto out; 772 773 /* Read completed successfully */ 774 found_key = ok; 775 out: 776 if (f != NULL) 777 fclose(f); 778 signal(SIGCHLD, osigchld); 779 for (i = 0; i < ac; i++) 780 free(av[i]); 781 free(av); 782 if (uid_swapped) 783 restore_uid(); 784 free(command); 785 free(username); 786 free(key_fp); 787 free(keytext); 788 return found_key; 789 } 790 791 /* 792 * Check whether key authenticates and authorises the user. 793 */ 794 int 795 user_key_allowed(struct passwd *pw, struct sshkey *key, int auth_attempt) 796 { 797 u_int success, i; 798 char *file; 799 800 if (auth_key_is_revoked(key)) 801 return 0; 802 if (sshkey_is_cert(key) && 803 auth_key_is_revoked(key->cert->signature_key)) 804 return 0; 805 806 success = user_cert_trusted_ca(pw, key); 807 if (success) 808 return success; 809 810 success = user_key_command_allowed2(pw, key); 811 if (success > 0) 812 return success; 813 814 for (i = 0; !success && i < options.num_authkeys_files; i++) { 815 816 if (strcasecmp(options.authorized_keys_files[i], "none") == 0) 817 continue; 818 file = expand_authorized_keys( 819 options.authorized_keys_files[i], pw); 820 821 success = user_key_allowed2(pw, key, file); 822 free(file); 823 } 824 825 return success; 826 } 827 828 Authmethod method_pubkey = { 829 "publickey", 830 userauth_pubkey, 831 &options.pubkey_authentication 832 }; 833