1 /* $OpenBSD: auth2-pubkey.c,v 1.113 2022/02/27 01:33:59 naddy 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 <stdlib.h> 32 #include <errno.h> 33 #include <fcntl.h> 34 #ifdef HAVE_PATHS_H 35 # include <paths.h> 36 #endif 37 #include <pwd.h> 38 #include <signal.h> 39 #include <stdio.h> 40 #include <stdarg.h> 41 #include <string.h> 42 #include <time.h> 43 #include <unistd.h> 44 #include <limits.h> 45 46 #include "xmalloc.h" 47 #include "ssh.h" 48 #include "ssh2.h" 49 #include "packet.h" 50 #include "kex.h" 51 #include "sshbuf.h" 52 #include "log.h" 53 #include "misc.h" 54 #include "servconf.h" 55 #include "compat.h" 56 #include "sshkey.h" 57 #include "hostfile.h" 58 #include "auth.h" 59 #include "pathnames.h" 60 #include "uidswap.h" 61 #include "auth-options.h" 62 #include "canohost.h" 63 #ifdef GSSAPI 64 #include "ssh-gss.h" 65 #endif 66 #include "monitor_wrap.h" 67 #include "authfile.h" 68 #include "match.h" 69 #include "ssherr.h" 70 #include "kex.h" 71 #include "channels.h" /* XXX for session.h */ 72 #include "session.h" /* XXX for child_set_env(); refactor? */ 73 #include "sk-api.h" 74 75 /* import */ 76 extern ServerOptions options; 77 78 static char * 79 format_key(const struct sshkey *key) 80 { 81 char *ret, *fp = sshkey_fingerprint(key, 82 options.fingerprint_hash, SSH_FP_DEFAULT); 83 84 xasprintf(&ret, "%s %s", sshkey_type(key), fp); 85 free(fp); 86 return ret; 87 } 88 89 static int 90 userauth_pubkey(struct ssh *ssh, const char *method) 91 { 92 Authctxt *authctxt = ssh->authctxt; 93 struct passwd *pw = authctxt->pw; 94 struct sshbuf *b = NULL; 95 struct sshkey *key = NULL, *hostkey = NULL; 96 char *pkalg = NULL, *userstyle = NULL, *key_s = NULL, *ca_s = NULL; 97 u_char *pkblob = NULL, *sig = NULL, have_sig; 98 size_t blen, slen; 99 int hostbound, r, pktype; 100 int req_presence = 0, req_verify = 0, authenticated = 0; 101 struct sshauthopt *authopts = NULL; 102 struct sshkey_sig_details *sig_details = NULL; 103 104 hostbound = strcmp(method, "publickey-hostbound-v00@openssh.com") == 0; 105 106 if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0 || 107 (r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 || 108 (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0) 109 fatal_fr(r, "parse %s packet", method); 110 111 /* hostbound auth includes the hostkey offered at initial KEX */ 112 if (hostbound) { 113 if ((r = sshpkt_getb_froms(ssh, &b)) != 0 || 114 (r = sshkey_fromb(b, &hostkey)) != 0) 115 fatal_fr(r, "parse %s hostkey", method); 116 if (ssh->kex->initial_hostkey == NULL) 117 fatal_f("internal error: initial hostkey not recorded"); 118 if (!sshkey_equal(hostkey, ssh->kex->initial_hostkey)) 119 fatal_f("%s packet contained wrong host key", method); 120 sshbuf_free(b); 121 b = NULL; 122 } 123 124 if (log_level_get() >= SYSLOG_LEVEL_DEBUG2) { 125 char *keystring; 126 struct sshbuf *pkbuf; 127 128 if ((pkbuf = sshbuf_from(pkblob, blen)) == NULL) 129 fatal_f("sshbuf_from failed"); 130 if ((keystring = sshbuf_dtob64_string(pkbuf, 0)) == NULL) 131 fatal_f("sshbuf_dtob64 failed"); 132 debug2_f("%s user %s %s public key %s %s", 133 authctxt->valid ? "valid" : "invalid", authctxt->user, 134 have_sig ? "attempting" : "querying", pkalg, keystring); 135 sshbuf_free(pkbuf); 136 free(keystring); 137 } 138 139 pktype = sshkey_type_from_name(pkalg); 140 if (pktype == KEY_UNSPEC) { 141 /* this is perfectly legal */ 142 verbose_f("unsupported public key algorithm: %s", pkalg); 143 goto done; 144 } 145 if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) { 146 error_fr(r, "parse key"); 147 goto done; 148 } 149 if (key == NULL) { 150 error_f("cannot decode key: %s", pkalg); 151 goto done; 152 } 153 if (key->type != pktype) { 154 error_f("type mismatch for decoded key " 155 "(received %d, expected %d)", key->type, pktype); 156 goto done; 157 } 158 if (sshkey_type_plain(key->type) == KEY_RSA && 159 (ssh->compat & SSH_BUG_RSASIGMD5) != 0) { 160 logit("Refusing RSA key because client uses unsafe " 161 "signature scheme"); 162 goto done; 163 } 164 if (auth2_key_already_used(authctxt, key)) { 165 logit("refusing previously-used %s key", sshkey_type(key)); 166 goto done; 167 } 168 if (match_pattern_list(pkalg, options.pubkey_accepted_algos, 0) != 1) { 169 logit_f("signature algorithm %s not in " 170 "PubkeyAcceptedAlgorithms", pkalg); 171 goto done; 172 } 173 if ((r = sshkey_check_cert_sigtype(key, 174 options.ca_sign_algorithms)) != 0) { 175 logit_fr(r, "certificate signature algorithm %s", 176 (key->cert == NULL || key->cert->signature_type == NULL) ? 177 "(null)" : key->cert->signature_type); 178 goto done; 179 } 180 key_s = format_key(key); 181 if (sshkey_is_cert(key)) 182 ca_s = format_key(key->cert->signature_key); 183 184 if (have_sig) { 185 debug3_f("%s have %s signature for %s%s%s", 186 method, pkalg, key_s, 187 ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s); 188 if ((r = sshpkt_get_string(ssh, &sig, &slen)) != 0 || 189 (r = sshpkt_get_end(ssh)) != 0) 190 fatal_fr(r, "parse signature packet"); 191 if ((b = sshbuf_new()) == NULL) 192 fatal_f("sshbuf_new failed"); 193 if (ssh->compat & SSH_OLD_SESSIONID) { 194 if ((r = sshbuf_putb(b, ssh->kex->session_id)) != 0) 195 fatal_fr(r, "put old session id"); 196 } else { 197 if ((r = sshbuf_put_stringb(b, 198 ssh->kex->session_id)) != 0) 199 fatal_fr(r, "put session id"); 200 } 201 if (!authctxt->valid || authctxt->user == NULL) { 202 debug2_f("disabled because of invalid user"); 203 goto done; 204 } 205 /* reconstruct packet */ 206 xasprintf(&userstyle, "%s%s%s", authctxt->user, 207 authctxt->style ? ":" : "", 208 authctxt->style ? authctxt->style : ""); 209 if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 || 210 (r = sshbuf_put_cstring(b, userstyle)) != 0 || 211 (r = sshbuf_put_cstring(b, authctxt->service)) != 0 || 212 (r = sshbuf_put_cstring(b, method)) != 0 || 213 (r = sshbuf_put_u8(b, have_sig)) != 0 || 214 (r = sshbuf_put_cstring(b, pkalg)) != 0 || 215 (r = sshbuf_put_string(b, pkblob, blen)) != 0) 216 fatal_fr(r, "reconstruct %s packet", method); 217 if (hostbound && 218 (r = sshkey_puts(ssh->kex->initial_hostkey, b)) != 0) 219 fatal_fr(r, "reconstruct %s packet", method); 220 #ifdef DEBUG_PK 221 sshbuf_dump(b, stderr); 222 #endif 223 /* test for correct signature */ 224 authenticated = 0; 225 if (PRIVSEP(user_key_allowed(ssh, pw, key, 1, &authopts)) && 226 PRIVSEP(sshkey_verify(key, sig, slen, 227 sshbuf_ptr(b), sshbuf_len(b), 228 (ssh->compat & SSH_BUG_SIGTYPE) == 0 ? pkalg : NULL, 229 ssh->compat, &sig_details)) == 0) { 230 authenticated = 1; 231 } 232 if (authenticated == 1 && sig_details != NULL) { 233 auth2_record_info(authctxt, "signature count = %u", 234 sig_details->sk_counter); 235 debug_f("sk_counter = %u, sk_flags = 0x%02x", 236 sig_details->sk_counter, sig_details->sk_flags); 237 req_presence = (options.pubkey_auth_options & 238 PUBKEYAUTH_TOUCH_REQUIRED) || 239 !authopts->no_require_user_presence; 240 if (req_presence && (sig_details->sk_flags & 241 SSH_SK_USER_PRESENCE_REQD) == 0) { 242 error("public key %s signature for %s%s from " 243 "%.128s port %d rejected: user presence " 244 "(authenticator touch) requirement " 245 "not met ", key_s, 246 authctxt->valid ? "" : "invalid user ", 247 authctxt->user, ssh_remote_ipaddr(ssh), 248 ssh_remote_port(ssh)); 249 authenticated = 0; 250 goto done; 251 } 252 req_verify = (options.pubkey_auth_options & 253 PUBKEYAUTH_VERIFY_REQUIRED) || 254 authopts->require_verify; 255 if (req_verify && (sig_details->sk_flags & 256 SSH_SK_USER_VERIFICATION_REQD) == 0) { 257 error("public key %s signature for %s%s from " 258 "%.128s port %d rejected: user " 259 "verification requirement not met ", key_s, 260 authctxt->valid ? "" : "invalid user ", 261 authctxt->user, ssh_remote_ipaddr(ssh), 262 ssh_remote_port(ssh)); 263 authenticated = 0; 264 goto done; 265 } 266 } 267 auth2_record_key(authctxt, authenticated, key); 268 } else { 269 debug_f("%s test pkalg %s pkblob %s%s%s", method, pkalg, key_s, 270 ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s); 271 272 if ((r = sshpkt_get_end(ssh)) != 0) 273 fatal_fr(r, "parse packet"); 274 275 if (!authctxt->valid || authctxt->user == NULL) { 276 debug2_f("disabled because of invalid user"); 277 goto done; 278 } 279 /* XXX fake reply and always send PK_OK ? */ 280 /* 281 * XXX this allows testing whether a user is allowed 282 * to login: if you happen to have a valid pubkey this 283 * message is sent. the message is NEVER sent at all 284 * if a user is not allowed to login. is this an 285 * issue? -markus 286 */ 287 if (PRIVSEP(user_key_allowed(ssh, pw, key, 0, NULL))) { 288 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_PK_OK)) 289 != 0 || 290 (r = sshpkt_put_cstring(ssh, pkalg)) != 0 || 291 (r = sshpkt_put_string(ssh, pkblob, blen)) != 0 || 292 (r = sshpkt_send(ssh)) != 0 || 293 (r = ssh_packet_write_wait(ssh)) != 0) 294 fatal_fr(r, "send packet"); 295 authctxt->postponed = 1; 296 } 297 } 298 done: 299 if (authenticated == 1 && auth_activate_options(ssh, authopts) != 0) { 300 debug_f("key options inconsistent with existing"); 301 authenticated = 0; 302 } 303 debug2_f("authenticated %d pkalg %s", authenticated, pkalg); 304 305 sshbuf_free(b); 306 sshauthopt_free(authopts); 307 sshkey_free(key); 308 sshkey_free(hostkey); 309 free(userstyle); 310 free(pkalg); 311 free(pkblob); 312 free(key_s); 313 free(ca_s); 314 free(sig); 315 sshkey_sig_details_free(sig_details); 316 return authenticated; 317 } 318 319 static int 320 match_principals_option(const char *principal_list, struct sshkey_cert *cert) 321 { 322 char *result; 323 u_int i; 324 325 /* XXX percent_expand() sequences for authorized_principals? */ 326 327 for (i = 0; i < cert->nprincipals; i++) { 328 if ((result = match_list(cert->principals[i], 329 principal_list, NULL)) != NULL) { 330 debug3("matched principal from key options \"%.100s\"", 331 result); 332 free(result); 333 return 1; 334 } 335 } 336 return 0; 337 } 338 339 /* 340 * Process a single authorized_principals format line. Returns 0 and sets 341 * authoptsp is principal is authorised, -1 otherwise. "loc" is used as a 342 * log preamble for file/line information. 343 */ 344 static int 345 check_principals_line(struct ssh *ssh, char *cp, const struct sshkey_cert *cert, 346 const char *loc, struct sshauthopt **authoptsp) 347 { 348 u_int i, found = 0; 349 char *ep, *line_opts; 350 const char *reason = NULL; 351 struct sshauthopt *opts = NULL; 352 353 if (authoptsp != NULL) 354 *authoptsp = NULL; 355 356 /* Trim trailing whitespace. */ 357 ep = cp + strlen(cp) - 1; 358 while (ep > cp && (*ep == '\n' || *ep == ' ' || *ep == '\t')) 359 *ep-- = '\0'; 360 361 /* 362 * If the line has internal whitespace then assume it has 363 * key options. 364 */ 365 line_opts = NULL; 366 if ((ep = strrchr(cp, ' ')) != NULL || 367 (ep = strrchr(cp, '\t')) != NULL) { 368 for (; *ep == ' ' || *ep == '\t'; ep++) 369 ; 370 line_opts = cp; 371 cp = ep; 372 } 373 if ((opts = sshauthopt_parse(line_opts, &reason)) == NULL) { 374 debug("%s: bad principals options: %s", loc, reason); 375 auth_debug_add("%s: bad principals options: %s", loc, reason); 376 return -1; 377 } 378 /* Check principals in cert against those on line */ 379 for (i = 0; i < cert->nprincipals; i++) { 380 if (strcmp(cp, cert->principals[i]) != 0) 381 continue; 382 debug3("%s: matched principal \"%.100s\"", 383 loc, cert->principals[i]); 384 found = 1; 385 } 386 if (found && authoptsp != NULL) { 387 *authoptsp = opts; 388 opts = NULL; 389 } 390 sshauthopt_free(opts); 391 return found ? 0 : -1; 392 } 393 394 static int 395 process_principals(struct ssh *ssh, FILE *f, const char *file, 396 const struct sshkey_cert *cert, struct sshauthopt **authoptsp) 397 { 398 char loc[256], *line = NULL, *cp, *ep; 399 size_t linesize = 0; 400 u_long linenum = 0, nonblank = 0; 401 u_int found_principal = 0; 402 403 if (authoptsp != NULL) 404 *authoptsp = NULL; 405 406 while (getline(&line, &linesize, f) != -1) { 407 linenum++; 408 /* Always consume entire input */ 409 if (found_principal) 410 continue; 411 412 /* Skip leading whitespace. */ 413 for (cp = line; *cp == ' ' || *cp == '\t'; cp++) 414 ; 415 /* Skip blank and comment lines. */ 416 if ((ep = strchr(cp, '#')) != NULL) 417 *ep = '\0'; 418 if (!*cp || *cp == '\n') 419 continue; 420 421 nonblank++; 422 snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum); 423 if (check_principals_line(ssh, cp, cert, loc, authoptsp) == 0) 424 found_principal = 1; 425 } 426 debug2_f("%s: processed %lu/%lu lines", file, nonblank, linenum); 427 free(line); 428 return found_principal; 429 } 430 431 /* XXX remove pw args here and elsewhere once ssh->authctxt is guaranteed */ 432 433 static int 434 match_principals_file(struct ssh *ssh, struct passwd *pw, char *file, 435 struct sshkey_cert *cert, struct sshauthopt **authoptsp) 436 { 437 FILE *f; 438 int success; 439 440 if (authoptsp != NULL) 441 *authoptsp = NULL; 442 443 temporarily_use_uid(pw); 444 debug("trying authorized principals file %s", file); 445 if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) { 446 restore_uid(); 447 return 0; 448 } 449 success = process_principals(ssh, f, file, cert, authoptsp); 450 fclose(f); 451 restore_uid(); 452 return success; 453 } 454 455 /* 456 * Checks whether principal is allowed in output of command. 457 * returns 1 if the principal is allowed or 0 otherwise. 458 */ 459 static int 460 match_principals_command(struct ssh *ssh, struct passwd *user_pw, 461 const struct sshkey *key, struct sshauthopt **authoptsp) 462 { 463 struct passwd *runas_pw = NULL; 464 const struct sshkey_cert *cert = key->cert; 465 FILE *f = NULL; 466 int r, ok, found_principal = 0; 467 int i, ac = 0, uid_swapped = 0; 468 pid_t pid; 469 char *tmp, *username = NULL, *command = NULL, **av = NULL; 470 char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL; 471 char serial_s[32], uidstr[32]; 472 void (*osigchld)(int); 473 474 if (authoptsp != NULL) 475 *authoptsp = NULL; 476 if (options.authorized_principals_command == NULL) 477 return 0; 478 if (options.authorized_principals_command_user == NULL) { 479 error("No user for AuthorizedPrincipalsCommand specified, " 480 "skipping"); 481 return 0; 482 } 483 484 /* 485 * NB. all returns later this function should go via "out" to 486 * ensure the original SIGCHLD handler is restored properly. 487 */ 488 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 489 490 /* Prepare and verify the user for the command */ 491 username = percent_expand(options.authorized_principals_command_user, 492 "u", user_pw->pw_name, (char *)NULL); 493 runas_pw = getpwnam(username); 494 if (runas_pw == NULL) { 495 error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s", 496 username, strerror(errno)); 497 goto out; 498 } 499 500 /* Turn the command into an argument vector */ 501 if (argv_split(options.authorized_principals_command, 502 &ac, &av, 0) != 0) { 503 error("AuthorizedPrincipalsCommand \"%s\" contains " 504 "invalid quotes", options.authorized_principals_command); 505 goto out; 506 } 507 if (ac == 0) { 508 error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments", 509 options.authorized_principals_command); 510 goto out; 511 } 512 if ((ca_fp = sshkey_fingerprint(cert->signature_key, 513 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 514 error_f("sshkey_fingerprint failed"); 515 goto out; 516 } 517 if ((key_fp = sshkey_fingerprint(key, 518 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 519 error_f("sshkey_fingerprint failed"); 520 goto out; 521 } 522 if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) { 523 error_fr(r, "sshkey_to_base64 failed"); 524 goto out; 525 } 526 if ((r = sshkey_to_base64(key, &keytext)) != 0) { 527 error_fr(r, "sshkey_to_base64 failed"); 528 goto out; 529 } 530 snprintf(serial_s, sizeof(serial_s), "%llu", 531 (unsigned long long)cert->serial); 532 snprintf(uidstr, sizeof(uidstr), "%llu", 533 (unsigned long long)user_pw->pw_uid); 534 for (i = 1; i < ac; i++) { 535 tmp = percent_expand(av[i], 536 "U", uidstr, 537 "u", user_pw->pw_name, 538 "h", user_pw->pw_dir, 539 "t", sshkey_ssh_name(key), 540 "T", sshkey_ssh_name(cert->signature_key), 541 "f", key_fp, 542 "F", ca_fp, 543 "k", keytext, 544 "K", catext, 545 "i", cert->key_id, 546 "s", serial_s, 547 (char *)NULL); 548 if (tmp == NULL) 549 fatal_f("percent_expand failed"); 550 free(av[i]); 551 av[i] = tmp; 552 } 553 /* Prepare a printable command for logs, etc. */ 554 command = argv_assemble(ac, av); 555 556 if ((pid = subprocess("AuthorizedPrincipalsCommand", command, 557 ac, av, &f, 558 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD, 559 runas_pw, temporarily_use_uid, restore_uid)) == 0) 560 goto out; 561 562 uid_swapped = 1; 563 temporarily_use_uid(runas_pw); 564 565 ok = process_principals(ssh, f, "(command)", cert, authoptsp); 566 567 fclose(f); 568 f = NULL; 569 570 if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0) 571 goto out; 572 573 /* Read completed successfully */ 574 found_principal = ok; 575 out: 576 if (f != NULL) 577 fclose(f); 578 ssh_signal(SIGCHLD, osigchld); 579 for (i = 0; i < ac; i++) 580 free(av[i]); 581 free(av); 582 if (uid_swapped) 583 restore_uid(); 584 free(command); 585 free(username); 586 free(ca_fp); 587 free(key_fp); 588 free(catext); 589 free(keytext); 590 return found_principal; 591 } 592 593 /* 594 * Check a single line of an authorized_keys-format file. Returns 0 if key 595 * matches, -1 otherwise. Will return key/cert options via *authoptsp 596 * on success. "loc" is used as file/line location in log messages. 597 */ 598 static int 599 check_authkey_line(struct ssh *ssh, struct passwd *pw, struct sshkey *key, 600 char *cp, const char *loc, struct sshauthopt **authoptsp) 601 { 602 int want_keytype = sshkey_is_cert(key) ? KEY_UNSPEC : key->type; 603 struct sshkey *found = NULL; 604 struct sshauthopt *keyopts = NULL, *certopts = NULL, *finalopts = NULL; 605 char *key_options = NULL, *fp = NULL; 606 const char *reason = NULL; 607 int ret = -1; 608 609 if (authoptsp != NULL) 610 *authoptsp = NULL; 611 612 if ((found = sshkey_new(want_keytype)) == NULL) { 613 debug3_f("keytype %d failed", want_keytype); 614 goto out; 615 } 616 617 /* XXX djm: peek at key type in line and skip if unwanted */ 618 619 if (sshkey_read(found, &cp) != 0) { 620 /* no key? check for options */ 621 debug2("%s: check options: '%s'", loc, cp); 622 key_options = cp; 623 if (sshkey_advance_past_options(&cp) != 0) { 624 reason = "invalid key option string"; 625 goto fail_reason; 626 } 627 skip_space(&cp); 628 if (sshkey_read(found, &cp) != 0) { 629 /* still no key? advance to next line*/ 630 debug2("%s: advance: '%s'", loc, cp); 631 goto out; 632 } 633 } 634 /* Parse key options now; we need to know if this is a CA key */ 635 if ((keyopts = sshauthopt_parse(key_options, &reason)) == NULL) { 636 debug("%s: bad key options: %s", loc, reason); 637 auth_debug_add("%s: bad key options: %s", loc, reason); 638 goto out; 639 } 640 /* Ignore keys that don't match or incorrectly marked as CAs */ 641 if (sshkey_is_cert(key)) { 642 /* Certificate; check signature key against CA */ 643 if (!sshkey_equal(found, key->cert->signature_key) || 644 !keyopts->cert_authority) 645 goto out; 646 } else { 647 /* Plain key: check it against key found in file */ 648 if (!sshkey_equal(found, key) || keyopts->cert_authority) 649 goto out; 650 } 651 652 /* We have a candidate key, perform authorisation checks */ 653 if ((fp = sshkey_fingerprint(found, 654 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 655 fatal_f("fingerprint failed"); 656 657 debug("%s: matching %s found: %s %s", loc, 658 sshkey_is_cert(key) ? "CA" : "key", sshkey_type(found), fp); 659 660 if (auth_authorise_keyopts(ssh, pw, keyopts, 661 sshkey_is_cert(key), loc) != 0) { 662 reason = "Refused by key options"; 663 goto fail_reason; 664 } 665 /* That's all we need for plain keys. */ 666 if (!sshkey_is_cert(key)) { 667 verbose("Accepted key %s %s found at %s", 668 sshkey_type(found), fp, loc); 669 finalopts = keyopts; 670 keyopts = NULL; 671 goto success; 672 } 673 674 /* 675 * Additional authorisation for certificates. 676 */ 677 678 /* Parse and check options present in certificate */ 679 if ((certopts = sshauthopt_from_cert(key)) == NULL) { 680 reason = "Invalid certificate options"; 681 goto fail_reason; 682 } 683 if (auth_authorise_keyopts(ssh, pw, certopts, 0, loc) != 0) { 684 reason = "Refused by certificate options"; 685 goto fail_reason; 686 } 687 if ((finalopts = sshauthopt_merge(keyopts, certopts, &reason)) == NULL) 688 goto fail_reason; 689 690 /* 691 * If the user has specified a list of principals as 692 * a key option, then prefer that list to matching 693 * their username in the certificate principals list. 694 */ 695 if (keyopts->cert_principals != NULL && 696 !match_principals_option(keyopts->cert_principals, key->cert)) { 697 reason = "Certificate does not contain an authorized principal"; 698 goto fail_reason; 699 } 700 if (sshkey_cert_check_authority_now(key, 0, 0, 0, 701 keyopts->cert_principals == NULL ? pw->pw_name : NULL, 702 &reason) != 0) 703 goto fail_reason; 704 705 verbose("Accepted certificate ID \"%s\" (serial %llu) " 706 "signed by CA %s %s found at %s", 707 key->cert->key_id, 708 (unsigned long long)key->cert->serial, 709 sshkey_type(found), fp, loc); 710 711 success: 712 if (finalopts == NULL) 713 fatal_f("internal error: missing options"); 714 if (authoptsp != NULL) { 715 *authoptsp = finalopts; 716 finalopts = NULL; 717 } 718 /* success */ 719 ret = 0; 720 goto out; 721 722 fail_reason: 723 error("%s", reason); 724 auth_debug_add("%s", reason); 725 out: 726 free(fp); 727 sshauthopt_free(keyopts); 728 sshauthopt_free(certopts); 729 sshauthopt_free(finalopts); 730 sshkey_free(found); 731 return ret; 732 } 733 734 /* 735 * Checks whether key is allowed in authorized_keys-format file, 736 * returns 1 if the key is allowed or 0 otherwise. 737 */ 738 static int 739 check_authkeys_file(struct ssh *ssh, struct passwd *pw, FILE *f, 740 char *file, struct sshkey *key, struct sshauthopt **authoptsp) 741 { 742 char *cp, *line = NULL, loc[256]; 743 size_t linesize = 0; 744 int found_key = 0; 745 u_long linenum = 0, nonblank = 0; 746 747 if (authoptsp != NULL) 748 *authoptsp = NULL; 749 750 while (getline(&line, &linesize, f) != -1) { 751 linenum++; 752 /* Always consume entire file */ 753 if (found_key) 754 continue; 755 756 /* Skip leading whitespace, empty and comment lines. */ 757 cp = line; 758 skip_space(&cp); 759 if (!*cp || *cp == '\n' || *cp == '#') 760 continue; 761 762 nonblank++; 763 snprintf(loc, sizeof(loc), "%.200s:%lu", file, linenum); 764 if (check_authkey_line(ssh, pw, key, cp, loc, authoptsp) == 0) 765 found_key = 1; 766 } 767 free(line); 768 debug2_f("%s: processed %lu/%lu lines", file, nonblank, linenum); 769 return found_key; 770 } 771 772 /* Authenticate a certificate key against TrustedUserCAKeys */ 773 static int 774 user_cert_trusted_ca(struct ssh *ssh, struct passwd *pw, struct sshkey *key, 775 struct sshauthopt **authoptsp) 776 { 777 char *ca_fp, *principals_file = NULL; 778 const char *reason; 779 struct sshauthopt *principals_opts = NULL, *cert_opts = NULL; 780 struct sshauthopt *final_opts = NULL; 781 int r, ret = 0, found_principal = 0, use_authorized_principals; 782 783 if (authoptsp != NULL) 784 *authoptsp = NULL; 785 786 if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL) 787 return 0; 788 789 if ((ca_fp = sshkey_fingerprint(key->cert->signature_key, 790 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 791 return 0; 792 793 if ((r = sshkey_in_file(key->cert->signature_key, 794 options.trusted_user_ca_keys, 1, 0)) != 0) { 795 debug2_fr(r, "CA %s %s is not listed in %s", 796 sshkey_type(key->cert->signature_key), ca_fp, 797 options.trusted_user_ca_keys); 798 goto out; 799 } 800 /* 801 * If AuthorizedPrincipals is in use, then compare the certificate 802 * principals against the names in that file rather than matching 803 * against the username. 804 */ 805 if ((principals_file = authorized_principals_file(pw)) != NULL) { 806 if (match_principals_file(ssh, pw, principals_file, 807 key->cert, &principals_opts)) 808 found_principal = 1; 809 } 810 /* Try querying command if specified */ 811 if (!found_principal && match_principals_command(ssh, pw, key, 812 &principals_opts)) 813 found_principal = 1; 814 /* If principals file or command is specified, then require a match */ 815 use_authorized_principals = principals_file != NULL || 816 options.authorized_principals_command != NULL; 817 if (!found_principal && use_authorized_principals) { 818 reason = "Certificate does not contain an authorized principal"; 819 goto fail_reason; 820 } 821 if (use_authorized_principals && principals_opts == NULL) 822 fatal_f("internal error: missing principals_opts"); 823 if (sshkey_cert_check_authority_now(key, 0, 1, 0, 824 use_authorized_principals ? NULL : pw->pw_name, &reason) != 0) 825 goto fail_reason; 826 827 /* Check authority from options in key and from principals file/cmd */ 828 if ((cert_opts = sshauthopt_from_cert(key)) == NULL) { 829 reason = "Invalid certificate options"; 830 goto fail_reason; 831 } 832 if (auth_authorise_keyopts(ssh, pw, cert_opts, 0, "cert") != 0) { 833 reason = "Refused by certificate options"; 834 goto fail_reason; 835 } 836 if (principals_opts == NULL) { 837 final_opts = cert_opts; 838 cert_opts = NULL; 839 } else { 840 if (auth_authorise_keyopts(ssh, pw, principals_opts, 0, 841 "principals") != 0) { 842 reason = "Refused by certificate principals options"; 843 goto fail_reason; 844 } 845 if ((final_opts = sshauthopt_merge(principals_opts, 846 cert_opts, &reason)) == NULL) { 847 fail_reason: 848 error("%s", reason); 849 auth_debug_add("%s", reason); 850 goto out; 851 } 852 } 853 854 /* Success */ 855 verbose("Accepted certificate ID \"%s\" (serial %llu) signed by " 856 "%s CA %s via %s", key->cert->key_id, 857 (unsigned long long)key->cert->serial, 858 sshkey_type(key->cert->signature_key), ca_fp, 859 options.trusted_user_ca_keys); 860 if (authoptsp != NULL) { 861 *authoptsp = final_opts; 862 final_opts = NULL; 863 } 864 ret = 1; 865 out: 866 sshauthopt_free(principals_opts); 867 sshauthopt_free(cert_opts); 868 sshauthopt_free(final_opts); 869 free(principals_file); 870 free(ca_fp); 871 return ret; 872 } 873 874 /* 875 * Checks whether key is allowed in file. 876 * returns 1 if the key is allowed or 0 otherwise. 877 */ 878 static int 879 user_key_allowed2(struct ssh *ssh, struct passwd *pw, struct sshkey *key, 880 char *file, struct sshauthopt **authoptsp) 881 { 882 FILE *f; 883 int found_key = 0; 884 885 if (authoptsp != NULL) 886 *authoptsp = NULL; 887 888 /* Temporarily use the user's uid. */ 889 temporarily_use_uid(pw); 890 891 debug("trying public key file %s", file); 892 if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) { 893 found_key = check_authkeys_file(ssh, pw, f, file, 894 key, authoptsp); 895 fclose(f); 896 } 897 898 restore_uid(); 899 return found_key; 900 } 901 902 /* 903 * Checks whether key is allowed in output of command. 904 * returns 1 if the key is allowed or 0 otherwise. 905 */ 906 static int 907 user_key_command_allowed2(struct ssh *ssh, struct passwd *user_pw, 908 struct sshkey *key, struct sshauthopt **authoptsp) 909 { 910 struct passwd *runas_pw = NULL; 911 FILE *f = NULL; 912 int r, ok, found_key = 0; 913 int i, uid_swapped = 0, ac = 0; 914 pid_t pid; 915 char *username = NULL, *key_fp = NULL, *keytext = NULL; 916 char uidstr[32], *tmp, *command = NULL, **av = NULL; 917 void (*osigchld)(int); 918 919 if (authoptsp != NULL) 920 *authoptsp = NULL; 921 if (options.authorized_keys_command == NULL) 922 return 0; 923 if (options.authorized_keys_command_user == NULL) { 924 error("No user for AuthorizedKeysCommand specified, skipping"); 925 return 0; 926 } 927 928 /* 929 * NB. all returns later this function should go via "out" to 930 * ensure the original SIGCHLD handler is restored properly. 931 */ 932 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 933 934 /* Prepare and verify the user for the command */ 935 username = percent_expand(options.authorized_keys_command_user, 936 "u", user_pw->pw_name, (char *)NULL); 937 runas_pw = getpwnam(username); 938 if (runas_pw == NULL) { 939 error("AuthorizedKeysCommandUser \"%s\" not found: %s", 940 username, strerror(errno)); 941 goto out; 942 } 943 944 /* Prepare AuthorizedKeysCommand */ 945 if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash, 946 SSH_FP_DEFAULT)) == NULL) { 947 error_f("sshkey_fingerprint failed"); 948 goto out; 949 } 950 if ((r = sshkey_to_base64(key, &keytext)) != 0) { 951 error_fr(r, "sshkey_to_base64 failed"); 952 goto out; 953 } 954 955 /* Turn the command into an argument vector */ 956 if (argv_split(options.authorized_keys_command, &ac, &av, 0) != 0) { 957 error("AuthorizedKeysCommand \"%s\" contains invalid quotes", 958 options.authorized_keys_command); 959 goto out; 960 } 961 if (ac == 0) { 962 error("AuthorizedKeysCommand \"%s\" yielded no arguments", 963 options.authorized_keys_command); 964 goto out; 965 } 966 snprintf(uidstr, sizeof(uidstr), "%llu", 967 (unsigned long long)user_pw->pw_uid); 968 for (i = 1; i < ac; i++) { 969 tmp = percent_expand(av[i], 970 "U", uidstr, 971 "u", user_pw->pw_name, 972 "h", user_pw->pw_dir, 973 "t", sshkey_ssh_name(key), 974 "f", key_fp, 975 "k", keytext, 976 (char *)NULL); 977 if (tmp == NULL) 978 fatal_f("percent_expand failed"); 979 free(av[i]); 980 av[i] = tmp; 981 } 982 /* Prepare a printable command for logs, etc. */ 983 command = argv_assemble(ac, av); 984 985 /* 986 * If AuthorizedKeysCommand was run without arguments 987 * then fall back to the old behaviour of passing the 988 * target username as a single argument. 989 */ 990 if (ac == 1) { 991 av = xreallocarray(av, ac + 2, sizeof(*av)); 992 av[1] = xstrdup(user_pw->pw_name); 993 av[2] = NULL; 994 /* Fix up command too, since it is used in log messages */ 995 free(command); 996 xasprintf(&command, "%s %s", av[0], av[1]); 997 } 998 999 if ((pid = subprocess("AuthorizedKeysCommand", command, 1000 ac, av, &f, 1001 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD, 1002 runas_pw, temporarily_use_uid, restore_uid)) == 0) 1003 goto out; 1004 1005 uid_swapped = 1; 1006 temporarily_use_uid(runas_pw); 1007 1008 ok = check_authkeys_file(ssh, user_pw, f, 1009 options.authorized_keys_command, key, authoptsp); 1010 1011 fclose(f); 1012 f = NULL; 1013 1014 if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0) 1015 goto out; 1016 1017 /* Read completed successfully */ 1018 found_key = ok; 1019 out: 1020 if (f != NULL) 1021 fclose(f); 1022 ssh_signal(SIGCHLD, osigchld); 1023 for (i = 0; i < ac; i++) 1024 free(av[i]); 1025 free(av); 1026 if (uid_swapped) 1027 restore_uid(); 1028 free(command); 1029 free(username); 1030 free(key_fp); 1031 free(keytext); 1032 return found_key; 1033 } 1034 1035 /* 1036 * Check whether key authenticates and authorises the user. 1037 */ 1038 int 1039 user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key, 1040 int auth_attempt, struct sshauthopt **authoptsp) 1041 { 1042 u_int success = 0, i; 1043 char *file; 1044 struct sshauthopt *opts = NULL; 1045 1046 if (authoptsp != NULL) 1047 *authoptsp = NULL; 1048 1049 if (auth_key_is_revoked(key)) 1050 return 0; 1051 if (sshkey_is_cert(key) && 1052 auth_key_is_revoked(key->cert->signature_key)) 1053 return 0; 1054 1055 for (i = 0; !success && i < options.num_authkeys_files; i++) { 1056 if (strcasecmp(options.authorized_keys_files[i], "none") == 0) 1057 continue; 1058 file = expand_authorized_keys( 1059 options.authorized_keys_files[i], pw); 1060 success = user_key_allowed2(ssh, pw, key, file, &opts); 1061 free(file); 1062 if (!success) { 1063 sshauthopt_free(opts); 1064 opts = NULL; 1065 } 1066 } 1067 if (success) 1068 goto out; 1069 1070 if ((success = user_cert_trusted_ca(ssh, pw, key, &opts)) != 0) 1071 goto out; 1072 sshauthopt_free(opts); 1073 opts = NULL; 1074 1075 if ((success = user_key_command_allowed2(ssh, pw, key, &opts)) != 0) 1076 goto out; 1077 sshauthopt_free(opts); 1078 opts = NULL; 1079 1080 out: 1081 if (success && authoptsp != NULL) { 1082 *authoptsp = opts; 1083 opts = NULL; 1084 } 1085 sshauthopt_free(opts); 1086 return success; 1087 } 1088 1089 Authmethod method_pubkey = { 1090 "publickey", 1091 "publickey-hostbound-v00@openssh.com", 1092 userauth_pubkey, 1093 &options.pubkey_authentication 1094 }; 1095