1 /* $OpenBSD: auth2-pubkey.c,v 1.116 2022/06/15 16:08:25 djm Exp $ */ 2 /* 3 * Copyright (c) 2000 Markus Friedl. All rights reserved. 4 * Copyright (c) 2010 Damien Miller. 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 28 #include <sys/types.h> 29 30 #include <stdlib.h> 31 #include <errno.h> 32 #include <paths.h> 33 #include <pwd.h> 34 #include <signal.h> 35 #include <stdio.h> 36 #include <stdarg.h> 37 #include <string.h> 38 #include <time.h> 39 #include <unistd.h> 40 #include <limits.h> 41 42 #include "xmalloc.h" 43 #include "ssh.h" 44 #include "ssh2.h" 45 #include "packet.h" 46 #include "kex.h" 47 #include "sshbuf.h" 48 #include "log.h" 49 #include "misc.h" 50 #include "servconf.h" 51 #include "compat.h" 52 #include "sshkey.h" 53 #include "hostfile.h" 54 #include "auth.h" 55 #include "pathnames.h" 56 #include "uidswap.h" 57 #include "auth-options.h" 58 #include "canohost.h" 59 #ifdef GSSAPI 60 #include "ssh-gss.h" 61 #endif 62 #include "monitor_wrap.h" 63 #include "authfile.h" 64 #include "match.h" 65 #include "ssherr.h" 66 #include "channels.h" /* XXX for session.h */ 67 #include "session.h" /* XXX for child_set_env(); refactor? */ 68 #include "sk-api.h" 69 70 /* import */ 71 extern ServerOptions options; 72 73 static char * 74 format_key(const struct sshkey *key) 75 { 76 char *ret, *fp = sshkey_fingerprint(key, 77 options.fingerprint_hash, SSH_FP_DEFAULT); 78 79 xasprintf(&ret, "%s %s", sshkey_type(key), fp); 80 free(fp); 81 return ret; 82 } 83 84 static int 85 userauth_pubkey(struct ssh *ssh, const char *method) 86 { 87 Authctxt *authctxt = ssh->authctxt; 88 struct passwd *pw = authctxt->pw; 89 struct sshbuf *b = NULL; 90 struct sshkey *key = NULL, *hostkey = NULL; 91 char *pkalg = NULL, *userstyle = NULL, *key_s = NULL, *ca_s = NULL; 92 u_char *pkblob = NULL, *sig = NULL, have_sig; 93 size_t blen, slen; 94 int hostbound, r, pktype; 95 int req_presence = 0, req_verify = 0, authenticated = 0; 96 struct sshauthopt *authopts = NULL; 97 struct sshkey_sig_details *sig_details = NULL; 98 99 hostbound = strcmp(method, "publickey-hostbound-v00@openssh.com") == 0; 100 101 if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0 || 102 (r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 || 103 (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0) 104 fatal_fr(r, "parse %s packet", method); 105 106 /* hostbound auth includes the hostkey offered at initial KEX */ 107 if (hostbound) { 108 if ((r = sshpkt_getb_froms(ssh, &b)) != 0 || 109 (r = sshkey_fromb(b, &hostkey)) != 0) 110 fatal_fr(r, "parse %s hostkey", method); 111 if (ssh->kex->initial_hostkey == NULL) 112 fatal_f("internal error: initial hostkey not recorded"); 113 if (!sshkey_equal(hostkey, ssh->kex->initial_hostkey)) 114 fatal_f("%s packet contained wrong host key", method); 115 sshbuf_free(b); 116 b = NULL; 117 } 118 119 if (log_level_get() >= SYSLOG_LEVEL_DEBUG2) { 120 char *keystring; 121 struct sshbuf *pkbuf; 122 123 if ((pkbuf = sshbuf_from(pkblob, blen)) == NULL) 124 fatal_f("sshbuf_from failed"); 125 if ((keystring = sshbuf_dtob64_string(pkbuf, 0)) == NULL) 126 fatal_f("sshbuf_dtob64 failed"); 127 debug2_f("%s user %s %s public key %s %s", 128 authctxt->valid ? "valid" : "invalid", authctxt->user, 129 have_sig ? "attempting" : "querying", pkalg, keystring); 130 sshbuf_free(pkbuf); 131 free(keystring); 132 } 133 134 pktype = sshkey_type_from_name(pkalg); 135 if (pktype == KEY_UNSPEC) { 136 /* this is perfectly legal */ 137 verbose_f("unsupported public key algorithm: %s", pkalg); 138 goto done; 139 } 140 if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) { 141 error_fr(r, "parse key"); 142 goto done; 143 } 144 if (key == NULL) { 145 error_f("cannot decode key: %s", pkalg); 146 goto done; 147 } 148 if (key->type != pktype) { 149 error_f("type mismatch for decoded key " 150 "(received %d, expected %d)", key->type, pktype); 151 goto done; 152 } 153 if (sshkey_type_plain(key->type) == KEY_RSA && 154 (ssh->compat & SSH_BUG_RSASIGMD5) != 0) { 155 logit("Refusing RSA key because client uses unsafe " 156 "signature scheme"); 157 goto done; 158 } 159 if (auth2_key_already_used(authctxt, key)) { 160 logit("refusing previously-used %s key", sshkey_type(key)); 161 goto done; 162 } 163 if (match_pattern_list(pkalg, options.pubkey_accepted_algos, 0) != 1) { 164 logit_f("signature algorithm %s not in " 165 "PubkeyAcceptedAlgorithms", pkalg); 166 goto done; 167 } 168 if ((r = sshkey_check_cert_sigtype(key, 169 options.ca_sign_algorithms)) != 0) { 170 logit_fr(r, "certificate signature algorithm %s", 171 (key->cert == NULL || key->cert->signature_type == NULL) ? 172 "(null)" : key->cert->signature_type); 173 goto done; 174 } 175 key_s = format_key(key); 176 if (sshkey_is_cert(key)) 177 ca_s = format_key(key->cert->signature_key); 178 179 if (have_sig) { 180 debug3_f("%s have %s signature for %s%s%s", 181 method, pkalg, key_s, 182 ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s); 183 if ((r = sshpkt_get_string(ssh, &sig, &slen)) != 0 || 184 (r = sshpkt_get_end(ssh)) != 0) 185 fatal_fr(r, "parse signature packet"); 186 if ((b = sshbuf_new()) == NULL) 187 fatal_f("sshbuf_new failed"); 188 if (ssh->compat & SSH_OLD_SESSIONID) { 189 if ((r = sshbuf_putb(b, ssh->kex->session_id)) != 0) 190 fatal_fr(r, "put old session id"); 191 } else { 192 if ((r = sshbuf_put_stringb(b, 193 ssh->kex->session_id)) != 0) 194 fatal_fr(r, "put session id"); 195 } 196 if (!authctxt->valid || authctxt->user == NULL) { 197 debug2_f("disabled because of invalid user"); 198 goto done; 199 } 200 /* reconstruct packet */ 201 xasprintf(&userstyle, "%s%s%s", authctxt->user, 202 authctxt->style ? ":" : "", 203 authctxt->style ? authctxt->style : ""); 204 if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 || 205 (r = sshbuf_put_cstring(b, userstyle)) != 0 || 206 (r = sshbuf_put_cstring(b, authctxt->service)) != 0 || 207 (r = sshbuf_put_cstring(b, method)) != 0 || 208 (r = sshbuf_put_u8(b, have_sig)) != 0 || 209 (r = sshbuf_put_cstring(b, pkalg)) != 0 || 210 (r = sshbuf_put_string(b, pkblob, blen)) != 0) 211 fatal_fr(r, "reconstruct %s packet", method); 212 if (hostbound && 213 (r = sshkey_puts(ssh->kex->initial_hostkey, b)) != 0) 214 fatal_fr(r, "reconstruct %s packet", method); 215 #ifdef DEBUG_PK 216 sshbuf_dump(b, stderr); 217 #endif 218 /* test for correct signature */ 219 authenticated = 0; 220 if (PRIVSEP(user_key_allowed(ssh, pw, key, 1, &authopts)) && 221 PRIVSEP(sshkey_verify(key, sig, slen, 222 sshbuf_ptr(b), sshbuf_len(b), 223 (ssh->compat & SSH_BUG_SIGTYPE) == 0 ? pkalg : NULL, 224 ssh->compat, &sig_details)) == 0) { 225 authenticated = 1; 226 } 227 if (authenticated == 1 && sig_details != NULL) { 228 auth2_record_info(authctxt, "signature count = %u", 229 sig_details->sk_counter); 230 debug_f("sk_counter = %u, sk_flags = 0x%02x", 231 sig_details->sk_counter, 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 req_verify = (options.pubkey_auth_options & 248 PUBKEYAUTH_VERIFY_REQUIRED) || 249 authopts->require_verify; 250 if (req_verify && (sig_details->sk_flags & 251 SSH_SK_USER_VERIFICATION_REQD) == 0) { 252 error("public key %s signature for %s%s from " 253 "%.128s port %d rejected: user " 254 "verification requirement not met ", key_s, 255 authctxt->valid ? "" : "invalid user ", 256 authctxt->user, ssh_remote_ipaddr(ssh), 257 ssh_remote_port(ssh)); 258 authenticated = 0; 259 goto done; 260 } 261 } 262 auth2_record_key(authctxt, authenticated, key); 263 } else { 264 debug_f("%s test pkalg %s pkblob %s%s%s", method, pkalg, key_s, 265 ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s); 266 267 if ((r = sshpkt_get_end(ssh)) != 0) 268 fatal_fr(r, "parse packet"); 269 270 if (!authctxt->valid || authctxt->user == NULL) { 271 debug2_f("disabled because of invalid user"); 272 goto done; 273 } 274 /* XXX fake reply and always send PK_OK ? */ 275 /* 276 * XXX this allows testing whether a user is allowed 277 * to login: if you happen to have a valid pubkey this 278 * message is sent. the message is NEVER sent at all 279 * if a user is not allowed to login. is this an 280 * issue? -markus 281 */ 282 if (PRIVSEP(user_key_allowed(ssh, pw, key, 0, NULL))) { 283 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_PK_OK)) 284 != 0 || 285 (r = sshpkt_put_cstring(ssh, pkalg)) != 0 || 286 (r = sshpkt_put_string(ssh, pkblob, blen)) != 0 || 287 (r = sshpkt_send(ssh)) != 0 || 288 (r = ssh_packet_write_wait(ssh)) != 0) 289 fatal_fr(r, "send packet"); 290 authctxt->postponed = 1; 291 } 292 } 293 done: 294 if (authenticated == 1 && auth_activate_options(ssh, authopts) != 0) { 295 debug_f("key options inconsistent with existing"); 296 authenticated = 0; 297 } 298 debug2_f("authenticated %d pkalg %s", authenticated, pkalg); 299 300 sshbuf_free(b); 301 sshauthopt_free(authopts); 302 sshkey_free(key); 303 sshkey_free(hostkey); 304 free(userstyle); 305 free(pkalg); 306 free(pkblob); 307 free(key_s); 308 free(ca_s); 309 free(sig); 310 sshkey_sig_details_free(sig_details); 311 return authenticated; 312 } 313 314 static int 315 match_principals_file(struct passwd *pw, char *file, 316 struct sshkey_cert *cert, struct sshauthopt **authoptsp) 317 { 318 FILE *f; 319 int success; 320 321 if (authoptsp != NULL) 322 *authoptsp = NULL; 323 324 temporarily_use_uid(pw); 325 debug("trying authorized principals file %s", file); 326 if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) { 327 restore_uid(); 328 return 0; 329 } 330 success = auth_process_principals(f, file, cert, authoptsp); 331 fclose(f); 332 restore_uid(); 333 return success; 334 } 335 336 /* 337 * Checks whether principal is allowed in output of command. 338 * returns 1 if the principal is allowed or 0 otherwise. 339 */ 340 static int 341 match_principals_command(struct passwd *user_pw, 342 const struct sshkey *key, struct sshauthopt **authoptsp) 343 { 344 struct passwd *runas_pw = NULL; 345 const struct sshkey_cert *cert = key->cert; 346 FILE *f = NULL; 347 int r, ok, found_principal = 0; 348 int i, ac = 0, uid_swapped = 0; 349 pid_t pid; 350 char *tmp, *username = NULL, *command = NULL, **av = NULL; 351 char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL; 352 char serial_s[32], uidstr[32]; 353 void (*osigchld)(int); 354 355 if (authoptsp != NULL) 356 *authoptsp = NULL; 357 if (options.authorized_principals_command == NULL) 358 return 0; 359 if (options.authorized_principals_command_user == NULL) { 360 error("No user for AuthorizedPrincipalsCommand specified, " 361 "skipping"); 362 return 0; 363 } 364 365 /* 366 * NB. all returns later this function should go via "out" to 367 * ensure the original SIGCHLD handler is restored properly. 368 */ 369 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 370 371 /* Prepare and verify the user for the command */ 372 username = percent_expand(options.authorized_principals_command_user, 373 "u", user_pw->pw_name, (char *)NULL); 374 runas_pw = getpwnam(username); 375 if (runas_pw == NULL) { 376 error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s", 377 username, strerror(errno)); 378 goto out; 379 } 380 381 /* Turn the command into an argument vector */ 382 if (argv_split(options.authorized_principals_command, 383 &ac, &av, 0) != 0) { 384 error("AuthorizedPrincipalsCommand \"%s\" contains " 385 "invalid quotes", options.authorized_principals_command); 386 goto out; 387 } 388 if (ac == 0) { 389 error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments", 390 options.authorized_principals_command); 391 goto out; 392 } 393 if ((ca_fp = sshkey_fingerprint(cert->signature_key, 394 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 395 error_f("sshkey_fingerprint failed"); 396 goto out; 397 } 398 if ((key_fp = sshkey_fingerprint(key, 399 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 400 error_f("sshkey_fingerprint failed"); 401 goto out; 402 } 403 if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) { 404 error_fr(r, "sshkey_to_base64 failed"); 405 goto out; 406 } 407 if ((r = sshkey_to_base64(key, &keytext)) != 0) { 408 error_fr(r, "sshkey_to_base64 failed"); 409 goto out; 410 } 411 snprintf(serial_s, sizeof(serial_s), "%llu", 412 (unsigned long long)cert->serial); 413 snprintf(uidstr, sizeof(uidstr), "%llu", 414 (unsigned long long)user_pw->pw_uid); 415 for (i = 1; i < ac; i++) { 416 tmp = percent_expand(av[i], 417 "U", uidstr, 418 "u", user_pw->pw_name, 419 "h", user_pw->pw_dir, 420 "t", sshkey_ssh_name(key), 421 "T", sshkey_ssh_name(cert->signature_key), 422 "f", key_fp, 423 "F", ca_fp, 424 "k", keytext, 425 "K", catext, 426 "i", cert->key_id, 427 "s", serial_s, 428 (char *)NULL); 429 if (tmp == NULL) 430 fatal_f("percent_expand failed"); 431 free(av[i]); 432 av[i] = tmp; 433 } 434 /* Prepare a printable command for logs, etc. */ 435 command = argv_assemble(ac, av); 436 437 if ((pid = subprocess("AuthorizedPrincipalsCommand", command, 438 ac, av, &f, 439 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD, 440 runas_pw, temporarily_use_uid, restore_uid)) == 0) 441 goto out; 442 443 uid_swapped = 1; 444 temporarily_use_uid(runas_pw); 445 446 ok = auth_process_principals(f, "(command)", cert, authoptsp); 447 448 fclose(f); 449 f = NULL; 450 451 if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0) 452 goto out; 453 454 /* Read completed successfully */ 455 found_principal = ok; 456 out: 457 if (f != NULL) 458 fclose(f); 459 ssh_signal(SIGCHLD, osigchld); 460 for (i = 0; i < ac; i++) 461 free(av[i]); 462 free(av); 463 if (uid_swapped) 464 restore_uid(); 465 free(command); 466 free(username); 467 free(ca_fp); 468 free(key_fp); 469 free(catext); 470 free(keytext); 471 return found_principal; 472 } 473 474 /* Authenticate a certificate key against TrustedUserCAKeys */ 475 static int 476 user_cert_trusted_ca(struct passwd *pw, struct sshkey *key, 477 const char *remote_ip, const char *remote_host, 478 struct sshauthopt **authoptsp) 479 { 480 char *ca_fp, *principals_file = NULL; 481 const char *reason; 482 struct sshauthopt *principals_opts = NULL, *cert_opts = NULL; 483 struct sshauthopt *final_opts = NULL; 484 int r, ret = 0, found_principal = 0, use_authorized_principals; 485 486 if (authoptsp != NULL) 487 *authoptsp = NULL; 488 489 if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL) 490 return 0; 491 492 if ((ca_fp = sshkey_fingerprint(key->cert->signature_key, 493 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 494 return 0; 495 496 if ((r = sshkey_in_file(key->cert->signature_key, 497 options.trusted_user_ca_keys, 1, 0)) != 0) { 498 debug2_fr(r, "CA %s %s is not listed in %s", 499 sshkey_type(key->cert->signature_key), ca_fp, 500 options.trusted_user_ca_keys); 501 goto out; 502 } 503 /* 504 * If AuthorizedPrincipals is in use, then compare the certificate 505 * principals against the names in that file rather than matching 506 * against the username. 507 */ 508 if ((principals_file = authorized_principals_file(pw)) != NULL) { 509 if (match_principals_file(pw, principals_file, 510 key->cert, &principals_opts)) 511 found_principal = 1; 512 } 513 /* Try querying command if specified */ 514 if (!found_principal && match_principals_command(pw, key, 515 &principals_opts)) 516 found_principal = 1; 517 /* If principals file or command is specified, then require a match */ 518 use_authorized_principals = principals_file != NULL || 519 options.authorized_principals_command != NULL; 520 if (!found_principal && use_authorized_principals) { 521 reason = "Certificate does not contain an authorized principal"; 522 goto fail_reason; 523 } 524 if (use_authorized_principals && principals_opts == NULL) 525 fatal_f("internal error: missing principals_opts"); 526 if (sshkey_cert_check_authority_now(key, 0, 1, 0, 527 use_authorized_principals ? NULL : pw->pw_name, &reason) != 0) 528 goto fail_reason; 529 530 /* Check authority from options in key and from principals file/cmd */ 531 if ((cert_opts = sshauthopt_from_cert(key)) == NULL) { 532 reason = "Invalid certificate options"; 533 goto fail_reason; 534 } 535 if (auth_authorise_keyopts(pw, cert_opts, 0, 536 remote_ip, remote_host, "cert") != 0) { 537 reason = "Refused by certificate options"; 538 goto fail_reason; 539 } 540 if (principals_opts == NULL) { 541 final_opts = cert_opts; 542 cert_opts = NULL; 543 } else { 544 if (auth_authorise_keyopts(pw, principals_opts, 0, 545 remote_ip, remote_host, "principals") != 0) { 546 reason = "Refused by certificate principals options"; 547 goto fail_reason; 548 } 549 if ((final_opts = sshauthopt_merge(principals_opts, 550 cert_opts, &reason)) == NULL) { 551 fail_reason: 552 error("%s", reason); 553 auth_debug_add("%s", reason); 554 goto out; 555 } 556 } 557 558 /* Success */ 559 verbose("Accepted certificate ID \"%s\" (serial %llu) signed by " 560 "%s CA %s via %s", key->cert->key_id, 561 (unsigned long long)key->cert->serial, 562 sshkey_type(key->cert->signature_key), ca_fp, 563 options.trusted_user_ca_keys); 564 if (authoptsp != NULL) { 565 *authoptsp = final_opts; 566 final_opts = NULL; 567 } 568 ret = 1; 569 out: 570 sshauthopt_free(principals_opts); 571 sshauthopt_free(cert_opts); 572 sshauthopt_free(final_opts); 573 free(principals_file); 574 free(ca_fp); 575 return ret; 576 } 577 578 /* 579 * Checks whether key is allowed in file. 580 * returns 1 if the key is allowed or 0 otherwise. 581 */ 582 static int 583 user_key_allowed2(struct passwd *pw, struct sshkey *key, 584 char *file, const char *remote_ip, const char *remote_host, 585 struct sshauthopt **authoptsp) 586 { 587 FILE *f; 588 int found_key = 0; 589 590 if (authoptsp != NULL) 591 *authoptsp = NULL; 592 593 /* Temporarily use the user's uid. */ 594 temporarily_use_uid(pw); 595 596 debug("trying public key file %s", file); 597 if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) { 598 found_key = auth_check_authkeys_file(pw, f, file, 599 key, remote_ip, remote_host, authoptsp); 600 fclose(f); 601 } 602 603 restore_uid(); 604 return found_key; 605 } 606 607 /* 608 * Checks whether key is allowed in output of command. 609 * returns 1 if the key is allowed or 0 otherwise. 610 */ 611 static int 612 user_key_command_allowed2(struct passwd *user_pw, struct sshkey *key, 613 const char *remote_ip, const char *remote_host, 614 struct sshauthopt **authoptsp) 615 { 616 struct passwd *runas_pw = NULL; 617 FILE *f = NULL; 618 int r, ok, found_key = 0; 619 int i, uid_swapped = 0, ac = 0; 620 pid_t pid; 621 char *username = NULL, *key_fp = NULL, *keytext = NULL; 622 char uidstr[32], *tmp, *command = NULL, **av = NULL; 623 void (*osigchld)(int); 624 625 if (authoptsp != NULL) 626 *authoptsp = NULL; 627 if (options.authorized_keys_command == NULL) 628 return 0; 629 if (options.authorized_keys_command_user == NULL) { 630 error("No user for AuthorizedKeysCommand specified, skipping"); 631 return 0; 632 } 633 634 /* 635 * NB. all returns later this function should go via "out" to 636 * ensure the original SIGCHLD handler is restored properly. 637 */ 638 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 639 640 /* Prepare and verify the user for the command */ 641 username = percent_expand(options.authorized_keys_command_user, 642 "u", user_pw->pw_name, (char *)NULL); 643 runas_pw = getpwnam(username); 644 if (runas_pw == NULL) { 645 error("AuthorizedKeysCommandUser \"%s\" not found: %s", 646 username, strerror(errno)); 647 goto out; 648 } 649 650 /* Prepare AuthorizedKeysCommand */ 651 if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash, 652 SSH_FP_DEFAULT)) == NULL) { 653 error_f("sshkey_fingerprint failed"); 654 goto out; 655 } 656 if ((r = sshkey_to_base64(key, &keytext)) != 0) { 657 error_fr(r, "sshkey_to_base64 failed"); 658 goto out; 659 } 660 661 /* Turn the command into an argument vector */ 662 if (argv_split(options.authorized_keys_command, &ac, &av, 0) != 0) { 663 error("AuthorizedKeysCommand \"%s\" contains invalid quotes", 664 options.authorized_keys_command); 665 goto out; 666 } 667 if (ac == 0) { 668 error("AuthorizedKeysCommand \"%s\" yielded no arguments", 669 options.authorized_keys_command); 670 goto out; 671 } 672 snprintf(uidstr, sizeof(uidstr), "%llu", 673 (unsigned long long)user_pw->pw_uid); 674 for (i = 1; i < ac; i++) { 675 tmp = percent_expand(av[i], 676 "U", uidstr, 677 "u", user_pw->pw_name, 678 "h", user_pw->pw_dir, 679 "t", sshkey_ssh_name(key), 680 "f", key_fp, 681 "k", keytext, 682 (char *)NULL); 683 if (tmp == NULL) 684 fatal_f("percent_expand failed"); 685 free(av[i]); 686 av[i] = tmp; 687 } 688 /* Prepare a printable command for logs, etc. */ 689 command = argv_assemble(ac, av); 690 691 /* 692 * If AuthorizedKeysCommand was run without arguments 693 * then fall back to the old behaviour of passing the 694 * target username as a single argument. 695 */ 696 if (ac == 1) { 697 av = xreallocarray(av, ac + 2, sizeof(*av)); 698 av[1] = xstrdup(user_pw->pw_name); 699 av[2] = NULL; 700 /* Fix up command too, since it is used in log messages */ 701 free(command); 702 xasprintf(&command, "%s %s", av[0], av[1]); 703 } 704 705 if ((pid = subprocess("AuthorizedKeysCommand", command, 706 ac, av, &f, 707 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD, 708 runas_pw, temporarily_use_uid, restore_uid)) == 0) 709 goto out; 710 711 uid_swapped = 1; 712 temporarily_use_uid(runas_pw); 713 714 ok = auth_check_authkeys_file(user_pw, f, 715 options.authorized_keys_command, key, remote_ip, 716 remote_host, authoptsp); 717 718 fclose(f); 719 f = NULL; 720 721 if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0) 722 goto out; 723 724 /* Read completed successfully */ 725 found_key = ok; 726 out: 727 if (f != NULL) 728 fclose(f); 729 ssh_signal(SIGCHLD, osigchld); 730 for (i = 0; i < ac; i++) 731 free(av[i]); 732 free(av); 733 if (uid_swapped) 734 restore_uid(); 735 free(command); 736 free(username); 737 free(key_fp); 738 free(keytext); 739 return found_key; 740 } 741 742 /* 743 * Check whether key authenticates and authorises the user. 744 */ 745 int 746 user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key, 747 int auth_attempt, struct sshauthopt **authoptsp) 748 { 749 u_int success = 0, i; 750 char *file; 751 struct sshauthopt *opts = NULL; 752 const char *remote_ip = ssh_remote_ipaddr(ssh); 753 const char *remote_host = auth_get_canonical_hostname(ssh, 754 options.use_dns); 755 756 if (authoptsp != NULL) 757 *authoptsp = NULL; 758 759 if (auth_key_is_revoked(key)) 760 return 0; 761 if (sshkey_is_cert(key) && 762 auth_key_is_revoked(key->cert->signature_key)) 763 return 0; 764 765 for (i = 0; !success && i < options.num_authkeys_files; i++) { 766 if (strcasecmp(options.authorized_keys_files[i], "none") == 0) 767 continue; 768 file = expand_authorized_keys( 769 options.authorized_keys_files[i], pw); 770 success = user_key_allowed2(pw, key, file, 771 remote_ip, remote_host, &opts); 772 free(file); 773 if (!success) { 774 sshauthopt_free(opts); 775 opts = NULL; 776 } 777 } 778 if (success) 779 goto out; 780 781 if ((success = user_cert_trusted_ca(pw, key, remote_ip, remote_host, 782 &opts)) != 0) 783 goto out; 784 sshauthopt_free(opts); 785 opts = NULL; 786 787 if ((success = user_key_command_allowed2(pw, key, remote_ip, 788 remote_host, &opts)) != 0) 789 goto out; 790 sshauthopt_free(opts); 791 opts = NULL; 792 793 out: 794 if (success && authoptsp != NULL) { 795 *authoptsp = opts; 796 opts = NULL; 797 } 798 sshauthopt_free(opts); 799 return success; 800 } 801 802 Authmethod method_pubkey = { 803 "publickey", 804 "publickey-hostbound-v00@openssh.com", 805 userauth_pubkey, 806 &options.pubkey_authentication 807 }; 808