1 /* $OpenBSD: auth2-pubkey.c,v 1.118 2023/02/17 04:22:50 dtucker 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 (auth2_key_already_used(authctxt, key)) { 154 logit("refusing previously-used %s key", sshkey_type(key)); 155 goto done; 156 } 157 if (match_pattern_list(pkalg, options.pubkey_accepted_algos, 0) != 1) { 158 logit_f("signature algorithm %s not in " 159 "PubkeyAcceptedAlgorithms", pkalg); 160 goto done; 161 } 162 if ((r = sshkey_check_cert_sigtype(key, 163 options.ca_sign_algorithms)) != 0) { 164 logit_fr(r, "certificate signature algorithm %s", 165 (key->cert == NULL || key->cert->signature_type == NULL) ? 166 "(null)" : key->cert->signature_type); 167 goto done; 168 } 169 if ((r = sshkey_check_rsa_length(key, 170 options.required_rsa_size)) != 0) { 171 logit_r(r, "refusing %s key", sshkey_type(key)); 172 goto done; 173 } 174 key_s = format_key(key); 175 if (sshkey_is_cert(key)) 176 ca_s = format_key(key->cert->signature_key); 177 178 if (have_sig) { 179 debug3_f("%s have %s signature for %s%s%s", 180 method, pkalg, key_s, 181 ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s); 182 if ((r = sshpkt_get_string(ssh, &sig, &slen)) != 0 || 183 (r = sshpkt_get_end(ssh)) != 0) 184 fatal_fr(r, "parse signature packet"); 185 if ((b = sshbuf_new()) == NULL) 186 fatal_f("sshbuf_new failed"); 187 if (ssh->compat & SSH_OLD_SESSIONID) { 188 if ((r = sshbuf_putb(b, ssh->kex->session_id)) != 0) 189 fatal_fr(r, "put old session id"); 190 } else { 191 if ((r = sshbuf_put_stringb(b, 192 ssh->kex->session_id)) != 0) 193 fatal_fr(r, "put session id"); 194 } 195 if (!authctxt->valid || authctxt->user == NULL) { 196 debug2_f("disabled because of invalid user"); 197 goto done; 198 } 199 /* reconstruct packet */ 200 xasprintf(&userstyle, "%s%s%s", authctxt->user, 201 authctxt->style ? ":" : "", 202 authctxt->style ? authctxt->style : ""); 203 if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 || 204 (r = sshbuf_put_cstring(b, userstyle)) != 0 || 205 (r = sshbuf_put_cstring(b, authctxt->service)) != 0 || 206 (r = sshbuf_put_cstring(b, method)) != 0 || 207 (r = sshbuf_put_u8(b, have_sig)) != 0 || 208 (r = sshbuf_put_cstring(b, pkalg)) != 0 || 209 (r = sshbuf_put_string(b, pkblob, blen)) != 0) 210 fatal_fr(r, "reconstruct %s packet", method); 211 if (hostbound && 212 (r = sshkey_puts(ssh->kex->initial_hostkey, b)) != 0) 213 fatal_fr(r, "reconstruct %s packet", method); 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_f("sk_counter = %u, sk_flags = 0x%02x", 230 sig_details->sk_counter, sig_details->sk_flags); 231 req_presence = (options.pubkey_auth_options & 232 PUBKEYAUTH_TOUCH_REQUIRED) || 233 !authopts->no_require_user_presence; 234 if (req_presence && (sig_details->sk_flags & 235 SSH_SK_USER_PRESENCE_REQD) == 0) { 236 error("public key %s signature for %s%s from " 237 "%.128s port %d rejected: user presence " 238 "(authenticator touch) requirement " 239 "not met ", key_s, 240 authctxt->valid ? "" : "invalid user ", 241 authctxt->user, ssh_remote_ipaddr(ssh), 242 ssh_remote_port(ssh)); 243 authenticated = 0; 244 goto done; 245 } 246 req_verify = (options.pubkey_auth_options & 247 PUBKEYAUTH_VERIFY_REQUIRED) || 248 authopts->require_verify; 249 if (req_verify && (sig_details->sk_flags & 250 SSH_SK_USER_VERIFICATION_REQD) == 0) { 251 error("public key %s signature for %s%s from " 252 "%.128s port %d rejected: user " 253 "verification requirement not met ", key_s, 254 authctxt->valid ? "" : "invalid user ", 255 authctxt->user, ssh_remote_ipaddr(ssh), 256 ssh_remote_port(ssh)); 257 authenticated = 0; 258 goto done; 259 } 260 } 261 auth2_record_key(authctxt, authenticated, key); 262 } else { 263 debug_f("%s test pkalg %s pkblob %s%s%s", method, pkalg, key_s, 264 ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s); 265 266 if ((r = sshpkt_get_end(ssh)) != 0) 267 fatal_fr(r, "parse packet"); 268 269 if (!authctxt->valid || authctxt->user == NULL) { 270 debug2_f("disabled because of invalid user"); 271 goto done; 272 } 273 /* XXX fake reply and always send PK_OK ? */ 274 /* 275 * XXX this allows testing whether a user is allowed 276 * to login: if you happen to have a valid pubkey this 277 * message is sent. the message is NEVER sent at all 278 * if a user is not allowed to login. is this an 279 * issue? -markus 280 */ 281 if (PRIVSEP(user_key_allowed(ssh, pw, key, 0, NULL))) { 282 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_PK_OK)) 283 != 0 || 284 (r = sshpkt_put_cstring(ssh, pkalg)) != 0 || 285 (r = sshpkt_put_string(ssh, pkblob, blen)) != 0 || 286 (r = sshpkt_send(ssh)) != 0 || 287 (r = ssh_packet_write_wait(ssh)) != 0) 288 fatal_fr(r, "send packet"); 289 authctxt->postponed = 1; 290 } 291 } 292 done: 293 if (authenticated == 1 && auth_activate_options(ssh, authopts) != 0) { 294 debug_f("key options inconsistent with existing"); 295 authenticated = 0; 296 } 297 debug2_f("authenticated %d pkalg %s", authenticated, pkalg); 298 299 sshbuf_free(b); 300 sshauthopt_free(authopts); 301 sshkey_free(key); 302 sshkey_free(hostkey); 303 free(userstyle); 304 free(pkalg); 305 free(pkblob); 306 free(key_s); 307 free(ca_s); 308 free(sig); 309 sshkey_sig_details_free(sig_details); 310 return authenticated; 311 } 312 313 static int 314 match_principals_file(struct passwd *pw, char *file, 315 struct sshkey_cert *cert, struct sshauthopt **authoptsp) 316 { 317 FILE *f; 318 int success; 319 320 if (authoptsp != NULL) 321 *authoptsp = NULL; 322 323 temporarily_use_uid(pw); 324 debug("trying authorized principals file %s", file); 325 if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) { 326 restore_uid(); 327 return 0; 328 } 329 success = auth_process_principals(f, file, cert, authoptsp); 330 fclose(f); 331 restore_uid(); 332 return success; 333 } 334 335 /* 336 * Checks whether principal is allowed in output of command. 337 * returns 1 if the principal is allowed or 0 otherwise. 338 */ 339 static int 340 match_principals_command(struct passwd *user_pw, 341 const struct sshkey *key, struct sshauthopt **authoptsp) 342 { 343 struct passwd *runas_pw = NULL; 344 const struct sshkey_cert *cert = key->cert; 345 FILE *f = NULL; 346 int r, ok, found_principal = 0; 347 int i, ac = 0, uid_swapped = 0; 348 pid_t pid; 349 char *tmp, *username = NULL, *command = NULL, **av = NULL; 350 char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL; 351 char serial_s[32], uidstr[32]; 352 void (*osigchld)(int); 353 354 if (authoptsp != NULL) 355 *authoptsp = NULL; 356 if (options.authorized_principals_command == NULL) 357 return 0; 358 if (options.authorized_principals_command_user == NULL) { 359 error("No user for AuthorizedPrincipalsCommand specified, " 360 "skipping"); 361 return 0; 362 } 363 364 /* 365 * NB. all returns later this function should go via "out" to 366 * ensure the original SIGCHLD handler is restored properly. 367 */ 368 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 369 370 /* Prepare and verify the user for the command */ 371 username = percent_expand(options.authorized_principals_command_user, 372 "u", user_pw->pw_name, (char *)NULL); 373 runas_pw = getpwnam(username); 374 if (runas_pw == NULL) { 375 error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s", 376 username, strerror(errno)); 377 goto out; 378 } 379 380 /* Turn the command into an argument vector */ 381 if (argv_split(options.authorized_principals_command, 382 &ac, &av, 0) != 0) { 383 error("AuthorizedPrincipalsCommand \"%s\" contains " 384 "invalid quotes", options.authorized_principals_command); 385 goto out; 386 } 387 if (ac == 0) { 388 error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments", 389 options.authorized_principals_command); 390 goto out; 391 } 392 if ((ca_fp = sshkey_fingerprint(cert->signature_key, 393 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 394 error_f("sshkey_fingerprint failed"); 395 goto out; 396 } 397 if ((key_fp = sshkey_fingerprint(key, 398 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 399 error_f("sshkey_fingerprint failed"); 400 goto out; 401 } 402 if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) { 403 error_fr(r, "sshkey_to_base64 failed"); 404 goto out; 405 } 406 if ((r = sshkey_to_base64(key, &keytext)) != 0) { 407 error_fr(r, "sshkey_to_base64 failed"); 408 goto out; 409 } 410 snprintf(serial_s, sizeof(serial_s), "%llu", 411 (unsigned long long)cert->serial); 412 snprintf(uidstr, sizeof(uidstr), "%llu", 413 (unsigned long long)user_pw->pw_uid); 414 for (i = 1; i < ac; i++) { 415 tmp = percent_expand(av[i], 416 "U", uidstr, 417 "u", user_pw->pw_name, 418 "h", user_pw->pw_dir, 419 "t", sshkey_ssh_name(key), 420 "T", sshkey_ssh_name(cert->signature_key), 421 "f", key_fp, 422 "F", ca_fp, 423 "k", keytext, 424 "K", catext, 425 "i", cert->key_id, 426 "s", serial_s, 427 (char *)NULL); 428 if (tmp == NULL) 429 fatal_f("percent_expand failed"); 430 free(av[i]); 431 av[i] = tmp; 432 } 433 /* Prepare a printable command for logs, etc. */ 434 command = argv_assemble(ac, av); 435 436 if ((pid = subprocess("AuthorizedPrincipalsCommand", command, 437 ac, av, &f, 438 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD, 439 runas_pw, temporarily_use_uid, restore_uid)) == 0) 440 goto out; 441 442 uid_swapped = 1; 443 temporarily_use_uid(runas_pw); 444 445 ok = auth_process_principals(f, "(command)", cert, authoptsp); 446 447 fclose(f); 448 f = NULL; 449 450 if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0) 451 goto out; 452 453 /* Read completed successfully */ 454 found_principal = ok; 455 out: 456 if (f != NULL) 457 fclose(f); 458 ssh_signal(SIGCHLD, osigchld); 459 for (i = 0; i < ac; i++) 460 free(av[i]); 461 free(av); 462 if (uid_swapped) 463 restore_uid(); 464 free(command); 465 free(username); 466 free(ca_fp); 467 free(key_fp); 468 free(catext); 469 free(keytext); 470 return found_principal; 471 } 472 473 /* Authenticate a certificate key against TrustedUserCAKeys */ 474 static int 475 user_cert_trusted_ca(struct passwd *pw, struct sshkey *key, 476 const char *remote_ip, const char *remote_host, 477 struct sshauthopt **authoptsp) 478 { 479 char *ca_fp, *principals_file = NULL; 480 const char *reason; 481 struct sshauthopt *principals_opts = NULL, *cert_opts = NULL; 482 struct sshauthopt *final_opts = NULL; 483 int r, ret = 0, found_principal = 0, use_authorized_principals; 484 485 if (authoptsp != NULL) 486 *authoptsp = NULL; 487 488 if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL) 489 return 0; 490 491 if ((ca_fp = sshkey_fingerprint(key->cert->signature_key, 492 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 493 return 0; 494 495 if ((r = sshkey_in_file(key->cert->signature_key, 496 options.trusted_user_ca_keys, 1, 0)) != 0) { 497 debug2_fr(r, "CA %s %s is not listed in %s", 498 sshkey_type(key->cert->signature_key), ca_fp, 499 options.trusted_user_ca_keys); 500 goto out; 501 } 502 /* 503 * If AuthorizedPrincipals is in use, then compare the certificate 504 * principals against the names in that file rather than matching 505 * against the username. 506 */ 507 if ((principals_file = authorized_principals_file(pw)) != NULL) { 508 if (match_principals_file(pw, principals_file, 509 key->cert, &principals_opts)) 510 found_principal = 1; 511 } 512 /* Try querying command if specified */ 513 if (!found_principal && match_principals_command(pw, key, 514 &principals_opts)) 515 found_principal = 1; 516 /* If principals file or command is specified, then require a match */ 517 use_authorized_principals = principals_file != NULL || 518 options.authorized_principals_command != NULL; 519 if (!found_principal && use_authorized_principals) { 520 reason = "Certificate does not contain an authorized principal"; 521 goto fail_reason; 522 } 523 if (use_authorized_principals && principals_opts == NULL) 524 fatal_f("internal error: missing principals_opts"); 525 if (sshkey_cert_check_authority_now(key, 0, 1, 0, 526 use_authorized_principals ? NULL : pw->pw_name, &reason) != 0) 527 goto fail_reason; 528 529 /* Check authority from options in key and from principals file/cmd */ 530 if ((cert_opts = sshauthopt_from_cert(key)) == NULL) { 531 reason = "Invalid certificate options"; 532 goto fail_reason; 533 } 534 if (auth_authorise_keyopts(pw, cert_opts, 0, 535 remote_ip, remote_host, "cert") != 0) { 536 reason = "Refused by certificate options"; 537 goto fail_reason; 538 } 539 if (principals_opts == NULL) { 540 final_opts = cert_opts; 541 cert_opts = NULL; 542 } else { 543 if (auth_authorise_keyopts(pw, principals_opts, 0, 544 remote_ip, remote_host, "principals") != 0) { 545 reason = "Refused by certificate principals options"; 546 goto fail_reason; 547 } 548 if ((final_opts = sshauthopt_merge(principals_opts, 549 cert_opts, &reason)) == NULL) { 550 fail_reason: 551 error("%s", reason); 552 auth_debug_add("%s", reason); 553 goto out; 554 } 555 } 556 557 /* Success */ 558 verbose("Accepted certificate ID \"%s\" (serial %llu) signed by " 559 "%s CA %s via %s", key->cert->key_id, 560 (unsigned long long)key->cert->serial, 561 sshkey_type(key->cert->signature_key), ca_fp, 562 options.trusted_user_ca_keys); 563 if (authoptsp != NULL) { 564 *authoptsp = final_opts; 565 final_opts = NULL; 566 } 567 ret = 1; 568 out: 569 sshauthopt_free(principals_opts); 570 sshauthopt_free(cert_opts); 571 sshauthopt_free(final_opts); 572 free(principals_file); 573 free(ca_fp); 574 return ret; 575 } 576 577 /* 578 * Checks whether key is allowed in file. 579 * returns 1 if the key is allowed or 0 otherwise. 580 */ 581 static int 582 user_key_allowed2(struct passwd *pw, struct sshkey *key, 583 char *file, const char *remote_ip, const char *remote_host, 584 struct sshauthopt **authoptsp) 585 { 586 FILE *f; 587 int found_key = 0; 588 589 if (authoptsp != NULL) 590 *authoptsp = NULL; 591 592 /* Temporarily use the user's uid. */ 593 temporarily_use_uid(pw); 594 595 debug("trying public key file %s", file); 596 if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) { 597 found_key = auth_check_authkeys_file(pw, f, file, 598 key, remote_ip, remote_host, authoptsp); 599 fclose(f); 600 } 601 602 restore_uid(); 603 return found_key; 604 } 605 606 /* 607 * Checks whether key is allowed in output of command. 608 * returns 1 if the key is allowed or 0 otherwise. 609 */ 610 static int 611 user_key_command_allowed2(struct passwd *user_pw, struct sshkey *key, 612 const char *remote_ip, const char *remote_host, 613 struct sshauthopt **authoptsp) 614 { 615 struct passwd *runas_pw = NULL; 616 FILE *f = NULL; 617 int r, ok, found_key = 0; 618 int i, uid_swapped = 0, ac = 0; 619 pid_t pid; 620 char *username = NULL, *key_fp = NULL, *keytext = NULL; 621 char uidstr[32], *tmp, *command = NULL, **av = NULL; 622 void (*osigchld)(int); 623 624 if (authoptsp != NULL) 625 *authoptsp = NULL; 626 if (options.authorized_keys_command == NULL) 627 return 0; 628 if (options.authorized_keys_command_user == NULL) { 629 error("No user for AuthorizedKeysCommand specified, skipping"); 630 return 0; 631 } 632 633 /* 634 * NB. all returns later this function should go via "out" to 635 * ensure the original SIGCHLD handler is restored properly. 636 */ 637 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 638 639 /* Prepare and verify the user for the command */ 640 username = percent_expand(options.authorized_keys_command_user, 641 "u", user_pw->pw_name, (char *)NULL); 642 runas_pw = getpwnam(username); 643 if (runas_pw == NULL) { 644 error("AuthorizedKeysCommandUser \"%s\" not found: %s", 645 username, strerror(errno)); 646 goto out; 647 } 648 649 /* Prepare AuthorizedKeysCommand */ 650 if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash, 651 SSH_FP_DEFAULT)) == NULL) { 652 error_f("sshkey_fingerprint failed"); 653 goto out; 654 } 655 if ((r = sshkey_to_base64(key, &keytext)) != 0) { 656 error_fr(r, "sshkey_to_base64 failed"); 657 goto out; 658 } 659 660 /* Turn the command into an argument vector */ 661 if (argv_split(options.authorized_keys_command, &ac, &av, 0) != 0) { 662 error("AuthorizedKeysCommand \"%s\" contains invalid quotes", 663 options.authorized_keys_command); 664 goto out; 665 } 666 if (ac == 0) { 667 error("AuthorizedKeysCommand \"%s\" yielded no arguments", 668 options.authorized_keys_command); 669 goto out; 670 } 671 snprintf(uidstr, sizeof(uidstr), "%llu", 672 (unsigned long long)user_pw->pw_uid); 673 for (i = 1; i < ac; i++) { 674 tmp = percent_expand(av[i], 675 "U", uidstr, 676 "u", user_pw->pw_name, 677 "h", user_pw->pw_dir, 678 "t", sshkey_ssh_name(key), 679 "f", key_fp, 680 "k", keytext, 681 (char *)NULL); 682 if (tmp == NULL) 683 fatal_f("percent_expand failed"); 684 free(av[i]); 685 av[i] = tmp; 686 } 687 /* Prepare a printable command for logs, etc. */ 688 command = argv_assemble(ac, av); 689 690 /* 691 * If AuthorizedKeysCommand was run without arguments 692 * then fall back to the old behaviour of passing the 693 * target username as a single argument. 694 */ 695 if (ac == 1) { 696 av = xreallocarray(av, ac + 2, sizeof(*av)); 697 av[1] = xstrdup(user_pw->pw_name); 698 av[2] = NULL; 699 /* Fix up command too, since it is used in log messages */ 700 free(command); 701 xasprintf(&command, "%s %s", av[0], av[1]); 702 } 703 704 if ((pid = subprocess("AuthorizedKeysCommand", command, 705 ac, av, &f, 706 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD, 707 runas_pw, temporarily_use_uid, restore_uid)) == 0) 708 goto out; 709 710 uid_swapped = 1; 711 temporarily_use_uid(runas_pw); 712 713 ok = auth_check_authkeys_file(user_pw, f, 714 options.authorized_keys_command, key, remote_ip, 715 remote_host, authoptsp); 716 717 fclose(f); 718 f = NULL; 719 720 if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0) 721 goto out; 722 723 /* Read completed successfully */ 724 found_key = ok; 725 out: 726 if (f != NULL) 727 fclose(f); 728 ssh_signal(SIGCHLD, osigchld); 729 for (i = 0; i < ac; i++) 730 free(av[i]); 731 free(av); 732 if (uid_swapped) 733 restore_uid(); 734 free(command); 735 free(username); 736 free(key_fp); 737 free(keytext); 738 return found_key; 739 } 740 741 /* 742 * Check whether key authenticates and authorises the user. 743 */ 744 int 745 user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key, 746 int auth_attempt, struct sshauthopt **authoptsp) 747 { 748 u_int success = 0, i; 749 char *file; 750 struct sshauthopt *opts = NULL; 751 const char *remote_ip = ssh_remote_ipaddr(ssh); 752 const char *remote_host = auth_get_canonical_hostname(ssh, 753 options.use_dns); 754 755 if (authoptsp != NULL) 756 *authoptsp = NULL; 757 758 if (auth_key_is_revoked(key)) 759 return 0; 760 if (sshkey_is_cert(key) && 761 auth_key_is_revoked(key->cert->signature_key)) 762 return 0; 763 764 for (i = 0; !success && i < options.num_authkeys_files; i++) { 765 if (strcasecmp(options.authorized_keys_files[i], "none") == 0) 766 continue; 767 file = expand_authorized_keys( 768 options.authorized_keys_files[i], pw); 769 success = user_key_allowed2(pw, key, file, 770 remote_ip, remote_host, &opts); 771 free(file); 772 if (!success) { 773 sshauthopt_free(opts); 774 opts = NULL; 775 } 776 } 777 if (success) 778 goto out; 779 780 if ((success = user_cert_trusted_ca(pw, key, remote_ip, remote_host, 781 &opts)) != 0) 782 goto out; 783 sshauthopt_free(opts); 784 opts = NULL; 785 786 if ((success = user_key_command_allowed2(pw, key, remote_ip, 787 remote_host, &opts)) != 0) 788 goto out; 789 sshauthopt_free(opts); 790 opts = NULL; 791 792 out: 793 if (success && authoptsp != NULL) { 794 *authoptsp = opts; 795 opts = NULL; 796 } 797 sshauthopt_free(opts); 798 return success; 799 } 800 801 Authmethod method_pubkey = { 802 "publickey", 803 "publickey-hostbound-v00@openssh.com", 804 userauth_pubkey, 805 &options.pubkey_authentication 806 }; 807