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 #include "includes.h" 28 29 #include <sys/types.h> 30 31 #include <stdlib.h> 32 #include <errno.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 "kex.h" 50 #include "sshbuf.h" 51 #include "log.h" 52 #include "misc.h" 53 #include "servconf.h" 54 #include "compat.h" 55 #include "sshkey.h" 56 #include "hostfile.h" 57 #include "auth.h" 58 #include "pathnames.h" 59 #include "uidswap.h" 60 #include "auth-options.h" 61 #include "canohost.h" 62 #ifdef GSSAPI 63 #include "ssh-gss.h" 64 #endif 65 #include "monitor_wrap.h" 66 #include "authfile.h" 67 #include "match.h" 68 #include "ssherr.h" 69 #include "channels.h" /* XXX for session.h */ 70 #include "session.h" /* XXX for child_set_env(); refactor? */ 71 #include "sk-api.h" 72 73 /* import */ 74 extern ServerOptions options; 75 76 static char * 77 format_key(const struct sshkey *key) 78 { 79 char *ret, *fp = sshkey_fingerprint(key, 80 options.fingerprint_hash, SSH_FP_DEFAULT); 81 82 xasprintf(&ret, "%s %s", sshkey_type(key), fp); 83 free(fp); 84 return ret; 85 } 86 87 static int 88 userauth_pubkey(struct ssh *ssh, const char *method) 89 { 90 Authctxt *authctxt = ssh->authctxt; 91 struct passwd *pw = authctxt->pw; 92 struct sshbuf *b = NULL; 93 struct sshkey *key = NULL, *hostkey = NULL; 94 char *pkalg = NULL, *userstyle = NULL, *key_s = NULL, *ca_s = NULL; 95 u_char *pkblob = NULL, *sig = NULL, have_sig; 96 size_t blen, slen; 97 int hostbound, r, pktype; 98 int req_presence = 0, req_verify = 0, authenticated = 0; 99 struct sshauthopt *authopts = NULL; 100 struct sshkey_sig_details *sig_details = NULL; 101 102 hostbound = strcmp(method, "publickey-hostbound-v00@openssh.com") == 0; 103 104 if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0 || 105 (r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 || 106 (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0) 107 fatal_fr(r, "parse %s packet", method); 108 109 /* hostbound auth includes the hostkey offered at initial KEX */ 110 if (hostbound) { 111 if ((r = sshpkt_getb_froms(ssh, &b)) != 0 || 112 (r = sshkey_fromb(b, &hostkey)) != 0) 113 fatal_fr(r, "parse %s hostkey", method); 114 if (ssh->kex->initial_hostkey == NULL) 115 fatal_f("internal error: initial hostkey not recorded"); 116 if (!sshkey_equal(hostkey, ssh->kex->initial_hostkey)) 117 fatal_f("%s packet contained wrong host key", method); 118 sshbuf_free(b); 119 b = NULL; 120 } 121 122 if (log_level_get() >= SYSLOG_LEVEL_DEBUG2) { 123 char *keystring; 124 struct sshbuf *pkbuf; 125 126 if ((pkbuf = sshbuf_from(pkblob, blen)) == NULL) 127 fatal_f("sshbuf_from failed"); 128 if ((keystring = sshbuf_dtob64_string(pkbuf, 0)) == NULL) 129 fatal_f("sshbuf_dtob64 failed"); 130 debug2_f("%s user %s %s public key %s %s", 131 authctxt->valid ? "valid" : "invalid", authctxt->user, 132 have_sig ? "attempting" : "querying", pkalg, keystring); 133 sshbuf_free(pkbuf); 134 free(keystring); 135 } 136 137 pktype = sshkey_type_from_name(pkalg); 138 if (pktype == KEY_UNSPEC) { 139 /* this is perfectly legal */ 140 verbose_f("unsupported public key algorithm: %s", pkalg); 141 goto done; 142 } 143 if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) { 144 error_fr(r, "parse key"); 145 goto done; 146 } 147 if (key == NULL) { 148 error_f("cannot decode key: %s", pkalg); 149 goto done; 150 } 151 if (key->type != pktype) { 152 error_f("type mismatch for decoded key " 153 "(received %d, expected %d)", key->type, pktype); 154 goto done; 155 } 156 if (auth2_key_already_used(authctxt, key)) { 157 logit("refusing previously-used %s key", sshkey_type(key)); 158 goto done; 159 } 160 if (match_pattern_list(pkalg, options.pubkey_accepted_algos, 0) != 1) { 161 logit_f("signature algorithm %s not in " 162 "PubkeyAcceptedAlgorithms", pkalg); 163 goto done; 164 } 165 if ((r = sshkey_check_cert_sigtype(key, 166 options.ca_sign_algorithms)) != 0) { 167 logit_fr(r, "certificate signature algorithm %s", 168 (key->cert == NULL || key->cert->signature_type == NULL) ? 169 "(null)" : key->cert->signature_type); 170 goto done; 171 } 172 if ((r = sshkey_check_rsa_length(key, 173 options.required_rsa_size)) != 0) { 174 logit_r(r, "refusing %s key", sshkey_type(key)); 175 goto done; 176 } 177 key_s = format_key(key); 178 if (sshkey_is_cert(key)) 179 ca_s = format_key(key->cert->signature_key); 180 181 if (have_sig) { 182 debug3_f("%s have %s signature for %s%s%s", 183 method, pkalg, key_s, 184 ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s); 185 if ((r = sshpkt_get_string(ssh, &sig, &slen)) != 0 || 186 (r = sshpkt_get_end(ssh)) != 0) 187 fatal_fr(r, "parse signature packet"); 188 if ((b = sshbuf_new()) == NULL) 189 fatal_f("sshbuf_new failed"); 190 if (ssh->compat & SSH_OLD_SESSIONID) { 191 if ((r = sshbuf_putb(b, ssh->kex->session_id)) != 0) 192 fatal_fr(r, "put old session id"); 193 } else { 194 if ((r = sshbuf_put_stringb(b, 195 ssh->kex->session_id)) != 0) 196 fatal_fr(r, "put session id"); 197 } 198 if (!authctxt->valid || authctxt->user == NULL) { 199 debug2_f("disabled because of invalid user"); 200 goto done; 201 } 202 /* reconstruct packet */ 203 xasprintf(&userstyle, "%s%s%s", authctxt->user, 204 authctxt->style ? ":" : "", 205 authctxt->style ? authctxt->style : ""); 206 if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 || 207 (r = sshbuf_put_cstring(b, userstyle)) != 0 || 208 (r = sshbuf_put_cstring(b, authctxt->service)) != 0 || 209 (r = sshbuf_put_cstring(b, method)) != 0 || 210 (r = sshbuf_put_u8(b, have_sig)) != 0 || 211 (r = sshbuf_put_cstring(b, pkalg)) != 0 || 212 (r = sshbuf_put_string(b, pkblob, blen)) != 0) 213 fatal_fr(r, "reconstruct %s packet", method); 214 if (hostbound && 215 (r = sshkey_puts(ssh->kex->initial_hostkey, b)) != 0) 216 fatal_fr(r, "reconstruct %s packet", method); 217 #ifdef DEBUG_PK 218 sshbuf_dump(b, stderr); 219 #endif 220 /* test for correct signature */ 221 authenticated = 0; 222 if (PRIVSEP(user_key_allowed(ssh, pw, key, 1, &authopts)) && 223 PRIVSEP(sshkey_verify(key, sig, slen, 224 sshbuf_ptr(b), sshbuf_len(b), 225 (ssh->compat & SSH_BUG_SIGTYPE) == 0 ? pkalg : NULL, 226 ssh->compat, &sig_details)) == 0) { 227 authenticated = 1; 228 } 229 if (authenticated == 1 && sig_details != NULL) { 230 auth2_record_info(authctxt, "signature count = %u", 231 sig_details->sk_counter); 232 debug_f("sk_counter = %u, sk_flags = 0x%02x", 233 sig_details->sk_counter, sig_details->sk_flags); 234 req_presence = (options.pubkey_auth_options & 235 PUBKEYAUTH_TOUCH_REQUIRED) || 236 !authopts->no_require_user_presence; 237 if (req_presence && (sig_details->sk_flags & 238 SSH_SK_USER_PRESENCE_REQD) == 0) { 239 error("public key %s signature for %s%s from " 240 "%.128s port %d rejected: user presence " 241 "(authenticator touch) requirement " 242 "not met ", key_s, 243 authctxt->valid ? "" : "invalid user ", 244 authctxt->user, ssh_remote_ipaddr(ssh), 245 ssh_remote_port(ssh)); 246 authenticated = 0; 247 goto done; 248 } 249 req_verify = (options.pubkey_auth_options & 250 PUBKEYAUTH_VERIFY_REQUIRED) || 251 authopts->require_verify; 252 if (req_verify && (sig_details->sk_flags & 253 SSH_SK_USER_VERIFICATION_REQD) == 0) { 254 error("public key %s signature for %s%s from " 255 "%.128s port %d rejected: user " 256 "verification requirement not met ", key_s, 257 authctxt->valid ? "" : "invalid user ", 258 authctxt->user, ssh_remote_ipaddr(ssh), 259 ssh_remote_port(ssh)); 260 authenticated = 0; 261 goto done; 262 } 263 } 264 auth2_record_key(authctxt, authenticated, key); 265 } else { 266 debug_f("%s test pkalg %s pkblob %s%s%s", method, pkalg, key_s, 267 ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s); 268 269 if ((r = sshpkt_get_end(ssh)) != 0) 270 fatal_fr(r, "parse packet"); 271 272 if (!authctxt->valid || authctxt->user == NULL) { 273 debug2_f("disabled because of invalid user"); 274 goto done; 275 } 276 /* XXX fake reply and always send PK_OK ? */ 277 /* 278 * XXX this allows testing whether a user is allowed 279 * to login: if you happen to have a valid pubkey this 280 * message is sent. the message is NEVER sent at all 281 * if a user is not allowed to login. is this an 282 * issue? -markus 283 */ 284 if (PRIVSEP(user_key_allowed(ssh, pw, key, 0, NULL))) { 285 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_PK_OK)) 286 != 0 || 287 (r = sshpkt_put_cstring(ssh, pkalg)) != 0 || 288 (r = sshpkt_put_string(ssh, pkblob, blen)) != 0 || 289 (r = sshpkt_send(ssh)) != 0 || 290 (r = ssh_packet_write_wait(ssh)) != 0) 291 fatal_fr(r, "send packet"); 292 authctxt->postponed = 1; 293 } 294 } 295 done: 296 if (authenticated == 1 && auth_activate_options(ssh, authopts) != 0) { 297 debug_f("key options inconsistent with existing"); 298 authenticated = 0; 299 } 300 debug2_f("authenticated %d pkalg %s", authenticated, pkalg); 301 302 sshbuf_free(b); 303 sshauthopt_free(authopts); 304 sshkey_free(key); 305 sshkey_free(hostkey); 306 free(userstyle); 307 free(pkalg); 308 free(pkblob); 309 free(key_s); 310 free(ca_s); 311 free(sig); 312 sshkey_sig_details_free(sig_details); 313 return authenticated; 314 } 315 316 static int 317 match_principals_file(struct passwd *pw, char *file, 318 struct sshkey_cert *cert, struct sshauthopt **authoptsp) 319 { 320 FILE *f; 321 int success; 322 323 if (authoptsp != NULL) 324 *authoptsp = NULL; 325 326 temporarily_use_uid(pw); 327 debug("trying authorized principals file %s", file); 328 if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) { 329 restore_uid(); 330 return 0; 331 } 332 success = auth_process_principals(f, file, cert, authoptsp); 333 fclose(f); 334 restore_uid(); 335 return success; 336 } 337 338 /* 339 * Checks whether principal is allowed in output of command. 340 * returns 1 if the principal is allowed or 0 otherwise. 341 */ 342 static int 343 match_principals_command(struct passwd *user_pw, 344 const struct sshkey *key, struct sshauthopt **authoptsp) 345 { 346 struct passwd *runas_pw = NULL; 347 const struct sshkey_cert *cert = key->cert; 348 FILE *f = NULL; 349 int r, ok, found_principal = 0; 350 int i, ac = 0, uid_swapped = 0; 351 pid_t pid; 352 char *tmp, *username = NULL, *command = NULL, **av = NULL; 353 char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL; 354 char serial_s[32], uidstr[32]; 355 void (*osigchld)(int); 356 357 if (authoptsp != NULL) 358 *authoptsp = NULL; 359 if (options.authorized_principals_command == NULL) 360 return 0; 361 if (options.authorized_principals_command_user == NULL) { 362 error("No user for AuthorizedPrincipalsCommand specified, " 363 "skipping"); 364 return 0; 365 } 366 367 /* 368 * NB. all returns later this function should go via "out" to 369 * ensure the original SIGCHLD handler is restored properly. 370 */ 371 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 372 373 /* Prepare and verify the user for the command */ 374 username = percent_expand(options.authorized_principals_command_user, 375 "u", user_pw->pw_name, (char *)NULL); 376 runas_pw = getpwnam(username); 377 if (runas_pw == NULL) { 378 error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s", 379 username, strerror(errno)); 380 goto out; 381 } 382 383 /* Turn the command into an argument vector */ 384 if (argv_split(options.authorized_principals_command, 385 &ac, &av, 0) != 0) { 386 error("AuthorizedPrincipalsCommand \"%s\" contains " 387 "invalid quotes", options.authorized_principals_command); 388 goto out; 389 } 390 if (ac == 0) { 391 error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments", 392 options.authorized_principals_command); 393 goto out; 394 } 395 if ((ca_fp = sshkey_fingerprint(cert->signature_key, 396 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 397 error_f("sshkey_fingerprint failed"); 398 goto out; 399 } 400 if ((key_fp = sshkey_fingerprint(key, 401 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 402 error_f("sshkey_fingerprint failed"); 403 goto out; 404 } 405 if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) { 406 error_fr(r, "sshkey_to_base64 failed"); 407 goto out; 408 } 409 if ((r = sshkey_to_base64(key, &keytext)) != 0) { 410 error_fr(r, "sshkey_to_base64 failed"); 411 goto out; 412 } 413 snprintf(serial_s, sizeof(serial_s), "%llu", 414 (unsigned long long)cert->serial); 415 snprintf(uidstr, sizeof(uidstr), "%llu", 416 (unsigned long long)user_pw->pw_uid); 417 for (i = 1; i < ac; i++) { 418 tmp = percent_expand(av[i], 419 "U", uidstr, 420 "u", user_pw->pw_name, 421 "h", user_pw->pw_dir, 422 "t", sshkey_ssh_name(key), 423 "T", sshkey_ssh_name(cert->signature_key), 424 "f", key_fp, 425 "F", ca_fp, 426 "k", keytext, 427 "K", catext, 428 "i", cert->key_id, 429 "s", serial_s, 430 (char *)NULL); 431 if (tmp == NULL) 432 fatal_f("percent_expand failed"); 433 free(av[i]); 434 av[i] = tmp; 435 } 436 /* Prepare a printable command for logs, etc. */ 437 command = argv_assemble(ac, av); 438 439 if ((pid = subprocess("AuthorizedPrincipalsCommand", command, 440 ac, av, &f, 441 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD, 442 runas_pw, temporarily_use_uid, restore_uid)) == 0) 443 goto out; 444 445 uid_swapped = 1; 446 temporarily_use_uid(runas_pw); 447 448 ok = auth_process_principals(f, "(command)", cert, authoptsp); 449 450 fclose(f); 451 f = NULL; 452 453 if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0) 454 goto out; 455 456 /* Read completed successfully */ 457 found_principal = ok; 458 out: 459 if (f != NULL) 460 fclose(f); 461 ssh_signal(SIGCHLD, osigchld); 462 for (i = 0; i < ac; i++) 463 free(av[i]); 464 free(av); 465 if (uid_swapped) 466 restore_uid(); 467 free(command); 468 free(username); 469 free(ca_fp); 470 free(key_fp); 471 free(catext); 472 free(keytext); 473 return found_principal; 474 } 475 476 /* Authenticate a certificate key against TrustedUserCAKeys */ 477 static int 478 user_cert_trusted_ca(struct passwd *pw, struct sshkey *key, 479 const char *remote_ip, const char *remote_host, 480 struct sshauthopt **authoptsp) 481 { 482 char *ca_fp, *principals_file = NULL; 483 const char *reason; 484 struct sshauthopt *principals_opts = NULL, *cert_opts = NULL; 485 struct sshauthopt *final_opts = NULL; 486 int r, ret = 0, found_principal = 0, use_authorized_principals; 487 488 if (authoptsp != NULL) 489 *authoptsp = NULL; 490 491 if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL) 492 return 0; 493 494 if ((ca_fp = sshkey_fingerprint(key->cert->signature_key, 495 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 496 return 0; 497 498 if ((r = sshkey_in_file(key->cert->signature_key, 499 options.trusted_user_ca_keys, 1, 0)) != 0) { 500 debug2_fr(r, "CA %s %s is not listed in %s", 501 sshkey_type(key->cert->signature_key), ca_fp, 502 options.trusted_user_ca_keys); 503 goto out; 504 } 505 /* 506 * If AuthorizedPrincipals is in use, then compare the certificate 507 * principals against the names in that file rather than matching 508 * against the username. 509 */ 510 if ((principals_file = authorized_principals_file(pw)) != NULL) { 511 if (match_principals_file(pw, principals_file, 512 key->cert, &principals_opts)) 513 found_principal = 1; 514 } 515 /* Try querying command if specified */ 516 if (!found_principal && match_principals_command(pw, key, 517 &principals_opts)) 518 found_principal = 1; 519 /* If principals file or command is specified, then require a match */ 520 use_authorized_principals = principals_file != NULL || 521 options.authorized_principals_command != NULL; 522 if (!found_principal && use_authorized_principals) { 523 reason = "Certificate does not contain an authorized principal"; 524 goto fail_reason; 525 } 526 if (use_authorized_principals && principals_opts == NULL) 527 fatal_f("internal error: missing principals_opts"); 528 if (sshkey_cert_check_authority_now(key, 0, 1, 0, 529 use_authorized_principals ? NULL : pw->pw_name, &reason) != 0) 530 goto fail_reason; 531 532 /* Check authority from options in key and from principals file/cmd */ 533 if ((cert_opts = sshauthopt_from_cert(key)) == NULL) { 534 reason = "Invalid certificate options"; 535 goto fail_reason; 536 } 537 if (auth_authorise_keyopts(pw, cert_opts, 0, 538 remote_ip, remote_host, "cert") != 0) { 539 reason = "Refused by certificate options"; 540 goto fail_reason; 541 } 542 if (principals_opts == NULL) { 543 final_opts = cert_opts; 544 cert_opts = NULL; 545 } else { 546 if (auth_authorise_keyopts(pw, principals_opts, 0, 547 remote_ip, remote_host, "principals") != 0) { 548 reason = "Refused by certificate principals options"; 549 goto fail_reason; 550 } 551 if ((final_opts = sshauthopt_merge(principals_opts, 552 cert_opts, &reason)) == NULL) { 553 fail_reason: 554 error("%s", reason); 555 auth_debug_add("%s", reason); 556 goto out; 557 } 558 } 559 560 /* Success */ 561 verbose("Accepted certificate ID \"%s\" (serial %llu) signed by " 562 "%s CA %s via %s", key->cert->key_id, 563 (unsigned long long)key->cert->serial, 564 sshkey_type(key->cert->signature_key), ca_fp, 565 options.trusted_user_ca_keys); 566 if (authoptsp != NULL) { 567 *authoptsp = final_opts; 568 final_opts = NULL; 569 } 570 ret = 1; 571 out: 572 sshauthopt_free(principals_opts); 573 sshauthopt_free(cert_opts); 574 sshauthopt_free(final_opts); 575 free(principals_file); 576 free(ca_fp); 577 return ret; 578 } 579 580 /* 581 * Checks whether key is allowed in file. 582 * returns 1 if the key is allowed or 0 otherwise. 583 */ 584 static int 585 user_key_allowed2(struct passwd *pw, struct sshkey *key, 586 char *file, const char *remote_ip, const char *remote_host, 587 struct sshauthopt **authoptsp) 588 { 589 FILE *f; 590 int found_key = 0; 591 592 if (authoptsp != NULL) 593 *authoptsp = NULL; 594 595 /* Temporarily use the user's uid. */ 596 temporarily_use_uid(pw); 597 598 debug("trying public key file %s", file); 599 if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) { 600 found_key = auth_check_authkeys_file(pw, f, file, 601 key, remote_ip, remote_host, authoptsp); 602 fclose(f); 603 } 604 605 restore_uid(); 606 return found_key; 607 } 608 609 /* 610 * Checks whether key is allowed in output of command. 611 * returns 1 if the key is allowed or 0 otherwise. 612 */ 613 static int 614 user_key_command_allowed2(struct passwd *user_pw, struct sshkey *key, 615 const char *remote_ip, const char *remote_host, 616 struct sshauthopt **authoptsp) 617 { 618 struct passwd *runas_pw = NULL; 619 FILE *f = NULL; 620 int r, ok, found_key = 0; 621 int i, uid_swapped = 0, ac = 0; 622 pid_t pid; 623 char *username = NULL, *key_fp = NULL, *keytext = NULL; 624 char uidstr[32], *tmp, *command = NULL, **av = NULL; 625 void (*osigchld)(int); 626 627 if (authoptsp != NULL) 628 *authoptsp = NULL; 629 if (options.authorized_keys_command == NULL) 630 return 0; 631 if (options.authorized_keys_command_user == NULL) { 632 error("No user for AuthorizedKeysCommand specified, skipping"); 633 return 0; 634 } 635 636 /* 637 * NB. all returns later this function should go via "out" to 638 * ensure the original SIGCHLD handler is restored properly. 639 */ 640 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 641 642 /* Prepare and verify the user for the command */ 643 username = percent_expand(options.authorized_keys_command_user, 644 "u", user_pw->pw_name, (char *)NULL); 645 runas_pw = getpwnam(username); 646 if (runas_pw == NULL) { 647 error("AuthorizedKeysCommandUser \"%s\" not found: %s", 648 username, strerror(errno)); 649 goto out; 650 } 651 652 /* Prepare AuthorizedKeysCommand */ 653 if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash, 654 SSH_FP_DEFAULT)) == NULL) { 655 error_f("sshkey_fingerprint failed"); 656 goto out; 657 } 658 if ((r = sshkey_to_base64(key, &keytext)) != 0) { 659 error_fr(r, "sshkey_to_base64 failed"); 660 goto out; 661 } 662 663 /* Turn the command into an argument vector */ 664 if (argv_split(options.authorized_keys_command, &ac, &av, 0) != 0) { 665 error("AuthorizedKeysCommand \"%s\" contains invalid quotes", 666 options.authorized_keys_command); 667 goto out; 668 } 669 if (ac == 0) { 670 error("AuthorizedKeysCommand \"%s\" yielded no arguments", 671 options.authorized_keys_command); 672 goto out; 673 } 674 snprintf(uidstr, sizeof(uidstr), "%llu", 675 (unsigned long long)user_pw->pw_uid); 676 for (i = 1; i < ac; i++) { 677 tmp = percent_expand(av[i], 678 "U", uidstr, 679 "u", user_pw->pw_name, 680 "h", user_pw->pw_dir, 681 "t", sshkey_ssh_name(key), 682 "f", key_fp, 683 "k", keytext, 684 (char *)NULL); 685 if (tmp == NULL) 686 fatal_f("percent_expand failed"); 687 free(av[i]); 688 av[i] = tmp; 689 } 690 /* Prepare a printable command for logs, etc. */ 691 command = argv_assemble(ac, av); 692 693 /* 694 * If AuthorizedKeysCommand was run without arguments 695 * then fall back to the old behaviour of passing the 696 * target username as a single argument. 697 */ 698 if (ac == 1) { 699 av = xreallocarray(av, ac + 2, sizeof(*av)); 700 av[1] = xstrdup(user_pw->pw_name); 701 av[2] = NULL; 702 /* Fix up command too, since it is used in log messages */ 703 free(command); 704 xasprintf(&command, "%s %s", av[0], av[1]); 705 } 706 707 if ((pid = subprocess("AuthorizedKeysCommand", command, 708 ac, av, &f, 709 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD, 710 runas_pw, temporarily_use_uid, restore_uid)) == 0) 711 goto out; 712 713 uid_swapped = 1; 714 temporarily_use_uid(runas_pw); 715 716 ok = auth_check_authkeys_file(user_pw, f, 717 options.authorized_keys_command, key, remote_ip, 718 remote_host, authoptsp); 719 720 fclose(f); 721 f = NULL; 722 723 if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0) 724 goto out; 725 726 /* Read completed successfully */ 727 found_key = ok; 728 out: 729 if (f != NULL) 730 fclose(f); 731 ssh_signal(SIGCHLD, osigchld); 732 for (i = 0; i < ac; i++) 733 free(av[i]); 734 free(av); 735 if (uid_swapped) 736 restore_uid(); 737 free(command); 738 free(username); 739 free(key_fp); 740 free(keytext); 741 return found_key; 742 } 743 744 /* 745 * Check whether key authenticates and authorises the user. 746 */ 747 int 748 user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key, 749 int auth_attempt, struct sshauthopt **authoptsp) 750 { 751 u_int success = 0, i; 752 char *file; 753 struct sshauthopt *opts = NULL; 754 const char *remote_ip = ssh_remote_ipaddr(ssh); 755 const char *remote_host = auth_get_canonical_hostname(ssh, 756 options.use_dns); 757 758 if (authoptsp != NULL) 759 *authoptsp = NULL; 760 761 if (auth_key_is_revoked(key)) 762 return 0; 763 if (sshkey_is_cert(key) && 764 auth_key_is_revoked(key->cert->signature_key)) 765 return 0; 766 767 for (i = 0; !success && i < options.num_authkeys_files; i++) { 768 if (strcasecmp(options.authorized_keys_files[i], "none") == 0) 769 continue; 770 file = expand_authorized_keys( 771 options.authorized_keys_files[i], pw); 772 success = user_key_allowed2(pw, key, file, 773 remote_ip, remote_host, &opts); 774 free(file); 775 if (!success) { 776 sshauthopt_free(opts); 777 opts = NULL; 778 } 779 } 780 if (success) 781 goto out; 782 783 if ((success = user_cert_trusted_ca(pw, key, remote_ip, remote_host, 784 &opts)) != 0) 785 goto out; 786 sshauthopt_free(opts); 787 opts = NULL; 788 789 if ((success = user_key_command_allowed2(pw, key, remote_ip, 790 remote_host, &opts)) != 0) 791 goto out; 792 sshauthopt_free(opts); 793 opts = NULL; 794 795 out: 796 if (success && authoptsp != NULL) { 797 *authoptsp = opts; 798 opts = NULL; 799 } 800 sshauthopt_free(opts); 801 return success; 802 } 803 804 Authmethod method_pubkey = { 805 "publickey", 806 "publickey-hostbound-v00@openssh.com", 807 userauth_pubkey, 808 &options.pubkey_authentication 809 }; 810