1 /* $OpenBSD: auth2-pubkey.c,v 1.119 2023/07/27 22:25:17 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 #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, const struct sshkey *key, 344 const char *conn_id, const char *rdomain, 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 "C", conn_id, 420 "D", rdomain, 421 "U", uidstr, 422 "u", user_pw->pw_name, 423 "h", user_pw->pw_dir, 424 "t", sshkey_ssh_name(key), 425 "T", sshkey_ssh_name(cert->signature_key), 426 "f", key_fp, 427 "F", ca_fp, 428 "k", keytext, 429 "K", catext, 430 "i", cert->key_id, 431 "s", serial_s, 432 (char *)NULL); 433 if (tmp == NULL) 434 fatal_f("percent_expand failed"); 435 free(av[i]); 436 av[i] = tmp; 437 } 438 /* Prepare a printable command for logs, etc. */ 439 command = argv_assemble(ac, av); 440 441 if ((pid = subprocess("AuthorizedPrincipalsCommand", command, 442 ac, av, &f, 443 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD, 444 runas_pw, temporarily_use_uid, restore_uid)) == 0) 445 goto out; 446 447 uid_swapped = 1; 448 temporarily_use_uid(runas_pw); 449 450 ok = auth_process_principals(f, "(command)", cert, authoptsp); 451 452 fclose(f); 453 f = NULL; 454 455 if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0) 456 goto out; 457 458 /* Read completed successfully */ 459 found_principal = ok; 460 out: 461 if (f != NULL) 462 fclose(f); 463 ssh_signal(SIGCHLD, osigchld); 464 for (i = 0; i < ac; i++) 465 free(av[i]); 466 free(av); 467 if (uid_swapped) 468 restore_uid(); 469 free(command); 470 free(username); 471 free(ca_fp); 472 free(key_fp); 473 free(catext); 474 free(keytext); 475 return found_principal; 476 } 477 478 /* Authenticate a certificate key against TrustedUserCAKeys */ 479 static int 480 user_cert_trusted_ca(struct passwd *pw, struct sshkey *key, 481 const char *remote_ip, const char *remote_host, 482 const char *conn_id, const char *rdomain, struct sshauthopt **authoptsp) 483 { 484 char *ca_fp, *principals_file = NULL; 485 const char *reason; 486 struct sshauthopt *principals_opts = NULL, *cert_opts = NULL; 487 struct sshauthopt *final_opts = NULL; 488 int r, ret = 0, found_principal = 0, use_authorized_principals; 489 490 if (authoptsp != NULL) 491 *authoptsp = NULL; 492 493 if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL) 494 return 0; 495 496 if ((ca_fp = sshkey_fingerprint(key->cert->signature_key, 497 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 498 return 0; 499 500 if ((r = sshkey_in_file(key->cert->signature_key, 501 options.trusted_user_ca_keys, 1, 0)) != 0) { 502 debug2_fr(r, "CA %s %s is not listed in %s", 503 sshkey_type(key->cert->signature_key), ca_fp, 504 options.trusted_user_ca_keys); 505 goto out; 506 } 507 /* 508 * If AuthorizedPrincipals is in use, then compare the certificate 509 * principals against the names in that file rather than matching 510 * against the username. 511 */ 512 if ((principals_file = authorized_principals_file(pw)) != NULL) { 513 if (match_principals_file(pw, principals_file, 514 key->cert, &principals_opts)) 515 found_principal = 1; 516 } 517 /* Try querying command if specified */ 518 if (!found_principal && match_principals_command(pw, key, 519 conn_id, rdomain, &principals_opts)) 520 found_principal = 1; 521 /* If principals file or command is specified, then require a match */ 522 use_authorized_principals = principals_file != NULL || 523 options.authorized_principals_command != NULL; 524 if (!found_principal && use_authorized_principals) { 525 reason = "Certificate does not contain an authorized principal"; 526 goto fail_reason; 527 } 528 if (use_authorized_principals && principals_opts == NULL) 529 fatal_f("internal error: missing principals_opts"); 530 if (sshkey_cert_check_authority_now(key, 0, 1, 0, 531 use_authorized_principals ? NULL : pw->pw_name, &reason) != 0) 532 goto fail_reason; 533 534 /* Check authority from options in key and from principals file/cmd */ 535 if ((cert_opts = sshauthopt_from_cert(key)) == NULL) { 536 reason = "Invalid certificate options"; 537 goto fail_reason; 538 } 539 if (auth_authorise_keyopts(pw, cert_opts, 0, 540 remote_ip, remote_host, "cert") != 0) { 541 reason = "Refused by certificate options"; 542 goto fail_reason; 543 } 544 if (principals_opts == NULL) { 545 final_opts = cert_opts; 546 cert_opts = NULL; 547 } else { 548 if (auth_authorise_keyopts(pw, principals_opts, 0, 549 remote_ip, remote_host, "principals") != 0) { 550 reason = "Refused by certificate principals options"; 551 goto fail_reason; 552 } 553 if ((final_opts = sshauthopt_merge(principals_opts, 554 cert_opts, &reason)) == NULL) { 555 fail_reason: 556 error("%s", reason); 557 auth_debug_add("%s", reason); 558 goto out; 559 } 560 } 561 562 /* Success */ 563 verbose("Accepted certificate ID \"%s\" (serial %llu) signed by " 564 "%s CA %s via %s", key->cert->key_id, 565 (unsigned long long)key->cert->serial, 566 sshkey_type(key->cert->signature_key), ca_fp, 567 options.trusted_user_ca_keys); 568 if (authoptsp != NULL) { 569 *authoptsp = final_opts; 570 final_opts = NULL; 571 } 572 ret = 1; 573 out: 574 sshauthopt_free(principals_opts); 575 sshauthopt_free(cert_opts); 576 sshauthopt_free(final_opts); 577 free(principals_file); 578 free(ca_fp); 579 return ret; 580 } 581 582 /* 583 * Checks whether key is allowed in file. 584 * returns 1 if the key is allowed or 0 otherwise. 585 */ 586 static int 587 user_key_allowed2(struct passwd *pw, struct sshkey *key, 588 char *file, const char *remote_ip, const char *remote_host, 589 struct sshauthopt **authoptsp) 590 { 591 FILE *f; 592 int found_key = 0; 593 594 if (authoptsp != NULL) 595 *authoptsp = NULL; 596 597 /* Temporarily use the user's uid. */ 598 temporarily_use_uid(pw); 599 600 debug("trying public key file %s", file); 601 if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) { 602 found_key = auth_check_authkeys_file(pw, f, file, 603 key, remote_ip, remote_host, authoptsp); 604 fclose(f); 605 } 606 607 restore_uid(); 608 return found_key; 609 } 610 611 /* 612 * Checks whether key is allowed in output of command. 613 * returns 1 if the key is allowed or 0 otherwise. 614 */ 615 static int 616 user_key_command_allowed2(struct passwd *user_pw, struct sshkey *key, 617 const char *remote_ip, const char *remote_host, 618 const char *conn_id, const char *rdomain, struct sshauthopt **authoptsp) 619 { 620 struct passwd *runas_pw = NULL; 621 FILE *f = NULL; 622 int r, ok, found_key = 0; 623 int i, uid_swapped = 0, ac = 0; 624 pid_t pid; 625 char *username = NULL, *key_fp = NULL, *keytext = NULL; 626 char uidstr[32], *tmp, *command = NULL, **av = NULL; 627 void (*osigchld)(int); 628 629 if (authoptsp != NULL) 630 *authoptsp = NULL; 631 if (options.authorized_keys_command == NULL) 632 return 0; 633 if (options.authorized_keys_command_user == NULL) { 634 error("No user for AuthorizedKeysCommand specified, skipping"); 635 return 0; 636 } 637 638 /* 639 * NB. all returns later this function should go via "out" to 640 * ensure the original SIGCHLD handler is restored properly. 641 */ 642 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 643 644 /* Prepare and verify the user for the command */ 645 username = percent_expand(options.authorized_keys_command_user, 646 "u", user_pw->pw_name, (char *)NULL); 647 runas_pw = getpwnam(username); 648 if (runas_pw == NULL) { 649 error("AuthorizedKeysCommandUser \"%s\" not found: %s", 650 username, strerror(errno)); 651 goto out; 652 } 653 654 /* Prepare AuthorizedKeysCommand */ 655 if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash, 656 SSH_FP_DEFAULT)) == NULL) { 657 error_f("sshkey_fingerprint failed"); 658 goto out; 659 } 660 if ((r = sshkey_to_base64(key, &keytext)) != 0) { 661 error_fr(r, "sshkey_to_base64 failed"); 662 goto out; 663 } 664 665 /* Turn the command into an argument vector */ 666 if (argv_split(options.authorized_keys_command, &ac, &av, 0) != 0) { 667 error("AuthorizedKeysCommand \"%s\" contains invalid quotes", 668 options.authorized_keys_command); 669 goto out; 670 } 671 if (ac == 0) { 672 error("AuthorizedKeysCommand \"%s\" yielded no arguments", 673 options.authorized_keys_command); 674 goto out; 675 } 676 snprintf(uidstr, sizeof(uidstr), "%llu", 677 (unsigned long long)user_pw->pw_uid); 678 for (i = 1; i < ac; i++) { 679 tmp = percent_expand(av[i], 680 "C", conn_id, 681 "D", rdomain, 682 "U", uidstr, 683 "u", user_pw->pw_name, 684 "h", user_pw->pw_dir, 685 "t", sshkey_ssh_name(key), 686 "f", key_fp, 687 "k", keytext, 688 (char *)NULL); 689 if (tmp == NULL) 690 fatal_f("percent_expand failed"); 691 free(av[i]); 692 av[i] = tmp; 693 } 694 /* Prepare a printable command for logs, etc. */ 695 command = argv_assemble(ac, av); 696 697 /* 698 * If AuthorizedKeysCommand was run without arguments 699 * then fall back to the old behaviour of passing the 700 * target username as a single argument. 701 */ 702 if (ac == 1) { 703 av = xreallocarray(av, ac + 2, sizeof(*av)); 704 av[1] = xstrdup(user_pw->pw_name); 705 av[2] = NULL; 706 /* Fix up command too, since it is used in log messages */ 707 free(command); 708 xasprintf(&command, "%s %s", av[0], av[1]); 709 } 710 711 if ((pid = subprocess("AuthorizedKeysCommand", command, 712 ac, av, &f, 713 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD, 714 runas_pw, temporarily_use_uid, restore_uid)) == 0) 715 goto out; 716 717 uid_swapped = 1; 718 temporarily_use_uid(runas_pw); 719 720 ok = auth_check_authkeys_file(user_pw, f, 721 options.authorized_keys_command, key, remote_ip, 722 remote_host, authoptsp); 723 724 fclose(f); 725 f = NULL; 726 727 if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0) 728 goto out; 729 730 /* Read completed successfully */ 731 found_key = ok; 732 out: 733 if (f != NULL) 734 fclose(f); 735 ssh_signal(SIGCHLD, osigchld); 736 for (i = 0; i < ac; i++) 737 free(av[i]); 738 free(av); 739 if (uid_swapped) 740 restore_uid(); 741 free(command); 742 free(username); 743 free(key_fp); 744 free(keytext); 745 return found_key; 746 } 747 748 /* 749 * Check whether key authenticates and authorises the user. 750 */ 751 int 752 user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key, 753 int auth_attempt, struct sshauthopt **authoptsp) 754 { 755 u_int success = 0, i; 756 char *file, *conn_id; 757 struct sshauthopt *opts = NULL; 758 const char *rdomain, *remote_ip, *remote_host; 759 760 if (authoptsp != NULL) 761 *authoptsp = NULL; 762 763 if (auth_key_is_revoked(key)) 764 return 0; 765 if (sshkey_is_cert(key) && 766 auth_key_is_revoked(key->cert->signature_key)) 767 return 0; 768 769 if ((rdomain = ssh_packet_rdomain_in(ssh)) == NULL) 770 rdomain = ""; 771 remote_ip = ssh_remote_ipaddr(ssh); 772 remote_host = auth_get_canonical_hostname(ssh, options.use_dns); 773 xasprintf(&conn_id, "%s %d %s %d", 774 ssh_local_ipaddr(ssh), ssh_local_port(ssh), 775 remote_ip, ssh_remote_port(ssh)); 776 777 for (i = 0; !success && i < options.num_authkeys_files; i++) { 778 if (strcasecmp(options.authorized_keys_files[i], "none") == 0) 779 continue; 780 file = expand_authorized_keys( 781 options.authorized_keys_files[i], pw); 782 success = user_key_allowed2(pw, key, file, 783 remote_ip, remote_host, &opts); 784 free(file); 785 if (!success) { 786 sshauthopt_free(opts); 787 opts = NULL; 788 } 789 } 790 if (success) 791 goto out; 792 793 if ((success = user_cert_trusted_ca(pw, key, remote_ip, remote_host, 794 conn_id, rdomain, &opts)) != 0) 795 goto out; 796 sshauthopt_free(opts); 797 opts = NULL; 798 799 if ((success = user_key_command_allowed2(pw, key, remote_ip, 800 remote_host, conn_id, rdomain, &opts)) != 0) 801 goto out; 802 sshauthopt_free(opts); 803 opts = NULL; 804 805 out: 806 free(conn_id); 807 if (success && authoptsp != NULL) { 808 *authoptsp = opts; 809 opts = NULL; 810 } 811 sshauthopt_free(opts); 812 return success; 813 } 814 815 Authmethod method_pubkey = { 816 "publickey", 817 "publickey-hostbound-v00@openssh.com", 818 userauth_pubkey, 819 &options.pubkey_authentication 820 }; 821