1 /* $OpenBSD: auth2-pubkey.c,v 1.120 2024/05/17 00:30:23 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 extern struct authmethod_cfg methodcfg_pubkey; 76 77 static char * 78 format_key(const struct sshkey *key) 79 { 80 char *ret, *fp = sshkey_fingerprint(key, 81 options.fingerprint_hash, SSH_FP_DEFAULT); 82 83 xasprintf(&ret, "%s %s", sshkey_type(key), fp); 84 free(fp); 85 return ret; 86 } 87 88 static int 89 userauth_pubkey(struct ssh *ssh, const char *method) 90 { 91 Authctxt *authctxt = ssh->authctxt; 92 struct passwd *pw = authctxt->pw; 93 struct sshbuf *b = NULL; 94 struct sshkey *key = NULL, *hostkey = NULL; 95 char *pkalg = NULL, *userstyle = NULL, *key_s = NULL, *ca_s = NULL; 96 u_char *pkblob = NULL, *sig = NULL, have_sig; 97 size_t blen, slen; 98 int hostbound, r, pktype; 99 int req_presence = 0, req_verify = 0, authenticated = 0; 100 struct sshauthopt *authopts = NULL; 101 struct sshkey_sig_details *sig_details = NULL; 102 103 hostbound = strcmp(method, "publickey-hostbound-v00@openssh.com") == 0; 104 105 if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0 || 106 (r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 || 107 (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0) 108 fatal_fr(r, "parse %s packet", method); 109 110 /* hostbound auth includes the hostkey offered at initial KEX */ 111 if (hostbound) { 112 if ((r = sshpkt_getb_froms(ssh, &b)) != 0 || 113 (r = sshkey_fromb(b, &hostkey)) != 0) 114 fatal_fr(r, "parse %s hostkey", method); 115 if (ssh->kex->initial_hostkey == NULL) 116 fatal_f("internal error: initial hostkey not recorded"); 117 if (!sshkey_equal(hostkey, ssh->kex->initial_hostkey)) 118 fatal_f("%s packet contained wrong host key", method); 119 sshbuf_free(b); 120 b = NULL; 121 } 122 123 if (log_level_get() >= SYSLOG_LEVEL_DEBUG2) { 124 char *keystring; 125 struct sshbuf *pkbuf; 126 127 if ((pkbuf = sshbuf_from(pkblob, blen)) == NULL) 128 fatal_f("sshbuf_from failed"); 129 if ((keystring = sshbuf_dtob64_string(pkbuf, 0)) == NULL) 130 fatal_f("sshbuf_dtob64 failed"); 131 debug2_f("%s user %s %s public key %s %s", 132 authctxt->valid ? "valid" : "invalid", authctxt->user, 133 have_sig ? "attempting" : "querying", pkalg, keystring); 134 sshbuf_free(pkbuf); 135 free(keystring); 136 } 137 138 pktype = sshkey_type_from_name(pkalg); 139 if (pktype == KEY_UNSPEC) { 140 /* this is perfectly legal */ 141 verbose_f("unsupported public key algorithm: %s", pkalg); 142 goto done; 143 } 144 if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) { 145 error_fr(r, "parse key"); 146 goto done; 147 } 148 if (key == NULL) { 149 error_f("cannot decode key: %s", pkalg); 150 goto done; 151 } 152 if (key->type != pktype) { 153 error_f("type mismatch for decoded key " 154 "(received %d, expected %d)", key->type, pktype); 155 goto done; 156 } 157 if (auth2_key_already_used(authctxt, key)) { 158 logit("refusing previously-used %s key", sshkey_type(key)); 159 goto done; 160 } 161 if (match_pattern_list(pkalg, options.pubkey_accepted_algos, 0) != 1) { 162 logit_f("signature algorithm %s not in " 163 "PubkeyAcceptedAlgorithms", pkalg); 164 goto done; 165 } 166 if ((r = sshkey_check_cert_sigtype(key, 167 options.ca_sign_algorithms)) != 0) { 168 logit_fr(r, "certificate signature algorithm %s", 169 (key->cert == NULL || key->cert->signature_type == NULL) ? 170 "(null)" : key->cert->signature_type); 171 goto done; 172 } 173 if ((r = sshkey_check_rsa_length(key, 174 options.required_rsa_size)) != 0) { 175 logit_r(r, "refusing %s key", sshkey_type(key)); 176 goto done; 177 } 178 key_s = format_key(key); 179 if (sshkey_is_cert(key)) 180 ca_s = format_key(key->cert->signature_key); 181 182 if (have_sig) { 183 debug3_f("%s have %s signature for %s%s%s", 184 method, pkalg, key_s, 185 ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s); 186 if ((r = sshpkt_get_string(ssh, &sig, &slen)) != 0 || 187 (r = sshpkt_get_end(ssh)) != 0) 188 fatal_fr(r, "parse signature packet"); 189 if ((b = sshbuf_new()) == NULL) 190 fatal_f("sshbuf_new failed"); 191 if (ssh->compat & SSH_OLD_SESSIONID) { 192 if ((r = sshbuf_putb(b, ssh->kex->session_id)) != 0) 193 fatal_fr(r, "put old session id"); 194 } else { 195 if ((r = sshbuf_put_stringb(b, 196 ssh->kex->session_id)) != 0) 197 fatal_fr(r, "put session id"); 198 } 199 if (!authctxt->valid || authctxt->user == NULL) { 200 debug2_f("disabled because of invalid user"); 201 goto done; 202 } 203 /* reconstruct packet */ 204 xasprintf(&userstyle, "%s%s%s", authctxt->user, 205 authctxt->style ? ":" : "", 206 authctxt->style ? authctxt->style : ""); 207 if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 || 208 (r = sshbuf_put_cstring(b, userstyle)) != 0 || 209 (r = sshbuf_put_cstring(b, authctxt->service)) != 0 || 210 (r = sshbuf_put_cstring(b, method)) != 0 || 211 (r = sshbuf_put_u8(b, have_sig)) != 0 || 212 (r = sshbuf_put_cstring(b, pkalg)) != 0 || 213 (r = sshbuf_put_string(b, pkblob, blen)) != 0) 214 fatal_fr(r, "reconstruct %s packet", method); 215 if (hostbound && 216 (r = sshkey_puts(ssh->kex->initial_hostkey, b)) != 0) 217 fatal_fr(r, "reconstruct %s packet", method); 218 #ifdef DEBUG_PK 219 sshbuf_dump(b, stderr); 220 #endif 221 /* test for correct signature */ 222 authenticated = 0; 223 if (mm_user_key_allowed(ssh, pw, key, 1, &authopts) && 224 mm_sshkey_verify(key, sig, slen, 225 sshbuf_ptr(b), sshbuf_len(b), 226 (ssh->compat & SSH_BUG_SIGTYPE) == 0 ? pkalg : NULL, 227 ssh->compat, &sig_details) == 0) { 228 authenticated = 1; 229 } 230 if (authenticated == 1 && sig_details != NULL) { 231 auth2_record_info(authctxt, "signature count = %u", 232 sig_details->sk_counter); 233 debug_f("sk_counter = %u, sk_flags = 0x%02x", 234 sig_details->sk_counter, sig_details->sk_flags); 235 req_presence = (options.pubkey_auth_options & 236 PUBKEYAUTH_TOUCH_REQUIRED) || 237 !authopts->no_require_user_presence; 238 if (req_presence && (sig_details->sk_flags & 239 SSH_SK_USER_PRESENCE_REQD) == 0) { 240 error("public key %s signature for %s%s from " 241 "%.128s port %d rejected: user presence " 242 "(authenticator touch) requirement " 243 "not met ", key_s, 244 authctxt->valid ? "" : "invalid user ", 245 authctxt->user, ssh_remote_ipaddr(ssh), 246 ssh_remote_port(ssh)); 247 authenticated = 0; 248 goto done; 249 } 250 req_verify = (options.pubkey_auth_options & 251 PUBKEYAUTH_VERIFY_REQUIRED) || 252 authopts->require_verify; 253 if (req_verify && (sig_details->sk_flags & 254 SSH_SK_USER_VERIFICATION_REQD) == 0) { 255 error("public key %s signature for %s%s from " 256 "%.128s port %d rejected: user " 257 "verification requirement not met ", key_s, 258 authctxt->valid ? "" : "invalid user ", 259 authctxt->user, ssh_remote_ipaddr(ssh), 260 ssh_remote_port(ssh)); 261 authenticated = 0; 262 goto done; 263 } 264 } 265 auth2_record_key(authctxt, authenticated, key); 266 } else { 267 debug_f("%s test pkalg %s pkblob %s%s%s", method, pkalg, key_s, 268 ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s); 269 270 if ((r = sshpkt_get_end(ssh)) != 0) 271 fatal_fr(r, "parse packet"); 272 273 if (!authctxt->valid || authctxt->user == NULL) { 274 debug2_f("disabled because of invalid user"); 275 goto done; 276 } 277 /* XXX fake reply and always send PK_OK ? */ 278 /* 279 * XXX this allows testing whether a user is allowed 280 * to login: if you happen to have a valid pubkey this 281 * message is sent. the message is NEVER sent at all 282 * if a user is not allowed to login. is this an 283 * issue? -markus 284 */ 285 if (mm_user_key_allowed(ssh, pw, key, 0, NULL)) { 286 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_PK_OK)) 287 != 0 || 288 (r = sshpkt_put_cstring(ssh, pkalg)) != 0 || 289 (r = sshpkt_put_string(ssh, pkblob, blen)) != 0 || 290 (r = sshpkt_send(ssh)) != 0 || 291 (r = ssh_packet_write_wait(ssh)) != 0) 292 fatal_fr(r, "send packet"); 293 authctxt->postponed = 1; 294 } 295 } 296 done: 297 if (authenticated == 1 && auth_activate_options(ssh, authopts) != 0) { 298 debug_f("key options inconsistent with existing"); 299 authenticated = 0; 300 } 301 debug2_f("authenticated %d pkalg %s", authenticated, pkalg); 302 303 sshbuf_free(b); 304 sshauthopt_free(authopts); 305 sshkey_free(key); 306 sshkey_free(hostkey); 307 free(userstyle); 308 free(pkalg); 309 free(pkblob); 310 free(key_s); 311 free(ca_s); 312 free(sig); 313 sshkey_sig_details_free(sig_details); 314 return authenticated; 315 } 316 317 static int 318 match_principals_file(struct passwd *pw, char *file, 319 struct sshkey_cert *cert, struct sshauthopt **authoptsp) 320 { 321 FILE *f; 322 int success; 323 324 if (authoptsp != NULL) 325 *authoptsp = NULL; 326 327 temporarily_use_uid(pw); 328 debug("trying authorized principals file %s", file); 329 if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) { 330 restore_uid(); 331 return 0; 332 } 333 success = auth_process_principals(f, file, cert, authoptsp); 334 fclose(f); 335 restore_uid(); 336 return success; 337 } 338 339 /* 340 * Checks whether principal is allowed in output of command. 341 * returns 1 if the principal is allowed or 0 otherwise. 342 */ 343 static int 344 match_principals_command(struct passwd *user_pw, const struct sshkey *key, 345 const char *conn_id, const char *rdomain, struct sshauthopt **authoptsp) 346 { 347 struct passwd *runas_pw = NULL; 348 const struct sshkey_cert *cert = key->cert; 349 FILE *f = NULL; 350 int r, ok, found_principal = 0; 351 int i, ac = 0, uid_swapped = 0; 352 pid_t pid; 353 char *tmp, *username = NULL, *command = NULL, **av = NULL; 354 char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL; 355 char serial_s[32], uidstr[32]; 356 void (*osigchld)(int); 357 358 if (authoptsp != NULL) 359 *authoptsp = NULL; 360 if (options.authorized_principals_command == NULL) 361 return 0; 362 if (options.authorized_principals_command_user == NULL) { 363 error("No user for AuthorizedPrincipalsCommand specified, " 364 "skipping"); 365 return 0; 366 } 367 368 /* 369 * NB. all returns later this function should go via "out" to 370 * ensure the original SIGCHLD handler is restored properly. 371 */ 372 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 373 374 /* Prepare and verify the user for the command */ 375 username = percent_expand(options.authorized_principals_command_user, 376 "u", user_pw->pw_name, (char *)NULL); 377 runas_pw = getpwnam(username); 378 if (runas_pw == NULL) { 379 error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s", 380 username, strerror(errno)); 381 goto out; 382 } 383 384 /* Turn the command into an argument vector */ 385 if (argv_split(options.authorized_principals_command, 386 &ac, &av, 0) != 0) { 387 error("AuthorizedPrincipalsCommand \"%s\" contains " 388 "invalid quotes", options.authorized_principals_command); 389 goto out; 390 } 391 if (ac == 0) { 392 error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments", 393 options.authorized_principals_command); 394 goto out; 395 } 396 if ((ca_fp = sshkey_fingerprint(cert->signature_key, 397 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 398 error_f("sshkey_fingerprint failed"); 399 goto out; 400 } 401 if ((key_fp = sshkey_fingerprint(key, 402 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 403 error_f("sshkey_fingerprint failed"); 404 goto out; 405 } 406 if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) { 407 error_fr(r, "sshkey_to_base64 failed"); 408 goto out; 409 } 410 if ((r = sshkey_to_base64(key, &keytext)) != 0) { 411 error_fr(r, "sshkey_to_base64 failed"); 412 goto out; 413 } 414 snprintf(serial_s, sizeof(serial_s), "%llu", 415 (unsigned long long)cert->serial); 416 snprintf(uidstr, sizeof(uidstr), "%llu", 417 (unsigned long long)user_pw->pw_uid); 418 for (i = 1; i < ac; i++) { 419 tmp = percent_expand(av[i], 420 "C", conn_id, 421 "D", rdomain, 422 "U", uidstr, 423 "u", user_pw->pw_name, 424 "h", user_pw->pw_dir, 425 "t", sshkey_ssh_name(key), 426 "T", sshkey_ssh_name(cert->signature_key), 427 "f", key_fp, 428 "F", ca_fp, 429 "k", keytext, 430 "K", catext, 431 "i", cert->key_id, 432 "s", serial_s, 433 (char *)NULL); 434 if (tmp == NULL) 435 fatal_f("percent_expand failed"); 436 free(av[i]); 437 av[i] = tmp; 438 } 439 /* Prepare a printable command for logs, etc. */ 440 command = argv_assemble(ac, av); 441 442 if ((pid = subprocess("AuthorizedPrincipalsCommand", command, 443 ac, av, &f, 444 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD, 445 runas_pw, temporarily_use_uid, restore_uid)) == 0) 446 goto out; 447 448 uid_swapped = 1; 449 temporarily_use_uid(runas_pw); 450 451 ok = auth_process_principals(f, "(command)", cert, authoptsp); 452 453 fclose(f); 454 f = NULL; 455 456 if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0) 457 goto out; 458 459 /* Read completed successfully */ 460 found_principal = ok; 461 out: 462 if (f != NULL) 463 fclose(f); 464 ssh_signal(SIGCHLD, osigchld); 465 for (i = 0; i < ac; i++) 466 free(av[i]); 467 free(av); 468 if (uid_swapped) 469 restore_uid(); 470 free(command); 471 free(username); 472 free(ca_fp); 473 free(key_fp); 474 free(catext); 475 free(keytext); 476 return found_principal; 477 } 478 479 /* Authenticate a certificate key against TrustedUserCAKeys */ 480 static int 481 user_cert_trusted_ca(struct passwd *pw, struct sshkey *key, 482 const char *remote_ip, const char *remote_host, 483 const char *conn_id, const char *rdomain, struct sshauthopt **authoptsp) 484 { 485 char *ca_fp, *principals_file = NULL; 486 const char *reason; 487 struct sshauthopt *principals_opts = NULL, *cert_opts = NULL; 488 struct sshauthopt *final_opts = NULL; 489 int r, ret = 0, found_principal = 0, use_authorized_principals; 490 491 if (authoptsp != NULL) 492 *authoptsp = NULL; 493 494 if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL) 495 return 0; 496 497 if ((ca_fp = sshkey_fingerprint(key->cert->signature_key, 498 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 499 return 0; 500 501 if ((r = sshkey_in_file(key->cert->signature_key, 502 options.trusted_user_ca_keys, 1, 0)) != 0) { 503 debug2_fr(r, "CA %s %s is not listed in %s", 504 sshkey_type(key->cert->signature_key), ca_fp, 505 options.trusted_user_ca_keys); 506 goto out; 507 } 508 /* 509 * If AuthorizedPrincipals is in use, then compare the certificate 510 * principals against the names in that file rather than matching 511 * against the username. 512 */ 513 if ((principals_file = authorized_principals_file(pw)) != NULL) { 514 if (match_principals_file(pw, principals_file, 515 key->cert, &principals_opts)) 516 found_principal = 1; 517 } 518 /* Try querying command if specified */ 519 if (!found_principal && match_principals_command(pw, key, 520 conn_id, rdomain, &principals_opts)) 521 found_principal = 1; 522 /* If principals file or command is specified, then require a match */ 523 use_authorized_principals = principals_file != NULL || 524 options.authorized_principals_command != NULL; 525 if (!found_principal && use_authorized_principals) { 526 reason = "Certificate does not contain an authorized principal"; 527 goto fail_reason; 528 } 529 if (use_authorized_principals && principals_opts == NULL) 530 fatal_f("internal error: missing principals_opts"); 531 if (sshkey_cert_check_authority_now(key, 0, 1, 0, 532 use_authorized_principals ? NULL : pw->pw_name, &reason) != 0) 533 goto fail_reason; 534 535 /* Check authority from options in key and from principals file/cmd */ 536 if ((cert_opts = sshauthopt_from_cert(key)) == NULL) { 537 reason = "Invalid certificate options"; 538 goto fail_reason; 539 } 540 if (auth_authorise_keyopts(pw, cert_opts, 0, 541 remote_ip, remote_host, "cert") != 0) { 542 reason = "Refused by certificate options"; 543 goto fail_reason; 544 } 545 if (principals_opts == NULL) { 546 final_opts = cert_opts; 547 cert_opts = NULL; 548 } else { 549 if (auth_authorise_keyopts(pw, principals_opts, 0, 550 remote_ip, remote_host, "principals") != 0) { 551 reason = "Refused by certificate principals options"; 552 goto fail_reason; 553 } 554 if ((final_opts = sshauthopt_merge(principals_opts, 555 cert_opts, &reason)) == NULL) { 556 fail_reason: 557 error("%s", reason); 558 auth_debug_add("%s", reason); 559 goto out; 560 } 561 } 562 563 /* Success */ 564 verbose("Accepted certificate ID \"%s\" (serial %llu) signed by " 565 "%s CA %s via %s", key->cert->key_id, 566 (unsigned long long)key->cert->serial, 567 sshkey_type(key->cert->signature_key), ca_fp, 568 options.trusted_user_ca_keys); 569 if (authoptsp != NULL) { 570 *authoptsp = final_opts; 571 final_opts = NULL; 572 } 573 ret = 1; 574 out: 575 sshauthopt_free(principals_opts); 576 sshauthopt_free(cert_opts); 577 sshauthopt_free(final_opts); 578 free(principals_file); 579 free(ca_fp); 580 return ret; 581 } 582 583 /* 584 * Checks whether key is allowed in file. 585 * returns 1 if the key is allowed or 0 otherwise. 586 */ 587 static int 588 user_key_allowed2(struct passwd *pw, struct sshkey *key, 589 char *file, const char *remote_ip, const char *remote_host, 590 struct sshauthopt **authoptsp) 591 { 592 FILE *f; 593 int found_key = 0; 594 595 if (authoptsp != NULL) 596 *authoptsp = NULL; 597 598 /* Temporarily use the user's uid. */ 599 temporarily_use_uid(pw); 600 601 debug("trying public key file %s", file); 602 if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) { 603 found_key = auth_check_authkeys_file(pw, f, file, 604 key, remote_ip, remote_host, authoptsp); 605 fclose(f); 606 } 607 608 restore_uid(); 609 return found_key; 610 } 611 612 /* 613 * Checks whether key is allowed in output of command. 614 * returns 1 if the key is allowed or 0 otherwise. 615 */ 616 static int 617 user_key_command_allowed2(struct passwd *user_pw, struct sshkey *key, 618 const char *remote_ip, const char *remote_host, 619 const char *conn_id, const char *rdomain, struct sshauthopt **authoptsp) 620 { 621 struct passwd *runas_pw = NULL; 622 FILE *f = NULL; 623 int r, ok, found_key = 0; 624 int i, uid_swapped = 0, ac = 0; 625 pid_t pid; 626 char *username = NULL, *key_fp = NULL, *keytext = NULL; 627 char uidstr[32], *tmp, *command = NULL, **av = NULL; 628 void (*osigchld)(int); 629 630 if (authoptsp != NULL) 631 *authoptsp = NULL; 632 if (options.authorized_keys_command == NULL) 633 return 0; 634 if (options.authorized_keys_command_user == NULL) { 635 error("No user for AuthorizedKeysCommand specified, skipping"); 636 return 0; 637 } 638 639 /* 640 * NB. all returns later this function should go via "out" to 641 * ensure the original SIGCHLD handler is restored properly. 642 */ 643 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 644 645 /* Prepare and verify the user for the command */ 646 username = percent_expand(options.authorized_keys_command_user, 647 "u", user_pw->pw_name, (char *)NULL); 648 runas_pw = getpwnam(username); 649 if (runas_pw == NULL) { 650 error("AuthorizedKeysCommandUser \"%s\" not found: %s", 651 username, strerror(errno)); 652 goto out; 653 } 654 655 /* Prepare AuthorizedKeysCommand */ 656 if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash, 657 SSH_FP_DEFAULT)) == NULL) { 658 error_f("sshkey_fingerprint failed"); 659 goto out; 660 } 661 if ((r = sshkey_to_base64(key, &keytext)) != 0) { 662 error_fr(r, "sshkey_to_base64 failed"); 663 goto out; 664 } 665 666 /* Turn the command into an argument vector */ 667 if (argv_split(options.authorized_keys_command, &ac, &av, 0) != 0) { 668 error("AuthorizedKeysCommand \"%s\" contains invalid quotes", 669 options.authorized_keys_command); 670 goto out; 671 } 672 if (ac == 0) { 673 error("AuthorizedKeysCommand \"%s\" yielded no arguments", 674 options.authorized_keys_command); 675 goto out; 676 } 677 snprintf(uidstr, sizeof(uidstr), "%llu", 678 (unsigned long long)user_pw->pw_uid); 679 for (i = 1; i < ac; i++) { 680 tmp = percent_expand(av[i], 681 "C", conn_id, 682 "D", rdomain, 683 "U", uidstr, 684 "u", user_pw->pw_name, 685 "h", user_pw->pw_dir, 686 "t", sshkey_ssh_name(key), 687 "f", key_fp, 688 "k", keytext, 689 (char *)NULL); 690 if (tmp == NULL) 691 fatal_f("percent_expand failed"); 692 free(av[i]); 693 av[i] = tmp; 694 } 695 /* Prepare a printable command for logs, etc. */ 696 command = argv_assemble(ac, av); 697 698 /* 699 * If AuthorizedKeysCommand was run without arguments 700 * then fall back to the old behaviour of passing the 701 * target username as a single argument. 702 */ 703 if (ac == 1) { 704 av = xreallocarray(av, ac + 2, sizeof(*av)); 705 av[1] = xstrdup(user_pw->pw_name); 706 av[2] = NULL; 707 /* Fix up command too, since it is used in log messages */ 708 free(command); 709 xasprintf(&command, "%s %s", av[0], av[1]); 710 } 711 712 if ((pid = subprocess("AuthorizedKeysCommand", command, 713 ac, av, &f, 714 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD, 715 runas_pw, temporarily_use_uid, restore_uid)) == 0) 716 goto out; 717 718 uid_swapped = 1; 719 temporarily_use_uid(runas_pw); 720 721 ok = auth_check_authkeys_file(user_pw, f, 722 options.authorized_keys_command, key, remote_ip, 723 remote_host, authoptsp); 724 725 fclose(f); 726 f = NULL; 727 728 if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0) 729 goto out; 730 731 /* Read completed successfully */ 732 found_key = ok; 733 out: 734 if (f != NULL) 735 fclose(f); 736 ssh_signal(SIGCHLD, osigchld); 737 for (i = 0; i < ac; i++) 738 free(av[i]); 739 free(av); 740 if (uid_swapped) 741 restore_uid(); 742 free(command); 743 free(username); 744 free(key_fp); 745 free(keytext); 746 return found_key; 747 } 748 749 /* 750 * Check whether key authenticates and authorises the user. 751 */ 752 int 753 user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key, 754 int auth_attempt, struct sshauthopt **authoptsp) 755 { 756 u_int success = 0, i; 757 char *file, *conn_id; 758 struct sshauthopt *opts = NULL; 759 const char *rdomain, *remote_ip, *remote_host; 760 761 if (authoptsp != NULL) 762 *authoptsp = NULL; 763 764 if (auth_key_is_revoked(key)) 765 return 0; 766 if (sshkey_is_cert(key) && 767 auth_key_is_revoked(key->cert->signature_key)) 768 return 0; 769 770 if ((rdomain = ssh_packet_rdomain_in(ssh)) == NULL) 771 rdomain = ""; 772 remote_ip = ssh_remote_ipaddr(ssh); 773 remote_host = auth_get_canonical_hostname(ssh, options.use_dns); 774 xasprintf(&conn_id, "%s %d %s %d", 775 ssh_local_ipaddr(ssh), ssh_local_port(ssh), 776 remote_ip, ssh_remote_port(ssh)); 777 778 for (i = 0; !success && i < options.num_authkeys_files; i++) { 779 if (strcasecmp(options.authorized_keys_files[i], "none") == 0) 780 continue; 781 file = expand_authorized_keys( 782 options.authorized_keys_files[i], pw); 783 success = user_key_allowed2(pw, key, file, 784 remote_ip, remote_host, &opts); 785 free(file); 786 if (!success) { 787 sshauthopt_free(opts); 788 opts = NULL; 789 } 790 } 791 if (success) 792 goto out; 793 794 if ((success = user_cert_trusted_ca(pw, key, remote_ip, remote_host, 795 conn_id, rdomain, &opts)) != 0) 796 goto out; 797 sshauthopt_free(opts); 798 opts = NULL; 799 800 if ((success = user_key_command_allowed2(pw, key, remote_ip, 801 remote_host, conn_id, rdomain, &opts)) != 0) 802 goto out; 803 sshauthopt_free(opts); 804 opts = NULL; 805 806 out: 807 free(conn_id); 808 if (success && authoptsp != NULL) { 809 *authoptsp = opts; 810 opts = NULL; 811 } 812 sshauthopt_free(opts); 813 return success; 814 } 815 816 Authmethod method_pubkey = { 817 &methodcfg_pubkey, 818 userauth_pubkey, 819 }; 820