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 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 extern struct authmethod_cfg methodcfg_pubkey; 73 74 static char * 75 format_key(const struct sshkey *key) 76 { 77 char *ret, *fp = sshkey_fingerprint(key, 78 options.fingerprint_hash, SSH_FP_DEFAULT); 79 80 xasprintf(&ret, "%s %s", sshkey_type(key), fp); 81 free(fp); 82 return ret; 83 } 84 85 static int 86 userauth_pubkey(struct ssh *ssh, const char *method) 87 { 88 Authctxt *authctxt = ssh->authctxt; 89 struct passwd *pw = authctxt->pw; 90 struct sshbuf *b = NULL; 91 struct sshkey *key = NULL, *hostkey = NULL; 92 char *pkalg = NULL, *userstyle = NULL, *key_s = NULL, *ca_s = NULL; 93 u_char *pkblob = NULL, *sig = NULL, have_sig; 94 size_t blen, slen; 95 int hostbound, r, pktype; 96 int req_presence = 0, req_verify = 0, authenticated = 0; 97 struct sshauthopt *authopts = NULL; 98 struct sshkey_sig_details *sig_details = NULL; 99 100 hostbound = strcmp(method, "publickey-hostbound-v00@openssh.com") == 0; 101 102 if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0 || 103 (r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 || 104 (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0) 105 fatal_fr(r, "parse %s packet", method); 106 107 /* hostbound auth includes the hostkey offered at initial KEX */ 108 if (hostbound) { 109 if ((r = sshpkt_getb_froms(ssh, &b)) != 0 || 110 (r = sshkey_fromb(b, &hostkey)) != 0) 111 fatal_fr(r, "parse %s hostkey", method); 112 if (ssh->kex->initial_hostkey == NULL) 113 fatal_f("internal error: initial hostkey not recorded"); 114 if (!sshkey_equal(hostkey, ssh->kex->initial_hostkey)) 115 fatal_f("%s packet contained wrong host key", method); 116 sshbuf_free(b); 117 b = NULL; 118 } 119 120 if (log_level_get() >= SYSLOG_LEVEL_DEBUG2) { 121 char *keystring; 122 struct sshbuf *pkbuf; 123 124 if ((pkbuf = sshbuf_from(pkblob, blen)) == NULL) 125 fatal_f("sshbuf_from failed"); 126 if ((keystring = sshbuf_dtob64_string(pkbuf, 0)) == NULL) 127 fatal_f("sshbuf_dtob64 failed"); 128 debug2_f("%s user %s %s public key %s %s", 129 authctxt->valid ? "valid" : "invalid", authctxt->user, 130 have_sig ? "attempting" : "querying", pkalg, keystring); 131 sshbuf_free(pkbuf); 132 free(keystring); 133 } 134 135 pktype = sshkey_type_from_name(pkalg); 136 if (pktype == KEY_UNSPEC) { 137 /* this is perfectly legal */ 138 verbose_f("unsupported public key algorithm: %s", pkalg); 139 goto done; 140 } 141 if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) { 142 error_fr(r, "parse key"); 143 goto done; 144 } 145 if (key == NULL) { 146 error_f("cannot decode key: %s", pkalg); 147 goto done; 148 } 149 if (key->type != pktype) { 150 error_f("type mismatch for decoded key " 151 "(received %d, expected %d)", key->type, pktype); 152 goto done; 153 } 154 if (auth2_key_already_used(authctxt, key)) { 155 logit("refusing previously-used %s key", sshkey_type(key)); 156 goto done; 157 } 158 if (match_pattern_list(pkalg, options.pubkey_accepted_algos, 0) != 1) { 159 logit_f("signature algorithm %s not in " 160 "PubkeyAcceptedAlgorithms", pkalg); 161 goto done; 162 } 163 if ((r = sshkey_check_cert_sigtype(key, 164 options.ca_sign_algorithms)) != 0) { 165 logit_fr(r, "certificate signature algorithm %s", 166 (key->cert == NULL || key->cert->signature_type == NULL) ? 167 "(null)" : key->cert->signature_type); 168 goto done; 169 } 170 if ((r = sshkey_check_rsa_length(key, 171 options.required_rsa_size)) != 0) { 172 logit_r(r, "refusing %s key", sshkey_type(key)); 173 goto done; 174 } 175 key_s = format_key(key); 176 if (sshkey_is_cert(key)) 177 ca_s = format_key(key->cert->signature_key); 178 179 if (have_sig) { 180 debug3_f("%s have %s signature for %s%s%s", 181 method, pkalg, key_s, 182 ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s); 183 if ((r = sshpkt_get_string(ssh, &sig, &slen)) != 0 || 184 (r = sshpkt_get_end(ssh)) != 0) 185 fatal_fr(r, "parse signature packet"); 186 if ((b = sshbuf_new()) == NULL) 187 fatal_f("sshbuf_new failed"); 188 if (ssh->compat & SSH_OLD_SESSIONID) { 189 if ((r = sshbuf_putb(b, ssh->kex->session_id)) != 0) 190 fatal_fr(r, "put old session id"); 191 } else { 192 if ((r = sshbuf_put_stringb(b, 193 ssh->kex->session_id)) != 0) 194 fatal_fr(r, "put session id"); 195 } 196 if (!authctxt->valid || authctxt->user == NULL) { 197 debug2_f("disabled because of invalid user"); 198 goto done; 199 } 200 /* reconstruct packet */ 201 xasprintf(&userstyle, "%s%s%s", authctxt->user, 202 authctxt->style ? ":" : "", 203 authctxt->style ? authctxt->style : ""); 204 if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 || 205 (r = sshbuf_put_cstring(b, userstyle)) != 0 || 206 (r = sshbuf_put_cstring(b, authctxt->service)) != 0 || 207 (r = sshbuf_put_cstring(b, method)) != 0 || 208 (r = sshbuf_put_u8(b, have_sig)) != 0 || 209 (r = sshbuf_put_cstring(b, pkalg)) != 0 || 210 (r = sshbuf_put_string(b, pkblob, blen)) != 0) 211 fatal_fr(r, "reconstruct %s packet", method); 212 if (hostbound && 213 (r = sshkey_puts(ssh->kex->initial_hostkey, b)) != 0) 214 fatal_fr(r, "reconstruct %s packet", method); 215 #ifdef DEBUG_PK 216 sshbuf_dump(b, stderr); 217 #endif 218 /* test for correct signature */ 219 authenticated = 0; 220 if (mm_user_key_allowed(ssh, pw, key, 1, &authopts) && 221 mm_sshkey_verify(key, sig, slen, 222 sshbuf_ptr(b), sshbuf_len(b), 223 (ssh->compat & SSH_BUG_SIGTYPE) == 0 ? pkalg : NULL, 224 ssh->compat, &sig_details) == 0) { 225 authenticated = 1; 226 } 227 if (authenticated == 1 && sig_details != NULL) { 228 auth2_record_info(authctxt, "signature count = %u", 229 sig_details->sk_counter); 230 debug_f("sk_counter = %u, sk_flags = 0x%02x", 231 sig_details->sk_counter, sig_details->sk_flags); 232 req_presence = (options.pubkey_auth_options & 233 PUBKEYAUTH_TOUCH_REQUIRED) || 234 !authopts->no_require_user_presence; 235 if (req_presence && (sig_details->sk_flags & 236 SSH_SK_USER_PRESENCE_REQD) == 0) { 237 error("public key %s signature for %s%s from " 238 "%.128s port %d rejected: user presence " 239 "(authenticator touch) requirement " 240 "not met ", key_s, 241 authctxt->valid ? "" : "invalid user ", 242 authctxt->user, ssh_remote_ipaddr(ssh), 243 ssh_remote_port(ssh)); 244 authenticated = 0; 245 goto done; 246 } 247 req_verify = (options.pubkey_auth_options & 248 PUBKEYAUTH_VERIFY_REQUIRED) || 249 authopts->require_verify; 250 if (req_verify && (sig_details->sk_flags & 251 SSH_SK_USER_VERIFICATION_REQD) == 0) { 252 error("public key %s signature for %s%s from " 253 "%.128s port %d rejected: user " 254 "verification requirement not met ", key_s, 255 authctxt->valid ? "" : "invalid user ", 256 authctxt->user, ssh_remote_ipaddr(ssh), 257 ssh_remote_port(ssh)); 258 authenticated = 0; 259 goto done; 260 } 261 } 262 auth2_record_key(authctxt, authenticated, key); 263 } else { 264 debug_f("%s test pkalg %s pkblob %s%s%s", method, pkalg, key_s, 265 ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s); 266 267 if ((r = sshpkt_get_end(ssh)) != 0) 268 fatal_fr(r, "parse packet"); 269 270 if (!authctxt->valid || authctxt->user == NULL) { 271 debug2_f("disabled because of invalid user"); 272 goto done; 273 } 274 /* XXX fake reply and always send PK_OK ? */ 275 /* 276 * XXX this allows testing whether a user is allowed 277 * to login: if you happen to have a valid pubkey this 278 * message is sent. the message is NEVER sent at all 279 * if a user is not allowed to login. is this an 280 * issue? -markus 281 */ 282 if (mm_user_key_allowed(ssh, pw, key, 0, NULL)) { 283 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_PK_OK)) 284 != 0 || 285 (r = sshpkt_put_cstring(ssh, pkalg)) != 0 || 286 (r = sshpkt_put_string(ssh, pkblob, blen)) != 0 || 287 (r = sshpkt_send(ssh)) != 0 || 288 (r = ssh_packet_write_wait(ssh)) != 0) 289 fatal_fr(r, "send packet"); 290 authctxt->postponed = 1; 291 } 292 } 293 done: 294 if (authenticated == 1 && auth_activate_options(ssh, authopts) != 0) { 295 debug_f("key options inconsistent with existing"); 296 authenticated = 0; 297 } 298 debug2_f("authenticated %d pkalg %s", authenticated, pkalg); 299 300 sshbuf_free(b); 301 sshauthopt_free(authopts); 302 sshkey_free(key); 303 sshkey_free(hostkey); 304 free(userstyle); 305 free(pkalg); 306 free(pkblob); 307 free(key_s); 308 free(ca_s); 309 free(sig); 310 sshkey_sig_details_free(sig_details); 311 return authenticated; 312 } 313 314 static int 315 match_principals_file(struct passwd *pw, char *file, 316 struct sshkey_cert *cert, struct sshauthopt **authoptsp) 317 { 318 FILE *f; 319 int success; 320 321 if (authoptsp != NULL) 322 *authoptsp = NULL; 323 324 temporarily_use_uid(pw); 325 debug("trying authorized principals file %s", file); 326 if ((f = auth_openprincipals(file, pw, options.strict_modes)) == NULL) { 327 restore_uid(); 328 return 0; 329 } 330 success = auth_process_principals(f, file, cert, authoptsp); 331 fclose(f); 332 restore_uid(); 333 return success; 334 } 335 336 /* 337 * Checks whether principal is allowed in output of command. 338 * returns 1 if the principal is allowed or 0 otherwise. 339 */ 340 static int 341 match_principals_command(struct passwd *user_pw, const struct sshkey *key, 342 const char *conn_id, const char *rdomain, struct sshauthopt **authoptsp) 343 { 344 struct passwd *runas_pw = NULL; 345 const struct sshkey_cert *cert = key->cert; 346 FILE *f = NULL; 347 int r, ok, found_principal = 0; 348 int i, ac = 0, uid_swapped = 0; 349 pid_t pid; 350 char *tmp, *username = NULL, *command = NULL, **av = NULL; 351 char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL; 352 char serial_s[32], uidstr[32]; 353 void (*osigchld)(int); 354 355 if (authoptsp != NULL) 356 *authoptsp = NULL; 357 if (options.authorized_principals_command == NULL) 358 return 0; 359 if (options.authorized_principals_command_user == NULL) { 360 error("No user for AuthorizedPrincipalsCommand specified, " 361 "skipping"); 362 return 0; 363 } 364 365 /* 366 * NB. all returns later this function should go via "out" to 367 * ensure the original SIGCHLD handler is restored properly. 368 */ 369 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 370 371 /* Prepare and verify the user for the command */ 372 username = percent_expand(options.authorized_principals_command_user, 373 "u", user_pw->pw_name, (char *)NULL); 374 runas_pw = getpwnam(username); 375 if (runas_pw == NULL) { 376 error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s", 377 username, strerror(errno)); 378 goto out; 379 } 380 381 /* Turn the command into an argument vector */ 382 if (argv_split(options.authorized_principals_command, 383 &ac, &av, 0) != 0) { 384 error("AuthorizedPrincipalsCommand \"%s\" contains " 385 "invalid quotes", options.authorized_principals_command); 386 goto out; 387 } 388 if (ac == 0) { 389 error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments", 390 options.authorized_principals_command); 391 goto out; 392 } 393 if ((ca_fp = sshkey_fingerprint(cert->signature_key, 394 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 395 error_f("sshkey_fingerprint failed"); 396 goto out; 397 } 398 if ((key_fp = sshkey_fingerprint(key, 399 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 400 error_f("sshkey_fingerprint failed"); 401 goto out; 402 } 403 if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) { 404 error_fr(r, "sshkey_to_base64 failed"); 405 goto out; 406 } 407 if ((r = sshkey_to_base64(key, &keytext)) != 0) { 408 error_fr(r, "sshkey_to_base64 failed"); 409 goto out; 410 } 411 snprintf(serial_s, sizeof(serial_s), "%llu", 412 (unsigned long long)cert->serial); 413 snprintf(uidstr, sizeof(uidstr), "%llu", 414 (unsigned long long)user_pw->pw_uid); 415 for (i = 1; i < ac; i++) { 416 tmp = percent_expand(av[i], 417 "C", conn_id, 418 "D", rdomain, 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 const char *conn_id, const char *rdomain, 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 conn_id, rdomain, &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 const char *conn_id, const char *rdomain, 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 "C", conn_id, 679 "D", rdomain, 680 "U", uidstr, 681 "u", user_pw->pw_name, 682 "h", user_pw->pw_dir, 683 "t", sshkey_ssh_name(key), 684 "f", key_fp, 685 "k", keytext, 686 (char *)NULL); 687 if (tmp == NULL) 688 fatal_f("percent_expand failed"); 689 free(av[i]); 690 av[i] = tmp; 691 } 692 /* Prepare a printable command for logs, etc. */ 693 command = argv_assemble(ac, av); 694 695 /* 696 * If AuthorizedKeysCommand was run without arguments 697 * then fall back to the old behaviour of passing the 698 * target username as a single argument. 699 */ 700 if (ac == 1) { 701 av = xreallocarray(av, ac + 2, sizeof(*av)); 702 av[1] = xstrdup(user_pw->pw_name); 703 av[2] = NULL; 704 /* Fix up command too, since it is used in log messages */ 705 free(command); 706 xasprintf(&command, "%s %s", av[0], av[1]); 707 } 708 709 if ((pid = subprocess("AuthorizedKeysCommand", command, 710 ac, av, &f, 711 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD, 712 runas_pw, temporarily_use_uid, restore_uid)) == 0) 713 goto out; 714 715 uid_swapped = 1; 716 temporarily_use_uid(runas_pw); 717 718 ok = auth_check_authkeys_file(user_pw, f, 719 options.authorized_keys_command, key, remote_ip, 720 remote_host, authoptsp); 721 722 fclose(f); 723 f = NULL; 724 725 if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0) 726 goto out; 727 728 /* Read completed successfully */ 729 found_key = ok; 730 out: 731 if (f != NULL) 732 fclose(f); 733 ssh_signal(SIGCHLD, osigchld); 734 for (i = 0; i < ac; i++) 735 free(av[i]); 736 free(av); 737 if (uid_swapped) 738 restore_uid(); 739 free(command); 740 free(username); 741 free(key_fp); 742 free(keytext); 743 return found_key; 744 } 745 746 /* 747 * Check whether key authenticates and authorises the user. 748 */ 749 int 750 user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key, 751 int auth_attempt, struct sshauthopt **authoptsp) 752 { 753 u_int success = 0, i; 754 char *file, *conn_id; 755 struct sshauthopt *opts = NULL; 756 const char *rdomain, *remote_ip, *remote_host; 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 if ((rdomain = ssh_packet_rdomain_in(ssh)) == NULL) 768 rdomain = ""; 769 remote_ip = ssh_remote_ipaddr(ssh); 770 remote_host = auth_get_canonical_hostname(ssh, options.use_dns); 771 xasprintf(&conn_id, "%s %d %s %d", 772 ssh_local_ipaddr(ssh), ssh_local_port(ssh), 773 remote_ip, ssh_remote_port(ssh)); 774 775 for (i = 0; !success && i < options.num_authkeys_files; i++) { 776 if (strcasecmp(options.authorized_keys_files[i], "none") == 0) 777 continue; 778 file = expand_authorized_keys( 779 options.authorized_keys_files[i], pw); 780 success = user_key_allowed2(pw, key, file, 781 remote_ip, remote_host, &opts); 782 free(file); 783 if (!success) { 784 sshauthopt_free(opts); 785 opts = NULL; 786 } 787 } 788 if (success) 789 goto out; 790 791 if ((success = user_cert_trusted_ca(pw, key, remote_ip, remote_host, 792 conn_id, rdomain, &opts)) != 0) 793 goto out; 794 sshauthopt_free(opts); 795 opts = NULL; 796 797 if ((success = user_key_command_allowed2(pw, key, remote_ip, 798 remote_host, conn_id, rdomain, &opts)) != 0) 799 goto out; 800 sshauthopt_free(opts); 801 opts = NULL; 802 803 out: 804 free(conn_id); 805 if (success && authoptsp != NULL) { 806 *authoptsp = opts; 807 opts = NULL; 808 } 809 sshauthopt_free(opts); 810 return success; 811 } 812 813 Authmethod method_pubkey = { 814 &methodcfg_pubkey, 815 userauth_pubkey, 816 }; 817