1 /* $OpenBSD: auth2-pubkey.c,v 1.122 2024/12/12 09:09:09 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 #ifdef USE_SYSTEM_GLOB 45 # include <glob.h> 46 #else 47 # include "openbsd-compat/glob.h" 48 #endif 49 50 #include "xmalloc.h" 51 #include "ssh.h" 52 #include "ssh2.h" 53 #include "packet.h" 54 #include "kex.h" 55 #include "sshbuf.h" 56 #include "log.h" 57 #include "misc.h" 58 #include "servconf.h" 59 #include "compat.h" 60 #include "sshkey.h" 61 #include "hostfile.h" 62 #include "auth.h" 63 #include "pathnames.h" 64 #include "uidswap.h" 65 #include "auth-options.h" 66 #include "canohost.h" 67 #ifdef GSSAPI 68 #include "ssh-gss.h" 69 #endif 70 #include "monitor_wrap.h" 71 #include "authfile.h" 72 #include "match.h" 73 #include "ssherr.h" 74 #include "channels.h" /* XXX for session.h */ 75 #include "session.h" /* XXX for child_set_env(); refactor? */ 76 #include "sk-api.h" 77 78 /* import */ 79 extern ServerOptions options; 80 extern struct authmethod_cfg methodcfg_pubkey; 81 82 static char * 83 format_key(const struct sshkey *key) 84 { 85 char *ret, *fp = sshkey_fingerprint(key, 86 options.fingerprint_hash, SSH_FP_DEFAULT); 87 88 xasprintf(&ret, "%s %s", sshkey_type(key), fp); 89 free(fp); 90 return ret; 91 } 92 93 static int 94 userauth_pubkey(struct ssh *ssh, const char *method) 95 { 96 Authctxt *authctxt = ssh->authctxt; 97 struct passwd *pw = authctxt->pw; 98 struct sshbuf *b = NULL; 99 struct sshkey *key = NULL, *hostkey = NULL; 100 char *pkalg = NULL, *userstyle = NULL, *key_s = NULL, *ca_s = NULL; 101 u_char *pkblob = NULL, *sig = NULL, have_sig; 102 size_t blen, slen; 103 int hostbound, r, pktype; 104 int req_presence = 0, req_verify = 0, authenticated = 0; 105 struct sshauthopt *authopts = NULL; 106 struct sshkey_sig_details *sig_details = NULL; 107 108 hostbound = strcmp(method, "publickey-hostbound-v00@openssh.com") == 0; 109 110 if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0 || 111 (r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 || 112 (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0) 113 fatal_fr(r, "parse %s packet", method); 114 115 /* hostbound auth includes the hostkey offered at initial KEX */ 116 if (hostbound) { 117 if ((r = sshpkt_getb_froms(ssh, &b)) != 0 || 118 (r = sshkey_fromb(b, &hostkey)) != 0) 119 fatal_fr(r, "parse %s hostkey", method); 120 if (ssh->kex->initial_hostkey == NULL) 121 fatal_f("internal error: initial hostkey not recorded"); 122 if (!sshkey_equal(hostkey, ssh->kex->initial_hostkey)) 123 fatal_f("%s packet contained wrong host key", method); 124 sshbuf_free(b); 125 b = NULL; 126 } 127 128 if (log_level_get() >= SYSLOG_LEVEL_DEBUG2) { 129 char *keystring; 130 struct sshbuf *pkbuf; 131 132 if ((pkbuf = sshbuf_from(pkblob, blen)) == NULL) 133 fatal_f("sshbuf_from failed"); 134 if ((keystring = sshbuf_dtob64_string(pkbuf, 0)) == NULL) 135 fatal_f("sshbuf_dtob64 failed"); 136 debug2_f("%s user %s %s public key %s %s", 137 authctxt->valid ? "valid" : "invalid", authctxt->user, 138 have_sig ? "attempting" : "querying", pkalg, keystring); 139 sshbuf_free(pkbuf); 140 free(keystring); 141 } 142 143 pktype = sshkey_type_from_name(pkalg); 144 if (pktype == KEY_UNSPEC) { 145 /* this is perfectly legal */ 146 verbose_f("unsupported public key algorithm: %s", pkalg); 147 goto done; 148 } 149 if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) { 150 error_fr(r, "parse key"); 151 goto done; 152 } 153 if (key == NULL) { 154 error_f("cannot decode key: %s", pkalg); 155 goto done; 156 } 157 if (key->type != pktype) { 158 error_f("type mismatch for decoded key " 159 "(received %d, expected %d)", key->type, pktype); 160 goto done; 161 } 162 if (auth2_key_already_used(authctxt, key)) { 163 logit("refusing previously-used %s key", sshkey_type(key)); 164 goto done; 165 } 166 if (match_pattern_list(pkalg, options.pubkey_accepted_algos, 0) != 1) { 167 logit_f("signature algorithm %s not in " 168 "PubkeyAcceptedAlgorithms", pkalg); 169 goto done; 170 } 171 if ((r = sshkey_check_cert_sigtype(key, 172 options.ca_sign_algorithms)) != 0) { 173 logit_fr(r, "certificate signature algorithm %s", 174 (key->cert == NULL || key->cert->signature_type == NULL) ? 175 "(null)" : key->cert->signature_type); 176 goto done; 177 } 178 if ((r = sshkey_check_rsa_length(key, 179 options.required_rsa_size)) != 0) { 180 logit_r(r, "refusing %s key", sshkey_type(key)); 181 goto done; 182 } 183 key_s = format_key(key); 184 if (sshkey_is_cert(key)) 185 ca_s = format_key(key->cert->signature_key); 186 187 if (have_sig) { 188 debug3_f("%s have %s signature for %s%s%s", 189 method, pkalg, key_s, 190 ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s); 191 if ((r = sshpkt_get_string(ssh, &sig, &slen)) != 0 || 192 (r = sshpkt_get_end(ssh)) != 0) 193 fatal_fr(r, "parse signature packet"); 194 if ((b = sshbuf_new()) == NULL) 195 fatal_f("sshbuf_new failed"); 196 if (ssh->compat & SSH_OLD_SESSIONID) { 197 if ((r = sshbuf_putb(b, ssh->kex->session_id)) != 0) 198 fatal_fr(r, "put old session id"); 199 } else { 200 if ((r = sshbuf_put_stringb(b, 201 ssh->kex->session_id)) != 0) 202 fatal_fr(r, "put session id"); 203 } 204 if (!authctxt->valid || authctxt->user == NULL) { 205 debug2_f("disabled because of invalid user"); 206 goto done; 207 } 208 /* reconstruct packet */ 209 xasprintf(&userstyle, "%s%s%s", authctxt->user, 210 authctxt->style ? ":" : "", 211 authctxt->style ? authctxt->style : ""); 212 if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 || 213 (r = sshbuf_put_cstring(b, userstyle)) != 0 || 214 (r = sshbuf_put_cstring(b, authctxt->service)) != 0 || 215 (r = sshbuf_put_cstring(b, method)) != 0 || 216 (r = sshbuf_put_u8(b, have_sig)) != 0 || 217 (r = sshbuf_put_cstring(b, pkalg)) != 0 || 218 (r = sshbuf_put_string(b, pkblob, blen)) != 0) 219 fatal_fr(r, "reconstruct %s packet", method); 220 if (hostbound && 221 (r = sshkey_puts(ssh->kex->initial_hostkey, b)) != 0) 222 fatal_fr(r, "reconstruct %s packet", method); 223 #ifdef DEBUG_PK 224 sshbuf_dump(b, stderr); 225 #endif 226 /* test for correct signature */ 227 authenticated = 0; 228 if (mm_user_key_allowed(ssh, pw, key, 1, &authopts) && 229 mm_sshkey_verify(key, sig, slen, 230 sshbuf_ptr(b), sshbuf_len(b), 231 (ssh->compat & SSH_BUG_SIGTYPE) == 0 ? pkalg : NULL, 232 ssh->compat, &sig_details) == 0) { 233 authenticated = 1; 234 } 235 if (authenticated == 1 && sig_details != NULL) { 236 auth2_record_info(authctxt, "signature count = %u", 237 sig_details->sk_counter); 238 debug_f("sk_counter = %u, sk_flags = 0x%02x", 239 sig_details->sk_counter, sig_details->sk_flags); 240 req_presence = (options.pubkey_auth_options & 241 PUBKEYAUTH_TOUCH_REQUIRED) || 242 !authopts->no_require_user_presence; 243 if (req_presence && (sig_details->sk_flags & 244 SSH_SK_USER_PRESENCE_REQD) == 0) { 245 error("public key %s signature for %s%s from " 246 "%.128s port %d rejected: user presence " 247 "(authenticator touch) requirement " 248 "not met ", key_s, 249 authctxt->valid ? "" : "invalid user ", 250 authctxt->user, ssh_remote_ipaddr(ssh), 251 ssh_remote_port(ssh)); 252 authenticated = 0; 253 goto done; 254 } 255 req_verify = (options.pubkey_auth_options & 256 PUBKEYAUTH_VERIFY_REQUIRED) || 257 authopts->require_verify; 258 if (req_verify && (sig_details->sk_flags & 259 SSH_SK_USER_VERIFICATION_REQD) == 0) { 260 error("public key %s signature for %s%s from " 261 "%.128s port %d rejected: user " 262 "verification requirement not met ", key_s, 263 authctxt->valid ? "" : "invalid user ", 264 authctxt->user, ssh_remote_ipaddr(ssh), 265 ssh_remote_port(ssh)); 266 authenticated = 0; 267 goto done; 268 } 269 } 270 auth2_record_key(authctxt, authenticated, key); 271 } else { 272 debug_f("%s test pkalg %s pkblob %s%s%s", method, pkalg, key_s, 273 ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s); 274 275 if ((r = sshpkt_get_end(ssh)) != 0) 276 fatal_fr(r, "parse packet"); 277 278 if (!authctxt->valid || authctxt->user == NULL) { 279 debug2_f("disabled because of invalid user"); 280 goto done; 281 } 282 /* XXX fake reply and always send PK_OK ? */ 283 /* 284 * XXX this allows testing whether a user is allowed 285 * to login: if you happen to have a valid pubkey this 286 * message is sent. the message is NEVER sent at all 287 * if a user is not allowed to login. is this an 288 * issue? -markus 289 */ 290 if (mm_user_key_allowed(ssh, pw, key, 0, NULL)) { 291 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_PK_OK)) 292 != 0 || 293 (r = sshpkt_put_cstring(ssh, pkalg)) != 0 || 294 (r = sshpkt_put_string(ssh, pkblob, blen)) != 0 || 295 (r = sshpkt_send(ssh)) != 0 || 296 (r = ssh_packet_write_wait(ssh)) != 0) 297 fatal_fr(r, "send packet"); 298 authctxt->postponed = 1; 299 } 300 } 301 done: 302 if (authenticated == 1 && auth_activate_options(ssh, authopts) != 0) { 303 debug_f("key options inconsistent with existing"); 304 authenticated = 0; 305 } 306 debug2_f("authenticated %d pkalg %s", authenticated, pkalg); 307 308 sshbuf_free(b); 309 sshauthopt_free(authopts); 310 sshkey_free(key); 311 sshkey_free(hostkey); 312 free(userstyle); 313 free(pkalg); 314 free(pkblob); 315 free(key_s); 316 free(ca_s); 317 free(sig); 318 sshkey_sig_details_free(sig_details); 319 return authenticated; 320 } 321 322 static int 323 match_principals_file(struct passwd *pw, char *file, 324 struct sshkey_cert *cert, struct sshauthopt **authoptsp) 325 { 326 FILE *f; 327 int r, success = 0; 328 size_t i; 329 glob_t gl; 330 struct sshauthopt *opts = NULL; 331 332 if (authoptsp != NULL) 333 *authoptsp = NULL; 334 335 temporarily_use_uid(pw); 336 r = glob(file, 0, NULL, &gl); 337 restore_uid(); 338 if (r != 0) { 339 if (r != GLOB_NOMATCH) { 340 logit_f("glob \"%s\" failed", file); 341 } 342 return 0; 343 } else if (gl.gl_pathc > INT_MAX) { 344 fatal_f("too many glob results for \"%s\"", file); 345 } else if (gl.gl_pathc > 1) { 346 debug2_f("glob \"%s\" returned %zu matches", file, 347 gl.gl_pathc); 348 } 349 for (i = 0; !success && i < gl.gl_pathc; i++) { 350 temporarily_use_uid(pw); 351 debug("trying authorized principals file %s", file); 352 if ((f = auth_openprincipals(gl.gl_pathv[i], pw, 353 options.strict_modes)) == NULL) { 354 restore_uid(); 355 continue; 356 } 357 success = auth_process_principals(f, gl.gl_pathv[i], 358 cert, &opts); 359 fclose(f); 360 restore_uid(); 361 if (!success) { 362 sshauthopt_free(opts); 363 opts = NULL; 364 } 365 } 366 globfree(&gl); 367 if (success && authoptsp != NULL) { 368 *authoptsp = opts; 369 opts = NULL; 370 } 371 sshauthopt_free(opts); 372 return success; 373 } 374 375 /* 376 * Checks whether principal is allowed in output of command. 377 * returns 1 if the principal is allowed or 0 otherwise. 378 */ 379 static int 380 match_principals_command(struct passwd *user_pw, const struct sshkey *key, 381 const char *conn_id, const char *rdomain, struct sshauthopt **authoptsp) 382 { 383 struct passwd *runas_pw = NULL; 384 const struct sshkey_cert *cert = key->cert; 385 FILE *f = NULL; 386 int r, ok, found_principal = 0; 387 int i, ac = 0, uid_swapped = 0; 388 pid_t pid; 389 char *tmp, *username = NULL, *command = NULL, **av = NULL; 390 char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL; 391 char serial_s[32], uidstr[32]; 392 void (*osigchld)(int); 393 394 if (authoptsp != NULL) 395 *authoptsp = NULL; 396 if (options.authorized_principals_command == NULL) 397 return 0; 398 if (options.authorized_principals_command_user == NULL) { 399 error("No user for AuthorizedPrincipalsCommand specified, " 400 "skipping"); 401 return 0; 402 } 403 404 /* 405 * NB. all returns later this function should go via "out" to 406 * ensure the original SIGCHLD handler is restored properly. 407 */ 408 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 409 410 /* Prepare and verify the user for the command */ 411 username = percent_expand(options.authorized_principals_command_user, 412 "u", user_pw->pw_name, (char *)NULL); 413 runas_pw = getpwnam(username); 414 if (runas_pw == NULL) { 415 error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s", 416 username, strerror(errno)); 417 goto out; 418 } 419 420 /* Turn the command into an argument vector */ 421 if (argv_split(options.authorized_principals_command, 422 &ac, &av, 0) != 0) { 423 error("AuthorizedPrincipalsCommand \"%s\" contains " 424 "invalid quotes", options.authorized_principals_command); 425 goto out; 426 } 427 if (ac == 0) { 428 error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments", 429 options.authorized_principals_command); 430 goto out; 431 } 432 if ((ca_fp = sshkey_fingerprint(cert->signature_key, 433 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 434 error_f("sshkey_fingerprint failed"); 435 goto out; 436 } 437 if ((key_fp = sshkey_fingerprint(key, 438 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 439 error_f("sshkey_fingerprint failed"); 440 goto out; 441 } 442 if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) { 443 error_fr(r, "sshkey_to_base64 failed"); 444 goto out; 445 } 446 if ((r = sshkey_to_base64(key, &keytext)) != 0) { 447 error_fr(r, "sshkey_to_base64 failed"); 448 goto out; 449 } 450 snprintf(serial_s, sizeof(serial_s), "%llu", 451 (unsigned long long)cert->serial); 452 snprintf(uidstr, sizeof(uidstr), "%llu", 453 (unsigned long long)user_pw->pw_uid); 454 for (i = 1; i < ac; i++) { 455 tmp = percent_expand(av[i], 456 "C", conn_id, 457 "D", rdomain, 458 "U", uidstr, 459 "u", user_pw->pw_name, 460 "h", user_pw->pw_dir, 461 "t", sshkey_ssh_name(key), 462 "T", sshkey_ssh_name(cert->signature_key), 463 "f", key_fp, 464 "F", ca_fp, 465 "k", keytext, 466 "K", catext, 467 "i", cert->key_id, 468 "s", serial_s, 469 (char *)NULL); 470 if (tmp == NULL) 471 fatal_f("percent_expand failed"); 472 free(av[i]); 473 av[i] = tmp; 474 } 475 /* Prepare a printable command for logs, etc. */ 476 command = argv_assemble(ac, av); 477 478 if ((pid = subprocess("AuthorizedPrincipalsCommand", command, 479 ac, av, &f, 480 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD, 481 runas_pw, temporarily_use_uid, restore_uid)) == 0) 482 goto out; 483 484 uid_swapped = 1; 485 temporarily_use_uid(runas_pw); 486 487 ok = auth_process_principals(f, "(command)", cert, authoptsp); 488 489 fclose(f); 490 f = NULL; 491 492 if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0) 493 goto out; 494 495 /* Read completed successfully */ 496 found_principal = ok; 497 out: 498 if (f != NULL) 499 fclose(f); 500 ssh_signal(SIGCHLD, osigchld); 501 for (i = 0; i < ac; i++) 502 free(av[i]); 503 free(av); 504 if (uid_swapped) 505 restore_uid(); 506 free(command); 507 free(username); 508 free(ca_fp); 509 free(key_fp); 510 free(catext); 511 free(keytext); 512 return found_principal; 513 } 514 515 /* Authenticate a certificate key against TrustedUserCAKeys */ 516 static int 517 user_cert_trusted_ca(struct passwd *pw, struct sshkey *key, 518 const char *remote_ip, const char *remote_host, 519 const char *conn_id, const char *rdomain, struct sshauthopt **authoptsp) 520 { 521 char *ca_fp, *principals_file = NULL; 522 const char *reason; 523 struct sshauthopt *principals_opts = NULL, *cert_opts = NULL; 524 struct sshauthopt *final_opts = NULL; 525 int r, ret = 0, found_principal = 0, use_authorized_principals; 526 527 if (authoptsp != NULL) 528 *authoptsp = NULL; 529 530 if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL) 531 return 0; 532 533 if ((ca_fp = sshkey_fingerprint(key->cert->signature_key, 534 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 535 return 0; 536 537 if ((r = sshkey_in_file(key->cert->signature_key, 538 options.trusted_user_ca_keys, 1, 0)) != 0) { 539 debug2_fr(r, "CA %s %s is not listed in %s", 540 sshkey_type(key->cert->signature_key), ca_fp, 541 options.trusted_user_ca_keys); 542 goto out; 543 } 544 /* 545 * If AuthorizedPrincipals is in use, then compare the certificate 546 * principals against the names in that file rather than matching 547 * against the username. 548 */ 549 if ((principals_file = authorized_principals_file(pw)) != NULL) { 550 if (match_principals_file(pw, principals_file, 551 key->cert, &principals_opts)) 552 found_principal = 1; 553 } 554 /* Try querying command if specified */ 555 if (!found_principal && match_principals_command(pw, key, 556 conn_id, rdomain, &principals_opts)) 557 found_principal = 1; 558 /* If principals file or command is specified, then require a match */ 559 use_authorized_principals = principals_file != NULL || 560 options.authorized_principals_command != NULL; 561 if (!found_principal && use_authorized_principals) { 562 reason = "Certificate does not contain an authorized principal"; 563 goto fail_reason; 564 } 565 if (use_authorized_principals && principals_opts == NULL) 566 fatal_f("internal error: missing principals_opts"); 567 if (sshkey_cert_check_authority_now(key, 0, 1, 0, 568 use_authorized_principals ? NULL : pw->pw_name, &reason) != 0) 569 goto fail_reason; 570 571 /* Check authority from options in key and from principals file/cmd */ 572 if ((cert_opts = sshauthopt_from_cert(key)) == NULL) { 573 reason = "Invalid certificate options"; 574 goto fail_reason; 575 } 576 if (auth_authorise_keyopts(pw, cert_opts, 0, 577 remote_ip, remote_host, "cert") != 0) { 578 reason = "Refused by certificate options"; 579 goto fail_reason; 580 } 581 if (principals_opts == NULL) { 582 final_opts = cert_opts; 583 cert_opts = NULL; 584 } else { 585 if (auth_authorise_keyopts(pw, principals_opts, 0, 586 remote_ip, remote_host, "principals") != 0) { 587 reason = "Refused by certificate principals options"; 588 goto fail_reason; 589 } 590 if ((final_opts = sshauthopt_merge(principals_opts, 591 cert_opts, &reason)) == NULL) { 592 fail_reason: 593 error("%s", reason); 594 auth_debug_add("%s", reason); 595 goto out; 596 } 597 } 598 599 /* Success */ 600 verbose("Accepted certificate ID \"%s\" (serial %llu) signed by " 601 "%s CA %s via %s", key->cert->key_id, 602 (unsigned long long)key->cert->serial, 603 sshkey_type(key->cert->signature_key), ca_fp, 604 options.trusted_user_ca_keys); 605 if (authoptsp != NULL) { 606 *authoptsp = final_opts; 607 final_opts = NULL; 608 } 609 ret = 1; 610 out: 611 sshauthopt_free(principals_opts); 612 sshauthopt_free(cert_opts); 613 sshauthopt_free(final_opts); 614 free(principals_file); 615 free(ca_fp); 616 return ret; 617 } 618 619 /* 620 * Checks whether key is allowed in file. 621 * returns 1 if the key is allowed or 0 otherwise. 622 */ 623 static int 624 user_key_allowed2(struct passwd *pw, struct sshkey *key, 625 char *file, const char *remote_ip, const char *remote_host, 626 struct sshauthopt **authoptsp) 627 { 628 FILE *f; 629 int found_key = 0; 630 631 if (authoptsp != NULL) 632 *authoptsp = NULL; 633 634 /* Temporarily use the user's uid. */ 635 temporarily_use_uid(pw); 636 637 debug("trying public key file %s", file); 638 if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) { 639 found_key = auth_check_authkeys_file(pw, f, file, 640 key, remote_ip, remote_host, authoptsp); 641 fclose(f); 642 } 643 644 restore_uid(); 645 return found_key; 646 } 647 648 /* 649 * Checks whether key is allowed in output of command. 650 * returns 1 if the key is allowed or 0 otherwise. 651 */ 652 static int 653 user_key_command_allowed2(struct passwd *user_pw, struct sshkey *key, 654 const char *remote_ip, const char *remote_host, 655 const char *conn_id, const char *rdomain, struct sshauthopt **authoptsp) 656 { 657 struct passwd *runas_pw = NULL; 658 FILE *f = NULL; 659 int r, ok, found_key = 0; 660 int i, uid_swapped = 0, ac = 0; 661 pid_t pid; 662 char *username = NULL, *key_fp = NULL, *keytext = NULL; 663 char uidstr[32], *tmp, *command = NULL, **av = NULL; 664 void (*osigchld)(int); 665 666 if (authoptsp != NULL) 667 *authoptsp = NULL; 668 if (options.authorized_keys_command == NULL) 669 return 0; 670 if (options.authorized_keys_command_user == NULL) { 671 error("No user for AuthorizedKeysCommand specified, skipping"); 672 return 0; 673 } 674 675 /* 676 * NB. all returns later this function should go via "out" to 677 * ensure the original SIGCHLD handler is restored properly. 678 */ 679 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 680 681 /* Prepare and verify the user for the command */ 682 username = percent_expand(options.authorized_keys_command_user, 683 "u", user_pw->pw_name, (char *)NULL); 684 runas_pw = getpwnam(username); 685 if (runas_pw == NULL) { 686 error("AuthorizedKeysCommandUser \"%s\" not found: %s", 687 username, strerror(errno)); 688 goto out; 689 } 690 691 /* Prepare AuthorizedKeysCommand */ 692 if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash, 693 SSH_FP_DEFAULT)) == NULL) { 694 error_f("sshkey_fingerprint failed"); 695 goto out; 696 } 697 if ((r = sshkey_to_base64(key, &keytext)) != 0) { 698 error_fr(r, "sshkey_to_base64 failed"); 699 goto out; 700 } 701 702 /* Turn the command into an argument vector */ 703 if (argv_split(options.authorized_keys_command, &ac, &av, 0) != 0) { 704 error("AuthorizedKeysCommand \"%s\" contains invalid quotes", 705 options.authorized_keys_command); 706 goto out; 707 } 708 if (ac == 0) { 709 error("AuthorizedKeysCommand \"%s\" yielded no arguments", 710 options.authorized_keys_command); 711 goto out; 712 } 713 snprintf(uidstr, sizeof(uidstr), "%llu", 714 (unsigned long long)user_pw->pw_uid); 715 for (i = 1; i < ac; i++) { 716 tmp = percent_expand(av[i], 717 "C", conn_id, 718 "D", rdomain, 719 "U", uidstr, 720 "u", user_pw->pw_name, 721 "h", user_pw->pw_dir, 722 "t", sshkey_ssh_name(key), 723 "f", key_fp, 724 "k", keytext, 725 (char *)NULL); 726 if (tmp == NULL) 727 fatal_f("percent_expand failed"); 728 free(av[i]); 729 av[i] = tmp; 730 } 731 /* Prepare a printable command for logs, etc. */ 732 command = argv_assemble(ac, av); 733 734 /* 735 * If AuthorizedKeysCommand was run without arguments 736 * then fall back to the old behaviour of passing the 737 * target username as a single argument. 738 */ 739 if (ac == 1) { 740 av = xreallocarray(av, ac + 2, sizeof(*av)); 741 av[1] = xstrdup(user_pw->pw_name); 742 av[2] = NULL; 743 /* Fix up command too, since it is used in log messages */ 744 free(command); 745 xasprintf(&command, "%s %s", av[0], av[1]); 746 } 747 748 if ((pid = subprocess("AuthorizedKeysCommand", command, 749 ac, av, &f, 750 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD, 751 runas_pw, temporarily_use_uid, restore_uid)) == 0) 752 goto out; 753 754 uid_swapped = 1; 755 temporarily_use_uid(runas_pw); 756 757 ok = auth_check_authkeys_file(user_pw, f, 758 options.authorized_keys_command, key, remote_ip, 759 remote_host, authoptsp); 760 761 fclose(f); 762 f = NULL; 763 764 if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0) 765 goto out; 766 767 /* Read completed successfully */ 768 found_key = ok; 769 out: 770 if (f != NULL) 771 fclose(f); 772 ssh_signal(SIGCHLD, osigchld); 773 for (i = 0; i < ac; i++) 774 free(av[i]); 775 free(av); 776 if (uid_swapped) 777 restore_uid(); 778 free(command); 779 free(username); 780 free(key_fp); 781 free(keytext); 782 return found_key; 783 } 784 785 /* 786 * Check whether key authenticates and authorises the user. 787 */ 788 int 789 user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key, 790 int auth_attempt, struct sshauthopt **authoptsp) 791 { 792 u_int success = 0, i, j; 793 char *file = NULL, *conn_id; 794 struct sshauthopt *opts = NULL; 795 const char *rdomain, *remote_ip, *remote_host; 796 797 if (authoptsp != NULL) 798 *authoptsp = NULL; 799 800 if (auth_key_is_revoked(key)) 801 return 0; 802 if (sshkey_is_cert(key) && 803 auth_key_is_revoked(key->cert->signature_key)) 804 return 0; 805 806 if ((rdomain = ssh_packet_rdomain_in(ssh)) == NULL) 807 rdomain = ""; 808 remote_ip = ssh_remote_ipaddr(ssh); 809 remote_host = auth_get_canonical_hostname(ssh, options.use_dns); 810 xasprintf(&conn_id, "%s %d %s %d", 811 ssh_local_ipaddr(ssh), ssh_local_port(ssh), 812 remote_ip, ssh_remote_port(ssh)); 813 814 for (i = 0; !success && i < options.num_authkeys_files; i++) { 815 int r; 816 glob_t gl; 817 818 if (strcasecmp(options.authorized_keys_files[i], "none") == 0) 819 continue; 820 file = expand_authorized_keys( 821 options.authorized_keys_files[i], pw); 822 temporarily_use_uid(pw); 823 r = glob(file, 0, NULL, &gl); 824 restore_uid(); 825 if (r != 0) { 826 if (r != GLOB_NOMATCH) { 827 logit_f("glob \"%s\" failed", file); 828 } 829 free(file); 830 file = NULL; 831 continue; 832 } else if (gl.gl_pathc > INT_MAX) { 833 fatal_f("too many glob results for \"%s\"", file); 834 } else if (gl.gl_pathc > 1) { 835 debug2_f("glob \"%s\" returned %zu matches", file, 836 gl.gl_pathc); 837 } 838 for (j = 0; !success && j < gl.gl_pathc; j++) { 839 success = user_key_allowed2(pw, key, gl.gl_pathv[j], 840 remote_ip, remote_host, &opts); 841 if (!success) { 842 sshauthopt_free(opts); 843 opts = NULL; 844 } 845 } 846 free(file); 847 file = NULL; 848 globfree(&gl); 849 } 850 if (success) 851 goto out; 852 853 if ((success = user_cert_trusted_ca(pw, key, remote_ip, remote_host, 854 conn_id, rdomain, &opts)) != 0) 855 goto out; 856 sshauthopt_free(opts); 857 opts = NULL; 858 859 if ((success = user_key_command_allowed2(pw, key, remote_ip, 860 remote_host, conn_id, rdomain, &opts)) != 0) 861 goto out; 862 sshauthopt_free(opts); 863 opts = NULL; 864 865 out: 866 free(conn_id); 867 if (success && authoptsp != NULL) { 868 *authoptsp = opts; 869 opts = NULL; 870 } 871 sshauthopt_free(opts); 872 return success; 873 } 874 875 Authmethod method_pubkey = { 876 &methodcfg_pubkey, 877 userauth_pubkey, 878 }; 879