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 28 #include <sys/types.h> 29 30 #include <stdlib.h> 31 #include <errno.h> 32 #include <paths.h> 33 #include <pwd.h> 34 #include <glob.h> 35 #include <signal.h> 36 #include <stdio.h> 37 #include <stdarg.h> 38 #include <string.h> 39 #include <time.h> 40 #include <unistd.h> 41 #include <limits.h> 42 43 #include "xmalloc.h" 44 #include "ssh.h" 45 #include "ssh2.h" 46 #include "packet.h" 47 #include "kex.h" 48 #include "sshbuf.h" 49 #include "log.h" 50 #include "misc.h" 51 #include "servconf.h" 52 #include "compat.h" 53 #include "sshkey.h" 54 #include "hostfile.h" 55 #include "auth.h" 56 #include "pathnames.h" 57 #include "uidswap.h" 58 #include "auth-options.h" 59 #include "canohost.h" 60 #ifdef GSSAPI 61 #include "ssh-gss.h" 62 #endif 63 #include "monitor_wrap.h" 64 #include "authfile.h" 65 #include "match.h" 66 #include "ssherr.h" 67 #include "channels.h" /* XXX for session.h */ 68 #include "session.h" /* XXX for child_set_env(); refactor? */ 69 #include "sk-api.h" 70 71 /* import */ 72 extern ServerOptions options; 73 extern struct authmethod_cfg methodcfg_pubkey; 74 75 static char * 76 format_key(const struct sshkey *key) 77 { 78 char *ret, *fp = sshkey_fingerprint(key, 79 options.fingerprint_hash, SSH_FP_DEFAULT); 80 81 xasprintf(&ret, "%s %s", sshkey_type(key), fp); 82 free(fp); 83 return ret; 84 } 85 86 static int 87 userauth_pubkey(struct ssh *ssh, const char *method) 88 { 89 Authctxt *authctxt = ssh->authctxt; 90 struct passwd *pw = authctxt->pw; 91 struct sshbuf *b = NULL; 92 struct sshkey *key = NULL, *hostkey = NULL; 93 char *pkalg = NULL, *userstyle = NULL, *key_s = NULL, *ca_s = NULL; 94 u_char *pkblob = NULL, *sig = NULL, have_sig; 95 size_t blen, slen; 96 int hostbound, r, pktype; 97 int req_presence = 0, req_verify = 0, authenticated = 0; 98 struct sshauthopt *authopts = NULL; 99 struct sshkey_sig_details *sig_details = NULL; 100 101 hostbound = strcmp(method, "publickey-hostbound-v00@openssh.com") == 0; 102 103 if ((r = sshpkt_get_u8(ssh, &have_sig)) != 0 || 104 (r = sshpkt_get_cstring(ssh, &pkalg, NULL)) != 0 || 105 (r = sshpkt_get_string(ssh, &pkblob, &blen)) != 0) 106 fatal_fr(r, "parse %s packet", method); 107 108 /* hostbound auth includes the hostkey offered at initial KEX */ 109 if (hostbound) { 110 if ((r = sshpkt_getb_froms(ssh, &b)) != 0 || 111 (r = sshkey_fromb(b, &hostkey)) != 0) 112 fatal_fr(r, "parse %s hostkey", method); 113 if (ssh->kex->initial_hostkey == NULL) 114 fatal_f("internal error: initial hostkey not recorded"); 115 if (!sshkey_equal(hostkey, ssh->kex->initial_hostkey)) 116 fatal_f("%s packet contained wrong host key", method); 117 sshbuf_free(b); 118 b = NULL; 119 } 120 121 if (log_level_get() >= SYSLOG_LEVEL_DEBUG2) { 122 char *keystring; 123 struct sshbuf *pkbuf; 124 125 if ((pkbuf = sshbuf_from(pkblob, blen)) == NULL) 126 fatal_f("sshbuf_from failed"); 127 if ((keystring = sshbuf_dtob64_string(pkbuf, 0)) == NULL) 128 fatal_f("sshbuf_dtob64 failed"); 129 debug2_f("%s user %s %s public key %s %s", 130 authctxt->valid ? "valid" : "invalid", authctxt->user, 131 have_sig ? "attempting" : "querying", pkalg, keystring); 132 sshbuf_free(pkbuf); 133 free(keystring); 134 } 135 136 pktype = sshkey_type_from_name(pkalg); 137 if (pktype == KEY_UNSPEC) { 138 /* this is perfectly legal */ 139 verbose_f("unsupported public key algorithm: %s", pkalg); 140 goto done; 141 } 142 if ((r = sshkey_from_blob(pkblob, blen, &key)) != 0) { 143 error_fr(r, "parse key"); 144 goto done; 145 } 146 if (key == NULL) { 147 error_f("cannot decode key: %s", pkalg); 148 goto done; 149 } 150 if (key->type != pktype) { 151 error_f("type mismatch for decoded key " 152 "(received %d, expected %d)", key->type, pktype); 153 goto done; 154 } 155 if (auth2_key_already_used(authctxt, key)) { 156 logit("refusing previously-used %s key", sshkey_type(key)); 157 goto done; 158 } 159 if (match_pattern_list(pkalg, options.pubkey_accepted_algos, 0) != 1) { 160 logit_f("signature algorithm %s not in " 161 "PubkeyAcceptedAlgorithms", pkalg); 162 goto done; 163 } 164 if ((r = sshkey_check_cert_sigtype(key, 165 options.ca_sign_algorithms)) != 0) { 166 logit_fr(r, "certificate signature algorithm %s", 167 (key->cert == NULL || key->cert->signature_type == NULL) ? 168 "(null)" : key->cert->signature_type); 169 goto done; 170 } 171 if ((r = sshkey_check_rsa_length(key, 172 options.required_rsa_size)) != 0) { 173 logit_r(r, "refusing %s key", sshkey_type(key)); 174 goto done; 175 } 176 key_s = format_key(key); 177 if (sshkey_is_cert(key)) 178 ca_s = format_key(key->cert->signature_key); 179 180 if (have_sig) { 181 debug3_f("%s have %s signature for %s%s%s", 182 method, pkalg, key_s, 183 ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s); 184 if ((r = sshpkt_get_string(ssh, &sig, &slen)) != 0 || 185 (r = sshpkt_get_end(ssh)) != 0) 186 fatal_fr(r, "parse signature packet"); 187 if ((b = sshbuf_new()) == NULL) 188 fatal_f("sshbuf_new failed"); 189 if (ssh->compat & SSH_OLD_SESSIONID) { 190 if ((r = sshbuf_putb(b, ssh->kex->session_id)) != 0) 191 fatal_fr(r, "put old session id"); 192 } else { 193 if ((r = sshbuf_put_stringb(b, 194 ssh->kex->session_id)) != 0) 195 fatal_fr(r, "put session id"); 196 } 197 if (!authctxt->valid || authctxt->user == NULL) { 198 debug2_f("disabled because of invalid user"); 199 goto done; 200 } 201 /* reconstruct packet */ 202 xasprintf(&userstyle, "%s%s%s", authctxt->user, 203 authctxt->style ? ":" : "", 204 authctxt->style ? authctxt->style : ""); 205 if ((r = sshbuf_put_u8(b, SSH2_MSG_USERAUTH_REQUEST)) != 0 || 206 (r = sshbuf_put_cstring(b, userstyle)) != 0 || 207 (r = sshbuf_put_cstring(b, authctxt->service)) != 0 || 208 (r = sshbuf_put_cstring(b, method)) != 0 || 209 (r = sshbuf_put_u8(b, have_sig)) != 0 || 210 (r = sshbuf_put_cstring(b, pkalg)) != 0 || 211 (r = sshbuf_put_string(b, pkblob, blen)) != 0) 212 fatal_fr(r, "reconstruct %s packet", method); 213 if (hostbound && 214 (r = sshkey_puts(ssh->kex->initial_hostkey, b)) != 0) 215 fatal_fr(r, "reconstruct %s packet", method); 216 #ifdef DEBUG_PK 217 sshbuf_dump(b, stderr); 218 #endif 219 /* test for correct signature */ 220 authenticated = 0; 221 if (mm_user_key_allowed(ssh, pw, key, 1, &authopts) && 222 mm_sshkey_verify(key, sig, slen, 223 sshbuf_ptr(b), sshbuf_len(b), 224 (ssh->compat & SSH_BUG_SIGTYPE) == 0 ? pkalg : NULL, 225 ssh->compat, &sig_details) == 0) { 226 authenticated = 1; 227 } 228 if (authenticated == 1 && sig_details != NULL) { 229 auth2_record_info(authctxt, "signature count = %u", 230 sig_details->sk_counter); 231 debug_f("sk_counter = %u, sk_flags = 0x%02x", 232 sig_details->sk_counter, sig_details->sk_flags); 233 req_presence = (options.pubkey_auth_options & 234 PUBKEYAUTH_TOUCH_REQUIRED) || 235 !authopts->no_require_user_presence; 236 if (req_presence && (sig_details->sk_flags & 237 SSH_SK_USER_PRESENCE_REQD) == 0) { 238 error("public key %s signature for %s%s from " 239 "%.128s port %d rejected: user presence " 240 "(authenticator touch) requirement " 241 "not met ", key_s, 242 authctxt->valid ? "" : "invalid user ", 243 authctxt->user, ssh_remote_ipaddr(ssh), 244 ssh_remote_port(ssh)); 245 authenticated = 0; 246 goto done; 247 } 248 req_verify = (options.pubkey_auth_options & 249 PUBKEYAUTH_VERIFY_REQUIRED) || 250 authopts->require_verify; 251 if (req_verify && (sig_details->sk_flags & 252 SSH_SK_USER_VERIFICATION_REQD) == 0) { 253 error("public key %s signature for %s%s from " 254 "%.128s port %d rejected: user " 255 "verification requirement not met ", key_s, 256 authctxt->valid ? "" : "invalid user ", 257 authctxt->user, ssh_remote_ipaddr(ssh), 258 ssh_remote_port(ssh)); 259 authenticated = 0; 260 goto done; 261 } 262 } 263 auth2_record_key(authctxt, authenticated, key); 264 } else { 265 debug_f("%s test pkalg %s pkblob %s%s%s", method, pkalg, key_s, 266 ca_s == NULL ? "" : " CA ", ca_s == NULL ? "" : ca_s); 267 268 if ((r = sshpkt_get_end(ssh)) != 0) 269 fatal_fr(r, "parse packet"); 270 271 if (!authctxt->valid || authctxt->user == NULL) { 272 debug2_f("disabled because of invalid user"); 273 goto done; 274 } 275 /* XXX fake reply and always send PK_OK ? */ 276 /* 277 * XXX this allows testing whether a user is allowed 278 * to login: if you happen to have a valid pubkey this 279 * message is sent. the message is NEVER sent at all 280 * if a user is not allowed to login. is this an 281 * issue? -markus 282 */ 283 if (mm_user_key_allowed(ssh, pw, key, 0, NULL)) { 284 if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_PK_OK)) 285 != 0 || 286 (r = sshpkt_put_cstring(ssh, pkalg)) != 0 || 287 (r = sshpkt_put_string(ssh, pkblob, blen)) != 0 || 288 (r = sshpkt_send(ssh)) != 0 || 289 (r = ssh_packet_write_wait(ssh)) != 0) 290 fatal_fr(r, "send packet"); 291 authctxt->postponed = 1; 292 } 293 } 294 done: 295 if (authenticated == 1 && auth_activate_options(ssh, authopts) != 0) { 296 debug_f("key options inconsistent with existing"); 297 authenticated = 0; 298 } 299 debug2_f("authenticated %d pkalg %s", authenticated, pkalg); 300 301 sshbuf_free(b); 302 sshauthopt_free(authopts); 303 sshkey_free(key); 304 sshkey_free(hostkey); 305 free(userstyle); 306 free(pkalg); 307 free(pkblob); 308 free(key_s); 309 free(ca_s); 310 free(sig); 311 sshkey_sig_details_free(sig_details); 312 return authenticated; 313 } 314 315 static int 316 match_principals_file(struct passwd *pw, char *file, 317 struct sshkey_cert *cert, struct sshauthopt **authoptsp) 318 { 319 FILE *f; 320 int r, success = 0; 321 size_t i; 322 glob_t gl; 323 struct sshauthopt *opts = NULL; 324 325 if (authoptsp != NULL) 326 *authoptsp = NULL; 327 328 temporarily_use_uid(pw); 329 r = glob(file, 0, NULL, &gl); 330 restore_uid(); 331 if (r != 0) { 332 if (r != GLOB_NOMATCH) { 333 logit_f("glob \"%s\" failed", file); 334 } 335 return 0; 336 } else if (gl.gl_pathc > INT_MAX) { 337 fatal_f("too many glob results for \"%s\"", file); 338 } else if (gl.gl_pathc > 1) { 339 debug2_f("glob \"%s\" returned %zu matches", file, 340 gl.gl_pathc); 341 } 342 for (i = 0; !success && i < gl.gl_pathc; i++) { 343 temporarily_use_uid(pw); 344 debug("trying authorized principals file %s", file); 345 if ((f = auth_openprincipals(gl.gl_pathv[i], pw, 346 options.strict_modes)) == NULL) { 347 restore_uid(); 348 continue; 349 } 350 success = auth_process_principals(f, gl.gl_pathv[i], 351 cert, &opts); 352 fclose(f); 353 restore_uid(); 354 if (!success) { 355 sshauthopt_free(opts); 356 opts = NULL; 357 } 358 } 359 globfree(&gl); 360 if (success && authoptsp != NULL) { 361 *authoptsp = opts; 362 opts = NULL; 363 } 364 sshauthopt_free(opts); 365 return success; 366 } 367 368 /* 369 * Checks whether principal is allowed in output of command. 370 * returns 1 if the principal is allowed or 0 otherwise. 371 */ 372 static int 373 match_principals_command(struct passwd *user_pw, const struct sshkey *key, 374 const char *conn_id, const char *rdomain, struct sshauthopt **authoptsp) 375 { 376 struct passwd *runas_pw = NULL; 377 const struct sshkey_cert *cert = key->cert; 378 FILE *f = NULL; 379 int r, ok, found_principal = 0; 380 int i, ac = 0, uid_swapped = 0; 381 pid_t pid; 382 char *tmp, *username = NULL, *command = NULL, **av = NULL; 383 char *ca_fp = NULL, *key_fp = NULL, *catext = NULL, *keytext = NULL; 384 char serial_s[32], uidstr[32]; 385 void (*osigchld)(int); 386 387 if (authoptsp != NULL) 388 *authoptsp = NULL; 389 if (options.authorized_principals_command == NULL) 390 return 0; 391 if (options.authorized_principals_command_user == NULL) { 392 error("No user for AuthorizedPrincipalsCommand specified, " 393 "skipping"); 394 return 0; 395 } 396 397 /* 398 * NB. all returns later this function should go via "out" to 399 * ensure the original SIGCHLD handler is restored properly. 400 */ 401 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 402 403 /* Prepare and verify the user for the command */ 404 username = percent_expand(options.authorized_principals_command_user, 405 "u", user_pw->pw_name, (char *)NULL); 406 runas_pw = getpwnam(username); 407 if (runas_pw == NULL) { 408 error("AuthorizedPrincipalsCommandUser \"%s\" not found: %s", 409 username, strerror(errno)); 410 goto out; 411 } 412 413 /* Turn the command into an argument vector */ 414 if (argv_split(options.authorized_principals_command, 415 &ac, &av, 0) != 0) { 416 error("AuthorizedPrincipalsCommand \"%s\" contains " 417 "invalid quotes", options.authorized_principals_command); 418 goto out; 419 } 420 if (ac == 0) { 421 error("AuthorizedPrincipalsCommand \"%s\" yielded no arguments", 422 options.authorized_principals_command); 423 goto out; 424 } 425 if ((ca_fp = sshkey_fingerprint(cert->signature_key, 426 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 427 error_f("sshkey_fingerprint failed"); 428 goto out; 429 } 430 if ((key_fp = sshkey_fingerprint(key, 431 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) { 432 error_f("sshkey_fingerprint failed"); 433 goto out; 434 } 435 if ((r = sshkey_to_base64(cert->signature_key, &catext)) != 0) { 436 error_fr(r, "sshkey_to_base64 failed"); 437 goto out; 438 } 439 if ((r = sshkey_to_base64(key, &keytext)) != 0) { 440 error_fr(r, "sshkey_to_base64 failed"); 441 goto out; 442 } 443 snprintf(serial_s, sizeof(serial_s), "%llu", 444 (unsigned long long)cert->serial); 445 snprintf(uidstr, sizeof(uidstr), "%llu", 446 (unsigned long long)user_pw->pw_uid); 447 for (i = 1; i < ac; i++) { 448 tmp = percent_expand(av[i], 449 "C", conn_id, 450 "D", rdomain, 451 "U", uidstr, 452 "u", user_pw->pw_name, 453 "h", user_pw->pw_dir, 454 "t", sshkey_ssh_name(key), 455 "T", sshkey_ssh_name(cert->signature_key), 456 "f", key_fp, 457 "F", ca_fp, 458 "k", keytext, 459 "K", catext, 460 "i", cert->key_id, 461 "s", serial_s, 462 (char *)NULL); 463 if (tmp == NULL) 464 fatal_f("percent_expand failed"); 465 free(av[i]); 466 av[i] = tmp; 467 } 468 /* Prepare a printable command for logs, etc. */ 469 command = argv_assemble(ac, av); 470 471 if ((pid = subprocess("AuthorizedPrincipalsCommand", command, 472 ac, av, &f, 473 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD, 474 runas_pw, temporarily_use_uid, restore_uid)) == 0) 475 goto out; 476 477 uid_swapped = 1; 478 temporarily_use_uid(runas_pw); 479 480 ok = auth_process_principals(f, "(command)", cert, authoptsp); 481 482 fclose(f); 483 f = NULL; 484 485 if (exited_cleanly(pid, "AuthorizedPrincipalsCommand", command, 0) != 0) 486 goto out; 487 488 /* Read completed successfully */ 489 found_principal = ok; 490 out: 491 if (f != NULL) 492 fclose(f); 493 ssh_signal(SIGCHLD, osigchld); 494 for (i = 0; i < ac; i++) 495 free(av[i]); 496 free(av); 497 if (uid_swapped) 498 restore_uid(); 499 free(command); 500 free(username); 501 free(ca_fp); 502 free(key_fp); 503 free(catext); 504 free(keytext); 505 return found_principal; 506 } 507 508 /* Authenticate a certificate key against TrustedUserCAKeys */ 509 static int 510 user_cert_trusted_ca(struct passwd *pw, struct sshkey *key, 511 const char *remote_ip, const char *remote_host, 512 const char *conn_id, const char *rdomain, struct sshauthopt **authoptsp) 513 { 514 char *ca_fp, *principals_file = NULL; 515 const char *reason; 516 struct sshauthopt *principals_opts = NULL, *cert_opts = NULL; 517 struct sshauthopt *final_opts = NULL; 518 int r, ret = 0, found_principal = 0, use_authorized_principals; 519 520 if (authoptsp != NULL) 521 *authoptsp = NULL; 522 523 if (!sshkey_is_cert(key) || options.trusted_user_ca_keys == NULL) 524 return 0; 525 526 if ((ca_fp = sshkey_fingerprint(key->cert->signature_key, 527 options.fingerprint_hash, SSH_FP_DEFAULT)) == NULL) 528 return 0; 529 530 if ((r = sshkey_in_file(key->cert->signature_key, 531 options.trusted_user_ca_keys, 1, 0)) != 0) { 532 debug2_fr(r, "CA %s %s is not listed in %s", 533 sshkey_type(key->cert->signature_key), ca_fp, 534 options.trusted_user_ca_keys); 535 goto out; 536 } 537 /* 538 * If AuthorizedPrincipals is in use, then compare the certificate 539 * principals against the names in that file rather than matching 540 * against the username. 541 */ 542 if ((principals_file = authorized_principals_file(pw)) != NULL) { 543 if (match_principals_file(pw, principals_file, 544 key->cert, &principals_opts)) 545 found_principal = 1; 546 } 547 /* Try querying command if specified */ 548 if (!found_principal && match_principals_command(pw, key, 549 conn_id, rdomain, &principals_opts)) 550 found_principal = 1; 551 /* If principals file or command is specified, then require a match */ 552 use_authorized_principals = principals_file != NULL || 553 options.authorized_principals_command != NULL; 554 if (!found_principal && use_authorized_principals) { 555 reason = "Certificate does not contain an authorized principal"; 556 goto fail_reason; 557 } 558 if (use_authorized_principals && principals_opts == NULL) 559 fatal_f("internal error: missing principals_opts"); 560 if (sshkey_cert_check_authority_now(key, 0, 1, 0, 561 use_authorized_principals ? NULL : pw->pw_name, &reason) != 0) 562 goto fail_reason; 563 564 /* Check authority from options in key and from principals file/cmd */ 565 if ((cert_opts = sshauthopt_from_cert(key)) == NULL) { 566 reason = "Invalid certificate options"; 567 goto fail_reason; 568 } 569 if (auth_authorise_keyopts(pw, cert_opts, 0, 570 remote_ip, remote_host, "cert") != 0) { 571 reason = "Refused by certificate options"; 572 goto fail_reason; 573 } 574 if (principals_opts == NULL) { 575 final_opts = cert_opts; 576 cert_opts = NULL; 577 } else { 578 if (auth_authorise_keyopts(pw, principals_opts, 0, 579 remote_ip, remote_host, "principals") != 0) { 580 reason = "Refused by certificate principals options"; 581 goto fail_reason; 582 } 583 if ((final_opts = sshauthopt_merge(principals_opts, 584 cert_opts, &reason)) == NULL) { 585 fail_reason: 586 error("%s", reason); 587 auth_debug_add("%s", reason); 588 goto out; 589 } 590 } 591 592 /* Success */ 593 verbose("Accepted certificate ID \"%s\" (serial %llu) signed by " 594 "%s CA %s via %s", key->cert->key_id, 595 (unsigned long long)key->cert->serial, 596 sshkey_type(key->cert->signature_key), ca_fp, 597 options.trusted_user_ca_keys); 598 if (authoptsp != NULL) { 599 *authoptsp = final_opts; 600 final_opts = NULL; 601 } 602 ret = 1; 603 out: 604 sshauthopt_free(principals_opts); 605 sshauthopt_free(cert_opts); 606 sshauthopt_free(final_opts); 607 free(principals_file); 608 free(ca_fp); 609 return ret; 610 } 611 612 /* 613 * Checks whether key is allowed in file. 614 * returns 1 if the key is allowed or 0 otherwise. 615 */ 616 static int 617 user_key_allowed2(struct passwd *pw, struct sshkey *key, 618 char *file, const char *remote_ip, const char *remote_host, 619 struct sshauthopt **authoptsp) 620 { 621 FILE *f; 622 int found_key = 0; 623 624 if (authoptsp != NULL) 625 *authoptsp = NULL; 626 627 /* Temporarily use the user's uid. */ 628 temporarily_use_uid(pw); 629 630 debug("trying public key file %s", file); 631 if ((f = auth_openkeyfile(file, pw, options.strict_modes)) != NULL) { 632 found_key = auth_check_authkeys_file(pw, f, file, 633 key, remote_ip, remote_host, authoptsp); 634 fclose(f); 635 } 636 637 restore_uid(); 638 return found_key; 639 } 640 641 /* 642 * Checks whether key is allowed in output of command. 643 * returns 1 if the key is allowed or 0 otherwise. 644 */ 645 static int 646 user_key_command_allowed2(struct passwd *user_pw, struct sshkey *key, 647 const char *remote_ip, const char *remote_host, 648 const char *conn_id, const char *rdomain, struct sshauthopt **authoptsp) 649 { 650 struct passwd *runas_pw = NULL; 651 FILE *f = NULL; 652 int r, ok, found_key = 0; 653 int i, uid_swapped = 0, ac = 0; 654 pid_t pid; 655 char *username = NULL, *key_fp = NULL, *keytext = NULL; 656 char uidstr[32], *tmp, *command = NULL, **av = NULL; 657 void (*osigchld)(int); 658 659 if (authoptsp != NULL) 660 *authoptsp = NULL; 661 if (options.authorized_keys_command == NULL) 662 return 0; 663 if (options.authorized_keys_command_user == NULL) { 664 error("No user for AuthorizedKeysCommand specified, skipping"); 665 return 0; 666 } 667 668 /* 669 * NB. all returns later this function should go via "out" to 670 * ensure the original SIGCHLD handler is restored properly. 671 */ 672 osigchld = ssh_signal(SIGCHLD, SIG_DFL); 673 674 /* Prepare and verify the user for the command */ 675 username = percent_expand(options.authorized_keys_command_user, 676 "u", user_pw->pw_name, (char *)NULL); 677 runas_pw = getpwnam(username); 678 if (runas_pw == NULL) { 679 error("AuthorizedKeysCommandUser \"%s\" not found: %s", 680 username, strerror(errno)); 681 goto out; 682 } 683 684 /* Prepare AuthorizedKeysCommand */ 685 if ((key_fp = sshkey_fingerprint(key, options.fingerprint_hash, 686 SSH_FP_DEFAULT)) == NULL) { 687 error_f("sshkey_fingerprint failed"); 688 goto out; 689 } 690 if ((r = sshkey_to_base64(key, &keytext)) != 0) { 691 error_fr(r, "sshkey_to_base64 failed"); 692 goto out; 693 } 694 695 /* Turn the command into an argument vector */ 696 if (argv_split(options.authorized_keys_command, &ac, &av, 0) != 0) { 697 error("AuthorizedKeysCommand \"%s\" contains invalid quotes", 698 options.authorized_keys_command); 699 goto out; 700 } 701 if (ac == 0) { 702 error("AuthorizedKeysCommand \"%s\" yielded no arguments", 703 options.authorized_keys_command); 704 goto out; 705 } 706 snprintf(uidstr, sizeof(uidstr), "%llu", 707 (unsigned long long)user_pw->pw_uid); 708 for (i = 1; i < ac; i++) { 709 tmp = percent_expand(av[i], 710 "C", conn_id, 711 "D", rdomain, 712 "U", uidstr, 713 "u", user_pw->pw_name, 714 "h", user_pw->pw_dir, 715 "t", sshkey_ssh_name(key), 716 "f", key_fp, 717 "k", keytext, 718 (char *)NULL); 719 if (tmp == NULL) 720 fatal_f("percent_expand failed"); 721 free(av[i]); 722 av[i] = tmp; 723 } 724 /* Prepare a printable command for logs, etc. */ 725 command = argv_assemble(ac, av); 726 727 /* 728 * If AuthorizedKeysCommand was run without arguments 729 * then fall back to the old behaviour of passing the 730 * target username as a single argument. 731 */ 732 if (ac == 1) { 733 av = xreallocarray(av, ac + 2, sizeof(*av)); 734 av[1] = xstrdup(user_pw->pw_name); 735 av[2] = NULL; 736 /* Fix up command too, since it is used in log messages */ 737 free(command); 738 xasprintf(&command, "%s %s", av[0], av[1]); 739 } 740 741 if ((pid = subprocess("AuthorizedKeysCommand", command, 742 ac, av, &f, 743 SSH_SUBPROCESS_STDOUT_CAPTURE|SSH_SUBPROCESS_STDERR_DISCARD, 744 runas_pw, temporarily_use_uid, restore_uid)) == 0) 745 goto out; 746 747 uid_swapped = 1; 748 temporarily_use_uid(runas_pw); 749 750 ok = auth_check_authkeys_file(user_pw, f, 751 options.authorized_keys_command, key, remote_ip, 752 remote_host, authoptsp); 753 754 fclose(f); 755 f = NULL; 756 757 if (exited_cleanly(pid, "AuthorizedKeysCommand", command, 0) != 0) 758 goto out; 759 760 /* Read completed successfully */ 761 found_key = ok; 762 out: 763 if (f != NULL) 764 fclose(f); 765 ssh_signal(SIGCHLD, osigchld); 766 for (i = 0; i < ac; i++) 767 free(av[i]); 768 free(av); 769 if (uid_swapped) 770 restore_uid(); 771 free(command); 772 free(username); 773 free(key_fp); 774 free(keytext); 775 return found_key; 776 } 777 778 /* 779 * Check whether key authenticates and authorises the user. 780 */ 781 int 782 user_key_allowed(struct ssh *ssh, struct passwd *pw, struct sshkey *key, 783 int auth_attempt, struct sshauthopt **authoptsp) 784 { 785 u_int success = 0, i, j; 786 char *file = NULL, *conn_id; 787 struct sshauthopt *opts = NULL; 788 const char *rdomain, *remote_ip, *remote_host; 789 790 if (authoptsp != NULL) 791 *authoptsp = NULL; 792 793 if (auth_key_is_revoked(key)) 794 return 0; 795 if (sshkey_is_cert(key) && 796 auth_key_is_revoked(key->cert->signature_key)) 797 return 0; 798 799 if ((rdomain = ssh_packet_rdomain_in(ssh)) == NULL) 800 rdomain = ""; 801 remote_ip = ssh_remote_ipaddr(ssh); 802 remote_host = auth_get_canonical_hostname(ssh, options.use_dns); 803 xasprintf(&conn_id, "%s %d %s %d", 804 ssh_local_ipaddr(ssh), ssh_local_port(ssh), 805 remote_ip, ssh_remote_port(ssh)); 806 807 for (i = 0; !success && i < options.num_authkeys_files; i++) { 808 int r; 809 glob_t gl; 810 811 if (strcasecmp(options.authorized_keys_files[i], "none") == 0) 812 continue; 813 file = expand_authorized_keys( 814 options.authorized_keys_files[i], pw); 815 temporarily_use_uid(pw); 816 r = glob(file, 0, NULL, &gl); 817 restore_uid(); 818 if (r != 0) { 819 if (r != GLOB_NOMATCH) { 820 logit_f("glob \"%s\" failed", file); 821 } 822 free(file); 823 file = NULL; 824 continue; 825 } else if (gl.gl_pathc > INT_MAX) { 826 fatal_f("too many glob results for \"%s\"", file); 827 } else if (gl.gl_pathc > 1) { 828 debug2_f("glob \"%s\" returned %zu matches", file, 829 gl.gl_pathc); 830 } 831 for (j = 0; !success && j < gl.gl_pathc; j++) { 832 success = user_key_allowed2(pw, key, gl.gl_pathv[j], 833 remote_ip, remote_host, &opts); 834 if (!success) { 835 sshauthopt_free(opts); 836 opts = NULL; 837 } 838 } 839 free(file); 840 file = NULL; 841 globfree(&gl); 842 } 843 if (success) 844 goto out; 845 846 if ((success = user_cert_trusted_ca(pw, key, remote_ip, remote_host, 847 conn_id, rdomain, &opts)) != 0) 848 goto out; 849 sshauthopt_free(opts); 850 opts = NULL; 851 852 if ((success = user_key_command_allowed2(pw, key, remote_ip, 853 remote_host, conn_id, rdomain, &opts)) != 0) 854 goto out; 855 sshauthopt_free(opts); 856 opts = NULL; 857 858 out: 859 free(conn_id); 860 if (success && authoptsp != NULL) { 861 *authoptsp = opts; 862 opts = NULL; 863 } 864 sshauthopt_free(opts); 865 return success; 866 } 867 868 Authmethod method_pubkey = { 869 &methodcfg_pubkey, 870 userauth_pubkey, 871 }; 872