1 /* $OpenBSD: ssh-agent.c,v 1.298 2023/03/31 04:45:08 dtucker Exp $ */ 2 /* 3 * Author: Tatu Ylonen <ylo@cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 5 * All rights reserved 6 * The authentication agent program. 7 * 8 * As far as I am concerned, the code I have written for this software 9 * can be used freely for any purpose. Any derived versions of this 10 * software must be clearly marked as such, and if the derived work is 11 * incompatible with the protocol description in the RFC file, it must be 12 * called by a name other than "ssh" or "Secure Shell". 13 * 14 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. 15 * 16 * Redistribution and use in source and binary forms, with or without 17 * modification, are permitted provided that the following conditions 18 * are met: 19 * 1. Redistributions of source code must retain the above copyright 20 * notice, this list of conditions and the following disclaimer. 21 * 2. Redistributions in binary form must reproduce the above copyright 22 * notice, this list of conditions and the following disclaimer in the 23 * documentation and/or other materials provided with the distribution. 24 * 25 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 26 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 27 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 28 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 29 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 30 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 31 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 32 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 33 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 34 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 35 */ 36 37 #include <sys/types.h> 38 #include <sys/time.h> 39 #include <sys/queue.h> 40 #include <sys/resource.h> 41 #include <sys/socket.h> 42 #include <sys/stat.h> 43 #include <sys/un.h> 44 #include <sys/wait.h> 45 46 #ifdef WITH_OPENSSL 47 #include <openssl/evp.h> 48 #endif 49 50 #include <errno.h> 51 #include <fcntl.h> 52 #include <paths.h> 53 #include <poll.h> 54 #include <signal.h> 55 #include <stdlib.h> 56 #include <stdio.h> 57 #include <string.h> 58 #include <stdarg.h> 59 #include <limits.h> 60 #include <time.h> 61 #include <unistd.h> 62 #include <util.h> 63 64 #include "xmalloc.h" 65 #include "ssh.h" 66 #include "ssh2.h" 67 #include "sshbuf.h" 68 #include "sshkey.h" 69 #include "authfd.h" 70 #include "log.h" 71 #include "misc.h" 72 #include "digest.h" 73 #include "ssherr.h" 74 #include "match.h" 75 #include "msg.h" 76 #include "pathnames.h" 77 #include "ssh-pkcs11.h" 78 #include "sk-api.h" 79 #include "myproposal.h" 80 81 #ifndef DEFAULT_ALLOWED_PROVIDERS 82 # define DEFAULT_ALLOWED_PROVIDERS "/usr/lib*/*,/usr/local/lib*/*" 83 #endif 84 85 /* Maximum accepted message length */ 86 #define AGENT_MAX_LEN (256*1024) 87 /* Maximum bytes to read from client socket */ 88 #define AGENT_RBUF_LEN (4096) 89 /* Maximum number of recorded session IDs/hostkeys per connection */ 90 #define AGENT_MAX_SESSION_IDS 16 91 /* Maximum size of session ID */ 92 #define AGENT_MAX_SID_LEN 128 93 /* Maximum number of destination constraints to accept on a key */ 94 #define AGENT_MAX_DEST_CONSTRAINTS 1024 95 96 /* XXX store hostkey_sid in a refcounted tree */ 97 98 typedef enum { 99 AUTH_UNUSED = 0, 100 AUTH_SOCKET = 1, 101 AUTH_CONNECTION = 2, 102 } sock_type; 103 104 struct hostkey_sid { 105 struct sshkey *key; 106 struct sshbuf *sid; 107 int forwarded; 108 }; 109 110 typedef struct socket_entry { 111 int fd; 112 sock_type type; 113 struct sshbuf *input; 114 struct sshbuf *output; 115 struct sshbuf *request; 116 size_t nsession_ids; 117 struct hostkey_sid *session_ids; 118 } SocketEntry; 119 120 u_int sockets_alloc = 0; 121 SocketEntry *sockets = NULL; 122 123 typedef struct identity { 124 TAILQ_ENTRY(identity) next; 125 struct sshkey *key; 126 char *comment; 127 char *provider; 128 time_t death; 129 u_int confirm; 130 char *sk_provider; 131 struct dest_constraint *dest_constraints; 132 size_t ndest_constraints; 133 } Identity; 134 135 struct idtable { 136 int nentries; 137 TAILQ_HEAD(idqueue, identity) idlist; 138 }; 139 140 /* private key table */ 141 struct idtable *idtab; 142 143 int max_fd = 0; 144 145 /* pid of shell == parent of agent */ 146 pid_t parent_pid = -1; 147 time_t parent_alive_interval = 0; 148 149 /* pid of process for which cleanup_socket is applicable */ 150 pid_t cleanup_pid = 0; 151 152 /* pathname and directory for AUTH_SOCKET */ 153 char socket_name[PATH_MAX]; 154 char socket_dir[PATH_MAX]; 155 156 /* Pattern-list of allowed PKCS#11/Security key paths */ 157 static char *allowed_providers; 158 159 /* locking */ 160 #define LOCK_SIZE 32 161 #define LOCK_SALT_SIZE 16 162 #define LOCK_ROUNDS 1 163 int locked = 0; 164 u_char lock_pwhash[LOCK_SIZE]; 165 u_char lock_salt[LOCK_SALT_SIZE]; 166 167 extern char *__progname; 168 169 /* Default lifetime in seconds (0 == forever) */ 170 static int lifetime = 0; 171 172 static int fingerprint_hash = SSH_FP_HASH_DEFAULT; 173 174 /* Refuse signing of non-SSH messages for web-origin FIDO keys */ 175 static int restrict_websafe = 1; 176 177 static void 178 close_socket(SocketEntry *e) 179 { 180 size_t i; 181 182 close(e->fd); 183 sshbuf_free(e->input); 184 sshbuf_free(e->output); 185 sshbuf_free(e->request); 186 for (i = 0; i < e->nsession_ids; i++) { 187 sshkey_free(e->session_ids[i].key); 188 sshbuf_free(e->session_ids[i].sid); 189 } 190 free(e->session_ids); 191 memset(e, '\0', sizeof(*e)); 192 e->fd = -1; 193 e->type = AUTH_UNUSED; 194 } 195 196 static void 197 idtab_init(void) 198 { 199 idtab = xcalloc(1, sizeof(*idtab)); 200 TAILQ_INIT(&idtab->idlist); 201 idtab->nentries = 0; 202 } 203 204 static void 205 free_dest_constraint_hop(struct dest_constraint_hop *dch) 206 { 207 u_int i; 208 209 if (dch == NULL) 210 return; 211 free(dch->user); 212 free(dch->hostname); 213 for (i = 0; i < dch->nkeys; i++) 214 sshkey_free(dch->keys[i]); 215 free(dch->keys); 216 free(dch->key_is_ca); 217 } 218 219 static void 220 free_dest_constraints(struct dest_constraint *dcs, size_t ndcs) 221 { 222 size_t i; 223 224 for (i = 0; i < ndcs; i++) { 225 free_dest_constraint_hop(&dcs[i].from); 226 free_dest_constraint_hop(&dcs[i].to); 227 } 228 free(dcs); 229 } 230 231 static void 232 free_identity(Identity *id) 233 { 234 sshkey_free(id->key); 235 free(id->provider); 236 free(id->comment); 237 free(id->sk_provider); 238 free_dest_constraints(id->dest_constraints, id->ndest_constraints); 239 free(id); 240 } 241 242 /* 243 * Match 'key' against the key/CA list in a destination constraint hop 244 * Returns 0 on success or -1 otherwise. 245 */ 246 static int 247 match_key_hop(const char *tag, const struct sshkey *key, 248 const struct dest_constraint_hop *dch) 249 { 250 const char *reason = NULL; 251 const char *hostname = dch->hostname ? dch->hostname : "(ORIGIN)"; 252 u_int i; 253 char *fp; 254 255 if (key == NULL) 256 return -1; 257 /* XXX logspam */ 258 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT, 259 SSH_FP_DEFAULT)) == NULL) 260 fatal_f("fingerprint failed"); 261 debug3_f("%s: entering hostname %s, requested key %s %s, %u keys avail", 262 tag, hostname, sshkey_type(key), fp, dch->nkeys); 263 free(fp); 264 for (i = 0; i < dch->nkeys; i++) { 265 if (dch->keys[i] == NULL) 266 return -1; 267 /* XXX logspam */ 268 if ((fp = sshkey_fingerprint(dch->keys[i], SSH_FP_HASH_DEFAULT, 269 SSH_FP_DEFAULT)) == NULL) 270 fatal_f("fingerprint failed"); 271 debug3_f("%s: key %u: %s%s %s", tag, i, 272 dch->key_is_ca[i] ? "CA " : "", 273 sshkey_type(dch->keys[i]), fp); 274 free(fp); 275 if (!sshkey_is_cert(key)) { 276 /* plain key */ 277 if (dch->key_is_ca[i] || 278 !sshkey_equal(key, dch->keys[i])) 279 continue; 280 return 0; 281 } 282 /* certificate */ 283 if (!dch->key_is_ca[i]) 284 continue; 285 if (key->cert == NULL || key->cert->signature_key == NULL) 286 return -1; /* shouldn't happen */ 287 if (!sshkey_equal(key->cert->signature_key, dch->keys[i])) 288 continue; 289 if (sshkey_cert_check_host(key, hostname, 1, 290 SSH_ALLOWED_CA_SIGALGS, &reason) != 0) { 291 debug_f("cert %s / hostname %s rejected: %s", 292 key->cert->key_id, hostname, reason); 293 continue; 294 } 295 return 0; 296 } 297 return -1; 298 } 299 300 /* Check destination constraints on an identity against the hostkey/user */ 301 static int 302 permitted_by_dest_constraints(const struct sshkey *fromkey, 303 const struct sshkey *tokey, Identity *id, const char *user, 304 const char **hostnamep) 305 { 306 size_t i; 307 struct dest_constraint *d; 308 309 if (hostnamep != NULL) 310 *hostnamep = NULL; 311 for (i = 0; i < id->ndest_constraints; i++) { 312 d = id->dest_constraints + i; 313 /* XXX remove logspam */ 314 debug2_f("constraint %zu %s%s%s (%u keys) > %s%s%s (%u keys)", 315 i, d->from.user ? d->from.user : "", 316 d->from.user ? "@" : "", 317 d->from.hostname ? d->from.hostname : "(ORIGIN)", 318 d->from.nkeys, 319 d->to.user ? d->to.user : "", d->to.user ? "@" : "", 320 d->to.hostname ? d->to.hostname : "(ANY)", d->to.nkeys); 321 322 /* Match 'from' key */ 323 if (fromkey == NULL) { 324 /* We are matching the first hop */ 325 if (d->from.hostname != NULL || d->from.nkeys != 0) 326 continue; 327 } else if (match_key_hop("from", fromkey, &d->from) != 0) 328 continue; 329 330 /* Match 'to' key */ 331 if (tokey != NULL && match_key_hop("to", tokey, &d->to) != 0) 332 continue; 333 334 /* Match user if specified */ 335 if (d->to.user != NULL && user != NULL && 336 !match_pattern(user, d->to.user)) 337 continue; 338 339 /* successfully matched this constraint */ 340 if (hostnamep != NULL) 341 *hostnamep = d->to.hostname; 342 debug2_f("allowed for hostname %s", 343 d->to.hostname == NULL ? "*" : d->to.hostname); 344 return 0; 345 } 346 /* no match */ 347 debug2_f("%s identity \"%s\" not permitted for this destination", 348 sshkey_type(id->key), id->comment); 349 return -1; 350 } 351 352 /* 353 * Check whether hostkeys on a SocketEntry and the optionally specified user 354 * are permitted by the destination constraints on the Identity. 355 * Returns 0 on success or -1 otherwise. 356 */ 357 static int 358 identity_permitted(Identity *id, SocketEntry *e, char *user, 359 const char **forward_hostnamep, const char **last_hostnamep) 360 { 361 size_t i; 362 const char **hp; 363 struct hostkey_sid *hks; 364 const struct sshkey *fromkey = NULL; 365 const char *test_user; 366 char *fp1, *fp2; 367 368 /* XXX remove logspam */ 369 debug3_f("entering: key %s comment \"%s\", %zu socket bindings, " 370 "%zu constraints", sshkey_type(id->key), id->comment, 371 e->nsession_ids, id->ndest_constraints); 372 if (id->ndest_constraints == 0) 373 return 0; /* unconstrained */ 374 if (e->nsession_ids == 0) 375 return 0; /* local use */ 376 /* 377 * Walk through the hops recorded by session_id and try to find a 378 * constraint that satisfies each. 379 */ 380 for (i = 0; i < e->nsession_ids; i++) { 381 hks = e->session_ids + i; 382 if (hks->key == NULL) 383 fatal_f("internal error: no bound key"); 384 /* XXX remove logspam */ 385 fp1 = fp2 = NULL; 386 if (fromkey != NULL && 387 (fp1 = sshkey_fingerprint(fromkey, SSH_FP_HASH_DEFAULT, 388 SSH_FP_DEFAULT)) == NULL) 389 fatal_f("fingerprint failed"); 390 if ((fp2 = sshkey_fingerprint(hks->key, SSH_FP_HASH_DEFAULT, 391 SSH_FP_DEFAULT)) == NULL) 392 fatal_f("fingerprint failed"); 393 debug3_f("socketentry fd=%d, entry %zu %s, " 394 "from hostkey %s %s to user %s hostkey %s %s", 395 e->fd, i, hks->forwarded ? "FORWARD" : "AUTH", 396 fromkey ? sshkey_type(fromkey) : "(ORIGIN)", 397 fromkey ? fp1 : "", user ? user : "(ANY)", 398 sshkey_type(hks->key), fp2); 399 free(fp1); 400 free(fp2); 401 /* 402 * Record the hostnames for the initial forwarding and 403 * the final destination. 404 */ 405 hp = NULL; 406 if (i == e->nsession_ids - 1) 407 hp = last_hostnamep; 408 else if (i == 0) 409 hp = forward_hostnamep; 410 /* Special handling for final recorded binding */ 411 test_user = NULL; 412 if (i == e->nsession_ids - 1) { 413 /* Can only check user at final hop */ 414 test_user = user; 415 /* 416 * user is only presented for signature requests. 417 * If this is the case, make sure last binding is not 418 * for a forwarding. 419 */ 420 if (hks->forwarded && user != NULL) { 421 error_f("tried to sign on forwarding hop"); 422 return -1; 423 } 424 } else if (!hks->forwarded) { 425 error_f("tried to forward though signing bind"); 426 return -1; 427 } 428 if (permitted_by_dest_constraints(fromkey, hks->key, id, 429 test_user, hp) != 0) 430 return -1; 431 fromkey = hks->key; 432 } 433 /* 434 * Another special case: if the last bound session ID was for a 435 * forwarding, and this function is not being called to check a sign 436 * request (i.e. no 'user' supplied), then only permit the key if 437 * there is a permission that would allow it to be used at another 438 * destination. This hides keys that are allowed to be used to 439 * authenticate *to* a host but not permitted for *use* beyond it. 440 */ 441 hks = &e->session_ids[e->nsession_ids - 1]; 442 if (hks->forwarded && user == NULL && 443 permitted_by_dest_constraints(hks->key, NULL, id, 444 NULL, NULL) != 0) { 445 debug3_f("key permitted at host but not after"); 446 return -1; 447 } 448 449 /* success */ 450 return 0; 451 } 452 453 /* return matching private key for given public key */ 454 static Identity * 455 lookup_identity(struct sshkey *key) 456 { 457 Identity *id; 458 459 TAILQ_FOREACH(id, &idtab->idlist, next) { 460 if (sshkey_equal(key, id->key)) 461 return (id); 462 } 463 return (NULL); 464 } 465 466 /* Check confirmation of keysign request */ 467 static int 468 confirm_key(Identity *id, const char *extra) 469 { 470 char *p; 471 int ret = -1; 472 473 p = sshkey_fingerprint(id->key, fingerprint_hash, SSH_FP_DEFAULT); 474 if (p != NULL && 475 ask_permission("Allow use of key %s?\nKey fingerprint %s.%s%s", 476 id->comment, p, 477 extra == NULL ? "" : "\n", extra == NULL ? "" : extra)) 478 ret = 0; 479 free(p); 480 481 return (ret); 482 } 483 484 static void 485 send_status(SocketEntry *e, int success) 486 { 487 int r; 488 489 if ((r = sshbuf_put_u32(e->output, 1)) != 0 || 490 (r = sshbuf_put_u8(e->output, success ? 491 SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE)) != 0) 492 fatal_fr(r, "compose"); 493 } 494 495 /* send list of supported public keys to 'client' */ 496 static void 497 process_request_identities(SocketEntry *e) 498 { 499 Identity *id; 500 struct sshbuf *msg, *keys; 501 int r; 502 u_int nentries = 0; 503 504 debug2_f("entering"); 505 506 if ((msg = sshbuf_new()) == NULL || (keys = sshbuf_new()) == NULL) 507 fatal_f("sshbuf_new failed"); 508 TAILQ_FOREACH(id, &idtab->idlist, next) { 509 /* identity not visible, don't include in response */ 510 if (identity_permitted(id, e, NULL, NULL, NULL) != 0) 511 continue; 512 if ((r = sshkey_puts_opts(id->key, keys, 513 SSHKEY_SERIALIZE_INFO)) != 0 || 514 (r = sshbuf_put_cstring(keys, id->comment)) != 0) { 515 error_fr(r, "compose key/comment"); 516 continue; 517 } 518 nentries++; 519 } 520 debug2_f("replying with %u allowed of %u available keys", 521 nentries, idtab->nentries); 522 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 || 523 (r = sshbuf_put_u32(msg, nentries)) != 0 || 524 (r = sshbuf_putb(msg, keys)) != 0) 525 fatal_fr(r, "compose"); 526 if ((r = sshbuf_put_stringb(e->output, msg)) != 0) 527 fatal_fr(r, "enqueue"); 528 sshbuf_free(msg); 529 sshbuf_free(keys); 530 } 531 532 533 static char * 534 agent_decode_alg(struct sshkey *key, u_int flags) 535 { 536 if (key->type == KEY_RSA) { 537 if (flags & SSH_AGENT_RSA_SHA2_256) 538 return "rsa-sha2-256"; 539 else if (flags & SSH_AGENT_RSA_SHA2_512) 540 return "rsa-sha2-512"; 541 } else if (key->type == KEY_RSA_CERT) { 542 if (flags & SSH_AGENT_RSA_SHA2_256) 543 return "rsa-sha2-256-cert-v01@openssh.com"; 544 else if (flags & SSH_AGENT_RSA_SHA2_512) 545 return "rsa-sha2-512-cert-v01@openssh.com"; 546 } 547 return NULL; 548 } 549 550 /* 551 * Attempt to parse the contents of a buffer as a SSH publickey userauth 552 * request, checking its contents for consistency and matching the embedded 553 * key against the one that is being used for signing. 554 * Note: does not modify msg buffer. 555 * Optionally extract the username, session ID and/or hostkey from the request. 556 */ 557 static int 558 parse_userauth_request(struct sshbuf *msg, const struct sshkey *expected_key, 559 char **userp, struct sshbuf **sess_idp, struct sshkey **hostkeyp) 560 { 561 struct sshbuf *b = NULL, *sess_id = NULL; 562 char *user = NULL, *service = NULL, *method = NULL, *pkalg = NULL; 563 int r; 564 u_char t, sig_follows; 565 struct sshkey *mkey = NULL, *hostkey = NULL; 566 567 if (userp != NULL) 568 *userp = NULL; 569 if (sess_idp != NULL) 570 *sess_idp = NULL; 571 if (hostkeyp != NULL) 572 *hostkeyp = NULL; 573 if ((b = sshbuf_fromb(msg)) == NULL) 574 fatal_f("sshbuf_fromb"); 575 576 /* SSH userauth request */ 577 if ((r = sshbuf_froms(b, &sess_id)) != 0) 578 goto out; 579 if (sshbuf_len(sess_id) == 0) { 580 r = SSH_ERR_INVALID_FORMAT; 581 goto out; 582 } 583 if ((r = sshbuf_get_u8(b, &t)) != 0 || /* SSH2_MSG_USERAUTH_REQUEST */ 584 (r = sshbuf_get_cstring(b, &user, NULL)) != 0 || /* server user */ 585 (r = sshbuf_get_cstring(b, &service, NULL)) != 0 || /* service */ 586 (r = sshbuf_get_cstring(b, &method, NULL)) != 0 || /* method */ 587 (r = sshbuf_get_u8(b, &sig_follows)) != 0 || /* sig-follows */ 588 (r = sshbuf_get_cstring(b, &pkalg, NULL)) != 0 || /* alg */ 589 (r = sshkey_froms(b, &mkey)) != 0) /* key */ 590 goto out; 591 if (t != SSH2_MSG_USERAUTH_REQUEST || 592 sig_follows != 1 || 593 strcmp(service, "ssh-connection") != 0 || 594 !sshkey_equal(expected_key, mkey) || 595 sshkey_type_from_name(pkalg) != expected_key->type) { 596 r = SSH_ERR_INVALID_FORMAT; 597 goto out; 598 } 599 if (strcmp(method, "publickey-hostbound-v00@openssh.com") == 0) { 600 if ((r = sshkey_froms(b, &hostkey)) != 0) 601 goto out; 602 } else if (strcmp(method, "publickey") != 0) { 603 r = SSH_ERR_INVALID_FORMAT; 604 goto out; 605 } 606 if (sshbuf_len(b) != 0) { 607 r = SSH_ERR_INVALID_FORMAT; 608 goto out; 609 } 610 /* success */ 611 r = 0; 612 debug3_f("well formed userauth"); 613 if (userp != NULL) { 614 *userp = user; 615 user = NULL; 616 } 617 if (sess_idp != NULL) { 618 *sess_idp = sess_id; 619 sess_id = NULL; 620 } 621 if (hostkeyp != NULL) { 622 *hostkeyp = hostkey; 623 hostkey = NULL; 624 } 625 out: 626 sshbuf_free(b); 627 sshbuf_free(sess_id); 628 free(user); 629 free(service); 630 free(method); 631 free(pkalg); 632 sshkey_free(mkey); 633 sshkey_free(hostkey); 634 return r; 635 } 636 637 /* 638 * Attempt to parse the contents of a buffer as a SSHSIG signature request. 639 * Note: does not modify buffer. 640 */ 641 static int 642 parse_sshsig_request(struct sshbuf *msg) 643 { 644 int r; 645 struct sshbuf *b; 646 647 if ((b = sshbuf_fromb(msg)) == NULL) 648 fatal_f("sshbuf_fromb"); 649 650 if ((r = sshbuf_cmp(b, 0, "SSHSIG", 6)) != 0 || 651 (r = sshbuf_consume(b, 6)) != 0 || 652 (r = sshbuf_get_cstring(b, NULL, NULL)) != 0 || /* namespace */ 653 (r = sshbuf_get_string_direct(b, NULL, NULL)) != 0 || /* reserved */ 654 (r = sshbuf_get_cstring(b, NULL, NULL)) != 0 || /* hashalg */ 655 (r = sshbuf_get_string_direct(b, NULL, NULL)) != 0) /* H(msg) */ 656 goto out; 657 if (sshbuf_len(b) != 0) { 658 r = SSH_ERR_INVALID_FORMAT; 659 goto out; 660 } 661 /* success */ 662 r = 0; 663 out: 664 sshbuf_free(b); 665 return r; 666 } 667 668 /* 669 * This function inspects a message to be signed by a FIDO key that has a 670 * web-like application string (i.e. one that does not begin with "ssh:". 671 * It checks that the message is one of those expected for SSH operations 672 * (pubkey userauth, sshsig, CA key signing) to exclude signing challenges 673 * for the web. 674 */ 675 static int 676 check_websafe_message_contents(struct sshkey *key, struct sshbuf *data) 677 { 678 if (parse_userauth_request(data, key, NULL, NULL, NULL) == 0) { 679 debug_f("signed data matches public key userauth request"); 680 return 1; 681 } 682 if (parse_sshsig_request(data) == 0) { 683 debug_f("signed data matches SSHSIG signature request"); 684 return 1; 685 } 686 687 /* XXX check CA signature operation */ 688 689 error("web-origin key attempting to sign non-SSH message"); 690 return 0; 691 } 692 693 static int 694 buf_equal(const struct sshbuf *a, const struct sshbuf *b) 695 { 696 if (sshbuf_ptr(a) == NULL || sshbuf_ptr(b) == NULL) 697 return SSH_ERR_INVALID_ARGUMENT; 698 if (sshbuf_len(a) != sshbuf_len(b)) 699 return SSH_ERR_INVALID_FORMAT; 700 if (timingsafe_bcmp(sshbuf_ptr(a), sshbuf_ptr(b), sshbuf_len(a)) != 0) 701 return SSH_ERR_INVALID_FORMAT; 702 return 0; 703 } 704 705 /* ssh2 only */ 706 static void 707 process_sign_request2(SocketEntry *e) 708 { 709 u_char *signature = NULL; 710 size_t slen = 0; 711 u_int compat = 0, flags; 712 int r, ok = -1, retried = 0; 713 char *fp = NULL, *pin = NULL, *prompt = NULL; 714 char *user = NULL, *sig_dest = NULL; 715 const char *fwd_host = NULL, *dest_host = NULL; 716 struct sshbuf *msg = NULL, *data = NULL, *sid = NULL; 717 struct sshkey *key = NULL, *hostkey = NULL; 718 struct identity *id; 719 struct notifier_ctx *notifier = NULL; 720 721 debug_f("entering"); 722 723 if ((msg = sshbuf_new()) == NULL || (data = sshbuf_new()) == NULL) 724 fatal_f("sshbuf_new failed"); 725 if ((r = sshkey_froms(e->request, &key)) != 0 || 726 (r = sshbuf_get_stringb(e->request, data)) != 0 || 727 (r = sshbuf_get_u32(e->request, &flags)) != 0) { 728 error_fr(r, "parse"); 729 goto send; 730 } 731 732 if ((id = lookup_identity(key)) == NULL) { 733 verbose_f("%s key not found", sshkey_type(key)); 734 goto send; 735 } 736 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT, 737 SSH_FP_DEFAULT)) == NULL) 738 fatal_f("fingerprint failed"); 739 740 if (id->ndest_constraints != 0) { 741 if (e->nsession_ids == 0) { 742 logit_f("refusing use of destination-constrained key " 743 "to sign on unbound connection"); 744 goto send; 745 } 746 if (parse_userauth_request(data, key, &user, &sid, 747 &hostkey) != 0) { 748 logit_f("refusing use of destination-constrained key " 749 "to sign an unidentified signature"); 750 goto send; 751 } 752 /* XXX logspam */ 753 debug_f("user=%s", user); 754 if (identity_permitted(id, e, user, &fwd_host, &dest_host) != 0) 755 goto send; 756 /* XXX display fwd_host/dest_host in askpass UI */ 757 /* 758 * Ensure that the session ID is the most recent one 759 * registered on the socket - it should have been bound by 760 * ssh immediately before userauth. 761 */ 762 if (buf_equal(sid, 763 e->session_ids[e->nsession_ids - 1].sid) != 0) { 764 error_f("unexpected session ID (%zu listed) on " 765 "signature request for target user %s with " 766 "key %s %s", e->nsession_ids, user, 767 sshkey_type(id->key), fp); 768 goto send; 769 } 770 /* 771 * Ensure that the hostkey embedded in the signature matches 772 * the one most recently bound to the socket. An exception is 773 * made for the initial forwarding hop. 774 */ 775 if (e->nsession_ids > 1 && hostkey == NULL) { 776 error_f("refusing use of destination-constrained key: " 777 "no hostkey recorded in signature for forwarded " 778 "connection"); 779 goto send; 780 } 781 if (hostkey != NULL && !sshkey_equal(hostkey, 782 e->session_ids[e->nsession_ids - 1].key)) { 783 error_f("refusing use of destination-constrained key: " 784 "mismatch between hostkey in request and most " 785 "recently bound session"); 786 goto send; 787 } 788 xasprintf(&sig_dest, "public key authentication request for " 789 "user \"%s\" to listed host", user); 790 } 791 if (id->confirm && confirm_key(id, sig_dest) != 0) { 792 verbose_f("user refused key"); 793 goto send; 794 } 795 if (sshkey_is_sk(id->key)) { 796 if (restrict_websafe && 797 strncmp(id->key->sk_application, "ssh:", 4) != 0 && 798 !check_websafe_message_contents(key, data)) { 799 /* error already logged */ 800 goto send; 801 } 802 if (id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD) { 803 notifier = notify_start(0, 804 "Confirm user presence for key %s %s%s%s", 805 sshkey_type(id->key), fp, 806 sig_dest == NULL ? "" : "\n", 807 sig_dest == NULL ? "" : sig_dest); 808 } 809 } 810 retry_pin: 811 if ((r = sshkey_sign(id->key, &signature, &slen, 812 sshbuf_ptr(data), sshbuf_len(data), agent_decode_alg(key, flags), 813 id->sk_provider, pin, compat)) != 0) { 814 debug_fr(r, "sshkey_sign"); 815 if (pin == NULL && !retried && sshkey_is_sk(id->key) && 816 r == SSH_ERR_KEY_WRONG_PASSPHRASE) { 817 notify_complete(notifier, NULL); 818 notifier = NULL; 819 /* XXX include sig_dest */ 820 xasprintf(&prompt, "Enter PIN%sfor %s key %s: ", 821 (id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD) ? 822 " and confirm user presence " : " ", 823 sshkey_type(id->key), fp); 824 pin = read_passphrase(prompt, RP_USE_ASKPASS); 825 retried = 1; 826 goto retry_pin; 827 } 828 error_fr(r, "sshkey_sign"); 829 goto send; 830 } 831 /* Success */ 832 ok = 0; 833 send: 834 debug_f("good signature"); 835 notify_complete(notifier, "User presence confirmed"); 836 837 if (ok == 0) { 838 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 || 839 (r = sshbuf_put_string(msg, signature, slen)) != 0) 840 fatal_fr(r, "compose"); 841 } else if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0) 842 fatal_fr(r, "compose failure"); 843 844 if ((r = sshbuf_put_stringb(e->output, msg)) != 0) 845 fatal_fr(r, "enqueue"); 846 847 sshbuf_free(sid); 848 sshbuf_free(data); 849 sshbuf_free(msg); 850 sshkey_free(key); 851 sshkey_free(hostkey); 852 free(fp); 853 free(signature); 854 free(sig_dest); 855 free(user); 856 free(prompt); 857 if (pin != NULL) 858 freezero(pin, strlen(pin)); 859 } 860 861 /* shared */ 862 static void 863 process_remove_identity(SocketEntry *e) 864 { 865 int r, success = 0; 866 struct sshkey *key = NULL; 867 Identity *id; 868 869 debug2_f("entering"); 870 if ((r = sshkey_froms(e->request, &key)) != 0) { 871 error_fr(r, "parse key"); 872 goto done; 873 } 874 if ((id = lookup_identity(key)) == NULL) { 875 debug_f("key not found"); 876 goto done; 877 } 878 /* identity not visible, cannot be removed */ 879 if (identity_permitted(id, e, NULL, NULL, NULL) != 0) 880 goto done; /* error already logged */ 881 /* We have this key, free it. */ 882 if (idtab->nentries < 1) 883 fatal_f("internal error: nentries %d", idtab->nentries); 884 TAILQ_REMOVE(&idtab->idlist, id, next); 885 free_identity(id); 886 idtab->nentries--; 887 success = 1; 888 done: 889 sshkey_free(key); 890 send_status(e, success); 891 } 892 893 static void 894 process_remove_all_identities(SocketEntry *e) 895 { 896 Identity *id; 897 898 debug2_f("entering"); 899 /* Loop over all identities and clear the keys. */ 900 for (id = TAILQ_FIRST(&idtab->idlist); id; 901 id = TAILQ_FIRST(&idtab->idlist)) { 902 TAILQ_REMOVE(&idtab->idlist, id, next); 903 free_identity(id); 904 } 905 906 /* Mark that there are no identities. */ 907 idtab->nentries = 0; 908 909 /* Send success. */ 910 send_status(e, 1); 911 } 912 913 /* removes expired keys and returns number of seconds until the next expiry */ 914 static time_t 915 reaper(void) 916 { 917 time_t deadline = 0, now = monotime(); 918 Identity *id, *nxt; 919 920 for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) { 921 nxt = TAILQ_NEXT(id, next); 922 if (id->death == 0) 923 continue; 924 if (now >= id->death) { 925 debug("expiring key '%s'", id->comment); 926 TAILQ_REMOVE(&idtab->idlist, id, next); 927 free_identity(id); 928 idtab->nentries--; 929 } else 930 deadline = (deadline == 0) ? id->death : 931 MINIMUM(deadline, id->death); 932 } 933 if (deadline == 0 || deadline <= now) 934 return 0; 935 else 936 return (deadline - now); 937 } 938 939 static int 940 parse_dest_constraint_hop(struct sshbuf *b, struct dest_constraint_hop *dch) 941 { 942 u_char key_is_ca; 943 size_t elen = 0; 944 int r; 945 struct sshkey *k = NULL; 946 char *fp; 947 948 memset(dch, '\0', sizeof(*dch)); 949 if ((r = sshbuf_get_cstring(b, &dch->user, NULL)) != 0 || 950 (r = sshbuf_get_cstring(b, &dch->hostname, NULL)) != 0 || 951 (r = sshbuf_get_string_direct(b, NULL, &elen)) != 0) { 952 error_fr(r, "parse"); 953 goto out; 954 } 955 if (elen != 0) { 956 error_f("unsupported extensions (len %zu)", elen); 957 r = SSH_ERR_FEATURE_UNSUPPORTED; 958 goto out; 959 } 960 if (*dch->hostname == '\0') { 961 free(dch->hostname); 962 dch->hostname = NULL; 963 } 964 if (*dch->user == '\0') { 965 free(dch->user); 966 dch->user = NULL; 967 } 968 while (sshbuf_len(b) != 0) { 969 dch->keys = xrecallocarray(dch->keys, dch->nkeys, 970 dch->nkeys + 1, sizeof(*dch->keys)); 971 dch->key_is_ca = xrecallocarray(dch->key_is_ca, dch->nkeys, 972 dch->nkeys + 1, sizeof(*dch->key_is_ca)); 973 if ((r = sshkey_froms(b, &k)) != 0 || 974 (r = sshbuf_get_u8(b, &key_is_ca)) != 0) 975 goto out; 976 if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT, 977 SSH_FP_DEFAULT)) == NULL) 978 fatal_f("fingerprint failed"); 979 debug3_f("%s%s%s: adding %skey %s %s", 980 dch->user == NULL ? "" : dch->user, 981 dch->user == NULL ? "" : "@", 982 dch->hostname, key_is_ca ? "CA " : "", sshkey_type(k), fp); 983 free(fp); 984 dch->keys[dch->nkeys] = k; 985 dch->key_is_ca[dch->nkeys] = key_is_ca != 0; 986 dch->nkeys++; 987 k = NULL; /* transferred */ 988 } 989 /* success */ 990 r = 0; 991 out: 992 sshkey_free(k); 993 return r; 994 } 995 996 static int 997 parse_dest_constraint(struct sshbuf *m, struct dest_constraint *dc) 998 { 999 struct sshbuf *b = NULL, *frombuf = NULL, *tobuf = NULL; 1000 int r; 1001 size_t elen = 0; 1002 1003 debug3_f("entering"); 1004 1005 memset(dc, '\0', sizeof(*dc)); 1006 if ((r = sshbuf_froms(m, &b)) != 0 || 1007 (r = sshbuf_froms(b, &frombuf)) != 0 || 1008 (r = sshbuf_froms(b, &tobuf)) != 0 || 1009 (r = sshbuf_get_string_direct(b, NULL, &elen)) != 0) { 1010 error_fr(r, "parse"); 1011 goto out; 1012 } 1013 if ((r = parse_dest_constraint_hop(frombuf, &dc->from)) != 0 || 1014 (r = parse_dest_constraint_hop(tobuf, &dc->to)) != 0) 1015 goto out; /* already logged */ 1016 if (elen != 0) { 1017 error_f("unsupported extensions (len %zu)", elen); 1018 r = SSH_ERR_FEATURE_UNSUPPORTED; 1019 goto out; 1020 } 1021 debug2_f("parsed %s (%u keys) > %s%s%s (%u keys)", 1022 dc->from.hostname ? dc->from.hostname : "(ORIGIN)", dc->from.nkeys, 1023 dc->to.user ? dc->to.user : "", dc->to.user ? "@" : "", 1024 dc->to.hostname ? dc->to.hostname : "(ANY)", dc->to.nkeys); 1025 /* check consistency */ 1026 if ((dc->from.hostname == NULL) != (dc->from.nkeys == 0) || 1027 dc->from.user != NULL) { 1028 error_f("inconsistent \"from\" specification"); 1029 r = SSH_ERR_INVALID_FORMAT; 1030 goto out; 1031 } 1032 if (dc->to.hostname == NULL || dc->to.nkeys == 0) { 1033 error_f("incomplete \"to\" specification"); 1034 r = SSH_ERR_INVALID_FORMAT; 1035 goto out; 1036 } 1037 /* success */ 1038 r = 0; 1039 out: 1040 sshbuf_free(b); 1041 sshbuf_free(frombuf); 1042 sshbuf_free(tobuf); 1043 return r; 1044 } 1045 1046 static int 1047 parse_key_constraint_extension(struct sshbuf *m, char **sk_providerp, 1048 struct dest_constraint **dcsp, size_t *ndcsp) 1049 { 1050 char *ext_name = NULL; 1051 int r; 1052 struct sshbuf *b = NULL; 1053 1054 if ((r = sshbuf_get_cstring(m, &ext_name, NULL)) != 0) { 1055 error_fr(r, "parse constraint extension"); 1056 goto out; 1057 } 1058 debug_f("constraint ext %s", ext_name); 1059 if (strcmp(ext_name, "sk-provider@openssh.com") == 0) { 1060 if (sk_providerp == NULL) { 1061 error_f("%s not valid here", ext_name); 1062 r = SSH_ERR_INVALID_FORMAT; 1063 goto out; 1064 } 1065 if (*sk_providerp != NULL) { 1066 error_f("%s already set", ext_name); 1067 r = SSH_ERR_INVALID_FORMAT; 1068 goto out; 1069 } 1070 if ((r = sshbuf_get_cstring(m, sk_providerp, NULL)) != 0) { 1071 error_fr(r, "parse %s", ext_name); 1072 goto out; 1073 } 1074 } else if (strcmp(ext_name, 1075 "restrict-destination-v00@openssh.com") == 0) { 1076 if (*dcsp != NULL) { 1077 error_f("%s already set", ext_name); 1078 goto out; 1079 } 1080 if ((r = sshbuf_froms(m, &b)) != 0) { 1081 error_fr(r, "parse %s outer", ext_name); 1082 goto out; 1083 } 1084 while (sshbuf_len(b) != 0) { 1085 if (*ndcsp >= AGENT_MAX_DEST_CONSTRAINTS) { 1086 error_f("too many %s constraints", ext_name); 1087 goto out; 1088 } 1089 *dcsp = xrecallocarray(*dcsp, *ndcsp, *ndcsp + 1, 1090 sizeof(**dcsp)); 1091 if ((r = parse_dest_constraint(b, 1092 *dcsp + (*ndcsp)++)) != 0) 1093 goto out; /* error already logged */ 1094 } 1095 } else { 1096 error_f("unsupported constraint \"%s\"", ext_name); 1097 r = SSH_ERR_FEATURE_UNSUPPORTED; 1098 goto out; 1099 } 1100 /* success */ 1101 r = 0; 1102 out: 1103 free(ext_name); 1104 sshbuf_free(b); 1105 return r; 1106 } 1107 1108 static int 1109 parse_key_constraints(struct sshbuf *m, struct sshkey *k, time_t *deathp, 1110 u_int *secondsp, int *confirmp, char **sk_providerp, 1111 struct dest_constraint **dcsp, size_t *ndcsp) 1112 { 1113 u_char ctype; 1114 int r; 1115 u_int seconds, maxsign = 0; 1116 1117 while (sshbuf_len(m)) { 1118 if ((r = sshbuf_get_u8(m, &ctype)) != 0) { 1119 error_fr(r, "parse constraint type"); 1120 goto out; 1121 } 1122 switch (ctype) { 1123 case SSH_AGENT_CONSTRAIN_LIFETIME: 1124 if (*deathp != 0) { 1125 error_f("lifetime already set"); 1126 r = SSH_ERR_INVALID_FORMAT; 1127 goto out; 1128 } 1129 if ((r = sshbuf_get_u32(m, &seconds)) != 0) { 1130 error_fr(r, "parse lifetime constraint"); 1131 goto out; 1132 } 1133 *deathp = monotime() + seconds; 1134 *secondsp = seconds; 1135 break; 1136 case SSH_AGENT_CONSTRAIN_CONFIRM: 1137 if (*confirmp != 0) { 1138 error_f("confirm already set"); 1139 r = SSH_ERR_INVALID_FORMAT; 1140 goto out; 1141 } 1142 *confirmp = 1; 1143 break; 1144 case SSH_AGENT_CONSTRAIN_MAXSIGN: 1145 if (k == NULL) { 1146 error_f("maxsign not valid here"); 1147 r = SSH_ERR_INVALID_FORMAT; 1148 goto out; 1149 } 1150 if (maxsign != 0) { 1151 error_f("maxsign already set"); 1152 r = SSH_ERR_INVALID_FORMAT; 1153 goto out; 1154 } 1155 if ((r = sshbuf_get_u32(m, &maxsign)) != 0) { 1156 error_fr(r, "parse maxsign constraint"); 1157 goto out; 1158 } 1159 if ((r = sshkey_enable_maxsign(k, maxsign)) != 0) { 1160 error_fr(r, "enable maxsign"); 1161 goto out; 1162 } 1163 break; 1164 case SSH_AGENT_CONSTRAIN_EXTENSION: 1165 if ((r = parse_key_constraint_extension(m, 1166 sk_providerp, dcsp, ndcsp)) != 0) 1167 goto out; /* error already logged */ 1168 break; 1169 default: 1170 error_f("Unknown constraint %d", ctype); 1171 r = SSH_ERR_FEATURE_UNSUPPORTED; 1172 goto out; 1173 } 1174 } 1175 /* success */ 1176 r = 0; 1177 out: 1178 return r; 1179 } 1180 1181 static void 1182 process_add_identity(SocketEntry *e) 1183 { 1184 Identity *id; 1185 int success = 0, confirm = 0; 1186 char *fp, *comment = NULL, *sk_provider = NULL; 1187 char canonical_provider[PATH_MAX]; 1188 time_t death = 0; 1189 u_int seconds = 0; 1190 struct dest_constraint *dest_constraints = NULL; 1191 size_t ndest_constraints = 0; 1192 struct sshkey *k = NULL; 1193 int r = SSH_ERR_INTERNAL_ERROR; 1194 1195 debug2_f("entering"); 1196 if ((r = sshkey_private_deserialize(e->request, &k)) != 0 || 1197 k == NULL || 1198 (r = sshbuf_get_cstring(e->request, &comment, NULL)) != 0) { 1199 error_fr(r, "parse"); 1200 goto out; 1201 } 1202 if (parse_key_constraints(e->request, k, &death, &seconds, &confirm, 1203 &sk_provider, &dest_constraints, &ndest_constraints) != 0) { 1204 error_f("failed to parse constraints"); 1205 sshbuf_reset(e->request); 1206 goto out; 1207 } 1208 1209 if (sk_provider != NULL) { 1210 if (!sshkey_is_sk(k)) { 1211 error("Cannot add provider: %s is not an " 1212 "authenticator-hosted key", sshkey_type(k)); 1213 goto out; 1214 } 1215 if (strcasecmp(sk_provider, "internal") == 0) { 1216 debug_f("internal provider"); 1217 } else { 1218 if (realpath(sk_provider, canonical_provider) == NULL) { 1219 verbose("failed provider \"%.100s\": " 1220 "realpath: %s", sk_provider, 1221 strerror(errno)); 1222 goto out; 1223 } 1224 free(sk_provider); 1225 sk_provider = xstrdup(canonical_provider); 1226 if (match_pattern_list(sk_provider, 1227 allowed_providers, 0) != 1) { 1228 error("Refusing add key: " 1229 "provider %s not allowed", sk_provider); 1230 goto out; 1231 } 1232 } 1233 } 1234 if ((r = sshkey_shield_private(k)) != 0) { 1235 error_fr(r, "shield private"); 1236 goto out; 1237 } 1238 if (lifetime && !death) 1239 death = monotime() + lifetime; 1240 if ((id = lookup_identity(k)) == NULL) { 1241 id = xcalloc(1, sizeof(Identity)); 1242 TAILQ_INSERT_TAIL(&idtab->idlist, id, next); 1243 /* Increment the number of identities. */ 1244 idtab->nentries++; 1245 } else { 1246 /* identity not visible, do not update */ 1247 if (identity_permitted(id, e, NULL, NULL, NULL) != 0) 1248 goto out; /* error already logged */ 1249 /* key state might have been updated */ 1250 sshkey_free(id->key); 1251 free(id->comment); 1252 free(id->sk_provider); 1253 free_dest_constraints(id->dest_constraints, 1254 id->ndest_constraints); 1255 } 1256 /* success */ 1257 id->key = k; 1258 id->comment = comment; 1259 id->death = death; 1260 id->confirm = confirm; 1261 id->sk_provider = sk_provider; 1262 id->dest_constraints = dest_constraints; 1263 id->ndest_constraints = ndest_constraints; 1264 1265 if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT, 1266 SSH_FP_DEFAULT)) == NULL) 1267 fatal_f("sshkey_fingerprint failed"); 1268 debug_f("add %s %s \"%.100s\" (life: %u) (confirm: %u) " 1269 "(provider: %s) (destination constraints: %zu)", 1270 sshkey_ssh_name(k), fp, comment, seconds, confirm, 1271 sk_provider == NULL ? "none" : sk_provider, ndest_constraints); 1272 free(fp); 1273 /* transferred */ 1274 k = NULL; 1275 comment = NULL; 1276 sk_provider = NULL; 1277 dest_constraints = NULL; 1278 ndest_constraints = 0; 1279 success = 1; 1280 out: 1281 free(sk_provider); 1282 free(comment); 1283 sshkey_free(k); 1284 free_dest_constraints(dest_constraints, ndest_constraints); 1285 send_status(e, success); 1286 } 1287 1288 /* XXX todo: encrypt sensitive data with passphrase */ 1289 static void 1290 process_lock_agent(SocketEntry *e, int lock) 1291 { 1292 int r, success = 0, delay; 1293 char *passwd; 1294 u_char passwdhash[LOCK_SIZE]; 1295 static u_int fail_count = 0; 1296 size_t pwlen; 1297 1298 debug2_f("entering"); 1299 /* 1300 * This is deliberately fatal: the user has requested that we lock, 1301 * but we can't parse their request properly. The only safe thing to 1302 * do is abort. 1303 */ 1304 if ((r = sshbuf_get_cstring(e->request, &passwd, &pwlen)) != 0) 1305 fatal_fr(r, "parse"); 1306 if (pwlen == 0) { 1307 debug("empty password not supported"); 1308 } else if (locked && !lock) { 1309 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt), 1310 passwdhash, sizeof(passwdhash), LOCK_ROUNDS) < 0) 1311 fatal("bcrypt_pbkdf"); 1312 if (timingsafe_bcmp(passwdhash, lock_pwhash, LOCK_SIZE) == 0) { 1313 debug("agent unlocked"); 1314 locked = 0; 1315 fail_count = 0; 1316 explicit_bzero(lock_pwhash, sizeof(lock_pwhash)); 1317 success = 1; 1318 } else { 1319 /* delay in 0.1s increments up to 10s */ 1320 if (fail_count < 100) 1321 fail_count++; 1322 delay = 100000 * fail_count; 1323 debug("unlock failed, delaying %0.1lf seconds", 1324 (double)delay/1000000); 1325 usleep(delay); 1326 } 1327 explicit_bzero(passwdhash, sizeof(passwdhash)); 1328 } else if (!locked && lock) { 1329 debug("agent locked"); 1330 locked = 1; 1331 arc4random_buf(lock_salt, sizeof(lock_salt)); 1332 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt), 1333 lock_pwhash, sizeof(lock_pwhash), LOCK_ROUNDS) < 0) 1334 fatal("bcrypt_pbkdf"); 1335 success = 1; 1336 } 1337 freezero(passwd, pwlen); 1338 send_status(e, success); 1339 } 1340 1341 static void 1342 no_identities(SocketEntry *e) 1343 { 1344 struct sshbuf *msg; 1345 int r; 1346 1347 if ((msg = sshbuf_new()) == NULL) 1348 fatal_f("sshbuf_new failed"); 1349 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 || 1350 (r = sshbuf_put_u32(msg, 0)) != 0 || 1351 (r = sshbuf_put_stringb(e->output, msg)) != 0) 1352 fatal_fr(r, "compose"); 1353 sshbuf_free(msg); 1354 } 1355 1356 #ifdef ENABLE_PKCS11 1357 static void 1358 process_add_smartcard_key(SocketEntry *e) 1359 { 1360 char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX]; 1361 char **comments = NULL; 1362 int r, i, count = 0, success = 0, confirm = 0; 1363 u_int seconds = 0; 1364 time_t death = 0; 1365 struct sshkey **keys = NULL, *k; 1366 Identity *id; 1367 struct dest_constraint *dest_constraints = NULL; 1368 size_t ndest_constraints = 0; 1369 1370 debug2_f("entering"); 1371 if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 || 1372 (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) { 1373 error_fr(r, "parse"); 1374 goto send; 1375 } 1376 if (parse_key_constraints(e->request, NULL, &death, &seconds, &confirm, 1377 NULL, &dest_constraints, &ndest_constraints) != 0) { 1378 error_f("failed to parse constraints"); 1379 goto send; 1380 } 1381 if (realpath(provider, canonical_provider) == NULL) { 1382 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s", 1383 provider, strerror(errno)); 1384 goto send; 1385 } 1386 if (match_pattern_list(canonical_provider, allowed_providers, 0) != 1) { 1387 verbose("refusing PKCS#11 add of \"%.100s\": " 1388 "provider not allowed", canonical_provider); 1389 goto send; 1390 } 1391 debug_f("add %.100s", canonical_provider); 1392 if (lifetime && !death) 1393 death = monotime() + lifetime; 1394 1395 count = pkcs11_add_provider(canonical_provider, pin, &keys, &comments); 1396 for (i = 0; i < count; i++) { 1397 k = keys[i]; 1398 if (lookup_identity(k) == NULL) { 1399 id = xcalloc(1, sizeof(Identity)); 1400 id->key = k; 1401 keys[i] = NULL; /* transferred */ 1402 id->provider = xstrdup(canonical_provider); 1403 if (*comments[i] != '\0') { 1404 id->comment = comments[i]; 1405 comments[i] = NULL; /* transferred */ 1406 } else { 1407 id->comment = xstrdup(canonical_provider); 1408 } 1409 id->death = death; 1410 id->confirm = confirm; 1411 id->dest_constraints = dest_constraints; 1412 id->ndest_constraints = ndest_constraints; 1413 dest_constraints = NULL; /* transferred */ 1414 ndest_constraints = 0; 1415 TAILQ_INSERT_TAIL(&idtab->idlist, id, next); 1416 idtab->nentries++; 1417 success = 1; 1418 } 1419 /* XXX update constraints for existing keys */ 1420 sshkey_free(keys[i]); 1421 free(comments[i]); 1422 } 1423 send: 1424 free(pin); 1425 free(provider); 1426 free(keys); 1427 free(comments); 1428 free_dest_constraints(dest_constraints, ndest_constraints); 1429 send_status(e, success); 1430 } 1431 1432 static void 1433 process_remove_smartcard_key(SocketEntry *e) 1434 { 1435 char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX]; 1436 int r, success = 0; 1437 Identity *id, *nxt; 1438 1439 debug2_f("entering"); 1440 if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 || 1441 (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) { 1442 error_fr(r, "parse"); 1443 goto send; 1444 } 1445 free(pin); 1446 1447 if (realpath(provider, canonical_provider) == NULL) { 1448 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s", 1449 provider, strerror(errno)); 1450 goto send; 1451 } 1452 1453 debug_f("remove %.100s", canonical_provider); 1454 for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) { 1455 nxt = TAILQ_NEXT(id, next); 1456 /* Skip file--based keys */ 1457 if (id->provider == NULL) 1458 continue; 1459 if (!strcmp(canonical_provider, id->provider)) { 1460 TAILQ_REMOVE(&idtab->idlist, id, next); 1461 free_identity(id); 1462 idtab->nentries--; 1463 } 1464 } 1465 if (pkcs11_del_provider(canonical_provider) == 0) 1466 success = 1; 1467 else 1468 error_f("pkcs11_del_provider failed"); 1469 send: 1470 free(provider); 1471 send_status(e, success); 1472 } 1473 #endif /* ENABLE_PKCS11 */ 1474 1475 static int 1476 process_ext_session_bind(SocketEntry *e) 1477 { 1478 int r, sid_match, key_match; 1479 struct sshkey *key = NULL; 1480 struct sshbuf *sid = NULL, *sig = NULL; 1481 char *fp = NULL; 1482 size_t i; 1483 u_char fwd = 0; 1484 1485 debug2_f("entering"); 1486 if ((r = sshkey_froms(e->request, &key)) != 0 || 1487 (r = sshbuf_froms(e->request, &sid)) != 0 || 1488 (r = sshbuf_froms(e->request, &sig)) != 0 || 1489 (r = sshbuf_get_u8(e->request, &fwd)) != 0) { 1490 error_fr(r, "parse"); 1491 goto out; 1492 } 1493 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT, 1494 SSH_FP_DEFAULT)) == NULL) 1495 fatal_f("fingerprint failed"); 1496 /* check signature with hostkey on session ID */ 1497 if ((r = sshkey_verify(key, sshbuf_ptr(sig), sshbuf_len(sig), 1498 sshbuf_ptr(sid), sshbuf_len(sid), NULL, 0, NULL)) != 0) { 1499 error_fr(r, "sshkey_verify for %s %s", sshkey_type(key), fp); 1500 goto out; 1501 } 1502 /* check whether sid/key already recorded */ 1503 for (i = 0; i < e->nsession_ids; i++) { 1504 if (!e->session_ids[i].forwarded) { 1505 error_f("attempt to bind session ID to socket " 1506 "previously bound for authentication attempt"); 1507 r = -1; 1508 goto out; 1509 } 1510 sid_match = buf_equal(sid, e->session_ids[i].sid) == 0; 1511 key_match = sshkey_equal(key, e->session_ids[i].key); 1512 if (sid_match && key_match) { 1513 debug_f("session ID already recorded for %s %s", 1514 sshkey_type(key), fp); 1515 r = 0; 1516 goto out; 1517 } else if (sid_match) { 1518 error_f("session ID recorded against different key " 1519 "for %s %s", sshkey_type(key), fp); 1520 r = -1; 1521 goto out; 1522 } 1523 /* 1524 * new sid with previously-seen key can happen, e.g. multiple 1525 * connections to the same host. 1526 */ 1527 } 1528 /* record new key/sid */ 1529 if (e->nsession_ids >= AGENT_MAX_SESSION_IDS) { 1530 error_f("too many session IDs recorded"); 1531 goto out; 1532 } 1533 e->session_ids = xrecallocarray(e->session_ids, e->nsession_ids, 1534 e->nsession_ids + 1, sizeof(*e->session_ids)); 1535 i = e->nsession_ids++; 1536 debug_f("recorded %s %s (slot %zu of %d)", sshkey_type(key), fp, i, 1537 AGENT_MAX_SESSION_IDS); 1538 e->session_ids[i].key = key; 1539 e->session_ids[i].forwarded = fwd != 0; 1540 key = NULL; /* transferred */ 1541 /* can't transfer sid; it's refcounted and scoped to request's life */ 1542 if ((e->session_ids[i].sid = sshbuf_new()) == NULL) 1543 fatal_f("sshbuf_new"); 1544 if ((r = sshbuf_putb(e->session_ids[i].sid, sid)) != 0) 1545 fatal_fr(r, "sshbuf_putb session ID"); 1546 /* success */ 1547 r = 0; 1548 out: 1549 free(fp); 1550 sshkey_free(key); 1551 sshbuf_free(sid); 1552 sshbuf_free(sig); 1553 return r == 0 ? 1 : 0; 1554 } 1555 1556 static void 1557 process_extension(SocketEntry *e) 1558 { 1559 int r, success = 0; 1560 char *name; 1561 1562 debug2_f("entering"); 1563 if ((r = sshbuf_get_cstring(e->request, &name, NULL)) != 0) { 1564 error_fr(r, "parse"); 1565 goto send; 1566 } 1567 if (strcmp(name, "session-bind@openssh.com") == 0) 1568 success = process_ext_session_bind(e); 1569 else 1570 debug_f("unsupported extension \"%s\"", name); 1571 free(name); 1572 send: 1573 send_status(e, success); 1574 } 1575 /* 1576 * dispatch incoming message. 1577 * returns 1 on success, 0 for incomplete messages or -1 on error. 1578 */ 1579 static int 1580 process_message(u_int socknum) 1581 { 1582 u_int msg_len; 1583 u_char type; 1584 const u_char *cp; 1585 int r; 1586 SocketEntry *e; 1587 1588 if (socknum >= sockets_alloc) 1589 fatal_f("sock %u >= allocated %u", socknum, sockets_alloc); 1590 e = &sockets[socknum]; 1591 1592 if (sshbuf_len(e->input) < 5) 1593 return 0; /* Incomplete message header. */ 1594 cp = sshbuf_ptr(e->input); 1595 msg_len = PEEK_U32(cp); 1596 if (msg_len > AGENT_MAX_LEN) { 1597 debug_f("socket %u (fd=%d) message too long %u > %u", 1598 socknum, e->fd, msg_len, AGENT_MAX_LEN); 1599 return -1; 1600 } 1601 if (sshbuf_len(e->input) < msg_len + 4) 1602 return 0; /* Incomplete message body. */ 1603 1604 /* move the current input to e->request */ 1605 sshbuf_reset(e->request); 1606 if ((r = sshbuf_get_stringb(e->input, e->request)) != 0 || 1607 (r = sshbuf_get_u8(e->request, &type)) != 0) { 1608 if (r == SSH_ERR_MESSAGE_INCOMPLETE || 1609 r == SSH_ERR_STRING_TOO_LARGE) { 1610 error_fr(r, "parse"); 1611 return -1; 1612 } 1613 fatal_fr(r, "parse"); 1614 } 1615 1616 debug_f("socket %u (fd=%d) type %d", socknum, e->fd, type); 1617 1618 /* check whether agent is locked */ 1619 if (locked && type != SSH_AGENTC_UNLOCK) { 1620 sshbuf_reset(e->request); 1621 switch (type) { 1622 case SSH2_AGENTC_REQUEST_IDENTITIES: 1623 /* send empty lists */ 1624 no_identities(e); 1625 break; 1626 default: 1627 /* send a fail message for all other request types */ 1628 send_status(e, 0); 1629 } 1630 return 1; 1631 } 1632 1633 switch (type) { 1634 case SSH_AGENTC_LOCK: 1635 case SSH_AGENTC_UNLOCK: 1636 process_lock_agent(e, type == SSH_AGENTC_LOCK); 1637 break; 1638 case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES: 1639 process_remove_all_identities(e); /* safe for !WITH_SSH1 */ 1640 break; 1641 /* ssh2 */ 1642 case SSH2_AGENTC_SIGN_REQUEST: 1643 process_sign_request2(e); 1644 break; 1645 case SSH2_AGENTC_REQUEST_IDENTITIES: 1646 process_request_identities(e); 1647 break; 1648 case SSH2_AGENTC_ADD_IDENTITY: 1649 case SSH2_AGENTC_ADD_ID_CONSTRAINED: 1650 process_add_identity(e); 1651 break; 1652 case SSH2_AGENTC_REMOVE_IDENTITY: 1653 process_remove_identity(e); 1654 break; 1655 case SSH2_AGENTC_REMOVE_ALL_IDENTITIES: 1656 process_remove_all_identities(e); 1657 break; 1658 #ifdef ENABLE_PKCS11 1659 case SSH_AGENTC_ADD_SMARTCARD_KEY: 1660 case SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED: 1661 process_add_smartcard_key(e); 1662 break; 1663 case SSH_AGENTC_REMOVE_SMARTCARD_KEY: 1664 process_remove_smartcard_key(e); 1665 break; 1666 #endif /* ENABLE_PKCS11 */ 1667 case SSH_AGENTC_EXTENSION: 1668 process_extension(e); 1669 break; 1670 default: 1671 /* Unknown message. Respond with failure. */ 1672 error("Unknown message %d", type); 1673 sshbuf_reset(e->request); 1674 send_status(e, 0); 1675 break; 1676 } 1677 return 1; 1678 } 1679 1680 static void 1681 new_socket(sock_type type, int fd) 1682 { 1683 u_int i, old_alloc, new_alloc; 1684 1685 debug_f("type = %s", type == AUTH_CONNECTION ? "CONNECTION" : 1686 (type == AUTH_SOCKET ? "SOCKET" : "UNKNOWN")); 1687 set_nonblock(fd); 1688 1689 if (fd > max_fd) 1690 max_fd = fd; 1691 1692 for (i = 0; i < sockets_alloc; i++) 1693 if (sockets[i].type == AUTH_UNUSED) { 1694 sockets[i].fd = fd; 1695 if ((sockets[i].input = sshbuf_new()) == NULL || 1696 (sockets[i].output = sshbuf_new()) == NULL || 1697 (sockets[i].request = sshbuf_new()) == NULL) 1698 fatal_f("sshbuf_new failed"); 1699 sockets[i].type = type; 1700 return; 1701 } 1702 old_alloc = sockets_alloc; 1703 new_alloc = sockets_alloc + 10; 1704 sockets = xrecallocarray(sockets, old_alloc, new_alloc, 1705 sizeof(sockets[0])); 1706 for (i = old_alloc; i < new_alloc; i++) 1707 sockets[i].type = AUTH_UNUSED; 1708 sockets_alloc = new_alloc; 1709 sockets[old_alloc].fd = fd; 1710 if ((sockets[old_alloc].input = sshbuf_new()) == NULL || 1711 (sockets[old_alloc].output = sshbuf_new()) == NULL || 1712 (sockets[old_alloc].request = sshbuf_new()) == NULL) 1713 fatal_f("sshbuf_new failed"); 1714 sockets[old_alloc].type = type; 1715 } 1716 1717 static int 1718 handle_socket_read(u_int socknum) 1719 { 1720 struct sockaddr_un sunaddr; 1721 socklen_t slen; 1722 uid_t euid; 1723 gid_t egid; 1724 int fd; 1725 1726 slen = sizeof(sunaddr); 1727 fd = accept(sockets[socknum].fd, (struct sockaddr *)&sunaddr, &slen); 1728 if (fd == -1) { 1729 error("accept from AUTH_SOCKET: %s", strerror(errno)); 1730 return -1; 1731 } 1732 if (getpeereid(fd, &euid, &egid) == -1) { 1733 error("getpeereid %d failed: %s", fd, strerror(errno)); 1734 close(fd); 1735 return -1; 1736 } 1737 if ((euid != 0) && (getuid() != euid)) { 1738 error("uid mismatch: peer euid %u != uid %u", 1739 (u_int) euid, (u_int) getuid()); 1740 close(fd); 1741 return -1; 1742 } 1743 new_socket(AUTH_CONNECTION, fd); 1744 return 0; 1745 } 1746 1747 static int 1748 handle_conn_read(u_int socknum) 1749 { 1750 char buf[AGENT_RBUF_LEN]; 1751 ssize_t len; 1752 int r; 1753 1754 if ((len = read(sockets[socknum].fd, buf, sizeof(buf))) <= 0) { 1755 if (len == -1) { 1756 if (errno == EAGAIN || errno == EINTR) 1757 return 0; 1758 error_f("read error on socket %u (fd %d): %s", 1759 socknum, sockets[socknum].fd, strerror(errno)); 1760 } 1761 return -1; 1762 } 1763 if ((r = sshbuf_put(sockets[socknum].input, buf, len)) != 0) 1764 fatal_fr(r, "compose"); 1765 explicit_bzero(buf, sizeof(buf)); 1766 for (;;) { 1767 if ((r = process_message(socknum)) == -1) 1768 return -1; 1769 else if (r == 0) 1770 break; 1771 } 1772 return 0; 1773 } 1774 1775 static int 1776 handle_conn_write(u_int socknum) 1777 { 1778 ssize_t len; 1779 int r; 1780 1781 if (sshbuf_len(sockets[socknum].output) == 0) 1782 return 0; /* shouldn't happen */ 1783 if ((len = write(sockets[socknum].fd, 1784 sshbuf_ptr(sockets[socknum].output), 1785 sshbuf_len(sockets[socknum].output))) <= 0) { 1786 if (len == -1) { 1787 if (errno == EAGAIN || errno == EINTR) 1788 return 0; 1789 error_f("read error on socket %u (fd %d): %s", 1790 socknum, sockets[socknum].fd, strerror(errno)); 1791 } 1792 return -1; 1793 } 1794 if ((r = sshbuf_consume(sockets[socknum].output, len)) != 0) 1795 fatal_fr(r, "consume"); 1796 return 0; 1797 } 1798 1799 static void 1800 after_poll(struct pollfd *pfd, size_t npfd, u_int maxfds) 1801 { 1802 size_t i; 1803 u_int socknum, activefds = npfd; 1804 1805 for (i = 0; i < npfd; i++) { 1806 if (pfd[i].revents == 0) 1807 continue; 1808 /* Find sockets entry */ 1809 for (socknum = 0; socknum < sockets_alloc; socknum++) { 1810 if (sockets[socknum].type != AUTH_SOCKET && 1811 sockets[socknum].type != AUTH_CONNECTION) 1812 continue; 1813 if (pfd[i].fd == sockets[socknum].fd) 1814 break; 1815 } 1816 if (socknum >= sockets_alloc) { 1817 error_f("no socket for fd %d", pfd[i].fd); 1818 continue; 1819 } 1820 /* Process events */ 1821 switch (sockets[socknum].type) { 1822 case AUTH_SOCKET: 1823 if ((pfd[i].revents & (POLLIN|POLLERR)) == 0) 1824 break; 1825 if (npfd > maxfds) { 1826 debug3("out of fds (active %u >= limit %u); " 1827 "skipping accept", activefds, maxfds); 1828 break; 1829 } 1830 if (handle_socket_read(socknum) == 0) 1831 activefds++; 1832 break; 1833 case AUTH_CONNECTION: 1834 if ((pfd[i].revents & (POLLIN|POLLHUP|POLLERR)) != 0 && 1835 handle_conn_read(socknum) != 0) 1836 goto close_sock; 1837 if ((pfd[i].revents & (POLLOUT|POLLHUP)) != 0 && 1838 handle_conn_write(socknum) != 0) { 1839 close_sock: 1840 if (activefds == 0) 1841 fatal("activefds == 0 at close_sock"); 1842 close_socket(&sockets[socknum]); 1843 activefds--; 1844 break; 1845 } 1846 break; 1847 default: 1848 break; 1849 } 1850 } 1851 } 1852 1853 static int 1854 prepare_poll(struct pollfd **pfdp, size_t *npfdp, int *timeoutp, u_int maxfds) 1855 { 1856 struct pollfd *pfd = *pfdp; 1857 size_t i, j, npfd = 0; 1858 time_t deadline; 1859 int r; 1860 1861 /* Count active sockets */ 1862 for (i = 0; i < sockets_alloc; i++) { 1863 switch (sockets[i].type) { 1864 case AUTH_SOCKET: 1865 case AUTH_CONNECTION: 1866 npfd++; 1867 break; 1868 case AUTH_UNUSED: 1869 break; 1870 default: 1871 fatal("Unknown socket type %d", sockets[i].type); 1872 break; 1873 } 1874 } 1875 if (npfd != *npfdp && 1876 (pfd = recallocarray(pfd, *npfdp, npfd, sizeof(*pfd))) == NULL) 1877 fatal_f("recallocarray failed"); 1878 *pfdp = pfd; 1879 *npfdp = npfd; 1880 1881 for (i = j = 0; i < sockets_alloc; i++) { 1882 switch (sockets[i].type) { 1883 case AUTH_SOCKET: 1884 if (npfd > maxfds) { 1885 debug3("out of fds (active %zu >= limit %u); " 1886 "skipping arming listener", npfd, maxfds); 1887 break; 1888 } 1889 pfd[j].fd = sockets[i].fd; 1890 pfd[j].revents = 0; 1891 pfd[j].events = POLLIN; 1892 j++; 1893 break; 1894 case AUTH_CONNECTION: 1895 pfd[j].fd = sockets[i].fd; 1896 pfd[j].revents = 0; 1897 /* 1898 * Only prepare to read if we can handle a full-size 1899 * input read buffer and enqueue a max size reply.. 1900 */ 1901 if ((r = sshbuf_check_reserve(sockets[i].input, 1902 AGENT_RBUF_LEN)) == 0 && 1903 (r = sshbuf_check_reserve(sockets[i].output, 1904 AGENT_MAX_LEN)) == 0) 1905 pfd[j].events = POLLIN; 1906 else if (r != SSH_ERR_NO_BUFFER_SPACE) 1907 fatal_fr(r, "reserve"); 1908 if (sshbuf_len(sockets[i].output) > 0) 1909 pfd[j].events |= POLLOUT; 1910 j++; 1911 break; 1912 default: 1913 break; 1914 } 1915 } 1916 deadline = reaper(); 1917 if (parent_alive_interval != 0) 1918 deadline = (deadline == 0) ? parent_alive_interval : 1919 MINIMUM(deadline, parent_alive_interval); 1920 if (deadline == 0) { 1921 *timeoutp = -1; /* INFTIM */ 1922 } else { 1923 if (deadline > INT_MAX / 1000) 1924 *timeoutp = INT_MAX / 1000; 1925 else 1926 *timeoutp = deadline * 1000; 1927 } 1928 return (1); 1929 } 1930 1931 static void 1932 cleanup_socket(void) 1933 { 1934 if (cleanup_pid != 0 && getpid() != cleanup_pid) 1935 return; 1936 debug_f("cleanup"); 1937 if (socket_name[0]) 1938 unlink(socket_name); 1939 if (socket_dir[0]) 1940 rmdir(socket_dir); 1941 } 1942 1943 void 1944 cleanup_exit(int i) 1945 { 1946 cleanup_socket(); 1947 _exit(i); 1948 } 1949 1950 static void 1951 cleanup_handler(int sig) 1952 { 1953 cleanup_socket(); 1954 #ifdef ENABLE_PKCS11 1955 pkcs11_terminate(); 1956 #endif 1957 _exit(2); 1958 } 1959 1960 static void 1961 check_parent_exists(void) 1962 { 1963 /* 1964 * If our parent has exited then getppid() will return (pid_t)1, 1965 * so testing for that should be safe. 1966 */ 1967 if (parent_pid != -1 && getppid() != parent_pid) { 1968 /* printf("Parent has died - Authentication agent exiting.\n"); */ 1969 cleanup_socket(); 1970 _exit(2); 1971 } 1972 } 1973 1974 static void 1975 usage(void) 1976 { 1977 fprintf(stderr, 1978 "usage: ssh-agent [-c | -s] [-Dd] [-a bind_address] [-E fingerprint_hash]\n" 1979 " [-O option] [-P allowed_providers] [-t life]\n" 1980 " ssh-agent [-a bind_address] [-E fingerprint_hash] [-O option]\n" 1981 " [-P allowed_providers] [-t life] command [arg ...]\n" 1982 " ssh-agent [-c | -s] -k\n"); 1983 exit(1); 1984 } 1985 1986 int 1987 main(int ac, char **av) 1988 { 1989 int c_flag = 0, d_flag = 0, D_flag = 0, k_flag = 0, s_flag = 0; 1990 int sock, ch, result, saved_errno; 1991 char *shell, *format, *pidstr, *agentsocket = NULL; 1992 struct rlimit rlim; 1993 extern int optind; 1994 extern char *optarg; 1995 pid_t pid; 1996 char pidstrbuf[1 + 3 * sizeof pid]; 1997 size_t len; 1998 mode_t prev_mask; 1999 int timeout = -1; /* INFTIM */ 2000 struct pollfd *pfd = NULL; 2001 size_t npfd = 0; 2002 u_int maxfds; 2003 2004 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */ 2005 sanitise_stdfd(); 2006 2007 /* drop */ 2008 (void)setegid(getgid()); 2009 (void)setgid(getgid()); 2010 2011 if (getrlimit(RLIMIT_NOFILE, &rlim) == -1) 2012 fatal("%s: getrlimit: %s", __progname, strerror(errno)); 2013 2014 #ifdef WITH_OPENSSL 2015 OpenSSL_add_all_algorithms(); 2016 #endif 2017 2018 while ((ch = getopt(ac, av, "cDdksE:a:O:P:t:")) != -1) { 2019 switch (ch) { 2020 case 'E': 2021 fingerprint_hash = ssh_digest_alg_by_name(optarg); 2022 if (fingerprint_hash == -1) 2023 fatal("Invalid hash algorithm \"%s\"", optarg); 2024 break; 2025 case 'c': 2026 if (s_flag) 2027 usage(); 2028 c_flag++; 2029 break; 2030 case 'k': 2031 k_flag++; 2032 break; 2033 case 'O': 2034 if (strcmp(optarg, "no-restrict-websafe") == 0) 2035 restrict_websafe = 0; 2036 else 2037 fatal("Unknown -O option"); 2038 break; 2039 case 'P': 2040 if (allowed_providers != NULL) 2041 fatal("-P option already specified"); 2042 allowed_providers = xstrdup(optarg); 2043 break; 2044 case 's': 2045 if (c_flag) 2046 usage(); 2047 s_flag++; 2048 break; 2049 case 'd': 2050 if (d_flag || D_flag) 2051 usage(); 2052 d_flag++; 2053 break; 2054 case 'D': 2055 if (d_flag || D_flag) 2056 usage(); 2057 D_flag++; 2058 break; 2059 case 'a': 2060 agentsocket = optarg; 2061 break; 2062 case 't': 2063 if ((lifetime = convtime(optarg)) == -1) { 2064 fprintf(stderr, "Invalid lifetime\n"); 2065 usage(); 2066 } 2067 break; 2068 default: 2069 usage(); 2070 } 2071 } 2072 ac -= optind; 2073 av += optind; 2074 2075 if (ac > 0 && (c_flag || k_flag || s_flag || d_flag || D_flag)) 2076 usage(); 2077 2078 if (allowed_providers == NULL) 2079 allowed_providers = xstrdup(DEFAULT_ALLOWED_PROVIDERS); 2080 2081 if (ac == 0 && !c_flag && !s_flag) { 2082 shell = getenv("SHELL"); 2083 if (shell != NULL && (len = strlen(shell)) > 2 && 2084 strncmp(shell + len - 3, "csh", 3) == 0) 2085 c_flag = 1; 2086 } 2087 if (k_flag) { 2088 const char *errstr = NULL; 2089 2090 pidstr = getenv(SSH_AGENTPID_ENV_NAME); 2091 if (pidstr == NULL) { 2092 fprintf(stderr, "%s not set, cannot kill agent\n", 2093 SSH_AGENTPID_ENV_NAME); 2094 exit(1); 2095 } 2096 pid = (int)strtonum(pidstr, 2, INT_MAX, &errstr); 2097 if (errstr) { 2098 fprintf(stderr, 2099 "%s=\"%s\", which is not a good PID: %s\n", 2100 SSH_AGENTPID_ENV_NAME, pidstr, errstr); 2101 exit(1); 2102 } 2103 if (kill(pid, SIGTERM) == -1) { 2104 perror("kill"); 2105 exit(1); 2106 } 2107 format = c_flag ? "unsetenv %s;\n" : "unset %s;\n"; 2108 printf(format, SSH_AUTHSOCKET_ENV_NAME); 2109 printf(format, SSH_AGENTPID_ENV_NAME); 2110 printf("echo Agent pid %ld killed;\n", (long)pid); 2111 exit(0); 2112 } 2113 2114 /* 2115 * Minimum file descriptors: 2116 * stdio (3) + listener (1) + syslog (1 maybe) + connection (1) + 2117 * a few spare for libc / stack protectors / sanitisers, etc. 2118 */ 2119 #define SSH_AGENT_MIN_FDS (3+1+1+1+4) 2120 if (rlim.rlim_cur < SSH_AGENT_MIN_FDS) 2121 fatal("%s: file descriptor rlimit %lld too low (minimum %u)", 2122 __progname, (long long)rlim.rlim_cur, SSH_AGENT_MIN_FDS); 2123 maxfds = rlim.rlim_cur - SSH_AGENT_MIN_FDS; 2124 2125 parent_pid = getpid(); 2126 2127 if (agentsocket == NULL) { 2128 /* Create private directory for agent socket */ 2129 mktemp_proto(socket_dir, sizeof(socket_dir)); 2130 if (mkdtemp(socket_dir) == NULL) { 2131 perror("mkdtemp: private socket dir"); 2132 exit(1); 2133 } 2134 snprintf(socket_name, sizeof socket_name, "%s/agent.%ld", socket_dir, 2135 (long)parent_pid); 2136 } else { 2137 /* Try to use specified agent socket */ 2138 socket_dir[0] = '\0'; 2139 strlcpy(socket_name, agentsocket, sizeof socket_name); 2140 } 2141 2142 /* 2143 * Create socket early so it will exist before command gets run from 2144 * the parent. 2145 */ 2146 prev_mask = umask(0177); 2147 sock = unix_listener(socket_name, SSH_LISTEN_BACKLOG, 0); 2148 if (sock < 0) { 2149 /* XXX - unix_listener() calls error() not perror() */ 2150 *socket_name = '\0'; /* Don't unlink any existing file */ 2151 cleanup_exit(1); 2152 } 2153 umask(prev_mask); 2154 2155 /* 2156 * Fork, and have the parent execute the command, if any, or present 2157 * the socket data. The child continues as the authentication agent. 2158 */ 2159 if (D_flag || d_flag) { 2160 log_init(__progname, 2161 d_flag ? SYSLOG_LEVEL_DEBUG3 : SYSLOG_LEVEL_INFO, 2162 SYSLOG_FACILITY_AUTH, 1); 2163 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n"; 2164 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name, 2165 SSH_AUTHSOCKET_ENV_NAME); 2166 printf("echo Agent pid %ld;\n", (long)parent_pid); 2167 fflush(stdout); 2168 goto skip; 2169 } 2170 pid = fork(); 2171 if (pid == -1) { 2172 perror("fork"); 2173 cleanup_exit(1); 2174 } 2175 if (pid != 0) { /* Parent - execute the given command. */ 2176 close(sock); 2177 snprintf(pidstrbuf, sizeof pidstrbuf, "%ld", (long)pid); 2178 if (ac == 0) { 2179 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n"; 2180 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name, 2181 SSH_AUTHSOCKET_ENV_NAME); 2182 printf(format, SSH_AGENTPID_ENV_NAME, pidstrbuf, 2183 SSH_AGENTPID_ENV_NAME); 2184 printf("echo Agent pid %ld;\n", (long)pid); 2185 exit(0); 2186 } 2187 if (setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1) == -1 || 2188 setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1) == -1) { 2189 perror("setenv"); 2190 exit(1); 2191 } 2192 execvp(av[0], av); 2193 perror(av[0]); 2194 exit(1); 2195 } 2196 /* child */ 2197 log_init(__progname, SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_AUTH, 0); 2198 2199 if (setsid() == -1) { 2200 error("setsid: %s", strerror(errno)); 2201 cleanup_exit(1); 2202 } 2203 2204 (void)chdir("/"); 2205 if (stdfd_devnull(1, 1, 1) == -1) 2206 error_f("stdfd_devnull failed"); 2207 2208 /* deny core dumps, since memory contains unencrypted private keys */ 2209 rlim.rlim_cur = rlim.rlim_max = 0; 2210 if (setrlimit(RLIMIT_CORE, &rlim) == -1) { 2211 error("setrlimit RLIMIT_CORE: %s", strerror(errno)); 2212 cleanup_exit(1); 2213 } 2214 2215 skip: 2216 2217 cleanup_pid = getpid(); 2218 2219 #ifdef ENABLE_PKCS11 2220 pkcs11_init(0); 2221 #endif 2222 new_socket(AUTH_SOCKET, sock); 2223 if (ac > 0) 2224 parent_alive_interval = 10; 2225 idtab_init(); 2226 ssh_signal(SIGPIPE, SIG_IGN); 2227 ssh_signal(SIGINT, (d_flag | D_flag) ? cleanup_handler : SIG_IGN); 2228 ssh_signal(SIGHUP, cleanup_handler); 2229 ssh_signal(SIGTERM, cleanup_handler); 2230 2231 if (pledge("stdio rpath cpath unix id proc exec", NULL) == -1) 2232 fatal("%s: pledge: %s", __progname, strerror(errno)); 2233 2234 while (1) { 2235 prepare_poll(&pfd, &npfd, &timeout, maxfds); 2236 result = poll(pfd, npfd, timeout); 2237 saved_errno = errno; 2238 if (parent_alive_interval != 0) 2239 check_parent_exists(); 2240 (void) reaper(); /* remove expired keys */ 2241 if (result == -1) { 2242 if (saved_errno == EINTR) 2243 continue; 2244 fatal("poll: %s", strerror(saved_errno)); 2245 } else if (result > 0) 2246 after_poll(pfd, npfd, maxfds); 2247 } 2248 /* NOTREACHED */ 2249 } 2250