1 /* $OpenBSD: ssh-agent.c,v 1.306 2024/03/09 05:12:13 djm 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 /* Maximum number of associated certificate constraints to accept on a key */ 96 #define AGENT_MAX_EXT_CERTS 1024 97 98 /* XXX store hostkey_sid in a refcounted tree */ 99 100 typedef enum { 101 AUTH_UNUSED = 0, 102 AUTH_SOCKET = 1, 103 AUTH_CONNECTION = 2, 104 } sock_type; 105 106 struct hostkey_sid { 107 struct sshkey *key; 108 struct sshbuf *sid; 109 int forwarded; 110 }; 111 112 typedef struct socket_entry { 113 int fd; 114 sock_type type; 115 struct sshbuf *input; 116 struct sshbuf *output; 117 struct sshbuf *request; 118 size_t nsession_ids; 119 struct hostkey_sid *session_ids; 120 int session_bind_attempted; 121 } SocketEntry; 122 123 u_int sockets_alloc = 0; 124 SocketEntry *sockets = NULL; 125 126 typedef struct identity { 127 TAILQ_ENTRY(identity) next; 128 struct sshkey *key; 129 char *comment; 130 char *provider; 131 time_t death; 132 u_int confirm; 133 char *sk_provider; 134 struct dest_constraint *dest_constraints; 135 size_t ndest_constraints; 136 } Identity; 137 138 struct idtable { 139 int nentries; 140 TAILQ_HEAD(idqueue, identity) idlist; 141 }; 142 143 /* private key table */ 144 struct idtable *idtab; 145 146 int max_fd = 0; 147 148 /* pid of shell == parent of agent */ 149 pid_t parent_pid = -1; 150 time_t parent_alive_interval = 0; 151 152 sig_atomic_t signalled = 0; 153 154 /* pid of process for which cleanup_socket is applicable */ 155 pid_t cleanup_pid = 0; 156 157 /* pathname and directory for AUTH_SOCKET */ 158 char socket_name[PATH_MAX]; 159 char socket_dir[PATH_MAX]; 160 161 /* Pattern-list of allowed PKCS#11/Security key paths */ 162 static char *allowed_providers; 163 164 /* 165 * Allows PKCS11 providers or SK keys that use non-internal providers to 166 * be added over a remote connection (identified by session-bind@openssh.com). 167 */ 168 static int remote_add_provider; 169 170 /* locking */ 171 #define LOCK_SIZE 32 172 #define LOCK_SALT_SIZE 16 173 #define LOCK_ROUNDS 1 174 int locked = 0; 175 u_char lock_pwhash[LOCK_SIZE]; 176 u_char lock_salt[LOCK_SALT_SIZE]; 177 178 extern char *__progname; 179 180 /* Default lifetime in seconds (0 == forever) */ 181 static int lifetime = 0; 182 183 static int fingerprint_hash = SSH_FP_HASH_DEFAULT; 184 185 /* Refuse signing of non-SSH messages for web-origin FIDO keys */ 186 static int restrict_websafe = 1; 187 188 static void 189 close_socket(SocketEntry *e) 190 { 191 size_t i; 192 193 close(e->fd); 194 sshbuf_free(e->input); 195 sshbuf_free(e->output); 196 sshbuf_free(e->request); 197 for (i = 0; i < e->nsession_ids; i++) { 198 sshkey_free(e->session_ids[i].key); 199 sshbuf_free(e->session_ids[i].sid); 200 } 201 free(e->session_ids); 202 memset(e, '\0', sizeof(*e)); 203 e->fd = -1; 204 e->type = AUTH_UNUSED; 205 } 206 207 static void 208 idtab_init(void) 209 { 210 idtab = xcalloc(1, sizeof(*idtab)); 211 TAILQ_INIT(&idtab->idlist); 212 idtab->nentries = 0; 213 } 214 215 static void 216 free_dest_constraint_hop(struct dest_constraint_hop *dch) 217 { 218 u_int i; 219 220 if (dch == NULL) 221 return; 222 free(dch->user); 223 free(dch->hostname); 224 for (i = 0; i < dch->nkeys; i++) 225 sshkey_free(dch->keys[i]); 226 free(dch->keys); 227 free(dch->key_is_ca); 228 } 229 230 static void 231 free_dest_constraints(struct dest_constraint *dcs, size_t ndcs) 232 { 233 size_t i; 234 235 for (i = 0; i < ndcs; i++) { 236 free_dest_constraint_hop(&dcs[i].from); 237 free_dest_constraint_hop(&dcs[i].to); 238 } 239 free(dcs); 240 } 241 242 #ifdef ENABLE_PKCS11 243 static void 244 dup_dest_constraint_hop(const struct dest_constraint_hop *dch, 245 struct dest_constraint_hop *out) 246 { 247 u_int i; 248 int r; 249 250 out->user = dch->user == NULL ? NULL : xstrdup(dch->user); 251 out->hostname = dch->hostname == NULL ? NULL : xstrdup(dch->hostname); 252 out->is_ca = dch->is_ca; 253 out->nkeys = dch->nkeys; 254 out->keys = out->nkeys == 0 ? NULL : 255 xcalloc(out->nkeys, sizeof(*out->keys)); 256 out->key_is_ca = out->nkeys == 0 ? NULL : 257 xcalloc(out->nkeys, sizeof(*out->key_is_ca)); 258 for (i = 0; i < dch->nkeys; i++) { 259 if (dch->keys[i] != NULL && 260 (r = sshkey_from_private(dch->keys[i], 261 &(out->keys[i]))) != 0) 262 fatal_fr(r, "copy key"); 263 out->key_is_ca[i] = dch->key_is_ca[i]; 264 } 265 } 266 267 static struct dest_constraint * 268 dup_dest_constraints(const struct dest_constraint *dcs, size_t ndcs) 269 { 270 size_t i; 271 struct dest_constraint *ret; 272 273 if (ndcs == 0) 274 return NULL; 275 ret = xcalloc(ndcs, sizeof(*ret)); 276 for (i = 0; i < ndcs; i++) { 277 dup_dest_constraint_hop(&dcs[i].from, &ret[i].from); 278 dup_dest_constraint_hop(&dcs[i].to, &ret[i].to); 279 } 280 return ret; 281 } 282 #endif /* ENABLE_PKCS11 */ 283 284 #ifdef DEBUG_CONSTRAINTS 285 static void 286 dump_dest_constraint_hop(const struct dest_constraint_hop *dch) 287 { 288 u_int i; 289 char *fp; 290 291 debug_f("user %s hostname %s is_ca %d nkeys %u", 292 dch->user == NULL ? "(null)" : dch->user, 293 dch->hostname == NULL ? "(null)" : dch->hostname, 294 dch->is_ca, dch->nkeys); 295 for (i = 0; i < dch->nkeys; i++) { 296 fp = NULL; 297 if (dch->keys[i] != NULL && 298 (fp = sshkey_fingerprint(dch->keys[i], 299 SSH_FP_HASH_DEFAULT, SSH_FP_DEFAULT)) == NULL) 300 fatal_f("fingerprint failed"); 301 debug_f("key %u/%u: %s%s%s key_is_ca %d", i, dch->nkeys, 302 dch->keys[i] == NULL ? "" : sshkey_ssh_name(dch->keys[i]), 303 dch->keys[i] == NULL ? "" : " ", 304 dch->keys[i] == NULL ? "none" : fp, 305 dch->key_is_ca[i]); 306 free(fp); 307 } 308 } 309 #endif /* DEBUG_CONSTRAINTS */ 310 311 static void 312 dump_dest_constraints(const char *context, 313 const struct dest_constraint *dcs, size_t ndcs) 314 { 315 #ifdef DEBUG_CONSTRAINTS 316 size_t i; 317 318 debug_f("%s: %zu constraints", context, ndcs); 319 for (i = 0; i < ndcs; i++) { 320 debug_f("constraint %zu / %zu: from: ", i, ndcs); 321 dump_dest_constraint_hop(&dcs[i].from); 322 debug_f("constraint %zu / %zu: to: ", i, ndcs); 323 dump_dest_constraint_hop(&dcs[i].to); 324 } 325 debug_f("done for %s", context); 326 #endif /* DEBUG_CONSTRAINTS */ 327 } 328 329 static void 330 free_identity(Identity *id) 331 { 332 sshkey_free(id->key); 333 free(id->provider); 334 free(id->comment); 335 free(id->sk_provider); 336 free_dest_constraints(id->dest_constraints, id->ndest_constraints); 337 free(id); 338 } 339 340 /* 341 * Match 'key' against the key/CA list in a destination constraint hop 342 * Returns 0 on success or -1 otherwise. 343 */ 344 static int 345 match_key_hop(const char *tag, const struct sshkey *key, 346 const struct dest_constraint_hop *dch) 347 { 348 const char *reason = NULL; 349 const char *hostname = dch->hostname ? dch->hostname : "(ORIGIN)"; 350 u_int i; 351 char *fp; 352 353 if (key == NULL) 354 return -1; 355 /* XXX logspam */ 356 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT, 357 SSH_FP_DEFAULT)) == NULL) 358 fatal_f("fingerprint failed"); 359 debug3_f("%s: entering hostname %s, requested key %s %s, %u keys avail", 360 tag, hostname, sshkey_type(key), fp, dch->nkeys); 361 free(fp); 362 for (i = 0; i < dch->nkeys; i++) { 363 if (dch->keys[i] == NULL) 364 return -1; 365 /* XXX logspam */ 366 if ((fp = sshkey_fingerprint(dch->keys[i], SSH_FP_HASH_DEFAULT, 367 SSH_FP_DEFAULT)) == NULL) 368 fatal_f("fingerprint failed"); 369 debug3_f("%s: key %u: %s%s %s", tag, i, 370 dch->key_is_ca[i] ? "CA " : "", 371 sshkey_type(dch->keys[i]), fp); 372 free(fp); 373 if (!sshkey_is_cert(key)) { 374 /* plain key */ 375 if (dch->key_is_ca[i] || 376 !sshkey_equal(key, dch->keys[i])) 377 continue; 378 return 0; 379 } 380 /* certificate */ 381 if (!dch->key_is_ca[i]) 382 continue; 383 if (key->cert == NULL || key->cert->signature_key == NULL) 384 return -1; /* shouldn't happen */ 385 if (!sshkey_equal(key->cert->signature_key, dch->keys[i])) 386 continue; 387 if (sshkey_cert_check_host(key, hostname, 1, 388 SSH_ALLOWED_CA_SIGALGS, &reason) != 0) { 389 debug_f("cert %s / hostname %s rejected: %s", 390 key->cert->key_id, hostname, reason); 391 continue; 392 } 393 return 0; 394 } 395 return -1; 396 } 397 398 /* Check destination constraints on an identity against the hostkey/user */ 399 static int 400 permitted_by_dest_constraints(const struct sshkey *fromkey, 401 const struct sshkey *tokey, Identity *id, const char *user, 402 const char **hostnamep) 403 { 404 size_t i; 405 struct dest_constraint *d; 406 407 if (hostnamep != NULL) 408 *hostnamep = NULL; 409 for (i = 0; i < id->ndest_constraints; i++) { 410 d = id->dest_constraints + i; 411 /* XXX remove logspam */ 412 debug2_f("constraint %zu %s%s%s (%u keys) > %s%s%s (%u keys)", 413 i, d->from.user ? d->from.user : "", 414 d->from.user ? "@" : "", 415 d->from.hostname ? d->from.hostname : "(ORIGIN)", 416 d->from.nkeys, 417 d->to.user ? d->to.user : "", d->to.user ? "@" : "", 418 d->to.hostname ? d->to.hostname : "(ANY)", d->to.nkeys); 419 420 /* Match 'from' key */ 421 if (fromkey == NULL) { 422 /* We are matching the first hop */ 423 if (d->from.hostname != NULL || d->from.nkeys != 0) 424 continue; 425 } else if (match_key_hop("from", fromkey, &d->from) != 0) 426 continue; 427 428 /* Match 'to' key */ 429 if (tokey != NULL && match_key_hop("to", tokey, &d->to) != 0) 430 continue; 431 432 /* Match user if specified */ 433 if (d->to.user != NULL && user != NULL && 434 !match_pattern(user, d->to.user)) 435 continue; 436 437 /* successfully matched this constraint */ 438 if (hostnamep != NULL) 439 *hostnamep = d->to.hostname; 440 debug2_f("allowed for hostname %s", 441 d->to.hostname == NULL ? "*" : d->to.hostname); 442 return 0; 443 } 444 /* no match */ 445 debug2_f("%s identity \"%s\" not permitted for this destination", 446 sshkey_type(id->key), id->comment); 447 return -1; 448 } 449 450 /* 451 * Check whether hostkeys on a SocketEntry and the optionally specified user 452 * are permitted by the destination constraints on the Identity. 453 * Returns 0 on success or -1 otherwise. 454 */ 455 static int 456 identity_permitted(Identity *id, SocketEntry *e, char *user, 457 const char **forward_hostnamep, const char **last_hostnamep) 458 { 459 size_t i; 460 const char **hp; 461 struct hostkey_sid *hks; 462 const struct sshkey *fromkey = NULL; 463 const char *test_user; 464 char *fp1, *fp2; 465 466 /* XXX remove logspam */ 467 debug3_f("entering: key %s comment \"%s\", %zu socket bindings, " 468 "%zu constraints", sshkey_type(id->key), id->comment, 469 e->nsession_ids, id->ndest_constraints); 470 if (id->ndest_constraints == 0) 471 return 0; /* unconstrained */ 472 if (e->session_bind_attempted && e->nsession_ids == 0) { 473 error_f("previous session bind failed on socket"); 474 return -1; 475 } 476 if (e->nsession_ids == 0) 477 return 0; /* local use */ 478 /* 479 * Walk through the hops recorded by session_id and try to find a 480 * constraint that satisfies each. 481 */ 482 for (i = 0; i < e->nsession_ids; i++) { 483 hks = e->session_ids + i; 484 if (hks->key == NULL) 485 fatal_f("internal error: no bound key"); 486 /* XXX remove logspam */ 487 fp1 = fp2 = NULL; 488 if (fromkey != NULL && 489 (fp1 = sshkey_fingerprint(fromkey, SSH_FP_HASH_DEFAULT, 490 SSH_FP_DEFAULT)) == NULL) 491 fatal_f("fingerprint failed"); 492 if ((fp2 = sshkey_fingerprint(hks->key, SSH_FP_HASH_DEFAULT, 493 SSH_FP_DEFAULT)) == NULL) 494 fatal_f("fingerprint failed"); 495 debug3_f("socketentry fd=%d, entry %zu %s, " 496 "from hostkey %s %s to user %s hostkey %s %s", 497 e->fd, i, hks->forwarded ? "FORWARD" : "AUTH", 498 fromkey ? sshkey_type(fromkey) : "(ORIGIN)", 499 fromkey ? fp1 : "", user ? user : "(ANY)", 500 sshkey_type(hks->key), fp2); 501 free(fp1); 502 free(fp2); 503 /* 504 * Record the hostnames for the initial forwarding and 505 * the final destination. 506 */ 507 hp = NULL; 508 if (i == e->nsession_ids - 1) 509 hp = last_hostnamep; 510 else if (i == 0) 511 hp = forward_hostnamep; 512 /* Special handling for final recorded binding */ 513 test_user = NULL; 514 if (i == e->nsession_ids - 1) { 515 /* Can only check user at final hop */ 516 test_user = user; 517 /* 518 * user is only presented for signature requests. 519 * If this is the case, make sure last binding is not 520 * for a forwarding. 521 */ 522 if (hks->forwarded && user != NULL) { 523 error_f("tried to sign on forwarding hop"); 524 return -1; 525 } 526 } else if (!hks->forwarded) { 527 error_f("tried to forward though signing bind"); 528 return -1; 529 } 530 if (permitted_by_dest_constraints(fromkey, hks->key, id, 531 test_user, hp) != 0) 532 return -1; 533 fromkey = hks->key; 534 } 535 /* 536 * Another special case: if the last bound session ID was for a 537 * forwarding, and this function is not being called to check a sign 538 * request (i.e. no 'user' supplied), then only permit the key if 539 * there is a permission that would allow it to be used at another 540 * destination. This hides keys that are allowed to be used to 541 * authenticate *to* a host but not permitted for *use* beyond it. 542 */ 543 hks = &e->session_ids[e->nsession_ids - 1]; 544 if (hks->forwarded && user == NULL && 545 permitted_by_dest_constraints(hks->key, NULL, id, 546 NULL, NULL) != 0) { 547 debug3_f("key permitted at host but not after"); 548 return -1; 549 } 550 551 /* success */ 552 return 0; 553 } 554 555 static int 556 socket_is_remote(SocketEntry *e) 557 { 558 return e->session_bind_attempted || (e->nsession_ids != 0); 559 } 560 561 /* return matching private key for given public key */ 562 static Identity * 563 lookup_identity(struct sshkey *key) 564 { 565 Identity *id; 566 567 TAILQ_FOREACH(id, &idtab->idlist, next) { 568 if (sshkey_equal(key, id->key)) 569 return (id); 570 } 571 return (NULL); 572 } 573 574 /* Check confirmation of keysign request */ 575 static int 576 confirm_key(Identity *id, const char *extra) 577 { 578 char *p; 579 int ret = -1; 580 581 p = sshkey_fingerprint(id->key, fingerprint_hash, SSH_FP_DEFAULT); 582 if (p != NULL && 583 ask_permission("Allow use of key %s?\nKey fingerprint %s.%s%s", 584 id->comment, p, 585 extra == NULL ? "" : "\n", extra == NULL ? "" : extra)) 586 ret = 0; 587 free(p); 588 589 return (ret); 590 } 591 592 static void 593 send_status(SocketEntry *e, int success) 594 { 595 int r; 596 597 if ((r = sshbuf_put_u32(e->output, 1)) != 0 || 598 (r = sshbuf_put_u8(e->output, success ? 599 SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE)) != 0) 600 fatal_fr(r, "compose"); 601 } 602 603 /* send list of supported public keys to 'client' */ 604 static void 605 process_request_identities(SocketEntry *e) 606 { 607 Identity *id; 608 struct sshbuf *msg, *keys; 609 int r; 610 u_int i = 0, nentries = 0; 611 char *fp; 612 613 debug2_f("entering"); 614 615 if ((msg = sshbuf_new()) == NULL || (keys = sshbuf_new()) == NULL) 616 fatal_f("sshbuf_new failed"); 617 TAILQ_FOREACH(id, &idtab->idlist, next) { 618 if ((fp = sshkey_fingerprint(id->key, SSH_FP_HASH_DEFAULT, 619 SSH_FP_DEFAULT)) == NULL) 620 fatal_f("fingerprint failed"); 621 debug_f("key %u / %u: %s %s", i++, idtab->nentries, 622 sshkey_ssh_name(id->key), fp); 623 dump_dest_constraints(__func__, 624 id->dest_constraints, id->ndest_constraints); 625 free(fp); 626 /* identity not visible, don't include in response */ 627 if (identity_permitted(id, e, NULL, NULL, NULL) != 0) 628 continue; 629 if ((r = sshkey_puts_opts(id->key, keys, 630 SSHKEY_SERIALIZE_INFO)) != 0 || 631 (r = sshbuf_put_cstring(keys, id->comment)) != 0) { 632 error_fr(r, "compose key/comment"); 633 continue; 634 } 635 nentries++; 636 } 637 debug2_f("replying with %u allowed of %u available keys", 638 nentries, idtab->nentries); 639 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 || 640 (r = sshbuf_put_u32(msg, nentries)) != 0 || 641 (r = sshbuf_putb(msg, keys)) != 0) 642 fatal_fr(r, "compose"); 643 if ((r = sshbuf_put_stringb(e->output, msg)) != 0) 644 fatal_fr(r, "enqueue"); 645 sshbuf_free(msg); 646 sshbuf_free(keys); 647 } 648 649 650 static char * 651 agent_decode_alg(struct sshkey *key, u_int flags) 652 { 653 if (key->type == KEY_RSA) { 654 if (flags & SSH_AGENT_RSA_SHA2_256) 655 return "rsa-sha2-256"; 656 else if (flags & SSH_AGENT_RSA_SHA2_512) 657 return "rsa-sha2-512"; 658 } else if (key->type == KEY_RSA_CERT) { 659 if (flags & SSH_AGENT_RSA_SHA2_256) 660 return "rsa-sha2-256-cert-v01@openssh.com"; 661 else if (flags & SSH_AGENT_RSA_SHA2_512) 662 return "rsa-sha2-512-cert-v01@openssh.com"; 663 } 664 return NULL; 665 } 666 667 /* 668 * Attempt to parse the contents of a buffer as a SSH publickey userauth 669 * request, checking its contents for consistency and matching the embedded 670 * key against the one that is being used for signing. 671 * Note: does not modify msg buffer. 672 * Optionally extract the username, session ID and/or hostkey from the request. 673 */ 674 static int 675 parse_userauth_request(struct sshbuf *msg, const struct sshkey *expected_key, 676 char **userp, struct sshbuf **sess_idp, struct sshkey **hostkeyp) 677 { 678 struct sshbuf *b = NULL, *sess_id = NULL; 679 char *user = NULL, *service = NULL, *method = NULL, *pkalg = NULL; 680 int r; 681 u_char t, sig_follows; 682 struct sshkey *mkey = NULL, *hostkey = NULL; 683 684 if (userp != NULL) 685 *userp = NULL; 686 if (sess_idp != NULL) 687 *sess_idp = NULL; 688 if (hostkeyp != NULL) 689 *hostkeyp = NULL; 690 if ((b = sshbuf_fromb(msg)) == NULL) 691 fatal_f("sshbuf_fromb"); 692 693 /* SSH userauth request */ 694 if ((r = sshbuf_froms(b, &sess_id)) != 0) 695 goto out; 696 if (sshbuf_len(sess_id) == 0) { 697 r = SSH_ERR_INVALID_FORMAT; 698 goto out; 699 } 700 if ((r = sshbuf_get_u8(b, &t)) != 0 || /* SSH2_MSG_USERAUTH_REQUEST */ 701 (r = sshbuf_get_cstring(b, &user, NULL)) != 0 || /* server user */ 702 (r = sshbuf_get_cstring(b, &service, NULL)) != 0 || /* service */ 703 (r = sshbuf_get_cstring(b, &method, NULL)) != 0 || /* method */ 704 (r = sshbuf_get_u8(b, &sig_follows)) != 0 || /* sig-follows */ 705 (r = sshbuf_get_cstring(b, &pkalg, NULL)) != 0 || /* alg */ 706 (r = sshkey_froms(b, &mkey)) != 0) /* key */ 707 goto out; 708 if (t != SSH2_MSG_USERAUTH_REQUEST || 709 sig_follows != 1 || 710 strcmp(service, "ssh-connection") != 0 || 711 !sshkey_equal(expected_key, mkey) || 712 sshkey_type_from_name(pkalg) != expected_key->type) { 713 r = SSH_ERR_INVALID_FORMAT; 714 goto out; 715 } 716 if (strcmp(method, "publickey-hostbound-v00@openssh.com") == 0) { 717 if ((r = sshkey_froms(b, &hostkey)) != 0) 718 goto out; 719 } else if (strcmp(method, "publickey") != 0) { 720 r = SSH_ERR_INVALID_FORMAT; 721 goto out; 722 } 723 if (sshbuf_len(b) != 0) { 724 r = SSH_ERR_INVALID_FORMAT; 725 goto out; 726 } 727 /* success */ 728 r = 0; 729 debug3_f("well formed userauth"); 730 if (userp != NULL) { 731 *userp = user; 732 user = NULL; 733 } 734 if (sess_idp != NULL) { 735 *sess_idp = sess_id; 736 sess_id = NULL; 737 } 738 if (hostkeyp != NULL) { 739 *hostkeyp = hostkey; 740 hostkey = NULL; 741 } 742 out: 743 sshbuf_free(b); 744 sshbuf_free(sess_id); 745 free(user); 746 free(service); 747 free(method); 748 free(pkalg); 749 sshkey_free(mkey); 750 sshkey_free(hostkey); 751 return r; 752 } 753 754 /* 755 * Attempt to parse the contents of a buffer as a SSHSIG signature request. 756 * Note: does not modify buffer. 757 */ 758 static int 759 parse_sshsig_request(struct sshbuf *msg) 760 { 761 int r; 762 struct sshbuf *b; 763 764 if ((b = sshbuf_fromb(msg)) == NULL) 765 fatal_f("sshbuf_fromb"); 766 767 if ((r = sshbuf_cmp(b, 0, "SSHSIG", 6)) != 0 || 768 (r = sshbuf_consume(b, 6)) != 0 || 769 (r = sshbuf_get_cstring(b, NULL, NULL)) != 0 || /* namespace */ 770 (r = sshbuf_get_string_direct(b, NULL, NULL)) != 0 || /* reserved */ 771 (r = sshbuf_get_cstring(b, NULL, NULL)) != 0 || /* hashalg */ 772 (r = sshbuf_get_string_direct(b, NULL, NULL)) != 0) /* H(msg) */ 773 goto out; 774 if (sshbuf_len(b) != 0) { 775 r = SSH_ERR_INVALID_FORMAT; 776 goto out; 777 } 778 /* success */ 779 r = 0; 780 out: 781 sshbuf_free(b); 782 return r; 783 } 784 785 /* 786 * This function inspects a message to be signed by a FIDO key that has a 787 * web-like application string (i.e. one that does not begin with "ssh:". 788 * It checks that the message is one of those expected for SSH operations 789 * (pubkey userauth, sshsig, CA key signing) to exclude signing challenges 790 * for the web. 791 */ 792 static int 793 check_websafe_message_contents(struct sshkey *key, struct sshbuf *data) 794 { 795 if (parse_userauth_request(data, key, NULL, NULL, NULL) == 0) { 796 debug_f("signed data matches public key userauth request"); 797 return 1; 798 } 799 if (parse_sshsig_request(data) == 0) { 800 debug_f("signed data matches SSHSIG signature request"); 801 return 1; 802 } 803 804 /* XXX check CA signature operation */ 805 806 error("web-origin key attempting to sign non-SSH message"); 807 return 0; 808 } 809 810 static int 811 buf_equal(const struct sshbuf *a, const struct sshbuf *b) 812 { 813 if (sshbuf_ptr(a) == NULL || sshbuf_ptr(b) == NULL) 814 return SSH_ERR_INVALID_ARGUMENT; 815 if (sshbuf_len(a) != sshbuf_len(b)) 816 return SSH_ERR_INVALID_FORMAT; 817 if (timingsafe_bcmp(sshbuf_ptr(a), sshbuf_ptr(b), sshbuf_len(a)) != 0) 818 return SSH_ERR_INVALID_FORMAT; 819 return 0; 820 } 821 822 /* ssh2 only */ 823 static void 824 process_sign_request2(SocketEntry *e) 825 { 826 u_char *signature = NULL; 827 size_t slen = 0; 828 u_int compat = 0, flags; 829 int r, ok = -1, retried = 0; 830 char *fp = NULL, *pin = NULL, *prompt = NULL; 831 char *user = NULL, *sig_dest = NULL; 832 const char *fwd_host = NULL, *dest_host = NULL; 833 struct sshbuf *msg = NULL, *data = NULL, *sid = NULL; 834 struct sshkey *key = NULL, *hostkey = NULL; 835 struct identity *id; 836 struct notifier_ctx *notifier = NULL; 837 838 debug_f("entering"); 839 840 if ((msg = sshbuf_new()) == NULL || (data = sshbuf_new()) == NULL) 841 fatal_f("sshbuf_new failed"); 842 if ((r = sshkey_froms(e->request, &key)) != 0 || 843 (r = sshbuf_get_stringb(e->request, data)) != 0 || 844 (r = sshbuf_get_u32(e->request, &flags)) != 0) { 845 error_fr(r, "parse"); 846 goto send; 847 } 848 849 if ((id = lookup_identity(key)) == NULL) { 850 verbose_f("%s key not found", sshkey_type(key)); 851 goto send; 852 } 853 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT, 854 SSH_FP_DEFAULT)) == NULL) 855 fatal_f("fingerprint failed"); 856 857 if (id->ndest_constraints != 0) { 858 if (e->nsession_ids == 0) { 859 logit_f("refusing use of destination-constrained key " 860 "to sign on unbound connection"); 861 goto send; 862 } 863 if (parse_userauth_request(data, key, &user, &sid, 864 &hostkey) != 0) { 865 logit_f("refusing use of destination-constrained key " 866 "to sign an unidentified signature"); 867 goto send; 868 } 869 /* XXX logspam */ 870 debug_f("user=%s", user); 871 if (identity_permitted(id, e, user, &fwd_host, &dest_host) != 0) 872 goto send; 873 /* XXX display fwd_host/dest_host in askpass UI */ 874 /* 875 * Ensure that the session ID is the most recent one 876 * registered on the socket - it should have been bound by 877 * ssh immediately before userauth. 878 */ 879 if (buf_equal(sid, 880 e->session_ids[e->nsession_ids - 1].sid) != 0) { 881 error_f("unexpected session ID (%zu listed) on " 882 "signature request for target user %s with " 883 "key %s %s", e->nsession_ids, user, 884 sshkey_type(id->key), fp); 885 goto send; 886 } 887 /* 888 * Ensure that the hostkey embedded in the signature matches 889 * the one most recently bound to the socket. An exception is 890 * made for the initial forwarding hop. 891 */ 892 if (e->nsession_ids > 1 && hostkey == NULL) { 893 error_f("refusing use of destination-constrained key: " 894 "no hostkey recorded in signature for forwarded " 895 "connection"); 896 goto send; 897 } 898 if (hostkey != NULL && !sshkey_equal(hostkey, 899 e->session_ids[e->nsession_ids - 1].key)) { 900 error_f("refusing use of destination-constrained key: " 901 "mismatch between hostkey in request and most " 902 "recently bound session"); 903 goto send; 904 } 905 xasprintf(&sig_dest, "public key authentication request for " 906 "user \"%s\" to listed host", user); 907 } 908 if (id->confirm && confirm_key(id, sig_dest) != 0) { 909 verbose_f("user refused key"); 910 goto send; 911 } 912 if (sshkey_is_sk(id->key)) { 913 if (restrict_websafe && 914 strncmp(id->key->sk_application, "ssh:", 4) != 0 && 915 !check_websafe_message_contents(key, data)) { 916 /* error already logged */ 917 goto send; 918 } 919 if (id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD) { 920 notifier = notify_start(0, 921 "Confirm user presence for key %s %s%s%s", 922 sshkey_type(id->key), fp, 923 sig_dest == NULL ? "" : "\n", 924 sig_dest == NULL ? "" : sig_dest); 925 } 926 } 927 retry_pin: 928 if ((r = sshkey_sign(id->key, &signature, &slen, 929 sshbuf_ptr(data), sshbuf_len(data), agent_decode_alg(key, flags), 930 id->sk_provider, pin, compat)) != 0) { 931 debug_fr(r, "sshkey_sign"); 932 if (pin == NULL && !retried && sshkey_is_sk(id->key) && 933 r == SSH_ERR_KEY_WRONG_PASSPHRASE) { 934 notify_complete(notifier, NULL); 935 notifier = NULL; 936 /* XXX include sig_dest */ 937 xasprintf(&prompt, "Enter PIN%sfor %s key %s: ", 938 (id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD) ? 939 " and confirm user presence " : " ", 940 sshkey_type(id->key), fp); 941 pin = read_passphrase(prompt, RP_USE_ASKPASS); 942 retried = 1; 943 goto retry_pin; 944 } 945 error_fr(r, "sshkey_sign"); 946 goto send; 947 } 948 /* Success */ 949 ok = 0; 950 debug_f("good signature"); 951 send: 952 notify_complete(notifier, "User presence confirmed"); 953 954 if (ok == 0) { 955 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 || 956 (r = sshbuf_put_string(msg, signature, slen)) != 0) 957 fatal_fr(r, "compose"); 958 } else if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0) 959 fatal_fr(r, "compose failure"); 960 961 if ((r = sshbuf_put_stringb(e->output, msg)) != 0) 962 fatal_fr(r, "enqueue"); 963 964 sshbuf_free(sid); 965 sshbuf_free(data); 966 sshbuf_free(msg); 967 sshkey_free(key); 968 sshkey_free(hostkey); 969 free(fp); 970 free(signature); 971 free(sig_dest); 972 free(user); 973 free(prompt); 974 if (pin != NULL) 975 freezero(pin, strlen(pin)); 976 } 977 978 /* shared */ 979 static void 980 process_remove_identity(SocketEntry *e) 981 { 982 int r, success = 0; 983 struct sshkey *key = NULL; 984 Identity *id; 985 986 debug2_f("entering"); 987 if ((r = sshkey_froms(e->request, &key)) != 0) { 988 error_fr(r, "parse key"); 989 goto done; 990 } 991 if ((id = lookup_identity(key)) == NULL) { 992 debug_f("key not found"); 993 goto done; 994 } 995 /* identity not visible, cannot be removed */ 996 if (identity_permitted(id, e, NULL, NULL, NULL) != 0) 997 goto done; /* error already logged */ 998 /* We have this key, free it. */ 999 if (idtab->nentries < 1) 1000 fatal_f("internal error: nentries %d", idtab->nentries); 1001 TAILQ_REMOVE(&idtab->idlist, id, next); 1002 free_identity(id); 1003 idtab->nentries--; 1004 success = 1; 1005 done: 1006 sshkey_free(key); 1007 send_status(e, success); 1008 } 1009 1010 static void 1011 process_remove_all_identities(SocketEntry *e) 1012 { 1013 Identity *id; 1014 1015 debug2_f("entering"); 1016 /* Loop over all identities and clear the keys. */ 1017 for (id = TAILQ_FIRST(&idtab->idlist); id; 1018 id = TAILQ_FIRST(&idtab->idlist)) { 1019 TAILQ_REMOVE(&idtab->idlist, id, next); 1020 free_identity(id); 1021 } 1022 1023 /* Mark that there are no identities. */ 1024 idtab->nentries = 0; 1025 1026 /* Send success. */ 1027 send_status(e, 1); 1028 } 1029 1030 /* removes expired keys and returns number of seconds until the next expiry */ 1031 static time_t 1032 reaper(void) 1033 { 1034 time_t deadline = 0, now = monotime(); 1035 Identity *id, *nxt; 1036 1037 for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) { 1038 nxt = TAILQ_NEXT(id, next); 1039 if (id->death == 0) 1040 continue; 1041 if (now >= id->death) { 1042 debug("expiring key '%s'", id->comment); 1043 TAILQ_REMOVE(&idtab->idlist, id, next); 1044 free_identity(id); 1045 idtab->nentries--; 1046 } else 1047 deadline = (deadline == 0) ? id->death : 1048 MINIMUM(deadline, id->death); 1049 } 1050 if (deadline == 0 || deadline <= now) 1051 return 0; 1052 else 1053 return (deadline - now); 1054 } 1055 1056 static int 1057 parse_dest_constraint_hop(struct sshbuf *b, struct dest_constraint_hop *dch) 1058 { 1059 u_char key_is_ca; 1060 size_t elen = 0; 1061 int r; 1062 struct sshkey *k = NULL; 1063 char *fp; 1064 1065 memset(dch, '\0', sizeof(*dch)); 1066 if ((r = sshbuf_get_cstring(b, &dch->user, NULL)) != 0 || 1067 (r = sshbuf_get_cstring(b, &dch->hostname, NULL)) != 0 || 1068 (r = sshbuf_get_string_direct(b, NULL, &elen)) != 0) { 1069 error_fr(r, "parse"); 1070 goto out; 1071 } 1072 if (elen != 0) { 1073 error_f("unsupported extensions (len %zu)", elen); 1074 r = SSH_ERR_FEATURE_UNSUPPORTED; 1075 goto out; 1076 } 1077 if (*dch->hostname == '\0') { 1078 free(dch->hostname); 1079 dch->hostname = NULL; 1080 } 1081 if (*dch->user == '\0') { 1082 free(dch->user); 1083 dch->user = NULL; 1084 } 1085 while (sshbuf_len(b) != 0) { 1086 dch->keys = xrecallocarray(dch->keys, dch->nkeys, 1087 dch->nkeys + 1, sizeof(*dch->keys)); 1088 dch->key_is_ca = xrecallocarray(dch->key_is_ca, dch->nkeys, 1089 dch->nkeys + 1, sizeof(*dch->key_is_ca)); 1090 if ((r = sshkey_froms(b, &k)) != 0 || 1091 (r = sshbuf_get_u8(b, &key_is_ca)) != 0) 1092 goto out; 1093 if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT, 1094 SSH_FP_DEFAULT)) == NULL) 1095 fatal_f("fingerprint failed"); 1096 debug3_f("%s%s%s: adding %skey %s %s", 1097 dch->user == NULL ? "" : dch->user, 1098 dch->user == NULL ? "" : "@", 1099 dch->hostname, key_is_ca ? "CA " : "", sshkey_type(k), fp); 1100 free(fp); 1101 dch->keys[dch->nkeys] = k; 1102 dch->key_is_ca[dch->nkeys] = key_is_ca != 0; 1103 dch->nkeys++; 1104 k = NULL; /* transferred */ 1105 } 1106 /* success */ 1107 r = 0; 1108 out: 1109 sshkey_free(k); 1110 return r; 1111 } 1112 1113 static int 1114 parse_dest_constraint(struct sshbuf *m, struct dest_constraint *dc) 1115 { 1116 struct sshbuf *b = NULL, *frombuf = NULL, *tobuf = NULL; 1117 int r; 1118 size_t elen = 0; 1119 1120 debug3_f("entering"); 1121 1122 memset(dc, '\0', sizeof(*dc)); 1123 if ((r = sshbuf_froms(m, &b)) != 0 || 1124 (r = sshbuf_froms(b, &frombuf)) != 0 || 1125 (r = sshbuf_froms(b, &tobuf)) != 0 || 1126 (r = sshbuf_get_string_direct(b, NULL, &elen)) != 0) { 1127 error_fr(r, "parse"); 1128 goto out; 1129 } 1130 if ((r = parse_dest_constraint_hop(frombuf, &dc->from)) != 0 || 1131 (r = parse_dest_constraint_hop(tobuf, &dc->to)) != 0) 1132 goto out; /* already logged */ 1133 if (elen != 0) { 1134 error_f("unsupported extensions (len %zu)", elen); 1135 r = SSH_ERR_FEATURE_UNSUPPORTED; 1136 goto out; 1137 } 1138 debug2_f("parsed %s (%u keys) > %s%s%s (%u keys)", 1139 dc->from.hostname ? dc->from.hostname : "(ORIGIN)", dc->from.nkeys, 1140 dc->to.user ? dc->to.user : "", dc->to.user ? "@" : "", 1141 dc->to.hostname ? dc->to.hostname : "(ANY)", dc->to.nkeys); 1142 /* check consistency */ 1143 if ((dc->from.hostname == NULL) != (dc->from.nkeys == 0) || 1144 dc->from.user != NULL) { 1145 error_f("inconsistent \"from\" specification"); 1146 r = SSH_ERR_INVALID_FORMAT; 1147 goto out; 1148 } 1149 if (dc->to.hostname == NULL || dc->to.nkeys == 0) { 1150 error_f("incomplete \"to\" specification"); 1151 r = SSH_ERR_INVALID_FORMAT; 1152 goto out; 1153 } 1154 /* success */ 1155 r = 0; 1156 out: 1157 sshbuf_free(b); 1158 sshbuf_free(frombuf); 1159 sshbuf_free(tobuf); 1160 return r; 1161 } 1162 1163 static int 1164 parse_key_constraint_extension(struct sshbuf *m, char **sk_providerp, 1165 struct dest_constraint **dcsp, size_t *ndcsp, int *cert_onlyp, 1166 struct sshkey ***certs, size_t *ncerts) 1167 { 1168 char *ext_name = NULL; 1169 int r; 1170 struct sshbuf *b = NULL; 1171 u_char v; 1172 struct sshkey *k; 1173 1174 if ((r = sshbuf_get_cstring(m, &ext_name, NULL)) != 0) { 1175 error_fr(r, "parse constraint extension"); 1176 goto out; 1177 } 1178 debug_f("constraint ext %s", ext_name); 1179 if (strcmp(ext_name, "sk-provider@openssh.com") == 0) { 1180 if (sk_providerp == NULL) { 1181 error_f("%s not valid here", ext_name); 1182 r = SSH_ERR_INVALID_FORMAT; 1183 goto out; 1184 } 1185 if (*sk_providerp != NULL) { 1186 error_f("%s already set", ext_name); 1187 r = SSH_ERR_INVALID_FORMAT; 1188 goto out; 1189 } 1190 if ((r = sshbuf_get_cstring(m, sk_providerp, NULL)) != 0) { 1191 error_fr(r, "parse %s", ext_name); 1192 goto out; 1193 } 1194 } else if (strcmp(ext_name, 1195 "restrict-destination-v00@openssh.com") == 0) { 1196 if (*dcsp != NULL) { 1197 error_f("%s already set", ext_name); 1198 goto out; 1199 } 1200 if ((r = sshbuf_froms(m, &b)) != 0) { 1201 error_fr(r, "parse %s outer", ext_name); 1202 goto out; 1203 } 1204 while (sshbuf_len(b) != 0) { 1205 if (*ndcsp >= AGENT_MAX_DEST_CONSTRAINTS) { 1206 error_f("too many %s constraints", ext_name); 1207 goto out; 1208 } 1209 *dcsp = xrecallocarray(*dcsp, *ndcsp, *ndcsp + 1, 1210 sizeof(**dcsp)); 1211 if ((r = parse_dest_constraint(b, 1212 *dcsp + (*ndcsp)++)) != 0) 1213 goto out; /* error already logged */ 1214 } 1215 } else if (strcmp(ext_name, 1216 "associated-certs-v00@openssh.com") == 0) { 1217 if (certs == NULL || ncerts == NULL || cert_onlyp == NULL) { 1218 error_f("%s not valid here", ext_name); 1219 r = SSH_ERR_INVALID_FORMAT; 1220 goto out; 1221 } 1222 if (*certs != NULL) { 1223 error_f("%s already set", ext_name); 1224 goto out; 1225 } 1226 if ((r = sshbuf_get_u8(m, &v)) != 0 || 1227 (r = sshbuf_froms(m, &b)) != 0) { 1228 error_fr(r, "parse %s", ext_name); 1229 goto out; 1230 } 1231 *cert_onlyp = v != 0; 1232 while (sshbuf_len(b) != 0) { 1233 if (*ncerts >= AGENT_MAX_EXT_CERTS) { 1234 error_f("too many %s constraints", ext_name); 1235 goto out; 1236 } 1237 *certs = xrecallocarray(*certs, *ncerts, *ncerts + 1, 1238 sizeof(**certs)); 1239 if ((r = sshkey_froms(b, &k)) != 0) { 1240 error_fr(r, "parse key"); 1241 goto out; 1242 } 1243 (*certs)[(*ncerts)++] = k; 1244 } 1245 } else { 1246 error_f("unsupported constraint \"%s\"", ext_name); 1247 r = SSH_ERR_FEATURE_UNSUPPORTED; 1248 goto out; 1249 } 1250 /* success */ 1251 r = 0; 1252 out: 1253 free(ext_name); 1254 sshbuf_free(b); 1255 return r; 1256 } 1257 1258 static int 1259 parse_key_constraints(struct sshbuf *m, struct sshkey *k, time_t *deathp, 1260 u_int *secondsp, int *confirmp, char **sk_providerp, 1261 struct dest_constraint **dcsp, size_t *ndcsp, 1262 int *cert_onlyp, size_t *ncerts, struct sshkey ***certs) 1263 { 1264 u_char ctype; 1265 int r; 1266 u_int seconds, maxsign = 0; 1267 1268 while (sshbuf_len(m)) { 1269 if ((r = sshbuf_get_u8(m, &ctype)) != 0) { 1270 error_fr(r, "parse constraint type"); 1271 goto out; 1272 } 1273 switch (ctype) { 1274 case SSH_AGENT_CONSTRAIN_LIFETIME: 1275 if (*deathp != 0) { 1276 error_f("lifetime already set"); 1277 r = SSH_ERR_INVALID_FORMAT; 1278 goto out; 1279 } 1280 if ((r = sshbuf_get_u32(m, &seconds)) != 0) { 1281 error_fr(r, "parse lifetime constraint"); 1282 goto out; 1283 } 1284 *deathp = monotime() + seconds; 1285 *secondsp = seconds; 1286 break; 1287 case SSH_AGENT_CONSTRAIN_CONFIRM: 1288 if (*confirmp != 0) { 1289 error_f("confirm already set"); 1290 r = SSH_ERR_INVALID_FORMAT; 1291 goto out; 1292 } 1293 *confirmp = 1; 1294 break; 1295 case SSH_AGENT_CONSTRAIN_MAXSIGN: 1296 if (k == NULL) { 1297 error_f("maxsign not valid here"); 1298 r = SSH_ERR_INVALID_FORMAT; 1299 goto out; 1300 } 1301 if (maxsign != 0) { 1302 error_f("maxsign already set"); 1303 r = SSH_ERR_INVALID_FORMAT; 1304 goto out; 1305 } 1306 if ((r = sshbuf_get_u32(m, &maxsign)) != 0) { 1307 error_fr(r, "parse maxsign constraint"); 1308 goto out; 1309 } 1310 if ((r = sshkey_enable_maxsign(k, maxsign)) != 0) { 1311 error_fr(r, "enable maxsign"); 1312 goto out; 1313 } 1314 break; 1315 case SSH_AGENT_CONSTRAIN_EXTENSION: 1316 if ((r = parse_key_constraint_extension(m, 1317 sk_providerp, dcsp, ndcsp, 1318 cert_onlyp, certs, ncerts)) != 0) 1319 goto out; /* error already logged */ 1320 break; 1321 default: 1322 error_f("Unknown constraint %d", ctype); 1323 r = SSH_ERR_FEATURE_UNSUPPORTED; 1324 goto out; 1325 } 1326 } 1327 /* success */ 1328 r = 0; 1329 out: 1330 return r; 1331 } 1332 1333 static void 1334 process_add_identity(SocketEntry *e) 1335 { 1336 Identity *id; 1337 int success = 0, confirm = 0; 1338 char *fp, *comment = NULL, *sk_provider = NULL; 1339 char canonical_provider[PATH_MAX]; 1340 time_t death = 0; 1341 u_int seconds = 0; 1342 struct dest_constraint *dest_constraints = NULL; 1343 size_t ndest_constraints = 0; 1344 struct sshkey *k = NULL; 1345 int r = SSH_ERR_INTERNAL_ERROR; 1346 1347 debug2_f("entering"); 1348 if ((r = sshkey_private_deserialize(e->request, &k)) != 0 || 1349 k == NULL || 1350 (r = sshbuf_get_cstring(e->request, &comment, NULL)) != 0) { 1351 error_fr(r, "parse"); 1352 goto out; 1353 } 1354 if (parse_key_constraints(e->request, k, &death, &seconds, &confirm, 1355 &sk_provider, &dest_constraints, &ndest_constraints, 1356 NULL, NULL, NULL) != 0) { 1357 error_f("failed to parse constraints"); 1358 sshbuf_reset(e->request); 1359 goto out; 1360 } 1361 dump_dest_constraints(__func__, dest_constraints, ndest_constraints); 1362 1363 if (sk_provider != NULL) { 1364 if (!sshkey_is_sk(k)) { 1365 error("Cannot add provider: %s is not an " 1366 "authenticator-hosted key", sshkey_type(k)); 1367 goto out; 1368 } 1369 if (strcasecmp(sk_provider, "internal") == 0) { 1370 debug_f("internal provider"); 1371 } else { 1372 if (socket_is_remote(e) && !remote_add_provider) { 1373 verbose("failed add of SK provider \"%.100s\": " 1374 "remote addition of providers is disabled", 1375 sk_provider); 1376 goto out; 1377 } 1378 if (realpath(sk_provider, canonical_provider) == NULL) { 1379 verbose("failed provider \"%.100s\": " 1380 "realpath: %s", sk_provider, 1381 strerror(errno)); 1382 goto out; 1383 } 1384 free(sk_provider); 1385 sk_provider = xstrdup(canonical_provider); 1386 if (match_pattern_list(sk_provider, 1387 allowed_providers, 0) != 1) { 1388 error("Refusing add key: " 1389 "provider %s not allowed", sk_provider); 1390 goto out; 1391 } 1392 } 1393 } 1394 if ((r = sshkey_shield_private(k)) != 0) { 1395 error_fr(r, "shield private"); 1396 goto out; 1397 } 1398 if (lifetime && !death) 1399 death = monotime() + lifetime; 1400 if ((id = lookup_identity(k)) == NULL) { 1401 id = xcalloc(1, sizeof(Identity)); 1402 TAILQ_INSERT_TAIL(&idtab->idlist, id, next); 1403 /* Increment the number of identities. */ 1404 idtab->nentries++; 1405 } else { 1406 /* identity not visible, do not update */ 1407 if (identity_permitted(id, e, NULL, NULL, NULL) != 0) 1408 goto out; /* error already logged */ 1409 /* key state might have been updated */ 1410 sshkey_free(id->key); 1411 free(id->comment); 1412 free(id->sk_provider); 1413 free_dest_constraints(id->dest_constraints, 1414 id->ndest_constraints); 1415 } 1416 /* success */ 1417 id->key = k; 1418 id->comment = comment; 1419 id->death = death; 1420 id->confirm = confirm; 1421 id->sk_provider = sk_provider; 1422 id->dest_constraints = dest_constraints; 1423 id->ndest_constraints = ndest_constraints; 1424 1425 if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT, 1426 SSH_FP_DEFAULT)) == NULL) 1427 fatal_f("sshkey_fingerprint failed"); 1428 debug_f("add %s %s \"%.100s\" (life: %u) (confirm: %u) " 1429 "(provider: %s) (destination constraints: %zu)", 1430 sshkey_ssh_name(k), fp, comment, seconds, confirm, 1431 sk_provider == NULL ? "none" : sk_provider, ndest_constraints); 1432 free(fp); 1433 /* transferred */ 1434 k = NULL; 1435 comment = NULL; 1436 sk_provider = NULL; 1437 dest_constraints = NULL; 1438 ndest_constraints = 0; 1439 success = 1; 1440 out: 1441 free(sk_provider); 1442 free(comment); 1443 sshkey_free(k); 1444 free_dest_constraints(dest_constraints, ndest_constraints); 1445 send_status(e, success); 1446 } 1447 1448 /* XXX todo: encrypt sensitive data with passphrase */ 1449 static void 1450 process_lock_agent(SocketEntry *e, int lock) 1451 { 1452 int r, success = 0, delay; 1453 char *passwd; 1454 u_char passwdhash[LOCK_SIZE]; 1455 static u_int fail_count = 0; 1456 size_t pwlen; 1457 1458 debug2_f("entering"); 1459 /* 1460 * This is deliberately fatal: the user has requested that we lock, 1461 * but we can't parse their request properly. The only safe thing to 1462 * do is abort. 1463 */ 1464 if ((r = sshbuf_get_cstring(e->request, &passwd, &pwlen)) != 0) 1465 fatal_fr(r, "parse"); 1466 if (pwlen == 0) { 1467 debug("empty password not supported"); 1468 } else if (locked && !lock) { 1469 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt), 1470 passwdhash, sizeof(passwdhash), LOCK_ROUNDS) < 0) 1471 fatal("bcrypt_pbkdf"); 1472 if (timingsafe_bcmp(passwdhash, lock_pwhash, LOCK_SIZE) == 0) { 1473 debug("agent unlocked"); 1474 locked = 0; 1475 fail_count = 0; 1476 explicit_bzero(lock_pwhash, sizeof(lock_pwhash)); 1477 success = 1; 1478 } else { 1479 /* delay in 0.1s increments up to 10s */ 1480 if (fail_count < 100) 1481 fail_count++; 1482 delay = 100000 * fail_count; 1483 debug("unlock failed, delaying %0.1lf seconds", 1484 (double)delay/1000000); 1485 usleep(delay); 1486 } 1487 explicit_bzero(passwdhash, sizeof(passwdhash)); 1488 } else if (!locked && lock) { 1489 debug("agent locked"); 1490 locked = 1; 1491 arc4random_buf(lock_salt, sizeof(lock_salt)); 1492 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt), 1493 lock_pwhash, sizeof(lock_pwhash), LOCK_ROUNDS) < 0) 1494 fatal("bcrypt_pbkdf"); 1495 success = 1; 1496 } 1497 freezero(passwd, pwlen); 1498 send_status(e, success); 1499 } 1500 1501 static void 1502 no_identities(SocketEntry *e) 1503 { 1504 struct sshbuf *msg; 1505 int r; 1506 1507 if ((msg = sshbuf_new()) == NULL) 1508 fatal_f("sshbuf_new failed"); 1509 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 || 1510 (r = sshbuf_put_u32(msg, 0)) != 0 || 1511 (r = sshbuf_put_stringb(e->output, msg)) != 0) 1512 fatal_fr(r, "compose"); 1513 sshbuf_free(msg); 1514 } 1515 1516 #ifdef ENABLE_PKCS11 1517 /* Add an identity to idlist; takes ownership of 'key' and 'comment' */ 1518 static void 1519 add_p11_identity(struct sshkey *key, char *comment, const char *provider, 1520 time_t death, u_int confirm, struct dest_constraint *dest_constraints, 1521 size_t ndest_constraints) 1522 { 1523 Identity *id; 1524 1525 if (lookup_identity(key) != NULL) { 1526 sshkey_free(key); 1527 free(comment); 1528 return; 1529 } 1530 id = xcalloc(1, sizeof(Identity)); 1531 id->key = key; 1532 id->comment = comment; 1533 id->provider = xstrdup(provider); 1534 id->death = death; 1535 id->confirm = confirm; 1536 id->dest_constraints = dup_dest_constraints(dest_constraints, 1537 ndest_constraints); 1538 id->ndest_constraints = ndest_constraints; 1539 TAILQ_INSERT_TAIL(&idtab->idlist, id, next); 1540 idtab->nentries++; 1541 } 1542 1543 static void 1544 process_add_smartcard_key(SocketEntry *e) 1545 { 1546 char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX]; 1547 char **comments = NULL; 1548 int r, i, count = 0, success = 0, confirm = 0; 1549 u_int seconds = 0; 1550 time_t death = 0; 1551 struct sshkey **keys = NULL, *k; 1552 struct dest_constraint *dest_constraints = NULL; 1553 size_t j, ndest_constraints = 0, ncerts = 0; 1554 struct sshkey **certs = NULL; 1555 int cert_only = 0; 1556 1557 debug2_f("entering"); 1558 if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 || 1559 (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) { 1560 error_fr(r, "parse"); 1561 goto send; 1562 } 1563 if (parse_key_constraints(e->request, NULL, &death, &seconds, &confirm, 1564 NULL, &dest_constraints, &ndest_constraints, &cert_only, 1565 &ncerts, &certs) != 0) { 1566 error_f("failed to parse constraints"); 1567 goto send; 1568 } 1569 dump_dest_constraints(__func__, dest_constraints, ndest_constraints); 1570 if (socket_is_remote(e) && !remote_add_provider) { 1571 verbose("failed PKCS#11 add of \"%.100s\": remote addition of " 1572 "providers is disabled", provider); 1573 goto send; 1574 } 1575 if (realpath(provider, canonical_provider) == NULL) { 1576 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s", 1577 provider, strerror(errno)); 1578 goto send; 1579 } 1580 if (match_pattern_list(canonical_provider, allowed_providers, 0) != 1) { 1581 verbose("refusing PKCS#11 add of \"%.100s\": " 1582 "provider not allowed", canonical_provider); 1583 goto send; 1584 } 1585 debug_f("add %.100s", canonical_provider); 1586 if (lifetime && !death) 1587 death = monotime() + lifetime; 1588 1589 count = pkcs11_add_provider(canonical_provider, pin, &keys, &comments); 1590 for (i = 0; i < count; i++) { 1591 if (comments[i] == NULL || comments[i][0] == '\0') { 1592 free(comments[i]); 1593 comments[i] = xstrdup(canonical_provider); 1594 } 1595 for (j = 0; j < ncerts; j++) { 1596 if (!sshkey_is_cert(certs[j])) 1597 continue; 1598 if (!sshkey_equal_public(keys[i], certs[j])) 1599 continue; 1600 if (pkcs11_make_cert(keys[i], certs[j], &k) != 0) 1601 continue; 1602 add_p11_identity(k, xstrdup(comments[i]), 1603 canonical_provider, death, confirm, 1604 dest_constraints, ndest_constraints); 1605 success = 1; 1606 } 1607 if (!cert_only && lookup_identity(keys[i]) == NULL) { 1608 add_p11_identity(keys[i], comments[i], 1609 canonical_provider, death, confirm, 1610 dest_constraints, ndest_constraints); 1611 keys[i] = NULL; /* transferred */ 1612 comments[i] = NULL; /* transferred */ 1613 success = 1; 1614 } 1615 /* XXX update constraints for existing keys */ 1616 sshkey_free(keys[i]); 1617 free(comments[i]); 1618 } 1619 send: 1620 free(pin); 1621 free(provider); 1622 free(keys); 1623 free(comments); 1624 free_dest_constraints(dest_constraints, ndest_constraints); 1625 for (j = 0; j < ncerts; j++) 1626 sshkey_free(certs[j]); 1627 free(certs); 1628 send_status(e, success); 1629 } 1630 1631 static void 1632 process_remove_smartcard_key(SocketEntry *e) 1633 { 1634 char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX]; 1635 int r, success = 0; 1636 Identity *id, *nxt; 1637 1638 debug2_f("entering"); 1639 if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 || 1640 (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) { 1641 error_fr(r, "parse"); 1642 goto send; 1643 } 1644 free(pin); 1645 1646 if (realpath(provider, canonical_provider) == NULL) { 1647 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s", 1648 provider, strerror(errno)); 1649 goto send; 1650 } 1651 1652 debug_f("remove %.100s", canonical_provider); 1653 for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) { 1654 nxt = TAILQ_NEXT(id, next); 1655 /* Skip file--based keys */ 1656 if (id->provider == NULL) 1657 continue; 1658 if (!strcmp(canonical_provider, id->provider)) { 1659 TAILQ_REMOVE(&idtab->idlist, id, next); 1660 free_identity(id); 1661 idtab->nentries--; 1662 } 1663 } 1664 if (pkcs11_del_provider(canonical_provider) == 0) 1665 success = 1; 1666 else 1667 error_f("pkcs11_del_provider failed"); 1668 send: 1669 free(provider); 1670 send_status(e, success); 1671 } 1672 #endif /* ENABLE_PKCS11 */ 1673 1674 static int 1675 process_ext_session_bind(SocketEntry *e) 1676 { 1677 int r, sid_match, key_match; 1678 struct sshkey *key = NULL; 1679 struct sshbuf *sid = NULL, *sig = NULL; 1680 char *fp = NULL; 1681 size_t i; 1682 u_char fwd = 0; 1683 1684 debug2_f("entering"); 1685 e->session_bind_attempted = 1; 1686 if ((r = sshkey_froms(e->request, &key)) != 0 || 1687 (r = sshbuf_froms(e->request, &sid)) != 0 || 1688 (r = sshbuf_froms(e->request, &sig)) != 0 || 1689 (r = sshbuf_get_u8(e->request, &fwd)) != 0) { 1690 error_fr(r, "parse"); 1691 goto out; 1692 } 1693 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT, 1694 SSH_FP_DEFAULT)) == NULL) 1695 fatal_f("fingerprint failed"); 1696 /* check signature with hostkey on session ID */ 1697 if ((r = sshkey_verify(key, sshbuf_ptr(sig), sshbuf_len(sig), 1698 sshbuf_ptr(sid), sshbuf_len(sid), NULL, 0, NULL)) != 0) { 1699 error_fr(r, "sshkey_verify for %s %s", sshkey_type(key), fp); 1700 goto out; 1701 } 1702 /* check whether sid/key already recorded */ 1703 for (i = 0; i < e->nsession_ids; i++) { 1704 if (!e->session_ids[i].forwarded) { 1705 error_f("attempt to bind session ID to socket " 1706 "previously bound for authentication attempt"); 1707 r = -1; 1708 goto out; 1709 } 1710 sid_match = buf_equal(sid, e->session_ids[i].sid) == 0; 1711 key_match = sshkey_equal(key, e->session_ids[i].key); 1712 if (sid_match && key_match) { 1713 debug_f("session ID already recorded for %s %s", 1714 sshkey_type(key), fp); 1715 r = 0; 1716 goto out; 1717 } else if (sid_match) { 1718 error_f("session ID recorded against different key " 1719 "for %s %s", sshkey_type(key), fp); 1720 r = -1; 1721 goto out; 1722 } 1723 /* 1724 * new sid with previously-seen key can happen, e.g. multiple 1725 * connections to the same host. 1726 */ 1727 } 1728 /* record new key/sid */ 1729 if (e->nsession_ids >= AGENT_MAX_SESSION_IDS) { 1730 error_f("too many session IDs recorded"); 1731 goto out; 1732 } 1733 e->session_ids = xrecallocarray(e->session_ids, e->nsession_ids, 1734 e->nsession_ids + 1, sizeof(*e->session_ids)); 1735 i = e->nsession_ids++; 1736 debug_f("recorded %s %s (slot %zu of %d)", sshkey_type(key), fp, i, 1737 AGENT_MAX_SESSION_IDS); 1738 e->session_ids[i].key = key; 1739 e->session_ids[i].forwarded = fwd != 0; 1740 key = NULL; /* transferred */ 1741 /* can't transfer sid; it's refcounted and scoped to request's life */ 1742 if ((e->session_ids[i].sid = sshbuf_new()) == NULL) 1743 fatal_f("sshbuf_new"); 1744 if ((r = sshbuf_putb(e->session_ids[i].sid, sid)) != 0) 1745 fatal_fr(r, "sshbuf_putb session ID"); 1746 /* success */ 1747 r = 0; 1748 out: 1749 free(fp); 1750 sshkey_free(key); 1751 sshbuf_free(sid); 1752 sshbuf_free(sig); 1753 return r == 0 ? 1 : 0; 1754 } 1755 1756 static void 1757 process_extension(SocketEntry *e) 1758 { 1759 int r, success = 0; 1760 char *name; 1761 1762 debug2_f("entering"); 1763 if ((r = sshbuf_get_cstring(e->request, &name, NULL)) != 0) { 1764 error_fr(r, "parse"); 1765 goto send; 1766 } 1767 if (strcmp(name, "session-bind@openssh.com") == 0) 1768 success = process_ext_session_bind(e); 1769 else 1770 debug_f("unsupported extension \"%s\"", name); 1771 free(name); 1772 send: 1773 send_status(e, success); 1774 } 1775 /* 1776 * dispatch incoming message. 1777 * returns 1 on success, 0 for incomplete messages or -1 on error. 1778 */ 1779 static int 1780 process_message(u_int socknum) 1781 { 1782 u_int msg_len; 1783 u_char type; 1784 const u_char *cp; 1785 int r; 1786 SocketEntry *e; 1787 1788 if (socknum >= sockets_alloc) 1789 fatal_f("sock %u >= allocated %u", socknum, sockets_alloc); 1790 e = &sockets[socknum]; 1791 1792 if (sshbuf_len(e->input) < 5) 1793 return 0; /* Incomplete message header. */ 1794 cp = sshbuf_ptr(e->input); 1795 msg_len = PEEK_U32(cp); 1796 if (msg_len > AGENT_MAX_LEN) { 1797 debug_f("socket %u (fd=%d) message too long %u > %u", 1798 socknum, e->fd, msg_len, AGENT_MAX_LEN); 1799 return -1; 1800 } 1801 if (sshbuf_len(e->input) < msg_len + 4) 1802 return 0; /* Incomplete message body. */ 1803 1804 /* move the current input to e->request */ 1805 sshbuf_reset(e->request); 1806 if ((r = sshbuf_get_stringb(e->input, e->request)) != 0 || 1807 (r = sshbuf_get_u8(e->request, &type)) != 0) { 1808 if (r == SSH_ERR_MESSAGE_INCOMPLETE || 1809 r == SSH_ERR_STRING_TOO_LARGE) { 1810 error_fr(r, "parse"); 1811 return -1; 1812 } 1813 fatal_fr(r, "parse"); 1814 } 1815 1816 debug_f("socket %u (fd=%d) type %d", socknum, e->fd, type); 1817 1818 /* check whether agent is locked */ 1819 if (locked && type != SSH_AGENTC_UNLOCK) { 1820 sshbuf_reset(e->request); 1821 switch (type) { 1822 case SSH2_AGENTC_REQUEST_IDENTITIES: 1823 /* send empty lists */ 1824 no_identities(e); 1825 break; 1826 default: 1827 /* send a fail message for all other request types */ 1828 send_status(e, 0); 1829 } 1830 return 1; 1831 } 1832 1833 switch (type) { 1834 case SSH_AGENTC_LOCK: 1835 case SSH_AGENTC_UNLOCK: 1836 process_lock_agent(e, type == SSH_AGENTC_LOCK); 1837 break; 1838 case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES: 1839 process_remove_all_identities(e); /* safe for !WITH_SSH1 */ 1840 break; 1841 /* ssh2 */ 1842 case SSH2_AGENTC_SIGN_REQUEST: 1843 process_sign_request2(e); 1844 break; 1845 case SSH2_AGENTC_REQUEST_IDENTITIES: 1846 process_request_identities(e); 1847 break; 1848 case SSH2_AGENTC_ADD_IDENTITY: 1849 case SSH2_AGENTC_ADD_ID_CONSTRAINED: 1850 process_add_identity(e); 1851 break; 1852 case SSH2_AGENTC_REMOVE_IDENTITY: 1853 process_remove_identity(e); 1854 break; 1855 case SSH2_AGENTC_REMOVE_ALL_IDENTITIES: 1856 process_remove_all_identities(e); 1857 break; 1858 #ifdef ENABLE_PKCS11 1859 case SSH_AGENTC_ADD_SMARTCARD_KEY: 1860 case SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED: 1861 process_add_smartcard_key(e); 1862 break; 1863 case SSH_AGENTC_REMOVE_SMARTCARD_KEY: 1864 process_remove_smartcard_key(e); 1865 break; 1866 #endif /* ENABLE_PKCS11 */ 1867 case SSH_AGENTC_EXTENSION: 1868 process_extension(e); 1869 break; 1870 default: 1871 /* Unknown message. Respond with failure. */ 1872 error("Unknown message %d", type); 1873 sshbuf_reset(e->request); 1874 send_status(e, 0); 1875 break; 1876 } 1877 return 1; 1878 } 1879 1880 static void 1881 new_socket(sock_type type, int fd) 1882 { 1883 u_int i, old_alloc, new_alloc; 1884 1885 debug_f("type = %s", type == AUTH_CONNECTION ? "CONNECTION" : 1886 (type == AUTH_SOCKET ? "SOCKET" : "UNKNOWN")); 1887 set_nonblock(fd); 1888 1889 if (fd > max_fd) 1890 max_fd = fd; 1891 1892 for (i = 0; i < sockets_alloc; i++) 1893 if (sockets[i].type == AUTH_UNUSED) { 1894 sockets[i].fd = fd; 1895 if ((sockets[i].input = sshbuf_new()) == NULL || 1896 (sockets[i].output = sshbuf_new()) == NULL || 1897 (sockets[i].request = sshbuf_new()) == NULL) 1898 fatal_f("sshbuf_new failed"); 1899 sockets[i].type = type; 1900 return; 1901 } 1902 old_alloc = sockets_alloc; 1903 new_alloc = sockets_alloc + 10; 1904 sockets = xrecallocarray(sockets, old_alloc, new_alloc, 1905 sizeof(sockets[0])); 1906 for (i = old_alloc; i < new_alloc; i++) 1907 sockets[i].type = AUTH_UNUSED; 1908 sockets_alloc = new_alloc; 1909 sockets[old_alloc].fd = fd; 1910 if ((sockets[old_alloc].input = sshbuf_new()) == NULL || 1911 (sockets[old_alloc].output = sshbuf_new()) == NULL || 1912 (sockets[old_alloc].request = sshbuf_new()) == NULL) 1913 fatal_f("sshbuf_new failed"); 1914 sockets[old_alloc].type = type; 1915 } 1916 1917 static int 1918 handle_socket_read(u_int socknum) 1919 { 1920 struct sockaddr_un sunaddr; 1921 socklen_t slen; 1922 uid_t euid; 1923 gid_t egid; 1924 int fd; 1925 1926 slen = sizeof(sunaddr); 1927 fd = accept(sockets[socknum].fd, (struct sockaddr *)&sunaddr, &slen); 1928 if (fd == -1) { 1929 error("accept from AUTH_SOCKET: %s", strerror(errno)); 1930 return -1; 1931 } 1932 if (getpeereid(fd, &euid, &egid) == -1) { 1933 error("getpeereid %d failed: %s", fd, strerror(errno)); 1934 close(fd); 1935 return -1; 1936 } 1937 if ((euid != 0) && (getuid() != euid)) { 1938 error("uid mismatch: peer euid %u != uid %u", 1939 (u_int) euid, (u_int) getuid()); 1940 close(fd); 1941 return -1; 1942 } 1943 new_socket(AUTH_CONNECTION, fd); 1944 return 0; 1945 } 1946 1947 static int 1948 handle_conn_read(u_int socknum) 1949 { 1950 char buf[AGENT_RBUF_LEN]; 1951 ssize_t len; 1952 int r; 1953 1954 if ((len = read(sockets[socknum].fd, buf, sizeof(buf))) <= 0) { 1955 if (len == -1) { 1956 if (errno == EAGAIN || errno == EINTR) 1957 return 0; 1958 error_f("read error on socket %u (fd %d): %s", 1959 socknum, sockets[socknum].fd, strerror(errno)); 1960 } 1961 return -1; 1962 } 1963 if ((r = sshbuf_put(sockets[socknum].input, buf, len)) != 0) 1964 fatal_fr(r, "compose"); 1965 explicit_bzero(buf, sizeof(buf)); 1966 for (;;) { 1967 if ((r = process_message(socknum)) == -1) 1968 return -1; 1969 else if (r == 0) 1970 break; 1971 } 1972 return 0; 1973 } 1974 1975 static int 1976 handle_conn_write(u_int socknum) 1977 { 1978 ssize_t len; 1979 int r; 1980 1981 if (sshbuf_len(sockets[socknum].output) == 0) 1982 return 0; /* shouldn't happen */ 1983 if ((len = write(sockets[socknum].fd, 1984 sshbuf_ptr(sockets[socknum].output), 1985 sshbuf_len(sockets[socknum].output))) <= 0) { 1986 if (len == -1) { 1987 if (errno == EAGAIN || errno == EINTR) 1988 return 0; 1989 error_f("read error on socket %u (fd %d): %s", 1990 socknum, sockets[socknum].fd, strerror(errno)); 1991 } 1992 return -1; 1993 } 1994 if ((r = sshbuf_consume(sockets[socknum].output, len)) != 0) 1995 fatal_fr(r, "consume"); 1996 return 0; 1997 } 1998 1999 static void 2000 after_poll(struct pollfd *pfd, size_t npfd, u_int maxfds) 2001 { 2002 size_t i; 2003 u_int socknum, activefds = npfd; 2004 2005 for (i = 0; i < npfd; i++) { 2006 if (pfd[i].revents == 0) 2007 continue; 2008 /* Find sockets entry */ 2009 for (socknum = 0; socknum < sockets_alloc; socknum++) { 2010 if (sockets[socknum].type != AUTH_SOCKET && 2011 sockets[socknum].type != AUTH_CONNECTION) 2012 continue; 2013 if (pfd[i].fd == sockets[socknum].fd) 2014 break; 2015 } 2016 if (socknum >= sockets_alloc) { 2017 error_f("no socket for fd %d", pfd[i].fd); 2018 continue; 2019 } 2020 /* Process events */ 2021 switch (sockets[socknum].type) { 2022 case AUTH_SOCKET: 2023 if ((pfd[i].revents & (POLLIN|POLLERR)) == 0) 2024 break; 2025 if (npfd > maxfds) { 2026 debug3("out of fds (active %u >= limit %u); " 2027 "skipping accept", activefds, maxfds); 2028 break; 2029 } 2030 if (handle_socket_read(socknum) == 0) 2031 activefds++; 2032 break; 2033 case AUTH_CONNECTION: 2034 if ((pfd[i].revents & (POLLIN|POLLHUP|POLLERR)) != 0 && 2035 handle_conn_read(socknum) != 0) 2036 goto close_sock; 2037 if ((pfd[i].revents & (POLLOUT|POLLHUP)) != 0 && 2038 handle_conn_write(socknum) != 0) { 2039 close_sock: 2040 if (activefds == 0) 2041 fatal("activefds == 0 at close_sock"); 2042 close_socket(&sockets[socknum]); 2043 activefds--; 2044 break; 2045 } 2046 break; 2047 default: 2048 break; 2049 } 2050 } 2051 } 2052 2053 static int 2054 prepare_poll(struct pollfd **pfdp, size_t *npfdp, struct timespec *timeoutp, u_int maxfds) 2055 { 2056 struct pollfd *pfd = *pfdp; 2057 size_t i, j, npfd = 0; 2058 time_t deadline; 2059 int r; 2060 2061 /* Count active sockets */ 2062 for (i = 0; i < sockets_alloc; i++) { 2063 switch (sockets[i].type) { 2064 case AUTH_SOCKET: 2065 case AUTH_CONNECTION: 2066 npfd++; 2067 break; 2068 case AUTH_UNUSED: 2069 break; 2070 default: 2071 fatal("Unknown socket type %d", sockets[i].type); 2072 break; 2073 } 2074 } 2075 if (npfd != *npfdp && 2076 (pfd = recallocarray(pfd, *npfdp, npfd, sizeof(*pfd))) == NULL) 2077 fatal_f("recallocarray failed"); 2078 *pfdp = pfd; 2079 *npfdp = npfd; 2080 2081 for (i = j = 0; i < sockets_alloc; i++) { 2082 switch (sockets[i].type) { 2083 case AUTH_SOCKET: 2084 if (npfd > maxfds) { 2085 debug3("out of fds (active %zu >= limit %u); " 2086 "skipping arming listener", npfd, maxfds); 2087 break; 2088 } 2089 pfd[j].fd = sockets[i].fd; 2090 pfd[j].revents = 0; 2091 pfd[j].events = POLLIN; 2092 j++; 2093 break; 2094 case AUTH_CONNECTION: 2095 pfd[j].fd = sockets[i].fd; 2096 pfd[j].revents = 0; 2097 /* 2098 * Only prepare to read if we can handle a full-size 2099 * input read buffer and enqueue a max size reply.. 2100 */ 2101 if ((r = sshbuf_check_reserve(sockets[i].input, 2102 AGENT_RBUF_LEN)) == 0 && 2103 (r = sshbuf_check_reserve(sockets[i].output, 2104 AGENT_MAX_LEN)) == 0) 2105 pfd[j].events = POLLIN; 2106 else if (r != SSH_ERR_NO_BUFFER_SPACE) 2107 fatal_fr(r, "reserve"); 2108 if (sshbuf_len(sockets[i].output) > 0) 2109 pfd[j].events |= POLLOUT; 2110 j++; 2111 break; 2112 default: 2113 break; 2114 } 2115 } 2116 deadline = reaper(); 2117 if (parent_alive_interval != 0) 2118 deadline = (deadline == 0) ? parent_alive_interval : 2119 MINIMUM(deadline, parent_alive_interval); 2120 if (deadline != 0) 2121 ptimeout_deadline_sec(timeoutp, deadline); 2122 return (1); 2123 } 2124 2125 static void 2126 cleanup_socket(void) 2127 { 2128 if (cleanup_pid != 0 && getpid() != cleanup_pid) 2129 return; 2130 debug_f("cleanup"); 2131 if (socket_name[0]) 2132 unlink(socket_name); 2133 if (socket_dir[0]) 2134 rmdir(socket_dir); 2135 } 2136 2137 void 2138 cleanup_exit(int i) 2139 { 2140 cleanup_socket(); 2141 #ifdef ENABLE_PKCS11 2142 pkcs11_terminate(); 2143 #endif 2144 _exit(i); 2145 } 2146 2147 static void 2148 cleanup_handler(int sig) 2149 { 2150 signalled = sig; 2151 } 2152 2153 static void 2154 check_parent_exists(void) 2155 { 2156 /* 2157 * If our parent has exited then getppid() will return (pid_t)1, 2158 * so testing for that should be safe. 2159 */ 2160 if (parent_pid != -1 && getppid() != parent_pid) { 2161 /* printf("Parent has died - Authentication agent exiting.\n"); */ 2162 cleanup_socket(); 2163 _exit(2); 2164 } 2165 } 2166 2167 static void 2168 usage(void) 2169 { 2170 fprintf(stderr, 2171 "usage: ssh-agent [-c | -s] [-Dd] [-a bind_address] [-E fingerprint_hash]\n" 2172 " [-O option] [-P allowed_providers] [-t life]\n" 2173 " ssh-agent [-a bind_address] [-E fingerprint_hash] [-O option]\n" 2174 " [-P allowed_providers] [-t life] command [arg ...]\n" 2175 " ssh-agent [-c | -s] -k\n"); 2176 exit(1); 2177 } 2178 2179 int 2180 main(int ac, char **av) 2181 { 2182 int c_flag = 0, d_flag = 0, D_flag = 0, k_flag = 0, s_flag = 0; 2183 int sock, ch, result, saved_errno; 2184 char *shell, *format, *pidstr, *agentsocket = NULL; 2185 struct rlimit rlim; 2186 extern int optind; 2187 extern char *optarg; 2188 pid_t pid; 2189 char pidstrbuf[1 + 3 * sizeof pid]; 2190 size_t len; 2191 mode_t prev_mask; 2192 struct timespec timeout; 2193 struct pollfd *pfd = NULL; 2194 size_t npfd = 0; 2195 u_int maxfds; 2196 sigset_t nsigset, osigset; 2197 2198 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */ 2199 sanitise_stdfd(); 2200 2201 /* drop */ 2202 (void)setegid(getgid()); 2203 (void)setgid(getgid()); 2204 2205 if (getrlimit(RLIMIT_NOFILE, &rlim) == -1) 2206 fatal("%s: getrlimit: %s", __progname, strerror(errno)); 2207 2208 #ifdef WITH_OPENSSL 2209 OpenSSL_add_all_algorithms(); 2210 #endif 2211 2212 while ((ch = getopt(ac, av, "cDdksE:a:O:P:t:")) != -1) { 2213 switch (ch) { 2214 case 'E': 2215 fingerprint_hash = ssh_digest_alg_by_name(optarg); 2216 if (fingerprint_hash == -1) 2217 fatal("Invalid hash algorithm \"%s\"", optarg); 2218 break; 2219 case 'c': 2220 if (s_flag) 2221 usage(); 2222 c_flag++; 2223 break; 2224 case 'k': 2225 k_flag++; 2226 break; 2227 case 'O': 2228 if (strcmp(optarg, "no-restrict-websafe") == 0) 2229 restrict_websafe = 0; 2230 else if (strcmp(optarg, "allow-remote-pkcs11") == 0) 2231 remote_add_provider = 1; 2232 else 2233 fatal("Unknown -O option"); 2234 break; 2235 case 'P': 2236 if (allowed_providers != NULL) 2237 fatal("-P option already specified"); 2238 allowed_providers = xstrdup(optarg); 2239 break; 2240 case 's': 2241 if (c_flag) 2242 usage(); 2243 s_flag++; 2244 break; 2245 case 'd': 2246 if (d_flag || D_flag) 2247 usage(); 2248 d_flag++; 2249 break; 2250 case 'D': 2251 if (d_flag || D_flag) 2252 usage(); 2253 D_flag++; 2254 break; 2255 case 'a': 2256 agentsocket = optarg; 2257 break; 2258 case 't': 2259 if ((lifetime = convtime(optarg)) == -1) { 2260 fprintf(stderr, "Invalid lifetime\n"); 2261 usage(); 2262 } 2263 break; 2264 default: 2265 usage(); 2266 } 2267 } 2268 ac -= optind; 2269 av += optind; 2270 2271 if (ac > 0 && (c_flag || k_flag || s_flag || d_flag || D_flag)) 2272 usage(); 2273 2274 if (allowed_providers == NULL) 2275 allowed_providers = xstrdup(DEFAULT_ALLOWED_PROVIDERS); 2276 2277 if (ac == 0 && !c_flag && !s_flag) { 2278 shell = getenv("SHELL"); 2279 if (shell != NULL && (len = strlen(shell)) > 2 && 2280 strncmp(shell + len - 3, "csh", 3) == 0) 2281 c_flag = 1; 2282 } 2283 if (k_flag) { 2284 const char *errstr = NULL; 2285 2286 pidstr = getenv(SSH_AGENTPID_ENV_NAME); 2287 if (pidstr == NULL) { 2288 fprintf(stderr, "%s not set, cannot kill agent\n", 2289 SSH_AGENTPID_ENV_NAME); 2290 exit(1); 2291 } 2292 pid = (int)strtonum(pidstr, 2, INT_MAX, &errstr); 2293 if (errstr) { 2294 fprintf(stderr, 2295 "%s=\"%s\", which is not a good PID: %s\n", 2296 SSH_AGENTPID_ENV_NAME, pidstr, errstr); 2297 exit(1); 2298 } 2299 if (kill(pid, SIGTERM) == -1) { 2300 perror("kill"); 2301 exit(1); 2302 } 2303 format = c_flag ? "unsetenv %s;\n" : "unset %s;\n"; 2304 printf(format, SSH_AUTHSOCKET_ENV_NAME); 2305 printf(format, SSH_AGENTPID_ENV_NAME); 2306 printf("echo Agent pid %ld killed;\n", (long)pid); 2307 exit(0); 2308 } 2309 2310 /* 2311 * Minimum file descriptors: 2312 * stdio (3) + listener (1) + syslog (1 maybe) + connection (1) + 2313 * a few spare for libc / stack protectors / sanitisers, etc. 2314 */ 2315 #define SSH_AGENT_MIN_FDS (3+1+1+1+4) 2316 if (rlim.rlim_cur < SSH_AGENT_MIN_FDS) 2317 fatal("%s: file descriptor rlimit %lld too low (minimum %u)", 2318 __progname, (long long)rlim.rlim_cur, SSH_AGENT_MIN_FDS); 2319 maxfds = rlim.rlim_cur - SSH_AGENT_MIN_FDS; 2320 2321 parent_pid = getpid(); 2322 2323 if (agentsocket == NULL) { 2324 /* Create private directory for agent socket */ 2325 mktemp_proto(socket_dir, sizeof(socket_dir)); 2326 if (mkdtemp(socket_dir) == NULL) { 2327 perror("mkdtemp: private socket dir"); 2328 exit(1); 2329 } 2330 snprintf(socket_name, sizeof socket_name, "%s/agent.%ld", socket_dir, 2331 (long)parent_pid); 2332 } else { 2333 /* Try to use specified agent socket */ 2334 socket_dir[0] = '\0'; 2335 strlcpy(socket_name, agentsocket, sizeof socket_name); 2336 } 2337 2338 /* 2339 * Create socket early so it will exist before command gets run from 2340 * the parent. 2341 */ 2342 prev_mask = umask(0177); 2343 sock = unix_listener(socket_name, SSH_LISTEN_BACKLOG, 0); 2344 if (sock < 0) { 2345 /* XXX - unix_listener() calls error() not perror() */ 2346 *socket_name = '\0'; /* Don't unlink any existing file */ 2347 cleanup_exit(1); 2348 } 2349 umask(prev_mask); 2350 2351 /* 2352 * Fork, and have the parent execute the command, if any, or present 2353 * the socket data. The child continues as the authentication agent. 2354 */ 2355 if (D_flag || d_flag) { 2356 log_init(__progname, 2357 d_flag ? SYSLOG_LEVEL_DEBUG3 : SYSLOG_LEVEL_INFO, 2358 SYSLOG_FACILITY_AUTH, 1); 2359 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n"; 2360 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name, 2361 SSH_AUTHSOCKET_ENV_NAME); 2362 printf("echo Agent pid %ld;\n", (long)parent_pid); 2363 fflush(stdout); 2364 goto skip; 2365 } 2366 pid = fork(); 2367 if (pid == -1) { 2368 perror("fork"); 2369 cleanup_exit(1); 2370 } 2371 if (pid != 0) { /* Parent - execute the given command. */ 2372 close(sock); 2373 snprintf(pidstrbuf, sizeof pidstrbuf, "%ld", (long)pid); 2374 if (ac == 0) { 2375 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n"; 2376 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name, 2377 SSH_AUTHSOCKET_ENV_NAME); 2378 printf(format, SSH_AGENTPID_ENV_NAME, pidstrbuf, 2379 SSH_AGENTPID_ENV_NAME); 2380 printf("echo Agent pid %ld;\n", (long)pid); 2381 exit(0); 2382 } 2383 if (setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1) == -1 || 2384 setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1) == -1) { 2385 perror("setenv"); 2386 exit(1); 2387 } 2388 execvp(av[0], av); 2389 perror(av[0]); 2390 exit(1); 2391 } 2392 /* child */ 2393 log_init(__progname, SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_AUTH, 0); 2394 2395 if (setsid() == -1) { 2396 error("setsid: %s", strerror(errno)); 2397 cleanup_exit(1); 2398 } 2399 2400 (void)chdir("/"); 2401 if (stdfd_devnull(1, 1, 1) == -1) 2402 error_f("stdfd_devnull failed"); 2403 2404 /* deny core dumps, since memory contains unencrypted private keys */ 2405 rlim.rlim_cur = rlim.rlim_max = 0; 2406 if (setrlimit(RLIMIT_CORE, &rlim) == -1) { 2407 error("setrlimit RLIMIT_CORE: %s", strerror(errno)); 2408 cleanup_exit(1); 2409 } 2410 2411 skip: 2412 2413 cleanup_pid = getpid(); 2414 2415 #ifdef ENABLE_PKCS11 2416 pkcs11_init(0); 2417 #endif 2418 new_socket(AUTH_SOCKET, sock); 2419 if (ac > 0) 2420 parent_alive_interval = 10; 2421 idtab_init(); 2422 ssh_signal(SIGPIPE, SIG_IGN); 2423 ssh_signal(SIGINT, (d_flag | D_flag) ? cleanup_handler : SIG_IGN); 2424 ssh_signal(SIGHUP, cleanup_handler); 2425 ssh_signal(SIGTERM, cleanup_handler); 2426 2427 sigemptyset(&nsigset); 2428 sigaddset(&nsigset, SIGINT); 2429 sigaddset(&nsigset, SIGHUP); 2430 sigaddset(&nsigset, SIGTERM); 2431 2432 if (pledge("stdio rpath cpath unix id proc exec", NULL) == -1) 2433 fatal("%s: pledge: %s", __progname, strerror(errno)); 2434 2435 while (1) { 2436 sigprocmask(SIG_BLOCK, &nsigset, &osigset); 2437 if (signalled != 0) { 2438 logit("exiting on signal %d", (int)signalled); 2439 cleanup_exit(2); 2440 } 2441 ptimeout_init(&timeout); 2442 prepare_poll(&pfd, &npfd, &timeout, maxfds); 2443 result = ppoll(pfd, npfd, ptimeout_get_tsp(&timeout), &osigset); 2444 sigprocmask(SIG_SETMASK, &osigset, NULL); 2445 saved_errno = errno; 2446 if (parent_alive_interval != 0) 2447 check_parent_exists(); 2448 (void) reaper(); /* remove expired keys */ 2449 if (result == -1) { 2450 if (saved_errno == EINTR) 2451 continue; 2452 fatal("poll: %s", strerror(saved_errno)); 2453 } else if (result > 0) 2454 after_poll(pfd, npfd, maxfds); 2455 } 2456 /* NOTREACHED */ 2457 } 2458