1 /* $OpenBSD: ssh-agent.c,v 1.304 2023/12/18 15:58:56 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 /* pid of process for which cleanup_socket is applicable */ 153 pid_t cleanup_pid = 0; 154 155 /* pathname and directory for AUTH_SOCKET */ 156 char socket_name[PATH_MAX]; 157 char socket_dir[PATH_MAX]; 158 159 /* Pattern-list of allowed PKCS#11/Security key paths */ 160 static char *allowed_providers; 161 162 /* 163 * Allows PKCS11 providers or SK keys that use non-internal providers to 164 * be added over a remote connection (identified by session-bind@openssh.com). 165 */ 166 static int remote_add_provider; 167 168 /* locking */ 169 #define LOCK_SIZE 32 170 #define LOCK_SALT_SIZE 16 171 #define LOCK_ROUNDS 1 172 int locked = 0; 173 u_char lock_pwhash[LOCK_SIZE]; 174 u_char lock_salt[LOCK_SALT_SIZE]; 175 176 extern char *__progname; 177 178 /* Default lifetime in seconds (0 == forever) */ 179 static int lifetime = 0; 180 181 static int fingerprint_hash = SSH_FP_HASH_DEFAULT; 182 183 /* Refuse signing of non-SSH messages for web-origin FIDO keys */ 184 static int restrict_websafe = 1; 185 186 static void 187 close_socket(SocketEntry *e) 188 { 189 size_t i; 190 191 close(e->fd); 192 sshbuf_free(e->input); 193 sshbuf_free(e->output); 194 sshbuf_free(e->request); 195 for (i = 0; i < e->nsession_ids; i++) { 196 sshkey_free(e->session_ids[i].key); 197 sshbuf_free(e->session_ids[i].sid); 198 } 199 free(e->session_ids); 200 memset(e, '\0', sizeof(*e)); 201 e->fd = -1; 202 e->type = AUTH_UNUSED; 203 } 204 205 static void 206 idtab_init(void) 207 { 208 idtab = xcalloc(1, sizeof(*idtab)); 209 TAILQ_INIT(&idtab->idlist); 210 idtab->nentries = 0; 211 } 212 213 static void 214 free_dest_constraint_hop(struct dest_constraint_hop *dch) 215 { 216 u_int i; 217 218 if (dch == NULL) 219 return; 220 free(dch->user); 221 free(dch->hostname); 222 for (i = 0; i < dch->nkeys; i++) 223 sshkey_free(dch->keys[i]); 224 free(dch->keys); 225 free(dch->key_is_ca); 226 } 227 228 static void 229 free_dest_constraints(struct dest_constraint *dcs, size_t ndcs) 230 { 231 size_t i; 232 233 for (i = 0; i < ndcs; i++) { 234 free_dest_constraint_hop(&dcs[i].from); 235 free_dest_constraint_hop(&dcs[i].to); 236 } 237 free(dcs); 238 } 239 240 static void 241 dup_dest_constraint_hop(const struct dest_constraint_hop *dch, 242 struct dest_constraint_hop *out) 243 { 244 u_int i; 245 int r; 246 247 out->user = dch->user == NULL ? NULL : xstrdup(dch->user); 248 out->hostname = dch->hostname == NULL ? NULL : xstrdup(dch->hostname); 249 out->is_ca = dch->is_ca; 250 out->nkeys = dch->nkeys; 251 out->keys = out->nkeys == 0 ? NULL : 252 xcalloc(out->nkeys, sizeof(*out->keys)); 253 out->key_is_ca = out->nkeys == 0 ? NULL : 254 xcalloc(out->nkeys, sizeof(*out->key_is_ca)); 255 for (i = 0; i < dch->nkeys; i++) { 256 if (dch->keys[i] != NULL && 257 (r = sshkey_from_private(dch->keys[i], 258 &(out->keys[i]))) != 0) 259 fatal_fr(r, "copy key"); 260 out->key_is_ca[i] = dch->key_is_ca[i]; 261 } 262 } 263 264 static struct dest_constraint * 265 dup_dest_constraints(const struct dest_constraint *dcs, size_t ndcs) 266 { 267 size_t i; 268 struct dest_constraint *ret; 269 270 if (ndcs == 0) 271 return NULL; 272 ret = xcalloc(ndcs, sizeof(*ret)); 273 for (i = 0; i < ndcs; i++) { 274 dup_dest_constraint_hop(&dcs[i].from, &ret[i].from); 275 dup_dest_constraint_hop(&dcs[i].to, &ret[i].to); 276 } 277 return ret; 278 } 279 280 #ifdef DEBUG_CONSTRAINTS 281 static void 282 dump_dest_constraint_hop(const struct dest_constraint_hop *dch) 283 { 284 u_int i; 285 char *fp; 286 287 debug_f("user %s hostname %s is_ca %d nkeys %u", 288 dch->user == NULL ? "(null)" : dch->user, 289 dch->hostname == NULL ? "(null)" : dch->hostname, 290 dch->is_ca, dch->nkeys); 291 for (i = 0; i < dch->nkeys; i++) { 292 fp = NULL; 293 if (dch->keys[i] != NULL && 294 (fp = sshkey_fingerprint(dch->keys[i], 295 SSH_FP_HASH_DEFAULT, SSH_FP_DEFAULT)) == NULL) 296 fatal_f("fingerprint failed"); 297 debug_f("key %u/%u: %s%s%s key_is_ca %d", i, dch->nkeys, 298 dch->keys[i] == NULL ? "" : sshkey_ssh_name(dch->keys[i]), 299 dch->keys[i] == NULL ? "" : " ", 300 dch->keys[i] == NULL ? "none" : fp, 301 dch->key_is_ca[i]); 302 free(fp); 303 } 304 } 305 #endif /* DEBUG_CONSTRAINTS */ 306 307 static void 308 dump_dest_constraints(const char *context, 309 const struct dest_constraint *dcs, size_t ndcs) 310 { 311 #ifdef DEBUG_CONSTRAINTS 312 size_t i; 313 314 debug_f("%s: %zu constraints", context, ndcs); 315 for (i = 0; i < ndcs; i++) { 316 debug_f("constraint %zu / %zu: from: ", i, ndcs); 317 dump_dest_constraint_hop(&dcs[i].from); 318 debug_f("constraint %zu / %zu: to: ", i, ndcs); 319 dump_dest_constraint_hop(&dcs[i].to); 320 } 321 debug_f("done for %s", context); 322 #endif /* DEBUG_CONSTRAINTS */ 323 } 324 325 static void 326 free_identity(Identity *id) 327 { 328 sshkey_free(id->key); 329 free(id->provider); 330 free(id->comment); 331 free(id->sk_provider); 332 free_dest_constraints(id->dest_constraints, id->ndest_constraints); 333 free(id); 334 } 335 336 /* 337 * Match 'key' against the key/CA list in a destination constraint hop 338 * Returns 0 on success or -1 otherwise. 339 */ 340 static int 341 match_key_hop(const char *tag, const struct sshkey *key, 342 const struct dest_constraint_hop *dch) 343 { 344 const char *reason = NULL; 345 const char *hostname = dch->hostname ? dch->hostname : "(ORIGIN)"; 346 u_int i; 347 char *fp; 348 349 if (key == NULL) 350 return -1; 351 /* XXX logspam */ 352 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT, 353 SSH_FP_DEFAULT)) == NULL) 354 fatal_f("fingerprint failed"); 355 debug3_f("%s: entering hostname %s, requested key %s %s, %u keys avail", 356 tag, hostname, sshkey_type(key), fp, dch->nkeys); 357 free(fp); 358 for (i = 0; i < dch->nkeys; i++) { 359 if (dch->keys[i] == NULL) 360 return -1; 361 /* XXX logspam */ 362 if ((fp = sshkey_fingerprint(dch->keys[i], SSH_FP_HASH_DEFAULT, 363 SSH_FP_DEFAULT)) == NULL) 364 fatal_f("fingerprint failed"); 365 debug3_f("%s: key %u: %s%s %s", tag, i, 366 dch->key_is_ca[i] ? "CA " : "", 367 sshkey_type(dch->keys[i]), fp); 368 free(fp); 369 if (!sshkey_is_cert(key)) { 370 /* plain key */ 371 if (dch->key_is_ca[i] || 372 !sshkey_equal(key, dch->keys[i])) 373 continue; 374 return 0; 375 } 376 /* certificate */ 377 if (!dch->key_is_ca[i]) 378 continue; 379 if (key->cert == NULL || key->cert->signature_key == NULL) 380 return -1; /* shouldn't happen */ 381 if (!sshkey_equal(key->cert->signature_key, dch->keys[i])) 382 continue; 383 if (sshkey_cert_check_host(key, hostname, 1, 384 SSH_ALLOWED_CA_SIGALGS, &reason) != 0) { 385 debug_f("cert %s / hostname %s rejected: %s", 386 key->cert->key_id, hostname, reason); 387 continue; 388 } 389 return 0; 390 } 391 return -1; 392 } 393 394 /* Check destination constraints on an identity against the hostkey/user */ 395 static int 396 permitted_by_dest_constraints(const struct sshkey *fromkey, 397 const struct sshkey *tokey, Identity *id, const char *user, 398 const char **hostnamep) 399 { 400 size_t i; 401 struct dest_constraint *d; 402 403 if (hostnamep != NULL) 404 *hostnamep = NULL; 405 for (i = 0; i < id->ndest_constraints; i++) { 406 d = id->dest_constraints + i; 407 /* XXX remove logspam */ 408 debug2_f("constraint %zu %s%s%s (%u keys) > %s%s%s (%u keys)", 409 i, d->from.user ? d->from.user : "", 410 d->from.user ? "@" : "", 411 d->from.hostname ? d->from.hostname : "(ORIGIN)", 412 d->from.nkeys, 413 d->to.user ? d->to.user : "", d->to.user ? "@" : "", 414 d->to.hostname ? d->to.hostname : "(ANY)", d->to.nkeys); 415 416 /* Match 'from' key */ 417 if (fromkey == NULL) { 418 /* We are matching the first hop */ 419 if (d->from.hostname != NULL || d->from.nkeys != 0) 420 continue; 421 } else if (match_key_hop("from", fromkey, &d->from) != 0) 422 continue; 423 424 /* Match 'to' key */ 425 if (tokey != NULL && match_key_hop("to", tokey, &d->to) != 0) 426 continue; 427 428 /* Match user if specified */ 429 if (d->to.user != NULL && user != NULL && 430 !match_pattern(user, d->to.user)) 431 continue; 432 433 /* successfully matched this constraint */ 434 if (hostnamep != NULL) 435 *hostnamep = d->to.hostname; 436 debug2_f("allowed for hostname %s", 437 d->to.hostname == NULL ? "*" : d->to.hostname); 438 return 0; 439 } 440 /* no match */ 441 debug2_f("%s identity \"%s\" not permitted for this destination", 442 sshkey_type(id->key), id->comment); 443 return -1; 444 } 445 446 /* 447 * Check whether hostkeys on a SocketEntry and the optionally specified user 448 * are permitted by the destination constraints on the Identity. 449 * Returns 0 on success or -1 otherwise. 450 */ 451 static int 452 identity_permitted(Identity *id, SocketEntry *e, char *user, 453 const char **forward_hostnamep, const char **last_hostnamep) 454 { 455 size_t i; 456 const char **hp; 457 struct hostkey_sid *hks; 458 const struct sshkey *fromkey = NULL; 459 const char *test_user; 460 char *fp1, *fp2; 461 462 /* XXX remove logspam */ 463 debug3_f("entering: key %s comment \"%s\", %zu socket bindings, " 464 "%zu constraints", sshkey_type(id->key), id->comment, 465 e->nsession_ids, id->ndest_constraints); 466 if (id->ndest_constraints == 0) 467 return 0; /* unconstrained */ 468 if (e->session_bind_attempted && e->nsession_ids == 0) { 469 error_f("previous session bind failed on socket"); 470 return -1; 471 } 472 if (e->nsession_ids == 0) 473 return 0; /* local use */ 474 /* 475 * Walk through the hops recorded by session_id and try to find a 476 * constraint that satisfies each. 477 */ 478 for (i = 0; i < e->nsession_ids; i++) { 479 hks = e->session_ids + i; 480 if (hks->key == NULL) 481 fatal_f("internal error: no bound key"); 482 /* XXX remove logspam */ 483 fp1 = fp2 = NULL; 484 if (fromkey != NULL && 485 (fp1 = sshkey_fingerprint(fromkey, SSH_FP_HASH_DEFAULT, 486 SSH_FP_DEFAULT)) == NULL) 487 fatal_f("fingerprint failed"); 488 if ((fp2 = sshkey_fingerprint(hks->key, SSH_FP_HASH_DEFAULT, 489 SSH_FP_DEFAULT)) == NULL) 490 fatal_f("fingerprint failed"); 491 debug3_f("socketentry fd=%d, entry %zu %s, " 492 "from hostkey %s %s to user %s hostkey %s %s", 493 e->fd, i, hks->forwarded ? "FORWARD" : "AUTH", 494 fromkey ? sshkey_type(fromkey) : "(ORIGIN)", 495 fromkey ? fp1 : "", user ? user : "(ANY)", 496 sshkey_type(hks->key), fp2); 497 free(fp1); 498 free(fp2); 499 /* 500 * Record the hostnames for the initial forwarding and 501 * the final destination. 502 */ 503 hp = NULL; 504 if (i == e->nsession_ids - 1) 505 hp = last_hostnamep; 506 else if (i == 0) 507 hp = forward_hostnamep; 508 /* Special handling for final recorded binding */ 509 test_user = NULL; 510 if (i == e->nsession_ids - 1) { 511 /* Can only check user at final hop */ 512 test_user = user; 513 /* 514 * user is only presented for signature requests. 515 * If this is the case, make sure last binding is not 516 * for a forwarding. 517 */ 518 if (hks->forwarded && user != NULL) { 519 error_f("tried to sign on forwarding hop"); 520 return -1; 521 } 522 } else if (!hks->forwarded) { 523 error_f("tried to forward though signing bind"); 524 return -1; 525 } 526 if (permitted_by_dest_constraints(fromkey, hks->key, id, 527 test_user, hp) != 0) 528 return -1; 529 fromkey = hks->key; 530 } 531 /* 532 * Another special case: if the last bound session ID was for a 533 * forwarding, and this function is not being called to check a sign 534 * request (i.e. no 'user' supplied), then only permit the key if 535 * there is a permission that would allow it to be used at another 536 * destination. This hides keys that are allowed to be used to 537 * authenticate *to* a host but not permitted for *use* beyond it. 538 */ 539 hks = &e->session_ids[e->nsession_ids - 1]; 540 if (hks->forwarded && user == NULL && 541 permitted_by_dest_constraints(hks->key, NULL, id, 542 NULL, NULL) != 0) { 543 debug3_f("key permitted at host but not after"); 544 return -1; 545 } 546 547 /* success */ 548 return 0; 549 } 550 551 static int 552 socket_is_remote(SocketEntry *e) 553 { 554 return e->session_bind_attempted || (e->nsession_ids != 0); 555 } 556 557 /* return matching private key for given public key */ 558 static Identity * 559 lookup_identity(struct sshkey *key) 560 { 561 Identity *id; 562 563 TAILQ_FOREACH(id, &idtab->idlist, next) { 564 if (sshkey_equal(key, id->key)) 565 return (id); 566 } 567 return (NULL); 568 } 569 570 /* Check confirmation of keysign request */ 571 static int 572 confirm_key(Identity *id, const char *extra) 573 { 574 char *p; 575 int ret = -1; 576 577 p = sshkey_fingerprint(id->key, fingerprint_hash, SSH_FP_DEFAULT); 578 if (p != NULL && 579 ask_permission("Allow use of key %s?\nKey fingerprint %s.%s%s", 580 id->comment, p, 581 extra == NULL ? "" : "\n", extra == NULL ? "" : extra)) 582 ret = 0; 583 free(p); 584 585 return (ret); 586 } 587 588 static void 589 send_status(SocketEntry *e, int success) 590 { 591 int r; 592 593 if ((r = sshbuf_put_u32(e->output, 1)) != 0 || 594 (r = sshbuf_put_u8(e->output, success ? 595 SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE)) != 0) 596 fatal_fr(r, "compose"); 597 } 598 599 /* send list of supported public keys to 'client' */ 600 static void 601 process_request_identities(SocketEntry *e) 602 { 603 Identity *id; 604 struct sshbuf *msg, *keys; 605 int r; 606 u_int i = 0, nentries = 0; 607 char *fp; 608 609 debug2_f("entering"); 610 611 if ((msg = sshbuf_new()) == NULL || (keys = sshbuf_new()) == NULL) 612 fatal_f("sshbuf_new failed"); 613 TAILQ_FOREACH(id, &idtab->idlist, next) { 614 if ((fp = sshkey_fingerprint(id->key, SSH_FP_HASH_DEFAULT, 615 SSH_FP_DEFAULT)) == NULL) 616 fatal_f("fingerprint failed"); 617 debug_f("key %u / %u: %s %s", i++, idtab->nentries, 618 sshkey_ssh_name(id->key), fp); 619 dump_dest_constraints(__func__, 620 id->dest_constraints, id->ndest_constraints); 621 free(fp); 622 /* identity not visible, don't include in response */ 623 if (identity_permitted(id, e, NULL, NULL, NULL) != 0) 624 continue; 625 if ((r = sshkey_puts_opts(id->key, keys, 626 SSHKEY_SERIALIZE_INFO)) != 0 || 627 (r = sshbuf_put_cstring(keys, id->comment)) != 0) { 628 error_fr(r, "compose key/comment"); 629 continue; 630 } 631 nentries++; 632 } 633 debug2_f("replying with %u allowed of %u available keys", 634 nentries, idtab->nentries); 635 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 || 636 (r = sshbuf_put_u32(msg, nentries)) != 0 || 637 (r = sshbuf_putb(msg, keys)) != 0) 638 fatal_fr(r, "compose"); 639 if ((r = sshbuf_put_stringb(e->output, msg)) != 0) 640 fatal_fr(r, "enqueue"); 641 sshbuf_free(msg); 642 sshbuf_free(keys); 643 } 644 645 646 static char * 647 agent_decode_alg(struct sshkey *key, u_int flags) 648 { 649 if (key->type == KEY_RSA) { 650 if (flags & SSH_AGENT_RSA_SHA2_256) 651 return "rsa-sha2-256"; 652 else if (flags & SSH_AGENT_RSA_SHA2_512) 653 return "rsa-sha2-512"; 654 } else if (key->type == KEY_RSA_CERT) { 655 if (flags & SSH_AGENT_RSA_SHA2_256) 656 return "rsa-sha2-256-cert-v01@openssh.com"; 657 else if (flags & SSH_AGENT_RSA_SHA2_512) 658 return "rsa-sha2-512-cert-v01@openssh.com"; 659 } 660 return NULL; 661 } 662 663 /* 664 * Attempt to parse the contents of a buffer as a SSH publickey userauth 665 * request, checking its contents for consistency and matching the embedded 666 * key against the one that is being used for signing. 667 * Note: does not modify msg buffer. 668 * Optionally extract the username, session ID and/or hostkey from the request. 669 */ 670 static int 671 parse_userauth_request(struct sshbuf *msg, const struct sshkey *expected_key, 672 char **userp, struct sshbuf **sess_idp, struct sshkey **hostkeyp) 673 { 674 struct sshbuf *b = NULL, *sess_id = NULL; 675 char *user = NULL, *service = NULL, *method = NULL, *pkalg = NULL; 676 int r; 677 u_char t, sig_follows; 678 struct sshkey *mkey = NULL, *hostkey = NULL; 679 680 if (userp != NULL) 681 *userp = NULL; 682 if (sess_idp != NULL) 683 *sess_idp = NULL; 684 if (hostkeyp != NULL) 685 *hostkeyp = NULL; 686 if ((b = sshbuf_fromb(msg)) == NULL) 687 fatal_f("sshbuf_fromb"); 688 689 /* SSH userauth request */ 690 if ((r = sshbuf_froms(b, &sess_id)) != 0) 691 goto out; 692 if (sshbuf_len(sess_id) == 0) { 693 r = SSH_ERR_INVALID_FORMAT; 694 goto out; 695 } 696 if ((r = sshbuf_get_u8(b, &t)) != 0 || /* SSH2_MSG_USERAUTH_REQUEST */ 697 (r = sshbuf_get_cstring(b, &user, NULL)) != 0 || /* server user */ 698 (r = sshbuf_get_cstring(b, &service, NULL)) != 0 || /* service */ 699 (r = sshbuf_get_cstring(b, &method, NULL)) != 0 || /* method */ 700 (r = sshbuf_get_u8(b, &sig_follows)) != 0 || /* sig-follows */ 701 (r = sshbuf_get_cstring(b, &pkalg, NULL)) != 0 || /* alg */ 702 (r = sshkey_froms(b, &mkey)) != 0) /* key */ 703 goto out; 704 if (t != SSH2_MSG_USERAUTH_REQUEST || 705 sig_follows != 1 || 706 strcmp(service, "ssh-connection") != 0 || 707 !sshkey_equal(expected_key, mkey) || 708 sshkey_type_from_name(pkalg) != expected_key->type) { 709 r = SSH_ERR_INVALID_FORMAT; 710 goto out; 711 } 712 if (strcmp(method, "publickey-hostbound-v00@openssh.com") == 0) { 713 if ((r = sshkey_froms(b, &hostkey)) != 0) 714 goto out; 715 } else if (strcmp(method, "publickey") != 0) { 716 r = SSH_ERR_INVALID_FORMAT; 717 goto out; 718 } 719 if (sshbuf_len(b) != 0) { 720 r = SSH_ERR_INVALID_FORMAT; 721 goto out; 722 } 723 /* success */ 724 r = 0; 725 debug3_f("well formed userauth"); 726 if (userp != NULL) { 727 *userp = user; 728 user = NULL; 729 } 730 if (sess_idp != NULL) { 731 *sess_idp = sess_id; 732 sess_id = NULL; 733 } 734 if (hostkeyp != NULL) { 735 *hostkeyp = hostkey; 736 hostkey = NULL; 737 } 738 out: 739 sshbuf_free(b); 740 sshbuf_free(sess_id); 741 free(user); 742 free(service); 743 free(method); 744 free(pkalg); 745 sshkey_free(mkey); 746 sshkey_free(hostkey); 747 return r; 748 } 749 750 /* 751 * Attempt to parse the contents of a buffer as a SSHSIG signature request. 752 * Note: does not modify buffer. 753 */ 754 static int 755 parse_sshsig_request(struct sshbuf *msg) 756 { 757 int r; 758 struct sshbuf *b; 759 760 if ((b = sshbuf_fromb(msg)) == NULL) 761 fatal_f("sshbuf_fromb"); 762 763 if ((r = sshbuf_cmp(b, 0, "SSHSIG", 6)) != 0 || 764 (r = sshbuf_consume(b, 6)) != 0 || 765 (r = sshbuf_get_cstring(b, NULL, NULL)) != 0 || /* namespace */ 766 (r = sshbuf_get_string_direct(b, NULL, NULL)) != 0 || /* reserved */ 767 (r = sshbuf_get_cstring(b, NULL, NULL)) != 0 || /* hashalg */ 768 (r = sshbuf_get_string_direct(b, NULL, NULL)) != 0) /* H(msg) */ 769 goto out; 770 if (sshbuf_len(b) != 0) { 771 r = SSH_ERR_INVALID_FORMAT; 772 goto out; 773 } 774 /* success */ 775 r = 0; 776 out: 777 sshbuf_free(b); 778 return r; 779 } 780 781 /* 782 * This function inspects a message to be signed by a FIDO key that has a 783 * web-like application string (i.e. one that does not begin with "ssh:". 784 * It checks that the message is one of those expected for SSH operations 785 * (pubkey userauth, sshsig, CA key signing) to exclude signing challenges 786 * for the web. 787 */ 788 static int 789 check_websafe_message_contents(struct sshkey *key, struct sshbuf *data) 790 { 791 if (parse_userauth_request(data, key, NULL, NULL, NULL) == 0) { 792 debug_f("signed data matches public key userauth request"); 793 return 1; 794 } 795 if (parse_sshsig_request(data) == 0) { 796 debug_f("signed data matches SSHSIG signature request"); 797 return 1; 798 } 799 800 /* XXX check CA signature operation */ 801 802 error("web-origin key attempting to sign non-SSH message"); 803 return 0; 804 } 805 806 static int 807 buf_equal(const struct sshbuf *a, const struct sshbuf *b) 808 { 809 if (sshbuf_ptr(a) == NULL || sshbuf_ptr(b) == NULL) 810 return SSH_ERR_INVALID_ARGUMENT; 811 if (sshbuf_len(a) != sshbuf_len(b)) 812 return SSH_ERR_INVALID_FORMAT; 813 if (timingsafe_bcmp(sshbuf_ptr(a), sshbuf_ptr(b), sshbuf_len(a)) != 0) 814 return SSH_ERR_INVALID_FORMAT; 815 return 0; 816 } 817 818 /* ssh2 only */ 819 static void 820 process_sign_request2(SocketEntry *e) 821 { 822 u_char *signature = NULL; 823 size_t slen = 0; 824 u_int compat = 0, flags; 825 int r, ok = -1, retried = 0; 826 char *fp = NULL, *pin = NULL, *prompt = NULL; 827 char *user = NULL, *sig_dest = NULL; 828 const char *fwd_host = NULL, *dest_host = NULL; 829 struct sshbuf *msg = NULL, *data = NULL, *sid = NULL; 830 struct sshkey *key = NULL, *hostkey = NULL; 831 struct identity *id; 832 struct notifier_ctx *notifier = NULL; 833 834 debug_f("entering"); 835 836 if ((msg = sshbuf_new()) == NULL || (data = sshbuf_new()) == NULL) 837 fatal_f("sshbuf_new failed"); 838 if ((r = sshkey_froms(e->request, &key)) != 0 || 839 (r = sshbuf_get_stringb(e->request, data)) != 0 || 840 (r = sshbuf_get_u32(e->request, &flags)) != 0) { 841 error_fr(r, "parse"); 842 goto send; 843 } 844 845 if ((id = lookup_identity(key)) == NULL) { 846 verbose_f("%s key not found", sshkey_type(key)); 847 goto send; 848 } 849 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT, 850 SSH_FP_DEFAULT)) == NULL) 851 fatal_f("fingerprint failed"); 852 853 if (id->ndest_constraints != 0) { 854 if (e->nsession_ids == 0) { 855 logit_f("refusing use of destination-constrained key " 856 "to sign on unbound connection"); 857 goto send; 858 } 859 if (parse_userauth_request(data, key, &user, &sid, 860 &hostkey) != 0) { 861 logit_f("refusing use of destination-constrained key " 862 "to sign an unidentified signature"); 863 goto send; 864 } 865 /* XXX logspam */ 866 debug_f("user=%s", user); 867 if (identity_permitted(id, e, user, &fwd_host, &dest_host) != 0) 868 goto send; 869 /* XXX display fwd_host/dest_host in askpass UI */ 870 /* 871 * Ensure that the session ID is the most recent one 872 * registered on the socket - it should have been bound by 873 * ssh immediately before userauth. 874 */ 875 if (buf_equal(sid, 876 e->session_ids[e->nsession_ids - 1].sid) != 0) { 877 error_f("unexpected session ID (%zu listed) on " 878 "signature request for target user %s with " 879 "key %s %s", e->nsession_ids, user, 880 sshkey_type(id->key), fp); 881 goto send; 882 } 883 /* 884 * Ensure that the hostkey embedded in the signature matches 885 * the one most recently bound to the socket. An exception is 886 * made for the initial forwarding hop. 887 */ 888 if (e->nsession_ids > 1 && hostkey == NULL) { 889 error_f("refusing use of destination-constrained key: " 890 "no hostkey recorded in signature for forwarded " 891 "connection"); 892 goto send; 893 } 894 if (hostkey != NULL && !sshkey_equal(hostkey, 895 e->session_ids[e->nsession_ids - 1].key)) { 896 error_f("refusing use of destination-constrained key: " 897 "mismatch between hostkey in request and most " 898 "recently bound session"); 899 goto send; 900 } 901 xasprintf(&sig_dest, "public key authentication request for " 902 "user \"%s\" to listed host", user); 903 } 904 if (id->confirm && confirm_key(id, sig_dest) != 0) { 905 verbose_f("user refused key"); 906 goto send; 907 } 908 if (sshkey_is_sk(id->key)) { 909 if (restrict_websafe && 910 strncmp(id->key->sk_application, "ssh:", 4) != 0 && 911 !check_websafe_message_contents(key, data)) { 912 /* error already logged */ 913 goto send; 914 } 915 if (id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD) { 916 notifier = notify_start(0, 917 "Confirm user presence for key %s %s%s%s", 918 sshkey_type(id->key), fp, 919 sig_dest == NULL ? "" : "\n", 920 sig_dest == NULL ? "" : sig_dest); 921 } 922 } 923 retry_pin: 924 if ((r = sshkey_sign(id->key, &signature, &slen, 925 sshbuf_ptr(data), sshbuf_len(data), agent_decode_alg(key, flags), 926 id->sk_provider, pin, compat)) != 0) { 927 debug_fr(r, "sshkey_sign"); 928 if (pin == NULL && !retried && sshkey_is_sk(id->key) && 929 r == SSH_ERR_KEY_WRONG_PASSPHRASE) { 930 notify_complete(notifier, NULL); 931 notifier = NULL; 932 /* XXX include sig_dest */ 933 xasprintf(&prompt, "Enter PIN%sfor %s key %s: ", 934 (id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD) ? 935 " and confirm user presence " : " ", 936 sshkey_type(id->key), fp); 937 pin = read_passphrase(prompt, RP_USE_ASKPASS); 938 retried = 1; 939 goto retry_pin; 940 } 941 error_fr(r, "sshkey_sign"); 942 goto send; 943 } 944 /* Success */ 945 ok = 0; 946 debug_f("good signature"); 947 send: 948 notify_complete(notifier, "User presence confirmed"); 949 950 if (ok == 0) { 951 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 || 952 (r = sshbuf_put_string(msg, signature, slen)) != 0) 953 fatal_fr(r, "compose"); 954 } else if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0) 955 fatal_fr(r, "compose failure"); 956 957 if ((r = sshbuf_put_stringb(e->output, msg)) != 0) 958 fatal_fr(r, "enqueue"); 959 960 sshbuf_free(sid); 961 sshbuf_free(data); 962 sshbuf_free(msg); 963 sshkey_free(key); 964 sshkey_free(hostkey); 965 free(fp); 966 free(signature); 967 free(sig_dest); 968 free(user); 969 free(prompt); 970 if (pin != NULL) 971 freezero(pin, strlen(pin)); 972 } 973 974 /* shared */ 975 static void 976 process_remove_identity(SocketEntry *e) 977 { 978 int r, success = 0; 979 struct sshkey *key = NULL; 980 Identity *id; 981 982 debug2_f("entering"); 983 if ((r = sshkey_froms(e->request, &key)) != 0) { 984 error_fr(r, "parse key"); 985 goto done; 986 } 987 if ((id = lookup_identity(key)) == NULL) { 988 debug_f("key not found"); 989 goto done; 990 } 991 /* identity not visible, cannot be removed */ 992 if (identity_permitted(id, e, NULL, NULL, NULL) != 0) 993 goto done; /* error already logged */ 994 /* We have this key, free it. */ 995 if (idtab->nentries < 1) 996 fatal_f("internal error: nentries %d", idtab->nentries); 997 TAILQ_REMOVE(&idtab->idlist, id, next); 998 free_identity(id); 999 idtab->nentries--; 1000 success = 1; 1001 done: 1002 sshkey_free(key); 1003 send_status(e, success); 1004 } 1005 1006 static void 1007 process_remove_all_identities(SocketEntry *e) 1008 { 1009 Identity *id; 1010 1011 debug2_f("entering"); 1012 /* Loop over all identities and clear the keys. */ 1013 for (id = TAILQ_FIRST(&idtab->idlist); id; 1014 id = TAILQ_FIRST(&idtab->idlist)) { 1015 TAILQ_REMOVE(&idtab->idlist, id, next); 1016 free_identity(id); 1017 } 1018 1019 /* Mark that there are no identities. */ 1020 idtab->nentries = 0; 1021 1022 /* Send success. */ 1023 send_status(e, 1); 1024 } 1025 1026 /* removes expired keys and returns number of seconds until the next expiry */ 1027 static time_t 1028 reaper(void) 1029 { 1030 time_t deadline = 0, now = monotime(); 1031 Identity *id, *nxt; 1032 1033 for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) { 1034 nxt = TAILQ_NEXT(id, next); 1035 if (id->death == 0) 1036 continue; 1037 if (now >= id->death) { 1038 debug("expiring key '%s'", id->comment); 1039 TAILQ_REMOVE(&idtab->idlist, id, next); 1040 free_identity(id); 1041 idtab->nentries--; 1042 } else 1043 deadline = (deadline == 0) ? id->death : 1044 MINIMUM(deadline, id->death); 1045 } 1046 if (deadline == 0 || deadline <= now) 1047 return 0; 1048 else 1049 return (deadline - now); 1050 } 1051 1052 static int 1053 parse_dest_constraint_hop(struct sshbuf *b, struct dest_constraint_hop *dch) 1054 { 1055 u_char key_is_ca; 1056 size_t elen = 0; 1057 int r; 1058 struct sshkey *k = NULL; 1059 char *fp; 1060 1061 memset(dch, '\0', sizeof(*dch)); 1062 if ((r = sshbuf_get_cstring(b, &dch->user, NULL)) != 0 || 1063 (r = sshbuf_get_cstring(b, &dch->hostname, NULL)) != 0 || 1064 (r = sshbuf_get_string_direct(b, NULL, &elen)) != 0) { 1065 error_fr(r, "parse"); 1066 goto out; 1067 } 1068 if (elen != 0) { 1069 error_f("unsupported extensions (len %zu)", elen); 1070 r = SSH_ERR_FEATURE_UNSUPPORTED; 1071 goto out; 1072 } 1073 if (*dch->hostname == '\0') { 1074 free(dch->hostname); 1075 dch->hostname = NULL; 1076 } 1077 if (*dch->user == '\0') { 1078 free(dch->user); 1079 dch->user = NULL; 1080 } 1081 while (sshbuf_len(b) != 0) { 1082 dch->keys = xrecallocarray(dch->keys, dch->nkeys, 1083 dch->nkeys + 1, sizeof(*dch->keys)); 1084 dch->key_is_ca = xrecallocarray(dch->key_is_ca, dch->nkeys, 1085 dch->nkeys + 1, sizeof(*dch->key_is_ca)); 1086 if ((r = sshkey_froms(b, &k)) != 0 || 1087 (r = sshbuf_get_u8(b, &key_is_ca)) != 0) 1088 goto out; 1089 if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT, 1090 SSH_FP_DEFAULT)) == NULL) 1091 fatal_f("fingerprint failed"); 1092 debug3_f("%s%s%s: adding %skey %s %s", 1093 dch->user == NULL ? "" : dch->user, 1094 dch->user == NULL ? "" : "@", 1095 dch->hostname, key_is_ca ? "CA " : "", sshkey_type(k), fp); 1096 free(fp); 1097 dch->keys[dch->nkeys] = k; 1098 dch->key_is_ca[dch->nkeys] = key_is_ca != 0; 1099 dch->nkeys++; 1100 k = NULL; /* transferred */ 1101 } 1102 /* success */ 1103 r = 0; 1104 out: 1105 sshkey_free(k); 1106 return r; 1107 } 1108 1109 static int 1110 parse_dest_constraint(struct sshbuf *m, struct dest_constraint *dc) 1111 { 1112 struct sshbuf *b = NULL, *frombuf = NULL, *tobuf = NULL; 1113 int r; 1114 size_t elen = 0; 1115 1116 debug3_f("entering"); 1117 1118 memset(dc, '\0', sizeof(*dc)); 1119 if ((r = sshbuf_froms(m, &b)) != 0 || 1120 (r = sshbuf_froms(b, &frombuf)) != 0 || 1121 (r = sshbuf_froms(b, &tobuf)) != 0 || 1122 (r = sshbuf_get_string_direct(b, NULL, &elen)) != 0) { 1123 error_fr(r, "parse"); 1124 goto out; 1125 } 1126 if ((r = parse_dest_constraint_hop(frombuf, &dc->from)) != 0 || 1127 (r = parse_dest_constraint_hop(tobuf, &dc->to)) != 0) 1128 goto out; /* already logged */ 1129 if (elen != 0) { 1130 error_f("unsupported extensions (len %zu)", elen); 1131 r = SSH_ERR_FEATURE_UNSUPPORTED; 1132 goto out; 1133 } 1134 debug2_f("parsed %s (%u keys) > %s%s%s (%u keys)", 1135 dc->from.hostname ? dc->from.hostname : "(ORIGIN)", dc->from.nkeys, 1136 dc->to.user ? dc->to.user : "", dc->to.user ? "@" : "", 1137 dc->to.hostname ? dc->to.hostname : "(ANY)", dc->to.nkeys); 1138 /* check consistency */ 1139 if ((dc->from.hostname == NULL) != (dc->from.nkeys == 0) || 1140 dc->from.user != NULL) { 1141 error_f("inconsistent \"from\" specification"); 1142 r = SSH_ERR_INVALID_FORMAT; 1143 goto out; 1144 } 1145 if (dc->to.hostname == NULL || dc->to.nkeys == 0) { 1146 error_f("incomplete \"to\" specification"); 1147 r = SSH_ERR_INVALID_FORMAT; 1148 goto out; 1149 } 1150 /* success */ 1151 r = 0; 1152 out: 1153 sshbuf_free(b); 1154 sshbuf_free(frombuf); 1155 sshbuf_free(tobuf); 1156 return r; 1157 } 1158 1159 static int 1160 parse_key_constraint_extension(struct sshbuf *m, char **sk_providerp, 1161 struct dest_constraint **dcsp, size_t *ndcsp, int *cert_onlyp, 1162 struct sshkey ***certs, size_t *ncerts) 1163 { 1164 char *ext_name = NULL; 1165 int r; 1166 struct sshbuf *b = NULL; 1167 u_char v; 1168 struct sshkey *k; 1169 1170 if ((r = sshbuf_get_cstring(m, &ext_name, NULL)) != 0) { 1171 error_fr(r, "parse constraint extension"); 1172 goto out; 1173 } 1174 debug_f("constraint ext %s", ext_name); 1175 if (strcmp(ext_name, "sk-provider@openssh.com") == 0) { 1176 if (sk_providerp == NULL) { 1177 error_f("%s not valid here", ext_name); 1178 r = SSH_ERR_INVALID_FORMAT; 1179 goto out; 1180 } 1181 if (*sk_providerp != NULL) { 1182 error_f("%s already set", ext_name); 1183 r = SSH_ERR_INVALID_FORMAT; 1184 goto out; 1185 } 1186 if ((r = sshbuf_get_cstring(m, sk_providerp, NULL)) != 0) { 1187 error_fr(r, "parse %s", ext_name); 1188 goto out; 1189 } 1190 } else if (strcmp(ext_name, 1191 "restrict-destination-v00@openssh.com") == 0) { 1192 if (*dcsp != NULL) { 1193 error_f("%s already set", ext_name); 1194 goto out; 1195 } 1196 if ((r = sshbuf_froms(m, &b)) != 0) { 1197 error_fr(r, "parse %s outer", ext_name); 1198 goto out; 1199 } 1200 while (sshbuf_len(b) != 0) { 1201 if (*ndcsp >= AGENT_MAX_DEST_CONSTRAINTS) { 1202 error_f("too many %s constraints", ext_name); 1203 goto out; 1204 } 1205 *dcsp = xrecallocarray(*dcsp, *ndcsp, *ndcsp + 1, 1206 sizeof(**dcsp)); 1207 if ((r = parse_dest_constraint(b, 1208 *dcsp + (*ndcsp)++)) != 0) 1209 goto out; /* error already logged */ 1210 } 1211 } else if (strcmp(ext_name, 1212 "associated-certs-v00@openssh.com") == 0) { 1213 if (certs == NULL || ncerts == NULL || cert_onlyp == NULL) { 1214 error_f("%s not valid here", ext_name); 1215 r = SSH_ERR_INVALID_FORMAT; 1216 goto out; 1217 } 1218 if (*certs != NULL) { 1219 error_f("%s already set", ext_name); 1220 goto out; 1221 } 1222 if ((r = sshbuf_get_u8(m, &v)) != 0 || 1223 (r = sshbuf_froms(m, &b)) != 0) { 1224 error_fr(r, "parse %s", ext_name); 1225 goto out; 1226 } 1227 *cert_onlyp = v != 0; 1228 while (sshbuf_len(b) != 0) { 1229 if (*ncerts >= AGENT_MAX_EXT_CERTS) { 1230 error_f("too many %s constraints", ext_name); 1231 goto out; 1232 } 1233 *certs = xrecallocarray(*certs, *ncerts, *ncerts + 1, 1234 sizeof(**certs)); 1235 if ((r = sshkey_froms(b, &k)) != 0) { 1236 error_fr(r, "parse key"); 1237 goto out; 1238 } 1239 (*certs)[(*ncerts)++] = k; 1240 } 1241 } else { 1242 error_f("unsupported constraint \"%s\"", ext_name); 1243 r = SSH_ERR_FEATURE_UNSUPPORTED; 1244 goto out; 1245 } 1246 /* success */ 1247 r = 0; 1248 out: 1249 free(ext_name); 1250 sshbuf_free(b); 1251 return r; 1252 } 1253 1254 static int 1255 parse_key_constraints(struct sshbuf *m, struct sshkey *k, time_t *deathp, 1256 u_int *secondsp, int *confirmp, char **sk_providerp, 1257 struct dest_constraint **dcsp, size_t *ndcsp, 1258 int *cert_onlyp, size_t *ncerts, struct sshkey ***certs) 1259 { 1260 u_char ctype; 1261 int r; 1262 u_int seconds, maxsign = 0; 1263 1264 while (sshbuf_len(m)) { 1265 if ((r = sshbuf_get_u8(m, &ctype)) != 0) { 1266 error_fr(r, "parse constraint type"); 1267 goto out; 1268 } 1269 switch (ctype) { 1270 case SSH_AGENT_CONSTRAIN_LIFETIME: 1271 if (*deathp != 0) { 1272 error_f("lifetime already set"); 1273 r = SSH_ERR_INVALID_FORMAT; 1274 goto out; 1275 } 1276 if ((r = sshbuf_get_u32(m, &seconds)) != 0) { 1277 error_fr(r, "parse lifetime constraint"); 1278 goto out; 1279 } 1280 *deathp = monotime() + seconds; 1281 *secondsp = seconds; 1282 break; 1283 case SSH_AGENT_CONSTRAIN_CONFIRM: 1284 if (*confirmp != 0) { 1285 error_f("confirm already set"); 1286 r = SSH_ERR_INVALID_FORMAT; 1287 goto out; 1288 } 1289 *confirmp = 1; 1290 break; 1291 case SSH_AGENT_CONSTRAIN_MAXSIGN: 1292 if (k == NULL) { 1293 error_f("maxsign not valid here"); 1294 r = SSH_ERR_INVALID_FORMAT; 1295 goto out; 1296 } 1297 if (maxsign != 0) { 1298 error_f("maxsign already set"); 1299 r = SSH_ERR_INVALID_FORMAT; 1300 goto out; 1301 } 1302 if ((r = sshbuf_get_u32(m, &maxsign)) != 0) { 1303 error_fr(r, "parse maxsign constraint"); 1304 goto out; 1305 } 1306 if ((r = sshkey_enable_maxsign(k, maxsign)) != 0) { 1307 error_fr(r, "enable maxsign"); 1308 goto out; 1309 } 1310 break; 1311 case SSH_AGENT_CONSTRAIN_EXTENSION: 1312 if ((r = parse_key_constraint_extension(m, 1313 sk_providerp, dcsp, ndcsp, 1314 cert_onlyp, certs, ncerts)) != 0) 1315 goto out; /* error already logged */ 1316 break; 1317 default: 1318 error_f("Unknown constraint %d", ctype); 1319 r = SSH_ERR_FEATURE_UNSUPPORTED; 1320 goto out; 1321 } 1322 } 1323 /* success */ 1324 r = 0; 1325 out: 1326 return r; 1327 } 1328 1329 static void 1330 process_add_identity(SocketEntry *e) 1331 { 1332 Identity *id; 1333 int success = 0, confirm = 0; 1334 char *fp, *comment = NULL, *sk_provider = NULL; 1335 char canonical_provider[PATH_MAX]; 1336 time_t death = 0; 1337 u_int seconds = 0; 1338 struct dest_constraint *dest_constraints = NULL; 1339 size_t ndest_constraints = 0; 1340 struct sshkey *k = NULL; 1341 int r = SSH_ERR_INTERNAL_ERROR; 1342 1343 debug2_f("entering"); 1344 if ((r = sshkey_private_deserialize(e->request, &k)) != 0 || 1345 k == NULL || 1346 (r = sshbuf_get_cstring(e->request, &comment, NULL)) != 0) { 1347 error_fr(r, "parse"); 1348 goto out; 1349 } 1350 if (parse_key_constraints(e->request, k, &death, &seconds, &confirm, 1351 &sk_provider, &dest_constraints, &ndest_constraints, 1352 NULL, NULL, NULL) != 0) { 1353 error_f("failed to parse constraints"); 1354 sshbuf_reset(e->request); 1355 goto out; 1356 } 1357 dump_dest_constraints(__func__, dest_constraints, ndest_constraints); 1358 1359 if (sk_provider != NULL) { 1360 if (!sshkey_is_sk(k)) { 1361 error("Cannot add provider: %s is not an " 1362 "authenticator-hosted key", sshkey_type(k)); 1363 goto out; 1364 } 1365 if (strcasecmp(sk_provider, "internal") == 0) { 1366 debug_f("internal provider"); 1367 } else { 1368 if (socket_is_remote(e) && !remote_add_provider) { 1369 verbose("failed add of SK provider \"%.100s\": " 1370 "remote addition of providers is disabled", 1371 sk_provider); 1372 goto out; 1373 } 1374 if (realpath(sk_provider, canonical_provider) == NULL) { 1375 verbose("failed provider \"%.100s\": " 1376 "realpath: %s", sk_provider, 1377 strerror(errno)); 1378 goto out; 1379 } 1380 free(sk_provider); 1381 sk_provider = xstrdup(canonical_provider); 1382 if (match_pattern_list(sk_provider, 1383 allowed_providers, 0) != 1) { 1384 error("Refusing add key: " 1385 "provider %s not allowed", sk_provider); 1386 goto out; 1387 } 1388 } 1389 } 1390 if ((r = sshkey_shield_private(k)) != 0) { 1391 error_fr(r, "shield private"); 1392 goto out; 1393 } 1394 if (lifetime && !death) 1395 death = monotime() + lifetime; 1396 if ((id = lookup_identity(k)) == NULL) { 1397 id = xcalloc(1, sizeof(Identity)); 1398 TAILQ_INSERT_TAIL(&idtab->idlist, id, next); 1399 /* Increment the number of identities. */ 1400 idtab->nentries++; 1401 } else { 1402 /* identity not visible, do not update */ 1403 if (identity_permitted(id, e, NULL, NULL, NULL) != 0) 1404 goto out; /* error already logged */ 1405 /* key state might have been updated */ 1406 sshkey_free(id->key); 1407 free(id->comment); 1408 free(id->sk_provider); 1409 free_dest_constraints(id->dest_constraints, 1410 id->ndest_constraints); 1411 } 1412 /* success */ 1413 id->key = k; 1414 id->comment = comment; 1415 id->death = death; 1416 id->confirm = confirm; 1417 id->sk_provider = sk_provider; 1418 id->dest_constraints = dest_constraints; 1419 id->ndest_constraints = ndest_constraints; 1420 1421 if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT, 1422 SSH_FP_DEFAULT)) == NULL) 1423 fatal_f("sshkey_fingerprint failed"); 1424 debug_f("add %s %s \"%.100s\" (life: %u) (confirm: %u) " 1425 "(provider: %s) (destination constraints: %zu)", 1426 sshkey_ssh_name(k), fp, comment, seconds, confirm, 1427 sk_provider == NULL ? "none" : sk_provider, ndest_constraints); 1428 free(fp); 1429 /* transferred */ 1430 k = NULL; 1431 comment = NULL; 1432 sk_provider = NULL; 1433 dest_constraints = NULL; 1434 ndest_constraints = 0; 1435 success = 1; 1436 out: 1437 free(sk_provider); 1438 free(comment); 1439 sshkey_free(k); 1440 free_dest_constraints(dest_constraints, ndest_constraints); 1441 send_status(e, success); 1442 } 1443 1444 /* XXX todo: encrypt sensitive data with passphrase */ 1445 static void 1446 process_lock_agent(SocketEntry *e, int lock) 1447 { 1448 int r, success = 0, delay; 1449 char *passwd; 1450 u_char passwdhash[LOCK_SIZE]; 1451 static u_int fail_count = 0; 1452 size_t pwlen; 1453 1454 debug2_f("entering"); 1455 /* 1456 * This is deliberately fatal: the user has requested that we lock, 1457 * but we can't parse their request properly. The only safe thing to 1458 * do is abort. 1459 */ 1460 if ((r = sshbuf_get_cstring(e->request, &passwd, &pwlen)) != 0) 1461 fatal_fr(r, "parse"); 1462 if (pwlen == 0) { 1463 debug("empty password not supported"); 1464 } else if (locked && !lock) { 1465 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt), 1466 passwdhash, sizeof(passwdhash), LOCK_ROUNDS) < 0) 1467 fatal("bcrypt_pbkdf"); 1468 if (timingsafe_bcmp(passwdhash, lock_pwhash, LOCK_SIZE) == 0) { 1469 debug("agent unlocked"); 1470 locked = 0; 1471 fail_count = 0; 1472 explicit_bzero(lock_pwhash, sizeof(lock_pwhash)); 1473 success = 1; 1474 } else { 1475 /* delay in 0.1s increments up to 10s */ 1476 if (fail_count < 100) 1477 fail_count++; 1478 delay = 100000 * fail_count; 1479 debug("unlock failed, delaying %0.1lf seconds", 1480 (double)delay/1000000); 1481 usleep(delay); 1482 } 1483 explicit_bzero(passwdhash, sizeof(passwdhash)); 1484 } else if (!locked && lock) { 1485 debug("agent locked"); 1486 locked = 1; 1487 arc4random_buf(lock_salt, sizeof(lock_salt)); 1488 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt), 1489 lock_pwhash, sizeof(lock_pwhash), LOCK_ROUNDS) < 0) 1490 fatal("bcrypt_pbkdf"); 1491 success = 1; 1492 } 1493 freezero(passwd, pwlen); 1494 send_status(e, success); 1495 } 1496 1497 static void 1498 no_identities(SocketEntry *e) 1499 { 1500 struct sshbuf *msg; 1501 int r; 1502 1503 if ((msg = sshbuf_new()) == NULL) 1504 fatal_f("sshbuf_new failed"); 1505 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 || 1506 (r = sshbuf_put_u32(msg, 0)) != 0 || 1507 (r = sshbuf_put_stringb(e->output, msg)) != 0) 1508 fatal_fr(r, "compose"); 1509 sshbuf_free(msg); 1510 } 1511 1512 /* Add an identity to idlist; takes ownership of 'key' and 'comment' */ 1513 static void 1514 add_p11_identity(struct sshkey *key, char *comment, const char *provider, 1515 time_t death, u_int confirm, struct dest_constraint *dest_constraints, 1516 size_t ndest_constraints) 1517 { 1518 Identity *id; 1519 1520 if (lookup_identity(key) != NULL) { 1521 sshkey_free(key); 1522 free(comment); 1523 return; 1524 } 1525 id = xcalloc(1, sizeof(Identity)); 1526 id->key = key; 1527 id->comment = comment; 1528 id->provider = xstrdup(provider); 1529 id->death = death; 1530 id->confirm = confirm; 1531 id->dest_constraints = dup_dest_constraints(dest_constraints, 1532 ndest_constraints); 1533 id->ndest_constraints = ndest_constraints; 1534 TAILQ_INSERT_TAIL(&idtab->idlist, id, next); 1535 idtab->nentries++; 1536 } 1537 1538 #ifdef ENABLE_PKCS11 1539 static void 1540 process_add_smartcard_key(SocketEntry *e) 1541 { 1542 char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX]; 1543 char **comments = NULL; 1544 int r, i, count = 0, success = 0, confirm = 0; 1545 u_int seconds = 0; 1546 time_t death = 0; 1547 struct sshkey **keys = NULL, *k; 1548 struct dest_constraint *dest_constraints = NULL; 1549 size_t j, ndest_constraints = 0, ncerts = 0; 1550 struct sshkey **certs = NULL; 1551 int cert_only = 0; 1552 1553 debug2_f("entering"); 1554 if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 || 1555 (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) { 1556 error_fr(r, "parse"); 1557 goto send; 1558 } 1559 if (parse_key_constraints(e->request, NULL, &death, &seconds, &confirm, 1560 NULL, &dest_constraints, &ndest_constraints, &cert_only, 1561 &ncerts, &certs) != 0) { 1562 error_f("failed to parse constraints"); 1563 goto send; 1564 } 1565 dump_dest_constraints(__func__, dest_constraints, ndest_constraints); 1566 if (socket_is_remote(e) && !remote_add_provider) { 1567 verbose("failed PKCS#11 add of \"%.100s\": remote addition of " 1568 "providers is disabled", provider); 1569 goto send; 1570 } 1571 if (realpath(provider, canonical_provider) == NULL) { 1572 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s", 1573 provider, strerror(errno)); 1574 goto send; 1575 } 1576 if (match_pattern_list(canonical_provider, allowed_providers, 0) != 1) { 1577 verbose("refusing PKCS#11 add of \"%.100s\": " 1578 "provider not allowed", canonical_provider); 1579 goto send; 1580 } 1581 debug_f("add %.100s", canonical_provider); 1582 if (lifetime && !death) 1583 death = monotime() + lifetime; 1584 1585 count = pkcs11_add_provider(canonical_provider, pin, &keys, &comments); 1586 for (i = 0; i < count; i++) { 1587 if (comments[i] == NULL || comments[i][0] == '\0') { 1588 free(comments[i]); 1589 comments[i] = xstrdup(canonical_provider); 1590 } 1591 for (j = 0; j < ncerts; j++) { 1592 if (!sshkey_is_cert(certs[j])) 1593 continue; 1594 if (!sshkey_equal_public(keys[i], certs[j])) 1595 continue; 1596 if (pkcs11_make_cert(keys[i], certs[j], &k) != 0) 1597 continue; 1598 add_p11_identity(k, xstrdup(comments[i]), 1599 canonical_provider, death, confirm, 1600 dest_constraints, ndest_constraints); 1601 success = 1; 1602 } 1603 if (!cert_only && lookup_identity(keys[i]) == NULL) { 1604 add_p11_identity(keys[i], comments[i], 1605 canonical_provider, death, confirm, 1606 dest_constraints, ndest_constraints); 1607 keys[i] = NULL; /* transferred */ 1608 comments[i] = NULL; /* transferred */ 1609 success = 1; 1610 } 1611 /* XXX update constraints for existing keys */ 1612 sshkey_free(keys[i]); 1613 free(comments[i]); 1614 } 1615 send: 1616 free(pin); 1617 free(provider); 1618 free(keys); 1619 free(comments); 1620 free_dest_constraints(dest_constraints, ndest_constraints); 1621 for (j = 0; j < ncerts; j++) 1622 sshkey_free(certs[j]); 1623 free(certs); 1624 send_status(e, success); 1625 } 1626 1627 static void 1628 process_remove_smartcard_key(SocketEntry *e) 1629 { 1630 char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX]; 1631 int r, success = 0; 1632 Identity *id, *nxt; 1633 1634 debug2_f("entering"); 1635 if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 || 1636 (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) { 1637 error_fr(r, "parse"); 1638 goto send; 1639 } 1640 free(pin); 1641 1642 if (realpath(provider, canonical_provider) == NULL) { 1643 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s", 1644 provider, strerror(errno)); 1645 goto send; 1646 } 1647 1648 debug_f("remove %.100s", canonical_provider); 1649 for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) { 1650 nxt = TAILQ_NEXT(id, next); 1651 /* Skip file--based keys */ 1652 if (id->provider == NULL) 1653 continue; 1654 if (!strcmp(canonical_provider, id->provider)) { 1655 TAILQ_REMOVE(&idtab->idlist, id, next); 1656 free_identity(id); 1657 idtab->nentries--; 1658 } 1659 } 1660 if (pkcs11_del_provider(canonical_provider) == 0) 1661 success = 1; 1662 else 1663 error_f("pkcs11_del_provider failed"); 1664 send: 1665 free(provider); 1666 send_status(e, success); 1667 } 1668 #endif /* ENABLE_PKCS11 */ 1669 1670 static int 1671 process_ext_session_bind(SocketEntry *e) 1672 { 1673 int r, sid_match, key_match; 1674 struct sshkey *key = NULL; 1675 struct sshbuf *sid = NULL, *sig = NULL; 1676 char *fp = NULL; 1677 size_t i; 1678 u_char fwd = 0; 1679 1680 debug2_f("entering"); 1681 e->session_bind_attempted = 1; 1682 if ((r = sshkey_froms(e->request, &key)) != 0 || 1683 (r = sshbuf_froms(e->request, &sid)) != 0 || 1684 (r = sshbuf_froms(e->request, &sig)) != 0 || 1685 (r = sshbuf_get_u8(e->request, &fwd)) != 0) { 1686 error_fr(r, "parse"); 1687 goto out; 1688 } 1689 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT, 1690 SSH_FP_DEFAULT)) == NULL) 1691 fatal_f("fingerprint failed"); 1692 /* check signature with hostkey on session ID */ 1693 if ((r = sshkey_verify(key, sshbuf_ptr(sig), sshbuf_len(sig), 1694 sshbuf_ptr(sid), sshbuf_len(sid), NULL, 0, NULL)) != 0) { 1695 error_fr(r, "sshkey_verify for %s %s", sshkey_type(key), fp); 1696 goto out; 1697 } 1698 /* check whether sid/key already recorded */ 1699 for (i = 0; i < e->nsession_ids; i++) { 1700 if (!e->session_ids[i].forwarded) { 1701 error_f("attempt to bind session ID to socket " 1702 "previously bound for authentication attempt"); 1703 r = -1; 1704 goto out; 1705 } 1706 sid_match = buf_equal(sid, e->session_ids[i].sid) == 0; 1707 key_match = sshkey_equal(key, e->session_ids[i].key); 1708 if (sid_match && key_match) { 1709 debug_f("session ID already recorded for %s %s", 1710 sshkey_type(key), fp); 1711 r = 0; 1712 goto out; 1713 } else if (sid_match) { 1714 error_f("session ID recorded against different key " 1715 "for %s %s", sshkey_type(key), fp); 1716 r = -1; 1717 goto out; 1718 } 1719 /* 1720 * new sid with previously-seen key can happen, e.g. multiple 1721 * connections to the same host. 1722 */ 1723 } 1724 /* record new key/sid */ 1725 if (e->nsession_ids >= AGENT_MAX_SESSION_IDS) { 1726 error_f("too many session IDs recorded"); 1727 goto out; 1728 } 1729 e->session_ids = xrecallocarray(e->session_ids, e->nsession_ids, 1730 e->nsession_ids + 1, sizeof(*e->session_ids)); 1731 i = e->nsession_ids++; 1732 debug_f("recorded %s %s (slot %zu of %d)", sshkey_type(key), fp, i, 1733 AGENT_MAX_SESSION_IDS); 1734 e->session_ids[i].key = key; 1735 e->session_ids[i].forwarded = fwd != 0; 1736 key = NULL; /* transferred */ 1737 /* can't transfer sid; it's refcounted and scoped to request's life */ 1738 if ((e->session_ids[i].sid = sshbuf_new()) == NULL) 1739 fatal_f("sshbuf_new"); 1740 if ((r = sshbuf_putb(e->session_ids[i].sid, sid)) != 0) 1741 fatal_fr(r, "sshbuf_putb session ID"); 1742 /* success */ 1743 r = 0; 1744 out: 1745 free(fp); 1746 sshkey_free(key); 1747 sshbuf_free(sid); 1748 sshbuf_free(sig); 1749 return r == 0 ? 1 : 0; 1750 } 1751 1752 static void 1753 process_extension(SocketEntry *e) 1754 { 1755 int r, success = 0; 1756 char *name; 1757 1758 debug2_f("entering"); 1759 if ((r = sshbuf_get_cstring(e->request, &name, NULL)) != 0) { 1760 error_fr(r, "parse"); 1761 goto send; 1762 } 1763 if (strcmp(name, "session-bind@openssh.com") == 0) 1764 success = process_ext_session_bind(e); 1765 else 1766 debug_f("unsupported extension \"%s\"", name); 1767 free(name); 1768 send: 1769 send_status(e, success); 1770 } 1771 /* 1772 * dispatch incoming message. 1773 * returns 1 on success, 0 for incomplete messages or -1 on error. 1774 */ 1775 static int 1776 process_message(u_int socknum) 1777 { 1778 u_int msg_len; 1779 u_char type; 1780 const u_char *cp; 1781 int r; 1782 SocketEntry *e; 1783 1784 if (socknum >= sockets_alloc) 1785 fatal_f("sock %u >= allocated %u", socknum, sockets_alloc); 1786 e = &sockets[socknum]; 1787 1788 if (sshbuf_len(e->input) < 5) 1789 return 0; /* Incomplete message header. */ 1790 cp = sshbuf_ptr(e->input); 1791 msg_len = PEEK_U32(cp); 1792 if (msg_len > AGENT_MAX_LEN) { 1793 debug_f("socket %u (fd=%d) message too long %u > %u", 1794 socknum, e->fd, msg_len, AGENT_MAX_LEN); 1795 return -1; 1796 } 1797 if (sshbuf_len(e->input) < msg_len + 4) 1798 return 0; /* Incomplete message body. */ 1799 1800 /* move the current input to e->request */ 1801 sshbuf_reset(e->request); 1802 if ((r = sshbuf_get_stringb(e->input, e->request)) != 0 || 1803 (r = sshbuf_get_u8(e->request, &type)) != 0) { 1804 if (r == SSH_ERR_MESSAGE_INCOMPLETE || 1805 r == SSH_ERR_STRING_TOO_LARGE) { 1806 error_fr(r, "parse"); 1807 return -1; 1808 } 1809 fatal_fr(r, "parse"); 1810 } 1811 1812 debug_f("socket %u (fd=%d) type %d", socknum, e->fd, type); 1813 1814 /* check whether agent is locked */ 1815 if (locked && type != SSH_AGENTC_UNLOCK) { 1816 sshbuf_reset(e->request); 1817 switch (type) { 1818 case SSH2_AGENTC_REQUEST_IDENTITIES: 1819 /* send empty lists */ 1820 no_identities(e); 1821 break; 1822 default: 1823 /* send a fail message for all other request types */ 1824 send_status(e, 0); 1825 } 1826 return 1; 1827 } 1828 1829 switch (type) { 1830 case SSH_AGENTC_LOCK: 1831 case SSH_AGENTC_UNLOCK: 1832 process_lock_agent(e, type == SSH_AGENTC_LOCK); 1833 break; 1834 case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES: 1835 process_remove_all_identities(e); /* safe for !WITH_SSH1 */ 1836 break; 1837 /* ssh2 */ 1838 case SSH2_AGENTC_SIGN_REQUEST: 1839 process_sign_request2(e); 1840 break; 1841 case SSH2_AGENTC_REQUEST_IDENTITIES: 1842 process_request_identities(e); 1843 break; 1844 case SSH2_AGENTC_ADD_IDENTITY: 1845 case SSH2_AGENTC_ADD_ID_CONSTRAINED: 1846 process_add_identity(e); 1847 break; 1848 case SSH2_AGENTC_REMOVE_IDENTITY: 1849 process_remove_identity(e); 1850 break; 1851 case SSH2_AGENTC_REMOVE_ALL_IDENTITIES: 1852 process_remove_all_identities(e); 1853 break; 1854 #ifdef ENABLE_PKCS11 1855 case SSH_AGENTC_ADD_SMARTCARD_KEY: 1856 case SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED: 1857 process_add_smartcard_key(e); 1858 break; 1859 case SSH_AGENTC_REMOVE_SMARTCARD_KEY: 1860 process_remove_smartcard_key(e); 1861 break; 1862 #endif /* ENABLE_PKCS11 */ 1863 case SSH_AGENTC_EXTENSION: 1864 process_extension(e); 1865 break; 1866 default: 1867 /* Unknown message. Respond with failure. */ 1868 error("Unknown message %d", type); 1869 sshbuf_reset(e->request); 1870 send_status(e, 0); 1871 break; 1872 } 1873 return 1; 1874 } 1875 1876 static void 1877 new_socket(sock_type type, int fd) 1878 { 1879 u_int i, old_alloc, new_alloc; 1880 1881 debug_f("type = %s", type == AUTH_CONNECTION ? "CONNECTION" : 1882 (type == AUTH_SOCKET ? "SOCKET" : "UNKNOWN")); 1883 set_nonblock(fd); 1884 1885 if (fd > max_fd) 1886 max_fd = fd; 1887 1888 for (i = 0; i < sockets_alloc; i++) 1889 if (sockets[i].type == AUTH_UNUSED) { 1890 sockets[i].fd = fd; 1891 if ((sockets[i].input = sshbuf_new()) == NULL || 1892 (sockets[i].output = sshbuf_new()) == NULL || 1893 (sockets[i].request = sshbuf_new()) == NULL) 1894 fatal_f("sshbuf_new failed"); 1895 sockets[i].type = type; 1896 return; 1897 } 1898 old_alloc = sockets_alloc; 1899 new_alloc = sockets_alloc + 10; 1900 sockets = xrecallocarray(sockets, old_alloc, new_alloc, 1901 sizeof(sockets[0])); 1902 for (i = old_alloc; i < new_alloc; i++) 1903 sockets[i].type = AUTH_UNUSED; 1904 sockets_alloc = new_alloc; 1905 sockets[old_alloc].fd = fd; 1906 if ((sockets[old_alloc].input = sshbuf_new()) == NULL || 1907 (sockets[old_alloc].output = sshbuf_new()) == NULL || 1908 (sockets[old_alloc].request = sshbuf_new()) == NULL) 1909 fatal_f("sshbuf_new failed"); 1910 sockets[old_alloc].type = type; 1911 } 1912 1913 static int 1914 handle_socket_read(u_int socknum) 1915 { 1916 struct sockaddr_un sunaddr; 1917 socklen_t slen; 1918 uid_t euid; 1919 gid_t egid; 1920 int fd; 1921 1922 slen = sizeof(sunaddr); 1923 fd = accept(sockets[socknum].fd, (struct sockaddr *)&sunaddr, &slen); 1924 if (fd == -1) { 1925 error("accept from AUTH_SOCKET: %s", strerror(errno)); 1926 return -1; 1927 } 1928 if (getpeereid(fd, &euid, &egid) == -1) { 1929 error("getpeereid %d failed: %s", fd, strerror(errno)); 1930 close(fd); 1931 return -1; 1932 } 1933 if ((euid != 0) && (getuid() != euid)) { 1934 error("uid mismatch: peer euid %u != uid %u", 1935 (u_int) euid, (u_int) getuid()); 1936 close(fd); 1937 return -1; 1938 } 1939 new_socket(AUTH_CONNECTION, fd); 1940 return 0; 1941 } 1942 1943 static int 1944 handle_conn_read(u_int socknum) 1945 { 1946 char buf[AGENT_RBUF_LEN]; 1947 ssize_t len; 1948 int r; 1949 1950 if ((len = read(sockets[socknum].fd, buf, sizeof(buf))) <= 0) { 1951 if (len == -1) { 1952 if (errno == EAGAIN || errno == EINTR) 1953 return 0; 1954 error_f("read error on socket %u (fd %d): %s", 1955 socknum, sockets[socknum].fd, strerror(errno)); 1956 } 1957 return -1; 1958 } 1959 if ((r = sshbuf_put(sockets[socknum].input, buf, len)) != 0) 1960 fatal_fr(r, "compose"); 1961 explicit_bzero(buf, sizeof(buf)); 1962 for (;;) { 1963 if ((r = process_message(socknum)) == -1) 1964 return -1; 1965 else if (r == 0) 1966 break; 1967 } 1968 return 0; 1969 } 1970 1971 static int 1972 handle_conn_write(u_int socknum) 1973 { 1974 ssize_t len; 1975 int r; 1976 1977 if (sshbuf_len(sockets[socknum].output) == 0) 1978 return 0; /* shouldn't happen */ 1979 if ((len = write(sockets[socknum].fd, 1980 sshbuf_ptr(sockets[socknum].output), 1981 sshbuf_len(sockets[socknum].output))) <= 0) { 1982 if (len == -1) { 1983 if (errno == EAGAIN || errno == EINTR) 1984 return 0; 1985 error_f("read error on socket %u (fd %d): %s", 1986 socknum, sockets[socknum].fd, strerror(errno)); 1987 } 1988 return -1; 1989 } 1990 if ((r = sshbuf_consume(sockets[socknum].output, len)) != 0) 1991 fatal_fr(r, "consume"); 1992 return 0; 1993 } 1994 1995 static void 1996 after_poll(struct pollfd *pfd, size_t npfd, u_int maxfds) 1997 { 1998 size_t i; 1999 u_int socknum, activefds = npfd; 2000 2001 for (i = 0; i < npfd; i++) { 2002 if (pfd[i].revents == 0) 2003 continue; 2004 /* Find sockets entry */ 2005 for (socknum = 0; socknum < sockets_alloc; socknum++) { 2006 if (sockets[socknum].type != AUTH_SOCKET && 2007 sockets[socknum].type != AUTH_CONNECTION) 2008 continue; 2009 if (pfd[i].fd == sockets[socknum].fd) 2010 break; 2011 } 2012 if (socknum >= sockets_alloc) { 2013 error_f("no socket for fd %d", pfd[i].fd); 2014 continue; 2015 } 2016 /* Process events */ 2017 switch (sockets[socknum].type) { 2018 case AUTH_SOCKET: 2019 if ((pfd[i].revents & (POLLIN|POLLERR)) == 0) 2020 break; 2021 if (npfd > maxfds) { 2022 debug3("out of fds (active %u >= limit %u); " 2023 "skipping accept", activefds, maxfds); 2024 break; 2025 } 2026 if (handle_socket_read(socknum) == 0) 2027 activefds++; 2028 break; 2029 case AUTH_CONNECTION: 2030 if ((pfd[i].revents & (POLLIN|POLLHUP|POLLERR)) != 0 && 2031 handle_conn_read(socknum) != 0) 2032 goto close_sock; 2033 if ((pfd[i].revents & (POLLOUT|POLLHUP)) != 0 && 2034 handle_conn_write(socknum) != 0) { 2035 close_sock: 2036 if (activefds == 0) 2037 fatal("activefds == 0 at close_sock"); 2038 close_socket(&sockets[socknum]); 2039 activefds--; 2040 break; 2041 } 2042 break; 2043 default: 2044 break; 2045 } 2046 } 2047 } 2048 2049 static int 2050 prepare_poll(struct pollfd **pfdp, size_t *npfdp, int *timeoutp, u_int maxfds) 2051 { 2052 struct pollfd *pfd = *pfdp; 2053 size_t i, j, npfd = 0; 2054 time_t deadline; 2055 int r; 2056 2057 /* Count active sockets */ 2058 for (i = 0; i < sockets_alloc; i++) { 2059 switch (sockets[i].type) { 2060 case AUTH_SOCKET: 2061 case AUTH_CONNECTION: 2062 npfd++; 2063 break; 2064 case AUTH_UNUSED: 2065 break; 2066 default: 2067 fatal("Unknown socket type %d", sockets[i].type); 2068 break; 2069 } 2070 } 2071 if (npfd != *npfdp && 2072 (pfd = recallocarray(pfd, *npfdp, npfd, sizeof(*pfd))) == NULL) 2073 fatal_f("recallocarray failed"); 2074 *pfdp = pfd; 2075 *npfdp = npfd; 2076 2077 for (i = j = 0; i < sockets_alloc; i++) { 2078 switch (sockets[i].type) { 2079 case AUTH_SOCKET: 2080 if (npfd > maxfds) { 2081 debug3("out of fds (active %zu >= limit %u); " 2082 "skipping arming listener", npfd, maxfds); 2083 break; 2084 } 2085 pfd[j].fd = sockets[i].fd; 2086 pfd[j].revents = 0; 2087 pfd[j].events = POLLIN; 2088 j++; 2089 break; 2090 case AUTH_CONNECTION: 2091 pfd[j].fd = sockets[i].fd; 2092 pfd[j].revents = 0; 2093 /* 2094 * Only prepare to read if we can handle a full-size 2095 * input read buffer and enqueue a max size reply.. 2096 */ 2097 if ((r = sshbuf_check_reserve(sockets[i].input, 2098 AGENT_RBUF_LEN)) == 0 && 2099 (r = sshbuf_check_reserve(sockets[i].output, 2100 AGENT_MAX_LEN)) == 0) 2101 pfd[j].events = POLLIN; 2102 else if (r != SSH_ERR_NO_BUFFER_SPACE) 2103 fatal_fr(r, "reserve"); 2104 if (sshbuf_len(sockets[i].output) > 0) 2105 pfd[j].events |= POLLOUT; 2106 j++; 2107 break; 2108 default: 2109 break; 2110 } 2111 } 2112 deadline = reaper(); 2113 if (parent_alive_interval != 0) 2114 deadline = (deadline == 0) ? parent_alive_interval : 2115 MINIMUM(deadline, parent_alive_interval); 2116 if (deadline == 0) { 2117 *timeoutp = -1; /* INFTIM */ 2118 } else { 2119 if (deadline > INT_MAX / 1000) 2120 *timeoutp = INT_MAX / 1000; 2121 else 2122 *timeoutp = deadline * 1000; 2123 } 2124 return (1); 2125 } 2126 2127 static void 2128 cleanup_socket(void) 2129 { 2130 if (cleanup_pid != 0 && getpid() != cleanup_pid) 2131 return; 2132 debug_f("cleanup"); 2133 if (socket_name[0]) 2134 unlink(socket_name); 2135 if (socket_dir[0]) 2136 rmdir(socket_dir); 2137 } 2138 2139 void 2140 cleanup_exit(int i) 2141 { 2142 cleanup_socket(); 2143 _exit(i); 2144 } 2145 2146 static void 2147 cleanup_handler(int sig) 2148 { 2149 cleanup_socket(); 2150 #ifdef ENABLE_PKCS11 2151 pkcs11_terminate(); 2152 #endif 2153 _exit(2); 2154 } 2155 2156 static void 2157 check_parent_exists(void) 2158 { 2159 /* 2160 * If our parent has exited then getppid() will return (pid_t)1, 2161 * so testing for that should be safe. 2162 */ 2163 if (parent_pid != -1 && getppid() != parent_pid) { 2164 /* printf("Parent has died - Authentication agent exiting.\n"); */ 2165 cleanup_socket(); 2166 _exit(2); 2167 } 2168 } 2169 2170 static void 2171 usage(void) 2172 { 2173 fprintf(stderr, 2174 "usage: ssh-agent [-c | -s] [-Dd] [-a bind_address] [-E fingerprint_hash]\n" 2175 " [-O option] [-P allowed_providers] [-t life]\n" 2176 " ssh-agent [-a bind_address] [-E fingerprint_hash] [-O option]\n" 2177 " [-P allowed_providers] [-t life] command [arg ...]\n" 2178 " ssh-agent [-c | -s] -k\n"); 2179 exit(1); 2180 } 2181 2182 int 2183 main(int ac, char **av) 2184 { 2185 int c_flag = 0, d_flag = 0, D_flag = 0, k_flag = 0, s_flag = 0; 2186 int sock, ch, result, saved_errno; 2187 char *shell, *format, *pidstr, *agentsocket = NULL; 2188 struct rlimit rlim; 2189 extern int optind; 2190 extern char *optarg; 2191 pid_t pid; 2192 char pidstrbuf[1 + 3 * sizeof pid]; 2193 size_t len; 2194 mode_t prev_mask; 2195 int timeout = -1; /* INFTIM */ 2196 struct pollfd *pfd = NULL; 2197 size_t npfd = 0; 2198 u_int maxfds; 2199 2200 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */ 2201 sanitise_stdfd(); 2202 2203 /* drop */ 2204 (void)setegid(getgid()); 2205 (void)setgid(getgid()); 2206 2207 if (getrlimit(RLIMIT_NOFILE, &rlim) == -1) 2208 fatal("%s: getrlimit: %s", __progname, strerror(errno)); 2209 2210 #ifdef WITH_OPENSSL 2211 OpenSSL_add_all_algorithms(); 2212 #endif 2213 2214 while ((ch = getopt(ac, av, "cDdksE:a:O:P:t:")) != -1) { 2215 switch (ch) { 2216 case 'E': 2217 fingerprint_hash = ssh_digest_alg_by_name(optarg); 2218 if (fingerprint_hash == -1) 2219 fatal("Invalid hash algorithm \"%s\"", optarg); 2220 break; 2221 case 'c': 2222 if (s_flag) 2223 usage(); 2224 c_flag++; 2225 break; 2226 case 'k': 2227 k_flag++; 2228 break; 2229 case 'O': 2230 if (strcmp(optarg, "no-restrict-websafe") == 0) 2231 restrict_websafe = 0; 2232 else if (strcmp(optarg, "allow-remote-pkcs11") == 0) 2233 remote_add_provider = 1; 2234 else 2235 fatal("Unknown -O option"); 2236 break; 2237 case 'P': 2238 if (allowed_providers != NULL) 2239 fatal("-P option already specified"); 2240 allowed_providers = xstrdup(optarg); 2241 break; 2242 case 's': 2243 if (c_flag) 2244 usage(); 2245 s_flag++; 2246 break; 2247 case 'd': 2248 if (d_flag || D_flag) 2249 usage(); 2250 d_flag++; 2251 break; 2252 case 'D': 2253 if (d_flag || D_flag) 2254 usage(); 2255 D_flag++; 2256 break; 2257 case 'a': 2258 agentsocket = optarg; 2259 break; 2260 case 't': 2261 if ((lifetime = convtime(optarg)) == -1) { 2262 fprintf(stderr, "Invalid lifetime\n"); 2263 usage(); 2264 } 2265 break; 2266 default: 2267 usage(); 2268 } 2269 } 2270 ac -= optind; 2271 av += optind; 2272 2273 if (ac > 0 && (c_flag || k_flag || s_flag || d_flag || D_flag)) 2274 usage(); 2275 2276 if (allowed_providers == NULL) 2277 allowed_providers = xstrdup(DEFAULT_ALLOWED_PROVIDERS); 2278 2279 if (ac == 0 && !c_flag && !s_flag) { 2280 shell = getenv("SHELL"); 2281 if (shell != NULL && (len = strlen(shell)) > 2 && 2282 strncmp(shell + len - 3, "csh", 3) == 0) 2283 c_flag = 1; 2284 } 2285 if (k_flag) { 2286 const char *errstr = NULL; 2287 2288 pidstr = getenv(SSH_AGENTPID_ENV_NAME); 2289 if (pidstr == NULL) { 2290 fprintf(stderr, "%s not set, cannot kill agent\n", 2291 SSH_AGENTPID_ENV_NAME); 2292 exit(1); 2293 } 2294 pid = (int)strtonum(pidstr, 2, INT_MAX, &errstr); 2295 if (errstr) { 2296 fprintf(stderr, 2297 "%s=\"%s\", which is not a good PID: %s\n", 2298 SSH_AGENTPID_ENV_NAME, pidstr, errstr); 2299 exit(1); 2300 } 2301 if (kill(pid, SIGTERM) == -1) { 2302 perror("kill"); 2303 exit(1); 2304 } 2305 format = c_flag ? "unsetenv %s;\n" : "unset %s;\n"; 2306 printf(format, SSH_AUTHSOCKET_ENV_NAME); 2307 printf(format, SSH_AGENTPID_ENV_NAME); 2308 printf("echo Agent pid %ld killed;\n", (long)pid); 2309 exit(0); 2310 } 2311 2312 /* 2313 * Minimum file descriptors: 2314 * stdio (3) + listener (1) + syslog (1 maybe) + connection (1) + 2315 * a few spare for libc / stack protectors / sanitisers, etc. 2316 */ 2317 #define SSH_AGENT_MIN_FDS (3+1+1+1+4) 2318 if (rlim.rlim_cur < SSH_AGENT_MIN_FDS) 2319 fatal("%s: file descriptor rlimit %lld too low (minimum %u)", 2320 __progname, (long long)rlim.rlim_cur, SSH_AGENT_MIN_FDS); 2321 maxfds = rlim.rlim_cur - SSH_AGENT_MIN_FDS; 2322 2323 parent_pid = getpid(); 2324 2325 if (agentsocket == NULL) { 2326 /* Create private directory for agent socket */ 2327 mktemp_proto(socket_dir, sizeof(socket_dir)); 2328 if (mkdtemp(socket_dir) == NULL) { 2329 perror("mkdtemp: private socket dir"); 2330 exit(1); 2331 } 2332 snprintf(socket_name, sizeof socket_name, "%s/agent.%ld", socket_dir, 2333 (long)parent_pid); 2334 } else { 2335 /* Try to use specified agent socket */ 2336 socket_dir[0] = '\0'; 2337 strlcpy(socket_name, agentsocket, sizeof socket_name); 2338 } 2339 2340 /* 2341 * Create socket early so it will exist before command gets run from 2342 * the parent. 2343 */ 2344 prev_mask = umask(0177); 2345 sock = unix_listener(socket_name, SSH_LISTEN_BACKLOG, 0); 2346 if (sock < 0) { 2347 /* XXX - unix_listener() calls error() not perror() */ 2348 *socket_name = '\0'; /* Don't unlink any existing file */ 2349 cleanup_exit(1); 2350 } 2351 umask(prev_mask); 2352 2353 /* 2354 * Fork, and have the parent execute the command, if any, or present 2355 * the socket data. The child continues as the authentication agent. 2356 */ 2357 if (D_flag || d_flag) { 2358 log_init(__progname, 2359 d_flag ? SYSLOG_LEVEL_DEBUG3 : SYSLOG_LEVEL_INFO, 2360 SYSLOG_FACILITY_AUTH, 1); 2361 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n"; 2362 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name, 2363 SSH_AUTHSOCKET_ENV_NAME); 2364 printf("echo Agent pid %ld;\n", (long)parent_pid); 2365 fflush(stdout); 2366 goto skip; 2367 } 2368 pid = fork(); 2369 if (pid == -1) { 2370 perror("fork"); 2371 cleanup_exit(1); 2372 } 2373 if (pid != 0) { /* Parent - execute the given command. */ 2374 close(sock); 2375 snprintf(pidstrbuf, sizeof pidstrbuf, "%ld", (long)pid); 2376 if (ac == 0) { 2377 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n"; 2378 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name, 2379 SSH_AUTHSOCKET_ENV_NAME); 2380 printf(format, SSH_AGENTPID_ENV_NAME, pidstrbuf, 2381 SSH_AGENTPID_ENV_NAME); 2382 printf("echo Agent pid %ld;\n", (long)pid); 2383 exit(0); 2384 } 2385 if (setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1) == -1 || 2386 setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1) == -1) { 2387 perror("setenv"); 2388 exit(1); 2389 } 2390 execvp(av[0], av); 2391 perror(av[0]); 2392 exit(1); 2393 } 2394 /* child */ 2395 log_init(__progname, SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_AUTH, 0); 2396 2397 if (setsid() == -1) { 2398 error("setsid: %s", strerror(errno)); 2399 cleanup_exit(1); 2400 } 2401 2402 (void)chdir("/"); 2403 if (stdfd_devnull(1, 1, 1) == -1) 2404 error_f("stdfd_devnull failed"); 2405 2406 /* deny core dumps, since memory contains unencrypted private keys */ 2407 rlim.rlim_cur = rlim.rlim_max = 0; 2408 if (setrlimit(RLIMIT_CORE, &rlim) == -1) { 2409 error("setrlimit RLIMIT_CORE: %s", strerror(errno)); 2410 cleanup_exit(1); 2411 } 2412 2413 skip: 2414 2415 cleanup_pid = getpid(); 2416 2417 #ifdef ENABLE_PKCS11 2418 pkcs11_init(0); 2419 #endif 2420 new_socket(AUTH_SOCKET, sock); 2421 if (ac > 0) 2422 parent_alive_interval = 10; 2423 idtab_init(); 2424 ssh_signal(SIGPIPE, SIG_IGN); 2425 ssh_signal(SIGINT, (d_flag | D_flag) ? cleanup_handler : SIG_IGN); 2426 ssh_signal(SIGHUP, cleanup_handler); 2427 ssh_signal(SIGTERM, cleanup_handler); 2428 2429 if (pledge("stdio rpath cpath unix id proc exec", NULL) == -1) 2430 fatal("%s: pledge: %s", __progname, strerror(errno)); 2431 2432 while (1) { 2433 prepare_poll(&pfd, &npfd, &timeout, maxfds); 2434 result = poll(pfd, npfd, timeout); 2435 saved_errno = errno; 2436 if (parent_alive_interval != 0) 2437 check_parent_exists(); 2438 (void) reaper(); /* remove expired keys */ 2439 if (result == -1) { 2440 if (saved_errno == EINTR) 2441 continue; 2442 fatal("poll: %s", strerror(saved_errno)); 2443 } else if (result > 0) 2444 after_poll(pfd, npfd, maxfds); 2445 } 2446 /* NOTREACHED */ 2447 } 2448