1 /* $NetBSD: ssh-agent.c,v 1.37 2023/12/20 17:15:21 christos Exp $ */ 2 /* $OpenBSD: ssh-agent.c,v 1.303 2023/12/18 14:48:08 djm Exp $ */ 3 4 /* 5 * Author: Tatu Ylonen <ylo@cs.hut.fi> 6 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 7 * All rights reserved 8 * The authentication agent program. 9 * 10 * As far as I am concerned, the code I have written for this software 11 * can be used freely for any purpose. Any derived versions of this 12 * software must be clearly marked as such, and if the derived work is 13 * incompatible with the protocol description in the RFC file, it must be 14 * called by a name other than "ssh" or "Secure Shell". 15 * 16 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. 17 * 18 * Redistribution and use in source and binary forms, with or without 19 * modification, are permitted provided that the following conditions 20 * are met: 21 * 1. Redistributions of source code must retain the above copyright 22 * notice, this list of conditions and the following disclaimer. 23 * 2. Redistributions in binary form must reproduce the above copyright 24 * notice, this list of conditions and the following disclaimer in the 25 * documentation and/or other materials provided with the distribution. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 28 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 29 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 30 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 31 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 32 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 33 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 34 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 35 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 36 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 37 */ 38 39 #include "includes.h" 40 __RCSID("$NetBSD: ssh-agent.c,v 1.37 2023/12/20 17:15:21 christos Exp $"); 41 42 #include <sys/param.h> /* MIN MAX */ 43 #include <sys/types.h> 44 #include <sys/time.h> 45 #include <sys/queue.h> 46 #include <sys/resource.h> 47 #include <sys/socket.h> 48 #include <sys/stat.h> 49 #include <sys/un.h> 50 #include <sys/wait.h> 51 52 #ifdef WITH_OPENSSL 53 #include <openssl/evp.h> 54 #endif 55 56 #include <errno.h> 57 #include <fcntl.h> 58 #include <paths.h> 59 #include <poll.h> 60 #include <signal.h> 61 #include <stdlib.h> 62 #include <stdio.h> 63 #include <string.h> 64 #include <stdarg.h> 65 #include <limits.h> 66 #include <time.h> 67 #include <unistd.h> 68 #include <util.h> 69 70 #include "xmalloc.h" 71 #include "ssh.h" 72 #include "ssh2.h" 73 #include "sshbuf.h" 74 #include "sshkey.h" 75 #include "authfd.h" 76 #include "log.h" 77 #include "misc.h" 78 #include "getpeereid.h" 79 #include "digest.h" 80 #include "ssherr.h" 81 #include "match.h" 82 #include "msg.h" 83 #include "pathnames.h" 84 #include "ssh-pkcs11.h" 85 #include "sk-api.h" 86 #include "myproposal.h" 87 88 #ifndef DEFAULT_ALLOWED_PROVIDERS 89 # define DEFAULT_ALLOWED_PROVIDERS "/usr/lib*/*,/usr/pkg/lib*/*" 90 #endif 91 92 /* Maximum accepted message length */ 93 #define AGENT_MAX_LEN (256*1024) 94 /* Maximum bytes to read from client socket */ 95 #define AGENT_RBUF_LEN (4096) 96 /* Maximum number of recorded session IDs/hostkeys per connection */ 97 #define AGENT_MAX_SESSION_IDS 16 98 /* Maximum size of session ID */ 99 #define AGENT_MAX_SID_LEN 128 100 /* Maximum number of destination constraints to accept on a key */ 101 #define AGENT_MAX_DEST_CONSTRAINTS 1024 102 /* Maximum number of associated certificate constraints to accept on a key */ 103 #define AGENT_MAX_EXT_CERTS 1024 104 105 /* XXX store hostkey_sid in a refcounted tree */ 106 107 typedef enum { 108 AUTH_UNUSED = 0, 109 AUTH_SOCKET = 1, 110 AUTH_CONNECTION = 2, 111 } sock_type; 112 113 struct hostkey_sid { 114 struct sshkey *key; 115 struct sshbuf *sid; 116 int forwarded; 117 }; 118 119 typedef struct socket_entry { 120 int fd; 121 sock_type type; 122 struct sshbuf *input; 123 struct sshbuf *output; 124 struct sshbuf *request; 125 size_t nsession_ids; 126 struct hostkey_sid *session_ids; 127 int session_bind_attempted; 128 } SocketEntry; 129 130 u_int sockets_alloc = 0; 131 SocketEntry *sockets = NULL; 132 133 typedef struct identity { 134 TAILQ_ENTRY(identity) next; 135 struct sshkey *key; 136 char *comment; 137 char *provider; 138 time_t death; 139 u_int confirm; 140 char *sk_provider; 141 struct dest_constraint *dest_constraints; 142 size_t ndest_constraints; 143 } Identity; 144 145 struct idtable { 146 int nentries; 147 TAILQ_HEAD(idqueue, identity) idlist; 148 }; 149 150 /* private key table */ 151 struct idtable *idtab; 152 153 int max_fd = 0; 154 155 /* pid of shell == parent of agent */ 156 pid_t parent_pid = -1; 157 time_t parent_alive_interval = 0; 158 159 /* pid of process for which cleanup_socket is applicable */ 160 pid_t cleanup_pid = 0; 161 162 /* pathname and directory for AUTH_SOCKET */ 163 char socket_name[PATH_MAX]; 164 char socket_dir[PATH_MAX]; 165 166 /* Pattern-list of allowed PKCS#11/Security key paths */ 167 static char *allowed_providers; 168 169 /* 170 * Allows PKCS11 providers or SK keys that use non-internal providers to 171 * be added over a remote connection (identified by session-bind@openssh.com). 172 */ 173 static int remote_add_provider; 174 175 /* locking */ 176 #define LOCK_SIZE 32 177 #define LOCK_SALT_SIZE 16 178 #define LOCK_ROUNDS 1 179 int locked = 0; 180 u_char lock_pwhash[LOCK_SIZE]; 181 u_char lock_salt[LOCK_SALT_SIZE]; 182 183 extern char *__progname; 184 185 /* Default lifetime in seconds (0 == forever) */ 186 static int lifetime = 0; 187 188 static int fingerprint_hash = SSH_FP_HASH_DEFAULT; 189 190 /* Refuse signing of non-SSH messages for web-origin FIDO keys */ 191 static int restrict_websafe = 1; 192 193 static void 194 close_socket(SocketEntry *e) 195 { 196 size_t i; 197 198 close(e->fd); 199 sshbuf_free(e->input); 200 sshbuf_free(e->output); 201 sshbuf_free(e->request); 202 for (i = 0; i < e->nsession_ids; i++) { 203 sshkey_free(e->session_ids[i].key); 204 sshbuf_free(e->session_ids[i].sid); 205 } 206 free(e->session_ids); 207 memset(e, '\0', sizeof(*e)); 208 e->fd = -1; 209 e->type = AUTH_UNUSED; 210 } 211 212 static void 213 idtab_init(void) 214 { 215 idtab = xcalloc(1, sizeof(*idtab)); 216 TAILQ_INIT(&idtab->idlist); 217 idtab->nentries = 0; 218 } 219 220 static void 221 free_dest_constraint_hop(struct dest_constraint_hop *dch) 222 { 223 u_int i; 224 225 if (dch == NULL) 226 return; 227 free(dch->user); 228 free(dch->hostname); 229 for (i = 0; i < dch->nkeys; i++) 230 sshkey_free(dch->keys[i]); 231 free(dch->keys); 232 free(dch->key_is_ca); 233 } 234 235 static void 236 free_dest_constraints(struct dest_constraint *dcs, size_t ndcs) 237 { 238 size_t i; 239 240 for (i = 0; i < ndcs; i++) { 241 free_dest_constraint_hop(&dcs[i].from); 242 free_dest_constraint_hop(&dcs[i].to); 243 } 244 free(dcs); 245 } 246 247 static void 248 dup_dest_constraint_hop(const struct dest_constraint_hop *dch, 249 struct dest_constraint_hop *out) 250 { 251 u_int i; 252 int r; 253 254 out->user = dch->user == NULL ? NULL : xstrdup(dch->user); 255 out->hostname = dch->hostname == NULL ? NULL : xstrdup(dch->hostname); 256 out->is_ca = dch->is_ca; 257 out->nkeys = dch->nkeys; 258 out->keys = out->nkeys == 0 ? NULL : 259 xcalloc(out->nkeys, sizeof(*out->keys)); 260 out->key_is_ca = out->nkeys == 0 ? NULL : 261 xcalloc(out->nkeys, sizeof(*out->key_is_ca)); 262 for (i = 0; i < dch->nkeys; i++) { 263 if (dch->keys[i] != NULL && 264 (r = sshkey_from_private(dch->keys[i], 265 &(out->keys[i]))) != 0) 266 fatal_fr(r, "copy key"); 267 out->key_is_ca[i] = dch->key_is_ca[i]; 268 } 269 } 270 271 static struct dest_constraint * 272 dup_dest_constraints(const struct dest_constraint *dcs, size_t ndcs) 273 { 274 size_t i; 275 struct dest_constraint *ret; 276 277 if (ndcs == 0) 278 return NULL; 279 ret = xcalloc(ndcs, sizeof(*ret)); 280 for (i = 0; i < ndcs; i++) { 281 dup_dest_constraint_hop(&dcs[i].from, &ret[i].from); 282 dup_dest_constraint_hop(&dcs[i].to, &ret[i].to); 283 } 284 return ret; 285 } 286 287 #ifdef DEBUG_CONSTRAINTS 288 static void 289 dump_dest_constraint_hop(const struct dest_constraint_hop *dch) 290 { 291 u_int i; 292 char *fp; 293 294 debug_f("user %s hostname %s is_ca %d nkeys %u", 295 dch->user == NULL ? "(null)" : dch->user, 296 dch->hostname == NULL ? "(null)" : dch->hostname, 297 dch->is_ca, dch->nkeys); 298 for (i = 0; i < dch->nkeys; i++) { 299 fp = NULL; 300 if (dch->keys[i] != NULL && 301 (fp = sshkey_fingerprint(dch->keys[i], 302 SSH_FP_HASH_DEFAULT, SSH_FP_DEFAULT)) == NULL) 303 fatal_f("fingerprint failed"); 304 debug_f("key %u/%u: %s%s%s key_is_ca %d", i, dch->nkeys, 305 dch->keys[i] == NULL ? "" : sshkey_ssh_name(dch->keys[i]), 306 dch->keys[i] == NULL ? "" : " ", 307 dch->keys[i] == NULL ? "none" : fp, 308 dch->key_is_ca[i]); 309 free(fp); 310 } 311 } 312 #endif /* DEBUG_CONSTRAINTS */ 313 314 static void 315 dump_dest_constraints(const char *context, 316 const struct dest_constraint *dcs, size_t ndcs) 317 { 318 #ifdef DEBUG_CONSTRAINTS 319 size_t i; 320 321 debug_f("%s: %zu constraints", context, ndcs); 322 for (i = 0; i < ndcs; i++) { 323 debug_f("constraint %zu / %zu: from: ", i, ndcs); 324 dump_dest_constraint_hop(&dcs[i].from); 325 debug_f("constraint %zu / %zu: to: ", i, ndcs); 326 dump_dest_constraint_hop(&dcs[i].to); 327 } 328 debug_f("done for %s", context); 329 #endif /* DEBUG_CONSTRAINTS */ 330 } 331 332 static void 333 free_identity(Identity *id) 334 { 335 sshkey_free(id->key); 336 free(id->provider); 337 free(id->comment); 338 free(id->sk_provider); 339 free_dest_constraints(id->dest_constraints, id->ndest_constraints); 340 free(id); 341 } 342 343 /* 344 * Match 'key' against the key/CA list in a destination constraint hop 345 * Returns 0 on success or -1 otherwise. 346 */ 347 static int 348 match_key_hop(const char *tag, const struct sshkey *key, 349 const struct dest_constraint_hop *dch) 350 { 351 const char *reason = NULL; 352 const char *hostname = dch->hostname ? dch->hostname : "(ORIGIN)"; 353 u_int i; 354 char *fp; 355 356 if (key == NULL) 357 return -1; 358 /* XXX logspam */ 359 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT, 360 SSH_FP_DEFAULT)) == NULL) 361 fatal_f("fingerprint failed"); 362 debug3_f("%s: entering hostname %s, requested key %s %s, %u keys avail", 363 tag, hostname, sshkey_type(key), fp, dch->nkeys); 364 free(fp); 365 for (i = 0; i < dch->nkeys; i++) { 366 if (dch->keys[i] == NULL) 367 return -1; 368 /* XXX logspam */ 369 if ((fp = sshkey_fingerprint(dch->keys[i], SSH_FP_HASH_DEFAULT, 370 SSH_FP_DEFAULT)) == NULL) 371 fatal_f("fingerprint failed"); 372 debug3_f("%s: key %u: %s%s %s", tag, i, 373 dch->key_is_ca[i] ? "CA " : "", 374 sshkey_type(dch->keys[i]), fp); 375 free(fp); 376 if (!sshkey_is_cert(key)) { 377 /* plain key */ 378 if (dch->key_is_ca[i] || 379 !sshkey_equal(key, dch->keys[i])) 380 continue; 381 return 0; 382 } 383 /* certificate */ 384 if (!dch->key_is_ca[i]) 385 continue; 386 if (key->cert == NULL || key->cert->signature_key == NULL) 387 return -1; /* shouldn't happen */ 388 if (!sshkey_equal(key->cert->signature_key, dch->keys[i])) 389 continue; 390 if (sshkey_cert_check_host(key, hostname, 1, 391 SSH_ALLOWED_CA_SIGALGS, &reason) != 0) { 392 debug_f("cert %s / hostname %s rejected: %s", 393 key->cert->key_id, hostname, reason); 394 continue; 395 } 396 return 0; 397 } 398 return -1; 399 } 400 401 /* Check destination constraints on an identity against the hostkey/user */ 402 static int 403 permitted_by_dest_constraints(const struct sshkey *fromkey, 404 const struct sshkey *tokey, Identity *id, const char *user, 405 const char **hostnamep) 406 { 407 size_t i; 408 struct dest_constraint *d; 409 410 if (hostnamep != NULL) 411 *hostnamep = NULL; 412 for (i = 0; i < id->ndest_constraints; i++) { 413 d = id->dest_constraints + i; 414 /* XXX remove logspam */ 415 debug2_f("constraint %zu %s%s%s (%u keys) > %s%s%s (%u keys)", 416 i, d->from.user ? d->from.user : "", 417 d->from.user ? "@" : "", 418 d->from.hostname ? d->from.hostname : "(ORIGIN)", 419 d->from.nkeys, 420 d->to.user ? d->to.user : "", d->to.user ? "@" : "", 421 d->to.hostname ? d->to.hostname : "(ANY)", d->to.nkeys); 422 423 /* Match 'from' key */ 424 if (fromkey == NULL) { 425 /* We are matching the first hop */ 426 if (d->from.hostname != NULL || d->from.nkeys != 0) 427 continue; 428 } else if (match_key_hop("from", fromkey, &d->from) != 0) 429 continue; 430 431 /* Match 'to' key */ 432 if (tokey != NULL && match_key_hop("to", tokey, &d->to) != 0) 433 continue; 434 435 /* Match user if specified */ 436 if (d->to.user != NULL && user != NULL && 437 !match_pattern(user, d->to.user)) 438 continue; 439 440 /* successfully matched this constraint */ 441 if (hostnamep != NULL) 442 *hostnamep = d->to.hostname; 443 debug2_f("allowed for hostname %s", 444 d->to.hostname == NULL ? "*" : d->to.hostname); 445 return 0; 446 } 447 /* no match */ 448 debug2_f("%s identity \"%s\" not permitted for this destination", 449 sshkey_type(id->key), id->comment); 450 return -1; 451 } 452 453 /* 454 * Check whether hostkeys on a SocketEntry and the optionally specified user 455 * are permitted by the destination constraints on the Identity. 456 * Returns 0 on success or -1 otherwise. 457 */ 458 static int 459 identity_permitted(Identity *id, SocketEntry *e, char *user, 460 const char **forward_hostnamep, const char **last_hostnamep) 461 { 462 size_t i; 463 const char **hp; 464 struct hostkey_sid *hks; 465 const struct sshkey *fromkey = NULL; 466 const char *test_user; 467 char *fp1, *fp2; 468 469 /* XXX remove logspam */ 470 debug3_f("entering: key %s comment \"%s\", %zu socket bindings, " 471 "%zu constraints", sshkey_type(id->key), id->comment, 472 e->nsession_ids, id->ndest_constraints); 473 if (id->ndest_constraints == 0) 474 return 0; /* unconstrained */ 475 if (e->session_bind_attempted && e->nsession_ids == 0) { 476 error_f("previous session bind failed on socket"); 477 return -1; 478 } 479 if (e->nsession_ids == 0) 480 return 0; /* local use */ 481 /* 482 * Walk through the hops recorded by session_id and try to find a 483 * constraint that satisfies each. 484 */ 485 for (i = 0; i < e->nsession_ids; i++) { 486 hks = e->session_ids + i; 487 if (hks->key == NULL) 488 fatal_f("internal error: no bound key"); 489 /* XXX remove logspam */ 490 fp1 = fp2 = NULL; 491 if (fromkey != NULL && 492 (fp1 = sshkey_fingerprint(fromkey, SSH_FP_HASH_DEFAULT, 493 SSH_FP_DEFAULT)) == NULL) 494 fatal_f("fingerprint failed"); 495 if ((fp2 = sshkey_fingerprint(hks->key, SSH_FP_HASH_DEFAULT, 496 SSH_FP_DEFAULT)) == NULL) 497 fatal_f("fingerprint failed"); 498 debug3_f("socketentry fd=%d, entry %zu %s, " 499 "from hostkey %s %s to user %s hostkey %s %s", 500 e->fd, i, hks->forwarded ? "FORWARD" : "AUTH", 501 fromkey ? sshkey_type(fromkey) : "(ORIGIN)", 502 fromkey ? fp1 : "", user ? user : "(ANY)", 503 sshkey_type(hks->key), fp2); 504 free(fp1); 505 free(fp2); 506 /* 507 * Record the hostnames for the initial forwarding and 508 * the final destination. 509 */ 510 hp = NULL; 511 if (i == e->nsession_ids - 1) 512 hp = last_hostnamep; 513 else if (i == 0) 514 hp = forward_hostnamep; 515 /* Special handling for final recorded binding */ 516 test_user = NULL; 517 if (i == e->nsession_ids - 1) { 518 /* Can only check user at final hop */ 519 test_user = user; 520 /* 521 * user is only presented for signature requests. 522 * If this is the case, make sure last binding is not 523 * for a forwarding. 524 */ 525 if (hks->forwarded && user != NULL) { 526 error_f("tried to sign on forwarding hop"); 527 return -1; 528 } 529 } else if (!hks->forwarded) { 530 error_f("tried to forward though signing bind"); 531 return -1; 532 } 533 if (permitted_by_dest_constraints(fromkey, hks->key, id, 534 test_user, hp) != 0) 535 return -1; 536 fromkey = hks->key; 537 } 538 /* 539 * Another special case: if the last bound session ID was for a 540 * forwarding, and this function is not being called to check a sign 541 * request (i.e. no 'user' supplied), then only permit the key if 542 * there is a permission that would allow it to be used at another 543 * destination. This hides keys that are allowed to be used to 544 * authenticate *to* a host but not permitted for *use* beyond it. 545 */ 546 hks = &e->session_ids[e->nsession_ids - 1]; 547 if (hks->forwarded && user == NULL && 548 permitted_by_dest_constraints(hks->key, NULL, id, 549 NULL, NULL) != 0) { 550 debug3_f("key permitted at host but not after"); 551 return -1; 552 } 553 554 /* success */ 555 return 0; 556 } 557 558 static int 559 socket_is_remote(SocketEntry *e) 560 { 561 return e->session_bind_attempted || (e->nsession_ids != 0); 562 } 563 564 /* return matching private key for given public key */ 565 static Identity * 566 lookup_identity(struct sshkey *key) 567 { 568 Identity *id; 569 570 TAILQ_FOREACH(id, &idtab->idlist, next) { 571 if (sshkey_equal(key, id->key)) 572 return (id); 573 } 574 return (NULL); 575 } 576 577 /* Check confirmation of keysign request */ 578 static int 579 confirm_key(Identity *id, const char *extra) 580 { 581 char *p; 582 int ret = -1; 583 584 p = sshkey_fingerprint(id->key, fingerprint_hash, SSH_FP_DEFAULT); 585 if (p != NULL && 586 ask_permission("Allow use of key %s?\nKey fingerprint %s.%s%s", 587 id->comment, p, 588 extra == NULL ? "" : "\n", extra == NULL ? "" : extra)) 589 ret = 0; 590 free(p); 591 592 return (ret); 593 } 594 595 static void 596 send_status(SocketEntry *e, int success) 597 { 598 int r; 599 600 if ((r = sshbuf_put_u32(e->output, 1)) != 0 || 601 (r = sshbuf_put_u8(e->output, success ? 602 SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE)) != 0) 603 fatal_fr(r, "compose"); 604 } 605 606 /* send list of supported public keys to 'client' */ 607 static void 608 process_request_identities(SocketEntry *e) 609 { 610 Identity *id; 611 struct sshbuf *msg, *keys; 612 int r; 613 u_int i = 0, nentries = 0; 614 char *fp; 615 616 debug2_f("entering"); 617 618 if ((msg = sshbuf_new()) == NULL || (keys = sshbuf_new()) == NULL) 619 fatal_f("sshbuf_new failed"); 620 TAILQ_FOREACH(id, &idtab->idlist, next) { 621 if ((fp = sshkey_fingerprint(id->key, SSH_FP_HASH_DEFAULT, 622 SSH_FP_DEFAULT)) == NULL) 623 fatal_f("fingerprint failed"); 624 debug_f("key %u / %u: %s %s", i++, idtab->nentries, 625 sshkey_ssh_name(id->key), fp); 626 dump_dest_constraints(__func__, 627 id->dest_constraints, id->ndest_constraints); 628 free(fp); 629 /* identity not visible, don't include in response */ 630 if (identity_permitted(id, e, NULL, NULL, NULL) != 0) 631 continue; 632 if ((r = sshkey_puts_opts(id->key, keys, 633 SSHKEY_SERIALIZE_INFO)) != 0 || 634 (r = sshbuf_put_cstring(keys, id->comment)) != 0) { 635 error_fr(r, "compose key/comment"); 636 continue; 637 } 638 nentries++; 639 } 640 debug2_f("replying with %u allowed of %u available keys", 641 nentries, idtab->nentries); 642 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 || 643 (r = sshbuf_put_u32(msg, nentries)) != 0 || 644 (r = sshbuf_putb(msg, keys)) != 0) 645 fatal_fr(r, "compose"); 646 if ((r = sshbuf_put_stringb(e->output, msg)) != 0) 647 fatal_fr(r, "enqueue"); 648 sshbuf_free(msg); 649 sshbuf_free(keys); 650 } 651 652 653 static const char * 654 agent_decode_alg(struct sshkey *key, u_int flags) 655 { 656 if (key->type == KEY_RSA) { 657 if (flags & SSH_AGENT_RSA_SHA2_256) 658 return "rsa-sha2-256"; 659 else if (flags & SSH_AGENT_RSA_SHA2_512) 660 return "rsa-sha2-512"; 661 } else if (key->type == KEY_RSA_CERT) { 662 if (flags & SSH_AGENT_RSA_SHA2_256) 663 return "rsa-sha2-256-cert-v01@openssh.com"; 664 else if (flags & SSH_AGENT_RSA_SHA2_512) 665 return "rsa-sha2-512-cert-v01@openssh.com"; 666 } 667 return NULL; 668 } 669 670 /* 671 * Attempt to parse the contents of a buffer as a SSH publickey userauth 672 * request, checking its contents for consistency and matching the embedded 673 * key against the one that is being used for signing. 674 * Note: does not modify msg buffer. 675 * Optionally extract the username, session ID and/or hostkey from the request. 676 */ 677 static int 678 parse_userauth_request(struct sshbuf *msg, const struct sshkey *expected_key, 679 char **userp, struct sshbuf **sess_idp, struct sshkey **hostkeyp) 680 { 681 struct sshbuf *b = NULL, *sess_id = NULL; 682 char *user = NULL, *service = NULL, *method = NULL, *pkalg = NULL; 683 int r; 684 u_char t, sig_follows; 685 struct sshkey *mkey = NULL, *hostkey = NULL; 686 687 if (userp != NULL) 688 *userp = NULL; 689 if (sess_idp != NULL) 690 *sess_idp = NULL; 691 if (hostkeyp != NULL) 692 *hostkeyp = NULL; 693 if ((b = sshbuf_fromb(msg)) == NULL) 694 fatal_f("sshbuf_fromb"); 695 696 /* SSH userauth request */ 697 if ((r = sshbuf_froms(b, &sess_id)) != 0) 698 goto out; 699 if (sshbuf_len(sess_id) == 0) { 700 r = SSH_ERR_INVALID_FORMAT; 701 goto out; 702 } 703 if ((r = sshbuf_get_u8(b, &t)) != 0 || /* SSH2_MSG_USERAUTH_REQUEST */ 704 (r = sshbuf_get_cstring(b, &user, NULL)) != 0 || /* server user */ 705 (r = sshbuf_get_cstring(b, &service, NULL)) != 0 || /* service */ 706 (r = sshbuf_get_cstring(b, &method, NULL)) != 0 || /* method */ 707 (r = sshbuf_get_u8(b, &sig_follows)) != 0 || /* sig-follows */ 708 (r = sshbuf_get_cstring(b, &pkalg, NULL)) != 0 || /* alg */ 709 (r = sshkey_froms(b, &mkey)) != 0) /* key */ 710 goto out; 711 if (t != SSH2_MSG_USERAUTH_REQUEST || 712 sig_follows != 1 || 713 strcmp(service, "ssh-connection") != 0 || 714 !sshkey_equal(expected_key, mkey) || 715 sshkey_type_from_name(pkalg) != expected_key->type) { 716 r = SSH_ERR_INVALID_FORMAT; 717 goto out; 718 } 719 if (strcmp(method, "publickey-hostbound-v00@openssh.com") == 0) { 720 if ((r = sshkey_froms(b, &hostkey)) != 0) 721 goto out; 722 } else if (strcmp(method, "publickey") != 0) { 723 r = SSH_ERR_INVALID_FORMAT; 724 goto out; 725 } 726 if (sshbuf_len(b) != 0) { 727 r = SSH_ERR_INVALID_FORMAT; 728 goto out; 729 } 730 /* success */ 731 r = 0; 732 debug3_f("well formed userauth"); 733 if (userp != NULL) { 734 *userp = user; 735 user = NULL; 736 } 737 if (sess_idp != NULL) { 738 *sess_idp = sess_id; 739 sess_id = NULL; 740 } 741 if (hostkeyp != NULL) { 742 *hostkeyp = hostkey; 743 hostkey = NULL; 744 } 745 out: 746 sshbuf_free(b); 747 sshbuf_free(sess_id); 748 free(user); 749 free(service); 750 free(method); 751 free(pkalg); 752 sshkey_free(mkey); 753 sshkey_free(hostkey); 754 return r; 755 } 756 757 /* 758 * Attempt to parse the contents of a buffer as a SSHSIG signature request. 759 * Note: does not modify buffer. 760 */ 761 static int 762 parse_sshsig_request(struct sshbuf *msg) 763 { 764 int r; 765 struct sshbuf *b; 766 767 if ((b = sshbuf_fromb(msg)) == NULL) 768 fatal_f("sshbuf_fromb"); 769 770 if ((r = sshbuf_cmp(b, 0, "SSHSIG", 6)) != 0 || 771 (r = sshbuf_consume(b, 6)) != 0 || 772 (r = sshbuf_get_cstring(b, NULL, NULL)) != 0 || /* namespace */ 773 (r = sshbuf_get_string_direct(b, NULL, NULL)) != 0 || /* reserved */ 774 (r = sshbuf_get_cstring(b, NULL, NULL)) != 0 || /* hashalg */ 775 (r = sshbuf_get_string_direct(b, NULL, NULL)) != 0) /* H(msg) */ 776 goto out; 777 if (sshbuf_len(b) != 0) { 778 r = SSH_ERR_INVALID_FORMAT; 779 goto out; 780 } 781 /* success */ 782 r = 0; 783 out: 784 sshbuf_free(b); 785 return r; 786 } 787 788 /* 789 * This function inspects a message to be signed by a FIDO key that has a 790 * web-like application string (i.e. one that does not begin with "ssh:". 791 * It checks that the message is one of those expected for SSH operations 792 * (pubkey userauth, sshsig, CA key signing) to exclude signing challenges 793 * for the web. 794 */ 795 static int 796 check_websafe_message_contents(struct sshkey *key, struct sshbuf *data) 797 { 798 if (parse_userauth_request(data, key, NULL, NULL, NULL) == 0) { 799 debug_f("signed data matches public key userauth request"); 800 return 1; 801 } 802 if (parse_sshsig_request(data) == 0) { 803 debug_f("signed data matches SSHSIG signature request"); 804 return 1; 805 } 806 807 /* XXX check CA signature operation */ 808 809 error("web-origin key attempting to sign non-SSH message"); 810 return 0; 811 } 812 813 static int 814 buf_equal(const struct sshbuf *a, const struct sshbuf *b) 815 { 816 if (sshbuf_ptr(a) == NULL || sshbuf_ptr(b) == NULL) 817 return SSH_ERR_INVALID_ARGUMENT; 818 if (sshbuf_len(a) != sshbuf_len(b)) 819 return SSH_ERR_INVALID_FORMAT; 820 if (timingsafe_bcmp(sshbuf_ptr(a), sshbuf_ptr(b), sshbuf_len(a)) != 0) 821 return SSH_ERR_INVALID_FORMAT; 822 return 0; 823 } 824 825 /* ssh2 only */ 826 static void 827 process_sign_request2(SocketEntry *e) 828 { 829 u_char *signature = NULL; 830 size_t slen = 0; 831 u_int compat = 0, flags; 832 int r, ok = -1, retried = 0; 833 char *fp = NULL, *pin = NULL, *prompt = NULL; 834 char *user = NULL, *sig_dest = NULL; 835 const char *fwd_host = NULL, *dest_host = NULL; 836 struct sshbuf *msg = NULL, *data = NULL, *sid = NULL; 837 struct sshkey *key = NULL, *hostkey = NULL; 838 struct identity *id; 839 struct notifier_ctx *notifier = NULL; 840 841 debug_f("entering"); 842 843 if ((msg = sshbuf_new()) == NULL || (data = sshbuf_new()) == NULL) 844 fatal_f("sshbuf_new failed"); 845 if ((r = sshkey_froms(e->request, &key)) != 0 || 846 (r = sshbuf_get_stringb(e->request, data)) != 0 || 847 (r = sshbuf_get_u32(e->request, &flags)) != 0) { 848 error_fr(r, "parse"); 849 goto send; 850 } 851 852 if ((id = lookup_identity(key)) == NULL) { 853 verbose_f("%s key not found", sshkey_type(key)); 854 goto send; 855 } 856 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT, 857 SSH_FP_DEFAULT)) == NULL) 858 fatal_f("fingerprint failed"); 859 860 if (id->ndest_constraints != 0) { 861 if (e->nsession_ids == 0) { 862 logit_f("refusing use of destination-constrained key " 863 "to sign on unbound connection"); 864 goto send; 865 } 866 if (parse_userauth_request(data, key, &user, &sid, 867 &hostkey) != 0) { 868 logit_f("refusing use of destination-constrained key " 869 "to sign an unidentified signature"); 870 goto send; 871 } 872 /* XXX logspam */ 873 debug_f("user=%s", user); 874 if (identity_permitted(id, e, user, &fwd_host, &dest_host) != 0) 875 goto send; 876 /* XXX display fwd_host/dest_host in askpass UI */ 877 /* 878 * Ensure that the session ID is the most recent one 879 * registered on the socket - it should have been bound by 880 * ssh immediately before userauth. 881 */ 882 if (buf_equal(sid, 883 e->session_ids[e->nsession_ids - 1].sid) != 0) { 884 error_f("unexpected session ID (%zu listed) on " 885 "signature request for target user %s with " 886 "key %s %s", e->nsession_ids, user, 887 sshkey_type(id->key), fp); 888 goto send; 889 } 890 /* 891 * Ensure that the hostkey embedded in the signature matches 892 * the one most recently bound to the socket. An exception is 893 * made for the initial forwarding hop. 894 */ 895 if (e->nsession_ids > 1 && hostkey == NULL) { 896 error_f("refusing use of destination-constrained key: " 897 "no hostkey recorded in signature for forwarded " 898 "connection"); 899 goto send; 900 } 901 if (hostkey != NULL && !sshkey_equal(hostkey, 902 e->session_ids[e->nsession_ids - 1].key)) { 903 error_f("refusing use of destination-constrained key: " 904 "mismatch between hostkey in request and most " 905 "recently bound session"); 906 goto send; 907 } 908 xasprintf(&sig_dest, "public key authentication request for " 909 "user \"%s\" to listed host", user); 910 } 911 if (id->confirm && confirm_key(id, sig_dest) != 0) { 912 verbose_f("user refused key"); 913 goto send; 914 } 915 if (sshkey_is_sk(id->key)) { 916 if (restrict_websafe && 917 strncmp(id->key->sk_application, "ssh:", 4) != 0 && 918 !check_websafe_message_contents(key, data)) { 919 /* error already logged */ 920 goto send; 921 } 922 if (id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD) { 923 notifier = notify_start(0, 924 "Confirm user presence for key %s %s%s%s", 925 sshkey_type(id->key), fp, 926 sig_dest == NULL ? "" : "\n", 927 sig_dest == NULL ? "" : sig_dest); 928 } 929 } 930 retry_pin: 931 if ((r = sshkey_sign(id->key, &signature, &slen, 932 sshbuf_ptr(data), sshbuf_len(data), agent_decode_alg(key, flags), 933 id->sk_provider, pin, compat)) != 0) { 934 debug_fr(r, "sshkey_sign"); 935 if (pin == NULL && !retried && sshkey_is_sk(id->key) && 936 r == SSH_ERR_KEY_WRONG_PASSPHRASE) { 937 notify_complete(notifier, NULL); 938 notifier = NULL; 939 /* XXX include sig_dest */ 940 xasprintf(&prompt, "Enter PIN%sfor %s key %s: ", 941 (id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD) ? 942 " and confirm user presence " : " ", 943 sshkey_type(id->key), fp); 944 pin = read_passphrase(prompt, RP_USE_ASKPASS); 945 retried = 1; 946 goto retry_pin; 947 } 948 error_fr(r, "sshkey_sign"); 949 goto send; 950 } 951 /* Success */ 952 ok = 0; 953 debug_f("good signature"); 954 send: 955 notify_complete(notifier, "User presence confirmed"); 956 957 if (ok == 0) { 958 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 || 959 (r = sshbuf_put_string(msg, signature, slen)) != 0) 960 fatal_fr(r, "compose"); 961 } else if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0) 962 fatal_fr(r, "compose failure"); 963 964 if ((r = sshbuf_put_stringb(e->output, msg)) != 0) 965 fatal_fr(r, "enqueue"); 966 967 sshbuf_free(sid); 968 sshbuf_free(data); 969 sshbuf_free(msg); 970 sshkey_free(key); 971 sshkey_free(hostkey); 972 free(fp); 973 free(signature); 974 free(sig_dest); 975 free(user); 976 free(prompt); 977 if (pin != NULL) 978 freezero(pin, strlen(pin)); 979 } 980 981 /* shared */ 982 static void 983 process_remove_identity(SocketEntry *e) 984 { 985 int r, success = 0; 986 struct sshkey *key = NULL; 987 Identity *id; 988 989 debug2_f("entering"); 990 if ((r = sshkey_froms(e->request, &key)) != 0) { 991 error_fr(r, "parse key"); 992 goto done; 993 } 994 if ((id = lookup_identity(key)) == NULL) { 995 debug_f("key not found"); 996 goto done; 997 } 998 /* identity not visible, cannot be removed */ 999 if (identity_permitted(id, e, NULL, NULL, NULL) != 0) 1000 goto done; /* error already logged */ 1001 /* We have this key, free it. */ 1002 if (idtab->nentries < 1) 1003 fatal_f("internal error: nentries %d", idtab->nentries); 1004 TAILQ_REMOVE(&idtab->idlist, id, next); 1005 free_identity(id); 1006 idtab->nentries--; 1007 success = 1; 1008 done: 1009 sshkey_free(key); 1010 send_status(e, success); 1011 } 1012 1013 static void 1014 process_remove_all_identities(SocketEntry *e) 1015 { 1016 Identity *id; 1017 1018 debug2_f("entering"); 1019 /* Loop over all identities and clear the keys. */ 1020 for (id = TAILQ_FIRST(&idtab->idlist); id; 1021 id = TAILQ_FIRST(&idtab->idlist)) { 1022 TAILQ_REMOVE(&idtab->idlist, id, next); 1023 free_identity(id); 1024 } 1025 1026 /* Mark that there are no identities. */ 1027 idtab->nentries = 0; 1028 1029 /* Send success. */ 1030 send_status(e, 1); 1031 } 1032 1033 /* removes expired keys and returns number of seconds until the next expiry */ 1034 static time_t 1035 reaper(void) 1036 { 1037 time_t deadline = 0, now = monotime(); 1038 Identity *id, *nxt; 1039 1040 for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) { 1041 nxt = TAILQ_NEXT(id, next); 1042 if (id->death == 0) 1043 continue; 1044 if (now >= id->death) { 1045 debug("expiring key '%s'", id->comment); 1046 TAILQ_REMOVE(&idtab->idlist, id, next); 1047 free_identity(id); 1048 idtab->nentries--; 1049 } else 1050 deadline = (deadline == 0) ? id->death : 1051 MINIMUM(deadline, id->death); 1052 } 1053 if (deadline == 0 || deadline <= now) 1054 return 0; 1055 else 1056 return (deadline - now); 1057 } 1058 1059 static int 1060 parse_dest_constraint_hop(struct sshbuf *b, struct dest_constraint_hop *dch) 1061 { 1062 u_char key_is_ca; 1063 size_t elen = 0; 1064 int r; 1065 struct sshkey *k = NULL; 1066 char *fp; 1067 1068 memset(dch, '\0', sizeof(*dch)); 1069 if ((r = sshbuf_get_cstring(b, &dch->user, NULL)) != 0 || 1070 (r = sshbuf_get_cstring(b, &dch->hostname, NULL)) != 0 || 1071 (r = sshbuf_get_string_direct(b, NULL, &elen)) != 0) { 1072 error_fr(r, "parse"); 1073 goto out; 1074 } 1075 if (elen != 0) { 1076 error_f("unsupported extensions (len %zu)", elen); 1077 r = SSH_ERR_FEATURE_UNSUPPORTED; 1078 goto out; 1079 } 1080 if (*dch->hostname == '\0') { 1081 free(dch->hostname); 1082 dch->hostname = NULL; 1083 } 1084 if (*dch->user == '\0') { 1085 free(dch->user); 1086 dch->user = NULL; 1087 } 1088 while (sshbuf_len(b) != 0) { 1089 dch->keys = xrecallocarray(dch->keys, dch->nkeys, 1090 dch->nkeys + 1, sizeof(*dch->keys)); 1091 dch->key_is_ca = xrecallocarray(dch->key_is_ca, dch->nkeys, 1092 dch->nkeys + 1, sizeof(*dch->key_is_ca)); 1093 if ((r = sshkey_froms(b, &k)) != 0 || 1094 (r = sshbuf_get_u8(b, &key_is_ca)) != 0) 1095 goto out; 1096 if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT, 1097 SSH_FP_DEFAULT)) == NULL) 1098 fatal_f("fingerprint failed"); 1099 debug3_f("%s%s%s: adding %skey %s %s", 1100 dch->user == NULL ? "" : dch->user, 1101 dch->user == NULL ? "" : "@", 1102 dch->hostname, key_is_ca ? "CA " : "", sshkey_type(k), fp); 1103 free(fp); 1104 dch->keys[dch->nkeys] = k; 1105 dch->key_is_ca[dch->nkeys] = key_is_ca != 0; 1106 dch->nkeys++; 1107 k = NULL; /* transferred */ 1108 } 1109 /* success */ 1110 r = 0; 1111 out: 1112 sshkey_free(k); 1113 return r; 1114 } 1115 1116 static int 1117 parse_dest_constraint(struct sshbuf *m, struct dest_constraint *dc) 1118 { 1119 struct sshbuf *b = NULL, *frombuf = NULL, *tobuf = NULL; 1120 int r; 1121 size_t elen = 0; 1122 1123 debug3_f("entering"); 1124 1125 memset(dc, '\0', sizeof(*dc)); 1126 if ((r = sshbuf_froms(m, &b)) != 0 || 1127 (r = sshbuf_froms(b, &frombuf)) != 0 || 1128 (r = sshbuf_froms(b, &tobuf)) != 0 || 1129 (r = sshbuf_get_string_direct(b, NULL, &elen)) != 0) { 1130 error_fr(r, "parse"); 1131 goto out; 1132 } 1133 if ((r = parse_dest_constraint_hop(frombuf, &dc->from)) != 0 || 1134 (r = parse_dest_constraint_hop(tobuf, &dc->to)) != 0) 1135 goto out; /* already logged */ 1136 if (elen != 0) { 1137 error_f("unsupported extensions (len %zu)", elen); 1138 r = SSH_ERR_FEATURE_UNSUPPORTED; 1139 goto out; 1140 } 1141 debug2_f("parsed %s (%u keys) > %s%s%s (%u keys)", 1142 dc->from.hostname ? dc->from.hostname : "(ORIGIN)", dc->from.nkeys, 1143 dc->to.user ? dc->to.user : "", dc->to.user ? "@" : "", 1144 dc->to.hostname ? dc->to.hostname : "(ANY)", dc->to.nkeys); 1145 /* check consistency */ 1146 if ((dc->from.hostname == NULL) != (dc->from.nkeys == 0) || 1147 dc->from.user != NULL) { 1148 error_f("inconsistent \"from\" specification"); 1149 r = SSH_ERR_INVALID_FORMAT; 1150 goto out; 1151 } 1152 if (dc->to.hostname == NULL || dc->to.nkeys == 0) { 1153 error_f("incomplete \"to\" specification"); 1154 r = SSH_ERR_INVALID_FORMAT; 1155 goto out; 1156 } 1157 /* success */ 1158 r = 0; 1159 out: 1160 sshbuf_free(b); 1161 sshbuf_free(frombuf); 1162 sshbuf_free(tobuf); 1163 return r; 1164 } 1165 1166 static int 1167 parse_key_constraint_extension(struct sshbuf *m, char **sk_providerp, 1168 struct dest_constraint **dcsp, size_t *ndcsp, int *cert_onlyp, 1169 struct sshkey ***certs, size_t *ncerts) 1170 { 1171 char *ext_name = NULL; 1172 int r; 1173 struct sshbuf *b = NULL; 1174 u_char v; 1175 struct sshkey *k; 1176 1177 if ((r = sshbuf_get_cstring(m, &ext_name, NULL)) != 0) { 1178 error_fr(r, "parse constraint extension"); 1179 goto out; 1180 } 1181 debug_f("constraint ext %s", ext_name); 1182 if (strcmp(ext_name, "sk-provider@openssh.com") == 0) { 1183 if (sk_providerp == NULL) { 1184 error_f("%s not valid here", ext_name); 1185 r = SSH_ERR_INVALID_FORMAT; 1186 goto out; 1187 } 1188 if (*sk_providerp != NULL) { 1189 error_f("%s already set", ext_name); 1190 r = SSH_ERR_INVALID_FORMAT; 1191 goto out; 1192 } 1193 if ((r = sshbuf_get_cstring(m, sk_providerp, NULL)) != 0) { 1194 error_fr(r, "parse %s", ext_name); 1195 goto out; 1196 } 1197 } else if (strcmp(ext_name, 1198 "restrict-destination-v00@openssh.com") == 0) { 1199 if (*dcsp != NULL) { 1200 error_f("%s already set", ext_name); 1201 goto out; 1202 } 1203 if ((r = sshbuf_froms(m, &b)) != 0) { 1204 error_fr(r, "parse %s outer", ext_name); 1205 goto out; 1206 } 1207 while (sshbuf_len(b) != 0) { 1208 if (*ndcsp >= AGENT_MAX_DEST_CONSTRAINTS) { 1209 error_f("too many %s constraints", ext_name); 1210 goto out; 1211 } 1212 *dcsp = xrecallocarray(*dcsp, *ndcsp, *ndcsp + 1, 1213 sizeof(**dcsp)); 1214 if ((r = parse_dest_constraint(b, 1215 *dcsp + (*ndcsp)++)) != 0) 1216 goto out; /* error already logged */ 1217 } 1218 } else if (strcmp(ext_name, 1219 "associated-certs-v00@openssh.com") == 0) { 1220 if (certs == NULL || ncerts == NULL || cert_onlyp == NULL) { 1221 error_f("%s not valid here", ext_name); 1222 r = SSH_ERR_INVALID_FORMAT; 1223 goto out; 1224 } 1225 if (*certs != NULL) { 1226 error_f("%s already set", ext_name); 1227 goto out; 1228 } 1229 if ((r = sshbuf_get_u8(m, &v)) != 0 || 1230 (r = sshbuf_froms(m, &b)) != 0) { 1231 error_fr(r, "parse %s", ext_name); 1232 goto out; 1233 } 1234 *cert_onlyp = v != 0; 1235 while (sshbuf_len(b) != 0) { 1236 if (*ncerts >= AGENT_MAX_EXT_CERTS) { 1237 error_f("too many %s constraints", ext_name); 1238 goto out; 1239 } 1240 *certs = xrecallocarray(*certs, *ncerts, *ncerts + 1, 1241 sizeof(**certs)); 1242 if ((r = sshkey_froms(b, &k)) != 0) { 1243 error_fr(r, "parse key"); 1244 goto out; 1245 } 1246 (*certs)[(*ncerts)++] = k; 1247 } 1248 } else { 1249 error_f("unsupported constraint \"%s\"", ext_name); 1250 r = SSH_ERR_FEATURE_UNSUPPORTED; 1251 goto out; 1252 } 1253 /* success */ 1254 r = 0; 1255 out: 1256 free(ext_name); 1257 sshbuf_free(b); 1258 return r; 1259 } 1260 1261 static int 1262 parse_key_constraints(struct sshbuf *m, struct sshkey *k, time_t *deathp, 1263 u_int *secondsp, int *confirmp, char **sk_providerp, 1264 struct dest_constraint **dcsp, size_t *ndcsp, 1265 int *cert_onlyp, size_t *ncerts, struct sshkey ***certs) 1266 { 1267 u_char ctype; 1268 int r; 1269 u_int seconds, maxsign = 0; 1270 1271 while (sshbuf_len(m)) { 1272 if ((r = sshbuf_get_u8(m, &ctype)) != 0) { 1273 error_fr(r, "parse constraint type"); 1274 goto out; 1275 } 1276 switch (ctype) { 1277 case SSH_AGENT_CONSTRAIN_LIFETIME: 1278 if (*deathp != 0) { 1279 error_f("lifetime already set"); 1280 r = SSH_ERR_INVALID_FORMAT; 1281 goto out; 1282 } 1283 if ((r = sshbuf_get_u32(m, &seconds)) != 0) { 1284 error_fr(r, "parse lifetime constraint"); 1285 goto out; 1286 } 1287 *deathp = monotime() + seconds; 1288 *secondsp = seconds; 1289 break; 1290 case SSH_AGENT_CONSTRAIN_CONFIRM: 1291 if (*confirmp != 0) { 1292 error_f("confirm already set"); 1293 r = SSH_ERR_INVALID_FORMAT; 1294 goto out; 1295 } 1296 *confirmp = 1; 1297 break; 1298 case SSH_AGENT_CONSTRAIN_MAXSIGN: 1299 if (k == NULL) { 1300 error_f("maxsign not valid here"); 1301 r = SSH_ERR_INVALID_FORMAT; 1302 goto out; 1303 } 1304 if (maxsign != 0) { 1305 error_f("maxsign already set"); 1306 r = SSH_ERR_INVALID_FORMAT; 1307 goto out; 1308 } 1309 if ((r = sshbuf_get_u32(m, &maxsign)) != 0) { 1310 error_fr(r, "parse maxsign constraint"); 1311 goto out; 1312 } 1313 if ((r = sshkey_enable_maxsign(k, maxsign)) != 0) { 1314 error_fr(r, "enable maxsign"); 1315 goto out; 1316 } 1317 break; 1318 case SSH_AGENT_CONSTRAIN_EXTENSION: 1319 if ((r = parse_key_constraint_extension(m, 1320 sk_providerp, dcsp, ndcsp, 1321 cert_onlyp, certs, ncerts)) != 0) 1322 goto out; /* error already logged */ 1323 break; 1324 default: 1325 error_f("Unknown constraint %d", ctype); 1326 r = SSH_ERR_FEATURE_UNSUPPORTED; 1327 goto out; 1328 } 1329 } 1330 /* success */ 1331 r = 0; 1332 out: 1333 return r; 1334 } 1335 1336 static void 1337 process_add_identity(SocketEntry *e) 1338 { 1339 Identity *id; 1340 int success = 0, confirm = 0; 1341 char *fp, *comment = NULL, *sk_provider = NULL; 1342 char canonical_provider[PATH_MAX]; 1343 time_t death = 0; 1344 u_int seconds = 0; 1345 struct dest_constraint *dest_constraints = NULL; 1346 size_t ndest_constraints = 0; 1347 struct sshkey *k = NULL; 1348 int r = SSH_ERR_INTERNAL_ERROR; 1349 1350 debug2_f("entering"); 1351 if ((r = sshkey_private_deserialize(e->request, &k)) != 0 || 1352 k == NULL || 1353 (r = sshbuf_get_cstring(e->request, &comment, NULL)) != 0) { 1354 error_fr(r, "parse"); 1355 goto out; 1356 } 1357 if (parse_key_constraints(e->request, k, &death, &seconds, &confirm, 1358 &sk_provider, &dest_constraints, &ndest_constraints, 1359 NULL, NULL, NULL) != 0) { 1360 error_f("failed to parse constraints"); 1361 sshbuf_reset(e->request); 1362 goto out; 1363 } 1364 dump_dest_constraints(__func__, dest_constraints, ndest_constraints); 1365 1366 if (sk_provider != NULL) { 1367 if (!sshkey_is_sk(k)) { 1368 error("Cannot add provider: %s is not an " 1369 "authenticator-hosted key", sshkey_type(k)); 1370 goto out; 1371 } 1372 if (strcasecmp(sk_provider, "internal") == 0) { 1373 debug_f("internal provider"); 1374 } else { 1375 if (socket_is_remote(e) && !remote_add_provider) { 1376 verbose("failed add of SK provider \"%.100s\": " 1377 "remote addition of providers is disabled", 1378 sk_provider); 1379 goto out; 1380 } 1381 if (realpath(sk_provider, canonical_provider) == NULL) { 1382 verbose("failed provider \"%.100s\": " 1383 "realpath: %s", sk_provider, 1384 strerror(errno)); 1385 goto out; 1386 } 1387 free(sk_provider); 1388 sk_provider = xstrdup(canonical_provider); 1389 if (match_pattern_list(sk_provider, 1390 allowed_providers, 0) != 1) { 1391 error("Refusing add key: " 1392 "provider %s not allowed", sk_provider); 1393 goto out; 1394 } 1395 } 1396 } 1397 if ((r = sshkey_shield_private(k)) != 0) { 1398 error_fr(r, "shield private"); 1399 goto out; 1400 } 1401 if (lifetime && !death) 1402 death = monotime() + lifetime; 1403 if ((id = lookup_identity(k)) == NULL) { 1404 id = xcalloc(1, sizeof(Identity)); 1405 TAILQ_INSERT_TAIL(&idtab->idlist, id, next); 1406 /* Increment the number of identities. */ 1407 idtab->nentries++; 1408 } else { 1409 /* identity not visible, do not update */ 1410 if (identity_permitted(id, e, NULL, NULL, NULL) != 0) 1411 goto out; /* error already logged */ 1412 /* key state might have been updated */ 1413 sshkey_free(id->key); 1414 free(id->comment); 1415 free(id->sk_provider); 1416 free_dest_constraints(id->dest_constraints, 1417 id->ndest_constraints); 1418 } 1419 /* success */ 1420 id->key = k; 1421 id->comment = comment; 1422 id->death = death; 1423 id->confirm = confirm; 1424 id->sk_provider = sk_provider; 1425 id->dest_constraints = dest_constraints; 1426 id->ndest_constraints = ndest_constraints; 1427 1428 if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT, 1429 SSH_FP_DEFAULT)) == NULL) 1430 fatal_f("sshkey_fingerprint failed"); 1431 debug_f("add %s %s \"%.100s\" (life: %u) (confirm: %u) " 1432 "(provider: %s) (destination constraints: %zu)", 1433 sshkey_ssh_name(k), fp, comment, seconds, confirm, 1434 sk_provider == NULL ? "none" : sk_provider, ndest_constraints); 1435 free(fp); 1436 /* transferred */ 1437 k = NULL; 1438 comment = NULL; 1439 sk_provider = NULL; 1440 dest_constraints = NULL; 1441 ndest_constraints = 0; 1442 success = 1; 1443 out: 1444 free(sk_provider); 1445 free(comment); 1446 sshkey_free(k); 1447 free_dest_constraints(dest_constraints, ndest_constraints); 1448 send_status(e, success); 1449 } 1450 1451 /* XXX todo: encrypt sensitive data with passphrase */ 1452 static void 1453 process_lock_agent(SocketEntry *e, int lock) 1454 { 1455 int r, success = 0, delay; 1456 char *passwd; 1457 u_char passwdhash[LOCK_SIZE]; 1458 static u_int fail_count = 0; 1459 size_t pwlen; 1460 1461 debug2_f("entering"); 1462 /* 1463 * This is deliberately fatal: the user has requested that we lock, 1464 * but we can't parse their request properly. The only safe thing to 1465 * do is abort. 1466 */ 1467 if ((r = sshbuf_get_cstring(e->request, &passwd, &pwlen)) != 0) 1468 fatal_fr(r, "parse"); 1469 if (pwlen == 0) { 1470 debug("empty password not supported"); 1471 } else if (locked && !lock) { 1472 if (bcrypt_pbkdf(passwd, pwlen, (uint8_t *)lock_salt, sizeof(lock_salt), 1473 (uint8_t *)passwdhash, sizeof(passwdhash), LOCK_ROUNDS) < 0) 1474 fatal("bcrypt_pbkdf"); 1475 if (timingsafe_bcmp(passwdhash, lock_pwhash, LOCK_SIZE) == 0) { 1476 debug("agent unlocked"); 1477 locked = 0; 1478 fail_count = 0; 1479 explicit_bzero(lock_pwhash, sizeof(lock_pwhash)); 1480 success = 1; 1481 } else { 1482 /* delay in 0.1s increments up to 10s */ 1483 if (fail_count < 100) 1484 fail_count++; 1485 delay = 100000 * fail_count; 1486 debug("unlock failed, delaying %0.1lf seconds", 1487 (double)delay/1000000); 1488 usleep(delay); 1489 } 1490 explicit_bzero(passwdhash, sizeof(passwdhash)); 1491 } else if (!locked && lock) { 1492 debug("agent locked"); 1493 locked = 1; 1494 arc4random_buf(lock_salt, sizeof(lock_salt)); 1495 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt), 1496 lock_pwhash, sizeof(lock_pwhash), LOCK_ROUNDS) < 0) 1497 fatal("bcrypt_pbkdf"); 1498 success = 1; 1499 } 1500 freezero(passwd, pwlen); 1501 send_status(e, success); 1502 } 1503 1504 static void 1505 no_identities(SocketEntry *e) 1506 { 1507 struct sshbuf *msg; 1508 int r; 1509 1510 if ((msg = sshbuf_new()) == NULL) 1511 fatal_f("sshbuf_new failed"); 1512 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 || 1513 (r = sshbuf_put_u32(msg, 0)) != 0 || 1514 (r = sshbuf_put_stringb(e->output, msg)) != 0) 1515 fatal_fr(r, "compose"); 1516 sshbuf_free(msg); 1517 } 1518 1519 /* Add an identity to idlist; takes ownership of 'key' and 'comment' */ 1520 static void 1521 add_p11_identity(struct sshkey *key, char *comment, const char *provider, 1522 time_t death, int confirm, struct dest_constraint *dest_constraints, 1523 size_t ndest_constraints) 1524 { 1525 Identity *id; 1526 1527 if (lookup_identity(key) != NULL) { 1528 sshkey_free(key); 1529 free(comment); 1530 return; 1531 } 1532 id = xcalloc(1, sizeof(Identity)); 1533 id->key = key; 1534 id->comment = comment; 1535 id->provider = xstrdup(provider); 1536 id->death = death; 1537 id->confirm = confirm; 1538 id->dest_constraints = dup_dest_constraints(dest_constraints, 1539 ndest_constraints); 1540 id->ndest_constraints = ndest_constraints; 1541 TAILQ_INSERT_TAIL(&idtab->idlist, id, next); 1542 idtab->nentries++; 1543 } 1544 1545 #ifdef ENABLE_PKCS11 1546 static void 1547 process_add_smartcard_key(SocketEntry *e) 1548 { 1549 char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX]; 1550 char **comments = NULL; 1551 int r, i, count = 0, success = 0, confirm = 0; 1552 u_int seconds = 0; 1553 time_t death = 0; 1554 struct sshkey **keys = NULL, *k; 1555 struct dest_constraint *dest_constraints = NULL; 1556 size_t j, ndest_constraints = 0, ncerts = 0; 1557 struct sshkey **certs = NULL; 1558 int cert_only = 0; 1559 1560 debug2_f("entering"); 1561 if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 || 1562 (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) { 1563 error_fr(r, "parse"); 1564 goto send; 1565 } 1566 if (parse_key_constraints(e->request, NULL, &death, &seconds, &confirm, 1567 NULL, &dest_constraints, &ndest_constraints, &cert_only, 1568 &ncerts, &certs) != 0) { 1569 error_f("failed to parse constraints"); 1570 goto send; 1571 } 1572 dump_dest_constraints(__func__, dest_constraints, ndest_constraints); 1573 if (socket_is_remote(e) && !remote_add_provider) { 1574 verbose("failed PKCS#11 add of \"%.100s\": remote addition of " 1575 "providers is disabled", provider); 1576 goto send; 1577 } 1578 if (realpath(provider, canonical_provider) == NULL) { 1579 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s", 1580 provider, strerror(errno)); 1581 goto send; 1582 } 1583 if (match_pattern_list(canonical_provider, allowed_providers, 0) != 1) { 1584 verbose("refusing PKCS#11 add of \"%.100s\": " 1585 "provider not allowed", canonical_provider); 1586 goto send; 1587 } 1588 debug_f("add %.100s", canonical_provider); 1589 if (lifetime && !death) 1590 death = monotime() + lifetime; 1591 1592 count = pkcs11_add_provider(canonical_provider, pin, &keys, &comments); 1593 for (i = 0; i < count; i++) { 1594 if (comments[i] == NULL || comments[i][0] == '\0') { 1595 free(comments[i]); 1596 comments[i] = xstrdup(canonical_provider); 1597 } 1598 for (j = 0; j < ncerts; j++) { 1599 if (!sshkey_is_cert(certs[j])) 1600 continue; 1601 if (!sshkey_equal_public(keys[i], certs[j])) 1602 continue; 1603 if (pkcs11_make_cert(keys[i], certs[j], &k) != 0) 1604 continue; 1605 add_p11_identity(k, xstrdup(comments[i]), 1606 canonical_provider, death, confirm, 1607 dest_constraints, ndest_constraints); 1608 success = 1; 1609 } 1610 if (!cert_only && lookup_identity(keys[i]) == NULL) { 1611 add_p11_identity(keys[i], comments[i], 1612 canonical_provider, death, confirm, 1613 dest_constraints, ndest_constraints); 1614 keys[i] = NULL; /* transferred */ 1615 comments[i] = NULL; /* transferred */ 1616 success = 1; 1617 } 1618 /* XXX update constraints for existing keys */ 1619 sshkey_free(keys[i]); 1620 free(comments[i]); 1621 } 1622 send: 1623 free(pin); 1624 free(provider); 1625 free(keys); 1626 free(comments); 1627 free_dest_constraints(dest_constraints, ndest_constraints); 1628 for (j = 0; j < ncerts; j++) 1629 sshkey_free(certs[j]); 1630 free(certs); 1631 send_status(e, success); 1632 } 1633 1634 static void 1635 process_remove_smartcard_key(SocketEntry *e) 1636 { 1637 char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX]; 1638 int r, success = 0; 1639 Identity *id, *nxt; 1640 1641 debug2_f("entering"); 1642 if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 || 1643 (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) { 1644 error_fr(r, "parse"); 1645 goto send; 1646 } 1647 free(pin); 1648 1649 if (realpath(provider, canonical_provider) == NULL) { 1650 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s", 1651 provider, strerror(errno)); 1652 goto send; 1653 } 1654 1655 debug_f("remove %.100s", canonical_provider); 1656 for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) { 1657 nxt = TAILQ_NEXT(id, next); 1658 /* Skip file--based keys */ 1659 if (id->provider == NULL) 1660 continue; 1661 if (!strcmp(canonical_provider, id->provider)) { 1662 TAILQ_REMOVE(&idtab->idlist, id, next); 1663 free_identity(id); 1664 idtab->nentries--; 1665 } 1666 } 1667 if (pkcs11_del_provider(canonical_provider) == 0) 1668 success = 1; 1669 else 1670 error_f("pkcs11_del_provider failed"); 1671 send: 1672 free(provider); 1673 send_status(e, success); 1674 } 1675 #endif /* ENABLE_PKCS11 */ 1676 1677 static int 1678 process_ext_session_bind(SocketEntry *e) 1679 { 1680 int r, sid_match, key_match; 1681 struct sshkey *key = NULL; 1682 struct sshbuf *sid = NULL, *sig = NULL; 1683 char *fp = NULL; 1684 size_t i; 1685 u_char fwd = 0; 1686 1687 debug2_f("entering"); 1688 e->session_bind_attempted = 1; 1689 if ((r = sshkey_froms(e->request, &key)) != 0 || 1690 (r = sshbuf_froms(e->request, &sid)) != 0 || 1691 (r = sshbuf_froms(e->request, &sig)) != 0 || 1692 (r = sshbuf_get_u8(e->request, &fwd)) != 0) { 1693 error_fr(r, "parse"); 1694 goto out; 1695 } 1696 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT, 1697 SSH_FP_DEFAULT)) == NULL) 1698 fatal_f("fingerprint failed"); 1699 /* check signature with hostkey on session ID */ 1700 if ((r = sshkey_verify(key, sshbuf_ptr(sig), sshbuf_len(sig), 1701 sshbuf_ptr(sid), sshbuf_len(sid), NULL, 0, NULL)) != 0) { 1702 error_fr(r, "sshkey_verify for %s %s", sshkey_type(key), fp); 1703 goto out; 1704 } 1705 /* check whether sid/key already recorded */ 1706 for (i = 0; i < e->nsession_ids; i++) { 1707 if (!e->session_ids[i].forwarded) { 1708 error_f("attempt to bind session ID to socket " 1709 "previously bound for authentication attempt"); 1710 r = -1; 1711 goto out; 1712 } 1713 sid_match = buf_equal(sid, e->session_ids[i].sid) == 0; 1714 key_match = sshkey_equal(key, e->session_ids[i].key); 1715 if (sid_match && key_match) { 1716 debug_f("session ID already recorded for %s %s", 1717 sshkey_type(key), fp); 1718 r = 0; 1719 goto out; 1720 } else if (sid_match) { 1721 error_f("session ID recorded against different key " 1722 "for %s %s", sshkey_type(key), fp); 1723 r = -1; 1724 goto out; 1725 } 1726 /* 1727 * new sid with previously-seen key can happen, e.g. multiple 1728 * connections to the same host. 1729 */ 1730 } 1731 /* record new key/sid */ 1732 if (e->nsession_ids >= AGENT_MAX_SESSION_IDS) { 1733 error_f("too many session IDs recorded"); 1734 goto out; 1735 } 1736 e->session_ids = xrecallocarray(e->session_ids, e->nsession_ids, 1737 e->nsession_ids + 1, sizeof(*e->session_ids)); 1738 i = e->nsession_ids++; 1739 debug_f("recorded %s %s (slot %zu of %d)", sshkey_type(key), fp, i, 1740 AGENT_MAX_SESSION_IDS); 1741 e->session_ids[i].key = key; 1742 e->session_ids[i].forwarded = fwd != 0; 1743 key = NULL; /* transferred */ 1744 /* can't transfer sid; it's refcounted and scoped to request's life */ 1745 if ((e->session_ids[i].sid = sshbuf_new()) == NULL) 1746 fatal_f("sshbuf_new"); 1747 if ((r = sshbuf_putb(e->session_ids[i].sid, sid)) != 0) 1748 fatal_fr(r, "sshbuf_putb session ID"); 1749 /* success */ 1750 r = 0; 1751 out: 1752 free(fp); 1753 sshkey_free(key); 1754 sshbuf_free(sid); 1755 sshbuf_free(sig); 1756 return r == 0 ? 1 : 0; 1757 } 1758 1759 static void 1760 process_extension(SocketEntry *e) 1761 { 1762 int r, success = 0; 1763 char *name; 1764 1765 debug2_f("entering"); 1766 if ((r = sshbuf_get_cstring(e->request, &name, NULL)) != 0) { 1767 error_fr(r, "parse"); 1768 goto send; 1769 } 1770 if (strcmp(name, "session-bind@openssh.com") == 0) 1771 success = process_ext_session_bind(e); 1772 else 1773 debug_f("unsupported extension \"%s\"", name); 1774 free(name); 1775 send: 1776 send_status(e, success); 1777 } 1778 /* 1779 * dispatch incoming message. 1780 * returns 1 on success, 0 for incomplete messages or -1 on error. 1781 */ 1782 static int 1783 process_message(u_int socknum) 1784 { 1785 u_int msg_len; 1786 u_char type; 1787 const u_char *cp; 1788 int r; 1789 SocketEntry *e; 1790 1791 if (socknum >= sockets_alloc) 1792 fatal_f("sock %u >= allocated %u", socknum, sockets_alloc); 1793 e = &sockets[socknum]; 1794 1795 if (sshbuf_len(e->input) < 5) 1796 return 0; /* Incomplete message header. */ 1797 cp = sshbuf_ptr(e->input); 1798 msg_len = PEEK_U32(cp); 1799 if (msg_len > AGENT_MAX_LEN) { 1800 debug_f("socket %u (fd=%d) message too long %u > %u", 1801 socknum, e->fd, msg_len, AGENT_MAX_LEN); 1802 return -1; 1803 } 1804 if (sshbuf_len(e->input) < msg_len + 4) 1805 return 0; /* Incomplete message body. */ 1806 1807 /* move the current input to e->request */ 1808 sshbuf_reset(e->request); 1809 if ((r = sshbuf_get_stringb(e->input, e->request)) != 0 || 1810 (r = sshbuf_get_u8(e->request, &type)) != 0) { 1811 if (r == SSH_ERR_MESSAGE_INCOMPLETE || 1812 r == SSH_ERR_STRING_TOO_LARGE) { 1813 error_fr(r, "parse"); 1814 return -1; 1815 } 1816 fatal_fr(r, "parse"); 1817 } 1818 1819 debug_f("socket %u (fd=%d) type %d", socknum, e->fd, type); 1820 1821 /* check whether agent is locked */ 1822 if (locked && type != SSH_AGENTC_UNLOCK) { 1823 sshbuf_reset(e->request); 1824 switch (type) { 1825 case SSH2_AGENTC_REQUEST_IDENTITIES: 1826 /* send empty lists */ 1827 no_identities(e); 1828 break; 1829 default: 1830 /* send a fail message for all other request types */ 1831 send_status(e, 0); 1832 } 1833 return 1; 1834 } 1835 1836 switch (type) { 1837 case SSH_AGENTC_LOCK: 1838 case SSH_AGENTC_UNLOCK: 1839 process_lock_agent(e, type == SSH_AGENTC_LOCK); 1840 break; 1841 case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES: 1842 process_remove_all_identities(e); /* safe for !WITH_SSH1 */ 1843 break; 1844 /* ssh2 */ 1845 case SSH2_AGENTC_SIGN_REQUEST: 1846 process_sign_request2(e); 1847 break; 1848 case SSH2_AGENTC_REQUEST_IDENTITIES: 1849 process_request_identities(e); 1850 break; 1851 case SSH2_AGENTC_ADD_IDENTITY: 1852 case SSH2_AGENTC_ADD_ID_CONSTRAINED: 1853 process_add_identity(e); 1854 break; 1855 case SSH2_AGENTC_REMOVE_IDENTITY: 1856 process_remove_identity(e); 1857 break; 1858 case SSH2_AGENTC_REMOVE_ALL_IDENTITIES: 1859 process_remove_all_identities(e); 1860 break; 1861 #ifdef ENABLE_PKCS11 1862 case SSH_AGENTC_ADD_SMARTCARD_KEY: 1863 case SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED: 1864 process_add_smartcard_key(e); 1865 break; 1866 case SSH_AGENTC_REMOVE_SMARTCARD_KEY: 1867 process_remove_smartcard_key(e); 1868 break; 1869 #endif /* ENABLE_PKCS11 */ 1870 case SSH_AGENTC_EXTENSION: 1871 process_extension(e); 1872 break; 1873 default: 1874 /* Unknown message. Respond with failure. */ 1875 error("Unknown message %d", type); 1876 sshbuf_reset(e->request); 1877 send_status(e, 0); 1878 break; 1879 } 1880 return 1; 1881 } 1882 1883 static void 1884 new_socket(sock_type type, int fd) 1885 { 1886 u_int i, old_alloc, new_alloc; 1887 1888 debug_f("type = %s", type == AUTH_CONNECTION ? "CONNECTION" : 1889 (type == AUTH_SOCKET ? "SOCKET" : "UNKNOWN")); 1890 set_nonblock(fd); 1891 1892 if (fd > max_fd) 1893 max_fd = fd; 1894 1895 for (i = 0; i < sockets_alloc; i++) 1896 if (sockets[i].type == AUTH_UNUSED) { 1897 sockets[i].fd = fd; 1898 if ((sockets[i].input = sshbuf_new()) == NULL || 1899 (sockets[i].output = sshbuf_new()) == NULL || 1900 (sockets[i].request = sshbuf_new()) == NULL) 1901 fatal_f("sshbuf_new failed"); 1902 sockets[i].type = type; 1903 return; 1904 } 1905 old_alloc = sockets_alloc; 1906 new_alloc = sockets_alloc + 10; 1907 sockets = xrecallocarray(sockets, old_alloc, new_alloc, 1908 sizeof(sockets[0])); 1909 for (i = old_alloc; i < new_alloc; i++) 1910 sockets[i].type = AUTH_UNUSED; 1911 sockets_alloc = new_alloc; 1912 sockets[old_alloc].fd = fd; 1913 if ((sockets[old_alloc].input = sshbuf_new()) == NULL || 1914 (sockets[old_alloc].output = sshbuf_new()) == NULL || 1915 (sockets[old_alloc].request = sshbuf_new()) == NULL) 1916 fatal_f("sshbuf_new failed"); 1917 sockets[old_alloc].type = type; 1918 } 1919 1920 static int 1921 handle_socket_read(u_int socknum) 1922 { 1923 struct sockaddr_un sunaddr; 1924 socklen_t slen; 1925 uid_t euid; 1926 gid_t egid; 1927 int fd; 1928 1929 slen = sizeof(sunaddr); 1930 fd = accept(sockets[socknum].fd, (struct sockaddr *)&sunaddr, &slen); 1931 if (fd == -1) { 1932 error("accept from AUTH_SOCKET: %s", strerror(errno)); 1933 return -1; 1934 } 1935 if (getpeereid(fd, &euid, &egid) == -1) { 1936 error("getpeereid %d failed: %s", fd, strerror(errno)); 1937 close(fd); 1938 return -1; 1939 } 1940 if ((euid != 0) && (getuid() != euid)) { 1941 error("uid mismatch: peer euid %u != uid %u", 1942 (u_int) euid, (u_int) getuid()); 1943 close(fd); 1944 return -1; 1945 } 1946 new_socket(AUTH_CONNECTION, fd); 1947 return 0; 1948 } 1949 1950 static int 1951 handle_conn_read(u_int socknum) 1952 { 1953 char buf[AGENT_RBUF_LEN]; 1954 ssize_t len; 1955 int r; 1956 1957 if ((len = read(sockets[socknum].fd, buf, sizeof(buf))) <= 0) { 1958 if (len == -1) { 1959 if (errno == EAGAIN || errno == EINTR) 1960 return 0; 1961 error_f("read error on socket %u (fd %d): %s", 1962 socknum, sockets[socknum].fd, strerror(errno)); 1963 } 1964 return -1; 1965 } 1966 if ((r = sshbuf_put(sockets[socknum].input, buf, len)) != 0) 1967 fatal_fr(r, "compose"); 1968 explicit_bzero(buf, sizeof(buf)); 1969 for (;;) { 1970 if ((r = process_message(socknum)) == -1) 1971 return -1; 1972 else if (r == 0) 1973 break; 1974 } 1975 return 0; 1976 } 1977 1978 static int 1979 handle_conn_write(u_int socknum) 1980 { 1981 ssize_t len; 1982 int r; 1983 1984 if (sshbuf_len(sockets[socknum].output) == 0) 1985 return 0; /* shouldn't happen */ 1986 if ((len = write(sockets[socknum].fd, 1987 sshbuf_ptr(sockets[socknum].output), 1988 sshbuf_len(sockets[socknum].output))) <= 0) { 1989 if (len == -1) { 1990 if (errno == EAGAIN || errno == EINTR) 1991 return 0; 1992 error_f("read error on socket %u (fd %d): %s", 1993 socknum, sockets[socknum].fd, strerror(errno)); 1994 } 1995 return -1; 1996 } 1997 if ((r = sshbuf_consume(sockets[socknum].output, len)) != 0) 1998 fatal_fr(r, "consume"); 1999 return 0; 2000 } 2001 2002 static void 2003 after_poll(struct pollfd *pfd, size_t npfd, u_int maxfds) 2004 { 2005 size_t i; 2006 u_int socknum, activefds = npfd; 2007 2008 for (i = 0; i < npfd; i++) { 2009 if (pfd[i].revents == 0) 2010 continue; 2011 /* Find sockets entry */ 2012 for (socknum = 0; socknum < sockets_alloc; socknum++) { 2013 if (sockets[socknum].type != AUTH_SOCKET && 2014 sockets[socknum].type != AUTH_CONNECTION) 2015 continue; 2016 if (pfd[i].fd == sockets[socknum].fd) 2017 break; 2018 } 2019 if (socknum >= sockets_alloc) { 2020 error_f("no socket for fd %d", pfd[i].fd); 2021 continue; 2022 } 2023 /* Process events */ 2024 switch (sockets[socknum].type) { 2025 case AUTH_SOCKET: 2026 if ((pfd[i].revents & (POLLIN|POLLERR)) == 0) 2027 break; 2028 if (npfd > maxfds) { 2029 debug3("out of fds (active %u >= limit %u); " 2030 "skipping accept", activefds, maxfds); 2031 break; 2032 } 2033 if (handle_socket_read(socknum) == 0) 2034 activefds++; 2035 break; 2036 case AUTH_CONNECTION: 2037 if ((pfd[i].revents & (POLLIN|POLLHUP|POLLERR)) != 0 && 2038 handle_conn_read(socknum) != 0) 2039 goto close_sock; 2040 if ((pfd[i].revents & (POLLOUT|POLLHUP)) != 0 && 2041 handle_conn_write(socknum) != 0) { 2042 close_sock: 2043 if (activefds == 0) 2044 fatal("activefds == 0 at close_sock"); 2045 close_socket(&sockets[socknum]); 2046 activefds--; 2047 break; 2048 } 2049 break; 2050 default: 2051 break; 2052 } 2053 } 2054 } 2055 2056 static int 2057 prepare_poll(struct pollfd **pfdp, size_t *npfdp, int *timeoutp, u_int maxfds) 2058 { 2059 struct pollfd *pfd = *pfdp; 2060 size_t i, j, npfd = 0; 2061 time_t deadline; 2062 int r; 2063 2064 /* Count active sockets */ 2065 for (i = 0; i < sockets_alloc; i++) { 2066 switch (sockets[i].type) { 2067 case AUTH_SOCKET: 2068 case AUTH_CONNECTION: 2069 npfd++; 2070 break; 2071 case AUTH_UNUSED: 2072 break; 2073 default: 2074 fatal("Unknown socket type %d", sockets[i].type); 2075 break; 2076 } 2077 } 2078 if (npfd != *npfdp && 2079 (pfd = recallocarray(pfd, *npfdp, npfd, sizeof(*pfd))) == NULL) 2080 fatal_f("recallocarray failed"); 2081 *pfdp = pfd; 2082 *npfdp = npfd; 2083 2084 for (i = j = 0; i < sockets_alloc; i++) { 2085 switch (sockets[i].type) { 2086 case AUTH_SOCKET: 2087 if (npfd > maxfds) { 2088 debug3("out of fds (active %zu >= limit %u); " 2089 "skipping arming listener", npfd, maxfds); 2090 break; 2091 } 2092 pfd[j].fd = sockets[i].fd; 2093 pfd[j].revents = 0; 2094 pfd[j].events = POLLIN; 2095 j++; 2096 break; 2097 case AUTH_CONNECTION: 2098 pfd[j].fd = sockets[i].fd; 2099 pfd[j].revents = 0; 2100 /* 2101 * Only prepare to read if we can handle a full-size 2102 * input read buffer and enqueue a max size reply.. 2103 */ 2104 if ((r = sshbuf_check_reserve(sockets[i].input, 2105 AGENT_RBUF_LEN)) == 0 && 2106 (r = sshbuf_check_reserve(sockets[i].output, 2107 AGENT_MAX_LEN)) == 0) 2108 pfd[j].events = POLLIN; 2109 else if (r != SSH_ERR_NO_BUFFER_SPACE) 2110 fatal_fr(r, "reserve"); 2111 if (sshbuf_len(sockets[i].output) > 0) 2112 pfd[j].events |= POLLOUT; 2113 j++; 2114 break; 2115 default: 2116 break; 2117 } 2118 } 2119 deadline = reaper(); 2120 if (parent_alive_interval != 0) 2121 deadline = (deadline == 0) ? parent_alive_interval : 2122 MINIMUM(deadline, parent_alive_interval); 2123 if (deadline == 0) { 2124 *timeoutp = -1; /* INFTIM */ 2125 } else { 2126 if (deadline > INT_MAX / 1000) 2127 *timeoutp = INT_MAX / 1000; 2128 else 2129 *timeoutp = deadline * 1000; 2130 } 2131 return (1); 2132 } 2133 2134 static void 2135 cleanup_socket(void) 2136 { 2137 if (cleanup_pid != 0 && getpid() != cleanup_pid) 2138 return; 2139 debug_f("cleanup"); 2140 if (socket_name[0]) 2141 unlink(socket_name); 2142 if (socket_dir[0]) 2143 rmdir(socket_dir); 2144 } 2145 2146 void 2147 cleanup_exit(int i) 2148 { 2149 cleanup_socket(); 2150 _exit(i); 2151 } 2152 2153 /*ARGSUSED*/ 2154 __dead static void 2155 cleanup_handler(int sig) 2156 { 2157 cleanup_socket(); 2158 #ifdef ENABLE_PKCS11 2159 pkcs11_terminate(); 2160 #endif 2161 _exit(2); 2162 } 2163 2164 static void 2165 check_parent_exists(void) 2166 { 2167 /* 2168 * If our parent has exited then getppid() will return (pid_t)1, 2169 * so testing for that should be safe. 2170 */ 2171 if (parent_pid != -1 && getppid() != parent_pid) { 2172 /* printf("Parent has died - Authentication agent exiting.\n"); */ 2173 cleanup_socket(); 2174 _exit(2); 2175 } 2176 } 2177 2178 __dead static void 2179 usage(void) 2180 { 2181 fprintf(stderr, 2182 "usage: ssh-agent [-c | -s] [-Dd] [-a bind_address] [-E fingerprint_hash]\n" 2183 " [-O option] [-P allowed_providers] [-t life]\n" 2184 " ssh-agent [-a bind_address] [-E fingerprint_hash] [-O option]\n" 2185 " [-P allowed_providers] [-t life] command [arg ...]\n" 2186 " ssh-agent [-c | -s] -k\n"); 2187 exit(1); 2188 } 2189 2190 static void 2191 csh_setenv(const char *name, const char *value) 2192 { 2193 printf("setenv %s %s;\n", name, value); 2194 } 2195 2196 static void 2197 csh_unsetenv(const char *name) 2198 { 2199 printf("unsetenv %s;\n", name); 2200 } 2201 2202 static void 2203 sh_setenv(const char *name, const char *value) 2204 { 2205 printf("%s=%s; export %s;\n", name, value, name); 2206 } 2207 2208 static void 2209 sh_unsetenv(const char *name) 2210 { 2211 printf("unset %s;\n", name); 2212 } 2213 int 2214 main(int ac, char **av) 2215 { 2216 int c_flag = 0, d_flag = 0, D_flag = 0, k_flag = 0, s_flag = 0; 2217 int sock, ch, result, saved_errno; 2218 char *shell, *pidstr, *agentsocket = NULL; 2219 struct rlimit rlim; 2220 void (*f_setenv)(const char *, const char *); 2221 void (*f_unsetenv)(const char *); 2222 extern int optind; 2223 extern char *optarg; 2224 pid_t pid; 2225 char pidstrbuf[1 + 3 * sizeof pid]; 2226 size_t len; 2227 mode_t prev_mask; 2228 int timeout = -1; /* INFTIM */ 2229 struct pollfd *pfd = NULL; 2230 size_t npfd = 0; 2231 u_int maxfds; 2232 2233 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */ 2234 sanitise_stdfd(); 2235 2236 /* drop */ 2237 (void)setegid(getgid()); 2238 (void)setgid(getgid()); 2239 2240 if (getrlimit(RLIMIT_NOFILE, &rlim) == -1) 2241 fatal("%s: getrlimit: %s", __progname, strerror(errno)); 2242 2243 #ifdef WITH_OPENSSL 2244 OpenSSL_add_all_algorithms(); 2245 #endif 2246 2247 while ((ch = getopt(ac, av, "cDdksE:a:O:P:t:")) != -1) { 2248 switch (ch) { 2249 case 'E': 2250 fingerprint_hash = ssh_digest_alg_by_name(optarg); 2251 if (fingerprint_hash == -1) 2252 fatal("Invalid hash algorithm \"%s\"", optarg); 2253 break; 2254 case 'c': 2255 if (s_flag) 2256 usage(); 2257 c_flag++; 2258 break; 2259 case 'k': 2260 k_flag++; 2261 break; 2262 case 'O': 2263 if (strcmp(optarg, "no-restrict-websafe") == 0) 2264 restrict_websafe = 0; 2265 else if (strcmp(optarg, "allow-remote-pkcs11") == 0) 2266 remote_add_provider = 1; 2267 else 2268 fatal("Unknown -O option"); 2269 break; 2270 case 'P': 2271 if (allowed_providers != NULL) 2272 fatal("-P option already specified"); 2273 allowed_providers = xstrdup(optarg); 2274 break; 2275 case 's': 2276 if (c_flag) 2277 usage(); 2278 s_flag++; 2279 break; 2280 case 'd': 2281 if (d_flag || D_flag) 2282 usage(); 2283 d_flag++; 2284 break; 2285 case 'D': 2286 if (d_flag || D_flag) 2287 usage(); 2288 D_flag++; 2289 break; 2290 case 'a': 2291 agentsocket = optarg; 2292 break; 2293 case 't': 2294 if ((lifetime = convtime(optarg)) == -1) { 2295 fprintf(stderr, "Invalid lifetime\n"); 2296 usage(); 2297 } 2298 break; 2299 default: 2300 usage(); 2301 } 2302 } 2303 ac -= optind; 2304 av += optind; 2305 2306 if (ac > 0 && (c_flag || k_flag || s_flag || d_flag || D_flag)) 2307 usage(); 2308 2309 if (allowed_providers == NULL) 2310 allowed_providers = xstrdup(DEFAULT_ALLOWED_PROVIDERS); 2311 2312 if (ac == 0 && !c_flag && !s_flag) { 2313 shell = getenv("SHELL"); 2314 if (shell != NULL && (len = strlen(shell)) > 2 && 2315 strncmp(shell + len - 3, "csh", 3) == 0) 2316 c_flag = 1; 2317 } 2318 if (c_flag) { 2319 f_setenv = csh_setenv; 2320 f_unsetenv = csh_unsetenv; 2321 } else { 2322 f_setenv = sh_setenv; 2323 f_unsetenv = sh_unsetenv; 2324 } 2325 if (k_flag) { 2326 const char *errstr = NULL; 2327 2328 pidstr = getenv(SSH_AGENTPID_ENV_NAME); 2329 if (pidstr == NULL) { 2330 fprintf(stderr, "%s not set, cannot kill agent\n", 2331 SSH_AGENTPID_ENV_NAME); 2332 exit(1); 2333 } 2334 pid = (int)strtonum(pidstr, 2, INT_MAX, &errstr); 2335 if (errstr) { 2336 fprintf(stderr, 2337 "%s=\"%s\", which is not a good PID: %s\n", 2338 SSH_AGENTPID_ENV_NAME, pidstr, errstr); 2339 exit(1); 2340 } 2341 if (kill(pid, SIGTERM) == -1) { 2342 perror("kill"); 2343 exit(1); 2344 } 2345 (*f_unsetenv)(SSH_AUTHSOCKET_ENV_NAME); 2346 (*f_unsetenv)(SSH_AGENTPID_ENV_NAME); 2347 printf("echo Agent pid %ld killed;\n", (long)pid); 2348 exit(0); 2349 } 2350 2351 /* 2352 * Minimum file descriptors: 2353 * stdio (3) + listener (1) + syslog (1 maybe) + connection (1) + 2354 * a few spare for libc / stack protectors / sanitisers, etc. 2355 */ 2356 #define SSH_AGENT_MIN_FDS (3+1+1+1+4) 2357 if (rlim.rlim_cur < SSH_AGENT_MIN_FDS) 2358 fatal("%s: file descriptor rlimit %lld too low (minimum %u)", 2359 __progname, (long long)rlim.rlim_cur, SSH_AGENT_MIN_FDS); 2360 maxfds = rlim.rlim_cur - SSH_AGENT_MIN_FDS; 2361 2362 parent_pid = getpid(); 2363 2364 if (agentsocket == NULL) { 2365 /* Create private directory for agent socket */ 2366 mktemp_proto(socket_dir, sizeof(socket_dir)); 2367 if (mkdtemp(socket_dir) == NULL) { 2368 perror("mkdtemp: private socket dir"); 2369 exit(1); 2370 } 2371 snprintf(socket_name, sizeof socket_name, "%s/agent.%ld", socket_dir, 2372 (long)parent_pid); 2373 } else { 2374 /* Try to use specified agent socket */ 2375 socket_dir[0] = '\0'; 2376 strlcpy(socket_name, agentsocket, sizeof socket_name); 2377 } 2378 2379 /* 2380 * Create socket early so it will exist before command gets run from 2381 * the parent. 2382 */ 2383 prev_mask = umask(0177); 2384 sock = unix_listener(socket_name, SSH_LISTEN_BACKLOG, 0); 2385 if (sock < 0) { 2386 /* XXX - unix_listener() calls error() not perror() */ 2387 *socket_name = '\0'; /* Don't unlink any existing file */ 2388 cleanup_exit(1); 2389 } 2390 umask(prev_mask); 2391 2392 /* 2393 * Fork, and have the parent execute the command, if any, or present 2394 * the socket data. The child continues as the authentication agent. 2395 */ 2396 if (D_flag || d_flag) { 2397 log_init(__progname, 2398 d_flag ? SYSLOG_LEVEL_DEBUG3 : SYSLOG_LEVEL_INFO, 2399 SYSLOG_FACILITY_AUTH, 1); 2400 if (c_flag) 2401 printf("setenv %s %s;\n", 2402 SSH_AUTHSOCKET_ENV_NAME, socket_name); 2403 else 2404 printf("%s=%s; export %s;\n", 2405 SSH_AUTHSOCKET_ENV_NAME, socket_name, 2406 SSH_AUTHSOCKET_ENV_NAME); 2407 printf("echo Agent pid %ld;\n", (long)parent_pid); 2408 fflush(stdout); 2409 goto skip; 2410 } 2411 pid = fork(); 2412 if (pid == -1) { 2413 perror("fork"); 2414 cleanup_exit(1); 2415 } 2416 if (pid != 0) { /* Parent - execute the given command. */ 2417 close(sock); 2418 snprintf(pidstrbuf, sizeof pidstrbuf, "%ld", (long)pid); 2419 if (ac == 0) { 2420 (*f_setenv)(SSH_AUTHSOCKET_ENV_NAME, socket_name); 2421 (*f_setenv)(SSH_AGENTPID_ENV_NAME, pidstrbuf); 2422 printf("echo Agent pid %ld;\n", (long)pid); 2423 exit(0); 2424 } 2425 if (setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1) == -1 || 2426 setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1) == -1) { 2427 perror("setenv"); 2428 exit(1); 2429 } 2430 execvp(av[0], av); 2431 perror(av[0]); 2432 exit(1); 2433 } 2434 /* child */ 2435 log_init(__progname, SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_AUTH, 0); 2436 2437 if (setsid() == -1) { 2438 error("setsid: %s", strerror(errno)); 2439 cleanup_exit(1); 2440 } 2441 2442 (void)chdir("/"); 2443 if (stdfd_devnull(1, 1, 1) == -1) 2444 error_f("stdfd_devnull failed"); 2445 2446 /* deny core dumps, since memory contains unencrypted private keys */ 2447 rlim.rlim_cur = rlim.rlim_max = 0; 2448 if (setrlimit(RLIMIT_CORE, &rlim) == -1) { 2449 error("setrlimit RLIMIT_CORE: %s", strerror(errno)); 2450 cleanup_exit(1); 2451 } 2452 2453 skip: 2454 2455 cleanup_pid = getpid(); 2456 2457 #ifdef ENABLE_PKCS11 2458 pkcs11_init(0); 2459 #endif 2460 new_socket(AUTH_SOCKET, sock); 2461 if (ac > 0) 2462 parent_alive_interval = 10; 2463 idtab_init(); 2464 ssh_signal(SIGPIPE, SIG_IGN); 2465 ssh_signal(SIGINT, (d_flag | D_flag) ? cleanup_handler : SIG_IGN); 2466 ssh_signal(SIGHUP, cleanup_handler); 2467 ssh_signal(SIGTERM, cleanup_handler); 2468 2469 #ifdef __OpenBSD__ 2470 if (pledge("stdio rpath cpath unix id proc exec", NULL) == -1) 2471 fatal("%s: pledge: %s", __progname, strerror(errno)); 2472 #endif 2473 2474 while (1) { 2475 prepare_poll(&pfd, &npfd, &timeout, maxfds); 2476 result = poll(pfd, npfd, timeout); 2477 saved_errno = errno; 2478 if (parent_alive_interval != 0) 2479 check_parent_exists(); 2480 (void) reaper(); /* remove expired keys */ 2481 if (result == -1) { 2482 if (saved_errno == EINTR) 2483 continue; 2484 fatal("poll: %s", strerror(saved_errno)); 2485 } else if (result > 0) 2486 after_poll(pfd, npfd, maxfds); 2487 } 2488 /* NOTREACHED */ 2489 } 2490