1 /* $OpenBSD: ssh-agent.c,v 1.297 2023/03/09 21:06:24 jcs 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 "includes.h" 38 39 #include <sys/types.h> 40 #include <sys/resource.h> 41 #include <sys/stat.h> 42 #include <sys/socket.h> 43 #include <sys/wait.h> 44 #ifdef HAVE_SYS_TIME_H 45 # include <sys/time.h> 46 #endif 47 #ifdef HAVE_SYS_UN_H 48 # include <sys/un.h> 49 #endif 50 #include "openbsd-compat/sys-queue.h" 51 52 #ifdef WITH_OPENSSL 53 #include <openssl/evp.h> 54 #include "openbsd-compat/openssl-compat.h" 55 #endif 56 57 #include <errno.h> 58 #include <fcntl.h> 59 #include <limits.h> 60 #ifdef HAVE_PATHS_H 61 # include <paths.h> 62 #endif 63 #ifdef HAVE_POLL_H 64 # include <poll.h> 65 #endif 66 #include <signal.h> 67 #include <stdarg.h> 68 #include <stdio.h> 69 #include <stdlib.h> 70 #include <time.h> 71 #include <string.h> 72 #include <unistd.h> 73 #ifdef HAVE_UTIL_H 74 # include <util.h> 75 #endif 76 77 #include "xmalloc.h" 78 #include "ssh.h" 79 #include "ssh2.h" 80 #include "sshbuf.h" 81 #include "sshkey.h" 82 #include "authfd.h" 83 #include "log.h" 84 #include "misc.h" 85 #include "digest.h" 86 #include "ssherr.h" 87 #include "match.h" 88 #include "msg.h" 89 #include "pathnames.h" 90 #include "ssh-pkcs11.h" 91 #include "sk-api.h" 92 #include "myproposal.h" 93 94 #ifndef DEFAULT_ALLOWED_PROVIDERS 95 # define DEFAULT_ALLOWED_PROVIDERS "/usr/lib*/*,/usr/local/lib*/*" 96 #endif 97 98 /* Maximum accepted message length */ 99 #define AGENT_MAX_LEN (256*1024) 100 /* Maximum bytes to read from client socket */ 101 #define AGENT_RBUF_LEN (4096) 102 /* Maximum number of recorded session IDs/hostkeys per connection */ 103 #define AGENT_MAX_SESSION_IDS 16 104 /* Maximum size of session ID */ 105 #define AGENT_MAX_SID_LEN 128 106 /* Maximum number of destination constraints to accept on a key */ 107 #define AGENT_MAX_DEST_CONSTRAINTS 1024 108 109 /* XXX store hostkey_sid in a refcounted tree */ 110 111 typedef enum { 112 AUTH_UNUSED = 0, 113 AUTH_SOCKET = 1, 114 AUTH_CONNECTION = 2, 115 } sock_type; 116 117 struct hostkey_sid { 118 struct sshkey *key; 119 struct sshbuf *sid; 120 int forwarded; 121 }; 122 123 typedef struct socket_entry { 124 int fd; 125 sock_type type; 126 struct sshbuf *input; 127 struct sshbuf *output; 128 struct sshbuf *request; 129 size_t nsession_ids; 130 struct hostkey_sid *session_ids; 131 } SocketEntry; 132 133 u_int sockets_alloc = 0; 134 SocketEntry *sockets = NULL; 135 136 typedef struct identity { 137 TAILQ_ENTRY(identity) next; 138 struct sshkey *key; 139 char *comment; 140 char *provider; 141 time_t death; 142 u_int confirm; 143 char *sk_provider; 144 struct dest_constraint *dest_constraints; 145 size_t ndest_constraints; 146 } Identity; 147 148 struct idtable { 149 int nentries; 150 TAILQ_HEAD(idqueue, identity) idlist; 151 }; 152 153 /* private key table */ 154 struct idtable *idtab; 155 156 int max_fd = 0; 157 158 /* pid of shell == parent of agent */ 159 pid_t parent_pid = -1; 160 time_t parent_alive_interval = 0; 161 162 /* pid of process for which cleanup_socket is applicable */ 163 pid_t cleanup_pid = 0; 164 165 /* pathname and directory for AUTH_SOCKET */ 166 char socket_name[PATH_MAX]; 167 char socket_dir[PATH_MAX]; 168 169 /* Pattern-list of allowed PKCS#11/Security key paths */ 170 static char *allowed_providers; 171 172 /* 173 * Allows PKCS11 providers or SK keys that use non-internal providers to 174 * be added over a remote connection (identified by session-bind@openssh.com). 175 */ 176 static int remote_add_provider; 177 178 /* locking */ 179 #define LOCK_SIZE 32 180 #define LOCK_SALT_SIZE 16 181 #define LOCK_ROUNDS 1 182 int locked = 0; 183 u_char lock_pwhash[LOCK_SIZE]; 184 u_char lock_salt[LOCK_SALT_SIZE]; 185 186 extern char *__progname; 187 188 /* Default lifetime in seconds (0 == forever) */ 189 static int lifetime = 0; 190 191 static int fingerprint_hash = SSH_FP_HASH_DEFAULT; 192 193 /* Refuse signing of non-SSH messages for web-origin FIDO keys */ 194 static int restrict_websafe = 1; 195 196 /* 197 * Client connection count; incremented in new_socket() and decremented in 198 * close_socket(). When it reaches 0, ssh-agent will exit. Since it is 199 * normally initialized to 1, it will never reach 0. However, if the -x 200 * option is specified, it is initialized to 0 in main(); in that case, 201 * ssh-agent will exit as soon as it has had at least one client but no 202 * longer has any. 203 */ 204 static int xcount = 1; 205 206 static void 207 close_socket(SocketEntry *e) 208 { 209 size_t i; 210 int last = 0; 211 212 if (e->type == AUTH_CONNECTION) { 213 debug("xcount %d -> %d", xcount, xcount - 1); 214 if (--xcount == 0) 215 last = 1; 216 } 217 close(e->fd); 218 sshbuf_free(e->input); 219 sshbuf_free(e->output); 220 sshbuf_free(e->request); 221 for (i = 0; i < e->nsession_ids; i++) { 222 sshkey_free(e->session_ids[i].key); 223 sshbuf_free(e->session_ids[i].sid); 224 } 225 free(e->session_ids); 226 memset(e, '\0', sizeof(*e)); 227 e->fd = -1; 228 e->type = AUTH_UNUSED; 229 if (last) 230 cleanup_exit(0); 231 } 232 233 static void 234 idtab_init(void) 235 { 236 idtab = xcalloc(1, sizeof(*idtab)); 237 TAILQ_INIT(&idtab->idlist); 238 idtab->nentries = 0; 239 } 240 241 static void 242 free_dest_constraint_hop(struct dest_constraint_hop *dch) 243 { 244 u_int i; 245 246 if (dch == NULL) 247 return; 248 free(dch->user); 249 free(dch->hostname); 250 for (i = 0; i < dch->nkeys; i++) 251 sshkey_free(dch->keys[i]); 252 free(dch->keys); 253 free(dch->key_is_ca); 254 } 255 256 static void 257 free_dest_constraints(struct dest_constraint *dcs, size_t ndcs) 258 { 259 size_t i; 260 261 for (i = 0; i < ndcs; i++) { 262 free_dest_constraint_hop(&dcs[i].from); 263 free_dest_constraint_hop(&dcs[i].to); 264 } 265 free(dcs); 266 } 267 268 static void 269 free_identity(Identity *id) 270 { 271 sshkey_free(id->key); 272 free(id->provider); 273 free(id->comment); 274 free(id->sk_provider); 275 free_dest_constraints(id->dest_constraints, id->ndest_constraints); 276 free(id); 277 } 278 279 /* 280 * Match 'key' against the key/CA list in a destination constraint hop 281 * Returns 0 on success or -1 otherwise. 282 */ 283 static int 284 match_key_hop(const char *tag, const struct sshkey *key, 285 const struct dest_constraint_hop *dch) 286 { 287 const char *reason = NULL; 288 const char *hostname = dch->hostname ? dch->hostname : "(ORIGIN)"; 289 u_int i; 290 char *fp; 291 292 if (key == NULL) 293 return -1; 294 /* XXX logspam */ 295 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT, 296 SSH_FP_DEFAULT)) == NULL) 297 fatal_f("fingerprint failed"); 298 debug3_f("%s: entering hostname %s, requested key %s %s, %u keys avail", 299 tag, hostname, sshkey_type(key), fp, dch->nkeys); 300 free(fp); 301 for (i = 0; i < dch->nkeys; i++) { 302 if (dch->keys[i] == NULL) 303 return -1; 304 /* XXX logspam */ 305 if ((fp = sshkey_fingerprint(dch->keys[i], SSH_FP_HASH_DEFAULT, 306 SSH_FP_DEFAULT)) == NULL) 307 fatal_f("fingerprint failed"); 308 debug3_f("%s: key %u: %s%s %s", tag, i, 309 dch->key_is_ca[i] ? "CA " : "", 310 sshkey_type(dch->keys[i]), fp); 311 free(fp); 312 if (!sshkey_is_cert(key)) { 313 /* plain key */ 314 if (dch->key_is_ca[i] || 315 !sshkey_equal(key, dch->keys[i])) 316 continue; 317 return 0; 318 } 319 /* certificate */ 320 if (!dch->key_is_ca[i]) 321 continue; 322 if (key->cert == NULL || key->cert->signature_key == NULL) 323 return -1; /* shouldn't happen */ 324 if (!sshkey_equal(key->cert->signature_key, dch->keys[i])) 325 continue; 326 if (sshkey_cert_check_host(key, hostname, 1, 327 SSH_ALLOWED_CA_SIGALGS, &reason) != 0) { 328 debug_f("cert %s / hostname %s rejected: %s", 329 key->cert->key_id, hostname, reason); 330 continue; 331 } 332 return 0; 333 } 334 return -1; 335 } 336 337 /* Check destination constraints on an identity against the hostkey/user */ 338 static int 339 permitted_by_dest_constraints(const struct sshkey *fromkey, 340 const struct sshkey *tokey, Identity *id, const char *user, 341 const char **hostnamep) 342 { 343 size_t i; 344 struct dest_constraint *d; 345 346 if (hostnamep != NULL) 347 *hostnamep = NULL; 348 for (i = 0; i < id->ndest_constraints; i++) { 349 d = id->dest_constraints + i; 350 /* XXX remove logspam */ 351 debug2_f("constraint %zu %s%s%s (%u keys) > %s%s%s (%u keys)", 352 i, d->from.user ? d->from.user : "", 353 d->from.user ? "@" : "", 354 d->from.hostname ? d->from.hostname : "(ORIGIN)", 355 d->from.nkeys, 356 d->to.user ? d->to.user : "", d->to.user ? "@" : "", 357 d->to.hostname ? d->to.hostname : "(ANY)", d->to.nkeys); 358 359 /* Match 'from' key */ 360 if (fromkey == NULL) { 361 /* We are matching the first hop */ 362 if (d->from.hostname != NULL || d->from.nkeys != 0) 363 continue; 364 } else if (match_key_hop("from", fromkey, &d->from) != 0) 365 continue; 366 367 /* Match 'to' key */ 368 if (tokey != NULL && match_key_hop("to", tokey, &d->to) != 0) 369 continue; 370 371 /* Match user if specified */ 372 if (d->to.user != NULL && user != NULL && 373 !match_pattern(user, d->to.user)) 374 continue; 375 376 /* successfully matched this constraint */ 377 if (hostnamep != NULL) 378 *hostnamep = d->to.hostname; 379 debug2_f("allowed for hostname %s", 380 d->to.hostname == NULL ? "*" : d->to.hostname); 381 return 0; 382 } 383 /* no match */ 384 debug2_f("%s identity \"%s\" not permitted for this destination", 385 sshkey_type(id->key), id->comment); 386 return -1; 387 } 388 389 /* 390 * Check whether hostkeys on a SocketEntry and the optionally specified user 391 * are permitted by the destination constraints on the Identity. 392 * Returns 0 on success or -1 otherwise. 393 */ 394 static int 395 identity_permitted(Identity *id, SocketEntry *e, char *user, 396 const char **forward_hostnamep, const char **last_hostnamep) 397 { 398 size_t i; 399 const char **hp; 400 struct hostkey_sid *hks; 401 const struct sshkey *fromkey = NULL; 402 const char *test_user; 403 char *fp1, *fp2; 404 405 /* XXX remove logspam */ 406 debug3_f("entering: key %s comment \"%s\", %zu socket bindings, " 407 "%zu constraints", sshkey_type(id->key), id->comment, 408 e->nsession_ids, id->ndest_constraints); 409 if (id->ndest_constraints == 0) 410 return 0; /* unconstrained */ 411 if (e->nsession_ids == 0) 412 return 0; /* local use */ 413 /* 414 * Walk through the hops recorded by session_id and try to find a 415 * constraint that satisfies each. 416 */ 417 for (i = 0; i < e->nsession_ids; i++) { 418 hks = e->session_ids + i; 419 if (hks->key == NULL) 420 fatal_f("internal error: no bound key"); 421 /* XXX remove logspam */ 422 fp1 = fp2 = NULL; 423 if (fromkey != NULL && 424 (fp1 = sshkey_fingerprint(fromkey, SSH_FP_HASH_DEFAULT, 425 SSH_FP_DEFAULT)) == NULL) 426 fatal_f("fingerprint failed"); 427 if ((fp2 = sshkey_fingerprint(hks->key, SSH_FP_HASH_DEFAULT, 428 SSH_FP_DEFAULT)) == NULL) 429 fatal_f("fingerprint failed"); 430 debug3_f("socketentry fd=%d, entry %zu %s, " 431 "from hostkey %s %s to user %s hostkey %s %s", 432 e->fd, i, hks->forwarded ? "FORWARD" : "AUTH", 433 fromkey ? sshkey_type(fromkey) : "(ORIGIN)", 434 fromkey ? fp1 : "", user ? user : "(ANY)", 435 sshkey_type(hks->key), fp2); 436 free(fp1); 437 free(fp2); 438 /* 439 * Record the hostnames for the initial forwarding and 440 * the final destination. 441 */ 442 hp = NULL; 443 if (i == e->nsession_ids - 1) 444 hp = last_hostnamep; 445 else if (i == 0) 446 hp = forward_hostnamep; 447 /* Special handling for final recorded binding */ 448 test_user = NULL; 449 if (i == e->nsession_ids - 1) { 450 /* Can only check user at final hop */ 451 test_user = user; 452 /* 453 * user is only presented for signature requests. 454 * If this is the case, make sure last binding is not 455 * for a forwarding. 456 */ 457 if (hks->forwarded && user != NULL) { 458 error_f("tried to sign on forwarding hop"); 459 return -1; 460 } 461 } else if (!hks->forwarded) { 462 error_f("tried to forward though signing bind"); 463 return -1; 464 } 465 if (permitted_by_dest_constraints(fromkey, hks->key, id, 466 test_user, hp) != 0) 467 return -1; 468 fromkey = hks->key; 469 } 470 /* 471 * Another special case: if the last bound session ID was for a 472 * forwarding, and this function is not being called to check a sign 473 * request (i.e. no 'user' supplied), then only permit the key if 474 * there is a permission that would allow it to be used at another 475 * destination. This hides keys that are allowed to be used to 476 * authenticate *to* a host but not permitted for *use* beyond it. 477 */ 478 hks = &e->session_ids[e->nsession_ids - 1]; 479 if (hks->forwarded && user == NULL && 480 permitted_by_dest_constraints(hks->key, NULL, id, 481 NULL, NULL) != 0) { 482 debug3_f("key permitted at host but not after"); 483 return -1; 484 } 485 486 /* success */ 487 return 0; 488 } 489 490 /* return matching private key for given public key */ 491 static Identity * 492 lookup_identity(struct sshkey *key) 493 { 494 Identity *id; 495 496 TAILQ_FOREACH(id, &idtab->idlist, next) { 497 if (sshkey_equal(key, id->key)) 498 return (id); 499 } 500 return (NULL); 501 } 502 503 /* Check confirmation of keysign request */ 504 static int 505 confirm_key(Identity *id, const char *extra) 506 { 507 char *p; 508 int ret = -1; 509 510 p = sshkey_fingerprint(id->key, fingerprint_hash, SSH_FP_DEFAULT); 511 if (p != NULL && 512 ask_permission("Allow use of key %s?\nKey fingerprint %s.%s%s", 513 id->comment, p, 514 extra == NULL ? "" : "\n", extra == NULL ? "" : extra)) 515 ret = 0; 516 free(p); 517 518 return (ret); 519 } 520 521 static void 522 send_status(SocketEntry *e, int success) 523 { 524 int r; 525 526 if ((r = sshbuf_put_u32(e->output, 1)) != 0 || 527 (r = sshbuf_put_u8(e->output, success ? 528 SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE)) != 0) 529 fatal_fr(r, "compose"); 530 } 531 532 /* send list of supported public keys to 'client' */ 533 static void 534 process_request_identities(SocketEntry *e) 535 { 536 Identity *id; 537 struct sshbuf *msg, *keys; 538 int r; 539 u_int nentries = 0; 540 541 debug2_f("entering"); 542 543 if ((msg = sshbuf_new()) == NULL || (keys = sshbuf_new()) == NULL) 544 fatal_f("sshbuf_new failed"); 545 TAILQ_FOREACH(id, &idtab->idlist, next) { 546 /* identity not visible, don't include in response */ 547 if (identity_permitted(id, e, NULL, NULL, NULL) != 0) 548 continue; 549 if ((r = sshkey_puts_opts(id->key, keys, 550 SSHKEY_SERIALIZE_INFO)) != 0 || 551 (r = sshbuf_put_cstring(keys, id->comment)) != 0) { 552 error_fr(r, "compose key/comment"); 553 continue; 554 } 555 nentries++; 556 } 557 debug2_f("replying with %u allowed of %u available keys", 558 nentries, idtab->nentries); 559 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 || 560 (r = sshbuf_put_u32(msg, nentries)) != 0 || 561 (r = sshbuf_putb(msg, keys)) != 0) 562 fatal_fr(r, "compose"); 563 if ((r = sshbuf_put_stringb(e->output, msg)) != 0) 564 fatal_fr(r, "enqueue"); 565 sshbuf_free(msg); 566 sshbuf_free(keys); 567 } 568 569 570 static char * 571 agent_decode_alg(struct sshkey *key, u_int flags) 572 { 573 if (key->type == KEY_RSA) { 574 if (flags & SSH_AGENT_RSA_SHA2_256) 575 return "rsa-sha2-256"; 576 else if (flags & SSH_AGENT_RSA_SHA2_512) 577 return "rsa-sha2-512"; 578 } else if (key->type == KEY_RSA_CERT) { 579 if (flags & SSH_AGENT_RSA_SHA2_256) 580 return "rsa-sha2-256-cert-v01@openssh.com"; 581 else if (flags & SSH_AGENT_RSA_SHA2_512) 582 return "rsa-sha2-512-cert-v01@openssh.com"; 583 } 584 return NULL; 585 } 586 587 /* 588 * Attempt to parse the contents of a buffer as a SSH publickey userauth 589 * request, checking its contents for consistency and matching the embedded 590 * key against the one that is being used for signing. 591 * Note: does not modify msg buffer. 592 * Optionally extract the username, session ID and/or hostkey from the request. 593 */ 594 static int 595 parse_userauth_request(struct sshbuf *msg, const struct sshkey *expected_key, 596 char **userp, struct sshbuf **sess_idp, struct sshkey **hostkeyp) 597 { 598 struct sshbuf *b = NULL, *sess_id = NULL; 599 char *user = NULL, *service = NULL, *method = NULL, *pkalg = NULL; 600 int r; 601 u_char t, sig_follows; 602 struct sshkey *mkey = NULL, *hostkey = NULL; 603 604 if (userp != NULL) 605 *userp = NULL; 606 if (sess_idp != NULL) 607 *sess_idp = NULL; 608 if (hostkeyp != NULL) 609 *hostkeyp = NULL; 610 if ((b = sshbuf_fromb(msg)) == NULL) 611 fatal_f("sshbuf_fromb"); 612 613 /* SSH userauth request */ 614 if ((r = sshbuf_froms(b, &sess_id)) != 0) 615 goto out; 616 if (sshbuf_len(sess_id) == 0) { 617 r = SSH_ERR_INVALID_FORMAT; 618 goto out; 619 } 620 if ((r = sshbuf_get_u8(b, &t)) != 0 || /* SSH2_MSG_USERAUTH_REQUEST */ 621 (r = sshbuf_get_cstring(b, &user, NULL)) != 0 || /* server user */ 622 (r = sshbuf_get_cstring(b, &service, NULL)) != 0 || /* service */ 623 (r = sshbuf_get_cstring(b, &method, NULL)) != 0 || /* method */ 624 (r = sshbuf_get_u8(b, &sig_follows)) != 0 || /* sig-follows */ 625 (r = sshbuf_get_cstring(b, &pkalg, NULL)) != 0 || /* alg */ 626 (r = sshkey_froms(b, &mkey)) != 0) /* key */ 627 goto out; 628 if (t != SSH2_MSG_USERAUTH_REQUEST || 629 sig_follows != 1 || 630 strcmp(service, "ssh-connection") != 0 || 631 !sshkey_equal(expected_key, mkey) || 632 sshkey_type_from_name(pkalg) != expected_key->type) { 633 r = SSH_ERR_INVALID_FORMAT; 634 goto out; 635 } 636 if (strcmp(method, "publickey-hostbound-v00@openssh.com") == 0) { 637 if ((r = sshkey_froms(b, &hostkey)) != 0) 638 goto out; 639 } else if (strcmp(method, "publickey") != 0) { 640 r = SSH_ERR_INVALID_FORMAT; 641 goto out; 642 } 643 if (sshbuf_len(b) != 0) { 644 r = SSH_ERR_INVALID_FORMAT; 645 goto out; 646 } 647 /* success */ 648 r = 0; 649 debug3_f("well formed userauth"); 650 if (userp != NULL) { 651 *userp = user; 652 user = NULL; 653 } 654 if (sess_idp != NULL) { 655 *sess_idp = sess_id; 656 sess_id = NULL; 657 } 658 if (hostkeyp != NULL) { 659 *hostkeyp = hostkey; 660 hostkey = NULL; 661 } 662 out: 663 sshbuf_free(b); 664 sshbuf_free(sess_id); 665 free(user); 666 free(service); 667 free(method); 668 free(pkalg); 669 sshkey_free(mkey); 670 sshkey_free(hostkey); 671 return r; 672 } 673 674 /* 675 * Attempt to parse the contents of a buffer as a SSHSIG signature request. 676 * Note: does not modify buffer. 677 */ 678 static int 679 parse_sshsig_request(struct sshbuf *msg) 680 { 681 int r; 682 struct sshbuf *b; 683 684 if ((b = sshbuf_fromb(msg)) == NULL) 685 fatal_f("sshbuf_fromb"); 686 687 if ((r = sshbuf_cmp(b, 0, "SSHSIG", 6)) != 0 || 688 (r = sshbuf_consume(b, 6)) != 0 || 689 (r = sshbuf_get_cstring(b, NULL, NULL)) != 0 || /* namespace */ 690 (r = sshbuf_get_string_direct(b, NULL, NULL)) != 0 || /* reserved */ 691 (r = sshbuf_get_cstring(b, NULL, NULL)) != 0 || /* hashalg */ 692 (r = sshbuf_get_string_direct(b, NULL, NULL)) != 0) /* H(msg) */ 693 goto out; 694 if (sshbuf_len(b) != 0) { 695 r = SSH_ERR_INVALID_FORMAT; 696 goto out; 697 } 698 /* success */ 699 r = 0; 700 out: 701 sshbuf_free(b); 702 return r; 703 } 704 705 /* 706 * This function inspects a message to be signed by a FIDO key that has a 707 * web-like application string (i.e. one that does not begin with "ssh:". 708 * It checks that the message is one of those expected for SSH operations 709 * (pubkey userauth, sshsig, CA key signing) to exclude signing challenges 710 * for the web. 711 */ 712 static int 713 check_websafe_message_contents(struct sshkey *key, struct sshbuf *data) 714 { 715 if (parse_userauth_request(data, key, NULL, NULL, NULL) == 0) { 716 debug_f("signed data matches public key userauth request"); 717 return 1; 718 } 719 if (parse_sshsig_request(data) == 0) { 720 debug_f("signed data matches SSHSIG signature request"); 721 return 1; 722 } 723 724 /* XXX check CA signature operation */ 725 726 error("web-origin key attempting to sign non-SSH message"); 727 return 0; 728 } 729 730 static int 731 buf_equal(const struct sshbuf *a, const struct sshbuf *b) 732 { 733 if (sshbuf_ptr(a) == NULL || sshbuf_ptr(b) == NULL) 734 return SSH_ERR_INVALID_ARGUMENT; 735 if (sshbuf_len(a) != sshbuf_len(b)) 736 return SSH_ERR_INVALID_FORMAT; 737 if (timingsafe_bcmp(sshbuf_ptr(a), sshbuf_ptr(b), sshbuf_len(a)) != 0) 738 return SSH_ERR_INVALID_FORMAT; 739 return 0; 740 } 741 742 /* ssh2 only */ 743 static void 744 process_sign_request2(SocketEntry *e) 745 { 746 u_char *signature = NULL; 747 size_t slen = 0; 748 u_int compat = 0, flags; 749 int r, ok = -1, retried = 0; 750 char *fp = NULL, *pin = NULL, *prompt = NULL; 751 char *user = NULL, *sig_dest = NULL; 752 const char *fwd_host = NULL, *dest_host = NULL; 753 struct sshbuf *msg = NULL, *data = NULL, *sid = NULL; 754 struct sshkey *key = NULL, *hostkey = NULL; 755 struct identity *id; 756 struct notifier_ctx *notifier = NULL; 757 758 debug_f("entering"); 759 760 if ((msg = sshbuf_new()) == NULL || (data = sshbuf_new()) == NULL) 761 fatal_f("sshbuf_new failed"); 762 if ((r = sshkey_froms(e->request, &key)) != 0 || 763 (r = sshbuf_get_stringb(e->request, data)) != 0 || 764 (r = sshbuf_get_u32(e->request, &flags)) != 0) { 765 error_fr(r, "parse"); 766 goto send; 767 } 768 769 if ((id = lookup_identity(key)) == NULL) { 770 verbose_f("%s key not found", sshkey_type(key)); 771 goto send; 772 } 773 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT, 774 SSH_FP_DEFAULT)) == NULL) 775 fatal_f("fingerprint failed"); 776 777 if (id->ndest_constraints != 0) { 778 if (e->nsession_ids == 0) { 779 logit_f("refusing use of destination-constrained key " 780 "to sign on unbound connection"); 781 goto send; 782 } 783 if (parse_userauth_request(data, key, &user, &sid, 784 &hostkey) != 0) { 785 logit_f("refusing use of destination-constrained key " 786 "to sign an unidentified signature"); 787 goto send; 788 } 789 /* XXX logspam */ 790 debug_f("user=%s", user); 791 if (identity_permitted(id, e, user, &fwd_host, &dest_host) != 0) 792 goto send; 793 /* XXX display fwd_host/dest_host in askpass UI */ 794 /* 795 * Ensure that the session ID is the most recent one 796 * registered on the socket - it should have been bound by 797 * ssh immediately before userauth. 798 */ 799 if (buf_equal(sid, 800 e->session_ids[e->nsession_ids - 1].sid) != 0) { 801 error_f("unexpected session ID (%zu listed) on " 802 "signature request for target user %s with " 803 "key %s %s", e->nsession_ids, user, 804 sshkey_type(id->key), fp); 805 goto send; 806 } 807 /* 808 * Ensure that the hostkey embedded in the signature matches 809 * the one most recently bound to the socket. An exception is 810 * made for the initial forwarding hop. 811 */ 812 if (e->nsession_ids > 1 && hostkey == NULL) { 813 error_f("refusing use of destination-constrained key: " 814 "no hostkey recorded in signature for forwarded " 815 "connection"); 816 goto send; 817 } 818 if (hostkey != NULL && !sshkey_equal(hostkey, 819 e->session_ids[e->nsession_ids - 1].key)) { 820 error_f("refusing use of destination-constrained key: " 821 "mismatch between hostkey in request and most " 822 "recently bound session"); 823 goto send; 824 } 825 xasprintf(&sig_dest, "public key authentication request for " 826 "user \"%s\" to listed host", user); 827 } 828 if (id->confirm && confirm_key(id, sig_dest) != 0) { 829 verbose_f("user refused key"); 830 goto send; 831 } 832 if (sshkey_is_sk(id->key)) { 833 if (restrict_websafe && 834 strncmp(id->key->sk_application, "ssh:", 4) != 0 && 835 !check_websafe_message_contents(key, data)) { 836 /* error already logged */ 837 goto send; 838 } 839 if (id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD) { 840 notifier = notify_start(0, 841 "Confirm user presence for key %s %s%s%s", 842 sshkey_type(id->key), fp, 843 sig_dest == NULL ? "" : "\n", 844 sig_dest == NULL ? "" : sig_dest); 845 } 846 } 847 retry_pin: 848 if ((r = sshkey_sign(id->key, &signature, &slen, 849 sshbuf_ptr(data), sshbuf_len(data), agent_decode_alg(key, flags), 850 id->sk_provider, pin, compat)) != 0) { 851 debug_fr(r, "sshkey_sign"); 852 if (pin == NULL && !retried && sshkey_is_sk(id->key) && 853 r == SSH_ERR_KEY_WRONG_PASSPHRASE) { 854 notify_complete(notifier, NULL); 855 notifier = NULL; 856 /* XXX include sig_dest */ 857 xasprintf(&prompt, "Enter PIN%sfor %s key %s: ", 858 (id->key->sk_flags & SSH_SK_USER_PRESENCE_REQD) ? 859 " and confirm user presence " : " ", 860 sshkey_type(id->key), fp); 861 pin = read_passphrase(prompt, RP_USE_ASKPASS); 862 retried = 1; 863 goto retry_pin; 864 } 865 error_fr(r, "sshkey_sign"); 866 goto send; 867 } 868 /* Success */ 869 ok = 0; 870 send: 871 debug_f("good signature"); 872 notify_complete(notifier, "User presence confirmed"); 873 874 if (ok == 0) { 875 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 || 876 (r = sshbuf_put_string(msg, signature, slen)) != 0) 877 fatal_fr(r, "compose"); 878 } else if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0) 879 fatal_fr(r, "compose failure"); 880 881 if ((r = sshbuf_put_stringb(e->output, msg)) != 0) 882 fatal_fr(r, "enqueue"); 883 884 sshbuf_free(sid); 885 sshbuf_free(data); 886 sshbuf_free(msg); 887 sshkey_free(key); 888 sshkey_free(hostkey); 889 free(fp); 890 free(signature); 891 free(sig_dest); 892 free(user); 893 free(prompt); 894 if (pin != NULL) 895 freezero(pin, strlen(pin)); 896 } 897 898 /* shared */ 899 static void 900 process_remove_identity(SocketEntry *e) 901 { 902 int r, success = 0; 903 struct sshkey *key = NULL; 904 Identity *id; 905 906 debug2_f("entering"); 907 if ((r = sshkey_froms(e->request, &key)) != 0) { 908 error_fr(r, "parse key"); 909 goto done; 910 } 911 if ((id = lookup_identity(key)) == NULL) { 912 debug_f("key not found"); 913 goto done; 914 } 915 /* identity not visible, cannot be removed */ 916 if (identity_permitted(id, e, NULL, NULL, NULL) != 0) 917 goto done; /* error already logged */ 918 /* We have this key, free it. */ 919 if (idtab->nentries < 1) 920 fatal_f("internal error: nentries %d", idtab->nentries); 921 TAILQ_REMOVE(&idtab->idlist, id, next); 922 free_identity(id); 923 idtab->nentries--; 924 success = 1; 925 done: 926 sshkey_free(key); 927 send_status(e, success); 928 } 929 930 static void 931 process_remove_all_identities(SocketEntry *e) 932 { 933 Identity *id; 934 935 debug2_f("entering"); 936 /* Loop over all identities and clear the keys. */ 937 for (id = TAILQ_FIRST(&idtab->idlist); id; 938 id = TAILQ_FIRST(&idtab->idlist)) { 939 TAILQ_REMOVE(&idtab->idlist, id, next); 940 free_identity(id); 941 } 942 943 /* Mark that there are no identities. */ 944 idtab->nentries = 0; 945 946 /* Send success. */ 947 send_status(e, 1); 948 } 949 950 /* removes expired keys and returns number of seconds until the next expiry */ 951 static time_t 952 reaper(void) 953 { 954 time_t deadline = 0, now = monotime(); 955 Identity *id, *nxt; 956 957 for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) { 958 nxt = TAILQ_NEXT(id, next); 959 if (id->death == 0) 960 continue; 961 if (now >= id->death) { 962 debug("expiring key '%s'", id->comment); 963 TAILQ_REMOVE(&idtab->idlist, id, next); 964 free_identity(id); 965 idtab->nentries--; 966 } else 967 deadline = (deadline == 0) ? id->death : 968 MINIMUM(deadline, id->death); 969 } 970 if (deadline == 0 || deadline <= now) 971 return 0; 972 else 973 return (deadline - now); 974 } 975 976 static int 977 parse_dest_constraint_hop(struct sshbuf *b, struct dest_constraint_hop *dch) 978 { 979 u_char key_is_ca; 980 size_t elen = 0; 981 int r; 982 struct sshkey *k = NULL; 983 char *fp; 984 985 memset(dch, '\0', sizeof(*dch)); 986 if ((r = sshbuf_get_cstring(b, &dch->user, NULL)) != 0 || 987 (r = sshbuf_get_cstring(b, &dch->hostname, NULL)) != 0 || 988 (r = sshbuf_get_string_direct(b, NULL, &elen)) != 0) { 989 error_fr(r, "parse"); 990 goto out; 991 } 992 if (elen != 0) { 993 error_f("unsupported extensions (len %zu)", elen); 994 r = SSH_ERR_FEATURE_UNSUPPORTED; 995 goto out; 996 } 997 if (*dch->hostname == '\0') { 998 free(dch->hostname); 999 dch->hostname = NULL; 1000 } 1001 if (*dch->user == '\0') { 1002 free(dch->user); 1003 dch->user = NULL; 1004 } 1005 while (sshbuf_len(b) != 0) { 1006 dch->keys = xrecallocarray(dch->keys, dch->nkeys, 1007 dch->nkeys + 1, sizeof(*dch->keys)); 1008 dch->key_is_ca = xrecallocarray(dch->key_is_ca, dch->nkeys, 1009 dch->nkeys + 1, sizeof(*dch->key_is_ca)); 1010 if ((r = sshkey_froms(b, &k)) != 0 || 1011 (r = sshbuf_get_u8(b, &key_is_ca)) != 0) 1012 goto out; 1013 if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT, 1014 SSH_FP_DEFAULT)) == NULL) 1015 fatal_f("fingerprint failed"); 1016 debug3_f("%s%s%s: adding %skey %s %s", 1017 dch->user == NULL ? "" : dch->user, 1018 dch->user == NULL ? "" : "@", 1019 dch->hostname, key_is_ca ? "CA " : "", sshkey_type(k), fp); 1020 free(fp); 1021 dch->keys[dch->nkeys] = k; 1022 dch->key_is_ca[dch->nkeys] = key_is_ca != 0; 1023 dch->nkeys++; 1024 k = NULL; /* transferred */ 1025 } 1026 /* success */ 1027 r = 0; 1028 out: 1029 sshkey_free(k); 1030 return r; 1031 } 1032 1033 static int 1034 parse_dest_constraint(struct sshbuf *m, struct dest_constraint *dc) 1035 { 1036 struct sshbuf *b = NULL, *frombuf = NULL, *tobuf = NULL; 1037 int r; 1038 size_t elen = 0; 1039 1040 debug3_f("entering"); 1041 1042 memset(dc, '\0', sizeof(*dc)); 1043 if ((r = sshbuf_froms(m, &b)) != 0 || 1044 (r = sshbuf_froms(b, &frombuf)) != 0 || 1045 (r = sshbuf_froms(b, &tobuf)) != 0 || 1046 (r = sshbuf_get_string_direct(b, NULL, &elen)) != 0) { 1047 error_fr(r, "parse"); 1048 goto out; 1049 } 1050 if ((r = parse_dest_constraint_hop(frombuf, &dc->from)) != 0 || 1051 (r = parse_dest_constraint_hop(tobuf, &dc->to)) != 0) 1052 goto out; /* already logged */ 1053 if (elen != 0) { 1054 error_f("unsupported extensions (len %zu)", elen); 1055 r = SSH_ERR_FEATURE_UNSUPPORTED; 1056 goto out; 1057 } 1058 debug2_f("parsed %s (%u keys) > %s%s%s (%u keys)", 1059 dc->from.hostname ? dc->from.hostname : "(ORIGIN)", dc->from.nkeys, 1060 dc->to.user ? dc->to.user : "", dc->to.user ? "@" : "", 1061 dc->to.hostname ? dc->to.hostname : "(ANY)", dc->to.nkeys); 1062 /* check consistency */ 1063 if ((dc->from.hostname == NULL) != (dc->from.nkeys == 0) || 1064 dc->from.user != NULL) { 1065 error_f("inconsistent \"from\" specification"); 1066 r = SSH_ERR_INVALID_FORMAT; 1067 goto out; 1068 } 1069 if (dc->to.hostname == NULL || dc->to.nkeys == 0) { 1070 error_f("incomplete \"to\" specification"); 1071 r = SSH_ERR_INVALID_FORMAT; 1072 goto out; 1073 } 1074 /* success */ 1075 r = 0; 1076 out: 1077 sshbuf_free(b); 1078 sshbuf_free(frombuf); 1079 sshbuf_free(tobuf); 1080 return r; 1081 } 1082 1083 static int 1084 parse_key_constraint_extension(struct sshbuf *m, char **sk_providerp, 1085 struct dest_constraint **dcsp, size_t *ndcsp) 1086 { 1087 char *ext_name = NULL; 1088 int r; 1089 struct sshbuf *b = NULL; 1090 1091 if ((r = sshbuf_get_cstring(m, &ext_name, NULL)) != 0) { 1092 error_fr(r, "parse constraint extension"); 1093 goto out; 1094 } 1095 debug_f("constraint ext %s", ext_name); 1096 if (strcmp(ext_name, "sk-provider@openssh.com") == 0) { 1097 if (sk_providerp == NULL) { 1098 error_f("%s not valid here", ext_name); 1099 r = SSH_ERR_INVALID_FORMAT; 1100 goto out; 1101 } 1102 if (*sk_providerp != NULL) { 1103 error_f("%s already set", ext_name); 1104 r = SSH_ERR_INVALID_FORMAT; 1105 goto out; 1106 } 1107 if ((r = sshbuf_get_cstring(m, sk_providerp, NULL)) != 0) { 1108 error_fr(r, "parse %s", ext_name); 1109 goto out; 1110 } 1111 } else if (strcmp(ext_name, 1112 "restrict-destination-v00@openssh.com") == 0) { 1113 if (*dcsp != NULL) { 1114 error_f("%s already set", ext_name); 1115 goto out; 1116 } 1117 if ((r = sshbuf_froms(m, &b)) != 0) { 1118 error_fr(r, "parse %s outer", ext_name); 1119 goto out; 1120 } 1121 while (sshbuf_len(b) != 0) { 1122 if (*ndcsp >= AGENT_MAX_DEST_CONSTRAINTS) { 1123 error_f("too many %s constraints", ext_name); 1124 goto out; 1125 } 1126 *dcsp = xrecallocarray(*dcsp, *ndcsp, *ndcsp + 1, 1127 sizeof(**dcsp)); 1128 if ((r = parse_dest_constraint(b, 1129 *dcsp + (*ndcsp)++)) != 0) 1130 goto out; /* error already logged */ 1131 } 1132 } else { 1133 error_f("unsupported constraint \"%s\"", ext_name); 1134 r = SSH_ERR_FEATURE_UNSUPPORTED; 1135 goto out; 1136 } 1137 /* success */ 1138 r = 0; 1139 out: 1140 free(ext_name); 1141 sshbuf_free(b); 1142 return r; 1143 } 1144 1145 static int 1146 parse_key_constraints(struct sshbuf *m, struct sshkey *k, time_t *deathp, 1147 u_int *secondsp, int *confirmp, char **sk_providerp, 1148 struct dest_constraint **dcsp, size_t *ndcsp) 1149 { 1150 u_char ctype; 1151 int r; 1152 u_int seconds, maxsign = 0; 1153 1154 while (sshbuf_len(m)) { 1155 if ((r = sshbuf_get_u8(m, &ctype)) != 0) { 1156 error_fr(r, "parse constraint type"); 1157 goto out; 1158 } 1159 switch (ctype) { 1160 case SSH_AGENT_CONSTRAIN_LIFETIME: 1161 if (*deathp != 0) { 1162 error_f("lifetime already set"); 1163 r = SSH_ERR_INVALID_FORMAT; 1164 goto out; 1165 } 1166 if ((r = sshbuf_get_u32(m, &seconds)) != 0) { 1167 error_fr(r, "parse lifetime constraint"); 1168 goto out; 1169 } 1170 *deathp = monotime() + seconds; 1171 *secondsp = seconds; 1172 break; 1173 case SSH_AGENT_CONSTRAIN_CONFIRM: 1174 if (*confirmp != 0) { 1175 error_f("confirm already set"); 1176 r = SSH_ERR_INVALID_FORMAT; 1177 goto out; 1178 } 1179 *confirmp = 1; 1180 break; 1181 case SSH_AGENT_CONSTRAIN_MAXSIGN: 1182 if (k == NULL) { 1183 error_f("maxsign not valid here"); 1184 r = SSH_ERR_INVALID_FORMAT; 1185 goto out; 1186 } 1187 if (maxsign != 0) { 1188 error_f("maxsign already set"); 1189 r = SSH_ERR_INVALID_FORMAT; 1190 goto out; 1191 } 1192 if ((r = sshbuf_get_u32(m, &maxsign)) != 0) { 1193 error_fr(r, "parse maxsign constraint"); 1194 goto out; 1195 } 1196 if ((r = sshkey_enable_maxsign(k, maxsign)) != 0) { 1197 error_fr(r, "enable maxsign"); 1198 goto out; 1199 } 1200 break; 1201 case SSH_AGENT_CONSTRAIN_EXTENSION: 1202 if ((r = parse_key_constraint_extension(m, 1203 sk_providerp, dcsp, ndcsp)) != 0) 1204 goto out; /* error already logged */ 1205 break; 1206 default: 1207 error_f("Unknown constraint %d", ctype); 1208 r = SSH_ERR_FEATURE_UNSUPPORTED; 1209 goto out; 1210 } 1211 } 1212 /* success */ 1213 r = 0; 1214 out: 1215 return r; 1216 } 1217 1218 static void 1219 process_add_identity(SocketEntry *e) 1220 { 1221 Identity *id; 1222 int success = 0, confirm = 0; 1223 char *fp, *comment = NULL, *sk_provider = NULL; 1224 char canonical_provider[PATH_MAX]; 1225 time_t death = 0; 1226 u_int seconds = 0; 1227 struct dest_constraint *dest_constraints = NULL; 1228 size_t ndest_constraints = 0; 1229 struct sshkey *k = NULL; 1230 int r = SSH_ERR_INTERNAL_ERROR; 1231 1232 debug2_f("entering"); 1233 if ((r = sshkey_private_deserialize(e->request, &k)) != 0 || 1234 k == NULL || 1235 (r = sshbuf_get_cstring(e->request, &comment, NULL)) != 0) { 1236 error_fr(r, "parse"); 1237 goto out; 1238 } 1239 if (parse_key_constraints(e->request, k, &death, &seconds, &confirm, 1240 &sk_provider, &dest_constraints, &ndest_constraints) != 0) { 1241 error_f("failed to parse constraints"); 1242 sshbuf_reset(e->request); 1243 goto out; 1244 } 1245 1246 if (sk_provider != NULL) { 1247 if (!sshkey_is_sk(k)) { 1248 error("Cannot add provider: %s is not an " 1249 "authenticator-hosted key", sshkey_type(k)); 1250 goto out; 1251 } 1252 if (strcasecmp(sk_provider, "internal") == 0) { 1253 debug_f("internal provider"); 1254 } else { 1255 if (e->nsession_ids != 0 && !remote_add_provider) { 1256 verbose("failed add of SK provider \"%.100s\": " 1257 "remote addition of providers is disabled", 1258 sk_provider); 1259 goto out; 1260 } 1261 if (realpath(sk_provider, canonical_provider) == NULL) { 1262 verbose("failed provider \"%.100s\": " 1263 "realpath: %s", sk_provider, 1264 strerror(errno)); 1265 goto out; 1266 } 1267 free(sk_provider); 1268 sk_provider = xstrdup(canonical_provider); 1269 if (match_pattern_list(sk_provider, 1270 allowed_providers, 0) != 1) { 1271 error("Refusing add key: " 1272 "provider %s not allowed", sk_provider); 1273 goto out; 1274 } 1275 } 1276 } 1277 if ((r = sshkey_shield_private(k)) != 0) { 1278 error_fr(r, "shield private"); 1279 goto out; 1280 } 1281 if (lifetime && !death) 1282 death = monotime() + lifetime; 1283 if ((id = lookup_identity(k)) == NULL) { 1284 id = xcalloc(1, sizeof(Identity)); 1285 TAILQ_INSERT_TAIL(&idtab->idlist, id, next); 1286 /* Increment the number of identities. */ 1287 idtab->nentries++; 1288 } else { 1289 /* identity not visible, do not update */ 1290 if (identity_permitted(id, e, NULL, NULL, NULL) != 0) 1291 goto out; /* error already logged */ 1292 /* key state might have been updated */ 1293 sshkey_free(id->key); 1294 free(id->comment); 1295 free(id->sk_provider); 1296 free_dest_constraints(id->dest_constraints, 1297 id->ndest_constraints); 1298 } 1299 /* success */ 1300 id->key = k; 1301 id->comment = comment; 1302 id->death = death; 1303 id->confirm = confirm; 1304 id->sk_provider = sk_provider; 1305 id->dest_constraints = dest_constraints; 1306 id->ndest_constraints = ndest_constraints; 1307 1308 if ((fp = sshkey_fingerprint(k, SSH_FP_HASH_DEFAULT, 1309 SSH_FP_DEFAULT)) == NULL) 1310 fatal_f("sshkey_fingerprint failed"); 1311 debug_f("add %s %s \"%.100s\" (life: %u) (confirm: %u) " 1312 "(provider: %s) (destination constraints: %zu)", 1313 sshkey_ssh_name(k), fp, comment, seconds, confirm, 1314 sk_provider == NULL ? "none" : sk_provider, ndest_constraints); 1315 free(fp); 1316 /* transferred */ 1317 k = NULL; 1318 comment = NULL; 1319 sk_provider = NULL; 1320 dest_constraints = NULL; 1321 ndest_constraints = 0; 1322 success = 1; 1323 out: 1324 free(sk_provider); 1325 free(comment); 1326 sshkey_free(k); 1327 free_dest_constraints(dest_constraints, ndest_constraints); 1328 send_status(e, success); 1329 } 1330 1331 /* XXX todo: encrypt sensitive data with passphrase */ 1332 static void 1333 process_lock_agent(SocketEntry *e, int lock) 1334 { 1335 int r, success = 0, delay; 1336 char *passwd; 1337 u_char passwdhash[LOCK_SIZE]; 1338 static u_int fail_count = 0; 1339 size_t pwlen; 1340 1341 debug2_f("entering"); 1342 /* 1343 * This is deliberately fatal: the user has requested that we lock, 1344 * but we can't parse their request properly. The only safe thing to 1345 * do is abort. 1346 */ 1347 if ((r = sshbuf_get_cstring(e->request, &passwd, &pwlen)) != 0) 1348 fatal_fr(r, "parse"); 1349 if (pwlen == 0) { 1350 debug("empty password not supported"); 1351 } else if (locked && !lock) { 1352 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt), 1353 passwdhash, sizeof(passwdhash), LOCK_ROUNDS) < 0) 1354 fatal("bcrypt_pbkdf"); 1355 if (timingsafe_bcmp(passwdhash, lock_pwhash, LOCK_SIZE) == 0) { 1356 debug("agent unlocked"); 1357 locked = 0; 1358 fail_count = 0; 1359 explicit_bzero(lock_pwhash, sizeof(lock_pwhash)); 1360 success = 1; 1361 } else { 1362 /* delay in 0.1s increments up to 10s */ 1363 if (fail_count < 100) 1364 fail_count++; 1365 delay = 100000 * fail_count; 1366 debug("unlock failed, delaying %0.1lf seconds", 1367 (double)delay/1000000); 1368 usleep(delay); 1369 } 1370 explicit_bzero(passwdhash, sizeof(passwdhash)); 1371 } else if (!locked && lock) { 1372 debug("agent locked"); 1373 locked = 1; 1374 arc4random_buf(lock_salt, sizeof(lock_salt)); 1375 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt), 1376 lock_pwhash, sizeof(lock_pwhash), LOCK_ROUNDS) < 0) 1377 fatal("bcrypt_pbkdf"); 1378 success = 1; 1379 } 1380 freezero(passwd, pwlen); 1381 send_status(e, success); 1382 } 1383 1384 static void 1385 no_identities(SocketEntry *e) 1386 { 1387 struct sshbuf *msg; 1388 int r; 1389 1390 if ((msg = sshbuf_new()) == NULL) 1391 fatal_f("sshbuf_new failed"); 1392 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 || 1393 (r = sshbuf_put_u32(msg, 0)) != 0 || 1394 (r = sshbuf_put_stringb(e->output, msg)) != 0) 1395 fatal_fr(r, "compose"); 1396 sshbuf_free(msg); 1397 } 1398 1399 #ifdef ENABLE_PKCS11 1400 static void 1401 process_add_smartcard_key(SocketEntry *e) 1402 { 1403 char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX]; 1404 char **comments = NULL; 1405 int r, i, count = 0, success = 0, confirm = 0; 1406 u_int seconds = 0; 1407 time_t death = 0; 1408 struct sshkey **keys = NULL, *k; 1409 Identity *id; 1410 struct dest_constraint *dest_constraints = NULL; 1411 size_t ndest_constraints = 0; 1412 1413 debug2_f("entering"); 1414 if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 || 1415 (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) { 1416 error_fr(r, "parse"); 1417 goto send; 1418 } 1419 if (parse_key_constraints(e->request, NULL, &death, &seconds, &confirm, 1420 NULL, &dest_constraints, &ndest_constraints) != 0) { 1421 error_f("failed to parse constraints"); 1422 goto send; 1423 } 1424 if (e->nsession_ids != 0 && !remote_add_provider) { 1425 verbose("failed PKCS#11 add of \"%.100s\": remote addition of " 1426 "providers is disabled", provider); 1427 goto send; 1428 } 1429 if (realpath(provider, canonical_provider) == NULL) { 1430 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s", 1431 provider, strerror(errno)); 1432 goto send; 1433 } 1434 if (match_pattern_list(canonical_provider, allowed_providers, 0) != 1) { 1435 verbose("refusing PKCS#11 add of \"%.100s\": " 1436 "provider not allowed", canonical_provider); 1437 goto send; 1438 } 1439 debug_f("add %.100s", canonical_provider); 1440 if (lifetime && !death) 1441 death = monotime() + lifetime; 1442 1443 count = pkcs11_add_provider(canonical_provider, pin, &keys, &comments); 1444 for (i = 0; i < count; i++) { 1445 k = keys[i]; 1446 if (lookup_identity(k) == NULL) { 1447 id = xcalloc(1, sizeof(Identity)); 1448 id->key = k; 1449 keys[i] = NULL; /* transferred */ 1450 id->provider = xstrdup(canonical_provider); 1451 if (*comments[i] != '\0') { 1452 id->comment = comments[i]; 1453 comments[i] = NULL; /* transferred */ 1454 } else { 1455 id->comment = xstrdup(canonical_provider); 1456 } 1457 id->death = death; 1458 id->confirm = confirm; 1459 id->dest_constraints = dest_constraints; 1460 id->ndest_constraints = ndest_constraints; 1461 dest_constraints = NULL; /* transferred */ 1462 ndest_constraints = 0; 1463 TAILQ_INSERT_TAIL(&idtab->idlist, id, next); 1464 idtab->nentries++; 1465 success = 1; 1466 } 1467 /* XXX update constraints for existing keys */ 1468 sshkey_free(keys[i]); 1469 free(comments[i]); 1470 } 1471 send: 1472 free(pin); 1473 free(provider); 1474 free(keys); 1475 free(comments); 1476 free_dest_constraints(dest_constraints, ndest_constraints); 1477 send_status(e, success); 1478 } 1479 1480 static void 1481 process_remove_smartcard_key(SocketEntry *e) 1482 { 1483 char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX]; 1484 int r, success = 0; 1485 Identity *id, *nxt; 1486 1487 debug2_f("entering"); 1488 if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 || 1489 (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) { 1490 error_fr(r, "parse"); 1491 goto send; 1492 } 1493 free(pin); 1494 1495 if (realpath(provider, canonical_provider) == NULL) { 1496 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s", 1497 provider, strerror(errno)); 1498 goto send; 1499 } 1500 1501 debug_f("remove %.100s", canonical_provider); 1502 for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) { 1503 nxt = TAILQ_NEXT(id, next); 1504 /* Skip file--based keys */ 1505 if (id->provider == NULL) 1506 continue; 1507 if (!strcmp(canonical_provider, id->provider)) { 1508 TAILQ_REMOVE(&idtab->idlist, id, next); 1509 free_identity(id); 1510 idtab->nentries--; 1511 } 1512 } 1513 if (pkcs11_del_provider(canonical_provider) == 0) 1514 success = 1; 1515 else 1516 error_f("pkcs11_del_provider failed"); 1517 send: 1518 free(provider); 1519 send_status(e, success); 1520 } 1521 #endif /* ENABLE_PKCS11 */ 1522 1523 static int 1524 process_ext_session_bind(SocketEntry *e) 1525 { 1526 int r, sid_match, key_match; 1527 struct sshkey *key = NULL; 1528 struct sshbuf *sid = NULL, *sig = NULL; 1529 char *fp = NULL; 1530 size_t i; 1531 u_char fwd = 0; 1532 1533 debug2_f("entering"); 1534 if ((r = sshkey_froms(e->request, &key)) != 0 || 1535 (r = sshbuf_froms(e->request, &sid)) != 0 || 1536 (r = sshbuf_froms(e->request, &sig)) != 0 || 1537 (r = sshbuf_get_u8(e->request, &fwd)) != 0) { 1538 error_fr(r, "parse"); 1539 goto out; 1540 } 1541 if ((fp = sshkey_fingerprint(key, SSH_FP_HASH_DEFAULT, 1542 SSH_FP_DEFAULT)) == NULL) 1543 fatal_f("fingerprint failed"); 1544 /* check signature with hostkey on session ID */ 1545 if ((r = sshkey_verify(key, sshbuf_ptr(sig), sshbuf_len(sig), 1546 sshbuf_ptr(sid), sshbuf_len(sid), NULL, 0, NULL)) != 0) { 1547 error_fr(r, "sshkey_verify for %s %s", sshkey_type(key), fp); 1548 goto out; 1549 } 1550 /* check whether sid/key already recorded */ 1551 for (i = 0; i < e->nsession_ids; i++) { 1552 if (!e->session_ids[i].forwarded) { 1553 error_f("attempt to bind session ID to socket " 1554 "previously bound for authentication attempt"); 1555 r = -1; 1556 goto out; 1557 } 1558 sid_match = buf_equal(sid, e->session_ids[i].sid) == 0; 1559 key_match = sshkey_equal(key, e->session_ids[i].key); 1560 if (sid_match && key_match) { 1561 debug_f("session ID already recorded for %s %s", 1562 sshkey_type(key), fp); 1563 r = 0; 1564 goto out; 1565 } else if (sid_match) { 1566 error_f("session ID recorded against different key " 1567 "for %s %s", sshkey_type(key), fp); 1568 r = -1; 1569 goto out; 1570 } 1571 /* 1572 * new sid with previously-seen key can happen, e.g. multiple 1573 * connections to the same host. 1574 */ 1575 } 1576 /* record new key/sid */ 1577 if (e->nsession_ids >= AGENT_MAX_SESSION_IDS) { 1578 error_f("too many session IDs recorded"); 1579 goto out; 1580 } 1581 e->session_ids = xrecallocarray(e->session_ids, e->nsession_ids, 1582 e->nsession_ids + 1, sizeof(*e->session_ids)); 1583 i = e->nsession_ids++; 1584 debug_f("recorded %s %s (slot %zu of %d)", sshkey_type(key), fp, i, 1585 AGENT_MAX_SESSION_IDS); 1586 e->session_ids[i].key = key; 1587 e->session_ids[i].forwarded = fwd != 0; 1588 key = NULL; /* transferred */ 1589 /* can't transfer sid; it's refcounted and scoped to request's life */ 1590 if ((e->session_ids[i].sid = sshbuf_new()) == NULL) 1591 fatal_f("sshbuf_new"); 1592 if ((r = sshbuf_putb(e->session_ids[i].sid, sid)) != 0) 1593 fatal_fr(r, "sshbuf_putb session ID"); 1594 /* success */ 1595 r = 0; 1596 out: 1597 free(fp); 1598 sshkey_free(key); 1599 sshbuf_free(sid); 1600 sshbuf_free(sig); 1601 return r == 0 ? 1 : 0; 1602 } 1603 1604 static void 1605 process_extension(SocketEntry *e) 1606 { 1607 int r, success = 0; 1608 char *name; 1609 1610 debug2_f("entering"); 1611 if ((r = sshbuf_get_cstring(e->request, &name, NULL)) != 0) { 1612 error_fr(r, "parse"); 1613 goto send; 1614 } 1615 if (strcmp(name, "session-bind@openssh.com") == 0) 1616 success = process_ext_session_bind(e); 1617 else 1618 debug_f("unsupported extension \"%s\"", name); 1619 free(name); 1620 send: 1621 send_status(e, success); 1622 } 1623 /* 1624 * dispatch incoming message. 1625 * returns 1 on success, 0 for incomplete messages or -1 on error. 1626 */ 1627 static int 1628 process_message(u_int socknum) 1629 { 1630 u_int msg_len; 1631 u_char type; 1632 const u_char *cp; 1633 int r; 1634 SocketEntry *e; 1635 1636 if (socknum >= sockets_alloc) 1637 fatal_f("sock %u >= allocated %u", socknum, sockets_alloc); 1638 e = &sockets[socknum]; 1639 1640 if (sshbuf_len(e->input) < 5) 1641 return 0; /* Incomplete message header. */ 1642 cp = sshbuf_ptr(e->input); 1643 msg_len = PEEK_U32(cp); 1644 if (msg_len > AGENT_MAX_LEN) { 1645 debug_f("socket %u (fd=%d) message too long %u > %u", 1646 socknum, e->fd, msg_len, AGENT_MAX_LEN); 1647 return -1; 1648 } 1649 if (sshbuf_len(e->input) < msg_len + 4) 1650 return 0; /* Incomplete message body. */ 1651 1652 /* move the current input to e->request */ 1653 sshbuf_reset(e->request); 1654 if ((r = sshbuf_get_stringb(e->input, e->request)) != 0 || 1655 (r = sshbuf_get_u8(e->request, &type)) != 0) { 1656 if (r == SSH_ERR_MESSAGE_INCOMPLETE || 1657 r == SSH_ERR_STRING_TOO_LARGE) { 1658 error_fr(r, "parse"); 1659 return -1; 1660 } 1661 fatal_fr(r, "parse"); 1662 } 1663 1664 debug_f("socket %u (fd=%d) type %d", socknum, e->fd, type); 1665 1666 /* check whether agent is locked */ 1667 if (locked && type != SSH_AGENTC_UNLOCK) { 1668 sshbuf_reset(e->request); 1669 switch (type) { 1670 case SSH2_AGENTC_REQUEST_IDENTITIES: 1671 /* send empty lists */ 1672 no_identities(e); 1673 break; 1674 default: 1675 /* send a fail message for all other request types */ 1676 send_status(e, 0); 1677 } 1678 return 1; 1679 } 1680 1681 switch (type) { 1682 case SSH_AGENTC_LOCK: 1683 case SSH_AGENTC_UNLOCK: 1684 process_lock_agent(e, type == SSH_AGENTC_LOCK); 1685 break; 1686 case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES: 1687 process_remove_all_identities(e); /* safe for !WITH_SSH1 */ 1688 break; 1689 /* ssh2 */ 1690 case SSH2_AGENTC_SIGN_REQUEST: 1691 process_sign_request2(e); 1692 break; 1693 case SSH2_AGENTC_REQUEST_IDENTITIES: 1694 process_request_identities(e); 1695 break; 1696 case SSH2_AGENTC_ADD_IDENTITY: 1697 case SSH2_AGENTC_ADD_ID_CONSTRAINED: 1698 process_add_identity(e); 1699 break; 1700 case SSH2_AGENTC_REMOVE_IDENTITY: 1701 process_remove_identity(e); 1702 break; 1703 case SSH2_AGENTC_REMOVE_ALL_IDENTITIES: 1704 process_remove_all_identities(e); 1705 break; 1706 #ifdef ENABLE_PKCS11 1707 case SSH_AGENTC_ADD_SMARTCARD_KEY: 1708 case SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED: 1709 process_add_smartcard_key(e); 1710 break; 1711 case SSH_AGENTC_REMOVE_SMARTCARD_KEY: 1712 process_remove_smartcard_key(e); 1713 break; 1714 #endif /* ENABLE_PKCS11 */ 1715 case SSH_AGENTC_EXTENSION: 1716 process_extension(e); 1717 break; 1718 default: 1719 /* Unknown message. Respond with failure. */ 1720 error("Unknown message %d", type); 1721 sshbuf_reset(e->request); 1722 send_status(e, 0); 1723 break; 1724 } 1725 return 1; 1726 } 1727 1728 static void 1729 new_socket(sock_type type, int fd) 1730 { 1731 u_int i, old_alloc, new_alloc; 1732 1733 debug_f("type = %s", type == AUTH_CONNECTION ? "CONNECTION" : 1734 (type == AUTH_SOCKET ? "SOCKET" : "UNKNOWN")); 1735 if (type == AUTH_CONNECTION) { 1736 debug("xcount %d -> %d", xcount, xcount + 1); 1737 ++xcount; 1738 } 1739 set_nonblock(fd); 1740 1741 if (fd > max_fd) 1742 max_fd = fd; 1743 1744 for (i = 0; i < sockets_alloc; i++) 1745 if (sockets[i].type == AUTH_UNUSED) { 1746 sockets[i].fd = fd; 1747 if ((sockets[i].input = sshbuf_new()) == NULL || 1748 (sockets[i].output = sshbuf_new()) == NULL || 1749 (sockets[i].request = sshbuf_new()) == NULL) 1750 fatal_f("sshbuf_new failed"); 1751 sockets[i].type = type; 1752 return; 1753 } 1754 old_alloc = sockets_alloc; 1755 new_alloc = sockets_alloc + 10; 1756 sockets = xrecallocarray(sockets, old_alloc, new_alloc, 1757 sizeof(sockets[0])); 1758 for (i = old_alloc; i < new_alloc; i++) 1759 sockets[i].type = AUTH_UNUSED; 1760 sockets_alloc = new_alloc; 1761 sockets[old_alloc].fd = fd; 1762 if ((sockets[old_alloc].input = sshbuf_new()) == NULL || 1763 (sockets[old_alloc].output = sshbuf_new()) == NULL || 1764 (sockets[old_alloc].request = sshbuf_new()) == NULL) 1765 fatal_f("sshbuf_new failed"); 1766 sockets[old_alloc].type = type; 1767 } 1768 1769 static int 1770 handle_socket_read(u_int socknum) 1771 { 1772 struct sockaddr_un sunaddr; 1773 socklen_t slen; 1774 uid_t euid; 1775 gid_t egid; 1776 int fd; 1777 1778 slen = sizeof(sunaddr); 1779 fd = accept(sockets[socknum].fd, (struct sockaddr *)&sunaddr, &slen); 1780 if (fd == -1) { 1781 error("accept from AUTH_SOCKET: %s", strerror(errno)); 1782 return -1; 1783 } 1784 if (getpeereid(fd, &euid, &egid) == -1) { 1785 error("getpeereid %d failed: %s", fd, strerror(errno)); 1786 close(fd); 1787 return -1; 1788 } 1789 if ((euid != 0) && (getuid() != euid)) { 1790 error("uid mismatch: peer euid %u != uid %u", 1791 (u_int) euid, (u_int) getuid()); 1792 close(fd); 1793 return -1; 1794 } 1795 new_socket(AUTH_CONNECTION, fd); 1796 return 0; 1797 } 1798 1799 static int 1800 handle_conn_read(u_int socknum) 1801 { 1802 char buf[AGENT_RBUF_LEN]; 1803 ssize_t len; 1804 int r; 1805 1806 if ((len = read(sockets[socknum].fd, buf, sizeof(buf))) <= 0) { 1807 if (len == -1) { 1808 if (errno == EAGAIN || errno == EINTR) 1809 return 0; 1810 error_f("read error on socket %u (fd %d): %s", 1811 socknum, sockets[socknum].fd, strerror(errno)); 1812 } 1813 return -1; 1814 } 1815 if ((r = sshbuf_put(sockets[socknum].input, buf, len)) != 0) 1816 fatal_fr(r, "compose"); 1817 explicit_bzero(buf, sizeof(buf)); 1818 for (;;) { 1819 if ((r = process_message(socknum)) == -1) 1820 return -1; 1821 else if (r == 0) 1822 break; 1823 } 1824 return 0; 1825 } 1826 1827 static int 1828 handle_conn_write(u_int socknum) 1829 { 1830 ssize_t len; 1831 int r; 1832 1833 if (sshbuf_len(sockets[socknum].output) == 0) 1834 return 0; /* shouldn't happen */ 1835 if ((len = write(sockets[socknum].fd, 1836 sshbuf_ptr(sockets[socknum].output), 1837 sshbuf_len(sockets[socknum].output))) <= 0) { 1838 if (len == -1) { 1839 if (errno == EAGAIN || errno == EINTR) 1840 return 0; 1841 error_f("read error on socket %u (fd %d): %s", 1842 socknum, sockets[socknum].fd, strerror(errno)); 1843 } 1844 return -1; 1845 } 1846 if ((r = sshbuf_consume(sockets[socknum].output, len)) != 0) 1847 fatal_fr(r, "consume"); 1848 return 0; 1849 } 1850 1851 static void 1852 after_poll(struct pollfd *pfd, size_t npfd, u_int maxfds) 1853 { 1854 size_t i; 1855 u_int socknum, activefds = npfd; 1856 1857 for (i = 0; i < npfd; i++) { 1858 if (pfd[i].revents == 0) 1859 continue; 1860 /* Find sockets entry */ 1861 for (socknum = 0; socknum < sockets_alloc; socknum++) { 1862 if (sockets[socknum].type != AUTH_SOCKET && 1863 sockets[socknum].type != AUTH_CONNECTION) 1864 continue; 1865 if (pfd[i].fd == sockets[socknum].fd) 1866 break; 1867 } 1868 if (socknum >= sockets_alloc) { 1869 error_f("no socket for fd %d", pfd[i].fd); 1870 continue; 1871 } 1872 /* Process events */ 1873 switch (sockets[socknum].type) { 1874 case AUTH_SOCKET: 1875 if ((pfd[i].revents & (POLLIN|POLLERR)) == 0) 1876 break; 1877 if (npfd > maxfds) { 1878 debug3("out of fds (active %u >= limit %u); " 1879 "skipping accept", activefds, maxfds); 1880 break; 1881 } 1882 if (handle_socket_read(socknum) == 0) 1883 activefds++; 1884 break; 1885 case AUTH_CONNECTION: 1886 if ((pfd[i].revents & (POLLIN|POLLHUP|POLLERR)) != 0 && 1887 handle_conn_read(socknum) != 0) 1888 goto close_sock; 1889 if ((pfd[i].revents & (POLLOUT|POLLHUP)) != 0 && 1890 handle_conn_write(socknum) != 0) { 1891 close_sock: 1892 if (activefds == 0) 1893 fatal("activefds == 0 at close_sock"); 1894 close_socket(&sockets[socknum]); 1895 activefds--; 1896 break; 1897 } 1898 break; 1899 default: 1900 break; 1901 } 1902 } 1903 } 1904 1905 static int 1906 prepare_poll(struct pollfd **pfdp, size_t *npfdp, int *timeoutp, u_int maxfds) 1907 { 1908 struct pollfd *pfd = *pfdp; 1909 size_t i, j, npfd = 0; 1910 time_t deadline; 1911 int r; 1912 1913 /* Count active sockets */ 1914 for (i = 0; i < sockets_alloc; i++) { 1915 switch (sockets[i].type) { 1916 case AUTH_SOCKET: 1917 case AUTH_CONNECTION: 1918 npfd++; 1919 break; 1920 case AUTH_UNUSED: 1921 break; 1922 default: 1923 fatal("Unknown socket type %d", sockets[i].type); 1924 break; 1925 } 1926 } 1927 if (npfd != *npfdp && 1928 (pfd = recallocarray(pfd, *npfdp, npfd, sizeof(*pfd))) == NULL) 1929 fatal_f("recallocarray failed"); 1930 *pfdp = pfd; 1931 *npfdp = npfd; 1932 1933 for (i = j = 0; i < sockets_alloc; i++) { 1934 switch (sockets[i].type) { 1935 case AUTH_SOCKET: 1936 if (npfd > maxfds) { 1937 debug3("out of fds (active %zu >= limit %u); " 1938 "skipping arming listener", npfd, maxfds); 1939 break; 1940 } 1941 pfd[j].fd = sockets[i].fd; 1942 pfd[j].revents = 0; 1943 pfd[j].events = POLLIN; 1944 j++; 1945 break; 1946 case AUTH_CONNECTION: 1947 pfd[j].fd = sockets[i].fd; 1948 pfd[j].revents = 0; 1949 /* 1950 * Only prepare to read if we can handle a full-size 1951 * input read buffer and enqueue a max size reply.. 1952 */ 1953 if ((r = sshbuf_check_reserve(sockets[i].input, 1954 AGENT_RBUF_LEN)) == 0 && 1955 (r = sshbuf_check_reserve(sockets[i].output, 1956 AGENT_MAX_LEN)) == 0) 1957 pfd[j].events = POLLIN; 1958 else if (r != SSH_ERR_NO_BUFFER_SPACE) 1959 fatal_fr(r, "reserve"); 1960 if (sshbuf_len(sockets[i].output) > 0) 1961 pfd[j].events |= POLLOUT; 1962 j++; 1963 break; 1964 default: 1965 break; 1966 } 1967 } 1968 deadline = reaper(); 1969 if (parent_alive_interval != 0) 1970 deadline = (deadline == 0) ? parent_alive_interval : 1971 MINIMUM(deadline, parent_alive_interval); 1972 if (deadline == 0) { 1973 *timeoutp = -1; /* INFTIM */ 1974 } else { 1975 if (deadline > INT_MAX / 1000) 1976 *timeoutp = INT_MAX / 1000; 1977 else 1978 *timeoutp = deadline * 1000; 1979 } 1980 return (1); 1981 } 1982 1983 static void 1984 cleanup_socket(void) 1985 { 1986 if (cleanup_pid != 0 && getpid() != cleanup_pid) 1987 return; 1988 debug_f("cleanup"); 1989 if (socket_name[0]) 1990 unlink(socket_name); 1991 if (socket_dir[0]) 1992 rmdir(socket_dir); 1993 } 1994 1995 void 1996 cleanup_exit(int i) 1997 { 1998 cleanup_socket(); 1999 _exit(i); 2000 } 2001 2002 static void 2003 cleanup_handler(int sig) 2004 { 2005 cleanup_socket(); 2006 #ifdef ENABLE_PKCS11 2007 pkcs11_terminate(); 2008 #endif 2009 _exit(2); 2010 } 2011 2012 static void 2013 check_parent_exists(void) 2014 { 2015 /* 2016 * If our parent has exited then getppid() will return (pid_t)1, 2017 * so testing for that should be safe. 2018 */ 2019 if (parent_pid != -1 && getppid() != parent_pid) { 2020 /* printf("Parent has died - Authentication agent exiting.\n"); */ 2021 cleanup_socket(); 2022 _exit(2); 2023 } 2024 } 2025 2026 static void 2027 usage(void) 2028 { 2029 fprintf(stderr, 2030 "usage: ssh-agent [-c | -s] [-Ddx] [-a bind_address] [-E fingerprint_hash]\n" 2031 " [-O option] [-P allowed_providers] [-t life]\n" 2032 " ssh-agent [-a bind_address] [-E fingerprint_hash] [-O option]\n" 2033 " [-P allowed_providers] [-t life] command [arg ...]\n" 2034 " ssh-agent [-c | -s] -k\n"); 2035 exit(1); 2036 } 2037 2038 int 2039 main(int ac, char **av) 2040 { 2041 int c_flag = 0, d_flag = 0, D_flag = 0, k_flag = 0, s_flag = 0; 2042 int sock, ch, result, saved_errno; 2043 char *shell, *format, *pidstr, *agentsocket = NULL; 2044 #ifdef HAVE_SETRLIMIT 2045 struct rlimit rlim; 2046 #endif 2047 extern int optind; 2048 extern char *optarg; 2049 pid_t pid; 2050 char pidstrbuf[1 + 3 * sizeof pid]; 2051 size_t len; 2052 mode_t prev_mask; 2053 int timeout = -1; /* INFTIM */ 2054 struct pollfd *pfd = NULL; 2055 size_t npfd = 0; 2056 u_int maxfds; 2057 2058 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */ 2059 sanitise_stdfd(); 2060 2061 /* drop */ 2062 setegid(getgid()); 2063 setgid(getgid()); 2064 setuid(geteuid()); 2065 2066 platform_disable_tracing(0); /* strict=no */ 2067 2068 #ifdef RLIMIT_NOFILE 2069 if (getrlimit(RLIMIT_NOFILE, &rlim) == -1) 2070 fatal("%s: getrlimit: %s", __progname, strerror(errno)); 2071 #endif 2072 2073 __progname = ssh_get_progname(av[0]); 2074 seed_rng(); 2075 2076 while ((ch = getopt(ac, av, "cDdksE:a:O:P:t:x")) != -1) { 2077 switch (ch) { 2078 case 'E': 2079 fingerprint_hash = ssh_digest_alg_by_name(optarg); 2080 if (fingerprint_hash == -1) 2081 fatal("Invalid hash algorithm \"%s\"", optarg); 2082 break; 2083 case 'c': 2084 if (s_flag) 2085 usage(); 2086 c_flag++; 2087 break; 2088 case 'k': 2089 k_flag++; 2090 break; 2091 case 'O': 2092 if (strcmp(optarg, "no-restrict-websafe") == 0) 2093 restrict_websafe = 0; 2094 else if (strcmp(optarg, "allow-remote-pkcs11") == 0) 2095 remote_add_provider = 1; 2096 else 2097 fatal("Unknown -O option"); 2098 break; 2099 case 'P': 2100 if (allowed_providers != NULL) 2101 fatal("-P option already specified"); 2102 allowed_providers = xstrdup(optarg); 2103 break; 2104 case 's': 2105 if (c_flag) 2106 usage(); 2107 s_flag++; 2108 break; 2109 case 'd': 2110 if (d_flag || D_flag) 2111 usage(); 2112 d_flag++; 2113 break; 2114 case 'D': 2115 if (d_flag || D_flag) 2116 usage(); 2117 D_flag++; 2118 break; 2119 case 'a': 2120 agentsocket = optarg; 2121 break; 2122 case 't': 2123 if ((lifetime = convtime(optarg)) == -1) { 2124 fprintf(stderr, "Invalid lifetime\n"); 2125 usage(); 2126 } 2127 break; 2128 case 'x': 2129 xcount = 0; 2130 break; 2131 default: 2132 usage(); 2133 } 2134 } 2135 ac -= optind; 2136 av += optind; 2137 2138 if (ac > 0 && (c_flag || k_flag || s_flag || d_flag || D_flag)) 2139 usage(); 2140 2141 if (allowed_providers == NULL) 2142 allowed_providers = xstrdup(DEFAULT_ALLOWED_PROVIDERS); 2143 2144 if (ac == 0 && !c_flag && !s_flag) { 2145 shell = getenv("SHELL"); 2146 if (shell != NULL && (len = strlen(shell)) > 2 && 2147 strncmp(shell + len - 3, "csh", 3) == 0) 2148 c_flag = 1; 2149 } 2150 if (k_flag) { 2151 const char *errstr = NULL; 2152 2153 pidstr = getenv(SSH_AGENTPID_ENV_NAME); 2154 if (pidstr == NULL) { 2155 fprintf(stderr, "%s not set, cannot kill agent\n", 2156 SSH_AGENTPID_ENV_NAME); 2157 exit(1); 2158 } 2159 pid = (int)strtonum(pidstr, 2, INT_MAX, &errstr); 2160 if (errstr) { 2161 fprintf(stderr, 2162 "%s=\"%s\", which is not a good PID: %s\n", 2163 SSH_AGENTPID_ENV_NAME, pidstr, errstr); 2164 exit(1); 2165 } 2166 if (kill(pid, SIGTERM) == -1) { 2167 perror("kill"); 2168 exit(1); 2169 } 2170 format = c_flag ? "unsetenv %s;\n" : "unset %s;\n"; 2171 printf(format, SSH_AUTHSOCKET_ENV_NAME); 2172 printf(format, SSH_AGENTPID_ENV_NAME); 2173 printf("echo Agent pid %ld killed;\n", (long)pid); 2174 exit(0); 2175 } 2176 2177 /* 2178 * Minimum file descriptors: 2179 * stdio (3) + listener (1) + syslog (1 maybe) + connection (1) + 2180 * a few spare for libc / stack protectors / sanitisers, etc. 2181 */ 2182 #define SSH_AGENT_MIN_FDS (3+1+1+1+4) 2183 if (rlim.rlim_cur < SSH_AGENT_MIN_FDS) 2184 fatal("%s: file descriptor rlimit %lld too low (minimum %u)", 2185 __progname, (long long)rlim.rlim_cur, SSH_AGENT_MIN_FDS); 2186 maxfds = rlim.rlim_cur - SSH_AGENT_MIN_FDS; 2187 2188 parent_pid = getpid(); 2189 2190 if (agentsocket == NULL) { 2191 /* Create private directory for agent socket */ 2192 mktemp_proto(socket_dir, sizeof(socket_dir)); 2193 if (mkdtemp(socket_dir) == NULL) { 2194 perror("mkdtemp: private socket dir"); 2195 exit(1); 2196 } 2197 snprintf(socket_name, sizeof socket_name, "%s/agent.%ld", socket_dir, 2198 (long)parent_pid); 2199 } else { 2200 /* Try to use specified agent socket */ 2201 socket_dir[0] = '\0'; 2202 strlcpy(socket_name, agentsocket, sizeof socket_name); 2203 } 2204 2205 /* 2206 * Create socket early so it will exist before command gets run from 2207 * the parent. 2208 */ 2209 prev_mask = umask(0177); 2210 sock = unix_listener(socket_name, SSH_LISTEN_BACKLOG, 0); 2211 if (sock < 0) { 2212 /* XXX - unix_listener() calls error() not perror() */ 2213 *socket_name = '\0'; /* Don't unlink any existing file */ 2214 cleanup_exit(1); 2215 } 2216 umask(prev_mask); 2217 2218 /* 2219 * Fork, and have the parent execute the command, if any, or present 2220 * the socket data. The child continues as the authentication agent. 2221 */ 2222 if (D_flag || d_flag) { 2223 log_init(__progname, 2224 d_flag ? SYSLOG_LEVEL_DEBUG3 : SYSLOG_LEVEL_INFO, 2225 SYSLOG_FACILITY_AUTH, 1); 2226 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n"; 2227 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name, 2228 SSH_AUTHSOCKET_ENV_NAME); 2229 printf("echo Agent pid %ld;\n", (long)parent_pid); 2230 fflush(stdout); 2231 goto skip; 2232 } 2233 pid = fork(); 2234 if (pid == -1) { 2235 perror("fork"); 2236 cleanup_exit(1); 2237 } 2238 if (pid != 0) { /* Parent - execute the given command. */ 2239 close(sock); 2240 snprintf(pidstrbuf, sizeof pidstrbuf, "%ld", (long)pid); 2241 if (ac == 0) { 2242 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n"; 2243 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name, 2244 SSH_AUTHSOCKET_ENV_NAME); 2245 printf(format, SSH_AGENTPID_ENV_NAME, pidstrbuf, 2246 SSH_AGENTPID_ENV_NAME); 2247 printf("echo Agent pid %ld;\n", (long)pid); 2248 exit(0); 2249 } 2250 if (setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1) == -1 || 2251 setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1) == -1) { 2252 perror("setenv"); 2253 exit(1); 2254 } 2255 execvp(av[0], av); 2256 perror(av[0]); 2257 exit(1); 2258 } 2259 /* child */ 2260 log_init(__progname, SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_AUTH, 0); 2261 2262 if (setsid() == -1) { 2263 error("setsid: %s", strerror(errno)); 2264 cleanup_exit(1); 2265 } 2266 2267 (void)chdir("/"); 2268 if (stdfd_devnull(1, 1, 1) == -1) 2269 error_f("stdfd_devnull failed"); 2270 2271 #ifdef HAVE_SETRLIMIT 2272 /* deny core dumps, since memory contains unencrypted private keys */ 2273 rlim.rlim_cur = rlim.rlim_max = 0; 2274 if (setrlimit(RLIMIT_CORE, &rlim) == -1) { 2275 error("setrlimit RLIMIT_CORE: %s", strerror(errno)); 2276 cleanup_exit(1); 2277 } 2278 #endif 2279 2280 skip: 2281 2282 cleanup_pid = getpid(); 2283 2284 #ifdef ENABLE_PKCS11 2285 pkcs11_init(0); 2286 #endif 2287 new_socket(AUTH_SOCKET, sock); 2288 if (ac > 0) 2289 parent_alive_interval = 10; 2290 idtab_init(); 2291 ssh_signal(SIGPIPE, SIG_IGN); 2292 ssh_signal(SIGINT, (d_flag | D_flag) ? cleanup_handler : SIG_IGN); 2293 ssh_signal(SIGHUP, cleanup_handler); 2294 ssh_signal(SIGTERM, cleanup_handler); 2295 2296 if (pledge("stdio rpath cpath unix id proc exec", NULL) == -1) 2297 fatal("%s: pledge: %s", __progname, strerror(errno)); 2298 platform_pledge_agent(); 2299 2300 while (1) { 2301 prepare_poll(&pfd, &npfd, &timeout, maxfds); 2302 result = poll(pfd, npfd, timeout); 2303 saved_errno = errno; 2304 if (parent_alive_interval != 0) 2305 check_parent_exists(); 2306 (void) reaper(); /* remove expired keys */ 2307 if (result == -1) { 2308 if (saved_errno == EINTR) 2309 continue; 2310 fatal("poll: %s", strerror(saved_errno)); 2311 } else if (result > 0) 2312 after_poll(pfd, npfd, maxfds); 2313 } 2314 /* NOTREACHED */ 2315 } 2316