1 /* $OpenBSD: ssh-agent.c,v 1.233 2019/01/22 22:58:50 djm Exp $ */ 2 /* 3 * Author: Tatu Ylonen <ylo@cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 5 * All rights reserved 6 * The authentication agent program. 7 * 8 * As far as I am concerned, the code I have written for this software 9 * can be used freely for any purpose. Any derived versions of this 10 * software must be clearly marked as such, and if the derived work is 11 * incompatible with the protocol description in the RFC file, it must be 12 * called by a name other than "ssh" or "Secure Shell". 13 * 14 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. 15 * 16 * Redistribution and use in source and binary forms, with or without 17 * modification, are permitted provided that the following conditions 18 * are met: 19 * 1. Redistributions of source code must retain the above copyright 20 * notice, this list of conditions and the following disclaimer. 21 * 2. Redistributions in binary form must reproduce the above copyright 22 * notice, this list of conditions and the following disclaimer in the 23 * documentation and/or other materials provided with the distribution. 24 * 25 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 26 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 27 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 28 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 29 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 30 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 31 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 32 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 33 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 34 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 35 */ 36 37 #include <sys/types.h> 38 #include <sys/time.h> 39 #include <sys/queue.h> 40 #include <sys/resource.h> 41 #include <sys/socket.h> 42 #include <sys/stat.h> 43 #include <sys/un.h> 44 45 #ifdef WITH_OPENSSL 46 #include <openssl/evp.h> 47 #endif 48 49 #include <errno.h> 50 #include <fcntl.h> 51 #include <paths.h> 52 #include <poll.h> 53 #include <signal.h> 54 #include <stdlib.h> 55 #include <stdio.h> 56 #include <string.h> 57 #include <limits.h> 58 #include <time.h> 59 #include <unistd.h> 60 #include <util.h> 61 62 #include "xmalloc.h" 63 #include "ssh.h" 64 #include "sshbuf.h" 65 #include "sshkey.h" 66 #include "authfd.h" 67 #include "compat.h" 68 #include "log.h" 69 #include "misc.h" 70 #include "digest.h" 71 #include "ssherr.h" 72 #include "match.h" 73 74 #ifdef ENABLE_PKCS11 75 #include "ssh-pkcs11.h" 76 #endif 77 78 #ifndef DEFAULT_PKCS11_WHITELIST 79 # define DEFAULT_PKCS11_WHITELIST "/usr/lib*/*,/usr/local/lib*/*" 80 #endif 81 82 /* Maximum accepted message length */ 83 #define AGENT_MAX_LEN (256*1024) 84 /* Maximum bytes to read from client socket */ 85 #define AGENT_RBUF_LEN (4096) 86 87 typedef enum { 88 AUTH_UNUSED, 89 AUTH_SOCKET, 90 AUTH_CONNECTION 91 } sock_type; 92 93 typedef struct { 94 int fd; 95 sock_type type; 96 struct sshbuf *input; 97 struct sshbuf *output; 98 struct sshbuf *request; 99 } SocketEntry; 100 101 u_int sockets_alloc = 0; 102 SocketEntry *sockets = NULL; 103 104 typedef struct identity { 105 TAILQ_ENTRY(identity) next; 106 struct sshkey *key; 107 char *comment; 108 char *provider; 109 time_t death; 110 u_int confirm; 111 } Identity; 112 113 struct idtable { 114 int nentries; 115 TAILQ_HEAD(idqueue, identity) idlist; 116 }; 117 118 /* private key table */ 119 struct idtable *idtab; 120 121 int max_fd = 0; 122 123 /* pid of shell == parent of agent */ 124 pid_t parent_pid = -1; 125 time_t parent_alive_interval = 0; 126 127 /* pid of process for which cleanup_socket is applicable */ 128 pid_t cleanup_pid = 0; 129 130 /* pathname and directory for AUTH_SOCKET */ 131 char socket_name[PATH_MAX]; 132 char socket_dir[PATH_MAX]; 133 134 /* PKCS#11 path whitelist */ 135 static char *pkcs11_whitelist; 136 137 /* locking */ 138 #define LOCK_SIZE 32 139 #define LOCK_SALT_SIZE 16 140 #define LOCK_ROUNDS 1 141 int locked = 0; 142 u_char lock_pwhash[LOCK_SIZE]; 143 u_char lock_salt[LOCK_SALT_SIZE]; 144 145 extern char *__progname; 146 147 /* Default lifetime in seconds (0 == forever) */ 148 static long lifetime = 0; 149 150 static int fingerprint_hash = SSH_FP_HASH_DEFAULT; 151 152 static void 153 close_socket(SocketEntry *e) 154 { 155 close(e->fd); 156 e->fd = -1; 157 e->type = AUTH_UNUSED; 158 sshbuf_free(e->input); 159 sshbuf_free(e->output); 160 sshbuf_free(e->request); 161 } 162 163 static void 164 idtab_init(void) 165 { 166 idtab = xcalloc(1, sizeof(*idtab)); 167 TAILQ_INIT(&idtab->idlist); 168 idtab->nentries = 0; 169 } 170 171 static void 172 free_identity(Identity *id) 173 { 174 sshkey_free(id->key); 175 free(id->provider); 176 free(id->comment); 177 free(id); 178 } 179 180 /* return matching private key for given public key */ 181 static Identity * 182 lookup_identity(struct sshkey *key) 183 { 184 Identity *id; 185 186 TAILQ_FOREACH(id, &idtab->idlist, next) { 187 if (sshkey_equal(key, id->key)) 188 return (id); 189 } 190 return (NULL); 191 } 192 193 /* Check confirmation of keysign request */ 194 static int 195 confirm_key(Identity *id) 196 { 197 char *p; 198 int ret = -1; 199 200 p = sshkey_fingerprint(id->key, fingerprint_hash, SSH_FP_DEFAULT); 201 if (p != NULL && 202 ask_permission("Allow use of key %s?\nKey fingerprint %s.", 203 id->comment, p)) 204 ret = 0; 205 free(p); 206 207 return (ret); 208 } 209 210 static void 211 send_status(SocketEntry *e, int success) 212 { 213 int r; 214 215 if ((r = sshbuf_put_u32(e->output, 1)) != 0 || 216 (r = sshbuf_put_u8(e->output, success ? 217 SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE)) != 0) 218 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 219 } 220 221 /* send list of supported public keys to 'client' */ 222 static void 223 process_request_identities(SocketEntry *e) 224 { 225 Identity *id; 226 struct sshbuf *msg; 227 int r; 228 229 if ((msg = sshbuf_new()) == NULL) 230 fatal("%s: sshbuf_new failed", __func__); 231 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 || 232 (r = sshbuf_put_u32(msg, idtab->nentries)) != 0) 233 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 234 TAILQ_FOREACH(id, &idtab->idlist, next) { 235 if ((r = sshkey_puts_opts(id->key, msg, SSHKEY_SERIALIZE_INFO)) 236 != 0 || 237 (r = sshbuf_put_cstring(msg, id->comment)) != 0) { 238 error("%s: put key/comment: %s", __func__, 239 ssh_err(r)); 240 continue; 241 } 242 } 243 if ((r = sshbuf_put_stringb(e->output, msg)) != 0) 244 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 245 sshbuf_free(msg); 246 } 247 248 249 static char * 250 agent_decode_alg(struct sshkey *key, u_int flags) 251 { 252 if (key->type == KEY_RSA) { 253 if (flags & SSH_AGENT_RSA_SHA2_256) 254 return "rsa-sha2-256"; 255 else if (flags & SSH_AGENT_RSA_SHA2_512) 256 return "rsa-sha2-512"; 257 } 258 return NULL; 259 } 260 261 /* ssh2 only */ 262 static void 263 process_sign_request2(SocketEntry *e) 264 { 265 const u_char *data; 266 u_char *signature = NULL; 267 size_t dlen, slen = 0; 268 u_int compat = 0, flags; 269 int r, ok = -1; 270 struct sshbuf *msg; 271 struct sshkey *key = NULL; 272 struct identity *id; 273 274 if ((msg = sshbuf_new()) == NULL) 275 fatal("%s: sshbuf_new failed", __func__); 276 if ((r = sshkey_froms(e->request, &key)) != 0 || 277 (r = sshbuf_get_string_direct(e->request, &data, &dlen)) != 0 || 278 (r = sshbuf_get_u32(e->request, &flags)) != 0) { 279 error("%s: couldn't parse request: %s", __func__, ssh_err(r)); 280 goto send; 281 } 282 283 if ((id = lookup_identity(key)) == NULL) { 284 verbose("%s: %s key not found", __func__, sshkey_type(key)); 285 goto send; 286 } 287 if (id->confirm && confirm_key(id) != 0) { 288 verbose("%s: user refused key", __func__); 289 goto send; 290 } 291 if ((r = sshkey_sign(id->key, &signature, &slen, 292 data, dlen, agent_decode_alg(key, flags), compat)) != 0) { 293 error("%s: sshkey_sign: %s", __func__, ssh_err(r)); 294 goto send; 295 } 296 /* Success */ 297 ok = 0; 298 send: 299 sshkey_free(key); 300 if (ok == 0) { 301 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 || 302 (r = sshbuf_put_string(msg, signature, slen)) != 0) 303 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 304 } else if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0) 305 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 306 307 if ((r = sshbuf_put_stringb(e->output, msg)) != 0) 308 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 309 310 sshbuf_free(msg); 311 free(signature); 312 } 313 314 /* shared */ 315 static void 316 process_remove_identity(SocketEntry *e) 317 { 318 int r, success = 0; 319 struct sshkey *key = NULL; 320 Identity *id; 321 322 if ((r = sshkey_froms(e->request, &key)) != 0) { 323 error("%s: get key: %s", __func__, ssh_err(r)); 324 goto done; 325 } 326 if ((id = lookup_identity(key)) == NULL) { 327 debug("%s: key not found", __func__); 328 goto done; 329 } 330 /* We have this key, free it. */ 331 if (idtab->nentries < 1) 332 fatal("%s: internal error: nentries %d", 333 __func__, idtab->nentries); 334 TAILQ_REMOVE(&idtab->idlist, id, next); 335 free_identity(id); 336 idtab->nentries--; 337 sshkey_free(key); 338 success = 1; 339 done: 340 send_status(e, success); 341 } 342 343 static void 344 process_remove_all_identities(SocketEntry *e) 345 { 346 Identity *id; 347 348 /* Loop over all identities and clear the keys. */ 349 for (id = TAILQ_FIRST(&idtab->idlist); id; 350 id = TAILQ_FIRST(&idtab->idlist)) { 351 TAILQ_REMOVE(&idtab->idlist, id, next); 352 free_identity(id); 353 } 354 355 /* Mark that there are no identities. */ 356 idtab->nentries = 0; 357 358 /* Send success. */ 359 send_status(e, 1); 360 } 361 362 /* removes expired keys and returns number of seconds until the next expiry */ 363 static time_t 364 reaper(void) 365 { 366 time_t deadline = 0, now = monotime(); 367 Identity *id, *nxt; 368 369 for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) { 370 nxt = TAILQ_NEXT(id, next); 371 if (id->death == 0) 372 continue; 373 if (now >= id->death) { 374 debug("expiring key '%s'", id->comment); 375 TAILQ_REMOVE(&idtab->idlist, id, next); 376 free_identity(id); 377 idtab->nentries--; 378 } else 379 deadline = (deadline == 0) ? id->death : 380 MINIMUM(deadline, id->death); 381 } 382 if (deadline == 0 || deadline <= now) 383 return 0; 384 else 385 return (deadline - now); 386 } 387 388 static void 389 process_add_identity(SocketEntry *e) 390 { 391 Identity *id; 392 int success = 0, confirm = 0; 393 u_int seconds, maxsign; 394 char *comment = NULL; 395 time_t death = 0; 396 struct sshkey *k = NULL; 397 u_char ctype; 398 int r = SSH_ERR_INTERNAL_ERROR; 399 400 if ((r = sshkey_private_deserialize(e->request, &k)) != 0 || 401 k == NULL || 402 (r = sshbuf_get_cstring(e->request, &comment, NULL)) != 0) { 403 error("%s: decode private key: %s", __func__, ssh_err(r)); 404 goto err; 405 } 406 407 while (sshbuf_len(e->request)) { 408 if ((r = sshbuf_get_u8(e->request, &ctype)) != 0) { 409 error("%s: buffer error: %s", __func__, ssh_err(r)); 410 goto err; 411 } 412 switch (ctype) { 413 case SSH_AGENT_CONSTRAIN_LIFETIME: 414 if ((r = sshbuf_get_u32(e->request, &seconds)) != 0) { 415 error("%s: bad lifetime constraint: %s", 416 __func__, ssh_err(r)); 417 goto err; 418 } 419 death = monotime() + seconds; 420 break; 421 case SSH_AGENT_CONSTRAIN_CONFIRM: 422 confirm = 1; 423 break; 424 case SSH_AGENT_CONSTRAIN_MAXSIGN: 425 if ((r = sshbuf_get_u32(e->request, &maxsign)) != 0) { 426 error("%s: bad maxsign constraint: %s", 427 __func__, ssh_err(r)); 428 goto err; 429 } 430 if ((r = sshkey_enable_maxsign(k, maxsign)) != 0) { 431 error("%s: cannot enable maxsign: %s", 432 __func__, ssh_err(r)); 433 goto err; 434 } 435 break; 436 default: 437 error("%s: Unknown constraint %d", __func__, ctype); 438 err: 439 sshbuf_reset(e->request); 440 free(comment); 441 sshkey_free(k); 442 goto send; 443 } 444 } 445 446 success = 1; 447 if (lifetime && !death) 448 death = monotime() + lifetime; 449 if ((id = lookup_identity(k)) == NULL) { 450 id = xcalloc(1, sizeof(Identity)); 451 TAILQ_INSERT_TAIL(&idtab->idlist, id, next); 452 /* Increment the number of identities. */ 453 idtab->nentries++; 454 } else { 455 /* key state might have been updated */ 456 sshkey_free(id->key); 457 free(id->comment); 458 } 459 id->key = k; 460 id->comment = comment; 461 id->death = death; 462 id->confirm = confirm; 463 send: 464 send_status(e, success); 465 } 466 467 /* XXX todo: encrypt sensitive data with passphrase */ 468 static void 469 process_lock_agent(SocketEntry *e, int lock) 470 { 471 int r, success = 0, delay; 472 char *passwd; 473 u_char passwdhash[LOCK_SIZE]; 474 static u_int fail_count = 0; 475 size_t pwlen; 476 477 /* 478 * This is deliberately fatal: the user has requested that we lock, 479 * but we can't parse their request properly. The only safe thing to 480 * do is abort. 481 */ 482 if ((r = sshbuf_get_cstring(e->request, &passwd, &pwlen)) != 0) 483 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 484 if (pwlen == 0) { 485 debug("empty password not supported"); 486 } else if (locked && !lock) { 487 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt), 488 passwdhash, sizeof(passwdhash), LOCK_ROUNDS) < 0) 489 fatal("bcrypt_pbkdf"); 490 if (timingsafe_bcmp(passwdhash, lock_pwhash, LOCK_SIZE) == 0) { 491 debug("agent unlocked"); 492 locked = 0; 493 fail_count = 0; 494 explicit_bzero(lock_pwhash, sizeof(lock_pwhash)); 495 success = 1; 496 } else { 497 /* delay in 0.1s increments up to 10s */ 498 if (fail_count < 100) 499 fail_count++; 500 delay = 100000 * fail_count; 501 debug("unlock failed, delaying %0.1lf seconds", 502 (double)delay/1000000); 503 usleep(delay); 504 } 505 explicit_bzero(passwdhash, sizeof(passwdhash)); 506 } else if (!locked && lock) { 507 debug("agent locked"); 508 locked = 1; 509 arc4random_buf(lock_salt, sizeof(lock_salt)); 510 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt), 511 lock_pwhash, sizeof(lock_pwhash), LOCK_ROUNDS) < 0) 512 fatal("bcrypt_pbkdf"); 513 success = 1; 514 } 515 explicit_bzero(passwd, pwlen); 516 free(passwd); 517 send_status(e, success); 518 } 519 520 static void 521 no_identities(SocketEntry *e) 522 { 523 struct sshbuf *msg; 524 int r; 525 526 if ((msg = sshbuf_new()) == NULL) 527 fatal("%s: sshbuf_new failed", __func__); 528 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 || 529 (r = sshbuf_put_u32(msg, 0)) != 0 || 530 (r = sshbuf_put_stringb(e->output, msg)) != 0) 531 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 532 sshbuf_free(msg); 533 } 534 535 #ifdef ENABLE_PKCS11 536 static void 537 process_add_smartcard_key(SocketEntry *e) 538 { 539 char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX]; 540 int r, i, count = 0, success = 0, confirm = 0; 541 u_int seconds; 542 time_t death = 0; 543 u_char type; 544 struct sshkey **keys = NULL, *k; 545 Identity *id; 546 547 if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 || 548 (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) { 549 error("%s: buffer error: %s", __func__, ssh_err(r)); 550 goto send; 551 } 552 553 while (sshbuf_len(e->request)) { 554 if ((r = sshbuf_get_u8(e->request, &type)) != 0) { 555 error("%s: buffer error: %s", __func__, ssh_err(r)); 556 goto send; 557 } 558 switch (type) { 559 case SSH_AGENT_CONSTRAIN_LIFETIME: 560 if ((r = sshbuf_get_u32(e->request, &seconds)) != 0) { 561 error("%s: buffer error: %s", 562 __func__, ssh_err(r)); 563 goto send; 564 } 565 death = monotime() + seconds; 566 break; 567 case SSH_AGENT_CONSTRAIN_CONFIRM: 568 confirm = 1; 569 break; 570 default: 571 error("%s: Unknown constraint type %d", __func__, type); 572 goto send; 573 } 574 } 575 if (realpath(provider, canonical_provider) == NULL) { 576 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s", 577 provider, strerror(errno)); 578 goto send; 579 } 580 if (match_pattern_list(canonical_provider, pkcs11_whitelist, 0) != 1) { 581 verbose("refusing PKCS#11 add of \"%.100s\": " 582 "provider not whitelisted", canonical_provider); 583 goto send; 584 } 585 debug("%s: add %.100s", __func__, canonical_provider); 586 if (lifetime && !death) 587 death = monotime() + lifetime; 588 589 count = pkcs11_add_provider(canonical_provider, pin, &keys); 590 for (i = 0; i < count; i++) { 591 k = keys[i]; 592 if (lookup_identity(k) == NULL) { 593 id = xcalloc(1, sizeof(Identity)); 594 id->key = k; 595 id->provider = xstrdup(canonical_provider); 596 id->comment = xstrdup(canonical_provider); /* XXX */ 597 id->death = death; 598 id->confirm = confirm; 599 TAILQ_INSERT_TAIL(&idtab->idlist, id, next); 600 idtab->nentries++; 601 success = 1; 602 } else { 603 sshkey_free(k); 604 } 605 keys[i] = NULL; 606 } 607 send: 608 free(pin); 609 free(provider); 610 free(keys); 611 send_status(e, success); 612 } 613 614 static void 615 process_remove_smartcard_key(SocketEntry *e) 616 { 617 char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX]; 618 int r, success = 0; 619 Identity *id, *nxt; 620 621 if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 || 622 (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) { 623 error("%s: buffer error: %s", __func__, ssh_err(r)); 624 goto send; 625 } 626 free(pin); 627 628 if (realpath(provider, canonical_provider) == NULL) { 629 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s", 630 provider, strerror(errno)); 631 goto send; 632 } 633 634 debug("%s: remove %.100s", __func__, canonical_provider); 635 for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) { 636 nxt = TAILQ_NEXT(id, next); 637 /* Skip file--based keys */ 638 if (id->provider == NULL) 639 continue; 640 if (!strcmp(canonical_provider, id->provider)) { 641 TAILQ_REMOVE(&idtab->idlist, id, next); 642 free_identity(id); 643 idtab->nentries--; 644 } 645 } 646 if (pkcs11_del_provider(canonical_provider) == 0) 647 success = 1; 648 else 649 error("%s: pkcs11_del_provider failed", __func__); 650 send: 651 free(provider); 652 send_status(e, success); 653 } 654 #endif /* ENABLE_PKCS11 */ 655 656 /* dispatch incoming messages */ 657 658 static int 659 process_message(u_int socknum) 660 { 661 u_int msg_len; 662 u_char type; 663 const u_char *cp; 664 int r; 665 SocketEntry *e; 666 667 if (socknum >= sockets_alloc) { 668 fatal("%s: socket number %u >= allocated %u", 669 __func__, socknum, sockets_alloc); 670 } 671 e = &sockets[socknum]; 672 673 if (sshbuf_len(e->input) < 5) 674 return 0; /* Incomplete message header. */ 675 cp = sshbuf_ptr(e->input); 676 msg_len = PEEK_U32(cp); 677 if (msg_len > AGENT_MAX_LEN) { 678 debug("%s: socket %u (fd=%d) message too long %u > %u", 679 __func__, socknum, e->fd, msg_len, AGENT_MAX_LEN); 680 return -1; 681 } 682 if (sshbuf_len(e->input) < msg_len + 4) 683 return 0; /* Incomplete message body. */ 684 685 /* move the current input to e->request */ 686 sshbuf_reset(e->request); 687 if ((r = sshbuf_get_stringb(e->input, e->request)) != 0 || 688 (r = sshbuf_get_u8(e->request, &type)) != 0) { 689 if (r == SSH_ERR_MESSAGE_INCOMPLETE || 690 r == SSH_ERR_STRING_TOO_LARGE) { 691 debug("%s: buffer error: %s", __func__, ssh_err(r)); 692 return -1; 693 } 694 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 695 } 696 697 debug("%s: socket %u (fd=%d) type %d", __func__, socknum, e->fd, type); 698 699 /* check whether agent is locked */ 700 if (locked && type != SSH_AGENTC_UNLOCK) { 701 sshbuf_reset(e->request); 702 switch (type) { 703 case SSH2_AGENTC_REQUEST_IDENTITIES: 704 /* send empty lists */ 705 no_identities(e); 706 break; 707 default: 708 /* send a fail message for all other request types */ 709 send_status(e, 0); 710 } 711 return 0; 712 } 713 714 switch (type) { 715 case SSH_AGENTC_LOCK: 716 case SSH_AGENTC_UNLOCK: 717 process_lock_agent(e, type == SSH_AGENTC_LOCK); 718 break; 719 case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES: 720 process_remove_all_identities(e); /* safe for !WITH_SSH1 */ 721 break; 722 /* ssh2 */ 723 case SSH2_AGENTC_SIGN_REQUEST: 724 process_sign_request2(e); 725 break; 726 case SSH2_AGENTC_REQUEST_IDENTITIES: 727 process_request_identities(e); 728 break; 729 case SSH2_AGENTC_ADD_IDENTITY: 730 case SSH2_AGENTC_ADD_ID_CONSTRAINED: 731 process_add_identity(e); 732 break; 733 case SSH2_AGENTC_REMOVE_IDENTITY: 734 process_remove_identity(e); 735 break; 736 case SSH2_AGENTC_REMOVE_ALL_IDENTITIES: 737 process_remove_all_identities(e); 738 break; 739 #ifdef ENABLE_PKCS11 740 case SSH_AGENTC_ADD_SMARTCARD_KEY: 741 case SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED: 742 process_add_smartcard_key(e); 743 break; 744 case SSH_AGENTC_REMOVE_SMARTCARD_KEY: 745 process_remove_smartcard_key(e); 746 break; 747 #endif /* ENABLE_PKCS11 */ 748 default: 749 /* Unknown message. Respond with failure. */ 750 error("Unknown message %d", type); 751 sshbuf_reset(e->request); 752 send_status(e, 0); 753 break; 754 } 755 return 0; 756 } 757 758 static void 759 new_socket(sock_type type, int fd) 760 { 761 u_int i, old_alloc, new_alloc; 762 763 set_nonblock(fd); 764 765 if (fd > max_fd) 766 max_fd = fd; 767 768 for (i = 0; i < sockets_alloc; i++) 769 if (sockets[i].type == AUTH_UNUSED) { 770 sockets[i].fd = fd; 771 if ((sockets[i].input = sshbuf_new()) == NULL) 772 fatal("%s: sshbuf_new failed", __func__); 773 if ((sockets[i].output = sshbuf_new()) == NULL) 774 fatal("%s: sshbuf_new failed", __func__); 775 if ((sockets[i].request = sshbuf_new()) == NULL) 776 fatal("%s: sshbuf_new failed", __func__); 777 sockets[i].type = type; 778 return; 779 } 780 old_alloc = sockets_alloc; 781 new_alloc = sockets_alloc + 10; 782 sockets = xreallocarray(sockets, new_alloc, sizeof(sockets[0])); 783 for (i = old_alloc; i < new_alloc; i++) 784 sockets[i].type = AUTH_UNUSED; 785 sockets_alloc = new_alloc; 786 sockets[old_alloc].fd = fd; 787 if ((sockets[old_alloc].input = sshbuf_new()) == NULL) 788 fatal("%s: sshbuf_new failed", __func__); 789 if ((sockets[old_alloc].output = sshbuf_new()) == NULL) 790 fatal("%s: sshbuf_new failed", __func__); 791 if ((sockets[old_alloc].request = sshbuf_new()) == NULL) 792 fatal("%s: sshbuf_new failed", __func__); 793 sockets[old_alloc].type = type; 794 } 795 796 static int 797 handle_socket_read(u_int socknum) 798 { 799 struct sockaddr_un sunaddr; 800 socklen_t slen; 801 uid_t euid; 802 gid_t egid; 803 int fd; 804 805 slen = sizeof(sunaddr); 806 fd = accept(sockets[socknum].fd, (struct sockaddr *)&sunaddr, &slen); 807 if (fd < 0) { 808 error("accept from AUTH_SOCKET: %s", strerror(errno)); 809 return -1; 810 } 811 if (getpeereid(fd, &euid, &egid) < 0) { 812 error("getpeereid %d failed: %s", fd, strerror(errno)); 813 close(fd); 814 return -1; 815 } 816 if ((euid != 0) && (getuid() != euid)) { 817 error("uid mismatch: peer euid %u != uid %u", 818 (u_int) euid, (u_int) getuid()); 819 close(fd); 820 return -1; 821 } 822 new_socket(AUTH_CONNECTION, fd); 823 return 0; 824 } 825 826 static int 827 handle_conn_read(u_int socknum) 828 { 829 char buf[AGENT_RBUF_LEN]; 830 ssize_t len; 831 int r; 832 833 if ((len = read(sockets[socknum].fd, buf, sizeof(buf))) <= 0) { 834 if (len == -1) { 835 if (errno == EAGAIN || errno == EINTR) 836 return 0; 837 error("%s: read error on socket %u (fd %d): %s", 838 __func__, socknum, sockets[socknum].fd, 839 strerror(errno)); 840 } 841 return -1; 842 } 843 if ((r = sshbuf_put(sockets[socknum].input, buf, len)) != 0) 844 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 845 explicit_bzero(buf, sizeof(buf)); 846 process_message(socknum); 847 return 0; 848 } 849 850 static int 851 handle_conn_write(u_int socknum) 852 { 853 ssize_t len; 854 int r; 855 856 if (sshbuf_len(sockets[socknum].output) == 0) 857 return 0; /* shouldn't happen */ 858 if ((len = write(sockets[socknum].fd, 859 sshbuf_ptr(sockets[socknum].output), 860 sshbuf_len(sockets[socknum].output))) <= 0) { 861 if (len == -1) { 862 if (errno == EAGAIN || errno == EINTR) 863 return 0; 864 error("%s: read error on socket %u (fd %d): %s", 865 __func__, socknum, sockets[socknum].fd, 866 strerror(errno)); 867 } 868 return -1; 869 } 870 if ((r = sshbuf_consume(sockets[socknum].output, len)) != 0) 871 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 872 return 0; 873 } 874 875 static void 876 after_poll(struct pollfd *pfd, size_t npfd, u_int maxfds) 877 { 878 size_t i; 879 u_int socknum, activefds = npfd; 880 881 for (i = 0; i < npfd; i++) { 882 if (pfd[i].revents == 0) 883 continue; 884 /* Find sockets entry */ 885 for (socknum = 0; socknum < sockets_alloc; socknum++) { 886 if (sockets[socknum].type != AUTH_SOCKET && 887 sockets[socknum].type != AUTH_CONNECTION) 888 continue; 889 if (pfd[i].fd == sockets[socknum].fd) 890 break; 891 } 892 if (socknum >= sockets_alloc) { 893 error("%s: no socket for fd %d", __func__, pfd[i].fd); 894 continue; 895 } 896 /* Process events */ 897 switch (sockets[socknum].type) { 898 case AUTH_SOCKET: 899 if ((pfd[i].revents & (POLLIN|POLLERR)) == 0) 900 break; 901 if (npfd > maxfds) { 902 debug3("out of fds (active %u >= limit %u); " 903 "skipping accept", activefds, maxfds); 904 break; 905 } 906 if (handle_socket_read(socknum) == 0) 907 activefds++; 908 break; 909 case AUTH_CONNECTION: 910 if ((pfd[i].revents & (POLLIN|POLLERR)) != 0 && 911 handle_conn_read(socknum) != 0) { 912 goto close_sock; 913 } 914 if ((pfd[i].revents & (POLLOUT|POLLHUP)) != 0 && 915 handle_conn_write(socknum) != 0) { 916 close_sock: 917 if (activefds == 0) 918 fatal("activefds == 0 at close_sock"); 919 close_socket(&sockets[socknum]); 920 activefds--; 921 break; 922 } 923 break; 924 default: 925 break; 926 } 927 } 928 } 929 930 static int 931 prepare_poll(struct pollfd **pfdp, size_t *npfdp, int *timeoutp, u_int maxfds) 932 { 933 struct pollfd *pfd = *pfdp; 934 size_t i, j, npfd = 0; 935 time_t deadline; 936 int r; 937 938 /* Count active sockets */ 939 for (i = 0; i < sockets_alloc; i++) { 940 switch (sockets[i].type) { 941 case AUTH_SOCKET: 942 case AUTH_CONNECTION: 943 npfd++; 944 break; 945 case AUTH_UNUSED: 946 break; 947 default: 948 fatal("Unknown socket type %d", sockets[i].type); 949 break; 950 } 951 } 952 if (npfd != *npfdp && 953 (pfd = recallocarray(pfd, *npfdp, npfd, sizeof(*pfd))) == NULL) 954 fatal("%s: recallocarray failed", __func__); 955 *pfdp = pfd; 956 *npfdp = npfd; 957 958 for (i = j = 0; i < sockets_alloc; i++) { 959 switch (sockets[i].type) { 960 case AUTH_SOCKET: 961 if (npfd > maxfds) { 962 debug3("out of fds (active %zu >= limit %u); " 963 "skipping arming listener", npfd, maxfds); 964 break; 965 } 966 pfd[j].fd = sockets[i].fd; 967 pfd[j].revents = 0; 968 pfd[j].events = POLLIN; 969 j++; 970 break; 971 case AUTH_CONNECTION: 972 pfd[j].fd = sockets[i].fd; 973 pfd[j].revents = 0; 974 /* 975 * Only prepare to read if we can handle a full-size 976 * input read buffer and enqueue a max size reply.. 977 */ 978 if ((r = sshbuf_check_reserve(sockets[i].input, 979 AGENT_RBUF_LEN)) == 0 && 980 (r = sshbuf_check_reserve(sockets[i].output, 981 AGENT_MAX_LEN)) == 0) 982 pfd[j].events = POLLIN; 983 else if (r != SSH_ERR_NO_BUFFER_SPACE) { 984 fatal("%s: buffer error: %s", 985 __func__, ssh_err(r)); 986 } 987 if (sshbuf_len(sockets[i].output) > 0) 988 pfd[j].events |= POLLOUT; 989 j++; 990 break; 991 default: 992 break; 993 } 994 } 995 deadline = reaper(); 996 if (parent_alive_interval != 0) 997 deadline = (deadline == 0) ? parent_alive_interval : 998 MINIMUM(deadline, parent_alive_interval); 999 if (deadline == 0) { 1000 *timeoutp = -1; /* INFTIM */ 1001 } else { 1002 if (deadline > INT_MAX / 1000) 1003 *timeoutp = INT_MAX / 1000; 1004 else 1005 *timeoutp = deadline * 1000; 1006 } 1007 return (1); 1008 } 1009 1010 static void 1011 cleanup_socket(void) 1012 { 1013 if (cleanup_pid != 0 && getpid() != cleanup_pid) 1014 return; 1015 debug("%s: cleanup", __func__); 1016 if (socket_name[0]) 1017 unlink(socket_name); 1018 if (socket_dir[0]) 1019 rmdir(socket_dir); 1020 } 1021 1022 void 1023 cleanup_exit(int i) 1024 { 1025 cleanup_socket(); 1026 _exit(i); 1027 } 1028 1029 /*ARGSUSED*/ 1030 static void 1031 cleanup_handler(int sig) 1032 { 1033 cleanup_socket(); 1034 #ifdef ENABLE_PKCS11 1035 pkcs11_terminate(); 1036 #endif 1037 _exit(2); 1038 } 1039 1040 static void 1041 check_parent_exists(void) 1042 { 1043 /* 1044 * If our parent has exited then getppid() will return (pid_t)1, 1045 * so testing for that should be safe. 1046 */ 1047 if (parent_pid != -1 && getppid() != parent_pid) { 1048 /* printf("Parent has died - Authentication agent exiting.\n"); */ 1049 cleanup_socket(); 1050 _exit(2); 1051 } 1052 } 1053 1054 static void 1055 usage(void) 1056 { 1057 fprintf(stderr, 1058 "usage: ssh-agent [-c | -s] [-Dd] [-a bind_address] [-E fingerprint_hash]\n" 1059 " [-P pkcs11_whitelist] [-t life] [command [arg ...]]\n" 1060 " ssh-agent [-c | -s] -k\n"); 1061 exit(1); 1062 } 1063 1064 int 1065 main(int ac, char **av) 1066 { 1067 int c_flag = 0, d_flag = 0, D_flag = 0, k_flag = 0, s_flag = 0; 1068 int sock, fd, ch, result, saved_errno; 1069 char *shell, *format, *pidstr, *agentsocket = NULL; 1070 struct rlimit rlim; 1071 extern int optind; 1072 extern char *optarg; 1073 pid_t pid; 1074 char pidstrbuf[1 + 3 * sizeof pid]; 1075 size_t len; 1076 mode_t prev_mask; 1077 int timeout = -1; /* INFTIM */ 1078 struct pollfd *pfd = NULL; 1079 size_t npfd = 0; 1080 u_int maxfds; 1081 1082 ssh_malloc_init(); /* must be called before any mallocs */ 1083 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */ 1084 sanitise_stdfd(); 1085 1086 /* drop */ 1087 setegid(getgid()); 1088 setgid(getgid()); 1089 1090 if (getrlimit(RLIMIT_NOFILE, &rlim) == -1) 1091 fatal("%s: getrlimit: %s", __progname, strerror(errno)); 1092 1093 #ifdef WITH_OPENSSL 1094 OpenSSL_add_all_algorithms(); 1095 #endif 1096 1097 while ((ch = getopt(ac, av, "cDdksE:a:P:t:")) != -1) { 1098 switch (ch) { 1099 case 'E': 1100 fingerprint_hash = ssh_digest_alg_by_name(optarg); 1101 if (fingerprint_hash == -1) 1102 fatal("Invalid hash algorithm \"%s\"", optarg); 1103 break; 1104 case 'c': 1105 if (s_flag) 1106 usage(); 1107 c_flag++; 1108 break; 1109 case 'k': 1110 k_flag++; 1111 break; 1112 case 'P': 1113 if (pkcs11_whitelist != NULL) 1114 fatal("-P option already specified"); 1115 pkcs11_whitelist = xstrdup(optarg); 1116 break; 1117 case 's': 1118 if (c_flag) 1119 usage(); 1120 s_flag++; 1121 break; 1122 case 'd': 1123 if (d_flag || D_flag) 1124 usage(); 1125 d_flag++; 1126 break; 1127 case 'D': 1128 if (d_flag || D_flag) 1129 usage(); 1130 D_flag++; 1131 break; 1132 case 'a': 1133 agentsocket = optarg; 1134 break; 1135 case 't': 1136 if ((lifetime = convtime(optarg)) == -1) { 1137 fprintf(stderr, "Invalid lifetime\n"); 1138 usage(); 1139 } 1140 break; 1141 default: 1142 usage(); 1143 } 1144 } 1145 ac -= optind; 1146 av += optind; 1147 1148 if (ac > 0 && (c_flag || k_flag || s_flag || d_flag || D_flag)) 1149 usage(); 1150 1151 if (pkcs11_whitelist == NULL) 1152 pkcs11_whitelist = xstrdup(DEFAULT_PKCS11_WHITELIST); 1153 1154 if (ac == 0 && !c_flag && !s_flag) { 1155 shell = getenv("SHELL"); 1156 if (shell != NULL && (len = strlen(shell)) > 2 && 1157 strncmp(shell + len - 3, "csh", 3) == 0) 1158 c_flag = 1; 1159 } 1160 if (k_flag) { 1161 const char *errstr = NULL; 1162 1163 pidstr = getenv(SSH_AGENTPID_ENV_NAME); 1164 if (pidstr == NULL) { 1165 fprintf(stderr, "%s not set, cannot kill agent\n", 1166 SSH_AGENTPID_ENV_NAME); 1167 exit(1); 1168 } 1169 pid = (int)strtonum(pidstr, 2, INT_MAX, &errstr); 1170 if (errstr) { 1171 fprintf(stderr, 1172 "%s=\"%s\", which is not a good PID: %s\n", 1173 SSH_AGENTPID_ENV_NAME, pidstr, errstr); 1174 exit(1); 1175 } 1176 if (kill(pid, SIGTERM) == -1) { 1177 perror("kill"); 1178 exit(1); 1179 } 1180 format = c_flag ? "unsetenv %s;\n" : "unset %s;\n"; 1181 printf(format, SSH_AUTHSOCKET_ENV_NAME); 1182 printf(format, SSH_AGENTPID_ENV_NAME); 1183 printf("echo Agent pid %ld killed;\n", (long)pid); 1184 exit(0); 1185 } 1186 1187 /* 1188 * Minimum file descriptors: 1189 * stdio (3) + listener (1) + syslog (1 maybe) + connection (1) + 1190 * a few spare for libc / stack protectors / sanitisers, etc. 1191 */ 1192 #define SSH_AGENT_MIN_FDS (3+1+1+1+4) 1193 if (rlim.rlim_cur < SSH_AGENT_MIN_FDS) 1194 fatal("%s: file descriptor rlimit %lld too low (minimum %u)", 1195 __progname, (long long)rlim.rlim_cur, SSH_AGENT_MIN_FDS); 1196 maxfds = rlim.rlim_cur - SSH_AGENT_MIN_FDS; 1197 1198 parent_pid = getpid(); 1199 1200 if (agentsocket == NULL) { 1201 /* Create private directory for agent socket */ 1202 mktemp_proto(socket_dir, sizeof(socket_dir)); 1203 if (mkdtemp(socket_dir) == NULL) { 1204 perror("mkdtemp: private socket dir"); 1205 exit(1); 1206 } 1207 snprintf(socket_name, sizeof socket_name, "%s/agent.%ld", socket_dir, 1208 (long)parent_pid); 1209 } else { 1210 /* Try to use specified agent socket */ 1211 socket_dir[0] = '\0'; 1212 strlcpy(socket_name, agentsocket, sizeof socket_name); 1213 } 1214 1215 /* 1216 * Create socket early so it will exist before command gets run from 1217 * the parent. 1218 */ 1219 prev_mask = umask(0177); 1220 sock = unix_listener(socket_name, SSH_LISTEN_BACKLOG, 0); 1221 if (sock < 0) { 1222 /* XXX - unix_listener() calls error() not perror() */ 1223 *socket_name = '\0'; /* Don't unlink any existing file */ 1224 cleanup_exit(1); 1225 } 1226 umask(prev_mask); 1227 1228 /* 1229 * Fork, and have the parent execute the command, if any, or present 1230 * the socket data. The child continues as the authentication agent. 1231 */ 1232 if (D_flag || d_flag) { 1233 log_init(__progname, 1234 d_flag ? SYSLOG_LEVEL_DEBUG3 : SYSLOG_LEVEL_INFO, 1235 SYSLOG_FACILITY_AUTH, 1); 1236 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n"; 1237 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name, 1238 SSH_AUTHSOCKET_ENV_NAME); 1239 printf("echo Agent pid %ld;\n", (long)parent_pid); 1240 fflush(stdout); 1241 goto skip; 1242 } 1243 pid = fork(); 1244 if (pid == -1) { 1245 perror("fork"); 1246 cleanup_exit(1); 1247 } 1248 if (pid != 0) { /* Parent - execute the given command. */ 1249 close(sock); 1250 snprintf(pidstrbuf, sizeof pidstrbuf, "%ld", (long)pid); 1251 if (ac == 0) { 1252 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n"; 1253 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name, 1254 SSH_AUTHSOCKET_ENV_NAME); 1255 printf(format, SSH_AGENTPID_ENV_NAME, pidstrbuf, 1256 SSH_AGENTPID_ENV_NAME); 1257 printf("echo Agent pid %ld;\n", (long)pid); 1258 exit(0); 1259 } 1260 if (setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1) == -1 || 1261 setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1) == -1) { 1262 perror("setenv"); 1263 exit(1); 1264 } 1265 execvp(av[0], av); 1266 perror(av[0]); 1267 exit(1); 1268 } 1269 /* child */ 1270 log_init(__progname, SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_AUTH, 0); 1271 1272 if (setsid() == -1) { 1273 error("setsid: %s", strerror(errno)); 1274 cleanup_exit(1); 1275 } 1276 1277 (void)chdir("/"); 1278 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) { 1279 /* XXX might close listen socket */ 1280 (void)dup2(fd, STDIN_FILENO); 1281 (void)dup2(fd, STDOUT_FILENO); 1282 (void)dup2(fd, STDERR_FILENO); 1283 if (fd > 2) 1284 close(fd); 1285 } 1286 1287 /* deny core dumps, since memory contains unencrypted private keys */ 1288 rlim.rlim_cur = rlim.rlim_max = 0; 1289 if (setrlimit(RLIMIT_CORE, &rlim) < 0) { 1290 error("setrlimit RLIMIT_CORE: %s", strerror(errno)); 1291 cleanup_exit(1); 1292 } 1293 1294 skip: 1295 1296 cleanup_pid = getpid(); 1297 1298 #ifdef ENABLE_PKCS11 1299 pkcs11_init(0); 1300 #endif 1301 new_socket(AUTH_SOCKET, sock); 1302 if (ac > 0) 1303 parent_alive_interval = 10; 1304 idtab_init(); 1305 signal(SIGPIPE, SIG_IGN); 1306 signal(SIGINT, (d_flag | D_flag) ? cleanup_handler : SIG_IGN); 1307 signal(SIGHUP, cleanup_handler); 1308 signal(SIGTERM, cleanup_handler); 1309 1310 if (pledge("stdio rpath cpath unix id proc exec", NULL) == -1) 1311 fatal("%s: pledge: %s", __progname, strerror(errno)); 1312 1313 while (1) { 1314 prepare_poll(&pfd, &npfd, &timeout, maxfds); 1315 result = poll(pfd, npfd, timeout); 1316 saved_errno = errno; 1317 if (parent_alive_interval != 0) 1318 check_parent_exists(); 1319 (void) reaper(); /* remove expired keys */ 1320 if (result < 0) { 1321 if (saved_errno == EINTR) 1322 continue; 1323 fatal("poll: %s", strerror(saved_errno)); 1324 } else if (result > 0) 1325 after_poll(pfd, npfd, maxfds); 1326 } 1327 /* NOTREACHED */ 1328 } 1329