1 /* $OpenBSD: ssh-agent.c,v 1.236 2019/06/21 04:21:04 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 } else if (key->type == KEY_RSA_CERT) { 258 if (flags & SSH_AGENT_RSA_SHA2_256) 259 return "rsa-sha2-256-cert-v01@openssh.com"; 260 else if (flags & SSH_AGENT_RSA_SHA2_512) 261 return "rsa-sha2-512-cert-v01@openssh.com"; 262 } 263 return NULL; 264 } 265 266 /* ssh2 only */ 267 static void 268 process_sign_request2(SocketEntry *e) 269 { 270 const u_char *data; 271 u_char *signature = NULL; 272 size_t dlen, slen = 0; 273 u_int compat = 0, flags; 274 int r, ok = -1; 275 struct sshbuf *msg; 276 struct sshkey *key = NULL; 277 struct identity *id; 278 279 if ((msg = sshbuf_new()) == NULL) 280 fatal("%s: sshbuf_new failed", __func__); 281 if ((r = sshkey_froms(e->request, &key)) != 0 || 282 (r = sshbuf_get_string_direct(e->request, &data, &dlen)) != 0 || 283 (r = sshbuf_get_u32(e->request, &flags)) != 0) { 284 error("%s: couldn't parse request: %s", __func__, ssh_err(r)); 285 goto send; 286 } 287 288 if ((id = lookup_identity(key)) == NULL) { 289 verbose("%s: %s key not found", __func__, sshkey_type(key)); 290 goto send; 291 } 292 if (id->confirm && confirm_key(id) != 0) { 293 verbose("%s: user refused key", __func__); 294 goto send; 295 } 296 if ((r = sshkey_sign(id->key, &signature, &slen, 297 data, dlen, agent_decode_alg(key, flags), compat)) != 0) { 298 error("%s: sshkey_sign: %s", __func__, ssh_err(r)); 299 goto send; 300 } 301 /* Success */ 302 ok = 0; 303 send: 304 sshkey_free(key); 305 if (ok == 0) { 306 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 || 307 (r = sshbuf_put_string(msg, signature, slen)) != 0) 308 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 309 } else if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0) 310 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 311 312 if ((r = sshbuf_put_stringb(e->output, msg)) != 0) 313 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 314 315 sshbuf_free(msg); 316 free(signature); 317 } 318 319 /* shared */ 320 static void 321 process_remove_identity(SocketEntry *e) 322 { 323 int r, success = 0; 324 struct sshkey *key = NULL; 325 Identity *id; 326 327 if ((r = sshkey_froms(e->request, &key)) != 0) { 328 error("%s: get key: %s", __func__, ssh_err(r)); 329 goto done; 330 } 331 if ((id = lookup_identity(key)) == NULL) { 332 debug("%s: key not found", __func__); 333 goto done; 334 } 335 /* We have this key, free it. */ 336 if (idtab->nentries < 1) 337 fatal("%s: internal error: nentries %d", 338 __func__, idtab->nentries); 339 TAILQ_REMOVE(&idtab->idlist, id, next); 340 free_identity(id); 341 idtab->nentries--; 342 sshkey_free(key); 343 success = 1; 344 done: 345 send_status(e, success); 346 } 347 348 static void 349 process_remove_all_identities(SocketEntry *e) 350 { 351 Identity *id; 352 353 /* Loop over all identities and clear the keys. */ 354 for (id = TAILQ_FIRST(&idtab->idlist); id; 355 id = TAILQ_FIRST(&idtab->idlist)) { 356 TAILQ_REMOVE(&idtab->idlist, id, next); 357 free_identity(id); 358 } 359 360 /* Mark that there are no identities. */ 361 idtab->nentries = 0; 362 363 /* Send success. */ 364 send_status(e, 1); 365 } 366 367 /* removes expired keys and returns number of seconds until the next expiry */ 368 static time_t 369 reaper(void) 370 { 371 time_t deadline = 0, now = monotime(); 372 Identity *id, *nxt; 373 374 for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) { 375 nxt = TAILQ_NEXT(id, next); 376 if (id->death == 0) 377 continue; 378 if (now >= id->death) { 379 debug("expiring key '%s'", id->comment); 380 TAILQ_REMOVE(&idtab->idlist, id, next); 381 free_identity(id); 382 idtab->nentries--; 383 } else 384 deadline = (deadline == 0) ? id->death : 385 MINIMUM(deadline, id->death); 386 } 387 if (deadline == 0 || deadline <= now) 388 return 0; 389 else 390 return (deadline - now); 391 } 392 393 static void 394 process_add_identity(SocketEntry *e) 395 { 396 Identity *id; 397 int success = 0, confirm = 0; 398 u_int seconds, maxsign; 399 char *comment = NULL; 400 time_t death = 0; 401 struct sshkey *k = NULL; 402 u_char ctype; 403 int r = SSH_ERR_INTERNAL_ERROR; 404 405 if ((r = sshkey_private_deserialize(e->request, &k)) != 0 || 406 k == NULL || 407 (r = sshbuf_get_cstring(e->request, &comment, NULL)) != 0) { 408 error("%s: decode private key: %s", __func__, ssh_err(r)); 409 goto err; 410 } 411 if ((r = sshkey_shield_private(k)) != 0) { 412 error("%s: shield private key: %s", __func__, ssh_err(r)); 413 goto err; 414 } 415 while (sshbuf_len(e->request)) { 416 if ((r = sshbuf_get_u8(e->request, &ctype)) != 0) { 417 error("%s: buffer error: %s", __func__, ssh_err(r)); 418 goto err; 419 } 420 switch (ctype) { 421 case SSH_AGENT_CONSTRAIN_LIFETIME: 422 if ((r = sshbuf_get_u32(e->request, &seconds)) != 0) { 423 error("%s: bad lifetime constraint: %s", 424 __func__, ssh_err(r)); 425 goto err; 426 } 427 death = monotime() + seconds; 428 break; 429 case SSH_AGENT_CONSTRAIN_CONFIRM: 430 confirm = 1; 431 break; 432 case SSH_AGENT_CONSTRAIN_MAXSIGN: 433 if ((r = sshbuf_get_u32(e->request, &maxsign)) != 0) { 434 error("%s: bad maxsign constraint: %s", 435 __func__, ssh_err(r)); 436 goto err; 437 } 438 if ((r = sshkey_enable_maxsign(k, maxsign)) != 0) { 439 error("%s: cannot enable maxsign: %s", 440 __func__, ssh_err(r)); 441 goto err; 442 } 443 break; 444 default: 445 error("%s: Unknown constraint %d", __func__, ctype); 446 err: 447 sshbuf_reset(e->request); 448 free(comment); 449 sshkey_free(k); 450 goto send; 451 } 452 } 453 454 success = 1; 455 if (lifetime && !death) 456 death = monotime() + lifetime; 457 if ((id = lookup_identity(k)) == NULL) { 458 id = xcalloc(1, sizeof(Identity)); 459 TAILQ_INSERT_TAIL(&idtab->idlist, id, next); 460 /* Increment the number of identities. */ 461 idtab->nentries++; 462 } else { 463 /* key state might have been updated */ 464 sshkey_free(id->key); 465 free(id->comment); 466 } 467 id->key = k; 468 id->comment = comment; 469 id->death = death; 470 id->confirm = confirm; 471 send: 472 send_status(e, success); 473 } 474 475 /* XXX todo: encrypt sensitive data with passphrase */ 476 static void 477 process_lock_agent(SocketEntry *e, int lock) 478 { 479 int r, success = 0, delay; 480 char *passwd; 481 u_char passwdhash[LOCK_SIZE]; 482 static u_int fail_count = 0; 483 size_t pwlen; 484 485 /* 486 * This is deliberately fatal: the user has requested that we lock, 487 * but we can't parse their request properly. The only safe thing to 488 * do is abort. 489 */ 490 if ((r = sshbuf_get_cstring(e->request, &passwd, &pwlen)) != 0) 491 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 492 if (pwlen == 0) { 493 debug("empty password not supported"); 494 } else if (locked && !lock) { 495 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt), 496 passwdhash, sizeof(passwdhash), LOCK_ROUNDS) < 0) 497 fatal("bcrypt_pbkdf"); 498 if (timingsafe_bcmp(passwdhash, lock_pwhash, LOCK_SIZE) == 0) { 499 debug("agent unlocked"); 500 locked = 0; 501 fail_count = 0; 502 explicit_bzero(lock_pwhash, sizeof(lock_pwhash)); 503 success = 1; 504 } else { 505 /* delay in 0.1s increments up to 10s */ 506 if (fail_count < 100) 507 fail_count++; 508 delay = 100000 * fail_count; 509 debug("unlock failed, delaying %0.1lf seconds", 510 (double)delay/1000000); 511 usleep(delay); 512 } 513 explicit_bzero(passwdhash, sizeof(passwdhash)); 514 } else if (!locked && lock) { 515 debug("agent locked"); 516 locked = 1; 517 arc4random_buf(lock_salt, sizeof(lock_salt)); 518 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt), 519 lock_pwhash, sizeof(lock_pwhash), LOCK_ROUNDS) < 0) 520 fatal("bcrypt_pbkdf"); 521 success = 1; 522 } 523 explicit_bzero(passwd, pwlen); 524 free(passwd); 525 send_status(e, success); 526 } 527 528 static void 529 no_identities(SocketEntry *e) 530 { 531 struct sshbuf *msg; 532 int r; 533 534 if ((msg = sshbuf_new()) == NULL) 535 fatal("%s: sshbuf_new failed", __func__); 536 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 || 537 (r = sshbuf_put_u32(msg, 0)) != 0 || 538 (r = sshbuf_put_stringb(e->output, msg)) != 0) 539 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 540 sshbuf_free(msg); 541 } 542 543 #ifdef ENABLE_PKCS11 544 static void 545 process_add_smartcard_key(SocketEntry *e) 546 { 547 char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX]; 548 int r, i, count = 0, success = 0, confirm = 0; 549 u_int seconds; 550 time_t death = 0; 551 u_char type; 552 struct sshkey **keys = NULL, *k; 553 Identity *id; 554 555 if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 || 556 (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) { 557 error("%s: buffer error: %s", __func__, ssh_err(r)); 558 goto send; 559 } 560 561 while (sshbuf_len(e->request)) { 562 if ((r = sshbuf_get_u8(e->request, &type)) != 0) { 563 error("%s: buffer error: %s", __func__, ssh_err(r)); 564 goto send; 565 } 566 switch (type) { 567 case SSH_AGENT_CONSTRAIN_LIFETIME: 568 if ((r = sshbuf_get_u32(e->request, &seconds)) != 0) { 569 error("%s: buffer error: %s", 570 __func__, ssh_err(r)); 571 goto send; 572 } 573 death = monotime() + seconds; 574 break; 575 case SSH_AGENT_CONSTRAIN_CONFIRM: 576 confirm = 1; 577 break; 578 default: 579 error("%s: Unknown constraint type %d", __func__, type); 580 goto send; 581 } 582 } 583 if (realpath(provider, canonical_provider) == NULL) { 584 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s", 585 provider, strerror(errno)); 586 goto send; 587 } 588 if (match_pattern_list(canonical_provider, pkcs11_whitelist, 0) != 1) { 589 verbose("refusing PKCS#11 add of \"%.100s\": " 590 "provider not whitelisted", canonical_provider); 591 goto send; 592 } 593 debug("%s: add %.100s", __func__, canonical_provider); 594 if (lifetime && !death) 595 death = monotime() + lifetime; 596 597 count = pkcs11_add_provider(canonical_provider, pin, &keys); 598 for (i = 0; i < count; i++) { 599 k = keys[i]; 600 if (lookup_identity(k) == NULL) { 601 id = xcalloc(1, sizeof(Identity)); 602 id->key = k; 603 id->provider = xstrdup(canonical_provider); 604 id->comment = xstrdup(canonical_provider); /* XXX */ 605 id->death = death; 606 id->confirm = confirm; 607 TAILQ_INSERT_TAIL(&idtab->idlist, id, next); 608 idtab->nentries++; 609 success = 1; 610 } else { 611 sshkey_free(k); 612 } 613 keys[i] = NULL; 614 } 615 send: 616 free(pin); 617 free(provider); 618 free(keys); 619 send_status(e, success); 620 } 621 622 static void 623 process_remove_smartcard_key(SocketEntry *e) 624 { 625 char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX]; 626 int r, success = 0; 627 Identity *id, *nxt; 628 629 if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 || 630 (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0) { 631 error("%s: buffer error: %s", __func__, ssh_err(r)); 632 goto send; 633 } 634 free(pin); 635 636 if (realpath(provider, canonical_provider) == NULL) { 637 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s", 638 provider, strerror(errno)); 639 goto send; 640 } 641 642 debug("%s: remove %.100s", __func__, canonical_provider); 643 for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) { 644 nxt = TAILQ_NEXT(id, next); 645 /* Skip file--based keys */ 646 if (id->provider == NULL) 647 continue; 648 if (!strcmp(canonical_provider, id->provider)) { 649 TAILQ_REMOVE(&idtab->idlist, id, next); 650 free_identity(id); 651 idtab->nentries--; 652 } 653 } 654 if (pkcs11_del_provider(canonical_provider) == 0) 655 success = 1; 656 else 657 error("%s: pkcs11_del_provider failed", __func__); 658 send: 659 free(provider); 660 send_status(e, success); 661 } 662 #endif /* ENABLE_PKCS11 */ 663 664 /* dispatch incoming messages */ 665 666 static int 667 process_message(u_int socknum) 668 { 669 u_int msg_len; 670 u_char type; 671 const u_char *cp; 672 int r; 673 SocketEntry *e; 674 675 if (socknum >= sockets_alloc) { 676 fatal("%s: socket number %u >= allocated %u", 677 __func__, socknum, sockets_alloc); 678 } 679 e = &sockets[socknum]; 680 681 if (sshbuf_len(e->input) < 5) 682 return 0; /* Incomplete message header. */ 683 cp = sshbuf_ptr(e->input); 684 msg_len = PEEK_U32(cp); 685 if (msg_len > AGENT_MAX_LEN) { 686 debug("%s: socket %u (fd=%d) message too long %u > %u", 687 __func__, socknum, e->fd, msg_len, AGENT_MAX_LEN); 688 return -1; 689 } 690 if (sshbuf_len(e->input) < msg_len + 4) 691 return 0; /* Incomplete message body. */ 692 693 /* move the current input to e->request */ 694 sshbuf_reset(e->request); 695 if ((r = sshbuf_get_stringb(e->input, e->request)) != 0 || 696 (r = sshbuf_get_u8(e->request, &type)) != 0) { 697 if (r == SSH_ERR_MESSAGE_INCOMPLETE || 698 r == SSH_ERR_STRING_TOO_LARGE) { 699 debug("%s: buffer error: %s", __func__, ssh_err(r)); 700 return -1; 701 } 702 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 703 } 704 705 debug("%s: socket %u (fd=%d) type %d", __func__, socknum, e->fd, type); 706 707 /* check whether agent is locked */ 708 if (locked && type != SSH_AGENTC_UNLOCK) { 709 sshbuf_reset(e->request); 710 switch (type) { 711 case SSH2_AGENTC_REQUEST_IDENTITIES: 712 /* send empty lists */ 713 no_identities(e); 714 break; 715 default: 716 /* send a fail message for all other request types */ 717 send_status(e, 0); 718 } 719 return 0; 720 } 721 722 switch (type) { 723 case SSH_AGENTC_LOCK: 724 case SSH_AGENTC_UNLOCK: 725 process_lock_agent(e, type == SSH_AGENTC_LOCK); 726 break; 727 case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES: 728 process_remove_all_identities(e); /* safe for !WITH_SSH1 */ 729 break; 730 /* ssh2 */ 731 case SSH2_AGENTC_SIGN_REQUEST: 732 process_sign_request2(e); 733 break; 734 case SSH2_AGENTC_REQUEST_IDENTITIES: 735 process_request_identities(e); 736 break; 737 case SSH2_AGENTC_ADD_IDENTITY: 738 case SSH2_AGENTC_ADD_ID_CONSTRAINED: 739 process_add_identity(e); 740 break; 741 case SSH2_AGENTC_REMOVE_IDENTITY: 742 process_remove_identity(e); 743 break; 744 case SSH2_AGENTC_REMOVE_ALL_IDENTITIES: 745 process_remove_all_identities(e); 746 break; 747 #ifdef ENABLE_PKCS11 748 case SSH_AGENTC_ADD_SMARTCARD_KEY: 749 case SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED: 750 process_add_smartcard_key(e); 751 break; 752 case SSH_AGENTC_REMOVE_SMARTCARD_KEY: 753 process_remove_smartcard_key(e); 754 break; 755 #endif /* ENABLE_PKCS11 */ 756 default: 757 /* Unknown message. Respond with failure. */ 758 error("Unknown message %d", type); 759 sshbuf_reset(e->request); 760 send_status(e, 0); 761 break; 762 } 763 return 0; 764 } 765 766 static void 767 new_socket(sock_type type, int fd) 768 { 769 u_int i, old_alloc, new_alloc; 770 771 set_nonblock(fd); 772 773 if (fd > max_fd) 774 max_fd = fd; 775 776 for (i = 0; i < sockets_alloc; i++) 777 if (sockets[i].type == AUTH_UNUSED) { 778 sockets[i].fd = fd; 779 if ((sockets[i].input = sshbuf_new()) == NULL) 780 fatal("%s: sshbuf_new failed", __func__); 781 if ((sockets[i].output = sshbuf_new()) == NULL) 782 fatal("%s: sshbuf_new failed", __func__); 783 if ((sockets[i].request = sshbuf_new()) == NULL) 784 fatal("%s: sshbuf_new failed", __func__); 785 sockets[i].type = type; 786 return; 787 } 788 old_alloc = sockets_alloc; 789 new_alloc = sockets_alloc + 10; 790 sockets = xreallocarray(sockets, new_alloc, sizeof(sockets[0])); 791 for (i = old_alloc; i < new_alloc; i++) 792 sockets[i].type = AUTH_UNUSED; 793 sockets_alloc = new_alloc; 794 sockets[old_alloc].fd = fd; 795 if ((sockets[old_alloc].input = sshbuf_new()) == NULL) 796 fatal("%s: sshbuf_new failed", __func__); 797 if ((sockets[old_alloc].output = sshbuf_new()) == NULL) 798 fatal("%s: sshbuf_new failed", __func__); 799 if ((sockets[old_alloc].request = sshbuf_new()) == NULL) 800 fatal("%s: sshbuf_new failed", __func__); 801 sockets[old_alloc].type = type; 802 } 803 804 static int 805 handle_socket_read(u_int socknum) 806 { 807 struct sockaddr_un sunaddr; 808 socklen_t slen; 809 uid_t euid; 810 gid_t egid; 811 int fd; 812 813 slen = sizeof(sunaddr); 814 fd = accept(sockets[socknum].fd, (struct sockaddr *)&sunaddr, &slen); 815 if (fd < 0) { 816 error("accept from AUTH_SOCKET: %s", strerror(errno)); 817 return -1; 818 } 819 if (getpeereid(fd, &euid, &egid) < 0) { 820 error("getpeereid %d failed: %s", fd, strerror(errno)); 821 close(fd); 822 return -1; 823 } 824 if ((euid != 0) && (getuid() != euid)) { 825 error("uid mismatch: peer euid %u != uid %u", 826 (u_int) euid, (u_int) getuid()); 827 close(fd); 828 return -1; 829 } 830 new_socket(AUTH_CONNECTION, fd); 831 return 0; 832 } 833 834 static int 835 handle_conn_read(u_int socknum) 836 { 837 char buf[AGENT_RBUF_LEN]; 838 ssize_t len; 839 int r; 840 841 if ((len = read(sockets[socknum].fd, buf, sizeof(buf))) <= 0) { 842 if (len == -1) { 843 if (errno == EAGAIN || errno == EINTR) 844 return 0; 845 error("%s: read error on socket %u (fd %d): %s", 846 __func__, socknum, sockets[socknum].fd, 847 strerror(errno)); 848 } 849 return -1; 850 } 851 if ((r = sshbuf_put(sockets[socknum].input, buf, len)) != 0) 852 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 853 explicit_bzero(buf, sizeof(buf)); 854 process_message(socknum); 855 return 0; 856 } 857 858 static int 859 handle_conn_write(u_int socknum) 860 { 861 ssize_t len; 862 int r; 863 864 if (sshbuf_len(sockets[socknum].output) == 0) 865 return 0; /* shouldn't happen */ 866 if ((len = write(sockets[socknum].fd, 867 sshbuf_ptr(sockets[socknum].output), 868 sshbuf_len(sockets[socknum].output))) <= 0) { 869 if (len == -1) { 870 if (errno == EAGAIN || errno == EINTR) 871 return 0; 872 error("%s: read error on socket %u (fd %d): %s", 873 __func__, socknum, sockets[socknum].fd, 874 strerror(errno)); 875 } 876 return -1; 877 } 878 if ((r = sshbuf_consume(sockets[socknum].output, len)) != 0) 879 fatal("%s: buffer error: %s", __func__, ssh_err(r)); 880 return 0; 881 } 882 883 static void 884 after_poll(struct pollfd *pfd, size_t npfd, u_int maxfds) 885 { 886 size_t i; 887 u_int socknum, activefds = npfd; 888 889 for (i = 0; i < npfd; i++) { 890 if (pfd[i].revents == 0) 891 continue; 892 /* Find sockets entry */ 893 for (socknum = 0; socknum < sockets_alloc; socknum++) { 894 if (sockets[socknum].type != AUTH_SOCKET && 895 sockets[socknum].type != AUTH_CONNECTION) 896 continue; 897 if (pfd[i].fd == sockets[socknum].fd) 898 break; 899 } 900 if (socknum >= sockets_alloc) { 901 error("%s: no socket for fd %d", __func__, pfd[i].fd); 902 continue; 903 } 904 /* Process events */ 905 switch (sockets[socknum].type) { 906 case AUTH_SOCKET: 907 if ((pfd[i].revents & (POLLIN|POLLERR)) == 0) 908 break; 909 if (npfd > maxfds) { 910 debug3("out of fds (active %u >= limit %u); " 911 "skipping accept", activefds, maxfds); 912 break; 913 } 914 if (handle_socket_read(socknum) == 0) 915 activefds++; 916 break; 917 case AUTH_CONNECTION: 918 if ((pfd[i].revents & (POLLIN|POLLERR)) != 0 && 919 handle_conn_read(socknum) != 0) { 920 goto close_sock; 921 } 922 if ((pfd[i].revents & (POLLOUT|POLLHUP)) != 0 && 923 handle_conn_write(socknum) != 0) { 924 close_sock: 925 if (activefds == 0) 926 fatal("activefds == 0 at close_sock"); 927 close_socket(&sockets[socknum]); 928 activefds--; 929 break; 930 } 931 break; 932 default: 933 break; 934 } 935 } 936 } 937 938 static int 939 prepare_poll(struct pollfd **pfdp, size_t *npfdp, int *timeoutp, u_int maxfds) 940 { 941 struct pollfd *pfd = *pfdp; 942 size_t i, j, npfd = 0; 943 time_t deadline; 944 int r; 945 946 /* Count active sockets */ 947 for (i = 0; i < sockets_alloc; i++) { 948 switch (sockets[i].type) { 949 case AUTH_SOCKET: 950 case AUTH_CONNECTION: 951 npfd++; 952 break; 953 case AUTH_UNUSED: 954 break; 955 default: 956 fatal("Unknown socket type %d", sockets[i].type); 957 break; 958 } 959 } 960 if (npfd != *npfdp && 961 (pfd = recallocarray(pfd, *npfdp, npfd, sizeof(*pfd))) == NULL) 962 fatal("%s: recallocarray failed", __func__); 963 *pfdp = pfd; 964 *npfdp = npfd; 965 966 for (i = j = 0; i < sockets_alloc; i++) { 967 switch (sockets[i].type) { 968 case AUTH_SOCKET: 969 if (npfd > maxfds) { 970 debug3("out of fds (active %zu >= limit %u); " 971 "skipping arming listener", npfd, maxfds); 972 break; 973 } 974 pfd[j].fd = sockets[i].fd; 975 pfd[j].revents = 0; 976 pfd[j].events = POLLIN; 977 j++; 978 break; 979 case AUTH_CONNECTION: 980 pfd[j].fd = sockets[i].fd; 981 pfd[j].revents = 0; 982 /* 983 * Only prepare to read if we can handle a full-size 984 * input read buffer and enqueue a max size reply.. 985 */ 986 if ((r = sshbuf_check_reserve(sockets[i].input, 987 AGENT_RBUF_LEN)) == 0 && 988 (r = sshbuf_check_reserve(sockets[i].output, 989 AGENT_MAX_LEN)) == 0) 990 pfd[j].events = POLLIN; 991 else if (r != SSH_ERR_NO_BUFFER_SPACE) { 992 fatal("%s: buffer error: %s", 993 __func__, ssh_err(r)); 994 } 995 if (sshbuf_len(sockets[i].output) > 0) 996 pfd[j].events |= POLLOUT; 997 j++; 998 break; 999 default: 1000 break; 1001 } 1002 } 1003 deadline = reaper(); 1004 if (parent_alive_interval != 0) 1005 deadline = (deadline == 0) ? parent_alive_interval : 1006 MINIMUM(deadline, parent_alive_interval); 1007 if (deadline == 0) { 1008 *timeoutp = -1; /* INFTIM */ 1009 } else { 1010 if (deadline > INT_MAX / 1000) 1011 *timeoutp = INT_MAX / 1000; 1012 else 1013 *timeoutp = deadline * 1000; 1014 } 1015 return (1); 1016 } 1017 1018 static void 1019 cleanup_socket(void) 1020 { 1021 if (cleanup_pid != 0 && getpid() != cleanup_pid) 1022 return; 1023 debug("%s: cleanup", __func__); 1024 if (socket_name[0]) 1025 unlink(socket_name); 1026 if (socket_dir[0]) 1027 rmdir(socket_dir); 1028 } 1029 1030 void 1031 cleanup_exit(int i) 1032 { 1033 cleanup_socket(); 1034 _exit(i); 1035 } 1036 1037 /*ARGSUSED*/ 1038 static void 1039 cleanup_handler(int sig) 1040 { 1041 cleanup_socket(); 1042 #ifdef ENABLE_PKCS11 1043 pkcs11_terminate(); 1044 #endif 1045 _exit(2); 1046 } 1047 1048 static void 1049 check_parent_exists(void) 1050 { 1051 /* 1052 * If our parent has exited then getppid() will return (pid_t)1, 1053 * so testing for that should be safe. 1054 */ 1055 if (parent_pid != -1 && getppid() != parent_pid) { 1056 /* printf("Parent has died - Authentication agent exiting.\n"); */ 1057 cleanup_socket(); 1058 _exit(2); 1059 } 1060 } 1061 1062 static void 1063 usage(void) 1064 { 1065 fprintf(stderr, 1066 "usage: ssh-agent [-c | -s] [-Dd] [-a bind_address] [-E fingerprint_hash]\n" 1067 " [-P pkcs11_whitelist] [-t life] [command [arg ...]]\n" 1068 " ssh-agent [-c | -s] -k\n"); 1069 exit(1); 1070 } 1071 1072 int 1073 main(int ac, char **av) 1074 { 1075 int c_flag = 0, d_flag = 0, D_flag = 0, k_flag = 0, s_flag = 0; 1076 int sock, fd, ch, result, saved_errno; 1077 char *shell, *format, *pidstr, *agentsocket = NULL; 1078 struct rlimit rlim; 1079 extern int optind; 1080 extern char *optarg; 1081 pid_t pid; 1082 char pidstrbuf[1 + 3 * sizeof pid]; 1083 size_t len; 1084 mode_t prev_mask; 1085 int timeout = -1; /* INFTIM */ 1086 struct pollfd *pfd = NULL; 1087 size_t npfd = 0; 1088 u_int maxfds; 1089 1090 /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */ 1091 sanitise_stdfd(); 1092 1093 /* drop */ 1094 setegid(getgid()); 1095 setgid(getgid()); 1096 1097 if (getrlimit(RLIMIT_NOFILE, &rlim) == -1) 1098 fatal("%s: getrlimit: %s", __progname, strerror(errno)); 1099 1100 #ifdef WITH_OPENSSL 1101 OpenSSL_add_all_algorithms(); 1102 #endif 1103 1104 while ((ch = getopt(ac, av, "cDdksE:a:P:t:")) != -1) { 1105 switch (ch) { 1106 case 'E': 1107 fingerprint_hash = ssh_digest_alg_by_name(optarg); 1108 if (fingerprint_hash == -1) 1109 fatal("Invalid hash algorithm \"%s\"", optarg); 1110 break; 1111 case 'c': 1112 if (s_flag) 1113 usage(); 1114 c_flag++; 1115 break; 1116 case 'k': 1117 k_flag++; 1118 break; 1119 case 'P': 1120 if (pkcs11_whitelist != NULL) 1121 fatal("-P option already specified"); 1122 pkcs11_whitelist = xstrdup(optarg); 1123 break; 1124 case 's': 1125 if (c_flag) 1126 usage(); 1127 s_flag++; 1128 break; 1129 case 'd': 1130 if (d_flag || D_flag) 1131 usage(); 1132 d_flag++; 1133 break; 1134 case 'D': 1135 if (d_flag || D_flag) 1136 usage(); 1137 D_flag++; 1138 break; 1139 case 'a': 1140 agentsocket = optarg; 1141 break; 1142 case 't': 1143 if ((lifetime = convtime(optarg)) == -1) { 1144 fprintf(stderr, "Invalid lifetime\n"); 1145 usage(); 1146 } 1147 break; 1148 default: 1149 usage(); 1150 } 1151 } 1152 ac -= optind; 1153 av += optind; 1154 1155 if (ac > 0 && (c_flag || k_flag || s_flag || d_flag || D_flag)) 1156 usage(); 1157 1158 if (pkcs11_whitelist == NULL) 1159 pkcs11_whitelist = xstrdup(DEFAULT_PKCS11_WHITELIST); 1160 1161 if (ac == 0 && !c_flag && !s_flag) { 1162 shell = getenv("SHELL"); 1163 if (shell != NULL && (len = strlen(shell)) > 2 && 1164 strncmp(shell + len - 3, "csh", 3) == 0) 1165 c_flag = 1; 1166 } 1167 if (k_flag) { 1168 const char *errstr = NULL; 1169 1170 pidstr = getenv(SSH_AGENTPID_ENV_NAME); 1171 if (pidstr == NULL) { 1172 fprintf(stderr, "%s not set, cannot kill agent\n", 1173 SSH_AGENTPID_ENV_NAME); 1174 exit(1); 1175 } 1176 pid = (int)strtonum(pidstr, 2, INT_MAX, &errstr); 1177 if (errstr) { 1178 fprintf(stderr, 1179 "%s=\"%s\", which is not a good PID: %s\n", 1180 SSH_AGENTPID_ENV_NAME, pidstr, errstr); 1181 exit(1); 1182 } 1183 if (kill(pid, SIGTERM) == -1) { 1184 perror("kill"); 1185 exit(1); 1186 } 1187 format = c_flag ? "unsetenv %s;\n" : "unset %s;\n"; 1188 printf(format, SSH_AUTHSOCKET_ENV_NAME); 1189 printf(format, SSH_AGENTPID_ENV_NAME); 1190 printf("echo Agent pid %ld killed;\n", (long)pid); 1191 exit(0); 1192 } 1193 1194 /* 1195 * Minimum file descriptors: 1196 * stdio (3) + listener (1) + syslog (1 maybe) + connection (1) + 1197 * a few spare for libc / stack protectors / sanitisers, etc. 1198 */ 1199 #define SSH_AGENT_MIN_FDS (3+1+1+1+4) 1200 if (rlim.rlim_cur < SSH_AGENT_MIN_FDS) 1201 fatal("%s: file descriptor rlimit %lld too low (minimum %u)", 1202 __progname, (long long)rlim.rlim_cur, SSH_AGENT_MIN_FDS); 1203 maxfds = rlim.rlim_cur - SSH_AGENT_MIN_FDS; 1204 1205 parent_pid = getpid(); 1206 1207 if (agentsocket == NULL) { 1208 /* Create private directory for agent socket */ 1209 mktemp_proto(socket_dir, sizeof(socket_dir)); 1210 if (mkdtemp(socket_dir) == NULL) { 1211 perror("mkdtemp: private socket dir"); 1212 exit(1); 1213 } 1214 snprintf(socket_name, sizeof socket_name, "%s/agent.%ld", socket_dir, 1215 (long)parent_pid); 1216 } else { 1217 /* Try to use specified agent socket */ 1218 socket_dir[0] = '\0'; 1219 strlcpy(socket_name, agentsocket, sizeof socket_name); 1220 } 1221 1222 /* 1223 * Create socket early so it will exist before command gets run from 1224 * the parent. 1225 */ 1226 prev_mask = umask(0177); 1227 sock = unix_listener(socket_name, SSH_LISTEN_BACKLOG, 0); 1228 if (sock < 0) { 1229 /* XXX - unix_listener() calls error() not perror() */ 1230 *socket_name = '\0'; /* Don't unlink any existing file */ 1231 cleanup_exit(1); 1232 } 1233 umask(prev_mask); 1234 1235 /* 1236 * Fork, and have the parent execute the command, if any, or present 1237 * the socket data. The child continues as the authentication agent. 1238 */ 1239 if (D_flag || d_flag) { 1240 log_init(__progname, 1241 d_flag ? SYSLOG_LEVEL_DEBUG3 : SYSLOG_LEVEL_INFO, 1242 SYSLOG_FACILITY_AUTH, 1); 1243 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n"; 1244 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name, 1245 SSH_AUTHSOCKET_ENV_NAME); 1246 printf("echo Agent pid %ld;\n", (long)parent_pid); 1247 fflush(stdout); 1248 goto skip; 1249 } 1250 pid = fork(); 1251 if (pid == -1) { 1252 perror("fork"); 1253 cleanup_exit(1); 1254 } 1255 if (pid != 0) { /* Parent - execute the given command. */ 1256 close(sock); 1257 snprintf(pidstrbuf, sizeof pidstrbuf, "%ld", (long)pid); 1258 if (ac == 0) { 1259 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n"; 1260 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name, 1261 SSH_AUTHSOCKET_ENV_NAME); 1262 printf(format, SSH_AGENTPID_ENV_NAME, pidstrbuf, 1263 SSH_AGENTPID_ENV_NAME); 1264 printf("echo Agent pid %ld;\n", (long)pid); 1265 exit(0); 1266 } 1267 if (setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1) == -1 || 1268 setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1) == -1) { 1269 perror("setenv"); 1270 exit(1); 1271 } 1272 execvp(av[0], av); 1273 perror(av[0]); 1274 exit(1); 1275 } 1276 /* child */ 1277 log_init(__progname, SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_AUTH, 0); 1278 1279 if (setsid() == -1) { 1280 error("setsid: %s", strerror(errno)); 1281 cleanup_exit(1); 1282 } 1283 1284 (void)chdir("/"); 1285 if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) { 1286 /* XXX might close listen socket */ 1287 (void)dup2(fd, STDIN_FILENO); 1288 (void)dup2(fd, STDOUT_FILENO); 1289 (void)dup2(fd, STDERR_FILENO); 1290 if (fd > 2) 1291 close(fd); 1292 } 1293 1294 /* deny core dumps, since memory contains unencrypted private keys */ 1295 rlim.rlim_cur = rlim.rlim_max = 0; 1296 if (setrlimit(RLIMIT_CORE, &rlim) < 0) { 1297 error("setrlimit RLIMIT_CORE: %s", strerror(errno)); 1298 cleanup_exit(1); 1299 } 1300 1301 skip: 1302 1303 cleanup_pid = getpid(); 1304 1305 #ifdef ENABLE_PKCS11 1306 pkcs11_init(0); 1307 #endif 1308 new_socket(AUTH_SOCKET, sock); 1309 if (ac > 0) 1310 parent_alive_interval = 10; 1311 idtab_init(); 1312 signal(SIGPIPE, SIG_IGN); 1313 signal(SIGINT, (d_flag | D_flag) ? cleanup_handler : SIG_IGN); 1314 signal(SIGHUP, cleanup_handler); 1315 signal(SIGTERM, cleanup_handler); 1316 1317 if (pledge("stdio rpath cpath unix id proc exec", NULL) == -1) 1318 fatal("%s: pledge: %s", __progname, strerror(errno)); 1319 1320 while (1) { 1321 prepare_poll(&pfd, &npfd, &timeout, maxfds); 1322 result = poll(pfd, npfd, timeout); 1323 saved_errno = errno; 1324 if (parent_alive_interval != 0) 1325 check_parent_exists(); 1326 (void) reaper(); /* remove expired keys */ 1327 if (result < 0) { 1328 if (saved_errno == EINTR) 1329 continue; 1330 fatal("poll: %s", strerror(saved_errno)); 1331 } else if (result > 0) 1332 after_poll(pfd, npfd, maxfds); 1333 } 1334 /* NOTREACHED */ 1335 } 1336