crypto/openssh/ssh-agent.c

   1 /* $OpenBSD: ssh-agent.c,v 1.224 2017/07/24 04:34:28 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 "includes.h"
  38
  39 #include <sys/types.h>
  40 #include <sys/param.h>
  41 #include <sys/resource.h>
  42 #include <sys/stat.h>
  43 #include <sys/socket.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 "sshbuf.h"
  80 #include "sshkey.h"
  81 #include "authfd.h"
  82 #include "compat.h"
  83 #include "log.h"
  84 #include "misc.h"
  85 #include "digest.h"
  86 #include "ssherr.h"
  87 #include "match.h"
  88
  89 #ifdef ENABLE_PKCS11
  90 #include "ssh-pkcs11.h"
  91 #endif
  92
  93 #ifndef DEFAULT_PKCS11_WHITELIST
  94 # define DEFAULT_PKCS11_WHITELIST "/usr/lib*/*,/usr/local/lib*/*"
  95 #endif
  96
  97 /* Maximum accepted message length */
  98 #define AGENT_MAX_LEN   (256*1024)
  99
 100 typedef enum {
 101         AUTH_UNUSED,
 102         AUTH_SOCKET,
 103         AUTH_CONNECTION
 104 } sock_type;
 105
 106 typedef struct {
 107         int fd;
 108         sock_type type;
 109         struct sshbuf *input;
 110         struct sshbuf *output;
 111         struct sshbuf *request;
 112 } SocketEntry;
 113
 114 u_int sockets_alloc = 0;
 115 SocketEntry *sockets = NULL;
 116
 117 typedef struct identity {
 118         TAILQ_ENTRY(identity) next;
 119         struct sshkey *key;
 120         char *comment;
 121         char *provider;
 122         time_t death;
 123         u_int confirm;
 124 } Identity;
 125
 126 struct idtable {
 127         int nentries;
 128         TAILQ_HEAD(idqueue, identity) idlist;
 129 };
 130
 131 /* private key table */
 132 struct idtable *idtab;
 133
 134 int max_fd = 0;
 135
 136 /* pid of shell == parent of agent */
 137 pid_t parent_pid = -1;
 138 time_t parent_alive_interval = 0;
 139
 140 /* pid of process for which cleanup_socket is applicable */
 141 pid_t cleanup_pid = 0;
 142
 143 /* pathname and directory for AUTH_SOCKET */
 144 char socket_name[PATH_MAX];
 145 char socket_dir[PATH_MAX];
 146
 147 /* PKCS#11 path whitelist */
 148 static char *pkcs11_whitelist;
 149
 150 /* locking */
 151 #define LOCK_SIZE       32
 152 #define LOCK_SALT_SIZE  16
 153 #define LOCK_ROUNDS     1
 154 int locked = 0;
 155 u_char lock_pwhash[LOCK_SIZE];
 156 u_char lock_salt[LOCK_SALT_SIZE];
 157
 158 extern char *__progname;
 159
 160 /* Default lifetime in seconds (0 == forever) */
 161 static long lifetime = 0;
 162
 163 static int fingerprint_hash = SSH_FP_HASH_DEFAULT;
 164
 165 static void
 166 close_socket(SocketEntry *e)
 167 {
 168         close(e->fd);
 169         e->fd = -1;
 170         e->type = AUTH_UNUSED;
 171         sshbuf_free(e->input);
 172         sshbuf_free(e->output);
 173         sshbuf_free(e->request);
 174 }
 175
 176 static void
 177 idtab_init(void)
 178 {
 179         idtab = xcalloc(1, sizeof(*idtab));
 180         TAILQ_INIT(&idtab->idlist);
 181         idtab->nentries = 0;
 182 }
 183
 184 static void
 185 free_identity(Identity *id)
 186 {
 187         sshkey_free(id->key);
 188         free(id->provider);
 189         free(id->comment);
 190         free(id);
 191 }
 192
 193 /* return matching private key for given public key */
 194 static Identity *
 195 lookup_identity(struct sshkey *key)
 196 {
 197         Identity *id;
 198
 199         TAILQ_FOREACH(id, &idtab->idlist, next) {
 200                 if (sshkey_equal(key, id->key))
 201                         return (id);
 202         }
 203         return (NULL);
 204 }
 205
 206 /* Check confirmation of keysign request */
 207 static int
 208 confirm_key(Identity *id)
 209 {
 210         char *p;
 211         int ret = -1;
 212
 213         p = sshkey_fingerprint(id->key, fingerprint_hash, SSH_FP_DEFAULT);
 214         if (p != NULL &&
 215             ask_permission("Allow use of key %s?\nKey fingerprint %s.",
 216             id->comment, p))
 217                 ret = 0;
 218         free(p);
 219
 220         return (ret);
 221 }
 222
 223 static void
 224 send_status(SocketEntry *e, int success)
 225 {
 226         int r;
 227
 228         if ((r = sshbuf_put_u32(e->output, 1)) != 0 ||
 229             (r = sshbuf_put_u8(e->output, success ?
 230             SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE)) != 0)
 231                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 232 }
 233
 234 /* send list of supported public keys to 'client' */
 235 static void
 236 process_request_identities(SocketEntry *e)
 237 {
 238         Identity *id;
 239         struct sshbuf *msg;
 240         int r;
 241
 242         if ((msg = sshbuf_new()) == NULL)
 243                 fatal("%s: sshbuf_new failed", __func__);
 244         if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
 245             (r = sshbuf_put_u32(msg, idtab->nentries)) != 0)
 246                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 247         TAILQ_FOREACH(id, &idtab->idlist, next) {
 248                 if ((r = sshkey_puts(id->key, msg)) != 0 ||
 249                     (r = sshbuf_put_cstring(msg, id->comment)) != 0) {
 250                         error("%s: put key/comment: %s", __func__,
 251                             ssh_err(r));
 252                         continue;
 253                 }
 254         }
 255         if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
 256                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 257         sshbuf_free(msg);
 258 }
 259
 260
 261 static char *
 262 agent_decode_alg(struct sshkey *key, u_int flags)
 263 {
 264         if (key->type == KEY_RSA) {
 265                 if (flags & SSH_AGENT_RSA_SHA2_256)
 266                         return "rsa-sha2-256";
 267                 else if (flags & SSH_AGENT_RSA_SHA2_512)
 268                         return "rsa-sha2-512";
 269         }
 270         return NULL;
 271 }
 272
 273 /* ssh2 only */
 274 static void
 275 process_sign_request2(SocketEntry *e)
 276 {
 277         const u_char *data;
 278         u_char *signature = NULL;
 279         size_t dlen, slen = 0;
 280         u_int compat = 0, flags;
 281         int r, ok = -1;
 282         struct sshbuf *msg;
 283         struct sshkey *key = NULL;
 284         struct identity *id;
 285
 286         if ((msg = sshbuf_new()) == NULL)
 287                 fatal("%s: sshbuf_new failed", __func__);
 288         if ((r = sshkey_froms(e->request, &key)) != 0 ||
 289             (r = sshbuf_get_string_direct(e->request, &data, &dlen)) != 0 ||
 290             (r = sshbuf_get_u32(e->request, &flags)) != 0)
 291                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 292         if (flags & SSH_AGENT_OLD_SIGNATURE)
 293                 compat = SSH_BUG_SIGBLOB;
 294         if ((id = lookup_identity(key)) == NULL) {
 295                 verbose("%s: %s key not found", __func__, sshkey_type(key));
 296                 goto send;
 297         }
 298         if (id->confirm && confirm_key(id) != 0) {
 299                 verbose("%s: user refused key", __func__);
 300                 goto send;
 301         }
 302         if ((r = sshkey_sign(id->key, &signature, &slen,
 303             data, dlen, agent_decode_alg(key, flags), compat)) != 0) {
 304                 error("%s: sshkey_sign: %s", __func__, ssh_err(r));
 305                 goto send;
 306         }
 307         /* Success */
 308         ok = 0;
 309  send:
 310         sshkey_free(key);
 311         if (ok == 0) {
 312                 if ((r = sshbuf_put_u8(msg, SSH2_AGENT_SIGN_RESPONSE)) != 0 ||
 313                     (r = sshbuf_put_string(msg, signature, slen)) != 0)
 314                         fatal("%s: buffer error: %s", __func__, ssh_err(r));
 315         } else if ((r = sshbuf_put_u8(msg, SSH_AGENT_FAILURE)) != 0)
 316                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 317
 318         if ((r = sshbuf_put_stringb(e->output, msg)) != 0)
 319                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 320
 321         sshbuf_free(msg);
 322         free(signature);
 323 }
 324
 325 /* shared */
 326 static void
 327 process_remove_identity(SocketEntry *e)
 328 {
 329         int r, success = 0;
 330         struct sshkey *key = NULL;
 331         Identity *id;
 332
 333         if ((r = sshkey_froms(e->request, &key)) != 0) {
 334                 error("%s: get key: %s", __func__, ssh_err(r));
 335                 goto done;
 336         }
 337         if ((id = lookup_identity(key)) == NULL) {
 338                 debug("%s: key not found", __func__);
 339                 goto done;
 340         }
 341         /* We have this key, free it. */
 342         if (idtab->nentries < 1)
 343                 fatal("%s: internal error: nentries %d",
 344                     __func__, idtab->nentries);
 345         TAILQ_REMOVE(&idtab->idlist, id, next);
 346         free_identity(id);
 347         idtab->nentries--;
 348         sshkey_free(key);
 349         success = 1;
 350  done:
 351         send_status(e, success);
 352 }
 353
 354 static void
 355 process_remove_all_identities(SocketEntry *e)
 356 {
 357         Identity *id;
 358
 359         /* Loop over all identities and clear the keys. */
 360         for (id = TAILQ_FIRST(&idtab->idlist); id;
 361             id = TAILQ_FIRST(&idtab->idlist)) {
 362                 TAILQ_REMOVE(&idtab->idlist, id, next);
 363                 free_identity(id);
 364         }
 365
 366         /* Mark that there are no identities. */
 367         idtab->nentries = 0;
 368
 369         /* Send success. */
 370         send_status(e, 1);
 371 }
 372
 373 /* removes expired keys and returns number of seconds until the next expiry */
 374 static time_t
 375 reaper(void)
 376 {
 377         time_t deadline = 0, now = monotime();
 378         Identity *id, *nxt;
 379
 380         for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) {
 381                 nxt = TAILQ_NEXT(id, next);
 382                 if (id->death == 0)
 383                         continue;
 384                 if (now >= id->death) {
 385                         debug("expiring key '%s'", id->comment);
 386                         TAILQ_REMOVE(&idtab->idlist, id, next);
 387                         free_identity(id);
 388                         idtab->nentries--;
 389                 } else
 390                         deadline = (deadline == 0) ? id->death :
 391                             MINIMUM(deadline, id->death);
 392         }
 393         if (deadline == 0 || deadline <= now)
 394                 return 0;
 395         else
 396                 return (deadline - now);
 397 }
 398
 399 static void
 400 process_add_identity(SocketEntry *e)
 401 {
 402         Identity *id;
 403         int success = 0, confirm = 0;
 404         u_int seconds;
 405         char *comment = NULL;
 406         time_t death = 0;
 407         struct sshkey *k = NULL;
 408         u_char ctype;
 409         int r = SSH_ERR_INTERNAL_ERROR;
 410
 411         if ((r = sshkey_private_deserialize(e->request, &k)) != 0 ||
 412             k == NULL ||
 413             (r = sshbuf_get_cstring(e->request, &comment, NULL)) != 0) {
 414                 error("%s: decode private key: %s", __func__, ssh_err(r));
 415                 goto err;
 416         }
 417
 418         while (sshbuf_len(e->request)) {
 419                 if ((r = sshbuf_get_u8(e->request, &ctype)) != 0) {
 420                         error("%s: buffer error: %s", __func__, ssh_err(r));
 421                         goto err;
 422                 }
 423                 switch (ctype) {
 424                 case SSH_AGENT_CONSTRAIN_LIFETIME:
 425                         if ((r = sshbuf_get_u32(e->request, &seconds)) != 0) {
 426                                 error("%s: bad lifetime constraint: %s",
 427                                     __func__, ssh_err(r));
 428                                 goto err;
 429                         }
 430                         death = monotime() + seconds;
 431                         break;
 432                 case SSH_AGENT_CONSTRAIN_CONFIRM:
 433                         confirm = 1;
 434                         break;
 435                 default:
 436                         error("%s: Unknown constraint %d", __func__, ctype);
 437  err:
 438                         sshbuf_reset(e->request);
 439                         free(comment);
 440                         sshkey_free(k);
 441                         goto send;
 442                 }
 443         }
 444
 445         success = 1;
 446         if (lifetime && !death)
 447                 death = monotime() + lifetime;
 448         if ((id = lookup_identity(k)) == NULL) {
 449                 id = xcalloc(1, sizeof(Identity));
 450                 id->key = k;
 451                 TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
 452                 /* Increment the number of identities. */
 453                 idtab->nentries++;
 454         } else {
 455                 sshkey_free(k);
 456                 free(id->comment);
 457         }
 458         id->comment = comment;
 459         id->death = death;
 460         id->confirm = confirm;
 461 send:
 462         send_status(e, success);
 463 }
 464
 465 /* XXX todo: encrypt sensitive data with passphrase */
 466 static void
 467 process_lock_agent(SocketEntry *e, int lock)
 468 {
 469         int r, success = 0, delay;
 470         char *passwd;
 471         u_char passwdhash[LOCK_SIZE];
 472         static u_int fail_count = 0;
 473         size_t pwlen;
 474
 475         if ((r = sshbuf_get_cstring(e->request, &passwd, &pwlen)) != 0)
 476                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 477         if (pwlen == 0) {
 478                 debug("empty password not supported");
 479         } else if (locked && !lock) {
 480                 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt),
 481                     passwdhash, sizeof(passwdhash), LOCK_ROUNDS) < 0)
 482                         fatal("bcrypt_pbkdf");
 483                 if (timingsafe_bcmp(passwdhash, lock_pwhash, LOCK_SIZE) == 0) {
 484                         debug("agent unlocked");
 485                         locked = 0;
 486                         fail_count = 0;
 487                         explicit_bzero(lock_pwhash, sizeof(lock_pwhash));
 488                         success = 1;
 489                 } else {
 490                         /* delay in 0.1s increments up to 10s */
 491                         if (fail_count < 100)
 492                                 fail_count++;
 493                         delay = 100000 * fail_count;
 494                         debug("unlock failed, delaying %0.1lf seconds",
 495                             (double)delay/1000000);
 496                         usleep(delay);
 497                 }
 498                 explicit_bzero(passwdhash, sizeof(passwdhash));
 499         } else if (!locked && lock) {
 500                 debug("agent locked");
 501                 locked = 1;
 502                 arc4random_buf(lock_salt, sizeof(lock_salt));
 503                 if (bcrypt_pbkdf(passwd, pwlen, lock_salt, sizeof(lock_salt),
 504                     lock_pwhash, sizeof(lock_pwhash), LOCK_ROUNDS) < 0)
 505                         fatal("bcrypt_pbkdf");
 506                 success = 1;
 507         }
 508         explicit_bzero(passwd, pwlen);
 509         free(passwd);
 510         send_status(e, success);
 511 }
 512
 513 static void
 514 no_identities(SocketEntry *e)
 515 {
 516         struct sshbuf *msg;
 517         int r;
 518
 519         if ((msg = sshbuf_new()) == NULL)
 520                 fatal("%s: sshbuf_new failed", __func__);
 521         if ((r = sshbuf_put_u8(msg, SSH2_AGENT_IDENTITIES_ANSWER)) != 0 ||
 522             (r = sshbuf_put_u32(msg, 0)) != 0 ||
 523             (r = sshbuf_put_stringb(e->output, msg)) != 0)
 524                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 525         sshbuf_free(msg);
 526 }
 527
 528 #ifdef ENABLE_PKCS11
 529 static void
 530 process_add_smartcard_key(SocketEntry *e)
 531 {
 532         char *provider = NULL, *pin, canonical_provider[PATH_MAX];
 533         int r, i, count = 0, success = 0, confirm = 0;
 534         u_int seconds;
 535         time_t death = 0;
 536         u_char type;
 537         struct sshkey **keys = NULL, *k;
 538         Identity *id;
 539
 540         if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
 541             (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0)
 542                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 543
 544         while (sshbuf_len(e->request)) {
 545                 if ((r = sshbuf_get_u8(e->request, &type)) != 0)
 546                         fatal("%s: buffer error: %s", __func__, ssh_err(r));
 547                 switch (type) {
 548                 case SSH_AGENT_CONSTRAIN_LIFETIME:
 549                         if ((r = sshbuf_get_u32(e->request, &seconds)) != 0)
 550                                 fatal("%s: buffer error: %s",
 551                                     __func__, ssh_err(r));
 552                         death = monotime() + seconds;
 553                         break;
 554                 case SSH_AGENT_CONSTRAIN_CONFIRM:
 555                         confirm = 1;
 556                         break;
 557                 default:
 558                         error("%s: Unknown constraint type %d", __func__, type);
 559                         goto send;
 560                 }
 561         }
 562         if (realpath(provider, canonical_provider) == NULL) {
 563                 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
 564                     provider, strerror(errno));
 565                 goto send;
 566         }
 567         if (match_pattern_list(canonical_provider, pkcs11_whitelist, 0) != 1) {
 568                 verbose("refusing PKCS#11 add of \"%.100s\": "
 569                     "provider not whitelisted", canonical_provider);
 570                 goto send;
 571         }
 572         debug("%s: add %.100s", __func__, canonical_provider);
 573         if (lifetime && !death)
 574                 death = monotime() + lifetime;
 575
 576         count = pkcs11_add_provider(canonical_provider, pin, &keys);
 577         for (i = 0; i < count; i++) {
 578                 k = keys[i];
 579                 if (lookup_identity(k) == NULL) {
 580                         id = xcalloc(1, sizeof(Identity));
 581                         id->key = k;
 582                         id->provider = xstrdup(canonical_provider);
 583                         id->comment = xstrdup(canonical_provider); /* XXX */
 584                         id->death = death;
 585                         id->confirm = confirm;
 586                         TAILQ_INSERT_TAIL(&idtab->idlist, id, next);
 587                         idtab->nentries++;
 588                         success = 1;
 589                 } else {
 590                         sshkey_free(k);
 591                 }
 592                 keys[i] = NULL;
 593         }
 594 send:
 595         free(pin);
 596         free(provider);
 597         free(keys);
 598         send_status(e, success);
 599 }
 600
 601 static void
 602 process_remove_smartcard_key(SocketEntry *e)
 603 {
 604         char *provider = NULL, *pin = NULL, canonical_provider[PATH_MAX];
 605         int r, success = 0;
 606         Identity *id, *nxt;
 607
 608         if ((r = sshbuf_get_cstring(e->request, &provider, NULL)) != 0 ||
 609             (r = sshbuf_get_cstring(e->request, &pin, NULL)) != 0)
 610                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 611         free(pin);
 612
 613         if (realpath(provider, canonical_provider) == NULL) {
 614                 verbose("failed PKCS#11 add of \"%.100s\": realpath: %s",
 615                     provider, strerror(errno));
 616                 goto send;
 617         }
 618
 619         debug("%s: remove %.100s", __func__, canonical_provider);
 620         for (id = TAILQ_FIRST(&idtab->idlist); id; id = nxt) {
 621                 nxt = TAILQ_NEXT(id, next);
 622                 /* Skip file--based keys */
 623                 if (id->provider == NULL)
 624                         continue;
 625                 if (!strcmp(canonical_provider, id->provider)) {
 626                         TAILQ_REMOVE(&idtab->idlist, id, next);
 627                         free_identity(id);
 628                         idtab->nentries--;
 629                 }
 630         }
 631         if (pkcs11_del_provider(canonical_provider) == 0)
 632                 success = 1;
 633         else
 634                 error("%s: pkcs11_del_provider failed", __func__);
 635 send:
 636         free(provider);
 637         send_status(e, success);
 638 }
 639 #endif /* ENABLE_PKCS11 */
 640
 641 /* dispatch incoming messages */
 642
 643 static int
 644 process_message(u_int socknum)
 645 {
 646         u_int msg_len;
 647         u_char type;
 648         const u_char *cp;
 649         int r;
 650         SocketEntry *e;
 651
 652         if (socknum >= sockets_alloc) {
 653                 fatal("%s: socket number %u >= allocated %u",
 654                     __func__, socknum, sockets_alloc);
 655         }
 656         e = &sockets[socknum];
 657
 658         if (sshbuf_len(e->input) < 5)
 659                 return 0;               /* Incomplete message header. */
 660         cp = sshbuf_ptr(e->input);
 661         msg_len = PEEK_U32(cp);
 662         if (msg_len > AGENT_MAX_LEN) {
 663                 debug("%s: socket %u (fd=%d) message too long %u > %u",
 664                     __func__, socknum, e->fd, msg_len, AGENT_MAX_LEN);
 665                 return -1;
 666         }
 667         if (sshbuf_len(e->input) < msg_len + 4)
 668                 return 0;               /* Incomplete message body. */
 669
 670         /* move the current input to e->request */
 671         sshbuf_reset(e->request);
 672         if ((r = sshbuf_get_stringb(e->input, e->request)) != 0 ||
 673             (r = sshbuf_get_u8(e->request, &type)) != 0) {
 674                 if (r == SSH_ERR_MESSAGE_INCOMPLETE ||
 675                     r == SSH_ERR_STRING_TOO_LARGE) {
 676                         debug("%s: buffer error: %s", __func__, ssh_err(r));
 677                         return -1;
 678                 }
 679                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 680         }
 681
 682         debug("%s: socket %u (fd=%d) type %d", __func__, socknum, e->fd, type);
 683
 684         /* check wheter agent is locked */
 685         if (locked && type != SSH_AGENTC_UNLOCK) {
 686                 sshbuf_reset(e->request);
 687                 switch (type) {
 688                 case SSH2_AGENTC_REQUEST_IDENTITIES:
 689                         /* send empty lists */
 690                         no_identities(e);
 691                         break;
 692                 default:
 693                         /* send a fail message for all other request types */
 694                         send_status(e, 0);
 695                 }
 696                 return 0;
 697         }
 698
 699         switch (type) {
 700         case SSH_AGENTC_LOCK:
 701         case SSH_AGENTC_UNLOCK:
 702                 process_lock_agent(e, type == SSH_AGENTC_LOCK);
 703                 break;
 704         case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES:
 705                 process_remove_all_identities(e); /* safe for !WITH_SSH1 */
 706                 break;
 707         /* ssh2 */
 708         case SSH2_AGENTC_SIGN_REQUEST:
 709                 process_sign_request2(e);
 710                 break;
 711         case SSH2_AGENTC_REQUEST_IDENTITIES:
 712                 process_request_identities(e);
 713                 break;
 714         case SSH2_AGENTC_ADD_IDENTITY:
 715         case SSH2_AGENTC_ADD_ID_CONSTRAINED:
 716                 process_add_identity(e);
 717                 break;
 718         case SSH2_AGENTC_REMOVE_IDENTITY:
 719                 process_remove_identity(e);
 720                 break;
 721         case SSH2_AGENTC_REMOVE_ALL_IDENTITIES:
 722                 process_remove_all_identities(e);
 723                 break;
 724 #ifdef ENABLE_PKCS11
 725         case SSH_AGENTC_ADD_SMARTCARD_KEY:
 726         case SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED:
 727                 process_add_smartcard_key(e);
 728                 break;
 729         case SSH_AGENTC_REMOVE_SMARTCARD_KEY:
 730                 process_remove_smartcard_key(e);
 731                 break;
 732 #endif /* ENABLE_PKCS11 */
 733         default:
 734                 /* Unknown message.  Respond with failure. */
 735                 error("Unknown message %d", type);
 736                 sshbuf_reset(e->request);
 737                 send_status(e, 0);
 738                 break;
 739         }
 740         return 0;
 741 }
 742
 743 static void
 744 new_socket(sock_type type, int fd)
 745 {
 746         u_int i, old_alloc, new_alloc;
 747
 748         set_nonblock(fd);
 749
 750         if (fd > max_fd)
 751                 max_fd = fd;
 752
 753         for (i = 0; i < sockets_alloc; i++)
 754                 if (sockets[i].type == AUTH_UNUSED) {
 755                         sockets[i].fd = fd;
 756                         if ((sockets[i].input = sshbuf_new()) == NULL)
 757                                 fatal("%s: sshbuf_new failed", __func__);
 758                         if ((sockets[i].output = sshbuf_new()) == NULL)
 759                                 fatal("%s: sshbuf_new failed", __func__);
 760                         if ((sockets[i].request = sshbuf_new()) == NULL)
 761                                 fatal("%s: sshbuf_new failed", __func__);
 762                         sockets[i].type = type;
 763                         return;
 764                 }
 765         old_alloc = sockets_alloc;
 766         new_alloc = sockets_alloc + 10;
 767         sockets = xreallocarray(sockets, new_alloc, sizeof(sockets[0]));
 768         for (i = old_alloc; i < new_alloc; i++)
 769                 sockets[i].type = AUTH_UNUSED;
 770         sockets_alloc = new_alloc;
 771         sockets[old_alloc].fd = fd;
 772         if ((sockets[old_alloc].input = sshbuf_new()) == NULL)
 773                 fatal("%s: sshbuf_new failed", __func__);
 774         if ((sockets[old_alloc].output = sshbuf_new()) == NULL)
 775                 fatal("%s: sshbuf_new failed", __func__);
 776         if ((sockets[old_alloc].request = sshbuf_new()) == NULL)
 777                 fatal("%s: sshbuf_new failed", __func__);
 778         sockets[old_alloc].type = type;
 779 }
 780
 781 static int
 782 handle_socket_read(u_int socknum)
 783 {
 784         struct sockaddr_un sunaddr;
 785         socklen_t slen;
 786         uid_t euid;
 787         gid_t egid;
 788         int fd;
 789
 790         slen = sizeof(sunaddr);
 791         fd = accept(sockets[socknum].fd, (struct sockaddr *)&sunaddr, &slen);
 792         if (fd < 0) {
 793                 error("accept from AUTH_SOCKET: %s", strerror(errno));
 794                 return -1;
 795         }
 796         if (getpeereid(fd, &euid, &egid) < 0) {
 797                 error("getpeereid %d failed: %s", fd, strerror(errno));
 798                 close(fd);
 799                 return -1;
 800         }
 801         if ((euid != 0) && (getuid() != euid)) {
 802                 error("uid mismatch: peer euid %u != uid %u",
 803                     (u_int) euid, (u_int) getuid());
 804                 close(fd);
 805                 return -1;
 806         }
 807         new_socket(AUTH_CONNECTION, fd);
 808         return 0;
 809 }
 810
 811 static int
 812 handle_conn_read(u_int socknum)
 813 {
 814         char buf[1024];
 815         ssize_t len;
 816         int r;
 817
 818         if ((len = read(sockets[socknum].fd, buf, sizeof(buf))) <= 0) {
 819                 if (len == -1) {
 820                         if (errno == EAGAIN || errno == EINTR)
 821                                 return 0;
 822                         error("%s: read error on socket %u (fd %d): %s",
 823                             __func__, socknum, sockets[socknum].fd,
 824                             strerror(errno));
 825                 }
 826                 return -1;
 827         }
 828         if ((r = sshbuf_put(sockets[socknum].input, buf, len)) != 0)
 829                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 830         explicit_bzero(buf, sizeof(buf));
 831         process_message(socknum);
 832         return 0;
 833 }
 834
 835 static int
 836 handle_conn_write(u_int socknum)
 837 {
 838         ssize_t len;
 839         int r;
 840
 841         if (sshbuf_len(sockets[socknum].output) == 0)
 842                 return 0; /* shouldn't happen */
 843         if ((len = write(sockets[socknum].fd,
 844             sshbuf_ptr(sockets[socknum].output),
 845             sshbuf_len(sockets[socknum].output))) <= 0) {
 846                 if (len == -1) {
 847                         if (errno == EAGAIN || errno == EINTR)
 848                                 return 0;
 849                         error("%s: read error on socket %u (fd %d): %s",
 850                             __func__, socknum, sockets[socknum].fd,
 851                             strerror(errno));
 852                 }
 853                 return -1;
 854         }
 855         if ((r = sshbuf_consume(sockets[socknum].output, len)) != 0)
 856                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 857         return 0;
 858 }
 859
 860 static void
 861 after_poll(struct pollfd *pfd, size_t npfd)
 862 {
 863         size_t i;
 864         u_int socknum;
 865
 866         for (i = 0; i < npfd; i++) {
 867                 if (pfd[i].revents == 0)
 868                         continue;
 869                 /* Find sockets entry */
 870                 for (socknum = 0; socknum < sockets_alloc; socknum++) {
 871                         if (sockets[socknum].type != AUTH_SOCKET &&
 872                             sockets[socknum].type != AUTH_CONNECTION)
 873                                 continue;
 874                         if (pfd[i].fd == sockets[socknum].fd)
 875                                 break;
 876                 }
 877                 if (socknum >= sockets_alloc) {
 878                         error("%s: no socket for fd %d", __func__, pfd[i].fd);
 879                         continue;
 880                 }
 881                 /* Process events */
 882                 switch (sockets[socknum].type) {
 883                 case AUTH_SOCKET:
 884                         if ((pfd[i].revents & (POLLIN|POLLERR)) != 0 &&
 885                             handle_socket_read(socknum) != 0)
 886                                 close_socket(&sockets[socknum]);
 887                         break;
 888                 case AUTH_CONNECTION:
 889                         if ((pfd[i].revents & (POLLIN|POLLERR)) != 0 &&
 890                             handle_conn_read(socknum) != 0) {
 891                                 close_socket(&sockets[socknum]);
 892                                 break;
 893                         }
 894                         if ((pfd[i].revents & (POLLOUT|POLLHUP)) != 0 &&
 895                             handle_conn_write(socknum) != 0)
 896                                 close_socket(&sockets[socknum]);
 897                         break;
 898                 default:
 899                         break;
 900                 }
 901         }
 902 }
 903
 904 static int
 905 prepare_poll(struct pollfd **pfdp, size_t *npfdp, int *timeoutp)
 906 {
 907         struct pollfd *pfd = *pfdp;
 908         size_t i, j, npfd = 0;
 909         time_t deadline;
 910
 911         /* Count active sockets */
 912         for (i = 0; i < sockets_alloc; i++) {
 913                 switch (sockets[i].type) {
 914                 case AUTH_SOCKET:
 915                 case AUTH_CONNECTION:
 916                         npfd++;
 917                         break;
 918                 case AUTH_UNUSED:
 919                         break;
 920                 default:
 921                         fatal("Unknown socket type %d", sockets[i].type);
 922                         break;
 923                 }
 924         }
 925         if (npfd != *npfdp &&
 926             (pfd = recallocarray(pfd, *npfdp, npfd, sizeof(*pfd))) == NULL)
 927                 fatal("%s: recallocarray failed", __func__);
 928         *pfdp = pfd;
 929         *npfdp = npfd;
 930
 931         for (i = j = 0; i < sockets_alloc; i++) {
 932                 switch (sockets[i].type) {
 933                 case AUTH_SOCKET:
 934                 case AUTH_CONNECTION:
 935                         pfd[j].fd = sockets[i].fd;
 936                         pfd[j].revents = 0;
 937                         /* XXX backoff when input buffer full */
 938                         pfd[j].events = POLLIN;
 939                         if (sshbuf_len(sockets[i].output) > 0)
 940                                 pfd[j].events |= POLLOUT;
 941                         j++;
 942                         break;
 943                 default:
 944                         break;
 945                 }
 946         }
 947         deadline = reaper();
 948         if (parent_alive_interval != 0)
 949                 deadline = (deadline == 0) ? parent_alive_interval :
 950                     MINIMUM(deadline, parent_alive_interval);
 951         if (deadline == 0) {
 952                 *timeoutp = -1; /* INFTIM */
 953         } else {
 954                 if (deadline > INT_MAX / 1000)
 955                         *timeoutp = INT_MAX / 1000;
 956                 else
 957                         *timeoutp = deadline * 1000;
 958         }
 959         return (1);
 960 }
 961
 962 static void
 963 cleanup_socket(void)
 964 {
 965         if (cleanup_pid != 0 && getpid() != cleanup_pid)
 966                 return;
 967         debug("%s: cleanup", __func__);
 968         if (socket_name[0])
 969                 unlink(socket_name);
 970         if (socket_dir[0])
 971                 rmdir(socket_dir);
 972 }
 973
 974 void
 975 cleanup_exit(int i)
 976 {
 977         cleanup_socket();
 978         _exit(i);
 979 }
 980
 981 /*ARGSUSED*/
 982 static void
 983 cleanup_handler(int sig)
 984 {
 985         cleanup_socket();
 986 #ifdef ENABLE_PKCS11
 987         pkcs11_terminate();
 988 #endif
 989         _exit(2);
 990 }
 991
 992 static void
 993 check_parent_exists(void)
 994 {
 995         /*
 996          * If our parent has exited then getppid() will return (pid_t)1,
 997          * so testing for that should be safe.
 998          */
 999         if (parent_pid != -1 && getppid() != parent_pid) {
1000                 /* printf("Parent has died - Authentication agent exiting.\n"); */
1001                 cleanup_socket();
1002                 _exit(2);
1003         }
1004 }
1005
1006 static void
1007 usage(void)
1008 {
1009         fprintf(stderr,
1010             "usage: ssh-agent [-c | -s] [-Dd] [-a bind_address] [-E fingerprint_hash]\n"
1011             "                 [-P pkcs11_whitelist] [-t life] [command [arg ...]]\n"
1012             "       ssh-agent [-c | -s] -k\n");
1013         exit(1);
1014 }
1015
1016 int
1017 main(int ac, char **av)
1018 {
1019         int c_flag = 0, d_flag = 0, D_flag = 0, k_flag = 0, s_flag = 0;
1020         int sock, fd, ch, result, saved_errno;
1021         char *shell, *format, *pidstr, *agentsocket = NULL;
1022 #ifdef HAVE_SETRLIMIT
1023         struct rlimit rlim;
1024 #endif
1025         extern int optind;
1026         extern char *optarg;
1027         pid_t pid;
1028         char pidstrbuf[1 + 3 * sizeof pid];
1029         size_t len;
1030         mode_t prev_mask;
1031         int timeout = -1; /* INFTIM */
1032         struct pollfd *pfd = NULL;
1033         size_t npfd = 0;
1034
1035         ssh_malloc_init();      /* must be called before any mallocs */
1036         /* Ensure that fds 0, 1 and 2 are open or directed to /dev/null */
1037         sanitise_stdfd();
1038
1039         /* drop */
1040         setegid(getgid());
1041         setgid(getgid());
1042
1043         platform_disable_tracing(0);    /* strict=no */
1044
1045 #ifdef WITH_OPENSSL
1046         OpenSSL_add_all_algorithms();
1047 #endif
1048
1049         __progname = ssh_get_progname(av[0]);
1050         seed_rng();
1051
1052         while ((ch = getopt(ac, av, "cDdksE:a:P:t:")) != -1) {
1053                 switch (ch) {
1054                 case 'E':
1055                         fingerprint_hash = ssh_digest_alg_by_name(optarg);
1056                         if (fingerprint_hash == -1)
1057                                 fatal("Invalid hash algorithm \"%s\"", optarg);
1058                         break;
1059                 case 'c':
1060                         if (s_flag)
1061                                 usage();
1062                         c_flag++;
1063                         break;
1064                 case 'k':
1065                         k_flag++;
1066                         break;
1067                 case 'P':
1068                         if (pkcs11_whitelist != NULL)
1069                                 fatal("-P option already specified");
1070                         pkcs11_whitelist = xstrdup(optarg);
1071                         break;
1072                 case 's':
1073                         if (c_flag)
1074                                 usage();
1075                         s_flag++;
1076                         break;
1077                 case 'd':
1078                         if (d_flag || D_flag)
1079                                 usage();
1080                         d_flag++;
1081                         break;
1082                 case 'D':
1083                         if (d_flag || D_flag)
1084                                 usage();
1085                         D_flag++;
1086                         break;
1087                 case 'a':
1088                         agentsocket = optarg;
1089                         break;
1090                 case 't':
1091                         if ((lifetime = convtime(optarg)) == -1) {
1092                                 fprintf(stderr, "Invalid lifetime\n");
1093                                 usage();
1094                         }
1095                         break;
1096                 default:
1097                         usage();
1098                 }
1099         }
1100         ac -= optind;
1101         av += optind;
1102
1103         if (ac > 0 && (c_flag || k_flag || s_flag || d_flag || D_flag))
1104                 usage();
1105
1106         if (pkcs11_whitelist == NULL)
1107                 pkcs11_whitelist = xstrdup(DEFAULT_PKCS11_WHITELIST);
1108
1109         if (ac == 0 && !c_flag && !s_flag) {
1110                 shell = getenv("SHELL");
1111                 if (shell != NULL && (len = strlen(shell)) > 2 &&
1112                     strncmp(shell + len - 3, "csh", 3) == 0)
1113                         c_flag = 1;
1114         }
1115         if (k_flag) {
1116                 const char *errstr = NULL;
1117
1118                 pidstr = getenv(SSH_AGENTPID_ENV_NAME);
1119                 if (pidstr == NULL) {
1120                         fprintf(stderr, "%s not set, cannot kill agent\n",
1121                             SSH_AGENTPID_ENV_NAME);
1122                         exit(1);
1123                 }
1124                 pid = (int)strtonum(pidstr, 2, INT_MAX, &errstr);
1125                 if (errstr) {
1126                         fprintf(stderr,
1127                             "%s=\"%s\", which is not a good PID: %s\n",
1128                             SSH_AGENTPID_ENV_NAME, pidstr, errstr);
1129                         exit(1);
1130                 }
1131                 if (kill(pid, SIGTERM) == -1) {
1132                         perror("kill");
1133                         exit(1);
1134                 }
1135                 format = c_flag ? "unsetenv %s;\n" : "unset %s;\n";
1136                 printf(format, SSH_AUTHSOCKET_ENV_NAME);
1137                 printf(format, SSH_AGENTPID_ENV_NAME);
1138                 printf("echo Agent pid %ld killed;\n", (long)pid);
1139                 exit(0);
1140         }
1141         parent_pid = getpid();
1142
1143         if (agentsocket == NULL) {
1144                 /* Create private directory for agent socket */
1145                 mktemp_proto(socket_dir, sizeof(socket_dir));
1146                 if (mkdtemp(socket_dir) == NULL) {
1147                         perror("mkdtemp: private socket dir");
1148                         exit(1);
1149                 }
1150                 snprintf(socket_name, sizeof socket_name, "%s/agent.%ld", socket_dir,
1151                     (long)parent_pid);
1152         } else {
1153                 /* Try to use specified agent socket */
1154                 socket_dir[0] = '\0';
1155                 strlcpy(socket_name, agentsocket, sizeof socket_name);
1156         }
1157
1158         /*
1159          * Create socket early so it will exist before command gets run from
1160          * the parent.
1161          */
1162         prev_mask = umask(0177);
1163         sock = unix_listener(socket_name, SSH_LISTEN_BACKLOG, 0);
1164         if (sock < 0) {
1165                 /* XXX - unix_listener() calls error() not perror() */
1166                 *socket_name = '\0'; /* Don't unlink any existing file */
1167                 cleanup_exit(1);
1168         }
1169         umask(prev_mask);
1170
1171         /*
1172          * Fork, and have the parent execute the command, if any, or present
1173          * the socket data.  The child continues as the authentication agent.
1174          */
1175         if (D_flag || d_flag) {
1176                 log_init(__progname,
1177                     d_flag ? SYSLOG_LEVEL_DEBUG3 : SYSLOG_LEVEL_INFO,
1178                     SYSLOG_FACILITY_AUTH, 1);
1179                 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
1180                 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
1181                     SSH_AUTHSOCKET_ENV_NAME);
1182                 printf("echo Agent pid %ld;\n", (long)parent_pid);
1183                 fflush(stdout);
1184                 goto skip;
1185         }
1186         pid = fork();
1187         if (pid == -1) {
1188                 perror("fork");
1189                 cleanup_exit(1);
1190         }
1191         if (pid != 0) {         /* Parent - execute the given command. */
1192                 close(sock);
1193                 snprintf(pidstrbuf, sizeof pidstrbuf, "%ld", (long)pid);
1194                 if (ac == 0) {
1195                         format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
1196                         printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
1197                             SSH_AUTHSOCKET_ENV_NAME);
1198                         printf(format, SSH_AGENTPID_ENV_NAME, pidstrbuf,
1199                             SSH_AGENTPID_ENV_NAME);
1200                         printf("echo Agent pid %ld;\n", (long)pid);
1201                         exit(0);
1202                 }
1203                 if (setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1) == -1 ||
1204                     setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1) == -1) {
1205                         perror("setenv");
1206                         exit(1);
1207                 }
1208                 execvp(av[0], av);
1209                 perror(av[0]);
1210                 exit(1);
1211         }
1212         /* child */
1213         log_init(__progname, SYSLOG_LEVEL_INFO, SYSLOG_FACILITY_AUTH, 0);
1214
1215         if (setsid() == -1) {
1216                 error("setsid: %s", strerror(errno));
1217                 cleanup_exit(1);
1218         }
1219
1220         (void)chdir("/");
1221         if ((fd = open(_PATH_DEVNULL, O_RDWR, 0)) != -1) {
1222                 /* XXX might close listen socket */
1223                 (void)dup2(fd, STDIN_FILENO);
1224                 (void)dup2(fd, STDOUT_FILENO);
1225                 (void)dup2(fd, STDERR_FILENO);
1226                 if (fd > 2)
1227                         close(fd);
1228         }
1229
1230 #ifdef HAVE_SETRLIMIT
1231         /* deny core dumps, since memory contains unencrypted private keys */
1232         rlim.rlim_cur = rlim.rlim_max = 0;
1233         if (setrlimit(RLIMIT_CORE, &rlim) < 0) {
1234                 error("setrlimit RLIMIT_CORE: %s", strerror(errno));
1235                 cleanup_exit(1);
1236         }
1237 #endif
1238
1239 skip:
1240
1241         cleanup_pid = getpid();
1242
1243 #ifdef ENABLE_PKCS11
1244         pkcs11_init(0);
1245 #endif
1246         new_socket(AUTH_SOCKET, sock);
1247         if (ac > 0)
1248                 parent_alive_interval = 10;
1249         idtab_init();
1250         signal(SIGPIPE, SIG_IGN);
1251         signal(SIGINT, (d_flag | D_flag) ? cleanup_handler : SIG_IGN);
1252         signal(SIGHUP, cleanup_handler);
1253         signal(SIGTERM, cleanup_handler);
1254
1255         if (pledge("stdio rpath cpath unix id proc exec", NULL) == -1)
1256                 fatal("%s: pledge: %s", __progname, strerror(errno));
1257         platform_pledge_agent();
1258
1259         while (1) {
1260                 prepare_poll(&pfd, &npfd, &timeout);
1261                 result = poll(pfd, npfd, timeout);
1262                 saved_errno = errno;
1263                 if (parent_alive_interval != 0)
1264                         check_parent_exists();
1265                 (void) reaper();        /* remove expired keys */
1266                 if (result < 0) {
1267                         if (saved_errno == EINTR)
1268                                 continue;
1269                         fatal("poll: %s", strerror(saved_errno));
1270                 } else if (result > 0)
1271                         after_poll(pfd, npfd);
1272         }
1273         /* NOTREACHED */
1274 }