ssh-agent.c

   1 /*      $OpenBSD: ssh-agent.c,v 1.36 2000/09/15 07:13:49 deraadt Exp $  */
   2
   3 /*
   4  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   5  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   6  *                    All rights reserved
   7  * The authentication agent program.
   8  *
   9  * As far as I am concerned, the code I have written for this software
  10  * can be used freely for any purpose.  Any derived versions of this
  11  * software must be clearly marked as such, and if the derived work is
  12  * incompatible with the protocol description in the RFC file, it must be
  13  * called by a name other than "ssh" or "Secure Shell".
  14  *
  15  * SSH2 implementation,
  16  * Copyright (c) 2000 Markus Friedl. All rights reserved.
  17  *
  18  * Redistribution and use in source and binary forms, with or without
  19  * modification, are permitted provided that the following conditions
  20  * are met:
  21  * 1. Redistributions of source code must retain the above copyright
  22  *    notice, this list of conditions and the following disclaimer.
  23  * 2. Redistributions in binary form must reproduce the above copyright
  24  *    notice, this list of conditions and the following disclaimer in the
  25  *    documentation and/or other materials provided with the distribution.
  26  *
  27  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  28  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  29  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  30  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  31  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  32  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  33  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  34  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  35  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  36  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  37  */
  38
  39 #include "includes.h"
  40 RCSID("$OpenBSD: ssh-agent.c,v 1.36 2000/09/15 07:13:49 deraadt Exp $");
  41
  42 #include "ssh.h"
  43 #include "rsa.h"
  44 #include "buffer.h"
  45 #include "bufaux.h"
  46 #include "xmalloc.h"
  47 #include "packet.h"
  48 #include "getput.h"
  49 #include "mpaux.h"
  50
  51 #include <openssl/evp.h>
  52 #include <openssl/md5.h>
  53 #include <openssl/dsa.h>
  54 #include <openssl/rsa.h>
  55 #include "key.h"
  56 #include "authfd.h"
  57 #include "dsa.h"
  58 #include "kex.h"
  59
  60 typedef struct {
  61         int fd;
  62         enum {
  63                 AUTH_UNUSED, AUTH_SOCKET, AUTH_CONNECTION
  64         } type;
  65         Buffer input;
  66         Buffer output;
  67 } SocketEntry;
  68
  69 unsigned int sockets_alloc = 0;
  70 SocketEntry *sockets = NULL;
  71
  72 typedef struct {
  73         Key *key;
  74         char *comment;
  75 } Identity;
  76
  77 typedef struct {
  78         int nentries;
  79         Identity *identities;
  80 } Idtab;
  81
  82 /* private key table, one per protocol version */
  83 Idtab idtable[3];
  84
  85 int max_fd = 0;
  86
  87 /* pid of shell == parent of agent */
  88 pid_t parent_pid = -1;
  89
  90 /* pathname and directory for AUTH_SOCKET */
  91 char socket_name[1024];
  92 char socket_dir[1024];
  93
  94 #ifdef HAVE___PROGNAME
  95 extern char *__progname;
  96 #else /* HAVE___PROGNAME */
  97 static const char *__progname = "ssh-agent";
  98 #endif /* HAVE___PROGNAME */
  99
 100 void
 101 idtab_init(void)
 102 {
 103         int i;
 104         for (i = 0; i <=2; i++){
 105                 idtable[i].identities = NULL;
 106                 idtable[i].nentries = 0;
 107         }
 108 }
 109
 110 /* return private key table for requested protocol version */
 111 Idtab *
 112 idtab_lookup(int version)
 113 {
 114         if (version < 1 || version > 2)
 115                 fatal("internal error, bad protocol version %d", version);
 116         return &idtable[version];
 117 }
 118
 119 /* return matching private key for given public key */
 120 Key *
 121 lookup_private_key(Key *key, int *idx, int version)
 122 {
 123         int i;
 124         Idtab *tab = idtab_lookup(version);
 125         for (i = 0; i < tab->nentries; i++) {
 126                 if (key_equal(key, tab->identities[i].key)) {
 127                         if (idx != NULL)
 128                                 *idx = i;
 129                         return tab->identities[i].key;
 130                 }
 131         }
 132         return NULL;
 133 }
 134
 135 /* send list of supported public keys to 'client' */
 136 void
 137 process_request_identities(SocketEntry *e, int version)
 138 {
 139         Idtab *tab = idtab_lookup(version);
 140         Buffer msg;
 141         int i;
 142
 143         buffer_init(&msg);
 144         buffer_put_char(&msg, (version == 1) ?
 145             SSH_AGENT_RSA_IDENTITIES_ANSWER : SSH2_AGENT_IDENTITIES_ANSWER);
 146         buffer_put_int(&msg, tab->nentries);
 147         for (i = 0; i < tab->nentries; i++) {
 148                 Identity *id = &tab->identities[i];
 149                 if (id->key->type == KEY_RSA) {
 150                         buffer_put_int(&msg, BN_num_bits(id->key->rsa->n));
 151                         buffer_put_bignum(&msg, id->key->rsa->e);
 152                         buffer_put_bignum(&msg, id->key->rsa->n);
 153                 } else {
 154                         unsigned char *blob;
 155                         unsigned int blen;
 156                         dsa_make_key_blob(id->key, &blob, &blen);
 157                         buffer_put_string(&msg, blob, blen);
 158                         xfree(blob);
 159                 }
 160                 buffer_put_cstring(&msg, id->comment);
 161         }
 162         buffer_put_int(&e->output, buffer_len(&msg));
 163         buffer_append(&e->output, buffer_ptr(&msg), buffer_len(&msg));
 164         buffer_free(&msg);
 165 }
 166
 167 /* ssh1 only */
 168 void
 169 process_authentication_challenge1(SocketEntry *e)
 170 {
 171         Key *key, *private;
 172         BIGNUM *challenge;
 173         int i, len;
 174         Buffer msg;
 175         MD5_CTX md;
 176         unsigned char buf[32], mdbuf[16], session_id[16];
 177         unsigned int response_type;
 178
 179         buffer_init(&msg);
 180         key = key_new(KEY_RSA);
 181         challenge = BN_new();
 182
 183         buffer_get_int(&e->input);                              /* ignored */
 184         buffer_get_bignum(&e->input, key->rsa->e);
 185         buffer_get_bignum(&e->input, key->rsa->n);
 186         buffer_get_bignum(&e->input, challenge);
 187
 188         /* Only protocol 1.1 is supported */
 189         if (buffer_len(&e->input) == 0)
 190                 goto failure;
 191         buffer_get(&e->input, (char *) session_id, 16);
 192         response_type = buffer_get_int(&e->input);
 193         if (response_type != 1)
 194                 goto failure;
 195
 196         private = lookup_private_key(key, NULL, 1);
 197         if (private != NULL) {
 198                 /* Decrypt the challenge using the private key. */
 199                 rsa_private_decrypt(challenge, challenge, private->rsa);
 200
 201                 /* The response is MD5 of decrypted challenge plus session id. */
 202                 len = BN_num_bytes(challenge);
 203                 if (len <= 0 || len > 32) {
 204                         log("process_authentication_challenge: bad challenge length %d", len);
 205                         goto failure;
 206                 }
 207                 memset(buf, 0, 32);
 208                 BN_bn2bin(challenge, buf + 32 - len);
 209                 MD5_Init(&md);
 210                 MD5_Update(&md, buf, 32);
 211                 MD5_Update(&md, session_id, 16);
 212                 MD5_Final(mdbuf, &md);
 213
 214                 /* Send the response. */
 215                 buffer_put_char(&msg, SSH_AGENT_RSA_RESPONSE);
 216                 for (i = 0; i < 16; i++)
 217                         buffer_put_char(&msg, mdbuf[i]);
 218                 goto send;
 219         }
 220
 221 failure:
 222         /* Unknown identity or protocol error.  Send failure. */
 223         buffer_put_char(&msg, SSH_AGENT_FAILURE);
 224 send:
 225         buffer_put_int(&e->output, buffer_len(&msg));
 226         buffer_append(&e->output, buffer_ptr(&msg), buffer_len(&msg));
 227         key_free(key);
 228         BN_clear_free(challenge);
 229         buffer_free(&msg);
 230 }
 231
 232 /* ssh2 only */
 233 void
 234 process_sign_request2(SocketEntry *e)
 235 {
 236         extern int datafellows;
 237         Key *key, *private;
 238         unsigned char *blob, *data, *signature = NULL;
 239         unsigned int blen, dlen, slen = 0;
 240         Buffer msg;
 241         int ok = -1;
 242
 243         datafellows = 0;
 244
 245         blob = buffer_get_string(&e->input, &blen);
 246         data = buffer_get_string(&e->input, &dlen);
 247         buffer_get_int(&e->input);                      /* flags, unused */
 248
 249         key = dsa_key_from_blob(blob, blen);
 250         if (key != NULL) {
 251                 private = lookup_private_key(key, NULL, 2);
 252                 if (private != NULL)
 253                         ok = dsa_sign(private, &signature, &slen, data, dlen);
 254         }
 255         key_free(key);
 256         buffer_init(&msg);
 257         if (ok == 0) {
 258                 buffer_put_char(&msg, SSH2_AGENT_SIGN_RESPONSE);
 259                 buffer_put_string(&msg, signature, slen);
 260         } else {
 261                 buffer_put_char(&msg, SSH_AGENT_FAILURE);
 262         }
 263         buffer_put_int(&e->output, buffer_len(&msg));
 264         buffer_append(&e->output, buffer_ptr(&msg),
 265             buffer_len(&msg));
 266         buffer_free(&msg);
 267         xfree(data);
 268         xfree(blob);
 269         if (signature != NULL)
 270                 xfree(signature);
 271 }
 272
 273 /* shared */
 274 void
 275 process_remove_identity(SocketEntry *e, int version)
 276 {
 277         Key *key = NULL, *private;
 278         unsigned char *blob;
 279         unsigned int blen;
 280         unsigned int bits;
 281         int success = 0;
 282
 283         switch(version){
 284         case 1:
 285                 key = key_new(KEY_RSA);
 286                 bits = buffer_get_int(&e->input);
 287                 buffer_get_bignum(&e->input, key->rsa->e);
 288                 buffer_get_bignum(&e->input, key->rsa->n);
 289
 290                 if (bits != key_size(key))
 291                         log("Warning: identity keysize mismatch: actual %d, announced %d",
 292                               key_size(key), bits);
 293                 break;
 294         case 2:
 295                 blob = buffer_get_string(&e->input, &blen);
 296                 key = dsa_key_from_blob(blob, blen);
 297                 xfree(blob);
 298                 break;
 299         }
 300         if (key != NULL) {
 301                 int idx;
 302                 private = lookup_private_key(key, &idx, version);
 303                 if (private != NULL) {
 304                         /*
 305                          * We have this key.  Free the old key.  Since we
 306                          * don\'t want to leave empty slots in the middle of
 307                          * the array, we actually free the key there and copy
 308                          * data from the last entry.
 309                          */
 310                         Idtab *tab = idtab_lookup(version);
 311                         key_free(tab->identities[idx].key);
 312                         xfree(tab->identities[idx].comment);
 313                         if (idx != tab->nentries)
 314                                 tab->identities[idx] = tab->identities[tab->nentries];
 315                         tab->nentries--;
 316                         success = 1;
 317                 }
 318                 key_free(key);
 319         }
 320         buffer_put_int(&e->output, 1);
 321         buffer_put_char(&e->output,
 322             success ? SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE);
 323 }
 324
 325 void
 326 process_remove_all_identities(SocketEntry *e, int version)
 327 {
 328         unsigned int i;
 329         Idtab *tab = idtab_lookup(version);
 330
 331         /* Loop over all identities and clear the keys. */
 332         for (i = 0; i < tab->nentries; i++) {
 333                 key_free(tab->identities[i].key);
 334                 xfree(tab->identities[i].comment);
 335         }
 336
 337         /* Mark that there are no identities. */
 338         tab->nentries = 0;
 339
 340         /* Send success. */
 341         buffer_put_int(&e->output, 1);
 342         buffer_put_char(&e->output, SSH_AGENT_SUCCESS);
 343         return;
 344 }
 345
 346 void
 347 process_add_identity(SocketEntry *e, int version)
 348 {
 349         Key *k = NULL;
 350         RSA *rsa;
 351         BIGNUM *aux;
 352         BN_CTX *ctx;
 353         char *type;
 354         char *comment;
 355         int success = 0;
 356         Idtab *tab = idtab_lookup(version);
 357
 358         switch (version) {
 359         case 1:
 360                 k = key_new(KEY_RSA);
 361                 rsa = k->rsa;
 362
 363                 /* allocate mem for private key */
 364                 /* XXX rsa->n and rsa->e are already allocated */
 365                 rsa->d = BN_new();
 366                 rsa->iqmp = BN_new();
 367                 rsa->q = BN_new();
 368                 rsa->p = BN_new();
 369                 rsa->dmq1 = BN_new();
 370                 rsa->dmp1 = BN_new();
 371
 372                 buffer_get_int(&e->input);               /* ignored */
 373
 374                 buffer_get_bignum(&e->input, rsa->n);
 375                 buffer_get_bignum(&e->input, rsa->e);
 376                 buffer_get_bignum(&e->input, rsa->d);
 377                 buffer_get_bignum(&e->input, rsa->iqmp);
 378
 379                 /* SSH and SSL have p and q swapped */
 380                 buffer_get_bignum(&e->input, rsa->q);   /* p */
 381                 buffer_get_bignum(&e->input, rsa->p);   /* q */
 382
 383                 /* Generate additional parameters */
 384                 aux = BN_new();
 385                 ctx = BN_CTX_new();
 386
 387                 BN_sub(aux, rsa->q, BN_value_one());
 388                 BN_mod(rsa->dmq1, rsa->d, aux, ctx);
 389
 390                 BN_sub(aux, rsa->p, BN_value_one());
 391                 BN_mod(rsa->dmp1, rsa->d, aux, ctx);
 392
 393                 BN_clear_free(aux);
 394                 BN_CTX_free(ctx);
 395
 396                 break;
 397         case 2:
 398                 type = buffer_get_string(&e->input, NULL);
 399                 if (strcmp(type, KEX_DSS)) {
 400                         buffer_clear(&e->input);
 401                         xfree(type);
 402                         goto send;
 403                 }
 404                 xfree(type);
 405
 406                 k = key_new(KEY_DSA);
 407
 408                 /* allocate mem for private key */
 409                 k->dsa->priv_key = BN_new();
 410
 411                 buffer_get_bignum2(&e->input, k->dsa->p);
 412                 buffer_get_bignum2(&e->input, k->dsa->q);
 413                 buffer_get_bignum2(&e->input, k->dsa->g);
 414                 buffer_get_bignum2(&e->input, k->dsa->pub_key);
 415                 buffer_get_bignum2(&e->input, k->dsa->priv_key);
 416
 417                 break;
 418         }
 419
 420         comment = buffer_get_string(&e->input, NULL);
 421         if (k == NULL) {
 422                 xfree(comment);
 423                 goto send;
 424         }
 425         success = 1;
 426         if (lookup_private_key(k, NULL, version) == NULL) {
 427                 if (tab->nentries == 0)
 428                         tab->identities = xmalloc(sizeof(Identity));
 429                 else
 430                         tab->identities = xrealloc(tab->identities,
 431                             (tab->nentries + 1) * sizeof(Identity));
 432                 tab->identities[tab->nentries].key = k;
 433                 tab->identities[tab->nentries].comment = comment;
 434                 /* Increment the number of identities. */
 435                 tab->nentries++;
 436         } else {
 437                 key_free(k);
 438                 xfree(comment);
 439         }
 440 send:
 441         buffer_put_int(&e->output, 1);
 442         buffer_put_char(&e->output,
 443             success ? SSH_AGENT_SUCCESS : SSH_AGENT_FAILURE);
 444 }
 445
 446 /* dispatch incoming messages */
 447
 448 void
 449 process_message(SocketEntry *e)
 450 {
 451         unsigned int msg_len;
 452         unsigned int type;
 453         unsigned char *cp;
 454         if (buffer_len(&e->input) < 5)
 455                 return;         /* Incomplete message. */
 456         cp = (unsigned char *) buffer_ptr(&e->input);
 457         msg_len = GET_32BIT(cp);
 458         if (msg_len > 256 * 1024) {
 459                 shutdown(e->fd, SHUT_RDWR);
 460                 close(e->fd);
 461                 e->type = AUTH_UNUSED;
 462                 return;
 463         }
 464         if (buffer_len(&e->input) < msg_len + 4)
 465                 return;
 466         buffer_consume(&e->input, 4);
 467         type = buffer_get_char(&e->input);
 468
 469         switch (type) {
 470         /* ssh1 */
 471         case SSH_AGENTC_RSA_CHALLENGE:
 472                 process_authentication_challenge1(e);
 473                 break;
 474         case SSH_AGENTC_REQUEST_RSA_IDENTITIES:
 475                 process_request_identities(e, 1);
 476                 break;
 477         case SSH_AGENTC_ADD_RSA_IDENTITY:
 478                 process_add_identity(e, 1);
 479                 break;
 480         case SSH_AGENTC_REMOVE_RSA_IDENTITY:
 481                 process_remove_identity(e, 1);
 482                 break;
 483         case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES:
 484                 process_remove_all_identities(e, 1);
 485                 break;
 486         /* ssh2 */
 487         case SSH2_AGENTC_SIGN_REQUEST:
 488                 process_sign_request2(e);
 489                 break;
 490         case SSH2_AGENTC_REQUEST_IDENTITIES:
 491                 process_request_identities(e, 2);
 492                 break;
 493         case SSH2_AGENTC_ADD_IDENTITY:
 494                 process_add_identity(e, 2);
 495                 break;
 496         case SSH2_AGENTC_REMOVE_IDENTITY:
 497                 process_remove_identity(e, 2);
 498                 break;
 499         case SSH2_AGENTC_REMOVE_ALL_IDENTITIES:
 500                 process_remove_all_identities(e, 2);
 501                 break;
 502         default:
 503                 /* Unknown message.  Respond with failure. */
 504                 error("Unknown message %d", type);
 505                 buffer_clear(&e->input);
 506                 buffer_put_int(&e->output, 1);
 507                 buffer_put_char(&e->output, SSH_AGENT_FAILURE);
 508                 break;
 509         }
 510 }
 511
 512 void
 513 new_socket(int type, int fd)
 514 {
 515         unsigned int i, old_alloc;
 516         if (fcntl(fd, F_SETFL, O_NONBLOCK) < 0)
 517                 error("fcntl O_NONBLOCK: %s", strerror(errno));
 518
 519         if (fd > max_fd)
 520                 max_fd = fd;
 521
 522         for (i = 0; i < sockets_alloc; i++)
 523                 if (sockets[i].type == AUTH_UNUSED) {
 524                         sockets[i].fd = fd;
 525                         sockets[i].type = type;
 526                         buffer_init(&sockets[i].input);
 527                         buffer_init(&sockets[i].output);
 528                         return;
 529                 }
 530         old_alloc = sockets_alloc;
 531         sockets_alloc += 10;
 532         if (sockets)
 533                 sockets = xrealloc(sockets, sockets_alloc * sizeof(sockets[0]));
 534         else
 535                 sockets = xmalloc(sockets_alloc * sizeof(sockets[0]));
 536         for (i = old_alloc; i < sockets_alloc; i++)
 537                 sockets[i].type = AUTH_UNUSED;
 538         sockets[old_alloc].type = type;
 539         sockets[old_alloc].fd = fd;
 540         buffer_init(&sockets[old_alloc].input);
 541         buffer_init(&sockets[old_alloc].output);
 542 }
 543
 544 void
 545 prepare_select(fd_set *readset, fd_set *writeset)
 546 {
 547         unsigned int i;
 548         for (i = 0; i < sockets_alloc; i++)
 549                 switch (sockets[i].type) {
 550                 case AUTH_SOCKET:
 551                 case AUTH_CONNECTION:
 552                         FD_SET(sockets[i].fd, readset);
 553                         if (buffer_len(&sockets[i].output) > 0)
 554                                 FD_SET(sockets[i].fd, writeset);
 555                         break;
 556                 case AUTH_UNUSED:
 557                         break;
 558                 default:
 559                         fatal("Unknown socket type %d", sockets[i].type);
 560                         break;
 561                 }
 562 }
 563
 564 void
 565 after_select(fd_set *readset, fd_set *writeset)
 566 {
 567         unsigned int i;
 568         int len, sock;
 569         socklen_t slen;
 570         char buf[1024];
 571         struct sockaddr_un sunaddr;
 572
 573         for (i = 0; i < sockets_alloc; i++)
 574                 switch (sockets[i].type) {
 575                 case AUTH_UNUSED:
 576                         break;
 577                 case AUTH_SOCKET:
 578                         if (FD_ISSET(sockets[i].fd, readset)) {
 579                                 slen = sizeof(sunaddr);
 580                                 sock = accept(sockets[i].fd, (struct sockaddr *) & sunaddr, &slen);
 581                                 if (sock < 0) {
 582                                         perror("accept from AUTH_SOCKET");
 583                                         break;
 584                                 }
 585                                 new_socket(AUTH_CONNECTION, sock);
 586                         }
 587                         break;
 588                 case AUTH_CONNECTION:
 589                         if (buffer_len(&sockets[i].output) > 0 &&
 590                             FD_ISSET(sockets[i].fd, writeset)) {
 591                                 len = write(sockets[i].fd, buffer_ptr(&sockets[i].output),
 592                                          buffer_len(&sockets[i].output));
 593                                 if (len <= 0) {
 594                                         shutdown(sockets[i].fd, SHUT_RDWR);
 595                                         close(sockets[i].fd);
 596                                         sockets[i].type = AUTH_UNUSED;
 597                                         buffer_free(&sockets[i].input);
 598                                         buffer_free(&sockets[i].output);
 599                                         break;
 600                                 }
 601                                 buffer_consume(&sockets[i].output, len);
 602                         }
 603                         if (FD_ISSET(sockets[i].fd, readset)) {
 604                                 len = read(sockets[i].fd, buf, sizeof(buf));
 605                                 if (len <= 0) {
 606                                         shutdown(sockets[i].fd, SHUT_RDWR);
 607                                         close(sockets[i].fd);
 608                                         sockets[i].type = AUTH_UNUSED;
 609                                         buffer_free(&sockets[i].input);
 610                                         buffer_free(&sockets[i].output);
 611                                         break;
 612                                 }
 613                                 buffer_append(&sockets[i].input, buf, len);
 614                                 process_message(&sockets[i]);
 615                         }
 616                         break;
 617                 default:
 618                         fatal("Unknown type %d", sockets[i].type);
 619                 }
 620 }
 621
 622 void
 623 check_parent_exists(int sig)
 624 {
 625         if (parent_pid != -1 && kill(parent_pid, 0) < 0) {
 626                 /* printf("Parent has died - Authentication agent exiting.\n"); */
 627                 exit(1);
 628         }
 629         signal(SIGALRM, check_parent_exists);
 630         alarm(10);
 631 }
 632
 633 void
 634 cleanup_socket(void)
 635 {
 636         remove(socket_name);
 637         rmdir(socket_dir);
 638 }
 639
 640 void
 641 cleanup_exit(int i)
 642 {
 643         cleanup_socket();
 644         exit(i);
 645 }
 646
 647 void
 648 usage()
 649 {
 650         fprintf(stderr, "ssh-agent version %s\n", SSH_VERSION);
 651         fprintf(stderr, "Usage: %s [-c | -s] [-k] [command {args...]]\n",
 652                 __progname);
 653         exit(1);
 654 }
 655
 656 int
 657 main(int ac, char **av)
 658 {
 659         fd_set readset, writeset;
 660         int sock, c_flag = 0, k_flag = 0, s_flag = 0, ch;
 661         struct sockaddr_un sunaddr;
 662         pid_t pid;
 663         char *shell, *format, *pidstr, pidstrbuf[1 + 3 * sizeof pid];
 664         extern int optind;
 665
 666         init_rng();
 667
 668         /* check if RSA support exists */
 669         if (rsa_alive() == 0) {
 670                 fprintf(stderr,
 671                         "%s: no RSA support in libssl and libcrypto.  See ssl(8).\n",
 672                         __progname);
 673                 exit(1);
 674         }
 675 #ifdef __GNU_LIBRARY__
 676         while ((ch = getopt(ac, av, "+cks")) != -1) {
 677 #else /* __GNU_LIBRARY__ */
 678         while ((ch = getopt(ac, av, "cks")) != -1) {
 679 #endif /* __GNU_LIBRARY__ */
 680                 switch (ch) {
 681                 case 'c':
 682                         if (s_flag)
 683                                 usage();
 684                         c_flag++;
 685                         break;
 686                 case 'k':
 687                         k_flag++;
 688                         break;
 689                 case 's':
 690                         if (c_flag)
 691                                 usage();
 692                         s_flag++;
 693                         break;
 694                 default:
 695                         usage();
 696                 }
 697         }
 698         ac -= optind;
 699         av += optind;
 700
 701         if (ac > 0 && (c_flag || k_flag || s_flag))
 702                 usage();
 703
 704         if (ac == 0 && !c_flag && !k_flag && !s_flag) {
 705                 shell = getenv("SHELL");
 706                 if (shell != NULL && strncmp(shell + strlen(shell) - 3, "csh", 3) == 0)
 707                         c_flag = 1;
 708         }
 709         if (k_flag) {
 710                 pidstr = getenv(SSH_AGENTPID_ENV_NAME);
 711                 if (pidstr == NULL) {
 712                         fprintf(stderr, "%s not set, cannot kill agent\n",
 713                                 SSH_AGENTPID_ENV_NAME);
 714                         exit(1);
 715                 }
 716                 pid = atoi(pidstr);
 717                 if (pid < 1) {  /* XXX PID_MAX check too */
 718                 /* Yes, PID_MAX check please */
 719                         fprintf(stderr, "%s=\"%s\", which is not a good PID\n",
 720                                 SSH_AGENTPID_ENV_NAME, pidstr);
 721                         exit(1);
 722                 }
 723                 if (kill(pid, SIGTERM) == -1) {
 724                         perror("kill");
 725                         exit(1);
 726                 }
 727                 format = c_flag ? "unsetenv %s;\n" : "unset %s;\n";
 728                 printf(format, SSH_AUTHSOCKET_ENV_NAME);
 729                 printf(format, SSH_AGENTPID_ENV_NAME);
 730                 printf("echo Agent pid %d killed;\n", pid);
 731                 exit(0);
 732         }
 733         parent_pid = getpid();
 734
 735         /* Create private directory for agent socket */
 736         strlcpy(socket_dir, "/tmp/ssh-XXXXXXXX", sizeof socket_dir);
 737         if (mkdtemp(socket_dir) == NULL) {
 738                 perror("mkdtemp: private socket dir");
 739                 exit(1);
 740         }
 741         snprintf(socket_name, sizeof socket_name, "%s/agent.%d", socket_dir,
 742                  parent_pid);
 743
 744         /*
 745          * Create socket early so it will exist before command gets run from
 746          * the parent.
 747          */
 748         sock = socket(AF_UNIX, SOCK_STREAM, 0);
 749         if (sock < 0) {
 750                 perror("socket");
 751                 cleanup_exit(1);
 752         }
 753         memset(&sunaddr, 0, sizeof(sunaddr));
 754         sunaddr.sun_family = AF_UNIX;
 755         strlcpy(sunaddr.sun_path, socket_name, sizeof(sunaddr.sun_path));
 756         if (bind(sock, (struct sockaddr *) & sunaddr, sizeof(sunaddr)) < 0) {
 757                 perror("bind");
 758                 cleanup_exit(1);
 759         }
 760         if (listen(sock, 5) < 0) {
 761                 perror("listen");
 762                 cleanup_exit(1);
 763         }
 764         /*
 765          * Fork, and have the parent execute the command, if any, or present
 766          * the socket data.  The child continues as the authentication agent.
 767          */
 768         pid = fork();
 769         if (pid == -1) {
 770                 perror("fork");
 771                 exit(1);
 772         }
 773         if (pid != 0) {         /* Parent - execute the given command. */
 774                 close(sock);
 775                 snprintf(pidstrbuf, sizeof pidstrbuf, "%d", pid);
 776                 if (ac == 0) {
 777                         format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n";
 778                         printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name,
 779                                SSH_AUTHSOCKET_ENV_NAME);
 780                         printf(format, SSH_AGENTPID_ENV_NAME, pidstrbuf,
 781                                SSH_AGENTPID_ENV_NAME);
 782                         printf("echo Agent pid %d;\n", pid);
 783                         exit(0);
 784                 }
 785                 if (setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1) == -1 ||
 786                     setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1) == -1) {
 787                         perror("setenv");
 788                         exit(1);
 789                 }
 790                 execvp(av[0], av);
 791                 perror(av[0]);
 792                 exit(1);
 793         }
 794         close(0);
 795         close(1);
 796         close(2);
 797
 798         if (setsid() == -1) {
 799                 perror("setsid");
 800                 cleanup_exit(1);
 801         }
 802         if (atexit(cleanup_socket) < 0) {
 803                 perror("atexit");
 804                 cleanup_exit(1);
 805         }
 806         new_socket(AUTH_SOCKET, sock);
 807         if (ac > 0) {
 808                 signal(SIGALRM, check_parent_exists);
 809                 alarm(10);
 810         }
 811         idtab_init();
 812         signal(SIGINT, SIG_IGN);
 813         signal(SIGPIPE, SIG_IGN);
 814         signal(SIGHUP, cleanup_exit);
 815         signal(SIGTERM, cleanup_exit);
 816         while (1) {
 817                 FD_ZERO(&readset);
 818                 FD_ZERO(&writeset);
 819                 prepare_select(&readset, &writeset);
 820                 if (select(max_fd + 1, &readset, &writeset, NULL, NULL) < 0) {
 821                         if (errno == EINTR)
 822                                 continue;
 823                         exit(1);
 824                 }
 825                 after_select(&readset, &writeset);
 826         }
 827         /* NOTREACHED */
 828 }