1 /* $OpenBSD: ssh-agent.c,v 1.25 2000/01/02 21:51:03 markus 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 * Created: Wed Mar 29 03:46:59 1995 ylo 8 * The authentication agent program. 9 */ 10 11 #include "includes.h" 12 RCSID("$OpenBSD: ssh-agent.c,v 1.25 2000/01/02 21:51:03 markus Exp $"); 13 14 #include "ssh.h" 15 #include "rsa.h" 16 #include "authfd.h" 17 #include "buffer.h" 18 #include "bufaux.h" 19 #include "xmalloc.h" 20 #include "packet.h" 21 #include "getput.h" 22 #include "mpaux.h" 23 24 #include <ssl/md5.h> 25 26 typedef struct { 27 int fd; 28 enum { 29 AUTH_UNUSED, AUTH_SOCKET, AUTH_CONNECTION 30 } type; 31 Buffer input; 32 Buffer output; 33 } SocketEntry; 34 35 unsigned int sockets_alloc = 0; 36 SocketEntry *sockets = NULL; 37 38 typedef struct { 39 RSA *key; 40 char *comment; 41 } Identity; 42 43 unsigned int num_identities = 0; 44 Identity *identities = NULL; 45 46 int max_fd = 0; 47 48 /* pid of shell == parent of agent */ 49 int parent_pid = -1; 50 51 /* pathname and directory for AUTH_SOCKET */ 52 char socket_name[1024]; 53 char socket_dir[1024]; 54 55 extern char *__progname; 56 57 void 58 process_request_identity(SocketEntry *e) 59 { 60 Buffer msg; 61 int i; 62 63 buffer_init(&msg); 64 buffer_put_char(&msg, SSH_AGENT_RSA_IDENTITIES_ANSWER); 65 buffer_put_int(&msg, num_identities); 66 for (i = 0; i < num_identities; i++) { 67 buffer_put_int(&msg, BN_num_bits(identities[i].key->n)); 68 buffer_put_bignum(&msg, identities[i].key->e); 69 buffer_put_bignum(&msg, identities[i].key->n); 70 buffer_put_string(&msg, identities[i].comment, 71 strlen(identities[i].comment)); 72 } 73 buffer_put_int(&e->output, buffer_len(&msg)); 74 buffer_append(&e->output, buffer_ptr(&msg), buffer_len(&msg)); 75 buffer_free(&msg); 76 } 77 78 void 79 process_authentication_challenge(SocketEntry *e) 80 { 81 int i, pub_bits, len; 82 BIGNUM *pub_e, *pub_n, *challenge; 83 Buffer msg; 84 MD5_CTX md; 85 unsigned char buf[32], mdbuf[16], session_id[16]; 86 unsigned int response_type; 87 88 buffer_init(&msg); 89 pub_e = BN_new(); 90 pub_n = BN_new(); 91 challenge = BN_new(); 92 pub_bits = buffer_get_int(&e->input); 93 buffer_get_bignum(&e->input, pub_e); 94 buffer_get_bignum(&e->input, pub_n); 95 buffer_get_bignum(&e->input, challenge); 96 if (buffer_len(&e->input) == 0) { 97 /* Compatibility code for old servers. */ 98 memset(session_id, 0, 16); 99 response_type = 0; 100 } else { 101 /* New code. */ 102 buffer_get(&e->input, (char *) session_id, 16); 103 response_type = buffer_get_int(&e->input); 104 } 105 for (i = 0; i < num_identities; i++) 106 if (pub_bits == BN_num_bits(identities[i].key->n) && 107 BN_cmp(pub_e, identities[i].key->e) == 0 && 108 BN_cmp(pub_n, identities[i].key->n) == 0) { 109 /* Decrypt the challenge using the private key. */ 110 rsa_private_decrypt(challenge, challenge, identities[i].key); 111 112 /* Compute the desired response. */ 113 switch (response_type) { 114 case 0:/* As of protocol 1.0 */ 115 /* This response type is no longer supported. */ 116 log("Compatibility with ssh protocol 1.0 no longer supported."); 117 buffer_put_char(&msg, SSH_AGENT_FAILURE); 118 goto send; 119 120 case 1:/* As of protocol 1.1 */ 121 /* The response is MD5 of decrypted challenge plus session id. */ 122 len = BN_num_bytes(challenge); 123 124 if (len <= 0 || len > 32) { 125 fatal("process_authentication_challenge: " 126 "bad challenge length %d", len); 127 } 128 memset(buf, 0, 32); 129 BN_bn2bin(challenge, buf + 32 - len); 130 MD5_Init(&md); 131 MD5_Update(&md, buf, 32); 132 MD5_Update(&md, session_id, 16); 133 MD5_Final(mdbuf, &md); 134 break; 135 136 default: 137 fatal("process_authentication_challenge: bad response_type %d", 138 response_type); 139 break; 140 } 141 142 /* Send the response. */ 143 buffer_put_char(&msg, SSH_AGENT_RSA_RESPONSE); 144 for (i = 0; i < 16; i++) 145 buffer_put_char(&msg, mdbuf[i]); 146 147 goto send; 148 } 149 /* Unknown identity. Send failure. */ 150 buffer_put_char(&msg, SSH_AGENT_FAILURE); 151 send: 152 buffer_put_int(&e->output, buffer_len(&msg)); 153 buffer_append(&e->output, buffer_ptr(&msg), 154 buffer_len(&msg)); 155 buffer_free(&msg); 156 BN_clear_free(pub_e); 157 BN_clear_free(pub_n); 158 BN_clear_free(challenge); 159 } 160 161 void 162 process_remove_identity(SocketEntry *e) 163 { 164 unsigned int bits; 165 unsigned int i; 166 BIGNUM *dummy, *n; 167 168 dummy = BN_new(); 169 n = BN_new(); 170 171 /* Get the key from the packet. */ 172 bits = buffer_get_int(&e->input); 173 buffer_get_bignum(&e->input, dummy); 174 buffer_get_bignum(&e->input, n); 175 176 if (bits != BN_num_bits(n)) 177 error("Warning: identity keysize mismatch: actual %d, announced %d", 178 BN_num_bits(n), bits); 179 180 /* Check if we have the key. */ 181 for (i = 0; i < num_identities; i++) 182 if (BN_cmp(identities[i].key->n, n) == 0) { 183 /* 184 * We have this key. Free the old key. Since we 185 * don\'t want to leave empty slots in the middle of 186 * the array, we actually free the key there and copy 187 * data from the last entry. 188 */ 189 RSA_free(identities[i].key); 190 xfree(identities[i].comment); 191 if (i < num_identities - 1) 192 identities[i] = identities[num_identities - 1]; 193 num_identities--; 194 BN_clear_free(dummy); 195 BN_clear_free(n); 196 197 /* Send success. */ 198 buffer_put_int(&e->output, 1); 199 buffer_put_char(&e->output, SSH_AGENT_SUCCESS); 200 return; 201 } 202 /* We did not have the key. */ 203 BN_clear(dummy); 204 BN_clear(n); 205 206 /* Send failure. */ 207 buffer_put_int(&e->output, 1); 208 buffer_put_char(&e->output, SSH_AGENT_FAILURE); 209 } 210 211 /* 212 * Removes all identities from the agent. 213 */ 214 void 215 process_remove_all_identities(SocketEntry *e) 216 { 217 unsigned int i; 218 219 /* Loop over all identities and clear the keys. */ 220 for (i = 0; i < num_identities; i++) { 221 RSA_free(identities[i].key); 222 xfree(identities[i].comment); 223 } 224 225 /* Mark that there are no identities. */ 226 num_identities = 0; 227 228 /* Send success. */ 229 buffer_put_int(&e->output, 1); 230 buffer_put_char(&e->output, SSH_AGENT_SUCCESS); 231 return; 232 } 233 234 /* 235 * Adds an identity to the agent. 236 */ 237 void 238 process_add_identity(SocketEntry *e) 239 { 240 RSA *k; 241 int i; 242 BIGNUM *aux; 243 BN_CTX *ctx; 244 245 if (num_identities == 0) 246 identities = xmalloc(sizeof(Identity)); 247 else 248 identities = xrealloc(identities, (num_identities + 1) * sizeof(Identity)); 249 250 identities[num_identities].key = RSA_new(); 251 k = identities[num_identities].key; 252 buffer_get_int(&e->input); /* bits */ 253 k->n = BN_new(); 254 buffer_get_bignum(&e->input, k->n); 255 k->e = BN_new(); 256 buffer_get_bignum(&e->input, k->e); 257 k->d = BN_new(); 258 buffer_get_bignum(&e->input, k->d); 259 k->iqmp = BN_new(); 260 buffer_get_bignum(&e->input, k->iqmp); 261 /* SSH and SSL have p and q swapped */ 262 k->q = BN_new(); 263 buffer_get_bignum(&e->input, k->q); /* p */ 264 k->p = BN_new(); 265 buffer_get_bignum(&e->input, k->p); /* q */ 266 267 /* Generate additional parameters */ 268 aux = BN_new(); 269 ctx = BN_CTX_new(); 270 271 BN_sub(aux, k->q, BN_value_one()); 272 k->dmq1 = BN_new(); 273 BN_mod(k->dmq1, k->d, aux, ctx); 274 275 BN_sub(aux, k->p, BN_value_one()); 276 k->dmp1 = BN_new(); 277 BN_mod(k->dmp1, k->d, aux, ctx); 278 279 BN_clear_free(aux); 280 BN_CTX_free(ctx); 281 282 identities[num_identities].comment = buffer_get_string(&e->input, NULL); 283 284 /* Check if we already have the key. */ 285 for (i = 0; i < num_identities; i++) 286 if (BN_cmp(identities[i].key->n, k->n) == 0) { 287 /* 288 * We already have this key. Clear and free the new 289 * data and return success. 290 */ 291 RSA_free(k); 292 xfree(identities[num_identities].comment); 293 294 /* Send success. */ 295 buffer_put_int(&e->output, 1); 296 buffer_put_char(&e->output, SSH_AGENT_SUCCESS); 297 return; 298 } 299 /* Increment the number of identities. */ 300 num_identities++; 301 302 /* Send a success message. */ 303 buffer_put_int(&e->output, 1); 304 buffer_put_char(&e->output, SSH_AGENT_SUCCESS); 305 } 306 307 void 308 process_message(SocketEntry *e) 309 { 310 unsigned int msg_len; 311 unsigned int type; 312 unsigned char *cp; 313 if (buffer_len(&e->input) < 5) 314 return; /* Incomplete message. */ 315 cp = (unsigned char *) buffer_ptr(&e->input); 316 msg_len = GET_32BIT(cp); 317 if (msg_len > 256 * 1024) { 318 shutdown(e->fd, SHUT_RDWR); 319 close(e->fd); 320 e->type = AUTH_UNUSED; 321 return; 322 } 323 if (buffer_len(&e->input) < msg_len + 4) 324 return; 325 buffer_consume(&e->input, 4); 326 type = buffer_get_char(&e->input); 327 328 switch (type) { 329 case SSH_AGENTC_REQUEST_RSA_IDENTITIES: 330 process_request_identity(e); 331 break; 332 case SSH_AGENTC_RSA_CHALLENGE: 333 process_authentication_challenge(e); 334 break; 335 case SSH_AGENTC_ADD_RSA_IDENTITY: 336 process_add_identity(e); 337 break; 338 case SSH_AGENTC_REMOVE_RSA_IDENTITY: 339 process_remove_identity(e); 340 break; 341 case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES: 342 process_remove_all_identities(e); 343 break; 344 default: 345 /* Unknown message. Respond with failure. */ 346 error("Unknown message %d", type); 347 buffer_clear(&e->input); 348 buffer_put_int(&e->output, 1); 349 buffer_put_char(&e->output, SSH_AGENT_FAILURE); 350 break; 351 } 352 } 353 354 void 355 new_socket(int type, int fd) 356 { 357 unsigned int i, old_alloc; 358 if (fcntl(fd, F_SETFL, O_NONBLOCK) < 0) 359 error("fcntl O_NONBLOCK: %s", strerror(errno)); 360 361 if (fd > max_fd) 362 max_fd = fd; 363 364 for (i = 0; i < sockets_alloc; i++) 365 if (sockets[i].type == AUTH_UNUSED) { 366 sockets[i].fd = fd; 367 sockets[i].type = type; 368 buffer_init(&sockets[i].input); 369 buffer_init(&sockets[i].output); 370 return; 371 } 372 old_alloc = sockets_alloc; 373 sockets_alloc += 10; 374 if (sockets) 375 sockets = xrealloc(sockets, sockets_alloc * sizeof(sockets[0])); 376 else 377 sockets = xmalloc(sockets_alloc * sizeof(sockets[0])); 378 for (i = old_alloc; i < sockets_alloc; i++) 379 sockets[i].type = AUTH_UNUSED; 380 sockets[old_alloc].type = type; 381 sockets[old_alloc].fd = fd; 382 buffer_init(&sockets[old_alloc].input); 383 buffer_init(&sockets[old_alloc].output); 384 } 385 386 void 387 prepare_select(fd_set *readset, fd_set *writeset) 388 { 389 unsigned int i; 390 for (i = 0; i < sockets_alloc; i++) 391 switch (sockets[i].type) { 392 case AUTH_SOCKET: 393 case AUTH_CONNECTION: 394 FD_SET(sockets[i].fd, readset); 395 if (buffer_len(&sockets[i].output) > 0) 396 FD_SET(sockets[i].fd, writeset); 397 break; 398 case AUTH_UNUSED: 399 break; 400 default: 401 fatal("Unknown socket type %d", sockets[i].type); 402 break; 403 } 404 } 405 406 void 407 after_select(fd_set *readset, fd_set *writeset) 408 { 409 unsigned int i; 410 int len, sock; 411 char buf[1024]; 412 struct sockaddr_un sunaddr; 413 414 for (i = 0; i < sockets_alloc; i++) 415 switch (sockets[i].type) { 416 case AUTH_UNUSED: 417 break; 418 case AUTH_SOCKET: 419 if (FD_ISSET(sockets[i].fd, readset)) { 420 len = sizeof(sunaddr); 421 sock = accept(sockets[i].fd, (struct sockaddr *) & sunaddr, &len); 422 if (sock < 0) { 423 perror("accept from AUTH_SOCKET"); 424 break; 425 } 426 new_socket(AUTH_CONNECTION, sock); 427 } 428 break; 429 case AUTH_CONNECTION: 430 if (buffer_len(&sockets[i].output) > 0 && 431 FD_ISSET(sockets[i].fd, writeset)) { 432 len = write(sockets[i].fd, buffer_ptr(&sockets[i].output), 433 buffer_len(&sockets[i].output)); 434 if (len <= 0) { 435 shutdown(sockets[i].fd, SHUT_RDWR); 436 close(sockets[i].fd); 437 sockets[i].type = AUTH_UNUSED; 438 break; 439 } 440 buffer_consume(&sockets[i].output, len); 441 } 442 if (FD_ISSET(sockets[i].fd, readset)) { 443 len = read(sockets[i].fd, buf, sizeof(buf)); 444 if (len <= 0) { 445 shutdown(sockets[i].fd, SHUT_RDWR); 446 close(sockets[i].fd); 447 sockets[i].type = AUTH_UNUSED; 448 break; 449 } 450 buffer_append(&sockets[i].input, buf, len); 451 process_message(&sockets[i]); 452 } 453 break; 454 default: 455 fatal("Unknown type %d", sockets[i].type); 456 } 457 } 458 459 void 460 check_parent_exists(int sig) 461 { 462 if (kill(parent_pid, 0) < 0) { 463 /* printf("Parent has died - Authentication agent exiting.\n"); */ 464 exit(1); 465 } 466 signal(SIGALRM, check_parent_exists); 467 alarm(10); 468 } 469 470 void 471 cleanup_socket(void) 472 { 473 remove(socket_name); 474 rmdir(socket_dir); 475 } 476 477 void 478 cleanup_exit(int i) 479 { 480 cleanup_socket(); 481 exit(i); 482 } 483 484 void 485 usage() 486 { 487 fprintf(stderr, "ssh-agent version %s\n", SSH_VERSION); 488 fprintf(stderr, "Usage: %s [-c | -s] [-k] [command {args...]]\n", 489 __progname); 490 exit(1); 491 } 492 493 int 494 main(int ac, char **av) 495 { 496 fd_set readset, writeset; 497 int sock, c_flag = 0, k_flag = 0, s_flag = 0, ch; 498 struct sockaddr_un sunaddr; 499 pid_t pid; 500 char *shell, *format, *pidstr, pidstrbuf[1 + 3 * sizeof pid]; 501 502 /* check if RSA support exists */ 503 if (rsa_alive() == 0) { 504 fprintf(stderr, 505 "%s: no RSA support in libssl and libcrypto. See ssl(8).\n", 506 __progname); 507 exit(1); 508 } 509 while ((ch = getopt(ac, av, "cks")) != -1) { 510 switch (ch) { 511 case 'c': 512 if (s_flag) 513 usage(); 514 c_flag++; 515 break; 516 case 'k': 517 k_flag++; 518 break; 519 case 's': 520 if (c_flag) 521 usage(); 522 s_flag++; 523 break; 524 default: 525 usage(); 526 } 527 } 528 ac -= optind; 529 av += optind; 530 531 if (ac > 0 && (c_flag || k_flag || s_flag)) 532 usage(); 533 534 if (ac == 0 && !c_flag && !k_flag && !s_flag) { 535 shell = getenv("SHELL"); 536 if (shell != NULL && strncmp(shell + strlen(shell) - 3, "csh", 3) == 0) 537 c_flag = 1; 538 } 539 if (k_flag) { 540 pidstr = getenv(SSH_AGENTPID_ENV_NAME); 541 if (pidstr == NULL) { 542 fprintf(stderr, "%s not set, cannot kill agent\n", 543 SSH_AGENTPID_ENV_NAME); 544 exit(1); 545 } 546 pid = atoi(pidstr); 547 if (pid < 1) { /* XXX PID_MAX check too */ 548 fprintf(stderr, "%s=\"%s\", which is not a good PID\n", 549 SSH_AGENTPID_ENV_NAME, pidstr); 550 exit(1); 551 } 552 if (kill(pid, SIGTERM) == -1) { 553 perror("kill"); 554 exit(1); 555 } 556 format = c_flag ? "unsetenv %s;\n" : "unset %s;\n"; 557 printf(format, SSH_AUTHSOCKET_ENV_NAME); 558 printf(format, SSH_AGENTPID_ENV_NAME); 559 printf("echo Agent pid %d killed;\n", pid); 560 exit(0); 561 } 562 parent_pid = getpid(); 563 564 /* Create private directory for agent socket */ 565 strlcpy(socket_dir, "/tmp/ssh-XXXXXXXX", sizeof socket_dir); 566 if (mkdtemp(socket_dir) == NULL) { 567 perror("mkdtemp: private socket dir"); 568 exit(1); 569 } 570 snprintf(socket_name, sizeof socket_name, "%s/agent.%d", socket_dir, 571 parent_pid); 572 573 /* 574 * Create socket early so it will exist before command gets run from 575 * the parent. 576 */ 577 sock = socket(AF_UNIX, SOCK_STREAM, 0); 578 if (sock < 0) { 579 perror("socket"); 580 cleanup_exit(1); 581 } 582 memset(&sunaddr, 0, sizeof(sunaddr)); 583 sunaddr.sun_family = AF_UNIX; 584 strlcpy(sunaddr.sun_path, socket_name, sizeof(sunaddr.sun_path)); 585 if (bind(sock, (struct sockaddr *) & sunaddr, sizeof(sunaddr)) < 0) { 586 perror("bind"); 587 cleanup_exit(1); 588 } 589 if (listen(sock, 5) < 0) { 590 perror("listen"); 591 cleanup_exit(1); 592 } 593 /* 594 * Fork, and have the parent execute the command, if any, or present 595 * the socket data. The child continues as the authentication agent. 596 */ 597 pid = fork(); 598 if (pid == -1) { 599 perror("fork"); 600 exit(1); 601 } 602 if (pid != 0) { /* Parent - execute the given command. */ 603 close(sock); 604 snprintf(pidstrbuf, sizeof pidstrbuf, "%d", pid); 605 if (ac == 0) { 606 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n"; 607 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name, 608 SSH_AUTHSOCKET_ENV_NAME); 609 printf(format, SSH_AGENTPID_ENV_NAME, pidstrbuf, 610 SSH_AGENTPID_ENV_NAME); 611 printf("echo Agent pid %d;\n", pid); 612 exit(0); 613 } 614 setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1); 615 setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1); 616 execvp(av[0], av); 617 perror(av[0]); 618 exit(1); 619 } 620 close(0); 621 close(1); 622 close(2); 623 624 if (setsid() == -1) { 625 perror("setsid"); 626 cleanup_exit(1); 627 } 628 if (atexit(cleanup_socket) < 0) { 629 perror("atexit"); 630 cleanup_exit(1); 631 } 632 new_socket(AUTH_SOCKET, sock); 633 if (ac > 0) { 634 signal(SIGALRM, check_parent_exists); 635 alarm(10); 636 } 637 signal(SIGINT, SIG_IGN); 638 signal(SIGPIPE, SIG_IGN); 639 signal(SIGHUP, cleanup_exit); 640 signal(SIGTERM, cleanup_exit); 641 while (1) { 642 FD_ZERO(&readset); 643 FD_ZERO(&writeset); 644 prepare_select(&readset, &writeset); 645 if (select(max_fd + 1, &readset, &writeset, NULL, NULL) < 0) { 646 if (errno == EINTR) 647 continue; 648 exit(1); 649 } 650 after_select(&readset, &writeset); 651 } 652 /* NOTREACHED */ 653 } 654