1 /* $OpenBSD: ssh-agent.c,v 1.26 2000/03/16 20:56:14 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 * $FreeBSD$ 11 */ 12 13 #include "includes.h" 14 RCSID("$OpenBSD: ssh-agent.c,v 1.26 2000/03/16 20:56:14 markus Exp $"); 15 16 #include "ssh.h" 17 #include "rsa.h" 18 #include "authfd.h" 19 #include "buffer.h" 20 #include "bufaux.h" 21 #include "xmalloc.h" 22 #include "packet.h" 23 #include "getput.h" 24 #include "mpaux.h" 25 26 #include <openssl/md5.h> 27 28 typedef struct { 29 int fd; 30 enum { 31 AUTH_UNUSED, AUTH_SOCKET, AUTH_CONNECTION 32 } type; 33 Buffer input; 34 Buffer output; 35 } SocketEntry; 36 37 unsigned int sockets_alloc = 0; 38 SocketEntry *sockets = NULL; 39 40 typedef struct { 41 RSA *key; 42 char *comment; 43 } Identity; 44 45 unsigned int num_identities = 0; 46 Identity *identities = NULL; 47 48 int max_fd = 0; 49 50 /* pid of shell == parent of agent */ 51 int parent_pid = -1; 52 53 /* pathname and directory for AUTH_SOCKET */ 54 char socket_name[1024]; 55 char socket_dir[1024]; 56 57 extern char *__progname; 58 59 void 60 process_request_identity(SocketEntry *e) 61 { 62 Buffer msg; 63 int i; 64 65 buffer_init(&msg); 66 buffer_put_char(&msg, SSH_AGENT_RSA_IDENTITIES_ANSWER); 67 buffer_put_int(&msg, num_identities); 68 for (i = 0; i < num_identities; i++) { 69 buffer_put_int(&msg, BN_num_bits(identities[i].key->n)); 70 buffer_put_bignum(&msg, identities[i].key->e); 71 buffer_put_bignum(&msg, identities[i].key->n); 72 buffer_put_string(&msg, identities[i].comment, 73 strlen(identities[i].comment)); 74 } 75 buffer_put_int(&e->output, buffer_len(&msg)); 76 buffer_append(&e->output, buffer_ptr(&msg), buffer_len(&msg)); 77 buffer_free(&msg); 78 } 79 80 void 81 process_authentication_challenge(SocketEntry *e) 82 { 83 int i, pub_bits, len; 84 BIGNUM *pub_e, *pub_n, *challenge; 85 Buffer msg; 86 MD5_CTX md; 87 unsigned char buf[32], mdbuf[16], session_id[16]; 88 unsigned int response_type; 89 90 buffer_init(&msg); 91 pub_e = BN_new(); 92 pub_n = BN_new(); 93 challenge = BN_new(); 94 pub_bits = buffer_get_int(&e->input); 95 buffer_get_bignum(&e->input, pub_e); 96 buffer_get_bignum(&e->input, pub_n); 97 buffer_get_bignum(&e->input, challenge); 98 if (buffer_len(&e->input) == 0) { 99 /* Compatibility code for old servers. */ 100 memset(session_id, 0, 16); 101 response_type = 0; 102 } else { 103 /* New code. */ 104 buffer_get(&e->input, (char *) session_id, 16); 105 response_type = buffer_get_int(&e->input); 106 } 107 for (i = 0; i < num_identities; i++) 108 if (pub_bits == BN_num_bits(identities[i].key->n) && 109 BN_cmp(pub_e, identities[i].key->e) == 0 && 110 BN_cmp(pub_n, identities[i].key->n) == 0) { 111 /* Decrypt the challenge using the private key. */ 112 rsa_private_decrypt(challenge, challenge, identities[i].key); 113 114 /* Compute the desired response. */ 115 switch (response_type) { 116 case 0:/* As of protocol 1.0 */ 117 /* This response type is no longer supported. */ 118 log("Compatibility with ssh protocol 1.0 no longer supported."); 119 buffer_put_char(&msg, SSH_AGENT_FAILURE); 120 goto send; 121 122 case 1:/* As of protocol 1.1 */ 123 /* The response is MD5 of decrypted challenge plus session id. */ 124 len = BN_num_bytes(challenge); 125 126 if (len <= 0 || len > 32) { 127 fatal("process_authentication_challenge: " 128 "bad challenge length %d", len); 129 } 130 memset(buf, 0, 32); 131 BN_bn2bin(challenge, buf + 32 - len); 132 MD5_Init(&md); 133 MD5_Update(&md, buf, 32); 134 MD5_Update(&md, session_id, 16); 135 MD5_Final(mdbuf, &md); 136 break; 137 138 default: 139 fatal("process_authentication_challenge: bad response_type %d", 140 response_type); 141 break; 142 } 143 144 /* Send the response. */ 145 buffer_put_char(&msg, SSH_AGENT_RSA_RESPONSE); 146 for (i = 0; i < 16; i++) 147 buffer_put_char(&msg, mdbuf[i]); 148 149 goto send; 150 } 151 /* Unknown identity. Send failure. */ 152 buffer_put_char(&msg, SSH_AGENT_FAILURE); 153 send: 154 buffer_put_int(&e->output, buffer_len(&msg)); 155 buffer_append(&e->output, buffer_ptr(&msg), 156 buffer_len(&msg)); 157 buffer_free(&msg); 158 BN_clear_free(pub_e); 159 BN_clear_free(pub_n); 160 BN_clear_free(challenge); 161 } 162 163 void 164 process_remove_identity(SocketEntry *e) 165 { 166 unsigned int bits; 167 unsigned int i; 168 BIGNUM *dummy, *n; 169 170 dummy = BN_new(); 171 n = BN_new(); 172 173 /* Get the key from the packet. */ 174 bits = buffer_get_int(&e->input); 175 buffer_get_bignum(&e->input, dummy); 176 buffer_get_bignum(&e->input, n); 177 178 if (bits != BN_num_bits(n)) 179 error("Warning: identity keysize mismatch: actual %d, announced %d", 180 BN_num_bits(n), bits); 181 182 /* Check if we have the key. */ 183 for (i = 0; i < num_identities; i++) 184 if (BN_cmp(identities[i].key->n, n) == 0) { 185 /* 186 * We have this key. Free the old key. Since we 187 * don\'t want to leave empty slots in the middle of 188 * the array, we actually free the key there and copy 189 * data from the last entry. 190 */ 191 RSA_free(identities[i].key); 192 xfree(identities[i].comment); 193 if (i < num_identities - 1) 194 identities[i] = identities[num_identities - 1]; 195 num_identities--; 196 BN_clear_free(dummy); 197 BN_clear_free(n); 198 199 /* Send success. */ 200 buffer_put_int(&e->output, 1); 201 buffer_put_char(&e->output, SSH_AGENT_SUCCESS); 202 return; 203 } 204 /* We did not have the key. */ 205 BN_clear(dummy); 206 BN_clear(n); 207 208 /* Send failure. */ 209 buffer_put_int(&e->output, 1); 210 buffer_put_char(&e->output, SSH_AGENT_FAILURE); 211 } 212 213 /* 214 * Removes all identities from the agent. 215 */ 216 void 217 process_remove_all_identities(SocketEntry *e) 218 { 219 unsigned int i; 220 221 /* Loop over all identities and clear the keys. */ 222 for (i = 0; i < num_identities; i++) { 223 RSA_free(identities[i].key); 224 xfree(identities[i].comment); 225 } 226 227 /* Mark that there are no identities. */ 228 num_identities = 0; 229 230 /* Send success. */ 231 buffer_put_int(&e->output, 1); 232 buffer_put_char(&e->output, SSH_AGENT_SUCCESS); 233 return; 234 } 235 236 /* 237 * Adds an identity to the agent. 238 */ 239 void 240 process_add_identity(SocketEntry *e) 241 { 242 RSA *k; 243 int i; 244 BIGNUM *aux; 245 BN_CTX *ctx; 246 247 if (num_identities == 0) 248 identities = xmalloc(sizeof(Identity)); 249 else 250 identities = xrealloc(identities, (num_identities + 1) * sizeof(Identity)); 251 252 identities[num_identities].key = RSA_new(); 253 k = identities[num_identities].key; 254 buffer_get_int(&e->input); /* bits */ 255 k->n = BN_new(); 256 buffer_get_bignum(&e->input, k->n); 257 k->e = BN_new(); 258 buffer_get_bignum(&e->input, k->e); 259 k->d = BN_new(); 260 buffer_get_bignum(&e->input, k->d); 261 k->iqmp = BN_new(); 262 buffer_get_bignum(&e->input, k->iqmp); 263 /* SSH and SSL have p and q swapped */ 264 k->q = BN_new(); 265 buffer_get_bignum(&e->input, k->q); /* p */ 266 k->p = BN_new(); 267 buffer_get_bignum(&e->input, k->p); /* q */ 268 269 /* Generate additional parameters */ 270 aux = BN_new(); 271 ctx = BN_CTX_new(); 272 273 BN_sub(aux, k->q, BN_value_one()); 274 k->dmq1 = BN_new(); 275 BN_mod(k->dmq1, k->d, aux, ctx); 276 277 BN_sub(aux, k->p, BN_value_one()); 278 k->dmp1 = BN_new(); 279 BN_mod(k->dmp1, k->d, aux, ctx); 280 281 BN_clear_free(aux); 282 BN_CTX_free(ctx); 283 284 identities[num_identities].comment = buffer_get_string(&e->input, NULL); 285 286 /* Check if we already have the key. */ 287 for (i = 0; i < num_identities; i++) 288 if (BN_cmp(identities[i].key->n, k->n) == 0) { 289 /* 290 * We already have this key. Clear and free the new 291 * data and return success. 292 */ 293 RSA_free(k); 294 xfree(identities[num_identities].comment); 295 296 /* Send success. */ 297 buffer_put_int(&e->output, 1); 298 buffer_put_char(&e->output, SSH_AGENT_SUCCESS); 299 return; 300 } 301 /* Increment the number of identities. */ 302 num_identities++; 303 304 /* Send a success message. */ 305 buffer_put_int(&e->output, 1); 306 buffer_put_char(&e->output, SSH_AGENT_SUCCESS); 307 } 308 309 void 310 process_message(SocketEntry *e) 311 { 312 unsigned int msg_len; 313 unsigned int type; 314 unsigned char *cp; 315 if (buffer_len(&e->input) < 5) 316 return; /* Incomplete message. */ 317 cp = (unsigned char *) buffer_ptr(&e->input); 318 msg_len = GET_32BIT(cp); 319 if (msg_len > 256 * 1024) { 320 shutdown(e->fd, SHUT_RDWR); 321 close(e->fd); 322 e->type = AUTH_UNUSED; 323 return; 324 } 325 if (buffer_len(&e->input) < msg_len + 4) 326 return; 327 buffer_consume(&e->input, 4); 328 type = buffer_get_char(&e->input); 329 330 switch (type) { 331 case SSH_AGENTC_REQUEST_RSA_IDENTITIES: 332 process_request_identity(e); 333 break; 334 case SSH_AGENTC_RSA_CHALLENGE: 335 process_authentication_challenge(e); 336 break; 337 case SSH_AGENTC_ADD_RSA_IDENTITY: 338 process_add_identity(e); 339 break; 340 case SSH_AGENTC_REMOVE_RSA_IDENTITY: 341 process_remove_identity(e); 342 break; 343 case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES: 344 process_remove_all_identities(e); 345 break; 346 default: 347 /* Unknown message. Respond with failure. */ 348 error("Unknown message %d", type); 349 buffer_clear(&e->input); 350 buffer_put_int(&e->output, 1); 351 buffer_put_char(&e->output, SSH_AGENT_FAILURE); 352 break; 353 } 354 } 355 356 void 357 new_socket(int type, int fd) 358 { 359 unsigned int i, old_alloc; 360 if (fcntl(fd, F_SETFL, O_NONBLOCK) < 0) 361 error("fcntl O_NONBLOCK: %s", strerror(errno)); 362 363 if (fd > max_fd) 364 max_fd = fd; 365 366 for (i = 0; i < sockets_alloc; i++) 367 if (sockets[i].type == AUTH_UNUSED) { 368 sockets[i].fd = fd; 369 sockets[i].type = type; 370 buffer_init(&sockets[i].input); 371 buffer_init(&sockets[i].output); 372 return; 373 } 374 old_alloc = sockets_alloc; 375 sockets_alloc += 10; 376 if (sockets) 377 sockets = xrealloc(sockets, sockets_alloc * sizeof(sockets[0])); 378 else 379 sockets = xmalloc(sockets_alloc * sizeof(sockets[0])); 380 for (i = old_alloc; i < sockets_alloc; i++) 381 sockets[i].type = AUTH_UNUSED; 382 sockets[old_alloc].type = type; 383 sockets[old_alloc].fd = fd; 384 buffer_init(&sockets[old_alloc].input); 385 buffer_init(&sockets[old_alloc].output); 386 } 387 388 void 389 prepare_select(fd_set *readset, fd_set *writeset) 390 { 391 unsigned int i; 392 for (i = 0; i < sockets_alloc; i++) 393 switch (sockets[i].type) { 394 case AUTH_SOCKET: 395 case AUTH_CONNECTION: 396 FD_SET(sockets[i].fd, readset); 397 if (buffer_len(&sockets[i].output) > 0) 398 FD_SET(sockets[i].fd, writeset); 399 break; 400 case AUTH_UNUSED: 401 break; 402 default: 403 fatal("Unknown socket type %d", sockets[i].type); 404 break; 405 } 406 } 407 408 void 409 after_select(fd_set *readset, fd_set *writeset) 410 { 411 unsigned int i; 412 int len, sock; 413 socklen_t slen; 414 char buf[1024]; 415 struct sockaddr_un sunaddr; 416 417 for (i = 0; i < sockets_alloc; i++) 418 switch (sockets[i].type) { 419 case AUTH_UNUSED: 420 break; 421 case AUTH_SOCKET: 422 if (FD_ISSET(sockets[i].fd, readset)) { 423 slen = sizeof(sunaddr); 424 sock = accept(sockets[i].fd, (struct sockaddr *) & sunaddr, &slen); 425 if (sock < 0) { 426 perror("accept from AUTH_SOCKET"); 427 break; 428 } 429 new_socket(AUTH_CONNECTION, sock); 430 } 431 break; 432 case AUTH_CONNECTION: 433 if (buffer_len(&sockets[i].output) > 0 && 434 FD_ISSET(sockets[i].fd, writeset)) { 435 len = write(sockets[i].fd, buffer_ptr(&sockets[i].output), 436 buffer_len(&sockets[i].output)); 437 if (len <= 0) { 438 shutdown(sockets[i].fd, SHUT_RDWR); 439 close(sockets[i].fd); 440 sockets[i].type = AUTH_UNUSED; 441 break; 442 } 443 buffer_consume(&sockets[i].output, len); 444 } 445 if (FD_ISSET(sockets[i].fd, readset)) { 446 len = read(sockets[i].fd, buf, sizeof(buf)); 447 if (len <= 0) { 448 shutdown(sockets[i].fd, SHUT_RDWR); 449 close(sockets[i].fd); 450 sockets[i].type = AUTH_UNUSED; 451 break; 452 } 453 buffer_append(&sockets[i].input, buf, len); 454 process_message(&sockets[i]); 455 } 456 break; 457 default: 458 fatal("Unknown type %d", sockets[i].type); 459 } 460 } 461 462 void 463 check_parent_exists(int sig) 464 { 465 if (kill(parent_pid, 0) < 0) { 466 /* printf("Parent has died - Authentication agent exiting.\n"); */ 467 exit(1); 468 } 469 signal(SIGALRM, check_parent_exists); 470 alarm(10); 471 } 472 473 void 474 cleanup_socket(void) 475 { 476 remove(socket_name); 477 rmdir(socket_dir); 478 } 479 480 void 481 cleanup_exit(int i) 482 { 483 cleanup_socket(); 484 exit(i); 485 } 486 487 void 488 usage() 489 { 490 fprintf(stderr, "ssh-agent version %s\n", SSH_VERSION); 491 fprintf(stderr, "Usage: %s [-c | -s] [-k] [command {args...]]\n", 492 __progname); 493 exit(1); 494 } 495 496 int 497 main(int ac, char **av) 498 { 499 fd_set readset, writeset; 500 int sock, c_flag = 0, k_flag = 0, s_flag = 0, ch; 501 struct sockaddr_un sunaddr; 502 pid_t pid; 503 char *shell, *format, *pidstr, pidstrbuf[1 + 3 * sizeof pid]; 504 505 /* check if RSA support exists */ 506 if (rsa_alive() == 0) { 507 fprintf(stderr, 508 "%s: no RSA support in libssl and libcrypto. See ssl(8).\n", 509 __progname); 510 exit(1); 511 } 512 while ((ch = getopt(ac, av, "cks")) != -1) { 513 switch (ch) { 514 case 'c': 515 if (s_flag) 516 usage(); 517 c_flag++; 518 break; 519 case 'k': 520 k_flag++; 521 break; 522 case 's': 523 if (c_flag) 524 usage(); 525 s_flag++; 526 break; 527 default: 528 usage(); 529 } 530 } 531 ac -= optind; 532 av += optind; 533 534 if (ac > 0 && (c_flag || k_flag || s_flag)) 535 usage(); 536 537 if (ac == 0 && !c_flag && !k_flag && !s_flag) { 538 shell = getenv("SHELL"); 539 if (shell != NULL && strncmp(shell + strlen(shell) - 3, "csh", 3) == 0) 540 c_flag = 1; 541 } 542 if (k_flag) { 543 pidstr = getenv(SSH_AGENTPID_ENV_NAME); 544 if (pidstr == NULL) { 545 fprintf(stderr, "%s not set, cannot kill agent\n", 546 SSH_AGENTPID_ENV_NAME); 547 exit(1); 548 } 549 pid = atoi(pidstr); 550 if (pid < 1) { /* XXX PID_MAX check too */ 551 fprintf(stderr, "%s=\"%s\", which is not a good PID\n", 552 SSH_AGENTPID_ENV_NAME, pidstr); 553 exit(1); 554 } 555 if (kill(pid, SIGTERM) == -1) { 556 perror("kill"); 557 exit(1); 558 } 559 format = c_flag ? "unsetenv %s;\n" : "unset %s;\n"; 560 printf(format, SSH_AUTHSOCKET_ENV_NAME); 561 printf(format, SSH_AGENTPID_ENV_NAME); 562 printf("echo Agent pid %d killed;\n", pid); 563 exit(0); 564 } 565 parent_pid = getpid(); 566 567 /* Create private directory for agent socket */ 568 strlcpy(socket_dir, "/tmp/ssh-XXXXXXXX", sizeof socket_dir); 569 if (mkdtemp(socket_dir) == NULL) { 570 perror("mkdtemp: private socket dir"); 571 exit(1); 572 } 573 snprintf(socket_name, sizeof socket_name, "%s/agent.%d", socket_dir, 574 parent_pid); 575 576 /* 577 * Create socket early so it will exist before command gets run from 578 * the parent. 579 */ 580 sock = socket(AF_UNIX, SOCK_STREAM, 0); 581 if (sock < 0) { 582 perror("socket"); 583 cleanup_exit(1); 584 } 585 memset(&sunaddr, 0, sizeof(sunaddr)); 586 sunaddr.sun_family = AF_UNIX; 587 strlcpy(sunaddr.sun_path, socket_name, sizeof(sunaddr.sun_path)); 588 if (bind(sock, (struct sockaddr *) & sunaddr, sizeof(sunaddr)) < 0) { 589 perror("bind"); 590 cleanup_exit(1); 591 } 592 if (listen(sock, 5) < 0) { 593 perror("listen"); 594 cleanup_exit(1); 595 } 596 /* 597 * Fork, and have the parent execute the command, if any, or present 598 * the socket data. The child continues as the authentication agent. 599 */ 600 pid = fork(); 601 if (pid == -1) { 602 perror("fork"); 603 exit(1); 604 } 605 if (pid != 0) { /* Parent - execute the given command. */ 606 close(sock); 607 snprintf(pidstrbuf, sizeof pidstrbuf, "%d", pid); 608 if (ac == 0) { 609 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n"; 610 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name, 611 SSH_AUTHSOCKET_ENV_NAME); 612 printf(format, SSH_AGENTPID_ENV_NAME, pidstrbuf, 613 SSH_AGENTPID_ENV_NAME); 614 printf("echo Agent pid %d;\n", pid); 615 exit(0); 616 } 617 setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1); 618 setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1); 619 execvp(av[0], av); 620 perror(av[0]); 621 exit(1); 622 } 623 close(0); 624 close(1); 625 close(2); 626 627 if (setsid() == -1) { 628 perror("setsid"); 629 cleanup_exit(1); 630 } 631 if (atexit(cleanup_socket) < 0) { 632 perror("atexit"); 633 cleanup_exit(1); 634 } 635 new_socket(AUTH_SOCKET, sock); 636 if (ac > 0) { 637 signal(SIGALRM, check_parent_exists); 638 alarm(10); 639 } 640 signal(SIGINT, SIG_IGN); 641 signal(SIGPIPE, SIG_IGN); 642 signal(SIGHUP, cleanup_exit); 643 signal(SIGTERM, cleanup_exit); 644 while (1) { 645 FD_ZERO(&readset); 646 FD_ZERO(&writeset); 647 prepare_select(&readset, &writeset); 648 if (select(max_fd + 1, &readset, &writeset, NULL, NULL) < 0) { 649 if (errno == EINTR) 650 continue; 651 exit(1); 652 } 653 after_select(&readset, &writeset); 654 } 655 /* NOTREACHED */ 656 } 657