1 /* $FreeBSD$ */ 2 /* $OpenBSD: ssh-agent.c,v 1.31 2000/04/29 18:11:52 markus Exp $ */ 3 4 /* 5 * Author: Tatu Ylonen <ylo@cs.hut.fi> 6 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 7 * All rights reserved 8 * Created: Wed Mar 29 03:46:59 1995 ylo 9 * The authentication agent program. 10 */ 11 12 #include "includes.h" 13 RCSID("$OpenBSD: ssh-agent.c,v 1.31 2000/04/29 18:11:52 markus Exp $"); 14 15 #include "ssh.h" 16 #include "rsa.h" 17 #include "authfd.h" 18 #include "buffer.h" 19 #include "bufaux.h" 20 #include "xmalloc.h" 21 #include "packet.h" 22 #include "getput.h" 23 #include "mpaux.h" 24 25 #include <openssl/md5.h> 26 27 typedef struct { 28 int fd; 29 enum { 30 AUTH_UNUSED, AUTH_SOCKET, AUTH_CONNECTION 31 } type; 32 Buffer input; 33 Buffer output; 34 } SocketEntry; 35 36 unsigned int sockets_alloc = 0; 37 SocketEntry *sockets = NULL; 38 39 typedef struct { 40 RSA *key; 41 char *comment; 42 } Identity; 43 44 unsigned int num_identities = 0; 45 Identity *identities = NULL; 46 47 int max_fd = 0; 48 49 /* pid of shell == parent of agent */ 50 pid_t parent_pid = -1; 51 52 /* pathname and directory for AUTH_SOCKET */ 53 char socket_name[1024]; 54 char socket_dir[1024]; 55 56 extern char *__progname; 57 58 void 59 process_request_identity(SocketEntry *e) 60 { 61 Buffer msg; 62 int i; 63 64 buffer_init(&msg); 65 buffer_put_char(&msg, SSH_AGENT_RSA_IDENTITIES_ANSWER); 66 buffer_put_int(&msg, num_identities); 67 for (i = 0; i < num_identities; i++) { 68 buffer_put_int(&msg, BN_num_bits(identities[i].key->n)); 69 buffer_put_bignum(&msg, identities[i].key->e); 70 buffer_put_bignum(&msg, identities[i].key->n); 71 buffer_put_string(&msg, identities[i].comment, 72 strlen(identities[i].comment)); 73 } 74 buffer_put_int(&e->output, buffer_len(&msg)); 75 buffer_append(&e->output, buffer_ptr(&msg), buffer_len(&msg)); 76 buffer_free(&msg); 77 } 78 79 void 80 process_authentication_challenge(SocketEntry *e) 81 { 82 int i, pub_bits, len; 83 BIGNUM *pub_e, *pub_n, *challenge; 84 Buffer msg; 85 MD5_CTX md; 86 unsigned char buf[32], mdbuf[16], session_id[16]; 87 unsigned int response_type; 88 89 buffer_init(&msg); 90 pub_e = BN_new(); 91 pub_n = BN_new(); 92 challenge = BN_new(); 93 pub_bits = buffer_get_int(&e->input); 94 buffer_get_bignum(&e->input, pub_e); 95 buffer_get_bignum(&e->input, pub_n); 96 buffer_get_bignum(&e->input, challenge); 97 if (buffer_len(&e->input) == 0) { 98 /* Compatibility code for old servers. */ 99 memset(session_id, 0, 16); 100 response_type = 0; 101 } else { 102 /* New code. */ 103 buffer_get(&e->input, (char *) session_id, 16); 104 response_type = buffer_get_int(&e->input); 105 } 106 for (i = 0; i < num_identities; i++) 107 if (pub_bits == BN_num_bits(identities[i].key->n) && 108 BN_cmp(pub_e, identities[i].key->e) == 0 && 109 BN_cmp(pub_n, identities[i].key->n) == 0) { 110 /* Decrypt the challenge using the private key. */ 111 rsa_private_decrypt(challenge, challenge, identities[i].key); 112 113 /* Compute the desired response. */ 114 switch (response_type) { 115 case 0:/* As of protocol 1.0 */ 116 /* This response type is no longer supported. */ 117 log("Compatibility with ssh protocol 1.0 no longer supported."); 118 buffer_put_char(&msg, SSH_AGENT_FAILURE); 119 goto send; 120 121 case 1:/* As of protocol 1.1 */ 122 /* The response is MD5 of decrypted challenge plus session id. */ 123 len = BN_num_bytes(challenge); 124 125 if (len <= 0 || len > 32) { 126 fatal("process_authentication_challenge: " 127 "bad challenge length %d", len); 128 } 129 memset(buf, 0, 32); 130 BN_bn2bin(challenge, buf + 32 - len); 131 MD5_Init(&md); 132 MD5_Update(&md, buf, 32); 133 MD5_Update(&md, session_id, 16); 134 MD5_Final(mdbuf, &md); 135 break; 136 137 default: 138 fatal("process_authentication_challenge: bad response_type %d", 139 response_type); 140 break; 141 } 142 143 /* Send the response. */ 144 buffer_put_char(&msg, SSH_AGENT_RSA_RESPONSE); 145 for (i = 0; i < 16; i++) 146 buffer_put_char(&msg, mdbuf[i]); 147 148 goto send; 149 } 150 /* Unknown identity. Send failure. */ 151 buffer_put_char(&msg, SSH_AGENT_FAILURE); 152 send: 153 buffer_put_int(&e->output, buffer_len(&msg)); 154 buffer_append(&e->output, buffer_ptr(&msg), 155 buffer_len(&msg)); 156 buffer_free(&msg); 157 BN_clear_free(pub_e); 158 BN_clear_free(pub_n); 159 BN_clear_free(challenge); 160 } 161 162 void 163 process_remove_identity(SocketEntry *e) 164 { 165 unsigned int bits; 166 unsigned int i; 167 BIGNUM *dummy, *n; 168 169 dummy = BN_new(); 170 n = BN_new(); 171 172 /* Get the key from the packet. */ 173 bits = buffer_get_int(&e->input); 174 buffer_get_bignum(&e->input, dummy); 175 buffer_get_bignum(&e->input, n); 176 177 if (bits != BN_num_bits(n)) 178 log("Warning: identity keysize mismatch: actual %d, announced %d", 179 BN_num_bits(n), bits); 180 181 /* Check if we have the key. */ 182 for (i = 0; i < num_identities; i++) 183 if (BN_cmp(identities[i].key->n, n) == 0) { 184 /* 185 * We have this key. Free the old key. Since we 186 * don\'t want to leave empty slots in the middle of 187 * the array, we actually free the key there and copy 188 * data from the last entry. 189 */ 190 RSA_free(identities[i].key); 191 xfree(identities[i].comment); 192 if (i < num_identities - 1) 193 identities[i] = identities[num_identities - 1]; 194 num_identities--; 195 BN_clear_free(dummy); 196 BN_clear_free(n); 197 198 /* Send success. */ 199 buffer_put_int(&e->output, 1); 200 buffer_put_char(&e->output, SSH_AGENT_SUCCESS); 201 return; 202 } 203 /* We did not have the key. */ 204 BN_clear(dummy); 205 BN_clear(n); 206 207 /* Send failure. */ 208 buffer_put_int(&e->output, 1); 209 buffer_put_char(&e->output, SSH_AGENT_FAILURE); 210 } 211 212 /* 213 * Removes all identities from the agent. 214 */ 215 void 216 process_remove_all_identities(SocketEntry *e) 217 { 218 unsigned int i; 219 220 /* Loop over all identities and clear the keys. */ 221 for (i = 0; i < num_identities; i++) { 222 RSA_free(identities[i].key); 223 xfree(identities[i].comment); 224 } 225 226 /* Mark that there are no identities. */ 227 num_identities = 0; 228 229 /* Send success. */ 230 buffer_put_int(&e->output, 1); 231 buffer_put_char(&e->output, SSH_AGENT_SUCCESS); 232 return; 233 } 234 235 /* 236 * Adds an identity to the agent. 237 */ 238 void 239 process_add_identity(SocketEntry *e) 240 { 241 RSA *k; 242 int i; 243 BIGNUM *aux; 244 BN_CTX *ctx; 245 246 if (num_identities == 0) 247 identities = xmalloc(sizeof(Identity)); 248 else 249 identities = xrealloc(identities, (num_identities + 1) * sizeof(Identity)); 250 251 identities[num_identities].key = RSA_new(); 252 k = identities[num_identities].key; 253 buffer_get_int(&e->input); /* bits */ 254 k->n = BN_new(); 255 buffer_get_bignum(&e->input, k->n); 256 k->e = BN_new(); 257 buffer_get_bignum(&e->input, k->e); 258 k->d = BN_new(); 259 buffer_get_bignum(&e->input, k->d); 260 k->iqmp = BN_new(); 261 buffer_get_bignum(&e->input, k->iqmp); 262 /* SSH and SSL have p and q swapped */ 263 k->q = BN_new(); 264 buffer_get_bignum(&e->input, k->q); /* p */ 265 k->p = BN_new(); 266 buffer_get_bignum(&e->input, k->p); /* q */ 267 268 /* Generate additional parameters */ 269 aux = BN_new(); 270 ctx = BN_CTX_new(); 271 272 BN_sub(aux, k->q, BN_value_one()); 273 k->dmq1 = BN_new(); 274 BN_mod(k->dmq1, k->d, aux, ctx); 275 276 BN_sub(aux, k->p, BN_value_one()); 277 k->dmp1 = BN_new(); 278 BN_mod(k->dmp1, k->d, aux, ctx); 279 280 BN_clear_free(aux); 281 BN_CTX_free(ctx); 282 283 identities[num_identities].comment = buffer_get_string(&e->input, NULL); 284 285 /* Check if we already have the key. */ 286 for (i = 0; i < num_identities; i++) 287 if (BN_cmp(identities[i].key->n, k->n) == 0) { 288 /* 289 * We already have this key. Clear and free the new 290 * data and return success. 291 */ 292 RSA_free(k); 293 xfree(identities[num_identities].comment); 294 295 /* Send success. */ 296 buffer_put_int(&e->output, 1); 297 buffer_put_char(&e->output, SSH_AGENT_SUCCESS); 298 return; 299 } 300 /* Increment the number of identities. */ 301 num_identities++; 302 303 /* Send a success message. */ 304 buffer_put_int(&e->output, 1); 305 buffer_put_char(&e->output, SSH_AGENT_SUCCESS); 306 } 307 308 void 309 process_message(SocketEntry *e) 310 { 311 unsigned int msg_len; 312 unsigned int type; 313 unsigned char *cp; 314 if (buffer_len(&e->input) < 5) 315 return; /* Incomplete message. */ 316 cp = (unsigned char *) buffer_ptr(&e->input); 317 msg_len = GET_32BIT(cp); 318 if (msg_len > 256 * 1024) { 319 shutdown(e->fd, SHUT_RDWR); 320 close(e->fd); 321 e->type = AUTH_UNUSED; 322 return; 323 } 324 if (buffer_len(&e->input) < msg_len + 4) 325 return; 326 buffer_consume(&e->input, 4); 327 type = buffer_get_char(&e->input); 328 329 switch (type) { 330 case SSH_AGENTC_REQUEST_RSA_IDENTITIES: 331 process_request_identity(e); 332 break; 333 case SSH_AGENTC_RSA_CHALLENGE: 334 process_authentication_challenge(e); 335 break; 336 case SSH_AGENTC_ADD_RSA_IDENTITY: 337 process_add_identity(e); 338 break; 339 case SSH_AGENTC_REMOVE_RSA_IDENTITY: 340 process_remove_identity(e); 341 break; 342 case SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES: 343 process_remove_all_identities(e); 344 break; 345 default: 346 /* Unknown message. Respond with failure. */ 347 error("Unknown message %d", type); 348 buffer_clear(&e->input); 349 buffer_put_int(&e->output, 1); 350 buffer_put_char(&e->output, SSH_AGENT_FAILURE); 351 break; 352 } 353 } 354 355 void 356 new_socket(int type, int fd) 357 { 358 unsigned int i, old_alloc; 359 if (fcntl(fd, F_SETFL, O_NONBLOCK) < 0) 360 error("fcntl O_NONBLOCK: %s", strerror(errno)); 361 362 if (fd > max_fd) 363 max_fd = fd; 364 365 for (i = 0; i < sockets_alloc; i++) 366 if (sockets[i].type == AUTH_UNUSED) { 367 sockets[i].fd = fd; 368 sockets[i].type = type; 369 buffer_init(&sockets[i].input); 370 buffer_init(&sockets[i].output); 371 return; 372 } 373 old_alloc = sockets_alloc; 374 sockets_alloc += 10; 375 if (sockets) 376 sockets = xrealloc(sockets, sockets_alloc * sizeof(sockets[0])); 377 else 378 sockets = xmalloc(sockets_alloc * sizeof(sockets[0])); 379 for (i = old_alloc; i < sockets_alloc; i++) 380 sockets[i].type = AUTH_UNUSED; 381 sockets[old_alloc].type = type; 382 sockets[old_alloc].fd = fd; 383 buffer_init(&sockets[old_alloc].input); 384 buffer_init(&sockets[old_alloc].output); 385 } 386 387 void 388 prepare_select(fd_set *readset, fd_set *writeset) 389 { 390 unsigned int i; 391 for (i = 0; i < sockets_alloc; i++) 392 switch (sockets[i].type) { 393 case AUTH_SOCKET: 394 case AUTH_CONNECTION: 395 FD_SET(sockets[i].fd, readset); 396 if (buffer_len(&sockets[i].output) > 0) 397 FD_SET(sockets[i].fd, writeset); 398 break; 399 case AUTH_UNUSED: 400 break; 401 default: 402 fatal("Unknown socket type %d", sockets[i].type); 403 break; 404 } 405 } 406 407 void 408 after_select(fd_set *readset, fd_set *writeset) 409 { 410 unsigned int i; 411 int len, sock; 412 socklen_t slen; 413 char buf[1024]; 414 struct sockaddr_un sunaddr; 415 416 for (i = 0; i < sockets_alloc; i++) 417 switch (sockets[i].type) { 418 case AUTH_UNUSED: 419 break; 420 case AUTH_SOCKET: 421 if (FD_ISSET(sockets[i].fd, readset)) { 422 slen = sizeof(sunaddr); 423 sock = accept(sockets[i].fd, (struct sockaddr *) & sunaddr, &slen); 424 if (sock < 0) { 425 perror("accept from AUTH_SOCKET"); 426 break; 427 } 428 new_socket(AUTH_CONNECTION, sock); 429 } 430 break; 431 case AUTH_CONNECTION: 432 if (buffer_len(&sockets[i].output) > 0 && 433 FD_ISSET(sockets[i].fd, writeset)) { 434 len = write(sockets[i].fd, buffer_ptr(&sockets[i].output), 435 buffer_len(&sockets[i].output)); 436 if (len <= 0) { 437 shutdown(sockets[i].fd, SHUT_RDWR); 438 close(sockets[i].fd); 439 sockets[i].type = AUTH_UNUSED; 440 buffer_free(&sockets[i].input); 441 buffer_free(&sockets[i].output); 442 break; 443 } 444 buffer_consume(&sockets[i].output, len); 445 } 446 if (FD_ISSET(sockets[i].fd, readset)) { 447 len = read(sockets[i].fd, buf, sizeof(buf)); 448 if (len <= 0) { 449 shutdown(sockets[i].fd, SHUT_RDWR); 450 close(sockets[i].fd); 451 sockets[i].type = AUTH_UNUSED; 452 buffer_free(&sockets[i].input); 453 buffer_free(&sockets[i].output); 454 break; 455 } 456 buffer_append(&sockets[i].input, buf, len); 457 process_message(&sockets[i]); 458 } 459 break; 460 default: 461 fatal("Unknown type %d", sockets[i].type); 462 } 463 } 464 465 void 466 check_parent_exists(int sig) 467 { 468 if (parent_pid != -1 && kill(parent_pid, 0) < 0) { 469 /* printf("Parent has died - Authentication agent exiting.\n"); */ 470 exit(1); 471 } 472 signal(SIGALRM, check_parent_exists); 473 alarm(10); 474 } 475 476 void 477 cleanup_socket(void) 478 { 479 remove(socket_name); 480 rmdir(socket_dir); 481 } 482 483 void 484 cleanup_exit(int i) 485 { 486 cleanup_socket(); 487 exit(i); 488 } 489 490 void 491 usage() 492 { 493 fprintf(stderr, "ssh-agent version %s\n", SSH_VERSION); 494 fprintf(stderr, "Usage: %s [-c | -s] [-k] [command {args...]]\n", 495 __progname); 496 exit(1); 497 } 498 499 int 500 main(int ac, char **av) 501 { 502 fd_set readset, writeset; 503 int sock, c_flag = 0, k_flag = 0, s_flag = 0, ch; 504 struct sockaddr_un sunaddr; 505 pid_t pid; 506 char *shell, *format, *pidstr, pidstrbuf[1 + 3 * sizeof pid]; 507 508 /* check if RSA support exists */ 509 if (rsa_alive() == 0) { 510 fprintf(stderr, 511 "%s: no RSA support in libssl and libcrypto. See ssl(8).\n", 512 __progname); 513 exit(1); 514 } 515 while ((ch = getopt(ac, av, "cks")) != -1) { 516 switch (ch) { 517 case 'c': 518 if (s_flag) 519 usage(); 520 c_flag++; 521 break; 522 case 'k': 523 k_flag++; 524 break; 525 case 's': 526 if (c_flag) 527 usage(); 528 s_flag++; 529 break; 530 default: 531 usage(); 532 } 533 } 534 ac -= optind; 535 av += optind; 536 537 if (ac > 0 && (c_flag || k_flag || s_flag)) 538 usage(); 539 540 if (ac == 0 && !c_flag && !s_flag) { 541 shell = getenv("SHELL"); 542 if (shell != NULL && strncmp(shell + strlen(shell) - 3, "csh", 3) == 0) 543 c_flag = 1; 544 } 545 if (k_flag) { 546 pidstr = getenv(SSH_AGENTPID_ENV_NAME); 547 if (pidstr == NULL) { 548 fprintf(stderr, "%s not set, cannot kill agent\n", 549 SSH_AGENTPID_ENV_NAME); 550 exit(1); 551 } 552 pid = atoi(pidstr); 553 if (pid < 1) { /* XXX PID_MAX check too */ 554 /* Yes, PID_MAX check please */ 555 fprintf(stderr, "%s=\"%s\", which is not a good PID\n", 556 SSH_AGENTPID_ENV_NAME, pidstr); 557 exit(1); 558 } 559 if (kill(pid, SIGTERM) == -1) { 560 perror("kill"); 561 exit(1); 562 } 563 format = c_flag ? "unsetenv %s;\n" : "unset %s;\n"; 564 printf(format, SSH_AUTHSOCKET_ENV_NAME); 565 printf(format, SSH_AGENTPID_ENV_NAME); 566 printf("echo Agent pid %d killed;\n", pid); 567 exit(0); 568 } 569 parent_pid = getpid(); 570 571 /* Create private directory for agent socket */ 572 strlcpy(socket_dir, "/tmp/ssh-XXXXXXXX", sizeof socket_dir); 573 if (mkdtemp(socket_dir) == NULL) { 574 perror("mkdtemp: private socket dir"); 575 exit(1); 576 } 577 snprintf(socket_name, sizeof socket_name, "%s/agent.%d", socket_dir, 578 parent_pid); 579 580 /* 581 * Create socket early so it will exist before command gets run from 582 * the parent. 583 */ 584 sock = socket(AF_UNIX, SOCK_STREAM, 0); 585 if (sock < 0) { 586 perror("socket"); 587 cleanup_exit(1); 588 } 589 memset(&sunaddr, 0, sizeof(sunaddr)); 590 sunaddr.sun_family = AF_UNIX; 591 strlcpy(sunaddr.sun_path, socket_name, sizeof(sunaddr.sun_path)); 592 if (bind(sock, (struct sockaddr *) & sunaddr, sizeof(sunaddr)) < 0) { 593 perror("bind"); 594 cleanup_exit(1); 595 } 596 if (listen(sock, 5) < 0) { 597 perror("listen"); 598 cleanup_exit(1); 599 } 600 /* 601 * Fork, and have the parent execute the command, if any, or present 602 * the socket data. The child continues as the authentication agent. 603 */ 604 pid = fork(); 605 if (pid == -1) { 606 perror("fork"); 607 exit(1); 608 } 609 if (pid != 0) { /* Parent - execute the given command. */ 610 close(sock); 611 snprintf(pidstrbuf, sizeof pidstrbuf, "%d", pid); 612 if (ac == 0) { 613 format = c_flag ? "setenv %s %s;\n" : "%s=%s; export %s;\n"; 614 printf(format, SSH_AUTHSOCKET_ENV_NAME, socket_name, 615 SSH_AUTHSOCKET_ENV_NAME); 616 printf(format, SSH_AGENTPID_ENV_NAME, pidstrbuf, 617 SSH_AGENTPID_ENV_NAME); 618 printf("echo Agent pid %d;\n", pid); 619 exit(0); 620 } 621 setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1); 622 setenv(SSH_AGENTPID_ENV_NAME, pidstrbuf, 1); 623 execvp(av[0], av); 624 perror(av[0]); 625 exit(1); 626 } 627 close(0); 628 close(1); 629 close(2); 630 631 if (setsid() == -1) { 632 perror("setsid"); 633 cleanup_exit(1); 634 } 635 if (atexit(cleanup_socket) < 0) { 636 perror("atexit"); 637 cleanup_exit(1); 638 } 639 new_socket(AUTH_SOCKET, sock); 640 if (ac > 0) { 641 signal(SIGALRM, check_parent_exists); 642 alarm(10); 643 } 644 signal(SIGINT, SIG_IGN); 645 signal(SIGPIPE, SIG_IGN); 646 signal(SIGHUP, cleanup_exit); 647 signal(SIGTERM, cleanup_exit); 648 while (1) { 649 FD_ZERO(&readset); 650 FD_ZERO(&writeset); 651 prepare_select(&readset, &writeset); 652 if (select(max_fd + 1, &readset, &writeset, NULL, NULL) < 0) { 653 if (errno == EINTR) 654 continue; 655 exit(1); 656 } 657 after_select(&readset, &writeset); 658 } 659 /* NOTREACHED */ 660 } 661