Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame^] | 1 | /* |
| 2 | |
| 3 | ssh-agent.c |
| 4 | |
| 5 | Author: Tatu Ylonen <ylo@cs.hut.fi> |
| 6 | |
| 7 | Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland |
| 8 | All rights reserved |
| 9 | |
| 10 | Created: Wed Mar 29 03:46:59 1995 ylo |
| 11 | |
| 12 | The authentication agent program. |
| 13 | |
| 14 | */ |
| 15 | |
| 16 | #include "includes.h" |
| 17 | RCSID("$Id: ssh-agent.c,v 1.1 1999/10/27 03:42:45 damien Exp $"); |
| 18 | |
| 19 | #include "ssh.h" |
| 20 | #include "rsa.h" |
| 21 | #include "authfd.h" |
| 22 | #include "buffer.h" |
| 23 | #include "bufaux.h" |
| 24 | #include "xmalloc.h" |
| 25 | #include "packet.h" |
| 26 | #include "getput.h" |
| 27 | #include "mpaux.h" |
| 28 | |
| 29 | #include <openssl/md5.h> |
| 30 | |
| 31 | typedef struct |
| 32 | { |
| 33 | int fd; |
| 34 | enum { AUTH_UNUSED, AUTH_SOCKET, AUTH_CONNECTION } type; |
| 35 | Buffer input; |
| 36 | Buffer output; |
| 37 | } SocketEntry; |
| 38 | |
| 39 | unsigned int sockets_alloc = 0; |
| 40 | SocketEntry *sockets = NULL; |
| 41 | |
| 42 | typedef struct |
| 43 | { |
| 44 | RSA *key; |
| 45 | char *comment; |
| 46 | } Identity; |
| 47 | |
| 48 | unsigned int num_identities = 0; |
| 49 | Identity *identities = NULL; |
| 50 | |
| 51 | int max_fd = 0; |
| 52 | |
| 53 | /* pid of shell == parent of agent */ |
| 54 | int parent_pid = -1; |
| 55 | |
| 56 | /* pathname and directory for AUTH_SOCKET */ |
| 57 | char socket_name[1024]; |
| 58 | char socket_dir[1024]; |
| 59 | |
| 60 | void |
| 61 | process_request_identity(SocketEntry *e) |
| 62 | { |
| 63 | Buffer msg; |
| 64 | int i; |
| 65 | |
| 66 | buffer_init(&msg); |
| 67 | buffer_put_char(&msg, SSH_AGENT_RSA_IDENTITIES_ANSWER); |
| 68 | buffer_put_int(&msg, num_identities); |
| 69 | for (i = 0; i < num_identities; i++) |
| 70 | { |
| 71 | buffer_put_int(&msg, BN_num_bits(identities[i].key->n)); |
| 72 | buffer_put_bignum(&msg, identities[i].key->e); |
| 73 | buffer_put_bignum(&msg, identities[i].key->n); |
| 74 | buffer_put_string(&msg, identities[i].comment, |
| 75 | strlen(identities[i].comment)); |
| 76 | } |
| 77 | buffer_put_int(&e->output, buffer_len(&msg)); |
| 78 | buffer_append(&e->output, buffer_ptr(&msg), buffer_len(&msg)); |
| 79 | buffer_free(&msg); |
| 80 | } |
| 81 | |
| 82 | void |
| 83 | process_authentication_challenge(SocketEntry *e) |
| 84 | { |
| 85 | int i, pub_bits, len; |
| 86 | BIGNUM *pub_e, *pub_n, *challenge; |
| 87 | Buffer msg; |
| 88 | MD5_CTX md; |
| 89 | unsigned char buf[32], mdbuf[16], session_id[16]; |
| 90 | unsigned int response_type; |
| 91 | |
| 92 | buffer_init(&msg); |
| 93 | pub_e = BN_new(); |
| 94 | pub_n = BN_new(); |
| 95 | challenge = BN_new(); |
| 96 | pub_bits = buffer_get_int(&e->input); |
| 97 | buffer_get_bignum(&e->input, pub_e); |
| 98 | buffer_get_bignum(&e->input, pub_n); |
| 99 | buffer_get_bignum(&e->input, challenge); |
| 100 | if (buffer_len(&e->input) == 0) |
| 101 | { |
| 102 | /* Compatibility code for old servers. */ |
| 103 | memset(session_id, 0, 16); |
| 104 | response_type = 0; |
| 105 | } |
| 106 | else |
| 107 | { |
| 108 | /* New code. */ |
| 109 | buffer_get(&e->input, (char *)session_id, 16); |
| 110 | response_type = buffer_get_int(&e->input); |
| 111 | } |
| 112 | for (i = 0; i < num_identities; i++) |
| 113 | if (pub_bits == BN_num_bits(identities[i].key->n) && |
| 114 | BN_cmp(pub_e, identities[i].key->e) == 0 && |
| 115 | BN_cmp(pub_n, identities[i].key->n) == 0) |
| 116 | { |
| 117 | /* Decrypt the challenge using the private key. */ |
| 118 | rsa_private_decrypt(challenge, challenge, identities[i].key); |
| 119 | |
| 120 | /* Compute the desired response. */ |
| 121 | switch (response_type) |
| 122 | { |
| 123 | case 0: /* As of protocol 1.0 */ |
| 124 | /* This response type is no longer supported. */ |
| 125 | log("Compatibility with ssh protocol 1.0 no longer supported."); |
| 126 | buffer_put_char(&msg, SSH_AGENT_FAILURE); |
| 127 | goto send; |
| 128 | |
| 129 | case 1: /* As of protocol 1.1 */ |
| 130 | /* The response is MD5 of decrypted challenge plus session id. */ |
| 131 | len = BN_num_bytes(challenge); |
| 132 | assert(len <= 32 && len); |
| 133 | memset(buf, 0, 32); |
| 134 | BN_bn2bin(challenge, buf + 32 - len); |
| 135 | MD5_Init(&md); |
| 136 | MD5_Update(&md, buf, 32); |
| 137 | MD5_Update(&md, session_id, 16); |
| 138 | MD5_Final(mdbuf, &md); |
| 139 | break; |
| 140 | |
| 141 | default: |
| 142 | fatal("process_authentication_challenge: bad response_type %d", |
| 143 | response_type); |
| 144 | break; |
| 145 | } |
| 146 | |
| 147 | /* Send the response. */ |
| 148 | buffer_put_char(&msg, SSH_AGENT_RSA_RESPONSE); |
| 149 | for (i = 0; i < 16; i++) |
| 150 | buffer_put_char(&msg, mdbuf[i]); |
| 151 | |
| 152 | goto send; |
| 153 | } |
| 154 | /* Unknown identity. Send failure. */ |
| 155 | buffer_put_char(&msg, SSH_AGENT_FAILURE); |
| 156 | send: |
| 157 | buffer_put_int(&e->output, buffer_len(&msg)); |
| 158 | buffer_append(&e->output, buffer_ptr(&msg), |
| 159 | buffer_len(&msg)); |
| 160 | buffer_free(&msg); |
| 161 | BN_clear_free(pub_e); |
| 162 | BN_clear_free(pub_n); |
| 163 | BN_clear_free(challenge); |
| 164 | } |
| 165 | |
| 166 | void |
| 167 | process_remove_identity(SocketEntry *e) |
| 168 | { |
| 169 | unsigned int bits; |
| 170 | unsigned int i; |
| 171 | BIGNUM *dummy, *n; |
| 172 | |
| 173 | dummy = BN_new(); |
| 174 | n = BN_new(); |
| 175 | |
| 176 | /* Get the key from the packet. */ |
| 177 | bits = buffer_get_int(&e->input); |
| 178 | buffer_get_bignum(&e->input, dummy); |
| 179 | buffer_get_bignum(&e->input, n); |
| 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 don\'t want to leave |
| 186 | empty slots in the middle of the array, we actually free the |
| 187 | key there and copy data from the last entry. */ |
| 188 | RSA_free(identities[i].key); |
| 189 | xfree(identities[i].comment); |
| 190 | if (i < num_identities - 1) |
| 191 | identities[i] = identities[num_identities - 1]; |
| 192 | num_identities--; |
| 193 | BN_clear_free(dummy); |
| 194 | BN_clear_free(n); |
| 195 | |
| 196 | /* Send success. */ |
| 197 | buffer_put_int(&e->output, 1); |
| 198 | buffer_put_char(&e->output, SSH_AGENT_SUCCESS); |
| 199 | return; |
| 200 | } |
| 201 | /* We did not have the key. */ |
| 202 | BN_clear(dummy); |
| 203 | BN_clear(n); |
| 204 | |
| 205 | /* Send failure. */ |
| 206 | buffer_put_int(&e->output, 1); |
| 207 | buffer_put_char(&e->output, SSH_AGENT_FAILURE); |
| 208 | } |
| 209 | |
| 210 | /* Removes all identities from the agent. */ |
| 211 | |
| 212 | void |
| 213 | process_remove_all_identities(SocketEntry *e) |
| 214 | { |
| 215 | unsigned int i; |
| 216 | |
| 217 | /* Loop over all identities and clear the keys. */ |
| 218 | for (i = 0; i < num_identities; i++) |
| 219 | { |
| 220 | RSA_free(identities[i].key); |
| 221 | xfree(identities[i].comment); |
| 222 | } |
| 223 | |
| 224 | /* Mark that there are no identities. */ |
| 225 | num_identities = 0; |
| 226 | |
| 227 | /* Send success. */ |
| 228 | buffer_put_int(&e->output, 1); |
| 229 | buffer_put_char(&e->output, SSH_AGENT_SUCCESS); |
| 230 | return; |
| 231 | } |
| 232 | |
| 233 | /* Adds an identity to the agent. */ |
| 234 | |
| 235 | void |
| 236 | process_add_identity(SocketEntry *e) |
| 237 | { |
| 238 | RSA *k; |
| 239 | int i; |
| 240 | BIGNUM *aux; |
| 241 | BN_CTX *ctx; |
| 242 | |
| 243 | if (num_identities == 0) |
| 244 | identities = xmalloc(sizeof(Identity)); |
| 245 | else |
| 246 | identities = xrealloc(identities, (num_identities + 1) * sizeof(Identity)); |
| 247 | |
| 248 | identities[num_identities].key = RSA_new(); |
| 249 | k = identities[num_identities].key; |
| 250 | buffer_get_int(&e->input); /* bits */ |
| 251 | k->n = BN_new(); |
| 252 | buffer_get_bignum(&e->input, k->n); |
| 253 | k->e = BN_new(); |
| 254 | buffer_get_bignum(&e->input, k->e); |
| 255 | k->d = BN_new(); |
| 256 | buffer_get_bignum(&e->input, k->d); |
| 257 | k->iqmp = BN_new(); |
| 258 | buffer_get_bignum(&e->input, k->iqmp); |
| 259 | /* SSH and SSL have p and q swapped */ |
| 260 | k->q = BN_new(); |
| 261 | buffer_get_bignum(&e->input, k->q); /* p */ |
| 262 | k->p = BN_new(); |
| 263 | buffer_get_bignum(&e->input, k->p); /* q */ |
| 264 | |
| 265 | /* Generate additional parameters */ |
| 266 | aux = BN_new(); |
| 267 | ctx = BN_CTX_new(); |
| 268 | |
| 269 | BN_sub(aux, k->q, BN_value_one()); |
| 270 | k->dmq1 = BN_new(); |
| 271 | BN_mod(k->dmq1, k->d, aux, ctx); |
| 272 | |
| 273 | BN_sub(aux, k->p, BN_value_one()); |
| 274 | k->dmp1 = BN_new(); |
| 275 | BN_mod(k->dmp1, k->d, aux, ctx); |
| 276 | |
| 277 | BN_clear_free(aux); |
| 278 | BN_CTX_free(ctx); |
| 279 | |
| 280 | identities[num_identities].comment = buffer_get_string(&e->input, NULL); |
| 281 | |
| 282 | /* Check if we already have the key. */ |
| 283 | for (i = 0; i < num_identities; i++) |
| 284 | if (BN_cmp(identities[i].key->n, k->n) == 0) |
| 285 | { |
| 286 | /* We already have this key. Clear and free the new data and |
| 287 | return success. */ |
| 288 | RSA_free(k); |
| 289 | xfree(identities[num_identities].comment); |
| 290 | |
| 291 | /* Send success. */ |
| 292 | buffer_put_int(&e->output, 1); |
| 293 | buffer_put_char(&e->output, SSH_AGENT_SUCCESS); |
| 294 | return; |
| 295 | } |
| 296 | |
| 297 | /* Increment the number of identities. */ |
| 298 | num_identities++; |
| 299 | |
| 300 | /* Send a success message. */ |
| 301 | buffer_put_int(&e->output, 1); |
| 302 | buffer_put_char(&e->output, SSH_AGENT_SUCCESS); |
| 303 | } |
| 304 | |
| 305 | void |
| 306 | process_message(SocketEntry *e) |
| 307 | { |
| 308 | unsigned int msg_len; |
| 309 | unsigned int type; |
| 310 | unsigned char *cp; |
| 311 | if (buffer_len(&e->input) < 5) |
| 312 | return; /* Incomplete message. */ |
| 313 | cp = (unsigned char *)buffer_ptr(&e->input); |
| 314 | msg_len = GET_32BIT(cp); |
| 315 | if (msg_len > 256 * 1024) |
| 316 | { |
| 317 | shutdown(e->fd, SHUT_RDWR); |
| 318 | close(e->fd); |
| 319 | e->type = AUTH_UNUSED; |
| 320 | return; |
| 321 | } |
| 322 | if (buffer_len(&e->input) < msg_len + 4) |
| 323 | return; |
| 324 | buffer_consume(&e->input, 4); |
| 325 | type = buffer_get_char(&e->input); |
| 326 | |
| 327 | switch (type) |
| 328 | { |
| 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 | { |
| 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 | { |
| 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 after_select(fd_set *readset, fd_set *writeset) |
| 409 | { |
| 410 | unsigned int i; |
| 411 | int len, sock; |
| 412 | char buf[1024]; |
| 413 | struct sockaddr_un sunaddr; |
| 414 | |
| 415 | for (i = 0; i < sockets_alloc; i++) |
| 416 | switch (sockets[i].type) |
| 417 | { |
| 418 | case AUTH_UNUSED: |
| 419 | break; |
| 420 | case AUTH_SOCKET: |
| 421 | if (FD_ISSET(sockets[i].fd, readset)) |
| 422 | { |
| 423 | len = sizeof(sunaddr); |
| 424 | sock = accept(sockets[i].fd, (struct sockaddr *)&sunaddr, &len); |
| 425 | if (sock < 0) |
| 426 | { |
| 427 | perror("accept from AUTH_SOCKET"); |
| 428 | break; |
| 429 | } |
| 430 | new_socket(AUTH_CONNECTION, sock); |
| 431 | } |
| 432 | break; |
| 433 | case AUTH_CONNECTION: |
| 434 | if (buffer_len(&sockets[i].output) > 0 && |
| 435 | FD_ISSET(sockets[i].fd, writeset)) |
| 436 | { |
| 437 | len = write(sockets[i].fd, buffer_ptr(&sockets[i].output), |
| 438 | buffer_len(&sockets[i].output)); |
| 439 | if (len <= 0) |
| 440 | { |
| 441 | shutdown(sockets[i].fd, SHUT_RDWR); |
| 442 | close(sockets[i].fd); |
| 443 | sockets[i].type = AUTH_UNUSED; |
| 444 | break; |
| 445 | } |
| 446 | buffer_consume(&sockets[i].output, len); |
| 447 | } |
| 448 | if (FD_ISSET(sockets[i].fd, readset)) |
| 449 | { |
| 450 | len = read(sockets[i].fd, buf, sizeof(buf)); |
| 451 | if (len <= 0) |
| 452 | { |
| 453 | shutdown(sockets[i].fd, SHUT_RDWR); |
| 454 | close(sockets[i].fd); |
| 455 | sockets[i].type = AUTH_UNUSED; |
| 456 | break; |
| 457 | } |
| 458 | buffer_append(&sockets[i].input, buf, len); |
| 459 | process_message(&sockets[i]); |
| 460 | } |
| 461 | break; |
| 462 | default: |
| 463 | fatal("Unknown type %d", sockets[i].type); |
| 464 | } |
| 465 | } |
| 466 | |
| 467 | void |
| 468 | check_parent_exists(int sig) |
| 469 | { |
| 470 | if (kill(parent_pid, 0) < 0) |
| 471 | { |
| 472 | /* printf("Parent has died - Authentication agent exiting.\n"); */ |
| 473 | exit(1); |
| 474 | } |
| 475 | signal(SIGALRM, check_parent_exists); |
| 476 | alarm(10); |
| 477 | } |
| 478 | |
| 479 | void cleanup_socket(void) { |
| 480 | remove(socket_name); |
| 481 | rmdir(socket_dir); |
| 482 | } |
| 483 | |
| 484 | int |
| 485 | main(int ac, char **av) |
| 486 | { |
| 487 | fd_set readset, writeset; |
| 488 | int sock; |
| 489 | struct sockaddr_un sunaddr; |
| 490 | |
| 491 | /* check if RSA support exists */ |
| 492 | if (rsa_alive() == 0) { |
| 493 | extern char *__progname; |
| 494 | fprintf(stderr, |
| 495 | "%s: no RSA support in libssl and libcrypto. See ssl(8).\n", |
| 496 | __progname); |
| 497 | exit(1); |
| 498 | } |
| 499 | |
| 500 | if (ac < 2) |
| 501 | { |
| 502 | fprintf(stderr, "ssh-agent version %s\n", SSH_VERSION); |
| 503 | fprintf(stderr, "Usage: %s command\n", av[0]); |
| 504 | exit(1); |
| 505 | } |
| 506 | |
| 507 | parent_pid = getpid(); |
| 508 | |
| 509 | /* Create private directory for agent socket */ |
| 510 | strlcpy(socket_dir, "/tmp/ssh-XXXXXXXX", sizeof socket_dir); |
| 511 | if (mkdtemp(socket_dir) == NULL) { |
| 512 | perror("mkdtemp: private socket dir"); |
| 513 | exit(1); |
| 514 | } |
| 515 | snprintf(socket_name, sizeof socket_name, "%s/agent.%d", socket_dir, parent_pid); |
| 516 | |
| 517 | /* Fork, and have the parent execute the command. The child continues as |
| 518 | the authentication agent. */ |
| 519 | if (fork() != 0) |
| 520 | { /* Parent - execute the given command. */ |
| 521 | setenv(SSH_AUTHSOCKET_ENV_NAME, socket_name, 1); |
| 522 | execvp(av[1], av + 1); |
| 523 | perror(av[1]); |
| 524 | exit(1); |
| 525 | } |
| 526 | |
| 527 | if (atexit(cleanup_socket) < 0) { |
| 528 | perror("atexit"); |
| 529 | cleanup_socket(); |
| 530 | exit(1); |
| 531 | } |
| 532 | |
| 533 | sock = socket(AF_UNIX, SOCK_STREAM, 0); |
| 534 | if (sock < 0) |
| 535 | { |
| 536 | perror("socket"); |
| 537 | exit(1); |
| 538 | } |
| 539 | memset(&sunaddr, 0, sizeof(sunaddr)); |
| 540 | sunaddr.sun_family = AF_UNIX; |
| 541 | strlcpy(sunaddr.sun_path, socket_name, sizeof(sunaddr.sun_path)); |
| 542 | if (bind(sock, (struct sockaddr *)&sunaddr, sizeof(sunaddr)) < 0) |
| 543 | { |
| 544 | perror("bind"); |
| 545 | exit(1); |
| 546 | } |
| 547 | if (listen(sock, 5) < 0) |
| 548 | { |
| 549 | perror("listen"); |
| 550 | exit(1); |
| 551 | } |
| 552 | new_socket(AUTH_SOCKET, sock); |
| 553 | signal(SIGALRM, check_parent_exists); |
| 554 | alarm(10); |
| 555 | |
| 556 | signal(SIGINT, SIG_IGN); |
| 557 | while (1) |
| 558 | { |
| 559 | FD_ZERO(&readset); |
| 560 | FD_ZERO(&writeset); |
| 561 | prepare_select(&readset, &writeset); |
| 562 | if (select(max_fd + 1, &readset, &writeset, NULL, NULL) < 0) |
| 563 | { |
| 564 | if (errno == EINTR) |
| 565 | continue; |
| 566 | perror("select"); |
| 567 | exit(1); |
| 568 | } |
| 569 | after_select(&readset, &writeset); |
| 570 | } |
| 571 | /*NOTREACHED*/ |
| 572 | } |