1 /* 2 * Author: Tatu Ylonen <ylo@cs.hut.fi> 3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 4 * All rights reserved 5 * Functions for connecting the local authentication agent. 6 * 7 * As far as I am concerned, the code I have written for this software 8 * can be used freely for any purpose. Any derived versions of this 9 * software must be clearly marked as such, and if the derived work is 10 * incompatible with the protocol description in the RFC file, it must be 11 * called by a name other than "ssh" or "Secure Shell". 12 * 13 * SSH2 implementation, 14 * Copyright (c) 2000 Markus Friedl. All rights reserved. 15 * 16 * Redistribution and use in source and binary forms, with or without 17 * modification, are permitted provided that the following conditions 18 * are met: 19 * 1. Redistributions of source code must retain the above copyright 20 * notice, this list of conditions and the following disclaimer. 21 * 2. Redistributions in binary form must reproduce the above copyright 22 * notice, this list of conditions and the following disclaimer in the 23 * documentation and/or other materials provided with the distribution. 24 * 25 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 26 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 27 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 28 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 29 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 30 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 31 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 32 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 33 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 34 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 35 */ 36 37 #include "includes.h" 38 RCSID("$OpenBSD: authfd.c,v 1.57 2002/09/11 18:27:26 stevesk Exp $"); 39 40 #include <openssl/evp.h> 41 42 #include "ssh.h" 43 #include "rsa.h" 44 #include "buffer.h" 45 #include "bufaux.h" 46 #include "xmalloc.h" 47 #include "getput.h" 48 #include "key.h" 49 #include "authfd.h" 50 #include "cipher.h" 51 #include "kex.h" 52 #include "compat.h" 53 #include "log.h" 54 #include "atomicio.h" 55 56 static int agent_present = 0; 57 58 /* helper */ 59 int decode_reply(int type); 60 61 /* macro to check for "agent failure" message */ 62 #define agent_failed(x) \ 63 ((x == SSH_AGENT_FAILURE) || (x == SSH_COM_AGENT2_FAILURE) || \ 64 (x == SSH2_AGENT_FAILURE)) 65 66 int 67 ssh_agent_present(void) 68 { 69 int authfd; 70 71 if (agent_present) 72 return 1; 73 if ((authfd = ssh_get_authentication_socket()) == -1) 74 return 0; 75 else { 76 ssh_close_authentication_socket(authfd); 77 return 1; 78 } 79 } 80 81 /* Returns the number of the authentication fd, or -1 if there is none. */ 82 83 int 84 ssh_get_authentication_socket(void) 85 { 86 const char *authsocket; 87 int sock; 88 struct sockaddr_un sunaddr; 89 90 authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME); 91 if (!authsocket) 92 return -1; 93 94 sunaddr.sun_family = AF_UNIX; 95 strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path)); 96 97 sock = socket(AF_UNIX, SOCK_STREAM, 0); 98 if (sock < 0) 99 return -1; 100 101 /* close on exec */ 102 if (fcntl(sock, F_SETFD, FD_CLOEXEC) == -1) { 103 close(sock); 104 return -1; 105 } 106 if (connect(sock, (struct sockaddr *) &sunaddr, sizeof sunaddr) < 0) { 107 close(sock); 108 return -1; 109 } 110 agent_present = 1; 111 return sock; 112 } 113 114 static int 115 ssh_request_reply(AuthenticationConnection *auth, Buffer *request, Buffer *reply) 116 { 117 int l, len; 118 char buf[1024]; 119 120 /* Get the length of the message, and format it in the buffer. */ 121 len = buffer_len(request); 122 PUT_32BIT(buf, len); 123 124 /* Send the length and then the packet to the agent. */ 125 if (atomicio(write, auth->fd, buf, 4) != 4 || 126 atomicio(write, auth->fd, buffer_ptr(request), 127 buffer_len(request)) != buffer_len(request)) { 128 error("Error writing to authentication socket."); 129 return 0; 130 } 131 /* 132 * Wait for response from the agent. First read the length of the 133 * response packet. 134 */ 135 len = 4; 136 while (len > 0) { 137 l = read(auth->fd, buf + 4 - len, len); 138 if (l == -1 && (errno == EAGAIN || errno == EINTR)) 139 continue; 140 if (l <= 0) { 141 error("Error reading response length from authentication socket."); 142 return 0; 143 } 144 len -= l; 145 } 146 147 /* Extract the length, and check it for sanity. */ 148 len = GET_32BIT(buf); 149 if (len > 256 * 1024) 150 fatal("Authentication response too long: %d", len); 151 152 /* Read the rest of the response in to the buffer. */ 153 buffer_clear(reply); 154 while (len > 0) { 155 l = len; 156 if (l > sizeof(buf)) 157 l = sizeof(buf); 158 l = read(auth->fd, buf, l); 159 if (l == -1 && (errno == EAGAIN || errno == EINTR)) 160 continue; 161 if (l <= 0) { 162 error("Error reading response from authentication socket."); 163 return 0; 164 } 165 buffer_append(reply, buf, l); 166 len -= l; 167 } 168 return 1; 169 } 170 171 /* 172 * Closes the agent socket if it should be closed (depends on how it was 173 * obtained). The argument must have been returned by 174 * ssh_get_authentication_socket(). 175 */ 176 177 void 178 ssh_close_authentication_socket(int sock) 179 { 180 if (getenv(SSH_AUTHSOCKET_ENV_NAME)) 181 close(sock); 182 } 183 184 /* 185 * Opens and connects a private socket for communication with the 186 * authentication agent. Returns the file descriptor (which must be 187 * shut down and closed by the caller when no longer needed). 188 * Returns NULL if an error occurred and the connection could not be 189 * opened. 190 */ 191 192 AuthenticationConnection * 193 ssh_get_authentication_connection(void) 194 { 195 AuthenticationConnection *auth; 196 int sock; 197 198 sock = ssh_get_authentication_socket(); 199 200 /* 201 * Fail if we couldn't obtain a connection. This happens if we 202 * exited due to a timeout. 203 */ 204 if (sock < 0) 205 return NULL; 206 207 auth = xmalloc(sizeof(*auth)); 208 auth->fd = sock; 209 buffer_init(&auth->identities); 210 auth->howmany = 0; 211 212 return auth; 213 } 214 215 /* 216 * Closes the connection to the authentication agent and frees any associated 217 * memory. 218 */ 219 220 void 221 ssh_close_authentication_connection(AuthenticationConnection *auth) 222 { 223 buffer_free(&auth->identities); 224 close(auth->fd); 225 xfree(auth); 226 } 227 228 /* Lock/unlock agent */ 229 int 230 ssh_lock_agent(AuthenticationConnection *auth, int lock, const char *password) 231 { 232 int type; 233 Buffer msg; 234 235 buffer_init(&msg); 236 buffer_put_char(&msg, lock ? SSH_AGENTC_LOCK : SSH_AGENTC_UNLOCK); 237 buffer_put_cstring(&msg, password); 238 239 if (ssh_request_reply(auth, &msg, &msg) == 0) { 240 buffer_free(&msg); 241 return 0; 242 } 243 type = buffer_get_char(&msg); 244 buffer_free(&msg); 245 return decode_reply(type); 246 } 247 248 /* 249 * Returns the first authentication identity held by the agent. 250 */ 251 252 int 253 ssh_get_num_identities(AuthenticationConnection *auth, int version) 254 { 255 int type, code1 = 0, code2 = 0; 256 Buffer request; 257 258 switch (version) { 259 case 1: 260 code1 = SSH_AGENTC_REQUEST_RSA_IDENTITIES; 261 code2 = SSH_AGENT_RSA_IDENTITIES_ANSWER; 262 break; 263 case 2: 264 code1 = SSH2_AGENTC_REQUEST_IDENTITIES; 265 code2 = SSH2_AGENT_IDENTITIES_ANSWER; 266 break; 267 default: 268 return 0; 269 } 270 271 /* 272 * Send a message to the agent requesting for a list of the 273 * identities it can represent. 274 */ 275 buffer_init(&request); 276 buffer_put_char(&request, code1); 277 278 buffer_clear(&auth->identities); 279 if (ssh_request_reply(auth, &request, &auth->identities) == 0) { 280 buffer_free(&request); 281 return 0; 282 } 283 buffer_free(&request); 284 285 /* Get message type, and verify that we got a proper answer. */ 286 type = buffer_get_char(&auth->identities); 287 if (agent_failed(type)) { 288 return 0; 289 } else if (type != code2) { 290 fatal("Bad authentication reply message type: %d", type); 291 } 292 293 /* Get the number of entries in the response and check it for sanity. */ 294 auth->howmany = buffer_get_int(&auth->identities); 295 if (auth->howmany > 1024) 296 fatal("Too many identities in authentication reply: %d", 297 auth->howmany); 298 299 return auth->howmany; 300 } 301 302 Key * 303 ssh_get_first_identity(AuthenticationConnection *auth, char **comment, int version) 304 { 305 /* get number of identities and return the first entry (if any). */ 306 if (ssh_get_num_identities(auth, version) > 0) 307 return ssh_get_next_identity(auth, comment, version); 308 return NULL; 309 } 310 311 Key * 312 ssh_get_next_identity(AuthenticationConnection *auth, char **comment, int version) 313 { 314 u_int bits; 315 u_char *blob; 316 u_int blen; 317 Key *key = NULL; 318 319 /* Return failure if no more entries. */ 320 if (auth->howmany <= 0) 321 return NULL; 322 323 /* 324 * Get the next entry from the packet. These will abort with a fatal 325 * error if the packet is too short or contains corrupt data. 326 */ 327 switch (version) { 328 case 1: 329 key = key_new(KEY_RSA1); 330 bits = buffer_get_int(&auth->identities); 331 buffer_get_bignum(&auth->identities, key->rsa->e); 332 buffer_get_bignum(&auth->identities, key->rsa->n); 333 *comment = buffer_get_string(&auth->identities, NULL); 334 if (bits != BN_num_bits(key->rsa->n)) 335 log("Warning: identity keysize mismatch: actual %d, announced %u", 336 BN_num_bits(key->rsa->n), bits); 337 break; 338 case 2: 339 blob = buffer_get_string(&auth->identities, &blen); 340 *comment = buffer_get_string(&auth->identities, NULL); 341 key = key_from_blob(blob, blen); 342 xfree(blob); 343 break; 344 default: 345 return NULL; 346 break; 347 } 348 /* Decrement the number of remaining entries. */ 349 auth->howmany--; 350 return key; 351 } 352 353 /* 354 * Generates a random challenge, sends it to the agent, and waits for 355 * response from the agent. Returns true (non-zero) if the agent gave the 356 * correct answer, zero otherwise. Response type selects the style of 357 * response desired, with 0 corresponding to protocol version 1.0 (no longer 358 * supported) and 1 corresponding to protocol version 1.1. 359 */ 360 361 int 362 ssh_decrypt_challenge(AuthenticationConnection *auth, 363 Key* key, BIGNUM *challenge, 364 u_char session_id[16], 365 u_int response_type, 366 u_char response[16]) 367 { 368 Buffer buffer; 369 int success = 0; 370 int i; 371 int type; 372 373 if (key->type != KEY_RSA1) 374 return 0; 375 if (response_type == 0) { 376 log("Compatibility with ssh protocol version 1.0 no longer supported."); 377 return 0; 378 } 379 buffer_init(&buffer); 380 buffer_put_char(&buffer, SSH_AGENTC_RSA_CHALLENGE); 381 buffer_put_int(&buffer, BN_num_bits(key->rsa->n)); 382 buffer_put_bignum(&buffer, key->rsa->e); 383 buffer_put_bignum(&buffer, key->rsa->n); 384 buffer_put_bignum(&buffer, challenge); 385 buffer_append(&buffer, session_id, 16); 386 buffer_put_int(&buffer, response_type); 387 388 if (ssh_request_reply(auth, &buffer, &buffer) == 0) { 389 buffer_free(&buffer); 390 return 0; 391 } 392 type = buffer_get_char(&buffer); 393 394 if (agent_failed(type)) { 395 log("Agent admitted failure to authenticate using the key."); 396 } else if (type != SSH_AGENT_RSA_RESPONSE) { 397 fatal("Bad authentication response: %d", type); 398 } else { 399 success = 1; 400 /* 401 * Get the response from the packet. This will abort with a 402 * fatal error if the packet is corrupt. 403 */ 404 for (i = 0; i < 16; i++) 405 response[i] = buffer_get_char(&buffer); 406 } 407 buffer_free(&buffer); 408 return success; 409 } 410 411 /* ask agent to sign data, returns -1 on error, 0 on success */ 412 int 413 ssh_agent_sign(AuthenticationConnection *auth, 414 Key *key, 415 u_char **sigp, u_int *lenp, 416 u_char *data, u_int datalen) 417 { 418 Buffer msg; 419 u_char *blob; 420 u_int blen; 421 int type, flags = 0; 422 int ret = -1; 423 424 if (key_to_blob(key, &blob, &blen) == 0) 425 return -1; 426 427 if (datafellows & SSH_BUG_SIGBLOB) 428 flags = SSH_AGENT_OLD_SIGNATURE; 429 430 buffer_init(&msg); 431 buffer_put_char(&msg, SSH2_AGENTC_SIGN_REQUEST); 432 buffer_put_string(&msg, blob, blen); 433 buffer_put_string(&msg, data, datalen); 434 buffer_put_int(&msg, flags); 435 xfree(blob); 436 437 if (ssh_request_reply(auth, &msg, &msg) == 0) { 438 buffer_free(&msg); 439 return -1; 440 } 441 type = buffer_get_char(&msg); 442 if (agent_failed(type)) { 443 log("Agent admitted failure to sign using the key."); 444 } else if (type != SSH2_AGENT_SIGN_RESPONSE) { 445 fatal("Bad authentication response: %d", type); 446 } else { 447 ret = 0; 448 *sigp = buffer_get_string(&msg, lenp); 449 } 450 buffer_free(&msg); 451 return ret; 452 } 453 454 /* Encode key for a message to the agent. */ 455 456 static void 457 ssh_encode_identity_rsa1(Buffer *b, RSA *key, const char *comment) 458 { 459 buffer_put_int(b, BN_num_bits(key->n)); 460 buffer_put_bignum(b, key->n); 461 buffer_put_bignum(b, key->e); 462 buffer_put_bignum(b, key->d); 463 /* To keep within the protocol: p < q for ssh. in SSL p > q */ 464 buffer_put_bignum(b, key->iqmp); /* ssh key->u */ 465 buffer_put_bignum(b, key->q); /* ssh key->p, SSL key->q */ 466 buffer_put_bignum(b, key->p); /* ssh key->q, SSL key->p */ 467 buffer_put_cstring(b, comment); 468 } 469 470 static void 471 ssh_encode_identity_ssh2(Buffer *b, Key *key, const char *comment) 472 { 473 buffer_put_cstring(b, key_ssh_name(key)); 474 switch (key->type) { 475 case KEY_RSA: 476 buffer_put_bignum2(b, key->rsa->n); 477 buffer_put_bignum2(b, key->rsa->e); 478 buffer_put_bignum2(b, key->rsa->d); 479 buffer_put_bignum2(b, key->rsa->iqmp); 480 buffer_put_bignum2(b, key->rsa->p); 481 buffer_put_bignum2(b, key->rsa->q); 482 break; 483 case KEY_DSA: 484 buffer_put_bignum2(b, key->dsa->p); 485 buffer_put_bignum2(b, key->dsa->q); 486 buffer_put_bignum2(b, key->dsa->g); 487 buffer_put_bignum2(b, key->dsa->pub_key); 488 buffer_put_bignum2(b, key->dsa->priv_key); 489 break; 490 } 491 buffer_put_cstring(b, comment); 492 } 493 494 /* 495 * Adds an identity to the authentication server. This call is not meant to 496 * be used by normal applications. 497 */ 498 499 int 500 ssh_add_identity_constrained(AuthenticationConnection *auth, Key *key, 501 const char *comment, u_int life) 502 { 503 Buffer msg; 504 int type, constrained = (life != 0); 505 506 buffer_init(&msg); 507 508 switch (key->type) { 509 case KEY_RSA1: 510 type = constrained ? 511 SSH_AGENTC_ADD_RSA_ID_CONSTRAINED : 512 SSH_AGENTC_ADD_RSA_IDENTITY; 513 buffer_put_char(&msg, type); 514 ssh_encode_identity_rsa1(&msg, key->rsa, comment); 515 break; 516 case KEY_RSA: 517 case KEY_DSA: 518 type = constrained ? 519 SSH2_AGENTC_ADD_ID_CONSTRAINED : 520 SSH2_AGENTC_ADD_IDENTITY; 521 buffer_put_char(&msg, type); 522 ssh_encode_identity_ssh2(&msg, key, comment); 523 break; 524 default: 525 buffer_free(&msg); 526 return 0; 527 break; 528 } 529 if (constrained) { 530 if (life != 0) { 531 buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_LIFETIME); 532 buffer_put_int(&msg, life); 533 } 534 } 535 if (ssh_request_reply(auth, &msg, &msg) == 0) { 536 buffer_free(&msg); 537 return 0; 538 } 539 type = buffer_get_char(&msg); 540 buffer_free(&msg); 541 return decode_reply(type); 542 } 543 544 int 545 ssh_add_identity(AuthenticationConnection *auth, Key *key, const char *comment) 546 { 547 return ssh_add_identity_constrained(auth, key, comment, 0); 548 } 549 550 /* 551 * Removes an identity from the authentication server. This call is not 552 * meant to be used by normal applications. 553 */ 554 555 int 556 ssh_remove_identity(AuthenticationConnection *auth, Key *key) 557 { 558 Buffer msg; 559 int type; 560 u_char *blob; 561 u_int blen; 562 563 buffer_init(&msg); 564 565 if (key->type == KEY_RSA1) { 566 buffer_put_char(&msg, SSH_AGENTC_REMOVE_RSA_IDENTITY); 567 buffer_put_int(&msg, BN_num_bits(key->rsa->n)); 568 buffer_put_bignum(&msg, key->rsa->e); 569 buffer_put_bignum(&msg, key->rsa->n); 570 } else if (key->type == KEY_DSA || key->type == KEY_RSA) { 571 key_to_blob(key, &blob, &blen); 572 buffer_put_char(&msg, SSH2_AGENTC_REMOVE_IDENTITY); 573 buffer_put_string(&msg, blob, blen); 574 xfree(blob); 575 } else { 576 buffer_free(&msg); 577 return 0; 578 } 579 if (ssh_request_reply(auth, &msg, &msg) == 0) { 580 buffer_free(&msg); 581 return 0; 582 } 583 type = buffer_get_char(&msg); 584 buffer_free(&msg); 585 return decode_reply(type); 586 } 587 588 589 /* 590 * Removes all identities from the agent. This call is not meant to be used 591 * by normal applications. 592 */ 593 594 int 595 ssh_remove_all_identities(AuthenticationConnection *auth, int version) 596 { 597 Buffer msg; 598 int type; 599 int code = (version==1) ? 600 SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES : 601 SSH2_AGENTC_REMOVE_ALL_IDENTITIES; 602 603 buffer_init(&msg); 604 buffer_put_char(&msg, code); 605 606 if (ssh_request_reply(auth, &msg, &msg) == 0) { 607 buffer_free(&msg); 608 return 0; 609 } 610 type = buffer_get_char(&msg); 611 buffer_free(&msg); 612 return decode_reply(type); 613 } 614 615 int 616 decode_reply(int type) 617 { 618 switch (type) { 619 case SSH_AGENT_FAILURE: 620 case SSH_COM_AGENT2_FAILURE: 621 case SSH2_AGENT_FAILURE: 622 log("SSH_AGENT_FAILURE"); 623 return 0; 624 case SSH_AGENT_SUCCESS: 625 return 1; 626 default: 627 fatal("Bad response from authentication agent: %d", type); 628 } 629 /* NOTREACHED */ 630 return 0; 631 } 632