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 #pragma ident "%Z%%M% %I% %E% SMI" 41 42 #include <openssl/evp.h> 43 44 #include "ssh.h" 45 #include "rsa.h" 46 #include "buffer.h" 47 #include "bufaux.h" 48 #include "xmalloc.h" 49 #include "getput.h" 50 #include "key.h" 51 #include "authfd.h" 52 #include "cipher.h" 53 #include "kex.h" 54 #include "compat.h" 55 #include "log.h" 56 #include "atomicio.h" 57 58 static int agent_present = 0; 59 60 /* helper */ 61 int decode_reply(int type); 62 63 /* macro to check for "agent failure" message */ 64 #define agent_failed(x) \ 65 ((x == SSH_AGENT_FAILURE) || (x == SSH_COM_AGENT2_FAILURE) || \ 66 (x == SSH2_AGENT_FAILURE)) 67 68 int 69 ssh_agent_present(void) 70 { 71 int authfd; 72 73 if (agent_present) 74 return 1; 75 if ((authfd = ssh_get_authentication_socket()) == -1) 76 return 0; 77 else { 78 ssh_close_authentication_socket(authfd); 79 return 1; 80 } 81 } 82 83 /* Returns the number of the authentication fd, or -1 if there is none. */ 84 85 int 86 ssh_get_authentication_socket(void) 87 { 88 const char *authsocket; 89 int sock; 90 struct sockaddr_un sunaddr; 91 92 authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME); 93 if (!authsocket) 94 return -1; 95 96 sunaddr.sun_family = AF_UNIX; 97 strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path)); 98 99 sock = socket(AF_UNIX, SOCK_STREAM, 0); 100 if (sock < 0) 101 return -1; 102 103 /* close on exec */ 104 if (fcntl(sock, F_SETFD, 1) == -1) { 105 close(sock); 106 return -1; 107 } 108 if (connect(sock, (struct sockaddr *) &sunaddr, sizeof sunaddr) < 0) { 109 close(sock); 110 return -1; 111 } 112 agent_present = 1; 113 return sock; 114 } 115 116 static int 117 ssh_request_reply(AuthenticationConnection *auth, Buffer *request, Buffer *reply) 118 { 119 int l, len; 120 char buf[1024]; 121 122 /* Get the length of the message, and format it in the buffer. */ 123 len = buffer_len(request); 124 PUT_32BIT(buf, len); 125 126 /* Send the length and then the packet to the agent. */ 127 if (atomicio(write, auth->fd, buf, 4) != 4 || 128 atomicio(write, auth->fd, buffer_ptr(request), 129 buffer_len(request)) != buffer_len(request)) { 130 error("Error writing to authentication socket."); 131 return 0; 132 } 133 /* 134 * Wait for response from the agent. First read the length of the 135 * response packet. 136 */ 137 len = 4; 138 while (len > 0) { 139 l = read(auth->fd, buf + 4 - len, len); 140 if (l == -1 && (errno == EAGAIN || errno == EINTR)) 141 continue; 142 if (l <= 0) { 143 error("Error reading response length from authentication socket."); 144 return 0; 145 } 146 len -= l; 147 } 148 149 /* Extract the length, and check it for sanity. */ 150 len = GET_32BIT(buf); 151 if (len > 256 * 1024) 152 fatal("Authentication response too long: %d", len); 153 154 /* Read the rest of the response in to the buffer. */ 155 buffer_clear(reply); 156 while (len > 0) { 157 l = len; 158 if (l > sizeof(buf)) 159 l = sizeof(buf); 160 l = read(auth->fd, buf, l); 161 if (l == -1 && (errno == EAGAIN || errno == EINTR)) 162 continue; 163 if (l <= 0) { 164 error("Error reading response from authentication socket."); 165 return 0; 166 } 167 buffer_append(reply, buf, l); 168 len -= l; 169 } 170 return 1; 171 } 172 173 /* 174 * Closes the agent socket if it should be closed (depends on how it was 175 * obtained). The argument must have been returned by 176 * ssh_get_authentication_socket(). 177 */ 178 179 void 180 ssh_close_authentication_socket(int sock) 181 { 182 if (getenv(SSH_AUTHSOCKET_ENV_NAME)) 183 close(sock); 184 } 185 186 /* 187 * Opens and connects a private socket for communication with the 188 * authentication agent. Returns the file descriptor (which must be 189 * shut down and closed by the caller when no longer needed). 190 * Returns NULL if an error occurred and the connection could not be 191 * opened. 192 */ 193 194 AuthenticationConnection * 195 ssh_get_authentication_connection(void) 196 { 197 AuthenticationConnection *auth; 198 int sock; 199 200 sock = ssh_get_authentication_socket(); 201 202 /* 203 * Fail if we couldn't obtain a connection. This happens if we 204 * exited due to a timeout. 205 */ 206 if (sock < 0) 207 return NULL; 208 209 auth = xmalloc(sizeof(*auth)); 210 auth->fd = sock; 211 buffer_init(&auth->identities); 212 auth->howmany = 0; 213 214 return auth; 215 } 216 217 /* 218 * Closes the connection to the authentication agent and frees any associated 219 * memory. 220 */ 221 222 void 223 ssh_close_authentication_connection(AuthenticationConnection *auth) 224 { 225 buffer_free(&auth->identities); 226 close(auth->fd); 227 xfree(auth); 228 } 229 230 /* Lock/unlock agent */ 231 int 232 ssh_lock_agent(AuthenticationConnection *auth, int lock, const char *password) 233 { 234 int type; 235 Buffer msg; 236 237 buffer_init(&msg); 238 buffer_put_char(&msg, lock ? SSH_AGENTC_LOCK : SSH_AGENTC_UNLOCK); 239 buffer_put_cstring(&msg, password); 240 241 if (ssh_request_reply(auth, &msg, &msg) == 0) { 242 buffer_free(&msg); 243 return 0; 244 } 245 type = buffer_get_char(&msg); 246 buffer_free(&msg); 247 return decode_reply(type); 248 } 249 250 /* 251 * Returns the first authentication identity held by the agent. 252 */ 253 254 int 255 ssh_get_num_identities(AuthenticationConnection *auth, int version) 256 { 257 int type, code1 = 0, code2 = 0; 258 Buffer request; 259 260 switch (version) { 261 case 1: 262 code1 = SSH_AGENTC_REQUEST_RSA_IDENTITIES; 263 code2 = SSH_AGENT_RSA_IDENTITIES_ANSWER; 264 break; 265 case 2: 266 code1 = SSH2_AGENTC_REQUEST_IDENTITIES; 267 code2 = SSH2_AGENT_IDENTITIES_ANSWER; 268 break; 269 default: 270 return 0; 271 } 272 273 /* 274 * Send a message to the agent requesting for a list of the 275 * identities it can represent. 276 */ 277 buffer_init(&request); 278 buffer_put_char(&request, code1); 279 280 buffer_clear(&auth->identities); 281 if (ssh_request_reply(auth, &request, &auth->identities) == 0) { 282 buffer_free(&request); 283 return 0; 284 } 285 buffer_free(&request); 286 287 /* Get message type, and verify that we got a proper answer. */ 288 type = buffer_get_char(&auth->identities); 289 if (agent_failed(type)) { 290 return 0; 291 } else if (type != code2) { 292 fatal("Bad authentication reply message type: %d", type); 293 } 294 295 /* Get the number of entries in the response and check it for sanity. */ 296 auth->howmany = buffer_get_int(&auth->identities); 297 if (auth->howmany > 1024) 298 fatal("Too many identities in authentication reply: %d", 299 auth->howmany); 300 301 return auth->howmany; 302 } 303 304 Key * 305 ssh_get_first_identity(AuthenticationConnection *auth, char **comment, int version) 306 { 307 /* get number of identities and return the first entry (if any). */ 308 if (ssh_get_num_identities(auth, version) > 0) 309 return ssh_get_next_identity(auth, comment, version); 310 return NULL; 311 } 312 313 Key * 314 ssh_get_next_identity(AuthenticationConnection *auth, char **comment, int version) 315 { 316 u_int bits; 317 u_char *blob; 318 u_int blen; 319 Key *key = NULL; 320 321 /* Return failure if no more entries. */ 322 if (auth->howmany <= 0) 323 return NULL; 324 325 /* 326 * Get the next entry from the packet. These will abort with a fatal 327 * error if the packet is too short or contains corrupt data. 328 */ 329 switch (version) { 330 case 1: 331 key = key_new(KEY_RSA1); 332 bits = buffer_get_int(&auth->identities); 333 buffer_get_bignum(&auth->identities, key->rsa->e); 334 buffer_get_bignum(&auth->identities, key->rsa->n); 335 *comment = buffer_get_string(&auth->identities, NULL); 336 if (bits != BN_num_bits(key->rsa->n)) 337 log("Warning: identity keysize mismatch: actual %d, announced %u", 338 BN_num_bits(key->rsa->n), bits); 339 break; 340 case 2: 341 blob = buffer_get_string(&auth->identities, &blen); 342 *comment = buffer_get_string(&auth->identities, NULL); 343 key = key_from_blob(blob, blen); 344 xfree(blob); 345 break; 346 default: 347 return NULL; 348 break; 349 } 350 /* Decrement the number of remaining entries. */ 351 auth->howmany--; 352 return key; 353 } 354 355 /* 356 * Generates a random challenge, sends it to the agent, and waits for 357 * response from the agent. Returns true (non-zero) if the agent gave the 358 * correct answer, zero otherwise. Response type selects the style of 359 * response desired, with 0 corresponding to protocol version 1.0 (no longer 360 * supported) and 1 corresponding to protocol version 1.1. 361 */ 362 363 int 364 ssh_decrypt_challenge(AuthenticationConnection *auth, 365 Key* key, BIGNUM *challenge, 366 u_char session_id[16], 367 u_int response_type, 368 u_char response[16]) 369 { 370 Buffer buffer; 371 int success = 0; 372 int i; 373 int type; 374 375 if (key->type != KEY_RSA1) 376 return 0; 377 if (response_type == 0) { 378 log("Compatibility with ssh protocol version 1.0 no longer supported."); 379 return 0; 380 } 381 buffer_init(&buffer); 382 buffer_put_char(&buffer, SSH_AGENTC_RSA_CHALLENGE); 383 buffer_put_int(&buffer, BN_num_bits(key->rsa->n)); 384 buffer_put_bignum(&buffer, key->rsa->e); 385 buffer_put_bignum(&buffer, key->rsa->n); 386 buffer_put_bignum(&buffer, challenge); 387 buffer_append(&buffer, session_id, 16); 388 buffer_put_int(&buffer, response_type); 389 390 if (ssh_request_reply(auth, &buffer, &buffer) == 0) { 391 buffer_free(&buffer); 392 return 0; 393 } 394 type = buffer_get_char(&buffer); 395 396 if (agent_failed(type)) { 397 log("Agent admitted failure to authenticate using the key."); 398 } else if (type != SSH_AGENT_RSA_RESPONSE) { 399 fatal("Bad authentication response: %d", type); 400 } else { 401 success = 1; 402 /* 403 * Get the response from the packet. This will abort with a 404 * fatal error if the packet is corrupt. 405 */ 406 for (i = 0; i < 16; i++) 407 response[i] = buffer_get_char(&buffer); 408 } 409 buffer_free(&buffer); 410 return success; 411 } 412 413 /* ask agent to sign data, returns -1 on error, 0 on success */ 414 int 415 ssh_agent_sign(AuthenticationConnection *auth, 416 Key *key, 417 u_char **sigp, u_int *lenp, 418 u_char *data, u_int datalen) 419 { 420 extern int datafellows; 421 Buffer msg; 422 u_char *blob; 423 u_int blen; 424 int type, flags = 0; 425 int ret = -1; 426 427 if (key_to_blob(key, &blob, &blen) == 0) 428 return -1; 429 430 if (datafellows & SSH_BUG_SIGBLOB) 431 flags = SSH_AGENT_OLD_SIGNATURE; 432 433 buffer_init(&msg); 434 buffer_put_char(&msg, SSH2_AGENTC_SIGN_REQUEST); 435 buffer_put_string(&msg, blob, blen); 436 buffer_put_string(&msg, data, datalen); 437 buffer_put_int(&msg, flags); 438 xfree(blob); 439 440 if (ssh_request_reply(auth, &msg, &msg) == 0) { 441 buffer_free(&msg); 442 return -1; 443 } 444 type = buffer_get_char(&msg); 445 if (agent_failed(type)) { 446 log("Agent admitted failure to sign using the key."); 447 } else if (type != SSH2_AGENT_SIGN_RESPONSE) { 448 fatal("Bad authentication response: %d", type); 449 } else { 450 ret = 0; 451 *sigp = buffer_get_string(&msg, lenp); 452 } 453 buffer_free(&msg); 454 return ret; 455 } 456 457 /* Encode key for a message to the agent. */ 458 459 static void 460 ssh_encode_identity_rsa1(Buffer *b, RSA *key, const char *comment) 461 { 462 buffer_put_int(b, BN_num_bits(key->n)); 463 buffer_put_bignum(b, key->n); 464 buffer_put_bignum(b, key->e); 465 buffer_put_bignum(b, key->d); 466 /* To keep within the protocol: p < q for ssh. in SSL p > q */ 467 buffer_put_bignum(b, key->iqmp); /* ssh key->u */ 468 buffer_put_bignum(b, key->q); /* ssh key->p, SSL key->q */ 469 buffer_put_bignum(b, key->p); /* ssh key->q, SSL key->p */ 470 buffer_put_cstring(b, comment); 471 } 472 473 static void 474 ssh_encode_identity_ssh2(Buffer *b, Key *key, const char *comment) 475 { 476 buffer_put_cstring(b, key_ssh_name(key)); 477 switch (key->type) { 478 case KEY_RSA: 479 buffer_put_bignum2(b, key->rsa->n); 480 buffer_put_bignum2(b, key->rsa->e); 481 buffer_put_bignum2(b, key->rsa->d); 482 buffer_put_bignum2(b, key->rsa->iqmp); 483 buffer_put_bignum2(b, key->rsa->p); 484 buffer_put_bignum2(b, key->rsa->q); 485 break; 486 case KEY_DSA: 487 buffer_put_bignum2(b, key->dsa->p); 488 buffer_put_bignum2(b, key->dsa->q); 489 buffer_put_bignum2(b, key->dsa->g); 490 buffer_put_bignum2(b, key->dsa->pub_key); 491 buffer_put_bignum2(b, key->dsa->priv_key); 492 break; 493 } 494 buffer_put_cstring(b, comment); 495 } 496 497 /* 498 * Adds an identity to the authentication server. This call is not meant to 499 * be used by normal applications. 500 */ 501 502 int 503 ssh_add_identity_constrained(AuthenticationConnection *auth, Key *key, 504 const char *comment, u_int life) 505 { 506 Buffer msg; 507 int type, constrained = (life != 0); 508 509 buffer_init(&msg); 510 511 switch (key->type) { 512 case KEY_RSA1: 513 type = constrained ? 514 SSH_AGENTC_ADD_RSA_ID_CONSTRAINED : 515 SSH_AGENTC_ADD_RSA_IDENTITY; 516 buffer_put_char(&msg, type); 517 ssh_encode_identity_rsa1(&msg, key->rsa, comment); 518 break; 519 case KEY_RSA: 520 case KEY_DSA: 521 type = constrained ? 522 SSH2_AGENTC_ADD_ID_CONSTRAINED : 523 SSH2_AGENTC_ADD_IDENTITY; 524 buffer_put_char(&msg, type); 525 ssh_encode_identity_ssh2(&msg, key, comment); 526 break; 527 default: 528 buffer_free(&msg); 529 return 0; 530 break; 531 } 532 if (constrained) { 533 if (life != 0) { 534 buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_LIFETIME); 535 buffer_put_int(&msg, life); 536 } 537 } 538 if (ssh_request_reply(auth, &msg, &msg) == 0) { 539 buffer_free(&msg); 540 return 0; 541 } 542 type = buffer_get_char(&msg); 543 buffer_free(&msg); 544 return decode_reply(type); 545 } 546 547 int 548 ssh_add_identity(AuthenticationConnection *auth, Key *key, const char *comment) 549 { 550 return ssh_add_identity_constrained(auth, key, comment, 0); 551 } 552 553 /* 554 * Removes an identity from the authentication server. This call is not 555 * meant to be used by normal applications. 556 */ 557 558 int 559 ssh_remove_identity(AuthenticationConnection *auth, Key *key) 560 { 561 Buffer msg; 562 int type; 563 u_char *blob; 564 u_int blen; 565 566 buffer_init(&msg); 567 568 if (key->type == KEY_RSA1) { 569 buffer_put_char(&msg, SSH_AGENTC_REMOVE_RSA_IDENTITY); 570 buffer_put_int(&msg, BN_num_bits(key->rsa->n)); 571 buffer_put_bignum(&msg, key->rsa->e); 572 buffer_put_bignum(&msg, key->rsa->n); 573 } else if (key->type == KEY_DSA || key->type == KEY_RSA) { 574 key_to_blob(key, &blob, &blen); 575 buffer_put_char(&msg, SSH2_AGENTC_REMOVE_IDENTITY); 576 buffer_put_string(&msg, blob, blen); 577 xfree(blob); 578 } else { 579 buffer_free(&msg); 580 return 0; 581 } 582 if (ssh_request_reply(auth, &msg, &msg) == 0) { 583 buffer_free(&msg); 584 return 0; 585 } 586 type = buffer_get_char(&msg); 587 buffer_free(&msg); 588 return decode_reply(type); 589 } 590 591 int 592 ssh_update_card(AuthenticationConnection *auth, int add, const char *reader_id, const char *pin) 593 { 594 Buffer msg; 595 int type; 596 597 buffer_init(&msg); 598 buffer_put_char(&msg, add ? SSH_AGENTC_ADD_SMARTCARD_KEY : 599 SSH_AGENTC_REMOVE_SMARTCARD_KEY); 600 buffer_put_cstring(&msg, reader_id); 601 buffer_put_cstring(&msg, pin); 602 if (ssh_request_reply(auth, &msg, &msg) == 0) { 603 buffer_free(&msg); 604 return 0; 605 } 606 type = buffer_get_char(&msg); 607 buffer_free(&msg); 608 return decode_reply(type); 609 } 610 611 /* 612 * Removes all identities from the agent. This call is not meant to be used 613 * by normal applications. 614 */ 615 616 int 617 ssh_remove_all_identities(AuthenticationConnection *auth, int version) 618 { 619 Buffer msg; 620 int type; 621 int code = (version==1) ? 622 SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES : 623 SSH2_AGENTC_REMOVE_ALL_IDENTITIES; 624 625 buffer_init(&msg); 626 buffer_put_char(&msg, code); 627 628 if (ssh_request_reply(auth, &msg, &msg) == 0) { 629 buffer_free(&msg); 630 return 0; 631 } 632 type = buffer_get_char(&msg); 633 buffer_free(&msg); 634 return decode_reply(type); 635 } 636 637 int 638 decode_reply(int type) 639 { 640 switch (type) { 641 case SSH_AGENT_FAILURE: 642 case SSH_COM_AGENT2_FAILURE: 643 case SSH2_AGENT_FAILURE: 644 log("SSH_AGENT_FAILURE"); 645 return 0; 646 case SSH_AGENT_SUCCESS: 647 return 1; 648 default: 649 fatal("Bad response from authentication agent: %d", type); 650 } 651 /* NOTREACHED */ 652 return 0; 653 } 654