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 1.48 2002/02/24 19:14:59 markus Exp $"); 39 RCSID("$FreeBSD$"); 40 41 #include <openssl/evp.h> 42 43 #include "ssh.h" 44 #include "rsa.h" 45 #include "buffer.h" 46 #include "bufaux.h" 47 #include "xmalloc.h" 48 #include "getput.h" 49 #include "key.h" 50 #include "authfd.h" 51 #include "cipher.h" 52 #include "kex.h" 53 #include "compat.h" 54 #include "log.h" 55 #include "atomicio.h" 56 57 /* helper */ 58 int decode_reply(int type); 59 60 /* macro to check for "agent failure" message */ 61 #define agent_failed(x) \ 62 ((x == SSH_AGENT_FAILURE) || (x == SSH_COM_AGENT2_FAILURE) || \ 63 (x == SSH2_AGENT_FAILURE)) 64 65 /* Returns the number of the authentication fd, or -1 if there is none. */ 66 67 int 68 ssh_get_authentication_socket(void) 69 { 70 const char *authsocket; 71 int sock; 72 struct sockaddr_un sunaddr; 73 74 authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME); 75 if (!authsocket) 76 return -1; 77 78 sunaddr.sun_family = AF_UNIX; 79 strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path)); 80 81 sock = socket(AF_UNIX, SOCK_STREAM, 0); 82 if (sock < 0) 83 return -1; 84 85 /* close on exec */ 86 if (fcntl(sock, F_SETFD, 1) == -1) { 87 close(sock); 88 return -1; 89 } 90 if (connect(sock, (struct sockaddr *) &sunaddr, sizeof sunaddr) < 0) { 91 close(sock); 92 return -1; 93 } 94 return sock; 95 } 96 97 static int 98 ssh_request_reply(AuthenticationConnection *auth, Buffer *request, Buffer *reply) 99 { 100 int l, len; 101 char buf[1024]; 102 103 /* Get the length of the message, and format it in the buffer. */ 104 len = buffer_len(request); 105 PUT_32BIT(buf, len); 106 107 /* Send the length and then the packet to the agent. */ 108 if (atomicio(write, auth->fd, buf, 4) != 4 || 109 atomicio(write, auth->fd, buffer_ptr(request), 110 buffer_len(request)) != buffer_len(request)) { 111 error("Error writing to authentication socket."); 112 return 0; 113 } 114 /* 115 * Wait for response from the agent. First read the length of the 116 * response packet. 117 */ 118 len = 4; 119 while (len > 0) { 120 l = read(auth->fd, buf + 4 - len, len); 121 if (l == -1 && (errno == EAGAIN || errno == EINTR)) 122 continue; 123 if (l <= 0) { 124 error("Error reading response length from authentication socket."); 125 return 0; 126 } 127 len -= l; 128 } 129 130 /* Extract the length, and check it for sanity. */ 131 len = GET_32BIT(buf); 132 if (len > 256 * 1024) 133 fatal("Authentication response too long: %d", len); 134 135 /* Read the rest of the response in to the buffer. */ 136 buffer_clear(reply); 137 while (len > 0) { 138 l = len; 139 if (l > sizeof(buf)) 140 l = sizeof(buf); 141 l = read(auth->fd, buf, l); 142 if (l == -1 && (errno == EAGAIN || errno == EINTR)) 143 continue; 144 if (l <= 0) { 145 error("Error reading response from authentication socket."); 146 return 0; 147 } 148 buffer_append(reply, (char *) buf, l); 149 len -= l; 150 } 151 return 1; 152 } 153 154 /* 155 * Closes the agent socket if it should be closed (depends on how it was 156 * obtained). The argument must have been returned by 157 * ssh_get_authentication_socket(). 158 */ 159 160 void 161 ssh_close_authentication_socket(int sock) 162 { 163 if (getenv(SSH_AUTHSOCKET_ENV_NAME)) 164 close(sock); 165 } 166 167 /* 168 * Opens and connects a private socket for communication with the 169 * authentication agent. Returns the file descriptor (which must be 170 * shut down and closed by the caller when no longer needed). 171 * Returns NULL if an error occurred and the connection could not be 172 * opened. 173 */ 174 175 AuthenticationConnection * 176 ssh_get_authentication_connection(void) 177 { 178 AuthenticationConnection *auth; 179 int sock; 180 181 sock = ssh_get_authentication_socket(); 182 183 /* 184 * Fail if we couldn't obtain a connection. This happens if we 185 * exited due to a timeout. 186 */ 187 if (sock < 0) 188 return NULL; 189 190 auth = xmalloc(sizeof(*auth)); 191 auth->fd = sock; 192 buffer_init(&auth->identities); 193 auth->howmany = 0; 194 195 return auth; 196 } 197 198 /* 199 * Closes the connection to the authentication agent and frees any associated 200 * memory. 201 */ 202 203 void 204 ssh_close_authentication_connection(AuthenticationConnection *auth) 205 { 206 buffer_free(&auth->identities); 207 close(auth->fd); 208 xfree(auth); 209 } 210 211 /* 212 * Returns the first authentication identity held by the agent. 213 */ 214 215 int 216 ssh_get_num_identities(AuthenticationConnection *auth, int version) 217 { 218 int type, code1 = 0, code2 = 0; 219 Buffer request; 220 221 switch (version) { 222 case 1: 223 code1 = SSH_AGENTC_REQUEST_RSA_IDENTITIES; 224 code2 = SSH_AGENT_RSA_IDENTITIES_ANSWER; 225 break; 226 case 2: 227 code1 = SSH2_AGENTC_REQUEST_IDENTITIES; 228 code2 = SSH2_AGENT_IDENTITIES_ANSWER; 229 break; 230 default: 231 return 0; 232 } 233 234 /* 235 * Send a message to the agent requesting for a list of the 236 * identities it can represent. 237 */ 238 buffer_init(&request); 239 buffer_put_char(&request, code1); 240 241 buffer_clear(&auth->identities); 242 if (ssh_request_reply(auth, &request, &auth->identities) == 0) { 243 buffer_free(&request); 244 return 0; 245 } 246 buffer_free(&request); 247 248 /* Get message type, and verify that we got a proper answer. */ 249 type = buffer_get_char(&auth->identities); 250 if (agent_failed(type)) { 251 return 0; 252 } else if (type != code2) { 253 fatal("Bad authentication reply message type: %d", type); 254 } 255 256 /* Get the number of entries in the response and check it for sanity. */ 257 auth->howmany = buffer_get_int(&auth->identities); 258 if (auth->howmany > 1024) 259 fatal("Too many identities in authentication reply: %d", 260 auth->howmany); 261 262 return auth->howmany; 263 } 264 265 Key * 266 ssh_get_first_identity(AuthenticationConnection *auth, char **comment, int version) 267 { 268 /* get number of identities and return the first entry (if any). */ 269 if (ssh_get_num_identities(auth, version) > 0) 270 return ssh_get_next_identity(auth, comment, version); 271 return NULL; 272 } 273 274 Key * 275 ssh_get_next_identity(AuthenticationConnection *auth, char **comment, int version) 276 { 277 u_int bits; 278 u_char *blob; 279 u_int blen; 280 Key *key = NULL; 281 282 /* Return failure if no more entries. */ 283 if (auth->howmany <= 0) 284 return NULL; 285 286 /* 287 * Get the next entry from the packet. These will abort with a fatal 288 * error if the packet is too short or contains corrupt data. 289 */ 290 switch (version) { 291 case 1: 292 key = key_new(KEY_RSA1); 293 bits = buffer_get_int(&auth->identities); 294 buffer_get_bignum(&auth->identities, key->rsa->e); 295 buffer_get_bignum(&auth->identities, key->rsa->n); 296 *comment = buffer_get_string(&auth->identities, NULL); 297 if (bits != BN_num_bits(key->rsa->n)) 298 log("Warning: identity keysize mismatch: actual %d, announced %u", 299 BN_num_bits(key->rsa->n), bits); 300 break; 301 case 2: 302 blob = buffer_get_string(&auth->identities, &blen); 303 *comment = buffer_get_string(&auth->identities, NULL); 304 key = key_from_blob(blob, blen); 305 xfree(blob); 306 break; 307 default: 308 return NULL; 309 break; 310 } 311 /* Decrement the number of remaining entries. */ 312 auth->howmany--; 313 return key; 314 } 315 316 /* 317 * Generates a random challenge, sends it to the agent, and waits for 318 * response from the agent. Returns true (non-zero) if the agent gave the 319 * correct answer, zero otherwise. Response type selects the style of 320 * response desired, with 0 corresponding to protocol version 1.0 (no longer 321 * supported) and 1 corresponding to protocol version 1.1. 322 */ 323 324 int 325 ssh_decrypt_challenge(AuthenticationConnection *auth, 326 Key* key, BIGNUM *challenge, 327 u_char session_id[16], 328 u_int response_type, 329 u_char response[16]) 330 { 331 Buffer buffer; 332 int success = 0; 333 int i; 334 int type; 335 336 if (key->type != KEY_RSA1) 337 return 0; 338 if (response_type == 0) { 339 log("Compatibility with ssh protocol version 1.0 no longer supported."); 340 return 0; 341 } 342 buffer_init(&buffer); 343 buffer_put_char(&buffer, SSH_AGENTC_RSA_CHALLENGE); 344 buffer_put_int(&buffer, BN_num_bits(key->rsa->n)); 345 buffer_put_bignum(&buffer, key->rsa->e); 346 buffer_put_bignum(&buffer, key->rsa->n); 347 buffer_put_bignum(&buffer, challenge); 348 buffer_append(&buffer, session_id, 16); 349 buffer_put_int(&buffer, response_type); 350 351 if (ssh_request_reply(auth, &buffer, &buffer) == 0) { 352 buffer_free(&buffer); 353 return 0; 354 } 355 type = buffer_get_char(&buffer); 356 357 if (agent_failed(type)) { 358 log("Agent admitted failure to authenticate using the key."); 359 } else if (type != SSH_AGENT_RSA_RESPONSE) { 360 fatal("Bad authentication response: %d", type); 361 } else { 362 success = 1; 363 /* 364 * Get the response from the packet. This will abort with a 365 * fatal error if the packet is corrupt. 366 */ 367 for (i = 0; i < 16; i++) 368 response[i] = buffer_get_char(&buffer); 369 } 370 buffer_free(&buffer); 371 return success; 372 } 373 374 /* ask agent to sign data, returns -1 on error, 0 on success */ 375 int 376 ssh_agent_sign(AuthenticationConnection *auth, 377 Key *key, 378 u_char **sigp, u_int *lenp, 379 u_char *data, u_int datalen) 380 { 381 extern int datafellows; 382 Buffer msg; 383 u_char *blob; 384 u_int blen; 385 int type, flags = 0; 386 int ret = -1; 387 388 if (key_to_blob(key, &blob, &blen) == 0) 389 return -1; 390 391 if (datafellows & SSH_BUG_SIGBLOB) 392 flags = SSH_AGENT_OLD_SIGNATURE; 393 394 buffer_init(&msg); 395 buffer_put_char(&msg, SSH2_AGENTC_SIGN_REQUEST); 396 buffer_put_string(&msg, blob, blen); 397 buffer_put_string(&msg, data, datalen); 398 buffer_put_int(&msg, flags); 399 xfree(blob); 400 401 if (ssh_request_reply(auth, &msg, &msg) == 0) { 402 buffer_free(&msg); 403 return -1; 404 } 405 type = buffer_get_char(&msg); 406 if (agent_failed(type)) { 407 log("Agent admitted failure to sign using the key."); 408 } else if (type != SSH2_AGENT_SIGN_RESPONSE) { 409 fatal("Bad authentication response: %d", type); 410 } else { 411 ret = 0; 412 *sigp = buffer_get_string(&msg, lenp); 413 } 414 buffer_free(&msg); 415 return ret; 416 } 417 418 /* Encode key for a message to the agent. */ 419 420 static void 421 ssh_encode_identity_rsa1(Buffer *b, RSA *key, const char *comment) 422 { 423 buffer_clear(b); 424 buffer_put_char(b, SSH_AGENTC_ADD_RSA_IDENTITY); 425 buffer_put_int(b, BN_num_bits(key->n)); 426 buffer_put_bignum(b, key->n); 427 buffer_put_bignum(b, key->e); 428 buffer_put_bignum(b, key->d); 429 /* To keep within the protocol: p < q for ssh. in SSL p > q */ 430 buffer_put_bignum(b, key->iqmp); /* ssh key->u */ 431 buffer_put_bignum(b, key->q); /* ssh key->p, SSL key->q */ 432 buffer_put_bignum(b, key->p); /* ssh key->q, SSL key->p */ 433 buffer_put_cstring(b, comment); 434 } 435 436 static void 437 ssh_encode_identity_ssh2(Buffer *b, Key *key, const char *comment) 438 { 439 buffer_clear(b); 440 buffer_put_char(b, SSH2_AGENTC_ADD_IDENTITY); 441 buffer_put_cstring(b, key_ssh_name(key)); 442 switch (key->type) { 443 case KEY_RSA: 444 buffer_put_bignum2(b, key->rsa->n); 445 buffer_put_bignum2(b, key->rsa->e); 446 buffer_put_bignum2(b, key->rsa->d); 447 buffer_put_bignum2(b, key->rsa->iqmp); 448 buffer_put_bignum2(b, key->rsa->p); 449 buffer_put_bignum2(b, key->rsa->q); 450 break; 451 case KEY_DSA: 452 buffer_put_bignum2(b, key->dsa->p); 453 buffer_put_bignum2(b, key->dsa->q); 454 buffer_put_bignum2(b, key->dsa->g); 455 buffer_put_bignum2(b, key->dsa->pub_key); 456 buffer_put_bignum2(b, key->dsa->priv_key); 457 break; 458 } 459 buffer_put_cstring(b, comment); 460 } 461 462 /* 463 * Adds an identity to the authentication server. This call is not meant to 464 * be used by normal applications. 465 */ 466 467 int 468 ssh_add_identity(AuthenticationConnection *auth, Key *key, const char *comment) 469 { 470 Buffer msg; 471 int type; 472 473 buffer_init(&msg); 474 475 switch (key->type) { 476 case KEY_RSA1: 477 ssh_encode_identity_rsa1(&msg, key->rsa, comment); 478 break; 479 case KEY_RSA: 480 case KEY_DSA: 481 ssh_encode_identity_ssh2(&msg, key, comment); 482 break; 483 default: 484 buffer_free(&msg); 485 return 0; 486 break; 487 } 488 if (ssh_request_reply(auth, &msg, &msg) == 0) { 489 buffer_free(&msg); 490 return 0; 491 } 492 type = buffer_get_char(&msg); 493 buffer_free(&msg); 494 return decode_reply(type); 495 } 496 497 /* 498 * Removes an identity from the authentication server. This call is not 499 * meant to be used by normal applications. 500 */ 501 502 int 503 ssh_remove_identity(AuthenticationConnection *auth, Key *key) 504 { 505 Buffer msg; 506 int type; 507 u_char *blob; 508 u_int blen; 509 510 buffer_init(&msg); 511 512 if (key->type == KEY_RSA1) { 513 buffer_put_char(&msg, SSH_AGENTC_REMOVE_RSA_IDENTITY); 514 buffer_put_int(&msg, BN_num_bits(key->rsa->n)); 515 buffer_put_bignum(&msg, key->rsa->e); 516 buffer_put_bignum(&msg, key->rsa->n); 517 } else if (key->type == KEY_DSA || key->type == KEY_RSA) { 518 key_to_blob(key, &blob, &blen); 519 buffer_put_char(&msg, SSH2_AGENTC_REMOVE_IDENTITY); 520 buffer_put_string(&msg, blob, blen); 521 xfree(blob); 522 } else { 523 buffer_free(&msg); 524 return 0; 525 } 526 if (ssh_request_reply(auth, &msg, &msg) == 0) { 527 buffer_free(&msg); 528 return 0; 529 } 530 type = buffer_get_char(&msg); 531 buffer_free(&msg); 532 return decode_reply(type); 533 } 534 535 int 536 ssh_update_card(AuthenticationConnection *auth, int add, const char *reader_id) 537 { 538 Buffer msg; 539 int type; 540 541 buffer_init(&msg); 542 buffer_put_char(&msg, add ? SSH_AGENTC_ADD_SMARTCARD_KEY : 543 SSH_AGENTC_REMOVE_SMARTCARD_KEY); 544 buffer_put_cstring(&msg, reader_id); 545 if (ssh_request_reply(auth, &msg, &msg) == 0) { 546 buffer_free(&msg); 547 return 0; 548 } 549 type = buffer_get_char(&msg); 550 buffer_free(&msg); 551 return decode_reply(type); 552 } 553 554 /* 555 * Removes all identities from the agent. This call is not meant to be used 556 * by normal applications. 557 */ 558 559 int 560 ssh_remove_all_identities(AuthenticationConnection *auth, int version) 561 { 562 Buffer msg; 563 int type; 564 int code = (version==1) ? 565 SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES : 566 SSH2_AGENTC_REMOVE_ALL_IDENTITIES; 567 568 buffer_init(&msg); 569 buffer_put_char(&msg, code); 570 571 if (ssh_request_reply(auth, &msg, &msg) == 0) { 572 buffer_free(&msg); 573 return 0; 574 } 575 type = buffer_get_char(&msg); 576 buffer_free(&msg); 577 return decode_reply(type); 578 } 579 580 int 581 decode_reply(int type) 582 { 583 switch (type) { 584 case SSH_AGENT_FAILURE: 585 case SSH_COM_AGENT2_FAILURE: 586 case SSH2_AGENT_FAILURE: 587 log("SSH_AGENT_FAILURE"); 588 return 0; 589 case SSH_AGENT_SUCCESS: 590 return 1; 591 default: 592 fatal("Bad response from authentication agent: %d", type); 593 } 594 /* NOTREACHED */ 595 return 0; 596 } 597