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 1.39 2001/04/05 10:42:48 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 64 /* Returns the number of the authentication fd, or -1 if there is none. */ 65 66 int 67 ssh_get_authentication_socket(void) 68 { 69 const char *authsocket; 70 int sock, len; 71 struct sockaddr_un sunaddr; 72 73 authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME); 74 if (!authsocket) 75 return -1; 76 77 sunaddr.sun_family = AF_UNIX; 78 strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path)); 79 len = SUN_LEN(&sunaddr)+1; 80 sunaddr.sun_len = len; 81 82 sock = socket(AF_UNIX, SOCK_STREAM, 0); 83 if (sock < 0) 84 return -1; 85 86 /* close on exec */ 87 if (fcntl(sock, F_SETFD, 1) == -1) { 88 close(sock); 89 return -1; 90 } 91 if (connect(sock, (struct sockaddr *) & sunaddr, len) < 0) { 92 close(sock); 93 return -1; 94 } 95 return sock; 96 } 97 98 int 99 ssh_request_reply(AuthenticationConnection *auth, Buffer *request, Buffer *reply) 100 { 101 int l, len; 102 char buf[1024]; 103 104 /* Get the length of the message, and format it in the buffer. */ 105 len = buffer_len(request); 106 PUT_32BIT(buf, len); 107 108 /* Send the length and then the packet to the agent. */ 109 if (atomicio(write, auth->fd, buf, 4) != 4 || 110 atomicio(write, auth->fd, buffer_ptr(request), 111 buffer_len(request)) != buffer_len(request)) { 112 error("Error writing to authentication socket."); 113 return 0; 114 } 115 /* 116 * Wait for response from the agent. First read the length of the 117 * response packet. 118 */ 119 len = 4; 120 while (len > 0) { 121 l = read(auth->fd, buf + 4 - len, len); 122 if (l == -1 && (errno == EAGAIN || errno == EINTR)) 123 continue; 124 if (l <= 0) { 125 error("Error reading response length from authentication socket."); 126 return 0; 127 } 128 len -= l; 129 } 130 131 /* Extract the length, and check it for sanity. */ 132 len = GET_32BIT(buf); 133 if (len > 256 * 1024) 134 fatal("Authentication response too long: %d", len); 135 136 /* Read the rest of the response in to the buffer. */ 137 buffer_clear(reply); 138 while (len > 0) { 139 l = len; 140 if (l > sizeof(buf)) 141 l = sizeof(buf); 142 l = read(auth->fd, buf, l); 143 if (l == -1 && (errno == EAGAIN || errno == EINTR)) 144 continue; 145 if (l <= 0) { 146 error("Error reading response from authentication socket."); 147 return 0; 148 } 149 buffer_append(reply, (char *) buf, l); 150 len -= l; 151 } 152 return 1; 153 } 154 155 /* 156 * Closes the agent socket if it should be closed (depends on how it was 157 * obtained). The argument must have been returned by 158 * ssh_get_authentication_socket(). 159 */ 160 161 void 162 ssh_close_authentication_socket(int sock) 163 { 164 if (getenv(SSH_AUTHSOCKET_ENV_NAME)) 165 close(sock); 166 } 167 168 /* 169 * Opens and connects a private socket for communication with the 170 * authentication agent. Returns the file descriptor (which must be 171 * shut down and closed by the caller when no longer needed). 172 * Returns NULL if an error occurred and the connection could not be 173 * opened. 174 */ 175 176 AuthenticationConnection * 177 ssh_get_authentication_connection(void) 178 { 179 AuthenticationConnection *auth; 180 int sock; 181 182 sock = ssh_get_authentication_socket(); 183 184 /* 185 * Fail if we couldn't obtain a connection. This happens if we 186 * exited due to a timeout. 187 */ 188 if (sock < 0) 189 return NULL; 190 191 auth = xmalloc(sizeof(*auth)); 192 auth->fd = sock; 193 buffer_init(&auth->identities); 194 auth->howmany = 0; 195 196 return auth; 197 } 198 199 /* 200 * Closes the connection to the authentication agent and frees any associated 201 * memory. 202 */ 203 204 void 205 ssh_close_authentication_connection(AuthenticationConnection *auth) 206 { 207 buffer_free(&auth->identities); 208 close(auth->fd); 209 xfree(auth); 210 } 211 212 /* 213 * Returns the first authentication identity held by the agent. 214 */ 215 216 int 217 ssh_get_num_identities(AuthenticationConnection *auth, int version) 218 { 219 int type, code1 = 0, code2 = 0; 220 Buffer request; 221 222 switch(version){ 223 case 1: 224 code1 = SSH_AGENTC_REQUEST_RSA_IDENTITIES; 225 code2 = SSH_AGENT_RSA_IDENTITIES_ANSWER; 226 break; 227 case 2: 228 code1 = SSH2_AGENTC_REQUEST_IDENTITIES; 229 code2 = SSH2_AGENT_IDENTITIES_ANSWER; 230 break; 231 default: 232 return 0; 233 } 234 235 /* 236 * Send a message to the agent requesting for a list of the 237 * identities it can represent. 238 */ 239 buffer_init(&request); 240 buffer_put_char(&request, code1); 241 242 buffer_clear(&auth->identities); 243 if (ssh_request_reply(auth, &request, &auth->identities) == 0) { 244 buffer_free(&request); 245 return 0; 246 } 247 buffer_free(&request); 248 249 /* Get message type, and verify that we got a proper answer. */ 250 type = buffer_get_char(&auth->identities); 251 if (agent_failed(type)) { 252 return 0; 253 } else if (type != code2) { 254 fatal("Bad authentication reply message type: %d", type); 255 } 256 257 /* Get the number of entries in the response and check it for sanity. */ 258 auth->howmany = buffer_get_int(&auth->identities); 259 if (auth->howmany > 1024) 260 fatal("Too many identities in authentication reply: %d", 261 auth->howmany); 262 263 return auth->howmany; 264 } 265 266 Key * 267 ssh_get_first_identity(AuthenticationConnection *auth, char **comment, int version) 268 { 269 /* get number of identities and return the first entry (if any). */ 270 if (ssh_get_num_identities(auth, version) > 0) 271 return ssh_get_next_identity(auth, comment, version); 272 return NULL; 273 } 274 275 Key * 276 ssh_get_next_identity(AuthenticationConnection *auth, char **comment, int version) 277 { 278 u_int bits; 279 u_char *blob; 280 u_int blen; 281 Key *key = NULL; 282 283 /* Return failure if no more entries. */ 284 if (auth->howmany <= 0) 285 return NULL; 286 287 /* 288 * Get the next entry from the packet. These will abort with a fatal 289 * error if the packet is too short or contains corrupt data. 290 */ 291 switch(version){ 292 case 1: 293 key = key_new(KEY_RSA1); 294 bits = buffer_get_int(&auth->identities); 295 buffer_get_bignum(&auth->identities, key->rsa->e); 296 buffer_get_bignum(&auth->identities, key->rsa->n); 297 *comment = buffer_get_string(&auth->identities, NULL); 298 if (bits != BN_num_bits(key->rsa->n)) 299 log("Warning: identity keysize mismatch: actual %d, announced %u", 300 BN_num_bits(key->rsa->n), bits); 301 break; 302 case 2: 303 blob = buffer_get_string(&auth->identities, &blen); 304 *comment = buffer_get_string(&auth->identities, NULL); 305 key = key_from_blob(blob, blen); 306 xfree(blob); 307 break; 308 default: 309 return NULL; 310 break; 311 } 312 /* Decrement the number of remaining entries. */ 313 auth->howmany--; 314 return key; 315 } 316 317 /* 318 * Generates a random challenge, sends it to the agent, and waits for 319 * response from the agent. Returns true (non-zero) if the agent gave the 320 * correct answer, zero otherwise. Response type selects the style of 321 * response desired, with 0 corresponding to protocol version 1.0 (no longer 322 * supported) and 1 corresponding to protocol version 1.1. 323 */ 324 325 int 326 ssh_decrypt_challenge(AuthenticationConnection *auth, 327 Key* key, BIGNUM *challenge, 328 u_char session_id[16], 329 u_int response_type, 330 u_char response[16]) 331 { 332 Buffer buffer; 333 int success = 0; 334 int i; 335 int type; 336 337 if (key->type != KEY_RSA1) 338 return 0; 339 if (response_type == 0) { 340 log("Compatibility with ssh protocol version 1.0 no longer supported."); 341 return 0; 342 } 343 buffer_init(&buffer); 344 buffer_put_char(&buffer, SSH_AGENTC_RSA_CHALLENGE); 345 buffer_put_int(&buffer, BN_num_bits(key->rsa->n)); 346 buffer_put_bignum(&buffer, key->rsa->e); 347 buffer_put_bignum(&buffer, key->rsa->n); 348 buffer_put_bignum(&buffer, challenge); 349 buffer_append(&buffer, (char *) session_id, 16); 350 buffer_put_int(&buffer, response_type); 351 352 if (ssh_request_reply(auth, &buffer, &buffer) == 0) { 353 buffer_free(&buffer); 354 return 0; 355 } 356 type = buffer_get_char(&buffer); 357 358 if (agent_failed(type)) { 359 log("Agent admitted failure to authenticate using the key."); 360 } else if (type != SSH_AGENT_RSA_RESPONSE) { 361 fatal("Bad authentication response: %d", type); 362 } else { 363 success = 1; 364 /* 365 * Get the response from the packet. This will abort with a 366 * fatal error if the packet is corrupt. 367 */ 368 for (i = 0; i < 16; i++) 369 response[i] = buffer_get_char(&buffer); 370 } 371 buffer_free(&buffer); 372 return success; 373 } 374 375 /* ask agent to sign data, returns -1 on error, 0 on success */ 376 int 377 ssh_agent_sign(AuthenticationConnection *auth, 378 Key *key, 379 u_char **sigp, int *lenp, 380 u_char *data, int datalen) 381 { 382 extern int datafellows; 383 Buffer msg; 384 u_char *blob; 385 u_int blen; 386 int type, flags = 0; 387 int ret = -1; 388 389 if (key_to_blob(key, &blob, &blen) == 0) 390 return -1; 391 392 if (datafellows & SSH_BUG_SIGBLOB) 393 flags = SSH_AGENT_OLD_SIGNATURE; 394 395 buffer_init(&msg); 396 buffer_put_char(&msg, SSH2_AGENTC_SIGN_REQUEST); 397 buffer_put_string(&msg, blob, blen); 398 buffer_put_string(&msg, data, datalen); 399 buffer_put_int(&msg, flags); 400 xfree(blob); 401 402 if (ssh_request_reply(auth, &msg, &msg) == 0) { 403 buffer_free(&msg); 404 return -1; 405 } 406 type = buffer_get_char(&msg); 407 if (agent_failed(type)) { 408 log("Agent admitted failure to sign using the key."); 409 } else if (type != SSH2_AGENT_SIGN_RESPONSE) { 410 fatal("Bad authentication response: %d", type); 411 } else { 412 ret = 0; 413 *sigp = buffer_get_string(&msg, lenp); 414 } 415 buffer_free(&msg); 416 return ret; 417 } 418 419 /* Encode key for a message to the agent. */ 420 421 void 422 ssh_encode_identity_rsa1(Buffer *b, RSA *key, const char *comment) 423 { 424 buffer_clear(b); 425 buffer_put_char(b, SSH_AGENTC_ADD_RSA_IDENTITY); 426 buffer_put_int(b, BN_num_bits(key->n)); 427 buffer_put_bignum(b, key->n); 428 buffer_put_bignum(b, key->e); 429 buffer_put_bignum(b, key->d); 430 /* To keep within the protocol: p < q for ssh. in SSL p > q */ 431 buffer_put_bignum(b, key->iqmp); /* ssh key->u */ 432 buffer_put_bignum(b, key->q); /* ssh key->p, SSL key->q */ 433 buffer_put_bignum(b, key->p); /* ssh key->q, SSL key->p */ 434 buffer_put_string(b, comment, strlen(comment)); 435 } 436 437 void 438 ssh_encode_identity_ssh2(Buffer *b, Key *key, const char *comment) 439 { 440 buffer_clear(b); 441 buffer_put_char(b, SSH2_AGENTC_ADD_IDENTITY); 442 buffer_put_cstring(b, key_ssh_name(key)); 443 switch(key->type){ 444 case KEY_RSA: 445 buffer_put_bignum2(b, key->rsa->n); 446 buffer_put_bignum2(b, key->rsa->e); 447 buffer_put_bignum2(b, key->rsa->d); 448 buffer_put_bignum2(b, key->rsa->iqmp); 449 buffer_put_bignum2(b, key->rsa->p); 450 buffer_put_bignum2(b, key->rsa->q); 451 break; 452 case KEY_DSA: 453 buffer_put_bignum2(b, key->dsa->p); 454 buffer_put_bignum2(b, key->dsa->q); 455 buffer_put_bignum2(b, key->dsa->g); 456 buffer_put_bignum2(b, key->dsa->pub_key); 457 buffer_put_bignum2(b, key->dsa->priv_key); 458 break; 459 } 460 buffer_put_cstring(b, comment); 461 } 462 463 /* 464 * Adds an identity to the authentication server. This call is not meant to 465 * be used by normal applications. 466 */ 467 468 int 469 ssh_add_identity(AuthenticationConnection *auth, Key *key, const char *comment) 470 { 471 Buffer msg; 472 int type; 473 474 buffer_init(&msg); 475 476 switch (key->type) { 477 case KEY_RSA1: 478 ssh_encode_identity_rsa1(&msg, key->rsa, comment); 479 break; 480 case KEY_RSA: 481 case KEY_DSA: 482 ssh_encode_identity_ssh2(&msg, key, comment); 483 break; 484 default: 485 buffer_free(&msg); 486 return 0; 487 break; 488 } 489 if (ssh_request_reply(auth, &msg, &msg) == 0) { 490 buffer_free(&msg); 491 return 0; 492 } 493 type = buffer_get_char(&msg); 494 buffer_free(&msg); 495 return decode_reply(type); 496 } 497 498 /* 499 * Removes an identity from the authentication server. This call is not 500 * meant to be used by normal applications. 501 */ 502 503 int 504 ssh_remove_identity(AuthenticationConnection *auth, Key *key) 505 { 506 Buffer msg; 507 int type; 508 u_char *blob; 509 u_int blen; 510 511 buffer_init(&msg); 512 513 if (key->type == KEY_RSA1) { 514 buffer_put_char(&msg, SSH_AGENTC_REMOVE_RSA_IDENTITY); 515 buffer_put_int(&msg, BN_num_bits(key->rsa->n)); 516 buffer_put_bignum(&msg, key->rsa->e); 517 buffer_put_bignum(&msg, key->rsa->n); 518 } else if (key->type == KEY_DSA || key->type == KEY_RSA) { 519 key_to_blob(key, &blob, &blen); 520 buffer_put_char(&msg, SSH2_AGENTC_REMOVE_IDENTITY); 521 buffer_put_string(&msg, blob, blen); 522 xfree(blob); 523 } else { 524 buffer_free(&msg); 525 return 0; 526 } 527 if (ssh_request_reply(auth, &msg, &msg) == 0) { 528 buffer_free(&msg); 529 return 0; 530 } 531 type = buffer_get_char(&msg); 532 buffer_free(&msg); 533 return decode_reply(type); 534 } 535 536 /* 537 * Removes all identities from the agent. This call is not meant to be used 538 * by normal applications. 539 */ 540 541 int 542 ssh_remove_all_identities(AuthenticationConnection *auth, int version) 543 { 544 Buffer msg; 545 int type; 546 int code = (version==1) ? 547 SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES : 548 SSH2_AGENTC_REMOVE_ALL_IDENTITIES; 549 550 buffer_init(&msg); 551 buffer_put_char(&msg, code); 552 553 if (ssh_request_reply(auth, &msg, &msg) == 0) { 554 buffer_free(&msg); 555 return 0; 556 } 557 type = buffer_get_char(&msg); 558 buffer_free(&msg); 559 return decode_reply(type); 560 } 561 562 int 563 decode_reply(int type) 564 { 565 switch (type) { 566 case SSH_AGENT_FAILURE: 567 case SSH_COM_AGENT2_FAILURE: 568 log("SSH_AGENT_FAILURE"); 569 return 0; 570 case SSH_AGENT_SUCCESS: 571 return 1; 572 default: 573 fatal("Bad response from authentication agent: %d", type); 574 } 575 /* NOTREACHED */ 576 return 0; 577 } 578