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 1.63 2003/11/21 11:57:03 djm 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, 1) == -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; 118 u_int len; 119 char buf[1024]; 120 121 /* Get the length of the message, and format it in the buffer. */ 122 len = buffer_len(request); 123 PUT_32BIT(buf, len); 124 125 /* Send the length and then the packet to the agent. */ 126 if (atomicio(vwrite, auth->fd, buf, 4) != 4 || 127 atomicio(vwrite, auth->fd, buffer_ptr(request), 128 buffer_len(request)) != buffer_len(request)) { 129 error("Error writing to authentication socket."); 130 return 0; 131 } 132 /* 133 * Wait for response from the agent. First read the length of the 134 * response packet. 135 */ 136 len = 4; 137 while (len > 0) { 138 l = read(auth->fd, buf + 4 - len, len); 139 if (l == -1 && (errno == EAGAIN || errno == EINTR)) 140 continue; 141 if (l <= 0) { 142 error("Error reading response length from authentication socket."); 143 return 0; 144 } 145 len -= l; 146 } 147 148 /* Extract the length, and check it for sanity. */ 149 len = GET_32BIT(buf); 150 if (len > 256 * 1024) 151 fatal("Authentication response too long: %u", len); 152 153 /* Read the rest of the response in to the buffer. */ 154 buffer_clear(reply); 155 while (len > 0) { 156 l = len; 157 if (l > sizeof(buf)) 158 l = sizeof(buf); 159 l = read(auth->fd, buf, l); 160 if (l == -1 && (errno == EAGAIN || errno == EINTR)) 161 continue; 162 if (l <= 0) { 163 error("Error reading response from authentication socket."); 164 return 0; 165 } 166 buffer_append(reply, buf, l); 167 len -= l; 168 } 169 return 1; 170 } 171 172 /* 173 * Closes the agent socket if it should be closed (depends on how it was 174 * obtained). The argument must have been returned by 175 * ssh_get_authentication_socket(). 176 */ 177 178 void 179 ssh_close_authentication_socket(int sock) 180 { 181 if (getenv(SSH_AUTHSOCKET_ENV_NAME)) 182 close(sock); 183 } 184 185 /* 186 * Opens and connects a private socket for communication with the 187 * authentication agent. Returns the file descriptor (which must be 188 * shut down and closed by the caller when no longer needed). 189 * Returns NULL if an error occurred and the connection could not be 190 * opened. 191 */ 192 193 AuthenticationConnection * 194 ssh_get_authentication_connection(void) 195 { 196 AuthenticationConnection *auth; 197 int sock; 198 199 sock = ssh_get_authentication_socket(); 200 201 /* 202 * Fail if we couldn't obtain a connection. This happens if we 203 * exited due to a timeout. 204 */ 205 if (sock < 0) 206 return NULL; 207 208 auth = xmalloc(sizeof(*auth)); 209 auth->fd = sock; 210 buffer_init(&auth->identities); 211 auth->howmany = 0; 212 213 return auth; 214 } 215 216 /* 217 * Closes the connection to the authentication agent and frees any associated 218 * memory. 219 */ 220 221 void 222 ssh_close_authentication_connection(AuthenticationConnection *auth) 223 { 224 buffer_free(&auth->identities); 225 close(auth->fd); 226 xfree(auth); 227 } 228 229 /* Lock/unlock agent */ 230 int 231 ssh_lock_agent(AuthenticationConnection *auth, int lock, const char *password) 232 { 233 int type; 234 Buffer msg; 235 236 buffer_init(&msg); 237 buffer_put_char(&msg, lock ? SSH_AGENTC_LOCK : SSH_AGENTC_UNLOCK); 238 buffer_put_cstring(&msg, password); 239 240 if (ssh_request_reply(auth, &msg, &msg) == 0) { 241 buffer_free(&msg); 242 return 0; 243 } 244 type = buffer_get_char(&msg); 245 buffer_free(&msg); 246 return decode_reply(type); 247 } 248 249 /* 250 * Returns the first authentication identity held by the agent. 251 */ 252 253 int 254 ssh_get_num_identities(AuthenticationConnection *auth, int version) 255 { 256 int type, code1 = 0, code2 = 0; 257 Buffer request; 258 259 switch (version) { 260 case 1: 261 code1 = SSH_AGENTC_REQUEST_RSA_IDENTITIES; 262 code2 = SSH_AGENT_RSA_IDENTITIES_ANSWER; 263 break; 264 case 2: 265 code1 = SSH2_AGENTC_REQUEST_IDENTITIES; 266 code2 = SSH2_AGENT_IDENTITIES_ANSWER; 267 break; 268 default: 269 return 0; 270 } 271 272 /* 273 * Send a message to the agent requesting for a list of the 274 * identities it can represent. 275 */ 276 buffer_init(&request); 277 buffer_put_char(&request, code1); 278 279 buffer_clear(&auth->identities); 280 if (ssh_request_reply(auth, &request, &auth->identities) == 0) { 281 buffer_free(&request); 282 return 0; 283 } 284 buffer_free(&request); 285 286 /* Get message type, and verify that we got a proper answer. */ 287 type = buffer_get_char(&auth->identities); 288 if (agent_failed(type)) { 289 return 0; 290 } else if (type != code2) { 291 fatal("Bad authentication reply message type: %d", type); 292 } 293 294 /* Get the number of entries in the response and check it for sanity. */ 295 auth->howmany = buffer_get_int(&auth->identities); 296 if ((u_int)auth->howmany > 1024) 297 fatal("Too many identities in authentication reply: %d", 298 auth->howmany); 299 300 return auth->howmany; 301 } 302 303 Key * 304 ssh_get_first_identity(AuthenticationConnection *auth, char **comment, int version) 305 { 306 /* get number of identities and return the first entry (if any). */ 307 if (ssh_get_num_identities(auth, version) > 0) 308 return ssh_get_next_identity(auth, comment, version); 309 return NULL; 310 } 311 312 Key * 313 ssh_get_next_identity(AuthenticationConnection *auth, char **comment, int version) 314 { 315 u_int bits; 316 u_char *blob; 317 u_int blen; 318 Key *key = NULL; 319 320 /* Return failure if no more entries. */ 321 if (auth->howmany <= 0) 322 return NULL; 323 324 /* 325 * Get the next entry from the packet. These will abort with a fatal 326 * error if the packet is too short or contains corrupt data. 327 */ 328 switch (version) { 329 case 1: 330 key = key_new(KEY_RSA1); 331 bits = buffer_get_int(&auth->identities); 332 buffer_get_bignum(&auth->identities, key->rsa->e); 333 buffer_get_bignum(&auth->identities, key->rsa->n); 334 *comment = buffer_get_string(&auth->identities, NULL); 335 if (bits != BN_num_bits(key->rsa->n)) 336 logit("Warning: identity keysize mismatch: actual %d, announced %u", 337 BN_num_bits(key->rsa->n), bits); 338 break; 339 case 2: 340 blob = buffer_get_string(&auth->identities, &blen); 341 *comment = buffer_get_string(&auth->identities, NULL); 342 key = key_from_blob(blob, blen); 343 xfree(blob); 344 break; 345 default: 346 return NULL; 347 break; 348 } 349 /* Decrement the number of remaining entries. */ 350 auth->howmany--; 351 return key; 352 } 353 354 /* 355 * Generates a random challenge, sends it to the agent, and waits for 356 * response from the agent. Returns true (non-zero) if the agent gave the 357 * correct answer, zero otherwise. Response type selects the style of 358 * response desired, with 0 corresponding to protocol version 1.0 (no longer 359 * supported) and 1 corresponding to protocol version 1.1. 360 */ 361 362 int 363 ssh_decrypt_challenge(AuthenticationConnection *auth, 364 Key* key, BIGNUM *challenge, 365 u_char session_id[16], 366 u_int response_type, 367 u_char response[16]) 368 { 369 Buffer buffer; 370 int success = 0; 371 int i; 372 int type; 373 374 if (key->type != KEY_RSA1) 375 return 0; 376 if (response_type == 0) { 377 logit("Compatibility with ssh protocol version 1.0 no longer supported."); 378 return 0; 379 } 380 buffer_init(&buffer); 381 buffer_put_char(&buffer, SSH_AGENTC_RSA_CHALLENGE); 382 buffer_put_int(&buffer, BN_num_bits(key->rsa->n)); 383 buffer_put_bignum(&buffer, key->rsa->e); 384 buffer_put_bignum(&buffer, key->rsa->n); 385 buffer_put_bignum(&buffer, challenge); 386 buffer_append(&buffer, session_id, 16); 387 buffer_put_int(&buffer, response_type); 388 389 if (ssh_request_reply(auth, &buffer, &buffer) == 0) { 390 buffer_free(&buffer); 391 return 0; 392 } 393 type = buffer_get_char(&buffer); 394 395 if (agent_failed(type)) { 396 logit("Agent admitted failure to authenticate using the key."); 397 } else if (type != SSH_AGENT_RSA_RESPONSE) { 398 fatal("Bad authentication response: %d", type); 399 } else { 400 success = 1; 401 /* 402 * Get the response from the packet. This will abort with a 403 * fatal error if the packet is corrupt. 404 */ 405 for (i = 0; i < 16; i++) 406 response[i] = buffer_get_char(&buffer); 407 } 408 buffer_free(&buffer); 409 return success; 410 } 411 412 /* ask agent to sign data, returns -1 on error, 0 on success */ 413 int 414 ssh_agent_sign(AuthenticationConnection *auth, 415 Key *key, 416 u_char **sigp, u_int *lenp, 417 u_char *data, u_int datalen) 418 { 419 extern int datafellows; 420 Buffer msg; 421 u_char *blob; 422 u_int blen; 423 int type, flags = 0; 424 int ret = -1; 425 426 if (key_to_blob(key, &blob, &blen) == 0) 427 return -1; 428 429 if (datafellows & SSH_BUG_SIGBLOB) 430 flags = SSH_AGENT_OLD_SIGNATURE; 431 432 buffer_init(&msg); 433 buffer_put_char(&msg, SSH2_AGENTC_SIGN_REQUEST); 434 buffer_put_string(&msg, blob, blen); 435 buffer_put_string(&msg, data, datalen); 436 buffer_put_int(&msg, flags); 437 xfree(blob); 438 439 if (ssh_request_reply(auth, &msg, &msg) == 0) { 440 buffer_free(&msg); 441 return -1; 442 } 443 type = buffer_get_char(&msg); 444 if (agent_failed(type)) { 445 logit("Agent admitted failure to sign using the key."); 446 } else if (type != SSH2_AGENT_SIGN_RESPONSE) { 447 fatal("Bad authentication response: %d", type); 448 } else { 449 ret = 0; 450 *sigp = buffer_get_string(&msg, lenp); 451 } 452 buffer_free(&msg); 453 return ret; 454 } 455 456 /* Encode key for a message to the agent. */ 457 458 static void 459 ssh_encode_identity_rsa1(Buffer *b, RSA *key, const char *comment) 460 { 461 buffer_put_int(b, BN_num_bits(key->n)); 462 buffer_put_bignum(b, key->n); 463 buffer_put_bignum(b, key->e); 464 buffer_put_bignum(b, key->d); 465 /* To keep within the protocol: p < q for ssh. in SSL p > q */ 466 buffer_put_bignum(b, key->iqmp); /* ssh key->u */ 467 buffer_put_bignum(b, key->q); /* ssh key->p, SSL key->q */ 468 buffer_put_bignum(b, key->p); /* ssh key->q, SSL key->p */ 469 buffer_put_cstring(b, comment); 470 } 471 472 static void 473 ssh_encode_identity_ssh2(Buffer *b, Key *key, const char *comment) 474 { 475 buffer_put_cstring(b, key_ssh_name(key)); 476 switch (key->type) { 477 case KEY_RSA: 478 buffer_put_bignum2(b, key->rsa->n); 479 buffer_put_bignum2(b, key->rsa->e); 480 buffer_put_bignum2(b, key->rsa->d); 481 buffer_put_bignum2(b, key->rsa->iqmp); 482 buffer_put_bignum2(b, key->rsa->p); 483 buffer_put_bignum2(b, key->rsa->q); 484 break; 485 case KEY_DSA: 486 buffer_put_bignum2(b, key->dsa->p); 487 buffer_put_bignum2(b, key->dsa->q); 488 buffer_put_bignum2(b, key->dsa->g); 489 buffer_put_bignum2(b, key->dsa->pub_key); 490 buffer_put_bignum2(b, key->dsa->priv_key); 491 break; 492 } 493 buffer_put_cstring(b, comment); 494 } 495 496 /* 497 * Adds an identity to the authentication server. This call is not meant to 498 * be used by normal applications. 499 */ 500 501 int 502 ssh_add_identity_constrained(AuthenticationConnection *auth, Key *key, 503 const char *comment, u_int life, u_int confirm) 504 { 505 Buffer msg; 506 int type, constrained = (life || confirm); 507 508 buffer_init(&msg); 509 510 switch (key->type) { 511 case KEY_RSA1: 512 type = constrained ? 513 SSH_AGENTC_ADD_RSA_ID_CONSTRAINED : 514 SSH_AGENTC_ADD_RSA_IDENTITY; 515 buffer_put_char(&msg, type); 516 ssh_encode_identity_rsa1(&msg, key->rsa, comment); 517 break; 518 case KEY_RSA: 519 case KEY_DSA: 520 type = constrained ? 521 SSH2_AGENTC_ADD_ID_CONSTRAINED : 522 SSH2_AGENTC_ADD_IDENTITY; 523 buffer_put_char(&msg, type); 524 ssh_encode_identity_ssh2(&msg, key, comment); 525 break; 526 default: 527 buffer_free(&msg); 528 return 0; 529 break; 530 } 531 if (constrained) { 532 if (life != 0) { 533 buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_LIFETIME); 534 buffer_put_int(&msg, life); 535 } 536 if (confirm != 0) 537 buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_CONFIRM); 538 } 539 if (ssh_request_reply(auth, &msg, &msg) == 0) { 540 buffer_free(&msg); 541 return 0; 542 } 543 type = buffer_get_char(&msg); 544 buffer_free(&msg); 545 return decode_reply(type); 546 } 547 548 int 549 ssh_add_identity(AuthenticationConnection *auth, Key *key, const char *comment) 550 { 551 return ssh_add_identity_constrained(auth, key, comment, 0, 0); 552 } 553 554 /* 555 * Removes an identity from the authentication server. This call is not 556 * meant to be used by normal applications. 557 */ 558 559 int 560 ssh_remove_identity(AuthenticationConnection *auth, Key *key) 561 { 562 Buffer msg; 563 int type; 564 u_char *blob; 565 u_int blen; 566 567 buffer_init(&msg); 568 569 if (key->type == KEY_RSA1) { 570 buffer_put_char(&msg, SSH_AGENTC_REMOVE_RSA_IDENTITY); 571 buffer_put_int(&msg, BN_num_bits(key->rsa->n)); 572 buffer_put_bignum(&msg, key->rsa->e); 573 buffer_put_bignum(&msg, key->rsa->n); 574 } else if (key->type == KEY_DSA || key->type == KEY_RSA) { 575 key_to_blob(key, &blob, &blen); 576 buffer_put_char(&msg, SSH2_AGENTC_REMOVE_IDENTITY); 577 buffer_put_string(&msg, blob, blen); 578 xfree(blob); 579 } else { 580 buffer_free(&msg); 581 return 0; 582 } 583 if (ssh_request_reply(auth, &msg, &msg) == 0) { 584 buffer_free(&msg); 585 return 0; 586 } 587 type = buffer_get_char(&msg); 588 buffer_free(&msg); 589 return decode_reply(type); 590 } 591 592 int 593 ssh_update_card(AuthenticationConnection *auth, int add, 594 const char *reader_id, const char *pin, u_int life, u_int confirm) 595 { 596 Buffer msg; 597 int type, constrained = (life || confirm); 598 599 if (add) { 600 type = constrained ? 601 SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED : 602 SSH_AGENTC_ADD_SMARTCARD_KEY; 603 } else 604 type = SSH_AGENTC_REMOVE_SMARTCARD_KEY; 605 606 buffer_init(&msg); 607 buffer_put_char(&msg, type); 608 buffer_put_cstring(&msg, reader_id); 609 buffer_put_cstring(&msg, pin); 610 611 if (constrained) { 612 if (life != 0) { 613 buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_LIFETIME); 614 buffer_put_int(&msg, life); 615 } 616 if (confirm != 0) 617 buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_CONFIRM); 618 } 619 620 if (ssh_request_reply(auth, &msg, &msg) == 0) { 621 buffer_free(&msg); 622 return 0; 623 } 624 type = buffer_get_char(&msg); 625 buffer_free(&msg); 626 return decode_reply(type); 627 } 628 629 /* 630 * Removes all identities from the agent. This call is not meant to be used 631 * by normal applications. 632 */ 633 634 int 635 ssh_remove_all_identities(AuthenticationConnection *auth, int version) 636 { 637 Buffer msg; 638 int type; 639 int code = (version==1) ? 640 SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES : 641 SSH2_AGENTC_REMOVE_ALL_IDENTITIES; 642 643 buffer_init(&msg); 644 buffer_put_char(&msg, code); 645 646 if (ssh_request_reply(auth, &msg, &msg) == 0) { 647 buffer_free(&msg); 648 return 0; 649 } 650 type = buffer_get_char(&msg); 651 buffer_free(&msg); 652 return decode_reply(type); 653 } 654 655 int 656 decode_reply(int type) 657 { 658 switch (type) { 659 case SSH_AGENT_FAILURE: 660 case SSH_COM_AGENT2_FAILURE: 661 case SSH2_AGENT_FAILURE: 662 logit("SSH_AGENT_FAILURE"); 663 return 0; 664 case SSH_AGENT_SUCCESS: 665 return 1; 666 default: 667 fatal("Bad response from authentication agent: %d", type); 668 } 669 /* NOTREACHED */ 670 return 0; 671 } 672