1 /* $OpenBSD: authfd.c,v 1.80 2006/08/03 03:34:41 deraadt Exp $ */ 2 /* 3 * Author: Tatu Ylonen <ylo@cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 5 * All rights reserved 6 * Functions for connecting the local authentication agent. 7 * 8 * As far as I am concerned, the code I have written for this software 9 * can be used freely for any purpose. Any derived versions of this 10 * software must be clearly marked as such, and if the derived work is 11 * incompatible with the protocol description in the RFC file, it must be 12 * called by a name other than "ssh" or "Secure Shell". 13 * 14 * SSH2 implementation, 15 * Copyright (c) 2000 Markus Friedl. All rights reserved. 16 * 17 * Redistribution and use in source and binary forms, with or without 18 * modification, are permitted provided that the following conditions 19 * are met: 20 * 1. Redistributions of source code must retain the above copyright 21 * notice, this list of conditions and the following disclaimer. 22 * 2. Redistributions in binary form must reproduce the above copyright 23 * notice, this list of conditions and the following disclaimer in the 24 * documentation and/or other materials provided with the distribution. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 27 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 28 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 29 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 30 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 31 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 35 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 36 */ 37 38 #include "includes.h" 39 40 #include <sys/types.h> 41 #include <sys/un.h> 42 #include <sys/socket.h> 43 44 #include <openssl/evp.h> 45 46 #include <openssl/crypto.h> 47 #include <fcntl.h> 48 #include <stdlib.h> 49 #include <signal.h> 50 #include <stdarg.h> 51 #include <string.h> 52 #include <unistd.h> 53 54 #include "xmalloc.h" 55 #include "ssh.h" 56 #include "rsa.h" 57 #include "buffer.h" 58 #include "key.h" 59 #include "authfd.h" 60 #include "cipher.h" 61 #include "kex.h" 62 #include "compat.h" 63 #include "log.h" 64 #include "atomicio.h" 65 #include "misc.h" 66 67 static int agent_present = 0; 68 69 /* helper */ 70 int decode_reply(int type); 71 72 /* macro to check for "agent failure" message */ 73 #define agent_failed(x) \ 74 ((x == SSH_AGENT_FAILURE) || (x == SSH_COM_AGENT2_FAILURE) || \ 75 (x == SSH2_AGENT_FAILURE)) 76 77 int 78 ssh_agent_present(void) 79 { 80 int authfd; 81 82 if (agent_present) 83 return 1; 84 if ((authfd = ssh_get_authentication_socket()) == -1) 85 return 0; 86 else { 87 ssh_close_authentication_socket(authfd); 88 return 1; 89 } 90 } 91 92 /* Returns the number of the authentication fd, or -1 if there is none. */ 93 94 int 95 ssh_get_authentication_socket(void) 96 { 97 const char *authsocket; 98 int sock; 99 struct sockaddr_un sunaddr; 100 101 authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME); 102 if (!authsocket) 103 return -1; 104 105 sunaddr.sun_family = AF_UNIX; 106 strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path)); 107 108 sock = socket(AF_UNIX, SOCK_STREAM, 0); 109 if (sock < 0) 110 return -1; 111 112 /* close on exec */ 113 if (fcntl(sock, F_SETFD, 1) == -1) { 114 close(sock); 115 return -1; 116 } 117 if (connect(sock, (struct sockaddr *)&sunaddr, sizeof sunaddr) < 0) { 118 close(sock); 119 return -1; 120 } 121 agent_present = 1; 122 return sock; 123 } 124 125 static int 126 ssh_request_reply(AuthenticationConnection *auth, Buffer *request, Buffer *reply) 127 { 128 u_int l, len; 129 char buf[1024]; 130 131 /* Get the length of the message, and format it in the buffer. */ 132 len = buffer_len(request); 133 put_u32(buf, len); 134 135 /* Send the length and then the packet to the agent. */ 136 if (atomicio(vwrite, auth->fd, buf, 4) != 4 || 137 atomicio(vwrite, auth->fd, buffer_ptr(request), 138 buffer_len(request)) != buffer_len(request)) { 139 error("Error writing to authentication socket."); 140 return 0; 141 } 142 /* 143 * Wait for response from the agent. First read the length of the 144 * response packet. 145 */ 146 if (atomicio(read, auth->fd, buf, 4) != 4) { 147 error("Error reading response length from authentication socket."); 148 return 0; 149 } 150 151 /* Extract the length, and check it for sanity. */ 152 len = get_u32(buf); 153 if (len > 256 * 1024) 154 fatal("Authentication response too long: %u", len); 155 156 /* Read the rest of the response in to the buffer. */ 157 buffer_clear(reply); 158 while (len > 0) { 159 l = len; 160 if (l > sizeof(buf)) 161 l = sizeof(buf); 162 if (atomicio(read, auth->fd, buf, l) != l) { 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 int keybits; 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 keybits = BN_num_bits(key->rsa->n); 337 if (keybits < 0 || bits != (u_int)keybits) 338 logit("Warning: identity keysize mismatch: actual %d, announced %u", 339 BN_num_bits(key->rsa->n), bits); 340 break; 341 case 2: 342 blob = buffer_get_string(&auth->identities, &blen); 343 *comment = buffer_get_string(&auth->identities, NULL); 344 key = key_from_blob(blob, blen); 345 xfree(blob); 346 break; 347 default: 348 return NULL; 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 logit("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 logit("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] = (u_char)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 logit("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, u_int confirm) 505 { 506 Buffer msg; 507 int type, constrained = (life || confirm); 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 } 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