authfd.c revision 124211
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" 38RCSID("$OpenBSD: authfd.c,v 1.61 2003/06/28 16:23:06 deraadt 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 56static int agent_present = 0; 57 58/* helper */ 59int 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 66int 67ssh_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 83int 84ssh_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 114static int 115ssh_request_reply(AuthenticationConnection *auth, Buffer *request, Buffer *reply) 116{ 117 int l, len; 118 char buf[1024]; 119 120 /* Get the length of the message, and format it in the buffer. */ 121 len = buffer_len(request); 122 PUT_32BIT(buf, len); 123 124 /* Send the length and then the packet to the agent. */ 125 if (atomicio(vwrite, auth->fd, buf, 4) != 4 || 126 atomicio(vwrite, auth->fd, buffer_ptr(request), 127 buffer_len(request)) != buffer_len(request)) { 128 error("Error writing to authentication socket."); 129 return 0; 130 } 131 /* 132 * Wait for response from the agent. First read the length of the 133 * response packet. 134 */ 135 len = 4; 136 while (len > 0) { 137 l = read(auth->fd, buf + 4 - len, len); 138 if (l == -1 && (errno == EAGAIN || errno == EINTR)) 139 continue; 140 if (l <= 0) { 141 error("Error reading response length from authentication socket."); 142 return 0; 143 } 144 len -= l; 145 } 146 147 /* Extract the length, and check it for sanity. */ 148 len = GET_32BIT(buf); 149 if (len > 256 * 1024) 150 fatal("Authentication response too long: %d", len); 151 152 /* Read the rest of the response in to the buffer. */ 153 buffer_clear(reply); 154 while (len > 0) { 155 l = len; 156 if (l > sizeof(buf)) 157 l = sizeof(buf); 158 l = read(auth->fd, buf, l); 159 if (l == -1 && (errno == EAGAIN || errno == EINTR)) 160 continue; 161 if (l <= 0) { 162 error("Error reading response from authentication socket."); 163 return 0; 164 } 165 buffer_append(reply, buf, l); 166 len -= l; 167 } 168 return 1; 169} 170 171/* 172 * Closes the agent socket if it should be closed (depends on how it was 173 * obtained). The argument must have been returned by 174 * ssh_get_authentication_socket(). 175 */ 176 177void 178ssh_close_authentication_socket(int sock) 179{ 180 if (getenv(SSH_AUTHSOCKET_ENV_NAME)) 181 close(sock); 182} 183 184/* 185 * Opens and connects a private socket for communication with the 186 * authentication agent. Returns the file descriptor (which must be 187 * shut down and closed by the caller when no longer needed). 188 * Returns NULL if an error occurred and the connection could not be 189 * opened. 190 */ 191 192AuthenticationConnection * 193ssh_get_authentication_connection(void) 194{ 195 AuthenticationConnection *auth; 196 int sock; 197 198 sock = ssh_get_authentication_socket(); 199 200 /* 201 * Fail if we couldn't obtain a connection. This happens if we 202 * exited due to a timeout. 203 */ 204 if (sock < 0) 205 return NULL; 206 207 auth = xmalloc(sizeof(*auth)); 208 auth->fd = sock; 209 buffer_init(&auth->identities); 210 auth->howmany = 0; 211 212 return auth; 213} 214 215/* 216 * Closes the connection to the authentication agent and frees any associated 217 * memory. 218 */ 219 220void 221ssh_close_authentication_connection(AuthenticationConnection *auth) 222{ 223 buffer_free(&auth->identities); 224 close(auth->fd); 225 xfree(auth); 226} 227 228/* Lock/unlock agent */ 229int 230ssh_lock_agent(AuthenticationConnection *auth, int lock, const char *password) 231{ 232 int type; 233 Buffer msg; 234 235 buffer_init(&msg); 236 buffer_put_char(&msg, lock ? SSH_AGENTC_LOCK : SSH_AGENTC_UNLOCK); 237 buffer_put_cstring(&msg, password); 238 239 if (ssh_request_reply(auth, &msg, &msg) == 0) { 240 buffer_free(&msg); 241 return 0; 242 } 243 type = buffer_get_char(&msg); 244 buffer_free(&msg); 245 return decode_reply(type); 246} 247 248/* 249 * Returns the first authentication identity held by the agent. 250 */ 251 252int 253ssh_get_num_identities(AuthenticationConnection *auth, int version) 254{ 255 int type, code1 = 0, code2 = 0; 256 Buffer request; 257 258 switch (version) { 259 case 1: 260 code1 = SSH_AGENTC_REQUEST_RSA_IDENTITIES; 261 code2 = SSH_AGENT_RSA_IDENTITIES_ANSWER; 262 break; 263 case 2: 264 code1 = SSH2_AGENTC_REQUEST_IDENTITIES; 265 code2 = SSH2_AGENT_IDENTITIES_ANSWER; 266 break; 267 default: 268 return 0; 269 } 270 271 /* 272 * Send a message to the agent requesting for a list of the 273 * identities it can represent. 274 */ 275 buffer_init(&request); 276 buffer_put_char(&request, code1); 277 278 buffer_clear(&auth->identities); 279 if (ssh_request_reply(auth, &request, &auth->identities) == 0) { 280 buffer_free(&request); 281 return 0; 282 } 283 buffer_free(&request); 284 285 /* Get message type, and verify that we got a proper answer. */ 286 type = buffer_get_char(&auth->identities); 287 if (agent_failed(type)) { 288 return 0; 289 } else if (type != code2) { 290 fatal("Bad authentication reply message type: %d", type); 291 } 292 293 /* Get the number of entries in the response and check it for sanity. */ 294 auth->howmany = buffer_get_int(&auth->identities); 295 if (auth->howmany > 1024) 296 fatal("Too many identities in authentication reply: %d", 297 auth->howmany); 298 299 return auth->howmany; 300} 301 302Key * 303ssh_get_first_identity(AuthenticationConnection *auth, char **comment, int version) 304{ 305 /* get number of identities and return the first entry (if any). */ 306 if (ssh_get_num_identities(auth, version) > 0) 307 return ssh_get_next_identity(auth, comment, version); 308 return NULL; 309} 310 311Key * 312ssh_get_next_identity(AuthenticationConnection *auth, char **comment, int version) 313{ 314 u_int bits; 315 u_char *blob; 316 u_int blen; 317 Key *key = NULL; 318 319 /* Return failure if no more entries. */ 320 if (auth->howmany <= 0) 321 return NULL; 322 323 /* 324 * Get the next entry from the packet. These will abort with a fatal 325 * error if the packet is too short or contains corrupt data. 326 */ 327 switch (version) { 328 case 1: 329 key = key_new(KEY_RSA1); 330 bits = buffer_get_int(&auth->identities); 331 buffer_get_bignum(&auth->identities, key->rsa->e); 332 buffer_get_bignum(&auth->identities, key->rsa->n); 333 *comment = buffer_get_string(&auth->identities, NULL); 334 if (bits != BN_num_bits(key->rsa->n)) 335 logit("Warning: identity keysize mismatch: actual %d, announced %u", 336 BN_num_bits(key->rsa->n), bits); 337 break; 338 case 2: 339 blob = buffer_get_string(&auth->identities, &blen); 340 *comment = buffer_get_string(&auth->identities, NULL); 341 key = key_from_blob(blob, blen); 342 xfree(blob); 343 break; 344 default: 345 return NULL; 346 break; 347 } 348 /* Decrement the number of remaining entries. */ 349 auth->howmany--; 350 return key; 351} 352 353/* 354 * Generates a random challenge, sends it to the agent, and waits for 355 * response from the agent. Returns true (non-zero) if the agent gave the 356 * correct answer, zero otherwise. Response type selects the style of 357 * response desired, with 0 corresponding to protocol version 1.0 (no longer 358 * supported) and 1 corresponding to protocol version 1.1. 359 */ 360 361int 362ssh_decrypt_challenge(AuthenticationConnection *auth, 363 Key* key, BIGNUM *challenge, 364 u_char session_id[16], 365 u_int response_type, 366 u_char response[16]) 367{ 368 Buffer buffer; 369 int success = 0; 370 int i; 371 int type; 372 373 if (key->type != KEY_RSA1) 374 return 0; 375 if (response_type == 0) { 376 logit("Compatibility with ssh protocol version 1.0 no longer supported."); 377 return 0; 378 } 379 buffer_init(&buffer); 380 buffer_put_char(&buffer, SSH_AGENTC_RSA_CHALLENGE); 381 buffer_put_int(&buffer, BN_num_bits(key->rsa->n)); 382 buffer_put_bignum(&buffer, key->rsa->e); 383 buffer_put_bignum(&buffer, key->rsa->n); 384 buffer_put_bignum(&buffer, challenge); 385 buffer_append(&buffer, session_id, 16); 386 buffer_put_int(&buffer, response_type); 387 388 if (ssh_request_reply(auth, &buffer, &buffer) == 0) { 389 buffer_free(&buffer); 390 return 0; 391 } 392 type = buffer_get_char(&buffer); 393 394 if (agent_failed(type)) { 395 logit("Agent admitted failure to authenticate using the key."); 396 } else if (type != SSH_AGENT_RSA_RESPONSE) { 397 fatal("Bad authentication response: %d", type); 398 } else { 399 success = 1; 400 /* 401 * Get the response from the packet. This will abort with a 402 * fatal error if the packet is corrupt. 403 */ 404 for (i = 0; i < 16; i++) 405 response[i] = buffer_get_char(&buffer); 406 } 407 buffer_free(&buffer); 408 return success; 409} 410 411/* ask agent to sign data, returns -1 on error, 0 on success */ 412int 413ssh_agent_sign(AuthenticationConnection *auth, 414 Key *key, 415 u_char **sigp, u_int *lenp, 416 u_char *data, u_int datalen) 417{ 418 extern int datafellows; 419 Buffer msg; 420 u_char *blob; 421 u_int blen; 422 int type, flags = 0; 423 int ret = -1; 424 425 if (key_to_blob(key, &blob, &blen) == 0) 426 return -1; 427 428 if (datafellows & SSH_BUG_SIGBLOB) 429 flags = SSH_AGENT_OLD_SIGNATURE; 430 431 buffer_init(&msg); 432 buffer_put_char(&msg, SSH2_AGENTC_SIGN_REQUEST); 433 buffer_put_string(&msg, blob, blen); 434 buffer_put_string(&msg, data, datalen); 435 buffer_put_int(&msg, flags); 436 xfree(blob); 437 438 if (ssh_request_reply(auth, &msg, &msg) == 0) { 439 buffer_free(&msg); 440 return -1; 441 } 442 type = buffer_get_char(&msg); 443 if (agent_failed(type)) { 444 logit("Agent admitted failure to sign using the key."); 445 } else if (type != SSH2_AGENT_SIGN_RESPONSE) { 446 fatal("Bad authentication response: %d", type); 447 } else { 448 ret = 0; 449 *sigp = buffer_get_string(&msg, lenp); 450 } 451 buffer_free(&msg); 452 return ret; 453} 454 455/* Encode key for a message to the agent. */ 456 457static void 458ssh_encode_identity_rsa1(Buffer *b, RSA *key, const char *comment) 459{ 460 buffer_put_int(b, BN_num_bits(key->n)); 461 buffer_put_bignum(b, key->n); 462 buffer_put_bignum(b, key->e); 463 buffer_put_bignum(b, key->d); 464 /* To keep within the protocol: p < q for ssh. in SSL p > q */ 465 buffer_put_bignum(b, key->iqmp); /* ssh key->u */ 466 buffer_put_bignum(b, key->q); /* ssh key->p, SSL key->q */ 467 buffer_put_bignum(b, key->p); /* ssh key->q, SSL key->p */ 468 buffer_put_cstring(b, comment); 469} 470 471static void 472ssh_encode_identity_ssh2(Buffer *b, Key *key, const char *comment) 473{ 474 buffer_put_cstring(b, key_ssh_name(key)); 475 switch (key->type) { 476 case KEY_RSA: 477 buffer_put_bignum2(b, key->rsa->n); 478 buffer_put_bignum2(b, key->rsa->e); 479 buffer_put_bignum2(b, key->rsa->d); 480 buffer_put_bignum2(b, key->rsa->iqmp); 481 buffer_put_bignum2(b, key->rsa->p); 482 buffer_put_bignum2(b, key->rsa->q); 483 break; 484 case KEY_DSA: 485 buffer_put_bignum2(b, key->dsa->p); 486 buffer_put_bignum2(b, key->dsa->q); 487 buffer_put_bignum2(b, key->dsa->g); 488 buffer_put_bignum2(b, key->dsa->pub_key); 489 buffer_put_bignum2(b, key->dsa->priv_key); 490 break; 491 } 492 buffer_put_cstring(b, comment); 493} 494 495/* 496 * Adds an identity to the authentication server. This call is not meant to 497 * be used by normal applications. 498 */ 499 500int 501ssh_add_identity_constrained(AuthenticationConnection *auth, Key *key, 502 const char *comment, u_int life, u_int confirm) 503{ 504 Buffer msg; 505 int type, constrained = (life || confirm); 506 507 buffer_init(&msg); 508 509 switch (key->type) { 510 case KEY_RSA1: 511 type = constrained ? 512 SSH_AGENTC_ADD_RSA_ID_CONSTRAINED : 513 SSH_AGENTC_ADD_RSA_IDENTITY; 514 buffer_put_char(&msg, type); 515 ssh_encode_identity_rsa1(&msg, key->rsa, comment); 516 break; 517 case KEY_RSA: 518 case KEY_DSA: 519 type = constrained ? 520 SSH2_AGENTC_ADD_ID_CONSTRAINED : 521 SSH2_AGENTC_ADD_IDENTITY; 522 buffer_put_char(&msg, type); 523 ssh_encode_identity_ssh2(&msg, key, comment); 524 break; 525 default: 526 buffer_free(&msg); 527 return 0; 528 break; 529 } 530 if (constrained) { 531 if (life != 0) { 532 buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_LIFETIME); 533 buffer_put_int(&msg, life); 534 } 535 if (confirm != 0) 536 buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_CONFIRM); 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 547int 548ssh_add_identity(AuthenticationConnection *auth, Key *key, const char *comment) 549{ 550 return ssh_add_identity_constrained(auth, key, comment, 0, 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 558int 559ssh_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 591int 592ssh_update_card(AuthenticationConnection *auth, int add, 593 const char *reader_id, const char *pin, u_int life, u_int confirm) 594{ 595 Buffer msg; 596 int type, constrained = (life || confirm); 597 598 if (add) { 599 type = constrained ? 600 SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED : 601 SSH_AGENTC_ADD_SMARTCARD_KEY; 602 } else 603 type = SSH_AGENTC_REMOVE_SMARTCARD_KEY; 604 605 buffer_init(&msg); 606 buffer_put_char(&msg, type); 607 buffer_put_cstring(&msg, reader_id); 608 buffer_put_cstring(&msg, pin); 609 610 if (constrained) { 611 if (life != 0) { 612 buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_LIFETIME); 613 buffer_put_int(&msg, life); 614 } 615 if (confirm != 0) 616 buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_CONFIRM); 617 } 618 619 if (ssh_request_reply(auth, &msg, &msg) == 0) { 620 buffer_free(&msg); 621 return 0; 622 } 623 type = buffer_get_char(&msg); 624 buffer_free(&msg); 625 return decode_reply(type); 626} 627 628/* 629 * Removes all identities from the agent. This call is not meant to be used 630 * by normal applications. 631 */ 632 633int 634ssh_remove_all_identities(AuthenticationConnection *auth, int version) 635{ 636 Buffer msg; 637 int type; 638 int code = (version==1) ? 639 SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES : 640 SSH2_AGENTC_REMOVE_ALL_IDENTITIES; 641 642 buffer_init(&msg); 643 buffer_put_char(&msg, code); 644 645 if (ssh_request_reply(auth, &msg, &msg) == 0) { 646 buffer_free(&msg); 647 return 0; 648 } 649 type = buffer_get_char(&msg); 650 buffer_free(&msg); 651 return decode_reply(type); 652} 653 654int 655decode_reply(int type) 656{ 657 switch (type) { 658 case SSH_AGENT_FAILURE: 659 case SSH_COM_AGENT2_FAILURE: 660 case SSH2_AGENT_FAILURE: 661 logit("SSH_AGENT_FAILURE"); 662 return 0; 663 case SSH_AGENT_SUCCESS: 664 return 1; 665 default: 666 fatal("Bad response from authentication agent: %d", type); 667 } 668 /* NOTREACHED */ 669 return 0; 670} 671