1 /* $OpenBSD: authfd.c,v 1.93 2014/04/29 18:01:49 markus 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 39 #include <sys/types.h> 40 #include <sys/un.h> 41 #include <sys/socket.h> 42 43 #include <fcntl.h> 44 #include <stdlib.h> 45 #include <signal.h> 46 #include <string.h> 47 #include <unistd.h> 48 49 #include "xmalloc.h" 50 #include "ssh.h" 51 #include "rsa.h" 52 #include "buffer.h" 53 #include "key.h" 54 #include "authfd.h" 55 #include "cipher.h" 56 #include "kex.h" 57 #include "compat.h" 58 #include "log.h" 59 #include "atomicio.h" 60 #include "misc.h" 61 62 static int agent_present = 0; 63 64 /* helper */ 65 int decode_reply(int type); 66 67 /* macro to check for "agent failure" message */ 68 #define agent_failed(x) \ 69 ((x == SSH_AGENT_FAILURE) || (x == SSH_COM_AGENT2_FAILURE) || \ 70 (x == SSH2_AGENT_FAILURE)) 71 72 int 73 ssh_agent_present(void) 74 { 75 int authfd; 76 77 if (agent_present) 78 return 1; 79 if ((authfd = ssh_get_authentication_socket()) == -1) 80 return 0; 81 else { 82 ssh_close_authentication_socket(authfd); 83 return 1; 84 } 85 } 86 87 /* Returns the number of the authentication fd, or -1 if there is none. */ 88 89 int 90 ssh_get_authentication_socket(void) 91 { 92 const char *authsocket; 93 int sock; 94 struct sockaddr_un sunaddr; 95 96 authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME); 97 if (!authsocket) 98 return -1; 99 100 memset(&sunaddr, 0, sizeof(sunaddr)); 101 sunaddr.sun_family = AF_UNIX; 102 strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path)); 103 104 sock = socket(AF_UNIX, SOCK_STREAM, 0); 105 if (sock < 0) 106 return -1; 107 108 /* close on exec */ 109 if (fcntl(sock, F_SETFD, FD_CLOEXEC) == -1) { 110 close(sock); 111 return -1; 112 } 113 if (connect(sock, (struct sockaddr *)&sunaddr, sizeof sunaddr) < 0) { 114 close(sock); 115 return -1; 116 } 117 agent_present = 1; 118 return sock; 119 } 120 121 static int 122 ssh_request_reply(AuthenticationConnection *auth, Buffer *request, Buffer *reply) 123 { 124 u_int l, len; 125 char buf[1024]; 126 127 /* Get the length of the message, and format it in the buffer. */ 128 len = buffer_len(request); 129 put_u32(buf, len); 130 131 /* Send the length and then the packet to the agent. */ 132 if (atomicio(vwrite, auth->fd, buf, 4) != 4 || 133 atomicio(vwrite, auth->fd, buffer_ptr(request), 134 buffer_len(request)) != buffer_len(request)) { 135 error("Error writing to authentication socket."); 136 return 0; 137 } 138 /* 139 * Wait for response from the agent. First read the length of the 140 * response packet. 141 */ 142 if (atomicio(read, auth->fd, buf, 4) != 4) { 143 error("Error reading response length from authentication socket."); 144 return 0; 145 } 146 147 /* Extract the length, and check it for sanity. */ 148 len = get_u32(buf); 149 if (len > 256 * 1024) 150 fatal("Authentication response too long: %u", 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 if (atomicio(read, auth->fd, buf, l) != l) { 159 error("Error reading response from authentication socket."); 160 return 0; 161 } 162 buffer_append(reply, buf, l); 163 len -= l; 164 } 165 return 1; 166 } 167 168 /* 169 * Closes the agent socket if it should be closed (depends on how it was 170 * obtained). The argument must have been returned by 171 * ssh_get_authentication_socket(). 172 */ 173 174 void 175 ssh_close_authentication_socket(int sock) 176 { 177 if (getenv(SSH_AUTHSOCKET_ENV_NAME)) 178 close(sock); 179 } 180 181 /* 182 * Opens and connects a private socket for communication with the 183 * authentication agent. Returns the file descriptor (which must be 184 * shut down and closed by the caller when no longer needed). 185 * Returns NULL if an error occurred and the connection could not be 186 * opened. 187 */ 188 189 AuthenticationConnection * 190 ssh_get_authentication_connection(void) 191 { 192 AuthenticationConnection *auth; 193 int sock; 194 195 sock = ssh_get_authentication_socket(); 196 197 /* 198 * Fail if we couldn't obtain a connection. This happens if we 199 * exited due to a timeout. 200 */ 201 if (sock < 0) 202 return NULL; 203 204 auth = xcalloc(1, sizeof(*auth)); 205 auth->fd = sock; 206 buffer_init(&auth->identities); 207 auth->howmany = 0; 208 209 return auth; 210 } 211 212 /* 213 * Closes the connection to the authentication agent and frees any associated 214 * memory. 215 */ 216 217 void 218 ssh_close_authentication_connection(AuthenticationConnection *auth) 219 { 220 buffer_free(&auth->identities); 221 close(auth->fd); 222 free(auth); 223 } 224 225 /* Lock/unlock agent */ 226 int 227 ssh_lock_agent(AuthenticationConnection *auth, int lock, const char *password) 228 { 229 int type; 230 Buffer msg; 231 232 buffer_init(&msg); 233 buffer_put_char(&msg, lock ? SSH_AGENTC_LOCK : SSH_AGENTC_UNLOCK); 234 buffer_put_cstring(&msg, password); 235 236 if (ssh_request_reply(auth, &msg, &msg) == 0) { 237 buffer_free(&msg); 238 return 0; 239 } 240 type = buffer_get_char(&msg); 241 buffer_free(&msg); 242 return decode_reply(type); 243 } 244 245 /* 246 * Returns the first authentication identity held by the agent. 247 */ 248 249 int 250 ssh_get_num_identities(AuthenticationConnection *auth, int version) 251 { 252 int type, code1 = 0, code2 = 0; 253 Buffer request; 254 255 switch (version) { 256 case 1: 257 code1 = SSH_AGENTC_REQUEST_RSA_IDENTITIES; 258 code2 = SSH_AGENT_RSA_IDENTITIES_ANSWER; 259 break; 260 case 2: 261 code1 = SSH2_AGENTC_REQUEST_IDENTITIES; 262 code2 = SSH2_AGENT_IDENTITIES_ANSWER; 263 break; 264 default: 265 return 0; 266 } 267 268 /* 269 * Send a message to the agent requesting for a list of the 270 * identities it can represent. 271 */ 272 buffer_init(&request); 273 buffer_put_char(&request, code1); 274 275 buffer_clear(&auth->identities); 276 if (ssh_request_reply(auth, &request, &auth->identities) == 0) { 277 buffer_free(&request); 278 return 0; 279 } 280 buffer_free(&request); 281 282 /* Get message type, and verify that we got a proper answer. */ 283 type = buffer_get_char(&auth->identities); 284 if (agent_failed(type)) { 285 return 0; 286 } else if (type != code2) { 287 fatal("Bad authentication reply message type: %d", type); 288 } 289 290 /* Get the number of entries in the response and check it for sanity. */ 291 auth->howmany = buffer_get_int(&auth->identities); 292 if ((u_int)auth->howmany > 1024) 293 fatal("Too many identities in authentication reply: %d", 294 auth->howmany); 295 296 return auth->howmany; 297 } 298 299 Key * 300 ssh_get_first_identity(AuthenticationConnection *auth, char **comment, int version) 301 { 302 /* get number of identities and return the first entry (if any). */ 303 if (ssh_get_num_identities(auth, version) > 0) 304 return ssh_get_next_identity(auth, comment, version); 305 return NULL; 306 } 307 308 Key * 309 ssh_get_next_identity(AuthenticationConnection *auth, char **comment, int version) 310 { 311 #ifdef WITH_SSH1 312 int keybits; 313 u_int bits; 314 #endif 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 #ifdef WITH_SSH1 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 keybits = BN_num_bits(key->rsa->n); 336 if (keybits < 0 || bits != (u_int)keybits) 337 logit("Warning: identity keysize mismatch: actual %d, announced %u", 338 BN_num_bits(key->rsa->n), bits); 339 break; 340 #endif 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 free(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 #ifdef WITH_SSH1 364 int 365 ssh_decrypt_challenge(AuthenticationConnection *auth, 366 Key* key, BIGNUM *challenge, 367 u_char session_id[16], 368 u_int response_type, 369 u_char response[16]) 370 { 371 Buffer buffer; 372 int success = 0; 373 int i; 374 int type; 375 376 if (key->type != KEY_RSA1) 377 return 0; 378 if (response_type == 0) { 379 logit("Compatibility with ssh protocol version 1.0 no longer supported."); 380 return 0; 381 } 382 buffer_init(&buffer); 383 buffer_put_char(&buffer, SSH_AGENTC_RSA_CHALLENGE); 384 buffer_put_int(&buffer, BN_num_bits(key->rsa->n)); 385 buffer_put_bignum(&buffer, key->rsa->e); 386 buffer_put_bignum(&buffer, key->rsa->n); 387 buffer_put_bignum(&buffer, challenge); 388 buffer_append(&buffer, session_id, 16); 389 buffer_put_int(&buffer, response_type); 390 391 if (ssh_request_reply(auth, &buffer, &buffer) == 0) { 392 buffer_free(&buffer); 393 return 0; 394 } 395 type = buffer_get_char(&buffer); 396 397 if (agent_failed(type)) { 398 logit("Agent admitted failure to authenticate using the key."); 399 } else if (type != SSH_AGENT_RSA_RESPONSE) { 400 fatal("Bad authentication response: %d", type); 401 } else { 402 success = 1; 403 /* 404 * Get the response from the packet. This will abort with a 405 * fatal error if the packet is corrupt. 406 */ 407 for (i = 0; i < 16; i++) 408 response[i] = (u_char)buffer_get_char(&buffer); 409 } 410 buffer_free(&buffer); 411 return success; 412 } 413 #endif 414 415 /* ask agent to sign data, returns -1 on error, 0 on success */ 416 int 417 ssh_agent_sign(AuthenticationConnection *auth, 418 Key *key, 419 u_char **sigp, u_int *lenp, 420 u_char *data, u_int datalen) 421 { 422 extern int datafellows; 423 Buffer msg; 424 u_char *blob; 425 u_int blen; 426 int type, flags = 0; 427 int ret = -1; 428 429 if (key_to_blob(key, &blob, &blen) == 0) 430 return -1; 431 432 if (datafellows & SSH_BUG_SIGBLOB) 433 flags = SSH_AGENT_OLD_SIGNATURE; 434 435 buffer_init(&msg); 436 buffer_put_char(&msg, SSH2_AGENTC_SIGN_REQUEST); 437 buffer_put_string(&msg, blob, blen); 438 buffer_put_string(&msg, data, datalen); 439 buffer_put_int(&msg, flags); 440 free(blob); 441 442 if (ssh_request_reply(auth, &msg, &msg) == 0) { 443 buffer_free(&msg); 444 return -1; 445 } 446 type = buffer_get_char(&msg); 447 if (agent_failed(type)) { 448 logit("Agent admitted failure to sign using the key."); 449 } else if (type != SSH2_AGENT_SIGN_RESPONSE) { 450 fatal("Bad authentication response: %d", type); 451 } else { 452 ret = 0; 453 *sigp = buffer_get_string(&msg, lenp); 454 } 455 buffer_free(&msg); 456 return ret; 457 } 458 459 /* Encode key for a message to the agent. */ 460 461 #ifdef WITH_SSH1 462 static void 463 ssh_encode_identity_rsa1(Buffer *b, RSA *key, const char *comment) 464 { 465 buffer_put_int(b, BN_num_bits(key->n)); 466 buffer_put_bignum(b, key->n); 467 buffer_put_bignum(b, key->e); 468 buffer_put_bignum(b, key->d); 469 /* To keep within the protocol: p < q for ssh. in SSL p > q */ 470 buffer_put_bignum(b, key->iqmp); /* ssh key->u */ 471 buffer_put_bignum(b, key->q); /* ssh key->p, SSL key->q */ 472 buffer_put_bignum(b, key->p); /* ssh key->q, SSL key->p */ 473 buffer_put_cstring(b, comment); 474 } 475 #endif 476 477 static void 478 ssh_encode_identity_ssh2(Buffer *b, Key *key, const char *comment) 479 { 480 key_private_serialize(key, b); 481 buffer_put_cstring(b, comment); 482 } 483 484 /* 485 * Adds an identity to the authentication server. This call is not meant to 486 * be used by normal applications. 487 */ 488 489 int 490 ssh_add_identity_constrained(AuthenticationConnection *auth, Key *key, 491 const char *comment, u_int life, u_int confirm) 492 { 493 Buffer msg; 494 int type, constrained = (life || confirm); 495 496 buffer_init(&msg); 497 498 switch (key->type) { 499 #ifdef WITH_SSH1 500 case KEY_RSA1: 501 type = constrained ? 502 SSH_AGENTC_ADD_RSA_ID_CONSTRAINED : 503 SSH_AGENTC_ADD_RSA_IDENTITY; 504 buffer_put_char(&msg, type); 505 ssh_encode_identity_rsa1(&msg, key->rsa, comment); 506 break; 507 #endif 508 #ifdef WITH_OPENSSL 509 case KEY_RSA: 510 case KEY_RSA_CERT: 511 case KEY_RSA_CERT_V00: 512 case KEY_DSA: 513 case KEY_DSA_CERT: 514 case KEY_DSA_CERT_V00: 515 case KEY_ECDSA: 516 case KEY_ECDSA_CERT: 517 #endif 518 case KEY_ED25519: 519 case KEY_ED25519_CERT: 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 } 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 } 546 547 /* 548 * Removes an identity from the authentication server. This call is not 549 * meant to be used by normal applications. 550 */ 551 552 int 553 ssh_remove_identity(AuthenticationConnection *auth, Key *key) 554 { 555 Buffer msg; 556 int type; 557 u_char *blob; 558 u_int blen; 559 560 buffer_init(&msg); 561 562 #ifdef WITH_SSH1 563 if (key->type == KEY_RSA1) { 564 buffer_put_char(&msg, SSH_AGENTC_REMOVE_RSA_IDENTITY); 565 buffer_put_int(&msg, BN_num_bits(key->rsa->n)); 566 buffer_put_bignum(&msg, key->rsa->e); 567 buffer_put_bignum(&msg, key->rsa->n); 568 } else 569 #endif 570 if (key->type != KEY_UNSPEC) { 571 key_to_blob(key, &blob, &blen); 572 buffer_put_char(&msg, SSH2_AGENTC_REMOVE_IDENTITY); 573 buffer_put_string(&msg, blob, blen); 574 free(blob); 575 } else { 576 buffer_free(&msg); 577 return 0; 578 } 579 if (ssh_request_reply(auth, &msg, &msg) == 0) { 580 buffer_free(&msg); 581 return 0; 582 } 583 type = buffer_get_char(&msg); 584 buffer_free(&msg); 585 return decode_reply(type); 586 } 587 588 int 589 ssh_update_card(AuthenticationConnection *auth, int add, 590 const char *reader_id, const char *pin, u_int life, u_int confirm) 591 { 592 Buffer msg; 593 int type, constrained = (life || confirm); 594 595 if (add) { 596 type = constrained ? 597 SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED : 598 SSH_AGENTC_ADD_SMARTCARD_KEY; 599 } else 600 type = SSH_AGENTC_REMOVE_SMARTCARD_KEY; 601 602 buffer_init(&msg); 603 buffer_put_char(&msg, type); 604 buffer_put_cstring(&msg, reader_id); 605 buffer_put_cstring(&msg, pin); 606 607 if (constrained) { 608 if (life != 0) { 609 buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_LIFETIME); 610 buffer_put_int(&msg, life); 611 } 612 if (confirm != 0) 613 buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_CONFIRM); 614 } 615 616 if (ssh_request_reply(auth, &msg, &msg) == 0) { 617 buffer_free(&msg); 618 return 0; 619 } 620 type = buffer_get_char(&msg); 621 buffer_free(&msg); 622 return decode_reply(type); 623 } 624 625 /* 626 * Removes all identities from the agent. This call is not meant to be used 627 * by normal applications. 628 */ 629 630 int 631 ssh_remove_all_identities(AuthenticationConnection *auth, int version) 632 { 633 Buffer msg; 634 int type; 635 int code = (version==1) ? 636 SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES : 637 SSH2_AGENTC_REMOVE_ALL_IDENTITIES; 638 639 buffer_init(&msg); 640 buffer_put_char(&msg, code); 641 642 if (ssh_request_reply(auth, &msg, &msg) == 0) { 643 buffer_free(&msg); 644 return 0; 645 } 646 type = buffer_get_char(&msg); 647 buffer_free(&msg); 648 return decode_reply(type); 649 } 650 651 int 652 decode_reply(int type) 653 { 654 switch (type) { 655 case SSH_AGENT_FAILURE: 656 case SSH_COM_AGENT2_FAILURE: 657 case SSH2_AGENT_FAILURE: 658 logit("SSH_AGENT_FAILURE"); 659 return 0; 660 case SSH_AGENT_SUCCESS: 661 return 1; 662 default: 663 fatal("Bad response from authentication agent: %d", type); 664 } 665 /* NOTREACHED */ 666 return 0; 667 } 668