1 /* $OpenBSD: authfd.c,v 1.92 2014/01/31 16:39:19 tedu 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 #include <openssl/crypto.h> 46 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 memset(&sunaddr, 0, sizeof(sunaddr)); 106 sunaddr.sun_family = AF_UNIX; 107 strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path)); 108 109 sock = socket(AF_UNIX, SOCK_STREAM, 0); 110 if (sock < 0) 111 return -1; 112 113 /* close on exec */ 114 if (fcntl(sock, F_SETFD, FD_CLOEXEC) == -1) { 115 close(sock); 116 return -1; 117 } 118 if (connect(sock, (struct sockaddr *)&sunaddr, sizeof sunaddr) < 0) { 119 close(sock); 120 return -1; 121 } 122 agent_present = 1; 123 return sock; 124 } 125 126 static int 127 ssh_request_reply(AuthenticationConnection *auth, Buffer *request, Buffer *reply) 128 { 129 u_int l, len; 130 char buf[1024]; 131 132 /* Get the length of the message, and format it in the buffer. */ 133 len = buffer_len(request); 134 put_u32(buf, len); 135 136 /* Send the length and then the packet to the agent. */ 137 if (atomicio(vwrite, auth->fd, buf, 4) != 4 || 138 atomicio(vwrite, auth->fd, buffer_ptr(request), 139 buffer_len(request)) != buffer_len(request)) { 140 error("Error writing to authentication socket."); 141 return 0; 142 } 143 /* 144 * Wait for response from the agent. First read the length of the 145 * response packet. 146 */ 147 if (atomicio(read, auth->fd, buf, 4) != 4) { 148 error("Error reading response length from authentication socket."); 149 return 0; 150 } 151 152 /* Extract the length, and check it for sanity. */ 153 len = get_u32(buf); 154 if (len > 256 * 1024) 155 fatal("Authentication response too long: %u", len); 156 157 /* Read the rest of the response in to the buffer. */ 158 buffer_clear(reply); 159 while (len > 0) { 160 l = len; 161 if (l > sizeof(buf)) 162 l = sizeof(buf); 163 if (atomicio(read, auth->fd, buf, l) != l) { 164 error("Error reading response from authentication socket."); 165 return 0; 166 } 167 buffer_append(reply, buf, l); 168 len -= l; 169 } 170 return 1; 171 } 172 173 /* 174 * Closes the agent socket if it should be closed (depends on how it was 175 * obtained). The argument must have been returned by 176 * ssh_get_authentication_socket(). 177 */ 178 179 void 180 ssh_close_authentication_socket(int sock) 181 { 182 if (getenv(SSH_AUTHSOCKET_ENV_NAME)) 183 close(sock); 184 } 185 186 /* 187 * Opens and connects a private socket for communication with the 188 * authentication agent. Returns the file descriptor (which must be 189 * shut down and closed by the caller when no longer needed). 190 * Returns NULL if an error occurred and the connection could not be 191 * opened. 192 */ 193 194 AuthenticationConnection * 195 ssh_get_authentication_connection(void) 196 { 197 AuthenticationConnection *auth; 198 int sock; 199 200 sock = ssh_get_authentication_socket(); 201 202 /* 203 * Fail if we couldn't obtain a connection. This happens if we 204 * exited due to a timeout. 205 */ 206 if (sock < 0) 207 return NULL; 208 209 auth = xcalloc(1, sizeof(*auth)); 210 auth->fd = sock; 211 buffer_init(&auth->identities); 212 auth->howmany = 0; 213 214 return auth; 215 } 216 217 /* 218 * Closes the connection to the authentication agent and frees any associated 219 * memory. 220 */ 221 222 void 223 ssh_close_authentication_connection(AuthenticationConnection *auth) 224 { 225 buffer_free(&auth->identities); 226 close(auth->fd); 227 free(auth); 228 } 229 230 /* Lock/unlock agent */ 231 int 232 ssh_lock_agent(AuthenticationConnection *auth, int lock, const char *password) 233 { 234 int type; 235 Buffer msg; 236 237 buffer_init(&msg); 238 buffer_put_char(&msg, lock ? SSH_AGENTC_LOCK : SSH_AGENTC_UNLOCK); 239 buffer_put_cstring(&msg, password); 240 241 if (ssh_request_reply(auth, &msg, &msg) == 0) { 242 buffer_free(&msg); 243 return 0; 244 } 245 type = buffer_get_char(&msg); 246 buffer_free(&msg); 247 return decode_reply(type); 248 } 249 250 /* 251 * Returns the first authentication identity held by the agent. 252 */ 253 254 int 255 ssh_get_num_identities(AuthenticationConnection *auth, int version) 256 { 257 int type, code1 = 0, code2 = 0; 258 Buffer request; 259 260 switch (version) { 261 case 1: 262 code1 = SSH_AGENTC_REQUEST_RSA_IDENTITIES; 263 code2 = SSH_AGENT_RSA_IDENTITIES_ANSWER; 264 break; 265 case 2: 266 code1 = SSH2_AGENTC_REQUEST_IDENTITIES; 267 code2 = SSH2_AGENT_IDENTITIES_ANSWER; 268 break; 269 default: 270 return 0; 271 } 272 273 /* 274 * Send a message to the agent requesting for a list of the 275 * identities it can represent. 276 */ 277 buffer_init(&request); 278 buffer_put_char(&request, code1); 279 280 buffer_clear(&auth->identities); 281 if (ssh_request_reply(auth, &request, &auth->identities) == 0) { 282 buffer_free(&request); 283 return 0; 284 } 285 buffer_free(&request); 286 287 /* Get message type, and verify that we got a proper answer. */ 288 type = buffer_get_char(&auth->identities); 289 if (agent_failed(type)) { 290 return 0; 291 } else if (type != code2) { 292 fatal("Bad authentication reply message type: %d", type); 293 } 294 295 /* Get the number of entries in the response and check it for sanity. */ 296 auth->howmany = buffer_get_int(&auth->identities); 297 if ((u_int)auth->howmany > 1024) 298 fatal("Too many identities in authentication reply: %d", 299 auth->howmany); 300 301 return auth->howmany; 302 } 303 304 Key * 305 ssh_get_first_identity(AuthenticationConnection *auth, char **comment, int version) 306 { 307 /* get number of identities and return the first entry (if any). */ 308 if (ssh_get_num_identities(auth, version) > 0) 309 return ssh_get_next_identity(auth, comment, version); 310 return NULL; 311 } 312 313 Key * 314 ssh_get_next_identity(AuthenticationConnection *auth, char **comment, int version) 315 { 316 int keybits; 317 u_int bits; 318 u_char *blob; 319 u_int blen; 320 Key *key = NULL; 321 322 /* Return failure if no more entries. */ 323 if (auth->howmany <= 0) 324 return NULL; 325 326 /* 327 * Get the next entry from the packet. These will abort with a fatal 328 * error if the packet is too short or contains corrupt data. 329 */ 330 switch (version) { 331 case 1: 332 key = key_new(KEY_RSA1); 333 bits = buffer_get_int(&auth->identities); 334 buffer_get_bignum(&auth->identities, key->rsa->e); 335 buffer_get_bignum(&auth->identities, key->rsa->n); 336 *comment = buffer_get_string(&auth->identities, NULL); 337 keybits = BN_num_bits(key->rsa->n); 338 if (keybits < 0 || bits != (u_int)keybits) 339 logit("Warning: identity keysize mismatch: actual %d, announced %u", 340 BN_num_bits(key->rsa->n), bits); 341 break; 342 case 2: 343 blob = buffer_get_string(&auth->identities, &blen); 344 *comment = buffer_get_string(&auth->identities, NULL); 345 key = key_from_blob(blob, blen); 346 free(blob); 347 break; 348 default: 349 return NULL; 350 } 351 /* Decrement the number of remaining entries. */ 352 auth->howmany--; 353 return key; 354 } 355 356 /* 357 * Generates a random challenge, sends it to the agent, and waits for 358 * response from the agent. Returns true (non-zero) if the agent gave the 359 * correct answer, zero otherwise. Response type selects the style of 360 * response desired, with 0 corresponding to protocol version 1.0 (no longer 361 * supported) and 1 corresponding to protocol version 1.1. 362 */ 363 364 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 } 413 414 /* ask agent to sign data, returns -1 on error, 0 on success */ 415 int 416 ssh_agent_sign(AuthenticationConnection *auth, 417 Key *key, 418 u_char **sigp, u_int *lenp, 419 u_char *data, u_int datalen) 420 { 421 extern int datafellows; 422 Buffer msg; 423 u_char *blob; 424 u_int blen; 425 int type, flags = 0; 426 int ret = -1; 427 428 if (key_to_blob(key, &blob, &blen) == 0) 429 return -1; 430 431 if (datafellows & SSH_BUG_SIGBLOB) 432 flags = SSH_AGENT_OLD_SIGNATURE; 433 434 buffer_init(&msg); 435 buffer_put_char(&msg, SSH2_AGENTC_SIGN_REQUEST); 436 buffer_put_string(&msg, blob, blen); 437 buffer_put_string(&msg, data, datalen); 438 buffer_put_int(&msg, flags); 439 free(blob); 440 441 if (ssh_request_reply(auth, &msg, &msg) == 0) { 442 buffer_free(&msg); 443 return -1; 444 } 445 type = buffer_get_char(&msg); 446 if (agent_failed(type)) { 447 logit("Agent admitted failure to sign using the key."); 448 } else if (type != SSH2_AGENT_SIGN_RESPONSE) { 449 fatal("Bad authentication response: %d", type); 450 } else { 451 ret = 0; 452 *sigp = buffer_get_string(&msg, lenp); 453 } 454 buffer_free(&msg); 455 return ret; 456 } 457 458 /* Encode key for a message to the agent. */ 459 460 static void 461 ssh_encode_identity_rsa1(Buffer *b, RSA *key, const char *comment) 462 { 463 buffer_put_int(b, BN_num_bits(key->n)); 464 buffer_put_bignum(b, key->n); 465 buffer_put_bignum(b, key->e); 466 buffer_put_bignum(b, key->d); 467 /* To keep within the protocol: p < q for ssh. in SSL p > q */ 468 buffer_put_bignum(b, key->iqmp); /* ssh key->u */ 469 buffer_put_bignum(b, key->q); /* ssh key->p, SSL key->q */ 470 buffer_put_bignum(b, key->p); /* ssh key->q, SSL key->p */ 471 buffer_put_cstring(b, comment); 472 } 473 474 static void 475 ssh_encode_identity_ssh2(Buffer *b, Key *key, const char *comment) 476 { 477 key_private_serialize(key, b); 478 buffer_put_cstring(b, comment); 479 } 480 481 /* 482 * Adds an identity to the authentication server. This call is not meant to 483 * be used by normal applications. 484 */ 485 486 int 487 ssh_add_identity_constrained(AuthenticationConnection *auth, Key *key, 488 const char *comment, u_int life, u_int confirm) 489 { 490 Buffer msg; 491 int type, constrained = (life || confirm); 492 493 buffer_init(&msg); 494 495 switch (key->type) { 496 case KEY_RSA1: 497 type = constrained ? 498 SSH_AGENTC_ADD_RSA_ID_CONSTRAINED : 499 SSH_AGENTC_ADD_RSA_IDENTITY; 500 buffer_put_char(&msg, type); 501 ssh_encode_identity_rsa1(&msg, key->rsa, comment); 502 break; 503 case KEY_RSA: 504 case KEY_RSA_CERT: 505 case KEY_RSA_CERT_V00: 506 case KEY_DSA: 507 case KEY_DSA_CERT: 508 case KEY_DSA_CERT_V00: 509 case KEY_ECDSA: 510 case KEY_ECDSA_CERT: 511 case KEY_ED25519: 512 case KEY_ED25519_CERT: 513 type = constrained ? 514 SSH2_AGENTC_ADD_ID_CONSTRAINED : 515 SSH2_AGENTC_ADD_IDENTITY; 516 buffer_put_char(&msg, type); 517 ssh_encode_identity_ssh2(&msg, key, comment); 518 break; 519 default: 520 buffer_free(&msg); 521 return 0; 522 } 523 if (constrained) { 524 if (life != 0) { 525 buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_LIFETIME); 526 buffer_put_int(&msg, life); 527 } 528 if (confirm != 0) 529 buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_CONFIRM); 530 } 531 if (ssh_request_reply(auth, &msg, &msg) == 0) { 532 buffer_free(&msg); 533 return 0; 534 } 535 type = buffer_get_char(&msg); 536 buffer_free(&msg); 537 return decode_reply(type); 538 } 539 540 /* 541 * Removes an identity from the authentication server. This call is not 542 * meant to be used by normal applications. 543 */ 544 545 int 546 ssh_remove_identity(AuthenticationConnection *auth, Key *key) 547 { 548 Buffer msg; 549 int type; 550 u_char *blob; 551 u_int blen; 552 553 buffer_init(&msg); 554 555 if (key->type == KEY_RSA1) { 556 buffer_put_char(&msg, SSH_AGENTC_REMOVE_RSA_IDENTITY); 557 buffer_put_int(&msg, BN_num_bits(key->rsa->n)); 558 buffer_put_bignum(&msg, key->rsa->e); 559 buffer_put_bignum(&msg, key->rsa->n); 560 } else if (key->type != KEY_UNSPEC) { 561 key_to_blob(key, &blob, &blen); 562 buffer_put_char(&msg, SSH2_AGENTC_REMOVE_IDENTITY); 563 buffer_put_string(&msg, blob, blen); 564 free(blob); 565 } else { 566 buffer_free(&msg); 567 return 0; 568 } 569 if (ssh_request_reply(auth, &msg, &msg) == 0) { 570 buffer_free(&msg); 571 return 0; 572 } 573 type = buffer_get_char(&msg); 574 buffer_free(&msg); 575 return decode_reply(type); 576 } 577 578 int 579 ssh_update_card(AuthenticationConnection *auth, int add, 580 const char *reader_id, const char *pin, u_int life, u_int confirm) 581 { 582 Buffer msg; 583 int type, constrained = (life || confirm); 584 585 if (add) { 586 type = constrained ? 587 SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED : 588 SSH_AGENTC_ADD_SMARTCARD_KEY; 589 } else 590 type = SSH_AGENTC_REMOVE_SMARTCARD_KEY; 591 592 buffer_init(&msg); 593 buffer_put_char(&msg, type); 594 buffer_put_cstring(&msg, reader_id); 595 buffer_put_cstring(&msg, pin); 596 597 if (constrained) { 598 if (life != 0) { 599 buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_LIFETIME); 600 buffer_put_int(&msg, life); 601 } 602 if (confirm != 0) 603 buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_CONFIRM); 604 } 605 606 if (ssh_request_reply(auth, &msg, &msg) == 0) { 607 buffer_free(&msg); 608 return 0; 609 } 610 type = buffer_get_char(&msg); 611 buffer_free(&msg); 612 return decode_reply(type); 613 } 614 615 /* 616 * Removes all identities from the agent. This call is not meant to be used 617 * by normal applications. 618 */ 619 620 int 621 ssh_remove_all_identities(AuthenticationConnection *auth, int version) 622 { 623 Buffer msg; 624 int type; 625 int code = (version==1) ? 626 SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES : 627 SSH2_AGENTC_REMOVE_ALL_IDENTITIES; 628 629 buffer_init(&msg); 630 buffer_put_char(&msg, code); 631 632 if (ssh_request_reply(auth, &msg, &msg) == 0) { 633 buffer_free(&msg); 634 return 0; 635 } 636 type = buffer_get_char(&msg); 637 buffer_free(&msg); 638 return decode_reply(type); 639 } 640 641 int 642 decode_reply(int type) 643 { 644 switch (type) { 645 case SSH_AGENT_FAILURE: 646 case SSH_COM_AGENT2_FAILURE: 647 case SSH2_AGENT_FAILURE: 648 logit("SSH_AGENT_FAILURE"); 649 return 0; 650 case SSH_AGENT_SUCCESS: 651 return 1; 652 default: 653 fatal("Bad response from authentication agent: %d", type); 654 } 655 /* NOTREACHED */ 656 return 0; 657 } 658