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 #include "includes.h" 39 40 #include <sys/types.h> 41 #include <sys/un.h> 42 #include <sys/socket.h> 43 44 #include <fcntl.h> 45 #include <stdlib.h> 46 #include <signal.h> 47 #include <stdarg.h> 48 #include <string.h> 49 #include <unistd.h> 50 51 #include "xmalloc.h" 52 #include "ssh.h" 53 #include "rsa.h" 54 #include "buffer.h" 55 #include "key.h" 56 #include "authfd.h" 57 #include "cipher.h" 58 #include "kex.h" 59 #include "compat.h" 60 #include "log.h" 61 #include "atomicio.h" 62 #include "misc.h" 63 64 static int agent_present = 0; 65 66 /* helper */ 67 int decode_reply(int type); 68 69 /* macro to check for "agent failure" message */ 70 #define agent_failed(x) \ 71 ((x == SSH_AGENT_FAILURE) || (x == SSH_COM_AGENT2_FAILURE) || \ 72 (x == SSH2_AGENT_FAILURE)) 73 74 int 75 ssh_agent_present(void) 76 { 77 int authfd; 78 79 if (agent_present) 80 return 1; 81 if ((authfd = ssh_get_authentication_socket()) == -1) 82 return 0; 83 else { 84 ssh_close_authentication_socket(authfd); 85 return 1; 86 } 87 } 88 89 /* Returns the number of the authentication fd, or -1 if there is none. */ 90 91 int 92 ssh_get_authentication_socket(void) 93 { 94 const char *authsocket; 95 int sock; 96 struct sockaddr_un sunaddr; 97 98 authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME); 99 if (!authsocket) 100 return -1; 101 102 memset(&sunaddr, 0, sizeof(sunaddr)); 103 sunaddr.sun_family = AF_UNIX; 104 strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path)); 105 106 sock = socket(AF_UNIX, SOCK_STREAM, 0); 107 if (sock < 0) 108 return -1; 109 110 /* close on exec */ 111 if (fcntl(sock, F_SETFD, FD_CLOEXEC) == -1) { 112 close(sock); 113 return -1; 114 } 115 if (connect(sock, (struct sockaddr *)&sunaddr, sizeof sunaddr) < 0) { 116 close(sock); 117 return -1; 118 } 119 agent_present = 1; 120 return sock; 121 } 122 123 static int 124 ssh_request_reply(AuthenticationConnection *auth, Buffer *request, Buffer *reply) 125 { 126 u_int l, len; 127 char buf[1024]; 128 129 /* Get the length of the message, and format it in the buffer. */ 130 len = buffer_len(request); 131 put_u32(buf, len); 132 133 /* Send the length and then the packet to the agent. */ 134 if (atomicio(vwrite, auth->fd, buf, 4) != 4 || 135 atomicio(vwrite, auth->fd, buffer_ptr(request), 136 buffer_len(request)) != buffer_len(request)) { 137 error("Error writing to authentication socket."); 138 return 0; 139 } 140 /* 141 * Wait for response from the agent. First read the length of the 142 * response packet. 143 */ 144 if (atomicio(read, auth->fd, buf, 4) != 4) { 145 error("Error reading response length from authentication socket."); 146 return 0; 147 } 148 149 /* Extract the length, and check it for sanity. */ 150 len = get_u32(buf); 151 if (len > 256 * 1024) 152 fatal("Authentication response too long: %u", len); 153 154 /* Read the rest of the response in to the buffer. */ 155 buffer_clear(reply); 156 while (len > 0) { 157 l = len; 158 if (l > sizeof(buf)) 159 l = sizeof(buf); 160 if (atomicio(read, auth->fd, buf, l) != l) { 161 error("Error reading response from authentication socket."); 162 return 0; 163 } 164 buffer_append(reply, buf, l); 165 len -= l; 166 } 167 return 1; 168 } 169 170 /* 171 * Closes the agent socket if it should be closed (depends on how it was 172 * obtained). The argument must have been returned by 173 * ssh_get_authentication_socket(). 174 */ 175 176 void 177 ssh_close_authentication_socket(int sock) 178 { 179 if (getenv(SSH_AUTHSOCKET_ENV_NAME)) 180 close(sock); 181 } 182 183 /* 184 * Opens and connects a private socket for communication with the 185 * authentication agent. Returns the file descriptor (which must be 186 * shut down and closed by the caller when no longer needed). 187 * Returns NULL if an error occurred and the connection could not be 188 * opened. 189 */ 190 191 AuthenticationConnection * 192 ssh_get_authentication_connection(void) 193 { 194 AuthenticationConnection *auth; 195 int sock; 196 197 sock = ssh_get_authentication_socket(); 198 199 /* 200 * Fail if we couldn't obtain a connection. This happens if we 201 * exited due to a timeout. 202 */ 203 if (sock < 0) 204 return NULL; 205 206 auth = xcalloc(1, sizeof(*auth)); 207 auth->fd = sock; 208 buffer_init(&auth->identities); 209 auth->howmany = 0; 210 211 return auth; 212 } 213 214 /* 215 * Closes the connection to the authentication agent and frees any associated 216 * memory. 217 */ 218 219 void 220 ssh_close_authentication_connection(AuthenticationConnection *auth) 221 { 222 buffer_free(&auth->identities); 223 close(auth->fd); 224 free(auth); 225 } 226 227 /* Lock/unlock agent */ 228 int 229 ssh_lock_agent(AuthenticationConnection *auth, int lock, const char *password) 230 { 231 int type; 232 Buffer msg; 233 234 buffer_init(&msg); 235 buffer_put_char(&msg, lock ? SSH_AGENTC_LOCK : SSH_AGENTC_UNLOCK); 236 buffer_put_cstring(&msg, password); 237 238 if (ssh_request_reply(auth, &msg, &msg) == 0) { 239 buffer_free(&msg); 240 return 0; 241 } 242 type = buffer_get_char(&msg); 243 buffer_free(&msg); 244 return decode_reply(type); 245 } 246 247 /* 248 * Returns the first authentication identity held by the agent. 249 */ 250 251 int 252 ssh_get_num_identities(AuthenticationConnection *auth, int version) 253 { 254 int type, code1 = 0, code2 = 0; 255 Buffer request; 256 257 switch (version) { 258 case 1: 259 code1 = SSH_AGENTC_REQUEST_RSA_IDENTITIES; 260 code2 = SSH_AGENT_RSA_IDENTITIES_ANSWER; 261 break; 262 case 2: 263 code1 = SSH2_AGENTC_REQUEST_IDENTITIES; 264 code2 = SSH2_AGENT_IDENTITIES_ANSWER; 265 break; 266 default: 267 return 0; 268 } 269 270 /* 271 * Send a message to the agent requesting for a list of the 272 * identities it can represent. 273 */ 274 buffer_init(&request); 275 buffer_put_char(&request, code1); 276 277 buffer_clear(&auth->identities); 278 if (ssh_request_reply(auth, &request, &auth->identities) == 0) { 279 buffer_free(&request); 280 return 0; 281 } 282 buffer_free(&request); 283 284 /* Get message type, and verify that we got a proper answer. */ 285 type = buffer_get_char(&auth->identities); 286 if (agent_failed(type)) { 287 return 0; 288 } else if (type != code2) { 289 fatal("Bad authentication reply message type: %d", type); 290 } 291 292 /* Get the number of entries in the response and check it for sanity. */ 293 auth->howmany = buffer_get_int(&auth->identities); 294 if ((u_int)auth->howmany > 1024) 295 fatal("Too many identities in authentication reply: %d", 296 auth->howmany); 297 298 return auth->howmany; 299 } 300 301 Key * 302 ssh_get_first_identity(AuthenticationConnection *auth, char **comment, int version) 303 { 304 /* get number of identities and return the first entry (if any). */ 305 if (ssh_get_num_identities(auth, version) > 0) 306 return ssh_get_next_identity(auth, comment, version); 307 return NULL; 308 } 309 310 Key * 311 ssh_get_next_identity(AuthenticationConnection *auth, char **comment, int version) 312 { 313 #ifdef WITH_SSH1 314 int keybits; 315 u_int bits; 316 #endif 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 #ifdef WITH_SSH1 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 #endif 343 case 2: 344 blob = buffer_get_string(&auth->identities, &blen); 345 *comment = buffer_get_string(&auth->identities, NULL); 346 key = key_from_blob(blob, blen); 347 free(blob); 348 break; 349 default: 350 return NULL; 351 } 352 /* Decrement the number of remaining entries. */ 353 auth->howmany--; 354 return key; 355 } 356 357 /* 358 * Generates a random challenge, sends it to the agent, and waits for 359 * response from the agent. Returns true (non-zero) if the agent gave the 360 * correct answer, zero otherwise. Response type selects the style of 361 * response desired, with 0 corresponding to protocol version 1.0 (no longer 362 * supported) and 1 corresponding to protocol version 1.1. 363 */ 364 365 #ifdef WITH_SSH1 366 int 367 ssh_decrypt_challenge(AuthenticationConnection *auth, 368 Key* key, BIGNUM *challenge, 369 u_char session_id[16], 370 u_int response_type, 371 u_char response[16]) 372 { 373 Buffer buffer; 374 int success = 0; 375 int i; 376 int type; 377 378 if (key->type != KEY_RSA1) 379 return 0; 380 if (response_type == 0) { 381 logit("Compatibility with ssh protocol version 1.0 no longer supported."); 382 return 0; 383 } 384 buffer_init(&buffer); 385 buffer_put_char(&buffer, SSH_AGENTC_RSA_CHALLENGE); 386 buffer_put_int(&buffer, BN_num_bits(key->rsa->n)); 387 buffer_put_bignum(&buffer, key->rsa->e); 388 buffer_put_bignum(&buffer, key->rsa->n); 389 buffer_put_bignum(&buffer, challenge); 390 buffer_append(&buffer, session_id, 16); 391 buffer_put_int(&buffer, response_type); 392 393 if (ssh_request_reply(auth, &buffer, &buffer) == 0) { 394 buffer_free(&buffer); 395 return 0; 396 } 397 type = buffer_get_char(&buffer); 398 399 if (agent_failed(type)) { 400 logit("Agent admitted failure to authenticate using the key."); 401 } else if (type != SSH_AGENT_RSA_RESPONSE) { 402 fatal("Bad authentication response: %d", type); 403 } else { 404 success = 1; 405 /* 406 * Get the response from the packet. This will abort with a 407 * fatal error if the packet is corrupt. 408 */ 409 for (i = 0; i < 16; i++) 410 response[i] = (u_char)buffer_get_char(&buffer); 411 } 412 buffer_free(&buffer); 413 return success; 414 } 415 #endif 416 417 /* ask agent to sign data, returns -1 on error, 0 on success */ 418 int 419 ssh_agent_sign(AuthenticationConnection *auth, 420 Key *key, 421 u_char **sigp, u_int *lenp, 422 u_char *data, u_int datalen) 423 { 424 extern int datafellows; 425 Buffer msg; 426 u_char *blob; 427 u_int blen; 428 int type, flags = 0; 429 int ret = -1; 430 431 if (key_to_blob(key, &blob, &blen) == 0) 432 return -1; 433 434 if (datafellows & SSH_BUG_SIGBLOB) 435 flags = SSH_AGENT_OLD_SIGNATURE; 436 437 buffer_init(&msg); 438 buffer_put_char(&msg, SSH2_AGENTC_SIGN_REQUEST); 439 buffer_put_string(&msg, blob, blen); 440 buffer_put_string(&msg, data, datalen); 441 buffer_put_int(&msg, flags); 442 free(blob); 443 444 if (ssh_request_reply(auth, &msg, &msg) == 0) { 445 buffer_free(&msg); 446 return -1; 447 } 448 type = buffer_get_char(&msg); 449 if (agent_failed(type)) { 450 logit("Agent admitted failure to sign using the key."); 451 } else if (type != SSH2_AGENT_SIGN_RESPONSE) { 452 fatal("Bad authentication response: %d", type); 453 } else { 454 ret = 0; 455 *sigp = buffer_get_string(&msg, lenp); 456 } 457 buffer_free(&msg); 458 return ret; 459 } 460 461 /* Encode key for a message to the agent. */ 462 463 #ifdef WITH_SSH1 464 static void 465 ssh_encode_identity_rsa1(Buffer *b, RSA *key, const char *comment) 466 { 467 buffer_put_int(b, BN_num_bits(key->n)); 468 buffer_put_bignum(b, key->n); 469 buffer_put_bignum(b, key->e); 470 buffer_put_bignum(b, key->d); 471 /* To keep within the protocol: p < q for ssh. in SSL p > q */ 472 buffer_put_bignum(b, key->iqmp); /* ssh key->u */ 473 buffer_put_bignum(b, key->q); /* ssh key->p, SSL key->q */ 474 buffer_put_bignum(b, key->p); /* ssh key->q, SSL key->p */ 475 buffer_put_cstring(b, comment); 476 } 477 #endif 478 479 static void 480 ssh_encode_identity_ssh2(Buffer *b, Key *key, const char *comment) 481 { 482 key_private_serialize(key, b); 483 buffer_put_cstring(b, comment); 484 } 485 486 /* 487 * Adds an identity to the authentication server. This call is not meant to 488 * be used by normal applications. 489 */ 490 491 int 492 ssh_add_identity_constrained(AuthenticationConnection *auth, Key *key, 493 const char *comment, u_int life, u_int confirm) 494 { 495 Buffer msg; 496 int type, constrained = (life || confirm); 497 498 buffer_init(&msg); 499 500 switch (key->type) { 501 #ifdef WITH_SSH1 502 case KEY_RSA1: 503 type = constrained ? 504 SSH_AGENTC_ADD_RSA_ID_CONSTRAINED : 505 SSH_AGENTC_ADD_RSA_IDENTITY; 506 buffer_put_char(&msg, type); 507 ssh_encode_identity_rsa1(&msg, key->rsa, comment); 508 break; 509 #endif 510 #ifdef WITH_OPENSSL 511 case KEY_RSA: 512 case KEY_RSA_CERT: 513 case KEY_RSA_CERT_V00: 514 case KEY_DSA: 515 case KEY_DSA_CERT: 516 case KEY_DSA_CERT_V00: 517 case KEY_ECDSA: 518 case KEY_ECDSA_CERT: 519 #endif 520 case KEY_ED25519: 521 case KEY_ED25519_CERT: 522 type = constrained ? 523 SSH2_AGENTC_ADD_ID_CONSTRAINED : 524 SSH2_AGENTC_ADD_IDENTITY; 525 buffer_put_char(&msg, type); 526 ssh_encode_identity_ssh2(&msg, key, comment); 527 break; 528 default: 529 buffer_free(&msg); 530 return 0; 531 } 532 if (constrained) { 533 if (life != 0) { 534 buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_LIFETIME); 535 buffer_put_int(&msg, life); 536 } 537 if (confirm != 0) 538 buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_CONFIRM); 539 } 540 if (ssh_request_reply(auth, &msg, &msg) == 0) { 541 buffer_free(&msg); 542 return 0; 543 } 544 type = buffer_get_char(&msg); 545 buffer_free(&msg); 546 return decode_reply(type); 547 } 548 549 /* 550 * Removes an identity from the authentication server. This call is not 551 * meant to be used by normal applications. 552 */ 553 554 int 555 ssh_remove_identity(AuthenticationConnection *auth, Key *key) 556 { 557 Buffer msg; 558 int type; 559 u_char *blob; 560 u_int blen; 561 562 buffer_init(&msg); 563 564 #ifdef WITH_SSH1 565 if (key->type == KEY_RSA1) { 566 buffer_put_char(&msg, SSH_AGENTC_REMOVE_RSA_IDENTITY); 567 buffer_put_int(&msg, BN_num_bits(key->rsa->n)); 568 buffer_put_bignum(&msg, key->rsa->e); 569 buffer_put_bignum(&msg, key->rsa->n); 570 } else 571 #endif 572 if (key->type != KEY_UNSPEC) { 573 key_to_blob(key, &blob, &blen); 574 buffer_put_char(&msg, SSH2_AGENTC_REMOVE_IDENTITY); 575 buffer_put_string(&msg, blob, blen); 576 free(blob); 577 } else { 578 buffer_free(&msg); 579 return 0; 580 } 581 if (ssh_request_reply(auth, &msg, &msg) == 0) { 582 buffer_free(&msg); 583 return 0; 584 } 585 type = buffer_get_char(&msg); 586 buffer_free(&msg); 587 return decode_reply(type); 588 } 589 590 int 591 ssh_update_card(AuthenticationConnection *auth, int add, 592 const char *reader_id, const char *pin, u_int life, u_int confirm) 593 { 594 Buffer msg; 595 int type, constrained = (life || confirm); 596 597 if (add) { 598 type = constrained ? 599 SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED : 600 SSH_AGENTC_ADD_SMARTCARD_KEY; 601 } else 602 type = SSH_AGENTC_REMOVE_SMARTCARD_KEY; 603 604 buffer_init(&msg); 605 buffer_put_char(&msg, type); 606 buffer_put_cstring(&msg, reader_id); 607 buffer_put_cstring(&msg, pin); 608 609 if (constrained) { 610 if (life != 0) { 611 buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_LIFETIME); 612 buffer_put_int(&msg, life); 613 } 614 if (confirm != 0) 615 buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_CONFIRM); 616 } 617 618 if (ssh_request_reply(auth, &msg, &msg) == 0) { 619 buffer_free(&msg); 620 return 0; 621 } 622 type = buffer_get_char(&msg); 623 buffer_free(&msg); 624 return decode_reply(type); 625 } 626 627 /* 628 * Removes all identities from the agent. This call is not meant to be used 629 * by normal applications. 630 */ 631 632 int 633 ssh_remove_all_identities(AuthenticationConnection *auth, int version) 634 { 635 Buffer msg; 636 int type; 637 int code = (version==1) ? 638 SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES : 639 SSH2_AGENTC_REMOVE_ALL_IDENTITIES; 640 641 buffer_init(&msg); 642 buffer_put_char(&msg, code); 643 644 if (ssh_request_reply(auth, &msg, &msg) == 0) { 645 buffer_free(&msg); 646 return 0; 647 } 648 type = buffer_get_char(&msg); 649 buffer_free(&msg); 650 return decode_reply(type); 651 } 652 653 int 654 decode_reply(int type) 655 { 656 switch (type) { 657 case SSH_AGENT_FAILURE: 658 case SSH_COM_AGENT2_FAILURE: 659 case SSH2_AGENT_FAILURE: 660 logit("SSH_AGENT_FAILURE"); 661 return 0; 662 case SSH_AGENT_SUCCESS: 663 return 1; 664 default: 665 fatal("Bad response from authentication agent: %d", type); 666 } 667 /* NOTREACHED */ 668 return 0; 669 } 670