1 /* $OpenBSD: authfd.c,v 1.102 2017/05/04 06:10:57 djm 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 #include <errno.h> 49 50 #include "xmalloc.h" 51 #include "ssh.h" 52 #include "rsa.h" 53 #include "sshbuf.h" 54 #include "sshkey.h" 55 #include "authfd.h" 56 #include "cipher.h" 57 #include "compat.h" 58 #include "log.h" 59 #include "atomicio.h" 60 #include "misc.h" 61 #include "ssherr.h" 62 63 #define MAX_AGENT_IDENTITIES 2048 /* Max keys in agent reply */ 64 #define MAX_AGENT_REPLY_LEN (256 * 1024) /* Max bytes in agent reply */ 65 66 /* macro to check for "agent failure" message */ 67 #define agent_failed(x) \ 68 ((x == SSH_AGENT_FAILURE) || \ 69 (x == SSH_COM_AGENT2_FAILURE) || \ 70 (x == SSH2_AGENT_FAILURE)) 71 72 /* Convert success/failure response from agent to a err.h status */ 73 static int 74 decode_reply(u_char type) 75 { 76 if (agent_failed(type)) 77 return SSH_ERR_AGENT_FAILURE; 78 else if (type == SSH_AGENT_SUCCESS) 79 return 0; 80 else 81 return SSH_ERR_INVALID_FORMAT; 82 } 83 84 /* Returns the number of the authentication fd, or -1 if there is none. */ 85 int 86 ssh_get_authentication_socket(int *fdp) 87 { 88 const char *authsocket; 89 int sock, oerrno; 90 struct sockaddr_un sunaddr; 91 92 if (fdp != NULL) 93 *fdp = -1; 94 95 authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME); 96 if (!authsocket) 97 return SSH_ERR_AGENT_NOT_PRESENT; 98 99 memset(&sunaddr, 0, sizeof(sunaddr)); 100 sunaddr.sun_family = AF_UNIX; 101 strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path)); 102 103 if ((sock = socket(AF_UNIX, SOCK_STREAM, 0)) < 0) 104 return SSH_ERR_SYSTEM_ERROR; 105 106 /* close on exec */ 107 if (fcntl(sock, F_SETFD, FD_CLOEXEC) == -1 || 108 connect(sock, (struct sockaddr *)&sunaddr, sizeof(sunaddr)) < 0) { 109 oerrno = errno; 110 close(sock); 111 errno = oerrno; 112 return SSH_ERR_SYSTEM_ERROR; 113 } 114 if (fdp != NULL) 115 *fdp = sock; 116 else 117 close(sock); 118 return 0; 119 } 120 121 /* Communicate with agent: send request and read reply */ 122 static int 123 ssh_request_reply(int sock, struct sshbuf *request, struct sshbuf *reply) 124 { 125 int r; 126 size_t l, len; 127 char buf[1024]; 128 129 /* Get the length of the message, and format it in the buffer. */ 130 len = sshbuf_len(request); 131 put_u32(buf, len); 132 133 /* Send the length and then the packet to the agent. */ 134 if (atomicio(vwrite, sock, buf, 4) != 4 || 135 atomicio(vwrite, sock, (u_char *)sshbuf_ptr(request), 136 sshbuf_len(request)) != sshbuf_len(request)) 137 return SSH_ERR_AGENT_COMMUNICATION; 138 /* 139 * Wait for response from the agent. First read the length of the 140 * response packet. 141 */ 142 if (atomicio(read, sock, buf, 4) != 4) 143 return SSH_ERR_AGENT_COMMUNICATION; 144 145 /* Extract the length, and check it for sanity. */ 146 len = get_u32(buf); 147 if (len > MAX_AGENT_REPLY_LEN) 148 return SSH_ERR_INVALID_FORMAT; 149 150 /* Read the rest of the response in to the buffer. */ 151 sshbuf_reset(reply); 152 while (len > 0) { 153 l = len; 154 if (l > sizeof(buf)) 155 l = sizeof(buf); 156 if (atomicio(read, sock, buf, l) != l) 157 return SSH_ERR_AGENT_COMMUNICATION; 158 if ((r = sshbuf_put(reply, buf, l)) != 0) 159 return r; 160 len -= l; 161 } 162 return 0; 163 } 164 165 /* 166 * Closes the agent socket if it should be closed (depends on how it was 167 * obtained). The argument must have been returned by 168 * ssh_get_authentication_socket(). 169 */ 170 void 171 ssh_close_authentication_socket(int sock) 172 { 173 if (getenv(SSH_AUTHSOCKET_ENV_NAME)) 174 close(sock); 175 } 176 177 /* Lock/unlock agent */ 178 int 179 ssh_lock_agent(int sock, int lock, const char *password) 180 { 181 int r; 182 u_char type = lock ? SSH_AGENTC_LOCK : SSH_AGENTC_UNLOCK; 183 struct sshbuf *msg; 184 185 if ((msg = sshbuf_new()) == NULL) 186 return SSH_ERR_ALLOC_FAIL; 187 if ((r = sshbuf_put_u8(msg, type)) != 0 || 188 (r = sshbuf_put_cstring(msg, password)) != 0) 189 goto out; 190 if ((r = ssh_request_reply(sock, msg, msg)) != 0) 191 goto out; 192 if ((r = sshbuf_get_u8(msg, &type)) != 0) 193 goto out; 194 r = decode_reply(type); 195 out: 196 sshbuf_free(msg); 197 return r; 198 } 199 200 201 static int 202 deserialise_identity2(struct sshbuf *ids, struct sshkey **keyp, char **commentp) 203 { 204 int r; 205 char *comment = NULL; 206 const u_char *blob; 207 size_t blen; 208 209 if ((r = sshbuf_get_string_direct(ids, &blob, &blen)) != 0 || 210 (r = sshbuf_get_cstring(ids, &comment, NULL)) != 0) 211 goto out; 212 if ((r = sshkey_from_blob(blob, blen, keyp)) != 0) 213 goto out; 214 if (commentp != NULL) { 215 *commentp = comment; 216 comment = NULL; 217 } 218 r = 0; 219 out: 220 free(comment); 221 return r; 222 } 223 224 /* 225 * Fetch list of identities held by the agent. 226 */ 227 int 228 ssh_fetch_identitylist(int sock, int version, struct ssh_identitylist **idlp) 229 { 230 u_char type, code1 = 0, code2 = 0; 231 u_int32_t num, i; 232 struct sshbuf *msg; 233 struct ssh_identitylist *idl = NULL; 234 int r; 235 236 /* Determine request and expected response types */ 237 switch (version) { 238 case 1: 239 code1 = SSH_AGENTC_REQUEST_RSA_IDENTITIES; 240 code2 = SSH_AGENT_RSA_IDENTITIES_ANSWER; 241 break; 242 case 2: 243 code1 = SSH2_AGENTC_REQUEST_IDENTITIES; 244 code2 = SSH2_AGENT_IDENTITIES_ANSWER; 245 break; 246 default: 247 return SSH_ERR_INVALID_ARGUMENT; 248 } 249 250 /* 251 * Send a message to the agent requesting for a list of the 252 * identities it can represent. 253 */ 254 if ((msg = sshbuf_new()) == NULL) 255 return SSH_ERR_ALLOC_FAIL; 256 if ((r = sshbuf_put_u8(msg, code1)) != 0) 257 goto out; 258 259 if ((r = ssh_request_reply(sock, msg, msg)) != 0) 260 goto out; 261 262 /* Get message type, and verify that we got a proper answer. */ 263 if ((r = sshbuf_get_u8(msg, &type)) != 0) 264 goto out; 265 if (agent_failed(type)) { 266 r = SSH_ERR_AGENT_FAILURE; 267 goto out; 268 } else if (type != code2) { 269 r = SSH_ERR_INVALID_FORMAT; 270 goto out; 271 } 272 273 /* Get the number of entries in the response and check it for sanity. */ 274 if ((r = sshbuf_get_u32(msg, &num)) != 0) 275 goto out; 276 if (num > MAX_AGENT_IDENTITIES) { 277 r = SSH_ERR_INVALID_FORMAT; 278 goto out; 279 } 280 if (num == 0) { 281 r = SSH_ERR_AGENT_NO_IDENTITIES; 282 goto out; 283 } 284 285 /* Deserialise the response into a list of keys/comments */ 286 if ((idl = calloc(1, sizeof(*idl))) == NULL || 287 (idl->keys = calloc(num, sizeof(*idl->keys))) == NULL || 288 (idl->comments = calloc(num, sizeof(*idl->comments))) == NULL) { 289 r = SSH_ERR_ALLOC_FAIL; 290 goto out; 291 } 292 for (i = 0; i < num;) { 293 switch (version) { 294 case 1: 295 break; 296 case 2: 297 if ((r = deserialise_identity2(msg, 298 &(idl->keys[i]), &(idl->comments[i]))) != 0) { 299 if (r == SSH_ERR_KEY_TYPE_UNKNOWN) { 300 /* Gracefully skip unknown key types */ 301 num--; 302 continue; 303 } else 304 goto out; 305 } 306 break; 307 } 308 i++; 309 } 310 idl->nkeys = num; 311 *idlp = idl; 312 idl = NULL; 313 r = 0; 314 out: 315 sshbuf_free(msg); 316 if (idl != NULL) 317 ssh_free_identitylist(idl); 318 return r; 319 } 320 321 void 322 ssh_free_identitylist(struct ssh_identitylist *idl) 323 { 324 size_t i; 325 326 if (idl == NULL) 327 return; 328 for (i = 0; i < idl->nkeys; i++) { 329 if (idl->keys != NULL) 330 sshkey_free(idl->keys[i]); 331 if (idl->comments != NULL) 332 free(idl->comments[i]); 333 } 334 free(idl); 335 } 336 337 /* 338 * Sends a challenge (typically from a server via ssh(1)) to the agent, 339 * and waits for a response from the agent. 340 * Returns true (non-zero) if the agent gave the correct answer, zero 341 * otherwise. 342 */ 343 344 345 /* encode signature algoritm in flag bits, so we can keep the msg format */ 346 static u_int 347 agent_encode_alg(struct sshkey *key, const char *alg) 348 { 349 if (alg != NULL && key->type == KEY_RSA) { 350 if (strcmp(alg, "rsa-sha2-256") == 0) 351 return SSH_AGENT_RSA_SHA2_256; 352 else if (strcmp(alg, "rsa-sha2-512") == 0) 353 return SSH_AGENT_RSA_SHA2_512; 354 } 355 return 0; 356 } 357 358 /* ask agent to sign data, returns err.h code on error, 0 on success */ 359 int 360 ssh_agent_sign(int sock, struct sshkey *key, 361 u_char **sigp, size_t *lenp, 362 const u_char *data, size_t datalen, const char *alg, u_int compat) 363 { 364 struct sshbuf *msg; 365 u_char *blob = NULL, type; 366 size_t blen = 0, len = 0; 367 u_int flags = 0; 368 int r = SSH_ERR_INTERNAL_ERROR; 369 370 *sigp = NULL; 371 *lenp = 0; 372 373 if (datalen > SSH_KEY_MAX_SIGN_DATA_SIZE) 374 return SSH_ERR_INVALID_ARGUMENT; 375 if (compat & SSH_BUG_SIGBLOB) 376 flags |= SSH_AGENT_OLD_SIGNATURE; 377 if ((msg = sshbuf_new()) == NULL) 378 return SSH_ERR_ALLOC_FAIL; 379 if ((r = sshkey_to_blob(key, &blob, &blen)) != 0) 380 goto out; 381 flags |= agent_encode_alg(key, alg); 382 if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_SIGN_REQUEST)) != 0 || 383 (r = sshbuf_put_string(msg, blob, blen)) != 0 || 384 (r = sshbuf_put_string(msg, data, datalen)) != 0 || 385 (r = sshbuf_put_u32(msg, flags)) != 0) 386 goto out; 387 if ((r = ssh_request_reply(sock, msg, msg)) != 0) 388 goto out; 389 if ((r = sshbuf_get_u8(msg, &type)) != 0) 390 goto out; 391 if (agent_failed(type)) { 392 r = SSH_ERR_AGENT_FAILURE; 393 goto out; 394 } else if (type != SSH2_AGENT_SIGN_RESPONSE) { 395 r = SSH_ERR_INVALID_FORMAT; 396 goto out; 397 } 398 if ((r = sshbuf_get_string(msg, sigp, &len)) != 0) 399 goto out; 400 *lenp = len; 401 r = 0; 402 out: 403 if (blob != NULL) { 404 explicit_bzero(blob, blen); 405 free(blob); 406 } 407 sshbuf_free(msg); 408 return r; 409 } 410 411 /* Encode key for a message to the agent. */ 412 413 414 static int 415 ssh_encode_identity_ssh2(struct sshbuf *b, struct sshkey *key, 416 const char *comment) 417 { 418 int r; 419 420 if ((r = sshkey_private_serialize(key, b)) != 0 || 421 (r = sshbuf_put_cstring(b, comment)) != 0) 422 return r; 423 return 0; 424 } 425 426 static int 427 encode_constraints(struct sshbuf *m, u_int life, u_int confirm) 428 { 429 int r; 430 431 if (life != 0) { 432 if ((r = sshbuf_put_u8(m, SSH_AGENT_CONSTRAIN_LIFETIME)) != 0 || 433 (r = sshbuf_put_u32(m, life)) != 0) 434 goto out; 435 } 436 if (confirm != 0) { 437 if ((r = sshbuf_put_u8(m, SSH_AGENT_CONSTRAIN_CONFIRM)) != 0) 438 goto out; 439 } 440 r = 0; 441 out: 442 return r; 443 } 444 445 /* 446 * Adds an identity to the authentication server. 447 * This call is intended only for use by ssh-add(1) and like applications. 448 */ 449 int 450 ssh_add_identity_constrained(int sock, struct sshkey *key, const char *comment, 451 u_int life, u_int confirm) 452 { 453 struct sshbuf *msg; 454 int r, constrained = (life || confirm); 455 u_char type; 456 457 if ((msg = sshbuf_new()) == NULL) 458 return SSH_ERR_ALLOC_FAIL; 459 460 switch (key->type) { 461 #ifdef WITH_OPENSSL 462 case KEY_RSA: 463 case KEY_RSA_CERT: 464 case KEY_DSA: 465 case KEY_DSA_CERT: 466 case KEY_ECDSA: 467 case KEY_ECDSA_CERT: 468 #endif 469 case KEY_ED25519: 470 case KEY_ED25519_CERT: 471 type = constrained ? 472 SSH2_AGENTC_ADD_ID_CONSTRAINED : 473 SSH2_AGENTC_ADD_IDENTITY; 474 if ((r = sshbuf_put_u8(msg, type)) != 0 || 475 (r = ssh_encode_identity_ssh2(msg, key, comment)) != 0) 476 goto out; 477 break; 478 default: 479 r = SSH_ERR_INVALID_ARGUMENT; 480 goto out; 481 } 482 if (constrained && 483 (r = encode_constraints(msg, life, confirm)) != 0) 484 goto out; 485 if ((r = ssh_request_reply(sock, msg, msg)) != 0) 486 goto out; 487 if ((r = sshbuf_get_u8(msg, &type)) != 0) 488 goto out; 489 r = decode_reply(type); 490 out: 491 sshbuf_free(msg); 492 return r; 493 } 494 495 /* 496 * Removes an identity from the authentication server. 497 * This call is intended only for use by ssh-add(1) and like applications. 498 */ 499 int 500 ssh_remove_identity(int sock, struct sshkey *key) 501 { 502 struct sshbuf *msg; 503 int r; 504 u_char type, *blob = NULL; 505 size_t blen; 506 507 if ((msg = sshbuf_new()) == NULL) 508 return SSH_ERR_ALLOC_FAIL; 509 510 if (key->type != KEY_UNSPEC) { 511 if ((r = sshkey_to_blob(key, &blob, &blen)) != 0) 512 goto out; 513 if ((r = sshbuf_put_u8(msg, 514 SSH2_AGENTC_REMOVE_IDENTITY)) != 0 || 515 (r = sshbuf_put_string(msg, blob, blen)) != 0) 516 goto out; 517 } else { 518 r = SSH_ERR_INVALID_ARGUMENT; 519 goto out; 520 } 521 if ((r = ssh_request_reply(sock, msg, msg)) != 0) 522 goto out; 523 if ((r = sshbuf_get_u8(msg, &type)) != 0) 524 goto out; 525 r = decode_reply(type); 526 out: 527 if (blob != NULL) { 528 explicit_bzero(blob, blen); 529 free(blob); 530 } 531 sshbuf_free(msg); 532 return r; 533 } 534 535 /* 536 * Add/remove an token-based identity from the authentication server. 537 * This call is intended only for use by ssh-add(1) and like applications. 538 */ 539 int 540 ssh_update_card(int sock, int add, const char *reader_id, const char *pin, 541 u_int life, u_int confirm) 542 { 543 struct sshbuf *msg; 544 int r, constrained = (life || confirm); 545 u_char type; 546 547 if (add) { 548 type = constrained ? 549 SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED : 550 SSH_AGENTC_ADD_SMARTCARD_KEY; 551 } else 552 type = SSH_AGENTC_REMOVE_SMARTCARD_KEY; 553 554 if ((msg = sshbuf_new()) == NULL) 555 return SSH_ERR_ALLOC_FAIL; 556 if ((r = sshbuf_put_u8(msg, type)) != 0 || 557 (r = sshbuf_put_cstring(msg, reader_id)) != 0 || 558 (r = sshbuf_put_cstring(msg, pin)) != 0) 559 goto out; 560 if (constrained && 561 (r = encode_constraints(msg, life, confirm)) != 0) 562 goto out; 563 if ((r = ssh_request_reply(sock, msg, msg)) != 0) 564 goto out; 565 if ((r = sshbuf_get_u8(msg, &type)) != 0) 566 goto out; 567 r = decode_reply(type); 568 out: 569 sshbuf_free(msg); 570 return r; 571 } 572 573 /* 574 * Removes all identities from the agent. 575 * This call is intended only for use by ssh-add(1) and like applications. 576 * 577 * This supports the SSH protocol 1 message to because, when clearing all 578 * keys from an agent, we generally want to clear both protocol v1 and v2 579 * keys. 580 */ 581 int 582 ssh_remove_all_identities(int sock, int version) 583 { 584 struct sshbuf *msg; 585 u_char type = (version == 1) ? 586 SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES : 587 SSH2_AGENTC_REMOVE_ALL_IDENTITIES; 588 int r; 589 590 if ((msg = sshbuf_new()) == NULL) 591 return SSH_ERR_ALLOC_FAIL; 592 if ((r = sshbuf_put_u8(msg, type)) != 0) 593 goto out; 594 if ((r = ssh_request_reply(sock, msg, msg)) != 0) 595 goto out; 596 if ((r = sshbuf_get_u8(msg, &type)) != 0) 597 goto out; 598 r = decode_reply(type); 599 out: 600 sshbuf_free(msg); 601 return r; 602 } 603