1 /* $OpenBSD: authfd.c,v 1.113 2018/12/27 23:02:11 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 #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 #include <errno.h> 51 52 #include "xmalloc.h" 53 #include "ssh.h" 54 #include "sshbuf.h" 55 #include "sshkey.h" 56 #include "authfd.h" 57 #include "cipher.h" 58 #include "compat.h" 59 #include "log.h" 60 #include "atomicio.h" 61 #include "misc.h" 62 #include "ssherr.h" 63 64 #define MAX_AGENT_IDENTITIES 2048 /* Max keys in agent reply */ 65 #define MAX_AGENT_REPLY_LEN (256 * 1024) /* Max bytes in agent reply */ 66 67 /* macro to check for "agent failure" message */ 68 #define agent_failed(x) \ 69 ((x == SSH_AGENT_FAILURE) || \ 70 (x == SSH_COM_AGENT2_FAILURE) || \ 71 (x == SSH2_AGENT_FAILURE)) 72 73 /* Convert success/failure response from agent to a err.h status */ 74 static int 75 decode_reply(u_char type) 76 { 77 if (agent_failed(type)) 78 return SSH_ERR_AGENT_FAILURE; 79 else if (type == SSH_AGENT_SUCCESS) 80 return 0; 81 else 82 return SSH_ERR_INVALID_FORMAT; 83 } 84 85 /* Returns the number of the authentication fd, or -1 if there is none. */ 86 int 87 ssh_get_authentication_socket(int *fdp) 88 { 89 const char *authsocket; 90 int sock, oerrno; 91 struct sockaddr_un sunaddr; 92 93 if (fdp != NULL) 94 *fdp = -1; 95 96 authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME); 97 if (authsocket == NULL || *authsocket == '\0') 98 return SSH_ERR_AGENT_NOT_PRESENT; 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 if ((sock = socket(AF_UNIX, SOCK_STREAM, 0)) < 0) 105 return SSH_ERR_SYSTEM_ERROR; 106 107 /* close on exec */ 108 if (fcntl(sock, F_SETFD, FD_CLOEXEC) == -1 || 109 connect(sock, (struct sockaddr *)&sunaddr, sizeof(sunaddr)) < 0) { 110 oerrno = errno; 111 close(sock); 112 errno = oerrno; 113 return SSH_ERR_SYSTEM_ERROR; 114 } 115 if (fdp != NULL) 116 *fdp = sock; 117 else 118 close(sock); 119 return 0; 120 } 121 122 /* Communicate with agent: send request and read reply */ 123 static int 124 ssh_request_reply(int sock, struct sshbuf *request, struct sshbuf *reply) 125 { 126 int r; 127 size_t l, len; 128 char buf[1024]; 129 130 /* Get the length of the message, and format it in the buffer. */ 131 len = sshbuf_len(request); 132 POKE_U32(buf, len); 133 134 /* Send the length and then the packet to the agent. */ 135 if (atomicio(vwrite, sock, buf, 4) != 4 || 136 atomicio(vwrite, sock, sshbuf_mutable_ptr(request), 137 sshbuf_len(request)) != sshbuf_len(request)) 138 return SSH_ERR_AGENT_COMMUNICATION; 139 /* 140 * Wait for response from the agent. First read the length of the 141 * response packet. 142 */ 143 if (atomicio(read, sock, buf, 4) != 4) 144 return SSH_ERR_AGENT_COMMUNICATION; 145 146 /* Extract the length, and check it for sanity. */ 147 len = PEEK_U32(buf); 148 if (len > MAX_AGENT_REPLY_LEN) 149 return SSH_ERR_INVALID_FORMAT; 150 151 /* Read the rest of the response in to the buffer. */ 152 sshbuf_reset(reply); 153 while (len > 0) { 154 l = len; 155 if (l > sizeof(buf)) 156 l = sizeof(buf); 157 if (atomicio(read, sock, buf, l) != l) 158 return SSH_ERR_AGENT_COMMUNICATION; 159 if ((r = sshbuf_put(reply, buf, l)) != 0) 160 return r; 161 len -= l; 162 } 163 return 0; 164 } 165 166 /* 167 * Closes the agent socket if it should be closed (depends on how it was 168 * obtained). The argument must have been returned by 169 * ssh_get_authentication_socket(). 170 */ 171 void 172 ssh_close_authentication_socket(int sock) 173 { 174 if (getenv(SSH_AUTHSOCKET_ENV_NAME)) 175 close(sock); 176 } 177 178 /* Lock/unlock agent */ 179 int 180 ssh_lock_agent(int sock, int lock, const char *password) 181 { 182 int r; 183 u_char type = lock ? SSH_AGENTC_LOCK : SSH_AGENTC_UNLOCK; 184 struct sshbuf *msg; 185 186 if ((msg = sshbuf_new()) == NULL) 187 return SSH_ERR_ALLOC_FAIL; 188 if ((r = sshbuf_put_u8(msg, type)) != 0 || 189 (r = sshbuf_put_cstring(msg, password)) != 0) 190 goto out; 191 if ((r = ssh_request_reply(sock, msg, msg)) != 0) 192 goto out; 193 if ((r = sshbuf_get_u8(msg, &type)) != 0) 194 goto out; 195 r = decode_reply(type); 196 out: 197 sshbuf_free(msg); 198 return r; 199 } 200 201 202 static int 203 deserialise_identity2(struct sshbuf *ids, struct sshkey **keyp, char **commentp) 204 { 205 int r; 206 char *comment = NULL; 207 const u_char *blob; 208 size_t blen; 209 210 if ((r = sshbuf_get_string_direct(ids, &blob, &blen)) != 0 || 211 (r = sshbuf_get_cstring(ids, &comment, NULL)) != 0) 212 goto out; 213 if ((r = sshkey_from_blob(blob, blen, keyp)) != 0) 214 goto out; 215 if (commentp != NULL) { 216 *commentp = comment; 217 comment = NULL; 218 } 219 r = 0; 220 out: 221 free(comment); 222 return r; 223 } 224 225 /* 226 * Fetch list of identities held by the agent. 227 */ 228 int 229 ssh_fetch_identitylist(int sock, struct ssh_identitylist **idlp) 230 { 231 u_char type; 232 u_int32_t num, i; 233 struct sshbuf *msg; 234 struct ssh_identitylist *idl = NULL; 235 int r; 236 237 /* 238 * Send a message to the agent requesting for a list of the 239 * identities it can represent. 240 */ 241 if ((msg = sshbuf_new()) == NULL) 242 return SSH_ERR_ALLOC_FAIL; 243 if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_REQUEST_IDENTITIES)) != 0) 244 goto out; 245 246 if ((r = ssh_request_reply(sock, msg, msg)) != 0) 247 goto out; 248 249 /* Get message type, and verify that we got a proper answer. */ 250 if ((r = sshbuf_get_u8(msg, &type)) != 0) 251 goto out; 252 if (agent_failed(type)) { 253 r = SSH_ERR_AGENT_FAILURE; 254 goto out; 255 } else if (type != SSH2_AGENT_IDENTITIES_ANSWER) { 256 r = SSH_ERR_INVALID_FORMAT; 257 goto out; 258 } 259 260 /* Get the number of entries in the response and check it for sanity. */ 261 if ((r = sshbuf_get_u32(msg, &num)) != 0) 262 goto out; 263 if (num > MAX_AGENT_IDENTITIES) { 264 r = SSH_ERR_INVALID_FORMAT; 265 goto out; 266 } 267 if (num == 0) { 268 r = SSH_ERR_AGENT_NO_IDENTITIES; 269 goto out; 270 } 271 272 /* Deserialise the response into a list of keys/comments */ 273 if ((idl = calloc(1, sizeof(*idl))) == NULL || 274 (idl->keys = calloc(num, sizeof(*idl->keys))) == NULL || 275 (idl->comments = calloc(num, sizeof(*idl->comments))) == NULL) { 276 r = SSH_ERR_ALLOC_FAIL; 277 goto out; 278 } 279 for (i = 0; i < num;) { 280 if ((r = deserialise_identity2(msg, &(idl->keys[i]), 281 &(idl->comments[i]))) != 0) { 282 if (r == SSH_ERR_KEY_TYPE_UNKNOWN) { 283 /* Gracefully skip unknown key types */ 284 num--; 285 continue; 286 } else 287 goto out; 288 } 289 i++; 290 } 291 idl->nkeys = num; 292 *idlp = idl; 293 idl = NULL; 294 r = 0; 295 out: 296 sshbuf_free(msg); 297 if (idl != NULL) 298 ssh_free_identitylist(idl); 299 return r; 300 } 301 302 void 303 ssh_free_identitylist(struct ssh_identitylist *idl) 304 { 305 size_t i; 306 307 if (idl == NULL) 308 return; 309 for (i = 0; i < idl->nkeys; i++) { 310 if (idl->keys != NULL) 311 sshkey_free(idl->keys[i]); 312 if (idl->comments != NULL) 313 free(idl->comments[i]); 314 } 315 free(idl); 316 } 317 318 /* 319 * Sends a challenge (typically from a server via ssh(1)) to the agent, 320 * and waits for a response from the agent. 321 * Returns true (non-zero) if the agent gave the correct answer, zero 322 * otherwise. 323 */ 324 325 326 /* encode signature algorithm in flag bits, so we can keep the msg format */ 327 static u_int 328 agent_encode_alg(const struct sshkey *key, const char *alg) 329 { 330 if (alg != NULL && sshkey_type_plain(key->type) == KEY_RSA) { 331 if (strcmp(alg, "rsa-sha2-256") == 0 || 332 strcmp(alg, "rsa-sha2-256-cert-v01@openssh.com") == 0) 333 return SSH_AGENT_RSA_SHA2_256; 334 if (strcmp(alg, "rsa-sha2-512") == 0 || 335 strcmp(alg, "rsa-sha2-512-cert-v01@openssh.com") == 0) 336 return SSH_AGENT_RSA_SHA2_512; 337 } 338 return 0; 339 } 340 341 /* ask agent to sign data, returns err.h code on error, 0 on success */ 342 int 343 ssh_agent_sign(int sock, const struct sshkey *key, 344 u_char **sigp, size_t *lenp, 345 const u_char *data, size_t datalen, const char *alg, u_int compat) 346 { 347 struct sshbuf *msg; 348 u_char *sig = NULL, type = 0; 349 size_t len = 0; 350 u_int flags = 0; 351 int r = SSH_ERR_INTERNAL_ERROR; 352 353 *sigp = NULL; 354 *lenp = 0; 355 356 if (datalen > SSH_KEY_MAX_SIGN_DATA_SIZE) 357 return SSH_ERR_INVALID_ARGUMENT; 358 if ((msg = sshbuf_new()) == NULL) 359 return SSH_ERR_ALLOC_FAIL; 360 flags |= agent_encode_alg(key, alg); 361 if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_SIGN_REQUEST)) != 0 || 362 (r = sshkey_puts(key, msg)) != 0 || 363 (r = sshbuf_put_string(msg, data, datalen)) != 0 || 364 (r = sshbuf_put_u32(msg, flags)) != 0) 365 goto out; 366 if ((r = ssh_request_reply(sock, msg, msg)) != 0) 367 goto out; 368 if ((r = sshbuf_get_u8(msg, &type)) != 0) 369 goto out; 370 if (agent_failed(type)) { 371 r = SSH_ERR_AGENT_FAILURE; 372 goto out; 373 } else if (type != SSH2_AGENT_SIGN_RESPONSE) { 374 r = SSH_ERR_INVALID_FORMAT; 375 goto out; 376 } 377 if ((r = sshbuf_get_string(msg, &sig, &len)) != 0) 378 goto out; 379 /* Check what we actually got back from the agent. */ 380 if ((r = sshkey_check_sigtype(sig, len, alg)) != 0) 381 goto out; 382 /* success */ 383 *sigp = sig; 384 *lenp = len; 385 sig = NULL; 386 len = 0; 387 r = 0; 388 out: 389 freezero(sig, len); 390 sshbuf_free(msg); 391 return r; 392 } 393 394 /* Encode key for a message to the agent. */ 395 396 397 static int 398 encode_constraints(struct sshbuf *m, u_int life, u_int confirm, u_int maxsign) 399 { 400 int r; 401 402 if (life != 0) { 403 if ((r = sshbuf_put_u8(m, SSH_AGENT_CONSTRAIN_LIFETIME)) != 0 || 404 (r = sshbuf_put_u32(m, life)) != 0) 405 goto out; 406 } 407 if (confirm != 0) { 408 if ((r = sshbuf_put_u8(m, SSH_AGENT_CONSTRAIN_CONFIRM)) != 0) 409 goto out; 410 } 411 if (maxsign != 0) { 412 if ((r = sshbuf_put_u8(m, SSH_AGENT_CONSTRAIN_MAXSIGN)) != 0 || 413 (r = sshbuf_put_u32(m, maxsign)) != 0) 414 goto out; 415 } 416 r = 0; 417 out: 418 return r; 419 } 420 421 /* 422 * Adds an identity to the authentication server. 423 * This call is intended only for use by ssh-add(1) and like applications. 424 */ 425 int 426 ssh_add_identity_constrained(int sock, const struct sshkey *key, 427 const char *comment, u_int life, u_int confirm, u_int maxsign) 428 { 429 struct sshbuf *msg; 430 int r, constrained = (life || confirm || maxsign); 431 u_char type; 432 433 if ((msg = sshbuf_new()) == NULL) 434 return SSH_ERR_ALLOC_FAIL; 435 436 switch (key->type) { 437 #ifdef WITH_OPENSSL 438 case KEY_RSA: 439 case KEY_RSA_CERT: 440 case KEY_DSA: 441 case KEY_DSA_CERT: 442 case KEY_ECDSA: 443 case KEY_ECDSA_CERT: 444 #endif 445 case KEY_ED25519: 446 case KEY_ED25519_CERT: 447 case KEY_XMSS: 448 case KEY_XMSS_CERT: 449 type = constrained ? 450 SSH2_AGENTC_ADD_ID_CONSTRAINED : 451 SSH2_AGENTC_ADD_IDENTITY; 452 if ((r = sshbuf_put_u8(msg, type)) != 0 || 453 (r = sshkey_private_serialize_maxsign(key, msg, maxsign, 454 NULL)) != 0 || 455 (r = sshbuf_put_cstring(msg, comment)) != 0) 456 goto out; 457 break; 458 default: 459 r = SSH_ERR_INVALID_ARGUMENT; 460 goto out; 461 } 462 if (constrained && 463 (r = encode_constraints(msg, life, confirm, maxsign)) != 0) 464 goto out; 465 if ((r = ssh_request_reply(sock, msg, msg)) != 0) 466 goto out; 467 if ((r = sshbuf_get_u8(msg, &type)) != 0) 468 goto out; 469 r = decode_reply(type); 470 out: 471 sshbuf_free(msg); 472 return r; 473 } 474 475 /* 476 * Removes an identity from the authentication server. 477 * This call is intended only for use by ssh-add(1) and like applications. 478 */ 479 int 480 ssh_remove_identity(int sock, struct sshkey *key) 481 { 482 struct sshbuf *msg; 483 int r; 484 u_char type, *blob = NULL; 485 size_t blen; 486 487 if ((msg = sshbuf_new()) == NULL) 488 return SSH_ERR_ALLOC_FAIL; 489 490 if (key->type != KEY_UNSPEC) { 491 if ((r = sshkey_to_blob(key, &blob, &blen)) != 0) 492 goto out; 493 if ((r = sshbuf_put_u8(msg, 494 SSH2_AGENTC_REMOVE_IDENTITY)) != 0 || 495 (r = sshbuf_put_string(msg, blob, blen)) != 0) 496 goto out; 497 } else { 498 r = SSH_ERR_INVALID_ARGUMENT; 499 goto out; 500 } 501 if ((r = ssh_request_reply(sock, msg, msg)) != 0) 502 goto out; 503 if ((r = sshbuf_get_u8(msg, &type)) != 0) 504 goto out; 505 r = decode_reply(type); 506 out: 507 if (blob != NULL) { 508 explicit_bzero(blob, blen); 509 free(blob); 510 } 511 sshbuf_free(msg); 512 return r; 513 } 514 515 /* 516 * Add/remove an token-based identity from the authentication server. 517 * This call is intended only for use by ssh-add(1) and like applications. 518 */ 519 int 520 ssh_update_card(int sock, int add, const char *reader_id, const char *pin, 521 u_int life, u_int confirm) 522 { 523 struct sshbuf *msg; 524 int r, constrained = (life || confirm); 525 u_char type; 526 527 if (add) { 528 type = constrained ? 529 SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED : 530 SSH_AGENTC_ADD_SMARTCARD_KEY; 531 } else 532 type = SSH_AGENTC_REMOVE_SMARTCARD_KEY; 533 534 if ((msg = sshbuf_new()) == NULL) 535 return SSH_ERR_ALLOC_FAIL; 536 if ((r = sshbuf_put_u8(msg, type)) != 0 || 537 (r = sshbuf_put_cstring(msg, reader_id)) != 0 || 538 (r = sshbuf_put_cstring(msg, pin)) != 0) 539 goto out; 540 if (constrained && 541 (r = encode_constraints(msg, life, confirm, 0)) != 0) 542 goto out; 543 if ((r = ssh_request_reply(sock, msg, msg)) != 0) 544 goto out; 545 if ((r = sshbuf_get_u8(msg, &type)) != 0) 546 goto out; 547 r = decode_reply(type); 548 out: 549 sshbuf_free(msg); 550 return r; 551 } 552 553 /* 554 * Removes all identities from the agent. 555 * This call is intended only for use by ssh-add(1) and like applications. 556 * 557 * This supports the SSH protocol 1 message to because, when clearing all 558 * keys from an agent, we generally want to clear both protocol v1 and v2 559 * keys. 560 */ 561 int 562 ssh_remove_all_identities(int sock, int version) 563 { 564 struct sshbuf *msg; 565 u_char type = (version == 1) ? 566 SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES : 567 SSH2_AGENTC_REMOVE_ALL_IDENTITIES; 568 int r; 569 570 if ((msg = sshbuf_new()) == NULL) 571 return SSH_ERR_ALLOC_FAIL; 572 if ((r = sshbuf_put_u8(msg, type)) != 0) 573 goto out; 574 if ((r = ssh_request_reply(sock, msg, msg)) != 0) 575 goto out; 576 if ((r = sshbuf_get_u8(msg, &type)) != 0) 577 goto out; 578 r = decode_reply(type); 579 out: 580 sshbuf_free(msg); 581 return r; 582 } 583