1 /* $OpenBSD: ssh-pkcs11-client.c,v 1.18 2023/07/19 14:03:45 djm Exp $ */ 2 /* 3 * Copyright (c) 2010 Markus Friedl. All rights reserved. 4 * Copyright (c) 2014 Pedro Martelletto. All rights reserved. 5 * 6 * Permission to use, copy, modify, and distribute this software for any 7 * purpose with or without fee is hereby granted, provided that the above 8 * copyright notice and this permission notice appear in all copies. 9 * 10 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 11 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 12 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 13 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 14 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 15 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 16 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 17 */ 18 19 #include "includes.h" 20 21 #ifdef ENABLE_PKCS11 22 23 #include <sys/types.h> 24 #ifdef HAVE_SYS_TIME_H 25 # include <sys/time.h> 26 #endif 27 #include <sys/socket.h> 28 29 #include <stdarg.h> 30 #include <string.h> 31 #include <unistd.h> 32 #include <errno.h> 33 #include <limits.h> 34 35 #include <openssl/ecdsa.h> 36 #include <openssl/rsa.h> 37 38 #include "pathnames.h" 39 #include "xmalloc.h" 40 #include "sshbuf.h" 41 #include "log.h" 42 #include "misc.h" 43 #include "sshkey.h" 44 #include "authfd.h" 45 #include "atomicio.h" 46 #include "ssh-pkcs11.h" 47 #include "ssherr.h" 48 49 #include "openbsd-compat/openssl-compat.h" 50 51 #if !defined(OPENSSL_HAS_ECC) || !defined(HAVE_EC_KEY_METHOD_NEW) 52 #define EC_KEY_METHOD void 53 #define EC_KEY void 54 #endif 55 56 /* borrows code from sftp-server and ssh-agent */ 57 58 /* 59 * Maintain a list of ssh-pkcs11-helper subprocesses. These may be looked up 60 * by provider path or their unique EC/RSA METHOD pointers. 61 */ 62 struct helper { 63 char *path; 64 pid_t pid; 65 int fd; 66 RSA_METHOD *rsa_meth; 67 EC_KEY_METHOD *ec_meth; 68 int (*rsa_finish)(RSA *rsa); 69 void (*ec_finish)(EC_KEY *key); 70 size_t nrsa, nec; /* number of active keys of each type */ 71 }; 72 static struct helper **helpers; 73 static size_t nhelpers; 74 75 static struct helper * 76 helper_by_provider(const char *path) 77 { 78 size_t i; 79 80 for (i = 0; i < nhelpers; i++) { 81 if (helpers[i] == NULL || helpers[i]->path == NULL || 82 helpers[i]->fd == -1) 83 continue; 84 if (strcmp(helpers[i]->path, path) == 0) 85 return helpers[i]; 86 } 87 return NULL; 88 } 89 90 static struct helper * 91 helper_by_rsa(const RSA *rsa) 92 { 93 size_t i; 94 const RSA_METHOD *meth; 95 96 if ((meth = RSA_get_method(rsa)) == NULL) 97 return NULL; 98 for (i = 0; i < nhelpers; i++) { 99 if (helpers[i] != NULL && helpers[i]->rsa_meth == meth) 100 return helpers[i]; 101 } 102 return NULL; 103 104 } 105 106 #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW) 107 static struct helper * 108 helper_by_ec(const EC_KEY *ec) 109 { 110 size_t i; 111 const EC_KEY_METHOD *meth; 112 113 if ((meth = EC_KEY_get_method(ec)) == NULL) 114 return NULL; 115 for (i = 0; i < nhelpers; i++) { 116 if (helpers[i] != NULL && helpers[i]->ec_meth == meth) 117 return helpers[i]; 118 } 119 return NULL; 120 121 } 122 #endif /* defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW) */ 123 124 static void 125 helper_free(struct helper *helper) 126 { 127 size_t i; 128 int found = 0; 129 130 if (helper == NULL) 131 return; 132 if (helper->path == NULL || helper->ec_meth == NULL || 133 helper->rsa_meth == NULL) 134 fatal_f("inconsistent helper"); 135 debug3_f("free helper for provider %s", helper->path); 136 for (i = 0; i < nhelpers; i++) { 137 if (helpers[i] == helper) { 138 if (found) 139 fatal_f("helper recorded more than once"); 140 found = 1; 141 } 142 else if (found) 143 helpers[i - 1] = helpers[i]; 144 } 145 if (found) { 146 helpers = xrecallocarray(helpers, nhelpers, 147 nhelpers - 1, sizeof(*helpers)); 148 nhelpers--; 149 } 150 free(helper->path); 151 #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW) 152 EC_KEY_METHOD_free(helper->ec_meth); 153 #endif 154 RSA_meth_free(helper->rsa_meth); 155 free(helper); 156 } 157 158 static void 159 helper_terminate(struct helper *helper) 160 { 161 if (helper == NULL) { 162 return; 163 } else if (helper->fd == -1) { 164 debug3_f("already terminated"); 165 } else { 166 debug3_f("terminating helper for %s; " 167 "remaining %zu RSA %zu ECDSA", 168 helper->path, helper->nrsa, helper->nec); 169 close(helper->fd); 170 /* XXX waitpid() */ 171 helper->fd = -1; 172 helper->pid = -1; 173 } 174 /* 175 * Don't delete the helper entry until there are no remaining keys 176 * that reference it. Otherwise, any signing operation would call 177 * a free'd METHOD pointer and that would be bad. 178 */ 179 if (helper->nrsa == 0 && helper->nec == 0) 180 helper_free(helper); 181 } 182 183 static void 184 send_msg(int fd, struct sshbuf *m) 185 { 186 u_char buf[4]; 187 size_t mlen = sshbuf_len(m); 188 int r; 189 190 if (fd == -1) 191 return; 192 POKE_U32(buf, mlen); 193 if (atomicio(vwrite, fd, buf, 4) != 4 || 194 atomicio(vwrite, fd, sshbuf_mutable_ptr(m), 195 sshbuf_len(m)) != sshbuf_len(m)) 196 error("write to helper failed"); 197 if ((r = sshbuf_consume(m, mlen)) != 0) 198 fatal_fr(r, "consume"); 199 } 200 201 static int 202 recv_msg(int fd, struct sshbuf *m) 203 { 204 u_int l, len; 205 u_char c, buf[1024]; 206 int r; 207 208 sshbuf_reset(m); 209 if (fd == -1) 210 return 0; /* XXX */ 211 if ((len = atomicio(read, fd, buf, 4)) != 4) { 212 error("read from helper failed: %u", len); 213 return (0); /* XXX */ 214 } 215 len = PEEK_U32(buf); 216 if (len > 256 * 1024) 217 fatal("response too long: %u", len); 218 /* read len bytes into m */ 219 while (len > 0) { 220 l = len; 221 if (l > sizeof(buf)) 222 l = sizeof(buf); 223 if (atomicio(read, fd, buf, l) != l) { 224 error("response from helper failed."); 225 return (0); /* XXX */ 226 } 227 if ((r = sshbuf_put(m, buf, l)) != 0) 228 fatal_fr(r, "sshbuf_put"); 229 len -= l; 230 } 231 if ((r = sshbuf_get_u8(m, &c)) != 0) 232 fatal_fr(r, "parse type"); 233 return c; 234 } 235 236 int 237 pkcs11_init(int interactive) 238 { 239 return 0; 240 } 241 242 void 243 pkcs11_terminate(void) 244 { 245 size_t i; 246 247 debug3_f("terminating %zu helpers", nhelpers); 248 for (i = 0; i < nhelpers; i++) 249 helper_terminate(helpers[i]); 250 } 251 252 static int 253 rsa_encrypt(int flen, const u_char *from, u_char *to, RSA *rsa, int padding) 254 { 255 struct sshkey *key = NULL; 256 struct sshbuf *msg = NULL; 257 u_char *blob = NULL, *signature = NULL; 258 size_t blen, slen = 0; 259 int r, ret = -1; 260 struct helper *helper; 261 262 if ((helper = helper_by_rsa(rsa)) == NULL || helper->fd == -1) 263 fatal_f("no helper for PKCS11 key"); 264 debug3_f("signing with PKCS11 provider %s", helper->path); 265 if (padding != RSA_PKCS1_PADDING) 266 goto fail; 267 key = sshkey_new(KEY_UNSPEC); 268 if (key == NULL) { 269 error_f("sshkey_new failed"); 270 goto fail; 271 } 272 key->type = KEY_RSA; 273 RSA_up_ref(rsa); 274 key->rsa = rsa; 275 if ((r = sshkey_to_blob(key, &blob, &blen)) != 0) { 276 error_fr(r, "encode key"); 277 goto fail; 278 } 279 if ((msg = sshbuf_new()) == NULL) 280 fatal_f("sshbuf_new failed"); 281 if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_SIGN_REQUEST)) != 0 || 282 (r = sshbuf_put_string(msg, blob, blen)) != 0 || 283 (r = sshbuf_put_string(msg, from, flen)) != 0 || 284 (r = sshbuf_put_u32(msg, 0)) != 0) 285 fatal_fr(r, "compose"); 286 send_msg(helper->fd, msg); 287 sshbuf_reset(msg); 288 289 if (recv_msg(helper->fd, msg) == SSH2_AGENT_SIGN_RESPONSE) { 290 if ((r = sshbuf_get_string(msg, &signature, &slen)) != 0) 291 fatal_fr(r, "parse"); 292 if (slen <= (size_t)RSA_size(rsa)) { 293 memcpy(to, signature, slen); 294 ret = slen; 295 } 296 free(signature); 297 } 298 fail: 299 free(blob); 300 sshkey_free(key); 301 sshbuf_free(msg); 302 return (ret); 303 } 304 305 static int 306 rsa_finish(RSA *rsa) 307 { 308 struct helper *helper; 309 310 if ((helper = helper_by_rsa(rsa)) == NULL) 311 fatal_f("no helper for PKCS11 key"); 312 debug3_f("free PKCS11 RSA key for provider %s", helper->path); 313 if (helper->rsa_finish != NULL) 314 helper->rsa_finish(rsa); 315 if (helper->nrsa == 0) 316 fatal_f("RSA refcount error"); 317 helper->nrsa--; 318 debug3_f("provider %s remaining keys: %zu RSA %zu ECDSA", 319 helper->path, helper->nrsa, helper->nec); 320 if (helper->nrsa == 0 && helper->nec == 0) 321 helper_terminate(helper); 322 return 1; 323 } 324 325 #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW) 326 static ECDSA_SIG * 327 ecdsa_do_sign(const unsigned char *dgst, int dgst_len, const BIGNUM *inv, 328 const BIGNUM *rp, EC_KEY *ec) 329 { 330 struct sshkey *key = NULL; 331 struct sshbuf *msg = NULL; 332 ECDSA_SIG *ret = NULL; 333 const u_char *cp; 334 u_char *blob = NULL, *signature = NULL; 335 size_t blen, slen = 0; 336 int r, nid; 337 struct helper *helper; 338 339 if ((helper = helper_by_ec(ec)) == NULL || helper->fd == -1) 340 fatal_f("no helper for PKCS11 key"); 341 debug3_f("signing with PKCS11 provider %s", helper->path); 342 nid = sshkey_ecdsa_key_to_nid(ec); 343 if (nid < 0) { 344 error_f("couldn't get curve nid"); 345 goto fail; 346 } 347 348 key = sshkey_new(KEY_UNSPEC); 349 if (key == NULL) { 350 error_f("sshkey_new failed"); 351 goto fail; 352 } 353 key->ecdsa = ec; 354 key->ecdsa_nid = nid; 355 key->type = KEY_ECDSA; 356 EC_KEY_up_ref(ec); 357 358 if ((r = sshkey_to_blob(key, &blob, &blen)) != 0) { 359 error_fr(r, "encode key"); 360 goto fail; 361 } 362 if ((msg = sshbuf_new()) == NULL) 363 fatal_f("sshbuf_new failed"); 364 if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_SIGN_REQUEST)) != 0 || 365 (r = sshbuf_put_string(msg, blob, blen)) != 0 || 366 (r = sshbuf_put_string(msg, dgst, dgst_len)) != 0 || 367 (r = sshbuf_put_u32(msg, 0)) != 0) 368 fatal_fr(r, "compose"); 369 send_msg(helper->fd, msg); 370 sshbuf_reset(msg); 371 372 if (recv_msg(helper->fd, msg) == SSH2_AGENT_SIGN_RESPONSE) { 373 if ((r = sshbuf_get_string(msg, &signature, &slen)) != 0) 374 fatal_fr(r, "parse"); 375 cp = signature; 376 ret = d2i_ECDSA_SIG(NULL, &cp, slen); 377 free(signature); 378 } 379 380 fail: 381 free(blob); 382 sshkey_free(key); 383 sshbuf_free(msg); 384 return (ret); 385 } 386 387 static void 388 ecdsa_do_finish(EC_KEY *ec) 389 { 390 struct helper *helper; 391 392 if ((helper = helper_by_ec(ec)) == NULL) 393 fatal_f("no helper for PKCS11 key"); 394 debug3_f("free PKCS11 ECDSA key for provider %s", helper->path); 395 if (helper->ec_finish != NULL) 396 helper->ec_finish(ec); 397 if (helper->nec == 0) 398 fatal_f("ECDSA refcount error"); 399 helper->nec--; 400 debug3_f("provider %s remaining keys: %zu RSA %zu ECDSA", 401 helper->path, helper->nrsa, helper->nec); 402 if (helper->nrsa == 0 && helper->nec == 0) 403 helper_terminate(helper); 404 } 405 #endif /* defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW) */ 406 407 /* redirect private key crypto operations to the ssh-pkcs11-helper */ 408 static void 409 wrap_key(struct helper *helper, struct sshkey *k) 410 { 411 debug3_f("wrap %s for provider %s", sshkey_type(k), helper->path); 412 if (k->type == KEY_RSA) { 413 RSA_set_method(k->rsa, helper->rsa_meth); 414 if (helper->nrsa++ >= INT_MAX) 415 fatal_f("RSA refcount error"); 416 #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW) 417 } else if (k->type == KEY_ECDSA) { 418 EC_KEY_set_method(k->ecdsa, helper->ec_meth); 419 if (helper->nec++ >= INT_MAX) 420 fatal_f("EC refcount error"); 421 #endif 422 } else 423 fatal_f("unknown key type"); 424 k->flags |= SSHKEY_FLAG_EXT; 425 debug3_f("provider %s remaining keys: %zu RSA %zu ECDSA", 426 helper->path, helper->nrsa, helper->nec); 427 } 428 429 static int 430 pkcs11_start_helper_methods(struct helper *helper) 431 { 432 RSA_METHOD *rsa_meth; 433 EC_KEY_METHOD *ec_meth = NULL; 434 #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW) 435 int (*ec_init)(EC_KEY *key); 436 int (*ec_copy)(EC_KEY *dest, const EC_KEY *src); 437 int (*ec_set_group)(EC_KEY *key, const EC_GROUP *grp); 438 int (*ec_set_private)(EC_KEY *key, const BIGNUM *priv_key); 439 int (*ec_set_public)(EC_KEY *key, const EC_POINT *pub_key); 440 int (*ec_sign)(int, const unsigned char *, int, unsigned char *, 441 unsigned int *, const BIGNUM *, const BIGNUM *, EC_KEY *) = NULL; 442 443 if ((ec_meth = EC_KEY_METHOD_new(EC_KEY_OpenSSL())) == NULL) 444 return -1; 445 EC_KEY_METHOD_get_sign(ec_meth, &ec_sign, NULL, NULL); 446 EC_KEY_METHOD_set_sign(ec_meth, ec_sign, NULL, ecdsa_do_sign); 447 EC_KEY_METHOD_get_init(ec_meth, &ec_init, &helper->ec_finish, 448 &ec_copy, &ec_set_group, &ec_set_private, &ec_set_public); 449 EC_KEY_METHOD_set_init(ec_meth, ec_init, ecdsa_do_finish, 450 ec_copy, ec_set_group, ec_set_private, ec_set_public); 451 #endif /* defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW) */ 452 453 if ((rsa_meth = RSA_meth_dup(RSA_get_default_method())) == NULL) 454 fatal_f("RSA_meth_dup failed"); 455 helper->rsa_finish = RSA_meth_get_finish(rsa_meth); 456 if (!RSA_meth_set1_name(rsa_meth, "ssh-pkcs11-helper") || 457 !RSA_meth_set_priv_enc(rsa_meth, rsa_encrypt) || 458 !RSA_meth_set_finish(rsa_meth, rsa_finish)) 459 fatal_f("failed to prepare method"); 460 461 helper->ec_meth = ec_meth; 462 helper->rsa_meth = rsa_meth; 463 return 0; 464 } 465 466 static struct helper * 467 pkcs11_start_helper(const char *path) 468 { 469 int pair[2]; 470 char *prog, *verbosity = NULL; 471 struct helper *helper; 472 pid_t pid; 473 474 if (nhelpers >= INT_MAX) 475 fatal_f("too many helpers"); 476 debug3_f("start helper for %s", path); 477 if (socketpair(AF_UNIX, SOCK_STREAM, 0, pair) == -1) { 478 error_f("socketpair: %s", strerror(errno)); 479 return NULL; 480 } 481 helper = xcalloc(1, sizeof(*helper)); 482 if (pkcs11_start_helper_methods(helper) == -1) { 483 error_f("pkcs11_start_helper_methods failed"); 484 goto fail; 485 } 486 if ((pid = fork()) == -1) { 487 error_f("fork: %s", strerror(errno)); 488 fail: 489 close(pair[0]); 490 close(pair[1]); 491 RSA_meth_free(helper->rsa_meth); 492 #if defined(OPENSSL_HAS_ECC) && defined(HAVE_EC_KEY_METHOD_NEW) 493 EC_KEY_METHOD_free(helper->ec_meth); 494 #endif 495 free(helper); 496 return NULL; 497 } else if (pid == 0) { 498 if ((dup2(pair[1], STDIN_FILENO) == -1) || 499 (dup2(pair[1], STDOUT_FILENO) == -1)) { 500 fprintf(stderr, "dup2: %s\n", strerror(errno)); 501 _exit(1); 502 } 503 close(pair[0]); 504 close(pair[1]); 505 prog = getenv("SSH_PKCS11_HELPER"); 506 if (prog == NULL || strlen(prog) == 0) 507 prog = _PATH_SSH_PKCS11_HELPER; 508 if (log_level_get() >= SYSLOG_LEVEL_DEBUG1) 509 verbosity = "-vvv"; 510 debug_f("starting %s %s", prog, 511 verbosity == NULL ? "" : verbosity); 512 execlp(prog, prog, verbosity, (char *)NULL); 513 fprintf(stderr, "exec: %s: %s\n", prog, strerror(errno)); 514 _exit(1); 515 } 516 close(pair[1]); 517 helper->fd = pair[0]; 518 helper->path = xstrdup(path); 519 helper->pid = pid; 520 debug3_f("helper %zu for \"%s\" on fd %d pid %ld", nhelpers, 521 helper->path, helper->fd, (long)helper->pid); 522 helpers = xrecallocarray(helpers, nhelpers, 523 nhelpers + 1, sizeof(*helpers)); 524 helpers[nhelpers++] = helper; 525 return helper; 526 } 527 528 int 529 pkcs11_add_provider(char *name, char *pin, struct sshkey ***keysp, 530 char ***labelsp) 531 { 532 struct sshkey *k; 533 int r, type; 534 u_char *blob; 535 char *label; 536 size_t blen; 537 u_int nkeys, i; 538 struct sshbuf *msg; 539 struct helper *helper; 540 541 if ((helper = helper_by_provider(name)) == NULL && 542 (helper = pkcs11_start_helper(name)) == NULL) 543 return -1; 544 545 if ((msg = sshbuf_new()) == NULL) 546 fatal_f("sshbuf_new failed"); 547 if ((r = sshbuf_put_u8(msg, SSH_AGENTC_ADD_SMARTCARD_KEY)) != 0 || 548 (r = sshbuf_put_cstring(msg, name)) != 0 || 549 (r = sshbuf_put_cstring(msg, pin)) != 0) 550 fatal_fr(r, "compose"); 551 send_msg(helper->fd, msg); 552 sshbuf_reset(msg); 553 554 type = recv_msg(helper->fd, msg); 555 if (type == SSH2_AGENT_IDENTITIES_ANSWER) { 556 if ((r = sshbuf_get_u32(msg, &nkeys)) != 0) 557 fatal_fr(r, "parse nkeys"); 558 *keysp = xcalloc(nkeys, sizeof(struct sshkey *)); 559 if (labelsp) 560 *labelsp = xcalloc(nkeys, sizeof(char *)); 561 for (i = 0; i < nkeys; i++) { 562 /* XXX clean up properly instead of fatal() */ 563 if ((r = sshbuf_get_string(msg, &blob, &blen)) != 0 || 564 (r = sshbuf_get_cstring(msg, &label, NULL)) != 0) 565 fatal_fr(r, "parse key"); 566 if ((r = sshkey_from_blob(blob, blen, &k)) != 0) 567 fatal_fr(r, "decode key"); 568 wrap_key(helper, k); 569 (*keysp)[i] = k; 570 if (labelsp) 571 (*labelsp)[i] = label; 572 else 573 free(label); 574 free(blob); 575 } 576 } else if (type == SSH2_AGENT_FAILURE) { 577 if ((r = sshbuf_get_u32(msg, &nkeys)) != 0) 578 nkeys = -1; 579 } else { 580 nkeys = -1; 581 } 582 sshbuf_free(msg); 583 return (nkeys); 584 } 585 586 int 587 pkcs11_del_provider(char *name) 588 { 589 struct helper *helper; 590 591 /* 592 * ssh-agent deletes keys before calling this, so the helper entry 593 * should be gone before we get here. 594 */ 595 debug3_f("delete %s", name); 596 if ((helper = helper_by_provider(name)) != NULL) 597 helper_terminate(helper); 598 return 0; 599 } 600 #endif /* ENABLE_PKCS11 */ 601