1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Copyright (C) 2010 IBM Corporation 4 * Copyright (C) 2010 Politecnico di Torino, Italy 5 * TORSEC group -- https://security.polito.it 6 * 7 * Authors: 8 * Mimi Zohar <zohar@us.ibm.com> 9 * Roberto Sassu <roberto.sassu@polito.it> 10 * 11 * See Documentation/security/keys/trusted-encrypted.rst 12 */ 13 14 #include <linux/uaccess.h> 15 #include <linux/module.h> 16 #include <linux/init.h> 17 #include <linux/slab.h> 18 #include <linux/parser.h> 19 #include <linux/string.h> 20 #include <linux/err.h> 21 #include <keys/user-type.h> 22 #include <keys/trusted-type.h> 23 #include <keys/encrypted-type.h> 24 #include <linux/key-type.h> 25 #include <linux/random.h> 26 #include <linux/rcupdate.h> 27 #include <linux/scatterlist.h> 28 #include <linux/ctype.h> 29 #include <crypto/aes.h> 30 #include <crypto/algapi.h> 31 #include <crypto/hash.h> 32 #include <crypto/sha2.h> 33 #include <crypto/skcipher.h> 34 35 #include "encrypted.h" 36 #include "ecryptfs_format.h" 37 38 static const char KEY_TRUSTED_PREFIX[] = "trusted:"; 39 static const char KEY_USER_PREFIX[] = "user:"; 40 static const char hash_alg[] = "sha256"; 41 static const char hmac_alg[] = "hmac(sha256)"; 42 static const char blkcipher_alg[] = "cbc(aes)"; 43 static const char key_format_default[] = "default"; 44 static const char key_format_ecryptfs[] = "ecryptfs"; 45 static const char key_format_enc32[] = "enc32"; 46 static unsigned int ivsize; 47 static int blksize; 48 49 #define KEY_TRUSTED_PREFIX_LEN (sizeof (KEY_TRUSTED_PREFIX) - 1) 50 #define KEY_USER_PREFIX_LEN (sizeof (KEY_USER_PREFIX) - 1) 51 #define KEY_ECRYPTFS_DESC_LEN 16 52 #define HASH_SIZE SHA256_DIGEST_SIZE 53 #define MAX_DATA_SIZE 4096 54 #define MIN_DATA_SIZE 20 55 #define KEY_ENC32_PAYLOAD_LEN 32 56 57 static struct crypto_shash *hash_tfm; 58 59 enum { 60 Opt_new, Opt_load, Opt_update, Opt_err 61 }; 62 63 enum { 64 Opt_default, Opt_ecryptfs, Opt_enc32, Opt_error 65 }; 66 67 static const match_table_t key_format_tokens = { 68 {Opt_default, "default"}, 69 {Opt_ecryptfs, "ecryptfs"}, 70 {Opt_enc32, "enc32"}, 71 {Opt_error, NULL} 72 }; 73 74 static const match_table_t key_tokens = { 75 {Opt_new, "new"}, 76 {Opt_load, "load"}, 77 {Opt_update, "update"}, 78 {Opt_err, NULL} 79 }; 80 81 static bool user_decrypted_data = IS_ENABLED(CONFIG_USER_DECRYPTED_DATA); 82 module_param(user_decrypted_data, bool, 0); 83 MODULE_PARM_DESC(user_decrypted_data, 84 "Allow instantiation of encrypted keys using provided decrypted data"); 85 86 static int aes_get_sizes(void) 87 { 88 struct crypto_skcipher *tfm; 89 90 tfm = crypto_alloc_skcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC); 91 if (IS_ERR(tfm)) { 92 pr_err("encrypted_key: failed to alloc_cipher (%ld)\n", 93 PTR_ERR(tfm)); 94 return PTR_ERR(tfm); 95 } 96 ivsize = crypto_skcipher_ivsize(tfm); 97 blksize = crypto_skcipher_blocksize(tfm); 98 crypto_free_skcipher(tfm); 99 return 0; 100 } 101 102 /* 103 * valid_ecryptfs_desc - verify the description of a new/loaded encrypted key 104 * 105 * The description of a encrypted key with format 'ecryptfs' must contain 106 * exactly 16 hexadecimal characters. 107 * 108 */ 109 static int valid_ecryptfs_desc(const char *ecryptfs_desc) 110 { 111 int i; 112 113 if (strlen(ecryptfs_desc) != KEY_ECRYPTFS_DESC_LEN) { 114 pr_err("encrypted_key: key description must be %d hexadecimal " 115 "characters long\n", KEY_ECRYPTFS_DESC_LEN); 116 return -EINVAL; 117 } 118 119 for (i = 0; i < KEY_ECRYPTFS_DESC_LEN; i++) { 120 if (!isxdigit(ecryptfs_desc[i])) { 121 pr_err("encrypted_key: key description must contain " 122 "only hexadecimal characters\n"); 123 return -EINVAL; 124 } 125 } 126 127 return 0; 128 } 129 130 /* 131 * valid_master_desc - verify the 'key-type:desc' of a new/updated master-key 132 * 133 * key-type:= "trusted:" | "user:" 134 * desc:= master-key description 135 * 136 * Verify that 'key-type' is valid and that 'desc' exists. On key update, 137 * only the master key description is permitted to change, not the key-type. 138 * The key-type remains constant. 139 * 140 * On success returns 0, otherwise -EINVAL. 141 */ 142 static int valid_master_desc(const char *new_desc, const char *orig_desc) 143 { 144 int prefix_len; 145 146 if (!strncmp(new_desc, KEY_TRUSTED_PREFIX, KEY_TRUSTED_PREFIX_LEN)) 147 prefix_len = KEY_TRUSTED_PREFIX_LEN; 148 else if (!strncmp(new_desc, KEY_USER_PREFIX, KEY_USER_PREFIX_LEN)) 149 prefix_len = KEY_USER_PREFIX_LEN; 150 else 151 return -EINVAL; 152 153 if (!new_desc[prefix_len]) 154 return -EINVAL; 155 156 if (orig_desc && strncmp(new_desc, orig_desc, prefix_len)) 157 return -EINVAL; 158 159 return 0; 160 } 161 162 /* 163 * datablob_parse - parse the keyctl data 164 * 165 * datablob format: 166 * new [<format>] <master-key name> <decrypted data length> [<decrypted data>] 167 * load [<format>] <master-key name> <decrypted data length> 168 * <encrypted iv + data> 169 * update <new-master-key name> 170 * 171 * Tokenizes a copy of the keyctl data, returning a pointer to each token, 172 * which is null terminated. 173 * 174 * On success returns 0, otherwise -EINVAL. 175 */ 176 static int datablob_parse(char *datablob, const char **format, 177 char **master_desc, char **decrypted_datalen, 178 char **hex_encoded_iv, char **decrypted_data) 179 { 180 substring_t args[MAX_OPT_ARGS]; 181 int ret = -EINVAL; 182 int key_cmd; 183 int key_format; 184 char *p, *keyword; 185 186 keyword = strsep(&datablob, " \t"); 187 if (!keyword) { 188 pr_info("encrypted_key: insufficient parameters specified\n"); 189 return ret; 190 } 191 key_cmd = match_token(keyword, key_tokens, args); 192 193 /* Get optional format: default | ecryptfs */ 194 p = strsep(&datablob, " \t"); 195 if (!p) { 196 pr_err("encrypted_key: insufficient parameters specified\n"); 197 return ret; 198 } 199 200 key_format = match_token(p, key_format_tokens, args); 201 switch (key_format) { 202 case Opt_ecryptfs: 203 case Opt_enc32: 204 case Opt_default: 205 *format = p; 206 *master_desc = strsep(&datablob, " \t"); 207 break; 208 case Opt_error: 209 *master_desc = p; 210 break; 211 } 212 213 if (!*master_desc) { 214 pr_info("encrypted_key: master key parameter is missing\n"); 215 goto out; 216 } 217 218 if (valid_master_desc(*master_desc, NULL) < 0) { 219 pr_info("encrypted_key: master key parameter \'%s\' " 220 "is invalid\n", *master_desc); 221 goto out; 222 } 223 224 if (decrypted_datalen) { 225 *decrypted_datalen = strsep(&datablob, " \t"); 226 if (!*decrypted_datalen) { 227 pr_info("encrypted_key: keylen parameter is missing\n"); 228 goto out; 229 } 230 } 231 232 switch (key_cmd) { 233 case Opt_new: 234 if (!decrypted_datalen) { 235 pr_info("encrypted_key: keyword \'%s\' not allowed " 236 "when called from .update method\n", keyword); 237 break; 238 } 239 *decrypted_data = strsep(&datablob, " \t"); 240 if (!*decrypted_data) { 241 pr_info("encrypted_key: decrypted_data is missing\n"); 242 break; 243 } 244 ret = 0; 245 break; 246 case Opt_load: 247 if (!decrypted_datalen) { 248 pr_info("encrypted_key: keyword \'%s\' not allowed " 249 "when called from .update method\n", keyword); 250 break; 251 } 252 *hex_encoded_iv = strsep(&datablob, " \t"); 253 if (!*hex_encoded_iv) { 254 pr_info("encrypted_key: hex blob is missing\n"); 255 break; 256 } 257 ret = 0; 258 break; 259 case Opt_update: 260 if (decrypted_datalen) { 261 pr_info("encrypted_key: keyword \'%s\' not allowed " 262 "when called from .instantiate method\n", 263 keyword); 264 break; 265 } 266 ret = 0; 267 break; 268 case Opt_err: 269 pr_info("encrypted_key: keyword \'%s\' not recognized\n", 270 keyword); 271 break; 272 } 273 out: 274 return ret; 275 } 276 277 /* 278 * datablob_format - format as an ascii string, before copying to userspace 279 */ 280 static char *datablob_format(struct encrypted_key_payload *epayload, 281 size_t asciiblob_len) 282 { 283 char *ascii_buf, *bufp; 284 u8 *iv = epayload->iv; 285 int len; 286 int i; 287 288 ascii_buf = kmalloc(asciiblob_len + 1, GFP_KERNEL); 289 if (!ascii_buf) 290 goto out; 291 292 ascii_buf[asciiblob_len] = '\0'; 293 294 /* copy datablob master_desc and datalen strings */ 295 len = sprintf(ascii_buf, "%s %s %s ", epayload->format, 296 epayload->master_desc, epayload->datalen); 297 298 /* convert the hex encoded iv, encrypted-data and HMAC to ascii */ 299 bufp = &ascii_buf[len]; 300 for (i = 0; i < (asciiblob_len - len) / 2; i++) 301 bufp = hex_byte_pack(bufp, iv[i]); 302 out: 303 return ascii_buf; 304 } 305 306 /* 307 * request_user_key - request the user key 308 * 309 * Use a user provided key to encrypt/decrypt an encrypted-key. 310 */ 311 static struct key *request_user_key(const char *master_desc, const u8 **master_key, 312 size_t *master_keylen) 313 { 314 const struct user_key_payload *upayload; 315 struct key *ukey; 316 317 ukey = request_key(&key_type_user, master_desc, NULL); 318 if (IS_ERR(ukey)) 319 goto error; 320 321 down_read(&ukey->sem); 322 upayload = user_key_payload_locked(ukey); 323 if (!upayload) { 324 /* key was revoked before we acquired its semaphore */ 325 up_read(&ukey->sem); 326 key_put(ukey); 327 ukey = ERR_PTR(-EKEYREVOKED); 328 goto error; 329 } 330 *master_key = upayload->data; 331 *master_keylen = upayload->datalen; 332 error: 333 return ukey; 334 } 335 336 static int calc_hmac(u8 *digest, const u8 *key, unsigned int keylen, 337 const u8 *buf, unsigned int buflen) 338 { 339 struct crypto_shash *tfm; 340 int err; 341 342 tfm = crypto_alloc_shash(hmac_alg, 0, 0); 343 if (IS_ERR(tfm)) { 344 pr_err("encrypted_key: can't alloc %s transform: %ld\n", 345 hmac_alg, PTR_ERR(tfm)); 346 return PTR_ERR(tfm); 347 } 348 349 err = crypto_shash_setkey(tfm, key, keylen); 350 if (!err) 351 err = crypto_shash_tfm_digest(tfm, buf, buflen, digest); 352 crypto_free_shash(tfm); 353 return err; 354 } 355 356 enum derived_key_type { ENC_KEY, AUTH_KEY }; 357 358 /* Derive authentication/encryption key from trusted key */ 359 static int get_derived_key(u8 *derived_key, enum derived_key_type key_type, 360 const u8 *master_key, size_t master_keylen) 361 { 362 u8 *derived_buf; 363 unsigned int derived_buf_len; 364 int ret; 365 366 derived_buf_len = strlen("AUTH_KEY") + 1 + master_keylen; 367 if (derived_buf_len < HASH_SIZE) 368 derived_buf_len = HASH_SIZE; 369 370 derived_buf = kzalloc(derived_buf_len, GFP_KERNEL); 371 if (!derived_buf) 372 return -ENOMEM; 373 374 if (key_type) 375 strcpy(derived_buf, "AUTH_KEY"); 376 else 377 strcpy(derived_buf, "ENC_KEY"); 378 379 memcpy(derived_buf + strlen(derived_buf) + 1, master_key, 380 master_keylen); 381 ret = crypto_shash_tfm_digest(hash_tfm, derived_buf, derived_buf_len, 382 derived_key); 383 kfree_sensitive(derived_buf); 384 return ret; 385 } 386 387 static struct skcipher_request *init_skcipher_req(const u8 *key, 388 unsigned int key_len) 389 { 390 struct skcipher_request *req; 391 struct crypto_skcipher *tfm; 392 int ret; 393 394 tfm = crypto_alloc_skcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC); 395 if (IS_ERR(tfm)) { 396 pr_err("encrypted_key: failed to load %s transform (%ld)\n", 397 blkcipher_alg, PTR_ERR(tfm)); 398 return ERR_CAST(tfm); 399 } 400 401 ret = crypto_skcipher_setkey(tfm, key, key_len); 402 if (ret < 0) { 403 pr_err("encrypted_key: failed to setkey (%d)\n", ret); 404 crypto_free_skcipher(tfm); 405 return ERR_PTR(ret); 406 } 407 408 req = skcipher_request_alloc(tfm, GFP_KERNEL); 409 if (!req) { 410 pr_err("encrypted_key: failed to allocate request for %s\n", 411 blkcipher_alg); 412 crypto_free_skcipher(tfm); 413 return ERR_PTR(-ENOMEM); 414 } 415 416 skcipher_request_set_callback(req, 0, NULL, NULL); 417 return req; 418 } 419 420 static struct key *request_master_key(struct encrypted_key_payload *epayload, 421 const u8 **master_key, size_t *master_keylen) 422 { 423 struct key *mkey = ERR_PTR(-EINVAL); 424 425 if (!strncmp(epayload->master_desc, KEY_TRUSTED_PREFIX, 426 KEY_TRUSTED_PREFIX_LEN)) { 427 mkey = request_trusted_key(epayload->master_desc + 428 KEY_TRUSTED_PREFIX_LEN, 429 master_key, master_keylen); 430 } else if (!strncmp(epayload->master_desc, KEY_USER_PREFIX, 431 KEY_USER_PREFIX_LEN)) { 432 mkey = request_user_key(epayload->master_desc + 433 KEY_USER_PREFIX_LEN, 434 master_key, master_keylen); 435 } else 436 goto out; 437 438 if (IS_ERR(mkey)) { 439 int ret = PTR_ERR(mkey); 440 441 if (ret == -ENOTSUPP) 442 pr_info("encrypted_key: key %s not supported", 443 epayload->master_desc); 444 else 445 pr_info("encrypted_key: key %s not found", 446 epayload->master_desc); 447 goto out; 448 } 449 450 dump_master_key(*master_key, *master_keylen); 451 out: 452 return mkey; 453 } 454 455 /* Before returning data to userspace, encrypt decrypted data. */ 456 static int derived_key_encrypt(struct encrypted_key_payload *epayload, 457 const u8 *derived_key, 458 unsigned int derived_keylen) 459 { 460 struct scatterlist sg_in[2]; 461 struct scatterlist sg_out[1]; 462 struct crypto_skcipher *tfm; 463 struct skcipher_request *req; 464 unsigned int encrypted_datalen; 465 u8 iv[AES_BLOCK_SIZE]; 466 int ret; 467 468 encrypted_datalen = roundup(epayload->decrypted_datalen, blksize); 469 470 req = init_skcipher_req(derived_key, derived_keylen); 471 ret = PTR_ERR(req); 472 if (IS_ERR(req)) 473 goto out; 474 dump_decrypted_data(epayload); 475 476 sg_init_table(sg_in, 2); 477 sg_set_buf(&sg_in[0], epayload->decrypted_data, 478 epayload->decrypted_datalen); 479 sg_set_page(&sg_in[1], ZERO_PAGE(0), AES_BLOCK_SIZE, 0); 480 481 sg_init_table(sg_out, 1); 482 sg_set_buf(sg_out, epayload->encrypted_data, encrypted_datalen); 483 484 memcpy(iv, epayload->iv, sizeof(iv)); 485 skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv); 486 ret = crypto_skcipher_encrypt(req); 487 tfm = crypto_skcipher_reqtfm(req); 488 skcipher_request_free(req); 489 crypto_free_skcipher(tfm); 490 if (ret < 0) 491 pr_err("encrypted_key: failed to encrypt (%d)\n", ret); 492 else 493 dump_encrypted_data(epayload, encrypted_datalen); 494 out: 495 return ret; 496 } 497 498 static int datablob_hmac_append(struct encrypted_key_payload *epayload, 499 const u8 *master_key, size_t master_keylen) 500 { 501 u8 derived_key[HASH_SIZE]; 502 u8 *digest; 503 int ret; 504 505 ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen); 506 if (ret < 0) 507 goto out; 508 509 digest = epayload->format + epayload->datablob_len; 510 ret = calc_hmac(digest, derived_key, sizeof derived_key, 511 epayload->format, epayload->datablob_len); 512 if (!ret) 513 dump_hmac(NULL, digest, HASH_SIZE); 514 out: 515 memzero_explicit(derived_key, sizeof(derived_key)); 516 return ret; 517 } 518 519 /* verify HMAC before decrypting encrypted key */ 520 static int datablob_hmac_verify(struct encrypted_key_payload *epayload, 521 const u8 *format, const u8 *master_key, 522 size_t master_keylen) 523 { 524 u8 derived_key[HASH_SIZE]; 525 u8 digest[HASH_SIZE]; 526 int ret; 527 char *p; 528 unsigned short len; 529 530 ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen); 531 if (ret < 0) 532 goto out; 533 534 len = epayload->datablob_len; 535 if (!format) { 536 p = epayload->master_desc; 537 len -= strlen(epayload->format) + 1; 538 } else 539 p = epayload->format; 540 541 ret = calc_hmac(digest, derived_key, sizeof derived_key, p, len); 542 if (ret < 0) 543 goto out; 544 ret = crypto_memneq(digest, epayload->format + epayload->datablob_len, 545 sizeof(digest)); 546 if (ret) { 547 ret = -EINVAL; 548 dump_hmac("datablob", 549 epayload->format + epayload->datablob_len, 550 HASH_SIZE); 551 dump_hmac("calc", digest, HASH_SIZE); 552 } 553 out: 554 memzero_explicit(derived_key, sizeof(derived_key)); 555 return ret; 556 } 557 558 static int derived_key_decrypt(struct encrypted_key_payload *epayload, 559 const u8 *derived_key, 560 unsigned int derived_keylen) 561 { 562 struct scatterlist sg_in[1]; 563 struct scatterlist sg_out[2]; 564 struct crypto_skcipher *tfm; 565 struct skcipher_request *req; 566 unsigned int encrypted_datalen; 567 u8 iv[AES_BLOCK_SIZE]; 568 u8 *pad; 569 int ret; 570 571 /* Throwaway buffer to hold the unused zero padding at the end */ 572 pad = kmalloc(AES_BLOCK_SIZE, GFP_KERNEL); 573 if (!pad) 574 return -ENOMEM; 575 576 encrypted_datalen = roundup(epayload->decrypted_datalen, blksize); 577 req = init_skcipher_req(derived_key, derived_keylen); 578 ret = PTR_ERR(req); 579 if (IS_ERR(req)) 580 goto out; 581 dump_encrypted_data(epayload, encrypted_datalen); 582 583 sg_init_table(sg_in, 1); 584 sg_init_table(sg_out, 2); 585 sg_set_buf(sg_in, epayload->encrypted_data, encrypted_datalen); 586 sg_set_buf(&sg_out[0], epayload->decrypted_data, 587 epayload->decrypted_datalen); 588 sg_set_buf(&sg_out[1], pad, AES_BLOCK_SIZE); 589 590 memcpy(iv, epayload->iv, sizeof(iv)); 591 skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv); 592 ret = crypto_skcipher_decrypt(req); 593 tfm = crypto_skcipher_reqtfm(req); 594 skcipher_request_free(req); 595 crypto_free_skcipher(tfm); 596 if (ret < 0) 597 goto out; 598 dump_decrypted_data(epayload); 599 out: 600 kfree(pad); 601 return ret; 602 } 603 604 /* Allocate memory for decrypted key and datablob. */ 605 static struct encrypted_key_payload *encrypted_key_alloc(struct key *key, 606 const char *format, 607 const char *master_desc, 608 const char *datalen, 609 const char *decrypted_data) 610 { 611 struct encrypted_key_payload *epayload = NULL; 612 unsigned short datablob_len; 613 unsigned short decrypted_datalen; 614 unsigned short payload_datalen; 615 unsigned int encrypted_datalen; 616 unsigned int format_len; 617 long dlen; 618 int i; 619 int ret; 620 621 ret = kstrtol(datalen, 10, &dlen); 622 if (ret < 0 || dlen < MIN_DATA_SIZE || dlen > MAX_DATA_SIZE) 623 return ERR_PTR(-EINVAL); 624 625 format_len = (!format) ? strlen(key_format_default) : strlen(format); 626 decrypted_datalen = dlen; 627 payload_datalen = decrypted_datalen; 628 629 if (decrypted_data) { 630 if (!user_decrypted_data) { 631 pr_err("encrypted key: instantiation of keys using provided decrypted data is disabled since CONFIG_USER_DECRYPTED_DATA is set to false\n"); 632 return ERR_PTR(-EINVAL); 633 } 634 if (strlen(decrypted_data) != decrypted_datalen * 2) { 635 pr_err("encrypted key: decrypted data provided does not match decrypted data length provided\n"); 636 return ERR_PTR(-EINVAL); 637 } 638 for (i = 0; i < strlen(decrypted_data); i++) { 639 if (!isxdigit(decrypted_data[i])) { 640 pr_err("encrypted key: decrypted data provided must contain only hexadecimal characters\n"); 641 return ERR_PTR(-EINVAL); 642 } 643 } 644 } 645 646 if (format) { 647 if (!strcmp(format, key_format_ecryptfs)) { 648 if (dlen != ECRYPTFS_MAX_KEY_BYTES) { 649 pr_err("encrypted_key: keylen for the ecryptfs format must be equal to %d bytes\n", 650 ECRYPTFS_MAX_KEY_BYTES); 651 return ERR_PTR(-EINVAL); 652 } 653 decrypted_datalen = ECRYPTFS_MAX_KEY_BYTES; 654 payload_datalen = sizeof(struct ecryptfs_auth_tok); 655 } else if (!strcmp(format, key_format_enc32)) { 656 if (decrypted_datalen != KEY_ENC32_PAYLOAD_LEN) { 657 pr_err("encrypted_key: enc32 key payload incorrect length: %d\n", 658 decrypted_datalen); 659 return ERR_PTR(-EINVAL); 660 } 661 } 662 } 663 664 encrypted_datalen = roundup(decrypted_datalen, blksize); 665 666 datablob_len = format_len + 1 + strlen(master_desc) + 1 667 + strlen(datalen) + 1 + ivsize + 1 + encrypted_datalen; 668 669 ret = key_payload_reserve(key, payload_datalen + datablob_len 670 + HASH_SIZE + 1); 671 if (ret < 0) 672 return ERR_PTR(ret); 673 674 epayload = kzalloc(sizeof(*epayload) + payload_datalen + 675 datablob_len + HASH_SIZE + 1, GFP_KERNEL); 676 if (!epayload) 677 return ERR_PTR(-ENOMEM); 678 679 epayload->payload_datalen = payload_datalen; 680 epayload->decrypted_datalen = decrypted_datalen; 681 epayload->datablob_len = datablob_len; 682 return epayload; 683 } 684 685 static int encrypted_key_decrypt(struct encrypted_key_payload *epayload, 686 const char *format, const char *hex_encoded_iv) 687 { 688 struct key *mkey; 689 u8 derived_key[HASH_SIZE]; 690 const u8 *master_key; 691 u8 *hmac; 692 const char *hex_encoded_data; 693 unsigned int encrypted_datalen; 694 size_t master_keylen; 695 size_t asciilen; 696 int ret; 697 698 encrypted_datalen = roundup(epayload->decrypted_datalen, blksize); 699 asciilen = (ivsize + 1 + encrypted_datalen + HASH_SIZE) * 2; 700 if (strlen(hex_encoded_iv) != asciilen) 701 return -EINVAL; 702 703 hex_encoded_data = hex_encoded_iv + (2 * ivsize) + 2; 704 ret = hex2bin(epayload->iv, hex_encoded_iv, ivsize); 705 if (ret < 0) 706 return -EINVAL; 707 ret = hex2bin(epayload->encrypted_data, hex_encoded_data, 708 encrypted_datalen); 709 if (ret < 0) 710 return -EINVAL; 711 712 hmac = epayload->format + epayload->datablob_len; 713 ret = hex2bin(hmac, hex_encoded_data + (encrypted_datalen * 2), 714 HASH_SIZE); 715 if (ret < 0) 716 return -EINVAL; 717 718 mkey = request_master_key(epayload, &master_key, &master_keylen); 719 if (IS_ERR(mkey)) 720 return PTR_ERR(mkey); 721 722 ret = datablob_hmac_verify(epayload, format, master_key, master_keylen); 723 if (ret < 0) { 724 pr_err("encrypted_key: bad hmac (%d)\n", ret); 725 goto out; 726 } 727 728 ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen); 729 if (ret < 0) 730 goto out; 731 732 ret = derived_key_decrypt(epayload, derived_key, sizeof derived_key); 733 if (ret < 0) 734 pr_err("encrypted_key: failed to decrypt key (%d)\n", ret); 735 out: 736 up_read(&mkey->sem); 737 key_put(mkey); 738 memzero_explicit(derived_key, sizeof(derived_key)); 739 return ret; 740 } 741 742 static void __ekey_init(struct encrypted_key_payload *epayload, 743 const char *format, const char *master_desc, 744 const char *datalen) 745 { 746 unsigned int format_len; 747 748 format_len = (!format) ? strlen(key_format_default) : strlen(format); 749 epayload->format = epayload->payload_data + epayload->payload_datalen; 750 epayload->master_desc = epayload->format + format_len + 1; 751 epayload->datalen = epayload->master_desc + strlen(master_desc) + 1; 752 epayload->iv = epayload->datalen + strlen(datalen) + 1; 753 epayload->encrypted_data = epayload->iv + ivsize + 1; 754 epayload->decrypted_data = epayload->payload_data; 755 756 if (!format) 757 memcpy(epayload->format, key_format_default, format_len); 758 else { 759 if (!strcmp(format, key_format_ecryptfs)) 760 epayload->decrypted_data = 761 ecryptfs_get_auth_tok_key((struct ecryptfs_auth_tok *)epayload->payload_data); 762 763 memcpy(epayload->format, format, format_len); 764 } 765 766 memcpy(epayload->master_desc, master_desc, strlen(master_desc)); 767 memcpy(epayload->datalen, datalen, strlen(datalen)); 768 } 769 770 /* 771 * encrypted_init - initialize an encrypted key 772 * 773 * For a new key, use either a random number or user-provided decrypted data in 774 * case it is provided. A random number is used for the iv in both cases. For 775 * an old key, decrypt the hex encoded data. 776 */ 777 static int encrypted_init(struct encrypted_key_payload *epayload, 778 const char *key_desc, const char *format, 779 const char *master_desc, const char *datalen, 780 const char *hex_encoded_iv, const char *decrypted_data) 781 { 782 int ret = 0; 783 784 if (format && !strcmp(format, key_format_ecryptfs)) { 785 ret = valid_ecryptfs_desc(key_desc); 786 if (ret < 0) 787 return ret; 788 789 ecryptfs_fill_auth_tok((struct ecryptfs_auth_tok *)epayload->payload_data, 790 key_desc); 791 } 792 793 __ekey_init(epayload, format, master_desc, datalen); 794 if (hex_encoded_iv) { 795 ret = encrypted_key_decrypt(epayload, format, hex_encoded_iv); 796 } else if (decrypted_data) { 797 get_random_bytes(epayload->iv, ivsize); 798 ret = hex2bin(epayload->decrypted_data, decrypted_data, 799 epayload->decrypted_datalen); 800 } else { 801 get_random_bytes(epayload->iv, ivsize); 802 get_random_bytes(epayload->decrypted_data, epayload->decrypted_datalen); 803 } 804 return ret; 805 } 806 807 /* 808 * encrypted_instantiate - instantiate an encrypted key 809 * 810 * Instantiates the key: 811 * - by decrypting an existing encrypted datablob, or 812 * - by creating a new encrypted key based on a kernel random number, or 813 * - using provided decrypted data. 814 * 815 * On success, return 0. Otherwise return errno. 816 */ 817 static int encrypted_instantiate(struct key *key, 818 struct key_preparsed_payload *prep) 819 { 820 struct encrypted_key_payload *epayload = NULL; 821 char *datablob = NULL; 822 const char *format = NULL; 823 char *master_desc = NULL; 824 char *decrypted_datalen = NULL; 825 char *hex_encoded_iv = NULL; 826 char *decrypted_data = NULL; 827 size_t datalen = prep->datalen; 828 int ret; 829 830 if (datalen <= 0 || datalen > 32767 || !prep->data) 831 return -EINVAL; 832 833 datablob = kmalloc(datalen + 1, GFP_KERNEL); 834 if (!datablob) 835 return -ENOMEM; 836 datablob[datalen] = 0; 837 memcpy(datablob, prep->data, datalen); 838 ret = datablob_parse(datablob, &format, &master_desc, 839 &decrypted_datalen, &hex_encoded_iv, &decrypted_data); 840 if (ret < 0) 841 goto out; 842 843 epayload = encrypted_key_alloc(key, format, master_desc, 844 decrypted_datalen, decrypted_data); 845 if (IS_ERR(epayload)) { 846 ret = PTR_ERR(epayload); 847 goto out; 848 } 849 ret = encrypted_init(epayload, key->description, format, master_desc, 850 decrypted_datalen, hex_encoded_iv, decrypted_data); 851 if (ret < 0) { 852 kfree_sensitive(epayload); 853 goto out; 854 } 855 856 rcu_assign_keypointer(key, epayload); 857 out: 858 kfree_sensitive(datablob); 859 return ret; 860 } 861 862 static void encrypted_rcu_free(struct rcu_head *rcu) 863 { 864 struct encrypted_key_payload *epayload; 865 866 epayload = container_of(rcu, struct encrypted_key_payload, rcu); 867 kfree_sensitive(epayload); 868 } 869 870 /* 871 * encrypted_update - update the master key description 872 * 873 * Change the master key description for an existing encrypted key. 874 * The next read will return an encrypted datablob using the new 875 * master key description. 876 * 877 * On success, return 0. Otherwise return errno. 878 */ 879 static int encrypted_update(struct key *key, struct key_preparsed_payload *prep) 880 { 881 struct encrypted_key_payload *epayload = key->payload.data[0]; 882 struct encrypted_key_payload *new_epayload; 883 char *buf; 884 char *new_master_desc = NULL; 885 const char *format = NULL; 886 size_t datalen = prep->datalen; 887 int ret = 0; 888 889 if (key_is_negative(key)) 890 return -ENOKEY; 891 if (datalen <= 0 || datalen > 32767 || !prep->data) 892 return -EINVAL; 893 894 buf = kmalloc(datalen + 1, GFP_KERNEL); 895 if (!buf) 896 return -ENOMEM; 897 898 buf[datalen] = 0; 899 memcpy(buf, prep->data, datalen); 900 ret = datablob_parse(buf, &format, &new_master_desc, NULL, NULL, NULL); 901 if (ret < 0) 902 goto out; 903 904 ret = valid_master_desc(new_master_desc, epayload->master_desc); 905 if (ret < 0) 906 goto out; 907 908 new_epayload = encrypted_key_alloc(key, epayload->format, 909 new_master_desc, epayload->datalen, NULL); 910 if (IS_ERR(new_epayload)) { 911 ret = PTR_ERR(new_epayload); 912 goto out; 913 } 914 915 __ekey_init(new_epayload, epayload->format, new_master_desc, 916 epayload->datalen); 917 918 memcpy(new_epayload->iv, epayload->iv, ivsize); 919 memcpy(new_epayload->payload_data, epayload->payload_data, 920 epayload->payload_datalen); 921 922 rcu_assign_keypointer(key, new_epayload); 923 call_rcu(&epayload->rcu, encrypted_rcu_free); 924 out: 925 kfree_sensitive(buf); 926 return ret; 927 } 928 929 /* 930 * encrypted_read - format and copy out the encrypted data 931 * 932 * The resulting datablob format is: 933 * <master-key name> <decrypted data length> <encrypted iv> <encrypted data> 934 * 935 * On success, return to userspace the encrypted key datablob size. 936 */ 937 static long encrypted_read(const struct key *key, char *buffer, 938 size_t buflen) 939 { 940 struct encrypted_key_payload *epayload; 941 struct key *mkey; 942 const u8 *master_key; 943 size_t master_keylen; 944 char derived_key[HASH_SIZE]; 945 char *ascii_buf; 946 size_t asciiblob_len; 947 int ret; 948 949 epayload = dereference_key_locked(key); 950 951 /* returns the hex encoded iv, encrypted-data, and hmac as ascii */ 952 asciiblob_len = epayload->datablob_len + ivsize + 1 953 + roundup(epayload->decrypted_datalen, blksize) 954 + (HASH_SIZE * 2); 955 956 if (!buffer || buflen < asciiblob_len) 957 return asciiblob_len; 958 959 mkey = request_master_key(epayload, &master_key, &master_keylen); 960 if (IS_ERR(mkey)) 961 return PTR_ERR(mkey); 962 963 ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen); 964 if (ret < 0) 965 goto out; 966 967 ret = derived_key_encrypt(epayload, derived_key, sizeof derived_key); 968 if (ret < 0) 969 goto out; 970 971 ret = datablob_hmac_append(epayload, master_key, master_keylen); 972 if (ret < 0) 973 goto out; 974 975 ascii_buf = datablob_format(epayload, asciiblob_len); 976 if (!ascii_buf) { 977 ret = -ENOMEM; 978 goto out; 979 } 980 981 up_read(&mkey->sem); 982 key_put(mkey); 983 memzero_explicit(derived_key, sizeof(derived_key)); 984 985 memcpy(buffer, ascii_buf, asciiblob_len); 986 kfree_sensitive(ascii_buf); 987 988 return asciiblob_len; 989 out: 990 up_read(&mkey->sem); 991 key_put(mkey); 992 memzero_explicit(derived_key, sizeof(derived_key)); 993 return ret; 994 } 995 996 /* 997 * encrypted_destroy - clear and free the key's payload 998 */ 999 static void encrypted_destroy(struct key *key) 1000 { 1001 kfree_sensitive(key->payload.data[0]); 1002 } 1003 1004 struct key_type key_type_encrypted = { 1005 .name = "encrypted", 1006 .instantiate = encrypted_instantiate, 1007 .update = encrypted_update, 1008 .destroy = encrypted_destroy, 1009 .describe = user_describe, 1010 .read = encrypted_read, 1011 }; 1012 EXPORT_SYMBOL_GPL(key_type_encrypted); 1013 1014 static int __init init_encrypted(void) 1015 { 1016 int ret; 1017 1018 hash_tfm = crypto_alloc_shash(hash_alg, 0, 0); 1019 if (IS_ERR(hash_tfm)) { 1020 pr_err("encrypted_key: can't allocate %s transform: %ld\n", 1021 hash_alg, PTR_ERR(hash_tfm)); 1022 return PTR_ERR(hash_tfm); 1023 } 1024 1025 ret = aes_get_sizes(); 1026 if (ret < 0) 1027 goto out; 1028 ret = register_key_type(&key_type_encrypted); 1029 if (ret < 0) 1030 goto out; 1031 return 0; 1032 out: 1033 crypto_free_shash(hash_tfm); 1034 return ret; 1035 1036 } 1037 1038 static void __exit cleanup_encrypted(void) 1039 { 1040 crypto_free_shash(hash_tfm); 1041 unregister_key_type(&key_type_encrypted); 1042 } 1043 1044 late_initcall(init_encrypted); 1045 module_exit(cleanup_encrypted); 1046 1047 MODULE_LICENSE("GPL"); 1048