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/sha2.h> 31 #include <crypto/skcipher.h> 32 #include <crypto/utils.h> 33 34 #include "encrypted.h" 35 #include "ecryptfs_format.h" 36 37 static const char KEY_TRUSTED_PREFIX[] = "trusted:"; 38 static const char KEY_USER_PREFIX[] = "user:"; 39 static const char blkcipher_alg[] = "cbc(aes)"; 40 static const char key_format_default[] = "default"; 41 static const char key_format_ecryptfs[] = "ecryptfs"; 42 static const char key_format_enc32[] = "enc32"; 43 static unsigned int ivsize; 44 static int blksize; 45 46 #define KEY_TRUSTED_PREFIX_LEN (sizeof (KEY_TRUSTED_PREFIX) - 1) 47 #define KEY_USER_PREFIX_LEN (sizeof (KEY_USER_PREFIX) - 1) 48 #define KEY_ECRYPTFS_DESC_LEN 16 49 #define HASH_SIZE SHA256_DIGEST_SIZE 50 #define MAX_DATA_SIZE 4096 51 #define MIN_DATA_SIZE 20 52 #define KEY_ENC32_PAYLOAD_LEN 32 53 54 enum { 55 Opt_new, Opt_load, Opt_update, Opt_err 56 }; 57 58 enum { 59 Opt_default, Opt_ecryptfs, Opt_enc32, Opt_error 60 }; 61 62 static const match_table_t key_format_tokens = { 63 {Opt_default, "default"}, 64 {Opt_ecryptfs, "ecryptfs"}, 65 {Opt_enc32, "enc32"}, 66 {Opt_error, NULL} 67 }; 68 69 static const match_table_t key_tokens = { 70 {Opt_new, "new"}, 71 {Opt_load, "load"}, 72 {Opt_update, "update"}, 73 {Opt_err, NULL} 74 }; 75 76 static bool user_decrypted_data = IS_ENABLED(CONFIG_USER_DECRYPTED_DATA); 77 module_param(user_decrypted_data, bool, 0); 78 MODULE_PARM_DESC(user_decrypted_data, 79 "Allow instantiation of encrypted keys using provided decrypted data"); 80 81 static int aes_get_sizes(void) 82 { 83 struct crypto_skcipher *tfm; 84 85 tfm = crypto_alloc_skcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC); 86 if (IS_ERR(tfm)) { 87 pr_err("encrypted_key: failed to alloc_cipher (%ld)\n", 88 PTR_ERR(tfm)); 89 return PTR_ERR(tfm); 90 } 91 ivsize = crypto_skcipher_ivsize(tfm); 92 blksize = crypto_skcipher_blocksize(tfm); 93 crypto_free_skcipher(tfm); 94 return 0; 95 } 96 97 /* 98 * valid_ecryptfs_desc - verify the description of a new/loaded encrypted key 99 * 100 * The description of a encrypted key with format 'ecryptfs' must contain 101 * exactly 16 hexadecimal characters. 102 * 103 */ 104 static int valid_ecryptfs_desc(const char *ecryptfs_desc) 105 { 106 int i; 107 108 if (strlen(ecryptfs_desc) != KEY_ECRYPTFS_DESC_LEN) { 109 pr_err("encrypted_key: key description must be %d hexadecimal " 110 "characters long\n", KEY_ECRYPTFS_DESC_LEN); 111 return -EINVAL; 112 } 113 114 for (i = 0; i < KEY_ECRYPTFS_DESC_LEN; i++) { 115 if (!isxdigit(ecryptfs_desc[i])) { 116 pr_err("encrypted_key: key description must contain " 117 "only hexadecimal characters\n"); 118 return -EINVAL; 119 } 120 } 121 122 return 0; 123 } 124 125 /* 126 * valid_master_desc - verify the 'key-type:desc' of a new/updated master-key 127 * 128 * key-type:= "trusted:" | "user:" 129 * desc:= master-key description 130 * 131 * Verify that 'key-type' is valid and that 'desc' exists. On key update, 132 * only the master key description is permitted to change, not the key-type. 133 * The key-type remains constant. 134 * 135 * On success returns 0, otherwise -EINVAL. 136 */ 137 static int valid_master_desc(const char *new_desc, const char *orig_desc) 138 { 139 int prefix_len; 140 141 if (!strncmp(new_desc, KEY_TRUSTED_PREFIX, KEY_TRUSTED_PREFIX_LEN)) 142 prefix_len = KEY_TRUSTED_PREFIX_LEN; 143 else if (!strncmp(new_desc, KEY_USER_PREFIX, KEY_USER_PREFIX_LEN)) 144 prefix_len = KEY_USER_PREFIX_LEN; 145 else 146 return -EINVAL; 147 148 if (!new_desc[prefix_len]) 149 return -EINVAL; 150 151 if (orig_desc && strncmp(new_desc, orig_desc, prefix_len)) 152 return -EINVAL; 153 154 return 0; 155 } 156 157 /* 158 * datablob_parse - parse the keyctl data 159 * 160 * datablob format: 161 * new [<format>] <master-key name> <decrypted data length> [<decrypted data>] 162 * load [<format>] <master-key name> <decrypted data length> 163 * <encrypted iv + data> 164 * update <new-master-key name> 165 * 166 * Tokenizes a copy of the keyctl data, returning a pointer to each token, 167 * which is null terminated. 168 * 169 * On success returns 0, otherwise -EINVAL. 170 */ 171 static int datablob_parse(char *datablob, const char **format, 172 char **master_desc, char **decrypted_datalen, 173 char **hex_encoded_iv, char **decrypted_data) 174 { 175 substring_t args[MAX_OPT_ARGS]; 176 int ret = -EINVAL; 177 int key_cmd; 178 int key_format; 179 char *p, *keyword; 180 181 keyword = strsep(&datablob, " \t"); 182 if (!keyword) { 183 pr_info("encrypted_key: insufficient parameters specified\n"); 184 return ret; 185 } 186 key_cmd = match_token(keyword, key_tokens, args); 187 188 /* Get optional format: default | ecryptfs */ 189 p = strsep(&datablob, " \t"); 190 if (!p) { 191 pr_err("encrypted_key: insufficient parameters specified\n"); 192 return ret; 193 } 194 195 key_format = match_token(p, key_format_tokens, args); 196 switch (key_format) { 197 case Opt_ecryptfs: 198 case Opt_enc32: 199 case Opt_default: 200 *format = p; 201 *master_desc = strsep(&datablob, " \t"); 202 break; 203 case Opt_error: 204 *master_desc = p; 205 break; 206 } 207 208 if (!*master_desc) { 209 pr_info("encrypted_key: master key parameter is missing\n"); 210 goto out; 211 } 212 213 if (valid_master_desc(*master_desc, NULL) < 0) { 214 pr_info("encrypted_key: master key parameter \'%s\' " 215 "is invalid\n", *master_desc); 216 goto out; 217 } 218 219 if (decrypted_datalen) { 220 *decrypted_datalen = strsep(&datablob, " \t"); 221 if (!*decrypted_datalen) { 222 pr_info("encrypted_key: keylen parameter is missing\n"); 223 goto out; 224 } 225 } 226 227 switch (key_cmd) { 228 case Opt_new: 229 if (!decrypted_datalen) { 230 pr_info("encrypted_key: keyword \'%s\' not allowed " 231 "when called from .update method\n", keyword); 232 break; 233 } 234 *decrypted_data = strsep(&datablob, " \t"); 235 ret = 0; 236 break; 237 case Opt_load: 238 if (!decrypted_datalen) { 239 pr_info("encrypted_key: keyword \'%s\' not allowed " 240 "when called from .update method\n", keyword); 241 break; 242 } 243 *hex_encoded_iv = strsep(&datablob, " \t"); 244 if (!*hex_encoded_iv) { 245 pr_info("encrypted_key: hex blob is missing\n"); 246 break; 247 } 248 ret = 0; 249 break; 250 case Opt_update: 251 if (decrypted_datalen) { 252 pr_info("encrypted_key: keyword \'%s\' not allowed " 253 "when called from .instantiate method\n", 254 keyword); 255 break; 256 } 257 ret = 0; 258 break; 259 case Opt_err: 260 pr_info("encrypted_key: keyword \'%s\' not recognized\n", 261 keyword); 262 break; 263 } 264 out: 265 return ret; 266 } 267 268 /* 269 * datablob_format - format as an ascii string, before copying to userspace 270 */ 271 static char *datablob_format(struct encrypted_key_payload *epayload, 272 size_t asciiblob_len) 273 { 274 char *ascii_buf, *bufp; 275 u8 *iv = epayload->iv; 276 int len; 277 int i; 278 279 ascii_buf = kmalloc(asciiblob_len + 1, GFP_KERNEL); 280 if (!ascii_buf) 281 goto out; 282 283 ascii_buf[asciiblob_len] = '\0'; 284 285 /* copy datablob master_desc and datalen strings */ 286 len = sprintf(ascii_buf, "%s %s %s ", epayload->format, 287 epayload->master_desc, epayload->datalen); 288 289 /* convert the hex encoded iv, encrypted-data and HMAC to ascii */ 290 bufp = &ascii_buf[len]; 291 for (i = 0; i < (asciiblob_len - len) / 2; i++) 292 bufp = hex_byte_pack(bufp, iv[i]); 293 out: 294 return ascii_buf; 295 } 296 297 /* 298 * request_user_key - request the user key 299 * 300 * Use a user provided key to encrypt/decrypt an encrypted-key. 301 */ 302 static struct key *request_user_key(const char *master_desc, const u8 **master_key, 303 size_t *master_keylen) 304 { 305 const struct user_key_payload *upayload; 306 struct key *ukey; 307 308 ukey = request_key(&key_type_user, master_desc, NULL); 309 if (IS_ERR(ukey)) 310 goto error; 311 312 down_read(&ukey->sem); 313 upayload = user_key_payload_locked(ukey); 314 if (!upayload) { 315 /* key was revoked before we acquired its semaphore */ 316 up_read(&ukey->sem); 317 key_put(ukey); 318 ukey = ERR_PTR(-EKEYREVOKED); 319 goto error; 320 } 321 *master_key = upayload->data; 322 *master_keylen = upayload->datalen; 323 error: 324 return ukey; 325 } 326 327 enum derived_key_type { ENC_KEY, AUTH_KEY }; 328 329 /* Derive authentication/encryption key from trusted key */ 330 static int get_derived_key(u8 *derived_key, enum derived_key_type key_type, 331 const u8 *master_key, size_t master_keylen) 332 { 333 u8 *derived_buf; 334 unsigned int derived_buf_len; 335 336 derived_buf_len = strlen("AUTH_KEY") + 1 + master_keylen; 337 if (derived_buf_len < HASH_SIZE) 338 derived_buf_len = HASH_SIZE; 339 340 derived_buf = kzalloc(derived_buf_len, GFP_KERNEL); 341 if (!derived_buf) 342 return -ENOMEM; 343 344 if (key_type) 345 strcpy(derived_buf, "AUTH_KEY"); 346 else 347 strcpy(derived_buf, "ENC_KEY"); 348 349 memcpy(derived_buf + strlen(derived_buf) + 1, master_key, 350 master_keylen); 351 sha256(derived_buf, derived_buf_len, derived_key); 352 kfree_sensitive(derived_buf); 353 return 0; 354 } 355 356 static struct skcipher_request *init_skcipher_req(const u8 *key, 357 unsigned int key_len) 358 { 359 struct skcipher_request *req; 360 struct crypto_skcipher *tfm; 361 int ret; 362 363 tfm = crypto_alloc_skcipher(blkcipher_alg, 0, CRYPTO_ALG_ASYNC); 364 if (IS_ERR(tfm)) { 365 pr_err("encrypted_key: failed to load %s transform (%ld)\n", 366 blkcipher_alg, PTR_ERR(tfm)); 367 return ERR_CAST(tfm); 368 } 369 370 ret = crypto_skcipher_setkey(tfm, key, key_len); 371 if (ret < 0) { 372 pr_err("encrypted_key: failed to setkey (%d)\n", ret); 373 crypto_free_skcipher(tfm); 374 return ERR_PTR(ret); 375 } 376 377 req = skcipher_request_alloc(tfm, GFP_KERNEL); 378 if (!req) { 379 pr_err("encrypted_key: failed to allocate request for %s\n", 380 blkcipher_alg); 381 crypto_free_skcipher(tfm); 382 return ERR_PTR(-ENOMEM); 383 } 384 385 skcipher_request_set_callback(req, 0, NULL, NULL); 386 return req; 387 } 388 389 static struct key *request_master_key(struct encrypted_key_payload *epayload, 390 const u8 **master_key, size_t *master_keylen) 391 { 392 struct key *mkey = ERR_PTR(-EINVAL); 393 394 if (!strncmp(epayload->master_desc, KEY_TRUSTED_PREFIX, 395 KEY_TRUSTED_PREFIX_LEN)) { 396 mkey = request_trusted_key(epayload->master_desc + 397 KEY_TRUSTED_PREFIX_LEN, 398 master_key, master_keylen); 399 } else if (!strncmp(epayload->master_desc, KEY_USER_PREFIX, 400 KEY_USER_PREFIX_LEN)) { 401 mkey = request_user_key(epayload->master_desc + 402 KEY_USER_PREFIX_LEN, 403 master_key, master_keylen); 404 } else 405 goto out; 406 407 if (IS_ERR(mkey)) { 408 int ret = PTR_ERR(mkey); 409 410 if (ret == -ENOTSUPP) 411 pr_info("encrypted_key: key %s not supported", 412 epayload->master_desc); 413 else 414 pr_info("encrypted_key: key %s not found", 415 epayload->master_desc); 416 goto out; 417 } 418 419 dump_master_key(*master_key, *master_keylen); 420 out: 421 return mkey; 422 } 423 424 /* Before returning data to userspace, encrypt decrypted data. */ 425 static int derived_key_encrypt(struct encrypted_key_payload *epayload, 426 const u8 *derived_key, 427 unsigned int derived_keylen) 428 { 429 struct scatterlist sg_in[2]; 430 struct scatterlist sg_out[1]; 431 struct crypto_skcipher *tfm; 432 struct skcipher_request *req; 433 unsigned int encrypted_datalen; 434 u8 iv[AES_BLOCK_SIZE]; 435 int ret; 436 437 encrypted_datalen = roundup(epayload->decrypted_datalen, blksize); 438 439 req = init_skcipher_req(derived_key, derived_keylen); 440 ret = PTR_ERR(req); 441 if (IS_ERR(req)) 442 goto out; 443 dump_decrypted_data(epayload); 444 445 sg_init_table(sg_in, 2); 446 sg_set_buf(&sg_in[0], epayload->decrypted_data, 447 epayload->decrypted_datalen); 448 sg_set_page(&sg_in[1], ZERO_PAGE(0), AES_BLOCK_SIZE, 0); 449 450 sg_init_table(sg_out, 1); 451 sg_set_buf(sg_out, epayload->encrypted_data, encrypted_datalen); 452 453 memcpy(iv, epayload->iv, sizeof(iv)); 454 skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv); 455 ret = crypto_skcipher_encrypt(req); 456 tfm = crypto_skcipher_reqtfm(req); 457 skcipher_request_free(req); 458 crypto_free_skcipher(tfm); 459 if (ret < 0) 460 pr_err("encrypted_key: failed to encrypt (%d)\n", ret); 461 else 462 dump_encrypted_data(epayload, encrypted_datalen); 463 out: 464 return ret; 465 } 466 467 static int datablob_hmac_append(struct encrypted_key_payload *epayload, 468 const u8 *master_key, size_t master_keylen) 469 { 470 u8 derived_key[HASH_SIZE]; 471 u8 *digest; 472 int ret; 473 474 ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen); 475 if (ret < 0) 476 goto out; 477 478 digest = epayload->format + epayload->datablob_len; 479 hmac_sha256_usingrawkey(derived_key, sizeof(derived_key), 480 epayload->format, epayload->datablob_len, 481 digest); 482 dump_hmac(NULL, digest, HASH_SIZE); 483 out: 484 memzero_explicit(derived_key, sizeof(derived_key)); 485 return ret; 486 } 487 488 /* verify HMAC before decrypting encrypted key */ 489 static int datablob_hmac_verify(struct encrypted_key_payload *epayload, 490 const u8 *format, const u8 *master_key, 491 size_t master_keylen) 492 { 493 u8 derived_key[HASH_SIZE]; 494 u8 digest[HASH_SIZE]; 495 int ret; 496 char *p; 497 unsigned short len; 498 499 ret = get_derived_key(derived_key, AUTH_KEY, master_key, master_keylen); 500 if (ret < 0) 501 goto out; 502 503 len = epayload->datablob_len; 504 if (!format) { 505 p = epayload->master_desc; 506 len -= strlen(epayload->format) + 1; 507 } else 508 p = epayload->format; 509 510 hmac_sha256_usingrawkey(derived_key, sizeof(derived_key), p, len, 511 digest); 512 ret = crypto_memneq(digest, epayload->format + epayload->datablob_len, 513 sizeof(digest)); 514 if (ret) { 515 ret = -EINVAL; 516 dump_hmac("datablob", 517 epayload->format + epayload->datablob_len, 518 HASH_SIZE); 519 dump_hmac("calc", digest, HASH_SIZE); 520 } 521 out: 522 memzero_explicit(derived_key, sizeof(derived_key)); 523 return ret; 524 } 525 526 static int derived_key_decrypt(struct encrypted_key_payload *epayload, 527 const u8 *derived_key, 528 unsigned int derived_keylen) 529 { 530 struct scatterlist sg_in[1]; 531 struct scatterlist sg_out[2]; 532 struct crypto_skcipher *tfm; 533 struct skcipher_request *req; 534 unsigned int encrypted_datalen; 535 u8 iv[AES_BLOCK_SIZE]; 536 u8 *pad; 537 int ret; 538 539 /* Throwaway buffer to hold the unused zero padding at the end */ 540 pad = kmalloc(AES_BLOCK_SIZE, GFP_KERNEL); 541 if (!pad) 542 return -ENOMEM; 543 544 encrypted_datalen = roundup(epayload->decrypted_datalen, blksize); 545 req = init_skcipher_req(derived_key, derived_keylen); 546 ret = PTR_ERR(req); 547 if (IS_ERR(req)) 548 goto out; 549 dump_encrypted_data(epayload, encrypted_datalen); 550 551 sg_init_table(sg_in, 1); 552 sg_init_table(sg_out, 2); 553 sg_set_buf(sg_in, epayload->encrypted_data, encrypted_datalen); 554 sg_set_buf(&sg_out[0], epayload->decrypted_data, 555 epayload->decrypted_datalen); 556 sg_set_buf(&sg_out[1], pad, AES_BLOCK_SIZE); 557 558 memcpy(iv, epayload->iv, sizeof(iv)); 559 skcipher_request_set_crypt(req, sg_in, sg_out, encrypted_datalen, iv); 560 ret = crypto_skcipher_decrypt(req); 561 tfm = crypto_skcipher_reqtfm(req); 562 skcipher_request_free(req); 563 crypto_free_skcipher(tfm); 564 if (ret < 0) 565 goto out; 566 dump_decrypted_data(epayload); 567 out: 568 kfree(pad); 569 return ret; 570 } 571 572 /* Allocate memory for decrypted key and datablob. */ 573 static struct encrypted_key_payload *encrypted_key_alloc(struct key *key, 574 const char *format, 575 const char *master_desc, 576 const char *datalen, 577 const char *decrypted_data) 578 { 579 struct encrypted_key_payload *epayload = NULL; 580 unsigned short datablob_len; 581 unsigned short decrypted_datalen; 582 unsigned short payload_datalen; 583 unsigned int encrypted_datalen; 584 unsigned int format_len; 585 long dlen; 586 int i; 587 int ret; 588 589 ret = kstrtol(datalen, 10, &dlen); 590 if (ret < 0 || dlen < MIN_DATA_SIZE || dlen > MAX_DATA_SIZE) 591 return ERR_PTR(-EINVAL); 592 593 format_len = (!format) ? strlen(key_format_default) : strlen(format); 594 decrypted_datalen = dlen; 595 payload_datalen = decrypted_datalen; 596 597 if (decrypted_data) { 598 if (!user_decrypted_data) { 599 pr_err("encrypted key: instantiation of keys using provided decrypted data is disabled since CONFIG_USER_DECRYPTED_DATA is set to false\n"); 600 return ERR_PTR(-EINVAL); 601 } 602 if (strlen(decrypted_data) != decrypted_datalen * 2) { 603 pr_err("encrypted key: decrypted data provided does not match decrypted data length provided\n"); 604 return ERR_PTR(-EINVAL); 605 } 606 for (i = 0; i < strlen(decrypted_data); i++) { 607 if (!isxdigit(decrypted_data[i])) { 608 pr_err("encrypted key: decrypted data provided must contain only hexadecimal characters\n"); 609 return ERR_PTR(-EINVAL); 610 } 611 } 612 } 613 614 if (format) { 615 if (!strcmp(format, key_format_ecryptfs)) { 616 if (dlen != ECRYPTFS_MAX_KEY_BYTES) { 617 pr_err("encrypted_key: keylen for the ecryptfs format must be equal to %d bytes\n", 618 ECRYPTFS_MAX_KEY_BYTES); 619 return ERR_PTR(-EINVAL); 620 } 621 decrypted_datalen = ECRYPTFS_MAX_KEY_BYTES; 622 payload_datalen = sizeof(struct ecryptfs_auth_tok); 623 } else if (!strcmp(format, key_format_enc32)) { 624 if (decrypted_datalen != KEY_ENC32_PAYLOAD_LEN) { 625 pr_err("encrypted_key: enc32 key payload incorrect length: %d\n", 626 decrypted_datalen); 627 return ERR_PTR(-EINVAL); 628 } 629 } 630 } 631 632 encrypted_datalen = roundup(decrypted_datalen, blksize); 633 634 datablob_len = format_len + 1 + strlen(master_desc) + 1 635 + strlen(datalen) + 1 + ivsize + 1 + encrypted_datalen; 636 637 ret = key_payload_reserve(key, payload_datalen + datablob_len 638 + HASH_SIZE + 1); 639 if (ret < 0) 640 return ERR_PTR(ret); 641 642 epayload = kzalloc(sizeof(*epayload) + payload_datalen + 643 datablob_len + HASH_SIZE + 1, GFP_KERNEL); 644 if (!epayload) 645 return ERR_PTR(-ENOMEM); 646 647 epayload->payload_datalen = payload_datalen; 648 epayload->decrypted_datalen = decrypted_datalen; 649 epayload->datablob_len = datablob_len; 650 return epayload; 651 } 652 653 static int encrypted_key_decrypt(struct encrypted_key_payload *epayload, 654 const char *format, const char *hex_encoded_iv) 655 { 656 struct key *mkey; 657 u8 derived_key[HASH_SIZE]; 658 const u8 *master_key; 659 u8 *hmac; 660 const char *hex_encoded_data; 661 unsigned int encrypted_datalen; 662 size_t master_keylen; 663 size_t asciilen; 664 int ret; 665 666 encrypted_datalen = roundup(epayload->decrypted_datalen, blksize); 667 asciilen = (ivsize + 1 + encrypted_datalen + HASH_SIZE) * 2; 668 if (strlen(hex_encoded_iv) != asciilen) 669 return -EINVAL; 670 671 hex_encoded_data = hex_encoded_iv + (2 * ivsize) + 2; 672 ret = hex2bin(epayload->iv, hex_encoded_iv, ivsize); 673 if (ret < 0) 674 return -EINVAL; 675 ret = hex2bin(epayload->encrypted_data, hex_encoded_data, 676 encrypted_datalen); 677 if (ret < 0) 678 return -EINVAL; 679 680 hmac = epayload->format + epayload->datablob_len; 681 ret = hex2bin(hmac, hex_encoded_data + (encrypted_datalen * 2), 682 HASH_SIZE); 683 if (ret < 0) 684 return -EINVAL; 685 686 mkey = request_master_key(epayload, &master_key, &master_keylen); 687 if (IS_ERR(mkey)) 688 return PTR_ERR(mkey); 689 690 ret = datablob_hmac_verify(epayload, format, master_key, master_keylen); 691 if (ret < 0) { 692 pr_err("encrypted_key: bad hmac (%d)\n", ret); 693 goto out; 694 } 695 696 ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen); 697 if (ret < 0) 698 goto out; 699 700 ret = derived_key_decrypt(epayload, derived_key, sizeof derived_key); 701 if (ret < 0) 702 pr_err("encrypted_key: failed to decrypt key (%d)\n", ret); 703 out: 704 up_read(&mkey->sem); 705 key_put(mkey); 706 memzero_explicit(derived_key, sizeof(derived_key)); 707 return ret; 708 } 709 710 static void __ekey_init(struct encrypted_key_payload *epayload, 711 const char *format, const char *master_desc, 712 const char *datalen) 713 { 714 unsigned int format_len; 715 716 format_len = (!format) ? strlen(key_format_default) : strlen(format); 717 epayload->format = epayload->payload_data + epayload->payload_datalen; 718 epayload->master_desc = epayload->format + format_len + 1; 719 epayload->datalen = epayload->master_desc + strlen(master_desc) + 1; 720 epayload->iv = epayload->datalen + strlen(datalen) + 1; 721 epayload->encrypted_data = epayload->iv + ivsize + 1; 722 epayload->decrypted_data = epayload->payload_data; 723 724 if (!format) 725 memcpy(epayload->format, key_format_default, format_len); 726 else { 727 if (!strcmp(format, key_format_ecryptfs)) 728 epayload->decrypted_data = 729 ecryptfs_get_auth_tok_key((struct ecryptfs_auth_tok *)epayload->payload_data); 730 731 memcpy(epayload->format, format, format_len); 732 } 733 734 memcpy(epayload->master_desc, master_desc, strlen(master_desc)); 735 memcpy(epayload->datalen, datalen, strlen(datalen)); 736 } 737 738 /* 739 * encrypted_init - initialize an encrypted key 740 * 741 * For a new key, use either a random number or user-provided decrypted data in 742 * case it is provided. A random number is used for the iv in both cases. For 743 * an old key, decrypt the hex encoded data. 744 */ 745 static int encrypted_init(struct encrypted_key_payload *epayload, 746 const char *key_desc, const char *format, 747 const char *master_desc, const char *datalen, 748 const char *hex_encoded_iv, const char *decrypted_data) 749 { 750 int ret = 0; 751 752 if (format && !strcmp(format, key_format_ecryptfs)) { 753 ret = valid_ecryptfs_desc(key_desc); 754 if (ret < 0) 755 return ret; 756 757 ecryptfs_fill_auth_tok((struct ecryptfs_auth_tok *)epayload->payload_data, 758 key_desc); 759 } 760 761 __ekey_init(epayload, format, master_desc, datalen); 762 if (hex_encoded_iv) { 763 ret = encrypted_key_decrypt(epayload, format, hex_encoded_iv); 764 } else if (decrypted_data) { 765 get_random_bytes(epayload->iv, ivsize); 766 ret = hex2bin(epayload->decrypted_data, decrypted_data, 767 epayload->decrypted_datalen); 768 } else { 769 get_random_bytes(epayload->iv, ivsize); 770 get_random_bytes(epayload->decrypted_data, epayload->decrypted_datalen); 771 } 772 return ret; 773 } 774 775 /* 776 * encrypted_instantiate - instantiate an encrypted key 777 * 778 * Instantiates the key: 779 * - by decrypting an existing encrypted datablob, or 780 * - by creating a new encrypted key based on a kernel random number, or 781 * - using provided decrypted data. 782 * 783 * On success, return 0. Otherwise return errno. 784 */ 785 static int encrypted_instantiate(struct key *key, 786 struct key_preparsed_payload *prep) 787 { 788 struct encrypted_key_payload *epayload = NULL; 789 char *datablob = NULL; 790 const char *format = NULL; 791 char *master_desc = NULL; 792 char *decrypted_datalen = NULL; 793 char *hex_encoded_iv = NULL; 794 char *decrypted_data = NULL; 795 size_t datalen = prep->datalen; 796 int ret; 797 798 if (datalen <= 0 || datalen > 32767 || !prep->data) 799 return -EINVAL; 800 801 datablob = kmalloc(datalen + 1, GFP_KERNEL); 802 if (!datablob) 803 return -ENOMEM; 804 datablob[datalen] = 0; 805 memcpy(datablob, prep->data, datalen); 806 ret = datablob_parse(datablob, &format, &master_desc, 807 &decrypted_datalen, &hex_encoded_iv, &decrypted_data); 808 if (ret < 0) 809 goto out; 810 811 epayload = encrypted_key_alloc(key, format, master_desc, 812 decrypted_datalen, decrypted_data); 813 if (IS_ERR(epayload)) { 814 ret = PTR_ERR(epayload); 815 goto out; 816 } 817 ret = encrypted_init(epayload, key->description, format, master_desc, 818 decrypted_datalen, hex_encoded_iv, decrypted_data); 819 if (ret < 0) { 820 kfree_sensitive(epayload); 821 goto out; 822 } 823 824 rcu_assign_keypointer(key, epayload); 825 out: 826 kfree_sensitive(datablob); 827 return ret; 828 } 829 830 static void encrypted_rcu_free(struct rcu_head *rcu) 831 { 832 struct encrypted_key_payload *epayload; 833 834 epayload = container_of(rcu, struct encrypted_key_payload, rcu); 835 kfree_sensitive(epayload); 836 } 837 838 /* 839 * encrypted_update - update the master key description 840 * 841 * Change the master key description for an existing encrypted key. 842 * The next read will return an encrypted datablob using the new 843 * master key description. 844 * 845 * On success, return 0. Otherwise return errno. 846 */ 847 static int encrypted_update(struct key *key, struct key_preparsed_payload *prep) 848 { 849 struct encrypted_key_payload *epayload = key->payload.data[0]; 850 struct encrypted_key_payload *new_epayload; 851 char *buf; 852 char *new_master_desc = NULL; 853 const char *format = NULL; 854 size_t datalen = prep->datalen; 855 int ret = 0; 856 857 if (key_is_negative(key)) 858 return -ENOKEY; 859 if (datalen <= 0 || datalen > 32767 || !prep->data) 860 return -EINVAL; 861 862 buf = kmalloc(datalen + 1, GFP_KERNEL); 863 if (!buf) 864 return -ENOMEM; 865 866 buf[datalen] = 0; 867 memcpy(buf, prep->data, datalen); 868 ret = datablob_parse(buf, &format, &new_master_desc, NULL, NULL, NULL); 869 if (ret < 0) 870 goto out; 871 872 ret = valid_master_desc(new_master_desc, epayload->master_desc); 873 if (ret < 0) 874 goto out; 875 876 new_epayload = encrypted_key_alloc(key, epayload->format, 877 new_master_desc, epayload->datalen, NULL); 878 if (IS_ERR(new_epayload)) { 879 ret = PTR_ERR(new_epayload); 880 goto out; 881 } 882 883 __ekey_init(new_epayload, epayload->format, new_master_desc, 884 epayload->datalen); 885 886 memcpy(new_epayload->iv, epayload->iv, ivsize); 887 memcpy(new_epayload->payload_data, epayload->payload_data, 888 epayload->payload_datalen); 889 890 rcu_assign_keypointer(key, new_epayload); 891 call_rcu(&epayload->rcu, encrypted_rcu_free); 892 out: 893 kfree_sensitive(buf); 894 return ret; 895 } 896 897 /* 898 * encrypted_read - format and copy out the encrypted data 899 * 900 * The resulting datablob format is: 901 * <master-key name> <decrypted data length> <encrypted iv> <encrypted data> 902 * 903 * On success, return to userspace the encrypted key datablob size. 904 */ 905 static long encrypted_read(const struct key *key, char *buffer, 906 size_t buflen) 907 { 908 struct encrypted_key_payload *epayload; 909 struct key *mkey; 910 const u8 *master_key; 911 size_t master_keylen; 912 char derived_key[HASH_SIZE]; 913 char *ascii_buf; 914 size_t asciiblob_len; 915 int ret; 916 917 epayload = dereference_key_locked(key); 918 919 /* returns the hex encoded iv, encrypted-data, and hmac as ascii */ 920 asciiblob_len = epayload->datablob_len + ivsize + 1 921 + roundup(epayload->decrypted_datalen, blksize) 922 + (HASH_SIZE * 2); 923 924 if (!buffer || buflen < asciiblob_len) 925 return asciiblob_len; 926 927 mkey = request_master_key(epayload, &master_key, &master_keylen); 928 if (IS_ERR(mkey)) 929 return PTR_ERR(mkey); 930 931 ret = get_derived_key(derived_key, ENC_KEY, master_key, master_keylen); 932 if (ret < 0) 933 goto out; 934 935 ret = derived_key_encrypt(epayload, derived_key, sizeof derived_key); 936 if (ret < 0) 937 goto out; 938 939 ret = datablob_hmac_append(epayload, master_key, master_keylen); 940 if (ret < 0) 941 goto out; 942 943 ascii_buf = datablob_format(epayload, asciiblob_len); 944 if (!ascii_buf) { 945 ret = -ENOMEM; 946 goto out; 947 } 948 949 up_read(&mkey->sem); 950 key_put(mkey); 951 memzero_explicit(derived_key, sizeof(derived_key)); 952 953 memcpy(buffer, ascii_buf, asciiblob_len); 954 kfree_sensitive(ascii_buf); 955 956 return asciiblob_len; 957 out: 958 up_read(&mkey->sem); 959 key_put(mkey); 960 memzero_explicit(derived_key, sizeof(derived_key)); 961 return ret; 962 } 963 964 /* 965 * encrypted_destroy - clear and free the key's payload 966 */ 967 static void encrypted_destroy(struct key *key) 968 { 969 kfree_sensitive(key->payload.data[0]); 970 } 971 972 struct key_type key_type_encrypted = { 973 .name = "encrypted", 974 .instantiate = encrypted_instantiate, 975 .update = encrypted_update, 976 .destroy = encrypted_destroy, 977 .describe = user_describe, 978 .read = encrypted_read, 979 }; 980 EXPORT_SYMBOL_GPL(key_type_encrypted); 981 982 static int __init init_encrypted(void) 983 { 984 int ret; 985 986 ret = aes_get_sizes(); 987 if (ret < 0) 988 return ret; 989 return register_key_type(&key_type_encrypted); 990 } 991 992 static void __exit cleanup_encrypted(void) 993 { 994 unregister_key_type(&key_type_encrypted); 995 } 996 997 late_initcall(init_encrypted); 998 module_exit(cleanup_encrypted); 999 1000 MODULE_DESCRIPTION("Encrypted key type"); 1001 MODULE_LICENSE("GPL"); 1002