1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Key setup facility for FS encryption support. 4 * 5 * Copyright (C) 2015, Google, Inc. 6 * 7 * Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar. 8 * Heavily modified since then. 9 */ 10 11 #include <crypto/skcipher.h> 12 #include <linux/random.h> 13 14 #include "fscrypt_private.h" 15 16 struct fscrypt_mode fscrypt_modes[] = { 17 [FSCRYPT_MODE_AES_256_XTS] = { 18 .friendly_name = "AES-256-XTS", 19 .cipher_str = "xts(aes)", 20 .keysize = 64, 21 .security_strength = 32, 22 .ivsize = 16, 23 .blk_crypto_mode = BLK_ENCRYPTION_MODE_AES_256_XTS, 24 }, 25 [FSCRYPT_MODE_AES_256_CTS] = { 26 .friendly_name = "AES-256-CTS-CBC", 27 .cipher_str = "cts(cbc(aes))", 28 .keysize = 32, 29 .security_strength = 32, 30 .ivsize = 16, 31 }, 32 [FSCRYPT_MODE_AES_128_CBC] = { 33 .friendly_name = "AES-128-CBC-ESSIV", 34 .cipher_str = "essiv(cbc(aes),sha256)", 35 .keysize = 16, 36 .security_strength = 16, 37 .ivsize = 16, 38 .blk_crypto_mode = BLK_ENCRYPTION_MODE_AES_128_CBC_ESSIV, 39 }, 40 [FSCRYPT_MODE_AES_128_CTS] = { 41 .friendly_name = "AES-128-CTS-CBC", 42 .cipher_str = "cts(cbc(aes))", 43 .keysize = 16, 44 .security_strength = 16, 45 .ivsize = 16, 46 }, 47 [FSCRYPT_MODE_SM4_XTS] = { 48 .friendly_name = "SM4-XTS", 49 .cipher_str = "xts(sm4)", 50 .keysize = 32, 51 .security_strength = 16, 52 .ivsize = 16, 53 .blk_crypto_mode = BLK_ENCRYPTION_MODE_SM4_XTS, 54 }, 55 [FSCRYPT_MODE_SM4_CTS] = { 56 .friendly_name = "SM4-CTS-CBC", 57 .cipher_str = "cts(cbc(sm4))", 58 .keysize = 16, 59 .security_strength = 16, 60 .ivsize = 16, 61 }, 62 [FSCRYPT_MODE_ADIANTUM] = { 63 .friendly_name = "Adiantum", 64 .cipher_str = "adiantum(xchacha12,aes)", 65 .keysize = 32, 66 .security_strength = 32, 67 .ivsize = 32, 68 .blk_crypto_mode = BLK_ENCRYPTION_MODE_ADIANTUM, 69 }, 70 [FSCRYPT_MODE_AES_256_HCTR2] = { 71 .friendly_name = "AES-256-HCTR2", 72 .cipher_str = "hctr2(aes)", 73 .keysize = 32, 74 .security_strength = 32, 75 .ivsize = 32, 76 }, 77 }; 78 79 static DEFINE_MUTEX(fscrypt_mode_key_setup_mutex); 80 81 static struct fscrypt_mode * 82 select_encryption_mode(const union fscrypt_policy *policy, 83 const struct inode *inode) 84 { 85 BUILD_BUG_ON(ARRAY_SIZE(fscrypt_modes) != FSCRYPT_MODE_MAX + 1); 86 87 if (S_ISREG(inode->i_mode)) 88 return &fscrypt_modes[fscrypt_policy_contents_mode(policy)]; 89 90 if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) 91 return &fscrypt_modes[fscrypt_policy_fnames_mode(policy)]; 92 93 WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n", 94 inode->i_ino, (inode->i_mode & S_IFMT)); 95 return ERR_PTR(-EINVAL); 96 } 97 98 /* Create a symmetric cipher object for the given encryption mode and key */ 99 static struct crypto_skcipher * 100 fscrypt_allocate_skcipher(struct fscrypt_mode *mode, const u8 *raw_key, 101 const struct inode *inode) 102 { 103 struct crypto_skcipher *tfm; 104 int err; 105 106 tfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0); 107 if (IS_ERR(tfm)) { 108 if (PTR_ERR(tfm) == -ENOENT) { 109 fscrypt_warn(inode, 110 "Missing crypto API support for %s (API name: \"%s\")", 111 mode->friendly_name, mode->cipher_str); 112 return ERR_PTR(-ENOPKG); 113 } 114 fscrypt_err(inode, "Error allocating '%s' transform: %ld", 115 mode->cipher_str, PTR_ERR(tfm)); 116 return tfm; 117 } 118 if (!xchg(&mode->logged_cryptoapi_impl, 1)) { 119 /* 120 * fscrypt performance can vary greatly depending on which 121 * crypto algorithm implementation is used. Help people debug 122 * performance problems by logging the ->cra_driver_name the 123 * first time a mode is used. 124 */ 125 pr_info("fscrypt: %s using implementation \"%s\"\n", 126 mode->friendly_name, crypto_skcipher_driver_name(tfm)); 127 } 128 if (WARN_ON(crypto_skcipher_ivsize(tfm) != mode->ivsize)) { 129 err = -EINVAL; 130 goto err_free_tfm; 131 } 132 crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS); 133 err = crypto_skcipher_setkey(tfm, raw_key, mode->keysize); 134 if (err) 135 goto err_free_tfm; 136 137 return tfm; 138 139 err_free_tfm: 140 crypto_free_skcipher(tfm); 141 return ERR_PTR(err); 142 } 143 144 /* 145 * Prepare the crypto transform object or blk-crypto key in @prep_key, given the 146 * raw key, encryption mode (@ci->ci_mode), flag indicating which encryption 147 * implementation (fs-layer or blk-crypto) will be used (@ci->ci_inlinecrypt), 148 * and IV generation method (@ci->ci_policy.flags). 149 */ 150 int fscrypt_prepare_key(struct fscrypt_prepared_key *prep_key, 151 const u8 *raw_key, const struct fscrypt_info *ci) 152 { 153 struct crypto_skcipher *tfm; 154 155 if (fscrypt_using_inline_encryption(ci)) 156 return fscrypt_prepare_inline_crypt_key(prep_key, raw_key, ci); 157 158 tfm = fscrypt_allocate_skcipher(ci->ci_mode, raw_key, ci->ci_inode); 159 if (IS_ERR(tfm)) 160 return PTR_ERR(tfm); 161 /* 162 * Pairs with the smp_load_acquire() in fscrypt_is_key_prepared(). 163 * I.e., here we publish ->tfm with a RELEASE barrier so that 164 * concurrent tasks can ACQUIRE it. Note that this concurrency is only 165 * possible for per-mode keys, not for per-file keys. 166 */ 167 smp_store_release(&prep_key->tfm, tfm); 168 return 0; 169 } 170 171 /* Destroy a crypto transform object and/or blk-crypto key. */ 172 void fscrypt_destroy_prepared_key(struct super_block *sb, 173 struct fscrypt_prepared_key *prep_key) 174 { 175 crypto_free_skcipher(prep_key->tfm); 176 fscrypt_destroy_inline_crypt_key(sb, prep_key); 177 memzero_explicit(prep_key, sizeof(*prep_key)); 178 } 179 180 /* Given a per-file encryption key, set up the file's crypto transform object */ 181 int fscrypt_set_per_file_enc_key(struct fscrypt_info *ci, const u8 *raw_key) 182 { 183 ci->ci_owns_key = true; 184 return fscrypt_prepare_key(&ci->ci_enc_key, raw_key, ci); 185 } 186 187 static int setup_per_mode_enc_key(struct fscrypt_info *ci, 188 struct fscrypt_master_key *mk, 189 struct fscrypt_prepared_key *keys, 190 u8 hkdf_context, bool include_fs_uuid) 191 { 192 const struct inode *inode = ci->ci_inode; 193 const struct super_block *sb = inode->i_sb; 194 struct fscrypt_mode *mode = ci->ci_mode; 195 const u8 mode_num = mode - fscrypt_modes; 196 struct fscrypt_prepared_key *prep_key; 197 u8 mode_key[FSCRYPT_MAX_KEY_SIZE]; 198 u8 hkdf_info[sizeof(mode_num) + sizeof(sb->s_uuid)]; 199 unsigned int hkdf_infolen = 0; 200 int err; 201 202 if (WARN_ON(mode_num > FSCRYPT_MODE_MAX)) 203 return -EINVAL; 204 205 prep_key = &keys[mode_num]; 206 if (fscrypt_is_key_prepared(prep_key, ci)) { 207 ci->ci_enc_key = *prep_key; 208 return 0; 209 } 210 211 mutex_lock(&fscrypt_mode_key_setup_mutex); 212 213 if (fscrypt_is_key_prepared(prep_key, ci)) 214 goto done_unlock; 215 216 BUILD_BUG_ON(sizeof(mode_num) != 1); 217 BUILD_BUG_ON(sizeof(sb->s_uuid) != 16); 218 BUILD_BUG_ON(sizeof(hkdf_info) != 17); 219 hkdf_info[hkdf_infolen++] = mode_num; 220 if (include_fs_uuid) { 221 memcpy(&hkdf_info[hkdf_infolen], &sb->s_uuid, 222 sizeof(sb->s_uuid)); 223 hkdf_infolen += sizeof(sb->s_uuid); 224 } 225 err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, 226 hkdf_context, hkdf_info, hkdf_infolen, 227 mode_key, mode->keysize); 228 if (err) 229 goto out_unlock; 230 err = fscrypt_prepare_key(prep_key, mode_key, ci); 231 memzero_explicit(mode_key, mode->keysize); 232 if (err) 233 goto out_unlock; 234 done_unlock: 235 ci->ci_enc_key = *prep_key; 236 err = 0; 237 out_unlock: 238 mutex_unlock(&fscrypt_mode_key_setup_mutex); 239 return err; 240 } 241 242 /* 243 * Derive a SipHash key from the given fscrypt master key and the given 244 * application-specific information string. 245 * 246 * Note that the KDF produces a byte array, but the SipHash APIs expect the key 247 * as a pair of 64-bit words. Therefore, on big endian CPUs we have to do an 248 * endianness swap in order to get the same results as on little endian CPUs. 249 */ 250 static int fscrypt_derive_siphash_key(const struct fscrypt_master_key *mk, 251 u8 context, const u8 *info, 252 unsigned int infolen, siphash_key_t *key) 253 { 254 int err; 255 256 err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, context, info, infolen, 257 (u8 *)key, sizeof(*key)); 258 if (err) 259 return err; 260 261 BUILD_BUG_ON(sizeof(*key) != 16); 262 BUILD_BUG_ON(ARRAY_SIZE(key->key) != 2); 263 le64_to_cpus(&key->key[0]); 264 le64_to_cpus(&key->key[1]); 265 return 0; 266 } 267 268 int fscrypt_derive_dirhash_key(struct fscrypt_info *ci, 269 const struct fscrypt_master_key *mk) 270 { 271 int err; 272 273 err = fscrypt_derive_siphash_key(mk, HKDF_CONTEXT_DIRHASH_KEY, 274 ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE, 275 &ci->ci_dirhash_key); 276 if (err) 277 return err; 278 ci->ci_dirhash_key_initialized = true; 279 return 0; 280 } 281 282 void fscrypt_hash_inode_number(struct fscrypt_info *ci, 283 const struct fscrypt_master_key *mk) 284 { 285 WARN_ON(ci->ci_inode->i_ino == 0); 286 WARN_ON(!mk->mk_ino_hash_key_initialized); 287 288 ci->ci_hashed_ino = (u32)siphash_1u64(ci->ci_inode->i_ino, 289 &mk->mk_ino_hash_key); 290 } 291 292 static int fscrypt_setup_iv_ino_lblk_32_key(struct fscrypt_info *ci, 293 struct fscrypt_master_key *mk) 294 { 295 int err; 296 297 err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_32_keys, 298 HKDF_CONTEXT_IV_INO_LBLK_32_KEY, true); 299 if (err) 300 return err; 301 302 /* pairs with smp_store_release() below */ 303 if (!smp_load_acquire(&mk->mk_ino_hash_key_initialized)) { 304 305 mutex_lock(&fscrypt_mode_key_setup_mutex); 306 307 if (mk->mk_ino_hash_key_initialized) 308 goto unlock; 309 310 err = fscrypt_derive_siphash_key(mk, 311 HKDF_CONTEXT_INODE_HASH_KEY, 312 NULL, 0, &mk->mk_ino_hash_key); 313 if (err) 314 goto unlock; 315 /* pairs with smp_load_acquire() above */ 316 smp_store_release(&mk->mk_ino_hash_key_initialized, true); 317 unlock: 318 mutex_unlock(&fscrypt_mode_key_setup_mutex); 319 if (err) 320 return err; 321 } 322 323 /* 324 * New inodes may not have an inode number assigned yet. 325 * Hashing their inode number is delayed until later. 326 */ 327 if (ci->ci_inode->i_ino) 328 fscrypt_hash_inode_number(ci, mk); 329 return 0; 330 } 331 332 static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci, 333 struct fscrypt_master_key *mk, 334 bool need_dirhash_key) 335 { 336 int err; 337 338 if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { 339 /* 340 * DIRECT_KEY: instead of deriving per-file encryption keys, the 341 * per-file nonce will be included in all the IVs. But unlike 342 * v1 policies, for v2 policies in this case we don't encrypt 343 * with the master key directly but rather derive a per-mode 344 * encryption key. This ensures that the master key is 345 * consistently used only for HKDF, avoiding key reuse issues. 346 */ 347 err = setup_per_mode_enc_key(ci, mk, mk->mk_direct_keys, 348 HKDF_CONTEXT_DIRECT_KEY, false); 349 } else if (ci->ci_policy.v2.flags & 350 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) { 351 /* 352 * IV_INO_LBLK_64: encryption keys are derived from (master_key, 353 * mode_num, filesystem_uuid), and inode number is included in 354 * the IVs. This format is optimized for use with inline 355 * encryption hardware compliant with the UFS standard. 356 */ 357 err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_64_keys, 358 HKDF_CONTEXT_IV_INO_LBLK_64_KEY, 359 true); 360 } else if (ci->ci_policy.v2.flags & 361 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) { 362 err = fscrypt_setup_iv_ino_lblk_32_key(ci, mk); 363 } else { 364 u8 derived_key[FSCRYPT_MAX_KEY_SIZE]; 365 366 err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, 367 HKDF_CONTEXT_PER_FILE_ENC_KEY, 368 ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE, 369 derived_key, ci->ci_mode->keysize); 370 if (err) 371 return err; 372 373 err = fscrypt_set_per_file_enc_key(ci, derived_key); 374 memzero_explicit(derived_key, ci->ci_mode->keysize); 375 } 376 if (err) 377 return err; 378 379 /* Derive a secret dirhash key for directories that need it. */ 380 if (need_dirhash_key) { 381 err = fscrypt_derive_dirhash_key(ci, mk); 382 if (err) 383 return err; 384 } 385 386 return 0; 387 } 388 389 /* 390 * Check whether the size of the given master key (@mk) is appropriate for the 391 * encryption settings which a particular file will use (@ci). 392 * 393 * If the file uses a v1 encryption policy, then the master key must be at least 394 * as long as the derived key, as this is a requirement of the v1 KDF. 395 * 396 * Otherwise, the KDF can accept any size key, so we enforce a slightly looser 397 * requirement: we require that the size of the master key be at least the 398 * maximum security strength of any algorithm whose key will be derived from it 399 * (but in practice we only need to consider @ci->ci_mode, since any other 400 * possible subkeys such as DIRHASH and INODE_HASH will never increase the 401 * required key size over @ci->ci_mode). This allows AES-256-XTS keys to be 402 * derived from a 256-bit master key, which is cryptographically sufficient, 403 * rather than requiring a 512-bit master key which is unnecessarily long. (We 404 * still allow 512-bit master keys if the user chooses to use them, though.) 405 */ 406 static bool fscrypt_valid_master_key_size(const struct fscrypt_master_key *mk, 407 const struct fscrypt_info *ci) 408 { 409 unsigned int min_keysize; 410 411 if (ci->ci_policy.version == FSCRYPT_POLICY_V1) 412 min_keysize = ci->ci_mode->keysize; 413 else 414 min_keysize = ci->ci_mode->security_strength; 415 416 if (mk->mk_secret.size < min_keysize) { 417 fscrypt_warn(NULL, 418 "key with %s %*phN is too short (got %u bytes, need %u+ bytes)", 419 master_key_spec_type(&mk->mk_spec), 420 master_key_spec_len(&mk->mk_spec), 421 (u8 *)&mk->mk_spec.u, 422 mk->mk_secret.size, min_keysize); 423 return false; 424 } 425 return true; 426 } 427 428 /* 429 * Find the master key, then set up the inode's actual encryption key. 430 * 431 * If the master key is found in the filesystem-level keyring, then it is 432 * returned in *mk_ret with its semaphore read-locked. This is needed to ensure 433 * that only one task links the fscrypt_info into ->mk_decrypted_inodes (as 434 * multiple tasks may race to create an fscrypt_info for the same inode), and to 435 * synchronize the master key being removed with a new inode starting to use it. 436 */ 437 static int setup_file_encryption_key(struct fscrypt_info *ci, 438 bool need_dirhash_key, 439 struct fscrypt_master_key **mk_ret) 440 { 441 struct super_block *sb = ci->ci_inode->i_sb; 442 struct fscrypt_key_specifier mk_spec; 443 struct fscrypt_master_key *mk; 444 int err; 445 446 err = fscrypt_select_encryption_impl(ci); 447 if (err) 448 return err; 449 450 err = fscrypt_policy_to_key_spec(&ci->ci_policy, &mk_spec); 451 if (err) 452 return err; 453 454 mk = fscrypt_find_master_key(sb, &mk_spec); 455 if (unlikely(!mk)) { 456 const union fscrypt_policy *dummy_policy = 457 fscrypt_get_dummy_policy(sb); 458 459 /* 460 * Add the test_dummy_encryption key on-demand. In principle, 461 * it should be added at mount time. Do it here instead so that 462 * the individual filesystems don't need to worry about adding 463 * this key at mount time and cleaning up on mount failure. 464 */ 465 if (dummy_policy && 466 fscrypt_policies_equal(dummy_policy, &ci->ci_policy)) { 467 err = fscrypt_add_test_dummy_key(sb, &mk_spec); 468 if (err) 469 return err; 470 mk = fscrypt_find_master_key(sb, &mk_spec); 471 } 472 } 473 if (unlikely(!mk)) { 474 if (ci->ci_policy.version != FSCRYPT_POLICY_V1) 475 return -ENOKEY; 476 477 /* 478 * As a legacy fallback for v1 policies, search for the key in 479 * the current task's subscribed keyrings too. Don't move this 480 * to before the search of ->s_master_keys, since users 481 * shouldn't be able to override filesystem-level keys. 482 */ 483 return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci); 484 } 485 down_read(&mk->mk_sem); 486 487 /* Has the secret been removed (via FS_IOC_REMOVE_ENCRYPTION_KEY)? */ 488 if (!is_master_key_secret_present(&mk->mk_secret)) { 489 err = -ENOKEY; 490 goto out_release_key; 491 } 492 493 if (!fscrypt_valid_master_key_size(mk, ci)) { 494 err = -ENOKEY; 495 goto out_release_key; 496 } 497 498 switch (ci->ci_policy.version) { 499 case FSCRYPT_POLICY_V1: 500 err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw); 501 break; 502 case FSCRYPT_POLICY_V2: 503 err = fscrypt_setup_v2_file_key(ci, mk, need_dirhash_key); 504 break; 505 default: 506 WARN_ON(1); 507 err = -EINVAL; 508 break; 509 } 510 if (err) 511 goto out_release_key; 512 513 *mk_ret = mk; 514 return 0; 515 516 out_release_key: 517 up_read(&mk->mk_sem); 518 fscrypt_put_master_key(mk); 519 return err; 520 } 521 522 static void put_crypt_info(struct fscrypt_info *ci) 523 { 524 struct fscrypt_master_key *mk; 525 526 if (!ci) 527 return; 528 529 if (ci->ci_direct_key) 530 fscrypt_put_direct_key(ci->ci_direct_key); 531 else if (ci->ci_owns_key) 532 fscrypt_destroy_prepared_key(ci->ci_inode->i_sb, 533 &ci->ci_enc_key); 534 535 mk = ci->ci_master_key; 536 if (mk) { 537 /* 538 * Remove this inode from the list of inodes that were unlocked 539 * with the master key. In addition, if we're removing the last 540 * inode from a master key struct that already had its secret 541 * removed, then complete the full removal of the struct. 542 */ 543 spin_lock(&mk->mk_decrypted_inodes_lock); 544 list_del(&ci->ci_master_key_link); 545 spin_unlock(&mk->mk_decrypted_inodes_lock); 546 fscrypt_put_master_key_activeref(ci->ci_inode->i_sb, mk); 547 } 548 memzero_explicit(ci, sizeof(*ci)); 549 kmem_cache_free(fscrypt_info_cachep, ci); 550 } 551 552 static int 553 fscrypt_setup_encryption_info(struct inode *inode, 554 const union fscrypt_policy *policy, 555 const u8 nonce[FSCRYPT_FILE_NONCE_SIZE], 556 bool need_dirhash_key) 557 { 558 struct fscrypt_info *crypt_info; 559 struct fscrypt_mode *mode; 560 struct fscrypt_master_key *mk = NULL; 561 int res; 562 563 res = fscrypt_initialize(inode->i_sb->s_cop->flags); 564 if (res) 565 return res; 566 567 crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_KERNEL); 568 if (!crypt_info) 569 return -ENOMEM; 570 571 crypt_info->ci_inode = inode; 572 crypt_info->ci_policy = *policy; 573 memcpy(crypt_info->ci_nonce, nonce, FSCRYPT_FILE_NONCE_SIZE); 574 575 mode = select_encryption_mode(&crypt_info->ci_policy, inode); 576 if (IS_ERR(mode)) { 577 res = PTR_ERR(mode); 578 goto out; 579 } 580 WARN_ON(mode->ivsize > FSCRYPT_MAX_IV_SIZE); 581 crypt_info->ci_mode = mode; 582 583 res = setup_file_encryption_key(crypt_info, need_dirhash_key, &mk); 584 if (res) 585 goto out; 586 587 /* 588 * For existing inodes, multiple tasks may race to set ->i_crypt_info. 589 * So use cmpxchg_release(). This pairs with the smp_load_acquire() in 590 * fscrypt_get_info(). I.e., here we publish ->i_crypt_info with a 591 * RELEASE barrier so that other tasks can ACQUIRE it. 592 */ 593 if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL) { 594 /* 595 * We won the race and set ->i_crypt_info to our crypt_info. 596 * Now link it into the master key's inode list. 597 */ 598 if (mk) { 599 crypt_info->ci_master_key = mk; 600 refcount_inc(&mk->mk_active_refs); 601 spin_lock(&mk->mk_decrypted_inodes_lock); 602 list_add(&crypt_info->ci_master_key_link, 603 &mk->mk_decrypted_inodes); 604 spin_unlock(&mk->mk_decrypted_inodes_lock); 605 } 606 crypt_info = NULL; 607 } 608 res = 0; 609 out: 610 if (mk) { 611 up_read(&mk->mk_sem); 612 fscrypt_put_master_key(mk); 613 } 614 put_crypt_info(crypt_info); 615 return res; 616 } 617 618 /** 619 * fscrypt_get_encryption_info() - set up an inode's encryption key 620 * @inode: the inode to set up the key for. Must be encrypted. 621 * @allow_unsupported: if %true, treat an unsupported encryption policy (or 622 * unrecognized encryption context) the same way as the key 623 * being unavailable, instead of returning an error. Use 624 * %false unless the operation being performed is needed in 625 * order for files (or directories) to be deleted. 626 * 627 * Set up ->i_crypt_info, if it hasn't already been done. 628 * 629 * Note: unless ->i_crypt_info is already set, this isn't %GFP_NOFS-safe. So 630 * generally this shouldn't be called from within a filesystem transaction. 631 * 632 * Return: 0 if ->i_crypt_info was set or was already set, *or* if the 633 * encryption key is unavailable. (Use fscrypt_has_encryption_key() to 634 * distinguish these cases.) Also can return another -errno code. 635 */ 636 int fscrypt_get_encryption_info(struct inode *inode, bool allow_unsupported) 637 { 638 int res; 639 union fscrypt_context ctx; 640 union fscrypt_policy policy; 641 642 if (fscrypt_has_encryption_key(inode)) 643 return 0; 644 645 res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); 646 if (res < 0) { 647 if (res == -ERANGE && allow_unsupported) 648 return 0; 649 fscrypt_warn(inode, "Error %d getting encryption context", res); 650 return res; 651 } 652 653 res = fscrypt_policy_from_context(&policy, &ctx, res); 654 if (res) { 655 if (allow_unsupported) 656 return 0; 657 fscrypt_warn(inode, 658 "Unrecognized or corrupt encryption context"); 659 return res; 660 } 661 662 if (!fscrypt_supported_policy(&policy, inode)) { 663 if (allow_unsupported) 664 return 0; 665 return -EINVAL; 666 } 667 668 res = fscrypt_setup_encryption_info(inode, &policy, 669 fscrypt_context_nonce(&ctx), 670 IS_CASEFOLDED(inode) && 671 S_ISDIR(inode->i_mode)); 672 673 if (res == -ENOPKG && allow_unsupported) /* Algorithm unavailable? */ 674 res = 0; 675 if (res == -ENOKEY) 676 res = 0; 677 return res; 678 } 679 680 /** 681 * fscrypt_prepare_new_inode() - prepare to create a new inode in a directory 682 * @dir: a possibly-encrypted directory 683 * @inode: the new inode. ->i_mode must be set already. 684 * ->i_ino doesn't need to be set yet. 685 * @encrypt_ret: (output) set to %true if the new inode will be encrypted 686 * 687 * If the directory is encrypted, set up its ->i_crypt_info in preparation for 688 * encrypting the name of the new file. Also, if the new inode will be 689 * encrypted, set up its ->i_crypt_info and set *encrypt_ret=true. 690 * 691 * This isn't %GFP_NOFS-safe, and therefore it should be called before starting 692 * any filesystem transaction to create the inode. For this reason, ->i_ino 693 * isn't required to be set yet, as the filesystem may not have set it yet. 694 * 695 * This doesn't persist the new inode's encryption context. That still needs to 696 * be done later by calling fscrypt_set_context(). 697 * 698 * Return: 0 on success, -ENOKEY if the encryption key is missing, or another 699 * -errno code 700 */ 701 int fscrypt_prepare_new_inode(struct inode *dir, struct inode *inode, 702 bool *encrypt_ret) 703 { 704 const union fscrypt_policy *policy; 705 u8 nonce[FSCRYPT_FILE_NONCE_SIZE]; 706 707 policy = fscrypt_policy_to_inherit(dir); 708 if (policy == NULL) 709 return 0; 710 if (IS_ERR(policy)) 711 return PTR_ERR(policy); 712 713 if (WARN_ON_ONCE(inode->i_mode == 0)) 714 return -EINVAL; 715 716 /* 717 * Only regular files, directories, and symlinks are encrypted. 718 * Special files like device nodes and named pipes aren't. 719 */ 720 if (!S_ISREG(inode->i_mode) && 721 !S_ISDIR(inode->i_mode) && 722 !S_ISLNK(inode->i_mode)) 723 return 0; 724 725 *encrypt_ret = true; 726 727 get_random_bytes(nonce, FSCRYPT_FILE_NONCE_SIZE); 728 return fscrypt_setup_encryption_info(inode, policy, nonce, 729 IS_CASEFOLDED(dir) && 730 S_ISDIR(inode->i_mode)); 731 } 732 EXPORT_SYMBOL_GPL(fscrypt_prepare_new_inode); 733 734 /** 735 * fscrypt_put_encryption_info() - free most of an inode's fscrypt data 736 * @inode: an inode being evicted 737 * 738 * Free the inode's fscrypt_info. Filesystems must call this when the inode is 739 * being evicted. An RCU grace period need not have elapsed yet. 740 */ 741 void fscrypt_put_encryption_info(struct inode *inode) 742 { 743 put_crypt_info(inode->i_crypt_info); 744 inode->i_crypt_info = NULL; 745 } 746 EXPORT_SYMBOL(fscrypt_put_encryption_info); 747 748 /** 749 * fscrypt_free_inode() - free an inode's fscrypt data requiring RCU delay 750 * @inode: an inode being freed 751 * 752 * Free the inode's cached decrypted symlink target, if any. Filesystems must 753 * call this after an RCU grace period, just before they free the inode. 754 */ 755 void fscrypt_free_inode(struct inode *inode) 756 { 757 if (IS_ENCRYPTED(inode) && S_ISLNK(inode->i_mode)) { 758 kfree(inode->i_link); 759 inode->i_link = NULL; 760 } 761 } 762 EXPORT_SYMBOL(fscrypt_free_inode); 763 764 /** 765 * fscrypt_drop_inode() - check whether the inode's master key has been removed 766 * @inode: an inode being considered for eviction 767 * 768 * Filesystems supporting fscrypt must call this from their ->drop_inode() 769 * method so that encrypted inodes are evicted as soon as they're no longer in 770 * use and their master key has been removed. 771 * 772 * Return: 1 if fscrypt wants the inode to be evicted now, otherwise 0 773 */ 774 int fscrypt_drop_inode(struct inode *inode) 775 { 776 const struct fscrypt_info *ci = fscrypt_get_info(inode); 777 778 /* 779 * If ci is NULL, then the inode doesn't have an encryption key set up 780 * so it's irrelevant. If ci_master_key is NULL, then the master key 781 * was provided via the legacy mechanism of the process-subscribed 782 * keyrings, so we don't know whether it's been removed or not. 783 */ 784 if (!ci || !ci->ci_master_key) 785 return 0; 786 787 /* 788 * With proper, non-racy use of FS_IOC_REMOVE_ENCRYPTION_KEY, all inodes 789 * protected by the key were cleaned by sync_filesystem(). But if 790 * userspace is still using the files, inodes can be dirtied between 791 * then and now. We mustn't lose any writes, so skip dirty inodes here. 792 */ 793 if (inode->i_state & I_DIRTY_ALL) 794 return 0; 795 796 /* 797 * Note: since we aren't holding the key semaphore, the result here can 798 * immediately become outdated. But there's no correctness problem with 799 * unnecessarily evicting. Nor is there a correctness problem with not 800 * evicting while iput() is racing with the key being removed, since 801 * then the thread removing the key will either evict the inode itself 802 * or will correctly detect that it wasn't evicted due to the race. 803 */ 804 return !is_master_key_secret_present(&ci->ci_master_key->mk_secret); 805 } 806 EXPORT_SYMBOL_GPL(fscrypt_drop_inode); 807