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/export.h> 13 #include <linux/random.h> 14 15 #include "fscrypt_private.h" 16 17 struct fscrypt_mode fscrypt_modes[] = { 18 [FSCRYPT_MODE_AES_256_XTS] = { 19 .friendly_name = "AES-256-XTS", 20 .cipher_str = "xts(aes)", 21 .keysize = 64, 22 .security_strength = 32, 23 .ivsize = 16, 24 .blk_crypto_mode = BLK_ENCRYPTION_MODE_AES_256_XTS, 25 }, 26 [FSCRYPT_MODE_AES_256_CTS] = { 27 .friendly_name = "AES-256-CBC-CTS", 28 .cipher_str = "cts(cbc(aes))", 29 .keysize = 32, 30 .security_strength = 32, 31 .ivsize = 16, 32 }, 33 [FSCRYPT_MODE_AES_128_CBC] = { 34 .friendly_name = "AES-128-CBC-ESSIV", 35 .cipher_str = "essiv(cbc(aes),sha256)", 36 .keysize = 16, 37 .security_strength = 16, 38 .ivsize = 16, 39 .blk_crypto_mode = BLK_ENCRYPTION_MODE_AES_128_CBC_ESSIV, 40 }, 41 [FSCRYPT_MODE_AES_128_CTS] = { 42 .friendly_name = "AES-128-CBC-CTS", 43 .cipher_str = "cts(cbc(aes))", 44 .keysize = 16, 45 .security_strength = 16, 46 .ivsize = 16, 47 }, 48 [FSCRYPT_MODE_SM4_XTS] = { 49 .friendly_name = "SM4-XTS", 50 .cipher_str = "xts(sm4)", 51 .keysize = 32, 52 .security_strength = 16, 53 .ivsize = 16, 54 .blk_crypto_mode = BLK_ENCRYPTION_MODE_SM4_XTS, 55 }, 56 [FSCRYPT_MODE_SM4_CTS] = { 57 .friendly_name = "SM4-CBC-CTS", 58 .cipher_str = "cts(cbc(sm4))", 59 .keysize = 16, 60 .security_strength = 16, 61 .ivsize = 16, 62 }, 63 [FSCRYPT_MODE_ADIANTUM] = { 64 .friendly_name = "Adiantum", 65 .cipher_str = "adiantum(xchacha12,aes)", 66 .keysize = 32, 67 .security_strength = 32, 68 .ivsize = 32, 69 .blk_crypto_mode = BLK_ENCRYPTION_MODE_ADIANTUM, 70 }, 71 [FSCRYPT_MODE_AES_256_HCTR2] = { 72 .friendly_name = "AES-256-HCTR2", 73 .cipher_str = "hctr2(aes)", 74 .keysize = 32, 75 .security_strength = 32, 76 .ivsize = 32, 77 }, 78 }; 79 80 static DEFINE_MUTEX(fscrypt_mode_key_setup_mutex); 81 82 static struct fscrypt_mode * 83 select_encryption_mode(const union fscrypt_policy *policy, 84 const struct inode *inode) 85 { 86 BUILD_BUG_ON(ARRAY_SIZE(fscrypt_modes) != FSCRYPT_MODE_MAX + 1); 87 88 if (S_ISREG(inode->i_mode)) 89 return &fscrypt_modes[fscrypt_policy_contents_mode(policy)]; 90 91 if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) 92 return &fscrypt_modes[fscrypt_policy_fnames_mode(policy)]; 93 94 WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n", 95 inode->i_ino, (inode->i_mode & S_IFMT)); 96 return ERR_PTR(-EINVAL); 97 } 98 99 /* Create a symmetric cipher object for the given encryption mode and key */ 100 static struct crypto_sync_skcipher * 101 fscrypt_allocate_skcipher(struct fscrypt_mode *mode, const u8 *raw_key, 102 const struct inode *inode) 103 { 104 struct crypto_sync_skcipher *tfm; 105 int err; 106 107 tfm = crypto_alloc_sync_skcipher(mode->cipher_str, 0, 108 FSCRYPT_CRYPTOAPI_MASK); 109 if (IS_ERR(tfm)) { 110 if (PTR_ERR(tfm) == -ENOENT) { 111 fscrypt_warn(inode, 112 "Missing crypto API support for %s (API name: \"%s\")", 113 mode->friendly_name, mode->cipher_str); 114 return ERR_PTR(-ENOPKG); 115 } 116 fscrypt_err(inode, "Error allocating '%s' transform: %ld", 117 mode->cipher_str, PTR_ERR(tfm)); 118 return tfm; 119 } 120 if (!xchg(&mode->logged_cryptoapi_impl, 1)) { 121 /* 122 * fscrypt performance can vary greatly depending on which 123 * crypto algorithm implementation is used. Help people debug 124 * performance problems by logging the ->cra_driver_name the 125 * first time a mode is used. 126 */ 127 pr_info("fscrypt: %s using implementation \"%s\"\n", 128 mode->friendly_name, 129 crypto_skcipher_driver_name(&tfm->base)); 130 } 131 if (WARN_ON_ONCE(crypto_sync_skcipher_ivsize(tfm) != mode->ivsize)) { 132 err = -EINVAL; 133 goto err_free_tfm; 134 } 135 crypto_sync_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS); 136 err = crypto_sync_skcipher_setkey(tfm, raw_key, mode->keysize); 137 if (err) 138 goto err_free_tfm; 139 140 return tfm; 141 142 err_free_tfm: 143 crypto_free_sync_skcipher(tfm); 144 return ERR_PTR(err); 145 } 146 147 /* 148 * Prepare the crypto transform object or blk-crypto key in @prep_key, given the 149 * raw key, encryption mode (@ci->ci_mode), flag indicating which encryption 150 * implementation (fs-layer or blk-crypto) will be used (@ci->ci_inlinecrypt), 151 * and IV generation method (@ci->ci_policy.flags). 152 */ 153 int fscrypt_prepare_key(struct fscrypt_prepared_key *prep_key, 154 const u8 *raw_key, const struct fscrypt_inode_info *ci) 155 { 156 struct crypto_sync_skcipher *tfm; 157 158 if (fscrypt_using_inline_encryption(ci)) 159 return fscrypt_prepare_inline_crypt_key(prep_key, raw_key, 160 ci->ci_mode->keysize, 161 false, ci); 162 163 tfm = fscrypt_allocate_skcipher(ci->ci_mode, raw_key, ci->ci_inode); 164 if (IS_ERR(tfm)) 165 return PTR_ERR(tfm); 166 /* 167 * Pairs with the smp_load_acquire() in fscrypt_is_key_prepared(). 168 * I.e., here we publish ->tfm with a RELEASE barrier so that 169 * concurrent tasks can ACQUIRE it. Note that this concurrency is only 170 * possible for per-mode keys, not for per-file keys. 171 */ 172 smp_store_release(&prep_key->tfm, tfm); 173 return 0; 174 } 175 176 /* Destroy a crypto transform object and/or blk-crypto key. */ 177 void fscrypt_destroy_prepared_key(struct super_block *sb, 178 struct fscrypt_prepared_key *prep_key) 179 { 180 crypto_free_sync_skcipher(prep_key->tfm); 181 fscrypt_destroy_inline_crypt_key(sb, prep_key); 182 memzero_explicit(prep_key, sizeof(*prep_key)); 183 } 184 185 /* Given a per-file encryption key, set up the file's crypto transform object */ 186 int fscrypt_set_per_file_enc_key(struct fscrypt_inode_info *ci, 187 const u8 *raw_key) 188 { 189 ci->ci_owns_key = true; 190 return fscrypt_prepare_key(&ci->ci_enc_key, raw_key, ci); 191 } 192 193 static int setup_per_mode_enc_key(struct fscrypt_inode_info *ci, 194 struct fscrypt_master_key *mk, 195 struct fscrypt_prepared_key *keys, 196 u8 hkdf_context, bool include_fs_uuid) 197 { 198 const struct inode *inode = ci->ci_inode; 199 const struct super_block *sb = inode->i_sb; 200 struct fscrypt_mode *mode = ci->ci_mode; 201 const u8 mode_num = mode - fscrypt_modes; 202 struct fscrypt_prepared_key *prep_key; 203 u8 mode_key[FSCRYPT_MAX_RAW_KEY_SIZE]; 204 u8 hkdf_info[sizeof(mode_num) + sizeof(sb->s_uuid)]; 205 unsigned int hkdf_infolen = 0; 206 bool use_hw_wrapped_key = false; 207 int err; 208 209 if (WARN_ON_ONCE(mode_num > FSCRYPT_MODE_MAX)) 210 return -EINVAL; 211 212 if (mk->mk_secret.is_hw_wrapped && S_ISREG(inode->i_mode)) { 213 /* Using a hardware-wrapped key for file contents encryption */ 214 if (!fscrypt_using_inline_encryption(ci)) { 215 if (sb->s_flags & SB_INLINECRYPT) 216 fscrypt_warn(ci->ci_inode, 217 "Hardware-wrapped key required, but no suitable inline encryption capabilities are available"); 218 else 219 fscrypt_warn(ci->ci_inode, 220 "Hardware-wrapped keys require inline encryption (-o inlinecrypt)"); 221 return -EINVAL; 222 } 223 use_hw_wrapped_key = true; 224 } 225 226 prep_key = &keys[mode_num]; 227 if (fscrypt_is_key_prepared(prep_key, ci)) { 228 ci->ci_enc_key = *prep_key; 229 return 0; 230 } 231 232 mutex_lock(&fscrypt_mode_key_setup_mutex); 233 234 if (fscrypt_is_key_prepared(prep_key, ci)) 235 goto done_unlock; 236 237 if (use_hw_wrapped_key) { 238 err = fscrypt_prepare_inline_crypt_key(prep_key, 239 mk->mk_secret.bytes, 240 mk->mk_secret.size, true, 241 ci); 242 if (err) 243 goto out_unlock; 244 goto done_unlock; 245 } 246 247 BUILD_BUG_ON(sizeof(mode_num) != 1); 248 BUILD_BUG_ON(sizeof(sb->s_uuid) != 16); 249 BUILD_BUG_ON(sizeof(hkdf_info) != 17); 250 hkdf_info[hkdf_infolen++] = mode_num; 251 if (include_fs_uuid) { 252 memcpy(&hkdf_info[hkdf_infolen], &sb->s_uuid, 253 sizeof(sb->s_uuid)); 254 hkdf_infolen += sizeof(sb->s_uuid); 255 } 256 fscrypt_hkdf_expand(&mk->mk_secret.hkdf, hkdf_context, hkdf_info, 257 hkdf_infolen, mode_key, mode->keysize); 258 err = fscrypt_prepare_key(prep_key, mode_key, ci); 259 memzero_explicit(mode_key, mode->keysize); 260 if (err) 261 goto out_unlock; 262 done_unlock: 263 ci->ci_enc_key = *prep_key; 264 err = 0; 265 out_unlock: 266 mutex_unlock(&fscrypt_mode_key_setup_mutex); 267 return err; 268 } 269 270 /* 271 * Derive a SipHash key from the given fscrypt master key and the given 272 * application-specific information string. 273 * 274 * Note that the KDF produces a byte array, but the SipHash APIs expect the key 275 * as a pair of 64-bit words. Therefore, on big endian CPUs we have to do an 276 * endianness swap in order to get the same results as on little endian CPUs. 277 */ 278 static void fscrypt_derive_siphash_key(const struct fscrypt_master_key *mk, 279 u8 context, const u8 *info, 280 unsigned int infolen, siphash_key_t *key) 281 { 282 fscrypt_hkdf_expand(&mk->mk_secret.hkdf, context, info, infolen, 283 (u8 *)key, sizeof(*key)); 284 BUILD_BUG_ON(sizeof(*key) != 16); 285 BUILD_BUG_ON(ARRAY_SIZE(key->key) != 2); 286 le64_to_cpus(&key->key[0]); 287 le64_to_cpus(&key->key[1]); 288 } 289 290 void fscrypt_derive_dirhash_key(struct fscrypt_inode_info *ci, 291 const struct fscrypt_master_key *mk) 292 { 293 fscrypt_derive_siphash_key(mk, HKDF_CONTEXT_DIRHASH_KEY, 294 ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE, 295 &ci->ci_dirhash_key); 296 ci->ci_dirhash_key_initialized = true; 297 } 298 299 void fscrypt_hash_inode_number(struct fscrypt_inode_info *ci, 300 const struct fscrypt_master_key *mk) 301 { 302 WARN_ON_ONCE(ci->ci_inode->i_ino == 0); 303 WARN_ON_ONCE(!mk->mk_ino_hash_key_initialized); 304 305 ci->ci_hashed_ino = (u32)siphash_1u64(ci->ci_inode->i_ino, 306 &mk->mk_ino_hash_key); 307 } 308 309 static int fscrypt_setup_iv_ino_lblk_32_key(struct fscrypt_inode_info *ci, 310 struct fscrypt_master_key *mk) 311 { 312 int err; 313 314 err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_32_keys, 315 HKDF_CONTEXT_IV_INO_LBLK_32_KEY, true); 316 if (err) 317 return err; 318 319 /* pairs with smp_store_release() below */ 320 if (!smp_load_acquire(&mk->mk_ino_hash_key_initialized)) { 321 322 mutex_lock(&fscrypt_mode_key_setup_mutex); 323 324 if (mk->mk_ino_hash_key_initialized) 325 goto unlock; 326 327 fscrypt_derive_siphash_key(mk, HKDF_CONTEXT_INODE_HASH_KEY, 328 NULL, 0, &mk->mk_ino_hash_key); 329 /* pairs with smp_load_acquire() above */ 330 smp_store_release(&mk->mk_ino_hash_key_initialized, true); 331 unlock: 332 mutex_unlock(&fscrypt_mode_key_setup_mutex); 333 } 334 335 /* 336 * New inodes may not have an inode number assigned yet. 337 * Hashing their inode number is delayed until later. 338 */ 339 if (ci->ci_inode->i_ino) 340 fscrypt_hash_inode_number(ci, mk); 341 return 0; 342 } 343 344 static int fscrypt_setup_v2_file_key(struct fscrypt_inode_info *ci, 345 struct fscrypt_master_key *mk, 346 bool need_dirhash_key) 347 { 348 int err; 349 350 if (mk->mk_secret.is_hw_wrapped && 351 !(ci->ci_policy.v2.flags & (FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64 | 352 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32))) { 353 fscrypt_warn(ci->ci_inode, 354 "Hardware-wrapped keys are only supported with IV_INO_LBLK policies"); 355 return -EINVAL; 356 } 357 358 if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { 359 /* 360 * DIRECT_KEY: instead of deriving per-file encryption keys, the 361 * per-file nonce will be included in all the IVs. But unlike 362 * v1 policies, for v2 policies in this case we don't encrypt 363 * with the master key directly but rather derive a per-mode 364 * encryption key. This ensures that the master key is 365 * consistently used only for HKDF, avoiding key reuse issues. 366 */ 367 err = setup_per_mode_enc_key(ci, mk, mk->mk_direct_keys, 368 HKDF_CONTEXT_DIRECT_KEY, false); 369 } else if (ci->ci_policy.v2.flags & 370 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) { 371 /* 372 * IV_INO_LBLK_64: encryption keys are derived from (master_key, 373 * mode_num, filesystem_uuid), and inode number is included in 374 * the IVs. This format is optimized for use with inline 375 * encryption hardware compliant with the UFS standard. 376 */ 377 err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_64_keys, 378 HKDF_CONTEXT_IV_INO_LBLK_64_KEY, 379 true); 380 } else if (ci->ci_policy.v2.flags & 381 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) { 382 err = fscrypt_setup_iv_ino_lblk_32_key(ci, mk); 383 } else { 384 u8 derived_key[FSCRYPT_MAX_RAW_KEY_SIZE]; 385 386 fscrypt_hkdf_expand(&mk->mk_secret.hkdf, 387 HKDF_CONTEXT_PER_FILE_ENC_KEY, 388 ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE, 389 derived_key, ci->ci_mode->keysize); 390 err = fscrypt_set_per_file_enc_key(ci, derived_key); 391 memzero_explicit(derived_key, ci->ci_mode->keysize); 392 } 393 if (err) 394 return err; 395 396 /* Derive a secret dirhash key for directories that need it. */ 397 if (need_dirhash_key) 398 fscrypt_derive_dirhash_key(ci, mk); 399 400 return 0; 401 } 402 403 /* 404 * Check whether the size of the given master key (@mk) is appropriate for the 405 * encryption settings which a particular file will use (@ci). 406 * 407 * If the file uses a v1 encryption policy, then the master key must be at least 408 * as long as the derived key, as this is a requirement of the v1 KDF. 409 * 410 * Otherwise, the KDF can accept any size key, so we enforce a slightly looser 411 * requirement: we require that the size of the master key be at least the 412 * maximum security strength of any algorithm whose key will be derived from it 413 * (but in practice we only need to consider @ci->ci_mode, since any other 414 * possible subkeys such as DIRHASH and INODE_HASH will never increase the 415 * required key size over @ci->ci_mode). This allows AES-256-XTS keys to be 416 * derived from a 256-bit master key, which is cryptographically sufficient, 417 * rather than requiring a 512-bit master key which is unnecessarily long. (We 418 * still allow 512-bit master keys if the user chooses to use them, though.) 419 */ 420 static bool fscrypt_valid_master_key_size(const struct fscrypt_master_key *mk, 421 const struct fscrypt_inode_info *ci) 422 { 423 unsigned int min_keysize; 424 425 if (ci->ci_policy.version == FSCRYPT_POLICY_V1) 426 min_keysize = ci->ci_mode->keysize; 427 else 428 min_keysize = ci->ci_mode->security_strength; 429 430 if (mk->mk_secret.size < min_keysize) { 431 fscrypt_warn(NULL, 432 "key with %s %*phN is too short (got %u bytes, need %u+ bytes)", 433 master_key_spec_type(&mk->mk_spec), 434 master_key_spec_len(&mk->mk_spec), 435 (u8 *)&mk->mk_spec.u, 436 mk->mk_secret.size, min_keysize); 437 return false; 438 } 439 return true; 440 } 441 442 /* 443 * Find the master key, then set up the inode's actual encryption key. 444 * 445 * If the master key is found in the filesystem-level keyring, then it is 446 * returned in *mk_ret with its semaphore read-locked. This is needed to ensure 447 * that only one task links the fscrypt_inode_info into ->mk_decrypted_inodes 448 * (as multiple tasks may race to create an fscrypt_inode_info for the same 449 * inode), and to synchronize the master key being removed with a new inode 450 * starting to use it. 451 */ 452 static int setup_file_encryption_key(struct fscrypt_inode_info *ci, 453 bool need_dirhash_key, 454 struct fscrypt_master_key **mk_ret) 455 { 456 struct super_block *sb = ci->ci_inode->i_sb; 457 struct fscrypt_key_specifier mk_spec; 458 struct fscrypt_master_key *mk; 459 int err; 460 461 err = fscrypt_policy_to_key_spec(&ci->ci_policy, &mk_spec); 462 if (err) 463 return err; 464 465 mk = fscrypt_find_master_key(sb, &mk_spec); 466 if (unlikely(!mk)) { 467 const union fscrypt_policy *dummy_policy = 468 fscrypt_get_dummy_policy(sb); 469 470 /* 471 * Add the test_dummy_encryption key on-demand. In principle, 472 * it should be added at mount time. Do it here instead so that 473 * the individual filesystems don't need to worry about adding 474 * this key at mount time and cleaning up on mount failure. 475 */ 476 if (dummy_policy && 477 fscrypt_policies_equal(dummy_policy, &ci->ci_policy)) { 478 err = fscrypt_add_test_dummy_key(sb, &mk_spec); 479 if (err) 480 return err; 481 mk = fscrypt_find_master_key(sb, &mk_spec); 482 } 483 } 484 if (unlikely(!mk)) { 485 if (ci->ci_policy.version != FSCRYPT_POLICY_V1) 486 return -ENOKEY; 487 488 err = fscrypt_select_encryption_impl(ci, false); 489 if (err) 490 return err; 491 492 /* 493 * As a legacy fallback for v1 policies, search for the key in 494 * the current task's subscribed keyrings too. Don't move this 495 * to before the search of ->s_master_keys, since users 496 * shouldn't be able to override filesystem-level keys. 497 */ 498 return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci); 499 } 500 down_read(&mk->mk_sem); 501 502 if (!mk->mk_present) { 503 /* FS_IOC_REMOVE_ENCRYPTION_KEY has been executed on this key */ 504 err = -ENOKEY; 505 goto out_release_key; 506 } 507 508 if (!fscrypt_valid_master_key_size(mk, ci)) { 509 err = -ENOKEY; 510 goto out_release_key; 511 } 512 513 err = fscrypt_select_encryption_impl(ci, mk->mk_secret.is_hw_wrapped); 514 if (err) 515 goto out_release_key; 516 517 switch (ci->ci_policy.version) { 518 case FSCRYPT_POLICY_V1: 519 if (WARN_ON_ONCE(mk->mk_secret.is_hw_wrapped)) { 520 /* 521 * This should never happen, as adding a v1 policy key 522 * that is hardware-wrapped isn't allowed. 523 */ 524 err = -EINVAL; 525 goto out_release_key; 526 } 527 err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.bytes); 528 break; 529 case FSCRYPT_POLICY_V2: 530 err = fscrypt_setup_v2_file_key(ci, mk, need_dirhash_key); 531 break; 532 default: 533 WARN_ON_ONCE(1); 534 err = -EINVAL; 535 break; 536 } 537 if (err) 538 goto out_release_key; 539 540 *mk_ret = mk; 541 return 0; 542 543 out_release_key: 544 up_read(&mk->mk_sem); 545 fscrypt_put_master_key(mk); 546 return err; 547 } 548 549 static void put_crypt_info(struct fscrypt_inode_info *ci) 550 { 551 struct fscrypt_master_key *mk; 552 553 if (!ci) 554 return; 555 556 if (ci->ci_direct_key) 557 fscrypt_put_direct_key(ci->ci_direct_key); 558 else if (ci->ci_owns_key) 559 fscrypt_destroy_prepared_key(ci->ci_inode->i_sb, 560 &ci->ci_enc_key); 561 562 mk = ci->ci_master_key; 563 if (mk) { 564 /* 565 * Remove this inode from the list of inodes that were unlocked 566 * with the master key. In addition, if we're removing the last 567 * inode from an incompletely removed key, then complete the 568 * full removal of the key. 569 */ 570 spin_lock(&mk->mk_decrypted_inodes_lock); 571 list_del(&ci->ci_master_key_link); 572 spin_unlock(&mk->mk_decrypted_inodes_lock); 573 fscrypt_put_master_key_activeref(ci->ci_inode->i_sb, mk); 574 } 575 memzero_explicit(ci, sizeof(*ci)); 576 kmem_cache_free(fscrypt_inode_info_cachep, ci); 577 } 578 579 static int 580 fscrypt_setup_encryption_info(struct inode *inode, 581 const union fscrypt_policy *policy, 582 const u8 nonce[FSCRYPT_FILE_NONCE_SIZE], 583 bool need_dirhash_key) 584 { 585 struct fscrypt_inode_info *crypt_info; 586 struct fscrypt_mode *mode; 587 struct fscrypt_master_key *mk = NULL; 588 int res; 589 590 res = fscrypt_initialize(inode->i_sb); 591 if (res) 592 return res; 593 594 crypt_info = kmem_cache_zalloc(fscrypt_inode_info_cachep, GFP_KERNEL); 595 if (!crypt_info) 596 return -ENOMEM; 597 598 crypt_info->ci_inode = inode; 599 crypt_info->ci_policy = *policy; 600 memcpy(crypt_info->ci_nonce, nonce, FSCRYPT_FILE_NONCE_SIZE); 601 602 mode = select_encryption_mode(&crypt_info->ci_policy, inode); 603 if (IS_ERR(mode)) { 604 res = PTR_ERR(mode); 605 goto out; 606 } 607 WARN_ON_ONCE(mode->ivsize > FSCRYPT_MAX_IV_SIZE); 608 crypt_info->ci_mode = mode; 609 610 crypt_info->ci_data_unit_bits = 611 fscrypt_policy_du_bits(&crypt_info->ci_policy, inode); 612 crypt_info->ci_data_units_per_block_bits = 613 inode->i_blkbits - crypt_info->ci_data_unit_bits; 614 615 res = setup_file_encryption_key(crypt_info, need_dirhash_key, &mk); 616 if (res) 617 goto out; 618 619 /* 620 * For existing inodes, multiple tasks may race to set the inode's 621 * fscrypt info pointer. So use cmpxchg_release(). This pairs with the 622 * smp_load_acquire() in fscrypt_get_inode_info(). I.e., publish the 623 * pointer with a RELEASE barrier so that other tasks can ACQUIRE it. 624 */ 625 if (cmpxchg_release(fscrypt_inode_info_addr(inode), NULL, crypt_info) == 626 NULL) { 627 /* 628 * We won the race and set the inode's fscrypt info to our 629 * crypt_info. Now link it into the master key's inode list. 630 */ 631 if (mk) { 632 crypt_info->ci_master_key = mk; 633 refcount_inc(&mk->mk_active_refs); 634 spin_lock(&mk->mk_decrypted_inodes_lock); 635 list_add(&crypt_info->ci_master_key_link, 636 &mk->mk_decrypted_inodes); 637 spin_unlock(&mk->mk_decrypted_inodes_lock); 638 } 639 crypt_info = NULL; 640 } 641 res = 0; 642 out: 643 if (mk) { 644 up_read(&mk->mk_sem); 645 fscrypt_put_master_key(mk); 646 } 647 put_crypt_info(crypt_info); 648 return res; 649 } 650 651 /** 652 * fscrypt_get_encryption_info() - set up an inode's encryption key 653 * @inode: the inode to set up the key for. Must be encrypted. 654 * @allow_unsupported: if %true, treat an unsupported encryption policy (or 655 * unrecognized encryption context) the same way as the key 656 * being unavailable, instead of returning an error. Use 657 * %false unless the operation being performed is needed in 658 * order for files (or directories) to be deleted. 659 * 660 * Set up the inode's encryption key, if it hasn't already been done. 661 * 662 * Note: unless the key setup was already done, this isn't %GFP_NOFS-safe. So 663 * generally this shouldn't be called from within a filesystem transaction. 664 * 665 * Return: 0 if the key is now set up, *or* if it couldn't be set up because the 666 * needed master key is absent. (Use fscrypt_has_encryption_key() to 667 * distinguish these cases.) Also can return another -errno code. 668 */ 669 int fscrypt_get_encryption_info(struct inode *inode, bool allow_unsupported) 670 { 671 int res; 672 union fscrypt_context ctx; 673 union fscrypt_policy policy; 674 675 if (fscrypt_has_encryption_key(inode)) 676 return 0; 677 678 res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); 679 if (res < 0) { 680 if (res == -ERANGE && allow_unsupported) 681 return 0; 682 fscrypt_warn(inode, "Error %d getting encryption context", res); 683 return res; 684 } 685 686 res = fscrypt_policy_from_context(&policy, &ctx, res); 687 if (res) { 688 if (allow_unsupported) 689 return 0; 690 fscrypt_warn(inode, 691 "Unrecognized or corrupt encryption context"); 692 return res; 693 } 694 695 if (!fscrypt_supported_policy(&policy, inode)) { 696 if (allow_unsupported) 697 return 0; 698 return -EINVAL; 699 } 700 701 res = fscrypt_setup_encryption_info(inode, &policy, 702 fscrypt_context_nonce(&ctx), 703 IS_CASEFOLDED(inode) && 704 S_ISDIR(inode->i_mode)); 705 706 if (res == -ENOPKG && allow_unsupported) /* Algorithm unavailable? */ 707 res = 0; 708 if (res == -ENOKEY) 709 res = 0; 710 return res; 711 } 712 713 /** 714 * fscrypt_prepare_new_inode() - prepare to create a new inode in a directory 715 * @dir: a possibly-encrypted directory 716 * @inode: the new inode. ->i_mode and ->i_blkbits must be set already. 717 * ->i_ino doesn't need to be set yet. 718 * @encrypt_ret: (output) set to %true if the new inode will be encrypted 719 * 720 * If the directory is encrypted, set up its encryption key in preparation for 721 * encrypting the name of the new file. Also, if the new inode will be 722 * encrypted, set up its encryption key too and set *encrypt_ret=true. 723 * 724 * This isn't %GFP_NOFS-safe, and therefore it should be called before starting 725 * any filesystem transaction to create the inode. For this reason, ->i_ino 726 * isn't required to be set yet, as the filesystem may not have set it yet. 727 * 728 * This doesn't persist the new inode's encryption context. That still needs to 729 * be done later by calling fscrypt_set_context(). 730 * 731 * Return: 0 on success, -ENOKEY if a key needs to be set up for @dir or @inode 732 * but the needed master key is absent, or another -errno code 733 */ 734 int fscrypt_prepare_new_inode(struct inode *dir, struct inode *inode, 735 bool *encrypt_ret) 736 { 737 const union fscrypt_policy *policy; 738 u8 nonce[FSCRYPT_FILE_NONCE_SIZE]; 739 740 policy = fscrypt_policy_to_inherit(dir); 741 if (policy == NULL) 742 return 0; 743 if (IS_ERR(policy)) 744 return PTR_ERR(policy); 745 746 if (WARN_ON_ONCE(inode->i_blkbits == 0)) 747 return -EINVAL; 748 749 if (WARN_ON_ONCE(inode->i_mode == 0)) 750 return -EINVAL; 751 752 /* 753 * Only regular files, directories, and symlinks are encrypted. 754 * Special files like device nodes and named pipes aren't. 755 */ 756 if (!S_ISREG(inode->i_mode) && 757 !S_ISDIR(inode->i_mode) && 758 !S_ISLNK(inode->i_mode)) 759 return 0; 760 761 *encrypt_ret = true; 762 763 get_random_bytes(nonce, FSCRYPT_FILE_NONCE_SIZE); 764 return fscrypt_setup_encryption_info(inode, policy, nonce, 765 IS_CASEFOLDED(dir) && 766 S_ISDIR(inode->i_mode)); 767 } 768 EXPORT_SYMBOL_GPL(fscrypt_prepare_new_inode); 769 770 /** 771 * fscrypt_put_encryption_info() - free most of an inode's fscrypt data 772 * @inode: an inode being evicted 773 * 774 * Free the inode's fscrypt_inode_info. Filesystems must call this when the 775 * inode is being evicted. An RCU grace period need not have elapsed yet. 776 */ 777 void fscrypt_put_encryption_info(struct inode *inode) 778 { 779 /* 780 * Ideally we'd start with a lightweight IS_ENCRYPTED() check here 781 * before proceeding to retrieve and check the pointer. However, during 782 * inode creation, the fscrypt_inode_info is set before S_ENCRYPTED. If 783 * an error occurs, it needs to be cleaned up regardless. 784 */ 785 struct fscrypt_inode_info **ci_addr = fscrypt_inode_info_addr(inode); 786 787 put_crypt_info(*ci_addr); 788 *ci_addr = NULL; 789 } 790 EXPORT_SYMBOL(fscrypt_put_encryption_info); 791 792 /** 793 * fscrypt_free_inode() - free an inode's fscrypt data requiring RCU delay 794 * @inode: an inode being freed 795 * 796 * Free the inode's cached decrypted symlink target, if any. Filesystems must 797 * call this after an RCU grace period, just before they free the inode. 798 */ 799 void fscrypt_free_inode(struct inode *inode) 800 { 801 if (IS_ENCRYPTED(inode) && S_ISLNK(inode->i_mode)) { 802 kfree(inode->i_link); 803 inode->i_link = NULL; 804 } 805 } 806 EXPORT_SYMBOL(fscrypt_free_inode); 807 808 /** 809 * fscrypt_drop_inode() - check whether the inode's master key has been removed 810 * @inode: an inode being considered for eviction 811 * 812 * Filesystems supporting fscrypt must call this from their ->drop_inode() 813 * method so that encrypted inodes are evicted as soon as they're no longer in 814 * use and their master key has been removed. 815 * 816 * Return: 1 if fscrypt wants the inode to be evicted now, otherwise 0 817 */ 818 int fscrypt_drop_inode(struct inode *inode) 819 { 820 const struct fscrypt_inode_info *ci = fscrypt_get_inode_info(inode); 821 822 /* 823 * If ci is NULL, then the inode doesn't have an encryption key set up 824 * so it's irrelevant. If ci_master_key is NULL, then the master key 825 * was provided via the legacy mechanism of the process-subscribed 826 * keyrings, so we don't know whether it's been removed or not. 827 */ 828 if (!ci || !ci->ci_master_key) 829 return 0; 830 831 /* 832 * With proper, non-racy use of FS_IOC_REMOVE_ENCRYPTION_KEY, all inodes 833 * protected by the key were cleaned by sync_filesystem(). But if 834 * userspace is still using the files, inodes can be dirtied between 835 * then and now. We mustn't lose any writes, so skip dirty inodes here. 836 */ 837 if (inode->i_state & I_DIRTY_ALL) 838 return 0; 839 840 /* 841 * We can't take ->mk_sem here, since this runs in atomic context. 842 * Therefore, ->mk_present can change concurrently, and our result may 843 * immediately become outdated. But there's no correctness problem with 844 * unnecessarily evicting. Nor is there a correctness problem with not 845 * evicting while iput() is racing with the key being removed, since 846 * then the thread removing the key will either evict the inode itself 847 * or will correctly detect that it wasn't evicted due to the race. 848 */ 849 return !READ_ONCE(ci->ci_master_key->mk_present); 850 } 851 EXPORT_SYMBOL_GPL(fscrypt_drop_inode); 852