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 err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, 257 hkdf_context, hkdf_info, hkdf_infolen, 258 mode_key, mode->keysize); 259 if (err) 260 goto out_unlock; 261 err = fscrypt_prepare_key(prep_key, mode_key, ci); 262 memzero_explicit(mode_key, mode->keysize); 263 if (err) 264 goto out_unlock; 265 done_unlock: 266 ci->ci_enc_key = *prep_key; 267 err = 0; 268 out_unlock: 269 mutex_unlock(&fscrypt_mode_key_setup_mutex); 270 return err; 271 } 272 273 /* 274 * Derive a SipHash key from the given fscrypt master key and the given 275 * application-specific information string. 276 * 277 * Note that the KDF produces a byte array, but the SipHash APIs expect the key 278 * as a pair of 64-bit words. Therefore, on big endian CPUs we have to do an 279 * endianness swap in order to get the same results as on little endian CPUs. 280 */ 281 static int fscrypt_derive_siphash_key(const struct fscrypt_master_key *mk, 282 u8 context, const u8 *info, 283 unsigned int infolen, siphash_key_t *key) 284 { 285 int err; 286 287 err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, context, info, infolen, 288 (u8 *)key, sizeof(*key)); 289 if (err) 290 return err; 291 292 BUILD_BUG_ON(sizeof(*key) != 16); 293 BUILD_BUG_ON(ARRAY_SIZE(key->key) != 2); 294 le64_to_cpus(&key->key[0]); 295 le64_to_cpus(&key->key[1]); 296 return 0; 297 } 298 299 int fscrypt_derive_dirhash_key(struct fscrypt_inode_info *ci, 300 const struct fscrypt_master_key *mk) 301 { 302 int err; 303 304 err = fscrypt_derive_siphash_key(mk, HKDF_CONTEXT_DIRHASH_KEY, 305 ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE, 306 &ci->ci_dirhash_key); 307 if (err) 308 return err; 309 ci->ci_dirhash_key_initialized = true; 310 return 0; 311 } 312 313 void fscrypt_hash_inode_number(struct fscrypt_inode_info *ci, 314 const struct fscrypt_master_key *mk) 315 { 316 WARN_ON_ONCE(ci->ci_inode->i_ino == 0); 317 WARN_ON_ONCE(!mk->mk_ino_hash_key_initialized); 318 319 ci->ci_hashed_ino = (u32)siphash_1u64(ci->ci_inode->i_ino, 320 &mk->mk_ino_hash_key); 321 } 322 323 static int fscrypt_setup_iv_ino_lblk_32_key(struct fscrypt_inode_info *ci, 324 struct fscrypt_master_key *mk) 325 { 326 int err; 327 328 err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_32_keys, 329 HKDF_CONTEXT_IV_INO_LBLK_32_KEY, true); 330 if (err) 331 return err; 332 333 /* pairs with smp_store_release() below */ 334 if (!smp_load_acquire(&mk->mk_ino_hash_key_initialized)) { 335 336 mutex_lock(&fscrypt_mode_key_setup_mutex); 337 338 if (mk->mk_ino_hash_key_initialized) 339 goto unlock; 340 341 err = fscrypt_derive_siphash_key(mk, 342 HKDF_CONTEXT_INODE_HASH_KEY, 343 NULL, 0, &mk->mk_ino_hash_key); 344 if (err) 345 goto unlock; 346 /* pairs with smp_load_acquire() above */ 347 smp_store_release(&mk->mk_ino_hash_key_initialized, true); 348 unlock: 349 mutex_unlock(&fscrypt_mode_key_setup_mutex); 350 if (err) 351 return err; 352 } 353 354 /* 355 * New inodes may not have an inode number assigned yet. 356 * Hashing their inode number is delayed until later. 357 */ 358 if (ci->ci_inode->i_ino) 359 fscrypt_hash_inode_number(ci, mk); 360 return 0; 361 } 362 363 static int fscrypt_setup_v2_file_key(struct fscrypt_inode_info *ci, 364 struct fscrypt_master_key *mk, 365 bool need_dirhash_key) 366 { 367 int err; 368 369 if (mk->mk_secret.is_hw_wrapped && 370 !(ci->ci_policy.v2.flags & (FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64 | 371 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32))) { 372 fscrypt_warn(ci->ci_inode, 373 "Hardware-wrapped keys are only supported with IV_INO_LBLK policies"); 374 return -EINVAL; 375 } 376 377 if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { 378 /* 379 * DIRECT_KEY: instead of deriving per-file encryption keys, the 380 * per-file nonce will be included in all the IVs. But unlike 381 * v1 policies, for v2 policies in this case we don't encrypt 382 * with the master key directly but rather derive a per-mode 383 * encryption key. This ensures that the master key is 384 * consistently used only for HKDF, avoiding key reuse issues. 385 */ 386 err = setup_per_mode_enc_key(ci, mk, mk->mk_direct_keys, 387 HKDF_CONTEXT_DIRECT_KEY, false); 388 } else if (ci->ci_policy.v2.flags & 389 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) { 390 /* 391 * IV_INO_LBLK_64: encryption keys are derived from (master_key, 392 * mode_num, filesystem_uuid), and inode number is included in 393 * the IVs. This format is optimized for use with inline 394 * encryption hardware compliant with the UFS standard. 395 */ 396 err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_64_keys, 397 HKDF_CONTEXT_IV_INO_LBLK_64_KEY, 398 true); 399 } else if (ci->ci_policy.v2.flags & 400 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) { 401 err = fscrypt_setup_iv_ino_lblk_32_key(ci, mk); 402 } else { 403 u8 derived_key[FSCRYPT_MAX_RAW_KEY_SIZE]; 404 405 err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, 406 HKDF_CONTEXT_PER_FILE_ENC_KEY, 407 ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE, 408 derived_key, ci->ci_mode->keysize); 409 if (err) 410 return err; 411 412 err = fscrypt_set_per_file_enc_key(ci, derived_key); 413 memzero_explicit(derived_key, ci->ci_mode->keysize); 414 } 415 if (err) 416 return err; 417 418 /* Derive a secret dirhash key for directories that need it. */ 419 if (need_dirhash_key) { 420 err = fscrypt_derive_dirhash_key(ci, mk); 421 if (err) 422 return err; 423 } 424 425 return 0; 426 } 427 428 /* 429 * Check whether the size of the given master key (@mk) is appropriate for the 430 * encryption settings which a particular file will use (@ci). 431 * 432 * If the file uses a v1 encryption policy, then the master key must be at least 433 * as long as the derived key, as this is a requirement of the v1 KDF. 434 * 435 * Otherwise, the KDF can accept any size key, so we enforce a slightly looser 436 * requirement: we require that the size of the master key be at least the 437 * maximum security strength of any algorithm whose key will be derived from it 438 * (but in practice we only need to consider @ci->ci_mode, since any other 439 * possible subkeys such as DIRHASH and INODE_HASH will never increase the 440 * required key size over @ci->ci_mode). This allows AES-256-XTS keys to be 441 * derived from a 256-bit master key, which is cryptographically sufficient, 442 * rather than requiring a 512-bit master key which is unnecessarily long. (We 443 * still allow 512-bit master keys if the user chooses to use them, though.) 444 */ 445 static bool fscrypt_valid_master_key_size(const struct fscrypt_master_key *mk, 446 const struct fscrypt_inode_info *ci) 447 { 448 unsigned int min_keysize; 449 450 if (ci->ci_policy.version == FSCRYPT_POLICY_V1) 451 min_keysize = ci->ci_mode->keysize; 452 else 453 min_keysize = ci->ci_mode->security_strength; 454 455 if (mk->mk_secret.size < min_keysize) { 456 fscrypt_warn(NULL, 457 "key with %s %*phN is too short (got %u bytes, need %u+ bytes)", 458 master_key_spec_type(&mk->mk_spec), 459 master_key_spec_len(&mk->mk_spec), 460 (u8 *)&mk->mk_spec.u, 461 mk->mk_secret.size, min_keysize); 462 return false; 463 } 464 return true; 465 } 466 467 /* 468 * Find the master key, then set up the inode's actual encryption key. 469 * 470 * If the master key is found in the filesystem-level keyring, then it is 471 * returned in *mk_ret with its semaphore read-locked. This is needed to ensure 472 * that only one task links the fscrypt_inode_info into ->mk_decrypted_inodes 473 * (as multiple tasks may race to create an fscrypt_inode_info for the same 474 * inode), and to synchronize the master key being removed with a new inode 475 * starting to use it. 476 */ 477 static int setup_file_encryption_key(struct fscrypt_inode_info *ci, 478 bool need_dirhash_key, 479 struct fscrypt_master_key **mk_ret) 480 { 481 struct super_block *sb = ci->ci_inode->i_sb; 482 struct fscrypt_key_specifier mk_spec; 483 struct fscrypt_master_key *mk; 484 int err; 485 486 err = fscrypt_policy_to_key_spec(&ci->ci_policy, &mk_spec); 487 if (err) 488 return err; 489 490 mk = fscrypt_find_master_key(sb, &mk_spec); 491 if (unlikely(!mk)) { 492 const union fscrypt_policy *dummy_policy = 493 fscrypt_get_dummy_policy(sb); 494 495 /* 496 * Add the test_dummy_encryption key on-demand. In principle, 497 * it should be added at mount time. Do it here instead so that 498 * the individual filesystems don't need to worry about adding 499 * this key at mount time and cleaning up on mount failure. 500 */ 501 if (dummy_policy && 502 fscrypt_policies_equal(dummy_policy, &ci->ci_policy)) { 503 err = fscrypt_add_test_dummy_key(sb, &mk_spec); 504 if (err) 505 return err; 506 mk = fscrypt_find_master_key(sb, &mk_spec); 507 } 508 } 509 if (unlikely(!mk)) { 510 if (ci->ci_policy.version != FSCRYPT_POLICY_V1) 511 return -ENOKEY; 512 513 err = fscrypt_select_encryption_impl(ci, false); 514 if (err) 515 return err; 516 517 /* 518 * As a legacy fallback for v1 policies, search for the key in 519 * the current task's subscribed keyrings too. Don't move this 520 * to before the search of ->s_master_keys, since users 521 * shouldn't be able to override filesystem-level keys. 522 */ 523 return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci); 524 } 525 down_read(&mk->mk_sem); 526 527 if (!mk->mk_present) { 528 /* FS_IOC_REMOVE_ENCRYPTION_KEY has been executed on this key */ 529 err = -ENOKEY; 530 goto out_release_key; 531 } 532 533 if (!fscrypt_valid_master_key_size(mk, ci)) { 534 err = -ENOKEY; 535 goto out_release_key; 536 } 537 538 err = fscrypt_select_encryption_impl(ci, mk->mk_secret.is_hw_wrapped); 539 if (err) 540 goto out_release_key; 541 542 switch (ci->ci_policy.version) { 543 case FSCRYPT_POLICY_V1: 544 if (WARN_ON_ONCE(mk->mk_secret.is_hw_wrapped)) { 545 /* 546 * This should never happen, as adding a v1 policy key 547 * that is hardware-wrapped isn't allowed. 548 */ 549 err = -EINVAL; 550 goto out_release_key; 551 } 552 err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.bytes); 553 break; 554 case FSCRYPT_POLICY_V2: 555 err = fscrypt_setup_v2_file_key(ci, mk, need_dirhash_key); 556 break; 557 default: 558 WARN_ON_ONCE(1); 559 err = -EINVAL; 560 break; 561 } 562 if (err) 563 goto out_release_key; 564 565 *mk_ret = mk; 566 return 0; 567 568 out_release_key: 569 up_read(&mk->mk_sem); 570 fscrypt_put_master_key(mk); 571 return err; 572 } 573 574 static void put_crypt_info(struct fscrypt_inode_info *ci) 575 { 576 struct fscrypt_master_key *mk; 577 578 if (!ci) 579 return; 580 581 if (ci->ci_direct_key) 582 fscrypt_put_direct_key(ci->ci_direct_key); 583 else if (ci->ci_owns_key) 584 fscrypt_destroy_prepared_key(ci->ci_inode->i_sb, 585 &ci->ci_enc_key); 586 587 mk = ci->ci_master_key; 588 if (mk) { 589 /* 590 * Remove this inode from the list of inodes that were unlocked 591 * with the master key. In addition, if we're removing the last 592 * inode from an incompletely removed key, then complete the 593 * full removal of the key. 594 */ 595 spin_lock(&mk->mk_decrypted_inodes_lock); 596 list_del(&ci->ci_master_key_link); 597 spin_unlock(&mk->mk_decrypted_inodes_lock); 598 fscrypt_put_master_key_activeref(ci->ci_inode->i_sb, mk); 599 } 600 memzero_explicit(ci, sizeof(*ci)); 601 kmem_cache_free(fscrypt_inode_info_cachep, ci); 602 } 603 604 static int 605 fscrypt_setup_encryption_info(struct inode *inode, 606 const union fscrypt_policy *policy, 607 const u8 nonce[FSCRYPT_FILE_NONCE_SIZE], 608 bool need_dirhash_key) 609 { 610 struct fscrypt_inode_info *crypt_info; 611 struct fscrypt_mode *mode; 612 struct fscrypt_master_key *mk = NULL; 613 int res; 614 615 res = fscrypt_initialize(inode->i_sb); 616 if (res) 617 return res; 618 619 crypt_info = kmem_cache_zalloc(fscrypt_inode_info_cachep, GFP_KERNEL); 620 if (!crypt_info) 621 return -ENOMEM; 622 623 crypt_info->ci_inode = inode; 624 crypt_info->ci_policy = *policy; 625 memcpy(crypt_info->ci_nonce, nonce, FSCRYPT_FILE_NONCE_SIZE); 626 627 mode = select_encryption_mode(&crypt_info->ci_policy, inode); 628 if (IS_ERR(mode)) { 629 res = PTR_ERR(mode); 630 goto out; 631 } 632 WARN_ON_ONCE(mode->ivsize > FSCRYPT_MAX_IV_SIZE); 633 crypt_info->ci_mode = mode; 634 635 crypt_info->ci_data_unit_bits = 636 fscrypt_policy_du_bits(&crypt_info->ci_policy, inode); 637 crypt_info->ci_data_units_per_block_bits = 638 inode->i_blkbits - crypt_info->ci_data_unit_bits; 639 640 res = setup_file_encryption_key(crypt_info, need_dirhash_key, &mk); 641 if (res) 642 goto out; 643 644 /* 645 * For existing inodes, multiple tasks may race to set ->i_crypt_info. 646 * So use cmpxchg_release(). This pairs with the smp_load_acquire() in 647 * fscrypt_get_inode_info(). I.e., here we publish ->i_crypt_info with 648 * a RELEASE barrier so that other tasks can ACQUIRE it. 649 */ 650 if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL) { 651 /* 652 * We won the race and set ->i_crypt_info to our crypt_info. 653 * Now link it into the master key's inode list. 654 */ 655 if (mk) { 656 crypt_info->ci_master_key = mk; 657 refcount_inc(&mk->mk_active_refs); 658 spin_lock(&mk->mk_decrypted_inodes_lock); 659 list_add(&crypt_info->ci_master_key_link, 660 &mk->mk_decrypted_inodes); 661 spin_unlock(&mk->mk_decrypted_inodes_lock); 662 } 663 crypt_info = NULL; 664 } 665 res = 0; 666 out: 667 if (mk) { 668 up_read(&mk->mk_sem); 669 fscrypt_put_master_key(mk); 670 } 671 put_crypt_info(crypt_info); 672 return res; 673 } 674 675 /** 676 * fscrypt_get_encryption_info() - set up an inode's encryption key 677 * @inode: the inode to set up the key for. Must be encrypted. 678 * @allow_unsupported: if %true, treat an unsupported encryption policy (or 679 * unrecognized encryption context) the same way as the key 680 * being unavailable, instead of returning an error. Use 681 * %false unless the operation being performed is needed in 682 * order for files (or directories) to be deleted. 683 * 684 * Set up ->i_crypt_info, if it hasn't already been done. 685 * 686 * Note: unless ->i_crypt_info is already set, this isn't %GFP_NOFS-safe. So 687 * generally this shouldn't be called from within a filesystem transaction. 688 * 689 * Return: 0 if ->i_crypt_info was set or was already set, *or* if the 690 * encryption key is unavailable. (Use fscrypt_has_encryption_key() to 691 * distinguish these cases.) Also can return another -errno code. 692 */ 693 int fscrypt_get_encryption_info(struct inode *inode, bool allow_unsupported) 694 { 695 int res; 696 union fscrypt_context ctx; 697 union fscrypt_policy policy; 698 699 if (fscrypt_has_encryption_key(inode)) 700 return 0; 701 702 res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); 703 if (res < 0) { 704 if (res == -ERANGE && allow_unsupported) 705 return 0; 706 fscrypt_warn(inode, "Error %d getting encryption context", res); 707 return res; 708 } 709 710 res = fscrypt_policy_from_context(&policy, &ctx, res); 711 if (res) { 712 if (allow_unsupported) 713 return 0; 714 fscrypt_warn(inode, 715 "Unrecognized or corrupt encryption context"); 716 return res; 717 } 718 719 if (!fscrypt_supported_policy(&policy, inode)) { 720 if (allow_unsupported) 721 return 0; 722 return -EINVAL; 723 } 724 725 res = fscrypt_setup_encryption_info(inode, &policy, 726 fscrypt_context_nonce(&ctx), 727 IS_CASEFOLDED(inode) && 728 S_ISDIR(inode->i_mode)); 729 730 if (res == -ENOPKG && allow_unsupported) /* Algorithm unavailable? */ 731 res = 0; 732 if (res == -ENOKEY) 733 res = 0; 734 return res; 735 } 736 737 /** 738 * fscrypt_prepare_new_inode() - prepare to create a new inode in a directory 739 * @dir: a possibly-encrypted directory 740 * @inode: the new inode. ->i_mode and ->i_blkbits must be set already. 741 * ->i_ino doesn't need to be set yet. 742 * @encrypt_ret: (output) set to %true if the new inode will be encrypted 743 * 744 * If the directory is encrypted, set up its ->i_crypt_info in preparation for 745 * encrypting the name of the new file. Also, if the new inode will be 746 * encrypted, set up its ->i_crypt_info and set *encrypt_ret=true. 747 * 748 * This isn't %GFP_NOFS-safe, and therefore it should be called before starting 749 * any filesystem transaction to create the inode. For this reason, ->i_ino 750 * isn't required to be set yet, as the filesystem may not have set it yet. 751 * 752 * This doesn't persist the new inode's encryption context. That still needs to 753 * be done later by calling fscrypt_set_context(). 754 * 755 * Return: 0 on success, -ENOKEY if the encryption key is missing, or another 756 * -errno code 757 */ 758 int fscrypt_prepare_new_inode(struct inode *dir, struct inode *inode, 759 bool *encrypt_ret) 760 { 761 const union fscrypt_policy *policy; 762 u8 nonce[FSCRYPT_FILE_NONCE_SIZE]; 763 764 policy = fscrypt_policy_to_inherit(dir); 765 if (policy == NULL) 766 return 0; 767 if (IS_ERR(policy)) 768 return PTR_ERR(policy); 769 770 if (WARN_ON_ONCE(inode->i_blkbits == 0)) 771 return -EINVAL; 772 773 if (WARN_ON_ONCE(inode->i_mode == 0)) 774 return -EINVAL; 775 776 /* 777 * Only regular files, directories, and symlinks are encrypted. 778 * Special files like device nodes and named pipes aren't. 779 */ 780 if (!S_ISREG(inode->i_mode) && 781 !S_ISDIR(inode->i_mode) && 782 !S_ISLNK(inode->i_mode)) 783 return 0; 784 785 *encrypt_ret = true; 786 787 get_random_bytes(nonce, FSCRYPT_FILE_NONCE_SIZE); 788 return fscrypt_setup_encryption_info(inode, policy, nonce, 789 IS_CASEFOLDED(dir) && 790 S_ISDIR(inode->i_mode)); 791 } 792 EXPORT_SYMBOL_GPL(fscrypt_prepare_new_inode); 793 794 /** 795 * fscrypt_put_encryption_info() - free most of an inode's fscrypt data 796 * @inode: an inode being evicted 797 * 798 * Free the inode's fscrypt_inode_info. Filesystems must call this when the 799 * inode is being evicted. An RCU grace period need not have elapsed yet. 800 */ 801 void fscrypt_put_encryption_info(struct inode *inode) 802 { 803 put_crypt_info(inode->i_crypt_info); 804 inode->i_crypt_info = NULL; 805 } 806 EXPORT_SYMBOL(fscrypt_put_encryption_info); 807 808 /** 809 * fscrypt_free_inode() - free an inode's fscrypt data requiring RCU delay 810 * @inode: an inode being freed 811 * 812 * Free the inode's cached decrypted symlink target, if any. Filesystems must 813 * call this after an RCU grace period, just before they free the inode. 814 */ 815 void fscrypt_free_inode(struct inode *inode) 816 { 817 if (IS_ENCRYPTED(inode) && S_ISLNK(inode->i_mode)) { 818 kfree(inode->i_link); 819 inode->i_link = NULL; 820 } 821 } 822 EXPORT_SYMBOL(fscrypt_free_inode); 823 824 /** 825 * fscrypt_drop_inode() - check whether the inode's master key has been removed 826 * @inode: an inode being considered for eviction 827 * 828 * Filesystems supporting fscrypt must call this from their ->drop_inode() 829 * method so that encrypted inodes are evicted as soon as they're no longer in 830 * use and their master key has been removed. 831 * 832 * Return: 1 if fscrypt wants the inode to be evicted now, otherwise 0 833 */ 834 int fscrypt_drop_inode(struct inode *inode) 835 { 836 const struct fscrypt_inode_info *ci = fscrypt_get_inode_info(inode); 837 838 /* 839 * If ci is NULL, then the inode doesn't have an encryption key set up 840 * so it's irrelevant. If ci_master_key is NULL, then the master key 841 * was provided via the legacy mechanism of the process-subscribed 842 * keyrings, so we don't know whether it's been removed or not. 843 */ 844 if (!ci || !ci->ci_master_key) 845 return 0; 846 847 /* 848 * With proper, non-racy use of FS_IOC_REMOVE_ENCRYPTION_KEY, all inodes 849 * protected by the key were cleaned by sync_filesystem(). But if 850 * userspace is still using the files, inodes can be dirtied between 851 * then and now. We mustn't lose any writes, so skip dirty inodes here. 852 */ 853 if (inode->i_state & I_DIRTY_ALL) 854 return 0; 855 856 /* 857 * We can't take ->mk_sem here, since this runs in atomic context. 858 * Therefore, ->mk_present can change concurrently, and our result may 859 * immediately become outdated. But there's no correctness problem with 860 * unnecessarily evicting. Nor is there a correctness problem with not 861 * evicting while iput() is racing with the key being removed, since 862 * then the thread removing the key will either evict the inode itself 863 * or will correctly detect that it wasn't evicted due to the race. 864 */ 865 return !READ_ONCE(ci->ci_master_key->mk_present); 866 } 867 EXPORT_SYMBOL_GPL(fscrypt_drop_inode); 868