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-CBC-CTS", 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-CBC-CTS", 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-CBC-CTS", 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_ONCE(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_inode_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, 157 ci->ci_mode->keysize, 158 false, ci); 159 160 tfm = fscrypt_allocate_skcipher(ci->ci_mode, raw_key, ci->ci_inode); 161 if (IS_ERR(tfm)) 162 return PTR_ERR(tfm); 163 /* 164 * Pairs with the smp_load_acquire() in fscrypt_is_key_prepared(). 165 * I.e., here we publish ->tfm with a RELEASE barrier so that 166 * concurrent tasks can ACQUIRE it. Note that this concurrency is only 167 * possible for per-mode keys, not for per-file keys. 168 */ 169 smp_store_release(&prep_key->tfm, tfm); 170 return 0; 171 } 172 173 /* Destroy a crypto transform object and/or blk-crypto key. */ 174 void fscrypt_destroy_prepared_key(struct super_block *sb, 175 struct fscrypt_prepared_key *prep_key) 176 { 177 crypto_free_skcipher(prep_key->tfm); 178 fscrypt_destroy_inline_crypt_key(sb, prep_key); 179 memzero_explicit(prep_key, sizeof(*prep_key)); 180 } 181 182 /* Given a per-file encryption key, set up the file's crypto transform object */ 183 int fscrypt_set_per_file_enc_key(struct fscrypt_inode_info *ci, 184 const u8 *raw_key) 185 { 186 ci->ci_owns_key = true; 187 return fscrypt_prepare_key(&ci->ci_enc_key, raw_key, ci); 188 } 189 190 static int setup_per_mode_enc_key(struct fscrypt_inode_info *ci, 191 struct fscrypt_master_key *mk, 192 struct fscrypt_prepared_key *keys, 193 u8 hkdf_context, bool include_fs_uuid) 194 { 195 const struct inode *inode = ci->ci_inode; 196 const struct super_block *sb = inode->i_sb; 197 struct fscrypt_mode *mode = ci->ci_mode; 198 const u8 mode_num = mode - fscrypt_modes; 199 struct fscrypt_prepared_key *prep_key; 200 u8 mode_key[FSCRYPT_MAX_RAW_KEY_SIZE]; 201 u8 hkdf_info[sizeof(mode_num) + sizeof(sb->s_uuid)]; 202 unsigned int hkdf_infolen = 0; 203 bool use_hw_wrapped_key = false; 204 int err; 205 206 if (WARN_ON_ONCE(mode_num > FSCRYPT_MODE_MAX)) 207 return -EINVAL; 208 209 if (mk->mk_secret.is_hw_wrapped && S_ISREG(inode->i_mode)) { 210 /* Using a hardware-wrapped key for file contents encryption */ 211 if (!fscrypt_using_inline_encryption(ci)) { 212 if (sb->s_flags & SB_INLINECRYPT) 213 fscrypt_warn(ci->ci_inode, 214 "Hardware-wrapped key required, but no suitable inline encryption capabilities are available"); 215 else 216 fscrypt_warn(ci->ci_inode, 217 "Hardware-wrapped keys require inline encryption (-o inlinecrypt)"); 218 return -EINVAL; 219 } 220 use_hw_wrapped_key = true; 221 } 222 223 prep_key = &keys[mode_num]; 224 if (fscrypt_is_key_prepared(prep_key, ci)) { 225 ci->ci_enc_key = *prep_key; 226 return 0; 227 } 228 229 mutex_lock(&fscrypt_mode_key_setup_mutex); 230 231 if (fscrypt_is_key_prepared(prep_key, ci)) 232 goto done_unlock; 233 234 if (use_hw_wrapped_key) { 235 err = fscrypt_prepare_inline_crypt_key(prep_key, 236 mk->mk_secret.bytes, 237 mk->mk_secret.size, true, 238 ci); 239 if (err) 240 goto out_unlock; 241 goto done_unlock; 242 } 243 244 BUILD_BUG_ON(sizeof(mode_num) != 1); 245 BUILD_BUG_ON(sizeof(sb->s_uuid) != 16); 246 BUILD_BUG_ON(sizeof(hkdf_info) != 17); 247 hkdf_info[hkdf_infolen++] = mode_num; 248 if (include_fs_uuid) { 249 memcpy(&hkdf_info[hkdf_infolen], &sb->s_uuid, 250 sizeof(sb->s_uuid)); 251 hkdf_infolen += sizeof(sb->s_uuid); 252 } 253 err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, 254 hkdf_context, hkdf_info, hkdf_infolen, 255 mode_key, mode->keysize); 256 if (err) 257 goto out_unlock; 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 int 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 int err; 283 284 err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, context, info, infolen, 285 (u8 *)key, sizeof(*key)); 286 if (err) 287 return err; 288 289 BUILD_BUG_ON(sizeof(*key) != 16); 290 BUILD_BUG_ON(ARRAY_SIZE(key->key) != 2); 291 le64_to_cpus(&key->key[0]); 292 le64_to_cpus(&key->key[1]); 293 return 0; 294 } 295 296 int fscrypt_derive_dirhash_key(struct fscrypt_inode_info *ci, 297 const struct fscrypt_master_key *mk) 298 { 299 int err; 300 301 err = fscrypt_derive_siphash_key(mk, HKDF_CONTEXT_DIRHASH_KEY, 302 ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE, 303 &ci->ci_dirhash_key); 304 if (err) 305 return err; 306 ci->ci_dirhash_key_initialized = true; 307 return 0; 308 } 309 310 void fscrypt_hash_inode_number(struct fscrypt_inode_info *ci, 311 const struct fscrypt_master_key *mk) 312 { 313 WARN_ON_ONCE(ci->ci_inode->i_ino == 0); 314 WARN_ON_ONCE(!mk->mk_ino_hash_key_initialized); 315 316 ci->ci_hashed_ino = (u32)siphash_1u64(ci->ci_inode->i_ino, 317 &mk->mk_ino_hash_key); 318 } 319 320 static int fscrypt_setup_iv_ino_lblk_32_key(struct fscrypt_inode_info *ci, 321 struct fscrypt_master_key *mk) 322 { 323 int err; 324 325 err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_32_keys, 326 HKDF_CONTEXT_IV_INO_LBLK_32_KEY, true); 327 if (err) 328 return err; 329 330 /* pairs with smp_store_release() below */ 331 if (!smp_load_acquire(&mk->mk_ino_hash_key_initialized)) { 332 333 mutex_lock(&fscrypt_mode_key_setup_mutex); 334 335 if (mk->mk_ino_hash_key_initialized) 336 goto unlock; 337 338 err = fscrypt_derive_siphash_key(mk, 339 HKDF_CONTEXT_INODE_HASH_KEY, 340 NULL, 0, &mk->mk_ino_hash_key); 341 if (err) 342 goto unlock; 343 /* pairs with smp_load_acquire() above */ 344 smp_store_release(&mk->mk_ino_hash_key_initialized, true); 345 unlock: 346 mutex_unlock(&fscrypt_mode_key_setup_mutex); 347 if (err) 348 return err; 349 } 350 351 /* 352 * New inodes may not have an inode number assigned yet. 353 * Hashing their inode number is delayed until later. 354 */ 355 if (ci->ci_inode->i_ino) 356 fscrypt_hash_inode_number(ci, mk); 357 return 0; 358 } 359 360 static int fscrypt_setup_v2_file_key(struct fscrypt_inode_info *ci, 361 struct fscrypt_master_key *mk, 362 bool need_dirhash_key) 363 { 364 int err; 365 366 if (mk->mk_secret.is_hw_wrapped && 367 !(ci->ci_policy.v2.flags & (FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64 | 368 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32))) { 369 fscrypt_warn(ci->ci_inode, 370 "Hardware-wrapped keys are only supported with IV_INO_LBLK policies"); 371 return -EINVAL; 372 } 373 374 if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { 375 /* 376 * DIRECT_KEY: instead of deriving per-file encryption keys, the 377 * per-file nonce will be included in all the IVs. But unlike 378 * v1 policies, for v2 policies in this case we don't encrypt 379 * with the master key directly but rather derive a per-mode 380 * encryption key. This ensures that the master key is 381 * consistently used only for HKDF, avoiding key reuse issues. 382 */ 383 err = setup_per_mode_enc_key(ci, mk, mk->mk_direct_keys, 384 HKDF_CONTEXT_DIRECT_KEY, false); 385 } else if (ci->ci_policy.v2.flags & 386 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) { 387 /* 388 * IV_INO_LBLK_64: encryption keys are derived from (master_key, 389 * mode_num, filesystem_uuid), and inode number is included in 390 * the IVs. This format is optimized for use with inline 391 * encryption hardware compliant with the UFS standard. 392 */ 393 err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_64_keys, 394 HKDF_CONTEXT_IV_INO_LBLK_64_KEY, 395 true); 396 } else if (ci->ci_policy.v2.flags & 397 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) { 398 err = fscrypt_setup_iv_ino_lblk_32_key(ci, mk); 399 } else { 400 u8 derived_key[FSCRYPT_MAX_RAW_KEY_SIZE]; 401 402 err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, 403 HKDF_CONTEXT_PER_FILE_ENC_KEY, 404 ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE, 405 derived_key, ci->ci_mode->keysize); 406 if (err) 407 return err; 408 409 err = fscrypt_set_per_file_enc_key(ci, derived_key); 410 memzero_explicit(derived_key, ci->ci_mode->keysize); 411 } 412 if (err) 413 return err; 414 415 /* Derive a secret dirhash key for directories that need it. */ 416 if (need_dirhash_key) { 417 err = fscrypt_derive_dirhash_key(ci, mk); 418 if (err) 419 return err; 420 } 421 422 return 0; 423 } 424 425 /* 426 * Check whether the size of the given master key (@mk) is appropriate for the 427 * encryption settings which a particular file will use (@ci). 428 * 429 * If the file uses a v1 encryption policy, then the master key must be at least 430 * as long as the derived key, as this is a requirement of the v1 KDF. 431 * 432 * Otherwise, the KDF can accept any size key, so we enforce a slightly looser 433 * requirement: we require that the size of the master key be at least the 434 * maximum security strength of any algorithm whose key will be derived from it 435 * (but in practice we only need to consider @ci->ci_mode, since any other 436 * possible subkeys such as DIRHASH and INODE_HASH will never increase the 437 * required key size over @ci->ci_mode). This allows AES-256-XTS keys to be 438 * derived from a 256-bit master key, which is cryptographically sufficient, 439 * rather than requiring a 512-bit master key which is unnecessarily long. (We 440 * still allow 512-bit master keys if the user chooses to use them, though.) 441 */ 442 static bool fscrypt_valid_master_key_size(const struct fscrypt_master_key *mk, 443 const struct fscrypt_inode_info *ci) 444 { 445 unsigned int min_keysize; 446 447 if (ci->ci_policy.version == FSCRYPT_POLICY_V1) 448 min_keysize = ci->ci_mode->keysize; 449 else 450 min_keysize = ci->ci_mode->security_strength; 451 452 if (mk->mk_secret.size < min_keysize) { 453 fscrypt_warn(NULL, 454 "key with %s %*phN is too short (got %u bytes, need %u+ bytes)", 455 master_key_spec_type(&mk->mk_spec), 456 master_key_spec_len(&mk->mk_spec), 457 (u8 *)&mk->mk_spec.u, 458 mk->mk_secret.size, min_keysize); 459 return false; 460 } 461 return true; 462 } 463 464 /* 465 * Find the master key, then set up the inode's actual encryption key. 466 * 467 * If the master key is found in the filesystem-level keyring, then it is 468 * returned in *mk_ret with its semaphore read-locked. This is needed to ensure 469 * that only one task links the fscrypt_inode_info into ->mk_decrypted_inodes 470 * (as multiple tasks may race to create an fscrypt_inode_info for the same 471 * inode), and to synchronize the master key being removed with a new inode 472 * starting to use it. 473 */ 474 static int setup_file_encryption_key(struct fscrypt_inode_info *ci, 475 bool need_dirhash_key, 476 struct fscrypt_master_key **mk_ret) 477 { 478 struct super_block *sb = ci->ci_inode->i_sb; 479 struct fscrypt_key_specifier mk_spec; 480 struct fscrypt_master_key *mk; 481 int err; 482 483 err = fscrypt_policy_to_key_spec(&ci->ci_policy, &mk_spec); 484 if (err) 485 return err; 486 487 mk = fscrypt_find_master_key(sb, &mk_spec); 488 if (unlikely(!mk)) { 489 const union fscrypt_policy *dummy_policy = 490 fscrypt_get_dummy_policy(sb); 491 492 /* 493 * Add the test_dummy_encryption key on-demand. In principle, 494 * it should be added at mount time. Do it here instead so that 495 * the individual filesystems don't need to worry about adding 496 * this key at mount time and cleaning up on mount failure. 497 */ 498 if (dummy_policy && 499 fscrypt_policies_equal(dummy_policy, &ci->ci_policy)) { 500 err = fscrypt_add_test_dummy_key(sb, &mk_spec); 501 if (err) 502 return err; 503 mk = fscrypt_find_master_key(sb, &mk_spec); 504 } 505 } 506 if (unlikely(!mk)) { 507 if (ci->ci_policy.version != FSCRYPT_POLICY_V1) 508 return -ENOKEY; 509 510 err = fscrypt_select_encryption_impl(ci, false); 511 if (err) 512 return err; 513 514 /* 515 * As a legacy fallback for v1 policies, search for the key in 516 * the current task's subscribed keyrings too. Don't move this 517 * to before the search of ->s_master_keys, since users 518 * shouldn't be able to override filesystem-level keys. 519 */ 520 return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci); 521 } 522 down_read(&mk->mk_sem); 523 524 if (!mk->mk_present) { 525 /* FS_IOC_REMOVE_ENCRYPTION_KEY has been executed on this key */ 526 err = -ENOKEY; 527 goto out_release_key; 528 } 529 530 if (!fscrypt_valid_master_key_size(mk, ci)) { 531 err = -ENOKEY; 532 goto out_release_key; 533 } 534 535 err = fscrypt_select_encryption_impl(ci, mk->mk_secret.is_hw_wrapped); 536 if (err) 537 goto out_release_key; 538 539 switch (ci->ci_policy.version) { 540 case FSCRYPT_POLICY_V1: 541 if (WARN_ON_ONCE(mk->mk_secret.is_hw_wrapped)) { 542 /* 543 * This should never happen, as adding a v1 policy key 544 * that is hardware-wrapped isn't allowed. 545 */ 546 err = -EINVAL; 547 goto out_release_key; 548 } 549 err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.bytes); 550 break; 551 case FSCRYPT_POLICY_V2: 552 err = fscrypt_setup_v2_file_key(ci, mk, need_dirhash_key); 553 break; 554 default: 555 WARN_ON_ONCE(1); 556 err = -EINVAL; 557 break; 558 } 559 if (err) 560 goto out_release_key; 561 562 *mk_ret = mk; 563 return 0; 564 565 out_release_key: 566 up_read(&mk->mk_sem); 567 fscrypt_put_master_key(mk); 568 return err; 569 } 570 571 static void put_crypt_info(struct fscrypt_inode_info *ci) 572 { 573 struct fscrypt_master_key *mk; 574 575 if (!ci) 576 return; 577 578 if (ci->ci_direct_key) 579 fscrypt_put_direct_key(ci->ci_direct_key); 580 else if (ci->ci_owns_key) 581 fscrypt_destroy_prepared_key(ci->ci_inode->i_sb, 582 &ci->ci_enc_key); 583 584 mk = ci->ci_master_key; 585 if (mk) { 586 /* 587 * Remove this inode from the list of inodes that were unlocked 588 * with the master key. In addition, if we're removing the last 589 * inode from an incompletely removed key, then complete the 590 * full removal of the key. 591 */ 592 spin_lock(&mk->mk_decrypted_inodes_lock); 593 list_del(&ci->ci_master_key_link); 594 spin_unlock(&mk->mk_decrypted_inodes_lock); 595 fscrypt_put_master_key_activeref(ci->ci_inode->i_sb, mk); 596 } 597 memzero_explicit(ci, sizeof(*ci)); 598 kmem_cache_free(fscrypt_inode_info_cachep, ci); 599 } 600 601 static int 602 fscrypt_setup_encryption_info(struct inode *inode, 603 const union fscrypt_policy *policy, 604 const u8 nonce[FSCRYPT_FILE_NONCE_SIZE], 605 bool need_dirhash_key) 606 { 607 struct fscrypt_inode_info *crypt_info; 608 struct fscrypt_mode *mode; 609 struct fscrypt_master_key *mk = NULL; 610 int res; 611 612 res = fscrypt_initialize(inode->i_sb); 613 if (res) 614 return res; 615 616 crypt_info = kmem_cache_zalloc(fscrypt_inode_info_cachep, GFP_KERNEL); 617 if (!crypt_info) 618 return -ENOMEM; 619 620 crypt_info->ci_inode = inode; 621 crypt_info->ci_policy = *policy; 622 memcpy(crypt_info->ci_nonce, nonce, FSCRYPT_FILE_NONCE_SIZE); 623 624 mode = select_encryption_mode(&crypt_info->ci_policy, inode); 625 if (IS_ERR(mode)) { 626 res = PTR_ERR(mode); 627 goto out; 628 } 629 WARN_ON_ONCE(mode->ivsize > FSCRYPT_MAX_IV_SIZE); 630 crypt_info->ci_mode = mode; 631 632 crypt_info->ci_data_unit_bits = 633 fscrypt_policy_du_bits(&crypt_info->ci_policy, inode); 634 crypt_info->ci_data_units_per_block_bits = 635 inode->i_blkbits - crypt_info->ci_data_unit_bits; 636 637 res = setup_file_encryption_key(crypt_info, need_dirhash_key, &mk); 638 if (res) 639 goto out; 640 641 /* 642 * For existing inodes, multiple tasks may race to set ->i_crypt_info. 643 * So use cmpxchg_release(). This pairs with the smp_load_acquire() in 644 * fscrypt_get_inode_info(). I.e., here we publish ->i_crypt_info with 645 * a RELEASE barrier so that other tasks can ACQUIRE it. 646 */ 647 if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL) { 648 /* 649 * We won the race and set ->i_crypt_info to our crypt_info. 650 * Now link it into the master key's inode list. 651 */ 652 if (mk) { 653 crypt_info->ci_master_key = mk; 654 refcount_inc(&mk->mk_active_refs); 655 spin_lock(&mk->mk_decrypted_inodes_lock); 656 list_add(&crypt_info->ci_master_key_link, 657 &mk->mk_decrypted_inodes); 658 spin_unlock(&mk->mk_decrypted_inodes_lock); 659 } 660 crypt_info = NULL; 661 } 662 res = 0; 663 out: 664 if (mk) { 665 up_read(&mk->mk_sem); 666 fscrypt_put_master_key(mk); 667 } 668 put_crypt_info(crypt_info); 669 return res; 670 } 671 672 /** 673 * fscrypt_get_encryption_info() - set up an inode's encryption key 674 * @inode: the inode to set up the key for. Must be encrypted. 675 * @allow_unsupported: if %true, treat an unsupported encryption policy (or 676 * unrecognized encryption context) the same way as the key 677 * being unavailable, instead of returning an error. Use 678 * %false unless the operation being performed is needed in 679 * order for files (or directories) to be deleted. 680 * 681 * Set up ->i_crypt_info, if it hasn't already been done. 682 * 683 * Note: unless ->i_crypt_info is already set, this isn't %GFP_NOFS-safe. So 684 * generally this shouldn't be called from within a filesystem transaction. 685 * 686 * Return: 0 if ->i_crypt_info was set or was already set, *or* if the 687 * encryption key is unavailable. (Use fscrypt_has_encryption_key() to 688 * distinguish these cases.) Also can return another -errno code. 689 */ 690 int fscrypt_get_encryption_info(struct inode *inode, bool allow_unsupported) 691 { 692 int res; 693 union fscrypt_context ctx; 694 union fscrypt_policy policy; 695 696 if (fscrypt_has_encryption_key(inode)) 697 return 0; 698 699 res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); 700 if (res < 0) { 701 if (res == -ERANGE && allow_unsupported) 702 return 0; 703 fscrypt_warn(inode, "Error %d getting encryption context", res); 704 return res; 705 } 706 707 res = fscrypt_policy_from_context(&policy, &ctx, res); 708 if (res) { 709 if (allow_unsupported) 710 return 0; 711 fscrypt_warn(inode, 712 "Unrecognized or corrupt encryption context"); 713 return res; 714 } 715 716 if (!fscrypt_supported_policy(&policy, inode)) { 717 if (allow_unsupported) 718 return 0; 719 return -EINVAL; 720 } 721 722 res = fscrypt_setup_encryption_info(inode, &policy, 723 fscrypt_context_nonce(&ctx), 724 IS_CASEFOLDED(inode) && 725 S_ISDIR(inode->i_mode)); 726 727 if (res == -ENOPKG && allow_unsupported) /* Algorithm unavailable? */ 728 res = 0; 729 if (res == -ENOKEY) 730 res = 0; 731 return res; 732 } 733 734 /** 735 * fscrypt_prepare_new_inode() - prepare to create a new inode in a directory 736 * @dir: a possibly-encrypted directory 737 * @inode: the new inode. ->i_mode and ->i_blkbits must be set already. 738 * ->i_ino doesn't need to be set yet. 739 * @encrypt_ret: (output) set to %true if the new inode will be encrypted 740 * 741 * If the directory is encrypted, set up its ->i_crypt_info in preparation for 742 * encrypting the name of the new file. Also, if the new inode will be 743 * encrypted, set up its ->i_crypt_info and set *encrypt_ret=true. 744 * 745 * This isn't %GFP_NOFS-safe, and therefore it should be called before starting 746 * any filesystem transaction to create the inode. For this reason, ->i_ino 747 * isn't required to be set yet, as the filesystem may not have set it yet. 748 * 749 * This doesn't persist the new inode's encryption context. That still needs to 750 * be done later by calling fscrypt_set_context(). 751 * 752 * Return: 0 on success, -ENOKEY if the encryption key is missing, or another 753 * -errno code 754 */ 755 int fscrypt_prepare_new_inode(struct inode *dir, struct inode *inode, 756 bool *encrypt_ret) 757 { 758 const union fscrypt_policy *policy; 759 u8 nonce[FSCRYPT_FILE_NONCE_SIZE]; 760 761 policy = fscrypt_policy_to_inherit(dir); 762 if (policy == NULL) 763 return 0; 764 if (IS_ERR(policy)) 765 return PTR_ERR(policy); 766 767 if (WARN_ON_ONCE(inode->i_blkbits == 0)) 768 return -EINVAL; 769 770 if (WARN_ON_ONCE(inode->i_mode == 0)) 771 return -EINVAL; 772 773 /* 774 * Only regular files, directories, and symlinks are encrypted. 775 * Special files like device nodes and named pipes aren't. 776 */ 777 if (!S_ISREG(inode->i_mode) && 778 !S_ISDIR(inode->i_mode) && 779 !S_ISLNK(inode->i_mode)) 780 return 0; 781 782 *encrypt_ret = true; 783 784 get_random_bytes(nonce, FSCRYPT_FILE_NONCE_SIZE); 785 return fscrypt_setup_encryption_info(inode, policy, nonce, 786 IS_CASEFOLDED(dir) && 787 S_ISDIR(inode->i_mode)); 788 } 789 EXPORT_SYMBOL_GPL(fscrypt_prepare_new_inode); 790 791 /** 792 * fscrypt_put_encryption_info() - free most of an inode's fscrypt data 793 * @inode: an inode being evicted 794 * 795 * Free the inode's fscrypt_inode_info. Filesystems must call this when the 796 * inode is being evicted. An RCU grace period need not have elapsed yet. 797 */ 798 void fscrypt_put_encryption_info(struct inode *inode) 799 { 800 put_crypt_info(inode->i_crypt_info); 801 inode->i_crypt_info = NULL; 802 } 803 EXPORT_SYMBOL(fscrypt_put_encryption_info); 804 805 /** 806 * fscrypt_free_inode() - free an inode's fscrypt data requiring RCU delay 807 * @inode: an inode being freed 808 * 809 * Free the inode's cached decrypted symlink target, if any. Filesystems must 810 * call this after an RCU grace period, just before they free the inode. 811 */ 812 void fscrypt_free_inode(struct inode *inode) 813 { 814 if (IS_ENCRYPTED(inode) && S_ISLNK(inode->i_mode)) { 815 kfree(inode->i_link); 816 inode->i_link = NULL; 817 } 818 } 819 EXPORT_SYMBOL(fscrypt_free_inode); 820 821 /** 822 * fscrypt_drop_inode() - check whether the inode's master key has been removed 823 * @inode: an inode being considered for eviction 824 * 825 * Filesystems supporting fscrypt must call this from their ->drop_inode() 826 * method so that encrypted inodes are evicted as soon as they're no longer in 827 * use and their master key has been removed. 828 * 829 * Return: 1 if fscrypt wants the inode to be evicted now, otherwise 0 830 */ 831 int fscrypt_drop_inode(struct inode *inode) 832 { 833 const struct fscrypt_inode_info *ci = fscrypt_get_inode_info(inode); 834 835 /* 836 * If ci is NULL, then the inode doesn't have an encryption key set up 837 * so it's irrelevant. If ci_master_key is NULL, then the master key 838 * was provided via the legacy mechanism of the process-subscribed 839 * keyrings, so we don't know whether it's been removed or not. 840 */ 841 if (!ci || !ci->ci_master_key) 842 return 0; 843 844 /* 845 * With proper, non-racy use of FS_IOC_REMOVE_ENCRYPTION_KEY, all inodes 846 * protected by the key were cleaned by sync_filesystem(). But if 847 * userspace is still using the files, inodes can be dirtied between 848 * then and now. We mustn't lose any writes, so skip dirty inodes here. 849 */ 850 if (inode->i_state & I_DIRTY_ALL) 851 return 0; 852 853 /* 854 * We can't take ->mk_sem here, since this runs in atomic context. 855 * Therefore, ->mk_present can change concurrently, and our result may 856 * immediately become outdated. But there's no correctness problem with 857 * unnecessarily evicting. Nor is there a correctness problem with not 858 * evicting while iput() is racing with the key being removed, since 859 * then the thread removing the key will either evict the inode itself 860 * or will correctly detect that it wasn't evicted due to the race. 861 */ 862 return !READ_ONCE(ci->ci_master_key->mk_present); 863 } 864 EXPORT_SYMBOL_GPL(fscrypt_drop_inode); 865