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 16struct 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 79static DEFINE_MUTEX(fscrypt_mode_key_setup_mutex); 80 81static struct fscrypt_mode * 82select_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 */ 99static struct crypto_skcipher * 100fscrypt_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 139err_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 */ 150int 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, 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. */ 172void 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 */ 181int fscrypt_set_per_file_enc_key(struct fscrypt_inode_info *ci, 182 const u8 *raw_key) 183{ 184 ci->ci_owns_key = true; 185 return fscrypt_prepare_key(&ci->ci_enc_key, raw_key, ci); 186} 187 188static int setup_per_mode_enc_key(struct fscrypt_inode_info *ci, 189 struct fscrypt_master_key *mk, 190 struct fscrypt_prepared_key *keys, 191 u8 hkdf_context, bool include_fs_uuid) 192{ 193 const struct inode *inode = ci->ci_inode; 194 const struct super_block *sb = inode->i_sb; 195 struct fscrypt_mode *mode = ci->ci_mode; 196 const u8 mode_num = mode - fscrypt_modes; 197 struct fscrypt_prepared_key *prep_key; 198 u8 mode_key[FSCRYPT_MAX_KEY_SIZE]; 199 u8 hkdf_info[sizeof(mode_num) + sizeof(sb->s_uuid)]; 200 unsigned int hkdf_infolen = 0; 201 int err; 202 203 if (WARN_ON_ONCE(mode_num > FSCRYPT_MODE_MAX)) 204 return -EINVAL; 205 206 prep_key = &keys[mode_num]; 207 if (fscrypt_is_key_prepared(prep_key, ci)) { 208 ci->ci_enc_key = *prep_key; 209 return 0; 210 } 211 212 mutex_lock(&fscrypt_mode_key_setup_mutex); 213 214 if (fscrypt_is_key_prepared(prep_key, ci)) 215 goto done_unlock; 216 217 BUILD_BUG_ON(sizeof(mode_num) != 1); 218 BUILD_BUG_ON(sizeof(sb->s_uuid) != 16); 219 BUILD_BUG_ON(sizeof(hkdf_info) != 17); 220 hkdf_info[hkdf_infolen++] = mode_num; 221 if (include_fs_uuid) { 222 memcpy(&hkdf_info[hkdf_infolen], &sb->s_uuid, 223 sizeof(sb->s_uuid)); 224 hkdf_infolen += sizeof(sb->s_uuid); 225 } 226 err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, 227 hkdf_context, hkdf_info, hkdf_infolen, 228 mode_key, mode->keysize); 229 if (err) 230 goto out_unlock; 231 err = fscrypt_prepare_key(prep_key, mode_key, ci); 232 memzero_explicit(mode_key, mode->keysize); 233 if (err) 234 goto out_unlock; 235done_unlock: 236 ci->ci_enc_key = *prep_key; 237 err = 0; 238out_unlock: 239 mutex_unlock(&fscrypt_mode_key_setup_mutex); 240 return err; 241} 242 243/* 244 * Derive a SipHash key from the given fscrypt master key and the given 245 * application-specific information string. 246 * 247 * Note that the KDF produces a byte array, but the SipHash APIs expect the key 248 * as a pair of 64-bit words. Therefore, on big endian CPUs we have to do an 249 * endianness swap in order to get the same results as on little endian CPUs. 250 */ 251static int fscrypt_derive_siphash_key(const struct fscrypt_master_key *mk, 252 u8 context, const u8 *info, 253 unsigned int infolen, siphash_key_t *key) 254{ 255 int err; 256 257 err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, context, info, infolen, 258 (u8 *)key, sizeof(*key)); 259 if (err) 260 return err; 261 262 BUILD_BUG_ON(sizeof(*key) != 16); 263 BUILD_BUG_ON(ARRAY_SIZE(key->key) != 2); 264 le64_to_cpus(&key->key[0]); 265 le64_to_cpus(&key->key[1]); 266 return 0; 267} 268 269int fscrypt_derive_dirhash_key(struct fscrypt_inode_info *ci, 270 const struct fscrypt_master_key *mk) 271{ 272 int err; 273 274 err = fscrypt_derive_siphash_key(mk, HKDF_CONTEXT_DIRHASH_KEY, 275 ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE, 276 &ci->ci_dirhash_key); 277 if (err) 278 return err; 279 ci->ci_dirhash_key_initialized = true; 280 return 0; 281} 282 283void fscrypt_hash_inode_number(struct fscrypt_inode_info *ci, 284 const struct fscrypt_master_key *mk) 285{ 286 WARN_ON_ONCE(ci->ci_inode->i_ino == 0); 287 WARN_ON_ONCE(!mk->mk_ino_hash_key_initialized); 288 289 ci->ci_hashed_ino = (u32)siphash_1u64(ci->ci_inode->i_ino, 290 &mk->mk_ino_hash_key); 291} 292 293static int fscrypt_setup_iv_ino_lblk_32_key(struct fscrypt_inode_info *ci, 294 struct fscrypt_master_key *mk) 295{ 296 int err; 297 298 err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_32_keys, 299 HKDF_CONTEXT_IV_INO_LBLK_32_KEY, true); 300 if (err) 301 return err; 302 303 /* pairs with smp_store_release() below */ 304 if (!smp_load_acquire(&mk->mk_ino_hash_key_initialized)) { 305 306 mutex_lock(&fscrypt_mode_key_setup_mutex); 307 308 if (mk->mk_ino_hash_key_initialized) 309 goto unlock; 310 311 err = fscrypt_derive_siphash_key(mk, 312 HKDF_CONTEXT_INODE_HASH_KEY, 313 NULL, 0, &mk->mk_ino_hash_key); 314 if (err) 315 goto unlock; 316 /* pairs with smp_load_acquire() above */ 317 smp_store_release(&mk->mk_ino_hash_key_initialized, true); 318unlock: 319 mutex_unlock(&fscrypt_mode_key_setup_mutex); 320 if (err) 321 return err; 322 } 323 324 /* 325 * New inodes may not have an inode number assigned yet. 326 * Hashing their inode number is delayed until later. 327 */ 328 if (ci->ci_inode->i_ino) 329 fscrypt_hash_inode_number(ci, mk); 330 return 0; 331} 332 333static int fscrypt_setup_v2_file_key(struct fscrypt_inode_info *ci, 334 struct fscrypt_master_key *mk, 335 bool need_dirhash_key) 336{ 337 int err; 338 339 if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { 340 /* 341 * DIRECT_KEY: instead of deriving per-file encryption keys, the 342 * per-file nonce will be included in all the IVs. But unlike 343 * v1 policies, for v2 policies in this case we don't encrypt 344 * with the master key directly but rather derive a per-mode 345 * encryption key. This ensures that the master key is 346 * consistently used only for HKDF, avoiding key reuse issues. 347 */ 348 err = setup_per_mode_enc_key(ci, mk, mk->mk_direct_keys, 349 HKDF_CONTEXT_DIRECT_KEY, false); 350 } else if (ci->ci_policy.v2.flags & 351 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) { 352 /* 353 * IV_INO_LBLK_64: encryption keys are derived from (master_key, 354 * mode_num, filesystem_uuid), and inode number is included in 355 * the IVs. This format is optimized for use with inline 356 * encryption hardware compliant with the UFS standard. 357 */ 358 err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_64_keys, 359 HKDF_CONTEXT_IV_INO_LBLK_64_KEY, 360 true); 361 } else if (ci->ci_policy.v2.flags & 362 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) { 363 err = fscrypt_setup_iv_ino_lblk_32_key(ci, mk); 364 } else { 365 u8 derived_key[FSCRYPT_MAX_KEY_SIZE]; 366 367 err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, 368 HKDF_CONTEXT_PER_FILE_ENC_KEY, 369 ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE, 370 derived_key, ci->ci_mode->keysize); 371 if (err) 372 return err; 373 374 err = fscrypt_set_per_file_enc_key(ci, derived_key); 375 memzero_explicit(derived_key, ci->ci_mode->keysize); 376 } 377 if (err) 378 return err; 379 380 /* Derive a secret dirhash key for directories that need it. */ 381 if (need_dirhash_key) { 382 err = fscrypt_derive_dirhash_key(ci, mk); 383 if (err) 384 return err; 385 } 386 387 return 0; 388} 389 390/* 391 * Check whether the size of the given master key (@mk) is appropriate for the 392 * encryption settings which a particular file will use (@ci). 393 * 394 * If the file uses a v1 encryption policy, then the master key must be at least 395 * as long as the derived key, as this is a requirement of the v1 KDF. 396 * 397 * Otherwise, the KDF can accept any size key, so we enforce a slightly looser 398 * requirement: we require that the size of the master key be at least the 399 * maximum security strength of any algorithm whose key will be derived from it 400 * (but in practice we only need to consider @ci->ci_mode, since any other 401 * possible subkeys such as DIRHASH and INODE_HASH will never increase the 402 * required key size over @ci->ci_mode). This allows AES-256-XTS keys to be 403 * derived from a 256-bit master key, which is cryptographically sufficient, 404 * rather than requiring a 512-bit master key which is unnecessarily long. (We 405 * still allow 512-bit master keys if the user chooses to use them, though.) 406 */ 407static bool fscrypt_valid_master_key_size(const struct fscrypt_master_key *mk, 408 const struct fscrypt_inode_info *ci) 409{ 410 unsigned int min_keysize; 411 412 if (ci->ci_policy.version == FSCRYPT_POLICY_V1) 413 min_keysize = ci->ci_mode->keysize; 414 else 415 min_keysize = ci->ci_mode->security_strength; 416 417 if (mk->mk_secret.size < min_keysize) { 418 fscrypt_warn(NULL, 419 "key with %s %*phN is too short (got %u bytes, need %u+ bytes)", 420 master_key_spec_type(&mk->mk_spec), 421 master_key_spec_len(&mk->mk_spec), 422 (u8 *)&mk->mk_spec.u, 423 mk->mk_secret.size, min_keysize); 424 return false; 425 } 426 return true; 427} 428 429/* 430 * Find the master key, then set up the inode's actual encryption key. 431 * 432 * If the master key is found in the filesystem-level keyring, then it is 433 * returned in *mk_ret with its semaphore read-locked. This is needed to ensure 434 * that only one task links the fscrypt_inode_info into ->mk_decrypted_inodes 435 * (as multiple tasks may race to create an fscrypt_inode_info for the same 436 * inode), and to synchronize the master key being removed with a new inode 437 * starting to use it. 438 */ 439static int setup_file_encryption_key(struct fscrypt_inode_info *ci, 440 bool need_dirhash_key, 441 struct fscrypt_master_key **mk_ret) 442{ 443 struct super_block *sb = ci->ci_inode->i_sb; 444 struct fscrypt_key_specifier mk_spec; 445 struct fscrypt_master_key *mk; 446 int err; 447 448 err = fscrypt_select_encryption_impl(ci); 449 if (err) 450 return err; 451 452 err = fscrypt_policy_to_key_spec(&ci->ci_policy, &mk_spec); 453 if (err) 454 return err; 455 456 mk = fscrypt_find_master_key(sb, &mk_spec); 457 if (unlikely(!mk)) { 458 const union fscrypt_policy *dummy_policy = 459 fscrypt_get_dummy_policy(sb); 460 461 /* 462 * Add the test_dummy_encryption key on-demand. In principle, 463 * it should be added at mount time. Do it here instead so that 464 * the individual filesystems don't need to worry about adding 465 * this key at mount time and cleaning up on mount failure. 466 */ 467 if (dummy_policy && 468 fscrypt_policies_equal(dummy_policy, &ci->ci_policy)) { 469 err = fscrypt_add_test_dummy_key(sb, &mk_spec); 470 if (err) 471 return err; 472 mk = fscrypt_find_master_key(sb, &mk_spec); 473 } 474 } 475 if (unlikely(!mk)) { 476 if (ci->ci_policy.version != FSCRYPT_POLICY_V1) 477 return -ENOKEY; 478 479 /* 480 * As a legacy fallback for v1 policies, search for the key in 481 * the current task's subscribed keyrings too. Don't move this 482 * to before the search of ->s_master_keys, since users 483 * shouldn't be able to override filesystem-level keys. 484 */ 485 return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci); 486 } 487 down_read(&mk->mk_sem); 488 489 if (!mk->mk_present) { 490 /* FS_IOC_REMOVE_ENCRYPTION_KEY has been executed on this key */ 491 err = -ENOKEY; 492 goto out_release_key; 493 } 494 495 if (!fscrypt_valid_master_key_size(mk, ci)) { 496 err = -ENOKEY; 497 goto out_release_key; 498 } 499 500 switch (ci->ci_policy.version) { 501 case FSCRYPT_POLICY_V1: 502 err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw); 503 break; 504 case FSCRYPT_POLICY_V2: 505 err = fscrypt_setup_v2_file_key(ci, mk, need_dirhash_key); 506 break; 507 default: 508 WARN_ON_ONCE(1); 509 err = -EINVAL; 510 break; 511 } 512 if (err) 513 goto out_release_key; 514 515 *mk_ret = mk; 516 return 0; 517 518out_release_key: 519 up_read(&mk->mk_sem); 520 fscrypt_put_master_key(mk); 521 return err; 522} 523 524static void put_crypt_info(struct fscrypt_inode_info *ci) 525{ 526 struct fscrypt_master_key *mk; 527 528 if (!ci) 529 return; 530 531 if (ci->ci_direct_key) 532 fscrypt_put_direct_key(ci->ci_direct_key); 533 else if (ci->ci_owns_key) 534 fscrypt_destroy_prepared_key(ci->ci_inode->i_sb, 535 &ci->ci_enc_key); 536 537 mk = ci->ci_master_key; 538 if (mk) { 539 /* 540 * Remove this inode from the list of inodes that were unlocked 541 * with the master key. In addition, if we're removing the last 542 * inode from an incompletely removed key, then complete the 543 * full removal of the key. 544 */ 545 spin_lock(&mk->mk_decrypted_inodes_lock); 546 list_del(&ci->ci_master_key_link); 547 spin_unlock(&mk->mk_decrypted_inodes_lock); 548 fscrypt_put_master_key_activeref(ci->ci_inode->i_sb, mk); 549 } 550 memzero_explicit(ci, sizeof(*ci)); 551 kmem_cache_free(fscrypt_inode_info_cachep, ci); 552} 553 554static int 555fscrypt_setup_encryption_info(struct inode *inode, 556 const union fscrypt_policy *policy, 557 const u8 nonce[FSCRYPT_FILE_NONCE_SIZE], 558 bool need_dirhash_key) 559{ 560 struct fscrypt_inode_info *crypt_info; 561 struct fscrypt_mode *mode; 562 struct fscrypt_master_key *mk = NULL; 563 int res; 564 565 res = fscrypt_initialize(inode->i_sb); 566 if (res) 567 return res; 568 569 crypt_info = kmem_cache_zalloc(fscrypt_inode_info_cachep, GFP_KERNEL); 570 if (!crypt_info) 571 return -ENOMEM; 572 573 crypt_info->ci_inode = inode; 574 crypt_info->ci_policy = *policy; 575 memcpy(crypt_info->ci_nonce, nonce, FSCRYPT_FILE_NONCE_SIZE); 576 577 mode = select_encryption_mode(&crypt_info->ci_policy, inode); 578 if (IS_ERR(mode)) { 579 res = PTR_ERR(mode); 580 goto out; 581 } 582 WARN_ON_ONCE(mode->ivsize > FSCRYPT_MAX_IV_SIZE); 583 crypt_info->ci_mode = mode; 584 585 crypt_info->ci_data_unit_bits = 586 fscrypt_policy_du_bits(&crypt_info->ci_policy, inode); 587 crypt_info->ci_data_units_per_block_bits = 588 inode->i_blkbits - crypt_info->ci_data_unit_bits; 589 590 res = setup_file_encryption_key(crypt_info, need_dirhash_key, &mk); 591 if (res) 592 goto out; 593 594 /* 595 * For existing inodes, multiple tasks may race to set ->i_crypt_info. 596 * So use cmpxchg_release(). This pairs with the smp_load_acquire() in 597 * fscrypt_get_inode_info(). I.e., here we publish ->i_crypt_info with 598 * a RELEASE barrier so that other tasks can ACQUIRE it. 599 */ 600 if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL) { 601 /* 602 * We won the race and set ->i_crypt_info to our crypt_info. 603 * Now link it into the master key's inode list. 604 */ 605 if (mk) { 606 crypt_info->ci_master_key = mk; 607 refcount_inc(&mk->mk_active_refs); 608 spin_lock(&mk->mk_decrypted_inodes_lock); 609 list_add(&crypt_info->ci_master_key_link, 610 &mk->mk_decrypted_inodes); 611 spin_unlock(&mk->mk_decrypted_inodes_lock); 612 } 613 crypt_info = NULL; 614 } 615 res = 0; 616out: 617 if (mk) { 618 up_read(&mk->mk_sem); 619 fscrypt_put_master_key(mk); 620 } 621 put_crypt_info(crypt_info); 622 return res; 623} 624 625/** 626 * fscrypt_get_encryption_info() - set up an inode's encryption key 627 * @inode: the inode to set up the key for. Must be encrypted. 628 * @allow_unsupported: if %true, treat an unsupported encryption policy (or 629 * unrecognized encryption context) the same way as the key 630 * being unavailable, instead of returning an error. Use 631 * %false unless the operation being performed is needed in 632 * order for files (or directories) to be deleted. 633 * 634 * Set up ->i_crypt_info, if it hasn't already been done. 635 * 636 * Note: unless ->i_crypt_info is already set, this isn't %GFP_NOFS-safe. So 637 * generally this shouldn't be called from within a filesystem transaction. 638 * 639 * Return: 0 if ->i_crypt_info was set or was already set, *or* if the 640 * encryption key is unavailable. (Use fscrypt_has_encryption_key() to 641 * distinguish these cases.) Also can return another -errno code. 642 */ 643int fscrypt_get_encryption_info(struct inode *inode, bool allow_unsupported) 644{ 645 int res; 646 union fscrypt_context ctx; 647 union fscrypt_policy policy; 648 649 if (fscrypt_has_encryption_key(inode)) 650 return 0; 651 652 res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); 653 if (res < 0) { 654 if (res == -ERANGE && allow_unsupported) 655 return 0; 656 fscrypt_warn(inode, "Error %d getting encryption context", res); 657 return res; 658 } 659 660 res = fscrypt_policy_from_context(&policy, &ctx, res); 661 if (res) { 662 if (allow_unsupported) 663 return 0; 664 fscrypt_warn(inode, 665 "Unrecognized or corrupt encryption context"); 666 return res; 667 } 668 669 if (!fscrypt_supported_policy(&policy, inode)) { 670 if (allow_unsupported) 671 return 0; 672 return -EINVAL; 673 } 674 675 res = fscrypt_setup_encryption_info(inode, &policy, 676 fscrypt_context_nonce(&ctx), 677 IS_CASEFOLDED(inode) && 678 S_ISDIR(inode->i_mode)); 679 680 if (res == -ENOPKG && allow_unsupported) /* Algorithm unavailable? */ 681 res = 0; 682 if (res == -ENOKEY) 683 res = 0; 684 return res; 685} 686 687/** 688 * fscrypt_prepare_new_inode() - prepare to create a new inode in a directory 689 * @dir: a possibly-encrypted directory 690 * @inode: the new inode. ->i_mode and ->i_blkbits must be set already. 691 * ->i_ino doesn't need to be set yet. 692 * @encrypt_ret: (output) set to %true if the new inode will be encrypted 693 * 694 * If the directory is encrypted, set up its ->i_crypt_info in preparation for 695 * encrypting the name of the new file. Also, if the new inode will be 696 * encrypted, set up its ->i_crypt_info and set *encrypt_ret=true. 697 * 698 * This isn't %GFP_NOFS-safe, and therefore it should be called before starting 699 * any filesystem transaction to create the inode. For this reason, ->i_ino 700 * isn't required to be set yet, as the filesystem may not have set it yet. 701 * 702 * This doesn't persist the new inode's encryption context. That still needs to 703 * be done later by calling fscrypt_set_context(). 704 * 705 * Return: 0 on success, -ENOKEY if the encryption key is missing, or another 706 * -errno code 707 */ 708int fscrypt_prepare_new_inode(struct inode *dir, struct inode *inode, 709 bool *encrypt_ret) 710{ 711 const union fscrypt_policy *policy; 712 u8 nonce[FSCRYPT_FILE_NONCE_SIZE]; 713 714 policy = fscrypt_policy_to_inherit(dir); 715 if (policy == NULL) 716 return 0; 717 if (IS_ERR(policy)) 718 return PTR_ERR(policy); 719 720 if (WARN_ON_ONCE(inode->i_blkbits == 0)) 721 return -EINVAL; 722 723 if (WARN_ON_ONCE(inode->i_mode == 0)) 724 return -EINVAL; 725 726 /* 727 * Only regular files, directories, and symlinks are encrypted. 728 * Special files like device nodes and named pipes aren't. 729 */ 730 if (!S_ISREG(inode->i_mode) && 731 !S_ISDIR(inode->i_mode) && 732 !S_ISLNK(inode->i_mode)) 733 return 0; 734 735 *encrypt_ret = true; 736 737 get_random_bytes(nonce, FSCRYPT_FILE_NONCE_SIZE); 738 return fscrypt_setup_encryption_info(inode, policy, nonce, 739 IS_CASEFOLDED(dir) && 740 S_ISDIR(inode->i_mode)); 741} 742EXPORT_SYMBOL_GPL(fscrypt_prepare_new_inode); 743 744/** 745 * fscrypt_put_encryption_info() - free most of an inode's fscrypt data 746 * @inode: an inode being evicted 747 * 748 * Free the inode's fscrypt_inode_info. Filesystems must call this when the 749 * inode is being evicted. An RCU grace period need not have elapsed yet. 750 */ 751void fscrypt_put_encryption_info(struct inode *inode) 752{ 753 put_crypt_info(inode->i_crypt_info); 754 inode->i_crypt_info = NULL; 755} 756EXPORT_SYMBOL(fscrypt_put_encryption_info); 757 758/** 759 * fscrypt_free_inode() - free an inode's fscrypt data requiring RCU delay 760 * @inode: an inode being freed 761 * 762 * Free the inode's cached decrypted symlink target, if any. Filesystems must 763 * call this after an RCU grace period, just before they free the inode. 764 */ 765void fscrypt_free_inode(struct inode *inode) 766{ 767 if (IS_ENCRYPTED(inode) && S_ISLNK(inode->i_mode)) { 768 kfree(inode->i_link); 769 inode->i_link = NULL; 770 } 771} 772EXPORT_SYMBOL(fscrypt_free_inode); 773 774/** 775 * fscrypt_drop_inode() - check whether the inode's master key has been removed 776 * @inode: an inode being considered for eviction 777 * 778 * Filesystems supporting fscrypt must call this from their ->drop_inode() 779 * method so that encrypted inodes are evicted as soon as they're no longer in 780 * use and their master key has been removed. 781 * 782 * Return: 1 if fscrypt wants the inode to be evicted now, otherwise 0 783 */ 784int fscrypt_drop_inode(struct inode *inode) 785{ 786 const struct fscrypt_inode_info *ci = fscrypt_get_inode_info(inode); 787 788 /* 789 * If ci is NULL, then the inode doesn't have an encryption key set up 790 * so it's irrelevant. If ci_master_key is NULL, then the master key 791 * was provided via the legacy mechanism of the process-subscribed 792 * keyrings, so we don't know whether it's been removed or not. 793 */ 794 if (!ci || !ci->ci_master_key) 795 return 0; 796 797 /* 798 * With proper, non-racy use of FS_IOC_REMOVE_ENCRYPTION_KEY, all inodes 799 * protected by the key were cleaned by sync_filesystem(). But if 800 * userspace is still using the files, inodes can be dirtied between 801 * then and now. We mustn't lose any writes, so skip dirty inodes here. 802 */ 803 if (inode->i_state & I_DIRTY_ALL) 804 return 0; 805 806 /* 807 * We can't take ->mk_sem here, since this runs in atomic context. 808 * Therefore, ->mk_present can change concurrently, and our result may 809 * immediately become outdated. But there's no correctness problem with 810 * unnecessarily evicting. Nor is there a correctness problem with not 811 * evicting while iput() is racing with the key being removed, since 812 * then the thread removing the key will either evict the inode itself 813 * or will correctly detect that it wasn't evicted due to the race. 814 */ 815 return !READ_ONCE(ci->ci_master_key->mk_present); 816} 817EXPORT_SYMBOL_GPL(fscrypt_drop_inode); 818