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1// SPDX-License-Identifier: GPL-2.02/*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 which121 * crypto algorithm implementation is used. Help people debug122 * performance problems by logging the ->cra_driver_name the123 * 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 the146 * raw key, encryption mode (@ci->ci_mode), flag indicating which encryption147 * 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 that164 * concurrent tasks can ACQUIRE it. Note that this concurrency is only165 * 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 given245 * application-specific information string.246 *247 * Note that the KDF produces a byte array, but the SipHash APIs expect the key248 * as a pair of 64-bit words. Therefore, on big endian CPUs we have to do an249 * 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, the342 * per-file nonce will be included in all the IVs. But unlike343 * v1 policies, for v2 policies in this case we don't encrypt344 * with the master key directly but rather derive a per-mode345 * encryption key. This ensures that the master key is346 * 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 in355 * the IVs. This format is optimized for use with inline356 * 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 the392 * 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 least395 * 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 looser398 * requirement: we require that the size of the master key be at least the399 * maximum security strength of any algorithm whose key will be derived from it400 * (but in practice we only need to consider @ci->ci_mode, since any other401 * possible subkeys such as DIRHASH and INODE_HASH will never increase the402 * required key size over @ci->ci_mode). This allows AES-256-XTS keys to be403 * derived from a 256-bit master key, which is cryptographically sufficient,404 * rather than requiring a 512-bit master key which is unnecessarily long. (We405 * 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 else415 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 is433 * returned in *mk_ret with its semaphore read-locked. This is needed to ensure434 * that only one task links the fscrypt_inode_info into ->mk_decrypted_inodes435 * (as multiple tasks may race to create an fscrypt_inode_info for the same436 * inode), and to synchronize the master key being removed with a new inode437 * 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 that464 * the individual filesystems don't need to worry about adding465 * 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 in481 * the current task's subscribed keyrings too. Don't move this482 * to before the search of ->s_master_keys, since users483 * 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 unlocked541 * with the master key. In addition, if we're removing the last542 * inode from an incompletely removed key, then complete the543 * 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 int555fscrypt_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() in597 * fscrypt_get_inode_info(). I.e., here we publish ->i_crypt_info with598 * 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 key627 * @inode: the inode to set up the key for. Must be encrypted.628 * @allow_unsupported: if %true, treat an unsupported encryption policy (or629 * unrecognized encryption context) the same way as the key630 * being unavailable, instead of returning an error. Use631 * %false unless the operation being performed is needed in632 * 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. So637 * 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 the640 * encryption key is unavailable. (Use fscrypt_has_encryption_key() to641 * 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 directory689 * @dir: a possibly-encrypted directory690 * @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 encrypted693 *694 * If the directory is encrypted, set up its ->i_crypt_info in preparation for695 * encrypting the name of the new file. Also, if the new inode will be696 * 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 starting699 * any filesystem transaction to create the inode. For this reason, ->i_ino700 * 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 to703 * be done later by calling fscrypt_set_context().704 *705 * Return: 0 on success, -ENOKEY if the encryption key is missing, or another706 * -errno code707 */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 data746 * @inode: an inode being evicted747 *748 * Free the inode's fscrypt_inode_info. Filesystems must call this when the749 * 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 delay760 * @inode: an inode being freed761 *762 * Free the inode's cached decrypted symlink target, if any. Filesystems must763 * 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 removed776 * @inode: an inode being considered for eviction777 *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 in780 * use and their master key has been removed.781 *782 * Return: 1 if fscrypt wants the inode to be evicted now, otherwise 0783 */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 up790 * so it's irrelevant. If ci_master_key is NULL, then the master key791 * was provided via the legacy mechanism of the process-subscribed792 * 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 inodes799 * protected by the key were cleaned by sync_filesystem(). But if800 * userspace is still using the files, inodes can be dirtied between801 * 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 may809 * immediately become outdated. But there's no correctness problem with810 * unnecessarily evicting. Nor is there a correctness problem with not811 * evicting while iput() is racing with the key being removed, since812 * then the thread removing the key will either evict the inode itself813 * 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