diff options
Diffstat (limited to 'fs/crypto/keysetup.c')
| -rw-r--r-- | fs/crypto/keysetup.c | 806 |
1 files changed, 806 insertions, 0 deletions
diff --git a/fs/crypto/keysetup.c b/fs/crypto/keysetup.c new file mode 100644 index 0000000000..361f41ef46 --- /dev/null +++ b/fs/crypto/keysetup.c @@ -0,0 +1,806 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Key setup facility for FS encryption support. + * + * Copyright (C) 2015, Google, Inc. + * + * Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar. + * Heavily modified since then. + */ + +#include <crypto/skcipher.h> +#include <linux/random.h> + +#include "fscrypt_private.h" + +struct fscrypt_mode fscrypt_modes[] = { + [FSCRYPT_MODE_AES_256_XTS] = { + .friendly_name = "AES-256-XTS", + .cipher_str = "xts(aes)", + .keysize = 64, + .security_strength = 32, + .ivsize = 16, + .blk_crypto_mode = BLK_ENCRYPTION_MODE_AES_256_XTS, + }, + [FSCRYPT_MODE_AES_256_CTS] = { + .friendly_name = "AES-256-CTS-CBC", + .cipher_str = "cts(cbc(aes))", + .keysize = 32, + .security_strength = 32, + .ivsize = 16, + }, + [FSCRYPT_MODE_AES_128_CBC] = { + .friendly_name = "AES-128-CBC-ESSIV", + .cipher_str = "essiv(cbc(aes),sha256)", + .keysize = 16, + .security_strength = 16, + .ivsize = 16, + .blk_crypto_mode = BLK_ENCRYPTION_MODE_AES_128_CBC_ESSIV, + }, + [FSCRYPT_MODE_AES_128_CTS] = { + .friendly_name = "AES-128-CTS-CBC", + .cipher_str = "cts(cbc(aes))", + .keysize = 16, + .security_strength = 16, + .ivsize = 16, + }, + [FSCRYPT_MODE_SM4_XTS] = { + .friendly_name = "SM4-XTS", + .cipher_str = "xts(sm4)", + .keysize = 32, + .security_strength = 16, + .ivsize = 16, + .blk_crypto_mode = BLK_ENCRYPTION_MODE_SM4_XTS, + }, + [FSCRYPT_MODE_SM4_CTS] = { + .friendly_name = "SM4-CTS-CBC", + .cipher_str = "cts(cbc(sm4))", + .keysize = 16, + .security_strength = 16, + .ivsize = 16, + }, + [FSCRYPT_MODE_ADIANTUM] = { + .friendly_name = "Adiantum", + .cipher_str = "adiantum(xchacha12,aes)", + .keysize = 32, + .security_strength = 32, + .ivsize = 32, + .blk_crypto_mode = BLK_ENCRYPTION_MODE_ADIANTUM, + }, + [FSCRYPT_MODE_AES_256_HCTR2] = { + .friendly_name = "AES-256-HCTR2", + .cipher_str = "hctr2(aes)", + .keysize = 32, + .security_strength = 32, + .ivsize = 32, + }, +}; + +static DEFINE_MUTEX(fscrypt_mode_key_setup_mutex); + +static struct fscrypt_mode * +select_encryption_mode(const union fscrypt_policy *policy, + const struct inode *inode) +{ + BUILD_BUG_ON(ARRAY_SIZE(fscrypt_modes) != FSCRYPT_MODE_MAX + 1); + + if (S_ISREG(inode->i_mode)) + return &fscrypt_modes[fscrypt_policy_contents_mode(policy)]; + + if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) + return &fscrypt_modes[fscrypt_policy_fnames_mode(policy)]; + + WARN_ONCE(1, "fscrypt: filesystem tried to load encryption info for inode %lu, which is not encryptable (file type %d)\n", + inode->i_ino, (inode->i_mode & S_IFMT)); + return ERR_PTR(-EINVAL); +} + +/* Create a symmetric cipher object for the given encryption mode and key */ +static struct crypto_skcipher * +fscrypt_allocate_skcipher(struct fscrypt_mode *mode, const u8 *raw_key, + const struct inode *inode) +{ + struct crypto_skcipher *tfm; + int err; + + tfm = crypto_alloc_skcipher(mode->cipher_str, 0, 0); + if (IS_ERR(tfm)) { + if (PTR_ERR(tfm) == -ENOENT) { + fscrypt_warn(inode, + "Missing crypto API support for %s (API name: \"%s\")", + mode->friendly_name, mode->cipher_str); + return ERR_PTR(-ENOPKG); + } + fscrypt_err(inode, "Error allocating '%s' transform: %ld", + mode->cipher_str, PTR_ERR(tfm)); + return tfm; + } + if (!xchg(&mode->logged_cryptoapi_impl, 1)) { + /* + * fscrypt performance can vary greatly depending on which + * crypto algorithm implementation is used. Help people debug + * performance problems by logging the ->cra_driver_name the + * first time a mode is used. + */ + pr_info("fscrypt: %s using implementation \"%s\"\n", + mode->friendly_name, crypto_skcipher_driver_name(tfm)); + } + if (WARN_ON_ONCE(crypto_skcipher_ivsize(tfm) != mode->ivsize)) { + err = -EINVAL; + goto err_free_tfm; + } + crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_FORBID_WEAK_KEYS); + err = crypto_skcipher_setkey(tfm, raw_key, mode->keysize); + if (err) + goto err_free_tfm; + + return tfm; + +err_free_tfm: + crypto_free_skcipher(tfm); + return ERR_PTR(err); +} + +/* + * Prepare the crypto transform object or blk-crypto key in @prep_key, given the + * raw key, encryption mode (@ci->ci_mode), flag indicating which encryption + * implementation (fs-layer or blk-crypto) will be used (@ci->ci_inlinecrypt), + * and IV generation method (@ci->ci_policy.flags). + */ +int fscrypt_prepare_key(struct fscrypt_prepared_key *prep_key, + const u8 *raw_key, const struct fscrypt_info *ci) +{ + struct crypto_skcipher *tfm; + + if (fscrypt_using_inline_encryption(ci)) + return fscrypt_prepare_inline_crypt_key(prep_key, raw_key, ci); + + tfm = fscrypt_allocate_skcipher(ci->ci_mode, raw_key, ci->ci_inode); + if (IS_ERR(tfm)) + return PTR_ERR(tfm); + /* + * Pairs with the smp_load_acquire() in fscrypt_is_key_prepared(). + * I.e., here we publish ->tfm with a RELEASE barrier so that + * concurrent tasks can ACQUIRE it. Note that this concurrency is only + * possible for per-mode keys, not for per-file keys. + */ + smp_store_release(&prep_key->tfm, tfm); + return 0; +} + +/* Destroy a crypto transform object and/or blk-crypto key. */ +void fscrypt_destroy_prepared_key(struct super_block *sb, + struct fscrypt_prepared_key *prep_key) +{ + crypto_free_skcipher(prep_key->tfm); + fscrypt_destroy_inline_crypt_key(sb, prep_key); + memzero_explicit(prep_key, sizeof(*prep_key)); +} + +/* Given a per-file encryption key, set up the file's crypto transform object */ +int fscrypt_set_per_file_enc_key(struct fscrypt_info *ci, const u8 *raw_key) +{ + ci->ci_owns_key = true; + return fscrypt_prepare_key(&ci->ci_enc_key, raw_key, ci); +} + +static int setup_per_mode_enc_key(struct fscrypt_info *ci, + struct fscrypt_master_key *mk, + struct fscrypt_prepared_key *keys, + u8 hkdf_context, bool include_fs_uuid) +{ + const struct inode *inode = ci->ci_inode; + const struct super_block *sb = inode->i_sb; + struct fscrypt_mode *mode = ci->ci_mode; + const u8 mode_num = mode - fscrypt_modes; + struct fscrypt_prepared_key *prep_key; + u8 mode_key[FSCRYPT_MAX_KEY_SIZE]; + u8 hkdf_info[sizeof(mode_num) + sizeof(sb->s_uuid)]; + unsigned int hkdf_infolen = 0; + int err; + + if (WARN_ON_ONCE(mode_num > FSCRYPT_MODE_MAX)) + return -EINVAL; + + prep_key = &keys[mode_num]; + if (fscrypt_is_key_prepared(prep_key, ci)) { + ci->ci_enc_key = *prep_key; + return 0; + } + + mutex_lock(&fscrypt_mode_key_setup_mutex); + + if (fscrypt_is_key_prepared(prep_key, ci)) + goto done_unlock; + + BUILD_BUG_ON(sizeof(mode_num) != 1); + BUILD_BUG_ON(sizeof(sb->s_uuid) != 16); + BUILD_BUG_ON(sizeof(hkdf_info) != 17); + hkdf_info[hkdf_infolen++] = mode_num; + if (include_fs_uuid) { + memcpy(&hkdf_info[hkdf_infolen], &sb->s_uuid, + sizeof(sb->s_uuid)); + hkdf_infolen += sizeof(sb->s_uuid); + } + err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, + hkdf_context, hkdf_info, hkdf_infolen, + mode_key, mode->keysize); + if (err) + goto out_unlock; + err = fscrypt_prepare_key(prep_key, mode_key, ci); + memzero_explicit(mode_key, mode->keysize); + if (err) + goto out_unlock; +done_unlock: + ci->ci_enc_key = *prep_key; + err = 0; +out_unlock: + mutex_unlock(&fscrypt_mode_key_setup_mutex); + return err; +} + +/* + * Derive a SipHash key from the given fscrypt master key and the given + * application-specific information string. + * + * Note that the KDF produces a byte array, but the SipHash APIs expect the key + * as a pair of 64-bit words. Therefore, on big endian CPUs we have to do an + * endianness swap in order to get the same results as on little endian CPUs. + */ +static int fscrypt_derive_siphash_key(const struct fscrypt_master_key *mk, + u8 context, const u8 *info, + unsigned int infolen, siphash_key_t *key) +{ + int err; + + err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, context, info, infolen, + (u8 *)key, sizeof(*key)); + if (err) + return err; + + BUILD_BUG_ON(sizeof(*key) != 16); + BUILD_BUG_ON(ARRAY_SIZE(key->key) != 2); + le64_to_cpus(&key->key[0]); + le64_to_cpus(&key->key[1]); + return 0; +} + +int fscrypt_derive_dirhash_key(struct fscrypt_info *ci, + const struct fscrypt_master_key *mk) +{ + int err; + + err = fscrypt_derive_siphash_key(mk, HKDF_CONTEXT_DIRHASH_KEY, + ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE, + &ci->ci_dirhash_key); + if (err) + return err; + ci->ci_dirhash_key_initialized = true; + return 0; +} + +void fscrypt_hash_inode_number(struct fscrypt_info *ci, + const struct fscrypt_master_key *mk) +{ + WARN_ON_ONCE(ci->ci_inode->i_ino == 0); + WARN_ON_ONCE(!mk->mk_ino_hash_key_initialized); + + ci->ci_hashed_ino = (u32)siphash_1u64(ci->ci_inode->i_ino, + &mk->mk_ino_hash_key); +} + +static int fscrypt_setup_iv_ino_lblk_32_key(struct fscrypt_info *ci, + struct fscrypt_master_key *mk) +{ + int err; + + err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_32_keys, + HKDF_CONTEXT_IV_INO_LBLK_32_KEY, true); + if (err) + return err; + + /* pairs with smp_store_release() below */ + if (!smp_load_acquire(&mk->mk_ino_hash_key_initialized)) { + + mutex_lock(&fscrypt_mode_key_setup_mutex); + + if (mk->mk_ino_hash_key_initialized) + goto unlock; + + err = fscrypt_derive_siphash_key(mk, + HKDF_CONTEXT_INODE_HASH_KEY, + NULL, 0, &mk->mk_ino_hash_key); + if (err) + goto unlock; + /* pairs with smp_load_acquire() above */ + smp_store_release(&mk->mk_ino_hash_key_initialized, true); +unlock: + mutex_unlock(&fscrypt_mode_key_setup_mutex); + if (err) + return err; + } + + /* + * New inodes may not have an inode number assigned yet. + * Hashing their inode number is delayed until later. + */ + if (ci->ci_inode->i_ino) + fscrypt_hash_inode_number(ci, mk); + return 0; +} + +static int fscrypt_setup_v2_file_key(struct fscrypt_info *ci, + struct fscrypt_master_key *mk, + bool need_dirhash_key) +{ + int err; + + if (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) { + /* + * DIRECT_KEY: instead of deriving per-file encryption keys, the + * per-file nonce will be included in all the IVs. But unlike + * v1 policies, for v2 policies in this case we don't encrypt + * with the master key directly but rather derive a per-mode + * encryption key. This ensures that the master key is + * consistently used only for HKDF, avoiding key reuse issues. + */ + err = setup_per_mode_enc_key(ci, mk, mk->mk_direct_keys, + HKDF_CONTEXT_DIRECT_KEY, false); + } else if (ci->ci_policy.v2.flags & + FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) { + /* + * IV_INO_LBLK_64: encryption keys are derived from (master_key, + * mode_num, filesystem_uuid), and inode number is included in + * the IVs. This format is optimized for use with inline + * encryption hardware compliant with the UFS standard. + */ + err = setup_per_mode_enc_key(ci, mk, mk->mk_iv_ino_lblk_64_keys, + HKDF_CONTEXT_IV_INO_LBLK_64_KEY, + true); + } else if (ci->ci_policy.v2.flags & + FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) { + err = fscrypt_setup_iv_ino_lblk_32_key(ci, mk); + } else { + u8 derived_key[FSCRYPT_MAX_KEY_SIZE]; + + err = fscrypt_hkdf_expand(&mk->mk_secret.hkdf, + HKDF_CONTEXT_PER_FILE_ENC_KEY, + ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE, + derived_key, ci->ci_mode->keysize); + if (err) + return err; + + err = fscrypt_set_per_file_enc_key(ci, derived_key); + memzero_explicit(derived_key, ci->ci_mode->keysize); + } + if (err) + return err; + + /* Derive a secret dirhash key for directories that need it. */ + if (need_dirhash_key) { + err = fscrypt_derive_dirhash_key(ci, mk); + if (err) + return err; + } + + return 0; +} + +/* + * Check whether the size of the given master key (@mk) is appropriate for the + * encryption settings which a particular file will use (@ci). + * + * If the file uses a v1 encryption policy, then the master key must be at least + * as long as the derived key, as this is a requirement of the v1 KDF. + * + * Otherwise, the KDF can accept any size key, so we enforce a slightly looser + * requirement: we require that the size of the master key be at least the + * maximum security strength of any algorithm whose key will be derived from it + * (but in practice we only need to consider @ci->ci_mode, since any other + * possible subkeys such as DIRHASH and INODE_HASH will never increase the + * required key size over @ci->ci_mode). This allows AES-256-XTS keys to be + * derived from a 256-bit master key, which is cryptographically sufficient, + * rather than requiring a 512-bit master key which is unnecessarily long. (We + * still allow 512-bit master keys if the user chooses to use them, though.) + */ +static bool fscrypt_valid_master_key_size(const struct fscrypt_master_key *mk, + const struct fscrypt_info *ci) +{ + unsigned int min_keysize; + + if (ci->ci_policy.version == FSCRYPT_POLICY_V1) + min_keysize = ci->ci_mode->keysize; + else + min_keysize = ci->ci_mode->security_strength; + + if (mk->mk_secret.size < min_keysize) { + fscrypt_warn(NULL, + "key with %s %*phN is too short (got %u bytes, need %u+ bytes)", + master_key_spec_type(&mk->mk_spec), + master_key_spec_len(&mk->mk_spec), + (u8 *)&mk->mk_spec.u, + mk->mk_secret.size, min_keysize); + return false; + } + return true; +} + +/* + * Find the master key, then set up the inode's actual encryption key. + * + * If the master key is found in the filesystem-level keyring, then it is + * returned in *mk_ret with its semaphore read-locked. This is needed to ensure + * that only one task links the fscrypt_info into ->mk_decrypted_inodes (as + * multiple tasks may race to create an fscrypt_info for the same inode), and to + * synchronize the master key being removed with a new inode starting to use it. + */ +static int setup_file_encryption_key(struct fscrypt_info *ci, + bool need_dirhash_key, + struct fscrypt_master_key **mk_ret) +{ + struct super_block *sb = ci->ci_inode->i_sb; + struct fscrypt_key_specifier mk_spec; + struct fscrypt_master_key *mk; + int err; + + err = fscrypt_select_encryption_impl(ci); + if (err) + return err; + + err = fscrypt_policy_to_key_spec(&ci->ci_policy, &mk_spec); + if (err) + return err; + + mk = fscrypt_find_master_key(sb, &mk_spec); + if (unlikely(!mk)) { + const union fscrypt_policy *dummy_policy = + fscrypt_get_dummy_policy(sb); + + /* + * Add the test_dummy_encryption key on-demand. In principle, + * it should be added at mount time. Do it here instead so that + * the individual filesystems don't need to worry about adding + * this key at mount time and cleaning up on mount failure. + */ + if (dummy_policy && + fscrypt_policies_equal(dummy_policy, &ci->ci_policy)) { + err = fscrypt_add_test_dummy_key(sb, &mk_spec); + if (err) + return err; + mk = fscrypt_find_master_key(sb, &mk_spec); + } + } + if (unlikely(!mk)) { + if (ci->ci_policy.version != FSCRYPT_POLICY_V1) + return -ENOKEY; + + /* + * As a legacy fallback for v1 policies, search for the key in + * the current task's subscribed keyrings too. Don't move this + * to before the search of ->s_master_keys, since users + * shouldn't be able to override filesystem-level keys. + */ + return fscrypt_setup_v1_file_key_via_subscribed_keyrings(ci); + } + down_read(&mk->mk_sem); + + /* Has the secret been removed (via FS_IOC_REMOVE_ENCRYPTION_KEY)? */ + if (!is_master_key_secret_present(&mk->mk_secret)) { + err = -ENOKEY; + goto out_release_key; + } + + if (!fscrypt_valid_master_key_size(mk, ci)) { + err = -ENOKEY; + goto out_release_key; + } + + switch (ci->ci_policy.version) { + case FSCRYPT_POLICY_V1: + err = fscrypt_setup_v1_file_key(ci, mk->mk_secret.raw); + break; + case FSCRYPT_POLICY_V2: + err = fscrypt_setup_v2_file_key(ci, mk, need_dirhash_key); + break; + default: + WARN_ON_ONCE(1); + err = -EINVAL; + break; + } + if (err) + goto out_release_key; + + *mk_ret = mk; + return 0; + +out_release_key: + up_read(&mk->mk_sem); + fscrypt_put_master_key(mk); + return err; +} + +static void put_crypt_info(struct fscrypt_info *ci) +{ + struct fscrypt_master_key *mk; + + if (!ci) + return; + + if (ci->ci_direct_key) + fscrypt_put_direct_key(ci->ci_direct_key); + else if (ci->ci_owns_key) + fscrypt_destroy_prepared_key(ci->ci_inode->i_sb, + &ci->ci_enc_key); + + mk = ci->ci_master_key; + if (mk) { + /* + * Remove this inode from the list of inodes that were unlocked + * with the master key. In addition, if we're removing the last + * inode from a master key struct that already had its secret + * removed, then complete the full removal of the struct. + */ + spin_lock(&mk->mk_decrypted_inodes_lock); + list_del(&ci->ci_master_key_link); + spin_unlock(&mk->mk_decrypted_inodes_lock); + fscrypt_put_master_key_activeref(ci->ci_inode->i_sb, mk); + } + memzero_explicit(ci, sizeof(*ci)); + kmem_cache_free(fscrypt_info_cachep, ci); +} + +static int +fscrypt_setup_encryption_info(struct inode *inode, + const union fscrypt_policy *policy, + const u8 nonce[FSCRYPT_FILE_NONCE_SIZE], + bool need_dirhash_key) +{ + struct fscrypt_info *crypt_info; + struct fscrypt_mode *mode; + struct fscrypt_master_key *mk = NULL; + int res; + + res = fscrypt_initialize(inode->i_sb); + if (res) + return res; + + crypt_info = kmem_cache_zalloc(fscrypt_info_cachep, GFP_KERNEL); + if (!crypt_info) + return -ENOMEM; + + crypt_info->ci_inode = inode; + crypt_info->ci_policy = *policy; + memcpy(crypt_info->ci_nonce, nonce, FSCRYPT_FILE_NONCE_SIZE); + + mode = select_encryption_mode(&crypt_info->ci_policy, inode); + if (IS_ERR(mode)) { + res = PTR_ERR(mode); + goto out; + } + WARN_ON_ONCE(mode->ivsize > FSCRYPT_MAX_IV_SIZE); + crypt_info->ci_mode = mode; + + res = setup_file_encryption_key(crypt_info, need_dirhash_key, &mk); + if (res) + goto out; + + /* + * For existing inodes, multiple tasks may race to set ->i_crypt_info. + * So use cmpxchg_release(). This pairs with the smp_load_acquire() in + * fscrypt_get_info(). I.e., here we publish ->i_crypt_info with a + * RELEASE barrier so that other tasks can ACQUIRE it. + */ + if (cmpxchg_release(&inode->i_crypt_info, NULL, crypt_info) == NULL) { + /* + * We won the race and set ->i_crypt_info to our crypt_info. + * Now link it into the master key's inode list. + */ + if (mk) { + crypt_info->ci_master_key = mk; + refcount_inc(&mk->mk_active_refs); + spin_lock(&mk->mk_decrypted_inodes_lock); + list_add(&crypt_info->ci_master_key_link, + &mk->mk_decrypted_inodes); + spin_unlock(&mk->mk_decrypted_inodes_lock); + } + crypt_info = NULL; + } + res = 0; +out: + if (mk) { + up_read(&mk->mk_sem); + fscrypt_put_master_key(mk); + } + put_crypt_info(crypt_info); + return res; +} + +/** + * fscrypt_get_encryption_info() - set up an inode's encryption key + * @inode: the inode to set up the key for. Must be encrypted. + * @allow_unsupported: if %true, treat an unsupported encryption policy (or + * unrecognized encryption context) the same way as the key + * being unavailable, instead of returning an error. Use + * %false unless the operation being performed is needed in + * order for files (or directories) to be deleted. + * + * Set up ->i_crypt_info, if it hasn't already been done. + * + * Note: unless ->i_crypt_info is already set, this isn't %GFP_NOFS-safe. So + * generally this shouldn't be called from within a filesystem transaction. + * + * Return: 0 if ->i_crypt_info was set or was already set, *or* if the + * encryption key is unavailable. (Use fscrypt_has_encryption_key() to + * distinguish these cases.) Also can return another -errno code. + */ +int fscrypt_get_encryption_info(struct inode *inode, bool allow_unsupported) +{ + int res; + union fscrypt_context ctx; + union fscrypt_policy policy; + + if (fscrypt_has_encryption_key(inode)) + return 0; + + res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); + if (res < 0) { + if (res == -ERANGE && allow_unsupported) + return 0; + fscrypt_warn(inode, "Error %d getting encryption context", res); + return res; + } + + res = fscrypt_policy_from_context(&policy, &ctx, res); + if (res) { + if (allow_unsupported) + return 0; + fscrypt_warn(inode, + "Unrecognized or corrupt encryption context"); + return res; + } + + if (!fscrypt_supported_policy(&policy, inode)) { + if (allow_unsupported) + return 0; + return -EINVAL; + } + + res = fscrypt_setup_encryption_info(inode, &policy, + fscrypt_context_nonce(&ctx), + IS_CASEFOLDED(inode) && + S_ISDIR(inode->i_mode)); + + if (res == -ENOPKG && allow_unsupported) /* Algorithm unavailable? */ + res = 0; + if (res == -ENOKEY) + res = 0; + return res; +} + +/** + * fscrypt_prepare_new_inode() - prepare to create a new inode in a directory + * @dir: a possibly-encrypted directory + * @inode: the new inode. ->i_mode must be set already. + * ->i_ino doesn't need to be set yet. + * @encrypt_ret: (output) set to %true if the new inode will be encrypted + * + * If the directory is encrypted, set up its ->i_crypt_info in preparation for + * encrypting the name of the new file. Also, if the new inode will be + * encrypted, set up its ->i_crypt_info and set *encrypt_ret=true. + * + * This isn't %GFP_NOFS-safe, and therefore it should be called before starting + * any filesystem transaction to create the inode. For this reason, ->i_ino + * isn't required to be set yet, as the filesystem may not have set it yet. + * + * This doesn't persist the new inode's encryption context. That still needs to + * be done later by calling fscrypt_set_context(). + * + * Return: 0 on success, -ENOKEY if the encryption key is missing, or another + * -errno code + */ +int fscrypt_prepare_new_inode(struct inode *dir, struct inode *inode, + bool *encrypt_ret) +{ + const union fscrypt_policy *policy; + u8 nonce[FSCRYPT_FILE_NONCE_SIZE]; + + policy = fscrypt_policy_to_inherit(dir); + if (policy == NULL) + return 0; + if (IS_ERR(policy)) + return PTR_ERR(policy); + + if (WARN_ON_ONCE(inode->i_mode == 0)) + return -EINVAL; + + /* + * Only regular files, directories, and symlinks are encrypted. + * Special files like device nodes and named pipes aren't. + */ + if (!S_ISREG(inode->i_mode) && + !S_ISDIR(inode->i_mode) && + !S_ISLNK(inode->i_mode)) + return 0; + + *encrypt_ret = true; + + get_random_bytes(nonce, FSCRYPT_FILE_NONCE_SIZE); + return fscrypt_setup_encryption_info(inode, policy, nonce, + IS_CASEFOLDED(dir) && + S_ISDIR(inode->i_mode)); +} +EXPORT_SYMBOL_GPL(fscrypt_prepare_new_inode); + +/** + * fscrypt_put_encryption_info() - free most of an inode's fscrypt data + * @inode: an inode being evicted + * + * Free the inode's fscrypt_info. Filesystems must call this when the inode is + * being evicted. An RCU grace period need not have elapsed yet. + */ +void fscrypt_put_encryption_info(struct inode *inode) +{ + put_crypt_info(inode->i_crypt_info); + inode->i_crypt_info = NULL; +} +EXPORT_SYMBOL(fscrypt_put_encryption_info); + +/** + * fscrypt_free_inode() - free an inode's fscrypt data requiring RCU delay + * @inode: an inode being freed + * + * Free the inode's cached decrypted symlink target, if any. Filesystems must + * call this after an RCU grace period, just before they free the inode. + */ +void fscrypt_free_inode(struct inode *inode) +{ + if (IS_ENCRYPTED(inode) && S_ISLNK(inode->i_mode)) { + kfree(inode->i_link); + inode->i_link = NULL; + } +} +EXPORT_SYMBOL(fscrypt_free_inode); + +/** + * fscrypt_drop_inode() - check whether the inode's master key has been removed + * @inode: an inode being considered for eviction + * + * Filesystems supporting fscrypt must call this from their ->drop_inode() + * method so that encrypted inodes are evicted as soon as they're no longer in + * use and their master key has been removed. + * + * Return: 1 if fscrypt wants the inode to be evicted now, otherwise 0 + */ +int fscrypt_drop_inode(struct inode *inode) +{ + const struct fscrypt_info *ci = fscrypt_get_info(inode); + + /* + * If ci is NULL, then the inode doesn't have an encryption key set up + * so it's irrelevant. If ci_master_key is NULL, then the master key + * was provided via the legacy mechanism of the process-subscribed + * keyrings, so we don't know whether it's been removed or not. + */ + if (!ci || !ci->ci_master_key) + return 0; + + /* + * With proper, non-racy use of FS_IOC_REMOVE_ENCRYPTION_KEY, all inodes + * protected by the key were cleaned by sync_filesystem(). But if + * userspace is still using the files, inodes can be dirtied between + * then and now. We mustn't lose any writes, so skip dirty inodes here. + */ + if (inode->i_state & I_DIRTY_ALL) + return 0; + + /* + * Note: since we aren't holding the key semaphore, the result here can + * immediately become outdated. But there's no correctness problem with + * unnecessarily evicting. Nor is there a correctness problem with not + * evicting while iput() is racing with the key being removed, since + * then the thread removing the key will either evict the inode itself + * or will correctly detect that it wasn't evicted due to the race. + */ + return !is_master_key_secret_present(&ci->ci_master_key->mk_secret); +} +EXPORT_SYMBOL_GPL(fscrypt_drop_inode); |