// 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-CBC-CTS",
.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-CBC-CTS",
.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-CBC-CTS",
.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_inode_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_inode_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_inode_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_inode_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_inode_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_inode_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_inode_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_inode_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_inode_info into ->mk_decrypted_inodes
* (as multiple tasks may race to create an fscrypt_inode_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_inode_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);
if (!mk->mk_present) {
/* FS_IOC_REMOVE_ENCRYPTION_KEY has been executed on this key */
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_inode_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 an incompletely removed key, then complete the
* full removal of the key.
*/
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_inode_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_inode_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_inode_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;
crypt_info->ci_data_unit_bits =
fscrypt_policy_du_bits(&crypt_info->ci_policy, inode);
crypt_info->ci_data_units_per_block_bits =
inode->i_blkbits - crypt_info->ci_data_unit_bits;
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_inode_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 and ->i_blkbits 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_blkbits == 0))
return -EINVAL;
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_inode_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_inode_info *ci = fscrypt_get_inode_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;
/*
* We can't take ->mk_sem here, since this runs in atomic context.
* Therefore, ->mk_present can change concurrently, and our result may
* 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 !READ_ONCE(ci->ci_master_key->mk_present);
}
EXPORT_SYMBOL_GPL(fscrypt_drop_inode);
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