/* SPDX-License-Identifier: GPL-2.0 */
/*
* fscrypt_private.h
*
* Copyright (C) 2015, Google, Inc.
*
* Originally written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar.
* Heavily modified since then.
*/
#ifndef _FSCRYPT_PRIVATE_H
#define _FSCRYPT_PRIVATE_H
#include <linux/fscrypt.h>
#include <linux/siphash.h>
#include <crypto/hash.h>
#include <linux/blk-crypto.h>
#define CONST_STRLEN(str) (sizeof(str) - 1)
#define FSCRYPT_FILE_NONCE_SIZE 16
/*
* Minimum size of an fscrypt master key. Note: a longer key will be required
* if ciphers with a 256-bit security strength are used. This is just the
* absolute minimum, which applies when only 128-bit encryption is used.
*/
#define FSCRYPT_MIN_KEY_SIZE 16
#define FSCRYPT_CONTEXT_V1 1
#define FSCRYPT_CONTEXT_V2 2
/* Keep this in sync with include/uapi/linux/fscrypt.h */
#define FSCRYPT_MODE_MAX FSCRYPT_MODE_AES_256_HCTR2
struct fscrypt_context_v1 {
u8 version; /* FSCRYPT_CONTEXT_V1 */
u8 contents_encryption_mode;
u8 filenames_encryption_mode;
u8 flags;
u8 master_key_descriptor[FSCRYPT_KEY_DESCRIPTOR_SIZE];
u8 nonce[FSCRYPT_FILE_NONCE_SIZE];
};
struct fscrypt_context_v2 {
u8 version; /* FSCRYPT_CONTEXT_V2 */
u8 contents_encryption_mode;
u8 filenames_encryption_mode;
u8 flags;
u8 log2_data_unit_size;
u8 __reserved[3];
u8 master_key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE];
u8 nonce[FSCRYPT_FILE_NONCE_SIZE];
};
/*
* fscrypt_context - the encryption context of an inode
*
* This is the on-disk equivalent of an fscrypt_policy, stored alongside each
* encrypted file usually in a hidden extended attribute. It contains the
* fields from the fscrypt_policy, in order to identify the encryption algorithm
* and key with which the file is encrypted. It also contains a nonce that was
* randomly generated by fscrypt itself; this is used as KDF input or as a tweak
* to cause different files to be encrypted differently.
*/
union fscrypt_context {
u8 version;
struct fscrypt_context_v1 v1;
struct fscrypt_context_v2 v2;
};
/*
* Return the size expected for the given fscrypt_context based on its version
* number, or 0 if the context version is unrecognized.
*/
static inline int fscrypt_context_size(const union fscrypt_context *ctx)
{
switch (ctx->version) {
case FSCRYPT_CONTEXT_V1:
BUILD_BUG_ON(sizeof(ctx->v1) != 28);
return sizeof(ctx->v1);
case FSCRYPT_CONTEXT_V2:
BUILD_BUG_ON(sizeof(ctx->v2) != 40);
return sizeof(ctx->v2);
}
return 0;
}
/* Check whether an fscrypt_context has a recognized version number and size */
static inline bool fscrypt_context_is_valid(const union fscrypt_context *ctx,
int ctx_size)
{
return ctx_size >= 1 && ctx_size == fscrypt_context_size(ctx);
}
/* Retrieve the context's nonce, assuming the context was already validated */
static inline const u8 *fscrypt_context_nonce(const union fscrypt_context *ctx)
{
switch (ctx->version) {
case FSCRYPT_CONTEXT_V1:
return ctx->v1.nonce;
case FSCRYPT_CONTEXT_V2:
return ctx->v2.nonce;
}
WARN_ON_ONCE(1);
return NULL;
}
union fscrypt_policy {
u8 version;
struct fscrypt_policy_v1 v1;
struct fscrypt_policy_v2 v2;
};
/*
* Return the size expected for the given fscrypt_policy based on its version
* number, or 0 if the policy version is unrecognized.
*/
static inline int fscrypt_policy_size(const union fscrypt_policy *policy)
{
switch (policy->version) {
case FSCRYPT_POLICY_V1:
return sizeof(policy->v1);
case FSCRYPT_POLICY_V2:
return sizeof(policy->v2);
}
return 0;
}
/* Return the contents encryption mode of a valid encryption policy */
static inline u8
fscrypt_policy_contents_mode(const union fscrypt_policy *policy)
{
switch (policy->version) {
case FSCRYPT_POLICY_V1:
return policy->v1.contents_encryption_mode;
case FSCRYPT_POLICY_V2:
return policy->v2.contents_encryption_mode;
}
BUG();
}
/* Return the filenames encryption mode of a valid encryption policy */
static inline u8
fscrypt_policy_fnames_mode(const union fscrypt_policy *policy)
{
switch (policy->version) {
case FSCRYPT_POLICY_V1:
return policy->v1.filenames_encryption_mode;
case FSCRYPT_POLICY_V2:
return policy->v2.filenames_encryption_mode;
}
BUG();
}
/* Return the flags (FSCRYPT_POLICY_FLAG*) of a valid encryption policy */
static inline u8
fscrypt_policy_flags(const union fscrypt_policy *policy)
{
switch (policy->version) {
case FSCRYPT_POLICY_V1:
return policy->v1.flags;
case FSCRYPT_POLICY_V2:
return policy->v2.flags;
}
BUG();
}
static inline int
fscrypt_policy_v2_du_bits(const struct fscrypt_policy_v2 *policy,
const struct inode *inode)
{
return policy->log2_data_unit_size ?: inode->i_blkbits;
}
static inline int
fscrypt_policy_du_bits(const union fscrypt_policy *policy,
const struct inode *inode)
{
switch (policy->version) {
case FSCRYPT_POLICY_V1:
return inode->i_blkbits;
case FSCRYPT_POLICY_V2:
return fscrypt_policy_v2_du_bits(&policy->v2, inode);
}
BUG();
}
/*
* For encrypted symlinks, the ciphertext length is stored at the beginning
* of the string in little-endian format.
*/
struct fscrypt_symlink_data {
__le16 len;
char encrypted_path[];
} __packed;
/**
* struct fscrypt_prepared_key - a key prepared for actual encryption/decryption
* @tfm: crypto API transform object
* @blk_key: key for blk-crypto
*
* Normally only one of the fields will be non-NULL.
*/
struct fscrypt_prepared_key {
struct crypto_skcipher *tfm;
#ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
struct blk_crypto_key *blk_key;
#endif
};
/*
* fscrypt_inode_info - the "encryption key" for an inode
*
* When an encrypted file's key is made available, an instance of this struct is
* allocated and stored in ->i_crypt_info. Once created, it remains until the
* inode is evicted.
*/
struct fscrypt_inode_info {
/* The key in a form prepared for actual encryption/decryption */
struct fscrypt_prepared_key ci_enc_key;
/* True if ci_enc_key should be freed when this struct is freed */
u8 ci_owns_key : 1;
#ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
/*
* True if this inode will use inline encryption (blk-crypto) instead of
* the traditional filesystem-layer encryption.
*/
u8 ci_inlinecrypt : 1;
#endif
/* True if ci_dirhash_key is initialized */
u8 ci_dirhash_key_initialized : 1;
/*
* log2 of the data unit size (granularity of contents encryption) of
* this file. This is computable from ci_policy and ci_inode but is
* cached here for efficiency. Only used for regular files.
*/
u8 ci_data_unit_bits;
/* Cached value: log2 of number of data units per FS block */
u8 ci_data_units_per_block_bits;
/* Hashed inode number. Only set for IV_INO_LBLK_32 */
u32 ci_hashed_ino;
/*
* Encryption mode used for this inode. It corresponds to either the
* contents or filenames encryption mode, depending on the inode type.
*/
struct fscrypt_mode *ci_mode;
/* Back-pointer to the inode */
struct inode *ci_inode;
/*
* The master key with which this inode was unlocked (decrypted). This
* will be NULL if the master key was found in a process-subscribed
* keyring rather than in the filesystem-level keyring.
*/
struct fscrypt_master_key *ci_master_key;
/*
* Link in list of inodes that were unlocked with the master key.
* Only used when ->ci_master_key is set.
*/
struct list_head ci_master_key_link;
/*
* If non-NULL, then encryption is done using the master key directly
* and ci_enc_key will equal ci_direct_key->dk_key.
*/
struct fscrypt_direct_key *ci_direct_key;
/*
* This inode's hash key for filenames. This is a 128-bit SipHash-2-4
* key. This is only set for directories that use a keyed dirhash over
* the plaintext filenames -- currently just casefolded directories.
*/
siphash_key_t ci_dirhash_key;
/* The encryption policy used by this inode */
union fscrypt_policy ci_policy;
/* This inode's nonce, copied from the fscrypt_context */
u8 ci_nonce[FSCRYPT_FILE_NONCE_SIZE];
};
typedef enum {
FS_DECRYPT = 0,
FS_ENCRYPT,
} fscrypt_direction_t;
/* crypto.c */
extern struct kmem_cache *fscrypt_inode_info_cachep;
int fscrypt_initialize(struct super_block *sb);
int fscrypt_crypt_data_unit(const struct fscrypt_inode_info *ci,
fscrypt_direction_t rw, u64 index,
struct page *src_page, struct page *dest_page,
unsigned int len, unsigned int offs,
gfp_t gfp_flags);
struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags);
void __printf(3, 4) __cold
fscrypt_msg(const struct inode *inode, const char *level, const char *fmt, ...);
#define fscrypt_warn(inode, fmt, ...) \
fscrypt_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
#define fscrypt_err(inode, fmt, ...) \
fscrypt_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
#define FSCRYPT_MAX_IV_SIZE 32
union fscrypt_iv {
struct {
/* zero-based index of data unit within the file */
__le64 index;
/* per-file nonce; only set in DIRECT_KEY mode */
u8 nonce[FSCRYPT_FILE_NONCE_SIZE];
};
u8 raw[FSCRYPT_MAX_IV_SIZE];
__le64 dun[FSCRYPT_MAX_IV_SIZE / sizeof(__le64)];
};
void fscrypt_generate_iv(union fscrypt_iv *iv, u64 index,
const struct fscrypt_inode_info *ci);
/*
* Return the number of bits used by the maximum file data unit index that is
* possible on the given filesystem, using the given log2 data unit size.
*/
static inline int
fscrypt_max_file_dun_bits(const struct super_block *sb, int du_bits)
{
return fls64(sb->s_maxbytes - 1) - du_bits;
}
/* fname.c */
bool __fscrypt_fname_encrypted_size(const union fscrypt_policy *policy,
u32 orig_len, u32 max_len,
u32 *encrypted_len_ret);
/* hkdf.c */
struct fscrypt_hkdf {
struct crypto_shash *hmac_tfm;
};
int fscrypt_init_hkdf(struct fscrypt_hkdf *hkdf, const u8 *master_key,
unsigned int master_key_size);
/*
* The list of contexts in which fscrypt uses HKDF. These values are used as
* the first byte of the HKDF application-specific info string to guarantee that
* info strings are never repeated between contexts. This ensures that all HKDF
* outputs are unique and cryptographically isolated, i.e. knowledge of one
* output doesn't reveal another.
*/
#define HKDF_CONTEXT_KEY_IDENTIFIER 1 /* info=<empty> */
#define HKDF_CONTEXT_PER_FILE_ENC_KEY 2 /* info=file_nonce */
#define HKDF_CONTEXT_DIRECT_KEY 3 /* info=mode_num */
#define HKDF_CONTEXT_IV_INO_LBLK_64_KEY 4 /* info=mode_num||fs_uuid */
#define HKDF_CONTEXT_DIRHASH_KEY 5 /* info=file_nonce */
#define HKDF_CONTEXT_IV_INO_LBLK_32_KEY 6 /* info=mode_num||fs_uuid */
#define HKDF_CONTEXT_INODE_HASH_KEY 7 /* info=<empty> */
int fscrypt_hkdf_expand(const struct fscrypt_hkdf *hkdf, u8 context,
const u8 *info, unsigned int infolen,
u8 *okm, unsigned int okmlen);
void fscrypt_destroy_hkdf(struct fscrypt_hkdf *hkdf);
/* inline_crypt.c */
#ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
int fscrypt_select_encryption_impl(struct fscrypt_inode_info *ci);
static inline bool
fscrypt_using_inline_encryption(const struct fscrypt_inode_info *ci)
{
return ci->ci_inlinecrypt;
}
int fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,
const u8 *raw_key,
const struct fscrypt_inode_info *ci);
void fscrypt_destroy_inline_crypt_key(struct super_block *sb,
struct fscrypt_prepared_key *prep_key);
/*
* Check whether the crypto transform or blk-crypto key has been allocated in
* @prep_key, depending on which encryption implementation the file will use.
*/
static inline bool
fscrypt_is_key_prepared(struct fscrypt_prepared_key *prep_key,
const struct fscrypt_inode_info *ci)
{
/*
* The two smp_load_acquire()'s here pair with the smp_store_release()'s
* in fscrypt_prepare_inline_crypt_key() and fscrypt_prepare_key().
* I.e., in some cases (namely, if this prep_key is a per-mode
* encryption key) another task can publish blk_key or tfm concurrently,
* executing a RELEASE barrier. We need to use smp_load_acquire() here
* to safely ACQUIRE the memory the other task published.
*/
if (fscrypt_using_inline_encryption(ci))
return smp_load_acquire(&prep_key->blk_key) != NULL;
return smp_load_acquire(&prep_key->tfm) != NULL;
}
#else /* CONFIG_FS_ENCRYPTION_INLINE_CRYPT */
static inline int fscrypt_select_encryption_impl(struct fscrypt_inode_info *ci)
{
return 0;
}
static inline bool
fscrypt_using_inline_encryption(const struct fscrypt_inode_info *ci)
{
return false;
}
static inline int
fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key,
const u8 *raw_key,
const struct fscrypt_inode_info *ci)
{
WARN_ON_ONCE(1);
return -EOPNOTSUPP;
}
static inline void
fscrypt_destroy_inline_crypt_key(struct super_block *sb,
struct fscrypt_prepared_key *prep_key)
{
}
static inline bool
fscrypt_is_key_prepared(struct fscrypt_prepared_key *prep_key,
const struct fscrypt_inode_info *ci)
{
return smp_load_acquire(&prep_key->tfm) != NULL;
}
#endif /* !CONFIG_FS_ENCRYPTION_INLINE_CRYPT */
/* keyring.c */
/*
* fscrypt_master_key_secret - secret key material of an in-use master key
*/
struct fscrypt_master_key_secret {
/*
* For v2 policy keys: HKDF context keyed by this master key.
* For v1 policy keys: not set (hkdf.hmac_tfm == NULL).
*/
struct fscrypt_hkdf hkdf;
/*
* Size of the raw key in bytes. This remains set even if ->raw was
* zeroized due to no longer being needed. I.e. we still remember the
* size of the key even if we don't need to remember the key itself.
*/
u32 size;
/* For v1 policy keys: the raw key. Wiped for v2 policy keys. */
u8 raw[FSCRYPT_MAX_KEY_SIZE];
} __randomize_layout;
/*
* fscrypt_master_key - an in-use master key
*
* This represents a master encryption key which has been added to the
* filesystem. There are three high-level states that a key can be in:
*
* FSCRYPT_KEY_STATUS_PRESENT
* Key is fully usable; it can be used to unlock inodes that are encrypted
* with it (this includes being able to create new inodes). ->mk_present
* indicates whether the key is in this state. ->mk_secret exists, the key
* is in the keyring, and ->mk_active_refs > 0 due to ->mk_present.
*
* FSCRYPT_KEY_STATUS_INCOMPLETELY_REMOVED
* Removal of this key has been initiated, but some inodes that were
* unlocked with it are still in-use. Like ABSENT, ->mk_secret is wiped,
* and the key can no longer be used to unlock inodes. Unlike ABSENT, the
* key is still in the keyring; ->mk_decrypted_inodes is nonempty; and
* ->mk_active_refs > 0, being equal to the size of ->mk_decrypted_inodes.
*
* This state transitions to ABSENT if ->mk_decrypted_inodes becomes empty,
* or to PRESENT if FS_IOC_ADD_ENCRYPTION_KEY is called again for this key.
*
* FSCRYPT_KEY_STATUS_ABSENT
* Key is fully removed. The key is no longer in the keyring,
* ->mk_decrypted_inodes is empty, ->mk_active_refs == 0, ->mk_secret is
* wiped, and the key can no longer be used to unlock inodes.
*/
struct fscrypt_master_key {
/*
* Link in ->s_master_keys->key_hashtable.
* Only valid if ->mk_active_refs > 0.
*/
struct hlist_node mk_node;
/* Semaphore that protects ->mk_secret, ->mk_users, and ->mk_present */
struct rw_semaphore mk_sem;
/*
* Active and structural reference counts. An active ref guarantees
* that the struct continues to exist, continues to be in the keyring
* ->s_master_keys, and that any embedded subkeys (e.g.
* ->mk_direct_keys) that have been prepared continue to exist.
* A structural ref only guarantees that the struct continues to exist.
*
* There is one active ref associated with ->mk_present being true, and
* one active ref for each inode in ->mk_decrypted_inodes.
*
* There is one structural ref associated with the active refcount being
* nonzero. Finding a key in the keyring also takes a structural ref,
* which is then held temporarily while the key is operated on.
*/
refcount_t mk_active_refs;
refcount_t mk_struct_refs;
struct rcu_head mk_rcu_head;
/*
* The secret key material. Wiped as soon as it is no longer needed;
* for details, see the fscrypt_master_key struct comment.
*
* Locking: protected by ->mk_sem.
*/
struct fscrypt_master_key_secret mk_secret;
/*
* For v1 policy keys: an arbitrary key descriptor which was assigned by
* userspace (->descriptor).
*
* For v2 policy keys: a cryptographic hash of this key (->identifier).
*/
struct fscrypt_key_specifier mk_spec;
/*
* Keyring which contains a key of type 'key_type_fscrypt_user' for each
* user who has added this key. Normally each key will be added by just
* one user, but it's possible that multiple users share a key, and in
* that case we need to keep track of those users so that one user can't
* remove the key before the others want it removed too.
*
* This is NULL for v1 policy keys; those can only be added by root.
*
* Locking: protected by ->mk_sem. (We don't just rely on the keyrings
* subsystem semaphore ->mk_users->sem, as we need support for atomic
* search+insert along with proper synchronization with other fields.)
*/
struct key *mk_users;
/*
* List of inodes that were unlocked using this key. This allows the
* inodes to be evicted efficiently if the key is removed.
*/
struct list_head mk_decrypted_inodes;
spinlock_t mk_decrypted_inodes_lock;
/*
* Per-mode encryption keys for the various types of encryption policies
* that use them. Allocated and derived on-demand.
*/
struct fscrypt_prepared_key mk_direct_keys[FSCRYPT_MODE_MAX + 1];
struct fscrypt_prepared_key mk_iv_ino_lblk_64_keys[FSCRYPT_MODE_MAX + 1];
struct fscrypt_prepared_key mk_iv_ino_lblk_32_keys[FSCRYPT_MODE_MAX + 1];
/* Hash key for inode numbers. Initialized only when needed. */
siphash_key_t mk_ino_hash_key;
bool mk_ino_hash_key_initialized;
/*
* Whether this key is in the "present" state, i.e. fully usable. For
* details, see the fscrypt_master_key struct comment.
*
* Locking: protected by ->mk_sem, but can be read locklessly using
* READ_ONCE(). Writers must use WRITE_ONCE() when concurrent readers
* are possible.
*/
bool mk_present;
} __randomize_layout;
static inline const char *master_key_spec_type(
const struct fscrypt_key_specifier *spec)
{
switch (spec->type) {
case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
return "descriptor";
case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
return "identifier";
}
return "[unknown]";
}
static inline int master_key_spec_len(const struct fscrypt_key_specifier *spec)
{
switch (spec->type) {
case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR:
return FSCRYPT_KEY_DESCRIPTOR_SIZE;
case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER:
return FSCRYPT_KEY_IDENTIFIER_SIZE;
}
return 0;
}
void fscrypt_put_master_key(struct fscrypt_master_key *mk);
void fscrypt_put_master_key_activeref(struct super_block *sb,
struct fscrypt_master_key *mk);
struct fscrypt_master_key *
fscrypt_find_master_key(struct super_block *sb,
const struct fscrypt_key_specifier *mk_spec);
int fscrypt_get_test_dummy_key_identifier(
u8 key_identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]);
int fscrypt_add_test_dummy_key(struct super_block *sb,
struct fscrypt_key_specifier *key_spec);
int fscrypt_verify_key_added(struct super_block *sb,
const u8 identifier[FSCRYPT_KEY_IDENTIFIER_SIZE]);
int __init fscrypt_init_keyring(void);
/* keysetup.c */
struct fscrypt_mode {
const char *friendly_name;
const char *cipher_str;
int keysize; /* key size in bytes */
int security_strength; /* security strength in bytes */
int ivsize; /* IV size in bytes */
int logged_cryptoapi_impl;
int logged_blk_crypto_native;
int logged_blk_crypto_fallback;
enum blk_crypto_mode_num blk_crypto_mode;
};
extern struct fscrypt_mode fscrypt_modes[];
int fscrypt_prepare_key(struct fscrypt_prepared_key *prep_key,
const u8 *raw_key, const struct fscrypt_inode_info *ci);
void fscrypt_destroy_prepared_key(struct super_block *sb,
struct fscrypt_prepared_key *prep_key);
int fscrypt_set_per_file_enc_key(struct fscrypt_inode_info *ci,
const u8 *raw_key);
int fscrypt_derive_dirhash_key(struct fscrypt_inode_info *ci,
const struct fscrypt_master_key *mk);
void fscrypt_hash_inode_number(struct fscrypt_inode_info *ci,
const struct fscrypt_master_key *mk);
int fscrypt_get_encryption_info(struct inode *inode, bool allow_unsupported);
/**
* fscrypt_require_key() - require an inode's encryption key
* @inode: the inode we need the key for
*
* If the inode is encrypted, set up its encryption key if not already done.
* Then require that the key be present and return -ENOKEY otherwise.
*
* No locks are needed, and the key will live as long as the struct inode --- so
* it won't go away from under you.
*
* Return: 0 on success, -ENOKEY if the key is missing, or another -errno code
* if a problem occurred while setting up the encryption key.
*/
static inline int fscrypt_require_key(struct inode *inode)
{
if (IS_ENCRYPTED(inode)) {
int err = fscrypt_get_encryption_info(inode, false);
if (err)
return err;
if (!fscrypt_has_encryption_key(inode))
return -ENOKEY;
}
return 0;
}
/* keysetup_v1.c */
void fscrypt_put_direct_key(struct fscrypt_direct_key *dk);
int fscrypt_setup_v1_file_key(struct fscrypt_inode_info *ci,
const u8 *raw_master_key);
int fscrypt_setup_v1_file_key_via_subscribed_keyrings(
struct fscrypt_inode_info *ci);
/* policy.c */
bool fscrypt_policies_equal(const union fscrypt_policy *policy1,
const union fscrypt_policy *policy2);
int fscrypt_policy_to_key_spec(const union fscrypt_policy *policy,
struct fscrypt_key_specifier *key_spec);
const union fscrypt_policy *fscrypt_get_dummy_policy(struct super_block *sb);
bool fscrypt_supported_policy(const union fscrypt_policy *policy_u,
const struct inode *inode);
int fscrypt_policy_from_context(union fscrypt_policy *policy_u,
const union fscrypt_context *ctx_u,
int ctx_size);
const union fscrypt_policy *fscrypt_policy_to_inherit(struct inode *dir);
#endif /* _FSCRYPT_PRIVATE_H */
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