kernel / fs / crypto / fscrypt_private.h

/* 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/minmax.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

/* Maximum size of a raw fscrypt master key */
#define FSCRYPT_MAX_RAW_KEY_SIZE	64

/* Maximum size of a hardware-wrapped fscrypt master key */
#define FSCRYPT_MAX_HW_WRAPPED_KEY_SIZE	BLK_CRYPTO_MAX_HW_WRAPPED_KEY_SIZE

/* Maximum size of an fscrypt master key across both key types */
#define FSCRYPT_MAX_ANY_KEY_SIZE \
	MAX(FSCRYPT_MAX_RAW_KEY_SIZE, FSCRYPT_MAX_HW_WRAPPED_KEY_SIZE)

/*
 * FSCRYPT_MAX_KEY_SIZE is defined in the UAPI header, but the addition of
 * hardware-wrapped keys has made it misleading as it's only for raw keys.
 * Don't use it in kernel code; use one of the above constants instead.
 */
#undef FSCRYPT_MAX_KEY_SIZE

/*
 * This mask is passed as the third argument to the crypto_alloc_*() functions
 * to prevent fscrypt from using the Crypto API drivers for non-inline crypto
 * engines.  Those drivers have been problematic for fscrypt.  fscrypt users
 * have reported hangs and even incorrect en/decryption with these drivers.
 * Since going to the driver, off CPU, and back again is really slow, such
 * drivers can be over 50 times slower than the CPU-based code for fscrypt's
 * workload.  Even on platforms that lack AES instructions on the CPU, using the
 * offloads has been shown to be slower, even staying with AES.  (Of course,
 * Adiantum is faster still, and is the recommended option on such platforms...)
 *
 * Note that fscrypt also supports inline crypto engines.  Those don't use the
 * Crypto API and work much better than the old-style (non-inline) engines.
 */
#define FSCRYPT_CRYPTOAPI_MASK                            \
	(CRYPTO_ALG_ASYNC | CRYPTO_ALG_ALLOCATES_MEMORY | \
	 CRYPTO_ALG_KERN_DRIVER_ONLY)

#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_sync_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);
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_FOR_RAW_KEY	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>		*/
#define HKDF_CONTEXT_KEY_IDENTIFIER_FOR_HW_WRAPPED_KEY \
					8 /* 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,
				   bool is_hw_wrapped_key);

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 *key_bytes, size_t key_size,
				     bool is_hw_wrapped,
				     const struct fscrypt_inode_info *ci);

void fscrypt_destroy_inline_crypt_key(struct super_block *sb,
				      struct fscrypt_prepared_key *prep_key);

int fscrypt_derive_sw_secret(struct super_block *sb,
			     const u8 *wrapped_key, size_t wrapped_key_size,
			     u8 sw_secret[BLK_CRYPTO_SW_SECRET_SIZE]);

/*
 * 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,
						 bool is_hw_wrapped_key)
{
	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 *key_bytes, size_t key_size,
				 bool is_hw_wrapped,
				 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 int
fscrypt_derive_sw_secret(struct super_block *sb,
			 const u8 *wrapped_key, size_t wrapped_key_size,
			 u8 sw_secret[BLK_CRYPTO_SW_SECRET_SIZE])
{
	fscrypt_warn(NULL, "kernel doesn't support hardware-wrapped keys");
	return -EOPNOTSUPP;
}

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 {

	/*
	 * The KDF with which subkeys of this key can be derived.
	 *
	 * For v1 policy keys, this isn't applicable and won't be set.
	 * Otherwise, this KDF will be keyed by this master key if
	 * ->is_hw_wrapped=false, or by the "software secret" that hardware
	 * derived from this master key if ->is_hw_wrapped=true.
	 */
	struct fscrypt_hkdf	hkdf;

	/*
	 * True if this key is a hardware-wrapped key; false if this key is a
	 * raw key (i.e. a "software key").  For v1 policy keys this will always
	 * be false, as v1 policy support is a legacy feature which doesn't
	 * support newer functionality such as hardware-wrapped keys.
	 */
	bool			is_hw_wrapped;

	/*
	 * Size of the key in bytes.  This remains set even if ->bytes 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;

	/*
	 * The bytes of the key, when still needed.  This can be either a raw
	 * key or a hardware-wrapped key, as indicated by ->is_hw_wrapped.  In
	 * the case of a raw, v2 policy key, there is no need to remember the
	 * actual key separately from ->hkdf so this field will be zeroized as
	 * soon as ->hkdf is initialized.
	 */
	u8			bytes[FSCRYPT_MAX_ANY_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 */