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 /* 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 __reserved[4];
     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(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();
 }
 
 /*
  * 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[1];
 } __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 fscrypt_blk_crypto_key *blk_key;
 #endif
 };
 
 /*
  * fscrypt_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_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 fscrypt_info is freed */
     bool ci_owns_key;
 
 #ifdef CONFIG_FS_ENCRYPTION_INLINE_CRYPT
     /*
      * True if this inode will use inline encryption (blk-crypto) instead of
      * the traditional filesystem-layer encryption.
      */
     bool ci_inlinecrypt;
 #endif
 
     /*
      * 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 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;
     bool ci_dirhash_key_initialized;
 
     /* 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];
 
     /* Hashed inode number.  Only set for IV_INO_LBLK_32 */
     u32 ci_hashed_ino;
 };
 
 typedef enum {
     FS_DECRYPT = 0,
     FS_ENCRYPT,
 } fscrypt_direction_t;
 
 /* crypto.c */
 extern struct kmem_cache *fscrypt_info_cachep;
 int fscrypt_initialize(unsigned int cop_flags);
 int fscrypt_crypt_block(const struct inode *inode, fscrypt_direction_t rw,
             u64 lblk_num, 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 {
         /* logical block number within the file */
         __le64 lblk_num;
 
         /* 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 lblk_num,
              const struct fscrypt_info *ci);
 
 /* 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_info *ci);
 
 static inline bool
 fscrypt_using_inline_encryption(const struct fscrypt_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_info *ci);
 
 void fscrypt_destroy_inline_crypt_key(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_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_info *ci)
 {
     return 0;
 }
 
 static inline bool
 fscrypt_using_inline_encryption(const struct fscrypt_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_info *ci)
 {
     WARN_ON(1);
     return -EOPNOTSUPP;
 }
 
 static inline void
 fscrypt_destroy_inline_crypt_key(struct fscrypt_prepared_key *prep_key)
 {
 }
 
 static inline bool
 fscrypt_is_key_prepared(struct fscrypt_prepared_key *prep_key,
             const struct fscrypt_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 and can be used to "unlock" the encrypted files which were
  * encrypted with it.
  */
 struct fscrypt_master_key {
 
     /*
      * The secret key material.  After FS_IOC_REMOVE_ENCRYPTION_KEY is
      * executed, this is wiped and no new inodes can be unlocked with this
      * key; however, there may still be inodes in ->mk_decrypted_inodes
      * which could not be evicted.  As long as some inodes still remain,
      * FS_IOC_REMOVE_ENCRYPTION_KEY can be retried, or
      * FS_IOC_ADD_ENCRYPTION_KEY can add the secret again.
      *
      * Locking: protected by this master key's key->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: in addition to this keyring's own semaphore, this is
      * protected by this master key's key->sem, so we can do atomic
      * search+insert.  It can also be searched without taking any locks, but
      * in that case the returned key may have already been removed.
      */
     struct key      *mk_users;
 
     /*
      * Length of ->mk_decrypted_inodes, plus one if mk_secret is present.
      * Once this goes to 0, the master key is removed from ->s_master_keys.
      * The 'struct fscrypt_master_key' will continue to live as long as the
      * 'struct key' whose payload it is, but we won't let this reference
      * count rise again.
      */
     refcount_t      mk_refcount;
 
     /*
      * 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;
 
 } __randomize_layout;
 
 static inline bool
 is_master_key_secret_present(const struct fscrypt_master_key_secret *secret)
 {
     /*
      * The READ_ONCE() is only necessary for fscrypt_drop_inode() and
      * fscrypt_key_describe().  These run in atomic context, so they can't
      * take the key semaphore and thus 'secret' can change concurrently
      * which would be a data race.  But they only need to know whether the
      * secret *was* present at the time of check, so READ_ONCE() suffices.
      */
     return READ_ONCE(secret->size) != 0;
 }
 
 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;
 }
 
 struct 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_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_info *ci);
 
 void fscrypt_destroy_prepared_key(struct fscrypt_prepared_key *prep_key);
 
 int fscrypt_set_per_file_enc_key(struct fscrypt_info *ci, const u8 *raw_key);
 
 int fscrypt_derive_dirhash_key(struct fscrypt_info *ci,
                    const struct fscrypt_master_key *mk);
 
 void fscrypt_hash_inode_number(struct fscrypt_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_info *ci,
                   const u8 *raw_master_key);
 
 int fscrypt_setup_v1_file_key_via_subscribed_keyrings(struct fscrypt_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);
 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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