/* 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 #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_ADIANTUM 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 */ int fscrypt_fname_encrypt(const struct inode *inode, const struct qstr *iname, u8 *out, unsigned int olen); bool fscrypt_fname_encrypted_size(const union fscrypt_policy *policy, u32 orig_len, u32 max_len, u32 *encrypted_len_ret); extern const struct dentry_operations fscrypt_d_ops; /* 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. Set even if ->raw isn't set. */ 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 key->sem (outer) and mk_secret_sem (inner). * The reason for two locks is that key->sem also protects modifying * mk_users, which ranks it above the semaphore for the keyring key * type, which is in turn above page faults (via keyring_read). But * sometimes filesystems call fscrypt_get_encryption_info() from within * a transaction, which ranks it below page faults. So we need a * separate lock which protects mk_secret but not also mk_users. */ struct fscrypt_master_key_secret mk_secret; struct rw_semaphore mk_secret_sem; /* * 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 keyrings own semaphore, this is * protected by the 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 ->mk_secret_sem 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_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; int ivsize; int logged_impl_name; 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); /* 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); 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 */