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/* SPDX-License-Identifier: GPL-2.0 */
/*
* fs-verity: read-only file-based authenticity protection
*
* Copyright 2019 Google LLC
*/
#ifndef _FSVERITY_PRIVATE_H
#define _FSVERITY_PRIVATE_H
#define pr_fmt(fmt) "fs-verity: " fmt
#include <linux/fsverity.h>
/*
* Implementation limit: maximum depth of the Merkle tree. For now 8 is plenty;
* it's enough for over U64_MAX bytes of data using SHA-256 and 4K blocks.
*/
#define FS_VERITY_MAX_LEVELS 8
/* A hash algorithm supported by fs-verity */
struct fsverity_hash_alg {
struct crypto_shash *tfm; /* hash tfm, allocated on demand */
const char *name; /* crypto API name, e.g. sha256 */
unsigned int digest_size; /* digest size in bytes, e.g. 32 for SHA-256 */
unsigned int block_size; /* block size in bytes, e.g. 64 for SHA-256 */
/*
* The HASH_ALGO_* constant for this algorithm. This is different from
* FS_VERITY_HASH_ALG_*, which uses a different numbering scheme.
*/
enum hash_algo algo_id;
};
/* Merkle tree parameters: hash algorithm, initial hash state, and topology */
struct merkle_tree_params {
const struct fsverity_hash_alg *hash_alg; /* the hash algorithm */
const u8 *hashstate; /* initial hash state or NULL */
unsigned int digest_size; /* same as hash_alg->digest_size */
unsigned int block_size; /* size of data and tree blocks */
unsigned int hashes_per_block; /* number of hashes per tree block */
unsigned int blocks_per_page; /* PAGE_SIZE / block_size */
u8 log_digestsize; /* log2(digest_size) */
u8 log_blocksize; /* log2(block_size) */
u8 log_arity; /* log2(hashes_per_block) */
u8 log_blocks_per_page; /* log2(blocks_per_page) */
unsigned int num_levels; /* number of levels in Merkle tree */
u64 tree_size; /* Merkle tree size in bytes */
unsigned long tree_pages; /* Merkle tree size in pages */
/*
* Starting block index for each tree level, ordered from leaf level (0)
* to root level ('num_levels - 1')
*/
unsigned long level_start[FS_VERITY_MAX_LEVELS];
};
/*
* fsverity_info - cached verity metadata for an inode
*
* When a verity file is first opened, an instance of this struct is allocated
* and stored in ->i_verity_info; it remains until the inode is evicted. It
* caches information about the Merkle tree that's needed to efficiently verify
* data read from the file. It also caches the file digest. The Merkle tree
* pages themselves are not cached here, but the filesystem may cache them.
*/
struct fsverity_info {
struct merkle_tree_params tree_params;
u8 root_hash[FS_VERITY_MAX_DIGEST_SIZE];
u8 file_digest[FS_VERITY_MAX_DIGEST_SIZE];
const struct inode *inode;
unsigned long *hash_block_verified;
spinlock_t hash_page_init_lock;
};
#define FS_VERITY_MAX_SIGNATURE_SIZE (FS_VERITY_MAX_DESCRIPTOR_SIZE - \
sizeof(struct fsverity_descriptor))
/* hash_algs.c */
extern struct fsverity_hash_alg fsverity_hash_algs[];
const struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode,
unsigned int num);
const u8 *fsverity_prepare_hash_state(const struct fsverity_hash_alg *alg,
const u8 *salt, size_t salt_size);
int fsverity_hash_block(const struct merkle_tree_params *params,
const struct inode *inode, const void *data, u8 *out);
int fsverity_hash_buffer(const struct fsverity_hash_alg *alg,
const void *data, size_t size, u8 *out);
void __init fsverity_check_hash_algs(void);
/* init.c */
void __printf(3, 4) __cold
fsverity_msg(const struct inode *inode, const char *level,
const char *fmt, ...);
#define fsverity_warn(inode, fmt, ...) \
fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
#define fsverity_err(inode, fmt, ...) \
fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
/* open.c */
int fsverity_init_merkle_tree_params(struct merkle_tree_params *params,
const struct inode *inode,
unsigned int hash_algorithm,
unsigned int log_blocksize,
const u8 *salt, size_t salt_size);
struct fsverity_info *fsverity_create_info(const struct inode *inode,
struct fsverity_descriptor *desc);
void fsverity_set_info(struct inode *inode, struct fsverity_info *vi);
void fsverity_free_info(struct fsverity_info *vi);
int fsverity_get_descriptor(struct inode *inode,
struct fsverity_descriptor **desc_ret);
void __init fsverity_init_info_cache(void);
/* signature.c */
#ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
extern int fsverity_require_signatures;
int fsverity_verify_signature(const struct fsverity_info *vi,
const u8 *signature, size_t sig_size);
void __init fsverity_init_signature(void);
#else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
static inline int
fsverity_verify_signature(const struct fsverity_info *vi,
const u8 *signature, size_t sig_size)
{
return 0;
}
static inline void fsverity_init_signature(void)
{
}
#endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
/* verify.c */
void __init fsverity_init_workqueue(void);
#endif /* _FSVERITY_PRIVATE_H */
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