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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
#ifdef CONFIG_FS_VERITY_DEBUG
#define DEBUG
#endif
#define pr_fmt(fmt) "fs-verity: " fmt
#include <crypto/sha.h>
#include <linux/fs.h>
#include <uapi/linux/fsverity.h>
struct ahash_request;
/*
* 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
/*
* Largest digest size among all hash algorithms supported by fs-verity.
* Currently assumed to be <= size of fsverity_descriptor::root_hash.
*/
#define FS_VERITY_MAX_DIGEST_SIZE SHA256_DIGEST_SIZE
/* A hash algorithm supported by fs-verity */
struct fsverity_hash_alg {
struct crypto_ahash *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 */
};
/* 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 log_blocksize; /* log2(block_size) */
unsigned int log_arity; /* log2(hashes_per_block) */
unsigned int num_levels; /* number of levels in Merkle tree */
u64 tree_size; /* Merkle tree size in bytes */
/*
* Starting block index for each tree level, ordered from leaf level (0)
* to root level ('num_levels - 1')
*/
u64 level_start[FS_VERITY_MAX_LEVELS];
};
/* 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_page(const struct merkle_tree_params *params,
const struct inode *inode,
struct ahash_request *req, struct page *page, 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 */
extern 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__)
#endif /* _FSVERITY_PRIVATE_H */
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