89 lines
2.9 KiB
C
89 lines
2.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* fs-verity: read-only file-based authenticity protection
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*
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* Copyright 2019 Google LLC
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*/
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#ifndef _FSVERITY_PRIVATE_H
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#define _FSVERITY_PRIVATE_H
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#ifdef CONFIG_FS_VERITY_DEBUG
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#define DEBUG
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#endif
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#define pr_fmt(fmt) "fs-verity: " fmt
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#include <crypto/sha.h>
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#include <linux/fs.h>
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#include <uapi/linux/fsverity.h>
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struct ahash_request;
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/*
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* Implementation limit: maximum depth of the Merkle tree. For now 8 is plenty;
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* it's enough for over U64_MAX bytes of data using SHA-256 and 4K blocks.
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*/
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#define FS_VERITY_MAX_LEVELS 8
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/*
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* Largest digest size among all hash algorithms supported by fs-verity.
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* Currently assumed to be <= size of fsverity_descriptor::root_hash.
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*/
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#define FS_VERITY_MAX_DIGEST_SIZE SHA256_DIGEST_SIZE
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/* A hash algorithm supported by fs-verity */
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struct fsverity_hash_alg {
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struct crypto_ahash *tfm; /* hash tfm, allocated on demand */
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const char *name; /* crypto API name, e.g. sha256 */
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unsigned int digest_size; /* digest size in bytes, e.g. 32 for SHA-256 */
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unsigned int block_size; /* block size in bytes, e.g. 64 for SHA-256 */
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};
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/* Merkle tree parameters: hash algorithm, initial hash state, and topology */
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struct merkle_tree_params {
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const struct fsverity_hash_alg *hash_alg; /* the hash algorithm */
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const u8 *hashstate; /* initial hash state or NULL */
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unsigned int digest_size; /* same as hash_alg->digest_size */
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unsigned int block_size; /* size of data and tree blocks */
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unsigned int hashes_per_block; /* number of hashes per tree block */
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unsigned int log_blocksize; /* log2(block_size) */
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unsigned int log_arity; /* log2(hashes_per_block) */
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unsigned int num_levels; /* number of levels in Merkle tree */
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u64 tree_size; /* Merkle tree size in bytes */
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/*
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* Starting block index for each tree level, ordered from leaf level (0)
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* to root level ('num_levels - 1')
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*/
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u64 level_start[FS_VERITY_MAX_LEVELS];
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};
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/* hash_algs.c */
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extern struct fsverity_hash_alg fsverity_hash_algs[];
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const struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode,
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unsigned int num);
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const u8 *fsverity_prepare_hash_state(const struct fsverity_hash_alg *alg,
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const u8 *salt, size_t salt_size);
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int fsverity_hash_page(const struct merkle_tree_params *params,
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const struct inode *inode,
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struct ahash_request *req, struct page *page, u8 *out);
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int fsverity_hash_buffer(const struct fsverity_hash_alg *alg,
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const void *data, size_t size, u8 *out);
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void __init fsverity_check_hash_algs(void);
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/* init.c */
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extern void __printf(3, 4) __cold
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fsverity_msg(const struct inode *inode, const char *level,
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const char *fmt, ...);
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#define fsverity_warn(inode, fmt, ...) \
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fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
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#define fsverity_err(inode, fmt, ...) \
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fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
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#endif /* _FSVERITY_PRIVATE_H */
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