1671e67b4SEric Biggers /* SPDX-License-Identifier: GPL-2.0 */ 2671e67b4SEric Biggers /* 3671e67b4SEric Biggers * fs-verity: read-only file-based authenticity protection 4671e67b4SEric Biggers * 5671e67b4SEric Biggers * Copyright 2019 Google LLC 6671e67b4SEric Biggers */ 7671e67b4SEric Biggers 8671e67b4SEric Biggers #ifndef _FSVERITY_PRIVATE_H 9671e67b4SEric Biggers #define _FSVERITY_PRIVATE_H 10671e67b4SEric Biggers 11671e67b4SEric Biggers #ifdef CONFIG_FS_VERITY_DEBUG 12671e67b4SEric Biggers #define DEBUG 13671e67b4SEric Biggers #endif 14671e67b4SEric Biggers 15671e67b4SEric Biggers #define pr_fmt(fmt) "fs-verity: " fmt 16671e67b4SEric Biggers 17671e67b4SEric Biggers #include <crypto/sha.h> 18671e67b4SEric Biggers #include <linux/fs.h> 19671e67b4SEric Biggers #include <uapi/linux/fsverity.h> 20671e67b4SEric Biggers 21671e67b4SEric Biggers struct ahash_request; 22671e67b4SEric Biggers 23671e67b4SEric Biggers /* 24671e67b4SEric Biggers * Implementation limit: maximum depth of the Merkle tree. For now 8 is plenty; 25671e67b4SEric Biggers * it's enough for over U64_MAX bytes of data using SHA-256 and 4K blocks. 26671e67b4SEric Biggers */ 27671e67b4SEric Biggers #define FS_VERITY_MAX_LEVELS 8 28671e67b4SEric Biggers 29671e67b4SEric Biggers /* 30671e67b4SEric Biggers * Largest digest size among all hash algorithms supported by fs-verity. 31671e67b4SEric Biggers * Currently assumed to be <= size of fsverity_descriptor::root_hash. 32671e67b4SEric Biggers */ 33671e67b4SEric Biggers #define FS_VERITY_MAX_DIGEST_SIZE SHA256_DIGEST_SIZE 34671e67b4SEric Biggers 35671e67b4SEric Biggers /* A hash algorithm supported by fs-verity */ 36671e67b4SEric Biggers struct fsverity_hash_alg { 37671e67b4SEric Biggers struct crypto_ahash *tfm; /* hash tfm, allocated on demand */ 38671e67b4SEric Biggers const char *name; /* crypto API name, e.g. sha256 */ 39671e67b4SEric Biggers unsigned int digest_size; /* digest size in bytes, e.g. 32 for SHA-256 */ 40671e67b4SEric Biggers unsigned int block_size; /* block size in bytes, e.g. 64 for SHA-256 */ 41671e67b4SEric Biggers }; 42671e67b4SEric Biggers 43671e67b4SEric Biggers /* Merkle tree parameters: hash algorithm, initial hash state, and topology */ 44671e67b4SEric Biggers struct merkle_tree_params { 45671e67b4SEric Biggers const struct fsverity_hash_alg *hash_alg; /* the hash algorithm */ 46671e67b4SEric Biggers const u8 *hashstate; /* initial hash state or NULL */ 47671e67b4SEric Biggers unsigned int digest_size; /* same as hash_alg->digest_size */ 48671e67b4SEric Biggers unsigned int block_size; /* size of data and tree blocks */ 49671e67b4SEric Biggers unsigned int hashes_per_block; /* number of hashes per tree block */ 50671e67b4SEric Biggers unsigned int log_blocksize; /* log2(block_size) */ 51671e67b4SEric Biggers unsigned int log_arity; /* log2(hashes_per_block) */ 52671e67b4SEric Biggers unsigned int num_levels; /* number of levels in Merkle tree */ 53671e67b4SEric Biggers u64 tree_size; /* Merkle tree size in bytes */ 54671e67b4SEric Biggers 55671e67b4SEric Biggers /* 56671e67b4SEric Biggers * Starting block index for each tree level, ordered from leaf level (0) 57671e67b4SEric Biggers * to root level ('num_levels - 1') 58671e67b4SEric Biggers */ 59671e67b4SEric Biggers u64 level_start[FS_VERITY_MAX_LEVELS]; 60671e67b4SEric Biggers }; 61671e67b4SEric Biggers 62671e67b4SEric Biggers /* hash_algs.c */ 63671e67b4SEric Biggers 64671e67b4SEric Biggers extern struct fsverity_hash_alg fsverity_hash_algs[]; 65671e67b4SEric Biggers 66671e67b4SEric Biggers const struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode, 67671e67b4SEric Biggers unsigned int num); 68671e67b4SEric Biggers const u8 *fsverity_prepare_hash_state(const struct fsverity_hash_alg *alg, 69671e67b4SEric Biggers const u8 *salt, size_t salt_size); 70671e67b4SEric Biggers int fsverity_hash_page(const struct merkle_tree_params *params, 71671e67b4SEric Biggers const struct inode *inode, 72671e67b4SEric Biggers struct ahash_request *req, struct page *page, u8 *out); 73671e67b4SEric Biggers int fsverity_hash_buffer(const struct fsverity_hash_alg *alg, 74671e67b4SEric Biggers const void *data, size_t size, u8 *out); 75671e67b4SEric Biggers void __init fsverity_check_hash_algs(void); 76671e67b4SEric Biggers 77671e67b4SEric Biggers /* init.c */ 78671e67b4SEric Biggers 79671e67b4SEric Biggers extern void __printf(3, 4) __cold 80671e67b4SEric Biggers fsverity_msg(const struct inode *inode, const char *level, 81671e67b4SEric Biggers const char *fmt, ...); 82671e67b4SEric Biggers 83671e67b4SEric Biggers #define fsverity_warn(inode, fmt, ...) \ 84671e67b4SEric Biggers fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__) 85671e67b4SEric Biggers #define fsverity_err(inode, fmt, ...) \ 86671e67b4SEric Biggers fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__) 87671e67b4SEric Biggers 88671e67b4SEric Biggers #endif /* _FSVERITY_PRIVATE_H */ 89