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> 18fd2d1acfSEric Biggers #include <linux/fsverity.h> 19671e67b4SEric Biggers 20671e67b4SEric Biggers struct ahash_request; 21671e67b4SEric Biggers 22671e67b4SEric Biggers /* 23671e67b4SEric Biggers * Implementation limit: maximum depth of the Merkle tree. For now 8 is plenty; 24671e67b4SEric Biggers * it's enough for over U64_MAX bytes of data using SHA-256 and 4K blocks. 25671e67b4SEric Biggers */ 26671e67b4SEric Biggers #define FS_VERITY_MAX_LEVELS 8 27671e67b4SEric Biggers 28671e67b4SEric Biggers /* 29671e67b4SEric Biggers * Largest digest size among all hash algorithms supported by fs-verity. 30671e67b4SEric Biggers * Currently assumed to be <= size of fsverity_descriptor::root_hash. 31671e67b4SEric Biggers */ 32671e67b4SEric Biggers #define FS_VERITY_MAX_DIGEST_SIZE SHA256_DIGEST_SIZE 33671e67b4SEric Biggers 34671e67b4SEric Biggers /* A hash algorithm supported by fs-verity */ 35671e67b4SEric Biggers struct fsverity_hash_alg { 36671e67b4SEric Biggers struct crypto_ahash *tfm; /* hash tfm, allocated on demand */ 37671e67b4SEric Biggers const char *name; /* crypto API name, e.g. sha256 */ 38671e67b4SEric Biggers unsigned int digest_size; /* digest size in bytes, e.g. 32 for SHA-256 */ 39671e67b4SEric Biggers unsigned int block_size; /* block size in bytes, e.g. 64 for SHA-256 */ 40671e67b4SEric Biggers }; 41671e67b4SEric Biggers 42671e67b4SEric Biggers /* Merkle tree parameters: hash algorithm, initial hash state, and topology */ 43671e67b4SEric Biggers struct merkle_tree_params { 44671e67b4SEric Biggers const struct fsverity_hash_alg *hash_alg; /* the hash algorithm */ 45671e67b4SEric Biggers const u8 *hashstate; /* initial hash state or NULL */ 46671e67b4SEric Biggers unsigned int digest_size; /* same as hash_alg->digest_size */ 47671e67b4SEric Biggers unsigned int block_size; /* size of data and tree blocks */ 48671e67b4SEric Biggers unsigned int hashes_per_block; /* number of hashes per tree block */ 49671e67b4SEric Biggers unsigned int log_blocksize; /* log2(block_size) */ 50671e67b4SEric Biggers unsigned int log_arity; /* log2(hashes_per_block) */ 51671e67b4SEric Biggers unsigned int num_levels; /* number of levels in Merkle tree */ 52671e67b4SEric Biggers u64 tree_size; /* Merkle tree size in bytes */ 53671e67b4SEric Biggers 54671e67b4SEric Biggers /* 55671e67b4SEric Biggers * Starting block index for each tree level, ordered from leaf level (0) 56671e67b4SEric Biggers * to root level ('num_levels - 1') 57671e67b4SEric Biggers */ 58671e67b4SEric Biggers u64 level_start[FS_VERITY_MAX_LEVELS]; 59671e67b4SEric Biggers }; 60671e67b4SEric Biggers 61fd2d1acfSEric Biggers /** 62fd2d1acfSEric Biggers * fsverity_info - cached verity metadata for an inode 63fd2d1acfSEric Biggers * 64fd2d1acfSEric Biggers * When a verity file is first opened, an instance of this struct is allocated 65fd2d1acfSEric Biggers * and stored in ->i_verity_info; it remains until the inode is evicted. It 66fd2d1acfSEric Biggers * caches information about the Merkle tree that's needed to efficiently verify 67fd2d1acfSEric Biggers * data read from the file. It also caches the file measurement. The Merkle 68fd2d1acfSEric Biggers * tree pages themselves are not cached here, but the filesystem may cache them. 69fd2d1acfSEric Biggers */ 70fd2d1acfSEric Biggers struct fsverity_info { 71fd2d1acfSEric Biggers struct merkle_tree_params tree_params; 72fd2d1acfSEric Biggers u8 root_hash[FS_VERITY_MAX_DIGEST_SIZE]; 73fd2d1acfSEric Biggers u8 measurement[FS_VERITY_MAX_DIGEST_SIZE]; 74fd2d1acfSEric Biggers const struct inode *inode; 75fd2d1acfSEric Biggers }; 76fd2d1acfSEric Biggers 77fd2d1acfSEric Biggers /* 78fd2d1acfSEric Biggers * Merkle tree properties. The file measurement is the hash of this structure. 79fd2d1acfSEric Biggers */ 80fd2d1acfSEric Biggers struct fsverity_descriptor { 81fd2d1acfSEric Biggers __u8 version; /* must be 1 */ 82fd2d1acfSEric Biggers __u8 hash_algorithm; /* Merkle tree hash algorithm */ 83fd2d1acfSEric Biggers __u8 log_blocksize; /* log2 of size of data and tree blocks */ 84fd2d1acfSEric Biggers __u8 salt_size; /* size of salt in bytes; 0 if none */ 85fd2d1acfSEric Biggers __le32 sig_size; /* reserved, must be 0 */ 86fd2d1acfSEric Biggers __le64 data_size; /* size of file the Merkle tree is built over */ 87fd2d1acfSEric Biggers __u8 root_hash[64]; /* Merkle tree root hash */ 88fd2d1acfSEric Biggers __u8 salt[32]; /* salt prepended to each hashed block */ 89fd2d1acfSEric Biggers __u8 __reserved[144]; /* must be 0's */ 90fd2d1acfSEric Biggers }; 91fd2d1acfSEric Biggers 92fd2d1acfSEric Biggers /* Arbitrary limit to bound the kmalloc() size. Can be changed. */ 93fd2d1acfSEric Biggers #define FS_VERITY_MAX_DESCRIPTOR_SIZE 16384 94fd2d1acfSEric Biggers 95671e67b4SEric Biggers /* hash_algs.c */ 96671e67b4SEric Biggers 97671e67b4SEric Biggers extern struct fsverity_hash_alg fsverity_hash_algs[]; 98671e67b4SEric Biggers 99671e67b4SEric Biggers const struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode, 100671e67b4SEric Biggers unsigned int num); 101671e67b4SEric Biggers const u8 *fsverity_prepare_hash_state(const struct fsverity_hash_alg *alg, 102671e67b4SEric Biggers const u8 *salt, size_t salt_size); 103671e67b4SEric Biggers int fsverity_hash_page(const struct merkle_tree_params *params, 104671e67b4SEric Biggers const struct inode *inode, 105671e67b4SEric Biggers struct ahash_request *req, struct page *page, u8 *out); 106671e67b4SEric Biggers int fsverity_hash_buffer(const struct fsverity_hash_alg *alg, 107671e67b4SEric Biggers const void *data, size_t size, u8 *out); 108671e67b4SEric Biggers void __init fsverity_check_hash_algs(void); 109671e67b4SEric Biggers 110671e67b4SEric Biggers /* init.c */ 111671e67b4SEric Biggers 112671e67b4SEric Biggers extern void __printf(3, 4) __cold 113671e67b4SEric Biggers fsverity_msg(const struct inode *inode, const char *level, 114671e67b4SEric Biggers const char *fmt, ...); 115671e67b4SEric Biggers 116671e67b4SEric Biggers #define fsverity_warn(inode, fmt, ...) \ 117671e67b4SEric Biggers fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__) 118671e67b4SEric Biggers #define fsverity_err(inode, fmt, ...) \ 119671e67b4SEric Biggers fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__) 120671e67b4SEric Biggers 121fd2d1acfSEric Biggers /* open.c */ 122fd2d1acfSEric Biggers 123fd2d1acfSEric Biggers int fsverity_init_merkle_tree_params(struct merkle_tree_params *params, 124fd2d1acfSEric Biggers const struct inode *inode, 125fd2d1acfSEric Biggers unsigned int hash_algorithm, 126fd2d1acfSEric Biggers unsigned int log_blocksize, 127fd2d1acfSEric Biggers const u8 *salt, size_t salt_size); 128fd2d1acfSEric Biggers 129fd2d1acfSEric Biggers struct fsverity_info *fsverity_create_info(const struct inode *inode, 130fd2d1acfSEric Biggers const void *desc, size_t desc_size); 131fd2d1acfSEric Biggers 132fd2d1acfSEric Biggers void fsverity_set_info(struct inode *inode, struct fsverity_info *vi); 133fd2d1acfSEric Biggers 134fd2d1acfSEric Biggers void fsverity_free_info(struct fsverity_info *vi); 135fd2d1acfSEric Biggers 136fd2d1acfSEric Biggers int __init fsverity_init_info_cache(void); 137fd2d1acfSEric Biggers 138671e67b4SEric Biggers #endif /* _FSVERITY_PRIVATE_H */ 139