1/* SPDX-License-Identifier: GPL-2.0 */ 2/* 3 * fs-verity: read-only file-based authenticity protection 4 * 5 * Copyright 2019 Google LLC 6 */ 7 8#ifndef _FSVERITY_PRIVATE_H 9#define _FSVERITY_PRIVATE_H 10 11#define pr_fmt(fmt) "fs-verity: " fmt 12 13#include <linux/fsverity.h> 14 15/* 16 * Implementation limit: maximum depth of the Merkle tree. For now 8 is plenty; 17 * it's enough for over U64_MAX bytes of data using SHA-256 and 4K blocks. 18 */ 19#define FS_VERITY_MAX_LEVELS 8 20 21/* A hash algorithm supported by fs-verity */ 22struct fsverity_hash_alg { 23 struct crypto_shash *tfm; /* hash tfm, allocated on demand */ 24 const char *name; /* crypto API name, e.g. sha256 */ 25 unsigned int digest_size; /* digest size in bytes, e.g. 32 for SHA-256 */ 26 unsigned int block_size; /* block size in bytes, e.g. 64 for SHA-256 */ 27 /* 28 * The HASH_ALGO_* constant for this algorithm. This is different from 29 * FS_VERITY_HASH_ALG_*, which uses a different numbering scheme. 30 */ 31 enum hash_algo algo_id; 32}; 33 34/* Merkle tree parameters: hash algorithm, initial hash state, and topology */ 35struct merkle_tree_params { 36 const struct fsverity_hash_alg *hash_alg; /* the hash algorithm */ 37 const u8 *hashstate; /* initial hash state or NULL */ 38 unsigned int digest_size; /* same as hash_alg->digest_size */ 39 unsigned int block_size; /* size of data and tree blocks */ 40 unsigned int hashes_per_block; /* number of hashes per tree block */ 41 unsigned int blocks_per_page; /* PAGE_SIZE / block_size */ 42 u8 log_digestsize; /* log2(digest_size) */ 43 u8 log_blocksize; /* log2(block_size) */ 44 u8 log_arity; /* log2(hashes_per_block) */ 45 u8 log_blocks_per_page; /* log2(blocks_per_page) */ 46 unsigned int num_levels; /* number of levels in Merkle tree */ 47 u64 tree_size; /* Merkle tree size in bytes */ 48 unsigned long tree_pages; /* Merkle tree size in pages */ 49 50 /* 51 * Starting block index for each tree level, ordered from leaf level (0) 52 * to root level ('num_levels - 1') 53 */ 54 unsigned long level_start[FS_VERITY_MAX_LEVELS]; 55}; 56 57/* 58 * fsverity_info - cached verity metadata for an inode 59 * 60 * When a verity file is first opened, an instance of this struct is allocated 61 * and stored in ->i_verity_info; it remains until the inode is evicted. It 62 * caches information about the Merkle tree that's needed to efficiently verify 63 * data read from the file. It also caches the file digest. The Merkle tree 64 * pages themselves are not cached here, but the filesystem may cache them. 65 */ 66struct fsverity_info { 67 struct merkle_tree_params tree_params; 68 u8 root_hash[FS_VERITY_MAX_DIGEST_SIZE]; 69 u8 file_digest[FS_VERITY_MAX_DIGEST_SIZE]; 70 const struct inode *inode; 71 unsigned long *hash_block_verified; 72}; 73 74#define FS_VERITY_MAX_SIGNATURE_SIZE (FS_VERITY_MAX_DESCRIPTOR_SIZE - \ 75 sizeof(struct fsverity_descriptor)) 76 77/* hash_algs.c */ 78 79extern struct fsverity_hash_alg fsverity_hash_algs[]; 80 81const struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode, 82 unsigned int num); 83const u8 *fsverity_prepare_hash_state(const struct fsverity_hash_alg *alg, 84 const u8 *salt, size_t salt_size); 85int fsverity_hash_block(const struct merkle_tree_params *params, 86 const struct inode *inode, const void *data, u8 *out); 87int fsverity_hash_buffer(const struct fsverity_hash_alg *alg, 88 const void *data, size_t size, u8 *out); 89void __init fsverity_check_hash_algs(void); 90 91/* init.c */ 92 93void __printf(3, 4) __cold 94fsverity_msg(const struct inode *inode, const char *level, 95 const char *fmt, ...); 96 97#define fsverity_warn(inode, fmt, ...) \ 98 fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__) 99#define fsverity_err(inode, fmt, ...) \ 100 fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__) 101 102/* measure.c */ 103 104#ifdef CONFIG_BPF_SYSCALL 105void __init fsverity_init_bpf(void); 106#else 107static inline void fsverity_init_bpf(void) 108{ 109} 110#endif 111 112/* open.c */ 113 114int fsverity_init_merkle_tree_params(struct merkle_tree_params *params, 115 const struct inode *inode, 116 unsigned int hash_algorithm, 117 unsigned int log_blocksize, 118 const u8 *salt, size_t salt_size); 119 120struct fsverity_info *fsverity_create_info(const struct inode *inode, 121 struct fsverity_descriptor *desc); 122 123void fsverity_set_info(struct inode *inode, struct fsverity_info *vi); 124 125void fsverity_free_info(struct fsverity_info *vi); 126 127int fsverity_get_descriptor(struct inode *inode, 128 struct fsverity_descriptor **desc_ret); 129 130void __init fsverity_init_info_cache(void); 131 132/* signature.c */ 133 134#ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES 135extern int fsverity_require_signatures; 136int fsverity_verify_signature(const struct fsverity_info *vi, 137 const u8 *signature, size_t sig_size); 138 139void __init fsverity_init_signature(void); 140#else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ 141static inline int 142fsverity_verify_signature(const struct fsverity_info *vi, 143 const u8 *signature, size_t sig_size) 144{ 145 return 0; 146} 147 148static inline void fsverity_init_signature(void) 149{ 150} 151#endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ 152 153/* verify.c */ 154 155void __init fsverity_init_workqueue(void); 156 157#endif /* _FSVERITY_PRIVATE_H */ 158