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 #ifdef CONFIG_FS_VERITY_DEBUG 12 #define DEBUG 13 #endif 14 15 #define pr_fmt(fmt) "fs-verity: " fmt 16 17 #include <linux/fsverity.h> 18 #include <linux/mempool.h> 19 20 struct ahash_request; 21 22 /* 23 * Implementation limit: maximum depth of the Merkle tree. For now 8 is plenty; 24 * it's enough for over U64_MAX bytes of data using SHA-256 and 4K blocks. 25 */ 26 #define FS_VERITY_MAX_LEVELS 8 27 28 /* A hash algorithm supported by fs-verity */ 29 struct fsverity_hash_alg { 30 struct crypto_ahash *tfm; /* hash tfm, allocated on demand */ 31 const char *name; /* crypto API name, e.g. sha256 */ 32 unsigned int digest_size; /* digest size in bytes, e.g. 32 for SHA-256 */ 33 unsigned int block_size; /* block size in bytes, e.g. 64 for SHA-256 */ 34 mempool_t req_pool; /* mempool with a preallocated hash request */ 35 /* 36 * The HASH_ALGO_* constant for this algorithm. This is different from 37 * FS_VERITY_HASH_ALG_*, which uses a different numbering scheme. 38 */ 39 enum hash_algo algo_id; 40 }; 41 42 /* Merkle tree parameters: hash algorithm, initial hash state, and topology */ 43 struct merkle_tree_params { 44 struct fsverity_hash_alg *hash_alg; /* the hash algorithm */ 45 const u8 *hashstate; /* initial hash state or NULL */ 46 unsigned int digest_size; /* same as hash_alg->digest_size */ 47 unsigned int block_size; /* size of data and tree blocks */ 48 unsigned int hashes_per_block; /* number of hashes per tree block */ 49 unsigned int log_blocksize; /* log2(block_size) */ 50 unsigned int log_arity; /* log2(hashes_per_block) */ 51 unsigned int num_levels; /* number of levels in Merkle tree */ 52 u64 tree_size; /* Merkle tree size in bytes */ 53 unsigned long level0_blocks; /* number of blocks in tree level 0 */ 54 55 /* 56 * Starting block index for each tree level, ordered from leaf level (0) 57 * to root level ('num_levels - 1') 58 */ 59 u64 level_start[FS_VERITY_MAX_LEVELS]; 60 }; 61 62 /* 63 * fsverity_info - cached verity metadata for an inode 64 * 65 * When a verity file is first opened, an instance of this struct is allocated 66 * and stored in ->i_verity_info; it remains until the inode is evicted. It 67 * caches information about the Merkle tree that's needed to efficiently verify 68 * data read from the file. It also caches the file digest. The Merkle tree 69 * pages themselves are not cached here, but the filesystem may cache them. 70 */ 71 struct fsverity_info { 72 struct merkle_tree_params tree_params; 73 u8 root_hash[FS_VERITY_MAX_DIGEST_SIZE]; 74 u8 file_digest[FS_VERITY_MAX_DIGEST_SIZE]; 75 const struct inode *inode; 76 }; 77 78 79 #define FS_VERITY_MAX_SIGNATURE_SIZE (FS_VERITY_MAX_DESCRIPTOR_SIZE - \ 80 sizeof(struct fsverity_descriptor)) 81 82 /* hash_algs.c */ 83 84 extern struct fsverity_hash_alg fsverity_hash_algs[]; 85 86 struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode, 87 unsigned int num); 88 struct ahash_request *fsverity_alloc_hash_request(struct fsverity_hash_alg *alg, 89 gfp_t gfp_flags); 90 void fsverity_free_hash_request(struct fsverity_hash_alg *alg, 91 struct ahash_request *req); 92 const u8 *fsverity_prepare_hash_state(struct fsverity_hash_alg *alg, 93 const u8 *salt, size_t salt_size); 94 int fsverity_hash_page(const struct merkle_tree_params *params, 95 const struct inode *inode, 96 struct ahash_request *req, struct page *page, u8 *out); 97 int fsverity_hash_buffer(struct fsverity_hash_alg *alg, 98 const void *data, size_t size, u8 *out); 99 void __init fsverity_check_hash_algs(void); 100 101 /* init.c */ 102 103 void __printf(3, 4) __cold 104 fsverity_msg(const struct inode *inode, const char *level, 105 const char *fmt, ...); 106 107 #define fsverity_warn(inode, fmt, ...) \ 108 fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__) 109 #define fsverity_err(inode, fmt, ...) \ 110 fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__) 111 112 /* open.c */ 113 114 int 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); 119 120 struct fsverity_info *fsverity_create_info(const struct inode *inode, 121 struct fsverity_descriptor *desc); 122 123 void fsverity_set_info(struct inode *inode, struct fsverity_info *vi); 124 125 void fsverity_free_info(struct fsverity_info *vi); 126 127 int fsverity_get_descriptor(struct inode *inode, 128 struct fsverity_descriptor **desc_ret); 129 130 int __init fsverity_init_info_cache(void); 131 void __init fsverity_exit_info_cache(void); 132 133 /* signature.c */ 134 135 #ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES 136 int fsverity_verify_signature(const struct fsverity_info *vi, 137 const u8 *signature, size_t sig_size); 138 139 int __init fsverity_init_signature(void); 140 #else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ 141 static inline int 142 fsverity_verify_signature(const struct fsverity_info *vi, 143 const u8 *signature, size_t sig_size) 144 { 145 return 0; 146 } 147 148 static inline int fsverity_init_signature(void) 149 { 150 return 0; 151 } 152 #endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ 153 154 /* verify.c */ 155 156 int __init fsverity_init_workqueue(void); 157 void __init fsverity_exit_workqueue(void); 158 159 #endif /* _FSVERITY_PRIVATE_H */ 160