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 #include <linux/mempool.h> 15 16 struct ahash_request; 17 18 /* 19 * Implementation limit: maximum depth of the Merkle tree. For now 8 is plenty; 20 * it's enough for over U64_MAX bytes of data using SHA-256 and 4K blocks. 21 */ 22 #define FS_VERITY_MAX_LEVELS 8 23 24 /* A hash algorithm supported by fs-verity */ 25 struct fsverity_hash_alg { 26 struct crypto_ahash *tfm; /* hash tfm, allocated on demand */ 27 const char *name; /* crypto API name, e.g. sha256 */ 28 unsigned int digest_size; /* digest size in bytes, e.g. 32 for SHA-256 */ 29 unsigned int block_size; /* block size in bytes, e.g. 64 for SHA-256 */ 30 mempool_t req_pool; /* mempool with a preallocated hash request */ 31 /* 32 * The HASH_ALGO_* constant for this algorithm. This is different from 33 * FS_VERITY_HASH_ALG_*, which uses a different numbering scheme. 34 */ 35 enum hash_algo algo_id; 36 }; 37 38 /* Merkle tree parameters: hash algorithm, initial hash state, and topology */ 39 struct merkle_tree_params { 40 struct fsverity_hash_alg *hash_alg; /* the hash algorithm */ 41 const u8 *hashstate; /* initial hash state or NULL */ 42 unsigned int digest_size; /* same as hash_alg->digest_size */ 43 unsigned int block_size; /* size of data and tree blocks */ 44 unsigned int hashes_per_block; /* number of hashes per tree block */ 45 unsigned int blocks_per_page; /* PAGE_SIZE / block_size */ 46 u8 log_digestsize; /* log2(digest_size) */ 47 u8 log_blocksize; /* log2(block_size) */ 48 u8 log_arity; /* log2(hashes_per_block) */ 49 u8 log_blocks_per_page; /* log2(blocks_per_page) */ 50 unsigned int num_levels; /* number of levels in Merkle tree */ 51 u64 tree_size; /* Merkle tree size in bytes */ 52 unsigned long tree_pages; /* Merkle tree size in pages */ 53 54 /* 55 * Starting block index for each tree level, ordered from leaf level (0) 56 * to root level ('num_levels - 1') 57 */ 58 unsigned long level_start[FS_VERITY_MAX_LEVELS]; 59 }; 60 61 /* 62 * fsverity_info - cached verity metadata for an inode 63 * 64 * When a verity file is first opened, an instance of this struct is allocated 65 * and stored in ->i_verity_info; it remains until the inode is evicted. It 66 * caches information about the Merkle tree that's needed to efficiently verify 67 * data read from the file. It also caches the file digest. The Merkle tree 68 * pages themselves are not cached here, but the filesystem may cache them. 69 */ 70 struct fsverity_info { 71 struct merkle_tree_params tree_params; 72 u8 root_hash[FS_VERITY_MAX_DIGEST_SIZE]; 73 u8 file_digest[FS_VERITY_MAX_DIGEST_SIZE]; 74 const struct inode *inode; 75 unsigned long *hash_block_verified; 76 spinlock_t hash_page_init_lock; 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_block(const struct merkle_tree_params *params, 95 const struct inode *inode, struct ahash_request *req, 96 struct page *page, unsigned int offset, 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