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 */ 22 struct 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 */ 35 struct 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 */ 66 struct 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 spinlock_t hash_page_init_lock; 73 }; 74 75 #define FS_VERITY_MAX_SIGNATURE_SIZE (FS_VERITY_MAX_DESCRIPTOR_SIZE - \ 76 sizeof(struct fsverity_descriptor)) 77 78 /* hash_algs.c */ 79 80 extern struct fsverity_hash_alg fsverity_hash_algs[]; 81 82 const struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode, 83 unsigned int num); 84 const u8 *fsverity_prepare_hash_state(const struct fsverity_hash_alg *alg, 85 const u8 *salt, size_t salt_size); 86 int fsverity_hash_block(const struct merkle_tree_params *params, 87 const struct inode *inode, const void *data, u8 *out); 88 int fsverity_hash_buffer(const struct fsverity_hash_alg *alg, 89 const void *data, size_t size, u8 *out); 90 void __init fsverity_check_hash_algs(void); 91 92 /* init.c */ 93 94 void __printf(3, 4) __cold 95 fsverity_msg(const struct inode *inode, const char *level, 96 const char *fmt, ...); 97 98 #define fsverity_warn(inode, fmt, ...) \ 99 fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__) 100 #define fsverity_err(inode, fmt, ...) \ 101 fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__) 102 103 /* open.c */ 104 105 int fsverity_init_merkle_tree_params(struct merkle_tree_params *params, 106 const struct inode *inode, 107 unsigned int hash_algorithm, 108 unsigned int log_blocksize, 109 const u8 *salt, size_t salt_size); 110 111 struct fsverity_info *fsverity_create_info(const struct inode *inode, 112 struct fsverity_descriptor *desc); 113 114 void fsverity_set_info(struct inode *inode, struct fsverity_info *vi); 115 116 void fsverity_free_info(struct fsverity_info *vi); 117 118 int fsverity_get_descriptor(struct inode *inode, 119 struct fsverity_descriptor **desc_ret); 120 121 int __init fsverity_init_info_cache(void); 122 void __init fsverity_exit_info_cache(void); 123 124 /* signature.c */ 125 126 #ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES 127 int fsverity_verify_signature(const struct fsverity_info *vi, 128 const u8 *signature, size_t sig_size); 129 130 int __init fsverity_init_signature(void); 131 #else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ 132 static inline int 133 fsverity_verify_signature(const struct fsverity_info *vi, 134 const u8 *signature, size_t sig_size) 135 { 136 return 0; 137 } 138 139 static inline int fsverity_init_signature(void) 140 { 141 return 0; 142 } 143 #endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ 144 145 /* verify.c */ 146 147 int __init fsverity_init_workqueue(void); 148 void __init fsverity_exit_workqueue(void); 149 150 #endif /* _FSVERITY_PRIVATE_H */ 151