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 const char *name; /* crypto API name, e.g. sha256 */ 24 unsigned int digest_size; /* digest size in bytes, e.g. 32 for SHA-256 */ 25 unsigned int block_size; /* block size in bytes, e.g. 64 for SHA-256 */ 26 /* 27 * The HASH_ALGO_* constant for this algorithm. This is different from 28 * FS_VERITY_HASH_ALG_*, which uses a different numbering scheme. 29 */ 30 enum hash_algo algo_id; 31 }; 32 33 union fsverity_hash_ctx { 34 struct sha256_ctx sha256; 35 struct sha512_ctx sha512; 36 }; 37 38 /* Merkle tree parameters: hash algorithm, initial hash state, and topology */ 39 struct merkle_tree_params { 40 const struct fsverity_hash_alg *hash_alg; /* the hash algorithm */ 41 /* initial hash state if salted, NULL if unsalted */ 42 const union fsverity_hash_ctx *hashstate; 43 unsigned int digest_size; /* same as hash_alg->digest_size */ 44 unsigned int block_size; /* size of data and tree blocks */ 45 unsigned int hashes_per_block; /* number of hashes per tree block */ 46 unsigned int blocks_per_page; /* PAGE_SIZE / block_size */ 47 u8 log_digestsize; /* log2(digest_size) */ 48 u8 log_blocksize; /* log2(block_size) */ 49 u8 log_arity; /* log2(hashes_per_block) */ 50 u8 log_blocks_per_page; /* log2(blocks_per_page) */ 51 unsigned int num_levels; /* number of levels in Merkle tree */ 52 u64 tree_size; /* Merkle tree size in bytes */ 53 unsigned long tree_pages; /* Merkle tree size in pages */ 54 55 /* 56 * Starting block index for each tree level, ordered from leaf level (0) 57 * to root level ('num_levels - 1') 58 */ 59 unsigned long 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 a pointer to it is stored in the file's in-memory inode. It remains 67 * until the inode is evicted. It caches information about the Merkle tree 68 * that's needed to efficiently verify data read from the file. It also caches 69 * the file digest. The Merkle tree pages themselves are not cached here, but 70 * the filesystem may cache them. 71 */ 72 struct fsverity_info { 73 struct merkle_tree_params tree_params; 74 u8 root_hash[FS_VERITY_MAX_DIGEST_SIZE]; 75 u8 file_digest[FS_VERITY_MAX_DIGEST_SIZE]; 76 const struct inode *inode; 77 unsigned long *hash_block_verified; 78 }; 79 80 #define FS_VERITY_MAX_SIGNATURE_SIZE (FS_VERITY_MAX_DESCRIPTOR_SIZE - \ 81 sizeof(struct fsverity_descriptor)) 82 83 /* hash_algs.c */ 84 85 extern const struct fsverity_hash_alg fsverity_hash_algs[]; 86 87 const struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode, 88 unsigned int num); 89 union fsverity_hash_ctx * 90 fsverity_prepare_hash_state(const struct fsverity_hash_alg *alg, 91 const u8 *salt, size_t salt_size); 92 void fsverity_hash_block(const struct merkle_tree_params *params, 93 const void *data, u8 *out); 94 void fsverity_hash_buffer(const struct fsverity_hash_alg *alg, 95 const void *data, size_t size, u8 *out); 96 void __init fsverity_check_hash_algs(void); 97 98 /* init.c */ 99 100 void __printf(3, 4) __cold 101 fsverity_msg(const struct inode *inode, const char *level, 102 const char *fmt, ...); 103 104 #define fsverity_warn(inode, fmt, ...) \ 105 fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__) 106 #define fsverity_err(inode, fmt, ...) \ 107 fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__) 108 109 /* measure.c */ 110 111 #ifdef CONFIG_BPF_SYSCALL 112 void __init fsverity_init_bpf(void); 113 #else 114 static inline void fsverity_init_bpf(void) 115 { 116 } 117 #endif 118 119 /* open.c */ 120 121 int fsverity_init_merkle_tree_params(struct merkle_tree_params *params, 122 const struct inode *inode, 123 unsigned int hash_algorithm, 124 unsigned int log_blocksize, 125 const u8 *salt, size_t salt_size); 126 127 struct fsverity_info *fsverity_create_info(const struct inode *inode, 128 struct fsverity_descriptor *desc); 129 130 void fsverity_set_info(struct inode *inode, struct fsverity_info *vi); 131 132 void fsverity_free_info(struct fsverity_info *vi); 133 134 int fsverity_get_descriptor(struct inode *inode, 135 struct fsverity_descriptor **desc_ret); 136 137 void __init fsverity_init_info_cache(void); 138 139 /* signature.c */ 140 141 #ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES 142 extern int fsverity_require_signatures; 143 int fsverity_verify_signature(const struct fsverity_info *vi, 144 const u8 *signature, size_t sig_size); 145 146 void __init fsverity_init_signature(void); 147 #else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ 148 static inline int 149 fsverity_verify_signature(const struct fsverity_info *vi, 150 const u8 *signature, size_t sig_size) 151 { 152 return 0; 153 } 154 155 static inline void fsverity_init_signature(void) 156 { 157 } 158 #endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ 159 160 /* verify.c */ 161 162 void __init fsverity_init_workqueue(void); 163 164 #endif /* _FSVERITY_PRIVATE_H */ 165