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/rhashtable.h> 15 16 /* 17 * Implementation limit: maximum depth of the Merkle tree. For now 8 is plenty; 18 * it's enough for over U64_MAX bytes of data using SHA-256 and 4K blocks. 19 */ 20 #define FS_VERITY_MAX_LEVELS 8 21 22 /* A hash algorithm supported by fs-verity */ 23 struct fsverity_hash_alg { 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 union fsverity_hash_ctx { 35 struct sha256_ctx sha256; 36 struct sha512_ctx sha512; 37 }; 38 39 /* Merkle tree parameters: hash algorithm, initial hash state, and topology */ 40 struct merkle_tree_params { 41 const struct fsverity_hash_alg *hash_alg; /* the hash algorithm */ 42 /* initial hash state if salted, NULL if unsalted */ 43 const union fsverity_hash_ctx *hashstate; 44 unsigned int digest_size; /* same as hash_alg->digest_size */ 45 unsigned int block_size; /* size of data and tree blocks */ 46 unsigned int hashes_per_block; /* number of hashes per tree block */ 47 unsigned int blocks_per_page; /* PAGE_SIZE / block_size */ 48 u8 log_digestsize; /* log2(digest_size) */ 49 u8 log_blocksize; /* log2(block_size) */ 50 u8 log_arity; /* log2(hashes_per_block) */ 51 u8 log_blocks_per_page; /* log2(blocks_per_page) */ 52 unsigned int num_levels; /* number of levels in Merkle tree */ 53 u64 tree_size; /* Merkle tree size in bytes */ 54 unsigned long tree_pages; /* Merkle tree size in pages */ 55 56 /* 57 * Starting block index for each tree level, ordered from leaf level (0) 58 * to root level ('num_levels - 1') 59 */ 60 unsigned long level_start[FS_VERITY_MAX_LEVELS]; 61 }; 62 63 /* 64 * fsverity_info - cached verity metadata for an inode 65 * 66 * When a verity file is first opened, an instance of this struct is allocated 67 * and a pointer to it is stored in the global hash table, indexed by the inode 68 * pointer value. It remains alive until the inode is evicted. It caches 69 * information about the Merkle tree that's needed to efficiently verify data 70 * read from the file. It also caches the file digest. The Merkle tree pages 71 * themselves are not cached here, but the filesystem may cache them. 72 */ 73 struct fsverity_info { 74 struct rhash_head rhash_head; 75 struct merkle_tree_params tree_params; 76 u8 root_hash[FS_VERITY_MAX_DIGEST_SIZE]; 77 u8 file_digest[FS_VERITY_MAX_DIGEST_SIZE]; 78 struct inode *inode; 79 unsigned long *hash_block_verified; 80 }; 81 82 #define FS_VERITY_MAX_SIGNATURE_SIZE (FS_VERITY_MAX_DESCRIPTOR_SIZE - \ 83 sizeof(struct fsverity_descriptor)) 84 85 /* hash_algs.c */ 86 87 extern const struct fsverity_hash_alg fsverity_hash_algs[]; 88 89 const struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode, 90 unsigned int num); 91 union fsverity_hash_ctx * 92 fsverity_prepare_hash_state(const struct fsverity_hash_alg *alg, 93 const u8 *salt, size_t salt_size); 94 void fsverity_hash_block(const struct merkle_tree_params *params, 95 const void *data, u8 *out); 96 void fsverity_hash_buffer(const struct fsverity_hash_alg *alg, 97 const void *data, size_t size, u8 *out); 98 void __init fsverity_check_hash_algs(void); 99 100 /* init.c */ 101 102 void __printf(3, 4) __cold 103 fsverity_msg(const struct inode *inode, const char *level, 104 const char *fmt, ...); 105 106 #define fsverity_warn(inode, fmt, ...) \ 107 fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__) 108 #define fsverity_err(inode, fmt, ...) \ 109 fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__) 110 111 /* measure.c */ 112 113 #ifdef CONFIG_BPF_SYSCALL 114 void __init fsverity_init_bpf(void); 115 #else 116 static inline void fsverity_init_bpf(void) 117 { 118 } 119 #endif 120 121 /* open.c */ 122 123 int fsverity_init_merkle_tree_params(struct merkle_tree_params *params, 124 const struct inode *inode, 125 unsigned int hash_algorithm, 126 unsigned int log_blocksize, 127 const u8 *salt, size_t salt_size); 128 129 struct fsverity_info *fsverity_create_info(struct inode *inode, 130 struct fsverity_descriptor *desc); 131 132 int fsverity_set_info(struct fsverity_info *vi); 133 void fsverity_free_info(struct fsverity_info *vi); 134 void fsverity_remove_info(struct fsverity_info *vi); 135 136 int fsverity_get_descriptor(struct inode *inode, 137 struct fsverity_descriptor **desc_ret); 138 139 void __init fsverity_init_info_cache(void); 140 141 /* signature.c */ 142 143 #ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES 144 extern int fsverity_require_signatures; 145 int fsverity_verify_signature(const struct fsverity_info *vi, 146 const u8 *signature, size_t sig_size); 147 148 void __init fsverity_init_signature(void); 149 #else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ 150 static inline int 151 fsverity_verify_signature(const struct fsverity_info *vi, 152 const u8 *signature, size_t sig_size) 153 { 154 return 0; 155 } 156 157 static inline void fsverity_init_signature(void) 158 { 159 } 160 #endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ 161 162 /* verify.c */ 163 164 void __init fsverity_init_workqueue(void); 165 166 #endif /* _FSVERITY_PRIVATE_H */ 167