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 37 /* Merkle tree parameters: hash algorithm, initial hash state, and topology */ 38 struct merkle_tree_params { 39 struct fsverity_hash_alg *hash_alg; /* the hash algorithm */ 40 const u8 *hashstate; /* initial hash state or NULL */ 41 unsigned int digest_size; /* same as hash_alg->digest_size */ 42 unsigned int block_size; /* size of data and tree blocks */ 43 unsigned int hashes_per_block; /* number of hashes per tree block */ 44 unsigned int log_blocksize; /* log2(block_size) */ 45 unsigned int log_arity; /* log2(hashes_per_block) */ 46 unsigned int num_levels; /* number of levels in Merkle tree */ 47 u64 tree_size; /* Merkle tree size in bytes */ 48 unsigned long level0_blocks; /* number of blocks in tree level 0 */ 49 50 /* 51 * Starting block index for each tree level, ordered from leaf level (0) 52 * to root level ('num_levels - 1') 53 */ 54 u64 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 }; 72 73 /* Arbitrary limit to bound the kmalloc() size. Can be changed. */ 74 #define FS_VERITY_MAX_DESCRIPTOR_SIZE 16384 75 76 #define FS_VERITY_MAX_SIGNATURE_SIZE (FS_VERITY_MAX_DESCRIPTOR_SIZE - \ 77 sizeof(struct fsverity_descriptor)) 78 79 /* hash_algs.c */ 80 81 extern struct fsverity_hash_alg fsverity_hash_algs[]; 82 83 struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode, 84 unsigned int num); 85 struct ahash_request *fsverity_alloc_hash_request(struct fsverity_hash_alg *alg, 86 gfp_t gfp_flags); 87 void fsverity_free_hash_request(struct fsverity_hash_alg *alg, 88 struct ahash_request *req); 89 const u8 *fsverity_prepare_hash_state(struct fsverity_hash_alg *alg, 90 const u8 *salt, size_t salt_size); 91 int fsverity_hash_page(const struct merkle_tree_params *params, 92 const struct inode *inode, 93 struct ahash_request *req, struct page *page, u8 *out); 94 int fsverity_hash_buffer(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 /* open.c */ 110 111 int fsverity_init_merkle_tree_params(struct merkle_tree_params *params, 112 const struct inode *inode, 113 unsigned int hash_algorithm, 114 unsigned int log_blocksize, 115 const u8 *salt, size_t salt_size); 116 117 struct fsverity_info *fsverity_create_info(const struct inode *inode, 118 struct fsverity_descriptor *desc); 119 120 void fsverity_set_info(struct inode *inode, struct fsverity_info *vi); 121 122 void fsverity_free_info(struct fsverity_info *vi); 123 124 int fsverity_get_descriptor(struct inode *inode, 125 struct fsverity_descriptor **desc_ret); 126 127 int __init fsverity_init_info_cache(void); 128 void __init fsverity_exit_info_cache(void); 129 130 /* signature.c */ 131 132 #ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES 133 int fsverity_verify_signature(const struct fsverity_info *vi, 134 const u8 *signature, size_t sig_size); 135 136 int __init fsverity_init_signature(void); 137 #else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ 138 static inline int 139 fsverity_verify_signature(const struct fsverity_info *vi, 140 const u8 *signature, size_t sig_size) 141 { 142 return 0; 143 } 144 145 static inline int fsverity_init_signature(void) 146 { 147 return 0; 148 } 149 #endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ 150 151 /* verify.c */ 152 153 int __init fsverity_init_workqueue(void); 154 void __init fsverity_exit_workqueue(void); 155 156 #endif /* _FSVERITY_PRIVATE_H */ 157