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 <crypto/sha2.h> 18 #include <linux/fsverity.h> 19 #include <linux/mempool.h> 20 21 struct ahash_request; 22 23 /* 24 * Implementation limit: maximum depth of the Merkle tree. For now 8 is plenty; 25 * it's enough for over U64_MAX bytes of data using SHA-256 and 4K blocks. 26 */ 27 #define FS_VERITY_MAX_LEVELS 8 28 29 /* 30 * Largest digest size among all hash algorithms supported by fs-verity. 31 * Currently assumed to be <= size of fsverity_descriptor::root_hash. 32 */ 33 #define FS_VERITY_MAX_DIGEST_SIZE SHA512_DIGEST_SIZE 34 35 /* A hash algorithm supported by fs-verity */ 36 struct fsverity_hash_alg { 37 struct crypto_ahash *tfm; /* hash tfm, allocated on demand */ 38 const char *name; /* crypto API name, e.g. sha256 */ 39 unsigned int digest_size; /* digest size in bytes, e.g. 32 for SHA-256 */ 40 unsigned int block_size; /* block size in bytes, e.g. 64 for SHA-256 */ 41 mempool_t req_pool; /* mempool with a preallocated hash request */ 42 }; 43 44 /* Merkle tree parameters: hash algorithm, initial hash state, and topology */ 45 struct merkle_tree_params { 46 struct fsverity_hash_alg *hash_alg; /* the hash algorithm */ 47 const u8 *hashstate; /* initial hash state or NULL */ 48 unsigned int digest_size; /* same as hash_alg->digest_size */ 49 unsigned int block_size; /* size of data and tree blocks */ 50 unsigned int hashes_per_block; /* number of hashes per tree block */ 51 unsigned int log_blocksize; /* log2(block_size) */ 52 unsigned int log_arity; /* log2(hashes_per_block) */ 53 unsigned int num_levels; /* number of levels in Merkle tree */ 54 u64 tree_size; /* Merkle tree size in bytes */ 55 unsigned long level0_blocks; /* number of blocks in tree level 0 */ 56 57 /* 58 * Starting block index for each tree level, ordered from leaf level (0) 59 * to root level ('num_levels - 1') 60 */ 61 u64 level_start[FS_VERITY_MAX_LEVELS]; 62 }; 63 64 /* 65 * fsverity_info - cached verity metadata for an inode 66 * 67 * When a verity file is first opened, an instance of this struct is allocated 68 * and stored in ->i_verity_info; it remains until the inode is evicted. It 69 * caches information about the Merkle tree that's needed to efficiently verify 70 * data read from the file. It also caches the file digest. The Merkle tree 71 * pages themselves are not cached here, but the filesystem may cache them. 72 */ 73 struct fsverity_info { 74 struct merkle_tree_params tree_params; 75 u8 root_hash[FS_VERITY_MAX_DIGEST_SIZE]; 76 u8 file_digest[FS_VERITY_MAX_DIGEST_SIZE]; 77 const struct inode *inode; 78 }; 79 80 /* Arbitrary limit to bound the kmalloc() size. Can be changed. */ 81 #define FS_VERITY_MAX_DESCRIPTOR_SIZE 16384 82 83 #define FS_VERITY_MAX_SIGNATURE_SIZE (FS_VERITY_MAX_DESCRIPTOR_SIZE - \ 84 sizeof(struct fsverity_descriptor)) 85 86 /* hash_algs.c */ 87 88 extern struct fsverity_hash_alg fsverity_hash_algs[]; 89 90 struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode, 91 unsigned int num); 92 struct ahash_request *fsverity_alloc_hash_request(struct fsverity_hash_alg *alg, 93 gfp_t gfp_flags); 94 void fsverity_free_hash_request(struct fsverity_hash_alg *alg, 95 struct ahash_request *req); 96 const u8 *fsverity_prepare_hash_state(struct fsverity_hash_alg *alg, 97 const u8 *salt, size_t salt_size); 98 int fsverity_hash_page(const struct merkle_tree_params *params, 99 const struct inode *inode, 100 struct ahash_request *req, struct page *page, u8 *out); 101 int fsverity_hash_buffer(struct fsverity_hash_alg *alg, 102 const void *data, size_t size, u8 *out); 103 void __init fsverity_check_hash_algs(void); 104 105 /* init.c */ 106 107 void __printf(3, 4) __cold 108 fsverity_msg(const struct inode *inode, const char *level, 109 const char *fmt, ...); 110 111 #define fsverity_warn(inode, fmt, ...) \ 112 fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__) 113 #define fsverity_err(inode, fmt, ...) \ 114 fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__) 115 116 /* open.c */ 117 118 int fsverity_init_merkle_tree_params(struct merkle_tree_params *params, 119 const struct inode *inode, 120 unsigned int hash_algorithm, 121 unsigned int log_blocksize, 122 const u8 *salt, size_t salt_size); 123 124 struct fsverity_info *fsverity_create_info(const struct inode *inode, 125 struct fsverity_descriptor *desc, 126 size_t desc_size); 127 128 void fsverity_set_info(struct inode *inode, struct fsverity_info *vi); 129 130 void fsverity_free_info(struct fsverity_info *vi); 131 132 int fsverity_get_descriptor(struct inode *inode, 133 struct fsverity_descriptor **desc_ret, 134 size_t *desc_size_ret); 135 136 int __init fsverity_init_info_cache(void); 137 void __init fsverity_exit_info_cache(void); 138 139 /* signature.c */ 140 141 #ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES 142 int fsverity_verify_signature(const struct fsverity_info *vi, 143 const u8 *signature, size_t sig_size); 144 145 int __init fsverity_init_signature(void); 146 #else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ 147 static inline int 148 fsverity_verify_signature(const struct fsverity_info *vi, 149 const u8 *signature, size_t sig_size) 150 { 151 return 0; 152 } 153 154 static inline int fsverity_init_signature(void) 155 { 156 return 0; 157 } 158 #endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ 159 160 /* verify.c */ 161 162 int __init fsverity_init_workqueue(void); 163 void __init fsverity_exit_workqueue(void); 164 165 #endif /* _FSVERITY_PRIVATE_H */ 166