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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 | ||
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11 | #define pr_fmt(fmt) "fs-verity: " fmt |
12 | ||
fd2d1acf | 13 | #include <linux/fsverity.h> |
439bea10 | 14 | #include <linux/mempool.h> |
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15 | |
16 | struct ahash_request; | |
17 | ||
18 | /* | |
19 | * Implementation limit: maximum depth of the Merkle tree. For now 8 is plenty; | |
20 | * it's enough for over U64_MAX bytes of data using SHA-256 and 4K blocks. | |
21 | */ | |
22 | #define FS_VERITY_MAX_LEVELS 8 | |
23 | ||
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24 | /* A hash algorithm supported by fs-verity */ |
25 | struct fsverity_hash_alg { | |
26 | struct crypto_ahash *tfm; /* hash tfm, allocated on demand */ | |
27 | const char *name; /* crypto API name, e.g. sha256 */ | |
28 | unsigned int digest_size; /* digest size in bytes, e.g. 32 for SHA-256 */ | |
29 | unsigned int block_size; /* block size in bytes, e.g. 64 for SHA-256 */ | |
439bea10 | 30 | mempool_t req_pool; /* mempool with a preallocated hash request */ |
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31 | /* |
32 | * The HASH_ALGO_* constant for this algorithm. This is different from | |
33 | * FS_VERITY_HASH_ALG_*, which uses a different numbering scheme. | |
34 | */ | |
35 | enum hash_algo algo_id; | |
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36 | }; |
37 | ||
38 | /* Merkle tree parameters: hash algorithm, initial hash state, and topology */ | |
39 | struct merkle_tree_params { | |
439bea10 | 40 | struct fsverity_hash_alg *hash_alg; /* the hash algorithm */ |
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41 | const u8 *hashstate; /* initial hash state or NULL */ |
42 | unsigned int digest_size; /* same as hash_alg->digest_size */ | |
43 | unsigned int block_size; /* size of data and tree blocks */ | |
44 | unsigned int hashes_per_block; /* number of hashes per tree block */ | |
5306892a | 45 | unsigned int blocks_per_page; /* PAGE_SIZE / block_size */ |
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46 | u8 log_digestsize; /* log2(digest_size) */ |
47 | u8 log_blocksize; /* log2(block_size) */ | |
48 | u8 log_arity; /* log2(hashes_per_block) */ | |
5306892a | 49 | u8 log_blocks_per_page; /* log2(blocks_per_page) */ |
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50 | unsigned int num_levels; /* number of levels in Merkle tree */ |
51 | u64 tree_size; /* Merkle tree size in bytes */ | |
9098f36b | 52 | unsigned long tree_pages; /* Merkle tree size in pages */ |
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53 | |
54 | /* | |
55 | * Starting block index for each tree level, ordered from leaf level (0) | |
56 | * to root level ('num_levels - 1') | |
57 | */ | |
284d5db5 | 58 | unsigned long level_start[FS_VERITY_MAX_LEVELS]; |
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59 | }; |
60 | ||
6377a38b | 61 | /* |
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62 | * fsverity_info - cached verity metadata for an inode |
63 | * | |
64 | * When a verity file is first opened, an instance of this struct is allocated | |
65 | * and stored in ->i_verity_info; it remains until the inode is evicted. It | |
66 | * caches information about the Merkle tree that's needed to efficiently verify | |
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67 | * data read from the file. It also caches the file digest. The Merkle tree |
68 | * pages themselves are not cached here, but the filesystem may cache them. | |
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69 | */ |
70 | struct fsverity_info { | |
71 | struct merkle_tree_params tree_params; | |
72 | u8 root_hash[FS_VERITY_MAX_DIGEST_SIZE]; | |
ed45e201 | 73 | u8 file_digest[FS_VERITY_MAX_DIGEST_SIZE]; |
fd2d1acf | 74 | const struct inode *inode; |
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75 | unsigned long *hash_block_verified; |
76 | spinlock_t hash_page_init_lock; | |
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77 | }; |
78 | ||
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79 | #define FS_VERITY_MAX_SIGNATURE_SIZE (FS_VERITY_MAX_DESCRIPTOR_SIZE - \ |
80 | sizeof(struct fsverity_descriptor)) | |
81 | ||
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82 | /* hash_algs.c */ |
83 | ||
84 | extern struct fsverity_hash_alg fsverity_hash_algs[]; | |
85 | ||
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86 | struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode, |
87 | unsigned int num); | |
88 | struct ahash_request *fsverity_alloc_hash_request(struct fsverity_hash_alg *alg, | |
89 | gfp_t gfp_flags); | |
90 | void fsverity_free_hash_request(struct fsverity_hash_alg *alg, | |
91 | struct ahash_request *req); | |
92 | const u8 *fsverity_prepare_hash_state(struct fsverity_hash_alg *alg, | |
671e67b4 | 93 | const u8 *salt, size_t salt_size); |
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94 | int fsverity_hash_block(const struct merkle_tree_params *params, |
95 | const struct inode *inode, struct ahash_request *req, | |
96 | struct page *page, unsigned int offset, u8 *out); | |
439bea10 | 97 | int fsverity_hash_buffer(struct fsverity_hash_alg *alg, |
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98 | const void *data, size_t size, u8 *out); |
99 | void __init fsverity_check_hash_algs(void); | |
100 | ||
101 | /* init.c */ | |
102 | ||
9cd6b593 | 103 | void __printf(3, 4) __cold |
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104 | fsverity_msg(const struct inode *inode, const char *level, |
105 | const char *fmt, ...); | |
106 | ||
107 | #define fsverity_warn(inode, fmt, ...) \ | |
108 | fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__) | |
109 | #define fsverity_err(inode, fmt, ...) \ | |
110 | fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__) | |
111 | ||
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112 | /* open.c */ |
113 | ||
114 | int fsverity_init_merkle_tree_params(struct merkle_tree_params *params, | |
115 | const struct inode *inode, | |
116 | unsigned int hash_algorithm, | |
117 | unsigned int log_blocksize, | |
118 | const u8 *salt, size_t salt_size); | |
119 | ||
120 | struct fsverity_info *fsverity_create_info(const struct inode *inode, | |
b0487ede | 121 | struct fsverity_descriptor *desc); |
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122 | |
123 | void fsverity_set_info(struct inode *inode, struct fsverity_info *vi); | |
124 | ||
125 | void fsverity_free_info(struct fsverity_info *vi); | |
126 | ||
c2c82611 | 127 | int fsverity_get_descriptor(struct inode *inode, |
b0487ede | 128 | struct fsverity_descriptor **desc_ret); |
c2c82611 | 129 | |
fd2d1acf | 130 | int __init fsverity_init_info_cache(void); |
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131 | void __init fsverity_exit_info_cache(void); |
132 | ||
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133 | /* signature.c */ |
134 | ||
135 | #ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES | |
136 | int fsverity_verify_signature(const struct fsverity_info *vi, | |
fab634c4 | 137 | const u8 *signature, size_t sig_size); |
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138 | |
139 | int __init fsverity_init_signature(void); | |
140 | #else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ | |
141 | static inline int | |
142 | fsverity_verify_signature(const struct fsverity_info *vi, | |
fab634c4 | 143 | const u8 *signature, size_t sig_size) |
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144 | { |
145 | return 0; | |
146 | } | |
147 | ||
148 | static inline int fsverity_init_signature(void) | |
149 | { | |
150 | return 0; | |
151 | } | |
152 | #endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ | |
153 | ||
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154 | /* verify.c */ |
155 | ||
156 | int __init fsverity_init_workqueue(void); | |
432434c9 | 157 | void __init fsverity_exit_workqueue(void); |
fd2d1acf | 158 | |
671e67b4 | 159 | #endif /* _FSVERITY_PRIVATE_H */ |