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 | struct crypto_shash *tfm; /* hash tfm, allocated on demand */ |
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 | /* Merkle tree parameters: hash algorithm, initial hash state, and topology */ |
35 | struct merkle_tree_params { |
36 | const struct fsverity_hash_alg *hash_alg; /* the hash algorithm */ |
37 | const u8 *hashstate; /* initial hash state or NULL */ |
38 | unsigned int digest_size; /* same as hash_alg->digest_size */ |
39 | unsigned int block_size; /* size of data and tree blocks */ |
40 | unsigned int hashes_per_block; /* number of hashes per tree block */ |
41 | unsigned int blocks_per_page; /* PAGE_SIZE / block_size */ |
42 | u8 log_digestsize; /* log2(digest_size) */ |
43 | u8 log_blocksize; /* log2(block_size) */ |
44 | u8 log_arity; /* log2(hashes_per_block) */ |
45 | u8 log_blocks_per_page; /* log2(blocks_per_page) */ |
46 | unsigned int num_levels; /* number of levels in Merkle tree */ |
47 | u64 tree_size; /* Merkle tree size in bytes */ |
48 | unsigned long tree_pages; /* Merkle tree size in pages */ |
49 | |
50 | /* |
51 | * Starting block index for each tree level, ordered from leaf level (0) |
52 | * to root level ('num_levels - 1') |
53 | */ |
54 | unsigned long 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 | unsigned long *hash_block_verified; |
72 | spinlock_t hash_page_init_lock; |
73 | }; |
74 | |
75 | #define FS_VERITY_MAX_SIGNATURE_SIZE (FS_VERITY_MAX_DESCRIPTOR_SIZE - \ |
76 | sizeof(struct fsverity_descriptor)) |
77 | |
78 | /* hash_algs.c */ |
79 | |
80 | extern struct fsverity_hash_alg fsverity_hash_algs[]; |
81 | |
82 | const struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode, |
83 | unsigned int num); |
84 | const u8 *fsverity_prepare_hash_state(const struct fsverity_hash_alg *alg, |
85 | const u8 *salt, size_t salt_size); |
86 | int fsverity_hash_block(const struct merkle_tree_params *params, |
87 | const struct inode *inode, const void *data, u8 *out); |
88 | int fsverity_hash_buffer(const struct fsverity_hash_alg *alg, |
89 | const void *data, size_t size, u8 *out); |
90 | void __init fsverity_check_hash_algs(void); |
91 | |
92 | /* init.c */ |
93 | |
94 | void __printf(3, 4) __cold |
95 | fsverity_msg(const struct inode *inode, const char *level, |
96 | const char *fmt, ...); |
97 | |
98 | #define fsverity_warn(inode, fmt, ...) \ |
99 | fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__) |
100 | #define fsverity_err(inode, fmt, ...) \ |
101 | fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__) |
102 | |
103 | /* open.c */ |
104 | |
105 | int fsverity_init_merkle_tree_params(struct merkle_tree_params *params, |
106 | const struct inode *inode, |
107 | unsigned int hash_algorithm, |
108 | unsigned int log_blocksize, |
109 | const u8 *salt, size_t salt_size); |
110 | |
111 | struct fsverity_info *fsverity_create_info(const struct inode *inode, |
112 | struct fsverity_descriptor *desc); |
113 | |
114 | void fsverity_set_info(struct inode *inode, struct fsverity_info *vi); |
115 | |
116 | void fsverity_free_info(struct fsverity_info *vi); |
117 | |
118 | int fsverity_get_descriptor(struct inode *inode, |
119 | struct fsverity_descriptor **desc_ret); |
120 | |
121 | void __init fsverity_init_info_cache(void); |
122 | |
123 | /* signature.c */ |
124 | |
125 | #ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES |
126 | extern int fsverity_require_signatures; |
127 | int fsverity_verify_signature(const struct fsverity_info *vi, |
128 | const u8 *signature, size_t sig_size); |
129 | |
130 | void __init fsverity_init_signature(void); |
131 | #else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ |
132 | static inline int |
133 | fsverity_verify_signature(const struct fsverity_info *vi, |
134 | const u8 *signature, size_t sig_size) |
135 | { |
136 | return 0; |
137 | } |
138 | |
139 | static inline void fsverity_init_signature(void) |
140 | { |
141 | } |
142 | #endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ |
143 | |
144 | /* verify.c */ |
145 | |
146 | void __init fsverity_init_workqueue(void); |
147 | |
148 | #endif /* _FSVERITY_PRIVATE_H */ |
149 | |