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 const char *name; /* crypto API name, e.g. sha256 */
24 unsigned int digest_size; /* digest size in bytes, e.g. 32 for SHA-256 */
25 unsigned int block_size; /* block size in bytes, e.g. 64 for SHA-256 */
26 /*
27 * The HASH_ALGO_* constant for this algorithm. This is different from
28 * FS_VERITY_HASH_ALG_*, which uses a different numbering scheme.
29 */
30 enum hash_algo algo_id;
31 };
32
33 union fsverity_hash_ctx {
34 struct sha256_ctx sha256;
35 struct sha512_ctx sha512;
36 };
37
38 /* Merkle tree parameters: hash algorithm, initial hash state, and topology */
39 struct merkle_tree_params {
40 const struct fsverity_hash_alg *hash_alg; /* the hash algorithm */
41 /* initial hash state if salted, NULL if unsalted */
42 const union fsverity_hash_ctx *hashstate;
43 unsigned int digest_size; /* same as hash_alg->digest_size */
44 unsigned int block_size; /* size of data and tree blocks */
45 unsigned int hashes_per_block; /* number of hashes per tree block */
46 unsigned int blocks_per_page; /* PAGE_SIZE / block_size */
47 u8 log_digestsize; /* log2(digest_size) */
48 u8 log_blocksize; /* log2(block_size) */
49 u8 log_arity; /* log2(hashes_per_block) */
50 u8 log_blocks_per_page; /* log2(blocks_per_page) */
51 unsigned int num_levels; /* number of levels in Merkle tree */
52 u64 tree_size; /* Merkle tree size in bytes */
53 unsigned long tree_pages; /* Merkle tree size in pages */
54
55 /*
56 * Starting block index for each tree level, ordered from leaf level (0)
57 * to root level ('num_levels - 1')
58 */
59 unsigned long level_start[FS_VERITY_MAX_LEVELS];
60 };
61
62 /*
63 * fsverity_info - cached verity metadata for an inode
64 *
65 * When a verity file is first opened, an instance of this struct is allocated
66 * and stored in ->i_verity_info; it remains until the inode is evicted. It
67 * caches information about the Merkle tree that's needed to efficiently verify
68 * data read from the file. It also caches the file digest. The Merkle tree
69 * pages themselves are not cached here, but the filesystem may cache them.
70 */
71 struct fsverity_info {
72 struct merkle_tree_params tree_params;
73 u8 root_hash[FS_VERITY_MAX_DIGEST_SIZE];
74 u8 file_digest[FS_VERITY_MAX_DIGEST_SIZE];
75 const struct inode *inode;
76 unsigned long *hash_block_verified;
77 };
78
79 #define FS_VERITY_MAX_SIGNATURE_SIZE (FS_VERITY_MAX_DESCRIPTOR_SIZE - \
80 sizeof(struct fsverity_descriptor))
81
82 /* hash_algs.c */
83
84 extern const struct fsverity_hash_alg fsverity_hash_algs[];
85
86 const struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode,
87 unsigned int num);
88 union fsverity_hash_ctx *
89 fsverity_prepare_hash_state(const struct fsverity_hash_alg *alg,
90 const u8 *salt, size_t salt_size);
91 void fsverity_hash_block(const struct merkle_tree_params *params,
92 const struct inode *inode, const void *data, u8 *out);
93 void fsverity_hash_buffer(const struct fsverity_hash_alg *alg,
94 const void *data, size_t size, u8 *out);
95 void __init fsverity_check_hash_algs(void);
96
97 /* init.c */
98
99 void __printf(3, 4) __cold
100 fsverity_msg(const struct inode *inode, const char *level,
101 const char *fmt, ...);
102
103 #define fsverity_warn(inode, fmt, ...) \
104 fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
105 #define fsverity_err(inode, fmt, ...) \
106 fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
107
108 /* measure.c */
109
110 #ifdef CONFIG_BPF_SYSCALL
111 void __init fsverity_init_bpf(void);
112 #else
fsverity_init_bpf(void)113 static inline void fsverity_init_bpf(void)
114 {
115 }
116 #endif
117
118 /* open.c */
119
120 int fsverity_init_merkle_tree_params(struct merkle_tree_params *params,
121 const struct inode *inode,
122 unsigned int hash_algorithm,
123 unsigned int log_blocksize,
124 const u8 *salt, size_t salt_size);
125
126 struct fsverity_info *fsverity_create_info(const struct inode *inode,
127 struct fsverity_descriptor *desc);
128
129 void fsverity_set_info(struct inode *inode, struct fsverity_info *vi);
130
131 void fsverity_free_info(struct fsverity_info *vi);
132
133 int fsverity_get_descriptor(struct inode *inode,
134 struct fsverity_descriptor **desc_ret);
135
136 void __init fsverity_init_info_cache(void);
137
138 /* signature.c */
139
140 #ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
141 extern int fsverity_require_signatures;
142 int fsverity_verify_signature(const struct fsverity_info *vi,
143 const u8 *signature, size_t sig_size);
144
145 void __init fsverity_init_signature(void);
146 #else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
147 static inline int
fsverity_verify_signature(const struct fsverity_info * vi,const u8 * signature,size_t sig_size)148 fsverity_verify_signature(const struct fsverity_info *vi,
149 const u8 *signature, size_t sig_size)
150 {
151 return 0;
152 }
153
fsverity_init_signature(void)154 static inline void fsverity_init_signature(void)
155 {
156 }
157 #endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
158
159 /* verify.c */
160
161 void __init fsverity_init_workqueue(void);
162
163 #endif /* _FSVERITY_PRIVATE_H */
164