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 * The maximum supported interleaving factor for multibuffer hashing, or
34 * 1 if the algorithm doesn't support multibuffer hashing
35 */
36 int mb_max_msgs;
37 };
38
39 /* Merkle tree parameters: hash algorithm, initial hash state, and topology */
40 struct merkle_tree_params {
41 const struct fsverity_hash_alg *hash_alg; /* the hash algorithm */
42 const u8 *hashstate; /* initial hash state or NULL */
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 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 const u8 *fsverity_prepare_hash_state(const struct fsverity_hash_alg *alg,
89 const u8 *salt, size_t salt_size);
90 int fsverity_hash_block(const struct merkle_tree_params *params,
91 const struct inode *inode, const void *data, u8 *out);
92 int fsverity_hash_buffer(const struct fsverity_hash_alg *alg,
93 const void *data, size_t size, u8 *out);
94 void __init fsverity_check_hash_algs(void);
95
96 /* init.c */
97
98 void __printf(3, 4) __cold
99 fsverity_msg(const struct inode *inode, const char *level,
100 const char *fmt, ...);
101
102 #define fsverity_warn(inode, fmt, ...) \
103 fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
104 #define fsverity_err(inode, fmt, ...) \
105 fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
106
107 /* measure.c */
108
109 #ifdef CONFIG_BPF_SYSCALL
110 void __init fsverity_init_bpf(void);
111 #else
fsverity_init_bpf(void)112 static inline void fsverity_init_bpf(void)
113 {
114 }
115 #endif
116
117 /* open.c */
118
119 int fsverity_init_merkle_tree_params(struct merkle_tree_params *params,
120 const struct inode *inode,
121 unsigned int hash_algorithm,
122 unsigned int log_blocksize,
123 const u8 *salt, size_t salt_size);
124
125 struct fsverity_info *fsverity_create_info(const struct inode *inode,
126 struct fsverity_descriptor *desc);
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
135 void __init fsverity_init_info_cache(void);
136
137 /* signature.c */
138
139 #ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
140 extern int fsverity_require_signatures;
141 int fsverity_verify_signature(const struct fsverity_info *vi,
142 const u8 *signature, size_t sig_size);
143
144 void __init fsverity_init_signature(void);
145 #else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
146 static inline int
fsverity_verify_signature(const struct fsverity_info * vi,const u8 * signature,size_t sig_size)147 fsverity_verify_signature(const struct fsverity_info *vi,
148 const u8 *signature, size_t sig_size)
149 {
150 return 0;
151 }
152
fsverity_init_signature(void)153 static inline void fsverity_init_signature(void)
154 {
155 }
156 #endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
157
158 /* verify.c */
159
160 #define FS_VERITY_MAX_PENDING_DATA_BLOCKS 2
161
162 void __init fsverity_init_workqueue(void);
163
164 #endif /* _FSVERITY_PRIVATE_H */
165