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