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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
11#define pr_fmt(fmt) "fs-verity: " fmt
12
13#include <linux/fsverity.h>
14#include <linux/mempool.h>
15
16struct 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
24/* A hash algorithm supported by fs-verity */
25struct 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 */
30 mempool_t req_pool; /* mempool with a preallocated hash request */
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;
36};
37
38/* Merkle tree parameters: hash algorithm, initial hash state, and topology */
39struct merkle_tree_params {
40 struct fsverity_hash_alg *hash_alg; /* the hash algorithm */
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 */
45 unsigned int blocks_per_page; /* PAGE_SIZE / block_size */
46 u8 log_digestsize; /* log2(digest_size) */
47 u8 log_blocksize; /* log2(block_size) */
48 u8 log_arity; /* log2(hashes_per_block) */
49 u8 log_blocks_per_page; /* log2(blocks_per_page) */
50 unsigned int num_levels; /* number of levels in Merkle tree */
51 u64 tree_size; /* Merkle tree size in bytes */
52 unsigned long tree_pages; /* Merkle tree size in pages */
53
54 /*
55 * Starting block index for each tree level, ordered from leaf level (0)
56 * to root level ('num_levels - 1')
57 */
58 unsigned long level_start[FS_VERITY_MAX_LEVELS];
59};
60
61/*
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
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.
69 */
70struct fsverity_info {
71 struct merkle_tree_params tree_params;
72 u8 root_hash[FS_VERITY_MAX_DIGEST_SIZE];
73 u8 file_digest[FS_VERITY_MAX_DIGEST_SIZE];
74 const struct inode *inode;
75 unsigned long *hash_block_verified;
76 spinlock_t hash_page_init_lock;
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
84extern struct fsverity_hash_alg fsverity_hash_algs[];
85
86struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode,
87 unsigned int num);
88struct ahash_request *fsverity_alloc_hash_request(struct fsverity_hash_alg *alg,
89 gfp_t gfp_flags);
90void fsverity_free_hash_request(struct fsverity_hash_alg *alg,
91 struct ahash_request *req);
92const u8 *fsverity_prepare_hash_state(struct fsverity_hash_alg *alg,
93 const u8 *salt, size_t salt_size);
94int 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);
97int fsverity_hash_buffer(struct fsverity_hash_alg *alg,
98 const void *data, size_t size, u8 *out);
99void __init fsverity_check_hash_algs(void);
100
101/* init.c */
102
103void __printf(3, 4) __cold
104fsverity_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
114int 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
120struct fsverity_info *fsverity_create_info(const struct inode *inode,
121 struct fsverity_descriptor *desc);
122
123void fsverity_set_info(struct inode *inode, struct fsverity_info *vi);
124
125void fsverity_free_info(struct fsverity_info *vi);
126
127int fsverity_get_descriptor(struct inode *inode,
128 struct fsverity_descriptor **desc_ret);
129
130int __init fsverity_init_info_cache(void);
131void __init fsverity_exit_info_cache(void);
132
133/* signature.c */
134
135#ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
136int fsverity_verify_signature(const struct fsverity_info *vi,
137 const u8 *signature, size_t sig_size);
138
139int __init fsverity_init_signature(void);
140#else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
141static inline int
142fsverity_verify_signature(const struct fsverity_info *vi,
143 const u8 *signature, size_t sig_size)
144{
145 return 0;
146}
147
148static inline int fsverity_init_signature(void)
149{
150 return 0;
151}
152#endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
153
154/* verify.c */
155
156int __init fsverity_init_workqueue(void);
157void __init fsverity_exit_workqueue(void);
158
159#endif /* _FSVERITY_PRIVATE_H */