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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#ifdef CONFIG_FS_VERITY_DEBUG
12#define DEBUG
13#endif
14
15#define pr_fmt(fmt) "fs-verity: " fmt
16
17#include <linux/fsverity.h>
18#include <linux/mempool.h>
19
20struct ahash_request;
21
22/*
23 * Implementation limit: maximum depth of the Merkle tree. For now 8 is plenty;
24 * it's enough for over U64_MAX bytes of data using SHA-256 and 4K blocks.
25 */
26#define FS_VERITY_MAX_LEVELS 8
27
28/* A hash algorithm supported by fs-verity */
29struct fsverity_hash_alg {
30 struct crypto_ahash *tfm; /* hash tfm, allocated on demand */
31 const char *name; /* crypto API name, e.g. sha256 */
32 unsigned int digest_size; /* digest size in bytes, e.g. 32 for SHA-256 */
33 unsigned int block_size; /* block size in bytes, e.g. 64 for SHA-256 */
34 mempool_t req_pool; /* mempool with a preallocated hash request */
35};
36
37/* Merkle tree parameters: hash algorithm, initial hash state, and topology */
38struct merkle_tree_params {
39 struct fsverity_hash_alg *hash_alg; /* the hash algorithm */
40 const u8 *hashstate; /* initial hash state or NULL */
41 unsigned int digest_size; /* same as hash_alg->digest_size */
42 unsigned int block_size; /* size of data and tree blocks */
43 unsigned int hashes_per_block; /* number of hashes per tree block */
44 unsigned int log_blocksize; /* log2(block_size) */
45 unsigned int log_arity; /* log2(hashes_per_block) */
46 unsigned int num_levels; /* number of levels in Merkle tree */
47 u64 tree_size; /* Merkle tree size in bytes */
48 unsigned long level0_blocks; /* number of blocks in tree level 0 */
49
50 /*
51 * Starting block index for each tree level, ordered from leaf level (0)
52 * to root level ('num_levels - 1')
53 */
54 u64 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 */
66struct 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};
72
73
74#define FS_VERITY_MAX_SIGNATURE_SIZE (FS_VERITY_MAX_DESCRIPTOR_SIZE - \
75 sizeof(struct fsverity_descriptor))
76
77/* hash_algs.c */
78
79extern struct fsverity_hash_alg fsverity_hash_algs[];
80
81struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode,
82 unsigned int num);
83struct ahash_request *fsverity_alloc_hash_request(struct fsverity_hash_alg *alg,
84 gfp_t gfp_flags);
85void fsverity_free_hash_request(struct fsverity_hash_alg *alg,
86 struct ahash_request *req);
87const u8 *fsverity_prepare_hash_state(struct fsverity_hash_alg *alg,
88 const u8 *salt, size_t salt_size);
89int fsverity_hash_page(const struct merkle_tree_params *params,
90 const struct inode *inode,
91 struct ahash_request *req, struct page *page, u8 *out);
92int fsverity_hash_buffer(struct fsverity_hash_alg *alg,
93 const void *data, size_t size, u8 *out);
94void __init fsverity_check_hash_algs(void);
95
96/* init.c */
97
98void __printf(3, 4) __cold
99fsverity_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/* open.c */
108
109int fsverity_init_merkle_tree_params(struct merkle_tree_params *params,
110 const struct inode *inode,
111 unsigned int hash_algorithm,
112 unsigned int log_blocksize,
113 const u8 *salt, size_t salt_size);
114
115struct fsverity_info *fsverity_create_info(const struct inode *inode,
116 struct fsverity_descriptor *desc);
117
118void fsverity_set_info(struct inode *inode, struct fsverity_info *vi);
119
120void fsverity_free_info(struct fsverity_info *vi);
121
122int fsverity_get_descriptor(struct inode *inode,
123 struct fsverity_descriptor **desc_ret);
124
125int __init fsverity_init_info_cache(void);
126void __init fsverity_exit_info_cache(void);
127
128/* signature.c */
129
130#ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
131int fsverity_verify_signature(const struct fsverity_info *vi,
132 const u8 *signature, size_t sig_size);
133
134int __init fsverity_init_signature(void);
135#else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
136static inline int
137fsverity_verify_signature(const struct fsverity_info *vi,
138 const u8 *signature, size_t sig_size)
139{
140 return 0;
141}
142
143static inline int fsverity_init_signature(void)
144{
145 return 0;
146}
147#endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
148
149/* verify.c */
150
151int __init fsverity_init_workqueue(void);
152void __init fsverity_exit_workqueue(void);
153
154#endif /* _FSVERITY_PRIVATE_H */