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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
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 */
22struct 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
33union 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 */
39struct 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 a pointer to it is stored in the file's in-memory inode. It remains
67 * until the inode is evicted. It caches information about the Merkle tree
68 * that's needed to efficiently verify data read from the file. It also caches
69 * the file digest. The Merkle tree pages themselves are not cached here, but
70 * the filesystem may cache them.
71 */
72struct fsverity_info {
73 struct merkle_tree_params tree_params;
74 u8 root_hash[FS_VERITY_MAX_DIGEST_SIZE];
75 u8 file_digest[FS_VERITY_MAX_DIGEST_SIZE];
76 const struct inode *inode;
77 unsigned long *hash_block_verified;
78};
79
80#define FS_VERITY_MAX_SIGNATURE_SIZE (FS_VERITY_MAX_DESCRIPTOR_SIZE - \
81 sizeof(struct fsverity_descriptor))
82
83/* hash_algs.c */
84
85extern const struct fsverity_hash_alg fsverity_hash_algs[];
86
87const struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode,
88 unsigned int num);
89union fsverity_hash_ctx *
90fsverity_prepare_hash_state(const struct fsverity_hash_alg *alg,
91 const u8 *salt, size_t salt_size);
92void fsverity_hash_block(const struct merkle_tree_params *params,
93 const void *data, u8 *out);
94void fsverity_hash_buffer(const struct fsverity_hash_alg *alg,
95 const void *data, size_t size, u8 *out);
96void __init fsverity_check_hash_algs(void);
97
98/* init.c */
99
100void __printf(3, 4) __cold
101fsverity_msg(const struct inode *inode, const char *level,
102 const char *fmt, ...);
103
104#define fsverity_warn(inode, fmt, ...) \
105 fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
106#define fsverity_err(inode, fmt, ...) \
107 fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
108
109/* measure.c */
110
111#ifdef CONFIG_BPF_SYSCALL
112void __init fsverity_init_bpf(void);
113#else
114static inline void fsverity_init_bpf(void)
115{
116}
117#endif
118
119/* open.c */
120
121int fsverity_init_merkle_tree_params(struct merkle_tree_params *params,
122 const struct inode *inode,
123 unsigned int hash_algorithm,
124 unsigned int log_blocksize,
125 const u8 *salt, size_t salt_size);
126
127struct fsverity_info *fsverity_create_info(const struct inode *inode,
128 struct fsverity_descriptor *desc);
129
130void fsverity_set_info(struct inode *inode, struct fsverity_info *vi);
131
132void fsverity_free_info(struct fsverity_info *vi);
133
134int fsverity_get_descriptor(struct inode *inode,
135 struct fsverity_descriptor **desc_ret);
136
137void __init fsverity_init_info_cache(void);
138
139/* signature.c */
140
141#ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
142extern int fsverity_require_signatures;
143int fsverity_verify_signature(const struct fsverity_info *vi,
144 const u8 *signature, size_t sig_size);
145
146void __init fsverity_init_signature(void);
147#else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
148static inline int
149fsverity_verify_signature(const struct fsverity_info *vi,
150 const u8 *signature, size_t sig_size)
151{
152 return 0;
153}
154
155static inline void fsverity_init_signature(void)
156{
157}
158#endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
159
160/* verify.c */
161
162void __init fsverity_init_workqueue(void);
163
164#endif /* _FSVERITY_PRIVATE_H */