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	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
34/* Merkle tree parameters: hash algorithm, initial hash state, and topology */
35struct merkle_tree_params {
36	const struct fsverity_hash_alg *hash_alg; /* the hash algorithm */
37	const u8 *hashstate;		/* initial hash state or NULL */
38	unsigned int digest_size;	/* same as hash_alg->digest_size */
39	unsigned int block_size;	/* size of data and tree blocks */
40	unsigned int hashes_per_block;	/* number of hashes per tree block */
41	unsigned int blocks_per_page;	/* PAGE_SIZE / block_size */
42	u8 log_digestsize;		/* log2(digest_size) */
43	u8 log_blocksize;		/* log2(block_size) */
44	u8 log_arity;			/* log2(hashes_per_block) */
45	u8 log_blocks_per_page;		/* log2(blocks_per_page) */
46	unsigned int num_levels;	/* number of levels in Merkle tree */
47	u64 tree_size;			/* Merkle tree size in bytes */
48	unsigned long tree_pages;	/* Merkle tree size in pages */
49
50	/*
51	 * Starting block index for each tree level, ordered from leaf level (0)
52	 * to root level ('num_levels - 1')
53	 */
54	unsigned long 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	unsigned long *hash_block_verified;
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
81const struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode,
82						      unsigned int num);
83const u8 *fsverity_prepare_hash_state(const struct fsverity_hash_alg *alg,
84				      const u8 *salt, size_t salt_size);
85int fsverity_hash_block(const struct merkle_tree_params *params,
86			const struct inode *inode, const void *data, u8 *out);
87int fsverity_hash_buffer(const struct fsverity_hash_alg *alg,
88			 const void *data, size_t size, u8 *out);
89void __init fsverity_check_hash_algs(void);
90
91/* init.c */
92
93void __printf(3, 4) __cold
94fsverity_msg(const struct inode *inode, const char *level,
95	     const char *fmt, ...);
96
97#define fsverity_warn(inode, fmt, ...)		\
98	fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
99#define fsverity_err(inode, fmt, ...)		\
100	fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
101
102/* measure.c */
103
104#ifdef CONFIG_BPF_SYSCALL
105void __init fsverity_init_bpf(void);
106#else
107static inline void fsverity_init_bpf(void)
108{
109}
110#endif
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
130void __init fsverity_init_info_cache(void);
131
132/* signature.c */
133
134#ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
135extern int fsverity_require_signatures;
136int fsverity_verify_signature(const struct fsverity_info *vi,
137			      const u8 *signature, size_t sig_size);
138
139void __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 void fsverity_init_signature(void)
149{
150}
151#endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
152
153/* verify.c */
154
155void __init fsverity_init_workqueue(void);
156
157#endif /* _FSVERITY_PRIVATE_H */
158