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	spinlock_t hash_page_init_lock;
 73};
 74
 75#define FS_VERITY_MAX_SIGNATURE_SIZE	(FS_VERITY_MAX_DESCRIPTOR_SIZE - \
 76					 sizeof(struct fsverity_descriptor))
 77
 78/* hash_algs.c */
 79
 80extern struct fsverity_hash_alg fsverity_hash_algs[];
 81
 82const struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode,
 83						      unsigned int num);
 84const u8 *fsverity_prepare_hash_state(const struct fsverity_hash_alg *alg,
 85				      const u8 *salt, size_t salt_size);
 86int fsverity_hash_block(const struct merkle_tree_params *params,
 87			const struct inode *inode, const void *data, u8 *out);
 88int fsverity_hash_buffer(const struct fsverity_hash_alg *alg,
 89			 const void *data, size_t size, u8 *out);
 90void __init fsverity_check_hash_algs(void);
 91
 92/* init.c */
 93
 94void __printf(3, 4) __cold
 95fsverity_msg(const struct inode *inode, const char *level,
 96	     const char *fmt, ...);
 97
 98#define fsverity_warn(inode, fmt, ...)		\
 99	fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
100#define fsverity_err(inode, fmt, ...)		\
101	fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
102
103/* measure.c */
104
105#ifdef CONFIG_BPF_SYSCALL
106void __init fsverity_init_bpf(void);
107#else
108static inline void fsverity_init_bpf(void)
109{
110}
111#endif
112
113/* open.c */
114
115int fsverity_init_merkle_tree_params(struct merkle_tree_params *params,
116				     const struct inode *inode,
117				     unsigned int hash_algorithm,
118				     unsigned int log_blocksize,
119				     const u8 *salt, size_t salt_size);
120
121struct fsverity_info *fsverity_create_info(const struct inode *inode,
122					   struct fsverity_descriptor *desc);
123
124void fsverity_set_info(struct inode *inode, struct fsverity_info *vi);
125
126void fsverity_free_info(struct fsverity_info *vi);
127
128int fsverity_get_descriptor(struct inode *inode,
129			    struct fsverity_descriptor **desc_ret);
130
131void __init fsverity_init_info_cache(void);
132
133/* signature.c */
134
135#ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
136extern int fsverity_require_signatures;
137int fsverity_verify_signature(const struct fsverity_info *vi,
138			      const u8 *signature, size_t sig_size);
139
140void __init fsverity_init_signature(void);
141#else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
142static inline int
143fsverity_verify_signature(const struct fsverity_info *vi,
144			  const u8 *signature, size_t sig_size)
145{
146	return 0;
147}
148
149static inline void fsverity_init_signature(void)
150{
151}
152#endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
153
154/* verify.c */
155
156void __init fsverity_init_workqueue(void);
157
158#endif /* _FSVERITY_PRIVATE_H */