[linux-block.git] / fs / verity / fsverity_private.h

/* SPDX-License-Identifier: GPL-2.0 */
/*
 * fs-verity: read-only file-based authenticity protection
 *
 * Copyright 2019 Google LLC
 */

#ifndef _FSVERITY_PRIVATE_H
#define _FSVERITY_PRIVATE_H

#define pr_fmt(fmt) "fs-verity: " fmt

#include <linux/fsverity.h>

/*
 * Implementation limit: maximum depth of the Merkle tree.  For now 8 is plenty;
 * it's enough for over U64_MAX bytes of data using SHA-256 and 4K blocks.
 */
#define FS_VERITY_MAX_LEVELS		8

/* A hash algorithm supported by fs-verity */
struct fsverity_hash_alg {
	struct crypto_shash *tfm; /* hash tfm, allocated on demand */
	const char *name;	  /* crypto API name, e.g. sha256 */
	unsigned int digest_size; /* digest size in bytes, e.g. 32 for SHA-256 */
	unsigned int block_size;  /* block size in bytes, e.g. 64 for SHA-256 */
	/*
	 * The HASH_ALGO_* constant for this algorithm.  This is different from
	 * FS_VERITY_HASH_ALG_*, which uses a different numbering scheme.
	 */
	enum hash_algo algo_id;
};

/* Merkle tree parameters: hash algorithm, initial hash state, and topology */
struct merkle_tree_params {
	const struct fsverity_hash_alg *hash_alg; /* the hash algorithm */
	const u8 *hashstate;		/* initial hash state or NULL */
	unsigned int digest_size;	/* same as hash_alg->digest_size */
	unsigned int block_size;	/* size of data and tree blocks */
	unsigned int hashes_per_block;	/* number of hashes per tree block */
	unsigned int blocks_per_page;	/* PAGE_SIZE / block_size */
	u8 log_digestsize;		/* log2(digest_size) */
	u8 log_blocksize;		/* log2(block_size) */
	u8 log_arity;			/* log2(hashes_per_block) */
	u8 log_blocks_per_page;		/* log2(blocks_per_page) */
	unsigned int num_levels;	/* number of levels in Merkle tree */
	u64 tree_size;			/* Merkle tree size in bytes */
	unsigned long tree_pages;	/* Merkle tree size in pages */

	/*
	 * Starting block index for each tree level, ordered from leaf level (0)
	 * to root level ('num_levels - 1')
	 */
	unsigned long level_start[FS_VERITY_MAX_LEVELS];
};

/*
 * fsverity_info - cached verity metadata for an inode
 *
 * When a verity file is first opened, an instance of this struct is allocated
 * and stored in ->i_verity_info; it remains until the inode is evicted.  It
 * caches information about the Merkle tree that's needed to efficiently verify
 * data read from the file.  It also caches the file digest.  The Merkle tree
 * pages themselves are not cached here, but the filesystem may cache them.
 */
struct fsverity_info {
	struct merkle_tree_params tree_params;
	u8 root_hash[FS_VERITY_MAX_DIGEST_SIZE];
	u8 file_digest[FS_VERITY_MAX_DIGEST_SIZE];
	const struct inode *inode;
	unsigned long *hash_block_verified;
};

#define FS_VERITY_MAX_SIGNATURE_SIZE	(FS_VERITY_MAX_DESCRIPTOR_SIZE - \
					 sizeof(struct fsverity_descriptor))

/* hash_algs.c */

extern struct fsverity_hash_alg fsverity_hash_algs[];

const struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode,
						      unsigned int num);
const u8 *fsverity_prepare_hash_state(const struct fsverity_hash_alg *alg,
				      const u8 *salt, size_t salt_size);
int fsverity_hash_block(const struct merkle_tree_params *params,
			const struct inode *inode, const void *data, u8 *out);
int fsverity_hash_buffer(const struct fsverity_hash_alg *alg,
			 const void *data, size_t size, u8 *out);
void __init fsverity_check_hash_algs(void);

/* init.c */

void __printf(3, 4) __cold
fsverity_msg(const struct inode *inode, const char *level,
	     const char *fmt, ...);

#define fsverity_warn(inode, fmt, ...)		\
	fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
#define fsverity_err(inode, fmt, ...)		\
	fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)

/* measure.c */

#ifdef CONFIG_BPF_SYSCALL
void __init fsverity_init_bpf(void);
#else
static inline void fsverity_init_bpf(void)
{
}
#endif

/* open.c */

int fsverity_init_merkle_tree_params(struct merkle_tree_params *params,
				     const struct inode *inode,
				     unsigned int hash_algorithm,
				     unsigned int log_blocksize,
				     const u8 *salt, size_t salt_size);

struct fsverity_info *fsverity_create_info(const struct inode *inode,
					   struct fsverity_descriptor *desc);

void fsverity_set_info(struct inode *inode, struct fsverity_info *vi);

void fsverity_free_info(struct fsverity_info *vi);

int fsverity_get_descriptor(struct inode *inode,
			    struct fsverity_descriptor **desc_ret);

void __init fsverity_init_info_cache(void);

/* signature.c */

#ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
extern int fsverity_require_signatures;
int fsverity_verify_signature(const struct fsverity_info *vi,
			      const u8 *signature, size_t sig_size);

void __init fsverity_init_signature(void);
#else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
static inline int
fsverity_verify_signature(const struct fsverity_info *vi,
			  const u8 *signature, size_t sig_size)
{
	return 0;
}

static inline void fsverity_init_signature(void)
{
}
#endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */

/* verify.c */

void __init fsverity_init_workqueue(void);

#endif /* _FSVERITY_PRIVATE_H */
Commit	Line	Data
	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 */
	22	struct 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 */
	35	struct 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	*/
	66	struct 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
	79	extern struct fsverity_hash_alg fsverity_hash_algs[];
	80
	81	const struct fsverity_hash_alg fsverity_get_hash_alg(const struct inode inode,
	82	unsigned int num);
	83	const u8 fsverity_prepare_hash_state(const struct fsverity_hash_alg alg,
	84	const u8 *salt, size_t salt_size);
	85	int fsverity_hash_block(const struct merkle_tree_params *params,
	86	const struct inode inode, const void data, u8 *out);
	87	int fsverity_hash_buffer(const struct fsverity_hash_alg *alg,
	88	const void data, size_t size, u8 out);
	89	void __init fsverity_check_hash_algs(void);
	90
	91	/* init.c */
	92
	93	void __printf(3, 4) __cold
	94	fsverity_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
	105	void __init fsverity_init_bpf(void);
	106	#else
	107	static inline void fsverity_init_bpf(void)
	108	{
	109	}
	110	#endif
	111
	112	/* open.c */
	113
	114	int 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
	120	struct fsverity_info fsverity_create_info(const struct inode inode,
	121	struct fsverity_descriptor *desc);
	122
	123	void fsverity_set_info(struct inode inode, struct fsverity_info vi);
	124
	125	void fsverity_free_info(struct fsverity_info *vi);
	126
	127	int fsverity_get_descriptor(struct inode *inode,
	128	struct fsverity_descriptor **desc_ret);
	129
	130	void __init fsverity_init_info_cache(void);
	131
	132	/* signature.c */
	133
	134	#ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
	135	extern int fsverity_require_signatures;
	136	int fsverity_verify_signature(const struct fsverity_info *vi,
	137	const u8 *signature, size_t sig_size);
	138
	139	void __init fsverity_init_signature(void);
	140	#else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
	141	static inline int
	142	fsverity_verify_signature(const struct fsverity_info *vi,
	143	const u8 *signature, size_t sig_size)
	144	{
	145	return 0;
	146	}
	147
	148	static inline void fsverity_init_signature(void)
	149	{
	150	}
	151	#endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
	152
	153	/* verify.c */
	154
	155	void __init fsverity_init_workqueue(void);
	156
	157	#endif /* _FSVERITY_PRIVATE_H */