[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

#ifdef CONFIG_FS_VERITY_DEBUG
#define DEBUG
#endif

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

#include <crypto/sha2.h>
#include <linux/fsverity.h>
#include <linux/mempool.h>

struct ahash_request;

/*
 * 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

/*
 * Largest digest size among all hash algorithms supported by fs-verity.
 * Currently assumed to be <= size of fsverity_descriptor::root_hash.
 */
#define FS_VERITY_MAX_DIGEST_SIZE	SHA512_DIGEST_SIZE

/* A hash algorithm supported by fs-verity */
struct fsverity_hash_alg {
	struct crypto_ahash *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 */
	mempool_t req_pool;	  /* mempool with a preallocated hash request */
};

/* Merkle tree parameters: hash algorithm, initial hash state, and topology */
struct merkle_tree_params {
	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 log_blocksize;	/* log2(block_size) */
	unsigned int log_arity;		/* log2(hashes_per_block) */
	unsigned int num_levels;	/* number of levels in Merkle tree */
	u64 tree_size;			/* Merkle tree size in bytes */
	unsigned long level0_blocks;	/* number of blocks in tree level 0 */

	/*
	 * Starting block index for each tree level, ordered from leaf level (0)
	 * to root level ('num_levels - 1')
	 */
	u64 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;
};

/* Arbitrary limit to bound the kmalloc() size.  Can be changed. */
#define FS_VERITY_MAX_DESCRIPTOR_SIZE	16384

#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[];

struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode,
						unsigned int num);
struct ahash_request *fsverity_alloc_hash_request(struct fsverity_hash_alg *alg,
						  gfp_t gfp_flags);
void fsverity_free_hash_request(struct fsverity_hash_alg *alg,
				struct ahash_request *req);
const u8 *fsverity_prepare_hash_state(struct fsverity_hash_alg *alg,
				      const u8 *salt, size_t salt_size);
int fsverity_hash_page(const struct merkle_tree_params *params,
		       const struct inode *inode,
		       struct ahash_request *req, struct page *page, u8 *out);
int fsverity_hash_buffer(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__)

/* 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,
					   size_t desc_size);

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,
			    size_t *desc_size_ret);

int __init fsverity_init_info_cache(void);
void __init fsverity_exit_info_cache(void);

/* signature.c */

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

int __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 int fsverity_init_signature(void)
{
	return 0;
}
#endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */

/* verify.c */

int __init fsverity_init_workqueue(void);
void __init fsverity_exit_workqueue(void);

#endif /* _FSVERITY_PRIVATE_H */
Commit	Line	Data
671e67b4 EB	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
a24d22b2	17	#include <crypto/sha2.h>
fd2d1acf	18	#include <linux/fsverity.h>
439bea10	19	#include <linux/mempool.h>
671e67b4 EB	20
	21	struct ahash_request;
	22
	23	/*
	24	* Implementation limit: maximum depth of the Merkle tree. For now 8 is plenty;
	25	* it's enough for over U64_MAX bytes of data using SHA-256 and 4K blocks.
	26	*/
	27	#define FS_VERITY_MAX_LEVELS 8
	28
	29	/*
	30	* Largest digest size among all hash algorithms supported by fs-verity.
	31	* Currently assumed to be <= size of fsverity_descriptor::root_hash.
	32	*/
add890c9	33	#define FS_VERITY_MAX_DIGEST_SIZE SHA512_DIGEST_SIZE
671e67b4 EB	34
	35	/* A hash algorithm supported by fs-verity */
	36	struct fsverity_hash_alg {
	37	struct crypto_ahash tfm; / hash tfm, allocated on demand */
	38	const char name; / crypto API name, e.g. sha256 */
	39	unsigned int digest_size; /* digest size in bytes, e.g. 32 for SHA-256 */
	40	unsigned int block_size; /* block size in bytes, e.g. 64 for SHA-256 */
439bea10	41	mempool_t req_pool; /* mempool with a preallocated hash request */
671e67b4 EB	42	};
	43
	44	/* Merkle tree parameters: hash algorithm, initial hash state, and topology */
	45	struct merkle_tree_params {
439bea10	46	struct fsverity_hash_alg hash_alg; / the hash algorithm */
671e67b4 EB	47	const u8 hashstate; / initial hash state or NULL */
	48	unsigned int digest_size; /* same as hash_alg->digest_size */
	49	unsigned int block_size; /* size of data and tree blocks */
	50	unsigned int hashes_per_block; /* number of hashes per tree block */
	51	unsigned int log_blocksize; /* log2(block_size) */
	52	unsigned int log_arity; /* log2(hashes_per_block) */
	53	unsigned int num_levels; /* number of levels in Merkle tree */
	54	u64 tree_size; /* Merkle tree size in bytes */
fd39073d	55	unsigned long level0_blocks; /* number of blocks in tree level 0 */
671e67b4 EB	56
	57	/*
	58	* Starting block index for each tree level, ordered from leaf level (0)
	59	* to root level ('num_levels - 1')
	60	*/
	61	u64 level_start[FS_VERITY_MAX_LEVELS];
	62	};
	63
6377a38b	64	/*
fd2d1acf EB	65	* fsverity_info - cached verity metadata for an inode
	66	*
	67	* When a verity file is first opened, an instance of this struct is allocated
	68	* and stored in ->i_verity_info; it remains until the inode is evicted. It
	69	* caches information about the Merkle tree that's needed to efficiently verify
ed45e201 EB	70	* data read from the file. It also caches the file digest. The Merkle tree
ed45e201 EB	71	* pages themselves are not cached here, but the filesystem may cache them.
fd2d1acf EB	72	*/
	73	struct fsverity_info {
	74	struct merkle_tree_params tree_params;
	75	u8 root_hash[FS_VERITY_MAX_DIGEST_SIZE];
ed45e201	76	u8 file_digest[FS_VERITY_MAX_DIGEST_SIZE];
fd2d1acf EB	77	const struct inode *inode;
	78	};
	79
fd2d1acf EB	80	/* Arbitrary limit to bound the kmalloc() size. Can be changed. */
	81	#define FS_VERITY_MAX_DESCRIPTOR_SIZE 16384
	82
432434c9 EB	83	#define FS_VERITY_MAX_SIGNATURE_SIZE (FS_VERITY_MAX_DESCRIPTOR_SIZE - \
	84	sizeof(struct fsverity_descriptor))
	85
671e67b4 EB	86	/* hash_algs.c */
	87
	88	extern struct fsverity_hash_alg fsverity_hash_algs[];
	89
439bea10 EB	90	struct fsverity_hash_alg fsverity_get_hash_alg(const struct inode inode,
	91	unsigned int num);
	92	struct ahash_request fsverity_alloc_hash_request(struct fsverity_hash_alg alg,
	93	gfp_t gfp_flags);
	94	void fsverity_free_hash_request(struct fsverity_hash_alg *alg,
	95	struct ahash_request *req);
	96	const u8 fsverity_prepare_hash_state(struct fsverity_hash_alg alg,
671e67b4 EB	97	const u8 *salt, size_t salt_size);
	98	int fsverity_hash_page(const struct merkle_tree_params *params,
	99	const struct inode *inode,
	100	struct ahash_request req, struct page page, u8 *out);
439bea10	101	int fsverity_hash_buffer(struct fsverity_hash_alg *alg,
671e67b4 EB	102	const void data, size_t size, u8 out);
	103	void __init fsverity_check_hash_algs(void);
	104
	105	/* init.c */
	106
9cd6b593	107	void __printf(3, 4) __cold
671e67b4 EB	108	fsverity_msg(const struct inode inode, const char level,
	109	const char *fmt, ...);
	110
	111	#define fsverity_warn(inode, fmt, ...) \
	112	fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
	113	#define fsverity_err(inode, fmt, ...) \
	114	fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
	115
fd2d1acf EB	116	/* open.c */
	117
	118	int fsverity_init_merkle_tree_params(struct merkle_tree_params *params,
	119	const struct inode *inode,
	120	unsigned int hash_algorithm,
	121	unsigned int log_blocksize,
	122	const u8 *salt, size_t salt_size);
	123
	124	struct fsverity_info fsverity_create_info(const struct inode inode,
c2c82611 EB	125	struct fsverity_descriptor *desc,
c2c82611 EB	126	size_t desc_size);
fd2d1acf EB	127
	128	void fsverity_set_info(struct inode inode, struct fsverity_info vi);
	129
	130	void fsverity_free_info(struct fsverity_info *vi);
	131
c2c82611 EB	132	int fsverity_get_descriptor(struct inode *inode,
	133	struct fsverity_descriptor **desc_ret,
	134	size_t *desc_size_ret);
	135
fd2d1acf	136	int __init fsverity_init_info_cache(void);
8a1d0f9c EB	137	void __init fsverity_exit_info_cache(void);
8a1d0f9c EB	138
432434c9 EB	139	/* signature.c */
	140
	141	#ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
	142	int fsverity_verify_signature(const struct fsverity_info *vi,
fab634c4	143	const u8 *signature, size_t sig_size);
432434c9 EB	144
	145	int __init fsverity_init_signature(void);
	146	#else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
	147	static inline int
	148	fsverity_verify_signature(const struct fsverity_info *vi,
fab634c4	149	const u8 *signature, size_t sig_size)
432434c9 EB	150	{
	151	return 0;
	152	}
	153
	154	static inline int fsverity_init_signature(void)
	155	{
	156	return 0;
	157	}
	158	#endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
	159
8a1d0f9c EB	160	/* verify.c */
	161
	162	int __init fsverity_init_workqueue(void);
432434c9	163	void __init fsverity_exit_workqueue(void);
fd2d1acf	164
671e67b4	165	#endif /* _FSVERITY_PRIVATE_H */