fs/verity/fsverity_private.h - linux - Git at Google

 /* 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/sha.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 measurement.  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 measurement[FS_VERITY_MAX_DIGEST_SIZE];
 	const struct inode *inode;
 };

 /*
  * Merkle tree properties.  The file measurement is the hash of this structure
  * excluding the signature and with the sig_size field set to 0.
  */
 struct fsverity_descriptor {
 	__u8 version;		/* must be 1 */
 	__u8 hash_algorithm;	/* Merkle tree hash algorithm */
 	__u8 log_blocksize;	/* log2 of size of data and tree blocks */
 	__u8 salt_size;		/* size of salt in bytes; 0 if none */
 	__le32 sig_size;	/* size of signature in bytes; 0 if none */
 	__le64 data_size;	/* size of file the Merkle tree is built over */
 	__u8 root_hash[64];	/* Merkle tree root hash */
 	__u8 salt[32];		/* salt prepended to each hashed block */
 	__u8 __reserved[144];	/* must be 0's */
 	__u8 signature[];	/* optional PKCS#7 signature */
 };

 /* 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))

 /*
  * Format in which verity file measurements are signed.  This is the same as
  * 'struct fsverity_digest', except here some magic bytes are prepended to
  * provide some context about what is being signed in case the same key is used
  * for non-fsverity purposes, and here the fields have fixed endianness.
  */
 struct fsverity_signed_digest {
 	char magic[8];			/* must be "FSVerity" */
 	__le16 digest_algorithm;
 	__le16 digest_size;
 	__u8 digest[];
 };

 /* 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,
 					   void *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 __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 struct fsverity_descriptor *desc,
 			      size_t desc_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 struct fsverity_descriptor *desc,
 			  size_t desc_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 */
	/* 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/sha.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 measurement. 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 measurement[FS_VERITY_MAX_DIGEST_SIZE];
	const struct inode *inode;
	};

	/*
	* Merkle tree properties. The file measurement is the hash of this structure
	* excluding the signature and with the sig_size field set to 0.
	*/
	struct fsverity_descriptor {
	__u8 version; /* must be 1 */
	__u8 hash_algorithm; /* Merkle tree hash algorithm */
	__u8 log_blocksize; /* log2 of size of data and tree blocks */
	__u8 salt_size; /* size of salt in bytes; 0 if none */
	__le32 sig_size; /* size of signature in bytes; 0 if none */
	__le64 data_size; /* size of file the Merkle tree is built over */
	__u8 root_hash[64]; /* Merkle tree root hash */
	__u8 salt[32]; /* salt prepended to each hashed block */
	__u8 __reserved[144]; /* must be 0's */
	__u8 signature[]; /* optional PKCS#7 signature */
	};

	/* 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))

	/*
	* Format in which verity file measurements are signed. This is the same as
	* 'struct fsverity_digest', except here some magic bytes are prepended to
	* provide some context about what is being signed in case the same key is used
	* for non-fsverity purposes, and here the fields have fixed endianness.
	*/
	struct fsverity_signed_digest {
	char magic[8]; /* must be "FSVerity" */
	__le16 digest_algorithm;
	__le16 digest_size;
	__u8 digest[];
	};

	/* 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,
	void *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 __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 struct fsverity_descriptor *desc,
	size_t desc_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 struct fsverity_descriptor *desc,
	size_t desc_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 */