text: /* 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 */
  