fs/verity/fsverity_private.h

   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 #include <linux/mempool.h>
  15
  16 struct ahash_request;
  17
  18 /*
  19  * Implementation limit: maximum depth of the Merkle tree.  For now 8 is plenty;
  20  * it's enough for over U64_MAX bytes of data using SHA-256 and 4K blocks.
  21  */
  22 #define FS_VERITY_MAX_LEVELS            8
  23
  24 /* A hash algorithm supported by fs-verity */
  25 struct fsverity_hash_alg {
  26         struct crypto_ahash *tfm; /* hash tfm, allocated on demand */
  27         const char *name;         /* crypto API name, e.g. sha256 */
  28         unsigned int digest_size; /* digest size in bytes, e.g. 32 for SHA-256 */
  29         unsigned int block_size;  /* block size in bytes, e.g. 64 for SHA-256 */
  30         mempool_t req_pool;       /* mempool with a preallocated hash request */
  31         /*
  32          * The HASH_ALGO_* constant for this algorithm.  This is different from
  33          * FS_VERITY_HASH_ALG_*, which uses a different numbering scheme.
  34          */
  35         enum hash_algo algo_id;
  36 };
  37
  38 /* Merkle tree parameters: hash algorithm, initial hash state, and topology */
  39 struct merkle_tree_params {
  40         struct fsverity_hash_alg *hash_alg; /* the hash algorithm */
  41         const u8 *hashstate;            /* initial hash state or NULL */
  42         unsigned int digest_size;       /* same as hash_alg->digest_size */
  43         unsigned int block_size;        /* size of data and tree blocks */
  44         unsigned int hashes_per_block;  /* number of hashes per tree block */
  45         unsigned int blocks_per_page;   /* PAGE_SIZE / block_size */
  46         u8 log_digestsize;              /* log2(digest_size) */
  47         u8 log_blocksize;               /* log2(block_size) */
  48         u8 log_arity;                   /* log2(hashes_per_block) */
  49         u8 log_blocks_per_page;         /* log2(blocks_per_page) */
  50         unsigned int num_levels;        /* number of levels in Merkle tree */
  51         u64 tree_size;                  /* Merkle tree size in bytes */
  52         unsigned long tree_pages;       /* Merkle tree size in pages */
  53
  54         /*
  55          * Starting block index for each tree level, ordered from leaf level (0)
  56          * to root level ('num_levels - 1')
  57          */
  58         unsigned long level_start[FS_VERITY_MAX_LEVELS];
  59 };
  60
  61 /*
  62  * fsverity_info - cached verity metadata for an inode
  63  *
  64  * When a verity file is first opened, an instance of this struct is allocated
  65  * and stored in ->i_verity_info; it remains until the inode is evicted.  It
  66  * caches information about the Merkle tree that's needed to efficiently verify
  67  * data read from the file.  It also caches the file digest.  The Merkle tree
  68  * pages themselves are not cached here, but the filesystem may cache them.
  69  */
  70 struct fsverity_info {
  71         struct merkle_tree_params tree_params;
  72         u8 root_hash[FS_VERITY_MAX_DIGEST_SIZE];
  73         u8 file_digest[FS_VERITY_MAX_DIGEST_SIZE];
  74         const struct inode *inode;
  75         unsigned long *hash_block_verified;
  76         spinlock_t hash_page_init_lock;
  77 };
  78
  79 #define FS_VERITY_MAX_SIGNATURE_SIZE    (FS_VERITY_MAX_DESCRIPTOR_SIZE - \
  80                                          sizeof(struct fsverity_descriptor))
  81
  82 /* hash_algs.c */
  83
  84 extern struct fsverity_hash_alg fsverity_hash_algs[];
  85
  86 struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode,
  87                                                 unsigned int num);
  88 struct ahash_request *fsverity_alloc_hash_request(struct fsverity_hash_alg *alg,
  89                                                   gfp_t gfp_flags);
  90 void fsverity_free_hash_request(struct fsverity_hash_alg *alg,
  91                                 struct ahash_request *req);
  92 const u8 *fsverity_prepare_hash_state(struct fsverity_hash_alg *alg,
  93                                       const u8 *salt, size_t salt_size);
  94 int fsverity_hash_block(const struct merkle_tree_params *params,
  95                         const struct inode *inode, struct ahash_request *req,
  96                         struct page *page, unsigned int offset, u8 *out);
  97 int fsverity_hash_buffer(struct fsverity_hash_alg *alg,
  98                          const void *data, size_t size, u8 *out);
  99 void __init fsverity_check_hash_algs(void);
 100
 101 /* init.c */
 102
 103 void __printf(3, 4) __cold
 104 fsverity_msg(const struct inode *inode, const char *level,
 105              const char *fmt, ...);
 106
 107 #define fsverity_warn(inode, fmt, ...)          \
 108         fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
 109 #define fsverity_err(inode, fmt, ...)           \
 110         fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
 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 int __init fsverity_init_info_cache(void);
 131 void __init fsverity_exit_info_cache(void);
 132
 133 /* signature.c */
 134
 135 #ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
 136 int fsverity_verify_signature(const struct fsverity_info *vi,
 137                               const u8 *signature, size_t sig_size);
 138
 139 int __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 int fsverity_init_signature(void)
 149 {
 150         return 0;
 151 }
 152 #endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
 153
 154 /* verify.c */
 155
 156 int __init fsverity_init_workqueue(void);
 157 void __init fsverity_exit_workqueue(void);
 158
 159 #endif /* _FSVERITY_PRIVATE_H */