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 #ifdef CONFIG_FS_VERITY_DEBUG
  12 #define DEBUG
  13 #endif
  14
  15 #define pr_fmt(fmt) "fs-verity: " fmt
  16
  17 #include <linux/fsverity.h>
  18 #include <linux/mempool.h>
  19
  20 struct ahash_request;
  21
  22 /*
  23  * Implementation limit: maximum depth of the Merkle tree.  For now 8 is plenty;
  24  * it's enough for over U64_MAX bytes of data using SHA-256 and 4K blocks.
  25  */
  26 #define FS_VERITY_MAX_LEVELS            8
  27
  28 /* A hash algorithm supported by fs-verity */
  29 struct fsverity_hash_alg {
  30         struct crypto_ahash *tfm; /* hash tfm, allocated on demand */
  31         const char *name;         /* crypto API name, e.g. sha256 */
  32         unsigned int digest_size; /* digest size in bytes, e.g. 32 for SHA-256 */
  33         unsigned int block_size;  /* block size in bytes, e.g. 64 for SHA-256 */
  34         mempool_t req_pool;       /* mempool with a preallocated hash request */
  35 };
  36
  37 /* Merkle tree parameters: hash algorithm, initial hash state, and topology */
  38 struct merkle_tree_params {
  39         struct fsverity_hash_alg *hash_alg; /* the hash algorithm */
  40         const u8 *hashstate;            /* initial hash state or NULL */
  41         unsigned int digest_size;       /* same as hash_alg->digest_size */
  42         unsigned int block_size;        /* size of data and tree blocks */
  43         unsigned int hashes_per_block;  /* number of hashes per tree block */
  44         unsigned int log_blocksize;     /* log2(block_size) */
  45         unsigned int log_arity;         /* log2(hashes_per_block) */
  46         unsigned int num_levels;        /* number of levels in Merkle tree */
  47         u64 tree_size;                  /* Merkle tree size in bytes */
  48         unsigned long level0_blocks;    /* number of blocks in tree level 0 */
  49
  50         /*
  51          * Starting block index for each tree level, ordered from leaf level (0)
  52          * to root level ('num_levels - 1')
  53          */
  54         u64 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 };
  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 struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode,
  82                                                 unsigned int num);
  83 struct ahash_request *fsverity_alloc_hash_request(struct fsverity_hash_alg *alg,
  84                                                   gfp_t gfp_flags);
  85 void fsverity_free_hash_request(struct fsverity_hash_alg *alg,
  86                                 struct ahash_request *req);
  87 const u8 *fsverity_prepare_hash_state(struct fsverity_hash_alg *alg,
  88                                       const u8 *salt, size_t salt_size);
  89 int fsverity_hash_page(const struct merkle_tree_params *params,
  90                        const struct inode *inode,
  91                        struct ahash_request *req, struct page *page, u8 *out);
  92 int fsverity_hash_buffer(struct fsverity_hash_alg *alg,
  93                          const void *data, size_t size, u8 *out);
  94 void __init fsverity_check_hash_algs(void);
  95
  96 /* init.c */
  97
  98 void __printf(3, 4) __cold
  99 fsverity_msg(const struct inode *inode, const char *level,
 100              const char *fmt, ...);
 101
 102 #define fsverity_warn(inode, fmt, ...)          \
 103         fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
 104 #define fsverity_err(inode, fmt, ...)           \
 105         fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
 106
 107 /* open.c */
 108
 109 int fsverity_init_merkle_tree_params(struct merkle_tree_params *params,
 110                                      const struct inode *inode,
 111                                      unsigned int hash_algorithm,
 112                                      unsigned int log_blocksize,
 113                                      const u8 *salt, size_t salt_size);
 114
 115 struct fsverity_info *fsverity_create_info(const struct inode *inode,
 116                                            struct fsverity_descriptor *desc);
 117
 118 void fsverity_set_info(struct inode *inode, struct fsverity_info *vi);
 119
 120 void fsverity_free_info(struct fsverity_info *vi);
 121
 122 int fsverity_get_descriptor(struct inode *inode,
 123                             struct fsverity_descriptor **desc_ret);
 124
 125 int __init fsverity_init_info_cache(void);
 126 void __init fsverity_exit_info_cache(void);
 127
 128 /* signature.c */
 129
 130 #ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
 131 int fsverity_verify_signature(const struct fsverity_info *vi,
 132                               const u8 *signature, size_t sig_size);
 133
 134 int __init fsverity_init_signature(void);
 135 #else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
 136 static inline int
 137 fsverity_verify_signature(const struct fsverity_info *vi,
 138                           const u8 *signature, size_t sig_size)
 139 {
 140         return 0;
 141 }
 142
 143 static inline int fsverity_init_signature(void)
 144 {
 145         return 0;
 146 }
 147 #endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
 148
 149 /* verify.c */
 150
 151 int __init fsverity_init_workqueue(void);
 152 void __init fsverity_exit_workqueue(void);
 153
 154 #endif /* _FSVERITY_PRIVATE_H */