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 /* Arbitrary limit to bound the kmalloc() size.  Can be changed. */
  74 #define FS_VERITY_MAX_DESCRIPTOR_SIZE   16384
  75
  76 #define FS_VERITY_MAX_SIGNATURE_SIZE    (FS_VERITY_MAX_DESCRIPTOR_SIZE - \
  77                                          sizeof(struct fsverity_descriptor))
  78
  79 /* hash_algs.c */
  80
  81 extern struct fsverity_hash_alg fsverity_hash_algs[];
  82
  83 struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode,
  84                                                 unsigned int num);
  85 struct ahash_request *fsverity_alloc_hash_request(struct fsverity_hash_alg *alg,
  86                                                   gfp_t gfp_flags);
  87 void fsverity_free_hash_request(struct fsverity_hash_alg *alg,
  88                                 struct ahash_request *req);
  89 const u8 *fsverity_prepare_hash_state(struct fsverity_hash_alg *alg,
  90                                       const u8 *salt, size_t salt_size);
  91 int fsverity_hash_page(const struct merkle_tree_params *params,
  92                        const struct inode *inode,
  93                        struct ahash_request *req, struct page *page, u8 *out);
  94 int fsverity_hash_buffer(struct fsverity_hash_alg *alg,
  95                          const void *data, size_t size, u8 *out);
  96 void __init fsverity_check_hash_algs(void);
  97
  98 /* init.c */
  99
 100 void __printf(3, 4) __cold
 101 fsverity_msg(const struct inode *inode, const char *level,
 102              const char *fmt, ...);
 103
 104 #define fsverity_warn(inode, fmt, ...)          \
 105         fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
 106 #define fsverity_err(inode, fmt, ...)           \
 107         fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
 108
 109 /* open.c */
 110
 111 int fsverity_init_merkle_tree_params(struct merkle_tree_params *params,
 112                                      const struct inode *inode,
 113                                      unsigned int hash_algorithm,
 114                                      unsigned int log_blocksize,
 115                                      const u8 *salt, size_t salt_size);
 116
 117 struct fsverity_info *fsverity_create_info(const struct inode *inode,
 118                                            struct fsverity_descriptor *desc);
 119
 120 void fsverity_set_info(struct inode *inode, struct fsverity_info *vi);
 121
 122 void fsverity_free_info(struct fsverity_info *vi);
 123
 124 int fsverity_get_descriptor(struct inode *inode,
 125                             struct fsverity_descriptor **desc_ret);
 126
 127 int __init fsverity_init_info_cache(void);
 128 void __init fsverity_exit_info_cache(void);
 129
 130 /* signature.c */
 131
 132 #ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
 133 int fsverity_verify_signature(const struct fsverity_info *vi,
 134                               const u8 *signature, size_t sig_size);
 135
 136 int __init fsverity_init_signature(void);
 137 #else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
 138 static inline int
 139 fsverity_verify_signature(const struct fsverity_info *vi,
 140                           const u8 *signature, size_t sig_size)
 141 {
 142         return 0;
 143 }
 144
 145 static inline int fsverity_init_signature(void)
 146 {
 147         return 0;
 148 }
 149 #endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
 150
 151 /* verify.c */
 152
 153 int __init fsverity_init_workqueue(void);
 154 void __init fsverity_exit_workqueue(void);
 155
 156 #endif /* _FSVERITY_PRIVATE_H */