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
  15 /*
  16  * Implementation limit: maximum depth of the Merkle tree.  For now 8 is plenty;
  17  * it's enough for over U64_MAX bytes of data using SHA-256 and 4K blocks.
  18  */
  19 #define FS_VERITY_MAX_LEVELS            8
  20
  21 /* A hash algorithm supported by fs-verity */
  22 struct fsverity_hash_alg {
  23         struct crypto_shash *tfm; /* hash tfm, allocated on demand */
  24         const char *name;         /* crypto API name, e.g. sha256 */
  25         unsigned int digest_size; /* digest size in bytes, e.g. 32 for SHA-256 */
  26         unsigned int block_size;  /* block size in bytes, e.g. 64 for SHA-256 */
  27         /*
  28          * The HASH_ALGO_* constant for this algorithm.  This is different from
  29          * FS_VERITY_HASH_ALG_*, which uses a different numbering scheme.
  30          */
  31         enum hash_algo algo_id;
  32 };
  33
  34 /* Merkle tree parameters: hash algorithm, initial hash state, and topology */
  35 struct merkle_tree_params {
  36         const struct fsverity_hash_alg *hash_alg; /* the hash algorithm */
  37         const u8 *hashstate;            /* initial hash state or NULL */
  38         unsigned int digest_size;       /* same as hash_alg->digest_size */
  39         unsigned int block_size;        /* size of data and tree blocks */
  40         unsigned int hashes_per_block;  /* number of hashes per tree block */
  41         unsigned int blocks_per_page;   /* PAGE_SIZE / block_size */
  42         u8 log_digestsize;              /* log2(digest_size) */
  43         u8 log_blocksize;               /* log2(block_size) */
  44         u8 log_arity;                   /* log2(hashes_per_block) */
  45         u8 log_blocks_per_page;         /* log2(blocks_per_page) */
  46         unsigned int num_levels;        /* number of levels in Merkle tree */
  47         u64 tree_size;                  /* Merkle tree size in bytes */
  48         unsigned long tree_pages;       /* Merkle tree size in pages */
  49
  50         /*
  51          * Starting block index for each tree level, ordered from leaf level (0)
  52          * to root level ('num_levels - 1')
  53          */
  54         unsigned long 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         unsigned long *hash_block_verified;
  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 const struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode,
  82                                                       unsigned int num);
  83 const u8 *fsverity_prepare_hash_state(const struct fsverity_hash_alg *alg,
  84                                       const u8 *salt, size_t salt_size);
  85 int fsverity_hash_block(const struct merkle_tree_params *params,
  86                         const struct inode *inode, const void *data, u8 *out);
  87 int fsverity_hash_buffer(const struct fsverity_hash_alg *alg,
  88                          const void *data, size_t size, u8 *out);
  89 void __init fsverity_check_hash_algs(void);
  90
  91 /* init.c */
  92
  93 void __printf(3, 4) __cold
  94 fsverity_msg(const struct inode *inode, const char *level,
  95              const char *fmt, ...);
  96
  97 #define fsverity_warn(inode, fmt, ...)          \
  98         fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
  99 #define fsverity_err(inode, fmt, ...)           \
 100         fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
 101
 102 /* measure.c */
 103
 104 #ifdef CONFIG_BPF_SYSCALL
 105 void __init fsverity_init_bpf(void);
 106 #else
 107 static inline void fsverity_init_bpf(void)
 108 {
 109 }
 110 #endif
 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 void __init fsverity_init_info_cache(void);
 131
 132 /* signature.c */
 133
 134 #ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
 135 extern int fsverity_require_signatures;
 136 int fsverity_verify_signature(const struct fsverity_info *vi,
 137                               const u8 *signature, size_t sig_size);
 138
 139 void __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 void fsverity_init_signature(void)
 149 {
 150 }
 151 #endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
 152
 153 /* verify.c */
 154
 155 void __init fsverity_init_workqueue(void);
 156
 157 #endif /* _FSVERITY_PRIVATE_H */