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         const char *name;         /* crypto API name, e.g. sha256 */
  24         unsigned int digest_size; /* digest size in bytes, e.g. 32 for SHA-256 */
  25         unsigned int block_size;  /* block size in bytes, e.g. 64 for SHA-256 */
  26         /*
  27          * The HASH_ALGO_* constant for this algorithm.  This is different from
  28          * FS_VERITY_HASH_ALG_*, which uses a different numbering scheme.
  29          */
  30         enum hash_algo algo_id;
  31 };
  32
  33 union fsverity_hash_ctx {
  34         struct sha256_ctx sha256;
  35         struct sha512_ctx sha512;
  36 };
  37
  38 /* Merkle tree parameters: hash algorithm, initial hash state, and topology */
  39 struct merkle_tree_params {
  40         const struct fsverity_hash_alg *hash_alg; /* the hash algorithm */
  41         /* initial hash state if salted, NULL if unsalted */
  42         const union fsverity_hash_ctx *hashstate;
  43         unsigned int digest_size;       /* same as hash_alg->digest_size */
  44         unsigned int block_size;        /* size of data and tree blocks */
  45         unsigned int hashes_per_block;  /* number of hashes per tree block */
  46         unsigned int blocks_per_page;   /* PAGE_SIZE / block_size */
  47         u8 log_digestsize;              /* log2(digest_size) */
  48         u8 log_blocksize;               /* log2(block_size) */
  49         u8 log_arity;                   /* log2(hashes_per_block) */
  50         u8 log_blocks_per_page;         /* log2(blocks_per_page) */
  51         unsigned int num_levels;        /* number of levels in Merkle tree */
  52         u64 tree_size;                  /* Merkle tree size in bytes */
  53         unsigned long tree_pages;       /* Merkle tree size in pages */
  54
  55         /*
  56          * Starting block index for each tree level, ordered from leaf level (0)
  57          * to root level ('num_levels - 1')
  58          */
  59         unsigned long level_start[FS_VERITY_MAX_LEVELS];
  60 };
  61
  62 /*
  63  * fsverity_info - cached verity metadata for an inode
  64  *
  65  * When a verity file is first opened, an instance of this struct is allocated
  66  * and stored in ->i_verity_info; it remains until the inode is evicted.  It
  67  * caches information about the Merkle tree that's needed to efficiently verify
  68  * data read from the file.  It also caches the file digest.  The Merkle tree
  69  * pages themselves are not cached here, but the filesystem may cache them.
  70  */
  71 struct fsverity_info {
  72         struct merkle_tree_params tree_params;
  73         u8 root_hash[FS_VERITY_MAX_DIGEST_SIZE];
  74         u8 file_digest[FS_VERITY_MAX_DIGEST_SIZE];
  75         const struct inode *inode;
  76         unsigned long *hash_block_verified;
  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 const struct fsverity_hash_alg fsverity_hash_algs[];
  85
  86 const struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode,
  87                                                       unsigned int num);
  88 union fsverity_hash_ctx *
  89 fsverity_prepare_hash_state(const struct fsverity_hash_alg *alg,
  90                             const u8 *salt, size_t salt_size);
  91 void fsverity_hash_block(const struct merkle_tree_params *params,
  92                          const struct inode *inode, const void *data, u8 *out);
  93 void fsverity_hash_buffer(const struct fsverity_hash_alg *alg,
  94                           const void *data, size_t size, u8 *out);
  95 void __init fsverity_check_hash_algs(void);
  96
  97 /* init.c */
  98
  99 void __printf(3, 4) __cold
 100 fsverity_msg(const struct inode *inode, const char *level,
 101              const char *fmt, ...);
 102
 103 #define fsverity_warn(inode, fmt, ...)          \
 104         fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
 105 #define fsverity_err(inode, fmt, ...)           \
 106         fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
 107
 108 /* measure.c */
 109
 110 #ifdef CONFIG_BPF_SYSCALL
 111 void __init fsverity_init_bpf(void);
 112 #else
 113 static inline void fsverity_init_bpf(void)
 114 {
 115 }
 116 #endif
 117
 118 /* open.c */
 119
 120 int fsverity_init_merkle_tree_params(struct merkle_tree_params *params,
 121                                      const struct inode *inode,
 122                                      unsigned int hash_algorithm,
 123                                      unsigned int log_blocksize,
 124                                      const u8 *salt, size_t salt_size);
 125
 126 struct fsverity_info *fsverity_create_info(const struct inode *inode,
 127                                            struct fsverity_descriptor *desc);
 128
 129 void fsverity_set_info(struct inode *inode, struct fsverity_info *vi);
 130
 131 void fsverity_free_info(struct fsverity_info *vi);
 132
 133 int fsverity_get_descriptor(struct inode *inode,
 134                             struct fsverity_descriptor **desc_ret);
 135
 136 void __init fsverity_init_info_cache(void);
 137
 138 /* signature.c */
 139
 140 #ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
 141 extern int fsverity_require_signatures;
 142 int fsverity_verify_signature(const struct fsverity_info *vi,
 143                               const u8 *signature, size_t sig_size);
 144
 145 void __init fsverity_init_signature(void);
 146 #else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
 147 static inline int
 148 fsverity_verify_signature(const struct fsverity_info *vi,
 149                           const u8 *signature, size_t sig_size)
 150 {
 151         return 0;
 152 }
 153
 154 static inline void fsverity_init_signature(void)
 155 {
 156 }
 157 #endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
 158
 159 /* verify.c */
 160
 161 void __init fsverity_init_workqueue(void);
 162
 163 #endif /* _FSVERITY_PRIVATE_H */