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 <crypto/sha2.h>
  18 #include <linux/fsverity.h>
  19 #include <linux/mempool.h>
  20
  21 struct ahash_request;
  22
  23 /*
  24  * Implementation limit: maximum depth of the Merkle tree.  For now 8 is plenty;
  25  * it's enough for over U64_MAX bytes of data using SHA-256 and 4K blocks.
  26  */
  27 #define FS_VERITY_MAX_LEVELS            8
  28
  29 /*
  30  * Largest digest size among all hash algorithms supported by fs-verity.
  31  * Currently assumed to be <= size of fsverity_descriptor::root_hash.
  32  */
  33 #define FS_VERITY_MAX_DIGEST_SIZE       SHA512_DIGEST_SIZE
  34
  35 /* A hash algorithm supported by fs-verity */
  36 struct fsverity_hash_alg {
  37         struct crypto_ahash *tfm; /* hash tfm, allocated on demand */
  38         const char *name;         /* crypto API name, e.g. sha256 */
  39         unsigned int digest_size; /* digest size in bytes, e.g. 32 for SHA-256 */
  40         unsigned int block_size;  /* block size in bytes, e.g. 64 for SHA-256 */
  41         mempool_t req_pool;       /* mempool with a preallocated hash request */
  42 };
  43
  44 /* Merkle tree parameters: hash algorithm, initial hash state, and topology */
  45 struct merkle_tree_params {
  46         struct fsverity_hash_alg *hash_alg; /* the hash algorithm */
  47         const u8 *hashstate;            /* initial hash state or NULL */
  48         unsigned int digest_size;       /* same as hash_alg->digest_size */
  49         unsigned int block_size;        /* size of data and tree blocks */
  50         unsigned int hashes_per_block;  /* number of hashes per tree block */
  51         unsigned int log_blocksize;     /* log2(block_size) */
  52         unsigned int log_arity;         /* log2(hashes_per_block) */
  53         unsigned int num_levels;        /* number of levels in Merkle tree */
  54         u64 tree_size;                  /* Merkle tree size in bytes */
  55         unsigned long level0_blocks;    /* number of blocks in tree level 0 */
  56
  57         /*
  58          * Starting block index for each tree level, ordered from leaf level (0)
  59          * to root level ('num_levels - 1')
  60          */
  61         u64 level_start[FS_VERITY_MAX_LEVELS];
  62 };
  63
  64 /*
  65  * fsverity_info - cached verity metadata for an inode
  66  *
  67  * When a verity file is first opened, an instance of this struct is allocated
  68  * and stored in ->i_verity_info; it remains until the inode is evicted.  It
  69  * caches information about the Merkle tree that's needed to efficiently verify
  70  * data read from the file.  It also caches the file digest.  The Merkle tree
  71  * pages themselves are not cached here, but the filesystem may cache them.
  72  */
  73 struct fsverity_info {
  74         struct merkle_tree_params tree_params;
  75         u8 root_hash[FS_VERITY_MAX_DIGEST_SIZE];
  76         u8 file_digest[FS_VERITY_MAX_DIGEST_SIZE];
  77         const struct inode *inode;
  78 };
  79
  80 /* Arbitrary limit to bound the kmalloc() size.  Can be changed. */
  81 #define FS_VERITY_MAX_DESCRIPTOR_SIZE   16384
  82
  83 #define FS_VERITY_MAX_SIGNATURE_SIZE    (FS_VERITY_MAX_DESCRIPTOR_SIZE - \
  84                                          sizeof(struct fsverity_descriptor))
  85
  86 /* hash_algs.c */
  87
  88 extern struct fsverity_hash_alg fsverity_hash_algs[];
  89
  90 struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode,
  91                                                 unsigned int num);
  92 struct ahash_request *fsverity_alloc_hash_request(struct fsverity_hash_alg *alg,
  93                                                   gfp_t gfp_flags);
  94 void fsverity_free_hash_request(struct fsverity_hash_alg *alg,
  95                                 struct ahash_request *req);
  96 const u8 *fsverity_prepare_hash_state(struct fsverity_hash_alg *alg,
  97                                       const u8 *salt, size_t salt_size);
  98 int fsverity_hash_page(const struct merkle_tree_params *params,
  99                        const struct inode *inode,
 100                        struct ahash_request *req, struct page *page, u8 *out);
 101 int fsverity_hash_buffer(struct fsverity_hash_alg *alg,
 102                          const void *data, size_t size, u8 *out);
 103 void __init fsverity_check_hash_algs(void);
 104
 105 /* init.c */
 106
 107 void __printf(3, 4) __cold
 108 fsverity_msg(const struct inode *inode, const char *level,
 109              const char *fmt, ...);
 110
 111 #define fsverity_warn(inode, fmt, ...)          \
 112         fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__)
 113 #define fsverity_err(inode, fmt, ...)           \
 114         fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__)
 115
 116 /* open.c */
 117
 118 int fsverity_init_merkle_tree_params(struct merkle_tree_params *params,
 119                                      const struct inode *inode,
 120                                      unsigned int hash_algorithm,
 121                                      unsigned int log_blocksize,
 122                                      const u8 *salt, size_t salt_size);
 123
 124 struct fsverity_info *fsverity_create_info(const struct inode *inode,
 125                                            struct fsverity_descriptor *desc,
 126                                            size_t desc_size);
 127
 128 void fsverity_set_info(struct inode *inode, struct fsverity_info *vi);
 129
 130 void fsverity_free_info(struct fsverity_info *vi);
 131
 132 int fsverity_get_descriptor(struct inode *inode,
 133                             struct fsverity_descriptor **desc_ret,
 134                             size_t *desc_size_ret);
 135
 136 int __init fsverity_init_info_cache(void);
 137 void __init fsverity_exit_info_cache(void);
 138
 139 /* signature.c */
 140
 141 #ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
 142 int fsverity_verify_signature(const struct fsverity_info *vi,
 143                               const u8 *signature, size_t sig_size);
 144
 145 int __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 int fsverity_init_signature(void)
 155 {
 156         return 0;
 157 }
 158 #endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */
 159
 160 /* verify.c */
 161
 162 int __init fsverity_init_workqueue(void);
 163 void __init fsverity_exit_workqueue(void);
 164
 165 #endif /* _FSVERITY_PRIVATE_H */