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Diffstat (limited to 'fs/verity/fsverity_private.h')
| -rw-r--r-- | fs/verity/fsverity_private.h | 154 |
1 files changed, 154 insertions, 0 deletions
diff --git a/fs/verity/fsverity_private.h b/fs/verity/fsverity_private.h new file mode 100644 index 000000000..dbe1ce5b4 --- /dev/null +++ b/fs/verity/fsverity_private.h @@ -0,0 +1,154 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * fs-verity: read-only file-based authenticity protection + * + * Copyright 2019 Google LLC + */ + +#ifndef _FSVERITY_PRIVATE_H +#define _FSVERITY_PRIVATE_H + +#ifdef CONFIG_FS_VERITY_DEBUG +#define DEBUG +#endif + +#define pr_fmt(fmt) "fs-verity: " fmt + +#include <linux/fsverity.h> +#include <linux/mempool.h> + +struct ahash_request; + +/* + * Implementation limit: maximum depth of the Merkle tree. For now 8 is plenty; + * it's enough for over U64_MAX bytes of data using SHA-256 and 4K blocks. + */ +#define FS_VERITY_MAX_LEVELS 8 + +/* A hash algorithm supported by fs-verity */ +struct fsverity_hash_alg { + struct crypto_ahash *tfm; /* hash tfm, allocated on demand */ + const char *name; /* crypto API name, e.g. sha256 */ + unsigned int digest_size; /* digest size in bytes, e.g. 32 for SHA-256 */ + unsigned int block_size; /* block size in bytes, e.g. 64 for SHA-256 */ + mempool_t req_pool; /* mempool with a preallocated hash request */ +}; + +/* Merkle tree parameters: hash algorithm, initial hash state, and topology */ +struct merkle_tree_params { + struct fsverity_hash_alg *hash_alg; /* the hash algorithm */ + const u8 *hashstate; /* initial hash state or NULL */ + unsigned int digest_size; /* same as hash_alg->digest_size */ + unsigned int block_size; /* size of data and tree blocks */ + unsigned int hashes_per_block; /* number of hashes per tree block */ + unsigned int log_blocksize; /* log2(block_size) */ + unsigned int log_arity; /* log2(hashes_per_block) */ + unsigned int num_levels; /* number of levels in Merkle tree */ + u64 tree_size; /* Merkle tree size in bytes */ + unsigned long level0_blocks; /* number of blocks in tree level 0 */ + + /* + * Starting block index for each tree level, ordered from leaf level (0) + * to root level ('num_levels - 1') + */ + u64 level_start[FS_VERITY_MAX_LEVELS]; +}; + +/* + * fsverity_info - cached verity metadata for an inode + * + * When a verity file is first opened, an instance of this struct is allocated + * and stored in ->i_verity_info; it remains until the inode is evicted. It + * caches information about the Merkle tree that's needed to efficiently verify + * data read from the file. It also caches the file digest. The Merkle tree + * pages themselves are not cached here, but the filesystem may cache them. + */ +struct fsverity_info { + struct merkle_tree_params tree_params; + u8 root_hash[FS_VERITY_MAX_DIGEST_SIZE]; + u8 file_digest[FS_VERITY_MAX_DIGEST_SIZE]; + const struct inode *inode; +}; + + +#define FS_VERITY_MAX_SIGNATURE_SIZE (FS_VERITY_MAX_DESCRIPTOR_SIZE - \ + sizeof(struct fsverity_descriptor)) + +/* hash_algs.c */ + +extern struct fsverity_hash_alg fsverity_hash_algs[]; + +struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode, + unsigned int num); +struct ahash_request *fsverity_alloc_hash_request(struct fsverity_hash_alg *alg, + gfp_t gfp_flags); +void fsverity_free_hash_request(struct fsverity_hash_alg *alg, + struct ahash_request *req); +const u8 *fsverity_prepare_hash_state(struct fsverity_hash_alg *alg, + const u8 *salt, size_t salt_size); +int fsverity_hash_page(const struct merkle_tree_params *params, + const struct inode *inode, + struct ahash_request *req, struct page *page, u8 *out); +int fsverity_hash_buffer(struct fsverity_hash_alg *alg, + const void *data, size_t size, u8 *out); +void __init fsverity_check_hash_algs(void); + +/* init.c */ + +void __printf(3, 4) __cold +fsverity_msg(const struct inode *inode, const char *level, + const char *fmt, ...); + +#define fsverity_warn(inode, fmt, ...) \ + fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__) +#define fsverity_err(inode, fmt, ...) \ + fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__) + +/* open.c */ + +int fsverity_init_merkle_tree_params(struct merkle_tree_params *params, + const struct inode *inode, + unsigned int hash_algorithm, + unsigned int log_blocksize, + const u8 *salt, size_t salt_size); + +struct fsverity_info *fsverity_create_info(const struct inode *inode, + struct fsverity_descriptor *desc); + +void fsverity_set_info(struct inode *inode, struct fsverity_info *vi); + +void fsverity_free_info(struct fsverity_info *vi); + +int fsverity_get_descriptor(struct inode *inode, + struct fsverity_descriptor **desc_ret); + +int __init fsverity_init_info_cache(void); +void __init fsverity_exit_info_cache(void); + +/* signature.c */ + +#ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES +int fsverity_verify_signature(const struct fsverity_info *vi, + const u8 *signature, size_t sig_size); + +int __init fsverity_init_signature(void); +#else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ +static inline int +fsverity_verify_signature(const struct fsverity_info *vi, + const u8 *signature, size_t sig_size) +{ + return 0; +} + +static inline int fsverity_init_signature(void) +{ + return 0; +} +#endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ + +/* verify.c */ + +int __init fsverity_init_workqueue(void); +void __init fsverity_exit_workqueue(void); + +#endif /* _FSVERITY_PRIVATE_H */ |