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192 lines
6.4 KiB
192 lines
6.4 KiB
/* SPDX-License-Identifier: GPL-2.0 */ |
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/* |
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* fs-verity: read-only file-based authenticity protection |
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* |
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* Copyright 2019 Google LLC |
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*/ |
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#ifndef _FSVERITY_PRIVATE_H |
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#define _FSVERITY_PRIVATE_H |
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#ifdef CONFIG_FS_VERITY_DEBUG |
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#define DEBUG |
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#endif |
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#define pr_fmt(fmt) "fs-verity: " fmt |
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#include <crypto/sha.h> |
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#include <linux/fsverity.h> |
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#include <linux/mempool.h> |
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struct ahash_request; |
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/* |
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* Implementation limit: maximum depth of the Merkle tree. For now 8 is plenty; |
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* it's enough for over U64_MAX bytes of data using SHA-256 and 4K blocks. |
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*/ |
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#define FS_VERITY_MAX_LEVELS 8 |
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/* |
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* Largest digest size among all hash algorithms supported by fs-verity. |
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* Currently assumed to be <= size of fsverity_descriptor::root_hash. |
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*/ |
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#define FS_VERITY_MAX_DIGEST_SIZE SHA512_DIGEST_SIZE |
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/* A hash algorithm supported by fs-verity */ |
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struct fsverity_hash_alg { |
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struct crypto_ahash *tfm; /* hash tfm, allocated on demand */ |
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const char *name; /* crypto API name, e.g. sha256 */ |
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unsigned int digest_size; /* digest size in bytes, e.g. 32 for SHA-256 */ |
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unsigned int block_size; /* block size in bytes, e.g. 64 for SHA-256 */ |
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mempool_t req_pool; /* mempool with a preallocated hash request */ |
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}; |
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/* Merkle tree parameters: hash algorithm, initial hash state, and topology */ |
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struct merkle_tree_params { |
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struct fsverity_hash_alg *hash_alg; /* the hash algorithm */ |
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const u8 *hashstate; /* initial hash state or NULL */ |
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unsigned int digest_size; /* same as hash_alg->digest_size */ |
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unsigned int block_size; /* size of data and tree blocks */ |
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unsigned int hashes_per_block; /* number of hashes per tree block */ |
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unsigned int log_blocksize; /* log2(block_size) */ |
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unsigned int log_arity; /* log2(hashes_per_block) */ |
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unsigned int num_levels; /* number of levels in Merkle tree */ |
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u64 tree_size; /* Merkle tree size in bytes */ |
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unsigned long level0_blocks; /* number of blocks in tree level 0 */ |
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/* |
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* Starting block index for each tree level, ordered from leaf level (0) |
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* to root level ('num_levels - 1') |
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*/ |
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u64 level_start[FS_VERITY_MAX_LEVELS]; |
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}; |
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/* |
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* fsverity_info - cached verity metadata for an inode |
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* |
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* When a verity file is first opened, an instance of this struct is allocated |
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* and stored in ->i_verity_info; it remains until the inode is evicted. It |
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* caches information about the Merkle tree that's needed to efficiently verify |
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* data read from the file. It also caches the file measurement. The Merkle |
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* tree pages themselves are not cached here, but the filesystem may cache them. |
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*/ |
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struct fsverity_info { |
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struct merkle_tree_params tree_params; |
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u8 root_hash[FS_VERITY_MAX_DIGEST_SIZE]; |
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u8 measurement[FS_VERITY_MAX_DIGEST_SIZE]; |
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const struct inode *inode; |
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}; |
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/* |
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* Merkle tree properties. The file measurement is the hash of this structure |
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* excluding the signature and with the sig_size field set to 0. |
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*/ |
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struct fsverity_descriptor { |
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__u8 version; /* must be 1 */ |
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__u8 hash_algorithm; /* Merkle tree hash algorithm */ |
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__u8 log_blocksize; /* log2 of size of data and tree blocks */ |
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__u8 salt_size; /* size of salt in bytes; 0 if none */ |
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__le32 sig_size; /* size of signature in bytes; 0 if none */ |
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__le64 data_size; /* size of file the Merkle tree is built over */ |
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__u8 root_hash[64]; /* Merkle tree root hash */ |
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__u8 salt[32]; /* salt prepended to each hashed block */ |
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__u8 __reserved[144]; /* must be 0's */ |
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__u8 signature[]; /* optional PKCS#7 signature */ |
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}; |
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/* Arbitrary limit to bound the kmalloc() size. Can be changed. */ |
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#define FS_VERITY_MAX_DESCRIPTOR_SIZE 16384 |
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#define FS_VERITY_MAX_SIGNATURE_SIZE (FS_VERITY_MAX_DESCRIPTOR_SIZE - \ |
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sizeof(struct fsverity_descriptor)) |
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/* |
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* Format in which verity file measurements are signed. This is the same as |
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* 'struct fsverity_digest', except here some magic bytes are prepended to |
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* provide some context about what is being signed in case the same key is used |
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* for non-fsverity purposes, and here the fields have fixed endianness. |
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*/ |
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struct fsverity_signed_digest { |
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char magic[8]; /* must be "FSVerity" */ |
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__le16 digest_algorithm; |
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__le16 digest_size; |
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__u8 digest[]; |
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}; |
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/* hash_algs.c */ |
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extern struct fsverity_hash_alg fsverity_hash_algs[]; |
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struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode, |
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unsigned int num); |
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struct ahash_request *fsverity_alloc_hash_request(struct fsverity_hash_alg *alg, |
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gfp_t gfp_flags); |
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void fsverity_free_hash_request(struct fsverity_hash_alg *alg, |
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struct ahash_request *req); |
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const u8 *fsverity_prepare_hash_state(struct fsverity_hash_alg *alg, |
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const u8 *salt, size_t salt_size); |
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int fsverity_hash_page(const struct merkle_tree_params *params, |
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const struct inode *inode, |
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struct ahash_request *req, struct page *page, u8 *out); |
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int fsverity_hash_buffer(struct fsverity_hash_alg *alg, |
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const void *data, size_t size, u8 *out); |
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void __init fsverity_check_hash_algs(void); |
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/* init.c */ |
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void __printf(3, 4) __cold |
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fsverity_msg(const struct inode *inode, const char *level, |
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const char *fmt, ...); |
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#define fsverity_warn(inode, fmt, ...) \ |
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fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__) |
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#define fsverity_err(inode, fmt, ...) \ |
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fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__) |
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/* open.c */ |
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int fsverity_init_merkle_tree_params(struct merkle_tree_params *params, |
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const struct inode *inode, |
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unsigned int hash_algorithm, |
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unsigned int log_blocksize, |
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const u8 *salt, size_t salt_size); |
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struct fsverity_info *fsverity_create_info(const struct inode *inode, |
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void *desc, size_t desc_size); |
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void fsverity_set_info(struct inode *inode, struct fsverity_info *vi); |
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void fsverity_free_info(struct fsverity_info *vi); |
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int __init fsverity_init_info_cache(void); |
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void __init fsverity_exit_info_cache(void); |
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/* signature.c */ |
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#ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES |
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int fsverity_verify_signature(const struct fsverity_info *vi, |
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const struct fsverity_descriptor *desc, |
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size_t desc_size); |
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int __init fsverity_init_signature(void); |
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#else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ |
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static inline int |
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fsverity_verify_signature(const struct fsverity_info *vi, |
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const struct fsverity_descriptor *desc, |
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size_t desc_size) |
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{ |
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return 0; |
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} |
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static inline int fsverity_init_signature(void) |
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{ |
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return 0; |
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} |
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#endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ |
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/* verify.c */ |
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int __init fsverity_init_workqueue(void); |
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void __init fsverity_exit_workqueue(void); |
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#endif /* _FSVERITY_PRIVATE_H */
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