1671e67b4SEric Biggers /* SPDX-License-Identifier: GPL-2.0 */ 2671e67b4SEric Biggers /* 3671e67b4SEric Biggers * fs-verity: read-only file-based authenticity protection 4671e67b4SEric Biggers * 5671e67b4SEric Biggers * Copyright 2019 Google LLC 6671e67b4SEric Biggers */ 7671e67b4SEric Biggers 8671e67b4SEric Biggers #ifndef _FSVERITY_PRIVATE_H 9671e67b4SEric Biggers #define _FSVERITY_PRIVATE_H 10671e67b4SEric Biggers 11671e67b4SEric Biggers #ifdef CONFIG_FS_VERITY_DEBUG 12671e67b4SEric Biggers #define DEBUG 13671e67b4SEric Biggers #endif 14671e67b4SEric Biggers 15671e67b4SEric Biggers #define pr_fmt(fmt) "fs-verity: " fmt 16671e67b4SEric Biggers 17a24d22b2SEric Biggers #include <crypto/sha2.h> 18fd2d1acfSEric Biggers #include <linux/fsverity.h> 19439bea10SEric Biggers #include <linux/mempool.h> 20671e67b4SEric Biggers 21671e67b4SEric Biggers struct ahash_request; 22671e67b4SEric Biggers 23671e67b4SEric Biggers /* 24671e67b4SEric Biggers * Implementation limit: maximum depth of the Merkle tree. For now 8 is plenty; 25671e67b4SEric Biggers * it's enough for over U64_MAX bytes of data using SHA-256 and 4K blocks. 26671e67b4SEric Biggers */ 27671e67b4SEric Biggers #define FS_VERITY_MAX_LEVELS 8 28671e67b4SEric Biggers 29671e67b4SEric Biggers /* 30671e67b4SEric Biggers * Largest digest size among all hash algorithms supported by fs-verity. 31671e67b4SEric Biggers * Currently assumed to be <= size of fsverity_descriptor::root_hash. 32671e67b4SEric Biggers */ 33add890c9SEric Biggers #define FS_VERITY_MAX_DIGEST_SIZE SHA512_DIGEST_SIZE 34671e67b4SEric Biggers 35671e67b4SEric Biggers /* A hash algorithm supported by fs-verity */ 36671e67b4SEric Biggers struct fsverity_hash_alg { 37671e67b4SEric Biggers struct crypto_ahash *tfm; /* hash tfm, allocated on demand */ 38671e67b4SEric Biggers const char *name; /* crypto API name, e.g. sha256 */ 39671e67b4SEric Biggers unsigned int digest_size; /* digest size in bytes, e.g. 32 for SHA-256 */ 40671e67b4SEric Biggers unsigned int block_size; /* block size in bytes, e.g. 64 for SHA-256 */ 41439bea10SEric Biggers mempool_t req_pool; /* mempool with a preallocated hash request */ 42671e67b4SEric Biggers }; 43671e67b4SEric Biggers 44671e67b4SEric Biggers /* Merkle tree parameters: hash algorithm, initial hash state, and topology */ 45671e67b4SEric Biggers struct merkle_tree_params { 46439bea10SEric Biggers struct fsverity_hash_alg *hash_alg; /* the hash algorithm */ 47671e67b4SEric Biggers const u8 *hashstate; /* initial hash state or NULL */ 48671e67b4SEric Biggers unsigned int digest_size; /* same as hash_alg->digest_size */ 49671e67b4SEric Biggers unsigned int block_size; /* size of data and tree blocks */ 50671e67b4SEric Biggers unsigned int hashes_per_block; /* number of hashes per tree block */ 51671e67b4SEric Biggers unsigned int log_blocksize; /* log2(block_size) */ 52671e67b4SEric Biggers unsigned int log_arity; /* log2(hashes_per_block) */ 53671e67b4SEric Biggers unsigned int num_levels; /* number of levels in Merkle tree */ 54671e67b4SEric Biggers u64 tree_size; /* Merkle tree size in bytes */ 55fd39073dSEric Biggers unsigned long level0_blocks; /* number of blocks in tree level 0 */ 56671e67b4SEric Biggers 57671e67b4SEric Biggers /* 58671e67b4SEric Biggers * Starting block index for each tree level, ordered from leaf level (0) 59671e67b4SEric Biggers * to root level ('num_levels - 1') 60671e67b4SEric Biggers */ 61671e67b4SEric Biggers u64 level_start[FS_VERITY_MAX_LEVELS]; 62671e67b4SEric Biggers }; 63671e67b4SEric Biggers 646377a38bSEric Biggers /* 65fd2d1acfSEric Biggers * fsverity_info - cached verity metadata for an inode 66fd2d1acfSEric Biggers * 67fd2d1acfSEric Biggers * When a verity file is first opened, an instance of this struct is allocated 68fd2d1acfSEric Biggers * and stored in ->i_verity_info; it remains until the inode is evicted. It 69fd2d1acfSEric Biggers * caches information about the Merkle tree that's needed to efficiently verify 70ed45e201SEric Biggers * data read from the file. It also caches the file digest. The Merkle tree 71ed45e201SEric Biggers * pages themselves are not cached here, but the filesystem may cache them. 72fd2d1acfSEric Biggers */ 73fd2d1acfSEric Biggers struct fsverity_info { 74fd2d1acfSEric Biggers struct merkle_tree_params tree_params; 75fd2d1acfSEric Biggers u8 root_hash[FS_VERITY_MAX_DIGEST_SIZE]; 76ed45e201SEric Biggers u8 file_digest[FS_VERITY_MAX_DIGEST_SIZE]; 77fd2d1acfSEric Biggers const struct inode *inode; 78fd2d1acfSEric Biggers }; 79fd2d1acfSEric Biggers 80fd2d1acfSEric Biggers /* Arbitrary limit to bound the kmalloc() size. Can be changed. */ 81fd2d1acfSEric Biggers #define FS_VERITY_MAX_DESCRIPTOR_SIZE 16384 82fd2d1acfSEric Biggers 83432434c9SEric Biggers #define FS_VERITY_MAX_SIGNATURE_SIZE (FS_VERITY_MAX_DESCRIPTOR_SIZE - \ 84432434c9SEric Biggers sizeof(struct fsverity_descriptor)) 85432434c9SEric Biggers 86671e67b4SEric Biggers /* hash_algs.c */ 87671e67b4SEric Biggers 88671e67b4SEric Biggers extern struct fsverity_hash_alg fsverity_hash_algs[]; 89671e67b4SEric Biggers 90439bea10SEric Biggers struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode, 91671e67b4SEric Biggers unsigned int num); 92439bea10SEric Biggers struct ahash_request *fsverity_alloc_hash_request(struct fsverity_hash_alg *alg, 93439bea10SEric Biggers gfp_t gfp_flags); 94439bea10SEric Biggers void fsverity_free_hash_request(struct fsverity_hash_alg *alg, 95439bea10SEric Biggers struct ahash_request *req); 96439bea10SEric Biggers const u8 *fsverity_prepare_hash_state(struct fsverity_hash_alg *alg, 97671e67b4SEric Biggers const u8 *salt, size_t salt_size); 98671e67b4SEric Biggers int fsverity_hash_page(const struct merkle_tree_params *params, 99671e67b4SEric Biggers const struct inode *inode, 100671e67b4SEric Biggers struct ahash_request *req, struct page *page, u8 *out); 101439bea10SEric Biggers int fsverity_hash_buffer(struct fsverity_hash_alg *alg, 102671e67b4SEric Biggers const void *data, size_t size, u8 *out); 103671e67b4SEric Biggers void __init fsverity_check_hash_algs(void); 104671e67b4SEric Biggers 105671e67b4SEric Biggers /* init.c */ 106671e67b4SEric Biggers 1079cd6b593SEric Biggers void __printf(3, 4) __cold 108671e67b4SEric Biggers fsverity_msg(const struct inode *inode, const char *level, 109671e67b4SEric Biggers const char *fmt, ...); 110671e67b4SEric Biggers 111671e67b4SEric Biggers #define fsverity_warn(inode, fmt, ...) \ 112671e67b4SEric Biggers fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__) 113671e67b4SEric Biggers #define fsverity_err(inode, fmt, ...) \ 114671e67b4SEric Biggers fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__) 115671e67b4SEric Biggers 116fd2d1acfSEric Biggers /* open.c */ 117fd2d1acfSEric Biggers 118fd2d1acfSEric Biggers int fsverity_init_merkle_tree_params(struct merkle_tree_params *params, 119fd2d1acfSEric Biggers const struct inode *inode, 120fd2d1acfSEric Biggers unsigned int hash_algorithm, 121fd2d1acfSEric Biggers unsigned int log_blocksize, 122fd2d1acfSEric Biggers const u8 *salt, size_t salt_size); 123fd2d1acfSEric Biggers 124fd2d1acfSEric Biggers struct fsverity_info *fsverity_create_info(const struct inode *inode, 125c2c82611SEric Biggers struct fsverity_descriptor *desc, 126c2c82611SEric Biggers size_t desc_size); 127fd2d1acfSEric Biggers 128fd2d1acfSEric Biggers void fsverity_set_info(struct inode *inode, struct fsverity_info *vi); 129fd2d1acfSEric Biggers 130fd2d1acfSEric Biggers void fsverity_free_info(struct fsverity_info *vi); 131fd2d1acfSEric Biggers 132c2c82611SEric Biggers int fsverity_get_descriptor(struct inode *inode, 133c2c82611SEric Biggers struct fsverity_descriptor **desc_ret, 134c2c82611SEric Biggers size_t *desc_size_ret); 135c2c82611SEric Biggers 136fd2d1acfSEric Biggers int __init fsverity_init_info_cache(void); 1378a1d0f9cSEric Biggers void __init fsverity_exit_info_cache(void); 1388a1d0f9cSEric Biggers 139432434c9SEric Biggers /* signature.c */ 140432434c9SEric Biggers 141432434c9SEric Biggers #ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES 142432434c9SEric Biggers int fsverity_verify_signature(const struct fsverity_info *vi, 143*fab634c4SEric Biggers const u8 *signature, size_t sig_size); 144432434c9SEric Biggers 145432434c9SEric Biggers int __init fsverity_init_signature(void); 146432434c9SEric Biggers #else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ 147432434c9SEric Biggers static inline int 148432434c9SEric Biggers fsverity_verify_signature(const struct fsverity_info *vi, 149*fab634c4SEric Biggers const u8 *signature, size_t sig_size) 150432434c9SEric Biggers { 151432434c9SEric Biggers return 0; 152432434c9SEric Biggers } 153432434c9SEric Biggers 154432434c9SEric Biggers static inline int fsverity_init_signature(void) 155432434c9SEric Biggers { 156432434c9SEric Biggers return 0; 157432434c9SEric Biggers } 158432434c9SEric Biggers #endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ 159432434c9SEric Biggers 1608a1d0f9cSEric Biggers /* verify.c */ 1618a1d0f9cSEric Biggers 1628a1d0f9cSEric Biggers int __init fsverity_init_workqueue(void); 163432434c9SEric Biggers void __init fsverity_exit_workqueue(void); 164fd2d1acfSEric Biggers 165671e67b4SEric Biggers #endif /* _FSVERITY_PRIVATE_H */ 166