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 17671e67b4SEric Biggers #include <crypto/sha.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 70fd2d1acfSEric Biggers * data read from the file. It also caches the file measurement. The Merkle 71fd2d1acfSEric Biggers * tree 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]; 76fd2d1acfSEric Biggers u8 measurement[FS_VERITY_MAX_DIGEST_SIZE]; 77fd2d1acfSEric Biggers const struct inode *inode; 78fd2d1acfSEric Biggers }; 79fd2d1acfSEric Biggers 80fd2d1acfSEric Biggers /* 81432434c9SEric Biggers * Merkle tree properties. The file measurement is the hash of this structure 82432434c9SEric Biggers * excluding the signature and with the sig_size field set to 0. 83fd2d1acfSEric Biggers */ 84fd2d1acfSEric Biggers struct fsverity_descriptor { 85fd2d1acfSEric Biggers __u8 version; /* must be 1 */ 86fd2d1acfSEric Biggers __u8 hash_algorithm; /* Merkle tree hash algorithm */ 87fd2d1acfSEric Biggers __u8 log_blocksize; /* log2 of size of data and tree blocks */ 88fd2d1acfSEric Biggers __u8 salt_size; /* size of salt in bytes; 0 if none */ 89432434c9SEric Biggers __le32 sig_size; /* size of signature in bytes; 0 if none */ 90fd2d1acfSEric Biggers __le64 data_size; /* size of file the Merkle tree is built over */ 91fd2d1acfSEric Biggers __u8 root_hash[64]; /* Merkle tree root hash */ 92fd2d1acfSEric Biggers __u8 salt[32]; /* salt prepended to each hashed block */ 93fd2d1acfSEric Biggers __u8 __reserved[144]; /* must be 0's */ 94432434c9SEric Biggers __u8 signature[]; /* optional PKCS#7 signature */ 95fd2d1acfSEric Biggers }; 96fd2d1acfSEric Biggers 97fd2d1acfSEric Biggers /* Arbitrary limit to bound the kmalloc() size. Can be changed. */ 98fd2d1acfSEric Biggers #define FS_VERITY_MAX_DESCRIPTOR_SIZE 16384 99fd2d1acfSEric Biggers 100432434c9SEric Biggers #define FS_VERITY_MAX_SIGNATURE_SIZE (FS_VERITY_MAX_DESCRIPTOR_SIZE - \ 101432434c9SEric Biggers sizeof(struct fsverity_descriptor)) 102432434c9SEric Biggers 103432434c9SEric Biggers /* 104432434c9SEric Biggers * Format in which verity file measurements are signed. This is the same as 105432434c9SEric Biggers * 'struct fsverity_digest', except here some magic bytes are prepended to 106432434c9SEric Biggers * provide some context about what is being signed in case the same key is used 107432434c9SEric Biggers * for non-fsverity purposes, and here the fields have fixed endianness. 108432434c9SEric Biggers */ 109432434c9SEric Biggers struct fsverity_signed_digest { 110432434c9SEric Biggers char magic[8]; /* must be "FSVerity" */ 111432434c9SEric Biggers __le16 digest_algorithm; 112432434c9SEric Biggers __le16 digest_size; 113432434c9SEric Biggers __u8 digest[]; 114432434c9SEric Biggers }; 115432434c9SEric Biggers 116671e67b4SEric Biggers /* hash_algs.c */ 117671e67b4SEric Biggers 118671e67b4SEric Biggers extern struct fsverity_hash_alg fsverity_hash_algs[]; 119671e67b4SEric Biggers 120439bea10SEric Biggers struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode, 121671e67b4SEric Biggers unsigned int num); 122439bea10SEric Biggers struct ahash_request *fsverity_alloc_hash_request(struct fsverity_hash_alg *alg, 123439bea10SEric Biggers gfp_t gfp_flags); 124439bea10SEric Biggers void fsverity_free_hash_request(struct fsverity_hash_alg *alg, 125439bea10SEric Biggers struct ahash_request *req); 126439bea10SEric Biggers const u8 *fsverity_prepare_hash_state(struct fsverity_hash_alg *alg, 127671e67b4SEric Biggers const u8 *salt, size_t salt_size); 128671e67b4SEric Biggers int fsverity_hash_page(const struct merkle_tree_params *params, 129671e67b4SEric Biggers const struct inode *inode, 130671e67b4SEric Biggers struct ahash_request *req, struct page *page, u8 *out); 131439bea10SEric Biggers int fsverity_hash_buffer(struct fsverity_hash_alg *alg, 132671e67b4SEric Biggers const void *data, size_t size, u8 *out); 133671e67b4SEric Biggers void __init fsverity_check_hash_algs(void); 134671e67b4SEric Biggers 135671e67b4SEric Biggers /* init.c */ 136671e67b4SEric Biggers 137671e67b4SEric Biggers extern void __printf(3, 4) __cold 138671e67b4SEric Biggers fsverity_msg(const struct inode *inode, const char *level, 139671e67b4SEric Biggers const char *fmt, ...); 140671e67b4SEric Biggers 141671e67b4SEric Biggers #define fsverity_warn(inode, fmt, ...) \ 142671e67b4SEric Biggers fsverity_msg((inode), KERN_WARNING, fmt, ##__VA_ARGS__) 143671e67b4SEric Biggers #define fsverity_err(inode, fmt, ...) \ 144671e67b4SEric Biggers fsverity_msg((inode), KERN_ERR, fmt, ##__VA_ARGS__) 145671e67b4SEric Biggers 146fd2d1acfSEric Biggers /* open.c */ 147fd2d1acfSEric Biggers 148fd2d1acfSEric Biggers int fsverity_init_merkle_tree_params(struct merkle_tree_params *params, 149fd2d1acfSEric Biggers const struct inode *inode, 150fd2d1acfSEric Biggers unsigned int hash_algorithm, 151fd2d1acfSEric Biggers unsigned int log_blocksize, 152fd2d1acfSEric Biggers const u8 *salt, size_t salt_size); 153fd2d1acfSEric Biggers 154fd2d1acfSEric Biggers struct fsverity_info *fsverity_create_info(const struct inode *inode, 155432434c9SEric Biggers void *desc, size_t desc_size); 156fd2d1acfSEric Biggers 157fd2d1acfSEric Biggers void fsverity_set_info(struct inode *inode, struct fsverity_info *vi); 158fd2d1acfSEric Biggers 159fd2d1acfSEric Biggers void fsverity_free_info(struct fsverity_info *vi); 160fd2d1acfSEric Biggers 161fd2d1acfSEric Biggers int __init fsverity_init_info_cache(void); 1628a1d0f9cSEric Biggers void __init fsverity_exit_info_cache(void); 1638a1d0f9cSEric Biggers 164432434c9SEric Biggers /* signature.c */ 165432434c9SEric Biggers 166432434c9SEric Biggers #ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES 167432434c9SEric Biggers int fsverity_verify_signature(const struct fsverity_info *vi, 168432434c9SEric Biggers const struct fsverity_descriptor *desc, 169432434c9SEric Biggers size_t desc_size); 170432434c9SEric Biggers 171432434c9SEric Biggers int __init fsverity_init_signature(void); 172432434c9SEric Biggers #else /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ 173432434c9SEric Biggers static inline int 174432434c9SEric Biggers fsverity_verify_signature(const struct fsverity_info *vi, 175432434c9SEric Biggers const struct fsverity_descriptor *desc, 176432434c9SEric Biggers size_t desc_size) 177432434c9SEric Biggers { 178432434c9SEric Biggers return 0; 179432434c9SEric Biggers } 180432434c9SEric Biggers 181432434c9SEric Biggers static inline int fsverity_init_signature(void) 182432434c9SEric Biggers { 183432434c9SEric Biggers return 0; 184432434c9SEric Biggers } 185432434c9SEric Biggers #endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */ 186432434c9SEric Biggers 1878a1d0f9cSEric Biggers /* verify.c */ 1888a1d0f9cSEric Biggers 1898a1d0f9cSEric Biggers int __init fsverity_init_workqueue(void); 190432434c9SEric Biggers void __init fsverity_exit_workqueue(void); 191fd2d1acfSEric Biggers 192671e67b4SEric Biggers #endif /* _FSVERITY_PRIVATE_H */ 193