/* 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

#define pr_fmt(fmt) "fs-verity: " fmt

#include <linux/fsverity.h>
#include <linux/rhashtable.h>

/*
 * 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 {
        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 */
        /*
         * The HASH_ALGO_* constant for this algorithm.  This is different from
         * FS_VERITY_HASH_ALG_*, which uses a different numbering scheme.
         */
        enum hash_algo algo_id;
};

union fsverity_hash_ctx {
        struct sha256_ctx sha256;
        struct sha512_ctx sha512;
};

/* Merkle tree parameters: hash algorithm, initial hash state, and topology */
struct merkle_tree_params {
        const struct fsverity_hash_alg *hash_alg; /* the hash algorithm */
        /* initial hash state if salted, NULL if unsalted */
        const union fsverity_hash_ctx *hashstate;
        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 blocks_per_page;   /* PAGE_SIZE / block_size */
        u8 log_digestsize;              /* log2(digest_size) */
        u8 log_blocksize;               /* log2(block_size) */
        u8 log_arity;                   /* log2(hashes_per_block) */
        u8 log_blocks_per_page;         /* log2(blocks_per_page) */
        unsigned int num_levels;        /* number of levels in Merkle tree */
        u64 tree_size;                  /* Merkle tree size in bytes */
        unsigned long tree_pages;       /* Merkle tree size in pages */

        /*
         * Starting block index for each tree level, ordered from leaf level (0)
         * to root level ('num_levels - 1')
         */
        unsigned long 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 a pointer to it is stored in the global hash table, indexed by the inode
 * pointer value.  It remains alive 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 rhash_head rhash_head;
        struct merkle_tree_params tree_params;
        u8 root_hash[FS_VERITY_MAX_DIGEST_SIZE];
        u8 file_digest[FS_VERITY_MAX_DIGEST_SIZE];
        struct inode *inode;
        unsigned long *hash_block_verified;
};

#define FS_VERITY_MAX_SIGNATURE_SIZE    (FS_VERITY_MAX_DESCRIPTOR_SIZE - \
                                         sizeof(struct fsverity_descriptor))

/* hash_algs.c */

extern const struct fsverity_hash_alg fsverity_hash_algs[];

const struct fsverity_hash_alg *fsverity_get_hash_alg(const struct inode *inode,
                                                      unsigned int num);
union fsverity_hash_ctx *
fsverity_prepare_hash_state(const struct fsverity_hash_alg *alg,
                            const u8 *salt, size_t salt_size);
void fsverity_hash_block(const struct merkle_tree_params *params,
                         const void *data, u8 *out);
void fsverity_hash_buffer(const 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__)

/* measure.c */

#ifdef CONFIG_BPF_SYSCALL
void __init fsverity_init_bpf(void);
#else
static inline void fsverity_init_bpf(void)
{
}
#endif

/* 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(struct inode *inode,
                                           struct fsverity_descriptor *desc);

int fsverity_set_info(struct fsverity_info *vi);
void fsverity_free_info(struct fsverity_info *vi);
void fsverity_remove_info(struct fsverity_info *vi);

int fsverity_get_descriptor(struct inode *inode,
                            struct fsverity_descriptor **desc_ret);

void __init fsverity_init_info_cache(void);

/* signature.c */

#ifdef CONFIG_FS_VERITY_BUILTIN_SIGNATURES
extern int fsverity_require_signatures;
int fsverity_verify_signature(const struct fsverity_info *vi,
                              const u8 *signature, size_t sig_size);

void __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 void fsverity_init_signature(void)
{
}
#endif /* !CONFIG_FS_VERITY_BUILTIN_SIGNATURES */

/* verify.c */

void __init fsverity_init_workqueue(void);

#include <trace/events/fsverity.h>

#endif /* _FSVERITY_PRIVATE_H */