`bpak_merkle` — BPAK merkle hash tree¶

This documents the BPAK merkle hash tree generator which is used to create dm verity compatiable hash trees.

Source code: include/bpak/merkle.h, lib/merkle.c

BPAK - Bit Packer

SPDX-License-Identifier: BSD-3-Clause

Defines

BPAK_MERKLE_BLOCK_SZ¶

BPAK_MERKLE_MAX_LEVELS¶

BPAK_MERKLE_BLOCK_BITS¶

BPAK_MERKLE_HASH_BYTES¶

Typedefs

typedef unsigned char bpak_merkle_hash_t[BPAK_MERKLE_HASH_BYTES]¶: Only sha256 is used in this implementation

Functions

ssize_t bpak_merkle_compute_size(size_t input_data_length)¶

size_t bpak_merkle_get_size(struct bpak_merkle_context *ctx)¶

Returns the total size in bytes of the hash tree

Parameters:: ctx – [in] Context
Returns:: Size in bytes

int bpak_merkle_init(struct bpak_merkle_context *ctx, size_t input_data_length, const uint8_t *salt, size_t salt_length, bpak_io_t wr, bpak_io_t rd, off_t offset, bool zero_fill_output, void *priv)¶

Initializes the merkle algorithm

Parameters:

ctx – [in] Context
input_data_length – [in] Size of filesystem in bytes
salt – [in] Salt to use for hash computation
salt_length – [in] Length of salt in bytes
wr – [in] Write callback function
rd – [in] Read callback function
offset – [in] Offset where hash tree data starts
priv – [in] Optional private context

Returns:

BPAK_OK on success and non zero number on error

int bpak_merkle_write_chunk(struct bpak_merkle_context *ctx, uint8_t *buffer, size_t length)¶

Process input data stream. This function can also be called with no buffer and sz set to zero to complete the hash tree computation.

Parameters:

ctx – [in] Context
buffer – [in] Input data buffer
length – [in] Available bytes in buffer

Returns:

BPAK_OK on success

int bpak_merkle_finish(struct bpak_merkle_context *ctx, bpak_merkle_hash_t roothash)¶

Outputs the root hash when the tree is computed

Parameters:

ctx – [in] Context
roothash – [out] Root hash output

Returns:

BPAK_OK on success

struct bpak_merkle_context¶

Public Members

struct bpak_hash_context running_hash¶

uint8_t buffer[BPAK_MERKLE_HASH_BYTES]¶

size_t level_length[BPAK_MERKLE_MAX_LEVELS]¶

off_t level_offset[BPAK_MERKLE_MAX_LEVELS]¶

unsigned int no_of_levels¶

size_t input_chunk_counter¶

size_t block_byte_counter¶

size_t input_data_length¶: Total size of the input filesystem in bytes

size_t hash_tree_length¶: Hash tree output size

size_t salt_length¶

bool finished¶

uint8_t salt[32]¶: Input salt for hashing

bpak_io_t wr¶: Function to write to the hash tree

bpak_io_t rd¶: Function to read from the hash tree

off_t offset¶

void *priv¶: Externalt context variable

bpak_merkle — BPAK merkle hash tree¶

`bpak_merkle` — BPAK merkle hash tree¶