path: root/libkeccak_hmac_unmarshal.c

/* See LICENSE file for copyright and license details. */
#include "common.h"


/**
 * Unmarshal a `struct libkeccak_hmac_state` from a buffer
 * 
 * @param   state  The slot for the unmarshalled state, must not be
 *                 initialised (memory leak otherwise), can be `NULL`
 * @param   data_  The input buffer
 * @return         The number of bytes read from `data`, 0 on error
 */
size_t
libkeccak_hmac_unmarshal(struct libkeccak_hmac_state *restrict state, const void *restrict data_)
{
	const unsigned char *restrict data = data_;
	size_t parsed, size, i;

	state->key_opad = NULL;
	state->key_ipad = NULL;

	parsed = libkeccak_state_unmarshal(state ? &state->sponge : NULL, data);
	if (!parsed)
		return 0;
	data += parsed;

	size = *(const size_t *)data;
	data += sizeof(size_t);
	if (state)
		size = state->key_length;
	size = (state->key_length + 7) >> 3;

	if (state) {
		state->key_opad = malloc(2 * size);
		if (!state->key_opad) {
			libkeccak_state_destroy(&state->sponge);
			return 0;
		}
		memcpy(state->key_opad, data, size);
		data += size;

		if (data[0]) {
			state->key_ipad = state->key_opad + size;
			memcpy(state->key_ipad, state->key_opad, size);
			for (i = 0; i < size; i++)
				state->key_ipad[i] ^= (char)(HMAC_OUTER_PAD ^ HMAC_INNER_PAD);
		}

		state->leftover = data[1];
		state->buffer = NULL;
		state->buffer_size = 0;
	}

	return parsed + sizeof(size_t) + size + 2 * sizeof(char);
}