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/*
* Copyright (C) 2009-2010 Freescale Semiconductor, Inc. All Rights Reserved.
*/
/*
* The code contained herein is licensed under the GNU General Public
* License. You may obtain a copy of the GNU General Public License
* Version 2 or later at the following locations:
*
* http://www.opensource.org/licenses/gpl-license.html
* http://www.gnu.org/copyleft/gpl.html
*/
/*!
* @file shw_hmac.c
*
* This file contains implementations for use of the (internal) SHW HMAC
* software computation. It defines the usual three steps:
*
* - #shw_hmac_init()
* - #shw_hmac_update()
* - #shw_hmac_final()
*
*
*/
#include "shw_driver.h"
#include "shw_hmac.h"
#ifndef __KERNEL__
#include <asm/types.h>
#include <linux/byteorder/little_endian.h> /* or whichever is proper for target arch */
#define printk printf
#endif
/*! XOR value for HMAC inner key */
#define INNER_HASH_CONSTANT 0x36
/*! XOR value for HMAC outer key */
#define OUTER_HASH_CONSTANT 0x5C
/*!
* Initialize the HMAC state structure with the HMAC key
*
* @param state Address of HMAC state structure
* @param key Address of the key to be used for the HMAC.
* @param key_len Number of bytes of @c key.
*
* Convert the key into its equivalent inner and outer hash state objects.
*
* @return FSL_RETURN_OK_S if all went well, otherwise an error code.
*/
fsl_shw_return_t shw_hmac_init(shw_hmac_state_t * state,
const uint8_t * key, unsigned int key_len)
{
fsl_shw_return_t code = FSL_RETURN_ERROR_S;
uint8_t first_block[SHW_HASH_BLOCK_LEN];
unsigned int i;
/* Don't bother handling the pre-hash. */
if (key_len > SHW_HASH_BLOCK_LEN) {
code = FSL_RETURN_BAD_KEY_LENGTH_S;
goto out;
}
/* Prepare inner hash */
for (i = 0; i < SHW_HASH_BLOCK_LEN; i++) {
if (i < key_len) {
first_block[i] = key[i] ^ INNER_HASH_CONSTANT;
} else {
first_block[i] = INNER_HASH_CONSTANT;
}
}
code = shw_hash_init(&state->inner_hash, FSL_HASH_ALG_SHA256);
if (code != FSL_RETURN_OK_S) {
goto out;
}
shw_hash_update(&state->inner_hash, first_block, SHW_HASH_BLOCK_LEN);
/* Prepare outer hash */
for (i = 0; i < SHW_HASH_BLOCK_LEN; i++) {
if (i < key_len) {
first_block[i] = key[i] ^ OUTER_HASH_CONSTANT;
} else {
first_block[i] = OUTER_HASH_CONSTANT;
}
}
code = shw_hash_init(&state->outer_hash, FSL_HASH_ALG_SHA256);
if (code != FSL_RETURN_OK_S) {
goto out;
}
shw_hash_update(&state->outer_hash, first_block, SHW_HASH_BLOCK_LEN);
/* Wipe evidence of key */
memset(first_block, 0, SHW_HASH_BLOCK_LEN);
out:
return code;
}
/*!
* Put data into the HMAC calculation
*
* Send the msg data inner inner hash's update function.
*
* @param state Address of HMAC state structure.
* @param msg Address of the message data for the HMAC.
* @param msg_len Number of bytes of @c msg.
*
* @return FSL_RETURN_OK_S if all went well, otherwise an error code.
*/
fsl_shw_return_t shw_hmac_update(shw_hmac_state_t * state,
const uint8_t * msg, unsigned int msg_len)
{
shw_hash_update(&state->inner_hash, msg, msg_len);
return FSL_RETURN_OK_S;
}
/*!
* Calculate the final HMAC
*
* @param state Address of HMAC state structure.
* @param hmac Address of location to store the HMAC.
* @param hmac_len Number of bytes of @c mac to be stored. Probably best if
* this value is no greater than #SHW_HASH_LEN.
*
* This function finalizes the internal hash, and uses that result as
* data for the outer hash. As many bytes of that result are passed
* to the user as desired.
*
* @return FSL_RETURN_OK_S if all went well, otherwise an error code.
*/
fsl_shw_return_t shw_hmac_final(shw_hmac_state_t * state,
uint8_t * hmac, unsigned int hmac_len)
{
uint8_t hash_result[SHW_HASH_LEN];
shw_hash_final(&state->inner_hash, hash_result, sizeof(hash_result));
shw_hash_update(&state->outer_hash, hash_result, SHW_HASH_LEN);
shw_hash_final(&state->outer_hash, hmac, hmac_len);
return FSL_RETURN_OK_S;
}
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