sgx_status_t derive_key(
const sgx_ec256_dh_shared_t* shared_key,
const char* label,
uint32_t label_length,
sgx_ec_key_128bit_t* derived_key)
{
sgx_status_t se_ret = SGX_SUCCESS;
uint8_t cmac_key[MAC_KEY_SIZE];
sgx_ec_key_128bit_t key_derive_key;
if (!shared_key || !derived_key || !label)
{
return SGX_ERROR_INVALID_PARAMETER;
}
/*check integer overflow */
if (label_length > EC_DERIVATION_BUFFER_SIZE(label_length))
{
return SGX_ERROR_INVALID_PARAMETER;
}
memset(cmac_key, 0, MAC_KEY_SIZE);
se_ret = sgx_rijndael128_cmac_msg((sgx_cmac_128bit_key_t *)cmac_key,
(uint8_t*)shared_key,
sizeof(sgx_ec256_dh_shared_t),
(sgx_cmac_128bit_tag_t *)&key_derive_key);
if (SGX_SUCCESS != se_ret)
{
memset_s(&key_derive_key, sizeof(key_derive_key), 0, sizeof(key_derive_key));
INTERNAL_SGX_ERROR_CODE_CONVERTOR(se_ret);
return se_ret;
}
/* derivation_buffer = counter(0x01) || label || 0x00 || output_key_len(0x0080) */
uint32_t derivation_buffer_length = EC_DERIVATION_BUFFER_SIZE(label_length);
uint8_t *p_derivation_buffer = (uint8_t *)malloc(derivation_buffer_length);
if (p_derivation_buffer == NULL)
{
return SGX_ERROR_OUT_OF_MEMORY;
}
memset(p_derivation_buffer, 0, derivation_buffer_length);
/*counter = 0x01 */
p_derivation_buffer[0] = 0x01;
/*label*/
memcpy(&p_derivation_buffer[1], label, label_length);
/*output_key_len=0x0080*/
uint16_t *key_len = (uint16_t *)&p_derivation_buffer[derivation_buffer_length - 2];
*key_len = 0x0080;
se_ret = sgx_rijndael128_cmac_msg((sgx_cmac_128bit_key_t *)&key_derive_key,
p_derivation_buffer,
derivation_buffer_length,
(sgx_cmac_128bit_tag_t *)derived_key);
memset_s(&key_derive_key, sizeof(key_derive_key), 0, sizeof(key_derive_key));
free(p_derivation_buffer);
if(SGX_SUCCESS != se_ret)
{
INTERNAL_SGX_ERROR_CODE_CONVERTOR(se_ret);
}
return se_ret;
}
// Derive key from shared key and key id.
// key id should be sample_derive_key_type_t.
bool derive_key(
const sample_ec_dh_shared_t *p_shared_key,
uint8_t key_id,
sample_ec_key_128bit_t* derived_key)
{
sample_status_t sample_ret = SAMPLE_SUCCESS;
uint8_t cmac_key[MAC_KEY_SIZE];
sample_ec_key_128bit_t key_derive_key;
memset(&cmac_key, 0, MAC_KEY_SIZE);
sample_ret = sample_rijndael128_cmac_msg(
(sample_cmac_128bit_key_t *)&cmac_key,
(uint8_t*)p_shared_key,
sizeof(sample_ec_dh_shared_t),
(sample_cmac_128bit_tag_t *)&key_derive_key);
if (sample_ret != SAMPLE_SUCCESS)
{
// memset here can be optimized away by compiler, so please use memset_s on
// windows for production code and similar functions on other OSes.
memset(&key_derive_key, 0, sizeof(key_derive_key));
return false;
}
const char *label = NULL;
uint32_t label_length = 0;
switch (key_id)
{
case SAMPLE_DERIVE_KEY_SMK:
label = str_SMK;
label_length = sizeof(str_SMK) -1;
break;
case SAMPLE_DERIVE_KEY_SK:
label = str_SK;
label_length = sizeof(str_SK) -1;
break;
case SAMPLE_DERIVE_KEY_MK:
label = str_MK;
label_length = sizeof(str_MK) -1;
break;
case SAMPLE_DERIVE_KEY_VK:
label = str_VK;
label_length = sizeof(str_VK) -1;
break;
default:
// memset here can be optimized away by compiler, so please use memset_s on
// windows for production code and similar functions on other OSes.
memset(&key_derive_key, 0, sizeof(key_derive_key));
return false;
break;
}
/* derivation_buffer = counter(0x01) || label || 0x00 || output_key_len(0x0080) */
uint32_t derivation_buffer_length = EC_DERIVATION_BUFFER_SIZE(label_length);
uint8_t *p_derivation_buffer = (uint8_t *)malloc(derivation_buffer_length);
if (p_derivation_buffer == NULL)
{
// memset here can be optimized away by compiler, so please use memset_s on
// windows for production code and similar functions on other OSes.
memset(&key_derive_key, 0, sizeof(key_derive_key));
return false;
}
memset(p_derivation_buffer, 0, derivation_buffer_length);
/*counter = 0x01 */
p_derivation_buffer[0] = 0x01;
/*label*/
memcpy(&p_derivation_buffer[1], label, label_length);
/*output_key_len=0x0080*/
uint16_t *key_len = (uint16_t *)(&(p_derivation_buffer[derivation_buffer_length - 2]));
*key_len = 0x0080;
sample_ret = sample_rijndael128_cmac_msg(
(sample_cmac_128bit_key_t *)&key_derive_key,
p_derivation_buffer,
derivation_buffer_length,
(sample_cmac_128bit_tag_t *)derived_key);
free(p_derivation_buffer);
// memset here can be optimized away by compiler, so please use memset_s on
// windows for production code and similar functions on other OSes.
memset(&key_derive_key, 0, sizeof(key_derive_key));
if (sample_ret != SAMPLE_SUCCESS)
{
return false;
}
return true;
}
