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#include "sgx_tcrypto_common.h"
#include "sgx_ecc256_internal.h"
/* Computes a point with scalar multiplication based on private B key (local) and remote public Ga Key
* Parameters:
* Return: sgx_status_t - SGX_SUCCESS or failure as defined sgx_error.h
* Inputs: sgx_ecc_state_handle_t ecc_handle - Handle to ECC crypto system
* sgx_ec256_private_t *p_private_b - Pointer to the local private key - LITTLE ENDIAN
* sgx_ec256_public_t *p_public_ga - Pointer to the remote public key - LITTLE ENDIAN
* Output: sgx_ec256_shared_point_t *p_shared_key - Pointer to the target shared point - LITTLE ENDIAN
x-coordinate of (privKeyB - pubKeyA) */
sgx_status_t sgx_ecc256_compute_shared_point(sgx_ec256_private_t *p_private_b,
sgx_ec256_public_t *p_public_ga,
sgx_ec256_shared_point_t *p_shared_key,
sgx_ecc_state_handle_t ecc_handle)
{
if ((ecc_handle == NULL) || (p_private_b == NULL) || (p_public_ga == NULL) || (p_shared_key == NULL))
{
return SGX_ERROR_INVALID_PARAMETER;
}
IppsBigNumState* BN_dh_privB = NULL;
IppsBigNumState* BN_dh_shared_x = NULL;
IppsBigNumState* BN_dh_shared_y = NULL;
IppsBigNumState* pubA_gx = NULL;
IppsBigNumState* pubA_gy = NULL;
IppsECCPPointState* point_pubA = NULL;
IppsECCPPointState* point_R = NULL;
IppStatus ipp_ret = ippStsNoErr;
int ecPointSize = 0;
IppECResult ipp_result = ippECValid;
IppsECCPState* p_ecc_state = (IppsECCPState*)ecc_handle;
do
{
ipp_ret = sgx_ipp_newBN((Ipp32u*)p_private_b->r, sizeof(sgx_ec256_private_t), &BN_dh_privB);
ERROR_BREAK(ipp_ret);
ipp_ret = sgx_ipp_newBN((uint32_t*)p_public_ga->gx, sizeof(p_public_ga->gx), &pubA_gx);
ERROR_BREAK(ipp_ret);
ipp_ret = sgx_ipp_newBN((uint32_t*)p_public_ga->gy, sizeof(p_public_ga->gy), &pubA_gy);
ERROR_BREAK(ipp_ret);
ipp_ret = ippsECCPPointGetSize(256, &ecPointSize);
ERROR_BREAK(ipp_ret);
point_pubA = (IppsECCPPointState*)( malloc(ecPointSize) );
if(!point_pubA)
{
ipp_ret = ippStsNoMemErr;
break;
}
ipp_ret = ippsECCPPointInit(256, point_pubA);
ERROR_BREAK(ipp_ret);
ipp_ret = ippsECCPSetPoint(pubA_gx, pubA_gy, point_pubA, p_ecc_state);
ERROR_BREAK(ipp_ret);
//defense in depth to verify that input public key in ECC group
//a return value of ippECValid indicates the point is on the elliptic curve
//and is not the point at infinity
ipp_ret = ippsECCPCheckPoint(point_pubA, &ipp_result, p_ecc_state);
ERROR_BREAK(ipp_ret);
if (ipp_result != ippECValid )
{
ipp_ret = ippStsPointAtInfinity;
break;
}
point_R = (IppsECCPPointState*)( malloc(ecPointSize) );
if(!point_R)
{
ipp_ret = ippStsNoMemErr;
break;
}
ipp_ret = ippsECCPPointInit(256, point_R);
ERROR_BREAK(ipp_ret);
ipp_ret = sgx_ipp_newBN(NULL, sizeof(sgx_ec256_dh_shared_t), &BN_dh_shared_x);
ERROR_BREAK(ipp_ret);
ipp_ret = sgx_ipp_newBN(NULL, sizeof(sgx_ec256_dh_shared_t), &BN_dh_shared_y);
ERROR_BREAK(ipp_ret);
ipp_ret = ippsECCPMulPointScalar(point_pubA, BN_dh_privB, point_R, p_ecc_state);
ERROR_BREAK(ipp_ret);
//defense in depth to verify that point_R in ECC group
//a return value of ippECValid indicates the point is on the elliptic curve
//and is not the point at infinity
ipp_ret = ippsECCPCheckPoint(point_R, &ipp_result, p_ecc_state);
ERROR_BREAK(ipp_ret);
if (ipp_result != ippECValid)
{
ipp_ret = ippStsPointAtInfinity;
break;
}
ipp_ret = ippsECCPGetPoint(BN_dh_shared_x, BN_dh_shared_y, point_R, p_ecc_state);
ERROR_BREAK(ipp_ret);
IppsBigNumSGN sgn = IppsBigNumPOS;
int length = 0;
Ipp32u *pdata = NULL;
ipp_ret = ippsRef_BN(&sgn, &length, &pdata, BN_dh_shared_x);
ERROR_BREAK(ipp_ret);
memset(p_shared_key->x, 0, sizeof(p_shared_key->x));
memcpy(p_shared_key->x, pdata, ROUND_TO(length, 8)/8);
// Clear memory securely
memset_s(pdata, sizeof(p_shared_key->x), 0, ROUND_TO(length, 8)/8);
ipp_ret = ippsRef_BN(&sgn, &length, &pdata, BN_dh_shared_y);
ERROR_BREAK(ipp_ret);
memset(p_shared_key->y, 0, sizeof(p_shared_key->y));
memcpy(p_shared_key->y, pdata, ROUND_TO(length, 8)/8);
// Clear memory securely
memset_s(pdata, sizeof(p_shared_key->x), 0, ROUND_TO(length, 8)/8);
}while(0);
SAFE_FREE(point_pubA);
if (point_R) memset_s(point_R, ecPointSize, 0, ecPointSize);
SAFE_FREE(point_R);
sgx_ipp_secure_free_BN(pubA_gx, sizeof(p_public_ga->gx));
sgx_ipp_secure_free_BN(pubA_gy, sizeof(p_public_ga->gy));
sgx_ipp_secure_free_BN(BN_dh_privB, sizeof(sgx_ec256_private_t));
sgx_ipp_secure_free_BN(BN_dh_shared_x, sizeof(sgx_ec256_dh_shared_t));
sgx_ipp_secure_free_BN(BN_dh_shared_y, sizeof(sgx_ec256_dh_shared_t));
if (ipp_ret == ippStsNoMemErr || ipp_ret == ippStsMemAllocErr)
{
return SGX_ERROR_OUT_OF_MEMORY;
}
if (ipp_ret != ippStsNoErr)
{
return SGX_ERROR_UNEXPECTED;
}
return SGX_SUCCESS;
}