/*
* EC public key is an EC point
*
* The caller is responsible for clearing the structure upon failure if
* desired. Take care to pass along the possible ECP_FEATURE_UNAVAILABLE
* return code of mbedtls_ecp_point_read_binary() and leave p in a usable state.
*/
static int pk_get_ecpubkey( unsigned char **p, const unsigned char *end,
mbedtls_ecp_keypair *key )
{
int ret;
if( ( ret = mbedtls_ecp_point_read_binary( &key->grp, &key->Q,
(const unsigned char *) *p, end - *p ) ) == 0 )
{
ret = mbedtls_ecp_check_pubkey( &key->grp, &key->Q );
}
/*
* We know mbedtls_ecp_point_read_binary consumed all bytes or failed
*/
*p = (unsigned char *) end;
return( ret );
}
/*
* Verify ECDSA signature of hashed message (SEC1 4.1.4)
* Obviously, compared to SEC1 4.1.3, we skip step 2 (hash message)
*/
int mbedtls_ecdsa_verify( mbedtls_ecp_group *grp,
const unsigned char *buf, size_t blen,
const mbedtls_ecp_point *Q, const mbedtls_mpi *r, const mbedtls_mpi *s)
{
int ret;
mbedtls_mpi e, s_inv, u1, u2;
mbedtls_ecp_point R;
mbedtls_ecp_point_init( &R );
mbedtls_mpi_init( &e ); mbedtls_mpi_init( &s_inv ); mbedtls_mpi_init( &u1 ); mbedtls_mpi_init( &u2 );
/* Fail cleanly on curves such as Curve25519 that can't be used for ECDSA */
if( grp->N.p == NULL )
return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
/*
* Step 1: make sure r and s are in range 1..n-1
*/
if( mbedtls_mpi_cmp_int( r, 1 ) < 0 || mbedtls_mpi_cmp_mpi( r, &grp->N ) >= 0 ||
mbedtls_mpi_cmp_int( s, 1 ) < 0 || mbedtls_mpi_cmp_mpi( s, &grp->N ) >= 0 )
{
ret = MBEDTLS_ERR_ECP_VERIFY_FAILED;
goto cleanup;
}
/*
* Additional precaution: make sure Q is valid
*/
MBEDTLS_MPI_CHK( mbedtls_ecp_check_pubkey( grp, Q ) );
/*
* Step 3: derive MPI from hashed message
*/
MBEDTLS_MPI_CHK( derive_mpi( grp, &e, buf, blen ) );
/*
* Step 4: u1 = e / s mod n, u2 = r / s mod n
*/
MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( &s_inv, s, &grp->N ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &u1, &e, &s_inv ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &u1, &u1, &grp->N ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &u2, r, &s_inv ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &u2, &u2, &grp->N ) );
/*
* Step 5: R = u1 G + u2 Q
*
* Since we're not using any secret data, no need to pass a RNG to
* mbedtls_ecp_mul() for countermesures.
*/
MBEDTLS_MPI_CHK( mbedtls_ecp_muladd( grp, &R, &u1, &grp->G, &u2, Q ) );
if( mbedtls_ecp_is_zero( &R ) )
{
ret = MBEDTLS_ERR_ECP_VERIFY_FAILED;
goto cleanup;
}
/*
* Step 6: convert xR to an integer (no-op)
* Step 7: reduce xR mod n (gives v)
*/
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &R.X, &R.X, &grp->N ) );
/*
* Step 8: check if v (that is, R.X) is equal to r
*/
if( mbedtls_mpi_cmp_mpi( &R.X, r ) != 0 )
{
ret = MBEDTLS_ERR_ECP_VERIFY_FAILED;
goto cleanup;
}
cleanup:
mbedtls_ecp_point_free( &R );
mbedtls_mpi_free( &e ); mbedtls_mpi_free( &s_inv ); mbedtls_mpi_free( &u1 ); mbedtls_mpi_free( &u2 );
return( ret );
}
int mbedtls_ecdh_compute_shared( mbedtls_ecp_group *grp, mbedtls_mpi *z,
const mbedtls_ecp_point *Q, const mbedtls_mpi *d,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng )
{
int ret;
void* pHeap = NULL;
size_t heapSize = 0;
size_t public_key_size = (grp->nbits+7)/8 ;
const CRYS_ECPKI_Domain_t* pDomain = CRYS_ECPKI_GetEcDomain ( convert_mbedtls_grp_id_to_crys_domain_id( grp->id ) );
uint32_t secret_size = ( ( grp->nbits + 7 ) / 8 ) ;
const uint32_t secret_size_in_heap = secret_size;
uint8_t* secret = mbedtls_calloc( 1, secret_size_in_heap );
if ( secret == NULL )
return ( MBEDTLS_ERR_ECP_ALLOC_FAILED );
/*
* Make sure Q is a valid pubkey before using it
*/
MBEDTLS_MPI_CHK( mbedtls_ecp_check_pubkey( grp, Q ) );
if ( pDomain )
{
uint8_t temp_buf[ 2 * MAX_KEY_SIZE_IN_BYTES + 1 ] = {0};
cc_ecc_ws_comp_shared_params_t* ecdhParams = mbedtls_calloc( 1, sizeof(cc_ecc_ws_comp_shared_params_t) );
if ( ecdhParams == NULL )
{
ret = MBEDTLS_ERR_ECP_ALLOC_FAILED;
goto cleanup;
}
pHeap = ecdhParams;
heapSize = sizeof(cc_ecc_ws_comp_shared_params_t);
MBEDTLS_MPI_CHK( mbedtls_ecp_point_write_binary( grp, Q, MBEDTLS_ECP_PF_UNCOMPRESSED,
&public_key_size, temp_buf, sizeof(temp_buf) ) );
ret = convert_CrysError_to_mbedtls_err( CRYS_ECPKI_BuildPublKey( pDomain, temp_buf, public_key_size,
&ecdhParams->pubKey ) );
if ( ret != 0 )
{
goto cleanup;
}
memset ( temp_buf, 0, sizeof(temp_buf) );
MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( d, temp_buf, mbedtls_mpi_size( d ) ) );
ret = convert_CrysError_to_mbedtls_err( CRYS_ECPKI_BuildPrivKey( pDomain,
temp_buf,
mbedtls_mpi_size( d ),
&ecdhParams->privKey ) );
mbedtls_zeroize( temp_buf, sizeof( temp_buf ) );
if ( ret != 0 )
{
goto cleanup;
}
ret = convert_CrysError_to_mbedtls_err( CRYS_ECDH_SVDP_DH( &ecdhParams->pubKey, &ecdhParams->privKey,
secret, &secret_size,
&ecdhParams->ecdhTempData ) );
if ( ret != 0 )
{
goto cleanup;
}
}
else if ( grp->id == MBEDTLS_ECP_DP_CURVE25519 )
{
cc_ecc_25519_comp_shared_params_t* ecdhParams = mbedtls_calloc( 1, sizeof(cc_ecc_25519_comp_shared_params_t) );
if ( ecdhParams == NULL )
{
ret = MBEDTLS_ERR_ECP_ALLOC_FAILED;
goto cleanup;
}
pHeap = ecdhParams;
heapSize = sizeof(cc_ecc_25519_comp_shared_params_t);
MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( d, ecdhParams->privKey, mbedtls_mpi_size( d ) ) ) ;
MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &Q->X, ecdhParams->pubKey, public_key_size ) );
ret = convert_CrysError_to_mbedtls_err( CRYS_ECMONT_Scalarmult( secret, ( size_t* )&secret_size,
ecdhParams->privKey, CURVE_25519_KEY_SIZE ,
ecdhParams->pubKey, CURVE_25519_KEY_SIZE ,
&ecdhParams->kgTempData ) );
if ( ret != 0 )
{
goto cleanup;
}
}
else
{
ret = MBEDTLS_ERR_PLATFORM_FEATURE_UNSUPPORTED;
goto cleanup;
}
MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( z, secret, secret_size ) );
cleanup:
if ( pHeap )
{
mbedtls_zeroize( pHeap, heapSize );
mbedtls_free ( pHeap );
}
if ( secret )
{
mbedtls_zeroize( secret, secret_size_in_heap );
mbedtls_free ( secret );
}
return ( ret );
}
