// SetEllipticCurve sets the elliptic curve used by the SSL context to
// enable an ECDH cipher suite to be selected during the handshake.
func (c *Ctx) SetEllipticCurve(curve EllipticCurve) error {
runtime.LockOSThread()
defer runtime.UnlockOSThread()
k := C.EC_KEY_new_by_curve_name(C.int(curve))
if k == nil {
return errors.New("Unknown curve")
}
defer C.EC_KEY_free(k)
if int(C.SSL_CTX_set_tmp_ecdh_not_a_macro(c.ctx, k)) != 1 {
return errorFromErrorQueue()
}
return nil
}
// GenerateKey returns a public/private key pair. The private key is
// generated using the given reader, which must return random data.
// TODO(runcom): add support for Go stdlib `elliptic.Curve`, for now unsupported
func GenerateKey(curve elliptic.Curve, rand io.Reader) (priv []byte, x, y *big.Int, err error) {
// rand isn't used with openssl...
// for go stdlib compatibility
//c, _ := curve.(*elliptic.CurveParams)
// to use this pkg
c, ok := curve.(CurveParams)
if !ok {
return nil, nil, nil, errors.New("provided curve is unsupported")
}
k := C.EC_KEY_new()
if k == nil {
return nil, nil, nil, errors.New("can't create key")
}
defer C.EC_KEY_free(k)
if C.EC_KEY_set_group(k, c.curve) != 1 {
return nil, nil, nil, errors.New("can't set ec_group on key")
}
if C.EC_KEY_generate_key(k) != 1 {
return nil, nil, nil, errors.New("can't generate key")
}
blen := C.i2d_ECPrivateKey(k, nil)
if blen == 0 {
return nil, nil, nil, errors.New("can't get private key")
}
buf := make([]C.uchar, int(blen))
pkey := (*C.uchar)(&buf[0])
if C.i2d_ECPrivateKey(k, &pkey) == 0 {
return nil, nil, nil, errors.New("can't get private key")
}
point := C.EC_KEY_get0_public_key(k)
if point == nil {
return nil, nil, nil, errors.New("can't get public key")
}
defer C.EC_POINT_free(point)
rx := C.BN_new()
if rx == nil {
return nil, nil, nil, errors.New("error creating big num")
}
defer C.BN_free(rx)
ry := C.BN_new()
if ry == nil {
return nil, nil, nil, errors.New("errors creating big num")
}
defer C.BN_free(ry)
if C.EC_POINT_get_affine_coordinates_GFp(c.curve, point, rx, ry, nil) != 1 {
return nil, nil, nil, errors.New("can't get public key")
}
x, _ = new(big.Int).SetString(C.GoString(C.BN_bn2hex(rx)), 16)
y, _ = new(big.Int).SetString(C.GoString(C.BN_bn2hex(ry)), 16)
priv = C.GoBytes(unsafe.Pointer(pkey), C.int(blen))
return priv, x, y, nil
}