public static ECDomainParameters ReadECParameters(int[] namedCurves, byte[] ecPointFormats, Stream input)
{
try
{
byte curveType = TlsUtilities.ReadUint8(input);
switch (curveType)
{
case ECCurveType.explicit_prime:
{
CheckNamedCurve(namedCurves, NamedCurve.arbitrary_explicit_prime_curves);
BigInteger prime_p = ReadECParameter(input);
BigInteger a = ReadECFieldElement(prime_p.BitLength, input);
BigInteger b = ReadECFieldElement(prime_p.BitLength, input);
byte[] baseEncoding = TlsUtilities.ReadOpaque8(input);
BigInteger order = ReadECParameter(input);
BigInteger cofactor = ReadECParameter(input);
ECCurve curve = new FpCurve(prime_p, a, b, order, cofactor);
ECPoint basePoint = DeserializeECPoint(ecPointFormats, curve, baseEncoding);
return(new ECDomainParameters(curve, basePoint, order, cofactor));
}
case ECCurveType.explicit_char2:
{
CheckNamedCurve(namedCurves, NamedCurve.arbitrary_explicit_char2_curves);
int m = TlsUtilities.ReadUint16(input);
byte basis = TlsUtilities.ReadUint8(input);
if (!ECBasisType.IsValid(basis))
{
throw new TlsFatalAlert(AlertDescription.illegal_parameter);
}
int k1 = ReadECExponent(m, input), k2 = -1, k3 = -1;
if (basis == ECBasisType.ec_basis_pentanomial)
{
k2 = ReadECExponent(m, input);
k3 = ReadECExponent(m, input);
}
BigInteger a = ReadECFieldElement(m, input);
BigInteger b = ReadECFieldElement(m, input);
byte[] baseEncoding = TlsUtilities.ReadOpaque8(input);
BigInteger order = ReadECParameter(input);
BigInteger cofactor = ReadECParameter(input);
ECCurve curve = (basis == ECBasisType.ec_basis_pentanomial)
? new F2mCurve(m, k1, k2, k3, a, b, order, cofactor)
: new F2mCurve(m, k1, a, b, order, cofactor);
ECPoint basePoint = DeserializeECPoint(ecPointFormats, curve, baseEncoding);
return(new ECDomainParameters(curve, basePoint, order, cofactor));
}
case ECCurveType.named_curve:
{
int namedCurve = TlsUtilities.ReadUint16(input);
if (!NamedCurve.RefersToASpecificNamedCurve(namedCurve))
{
/*
* RFC 4492 5.4. All those values of NamedCurve are allowed that refer to a
* specific curve. Values of NamedCurve that indicate support for a class of
* explicitly defined curves are not allowed here [...].
*/
throw new TlsFatalAlert(AlertDescription.illegal_parameter);
}
CheckNamedCurve(namedCurves, namedCurve);
return(GetParametersForNamedCurve(namedCurve));
}
default:
throw new TlsFatalAlert(AlertDescription.illegal_parameter);
}
}
catch (Exception e)
{
throw new TlsFatalAlert(AlertDescription.illegal_parameter, e);
}
}
// TODO Refactor around ServerECDHParams before making this public
internal static ECPrivateKeyParameters GenerateEphemeralServerKeyExchange(SecureRandom random, int[] namedCurves,
byte[] ecPointFormats, Stream output)
{
/* First we try to find a supported named curve from the client's list. */
int namedCurve = -1;
if (namedCurves == null)
{
// TODO Let the peer choose the default named curve
namedCurve = NamedCurve.secp256r1;
}
else
{
for (int i = 0; i < namedCurves.Length; ++i)
{
int entry = namedCurves[i];
if (NamedCurve.IsValid(entry) && IsSupportedNamedCurve(entry))
{
namedCurve = entry;
break;
}
}
}
ECDomainParameters ecParams = null;
if (namedCurve >= 0)
{
ecParams = GetParametersForNamedCurve(namedCurve);
}
else
{
/* If no named curves are suitable, check if the client supports explicit curves. */
if (Arrays.Contains(namedCurves, NamedCurve.arbitrary_explicit_prime_curves))
{
ecParams = GetParametersForNamedCurve(NamedCurve.secp256r1);
}
else if (Arrays.Contains(namedCurves, NamedCurve.arbitrary_explicit_char2_curves))
{
ecParams = GetParametersForNamedCurve(NamedCurve.sect283r1);
}
}
if (ecParams == null)
{
/*
* NOTE: We shouldn't have negotiated ECDHE key exchange since we apparently can't find
* a suitable curve.
*/
throw new TlsFatalAlert(AlertDescription.internal_error);
}
if (namedCurve < 0)
{
WriteExplicitECParameters(ecPointFormats, ecParams, output);
}
else
{
WriteNamedECParameters(namedCurve, output);
}
return(GenerateEphemeralClientKeyExchange(random, ecPointFormats, ecParams, output));
}
