protected virtual bool SupportsClientEccCapabilities(int[] namedCurves, byte[] ecPointFormats)
{
// NOTE: BC supports all the current set of point formats so we don't check them here
if (namedCurves == null)
{
/*
* RFC 4492 4. A client that proposes ECC cipher suites may choose not to include these
* extensions. In this case, the server is free to choose any one of the elliptic curves
* or point formats [...].
*/
return(TlsEccUtilities.HasAnySupportedNamedCurves());
}
for (int i = 0; i < namedCurves.Length; ++i)
{
int namedCurve = namedCurves[i];
if (NamedCurve.IsValid(namedCurve) &&
(!NamedCurve.RefersToASpecificNamedCurve(namedCurve) || TlsEccUtilities.IsSupportedNamedCurve(namedCurve)))
{
return(true);
}
}
return(false);
}
// 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));
}