internal static bool VerifyServerCertificate(TlsContext context, MX.X509Certificate certificate, ExchangeAlgorithmType algorithm)
{
if (context.NegotiatedProtocol == TlsProtocolCode.Tls12 && certificate.Version < 3)
{
throw new TlsException(AlertDescription.UnsupportedCertificate, "X.509v3 server certificate required");
}
if (certificate.KeyAlgorithm != null && !certificate.KeyAlgorithm.Equals(OidKeyAlgorithmRsa))
{
return(false);
}
if (certificate.SignatureAlgorithm != null && !VerifySignatureAlgorithm(certificate.SignatureAlgorithm))
{
return(false);
}
switch (algorithm)
{
case ExchangeAlgorithmType.Rsa:
return(VerifyKeyUsage(certificate, KeyUsages.keyEncipherment, OidServerAuth));
case ExchangeAlgorithmType.Dhe:
case ExchangeAlgorithmType.EcDhe:
return(VerifyKeyUsage(certificate, KeyUsages.digitalSignature, OidServerAuth));
default:
throw new TlsException(AlertDescription.InternalError);
}
}
internal static bool VerifyKeyUsage(MX.X509Certificate certificate, KeyUsages keyUsages, string purpose)
{
if (certificate.Extensions == null)
{
return(true);
}
KeyUsageExtension kux = null;
ExtendedKeyUsageExtension eku = null;
var xtn = certificate.Extensions [OidKeyUsage];
if (xtn != null)
{
kux = new KeyUsageExtension(xtn);
}
xtn = certificate.Extensions [OidExtendedKeyUsage];
if (xtn != null)
{
eku = new ExtendedKeyUsageExtension(xtn);
}
if ((kux != null) && (eku != null))
{
// RFC3280 states that when both KeyUsageExtension and
// ExtendedKeyUsageExtension are present then BOTH should
// be valid
if (!kux.Support(keyUsages))
{
return(false);
}
return(eku.KeyPurpose.Contains(purpose));
}
else if (kux != null)
{
return(kux.Support(keyUsages));
}
else if (eku != null)
{
return(eku.KeyPurpose.Contains(purpose));
}
return(true);
}