public virtual void ProcessServerExtensions(IDictionary serverExtensions)
{
/*
* TlsProtocol implementation validates that any server extensions received correspond to
* client extensions sent. By default, we don't send any, and this method is not called.
*/
if (serverExtensions != null)
{
/*
* RFC 5246 7.4.1.4.1. Servers MUST NOT send this extension.
*/
CheckForUnexpectedServerExtension(serverExtensions, ExtensionType.signature_algorithms);
CheckForUnexpectedServerExtension(serverExtensions, ExtensionType.elliptic_curves);
if (TlsEccUtilities.IsEccCipherSuite(this.mSelectedCipherSuite))
{
this.mServerECPointFormats = TlsEccUtilities.GetSupportedPointFormatsExtension(serverExtensions);
}
else
{
CheckForUnexpectedServerExtension(serverExtensions, ExtensionType.ec_point_formats);
}
}
}
public virtual int GetSelectedCipherSuite()
{
/*
* TODO RFC 5246 7.4.3. In order to negotiate correctly, the server MUST check any candidate
* cipher suites against the "signature_algorithms" extension before selecting them. This is
* somewhat inelegant but is a compromise designed to minimize changes to the original
* cipher suite design.
*/
/*
* RFC 4429 5.1. A server that receives a ClientHello containing one or both of these
* extensions MUST use the client's enumerated capabilities to guide its selection of an
* appropriate cipher suite. One of the proposed ECC cipher suites must be negotiated only
* if the server can successfully complete the handshake while using the curves and point
* formats supported by the client [...].
*/
bool eccCipherSuitesEnabled = SupportsClientEccCapabilities(this.mNamedCurves, this.mClientECPointFormats);
int[] cipherSuites = GetCipherSuites();
for (int i = 0; i < cipherSuites.Length; ++i)
{
int cipherSuite = cipherSuites[i];
if (Arrays.Contains(this.mOfferedCipherSuites, cipherSuite) &&
(eccCipherSuitesEnabled || !TlsEccUtilities.IsEccCipherSuite(cipherSuite)) &&
TlsUtilities.IsValidCipherSuiteForVersion(cipherSuite, mServerVersion))
{
return(this.mSelectedCipherSuite = cipherSuite);
}
}
throw new TlsFatalAlert(AlertDescription.handshake_failure);
}
// IDictionary is (Int32 -> byte[])
public virtual IDictionary GetServerExtensions()
{
if (this.mEncryptThenMacOffered && AllowEncryptThenMac)
{
/*
* RFC 7366 3. If a server receives an encrypt-then-MAC request extension from a client
* and then selects a stream or Authenticated Encryption with Associated Data (AEAD)
* ciphersuite, it MUST NOT send an encrypt-then-MAC response extension back to the
* client.
*/
if (TlsUtilities.IsBlockCipherSuite(this.mSelectedCipherSuite))
{
TlsExtensionsUtilities.AddEncryptThenMacExtension(CheckServerExtensions());
}
}
if (this.mMaxFragmentLengthOffered >= 0 &&
TlsUtilities.IsValidUint8(mMaxFragmentLengthOffered) &&
MaxFragmentLength.IsValid((byte)mMaxFragmentLengthOffered))
{
TlsExtensionsUtilities.AddMaxFragmentLengthExtension(CheckServerExtensions(), (byte)mMaxFragmentLengthOffered);
}
if (this.mTruncatedHMacOffered && AllowTruncatedHMac)
{
TlsExtensionsUtilities.AddTruncatedHMacExtension(CheckServerExtensions());
}
if (this.mClientECPointFormats != null && TlsEccUtilities.IsEccCipherSuite(this.mSelectedCipherSuite))
{
/*
* RFC 4492 5.2. A server that selects an ECC cipher suite in response to a ClientHello
* message including a Supported Point Formats Extension appends this extension (along
* with others) to its ServerHello message, enumerating the point formats it can parse.
*/
this.mServerECPointFormats = new byte[] { ECPointFormat.uncompressed,
ECPointFormat.ansiX962_compressed_prime, ECPointFormat.ansiX962_compressed_char2, };
TlsEccUtilities.AddSupportedPointFormatsExtension(CheckServerExtensions(), mServerECPointFormats);
}
return(mServerExtensions);
}
