protected byte[] GenerateMasterKey(SecureChannelPacket.Hello clientHello, SecureChannelPacket.Hello serverHello, byte[] preSharedKey, KeyAgreement keyAgreement, byte[] otherPartyPublicKey)
{
using (MemoryStream mS = new MemoryStream(128))
{
clientHello.WriteTo(mS);
serverHello.WriteTo(mS);
if (preSharedKey == null)
{
keyAgreement.HmacMessage = mS.ToArray();
}
else
{
keyAgreement.HmacMessage = (new HMACSHA256(preSharedKey)).ComputeHash(mS.ToArray());
}
}
return(keyAgreement.DeriveKeyMaterial(otherPartyPublicKey));
}
private void ProtocolV4(Stream stream)
{
#region 1. hello handshake
//read client hello
SecureChannelPacket.Hello clientHello = (new SecureChannelPacket(stream)).GetHello();
//select crypto option
_selectedCryptoOption = _supportedOptions & clientHello.CryptoOptions;
if (_selectedCryptoOption == SecureChannelCryptoOptionFlags.None)
{
throw new SecureChannelException(SecureChannelCode.NoMatchingCryptoAvailable, _remotePeerEP, _remotePeerCert);
}
else if ((_selectedCryptoOption & SecureChannelCryptoOptionFlags.ECDHE256_RSA_WITH_AES256_CBC_HMAC_SHA256) > 0)
{
_selectedCryptoOption = SecureChannelCryptoOptionFlags.ECDHE256_RSA_WITH_AES256_CBC_HMAC_SHA256;
}
else if ((_selectedCryptoOption & SecureChannelCryptoOptionFlags.DHE2048_RSA_WITH_AES256_CBC_HMAC_SHA256) > 0)
{
_selectedCryptoOption = SecureChannelCryptoOptionFlags.DHE2048_RSA_WITH_AES256_CBC_HMAC_SHA256;
}
else
{
throw new SecureChannelException(SecureChannelCode.NoMatchingCryptoAvailable, _remotePeerEP, _remotePeerCert);
}
//send server hello
SecureChannelPacket.Hello serverHello = new SecureChannelPacket.Hello(BinaryID.GenerateRandomID256(), _selectedCryptoOption);
SecureChannelPacket.WritePacket(stream, serverHello);
#endregion
#region 2. key exchange
SymmetricEncryptionAlgorithm encAlgo;
string hashAlgo;
KeyAgreement keyAgreement;
switch (_selectedCryptoOption)
{
case SecureChannelCryptoOptionFlags.DHE2048_RSA_WITH_AES256_CBC_HMAC_SHA256:
encAlgo = SymmetricEncryptionAlgorithm.Rijndael;
hashAlgo = "SHA256";
keyAgreement = new DiffieHellman(DiffieHellmanGroupType.RFC3526, 2048, KeyAgreementKeyDerivationFunction.Hmac, KeyAgreementKeyDerivationHashAlgorithm.SHA256);
break;
case SecureChannelCryptoOptionFlags.ECDHE256_RSA_WITH_AES256_CBC_HMAC_SHA256:
encAlgo = SymmetricEncryptionAlgorithm.Rijndael;
hashAlgo = "SHA256";
keyAgreement = new TechnitiumLibrary.Security.Cryptography.ECDiffieHellman(256, KeyAgreementKeyDerivationFunction.Hmac, KeyAgreementKeyDerivationHashAlgorithm.SHA256);
break;
default:
throw new SecureChannelException(SecureChannelCode.NoMatchingCryptoAvailable, _remotePeerEP, _remotePeerCert);
}
//send server key exchange data
SecureChannelPacket.KeyExchange serverKeyExchange = new SecureChannelPacket.KeyExchange(keyAgreement.GetPublicKey(), _serverCredentials.PrivateKey, hashAlgo);
SecureChannelPacket.WritePacket(stream, serverKeyExchange);
//read client key exchange data
SecureChannelPacket.KeyExchange clientKeyExchange = (new SecureChannelPacket(stream)).GetKeyExchange();
//generate master key
byte[] masterKey = GenerateMasterKey(clientHello, serverHello, _preSharedKey, keyAgreement, clientKeyExchange.PublicKey);
//verify master key using HMAC authentication
{
SecureChannelPacket.Authentication clientAuthentication = (new SecureChannelPacket(stream)).GetAuthentication();
if (!clientAuthentication.IsValid(serverHello, masterKey))
{
throw new SecureChannelException(SecureChannelCode.ProtocolAuthenticationFailed, _remotePeerEP, _remotePeerCert);
}
SecureChannelPacket.Authentication serverAuthentication = new SecureChannelPacket.Authentication(clientHello, masterKey);
SecureChannelPacket.WritePacket(stream, serverAuthentication);
}
//enable channel encryption
switch (encAlgo)
{
case SymmetricEncryptionAlgorithm.Rijndael:
//using MD5 for generating AES IV of 128bit block size
HashAlgorithm md5Hash = HashAlgorithm.Create("MD5");
byte[] eIV = md5Hash.ComputeHash(serverHello.Nonce.ID);
byte[] dIV = md5Hash.ComputeHash(clientHello.Nonce.ID);
//create encryption and decryption objects
SymmetricCryptoKey encryptionKey = new SymmetricCryptoKey(SymmetricEncryptionAlgorithm.Rijndael, masterKey, eIV, PaddingMode.None);
SymmetricCryptoKey decryptionKey = new SymmetricCryptoKey(SymmetricEncryptionAlgorithm.Rijndael, masterKey, dIV, PaddingMode.None);
//enable encryption
EnableEncryption(stream, encryptionKey, decryptionKey, new HMACSHA256(masterKey), new HMACSHA256(masterKey));
break;
default:
throw new SecureChannelException(SecureChannelCode.NoMatchingCryptoAvailable, _remotePeerEP, _remotePeerCert);
}
//channel encryption is ON!
#endregion
#region 3. exchange & verify certificates & signatures
if (!IsReNegotiating())
{
//read client certificate
_remotePeerCert = (new SecureChannelPacket(this)).GetCertificate();
//verify client certificate
try
{
_remotePeerCert.Verify(_trustedRootCertificates);
}
catch (Exception ex)
{
throw new SecureChannelException(SecureChannelCode.InvalidRemoteCertificate, _remotePeerEP, _remotePeerCert, "Invalid remote certificate.", ex);
}
}
//verify key exchange signature
switch (_selectedCryptoOption)
{
case SecureChannelCryptoOptionFlags.DHE2048_RSA_WITH_AES256_CBC_HMAC_SHA256:
case SecureChannelCryptoOptionFlags.ECDHE256_RSA_WITH_AES256_CBC_HMAC_SHA256:
if (_remotePeerCert.PublicKeyEncryptionAlgorithm != AsymmetricEncryptionAlgorithm.RSA)
{
throw new SecureChannelException(SecureChannelCode.InvalidRemoteCertificateAlgorithm, _remotePeerEP, _remotePeerCert);
}
if (!clientKeyExchange.IsSignatureValid(_remotePeerCert, "SHA256"))
{
throw new SecureChannelException(SecureChannelCode.InvalidRemoteKeyExchangeSignature, _remotePeerEP, _remotePeerCert);
}
break;
default:
throw new SecureChannelException(SecureChannelCode.NoMatchingCryptoAvailable, _remotePeerEP, _remotePeerCert);
}
if ((_manager != null) && !_manager.ProceedConnection(_remotePeerCert))
{
throw new SecureChannelException(SecureChannelCode.SecurityManagerDeclinedAccess, _remotePeerEP, _remotePeerCert, "Security manager declined access.");
}
//send server certificate
if (!IsReNegotiating())
{
SecureChannelPacket.WritePacket(this, _serverCredentials.Certificate);
}
#endregion
}
