public byte[] Expand(HashAlgorithm hash, byte[] secret, byte[] seed, int length)
{
var hashLength = hash.HashSize / 8;
var iterations = length / hashLength;
if (length % hashLength > 0)
{
iterations++;
}
var hmac = new HMAC(hash, secret);
var resMacs = new TlsStream();
var hmacs = new byte[iterations + 1][];
hmacs[0] = seed;
for (var i = 1; i <= iterations; i++)
{
var hcseed = new TlsStream();
hmac.TransformFinalBlock(hmacs[i - 1], 0, hmacs[i - 1].Length);
hmacs[i] = hmac.Hash;
hcseed.Write(hmacs[i]);
hcseed.Write(seed);
hmac.TransformFinalBlock(hcseed.ToArray(), 0, (int)hcseed.Length);
resMacs.Write(hmac.Hash);
hcseed.Reset();
}
var res = new byte[length];
Buffer.BlockCopy(resMacs.ToArray(), 0, res, 0, res.Length);
resMacs.Reset();
return(res);
}
private void createDecryptionCipher()
{
// Create and configure the symmetric algorithm
switch (CipherAlgorithmType)
{
case CipherAlgorithmType.Des:
decryptionAlgorithm = DES.Create();
break;
case CipherAlgorithmType.Rc2:
decryptionAlgorithm = RC2.Create();
break;
case CipherAlgorithmType.Rc4:
decryptionAlgorithm = new M.ARC4Managed();
break;
case CipherAlgorithmType.TripleDes:
decryptionAlgorithm = TripleDES.Create();
break;
case CipherAlgorithmType.Rijndael:
// only AES is really used - and we can use CommonCrypto for iOS and OSX this way
decryptionAlgorithm = Aes.Create();
break;
}
// If it's a block cipher
if (CipherMode == CipherMode.CBC)
{
// Configure encrypt algorithm
decryptionAlgorithm.Mode = CipherMode;
decryptionAlgorithm.Padding = PaddingMode.None;
decryptionAlgorithm.KeySize = ExpandedKeyMaterialSize * 8;
decryptionAlgorithm.BlockSize = blockSize * 8;
}
// Set the key and IV for the algorithm
if (Context is ClientContext)
{
decryptionAlgorithm.Key = Context.ServerWriteKey;
decryptionAlgorithm.IV = Context.ServerWriteIV;
}
else
{
decryptionAlgorithm.Key = Context.ClientWriteKey;
decryptionAlgorithm.IV = Context.ClientWriteIV;
}
// Create decryption cipher
DecryptionCipher = decryptionAlgorithm.CreateDecryptor();
// Create the HMAC
if (Context is ClientContext)
{
ServerHMAC = new HMAC(
CreateHashAlgorithm(),
Context.Negotiating.ServerWriteMAC);
}
else
{
ClientHMAC = new HMAC(
CreateHashAlgorithm(),
Context.Negotiating.ClientWriteMAC);
}
}
