private byte[] EncryptCookieData(byte[] cookieBlob, int length, Sha1HashProvider hasher = null)
{
using (var aesProvider = Aes.Create())
{
aesProvider.Key = _DecryptionKeyBlob;
aesProvider.BlockSize = 128;
aesProvider.GenerateIV();
aesProvider.IV = new byte[aesProvider.IV.Length];
aesProvider.Mode = CipherMode.CBC;
var decryptor = aesProvider.CreateEncryptor();
using (var ms = new MemoryStream())
{
using (var cs = new CryptoStream(ms, decryptor, CryptoStreamMode.Write))
{
bool createIv = true;
bool useRandomIv = true;
bool sign = false;
if (createIv)
{
int ivLength = RoundupNumBitsToNumBytes(aesProvider.KeySize);
byte[] iv = null;
if (hasher != null)
{
iv = hasher.GetIVHash(cookieBlob, ivLength);
}
else if (useRandomIv)
{
iv = new byte[ivLength];
RandomNumberGenerator.GetBytes(iv);
}
// first write the iv.
cs.Write(iv, 0, iv.Length);
}
// then write ticket data.
cs.Write(cookieBlob, 0, cookieBlob.Length);
cs.FlushFinalBlock();
byte[] paddedData = ms.ToArray();
if (sign)
{
throw new NotImplementedException();
// append signature to encrypted bytes.
}
return(paddedData);
}
}
}
}
private byte[] Decrypt(byte[] cookieBlob, Sha1HashProvider hasher, bool isHashAppended)
{
if (hasher == null)
{
throw new ArgumentNullException("hasher");
}
if (isHashAppended)
{
// need to check the hash signature, and strip it off the end of the byte array.
cookieBlob = hasher.CheckHashAndRemove(cookieBlob);
if (cookieBlob == null)
{
// signature verification failed
throw new Exception();
}
}
// Now decrypt the encrypted cookie data.
using (var aesProvider = Aes.Create())
{
aesProvider.Key = _DecryptionKeyBlob;
aesProvider.BlockSize = 128;
aesProvider.GenerateIV();
aesProvider.IV = new byte[aesProvider.IV.Length];
aesProvider.Mode = CipherMode.CBC;
using (var ms = new MemoryStream())
{
using (var decryptor = aesProvider.CreateDecryptor())
{
using (var cs = new CryptoStream(ms, decryptor, CryptoStreamMode.Write))
{
cs.Write(cookieBlob, 0, cookieBlob.Length);
cs.FlushFinalBlock();
byte[] paddedData = ms.ToArray();
// The data contains some random bytes prepended at the start. Remove them.
int ivLength = RoundupNumBitsToNumBytes(aesProvider.KeySize);
int dataLength = paddedData.Length - ivLength;
if (dataLength < 0)
{
throw new Exception();
}
byte[] decryptedData = new byte[dataLength];
Buffer.BlockCopy(paddedData, ivLength, decryptedData, 0, dataLength);
return(decryptedData);
}
}
}
}
}
private void Initialize(byte[] decryptionKey, byte[] validationKey)
{
_DecryptionKeyBlob = decryptionKey;
_hasher = new Sha1HashProvider(validationKey);
}
