/// <summary>
/// Encode the data. The data is encrypted using the default encryption algorithm (AES-256),
/// then the AES key is encrypted using RSA and the RSA public key is appended.
/// </summary>
/// <param name="value">The data to encode</param>
/// <exception cref="ArgumentNullException">The argument 'value' is null.</exception>
/// <exception cref="ArgumentException">The argument 'value' contains zero bytes.</exception>
/// <exception cref="InvalidOperationException">The EncryptionKey is null.</exception>
/// <returns>Encoded data</returns>
public override byte[] Encode(byte[] value)
{
if (null == value)
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgumentNull("value");
}
if (0 == value.Length)
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgument("value", SR.GetString(SR.ID6044));
}
RSA encryptionKey = EncryptionKey;
if (null == encryptionKey)
{
throw DiagnosticUtility.ThrowHelperInvalidOperation(SR.GetString(SR.ID6043));
}
byte[] rsaHash;
byte[] encryptedKeyAndIV;
byte[] encryptedData;
using (HashAlgorithm hash = CryptoHelper.CreateHashAlgorithm(_hashName))
{
rsaHash = hash.ComputeHash(Encoding.UTF8.GetBytes(encryptionKey.ToXmlString(false)));
}
using (SymmetricAlgorithm encryptionAlgorithm = CryptoHelper.NewDefaultEncryption())
{
encryptionAlgorithm.GenerateIV();
encryptionAlgorithm.GenerateKey();
using (ICryptoTransform encryptor = encryptionAlgorithm.CreateEncryptor())
{
encryptedData = encryptor.TransformFinalBlock(value, 0, value.Length);
}
RSACryptoServiceProvider provider = encryptionKey as RSACryptoServiceProvider;
if (provider == null)
{
throw DiagnosticUtility.ThrowHelperInvalidOperation(SR.GetString(SR.ID6041));
}
//
// Concatenate the Key and IV in an attempt to avoid two minimum block lengths in the cookie
//
byte[] keyAndIV = new byte[encryptionAlgorithm.Key.Length + encryptionAlgorithm.IV.Length];
Array.Copy(encryptionAlgorithm.Key, keyAndIV, encryptionAlgorithm.Key.Length);
Array.Copy(encryptionAlgorithm.IV, 0, keyAndIV, encryptionAlgorithm.Key.Length, encryptionAlgorithm.IV.Length);
encryptedKeyAndIV = CngLightup.OaepSha1Encrypt(encryptionKey, keyAndIV);
}
using (MemoryStream ms = new MemoryStream())
{
using (BinaryWriter bw = new BinaryWriter(ms))
{
bw.Write(rsaHash);
bw.Write(encryptedKeyAndIV.Length);
bw.Write(encryptedKeyAndIV);
bw.Write(encryptedData.Length);
bw.Write(encryptedData);
bw.Flush();
}
return(ms.ToArray());
}
}
/// <summary>
/// Decrypts data using the provided RSA key(s) to decrypt an AES key, which decrypts the cookie.
/// </summary>
/// <param name="encoded">The encoded data</param>
/// <returns>The decoded data</returns>
/// <exception cref="ArgumentNullException">The argument 'encoded' is null.</exception>
/// <exception cref="ArgumentException">The argument 'encoded' contains zero bytes.</exception>
/// <exception cref="NotSupportedException">The platform does not support the requested algorithm.</exception>
/// <exception cref="InvalidOperationException">There are no decryption keys or none of the keys match.</exception>
public override byte[] Decode(byte[] encoded)
{
if (null == encoded)
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgumentNull("encoded");
}
if (0 == encoded.Length)
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperArgument("encoded", SR.GetString(SR.ID6045));
}
ReadOnlyCollection <RSA> decryptionKeys = DecryptionKeys;
if (0 == decryptionKeys.Count)
{
throw DiagnosticUtility.ThrowHelperInvalidOperation(SR.GetString(SR.ID6039));
}
byte[] encryptedKeyAndIV;
byte[] encryptedData;
byte[] rsaHash;
RSA rsaDecryptionKey = null;
using (HashAlgorithm hash = CryptoHelper.CreateHashAlgorithm(_hashName))
{
int hashSizeInBytes = hash.HashSize / 8;
using (BinaryReader br = new BinaryReader(new MemoryStream(encoded)))
{
rsaHash = br.ReadBytes(hashSizeInBytes);
int encryptedKeyAndIVSize = br.ReadInt32();
if (encryptedKeyAndIVSize < 0)
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new FormatException(SR.GetString(SR.ID1006, encryptedKeyAndIVSize)));
}
//
// Enforce upper limit on key size to prevent large buffer allocation in br.ReadBytes()
//
if (encryptedKeyAndIVSize > encoded.Length)
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new FormatException(SR.GetString(SR.ID1007)));
}
encryptedKeyAndIV = br.ReadBytes(encryptedKeyAndIVSize);
int encryptedDataSize = br.ReadInt32();
if (encryptedDataSize < 0)
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new FormatException(SR.GetString(SR.ID1008, encryptedDataSize)));
}
//
// Enforce upper limit on data size to prevent large buffer allocation in br.ReadBytes()
//
if (encryptedDataSize > encoded.Length)
{
throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(new FormatException(SR.GetString(SR.ID1009)));
}
encryptedData = br.ReadBytes(encryptedDataSize);
}
//
// Find the decryption key matching the one in XML
//
foreach (RSA key in decryptionKeys)
{
byte[] hashedKey = hash.ComputeHash(Encoding.UTF8.GetBytes(key.ToXmlString(false)));
if (CryptoHelper.IsEqual(hashedKey, rsaHash))
{
rsaDecryptionKey = key;
break;
}
}
}
if (rsaDecryptionKey == null)
{
throw DiagnosticUtility.ThrowHelperInvalidOperation(SR.GetString(SR.ID6040));
}
byte[] decryptedKeyAndIV = CngLightup.OaepSha1Decrypt(rsaDecryptionKey, encryptedKeyAndIV);
using (SymmetricAlgorithm symmetricAlgorithm = CryptoHelper.NewDefaultEncryption())
{
byte[] decryptionKey = new byte[symmetricAlgorithm.KeySize / 8];
//
// Ensure there is sufficient length in the descrypted key and IV buffer for an IV.
//
if (decryptedKeyAndIV.Length < decryptionKey.Length)
{
throw DiagnosticUtility.ThrowHelperInvalidOperation(SR.GetString(SR.ID6047, decryptedKeyAndIV.Length, decryptionKey.Length));
}
byte[] decryptionIV = new byte[decryptedKeyAndIV.Length - decryptionKey.Length];
//
// Copy key into its own buffer.
// The remaining bytes are the IV copy those into a buffer as well.
//
Array.Copy(decryptedKeyAndIV, decryptionKey, decryptionKey.Length);
Array.Copy(decryptedKeyAndIV, decryptionKey.Length, decryptionIV, 0, decryptionIV.Length);
using (ICryptoTransform decryptor = symmetricAlgorithm.CreateDecryptor(decryptionKey, decryptionIV))
{
return(decryptor.TransformFinalBlock(encryptedData, 0, encryptedData.Length));
}
}
}