/// <summary>
/// See <see cref="ProtectedData"/>.
/// </summary>
/// <param name="encryptedData">Data to unprotect.</param>
/// <param name="optionalEntropy">Additional material to be added to the symmetric key used for encryption.</param>
/// <param name="scope">See <see cref="DataProtectionScope"/>.</param>
/// <returns>Plain text data.</returns>
/// <exception cref="ArgumentNullException">The specified parameter is a null reference (Nothing in Visual Basic).</exception>
/// <exception cref="CryptographicException">Exception when executing unmanaged code.</exception>
/// <permission cref="CryptographicPermission">Demand for decryption permission.</permission>
public static byte[] Unprotect(byte[] encryptedData, byte[] optionalEntropy, DataProtectionScope scope)
{
// Verify input
if (encryptedData == null || encryptedData.Length == 0)
{
throw new ArgumentNullException("encryptedData");
}
if (!IsValidScope(scope))
{
throw new ArgumentException(Resource.ResourceManager[Resource.MessageKey.InvalidDataProtectionScope]);
}
// Demand Permission
new CryptographicPermission(CryptographicPermissionFlags.Decrypt).Demand();
// Assert UnamanagedCode (replaced by the SuppressUnmanagedCodeSecurity attribute of the Win32Native class
// Initialize vars.
// Check to see if the entropy is null
if (optionalEntropy == null)
{
// Allocate something
optionalEntropy = new byte[0];
}
Win32Native.CRYPTOAPI_BLOB plainTextBlob = new Win32Native.CRYPTOAPI_BLOB();
GCHandle encryptedDataHandle = GCHandle.Alloc(encryptedData, GCHandleType.Pinned);
GCHandle entropyHandle = GCHandle.Alloc(optionalEntropy, GCHandleType.Pinned);
try
{
Win32Native.CRYPTPROTECT_PROMPTSTRUCT prompt = new Win32Native.CRYPTPROTECT_PROMPTSTRUCT(0);
Win32Native.CRYPTOAPI_BLOB encryptedDataBlob = new Win32Native.CRYPTOAPI_BLOB();
encryptedDataBlob.cbData = (uint)encryptedData.Length;
encryptedDataBlob.pbData = encryptedDataHandle.AddrOfPinnedObject();
Win32Native.CRYPTOAPI_BLOB entropyBlob = new Win32Native.CRYPTOAPI_BLOB();
entropyBlob.cbData = (uint)optionalEntropy.Length;
entropyBlob.pbData = entropyHandle.AddrOfPinnedObject();
if (!Win32Native.CryptUnprotectData(ref encryptedDataBlob,
null,
ref entropyBlob,
IntPtr.Zero,
ref prompt,
(uint)scope,
ref plainTextBlob))
{
throw new CryptographicException(Resource.ResourceManager[Resource.MessageKey.UnprotectDataException], new Win32Exception(Marshal.GetLastWin32Error()));
}
if (plainTextBlob.pbData == IntPtr.Zero)
{
throw new OutOfMemoryException(Resource.ResourceManager[Resource.MessageKey.OutOfMemoryException, "plainTextBlob"]);
}
byte[] plainText = new byte[plainTextBlob.cbData];
Marshal.Copy(plainTextBlob.pbData, plainText, 0, plainText.Length);
return(plainText);
}
finally
{
// Free handles
if (encryptedDataHandle.IsAllocated)
{
encryptedDataHandle.Free();
}
if (entropyHandle.IsAllocated)
{
entropyHandle.Free();
}
//Free the unmanaged resource ...
// Free and erase the plainTextBlob
if (plainTextBlob.pbData != IntPtr.Zero)
{
Win32Native.ZeroMemory(plainTextBlob.pbData, plainTextBlob.cbData);
Win32Native.LocalFree(plainTextBlob.pbData);
}
}
}
/// <summary>
/// This function performs encryption on the data in a byte array input data.
/// If <see cref="DataProtectionScope.CurrentUser"/> is specified, only a user
/// with the same logon credentials as the encrypter can decrypt the data.
/// <b>Warning</b>If the logon credentials are lost or forgotten, the data is usually unrecoverable.
/// If the <see cref="DataProtectionScope.LocalMachine"/> is used, the encryption and decryption must be done on the same computer
/// therefore any user on the same computer where the data was encrypted can recover the data.
/// </summary>
/// <remarks>
/// The function creates a session key to perform the encryption.
/// The session key is rederived when the data is to be decrypted.
/// The function also adds a message authentication code (MAC), which is a keyed integrity check, to the encrypted data to guard against data tampering.
/// </remarks>
/// <param name="userData">Data to be protected. This array should be erased after use with <see cref="Array.Clear"/>.</param>
/// <param name="optionalEntropy">Additional material to be added to the symmetric key used for encryption.</param>
/// <param name="scope">See <see cref="DataProtectionScope"/>.</param>
/// <returns>Protected data.</returns>
/// <exception cref="ArgumentNullException">The specified parameter is a null reference (Nothing in Visual Basic).</exception>
/// <exception cref="CryptographicException">Exception when executing unmanaged code.</exception>
/// <permission cref="CryptographicPermission">Demand for encryption permission.</permission>
public static byte[] Protect(byte[] userData, byte[] optionalEntropy, DataProtectionScope scope)
{
// Verify input
if (userData == null)
{
throw new ArgumentNullException("userData");
}
if (!IsValidScope(scope))
{
throw new ArgumentException(Resource.ResourceManager[Resource.MessageKey.InvalidDataProtectionScope]);
}
// Demand Permission
new CryptographicPermission(CryptographicPermissionFlags.Encrypt).Demand();
// Assert UnamanagedCode (replaced by the SuppressUnmanagedCodeSecurity attribute of the Win32Native class
// Check to see if the entropy is null
if (optionalEntropy == null)
{
// Allocate something
optionalEntropy = new byte[0];
}
Win32Native.CRYPTOAPI_BLOB cipherTextBlob = new Win32Native.CRYPTOAPI_BLOB();
// This prevents the garbage collector from moving the object and hence
// undermines the efficiency of the garbage collector. We 'll release
// the reference on the finally block.
GCHandle userDataHandle = GCHandle.Alloc(userData, GCHandleType.Pinned);
GCHandle entropyHandle = GCHandle.Alloc(optionalEntropy, GCHandleType.Pinned);
try
{
Win32Native.CRYPTPROTECT_PROMPTSTRUCT prompt = new Win32Native.CRYPTPROTECT_PROMPTSTRUCT(0);
Win32Native.CRYPTOAPI_BLOB plainTextBlob = new Win32Native.CRYPTOAPI_BLOB();
plainTextBlob.cbData = (uint)userData.Length;
plainTextBlob.pbData = userDataHandle.AddrOfPinnedObject();
Win32Native.CRYPTOAPI_BLOB entropyBlob = new Win32Native.CRYPTOAPI_BLOB();
entropyBlob.cbData = (uint)optionalEntropy.Length;
entropyBlob.pbData = entropyHandle.AddrOfPinnedObject();
if (!Win32Native.CryptProtectData(ref plainTextBlob,
null,
ref entropyBlob,
IntPtr.Zero,
ref prompt,
(uint)scope,
ref cipherTextBlob))
{
throw new CryptographicException(Resource.ResourceManager[Resource.MessageKey.ProtectDataException], new Win32Exception(Marshal.GetLastWin32Error()));
}
//Check returned data
if (cipherTextBlob.pbData == IntPtr.Zero)
{
throw new OutOfMemoryException(Resource.ResourceManager[Resource.MessageKey.OutOfMemoryException, "cipherTextBlob"]);
}
// Move encrypted data to the returned array
byte[] cipherText = new byte[cipherTextBlob.cbData];
Marshal.Copy(cipherTextBlob.pbData, cipherText, 0, cipherText.Length);
return(cipherText);
}
finally
{
// Free the allocated handles
if (userDataHandle.IsAllocated)
{
userDataHandle.Free();
}
if (entropyHandle.IsAllocated)
{
entropyHandle.Free();
}
//Free the unmanaged resource ...
// Free and erase the cipherTextBlob
if (cipherTextBlob.pbData != IntPtr.Zero)
{
Win32Native.ZeroMemory(cipherTextBlob.pbData, cipherTextBlob.cbData);
Win32Native.LocalFree(cipherTextBlob.pbData);
}
}
}
