//
// ProtectedData.cs: Protect (encrypt) data without (user involved) key management
//
// Author:
//	Sebastien Pouliot  <sebastien@ximian.com>
//
// (C) 2003 Motus Technologies Inc. (http://www.motus.com)
// Copyright (C) 2004-2005 Novell, Inc (http://www.novell.com)
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
// 
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//


using System.Runtime.InteropServices;
using System.Security.Permissions;

using Mono.Security.Cryptography;

namespace System.Security.Cryptography {

	// References:
	// a.	Windows Data Protection
	//	http://msdn.microsoft.com/library/en-us/dnsecure/html/windataprotection-dpapi.asp?frame=true

	public sealed class ProtectedData {

		private ProtectedData ()
		{
		}

// FIXME	[DataProtectionPermission (SecurityAction.Demand, ProtectData = true)]
		public static byte[] Protect (byte[] userData, byte[] optionalEntropy, DataProtectionScope scope) 
		{
			if (userData == null)
				throw new ArgumentNullException ("userData");

			// on Windows this is supported only under 2000 and later OS
			Check (scope);

			switch (impl) {
			case DataProtectionImplementation.ManagedProtection:
				try {
					return ManagedProtection.Protect (userData, optionalEntropy, scope);
				}
				catch (Exception e) {
					string msg = Locale.GetText ("Data protection failed.");
					throw new CryptographicException (msg, e);
				}
			case DataProtectionImplementation.Win32CryptoProtect:
				try {
					return NativeDapiProtection.Protect (userData, optionalEntropy, scope);
				}
				catch (Exception e) {
					string msg = Locale.GetText ("Data protection failed.");
					throw new CryptographicException (msg, e);
				}
			default:
				throw new PlatformNotSupportedException ();
			}
		}

// FIXME	[DataProtectionPermission (SecurityAction.Demand, UnprotectData = true)]
		public static byte[] Unprotect (byte[] encryptedData, byte[] optionalEntropy, DataProtectionScope scope) 
		{
			if (encryptedData == null)
				throw new ArgumentNullException ("encryptedData");

			// on Windows this is supported only under 2000 and later OS
			Check (scope);

			switch (impl) {
			case DataProtectionImplementation.ManagedProtection:
				try {
					return ManagedProtection.Unprotect (encryptedData, optionalEntropy, scope);
				}
				catch (Exception e) {
					string msg = Locale.GetText ("Data unprotection failed.");
					throw new CryptographicException (msg, e);
				}
			case DataProtectionImplementation.Win32CryptoProtect:
				try {
					return NativeDapiProtection.Unprotect (encryptedData, optionalEntropy, scope);
				}
				catch (Exception e) {
					string msg = Locale.GetText ("Data unprotection failed.");
					throw new CryptographicException (msg, e);
				}
			default:
				throw new PlatformNotSupportedException ();
			}
		}

		// private stuff

		enum DataProtectionImplementation {
			Unknown,
			Win32CryptoProtect,
			ManagedProtection,
			Unsupported = Int32.MinValue
		}

		private static DataProtectionImplementation impl;

		private static void Detect ()
		{
			OperatingSystem os = Environment.OSVersion;
			switch (os.Platform) {
			case PlatformID.Win32NT:
				Version v = os.Version;
				if (v.Major < 5) {
					impl = DataProtectionImplementation.Unsupported;
				} else {
					// Windows 2000 (5.0) and later
					impl = DataProtectionImplementation.Win32CryptoProtect;
				}
				break;
			case PlatformID.Unix:
				impl = DataProtectionImplementation.ManagedProtection;
				break;
			default:
				impl = DataProtectionImplementation.Unsupported;
				break;
			}
		}

		private static void Check (DataProtectionScope scope)
		{
			if ((scope < DataProtectionScope.CurrentUser) || (scope > DataProtectionScope.LocalMachine)) {
				string msg = Locale.GetText ("Invalid enum value '{0}' for '{1}'.", 
					scope, "DataProtectionScope");
				throw new ArgumentException (msg, "scope");
			}

			switch (impl) {
			case DataProtectionImplementation.Unknown:
				Detect ();
				break;
			case DataProtectionImplementation.Unsupported:
				throw new PlatformNotSupportedException ();
			}
		}
	}
}