OpenSslCryptoTransform.cs

//
// Author: 
//	Bassam Tabbara  <bassam@symform.com>
// 
// Copyright 2013 Symform Inc.
// 
// 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.
//
namespace Crimson.OpenSsl
{
	using System;
	using System.Security.Cryptography;
	using Crimson.Common;

	internal unsafe class OpenSslCryptoTransform : CryptoTransformBase
	{
		private readonly Native.SafeCipherContextHandle context;

		public OpenSslCryptoTransform (SymmetricAlgorithm algo, bool encrypt, byte[] rgbKey, byte[] rgbIV)
            : base (algo, encrypt, rgbKey, rgbIV)
		{
			OpenSslUtil.EnsureAvailability ();

			this.context = Native.EVP_CIPHER_CTX_new ();

			var cptr = this.GetCipher (algo.Mode, rgbKey.Length);
			var op = encrypt ? Native.CipherOperation.Encrypt : Native.CipherOperation.Decrypt;

			fixed (byte* pkey = &rgbKey[0])
				fixed (byte* piv = &iv[0]) {
					Native.ExpectSuccess (Native.EVP_CipherInit_ex (this.context, cptr, IntPtr.Zero, (IntPtr)pkey, (IntPtr)piv, op));
				}

			Native.ExpectSuccess (Native.EVP_CIPHER_CTX_set_key_length (this.context, rgbKey.Length));
			Native.ExpectSuccess (Native.EVP_CIPHER_CTX_set_padding (this.context, 0));
		}

		protected override void Dispose (bool disposing)
		{
			if (disposing) {
				this.context.Dispose ();
			}

			base.Dispose (disposing);
		}

		protected override void Transform (byte[] inputBuffer, int inputOffset, byte[] outputBuffer, int outputOffset, int inputCount)
		{
			fixed (byte* input = &inputBuffer[inputOffset])
				fixed (byte* output = &outputBuffer[outputOffset]) {
					int outputCount;
					Native.ExpectSuccess (Native.EVP_CipherUpdate (this.context, (IntPtr)output, out outputCount, (IntPtr)input, inputCount));
				}
		}

		private Native.SafeCipherHandle GetCipher (CipherMode mode, int keyLength)
		{
			if (mode == CipherMode.CBC) {
				switch (keyLength) {
				case 16:
					return Native.EVP_aes_128_cbc ();

				case 24:
					return Native.EVP_aes_192_cbc ();

				case 32:
					return Native.EVP_aes_256_cbc ();
				}
			} else if (mode == CipherMode.ECB) {
				switch (keyLength) {
				case 16:
					return Native.EVP_aes_128_ecb ();

				case 24:
					return Native.EVP_aes_192_ecb ();

				case 32:
					return Native.EVP_aes_256_ecb ();
				}
			}

			throw new CryptographicException (string.Format ("{0} not supported", mode));
		}
	}
}