GARbro-mirror/ArcFormats/SimpleEncryption.cs
morkt b6f472ab25 (InputCryptoStream): new class derived from CryptoStream.
properly dispose transformations used by CryptoStream.
2016-12-25 06:51:33 +04:00

165 lines
5.6 KiB
C#

//! \file SimpleEncryption.cs
//! \date Mon Feb 29 08:19:07 2016
//! \brief Primitive encryption methods implementations.
//
// Copyright (C) 2016 by morkt
//
// 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.IO;
using System.Security.Cryptography;
namespace GameRes.Formats
{
public sealed class NotTransform : ICryptoTransform
{
private const int BlockSize = 1;
public bool CanReuseTransform { get { return true; } }
public bool CanTransformMultipleBlocks { get { return true; } }
public int InputBlockSize { get { return BlockSize; } }
public int OutputBlockSize { get { return BlockSize; } }
public int TransformBlock (byte[] inputBuffer, int inputOffset, int inputCount,
byte[] outputBuffer, int outputOffset)
{
for (int i = 0; i < inputCount; ++i)
{
outputBuffer[outputOffset++] = (byte)~inputBuffer[inputOffset+i];
}
return inputCount;
}
public byte[] TransformFinalBlock (byte[] inputBuffer, int inputOffset, int inputCount)
{
byte[] outputBuffer = new byte[inputCount];
TransformBlock (inputBuffer, inputOffset, inputCount, outputBuffer, 0);
return outputBuffer;
}
public void Dispose ()
{
System.GC.SuppressFinalize (this);
}
}
public sealed class XorTransform : ICryptoTransform
{
private const int BlockSize = 1;
private byte m_key;
public bool CanReuseTransform { get { return true; } }
public bool CanTransformMultipleBlocks { get { return true; } }
public int InputBlockSize { get { return BlockSize; } }
public int OutputBlockSize { get { return BlockSize; } }
public XorTransform (byte key)
{
m_key = key;
}
public int TransformBlock (byte[] inputBuffer, int inputOffset, int inputCount,
byte[] outputBuffer, int outputOffset)
{
for (int i = 0; i < inputCount; ++i)
{
outputBuffer[outputOffset++] = (byte)(m_key ^ inputBuffer[inputOffset+i]);
}
return inputCount;
}
public byte[] TransformFinalBlock (byte[] inputBuffer, int inputOffset, int inputCount)
{
byte[] outputBuffer = new byte[inputCount];
TransformBlock (inputBuffer, inputOffset, inputCount, outputBuffer, 0);
return outputBuffer;
}
public void Dispose ()
{
System.GC.SuppressFinalize (this);
}
}
public class ByteStringEncryptedStream : InputProxyStream
{
byte[] m_key;
int m_base_pos;
public ByteStringEncryptedStream (Stream main, byte[] key, bool leave_open = false)
: this (main, 0, key, leave_open)
{
}
public ByteStringEncryptedStream (Stream main, long start_pos, byte[] key, bool leave_open = false)
: base (main, leave_open)
{
m_key = key;
m_base_pos = (int)(start_pos % m_key.Length);
}
public override int Read (byte[] buffer, int offset, int count)
{
int start_pos = (int)((m_base_pos + BaseStream.Position) % m_key.Length);
int read = BaseStream.Read (buffer, offset, count);
for (int i = 0; i < read; ++i)
{
buffer[offset+i] ^= m_key[(start_pos + i) % m_key.Length];
}
return read;
}
public override int ReadByte ()
{
long pos = BaseStream.Position;
int b = BaseStream.ReadByte();
if (-1 != b)
{
b ^= m_key[(m_base_pos + pos) % m_key.Length];
}
return b;
}
}
/// <summary>
/// CryptoStream that disposes transformation object upon close.
/// </summary>
public class InputCryptoStream : CryptoStream
{
ICryptoTransform m_transform;
public InputCryptoStream (Stream input, ICryptoTransform transform)
: base (input, transform, CryptoStreamMode.Read)
{
m_transform = transform;
}
protected override void Dispose (bool disposing)
{
base.Dispose (disposing);
if (disposing && m_transform != null)
{
m_transform.Dispose();
m_transform = null;
}
}
}
}