GARbro-mirror/ArcFormats/Dogenzaka/ImageRSA.cs

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2016-07-06 12:31:30 +08:00
//! \file ImageRSA.cs
//! \date Tue Jul 05 20:38:47 2016
//! \brief RSA-encrypted PNG image.
//
// 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;
using System.ComponentModel.Composition;
using System.IO;
using System.Linq;
using System.Security.Cryptography;
using System.Text;
namespace GameRes.Formats.Dogenzaka
{
internal class Rc4PngMetaData : ImageMetaData
{
public byte[] Key;
}
[Export(typeof(ImageFormat))]
public class Rc4PngFormat : PngFormat
{
public override string Tag { get { return "PNG/RC4"; } }
public override string Description { get { return "RC4 encrypted PNG image"; } }
public override uint Signature { get { return 0xC4F7F61A; } }
public Rc4PngFormat ()
{
Extensions = new string[] { "a" };
}
public static readonly byte[] KnownKey = Encoding.ASCII.GetBytes ("Hlk9D28p");
public override ImageMetaData ReadMetaData (Stream stream)
{
using (var sha = SHA1.Create())
{
var key = sha.ComputeHash (KnownKey).Take (16).ToArray();
using (var proxy = new InputProxyStream (stream, true))
using (var input = new CryptoStream (proxy, new Rc4Transform (key), CryptoStreamMode.Read))
{
var info = base.ReadMetaData (input);
if (null == info)
return null;
return new Rc4PngMetaData
{
Width = info.Width,
Height = info.Height,
OffsetX = info.OffsetX,
OffsetY = info.OffsetY,
BPP = info.BPP,
Key = key,
};
}
}
}
public override ImageData Read (Stream stream, ImageMetaData info)
{
var rc4 = (Rc4PngMetaData)info;
using (var sha = SHA1.Create())
using (var proxy = new InputProxyStream (stream, true))
using (var input = new CryptoStream (proxy, new Rc4Transform (rc4.Key), CryptoStreamMode.Read))
return base.Read (input, info);
}
public override void Write (Stream file, ImageData image)
{
throw new NotImplementedException ("Rc4PngFormat.Write not implemented");
}
}
public sealed class Rc4Transform : ICryptoTransform
{
private const int StateLength = 256;
private const int BlockSize = 256;
private byte[] m_state = new byte[StateLength];
private int x;
private int y;
private byte[] m_key;
public bool CanReuseTransform { get { return false; } }
public bool CanTransformMultipleBlocks { get { return true; } }
public int InputBlockSize { get { return BlockSize; } }
public int OutputBlockSize { get { return BlockSize; } }
public Rc4Transform (byte[] key)
{
m_key = key;
x = 0;
y = 0;
for (int i = 0; i < StateLength; ++i)
{
m_state[i] = (byte)i;
}
int i1 = 0;
int i2 = 0;
for (int i = 0; i < StateLength; ++i)
{
i2 = ((m_key[i1] & 0xFF) + m_state[i] + i2) & 0xFF;
byte t = m_state[i];
m_state[i] = m_state[i2];
m_state[i2] = t;
i1 = (i1+1) % m_key.Length;
}
}
public int TransformBlock (byte[] inBuf, int inOffset, int inCount,
byte[] outBuf, int outOffset)
{
for (int i = 0; i < inCount; i++)
{
x = (x + 1) & 0xFF;
y = (m_state[x] + y) & 0xFF;
byte t = m_state[x];
m_state[x] = m_state[y];
m_state[y] = t;
outBuf[i+outOffset] = (byte)(inBuf[i + inOffset] ^ m_state[(m_state[x] + m_state[y]) & 0xFF]);
}
return inCount;
}
public byte[] TransformFinalBlock (byte[] inBuf, int inOffset, int inCount)
{
byte[] output = new byte[inCount];
TransformBlock (inBuf, inOffset, inCount, output, 0);
return output;
}
public void Dispose ()
{
GC.SuppressFinalize (this);
}
}
}