GARbro-mirror/ArcFormats/KiriKiri/CzCrypt.cs

134 lines
5.0 KiB
C#
Raw Normal View History

//! \file CzCrypt.cs
//! \date 2017 Sep 27
//! \brief implementation of cZLIB extraction filter for KiriKiri engine.
//
// Copyright (C) 2017 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.IO;
using System.Security.Cryptography;
using GameRes.Compression;
namespace GameRes.Formats.KiriKiri
{
/// <summary>
/// cZLIB entry filter.
/// </summary>
[Serializable]
public abstract class CzCrypt : ICrypt
{
const uint CzMagic = 0xA590D7FDu;
const uint CzIvSeed = 0xBFBFBFBFu;
static readonly byte[] CzHeaderKey = { 0x9D, 0x1D, 0x9A, 0xF2 };
static readonly byte[] CzDefaultKey = {
0x91, 0x10, 0xFC, 0x75, 0x45, 0x8F, 0xB5, 0xE6, 0xFE, 0xAC, 0xBA, 0x44, 0x76, 0x58, 0xC2, 0x1A
};
public override Stream EntryReadFilter (Xp3Entry entry, Stream input)
{
if (entry.UnpackedSize <= 15 || "audio" == entry.Type)
return input;
var header = new byte[15];
input.Read (header, 0, 15);
if (CzMagic == header.ToUInt32 (0))
{
var type = new char[3] {
(char)(header[4] ^ 0x11),
(char)(header[5] ^ 0x7F),
(char)(header[6] ^ 0x9A)
};
byte key = (byte)type[0];
int unpacked_size = CzDecryptInt (header, 7, key);
int packed_size = CzDecryptInt (header, 11, key);
if (packed_size < entry.UnpackedSize && 0 == ((packed_size-5) & 0xF))
{
var data = new byte[packed_size];
input.Read (data, 0, packed_size);
input.Dispose();
data = CzDecryptData (data);
input = new BinMemoryStream (data);
if ('C' == type[0])
input = new ZLibStream (input, CompressionMode.Decompress);
return input;
}
}
if (!input.CanSeek)
return new PrefixStream (header, input);
input.Position = 0;
return input;
}
static int CzDecryptInt (byte[] data, int offset, byte key)
{
for (int i = 0; i < 4; ++i)
{
data[offset+i] ^= (byte)(key ^ CzHeaderKey[i]);
}
return data.ToInt32 (offset);
}
static byte[] CzDecryptData (byte[] data)
{
int padded_size = data.Length - 5;
int original_size = padded_size - (data[padded_size+1] ^ data[padded_size]);
uint iv_seed = data.ToUInt32 (padded_size+1) ^ CzIvSeed;
using (var aes = Aes.Create())
{
aes.Mode = CipherMode.CBC;
aes.Padding = PaddingMode.Zeros;
aes.Key = CzDefaultKey;
aes.IV = CzCreateIV (iv_seed);
using (var enc = new MemoryStream (data, 0, padded_size))
using (var dec = new InputCryptoStream (enc, aes.CreateDecryptor()))
{
var original = new byte[original_size];
dec.Read (original, 0, original_size);
return original;
}
}
}
static byte[] CzCreateIV (uint seed)
{
var state = new uint[4];
state[0] = 123456789; // field_0
state[1] = 972436830; // field_4
state[2] = 524018621; // field_8
state[3] = seed; // field_C
var iv = new byte[16];
for (int i = 0; i < 16; ++i)
{
uint a = state[3];
uint b = state[0] ^ (state[0] << 11);
state[0] = state[1];
state[1] = state[2];
state[2] = a;
state[3] = b ^ a ^ ((b ^ (a >> 11)) >> 8);
iv[i] = (byte)state[3];
}
return iv;
}
}
}