GARbro-mirror/ArcFormats/NScripter/EncryptedStream.cs

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//! \file ArcEncrypted.cs
//! \date Mon Aug 31 11:43:25 2015
//! \brief Encrypted NSA archives implementation.
//
// Copyright (C) 2015 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.Linq;
using System.Security.Cryptography;
using GameRes.Utility;
namespace GameRes.Formats.NScripter
{
internal class EncryptedViewStream : Stream
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{
ArcView.Frame m_view;
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byte[] m_key;
long m_max_offset;
long m_position = 0;
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byte[] m_current_block = new byte[BlockLength];
int m_current_block_length = 0;
long m_current_block_position = 0;
static readonly HashAlgorithm MD5 = System.Security.Cryptography.MD5.Create();
static readonly HashAlgorithm SHA1 = System.Security.Cryptography.SHA1.Create();
public const int BlockLength = 1024;
public EncryptedViewStream (ArcView mmap, byte[] key)
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{
m_view = mmap.CreateFrame();
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m_key = key;
m_max_offset = mmap.MaxOffset;
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}
public override int Read (byte[] buf, int index, int count)
{
int total_read = 0;
bool refill_buffer = !(m_position >= m_current_block_position && m_position < m_current_block_position + m_current_block_length);
while (count > 0 && m_position < m_max_offset)
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{
if (refill_buffer)
{
int block_num = (int)(m_position / BlockLength);
m_current_block_position = m_position & ~((long)BlockLength-1);
m_current_block_length = m_view.Read (m_current_block_position, m_current_block, 0, (uint)BlockLength);
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DecryptBlock (block_num);
}
int src_offset = (int)m_position & (BlockLength-1);
int available = Math.Min (count, m_current_block_length - src_offset);
Buffer.BlockCopy (m_current_block, src_offset, buf, index, available);
m_position += available;
total_read += available;
index += available;
count -= available;
refill_buffer = true;
}
return total_read;
}
private void DecryptBlock (int block_num)
{
byte[] bn = new byte[8];
LittleEndian.Pack (block_num, bn, 0);
var md5_hash = MD5.ComputeHash (bn);
var sha1_hash = SHA1.ComputeHash (bn);
var hmac_key = new byte[16];
for (int i = 0; i < 16; i++)
hmac_key[i] = (byte)(md5_hash[i] ^ sha1_hash[i]);
var HMAC = new HMACSHA512 (hmac_key);
var hmac_hash = HMAC.ComputeHash (m_key);
int[] map = Enumerable.Range (0, 256).ToArray();
byte index = 0;
int h = 0;
for (int i = 0; i < 256; i++)
{
if (hmac_hash.Length == h)
h = 0;
int tmp = map[i];
index = (byte)(tmp + hmac_hash[h++] + index);
map[i] = map[index];
map[index] = tmp;
}
int i0 = 0, i1 = 0;
for (int i = 0; i < 300; i++)
{
i0 = (i0 + 1) & 0xFF;
int tmp = map[i0];
i1 = (i1 + tmp) & 0xFF;
map[i0] = map[i1];
map[i1] = tmp;
}
for (int i = 0; i < m_current_block_length; i++)
{
i0 = (i0 + 1) & 0xFF;
int tmp = map[i0];
i1 = (i1 + tmp) & 0xFF;
map[i0] = map[i1];
map[i1] = tmp;
m_current_block[i] ^= (byte)map[(map[i0] + tmp) & 0xFF];
}
}
#region IO.Stream methods
public override bool CanRead { get { return !m_disposed; } }
public override bool CanWrite { get { return false; } }
public override bool CanSeek { get { return !m_disposed; } }
public override long Length { get { return m_max_offset; } }
public override long Position
{
get { return m_position; }
set { m_position = value; }
}
public override long Seek (long pos, SeekOrigin whence)
{
if (SeekOrigin.Current == whence)
m_position += pos;
else if (SeekOrigin.End == whence)
m_position = m_max_offset + pos;
else
m_position = pos;
return m_position;
}
public override void Write (byte[] buf, int index, int count)
{
throw new NotSupportedException();
}
public override void SetLength (long length)
{
throw new NotSupportedException();
}
public override void Flush ()
{
}
#endregion
#region IDisposable methods
bool m_disposed = false;
protected override void Dispose (bool disposing)
{
if (!m_disposed)
{
if (disposing)
m_view.Dispose();
m_disposed = true;
base.Dispose();
}
}
#endregion
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}
}