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/*
KeePass Password Safe - The Open-Source Password Manager
Copyright (C) 2003-2019 Dominik Reichl <dominik.reichl@t-online.de>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Text;
using KeePassLib.Utility;
namespace KeePassLib.Cryptography.Cipher
{
public abstract class CtrBlockCipher : IDisposable
{
private bool m_bDisposed = false;
private byte[] m_pBlock;
private int m_iBlockPos;
public abstract int BlockSize
{
get;
}
public CtrBlockCipher()
{
int cb = this.BlockSize;
if(cb <= 0) throw new InvalidOperationException("this.BlockSize");
m_pBlock = new byte[cb];
m_iBlockPos = cb;
}
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
protected virtual void Dispose(bool bDisposing)
{
if(bDisposing)
{
MemUtil.ZeroByteArray(m_pBlock);
m_iBlockPos = m_pBlock.Length;
m_bDisposed = true;
}
}
protected void InvalidateBlock()
{
m_iBlockPos = m_pBlock.Length;
}
protected abstract void NextBlock(byte[] pBlock);
public void Encrypt(byte[] m, int iOffset, int cb)
{
if(m_bDisposed) throw new ObjectDisposedException(null);
if(m == null) throw new ArgumentNullException("m");
if(iOffset < 0) throw new ArgumentOutOfRangeException("iOffset");
if(cb < 0) throw new ArgumentOutOfRangeException("cb");
if(iOffset > (m.Length - cb)) throw new ArgumentOutOfRangeException("cb");
int cbBlock = m_pBlock.Length;
while(cb > 0)
{
Debug.Assert(m_iBlockPos <= cbBlock);
if(m_iBlockPos == cbBlock)
{
NextBlock(m_pBlock);
m_iBlockPos = 0;
}
int cbCopy = Math.Min(cbBlock - m_iBlockPos, cb);
Debug.Assert(cbCopy > 0);
MemUtil.XorArray(m_pBlock, m_iBlockPos, m, iOffset, cbCopy);
m_iBlockPos += cbCopy;
iOffset += cbCopy;
cb -= cbCopy;
}
}
public void Decrypt(byte[] m, int iOffset, int cb)
{
Encrypt(m, iOffset, cb);
}
}
}
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