Setup solution

ModernKeePassLib/Security/XorredBuffer.cs

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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.Diagnostics;
+
+using ModernKeePassLib.Utility;
+
+namespace ModernKeePassLib.Security
+{
+	/// <summary>
+	/// A <c>XorredBuffer</c> object stores data that is encrypted
+	/// using a XOR pad.
+	/// </summary>
+	public sealed class XorredBuffer : IDisposable
+	{
+		private byte[] m_pbCT;
+		private byte[] m_pbXorPad;
+
+		public uint Length
+		{
+			get
+			{
+				if(m_pbCT == null) { Debug.Assert(false); throw new ObjectDisposedException(null); }
+				return (uint)m_pbCT.Length;
+			}
+		}
+
+		/// <summary>
+		/// Construct a new <c>XorredBuffer</c> object.
+		/// The <paramref name="pbCT" /> byte array must have the same
+		/// length as the <paramref name="pbXorPad" /> byte array.
+		/// The <c>XorredBuffer</c> object takes ownership of the two byte
+		/// arrays, i.e. the caller must not use them afterwards.
+		/// </summary>
+		/// <param name="pbCT">Data with XOR pad applied.</param>
+		/// <param name="pbXorPad">XOR pad that can be used to decrypt the
+		/// <paramref name="pbCT" /> byte array.</param>
+		public XorredBuffer(byte[] pbCT, byte[] pbXorPad)
+		{
+			if(pbCT == null) { Debug.Assert(false); throw new ArgumentNullException("pbCT"); }
+			if(pbXorPad == null) { Debug.Assert(false); throw new ArgumentNullException("pbXorPad"); }
+			if(pbCT.Length != pbXorPad.Length)
+			{
+				Debug.Assert(false);
+				throw new ArgumentOutOfRangeException("pbXorPad");
+			}
+
+			m_pbCT = pbCT;
+			m_pbXorPad = pbXorPad;
+		}
+
+#if DEBUG
+		~XorredBuffer()
+		{
+			Debug.Assert((m_pbCT == null) && (m_pbXorPad == null));
+		}
+#endif
+
+		public void Dispose()
+		{
+			if(m_pbCT == null) return;
+
+			MemUtil.ZeroByteArray(m_pbCT);
+			m_pbCT = null;
+
+			MemUtil.ZeroByteArray(m_pbXorPad);
+			m_pbXorPad = null;
+		}
+
+		/// <summary>
+		/// Get a copy of the plain-text. The caller is responsible
+		/// for clearing the byte array safely after using it.
+		/// </summary>
+		/// <returns>Plain-text byte array.</returns>
+		public byte[] ReadPlainText()
+		{
+			byte[] pbCT = m_pbCT, pbX = m_pbXorPad;
+			if((pbCT == null) || (pbX == null) || (pbCT.Length != pbX.Length))
+			{
+				Debug.Assert(false);
+				throw new ObjectDisposedException(null);
+			}
+
+			byte[] pbPT = new byte[pbCT.Length];
+
+			for(int i = 0; i < pbPT.Length; ++i)
+				pbPT[i] = (byte)(pbCT[i] ^ pbX[i]);
+
+			return pbPT;
+		}
+	}
+}