source: trunk/eraser6/Eraser.DefaultPlugins/FileSystems/Ntfs.cs @ 1859

/* 
 * $Id$
 * Copyright 2008-2010 The Eraser Project
 * Original Author: Joel Low <lowjoel@users.sourceforge.net>
 * Modified By:
 * 
 * This file is part of Eraser.
 * 
 * Eraser 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 3 of the License, or (at your option) any later
 * version.
 * 
 * Eraser 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.
 * 
 * A copy of the GNU General Public License can be found at
 * <http://www.gnu.org/licenses/>.
 */

using System;
using System.Collections.Generic;
using System.Text;
using System.Runtime.InteropServices;

using System.IO;
using Eraser.Manager;
using Eraser.Util;

namespace Eraser.DefaultPlugins
{
    /// <summary>
    /// Provides functions to handle erasures specific to NTFS volumes.
    /// </summary>
    [Guid("34399F62-0AD4-411c-8C71-5E1E6213545C")]
    public class NtfsFileSystem : WindowsFileSystem
    {
        public override Guid Guid
        {
            get { return GetType().GUID; }
        }

        public override string Name
        {
            get { return "NTFS"; }
        }

        public override void EraseOldFileSystemResidentFiles(VolumeInfo volume,
            DirectoryInfo tempDirectory, ErasureMethod method,
            FileSystemEntriesEraseProgress callback)
        {
            try
            {
                //Squeeze one-byte files until the volume or the MFT is full.
                long oldMFTSize = NtfsApi.GetMftValidSize(volume);

                for ( ; ; )
                {
                    //Open this stream
                    using (FileStream strm = new FileStream(
                        GenerateRandomFileName(tempDirectory, 18), FileMode.CreateNew,
                        FileAccess.Write, FileShare.None, 8, FileOptions.WriteThrough))
                    {
                        long streamSize = 0;
                        try
                        {
                            while (true)
                            {
                                //Stretch the file size to use up some of the resident space.
                                strm.SetLength(++streamSize);

                                //Then run the erase task
                                method.Erase(strm, long.MaxValue,
                                    ManagerLibrary.Instance.PrngRegistrar[ManagerLibrary.Settings.ActivePrng],
                                    null);

                                //Call the callback function if one is provided. We'll provide a dummy
                                //value since we really have no idea how much of the MFT we can clean.
                                if (callback != null)
                                    callback(0, 1);
                            }
                        }
                        catch (IOException)
                        {
                            if (streamSize == 1)
                                return;
                        }
                    }

                    //We can stop when the MFT has grown.
                    if (NtfsApi.GetMftValidSize(volume) > oldMFTSize)
                        break;
                }
            }
            catch (IOException)
            {
                //OK, enough squeezing: there isn't enough space to even create a new MFT record.
            }
        }

        public override void EraseDirectoryStructures(VolumeInfo info,
            FileSystemEntriesEraseProgress callback)
        {
            //Create a directory to hold all the temporary files
            DirectoryInfo tempDir = new DirectoryInfo(FileSystem.GenerateRandomFileName(
                new DirectoryInfo(info.MountPoints[0]), 32));
            tempDir.Create();

            try
            {
                //Get the size of the MFT
                long mftSize = NtfsApi.GetMftValidSize(info);
                long mftRecordSegmentSize = NtfsApi.GetMftRecordSegmentSize(info);
                int pollingInterval = (int)Math.Min(Math.Max(1, mftSize / info.ClusterSize / 20), 128);
                int totalFiles = (int)Math.Max(1L, mftSize / mftRecordSegmentSize);
                int filesCreated = 0;

                while (true)
                {
                    ++filesCreated;
                    using (FileStream strm = new FileStream(FileSystem.GenerateRandomFileName(
                        tempDir, 220), FileMode.CreateNew, FileAccess.Write))
                    {
                    }

                    if (filesCreated % pollingInterval == 0)
                    {
                        //Call back to our progress function: this is the first half of the
                        //procedure so divide the effective progress by 2.
                        if (callback != null)
                        {
                            int halfFilesCreated = filesCreated / 2;
                            callback(halfFilesCreated, Math.Max(halfFilesCreated, totalFiles));
                        }

                        //Check if the MFT has grown.
                        if (mftSize < NtfsApi.GetMftValidSize(info))
                            break;
                    }
                }
            }
            catch (IOException)
            {
            }
            finally
            {
                //Clear up all the temporary files
                FileInfo[] files = tempDir.GetFiles("*", SearchOption.AllDirectories);
                for (int i = 0; i < files.Length; ++i)
                {
                    if (callback != null && i % 50 == 0)
                        callback(files.Length + i, files.Length * 2);
                    DeleteFile(files[i]);
                }

                DeleteFolder(tempDir);
            }
        }

        public override void EraseFileSystemObject(StreamInfo info, ErasureMethod method,
            ErasureMethodProgressFunction callback)
        {
            //Check if the file fits in one cluster - if it does it may be MFT resident
            //TODO: any more deterministic way of finding out?
            VolumeInfo volume = VolumeInfo.FromMountPoint(info.DirectoryName);
            if (info.Length < NtfsApi.GetMftRecordSegmentSize(volume))
            {
                //Yes it does, erase exactly to the file length
                using (FileStream strm = info.Open(FileMode.Open, FileAccess.Write,
                    FileShare.None))
                {
                    method.Erase(strm, long.MaxValue,
                        ManagerLibrary.Instance.PrngRegistrar[ManagerLibrary.Settings.ActivePrng],
                        null);
                }
            }

            //Create the file stream, and call the erasure method to write to
            //the stream.
            long fileArea = GetFileArea(info.FullName);

            //If the stream is empty, there's nothing to overwrite. Continue
            //to the next entry
            if (fileArea == 0)
                return;

            using (FileStream strm = info.Open(FileMode.Open, FileAccess.Write,
                FileShare.None, FileOptions.WriteThrough))
            {
                //Set the end of the stream after the wrap-round the cluster size
                strm.SetLength(fileArea);

                //Then erase the file.
                method.Erase(strm, long.MaxValue,
                    ManagerLibrary.Instance.PrngRegistrar[ManagerLibrary.Settings.ActivePrng],
                    callback
                );

                //Set the length of the file to 0.
                strm.Seek(0, SeekOrigin.Begin);
                strm.SetLength(0);
            }
        }

        protected override DateTime MinTimestamp
        {
            get
            {
                return new DateTime(1601, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc);
            }
        }
    }
}