source: branches/eraser6/CodeReview/Eraser.DefaultPlugins/FileSystems/Windows.cs @ 1793

/* 
 * $Id$
 * 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.IO;
using System.Threading;
using Eraser.Manager;
using Eraser.Util;
using Eraser.Util.ExtensionMethods;

namespace Eraser.DefaultPlugins
{
    /// <summary>
    /// Base class for all Windows filesystems.
    /// </summary>
    public abstract class WindowsFileSystem : FileSystem
    {
        public override void DeleteFile(FileInfo info)
        {
            //If the user wants plausible deniability, find a random file from the
            //list of decoys and write it over.
            if (Manager.ManagerLibrary.Settings.PlausibleDeniability)
            {
                using (FileStream fileStream = info.OpenWrite())
                    CopyPlausibleDeniabilityFile(fileStream);
            }

            DeleteFileSystemInfo(info);
        }

        public override void DeleteFolder(DirectoryInfo info, bool recursive)
        {
            if (!recursive && info.GetFileSystemInfos().Length != 0)
                throw new InvalidOperationException(S._("The folder {0} cannot be deleted as it is " +
                    "not empty."));

            //TODO: check for reparse points
            foreach (DirectoryInfo dir in info.GetDirectories())
                DeleteFolder(dir);
            foreach (FileInfo file in info.GetFiles())
                DeleteFile(file);

            DeleteFileSystemInfo(info);
        }

        /// <summary>
        /// Deletes a directory or file from disk. This assumes that directories already
        /// have been deleted.
        /// </summary>
        /// <param name="info">The file or directory to delete.</param>
        private void DeleteFileSystemInfo(FileSystemInfo info)
        {
            //If the file/directory doesn't exist, pass.
            if (!info.Exists)
                return;

            //Set the date of the file to be invalid to prevent forensic
            //detection
            info.Attributes = FileAttributes.NotContentIndexed;
            info.CreationTime = info.LastWriteTime = info.LastAccessTime = MinTimestamp;

            //Rename the file a few times to erase the entry from the file system
            //table.
            for (int i = 0, tries = 0; i < FileNameErasePasses; ++tries)
            {
                //Generate a new file name for the file/directory.
                string newPath = GenerateRandomFileName(info.GetParent(), info.Name.Length);

                try
                {
                    //Try to rename the file. If it fails, it is probably due to another
                    //process locking the file. Defer, then rename again.
                    info.MoveTo(newPath);
                    ++i;
                }
                catch (IOException e)
                {
                    switch (System.Runtime.InteropServices.Marshal.GetLastWin32Error())
                    {
                        case Win32ErrorCode.AccessDenied:
                            throw new UnauthorizedAccessException(S._("The file {0} could not " +
                                "be erased because the file's permissions prevent access to the file.",
                                info.FullName));

                        case Win32ErrorCode.SharingViolation:
                            //If after FilenameEraseTries the file is still locked, some program is
                            //definitely using the file; throw an exception.
                            if (tries > FileNameEraseTries)
                                throw new IOException(S._("The file {0} is currently in use and " +
                                    "cannot be removed.", info.FullName), e);

                            //Let the process locking the file release the lock
                            Thread.Sleep(100);
                            break;

                        default:
                            throw;
                    }
                }
            }

            //Then delete the file.
            for (int i = 0; i < FileNameEraseTries; ++i)
                try
                {
                    info.Delete();
                    break;
                }
                catch (IOException e)
                {
                    switch (System.Runtime.InteropServices.Marshal.GetLastWin32Error())
                    {
                        case Win32ErrorCode.AccessDenied:
                            throw new UnauthorizedAccessException(S._("The file {0} could not " +
                                "be erased because the file's permissions prevent access to the file.",
                                info.FullName), e);

                        case Win32ErrorCode.SharingViolation:
                            //If after FilenameEraseTries the file is still locked, some program is
                            //definitely using the file; throw an exception.
                            if (i > FileNameEraseTries)
                                throw new IOException(S._("The file {0} is currently in use and " +
                                    "cannot be removed.", info.FullName), e);

                            //Let the process locking the file release the lock
                            Thread.Sleep(100);
                            break;

                        default:
                            throw;
                    }
                }
        }

        public override void EraseClusterTips(VolumeInfo info, ErasureMethod method,
            ClusterTipsSearchProgress searchCallback, ClusterTipsEraseProgress eraseCallback)
        {
            //List all the files which can be erased.
            List<string> files = new List<string>();
            if (!info.IsMounted)
                throw new InvalidOperationException(S._("Could not erase cluster tips in {0} " +
                    "as the volume is not mounted.", info.VolumeId));
            ListFiles(new DirectoryInfo(info.MountPoints[0]), files, searchCallback);

            //For every file, erase the cluster tips.
            for (int i = 0, j = files.Count; i != j; ++i)
            {
                //Get the file attributes for restoring later
                StreamInfo streamInfo = new StreamInfo(files[i]);
                FileAttributes fileAttr = streamInfo.Attributes;

                try
                {
                    //Reset the file attributes.
                    streamInfo.Attributes = FileAttributes.Normal;
                    EraseFileClusterTips(files[i], method);
                }
                catch (UnauthorizedAccessException)
                {
                    Logger.Log(S._("{0} did not have its cluster tips erased because you do not " +
                        "have the required permissions to erase the file cluster tips.", files[i]),
                        LogLevel.Information);
                }
                catch (IOException e)
                {
                    Logger.Log(S._("{0} did not have its cluster tips erased. The error returned " +
                        "was: {1}", files[i], e.Message), LogLevel.Error);
                }
                finally
                {
                    streamInfo.Attributes = fileAttr;
                }

                eraseCallback(i, files.Count, files[i]);
            }
        }

        private void ListFiles(DirectoryInfo info, List<string> files,
            ClusterTipsSearchProgress searchCallback)
        {
            try
            {
                //Skip this directory if it is a reparse point
                if ((info.Attributes & FileAttributes.ReparsePoint) != 0)
                {
                    Logger.Log(S._("Files in {0} did not have their cluster tips erased because " +
                        "it is a hard link or a symbolic link.", info.FullName),
                        LogLevel.Information);
                    return;
                }

                foreach (FileInfo file in info.GetFiles())
                    if (file.IsProtectedSystemFile())
                        Logger.Log(S._("{0} did not have its cluster tips erased, because it is " +
                            "a system file", file.FullName), LogLevel.Information);
                    else if ((file.Attributes & FileAttributes.ReparsePoint) != 0)
                        Logger.Log(S._("{0} did not have its cluster tips erased because it is a " +
                            "hard link or a symbolic link.", file.FullName), LogLevel.Information);
                    else if ((file.Attributes & FileAttributes.Compressed) != 0 ||
                        (file.Attributes & FileAttributes.Encrypted) != 0 ||
                        (file.Attributes & FileAttributes.SparseFile) != 0)
                    {
                        Logger.Log(S._("{0} did not have its cluster tips erased because it is " +
                            "compressed, encrypted or a sparse file.", file.FullName),
                            LogLevel.Information);
                    }
                    else
                    {
                        try
                        {
                            foreach (string i in file.GetADSes())
                                files.Add(file.FullName + ':' + i);

                            files.Add(file.FullName);
                        }
                        catch (UnauthorizedAccessException e)
                        {
                            Logger.Log(S._("{0} did not have its cluster tips erased because of " +
                                "the following error: {1}", info.FullName, e.Message),
                                LogLevel.Error);
                        }
                        catch (IOException e)
                        {
                            Logger.Log(S._("{0} did not have its cluster tips erased because of " +
                                "the following error: {1}", info.FullName, e.Message),
                                LogLevel.Error);
                        }
                    }

                foreach (DirectoryInfo subDirInfo in info.GetDirectories())
                {
                    searchCallback(subDirInfo.FullName);
                    ListFiles(subDirInfo, files, searchCallback);
                }
            }
            catch (UnauthorizedAccessException e)
            {
                Logger.Log(S._("{0} did not have its cluster tips erased because of the " +
                    "following error: {1}", info.FullName, e.Message), LogLevel.Error);
            }
            catch (IOException e)
            {
                Logger.Log(S._("{0} did not have its cluster tips erased because of the " +
                    "following error: {1}", info.FullName, e.Message), LogLevel.Error);
            }
        }

        /// <summary>
        /// Erases the cluster tips of the given file.
        /// </summary>
        /// <param name="file">The file to erase.</param>
        /// <param name="method">The erasure method to use.</param>
        private void EraseFileClusterTips(string file, ErasureMethod method)
        {
            //Get the file access times
            StreamInfo streamInfo = new StreamInfo(file);
            DateTime lastAccess = streamInfo.LastAccessTime;
            DateTime lastWrite = streamInfo.LastWriteTime;
            DateTime created = streamInfo.CreationTime;

            //And get the file lengths to know how much to overwrite
            long fileArea = GetFileArea(file);
            long fileLength = streamInfo.Length;

            //If the file length equals the file area there is no cluster tip to overwrite
            if (fileArea == fileLength)
                return;

            //Otherwise, create the stream, lengthen the file, then tell the erasure
            //method to erase the cluster tips.
            using (FileStream stream = streamInfo.Open(FileMode.Open, FileAccess.Write,
                FileShare.None, FileOptions.WriteThrough))
            {
                try
                {
                    stream.SetLength(fileArea);
                    stream.Seek(fileLength, SeekOrigin.Begin);

                    //Erase the file
                    method.Erase(stream, long.MaxValue,
                        ManagerLibrary.Instance.PRNGManager[ManagerLibrary.Settings.ActivePrng],
                        null);
                }
                finally
                {
                    //Make sure the file length is restored!
                    stream.SetLength(fileLength);

                    //Reset the file times
                    streamInfo.LastAccessTime = lastAccess;
                    streamInfo.LastWriteTime = lastWrite;
                    streamInfo.CreationTime = created;
                }
            }
        }

        public override long GetFileArea(string filePath)
        {
            StreamInfo info = new StreamInfo(filePath);
            VolumeInfo volume = VolumeInfo.FromMountPoint(info.Directory.FullName);
            long clusterSize = volume.ClusterSize;
            return (info.Length + (clusterSize - 1)) & ~(clusterSize - 1);
        }

        /// <summary>
        /// The minimum timestamp the file system can take. This is for secure file
        /// deletion.
        /// </summary>
        protected abstract DateTime MinTimestamp { get; }
    }
}