source: branches/eraser6/6.0/Eraser.Manager/FileSystem.cs @ 1878

/* 
 * $Id$
 * Copyright 2008-2010 The Eraser Project
 * Original Author: Joel Low <lowjoel@users.sourceforge.net>
 * Modified By: Kasra Nassiri <cjax@users.sourceforge.net> @17/10/2008
 * 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 Eraser.Util;

namespace Eraser.Manager
{
    /// <summary>
    /// Provides functions to handle erasures specfic to file systems.
    /// </summary>
    public abstract class FileSystem
    {
        /// <summary>
        /// Generates a random file name with the given length.
        /// </summary>
        /// <remarks>The generated file name is guaranteed not to exist.</remarks>
        /// <param name="info">The directory to generate the file name in. This
        /// parameter can be null to indicate merely a random file name</param>
        /// <param name="length">The length of the file name to generate.</param>
        /// <returns>A full path to a file containing random file name.</returns>
        public static string GenerateRandomFileName(DirectoryInfo info, int length)
        {
            //Initialise the base name, if any.
            Prng prng = PrngManager.GetInstance(ManagerLibrary.Settings.ActivePrng);
            string resultPrefix = info == null ? string.Empty : info.FullName +
                Path.DirectorySeparatorChar;

            //Variables to store the intermediates.
            byte[] resultAry = new byte[length];
            string result = string.Empty;
            List<string> prohibitedFileNames = new List<string>(new string[] {
                "CON", "PRN", "AUX", "NUL", "COM1", "COM2", "COM3", "COM4",
                "COM5", "COM6", "COM7", "COM8", "COM9", "LPT1", "LPT2", "LPT3",
                "LPT4", "LPT5", "LPT6", "LPT7", "LPT8", "LPT9"
            });

            do
            {
                prng.NextBytes(resultAry);

                //Validate the name
                string validFileNameChars = "0123456789abcdefghijklmnopqrstuvwxyz" +
                    "ABCDEFGHIJKLMNOPQRSTUVWXYZ _+=-()[]{}',`~!";
                for (int j = 0, k = resultAry.Length; j < k; ++j)
                    resultAry[j] = (byte)validFileNameChars[
                        (int)resultAry[j] % validFileNameChars.Length];

                result = Encoding.UTF8.GetString(resultAry);
            }
            while (info != null &&
                prohibitedFileNames.IndexOf(Path.GetFileNameWithoutExtension(result)) != -1 ||
                (Directory.Exists(resultPrefix + result) ||
                    System.IO.File.Exists(resultPrefix + result))
            );
            return resultPrefix + result;
        }

        /// <summary>
        /// Gets a random file from within the provided directory.
        /// </summary>
        /// <param name="info">The directory to get a random file name from.</param>
        /// <returns>A string containing the full path to the file.</returns>
        public static string GetRandomFile(DirectoryInfo info)
        {
            //First retrieve the list of files and folders in the provided directory.
            FileSystemInfo[] entries = null;
            try
            {
                entries = info.GetFileSystemInfos();
            }
            catch (DirectoryNotFoundException)
            {
                return string.Empty;
            }
            if (entries.Length == 0)
                return string.Empty;

            //Find a random entry.
            Prng prng = PrngManager.GetInstance(ManagerLibrary.Settings.ActivePrng);
            string result = string.Empty;
            while (result.Length == 0)
            {
                int index = prng.Next(entries.Length - 1);
                if (entries[index] is DirectoryInfo)
                    result = GetRandomFile((DirectoryInfo)entries[index]);
                else
                    result = ((FileInfo)entries[index]).FullName;
            }

            return result;
        }

        /// <summary>
        /// Writes a file for plausible deniability over the current stream.
        /// </summary>
        /// <param name="stream">The stream to write the data to.</param>
        protected static void CopyPlausibleDeniabilityFile(Stream stream)
        {
            //Get the template file to copy
            FileInfo shadowFileInfo;
            {
                string shadowFile = null;
                List<string> entries = new List<string>(
                    ManagerLibrary.Settings.PlausibleDeniabilityFiles);
                Prng prng = PrngManager.GetInstance(ManagerLibrary.Settings.ActivePrng);
                do
                {
                    if (entries.Count == 0)
                        throw new FatalException(S._("Plausible deniability was selected, " +
                            "but no decoy files were found. The current file has been only " +
                            "replaced with random data."));

                    int index = prng.Next(entries.Count - 1);
                    if ((System.IO.File.GetAttributes(entries[index]) & FileAttributes.Directory) != 0)
                    {
                        DirectoryInfo dir = new DirectoryInfo(entries[index]);
                        FileInfo[] files = dir.GetFiles("*", SearchOption.AllDirectories);
                        foreach (FileInfo f in files)
                            entries.Add(f.FullName);
                    }
                    else
                        shadowFile = entries[index];

                    entries.RemoveAt(index);
                }
                while (shadowFile == null || shadowFile.Length == 0 ||
                    !System.IO.File.Exists(shadowFile));
                shadowFileInfo = new FileInfo(shadowFile);
            }

            //Dump the copy (the first 4MB, or less, depending on the file size and size of
            //the original file)
            long amountToCopy = Math.Min(stream.Length,
                Math.Min(4 * 1024 * 1024, shadowFileInfo.Length));
            using (FileStream shadowFileStream = shadowFileInfo.OpenRead())
            {
                while (stream.Position < amountToCopy)
                {
                    byte[] buf = new byte[524288];
                    int bytesRead = shadowFileStream.Read(buf, 0, buf.Length);

                    //Stop bothering if the input stream is at the end
                    if (bytesRead == 0)
                        break;

                    //Dump the read contents onto the file to be deleted
                    stream.Write(buf, 0,
                        (int)Math.Min(bytesRead, amountToCopy - stream.Position));
                }
            }
        }

        /// <summary>
        /// Checks whether the given file system is supported by the current provider.
        /// </summary>
        /// <param name="fileSystemName">The file system name to check.</param>
        /// <returns>True if the current provider supports the file system.</returns>
        public abstract bool Supports(string fileSystemName);

        /// <summary>
        /// Securely deletes the file reference from the directory structures
        /// as well as resetting the Date Created, Date Accessed and Date Modified
        /// records.
        /// </summary>
        /// <param name="info">The file to delete.</param>
        public abstract void DeleteFile(FileInfo info);

        /// <summary>
        /// Securely deletes the folder reference from the directory structures
        /// as well as all subfolders and files, resetting the Date Created, Date
        /// Accessed and Date Modified records.
        /// </summary>
        /// <param name="info">The folder to delete</param>
        /// <param name="recursive">True if the folder and all its subfolders and
        /// files to be securely deleted.</param>
        public abstract void DeleteFolder(DirectoryInfo info, bool recursive);

        /// <seealso cref="DeleteFolder"/>
        /// <param name="info">The folder to delete.</param>
        public void DeleteFolder(DirectoryInfo info)
        {
            DeleteFolder(info, true);
        }

        /// <summary>
        /// Erases all file cluster tips in the given volume.
        /// </summary>
        /// <param name="info">The volume to search for file cluster tips and erase them.</param>
        /// <param name="method">The erasure method being employed.</param>
        /// <param name="log">The log manager instance that tracks log messages.</param>
        /// <param name="searchCallback">The callback function for search progress.</param>
        /// <param name="eraseCallback">The callback function for erasure progress.</param>
        public abstract void EraseClusterTips(VolumeInfo info, ErasureMethod method,
            Logger log, ClusterTipsSearchProgress searchCallback,
            ClusterTipsEraseProgress eraseCallback);

        /// <summary>
        /// Erases old file system table-resident files. This creates small one-byte
        /// files until disk is full. This will erase unused space which was used for
        /// files resident in the file system table.
        /// </summary>
        /// <param name="volume">The directory information structure containing
        /// the path to store the temporary one-byte files. The file system table
        /// of that drive will be erased.</param>
        /// <param name="tempDirectory">The directory structure containing the path
        /// to store temporary files used for resident file cleaning.</param>
        /// <param name="method">The method used to erase the files.</param>
        public abstract void EraseOldFileSystemResidentFiles(VolumeInfo volume,
            DirectoryInfo tempDirectory, ErasureMethod method,
            FileSystemEntriesEraseProgress callback);

        /// <summary>
        /// Erases the unused space in the main filesystem structures by creating,
        /// files until the table grows.
        /// 
        /// This will overwrite unused portions of the table which were previously
        /// used to store file entries.
        /// </summary>
        /// <param name="info">The directory information structure containing
        /// the path to store the temporary files.</param>
        /// <param name="callback">The callback function to handle the progress
        /// of the file system entry erasure.</param>
        public abstract void EraseDirectoryStructures(VolumeInfo info,
            FileSystemEntriesEraseProgress callback);

        /// <summary>
        /// Erases the file system object from the drive.
        /// </summary>
        /// <param name="info"></param>
        public abstract void EraseFileSystemObject(StreamInfo info, ErasureMethod method,
            ErasureMethodProgressFunction callback);

        /// <summary>
        /// Retrieves the size of the file on disk, calculated by the amount of
        /// clusters allocated by it.
        /// </summary>
        /// <param name="filePath">The path to the file.</param>
        /// <returns>The area of the file.</returns>
        public abstract long GetFileArea(string filePath);

        /// <summary>
        /// The number of times file names are renamed to erase the file name from
        /// the file system table.
        /// </summary>
        public const int FileNameErasePasses = 7;

        /// <summary>
        /// The maximum number of times Eraser tries to erase a file/folder before
        /// it gives up.
        /// </summary>
        public const int FileNameEraseTries = 50;
    }

    /// <summary>
    /// The function prototype for cluster tip search progress callbacks. This is
    /// called when the cluster tips are being searched.
    /// </summary>
    /// <param name="currentPath">The directory being searched</param>
    public delegate void ClusterTipsSearchProgress(string currentPath);

    /// <summary>
    /// The function prototype for cluster tip erasure callbacks. This is called when
    /// the cluster tips are being erased.
    /// </summary>
    /// <param name="currentFile">The current file index being erased.</param>
    /// <param name="totalFiles">The total number of files to be erased.</param>
    /// <param name="currentFilePath">The path to the current file being erased.</param>
    public delegate void ClusterTipsEraseProgress(int currentFile, int totalFiles,
        string currentFilePath);

    /// <summary>
    /// The prototype of callbacks handling the file system table erase progress.
    /// </summary>
    /// <param name="currentFile">The current file being erased.</param>
    /// <param name="totalFiles">The estimated number of files that must be
    /// erased.</param>
    public delegate void FileSystemEntriesEraseProgress(int currentFile, int totalFiles);

    public class FileSystemManager
    {
        #region Registrar fields
        /// <summary>
        /// Gets the FileSystem object that implements the FileSystem interface
        /// for the given file system.
        /// </summary>
        /// <param name="volume">The volume to get the FileSystem provider for.</param>
        /// <returns>The FileSystem object providing interfaces to handle the
        /// given volume.</returns>
        /// <exception cref="NotSupportedException">Thrown when an unimplemented
        /// file system is requested.</exception>
        public static FileSystem Get(VolumeInfo volume)
        {
            lock (ManagerLibrary.Instance.FileSystemManager.FileSystems)
                foreach (FileSystem filesystem in ManagerLibrary.Instance.FileSystemManager.FileSystems)
                    if (filesystem.Supports(volume.VolumeFormat))
                        return filesystem;

            throw new NotSupportedException(S._("The file system on the drive {0} is not " +
                "supported.", volume.IsMounted ? volume.MountPoints[0] : volume.VolumeId));
        }

        /// <summary>
        /// Allows plug-ins to register file system providers with the main program.
        /// Thread-safe.
        /// </summary>
        /// <param name="method">The filesystem to register.</param>
        public static void Register(FileSystem filesystem)
        {
            //Insert the entry
            lock (ManagerLibrary.Instance.FileSystemManager.FileSystems)
            {
                ManagerLibrary.Instance.FileSystemManager.FileSystems.Add(filesystem);
            }
        }

        /// <summary>
        /// The list of currently registered erasure methods.
        /// </summary>
        private List<FileSystem> FileSystems = new List<FileSystem>();
        #endregion
    }
}