source: branches/eraser6/Manager/DirectExecutor.cs @ 202

using System;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Text;
using System.Threading;
using System.IO;

using Eraser.Util;

namespace Eraser.Manager
{
    /// <summary>
    /// The DirectExecutor class is used by the Eraser GUI directly when the program
    /// is run without the help of a Service.
    /// </summary>
    public class DirectExecutor : Executor, IDisposable
    {
        public DirectExecutor()
        {
            thread = new Thread(delegate()
            {
                this.Main();
            });

            thread.Start();
            Thread.Sleep(0);
        }

        void IDisposable.Dispose()
        {
            thread.Abort();
            schedulerInterrupt.Set();
        }

        public override void AddTask(ref Task task)
        {
            lock (unusedIdsLock)
            {
                if (unusedIds.Count != 0)
                {
                    task.ID = unusedIds[0];
                    unusedIds.RemoveAt(0);
                }
                else
                    task.ID = ++nextId;
            }

            //Add the task to the set of tasks
            lock (tasksLock)
            {
                tasks.Add(task.ID, task);

                //If the task is scheduled to run now, break the waiting thread and
                //run it immediately
                if (task.Schedule == Schedule.RunNow)
                {
                    scheduledTasks.Add(DateTime.Now, task);
                    schedulerInterrupt.Set();
                }
                //If the task is scheduled, add the next execution time to the list
                //of schduled tasks.
                else if (task.Schedule != Schedule.RunOnRestart)
                {
                    scheduledTasks.Add((task.Schedule as RecurringSchedule).NextRun, task);
                }
            }
        }

        public override bool DeleteTask(uint taskId)
        {
            lock (tasksLock)
            {
                if (!tasks.ContainsKey(taskId))
                    return false;

                lock (unusedIdsLock)
                    unusedIds.Add(taskId);
                tasks.Remove(taskId);
            }
            return true;
        }

        public override Task GetTask(uint taskId)
        {
            lock (tasksLock)
            {
                if (!tasks.ContainsKey(taskId))
                    return null;
                return tasks[taskId];
            }
        }

        /// <summary>
        /// The thread entry point for this object. This object operates on a queue
        /// and hence the thread will sequentially execute tasks.
        /// </summary>
        private void Main()
        {
            //The waiting thread will utilize a polling loop to check for new
            //scheduled tasks. This will be checked every 30 seconds. However,
            //when the thread is waiting for a new task, it can be interrupted.
            while (thread.ThreadState != ThreadState.AbortRequested)
            {
                //Check for a new task
                Task task = null;
                lock (tasksLock)
                {
                    if (scheduledTasks.Count != 0 &&
                        (scheduledTasks.Values[0].Schedule == Schedule.RunNow ||
                         scheduledTasks.Keys[0] <= DateTime.Now))
                    {
                        task = scheduledTasks.Values[0];
                        scheduledTasks.RemoveAt(0);
                    }
                }

                if (task != null)
                {
                    try
                    {
                        //Run the task
                        foreach (Task.ErasureTarget target in task.Entries)
                            try
                            {
                                if (target is Task.UnusedSpace)
                                    EraseUnusedSpace(task, (Task.UnusedSpace)target);
                                else if (target is Task.FilesystemObject)
                                    EraseFilesystemObject(task, (Task.FilesystemObject)target);
                                else
                                    throw new ArgumentException("Unknown erasure target.");
                            }
                            catch (FatalException)
                            {
                                throw;
                            }
                            catch (Exception e)
                            {
                                task.LogEntry(new LogEntry(e.Message, LogLevel.ERROR));
                            }
                    }
                    catch (FatalException e)
                    {
                        task.LogEntry(new LogEntry(e.Message, LogLevel.FATAL));
                    }

                    //If the task is a recurring task, reschedule it since we are done.
                    if (task.Schedule is RecurringSchedule)
                        ((RecurringSchedule)task.Schedule).Reschedule(DateTime.Now);
                }

                //Wait for half a minute to check for the next scheduled task.
                schedulerInterrupt.WaitOne(30000, false);
            }
        }

        /// <summary>
        /// Executes a unused space erase.
        /// </summary>
        /// <param name="target">The target of the unused space erase.</param>
        private void EraseUnusedSpace(Task task, Task.UnusedSpace target)
        {
            throw new NotImplementedException("Unused space erasures are not "+
                "currently implemented");
        }

        /// <summary>
        /// Erases a file or folder on the volume.
        /// </summary>
        /// <param name="target">The target of the erasure.</param>
        private void EraseFilesystemObject(Task task, Task.FilesystemObject target)
        {
            List<string> paths = target.GetPaths();
            TaskProgressEventArgs eventArgs = new TaskProgressEventArgs(task, 0, 0);

            //Get the erasure method if the user specified he wants the default.
            ErasureMethod method = target.Method;
            if (method == ErasureMethodManager.Default)
                method = ErasureMethodManager.GetInstance(Globals.Settings.DefaultFileErasureMethod);

            //Iterate over every path, and erase the path.
            for (int i = 0; i < paths.Count; ++i)
            {
                //Update the task progress
                eventArgs.overallProgress = (uint)(i * 100) / (uint)paths.Count;
                eventArgs.currentItemName = paths[i];
                eventArgs.currentItemProgress = 0;
                eventArgs.totalPasses = method.Passes;
                task.OnProgressChanged(eventArgs);

                //Make sure the file does not have any attributes which may
                //affect the erasure process
                FileInfo info = new FileInfo(paths[i]);
                if ((info.Attributes & FileAttributes.Compressed) != 0 ||
                    (info.Attributes & FileAttributes.Encrypted) != 0 ||
                    (info.Attributes & FileAttributes.SparseFile) != 0 ||
                    (info.Attributes & FileAttributes.ReparsePoint) != 0)
                {
                    //Log the error
                    throw new ArgumentException("Compressed, encrypted, or sparse" +
                        "files cannot be erased with Eraser.");
                }

                //Remove the read-only flag, if it is set.
                if ((info.Attributes & FileAttributes.ReadOnly) != 0)
                    info.Attributes &= ~FileAttributes.ReadOnly;

                //Create the file stream, and call the erasure method
                //to write to the stream.
                using (FileStream strm = new FileStream(info.FullName,
                    FileMode.Open, FileAccess.Write, FileShare.None,
                    8, FileOptions.WriteThrough))
                {
                    //Set the end of the stream after the wrap-round the cluster size
                    uint clusterSize = Drives.GetDriveClusterSize(info.Directory.Root.FullName);
                    long roundUpFileLength = strm.Length % clusterSize;
                    if (roundUpFileLength != 0)
                        strm.SetLength(strm.Length + (clusterSize - roundUpFileLength));

                    //Then erase the file.
                    method.Erase(strm, PRNGManager.GetInstance(Globals.Settings.ActivePRNG),
                        delegate(float currentProgress, uint currentPass)
                        {
                            eventArgs.currentPass = currentPass;
                            eventArgs.currentItemProgress = (uint)currentProgress * 100;
                            eventArgs.overallProgress = (uint)(((i + currentProgress) /
                                (float)paths.Count) * 100);
                            task.OnProgressChanged(eventArgs);
                        }
                    );

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

                //Remove the file.
                RemoveFile(info);
            }
        }

        /// <summary>
        /// Securely removes the filename of the file.
        /// </summary>
        /// <param name="info">The FileInfo object representing the file.</param>
        private void RemoveFile(FileInfo info)
        {
            //Set the date of the file to be invalid to prevent forensic
            //detection
            info.CreationTime = info.LastWriteTime = info.LastAccessTime =
                new DateTime(1800, 1, 1, 0, 0, 0);
            info.Attributes = FileAttributes.Normal;
            info.Attributes = FileAttributes.NotContentIndexed;

            //Rename the file a few times to erase the record from the MFT.
            for (uint i = 0; i < FilenameErasePasses; ++i)
            {
                //Get a random file name
                PRNG prng = PRNGManager.GetInstance(Globals.Settings.ActivePRNG);
                byte[] newFileNameAry = new byte[info.Name.Length];
                prng.NextBytes(newFileNameAry);

                //Validate the name
                const string validFileNameChars = "0123456789abcdefghijklmnopqrs" +
                    "tuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
                for (int j = 0, k = newFileNameAry.Length; j < k; ++j)
                    newFileNameAry[j] = (byte)validFileNameChars[
                        (int)newFileNameAry[j] % validFileNameChars.Length];

                //Rename the file.
                string newPath = info.DirectoryName + Path.DirectorySeparatorChar +
                    (new System.Text.UTF8Encoding()).GetString(newFileNameAry);
                info.MoveTo(newPath);
            }

            //Then delete the file.
            info.Delete();
        }

        /// <summary>
        /// The thread object.
        /// </summary>
        private Thread thread;

        /// <summary>
        /// The lock preventing concurrent access for the tasks list and the
        /// tasks queue.
        /// </summary>
        private object tasksLock = new object();

        /// <summary>
        /// The list of tasks. Includes all immediate, reboot, and recurring tasks
        /// </summary>
        private Dictionary<uint, Task> tasks = new Dictionary<uint, Task>();

        /// <summary>
        /// The queue of tasks. This queue is executed when the first element's
        /// timestamp (the key) has been past. This list assumes that all tasks
        /// are sorted by timestamp, smallest one first.
        /// </summary>
        private SortedList<DateTime, Task> scheduledTasks =
            new SortedList<DateTime, Task>();

        /// <summary>
        /// The list of task IDs for recycling.
        /// </summary>
        private List<uint> unusedIds = new List<uint>();

        /// <summary>
        /// Lock preventing concurrent access for the IDs.
        /// </summary>
        private object unusedIdsLock = new object();

        /// <summary>
        /// Incrementing ID. This value is incremented by one every time an ID
        /// is required by no unused IDs remain.
        /// </summary>
        private uint nextId = 0;

        /// <summary>
        /// An automatically reset event allowing the addition of new tasks to
        /// interrupt the thread's sleeping state waiting for the next recurring
        /// task to be due.
        /// </summary>
        AutoResetEvent schedulerInterrupt = new AutoResetEvent(true);
    }
}