/// <summary>
/// Shuffles the passes in the input array, effectively randomizing the
/// order or rewrites.
/// </summary>
/// <param name="passes">The input set of passes.</param>
/// <returns>The shuffled set of passes.</returns>
protected static ErasureMethodPass[] ShufflePasses(ErasureMethodPass[] passes)
{
//Make a copy.
ErasureMethodPass[] result = new ErasureMethodPass[passes.Length];
passes.CopyTo(result, 0);
//Randomize.
IPrng rand = Host.Instance.Prngs.ActivePrng;
for (int i = 0; i < result.Length; ++i)
{
int val = rand.Next(result.Length - 1);
ErasureMethodPass tmpPass = result[val];
result[val] = result[i];
result[i] = tmpPass;
}
return(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.
IPrng prng = Host.Instance.Prngs.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>
private void DeleteFileWithPlausibleDeniability(FileInfo info)
{
ObfuscateFileSystemInfoName(info);
//Get the template file to copy
FileInfo shadowFileInfo;
{
string shadowFile = null;
List <string> entries = new List <string>(
Host.Instance.Settings.PlausibleDeniabilityFiles);
IPrng prng = Host.Instance.Prngs.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."));
}
//Get an item from the list of files, and then check that the item exists.
int index = prng.Next(entries.Count - 1);
shadowFile = entries[index];
if (File.Exists(shadowFile) || Directory.Exists(shadowFile))
{
if ((File.GetAttributes(shadowFile) & FileAttributes.Directory) != 0)
{
DirectoryInfo dir = new DirectoryInfo(shadowFile);
FileInfo[] files = dir.GetFiles("*", SearchOption.AllDirectories);
entries.Capacity += files.Length;
foreach (FileInfo f in files)
{
entries.Add(f.FullName);
}
shadowFile = null;
}
else
{
shadowFile = entries[index];
}
}
else
{
shadowFile = null;
}
entries.RemoveAt(index);
}while (string.IsNullOrEmpty(shadowFile));
shadowFileInfo = new FileInfo(shadowFile);
}
//Copy the contents of the shadow.
using (Stream stream = info.OpenWrite())
{
//Dump the copy (the first 4MB, or less, depending on the file size and size of
//the original file)
long amountToCopy = Math.Min(4 * 1024 * 1024, shadowFileInfo.Length);
using (FileStream shadowFileStream = shadowFileInfo.Open(
FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
{
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));
}
}
//Make the file to be deleted have the same length as the file
//which is being used as a decoy. The end of the file might contain
//noise, which should make the decoy more convincing.
stream.SetLength(shadowFileInfo.Length);
}
//Make the file to be deleted look like the shadow.
info.MoveTo(Path.Combine(info.DirectoryName, shadowFileInfo.Name));
if (shadowFileInfo.IsCompressed())
{
info.Compress();
}
info.SetAccessControl(shadowFileInfo.GetAccessControl());
info.Attributes = shadowFileInfo.Attributes;
info.CopyTimes(shadowFileInfo);
//Just delete the file.
info.Delete();
}