public bool Access(string password, out string decryptedText)
{
decryptedText = string.Empty;
if (!Exists())
{
return(false);
}
int aglSize = Size();
var stream = new FileStream(Filename, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
/*
* // verifica che nel file ci sia l'AGL
* var ssBytes = Encoding.UTF8.GetBytes(BlockIdString);
* stream.Seek(-ssBytes.Length, SeekOrigin.End);
* var ss = new byte[ssBytes.Length];
* stream.Read(ss, 0, ssBytes.Length);
* if (Encoding.UTF8.GetString(ssBytes) != Encoding.UTF8.GetString(ss))
* return false;
*
* // Ottieni la lunghezza dell'AGL
* stream.Seek(-sizeof(int) - ssBytes.Length, SeekOrigin.End);
* byte[] aglSizeBytes = new byte[sizeof(int)];
* stream.Read(aglSizeBytes, 0, sizeof(int));
*
* int aglSize = BitConverter.ToInt32(aglSizeBytes, 0);
*/
var current = stream.Seek(-aglSize, SeekOrigin.End);
int amount = 1;
while (amount != 0 || stream.Position != stream.Length)
{
var lengthBytes = new byte[sizeof(int)];
stream.Read(lengthBytes, 0, sizeof(int));
int length = BitConverter.ToInt32(lengthBytes, 0);
var data = new byte[length];
amount = stream.Read(data, 0, length);
try
{
decryptedText = RijndaelService.Decrypt(data, password);
return(true);
}
catch (Exception)
{
}
}
return(false);
}
public void Encrypt(string key)
{
var stream = new FileStream(Filename, FileMode.Open, FileAccess.ReadWrite, FileShare.ReadWrite);
// decido quanti byte di inizio file criptare
// ovviamente devo tener conto della dimensione del file
int headerSize = 254;
if (headerSize > stream.Length)
{
headerSize = (int)stream.Length;
}
var firstBytes = new byte[headerSize];
stream.Read(firstBytes, 0, firstBytes.Length);
// crittografa il primo blocco di N bytes
var crypto = RijndaelService.EncryptBytes(firstBytes, key);
// leggi tutto il contenuto restante
byte[] bytes = new byte[stream.Length - firstBytes.Length];
stream.Read(bytes, 0, bytes.Length);
stream.Close();
stream.Dispose();
// LA situazione ora è definita da
// crypto: primi N bytes criptati
// bytes: i restanti bytes del file, normali
stream = new FileStream(Filename, FileMode.Create);
// All'inizio del blocco specifica il numero dei byte adibiti all'header section
stream.Write(BitConverter.GetBytes(crypto.Length), 0, sizeof(int));
stream.Write(crypto, 0, crypto.Length);
stream.Write(bytes, 0, bytes.Length);
stream.Close();
stream.Dispose();
}
/// <summary>
/// Struttura AGL:
/// blocchi costituiti da -> size(crypt(testo, key)) + crypt(testo, key)
/// + size(AGLblocks) + securityIdBlock
/// </summary>
/// <param name="data"></param>
public void Write(string phrase, List <string> keys)
{
List <byte> AGLbytes = new List <byte>();
foreach (var key in keys)
{
var enc = RijndaelService.Encrypt(phrase, key);
AGLbytes.AddRange(BitConverter.GetBytes(enc.Length));
AGLbytes.AddRange(enc);
}
var ssBytes = Encoding.UTF8.GetBytes(BlockIdString);
AGLbytes.AddRange(BitConverter.GetBytes(AGLbytes.Count + sizeof(int) + ssBytes.Length));
AGLbytes.AddRange(ssBytes);
var bytesArr = AGLbytes.ToArray();
var stream = new FileStream(Filename, FileMode.Append, FileAccess.Write, FileShare.ReadWrite);
stream.Write(bytesArr, 0, bytesArr.Length);
stream.Close();
stream.Dispose();
}
public bool Decrypt(string key, bool ownermode = true)
{
string password = key;
var aglService = new FileAGLService(Filename);
string decryptoAGL = string.Empty;
if (aglService.Access(key, out decryptoAGL))
{
if (decryptoAGL.Contains(FileAGLService.SecurityPhrase + ":"))
{
password = decryptoAGL.Replace(FileAGLService.SecurityPhrase + ":", string.Empty);
}
}
else
{
return(false);
}
int aglSize = aglService.Size();
var stream = new FileStream(Filename, FileMode.Open, FileAccess.Read, FileShare.ReadWrite);
// Ottieni la lunghezza dell'header
stream.Seek(0, SeekOrigin.Begin);
byte[] headerSizeBytes = new byte[sizeof(int)];
stream.Read(headerSizeBytes, 0, headerSizeBytes.Length);
int headerSize = BitConverter.ToInt32(headerSizeBytes, 0);
// leggi l'header
var headerBytes = new byte[headerSize];
stream.Read(headerBytes, 0, headerBytes.Length);
// decripta l'header
byte[] decrypto;
try
{
decrypto = RijndaelService.DecryptBytes(headerBytes, password);
Key = password;
}
catch (Exception) { return(false); }
// se è riuscito a decriptarlo, sostituisci il file con quello originale, rimuovendo anchel'AGL
var bytes = new byte[stream.Length - sizeof(int) - headerBytes.Length - aglSize];
stream.Read(bytes, 0, bytes.Length);
stream.Close();
stream.Dispose();
// Ripristina il file
stream = new FileStream(Filename, FileMode.Create, FileAccess.Write, FileShare.ReadWrite);
// All'inizio del blocco specifica il numero dei byte adibiti all'header section
stream.Write(decrypto, 0, decrypto.Length);
stream.Write(bytes, 0, bytes.Length);
stream.Close();
stream.Dispose();
return(true);
}
