/// <summary>
/// Decrypts a stream
/// </summary>
/// <param name="Input">Input stream</param>
/// <param name="Output">Output stream</param>
/// <returns>true, if successfull</returns>
public CryptResult Decrypt(Stream Input, Stream Output, string Password)
{
if (!Input.CanRead)
{
return(CryptResult.StreamCantRead);
}
if (!Output.CanWrite)
{
return(CryptResult.StreamCantWrite);
}
var Header = GetHeader(Input);
if (!Header.Valid)
{
return(CryptResult.InvalidFileState);
}
using (Rijndael R = Rijndael.Create())
{
NotClosingCryptoStream CS;
byte[] Key = DeriveBytes(Password, MaxKeySize, Header.Salt, Header.Cycles);
if (!CheckPasswordBytes(Key, Header.KeyHash))
{
return(CryptResult.PasswordInvalid);
}
try
{
CS = new NotClosingCryptoStream(Input, R.CreateDecryptor(Key, Header.IV), CryptoStreamMode.Read);
}
catch
{
return(CryptResult.CryptoStreamError);
}
using (CS)
{
using (var Hasher = (SHA256)HashAlgorithm.Create(HASHALG))
{
byte[] Data = new byte[R.BlockSize * 100];
int readed = 0;
do
{
try
{
readed = CS.Read(Data, 0, Data.Length);
}
catch (IOException)
{
return(CryptResult.IOError);
}
catch
{
return(CryptResult.CryptoStreamError);
}
if (readed > 0)
{
try
{
Output.Write(Data, 0, readed);
}
catch
{
return(CryptResult.IOError);
}
//Always read a multiple of the supported blocksize to avoid problems with readahead
if (Input.Position == Input.Length)
{
Hasher.TransformFinalBlock(Data, 0, readed);
}
else
{
Hasher.TransformBlock(Data, 0, readed, Data, 0);
}
}
} while (readed > 0);
if (!VerifyHMAC(Key, Header.FileHash, Hasher.Hash))
{
return(CryptResult.FileHashInvalid);
}
}
}
}
return(CryptResult.Success);
}
/// <summary>
/// Encrypts a stream
/// </summary>
/// <param name="Input">Source stream</param>
/// <param name="Output">Output stream</param>
/// <returns>true, if successfull</returns>
/// <remarks>Output stream must be seekable</remarks>
public CryptResult Encrypt(Stream Input, Stream Output)
{
if (Key == null || Salt == null)
{
return(CryptResult.PasswordInvalid);
}
if (!Input.CanRead)
{
return(CryptResult.StreamCantRead);
}
if (!Output.CanWrite)
{
return(CryptResult.StreamCantWrite);
}
if (!Output.CanSeek)
{
return(CryptResult.IOError);
}
else
{
using (Rijndael R = Rijndael.Create())
{
var Header = new CryptHeader();
Header.Valid = true;
Header.Cycles = Difficulty;
R.GenerateIV();
Header.IV = R.IV;
//Randomly generate a salt for each encryption task.
//This makes the password different for each file even if the source file and password are identical.
Header.Salt = Salt;
//Get Hash for password verification.
//This hash allows us to check if a user supplied the correct password for decryption.
//This should not be insecure as it still goes through the password generator and thus is very slow.
Header.KeyHash = GetPasswordByteHash(Key);
//Placeholder for the File hash. When decrypting, this is used to verify integrity.
Header.FileHash = new byte[256 / 8];
long HashPos = 0;
NotClosingCryptoStream CS;
Header.WriteTo(Output);
HashPos = Output.Position - Header.FileHash.Length - sizeof(int) /*Header.Cycles*/;
try
{
CS = new NotClosingCryptoStream(Output, R.CreateEncryptor(Key, R.IV), CryptoStreamMode.Write);
}
catch
{
return(CryptResult.CryptoStreamError);
}
using (CS)
{
using (var Hasher = (SHA256)HashAlgorithm.Create(HASHALG))
{
int readed = 0;
byte[] Buffer = new byte[R.BlockSize * 10];
do
{
try
{
readed = Input.Read(Buffer, 0, Buffer.Length);
}
catch
{
return(CryptResult.IOError);
}
if (readed > 0)
{
try
{
CS.Write(Buffer, 0, readed);
}
catch (IOException)
{
return(CryptResult.IOError);
}
catch
{
return(CryptResult.CryptoStreamError);
}
if (Input.Position == Input.Length)
{
var temp = Hasher.TransformFinalBlock(Buffer, 0, readed);
}
else
{
Hasher.TransformBlock(Buffer, 0, readed, Buffer, 0);
}
}
} while (readed > 0);
Header.FileHash = CreateHMAC(Key, (byte[])Hasher.Hash.Clone());
}
try
{
CS.FlushFinalBlock();
}
catch (IOException)
{
return(CryptResult.IOError);
}
catch
{
return(CryptResult.CryptoStreamError);
}
//Store File hash and seek back to the end
try
{
Output.Flush();
long CurrentPos = Output.Position;
Output.Seek(HashPos, SeekOrigin.Begin);
Output.Write(Header.FileHash, 0, Header.FileHash.Length);
Output.Flush();
Output.Seek(Output.Position, SeekOrigin.Begin);
}
catch
{
return(CryptResult.IOError);
}
}
}
}
return(CryptResult.Success);
}
