public MeshNode(Stream s, string password, string profileFolder, TorController torController)
{
_password = password;
_profileFolder = profileFolder;
switch (s.ReadByte()) //version
{
case 1:
//read headers and init decryptor
Aes decryptionAlgo = Aes.Create();
decryptionAlgo.Key = MeshNetwork.GetKdfValue32(Encoding.UTF8.GetBytes(password), s.ReadBytes(32), 1, 1 * 1024 * 1024); //salt
decryptionAlgo.IV = s.ReadBytes(16); //IV
decryptionAlgo.Padding = PaddingMode.ISO10126;
decryptionAlgo.Mode = CipherMode.CBC;
byte[] hmac = s.ReadBytes(32); //hmac
long cipherTextStartPosition = s.Position;
//authenticate data in Encrypt-then-MAC (EtM) mode
using (HMAC aeHmac = new HMACSHA256(decryptionAlgo.Key))
{
byte[] computedHmac = aeHmac.ComputeHash(s);
if (!BinaryNumber.Equals(hmac, computedHmac))
{
throw new CryptographicException("Invalid password or data tampered.");
}
}
//decrypt data and init node
s.Position = cipherTextStartPosition;
CryptoStream cS = new CryptoStream(s, decryptionAlgo.CreateDecryptor(), CryptoStreamMode.Read);
InitMeshNode(new BinaryReader(cS), torController);
break;
case -1:
throw new EndOfStreamException();
default:
throw new InvalidDataException("MeshNode format version not supported.");
}
}
public void SaveTo(Stream s)
{
//generate salt for KDF
byte[] salt = new byte[32];
_rng.GetBytes(salt);
//create encryptor
Aes encryptionAlgo = Aes.Create();
encryptionAlgo.Key = MeshNetwork.GetKdfValue32(Encoding.UTF8.GetBytes(_password), salt, 1, 1 * 1024 * 1024);
encryptionAlgo.GenerateIV();
encryptionAlgo.Padding = PaddingMode.ISO10126;
encryptionAlgo.Mode = CipherMode.CBC;
//write headers
s.WriteByte((byte)1); //version
s.Write(salt); //salt
s.Write(encryptionAlgo.IV); //IV
s.Write(new byte[32]); //placeholder for HMAC
long cipherTextStartPosition = s.Position;
//write encrypted data
{
CryptoStream cS = new CryptoStream(s, encryptionAlgo.CreateEncryptor(), CryptoStreamMode.Write);
BufferedStream bS = new BufferedStream(cS);
WriteTo(new BinaryWriter(bS));
bS.Flush();
cS.FlushFinalBlock();
}
//write hmac for authenticated encryption Encrypt-then-MAC (EtM) mode
using (HMAC aeHmac = new HMACSHA256(encryptionAlgo.Key))
{
s.Position = cipherTextStartPosition;
byte[] hmac = aeHmac.ComputeHash(s);
//write hmac
s.Position = cipherTextStartPosition - 32;
s.Write(hmac);
}
}