/// <summary>
/// Encrypt a file
/// </summary>
/// <param name="inputStream">File to read data from</param>
/// <param name="publicKey"></param>
/// <returns>EncryptedPacket with all info for receiver to decrypt</returns>
public static EncryptedPacket EncryptFile(Stream inputStream, RSAParameters publicKey)
{
MemoryStream outputStream = new MemoryStream();
byte[] aesKey = Random.GetNumbers(32);
byte[] iv = Random.GetNumbers(16);
EncryptedPacket encryptedPacket = new EncryptedPacket
{
DataType = DataType.File,
EncryptedSessionKey = AsymmetricEncryption.Encrypt(aesKey, publicKey),
Iv = iv
};
try
{
// create streamers
using (HashStreamer hashStreamer = new HashStreamer(aesKey))
using (SymmetricStreamer symmetricStreamer = new SymmetricStreamer(aesKey, iv))
{
// create streams
var hmacStream = hashStreamer.HmacShaStream(outputStream, aesKey, CryptoStreamMode.Write);
var encryptedStream = symmetricStreamer.EncryptStream(hmacStream, CryptoStreamMode.Write);
// read all data
inputStream.CopyTo(encryptedStream);
// get hash
encryptedPacket.Hmac = hashStreamer.Hash;
// create signature
encryptedPacket.Signature = AsymmetricEncryption.Sign(encryptedPacket.Hmac);
// close file streams
inputStream.Close();
}
}
catch (CryptographicException e)
{
throw new CryptoException("Error while encrypting stream", e);
}
// read encrypted data from memory stream
encryptedPacket.EncryptedData = outputStream.ToArray();
return(encryptedPacket);
}
/// <summary>
/// Decrypt a file and write it to another file
/// </summary>
/// <param name="inputStream">File to read encrypted packet from</param>
/// <param name="outputStream">File to write decrypted data to</param>
/// <param name="publicKey">Public key of sender</param>
public static async Task <bool> DecryptFile(Stream inputStream, Stream outputStream, RSAParameters publicKey)
{
// roll back stream to start
inputStream.Position = 0;
// read data type
inputStream.ReadByte();
// read and decrypt aes key
byte[] encryptedAesKeyLengthBuffer = new byte[2];
await inputStream.ReadAsync(encryptedAesKeyLengthBuffer, 0, 2);
await inputStream.FlushAsync();
ushort encryptedAesKeyLength = BitConverter.ToUInt16(encryptedAesKeyLengthBuffer, 0);
byte[] encryptedAesKey = new byte[encryptedAesKeyLength];
await inputStream.ReadAsync(encryptedAesKey, 0, encryptedAesKeyLength);
await inputStream.FlushAsync();
byte[] aesKey = AsymmetricEncryption.Decrypt(encryptedAesKey);
// read aes iv
byte[] iv = new byte[16];
await inputStream.ReadAsync(iv, 0, 16);
await inputStream.FlushAsync();
// read hash
byte[] hmac = new byte[64];
await inputStream.ReadAsync(hmac, 0, 64);
await inputStream.FlushAsync();
// read signature
int signatureLength = AsymmetricEncryption.PublicKey.Modulus.Length;
byte[] signature = new byte[signatureLength];
await inputStream.ReadAsync(signature, 0, signatureLength);
await inputStream.FlushAsync();
// check signature
if (!AsymmetricEncryption.CheckSignature(signature, publicKey, hmac))
{
throw new CryptoException("Signature check failed, file could have been sent by somebody else!");
}
try
{
// create streamers
using (HashStreamer hashStreamer = new HashStreamer(aesKey))
using (SymmetricStreamer symmetricStreamer = new SymmetricStreamer(aesKey, iv))
{
long currentPos = inputStream.Position;
// create streams
var hmacStream = hashStreamer.HmacShaStream(new MemoryStream(), aesKey, CryptoStreamMode.Write);
var decryptStream = symmetricStreamer.DecryptStream(outputStream, CryptoStreamMode.Write);
// create hash
await inputStream.CopyToAsync(hmacStream);
inputStream.Position = currentPos;
await inputStream.FlushAsync();
// skip decrypting if the hash isn't correct
if (!Hashing.CompareHashes(hashStreamer.Hash, hmac))
{
return(false);
}
// decrypt the actual data
await inputStream.CopyToAsync(decryptStream);
await inputStream.FlushAsync();
// Something something, absolute bullshit
inputStream.Position = inputStream.Seek(-16, SeekOrigin.End);
await inputStream.CopyToAsync(decryptStream);
// flush it all
await outputStream.FlushAsync();
return(true);
}
}
catch (CryptographicException e)
{
throw new CryptoException("Error while decrypting stream", e);
}
}
/// <summary>
/// Encrypt a file and store all data in another file
/// </summary>
/// <param name="inputStream">Stream to read data from</param>
/// <param name="outputStream">Stream to write encrypted packet to</param>
/// <param name="publicKey"></param>
/// <returns>Length of output stream</returns>
public static async Task <long> EncryptFile(Stream inputStream, Stream outputStream, RSAParameters publicKey)
{
byte[] aesKey = Random.GetNumbers(32);
byte[] iv = Random.GetNumbers(16);
// write header
byte[] encryptedSessionKey = AsymmetricEncryption.Encrypt(aesKey, publicKey);
List <byte> firstData = new List <byte>();
firstData.Add((byte)DataType.File);
firstData.AddRange(BitConverter.GetBytes((ushort)encryptedSessionKey.Length));
firstData.AddRange(encryptedSessionKey);
firstData.AddRange(iv);
await outputStream.WriteAsync(firstData.ToArray(), 0, firstData.Count); // write datatype, encrypted aes key and aes iv
await outputStream.FlushAsync();
await outputStream.WriteAsync(new byte[64], 0, 64); // reserve space for hmac
await outputStream.FlushAsync();
int signatureLength = publicKey.Modulus.Length;
await outputStream.WriteAsync(new byte[signatureLength], 0, signatureLength); // reserve space for signature
await outputStream.FlushAsync();
try
{
using (HashStreamer hashStreamer = new HashStreamer(aesKey))
using (SymmetricStreamer symmetricStreamer = new SymmetricStreamer(aesKey, iv))
{
var hmacStream = hashStreamer.HmacShaStream(outputStream, aesKey, CryptoStreamMode.Write);
var encryptedStream = symmetricStreamer.EncryptStream(hmacStream, CryptoStreamMode.Write);
outputStream.SetLength(firstData.Count + 64 + signatureLength);
outputStream.Position = firstData.Count + 64 + signatureLength;
await inputStream.CopyToAsync(encryptedStream);
// write hash in front of file
outputStream.Position = 0;
await outputStream.WriteAsync(firstData.ToArray(), 0, firstData.Count);
byte[] hash = hashStreamer.Hash;
await outputStream.WriteAsync(hash, 0, 64);
// write signature in front of file
await outputStream.WriteAsync(AsymmetricEncryption.Sign(hash), 0, signatureLength);
// flush it all the way
await outputStream.FlushAsync();
return(outputStream.Length);
}
}
catch (CryptographicException e)
{
throw new CryptoException("Error while encrypting file", e);
}
}
