public static Stream DecryptSingleFile(Stream encryptedStream, SecureString passphrase, out string filename, out DateTime fileDate)
{
SymmetricAlgorithm symmetricAlgorithm = null;
foreach (var packet in OpenPgpPacketReader.ReadAllPackets(encryptedStream))
{
var encryptedSessionKey = packet as SymmetricKeyEncryptedSessionKeyOpenPgpPacket;
if (encryptedSessionKey != null)
{
symmetricAlgorithm = encryptedSessionKey.GetKeyedSymmetricAlgorithm(passphrase);
}
var encryptedIntegrityProtectedData = packet as SymmetricallyEncryptedIntegrityProtectedDataOpenPgpPacket;
if (encryptedIntegrityProtectedData != null)
{
foreach (var decryptedPacket in encryptedIntegrityProtectedData.GetDecryptedPackets(symmetricAlgorithm))
{
var compressedPacket = decryptedPacket as CompressedDataOpenPgpPacket;
if (compressedPacket != null)
{
Stream literalStream = null;
filename = null;
fileDate = DateTime.MinValue;
foreach (var decompressedPacket in OpenPgpPacketReader.ReadAllPackets(compressedPacket.DecompressedStream))
{
var literalData = decompressedPacket as LiteralDataOpenPgpPacket;
if (literalData != null)
{
filename = literalData.FileName;
fileDate = literalData.FileDate;
literalStream = literalData.LiteralStream;
}
}
return(literalStream);
}
}
}
}
throw new CryptographicException();
}
// Throw error if not valid
public IEnumerable <OpenPgpPacket> GetDecryptedPackets(SymmetricAlgorithm keyedAlgorithm)
{
var transform = new OpenPgpCfbTransform(keyedAlgorithm, encrypt: false);
var decryptor = new CryptoStream(EncryptedStream, transform, CryptoStreamMode.Read);
var decrypted = new MemoryStream();
decryptor.CopyTo(decrypted);
// Get rid of the modification detection code, but verify it
var mdcStart = decrypted.Length - (1 + 1 + 20);
decrypted.Position = mdcStart;
var mdcStream = new MemoryStream();
decrypted.CopyTo(mdcStream);
decrypted.Position = 0;
decrypted.SetLength(mdcStart + 2);
var hasher = SHA1.Create();
var hashIncludingHeaderAndLength = hasher.ComputeHash(transform.PrefixBytes.Concat(decrypted.ToArray()).ToArray());
decrypted.SetLength(decrypted.Length - 2);
decrypted.Position = 0;
// TODO:
mdcStream.Position = 0;
var mdc = OpenPgpPacketReader.ReadAllPackets(mdcStream).First() as ModificationDetectionCodeOpenPgpPacket;
for (int i = 0; i < hashIncludingHeaderAndLength.Length; i++)
{
if (hashIncludingHeaderAndLength[i] != mdc.HashValue[i])
{
throw new ModificationDetectedException();
}
}
return(OpenPgpPacketReader.ReadAllPackets(decrypted));
}
