private void ExtractData()
{
string DecryptedFileName = null;
string Password = null;
if (MessageBox.Show("Decrypt Encrypted Data", "Please Confirm", MessageBoxButtons.YesNo, MessageBoxIcon.Question) != System.Windows.Forms.DialogResult.Yes)
{
return;
}
PGPPacket Packet = this;
List <byte[]> SessionKeys = new List <byte[]>();
List <PKEncSessionKeyPacket> PKSessions = new List <PKEncSessionKeyPacket>();
List <SymEncSessionKeyPacket> SymSessions = new List <SymEncSessionKeyPacket>();
//byte SymmetricAlgorithm = 0;
string ErrorMsg = "";
while ((Packet = OpenPGP.GetPreviousPacket(Packet)) != null)
{
if (Packet is PKEncSessionKeyPacket PKSessionPacket)
{
PKSessions.Add(PKSessionPacket);
}
else if (Packet is SymEncSessionKeyPacket SymKeySessionPacket)
{
SymSessions.Add(SymKeySessionPacket);
}
}
// First try to see if we have any PK Secret keys
foreach (var PKSession in PKSessions)
{
// Get all matching secret keys
var SecKeyList = OpenPGP.FindPrimaryKey(PKSession.KeyId, true).Where(p => p.PacketTag == 5 || p.PacketTag == 7).ToList();
foreach (SecretKeyPacket SecKey in SecKeyList)
{
var PKAlgorithm = SecKey.PublicKeyAlgorithm;
if (!PKAlgorithm.PrivateKeyDecrypted)
{
ErrorMsg = "Secret Key is encrypted, click on the encrypted node to decrypt it first";
continue;
}
var ClearBytes = PKAlgorithm.Decrypt(PKSession.PublicKeyTransformedData);
long CheckSum = 0;
for (int i = 1; i < ClearBytes.Length - 2; i++)
{
CheckSum += ClearBytes[i];
}
CheckSum %= 65536;
if ((CheckSum >> 8) != ClearBytes[ClearBytes.Length - 2] || (CheckSum & 0xFF) != ClearBytes[ClearBytes.Length - 1])
{
continue;
}
//SymmetricAlgorithm = ClearBytes[0];
SessionKeys.Add(ClearBytes.SubArray(0, ClearBytes.Length - 2));
}
}
if (SessionKeys.Count() == 0)
{
if (ErrorMsg != "")
{
throw new Exception(ErrorMsg);
}
}
// If no Public Key Encrypted keys found, then try any Sym keys
if (SessionKeys.Count() == 0)
{
foreach (var SymSession in SymSessions)
{
if (Password == null)
{
// Ask for password only once
PinEntry frm = new PinEntry();
if (frm.ShowDialog() == DialogResult.Cancel)
{
break;
}
Password = frm.Password;
}
byte[] DecryptionKey = SymSession.S2K.GetKey(Password);
if (SymSession.EncryptedSessionKey == null)
{
byte[] SessionKey = new byte[DecryptionKey.Length + 1];
SessionKey[0] = SymSession.S2K.SymAlgo;
Array.Copy(DecryptionKey, 0, SessionKey, 1, DecryptionKey.Length);
SessionKeys.Add(SessionKey);
}
else
{
var KeyDecryptor = SymmProcess.GetDecryptor(SymSession.S2K.SymAlgo, DecryptionKey);
var BlockSizeBytes = KeyDecryptor.InputBlockSize;
int EncryptedLength = SymSession.EncryptedSessionKey.Length;
int BlockFillLength = BlockSizeBytes * ((EncryptedLength / BlockSizeBytes) + 1);
byte[] CryptBytes = new byte[BlockFillLength];
Array.Copy(SymSession.EncryptedSessionKey, 0, CryptBytes, 0, EncryptedLength);
byte[] ClearBytes;
using (MemoryStream msDecrypt = new MemoryStream())
{
using (CryptoStream csDecrypt = new CryptoStream(msDecrypt, KeyDecryptor, CryptoStreamMode.Write))
csDecrypt.Write(CryptBytes, 0, CryptBytes.Length);
ClearBytes = msDecrypt.ToArray().SubArray(0, EncryptedLength);
}
SessionKeys.Add(ClearBytes);
}
}
}
//if (Packet == null || (Packet.PacketTag != 1 && Packet.PacketTag != 3))
// throw new Exception("No Public-Key/Symmetric-Key encrypted session key packet");
//if (SecKeyList.Count() == 0)
// throw new Exception("Secret Key not available, please add the secret key to decrypt data");
if (SessionKeys.Count() == 0)
{
throw new Exception("Unable to Decrypt");
}
// Session Key found
DecryptedFileName = TempFiles.GetNewTempFile();
bool Success = false;
using (PGPReader fsSource = new PGPReader(FileName))
{
fsSource.DoIndexUpdate += OnIndexUpdate;
fsSource.GetPacket(PacketIndex);
fsSource.DoIndexUpdate -= OnIndexUpdate;
byte version = fsSource.ReadByte();
long FileSize = fsSource.BytesRemaining;
fsSource.BookMark();
foreach (var SessionKey in SessionKeys)
{
try
{
var decryptor = SymmProcess.GetDecryptor(SessionKey[0], SessionKey.SubArray(1, SessionKey.Length - 1));
int BlockSize = decryptor.InputBlockSize;
fsSource.GoToBookMark();
using (FileStream fsDecrypt = new FileStream(DecryptedFileName, FileMode.Create, FileAccess.Write))
{
SHA1 Sha1 = new SHA1Managed();
byte[] CryptBytes = new byte[BlockSize * 256]; // IMPORTANT: Make sure it is a multiple of block size
byte[] PlainBytes = new byte[BlockSize * 256];
var BytesRemaining = FileSize - 22; // 2 byte MDC tag (0xD3, 0x14) and length, 20 byte SHA-1 hash
int BlockAlign = (int)(BytesRemaining % BlockSize);
BytesRemaining -= BlockAlign; // Transformation has to be done in blocks, so make sure it fits in blocks
bool FirstTime = true;
while (BytesRemaining > 0)
{
int ReadBytes = (int)BytesRemaining;
if (BytesRemaining > CryptBytes.Length)
{
ReadBytes = CryptBytes.Length;
}
fsSource.Read(CryptBytes, 0, ReadBytes);
decryptor.TransformBlock(CryptBytes, 0, ReadBytes, PlainBytes, 0);
if (FirstTime)
{
// Validate the repeating bytes
if (PlainBytes[BlockSize - 2] != PlainBytes[BlockSize] || PlainBytes[BlockSize - 1] != PlainBytes[BlockSize + 1])
{
throw new Exception("Pre validation failed, session key may be invalid");
}
fsDecrypt.Write(PlainBytes, BlockSize + 2, ReadBytes - BlockSize - 2);
FirstTime = false;
}
else
{
fsDecrypt.Write(PlainBytes, 0, ReadBytes);
}
Sha1.TransformBlock(PlainBytes, 0, ReadBytes, PlainBytes, 0);
StatusUpdate("Decrypting...", (int)(100 * (FileSize - BytesRemaining) / FileSize));
BytesRemaining -= ReadBytes;
}
int FinalBytes = BlockAlign + 22;
fsSource.Read(CryptBytes, 0, FinalBytes);
decryptor.TransformBlock(CryptBytes, 0, FinalBytes + Program.GetBlockAlignRemainder(FinalBytes, BlockSize), PlainBytes, 0);
fsDecrypt.Write(PlainBytes, 0, BlockAlign);
// Validate the MDC Packet
if (PlainBytes[BlockAlign] != 0xD3 || PlainBytes[BlockAlign + 1] != 0x14)
{
throw new Exception("Modification Detection validation failed, data is corrupt");
}
Sha1.TransformFinalBlock(PlainBytes, 0, BlockAlign + 2); // 0xD3, 0x14 bytes
if (!PlainBytes.SubArray(BlockAlign + 2, 20).SequenceEqual(Sha1.Hash))
{
throw new Exception("MDC hash verification failed, Data may have been modified or is corrupt");
}
Success = true;
break;
}
}
catch (Exception ex)
{
}
}
}
if (Success)
{
ByteBlock StartBlock = OpenPGP.Process(DecryptedFileName);
OpenPGP.Validate();
ThisBlock.AddChildBlock(StartBlock);
}
}
