/// <summary>Return the decrypted data stream for the packet.</summary>
public Stream GetDataStream(
PgpPrivateKey privKey)
{
byte[] sessionData = RecoverSessionData(privKey);
if (!ConfirmCheckSum(sessionData))
{
throw new PgpKeyValidationException("key checksum failed");
}
SymmetricKeyAlgorithmTag symmAlg = (SymmetricKeyAlgorithmTag)sessionData[0];
if (symmAlg == SymmetricKeyAlgorithmTag.Null)
{
return(encData.GetInputStream());
}
IBufferedCipher cipher;
string cipherName = PgpUtilities.GetSymmetricCipherName(symmAlg);
string cName = cipherName;
try
{
if (encData is SymmetricEncIntegrityPacket)
{
cName += "/CFB/NoPadding";
}
else
{
cName += "/OpenPGPCFB/NoPadding";
}
cipher = CipherUtilities.GetCipher(cName);
}
catch (PgpException e)
{
throw e;
}
catch (Exception e)
{
throw new PgpException("exception creating cipher", e);
}
try
{
KeyParameter key = ParameterUtilities.CreateKeyParameter(
cipherName, sessionData, 1, sessionData.Length - 3);
byte[] iv = new byte[cipher.GetBlockSize()];
cipher.Init(false, new ParametersWithIV(key, iv));
encStream = BcpgInputStream.Wrap(new CipherStream(encData.GetInputStream(), cipher, null));
if (encData is SymmetricEncIntegrityPacket)
{
truncStream = new TruncatedStream(encStream);
string digestName = PgpUtilities.GetDigestName(HashAlgorithmTag.Sha1);
IDigest digest = DigestUtilities.GetDigest(digestName);
encStream = new DigestStream(truncStream, digest, null);
}
if (Streams.ReadFully(encStream, iv, 0, iv.Length) < iv.Length)
{
throw new EndOfStreamException("unexpected end of stream.");
}
int v1 = encStream.ReadByte();
int v2 = encStream.ReadByte();
if (v1 < 0 || v2 < 0)
{
throw new EndOfStreamException("unexpected end of stream.");
}
// Note: the oracle attack on the "quick check" bytes is deemed
// a security risk for typical public key encryption usages,
// therefore we do not perform the check.
// bool repeatCheckPassed =
// iv[iv.Length - 2] == (byte)v1
// && iv[iv.Length - 1] == (byte)v2;
//
// // Note: some versions of PGP appear to produce 0 for the extra
// // bytes rather than repeating the two previous bytes
// bool zeroesCheckPassed =
// v1 == 0
// && v2 == 0;
//
// if (!repeatCheckPassed && !zeroesCheckPassed)
// {
// throw new PgpDataValidationException("quick check failed.");
// }
return(encStream);
}
catch (PgpException e)
{
throw e;
}
catch (Exception e)
{
throw new PgpException("Exception starting decryption", e);
}
}
internal Stream DoGetDataStream(byte[] rawPassPhrase, bool clearPassPhrase)
{
try
{
SymmetricKeyAlgorithmTag keyAlgorithm = keyData.EncAlgorithm;
KeyParameter key = PgpUtilities.DoMakeKeyFromPassPhrase(
keyAlgorithm, keyData.S2k, rawPassPhrase, clearPassPhrase);
byte[] secKeyData = keyData.GetSecKeyData();
if (secKeyData != null && secKeyData.Length > 0)
{
IBufferedCipher keyCipher = CipherUtilities.GetCipher(
PgpUtilities.GetSymmetricCipherName(keyAlgorithm) + "/CFB/NoPadding");
keyCipher.Init(false,
new ParametersWithIV(key, new byte[keyCipher.GetBlockSize()]));
byte[] keyBytes = keyCipher.DoFinal(secKeyData);
keyAlgorithm = (SymmetricKeyAlgorithmTag)keyBytes[0];
key = ParameterUtilities.CreateKeyParameter(
PgpUtilities.GetSymmetricCipherName(keyAlgorithm),
keyBytes, 1, keyBytes.Length - 1);
}
IBufferedCipher c = CreateStreamCipher(keyAlgorithm);
byte[] iv = new byte[c.GetBlockSize()];
c.Init(false, new ParametersWithIV(key, iv));
encStream = BcpgInputStream.Wrap(new CipherStream(encData.GetInputStream(), c, null));
if (encData is SymmetricEncIntegrityPacket)
{
truncStream = new TruncatedStream(encStream);
string digestName = PgpUtilities.GetDigestName(HashAlgorithmTag.Sha1);
IDigest digest = DigestUtilities.GetDigest(digestName);
encStream = new DigestStream(truncStream, digest, null);
}
if (Streams.ReadFully(encStream, iv, 0, iv.Length) < iv.Length)
{
throw new EndOfStreamException("unexpected end of stream.");
}
int v1 = encStream.ReadByte();
int v2 = encStream.ReadByte();
if (v1 < 0 || v2 < 0)
{
throw new EndOfStreamException("unexpected end of stream.");
}
// Note: the oracle attack on the "quick check" bytes is not deemed
// a security risk for PBE (see PgpPublicKeyEncryptedData)
bool repeatCheckPassed =
iv[iv.Length - 2] == (byte)v1 &&
iv[iv.Length - 1] == (byte)v2;
// Note: some versions of PGP appear to produce 0 for the extra
// bytes rather than repeating the two previous bytes
bool zeroesCheckPassed =
v1 == 0 &&
v2 == 0;
if (!repeatCheckPassed && !zeroesCheckPassed)
{
throw new PgpDataValidationException("quick check failed.");
}
return(encStream);
}
catch (PgpException e)
{
throw e;
}
catch (Exception e)
{
throw new PgpException("Exception creating cipher", e);
}
}
private byte[] RecoverSessionData(PgpPrivateKey privKey)
{
byte[][] secKeyData = keyData.GetEncSessionKey();
if (keyData.Algorithm == PublicKeyAlgorithmTag.ECDH)
{
ECDHPublicBcpgKey ecKey = (ECDHPublicBcpgKey)privKey.PublicKeyPacket.Key;
X9ECParameters x9Params = ECKeyPairGenerator.FindECCurveByOid(ecKey.CurveOid);
byte[] enc = secKeyData[0];
int pLen = ((((enc[0] & 0xff) << 8) + (enc[1] & 0xff)) + 7) / 8;
byte[] pEnc = new byte[pLen];
Array.Copy(enc, 2, pEnc, 0, pLen);
byte[] keyEnc = new byte[enc[pLen + 2]];
Array.Copy(enc, 2 + pLen + 1, keyEnc, 0, keyEnc.Length);
ECPoint publicPoint = x9Params.Curve.DecodePoint(pEnc);
ECPrivateKeyParameters privKeyParams = (ECPrivateKeyParameters)privKey.Key;
ECPoint S = publicPoint.Multiply(privKeyParams.D).Normalize();
KeyParameter key = new KeyParameter(Rfc6637Utilities.CreateKey(privKey.PublicKeyPacket, S));
IWrapper w = PgpUtilities.CreateWrapper(ecKey.SymmetricKeyAlgorithm);
w.Init(false, key);
return(PgpPad.UnpadSessionData(w.Unwrap(keyEnc, 0, keyEnc.Length)));
}
IBufferedCipher cipher = GetKeyCipher(keyData.Algorithm);
try
{
cipher.Init(false, privKey.Key);
}
catch (InvalidKeyException e)
{
throw new PgpException("error setting asymmetric cipher", e);
}
if (keyData.Algorithm == PublicKeyAlgorithmTag.RsaEncrypt ||
keyData.Algorithm == PublicKeyAlgorithmTag.RsaGeneral)
{
byte[] bi = secKeyData[0];
cipher.ProcessBytes(bi, 2, bi.Length - 2);
}
else
{
ElGamalPrivateKeyParameters k = (ElGamalPrivateKeyParameters)privKey.Key;
int size = (k.Parameters.P.BitLength + 7) / 8;
ProcessEncodedMpi(cipher, size, secKeyData[0]);
ProcessEncodedMpi(cipher, size, secKeyData[1]);
}
try
{
return(cipher.DoFinal());
}
catch (Exception e)
{
throw new PgpException("exception decrypting secret key", e);
}
}
/// <summary>Return the decrypted input stream, using the passed in passphrase.</summary>
/// <remarks>
/// The passphrase is encoded to bytes using UTF8 (Encoding.UTF8.GetBytes).
/// </remarks>
public Stream GetDataStreamUtf8(char[] passPhrase)
{
return(DoGetDataStream(PgpUtilities.EncodePassPhrase(passPhrase, true), true));
}