public virtual int DecryptReceivedClient(byte[] pbyBufIn, int nBufLen,
out byte[] ppbyBufOut, uint dwIP, out uint nReceiverVerifyKey, out uint nSenderVerifyKey)
{
int nResult = nBufLen;
ppbyBufOut = pbyBufIn;
nReceiverVerifyKey = 0;
nSenderVerifyKey = 0;
if (nResult <= CRYPT_HEADER_WITHOUTPADDING /*|| !MuleApplication.Instance.Preference.IsClientCryptLayerSupported()*/)
{
return(nResult);
}
switch (pbyBufIn[0])
{
case MuleConstants.PROTOCOL_EMULEPROT:
case MuleConstants.PROTOCOL_KADEMLIAPACKEDPROT:
case MuleConstants.PROTOCOL_KADEMLIAHEADER:
case MuleConstants.PROTOCOL_UDPRESERVEDPROT1:
case MuleConstants.PROTOCOL_UDPRESERVEDPROT2:
case MuleConstants.PROTOCOL_PACKEDPROT:
return(nResult); // no encrypted packet (see description on top)
}
// might be an encrypted packet, try to decrypt
RC4Key keyReceiveKey = null;
uint dwValue = 0;
// check the marker bit which type this packet could be and which key to test first, this is only an indicator since old clients have it set random
// see the header for marker bits explanation
byte byCurrentTry = (byte)(((pbyBufIn[0] & 0x03) == 3) ? 1 : (pbyBufIn[0] & 0x03));
byte byTries;
if (MuleApplication.Instance.KadEngine.Preference == null)
{
// if kad never run, no point in checking anything except for ed2k encryption
byTries = 1;
byCurrentTry = 1;
}
else
{
byTries = 3;
}
bool bKadRecvKeyUsed = false;
bool bKad = false;
do
{
byTries--;
MD5 md5 = MD5.Create();
byte[] rawHash = null;
if (byCurrentTry == 0)
{
// kad packet with NodeID as key
bKad = true;
bKadRecvKeyUsed = false;
if (MuleApplication.Instance.KadEngine.Preference != null)
{
byte[] achKeyData = new byte[18];
Array.Copy(MuleApplication.Instance.KadEngine.Preference.KadID.Bytes, 0, achKeyData, 0, 16);
Array.Copy(pbyBufIn, 1, achKeyData, 16, 2); // random key part sent from remote client
rawHash = md5.ComputeHash(achKeyData);
}
}
else if (byCurrentTry == 1)
{
// ed2k packet
bKad = false;
bKadRecvKeyUsed = false;
byte[] achKeyData = new byte[23];
MpdUtilities.Md4Cpy(achKeyData, MuleApplication.Instance.Preference.UserHash);
achKeyData[20] = MAGICVALUE_UDP;
Array.Copy(BitConverter.GetBytes(dwIP), 0, achKeyData, 16, 4);
Array.Copy(pbyBufIn, 1, achKeyData, 21, 2); // random key part sent from remote client
rawHash = md5.ComputeHash(achKeyData);
}
else if (byCurrentTry == 2)
{
// kad packet with ReceiverKey as key
bKad = true;
bKadRecvKeyUsed = true;
if (MuleApplication.Instance.KadEngine.Preference != null)
{
byte[] achKeyData = new byte[6];
Array.Copy(BitConverter.GetBytes(MuleApplication.Instance.KadEngine.Preference.GetUDPVerifyKey(dwIP)),
achKeyData, 4);
Array.Copy(pbyBufIn, 1, achKeyData, 4, 2); // random key part sent from remote client
rawHash = md5.ComputeHash(achKeyData);
}
}
else
{
Debug.Assert(false);
}
MuleUtilities.RC4CreateKey(rawHash, 16, ref keyReceiveKey, true);
byte[] outBuf = new byte[4];
MuleUtilities.RC4Crypt(pbyBufIn, 3, outBuf, 0, 4, keyReceiveKey);
dwIP = BitConverter.ToUInt32(outBuf, 0);
byCurrentTry = (byte)((byCurrentTry + 1) % 3);
} while (dwValue != MAGICVALUE_UDP_SYNC_CLIENT && byTries > 0); // try to decrypt as ed2k as well as kad packet if needed (max 3 rounds)
if (dwValue == MAGICVALUE_UDP_SYNC_CLIENT)
{
// yup this is an encrypted packet
// debugoutput notices
// the following cases are "allowed" but shouldn't happen given that there is only our implementation yet
if (bKad && (pbyBufIn[0] & 0x01) != 0)
{
MpdUtilities.DebugLog(
string.Format("Received obfuscated UDP packet from clientIP: {0} with wrong key marker bits (kad packet, ed2k bit)", MpdUtilities.IP2String(dwIP)));
}
else if (bKad && !bKadRecvKeyUsed && (pbyBufIn[0] & 0x02) != 0)
{
MpdUtilities.DebugLog(
string.Format("Received obfuscated UDP packet from clientIP: {0} with wrong key marker bits (kad packet, nodeid key, recvkey bit)", MpdUtilities.IP2String(dwIP)));
}
else if (bKad && bKadRecvKeyUsed && (pbyBufIn[0] & 0x02) == 0)
{
MpdUtilities.DebugLog(
string.Format("Received obfuscated UDP packet from clientIP: {0} with wrong key marker bits (kad packet, recvkey key, nodeid bit)", MpdUtilities.IP2String(dwIP)));
}
byte byPadLen;
byte[] outBuf = new byte[1];
MuleUtilities.RC4Crypt(pbyBufIn, 7, outBuf, 0, 1, keyReceiveKey);
byPadLen = outBuf[0];
nResult -= CRYPT_HEADER_WITHOUTPADDING;
if (nResult <= byPadLen)
{
MpdUtilities.DebugLogError(
string.Format("Invalid obfuscated UDP packet from clientIP: {0}, Paddingsize ({1}) larger than received bytes",
MpdUtilities.IP2String(dwIP), byPadLen));
return(nBufLen); // pass through, let the Receivefunction do the errorhandling on this junk
}
if (byPadLen > 0)
{
MuleUtilities.RC4Crypt(null, null, byPadLen, keyReceiveKey);
}
nResult -= byPadLen;
if (bKad)
{
if (nResult <= 8)
{
MpdUtilities.DebugLogError(
string.Format("Obfuscated Kad packet with mismatching size (verify keys missing) received from clientIP: {0}",
MpdUtilities.IP2String(dwIP)));
return(nBufLen); // pass through, let the Receivefunction do the errorhandling on this junk;
}
// read the verify keys
outBuf = new byte[4];
MuleUtilities.RC4Crypt(pbyBufIn, (int)(CRYPT_HEADER_WITHOUTPADDING + byPadLen),
outBuf, 0, 4, keyReceiveKey);
nReceiverVerifyKey = BitConverter.ToUInt32(outBuf, 0);
MuleUtilities.RC4Crypt(pbyBufIn, (int)(CRYPT_HEADER_WITHOUTPADDING + byPadLen + 4),
outBuf, 0, 4, keyReceiveKey);
nSenderVerifyKey = BitConverter.ToUInt32(outBuf, 0);
nResult -= 8;
}
ppbyBufOut = new byte[nResult];
Array.Copy(pbyBufIn, (nBufLen - nResult), ppbyBufOut, 0, nResult);
MuleUtilities.RC4Crypt(ppbyBufOut, ppbyBufOut, (uint)nResult, keyReceiveKey);
MuleApplication.Instance.Statistics.AddDownDataOverheadCrypt((uint)(nBufLen - nResult));
//DEBUG_ONLY( MpdUtilities.DebugLog(("Received obfuscated UDP packet from clientIP: %s, Key: %s, RKey: %u, SKey: %u"), MpdUtilities.IP2String(dwIP), bKad ? (bKadRecvKeyUsed ? ("ReceiverKey") : ("NodeID")) : ("UserHash")
// , nReceiverVerifyKey != 0 ? *nReceiverVerifyKey : 0, nSenderVerifyKey != 0 ? *nSenderVerifyKey : 0) );
return(nResult); // done
}
else
{
MpdUtilities.DebugLogWarning(
string.Format("Obfuscated packet expected but magicvalue mismatch on UDP packet from clientIP: {0}, Possible RecvKey: {1}",
MpdUtilities.IP2String(dwIP), MuleApplication.Instance.KadEngine.Preference.GetUDPVerifyKey(dwIP)));
return(nBufLen); // pass through, let the Receivefunction do the errorhandling on this junk
}
}
private int Negotiate(byte[] pBuffer, int offset, int nLen)
{
int nRead = 0;
Debug.Assert(receiveBytesWanted_ > 0);
try
{
while (negotiatingState_ != NegotiatingStateEnum.ONS_COMPLETE && receiveBytesWanted_ > 0)
{
if (receiveBytesWanted_ > 512)
{
Debug.Assert(false);
return(0);
}
if (fiReceiveBuffer_ == null)
{
byte[] pReceiveBuffer = new byte[512]; // use a fixed size buffer
fiReceiveBuffer_ = MpdObjectManager.CreateSafeMemFile(pReceiveBuffer);
}
int nToRead = Math.Min(Convert.ToInt32(nLen) - nRead, Convert.ToInt32(receiveBytesWanted_));
fiReceiveBuffer_.Write(pBuffer, nRead, nToRead);
nRead += nToRead;
receiveBytesWanted_ -= Convert.ToUInt32(nToRead);
if (receiveBytesWanted_ > 0)
{
return(nRead);
}
uint nCurrentBytesLen = (uint)fiReceiveBuffer_.Position;
if (negotiatingState_ != NegotiatingStateEnum.ONS_BASIC_CLIENTA_RANDOMPART &&
negotiatingState_ != NegotiatingStateEnum.ONS_BASIC_SERVER_DHANSWER)
{ // don't have the keys yet
byte[] pCryptBuffer = fiReceiveBuffer_.Buffer;
MuleUtilities.RC4Crypt(pCryptBuffer, pCryptBuffer, nCurrentBytesLen, rc4ReceiveKey_);
}
fiReceiveBuffer_.SeekToBegin();
switch (negotiatingState_)
{
case NegotiatingStateEnum.ONS_NONE: // would be a bug
Debug.Assert(false);
return(0);
case NegotiatingStateEnum.ONS_BASIC_CLIENTA_RANDOMPART:
{
Debug.Assert(rc4ReceiveKey_ == null);
byte[] achKeyData = new byte[21];
MpdUtilities.Md4Cpy(achKeyData, MuleApplication.Instance.Preference.UserHash);
achKeyData[16] = Convert.ToByte(MuleConstants.MAGICVALUE_REQUESTER);
fiReceiveBuffer_.Read(achKeyData, 17, 4); // random key part sent from remote client
MD5 md5 = MD5.Create();
rc4ReceiveKey_ =
MuleUtilities.RC4CreateKey(md5.ComputeHash(achKeyData), 16);
achKeyData[16] = Convert.ToByte(MuleConstants.MAGICVALUE_SERVER);
rc4SendKey_ =
MuleUtilities.RC4CreateKey(md5.ComputeHash(achKeyData), 16);
negotiatingState_ = NegotiatingStateEnum.ONS_BASIC_CLIENTA_MAGICVALUE;
receiveBytesWanted_ = 4;
break;
}
case NegotiatingStateEnum.ONS_BASIC_CLIENTA_MAGICVALUE:
{
uint dwValue = fiReceiveBuffer_.ReadUInt32();
if (dwValue == MuleConstants.MAGICVALUE_SYNC)
{
// yup, the one or the other way it worked, this is an encrypted stream
//DEBUG_ONLY( MpdUtilities.DebugLog(("Received proper magic value, clientIP: %s"), DbgGetIPString()) );
// set the receiver key
negotiatingState_ = NegotiatingStateEnum.ONS_BASIC_CLIENTA_METHODTAGSPADLEN;
receiveBytesWanted_ = 3;
}
else
{
MpdUtilities.DebugLogError(("CEncryptedStreamSocket: Received wrong magic value from clientIP %s on a supposly encrytped stream / Wrong Header"), DbgGetIPString());
OnError(Convert.ToInt32(EMSocketErrorCodeEnum.ERR_ENCRYPTION));
return(-1);
}
break;
}
case NegotiatingStateEnum.ONS_BASIC_CLIENTA_METHODTAGSPADLEN:
DbgByEncryptionSupported = fiReceiveBuffer_.ReadUInt8();
DbgByEncryptionRequested = fiReceiveBuffer_.ReadUInt8();
if (DbgByEncryptionRequested != Convert.ToByte(EncryptionMethodsEnum.ENM_OBFUSCATION))
{
MpdUtilities.AddDebugLogLine(EDebugLogPriority.DLP_LOW, false, ("CEncryptedStreamSocket: Client %s preffered unsupported encryption method (%i)"), DbgGetIPString(), DbgByEncryptionRequested);
}
receiveBytesWanted_ = fiReceiveBuffer_.ReadUInt8();
negotiatingState_ = NegotiatingStateEnum.ONS_BASIC_CLIENTA_PADDING;
if (receiveBytesWanted_ > 0)
{
break;
}
else
{
goto case NegotiatingStateEnum.ONS_BASIC_CLIENTA_PADDING;
}
case NegotiatingStateEnum.ONS_BASIC_CLIENTA_PADDING:
{
// ignore the random bytes, send the response, set status complete
SafeMemFile fileResponse = MpdObjectManager.CreateSafeMemFile(26);
fileResponse.WriteUInt32(MuleConstants.MAGICVALUE_SYNC);
byte bySelectedEncryptionMethod = Convert.ToByte(EncryptionMethodsEnum.ENM_OBFUSCATION); // we do not support any further encryption in this version, so no need to look which the other client preferred
fileResponse.WriteUInt8(bySelectedEncryptionMethod);
IPEndPoint remoteEp = RemoteEndPoint as IPEndPoint;
byte byPaddingLen =
MuleApplication.Instance.ServerConnect.AwaitingTestFromIP(BitConverter.ToUInt32(remoteEp.Address.GetAddressBytes(), 0))
? Convert.ToByte(16) :
Convert.ToByte(MuleApplication.Instance.Preference.CryptTCPPaddingLength + 1);
byte byPadding = Convert.ToByte(MpdUtilities.GetRandomUInt8() % byPaddingLen);
fileResponse.WriteUInt8(byPadding);
for (int i = 0; i < byPadding; i++)
{
fileResponse.WriteUInt8(MpdUtilities.GetRandomUInt8());
}
SendNegotiatingData(fileResponse.Buffer, (uint)fileResponse.Length);
negotiatingState_ = NegotiatingStateEnum.ONS_COMPLETE;
streamCryptState_ = StreamCryptStateEnum.ECS_ENCRYPTING;
//DEBUG_ONLY( MpdUtilities.DebugLog(("CEncryptedStreamSocket: Finished Obufscation handshake with client %s (incoming)"), DbgGetIPString()) );
break;
}
case NegotiatingStateEnum.ONS_BASIC_CLIENTB_MAGICVALUE:
{
if (fiReceiveBuffer_.ReadUInt32() != MuleConstants.MAGICVALUE_SYNC)
{
MpdUtilities.DebugLogError(("CEncryptedStreamSocket: EncryptedstreamSyncError: Client sent wrong Magic Value as answer, cannot complete handshake (%s)"), DbgGetIPString());
OnError(Convert.ToInt32(EMSocketErrorCodeEnum.ERR_ENCRYPTION));
return(-1);
}
negotiatingState_ = NegotiatingStateEnum.ONS_BASIC_CLIENTB_METHODTAGSPADLEN;
receiveBytesWanted_ = 2;
break;
}
case NegotiatingStateEnum.ONS_BASIC_CLIENTB_METHODTAGSPADLEN:
{
DbgByEncryptionMethodSet = fiReceiveBuffer_.ReadUInt8();
if (DbgByEncryptionMethodSet != Convert.ToByte(EncryptionMethodsEnum.ENM_OBFUSCATION))
{
MpdUtilities.DebugLogError(("CEncryptedStreamSocket: Client %s set unsupported encryption method (%i), handshake failed"),
DbgGetIPString(), DbgByEncryptionMethodSet);
OnError(Convert.ToInt32(EMSocketErrorCodeEnum.ERR_ENCRYPTION));
return(-1);
}
receiveBytesWanted_ = fiReceiveBuffer_.ReadUInt8();
negotiatingState_ = NegotiatingStateEnum.ONS_BASIC_CLIENTB_PADDING;
if (receiveBytesWanted_ > 0)
{
break;
}
else
{
goto case NegotiatingStateEnum.ONS_BASIC_CLIENTB_PADDING;
}
}
case NegotiatingStateEnum.ONS_BASIC_CLIENTB_PADDING:
// ignore the random bytes, the handshake is complete
negotiatingState_ = NegotiatingStateEnum.ONS_COMPLETE;
streamCryptState_ = StreamCryptStateEnum.ECS_ENCRYPTING;
//DEBUG_ONLY( MpdUtilities.DebugLog(("CEncryptedStreamSocket: Finished Obufscation handshake with client %s (outgoing)"), DbgGetIPString()) );
break;
case NegotiatingStateEnum.ONS_BASIC_SERVER_DHANSWER:
{
Debug.Assert(cryptDHA_ != new BigInteger(0));
byte[] aBuffer = new byte[MuleConstants.PRIMESIZE_BYTES + 1];
fiReceiveBuffer_.Read(aBuffer, 0, Convert.ToInt32(MuleConstants.PRIMESIZE_BYTES));
BigInteger cryptDHAnswer =
new BigInteger(aBuffer, (int)MuleConstants.PRIMESIZE_BYTES);
BigInteger cryptDHPrime =
new BigInteger(dh768_p_, (int)MuleConstants.PRIMESIZE_BYTES); // our fixed prime
BigInteger cryptResult =
cryptDHAnswer.modPow(cryptDHA_, cryptDHPrime);
cryptDHA_ = 0;
Array.Clear(aBuffer, 0, aBuffer.Length);
// create the keys
Array.Copy(cryptResult.getBytes(), aBuffer, MuleConstants.PRIMESIZE_BYTES);
aBuffer[MuleConstants.PRIMESIZE_BYTES] = Convert.ToByte(MuleConstants.MAGICVALUE_REQUESTER);
MD5 md5 = MD5.Create();
rc4SendKey_ =
MuleUtilities.RC4CreateKey(md5.ComputeHash(aBuffer), 16);
aBuffer[MuleConstants.PRIMESIZE_BYTES] = Convert.ToByte(MuleConstants.MAGICVALUE_SERVER);
rc4ReceiveKey_ =
MuleUtilities.RC4CreateKey(md5.ComputeHash(aBuffer), 16);
negotiatingState_ = NegotiatingStateEnum.ONS_BASIC_SERVER_MAGICVALUE;
receiveBytesWanted_ = 4;
break;
}
case NegotiatingStateEnum.ONS_BASIC_SERVER_MAGICVALUE:
{
uint dwValue = fiReceiveBuffer_.ReadUInt32();
if (dwValue == MuleConstants.MAGICVALUE_SYNC)
{
// yup, the one or the other way it worked, this is an encrypted stream
MpdUtilities.DebugLog(("Received proper magic value after DH-Agreement from Serverconnection IP: %s"), DbgGetIPString());
// set the receiver key
negotiatingState_ = NegotiatingStateEnum.ONS_BASIC_SERVER_METHODTAGSPADLEN;
receiveBytesWanted_ = 3;
}
else
{
MpdUtilities.DebugLogError(("CEncryptedStreamSocket: Received wrong magic value after DH-Agreement from Serverconnection"), DbgGetIPString());
OnError(Convert.ToInt32(EMSocketErrorCodeEnum.ERR_ENCRYPTION));
return(-1);
}
break;
}
case NegotiatingStateEnum.ONS_BASIC_SERVER_METHODTAGSPADLEN:
DbgByEncryptionSupported = fiReceiveBuffer_.ReadUInt8();
DbgByEncryptionRequested = fiReceiveBuffer_.ReadUInt8();
if (DbgByEncryptionRequested != Convert.ToByte(EncryptionMethodsEnum.ENM_OBFUSCATION))
{
MpdUtilities.AddDebugLogLine(EDebugLogPriority.DLP_LOW, false, ("CEncryptedStreamSocket: Server %s preffered unsupported encryption method (%i)"), DbgGetIPString(), DbgByEncryptionRequested);
}
receiveBytesWanted_ = fiReceiveBuffer_.ReadUInt8();
negotiatingState_ = NegotiatingStateEnum.ONS_BASIC_SERVER_PADDING;
if (receiveBytesWanted_ > 16)
{
MpdUtilities.AddDebugLogLine(EDebugLogPriority.DLP_LOW, false, ("CEncryptedStreamSocket: Server %s sent more than 16 (%i) padding bytes"), DbgGetIPString(), receiveBytesWanted_);
}
if (receiveBytesWanted_ > 0)
{
break;
}
else
{
goto case NegotiatingStateEnum.ONS_BASIC_SERVER_PADDING;
}
case NegotiatingStateEnum.ONS_BASIC_SERVER_PADDING:
{
// ignore the random bytes (they are decrypted already), send the response, set status complete
SafeMemFile fileResponse = MpdObjectManager.CreateSafeMemFile(26);
fileResponse.WriteUInt32(MuleConstants.MAGICVALUE_SYNC);
byte bySelectedEncryptionMethod =
Convert.ToByte(EncryptionMethodsEnum.ENM_OBFUSCATION); // we do not support any further encryption in this version, so no need to look which the other client preferred
fileResponse.WriteUInt8(bySelectedEncryptionMethod);
byte byPadding = (byte)(MpdUtilities.GetRandomUInt8() % 16);
fileResponse.WriteUInt8(byPadding);
for (int i = 0; i < byPadding; i++)
{
fileResponse.WriteUInt8(MpdUtilities.GetRandomUInt8());
}
negotiatingState_ = NegotiatingStateEnum.ONS_BASIC_SERVER_DELAYEDSENDING;
SendNegotiatingData(fileResponse.Buffer, (uint)fileResponse.Length, 0, true); // don't actually send it right now, store it in our sendbuffer
streamCryptState_ = StreamCryptStateEnum.ECS_ENCRYPTING;
MpdUtilities.DebugLog(("CEncryptedStreamSocket: Finished DH Obufscation handshake with Server %s"), DbgGetIPString());
break;
}
default:
Debug.Assert(false);
break;
}
fiReceiveBuffer_.SeekToBegin();
}
fiReceiveBuffer_ = null;
return(nRead);
}
catch (Exception)
{
Debug.Assert(false);
OnError(Convert.ToInt32(EMSocketErrorCodeEnum.ERR_ENCRYPTION));
fiReceiveBuffer_ = null;
return(-1);
}
}
