int CEncryptedStreamSocket::Negotiate(const uchar* pBuffer, uint32_t nLen){
	uint32_t nRead = 0;
	ASSERT( m_nReceiveBytesWanted > 0 );
	try{
		while (m_NegotiatingState != ONS_COMPLETE && m_nReceiveBytesWanted > 0){		
			if (m_nReceiveBytesWanted > 512){
				ASSERT( false );
				return 0;
			}
			
			if (m_pfiReceiveBuffer == NULL){
				BYTE* pReceiveBuffer = (BYTE*)malloc(512); // use a fixed size buffer
				if (pReceiveBuffer == NULL)
					AfxThrowMemoryException();
				m_pfiReceiveBuffer = new CSafeMemFile(pReceiveBuffer, 512);
			}
			const uint32_t nToRead =  min(nLen - nRead, m_nReceiveBytesWanted);
			m_pfiReceiveBuffer->Write(pBuffer + nRead, nToRead);
			nRead += nToRead;
			m_nReceiveBytesWanted -= nToRead;
			if (m_nReceiveBytesWanted > 0)
				return nRead;
			const uint32_t nCurrentBytesLen = (uint32_t)m_pfiReceiveBuffer->GetPosition();

			if (m_NegotiatingState != ONS_BASIC_CLIENTA_RANDOMPART && m_NegotiatingState != ONS_BASIC_SERVER_DHANSWER){ // don't have the keys yet
				BYTE* pCryptBuffer = m_pfiReceiveBuffer->Detach();
				RC4Crypt(pCryptBuffer, pCryptBuffer, nCurrentBytesLen, m_pRC4ReceiveKey);
				m_pfiReceiveBuffer->Attach(pCryptBuffer, 512);
			}
			m_pfiReceiveBuffer->SeekToBegin();

			switch (m_NegotiatingState){
				case ONS_NONE: // would be a bug
					ASSERT( false ); 
					return 0;
				case ONS_BASIC_CLIENTA_RANDOMPART:{
					ASSERT( m_pRC4ReceiveKey == NULL );

					uchar achKeyData[21];
					md4cpy(achKeyData, thePrefs.GetUserHash());
					achKeyData[16] = MAGICVALUE_REQUESTER;
					m_pfiReceiveBuffer->Read(achKeyData + 17, 4); // random key part sent from remote client

					MD5Sum md5(achKeyData, sizeof(achKeyData));
					m_pRC4ReceiveKey = RC4CreateKey(md5.GetRawHash(), 16, NULL);
					achKeyData[16] = MAGICVALUE_SERVER;
					md5.Calculate(achKeyData, sizeof(achKeyData));
					m_pRC4SendKey = RC4CreateKey(md5.GetRawHash(), 16, NULL);
						
					m_NegotiatingState = ONS_BASIC_CLIENTA_MAGICVALUE;
					m_nReceiveBytesWanted = 4;
					break;
				}
				case ONS_BASIC_CLIENTA_MAGICVALUE:{
					uint32_t dwValue = m_pfiReceiveBuffer->ReadUInt32();
					if (dwValue == MAGICVALUE_SYNC){
						// yup, the one or the other way it worked, this is an encrypted stream
						//DEBUG_ONLY( DebugLog(_T("Received proper magic value, clientIP: %s"), DbgGetIPString()) );
						// set the receiver key
						m_NegotiatingState = ONS_BASIC_CLIENTA_METHODTAGSPADLEN;
						m_nReceiveBytesWanted = 3;	
					}
					else{
						DebugLogError(_T("CEncryptedStreamSocket: Received wrong magic value from clientIP %s on a supposly encrytped stream / Wrong Header"), DbgGetIPString());
						OnError(ERR_ENCRYPTION);
						return (-1);
					}
					break;
			    }
				case ONS_BASIC_CLIENTA_METHODTAGSPADLEN:
					m_dbgbyEncryptionSupported = m_pfiReceiveBuffer->ReadUInt8();
					m_dbgbyEncryptionRequested = m_pfiReceiveBuffer->ReadUInt8();
					if (m_dbgbyEncryptionRequested != ENM_OBFUSCATION)
						AddDebugLogLine(DLP_LOW, false, _T("CEncryptedStreamSocket: Client %s preffered unsupported encryption method (%i)"), DbgGetIPString(), m_dbgbyEncryptionRequested);
					m_nReceiveBytesWanted = m_pfiReceiveBuffer->ReadUInt8();
					m_NegotiatingState = ONS_BASIC_CLIENTA_PADDING;
					//if (m_nReceiveBytesWanted > 16)
					//	AddDebugLogLine(DLP_LOW, false, _T("CEncryptedStreamSocket: Client %s sent more than 16 (%i) padding bytes"), DbgGetIPString(), m_nReceiveBytesWanted);
					if (m_nReceiveBytesWanted > 0)
						break;
				case ONS_BASIC_CLIENTA_PADDING:{
					// ignore the random bytes, send the response, set status complete
					CSafeMemFile fileResponse(26);
					fileResponse.WriteUInt32(MAGICVALUE_SYNC);
					const uint8_t bySelectedEncryptionMethod = 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);
					
					SOCKADDR_IN sockAddr = {0};
					int nSockAddrLen = sizeof(sockAddr);
					GetPeerName((SOCKADDR*)&sockAddr, &nSockAddrLen);	
					const uint8_t byPaddingLen = theApp.serverconnect->AwaitingTestFromIP(sockAddr.sin_addr.S_un.S_addr) ? 16 : (thePrefs.GetCryptTCPPaddingLength() + 1);
					uint8_t byPadding = (uint8_t)(cryptRandomGen.GenerateByte() % byPaddingLen);
					
					fileResponse.WriteUInt8(byPadding);
					for (int i = 0; i < byPadding; i++)
						fileResponse.WriteUInt8(static_cast<uint8_t>(rand() & 0xFF));
					SendNegotiatingData(fileResponse.GetBuffer(), (uint32_t)fileResponse.GetLength());
					m_NegotiatingState = ONS_COMPLETE;
					m_StreamCryptState = ECS_ENCRYPTING;
					//DEBUG_ONLY( DebugLog(_T("CEncryptedStreamSocket: Finished Obufscation handshake with client %s (incoming)"), DbgGetIPString()) );
					break;
				}
				case ONS_BASIC_CLIENTB_MAGICVALUE:{
					if (m_pfiReceiveBuffer->ReadUInt32() != MAGICVALUE_SYNC){
						DebugLogError(_T("CEncryptedStreamSocket: EncryptedstreamSyncError: Client sent wrong Magic Value as answer, cannot complete handshake (%s)"), DbgGetIPString());
						OnError(ERR_ENCRYPTION);
						return (-1);
					}
					m_NegotiatingState = ONS_BASIC_CLIENTB_METHODTAGSPADLEN;
					m_nReceiveBytesWanted = 2;
					break;
				}
				case ONS_BASIC_CLIENTB_METHODTAGSPADLEN:{
					m_dbgbyEncryptionMethodSet = m_pfiReceiveBuffer->ReadUInt8();
					if (m_dbgbyEncryptionMethodSet != ENM_OBFUSCATION){
						DebugLogError( _T("CEncryptedStreamSocket: Client %s set unsupported encryption method (%i), handshake failed"), DbgGetIPString(), m_dbgbyEncryptionMethodSet);
						OnError(ERR_ENCRYPTION);
						return (-1);						
					}
					m_nReceiveBytesWanted = m_pfiReceiveBuffer->ReadUInt8();
					m_NegotiatingState = ONS_BASIC_CLIENTB_PADDING;
					if (m_nReceiveBytesWanted > 0)
						break;
				}
				case ONS_BASIC_CLIENTB_PADDING:
					// ignore the random bytes, the handshake is complete
					m_NegotiatingState = ONS_COMPLETE;
					m_StreamCryptState = ECS_ENCRYPTING;
					//DEBUG_ONLY( DebugLog(_T("CEncryptedStreamSocket: Finished Obufscation handshake with client %s (outgoing)"), DbgGetIPString()) );
					break;
				case ONS_BASIC_SERVER_DHANSWER:{
					ASSERT( !m_cryptDHA.IsZero() );
					uchar aBuffer[PRIMESIZE_BYTES + 1];
					m_pfiReceiveBuffer->Read(aBuffer, PRIMESIZE_BYTES);
					CryptoPP::Integer cryptDHAnswer((byte*)aBuffer, PRIMESIZE_BYTES);
					CryptoPP::Integer cryptDHPrime((byte*)dh768_p, PRIMESIZE_BYTES);  // our fixed prime
					CryptoPP::Integer cryptResult = CryptoPP::a_exp_b_mod_c(cryptDHAnswer, m_cryptDHA, cryptDHPrime);
					
					m_cryptDHA = 0;
					DEBUG_ONLY( ZeroMemory(aBuffer, sizeof(aBuffer)) );
					ASSERT( cryptResult.MinEncodedSize() <= PRIMESIZE_BYTES );
					
					// create the keys
					cryptResult.Encode(aBuffer, PRIMESIZE_BYTES);					
					aBuffer[PRIMESIZE_BYTES] = MAGICVALUE_REQUESTER;
					MD5Sum md5(aBuffer, sizeof(aBuffer));
					m_pRC4SendKey = RC4CreateKey(md5.GetRawHash(), 16, NULL);
					aBuffer[PRIMESIZE_BYTES] = MAGICVALUE_SERVER;
					md5.Calculate(aBuffer, sizeof(aBuffer));
					m_pRC4ReceiveKey = RC4CreateKey(md5.GetRawHash(), 16, NULL);

					m_NegotiatingState = ONS_BASIC_SERVER_MAGICVALUE;
					m_nReceiveBytesWanted = 4;
					break;
				}
				case ONS_BASIC_SERVER_MAGICVALUE:{
					uint32_t dwValue = m_pfiReceiveBuffer->ReadUInt32();
					if (dwValue == MAGICVALUE_SYNC){
						// yup, the one or the other way it worked, this is an encrypted stream
						DebugLog(_T("Received proper magic value after DH-Agreement from Serverconnection IP: %s"), DbgGetIPString());
						// set the receiver key
						m_NegotiatingState = ONS_BASIC_SERVER_METHODTAGSPADLEN;
						m_nReceiveBytesWanted = 3;	
					}
					else{
						DebugLogError(_T("CEncryptedStreamSocket: Received wrong magic value after DH-Agreement from Serverconnection"), DbgGetIPString());
						OnError(ERR_ENCRYPTION);
						return (-1);
					}
					break;
			    }
				case ONS_BASIC_SERVER_METHODTAGSPADLEN:
					m_dbgbyEncryptionSupported = m_pfiReceiveBuffer->ReadUInt8();
					m_dbgbyEncryptionRequested = m_pfiReceiveBuffer->ReadUInt8();
					if (m_dbgbyEncryptionRequested != ENM_OBFUSCATION)
						AddDebugLogLine(DLP_LOW, false, _T("CEncryptedStreamSocket: Server %s preffered unsupported encryption method (%i)"), DbgGetIPString(), m_dbgbyEncryptionRequested);
					m_nReceiveBytesWanted = m_pfiReceiveBuffer->ReadUInt8();
					m_NegotiatingState = ONS_BASIC_SERVER_PADDING;
					if (m_nReceiveBytesWanted > 16)
						AddDebugLogLine(DLP_LOW, false, _T("CEncryptedStreamSocket: Server %s sent more than 16 (%i) padding bytes"), DbgGetIPString(), m_nReceiveBytesWanted);
					if (m_nReceiveBytesWanted > 0)
						break;
				case ONS_BASIC_SERVER_PADDING:{
					// ignore the random bytes (they are decrypted already), send the response, set status complete
					CSafeMemFile fileResponse(26);
					fileResponse.WriteUInt32(MAGICVALUE_SYNC);
					const uint8_t bySelectedEncryptionMethod = 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);
					uint8_t byPadding = (uint8_t)(cryptRandomGen.GenerateByte() % 16);
					fileResponse.WriteUInt8(byPadding);
					for (int i = 0; i < byPadding; i++)
						fileResponse.WriteUInt8(static_cast<uint8_t>(rand() & 0xFF));
					
					m_NegotiatingState = ONS_BASIC_SERVER_DELAYEDSENDING;
					SendNegotiatingData(fileResponse.GetBuffer(), (uint32_t)fileResponse.GetLength(), 0, true); // don't actually send it right now, store it in our sendbuffer
					m_StreamCryptState = ECS_ENCRYPTING;
					DEBUG_ONLY( DebugLog(_T("CEncryptedStreamSocket: Finished DH Obufscation handshake with Server %s"), DbgGetIPString()) );
					break;
				}
				default:
					ASSERT( false );
			}
			m_pfiReceiveBuffer->SeekToBegin();
		}
		if (m_pfiReceiveBuffer != NULL)
			free(m_pfiReceiveBuffer->Detach());
		delete m_pfiReceiveBuffer;
		m_pfiReceiveBuffer = NULL;
		return nRead;
	}
	catch(CFileException* error){
		// can only be caused by a bug in negationhandling, not by the datastream
		error->Delete();
		ASSERT( false );
		OnError(ERR_ENCRYPTION);
		if (m_pfiReceiveBuffer != NULL)
			free(m_pfiReceiveBuffer->Detach());
		delete m_pfiReceiveBuffer;
		m_pfiReceiveBuffer = NULL;
		return (-1);
	}

}
Пример #2
0
int CEncryptedStreamSocket::Negotiate(const uint8* pBuffer, uint32 nLen)
{
	uint32_t nRead = 0;
	wxASSERT( m_nReceiveBytesWanted > 0 );

	//DumpMem(pBuffer, nLen, wxT("Negotiate buffer: "));

	try {
		while (m_NegotiatingState != ONS_COMPLETE && m_nReceiveBytesWanted > 0) {
			if (m_nReceiveBytesWanted > 512) {
				wxFAIL;
				return 0;
			}

			const uint32_t nToRead =  std::min(nLen - nRead, m_nReceiveBytesWanted);
			//printf("Reading %i bytes, add from %i position on %i position\n",nToRead, nRead, (int)m_pfiReceiveBuffer.GetPosition());
			//DumpMem(pBuffer + nRead, nToRead, wxT("Recv Buffer: "));
			m_pfiReceiveBuffer.Write(pBuffer + nRead, nToRead);
			nRead += nToRead;
			m_nReceiveBytesWanted -= nToRead;
			if (m_nReceiveBytesWanted > 0)  {
				return nRead;
			}

			if (m_NegotiatingState != ONS_BASIC_CLIENTA_RANDOMPART && m_NegotiatingState != ONS_BASIC_SERVER_DHANSWER) {
				// We have the keys, decrypt
				//printf("We have the keys, so decrypt away on %s\n", (const char*) unicode2char(DbgGetIPString()));
				m_pfiReceiveBuffer.Encrypt();
			}

			m_pfiReceiveBuffer.Seek(0);

			switch (m_NegotiatingState) {
				case ONS_NONE: // would be a bug
					wxFAIL;
					return 0;
				case ONS_BASIC_CLIENTA_RANDOMPART: {
					//printf("We are on ONS_BASIC_CLIENTA_RANDOMPART, create the keys on %s\n", (const char*) unicode2char(DbgGetIPString()));
					// This creates the send/receive keys.

					uint8_t achKeyData[21];
					md4cpy(achKeyData, thePrefs::GetUserHash().GetHash());
					m_pfiReceiveBuffer.Read(achKeyData + 17, 4);

					achKeyData[16] = MAGICVALUE_REQUESTER;

					//DumpMem(achKeyData, sizeof(achKeyData), wxT("ach:"));

					MD5Sum md5(achKeyData, sizeof(achKeyData));
					//DumpMem(md5.GetRawHash(), 16, wxT("Md5:"));
					m_pfiReceiveBuffer.SetKey(md5);

					achKeyData[16] = MAGICVALUE_SERVER;
					md5.Calculate(achKeyData, sizeof(achKeyData));
					m_pfiSendBuffer.SetKey(md5);

					m_NegotiatingState = ONS_BASIC_CLIENTA_MAGICVALUE;
					m_nReceiveBytesWanted = 4;
					break;
				}
				case ONS_BASIC_CLIENTA_MAGICVALUE: {
					// Check the magic value to confirm encryption works.
					//printf("Creating magic value on negotiate on %s\n", (const char*) unicode2char(DbgGetIPString()));

					uint32_t dwValue = m_pfiReceiveBuffer.ReadUInt32();

					if (dwValue == MAGICVALUE_SYNC) {
						// yup, the one or the other way it worked, this is an encrypted stream
						//DEBUG_ONLY( DebugLog(_T("Received proper magic value, clientIP: %s"), DbgGetIPString()) );
						// set the receiver key
						//printf("Magic value works on %s\n", (const char*) unicode2char(DbgGetIPString()));
						m_NegotiatingState = ONS_BASIC_CLIENTA_METHODTAGSPADLEN;
						m_nReceiveBytesWanted = 3;
					} else {
						//printf("Wrong magic value: 0x%x != 0x%x on %s\n",dwValue, MAGICVALUE_SYNC, (const char*)unicode2char(DbgGetIPString()));
						//DebugLogError(_T("CEncryptedStreamSocket: Received wrong magic value from clientIP %s on a supposly encrytped stream / Wrong Header"), DbgGetIPString());
						OnError(ERR_ENCRYPTION);
						return (-1);
					}
					break;
				}
				case ONS_BASIC_CLIENTA_METHODTAGSPADLEN: {
					// Get encryption method and padding.
					// Might fall back to padding process, but the bytes will be ignored.
					//printf("Getting encryption method on negotiation\n");

					m_dbgbyEncryptionSupported = m_pfiReceiveBuffer.ReadUInt8();
					m_dbgbyEncryptionRequested = m_pfiReceiveBuffer.ReadUInt8();

					if (m_dbgbyEncryptionRequested != ENM_OBFUSCATION) {
						//printf("Unsupported encryption method!\n");
//						AddDebugLogLine(DLP_LOW, false, _T("CEncryptedStreamSocket: Client %s preffered unsupported encryption method (%i)"), DbgGetIPString(), m_dbgbyEncryptionRequested);
					}

					m_nReceiveBytesWanted = m_pfiReceiveBuffer.ReadUInt8();
					m_NegotiatingState = ONS_BASIC_CLIENTA_PADDING;

					if (m_nReceiveBytesWanted > 0) {
						// No padding
						break;
					}
				}
				case ONS_BASIC_CLIENTA_PADDING: {
					//printf("Negotiating on padding, completing\n");
					// ignore the random bytes, send the response, set status complete
					CMemFile fileResponse(26);
					fileResponse.WriteUInt32(MAGICVALUE_SYNC);
					const uint8_t bySelectedEncryptionMethod = 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);

					amuleIPV4Address address;
					GetPeer(address);
					const uint8_t byPaddingLen = theApp->serverconnect->AwaitingTestFromIP(StringIPtoUint32(address.IPAddress())) ? 16 : (thePrefs::GetCryptTCPPaddingLength() + 1);
					uint8_t byPadding = (uint8_t)(GetRandomUint8() % byPaddingLen);

					fileResponse.WriteUInt8(byPadding);
					for (int i = 0; i < byPadding; i++) {
						fileResponse.WriteUInt8((uint8_t)rand());
					}
					SendNegotiatingData(fileResponse.GetRawBuffer(), (uint32_t)fileResponse.GetLength());
					m_NegotiatingState = ONS_COMPLETE;
					m_StreamCryptState = ECS_ENCRYPTING;
					//DEBUG_ONLY( DebugLog(_T("CEncryptedStreamSocket: Finished Obufscation handshake with client %s (incoming)"), DbgGetIPString()) );
					break;
				}
				case ONS_BASIC_CLIENTB_MAGICVALUE: {
					//printf("Negotiating on magic value\n");
					if (m_pfiReceiveBuffer.ReadUInt32() != MAGICVALUE_SYNC) {
						//DebugLogError(_T("CEncryptedStreamSocket: EncryptedstreamSyncError: Client sent wrong Magic Value as answer, cannot complete handshake (%s)"), DbgGetIPString());
						OnError(ERR_ENCRYPTION);
						return (-1);
					}
					m_NegotiatingState = ONS_BASIC_CLIENTB_METHODTAGSPADLEN;
					m_nReceiveBytesWanted = 2;
					break;
				}
				case ONS_BASIC_CLIENTB_METHODTAGSPADLEN: {
					//printf("Negotiating on client B pad length\n");
					m_dbgbyEncryptionMethodSet = m_pfiReceiveBuffer.ReadUInt8();
					if (m_dbgbyEncryptionMethodSet != ENM_OBFUSCATION) {
						//DebugLogError( _T("CEncryptedStreamSocket: Client %s set unsupported encryption method (%i), handshake failed"), DbgGetIPString(), m_dbgbyEncryptionMethodSet);
						OnError(ERR_ENCRYPTION);
						return (-1);
					}
					m_nReceiveBytesWanted = m_pfiReceiveBuffer.ReadUInt8();
					m_NegotiatingState = ONS_BASIC_CLIENTB_PADDING;
					if (m_nReceiveBytesWanted > 0) {
						break;
					}
				}
				case ONS_BASIC_CLIENTB_PADDING:
					//printf("Negotiating on client B padding, handshake complete\n");
					// ignore the random bytes, the handshake is complete
					m_NegotiatingState = ONS_COMPLETE;
					m_StreamCryptState = ECS_ENCRYPTING;
					//DEBUG_ONLY( DebugLog(_T("CEncryptedStreamSocket: Finished Obufscation handshake with client %s (outgoing)"), DbgGetIPString()) );
					break;
				case ONS_BASIC_SERVER_DHANSWER: {
					wxASSERT( !m_cryptDHA.IsZero() );
					uint8_t aBuffer[PRIMESIZE_BYTES + 1];
					m_pfiReceiveBuffer.Read(aBuffer, PRIMESIZE_BYTES);
					CryptoPP::Integer cryptDHAnswer((byte*)aBuffer, PRIMESIZE_BYTES);
					CryptoPP::Integer cryptDHPrime((byte*)dh768_p, PRIMESIZE_BYTES);  // our fixed prime
					CryptoPP::Integer cryptResult = a_exp_b_mod_c(cryptDHAnswer, m_cryptDHA, cryptDHPrime);

					m_cryptDHA = 0;
					//DEBUG_ONLY( ZeroMemory(aBuffer, sizeof(aBuffer)) );
					wxASSERT( cryptResult.MinEncodedSize() <= PRIMESIZE_BYTES );

					// create the keys
					cryptResult.Encode(aBuffer, PRIMESIZE_BYTES);
					aBuffer[PRIMESIZE_BYTES] = MAGICVALUE_REQUESTER;
					MD5Sum md5(aBuffer, sizeof(aBuffer));
					m_pfiSendBuffer.SetKey(md5);
					aBuffer[PRIMESIZE_BYTES] = MAGICVALUE_SERVER;
					md5.Calculate(aBuffer, sizeof(aBuffer));
					m_pfiReceiveBuffer.SetKey(md5);

					m_NegotiatingState = ONS_BASIC_SERVER_MAGICVALUE;
					m_nReceiveBytesWanted = 4;
					break;
				}
				case ONS_BASIC_SERVER_MAGICVALUE: {
					uint32_t dwValue = m_pfiReceiveBuffer.ReadUInt32();
					if (dwValue == MAGICVALUE_SYNC) {
						// yup, the one or the other way it worked, this is an encrypted stream
						//DebugLog(_T("Received proper magic value after DH-Agreement from Serverconnection IP: %s"), DbgGetIPString());
						// set the receiver key
						m_NegotiatingState = ONS_BASIC_SERVER_METHODTAGSPADLEN;
						m_nReceiveBytesWanted = 3;
					} else {
						//DebugLogError(_T("CEncryptedStreamSocket: Received wrong magic value after DH-Agreement from Serverconnection"), DbgGetIPString());
						OnError(ERR_ENCRYPTION);
						return (-1);
					}
					break;
				}
				case ONS_BASIC_SERVER_METHODTAGSPADLEN:
					m_dbgbyEncryptionSupported = m_pfiReceiveBuffer.ReadUInt8();
					m_dbgbyEncryptionRequested = m_pfiReceiveBuffer.ReadUInt8();
					if (m_dbgbyEncryptionRequested != ENM_OBFUSCATION) {
	//					AddDebugLogLine(DLP_LOW, false, _T("CEncryptedStreamSocket: Server %s preffered unsupported encryption method (%i)"), DbgGetIPString(), m_dbgbyEncryptionRequested);
					}
					m_nReceiveBytesWanted = m_pfiReceiveBuffer.ReadUInt8();
					m_NegotiatingState = ONS_BASIC_SERVER_PADDING;
					if (m_nReceiveBytesWanted > 0) {
						break;
					}
				case ONS_BASIC_SERVER_PADDING: {
					// ignore the random bytes (they are decrypted already), send the response, set status complete
					CMemFile fileResponse(26);
					fileResponse.WriteUInt32(MAGICVALUE_SYNC);
					const uint8_t bySelectedEncryptionMethod = 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);

					// Server callback connection only allows 16 bytes of padding.
					uint8_t byPadding = (uint8_t)(GetRandomUint8() % 16);
					fileResponse.WriteUInt8(byPadding);

					for (int i = 0; i < byPadding; i++) {
						fileResponse.WriteUInt8((uint8_t)rand());
					}

					m_NegotiatingState = ONS_BASIC_SERVER_DELAYEDSENDING;
					SendNegotiatingData(fileResponse.GetRawBuffer(), (uint32_t)fileResponse.GetLength(), 0, true); // don't actually send it right now, store it in our sendbuffer
					m_StreamCryptState = ECS_ENCRYPTING;
					//DEBUG_ONLY( DebugLog(_T("CEncryptedStreamSocket: Finished DH Obufscation handshake with Server %s"), DbgGetIPString()) );
					break;
				}
				default:
					wxFAIL;
			}
			m_pfiReceiveBuffer.ResetData();
		}
		return nRead;
	} catch(...) {
		// can only be caused by a bug in negationhandling, not by the datastream
		//error->Delete();
		//printf("Bug on negotiation?\n");
		wxFAIL;
		OnError(ERR_ENCRYPTION);
		m_pfiReceiveBuffer.ResetData();
		return (-1);
	}
}