Method StartNegotiation

src/EncryptedStreamSocket.cpp:369–432

}

void CEncryptedStreamSocket::StartNegotiation(bool bOutgoing)
{
	//printf("Starting socket negotiation\n");
	if (!bOutgoing) {
		//printf("Incoming connection negotiation on %s\n", (const char*) unicode2char(GetPeer()));
		m_NegotiatingState = ONS_BASIC_CLIENTA_RANDOMPART;
		m_StreamCryptState = ECS_NEGOTIATING;
		m_nReceiveBytesWanted = 4;
	} else if (m_StreamCryptState == ECS_PENDING) {
		//printf("Socket is client.pending on negotiation\n");
		CMemFile fileRequest(29);
		const uint8_t bySemiRandomNotProtocolMarker = GetSemiRandomNotProtocolMarker();
		fileRequest.WriteUInt8(bySemiRandomNotProtocolMarker);
		fileRequest.WriteUInt32(m_nRandomKeyPart);
		fileRequest.WriteUInt32(MAGICVALUE_SYNC);
		const uint8_t bySupportedEncryptionMethod = ENM_OBFUSCATION; // we do not support any further encryption in this version
		fileRequest.WriteUInt8(bySupportedEncryptionMethod);
		fileRequest.WriteUInt8(bySupportedEncryptionMethod); // so we also prefer this one
		uint8_t byPadding = (uint8_t)(GetRandomUint8() % (thePrefs::GetCryptTCPPaddingLength() + 1));
		fileRequest.WriteUInt8(byPadding);
		for (int i = 0; i < byPadding; i++) {
			fileRequest.WriteUInt8(GetRandomUint8());
		}

		m_NegotiatingState = ONS_BASIC_CLIENTB_MAGICVALUE;
		m_StreamCryptState = ECS_NEGOTIATING;
		m_nReceiveBytesWanted = 4;

		SendNegotiatingData(fileRequest.GetRawBuffer(), (uint32_t)fileRequest.GetLength(), 5);
	} else if (m_StreamCryptState == ECS_PENDING_SERVER) {
		//printf("Socket is server.pending on negotiation\n");
		CMemFile fileRequest(113);
		const uint8_t bySemiRandomNotProtocolMarker = GetSemiRandomNotProtocolMarker();
		fileRequest.WriteUInt8(bySemiRandomNotProtocolMarker);

		m_cryptDHA.Randomize((CryptoPP::AutoSeededRandomPool&)GetRandomPool(), DHAGREEMENT_A_BITS); // our random a
		wxASSERT( m_cryptDHA.MinEncodedSize() <= DHAGREEMENT_A_BITS / 8 );
		CryptoPP::Integer cryptDHPrime((uint8_t*)dh768_p, PRIMESIZE_BYTES);  // our fixed prime
		// calculate g^a % p
		CryptoPP::Integer cryptDHGexpAmodP = a_exp_b_mod_c(CryptoPP::Integer(2), m_cryptDHA, cryptDHPrime);
		wxASSERT( m_cryptDHA.MinEncodedSize() <= PRIMESIZE_BYTES );
		// put the result into a buffer
		uint8_t aBuffer[PRIMESIZE_BYTES];
		cryptDHGexpAmodP.Encode(aBuffer, PRIMESIZE_BYTES);

		fileRequest.Write(aBuffer, PRIMESIZE_BYTES);
		uint8 byPadding = (uint8)(GetRandomUint8() % 16); // add random padding
		fileRequest.WriteUInt8(byPadding);

		for (int i = 0; i < byPadding; i++) {
			fileRequest.WriteUInt8(GetRandomUint8());
		}

		m_NegotiatingState = ONS_BASIC_SERVER_DHANSWER;
		m_StreamCryptState = ECS_NEGOTIATING;
		m_nReceiveBytesWanted = 96;

		SendNegotiatingData(fileRequest.GetRawBuffer(), (uint32_t)fileRequest.GetLength(), (uint32_t)fileRequest.GetLength());