Method EncryptSendServer

src/EncryptedDatagramSocket.cpp:432–486

}

int CEncryptedDatagramSocket::EncryptSendServer(uint8_t** ppbyBuf, int nBufLen, uint32_t dwBaseKey)
{
	wxASSERT( thePrefs::IsServerCryptLayerUDPEnabled() );
	wxASSERT( dwBaseKey != 0 );

	uint16_t nRandomKeyPart = GetRandomUint16();

	uint8_t achKeyData[7];
	PokeUInt32(achKeyData, dwBaseKey);
	achKeyData[4] = MAGICVALUE_UDP_CLIENTSERVER;
	PokeUInt16(achKeyData + 5, nRandomKeyPart);
	MD5Sum md5(achKeyData, sizeof(achKeyData));
	CRC4EncryptableBuffer sendbuffer;
	sendbuffer.SetKey(md5, true);

	// create the semi random byte encryption header
	uint8_t bySemiRandomNotProtocolMarker = 0;
	int i;

	for (i = 0; i < 128; i++) {
		bySemiRandomNotProtocolMarker = GetRandomUint8();
		if (bySemiRandomNotProtocolMarker != OP_EDONKEYPROT) { // not allowed values
			break;
		}
	}

	if (i >= 128) {
		// either we have _real_ bad luck or the randomgenerator is a bit messed up
		wxFAIL;
		bySemiRandomNotProtocolMarker = 0x01;
	}

	uint8_t byPadLen = 0;			// padding disabled for UDP currently
	uint32_t nCryptedLen = nBufLen + byPadLen + CRYPT_HEADER_WITHOUTPADDING;
	uint8_t* pachCryptedBuffer = new uint8_t[nCryptedLen];

	pachCryptedBuffer[0] = bySemiRandomNotProtocolMarker;
	PokeUInt16(pachCryptedBuffer + 1, nRandomKeyPart);

	uint32_t dwMagicValue = ENDIAN_SWAP_32(MAGICVALUE_UDP_SYNC_SERVER);
	sendbuffer.RC4Crypt((uint8_t*)&dwMagicValue, pachCryptedBuffer + 3, 4);

	sendbuffer.RC4Crypt((uint8_t*)&byPadLen, pachCryptedBuffer + 7, 1);

	for (int j = 0; j < byPadLen; j++){
		uint8_t byRand = (uint8_t)rand();	// they actually don't really need to be random, but it doesn't hurt either
		sendbuffer.RC4Crypt((uint8_t*)&byRand, pachCryptedBuffer + CRYPT_HEADER_WITHOUTPADDING + j, 1);
	}
	sendbuffer.RC4Crypt(*ppbyBuf, pachCryptedBuffer + CRYPT_HEADER_WITHOUTPADDING + byPadLen, nBufLen);
	delete[] *ppbyBuf;
	*ppbyBuf = pachCryptedBuffer;

	theStats::AddUpOverheadCrypt(nCryptedLen - nBufLen);
	return nCryptedLen;
}