Method EncryptSendClient

src/EncryptedDatagramSocket.cpp:264–375

Encrypt packet. Key used: clientHashOrKadID != NULL -> clientHashOrKadID clientHashOrKadID == NULL && kad && receiverVerifyKey != 0 -> receiverVerifyKey else -> ASSERT

// clientHashOrKadID == NULL && kad && receiverVerifyKey != 0	-> receiverVerifyKey
// else								-> ASSERT
int CEncryptedDatagramSocket::EncryptSendClient(uint8_t **buf, int bufLen, const uint8_t *clientHashOrKadID, bool kad, uint32_t receiverVerifyKey, uint32_t senderVerifyKey)
{
	wxASSERT(theApp->GetPublicIP() != 0 || kad);
	wxASSERT(thePrefs::IsClientCryptLayerSupported());
	wxASSERT(clientHashOrKadID != NULL || receiverVerifyKey != 0);
	wxASSERT((receiverVerifyKey == 0 && senderVerifyKey == 0) || kad);

	uint8_t padLen = 0;			// padding disabled for UDP currently
	const uint32_t cryptHeaderLen = padLen + CRYPT_HEADER_WITHOUTPADDING + (kad ? 8 : 0);
	uint32_t cryptedLen = bufLen + cryptHeaderLen;
	uint8_t *cryptedBuffer = new uint8_t[cryptedLen];
	bool kadRecvKeyUsed = false;

	uint16_t randomKeyPart = GetRandomUint16();
	CRC4EncryptableBuffer sendbuffer;
	MD5Sum md5;
	if (kad) {
		if ((clientHashOrKadID == NULL || CMD4Hash(clientHashOrKadID).IsEmpty()) && receiverVerifyKey != 0) {
			kadRecvKeyUsed = true;
			uint8_t keyData[6];
			PokeUInt32(keyData, receiverVerifyKey);
			PokeUInt16(keyData+4, randomKeyPart);
			md5.Calculate(keyData, sizeof(keyData));
			//DEBUG_ONLY( DebugLog(_T("Creating obfuscated Kad packet encrypted by ReceiverKey (%u)"), nReceiverVerifyKey) );
		}
		else if (clientHashOrKadID != NULL && !CMD4Hash(clientHashOrKadID).IsEmpty()) {
			uint8_t keyData[18];
			md4cpy(keyData, clientHashOrKadID);
			PokeUInt16(keyData+16, randomKeyPart);
			md5.Calculate(keyData, sizeof(keyData));
			//DEBUG_ONLY( DebugLog(_T("Creating obfuscated Kad packet encrypted by Hash/NodeID %s"), md4str(pachClientHashOrKadID)) );
		}
		else {
			delete [] cryptedBuffer;
			wxFAIL;
			return bufLen;
		}
	} else {
		uint8_t keyData[23];
		md4cpy(keyData, clientHashOrKadID);
		PokeUInt32(keyData+16, theApp->GetPublicIP());
		PokeUInt16(keyData+21, randomKeyPart);
		keyData[20] = MAGICVALUE_UDP;
		md5.Calculate(keyData, sizeof(keyData));
	}

	sendbuffer.SetKey(md5, true);

	// create the semi random byte encryption header
	uint8_t semiRandomNotProtocolMarker = 0;
	int i;
	for (i = 0; i < 128; i++) {
		semiRandomNotProtocolMarker = GetRandomUint8();
		semiRandomNotProtocolMarker = kad ? (semiRandomNotProtocolMarker & 0xFE) : (semiRandomNotProtocolMarker | 0x01); // set the ed2k/kad marker bit
		if (kad) {
			// set the ed2k/kad and nodeid/recvkey markerbit
			semiRandomNotProtocolMarker = kadRecvKeyUsed ? ((semiRandomNotProtocolMarker & 0xFE) | 0x02) : (semiRandomNotProtocolMarker & 0xFC);
		} else {