Method DecryptReceivedClient

src/EncryptedDatagramSocket.cpp:123–258

{}

int CEncryptedDatagramSocket::DecryptReceivedClient(uint8_t *bufIn, int bufLen, uint8_t **bufOut, uint32_t ip, uint32_t *receiverVerifyKey, uint32_t *senderVerifyKey)
{
	int result = bufLen;
	*bufOut = bufIn;

	if (receiverVerifyKey == NULL || senderVerifyKey == NULL) {
		wxFAIL;
		return result;
	}

	*receiverVerifyKey = 0;
	*senderVerifyKey = 0;

	if (result <= CRYPT_HEADER_WITHOUTPADDING /*|| !thePrefs.IsClientCryptLayerSupported()*/) {
		return result;
	}

	switch (bufIn[0]) {
		case OP_EMULEPROT:
		case OP_KADEMLIAPACKEDPROT:
		case OP_KADEMLIAHEADER:
		case OP_UDPRESERVEDPROT1:
		case OP_UDPRESERVEDPROT2:
		case OP_PACKEDPROT:
			return result; // no encrypted packet (see description on top)
		default:
			;
	}

	// might be an encrypted packet, try to decrypt
	CRC4EncryptableBuffer receivebuffer;
	uint32_t value = 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
	uint8_t currentTry = ((bufIn[0] & 0x03) == 3) ? 1 : (bufIn[0] & 0x03);
	uint8_t tries;
	if (Kademlia::CKademlia::GetPrefs() == NULL) {
		// if kad never run, no point in checking anything except for ed2k encryption
		tries = 1;
		currentTry = 1;
	} else {
		tries = 3;
	}
	bool kad = false;
	do {
		receivebuffer.FullReset();
		tries--;
		MD5Sum md5;

		if (currentTry == 0) {
			// kad packet with NodeID as key
			kad = true;
			if (Kademlia::CKademlia::GetPrefs()) {
				uint8_t keyData[18];
				Kademlia::CKademlia::GetPrefs()->GetKadID().StoreCryptValue((uint8_t *)&keyData);
				memcpy(keyData + 16, bufIn + 1, 2); // random key part sent from remote client
				md5.Calculate(keyData, sizeof(keyData));
			}