An posssible security issue in RakNet connect()

[Kiddinglife]

Raknet uses Diffie-Hellman key agreement protocol to do key exchange with a precondition that the long-term server public key is given to clients in some secured way(possibly hard-coded in executive).
PS. the public key i refer to has nothing to do with RSA. Some possible bugs in connect() function makes it very vulnerable to the MITM attacks, the explanations are shown below:

1. Client keeps secret of its private key c but send its public key C to server in challenge
2. Server answers the challenge
3. the client side public key and private key is generated based on the server side public key

in function KeyAgreementInitiator::GenerateChallenge()
// A = client public key,a = client private key
GenerateKey(math, csprng, a);

However math is initialised based on server side public key in function KeyAgreementInitiator::Initialize()
// Unpack the responder's public key
if (!math->LoadVerifyAffineXY(responder_public_key, responder_public_key + KeyBytes, B))
return false;

So, as we see, in the whole sage, the most important variable is server side public key that is pre-given to client. However, Raknet send it to client in the id_connection_request_replay_1 message in clear text !

Someone has done research on this part and we can talk about it. This problem really has been bothering me a long time.

[larku]

Hey Kiddinglife,

This is some interesting analysis..

Do you have any ideas on how to address this? I haven't yet absorbed the issue properly so I don't have anything of value to add. I'd like to find some time to remedy this, so ideas would be great.