Correct way to implement private relay?

[Snarpix]

What is the correct way to implement private relay?

I'm thinking about modifying quic or tls config, to check server and client certificates, but rustls::Server/ClientConfig are private in quic and tls.

I can create a copy of libp2p-tls crate and add client\server cert validation, but it seems non-idiomatic.

[Snarpix]

I have found pnet module that does what I want for TCP.

But how can I use pnet for quic?

 let mut swarm = libp2p::SwarmBuilder::with_existing_identity(keypair)
        .with_tokio()
        .with_other_transport(|keypair| {
            let transport = tcp::tokio::Transport::new(tcp::Config::new())
                .and_then(move |socket, _| pnet::PnetConfig::new(psk).handshake(socket));
            let auth = noise::Config::new(keypair)?;
            let mux = yamux::Config::default();

            let tcp_transport = transport
                .upgrade(Version::V1Lazy)
                .authenticate(auth)
                .multiplex(mux);

            Ok(tcp_transport)
        })
        .unwrap()

[gnattu]

I encountered a similar issue and ended up forking libp2p-tls to create my own certification validation mechanism. Upon examining the current implementations, I found that much of the connection handling focuses on ensuring that the other end is libp2p based rather than based on my-program, which makes it difficult to reject connections from other libp2p clients.

A more supported approach would be to implement your own protocol and include it in libp2p::identify. Then, you can reject all clients (such as by immediately closing the connection) that do not support your defined protocol. You can use a method to encrypt your protocol string with the PSK, and then let the remote side decrypt this string using the pre-shared key and check if the protocol string matches, if you want to additionally authenticate clients using PSK. However, I'm not a big fan of this approach because I prefer the connection to be rejected by TLS, as tearing down the connections in the swarm would trigger many event listeners, which would add unnecessary complexity for me to handle.

Additionally, the concept of pnet is somewhat outdated in 2024, and we want to use something better. I don't like the idea of encrypting twice when we can simply reject the remote certificate, but I understand that not all libp2p programs are TLS-based, so they need to come up with a solution that works in general. However, if we are implementing something like this we are very likely to have our own program-defined auth and we don't have to care about other programs.

[thomaseizinger]

Another option is to use https://github.com/libp2p/rust-libp2p/tree/master/misc/allow-block-list and just define which peers are allowed to connect to you. Or you implement your own connection management by implementing NetworkBehaviour.

[dhuseby]

This is what I use for my private relays (i.e. a hard coded list of allowed peers since I control the identities all peers use)