AuraVPN/crates/aura-transport/tests/tcp_loopback.rs

//! End-to-end loopback test for the TLS-443 / TCP fallback transport: real outer rustls TLS over
//! plain TCP on 127.0.0.1, full inner Aura mutual-auth handshake, packet echo.
//!
//! Also covers:
//! * A custom (non-default) ALPN advertisement.
//! * The "accept-any" outer-cert guarantee: the client connects with an outer SNI that does NOT
//!   match the server's outer-TLS certificate, the outer TLS handshake completes anyway (because
//!   the client uses [`AcceptAnyServerCert`]), and the inner Aura mutual auth still succeeds.

use aura_pki::AuraCa;
use aura_proto::{ClientConfig, PacketConnection, ServerConfig};
use aura_transport::{TcpClient, TcpOpts, TcpServer};

const SERVER_NAME: &str = "localhost";
const CLIENT_ID: &str = "client-tcp";

/// Mint a fresh CA + server("localhost") + client("client-tcp") and build the proto configs.
fn make_configs() -> (ServerConfig, ClientConfig) {
    let ca = AuraCa::generate("Aura Test CA").expect("generate CA");
    let server = ca
        .issue_server_cert(SERVER_NAME)
        .expect("issue server cert");
    let client = ca.issue_client_cert(CLIENT_ID).expect("issue client cert");
    let ca_pem = ca.ca_cert_pem();
    let scfg = ServerConfig {
        ca_cert_pem: ca_pem.clone(),
        server_cert_pem: server.cert_pem,
        server_key_pem: server.key_pem,
    };
    let ccfg = ClientConfig {
        ca_cert_pem: ca_pem,
        client_cert_pem: client.cert_pem,
        client_key_pem: client.key_pem,
        server_name: SERVER_NAME.to_string(),
    };
    (scfg, ccfg)
}

/// Drive a single loopback handshake + 3-packet echo. `client_sni` is the OUTER TLS SNI the client
/// presents; it is independent of the server cert (the client uses an accept-any verifier).
async fn run_case(opts: TcpOpts, client_sni: &str) {
    let (scfg, ccfg) = make_configs();
    let server = TcpServer::bind("127.0.0.1:0".parse().unwrap(), scfg, opts.clone())
        .await
        .expect("bind server");
    let addr = server.local_addr().expect("local addr");

    let server_task = tokio::spawn(async move {
        let conn = server.accept().await.expect("server handshake");
        assert_eq!(conn.peer_id(), Some(CLIENT_ID), "verified client id");
        // Echo three packets back to the client.
        for _ in 0..3 {
            let pkt = conn.recv_packet().await.expect("server recv");
            conn.send_packet(&pkt).await.expect("server echo");
        }
    });

    let client = TcpClient::connect(addr, client_sni, ccfg, opts)
        .await
        .expect("client handshake");
    assert_eq!(
        client.peer_id(),
        Some(SERVER_NAME),
        "inner handshake verified the server CN"
    );

    // Exchange packets of varying sizes (incl. a large one) and assert the echo matches.
    for i in 0..3u16 {
        let payload = vec![(i as u8).wrapping_add(1); 100 + (i as usize) * 600]; // 100, 700, 1300 bytes
        client.send_packet(&payload).await.expect("client send");
        let echoed = client.recv_packet().await.expect("client recv");
        assert_eq!(echoed, payload, "round-trip payload mismatch");
    }

    server_task.await.expect("server task");
}

/// Baseline: default ALPN advert (`h2`, `http/1.1`), outer SNI matches the server cert SAN.
#[tokio::test]
async fn tcp_loopback_end_to_end() {
    run_case(TcpOpts::default(), SERVER_NAME).await;
}

/// A custom ALPN list still negotiates and runs the handshake.
#[tokio::test]
async fn tcp_loopback_with_custom_alpn() {
    let opts = TcpOpts {
        alpn: Some(vec![b"http/1.1".to_vec()]),
    };
    run_case(opts, SERVER_NAME).await;
}

/// The client uses [`AcceptAnyServerCert`] on the outer TLS layer, so an outer SNI that has nothing
/// to do with the server's real certificate must still complete the TLS handshake; the inner Aura
/// mutual auth then proves identity. This is the security model: outer = camouflage, inner = trust.
#[tokio::test]
async fn tcp_loopback_outer_sni_mismatch_still_connects() {
    run_case(TcpOpts::default(), "definitely-not-the-server.example").await;
}