Add low level OpenSSL example (#1828)

Co-authored-by: David Pedersen <[email protected]>

examples/low-level-openssl/src/main.rs

@@ -0,0 +1,88 @@
+use openssl::ssl::{Ssl, SslAcceptor, SslFiletype, SslMethod};
+use tokio_openssl::SslStream;
+
+use axum::{extract::ConnectInfo, routing::get, Router};
+use futures_util::future::poll_fn;
+use hyper::server::{
+    accept::Accept,
+    conn::{AddrIncoming, Http},
+};
+use std::{net::SocketAddr, path::PathBuf, pin::Pin, sync::Arc};
+use tokio::net::TcpListener;
+use tower::MakeService;
+
+use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt};
+
+#[tokio::main]
+async fn main() {
+    tracing_subscriber::registry()
+        .with(
+            tracing_subscriber::EnvFilter::try_from_default_env()
+                .unwrap_or_else(|_| "example_low_level_openssl=debug".into()),
+        )
+        .with(tracing_subscriber::fmt::layer())
+        .init();
+
+    let mut tls_builder = SslAcceptor::mozilla_modern_v5(SslMethod::tls()).unwrap();
+
+    tls_builder
+        .set_certificate_file(
+            PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+                .join("self_signed_certs")
+                .join("cert.pem"),
+            SslFiletype::PEM,
+        )
+        .unwrap();
+
+    tls_builder
+        .set_private_key_file(
+            PathBuf::from(env!("CARGO_MANIFEST_DIR"))
+                .join("self_signed_certs")
+                .join("key.pem"),
+            SslFiletype::PEM,
+        )
+        .unwrap();
+
+    tls_builder.check_private_key().unwrap();
+
+    let acceptor = tls_builder.build();
+
+    let listener = TcpListener::bind("127.0.0.1:3000").await.unwrap();
+    let mut listener = AddrIncoming::from_listener(listener).unwrap();
+
+    let protocol = Arc::new(Http::new());
+
+    let mut app = Router::new()
+        .route("/", get(handler))
+        .into_make_service_with_connect_info::<SocketAddr>();
+
+    tracing::info!("listening on https://localhost:3000");
+
+    loop {
+        let stream = poll_fn(|cx| Pin::new(&mut listener).poll_accept(cx))
+            .await
+            .unwrap()
+            .unwrap();
+
+        let acceptor = acceptor.clone();
+
+        let protocol = protocol.clone();
+
+        let svc = app.make_service(&stream);
+
+        tokio::spawn(async move {
+            let ssl = Ssl::new(acceptor.context()).unwrap();
+            let mut tls_stream = SslStream::new(ssl, stream).unwrap();
+
+            SslStream::accept(Pin::new(&mut tls_stream)).await.unwrap();
+
+            let _ = protocol
+                .serve_connection(tls_stream, svc.await.unwrap())
+                .await;
+        });
+    }
+}
+
+async fn handler(ConnectInfo(addr): ConnectInfo<SocketAddr>) -> String {
+    addr.to_string()
+}