Add tests for holding back alerts

src/server.rs

@@ -111,7 +111,7 @@ where
     /// let listener = tokio::net::TcpListener::bind("127.0.0.1:4443").await.unwrap();
     /// let (stream, _) = listener.accept().await.unwrap();
     ///
-    /// let acceptor = tokio_rustls::LazyConfigAcceptor::new(rustls::server::Acceptor::default(), stream);
+    /// let acceptor = tokio_rustls::LazyConfigAcceptor::new(rustls::server::Acceptor::default(), stream).send_alert(false);
     /// tokio::pin!(acceptor);
     ///
     /// match acceptor.as_mut().await {
@@ -146,6 +146,57 @@ where
             None => None,
         }
     }
+
+    /// Writes a stored alert, consuming the alert (if any) and IO.
+    pub async fn write_alert(&mut self) -> io::Result<()> {
+        let Some(alert) = self.take_alert() else {
+            return Ok(());
+        };
+        let Some(io) = self.take_io() else {
+            return Ok(());
+        };
+        WritingAlert {
+            io,
+            alert: Some(alert),
+        }
+        .await
+    }
+}
+
+struct WritingAlert<IO> {
+    io: IO,
+    alert: Option<AcceptedAlert>,
+}
+
+impl<IO> Future for WritingAlert<IO>
+where
+    IO: AsyncRead + AsyncWrite + Unpin,
+{
+    type Output = Result<(), io::Error>;
+    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        let this = self.get_mut();
+        let io = &mut this.io;
+        loop {
+            if let Some(mut alert) = this.alert.take() {
+                match alert.write(&mut SyncWriteAdapter { io, cx }) {
+                    Err(e) if e.kind() == io::ErrorKind::WouldBlock => {
+                        this.alert = Some(alert);
+                        return Poll::Pending;
+                    }
+                    Err(e) => {
+                        return Poll::Ready(Err(io::Error::new(io::ErrorKind::InvalidData, e)));
+                    }
+                    Ok(0) => {
+                        return Poll::Ready(Ok(()));
+                    }
+                    Ok(_) => {
+                        this.alert = Some(alert);
+                        continue;
+                    }
+                };
+            }
+        }
+    }
 }
 
 impl<IO> Future for LazyConfigAcceptor<IO>
@@ -199,7 +250,10 @@ where
                 Ok(None) => {}
                 Err((err, alert)) => match this.send_alert {
                     true => this.alert = Some(AlertState::Sending(err, alert)),
-                    false => this.alert = Some(AlertState::Saved(alert)),
+                    false => {
+                        this.alert = Some(AlertState::Saved(alert));
+                        return Poll::Ready(Err(io::Error::new(io::ErrorKind::InvalidData, err)));
+                    }
                 },
             }
         }

tests/test.rs

@@ -318,6 +318,77 @@ async fn lazy_config_acceptor_alert() {
     assert_eq!(received, fatal_alert_decode_error)
 }
 
+#[tokio::test]
+async fn lazy_config_acceptor_return_http() {
+    let (mut cstream, sstream) = tokio::io::duplex(1024);
+
+    let (tx, rx) = oneshot::channel();
+
+    tokio::spawn(async move {
+        // This is write instead of write_all because of the short duplex size, which is necessarily
+        // symmetrical. We never finish writing because the LazyConfigAcceptor returns an error
+        let _ = cstream.write(b"not tls").await;
+        let mut buf = Vec::new();
+        cstream.read_to_end(&mut buf).await.unwrap();
+        tx.send(buf).unwrap();
+    });
+
+    let acceptor =
+        LazyConfigAcceptor::new(rustls::server::Acceptor::default(), sstream).send_alert(false);
+    tokio::pin!(acceptor);
+
+    let Ok(accept_result) = time::timeout(Duration::from_secs(3), acceptor.as_mut()).await else {
+        panic!("timeout");
+    };
+
+    assert!(accept_result.is_err());
+    let mut io = acceptor.take_io().unwrap();
+    io.write_all(b"HTTP/1.1 400 Invalid Input\r\n\r\n\r\nNot TLS\n")
+        .await
+        .unwrap();
+    io.shutdown().await.unwrap();
+
+    let Ok(Ok(received)) = time::timeout(Duration::from_secs(3), rx).await else {
+        panic!("failed to receive");
+    };
+
+    let recv = b"HTTP/1.1 400 Invalid Input\r\n\r\n\r\nNot TLS\n";
+    assert_eq!(received, recv)
+}
+
+#[tokio::test]
+async fn lazy_config_acceptor_manual_alert() {
+    let (mut cstream, sstream) = tokio::io::duplex(2);
+
+    let (tx, rx) = oneshot::channel();
+
+    tokio::spawn(async move {
+        // This is write instead of write_all because of the short duplex size, which is necessarily
+        // symmetrical. We never finish writing because the LazyConfigAcceptor returns an error
+        let _ = cstream.write(b"not tls").await;
+        let mut buf = Vec::new();
+        cstream.read_to_end(&mut buf).await.unwrap();
+        tx.send(buf).unwrap();
+    });
+
+    let acceptor =
+        LazyConfigAcceptor::new(rustls::server::Acceptor::default(), sstream).send_alert(false);
+    tokio::pin!(acceptor);
+
+    let Ok(accept_result) = time::timeout(Duration::from_secs(3), acceptor.as_mut()).await else {
+        panic!("timeout");
+    };
+
+    assert!(accept_result.is_err());
+    acceptor.write_alert().await.unwrap();
+    let Ok(Ok(received)) = time::timeout(Duration::from_secs(3), rx).await else {
+        panic!("failed to receive");
+    };
+
+    let fatal_alert_decode_error = b"\x15\x03\x03\x00\x02\x02\x32";
+    assert_eq!(received, fatal_alert_decode_error)
+}
+
 #[tokio::test]
 async fn handshake_flush_pending() -> io::Result<()> {
     pass_impl(utils::FlushWrapper::new, false).await