fix(server): fix TOCTOU race condition in tests

src/lib.rs

@@ -24,7 +24,7 @@ pub mod startup;
 /// Logging and tracing setup
 pub mod telemetry;
 
-type MaybeListener = Option<poem::listener::TcpListener<String>>;
+type MaybeListener = Option<std::net::TcpListener>;
 
 fn prepare(listener: MaybeListener) -> startup::Application {
     dotenvy::dotenv().ok();
@@ -70,11 +70,8 @@ pub async fn run(listener: MaybeListener) -> Result<(), std::io::Error> {
 }
 
 #[cfg(test)]
-fn make_random_tcp_listener() -> poem::listener::TcpListener<String> {
-    let tcp_listener =
-        std::net::TcpListener::bind("127.0.0.1:0").expect("Failed to bind a random TCP listener");
-    let port = tcp_listener.local_addr().unwrap().port();
-    poem::listener::TcpListener::bind(format!("127.0.0.1:{port}"))
+fn make_random_tcp_listener() -> std::net::TcpListener {
+    std::net::TcpListener::bind("127.0.0.1:0").expect("Failed to bind a random TCP listener")
 }
 
 #[cfg(test)]

src/startup.rs

@@ -6,6 +6,7 @@
 //! - Configuring CORS
 //! - Starting the HTTP server
 
+use poem::listener::{Listener, TcpAcceptor};
 use poem::middleware::{AddDataEndpoint, Cors, CorsEndpoint};
 use poem::{EndpointExt, Route};
 use poem_openapi::OpenApiService;
@@ -19,10 +20,21 @@ use crate::{
 
 use crate::middleware::rate_limit::RateLimitEndpoint;
 
-type Server = poem::Server<poem::listener::TcpListener<String>, std::convert::Infallible>;
+type Server = poem::Server<poem::listener::BoxListener, std::convert::Infallible>;
+
 /// The configured application with rate limiting, CORS, and settings data.
 pub type App = AddDataEndpoint<CorsEndpoint<RateLimitEndpoint<Route>>, Settings>;
 
+struct PreBoundListener(std::net::TcpListener);
+
+impl Listener for PreBoundListener {
+    type Acceptor = TcpAcceptor;
+
+    async fn into_acceptor(self) -> std::io::Result<Self::Acceptor> {
+        TcpAcceptor::from_std(self.0)
+    }
+}
+
 /// Application builder that holds the server configuration before running.
 pub struct Application {
     server: Server,
@@ -135,30 +147,33 @@ impl Application {
 
     fn setup_server(
         settings: &Settings,
-        tcp_listener: Option<poem::listener::TcpListener<String>>,
-    ) -> Server {
-        let tcp_listener = tcp_listener.unwrap_or_else(|| {
-            let address = format!(
-                "{}:{}",
-                settings.application.host, settings.application.port
-            );
-            poem::listener::TcpListener::bind(address)
-        });
-        poem::Server::new(tcp_listener)
+        tcp_listener: Option<std::net::TcpListener>,
+    ) -> (Server, u16, String) {
+        tcp_listener.map_or_else(
+            || {
+                let port = settings.application.port;
+                let host = settings.application.host.clone();
+                let address = format!("{host}:{port}");
+                let server = poem::Server::new(poem::listener::TcpListener::bind(address).boxed());
+                (server, port, host)
+            },
+            |listener| {
+                let addr = listener.local_addr().expect("Failed to get bound address");
+                let port = addr.port();
+                let host = addr.ip().to_string();
+                let server = poem::Server::new(PreBoundListener(listener).boxed());
+                (server, port, host)
+            },
+        )
     }
 
     /// Builds a new application with the given settings and optional TCP listener.
     ///
     /// If no listener is provided, one will be created based on the settings.
     #[must_use]
-    pub fn build(
-        settings: Settings,
-        tcp_listener: Option<poem::listener::TcpListener<String>>,
-    ) -> Self {
-        let port = settings.application.port;
-        let host = settings.application.host.clone();
+    pub fn build(settings: Settings, tcp_listener: Option<std::net::TcpListener>) -> Self {
+        let (server, port, host) = Self::setup_server(&settings, tcp_listener);
         let app = Self::setup_app(&settings);
-        let server = Self::setup_server(&settings, tcp_listener);
         Self {
             server,
             app,
@@ -243,13 +258,11 @@ mod tests {
     #[test]
     fn application_with_custom_listener() {
         let settings = create_test_settings();
-        let tcp_listener =
+        let listener =
             std::net::TcpListener::bind("127.0.0.1:0").expect("Failed to bind random port");
-        let port = tcp_listener.local_addr().unwrap().port();
-        let listener = poem::listener::TcpListener::bind(format!("127.0.0.1:{port}"));
-
+        let expected_port = listener.local_addr().unwrap().port();
         let app = Application::build(settings, Some(listener));
         assert_eq!(app.host(), "127.0.0.1");
-        assert_eq!(app.port(), 8080);
+        assert_eq!(app.port(), expected_port);
     }
 }