feat: Add earlydata middleware

The docs should pretty much explain what it does. This is essentially a
port of https://docs.gofiber.io/api/middleware/earlydata

actix-web/CHANGES.md

@@ -6,6 +6,7 @@
 
 - Add `HttpServer::{bind,listen}_auto_h2c()` method.
 - Add `Resource::{get, post, etc...}` methods for more concisely adding routes that don't need additional guards.
+- Add `earlydata::EarlyData` middleware.
 
 ### Changed
 

actix-web/src/middleware/earlydata.rs

@@ -0,0 +1,238 @@
+//! For middleware documentation, see [`Earlydata`].
+
+use crate::{
+    body::EitherBody,
+    http::{header::HeaderValue, StatusCode},
+    service::{ServiceRequest, ServiceResponse},
+    Error, HttpResponse,
+};
+use actix_service::{Service, Transform};
+use actix_utils::future::{ready, Ready};
+use futures_util::future::LocalBoxFuture;
+use std::rc::Rc;
+
+/// The Early Data middleware adds support for TLS 1.3's early data ("0-RTT") feature.
+/// Citing [[RFC8446](https://datatracker.ietf.org/doc/html/rfc8446#section-2-3)],
+/// when a client and server share a PSK, TLS 1.3 allows clients to send data on the
+/// first flight ("early data") to speed up the request, effectively reducing the
+/// regular 1-RTT request to a 0-RTT request.
+///
+/// This 0-RTT request is susceptible to replay attacks, hence it should only be allowed when it's
+/// safe to be replayed. By standard, this applies to "safe" HTTP methods. This middleware checks
+/// for exactly this and if the used method is not safe, the client is asked to re-perform the
+/// request without early data.
+///
+/// Since the source of the `Early-Data` header has to be trusted, this middleware also allows
+/// supplying a function that returns whether the reverse proxy is trusted. If the proxy is not
+/// trusted, early data is not allowed.
+#[derive(Clone)]
+#[non_exhaustive]
+pub struct Earlydata {
+    /// Function that returns whether the reverse proxy for a given request is trusted.
+    is_proxy_trusted: fn(&ServiceRequest) -> bool,
+    /// Function that returns whether early data is allowed.
+    allow_early_data: fn(&ServiceRequest) -> bool,
+}
+
+/// Default function that determines whether early data is allowed. This is accomplished by
+/// checking if the method used is safe.
+pub fn default_allow_early_data(req: &ServiceRequest) -> bool {
+    req.method().is_safe()
+}
+
+impl Default for Earlydata {
+    /// Returns a default `Earlydata` instance that trusts all proxies and that uses
+    /// [`default_allow_early_data`].
+    fn default() -> Self {
+        Self {
+            is_proxy_trusted: |_| -> bool { true },
+            allow_early_data: default_allow_early_data,
+        }
+    }
+}
+
+impl Earlydata {
+    /// Creates a new `Earlydata` middleware with given functions for determining the behavior.
+    pub fn new(
+        is_proxy_trusted: fn(&ServiceRequest) -> bool,
+        allow_early_data: fn(&ServiceRequest) -> bool,
+    ) -> Self {
+        Self {
+            is_proxy_trusted,
+            allow_early_data,
+        }
+    }
+}
+
+impl<S, B> Transform<S, ServiceRequest> for Earlydata
+where
+    S: Service<ServiceRequest, Response = ServiceResponse<B>, Error = Error> + 'static,
+{
+    type Response = ServiceResponse<EitherBody<B>>;
+    type Error = Error;
+    type Transform = EarlydataMiddleware<S>;
+    type InitError = ();
+    type Future = Ready<Result<Self::Transform, Self::InitError>>;
+
+    fn new_transform(&self, service: S) -> Self::Future {
+        ready(Ok(EarlydataMiddleware {
+            service: Rc::new(service),
+            is_proxy_trusted: self.is_proxy_trusted,
+            allow_early_data: self.allow_early_data,
+        }))
+    }
+}
+
+pub struct EarlydataMiddleware<S> {
+    service: Rc<S>,
+    is_proxy_trusted: fn(&ServiceRequest) -> bool,
+    allow_early_data: fn(&ServiceRequest) -> bool,
+}
+
+impl<S, B> Service<ServiceRequest> for EarlydataMiddleware<S>
+where
+    S: Service<ServiceRequest, Response = ServiceResponse<B>, Error = Error> + 'static,
+{
+    type Response = ServiceResponse<EitherBody<B>>;
+    type Error = Error;
+    type Future = LocalBoxFuture<'static, Result<Self::Response, Self::Error>>;
+
+    actix_service::forward_ready!(service);
+
+    fn call(&self, req: ServiceRequest) -> Self::Future {
+        let service = Rc::clone(&self.service);
+        let is_proxy_trusted = self.is_proxy_trusted;
+        let allow_early_data = self.allow_early_data;
+
+        Box::pin(async move {
+            // Check if this is early data
+            // TODO wait for the http PR
+            if req.headers().get("early-data") != Some(&HeaderValue::from_static("1")) {
+                return service.call(req).await.map(|res| res.map_into_left_body());
+            }
+
+            // Do we trust the header?
+            if !is_proxy_trusted(&req) {
+                return Ok(req.into_response(
+                    // TODO wait for PR
+                    HttpResponse::new(StatusCode::from_u16(425).unwrap()).map_into_right_body(),
+                ));
+            }
+
+            if allow_early_data(&req) {
+                service.call(req).await.map(|res| res.map_into_left_body())
+            } else {
+                Ok(req.into_response(
+                    // TODO wait for PR
+                    HttpResponse::new(StatusCode::from_u16(425).unwrap()).map_into_right_body(),
+                ))
+            }
+        })
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::test::{call_service, init_service, TestRequest};
+    use crate::{
+        http::{header::HeaderValue, Method, StatusCode},
+        middleware::earlydata::default_allow_early_data,
+        middleware::Earlydata,
+        web, App, HttpResponse,
+    };
+
+    #[actix_rt::test]
+    async fn early_data() {
+        let app = init_service(
+            App::new()
+                .wrap(Earlydata::default())
+                .service(web::resource("/").to(HttpResponse::Ok)),
+        )
+        .await;
+
+        // No early data
+        let req = TestRequest::default().uri("/").to_request();
+        let res = call_service(&app, req).await;
+        assert_eq!(res.status(), StatusCode::OK);
+
+        // Early data (but trusted)
+        let req = TestRequest::default()
+            .uri("/")
+            .insert_header(("early-data", "1"))
+            .to_request();
+        let res = call_service(&app, req).await;
+        assert_eq!(res.status(), StatusCode::OK);
+
+        // Explicitly no early data
+        let req = TestRequest::default()
+            .uri("/")
+            .method(Method::PUT)
+            .insert_header(("early-data", "0"))
+            .to_request();
+        let res = call_service(&app, req).await;
+        assert_eq!(res.status(), StatusCode::OK);
+
+        // Early data but PUT
+        let req = TestRequest::default()
+            .uri("/")
+            .method(Method::PUT)
+            .insert_header(("early-data", "1"))
+            .to_request();
+        let res = call_service(&app, req).await;
+        assert_eq!(res.status(), StatusCode::from_u16(425).unwrap());
+    }
+
+    #[actix_rt::test]
+    async fn early_data_custom_function() {
+        let app = init_service(
+            App::new()
+                .wrap(Earlydata::new(|_| true, |req| req.method() == Method::PUT))
+                .service(web::resource("/").to(HttpResponse::Ok)),
+        )
+        .await;
+
+        // Should return `true` for PUT now
+        let req = TestRequest::default()
+            .uri("/")
+            .method(Method::PUT)
+            .insert_header(("early-data", "1"))
+            .to_request();
+        let res = call_service(&app, req).await;
+        assert_eq!(res.status(), StatusCode::OK);
+    }
+
+    #[actix_rt::test]
+    async fn early_data_proxy_trust() {
+        let app = init_service(
+            App::new()
+                .wrap(Earlydata::new(
+                    |req| {
+                        req.headers().get("please-trust-me")
+                            == Some(&HeaderValue::from_static("1"))
+                    },
+                    default_allow_early_data,
+                ))
+                .service(web::resource("/").to(HttpResponse::Ok)),
+        )
+        .await;
+
+        // Not trusted -> No 200
+        let req = TestRequest::default()
+            .uri("/")
+            .method(Method::GET)
+            .insert_header(("early-data", "1"))
+            .to_request();
+        let res = call_service(&app, req).await;
+        assert_eq!(res.status(), StatusCode::from_u16(425).unwrap());
+
+        // Trusted -> 200
+        let req = TestRequest::default()
+            .uri("/")
+            .method(Method::GET)
+            .insert_header(("early-data", "1"))
+            .insert_header(("please-trust-me", "1"))
+            .to_request();
+        let res = call_service(&app, req).await;
+        assert_eq!(res.status(), StatusCode::OK);
+    }
+}

actix-web/src/middleware/mod.rs

@@ -3,6 +3,7 @@
 mod compat;
 mod condition;
 mod default_headers;
+mod earlydata;
 mod err_handlers;
 mod logger;
 #[cfg(test)]
@@ -12,6 +13,7 @@ mod normalize;
 pub use self::compat::Compat;
 pub use self::condition::Condition;
 pub use self::default_headers::DefaultHeaders;
+pub use self::earlydata::Earlydata;
 pub use self::err_handlers::{ErrorHandlerResponse, ErrorHandlers};
 pub use self::logger::Logger;
 #[cfg(test)]