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//! Middleware for following redirections.
//!
//! # Overview
//!
//! The [`FollowRedirect`] middleware retries requests with the inner [`Service`] to follow HTTP
//! redirections.
//!
//! The middleware tries to clone the original [`Request`] when making a redirected request.
//! However, since [`Extensions`][http::Extensions] are `!Clone`, any extensions set by outer
//! middleware will be discarded. Also, the request body cannot always be cloned. When the
//! original body is known to be empty by [`Body::size_hint`], the middleware uses `Default`
//! implementation of the body type to create a new request body. If you know that the body can be
//! cloned in some way, you can tell the middleware to clone it by configuring a [`policy`].
//!
//! # Examples
//!
//! ## Basic usage
//!
//! ```
//! use http::{Request, Response};
//! use hyper::Body;
//! use tower::{Service, ServiceBuilder, ServiceExt};
//! use tower_http::follow_redirect::{FollowRedirectLayer, RequestUri};
//!
//! # #[tokio::main]
//! # async fn main() -> Result<(), std::convert::Infallible> {
//! # let http_client = tower::service_fn(|req: Request<_>| async move {
//! # let dest = "https://www.rust-lang.org/";
//! # let mut res = http::Response::builder();
//! # if req.uri() != dest {
//! # res = res
//! # .status(http::StatusCode::MOVED_PERMANENTLY)
//! # .header(http::header::LOCATION, dest);
//! # }
//! # Ok::<_, std::convert::Infallible>(res.body(Body::empty()).unwrap())
//! # });
//! let mut client = ServiceBuilder::new()
//! .layer(FollowRedirectLayer::new())
//! .service(http_client);
//!
//! let request = Request::builder()
//! .uri("https://rust-lang.org/")
//! .body(Body::empty())
//! .unwrap();
//!
//! let response = client.ready().await?.call(request).await?;
//! // Get the final request URI.
//! assert_eq!(response.extensions().get::<RequestUri>().unwrap().0, "https://www.rust-lang.org/");
//! # Ok(())
//! # }
//! ```
//!
//! ## Customizing the `Policy`
//!
//! You can use a [`Policy`] value to customize how the middleware handles redirections.
//!
//! ```
//! use http::{Request, Response};
//! use hyper::Body;
//! use tower::{Service, ServiceBuilder, ServiceExt};
//! use tower_http::follow_redirect::{
//! policy::{self, PolicyExt},
//! FollowRedirectLayer,
//! };
//!
//! #[derive(Debug)]
//! enum MyError {
//! Hyper(hyper::Error),
//! TooManyRedirects,
//! }
//!
//! # #[tokio::main]
//! # async fn main() -> Result<(), MyError> {
//! # let http_client =
//! # tower::service_fn(|_: Request<Body>| async { Ok(Response::new(Body::empty())) });
//! let policy = policy::Limited::new(10) // Set the maximum number of redirections to 10.
//! // Return an error when the limit was reached.
//! .or::<_, (), _>(policy::redirect_fn(|_| Err(MyError::TooManyRedirects)))
//! // Do not follow cross-origin redirections, and return the redirection responses as-is.
//! .and::<_, (), _>(policy::SameOrigin::new());
//!
//! let mut client = ServiceBuilder::new()
//! .layer(FollowRedirectLayer::with_policy(policy))
//! .map_err(MyError::Hyper)
//! .service(http_client);
//!
//! // ...
//! # let _ = client.ready().await?.call(Request::default()).await?;
//! # Ok(())
//! # }
//! ```
pub mod policy;
use self::policy::{Action, Attempt, Policy, Standard};
use futures_core::ready;
use futures_util::future::Either;
use http::{
header::LOCATION, HeaderMap, HeaderValue, Method, Request, Response, StatusCode, Uri, Version,
};
use http_body::Body;
use iri_string::types::{UriAbsoluteString, UriReferenceStr};
use pin_project_lite::pin_project;
use std::{
convert::TryFrom,
future::Future,
mem,
pin::Pin,
str,
task::{Context, Poll},
};
use tower::util::Oneshot;
use tower_layer::Layer;
use tower_service::Service;
/// [`Layer`] for retrying requests with a [`Service`] to follow redirection responses.
///
/// See the [module docs](self) for more details.
#[derive(Clone, Copy, Debug, Default)]
pub struct FollowRedirectLayer<P = Standard> {
policy: P,
}
impl FollowRedirectLayer {
/// Create a new [`FollowRedirectLayer`] with a [`Standard`] redirection policy.
pub fn new() -> Self {
Self::default()
}
}
impl<P> FollowRedirectLayer<P> {
/// Create a new [`FollowRedirectLayer`] with the given redirection [`Policy`].
pub fn with_policy(policy: P) -> Self {
FollowRedirectLayer { policy }
}
}
impl<S, P> Layer<S> for FollowRedirectLayer<P>
where
S: Clone,
P: Clone,
{
type Service = FollowRedirect<S, P>;
fn layer(&self, inner: S) -> Self::Service {
FollowRedirect::with_policy(inner, self.policy.clone())
}
}
/// Middleware that retries requests with a [`Service`] to follow redirection responses.
///
/// See the [module docs](self) for more details.
#[derive(Clone, Copy, Debug)]
pub struct FollowRedirect<S, P = Standard> {
inner: S,
policy: P,
}
impl<S> FollowRedirect<S> {
/// Create a new [`FollowRedirect`] with a [`Standard`] redirection policy.
pub fn new(inner: S) -> Self {
Self::with_policy(inner, Standard::default())
}
/// Returns a new [`Layer`] that wraps services with a `FollowRedirect` middleware.
///
/// [`Layer`]: tower_layer::Layer
pub fn layer() -> FollowRedirectLayer {
FollowRedirectLayer::new()
}
}
impl<S, P> FollowRedirect<S, P>
where
P: Clone,
{
/// Create a new [`FollowRedirect`] with the given redirection [`Policy`].
pub fn with_policy(inner: S, policy: P) -> Self {
FollowRedirect { inner, policy }
}
/// Returns a new [`Layer`] that wraps services with a `FollowRedirect` middleware
/// with the given redirection [`Policy`].
///
/// [`Layer`]: tower_layer::Layer
pub fn layer_with_policy(policy: P) -> FollowRedirectLayer<P> {
FollowRedirectLayer::with_policy(policy)
}
define_inner_service_accessors!();
}
impl<ReqBody, ResBody, S, P> Service<Request<ReqBody>> for FollowRedirect<S, P>
where
S: Service<Request<ReqBody>, Response = Response<ResBody>> + Clone,
ReqBody: Body + Default,
P: Policy<ReqBody, S::Error> + Clone,
{
type Response = Response<ResBody>;
type Error = S::Error;
type Future = ResponseFuture<S, ReqBody, P>;
fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
self.inner.poll_ready(cx)
}
fn call(&mut self, mut req: Request<ReqBody>) -> Self::Future {
let service = self.inner.clone();
let mut service = mem::replace(&mut self.inner, service);
let mut policy = self.policy.clone();
let mut body = BodyRepr::None;
body.try_clone_from(req.body(), &policy);
policy.on_request(&mut req);
ResponseFuture {
method: req.method().clone(),
uri: req.uri().clone(),
version: req.version(),
headers: req.headers().clone(),
body,
future: Either::Left(service.call(req)),
service,
policy,
}
}
}
pin_project! {
/// Response future for [`FollowRedirect`].
#[derive(Debug)]
pub struct ResponseFuture<S, B, P>
where
S: Service<Request<B>>,
{
#[pin]
future: Either<S::Future, Oneshot<S, Request<B>>>,
service: S,
policy: P,
method: Method,
uri: Uri,
version: Version,
headers: HeaderMap<HeaderValue>,
body: BodyRepr<B>,
}
}
impl<S, ReqBody, ResBody, P> Future for ResponseFuture<S, ReqBody, P>
where
S: Service<Request<ReqBody>, Response = Response<ResBody>> + Clone,
ReqBody: Body + Default,
P: Policy<ReqBody, S::Error>,
{
type Output = Result<Response<ResBody>, S::Error>;
fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
let mut this = self.project();
let mut res = ready!(this.future.as_mut().poll(cx)?);
res.extensions_mut().insert(RequestUri(this.uri.clone()));
match res.status() {
StatusCode::MOVED_PERMANENTLY | StatusCode::FOUND => {
// User agents MAY change the request method from POST to GET
// (RFC 7231 section 6.4.2. and 6.4.3.).
if *this.method == Method::POST {
*this.method = Method::GET;
*this.body = BodyRepr::Empty;
}
}
StatusCode::SEE_OTHER => {
// A user agent can perform a GET or HEAD request (RFC 7231 section 6.4.4.).
if *this.method != Method::HEAD {
*this.method = Method::GET;
}
*this.body = BodyRepr::Empty;
}
StatusCode::TEMPORARY_REDIRECT | StatusCode::PERMANENT_REDIRECT => {}
_ => return Poll::Ready(Ok(res)),
};
let body = if let Some(body) = this.body.take() {
body
} else {
return Poll::Ready(Ok(res));
};
let location = res
.headers()
.get(&LOCATION)
.and_then(|loc| resolve_uri(str::from_utf8(loc.as_bytes()).ok()?, this.uri));
let location = if let Some(loc) = location {
loc
} else {
return Poll::Ready(Ok(res));
};
let attempt = Attempt {
status: res.status(),
location: &location,
previous: this.uri,
};
match this.policy.redirect(&attempt)? {
Action::Follow => {
*this.uri = location;
this.body.try_clone_from(&body, &this.policy);
let mut req = Request::new(body);
*req.uri_mut() = this.uri.clone();
*req.method_mut() = this.method.clone();
*req.version_mut() = *this.version;
*req.headers_mut() = this.headers.clone();
this.policy.on_request(&mut req);
this.future
.set(Either::Right(Oneshot::new(this.service.clone(), req)));
cx.waker().wake_by_ref();
Poll::Pending
}
Action::Stop => Poll::Ready(Ok(res)),
}
}
}
/// Response [`Extensions`][http::Extensions] value that represents the effective request URI of
/// a response returned by a [`FollowRedirect`] middleware.
///
/// The value differs from the original request's effective URI if the middleware has followed
/// redirections.
pub struct RequestUri(pub Uri);
#[derive(Debug)]
enum BodyRepr<B> {
Some(B),
Empty,
None,
}
impl<B> BodyRepr<B>
where
B: Body + Default,
{
fn take(&mut self) -> Option<B> {
match mem::replace(self, BodyRepr::None) {
BodyRepr::Some(body) => Some(body),
BodyRepr::Empty => {
*self = BodyRepr::Empty;
Some(B::default())
}
BodyRepr::None => None,
}
}
fn try_clone_from<P, E>(&mut self, body: &B, policy: &P)
where
P: Policy<B, E>,
{
match self {
BodyRepr::Some(_) | BodyRepr::Empty => {}
BodyRepr::None => {
if let Some(body) = clone_body(policy, body) {
*self = BodyRepr::Some(body);
}
}
}
}
}
fn clone_body<P, B, E>(policy: &P, body: &B) -> Option<B>
where
P: Policy<B, E>,
B: Body + Default,
{
if body.size_hint().exact() == Some(0) {
Some(B::default())
} else {
policy.clone_body(body)
}
}
/// Try to resolve a URI reference `relative` against a base URI `base`.
fn resolve_uri(relative: &str, base: &Uri) -> Option<Uri> {
let relative = UriReferenceStr::new(relative).ok()?;
let base = UriAbsoluteString::try_from(base.to_string()).ok()?;
let uri = relative.resolve_against(&base).to_string();
Uri::try_from(uri).ok()
}
#[cfg(test)]
mod tests {
use super::{policy::*, *};
use hyper::{header::LOCATION, Body};
use std::convert::Infallible;
use tower::{ServiceBuilder, ServiceExt};
#[tokio::test]
async fn follows() {
let svc = ServiceBuilder::new()
.layer(FollowRedirectLayer::with_policy(Action::Follow))
.buffer(1)
.service_fn(handle);
let req = Request::builder()
.uri("http://example.com/42")
.body(Body::empty())
.unwrap();
let res = svc.oneshot(req).await.unwrap();
assert_eq!(*res.body(), 0);
assert_eq!(
res.extensions().get::<RequestUri>().unwrap().0,
"http://example.com/0"
);
}
#[tokio::test]
async fn stops() {
let svc = ServiceBuilder::new()
.layer(FollowRedirectLayer::with_policy(Action::Stop))
.buffer(1)
.service_fn(handle);
let req = Request::builder()
.uri("http://example.com/42")
.body(Body::empty())
.unwrap();
let res = svc.oneshot(req).await.unwrap();
assert_eq!(*res.body(), 42);
assert_eq!(
res.extensions().get::<RequestUri>().unwrap().0,
"http://example.com/42"
);
}
#[tokio::test]
async fn limited() {
let svc = ServiceBuilder::new()
.layer(FollowRedirectLayer::with_policy(Limited::new(10)))
.buffer(1)
.service_fn(handle);
let req = Request::builder()
.uri("http://example.com/42")
.body(Body::empty())
.unwrap();
let res = svc.oneshot(req).await.unwrap();
assert_eq!(*res.body(), 42 - 10);
assert_eq!(
res.extensions().get::<RequestUri>().unwrap().0,
"http://example.com/32"
);
}
/// A server with an endpoint `GET /{n}` which redirects to `/{n-1}` unless `n` equals zero,
/// returning `n` as the response body.
async fn handle<B>(req: Request<B>) -> Result<Response<u64>, Infallible> {
let n: u64 = req.uri().path()[1..].parse().unwrap();
let mut res = Response::builder();
if n > 0 {
res = res
.status(StatusCode::MOVED_PERMANENTLY)
.header(LOCATION, format!("/{}", n - 1));
}
Ok::<_, Infallible>(res.body(n).unwrap())
}
}