# redirect.rs - source
Source of the Rust file `/home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/reqwest-0.11.2/src/redirect.rs`.
Keywords: rust, rustlang, rust-lang

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    //! Redirect Handling
    //!
    //! By default, a `Client` will automatically handle HTTP redirects, having a
    //! maximum redirect chain of 10 hops. To customize this behavior, a
    //! `redirect::Policy` can be used with a `ClientBuilder`.

    use std::error::Error as StdError;
    use std::fmt;

    use crate::header::{HeaderMap, AUTHORIZATION, COOKIE, PROXY_AUTHORIZATION, WWW_AUTHENTICATE};
    use hyper::StatusCode;

    use crate::Url;

    /// A type that controls the policy on how to handle the following of redirects.
    ///
    /// The default value will catch redirect loops, and has a maximum of 10
    /// redirects it will follow in a chain before returning an error.
    ///
    /// - `limited` can be used have the same as the default behavior, but adjust
    ///   the allowed maximum redirect hops in a chain.
    /// - `none` can be used to disable all redirect behavior.
    /// - `custom` can be used to create a customized policy.
    pub struct Policy {
        inner: PolicyKind,
    }

    /// A type that holds information on the next request and previous requests
    /// in redirect chain.
    #[derive(Debug)]
    pub struct Attempt<'a> {
        status: StatusCode,
        next: &'a Url,
        previous: &'a [Url],
    }

    /// An action to perform when a redirect status code is found.
    #[derive(Debug)]
    pub struct Action {
        inner: ActionKind,
    }

    impl Policy {
        /// Create a `Policy` with a maximum number of redirects.
        ///
        /// An `Error` will be returned if the max is reached.
        pub fn limited(max: usize) -> Self {
            Self {
                inner: PolicyKind::Limit(max),
            }
        }

        /// Create a `Policy` that does not follow any redirect.
        pub fn none() -> Self {
            Self {
                inner: PolicyKind::None,
            }
        }

        /// Create a custom `Policy` using the passed function.
        ///
        /// # Note
        ///
        /// The default `Policy` handles a maximum loop
        /// chain, but the custom variant does not do that for you automatically.
        /// The custom policy should have some way of handling those.
        ///
        /// Information on the next request and previous requests can be found
        /// on the [`Attempt`] argument passed to the closure.
        ///
        /// Actions can be conveniently created from methods on the
        /// [`Attempt`].
        ///
        /// # Example
        ///
        /// ```rust
        /// # use reqwest::{Error, redirect};
        /// #
        /// # fn run() -> Result<(), Error> {
        /// let custom = redirect::Policy::custom(|attempt| {
        ///     if attempt.previous().len() > 5 {
        ///         attempt.error("too many redirects")
        ///     } else if attempt.url().host_str() == Some("example.domain") {
        ///         // prevent redirects to 'example.domain'
        ///         attempt.stop()
        ///     } else {
        ///         attempt.follow()
        ///     }
        /// });
        /// let client = reqwest::Client::builder()
        ///     .redirect(custom)
        ///     .build()?;
        /// # Ok(())
        /// # }
        /// ```
        ///
        /// [`Attempt`]: struct.Attempt.html
        pub fn custom<T>(policy: T) -> Self
        where
            T: Fn(Attempt) -> Action + Send + Sync + 'static,
        {
            Self {
                inner: PolicyKind::Custom(Box::new(policy)),
            }
        }

        /// Apply this policy to a given [`Attempt`] to produce a [`Action`].
        ///
        /// # Note
        ///
        /// This method can be used together with `Policy::custom()`
        /// to construct one `Policy` that wraps another.
        ///
        /// # Example
        ///
        /// ```rust
        /// # use reqwest::{Error, redirect};
        /// #
        /// # fn run() -> Result<(), Error> {
        /// let custom = redirect::Policy::custom(|attempt| {
        ///     eprintln!("{}, Location: {:?}", attempt.status(), attempt.url());
        ///     redirect::Policy::default().redirect(attempt)
        /// });
        /// # Ok(())
        /// # }
        /// ```
        pub fn redirect(&self, attempt: Attempt) -> Action {
            match self.inner {
                PolicyKind::Custom(ref custom) => custom(attempt),
                PolicyKind::Limit(max) => {
                    if attempt.previous.len() == max {
                        attempt.error(TooManyRedirects)
                    } else {
                        attempt.follow()
                    }
                }
                PolicyKind::None => attempt.stop(),
            }
        }

        pub(crate) fn check(&self, status: StatusCode, next: &Url, previous: &[Url]) -> ActionKind {
            self.redirect(Attempt {
                status,
                next,
                previous,
            })
            .inner
        }

        pub(crate) fn is_default(&self) -> bool {
            matches!(self.inner, PolicyKind::Limit(10))
        }
    }

    impl Default for Policy {
        fn default() -> Policy {
            // Keep `is_default` in sync
            Policy::limited(10)
        }
    }

    impl<'a> Attempt<'a> {
        /// Get the type of redirect.
        pub fn status(&self) -> StatusCode {
            self.status
        }

        /// Get the next URL to redirect to.
        pub fn url(&self) -> &Url {
            self.next
        }

        /// Get the list of previous URLs that have already been requested in this chain.
        pub fn previous(&self) -> &[Url] {
            self.previous
        }
        /// Returns an action meaning reqwest should follow the next URL.
        pub fn follow(self) -> Action {
            Action {
                inner: ActionKind::Follow,
            }
        }

        /// Returns an action meaning reqwest should not follow the next URL.
        ///
        /// The 30x response will be returned as the `Ok` result.
        pub fn stop(self) -> Action {
            Action {
                inner: ActionKind::Stop,
            }
        }

        /// Returns an action failing the redirect with an error.
        ///
        /// The `Error` will be returned for the result of the sent request.
        pub fn error<E: Into<Box<dyn StdError + Send + Sync>>>(self, error: E) -> Action {
            Action {
                inner: ActionKind::Error(error.into()),
            }
        }
    }

    enum PolicyKind {
        Custom(Box<dyn Fn(Attempt) -> Action + Send + Sync + 'static>),
        Limit(usize),
        None,
    }

    impl fmt::Debug for Policy {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            f.debug_tuple("Policy").field(&self.inner).finish()
        }
    }

    impl fmt::Debug for PolicyKind {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            match *self {
                PolicyKind::Custom(..) => f.pad("Custom"),
                PolicyKind::Limit(max) => f.debug_tuple("Limit").field(&max).finish(),
                PolicyKind::None => f.pad("None"),
            }
        }
    }

    // pub(crate)

    #[derive(Debug)]
    pub(crate) enum ActionKind {
        Follow,
        Stop,
        Error(Box<dyn StdError + Send + Sync>),
    }

    pub(crate) fn remove_sensitive_headers(headers: &mut HeaderMap, next: &Url, previous: &[Url]) {
        if let Some(previous) = previous.last() {
            let cross_host = next.host_str() != previous.host_str()
                || next.port_or_known_default() != previous.port_or_known_default();
            if cross_host {
                headers.remove(AUTHORIZATION);
                headers.remove(COOKIE);
                headers.remove("cookie2");
                headers.remove(PROXY_AUTHORIZATION);
                headers.remove(WWW_AUTHENTICATE);
            }
        }
    }

    #[derive(Debug)]
    struct TooManyRedirects;

    impl fmt::Display for TooManyRedirects {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            f.write_str("too many redirects")
        }
    }

    impl StdError for TooManyRedirects {}

    #[test]
    fn test_redirect_policy_limit() {
        let policy = Policy::default();
        let next = Url::parse("http://x.y/z").unwrap();
        let mut previous = (0..9)
            .map(|i| Url::parse(&format!("http://a.b/c/{}", i)).unwrap())
            .collect::<Vec<_>>();

        match policy.check(StatusCode::FOUND, &next, &previous) {
            ActionKind::Follow => (),
            other => panic!("unexpected {:?}", other),
        }

        previous.push(Url::parse("http://a.b.d/e/33").unwrap());

        match policy.check(StatusCode::FOUND, &next, &previous) {
            ActionKind::Error(err) if err.is::<TooManyRedirects>() => (),
            other => panic!("unexpected {:?}", other),
        }
    }

    #[test]
    fn test_redirect_policy_custom() {
        let policy = Policy::custom(|attempt| {
            if attempt.url().host_str() == Some("foo") {
                attempt.stop()
            } else {
                attempt.follow()
            }
        });

        let next = Url::parse("http://bar/baz").unwrap();
        match policy.check(StatusCode::FOUND, &next, &[]) {
            ActionKind::Follow => (),
            other => panic!("unexpected {:?}", other),
        }

        let next = Url::parse("http://foo/baz").unwrap();
        match policy.check(StatusCode::FOUND, &next, &[]) {
            ActionKind::Stop => (),
            other => panic!("unexpected {:?}", other),
        }
    }

    #[test]
    fn test_remove_sensitive_headers() {
        use hyper::header::{HeaderValue, ACCEPT, AUTHORIZATION, COOKIE};

        let mut headers = HeaderMap::new();
        headers.insert(ACCEPT, HeaderValue::from_static("*/*"));
        headers.insert(AUTHORIZATION, HeaderValue::from_static("let me in"));
        headers.insert(COOKIE, HeaderValue::from_static("foo=bar"));

        let next = Url::parse("http://initial-domain.com/path").unwrap();
        let mut prev = vec![Url::parse("http://initial-domain.com/new_path").unwrap()];
        let mut filtered_headers = headers.clone();

        remove_sensitive_headers(&mut headers, &next, &prev);
        assert_eq!(headers, filtered_headers);

        prev.push(Url::parse("http://new-domain.com/path").unwrap());
        filtered_headers.remove(AUTHORIZATION);
        filtered_headers.remove(COOKIE);

        remove_sensitive_headers(&mut headers, &next, &prev);
        assert_eq!(headers, filtered_headers);
    }