reqwest/
redirect.rs

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
//! 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_limit_to_0() {
    let policy = Policy::limited(0);
    let next = Url::parse("http://x.y/z").unwrap();
    let previous = vec![Url::parse("http://a.b/c").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);
}