rustango 0.27.7

Django-shaped batteries-included web framework for Rust: ORM + migrations + auto-admin + multi-tenancy + audit log + auth (sessions, JWT, OAuth2/OIDC, HMAC) + APIs (ViewSet, OpenAPI auto-derive, JSON:API) + jobs (in-mem + Postgres) + email + media (S3 / R2 / B2 / MinIO + presigned uploads + collections + tags) + production middleware (CSRF, CSP, rate-limiting, compression, idempotency, etc.).
Documentation 
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

//! Request body size limit middleware.
//!
//! axum's `DefaultBodyLimit` already caps incoming bodies at 2 MiB
//! per-extractor — this layer adds a router-wide cap that fires
//! BEFORE the body is read into memory by checking `Content-Length`
//! upfront, returning a structured `413 Payload Too Large` JSON
//! response instead of axum's default plain-text error.
//!
//! ## Quick start
//!
//! ```ignore
//! use rustango::body_limit::{BodyLimitLayer, BodyLimitRouterExt};
//!
//! let app = axum::Router::new()
//!     .route("/api/upload", axum::routing::post(upload))
//!     .body_limit(BodyLimitLayer::new(10 * 1024 * 1024)); // 10 MiB
//! ```
//!
//! Per-route override: build a sub-router for the route(s) that need a
//! different cap and merge it after the global layer is applied.

use std::sync::Arc;

use axum::body::Body;
use axum::extract::Request;
use axum::http::{header, HeaderValue, StatusCode};
use axum::middleware::Next;
use axum::response::Response;
use axum::Router;

#[derive(Clone, Debug)]
pub struct BodyLimitLayer {
    /// Maximum body size in bytes. Requests with a `Content-Length`
    /// above this get a `413 Payload Too Large` upfront.
    pub max_bytes: usize,
    /// Method names whose bodies we check. Default: POST, PUT, PATCH.
    /// GET / DELETE / HEAD typically have no body so we skip them.
    pub methods: Vec<axum::http::Method>,
}

impl Default for BodyLimitLayer {
    fn default() -> Self {
        Self::new(2 * 1024 * 1024)
    }
}

impl BodyLimitLayer {
    #[must_use]
    pub fn new(max_bytes: usize) -> Self {
        use axum::http::Method;
        Self {
            max_bytes,
            methods: vec![Method::POST, Method::PUT, Method::PATCH],
        }
    }

    /// Override the methods checked. Pass an empty vec to check every
    /// request regardless of method.
    #[must_use]
    pub fn methods(mut self, m: Vec<axum::http::Method>) -> Self {
        self.methods = m;
        self
    }
}

pub trait BodyLimitRouterExt {
    #[must_use]
    fn body_limit(self, layer: BodyLimitLayer) -> Self;
}

impl<S: Clone + Send + Sync + 'static> BodyLimitRouterExt for Router<S> {
    fn body_limit(self, layer: BodyLimitLayer) -> Self {
        let cfg = Arc::new(layer);
        self.layer(axum::middleware::from_fn(
            move |req: Request<Body>, next: Next| {
                let cfg = cfg.clone();
                async move { handle(cfg, req, next).await }
            },
        ))
    }
}

async fn handle(cfg: Arc<BodyLimitLayer>, req: Request<Body>, next: Next) -> Response {
    if !cfg.methods.is_empty() && !cfg.methods.contains(req.method()) {
        return next.run(req).await;
    }
    if let Some(declared) = req
        .headers()
        .get(header::CONTENT_LENGTH)
        .and_then(|v| v.to_str().ok())
        .and_then(|s| s.parse::<u64>().ok())
    {
        if usize::try_from(declared).map_or(true, |n| n > cfg.max_bytes) {
            return too_large(cfg.max_bytes);
        }
    }
    next.run(req).await
}

fn too_large(limit: usize) -> Response {
    let body = format!(r#"{{"error":"payload too large","limit_bytes":{limit}}}"#);
    let mut resp = Response::builder()
        .status(StatusCode::PAYLOAD_TOO_LARGE)
        .body(Body::from(body))
        .unwrap_or_else(|_| Response::new(Body::empty()));
    resp.headers_mut().insert(
        header::CONTENT_TYPE,
        HeaderValue::from_static("application/json"),
    );
    resp
}

#[cfg(test)]
mod tests {
    use super::*;
    use axum::http::Method;
    use axum::routing::{get, post};
    use tower::ServiceExt;

    fn app(limit: usize) -> Router {
        Router::new()
            .route("/", post(|| async { "ok" }))
            .route("/get", get(|| async { "ok" }))
            .body_limit(BodyLimitLayer::new(limit))
    }

    #[tokio::test]
    async fn small_body_passes_through() {
        let resp = app(1024)
            .oneshot(
                Request::builder()
                    .method(Method::POST)
                    .uri("/")
                    .header(header::CONTENT_LENGTH, "10")
                    .body(Body::from("0123456789"))
                    .unwrap(),
            )
            .await
            .unwrap();
        assert_eq!(resp.status(), 200);
    }

    #[tokio::test]
    async fn body_at_exact_limit_passes() {
        let resp = app(10)
            .oneshot(
                Request::builder()
                    .method(Method::POST)
                    .uri("/")
                    .header(header::CONTENT_LENGTH, "10")
                    .body(Body::from("0123456789"))
                    .unwrap(),
            )
            .await
            .unwrap();
        assert_eq!(resp.status(), 200);
    }

    #[tokio::test]
    async fn body_over_limit_rejected_with_413_json() {
        let resp = app(10)
            .oneshot(
                Request::builder()
                    .method(Method::POST)
                    .uri("/")
                    .header(header::CONTENT_LENGTH, "100")
                    .body(Body::from("0".repeat(100)))
                    .unwrap(),
            )
            .await
            .unwrap();
        assert_eq!(resp.status(), StatusCode::PAYLOAD_TOO_LARGE);
        assert_eq!(
            resp.headers()
                .get(header::CONTENT_TYPE)
                .unwrap()
                .to_str()
                .unwrap(),
            "application/json"
        );
        let bytes = axum::body::to_bytes(resp.into_body(), 1 << 16)
            .await
            .unwrap();
        let v: serde_json::Value = serde_json::from_slice(&bytes).unwrap();
        assert_eq!(v["error"], "payload too large");
        assert_eq!(v["limit_bytes"], 10);
    }

    #[tokio::test]
    async fn get_requests_skipped_by_default() {
        // GET shouldn't have a body, but a malicious client can lie about
        // Content-Length. By default we don't check GET so handlers see
        // it for what it is.
        let resp = app(10)
            .oneshot(
                Request::builder()
                    .method(Method::GET)
                    .uri("/get")
                    .header(header::CONTENT_LENGTH, "999")
                    .body(Body::empty())
                    .unwrap(),
            )
            .await
            .unwrap();
        assert_eq!(resp.status(), 200);
    }

    #[tokio::test]
    async fn missing_content_length_lets_request_through() {
        // Without Content-Length we can't enforce upfront; defer to
        // axum's per-extractor DefaultBodyLimit (or the user's choice).
        let resp = app(10)
            .oneshot(
                Request::builder()
                    .method(Method::POST)
                    .uri("/")
                    .body(Body::from("0".repeat(100)))
                    .unwrap(),
            )
            .await
            .unwrap();
        assert_eq!(resp.status(), 200);
    }

    #[tokio::test]
    async fn empty_methods_list_checks_every_method() {
        let app = Router::new()
            .route("/", get(|| async { "ok" }))
            .body_limit(BodyLimitLayer::new(10).methods(Vec::new()));
        let resp = app
            .oneshot(
                Request::builder()
                    .method(Method::GET)
                    .uri("/")
                    .header(header::CONTENT_LENGTH, "100")
                    .body(Body::empty())
                    .unwrap(),
            )
            .await
            .unwrap();
        assert_eq!(resp.status(), StatusCode::PAYLOAD_TOO_LARGE);
    }

    #[test]
    fn default_layer_has_2mib_limit() {
        let l = BodyLimitLayer::default();
        assert_eq!(l.max_bytes, 2 * 1024 * 1024);
    }

    #[test]
    fn default_methods_are_post_put_patch() {
        let l = BodyLimitLayer::default();
        assert_eq!(l.methods.len(), 3);
        assert!(l.methods.contains(&Method::POST));
        assert!(l.methods.contains(&Method::PUT));
        assert!(l.methods.contains(&Method::PATCH));
    }
}