From 759e9887473b2c6fee3cb5650b286a0a72215150 Mon Sep 17 00:00:00 2001 From: David Pedersen Date: Sat, 10 Sep 2022 08:36:30 +0200 Subject: [PATCH] Limit size of request bodies in `Bytes` extractor (#1346) * Apply default limit to request body size * Support disabling the default limit * docs * changelog --- axum-core/CHANGELOG.md | 15 ++- axum-core/Cargo.toml | 3 + axum-core/src/extract/default_body_limit.rs | 101 ++++++++++++++++++++ axum-core/src/extract/mod.rs | 3 +- axum-core/src/extract/request_parts.rs | 42 +++++--- axum/CHANGELOG.md | 20 ++++ axum/src/docs/extract.md | 10 ++ axum/src/extract/mod.rs | 2 +- axum/src/routing/tests/mod.rs | 47 ++++++++- 9 files changed, 225 insertions(+), 18 deletions(-) create mode 100644 axum-core/src/extract/default_body_limit.rs diff --git a/axum-core/CHANGELOG.md b/axum-core/CHANGELOG.md index ccc1f62a2a..b61b5fae09 100644 --- a/axum-core/CHANGELOG.md +++ b/axum-core/CHANGELOG.md @@ -7,7 +7,20 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0 # Unreleased -- None. +- **breaking:** Added default limit to how much data `Bytes::from_request` will + consume. Previously it would attempt to consume the entire request body + without checking its length. This meant if a malicious peer sent an large (or + infinite) request body your server might run out of memory and crash. + + The default limit is at 2 MB and can be disabled by adding the new + `DefaultBodyLimit::disable()` middleware. See its documentation for more + details. + + This also applies to `String` which used `Bytes::from_request` internally. + + ([#1346]) + +[#1346]: https://github.com/tokio-rs/axum/pull/1346 # 0.3.0-rc.1 (23. August, 2022) diff --git a/axum-core/Cargo.toml b/axum-core/Cargo.toml index 1868a83cf2..94f672faae 100644 --- a/axum-core/Cargo.toml +++ b/axum-core/Cargo.toml @@ -18,9 +18,12 @@ futures-util = { version = "0.3", default-features = false, features = ["alloc"] http = "0.2.7" http-body = "0.4.5" mime = "0.3.16" +tower-layer = "0.3" +tower-service = "0.3" [dev-dependencies] axum = { path = "../axum", version = "0.6.0-rc.1" } futures-util = "0.3" hyper = "0.14" tokio = { version = "1.0", features = ["macros"] } +tower-http = { version = "0.3.4", features = ["limit"] } diff --git a/axum-core/src/extract/default_body_limit.rs b/axum-core/src/extract/default_body_limit.rs new file mode 100644 index 0000000000..87759c8a9a --- /dev/null +++ b/axum-core/src/extract/default_body_limit.rs @@ -0,0 +1,101 @@ +use self::private::DefaultBodyLimitService; +use tower_layer::Layer; + +/// Layer for configuring the default request body limit. +/// +/// For security reasons, [`Bytes`] will, by default, not accept bodies larger than 2MB. This also +/// applies to extractors that uses [`Bytes`] internally such as `String`, [`Json`], and [`Form`]. +/// +/// This middleware provides ways to configure that. +/// +/// Note that if an extractor consumes the body directly with [`Body::data`], or similar, the +/// default limit is _not_ applied. +/// +/// [`Body::data`]: http_body::Body::data +/// [`Bytes`]: bytes::Bytes +/// [`Json`]: https://docs.rs/axum/0.6.0-rc.1/axum/struct.Json.html +/// [`Form`]: https://docs.rs/axum/0.6.0-rc.1/axum/struct.Form.html +#[derive(Debug, Clone)] +#[non_exhaustive] +pub struct DefaultBodyLimit; + +impl DefaultBodyLimit { + /// Disable the default request body limit. + /// + /// This must be used to receive bodies larger than the default limit of 2MB using [`Bytes`] or + /// an extractor built on it such as `String`, [`Json`], [`Form`]. + /// + /// Note that if you're accepting data from untrusted remotes it is recommend to add your own + /// limit such as [`tower_http::limit`]. + /// + /// # Example + /// + /// ``` + /// use axum::{ + /// Router, + /// routing::get, + /// body::{Bytes, Body}, + /// extract::DefaultBodyLimit, + /// }; + /// use tower_http::limit::RequestBodyLimitLayer; + /// use http_body::Limited; + /// + /// let app: Router<_, Limited> = Router::new() + /// .route("/", get(|body: Bytes| async {})) + /// // Disable the default limit + /// .layer(DefaultBodyLimit::disable()) + /// // Set a different limit + /// .layer(RequestBodyLimitLayer::new(10 * 1000 * 1000)); + /// ``` + /// + /// [`tower_http::limit`]: https://docs.rs/tower-http/0.3.4/tower_http/limit/index.html + /// [`Bytes`]: bytes::Bytes + /// [`Json`]: https://docs.rs/axum/0.6.0-rc.1/axum/struct.Json.html + /// [`Form`]: https://docs.rs/axum/0.6.0-rc.1/axum/struct.Form.html + pub fn disable() -> Self { + Self + } +} + +impl Layer for DefaultBodyLimit { + type Service = DefaultBodyLimitService; + + fn layer(&self, inner: S) -> Self::Service { + DefaultBodyLimitService { inner } + } +} + +#[derive(Copy, Clone, Debug)] +pub(crate) struct DefaultBodyLimitDisabled; + +mod private { + use super::DefaultBodyLimitDisabled; + use http::Request; + use std::task::Context; + use tower_service::Service; + + #[derive(Debug, Clone, Copy)] + pub struct DefaultBodyLimitService { + pub(super) inner: S, + } + + impl Service> for DefaultBodyLimitService + where + S: Service>, + { + type Response = S::Response; + type Error = S::Error; + type Future = S::Future; + + #[inline] + fn poll_ready(&mut self, cx: &mut Context<'_>) -> std::task::Poll> { + self.inner.poll_ready(cx) + } + + #[inline] + fn call(&mut self, mut req: Request) -> Self::Future { + req.extensions_mut().insert(DefaultBodyLimitDisabled); + self.inner.call(req) + } + } +} diff --git a/axum-core/src/extract/mod.rs b/axum-core/src/extract/mod.rs index 36e42a4566..c25166290e 100644 --- a/axum-core/src/extract/mod.rs +++ b/axum-core/src/extract/mod.rs @@ -11,11 +11,12 @@ use std::convert::Infallible; pub mod rejection; +mod default_body_limit; mod from_ref; mod request_parts; mod tuple; -pub use self::from_ref::FromRef; +pub use self::{default_body_limit::DefaultBodyLimit, from_ref::FromRef}; mod private { #[derive(Debug, Clone, Copy)] diff --git a/axum-core/src/extract/request_parts.rs b/axum-core/src/extract/request_parts.rs index 245657cf3d..60ef1b79ad 100644 --- a/axum-core/src/extract/request_parts.rs +++ b/axum-core/src/extract/request_parts.rs @@ -1,4 +1,6 @@ -use super::{rejection::*, FromRequest, FromRequestParts}; +use super::{ + default_body_limit::DefaultBodyLimitDisabled, rejection::*, FromRequest, FromRequestParts, +}; use crate::BoxError; use async_trait::async_trait; use bytes::Bytes; @@ -82,11 +84,20 @@ where type Rejection = BytesRejection; async fn from_request(req: Request, _: &S) -> Result { - let body = req.into_body(); - - let bytes = crate::body::to_bytes(body) - .await - .map_err(FailedToBufferBody::from_err)?; + // update docs in `axum-core/src/extract/default_body_limit.rs` and + // `axum/src/docs/extract.md` if this changes + const DEFAULT_LIMIT: usize = 2_097_152; // 2 mb + + let bytes = if req.extensions().get::().is_some() { + crate::body::to_bytes(req.into_body()) + .await + .map_err(FailedToBufferBody::from_err)? + } else { + let body = http_body::Limited::new(req.into_body(), DEFAULT_LIMIT); + crate::body::to_bytes(body) + .await + .map_err(FailedToBufferBody::from_err)? + }; Ok(bytes) } @@ -102,15 +113,18 @@ where { type Rejection = StringRejection; - async fn from_request(req: Request, _: &S) -> Result { - let body = req.into_body(); - - let bytes = crate::body::to_bytes(body) + async fn from_request(req: Request, state: &S) -> Result { + let bytes = Bytes::from_request(req, state) .await - .map_err(FailedToBufferBody::from_err)? - .to_vec(); - - let string = String::from_utf8(bytes).map_err(InvalidUtf8::from_err)?; + .map_err(|err| match err { + BytesRejection::FailedToBufferBody(inner) => { + StringRejection::FailedToBufferBody(inner) + } + })?; + + let string = std::str::from_utf8(&bytes) + .map_err(InvalidUtf8::from_err)? + .to_owned(); Ok(string) } diff --git a/axum/CHANGELOG.md b/axum/CHANGELOG.md index b8ae2b5706..e3239f02c1 100644 --- a/axum/CHANGELOG.md +++ b/axum/CHANGELOG.md @@ -7,6 +7,25 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0 # Unreleased +## Security + +- **breaking:** Added default limit to how much data `Bytes::from_request` will + consume. Previously it would attempt to consume the entire request body + without checking its length. This meant if a malicious peer sent an large (or + infinite) request body your server might run out of memory and crash. + + The default limit is at 2 MB and can be disabled by adding the new + `DefaultBodyLimit::disable()` middleware. See its documentation for more + details. + + This also applies to these extractors which used `Bytes::from_request` + internally: + - `Form` + - `Json` + - `String` + + ([#1346]) + ## Routing - **breaking:** Adding a `.route_layer` onto a `Router` or `MethodRouter` @@ -21,6 +40,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0 [#1327]: https://github.com/tokio-rs/axum/pull/1327 [#1342]: https://github.com/tokio-rs/axum/pull/1342 +[#1346]: https://github.com/tokio-rs/axum/pull/1346 # 0.6.0-rc.1 (23. August, 2022) diff --git a/axum/src/docs/extract.md b/axum/src/docs/extract.md index a7000e59b2..488032d2a3 100644 --- a/axum/src/docs/extract.md +++ b/axum/src/docs/extract.md @@ -11,6 +11,7 @@ Types and traits for extracting data from requests. - [Accessing inner errors](#accessing-inner-errors) - [Defining custom extractors](#defining-custom-extractors) - [Accessing other extractors in `FromRequest` or `FromRequestParts` implementations](#accessing-other-extractors-in-fromrequest-or-fromrequestparts-implementations) +- [Request body limits](#request-body-limits) - [Request body extractors](#request-body-extractors) - [Running extractors from middleware](#running-extractors-from-middleware) - [Wrapping extractors](#wrapping-extractors) @@ -620,6 +621,14 @@ let app = Router::new().route("/", get(handler)).layer(Extension(state)); # }; ``` +# Request body limits + +For security reasons, [`Bytes`] will, by default, not accept bodies larger than +2MB. This also applies to extractors that uses [`Bytes`] internally such as +`String`, [`Json`], and [`Form`]. + +For more details, including how to disable this limit, see [`DefaultBodyLimit`]. + # Request body extractors Most of the time your request body type will be [`body::Body`] (a re-export @@ -816,6 +825,7 @@ async fn handler( ``` [`body::Body`]: crate::body::Body +[`Bytes`]: crate::body::Bytes [customize-extractor-error]: https://github.com/tokio-rs/axum/blob/main/examples/customize-extractor-error/src/main.rs [`HeaderMap`]: https://docs.rs/http/latest/http/header/struct.HeaderMap.html [`Request`]: https://docs.rs/http/latest/http/struct.Request.html diff --git a/axum/src/extract/mod.rs b/axum/src/extract/mod.rs index c3d0ce3329..76e780b22c 100644 --- a/axum/src/extract/mod.rs +++ b/axum/src/extract/mod.rs @@ -16,7 +16,7 @@ mod request_parts; mod state; #[doc(inline)] -pub use axum_core::extract::{FromRef, FromRequest, FromRequestParts}; +pub use axum_core::extract::{DefaultBodyLimit, FromRef, FromRequest, FromRequestParts}; #[doc(inline)] #[allow(deprecated)] diff --git a/axum/src/routing/tests/mod.rs b/axum/src/routing/tests/mod.rs index 5eeac6148c..08efd28f07 100644 --- a/axum/src/routing/tests/mod.rs +++ b/axum/src/routing/tests/mod.rs @@ -1,13 +1,14 @@ use crate::{ body::{Bytes, Empty}, error_handling::HandleErrorLayer, - extract::{self, FromRef, Path, State}, + extract::{self, DefaultBodyLimit, FromRef, Path, State}, handler::{Handler, HandlerWithoutStateExt}, response::IntoResponse, routing::{delete, get, get_service, on, on_service, patch, patch_service, post, MethodFilter}, test_helpers::*, BoxError, Json, Router, }; +use futures_util::stream::StreamExt; use http::{header::CONTENT_LENGTH, HeaderMap, Request, Response, StatusCode, Uri}; use hyper::Body; use serde_json::json; @@ -604,6 +605,50 @@ async fn routes_must_start_with_slash() { TestClient::new(app); } +#[tokio::test] +async fn body_limited_by_default() { + let app = Router::new() + .route("/bytes", post(|_: Bytes| async {})) + .route("/string", post(|_: String| async {})) + .route("/json", post(|_: Json| async {})); + + let client = TestClient::new(app); + + for uri in ["/bytes", "/string", "/json"] { + println!("calling {}", uri); + + let stream = futures_util::stream::repeat("a".repeat(1000)).map(Ok::<_, hyper::Error>); + let body = Body::wrap_stream(stream); + + let res_future = client + .post(uri) + .header("content-type", "application/json") + .body(body) + .send(); + let res = tokio::time::timeout(Duration::from_secs(3), res_future) + .await + .expect("never got response"); + + assert_eq!(res.status(), StatusCode::PAYLOAD_TOO_LARGE); + } +} + +#[tokio::test] +async fn disabling_the_default_limit() { + let app = Router::new() + .route("/", post(|_: Bytes| async {})) + .layer(DefaultBodyLimit::disable()); + + let client = TestClient::new(app); + + // `DEFAULT_LIMIT` is 2mb so make a body larger than that + let body = Body::from("a".repeat(3_000_000)); + + let res = client.post("/").body(body).send().await; + + assert_eq!(res.status(), StatusCode::OK); +} + #[tokio::test] async fn limited_body_with_content_length() { const LIMIT: usize = 3;