Fix an issue where Fairing on_response will inject CORS headers into failed CORS requests

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "rocket_cors"
-version = "0.1.1"
+version = "0.1.2"
 license = "Apache-2.0"
 authors = ["Yong Wen Chua <me@yongwen.xyz>"]
 build = "build.rs"

README.md

@@ -29,7 +29,7 @@ might work, but it's not guaranteed.
 Add the following to Cargo.toml:
 
 ```toml
-rocket_cors = "0.1.1"
+rocket_cors = "0.1.2"
 ```
 
 To use the latest `master` branch, for example:

examples/guard.rs

@@ -57,7 +57,10 @@ fn main() {
     };
 
     rocket::ignite()
-        .mount("/", routes![responder, responder_options, response, response_options])
+        .mount(
+            "/",
+            routes![responder, responder_options, response, response_options],
+        )
         .manage(options)
         .launch();
 }

src/fairing.rs

@@ -1,9 +1,39 @@
 //! Fairing implementation
 use rocket::{self, Request, Outcome};
-use rocket::http::{self, Status};
+use rocket::http::{self, Status, Header};
 
 use {Cors, Error, validate, preflight_response, actual_request_response, origin, request_headers};
 
+/// An injected header to quickly give the result of CORS
+static CORS_HEADER: &str = "ROCKET-CORS";
+enum InjectedHeader {
+    Success,
+    Failure,
+}
+
+impl InjectedHeader {
+    fn to_str(&self) -> &'static str {
+        match *self {
+            InjectedHeader::Success => "Success",
+            InjectedHeader::Failure => "Failure",
+        }
+    }
+
+    fn from_str(s: &str) -> Result<Self, Error> {
+        match s {
+            "Success" => Ok(InjectedHeader::Success),
+            "Failure" => Ok(InjectedHeader::Failure),
+            other => {
+                error_!(
+                    "Unknown injected header encountered: {}\nThis is probably a bug.",
+                    other
+                );
+                Err(Error::UnknownInjectedHeader)
+            }
+        }
+    }
+}
+
 /// Route for Fairing error handling
 pub(crate) fn fairing_error_route<'r>(
     request: &'r Request,
@@ -28,6 +58,11 @@ fn route_to_fairing_error_handler(options: &Cors, status: u16, request: &mut Req
     request.set_uri(format!("{}/{}", options.fairing_route_base, status));
 }
 
+/// Inject a header into the Request with result
+fn inject_request_header(header: InjectedHeader, request: &mut Request) {
+    request.replace_header(Header::new(CORS_HEADER, header.to_str()));
+}
+
 fn on_response_wrapper(
     options: &Cors,
     request: &Request,
@@ -41,6 +76,17 @@ fn on_response_wrapper(
         Some(origin) => origin,
     };
 
+    // Get validation result from injected header
+    let injected_header = request.headers().get_one(CORS_HEADER).ok_or_else(|| {
+        Error::MissingInjectedHeader
+    })?;
+    let result = InjectedHeader::from_str(injected_header)?;
+
+    if let InjectedHeader::Failure = result {
+        // Nothing else for us to do
+        return Ok(());
+    }
+
     let cors_response = if request.method() == http::Method::Options {
         let headers = request_headers(request)?;
         preflight_response(options, origin, headers)
@@ -87,13 +133,17 @@ impl rocket::fairing::Fairing for Cors {
     }
 
     fn on_request(&self, request: &mut Request, _: &rocket::Data) {
-        // Build and merge CORS response
-        let cors_response = validate(self, request);
-        if let Err(ref err) = cors_response {
-            error_!("CORS Error: {}", err);
-            let status = err.status();
-            route_to_fairing_error_handler(self, status.code, request);
-        }
+        let injected_header = match validate(self, request) {
+            Ok(_) => InjectedHeader::Success,
+            Err(err) => {
+                error_!("CORS Error: {}", err);
+                let status = err.status();
+                route_to_fairing_error_handler(self, status.code, request);
+                InjectedHeader::Failure
+            }
+        };
+
+        inject_request_header(injected_header, request);
     }
 
     fn on_response(&self, request: &Request, response: &mut rocket::Response) {

src/lib.rs

@@ -27,7 +27,7 @@
 //! Add the following to Cargo.toml:
 //!
 //! ```toml
-//! rocket_cors = "0.1.1"
+//! rocket_cors = "0.1.2"
 //! ```
 //!
 //! To use the latest `master` branch, for example:
@@ -355,6 +355,12 @@ pub enum Error {
     ///
     /// This is a misconfiguration. Use `Rocket::manage` to add a CORS options to managed state.
     MissingCorsInRocketState,
+    /// The `on_response` handler of Fairing could not find the injected header from the Request.
+    /// Either some other fairing has removed it, or this is a bug.
+    MissingInjectedHeader,
+    /// The `on_response` handler of Fairing found an unknown injected header value from the
+    /// Request. Either some other fairing has modified it, or this is a bug.
+    UnknownInjectedHeader,
 }
 
 impl Error {
@@ -363,7 +369,9 @@ impl Error {
             Error::MissingOrigin | Error::OriginNotAllowed | Error::MethodNotAllowed |
             Error::HeadersNotAllowed => Status::Forbidden,
             Error::CredentialsWithWildcardOrigin |
-            Error::MissingCorsInRocketState => Status::InternalServerError,
+            Error::MissingCorsInRocketState |
+            Error::MissingInjectedHeader |
+            Error::UnknownInjectedHeader => Status::InternalServerError,
             _ => Status::BadRequest,
         }
     }
@@ -395,6 +403,14 @@ impl error::Error for Error {
             Error::MissingCorsInRocketState => {
                 "A CORS Request Guard was used, but no CORS Options was available in Rocket's state"
             }
+            Error::MissingInjectedHeader => {
+                "The `on_response` handler of Fairing could not find the injected header from the \
+                 Request. Either some other fairing has removed it, or this is a bug."
+            }
+            Error::UnknownInjectedHeader => {
+                "The `on_response` handler of Fairing found an unknown injected header value from \
+                 the Request. Either some other fairing has modified it, or this is a bug."
+            }
         }
     }
 

tests/fairing.rs

@@ -83,6 +83,11 @@ fn smoke_test() {
     let body_str = response.body().and_then(|body| body.into_string());
     assert_eq!(body_str, Some("Hello CORS".to_string()));
 
+    let origin_header = response
+        .headers()
+        .get_one("Access-Control-Allow-Origin")
+        .expect("to exist");
+    assert_eq!("https://www.acme.com/", origin_header);
 }
 
 #[test]
@@ -107,6 +112,12 @@ fn cors_options_check() {
 
     let response = req.dispatch();
     assert!(response.status().class().is_success());
+
+    let origin_header = response
+        .headers()
+        .get_one("Access-Control-Allow-Origin")
+        .expect("to exist");
+    assert_eq!("https://www.acme.com/", origin_header);
 }
 
 #[test]
@@ -124,6 +135,12 @@ fn cors_get_check() {
     assert!(response.status().class().is_success());
     let body_str = response.body().and_then(|body| body.into_string());
     assert_eq!(body_str, Some("Hello CORS".to_string()));
+
+    let origin_header = response
+        .headers()
+        .get_one("Access-Control-Allow-Origin")
+        .expect("to exist");
+    assert_eq!("https://www.acme.com/", origin_header);
 }
 
 /// This test is to check that non CORS compliant requests to GET should still work. (i.e. curl)
@@ -182,6 +199,13 @@ fn cors_options_missing_origin() {
 
     let response = req.dispatch();
     assert_eq!(response.status(), Status::NotFound);
+
+    assert!(
+        response
+            .headers()
+            .get_one("Access-Control-Allow-Origin")
+            .is_none()
+    );
 }
 
 #[test]
@@ -206,6 +230,12 @@ fn cors_options_bad_request_method() {
 
     let response = req.dispatch();
     assert_eq!(response.status(), Status::Forbidden);
+    assert!(
+        response
+            .headers()
+            .get_one("Access-Control-Allow-Origin")
+            .is_none()
+    );
 }
 
 #[test]
@@ -229,6 +259,12 @@ fn cors_options_bad_request_header() {
 
     let response = req.dispatch();
     assert_eq!(response.status(), Status::Forbidden);
+    assert!(
+        response
+            .headers()
+            .get_one("Access-Control-Allow-Origin")
+            .is_none()
+    );
 }
 
 #[test]
@@ -243,6 +279,12 @@ fn cors_get_bad_origin() {
 
     let response = req.dispatch();
     assert_eq!(response.status(), Status::Forbidden);
+    assert!(
+        response
+            .headers()
+            .get_one("Access-Control-Allow-Origin")
+            .is_none()
+    );
 }
 
 /// This test ensures that on a failing CORS request, the route (along with its side effects)
@@ -270,4 +312,10 @@ fn routes_failing_checks_are_not_executed() {
 
     let response = req.dispatch();
     assert_eq!(response.status(), Status::Forbidden);
+    assert!(
+        response
+            .headers()
+            .get_one("Access-Control-Allow-Origin")
+            .is_none()
+    );
 }

tests/guard.rs

@@ -121,6 +121,11 @@ fn smoke_test() {
     let body_str = response.body().and_then(|body| body.into_string());
     assert_eq!(body_str, Some("Hello CORS".to_string()));
 
+    let origin_header = response
+        .headers()
+        .get_one("Access-Control-Allow-Origin")
+        .expect("to exist");
+    assert_eq!("https://www.acme.com/", origin_header);
 }
 
 #[test]
@@ -146,6 +151,12 @@ fn cors_options_check() {
 
     let response = req.dispatch();
     assert!(response.status().class().is_success());
+
+    let origin_header = response
+        .headers()
+        .get_one("Access-Control-Allow-Origin")
+        .expect("to exist");
+    assert_eq!("https://www.acme.com/", origin_header);
 }
 
 #[test]
@@ -164,6 +175,12 @@ fn cors_get_check() {
     assert!(response.status().class().is_success());
     let body_str = response.body().and_then(|body| body.into_string());
     assert_eq!(body_str, Some("Hello CORS".to_string()));
+
+    let origin_header = response
+        .headers()
+        .get_one("Access-Control-Allow-Origin")
+        .expect("to exist");
+    assert_eq!("https://www.acme.com/", origin_header);
 }
 
 /// This test is to check that non CORS compliant requests to GET should still work. (i.e. curl)
@@ -179,6 +196,12 @@ fn cors_get_no_origin() {
     assert!(response.status().class().is_success());
     let body_str = response.body().and_then(|body| body.into_string());
     assert_eq!(body_str, Some("Hello CORS".to_string()));
+    assert!(
+        response
+            .headers()
+            .get_one("Access-Control-Allow-Origin")
+            .is_none()
+    );
 }
 
 #[test]
@@ -204,6 +227,12 @@ fn cors_options_bad_origin() {
 
     let response = req.dispatch();
     assert_eq!(response.status(), Status::Forbidden);
+    assert!(
+        response
+            .headers()
+            .get_one("Access-Control-Allow-Origin")
+            .is_none()
+    );
 }
 
 #[test]
@@ -224,6 +253,12 @@ fn cors_options_missing_origin() {
 
     let response = req.dispatch();
     assert!(response.status().class().is_success());
+    assert!(
+        response
+            .headers()
+            .get_one("Access-Control-Allow-Origin")
+            .is_none()
+    );
 }
 
 #[test]
@@ -249,6 +284,12 @@ fn cors_options_bad_request_method() {
 
     let response = req.dispatch();
     assert_eq!(response.status(), Status::Forbidden);
+    assert!(
+        response
+            .headers()
+            .get_one("Access-Control-Allow-Origin")
+            .is_none()
+    );
 }
 
 #[test]
@@ -273,6 +314,12 @@ fn cors_options_bad_request_header() {
 
     let response = req.dispatch();
     assert_eq!(response.status(), Status::Forbidden);
+    assert!(
+        response
+            .headers()
+            .get_one("Access-Control-Allow-Origin")
+            .is_none()
+    );
 }
 
 #[test]
@@ -288,6 +335,12 @@ fn cors_get_bad_origin() {
 
     let response = req.dispatch();
     assert_eq!(response.status(), Status::Forbidden);
+    assert!(
+        response
+            .headers()
+            .get_one("Access-Control-Allow-Origin")
+            .is_none()
+    );
 }
 
 /// This test ensures that on a failing CORS request, the route (along with its side effects)
@@ -306,4 +359,10 @@ fn routes_failing_checks_are_not_executed() {
 
     let response = req.dispatch();
     assert_eq!(response.status(), Status::Forbidden);
+    assert!(
+        response
+            .headers()
+            .get_one("Access-Control-Allow-Origin")
+            .is_none()
+    );
 }