Refactor to separate out validation from response building step 1

src/fairing.rs

@@ -2,7 +2,7 @@
 use rocket::{self, Request, Outcome};
 use rocket::http::{self, Status};
 
-use {Cors, build_cors_response};
+use {Cors, Error, validate, preflight_response, actual_request_response, origin, request_headers};
 
 /// Route for Fairing error handling
 pub(crate) fn fairing_error_route<'r>(
@@ -28,6 +28,43 @@ fn route_to_fairing_error_handler(options: &Cors, status: u16, request: &mut Req
     request.set_uri(format!("{}/{}", options.fairing_route_base, status));
 }
 
+fn on_response_wrapper(
+    options: &Cors,
+    request: &Request,
+    response: &mut rocket::Response,
+) -> Result<(), Error> {
+    let origin = match origin(request)? {
+        None => {
+            // Not a CORS request
+            return Ok(());
+        }
+        Some(origin) => origin,
+    };
+
+    let cors_response = if request.method() == http::Method::Options {
+        let headers = request_headers(request)?;
+        preflight_response(options, origin, headers)
+    } else {
+        actual_request_response(options, origin)
+    };
+
+    cors_response.merge(response);
+
+    // If this was an OPTIONS request and no route can be found, we should turn this
+    // into a HTTP 204 with no content body.
+    // This allows the user to not have to specify an OPTIONS route for everything.
+    //
+    // TODO: Is there anyway we can make this smarter? Only modify status codes for
+    // requests where an actual route exist?
+    if request.method() == http::Method::Options && request.method() == http::Method::Options &&
+        request.route().is_none()
+    {
+        response.set_status(Status::NoContent);
+        let _ = response.take_body();
+    }
+    Ok(())
+}
+
 impl rocket::fairing::Fairing for Cors {
     fn info(&self) -> rocket::fairing::Info {
         rocket::fairing::Info {
@@ -52,7 +89,7 @@ impl rocket::fairing::Fairing for Cors {
     fn on_request(&self, request: &mut Request, _: &rocket::Data) {
         // Build and merge CORS response
         // Type annotation is for sanity check
-        let cors_response = build_cors_response(self, request);
+        let cors_response = validate(self, request);
         if let Err(ref err) = cors_response {
             error_!("CORS Error: {}", err);
             let status = err.status();
@@ -61,25 +98,10 @@ impl rocket::fairing::Fairing for Cors {
     }
 
     fn on_response(&self, request: &Request, response: &mut rocket::Response) {
-        // Rebuild the response
+        if let Err(err) = on_response_wrapper(self, request, response) {
-        match build_cors_response(self, request) {
+            error_!("Fairings on_response error: {}\nMost likely a bug", err);
-            Err(_) => {
+            response.set_status(Status::InternalServerError);
-                // We have dealt with this already
+            let _ = response.take_body();
-            }
-            Ok(cors_response) => {
-                cors_response.merge(response);
-
-                // If this was an OPTIONS request and no route can be found, we should turn this
-                // into a HTTP 204 with no content body.
-                // This allows the user to not have to specify an OPTIONS route for everything.
-                //
-                // TODO: Is there anyway we can make this smarter? Only modify status codes for
-                // requests where an actual route exist?
-                if request.method() == http::Method::Options && request.route().is_none() {
-                    response.set_status(Status::NoContent);
-                    let _ = response.take_body();
-                }
-            }
         }
     }
 }

src/lib.rs

@@ -506,7 +506,7 @@ impl Cors {
     /// `Guard` type. This is useful if you want an even more ad-hoc based approach to respond to
     /// CORS by using a `Cors` that is not in Rocket's managed state.
     pub fn guard<'a, 'r>(&'a self, request: &'a Request<'r>) -> Result<Guard<'r>, Error> {
-        let response = build_cors_response(self, request)?;
+        let response = validate_and_build(self, request)?;
         Ok(Guard::new(response))
     }
 
@@ -693,11 +693,11 @@ impl Response {
     }
 
     /// Validate and create a new CORS Response from a request and settings
-    pub fn build_cors_response<'a, 'r>(
+    pub fn validate_and_build<'a, 'r>(
         options: &'a Cors,
         request: &'a Request<'r>,
     ) -> Result<Self, Error> {
-        build_cors_response(options, request)
+        validate_and_build(options, request)
     }
 }
 
@@ -747,7 +747,7 @@ impl<'a, 'r> FromRequest<'a, 'r> for Guard<'r> {
             }
         };
 
-        match Response::build_cors_response(&options, request) {
+        match Response::validate_and_build(&options, request) {
             Ok(response) => Outcome::Success(Self::new(response)),
             Err(error) => Outcome::Failure((error.status(), error)),
         }
@@ -796,35 +796,60 @@ impl<'r, R: response::Responder<'r>> response::Responder<'r> for Responder<'r, R
     }
 }
 
-/// Validates a request for CORS and returns a CORS Response
+/// Result of CORS validation.
-fn build_cors_response(options: &Cors, request: &Request) -> Result<Response, Error> {
+///
-    // Existing CORS response?
+/// The variants hold enough information to build a response to the validation result
-    // if has_allow_origin(response) {
+enum ValidationResult {
-    //     return Ok(());
+    /// Not a CORS request
-    // }
+    None,
+    /// Successful preflight request
+    Preflight {
+        origin: Origin,
+        headers: Option<AccessControlRequestHeaders>,
+    },
+    /// Successful actual request
+    Request { origin: Origin },
+}
 
+/// Validates a request for CORS and returns a CORS Response
+fn validate_and_build(options: &Cors, request: &Request) -> Result<Response, Error> {
+    let result = validate(options, request)?;
+
+    Ok(match result {
+        ValidationResult::None => Response::new(),
+        ValidationResult::Preflight { origin, headers } => {
+            preflight_response(options, origin, headers)
+        }
+        ValidationResult::Request { origin } => actual_request_response(options, origin),
+    })
+}
+
+/// Validate a CORS request
+fn validate(options: &Cors, request: &Request) -> Result<ValidationResult, Error> {
     // 1. If the Origin header is not present terminate this set of steps.
     // The request is outside the scope of this specification.
     let origin = origin(request)?;
     let origin = match origin {
         None => {
             // Not a CORS request
-            return Ok(Response::new());
+            return Ok(ValidationResult::None);
         }
         Some(origin) => origin,
     };
 
     // Check if the request verb is an OPTION or something else
-    let cors_response = match request.method() {
+    match request.method() {
         http::Method::Options => {
             let method = request_method(request)?;
             let headers = request_headers(request)?;
-            preflight(options, origin, method, headers)
+            preflight_validate(options, &origin, &method, &headers)?;
+            Ok(ValidationResult::Preflight { origin, headers })
         }
-        _ => actual_request(options, origin),
+        _ => {
-    }?;
+            actual_request_validate(options, &origin)?;
-
+            Ok(ValidationResult::Request { origin })
-    Ok(cors_response)
+        }
+    }
 }
 
 /// Consumes the responder and based on the provided list of allowed origins,
@@ -905,35 +930,24 @@ fn request_headers(request: &Request) -> Result<Option<AccessControlRequestHeade
     }
 }
 
-/// Construct a preflight response based on the options. Will return an `Err`
+/// Do pre-flight validation checks
-/// if any of the preflight checks fail.
 ///
 /// This implementation references the
 /// [W3C recommendation](https://www.w3.org/TR/cors/#resource-preflight-requests).
-fn preflight(
+fn preflight_validate(
     options: &Cors,
-    origin: Origin,
+    origin: &Origin,
-    method: Option<AccessControlRequestMethod>,
+    method: &Option<AccessControlRequestMethod>,
-    headers: Option<AccessControlRequestHeaders>,
+    headers: &Option<AccessControlRequestHeaders>,
-) -> Result<Response, Error> {
+) -> Result<(), Error> {
-    options.validate()?;
+
-    let response = Response::new();
+    options.validate()?; // Fast-forward check for #7
 
     // Note: All header parse failures are dealt with in the `FromRequest` trait implementation
 
     // 2. If the value of the Origin header is not a case-sensitive match for any of the values
     // in list of origins do not set any additional headers and terminate this set of steps.
     validate_origin(&origin, &options.allowed_origins)?;
-    let response = match options.allowed_origins {
-        AllOrSome::All => {
-            if options.send_wildcard {
-                response.any()
-            } else {
-                response.origin(origin.as_str(), true)
-            }
-        }
-        AllOrSome::Some(_) => response.origin(origin.as_str(), false),
-    };
 
     // 3. Let `method` be the value as result of parsing the Access-Control-Request-Method
     // header.
@@ -941,7 +955,7 @@ fn preflight(
     // do not set any additional headers and terminate this set of steps.
     // The request is outside the scope of this specification.
 
-    let method = method.ok_or_else(|| Error::MissingRequestMethod)?;
+    let method = method.as_ref().ok_or_else(|| Error::MissingRequestMethod)?;
 
     // 4. Let header field-names be the values as result of parsing the
     // Access-Control-Request-Headers headers.
@@ -953,26 +967,29 @@ fn preflight(
     // 5. If method is not a case-sensitive match for any of the values in list of methods
     // do not set any additional headers and terminate this set of steps.
 
-    validate_allowed_method(&method, &options.allowed_methods)?;
+    validate_allowed_method(method, &options.allowed_methods)?;
-    let response = response.methods(&options.allowed_methods);
 
     // 6. If any of the header field-names is not a ASCII case-insensitive match for any of the
     // values in list of headers do not set any additional headers and terminate this set of
     // steps.
 
-    let response = if let Some(ref headers) = headers {
+    if let &Some(ref headers) = headers {
         validate_allowed_headers(headers, &options.allowed_headers)?;
-        let &AccessControlRequestHeaders(ref headers) = headers;
+    }
-        response.headers(
+
-            headers
+    Ok(())
-                .iter()
+}
-                .map(|s| &**s.deref())
+
-                .collect::<Vec<&str>>()
+/// Build a response for pre-flight checks
-                .as_slice(),
+///
-        )
+/// This implementation references the
-    } else {
+/// [W3C recommendation](https://www.w3.org/TR/cors/#resource-preflight-requests).
-        response
+fn preflight_response(
-    };
+    options: &Cors,
+    origin: Origin,
+    headers: Option<AccessControlRequestHeaders>,
+) -> Response {
+    let response = Response::new();
 
     // 7. If the resource supports credentials add a single Access-Control-Allow-Origin header,
     // with the value of the Origin header as value, and add a
@@ -983,6 +1000,16 @@ fn preflight(
     // Note: The string "*" cannot be used for a resource that supports credentials.
 
     // Validation has been done in options.validate
+    let response = match options.allowed_origins {
+        AllOrSome::All => {
+            if options.send_wildcard {
+                response.any()
+            } else {
+                response.origin(origin.as_str(), true)
+            }
+        }
+        AllOrSome::Some(_) => response.origin(origin.as_str(), false),
+    };
     let response = response.credentials(options.allow_credentials);
 
     // 8. Optionally add a single Access-Control-Max-Age header
@@ -998,7 +1025,7 @@ fn preflight(
     // simply returning the method indicated by Access-Control-Request-Method
     // (if supported) can be enough.
 
-    // Done above
+    let response = response.methods(&options.allowed_methods);
 
     // 10. If each of the header field-names is a simple header and none is Content-Type,
     // this step may be skipped.
@@ -1010,17 +1037,29 @@ fn preflight(
     // Since the list of headers can be unbounded, simply returning supported headers
     // from Access-Control-Allow-Headers can be enough.
 
-    // Done above -- we do not do anything special with simple headers
+    // We do not do anything special with simple headers
+    let response = if let Some(ref headers) = headers {
+        let &AccessControlRequestHeaders(ref headers) = headers;
+        response.headers(
+            headers
+                .iter()
+                .map(|s| &**s.deref())
+                .collect::<Vec<&str>>()
+                .as_slice(),
+        )
+    } else {
+        response
+    };
 
-    Ok(response)
+    response
 }
 
-/// Respond to an actual request based on the settings.
+/// Do checks for an actual request
-/// If the `Origin` is not provided, then this request was not made by a browser and there is no
+///
-/// CORS enforcement.
+/// This implementation references the
-fn actual_request(options: &Cors, origin: Origin) -> Result<Response, Error> {
+/// [W3C recommendation](https://www.w3.org/TR/cors/#resource-requests).
+fn actual_request_validate(options: &Cors, origin: &Origin) -> Result<(), Error> {
     options.validate()?;
-    let response = Response::new();
 
     // Note: All header parse failures are dealt with in the `FromRequest` trait implementation
 
@@ -1029,6 +1068,27 @@ fn actual_request(options: &Cors, origin: Origin) -> Result<Response, Error> {
     // Always matching is acceptable since the list of origins can be unbounded.
 
     validate_origin(&origin, &options.allowed_origins)?;
+
+    Ok(())
+}
+
+/// Build the response for an actual request
+///
+/// This implementation references the
+/// [W3C recommendation](https://www.w3.org/TR/cors/#resource-requests).
+fn actual_request_response(options: &Cors, origin: Origin) -> Response {
+    let response = Response::new();
+
+    // 3. If the resource supports credentials add a single Access-Control-Allow-Origin header,
+    // with the value of the Origin header as value, and add a
+    // single Access-Control-Allow-Credentials header with the case-sensitive string "true" as
+    // value.
+    // Otherwise, add a single Access-Control-Allow-Origin header,
+    // with either the value of the Origin header or the string "*" as value.
+    // Note: The string "*" cannot be used for a resource that supports credentials.
+
+    // Validation has been done in options.validate
+
     let response = match options.allowed_origins {
         AllOrSome::All => {
             if options.send_wildcard {
@@ -1040,15 +1100,6 @@ fn actual_request(options: &Cors, origin: Origin) -> Result<Response, Error> {
         AllOrSome::Some(_) => response.origin(origin.as_str(), false),
     };
 
-    // 3. If the resource supports credentials add a single Access-Control-Allow-Origin header,
-    // with the value of the Origin header as value, and add a
-    // single Access-Control-Allow-Credentials header with the case-sensitive string "true" as
-    // value.
-    // Otherwise, add a single Access-Control-Allow-Origin header,
-    // with either the value of the Origin header or the string "*" as value.
-    // Note: The string "*" cannot be used for a resource that supports credentials.
-
-    // Validation has been done in options.validate
     let response = response.credentials(options.allow_credentials);
 
     // 4. If the list of exposed headers is not empty add one or more
@@ -1066,7 +1117,8 @@ fn actual_request(options: &Cors, origin: Origin) -> Result<Response, Error> {
             .collect::<Vec<&str>>()
             .as_slice(),
     );
-    Ok(response)
+
+    response
 }
 
 #[cfg(test)]

tests/fairing.rs

@@ -172,6 +172,7 @@ fn cors_options_bad_origin() {
     assert_eq!(response.status(), Status::Forbidden);
 }
 
+/// Unlike the "ad-hoc" mode, this should return 404 because we don't have such a route
 #[test]
 fn cors_options_missing_origin() {
     let client = Client::new(rocket()).unwrap();
@@ -188,7 +189,7 @@ fn cors_options_missing_origin() {
     );
 
     let response = req.dispatch();
-    assert!(response.status().class().is_success());
+    assert_eq!(response.status(), Status::NotFound);
 }
 
 #[test]