.. _install_sandboxes_cors: CORS Filter =========== Cross-Origin Resource Sharing (CORS) is a method of enforcing client-side access controls on resources by specifying external domains that are able to access certain or all routes of your domain. Browsers use the presence of HTTP headers to determine if a response from a different origin is allowed. To help demonstrate how front-envoy can enforce CORS policies, we are releasing a set of `docker compose `_ sandboxes that deploy a frontend and backend service on different origins, both behind front-envoy. The frontend service has a field to input the remote domain of your backend service along with radio buttons to select the remote domain's CORS enforcement. The CORS enforcement choices are: * Disabled: CORS is disabled on the route requested. This will result in a client-side CORS error since the required headers to be considered a valid CORS request are not present. * Open: CORS is enabled on the route requested but the allowed origin is set to ``*``. This is a very permissive policy and means that origin can request data from this endpoint. * Restricted: CORS is enabled on the route requested and the only allowed origin is ``envoyproxy.io``. This will result in a client-side CORS error. Running the Sandboxes ~~~~~~~~~~~~~~~~~~~~~ The following documentation runs through the setup of both services. **Step 1: Install Docker** Ensure that you have a recent versions of ``docker`` and ``docker-compose``. A simple way to achieve this is via the `Docker Desktop `_. **Step 2: Clone the Envoy repo and start all of our containers** If you have not cloned the Envoy repo, clone it with ``git clone git@github.com:envoyproxy/envoy`` or ``git clone https://github.com/envoyproxy/envoy.git`` Terminal 1 .. code-block:: console $ pwd envoy/examples/cors/frontend $ docker-compose pull $ docker-compose up --build -d $ docker-compose ps Name Command State Ports ---------------------------------------------------------------------------------------------------------------------------- frontend_front-envoy_1 /docker-entrypoint.sh /bin ... Up 10000/tcp, 0.0.0.0:8000->80/tcp, 0.0.0.0:8001->8001/tcp frontend_frontend-service_1 /bin/sh -c /usr/local/bin/ ... Up 10000/tcp, 80/tcp Terminal 2 .. code-block:: console $ pwd envoy/examples/cors/backend $ docker-compose up --build -d $ docker-compose ps Name Command State Ports -------------------------------------------------------------------------------------------------------------------------- backend_backend-service_1 /bin/sh -c /usr/local/bin/ ... Up 10000/tcp, 80/tcp backend_front-envoy_1 /docker-entrypoint.sh /bin ... Up 10000/tcp, 0.0.0.0:8002->80/tcp, 0.0.0.0:8003->8001/tcp **Step 3: Test Envoy's CORS capabilities** You can now open a browser to view your frontend service at ``localhost:8000``. Results of the cross-origin request will be shown on the page under *Request Results*. Your browser's CORS enforcement logs can be found in the console. For example: .. code-block:: console Access to XMLHttpRequest at 'http://192.168.99.100:8002/cors/disabled' from origin 'http://192.168.99.101:8000' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. **Step 4: Check stats of backend via admin** When Envoy runs, it can listen to ``admin`` requests if a port is configured. In the example configs, the backend admin is bound to port ``8003``. If you go to ``localhost:8003/stats`` you will be able to view all of the Envoy stats for the backend. You should see the CORS stats for invalid and valid origins increment as you make requests from the frontend cluster. .. code-block:: none http.ingress_http.cors.origin_invalid: 2 http.ingress_http.cors.origin_valid: 7