For example, you can configure requests that are made on your behalf. At the same time, you can block requests that are made by attacks, such as Javascript code or malware. Consider the following request scenarios that you can configure with CORS.

  • A different domain, such as example.com site calls api.com
  • A different subdomain, such as example.com calls api.example.com
  • A different port, such as example.com calls example.com:3001
  • A different protocol, such as https://example.com calls http://example.com

For more information, see the following resources.

Before you begin

  1. Set up Gloo Mesh Gateway in a single cluster.
  2. Install Bookinfo and other sample apps.

  3. Configure an HTTP listener on your gateway and set up basic routing for the sample apps.

Configure CORS policies

You can apply a CORS policy at the route level. For more information, see Applying policies.

Review the following sample configuration files.

  apiVersion: security.policy.gloo.solo.io/v2
kind: CORSPolicy
metadata:
  name: simple-cors
  namespace: bookinfo
spec:
  applyToRoutes:
  - route:
      labels:
        route: ratings
  config:
    maxAge: 1m
    allowCredentials: true
    allowHeaders:
    - foo
    - bar
    allowMethods:
    - GET
    allowOrigins:
    - exact: http://istio.io

Review the following table to understand this configuration. For more information, see the API docs.

SettingDescription
spec.applyToRoutesUse labels to configure which routes to apply the policy to. This example label matches the app and route from the example route table that you apply separately. If omitted and you do not have another selector such as applyToDestinations, the policy applies to all routes in the workspace.
maxAgeOptionally specify how long the results of a preflight request are cached. This value translates to the Access-Control-Max-Age header. In this example, the value is 1m.
allowCredentialOptionally let the caller send the actual request with credentials, not just the preflight request. This value translates to the Access-Control-Allow-Credentials header. In this example, the value is true.
allowHeadersSpecify a list of HTTP headers that can be used in requests. This value is serialized to the Access-Control-Allow-Headers header. In this example, the foo and bar headers can be used in the request.
allowMethodsSpecify a list of HTTP methods that can be used in requests. This value is serialized to the Access-Control-Allow-Methods header. In this example, only the GET method can be used to access the resource.
allowOriginsEnter a string pattern to use to decide if an origin is allowed. An origin is allowed if any of the string patterns match the origin in the header. You can set up exact, prefix, suffix, or regex matches. By default, matching is case-sensitive for exact, prefix, and suffix matching, unless you include ignoreCase: true. This value is serialized to the Access-Control-Allow-Origin header. In this example, the origin header must match exactly http://istio.io.

Verify CORS policies

  1. Apply the example CORS policy in the cluster with the Bookinfo workspace in your example setup.

      kubectl apply -f - << EOF
apiVersion: security.policy.gloo.solo.io/v2
kind: CORSPolicy
metadata:
  name: simple-cors
  namespace: bookinfo
spec:
  applyToRoutes:
  - route:
      labels:
        route: ratings
  config:
    maxAge: 1m
    allowCredentials: true
    allowHeaders:
    - foo
    - bar
    allowMethods:
    - GET
    allowOrigins:
    - exact: http://istio.io
EOF

  2. Send a request to the app.

    • HTTP:
        curl -vik -H "Origin: http://istio.io" -H "Access-Control-Request-Method: GET" -X OPTIONS --resolve www.example.com:80:${INGRESS_GW_ADDRESS} https://www.example.com:80/ratings/1
    • HTTPS:
        curl -vik -H "Origin: http://istio.io" -H "Access-Control-Request-Method: GET" -X OPTIONS --resolve www.example.com:443:${INGRESS_GW_ADDRESS} https://www.example.com:443/ratings1

  3. Review the responses to verify your CORS policy. Depending on how you set up the policy, you might still expect to get a 200 response, but certain access control headers are missing, which let you know that the CORS is rejected.

    • If CORS is enabled, you see an Access-Control-Allow-Origin header in the response.
    • If CORS is disabled, you do not see any Access-Control-* headers in the response.
    • If the preflight request is successful, the response includes the Access-Control-Allow-Origin, Access-Control-Allow-Methods, and Access-Control-Allow-Headers. If the request was not successful, these headers are missing.

    Example response:

      HTTP/1.1 200 OK 
access-control-allow-origin: http://istio.io 
access-control-allow-credentials: true 
access-control-allow-methods: GET 
access-control-allow-headers: foo,bar 
access-control-max-age: 60

Cleanup

You can optionally remove the resources that you set up as part of this guide.
  kubectl -n bookinfo delete CORSPolicy simple-cors