CORS
Enforce client-site access controls with cross-origin resource sharing (CORS).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 callsapi.com
- A different subdomain, such as
example.com
callsapi.example.com
- A different port, such as
example.com
callsexample.com:3001
- A different protocol, such as
https://example.com
callshttp://example.com
For more information, see the following resources.
If you import or export resources across workspaces, your policies might not apply. For more information, see Import and export policies.
Before you begin
Follow the getting started instructions to:
- Set up Gloo Gateway in a single cluster.
- Deploy sample apps.
- 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.
Setting | Description |
---|---|
spec.applyToRoutes |
Use 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. |
maxAge |
Optionally 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 . |
allowCredential |
Optionally 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 . |
allowHeaders |
Specify 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. |
allowMethods |
Specify 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. |
allowOrigins |
Enter 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
-
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
-
Send a request to the ratings app through the ingress gateway that the route table is attached to.
curl -vik -H "Origin: http://istio.io" -H "Access-Control-Request-Method: GET" -X OPTIONS --resolve www.example.com:80:${INGRESS_GW_IP} https://www.example.com:80/ratings/1
curl -vik -H "Origin: http://istio.io" -H "Access-Control-Request-Method: GET" -X OPTIONS --resolve www.example.com:443:${INGRESS_GW_IP} https://www.example.com:443/ratings/1
-
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
, andAccess-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 date: Tue, 02 Feb 2022 22:29:04 GMT server: istio-envoy content-length: 0
- If CORS is enabled, you see an
-
Optional: Clean up the resources that you created.
kubectl -n bookinfo delete corspolicy simple-cors