Open Policy Agent Integration

Open Policy Agent (OPA) is a lightweight general-purpose policy engine that can be co-located with a service. OPA can be integrated as a sidecar, host-level daemon, or library.

Services can offload policy decisions to OPA by executing queries. Hence, policy enforcement can be decoupled from policy decisions.

Configure OPA

To configure OPA, load custom polices into OPA that control the resources users are allowed to access. Relevant data or context can also be loaded into OPA to make decisions.

Polices and data can be loaded into OPA in the following ways::
  • OPA’s RESTful APIs
  • OPA’s bundle feature that downloads polcies and data from remote HTTP servers
  • Filesystem

Configure the Ceph Object Gateway

The following configuration options are available for OPA integration:

rgw use opa authz = {use opa server to authorize client requests}
rgw opa url = {opa server url:opa server port}
rgw opa token = {opa bearer token}
rgw opa verify ssl = {verify opa server ssl certificate}

How does the RGW-OPA integration work

After a user is authenticated, OPA can be used to check if the user is authorized to perform the given action on the resource. OPA responds with an allow or deny decision which is sent back to the RGW which enforces the decision.

Example request:

POST /v1/data/ceph/authz HTTP/1.1
Host: opa.example.com:8181
Content-Type: application/json

{
    "input": {
        "method": "GET",
        "user_info": {
            "used_id": "john",
            "display_name": "John"
        },
        "bucket_info": {
            "bucket": {
                "name": "Testbucket",
                "bucket_id": "testbucket"
            },
            "owner": "john"
        }
    }
}

Response:

{"result": true}

The above is a sample request sent to OPA which contains information about the user, resource and the action to be performed on the resource. Based on the polices and data loaded into OPA, it will verify whether the request should be allowed or denied. In the sample request, RGW makes a POST request to the endpoint /v1/data/ceph/authz, where ceph is the package name and authz is the rule name.