By administering your own OPA server, you can make use of extended OPA use cases. For example, your Rego rules can live as a signed bundle in an external, central location, such as an AWS S3 bucket to meet your internal security requirements. Bringing your own OPA server increases the administrative complexity, but works better at scale and provides more OPA-native support for teams familiar with administering an OPA server. It also lets you take advantage of your existing OPA server configuration and enterprise OPA license.

Other OPA options:

About bringing your own OPA server

When you bring your own OPA server, you are responsible for setting up and administering the server per OPA best practices. You have a few setup options:

  • Deploy the OPA server to the same cluster as your Gloo external auth service. This option is best suited for testing purposes or simpler, single-cluster use cases.
  • Host the OPA server in a remote location that is accessible from your cluster. For this approach, you must create an external service to represent the OPA server and update the Gloo external auth server to refer to this external service. This option is best suited for existing, enterprise OPA deployments in complex, multicluster production scenarios.

The following diagram and the steps in the rest of this guide show how you can set up your own OPA server.

Figure: Architecture for bringing your own remote OPA server.
Figure: Architecture for bringing your own remote OPA server.
  1. A user sends a request that the ingress gateway receives. The request matches a route that is protected by an external auth policy that uses OPA.
  2. The ingress gateway sends the request to the external auth service for an authorization decision.
  3. The external auth service passes the request through to the OPA server to make an authorization decision.
    • If the OPA server is within the cluster, the external auth service can refer to the OPA server by using its Kubernetes service address.
    • If the OPA server is outside the cluster, the external auth service refers to the OPA server by a reachable address, such as on the same private network.
  4. The OPA server loads the OPA config of Rego rules from a bundle in a cloud provider. The OPA server uses these Rego rules to make an authorization decision on the request. You can provide the OPA config via a YAML file during the initial installation, or subsequently in a Kubernetes config map. Note that the request does not trigger loading the rules. You must restart the OPA server each time that you update the OPA config.
  5. The OPA server returns the authorization decision to the external auth service, which returns the authorization decision to the ingress gateway.
  6. The ingress gateway handles the request per the authorization decision.
    • If unauthorized, the ingress gateway denies the request.
    • If authorized, the ingress gateway forwards the request to the destination workload.

Before you begin

  1. Complete the multicluster getting started guide to set up the following testing environment.

    • Three clusters along with environment variables for the clusters and their Kubernetes contexts.
    • The Gloo meshctl CLI, along with other CLI tools such as kubectl and istioctl.
    • The Gloo management server in the management cluster, and the Gloo agents in the workload clusters.
    • Istio installed in the workload clusters.
    • A simple Gloo workspace setup.
  2. Install Bookinfo and other sample apps.
  3. Make sure that the external auth service is installed and running. If not, install the external auth service in your Gloo environment.

      kubectl get pods --context $REMOTE_CONTEXT1  -A -l app=ext-auth-service
      
  4. Download the opa CLI tool.

Bundle Rego rules

Prepare OPA configuration for the OPA server by creating, bundling, and referring to a Rego policy with the rules you want to enforce.

  1. Create a Rego policy file in a rego directory with the rules you want to enforce with OPA. The following policy allows GET and POST HTTP requests and denies requests to the /status endpoint.

      mkdir rego
    cat <<EOF > rego/policy.rego
    package httpbin
    
    import input.http_request
    
    # deny requests by default
    default allowed = false
    
    # set allowed to true if no error message
    allowed {
        not body
    }
    
    # return result and error message
    allow["allowed"] = allowed
    allow["body"] = body
    
    # main policy logic, with error message per rule
    body = "HTTP verb is not allowed" { not http_verb_allowed }
    else = "Path is not allowed" { not path_allowed }
    
    # allow only GET and POST requests
    http_verb_allowed {
       {"GET", "POST"}[_] == http_request.method
    }
    
    # deny requests to /status endpoint
    path_allowed {
       not startswith(http_request.path, "/status")
    }
    EOF
      
  2. Use the opa CLI to bundle your Rego rules. The output of the command is a bundle.tar.gz compressed file in your current directory. For more information, see the OPA docs.

      opa build -b rego/
      
  3. Store your bundle in a supported cloud provider. For options and steps, see the OPA implementation docs.

  4. Create a Kubernetes config map that refers to your bundle.

      kubectl apply --context $REMOTE_CONTEXT1  -f - <<EOF
    apiVersion: v1
    kind: ConfigMap
    metadata:
      name: opa-config
      namespace: gloo-mesh-addons
    data:
      config.yaml: |
        services:
          gcs:
            url: https://storage.googleapis.com/storage/v1/b/test-opa-bundles
        bundles:
          bundle:
            service: gcs
            resource: 'bundle.tar.gz?alt=media'
    EOF
      
    Review the following table to understand this configuration.
    SettingDescription
    namespaceCreate the config map in the same namespace as the OPA server, such as gloo-mesh-addons.
    config.yamlEnter the bundle configuration details that you created as part of uploading your bundle to the cloud provider. For more information, see the OPA implementation docs.
    servicesProvide the details of the cloud service where the bundle is located. In this example, the bundle is in a Google Cloud Storage (gcs) bucket at a test URL. The test URL is public, but you can also set up secure access with the credentials settings.
    bundlesProvide the details about the particular bundle that you want to use. In this example, the bundle is the bundle.tar.gz bundle that you previously created.
    Other settingsIf you use other features, you can configure those settings in the config map. Common settings include signed bundles and returning decision logs. For more information, see the OPA implementation docs.

Set up the OPA server

Set up your OPA server as a remote server or as a deployment within the cluster.

  1. Deploy the OPA server. For steps, you can follow the OPA deployment docs. Make sure to update the deployment with the OPA config map that you previously created. Later, if you want to update the OPA config, see Update OPA config.

  2. Verify that the OPA server is running.

      kubectl get pods -A -l app=opa --context $REMOTE_CONTEXT1 
      
  3. Get the service details, which you use later to refer to the OPA server in the external auth policy.

      kubectl get svc -A -l app=opa --context $REMOTE_CONTEXT1 
      

    Example output: Later, you use the OPA service address <service>.<namespace>:<port>, such as http://opa.gloo-mesh-addons:8181.

      NAMESPACE          NAME   TYPE       CLUSTER-IP     EXTERNAL-IP   PORT(S)          AGE
    gloo-mesh-addons   opa    NodePort   10.xx.xx.xxx   <none>        8181:32427/TCP   15s
      
  4. Confirm that the OPA server loaded the bundle that you referred to in the config map. Note that the following example command pipes the output to jq for readability.

      kubectl logs -n gloo-mesh-addons deploy/opa --context $REMOTE_CONTEXT1  | jq
      
       {
         "level": "info",
         "msg": "Bundle loaded and activated successfully. Etag updated to CMzq8eO/p4EDEAE=.",
         "name": "httpbin",
         "plugin": "bundle",
         "time": "2023-09-20T15:54:47Z"
       }
       

Create the OPA external auth policy

Create the Gloo external auth resources to enforce the OPA policy.

  1. Create an external auth server to use for your policy.

      kubectl apply --context $REMOTE_CONTEXT1  -f - <<EOF
    apiVersion: admin.gloo.solo.io/v2
    kind: ExtAuthServer
    metadata:
      name: opa-ext-auth-server
      namespace: httpbin
    spec:
      destinationServer:
        port:
          number: 8083
        ref:
          cluster: $CLUSTER_NAME
          name: ext-auth-service
          namespace: gloo-mesh-addons
    EOF
      
  2. Create an external auth policy that uses the OPA config map.

  kubectl apply --context ${REMOTE_CONTEXT1} -f - <<EOF
apiVersion: security.policy.gloo.solo.io/v2
kind: ExtAuthPolicy
metadata:
  name: opa-server
  namespace: httpbin
spec:
  applyToDestinations:
  - selector:
      labels:
        app: httpbin
  config:
    server:
      name: opa-ext-auth-server
      namespace: httpbin
    glooAuth:
      configs:
      - opaServerAuth:
          package: httpbin
          ruleName: allow/allowed
          serverAddr: http://opa.gloo-mesh-addons:8181
EOF
  

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

SettingDescription
applyToDestinationsUse labels to apply the policy to destinations. Destinations might be a Kubernetes service, VirtualDestination, or ExternalService (if supported by the policy). If you do not specify any destinations or routes, the policy applies to all destinations in the workspace by default. If you do not specify any destinations but you do specify a route, the policy applies to the route but to no destinations.
serverThe external auth server to use for the policy.
opaServerAuthConfigure the OPA server sidecar authentication details.
packageRefer to the package in the Rego bundle that you set up in the config map earlier, such as httpbin from the policy.rego file.
ruleNameSelect the Rego rules within the bundle that you want to enforce for this OPA external auth policy. From the policy.rego file, you set the allow input document and only the allowed decision for that document, allow/allowed. For more information about rule names, see the OPA Data API docs.
serverAddrThe reachable address of the OPA server that you previously retrieved when you deployed the OPA server.
  1. Confirm that the external auth policy’s state is ACCEPTED.
      kubectl get -n httpbin ExtAuthPolicy opa-server -o yaml --context $REMOTE_CONTEXT1 
      

Verify the OPA external auth policy

Verify that the Rego rules are evaluated by the OPA server and enforced by the external auth service.

  1. Send an allowed request to the httpbin app, such as a GET bytes request. You get a 200 response.Create a temporary curl pod in the bookinfo namespace, so that you can test the app setup. You can also use this method in Kubernetes 1.23 or later, but an ephemeral container might be simpler.

    1. Create the curl pod.
        kubectl run -it -n httpbin --context ${REMOTE_CONTEXT1} curl --image=curlimages/curl:7.73.0 --rm  -- sh
        
    2. Send a request to the httpbin app.
        curl -H "X-httpbin: true" -v http://httpbin:8000/bytes/5
        
  2. Send the request again along a path that is not allowed by the OPA policy, such as /status. Now, the request is blocked with a 404 Not Found response because the endpoint cannot be accessed.

      curl -H "X-httpbin: true" -v http://httpbin:8000/status
      
  3. This time, send a request to an allowed endpoint but with an HTTP method that is not allowed by the OPA policy, such as PUT. The request is blocked with a 405 Method Not Allowed response.

    1. Send the request to the httpbin app.
        curl -H "X-httpbin: true" -v http://httpbin:8000/status
        
    2. Exit the temporary pod. The pod deletes itself.
        exit
        

Cleanup

You can optionally remove the resources that you set up as part of this guide.

  1. Delete the external auth resources that you created.

      kubectl -n httpbin delete ExtAuthServer opa-ext-auth-server --context $REMOTE_CONTEXT1 
    kubectl -n httpbin delete ExtAuthPolicy opa-server --context $REMOTE_CONTEXT1 
      
  2. Optional: If you no longer need your OPA server, delete it.

      kubectl delete all -l app=opa --context $REMOTE_CONTEXT1 
      

Update OPA config

To update OPA config after initially deploying the OPA server sidecar, choose from the following options.

Steps for creating and updating config maps:

  1. Follow Steps 1 - 3 of Bundle Rego rules to create, bundle, and store your Rego rules in a cloud provider.

  2. Create a Kubernetes config map that refers to your bundle.

      kubectl apply --context $REMOTE_CONTEXT1  -f - <<EOF
    apiVersion: v1
    kind: ConfigMap
    metadata:
      name: opa-config
      namespace: gloo-mesh-addons
    data:
      config.yaml: |
        services:
          gcs:
            url: https://storage.googleapis.com/storage/v1/b/test-opa-bundles
        bundles:
          bundle:
            service: gcs
            resource: 'bundle.tar.gz?alt=media'
    EOF
      
    Review the following table to understand this configuration.
    SettingDescription
    namespaceCreate the config map in the same namespace as the OPA server, such as gloo-mesh-addons.
    config.yamlEnter the bundle configuration details that you created as part of uploading your bundle to the cloud provider. For more information, see the OPA implementation docs.
    servicesProvide the details of the cloud service where the bundle is located. In this example, the bundle is in a Google Cloud Storage (gcs) bucket at a test URL. The test URL is public, but you can also set up secure access with the credentials settings.
    bundlesProvide the details about the particular bundle that you want to use. In this example, the bundle is the bundle.tar.gz bundle that you previously created.
    Other settingsIf you use other features, you can configure those settings in the config map. Common settings include signed bundles and returning decision logs. For more information, see the OPA implementation docs.
  3. Update the OPA server to refer to the OPA config map.

    1. Get your current deployment configuration.

        kubectl get deployment -l app=opa -A -o yaml --context $REMOTE_CONTEXT1  > opa-deploy.yaml
      open opa-deploy.yaml
        
    2. Edit and save the deployment configuration to add the reference to the OPA config map that you previously created.

        ...
      spec:
        containers:
          volumeMounts:
            - readOnly: true
              mountPath: /policies
              name: opa-config
        volumes:
        - name: opa-config
          configMap:
            name: opa-config
        
    3. Update the deployment.

        kubectl apply -f opa-deploy.yaml --context $REMOTE_CONTEXT1 
        
    4. Optional: Later, if you change the contents of the config map, you must restart the OPA server for the OPA config changes to take effect. Optionally, you can create the config map before enabling the OPA server sidecar and refer to the config map during the Helm installation. This way, the first time the OPA server sidecar comes up, it has the OPA config already, reducing the number of times you might have to restart the service.

        kubectl rollout restart deployment/opa -n gloo-mesh-addons --context $REMOTE_CONTEXT1 
        
  4. Confirm that the OPA server loaded the bundle that you referred to in the config map. Note that the following example command pipes the output to jq for readability.

      kubectl logs -n gloo-mesh-addons deploy/opa --context $REMOTE_CONTEXT1  | jq
      
       {
         "level": "info",
         "msg": "Bundle loaded and activated successfully. Etag updated to CMzq8eO/p4EDEAE=.",
         "name": "httpbin",
         "plugin": "bundle",
         "time": "2023-09-20T15:54:47Z"
       }