This project provides a simple (not production ready) method for providing a Bundle Server for Open Policy Agent : see: https://www.openpolicyagent.org/docs/v0.12.2/bundles/

I created the sample bundle from the one provided by the above link but simply changed alice & bob to steve & anand to prove it was working

The trivial Golang server is built as usual (docker build .) and the resultant image should be tagged as follows:
docker tag <container built> stevef1uk/opa-opa-istio-plugin

    As an aside, whilst I was trying to get this to work I built my own opa-istio-plugin container and used mine as the image
    in the quick-start.yaml. I built this from the opa-istio-plugin (see: https://github.com/open-policy-agent/opa-istio-plugin)
    with extra trace in the opa bundle downloader in the main opa project (see:https://github.com/open-policy-agent/opa).
    Note: I needed to add to the end of the go.mod file the correct instruction to enable this e.g.
    replace github.com/open-policy-agent/opa => /Users/stevef/Source_Code/go/src/github.com/opa

    Building the opa-istio plugin uses the command:
      make clean build-linux image-quick

The deploy.yaml file deploys the simple server with the OPA Bundle file embedded within it to Kubernetes
The bundle file needs to be built in two stages (assuming policy data in the directory structure below istio)
1. tar cvf bundle.tar istio
2. gzip bundle.tar

The configuration file from the opa-istio-example (see: https://github.com/open-policy-agent/opa-istio-plugin) was modified as documented locally.
The configuration part of my file was as follows:

############################################################
# Example configuration to bootstrap OPA-Istio sidecars.
############################################################
apiVersion: v1
kind: ConfigMap
metadata:
  name: opa-istio-config
data:
  config.yaml: |
    services:
      - name: controller
        url: http://10.128.0.221:8080
    bundles:
      istio/authz:
        service: controller
    plugins:
        envoy_ext_authz_grpc:
            addr: :9191
            query: data.istio.authz.allow
            dry-run: false
            enable-reflection: false
---

Now, the hard coded IP needs to be replaced by a service name when I figure that out.
The IP address needs to be the cluster IP address of the bundle server Pod

The service entry file required is as follows:

apiVersion: networking.istio.io/v1alpha3
kind: ServiceEntry
metadata:
  name: opa-bundle
spec:
  hosts:
   - opa-bundle-server
  ports:
  - number: 8080
    name: http
    protocol: HTTP
  resolution: DNS
  location: MESH_EXTERNAL
---

I have successfully run this on minikube with the deploy.yaml being deployed to a separate namespace.
I needed to create a service entry for my service:
kubectl expose pod  opa-bundle-server -n test --type=LoadBalancer --port=8080

Deploying the bundle server in the same namespace as the sample bookinfo application did not work.

I have also run this on OpenShift, but there are more steps to follows.

Steps for how to get OPA to work with crc (OpenShift) and RedHat Service Mesh

crc version:
version: 1.0.0-rc.0+34371d3
OpenShift version: 4.2.0-0.nightly-2019-09-26-192831 (embedded in binary)

Service Mesh Install Steps:

crc start
crc console —url
Install RedHat Elastic Operator from Console logged in as kubeadmin using Operators -> OperatorHub & enable subscription
in a terminal login using kubeadmin
oc new-project istio-system
oc new-project myproject
Install RedHat Jaeger Operator & enable subscription
Install RedHat Kiali Operator & enable subscription
Wait for all operators to have a status of InstallSucceeded using Operators -> Installed Operators
Install RedHat OpenShift Service Mesh & enable subscription
Wait until the Service Mesh operators has installed
Switch to project istio-system and return to Installed Operators pane
Select the RedHat Service Mesh Operator API: ’Istio Service Mesh Control Plane’ and then ‘Create Service Mesh Control Plane’
Pods (12) are then created - wait for them to all be in running state & there should be 5 routes created - make a note of the istio-ingressgateway URL for later
Select the RedHat Service Mesh Operator API: ‘Istio Service Mesh Member Role’ and then ‘Create Service Mesh Member Rolls’. Edit the YAML to add myproject (or the project you want to use) within members & Create
Still in project istio-system edit the config map: istio and find disablePolicyChecks and change true to false and save
OPA Install Steps following: https://github.com/open-policy-agent/opa-istio-plugin :
1. kubectl apply -f https://raw.githubusercontent.com/open-policy-agent/opa-istio-plugin/master/quick_start.yaml
2. Using terminal give opa-istio project required permissions:
oc adm policy add-scc-to-user anyuid -z default -n opa-istio
oc adm policy add-scc-to-user privileged -z default -n opa-istio
3. From terminal or console delete the admission-controller pod in project opa-istio so that a new container is created and will run successfully
4. Using terminal switch to my project (oc project myproject) & give same permissions as above:
oc adm policy add-scc-to-user anyuid -z default -n myproject
oc adm policy add-scc-to-user privileged -z default -n myproject
oc adm policy add-scc-to-user anyuid -z bookinfo-reviews -n myproject
oc adm policy add-scc-to-user anyuid -z bookinfo-productpage -n myproject
oc adm policy add-scc-to-user privileged -z bookinfo-productpage -n myproject
oc adm policy add-scc-to-user privileged -z bookinfo-reviews -n myproject
5. Enable istio & op automatic injection into myproject: Note: need to use kubectl and namespace rather than oc and project
kubectl label namespace myproject opa-istio-injection="enabled"
kubectl label namespace myproject istio-injection="enabled"
6. oc apply -f https://raw.githubusercontent.com/Maistra/bookinfo/maistra-1.1/bookinfo.yaml
7. In myproject to ensure ope-config config maps are present:
kubectl apply -f https://raw.githubusercontent.com/open-policy-agent/opa-istio-plugin/master/quick_start.yaml
8. Wait until all Pods are running and you should see 3/3 for containers in each pod. This takes rather too long for my liking!
9. oc apply -f https://raw.githubusercontent.com/Maistra/bookinfo/maistra-1.1/bookinfo-gateway.yaml
10. Test end points as tutorial shows using ingress-gateway URL found above e.g.
curl --user alice:password -i http://istio-ingressgateway-istio-system.apps-crc.testing/productpage


I deployed my server in a separate project, test. In the test project I needed to:

1. Expose the service:
oc expose pod  opa-bundle-server -n test --type=LoadBalancer --port=8080

2. Enable a network Policy to enable the opa-istio sidecar to connect to it:

kind: NetworkPolicy
apiVersion: networking.k8s.io/v1
metadata:
  name: web-allow-external
  namespace: test
  selfLink: >-
    /apis/networking.k8s.io/v1/namespaces/test/networkpolicies/web-allow-external
  uid: 51871760-009a-11ea-a67e-5eb86bedde0f
  resourceVersion: '273789'
  generation: 1
  creationTimestamp: '2019-11-06T13:35:38Z'
spec:
  podSelector:
    matchLabels:
      app: opa-bundle-server
  ingress:
    - {}
  policyTypes:
    - Ingress
---

On OpenShift I created routes for the two pages linked to the product page service using the paths:
/productpage
/api/v1/products

This testing with:
curl --user anand:password -i http://productpage-myproject.apps-crc.testing/productpage
curl --user steve:password -i http://products-myproject.apps-crc.testing/api/v1/products