opa-istio-plugin

This repository contains an extended version of OPA (OPA-Istio) that allows you to enforce OPA policies at the Istio Proxy layer.

Overview

OPA-Istio extends OPA with a gRPC server that implements the Envoy External Authorization API. You can use this version of OPA to enforce fine-grained, context-aware access control policies at the Istio Proxy layer without modifying your microservice.

How does it work?

In addition to the Istio Proxy/Envoy sidecar, your application pods will include an OPA sidecar. When Istio Proxy receives API requests destined for your microservice, it checks with OPA to decide if the request should be allowed.

Evaluating policies locally at the Istio Proxy layer is preferable because it avoids introducing a network hop (which has implications on performance and availability) in order to perform the authorization check.

Quick Start

This section assumes you are testing with Istio v1.1.0 or later.

This section assumes you have Istio deployed on top of Kubernetes. See Istio's Quick Start page to get started.

Install OPA-Istio.
```
kubectl apply -f https://raw.githubusercontent.com/open-policy-agent/opa-istio-plugin/master/quick_start.yaml
```
The quick_start.yaml manifest defines the following resources:
- External Authorization Filter to direct authorization checks to the OPA-Istio sidecar. See kubectl -n istio-system get envoyfilter ext-authz for details.
- Kubernetes namespace (opa-istio) for OPA-Istio control plane components.
- Kubernetes admission controller in the opa-istio namespace that automatically injects the OPA-Istio sidecar into pods in namespaces labelled with opa-istio-injection=enabled.
- OPA configuration file and an OPA policy into ConfigMaps in the namespace where the app will be deployed, e.g., default.
Enable automatic injection of the Istio Proxy and OPA-Istio sidecars in the namespace where the app will be deployed, e.g., default.
```
kubectl label namespace default opa-istio-injection="enabled"
kubectl label namespace default istio-injection="enabled"
```

Deploy the BookInfo application and make it accessible outside the cluster.

kubectl apply -f https://raw.githubusercontent.com/istio/istio/master/samples/bookinfo/platform/kube/bookinfo.yaml

kubectl apply -f https://raw.githubusercontent.com/istio/istio/master/samples/bookinfo/networking/bookinfo-gateway.yaml

Set the GATEWAY_URL environment variable in your shell to the public IP/port of the Istio Ingress gateway.

minikube:

export INGRESS_PORT=$(kubectl -n istio-system get service istio-ingressgateway -o jsonpath='{.spec.ports[?(@.name=="http2")].nodePort}')
export INGRESS_HOST=$(minikube ip)
export GATEWAY_URL=$INGRESS_HOST:$INGRESS_PORT
echo $GATEWAY_URL

minikube (example):

192.168.99.100:31380

For other platforms see the Istio documentation on determining ingress IP and ports.

Exercise the sample policy. Check that alice can access /productpage BUT NOT /api/v1/products.

curl --user alice:password -i http://$GATEWAY_URL/productpage
curl --user alice:password -i http://$GATEWAY_URL/api/v1/products

Exercise the sample policy. Check that bob can access /productpage AND /api/v1/products.

curl --user bob:password -i http://$GATEWAY_URL/productpage
curl --user bob:password -i http://$GATEWAY_URL/api/v1/products

Configuration

To deploy OPA-Istio include the following container in your Kubernetes Deployments:

containers:
- image: openpolicyagent/opa:0.10.7-istio-2
  imagePullPolicy: IfNotPresent
  name: opa-istio
  volumeMounts:
  - mountPath: /config
    name: opa-istio-config
  args:
  - run
  - --server
  - --config-file=/config/config.yaml

The OPA-Istio configuration file should be volume mounted into the container. Add the following volume to your Kubernetes Deployments:

volumes:
- name: opa-istio-config
  configMap:
    name: opa-istio-config

The OPA-Istio plugin supports the following configuration fields:

Field	Required	Description
`plugins["envoy.ext_authz.grpc"].addr`	No	Set listening address of Envoy External Authorization gRPC server. This must match the value configured in the Envoy Filter resource. Default: `:9191`.
`plugins["envoy.ext_authz.grpc"].query`	No	Specifies the name of the policy decision to query. The policy decision must be return a `boolean` value. `true` indicates the request should be allowed and `false` indicates the request should be denied. Default: `data.istio.authz.allow`.

In the Quick Start section an OPA policy is loaded via a volume-mounted ConfigMap. For production deployments, we recommend serving policy Bundles from a remote HTTP server. For example:

config.yaml:

services:
  - name: default
    url: https://example.com                           # replace with your bundle service base URL
    credentials:                                       # replace with your bundle service credentials
      bearer:
        scheme: "Bearer"
        token: "BrXpzQ2cHXV06H0-8xSe79agaTiM5wPurYGS"
bundle:
  name: istio/authz
  service: bundle_service
plugins:
    envoy.ext_authz.grpc:
        addr: :9191
        query: data.istio.authz.allow

Example Policy

The following OPA policy is used in the Quick Start section above. This policy restricts access to the BookInfo such that:

Alice is granted a guest role and can access the /productpage frontend BUT NOT the /v1/api/products backend.
Bob is granted an admin role and can access the /productpage frontend AND the /v1/api/products backend.

package istio.authz

import input.attributes.request.http as http_request

default allow = false

allow {
    roles_for_user[r]
    required_roles[r]
}

roles_for_user[r] {
    r := user_roles[user_name][_]
}

required_roles[r] {
    perm := role_perms[r][_]
    perm.method = http_request.method
    perm.path = http_request.path
}

user_name = parsed {
    [_, encoded] := split(http_request.headers.authorization, " ")
    [parsed, _] := split(base64url.decode(encoded), ":")
}

user_roles = {
    "alice": ["guest"],
    "bob": ["admin"]
}

role_perms = {
    "guest": [
        {"method": "GET",  "path": "/productpage"},
    ],
    "admin": [
        {"method": "GET",  "path": "/productpage"},
        {"method": "GET",  "path": "/api/v1/products"},
    ],
}

Example Input

The input value defined for your policy will resemble the JSON below:

{
  "attributes": {
    "source": {
      "address": {
        "Address": {
          "SocketAddress": {
            "address": "172.17.0.10",
            "PortSpecifier": {
              "PortValue": 36472
            }
          }
        }
      }
    },
    "destination": {
      "address": {
        "Address": {
          "SocketAddress": {
            "address": "172.17.0.17",
            "PortSpecifier": {
              "PortValue": 9080
            }
          }
        }
      }
    },
    "request": {
      "http": {
        "id": "13359530607844510314",
        "method": "GET",
        "headers": {
          ":authority": "192.168.99.100:31380",
          ":method": "GET",
          ":path": "/api/v1/products",
          "accept": "*/*",
          "authorization": "Basic YWxpY2U6cGFzc3dvcmQ=",
          "content-length": "0",
          "user-agent": "curl/7.54.0",
          "x-b3-sampled": "1",
          "x-b3-spanid": "537f473f27475073",
          "x-b3-traceid": "537f473f27475073",
          "x-envoy-internal": "true",
          "x-forwarded-for": "172.17.0.1",
          "x-forwarded-proto": "http",
          "x-istio-attributes": "Cj4KE2Rlc3RpbmF0aW9uLnNlcnZpY2USJxIlcHJvZHVjdHBhZ2UuZGVmYXVsdC5zdmMuY2x1c3Rlci5sb2NhbApPCgpzb3VyY2UudWlkEkESP2t1YmVybmV0ZXM6Ly9pc3Rpby1pbmdyZXNzZ2F0ZXdheS02Nzk5NWM0ODZjLXFwOGpyLmlzdGlvLXN5c3RlbQpBChdkZXN0aW5hdGlvbi5zZXJ2aWNlLnVpZBImEiRpc3RpbzovL2RlZmF1bHQvc2VydmljZXMvcHJvZHVjdHBhZ2UKQwoYZGVzdGluYXRpb24uc2VydmljZS5ob3N0EicSJXByb2R1Y3RwYWdlLmRlZmF1bHQuc3ZjLmNsdXN0ZXIubG9jYWwKKgodZGVzdGluYXRpb24uc2VydmljZS5uYW1lc3BhY2USCRIHZGVmYXVsdAopChhkZXN0aW5hdGlvbi5zZXJ2aWNlLm5hbWUSDRILcHJvZHVjdHBhZ2U=",
          "x-request-id": "92a6c0f7-0250-944b-9cfc-ae10cbcedd8e"
        },
        "path": "/api/v1/products",
        "host": "192.168.99.100:31380",
        "protocol": "HTTP/1.1"
      }
    }
  }
}

Dependencies

Dependencies are managed with Glide. If you need to add or update dependencies, modify the glide.yaml file and then run glide update --strip-vendor and then commit all changes to the repository. You will need to have Glide v0.13 or newer installed.

If you update any of the gRPC, protobuf, or github.com/envoyproxy/data-plane-api dependencies, you should regenerate the Go code that depends on them by running gen-protos.sh in this directory.

jfyne/opa-istio-plugin