Tutorial: Gloo Edge

Tutorial: Gloo Edge Edit

Gloo Edge is an Envoy based API Gateway that provides a Kubernetes CRD to manage Envoy configuration for performing traffic management and routing.

Gloo Edge allows creation of a Custom External Auth Service that implements the Envoy spec for an External Authorization Server.

The purpose of this tutorial is to show how OPA could be used with Gloo Edge to apply security policies for upstream services.

Prerequisites

This tutorial requires Kubernetes 1.14 or later. To run the tutorial locally, we recommend using minikube in version v1.0+ with Kubernetes 1.14+.

The tutorial also requires Helm to install Gloo Edge on a Kubernetes cluster.

Steps

1. Start Minikube

minikube start

2. Setup and Configure Gloo Edge

helm repo add gloo https://storage.googleapis.com/solo-public-helm
helm upgrade --install --namespace gloo-system --create-namespace gloo gloo/gloo
kubectl config set-context $(kubectl config current-context) --namespace=gloo-system

Ensure all the pods are running using kubectl get pod command.

3. Create Virtual Service and Upstream

Virtual Services define a set of route rules, security configuration, rate limiting, transformations, and other core routing capabilities supported by Gloo Edge.

Upstreams define destinations for routes.

Save the configuration as vs.yaml.

apiVersion: gloo.solo.io/v1
kind: Upstream
metadata:
  name: httpbin
spec:
  static:
    hosts:
      - addr: httpbin.org
        port: 80
---
apiVersion: gateway.solo.io/v1
kind: VirtualService
metadata:
  name: httpbin
spec:
  virtualHost:
    domains:
      - '*'
    routes:
      - matchers:
         - prefix: /
        routeAction:
          single:
            upstream:
              name: httpbin
              namespace: gloo-system
        options:
          autoHostRewrite: true

kubectl apply -f vs.yaml

4. Test Gloo

For simplification port-forwarding will be used. Open another terminal and execute.

kubectl port-forward deployment/gateway-proxy 8080:8080

The VirtualService created in the previous step forwards requests to http://httpbin.org

Let’s test that Gloo works properly by running the below command in the first terminal.

curl -XGET -Is localhost:8080/get | head -n 1
HTTP/1.1 200 OK

curl http -XPOST -Is localhost:8080/post | head -n1
HTTP/1.1 200 OK

5. Define an OPA Policy

The following OPA policy will work as follows:

Alice is granted a guest role and can perform GET requests.
Bob is granted an admin role and can perform GET and POST requests.

policy.rego

package envoy.authz

import rego.v1

import input.attributes.request.http as http_request

default allow := false

allow if {
	is_token_valid
	action_allowed
}

is_token_valid if {
	token.valid
	now := time.now_ns() / 1000000000
	token.payload.nbf <= now
	now < token.payload.exp
}

action_allowed if {
	http_request.method == "GET"
	token.payload.role == "guest"
}

action_allowed if {
	http_request.method == "GET"
	token.payload.role == "admin"
}

action_allowed if {
	http_request.method == "POST"
	token.payload.role == "admin"
}

token := {"valid": valid, "payload": payload} if {
	[_, encoded] := split(http_request.headers.authorization, " ")
	[valid, _, payload] := io.jwt.decode_verify(encoded, {"secret": "secret"})
}

A sample input can be seen below using Alice’s token, Alice should be able to GET but not POST

{
  "attributes": {
    "request": {
      "http": {
        "method": "GET",
        "headers": {
          "authorization": "Bearer eyJhbGciOiAiSFMyNTYiLCAidHlwIjogIkpXVCJ9.eyJleHAiOiAyMjQxMDgxNTM5LCAibmJmIjogMTUxNDg1MTEzOSwgInJvbGUiOiAiZ3Vlc3QiLCAic3ViIjogIllXeHBZMlU9In0.Uk5hgUqMuUfDLvBLnlXMD0-X53aM_Hlziqg3vhOsCc8"
        }
      }
    }
  }
}

With the input value above, the answer is:

{
  "action_allowed": true,
  "allow": true,
  "is_token_valid": true,
  "token": {
    "payload": {
      "exp": 2241081539,
      "nbf": 1514851139,
      "role": "guest",
      "sub": "YWxpY2U="
    },
    "valid": true
  }
}

Next we build an OPA bundle.

opa build policy.rego

And now we serve the OPA bundle created above using Nginx.

docker run --rm --name bundle-server -d -p 8888:80 -v ${PWD}:/usr/share/nginx/html:ro nginx:latest

6. Setup OPA-Envoy

Create a deployment as shown below and save it in deployments.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: opa
  labels:
    app: opa
spec:
  replicas: 1
  selector:
    matchLabels:
      app: opa
  template:
    metadata:
      labels:
        app: opa
    spec:
      containers:
      - name: opa
        image: openpolicyagent/opa:0.69.0-envoy
        volumeMounts:
          - readOnly: true
            mountPath: /policy
            name: opa-policy
        args:
          - "run"
          - "--server"
          - "--addr=0.0.0.0:8181"
          - "--set=services.default.url=http://host.minikube.internal:8888"
          - "--set=bundles.default.resource=bundle.tar.gz"
          - "--set=plugins.envoy_ext_authz_grpc.addr=0.0.0.0:9191"
          - "--set=plugins.envoy_ext_authz_grpc.path=envoy/authz/allow"
          - "--set=decision_logs.console=true"
          - "--set=status.console=true"
          - "--ignore=.*"
      volumes:
      - name: opa-policy

kubectl apply -f deployments.yaml

Ensure all pods are running using kubectl get pod command.

Next, define a Kubernetes service for OPA-Envoy. This is required to create a DNS record and thereby create a Gloo Upstream object.

service.yaml

apiVersion: v1
kind: Service
metadata:
  name: opa
spec:
  selector:
    app: opa
  ports:
    - name: grpc
      protocol: TCP
      port: 9191
      targetPort: 9191

Note: Since the name of the service port is grpc, Gloo will understand that traffic should be routed using HTTP2 protocol.

kubectl apply -f service.yaml

7. Configure Gloo Edge to use OPA

To use OPA as a custom auth server, we need to add the extauth attribute as described below:

gloo.yaml

global:
  extensions:
    extAuth:
      extauthzServerRef:
        name: gloo-system-opa-9191
        namespace: gloo-system

To apply it, run the following command:

helm upgrade --install --namespace gloo-system --create-namespace -f gloo.yaml gloo gloo/gloo

Configure Gloo Edge routes to perform authorization via configured extauth before regular processing.

vs-patch.yaml

spec:
  virtualHost:
    options:
      extauth:
        customAuth: {}

Then apply the patch to our VirtualService as shown below:

kubectl patch vs httpbin --type=merge --patch "$(cat vs-patch.yaml)"

8. Exercise the OPA Policy

Before we exercise the policy, for convenience sake, we will want to store Alice and Bob’s tokens in environment variables as such:

export ALICE_TOKEN="eyJhbGciOiAiSFMyNTYiLCAidHlwIjogIkpXVCJ9.eyJleHAiOiAyMjQxMDgxNTM5LCAibmJmIjogMTUxNDg1MTEzOSwgInJvbGUiOiAiZ3Vlc3QiLCAic3ViIjogIllXeHBZMlU9In0.Uk5hgUqMuUfDLvBLnlXMD0-X53aM_Hlziqg3vhOsCc8"
export BOB_TOKEN="eyJhbGciOiAiSFMyNTYiLCAidHlwIjogIkpXVCJ9.eyJleHAiOiAyMjQxMDgxNTM5LCAibmJmIjogMTUxNDg1MTEzOSwgInJvbGUiOiAiYWRtaW4iLCAic3ViIjogIlltOWkifQ.5qsm7rRTvqFHAgiB6evX0a_hWnGbWquZC0HImVQPQo8"

Now let’s verify that OPA only allows Alice to perform GET requests.

curl -XGET -Is -H "Authorization: Bearer $ALICE_TOKEN" localhost:8080/get
HTTP/1.1 200 OK

And with a POST request, we get:

curl http -XPOST -Is -H "Authorization: Bearer $ALICE_TOKEN" localhost:8080/post
HTTP/1.1 403 Forbidden

And for Bob, we should be able to GET and POST:

curl -XGET -Is -H "Authorization: Bearer $BOB_TOKEN" localhost:8080/get    
HTTP/1.1 200 OK

And the POST:

curl http -XPOST -Is -H "Authorization: Bearer $BOB_TOKEN" localhost:8080/post
HTTP/1.1 200 OK

Check OPA’s decision logs to view the inputs received by OPA from Gloo Edge and the results generated by OPA.

kubectl logs deployment/opa -n gloo-system

Wrap Up

Congratulations for finishing the tutorial!

This tutorial showed how you can use OPA with Gloo Edge to apply security policies for upstream services and how to create and test a policy that would allow GET or POST requests based on your user role.

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