Creating policies from verdicts

Policy Audit Mode configures Cilium to allow all traffic while logging all connections that would otherwise be dropped by policy. Policy Audit Mode may be configured for the entire daemon using --policy-audit-mode=true. When Policy Audit Mode is enabled, no network policy is enforced so this setting is not recommended for production deployment. Policy Audit Mode supports auditing network policies implemented at networks layers 3 and 4. This guide walks through the process of creating policies using Policy Audit Mode.

If you haven’t read the Introduction to Cilium & Hubble yet, we’d encourage you to do that first.

The best way to get help if you get stuck is to ask a question on the Cilium Slack channel. With Cilium contributors across the globe, there is almost always someone available to help.

Setup Cilium

If you have not set up Cilium yet, pick any installation method as described in section Installation to set up Cilium for your Kubernetes environment. If in doubt, pick Getting Started Using Minikube as the simplest way to set up a Kubernetes cluster with Cilium:

minikube start --network-plugin=cni --memory=4096
minikube ssh -- sudo mount bpffs -t bpf /sys/fs/bpf
kubectl create -f https://raw.githubusercontent.com/cilium/cilium/1.8.3/install/kubernetes/quick-install.yaml

Deploy the Demo Application

Now that we have Cilium deployed and kube-dns operating correctly we can deploy our demo application.

In our Star Wars-inspired example, there are three microservices applications: deathstar, tiefighter, and xwing. The deathstar runs an HTTP webservice on port 80, which is exposed as a Kubernetes Service to load-balance requests to deathstar across two pod replicas. The deathstar service provides landing services to the empire’s spaceships so that they can request a landing port. The tiefighter pod represents a landing-request client service on a typical empire ship and xwing represents a similar service on an alliance ship. They exist so that we can test different security policies for access control to deathstar landing services.

Application Topology for Cilium and Kubernetes

../../_images/cilium_http_gsg.png

The file http-sw-app.yaml contains a Kubernetes Deployment for each of the three services. Each deployment is identified using the Kubernetes labels (org=empire, class=deathstar), (org=empire, class=tiefighter), and (org=alliance, class=xwing). It also includes a deathstar-service, which load-balances traffic to all pods with label (org=empire, class=deathstar).

$ kubectl create -f https://raw.githubusercontent.com/cilium/cilium/1.8.3/examples/minikube/http-sw-app.yaml
service/deathstar created
deployment.extensions/deathstar created
pod/tiefighter created
pod/xwing created

Kubernetes will deploy the pods and service in the background. Running kubectl get pods,svc will inform you about the progress of the operation. Each pod will go through several states until it reaches Running at which point the pod is ready.

$ kubectl get pods,svc
NAME                             READY   STATUS    RESTARTS   AGE
pod/deathstar-6fb5694d48-5hmds   1/1     Running   0          107s
pod/deathstar-6fb5694d48-fhf65   1/1     Running   0          107s
pod/tiefighter                   1/1     Running   0          107s
pod/xwing                        1/1     Running   0          107s

NAME                 TYPE        CLUSTER-IP    EXTERNAL-IP   PORT(S)   AGE
service/deathstar    ClusterIP   10.96.110.8   <none>        80/TCP    107s
service/kubernetes   ClusterIP   10.96.0.1     <none>        443/TCP   3m53s

Each pod will be represented in Cilium as an Endpoint. We can invoke the cilium tool inside the Cilium pod to list them:

$ kubectl -n kube-system get pods -l k8s-app=cilium
NAME           READY   STATUS    RESTARTS   AGE
cilium-5ngzd   1/1     Running   0          3m19s

$ kubectl -n kube-system exec cilium-1c2cz -- cilium endpoint list
ENDPOINT   POLICY (ingress)   POLICY (egress)   IDENTITY   LABELS (source:key[=value])                       IPv6   IPv4         STATUS
           ENFORCEMENT        ENFORCEMENT
232        Disabled           Disabled          16530      k8s:class=deathstar                                      10.0.0.147   ready
                                                           k8s:io.cilium.k8s.policy.cluster=default
                                                           k8s:io.cilium.k8s.policy.serviceaccount=default
                                                           k8s:io.kubernetes.pod.namespace=default
                                                           k8s:org=empire
726        Disabled           Disabled          1          reserved:host                                                         ready
883        Disabled           Disabled          4          reserved:health                                          10.0.0.244   ready
1634       Disabled           Disabled          51373      k8s:io.cilium.k8s.policy.cluster=default                 10.0.0.118   ready
                                                           k8s:io.cilium.k8s.policy.serviceaccount=coredns
                                                           k8s:io.kubernetes.pod.namespace=kube-system
                                                           k8s:k8s-app=kube-dns
1673       Disabled           Disabled          31028      k8s:class=tiefighter                                     10.0.0.112   ready
                                                           k8s:io.cilium.k8s.policy.cluster=default
                                                           k8s:io.cilium.k8s.policy.serviceaccount=default
                                                           k8s:io.kubernetes.pod.namespace=default
                                                           k8s:org=empire
2811       Disabled           Disabled          51373      k8s:io.cilium.k8s.policy.cluster=default                 10.0.0.47    ready
                                                           k8s:io.cilium.k8s.policy.serviceaccount=coredns
                                                           k8s:io.kubernetes.pod.namespace=kube-system
                                                           k8s:k8s-app=kube-dns
2843       Disabled           Disabled          16530      k8s:class=deathstar                                      10.0.0.89    ready
                                                           k8s:io.cilium.k8s.policy.cluster=default
                                                           k8s:io.cilium.k8s.policy.serviceaccount=default
                                                           k8s:io.kubernetes.pod.namespace=default
                                                           k8s:org=empire
3184       Disabled           Disabled          22654      k8s:class=xwing                                          10.0.0.30    ready
                                                           k8s:io.cilium.k8s.policy.cluster=default
                                                           k8s:io.cilium.k8s.policy.serviceaccount=default
                                                           k8s:io.kubernetes.pod.namespace=default
                                                           k8s:org=alliance

Both ingress and egress policy enforcement is still disabled on all of these pods because no network policy has been imported yet which select any of the pods.

Enable Policy Audit Mode

To observe policy audit messages, follow these steps:

  1. Enable Policy Audit Mode in the daemon

    $ kubectl patch -n $CILIUM_NAMESPACE configmap cilium-config --type merge --patch '{"data":{"policy-audit-mode":"true"}}'
    configmap/cilium-config patched
    $ kubectl -n $CILIUM_NAMESPACE rollout restart ds/cilium
    daemonset.apps/cilium restarted
    $ kubectl -n kube-system rollout status ds/cilium
    Waiting for daemon set "cilium" rollout to finish: 0 of 1 updated pods are available...
    daemon set "cilium" successfully rolled out
    

    If you installed Cilium via helm install, then you can use helm upgrade to enable Policy Audit Mode:

    helm upgrade cilium cilium/cilium --version 1.8.3 \
       --namespace $CILIUM_NAMESPACE \
       --reuse-values \
       --set config.policyAuditMode=true
    
  2. Apply a default-deny policy:

    apiVersion: "cilium.io/v2"
    kind: CiliumNetworkPolicy
    description: "Default-deny ingress policy for the empire"
    metadata:
      name: "empire-default-deny"
    spec:
      endpointSelector:
        matchLabels:
          org: empire
      ingress:
      - {}
    

    CiliumNetworkPolicies match on pod labels using an “endpointSelector” to identify the sources and destinations to which the policy applies. The above policy denies traffic sent to any pods with label (org=empire). Due to the Policy Audit Mode enabled above, the traffic will not actually be denied but will instead trigger policy verdict notifications.

    To apply this policy, run:

    $ kubectl create -f https://raw.githubusercontent.com/cilium/cilium/1.8.3/examples/minikube/sw_deny_policy.yaml
    ciliumnetworkpolicy.cilium.io/empire-default-deny created
    

    With the above policy, we will enable default-deny posture on ingress to pods with the label org=empire and enable the policy verdict notifications for those pods. The same principle applies on egress as well.

Observe policy verdicts

In this example, we are tasked with applying security policy for the deathstar. First, from the Cilium pod we need to monitor the notifications for policy verdicts using cilium monitor -t policy-verdict. We’ll be monitoring for inbound traffic towards the deathstar to identify that traffic and determine whether to extend the network policy to allow that traffic.

From another terminal with kubectl access, send some traffic from the tiefighter to the deathstar:

$ kubectl exec tiefighter -- curl -s -XPOST deathstar.default.svc.cluster.local/v1/request-landing
Ship landed

Back in the Cilium pod, the policy verdict logs are printed in the monitor output:

# cilium monitor -t policy-verdict
...
Policy verdict log: flow 0x63113709 local EP ID 232, remote ID 31028, dst port 80, proto 6, ingress true, action audit, match none, 10.0.0.112 :54134 -> 10.29.50.40:80 tcp SYN

In the above example, we can see that endpoint 232 has received traffic (ingress true) which doesn’t match the policy (action audit match none). The source of this traffic has the identity 31028. Let’s gather a bit more information about what these numbers mean:

# cilium endpoint list
ENDPOINT   POLICY (ingress)   POLICY (egress)   IDENTITY   LABELS (source:key[=value])                                 IPv6                 IPv4            STATUS
           ENFORCEMENT        ENFORCEMENT
232        Disabled (Audit)   Disabled          16530      k8s:class=deathstar                                                              10.29.50.40     ready
                                                           k8s:io.cilium.k8s.policy.cluster=default
                                                           k8s:io.cilium.k8s.policy.serviceaccount=default
                                                           k8s:io.kubernetes.pod.namespace=default
                                                           k8s:org=empire
...
# cilium identity get 31028
ID     LABELS
31028  k8s:class=tiefighter
       k8s:io.cilium.k8s.policy.cluster=default
       k8s:io.cilium.k8s.policy.serviceaccount=default
       k8s:io.kubernetes.pod.namespace=default
       k8s:org=empire

Create the Network Policy

Given the above information, we now know the labels of the target pod, the labels of the peer that’s attempting to connect, the direction of the traffic and the port. In this case, we can see clearly that it’s an empire craft so once we’ve determined that we expect this traffic to arrive at the deathstar, we can form a policy to match the traffic:

apiVersion: "cilium.io/v2"
kind: CiliumNetworkPolicy
description: "L3-L4 policy to restrict deathstar access to empire ships only"
metadata:
  name: "rule1"
spec:
  endpointSelector:
    matchLabels:
      org: empire
      class: deathstar
  ingress:
  - fromEndpoints:
    - matchLabels:
        org: empire
    toPorts:
    - ports:
      - port: "80"
        protocol: TCP

To apply this L3/L4 policy, run:

$ kubectl create -f https://raw.githubusercontent.com/cilium/cilium/1.8.3/examples/minikube/sw_l3_l4_policy.yaml
ciliumnetworkpolicy.cilium.io/rule1 created

Now if we run the landing requests again, we can observe in the monitor output that the traffic which was previously audited to be dropped by the policy are now reported as allowed:

$ kubectl exec tiefighter -- curl -s -XPOST deathstar.default.svc.cluster.local/v1/request-landing
Ship landed

Executed from the cilium pod:

# cilium monitor -t policy-verdict
Policy verdict log: flow 0xabf3bda6 local EP ID 232, remote ID 31028, dst port 80, proto 6, ingress true, action allow, match L3-L4, 10.0.0.112 :59824 -> 10.0.0.147:80 tcp SYN

Now the policy verdict states that the traffic would be allowed: action allow. Success!

Disable Policy Audit Mode

These steps should be repeated for each connection in the cluster to ensure that the network policy allows all of the expected traffic. The final step after deploying the policy is to disable Policy Audit Mode again:

$ kubectl patch -n $CILIUM_NAMESPACE configmap cilium-config --type merge --patch '{"data":{"policy-audit-mode":"false"}}'
configmap/cilium-config patched
$ kubectl -n $CILIUM_NAMESPACE rollout restart ds/cilium
daemonset.apps/cilium restarted
$ kubectl -n kube-system rollout status ds/cilium
Waiting for daemon set "cilium" rollout to finish: 0 of 1 updated pods are available...
daemon set "cilium" successfully rolled out
helm upgrade cilium cilium/cilium --version 1.8.3 \
   --namespace $CILIUM_NAMESPACE \
   --reuse-values \
   --set config.policyAuditMode=false

Now if we run the landing requests again, only the tiefighter pods with the label org=empire will succeed. The xwing pods will be blocked!

$ kubectl exec tiefighter -- curl -s -XPOST deathstar.default.svc.cluster.local/v1/request-landing
Ship landed

This works as expected. Now the same request run from an xwing pod will fail:

$ kubectl exec xwing -- curl -s -XPOST deathstar.default.svc.cluster.local/v1/request-landing

This request will hang, so press Control-C to kill the curl request, or wait for it to time out.

We hope you enjoyed the tutorial. Feel free to play more with the setup, follow the Identity-Aware and HTTP-Aware Policy Enforcement guide, and reach out to us on the Cilium Slack channel with any questions!

Clean-up

$ kubectl delete -f https://raw.githubusercontent.com/cilium/cilium/1.8.3/examples/minikube/http-sw-app.yaml
$ kubectl delete cnp rule1