khaledemaradev/kubewarden-policy-psp-apparmor

A Kubewarden Pod Security Policy that controls usage of AppArmor profiles

This Kubewarden Policy is a replacement for the Kubernetes Pod Security Policy that controls the usage of AppArmor profiles.

How the policy works

This policy works by defining a whitelist of allowed AppArmor profiles. Pods are then inspected at creation and update time, to ensure only approved profiles are used.

When no AppArmor profile is defined, Kubernetes will leave the final choice to the underlying container runtime. This will result in using the default AppArmor profile provided by Container Runtime. Because of that, the default behaviour of this policy is to accept workloads that do not have an AppArmor profile specified.

Configuration

The policy can be configured with the following data structure:

# list of allowed profiles
allowed_profiles:
- runtime/default
- localhost/my-special-workload

Examples

Do not allow unconfined workloads

Running a container with the unconfined profile is considered a bad security practice.

This can be prevented by using this setting values:

allowed_profiles:
- runtime/default

This configuration would allow these Pods:

apiVersion: v1
kind: Pod
metadata:
  name: hello-apparmor
  annotations:
    container.apparmor.security.beta.kubernetes.io/hello: runtime/default
spec:
  containers:
  - name: hello
    image: busybox
    command: [ "sh", "-c", "echo 'Hello AppArmor!' && sleep 1h" ]
---
apiVersion: v1
kind: Pod
metadata:
  name: hello-apparmor-default-profile
spec:
  containers:
  - name: hello
    image: busybox
    command: [ "sh", "-c", "echo 'Hello AppArmor!' && sleep 1h" ]

While these Pods would not be allowed on the cluster:

apiVersion: v1
kind: Pod
metadata:
  name: hello-unconfined
  annotations:
    container.apparmor.security.beta.kubernetes.io/hello: unconfined
spec:
  containers:
  - name: hello
    image: busybox
    command: [ "sh", "-c", "echo 'Hello AppArmor!' && sleep 1h" ]
---
apiVersion: v1
kind: Pod
metadata:
  name: hello-custom-profile
  annotations:
    container.apparmor.security.beta.kubernetes.io/hello: localhost/my-custom-profile
spec:
  containers:
  - name: hello
    image: busybox
    command: [ "sh", "-c", "echo 'Hello AppArmor!' && sleep 1h" ]

Limit the AppArmor profiles that can be used

The following profile would force all the workloads to either not specify an AppArmor profile (and hence use the default one provided by the Container Runtime) or use one of the approved profiles:

allowed_profiles:
- runtime/default
- localhost/my-custom-profile

This configuration would allow these Pods:

apiVersion: v1
kind: Pod
metadata:
  name: hello-apparmor
  annotations:
    container.apparmor.security.beta.kubernetes.io/hello: runtime/default
spec:
  containers:
  - name: hello
    image: busybox
    command: [ "sh", "-c", "echo 'Hello AppArmor!' && sleep 1h" ]
---
apiVersion: v1
kind: Pod
metadata:
  name: hello-apparmor-default-profile
spec:
  containers:
  - name: hello
    image: busybox
    command: [ "sh", "-c", "echo 'Hello AppArmor!' && sleep 1h" ]
---
apiVersion: v1
kind: Pod
metadata:
  name: hello-apparmor-custom-profile
  annotations:
    container.apparmor.security.beta.kubernetes.io/hello: localhost/my-custom-profile
spec:
  containers:
  - name: hello
    image: busybox
    command: [ "sh", "-c", "echo 'Hello AppArmor!' && sleep 1h" ]

While these Pods would not be allowed on the cluster:

apiVersion: v1
kind: Pod
metadata:
  name: hello-unconfined
  annotations:
    container.apparmor.security.beta.kubernetes.io/hello: unconfined
spec:
  containers:
  - name: hello
    image: busybox
    command: [ "sh", "-c", "echo 'Hello AppArmor!' && sleep 1h" ]
---
apiVersion: v1
kind: Pod
metadata:
  name: hello-unknown-profile
  annotations:
    container.apparmor.security.beta.kubernetes.io/hello: localhost/unknown-profile
spec:
  containers:
  - name: hello
    image: busybox
    command: [ "sh", "-c", "echo 'Hello AppArmor!' && sleep 1h" ]