Common tasks

This describes tasks that can be performed after you install Kubewarden in your Kubernetes cluster.

Each task can be done separately; they are shown here in a logical ordering.

Test Policies

Kubewarden has two tools to help you find policies and test them locally:

Artifact hub

Artifact hub hosts policies contributed by the community. For example, you can find substitutes to the deprecated Kubernetes Pod Security Policies, created by the Kubewarden developers.

As shown in the screenshot below, once you find a policy of interest, select the Install button and use kwctl to fetch the policy for your cluster.

Artifact Hub

Previously, Kubewarden policies could be found at the Kubewarden Policy Hub. This has been retired. Policies are now available from https://artifacthub.io.

kwctl CLI tool

kwctl is our CLI tool for policy authors and the cluster administrators to test policies before they are applied to the Kubernetes cluster.

This tool has a similar interface to the docker CLI tool.

Use cases

You can use kwctl to help in these scenarios:

As a policy author

  • End-to-end testing of your policy: Test your policy against crafted Kubernetes requests and ensure your policy behaves as you expect. You can even test context-aware policies that require access to a running cluster.

  • Embed metadata in your Wasm module: the binary contains annotations of the permissions it needs to be executed. You can inspect and modify these annotations with kwctl.

  • Publish policies to OCI registries: The binary is a fully compliant OCI object and can be stored in OCI registries.

As a cluster administrator

  • Inspect remote policies: Given a policy in an OCI registry or in an HTTP server, show all static information about the policy.

  • Dry-run of a policy in your cluster: Test the policy against crafted Kubernetes requests and ensure the policy behaves as you expect given the input data you provide. You can even test context-aware policies that require access to a running cluster, also in a dry-run mode.

  • Generate initial ClusterAdmissionPolicy scaffolding for your policy: Generate a YAML file with all the required settings, which can be applied to your Kubernetes cluster using kubectl.

Installation

kwctl binaries for the stable releases are available from the GitHub repository. To build kwctl from the GitHub repo, you will need a Rust development environment.

Usage

You can list all the kwctl options and sub-commands by running the following command:

$ kwctl --help
kwctl 0.2.5
Kubewarden Developers <kubewarden@suse.de>
Tool to manage Kubewarden policies

USAGE:
    kwctl [OPTIONS] <SUBCOMMAND>

OPTIONS:
    -h, --help       Print help information
    -v               Increase verbosity
    -V, --version    Print version information

SUBCOMMANDS:
    annotate       Add Kubewarden metadata to a WebAssembly module
    completions    Generate shell completions
    digest         Fetch the digest of its OCI manifest
    help           Print this message or the help of the given subcommand(s)
    inspect        Inspect Kubewarden policy
    policies       Lists all downloaded policies
    pull           Pulls a Kubewarden policy from a given URI
    push           Pushes a Kubewarden policy to an OCI registry
    rm             Removes a Kubewarden policy from the store
    run            Runs a Kubewarden policy from a given URI
    scaffold       Scaffold a Kubernetes resource or configuration file
    verify         Verify a Kubewarden policy from a given URI using Sigstore

Here are a few command usage examples:

  • List the policies: lists all the policies stored in the local kwctl registry

    • Command: kwctl policies

  • Obtain the policy: download and store the policy inside the local kwctl store

    • Command: kwctl pull <policy URI>

      $ kwctl pull registry://ghcr.io/kubewarden/policies/pod-privileged:v0.1.9

$ kwctl policies
+--------------------------------------------------------------+----------+---------------+--------------+----------+
| Policy                                                       | Mutating | Context aware | SHA-256      | Size     |
+--------------------------------------------------------------+----------+---------------+--------------+----------+
| registry://ghcr.io/kubewarden/policies/pod-privileged:v0.1.9 | no       | no            | 59e34f482b40 | 21.86 kB |
+--------------------------------------------------------------+----------+---------------+--------------+----------+

  • Understand how the policy works: inspect the policy metadata

    • Command: kwctl inspect <policy URI>

        $ kwctl inspect registry://ghcr.io/kubewarden/policies/pod-privileged:v0.1.9
  Details
  title:              pod-privileged
  description:        Limit the ability to create privileged containers
  author:             Flavio Castelli
  url:                https://github.com/kubewarden/pod-privileged-policy
  source:             https://github.com/kubewarden/pod-privileged-policy
  license:            Apache-2.0
  mutating:           false
  context aware:      false
  execution mode:     kubewarden-wapc
  protocol version:   1

  Annotations
  io.kubewarden.kwctl 0.1.9

  Rules
  ────────────────────
  ---
  - apiGroups:
      - ""
    apiVersions:
      - v1
    resources:
      - pods
    operations:
      - CREATE
  ────────────────────

  Usage
  This policy doesn't have a configuration. Once enforced, it will reject
  the creation of Pods that have at least a privileged container defined.

  • Evaluate the policy: Assess the policy and, if available, find the right configuration values to match your requirements.

    You will need some familiarity with the Kubernetes REST APIs.

    • Command: kwctl run -r <"Kubernetes Admission request" file path> -s <"JSON document" file path> <policy URI>

    • Scenario 1:

      • Request to be evaluated: Create a pod with no 'privileged' container

        $ kwctl run registry://ghcr.io/kubewarden/policies/pod-privileged:v0.1.9 -r unprivileged-pod-request.json
{"uid":"C6E115F4-A789-49F8-B0C9-7F84C5961FDE","allowed":true,"status":{"message":""}}

      • Equivalent command with the policy binary downloaded:

        `$ kwctl run file://$PWD/pod-privileged-policy.wasm -r unprivileged-pod-request.json
{"uid":"C6E115F4-A789-49F8-B0C9-7F84C5961FDE","allowed":true,"status":{"message":""}}

      • Result: The policy allows the request

    • Scenario 2:

      • Request to be evaluated: Create a pod with at least one 'privileged' container

      • Command:

        kwctl run registry://ghcr.io/kubewarden/policies/pod-privileged:v0.1.9 -r privileged-pod-request.json

      • Equivalent command with the policy binary downloaded: kwctl run file://$PWD/pod-privileged-policy.wasm -r privileged-pod-request.json

      • Output:

        {
  "uid": "8EE6AF8C-C8C8-45B0-9A86-CB52A70EC50D",
  "allowed": false,
  "status": { "message": "User 'kubernetes-admin' cannot schedule privileged containers" }
}

      • Result: The policy denies the request

    For some more complex examples, see the blog post Introducing kwctl to Kubernetes Administrators.

Enforce Policies

You enforce a policy by defining a ClusterAdmissionPolicy and then deploy it to your cluster using kubectl.

kwctl helps generate a ClusterAdmissionPolicy from the policy you want to enforce.

After you have generated the ClusterAdmissionPolicy and applied it to your cluster, you can follow the steps described in the Quick Start below:

  • Generate the ClusterAdmissionPolicy from the policy manifest and save it to a file

    • Command: kwctl scaffold manifest -t ClusterAdmissionPolicy <policy URI> > <"policy name".yaml>

      $ kwctl scaffold manifest -t ClusterAdmissionPolicy registry://ghcr.io/kubewarden/policies/pod-privileged:v0.1.9
---
apiVersion: policies.kubewarden.io/v1alpha2
kind: ClusterAdmissionPolicy
metadata:
  name: privileged-pods
spec:
  module: "registry://ghcr.io/kubewarden/policies/pod-privileged:v0.1.9"
  settings: {}
  rules:
    - apiGroups:
        - ""
      apiVersions:
        - v1
      resources:
        - pods
      operations:
        - CREATE
  mutating: false

    By default, the name value is set to generated-policy. You might want to edit it before you deploy the ClusterAdmissionPolicy. The name in the immediately previous example has been set to privileged-pods.

  • Deploy the ClusterAdmissionPolicy to your Kubernetes cluster

    • Command: kubectl apply -f <"policy name".yaml>

      $ kubectl apply -f pod-privileged-policy.yaml
clusteradmissionpolicy.policies.kubewarden.io/privileged-pods created

After the ClusterAdmissionPolicy is deployed, all requests sent to your cluster will be evaluated by the policy if they’re within the policy scope.

Next steps