kwctl

kwctl is the go-to CLI tool for Kubewarden users.

Think of it as the docker CLI tool if you were working with containers.

How does kwctl help me?

As a policy author

• e2e 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, so the binary is annotated with the permissions it needs to execute.

• Publish policies to OCI registries.

• Generate initial ClusterAdmissionPolicy scaffolding for your policy.

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 ClusterAdmissionPolicy scaffolding for a given policy.

Everyone

• The UX of this tool is intended to be as easy and intuitive as possible.

Install

Built binaries for Linux x86_64, Windows x86_64, MacOS x86_64 and MacOS aarch64 (M1) are available in GH Releases.

There is also:

• Community-created Homebrew 🍺 formula for kwctl
• Community-created AUR 🐧 package

Usage

These are the commands currently supported by kwctl.

List policies

The list of policies downloaded on the local machine can be obtained by doing:

kwctl policies

Download policies

Policies can be downloaded using the pull command.

The name of the policy must be expressed as a url with one of the following protocols:

• http://: pull from a HTTP server
• https://: pull from a HTTPS server
• registry://: pull from an OCI registry

Pulling from a registry, by tag:

kwctl pull registry://ghcr.io/kubewarden/policies/psp-capabilities:latest

It's possible to pull from a registry using an immutable reference (in the same way as with regular container images):

kwctl pull registry://ghcr.io/kubewarden/policies/psp-capabilities@sha256:61ef63621fa5be8e422881d96d05edfef810992fbf9468e35d1fa5ae815bd97c

Note well, the shasum is the digest of the OCI artifact containig the policy. This value can be obtained using a tool like crane:

crane digest ghcr.io/kubewarden/policies/psp-capabilities:v0.1.6

Run a policy locally

kwctl can be used to run a policy locally, outside of Kubernetes. This can be used to quickly evaluate a policy and find the right settings for it.

The evalution is done against a pre-recorded AdmissionReview.

Running a policy locally:

kwctl run \
  --settings-json '{"constrained_labels": {"owner": ".*"}}' \
  -r test_data/ingress.json \
  registry://ghcr.io/kubewarden/policies/safe-labels:v0.1.5

Policy configuration can be passed on the CLI via the --settings-json flag or can be loaded from the disk via the --settings-path flag.

Annotate a policy

Kubewarden policies are WebAssembly module, which must contain some Kubewarden-spefic metadata.

The act of adding metadata to the policy is done by the policy author, right before policy distribution.

The kwctl annotate command can be used to perform this operation.

Inspect a policy

The metadata attached to a policy, plus other details can be seen via the kwctl inspect command.

This command works against a policy that has been previously downloaded.

Publish a policy

kwctl can be used to publish a local policy into an OCI registry. This is done via the push sub-command.

The push sub-command can also be used to copy a policy into another registry:

kwctl push registry://ghcr.io/kubewarden/policies/safe-labels:v0.1.5 \
  registry://registry.local.lan/kubewarden/safe-labels:v0.1.5

The above command copies a local policy that was downloaded from the GitHub Container Registry, into a local registry.

Note well: the policy must be previously downloaded locally via kwctl pull

Remove a local policy

Local policies can be removed via the rm sub-command:

kwctl rm <name of the policy>

Scaffold Kubernetes Custom Resources

Kubewarden policies are enforced on Kubernetes clusters by using special Custom Resources provided by our Kubernetes integration.

The manifest sub-command can be used to quickly scaffold the definition of Kubewarden Custom Resources.

The manifest command shares some of the arguments of the run command, it's typical to test a policy locally via the kwctl run command and then, once satisfied about the policy settings, create a deployment manifest for it via the manifest command.

Step #1, find the right policy settings:

kwctl run \
  --settings-json '{"constrained_labels": {"owner": ".*"}}' \
  -r test_data/ingress.json \
  registry://ghcr.io/kubewarden/policies/safe-labels:v0.1.5

Step #2, generate a manifest to enforce the policy inside of a Kubernetes cluster:

kwctl manifest\
  --settings-json '{"constrained_labels": {"owner": ".*"}}' \
  -t ClusterAdmissionPolicy \
  registry://ghcr.io/kubewarden/policies/safe-labels:v0.1.5

This will produce the following output:

---
apiVersion: policies.kubewarden.io/v1
kind: ClusterAdmissionPolicy
metadata:
  name: generated-policy
spec:
  module: "registry://ghcr.io/kubewarden/policies/safe-labels:v0.1.5"
  settings:
    constrained_labels:
      owner: ".*"
  rules:
    - apiGroups:
        - "*"
      apiVersions:
        - "*"
      resources:
        - "*"
      operations:
        - CREATE
        - UPDATE
  mutating: false

Which can then be customized by hand, and then applied into a Kubernetes cluster.

Shell completion

kwctl can generate autocompletion scripts for the following shells:

• bash
• elvish
• fish
• powershell
• zsh

The completion script can be generated with the following command:

$ kwctl completions -s <SHELL>

The command will print to the stdout the completion script.

Bash

To load completions in your current shell session:

$ source <(kwctl completions -s bash)

To load completions for every new session, execute once:

• Linux: $ kwctl completions -s bash > /etc/bash_completion.d/kwctl
• MacOS: $ kwctl completions -s bash > /usr/local/etc/bash_completion.d/kwctl

You will need to start a new shell for this setup to take effect.

Fish

To load completions in your current shell session:

$ kwctl completions -s fish | source

To load completions for every new session, execute once:

$ kwctl completions -s fish > ~/.config/fish/completions/kwctl.fish

You will need to start a new shell for this setup to take effect.

Zsh

To load completions in your current shell session:

$ source <(kwctl completions -s zsh)

To load completions for every new session, execute once:

$ kwctl completions -s zsh > "${fpath[1]}/_kwctl"

Oh My Zsh users

These steps are required by oh-my-zsh users:

$ print -l $fpath | grep '.oh-my-zsh/completions'
$ mkdir ~/.oh-my-zsh/completions
$ kwctl completions -s zsh > ~/.oh-my-zsh/completions/_kwctl
rm ~/.zcompdump*

Then start a new shell or run source ~/.zshrc once.

Verify kwctl binaries

kwctl binaries are signed using Sigstore's blog signing. When you download a kwctl release each zip file contains two files that can be used for verification: kwctl.sig and kwctl.pem.

In order to verify kwctl you need cosign installed, and then execute the following command:

cosign verify-blob \
  --signature kwctl-linux-x86_64.sig \
  --cert kwctl-linux-x86_64.pem kwctl-linux-x86_64 
  --certificate-identity-regexp 'https://github.com/kubewarden/*' \
  --certificate-oidc-issuer https://token.actions.githubusercontent.com

The output should be:

Verified OK