Chainguard Container for kubelet-csr-approver

Kubernetes controller to enable automatic kubelet CSR validation after a series of (configurable) security checks

Chainguard Containers are regularly-updated, secure-by-default container images.

Download this Container Image

For those with access, this container image is available on cgr.dev:

docker pull cgr.dev/ORGANIZATION/kubelet-csr-approver:latest

Be sure to replace the ORGANIZATION placeholder with the name used for your organization's private repository within the Chainguard Registry.

Compatibility Notes

Chaingaurd's kubelet-csr-approver container image is comparable to the kubelet-csr-approver image. Like most other Chainguard container images, the kubelet-csr-approver container image contains only the dependencies it needs to function, and doesn't include things like a shell or package manager.

Getting Started

The Chainguard's kubelet-csr-approver container image can be installed via the kubelet-csr-approver helm chart.

Create a values.yaml file with the following values

operator:
  image:
    repository: cgr.dev/ORGANIZATION/kubelet-csr-approver
    tag: latest
  providerRegex: '^node-\w*\.int\.company\.ch$'
  providerIpPrefixes: '192.168.8.0/22'
  maxExpirationSeconds: '86400'
  bypassDnsResolution: 'false'

Make sure to replace ORGANIZATION with your organization.

Run the following command to install the helm chart:

helm repo add kubelet-csr-approver https://postfinance.github.io/kubelet-csr-approver
helm install kubelet-csr-approver kubelet-csr-approver/kubelet-csr-approver -n kube-system -f values.yaml

We can then try creating a CertificateSigningRequest resource like below:

apiVersion: certificates.k8s.io/v1
kind: CertificateSigningRequest
metadata:
  name: test-node-csr-valid
spec:
  request: $(base64 -w0 < /tmp/test-node.csr)
  signerName: kubernetes.io/kubelet-serving
  usages: ["digital signature","key encipherment","server auth"]
  groups: ["system:nodes"]

This should be Approved/Denied by the controller accordingly.

Documentation and Resources

• Official Quick Start
• Helm Chart

What are Chainguard Containers?

Chainguard Containers are minimal container images that are secure by default.

In many cases, the Chainguard Containers tagged as :latest contain only an open-source application and its runtime dependencies. These minimal container images typically do not contain a shell or package manager. Chainguard Containers are built with Wolfi, our Linux undistro designed to produce container images that meet the requirements of a more secure software supply chain.

The main features of Chainguard Containers include:

• Minimal design, without unnecessary software bloat
• Daily builds to ensure container images are up-to-date with available security patches
• High quality build-time SBOMs attesting to the provenance of all artifacts within the image
• Verifiable signatures provided by Sigstore
• Reproducible builds with Cosign and apko (read more about reproducibility)

For cases where you need container images with shells and package managers to build or debug, most Chainguard Containers come paired with a -dev variant.

Although the -dev container image variants have similar security features as their more minimal versions, they feature additional software that is typically not necessary in production environments. We recommend using multi-stage builds to leverage the -dev variants, copying application artifacts into a final minimal container that offers a reduced attack surface that won’t allow package installations or logins.

Learn More

To better understand how to work with Chainguard Containers, please visit Chainguard Academy and Chainguard Courses.

In addition to Containers, Chainguard offers VMs and Libraries. Contact Chainguard to access additional products.

Trademarks

This software listing is packaged by Chainguard. The trademarks set forth in this offering are owned by their respective companies, and use of them does not imply any affiliation, sponsorship, or endorsement by such companies.