k3s-fips

packaged by Chainguard

Chainguard Container for k3s-fips

Minimal FIPS image of K3s, a lightweight Kubernetes distribution

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/k3s-fips:latest

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

Compatibility Notes

Chainguard's k3s-fips image is comparable to the upstream rancher/k3s image and uses the same /bin/k3s entrypoint, agent default command, and volumes. It differs from the upstream image in the following ways:

• k3s is built with a FIPS-enabled Go toolchain, as described in FIPS Support below.
• k3s derives the keys for bootstrap data encryption and node password hashes with PBKDF2-HMAC-SHA256, instead of upstream's PBKDF2-HMAC-SHA1 and scrypt. Data written in the upstream formats is rejected, so moving an existing cluster to k3s-fips isn't supported. Create new clusters with k3s-fips instead.
• Join tokens must be at least 16 characters long, the minimum HMAC key length FIPS allows.
• The image doesn't include fuse-overlayfs-snapshotter, which upstream doesn't ship either. k3s's built-in --snapshotter=fuse-overlayfs option still works, using the fuse-overlayfs binary in the image.

FIPS Support

This variant builds k3s with Chainguard's FIPS Go toolchain. Its preferred cryptographic backend is the system OpenSSL library with the Chainguard FIPS Provider for OpenSSL, which the image ships together with the openssl-config-fipshardened configuration that enforces FIPS mode for that provider. If the OpenSSL provider can't be loaded, the toolchain falls back to the embedded Go FIPS module rather than to non-FIPS cryptography. The image also uses the FIPS builds of runc and, from k3s 1.36, the containerd shim. See Chainguard's FIPS guidance for details about FIPS support in Chainguard Containers.

Set GODEBUG=cgr_verbose=1 to print the backend k3s selected:

docker run --rm -e GODEBUG=cgr_verbose=1 cgr.dev/ORGANIZATION/k3s-fips:latest --version 2>&1 | head -1

The output is cgr_fips: openssl when the OpenSSL FIPS provider is in use, or cgr_fips: openssl attempted, fallback to geomys: <reason> when the toolchain fell back to the embedded Go FIPS module.

The bundled self-test checks the OpenSSL FIPS provider itself:

docker run --rm --entrypoint openssl-fips-test cgr.dev/ORGANIZATION/k3s-fips:latest

Getting Started

Create a docker network so the nodes can reach each other by name, then start a server. The server writes its kubeconfig to the current directory:

docker network create k3s
docker run -d --name k3s-server --hostname k3s-server --network k3s --privileged \
  -p 6443:6443 -v "$(pwd)":/etc/rancher/k3s \
  cgr.dev/ORGANIZATION/k3s-fips:latest server \
  --token k3s-example-token-0001 --tls-san k3s-server \
  --snapshotter=fuse-overlayfs --write-kubeconfig-mode 0644

Once the server is up, list its pods:

KUBECONFIG=k3s.yaml kubectl get pods -A

Join an agent to the server with the same token:

docker run -d --name k3s-agent --hostname k3s-agent --network k3s --privileged \
  cgr.dev/ORGANIZATION/k3s-fips:latest agent \
  --server https://k3s-server:6443 --token k3s-example-token-0001 \
  --snapshotter=fuse-overlayfs

Both nodes are Ready after a short while:

KUBECONFIG=k3s.yaml kubectl get nodes

To add more servers, start the first one with --cluster-init so it runs embedded etcd, then join further servers with server --server https://k3s-server:6443 and the same token.

You can also use the image with k3d:

k3d cluster create -i cgr.dev/ORGANIZATION/k3s-fips:latest

Documentation and Resources

• k3s documentation
• k3s high availability with embedded etcd
• Chainguard FIPS images
• Chainguard Academy

What are Chainguard Containers?

Chainguard's free tier of Starter container images are built with Wolfi, our minimal Linux undistro.

All other Chainguard Containers are built with Chainguard OS, Chainguard's minimal Linux operating system 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 development, or -dev, variant.

In all other cases, including Chainguard Containers tagged as :latest or with a specific version number, the container images include only an open-source application and its runtime dependencies. These minimal container images typically do not contain a shell or package manager.

Although the -dev container image variants have similar security features as their more minimal versions, they include additional software that is typically not necessary in production environments. We recommend using multi-stage builds to copy artifacts from the -dev variant into a more minimal production image.

Need additional packages?

To improve security, Chainguard Containers include only essential dependencies. Need more packages? Chainguard customers can use Custom Assembly to add packages, either through the Console, chainctl, or API.

To use Custom Assembly in the Chainguard Console: navigate to the image you'd like to customize in your Organization's list of images, and click on the Customize image button at the top of the page.

Learn More

Refer to our Chainguard Containers documentation on Chainguard Academy. Chainguard also offers VMs and Libraries — contact us for access.

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.