sealed secrets controller
FIPS 140-3SecuritySealed Secrets is a Kubernetes controller and tool for one-way encrypted Secrets.
Sealed Secrets is a Kubernetes controller and tool for one-way encrypted Secrets.
Pull the latest version of this image from the Ghost registry. Pulling requires authentication — generate a token and run docker login first (see Authentication below).
The Ghost catalog is public to browse, but pulling images requires an account. Generate a pull token below (or from your Account → Tokens page) — you'll get a ready-to-paste docker login command, then docker pull works.
The username is generated automatically (it looks like robot$<project>+<auto-id>, not the name you typed) and is included in the docker login command above. The secret is shown only once when you create the token.
All Ghost images are signed with cosign. Verifying the signature before deployment ensures the image has not been tampered with.
Install cosign via brew install cosign or download from the Sigstore releases page.
Reference this image in your Dockerfile as a base layer:
This is a vendor-built FIPS-enabled image: its cryptography runs on FIPS 140-3 validated modules configured by the upstream vendor. You can inspect the image metadata:
| Standard | FIPS 140-3 |
| Crypto module | Vendor-configured validated modules |
| Cryptography | Validated modules only |
| Use case | Government, regulated industries, compliance workloads |
All examples in this guide use the public image. If you’ve mirrored the repository for your own use (for example, to your Docker Hub namespace), update your commands to reference the mirrored image instead of the public one.
For example:
registry.ghost-prod.alphabravo.io/ghost-base/<repository>:<tag><your-namespace>/dhi-<repository>:<tag>For the examples, you must first use docker login registry.ghost-prod.alphabravo.io to authenticate to the registry to pull the images.
This image contains sealed-secrets-controller, which is able to decrypt and interact with secrets deployed as
SealedSecret resources. The entry point for the image is controller which provides the internal CLI used to interact
with SealedSecrets.
Run the following command and replace <tag> with the image variant you want to run.
docker run --rm -it registry.ghost-prod.alphabravo.io/ghost-base/sealed-secrets-controller:<tag> --help
Sealed Secrets is designed to run in a Kubernetes cluster, and is frequently used with GitOps workflows to securely
manage Kubernetes Secrets. You can install Sealed Secrets using the official helm chart and replace the image. Replace
<your-registry-secret> with your Kubernetes image pull secret and <tag>
with the desired image tag.
helm repo add sealed-secrets https://bitnami.github.io/sealed-secrets
helm repo update
helm install sealed-secrets sealed-secrets/sealed-secrets --namespace kube-system --create-namespace \
--set "images.pullSecrets[0].name=<your-registry-secret>" \
--set image.registry=registry.ghost-prod.alphabravo.io \
--set image.repository=sealed-secrets-controller \
--set image.tag=<tag> \
This deploys the Sealed Secrets controller in the kube-system namespace using the specified image. This is the default namespace that kubeseal tool for encrypting secrets is expected, so changing the namespace will also require providing --controller-namespace argument to kubeseal whenever encrypting a secret.
To encrypt a secret, use kubeseal to generate a SealedSecret from the Kuebernetes Secret YAML.
First, create a Kubernetes Secret (if it is not already created)
kubectl create secret generic mysecret --dry-run=client \
--from-literal=password=secret \
-o yaml > mysecret.yaml
This will generate mysecret.yaml with the following content
apiVersion: v1
data:
password: c2VjcmV0
kind: Secret
metadata:
name: mysecret
Once the Kubernetes secret yaml or json is generated, create the SealedSecret resource and confirm it was applied correctly
kubeseal -f mysecret.yaml -w mysealedsecret.yaml
kubectl apply -f sealedsecret.yaml
kubectl get secrets mysecret
| Feature | Non-hardened sealed-secrets-controller | Docker Hardened sealed-secrets-controller |
|---|---|---|
| Security | Standard base with common utilities | Minimal, hardened base with security patches |
| Shell access | Full shell (bash/sh) available | No shell in runtime variants |
| Package manager | apt/apk available | No package manager in runtime variants |
| User | Runs as root by default | Runs as nonroot user |
| Attack surface | Larger due to additional utilities | Minimal, only essential components |
| Debugging | Traditional shell debugging | Use Docker Debug or Image Mount for troubleshooting |
Ghost hardened images prioritize security through minimalism:
The hardened images intended for runtime don't contain a shell nor any tools for debugging. Common debugging methods for applications built with Ghost hardened images include:
Docker Debug provides a shell, common debugging tools, and lets you install other tools in an ephemeral, writable layer that only exists during the debugging session.
For example, you can use Docker Debug:
docker debug registry.ghost-prod.alphabravo.io/ghost-base/sealed-secrets-controller
or mount debugging tools with the Image Mount feature:
docker run --rm -it --pid container:my-container \
--mount=type=image,source=registry.ghost-prod.alphabravo.io/ghost-base/busybox,destination=/dbg,ro \
registry.ghost-prod.alphabravo.io/ghost-base/sealed-secrets-controller:<tag> /dbg/bin/sh
Ghost hardened images come in different variants depending on their intended use.
Runtime variants are designed to run your application in production. These images are intended to be used either
directly or as the FROM image in the final stage of a multi-stage build. These images typically:
Build-time variants typically include dev in the variant name and are intended for use in the first stage of a
multi-stage Dockerfile. These images typically:
To migrate your application to a Ghost hardened image, you must update your Kubernetes manifests or Docker configurations. At minimum, you must update the base image in your existing deployment to a Ghost hardened image. This and a few other common changes are listed in the following table of migration notes.
| Item | Migration note |
|---|---|
| Base image | Replace your base images in your Kubernetes manifests with a Ghost hardened image. |
| Package management | Non-dev images, intended for runtime, don't contain package managers. Use package managers only in images with a dev tag. |
| Non-root user | By default, non-dev images, intended for runtime, run as the nonroot user. Ensure that necessary files and directories are accessible to the nonroot user. |
| Multi-stage build | Utilize images with a dev tag for build stages and non-dev images for runtime. For binary executables, use a static image for runtime. |
| TLS certificates | Ghost hardened images contain standard TLS certificates by default. There is no need to install TLS certificates. |
| Ports | Non-dev hardened images run as a nonroot user by default. sealed-secrets-controller binds to network ports 8080 and 8081 by default. Because hardened images run as nonroot, avoid privileged operations. |
| Entry point | Ghost hardened images may have different entry points than standard images. The DHI sealed-secrets-controller entry point is /usr/local/bin/controller. |
| No shell | By default, non-dev images, intended for runtime, don't contain a shell. Use dev images in build stages to run shell commands and then copy artifacts to the runtime stage. |
| Volume mounting | When using sealed-secrets-controller in containers, ensure proper volume mounting for accessing policy files and resources from the host filesystem. |
The following steps outline the general migration process.
Find hardened images for your CLI usage.
A hardened image may have several variants. Inspect the image tags and find the image variant that meets your needs. The sealed-secrets-controller CLI is typically used in CI/CD pipelines and local development environments.
Update your CI/CD pipeline configurations.
Update the image references in your CI/CD scripts, GitHub Actions, or other automation to use the hardened images.
For custom containers, update the base image in your Dockerfile.
If you're building custom images that include sealed-secrets-controller, ensure that your final image uses the
hardened sealed-secrets-controller as the base. For multi-stage builds, use images tagged as dev for build stages
and non-dev images for runtime.
Test Controller functionality.
To verify the controller is functioning properly, verify that is it able to read any existing SealedSecrets or generate a new SealedSecret.
# If the secret is not already generated
kubectl create secret generic mysecret --dry-run=client \
--from-literal=password=secret \
-o yaml > secret.yaml
kubeseal -f mysecret.yaml -w mysealedsecret.yaml
kubectl apply -f sealedsecret.yaml
kubectl get secret mysecret
The following are common issues that you may encounter during migration.
The hardened images intended for runtime don't contain a shell nor any tools for debugging. The recommended method for debugging applications built with Ghost hardened images is to use Docker Debug to attach to these containers. Docker Debug provides a shell, common debugging tools, and lets you install other tools in an ephemeral, writable layer that only exists during the debugging session.
By default image variants intended for runtime, run as the nonroot user. Ensure that necessary files and directories are accessible to the nonroot user. You may need to copy files to different directories or change permissions so your application running as the nonroot user can access them.
Non-dev hardened images run as a nonroot user by default. As a result, applications in these images can't bind to privileged ports (below 1024) when running in Kubernetes or in Docker Engine versions older than 20.10.
By default, image variants intended for runtime don't contain a shell. Use dev images in build stages to run shell
commands and then copy any necessary artifacts into the runtime stage. In addition, use Docker Debug to debug containers
with no shell.
Ghost hardened images may have different entry points than images such as Docker Official Images. Use docker inspect
to inspect entry points for Ghost hardened images and update your Dockerfile if necessary.