azure key vault controller

The controller is one of three components in the akv2k8s project. The companion env-injector webhook (spvest/azure-keyvault-webhook) and vaultenv init binary (spvest/azure-keyvault-env) are separate images and are not included here. Use those images alongside the controller if you need direct env-var injection into pods without persisting a Kubernetes Secret.

Run the azure-keyvault-controller container

Azure Key Vault Controller is designed to run inside a Kubernetes cluster. It needs access to the Kubernetes API and to Azure Key Vault, so it is not meaningfully run standalone with docker run against any real Key Vault. The image is still useful to inspect locally before deploying.

To display help information:

docker run --rm registry.ghost-prod.alphabravo.io/ghost-base/azure-keyvault-controller:<tag> --help

Deploy Azure Key Vault Controller in Kubernetes

The akv2k8s project publishes the controller as part of the akv2k8s Helm chart at https://charts.spvapi.no. The recommended deployment method is to install that chart and override the controller image to point at the Docker Hardened image. See the upstream installation guide for full chart details.

1. Add the upstream chart repository:

   helm repo add spv-charts https://charts.spvapi.no
   helm repo update
   

2. Install the chart, overriding the image to point at the Docker Hardened image:

   helm install azure-keyvault-controller \
     spv-charts/akv2k8s \
     --namespace akv2k8s \
     --create-namespace \
     --set controller.image.repository=registry.ghost-prod.alphabravo.io/ghost-base/azure-keyvault-controller \
     --set controller.image.tag=<tag> \
     --set env_injector.enabled=false
   

   Replace <tag> with a tag from the Tags tab of this listing — for example a version-specific tag like 1.8.2-debian13 or a floating tag like 1.

   The akv2k8s chart deploys both the controller and env-injector by default. The example above disables the env-injector because this image only replaces the controller component. Omit --set env_injector.enabled=false if you also want the chart to deploy the upstream env-injector images.

3. Verify the controller is running:

   kubectl -n akv2k8s get pod \
     -l app.kubernetes.io/component=azure-keyvault-controller-akv2k8s-controller
   

   You should see output similar to:

   NAME                                                         READY   STATUS    RESTARTS   AGE
   azure-keyvault-controller-akv2k8s-controller-76bd9c66c4-zk6vf 1/1     Running   0          30s
   

Note: The dev variants of this image run as root and include a shell and package manager. If your deployment sets runAsNonRoot: true in the pod security context, dev variants will not start. Use a runtime variant in production and drop runAsNonRoot only when you specifically need a dev variant for debugging.

Configure Azure authentication

The controller needs Azure credentials to read from Key Vault. The akv2k8s project supports several authentication modes — service principal credentials in environment variables, AKS managed identity, AKS pod-managed identity, and Microsoft Entra Workload Identity. Refer to the upstream authentication documentation for the trade-offs and choose the mode that fits your cluster.

For example, to use a service principal with environment-variable credentials, supply them through the chart's controller.env values:

helm upgrade --install azure-keyvault-controller \
  spv-charts/akv2k8s \
  --namespace akv2k8s \
  --create-namespace \
  --set controller.image.repository=registry.ghost-prod.alphabravo.io/ghost-base/azure-keyvault-controller \
  --set controller.image.tag=<tag> \
  --set env_injector.enabled=false \
  --set global.keyVaultAuth=environment \
  --set controller.env.AZURE_TENANT_ID=<tenant-id> \
  --set controller.env.AZURE_CLIENT_ID=<client-id> \
  --set controller.env.AZURE_CLIENT_SECRET=<client-secret>

Production deployments should mount the client secret from a Kubernetes Secret rather than passing it on the command line. See the upstream chart's values.yaml for the available knobs.

Synchronize an Azure Key Vault secret

After the controller is running, define an AzureKeyVaultSecret resource that references a secret stored in Azure Key Vault. The controller fetches the value and writes it as a native Kubernetes Secret that workloads can consume.

apiVersion: spv.no/v2beta1
kind: AzureKeyVaultSecret
metadata:
  name: my-app-secret
  namespace: default
spec:
  vault:
    name: my-keyvault
    object:
      type: secret
      name: my-secret
  output:
    secret:
      name: my-app-secret
      dataKey: my-key

Apply the resource and inspect the resulting Secret:

kubectl apply -f azurekeyvaultsecret.yaml
kubectl get secret my-app-secret -o yaml

Synchronize an Azure Key Vault certificate to a TLS Secret

The controller also handles certificates and writes them as Kubernetes TLS Secrets that ingress controllers and other TLS consumers can use directly.

apiVersion: spv.no/v2beta1
kind: AzureKeyVaultSecret
metadata:
  name: my-tls-cert
  namespace: default
spec:
  vault:
    name: my-keyvault
    object:
      type: certificate
      name: my-cert
  output:
    secret:
      name: my-tls-cert
      type: kubernetes.io/tls

Monitor the controller

Follow the controller logs to observe synchronization activity and authentication events:

kubectl -n akv2k8s logs -f \
  -l app.kubernetes.io/component=azure-keyvault-controller-akv2k8s-controller \
  -c controller

Image variants

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:

  • Run as the nonroot user
  • Do not include a shell or a package manager
  • Contain only the minimal set of libraries needed to run the app

• 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:

  • Run as the root user
  • Include a shell and package manager
  • Are used to build or compile applications

• FIPS variants include fips in the variant name and tag. They come in both runtime and build-time variants. These variants use cryptographic modules that have been validated under FIPS 140, a U.S. government standard for secure cryptographic operations. For example, usage of MD5 fails in FIPS variants.

Migrate to a Ghost hardened image

To migrate your application to a Ghost hardened image, you must update your Dockerfile. At minimum, you must update the base image in your existing Dockerfile to a Ghost hardened image. This and a few other common changes are listed in the following table of migration notes.

The following steps outline the general migration process.

1. Find hardened images for your app.

   A hardened image may have several variants. Inspect the image tags and find the image variant that meets your needs.

2. Update the base image in your Dockerfile.

   Update the base image in your application's Dockerfile to the hardened image you found in the previous step. For framework images, this is typically going to be an image tagged as dev because it has the tools needed to install packages and dependencies.

3. For multi-stage Dockerfiles, update the runtime image in your Dockerfile.

   To ensure that your final image is as minimal as possible, you should use a multi-stage build. All stages in your Dockerfile should use a hardened image. While intermediary stages will typically use images tagged as dev, your final runtime stage should use a non-dev image variant.

4. Install additional packages

   Ghost hardened images contain minimal packages in order to reduce the potential attack surface. You may need to install additional packages in your Dockerfile. Inspect the image variants to identify which packages are already installed.

   Only images tagged as dev typically have package managers. You should use a multi-stage Dockerfile to install the packages. Install the packages in the build stage that uses a dev image. Then, if needed, copy any necessary artifacts to the runtime stage that uses a non-dev image.

   For Alpine-based images, you can use apk to install packages. For Debian-based images, you can use apt-get to install packages.

Troubleshooting migration

The following are common issues that you may encounter during migration.

General debugging

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.

Permissions

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.

Privileged ports

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. To avoid issues, configure your application to listen on port 1025 or higher inside the container, even if you map it to a lower port on the host. For example, docker run -p 80:8080 my-image will work because the port inside the container is 8080, and docker run -p 80:81 my-image won't work because the port inside the container is 81.

No shell

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.

Entry point

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.