In order to store secrets safely in a public or private Git repository, you can use Bitnami’s sealed-secrets controller and encrypt your Kubernetes Secrets into SealedSecrets. The sealed secrets can be decrypted only by the controller running in your cluster and nobody else can obtain the original secret, even if they have access to the Git repository.
The sealed-secrets controller comes with a companion CLI tool called kubeseal. With kubeseal you can create SealedSecret custom resources in YAML format and store those in your Git repository.
Install the kubeseal CLI:
brew install kubeseal
For Linux or Windows you can download the kubeseal binary from GitHub.
Deploy sealed-secrets with a HelmRelease
First you have to register the Helm repository where the sealed-secrets chart is published:
flux create source helm sealed-secrets \ --interval=1h \ --url=https://bitnami-labs.github.io/sealed-secrets
interval we configure
source-controller to download
the Helm repository index every hour. If a newer version of sealed-secrets is published,
source-controller will signal helm-controller that a new chart is available.
Create a Helm release that installs the latest version of sealed-secrets controller:
flux create helmrelease sealed-secrets \ --interval=1h \ --release-name=sealed-secrets-controller \ --target-namespace=flux-system \ --source=HelmRepository/sealed-secrets \ --chart=sealed-secrets \ --chart-version=">=1.15.0-0" \ --crds=CreateReplace
With chart version
>=1.15.0-0 we configure helm-controller to automatically upgrade the release
when a new chart version is fetched by source-controller.
At startup, the sealed-secrets controller generates a 4096-bit RSA key pair and
persists the private and public keys as Kubernetes secrets in the
You can retrieve the public key with:
kubeseal --fetch-cert \ --controller-name=sealed-secrets-controller \ --controller-namespace=flux-system \ > pub-sealed-secrets.pem
The public key can be safely stored in Git, and can be used to encrypt secrets without direct access to the Kubernetes cluster.
Generate a Kubernetes secret manifest with kubectl:
kubectl -n default create secret generic basic-auth \ --from-literal=user=admin \ --from-literal=password=change-me \ --dry-run=client \ -o yaml > basic-auth.yaml
Encrypt the secret with kubeseal:
kubeseal --format=yaml --cert=pub-sealed-secrets.pem \ < basic-auth.yaml > basic-auth-sealed.yaml
Delete the plain secret and apply the sealed one:
rm basic-auth.yaml kubectl apply -f basic-auth-sealed.yaml
Verify that the sealed-secrets controller has created the
basic-auth Kubernetes Secret:
$ kubectl -n default get secrets basic-auth NAME TYPE DATA AGE basic-auth Opaque 2 1m43s
A cluster admin should add the stable
HelmRepository manifest and the sealed-secrets
to the fleet repository.
Helm repository manifest:
apiVersion: source.toolkit.fluxcd.io/v1beta2 kind: HelmRepository metadata: name: sealed-secrets namespace: flux-system spec: interval: 1h0m0s url: https://bitnami-labs.github.io/sealed-secrets
Helm release manifest:
apiVersion: helm.toolkit.fluxcd.io/v2beta1 kind: HelmRelease metadata: name: sealed-secrets namespace: flux-system spec: chart: spec: chart: sealed-secrets sourceRef: kind: HelmRepository name: sealed-secrets version: ">=1.15.0-0" interval: 1h0m0s releaseName: sealed-secrets-controller targetNamespace: flux-system install: crds: Create upgrade: crds: CreateReplace
flux create <kind> --export > manifest.yaml.
Once the sealed-secrets controller is installed, the admin fetches the public key and shares it with the teams that operate on the fleet clusters via Git.
When a team member wants to create a Kubernetes Secret on a cluster, they uses kubeseal and the public key corresponding to that cluster to generate a SealedSecret.
Assuming a team member wants to deploy an application that needs to connect to a database using a username and password, they’ll be doing the following:
- create a Kubernetes Secret manifest locally with the db credentials e.g.
- encrypt the secret with kubeseal as
- delete the original secret file
- create a Kubernetes Deployment manifest for the app e.g.
- add the Secret to the Deployment manifest as a
volume mount or env var using the original name
- commit the manifests
app-deployment.yamlto a Git repository that’s being synced by the GitOps toolkit controllers
Once the manifests have been pushed to the Git repository, the following happens:
- source-controller pulls the changes from Git
- kustomize-controller applies the SealedSecret and the Deployment manifests
- sealed-secrets controller decrypts the SealedSecret and creates a Kubernetes Secret
- kubelet creates the pods and mounts the secret as a volume or env variable inside the app container