Posts tagged: containers

For my reader app I am using cronjobs to schedule my a new build and upload to cloudflare pages every hour. In this example I have built a docker image docker.io/waylonwalker/reader-waylonwalker-com and pushed it to dockerhub. It uses a CLOUDFLARE_API_TOKEN secret to access cloudflare, and the entrypoint itself does the build and upload.

apiVersion: v1
kind: Namespace
metadata:
  creationTimestamp: null
  name: reader
  namespace: reader

---
apiVersion: batch/v1
kind: CronJob
metadata:
  name: reader-cronjob
  namespace: reader
spec:
  schedule: "0 * * * *"
  successfulJobsHistoryLimit: 6
  failedJobsHistoryLimit: 6
  jobTemplate:
    spec:
      template:
        spec:
          containers:
            - name: reader-container
              image: docker.io/waylonwalker/reader-waylonwalker-com:latest
              env:
                - name: CLOUDFLARE_API_TOKEN
                  valueFrom:
                    secretKeyRef:
                      name: cloudflare-secret
                      key: cloudflare-secret
          restartPolicy: OnFailure

In my homelab kubernetes cluster I am using kubeseal to encrypt secrets. I have been using it successfully for a few months now wtih great success. It allows me to commit all of my secrets manifests to git with out risk of leaking secrets.

You see kubeseal encrypts your secrets with a private key only stored in your cluster, so only the cluster itself can decrypt them using the kubeseal controller.

KubeSeal #

https://sealed-secrets.netlify.app/

installation #

Installation happens in two steps. You need the kubernetes controller and the client side cli to create a sealed secret.

For a more complete instruction see the [docs#installation](https://github.com/bitnami-labs/sealed-secrets?tab=readme-ov-file#installation]

installation - controller #

 **context**

kubectl config current-context

sealed-secrets is installed using the helm package manager. To install sealed-secrets run the following command.

helm repo add sealed-secrets https://bitnami-labs.github.io/sealed-secrets
helm install sealed-secrets -n kube-system --set-string fullnameOverride=sealed-secrets-controller sealed-secrets/sealed-secrets

installation - client #

For the client you can check your OS package manager, brew, or the github-releases. For me I found it in the main arch repos.

paru -S kubeseal
# or
sudo pacman -S kubeseal
# or
brew install kubeseal

 You will need to install kubeseal on every device that you will want to

Example #

Most of these commands come straight from the docs. From my experience I have always specified the namespace, my projects go per namespace and I don’t have any reason that other namepsaces should see the secret, and if they do I deploy another secret in that namespace.

# Create a json/yaml-encoded Secret somehow:
# (note use of `--dry-run` - this is just a local file!)
echo -n bar | kubectl create secret generic mysecret --dry-run=client --from-file=foo=/dev/stdin -o yaml -n thenamespace > mysecret.yaml

note that the key of the secret is foo and the value is bar

results

apiVersion: v1
data:
  foo: YmFy
kind: Secret
metadata:
  creationTimestamp: null
  name: mysecret
  namespace: thenamespace

 The data is base64 encoded.

echo -n bar | base64
# YmFy

# This is the important bit:
kubeseal -f mysecret.yaml -w mysealedsecret.yaml

# At this point mysealedsecret.json is safe to upload to Github,
# post on Twitter, etc.

# Eventually:
kubectl create -f mysealedsecret.yaml -n thenamespace
# sealedsecret.bitnami.com/mysecret created

# Profit!
kubectl get secret mysecret
kubectl get secret mysecret -n thenamespace
# NAME       TYPE     DATA   AGE
# mysecret   Opaque   1      27s

cat mysealedsecret.yaml | kubeseal --validate

echo -n bar | kubectl create secret generic mysecret --dry-run=client --from-file=foo=/dev/stdin -o yaml \
  | kubeseal -o yaml -n thenamespace > mysealedsecret.yaml
echo -n baz | kubectl create secret generic mysecret --dry-run=client --from-file=bar=/dev/stdin -o yaml \
  | kubeseal -o yaml -n thenamespace --merge-into mysealedsecret.yaml

Results

---
apiVersion: bitnami.com/v1alpha1
kind: SealedSecret
metadata:
  creationTimestamp: null
  name: mysecret
  namespace: thenamespace
spec:
  encryptedData:
    bar: 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
    foo: 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
  template:
    metadata:
      creationTimestamp: null
      name: mysecret
      namespace: thenamespace

backing up your sealing key #

kubectl get secret -n kube-system -l sealedsecrets.bitnami.com/sealed-secrets-key -o yaml >main.key

converting .env files to a secret #

Working with web applications .env is a common way to store credentials. Let’s look at how we can convert these to secrets.

kubectl create secret generic mysecret --from-env-file=.env -n thenamespace --dry-run=client -o yaml > mysecret.yaml

Now you have a secret that looks like this.

apiVersion: v1
data:
  foo: YmFy
kind: Secret
metadata:
  creationTimestamp: null
  name: mysecret
  namespace: thenamespace

Seal it up just like before.

kubeseal -f mysecret.yaml -w mysealedsecret.yaml

Using the secrets #

I typically use the secrets in the container spec.

containers:
  - name: myapp
    envFrom:
      - secretRef:
          name: mysecret
    # You can still have other env vars
    env:
      - name: foo
        value: bar

Sometimes I want to mount the secret as a volume.

containers:
  - name: myapp
    volumeMounts:
      - name: mysecret
        mountPath: /mysecret
volumes:
  - name: mysecret
    secret:
      secretName: mysecret

Image Pull Secrets #

I also need to use imagePullSecrets. Let’s walk through the whole process. Starting with the secret.

kubectl create secret docker-registry regcred --docker-server=myprivateregistry.example.com --docker-username=foo --docker-password=bar --dry-run=client -o yaml

Generates the following secret.

apiVersion: v1
data:
  .dockerconfigjson: eyJhdXRocyI6eyJteXByaXZhdGVyZWdpc3RyeS5leGFtcGxlLmNvbSI6eyJ1c2VybmFtZSI6ImZvbyIsInBhc3N3b3JkIjoiYmFyIiwiYXV0aCI6IlptOXZPbUpoY2c9PSJ9fX0=
kind: Secret
metadata:
  creationTimestamp: null
  name: regcred
type: kubernetes.io/dockerconfigjson

---

the secret

Now we we can seal that secret.

kubeseal -f regcred.yaml -w regcred-sealed.yaml

And that gives us the following sealed secret that we can deploy into our cluster.

---
apiVersion: bitnami.com/v1alpha1
kind: SealedSecret
metadata:
  creationTimestamp: null
  name: regcred
  namespace: default
spec:
  encryptedData:
    .dockerconfigjson: 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
  template:
    metadata:
      creationTimestamp: null
      name: regcred
      namespace: default
    type: kubernetes.io/dockerconfigjson

Now that we have our sealed registry secret, we can deploy it into our cluster.

kubectl apply -f regcred-sealed.yaml

Now we can use it to pull images from our private registry.

containers:
  imagePullSecrets:
    - name: regcred

Full example #

Here is a full deployment example using all the secrets we have created.

• regcred
• mounting a secret
• envFrom secret

---
apiVersion: apps/v1
kind: Deployment
metadata:
  creationTimestamp: null
  labels:
    service: myservice
  name: myservice
  namespace: mynamespace
spec:
  replicas: 1
  selector:
    matchLabels:
      service: myservice
  strategy:
    type: Recreate
  template:
    metadata:
      creationTimestamp: null
      labels:
        service: myservice
    spec:
      containers:
        - envFrom:
            - secretRef:
                name: mysecret
          env:
            - name: foo
              value: bar
          image: private-registry.io/myimage:1.0.0
          name: myimage
          ports:
            - containerPort: 5000
              protocol: TCP
          resources: {}
          volumeMounts:
            - mountPath: /mysecret
              name: mysecret
      restartPolicy: Always
      volumes:
        - name: mysecret
          secret:
            secretName: mysecret
      imagePullSecrets:
        - name: regcred

Downside #

Now the main downside I see with kubeseal is that it does not provide a way to store your secrets in a way that you can access outside of your cluster. So you need to make sure that you have another solution in place to store your secrets so that you still have them if you ever were to take the cluster down or move from k8s to something else.

Overall the likelyhood of you loosing a production cluster is pretty low, so maybe it’s ok to just trust it depending on what the secrets are. Especially for things you control and can rotate anyways its fine.