💂 Kubernetes External Secrets

Kubernetes External Secrets allows you to use external secret management systems (e.g., AWS Secrets Manager) to securely add secrets in Kubernetes. Read more about the design and motivation for Kubernetes External Secrets on the GoDaddy Engineering Blog.

How it works

The project extends the Kubernetes API by adding a ExternalSecrets object using Custom Resource Definition and a controller to implement the behavior of the object itself.

An ExternalSecret declares how to fetch the secret data, while the controller converts all ExternalSecrets to Secrets. The conversion is completely transparent to Pods that can access Secrets normally.

System architecture

1. ExternalSecrets are added in the cluster (e.g., kubectl apply -f external-secret-example.yml)
2. Controller fetches ExternalSecrets using the Kubernetes API
3. Controller uses ExternalSecrets to fetch secret data from external providers (e.g, AWS Secrets Manager)
4. Controller upsert Secrets
5. Pods can access Secrets normally

How to use it

Install with Helm

Alternatively, the included charts/kubernetes-external-secrets can be used to create the kubernetes-external-secrets resources and Deployment on a Kubernetes cluster using the Helm package manager.

Installing the Chart

helm install --name kubernetes-external-secrets \
--set env.AWS_REGION='<aws-region>' \
charts/kubernetes-external-secrets

Tip: A namespace can be specified by the Helm option '--namespace kube-external-secrets'

Uninstalling the Chart

To uninstall/delete the kubernetes-external-secrets deployment:

helm delete kubernetes-external-secrets

Configuration

The following table lists the configurable parameters of the kubernetes-external-secrets chart and their default values.

Parameter	Description	Default
env.AWS_REGION	Set AWS_REGION in Deployment Pod	us-west-2
env.EVENTS_INTERVAL_MILLISECONDS	Set EVENTS_INTERVAL_MILLISECONDS in Deployment Pod	60000
env.POLLER_INTERVAL_MILLISECONDS	Set POLLER_INTERVAL_MILLISECONDS in Deployment Pod	10000
image.repository	kubernetes-external-secrets Image name	godaddy/kubernetes-external-secrets
image.tag	kubernetes-external-secrets Image tag	1.2.0
image.pullPolicy	Image pull policy	IfNotPresent
rbac.create	Create & use RBAC resources	true
serviceAccount.create	Whether a new service account name should be created.	true
serviceAccount.name	Service account to be used.	automatically generated
podAnnotations	Annotations to be added to pods	{}
replicaCount	Number of replicas	1
nodeSelector	node labels for pod assignment	{}
tolerations	List of node taints to tolerate (requires Kubernetes >= 1.6)	[]
affinity	Affinity for pod assignment	{}
resources	Pod resource requests & limits	{}

Specify each parameter using the --set key=value[,key=value] argument to helm install. For example,

helm install --name kubernetes-external-secrets \
--set env.POLLER_INTERVAL_MILLISECONDS='300000' \
--set podAnnotations."iam\.amazonaws\.com/role"='Name-Of-IAM-Role-With-SecretManager-Access' \
charts/kubernetes-external-secrets

Add a secret

Add your secret data to your backend. For example, AWS Secrets Manager:

aws secretsmanager create-secret --name hello-service/password --secret-string "1234"

and then create a hello-service-external-secret.yml file:

apiVersion: 'kubernetes-client.io/v1'
kind: ExternalSecret
metadata:
  name: hello-service
secretDescriptor:
  backendType: secretsManager
  data:
    - key: hello-service/password
      name: password

Save the file and run:

kubectl apply -f hello-service-external-secret.yml

Wait a few minutes and verify that the associated Secret has been created:

kubectl get secret hello-service -o=yaml

The Secret created by the controller should look like:

apiVersion: v1
kind: Secret
metadata:
  name: hello-service
type: Opaque
data:
  password: MTIzNA==

Backends

kubernetes-external-secrets supports only AWS Secrets Manager.

AWS Secrets Manager

kubernetes-external-secrets supports both JSON objects ("Secret key/value" in the AWS console) or strings ("Plaintext" in the AWS console). Using JSON objects is useful when you need to atomically update multiple values. For example, when rotating a client certificate and private key.

When writing an ExternalSecret for a JSON object you must specify the properties to use. For example, if we add our hello-service credentials as a single JSON object:

aws secretsmanager create-secret --region us-west-2 --name hello-service/credentials --secret-string '{"username":"admin","password":"1234"}'

We can declare which properties we want from hello-service/credentials:

apiVersion: 'kubernetes-client.io/v1'
kind: ExternalSecret
metadata:
  name: hello-service
secretDescriptor:
  backendType: secretsManager
  data:
    - key: hello-service/credentials
      name: password
      property: password
    - key: hello-service/credentials
      name: username
      property: username

Development

Minikube is a tool that makes it easy to run a Kubernetes cluster locally.

Start minikube and the daemon. This creates the CustomerResourceDefinition, and starts to process ExternalSecrets:

minikube start

npm run nodemon

Development with localstack

Localstack mocks AWS services locally so you can test without connecting to AWS.

Run localstack in a seperate terminal window

npm run localstack

Start minikube as above

minikube start

Run the daemon with localstack

npm run local

Add secrets using the AWS cli (example)

 aws --endpoint-url=http://localhost:4584 secretsmanager create-secret --name hello-service/password --secret-string "1234"