pergon/kubernetes-external-secrets repository overview

⁠💂 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

⁠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.

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

⁠Use IAM credentials for Secrets Manager access

If not running on EKS you will have to use an IAM user (in lieu of a role). Set AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY env vars in the session/pod. You can use envVarsFromSecret in the helm chart to create these env vars from existing k8s 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"

AWS Parameter Store:

aws ssm put-parameter --name "/hello-service/password" --type "String" --value "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

or

apiVersion: 'kubernetes-client.io/v1'
kind: ExternalSecret
metadata:
  name: hello-service
secretDescriptor:
  backendType: systemManager
  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"