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k8s-secret-provisioner

Small application ensuring configured secret data is present in the kubernetes cluster. It will only:

  • create non existing secrets
  • add non existing secret keys

Motivation is to use this application together with helm generated random keys, without always modifying already present secrets. This will allow rolling upgrades, since present applications do not need to refresh their secrets.

The k8s-secret-provisioner also comes with a helm chart, providing a job to be executed as a helm hook.

The format of the secret values (base64 encoding, private keys, ...) is transparent for the application. It is handled by the helm chart, which provides explicit support for passwords and private keys, using sprig functions.

Using the k8s-secret-provisioner

The following example demonstrates the use for a service myservice that needs a system account at a different service.

The Helm release name of this example is demo.

The helm chart of the service contains the following values.yaml:

otherService:
  serviceName: other-service
  servicePort: 8080
  systemUser:
    user: _myservice_user
    secretName: myservice
    secretKey: other-service-password
    system: true
    authorities:
      - READ_ASSET
      - CREATE_ASSET
      - READ_ASSET_GROUP
      - READ_ASSET_GROUP_DEFINITION

These values are used in the deployment.yaml to create a deployment descriptor that takes the username and password for the myservice to connect to the other service:

kind: Deployment
spec:
  template:
    spec:
      containers:
        - name: {{ .Chart.Name }}
          env:
            - name: OTHER_SERVICE_URL
              value: http://{{ .Values.otherService.serviceName }}:{{ .Values.otherService.servicePort }}
            - name: OTHER_SERVICE_USERNAME
              value: {{ .Values.otherService.systemUser.user }}
            - name: OTHER_SERVICE_PASSWORD
              valueFrom:
                secretKeyRef:
                  name: {{ list .Release.Name .Values.otherService.systemUser.secretName  | join "-" }}
                  key: {{ .Values.otherService.systemUser.secretKey }}

Now, the myservice uses the K8s secret demo-myservice that contains the password in the key other-service-password.

The next step is to configure the k8s-secret-provisioner to automatically create the secret and to configure the other service to provide the system user _myservice_user with that password.

This can be achieved by telling Helm to copy the values to configuration of the k8-secret-provisioner and the other service. This is done in the requirements.yaml of the Chart that includes all services:

dependencies:
  - name: myservice
    version: ${myservice.version}
    repository: ${myservice.repository}
    condition: global.myservice.enabled
    import-values:
      - child: otherService.systemUser
        parent: other.other-service.systemUsers.myservice
      - child: otherService.systemUser
        parent: other.k8s-secret-provisioner.passwords.myservice
  - name: other
    version: ${other.version}
    repository: ${other.repository}

Used variables

The following table shows which values of the configuration are used in the k8s-secret-provisioner and in the other service:

variable Used in k8s-secret-provisioner Used in the other service
user X
secretName X X
secretKey X X
prefixRelease X X
system X
authorities X

Releasing

Creating a new release involves the following steps:

  • mvn gitflow:release-start
  • Update CHANGELOG.md
  • mvn gitflow:release-finish
  • git push origin master
  • git push --tags
  • git push origin develop