Using the Doppler Kubernetes Operator for Managing PKCS12 Certificates

Using the Doppler Kubernetes Operator for Managing PKCS12 Certificates

Ryan Blunden's photo
Ryan Blunden
·Sep 23, 2021·

4 min read

This tutorial will show you how to store and automatically sync PKCS12 certificates from Doppler to Kubernetes using the Doppler Kubernetes Operator.


  • Doppler account
  • Doppler CLI installed and authenticated
  • Privileged access to a Kubernetes cluster
  • An existing PKCS12 certificate

Installing the Kubernetes Operator

The Doppler Kubernetes Operator continuously syncs secrets to Kubernetes and can auto-reload deployments when secrets change.

Install the Operator using Helm:

helm repo add doppler
helm install --generate-name doppler/doppler-kubernetes-operator

Or kubectl:

kubectl apply -f

Installing the Kubernetes Operator creates the following resources:

  • doppler-operator-system namespace
  • DopplerSecret Custom Resource Definition (CRD)
  • Service account and RBAC role for the Operator
  • Operator Deployment

Visit the Kubernetes Operator GitHub repository to learn more.

Importing the PKCS12 Certificate to Doppler

As the PKCS12 certificate is in binary format, it must be base64 encoded before importing to Doppler.

If you haven't yet created a Doppler project, you can use the CLI:

doppler projects create pkcs12

Select the appropriate environment to import the secret to:

doppler setup --project pkcs12 --config prd

Then create the base64 encoded PKCS12 certificate secret:

doppler secrets set PKCS12_CERT="$(base64 -i doppler.p12)"

If your PKCS12 certificate is password-protected, you'll need to add that too:

doppler secrets set PKCS12_PASS="changeit"

Kubernetes Operator Secrets Sync

A Doppler Service Token is required to give the Operator access to the secrets for a specific project and config. It will be stored in a Kubernetes secret that the Operator will then access.

Create the Service Token and inject it as a Kubernetes secret in the doppler-operator-system namespace:

kubectl create secret generic doppler-project-pkcs12-token \
  --namespace doppler-operator-system \
  --from-literal=serviceToken=$(doppler configs tokens create kubernetes-operator --plain)

Next, we'll create a custom DopplerSecret which contains data the Operator uses to manage the Kubernetes secret containing the synced secrets.

Kubernetes secrets are base64 encoded, not for security, but to store binary values such as PKCS12 certificates. But as the PKCS12 certificate is already base64 encoded in Doppler, we'll use the optional processors: map, which tells the Operator to skip base64 encoding the PKCS12_CERT value.

Save the file contents as doppler-secret-pkcs12.yaml:

kind: DopplerSecret
  name: doppler-secret-pkcs12 # Name of custom resource 
  namespace: doppler-operator-system
    name: doppler-project-pkcs12-token # Name of Kubernetes service token secret from previous step
    name: doppler-pkcs12  # Name of Kubernetes secret Operator will sync secrets to
    namespace: default # Namespace of the deployment that will use the secret
      type: base64 # Instructs the Operator to not base64 encode the secret value again

Then create the DopplerSecret in Kubernetes:

kubectl apply -f pkcs12-secret.yaml

You can check the Operator created the Kubernetes synced secret by querying for secrets with the Operator's custom label:

kubectl describe secrets

The output should be similar to:

Name:         doppler-pkcs12
Namespace:    default

Type:  Opaque

PKCS12_PASS:          8 bytes
DOPPLER_CONFIG:       3 bytes
DOPPLER_PROJECT:      6 bytes
PKCS12_CERT:          3975 bytes

The final step is mounting the certificate inside a container.

Mount PKCS12 Certificate Inside a Kubernetes Deployment

The below deployment uses the doppler-pkcs12 managed secret created by the Operator to mount the certificate using a secrets volume and supply the certificate password using the PKCS12_PASS environment variable.

The command and args combine to verify the certificate by extracting its metadata for testing purposes.

Save the file contents as pkcs12-deployment.yaml:

apiVersion: apps/v1
kind: Deployment
  name: doppler-pkcs12
  annotations: 'true'
  replicas: 1
      app: doppler-pkcs12
          app: doppler-pkcs12
        - name: doppler-pkcs12
          image: alpine
          workingDir: /usr/src/app          
            - '/bin/sh'          
          args: # Install OpenSSL and verify certificate for testing purposes
            - '-c'
            - 'apk add openssl > /dev/null && 
              openssl pkcs12 -in ./secrets/doppler.p12 -nodes -passin pass:"$PKCS12_PASS" | openssl x509 -noout -text && 
              tail -f /dev/null'          
          env: # Set PKCS12_PASS environment variable needed to decrypt  certificate
            - name: PKCS12_PASS
                  name: doppler-pkcs12  # Operator managed secret
                  key: PKCS12_PASS
            - name: doppler-pkcs12-volume
              readOnly: true
              mountPath: /usr/src/app/secrets
              memory: '256Mi'
              cpu: '250m'
        - name: doppler-pkcs12-volume
            secretName: doppler-pkcs12 # Operator managed secret
            - key: PKCS12_CERT # Only select the PKCS12_CERT for mounting
              path: doppler.p12 # Certificate name at mount path

Create the deployment in Kubernetes:

kubectl apply -f  pkcs12-deployment.yaml

Then confirm the certificate was verified by viewing the container logs:

kubectl logs --selector app=doppler-pkcs12 --tail=70


Awesome work!

Now you know how to store and automatically sync PKCS12 certificates from Doppler to Kubernetes using the Doppler Kubernetes Operator.

Be sure to check out the Kubernetes Operator documentation and head over to the Doppler Community Forum if you need help or have any questions.