You can find better maintainted alternatives from Syncing Secrets Across Namespaces - cert-manager Documentation. I personally recommend mittwald/kubernetes-replicator.

secret-sync-operator

A K8s Operator that helps keep secrets in sync across multiple namespaces

What is this?

This sample is an example Kubenetes Operator that will syncronize Kubernetes Secrets that you annotate with target Secrets that you designate.

How does it work

The operator will watch the Kubernetes Events API for changes in corev1.Secret object types. When a change is detected, the operator examines the Secret for an annotation of secretsync.ibm.com/replicate=true. If it finds the annotation on the Secret, the operator then checks for the existance of the secretsync.ibm.com/replicate-to annotation and reads the values of that annotation in as a comma-delimited list. This list is the namespace and name of the secret(s) to be created (or updated) and kept in sync. For example, if the annotation value was default/mysecret1,default/mysecret2, the operator would create (or update) a Secret called mysecret in and a Secret called mysecret2 in the default namespace. As another example, if the annotation value was ALL/mysecret1, the operator would create (or update) a Secret called mysecret1 in any other namespaces.

If the value of the secretsync.ibm.com/replicate annotation was changed to false, the operator would no longer attempt to create or update the Secrets defined in the secretsync.ibm.com/replicate-to annotation.

When the operator creates or updates a target Secret object, it will attach some metadata to the secret:

• An annotation of secretsync.ibm.com/replicated-resource-version which contains the resourceVersion value taken from the source Secret. This is useful to understand what content you'll find in the data field of the secret

• An annotation of secretsync.ibm.com/replicated-time which contains the timestamp of the last create or update operation

• A label of secretsync.ibm.com/replicated-from which identifies the source Secret in the format namespace.secret-name. This label makes it easy to see all the Secrets in a cluster that are replicated from a certain source Secret. For example, the command kubectl get secret -l secretsync.ibm.com/replicated-from=default.mysecret --all-namespaces will show all the Secrets in the cluster that were synced from the mysecret Secret in the default namespace of the cluster.

Building and running

You have a few options are your disposal to get this operator running:

• docker build -t <desired container image name> . : If you can do local container builds (I.e. using Docker or a similar other OCI-compliant build method) you can simply use the Dockerfile provided to produce a container image that you can reference from the Kubernetes deployment YAMLs located in the deploy directory for this project.
• operator-sdk build <container image name> : If you have a working Go development environment on your machine, you can follow these instructions to get the Operator SDK CLI installed on your machine and use it to build the operator image.

After building the image you can push it to your choice of container registry (we're partial to the IBM Cloud Container Registry ourselves) and then reference it from the provided YAML deployment files in the deploy folder of this project.

To deploy the operator just run kubectl apply -f deploy/all-in-one.yaml. This will:

1. Create a service account for the operator that uses the provided IBM Cloud Container Registry pull secrets.
2. Create a ClusterRole that defines access to full access to Secrets and ConfigMap resource types in the cluster and read access to Namespaces, Pods, and ReplicaSets. This is the minimum required access for the operator to do it's function
3. Create a ClusterRoleBinding that binds the created ClusterRole to the operator's service account
4. Creates a Deployment that defines the operator's pods.

To delete the operator from your cluster, simply run kubectl delete -f deploy/all-in-one.yaml.