2020-02-02

Docker registry credentials as secretGeneratow with kustomize

So you just discovered your new friend kustomize, and now you want to convert all your pesky secrets into secretGenerators. Good for you!


But... what about the docker registry credentials secret? It seems like magic that just works. Fear not, here is the definitive guide to how you can convert it to secretGenerator!


So let's assume you start with the following working setup:


Inside secret-docker-reg.yaml we have the following YAML:

apiVersion: v1
files:
  - secret-docker-reg.json
kind: Secret
metadata:
  name: docker-reg
  namespace: whatever
type: kubernetes.io/dockerconfigjson

Inside secret-docker-reg.json we have the following JSON:

{"auths":{"https://registry.gitlab.com":{"username":"yourusername","password":"SOME SECRET PASSWORD STRING","auth":"SOME SECRET AUTH STRING"}}}

Alternatively your secret-docker-reg.yaml may look like this:
apiVersion: v1
data:
  - inlined-json: eyJhdXRocyI6eyJodHRwczovL3JlZ2lzdHJ5LmdpdGxhYi5jb20iOnsidXNlcm5hbWUiOiJ5b3VydXNlcm5hbWUiLCJwYXNzd29yZCI6IlNPTUUgU0VDUkVUIFBBU1NXT1JEIFNUUklORyIsImF1dGgiOiJTT01FIFNFQ1JFVCBBVVRIIFNUUklORyJ9fX0=
kind: Secret
metadata:
  name: docker-reg
  namespace: whatever
type: kubernetes.io/dockerconfigjson

As you can see the difference is that in the first example the credentials is in a separate .json file referenced by the YAML (secret-docker-reg.json) while in the second the json content has been base64 encoded diretly into the YAML file.

Now to convert this to a kustomize secretGenerator you will need to keep the json in a separate file. In the first example you are already good to go, in the second simply copy the rather long base64 string (eyJhdXRocyI6eyJodHRwczovL3JlZ2lzdHJ5LmdpdGxhYi5jb20iOnsidXNlcm5hbWUiOiJ5b3VydXNlcm5hbWUiLCJwYXNzd29yZCI6IlNPTUUgU0VDUkVUIFBBU1NXT1JEIFNUUklORyIsImF1dGgiOiJTT01FIFNFQ1JFVCBBVVRIIFNUUklORyJ9fX0=)  into a separate file such as temp.txt and run the following command:
cat temp.txt | base64 -d > secret-docker-reg.json

This will decode the base64 into the json format in the file we want. NOTE: You could also use an online base64 conversion tool, but since this string contains credentials to your docker registry, you may want to use one you really trust and only over https.

What remains is to create the kustomize secretGenerator stanza:

secretGenerator:
- name: docker-reg
  files:
  - secret-docker-reg.json
  type: kubernetes.io/dockerconfigjson

Things to watch out for:

  • The secretGenerator stanza must be inside a kustomization.yaml file as it is part of kustomize and NOT part of kubernetes/kubectl.
  • The .json file needs to be on the same level or below the kustomize.yaml file from which it is referenced. If not you will get nasty errors about this.
And that's it! I hope this saved your ass like it would have saved mine if I had found it before I knew. Oh wait...

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