Erlang cluster on Kubernetes: Using a namespace-scoped issuer

23 Dec 2022 17:06 kubernetes cert-manager

In an earlier post, I used a ClusterIssuer that I originally created when first setting up cert-manager. That needs fixing.

Create the CA Keypair

Note that this is just enough to get it working; I’ve not considered expiry, usages, whatever. Depending on your security policies, you might want to keep a root CA in an HSM and use an intermediate CA.

openssl ecparam -name prime256v1 -genkey -noout -out erlclu-ca.key
openssl req -new -x509 -key erlclu-ca.key -sha256 \
    -subj "/C=GB/L=London/ CA" -out erlclu-ca.crt
The default certificate lifetime is 30 days; you might want to do something about that. It’ll cause issues later if you don’t.

CA Secret

cert-manager will look for the CA certificate and key in a K8s secret:

kubectl --namespace erlclu \
    create secret tls erlclu-ca-key-pair \
        --cert=erlclu-ca.crt \

Create an Issuer object

For a namespace-scoped CA, we need an Issuer object:

kind: Issuer
  namespace: erlclu
  name: erlclu-issuer
    secretName: erlclu-ca-key-pair

Fix the deployment

Previously, I used a ClusterIssuer object, passed to the init container with thhe ISSUER_KIND and ISSUER_NAME environment variables. To use the new Issuer, we need to change those:

  - name: ISSUER_KIND
    value: Issuer
  - name: ISSUER_NAME
    value: erlclu-issuer

Then we just redeploy the pods and watch as they request (and get) certificates from the correct issuer:

NAME                      APPROVED   DENIED   READY   ISSUER                  REQUESTOR                                         AGE
erlclu-54b96fdb7c-zqlh8   True                True    erlclu-issuer           system:serviceaccount:erlclu:erlclu               1s
erlclu-54b96fdb7c-sdcts   True                True    erlclu-issuer           system:serviceaccount:erlclu:erlclu               1s