Internal CA and NodePort Example

This section provides an example of how to configure an application to use NodePort to expose its self-managed TLS-based service and to use an Internal CA for signing CERTIFICATEs.

Note that alternatively an External CA could be used with a NodePort-based solution as well.

Prerequisites

This example requires that:

• Ensure that your StarlingX administrator has enabled use of the cert-manager apiGroups in your RBAC policies.

Procedure

1. Create an internal RootCA ISSUER in the default namespace by applying the following manifest file.

   # Create a cluster-wide ISSUER for create self-signed certificates
   ---
   apiVersion: cert-manager.io/v1
   kind: ClusterIssuer
   metadata:
       name: system-selfsigning-issuer
   spec:
       selfSigned: {}
   
   
   # Create a Certificate (and key) for my RootCA
   ---
   apiVersion: cert-manager.io/v1
   kind: Certificate
   metadata:
       name: abccompany-starlingx-rootca-certificate
   spec:
       secretName: abccompany-starlingx-rootca-certificate
       duration: 8640h
       commonName: "abccompany-starlingx-rootca"
       isCA: true
       issuerRef:
           name: system-selfsigning-issuer
           kind: ClusterIssuer
   
   
   # Create the RootCA ISSUER
   ---
   apiVersion: cert-manager.io/v1
   kind: Issuer
   metadata:
       name: abccompany-starlingx-rootca-issuer
   spec:
       ca:
           secretName: abccompany-starlingx-rootca-certificate
   

2. Share the public certificate of your internal RootCA to clients such that they can trust certificates signed by this RootCA.

   CERT64=`kubectl get secret abccompany-starlingx-rootca-certificate -n default -o yaml | fgrep tls.crt | fgrep -v "f:tls.crt" | awk '{print $2}'`
   echo $CERT64 | base64 --decode > abccompany-starlingx-rootca-certificate.pem
   

3. Create a deployment of an example demo application that uses NodePort to expose its service and therefore manages its TLS connection on its own, using a certificate it creates on its own.

   Apply the following manifest.

   Where 10.10.10.45 is the OAM Floating IP of the StarlingX and abccompany-starlingx.mycompany.com is the FQDN for this address.

   (You should substitute with the IP Address and FQDN for the StarlingX installation.)

   apiVersion: cert-manager.io/v1
   kind: Certificate
   metadata:
     name: abccompany-starlingx.mycompany.com-certificate
   spec:
     duration: 2160h # 90d
     renewBefore: 360h # 15d
     secretName: abccompany-starlingx.mycompany.com-certificate
     issuerRef:
       name: abccompany-starlingx-rootca-issuer
       kind: Issuer
     commonName: abccompany-starlingx.mycompany.com
     dnsNames:
     - abccompany-starlingx.mycompany.com
     ipAddresses:
     - 10.10.10.45
   ---
   apiVersion: apps/v1
   kind: Deployment
   metadata:
     name: example-app
   spec:
     replicas: 1
     selector:
       matchLabels:
         app: example-app
     template:
       metadata:
         labels:
           app: example-app
       spec:
         containers:
         - name: example-app
           image: example-app         # not a real app, could substitute ‘busybox’ here to look at mounted cert files inside container
           imagePullPolicy: Always
           ports:
           - containerPort: 8443
           protocol: TCP
           volumeMounts:
           - name: mycert
             mountPath: "/etc/mycert"  # the files tls.crt, tls.key and ca.crt will be under /etc/mycert/ in container
             readOnly: true
         volumes:
         - name: mycert
           secret:
             secretName: abccompany-starlingx.mycompany.com-certificate
   ---
   apiVersion: v1
   kind: Service
   metadata:
     name: example-app
     labels:
       app: example-app
   spec:
     type: NodePort
     ports:
       - port: 443
         protocol: TCP
         targetPort: 8443
         nodePort: 31118
     selector:
       app: example-app
   

   Note

   The Certificate usage of Cert-manager Documentation (https://cert-manager.io/docs/usage/certificate/) states that one should “Take care when setting the renewBefore field to be very close to the duration as this can lead to a renewal loop, where the Certificate is always in the renewal period.”

   In the light of the statement above, you must not set renewBefore to a value very close to the “duration” value, such as a renewBefore of 29 days and a duration of 30 days. Instead, you could set values such as renewBefore=15 days and duration=30 days to avoid renewal loops.

4. If example-app existed, you would access it from your browser with https://abccompany-starlingx.mycompany.com:31118.

   If you are using busybox to look at mounted cert files, attach to container (e.g. kubectl exec busybox-... -it -- sh and cd /etc/mycert; ls).