Secure your Kubernetes application with HTTPS

Hope you were having fun with my Kubernetes tutorial!

Today, I've got a new comment from Thorsten Hirsch, asking about TLS certificate. Well, @thorstenhirsch , I'm interested as with this thing as well :), and it was the first thing I had to check while I was learning Kubernetes. So I'm gonna share with you guys how did I solve this problem.

Requirement

We'd like to add a TLS certificate to our application, which we built here

Problem

What? problem? there is no problem! we were using certbot thousands times before. Just install it, run a magical script to get a free Let's Encrypt, then config it with nginx.
If you are thinking like this, wait a second and think about this:

• Your application lives in read-only containers, managed by Pods. And Pods are added/removed dynamically, by your configurations. And you will need to give nginx certificates when you start it.
• You can generate certificates, then pack it within the image, and deloy it. It's a terrible solution. Because you'd need to deploy every time the certificates are gonna expired.
• You can store it in a shared volume, and config nginx to take certificates from it. It's another terrible solution. Because you'd still need to manage the certificates yourself (even when you want to run it via a cron?)
• ...

Solution

Let's try to think about another solution (Spoiler: It's awesome):

• We will keep our infrastructure as before, with minimum modifications. No changes to application, no changes to nginx, no changes to deployment.
• TLS certificate will be monitored and renewed automatically.

First of all, I'd like to introduce you a new guy - Ingress.

Basically, Ingress is like a Router, which takes the incoming traffic then passes it to the corresponding Service, with the help from Ingress Controllers.

Simple example: You have 3 services:

• apple-service (which runs apple.com website, selling fruits)
• pineapple-service (another website - pineapple.com, selling phone, tablet, computer,...)
• pineapple-cloud-service (offering some cloud services for Pineapple's clients)

What you want is:

• apple.com will be pointed to apple-service
• pineapple.com will be pointed to pineapple-service
• pineapple.com/cloud will be pointed to pineapple-cloud-service

Ingress comes to help you here: Just need to create an Ingress object, with routing rules you want, then point those domains into the Ingress IP. And everything will be handled correctly!

Preparing stuffs

Before everything, we need to prepare stuffs for our Ingress configuration.

Install ingress-nginx
ingress-nginx is a Ingress Controller, which helps Ingress to route the traffic easily.

kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/master/deploy/static/mandatory.yaml

kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/master/deploy/static/provider/cloud-generic.yaml

For this Lab, we'd like to expose the Ingress with the Kube master's IP (192.168.1.33 as we configured before), so let's edit this controller a bit:

kubectl edit svc/ingress-nginx -n ingress-nginx

spec:
  externalIPs:
  - 192.168.1.33

Install cert-manager
cert-manager is a Kubernetes controller, which helps you to manage certificates without pain. We're gonna use it to request & renew Let's encrypt TLS certificate for our application.

kubectl apply --validate=false -f https://github.com/jetstack/cert-manager/releases/download/v0.12.0/cert-manager.yaml

Check all the pods are running correctly

kubectl get pods --namespace cert-manager

Setup Ingress & TLS

Back to our infrastructure: Before we were using a LoadBalancer as the start point, now we can just change it to stay behind in the cluster, and add an Ingress as the start point.

Before

(Users) ---> Service ---> Pods

Now

(Users) ---> Ingress ---> Service ---> Pods

We're gonna edit a bit the service file service-loadbalancer.yml (We've created it before)

apiVersion: v1
kind: Service
metadata:
  name: service-loadbalancer
spec:
  selector:
    name: templated-pod

  type: ClusterIP
  ports:  
  - name: http
    nodePort: null
    port: 80
    targetPort: 80
    protocol: TCP

  # type: LoadBalancer
  # ports:
  #   - port: 80
  #     targetPort: 80
  # externalIPs:
  #   - 192.168.1.33

Apply it

kubectl apply -f service-loadbalancer.yml

Create a ClusterIssuer
Create new file cert_issuer.yml

apiVersion: cert-manager.io/v1alpha2
kind: ClusterIssuer
metadata:
  name: letsencrypt-prod-site
  namespace: cert-manager
spec:
  acme:
    server: https://acme-v02.api.letsencrypt.org/directory
    email: [e-mail]
    privateKeySecretRef:
      name: letsencrypt-prod-site
    solvers:
    - http01:
        ingress:
          class: nginx

Apply it

kubectl apply -f cert_issuer.yml

Create an Ingress
Here comes our Rockstar tonight: ingress.yml

apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
  name: ingress
  annotations:
    kubernetes.io/ingress.class: "nginx"
    cert-manager.io/cluster-issuer: "letsencrypt-prod-site"

spec:
  tls:
  - hosts:
    - YOUR-DOMAIN-HERE.TLD
    secretName: site-tls

  rules:
  - host: YOUR-DOMAIN-HERE.TLD
    http:
      paths:
      - path: /
        backend:
          serviceName: service-loadbalancer
          servicePort: 80

Nothing special:

• Line 12: Define your hostname which will run under this Ingress
• Line 16-22: Define a rule, to tell this Ingress: When user browses YOUR-DOMAIN-HERE.TLD, under path /, you'd like to pass him to the service service-loadbalancer on port 80 (defined in service-loadbalancer.yml)

Remember with this Lab, you must point YOUR-DOMAIN-HERE.TLD to your IP address, then forward all traffic on port 80 and 443 to the kube-master IP 192.168.1.33

Show time:

kubectl apply -f ingress.yml

*Note: requesting/renewing a new certificate from Let's encrypt could take some minutes. You can monitor here: *

kubectl describe certificate site-tls

Now you can try to browser https://YOUR-DOMAIN-HERE.TLD/ on your favorite web browser, and open a prosecco :)

---

I've updated the repository https://gitlab.com/martinpham/kubernetes-fun, so you can take all the files we were talking about.