Using Cloudflare Tunnel on Kubernetes

Typically in the Kubernetes environment, when we need to expose a service to the ouside world, we make use of Load Balancer techniques which in general means a load balancer from our cloud provider.

The problem with this approach is that our service will be reachable from the load balancer or, in more accurate terms, form the network where the load balancer lives.

One way to improve in terms of security is start using Cloudflare tunnels, which are a fundamental component of Cloudflare’s suite of services designed to enhance the performance, reliability, and security of websites and applications. At its core, a Cloudflare Tunnel serves as a secure conduit between the origin server, where the application is hosted, and Cloudflare’s global network. This tunneling architecture introduces several key benefits that set it apart from traditional load balancing approaches.

By using CF tunnels, instead of publicly exposing an endpoint, what we do is “connect” one little daemon (the CF tunnel) through Cloudflare’s global network. So, in theory, the connection is first established from our data center (cloud, on-prem, whatever) to the cloud and not the otherway around.

One benefit of this approach is that we don’t need to have any network ports opened, as all the communication between our services and the outside world will happen though the CF tunnel.

k8s requirements

What do we need to run CF tunnels alongside my public services in k8s? Not much, just a couple of deployments and services.

In my example, I’ll be using nginx as backend but anything else (Flask service, API, static site, whatever!) could be used.

The diagram of the request will look like the following:

User (cloud) --> CF Global Network <-- CF Tunnel container --> nginx

Which means that the connection is initialized from the CF tunnel to CF global network. Once this happens, all the magic that CF tunnels provides will happen as well.

k8s configuration

As mentioned, we’d need a couple of deployments and a service. In order to keep the deployment clean and simple, we could take advantage of namespaces: We could create one namespace per group of services, as they are free.

In this example, I have create two different deployments and one service:

> kubectl get deployments.apps
NAME                   READY   UP-TO-DATE   AVAILABLE   AGE
cf-tunnel-nginx-test   1/1     1            1           2m48s
cf-tunnel-test         1/1     1            1           2m48s

> kubectl get services
NAME                   TYPE        CLUSTER-IP       EXTERNAL-IP   PORT(S)   AGE
nginx                  ClusterIP    <none>        80/TCP    4m23s

Cloudflare configuartion

The configuration in Cloudflare is as simple as it follows:


In the code I have added a response header including the hostname of the container that handled the response:

> curl -I
HTTP/2 200 
date: Sun, 19 Nov 2023 02:55:19 GMT
content-type: text/html
accept-ranges: bytes
last-modified: Tue, 24 Oct 2023 13:46:47 GMT
x-container-hostname: cf-tunnel-nginx-test-869bdffcd4-kpgmx
cf-cache-status: DYNAMIC
nel: {"success_fraction":0,"report_to":"cf-nel","max_age":604800}
server: cloudflare
cf-ray: 82852c758ef22def-SCL
alt-svc: h3=":443"; ma=86400

Or, just to make it more clear:

> curl -sI | grep x-container-hostname
x-container-hostname: cf-tunnel-nginx-test-869bdffcd4-kpgmx

Show me the code

All the code used for this lab is available here.