acme-kong-kube-helper

acme-kong-kube-helper

A kong-ingress-controller helper utility needed short-term

Introduction

This is a simple helper designed to solve a particular integration problem facing the co-operative working of the kong-ingress-controller and cert-manager.

At the time of writing (March '19; kong-ingress-controller v0.3, cert-manager v0.6), the ACME http01 challenge doesn't quite work as it should. The reason for this is that the kong ingress controller, by default, sets "preserve_host" to false and "strip_path" to true when creating new routes, but the challenge endpoint automatically created by cert-mananger needs them the other way round in order to complete the verification.

More info here: https://github.com/jetstack/cert-manager/issues/958

The issue should go away in v0.5 when the defaults will be as needed, but it affects v0.3 (sets both false) and v0.4 (sets both true).

I contemplated hacking the ingress controller to treat the acme ingresses as special, but in the end decided to write a small helper tool as a temporary workaround.

It's designed to run as a sidecar to the ingress controller. It watches for new ingresses that are created with the cm-acme-http-solver-* pattern. When one is created, it starts polling kong until it sees the corresponding route created. It then patches the route to update preserve_host and strip_path to the necessary settings. It continues to monitor the route and patch if needed (as there's a possibility the ingress controller might undo the change - I'm not sure) until the route dissapears, which is a sign that the challenge has been successfully completed. It then goes back to quietly watching for new ingresses.

It's only had limited testing, but has thus far been successful in allowing http01 challenges to complete automatically.

DB-less Kong

Kong 1.1 now allows you to run without a database. Unfortunately, when running in this mode, patching routes is not allowed so this helper will fail to achieve it's goal. It will get a 405 error (method not allowed) response from the kong admin UI.

Fortunately, C45tr0 has patched a version of the controller that uses a default ingress and associates any acme requests with that. It's a different way of solving the problem and one that has the distinct advantage that it works with DB-less Kong. So I'd suggest using that version instead. Again, the need should go away with v0.5

A thread discussing the patch here: https://github.com/ollystephens/acme-kong-kube-helper/issues/5#issuecomment-494946699

The patched version of the helper here: https://hub.docker.com/r/c45tr0/acme-kong-kube-helper

Deploying it

Deploy it inside the kong-ingress-controller pod, as a third container (it already has the ingress controller and the admin api). Something as simple as:

      - name: acme-kong-kube-helper
        image: ollystephens/acme-kong-kube-helper:0.0.3
        imagePullPolicy: IfNotPresent

This should work if you've used the default yaml file for the ingress crontroller. If not, you might need to tweak the arguments to let it know the admin api url.

The helper needs to run with equivalent permissions to the ingress controller; it needs to be able to listen for ingress creation events across the whole cluter. The easiest way to give it the correct permissions is to include it in the same pod, as suggested above. If you don't want to do that, the second easiest thing to do is make sure it uses the same serviceaccount as the ingress controller.

Arguments

The first two arguments mirror their equivalents in kong-ingress-controller; if you are deploying this container alongside, as suggested above, they should reflect the same settings if present, or be left unset if not. The third argument defines the name pattern for the ingress controllers created by cert-manager

Watching it in action

Watching the log of the container whilst you add a 'Certificate' object in should show something like:

2019/03/15 13:48:41 Matching ingress added: cm-acme-http-solver-fpkj9
2019/03/15 13:48:41   path /.well-known/acme-challenge/a1b2c3
2019/03/15 13:48:51 found matching kong route: /.well-known/acme-challenge/a1b2c3 = d4e5-f6e7
2019/03/15 13:48:51 successfully patched kong route: d4e5-f6e7
2019/03/15 13:49:01 found matching kong route: /.well-known/acme-challenge/a1b2c3 = d4e5-f6e7
2019/03/15 13:49:01 nothing to do; route for /.well-known/acme-challenge/a1b2c3 already has correct preserve_host/strip_path settings
2019/03/15 13:49:31 mission accomplished for path /.well-known/acme-challenge/a1b2c3