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PROJECT NO LONGER ACTIVELY MAINTAINED, use https://github.com/tnozicka/openshift-acme instead (comparison here)

Automatic Certificates for Openshift Routes

It will manage all routes with (by default) butter.sh/letsencrypt-managed=yes labels in the project/namespace, it's deployed in.

Limitations

For now, there are the following limitations.

  1. It only supports domain names of length smaller than 64 characters.
  2. It only implements http-01-type verification, better known as "Well-Known".
  3. Multiple domains per certificate are not supported. See issue #1.
  4. It will not create the letsencrypt account. It needs to be created before deploying. See Section Installation below.
  5. It doesn't work cross-namespace. See issue #4.

Customizing

The following env variables can be used.

  • LETSENCRYPT_ROUTE_SELECTOR (optional, defaults to butter.sh/letsencrypt-managed=yes), to filter the routes to use;
  • LETSENCRYPT_RENEW_BEFORE_DAYS (optional, defaults to 30), renew this number of days before the certificate is about to expire;
  • LETSENCRYPT_CONTACT_EMAIL (required for account generation), the email that will be used by the ACME CA;
  • LETSENCRYPT_CA (optional, defaults to https://acme-v01.api.letsencrypt.org/directory);
  • LETSENCRYPT_KEYTYPE (optional, defaults to rsa), the key algorithm to use;
  • LETSENCRYPT_KEYSIZE (optional, defaults to 4096), the size in bit for the private keys (if applicable);

Troubleshooting

Route does not get admitted

Please test, whether DNS is set up correctly. In particular the hostname to get a certificate for has to point to the router (or the loadbalancer), also from within the cluster!

Implementation Details

Secrets

The ACME key is stored in letsencrypt-creds.

Containers

The pod consists of three containers, each doing exactly one thing. They share the filesystem /var/www/acme-challenge to store the challenges.

  • Watcher Container, watcher, watches routes and either generates a new certificate or set the already generated certificate.

  • Cron container, cron, periodically checks whether the certificates need to be regenerated. When Kubernetes cron jobs are implemented, this will move outside the pod.

  • Webserver Container, nginx, serves .well-known/acme-challenge when asking to sign the certificate. Uses ibotty/s2i-nginx on dockerhub.

Installing Openshift-Letsencrypt

Template

Create the template as usual.

> oc create -f template.yaml

Deploy openshift-letsencrypt

Instanciate the template.

> oc new-app --template=letsencrypt -p [email protected]

Service Account

The "letsencrypt" service account needs to be able to manage its secrets and manage routes.

> oc policy add-role-to-user edit -z letsencrypt

Let's encrypt credentials

Register an account key

You can skip that section, if you already use letsencrypt and already have an account key.

Get dehydrated and run the following commands.

> echo [email protected] > my_config
> /path/to/dehydrated -f config --register --accept-terms

This will generate a key in ./accounts/*/account_key.pem and info about it in ./accounts/*/registration_info.json.

Create the account key secret

Given an account-key, create a secret as follows.

> oc create secret generic letsencrypt-creds \
     --from-file=account-key=/path/to/account-key.pem \
     --from-file=registration-info=./accounts/*/registration_info.json

The registration info is not strictly necessary.

Notes

HPKP

It is necessary to pin at least one key to use for disaster recovery, outside the cluster!

Maybe pre-generate n keys and pin all of them. On key rollover, delete the previous key, use the oldest of the remaining keys to sign the certificate, generate a new key and pin the new keys. That way, the pin can stay valid for (n-1)* lifetime of a key. That is, if no key gets compromised!