kube-lego automatically requests certificates for Kubernetes Ingress resources from Let's Encrypt

• Recognizes the need of a new certificate for this cases:
  • No certificate existing
  • Existing certificate is not containing all domain names
  • Existing certificate is expired or near to its expiry date (cf. option LEGO_MINIMUM_VALIDITY)
  • Existing certificate is unparseable, invalid or not matching the secret key
• Creates a user account (incl. private key) for Let's Encrypt and stores it in Kubernetes secrets (secret name is configurable via LEGO_SECRET_NAME)
• Obtains the missing certificates from Let's Encrypt and authorizes the request with the HTTP-01 challenge
• Makes sure that the specific Kubernetes objects (Services, Ingress) contain the rights configuration for the HTTP-01 challenge to succeed
• Official Kubernetes Helm chart for simplistic deployment.

• Kubernetes 1.2+
• Compatible ingress controller (nginx or GCE see here)
• Non-production use case 😆

• GCE
• nginx controller

The default value of LEGO_URL is the Let's Encrypt staging environment. If you want to get "real" certificates you have to configure their production env.

If you change the LEGO_URL, it is required that you delete the existing secret kube-lego-account and all certificates you want to request from the new URL.

As soon as the kube-lego daemon is running, it will create a user account with LetsEncrypt, make a service resource, and look for ingress resources that have this annotation:

metadata:
  annotations:
    kubernetes.io/tls-acme: "true"

Every ingress resource that has this annotation will be monitored by kube-lego (cluster-wide in all namespaces). The only part that is watched is the list spec.tls. Every element will get its own certificate through Let's Encrypt.

Let's take a look at this ingress resource:

spec:
  tls:
  - secretName: mysql-tls
    hosts:
    - phpmyadmin.example.com
    - mysql.example.com
  - secretName: postgres-tls
    hosts:
    - postgres.example.com

On finding the above resource, the following happens:

1. An ingress resource is created coordinating where to send acme challenges for the said domains.

2. kube-lego will then perform its own check for i.e. http://mysql.example.com/.well-known/acme-challenge/_selftest to ensure all is well before reaching out to letsencrypt.

3. kube-lego will obtain two certificates (one with phpmyadmin.example.com and mysql.example.com, the other with postgres.example.com).

Please note:

• The secretName statements have to be unique per namespace
• secretName is required (even if no secret exists with that name, as it will be created by kube-lego)
• Setups which utilize 1:1 NAT need to ensure internal resources can reach gateway controlled public addresses.
• Additionally, your domain must point to your externally available Load Balancer (either directly or via 1:1 NAT)

• available through image gcr.io/google_containers/nginx-ingress-controller
• fully supports kube-lego from version 0.8 onwards

• you don't have to maintain the ingress controller yourself, you pay GCE to do that for you
• every ingress resource creates one GCE load balancer
• all service that you want to expose, have to be Type=NodePort

• Nginx Ingress Controller
• GCE Load Balancers

When interacting with kube-lego, its a good idea to run with LEGO_LOG_LEVEL=debug for more verbose details. Additionally, be aware of the automatically created resources (see environment variables) when cleaning up or testing.

Possible resources for help:

• The official channel #kube-lego on kubernetes.slack.com

There is also a good chance to get some support on non-official support channels for kube-lego, but be aware that these are rather general kubernetes discussion channels.

• #coreos on freenode
• Slack channels like #kubernetes-users or #kubernetes-novice on kubernetes.slack.com
• If you absolutely just can't figure out your problem, file an issue.

To enable the pprof tool run kube-lego with environment LEGO_LOG_LEVEL=debug.

Capture 20 seconds of the execution trace:

$ wget http://localhost:8080/debug/pprof/trace?seconds=20 -O kube-lego.trace

You can inspect the trace sample running

$ go tool trace kube-lego.trace

• Christian Simon for Jetstack Ltd
• PR contributors