kube-lego

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

Screencast

Features

• 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

Requirements

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

Usage

run kube-lego

• deployment for kube-lego
  • don't forget to configure
    • LEGO_EMAIL with your mail address
    • LEGO_POD_IP with the pod IP address using the downward API
  • 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.

how kube-lego works

As soon as the kube-lego daemon is running, it will 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

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)

##Ingress controllers

Nginx Ingress Controller

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

GCE Loadbalancers

• 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

Environment variables

Name	Required	Default	Description
LEGO_EMAIL	y	-	E-Mail address for the ACME account, used to recover from lost secrets
LEGO_POD_IP	y	-	Pod IP address (use the downward API)
LEGO_NAMESPACE	n	default	Namespace where kube-lego is running in
LEGO_URL	n	https://acme-staging.api.letsencrypt.org/directory	URL for the ACME server. To get "real" certificates set to the production API of Let's Encrypt: https://acme-v01.api.letsencrypt.org/directory
LEGO_SECRET_NAME	n	kube-lego-account	Name of the secret in the same namespace that contains ACME account secret
LEGO_SERVICE_NAME_NGINX	n	kube-lego-nginx	Service name for NGINX ingress
LEGO_SERVICE_NAME_GCE	n	kube-lego-gce	Service name for GCE ingress
LEGO_INGRESS_NAME_NGINX	n	kube-lego-nginx	Ingress name which contains the routing for HTTP verification for nginx ingress
LEGO_PORT	n	8080	Port where this daemon is listening for verifcation calls (HTTP method)
LEGO_CHECK_INTERVAL	n	8h	Interval for periodically certificate checks (to find expired certs)
LEGO_MINIMUM_VALIDITY	n	720h (30 days)	Request a renewal when the remaining certificate validitiy falls below that value
LEGO_DEFAULT_INGRESS_CLASS	n	nginx	Default ingress class for resources without specification
LEGO_KUBE_API_URL	n	http://127.0.0.1:8080	API server URL
LEGO_LOG_LEVEL	n	info	Set log level (`debug

Full deployment examples

• Nginx Ingress Controller
• GCE Load Balancers

Authors

Christian Simon for Jetstack Ltd