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
Official Kubernetes Helm chart for simplistic deployment.

Requirements

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

Usage

run kube-lego

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.

how kube-lego works

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:

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

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_SUPPORTED_INGRESS_CLASS`	n	`nginx,gce`	Specify the supported ingress class
`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 validity 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`, `info`, `warn` or `error`)
`LEGO_KUBE_ANNOTATION`	n	`kubernetes.io/tls-acme`	Set the ingress annotation used by this instance of kube-lego to get certificate for from Let's Encrypt. Allows you to run kube-lego against staging and production LE
`LEGO_WATCH_NAMESPACE`	n	``	Namespace that kube-lego should watch for ingresses and services

Full deployment examples

Troubleshooting

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.

Enable the pprof tool

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

Authors

Christian Simon for Jetstack Ltd
PR contributors

QSonx/kube-lego