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kube-lego

⚠️

kube-lego is no longer maintained. The officially endorsed successor is cert-manager.

If you are a current user of kube-lego, you can find a migration guide here.

⚠️

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

Build Status

Screencast

Kube Lego 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.

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:

  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)

Switching from staging to production

At some point you'll be ready to use LetsEncrypt production API URL. To make the switch in kube-lego, please do the following:

  • Update LEGO_URL to https://acme-v01.api.letsencrypt.org/directory.
  • Delete the existing k8s secret kube-lego-account.
  • Delete other secrets that hold data for certificates you want to replace.
  • Restart 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_SELECTOR n kube-lego Set the service selector to the the kube-lego pod
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_SUPPORTED_INGRESS_PROVIDER n nginx,gce Specify the supported ingress provider
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_DEFAULT_INGRESS_PROVIDER n $LEGO_DEFAULT_INGRESS_CLASS Default ingress provider 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_LOG_TYPE n text Set log type. Only json as custom value supported, everything else defaults to default logrus textFormat
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
LEGO_RSA_KEYSIZE n 2048 Size of the private RSA key
LEGO_EXPONENTIAL_BACKOFF_MAX_ELAPSED_TIME n 5m Max time to wait for each domain authorization attempt
LEGO_EXPONENTIAL_BACKOFF_MAX_INITIAL_INTERVAL n 30s Initial interval to wait for each domain authorization attempt
LEGO_EXPONENTIAL_BACKOFF_MAX_MULTIPLIER n 2.0 Multiplier for every step

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 #cert-manager on kubernetes.slack.com (The old channel was renamed)

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

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