Wildcard LetsEncrypt certificates with Traefik and Cloudflare
Table of Contents
Wildcard certificates make it easy to secure lots of subdomains under a single
domain. For example, you can secure
with a single certificate for
*.example.com. Fortunately, LetsEncrypt allows
you to get wildcard certificates via a DNS ownership check (often called a
Fortunately, Traefik can request a certificate from LetsEncrypt automatically and complete the challenge for you. It can publish DNS records to multiple providers, but my favorite is Cloudflare. They will host your DNS zones and records for free. They also have a robust API for managing DNS records (also free).
In this post, we will cover the basics of getting TLS working with Traefik. We can add a wildcard certificate on top and then re-use that same certificate for other containers running behind Traefik.
Basic setup #
First, we need a running instance of Traefik. The Traefik documentation explains this entire process in detail and I highly recommend reading the basics on configuration discovery, routers, and TLS settings.
We will use docker-compose to make this easier to manage. If you’re on Fedora, install docker-compose:
dnf install docker-compose
Now we need a
--- version: "3" services: traefik: image: traefik:latest container_name: traefik restart: unless-stopped command: # Tell Traefik to discover containers using the Docker API - --providers.docker=true # Enable the Trafik dashboard - --api.dashboard=true # Set up LetsEncrypt - --certificatesresolvers.letsencrypt.acme.dnschallenge=true - --certificatesresolvers.letsencrypt.acme.dnschallenge.provider=cloudflare - --certificatesresolvers.letsencrypt.acme.email=EMAIL_ADDRESS - --certificatesresolvers.letsencrypt.acme.storage=/letsencrypt/acme.json # Set up an insecure listener that redirects all traffic to TLS - --entrypoints.web.address=:80 - --entrypoints.web.http.redirections.entrypoint.to=websecure - --entrypoints.web.http.redirections.entrypoint.scheme=https - --entrypoints.websecure.address=:443 # Set up the TLS configuration for our websecure listener - --entrypoints.websecure.http.tls=true - --entrypoints.websecure.http.tls.certResolver=letsencrypt - --entrypoints.websecure.http.tls.domains.main=home.example.com - --entrypoints.websecure.http.tls.domains.sans=*.home.example.com environment: - CLOUDFLARE_EMAIL=CLOUDFLARE_ACCOUNT_EMAIL_ADDRESS - CLOUDFLARE_DNS_API_TOKEN=CLOUDFLARE_TOKEN_GOES_HERE ports: - 80:80 - 443:443 volumes: - /var/run/docker.sock:/var/run/docker.sock:ro - certs:/letsencrypt labels: - "traefik.enable=true" - 'traefik.http.routers.traefik.rule=Host(`home.example.com`)' - "traefik.http.routers.traefik.entrypoints=websecure" - "traefik.http.routers.traefik.tls.certresolver=letsencrypt" - "[email protected]" - 'traefik.http.routers.traefik.middlewares=strip' - 'traefik.http.middlewares.strip.stripprefix.prefixes=/traefik'
In this example, we tell Traefik about our desired setup in the
section, including our listeners. Our insecure listener on port 80 redirects to
secure connections on port 443 and we tell Traefik that we plan to use
LetsEncrypt to get the certificates.
We provide the username and Cloudflare API key in the
Follow Cloudflare’s guides for managing API tokens and keys carefully to
generate a token.
labels section sets up a rule where traffic destined for
home.example.com goes to the Traefik dashboard. this is helpful in case you
make mistakes or you can’t figure out why something is working. You can go to
the dashboard to show all of the existing services, listeners, and other
☝🏻 Before applying this docker-compose file, change a few things:
- Set your LetsEncrypt email address in the line with
- Set your Cloudflare account email address for the
- Set your Cloudflare DNS API token for the
- Change the
example.comto match your domain name
docker-compose up -d and then
docker-compose logs -f traefik to see if
Traefik came up successfully with certificates. If you run into any problems,
double check that your Cloudflare email and token are accurate. Also verify that
your Cloudflare token has the correct permissions to adjust the dns zone.
Adding a container #
At this point, we can add another container and it can use the same TLS certificate we requested from LetsEncrypt already!
The librespeed project provides a self-hosted network speed test that you can run on any network. It also runs perfectly inside a container. The linuxserver.io librespeed container is well maintained and easy to run.
Add this to your
docker-compose.yml right under the Traefik configuration:
librespeed: image: ghcr.io/linuxserver/librespeed container_name: librespeed restart: unless-stopped ports: - 80 labels: - "traefik.enable=true" - "traefik.http.routers.librespeed.rule=Host(`librespeed.home.example.com`)" - "traefik.http.routers.librespeed.entrypoints=websecure" - "traefik.http.routers.librespeed.tls.certresolver=letsencrypt"
labels section. We first enable Traefik so it will route requests to
the container. Then we set a host rule so that traffic for
librespeed.home.example.com comes to this container. We only listen for TLS
traffic (remember our redirect for insecure traffic earlier).
Finally, we tell Traefik to use the same
certresolver as before. Traefik is
smart enough to know that
*.home.example.com covers the
librespeed.home.example.com subdomain just fine.
docker-compose up -d once more and now librespeed has a secure connection
using the original wildcard certificate.
LetsEncrypt certificates are valid for only 90 days. That’s why automation plays such an important role in handling renewals. You certainly don’t want to set calendar reminders to log into your server and run a script every 90 days. 😱
Traefik automatically knows when the expiration date approaches. When the certificate has less than 30 days left until the expiration date, Traefik automatically renews the certificate.
💣 Be careful with your DNS zone and with your DNS API keys! If you accidentally delete the API key or make big changes to your DNS zone, there’s a chance that Traefik may not be able to renew the certificate.
Photo credit: Veron Wessels on Unsplash