Using wildcard certificates in Traefik v2 on Docker Swarm - docker

Question

I am using the following Docker Compose file to deploy Traefik on a swarm cluster.
version: "3.7"
services:
traefik:
image: traefik:v2.1
command:
- "--api.dashboard=true"
- "--accesslog=true"
- "--log.level=INFO"
- "--providers.docker.endpoint=unix:///var/run/docker.sock"
- "--providers.docker.swarmMode=true"
- "--providers.docker.exposedbydefault=false"
- "--providers.docker.network=traefik-public"
- "--providers.file.watch=true"
- "--providers.file.filename=/file_provider.yml"
- "--entrypoints.web.address=:80"
- "--entrypoints.websecure.address=:443"
- "--certificatesresolvers.letsencrypt.acme.dnsChallenge.provider=cloudflare"
- "--certificatesresolvers.letsencrypt.acme.dnsChallenge.delayBeforeCheck=15"
- "--certificatesresolvers.letsencrypt.acme.dnsChallenge.resolvers=1.1.1.1:53,1.0.0.1:53"
- "--certificatesresolvers.letsencrypt.acme.email=user#domain.tld"
- "--certificatesresolvers.letsencrypt.acme.storage=/letsencrypt/acme.json"
ports:
- 80:80
- 443:443
volumes:
- traefik-certificates:/letsencrypt
- /var/run/docker.sock:/var/run/docker.sock
networks:
- traefik-public
environment:
- "CF_API_EMAIL=user#domain.tld"
- "CF_API_KEY=api-key"
deploy:
placement:
constraints:
- node.role == manager
labels:
- "traefik.enable=true"
- "traefik.docker.lbswarm=true"
- "traefik.http.routers.http-catchall.rule=hostregexp(`{host:.+}`)"
- "traefik.http.routers.http-catchall.entrypoints=web"
- "traefik.http.routers.http-catchall.middlewares=redirect-to-https#docker"
- "traefik.http.middlewares.redirect-to-https.redirectscheme.scheme=https"
- "traefik.http.routers.api.tls.certresolver=letsencrypt"
- "traefik.http.routers.api.tls.domains[0].main=*.domain.tld"
- "traefik.http.routers.api.tls.domains[0].sans=domain.tld"
- "traefik.http.routers.api.rule=Host(`management.domain.tld`) && (PathPrefix(`/api`) || PathPrefix(`/dashboard`))"
- "traefik.http.routers.api.service=api#internal"
- "traefik.http.services.api.loadbalancer.server.port=8080"
configs:
- file_provider.yml
volumes:
traefik-certificates:
configs:
file_provider.yml:
file: /home/access/docker/traefik-provider.yml
networks:
traefik-public:
external: true
At the moment, I have hit the rate limit on management.domain.tld and I instead want to use a wildcard certificate so there is less likelihood that I will run into a rate limit again. I have Traefik configured to generate the wildcard certificate which works, but there is still a rate-limiting error on management.domain.tld in the logs. Also, when I go to management.domain.tld in the browser, I get an invalid SSL/TLS error. How do I get Traefik to use the wildcard certificate instead of issuing a new certificate for every host rule?

Answer 1

Looks like you have done everything right. But there is a slight mistake in the config.
main is the Subject field for the certificate. Meaning the domain/sub-domain the certificate is being issued to.
sans is the Subject Alternate Names field for the certificate. Meaning alternative domain/sub-domain that the certificate is also valid for.
So, Instead of using:
version: "3.7"
services:
traefik:
image: traefik:v2.1
...
labels:
- "traefik.http.routers.api.tls.domains[0].main=*.domain.tld"
- "traefik.http.routers.api.tls.domains[0].sans=domain.tld"
...
You should use:
version: "3.7"
services:
traefik:
image: traefik:v2.1
...
labels:
- "traefik.http.routers.api.tls.domains[0].main=domain.tld"
- "traefik.http.routers.api.tls.domains[0].sans=*.domain.tld"
...