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Wildcard certificates allow you to secure unlimited subdomains with a single SSL certificate, eliminating the need to generate individual certificates for each subdomain. Pangolin uses Traefik’s built-in Let’s Encrypt integration to automatically manage these certificates.
Before setting up wildcard certificates, you must have a domain that you own and control. You must also have access to the DNS records for this domain.
Since Pangolin uses Traefik as a reverse proxy, it has built-in support for Let’s Encrypt certificates. This allows you to easily secure your Pangolin instance and all proxied resources with HTTPS. Let’s Encrypt provides free SSL certificates, which are automatically renewed.
If you used the default settings during installation, your Traefik instance should be set up to use HTTP-01 challenge for certificate generation. This challenge is the easiest to configure and requires that the Traefik instance be accessible from the internet on port 80.
It is highly recommended that you read the official Traefik documentation on ACME and Let’s Encrypt before proceeding.

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Benefits of Wildcard Certificates

Single Certificate

Secure unlimited subdomains with one certificate, reducing management overhead.

Instant Subdomains

Add new subdomains without waiting for certificate generation (up to a few minutes).

Rate Limit Friendly

Reduce Let’s Encrypt rate limit impact by using fewer certificate requests.

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Examples

  • A wildcard cert *.example.com could protect:
    • api.example.com
    • blog.example.com
    • dashboard.example.com
  • Another wildcard *.subdomain.example.com could protect:
    • api.subdomain.example.com
    • blog.subdomain.example.com
The rate limits for Let’s Encrypt are per domain. Using a wildcard certificate reduces the number of domains you have, which can help you avoid hitting these limits.

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Setting Up Wildcard Certificates

1

Stop the stack

Make sure the stack is not running before making configuration changes.
2

Update Traefik configuration

Update the Traefik configuration to use the DNS-01 challenge instead of the HTTP-01 challenge. This tells Traefik to use your DNS provider to create the DNS records needed for the challenge.
3

Configure Pangolin

Set the prefer_wildcard_cert flag to true in the Pangolin configuration file for your domain. This is also configurable in the Pangolin dashboard (once restarted).
config.yml
  domains:
    domain1:
        base_domain: "example.com"
        prefer_wildcard_cert: true
This setting will try to encourage Traefik to request one wildcard certificate for each level of the domain used by your existing resources.Example: If you have two resources blog.example.com and blog.subdomain.example.com, Traefik should try to request a wildcard certificate for *.example.com and *.subdomain.example.com automatically for you.

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Traefik Configuration

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Default Config for HTTP-01 Challenge

This is the default config generated by the installer. This is shown here for reference to compare with the wildcard config below.
Tell Traefik to use the web entrypoint for the HTTP challenge.
traefik_config.yml
certificatesResolvers:
  letsencrypt:
    acme:
      httpChallenge:
        entryPoint: web
      email: admin@example.com
      storage: "/letsencrypt/acme.json"
      caServer: "https://acme-v02.api.letsencrypt.org/directory"
Set the cert resolver to letsencrypt and the entrypoint to websecure in the dynamic config.
dynamic_config.yml
next-router:
  rule: "Host(`pangolin.example.com`) && !PathPrefix(`/api/v1`)"
  service: next-service
  entryPoints:
    - websecure
  tls:
    certResolver: letsencrypt

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Wildcard Config for DNS-01 Challenge

1

1. Configure DNS Challenge

Tell Traefik to use your DNS provider for the DNS challenge. In this example, we are using Cloudflare.
traefik_config.yml
certificatesResolvers:
  letsencrypt:
    acme:
      dnsChallenge:
        provider: "cloudflare" # your DNS provider
        # see https://doc.traefik.io/traefik/https/acme/#providers
      email: "admin@example.com"
      storage: "/letsencrypt/acme.json"
      caServer: "https://acme-v02.api.letsencrypt.org/directory"
2

2. Add Wildcard Domains

Add the domain and wildcard domain to the domains section of the next (front end) router in the dynamic config. This tells Traefik to generate a wildcard certificate for the base domain and all subdomains.
dynamic_config.yml
next-router:
  rule: "Host(`pangolin.example.com`) && !PathPrefix(`/api/v1`)"
  service: next-service
  entryPoints:
    - websecure
  tls:
    certResolver: letsencrypt
    domains:
      - main: "example.com"
        sans:
          - "*.example.com"
3

3. Add Environment Variables

Add the environment variables for your DNS provider to the Traefik service in the docker compose file. This allows Traefik to authenticate with your DNS provider to create the DNS records needed for the challenge.
docker-compose.yml
traefik:
  image: traefik:v3.4.0
  container_name: traefik
  restart: unless-stopped
  network_mode: service:gerbil
  depends_on:
    pangolin:
      condition: service_healthy
  command:
    - --configFile=/etc/traefik/traefik_config.yml
  # Add the environment variables for your DNS provider.
  environment:
    CLOUDFLARE_DNS_API_TOKEN: "your-cloudflare-api-token"
  volumes:
    - ./config/traefik:/etc/traefik:ro
    - ./config/letsencrypt:/letsencrypt
If you’re using Cloudflare, make sure your API token has the permissions Zone/Zone/Read and Zone/DNS/Edit and make sure it applies to all zones.
Traefik supports most DNS providers. A full list of supported providers and configuration instructions (environment variables) can be found in the Lego documentation. Lego (Let’s Encrypt Go) is used by Traefik for DNS challenges.

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Verify it Works

1

Start the stack

Start the stack and watch the logs. You should notice that Traefik is making calls to your DNS provider to create the necessary records to complete the challenge.
2

Check logs

For debugging purposes, you may find it useful to set the log level of Traefik to debug in the traefik_config.yml file.
3

Test new resource

After Traefik is done waiting for the cert to verify, try to create a new resource with an unused subdomain. Traefik should not try to generate a new certificate, but instead use the wildcard certificate. The domain should also be secured immediately instead of waiting for a new certificate to be generated.
4

Verify certificate

You can also check the volume (in the example above at config/letsencrypt/) for the correct certificates. In the acme.json file you should see something similar to the following. Note the *. in the domain.
{
  "Certificates": [
    {
      "domain": {
        "main": "example.com",
        "sans": [
          "*.example.com"
        ]
      },
      "certificate": "...",
      "key": "...",
      "Store": "default"
    }
  ]
}

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Troubleshooting

Problem: Wildcard certificate not being created.Solutions:
  • Verify DNS provider credentials are correct
  • Check that API token has proper permissions
  • Ensure domain ownership and DNS access
  • Review Traefik logs for specific error messages
Problem: DNS-01 challenge not completing.Solutions:
  • Verify DNS provider is supported by Traefik
  • Check API token permissions and scope
  • Ensure DNS propagation has completed
  • Review provider-specific configuration
  • If your DNS provider has a firewall in place, ensure it allows incoming DNS traffic (typically UDP on port 53). Adding an ingress rule to permit such traffic may help resolve the issue, especially if the firewall is stateless.
Problem: Traefik using old HTTP-01 certificates.Solution: Delete the acme.json file to force new certificate generation.