Evaggelos Balaskas - System Engineer

Managing SSL/TLS certificates for your domains can be effortless with the right tools. In this post, I’ll walk you through using acme.sh and LuaDNS to issue wildcard certificates for your domain.

Let’s dive into the step-by-step process of setting up DNS-based validation using the LuaDNS API.

📋 Prerequisites

• You own a domain and manage its DNS records with LuaDNS.
• You have acme.sh installed.
• You’ve generated an API token from your LuaDNS account.

🧼 Step 1: Clean Up Old Certificates (Optional)

If you’ve previously issued a certificate for your domain and want to start fresh, you can remove it with:

acme.sh --remove -d ebalaskas.gr

This will remove the certificate metadata from acme.sh, but not delete the actual files. You’ll find those under:

/root/.acme.sh/ebalaskas.gr

Feel free to delete them manually if needed.

🔑 Step 2: Set Your LuaDNS API Credentials

Log into your LuaDNS account and generate your API token from:

👉 https://api.luadns.com/settings

Then export your credentials in your shell session:

export LUA_Email="youremail@example.com"
export LUA_Key="your_luadns_api_key"

Example:

export LUA_Email="api.luadns@example.org"
export LUA_Key="a86ee24d7087ad83dc51dadbd35b31e4"

📜 Step 3: Issue the Wildcard Certificate

Now you can issue a certificate using DNS-01 validation via the LuaDNS API:

acme.sh --issue --dns dns_lua -d ebalaskas.gr -d *.ebalaskas.gr --server letsencrypt

This command will:

• Use Let’s Encrypt as the Certificate Authority.
• Add two DNS TXT records (_acme-challenge.ebalaskas.gr) using LuaDNS API.
• Perform domain validation.
• Remove the TXT records after verification.
• Issue and store the certificate.

Sample output will include steps like:

Adding txt value: ... for domain: _acme-challenge.ebalaskas.gr
The txt record is added: Success.
Verifying: ebalaskas.gr
Verifying: *.ebalaskas.gr
Success
Removing DNS records.
Cert success.

You’ll find the certificate and key files in:

/root/.acme.sh/ebalaskas.gr/

File paths:

• Certificate: ebalaskas.gr.cer
• Private Key: ebalaskas.gr.key
• CA Chain: ca.cer
• Full Chain: fullchain.cer

✅ Step 4: Verify the Certificate

You can check your currently managed certificates with:

acme.sh --cron --list

Output should look like:

Main_Domain        KeyLength  SAN_Domains            CA                    Created                       Renew
ebalaskas.gr       ""         *.ebalaskas.gr         LetsEncrypt.org       Thu Apr 17 14:39:24 UTC 2025  Mon Jun 16 14:39:24 UTC 2025

🎉 Done!

That’s it! You’ve successfully issued and installed a wildcard SSL certificate using acme.sh with LuaDNS.

You can now automate renewals via cron, and integrate the certificate into your web server or load balancer.

🔁 Bonus Tip: Enable Auto-Renewal

acme.sh is cron-friendly. Just make sure your environment has access to the LUA_Key and LUA_Email variables, either by exporting them in a script or storing them in a config file.

Let me know if you’d like this blog post exported or published to a static site generator (like Hugo, Jekyll, or Hexo) or posted somewhere specific!

That’s it !

This blog post was made with chatgpt

ACME v2 and Wildcard Certificate Support is Live

We have some good news, letsencrypt support wildcard certificates! For more details click here.

The key phrase on the post is this:

Certbot has ACME v2 support since Version 0.22.0.

unfortunately -at this momment- using certbot on a centos6 is not so trivial, so here is an alternative approach using:

• acme.sh
• PowerDNS

acme.sh

acme.sh is a pure Unix shell script implementing ACME client protocol.

# curl -LO https://github.com/Neilpang/acme.sh/archive/2.7.7.tar.gz
# tar xf 2.7.7.tar.gz

# cd acme.sh-2.7.7/

[acme.sh-2.7.7]# ./acme.sh --version
https://github.com/Neilpang/acme.sh
v2.7.7

PowerDNS

I have my own Authoritative Na,e Server based on powerdns software.

PowerDNS has an API for direct control, also a built-in web server for statistics.

To enable these features make the appropriate changes to pdns.conf

api=yes
api-key=0123456789ABCDEF
webserver-port=8081

and restart your pdns service.

To read more about these capabilities, click here: Built-in Webserver and HTTP API

testing the API:

# curl -s -H 'X-API-Key: 0123456789ABCDEF' http://127.0.0.1:8081/api/v1/servers/localhost | jq .

{
  "zones_url": "/api/v1/servers/localhost/zones{/zone}",
  "version": "4.1.1",
  "url": "/api/v1/servers/localhost",
  "type": "Server",
  "id": "localhost",
  "daemon_type": "authoritative",
  "config_url": "/api/v1/servers/localhost/config{/config_setting}"
}

Enviroment

export PDNS_Url="http://127.0.0.1:8081"
export PDNS_ServerId="localhost"
export PDNS_Token="0123456789ABCDEF"
export PDNS_Ttl=60

Prepare Destination

I want to save the certificates under /etc/letsencrypt directory.
By default, acme.sh will save certificate files under /root/.acme.sh/balaskas.gr/ path.

I use selinux and I want to save them under /etc and on similar directory as before, so:

# mkdir -pv /etc/letsencrypt/acme.sh/balaskas.gr/

Create WildCard Certificate

Run:

# ./acme.sh
  --issue
  --dns dns_pdns
  --dnssleep 30
  -f
  -d balaskas.gr
  -d *.balaskas.gr
  --cert-file /etc/letsencrypt/acme.sh/balaskas.gr/cert.pem
  --key-file  /etc/letsencrypt/acme.sh/balaskas.gr/privkey.pem
  --ca-file   /etc/letsencrypt/acme.sh/balaskas.gr/ca.pem
  --fullchain-file /etc/letsencrypt/acme.sh/balaskas.gr/fullchain.pem

HSTS

Using HTTP Strict Transport Security means that the browsers probably already know that you are using a single certificate for your domains. So, you need to add every domain in your wildcard certificate.

Web Server

Change your VirtualHost

from something like this:

SSLCertificateFile /etc/letsencrypt/live/balaskas.gr/cert.pem
SSLCertificateKeyFile /etc/letsencrypt/live/balaskas.gr/privkey.pem
Include /etc/letsencrypt/options-ssl-apache.conf
SSLCertificateChainFile /etc/letsencrypt/live/balaskas.gr/chain.pem

to something like this:

SSLCertificateFile    /etc/letsencrypt/acme.sh/balaskas.gr/cert.pem
SSLCertificateKeyFile /etc/letsencrypt/acme.sh/balaskas.gr/privkey.pem
Include /etc/letsencrypt/options-ssl-apache.conf
SSLCertificateChainFile /etc/letsencrypt/acme.sh/balaskas.gr/fullchain.pem

and restart your web server.

Browser

Quallys

Qualys SSL Server Test)

Validation

X509v3 Subject Alternative Name

# openssl x509 -text -in /etc/letsencrypt/acme.sh/balaskas.gr/cert.pem | egrep balaskas

        Subject: CN=balaskas.gr
                DNS:*.balaskas.gr, DNS:balaskas.gr