Getting a Free Domain with a TLS Certificate

🐲

Difficulty: Easy / Basic

With this tutorial, you will get a valid TLS certificate from Let's Encrypt without having to open any incoming ports. You can use the certificate to enable HTTPS with your reverse proxy (Apache, Nginx, Caddy, etc.) or other self-hosted services. Since this only uses acme.sh, which is a shell script, it should work on anything that runs Linux.

The tutorial was written for and tested with Duck DNS and deSEC, but you can use any DNS provider supported by acme.sh. If you want to use a wildcard certificate, I recommend deSEC because Duck DNS has had compatibility issues with acme.sh wildcard certificates.

If you want to use another DNS provider, you can skip right to Install acme.sh. You will need to change the parameter --dns YOURDNS in all the commands below and set the necessary variables yourself according to the acme.sh DNS API wiki.

Select a DynDNS Provider

Duck DNS

Go to https://www.duckdns.org/ and sign in with one of the providers at the top.
After you are successfully logged in, enter the subdomain you want and press add domain. This domain name, including the .duckdns.org part, needs to replace $YOURDOMAIN in all commands.
Enter either:
- The local IP address of your server if your server is not accessible from the internet or the public IP address of your server if your server is accessible from the internet in the current ip field and press update ip.
  
  The chosen subdomain name will be the name you use to access the server or service when using the certificate. Since you set the subdomain to the IP address of your server, it should be reachable when DNS resolves that name. Depending on your home router, you might need to add an exception for the subdomain name to the DNS rebind protection.
Keep the website open, because you need it in a later step.

deSEC

Go to https://desec.io/signup and create a new account. It doesn't matter what you choose for Do you want to set up a domain right away? because you can add a domain afterwards.
Log into your deSEC account.
If you haven't added a domain during signup, click on the + button on the right, enter the subdomain you want, and add .dedyn.io after your subdomain so it looks like example.dedyn.io. If the subdomain was added successfully, there will be a popup with setup instructions, which you will not need and can close. This domain name needs to replace $YOURDOMAIN in all commands.
Optionally add a DNS record. Click on your subdomain name and then the + button on the right. A popup with Create New Record Set will show up. Choose the Record Set Type value A and enter either:
- The local IP address of your server if your server is not accessible from the internet or the public IP address of your server if your server is accessible from the internet in the 'IPv4 address' field and press Save.
  
  The chosen subdomain name will be the name you use to access the server or service when using the certificate. Since you set the subdomain to the IP address of your server, it should be reachable when DNS resolves that name. Depending on your home router, you might need to add an exception for the subdomain name to the DNS rebind protection.
In the top menu, change to TOKEN MANAGEMENT and press the + button on the right. A popup with Generate New Token will show up. Enter a token name of your choosing. The name doesn't matter; it is only for convenience. Press save.

Now there will be a green bar in the popup saying:
```
Your new token's secret value is: aaaabbbbccccddddeeeeffffgggg
It is only displayed once.
```
Copy the secret token value into a text editor because you'll need it later. Don't worry, you can always come back to this step and generate a new token if you lose the secret token value.

Install `acme.sh`

Run the following command on your server to install acme.sh:
```
curl https://get.acme.sh | sh -s
```
If you wish to receive an expiration notification email before your certificate expires, you can insert your email address and install acme.sh with the following command:
```
curl https://get.acme.sh | sh -s email=my@example.com
```
You can find more information on expiration emails here: https://letsencrypt.org/docs/expiration-emails/
Run exec $SHELL. This will pick up anything new that the installation added to your shell environment.

Configure `acme.sh`

First enable auto updates. This allows the script to keep itself updated:
```
acme.sh --upgrade --auto-upgrade
```
Next, change the default CA (Certificate Authority) to Let's Encrypt (see the explanation in the notes):
```
acme.sh --set-default-ca --server letsencrypt
```
Take the token from your DynDNS provider and insert it into one of the following commands between the quotation marks:
Duck DNS
```
export DuckDNS_Token="aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee"
```
deSEC
```
export DEDYN_TOKEN="aaaabbbbccccddddeeeeffffgggg"
```

Issuing a TLS Certificate

In the following commands, you need to replace $YOURDNS with either dns_duckdns for Duck DNS or dns_desec if you chose deSEC. Insert your registered subdomain in the following command to issue your first certificate:

acme.sh --issue --dns $YOURDNS --domain $YOURDOMAIN

If you have registered more domains you can add them as alternative names to the certificate by adding more --domain $YOURDOMAIN at the end, for example:

acme.sh --issue --dns $YOURDNS --domain subdomain.example.com --domain subdomain-nextcloud.example.com --domain subdomain-vaultwarden.example.com

The first given --domain of the --issue command will be the primary domain of the certificate and the only domain you will need to state when running other acme.sh commands. I recommend keeping the primary domain the same when adding or removing other subdomains.

Installing the Certificate to a Target Directory

After the certificate is issued, acme.sh needs to copy the certificate to a target directory. The target directory (or at least filename) must be unique. Your reloadcmd command must also be for this specific certificate.

The following command sets the variable CERTIFICATE_DIRECTORY with a directory of your choosing and creates the directory. The variable is just for ease of use in the next command.

CERTIFICATE_DIRECTORY=$HOME/certificates
mkdir -p "$CERTIFICATE_DIRECTORY"

Now tell acme.sh where and under which filenames it should copy the certificate (--cert-file and --fullchain-file) and key (--key-file) files, and which command (--reloadcmd) it should run to restart your reverse proxy or other service.

acme.sh --install-cert --domain $YOURDOMAIN --cert-file "$CERTIFICATE_DIRECTORY/certificate.pem" --fullchain-file "$CERTIFICATE_DIRECTORY/fullchain.pem" --key-file "$CERTIFICATE_DIRECTORY/key.pem" --reloadcmd "sudo service apache2 force-reload"

In the above example, we've set the directory to store the certificate files as a certificates directory within your home directory and to run the command sudo service apache2 force-reload once the certificate has been obtained.

Automatic Renewal

Certificates from Let's Encrypt are only valid for 90 days. Because of this, acme.sh will create a daily cron job that runs at a random time. When the task runs, it will:

Renew every certificate after 60 days.
Copy the certificate and key files to their previously configured destination directory.
Run the reloadcmd command as previously configured.

Notes

How can I add more domain names to my certificate?
Run the command from Issuing a TLS Certificate again with all domain names, old and new, that you want in your certificate. As long as the primary domain stays the same, it is not necessary to install the certificate again.

After changing the domain names with the --issue parameter, acme.sh will not copy the new certificate to its destination or run the --reloadcmd that was set with the --install-cert command. You will either have to do it yourself, run the --install-cert command again with all the same parameters as before, or copy the files manually from the .acme.sh directory in your home directory. If you don't know the parameters from last time, you can look them up in the info about the certificate (see next point).
Show configuration of acme.sh:
```
acme.sh --info
```
Show configuration of a certificate:
```
acme.sh --info -d $YOURDOMAIN
```
List all certificates issued with acme.sh:
```
acme.sh --list
```
Remove a certificate from acme.sh:
```
acme.sh --remove -d YOURDOMAIN
```
Why change the default CA to Let's Encrypt?
I encountered bugs with the default CA of acme.sh (ZeroSSL) which were gone once I switched to Let's Encrypt.
How to create a wildcard certificate:
Add *.YOURSUBDOMAIN.YOURSITEDOMAIN.com as an alternative domain name to your certificate:
```
acme.sh --issue --dns dns_... --domain YOURSUBDOMAIN.YOURSITEDOMAIN.com --domain *.YOURSUBDOMAIN.YOURSITEDOMAIN.com
```
In theory, it works with Duck DNS, but if you add the wildcard as an alternative name, acme.sh may run into a bug or incompatibility. It works if you only use the wildcard domain as the primary domain name. However, with only a wildcard in the certificate, I don't know if this certificate will work well with all devices, browsers, and applications.

If you want to use acme.sh and create a wildcard certificate, deSEC works as a DNS provider.
How to create a staging certificate for testing: Add the --test parameter to the --issue command to create test or staging certificates, which are not valid but are better if you are just testing things. The certificate will stay in the staging environment until you renew it without the --test parameter:
```
acme.sh --renew -d YOURSUBDOMAIN.YOURSITEDOMAIN.com
```
More on that topic here: https://letsencrypt.org/docs/staging-environment/
Uninstall acme.sh:
```
acme.sh --uninstall
```
Then delete the .acme.sh directory in your home directory.