Free Let's Encrypt certificate without opening any ports

tutorial.md

With this tutorial you will get a valid SSL 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, ...) or other self hosted service. Since it only uses acme.sh which is a shell script it should work on everything that runs linux.

The tutorial was written for and tested with Duck DNS and deSEC, but you can (in theory, because I did sadly encounter a few bugs/incompatibilities here and there) use every of the 150+ DNS provider supported by acme.sh (there is also a second page at the end!). If you want to use a wildcard certificate I would recommend deSEC because Duck DNS currently has a bug/incompatibility with acme.sh.

If you want to use another DNS provider you can skip right to 2. Install acme.sh, but need to change the parameter --dns YOURDNS in all the commands and set all necessary variables yourself according to the acme.sh DNS API wiki.

1. Sign in/up to a DynDNS provider

1. Duck DNS

1. Go to https://www.duckdns.org/ and sign in with one of the providers at the top.

2. After your are successfully logged in, enter the sub domain you want and press add domain. This domain name (including .duckdns.org) needs to be replaced in all commands where you see YOURDOMAIN.

3. Enter either

   1. the local IP address of your server if your server is not accessible from the internet

   2. 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 choosen sub domain name will be the one that the server/service needs to be addressed when using the certificate, for it to be valid. Since you set the sub domain to the IP address of your server it should be reachable when the sub domain name get's translated by any DNS. Depending on your home router you might need add an exception of the sub domain name to the DNS rebind protection.

4. Keep the website open, because you need it in a later step.

2. deSEC

1. 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.

2. Log into your deSEC account.

3. If you havent't added a domain during signup, click on the + button on the right and enter the subdomain you want and add .dedyn.io after your subdomain so it looks like example.dedyn.io. If the sub domain was added successfull there will be a popup with setup instructions which you will not need and can be closed. This domain name needs to be replaced in all commands where you see YOURDOMAIN.

4. Optionally add a DNS record: Click onto your sub domain 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:

   1. the local IP address of your server if your server is not accessible from the internet

   2. 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 choosen sub domain name will be the one that the server/service needs to be addressed when using the certificate, for it to be valid. Since you set the sub domain to the IP address of your server it should be reachable when the sub domain name get's translated by any DNS. Depending on your home router you might need add an exception of the sub domain name to the DNS rebind protection.

5. At 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 and is only for the convenience of knowing what the token is used for) and press save.

   Now there will be a green bar at in the popup saying

   Your new token's secret value is: aaaabbbbccccddddeeeeffffgggg
   It is only displayed once.
   

   Copy the secret token value into an editor because you need it later. But don't worry, you can always come back to this step and generate a new token in case you loose the secret token value.

2. Install acme.sh

1. Install acme.sh:

   curl https://get.acme.sh | sh -s

   If you wish to receive an expiration notification email before your certificates expires you can insert your email address and install acme.sh with the following command:

   curl https://get.acme.sh | sh -s [email protected]

   You can find more information on expiration emails here: https://letsencrypt.org/docs/expiration-emails/

2. Restart the terminal.

3. Configure acme.sh

1. Enable auto update:

   acme.sh --upgrade --auto-upgrade

2. Change the default CA to Let's Encrypt (see explanation in the remarks):

   acme.sh --set-default-ca --server letsencrypt

3. Take the token from the DynDNS provider website and insert it into either one of the following commands between the quotation marks:

   For deSEC:

   export DEDYN_TOKEN="aaaabbbbccccddddeeeeffffgggg"

   For Duck DNS:

   export DuckDNS_Token="aaaaaaaa-bbbb-cccc-dddd-eeeeeeeeeeee"

3. Issue a certificate

In the following commands you need to replace YOURDNS with either dns_duckdns when you chose Duck DNS or dns_desec when you chose deSEC.

Insert your registered sub domain 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:

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 one domain you will need to state when running other acme.sh commands. I would recommend to keep the primary domain the same when adding/removing other sub domains.

4. Install the certificate to a target directory

After the certificate is issued acme.sh needs to copy the certificate to a target directory and can a command after each renewal of the certificate.

The target directory and reload command specific to the primary domain (the domain of the first --domain parameter). So the target directory (or at least filename) must be unique and the reload command must be for this specific certificate.

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

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

Now you 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"

5. Automatic renewal

Certificates are only valid for 90 days. Because of this acme.sh will create a daily cron job running at a random time at night that will:

• renew every certificate after 60 days
• copy the certificate and key files to their destination (as configured in 4. Install the certificate to a target directory)
• run the reload command (as configured in 4. Install the certificate to a target directory)

---

Remarks:

1. How can I add more domain names to my certificate?

   Run the command from 3. Issue a 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 domnain names with the --issue command, it will not copy the new certificate to it's destination or run the --reloadcmd that was set with the --install-cert command. You will either have to do it by yourself or 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).

2. Show configuration of acme.sh:

   acme.sh --info

3. Show configuration of a certificate:

   acme.sh --info -d YOURDOMAIN

4. List all certificates issued with acme.sh:

   acme.sh --list

5. Remove a certificate from acme.sh:

   acme.sh --remove -d YOURDOMAIN

6. Why change the default CA to Let's Encrypt?

   I did encounter bugs with the default CA of acme.sh (ZeroSSL) which where gone once I switched to Let's Encrypt.

7. 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 there sadly is a bug or incompatibility (depending on who you want to blame) and acme.sh runs into an infitie loop. It works if you only use the wildcard domain as the primary domain name. But with only a wildcard in the certificate I don't know if this certificate will play nice with all devices, browsers and applications.

   If you want to use acme.sh and create a wildcard certificate desec.io works as a DNS provider.

8. 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/

9. Uninstall acme.sh:

   acme.sh --uninstall

   and delete the .acme.sh directory in your home directory.

Thank you so much for taking the time to put this guide together. I've wanted to setup a reverse proxy with SSL certs in a LAN-only environment, but recommendations are all over the place. This was straightforward for a beginner to setup without the complication of running your own CA or needing to buy a domain name with DNS API support.

I used deSEC with Nginx Proxy Manager wildcard certs instead of acme.sh, but instructions worked pretty similarly in the Nginx Proxy Manager Web UI.