How to setup Let's Encrypt with the Ubiquiti Edge Router Lite

Disclaimer:

You will be modifying some of the inner workings of your edgerouter. This could break your router. I believe the steps I outline here are generally safe, but you will be issuing commands as root and can do damage easily. Be careful.

For starters, you'll need:

• SSH Access to your Edgerouter
• acme_tiny.py, you can find it here: https://github.com/diafygi/acme-tiny
• A FQDN for your edge router that is accessable externally
• Port 80 open to your edge router externally

Please note you are opening your edgerouter to the outside world. Please use common sense and use a strong password and common security best practices.

Start by connecting to your edgerouter via SSH and issue the command

sudo -i

Let's setup a base directory to work with

mkdir /opt/letsencrypt
cd /opt/letsencrypt
curl -O https://github.com/raw/diafygi/acme-tiny/master/acme_tiny.py

Now we're going to do some initial setup for Let's Encrypt

openssl genrsa 4096 > account.key
openssl genrsa 4096 > domain.key

Next, replace "yoursite.com" with your edge routers FQDN

openssl req -new -sha256 -key domain.key -subj "/CN=**yoursite.com**" > domain.csr

Now that we've got the basics ready, this is where we will tweak the ubiquiti stock setup to allow us to use Let's Encrypt.

mkdir -p /var/www/htdocs/.well-known/acme-challenge/

We need to edit the Ubiquiti lighttpd configuration. You can either edit your existing configuration to change:

url.rewrite-once = ( 
        "^(/(lib|media|ws|tests)/.*)" => "$0",
        "^/([^\?]+)(\?(.*))?$" => "/index.php/$1?$3"
) 

$HTTP["scheme"] == "http" { 
    $HTTP["url"] !~ "^/index.php/error/" { 
        $HTTP["host"] =~ "^(.*)$" { 
                url.redirect = ( 
                        "^(.*)$" => "https://%1$1"
                ) 
        } 
    } 
  } 
} 

into

url.rewrite-once = ( 
        "^(/(lib|media|ws|tests|.well-known)/.*)" => "$0",
        "^/([^\?]+)(\?(.*))?$" => "/index.php/$1?$3"
) 

$HTTP["scheme"] == "http" { 
  $HTTP["url"] !~ "^/.well-known/acme-challenge/*" { 
    $HTTP["url"] !~ "^/index.php/error/" { 
        $HTTP["host"] =~ "^(.*)$" { 
          url.redirect = ( 
            "^(.*)$" => "https://%1$1"
          ) 
        } 
    } 
  } 
} 

Now we've got the foundation for our Let's Encrypt setup. Next we restart lighttpd to pick up the new configuration file and then we'll get our first certificate.

Restarting Lighttpd

ps -e | grep lighttpd | awk '{print $1;}' | xargs kill
/usr/sbin/lighttpd -f /etc/lighttpd/lighttpd.conf

Generating our first certificate

python /opt/letsencrypt/acme_tiny.py \
  --account-key /opt/letsencrypt/account.key \
  --csr /opt/letsencrypt/domain.csr \
  --acme-dir /var/www/htdocs/.well-known/acme-challenge/ \
  > /opt/letsencrypt/signed.crt

Now, if that worked without any issue, we can setup our cron script and run it for the first time to put our new certificate in place. Just place a copy of letsrenew.sh into your /etc/cron.monthly directory and chmod 755 it.

If everything went well you should have a shiny green lock icon next time you visit your Edgerouter's GUI.