If you like things a bit niche you might be running Moodle on Linux connecting to a MS SQL server running on Windows. This all works well with the MS SQL Server drivers for PHP.
The drivers support encrypted SQL connections but Moodle doesn’t provide an option to enable this. There is an issue logged on the Moodle tracker but it’s been sat there for ages and to be honest there seems a lot of politics around submitting patches to Moodle. If you just want a quick and dirty way of enabling this yourself you can use the wonderful patch I’ve created below against lib/dml/sqlsrv_native_moodle_database.php. Hold on to your hats though.
224a225 > 'Encrypt' => !empty($this->dboptions['encrypt']),
Yep, a beautiful one line change. This applies cleanly against 3.9 but I imagine it will work in most recent versions as this file hasn’t changed for a a while.
Once the change has been made you can modify your config.php. Just add encrypt => 1 to your dboptions array.
$CFG->dboptions = array ( 'dbpersist' => 1, 'encrypt' => 1, );
Obviously you need to ensure you have SSL/TLS set up correctly on the SQL side, you have the correct trusted root certs on your linux box and that you’re connecting to the FQDN of your SQL Server that matches the subject of the cert. If you’ve done everything correctly you’ll now be enjoying that sweet, sweet encryption.