Summary of Changes

The mcrypt extension has been abandonware for over a decade now, and was also fairly complex to use. It has therefore been deprecated in favour of OpenSSL, where it will be removed from the core and into PECL in PHP 7.2. It was deprecated in PHP 7.1

There is one use in Joomla 4 that can still be triggered, and that is to decrypt the configuration and OTEP values from the database, if previously encrypted with mcrypt.

If this case is triggered then Joomla decrypts using mcrypt and re-encrypts using openssl using the AES Class.

THIS CODE HAS NEVER WORKED ANYWAY SINCE BEING ADDED due to a typo in the constructor arguments when setting up the $mcrypt instance. The number of params provided meant that the mcrypt' value last in the params list was never used, meaning that $mcrypt` was always an instance using the openssl adapter.

As Joomla 4.0.0 is about to be released (cough, maybe some time, but the RC will be) we need to slip these deprecated tags in else it will be another decade before we can remove this code.

@wilsonge urgent review please :) :) :)

Testing Instructions

Code review.

// cc @nikosdion @joomdonation
// replacement for #33954