Does NADI work on WP Engine?
Yes. In case of WP Engine NADI does work without any further server side configuration only with unencrypted LDAP traffic. Because of obvious reasons we don't recommend this. To secure the communication, please do the following:
Create the file /ldaprc in your root (/) and /wp-admin directory. WP Engine loads the ldaprc not from the root directory of your webspace but from the directory where the PHP file has been initially loaded. This is / for index.php and /wp-admin for the administration backend.
Copy your domain controller's PEM file into / and /wp-admin so you have /dc.pem and /wp-admin/dc.pem
Paste the following content into both ldaprc files
TLS_REQCERT never TLS_CACERT dc.pem
If the connection fails due to network problems, you have to get in touch with WP Engine's staff to unblock external LDAP traffic.