Use LDAP for MySQL authentication?
Solution 1:
Enterprise MySQL (the version you pay Oracle to license) has a PAM module that allows for LDAP authentication: https://dev.mysql.com/doc/refman/5.5/en/pam-pluggable-authentication.html
MariaDB (a binary compatible version of MySQL developed by Monty) has an open source PAM module available for it: http://kb.askmonty.org/en/pam-authentication-plugin/
I do not have hands on experience with either - I present them only as features I have heard of but not tested or used myself.
Solution 2:
You can use the auth_ldap plugin provided by Infoscope Hellas L.P. under GPL.
It can be downloaded from sourceforge here.
(Homepage)
The plugin is still a Beta and works only for UNIX installations.
Solution 3:
A Mysql proxy can enable this for you using roles. More detail can be found here: https://stackoverflow.com/questions/1329963/using-ldap-ad-for-mysql-authenication and here: http://jan.kneschke.de/2009/6/25/mysql-proxy-roles/
Solution 4:
MySQL has a PAM authentication plugin that will let you use any available PAM module to provide authentication services. There is a pam_ldap module that is relatively easy to configure that should allow you to do what you want.
The plugin documentation includes an example using LDAP.
Solution 5:
I have published in my blog, an full example (with source code) of a LDAP Authentication plugin for MySQL.
http://nafiux.com/blog/2012/08/11/mysql-ldap-authentication-plugin/