Redmine

Hi folks!

So far, I have Redmine 2.3.3 installed in my corporate network and we are tracking our projects in it.
We have LDAP (MS AD) but we are not using it and our engineering team members don't have AD accounts. AD is for not-engineering departments (who works with our stocks and money).

Anyway, we have several web-services hosted with Redmine on same server and for today every one of us have different logins for different services (it is legacy). It is not good. These services written in PERL and some of them in PHP.
What am I thinking about is to find some easy way to authenticate users on our services using Redmine IDs.
I know that the easiest way is to post login/password into Redmine /login form and check an answer, but this way is not so cool as I want.

Does anyone have any idea what could be done inside Redmine (our outside?) to do this better way?