Yea, the logic I am looking for is:

If user authenticates with @domain.com, passthrough/redirect authentication on to LDAP backend, WITHOUT looking for a local entry in the OpenLDAP database.

This network doesn't have the resources to maintain another user database, even if it via some automated sync process... was just hoping to implement a "dumb" reverse proxy for LDAP in order to prevent storing usernames/passwords in an Internet facing DMZ (or in the case of using a Windows LDAP server, putting a DC member in the DMZ).

> Date: Tue, 14 Oct 2014 17:18:01 -0700
> Subject: Re: OpenLDAP as proxy to Active Directory backend
> From: bruce.carleton@dena.com
> To: jeflebo@outlook.com
> CC: openldap-technical@openldap.org
>
> That's right, you have to create LDAP entries for the passthrough
> authentication. I guess you could create some kind of sync service
> between AD and the LDAP proxy, but it might be kind of hairy to get it
> working properly. Others might have better suggestions.
>
> On Tue, Oct 14, 2014 at 5:11 PM, Jeff Lebo <jeflebo@outlook.com> wrote:
> > Bruce,
> >
> > My SASL authentication is working...
> >
> > I am still confused on how to setup OpenLDAP to pass ALL attempts through to
> > SASL. The only method I've found is to create users in a local OpenLDAP
> > database and set the userPassword attribute to {SASL}username@REALM.
> >
> > What am I missing here?
> >
> >> Date: Tue, 14 Oct 2014 16:23:26 -0700
> >> Subject: Re: OpenLDAP as proxy to Active Directory backend
> >> From: bruce.carleton@dena.com
> >> To: jeflebo@outlook.com
> >> CC: openldap-technical@openldap.org
> >
> >>
> >> Jeff,
> >>
> >> The basic functionality is there. You can tell OpenLDAP to use SASL
> >> for authentication, against any available SASL mechanism that's
> >> supported on your platform. Part of the story is here:
> >>
> >> http://www.openldap.org/doc/admin24/security.html#Pass-Through
> >> authentication
> >>
> >> Pay very close attention to paragraph 14.5.1. That little SASL config
> >> file (not part of OpenLDAP) will stop the show if it's not right.
> >>
> >> I almost had it working, but I couldn't do it, because I still needed
> >> local LDAP password hashes in my use case. I couldn't get the "{SASL}"
> >> password value to work for some reason. Turning on SASL pass-through
> >> seemed to be an all or nothing choice in my case. You will probably
> >> have to do some work to get it up and running.
> >>
> >> Best,
> >>
> >> --Bruce
> >>
> >> On Tue, Oct 14, 2014 at 1:46 PM, Jeff Lebo <jeflebo@outlook.com> wrote:
> >> > Goal: LDAP server in Internet facing DMZ to provide authentication for
> >> > externally hosted applications using internal AD credentials.
> >> >
> >> > I've done a LOT of reading and testing, and there is one thing I am
> >> > still
> >> > not 100% clear on:
> >> >
> >> > Is it possible to do this WITHOUT having a local user database on the
> >> > OpenLDAP proxy? We will have thousands of users that will need to
> >> > authenticate, and I can't maintain another user database (adds, removes,
> >> > etc..). Is there a way to make OpenLDAP just act more like a reverse
> >> > proxy
> >> > and forward anything that matches a specific domain on to the internal
> >> > LDAP/AD server for password verification?
> >>
>