I have an ASP.NET Web API (v4, specifically) application that currently authenticates using Forms authentication (through a SQL membership provider (i.e. using aspnet_Membership, aspnet_Users tables and all that)). It's basically the backend API hub for a bunch of other applications.
Alongside that, I have a third-party application, SP (for service provider), which supports SSO and single logout using SAML. My goal is to set up a SAML identity provider that can receive a SAML single logout request, which would in turn send a logout response to SP.
I started out looking at Auth0 to achieve this, but I am confused about what role Auth0 would actually play as the identity provider since all of my user creds are stored in my own database. Is there some way I can supply Auth0 (or any of these identity providers) with my user creds store for it to authenticate my users? Or is this not desirable/possible and I need to make my existing app to be the SAML identity provider?