Using the new Identy server in 9.1, it is still possible to implement a custom ASP.NET Membership provider?

Question

Reading the documentation here:

https://doc.sitecore.com/developers/91/sitecore-experience-management/en/sitecore-identity-server-authentication.html

"The SI server uses identityserver-contrib-membership. This project allows the ASP.NET 2.0 Membership Database to be used as the Identity Server User Store in IdentityServer4"

And

"You configure the connection string to the Membership database with the Sitecore:IdentityServer:SitecoreMembershipOptions:ConnectionString setting"

I get the impression that the Identity server can use user information from any domain stored in the core database, but it does not actually use the ASP.NET 2.0 Membership Provider, and will not use any custom membership providers (configured in web.config/membership element and domain.config)

Answer 1

I'm not an expert, but I've done a bit of research.

You are correct that the Identity server uses the user information stored in the Core database, but isn't implementing a Membership Provider and won't use a custom membership provider configured in the web.config.

The Sitecore Identity Server implements IdentityServer4. They are using IdentityServer's Membership Service to access Membership data in an Identity context. With some a respectable effort, you could probably branch the config and add another copy of the MembershipService to the Identity Server with your own data.

I know it's also possible to disable the Identity Server entirely and fall back to the old-style login page. I'm not sure if doing that will allow you to use a Membership Provider in the usual fashion, but that should be an easy experiment to run.