I have a custom membership provider and plenty of FBA users with assigned groups.
Now for example I have a user
i:0#.f|fba|user1 and he belongs to three groups (Group1, Group2, Group3).
I've added ability to authenticate using custom STS, and if I'm authenticating using same user name through STS, sharepoint creates new record in UserInfo table
i:05.t|sts|user1 and naturally it does not get any groups from existing user.
Is it possible somehow to tell Sharepoint, that those users should have same set of permissions, or to reuse existing fba user record if sts user name matches (in other words have several methods to login as same user - like many sites do - I can login to stackexchange using google/facebook/email and still end up with same user account)?
Or is it possible to authenticate as FBA user from external website (which is not a sharepoint website)?