SharePoint claims with single sign on redirects when accessing _trust subdirectory

Question

I have developed a cutom STS/Identity provider/SSO (Single sign on) website in MVC3 which acts as a claims provider. This site signs on a user to a sharepoint site using WSFederation.

It correctly signs on a user to "http://MYSP/_trust/" and then it redirects the user based on the wctx e.g. "http://MySP/library/1" etc. However the issuer I have is if SSO logs the user into Sharepoint, they leave without signing out of SharePoint, go back to the SSO which then tries to log them back into Sharepoint. This causes SharePoint to redirect the user back to the SSO (it ignores the wctx).

I think its related to the fact that if I browse "http://MYSP/_trust/" it automatically redirects me back to my SSO site even if I am logged into SharePoint. Does anyone know why it does that?

Also why does it ignore the wctx If the user is already logged in?

Thanks for any help you can provide me!

Answer 1

AFAIK, /_trust virtual directory is for handling the Ws-Fed Sign-In response sent by Identity Provider(in your case Custom STS).

In this case of IdP initiated Sign-on, please verify if wctx is passed to _trust url by Identity provider.