Some UCM notes from OnlineAppsDBA:
That was the only answer from the thread’s beginning in 2007 until December 2010, that is. At that point a document was published inside Oracle that described a way to “get it done”. Document ID 851622.1, available through the customer-only Oracle Support site. Last revision was 23-SEP-2011. Here’s the bad news: you need to write your own (C or C++) plugin for the web server to generate the REMOTE_USER variable.
There’s a follow on Document, ID 1162582.1, that describes a failed integration and how to fix it.