xPlore Index Agent login failure

If you are using Documentum xPlore for fulltext search, you might face the following issue: after starting the Index Agent process, you have to start the Index Agent from the Administration page (http://URL:port/IndexAgent/login_dss.jsp), but the login fails with the message:
User is not an Admin User!
even if your user is a superuser

The cause is a bug in the login_dss.jsp code:
IDfUser userObject = doc_session.getUserByOSName(uname, domain_name);
…
if (userObject != null)
isSysAdmin = userObject.isSysAdmin();

The bug here is that if the userObject is null (was not found), the flag isSysAdmin remains false, so the error message doesn’t say that the user was not found, instead you have the message above telling it’s not an Admin user.

Now why the userObject can happen to be null? (Note: at this point of code the user is already logged in against the repository). It’s because the user is searched using getUserByOSName(uname, domain_name) method. So if the user_os_domain is not set in the dm_user object and the Documentum repository runs in domain required mode (dm_docbase_config.auth_protocol='domain_required') : if you don’t specify the domain on login page – login doesn’t succeed, if you specify it – the userObject is not found – thus null.

To solve this issue it's enough to modify the login_dss.jsp page substituting the getUserByOSName(uname, domain_name) method with getUserByLoginName(uname, domain_name) or getUser(uname), or you could just set the user_os_domain in the dm_user object (however first option is preferred).