optional authentication and HTTP Basic

Hi all,

I have an app that originally only supported form-based
authentication, and showed pared-down content to unauthenticated
users. I then layered on HTTP Basic authentication using
authenticate_with_http_basic, which worked fine for scripts like LWP/

However, some web browsers refuse to submit credentials in the URL
(eg. http://username:password@example.com) since they never get a
challenge (401) response, since authentication is purely optional.
This is a bigger problem than one might expect, since there's a
desktop client in development that requires the ability to login with
HTTP Basic URL auth.

They way I hacked around it was to create an action that looks like

  def challenge
    authenticate_or_request_with_http_basic APP_NAME do |login,
      @user = User.authenticate(login, password)
    if @user
      self.current_user = @user

so browser clients (including the problematic desktop client) can GET
http://user:pass@example.com/sessions/challenge to do explicit HTTP
basic auth.

Is there a better way to do this?