[Zope] Access Permission by Domain and without Login?

For a Zope 2.7/Plone 2 site, I would like to restrict (otherwise) anonymous access to certain specific pages or methods to people making the request from specific domains. I know that I can specify a domain for a particular user, but I want this to apply to anyone, without any special per-user configuration, and without requiring a login. Also I want to do this without putting Zope behind Apache or any other proxy, if this is possible. I don't recall seeing this discussed. Does anyone have suggestions as to how to accomplish this? Cheers, Tom P