I'm searching for an existing Plone add-on that allows Facebook users to authenticate in Plone - version 4.x. There is plonesocial.auth.rpx but it's full of bugs and it doesn't work in Plone 4.
https://github.com/RedTurtle/pas.plugins.velruse
This Plone plugin let you to enable authentication of social networks users in Plone sites, using Velruse.
Velruse is a Pyramid application so defined:
Velruse is a set of authentication routines that provide a unified way to have a website user authenticate to a variety of different identity providers and/or a variety of different authentication schemes.
It is similar in some ways to Janrain Engage with the exception of being open-source, locally installable, and easily pluggable for custom identity providers and authentication schemes.
—from Velruse documentation