Plugin for "receiving user/password for a Like, Tweet and others"

Hello!

I’m using WordPress 3.5.2, WooCommerce 2, WP-require login to create a private shop, the users can only access receiving an user/password from me, can’t register by themselves.

I’d like that, similar to other coupon systems, if one person does a Like in Facebook, tweet a message, etc, can access to my private shop, receiving an user/password.

Does anyone know a plugin/extension for doing that or any idea about how to do it? Maybe a similar way?

Thanks in advance!