This Rack middleware checks the signature of Facebook params, and converts them to Ruby objects when appropiate. Also, it converts the request method from the Facebook POST to the original HTTP method used by the client.
If the signature is wrong, it returns a "400 Invalid Facebook Signature".
Optionally, it can take a block that receives the Rack environment and returns a value that evaluates to true when we want the middleware to be executed for the specific request.
In your config.ru:
require 'rack/facebook'
use Rack::Facebook, "my_facebook_secret_key"
Using a block condition:
use Rack::Facebook, "my_facebook_secret_key" do |env|
env['REQUEST_URI'] =~ /^\/facebook_only/
end
Carlos Paramio