Ext. verifier specific reading request body

So, when i have no external verifier, while i process token, MAC class read request body. 

My sinatra app, is next app in stack (MAC.middleware -> Sinatra.app), so MAC read body, and not rewind it back

And in my Sinatra app i have no post params (if it was POST request)
I can hack and in my authenticator ask for request params, but it's seems not correct

@nov what do u think?