Facebook iframe signed request

gistfile1.rb

require 'json'
require 'base64'

# Decoding functions
def base64_url_decode str
  encoded_str = str.gsub('-','+').gsub('_','/')
  encoded_str += '=' while !(encoded_str.size % 4).zero?
  Base64.decode64(encoded_str)
end

def decode_data(signed_request)
  encoded_sig, payload = signed_request.split('.')
  data = base64_url_decode(payload)
end

# Parsing in your route
post '/route?' do
  @encoded_request = params[:signed_request]
  @json_request = decode_data(@encoded_request)
  @signed_request = JSON.parse(@json_request)
end