callback_test.rb

  def callback_test

    require 'openssl'
    require 'base64'

    # Pull the original signature
    @signature = params[:signature]

    # Capture all of our parameters
    @parameters = params

    # delete signature, action, and controller params
    @parameters.delete('action')
    @parameters.delete('controller')
    @parameters.delete('signature')
    @parameters['signature'] = ''
    
    # Rebuild URL
    rebuilturl = "?"
    firstelement = true

    @parameters.sort.each do |p|
      if firstelement == true
        rebuilturl << "#{p[0].to_s}=#{p[1].to_s}"
        firstelement = false
      else
        rebuilturl << '&' << "#{p[0].to_s}=#{p[1].to_s}"
      end
    end
    
    @rebuilturl = rebuilturl 

    # Verify Signature
    publickeyid = OpenSSL::PKey::RSA.new(File.read("#{Rails.root}/certs/zong.pem"))
    @verified = publickeyid.verify( OpenSSL::Digest::SHA1.new, Base64.decode64(@signature), @rebuilturl )
    
    if @verified == true
      return true
    else
      return false
    end

  end