# Validate a cookie set by the Javascript SDK

FB_APP_ID = 'your_app_id'
FB_APP_SECRET = 'your_app_secret'

facebook_session = CGI.parse(cookies["fbs_#{FB_APP_ID}"].gsub('"', ''))
sig = facebook_session.delete('sig')
hash = Digest::MD5.hexdigest((facebook_session.sort.inject("") { |payload, cookie| payload + "#{cookie[0]}=#{cookie[1]}" }) + FB_APP_SECRET)

# sig == hash => You've got a valid Facebook session cookie