class ActionMailbox::Ingresses::Mandrill::InboundEmailsController::Authenticator

def authenticated?
  ActiveSupport::SecurityUtils.secure_compare given_signature, expected_signature
end

def expected_signature
  Base64.strict_encode64 OpenSSL::HMAC.digest(OpenSSL::Digest::SHA1.new, key, message)
end

def given_signature
  request.headers["X-Mandrill-Signature"]
end

def initialize(request, key)
  @request, @key = request, key
end

def message
  request.url + request.POST.sort.flatten.join
end