Refactor Rack::Session::Cookie#unpacked_cookie_data

lib/rack/session/cookie.rb

@@ -105,14 +105,7 @@ def unpacked_cookie_data(env)
 
           if @secrets.size > 0 && session_data
             session_data, digest = session_data.split("--")
-
-            if session_data && digest
-              ok = @secrets.any? do |secret|
-                digest == generate_hmac(session_data, secret)
-              end
-            end
-
-            session_data = nil unless ok
+            session_data = nil unless digest_match?(session_data, digest)
           end
 
           coder.decode(session_data) || {}
@@ -152,6 +145,13 @@ def destroy_session(env, session_id, options)
         generate_sid unless options[:drop]
       end
 
+      def digest_match?(data, digest)
+        return unless data && digest
+        @secrets.any? do |secret|
+          digest == generate_hmac(data, secret)
+        end
+      end
+
       def generate_hmac(data, secret)
         OpenSSL::HMAC.hexdigest(OpenSSL::Digest::SHA1.new, secret, data)
       end