FrozenNode: Static Linking of Node.js Applications

Web applications are ubiquitous. Accessible from almost anywhere, web applications support multiple platforms and can be easily customized. Most people interact with web applications daily for social media, communication, research, purchases, etc. Node.js has gained popularity as a programming language for web applications. A server-side JavaScript implementation, Node.js, allows both the front-end and back-end to be coded in JavaScript. Node.js contains many features such as dynamic inclusion of other modules using a built-in function named require which dynamically locates and loads code.

To be effective, web applications must perform actions quickly while avoiding unexpected interruptions. However, dynamically linked libraries can cause delays and thus downtime, because dynamically linked code must load multiple files, often from disk. As loading is one of the slowest operations a computer performs, seeking from disk can have a negative impact on performance which causes the server to feel less responsive for users. Dynamically linked code can also break when the underlying library is updated. Normally, when trying to update a server, developers will use test servers. However, if the developer accidentally updates a library in a dynamically linked system, it may be incompatible with another portion of the program.

Statically linking code makes it more reliable and faster (to load) than dynamically linking code. The static linking process varies by programming language. Therefore, different static linkers need to be developed for different languages. This thesis describes the creation of a static linker, called FrozenNode, for the popular back-end web application language, Node.js. FrozenNode resolves Node.js applications into a single file that does not rely on dynamic libraries. FrozenNode was built on top of Closure Compiler to accurately process JavaScript. We found that the resolved application was faster and self-contained yielding significant advantages over the dynamically loaded application. Furthermore, both had the same output.

Vulnerabilities in web applications can be found using static analysis tools, however static analysis tools must reason about dynamically linked application. FrozenNode can be used to statically link a Node.js application before being used by a JavaScript static analysis tool.