Treehouse: Javascript Sandboxes to Help Web Developers Help Themselves

Many Web applications (meaning sites that employ JavaScript) incorporate third-party code and, for reasons rooted in today’s Web ecosystem, are vulnerable to bugs or malice in that code. Our goal is to give Web developers a mechanism that (a) contains included code, limiting (or eliminating) its influence as appropriate; and (b) is deployable today, or very shortly. While the goal of containment is far from new, the requirement of deployability leads us to a new design point, one that applies the OS ideas of sandboxing and virtualization to the JavaScript context. Our approach, called TreeHouse, sandboxes JavaScript code by repurposing a feature of current browsers (namely Web Workers). TreeHouse virtualizes the browser’s API to the sandboxed code (allowing the code to run with few or no modifications) and gives the application author fine-grained control over that code. Our implementation and evaluation of TreeHouse show that its overhead is modest enough to handle performance-sensitive applications and that sandboxing existing code is not difficult.