Ripley: Automatically Sercuring Web 2.0 Applications Through Replicated Execution

摘要

Rich Internet applications are becoming increasingly distributed, as demonstrated by the popularity of AJAX or Web 2.0 applications such as Facebook, Google Maps, Hotmail and many others. A typical multi-tier AJAX application consists, at the least, of a server-side component implemented in Java J2EE, PHP or ASP .NET and a client-side component running JavaScript. The resulting application is more responsive because computation has moved closer to the client, avoiding unnecessary network round trips for frequent user actions. However, once a portion of the code has moved to the client, a malicious user can subvert the client side of the computation, jeopardizing the integrity of the server-side state. In this paper we propose RIPLEY, a system that uses replicated execution to automatically preserve the integrity of a distributed computation. RIP-LEY replicates a copy of the client-side computation on the trusted server tier. Every client-side event is transferred to the replica of the client for execution. RIPLEY observes results of the computation, both as computed on the client-side and on the server side using the replica of the client-side code. Any discrepancy is flagged as a potential violation of computational integrity. We built RIPLEY on top of Volta, a distributing compiler that translates .NET applications into JavaScript, effectively providing a measure of security by construction for Volta applications. We have evaluated the RIPLEY approach on five representative AJAX applications built in Volta and also on Hotmail, a large widely-used AJAX application. Our results so far suggest that RIPLEY provides a promising strategy for building secure distributed web applications, which places minimal burden on the application developer at the cost of a low performance overhead.