WASP: Protecting Web Applications Using Positive Tainting and Syntax-Aware Evaluation

Many software systems have evolved to include a web-based component that makes them available to the public via the Internet and can expose them to a variety of web-based attacks. One of these attacks is SQL injection, which can give attackers unrestricted access to the databases underlying web applications and has become increasingly frequent and serious. This paper presents a new, highly automated approach for protecting web applications against SQL injection that has both conceptual and practical advantages over most existing techniques. From a conceptual standpoint, the approach is based on the novel idea of positive tainting and on the concept of syntax-aware evaluation. From a practical standpoint, our technique is precise and efficient and has minimal deployment requirements. We also present an extensive empirical evaluation of our approach performed using WASP, a tool that implements our technique. In the evaluation, we used WASP to protect a wide range of web applications while subjecting them to a large and varied set of attacks and legitimate accesses. WASP was able to stop all attacks and did not generate any false positives. Our studies also show that the overhead imposed by WASP was negligible in most cases.