Side Channel Threats in the Software-as-a-Service Era: Challenges and Responses

Sep 15, 2010

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Abstract

With software-as-a-service becoming mainstream, more and more applications are delivered to the client through the Web. Unlike a desktop application, a web application is a "two-part" program, with its components deployed both in the browser and in the web server. The communication between these two components inevitably leaks out the program's internal states to those eavesdropping on its web traffic, simply through the side channel features of the communication such as packet length and timing, even if the traffic is entirely encrypted. In this talk, I will present our discovery showing that such side-channel leaks are both fundamental and realistic: a set of high-profile web applications are found to disclose highly sensitive user data such as one's family incomes, health profiles, investment secrets and more through their side channels. More importantly, we found that the root causes of the problem are some fundamental characteristics of web applications: stateful communication, low entropy input for better interaction, and significant traffic distinctions. This indicates that a significant improvement of the current web-application development practice becomes necessary. As a response to this urgent call, I will also describe in this talk a new technique we developed, called Sidebuster, which facilitates detection and quantification of side-channel vulnerabilities during development of web applications.