Attacks on software become increasingly sophisticated over time and while the community has a good understanding of many classes of vulnerabilities that are commonly exploited, the practical relevance of side-channel attacks is much less understood.
One common side-channel vulnerability that is present in many web applications today are timing side-channels which allow an attacker to extract information based on different response times. These side-channel vulnerabilities are easily introduced wherever sensitive values such as credentials or API keys are processed before responding to a client. Even though there is basic awareness of timing side-channel attacks in the community, they often go unnoticed or are flagged during code audits without a true understanding of their exploitability in practice.
In this talk, we provide both a tool 'time trial' and guidance on the detection and exploitability of timing side-channel vulnerabilities in common web application scenarios. Specifically, the focus of our presentation is on remote timing attacks, which are performed over a LAN, in a cloud environment, or on the Internet. To illustrate this, we first present experimental timing results that demonstrate how precisely timing can be measured and, more importantly, which timing differences can be distinguished remotely. Second, we compare our results with timing differences that are typically encountered in modern web frameworks and servers. The discussed attack scenarios include database queries, message authentication codes, web API keys, OAuth tokens, and login functions.
Our presentation has significance for a wide spectrum of the conference audience. Attendees in defensive security roles will gain a better understanding of the threat timing side-channel vulnerabilities pose and, based on the demonstrated attacks, will be better able to evaluate the severity and impact of a successful side-channel attack. Attendees in a penetration testing role will learn how to distinguish theoretical timing attacks from legitimately exploitable flaws by using our tool 'time trial'. Finally, attendees focused on research implications will receive a comprehensive update on the state-of-the-art in exploiting timing attacks in practice.