Concurrency Attacks

Just as errors in sequential programs can lead to security exploits, errors in concurrent programs can lead to concurrency attacks. Questions such as whether these attacks are feasible and what characteristics they have remain largely unknown. In this paper, we present a preliminary study of concurrency attacks and the security implications of real world concurrency errors. Our study yields several interesting findings. For instance, we observe that the exploitability of a concurrency error depends on the duration of the timing window within which the error may occur. We further observe that attackers can increase this window through carefully crafted inputs. We also find that four out of five commonly used sequential defenses become unsafe when applied to concurrent programs. Based on our findings, we propose new defense directions and fixes to existing defenses.