MexSync: Software Covert Channels Exploiting Mutual Exclusion and Synchronization

The mutual exclusion and synchronization mechanism (MESM) is a basic process management mechanism in modern operating systems. However, we first found that MESM has serious vulnerabilities. In this article, a new set of MESM-based software covert channels, named Mex +Sync, are proposed to transmit confidential information. Mex +Sync offer several advantages: 1) the covert channels are constructed at the software level and can be deployed on any hardware; 2) the closed shared resource ensures the quality of the channels with low interference and makes them hard to be detected; and 3) the attack utilizes the system s software resources which abound and hence difficult to isolate. We build the covert channels on Linux and Windows with the following MESMs: flock, FileLockEX, Mutex, Semaphore, Event, and WaitableTimer. Experimental results demonstrate that these covert channels can achieve transmission rate of 13.105, 12.383, and 6.552 kb/s, respectively, in the scenarios of local, cross-sandbox and cross-virtual machine, all with bit error rate under 1 %. Meanwhile, we carefully analyze and verify the impact of noise on channel performance.