The Port-in-Use Covert Channel Attack

Abstract

We propose a port-is-in-use attack, which is intended for leaking sensitive information in multilevel secure operating systems. Our approach is based on TCP socket mechanism widely used in Linux for interprocess communication. Despite the strong limitations inherent in operating systems with mandatory access control, sockets may not be restricted by the security policy, which makes it possible theoretically to transfer information from one process to another from a high security level to a low one. The proposed attack belongs to the operating system storage transition-based class attack. The main idea is to use the availability of TCP port, which is shared among processes at more than one security level, as the communication medium. The possibility or impossibility of binding a socket to a predefined port is used to transmit a bit of 0 or 1 respectively. We implement proof-of-concept exploit, which was used to check the idea and to evaluate covert channel capacity. Experimental results show that the proposed technique provides high rate covert channel, that means a significant threat of confidentiality in multilevel secure operating systems.