On the Expressiveness of Return-into-libc Attacks

Return-into-libc (RILC) is one of the most common forms of code-reuse attacks. In this attack, an intruder uses a buffer overflow or other exploit to redirect control flow through existing (libc) functions within the legitimate program. While dangerous, it is generally considered limited in its expressive power since it only allows the attacker to execute straight-line code. In other words, RILC attacks are believed to be incapable of arbitrary computation--they are not Turing complete. Consequently, to address this limitation, researchers have developed other code-reuse techniques, such as return-oriented programming (ROP). In this paper, we make the counterargument and demonstrate that the original RILC technique is indeed Turing complete. Specifically, we present a generalized RILC attack called Turing complete RILC (TC-RILC) that allows for arbitrary computations. We demonstrate that TC-RILC satisfies formal requirements of Turing-completeness. In addition, because it depends on the well-defined semantics of libc functions, we also show that a TC-RILC attack can be portable between different versions (or even different families) of operating systems and naturally has negative implications for some existing anti-ROP defenses. The development of TC-RILC on both Linux and Windows platforms demonstrates the expressiveness and practicality of the generalized RILC attack.