CFI: Control Flow Integrity or Control Flow Interruption?

Abstract

Runtime memory vulnerabilities, especially present in widely used languages as C and C++, are exploited by attackers to corrupt code pointers and hijack the execution flow of a program running on a target system to force it to behave abnormally. This is the principle of modern Code Reuse Attacks (CRAs) and of famous attack paradigms as Return-Oriented Programming (ROP) and Jump-Oriented Programming (JOP), which have defeated the previous defenses against malicious code injection such as Data Execution Prevention (DEP). Control-Flow Integrity (CFI) is a promising approach to protect against such runtime attacks. Recently, many CFI solutions have been proposed, with both hardware and software implementations. But how can a defense based on complying with a graph calculated a priori efficiently deal with something unpredictable as exceptions and interrupt requests? The present paper focuses on this dichotomy by analysing some of the CFI-based defenses and showing how the unexpected trigger of an interrupt and the sudden execution of an Interrupt Service Routine (ISR) can circumvent them.