Live Path CFI Against Control Flow Hijacking Attacks

Abstract

Through memory vulnerabilities, control flow hijacking allows an attacker to force a running program to execute other than what the programmer has intended. Control Flow Integrity (CFI) aims to prevent the adversarial effects of these attacks. CFI attempts to enforce the programmer’s intent by ensuring that a program only runs according to a control flow graph (CFG) of the program. The enforced CFG can be built statically or dynamically, and Per-Input Control Flow Integrity (PICFI) represents a recent advance in dynamic CFI techniques. PICFI begins execution with the empty CFG of a program and lazily adds edges to the CFG during execution according to concrete inputs. However, this CFG grows monotonically, i.e., edges are never removed when corresponding control flow transfers become illegal. This paper presents LPCFI, Live Path Control Flow Integrity, to more precisely enforce forward edge CFI using a dynamically computed CFG by both adding and removing edges for all indirect control flow transfers from indirect callsites, thereby raising the bar against control flow hijacking attacks.