Configuration-Driven Software Debloating

Abstract

With legitimate code becoming an attack surface due to the proliferation of code reuse attacks, software debloating is an effective mitigation that reduces the amount of instruction sequences that may be useful for an attacker, in addition to eliminating potentially exploitable bugs in the removed code. Existing debloating approaches either statically remove code that is guaranteed to not run (e.g., non-imported functions from shared libraries), or rely on profiling with realistic workloads to pinpoint and keep only the subset of code that was executed. In this work, we explore an alternative configuration-driven software debloating approach that removes feature-specific code that is exclusively needed only when certain configuration directives are specified---which are often disabled by default. Using a semi-automated approach, our technique identifies libraries solely needed for the implementation of a particular functionality and maps them to certain configuration directives. Based on this mapping, feature-specific libraries are not loaded at all if their corresponding directives are disabled. The results of our experimental evaluation with Nginx, VSFTPD, and OpenSSH show that using the default configuration in each case, configuration-driven debloating can remove 77% of the code for Nginx, 53% for VSFTPD, and 20% for OpenSSH, which represent a significant attack surface reduction.