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.

Attackers leverage memory corruption vulnerabilities to establish primitives for reading from or writing to the address space of a vulnerable process. These primitives form the foundation for code-reuse and data-oriented attacks. While various defenses against the former class of attacks have proven effective, mitigation of the latter remains an open problem. In this paper, we identify various shortcomings of the x86 architecture regarding memory isolation, and leverage virtualization to build an effective defense against data-oriented attacks. Our approach, called xMP, provides (in-guest) selective memory protection primitives that allow VMs to isolate sensitive data in user or kernel space in disjoint xMP domains. We interface the Xen altp2m subsystem with the Linux memory management system, lending VMs the flexibility to define custom policies. Contrary to conventional approaches, xMP takes advantage of virtualization extensions, but after initialization, it does not require any hypervisor intervention. To ensure the integrity of in-kernel management information and pointers to sensitive data within isolated domains, xMP protects pointers with HMACs bound to an immutable context, so that integrity validation succeeds only in the right context. We have applied xMP to protect the page tables and process credentials of the Linux kernel, as well as sensitive data in various user-space applications. Overall, our evaluation shows that xMP introduces minimal overhead for real-world workloads and applications, and offers effective protection against data-oriented attacks.

Centralized DNS over HTTPS/TLS (DoH/DoT) resolution, which has started being deployed by major hosting providers and web browsers, has sparked controversy among Internet activists and privacy advocates due to several privacy concerns. This design decision causes the trace of all DNS resolutions to be exposed to a third-party resolver, different than the one specified by the user's access network. In this work we propose K-resolver, a DNS resolution mechanism that disperses DNS queries across multiple DoH resolvers, reducing the amount of information about a user's browsing activity exposed to each individual resolver. As a result, none of the resolvers can learn a user's entire web browsing history. We have implemented a prototype of our approach for Mozilla Firefox, and used it to evaluate the performance of web page load time compared to the default centralized DoH approach. While our K-resolver mechanism has some effect on DNS resolution time and web page load time, we show that this is mainly due to the geographical location of the selected DoH servers. When more well-provisioned anycast servers are available, our approach incurs negligible overhead while improving user privacy.

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