Fault attacks enable adversaries to manipulate the control-flow of security-critical applications. By inducing targeted faults into the CPU, the software's call graph can be escaped and the control-flow can be redirected to arbitrary functions inside the program. To protect the control-flow from these attacks, dedicated fault control-flow integrity (CFI) countermeasures are commonly deployed. However, these schemes either have high detection latencies or require intrusive hardware changes. In this paper, we present EC-CFI, a software-based cryptographically enforced CFI scheme with no detection latency utilizing hardware features of recent Intel platforms. Our EC-CFI prototype is designed to prevent an adversary from escaping the program's call graph using faults by encrypting each function with a different key before execution. At runtime, the instrumented program dynamically derives the decryption key, ensuring that the code only can be successfully decrypted when the program follows the intended call graph. To enable this level of protection on Intel commodity systems, we introduce extended page table (EPT) aliasing allowing us to achieve function-granular encryption by combing Intel's TME-MK and virtualization technology. We open-source our custom LLVM-based toolchain automatically protecting arbitrary programs with EC-CFI. Furthermore, we evaluate our EPT aliasing approach with the SPEC CPU2017 and Embench-IoT benchmarks and discuss and evaluate potential TME-MK hardware changes minimizing runtime overheads.

翻译：故障攻击使攻击者能够操控安全关键型应用程序的控制流。通过向CPU注入特定故障，攻击者可突破软件的调用图，并将控制流重定向到程序内部的任意函数。为保护控制流免受此类攻击，通常采用专用的故障控制流完整性（CFI）防御机制。然而，现有方案要么存在高检测延迟，要么需要侵入式硬件修改。本文提出EC-CFI，一种基于软件实现的加密增强型CFI方案，利用近期Intel平台的硬件特性实现零检测延迟。我们的EC-CFI原型通过在执行前为每个函数分配不同密钥进行加密，旨在阻止攻击者利用故障突破程序调用图。在运行时，经插桩的程序动态推导解密密钥，确保仅在程序遵循预期调用图时才能成功解密代码。为在Intel商用系统上实现此防护等级，我们引入扩展页表（EPT）别名机制，通过结合Intel TME-MK与虚拟化技术实现函数粒度的加密。我们开源了基于LLVM的自定义工具链，可自动保护任意程序。此外，我们使用SPEC CPU2017和Embench-IoT基准测试评估了EPT别名方法，并讨论评估了减少运行时开销的潜在TME-MK硬件改进方案。