The security of computer systems fundamentally relies on memory isolation, e.g., kernel address ranges are marked as non-accessible and are protected from user access. In this paper, we present Meltdown. Meltdown exploits side effects of out-of-order execution on modern processors to read arbitrary kernel-memory locations including personal data and passwords. Out-of-order execution is an indispensable performance feature and present in a wide range of modern processors. The attack works on different Intel microarchitectures since at least 2010 and potentially other processors are affected. The root cause of Meltdown is the hardware. The attack is independent of the operating system, and it does not rely on any software vulnerabilities. Meltdown breaks all security assumptions given by address space isolation as well as paravirtualized environments and, thus, every security mechanism building upon this foundation. On affected systems, Meltdown enables an adversary to read memory of other processes or virtual machines in the cloud without any permissions or privileges, affecting millions of customers and virtually every user of a personal computer. We show that the KAISER defense mechanism for KASLR has the important (but inadvertent) side effect of impeding Meltdown. We stress that KAISER must be deployed immediately to prevent large-scale exploitation of this severe information leakage.
MI6: Secure Enclaves in a Speculative Out-of-Order Processor
最近的攻击通过利用允许间接访问共享微体系结构状态的微体系结构侧通道来打破进程隔离。飞地加强了进程抽象以恢复隔离保证。我们提出了MI6，一个积极的，投机性的顺序处理器，能够提供安全的飞地下的威胁模型，包括一个不受信任的操作系统和攻击者能够安装任何软件攻击目前认为是可行的，包括控制流投机攻击。MI6受到Sanctum [16]的启发，并将其隔离保证扩展到更现实的存储层次结构。它还介绍了一个清除指令，这是只使用时，一个安全的进程被调度，并实现了一个复杂的处理器微架构。我们通过在不受信任的Linux操作系统上运行SPEC CINT2006基准测试，在AWS F1 FPGA上进行FPGA仿真，对MI6中的飞地的性能影响进行建模。安全性的代价是受保护程序的平均速度降低约16.4%。
最近，乱序执行，在现代高端处理器中的一个重要的性能优化，已被发现构成了重大的安全威胁，允许跨安全域的信息泄漏。特别是Meltdown攻击，会将信息从操作系统内核泄露到用户空间，彻底侵蚀系统的安全性。为了解决这种和类似的攻击，而不产生软件对策的性能成本，英特尔在其最新的Coffee Lake R处理器中包含了基于硬件的防御。在这项工作中，我们表明，最近的硬件防御是不够的。具体来说，我们提出了辐射，一个新的瞬态执行攻击，从以前未开发的微架构组件称为存储缓冲区泄漏信息。我们展示了无特权的用户进程如何利用Fallout来重建内核最近写入的特权信息。我们进一步展示了如何使用Fallout来绕过内核地址空间随机化。最后，我们确定和探索微代码协助迄今被忽视的原因，瞬态执行。Fallout影响我们测试过的所有处理器代。然而，我们注意到一个令人担忧的回归，新的Coffee Lake R处理器比老一代更容易受到辐射的影响。
