Blocking unsafe behaviors in control systems through static and dynamic policy enforcement
Blocking unsafe behaviors in control systems through static and dynamic policy enforcement
复制标题
通过静态和动态策略执行来阻止控制系统中的不安全行为
DOI：
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发表时间：
2015
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通讯作者：
Stephen E. McLaughlin
中科院分区：
文献类型：
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作者：
Stephen E. McLaughlin
计算机安全中最普遍接受的做法之一是使用安全策略强制实施。在策略实施机制下，用户和程序只能执行安全策略授权的操作。不幸的是，现代控制系统未能有效利用政策执行。在许多情况下，控制系统中的特权是二进制的--单个密码就足以获得系统中的大部分或所有特权。在本文中，我们考虑了对在可编程逻辑控制器(PLC)上运行的代码实施安全策略的好处和挑战。我们首先总结前面的两种方法，这两种方法不信任PLC的正确行为。虽然这些方法很有希望，尤其是对于当前的PLC体系结构，但与基于可信PLC设计的方法相比，它们是缺乏的。因此，我们认为未来的PLC应该实现可信计算基础(TCB)。这样的TCB是一组受信任的硬件和软件，足以直接在PLC上实施策略。我们还提出了一种对支持小型TCB的PLC进行政策执行的方法，并认为这是对PLC进行政策执行的更简单和更有效的手段。我们的结论是，未来的PLC应该支持小型TCB。
One of the most universally accepted practices in computer security is the use of security policy enforcement. Under a policy enforcement regime, users and programs can only perform actions for which they are authorized by the security policy. Unfortunately, modern control systems fail to make effective use of policy enforcement. In many cases, privilege in control systems is binary-a single password is sufficient to gain most or all privileges within the system. In this paper, we consider the benefits and challenges of enforcing security policies for code running on Programmable Logic Controllers (PLCs). We first summarize two of our previous approaches, which place no trust in the PLC to behave correctly. While these approaches show promise, especially for current PLC architectures, they are lacking in comparison to approaches based on a trustworthy PLC design. Thus, we argue that future PLCs should implement a Trusted Computing Base (TCB). Such a TCB is a small set of trusted hardware and software that is sufficient for enforcing policies directly on the PLC. We also propose a method of doing policy enforcement on PLCs supporting a small TCB, and argue that it is the simpler and more effective means of doing policy enforcement for PLCs. We conclude that future PLCs should support a small TCB.