Expat: Expectation-based Policy Analysis and Enforcement for Appified Smart-Home Platforms
Expat: Expectation-based Policy Analysis and Enforcement for Appified Smart-Home Platforms
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DOI：
10.1145/3322431.3325107
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发表时间：
2019-05
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通讯作者：
Moosa Yahyazadeh;P. Podder;Md. Endadul Hoque;Omar Chowdhury
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作者：
Moosa Yahyazadeh;P. Podder;Md. Endadul Hoque;Omar Chowdhury
本文着重于开发针对适用的智能家庭平台的安全机制。这样的平台通常会暴露用于开发自动化应用程序的编程界面，以使智能传感器和执行器之间的不同任务机械化（例如，当室温高于80 F时，自动打开AC）。由于缺乏有效的访问控制机制，这些自动化应用程序不仅可以不受限制地访问用户的敏感信息（例如，用户不在家里），而且还可以通过执行不希望的操作来违反用户期望。由于用户经常从未经浏览的来源获取这些应用程序，因此恶意应用程序可以通过违反用户的安全性和隐私或造成安全危害来对智能家庭系统造成严重破坏（例如，在没有人在家时打开烤箱）。为了减轻此类威胁，我们提出了外国人的建议，以确保运行时安装的自动化应用程序永远不会违反用户期望。为了实现这一目标，Expat提供了一种平台不合时宜的正式规范语言UEI，以捕获对已安装的自动化应用程序行为的用户期望。对于UEI中这些期望（作为策略）的有效撰写，Expat还允许用户检查它们所需的属性（例如，一致性，支出）；由于其正式的语义，SMT求解器很容易放电。然后，Expat使用Inline参考监视器在原位执行UEI策略，该策略可以使用基础平台公开的同一应用程序编程接口来实现。我们实例化了一个代表性平台之一，OpenHab，并证明它可以通过执行用户期望，同时仅产生适度的性能开销，从而有效地减轻各种威胁。
This paper focuses on developing a security mechanism geared towards appified smart-home platforms. Such platforms often expose programming interfaces for developing automation apps that mechanize different tasks among smart sensors and actuators (e.g., automatically turning on the AC when the room temperature is above 80 F). Due to the lack of effective access control mechanisms, these automation apps can not only have unrestricted access to the user's sensitive information (e.g., the user is not at home) but also violate user expectations by performing undesired actions. As users often obtain these apps from unvetted sources, a malicious app can wreak havoc on a smart-home system by either violating the user's security and privacy, or creating safety hazards (e.g., turning on the oven when no one is at home). To mitigate such threats, we propose Expat which ensures that user expectations are never violated by the installed automation apps at runtime. To achieve this goal, Expat provides a platform-agnostic, formal specification language UEI for capturing user expectations of the installed automation apps' behavior. For effective authoring of these expectations (as policies) in UEI, Expat also allows a user to check the desired properties (e.g., consistency, entailment) of them; which due to their formal semantics can be easily discharged by an SMT solver. Expat then enforces UEI policies in situ with an inline reference monitor which can be realized using the same app programming interface exposed by the underlying platform. We instantiate Expat for one of the representative platforms, OpenHAB, and demonstrate it can effectively mitigate a wide array of threats by enforcing user expectations while incurring only modest performance overhead.