  Home automation platforms provide a new level of convenience by enabling
consumers to automate various aspects of physical objects in their homes. While
the convenience is beneficial, security flaws in the platforms or integrated
third-party products can have serious consequences for the integrity of a
user's physical environment. In this paper we perform a systematic security
evaluation of two popular smart home platforms, Google's Nest platform and
Philips Hue, that implement home automation "routines" (i.e., trigger-action
programs involving apps and devices) via manipulation of state variables in a
centralized data store. Our semi-automated analysis examines, among other
things, platform access control enforcement, the rigor of non-system
enforcement procedures, and the potential for misuse of routines. This analysis
results in ten key findings with serious security implications. For instance,
we demonstrate the potential for the misuse of smart home routines in the Nest
platform to perform a lateral privilege escalation, illustrate how Nest's
product review system is ineffective at preventing multiple stages of this
attack that it examines, and demonstrate how emerging platforms may fail to
provide even bare-minimum security by allowing apps to arbitrarily add/remove
other apps from the user's smart home. Our findings draw attention to the
unique security challenges of platforms that execute routines via centralized
data stores and highlight the importance of enforcing security by design in
emerging home automation platforms.
