Uncovering Intent based Leak of Sensitive Data in Android Framework

Abstract

To prevent unauthorized apps from retrieving the sensitive data, Android framework enforces a permission based access control. However, it has long been known that, to bypass the access control, unauthorized apps can intercept the Intent objects which are sent by authorized apps and carry the retrieved sensitive data. We find that there is a new (previously unknown) attack surface in Android framework that can be exploited by unauthorized apps to violate the access control. Specifically, we discover that part of Intent objects that are sent by Android framework and carry sensitive data can be received by unauthorized apps, resulting in the leak of sensitive data. In this paper, we conduct the first systematic investigation on the new attack surface namely the Intent based leak of sensitive data in Android framework. To automatically uncover such kind of vulnerability in Android framework, we design and develop a new tool named LeakDetector, which finds the Intent objects sent by Android framework that can be received by unauthorized apps and carry the sensitive data. Applying LeakDetector to 10 commercial Android systems, we find that it can effectively uncover the Intent based leak of sensitive data in Android framework. Specifically, we discover 36 exploitable cases of such kind of data leak, which can be abused by unauthorized apps to steal the sensitive data, violating the access control. At the time of writing, 16 of them have been confirmed by Google, Samsung, and Xiaomi, and we received bug bounty rewards from these mobile vendors.