A Small But Non-negligible Flaw in the Android Permission Scheme

Abstract

This paper presents a flaw in the permission scheme of Android. The Android framework enforces a permission-based security policy where an application can access the other parts of the system only when the application is explicitly permitted. The security of the framework depends to a large extent on the owner of a device since the authorization decisions are mainly made by the user. As a result, the permission scheme imposes much of the administrative burden on the user instead of keeping it simple. Moreover, the framework does not impose enough controls nor support dynamic adjustment in the following respects: No naming rule or constraint is applied for a new permission declaration; once an application acquires a permission, the permission is never revoked during the lifetime of the application, two different permissions can be in use having the same name. These features of the framework can result in a security flaw. We explain how we found the flaw, demonstrate an exploit example, and discuss the solution.