Reptor (MobiSys `17)


Reptor allows third-party developers to inject new third-party’s implementation of a platform API to an app, so that they can modify, reimplement, or customize existing Android APIs. This is achieved by (i) injecting a replacement class that contains custom code for each platform API class that a third-party developer wants to replace, (ii) rewriting the binary of an app so that the app code uses replacement classes instead of platform API classes, and (iii) distributing the new implementation through standard app distribution channels. Please visit our website for details.



To demonstrate that our approach is practical by showing that Reptor does not incur too much overhead. We have created a video of two users playing Temple Run side-by-side with the user on the left playing the game on the non-instrumented version and the user on the right playing the game on the instrumented version. As can be seen in the video, there is no noticeable delays in game play. Both games are being played on a Samsung Galaxy Nexus which is a phone that was released approximately four years ago.


Use Cases

Vendor-tied library switching

In this use case, we automatically transform Airbnb app developed with Google’s library to use Amazon’s library by using Reptor, specifically Google Maps APIs to Amazon Maps APIs. A user who uses an Amazon device can download an app that uses Google Maps from Google Play and change the app behavior that uses Amazon Maps instead of Google Maps by using Reptor without efforts from the original app developer.

Runtime permission mechanism

In this use case, we have implemented a runtime permission mechanism that asks a user to grant permission to an app at run time, mirroring the iOS permission model. We have used Twitter as a target app. By using Reptor, legacy apps that do not use runtime permissions can easily incorporate them; Also, Reptor can replace each and every sensitive API call with a call that requests a runtime permission first before making an actual call to the API.

HttpToHttps Translator

In this use case, we have implemented an HTTP-to-HTTPS Translator, where we replace URL, so that it returns an HTTPS object instead of an HTTP object. Reptor automatically makes apps use secure HTTPS connection instead of HTTP if HTTPS is available on a requested URL.