Android Internals: Package Verifiers

Inspired by Nikolay Elenkov’s detailed technical posts on Android Explorations, I decided to dig into the Android source code myself and document the package verification mechanism in Android.

Package verification was introduced in Android 4.2 to allow for apps to be verified or checked before they are installed. If you have tried to install a malicious app on a production Android device, you might have seen the following screen, displayed by the verifier:

screenshot of malicious app install warning

Android was built in such a way that it tries to be generic for third-parties to implement stuff. Package verification is a feature that is currently only used and implemented by Google, but it is abstracted in such a way that any manufacturer can implement their own. Documentation and examples on how to do this is almost non-existent, although anyone determined enough can read the Android source code and figure it out for themselves.

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