I recently realized that Xprivacy is not capable of restricting the file storage access. So now I'm looking for a reliable way to do that.
I guess denying the general storage permission would prevent apps from accessing it, but I have yet to find an app that doesn't immediately crash or become useless when you do that. ...So that's definitely not the way to go.
Also, I want way more fine-grained control. For instance I might want WhatsApp to be able access
/data/data/com.whatsapp, but deny access to everything else.
Xprivacy seems to be able to do that using its whitelisting functionality. But sadly it doesn't actually work.
I found out that every app in Android has it's own Linux user account. And this got me wondering:
Shouldn't it be possible to use standard Linux file permissions to manage which app can access which folder? If that requires changing the file system (e.g. switching from FAT to EXT4 for the SD card, as FAT wouldn't support those permissions), can that be done and how?
Has anyone tried that before?
What would I have to do? (Root access and a terminal are not a problem.)