I'm developing an application that going to be pr-installed (as a system app) on the firmware.
from the documentation so far about the relation between system apps, new permissions model, and the protection levels - I don't understand exactly when system app needs (if at all) to request user permission.
My problems starts when I try to use the WRITE_EXTERNAL_STORAGE
permission. from the documentation I can see that it marked as "dangerous" permission.
- does "dangerous" permissions grant automatically to system apps?
when I use WRITE_EXTERNAL_STORAGE
permission (as a system app) I'm getting security exception, and I don't know if it's mean that even tough my app installed as a system app - "dangerous" permissions must be requested by the user..
another point to mention:
to check the app behavior as a system app, I'm installing my application APK on the sys-priv
directory (the device is rooted) of a nexus 5 running SDK preview 3. this is when I'm getting the security exception when attep to use methods requires the external storage permission..
After a lot of digging and debugging, I finally found some clue of granting runtime permission on marshmallow for system app, with a lot of inspirations in this stackoverflow ticket.
The key logic is in DefaultPermissionGrantPolicy. After systemReady, PackageManagerService checks if this user's default runtime permissions are not set yet(i.e. this is a new user), if so, PackageManagerService calls DefaultPermissionGrantPolicy.grantDefaultPermissions() to check/grant permissions:
public void grantDefaultPermissions(int userId) {
grantPermissionsToSysComponentsAndPrivApps(userId);
grantDefaultSystemHandlerPermissions(userId);
}
There are two cases that your built-in app may be automatically granted with runtime permission.
A> grantPermissionsToSysComponentsAndPrivApps -> will grant runtime permission with FLAG_PERMISSION_SYSTEM_FIXED and FLAG_PERMISSION_GRANTED_BY_DEFAULT.
if your system app fits all below conditions, it will be granted the permissions.
B> grantDefaultSystemHandlerPermissions -> will grant runtime permission with FLAG_PERMISSION_GRANTED_BY_DEFAULT .
Other than that, your system application needs to ask user for granting dangerous permission, as long as it has targetSdk set to 23.
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