Fingerprinting - Apps have access to the total device storage used?

kjerehea

As a test, I installed Google Play Services in Owner and a Second profile, and under the settings for "Free up space" they both show the same amount of storage used by the device. This is about 10gb smaller than the value shown by the device Settings, but it means that any app can easily fingerprint the device across profiles as the amount used changes?

If this is confirmed, I propose to spoof to apps that all storage except for eg 20gb is being used. If an app requires more than 20gb then the user could increase the value. If the user wants to use the remaining 20gb then they could manually reduce each individual profile's value as needed.

treequell

I am not sure I understand your question properly, but I have one comment and one question.

When you install an app in two separate user profiles, the app data itself is stored only once on the device. It is only the user data associated with the app which is kept separate between the users.

I believe the information you are referring to here (device storage used) is viewable in the Settings app only, which is a special system app. I am curious how you think that a user installed app would access to such information? User installed apps do not have to the app data of other apps installed on the device.

kjerehea

In Google Play Services I click on my username and then "Manage apps and device" and then it shows the storage used.

When I click on the storage it shows "Free up space" and then the storage used by Apps and Other.

Both Google Play Services (different google accounts) agree on the total space used by the device (even though it's lower than the true System value). However, they show different values for Apps and Other, but the combined value of Apps+Owner is the same for both GPS apps.

I just added about 10gb of files to a Third profile (with no GPS ever installed on it), and both GPS installations recognised that the device storage usage had increased by 10gb.

I realise that preventing fingerprinting is almost impossible, but I'd no idea it was this easy for apps.