Same app - Different signatures - Two users - Installation of app failing

JayJay

I thought apps are fully sandboxed and users fully isolated, and even if I try to install it on a second user there seem to be some kind of communication in between. Am I doing something wrong ?

Main user no apps installed.
Second user install ProtonVPN directly from official source and set it up. All good!
Main user downloads f-droid and tries to install ProtonVPN but fails because of error "Failed to install due to an unknown error".

Replace ProtonVPN with any other apps tested, such as Tutanota mail client and same issue appears.

If I do the opposite, and install lets say Tutanota f-droid version on Main user
Second user I try install official version from github I get error "can not install app package conflicts with an existing package"

The only way I can install the app on second user is by uninstalling it in first. And make sure I have same signed app installed on both users.

Is this by design or an existing issue?
TQ1A.230105.001.A2.2023020200 on Pixel 7

unwat

JayJay even if I try to install it on a second user there seem to be some kind of communication in between.

There is no communication between the profiles. Profiles are still isolated from each other.

When installing an app, it's installed for the whole phone, but not "activated" for every user. Installing an app that's already installed in another profile could be better described as "activating" an already installed app.

It's probably an oversimplification, but that's the basic idea.

dlb

Use aurora store

JayJay

unwat

Thank you, that made sense now.

So if I understand this correct then, in a real case scenario this can also mean that if lets say your phone is confiscated by a 3 letter agency and they bruteforce successfully one of your dummy users, they can then also find out from that user what other apps you have activated/deactivated or installed for your other users but without accessing any profile data for them. ?
Example through trial and error test and install random apps with wrong signature and wait for error message to show up that it can not be installed meaning it is present in one of your other users.

Can this also be the same for your guest user then?

Of course an app without data means nothing, but at least it can then provide a reason to continue interrogate for answers if it is proven that a specific communication application is installed on the phone.

Graphite

When you create a new profile, you can see in settings > storage The new profile takes up very little storage.
Apps are installed system wide, only app data is separated by profile.

unwat

JayJay

Sure. Technically if they could log in, yes, that would be possible.

If this concerns you, remove certain profiles' permissions to install apps (Settings > System > Multiple users > *user name* > Disallow installing apps). Also, be sure to use good, truly random PINs/passwords. A good owner password, paired with good passwords for profiles, and auto reset set up, this kind of thing happening would be virtually impossible.

JayJay

unwat

Thank you, good idea about disabling install app access. I have done that now.
Can you define "auto reset set up" method? I tried finding sources for these phrases but failed.

unwat

JayJay

Oh. Sorry. I guess that wasn't very clear. I was talking about this feature: https://grapheneos.org/features#auto-reboot

Graphite

This video should explain too.
https://www.youtube-nocookie.com/embed/E3erRhXPPNY