privsec.dev/content/os/Android VPN Leakage with Secondary User Profiles.md

title	date	tags	author
Android VPN Leakage with Secondary User Profiles	2022-10-10	Operating Systems Android Privacy	Tommy

Before We Start...

I have been aware of this issue for awhile now (since at least Android 11), though I have not done enough testing to see what actually causes the leak nor do I have any workaround at the moment. My guess is that applications which launch early when you log into a secondary profile can bypass the VPN killswitch.

I have reported it on Google's issue tracker.

The Leak

You can reproduce the leak by doing the following:

1. Create a new user profile (you need to create a secondary user pfofile for this, as it is not reproducible on your owner profile or a work profile). Do not log into your Google account at this stage.
2. Sideload a VPN app. The leak happens with every VPN provider I have tried (since it is likely a platform issue), though if you do not have a VPN subscription I would recommend getting a free one with ProtonVPN.
3. Setup the VPN and the Android VPN killswitch.
4. Log into your Google account through Play Services.
5. Restart the phone. Open the secondary user profile again.
6. Go to Google's My Devices page. Observe that one of the sessions for your phone has your actual location obtained with GeoIP. In some cases, your actual IP address will be shown there as well.

Notes

1. It is unlikely that this is caused by Play Services being privileged applications. This issue is reproducible on GrapheneOS with the Sandboxed Play Services (which runs as a normal, unprivileged application) as well.

2. More testing is needed to find the root cause of the problem. I do not think that this is Play Services specific. Unfortunately, I do not have access to a router to do a packet capture right now. I would appreciate it if someone can help me get to the bottom of this. You can find my contact information here.