Open Radar

 
Summary:
We have developed an app (Checkout) that stimulates the user to cut back on smartphone usage in specific situations, such as in the car, where he is rewarded by his insurance and/or car lease company. We do so by setting up a VPN that is temporarily established, thus blocking all traffic to and from the smartphone. The user obviously sets up the VPN profile and is fully in the know of this as it is a voluntary service.

We have found out however, that Whatsapp manages to bypass this VPN connection and send/receive messages via the GSM network with a short delay of approximately two minutes after the VPN connection is established. 

This is not only undesired, but also not what we believe the OS platform should allow for as Whatsapp is supposed to work exclusively through the data connection. 

Our assumption is that Whatsapp uses timestamps (NTP) to 'secretly' send data packages and thus send/receive messages. Our assumption is underpinned by the fact that images and/or videos (due to filesize) are not being sent and/or received.

Steps to Reproduce:
1. Download the app via https://itunes.apple.com/nl/app/checkout-of-your-phone/id1051880452?mt=8
2. Install the app and the VPN profile
3. Checkout through the app to activate the VPN connection, or manually activate the installed VPN via settings
4. Open Whatsapp and send a random message
5. After approximately two minutes, the message will be sent and/or incoming messages received. 
6. As from that point onwards, all messages can be sent/received, with the exception of images and videos

Expected Results:
Whatsapp messages would not be able to be sent and/or received

Actual Results:
Whatsapp messages are received / sent after approximately two minutes

Version/Build:
All versions of the app

Configuration:
Default, VPN installed through app