How it Works
The Permanently Disable Camera app and setup process make use of two Android concepts: device administrator apps and device owner apps.
Device administrator apps
A device administrator (see the Device Administration docs) is an app that has been given special privileges to set policies on the device. For example, the app might require you to set a password on your device or require that your password be a certain length. Starting in Android 4.0, a device administrator app can disable all cameras on the device. The main use case for device administrators is enterprise scenarios where an employer wants to set policies for devices used by employees.
You can view the device administrator apps on your device by going to the Settings app, tapping “Security”, then tapping “Device administrators”. Any app can request permissions to be a device administrator, even ones downloaded from the Play Store.
However, normal device administrator apps (ones that aren’t device owners) have a significant limitation: they are not permanent. On the “Device administrators” page in the Settings app, you can revoke the permissions from any device administrator app, which also allows you to uninstall the app. To a user, that means that the policies are required as long as the app is installed, but the user is always free to opt out of both the app and the policies.
All camera-disabling apps on the Play Store use the device administration API, so all of these apps can have their permissions revoked.
Device owner apps
Android 5.0 introduced the concept of device owner apps (see the Provisioning for Device Administration docs). A device owner app is a special type of app that is permanently installed on the device and cannot have its device administration permissions revoked. Any Android device can only have a single device owner app set. An app can give up its status as a device owner, but that is the only way that an app can stop being a device owner.
Device owner apps are intended for an enterprise setting where the Android device is provisioned by an IT department before its first use, so trying to set an app as a device owner on a normal consumer phone/tablet is tricky, but not impossible.
There are multiple ways to set a device owner:
- For production purposes, the device owner can be initialized either through NFC or through an activation code, and this must be done as the very first step when setting up the device. This approach requires that the device has never had an account set.
- For development purposes, the
dpm set-device-ownercommand can be used to set an app as the device owner. This approach requires that the device currently have no accounts and have no secondary users.
Since the production approach only works on devices that have never been used, the setup instructions use the development approach.
Disabling the camera
Disabling the camera is done using the setCameraDisabled method, which instructs the Android system to disable all cameras. When any app uses an API to access the camera, an exception will be thrown. Well-written apps can handle this case and either display an error message or degrade gracefully, although some apps may crash when attempting to use the camera.
How Permanently Disable Camera works
The app itself is simple: it requests to be a device administrator, then allows the user to disable the camera. It also detects whether it is a device owner to know which message to display, but the app has no way to make itself a device owner. The app does not, and will not, have any code for re-enabling the camera or clearing its status as device owner.
Since the app cannot set itself as a device owner, this website provides
instructions for how to do so using the
dpm set-device-owner approach with