Android ADB has root access but no SU binary

Question

I recently purchased an Android TV box that claimed to come "pre-rooted", however there is no SuperSU apk or SU binary installed. The interesting thing is that I am automatically logged in as the root user when I connect to the device with ADB (I can run reboot commands etc), which tells me that I have at least some level of root access. Can anyone explain how this might have been set up and how I can grant root privileges to my apps as well?

Answer 1

Two different sides of the card deck:

• apps need the su binary to be able to use "root powers"
• the ADB daemon does not; it gains root access while being started by the system in the corresponding mode

The latter is a simple setting in your device's build.prop file: ro.secure=1 (default on most devices) tells the system to start the daemon in "secure mode", i.e. not with root powers – while ro.secure=0 would turn off that security and run the daemon "as root" – which will be the case with your device.

Knowing that, the claim of being "pre-rooted" is partially true: you can use ADB to "push" the relevant files to your device. Four steps should do it:

adb shell "mount -o remount,rw /system"
adb push su /system/bin/su
adb push superuser.apk /system/app
adb reboot

After that reboot, your device should be "fully rooted" – and "root apps" should find everything they need to work, with you being in control of it via the superuser app.