I noticed an undocumented service running as root on a Huawei phone called hwnffserver. On the phone, there is also a client to interact with it (called hwnff).
I investigated a little bit on this service that is used to recover some information even from an unprivileged user.
In particular, you can obtain:
/sys/class/power_supply/battery/temp/sys/class/power_supply/battery/voltage_now- Mobile Signal Strength Info
- Touch screen type
- Camera type
- LCD Type
- EMMC flash type
- IMEI
- SerialNumber
- MAC address
- product model
- bootloader status