System Policy deny of access to /dev/rdisk0 or /dev/disk0

[br0xpl]

• iOS version:11.2.5
• iDevice model:iPhone9,3
• electra version:1.0.1 (VFS)

Even having root and using the jailbreakd_client to get all entitlements I still cannot access the /dev/rdisk0 nor /dev/disk0. The message in dmesg says:

Sandbox: dd(4042) System Policy: deny(1) file-read-data /dev/rdisk0

No matter if I use dd, cat or even my own compiled and entiteled binary.

Anyone can shed some light how can I get such access. Is it something that only can be done by using the task_for_pid(0) process (like jailbreakd itself)? How could I do this most easily?

Thanks in advance for your help.