Critical security flaw: User should not be root when the Dockerfile completes

[philipjonsen]

DESCRIPTION:

Switching to the root USER opens up certain security risks if an attacker gets access to the container. In order to mitigate this, switch back to a non privileged user after running the commands you need as root.

BAD PRACTICE:

FROM debian:buster
USER root
RUN ...

RECOMMENDED:

FROM debian:buster
USER root
RUN ...
USER guest

Last USER should not be root on these places:

hive/blob/master/clients/besu/Dockerfile#L6-L6
hive/blob/master/clients/openethereum/Dockerfile#L11-L11
hive/blob/master/clients/teku-vc/Dockerfile#L6-L6