RHEL 8 must disable mounting of cramfs.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-230498	RHEL-08-040025	SV-230498r627750_rule		Low

Description
It is detrimental for operating systems to provide, or install by default, functionality exceeding requirements or mission objectives. These unnecessary capabilities or services are often overlooked and therefore may remain unsecured. They increase the risk to the platform by providing additional attack vectors. Removing support for unneeded filesystem types reduces the local attack surface of the server. Compressed ROM/RAM file system (or cramfs) is a read-only file system designed for simplicity and space-efficiency. It is mainly used in embedded and small-footprint systems.

Description

It is detrimental for operating systems to provide, or install by default, functionality exceeding requirements or mission objectives. These unnecessary capabilities or services are often overlooked and therefore may remain unsecured. They increase the risk to the platform by providing additional attack vectors. Removing support for unneeded filesystem types reduces the local attack surface of the server. Compressed ROM/RAM file system (or cramfs) is a read-only file system designed for simplicity and space-efficiency. It is mainly used in embedded and small-footprint systems.

STIG	Date
Red Hat Enterprise Linux 8 Security Technical Implementation Guide	2021-06-14

Details

Check Text ( C-33167r568240_chk )
Verify the operating system disables the ability to load the cramfs kernel module. $ sudo grep -ri cramfs /etc/modprobe.d/* \| grep -i "/bin/true" install cramfs /bin/true If the command does not return any output, or the line is commented out, and use of the cramfs protocol is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding. Verify the operating system disables the ability to use the cramfs kernel module. Check to see if the cramfs kernel module is disabled with the following command: $ sudo grep -ri cramfs /etc/modprobe.d/* \| grep -i "blacklist" blacklist cramfs If the command does not return any output or the output is not "blacklist cramfs", and use of the cramfs kernel module is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Check Text ( C-33167r568240_chk )

Verify the operating system disables the ability to load the cramfs kernel module.

$ sudo grep -ri cramfs /etc/modprobe.d/* | grep -i "/bin/true"

install cramfs /bin/true

If the command does not return any output, or the line is commented out, and use of the cramfs protocol is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Verify the operating system disables the ability to use the cramfs kernel module.

Check to see if the cramfs kernel module is disabled with the following command:

$ sudo grep -ri cramfs /etc/modprobe.d/* | grep -i "blacklist"

blacklist cramfs

If the command does not return any output or the output is not "blacklist cramfs", and use of the cramfs kernel module is not documented with the Information System Security Officer (ISSO) as an operational requirement, this is a finding.

Fix Text (F-33142r568241_fix)
Configure the operating system to disable the ability to use the cramfs kernel module. Add or update the following lines in the file "/etc/modprobe.d/blacklist.conf": install cramfs /bin/true blacklist cramfs Reboot the system for the settings to take effect.