1.1.1.3 Ensure mounting of udf filesystems is disabled

Information

The udf filesystem type is the universal disk format used to implement ISO/IEC 13346 and ECMA-167 specifications. This is an open vendor filesystem type for data storage on a broad range of media. This filesystem type is necessary to support writing DVDs and newer optical disc formats.

Rationale:

Removing support for unneeded filesystem types reduces the local attack surface of the system. If this filesystem type is not needed, disable it.

Impact:

Microsoft Azure requires the usage of udf.

udf should not be disabled on systems run on Microsoft Azure.

Solution

Run the following script to disable the udf filesystem:

#!/usr/bin/env bash

{
l_mname='udf' # set module name
# Check if the module exists on the system
if [ -z '$(modprobe -n -v '$l_mname' 2>&1 | grep -Pi -- 'h*modprobe:h+FATAL:h+Moduleh+$l_mnameh+noth+foundh+inh+directory')' ]; then
# Remediate loadable
l_loadable='$(modprobe -n -v '$l_mname')'
[ '$(wc -l <<< '$l_loadable')' -gt '1' ] && l_loadable='$(grep -P -- '(^h*install|b$l_mname)b' <<< '$l_loadable')'
if ! grep -Pq -- '^h*install /bin/(true|false)' <<< '$l_loadable'; then
echo -e ' - setting module: '$l_mname' to be not loadable'
echo -e 'install $l_mname /bin/false' >> /etc/modprobe.d/'$l_mname'.conf
fi
# Remediate loaded
if lsmod | grep '$l_mname' > /dev/null 2>&1; then
echo -e ' - unloading module '$l_mname''
modprobe -r '$l_mname'
fi
# Remediate deny list
if ! modprobe --showconfig | grep -Pq -- '^h*blacklisth+$l_mnameb'; then
echo -e ' - deny listing '$l_mname''
echo -e 'blacklist $l_mname' >> /etc/modprobe.d/'$l_mname'.conf
fi
else
echo -e ' - Nothing to remediate
- Module '$l_mname' doesn't exist on the system'
fi
}

See Also

https://workbench.cisecurity.org/files/4115

Item Details

Category: CONFIGURATION MANAGEMENT

References: 800-53|CM-6, 800-53|CM-7, CSCv7|9.2

Plugin: Unix

Control ID: d8bcee054f43db245b85f69fb195ee52b15423e4c5ce0873730fd881cf8c60d3