cis-ubuntu1804-v220-1-1-1-7

name	cis-ubuntu1804-v220-1-1-1-7
description	Ensure mounting of udf filesystems is disabled
category	cis-storage
version	2.2.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-18.04","filesystem","udf","kernel-module"]
cis_id	1.1.1.7
cis_benchmark	CIS Ubuntu Linux 18.04 LTS Benchmark v2.2.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

Ensure mounting of udf filesystems is disabled

Profile

Level 2 - Server / Level 2 - Workstation, Assessment: Automated

Description

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.

Audit Procedure

Command Line

Run the following script to verify the udf module is disabled. If the module is available in the running kernel:

• An entry including /bin/true or /bin/false exists in a file within the /etc/modprobe.d/ directory
• The module is deny listed in a file within the /etc/modprobe.d/ directory
• The module is not loaded in the kernel

#!/usr/bin/env bash
{
    l_output="" l_output2="" l_output3="" l_dl=""
    l_mname="udf"
    l_mtype="fs"
    l_searchloc="/lib/modprobe.d/*.conf /usr/local/lib/modprobe.d/*.conf /run/modprobe.d/*.conf /etc/modprobe.d/*.conf"
    l_mpath="/lib/modules/**/kernel/$l_mtype"
    l_mpname="$(tr '-' ' ' <<< "$l_mname")"
    l_mndir="$(tr '-' '/' <<< "$l_mname")"
    module_loadable_chk()
    {
        l_loadable="$(modprobe -n -v "$l_mname")"
        [ "$(wc -l <<< )" -gt  ] && l_loadable=
         grep -Pq --  <<< ; 
            l_output=
        
            l_output2=
        
    }
    ()
    {
         ! lsmod | grep  > /dev/null 2>&1; 
            l_output=
        
            l_output2=
        
    }
    ()
    {
        l_dl=
         modprobe --showconfig | grep -Pq -- ; 
            l_output=
        
            l_output2=
        
    }
     l_mdir  ; 
         [ -d  ] && [ -n  ]; 
            l_output3=
            [  !=  ] && module_deny_chk
             [  =  ]; 
                module_loadable_chk
                module_loaded_chk
            
        
            l_output=
        
    
    [ -n  ] &&  -e 
     [ -z  ]; 
         -e 
    
         -e 
        [ -n  ] &&  -e 
    
}