cis-ubuntu1804-v220-1-8-7

name	cis-ubuntu1804-v220-1-8-7
description	Ensure GDM disabling automatic mounting of removable media is not overridden
category	cis-networking
version	2.2.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-18.04","gdm","gnome","automount","lockdown","dconf"]
cis_id	1.8.7
cis_benchmark	CIS Ubuntu Linux 18.04 LTS Benchmark v2.2.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

1.8.7 Ensure GDM disabling automatic mounting of removable media is not overridden (Automated)

Profile Applicability

• Level 1 - Server
• Level 2 - Workstation

Description

By default GNOME automatically mounts removable media when inserted as a convenience to the user.

By using the lockdown mode in dconf, you can prevent users from changing specific settings.

To lock down a dconf key or subpath, create a locks subdirectory in the keyfile directory. The files inside this directory contain a list of keys or subpaths to lock. Just as with the keyfiles, you may add any number of files to this directory.

Example Lock File:

# Lock desktop media-handling settings
/org/gnome/desktop/media-handling/automount
/org/gnome/desktop/media-handling/automount-open

Rationale

With automounting enabled anyone with physical access could attach a USB drive or disc and have its contents available in system even if they lacked permissions to mount it themselves.

Impact

The use of portable hard drives is very common for workstation users.

Audit Procedure

Command Line

Run the following script to verify disable automatic mounting is locked:

#!/usr/bin/env bash

{
    # Check if GNOME Desktop Manager is installed. If package isn't installed, recommendation is Not Applicable\n
    # determine system's package manager
    l_pkgoutput=""
    if command -v dpkg-query > /dev/null 2>&1; then
        l_pq="dpkg-query -s"
    elif command -v rpm > /dev/null 2>&1; then
        l_pq="rpm -q"
    fi
    # Check if GDM is installed
    l_pcl="gdm gdm3" # Space separated list of packages to check
    for l_pn in $l_pcl; do
        $l_pq "$l_pn" > /dev/null 2>&1 && l_pkgoutput=
    
    
     [ -n  ]; 
        l_output= l_output2=
        
        l_kfd=. 
        l_kfd2=. 
         [ -d  ];  
             grep -Piq  ; 
                l_output=
            
                l_output2=
            
        
            l_output2=
        
         [ -d  ];  
             grep -Piq  ; 
                l_output=
            
                l_output2=
            
        
            l_output2=
        
    
        l_output=
    
    
    [ -n  ] &&  -e 
     [ -z  ]; 
         -e 
    
         -e 
        [ -n  ] &&  -e 
    
}