cis-ubuntu1804-v220-3-3-2

name	cis-ubuntu1804-v220-3-3-2
description	Ensure packet redirect sending is disabled
category	cis-networking
version	2.2.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-18.04","networking","kernel-parameter"]
cis_id	3.3.2
cis_benchmark	CIS Ubuntu Linux 18.04 LTS Benchmark v2.2.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

CIS Ubuntu Linux 18.04 LTS Benchmark v2.2.0 - Control 3.3.2

Description

ICMP Redirects are used to send routing information to other hosts. As a host itself does not act as a router (in a host only configuration), there is no need to send redirects.

Rationale

An attacker could use a compromised host to send invalid ICMP redirects to other router devices in an attempt to corrupt routing and have users access a system set up by the attacker as opposed to a valid system.

Impact

None.

Audit Procedure

Command Line

Run the following script to verify packet redirect sending is disabled:

#!/usr/bin/bash
{
  l_output="" l_output2=""
  a_parlist=("net.ipv4.conf.all.send_redirects=0" "net.ipv4.conf.default.send_redirects=0")

  for l_kpe in "${a_parlist[@]}"; do
    l_kpname="$(awk -F= '{print $1}' <<< "$l_kpe")"
    l_kpvalue="$(awk -F= '{print $2}' <<< "$l_kpe")"
    l_krp="$(sysctl "$l_kpname" | awk -F= '{print $2}' | xargs)"
    if [ "$l_krp" = "$l_kpvalue" ]; then
      l_output="$l_output\n - \"$l_kpname\" is correctly set to \"$l_krp\" in the running configuration"
    else
      l_output2="$l_output2\n - \"$l_kpname\" is incorrectly set to \"$l_krp\" and should have a value of: \"$l_kpvalue\""
    
  

   [ -z  ]; 
     -e 
  
     -e 
    [ -n  ] &&  -e 
  
}