cis-ubuntu1604-v200-5-3-10

name	cis-ubuntu1604-v200-5-3-10
description	Ensure SSH HostbasedAuthentication is disabled
category	cis-networking
version	2.0.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-16.04","ssh","remote-access"]
cis_id	5.3.10
cis_benchmark	CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0 - Control 5.3.10

Description

The HostbasedAuthentication parameter specifies if authentication is allowed through trusted hosts via the user of .rhosts, or /etc/hosts.equiv, along with successful public key client host authentication. This option only applies to SSH Protocol Version 2.

Rationale

Even though the .rhosts files are ineffective if support is disabled in /etc/pam.conf, disabling the ability to use .rhosts files in SSH provides an additional layer of protection.

Audit Procedure

Command Line

Run the following command and verify that output matches:

sshd -T -C user=root -C host="$(hostname)" -C addr="$(grep $(hostname) /etc/hosts | awk '{print $1}')" | grep hostbasedauthentication

Expected Result

hostbasedauthentication no

Run the following command and verify the output matches:

grep -Ei '^\s*HostbasedAuthentication\s+yes' /etc/ssh/sshd_config

Nothing should be returned.

Remediation

Command Line

Edit the /etc/ssh/sshd_config file to set the parameter as follows:

HostbasedAuthentication no

Default Value

HostbasedAuthentication no

References

1. SSHD_CONFIG(5)

CIS Controls

Version 7

16.3 Require Multi-factor Authentication - Require multi-factor authentication for all user accounts, on all systems, whether managed onsite or by a third-party provider.

Profile Applicability

• Level 1 - Server
• Level 1 - Workstation

Assessment Status

Automated