cis-ubuntu2004-v300-5-1-22

name	cis-ubuntu2004-v300-5-1-22
description	Ensure sshd UsePAM is enabled
category	cis-networking
version	3.0.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-20.04","ssh"]
cis_id	5.1.22
cis_benchmark	CIS Ubuntu Linux 20.04 LTS Benchmark v3.0.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

Ensure sshd UsePAM is enabled (Automated)

Profile Applicability

• Level 1 - Server
• Level 1 - Workstation

Description

The UsePAM directive enables the Pluggable Authentication Module (PAM) interface. If set to yes this will enable PAM authentication using ChallengeResponseAuthentication and PasswordAuthentication directives in addition to PAM account and session module processing for all authentication types.

Rationale

When usePAM is set to yes, PAM runs through account and session types properly. This is important if you want to restrict access to services based off of IP, time or other factors of the account. Additionally, you can make sure users inherit certain environment variables on login or disallow access to the server.

Audit Procedure

Command Line

Run the following command to verify UsePAM is set to yes:

# sshd -T | grep usepam

usepam yes

Expected Result

usepam yes

Remediation

Command Line

Edit the /etc/ssh/sshd_config file to set the UsePAM parameter to yes above any Include entries as follows:

UsePAM yes

Note: First occurrence of an option takes precedence. If Include locations are enabled, used, and order of precedence is understood in your environment, the entry may be created in a file in Include location.

Default Value

UsePAM yes

References

1. SSHD_CONFIG(5)
2. NIST SP 800-53 Rev. 5: CM-1, CM-2, CM-6, CM-7, IA-5
3. SSHD(8)

CIS Controls

v8 - 5.2 Use Unique Passwords Use unique passwords for all enterprise assets. Best practice implementation includes, at a minimum, an 8-character password for accounts using MFA and a 14-character password for accounts not using MFA.

v7 - 4.4 Use Unique Passwords Where multi-factor authentication is not supported (such as local administrator, root, or service accounts), accounts will use passwords that are unique to that system.

MITRE ATT&CK Mappings: T1021, T1021.004 | TA0001 | M1035