cis-ubuntu2004-v300-5-2-3

name	cis-ubuntu2004-v300-5-2-3
description	Ensure sudo log file exists
category	cis-iam
version	3.0.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-20.04","sudo"]
cis_id	5.2.3
cis_benchmark	CIS Ubuntu Linux 20.04 LTS Benchmark v3.0.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

Ensure sudo log file exists (Automated)

Profile Applicability

• Level 1 - Server
• Level 1 - Workstation

Description

sudo can use a custom log file.

Rationale

A sudo log file simplifies auditing of sudo commands.

Impact

WARNING: Editing the sudo configuration incorrectly can cause sudo to stop functioning. Always use visudo to modify sudo configuration files.

Audit Procedure

Command Line

Run the following command to verify that sudo has a custom log file configured:

# grep -rPsi "^\h*Defaults\h+([^#]+,\h*)?logfile\h*=\h*(\"|\')?\H+(\"|\')?(,\h*\H+\h*)*\h*(#.*)?$" /etc/sudoers*

Verify the output matches:

Defaults logfile="/var/log/sudo.log"

Expected Result

Defaults logfile="/var/log/sudo.log"

Remediation

Command Line

Edit the file /etc/sudoers or a file in /etc/sudoers.d/ with visudo or visudo -f <PATH TO FILE> and add the following line: Example:

Defaults logfile="/var/log/sudo.log"

Note:

• sudo will read each file in /etc/sudoers.d, skipping file names that end in ~ or contain a . character to avoid causing problems with package manager or editor temporary/backup files.
• Files are parsed in sorted lexical order. That is, /etc/sudoers.d/01_first will be parsed before /etc/sudoers.d/10_second.
• Be aware that because the sorting is lexical, not numeric, /etc/sudoers.d/1_whoops would be loaded after /etc/sudoers.d/10_second.
• Using a consistent number of leading zeroes in the file names can be used to avoid such problems.

References

1. SUDO(8)
2. VISUDO(8)
3. sudoers(5)
4. NIST SP 800-53 Rev. 5: AU-3, AU-12

Additional Information:

visudo edits the sudoers file in a safe fashion, analogous to vipw(8). visudo locks the sudoers file against multiple simultaneous edits, provides basic sanity checks, and checks for parse errors. If the sudoers file is currently being edited you will receive a message to try again later.