cis-ubuntu1604-v200-6-1-14

name	cis-ubuntu1604-v200-6-1-14
description	Audit SGID executables
category	cis-storage
version	2.0.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-16.04","file-permissions","maintenance"]
cis_id	6.1.14
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 - 6.1.14

Profile Applicability

• Level 1 - Server
• Level 1 - Workstation

Description

The owner of a file can set the file's permissions to run with the owner's or group's permissions, even if the user running the program is not the owner or a member of the group. The most common reason for a SGID program is to enable users to perform functions (such as changing their password) that require root privileges.

Rationale

There are valid reasons for SGID programs, but it is important to identify and review such programs to ensure they are legitimate. Review the files returned by the action in the audit section and check to see if system binaries have a different md5 checksum than what from the package. This is an indication that the binary may have been replaced.

Audit Procedure

Command Line

Run the following command to list SGID files:

df --local -P | awk '{if (NR!=1) print $6}' | xargs -I '{}' find '{}' -xdev -type f -perm -2000

The command above only searches local filesystems, there may still be compromised items on network mounted partitions. Additionally the --local option to df is not universal to all versions, it can be omitted to search all filesystems on a system including network mounted filesystems or the following command can be run manually for each partition:

find <partition> -xdev -type f -perm -2000

Expected Result

Review the list of SGID files and ensure no rogue programs have been introduced.

Remediation

Command Line

Ensure that no rogue SGID programs have been introduced into the system. Review the files returned by the action in the Audit section and confirm the integrity of these binaries.

Default Value

Not applicable.

References

1. CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0

CIS Controls

Controls Version	Control
v7	5.1 Establish Secure Configurations Maintain documented, standard security configuration standards for all authorized operating systems and software.