cis-ubuntu2004-v300-7-1-6

name	cis-ubuntu2004-v300-7-1-6
description	Ensure access to /etc/shadow- is configured
category	cis-iam
version	3.0.0
author	cyberstrike-official
tags	["cis","ubuntu","linux","ubuntu-20.04","file-permissions"]
cis_id	7.1.6
cis_benchmark	CIS Ubuntu Linux 20.04 LTS Benchmark v3.0.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

7.1.6 Ensure access to /etc/shadow- is configured (Automated)

Profile

• Level 1 - Server
• Level 1 - Workstation

Description

The /etc/shadow- file is used to store backup information about user accounts that is critical to the security of those accounts, such as the hashed password and other security information.

Rationale

It is critical to ensure that the /etc/shadow- file is protected from unauthorized access. Although it is protected by default, the file permissions could be changed either inadvertently or through malicious actions.

Impact

None

Audit Procedure

Command Line

Run the following command to verify /etc/shadow- is mode 640 or more restrictive, Uid is 0/root and Gid is 0/root or {GID}/shadow:

# stat -Lc 'Access: (%#a/%A) Uid: ( %u/ %U) Gid: ( %g/ %G)' /etc/shadow-

Example:

Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 42/ shadow)

Expected Result

Mode 640 or more restrictive, Uid 0/root, Gid 0/root or {GID}/shadow.

Remediation

Command Line

Run one of the following commands to set ownership of /etc/shadow- to root and group to either root or shadow:

# chown root:shadow /etc/shadow-
  -OR-
# chown root:root /etc/shadow-

Run the following command to remove excess permissions from /etc/shadow-:

# chmod u-x,g-wx,o-rwx /etc/shadow-

Default Value

Access: (0640/-rw-r-----) Uid: ( 0/ root) Gid: ( 42/ shadow)

References

1. NIST SP 800-53 Rev. 5: AC-3. MP-2

CIS Controls

Controls Version	Control	IG 1	IG 2	IG 3
v8	3.3 Configure Data Access Control Lists	X