cis-ubuntu1204-v110-10-4

name	cis-ubuntu1204-v110-10-4
description	Set Default umask for Users
category	cis-os-hardening
version	1.1.0
author	cyberstrike-official
tags	["cis","ubuntu",12.04,"linux","umask","file-permissions","user-environment"]
cis_id	10.4
cis_benchmark	CIS Ubuntu 12.04 LTS Server Benchmark v1.1.0
tech_stack	["ubuntu","linux"]
cwe_ids	[]
chains_with	[]
prerequisites	[]
severity_boost	{}

10.4 Set Default umask for Users (Scored)

Profile Applicability

• Level 1

Description

The default umask determines the permissions of files created by users. The user creating the file has the discretion of making their files and directories readable by others via the chmod command. Users who wish to allow their files and directories to be readable by others by default may choose a different default umask by inserting the umask command into the standard shell configuration files (.profile, .bashrc, etc.) in their home directories.

Rationale

Setting a very secure default value for umask ensures that users make a conscious choice about their file permissions. A default umask setting of 077 causes files and directories created by users to not be readable by any other user on the system. A umask of 027 would make files and directories readable by users in the same Unix group, while a umask of 022 would make files readable by every user on the system.

Note: The directives in this section apply to bash and shell. If other shells are supported on the system, it is recommended that their configuration files also are checked.

Audit Procedure

Using Command Line

grep "^UMASK" /etc/login.defs

Expected Result

UMASK 077

Remediation

Using Command Line

Edit the /etc/login.defs file (and the appropriate files for any other shell supported on your system as necessary) and set the UMASK parameter as shown:

# Edit /etc/login.defs and set:
UMASK 077

Default Value

UMASK 022

References

• CIS Ubuntu 12.04 LTS Server Benchmark v1.1.0

Profile

Level 1 - Scored