cis-ubuntu1804-v220-4-5-1-2

DevOps & Security

Ensure password expiration is 365 days or less

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CIS Ubuntu Linux 18.04 LTS Benchmark v2.2.0 - Control 4.5.1.2

Profile Applicability

Level 1 - Server
Level 1 - Workstation

Description

The PASS_MAX_DAYS parameter in /etc/login.defs allows an administrator to force passwords to expire once they reach a defined age. It is recommended that the PASS_MAX_DAYS parameter be set to less than or equal to 365 days.

Rationale

The window of opportunity for an attacker to leverage compromised credentials or successfully compromise credentials via an online brute force attack is limited by the age of the password. Therefore, reducing the maximum age of a password also reduces an attacker's window of opportunity.

Audit Procedure

Command Line

Run the following command and verify PASS_MAX_DAYS is 365 or less:

grep -Pi '^\h*PASS_MAX_DAYS\h+\d+\b' /etc/login.defs

Verify all users with a password have the maximum days set:

awk -F: '($2~/^\$.+\$/){print $1 " " $5}' /etc/shadow

Expected Result

PASS_MAX_DAYS should be 365 or less, but not 0 in /etc/login.defs.

No user should have a value greater than 365 in field 5 of /etc/shadow.

Remediation

Command Line

Set the PASS_MAX_DAYS parameter to conform to site policy in /etc/login.defs:

PASS_MAX_DAYS 365

Modify user parameters for all users with a password set to match:

chage --maxdays 365 <user>

Default Value

PASS_MAX_DAYS 99999

References

NIST SP 800-53 Rev. 5: IA-5

CIS Controls

v8 - 5.2 Use Unique Passwords - Use unique passwords for all enterprise assets.

v7 - 4.4 Use Unique Passwords.

Profile Applicability

Level 1 - Server
Level 1 - Workstation

Assessment Status

Automated