cyberstrikeus 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