cis-ubuntu1804-v220-4-4-3

DevOps & Security

Ensure password reuse is limited

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Source SKILL.md: https://github.com/CyberStrikeus/CyberStrike/blob/HEAD/.cyberstrike/skill/CIS_benchmarks/Operating_Systems/Ubuntu/CIS_Ubuntu_Linux_18.04_LTS_Benchmark_v2.2.0/cis-ubuntu1804-v220-4-4-3/SKILL.md

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CIS Ubuntu Linux 18.04 LTS Benchmark v2.2.0 - Control 4.4.3

Profile Applicability

Level 1 - Server
Level 1 - Workstation

Description

The /etc/security/opasswd file stores the users' old passwords and can be checked to ensure that users are not recycling recent passwords.

remember = 24 - Number of old passwords to remember. The user is not able to reuse any of the most recent remember passwords.

Rationale

Forcing users not to reuse their past 24 passwords make it less likely that an attacker will be able to guess the password. Note that these change only apply to accounts configured on the local system.

Audit Procedure

Command Line

Run the following command to verify password reuse is limited:

grep -Pi '^\h*password\h+(requisite|required|sufficient)\h+pam_unix\.so\h+([^#\n\r]+\h+)?remember=([5-9]|[1-9][0-9]+)\b' /etc/pam.d/common-password

Expected Result

The remember parameter should be set to 24 or more.

Remediation

Command Line

Edit /etc/pam.d/common-password and add or modify the pam_unix.so or pam_pwhistory.so line to include remember=24:

password required pam_pwhistory.so remember=24

OR ensure pam_unix.so includes remember=24:

password [success=1 default=ignore] pam_unix.so obscure use_authtok try_first_pass sha512 remember=24

References

NIST SP 800-53 Rev. 5: IA-5(1)

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