Vulnerability Discussion

The shorter the password, the lower the number of possible combinations that need to be tested before the password is compromised.

Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks. Password length is one factor of several that helps to determine strength and how long it takes to crack a password. Use of more characters in a password helps to increase exponentially the time and/or resources required to compromise the password.

RHEL 8 utilizes "pwquality" as a mechanism to enforce password complexity. Configurations are set in the "etc/security/pwquality.conf" file.

The "minlen", sometimes noted as minimum length, acts as a "score" of complexity based on the credit components of the "pwquality" module. By setting the credit components to a negative value, not only will those components be required, they will not count towards the total "score" of "minlen". This will enable "minlen" to require a 15-character minimum.

The DoD minimum password requirement is 15 characters.

Check

Verify the operating system enforces a minimum 15-character password length. The "minlen" option sets the minimum number of characters in a new password.

Check for the value of the "minlen" option with the following command:

$ sudo grep -r minlen /etc/security/pwquality.conf*

/etc/security/pwquality.conf:minlen = 15

If the command does not return a "minlen" value of 15 or greater, this is a finding.
If conflicting results are returned, this is a finding.

Fix

Configure operating system to enforce a minimum 15-character password length.

Add the following line to "/etc/security/pwquality.conf" (or modify the line to have the required value):

minlen = 15