RHEL 9 passwords must be created with a minimum of 15 characters.

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 9 uses "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, but they will not count toward the total "score" of "minlen". This will enable "minlen" to require a 15-character minimum.

The DoW minimum password requirement is 15 characters.

Verify that RHEL 9 enforces a minimum 15-character password length with the following command:

$ grep minlen /etc/security/pwquality.conf /etc/security/pwquality.conf.d/*.conf

minlen = 15

If the command does not return a "minlen" value of "15" or greater, does not return a line, or the line is commented out, this is a finding.

Configure RHEL 9 to enforce a minimum 15-character password length.

Add or update the following line in the "/etc/security/pwquality.conf" file or a configuration file in the "/etc/security/pwquality.conf.d/" directory to contain the "minlen" parameter:

minlen = 15