RHEL 8 must require the change of at least four character classes when passwords are changed.

Use of a complex password helps to increase the time and resources required to compromise the password. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks.

Password complexity is one factor of several that determines how long it takes to crack a password. The more complex the password, the greater the number of possible combinations that need to be tested before the password is compromised.

RHEL 8 utilizes "pwquality" as a mechanism to enforce password complexity. The "minclass" option sets the minimum number of required classes of characters for the new password (digits, uppercase, lowercase, others).

Verify the value of the "minclass" option with the following command:

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

/etc/security/pwquality.conf:minclass = 4

If the value of "minclass" is set to less than "4" or is commented out, this is a finding. If conflicting results are returned, this is a finding.

Configure the operating system to require the change of at least four character classes when passwords are changed by setting the "minclass" option.

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

minclass = 4

Remove any configurations that conflict with the above value.