The system must require at least eight characters be changed between the old and new passwords during a password change.

From Oracle Linux 6 Security Technical Implementation Guide

Associated with: CCI-000195

SV-65125r3_rule The system must require at least eight characters be changed between the old and new passwords during a password change.

Vulnerability discussion

Requiring a minimum number of different characters during password changes ensures that newly changed passwords should not resemble previously compromised ones. Note: Passwords which are changed on compromised systems will still be compromised.

Check content

To check how many characters must differ during a password change, run the following command: $ grep pam_cracklib /etc/pam.d/system-auth /etc/pam.d/password-auth The "difok" parameter will indicate how many characters must differ. The DoD requires eight characters differ during a password change. This would appear as "difok=8". If the “difok” parameter is not found or not set to the required value, this is a finding.

Fix text

The pam_cracklib module's "difok" parameter controls requirements for usage of different characters during a password change. Edit /etc/pam.d/system-auth and /etc/pam.d/password-auth adding "difok=[NUM]" after pam_cracklib.so to require differing characters when changing passwords, substituting [NUM] appropriately. The DoD requirement is “8”.

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