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5.3.2.4 Ensure pam_pwhistory module is enabled

Information

The pam_pwhistory.so module saves the last passwords for each user in order to force password change history and keep the user from alternating between the same password too frequently.

This module does not work together with kerberos. In general, it does not make much sense to use this module in conjunction with NIS or LDAP, since the old passwords are stored on the local machine and are not available on another machine for password history checking.

Use of a unique, complex passwords helps to increase the time and resources required to compromise the password.

Solution

Run the following script to verify the pam_pwhistory.so line exists in a pam-auth-update profile:

# grep -P -- '\bpam_pwhistory\.so\b' /usr/share/pam-configs/*

Output should be similar to:

/usr/share/pam-configs/pwhistory: requisite pam_pwhistory.so remember=24 enforce_for_root use_authtok

- IF - similar output is returned:

Run the following command to update /etc/pam.d/common-password with the returned profile:

# pam-auth-update --enable {PROFILE_NAME}

Example:

# pam-auth-update --enable pwhistory

- IF - similar output is NOT returned:

Create a pwhistory profile in /usr/share/pam-configs/ with the following lines:

Name: pwhistory password history checking
Default: yes
Priority: 1024
Password-Type: Primary
Password: requisite pam_pwhistory.so remember=24 enforce_for_root use_authtok

Example Script:

#!/usr/bin/env bash

{
 arr=('Name: pwhistory password history checking' 'Default: yes' 'Priority: 1024' 'Password-Type: Primary' 'Password:' ' requisite pam_pwhistory.so remember=24 enforce_for_root use_authtok')
 printf '%s\n' "${arr[@]}" > /usr/share/pam-configs/pwhistory
}

Run the following command to update /etc/pam.d/common-password with the pwhistory profile:

# pam-auth-update --enable pwhistory

Note:

 - The name used for the file must be used in the pam-auth-update --enable command
 - The Name: line should be easily recognizable and understood
 - The Priority: Line is important as it effects the order of the lines in the /etc/pam.d/ files
 - If a site specific custom profile is being used in your environment to configure PAM that includes the configuration for the pam_pwhistory module, enable that module instead

If the audit identified a non-compliant or conflicting pam_pwhistory entry directly in /etc/pam.d/common-password, run the following:

 - Check for a conflicting pam_pwhistory entry in common-password :

# grep -P '^\s*password\s+' /etc/pam.d/common-password | grep pam_pwhistory

- IF - a non-compliant entry is found (e.g., missing use_authtok, incorrect remember count, or wrong control flag), remove it and re-enable via pam-auth-update :

# sed -i '/pam_pwhistory/d' /etc/pam.d/common-password
# pam-auth-update --enable pwhistory

- IF - no pam_pwhistory entry exists in common-password, no direct action is needed; the pam-auth-update --enable step above will populate the entry correctly.

Impact:

Without pam_pwhistory enabled, the system will not enforce password history, allowing users to reuse previous passwords immediately after a change.

See Also

https://workbench.cisecurity.org/benchmarks/27798

Item Details

Category: IDENTIFICATION AND AUTHENTICATION

References: 800-53|IA-5(1), CSCv7|4.4

Plugin: Unix

Control ID: 054823d44a43000c294bb34f153ad9c5aee27c35c4abdaf18dad032daf78268a