Enforcing a strong password policy on your Ubuntu server is a critical step towards securing your system. This article will guide you through the process of implementing a password complexity policy using the
Enforcing a strong password policy on an Ubuntu server is possible by using the
pam_cracklib module. This module allows you to set password complexity requirements such as uppercase and lowercase letters, numbers, and special characters. By modifying the PAM configuration file, you can enforce these requirements and ensure that users create robust passwords that meet specific complexity criteria.
Password complexity policies are rules that enforce the creation of robust passwords by users. These policies can require a mix of uppercase and lowercase letters, numbers, special characters, and a minimum password length.
In Ubuntu, we can enforce these policies using Pluggable Authentication Modules (PAM). One such module is
pam_cracklib, which we’ll be using in this guide.
pam_cracklib module is a PAM module that checks password strength. It’s capable of enforcing password complexity requirements such as uppercase, lowercase, digits, and special characters.
Enforcing Password Complexity
Let’s start by enforcing password complexity on your Ubuntu server.
- Open the PAM configuration file
Open your terminal and type the following command to open the PAM configuration file in a text editor:
This command opens the file
sudo vi /etc/pam.d/common-password
vitext editor with root privileges.
- Modify the PAM configuration file
In the opened file, add the following line before the
This line sets the password requirements as follows:
password requisite pam_cracklib.so ucredit=-1 lcredit=-1 dcredit=-1 ocredit=-1
ucredit=-1: This enforces at least one upper-case character in the password.
lcredit=-1: This enforces at least one lower-case character in the password.
dcredit=-1: This enforces at least one digit in the password.
ocredit=-1: This enforces at least one special character in the password.
-1values to specify the minimum number of required characters for each category.
- Save and exit
Save the file and exit the text editor. With these changes, the
pam_cracklibmodule will enforce the specified password complexity policy. Users will be required to create passwords that meet these criteria.
Additional Password Requirements
If you want to further restrict the password requirements, you can use additional variables like
retries. For example:
password requisite pam_cracklib.so retry=3 minlen=10 difok=3 ucredit=-1 lcredit=-1 dcredit=-1 ocredit=-1
This line sets a maximum of three attempts to create an acceptable password (
retry=3), a minimum length of 10 characters (
minlen=10), and requires at least three characters different from the previous password (
Enforcing a strong password policy is an essential part of securing your Ubuntu server. By using the
pam_cracklib module, you can ensure that users create robust passwords that meet specific complexity requirements. For more information and examples, refer to the pam_cracklib man pages and the article on setting up stronger password policy rules in Linux.
Remember, while a strong password policy is a good start, it’s just one part of a comprehensive security strategy. Always keep your system updated, monitor for unusual activity, and educate your users about good security practices.
PAM stands for Pluggable Authentication Modules. It is a framework used in Linux systems to authenticate users and enforce security policies during the login process.
pam_cracklib module analyzes the strength of a password by checking for the presence of uppercase letters, lowercase letters, digits, and special characters. It enforces password complexity requirements by setting specific criteria that the password must meet.
Yes, you can customize the password complexity requirements by adjusting the values in the
pam_cracklib configuration line. For example, you can specify the minimum number of required characters for each category or set additional variables like
retries to further restrict the password requirements.
You can refer to the
pam_cracklib man pages for more detailed information. You can access them by visiting the pam_cracklib man pages online.
Enforcing a strong password policy is important, but it should be part of a comprehensive security strategy. Some additional measures you can take include keeping your system updated with security patches, monitoring for unusual activity, implementing firewall rules, and educating your users about good security practices.