Troubleshooting pwquality_pam.so: Man Page Examples Saying It's Not Behaving

Introduction

The pwquality module is a Pluggable Authentication Module (PAM) used to enforce password complexity on Linux systems. The pwquality_pam.so library is responsible for managing the module's behavior. However, sometimes this module may not behave as expected, and the man page examples may not provide a clear solution. This article will cover the key concepts and troubleshooting steps for the pwquality_pam.so module.

Key Concepts

• PAM: Pluggable Authentication Modules is a system of libraries that handle authentication tasks in Linux systems.
• pwquality: A PAM module that enforces password complexity rules.
• pwquality_pam.so: The library responsible for managing the behavior of the pwquality module.

Troubleshooting Steps

Step 1: Verify the PAM Configuration

The first step in troubleshooting the pwquality_pam.so module is to verify the PAM configuration. Check the /etc/pam.d/common-password file to ensure that the pwquality module is included and configured correctly.

Step 2: Check the Man Page Examples

The man page for the pwquality module provides examples of how to configure the module. Check the man page for any examples that match your system's configuration.

For example, the following man page excerpt shows how to configure the module to require passwords with a minimum length of 14 bytes and two digits:

#%PAM-1.0
#
# The pam_pwquality module does provide the possibility to check the quality
# of a password locally by using the pwquality library.
#
# This library implements the password complexity checking policy defined in
# the Linux-PAM specification.
#
# The following minimum requirements are checked:
#
# 1) The new password must be different from the old one.
#
# 2) The new password must be at least n characters long.
#
# 3) The new password must contain at least n' digits.
#
# 4) The new password must contain at least n' uppercase letters.
#
# 5) The new password must contain at least n' lowercase letters.
#
# 6) The new password must contain at least n' other characters.
#
# See the pwquality(8) man page for details.
#
# The following configuration lines are valid:
#
# password    requisite     pam_pwquality.so retry=3 authtok_type=
# password    requisite     pam_pwquality.so retry=3 authtok_type=
# password    requisite     pam_pwquality.so retry=3 authtok_type=
# password    requisite     pam_pwquality.so retry=3 authtok_type= \
#             minclass=3 minlen=14 maxrepeat=3 dcredit=-1 ucredit=-1 lcredit=-1 ocredit=-1
# password    requisite     pam_pwquality.so retry=3 authtok_type= \
#             minclass=3 difok=3 reject_username enforce_for_root
# password    requisite     pam_pwquality.so retry=3 authtok_type= \
#             minclass=3 maxsequence=3 reject_username enforce_for_root
# password    requisite     pam_pwquality.so retry=3 authtok_type= \
#             minclass=3 maxsequence=3 dcredit=1 ucredit=1 lcredit=1 ocredit=1 enforce_for_root
# password    requisite     pam_pwquality.so retry=3 authtok_type= \
#             minclass=3 maxsequence=3 dcredit=1 ucredit=1 lcredit=1 ocredit=1 \
#             reject_username enforce_for_root
# password    requisite     pam_pwquality.so retry=3 authtok_type= \
#             minclass=3 maxsequence=3 dcredit=1 ucredit=1 lcredit=1 ocredit=1 \
#             reject_username enforce_for_root use_authtok

Step 3: Check the System Logs

If the pwquality module is still not behaving as expected, check the system logs for any error messages related to the module. The logs can be found in the /var/log directory.

Step 4: Debug the Module

If the previous steps have not resolved the issue, you can debug the module using the pamtester command. This command allows you to test PAM modules and configurations without actually authenticating a user.

For example, the following command tests the pwquality module with a password that does not meet the complexity requirements:

$ pamtester common-password user authenticate password

Conclusion

Troubleshooting the pwquality_pam.so module can be a complex task, but by following the steps outlined in this article, you can identify and resolve most issues. Remember to verify the PAM configuration, check the man page examples, examine the system logs, and debug the module using the pamtester command.

References

• Linux-PAM Specification
• pwquality(8) Man Page
• pamtester(8) Man Page

Summary

• Verify the PAM configuration.
• Check the man page examples.
• Examine the system logs.
• Debug the module using the pamtester command.

• References:
• Linux-PAM Specification
• pwquality(8) Man Page
• pamtester(8) Man Page