Beyond Linux® From Scratch (System V Edition) - Version r11.2-1152

Chapter 4. Security

libpwquality-1.4.5

Introduction to libpwquality

The libpwquality package provides common functions for password quality checking and also scoring them based on their apparent randomness. The library also provides a function for generating random passwords with good pronounceability.

[Note]

Note

Development versions of BLFS may not build or run some packages properly if dependencies have been updated since the most recent stable versions of the book.

Package Information

libpwquality Dependencies

Required

CrackLib-2.9.8

Recommended

Linux-PAM-1.5.2

User Notes: https://wiki.linuxfromscratch.org/blfs/wiki/libpwquality

Installation of libpwquality

Install libpwquality by running the following commands: 

./configure --prefix=/usr                      \
            --disable-static                   \
            --with-securedir=/usr/lib/security \
            --with-python-binary=python3       &&
make

This package does not come with a test suite.

Now, as the root user: 

make install

Command Explanations

--with-python-binary=python3: This parameter gives the location of the Python binary. The default is python, and requires Python-2.7.18.

Configuring libpwquality

libpwquality is intended to be a functional replacement for the now-obsolete pam_cracklib.so PAM module. To configure the system to use the pam_pwquality module, execute the following commands as the root user: 

mv /etc/pam.d/system-password{,.orig} &&
cat > /etc/pam.d/system-password << "EOF"
# Begin /etc/pam.d/system-password

# check new passwords for strength (man pam_pwquality)
password  required    pam_pwquality.so   authtok_type=UNIX retry=1 difok=1 \
                                         minlen=8 dcredit=0 ucredit=0 \
                                         lcredit=0 ocredit=0 minclass=1 \
                                         maxrepeat=0 maxsequence=0 \
                                         maxclassrepeat=0 gecoscheck=0 \
                                         dictcheck=1 usercheck=1 \
                                         enforcing=1 badwords="" \
                                         dictpath=/usr/lib/cracklib/pw_dict
# use sha512 hash for encryption, use shadow, and use the
# authentication token (chosen password) set by pam_pwquality
# above (or any previous modules). Also set the number of crypt rounds
# to the value used in shadow.
password  required    pam_unix.so        sha512 shadow use_authtok \
                                         rounds=500000

# End /etc/pam.d/system-password
EOF

Contents

Installed Programs: pwscore and pwmake
Installed Libraries: pam_pwquality.so and libpwquality.so
Installed Directories: None

Short Descriptions

pwmake

is a simple configurable tool for generating random and relatively easily pronounceable passwords

pwscore

is a simple tool for checking quality of a password

libpwquality.so

contains API functions for checking the password quality

pam_pwquality.so

is a Linux PAM module used to perform password quality checking