CrackLib-2.9.6

#### Beyond Linux® From Scratch - Version 2019-02-27

### Chapter 4. Security

- Prev

  ConsoleKit2-1.2.1

- Next

  cryptsetup-2.0.6

- Up
- Home

# CrackLib-2.9.6

## Introduction to CrackLib

The CrackLib package contains a library used to enforce strong passwords by comparing user selected passwords to words in chosen word lists.

This package is known to build and work properly using an LFS-8.4 platform.

### Package Information

- Download (HTTP): https://github.com/cracklib/cracklib/releases/download/cracklib-2.9.6/cracklib-2.9.6.tar.gz

- Download MD5 sum: c52f463585d85924b28cdc1e373ae06d

- Download size: 628 KB

- Estimated disk space required: 3.8 MB

- Estimated build time: less than 0.1 SBU

### Additional Downloads

- Recommended word list for English-speaking countries (size: 5.3 MB; md5sum: cae1257e3a9f95c917cc9dbbab852316): https://github.com/cracklib/cracklib/releases/download/cracklib-2.9.6/cracklib-words-2.9.6.gz

There are additional word lists available for download, e.g., from http://www.cotse.com/tools/wordlists.htm. CrackLib can utilize as many, or as few word lists you choose to install.

### Important

Users tend to base their passwords on regular words of the spoken language, and crackers know that. CrackLib is intended to filter out such bad passwords at the source using a dictionary created from word lists. To accomplish this, the word list(s) for use with CrackLib must be an exhaustive list of words and word-based keystroke combinations likely to be chosen by users of the system as (guessable) passwords.

The default word list recommended above for downloading mostly satisfies this role in English-speaking countries. In other situations, it may be necessary to download (or even create) additional word lists.

Note that word lists suitable for spell-checking are not usable as CrackLib word lists in countries with non-Latin based alphabets, because of “word-based keystroke combinations” that make bad passwords.

### CrackLib Dependencies

#### Optional

Python-2.7.15

User Notes: http://wiki.linuxfromscratch.org/blfs/wiki/cracklib

## Installation of CrackLib

Install CrackLib by running the following commands:

    sed -i '/skipping/d' util/packer.c &&

    ./configure --prefix=/usr    \
                --disable-static \
                --with-default-dict=/lib/cracklib/pw_dict &&
    make

Now, as the `root` user:

    make install                      &&
    mv -v /usr/lib/libcrack.so.* /lib &&
    ln -sfv ../../lib/$(readlink /usr/lib/libcrack.so) /usr/lib/libcrack.so

Issue the following commands as the `root` user to install the recommended word list and create the CrackLib dictionary. Other word lists (text based, one word per line) can also be used by simply installing them into `/usr/share/dict` and adding them to the create-cracklib-dict command.

    install -v -m644 -D    ../cracklib-words-2.9.6.gz \
                             /usr/share/dict/cracklib-words.gz     &&

    gunzip -v                /usr/share/dict/cracklib-words.gz     &&
    ln -v -sf cracklib-words /usr/share/dict/words                 &&
    echo $(hostname) >>      /usr/share/dict/cracklib-extra-words  &&
    install -v -m755 -d      /lib/cracklib                         &&

    create-cracklib-dict     /usr/share/dict/cracklib-words \
                             /usr/share/dict/cracklib-extra-words

If desired, check the proper operation of the library as an unprivileged user by issuing the following command:

    make test

### Important

If you are installing CrackLib after your LFS system has been completed and you have the Shadow package installed, you must reinstall Shadow-4.6 if you wish to provide strong password support on your system. If you are now going to install the Linux-PAM-1.3.0 package, you may disregard this note as Shadow will be reinstalled after the Linux-PAM installation.

## Command Explanations

sed -i '/skipping/d' util/packer.c: Remove a meaningless warning.

`--with-default-dict=/lib/cracklib/pw_dict`: This parameter forces the installation of the CrackLib dictionary to the `/lib` hierarchy.

`--disable-static`: This switch prevents installation of static versions of the libraries.

mv -v /usr/lib/libcrack.so.2* /lib and ln -v -sf ../../lib/libcrack.so.2.8.1 ...: These two commands move the `libcrack.so.2.9.0` library and associated symlink from `/usr/lib` to `/lib`, then recreates the `/usr/lib/libcrack.so` symlink pointing to the relocated file.

install -v -m644 -D ...: This command creates the `/usr/share/dict` directory (if it doesn't already exist) and installs the compressed word list there.

ln -v -s cracklib-words /usr/share/dict/words: The word list is linked to `/usr/share/dict/words` as historically, `words` is the primary word list in the `/usr/share/dict` directory. Omit this command if you already have a `/usr/share/dict/words` file installed on your system.

echo $(hostname) >>...: The value of hostname is echoed to a file called `cracklib-extra-words`. This extra file is intended to be a site specific list which includes easy to guess passwords such as company or department names, user names, product names, computer names, domain names, etc.

create-cracklib-dict ...: This command creates the CrackLib dictionary from the word lists. Modify the command to add any additional word lists you have installed.

## Contents

Installed Programs: cracklib-check, cracklib-format, cracklib-packer, cracklib-unpacker and create-cracklib-dict
Installed Libraries: libcrack.so and the _cracklibmodule.so Python module
Installed Directories: /lib/cracklib, /usr/share/dict and /usr/share/cracklib

### Short Descriptions

cracklib-check | is used to determine if a password is strong.
cracklib-format | is used to format text files (lowercases all words, removes control characters and sorts the lists).
cracklib-packer | creates a database with words read from standard input.
cracklib-unpacker | displays on standard output the database specified.
create-cracklib-dict | is used to create the CrackLib dictionary from the given word list(s).
`libcrack.so` | provides a fast dictionary lookup method for strong password enforcement.

Last updated on 2019-02-15 15:01:29 -0600

- Prev

  ConsoleKit2-1.2.1

- Next

  cryptsetup-2.0.6

- Up
- Home