The CrackLib package contains a library used to enforce strong passwords by comparing user selected passwords to words in chosen word lists.
Download (HTTP): http://prdownloads.sourceforge.net/cracklib/cracklib-2.8.3.tar.gz
Download MD5 sum: 13f82f75b892cbd0ba7cb9069e307006
Download size: 480 KB
Estimated disk space required: 27.6 MB
Estimated build time: 0.1 SBU
Recommended word list for English-speaking countries (size: 4.4 MB; md5sum: d18e670e5df560a8745e1b4dede8f84f): http://prdownloads.sourceforge.net/cracklib/cracklib-words.gz
Required patch to create a library used with the Heimdal Kerberos 5 package: http://www.linuxfromscratch.org/blfs/downloads/6.1/cracklib-2.8.3-heimdal-1.patch
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]](../images/important.png)
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.
If desired, apply the Heimdal patch (note that with this patch the original library is not affected; this patch only creates an additional library used by the Heimdal password-checking routines):
patch -Np1 -i ../cracklib-2.8.3-heimdal-1.patch
Install CrackLib by running the following commands:
./configure --prefix=/usr --datadir=/lib && make
Now, as the root user:
make install && mv -v /usr/lib/libcrack.so.2* /lib && ln -v -sf ../../lib/libcrack.so.2.8.0 /usr/lib/libcrack.so
The following commands can be used to install the recommended word list. Other word lists (text based, one word per line) can also be used by simply installing them into /usr/share/dict.
install -v -m644 -D ../cracklib-words.gz \
/usr/share/dict/cracklib-words.gz &&
gunzip -v /usr/share/dict/cracklib-words.gz &&
ln -v -s cracklib-words /usr/share/dict/words &&
echo $(hostname) >>/usr/share/dict/cracklib-extra-words &&
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 using the tests included with the package:
make test
--datadir=/lib: This parameter forces the installation of the CrackLib dictionary to the /lib hierarchy.
mv -v /usr/lib/libcrack.so.2* /lib and ln -v -sf ../../lib/libcrack.so.2.8.0 ...: These two commands move the libcrack.so.2.8.0 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's 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.
Last updated on 2005-08-14 15:03:38 -0600