source: postlfs/security/cracklib.xml@ 42ddc30

<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
   "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
  <!ENTITY % general-entities SYSTEM "../../general.ent">
  %general-entities;

  <!ENTITY cracklib-url "https://github.com/cracklib/cracklib/releases/download">

  <!ENTITY cracklib-download-http "&cracklib-url;/v&cracklib-version;/cracklib-&cracklib-version;.tar.xz">
  <!ENTITY cracklib-download-ftp  " ">
  <!ENTITY cracklib-md5sum        "a6dfb1766aab43a54e1cbd78abf0a20a">
  <!ENTITY cracklib-size          "452 KB">
  <!ENTITY cracklib-buildsize     "6.8 MB">
  <!ENTITY cracklib-time          "0.1 SBU">

  <!ENTITY crackdict-download     "&cracklib-url;/v&cracklib-version;/cracklib-words-&cracklib-version;.xz">
  <!ENTITY crackdict-size         "4.0 MB">
  <!ENTITY crackdict-md5sum       "f27804022dbf2682a7f7c353317f9a53">
]>

<sect1 id="cracklib" xreflabel="CrackLib-&cracklib-version;">
  <?dbhtml filename="cracklib.html"?>


  <title>CrackLib-&cracklib-version;</title>

  <indexterm zone="cracklib">
    <primary sortas="a-CrackLib">CrackLib</primary>
  </indexterm>

  <sect2 role="package">
    <title>Introduction to CrackLib</title>

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

    &lfs113_checked;

    <bridgehead renderas="sect3">Package Information</bridgehead>
    <itemizedlist spacing="compact">
      <listitem>
        <para>
          Download (HTTP): <ulink url="&cracklib-download-http;"/>
        </para>
      </listitem>
      <listitem>
        <para>
          Download (FTP): <ulink url="&cracklib-download-ftp;"/>
        </para>
      </listitem>
      <listitem>
        <para>
          Download MD5 sum: &cracklib-md5sum;
        </para>
      </listitem>
      <listitem>
        <para>
          Download size: &cracklib-size;
        </para>
      </listitem>
      <listitem>
        <para>
          Estimated disk space required: &cracklib-buildsize;
        </para>
      </listitem>
      <listitem>
        <para>
          Estimated build time: &cracklib-time;
        </para>
      </listitem>
    </itemizedlist>

    <bridgehead renderas="sect3">Additional Downloads</bridgehead>
    <itemizedlist spacing="compact">
      <para>Recommended word list for English-speaking countries:</para>
      <listitem>
        <para>
          Download (HTTP): <ulink url="&crackdict-download;"/>
        </para>
      </listitem>
      <listitem>
        <para>
           Download MD5 sum: &crackdict-md5sum;
        </para>
      </listitem>
      <listitem>
        <para>
            Download size:  &crackdict-size;; 
        </para>
      </listitem>
    </itemizedlist>

    <para>
      There are additional word lists available for download, e.g., from
      <ulink url="https://wiki.skullsecurity.org/index.php/Passwords"/>.
      <application>CrackLib</application> can utilize as many, or as few word
      lists you choose to install.
    </para>

    <important>
      <para>
        Users tend to base their passwords on regular words of the spoken
        language, and crackers know that. <application>CrackLib</application>
        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 <application>CrackLib</application> must be an
        exhaustive list of words and word-based keystroke combinations likely
        to be chosen by users of the system as (guessable) passwords.
      </para>

      <para>
        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.
      </para>

      <para>
        Note that word lists suitable for spell-checking are not usable
        as <application>CrackLib</application> word lists in countries with
        non-Latin based alphabets, because of <quote>word-based keystroke
        combinations</quote> that make bad passwords.
      </para>
    </important>

  </sect2>

  <sect2 role="installation">
    <title>Installation of CrackLib</title>

    <para>
      Install <application>CrackLib</application> by running the following
      commands:
    </para>

<screen><userinput>autoreconf -fiv &amp;&amp;

PYTHON=python3               \
./configure --prefix=/usr    \
            --disable-static \
            --with-default-dict=/usr/lib/cracklib/pw_dict &amp;&amp;
make</userinput></screen>

    <para>
      Now, as the <systemitem class="username">root</systemitem> user:
    </para>

<screen role="root"><userinput>make install</userinput></screen>

    <para>
      Issue the following commands as the
      <systemitem class="username">root</systemitem> user to install the
      recommended word list and create the <application>CrackLib</application>
      dictionary. Other word lists (text based, one word per line) can also be
      used by simply installing them into
      <filename class="directory">/usr/share/dict</filename> and adding them
      to the <command>create-cracklib-dict</command> command.
    </para>

<screen role="root"><userinput>install -v -m644 -D    ../cracklib-words-&cracklib-version;.xz \
                         /usr/share/dict/cracklib-words.xz    &amp;&amp;

unxz -v                  /usr/share/dict/cracklib-words.xz    &amp;&amp;
ln -v -sf cracklib-words /usr/share/dict/words                &amp;&amp;
echo $(hostname) >>      /usr/share/dict/cracklib-extra-words &amp;&amp;
install -v -m755 -d      /usr/lib/cracklib                    &amp;&amp;

create-cracklib-dict     /usr/share/dict/cracklib-words \
                         /usr/share/dict/cracklib-extra-words</userinput></screen>

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

<screen remap="test"><userinput>make test</userinput></screen>

    <important>
      <para>
        If you are installing <application>CrackLib</application> after
        your LFS system has been completed and you have the
        <application>Shadow</application> package installed, you must
        reinstall <xref linkend="shadow"/> if you wish to provide strong
        password support on your system. If you are now going to install the
        <xref linkend="linux-pam"/> package, you may disregard this note as
        <application>Shadow</application> will be reinstalled after the
        <application>Linux-PAM</application> installation.
      </para>
    </important>

  </sect2>

  <sect2 role="commands">
    <title>Command Explanations</title>

    <para>
      <command>autoreconf -fiv</command>: The configure script shipped with
      the package is too old to get the right version string of Python
      3.10 or later. This command regenerates it with a more recent version
      of autotools, which fixes the issue.
    </para>

    <para>
      <envar>PYTHON=python3</envar>: This forces the installation of
      python bindings for Python 3, even if Python 2 is installed.
    </para>

    <para>
      <parameter>--with-default-dict=/lib/cracklib/pw_dict</parameter>:
      This parameter forces the installation of the
      <application>CrackLib</application> dictionary to the
      <filename class="directory">/lib</filename> hierarchy.
    </para>

    <xi:include xmlns:xi="http://www.w3.org/2001/XInclude"
      href="../../xincludes/static-libraries.xml"/>

    <para>
      <command>install -v -m644 -D ...</command>: This command creates the
      <filename class="directory">/usr/share/dict</filename> directory (if it
      doesn't already exist) and installs the compressed word list there.
    </para>

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

    <para>
      <command>echo $(hostname) >>...</command>: The value of
      <command>hostname</command> is echoed to a file called
      <filename>cracklib-extra-words</filename>. 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.
    </para>

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

  </sect2>

  <sect2 role="content">
    <title>Contents</title>

    <segmentedlist>
      <segtitle>Installed Programs</segtitle>
      <segtitle>Installed Libraries</segtitle>
      <segtitle>Installed Directories</segtitle>

      <seglistitem>
        <seg>cracklib-check, cracklib-format, cracklib-packer,
        cracklib-unpacker, cracklib-update, and create-cracklib-dict</seg>

        <seg>libcrack.so and the _cracklib.so
          (<application>Python</application> module)</seg>

        <seg>/usr/lib/cracklib, /usr/share/dict and /usr/share/cracklib</seg>
      </seglistitem>
    </segmentedlist>

    <variablelist>
      <bridgehead renderas="sect3">Short Descriptions</bridgehead>
      <?dbfo list-presentation="list"?>
      <?dbhtml list-presentation="table"?>

      <varlistentry id="cracklib-check">
        <term><command>cracklib-check</command></term>
        <listitem>
          <para>
            is used to determine if a password is strong
          </para>
          <indexterm zone="cracklib cracklib-check">
            <primary sortas="b-cracklib-check">cracklib-check</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="cracklib-format">
        <term><command>cracklib-format</command></term>
        <listitem>
          <para>
            is used to format text files (lowercases all words,
            removes control characters and sorts the lists)
          </para>
          <indexterm zone="cracklib cracklib-format">
            <primary sortas="b-cracklib-format">cracklib-format</primary>
          </indexterm>
        </listitem>
      </varlistentry>

     <varlistentry id="cracklib-packer">
        <term><command>cracklib-packer</command></term>
        <listitem>
          <para>
            creates a database with words read from standard input
          </para>
          <indexterm zone="cracklib cracklib-packer">
            <primary sortas="b-cracklib-packer">cracklib-packer</primary>
          </indexterm>
        </listitem>
      </varlistentry>

     <varlistentry id="cracklib-unpacker">
        <term><command>cracklib-unpacker</command></term>
        <listitem>
          <para>
            displays on standard output the database specified
          </para>
          <indexterm zone="cracklib cracklib-packer">
            <primary sortas="b-cracklib-packer">cracklib-packer</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="create-cracklib-dict">
        <term><command>create-cracklib-dict</command></term>
        <listitem>
          <para>
            is used to create the <application>CrackLib</application>
            dictionary from the given word list(s)
          </para>
          <indexterm zone="cracklib create-cracklib-dict">
            <primary sortas="b-create-cracklib-dict">create-cracklib-dict</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libcrack">
        <term><filename class="libraryfile">libcrack.so</filename></term>
        <listitem>
          <para>
            provides a fast dictionary lookup method for strong
            password enforcement
          </para>
          <indexterm zone="cracklib libcrack">
            <primary sortas="c-libcrack">libcrack.so</primary>
          </indexterm>
        </listitem>
      </varlistentry>

    </variablelist>

  </sect2>

</sect1>