lfs-book/chapter06/zlib.xml

<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN" "http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd" [
  <!ENTITY % general-entities SYSTEM "../general.ent">
  %general-entities;
]>
<sect1 id="ch-system-zlib" role="wrap">
<title>Zlib-&zlib-version;</title>
<?dbhtml filename="zlib.html"?>

<indexterm zone="ch-system-zlib"><primary sortas="a-Zlib">Zlib</primary></indexterm>

<sect2 role="package"><title/>
<para>The Zlib package contains compression and decompression routines used by
some programs.</para>

<segmentedlist>
<segtitle>&buildtime;</segtitle>
<segtitle>&diskspace;</segtitle>
<seglistitem><seg>0.1 SBU</seg><seg>2.7 MB</seg></seglistitem>
</segmentedlist>

<segmentedlist>
<segtitle>&dependencies;</segtitle>
<seglistitem><seg>Binutils, Coreutils, GCC, Glibc, Make, and Sed</seg></seglistitem>
</segmentedlist>
</sect2>

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

<para>Zlib has a buffer overflow vulnerability that can lead to a Denial of
Service attack. The following patch fixes the problem:</para>

<screen><userinput>patch -Np1 -i ../zlib-&zlib-version;-security_fix-1.patch</userinput></screen>

<note><para>Zlib is known to build its shared library incorrectly if
<envar>CFLAGS</envar> is specified in the environment. If using a 
specified <envar>CFLAGS</envar>
variable, be sure to add the <parameter>-fPIC</parameter> directive to
the <envar>CFLAGS</envar> variable for the duration of the
configure command below, then remove it afterwards.</para></note>

<para>Prepare Zlib for compilation:</para>

<screen><userinput>./configure --prefix=/usr --shared --libdir=/lib</userinput></screen>

<para>Compile the package:</para>

<screen><userinput>make</userinput></screen>

<para>To test the results, issue:
<userinput>make check</userinput>.</para>

<para>Install the shared library:</para>

<screen><userinput>make install</userinput></screen>

<para>The previous command installed a <filename
class="extension">.so</filename> file in <filename
class="directory">/lib</filename>. We will remove it and relink it into
<filename class="directory">/usr/lib</filename>:</para>

<screen><userinput>rm /lib/libz.so
ln -sf ../../lib/libz.so.&zlib-version; /usr/lib/libz.so</userinput></screen>

<para>Build the static library:</para>

<screen><userinput>make clean
./configure --prefix=/usr
make</userinput></screen>

<para>To test the results again, issue:
<userinput>make check</userinput>.</para>

<para>Install the static library:</para>

<screen><userinput>make install</userinput></screen>

<para>Fix the permissions on the static library:</para>

<screen><userinput>chmod 644 /usr/lib/libz.a</userinput></screen>

</sect2>


<sect2 id="contents-zlib" role="content"><title>Contents of Zlib</title>

<segmentedlist>
<segtitle>Installed libraries</segtitle>
<seglistitem><seg>libz.[a,so]</seg></seglistitem>
</segmentedlist>

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

<varlistentry id="libz">
<term><filename class="libraryfile">libz</filename></term>
<listitem>
<para>Contains compression and un-compression
functions used by some programs</para>
<indexterm zone="ch-system-zlib libz"><primary sortas="c-libz">libz</primary></indexterm>
</listitem>
</varlistentry>
</variablelist>

</sect2>

</sect1>