source: postlfs/security/libcap.xml

<?xml version="1.0" encoding="UTF-8"?>
<!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 libcap-download-http "&kernel-dl;/linux/libs/security/linux-privs/libcap2/libcap-&libcap-version;.tar.xz">
  <!ENTITY libcap-download-ftp  " ">
  <!ENTITY libcap-md5sum        "4667bacb837f9ac4adb4a1a0266f4b65">
  <!ENTITY libcap-size          "188 KB">
  <!ENTITY libcap-buildsize     "2.2 MB">
  <!ENTITY libcap-time          "less than 0.1 SBU">
]>

<sect1 id="libcap-pam" xreflabel="libcap-&libcap-version; with PAM">
  <?dbhtml filename="libcap.html"?>


  <title>libcap-&libcap-version; with PAM</title>

  <indexterm zone="libcap-pam">
    <primary sortas="a-libcap-pam">libcap</primary>
  </indexterm>

  <sect2 role="package">
    <title>Introduction to libcap with PAM</title>

    <para>
      The <application>libcap</application> package was installed in
      LFS, but if <application>Linux-PAM</application> support is desired,
      the PAM module must be built (after installation of
      <application>Linux-PAM</application>).
    </para>

    &lfs121_checked;

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

    <bridgehead renderas="sect3">libcap Dependencies</bridgehead>

    <bridgehead renderas="sect4">Required</bridgehead>
    <para role="required">
      <xref linkend="linux-pam"/>
    </para>


  </sect2>

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

    <note>
      <para>
        If you are upgrading libcap from a previous version, use the
        instructions in
        <ulink url="&lfs-root;/chapter08/libcap.html">
          LFS libcap page
        </ulink> to upgrade libcap. If <xref linkend="linux-pam"/> has been
        built, the PAM module will automatically be built too.
      </para>
    </note>

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

<screen><userinput>make -C pam_cap</userinput></screen>

    <para>
      This package does not come with a test suite.
    </para>

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

<screen role="root"><userinput>install -v -m755 pam_cap/pam_cap.so /usr/lib/security &amp;&amp;
install -v -m644 pam_cap/capability.conf /etc/security</userinput></screen>

  </sect2>

  <sect2 role="configuration">
    <title>Configuring Libcap</title>

    <para>
      In order to allow <application>Linux-PAM</application> to grant
      privileges based on POSIX capabilities, you need to add the libcap module
      to the beginning of the <filename>/etc/pam.d/system-auth</filename> file.
      Make the required edits with the following commands:
    </para>

<screen role="root"><userinput>mv -v /etc/pam.d/system-auth{,.bak} &amp;&amp;
cat &gt; /etc/pam.d/system-auth &lt;&lt; "EOF" &amp;&amp;
<literal># Begin /etc/pam.d/system-auth

auth      optional    pam_cap.so</literal>
EOF
tail -n +3 /etc/pam.d/system-auth.bak &gt;&gt; /etc/pam.d/system-auth</userinput></screen>

    <para>
      Additionally, you'll need to modify the
      <filename>/etc/security/capability.conf</filename> file to grant
      necessary privileges to users, and utilize the <command>setcap</command>
      utility to set capabilities on specific utilities as needed. See
      <command>man 8 setcap</command> and
      <command>man 3 cap_from_text</command> for additional information.
    </para>

  </sect2>

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

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

      <seglistitem>
        <seg>None</seg>
        <seg>pam_cap.so</seg>
        <seg>None</seg>
      </seglistitem>
    </segmentedlist>

  </sect2>

</sect1>