source: postlfs/security/stunnel.xml@ d7bee48

<?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 stunnel-download-http " ">
  <!-- Following ftp also has older releases -->
  <!ENTITY stunnel-download-ftp  "ftp://ftp.stunnel.org/stunnel/archive/5.x/stunnel-&stunnel-version;.tar.gz">
  <!-- Following ftp only has later release -->
<!--  "ftp://ftp.stunnel.org/stunnel/stunnel-&stunnel-version;.tar.gz" -->
  <!ENTITY stunnel-md5sum        "a39b89624984cefc6d229a54f34b33ec">
  <!ENTITY stunnel-size          "628 KB">
  <!ENTITY stunnel-buildsize     "6.9 MB">
  <!ENTITY stunnel-time          "0.1 SBU">
]>

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

  <sect1info>
    <othername>$LastChangedBy$</othername>
    <date>$Date$</date>
  </sect1info>

  <title>stunnel-&stunnel-version;</title>

  <indexterm zone="stunnel">
    <primary sortas="a-stunnel">stunnel</primary>
  </indexterm>

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

    <para>The <application>stunnel</application> package contains a program
    that allows you to encrypt arbitrary TCP connections inside SSL (Secure
    Sockets Layer) so you can easily communicate with clients over secure
    channels. <application>stunnel</application> can be used to add SSL
    functionality to commonly used <application>Inetd</application> daemons
    such as POP-2, POP-3, and IMAP servers, along with standalone daemons such
    as NNTP, SMTP, and HTTP. <application>stunnel</application> can also be
    used to tunnel PPP over network sockets without changes to the server
    package source code.</para>

    &lfs78_checked;

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

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

    <bridgehead renderas="sect4">Required</bridgehead>
    <para role="required">
      <xref linkend="openssl"/>
    </para>

    <bridgehead renderas="sect4">Optional</bridgehead>
    <para role="optional">
      <ulink url="ftp://ftp.porcupine.org/pub/security/">tcpwrappers</ulink> and
      <ulink url="https://dist.torproject.org/">TOR</ulink>
    </para>

    <para condition="html" role="usernotes">User Notes:
    <ulink url="&blfs-wiki;/stunnel"/></para>

  </sect2>

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

    <para>The <command>stunnel</command> daemon will be run in a
    <command>chroot</command> jail by an unprivileged user. Create the
    new user and group using the following commands as the
    <systemitem class="username">root</systemitem> user:</para>

<screen role="root"><userinput>groupadd -g 51 stunnel &amp;&amp;
useradd -c "stunnel Daemon" -d /var/lib/stunnel \
        -g stunnel -s /bin/false -u 51 stunnel</userinput></screen>

    <note>
      <para>A signed SSL Certificate and a Private Key is necessary to run the
      <command>stunnel</command> daemon. After the package is installed, there
      are instructions to generate them. However, if you own or have already
      created a signed SSL Certificate you wish to use, copy it to
      <filename>/etc/stunnel/stunnel.pem</filename> before starting the build
      (ensure only <systemitem class="username">root</systemitem> has read and
      write access).  The <filename class="extension">.pem</filename> file must
      be formatted as shown below:</para>

<screen><literal>-----BEGIN PRIVATE KEY-----
<replaceable>&lt;many encrypted lines of private key&gt;</replaceable>
-----END PRIVATE KEY-----
-----BEGIN CERTIFICATE-----
<replaceable>&lt;many encrypted lines of certificate&gt;</replaceable>
-----END CERTIFICATE-----
-----BEGIN DH PARAMETERS-----
<replaceable>&lt;encrypted lines of dh parms&gt;</replaceable>
-----END DH PARAMETERS-----</literal></screen>
    </note>

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

    <note>
      <para>For some systems with <application>binutils</application>
      versions prior to 2.25, <command>configure</command> may fail.  If
      necessary, fix it either with:</para>

<screen><userinput>sed -i '/LDFLAGS.*static_flag/ s/^/#/' configure</userinput></screen>

      <para>or, if <xref linkend="llvm"/> with Clang is installed, you can
      replace <command>./configure ...</command> with <command>CC=clang
      ./configure ...</command> in the first command below.</para>
    </note>

<screen><userinput>./configure --prefix=/usr        \
            --sysconfdir=/etc    \
            --localstatedir=/var &amp;&amp;
make</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>make docdir=/usr/share/doc/stunnel-&stunnel-version; install</userinput></screen>

    <para>
      Install the systemd unit by running the following command as the
      <systemitem class="username">root</systemitem> user:
    </para>

<screen role="root"><userinput>install -v -m644 tools/stunnel.service /lib/systemd/system/stunnel.service</userinput></screen>

    <para>If you do not already have a signed SSL Certificate and Private Key,
    create the <filename>stunnel.pem</filename> file in the
    <filename class="directory">/etc/stunnel</filename> directory using the
    command below. You will be prompted to enter the necessary
    information. Ensure you reply to the</para>

<screen><prompt>Common Name (FQDN of your server) [localhost]:</prompt></screen>

    <para>prompt with the name or IP address you will be using
    to access the service(s).</para>

    <para>To generate a certificate, as the
    <systemitem class="username">root</systemitem> user, issue:</para>

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

  </sect2>

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

    <para><command>make docdir=... install</command>: This command installs the
    package and changes the documentation installation directory to standard
    naming conventions.</para>

  </sect2>

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

    <sect3 id="stunnel-config">
      <title>Config Files</title>

      <para><filename>/etc/stunnel/stunnel.conf</filename></para>

      <indexterm zone="stunnel stunnel-config">
        <primary sortas="e-etc-stunnel-stunnel.conf">/etc/stunnel/stunnel.conf</primary>
      </indexterm>

    </sect3>

    <sect3>
      <title>Configuration Information</title>

      <para>As the <systemitem class="username">root</systemitem> user,
      create the directory used for the
      <filename class="extension">.pid</filename> file created
      when the <application>stunnel</application> daemon starts:</para>

<screen role="root"><userinput>install -v -m750 -o stunnel -g stunnel -d /var/lib/stunnel/run &amp;&amp;
chown stunnel:stunnel /var/lib/stunnel</userinput></screen>

      <para>Next, create a basic <filename>/etc/stunnel/stunnel.conf</filename>
      configuration file using the following commands as the
      <systemitem class="username">root</systemitem> user:</para>

<screen role="root"><userinput>cat &gt;/etc/stunnel/stunnel.conf &lt;&lt; "EOF" 
<literal>; File: /etc/stunnel/stunnel.conf

; Note: The pid and output locations are relative to the chroot location.

pid    = /run/stunnel.pid
chroot = /var/lib/stunnel
client = no
setuid = stunnel
setgid = stunnel
cert   = /etc/stunnel/stunnel.pem

;debug = 7
;output = stunnel.log

;[https]
;accept  = 443
;connect = 80
;; "TIMEOUTclose = 0" is a workaround for a design flaw in Microsoft SSL
;; Microsoft implementations do not use SSL close-notify alert and thus
;; they are vulnerable to truncation attacks
;TIMEOUTclose = 0</literal>

EOF</userinput></screen>

      <para>Finally, add the service(s) you wish to encrypt to the
      configuration file. The format is as follows:</para>

<screen><literal>[<replaceable>&lt;service&gt;</replaceable>]
accept  = <replaceable>&lt;hostname:portnumber&gt;</replaceable>
connect = <replaceable>&lt;hostname:portnumber&gt;</replaceable></literal></screen>

      <para>If you use <application>stunnel</application> to encrypt a daemon
      started from <command>[x]inetd</command>, you may need to disable that
      daemon in the <filename>/etc/[x]inetd.conf</filename> file and enable a
      corresponding <replaceable>&lt;service&gt;</replaceable>_stunnel service. You
      may have to add an appropriate entry in <filename>/etc/services</filename>
      as well.</para>

      <para>For a full explanation of the commands and syntax used in the
      configuration file, issue <command>man stunnel</command>.</para>

    </sect3>

    <sect3  id="stunnel-init">
      <title>Systemd Units</title>

      <para>
        To start the <command>stunnel</command> daemon at boot,
        enable the previously installed systemd unit by
        running the following command as the
        <systemitem class="username">root</systemitem> user:
      </para>

      <indexterm zone="stunnel stunnel-init">
        <primary sortas="f-stunnel">stunnel</primary>
      </indexterm>

<screen role="root"><userinput>systemctl enable stunnel</userinput></screen>

    </sect3>

  </sect2>

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

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

      <seglistitem>
        <seg>
          stunnel and stunnel3
        </seg>
        <seg>
          libstunnel.so
        </seg>
        <seg>
          /{etc,usr/lib,var/lib}/stunnel and
          /usr/share/doc/stunnel-&stunnel-version;
        </seg>
      </seglistitem>
    </segmentedlist>

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

      <varlistentry id="stunnel-prog">
        <term><command>stunnel</command></term>
        <listitem>
          <para> is a program designed to work as an SSL
          encryption wrapper between remote clients and local
          (<command>{x}inetd</command>-startable) or remote servers.</para>
          <indexterm zone="stunnel stunnel-prog">
            <primary sortas="b-stunnel">stunnel</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="stunnel3">
        <term><command>stunnel3</command></term>
        <listitem>
          <para>is a <application>Perl</application> wrapper script to use
          <command>stunnel</command> 3.x syntax with <command>stunnel</command>
          >=4.05.</para>
          <indexterm zone="stunnel stunnel3">
            <primary sortas="b-stunnel3">stunnel3</primary>
          </indexterm>
        </listitem>
      </varlistentry>

      <varlistentry id="libstunnel">
        <term><filename class='libraryfile'>libstunnel.so</filename></term>
        <listitem>
          <para> contains the API functions required by
          <application>stunnel</application>.</para>
          <indexterm zone="stunnel libstunnel">
            <primary sortas="c-libstunnel">libstunnel.so</primary>
          </indexterm>
        </listitem>
      </varlistentry>

    </variablelist>

  </sect2>

</sect1>