shorewall_code/docs/PPTP.xml
2008-07-07 20:42:54 +00:00

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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
"http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd">
<article id="PPTP">
<!--$Id$-->
<articleinfo>
<title>PPTP - Unmaintained</title>
<authorgroup>
<author>
<firstname>Tom</firstname>
<surname>Eastep</surname>
</author>
</authorgroup>
<pubdate><?dbtimestamp format="Y/m/d"?></pubdate>
<copyright>
<year>2001</year>
<year>2002</year>
<year>2003</year>
<year>2004</year>
<year>2005</year>
<year>2006</year>
<year>2007</year>
<holder>Thomas M. Eastep</holder>
</copyright>
<legalnotice>
<para>Permission is granted to copy, distribute and/or modify this
document under the terms of the GNU Free Documentation License, Version
1.2 or any later version published by the Free Software Foundation; with
no Invariant Sections, with no Front-Cover, and with no Back-Cover
Texts. A copy of the license is included in the section entitled
<quote><ulink url="GnuCopyright.htm">GNU Free Documentation
License</ulink></quote>.</para>
</legalnotice>
<abstract>
<para>Shorewall easily supports PPTP in a number of
configurations.</para>
</abstract>
</articleinfo>
<warning>
<para>I have not used PPTP in years and as a consequence, this document is
no longer maintained (any volunteers?).</para>
<para>As far as I know, the information regarding Shorewall configuration
is still valid but the configurations shown for for the other components
may no longer work. For the most part, they show configuration files that
I used when I worked for <trademark>Compaq</trademark> and used PPTP as my
work VPN.</para>
</warning>
<section id="Prelim">
<title>Preliminary Reading</title>
<para>I recommend reading the <ulink url="VPNBasics.html">VPN
Basics</ulink> article if you plan to implement any type of VPN.</para>
</section>
<section id="ServerFW">
<title>PPTP Server Running on your Firewall</title>
<section id="Samba">
<title>Configuring Samba</title>
<para>You will need a WINS server (Samba configured to run as a WINS
server is fine). Global section from /etc/samba/smb.conf on my WINS
server (192.168.1.3) is:</para>
<programlisting>[global]
workgroup = TDM-NSTOP
netbios name = WOOKIE
server string = GNU/Linux Box
encrypt passwords = Yes
log file = /var/log/samba/%m.log
max log size = 0
socket options = TCP_NODELAY SO_RCVBUF=8192 SO_SNDBUF=8192
os level = 65
domain master = True
preferred master = True
dns proxy = No
wins support = Yes
printing = lprng
[homes]
comment = Home Directories
valid users = %S
read only = No
create mask = 0664
directory mask = 0775
[printers]
comment = All Printers
path = /var/spool/samba
printable = Yes</programlisting>
</section>
<section id="ConfigPppd">
<title>Configuring pppd</title>
<para>Here is a copy of my /etc/ppp/options.poptop file:</para>
<programlisting>ipparam PoPToP
lock
mtu 1490
mru 1490
ms-wins 192.168.1.3
ms-dns 206.124.146.177
multilink
proxyarp
auth
+chap
+chapms
+chapms-v2
ipcp-accept-local
ipcp-accept-remote
lcp-echo-failure 30
lcp-echo-interval 5
deflate 0
mppe-128
mppe-stateless
require-mppe
require-mppe-stateless</programlisting>
<note>
<itemizedlist>
<listitem>
<para>System 192.168.1.3 acts as a WINS server so I have included
that IP as the <quote>ms-wins</quote> value.</para>
</listitem>
<listitem>
<para>I have pointed the remote clients at my DNS server -- it has
external address 206.124.146.177.</para>
</listitem>
<listitem>
<para>I am requiring 128-bit stateless compression.</para>
</listitem>
</itemizedlist>
</note>
<para>Here's my /etc/ppp/chap-secrets:</para>
<programlisting>Secrets for authentication using CHAP
# client server secret IP addresses
CPQTDM\\TEastep * &lt;shhhhhh&gt; 192.168.1.7
TEastep * &lt;shhhhhh&gt; 192.168.1.7</programlisting>
<para>I am the only user who connects to the server but I may connect
either with or without a domain being specified. The system I connect
from is my laptop so I give it the same IP address when tunneled in at
it has when I use its wireless LAN card around the house.</para>
<para>You will also want the following in /etc/modules.conf:</para>
<programlisting>alias ppp-compress-18 ppp_mppe
alias ppp-compress-21 bsd_comp
alias ppp-compress-24 ppp_deflate
alias ppp-compress-26 ppp_deflate</programlisting>
</section>
<section id="ConfigPptpd">
<title>Configuring pptpd</title>
<para>PoPTop (pptpd) is available from <ulink
url="http://www.poptop.org/">http://www.poptop.org/</ulink>.</para>
<para>Here is a copy of my /etc/pptpd.conf file:</para>
<programlisting>option /etc/ppp/options.poptop
speed 115200
localip 192.168.1.254
remoteip 192.168.1.33-38</programlisting>
<note>
<itemizedlist>
<listitem>
<para>I specify the /etc/ppp/options.poptop file as my ppp options
file (I have several).</para>
</listitem>
<listitem>
<para>The local IP is the same as my internal interface's
(192.168.1.254).</para>
</listitem>
<listitem>
<para>I have assigned a remote IP range that overlaps my local
network. This, together with <quote>proxyarp</quote> in my
/etc/ppp/options.poptop file make the remote hosts look like they
are part of the local subnetwork.</para>
</listitem>
</itemizedlist>
</note>
<para>I use this file to start/stop pptpd -- I have this in
/etc/init.d/pptpd:</para>
<programlisting>#!/bin/sh
#
# /etc/rc.d/init.d/pptpd
#
# chkconfig: 5 12 85
# description: control pptp server
#
case "$1" in
start)
echo 1 &gt; /proc/sys/net/ipv4/ip_forward
modprobe ppp_async
modprobe ppp_generic
modprobe ppp_mppe
modprobe slhc
if /usr/local/sbin/pptpd; then
touch /var/lock/subsys/pptpd
fi
;;
stop)
killall pptpd
rm -f /var/lock/subsys/pptpd
;;
restart)
killall pptpd
if /usr/local/sbin/pptpd; then
touch /var/lock/subsys/pptpd
fi
;;
status)
ifconfig
;;
*)
echo "Usage: $0 {start|stop|restart|status}"
;;
esac</programlisting>
</section>
<section id="ConfigFw">
<title>Configuring Shorewall</title>
<section id="Basic">
<title>Basic Setup</title>
<para>Here' a basic setup that treats your remote users as if they
were part of your <emphasis role="bold">loc</emphasis> zone. Note that
if your primary internet connection uses ppp0, then be sure that
<emphasis role="bold">loc</emphasis> follows <emphasis
role="bold">net</emphasis> in /etc/shorewall/zones.</para>
<para><filename>/etc/shorewall/tunnels</filename>:</para>
<programlisting>#TYPE ZONE GATEWAY GATEWAY ZONE
pptpserver net 0.0.0.0/0</programlisting>
<para><filename>/etc/shorewall/interfaces</filename>:</para>
<programlisting>#ZONE INTERFACE BROADCAST OPTIONS
loc ppp+</programlisting>
</section>
<section id="Zones">
<title>Remote Users in a Separate Zone</title>
<para>If you want to place your remote users in their own zone so that
you can control connections between these users and the local network,
follow this example. Note that if your primary internet connection
uses ppp0 then be sure that <emphasis role="bold">vpn</emphasis>
follows <emphasis role="bold">net</emphasis> in /etc/shorewall/zones
as shown below.</para>
<para><filename>/etc/shorewall/tunnels</filename>:</para>
<programlisting>#TYPE ZONE GATEWAY GATEWAY ZONE
pptpserver net 0.0.0.0/0</programlisting>
<para><filename>/etc/shorewall/zones</filename>:</para>
<programlisting>#ZONE TYPE
net ipv4
loc ipv4
vpn ipv4</programlisting>
<para><filename>/etc/shorewall/interfaces</filename>:</para>
<programlisting>#ZONE INTERFACE BROADCAST OPTIONS
net eth0 206.124.146.255 norfc1918
loc eth2 192.168.10.255
vpn ppp+</programlisting>
<para>Your policies and rules may now be configured for traffic
to/from the <emphasis role="bold">vpn</emphasis> zone.</para>
</section>
<section id="Hub">
<title>Multiple Remote Networks</title>
<para>Often there will be situations where you want multiple
connections from remote networks with these networks having different
firewalling requirements.<graphic
fileref="images/MultiPPTP.png" /></para>
<para>Here's how you configure this in Shorewall. Note that if your
primary internet connection uses ppp0 then be sure that the <emphasis
role="bold">vpn{1-3}</emphasis> zones follows <emphasis
role="bold">net</emphasis> in /etc/shorewall/zones as shown
below.</para>
<para><filename>/etc/shorewall/tunnels</filename>:</para>
<programlisting>#TYPE ZONE GATEWAY GATEWAY ZONE
pptpserver net 0.0.0.0/0</programlisting>
<para><filename>/etc/shorewall/zones</filename>:</para>
<programlisting>#ZONE TYPE
fw firewall
net ipv4
loc ipv4
vpn1 ipv4
vpn2 ipv4
vpn3 ipv4</programlisting>
<para><filename>/etc/shorewall/interfaces</filename>:</para>
<programlisting>#ZONE INTERFACE BROADCAST OPTIONS
net eth0 206.124.146.255 norfc1918
loc eth2 192.168.10.255
- ppp+</programlisting>
<para><filename>/etc/shorewall/hosts</filename>:</para>
<programlisting>#ZONE HOST(S) OPTIONS
vpn1 ppp+:192.168.1.0/24
vpn2 ppp+:192.168.2.0/24
vpn3 ppp+:192.168.3.0/24</programlisting>
<para>Your policies and rules can now be configured using separate
zones (vpn1, vpn2, and vpn3) for the three remote network.</para>
</section>
</section>
</section>
<section id="ServerBehind">
<title>PPTP Server Running Behind your Firewall</title>
<para>If you have a single external IP address, add the following to your
/etc/shorewall/rules file:</para>
<para><filename>/etc/shorewall/rules</filename>:</para>
<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S)
DNAT net loc:<emphasis>&lt;server address&gt;</emphasis> tcp 1723
DNAT net loc:<emphasis>&lt;server address&gt;</emphasis> 47</programlisting>
<para>If you have multiple external IP address and you want to forward a
single &lt;<emphasis>external address</emphasis>&gt;, add the following to
your /etc/shorewall/rules file:</para>
<para><filename>/etc/shorewall/rules</filename>:</para>
<programlisting>#ACTION SOURCE DEST PROTO DEST PORT(S) SOURCE ORIGINAL
# PORT(S) DEST
DNAT net loc:<emphasis>&lt;server address&gt;</emphasis> tcp 1723 - <emphasis>&lt;external address&gt;</emphasis>
DNAT net loc:<emphasis>&lt;server address&gt;</emphasis> 47 - - <emphasis>&lt;external address&gt;</emphasis></programlisting>
<para>You will also want to add this entry to your
<filename>/etc/shorewall/masq</filename> file:</para>
<programlisting>#INTERFACE SUBNET ADDRESS PROTO
&lt;<emphasis>external interface</emphasis>&gt; &lt;<emphasis>server address</emphasis>&gt; &lt;<emphasis>external address</emphasis>&gt; 47</programlisting>
<important>
<para>Be sure that the above entry comes <emphasis
role="bold">before</emphasis> any other entry that might match the
server's address.</para>
</important>
</section>
<section id="ClientsBehind">
<title>PPTP Clients Running Behind your Firewall</title>
<para>Pleas see <ulink url="VPM.htm">this article</ulink>.</para>
</section>
<section id="ClientFW">
<title>PPTP Client Running on your Firewall</title>
<para>The key elements of this setup are as follows:</para>
<orderedlist>
<listitem>
<para>Define a zone for the remote network accessed via PPTP.</para>
</listitem>
<listitem>
<para>Associate that zone with a ppp interface.</para>
</listitem>
<listitem>
<para>Define rules for PPTP traffic to/from the firewall.</para>
</listitem>
<listitem>
<para>Define rules for traffic two and from the remote zone.</para>
</listitem>
</orderedlist>
<para>Here are examples from one of my old setups:</para>
<para><filename>/etc/shorewall/zones</filename>:</para>
<programlisting>#ZONE TYPE
cpq ipv4</programlisting>
<para><filename>/etc/shorewall/interfaces</filename>:</para>
<programlisting>#ZONE INTERFACE BROADCAST OPTIONS
- ppp+</programlisting>
<para>/etc/shorewall/hosts:</para>
<programlisting>#ZONE HOST(S) OPTIONS
cpq ppp+:!192.168.1.0/24</programlisting>
<para><filename>/etc/shorewall/tunnels</filename>:</para>
<programlisting>#TYPE ZONE GATEWAY GATEWAY ZONE
pptpclient net 0.0.0.0/0</programlisting>
<para>I use the combination of interface and hosts file to define the
<quote>cpq</quote> zone because I also run a PPTP server on my firewall
(see above). Using this technique allows me to distinguish clients of my
own PPTP server from arbitrary hosts at Compaq; I assign addresses in
192.168.1.0/24 to my PPTP clients and Compaq doesn't use that RFC1918
Class C subnet.</para>
<para>I use this script in /etc/init.d to control the client. The reason
that I disable ECN when connecting is that the Compaq tunnel servers don't
do ECN yet and reject the initial TCP connection request if I enable ECN
:-(</para>
<programlisting>#!/bin/sh
#
# /etc/rc.d/init.d/pptp
#
# chkconfig: 5 60 85
# description: PPTP Link Control
#
NAME="Tandem"
ADDRESS=tunnel-tandem.compaq.com
USER='Tandem\tommy'
ECN=0
DEBUG=
start_pptp() {
echo $ECN &gt; /proc/sys/net/ipv4/tcp_ecn
if /usr/sbin/pptp $ADDRESS user $USER noauth $DEBUG; then
touch /var/lock/subsys/pptp
echo "PPTP Connection to $NAME Started"
fi
}
stop_pptp() {
if killall /usr/sbin/pptp 2&gt; /dev/null; then
echo "Stopped pptp"
else
rm -f /var/run/pptp/*
fi
# if killall pppd; then
# echo "Stopped pppd"
# fi
rm -f /var/lock/subsys/pptp
echo 1 &gt; /proc/sys/net/ipv4/tcp_ecn
}
case "$1" in
start)
echo "Starting PPTP Connection to ${NAME}..."
start_pptp
;;
stop)
echo "Stopping $NAME PPTP Connection..."
stop_pptp
;;
restart)
echo "Restarting $NAME PPTP Connection..."
stop_pptp
start_pptp
;;
status)
ifconfig
;;
*)
echo "Usage: $0 {start|stop|restart|status}"
;;
esac</programlisting>
<para>Here's my /etc/ppp/options file:</para>
<programlisting>#
# Identify this connection
#
ipparam Compaq
#
# Lock the port
#
lock
#
# We don't need the tunnel server to authenticate itself
#
noauth
+chap
+chapms
+chapms-v2
multilink
mrru 1614
#
# Turn off transmission protocols we know won't be used
#
nobsdcomp
nodeflate
#
# We want MPPE
#
mppe-128
mppe-stateless
#
# We want a sane mtu/mru
#
mtu 1000
mru 1000
#
# Time this thing out of it goes poof
#
lcp-echo-failure 10
lcp-echo-interval 10</programlisting>
<para>My /etc/ppp/ip-up.local file sets up the routes that I need to route
Compaq traffic through the PPTP tunnel:</para>
<programlisting>#/bin/sh
case $6 in
Compaq)
route add -net 16.0.0.0 netmask 255.0.0.0 gw $5 $1
route add -net 130.252.0.0 netmask 255.255.0.0 gw $5 $1
route add -net 131.124.0.0 netmask 255.255.0.0 gw $5 $1
...
;;
esac</programlisting>
<para>Finally, I run the following script every five minutes under crond
to restart the tunnel if it fails:</para>
<programlisting>#!/bin/sh
restart_pptp() {
/sbin/service pptp stop
sleep 10
if /sbin/service pptp start; then
/usr/bin/logger "PPTP Restarted"
fi
}
if [ -n "`ps ax | grep /usr/sbin/pptp | grep -v grep`" ]; then
exit 0
fi
echo "Attempting to restart PPTP"
restart_pptp &gt; /dev/null 2&gt;&amp;1 &amp;</programlisting>
<para><ulink url="ftp://ftp.shorewall.net/pub/shorewall/misc/Vonau">Here's
a script and corresponding ip-up.local</ulink> from Jerry Vonau
<email>jvonau@home.com</email> that controls two PPTP connections.</para>
</section>
<section id="PPTP_ADSL">
<title>PPTP Client running on your Firewall with PPTP Server in an ADSL
Modem</title>
<para>Some ADSL systems in Europe (most notably in Austria and the
Netherlands) feature a PPTP server built into an ADSL
<quote>Modem</quote>. In this setup, an ethernet interface is dedicated to
supporting the PPTP tunnel between the firewall and the
<quote>Modem</quote> while the actual internet access is through PPTP
(interface ppp0). If you have this type of setup, you need to modify the
sample configuration that you downloaded as described in this section.
<emphasis role="bold">These changes are in addition to those described in
the <ulink url="shorewall_quickstart_guide.htm">QuickStart
Guides</ulink>.</emphasis></para>
<para>Lets assume the following:</para>
<itemizedlist>
<listitem>
<para>ADSL Modem connected through eth0</para>
</listitem>
<listitem>
<para>Modem IP address = 192.168.1.1</para>
</listitem>
<listitem>
<para>eth0 IP address = 192.168.1.2</para>
</listitem>
</itemizedlist>
<para>The changes you need to make are as follows:</para>
<orderedlist>
<listitem>
<para>Add this entry to /etc/shorewall/zones:</para>
<programlisting>#ZONE TYPE
modem ipv4</programlisting>
<para>That entry defines a new zone called <quote>modem</quote> which
will contain only your ADSL modem.</para>
</listitem>
<listitem>
<para>Add the following entry to /etc/shorewall/interfaces:</para>
<programlisting>#ZONE INTERFACE BROADCAST OPTIONS
modem eth0 192.168.1.255 dhcp</programlisting>
<para>You will of course modify the <quote>net</quote> entry in
/etc/shorewall/interfaces to specify <quote>ppp0</quote> as the
interface as described in the QuickStart Guide corresponding to your
setup.</para>
</listitem>
<listitem>
<para>Add the following to /etc/shorewall/tunnels:</para>
<programlisting>#TYPE ZONE GATEWAY GATEWAY ZONE
pptpclient modem 192.168.1.1</programlisting>
<para>That entry allows a PPTP tunnel to be established between your
Shorewall system and the PPTP server in the modem.</para>
</listitem>
</orderedlist>
</section>
</article>