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<H1><A NAME="4">How to Configure Linux FreeS/WAN with Policy Groups</A></H1>
<A NAME="policygroups"></A>
<H2><A NAME="4_1">What are Policy Groups?</A></H2>
<P><STRONG>Policy Groups</STRONG> are an elegant general mechanism to
configure FreeS/WAN. They are useful for many FreeS/WAN users.</P>
<P>In previous FreeS/WAN versions, you needed to configure each IPsec
connection explicitly, on both local and remote hosts. This could
become complex.</P>
<P>By contrast, Policy Groups allow you to set local IPsec policy for
lists of remote hosts and networks, simply by listing the hosts and
networks which you wish to have special treatment in one of several
Policy Group files. FreeS/WAN then internally creates the connections
needed to implement each policy.</P>
<P>In the next section we describe our five Base Policy Groups, which
you can use to configure IPsec in many useful ways. Later, we will show
you how to create an IPsec VPN using one line of configuration for each
remote host or network.</P>
<A NAME="builtin_policygroups"></A>
<H3><A NAME="4_1_1">Built-In Security Options</A></H3>
<P>FreeS/WAN offers these Base Policy Groups:</P>
<DL>
<DT>private</DT>
<DD> FreeS/WAN only communicates privately with the listed<A HREF="glossary.html#CIDR">
CIDR</A> blocks. If needed, FreeS/WAN attempts to create a connection
opportunistically. If this fails, FreeS/WAN blocks communication.
Inbound blocking is assumed to be done by the firewall. FreeS/WAN
offers firewall hooks but no modern firewall rules to help with inbound
blocking.</DD>
<DT>private-or-clear</DT>
<DD> FreeS/WAN prefers private communication with the listed CIDR
blocks. If needed, FreeS/WAN attempts to create a connection
opportunistically. If this fails, FreeS/WAN allows traffic in the
clear.</DD>
<DT>clear-or-private</DT>
<DD> FreeS/WAN communicates cleartext with the listed CIDR blocks, but
also accepts inbound OE connection requests from them. Also known as<A HREF="glossary.html#passive.OE">
passive OE (pOE)</A>, this policy may be used to create an<A HREF="glossary.html#responder">
opportunistic responder</A>.</DD>
<DT>clear</DT>
<DD> FreeS/WAN only communicates cleartext with the listed CIDR blocks.</DD>
<DT>block</DT>
<DD>FreeS/WAN blocks traffic to and from and the listed CIDR blocks.
Inbound blocking is assumed to be done by the firewall. FreeS/WAN
offers firewall hooks but no modern firewall rules to help with inbound
blocking.
<!-- also called "blockdrop".-->
</DD>
</DL>
<A NAME="policy.group.notes"></A>
<P>Notes:</P>
<UL>
<LI>Base Policy Groups apply to communication with this host only.</LI>
<LI>The most specific rule (whether policy or pre-configured connection)
applies. This has several practical applications:
<UL>
<LI>If CIDR blocks overlap, FreeS/WAN chooses the most specific
applicable block.</LI>
<LI>This decision also takes into account any pre-configured connections
you may have.</LI>
<LI>If the most specific connection is a pre-configured connection, the
following procedure applies. If that connection is up, it will be used.
If it is routed, it will be brought up. If it is added, no action will
be taken.</LI>
</UL>
</LI>
<LI>Base Policy Groups are created using built-in connections. Details
in<A HREF="manpage.d/ipsec.conf.5.html"> man ipsec.conf</A>.</LI>
<LI>All Policy Groups are bidirectional.<A HREF="src/policy-groups-table.html">
This chart</A> shows some technical details. FreeS/WAN does not support
one-way encryption, since it can give users a false sense of security.</LI>
</UL>
<H2><A NAME="4_2">Using Policy Groups</A></H2>
<P>The Base Policy Groups which build IPsec connections rely on
Opportunistic Encryption. To use the following examples, you must first
become OE-capable, as described in our<A HREF="quickstart.html#quickstart">
quickstart guide</A>.<A NAME="example1"></A></P>
<H3><A NAME="4_2_1">Example 1: Using a Base Policy Group</A></H3>
<P>Simply place CIDR blocks (<A HREF="#dnswarning">names</A>, IPs or IP
ranges) in /etc/ipsec.d/policies/<VAR>[groupname]</VAR>, and reread the
policy group files.</P>
<P>For example, the<VAR> private-or-clear</VAR> policy tells FreeS/WAN
to prefer encrypted communication to the listed CIDR blocks. Failing
that, it allows talk in the clear.</P>
<P>To make this your default policy, place<A HREF="glossary.html#fullnet">
fullnet</A> in the<VAR> private-or-clear</VAR> policy group file:</P>
<PRE> [root@xy root]# cat /etc/ipsec.d/policies/private-or-clear
# This file defines the set of CIDRs (network/mask-length) to which
# communication should be private, if possible, but in the clear otherwise.
....
0.0.0.0/0</PRE>
<P>and reload your policies with</P>
<PRE> ipsec auto --rereadgroups</PRE>
<P>Use<A HREF="quickstart.html#opp.test"> this test</A> to verify
opportunistic connections.</P>
<A NAME="example2"></A>
<H3><A NAME="4_2_2">Example 2: Defining IPsec Security Policy with
Groups</A></H3>
<P>Defining IPsec security policy with Base Policy Groups is like
creating a shopping list: just put CIDR blocks in the appropriate group
files. For example:</P>
<PRE> [root@xy root]# cd /etc/ipsec.d/policies
[root@xy policies]# cat private
192.0.2.96/27 # The finance department
192.0.2.192/29 # HR
192.0.2.12 # HR gateway
irc.private.example.com # Private IRC server
[root@xy policies]# cat private-or-clear
0.0.0.0/0 # My default policy: try to encrypt.
[root@xy policies]# cat clear
192.0.2.18/32 # My POP3 server
192.0.2.19/32 # My Web proxy
[root@xy policies]# cat block
spamsource.example.com</PRE>
<P>To make these settings take effect, type:</P>
<PRE> ipsec auto --rereadgroups</PRE>
<P>Notes:</P>
<UL>
<LI>For opportunistic connection attempts to succeed, all participating
FreeS/WAN hosts and gateways must be configured for OE.</LI>
<LI>Examples 3 through 5 show how to implement a detailed<VAR> private</VAR>
policy.</LI>
<LI><A NAME="dnswarning"></A><FONT COLOR="RED"> Warning:</FONT> Using
DNS names in policy files and ipsec.conf can be tricky. If the name
does not resolve, the policy will not be implemented for that name. It
is therefore safer either to use IPs, or to put any critical names in
/etc/hosts. We plan to implement periodic DNS retry to help with this.
<BR> Names are resolved at FreeS/WAN startup, or when the policies are
reloaded. Unfortunately, name lookup can hold up the startup process.
If you have fast DNS servers, the problem may be less severe.</LI>
</UL>
<A HREF="example3"></A>
<H3><A NAME="4_2_3">Example 3: Creating a Simple IPsec VPN with the<VAR>
private</VAR> Group</A></H3>
<P>You can create an IPsec VPN between several hosts, with only one line
of configuration per host, using the<VAR> private</VAR> policy group.</P>
<P>First, use our<A HREF="quickstart.html"> quickstart guide</A> to set
up each participating host with a FreeS/WAN install and OE.</P>
<P>In one host's<VAR> /etc/ipsec.d/policies/private</VAR>, list the
peers to which you wish to protect traffic. For example:</P>
<PRE> [root@xy root]# cd /etc/ipsec.d/policies
[root@xy policies]# cat private
192.0.2.9 # several hosts at example.com
192.0.2.11
192.0.2.12
irc.private.example.com
</PRE>
<P>Copy the<VAR> private</VAR> file to each host. Remove the local host,
and add the initial host.</P>
<PRE> scp2 /etc/ipsec.d/policies/private root@192.0.2.12:/etc/ipsec.d/policies/private</PRE>
<P>On each host, reread the policy groups with</P>
<PRE> ipsec auto --rereadgroups</PRE>
<P>That's it! You're configured.</P>
<P>Test by pinging between two hosts. After a second or two, traffic
should flow, and</P>
<PRE> ipsec eroute</PRE>
<P>should yield something like</P>
<PRE> 192.0.2.11/32 -> 192.0.2.8/32 => tun0x149f@192.0.2.8</PRE>
<P>where your host IPs are substituted for 192.0.2.11 and 192.0.2.8.</P>
<P>If traffic does not flow, there may be an error in your OE setup.
Revisit our<A HREF="quickstart.html"> quickstart guide</A>.</P>
<P>Our next two examples show you how to add subnets to this IPsec VPN.</P>
<A NAME="example4"></A>
<H3><A NAME="4_2_4">Example 4: New Policy Groups to Protect a Subnet</A></H3>
<P>To protect traffic to a subnet behind your FreeS/WAN gateway, you'll
need additional DNS records, and new policy groups. To set up the DNS,
see our<A HREF="quickstart.html#opp.gate"> quickstart guide</A>. To
create five new policy groups for your subnet, copy these connections
to<VAR> /etc/ipsec.conf</VAR>. Substitute your subnet's IPs for
192.0.2.128/29.</P>
<PRE>
conn private-net
also=private # inherits settings (eg. auto=start) from built in conn
leftsubnet=192.0.2.128/29 # your subnet's IPs here
conn private-or-clear-net
also=private-or-clear
leftsubnet=192.0.2.128/29
conn clear-or-private-net
also=clear-or-private
leftsubnet=192.0.2.128/29
conn clear-net
also=clear
leftsubnet=192.0.2.128/29
conn block-net
also=block
leftsubnet=192.0.2.128/29
</PRE>
<P>Copy the gateway's files to serve as the initial policy group files
for the new groups:</P>
<PRE>
cp -p /etc/ipsec.d/policies/private /etc/ipsec.d/policies/private-net
cp -p /etc/ipsec.d/policies/private-or-clear /etc/ipsec.d/policies/private-or-clear-net
cp -p /etc/ipsec.d/policies/clear-or-private /etc/ipsec.d/policies/clear-or-private-net
cp -p /etc/ipsec.d/policies/clear /etc/ipsec.d/policies/clear-net
cp -p /etc/ipsec.d/policies/block /etc/ipsec.d/policies/block
</PRE>
<P><STRONG>Tip: Since a missing policy group file is equivalent to a
file with no entries, you need only create files for the connections
you'll use.</STRONG></P>
<P>To test one of your new groups, place the fullnet 0.0.0.0/0 in<VAR>
private-or-clear-net</VAR>. Perform the subnet test in<A HREF="quickstart.html#opp.test">
our quickstart guide</A>. You should see a connection, and</P>
<PRE> ipsec eroute</PRE>
<P>should include an entry which mentions the subnet node's IP and the
OE test site IP, like this:</P>
<PRE> 192.0.2.131/32 -> 192.139.46.77/32 => tun0x149f@192.0.2.11</PRE>
<A HREF="example5"></A>
<H3><A NAME="4_2_5">Example 5: Adding a Subnet to the VPN</A></H3>
<P>Suppose you wish to secure traffic to a subnet 192.0.2.192/29 behind
a FreeS/WAN box 192.0.2.12.</P>
<P>First, add DNS entries to configure 192.0.2.12 as an opportunistic
gateway for that subnet. Instructions are in our<A HREF="quickstart.html#opp.gate">
quickstart guide</A>. Next, create a<VAR> private-net</VAR> group on
192.0.2.12 as described in<A HREF="#example4"> Example 4</A>.</P>
<P>On each other host, add the subnet 192.0.2.192/29 to<VAR> private</VAR>
, yielding for example</P>
<PRE> [root@xy root]# cd /etc/ipsec.d/policies
[root@xy policies]# cat private
192.0.2.9 # several hosts at example.com
192.0.2.11
192.0.2.12 # HR department gateway
192.0.2.192/29 # HR subnet
irc.private.example.com
</PRE>
<P>and reread policy groups with</P>
<PRE> ipsec auto --rereadgroups</PRE>
<P>That's all the configuration you need.</P>
<P>Test your VPN by pinging from a machine on 192.0.2.192/29 to any
other host:</P>
<PRE> [root@192.0.2.194]# ping 192.0.2.11</PRE>
<P>After a second or two, traffic should flow, and</P>
<PRE> ipsec eroute</PRE>
<P>should yield something like</P>
<PRE> 192.0.2.11/32 -> 192.0.2.194/32 => tun0x149f@192.0.2.12
</PRE>
<P>Key:</P>
<TABLE>
<TR><TD>1.</TD><TD>192.0.2.11/32</TD><TD>Local start point of the
protected traffic.</TD></TR>
<TR><TD>2.</TD><TD>192.0.2.194/32</TD><TD>Remote end point of the
protected traffic.</TD></TR>
<TR><TD>3.</TD><TD>192.0.2.12</TD><TD>Remote FreeS/WAN node (gateway or
host). May be the same as (2).</TD></TR>
<TR><TD>4.</TD><TD>[not shown]</TD><TD>Local FreeS/WAN node (gateway or
host), where you've produced the output. May be the same as (1).</TD></TR>
</TABLE>
<P>For additional assurance, you can verify with a packet sniffer that
the traffic is being encrypted.</P>
<P>Note</P>
<UL>
<LI>Because strangers may also connect via OE, this type of VPN may
require a stricter firewalling policy than a conventional VPN.</LI>
</UL>
<H2><A NAME="4_3">Appendix</A></H2>
<A NAME="hiddenconn"></A>
<H3><A NAME="4_3_1">Our Hidden Connections</A></H3>
<P>Our Base Policy Groups are created using hidden connections. These
are spelled out in<A HREF="manpage.d/ipsec.conf.5.html"> man ipsec.conf</A>
and defined in<VAR> /usr/local/lib/ipsec/_confread</VAR>.</P>
<A NAME="custom_policygroups"></A>
<H3><A NAME="4_3_2">Custom Policy Groups</A></H3>
<P>A policy group is built using a special connection description in<VAR>
ipsec.conf</VAR>, which:</P>
<UL>
<LI>is<STRONG> generic</STRONG>. It uses<VAR>
right=[%group|%opportunisticgroup]</VAR> rather than specific IPs. The
connection is cloned for every name or IP range listed in its Policy
Group file.</LI>
<LI>often has a<STRONG> failure rule</STRONG>. This rule, written<VAR>
failureshunt=[passthrough|drop|reject|none]</VAR>, tells FreeS/WAN what
to do with packets for these CIDRs if it fails to establish the
connection. Default is<VAR> none</VAR>.</LI>
</UL>
<P>To create a new group:</P>
<OL>
<LI>Create its connection definition in<VAR> ipsec.conf</VAR>.</LI>
<LI>Create a Policy Group file in<VAR> /etc/ipsec.d/policies</VAR> with
the same name as your connection.</LI>
<LI>Put a CIDR block in that file.</LI>
<LI>Reread groups with<VAR> ipsec auto --rereadgroups</VAR>.</LI>
<LI>Test:<VAR> ping</VAR> to activate any OE connection, and view
results with<VAR> ipsec eroute</VAR>.</LI>
</OL>
<A NAME="disable_oe"></A><A NAME="disable_policygroups"></A>
<H3><A NAME="4_3_3">Disabling Opportunistic Encryption</A></H3>
<P>To disable OE (eg. policy groups and packetdefault), cut and paste
the following lines to<VAR> /etc/ipsec.conf</VAR>:</P>
<PRE>conn block
auto=ignore
conn private
auto=ignore
conn private-or-clear
auto=ignore
conn clear-or-private
auto=ignore
conn clear
auto=ignore
conn packetdefault
auto=ignore</PRE>
<P>Restart FreeS/WAN so that the changes take effect:</P>
<PRE> ipsec setup restart</PRE>
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