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<h1>How to Configure Linux FreeS/WAN with Policy Groups</h1>


<A NAME="policygroups"></A>

<H2>What are Policy Groups?</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>Built-In Security Options</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>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>Using Policy Groups</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><H3>Example 1: Using a Base Policy Group</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>Example 2: Defining IPsec Security Policy 
with Groups</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>Example 3: Creating a Simple IPsec VPN with the 
<VAR>private</VAR> Group</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>Example 4: New Policy Groups to Protect a
Subnet</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>Example 5: Adding a Subnet to the VPN</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>Appendix</H2>

<A NAME="hiddenconn"></A><H3>Our Hidden Connections</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>Custom Policy Groups</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>Disabling Opportunistic Encryption</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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