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<H1><A name="quickstart">Quickstart Guide to Opportunistic Encryption</A></H1>
<A name="quick_guide"></A>
<H2><A name="opp.setup">Purpose</A></H2>
<P>This page will get you started using Linux FreeS/WAN with opportunistic
encryption (OE). OE enables you to set up IPsec tunnels
without co-ordinating with another
site administrator, and without hand configuring each tunnel.
If enough sites support OE, a "FAX effect" occurs, and
many of us can communicate without eavesdroppers.</P>
<H3>OE "flag day"</H3>
<P>As of FreeS/WAN 2.01, OE uses DNS TXT resource records (RRs)
only (rather than TXT with KEY).
This change causes a
<a href="http://jargon.watson-net.com/jargon.asp?w=flag+day">"flag day"</a>.
Users of FreeS/WAN 2.00 (or earlier) OE who are upgrading may require
additional resource records, as detailed in our
<a href="upgrading.html#upgrading.flagday">upgrading document</a>.
OE setup instructions here are for 2.02 or later.</P>
<H2><A name="opp.dns">Requirements</A></H2>
<P>To set up opportunistic encryption, you will need:</P>
<UL>
<LI>a Linux box. For OE to the public Internet, this box must NOT
be behind <A HREF="glossary.html#NAT.gloss">Network Address Translation</A>
(NAT).</LI>
<LI>to install Linux FreeS/WAN 2.02 or later</LI>
<LI>either control over your reverse DNS (for full opportunism) or
the ability to write to some forward domain (for initiator-only).
<A HREF="http://www.fdns.net">This free DNS service</A> explicitly
supports forward TXT records for FreeS/WAN use.</LI>
<LI>(for full opportunism) a static IP</LI>
</UL>
<P>Note: Currently, only Linux FreeS/WAN supports opportunistic
encryption.</P>
<H2><A name="easy.install">RPM install</A></H2>
<P>Our instructions are for a recent Red Hat with a 2.4-series stock or
Red Hat updated kernel. For other ways to install, see our
<A href="install.html#install">install document</A>.</P>
<H3>Download RPMs</H3>
<P>If we have prebuilt RPMs for your Red Hat system,
this command will get them:
</P>
<PRE> ncftpget ftp://ftp.xs4all.nl/pub/crypto/freeswan/binaries/RedHat-RPMs/`uname -r | tr -d 'a-wy-z'`/\*</PRE>
<P>If that fails, you will need to try <A HREF="install.html">another install
method</A>.
Our kernel modules
<B>will only work on the Red Hat kernel they were built for</B>,
since they are very sensitive to small changes in the kernel.</P>
<P>If it succeeds, you will have userland tools, a kernel module, and an
RPM signing key:</P>
<PRE> freeswan-module-2.03_2.4.20_20.9-0.i386.rpm
freeswan-userland-2.03_2.4.20_20.9-0.i386.rpm
freeswan-rpmsign.asc</PRE>
<H3>Check signatures</H3>
<P>If you're running RedHat 8.x or later, import the RPM signing key into the
RPM database:</P>
<PRE> rpm --import freeswan-rpmsign.asc</PRE>
<P>For RedHat 7.x systems, you'll need to add it to your
<A HREF="glossary.html#PGP">PGP</A> keyring:</P>
<PRE> pgp -ka freeswan-rpmsign.asc</PRE>
<P>Check the digital signatures on both RPMs using:</P>
<PRE> rpm --checksig freeswan*.rpm </PRE>
<P>You should see that these signatures are good:</P>
<PRE> freeswan-module-2.03_2.4.20_20.9-0.i386.rpm: pgp md5 OK
freeswan-userland-2.03_2.4.20_20.9-0.i386.rpm: pgp md5 OK</PRE>
<H3>Install the RPMs</H3>
<P>Become root:</P>
<PRE> su</PRE>
<P>Install your RPMs with:<P>
<PRE> rpm -ivh freeswan*.rpm</PRE>
<P>If you're upgrading from FreeS/WAN 1.x RPMs, and have problems with that
command, see
<A HREF="upgrading.html#upgrading.rpms">this note</A>.</P>
<P>Then, start FreeS/WAN:</P>
<PRE> service ipsec start</PRE>
<H3><A name="testinstall">Test</A></H3>
<P>To check that you have a successful install, run:</P>
<PRE> ipsec verify</PRE>
<P>You should see as part of the <var>verify</var> output:</P>
<PRE>
Checking your system to see if IPsec got installed and started correctly
Version check and ipsec on-path [OK]
Checking for KLIPS support in kernel [OK]
Checking for RSA private key (/etc/ipsec.secrets) [OK]
Checking that pluto is running [OK]
...</PRE>
<P>If any of these first four checks fails, see our
<A href="trouble.html#install.check">troubleshooting guide</A>.
</P>
<H2><A name="opp.setups.list">Our Opportunistic Setups</A></H2>
<H3>Full or partial opportunism?</H3>
<P>Determine the best form of opportunism your system can support.</P>
<UL>
<LI>For <A HREF="#opp.incoming">full opportunism</A>, you'll need a static
IP and and either control over your reverse DNS or an ISP
that can add the required TXT record for you.</LI>
<LI>If you have a dynamic IP, and/or write access to forward DNS only,
you can do <A HREF="#opp.client">initiate-only opportunism</A></LI>
<LI>To protect traffic bound for real IPs behind your gateway, use
<A HREF="adv_config.html#opp.gate">this form of full opportunism</A>.</LI>
</UL>
<H2><A name="opp.client">Initiate-only setup</A></H2>
<H3>Restrictions</H3>
<P>When you set up initiate-only Opportunistic Encryption (iOE):</P>
<UL>
<LI>there will be <STRONG> no incoming connection requests</STRONG>; you
can initiate all the IPsec connections you need.</LI>
<LI><STRONG>only one machine is visible</STRONG> on your end of the
connection.</LI>
<LI>iOE also protects traffic on behalf of
<A HREF="glossary.html#NAT.gloss">NATted</A> hosts behind the iOE box.</LI>
</UL>
<P>You cannot network a group of initiator-only machines if none
of these is capable of responding to OE. If one is capable of responding,
you may be able to create a hub topology using routing.</P>
<H3><A name="forward.dns">Create and publish a forward DNS record</A></H3>
<H4>Find a domain you can use</H4>
<P>Find a DNS forward domain (e.g. example.com) where you can publish your key.
You'll need access to the DNS zone files for that domain.
This is common for a domain you own. Some free DNS providers,
such as <A HREF="http://www.fdns.net">this one</A>, also provide
this service.</P>
<P>Dynamic IP users take note: the domain where you place your key
need not be associated with the IP address for your system,
or even with your system's usual hostname.</P>
<H4>Choose your ID</H4>
<P>Choose a name within that domain which you will use to identify your
machine. It's convenient if this can be the same as your hostname:</P>
<PRE> [root@xy root]# hostname --fqdn
xy.example.com</PRE>
<P>This name in FQDN (fully-qualified domain name)
format will be your ID, for DNS key lookup and IPsec
negotiation.</P>
<H4>Create a forward TXT record</H4>
<P>Generate a forward TXT record containing your system's public key
with a command like:</P>
<PRE> ipsec showhostkey --txt @xy.example.com</PRE>
<P>using your chosen ID in place of
xy.example.com.
This command takes the contents of
/etc/ipsec.secrets and reformats it into something usable by ISC's BIND.
The result should look like this (with the key data trimmed down for
clarity):</P>
<PRE>
; RSA 2192 bits xy.example.com Thu Jan 2 12:41:44 2003
IN TXT "X-IPsec-Server(10)=@xy.example.com"
"AQOF8tZ2... ...+buFuFn/"
</PRE>
<H4>Publish the forward TXT record</H4>
<P>Insert the record into DNS, or have a system adminstrator do it
for you. It may take up to 48 hours for the record to propagate, but
it's usually much quicker.</P>
<H3>Test that your key has been published</H3>
<P>Check your DNS work</P>
<PRE> ipsec verify --host xy.example.com</PRE>
<P>As part of the <var>verify</var> output, you ought to see something
like:</P>
<PRE> ...
Looking for TXT in forward map: xy.example.com [OK]
...</PRE>
<P>For this type of opportunism, only the forward test is relevant;
you can ignore the tests designed to find reverse records.</P>
<H3>Configure, if necessary</H3>
<P>
If your ID is the same as your hostname,
you're ready to go.
FreeS/WAN will use its
<A HREF="policygroups.html">built-in connections</A> to create
your iOE functionality.
</P>
<P>If you have chosen a different ID, you must tell FreeS/WAN about it via
<A HREF="manpage.d/ipsec.conf.5.html"><VAR>ipsec.conf</VAR></A>:
<PRE> config setup
myid=@myname.freedns.example.com</PRE>
<P>and restart FreeS/WAN:
</P>
<PRE> service ipsec restart</PRE>
<P>The new ID will be applied to the built-in connections.</P>
<P>Note: you can create more complex iOE configurations as explained in our
<A HREF="policygroups.html#policygroups">policy groups document</A>, or
disable OE using
<A HREF="policygroups.html#disable_policygroups">these instructions</A>.</P>
<H3>Test</H3>
<P>That's it! <A HREF="#opp.test">Test your connections</A>.</P>
<A name="opp.incoming"></A><H2>Full Opportunism</H2>
<P>Full opportunism
allows you to initiate and receive opportunistic connections on your
machine.</P>
<A name="incoming.opp.dns"></A><H3>Put a TXT record in a Forward Domain</H3>
<P>To set up full opportunism, first
<A HREF="#forward.dns">set up a forward TXT record</A> as for
<A HREF="#opp.client">initiator-only OE</A>, using
an ID (for example, your hostname) that resolves to your IP. Do not
configure <VAR>/etc/ipsec.conf</VAR>, but continue with the
instructions for full opportunism, below.
</P>
<P>Note that this forward record is not currently necessary for full OE,
but will facilitate future features.</P>
<A name="incoming.opp.dns"></A><H3>Put a TXT record in Reverse DNS</H3>
<P>You must be able to publish your DNS RR directly in the reverse domain.
FreeS/WAN will not follow a PTR which appears in the reverse, since
a second lookup at connection start time is too costly.</P>
<H4>Create a Reverse DNS TXT record</H4>
<P>This record serves to publicize your FreeS/WAN public key. In
addition, it lets others know that this machine can receive opportunistic
connections, and asserts that the machine is authorized to encrypt on
its own behalf.</P>
<P>Use the command:</P>
<PRE> ipsec showhostkey --txt 192.0.2.11</PRE>
<P>where you replace 192.0.2.11 with your public IP.</P>
<P>The record (with key shortened) looks like:</P>
<PRE> ; RSA 2048 bits xy.example.com Sat Apr 15 13:53:22 2000
IN TXT "X-IPsec-Server(10)=192.0.2.11" " AQOF8tZ2...+buFuFn/"</PRE>
<H4>Publish your TXT record</H4>
<P>Send these records to your ISP, to be published in your IP's reverse map.
It may take up to 48 hours for these to propagate, but usually takes
much less time.</P>
<H3>Test your DNS record</H3>
<P>Check your DNS work with</P>
<PRE> ipsec verify --host xy.example.com</PRE>
<P>As part of the <var>verify</var> output, you ought to see something like:</P>
<PRE> ...
Looking for TXT in reverse map: 11.2.0.192.in-addr.arpa [OK]
...</PRE>
<P>which indicates that you've passed the reverse-map test.</P>
<H3>No Configuration Needed</H3>
<P>FreeS/WAN 2.x ships with full OE enabled, so you don't need to configure
anything.
To enable OE out of the box, FreeS/WAN 2.x uses the policy group
<VAR>private-or-clear</VAR>,
which creates IPsec connections if possible (using OE if needed),
and allows traffic in the clear otherwise. You can create more complex
OE configurations as described in our
<A HREF="policygroups.html#policygroups">policy groups document</A>, or
disable OE using
<A HREF="policygroups.html#disable_policygroups">these instructions</A>.</P>
<P>If you've previously configured for initiator-only opportunism, remove
<VAR>myid=</VAR> from <VAR>config setup</VAR>, so that peer FreeS/WANs
will look up your key by IP. Restart FreeS/WAN so that your change will
take effect, with</P>
<PRE> service ipsec restart</PRE>
<H3>Consider Firewalling</H3>
<P>If you are running a default install of RedHat 8.x, take note: you will
need to alter your iptables rule setup to allow IPSec traffic through your
firewall. See <A HREF="firewall.html#simple.rules">our firewall document</A>
for sample <VAR>iptables</VAR> rules.</P>
<H3>Test</H3>
<P>That's it. Now, <A HREF="#opp.test">test your connection</A>.
<H3>Test</H3>
<P>Instructions are in the next section.</P>
<H2><A NAME="opp.test">Testing opportunistic connections</A></H2>
<P>Be sure IPsec is running. You can see whether it is with:</P>
<PRE> ipsec setup status</PRE>
<P>If need be, you can restart it with:</P>
<PRE> service ipsec restart</PRE>
<P>Load a FreeS/WAN test website from the host on which you're running
FreeS/WAN. Note: the feds may be watching these sites. Type one of:<P>
<PRE> links oetest.freeswan.org</PRE>
<PRE> links oetest.freeswan.nl</PRE>
<!--<PRE> links oetest.freeswan.ca</PRE>-->
<P>A positive result looks like this:</P>
<PRE>
You seem to be connecting from: 192.0.2.11 which DNS says is:
gateway.example.com
_________________________________________________________________
Status E-route
OE enabled 16 192.139.46.73/32 -> 192.0.2.11/32 =>
tun0x2097@192.0.2.11
OE enabled 176 192.139.46.77/32 -> 192.0.2.11/32 =>
tun0x208a@192.0.2.11
</PRE>
<P>If you see this, congratulations! Your OE host or gateway will now encrypt
its own traffic whenever it can. For more OE tests, please see our
<A HREF="testing.html#test.oe">testing document</A>. If you have difficulty,
see our <A HREF="#oe.trouble">OE troubleshooting tips</A>.
</P>
<H2>Now what?</H2>
<P>Please see our <A HREF="policygroups.html">policy groups document</A>
for more ways to set up Opportunistic Encryption.</P>
<P>You may also wish to make some <A HREF="config.html">
pre-configured connections</A>.
</P>
<H2>Notes</H2>
<UL>
<LI>We assume some facts about your system in order to make Opportunistic
Encryption easier to configure. For example, we assume that you wish
to have FreeS/WAN secure your default interface.</LI>
<LI>You may change this, and other settings, by altering the
<VAR>config setup</VAR> section in
<VAR>/etc/ipsec.conf</VAR>.
</LI>
<LI>Note that the built-in connections used to build policy groups do
not inherit from <VAR>conn default</VAR>.</LI>
<!--
<LI>If you do not define your local identity
(eg. <VAR>leftid</VAR>), this will be the IP address of your default
FreeS/WAN interface.
-->
<LI>
If you fail to define your local identity and
do not fill in your reverse DNS entry, you will not be able to use OE.</LI>
</UL>
<A NAME="oe.trouble"></A><H2>Troubleshooting OE</H2>
<P>See the OE troubleshooting hints in our
<A HREF="trouble.html#oe.trouble">troubleshooting guide</A>.
</P>
<A NAME="oe.known-issues"></A><H2>Known Issues</H2>
<P>Please see
<A HREF="opportunism.known-issues">this list</A> of known issues
with Opportunistic Encryption.</P>
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