FireBrick IPsec (Road Warrior Howto)

FireBrick Road Warrior IPsec

The FireBrick manual goes into some detail on configuring IPsec. This page contains specific examples for a simple scenario where you have one or more clients devices - iPhones iPads, Android phones/tablets or Windows machines, and a FireBrick in your home or office, and you would like to VPN (using IPsec) to the FireBrick and have an IP address on your LAN.

In this example we are assuming you can allocate some IP addresses on you LAN. You do this by picking a range of addresses and setting up a roaming-pool (see below). You need to ensure the IP range does not clash with devices on the LAN and is not in the DHCP ranges that could allocate to the LAN. You also need to set proxy-arp on the LAN interface settings to allow communications to other devices on your LAN. Alternatively you could set private IP addresses in the pool and set the nat setting. You should probably also consider firewalling rules for traffic to/from IPsec connections.

Tools

There are three tools to help with setting up Road Warrior connections on the FireBrick web site. You can download these by viewing with a browser and saving the source, or using curl or wget. make-key creates a private key. make-cert makes a certificate (signed with a key). make-profile makes an iPhone profile file that allows the VPN to be configured on the iPhone. For security reasons, all of these need you to run them locally (e.g. on a linux box, or windows under Cygwin).

Certificate Authority

Let's start by making a Certificate Authority (CA). This signs certificates, such as the one we load in to the FireBrick end of the link. The CA ends up as being two files - one is the private key file, which you keep secret. This is what you need to sign things with the CA. The other is the actual certificate file, signed by the key.

First make the private key file for the CA. We'll call it ca-key.pem. This file should be kept secret.

./make-key ca-key.pem

Then make a certificate file, and sign it using the key file. We'll call it ca-cert.pem. This involves several attributes in the DN (Distinguished name) which mostly don't matter much for your own certificate (/C=Country, /ST=State, /L=Locality, /O=OrganisationName, /CN=CommonName). Typically you would set just the CommonName, using your home or company name (eg /CN=Acme Widget CA).

./make-cert CA DN="/C=GB/O=My Office/CN=example.com" KEY=ca-key.pem ca-cert.pem

FireBrick (server) certificate

Nest we make a certificate file for the FireBrick itself. This is how the FireBrick proves itself to the client device. Again, there is a key and a cert file for this, with both being loaded in to the FireBrick. The key is what allows the FireBrick to prove itself. The cert is signed by the CA key, which is how the phone knows to trust the FireBrick. Note the extra FQDN= which sets the SubjectAltName. The FQDN entry is just a name used to get the right certificate, and should match the local-id (prefixed FQDN:) in the config so that the FireBrick can work our which certificate to use when negotiating, and the client can check the certificate matches the server.

First make a private key, e.g. server-key.pem

./make-key server-key.pem

Then make a certificate, e.g. server-cert.pem

./make-cert DN="/C=GB/O=Server/CN=server.example.com" FQDN=server.example.com KEY=server-key.pem ISSUER-KEY=ca-key.pem ISSUER=ca-cert.pem server-cert.pem

FireBrick Certificate Config

The FireBrick needs copies of the CA certificate and the server certificate and private key.

Load these files - ca-cert.pem, server-key.pem, and server-cert.pem - using the FireBrick X.509 certificate and key management UI page (Config Certificates).

The private key associated with the CA certificate ca-key.pem is no longer needed once it has been used to sign the server certificate. It is a good idea to store this file in a safe place (eg on a memory stick in a secure location), and remove it from any networked machine. It can of course be retrieved and reused if you wish to make further server certificates using the same CA certificate.

FireBrick IPsec config

The FireBrick needs a configuration for the connection, and roaming pools and user identities. The connection can be used for any number of devices at once with the same pool of IP addresses; each would have a user name and password defined.

The basic server config is in ipsec-ike containing a connection and roaming entry, e.g.

<ipsec-ike>
 <connection name="server" roaming-pool="roam-pool" auth-method="Certificate" peer-auth-method="EAP" mode="Wait" local-ID="FQDN:server.example.com"/>
 <roaming name="roam-pool" ip="[ranges of LAN IPs]" DNS="[DNS, e.g. 8.8.8.8]"/>
</ipsec-ike>

Each roaming user then needs an eap user record.

<eap name="fred" full-name="Fred Bloggs" password="[password]" subsystem="IPsec" methods="MSChapV2"/>

iPhone profile

Each iPhone needs a profile file specific to that user. Once created you can email this, or make a web link to it, and the iPhone will recognise it and allow it to be installed. Let's call it fred.mobileconfig for our user called fred as in the above example config.

./make-profile SERVER=IP-of-server LOCALID="Fred's iPhone" CA=ca-cert.pem SERVERID=server.example.com USERNAME=fred PROFNAME="Office VPN" VPNNAME=FireBrick fred.mobileconfig

Note that the SERVERID must match the FQDN entry used when making the server certificate, and hence the local-ID in the config for the connection.

VPN up on an iPhone

Android setup

We recommend you use the StrongSwan app on Android. The app then needs the CA certificate which you can email yourself and install, and the settings for the host name, user name, password.