This is how you do it for various *nix types.

Debian/Ubuntu/SUSE

mandb

RHEL/CENTOS/SL/Fedora

makewhatis

AIX/Solaris/HP-UX

catman -w

This plugin is not enabled by default to enable it you need to add the following to your ./configure options

--enable-xauth-pam

You do require the pam development headers and libraries on your build machine to successfully compile.

System Configuration

The plugin is configurable in the strongswan.conf file, you are able to change the pam service that is used for authentication.

By default the login pam service is used for authentication.

I will create a new service called ipsec for demonstration.

charon {
    plugins{
        xauth-pam {
            pam_service = ipsec
        }
    }
}

The pam service configuration file is as follows.

#%PAM-1.0
# /etc/pam.d/ipsec
auth        required      pam_env.so
auth        sufficient    pam_unix.so nullok try_first_pass
auth        requisite     pam_succeed_if.so uid >= 500 quiet
auth        required      pam_deny.so

account     required      pam_unix.so
account     sufficient    pam_localuser.so
account     sufficient    pam_succeed_if.so uid < 500 quiet
account     required      pam_permit.so

password    requisite     pam_cracklib.so try_first_pass retry=3 type=
password    sufficient    pam_unix.so sha512 shadow nullok try_first_pass use_authtok
password    required      pam_deny.so

session     optional      pam_keyinit.so revoke
session     required      pam_limits.so
session     [success=1 default=ignore] pam_succeed_if.so service in crond quiet use_uid
session     required      pam_unix.so

Now to use PAM authentication in your connections you set for XAuth:

rightauth2=xauth-pam

Hybrid Authentication:

rightauth=xauth-pam

You are good to go and should be able to use any pam module to authenticate your users to your VPN. The options are endless: SQL, LDAP, RADIUS, LOCAL etc.

Related articles

• Iphone/Ipad/Mac OSX IPSEC VPN with Strongswan 5 on Centos/RHEL 6
• Mac OSX IPSEC VPN via command line using builtin Racoon client
• IPSEC split tunneling VPN with Mac OSX and Strongswan 5 on Centos/RHEL 6

With the release of Strongswan 5.0.1 it is no longer the only way to support split tunneling.

Strongswan 5.0.1 introduces the unity plugin which allows for the configuration of split tunneling either using a charon option or using the attr plugin which is enabled by default.

The unity plugin is not enabled by default to enable it you need to add the following to your ./configure options

--enable-unity

Charon option

To enable this option you need to edit the strongswan.conf file and set

charon {
    # ... other options
    cisco_unity = yes
    #...
}

As a client strongswan will install policies only for the received Split-Include attributes and IPsec bypass policies for received Local-LAN attributes.

As a server strongswan will send Split-Include attributes for leftsubnet definitions containing multiple subnets to clients that support the IKEv1 Cisco Unity Extensions.

Attr plugin option

It is also possible to configure split tunneling using the attr plugin. Two new options have been added:

• split-include - Comma-separated list of subnets to tunnel
• split-exclude - Comma-separated list of subnets not to tunnel

charon {
    # ... other options
    split-include = 192.168.1.0/24, 172.16.0.0/16
    split-exclude = 10.128.0.0/16
    #...
}

Related articles

• Iphone/Ipad/Mac OSX IPSEC VPN with Strongswan 5 on Centos/RHEL 6
• Mac OSX IPSEC VPN via command line using builtin Racoon client
• IPSEC split tunneling VPN with Mac OSX and Strongswan 5 on Centos/RHEL 6

In my previous post i described how to setup an IPSEC VPN for use with Iphone, Ipad and Mac OSX IPSEC VPN clients.

This post describes how to enable split tunneling which is supported by the Mac OSX IPSEC client. Although split tunneling is considered insecure there are cases where it is ideal to run split tunnels.

The scenario for this post is that you are connected to a LAN (10.128.0.0/24) with internet access via a gateway on the LAN, you want to connect to a different network 192.168.1.0/24 which is only accessible via VPN, but you want to retain access to resources on the LAN while accessing the remote 192.168.1.0/24 network.

To follow this howto you need to have strongswan rpm with the attr-sql plugin enabled with a sqlite or mysql backed plugin enabled. The EPEL rpm does not support these features at the time of writing. You need to build your own custom strongswan rpm. You can download my spec file and use it to build yourself the rpm.

Installation

Install the rpm

rpm -Uvh strongswan-5.0.0-5.el6.x86_64.rpm

Configuration

Use the following configuration files, if you installation is new refer to my previous post on how to create the certificates

Create strongswan configuration

This strongswan configuration allows you to use both certificates and pre shared keys.

Add the username and password to /etc/strongswan/ipsec.secrets

andrew : XAUTH "5tr0ngp4ss0rd"

Add the preshared key to /etc/strongswan/ipsec.secrets

: PSK "very long pre shared key difficlult to guess"

Edit /etc/strongswan/ipsec.conf with the following content.

config setup

conn %default
        ikelifetime=60m
        keylife=20m
        rekeymargin=3m
        keyingtries=1
        keyexchange=ikev1
        left=%defaultroute
        leftsubnet=192.168.1.0/24
        esp=aes256-sha256-modp2048,aes256-sha1!
        ike=aes256-sha1-modp1536,aes256-sha512-modp1024,aes256-sha1-modp1024!
        auto=add

conn rw-xauth
        leftcert=vpn.example.org.pem
        leftid=@vpn.example.org
        leftauth=pubkey
        leftfirewall=yes
        right=%any
        rightauth=pubkey
        rightauth2=xauth
        rightsourceip=%vpnclients
        rekey=yes

conn rw-xauth-psk
        leftfirewall=yes
        leftauth=psk
        right=%any
        rightauth=psk
        rightauth2=xauth
        rightsourceip=%vpnclients
        rekey=yes

Add the attr-sql plugin configuration to /etc/strongswan/strongswan.conf

libhydra {
        plugins {
                attr-sql {
                        database = sqlite:///var/lib/strongswan/ipsec.db
                }
        }
}

Restart the service

Restart the service for the configurations to take effect.

service strongswan restart

Create sql attr Database

Create a sqlite database to store the pool information.

wget http://bit.ly/PyMe08
cat sqlite.sql | sqlite3 /var/lib/strongswan/ipsec.db

Create a database based pool

The pool will store the address range, the split tunnel network (192.168.1.0/24), dns server to assign and a banner.

strongswan pool --add vpnclients --start 192.168.2.0 --end 192.168.2.254 --timeout 48
strongswan pool --addattr dns --server 192.168.1.1 --pool vpnclients
strongswan pool --addattr unity_def_domain --string "example.org" --pool vpnclients
strongswan pool --addattr banner --string "example.org - all activity is monitored" --pool vpnclients
strongswan pool --addattr unity_split_include --subnet "192.168.1.0/255.255.255.0" --pool vpnclients

Testing

Configure your Mac OSX VPN client.

• Launch System preferences then select Network > + > Interface > VPN > VPN Type > Cisco IPSEC > Create

Set the Fields

Description      Strongswan-IPSEC
Server           vpn.example.org
Account          andrew
Password         5tr0ngp4ss0rd
Use Certificate  ON
Certificate      name.example.org

Now when you connect, you will remain connected to your LAN as well as the remote network 10.128.0.0/24 if you run netstat -rn you will see the 10.128.0.0/24 network being routed via the tunnel interface.

Related articles

• Iphone/Ipad/Mac OSX IPSEC VPN with Strongswan 5 on Centos/RHEL 6
• Mac OSX IPSEC VPN via command line using builtin Racoon client

This howto describes setting up an IPSEC VPN for use with the Iphone, Ipad and Mac OSX VPN clients on Centos/RHEL 6. I am using the 5.x branch of Strongswan which is now the mainline actively maintained branch. At the time of writing the 5.x EPEL package was only available in the testing repo.

The configuration should work both with NAT and without NAT on both sides, if you are NATing on the server side make sure your forward UDP 500 and 4500 to the machine running strongswan.

This howto uses example.org and 192.168.1.0/24 and 192.168.2.0/24 networks for illustration purposes, you need to change these to suit your own setup.

Install

To access the EPEL packages you need to enable the EPEL repo. You are then able to install the strongswan package.

yum install --enablerepo=epel-testing strongswan

Create the required configuration directories

mkdir -p /etc/strongswan/ipsec.d/{aacerts,acerts,cacerts,certs,crls,ocspcerts,private}

Configuration

Create a CA

For RSA authentication you need to setup a CA which will issue the certificates to be used by the server and the clients.

cd /etc/pki/tls/misc
./CA -newca
echo 00 > /etc/pki/CA/crlnumber
openssl ca -gencrl -out /etc/pki/CA/crl.pem

Install to strongswan directories

ln -s /etc/pki/CA/cacert.pem /etc/strongswan/ipsec.d/cacerts/
ln -s /etc/pki/CA/crl.pem /etc/strongswan/ipsec.d/crls/

Create the server certificate

Apple clients require that the servers certificate subjectAltName attribute contain either the server IP address or server DNS name. To ensure the server certificate contains the subjectAltName attribute edit the openssl.cnf and set it under the [ usr_cert ] section

For DNS name set it to

subjectAltName=DNS:vpn.example.org

For IP address set it to

subjectAltName=IP:192.168.1.1

Now generate and sign the server certitifcate

./CA -newreq
./CA -sign

Install to strongswan directories.

mv newcert.pem /etc/strongswan/ipsec.d/certs/vpn.example.org.pem
mv newkey.pem /etc/strongswan/ipsec.d/private/vpn.example.org.key

Add the private key password to /etc/strongswan/ipsec.secrets

: RSA vpn.example.org.key "p4ssw0rd"

Create the client certificate

This is the certificate that will be used by you VPN clients ie Ipad/Iphone, edit the openssl.cnf and comment out the subjectAltName attribute setting.

Now generate and sign the client certificate, do this for all the clients you expect to use.

./CA -newreq
./CA -sign
openssl pkcs12 -export -in ipad.example.org.pem -inkey ipad.example.org.key \
 -certfile /etc/pki/CA/cacert.pem -out ipad.p12

You now need to import the CA certificate and the client p12 certificate on to the device. You need to download the Iphone configuration utility and use it to import the certificates to your device.

Add the username and password to /etc/strongswan/ipsec.secrets

andrew : XAUTH "5tr0ngp4ss0rd"

Create strongswan configuration

Edit /etc/strongswan/ipsec.conf with the following content.

config setup

conn %default
        ikelifetime=60m
        keylife=20m
        rekeymargin=3m
        keyingtries=1
        keyexchange=ikev1
        left=%defaultroute
        leftsubnet=192.168.1.0/24
        auto=add

conn rw-xauth
        leftcert=vpn.example.org.pem
        leftid=@vpn.example.org
        leftauth=pubkey
        leftfirewall=yes
        right=%any
        rightauth=pubkey
        rightauth2=xauth
        rightsourceip=192.168.2.0/24

The above setup assumes the network behind the vpn is 192.168.1.0/24 and virtual IP addresses will be assigned to VPN clients from the 192.168.2.0/24 network block.

Enable packet forwarding

If your system is not setup for packet forwarding enable it.

echo 1 > /proc/sys/net/ipv4/ip_forward

Edit /etc/sysctl.conf and set

net.ipv4.ip_forward = 1

Testing

Start strongswan.

service strongswan start

Check /var/log/messages and /var/log/secure for any errors.

Ipad configuration

• Launch Settings then select General > Network > VPN > Add VPN Configuration
• Toggle VPN type to IPSec

Set the Fields

Description      Strongswan-IPSEC
Server           vpn.example.org
Account          andrew
Password         5tr0ngp4ss0rd
Use Certificate  ON
Certificate      ipad.example.org

A VPN connection should now be possible by toggling VPN to ON under Settings > VPN.

Related articles

• IPSEC split tunneling VPN with Mac OSX and Strongswan 5 on Centos/RHEL 6
• Mac OSX IPSEC VPN via command line using builtin Racoon client

error (no valid KEY) resolving 'dlv.isc.org/DNSKEY/IN': 156.154.101.23#53
error (broken trust chain) resolving './NS/IN': 193.0.14.129#53

The issue is caused by the date on the system falling out of sync, which causes DLV validation to fail.

This issue can be fixed by doing the following on Centos / RHEL.

ntpdate ntp.pool.org
hwclock --systohc
rm /var/named/dynamic/managed-keys.bind*
service named restart

Name resolution so now work without any issues.

I have used Centos 5.1 in this howto however i am sure it can be adapted to work with any other Linux distribution as the concepts remain the same. The main components that i have used are the following.

• http server - apache
• tftp server
• dhcp server - isc dhcp
• dns server - isc bind

Installation of software

I will assume that you already have an installed bare bones Centos 5.1 system with the hostname server1.example.com. During this howto we will be using the fictitious domain example.com please substitute with your own domain, and the 192.168.1.0/24 network

DNS server

For this how to we will be using a DNS server because our media is stored on a virtual host, however it is possible to skip DNS setup and just use ip addresses if the installation servers http server is only going to be used to serve the media.

Install bind

# yum install bind bind-chroot

Configure bind and add the example.com zone, make the changes below to the file /var/named/chroot/etc/named.conf

options {
        directory       "/var/named";
        dump-file       "/var/named/data/cache_dump.db";
        statistics-file "/var/named/data/named_stats.txt";
        memstatistics-file "/var/named/data/named_mem_stats.txt";
        allow-query     { any; };
};
logging {
        channel default_debug {
                file "data/named.run";
                severity dynamic;
        };
};
view single_view {
        match-clients      { any; };
        match-destinations { any; };
        recursion yes;
        include "/etc/named.rfc1912.zones";

        zone "example.com" {
                type master;
                file "data/example.com.hosts";
        };

        zone "1.168.192.in-addr.arpa" {
                type master;
                file "data/1.168.192.in-addr.arpa.hosts";
        };
};

Add this to the file /var/named/chroot/var/named/data/example.com.hosts

$ttl 38400
@       IN      SOA     server1.example.com. root.example.com. (
                        2008012900
                        10800
                        3600
                        604800
                        38400 )
@       IN      NS      server1.example.com.
server1 IN A 192.168.1.2
kickstart IN A 192.168.1.2

Add this to the file /var/named/chroot/var/named/data/1.168.192.in-addr.arpa.hosts

$ttl 38400
@       IN      SOA     server1.example.com. root.example.com. (
                        2008012900
                        10800
                        3600
                        604800
                        38400 )
@       IN      NS      server1.example.com.
2 IN PTR server1.example.com.

Setup bind to start at boot

# chkconfig --level 345 named on
# service named start

DHCP server

We need a dhcp server to allow for pxebooting and automatic assignment of network parameters.

Install dhcp server

# yum install dhcp

Configure the dhcp server make changes to /etc/dhcpd.conf to look like below

option domain-name-servers 192.168.1.2;
allow booting;
allow bootp;

next-server 192.168.1.2;
filename "pxelinux.0";

subnet 192.168.1.0 netmask 255.255.255.0
{
        range 192.168.1.50 192.168.1.250;
        allow unknown-clients;
        ignore client-updates;
}

Enable dhcp server to start at boot

# chkconfig --level 345 dhcpd on
# service dhcpd start

Tftp server

The tftp server is used to serve the boot images that are required to pxe boot the machines to be installed.

Install tftp server

# yum install tftp-server

Configure tftp-server to start at boot

# chkconfig --level 345 tftp-server on

Copy syslinux image to tftp server directory

# cp /usr/lib/syslinux/pxelinux.0 /tftpboot

Create pxeboot directory structure

# mkdir /tftpboot/{pxelinux.cfg,msgs,os}

Start tftp server

# service xinetd restart

Http server

The http server is used to serve our install tree

Install apache

# yum install httpd

Configure virtual hosts, Since i need to allow for the server to be used for other purposes i am going to setup virtualhosts. The first virtual host is the default virtual host and the second one is the one that will be serving our network install. Edit the file /etc/httpd/conf/httpd.conf and add the following.

NameVirtualHost *:80
<VirtualHost *:80>
   Servername server1.example.com
</VirtualHost>
<VirtualHost *:80>
   Servername kickstart.example.com
   DocumentRoot /srv/www
   ErrorLog logs/kickstart.example.com-error_log
   CustomLog logs/kickstart.example.com-access_log common
   <Directory /srv/www/>
   Options +Indexes
   </Directory>
</VirtualHost>

Setup distributions

You can setup as many distributions as you want, i will be setting up Centos to serve as an example on how it is done.

Centos 5.1

Create directories to hold the install tree

# mkdir -p /srv/www/centos/5.1/os/i386

Copy files from the DVD or CD's

# mount /media/cdrom
# cp /media/cdrom/* /srv/www/centos/5.1/os/i386

Create the directory to hold pxe boot images

# mkdir /tftpboot/os/centos_5.1

Copy pxeboot images to server

# cp /media/cdrom/images/pxeboot/{vmlinuz,initrd.img} /tftpboot/os/centos_5.1

Create a minimal kickstart to point to http installation, create file /srv/www/centos_5.1.ks and add the following

install
url --url http://kickstart.example.com/centos/5.1/os/i386/

Add Centos 5.1 to tftpboot menu, edit the file /tftpboot/pxelinux/default and add the following

default centos5.1
prompt 1
timeout 600
display boot.msg

label centos5.1
        kernel os/centos_5.1/vmlinuz
        append ks=http://kickstart.example.com/centos_5.1.ks initrd=os/centos_5.1/initrd.img