To do so run the following command:

curl -v -s -k --key client.key --cert client.pem https://servername

Thats it.

OpenVPN 2 is available for Centos from the EPEL repository, so you need to have EPEL enabled.

If you do not have EPEL enabled run:

rpm -Uvh http://download.fedoraproject.org/pub/epel/6/i386/epel-release-6-8.noarch.rpm

Installation

To install OpenVPN run:

yum install openvpn lzo -y

Configuration

Setup the SSL CA and keys:

cp -r /usr/share/openvpn/easy-rsa/2.0 /etc/openvpn/open-rsa

Create and customize the vars file /etc/openvpn/open-rsa/vars, Make sure you change the KEY_ values to your own settings

export EASY_RSA="`pwd`"
export OPENSSL="openssl"
export PKCS11TOOL="pkcs11-tool"
export GREP="grep"
export KEY_CONFIG=`$EASY_RSA/whichopensslcnf $EASY_RSA`
export KEY_DIR="/etc/openvpn/keys"
echo NOTE: If you run ./clean-all, I will be doing a rm -rf on $KEY_DIR
export PKCS11_MODULE_PATH="dummy"
export PKCS11_PIN="dummy"
export KEY_SIZE=1024
export CA_EXPIRE=3650
export KEY_EXPIRE=3650
export KEY_COUNTRY="ZA"
export KEY_PROVINCE="Gauteng"
export KEY_CITY="Johannesburg"
export KEY_ORG="Topdog-software"
export KEY_EMAIL="andrew@topdog.za.net"
export KEY_CN="Topdog-software OpenVPN CA"
export KEY_NAME="tdss"
export KEY_OU="Topdog-software"

Create the keys directory:

mkdir /etc/openvpn/keys

Create the CA:

cd /etc/openvpn/open-rsa
source ./vars
./clean-all
./build-ca

Create the servers SSL certificate (replace vpn.home.topdog-software.com with name of your server):

./build-key-server vpn.home.topdog-software.com

Generate Diffie Hellman parameters:

./build-dh

Create the leases file:

touch /etc/openvpn/ipp.txt

Create the configuration file /etc/openvpn/server.conf:

port 1194
proto udp
dev tun
ca keys/ca.crt
cert keys/vpn.home.topdog-software.com.crt
key keys/vpn.home.topdog-software.com.key
dh keys/dh1024.pem
cipher AES-128-CBC
server 10.0.0.0 255.255.255.0
ifconfig-pool-persist ipp.txt
client-config-dir ccd
keepalive 10 120
comp-lzo
persist-key
persist-tun
status /var/log/openvpn-status.log
verb 3

Create iptables rules to allow traffic through:

*filter
..
..
-A INPUT -p udp -m state --state NEW -m udp --dport 1194 -j ACCEPT
-A FORWARD -i tun+ -o eth0 -j ACCEPT
-A FORWARD -i eth0 -o tun+ -j ACCEPT

Enable packet forwarding:

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

Make it permanent add the following to /etc/sysctl.conf:

net.ipv4.ip_forward = 1

Your OpenVPN should be ready to go, start OpenVPN:

service openvpn start

Client configuration

Each client requires a certificate & key pairing, lets create one:

./build-key client1.home.topdog-software.com

Copy the client1.home.topdog-software.com.crt, ca.crt and client1.home.topdog-software.com.key files to the OpenVPN keys directory on the client.

Create the client OpenVPN configuration /etc/openvpn/server.conf:

remote vpn.home.topdog-software.com 1194
client 
remote-cert-tls server 
dev tun0 
proto udp
resolv-retry infinite 
nobind 
persist-key 
persist-tun 
float 
ca keys/ca.crt 
cert keys/client1.home.topdog-software.com.crt
key keys/client1.home.topdog-software.com.key
cipher AES-128-CBC
comp-lzo
status /var/log/openvpn-client.log

Static addresses

If you want some clients to get static addresses:

mkdir /etc/openvpn/ccd

Create a client file for each of the clients you want to get a static address in /etc/openvpn/ccd the file name should match the CN in the client certificate.

ifconfig-push 10.0.0.2 10.0.0.1

To get OpenVPN up and running off the command line is a simple process. The commands below need to be run as a privileged user if your root account is not enabled use sudo to run the commands.

Install OpenVPN

To install OpenVPN 2 from macports run:

port install openvpn2

Install TunTap

To install TunTap from macports run:

port install tuntaposx

Configure it to startup at boot:

launchctl load -w /Library/LaunchDaemons/org.macports.tuntaposx.plist

You need TunTap as it allows you to create virtual interfaces using the supplied kernel extensions. If you don't install TunTap you will get the error Cannot allocate TUN/TAP dev dynamically when you try and make a OpenVPN connection.

Configuration

Create a directory to hold your configuration and keys.

mkdir /opt/local/etc/openvpn

Place your keys and configuration files in /opt/local/etc/openvpn/

A sample client configuration is provided below.

client
dev tun
proto udp
remote vpn.home.topdog-software.com 1194
nobind
resolv-retry infinite
tls-client
ca /opt/local/etc/openvpn/ca.crt
cert /opt/local/etc/openvpn/client.crt
key /opt/local/etc/openvpn/client.key
ns-cert-type server
cipher BF-CBC
tls-cipher DHE-RSA-AES256-SHA
tls-remote vpn.home.topdog-software.com
tls-auth /opt/local/etc/openvpn/tls-auth.key 1
remote-cert-tls server
comp-lzo
persist-key
persist-tun
mute-replay-warnings
verb 3
mlock

Connecting

To connect simply run:

openvpn2 --config /opt/local/etc/openvpn/openvpn.conf

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

The Mac OSX IPSEC VPN client setup via "System preferences" only supports IPSEC/XAUTH and IPSEC/L2TP both of which give you a different IP address for your tunnel interface. System preferences on the backend uses Racoon so it is possible via the command line to setup a pure IPSEC connection.

In my previous post i described how to configure a Strongswan server for use with Mac OSX, Ipad, Iphone clients. For the sake of brevity i will not repeat that in this post.

This scenario assumes you are connected to a lan 10.128.1.0/24 and your IP address is 10.128.1.2 and you are connecting to a remote network 192.168.1.0/24 protected by an IPSEC VPN running Strongswan on a gateway with a dynamic address being resolved via dynamic DNS. IPSEC Authentication is done using Certificates.

Configuration

Client configuration.

Edit /etc/racoon/racoon.conf and add the following to the bottom.

include "/opt/local/etc/cmdline-ipsec.conf" ;

Create a configuration template file /opt/local/etc/cmdline-ipsec.conf.tmpl. I am using a template because the remote side has a dynamic ip address and racoon does not support DNS names only IP addresses, a custom script resolves the hostname and then generates an updated racoon configuration from this template file with the resolved IP address.

remote %SERVERIP% {
        exchange_mode main;
        ca_type x509 "/opt/local/etc/pki/cacert.pem";
        certificate_type x509 "/opt/local/etc/pki/example.pem" "/opt/local/etc/pki/example.key.pem";
        proposal_check obey;
        mode_cfg off;
        dpd_delay 360;
        nat_traversal on;
        my_identifier asn1dn;
        ike_frag on;
        script "/opt/local/bin/phase1-up.sh" phase1_up;
        script "/opt/local/bin/phase1-down.sh" phase1_down;
        lifetime time 24 hour;
        passive off;
        proposal {
                encryption_algorithm aes256;
                hash_algorithm sha512;
                authentication_method rsasig;
                dh_group 2;
       }
}

sainfo anonymous {
        lifetime time 24 hour;
        pfs_group modp2048;
        encryption_algorithm aes256;
        authentication_algorithm hmac_sha1, hmac_sha256, hmac_sha512;
        compression_algorithm deflate ;
}

Create the phase1 up script /opt/local/bin/phase1-up.sh

#!/bin/sh

#
# sa-up.sh local configuration for a new SA
#
PATH=/bin:/sbin:/usr/bin:/usr/sbin:/opt/local/bin:/opt/local/sbin
MYIP=10.128.1.2
PROTECTEDNET=192.168.1.0/24

echo $@
echo "LOCAL_ADDR = ${LOCAL_ADDR}"
echo "LOCAL_PORT = ${LOCAL_PORT}"
echo "REMOTE_ADDR = ${REMOTE_ADDR}"
echo "REMOTE_PORT = ${REMOTE_PORT}"

LOCAL="${LOCAL_ADDR}[${LOCAL_PORT}]"
REMOTE="${REMOTE_ADDR}[${REMOTE_PORT}]"

echo "
spdadd ${MYIP}/32[any] ${PROTECTEDNET}[any] any
       -P out ipsec esp/tunnel/${LOCAL}-${REMOTE}/require;
spdadd ${PROTECTEDNET} ${MYIP}[any] any
       -P in ipsec esp/tunnel/${REMOTE}-${LOCAL}/require;
" | setkey -c

Create the phase1 down script /opt/local/bin/phase1-down.sh

#!/bin/sh

#
# sa-down.sh local remove SA
#

PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin
MYIP=10.128.1.2
PROTECTEDNET=192.168.1.0/24

echo $@
echo "LOCAL_ADDR = ${LOCAL_ADDR}"
echo "LOCAL_PORT = ${LOCAL_PORT}"
echo "REMOTE_ADDR = ${REMOTE_ADDR}"
echo "REMOTE_PORT = ${REMOTE_PORT}"

LOCAL="${LOCAL_ADDR}[${LOCAL_PORT}]"
REMOTE="${REMOTE_ADDR}[${REMOTE_PORT}]"

echo "
deleteall ${REMOTE_ADDR} ${LOCAL_ADDR} esp;
deleteall ${LOCAL_ADDR} ${REMOTE_ADDR} esp; 
spddelete ${MYIP}/32[any] ${PROTECTEDNET}[any] any
        -P out ipsec esp/tunnel/${LOCAL}-${REMOTE}/require;
spddelete ${PROTECTEDNET}[any] ${MYIP}[any] any
        -P in ipsec esp/tunnel/${REMOTE}-${LOCAL}/require;
" | setkey -c

Create the custom start script /opt/local/sbin/start-vpn

#!/bin/bash
#
#
SERVERNAME="strongswan-example.dyndns.org"
SERVERIP=$(host $SERVERNAME|awk '{print $4}')
status=$(racoonctl show-sa isakmp|wc -l|awk '{print $1}')
if [ "$status" != "2" ]; then
   echo "Not connected, starting conn"
   sed -e "s:%SERVERIP%:${SERVERIP}:" \
   /opt/local/etc/cmdline-ipsec.conf.tmpl > /opt/local/etc/cmdline-ipsec.conf
   racoonctl reload-config
   racoonctl vpn-connect $SERVERIP
else
   racoonctl show-sa isakmp
   echo "Already connect, exiting"
fi

Make the script executable

chmod +x /opt/local/sbin/start-vpn

Server configuration

Update the ipsec.conf configuration from my previous post to add the following conn

conn rw
        leftcert=vpn.example.org.pem
        leftid=@vpn.example.org
        leftfirewall=yes
        right=%any
        rightsubnet=0.0.0.0/0
        rekey=yes

Testing

Open a command prompt and run the command, as root or using sudo.

start-vpn

You should be able to connect to hosts on the protected network (192.168.1.0/24)

To stop the connection run the command.

racoonctl vpn-disconnect strongswan-example.dyndns.org

Related articles

• IPSEC split tunneling VPN with Mac OSX and Strongswan 5 on Centos/RHEL 6
• Iphone/Ipad/Mac OSX IPSEC VPN with Strongswan 5 on Centos/RHEL 6

The Baruwa project provides up to date deb packages for both distributions.

Packages are available for:

• squeeze
• wheezy
• sid
• lucid
• maverick
• natty
• oneiric
• precise
• quantal

Usage

To use the packages you need to enable the baruwa apt repo.

cat > /etc/apt/sources.list.d/baruwa.list << 'EOF'
deb http://apt.baruwa.org/ubuntu precise main
EOF

Change "precise" to your specific release name

Add the repo's GPG key

wget -O - http://apt.baruwa.org/baruwa-apt-keys.gpg | apt-key add -

Then run

apt-get update
apt-get install mailscanner

Support & Assistance

Use the friendly Baruwa project mailing list

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

So head off and get your copy.