Libreswan

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About

Openswan is a free implementation of IPsec& IKE for Linux. IPsec is the Internet Protocol Security and uses strong cryptography to provide both authentication and encryption services. These services allow you to build secure tunnels through untrusted networks. Everything passing through the untrusted net is encrypted by the ipsec gateway machine and decrypted by the gateway at the other end of the tunnel.The resulting tunnel is a virtual private network or VPN.

• Credits: John Crisp
• Discuss: This How-to can be discussed on the forums here

	Note:
	I am developing some ipsec contribs based on Libreswan - see bugs 8677 and 8890 Configuration is very similar. I have compiled Libreswan packages for v8. They are in repos already for v9

Installation

[edit]

• For SME8
• For SME9

For SME Server 8, at least openswan-2.6.38-1.x86_64.rpm is required. However, this version is not to be found in the default repo's, nor any of the additional repo's. A trusted copy of Openswan for SME8 can be found here. (This is only for 64bit systems!)

After you have downloaded the above file, you can install it by issuing the following command:

yum localinstall openswan-2.6.38-1.x86_64.rpm

For SME Server 9, the Openswan can be found in the default repo's, so to install Openswan on SME Server 9, simply enter the following command:

yum install openswan

Openswan as a SME Server service

To make the Openswan service start at boot time we need to issue the following commands as root:

ln -s /etc/rc.d/init.d/e-smith-service /etc/rc7.d/S99ipsec
chkconfig ipsec on
config set ipsec service
config setprop ipsec status enabled

This makes ipsec service start at boot time and you can disable/enable the ipsec service at will.

SME Server firewall configuration

Since Openswan/ipsec is all about security and private connections, the SME Server firewall rules play a crucial part of a correct configuration.

We need a new template fragment to allow ipsec through the firewall

mkdir -p /etc/e-smith/templates-custom/etc/rc.d/init.d/masq
nano -w /etc/e-smith/templates-custom/etc/rc.d/init.d/masq/15AllowIPsec

Add the following code :

# IPsec ports
/sbin/iptables -A INPUT -i $OUTERIF -p udp --sport 500 --dport 500 -j ACCEPT 
/sbin/iptables -t mangle -A PREROUTING -i $OUTERIF -p 50 -j MARK --set-mark 1  
/sbin/iptables -A INPUT -i $OUTERIF -m mark --mark 1 -j ACCEPT 
/sbin/iptables -A FORWARD -i $OUTERIF -m mark --mark 1 -j ACCEPT 
/sbin/iptables -A INPUT -i $OUTERIF -m mark --mark 2 -j ACCEPT 
/sbin/iptables -A FORWARD -i $OUTERIF -m mark --mark 2 -j ACCEPT 
/sbin/iptables -t nat -I POSTROUTING -m policy --dir out --pol ipsec -j ACCEPT 

expand-template /etc/rc.d/init.d/masq
service masq restart

We also need to disable redirects.

	Note:
	The below script will work for SME8 but NOT necessarily for SME9! Since in SME9 the NIC's have no longer fixed names like eth0 and eth1. We need to come up with an auto detect scipt. See experimental section below for an 'universal' approach for both SME8 and SME9. Feedback in the forum appreciated.

I have the following code in a file called Disable_Redirects.sh and a link to it in /etc/rc.d/rc.local

#!/bin/bash
# For OpenSwan
# Disable send redirects
echo 0 > /proc/sys/net/ipv4/conf/all/send_redirects
echo 0 > /proc/sys/net/ipv4/conf/default/send_redirects
echo 0 > /proc/sys/net/ipv4/conf/eth0/send_redirects
echo 0 > /proc/sys/net/ipv4/conf/eth1/send_redirects
echo 0 > /proc/sys/net/ipv4/conf/lo/send_redirects
# echo 0 > /proc/sys/net/ipv4/conf/ppp0/send_redirects
# Disable accept redirects
echo 0 > /proc/sys/net/ipv4/conf/all/accept_redirects
echo 0 > /proc/sys/net/ipv4/conf/default/accept_redirects
echo 0 > /proc/sys/net/ipv4/conf/eth0/accept_redirects
echo 0 > /Subscript textproc/sys/net/ipv4/conf/eth1/accept_redirects
echo 0 > /proc/sys/net/ipv4/conf/lo/accept_redirects
# echo 0 > /proc/sys/net/ipv4/conf/ppp0/accept_redirects

---

	Note:
	Experimental code to disable redirects for both SME8 and SME9

This is experimental. Please provide your feedback in the forums.

To disable redirects (port forwarding) within the IPsec tnnels, we have to create a custom template that will disable these at boot time. To create the custom template execute the following commands as root (simplefied):

mkdir -p /etc/e-smith/templates/templates-custom/etc/sysctl.conf
nano -w /etc/e-smith/templates/templates-custom/etc/sysctl.conf/net.ipv4.ip_deny_redirects

Then copy the below contents so you can paste them into the above custom template:

# SME Server Openswan specifics
# Send redirects, No!
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0
# Accept packets with SRR option? No!
net.ipv4.conf.all.accept_source_route = 0
# Accept Redirects? No!
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.all.secure_redirects = 0

Now we need to expand the newly created custome template:

expand-template /etc/sysctl.conf

and make them effective:

sysctl -p

Another way to disable/enable redirects on all interfaces on the fly from the console as root would be:

for f in /proc/sys/net/ipv4/conf/*/send_redirects; do echo 0 > $f; done
for f in /proc/sys/net/ipv4/conf/*/accept_redirects; do echo 0 > $f; done
for f in /proc/sys/net/ipv4/conf/*/secure_redirects; do echo 0 > $f; done

(these last commands will work for sure on both SME8 and SME9, but that's not the sustainable SME Server way that will stick on reboots, updates and upgrades.)

end of experimental section

---

IPSEC server to server configuration

Openswan/IPSEC can be used to setup a secue and permanent VPN connection between a SME Server and another (local or remote) IPSEC enabled device such as a router.

Here is an example:

On the online VPS it has a 'dummy' internal network adaptor but works fine with this.

Here is a sample of my /etc/ipsec.conf with some added notes.

LEFT side is your server. RIGHT side is your router.

# /etc/ipsec.conf
# basic configuration
#auto = 'start' for both ways or 'add' for incoming only

version 2.0 config setup

# Debug-logging controls:  "none" for (almost) none, "all" for lots.
#klipsdebug=none
plutodebug=none
interfaces=%defaultroute
oe=no
protostack=netkey
syslog=syslog.debug
# syslog=syslog.warning
virtual_private=%v4:192.168.0.0/24,   # Here you add the local/internal network of your server
nat_traversal=yes   # if required - probably yes
# Connection settings
# Router to Server
conn draytek-wan1 # Your connection name
type=tunnel
authby=secret
auto=start   # n.b. "auto = start" for ipsec to try and make a connection or "auto = add" to accept incoming
ikelifetime=28800s
keylife=3600s
left=%defaultroute
leftsourceip=192.168.98.1  # This is the IP address of your internal ethernet connection on your server
leftsubnet=192.168.98.0/24 # This is your local network on your server
pfs=yes  # If require
dpdaction=restart
dpddelay=30
dpdtimeout=10
right=1.2.3.4  # This is the WAN IP address of your router that is connecting in
rightsubnet=192.168.0.0/24	# This is the local network behind the router at the far end
# More incoming connections here

Passwords

It is recommended to create a very strong random password and keep this safe. One way of generating and store a random strong password is explained here

The following file needs to be looked after and should be set chmod 0600

# /etc/ipsec.secrets
# Format is 
# Incoming_IP Local_IP: PSK "Your#Strong#Password"
1.2.3.4 %any: PSK "Your#Strong#Password"
host.dnsalias.org %any: PSK "Your#Strong#Password"
1.2.3.4 192.168.98.1: PSK "Your#Strong#Password"
%any 192.168.98.1: PSK "Your#Strong#Password"

Verifying configuration

To verify your configuration give the following command:

ipsec verify

A reboot should get everything going.

Now set up your router. Create a new IPSEC VPN connection with the correct credentials and it should connect up.

Check /var/log/secure for debug messages, and once you are happy, change the debug settings in ipsec.conf from debug to warning.

If you need more debugging you can set plutodebug = all

Other articles in this category

Ipsec, Libreswan, Libreswan-xl2tpd, OpenVPN, OpenVPN Bridge, OpenVPN Bridge/fr, OpenVPN Routed, OpenVPN SiteToSite, SME Server wishlist, SoftEther VPN, Softethervpn-server, VPN, Wireguard