L2TP VPN Server on Raspberry Pi

The following are instructions for setting up an L2TP VPN server on a Raspberry Pi running Raspbian Jessie. This allows you to connect your iPhone or other device using L2TP VPN to your home network, to securely access resources on it. This set up uses a Raspberry Pi sitting behind your normal router.

These instructions are based on an older forum post on the Raspberry Pi forums.

All of the following commands will need to be run as root. Use sudo to become the root user.

$ sudo su -

Configuring a Static IP Address

Since your Raspberry Pi is running a server, it will be important to give it a consistent IP address so that we can forward the necessary ports to it. The IP address you choose depends on your local network setup. My network uses the 192.168.1.XXX range, so I have decided to use 192.168.1.16 for my Raspberry Pi. Here are the full settings for my setup:

IP Address: 192.168.1.16

Netmask: 255.255.255.0

Gateway: 192.168.1.254

DNS Server(s): 192.168.1.254

With the release of Raspbian Jessie, the method for configuring IP addresses has changed. Raspbian now uses dhcpcd as the default, so it is no longer recommended that you directly modify /etc/network/interfaces. Instead, we will modify dhcpcd’s configuration.

Edit /etc/dhcpcd.conf and add the following to the end. You will need to modify some of these values based on your setup.

interface eth0
static ip_address=192.168.1.16/24
static routers=192.168.1.254
static domain_name_servers=192.168.1.254

Once you reboot, your Raspberry Pi should now be using the address you have specified.

Installing xl2tpd and openswan

We need to install xl2tpd for our VPN tunnel and openswan for our IPSec security.

Warning: openswan is no longer maintained and has been replaced by strongswan. I have not yet tried this with strongswan.

$ apt-get update
$ apt-get install openswan xl2tpd ppp lsof

Configuring xl2tpd

xl2tpd provides our VPN tunnel into our network.

Replace the contents of /etc/xl2tpd/xl2tpd.conf with the following. You may need to make changes based on your network settings and your static IP address we configured previously.

[global]
ipsec saref = yes
listen-addr = 192.168.1.16

[lns default]
ip range = 192.168.1.201-192.168.1.250
local ip = 192.168.1.16
assign ip = yes
require chap = yes
refuse pap = yes
require authentication = yes
name = linkVPN
ppp debug = yes
pppoptfile = /etc/ppp/options.xl2tpd
length bit = yes

Replace your /etc/ppp/options.xl2tpd with the following:

ipcp-accept-local
ipcp-accept-remote
ms-dns 192.168.1.254
asyncmap 0
auth
crtscts
lock
idle 1800
mtu 1200
mru 1200
modem
debug
name l2tpd
proxyarp
lcp-echo-interval 30
lcp-echo-failure 4
nodefaultroute
connect-delay 5000

Configuring IPSec

IPSec is the encryption layer for your VPN tunnel. We are using the openswan implementation.

Replace your /etc/ipsec.conf with the following. Again, you will need to replace any values depending on your network setup.

# /etc/ipsec.conf - Openswan IPsec configuration file

# This file:  /usr/share/doc/openswan/ipsec.conf-sample
#
# Manual:     ipsec.conf.5


version    2.0    # conforms to second version of ipsec.conf specification

# basic configuration
config setup
    # Do not set debug options to debug configuration issues!
    # plutodebug / klipsdebug = "all", "none" or a combation from below:
    # "raw crypt parsing emitting control klips pfkey natt x509 dpd private"
    # eg:
    # plutodebug="control parsing"
    # Again: only enable plutodebug or klipsdebug when asked by a developer
    #
    # enable to get logs per-peer
    # plutoopts="--perpeerlog"
    #
    # Enable core dumps (might require system changes, like ulimit -C)
    # This is required for abrtd to work properly
    # Note: incorrect SElinux policies might prevent pluto writing the core
    dumpdir=/var/run/pluto/
    #
    # NAT-TRAVERSAL support, see README.NAT-Traversal
    nat_traversal=yes
    # exclude networks used on server side by adding %v4:!a.b.c.0/24
    # It seems that T-Mobile in the US and Rogers/Fido in Canada are
    # using 25/8 as "private" address space on their 3G network.
    # This range has not been announced via BGP (at least upto 2010-12-21)
    #virtual_private=%v4:10.0.0.0/8,%v4:192.168.0.0/16,%v4:172.16.0.0/12,%v4:25.0.0.0/8,%v6:fd00::/8,%v6:fe80::/10:
    virtual_private=%v4:192.168.0.0/16,%v4:10.10.0.0/16,%v4:172.16.0.0/12,%v4:25.0.0.0/8,%v4:!10.25.0.0/16
    # OE is now off by default. Uncomment and change to on, to enable.
    oe=off
    # which IPsec stack to use. auto will try netkey, then klips then mast
    protostack=netkey
    # Use this to log to a file, or disable logging on embedded systems (like openwrt)
    #plutostderrlog=/dev/null

# Add connections here

# sample VPN connection
# for more examples, see /etc/ipsec.d/examples/
#conn sample
#        # Left security gateway, subnet behind it, nexthop toward right.
#        left=10.0.0.1
#        leftsubnet=172.16.0.0/24
#        leftnexthop=10.22.33.44
#        # Right security gateway, subnet behind it, nexthop toward left.
#        right=10.12.12.1
#        rightsubnet=192.168.0.0/24
#        rightnexthop=10.101.102.103
#        # To authorize this connection, but not actually start it, 
#        # at startup, uncomment this.
#        #auto=add

conn L2TP-PSK-NAT
    # !mwd - disabling this fixed stuff
    #rightsubnet=vhost:%priv
    also=L2TP-PSK-noNAT

conn L2TP-PSK-noNAT
        authby=secret
        pfs=no
        auto=add
        keyingtries=3
        # we cannot rekey for %any, let client rekey
        rekey=no
        # Apple iOS doesn't send delete notify so we need dead peer detection
        # to detect vanishing clients
        dpddelay=30
        dpdtimeout=120
        dpdaction=clear
        # Set ikelifetime and keylife to same defaults windows has
        ikelifetime=8h
        keylife=1h
        # l2tp-over-ipsec is transport mode
        type=transport
        #
        left=192.168.1.16
        #
        # For updated Windows 2000/XP clients,
        # to support old clients as well, use leftprotoport=17/%any
        leftprotoport=17/1701
        #
        # The remote user.
        #
        right=%any
        # Using the magic port of "%any" means "any one single port". This is
        # a work around required for Apple OSX clients that use a randomly
        # high port.
        rightprotoport=17/%any
        #force all to be nat'ed. because of ios
        forceencaps=yes

# Normally, KLIPS drops all plaintext traffic from IP's it has a crypted
# connection with. With L2TP clients behind NAT, that's not really what
# you want. The connection below allows both l2tp/ipsec and plaintext
# connections from behind the same NAT router.
# The l2tpd use a leftprotoport, so they are more specific and will be used
# first. Then, packets for the host on different ports and protocols (eg ssh)
# will match this passthrough conn.
conn passthrough-for-non-l2tp
        type=passthrough
        left=192.168.1.16
        leftnexthop=192.168.1.254
        right=0.0.0.0
        rightsubnet=0.0.0.0/0
        auto=route

Configuring your Secret Key

The secret key is a shared key that all of your users will use. Edit /etc/ipsec.secrets

# This file holds shared secrets or RSA private keys for inter-Pluto
# authentication.  See ipsec_pluto(8) manpage, and HTML documentation.

# RSA private key for this host, authenticating it to any other host
# which knows the public part.  Suitable public keys, for ipsec.conf, DNS,
# or configuration of other implementations, can be extracted conveniently
# with "ipsec showhostkey".

# this file is managed with debconf and will contain the automatically created RSA keys
#include /var/lib/openswan/ipsec.secrets.inc

192.168.1.16  %any:   PSK "MYSECRET"

Configuring your Users

You can create as many vpn users as you want. These users are separate from any linux user accounts on your Raspberry Pi. Edit /etc/ppp/chap-secrets

# Secrets for authentication using CHAP
# client    server    secret            IP addresses
username    *    password    *

Modifying iptables and System Services

We need to make some changes to the routing table and system configuration. First we will set some values and add them to our /etc/sysctl.conf which will be loaded each time the system starts up:

$ echo "net.ipv4.ip_forward = 1" |  tee -a /etc/sysctl.conf
$ echo "net.ipv4.conf.all.accept_redirects = 0" |  tee -a /etc/sysctl.conf
$ echo "net.ipv4.conf.all.send_redirects = 0" |  tee -a /etc/sysctl.conf

$ sysctl -p

The iptables and /proc settings won’t survive a reboot. We’ll add these commands to the end of our /etc/rc.local to make sure they are executed on start up:

for vpn in /proc/sys/net/ipv4/conf/*; do echo 0 > $vpn/accept_redirects; echo 0 > $vpn/send_redirects; done
iptables --table nat --append POSTROUTING --jump MASQUERADE

Finally, let’s make sure our xl2tpd and ipsec services will be started on boot:

$ update-rc.d -f ipsec remove
$ update-rc.d ipsec defaults

At this point, you should restart your Raspberry Pi to make sure all settings have taken effect and is configured correctly.

Configuring your Router Port Forwarding

This section depends on your router. Most consumer routers/wifi have a web admin interface at either 192.168.1.1 or 192.168.1.254. Once you are logged in, you’ll need to find the port forwarding or NAT/Gaming section. You will need to have the following ports forwarded to your Raspberry Pi IP Address, which in my case is 192.168.1.16. Please be aware that these ports are UDP not TCP.

Port 4500 UDP

Port 500 UDP

Connecting an iPhone

On your iPhone, go to Setting > General > VPN

Choose “Add VPN Configuration”. Select “L2TP” as the Type.

Type: L2TP

Description: Home VPN

Server: Your public IP address (this is NOT your 192.168.1.16 address. You can get this from your router or from http://whatismyip.com)

Account: The username you configured in /etc/ppp/chap-secrets

RSA SecureID: Disabled

Password: The password you configured in /etc/ppp/chap-secrets

Secret: The Shared secret you configured in /etc/ipsec.secrets

Send All Traffic: If enabled, then ALL your internet traffic will be routed through your home network. If you disable this, then normal internet traffic won’t go through your home network. The VPN will only be used to access devices on your home network

ELO Touchscreen monitor under Linux

*Edit* I have updated this to no longer require you to edit xorg.conf. This also fixes issues if the touchscreen’s usb cable is hotplugged while X is already running.

I recently purchased an ELO 1537L 15-inch open-frame touchmonitor for a project I am doing at work.  I have successfully gotten the touchscreen monitor to work under linux (specifically Scientific 6.x) using USB (I haven’t tried the serial interface).  Plugging in the monitor, it is recognized as a 5020 Surface Capacitive:


19746:Aug 3 02:51:13 localhost kernel: usb 2-1: Product: Elo TouchSystems Surface Capacitive 5020
19747:Aug 3 02:51:13 localhost kernel: usb 2-1: Manufacturer: Elo TouchSystems
19750:Aug 3 02:51:13 localhost kernel: input: Elo TouchSystems Elo TouchSystems Surface Capacitive 5020 as /devices/pci0000:00/0000:00:1d.0/usb2/2-1/2-1:1.0/input/input7
19751:Aug 3 02:51:13 localhost kernel: generic-usb 0003:04E7:0042.0003: input,hidraw2: USB HID v1.11 Pointer [Elo TouchSystems Elo TouchSystems Surface Capacitive 5020] on usb-0000:00:1d.0-1/input0

ELO provides some generic drivers for this device. I first attempted to directly use them and found them to be a complete disaster. The whole configuration was really silly (putting stuff into /etc/opt, are you kidding me?). The elo daemon constantly hung and had to be restarted. Restarting X caused the daemon to stop working, thus the touchscreen stopped working.

I quickly removed these drivers and tried it with the evtouch drivers which I have used for a USB displaylink touchscreen monitor in the past (MIMO). With a few changes to my xorg.conf, the evtouch driver immediately recognized it and I was able to capture touch events. Although the calibration was initially completely off.

Here’s the steps I took to get this working on Scientific Linux 6.0

Install evtouch

Unfortunately, Scientific Linux does not come with the evtouch driver. I have built a 64-bit rpm for Scientific Linux here . If you need a 32-bit version or for another platform (Fedora), download the src rpm and rebuild it (rpmbuild –rebuild xorg-x11-drv-evtouch-0.8.8-1.el6.src.rpm).

Setup Xorg

It is not required to directly edit xorg.conf. Instead, we will create a hal fdi file

We will create an fdi file in /etc/hal/fdi/policy called elo_touchscreen.fdi

/etc/hal/fdi/policy/elo_touchscreen.fdi

<?xml version="1.0" encoding="ISO-8859-1"?>
<deviceinfo version="0.2">
<device>
<match key="input.product" contains="Elo TouchSystems, Inc. Elo TouchSystems Surface Capacitive 5010">
<merge key="input.x11_driver" type="string">evtouch</merge>
<merge key="input.x11_options.MinX" type="string">3724</merge>
<merge key="input.x11_options.MaxX" type="string">318</merge>
<merge key="input.x11_options.MinY" type="string">3724</merge>
<merge key="input.x11_options.MaxY" type="string">318</merge>
<merge key="input.x11_options.SwapX" type="string">true</merge>
<merge key="input.x11_options.SwapY" type="string">true</merge>
</match>
</device>
</deviceinfo>

If your monitor is slightly different, you will need to get the product id, and replace the match key=”input.product” line in the above file.


$ lshal | grep input.product
input.product = 'Sleep Button' (string)
input.product = 'Power Button' (string)
input.product = 'Macintosh mouse button emulation' (string)
input.product = 'ImExPS/2 Generic Explorer Mouse' (string)
input.product = 'AT Translated Set 2 keyboard' (string)
input.product = 'Elo TouchSystems, Inc. Elo TouchSystems Surface Capacitive 5010' (string)

You should now be able to unplug and plug your touchscreen back in and have it work without restarting X

Calibration

The MinX,MinY,MaxX,MaxY values are used for calibrating the touchscreen. The evtouch source available on their site comes with a calibration utility. However, I was unable to get this to run. For me I played with the MinX, MaxX, MinY, MaxY values in my xorg.conf until it was close enough. As you can see, I had to mirror both the X and Y values.

Other Drivers

I noticed that Scientific Linux also includes an elographics package: xorg-x11-drv-elographics. I have no idea if this works better or not although I have heard they only work with the serial interface. I have it working with evtouch, so I’m happy. If anyone has tried the elographics and had success, please comment!

Gnome Shell Extension: Search Window

The Gnome desktop recently release version 3 of their desktop, which includes their all new Gnome Shell. I have been using it for several months now, and I must say I really like the direction it is going. It is still early and is missing a lot of little things, but those will come soon. We are starting to see new extensions being built for it to extend the functionality.

One feature I have found blatantly missing is the ability to search active windows in the overview. In overview mode, you first see a live preview of all your windows. But if you’re like me, you have 15 terminals and 10 web browser windows up (I despise tabs!). Typing starts a search, which by default searches: your installed applications to quickly start one, files, and places. Search is completely missing the ability to search through open windows based on their title!

I quickly wrote my first gnome-shell extension to do just that. It is still an early version, and I would like to update it to add more features such as showing a live window preview instead of just the application icon.

Initial Overview Display
Initial Search for "fed" with results being narrowed down. Two open terminals and three open web browsers have titles that match
Search for "fed wiki" showing an open browser on the Fedora Wiki

Try it out, and send me your thoughts:

gnome-shell-extensions-window-search-0.0.1

You can use the gnome-tweak-tool to install it, or extract it into

$HOME/.local/share/gnome-shell/extensions