PPTP Client

pptpclient is a program implementing the Microsoft PPTP protocol. As such, it can be used to connect to a Microsoft VPN network (or any PPTP-based VPN) provided by a school or workplace.

Installing PPTP Client

PPTP Client is provided by the pptpclient package found in the official repositories.

Configure

To configure pptpclient you will need to collect the following information from your network administrator:

• The IP address or hostname of the VPN server
• The name you wish to use for the tunnel.
• The authentication (Windows) domain name. This is not provided or needed for certain networks.
• The username you will use to connect.
• The password you will use to connect.

Edit The options.pptp File

With your favorite text editor open /etc/ppp/options.pptp. This file enables a lot of security for your VPN connection by default. If you have trouble connecting to your network, you can relax the options down. At a minimum, your /etc/ppp/options.pptp file should contain:

lock
noauth
nobsdcomp
nodeflate

Edit The chap-secrets File

Next, open or create the /etc/ppp/chap-secrets file. We will be storing your password in this file, so make sure that the permissions are set such that no-one besides root can read this file.

chmod 0600 /etc/ppp/chap-secrets

The file should have the following format:

<DOMAIN>\\<USERNAME> PPTP <PASSWORD> *

Or, if your connection does not require a domain:

<USERNAME> PPTP <PASSWORD> *

Simply replace each bracketed term in the examples with the appropriate value.

Note: If your password contains a special character such as $ you should place the password in double quotation marks (").

Name Your Tunnel

With your favorite text editor create a /etc/ppp/peers/<TUNNEL> file, where <TUNNEL> is the name you wish to use for your VPN connection. The file should look like this:

pty "pptp <SERVER> --nolaunchpppd"
name <DOMAIN>\\<USERNAME>
remotename PPTP
require-mppe-128
file /etc/ppp/options.pptp
ipparam <TUNNEL>

Note: As before, if your connection does not require a domain, omit <DOMAIN>\\ from the file you create

Note: remotename PPTP is used to find <PASSWORD> in the /etc/ppp/chap-secrets File.

<SERVER> is the remote address of the VPN server, <DOMAIN> is the domain your user belongs to, <USERNAME> is the name you will use to connect to the server, and <TUNNEL> is the name of the connection.

Note: If you do not need MPPE support, you should remove the require-mppe-128 option from this file and from /etc/ppp/options.pptp

Making Your Connection

To make sure that everything is configured properly, as root execute:

# pon <TUNNEL> debug dump logfd 2 nodetach

If everything has been configured correctly, the pon command should not terminate. Once you are satisfied that it has connected successfully, you can terminate the command.

Note: As an additional verification you can run ip addr show and ensure that a new device, ppp0, is available.

To connect to your VPN normally, simply execute:

# pon <TUNNEL>

Where <TUNNEL> is the name of the tunnel you established earlier. Note that this command should be run as root.

Routing

Once you have connected to your VPN, you should be able to interact with anything available on the VPN server. To access anything on the remote network, you need to add a new route to your routing table.

Note: Depending on your configuration, you may need to re-add the routing information every time you connect to your VPN.

For more information on how to add routes, you can read this article which has many more examples: PPTP Routing Howto

Split Tunneling

Packets with a destination of your VPN's network should be routed through the VPN interface (usually ppp0). To do this, you create the route:

# ip route add 192.168.10.0/24 dev ppp0

This will route all the traffic with a destination of 192.168.10.* through your VPN's interface, (ppp0).

Route All Traffic

It may be desirable to route all traffic through your VPN connection. You can do this by running:

# ip route add default dev ppp0

Note: Routing all traffic through the VPN may result in slower over all connection speed because your traffic will be routed through the remote VPN before being routed normally.

Route All Traffic by /etc/ppp/ip-up.d

Note: All scripts in /etc/ppp/ip-up.d/ will called when the VPN connection is established.

/etc/ppp/ip-up.d/01-routes.sh

#!/bin/bash

# This script is called with the following arguments:
# Arg Name
# $1 Interface name
# $2 The tty
# $3 The link speed
# $4 Local IP number
# $5 Peer IP number
# $6 Optional ``ipparam'' value foo

route add default gw $4

Make sure the script is executable.

Note: This script currently uses net-tools instead of iproute2 which the other examples use.

Split Tunneling based on port by /etc/ppp/ip-up.d

Note: All scripts in /etc/ppp/ip-up.d/ will called when the VPN connection is established.

/etc/ppp/ip-up.d/01-routebyport.sh

#!/bin/bash

# This script is called with the following arguments:
# Arg Name
# $1 Interface name
# $2 The tty
# $3 The link speed
# $4 Local IP number
# $5 Peer IP number
# $6 Optional ``ipparam'' value foo

echo 0 > /proc/sys/net/ipv4/conf/$1/rp_filter
echo 1 > /proc/sys/net/ipv4/ip_forward
echo 1 > /proc/sys/net/ipv4/ip_dynaddr

ip route flush table vpn
ip route add default via $5 dev $1 table vpn
iptables -t mangle -A OUTPUT -p tcp -m multiport --dports 6667,6697 -j MARK --set-mark 0x1
iptables -t nat    -A POSTROUTING -o $1 -j MASQUERADE
ip rule  add fwmark 0x1 pri 100 lookup vpn
ip rule  add from $4 pri 200 table vpn
ip route flush cache

Make sure the script is executable and that the vpn table is added to /etc/iproute2/rt_tables

201 vpn

Disconnecting

To disconnect from your VPN simply execute:

# poff <TUNNEL>

Where <TUNNEL> is the name of your connection.

Making A VPN Daemon and Connecting On Boot

You can create a simple daemon for your VPN connection by creating an appropriate /etc/rc.d/* script:

Note: As always, <TUNNEL> is the name of your tunnel. <ROUTING COMMAND> is the command you use to add the appropriate route to the routing table.

Note: The stop functionality of this script will not work if the updetach and persist arguments are passed to /usr/bin/pon when pon is started. The reason for this is that the /usr/bin/poff script contains a bug when determining the PID of the specified pppd process if arguments were passed to pon.

To resolve this issue, you can patch your /usr/bin/poff file by making the following changes on line 93:

-PID=`ps axw | grep "[ /]pppd call $1 *\$" | awk '{print $1}'`
+PID=`ps axw | grep "[ /]pppd call $1" | awk '{print $1}'`

/etc/rc.d/name-of-your-vpn

#!/bin/bash

. /etc/rc.conf
. /etc/rc.d/functions

DAEMON=<TUNNEL>-vpn
ARGS=

[ -r /etc/conf.d/$DAEMON ] && . /etc/conf.d/$DAEMON


case "$1" in
 start)
   stat_busy "Starting $DAEMON"
   pon <TUNNEL> updetach persist &>/dev/null && <ROUTING COMMAND> &>/dev/null
   if [ $? = 0 ]; then
     add_daemon $DAEMON
     stat_done
   else
     stat_fail
     exit 1
   fi
   ;;
 stop)
   stat_busy "Stopping $DAEMON"
   poff <TUNNEL> &>/dev/null
   if [ $? = 0 ]; then
     rm_daemon $DAEMON
     stat_done
   else
     stat_fail
     exit 1
   fi
   ;;
 restart)
   $0 stop
   sleep 1
   $0 start
   ;;
 *)
   echo "usage: $0 {start|stop|restart}"  
esac

Note: We call pon in the script with two additional arguments: updetach and persist. The argument updetach makes pon block until the connection has been established. The other argument, persist, makes the network automatically reconnect in the event of a failure. To connect at boot add @<TUNNEL>-vpn to the end of your DAEMONS array in /etc/rc.conf.

Remarks

You can find more information about configuring pptpclient at their website: pptpclient website. The contents of this article where adapted from their Ubuntu How-To which also provides some hints on how to do things such as connecting on boot. These examples should be easy to adapt into daemons or other scripts to help automate your configuration.