Linux Setup OpenVpn Server And Client

How to Setup Openvpn Server
--------------------------------------------------------------

INSTALLATION ( Both For Server And Client )

1. Download openvpn-2.1_rc22.tar.gz
2. tar -zxvf openvpn-2.1_rc22.tar.gz
3. cd openvpn-2.1_rc22
4. ./configure
5. make & make install

--------------------------------------------------------------
Make a directory for OpenVpn Server Configuartion:

1. mkdir /etc/openvpn
2. create server.conf file.

Sample server.conf

==========================================

#################################################
# Sample OpenVPN 2.0 config file for            #
# multi-client server.                          #
#                                               #
# This file is for the server side              #
# of a many-clients <-> one-server              #
# OpenVPN configuration.                        #
#                                               #
# OpenVPN also supports                         #
# single-machine <-> single-machine             #
# configurations (See the Examples page         #
# on the web site for more info).               #
#                                               #
# This config should work on Windows            #
# or Linux/BSD systems.  Remember on            #
# Windows to quote pathnames and use            #
# double backslashes, e.g.:                     #
# "C:\\Program Files\\OpenVPN\\config\\foo.key" #
#                                               #
# Comments are preceded with '#' or ';'         #
#################################################
# Which local IP address should OpenVPN
# listen on? (optional)
;local a.b.c.d
# Which TCP/UDP port should OpenVPN listen on?
# If you want to run multiple OpenVPN instances
# on the same machine, use a different port
# number for each one.  You will need to
# open up this port on your firewall.
port 1194
# TCP or UDP server?
;proto tcp
proto udp
# "dev tun" will create a routed IP tunnel,
# "dev tap" will create an ethernet tunnel.
# Use "dev tap0" if you are ethernet bridging
# and have precreated a tap0 virtual interface
# and bridged it with your ethernet interface.
# If you want to control access policies
# over the VPN, you must create firewall
# rules for the the TUN/TAP interface.
# On non-Windows systems, you can give
# an explicit unit number, such as tun0.
# On Windows, use "dev-node" for this.
# On most systems, the VPN will not function
# unless you partially or fully disable
# the firewall for the TUN/TAP interface.
;dev tap
dev tun
# Windows needs the TAP-Win32 adapter name
# from the Network Connections panel if you
# have more than one.  On XP SP2 or higher,
# you may need to selectively disable the
# Windows firewall for the TAP adapter.
# Non-Windows systems usually don't need this.
;dev-node MyTap
# SSL/TLS root certificate (ca), certificate
# (cert), and private key (key).  Each client
# and the server must have their own cert and
# key file.  The server and all clients will
# use the same ca file.
#
# See the "easy-rsa" directory for a series
# of scripts for generating RSA certificates
# and private keys.  Remember to use
# a unique Common Name for the server
# and each of the client certificates.
#
# Any X509 key management system can be used.
# OpenVPN can also use a PKCS #12 formatted key file
# (see "pkcs12" directive in man page).
ca ca.crt
cert server.crt
key server.key  # This file should be kept secret
# Diffie hellman parameters.
# Generate your own with:
#   openssl dhparam -out dh1024.pem 1024
# Substitute 2048 for 1024 if you are using
# 2048 bit keys.
dh dh1024.pem
# Configure server mode and supply a VPN subnet
# for OpenVPN to draw client addresses from.
# The server will take 10.8.0.1 for itself,
# the rest will be made available to clients.
# Each client will be able to reach the server
# on 10.8.0.1. Comment this line out if you are
# ethernet bridging. See the man page for more info.
server 10.8.0.0 255.255.255.0
# Maintain a record of client <-> virtual IP address
# associations in this file.  If OpenVPN goes down or
# is restarted, reconnecting clients can be assigned
# the same virtual IP address from the pool that was
# previously assigned.
ifconfig-pool-persist ipp.txt
# Configure server mode for ethernet bridging.
# You must first use your OS's bridging capability
# to bridge the TAP interface with the ethernet
# NIC interface.  Then you must manually set the
# IP/netmask on the bridge interface, here we
# assume 10.8.0.4/255.255.255.0.  Finally we
# must set aside an IP range in this subnet
# (start=10.8.0.50 end=10.8.0.100) to allocate
# to connecting clients.  Leave this line commented
# out unless you are ethernet bridging.
#server-bridge 192.168.2.254 255.255.255.0 192.168.2.1 192.168.2.100
# Configure server mode for ethernet bridging
# using a DHCP-proxy, where clients talk
# to the OpenVPN server-side DHCP server
# to receive their IP address allocation
# and DNS server addresses.  You must first use
# your OS's bridging capability to bridge the TAP
# interface with the ethernet NIC interface.
# Note: this mode only works on clients (such as
# Windows), where the client-side TAP adapter is
# bound to a DHCP client.
;server-bridge
# Push routes to the client to allow it
# to reach other private subnets behind
# the server.  Remember that these
# private subnets will also need
# to know to route the OpenVPN client
# address pool (10.8.0.0/255.255.255.0)
# back to the OpenVPN server.
;push "route 192.168.100.0 255.255.255.0"
;push "route 192.168.20.0 255.255.255.0"
# To assign specific IP addresses to specific
# clients or if a connecting client has a private
# subnet behind it that should also have VPN access,
# use the subdirectory "ccd" for client-specific
# configuration files (see man page for more info).
# EXAMPLE: Suppose the client
# having the certificate common name "Thelonious"
# also has a small subnet behind his connecting
# machine, such as 192.168.40.128/255.255.255.248.
# First, uncomment out these lines:
;client-config-dir ccd
;route 192.168.40.128 255.255.255.248
# Then create a file ccd/Thelonious with this line:
#   iroute 192.168.40.128 255.255.255.248
# This will allow Thelonious' private subnet to
# access the VPN.  This example will only work
# if you are routing, not bridging, i.e. you are
# using "dev tun" and "server" directives.
# EXAMPLE: Suppose you want to give
# Thelonious a fixed VPN IP address of 10.9.0.1.
# First uncomment out these lines:
client-config-dir ccd
;route 10.8.0.0 255.255.255.0
# Then add this line to ccd/Thelonious:
#   ifconfig-push 10.9.0.1 10.9.0.2
# Suppose that you want to enable different
# firewall access policies for different groups
# of clients.  There are two methods:
# (1) Run multiple OpenVPN daemons, one for each
#     group, and firewall the TUN/TAP interface
#     for each group/daemon appropriately.
# (2) (Advanced) Create a script to dynamically
#     modify the firewall in response to access
#     from different clients.  See man
#     page for more info on learn-address script.
;learn-address ./script
# If enabled, this directive will configure
# all clients to redirect their default
# network gateway through the VPN, causing
# all IP traffic such as web browsing and
# and DNS lookups to go through the VPN
# (The OpenVPN server machine may need to NAT
# or bridge the TUN/TAP interface to the internet
# in order for this to work properly).
push "redirect-gateway def1 bypass-dhcp"
# Certain Windows-specific network settings
# can be pushed to clients, such as DNS
# or WINS server addresses.  CAVEAT:
# http://openvpn.net/faq.html#dhcpcaveats
# The addresses below refer to the public
# DNS servers provided by opendns.com.
;push "dhcp-option DNS 208.67.220.220"
# Uncomment this directive to allow different
# clients to be able to "see" each other.
# By default, clients will only see the server.
# To force clients to only see the server, you
# will also need to appropriately firewall the
# server's TUN/TAP interface.
client-to-client
# Uncomment this directive if multiple clients
# might connect with the same certificate/key
# files or common names.  This is recommended
# only for testing purposes.  For production use,
# each client should have its own certificate/key
# pair.
#
# IF YOU HAVE NOT GENERATED INDIVIDUAL
# CERTIFICATE/KEY PAIRS FOR EACH CLIENT,
# EACH HAVING ITS OWN UNIQUE "COMMON NAME",
# UNCOMMENT THIS LINE OUT.
;duplicate-cn
# The keepalive directive causes ping-like
# messages to be sent back and forth over
# the link so that each side knows when
# the other side has gone down.
# Ping every 10 seconds, assume that remote
# peer is down if no ping received during
# a 120 second time period.
keepalive 10 120
# For extra security beyond that provided
# by SSL/TLS, create an "HMAC firewall"
# to help block DoS attacks and UDP port flooding.
#
# Generate with:
#   openvpn --genkey --secret ta.key
#
# The server and each client must have
# a copy of this key.
# The second parameter should be '0'
# on the server and '1' on the clients.
;tls-auth ta.key 0 # This file is secret
# Select a cryptographic cipher.
# This config item must be copied to
# the client config file as well.
;cipher BF-CBC        # Blowfish (default)
;cipher AES-128-CBC   # AES
;cipher DES-EDE3-CBC  # Triple-DES
# Enable compression on the VPN link.
# If you enable it here, you must also
# enable it in the client config file.
;comp-lzo
# The maximum number of concurrently connected
# clients we want to allow.
;max-clients 100
# It's a good idea to reduce the OpenVPN
# daemon's privileges after initialization.
#
# You can uncomment this out on
# non-Windows systems.
;user nobody
;group nobody
# The persist options will try to avoid
# accessing certain resources on restart
# that may no longer be accessible because
# of the privilege downgrade.
persist-key
persist-tun
# Output a short status file showing
# current connections, truncated
# and rewritten every minute.
status openvpn-status.log
# By default, log messages will go to the syslog (or
# on Windows, if running as a service, they will go to
# the "\Program Files\OpenVPN\log" directory).
# Use log or log-append to override this default.
# "log" will truncate the log file on OpenVPN startup,
# while "log-append" will append to it.  Use one
# or the other (but not both).
log         openvpn.log
;log-append  openvpn.log
# Set the appropriate level of log
# file verbosity.
#
# 0 is silent, except for fatal errors
# 4 is reasonable for general usage
# 5 and 6 can help to debug connection problems
# 9 is extremely verbose
verb 3
# Silence repeating messages.  At most 20
# sequential messages of the same message
# category will be output to the log.
;mute 20
==========================================

3. cd "/usr/share/openvpn/easy-rsa/2.0/"
4. Create "ca.crt" file in /etc/openvpn directory ( Using build-ca tool in  "/usr/share/openvpn/easy-rsa/2.0/").
4. Create "dh1024.pem" file in /etc/openvpn directory. ( Using build-dh tool in "/usr/share/openvpn/easy-rsa/2.0/").
5. Create a client key and clien certificate using "build-key" tool.
 ==========================================

Starting Server:

Crete a file /etc/init.d/openvpn


File Content:
==========================================
#!/bin/sh
#
# openvpn       This shell script takes care of starting and stopping
#               openvpn on RedHat or other chkconfig-based system.
#
# chkconfig: - 24 76
#
# processname: openvpn
# description: OpenVPN is a robust and highly flexible tunneling \
#              application that uses all of the encryption, \
#              authentication, and certification features of the OpenSSL \
#              library to securely tunnel IP networks over a single UDP \
#              port.
#
# Contributed to the OpenVPN project by
# Douglas Keller <doug@voidstar.dyndns.org>
# 2002.05.15
# To install:
#   copy this file to /etc/rc.d/init.d/openvpn
#   shell> chkconfig --add openvpn
#   shell> mkdir /etc/openvpn
#   make .conf or .sh files in /etc/openvpn (see below)
# To uninstall:
#   run: chkconfig --del openvpn
# Author's Notes:
#
# I have created an /etc/init.d init script and enhanced openvpn.spec to
# automatically register the init script.  Once the RPM is installed you
# can start and stop OpenVPN with "service openvpn start" and "service
# openvpn stop".
#
# The init script does the following:
#
# - Starts an openvpn process for each .conf file it finds in
#   /etc/openvpn.
#
# - If /etc/openvpn/xxx.sh exists for a xxx.conf file then it executes
#   it before starting openvpn (useful for doing openvpn --mktun...).
#
# - In addition to start/stop you can do:
#
#   service openvpn reload - SIGHUP
#   service openvpn reopen - SIGUSR1
#   service openvpn status - SIGUSR2
#
# Modifications:
#
# 2003.05.02
#   * Changed == to = for sh compliance (Bishop Clark).
#   * If condrestart|reload|reopen|status, check that we were
#     actually started (James Yonan).
#   * Added lock, piddir, and work variables (James Yonan).
#   * If start is attempted twice, without an intervening stop, or
#     if start is attempted when previous start was not properly
#     shut down, then kill any previously started processes, before
#     commencing new start operation (James Yonan).
#   * Do a better job of flagging errors on start, and properly
#     returning success or failure status to caller (James Yonan).
#
# 2005.04.04
#   * Added openvpn-startup and openvpn-shutdown script calls
#     (James Yonan).
#
# Location of openvpn binary
openvpn=""
openvpn_locations="/usr/sbin/openvpn /usr/local/sbin/openvpn"
for location in $openvpn_locations
do
  if [ -f "$location" ]
  then
    openvpn=$location
  fi
done
# Lockfile
lock="/var/lock/subsys/openvpn"
# PID directory
piddir="/var/run/openvpn"
# Our working directory
work=/etc/openvpn
# Source function library.
. /etc/rc.d/init.d/functions
# Source networking configuration.
. /etc/sysconfig/network
# Check that networking is up.
if [ ${NETWORKING} = "no" ]
then
  echo "Networking is down"
  exit 0
fi
# Check that binary exists
if ! [ -f  $openvpn ]
then
  echo "openvpn binary not found"
  exit 0
fi
# See how we were called.
case "$1" in
  start)
        echo -n $"Starting openvpn: "
        /sbin/modprobe tun >/dev/null 2>&1
        # From a security perspective, I think it makes
        # sense to remove this, and have users who need
        # it explictly enable in their --up scripts or
        # firewall setups.
        #echo 1 > /proc/sys/net/ipv4/ip_forward
        # Run startup script, if defined
        if [ -f $work/openvpn-startup ]; then
            $work/openvpn-startup
        fi
        if [ ! -d  $piddir ]; then
            mkdir $piddir
        fi
        if [ -f $lock ]; then
            # we were not shut down correctly
            for pidf in `/bin/ls $piddir/*.pid 2>/dev/null`; do
              if [ -s $pidf ]; then
                kill `cat $pidf` >/dev/null 2>&1
              fi
              rm -f $pidf
            done
            rm -f $lock
            sleep 2
        fi
        rm -f $piddir/*.pid
        cd $work
        # Start every .conf in $work and run .sh if exists
        errors=0
        successes=0
        for c in `/bin/ls *.conf 2>/dev/null`; do
            bn=${c%%.conf}
            if [ -f "$bn.sh" ]; then
                . $bn.sh
            fi
            rm -f $piddir/$bn.pid
            # Handle backward compatibility, see Red Hat Bugzilla ID #458594
            if [ -z "$( grep '^[[:space:]]*script-security[[:space:]]' $c )" ];                                                                                         then
                script_security="--script-security 2"
            fi
            $openvpn --daemon --writepid $piddir/$bn.pid --config /etc/openvpn/s                                                                                        erver.conf --cd $work $script_security
            if [ $? = 0 ]; then
                successes=1
            else
                errors=1
            fi
        done
        if [ $errors = 1 ]; then
            failure; echo
        else
            success; echo
        fi
        if [ $successes = 1 ]; then
            touch $lock
        fi
        ;;
  stop)
        echo -n $"Shutting down openvpn: "
        for pidf in `/bin/ls $piddir/*.pid 2>/dev/null`; do
          if [ -s $pidf ]; then
            kill `cat $pidf` >/dev/null 2>&1
          fi
          rm -f $pidf
        done
        # Run shutdown script, if defined
        if [ -f $work/openvpn-shutdown ]; then
            $work/openvpn-shutdown
        fi
        success; echo
        rm -f $lock
        ;;
  restart)
        $0 stop
        sleep 2
        $0 start
        ;;
  reload)
        if [ -f $lock ]; then
            for pidf in `/bin/ls $piddir/*.pid 2>/dev/null`; do
                if [ -s $pidf ]; then
                    kill -HUP `cat $pidf` >/dev/null 2>&1
                fi
            done
        else
            echo "openvpn: service not started"
            exit 1
        fi
        ;;
  reopen)
        if [ -f $lock ]; then
            for pidf in `/bin/ls $piddir/*.pid 2>/dev/null`; do
                if [ -s $pidf ]; then
                    kill -USR1 `cat $pidf` >/dev/null 2>&1
                fi
            done
        else
            echo "openvpn: service not started"
            exit 1
        fi
        ;;
  condrestart)
        if [ -f $lock ]; then
            $0 stop
            # avoid race
            sleep 2
            $0 start
        fi
        ;;
  status)
        if [ -f $lock ]; then
            for pidf in `/bin/ls $piddir/*.pid 2>/dev/null`; do
                if [ -s $pidf ]; then
                    kill -USR2 `cat $pidf` >/dev/null 2>&1
                fi
            done
            echo "Status written to /var/log/messages"
        else
            echo "openvpn: service not started"
            exit 1
        fi
        ;;
  *)
        echo "Usage: openvpn {start|stop|restart|condrestart|reload|reopen|statu                                                                                        s}"
        exit 1
        ;;
esac
exit 0
==================================================================

chmod 755 /etc/init.d/openvpn
service openvpn start.

==================================================================

Client Setup

cp the client.crt, ca.crt and client.key in client machine openvpn folder.

start openvpn client with client.conf