Debian 8 - Install OpenVPN

Just execute the script below as root or with sudo and answer all of the questions. At the end of it you will have a .tar.gz file in your /root directory containing all the keys that you need on your client to connect with.

Unlike my previous tutorials that used a 2048 bit key, I have switched over to 4096 bit keys which should be more secure but do take a while to generate. I have not noticed any degradation in performance.

#!/bin/bash
if ! [ -n "$BASH_VERSION" ];then
    echo "This is not bash, calling self with bash....";
    SCRIPT=$(readlink -f "$0")
    /bin/bash $SCRIPT
    exit;
fi

# Check have sudo/root permissions.
USER=`whoami`

if [ "$USER" != "root" ]; then
        echo "You need to run me with sudo!"
        exit
fi

# Ask the user for the path where they are going to stick the VPN config files
read -e -p "Path where you will store client configs (your local machine): 
" \
-i "/home/USER/my-vpn" CONFIG_FILE_PATH

# Update OS to latest
sudo apt-get update && sudo apt-get dist-upgrade -y

# Install needed packages
sudo apt-get install openvpn openssl udev -y

sudo cp -R /usr/share/easy-rsa /etc/openvpn/.



# Rather than execute the vars dir, lets just define them here:
export EASY_RSA="/etc/openvpn/easy-rsa/"
export OPENSSL="openssl"
export PKCS11TOOL="pkcs11-tool"
export GREP="grep"
export KEY_CONFIG=`$EASY_RSA/whichopensslcnf $EASY_RSA`
export KEY_DIR="$EASY_RSA/keys"
export PKCS11_MODULE_PATH="dummy"
export PKCS11_PIN="dummy"
export KEY_SIZE=4096
export CA_EXPIRE=3650
export KEY_EXPIRE=3650

# These are the fields which will be placed in the certificate.
# Don't leave any of these fields blank. Update if you want
export KEY_COUNTRY="US"
export KEY_PROVINCE="CA"
export KEY_CITY="SanFrancisco"
export KEY_ORG="Fort-Funston"
export KEY_EMAIL="noreply@getlost.com"
export KEY_OU="MyOrganizationalUnit"
export KEY_NAME="client1"
# END OF vars

. /etc/openvpn/easy-rsa/clean-all
. /etc/openvpn/easy-rsa/build-ca

# create the server key
. /etc/openvpn/easy-rsa/build-key-server server


# Create the client Key, update these if you want. The details MUST be slightly diff to server
export KEY_COUNTRY="US"
export KEY_PROVINCE="TX"
export KEY_CITY="Austin"
export KEY_ORG="The Alamo"
export KEY_EMAIL="noreply@getlost2.com"
export KEY_CN=changeme
export KEY_NAME=keyname
export KEY_OU=noidea
export PKCS11_MODULE_PATH=changeme
export PKCS11_PIN=1234
. /etc/openvpn/easy-rsa/build-key client1

# generate Deffie Hellman Parameters
. /etc/openvpn/easy-rsa/build-dh

# Move the keys we just generated to the directory that actually runs the openvpn service
cd /etc/openvpn/easy-rsa/keys
cp ca.crt ca.key client1.key client1.crt dh4096.pem server.crt server.key /etc/openvpn 


# Copy the sample server configuration file to the directory that will run it.
cd /usr/share/doc/openvpn/examples/sample-config-files
uncompress server.conf.gz
cp server.conf /etc/openvpn/.
cp client.conf /etc/openvpn/.


# Update the client.conf
SERVER_IP=`/sbin/ifconfig eth0 | grep 'inet addr:' | cut -d: -f2 | awk '{ print $1}'`
sed -i "s;remote my-server-1 1194;remote $SERVER_IP 1194;" /etc/openvpn/client.conf
sed -i "s;ca ca.crt;ca $CONFIG_FILE_PATH/ca.crt;" /etc/openvpn/client.conf
sed -i "s;cert client.crt;cert $CONFIG_FILE_PATH/client1.crt;" /etc/openvpn/client.conf
sed -i "s;key client.key;key $CONFIG_FILE_PATH/client1.key;" /etc/openvpn/client.conf

# Update the server.conf by uncommenting the redirect of gateway
sed -i 's:;push "redirect-gateway def1 bypass-dhcp":push "redirect-gateway def1 bypass-dhcp":' \
/etc/openvpn/server.conf

# Update the dhcp-option to push google as the DNS
sed -i 's:;push "dhcp-option DNS 208.67.220.220":push "dhcp-option DNS 8.8.8.8":' \
/etc/openvpn/server.conf

sed -i 's:;push "dhcp-option DNS 208.67.220.220":push "dhcp-option DNS 10.8.0.1":' \
/etc/openvpn/server.conf

# Update the pem location
SEARCH="dh dh1024.pem"
REPLACE="dh dh4096.pem"
FILEPATH="/etc/openvpn/server.conf"
sed -i "s;$SEARCH;$REPLACE;" $FILEPATH


# Set up packet forwarding.
sed -i "s;#net.ipv4.ip_forward=1;net.ipv4.ip_forward=1;" /etc/sysctl.conf
echo 1 > /proc/sys/net/ipv4/ip_forward

# Set up iptables to forward packets for vpn and do this upon startup.
echo '#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.

iptables -A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A FORWARD -s 10.8.0.0/24 -j ACCEPT
iptables -A FORWARD -j REJECT
iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE
exit 0' > /etc/rc.local

# Call the startup script immediately so user does not have to reboot to get going.
sudo bash /etc/rc.local

# Package up the files we need into a tar for sending
mkdir /etc/openvpn/vpn-details

cp /etc/openvpn/client.conf \
/etc/openvpn/ca.crt \
/etc/openvpn/client1.crt \
/etc/openvpn/client1.key \
/etc/openvpn/vpn-details/

cd /etc/openvpn/
tar --create --gzip --file ~/vpn-details.tar.gz vpn-details

# clean up
sudo rm -rf /etc/openvpn/vpn-details
sudo rm /etc/openvpn/client.conf
service openvpn restart

echo 'Now move the "vpn-details.tar.gz" folder to your local computer and carry on from there.'
echo "You may want to reboot this server."

Finally, there is one extra step where you need to edit the server.conf file on the server and change dh1024.pem to dh4096.pem. Then reboot.

Author

Programster

Stuart is a software developer with a passion for Linux and open source projects.

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