OpenVPN on Amazon Linux

OpenVPN on an AWS EC2 T2.Nano Instance

The T2.Nano instance is the smallest instance generally available for AWS EC2. As of 17-June-2017, the Nano includes the following resources: - 512mb RAM - 1 vcpu (30 credits + 3/hr, up to 72 credits) - 1gb network out traffic Alternatively, a $5 USD Amazon Lightsail instance can be used (see below)

Amazon Linux AMI

For those who prefer RHEL/CentOS, these are not available for the T2.Nano instance, rather Amazon Linux AMI is the only RHEL-derrived OS available. Note that Amazon AMI Linux is akin to CentOS 6.x (no systemd). Alternatively, Ubuntu is also available for the Nano. Note, there is now (Dec 2017) an Amazon Linux 2 option. Some say not to use any Amazon Linux. I tend to agree, though the main reason of not being able to use AMI outside of EC2 isn't correct, as there are container versions available for use locally.

Amazon Lightsail as an Alternative to EC2 T2.Nano

Amazon Lightsail is a VPS package that provides simplified control panel, and greater resources. For $5 USD/month, the smallest Lightsail instance is essentially a T2.Nano plus Elastic IP address, 20gb EBS storage, 1tb of outbound data, and Route53 DNS interface. Since outbound data can run 0.10/gb (with elastic IP), this is potentially $10/mo in database. The EBS storage is ~$2 USD, Route53 is $0.50 USD, and a nano instance with 1 year contract is ~$3.50 USD. This means for $5 USD/mo, one gets between $6-106 USD in AWS resources. For the $10 USD Lightsail, the value consists of a T2.Micro, and all the rest, which is worth $11-$211 USD in services due to an increase to 30gb EBS and 2TB data transfer out. - Amazon Lightsail FAQ Note: on Lightsail, the Security Groups are port-based only, so any IP filtering needs to be done wiht a separate firewall, such as iptables.

Steps to install OpenVPN on AMI - Pre-Installation

These steps are similar for a Nano instance. This should work on a Lightsail instance, though some control panel settings may be in different places.

Assume Root

sudo su

Set the hostname, timezone, nameservers

hostname server.domain.tld

Set the timezone

nano /etc/sysconfig/clock

Change the ZONE line to appropriate continent/city, e.g.,

ZONE="Continent/City"
UTC=false
ARC=false

Create a symbolic link

rm -rf /etc/localtime
ln -sf /usr/share/zoneinfo/Continent/City /etc/localtime

Update nameservers (using dns.watch resolvers)

echo "nameserver 84.200.69.80" > /etc/resolv.conf
echo "nameserver 84.200.70.40" >> /etc/resolv.conf

Edit the network sysconfig

nano /etc/sysconfig/network

Change HOSTNAME to server.domain.tld Check to ensure the change with the command:

hostname

Don't worry about /etc/hosts for now...

reboot

Update yum, configure EPEL

Note that we want the Amazon EPEL Repository

yum clean all
yum update
yum -y install epel-release
yum -y install yum-utils
yum-config-manager --enable epel

Update AMI without EPEL

This is done by disabling the repositories, which can be enabled later, including:

yum-config-manager --disable epel
yum clean all
yum update
cat /etc/system-release
uname -r

After the update version is confirmed, then re-enable the repositories with:

yum-config-manager --enable epel

Secure SSHD

nano /etc/ssh/sshd_config

make sure of the following:

PasswordAuthentication no
PermitRootLogin no

If you want to do fancy stuff like have an sftp login inside of a web directory, and need different than 700, 750, or 755 rights (say, for example, having the group be apache, and the user be a login) then include:

StrictModes no

Restart sshd

service sshd restart

Install and enable MOSH

yum -y install mosh

Mosh makes connections more resilient, but there is a cost of disabling the ability to scroll up in the console.

firewalld or ufw

This may or may not be desirable, in addition to the AWS firewall configuration. Likely desirable.

Install OpenVPN on AMI

yum -y install openvpn

Install Easy-RSA on AMI

Note that since there is a version 3.x, have to get an older distribution or it won't work. Note the below might still be a bit of a mess. Inspect directories as you go.

cd /etc/openvpn
wget -v https://github.com/OpenVPN/easy-rsa/releases/download/2.2.2/EasyRSA-2.2.2.tgz
tar -xvzf EasyRSA-2.2.2.tgz
mkdir easy-rsa
mv EasyRSA-2.2.2 /etc/openvpn/easy-rsa
cd easy-rsa
mv EasyRSA-2.2.2 2.0
mkdir -p /etc/openvpn/easy-rsa/keys
cp -R /usr/share/easy-rsa/2.0/ /etc/openvpn/easy-rsa/

NAT routing using iptables

Put in nat routing, ensure that the network on the masquarade is the same as in /etc/openvpn/server.conf First edit the iptables-config file

nano /etc/sysconfig/iptables-config

Change most things to yes, with a final config looking like:

IPTABLES_MODULES=""
IPTABLES_MODULES_UNLOAD="yes"
IPTABLES_SAVE_ON_STOP="yes"
IPTABLES_SAVE_ON_RESTART="yes"
IPTABLES_SAVE_COUNTER="no"
IPTABLES_STATUS_NUMERIC="yes"
IPTABLES_STATUS_VERBOSE="yes"
IPTABLES_STATUS_LINENUMBERS="yes"

Now do the rest of the iptables configuration

touch /etc/sysconfig/iptables
chkconfig iptables on
service iptables start
modprobe iptable_nat
echo 1 | tee /proc/sys/net/ipv4/ip_forward
iptables -t nat -A POSTROUTING -o eth0 -s 10.8.0.0/24 -j MASQUERADE
service iptables save
service iptables restart

Edit the Easy RSA settings

nano /etc/openvpn/easy-rsa/2.0/vars

Find and modify these values:

# These are the default values for fields
# which will be placed in the certificate.
# Don't leave any of these fields blank.
export KEY_COUNTRY="CA"
export KEY_PROVINCE=""
export KEY_CITY="SanFrancisco"
export KEY_ORG="Fort-Funston"
export KEY_EMAIL="me@myhost.mydomain"
export KEY_OU="MyOrganizationalUnit"

Also change

export KEY_CONFIG=`$EASY_RSA/whichopensslcnf $EASY_RSA`

to

export KEY_CONFIG=/etc/openvpn/easy-rsa/2.0/openssl-1.0.0.cnf

Initialize Easy RSA and create Certs and Keys

cd /etc/openvpn/easy-rsa/2.0
chmod 0755 *
source ./vars
./clean-all
./build-ca

Verify success

ls -la keys

Now build the cert and key

./build-key-server server

Note: leave the challenge password and optional company name blank Next, Verify success

ls -la keys

Next build a cert and key for each vpn user:

./build-key username

Provide this with a challenge password Next, build the .pem

./build-dh

Next, build the ta.key // rather forget about this, just comment out, it is trouble // get this going later openvpn --genkey --secret /etc/openvpn/easy-rsa/2.0/keys/ta.key Copy the keys and certs

cd /etc/openvpn/easy-rsa/2.0/keys
cp dh2048.pem ca.crt server.crt server.key username.crt username.key /etc/openvpn

Create OpenVPN Config File

Note that previously a version was copied and edited from the /usr/share/doc directory, but latest versions of OpenVPN no longer include this. Instead touch and then use the following file below as the base server.conf:

touch /etc/openvpn/server.conf
cd /etc/openvpn
chmod 0644 dh2048.pem ca.crt server.crt server.key server.conf username.crt username.key

Next, edit server.conf

nano /etc/openvpn/server.conf

Here is an example of server.conf. Ensure the masquerade iptables and server configuration are identical.

port 1194
proto udp
dev tun
tun-mtu 1500
tun-mtu-extra 32
mssfix 1450
reneg-sec 0
ca ca.crt
cert server.crt
key server.key  # This file should be kept secret
dh dh2048.pem
server 10.8.0.0 255.255.255.0
ifconfig-pool-persist ipp.txt
push "redirect-gateway def1 bypass-dhcp"
push "dhcp-option DNS 84.200.69.80"
push "dhcp-option DNS 84.200.70.40"
duplicate-cn
keepalive 10 120
;cipher BF-CBC        # Blowfish (default)
;cipher AES-128-CBC   # AES
;cipher DES-EDE3-CBC  # Triple-DES
comp-lzo
user nobody
group nobody
persist-key
persist-tun
status openvpn-status.log
verb 3
explicit-exit-notify 0

Enable Routing

nano /etc/sysctl.conf

Change ip forwarding to 1

net.ipv4.ip_forward = 1

Restart networking services

service network restart

Enable and start the OpenVPN service

chkconfig openvpn on
service openvpn restart

Install and Configure OpenVPN Client

For OSX, there is Tunnelblick, which sucks, and Viscosity which sucks less (but costs $9). An example Viscosity config file looks like:

#viscosity startonopen false
#viscosity protocol openvpn
#viscosity dns off
#viscosity usepeerdns false
#viscosity autoreconnect true
#viscosity name host.domain.tld
#viscosity dhcp true
remote 12.34.56.78 1194 udp
nobind
dev tun
redirect-gateway def1
tun-mtu 1500
pull
tls-client
ca ca.crt
cert cert.crt
key key.key
push "redirect-gateway def1"
comp-lzo
mssfix 1450
resolv-retry infinite
tun-mtu-extra 32
reneg-sec 0

For installing an OVPN command line client on Linux, simply taking the config.conf file, along with ca.crt, cert.crt, and key.key files. Installation on a Debian system looks like:

sudo apt-get update
apt-get install openvpn

Then scp the four files into the home directory and run:

openvpn config.conf

After this works, then set up OVPN as a service with scripts for automation. - See also OpenVPN on ChromeOS and Android

Resources Consulted

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