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Working with OpenVPN (and iptables)

Understanding Virtual Private Networks (VPsN) is essential for many advanced level certification tests. OpenVPN is a popular VPN solution that enjoys somewhat common use. This exercise focuses on configuring a basic VPN server and client.

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Path Info

Level
Clock icon Advanced
Duration
Clock icon 1h 30m
Published
Clock icon Nov 05, 2018

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Table of Contents

  1. Challenge

    Install and configure the OpenVPN server on `vpn-server`.

    Install OpenVPN:

    1. Run yum install -y openvpn.

    2. Copy the server config: cp /usr/share/doc/openvpn-2.4.7/sample/sample-config-files/server.conf /etc/openvpn/

    3. Edit the server config to contain the following topology configuration: topology subnet

  2. Challenge

    Install the provided server certificates.

    Run:

    cp /home/cloud_user/certs/ca.crt /home/cloud_user/certs/server.crt /home/cloud_user/certs/server.key /etc/openvpn

  3. Challenge

    Generate the required server keys.

    1. Generate the dhparam key (this may take a few minutes):
    openssl dhparam -out /etc/openvpn/dh2048.pem 2048
    1. Generate the key for tls-auth and copy it to client:
    openvpn --genkey --secret /etc/openvpn/ta.key

    scp /etc/openvpn/ta.key cloud_user:/home/cloud_user/ta.key

  4. Challenge

    Make the necessary firewall and routing configurations for OpenVPN on `vpn-server`.

    Run the following commands:

    iptables -I INPUT -p udp --dport 1194 -j ACCEPT

    iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE

    iptables-save > /etc/sysconfig/iptables

    sysctl -w net.ipv4.ip_forward=1

  5. Challenge

    Enable and start the OpenVPN server.

    Run the following:

    systemctl enable openvpn@server

    systemctl start openvpn@server

  6. Challenge

    Install and configure the OpenVPN client on `vpn-client`.

    On vpn-client, perform the following steps:

    1. Install OpenVPN:
    yum install y openvpn
    1. Copy the client.conf file from /usr/share/doc:
    cp /usr/share/doc/openvpn-2.4.7/sample/sample-config-files/client.conf /etc/openvpn/
    1. Update the remote command hostname directive in /etc/openvpn/client.conf as follows:
    remote vpn-server 1194

  7. Challenge

    Install the provided client and ca-certificates on `vpn-client`.

    Copy the provided certificates off of vpn-server and to the noted directories on vpn-client with the following commands.

    Run on the host vpn-client:

    cp /home/cloud_user/ca.crt /etc/openvpn/

    cp /home/cloud_user/client.key /etc/openvpn/

    cp /home/cloud_user/client.crt /etc/openvpn/

  8. Challenge

    Install the `tls` key from `vpn-server` on `vpn-client`.

    Assuming you copied the tls key over to /home/cloud_user/ta.key when you created it in the earlier tasks, run cp /home/cloud_user/ta.key /etc/openvpn/ta.key.

    If not, you will need to retrieve the file from vpn-server:/etc/openvpn/ta.key.

  9. Challenge

    Enable and start the OpenVPN client.

    Run the following commands:

    systemctl enable openvpn@client

    systemctl start openvpn@client
A Cloud Guru - Labs - Working with OpenVPN (and iptables)
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A Cloud Guru

The Cloud Content team comprises subject matter experts hyper focused on services offered by the leading cloud vendors (AWS, GCP, and Azure), as well as cloud-related technologies such as Linux and DevOps. The team is thrilled to share their knowledge to help you build modern tech solutions from the ground up, secure and optimize your environments, and so much more!

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