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Design a Container to Run a Proxy

For this lab, the aim is to design a container to run a proxy. We need to connect to the server, create our configuration there, and test it out from a client. We recommended opening two terminals for this lab, one for connecting to the server and one to the client. The client is a playground instance of our choice. Once that is set, we need to create a container with a CentOS 7 image on the server. Within the container, we must install and configure the open ssh server so that it cannot allow `root` login and allows only key-based authentication. After that, we must change it to run on the nonstandard port 61613. After that, we need to copy the public key generated on the client over to the container on the server. Next, we have to create a proxy tunnel from the client and run tests to see if the tunnel works properly. For testing this, we need Proxychains 4.

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Path Info

Clock icon Intermediate
Clock icon 1h 30m
Clock icon May 15, 2020

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Table of Contents

  1. Challenge

    Create a Container from a CentOS 7 image and Access It

    lxc launch images:centos/7/amd64 SOCKS5-Proxy
    lxc exec SOCKS5-Proxy bash
  2. Challenge

    Configure SSH to not Allow root Login and Only Allow Key-Based Authentication

    adduser tunnel -m
    passwd tunnel
    yum install openssh-server vim
    vim /etc/ssh/sshd_config
    PermitRootLogin no
    PubkeyAuthentication yes
    ChallengeResponseAuthentication no
    PasswordAuthentication no
    UsePAM yes
    su tunnel
    mkdir /home/tunnel/.ssh
    touch /home/tunnel/.ssh/authorized_keys
    chmod 700 /home/tunnel/.ssh
    chmod 600 /home/tunnel/.ssh/authorized_keys
  3. Challenge

    On the Client, Generate a Key Pair and Copy the Public Key to /home/tunnel/.ssh/authorized_keys

    Set the path to /home/cloud_user/.ssh/SOCKS5.

    cat /home/cloud_user/.ssh/ 

    Copy the client public key to the server into authorized_keys

  4. Challenge

    Configure SSH for Port 61613 and Expose the Container to the Outside World

    If under a diffrent user in the container, just exit to root.

    vim /etc/ssh/sshd_config
    Port 61613
    systemctl restart sshd 

    Create a redirect on the host server.

    lxc list
    lxc config device add SOCKS5-Proxy myport443 proxy listen=tcp: connect=tcp:Container_IP:61613
  5. Challenge

    Run Tests to Confirm the Proxy Works on the Client (Refer to Lab Instructions for proxychains)

    ssh tunnel@SERVER_IP -i /home/cloud_user/.ssh/SOCKS5 -p 443
    ssh -D 65535 -q -C -N -f tunnel@SERVER_IP  -i /home/cloud_user/.ssh/SOCKS5 -p 443
    sudo apt install proxychains4 
    vim /etc/proxychains.conf 

    Change the last line to:

    socks5 65535
    curl ''
    proxychains4 curl ''

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