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In today's digital age, securing network infrastructure is paramount. One proven method to secure access to internal networks is through the use of an SSH jump server, which acts as an intermediary between the user and the internal servers. This article will focus on how to set up and manage an SSH jump server on the CentOS 7 operating system.

Introduction

SSH (Secure Shell) is a network protocol that enables secure access over unsecured networks. A jump server, also known as a bastion host, is exposed to the public internet and serves as the sole entry point for SSH access into an internal network, greatly increasing security by minimizing the number of potential entry points for attackers.

Prerequisites

• A CentOS 7 server installed and running, which will serve as the jump server.
• Basic knowledge of command-line interface and CentOS system management.

1. Installation and Configuration of the SSH Server

The first step is to ensure that the SSH server is installed on the jump server.

• Install the SSH server by running:

  sudo yum install -y openssh-server
  ​

• After installation, check and enable the SSH service:

  sudo systemctl start sshd
  sudo systemctl enable sshd
  ​

2. Configuring SSH for Secure Access

Configuring secure SSH access involves modifying the sshd_config configuration file.

• Open the SSH configuration file:

  sudo vi /etc/ssh/sshd_config
  ​

• To enhance security, consider making the following changes:
  • Disable root user login:

    PermitRootLogin no
    ​

  • Limit the users who can use the jump server:

    AllowUsers your_user
    ​

  • After making changes, restart the SSH service:

    sudo systemctl restart sshd
    ​

3. Setting Up Key-based Authentication

For increased security, it's recommended to use key-based authentication instead of passwords.

• Generate an SSH key on your local computer (if you haven't already):

  ssh-keygen
  ​

• Copy the public key to the jump server:

  ssh-copy-id your_user@jump_server_address
  ​

4. Accessing Through the Jump Server

After setting up the jump server, you can use the following command to access internal servers through the jump server:

ssh -J your_user@jump_server_address internal_server_address

This command first establishes a connection to the jump server and then connects to the internal server.

 

Setting up an SSH jump server on CentOS 7 is an effective way to enhance the security of access to your internal network. The steps outlined above should help you with a secure setup and configuration. Remember, keeping software up-to-date and following security best practices is key to protecting your infrastructure.