Implementing Bastion Host for Secure Access: A Hands-On Guide for AWS

In this article, we will delve into the concept of Bastion hosts and learn how to implement them effectively. As this topic requires careful consideration and implementation, we will divide it into two parts. In the first part, we will explore the purpose of Bastion hosts, and in the second part, we will walk through the process of setting up and configuring these hosts step by step.

Understanding the Purpose of Bastion Hosts

Bastion hosts, also known as jump servers, play a crucial role in securing access to instances within a network. Imagine a scenario where you have set up a Virtual Private Cloud (VPC) with both private and public subnets. In the private subnet, you have sensitive instances like database servers, while the public subnet hosts instances accessible from the internet, such as web servers.

Now, let’s say you need to grant administrative access to the database server from the internet while maintaining the security of the private subnet. You might be tempted to mark the private subnet as public, but this introduces security risks.

Here’s where Bastion hosts come into play. A Bastion host acts as an intermediary gateway between your local workstation and instances in the private subnet. This adds an extra layer of security. By connecting to the Bastion host, you can then access the instances within the private subnet without directly exposing them to the internet.

To summarize, the purpose of a Bastion host is to enable secure connectivity to instances in a private subnet. Now, let’s proceed to the hands-on implementation.

Hands-On Implementation: Setting Up Bastion Hosts

Step 1: Creating Subnets and Route Tables

1. In your AWS Console, navigate to the VPC Dashboard.
2. Create a new subnet named “subnet C.” This will be your private subnet.
3. Create a custom route table and associate it with “subnet A” and “subnet B.”
4. Ensure the custom route table has a route to the internet gateway, allowing communication for instances in the public subnets.

Step 2: Launching Instances

1. Launch an Amazon EC2 instance in “subnet B.” This will be your Bastion host.
   • Choose the appropriate instance type and configuration.
   • Assign a security group that limits incoming traffic to secure workstations.
2. Launch another EC2 instance in “subnet C,” the private subnet.
   • Choose the desired instance type and configuration.
   • Do not assign a public IP address, as this is the private instance.

Step 3: Configuring Security Groups

1. For the Bastion host:
   • Adjust the security group to only allow incoming traffic from select workstations.
2. For the private instance:
   • Apply security group rules to allow communication from the Bastion host.

Step 4: Connecting to Private Server from Bastion Host

1. Access your Bastion host using SSH from your local workstation.
2. From the Bastion host, SSH into the private instance using its private IP address.

Conclusion

In this hands-on guide, we explored the purpose and implementation of Bastion hosts. These hosts provide a secure gateway for accessing instances in private subnets while maintaining network security. By setting up a Bastion host, you can effectively control and manage access to sensitive resources without exposing them directly to the internet. Through careful configuration of subnets, route tables, security groups, and SSH connections, you can establish a robust and secure architecture for your cloud environment.