In the case of the Windows environment, SSH can be replaced with RDP, and Linux bastion can be replaced with a Windows machine. How to deploy bastion and configure host?įor this exercise, we will deploy Linux bastion host in the same architecture which we used while creating our last custom VPC. In a nutshell, bastion hosts used to secure administrative access to instances in private and public subnets. Your all instances no matter they are in which subnet should be accessible via bastion host only. This way one can secure administrative level access to instances in public and private subnets. One should block access (SSH or RDP) to instances in the public subnet as well and allow them only through the bastion host. Sometimes, cloud newbies treat bastion host as a way of accessing instances in the private subnet only. What is the role of bastion host in AWS infrastructure?Īs explained above, the bastion host will be used to access the rest of the infrastructure. Secure this machine at OS level with all available hardening techniques since this machine is a gateway to your whole infrastructure. Since you don’t want to expose everything in your infra to the internet, the bastion host will do that heavy lifting and hence securing the infrastructure.Īs this host is exposed to the internet it is recommended to implement a strong system hardening on this machine. It’s a machine that is used to securely access the rest of the infrastructure for administration purposes. What is bastion host?Ī bastion host is a Windows or Linux machine sitting in the Public subnet of your AWS infrastructure. Lets start with the introduction to bastion host. How to deploy and configure a bastion host?.What is the role of bastion host in AWS infrastructure?.In the next post we’ll discuss SSH connection multiplexing, port forwarding, and using SSH as a SOCKS proxy.In this article, we will touch base below points in context to bastion host: Now you should be able to connect to any machine matching one of the host patterns and it will automatically and transparently look up and use the bastion host. You will likely want to adjust *. and SSHBastion to match your environment. Prox圜ommand ssh -A ec2 describe-instances -filters "Name=instance-state-name,Values=running" "Name=tag:Name,Values= SSHBastion" "Name=tag:Subnet,Values=public" | jq -r. Now all we need to do is incorporate that command in place of the bastion host address in the ssh configuration: Host *. If that fails, make sure that all the requirements mentioned above have been met. That command should return a public address of the bastion host, such as: You will likely wish to replace the bolded “SSHBastion” with whatever tag value you wish to use. "Name=instance-state-name,Values=running" Now, to test that we can get the relevant bastion host’s address, let’s run a simple command and verify that we get the correct result (lines broken for readability, but this is one long command): aws ec2 describe-instances -filters Basically, anything that can consume JSON, search for specific subkeys, and return the relevant values will work. It’s possible to use one of a number of other utilities for that same purpose.The command line utility jq must be installed.You could also have various bastion servers in the same AWS environment, but you will need to be able to map the destination machines (via DNS or IP range in a way that can be put in the Host line of the SSH configuration) to the relevant EC2 tag.In this example, we have a machine with the tag Name with a value of SSHBastion.You must be able to SSH into this machine, since it will be the bastion server. That EC2 instance must be on a public subnet that you have access to. There need to be a single EC2 instance in each target AWS environment with a unique tag, so that we can search for that tag and get the address of that single EC2.You can test if it’s working by running: aws ec2 describe-instances.It’s possible to change the AWS access credentials in the shell environment to switch to a different AWS environment.The aws command-line utility must be installed and the shell environment must be configured to allow access to the destination AWS environment.This could easily be extended or modified to use any other means of dynamically loading the hostname during the connection. Here we will describe how to load the bastion server’s address from AWS, using AWS tags and the shell environment’s AWS authentication information. Part 1: Using SSH Through A Bastion Host Transparentlyĭynamically loading the bastion server address from AWSĬredit to my colleague Jason Mao for devising this technique.This is the second part of a series about using SSH with bastion hosts. You may wish to read the first part for background about using SSH bastion hosts:
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