_AWS_SSM_SSH_Tunnel.md

EC2 Instance Connect meets AWS Session Manager via SSH

Both things have been introduced recently, and let you access even private ec2 instances

1. Without VPN
2. No open SSH port
3. Authentication / Authorization is fully delegated to IAM

# Assumes valid AWS Credentials in ENV
ssh -v ec2-user@i-002afb820244e392f

What this will do (through the aws-proxy script below):

• Generate a single use ssh key
• Push the generated publich key to AWS for the given user of the provided ec2 instance id
• Adds the private key to the ssh agent
• Create a tunnel through Session Manager
• Establish an SSH session

The host has to be configured to run:

• SSM Agent
• ec2-instance-connect

Locally, you'll have to have a recent version of the AWS cli and the SSM plugin

aws-proxy

#!/usr/bin/env bash

USER=$1
HOSTNAME=$2
PORT=$3
INSTANCE_AZ=$(aws ec2 describe-instances --instance-ids ${HOSTNAME} | jq -r '.Reservations | .[] | .Instances | .[] | .Placement.AvailabilityZone')
ONE_TIME_KEY_FILE_NAME="$(mktemp /tmp/${HOSTNAME}.${USER}.XXXXXX)"

yes | ssh-keygen -t rsa -b 2048 -f ${ONE_TIME_KEY_FILE_NAME} -N ''

aws ec2-instance-connect send-ssh-public-key \
  --region eu-central-1 \
  --availability-zone ${INSTANCE_AZ} \
  --instance-id ${HOSTNAME} \
  --instance-os-user ${USER} \
  --ssh-public-key "file://${ONE_TIME_KEY_FILE_NAME}.pub"

ssh-add -t 60 ${ONE_TIME_KEY_FILE_NAME}

aws ssm start-session \
  --target ${HOSTNAME} \
  --document-name AWS-StartSSHSession \
  --parameters "portNumber=${PORT}"

ssh_config

# SSH over Session Manager and EC2 Instance Connect

host i-* mi-*
  ProxyCommand sh -c "aws-proxy %r %h %p"

I have made a fork from your post with some changes for avoid the use of SSH Agent. Take a look I think you will find some nice improvements.

Thanks for sharing :) For reference here's the link to the fork

I've made a totally new refactor using the "Match exec" feature. By this way I have be able to generate the pair of keys earlier and outside from the ProxyCommand context.

This solves the SCP compatibility from my earliest version.