SSH to AWS EC2 instances behind a bastion, using ec2-ssh

aws-ssh.sh

#!/bin/sh

usage() {
  echo "Usage: $(basename "$0") [-h|--help] [-J USER@HOST] [-l user] [ssh-opts] \$ec2-host"
}

help() {
  usage
  echo
  echo "SSH to an EC2 host determined by the Name tag, via a bastion host."
  echo
  echo "Options:"
  echo "-J USER@HOST  Connection info for the bastion server, defaults to 'ec2-user@bastion'."
  echo "-l USER       SSH user to connect as to the final host, defaults to 'ec2-user'."
  echo
  echo "Where:"
  echo "  \$ec2-host  is a tag that will be resolved by the ec2-host tool from which"
  echo "              the first entry will be used for the connection."
}

shortoptions='hJ:l:'
longoptions='help,jump:,login:'

getopt=$(getopt -o $shortoptions --longoptions  $longoptions -- "$@")
if [ $? != 0 ] || [ $# -eq 0 ]; then
    usage
    exit 1;
fi

eval set -- "$getopt"

while true; do
  case "$1" in
    -h|--help) help; exit 1;;
    -J|--jump) BASTION=$2; shift 2;;
    -l|--login) LOGIN=$2; shift 2;;
    --) shift; break;;
  esac
done

if [ -z "$1" ]; then 
  help; exit 1
fi

EC2_HOST=$1
shift

[ -z "$BASTION" ] && BASTION="ec2-user@bastion"
[ -z "$LOGIN" ] && LOGIN="ec2-user"

ssh -o "ProxyCommand ec2-ssh $BASTION nc %h %p" -l $LOGIN $SSH_OPTS $@ $(ec2-host $EC2_HOST | head -n1)