ec2-proxy-command.sh

#!/usr/bin/env bash
set -Eeufo pipefail

# ec2-proxy-command
# ==================
#
# Use this script with the ssh ProxyCommand option to automatically
# start an EC2 instance and then connect to its public DNS name.
#
# For example, consider the following stanza in ~/.ssh/config:
#
#  Host my-ec2-instance i-0123456789abcdef0
#          HostName my-ec2-instance
#          ProxyCommand ~/.local/bin/ec2-proxy-command i-0123456789abcdef0
#          User ec2-user
#          ForwardAgent no
#
# With this stanza in place, and this script saved with the filename
# ~/.local/bin/ec2-proxy-command, you can then execute "ssh my-ec2-instance"
# to automatically start and connect to the EC2 instance with id
# i-0123456789abcdef0.

PROGRAM_NAME="$(basename $0)"

show_help() {
    echo "Usage: $PROGRAM_NAME [-p profile] [-r region] <instance id>"
    echo "Use this script with the ssh ProxyCommand option to automatically"
    echo "start an EC2 instance and then connect to its public DNS name."
    echo ""
    echo "    -p profile  the name of the AWS CLI profile to use"
    echo "    -r region   the AWS region where the instance exists"
}

while getopts ":hp:r:" opt; do
    case "$opt" in
        h) show_help; exit 0;;
        p) export AWS_PROFILE="$OPTARG";;
        r) export AWS_REGION="$OPTARG";;
        :)
            echo "$PROGRAM_NAME: Missing argument: -$OPTARG" >&2
            show_help >&2
            exit 1;;
        \?)
            echo "$PROGRAM_NAME: Invalid option: -$OPTARG" >&2
            show_help >&2
            exit 1;;
    esac
done
shift "$((OPTIND-1))"

if [ "$#" -eq 0 ]; then
    echo "$PROGRAM_NAME: No instance ID specified." >&2
    show_help >&2
    exit 1
elif [ "$#" -gt 1 ]; then
    echo "$PROGRAM_NAME: Too many arguments specified." >&2
    show_help >&2
    exit 1
fi

INSTANCE_ID="$1"
echo "Starting instance $INSTANCE_ID..." >&2
aws ec2 start-instances --instance-ids "$INSTANCE_ID" > /dev/null
echo "Waiting for instance to be ready..." >&2
aws ec2 wait instance-status-ok --instance-ids "$INSTANCE_ID"
INSTANCE_PUBLIC_DNS_NAME="$(aws ec2 describe-instances   \
    --instance-ids "$INSTANCE_ID"                        \
    --query "Reservations[0].Instances[0].PublicDnsName" \
    --output text)"
echo "Connecting to public DNS name $INSTANCE_PUBLIC_DNS_NAME..." >&2
socat stdio "tcp:$INSTANCE_PUBLIC_DNS_NAME:22"