Dropbear (SSH) Static Build

This document provides instructions for building a static version of Dropbear, a lightweight SSH server and client. It can be run on any Linux system, including embedded devices.

Step 1: Download Dropbear Source

wget https://matt.ucc.asn.au/dropbear/dropbear-2025.88.tar.bz2

Step 2: Build Inside a Docker Container

docker run --rm -it -v $(pwd):/build ubuntu:noble /bin/bash

# Run the following commands inside the Docker container
apt update
apt -y install build-essential
apt -y install zlib1g-dev

# Change to the dropbear source directory, then run 
./configure --enable-static
make PROGRAMS="dropbear dbclient dropbearkey dropbearconvert scp" MULTI=1 STATIC=1
strip dropbearmulti

Usage

dropbearmulti is a multi-call binary that contains all the Dropbear programs.

# Genrate SSH host keys
# RSA key (required)
dropbearkey -t rsa -f ./dropbear_rsa_host_key

# Optional ECDSA key (modern systems)
dropbearkey -t ecdsa -f ./dropbear_ecdsa_host_key

# Run the Dropbear server in foreground on port 2223, no need for root
./dropbearmulti  dropbear -F -p 2223 -E  -D ./ -r ./dropbear_rsa_host_key -r ./dropbear_ecdsa_host_key