Introduction

serversideup/docker-ssh is a hardened SSH server container based on Debian. It works great if you need to create a secure tunnel into your cluster.

Features

• 🐧 Debian-based - Get a lightweight experience, while still having Bash
• 🤝 Key-based auth via ENV - Grant access with the AUTHORIZED_KEYS environment variable
• ⛔️ Block IPs via ENV - Block access with the ALLOWED_IPS environment variable
• 🔒 Unprivileged user - All SSH connections are made as an unprivileged user
• 🔑 Set your own PUID and PGID - Have the PUID and PGID match your host user
• 🔐 Hardened SSH - Prevent bot attacks and ensure quality security
• 📦 DockerHub and GitHub Container Registry - Choose where you'd like to pull your image from
• 🤖 Multi-architecture - Every image ships with x86_64 and arm64 architectures

Usage

This is a list of the docker images this repository creates:

Image	Image Size	Description
serversideup/docker-ssh		A hardened SSH server based on Debian Bookworm.

Usage instructions

All variables are documented here:

🔀 Variable Name	📚 Description	#️⃣ Default Value
ALLOWED_IPS	Content of allowed IP addresses (see below)	AllowUsers tunnel (allow the tunnel user from any IP)
AUTHORIZED_KEYS	🚨 Required to be set by you. Content of your authorized keys file (see below)
DEBUG	Display a bunch of helpful content for debugging.	false
PGID	Group ID the SSH user should run as.	9999
PUID	User ID the SSH user should run as.	9999
SSH_GROUP	Group name used for our SSH user.	tunnelgroup
SSH_HOST_KEY_DIR	Location of where the SSH host keys should be stored.	/etc/ssh/ssh_host_keys/
SSH_PORT	Listening port for SSH server (on container only. You'll still need to publish this port).	2222
SSH_USER	Username for the SSH user that other users will connect into as.	tunnel

1. Set your AUTHORIZED_KEYS environment variable or provide a /authorized_keys file

You can provide multiple keys by loading the contents of a file into an environment variable.

AUTHORIZED_KEYS="$(cat .ssh/my_many_ssh_public_keys_in_one_file.txt)"

Or you can provide the authorized_keys file via a volume. Ensure the volume references matches the path of /authorized_keys. The image will automatically take the file from /authorized_keys and configure it for use with your selected user.

ℹ️ NOTE: If both a file and variable are provided, the image will respect the value of the variable over the file.

2. Set your ALLOWED_IPS environment variable

Set this in the same context of AllowUsersThis example shows a few scenarios you can do:

ALLOWED_IPS="AllowUsers *@192.168.1.0/24 *@172.16.0.1 *@10.0.*.1"

3. Forward your external port to 2222 on the container

You can see I'm forwarding 12345 to 2222.

docker run --rm --name=ssh --network=web -p 12345:2222 localhost/ssh

This means I would connect with:

ssh -p 12345 tunnel@myserver.test

Working example with MariaDB + SSH + Docker Swarm

Here's a perfect example how you can use it with MariaDB. This allows you to use Sequel Pro or TablePlus to connect securely into your database server 🥳

Example using ALLOWED_IPS variable:

services:
  mariadb:
    image: mariadb:10.11
    networks:
      - database
    environment:
        MARIADB_ROOT_PASSWORD: "myrootpassword"
  ssh:
    image: serversideup/docker-ssh
    ports:
      - target: 2222
        published: 2222
        mode: host
    # Set the Authorized Keys of who can connect
    environment:
      AUTHORIZED_KEYS: >
        "# Start Keys
         ssh-ed25519 1234567890abcdefghijklmnoqrstuvwxyz user-a
         ssh-ed25519 abcdefghijklmnoqrstuvwxyz1234567890 user-b
         # End Keys"
      # Lock down the access to certain IP addresses
      ALLOWED_IPS: "AllowUsers tunnel@1.2.3.4"
    networks:
        - database

networks:
  database:

Example using $SSH_USER_HOME/.ssh/authorized_keys file:

services:
  mariadb:
    image: mariadb:10.11
    networks:
      - database
    environment:
        MARIADB_ROOT_PASSWORD: "myrootpassword"

  ssh:
    image: serversideup/docker-ssh
    ports:
      - target: 2222
        published: 2222
        mode: host
    # Set the Authorized Keys of who can connect
    environment:
      # Lock down the access to certain IP addresses
      ALLOWED_IPS: "AllowUsers tunnel@1.2.3.4"
    configs:
      - source: ssh_authorized_keys
        # Mount the file to "/authorized_keys". The image will handle everything else
        target: /authorized_keys
        mode: 0600
    networks:
        - database

# Define the config to be used
configs:
  ssh_authorized_keys:
    file: ./authorized_keys

networks:
  database:

Resources

• DockerHub to browse the images.
• Discord for friendly support from the community and the team.
• GitHub for source code, bug reports, and project management.
• Get Professional Help - Get video + screen-sharing help directly from the core contributors.

Contributing

As an open-source project, we strive for transparency and collaboration in our development process. We greatly appreciate any contributions members of our community can provide. Whether you're fixing bugs, proposing features, improving documentation, or spreading awareness - your involvement strengthens the project. Please review our code of conduct to understand how we work together respectfully.

• Bug Report: If you're experiencing an issue while using these images, please create an issue.
• Feature Request: Make this project better by submitting a feature request.
• Documentation: Improve our documentation by submitting a documentation change.
• Community Support: Help others on GitHub Discussions or Discord.
• Security Report: Report critical security issues via our responsible disclosure policy.

Need help getting started? Join our Discord community and we'll help you out!

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About Us

We're Dan and Jay - a two person team with a passion for open source products. We created Server Side Up to help share what we learn.

Dan Pastori	Jay Rogers

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