SOCKET-PROXY

Access your docker socket safely as read-only, rootless and distroless

SYNOPSIS 📖

What can I do with this? This image will run a proxy to access your docker socket as read-only. The exposed proxy socket is run as 1000:1000, not as root, although the image starts the proxy process as root to interact with the actual docker socket. There is also a TCP endpoint started at 2375 that will also proxy to the actual docker socket if needed. It is not exposed by default and must be exposed via using - "2375:2375/tcp" in your compose.

Make sure that the docker socket is accessible by the user: specification in your compose, if the UID/GID are not correct, the image will print out the correct UID/GID for you to set:

socket-proxy-1  | 2025/03/26 10:16:33 can’t access docker socket as GID 0 owned by GID 991
socket-proxy-1  | please change the user setting in your compose to the correct UID/GID pair like this:
socket-proxy-1  | services:
socket-proxy-1  |   socket-proxy:
socket-proxy-1  |     user: "0:991"

You find the list of all available Docker API endpoints here. The following paths are still blocked, even though they are accesses only via GET:

• GET /containers/{id}/attach/ws
• GET /containers/{id}/export
• GET /containers/{id}/archive
• GET /secrets
• GET /configs
• GET /swarm/unlockkey
• GET /images/{name}/get

UNIQUE VALUE PROPOSITION 💶

Why should I run this image and not the other image(s) that already exist? Good question! Because ...

Important

• ... this image exposes the socket not as root but as 1000:1000
• ... this image has no shell since it is distroless
• ... this image is auto updated to the latest version via CI/CD
• ... this image has a health check
• ... this image runs read-only
• ... this image is automatically scanned for CVEs before and after publishing
• ... this image is created via a secure and pinned CI/CD process
• ... this image is very small

If you value security, simplicity and optimizations to the extreme, then this image might be for you.

COMPOSE ✂️

name: "reverse-proxy"
services:
  socket-proxy:
    # this image is used to expose the docker socket as read-only to traefik
    # you can check https://github.com/11notes/docker-socket-proxy for all details
    image: "11notes/socket-proxy:2.1.4"
    read_only: true
    user: "0:108" 
    environment:
      TZ: "Europe/Zurich"
    volumes:
      - "/run/docker.sock:/run/docker.sock:ro" 
      - "socket-proxy.run:/run/proxy"
    restart: "always"

  traefik:
    depends_on:
      socket-proxy:
        condition: "service_healthy"
        restart: true
    image: "11notes/traefik:3.5.0"
    read_only: true
    labels:
      - "traefik.enable=true"

      # default errors middleware
      - "traefik.http.middlewares.default-errors.errors.status=402-599"
      - "traefik.http.middlewares.default-errors.errors.query=/{status}"
      - "traefik.http.middlewares.default-errors.errors.service=default-errors"

      # default ratelimit
      - "traefik.http.middlewares.default-ratelimit.ratelimit.average=100"
      - "traefik.http.middlewares.default-ratelimit.ratelimit.burst=120"
      - "traefik.http.middlewares.default-ratelimit.ratelimit.period=1s"

      # default CSP
      - "traefik.http.middlewares.default-csp.headers.contentSecurityPolicy=default-src 'self' blob: data: 'unsafe-inline'"

      # default allowlist
      - "traefik.http.middlewares.default-ipallowlist-RFC1918.ipallowlist.sourcerange=10.0.0.0/8,172.16.0.0/12,192.168.0.0/16"

      # example on how to secure the traefik dashboard and api
      - "traefik.http.routers.dashboard.rule=Host(`${TRAEFIK_FQDN}`)"
      - "traefik.http.routers.dashboard.service=api@internal"
      - "traefik.http.routers.dashboard.middlewares=dashboard-auth"
      - "traefik.http.routers.dashboard.entrypoints=https"
      # admin / traefik, please change!
      - "traefik.http.middlewares.dashboard-auth.basicauth.users=admin:$2a$12$ktgZsFQZ0S1FeQbI1JjS9u36fAJMHDQaY6LNi9EkEp8sKtP5BK43C"

      # default catch-all router
      - "traefik.http.routers.default.rule=HostRegexp(`.+`)"
      - "traefik.http.routers.default.priority=1"
      - "traefik.http.routers.default.entrypoints=https"
      - "traefik.http.routers.default.service=default-errors"

      # default http to https redirection
      - "traefik.http.middlewares.default-http.redirectscheme.permanent=true"
      - "traefik.http.middlewares.default-http.redirectscheme.scheme=https"
      - "traefik.http.routers.default-http.priority=1"
      - "traefik.http.routers.default-http.rule=HostRegexp(`.+`)"
      - "traefik.http.routers.default-http.entrypoints=http"
      - "traefik.http.routers.default-http.middlewares=default-http"
      - "traefik.http.routers.default-http.service=default-http"
      - "traefik.http.services.default-http.loadbalancer.passhostheader=true"
    environment:
      TZ: "Europe/Zurich"
    command:
      # ping is needed for the health check to work!
      - "--ping=true"
      - "--ping.terminatingStatusCode=204"
      - "--global.checkNewVersion=false"
      - "--global.sendAnonymousUsage=false"
      - "--accesslog=true"
      - "--api.dashboard=true"
      # disable insecure api and dashboard access
      - "--api.insecure=false"
      - "--log.level=INFO"
      - "--log.format=json"
      - "--providers.docker.exposedByDefault=false"
      - "--providers.file.directory=/traefik/var"
      - "--entrypoints.http.address=:80"
      - "--entrypoints.http.http.middlewares=default-errors,default-ratelimit,default-ipallowlist-RFC1918,default-csp"
      - "--entrypoints.https.address=:443"
      - "--entrypoints.https.http.tls=true"
      - "--entrypoints.https.http.middlewares=default-errors,default-ratelimit,default-ipallowlist-RFC1918,default-csp"
      # disable upstream HTTPS certificate checks (https > https)
      - "--serversTransport.insecureSkipVerify=true"
      - "--experimental.plugins.rewriteResponseHeaders.moduleName=github.com/jamesmcroft/traefik-plugin-rewrite-response-headers"
      - "--experimental.plugins.rewriteResponseHeaders.version=v1.1.2"
      - "--experimental.plugins.geoblock.moduleName=github.com/PascalMinder/geoblock"
      - "--experimental.plugins.geoblock.version=v0.3.3"
    ports:
      - "80:80/tcp"
      - "443:443/tcp"
    volumes:
      - "var:/traefik/var"
      - "plugins:/traefik/plugins"
      # access docker socket via proxy read-only
      - "socket-proxy.run:/var/run"
    networks:
      backend:
      frontend:
    sysctls:
      # allow rootless container to access ports < 1024
      net.ipv4.ip_unprivileged_port_start: 80
    restart: "always"

  errors:
    # this image can be used to display a simple error message since Traefik can’t serve content
    image: "11notes/traefik:errors"
    read_only: true
    labels:
      - "traefik.enable=true"
      - "traefik.http.services.default-errors.loadbalancer.server.port=8080"
    environment:
      TZ: "Europe/Zurich"
    networks:
      backend:
    restart: "always"

  # example container
  nginx:
    image: "11notes/nginx:stable"
    read_only: true
    labels:
      - "traefik.enable=true"
      - "traefik.http.routers.nginx-example.rule=Host(`${NGINX_FQDN}`)"
      - "traefik.http.routers.nginx-example.entrypoints=https"
      - "traefik.http.routers.nginx-example.service=nginx-example"
    ports:
      - "3000:3000/tcp"
    tmpfs:
      # needed for read_only: true
      - "/nginx/cache:uid=1000,gid=1000"
      - "/nginx/run:uid=1000,gid=1000"
    networks:
      backend:
    restart: "always"

volumes:
  var:
  plugins:
  socket-proxy.run:

networks:
  frontend:
  backend:
    internal: true

ENVIRONMENT 📝

Parameter	Value	Default
TZ	Time Zone
DEBUG	Will activate debug option for container image and app (if available)
SOCKET_PROXY_VOLUME	path to the docker volume used to expose the prox socket	/run/proxy
SOCKET_PROXY_DOCKER_SOCKET	path to the actual docker socket	/run/docker.sock
SOCKET_PROXY_UID	the UID used to run the proxy parts	1000
SOCKET_PROXY_GID	the GID used to run the proxy parts	1000
SOCKET_PROXY_KEEPALIVE	connection keep alive interval to SOCKET_PROXY_DOCKER_SOCKET	10s
SOCKET_PROXY_TIMEOUT	connection max. timeout to SOCKET_PROXY_DOCKER_SOCKET	30s

MAIN TAGS 🏷️

These are the main tags for the image. There is also a tag for each commit and its shorthand sha256 value.

• 2.1.4

There is no latest tag, what am I supposed to do about updates?

It is of my opinion that the :latest tag is dangerous. Many times, I’ve introduced breaking changes to my images. This would have messed up everything for some people. If you don’t want to change the tag to the latest semver, simply use the short versions of semver. Instead of using :2.1.4 you can use :2 or :2.1. Since on each new version these tags are updated to the latest version of the software, using them is identical to using :latest but at least fixed to a major or minor version.

If you still insist on having the bleeding edge release of this app, simply use the :rolling tag, but be warned! You will get the latest version of the app instantly, regardless of breaking changes or security issues or what so ever. You do this at your own risk!

REGISTRIES ☁️

docker pull 11notes/socket-proxy:2.1.4
docker pull ghcr.io/11notes/socket-proxy:2.1.4
docker pull quay.io/11notes/socket-proxy:2.1.4

SOURCE 💾

• 11notes/socket-proxy

PARENT IMAGE 🏛️

Important

This image is not based on another image but uses scratch as the starting layer. The image consists of the following distroless layers that were added:

• 11notes/distroless - contains users, timezones and Root CA certificates

GENERAL TIPS 📌

Tip

• Use a reverse proxy like Traefik, Nginx, HAproxy to terminate TLS and to protect your endpoints
• Use Let’s Encrypt DNS-01 challenge to obtain valid SSL certificates for your services

ElevenNotes™️

This image is provided to you at your own risk. Always make backups before updating an image to a different version. Check the releases for breaking changes. If you have any problems with using this image simply raise an issue, thanks. If you have a question or inputs please create a new discussion instead of an issue. You can find all my other repositories on github.

created 12.08.2025, 08:20:27 (CET)