sslh – A ssl/ssh multiplexer

sslh accepts connections on specified ports, and forwards them further based on tests performed on the first data packet sent by the remote client.

Probes for HTTP, TLS/SSL (including SNI and ALPN), SSH, OpenVPN, tinc, XMPP, SOCKS5, are implemented, and any other protocol that can be tested using a regular expression, can be recognised. A typical use case is to allow serving several services on port 443 (e.g. to connect to SSH from inside a corporate firewall, which almost never block port 443) while still serving HTTPS on that port.

Hence sslh acts as a protocol demultiplexer, or a switchboard. With the SNI and ALPN probe, it makes a good front-end to a virtual host farm hosted behind a single IP address.

sslh has the bells and whistles expected from a mature daemon: privilege and capabilities dropping, inetd support, systemd support, transparent proxying, chroot, logging, IPv4 and IPv6, TCP and UDP, a fork-based, a select-based model, and yet another based on libev for larger installations.

Install

Please refer to the install guide.

Configuration

Please refer to the configuration guide.

Docker image

How to use

docker run \
  --cap-add CAP_NET_RAW \
  --cap-add CAP_NET_BIND_SERVICE \
  --rm \
  -it \
  ghcr.io/yrutschle/sslh:latest \
  --foreground \
  --listen=0.0.0.0:443 \
  --ssh=hostname:22 \
  --tls=hostname:443

docker-compose example

version: "3"

services:
  sslh:
    image: sslh:latest
    hostname: sslh
    ports:
      - 443:443
    command: --foreground --listen=0.0.0.0:443 --tls=nginx:443 --openvpn=openvpn:1194
    depends_on:
      - nginx
      - openvpn

  nginx:
    image: nginx

  openvpn:
    image: openvpn

Transparent mode 1: using sslh container for networking

Note: For transparent mode to work, the sslh container must be able to reach your services via localhost

version: "3"

services:
  sslh:
    build: https://github.com/yrutschle/sslh.git
    container_name: sslh
    environment:
      - TZ=${TZ}
    cap_add:
      - NET_ADMIN
      - NET_RAW
      - NET_BIND_SERVICE
    sysctls:
      - net.ipv4.conf.default.route_localnet=1
      - net.ipv4.conf.all.route_localnet=1
    command: --transparent --foreground --listen=0.0.0.0:443 --tls=localhost:8443 --openvpn=localhost:1194
    ports:
      - 443:443 #sslh

      - 80:80 #nginx
      - 8443:8443 #nginx

      - 1194:1194 #openvpn
    extra_hosts:
      - localbox:host-gateway
    restart: unless-stopped

  nginx:
    image: nginx:latest
    .....
    network_mode: service:sslh #set nginx container to use sslh networking.
    # ^^^ This is required. This makes nginx reachable by sslh via localhost
  
  openvpn:
    image: openvpn:latest
    .....
    network_mode: service:sslh #set openvpn container to use sslh networking

Transparent mode 2: using host networking

version: "3"

services:
  sslh:
    build: https://github.com/yrutschle/sslh.git
    container_name: sslh
    environment:
      - TZ=${TZ}
    cap_add:
      - NET_ADMIN
      - NET_RAW
      - NET_BIND_SERVICE
    # must be set manually
    #sysctls:
    #  - net.ipv4.conf.default.route_localnet=1
    #  - net.ipv4.conf.all.route_localnet=1
    command: --transparent --foreground --listen=0.0.0.0:443 --tls=localhost:8443 --openvpn=localhost:1194
    network_mode: host
    restart: unless-stopped
  
  nginx:
    image: nginx:latest
    .....
    ports:
      - 8443:8443 # bind to docker host on port 8443

  openvpn:
    image: openvpn:latest
    .....
    ports:
      - 1194:1194 # bind to docker host on port 1194

Comments? Questions?

You can subscribe to the sslh mailing list here: https://lists.rutschle.net/mailman/listinfo/sslh

This mailing list should be used for discussion, feature requests, and will be the preferred channel for announcements.

Of course, check the FAQ first!