Dockerized efingerd Finger Daemon

Thanks to @[email protected] for some insight about socat that allowed a rebase from Ubuntu to Alpine, reducing the image size from ~120MB to about ~8MB. Also, binaries had to be recompiled for Alpine (musl) from efingerd_1.6.7 and libident_0.32.

Have a look at the efingerd man page.

All volume mounts are optional, but you probably want to use them.

Docker Run

docker run -d -p 79:79 \
  --name efingerd \
  -v <world-scripts>:/etc/efingerd \
  -v <user-scripts>:/home \
  -v <logfile>:/var/log/efingerd.log \
  ja2ui0/efingerd

Docker Compose

version: "3"
services:
  efingerd:
    image: ja2ui0/efingerd
    container_name: efingerd
    volumes:
      - <world-scripts>:/etc/efingerd
      - <user-scripts>:/home
      - <logfile>:/var/log/efingerd.log
    ports:
      - 79:79
    restart: unless-stopped

Volumes

• world-scripts: how efingerd handles requests you don't explicitly define
  • if you want to change logging, or anything related to undefined users, mount your own here
  • don't change the names of the scripts, only the contents
• user-scripts: - Where you put your .efingerd scripts for named users
• logfile: if you want to see the IPs that are fingering your host

Considerations

• To add new users, run docker exec efingerd useradd <name>. If you don't add the user, efingerd won't run their script even if it's there.
• To make efingerd respond to a query, you must:
  • add a /home/<name>/.efingerd containing a shebang and a command interpreter, ie: #!/bin/sh, or efingerd won't know what to do.
  • ensure .efingerd is readable and executable by nobody (chmod 755 is fine)
• The user script can be as simple as echoing information, reading in a file and spitting it out, or really anything you want
• You might want to include . /etc/efingerd/log at the top of your script so successful fingers are logged the same as unsuccessful ones
• If you choose to bind mount a log file, make sure it is writable by nobody (chmod 644 is fine)
• The image on Docker Hub is built with the -n and -f flags. See the man page for details.

examples-standard

These are the main scripts that ship with the original package. They will break horribly if you use them, since many of the binaries on which they depend are not available in the image (or Alpine in general, unless you compile from source). They are included in this repo so you can see what this daemon was designed to be able to do.