Create an mqtt-dasher service. (Debian/Ubuntu distros).

mqtt-dasher : https://github.com/stjohnjohnson/mqtt-dasher

Limits permissions for promiscuous net socket access via libpcap.

This assumes npm install without the global flag so uses /opt/node_modules instead of /usr/lib.

Install

install nodejs from debsource

curl -sL https://deb.nodesource.com/setup_5.x | sudo -E bash -
sudo apt-get install -y nodejs

install mqtt-dasher and libpcap dependency

sudo apt-get install libpcap-dev
sudo npm install mqtt-dasher

add user to run the service, and group to limit access to setcap files

sudo useradd mqtt-dasher -d /opt/node_modules/mqtt-dasher -U

make a copy of nodejs to set privileged net capabilities on

sudo cp which nodejs /opt/node_modules/mqtt-dasher/nodejs.setcap

set user and group for mqtt-dasher first

sudo chgrp mqtt-dasher /opt/node_modules/mqtt-dasher/nodejs.setcap
sudo chmod 750 /opt/node_modules/mqtt-dasher/nodejs.setcap

allow raw sockets and net admin for promiscuous mode

sudo setcap 'CAP_NET_RAW+eip CAP_NET_ADMIN+eip' /opt/node_modules/mqtt-dasher/nodejs.setcap

$[Get Code]1

Create the Service

/etc/systemd/system/mqtt-dasher.service 

[Unit]
Description=mqtt-dasher service

[Service]
ExecStart=/opt/node_modules/mqtt-dasher/nodejs.setcap /opt/node_modules/mqtt-dasher/server.js
# WorkingDirectory=/opt/node_modules/mqtt-dasher   # Required on some systems
Restart=always
RestartSec=10             # Restart service after 10 seconds if node service crashes
StandardOutput=syslog     # Output to syslog
StandardError=syslog      # Output to syslog
SyslogIdentifier=mqtt-dasher
User=mqtt-dasher
Group=mqtt-dasher
Environment=CONFIG_DIR=/etc/mqtt-dasher NODE_ENV=production

[Install]
WantedBy=multi-user.target

Configure and start

sudo mkdir /etc/mqtt-dasher

$[Get Code]2

/etc/mqtt-dasher/config.yml 

mqtt:
  host: localhost
  ## Preface for the topics $PREFACE/$TOPIC
  ## (not in mqtt-dasher 0.1.0)
  #preface: ha/dash

buttons:
  abcdef:12:34:56: ha/dash/listerine

sudo systemctl enable mqtt-dasher
sudo systemctl start mqtt-dasher

$[Get Code]3

Home Assistant Switch

An mqtt switch which:

  • turns on when the dash button is activated
  • turns off when the dash button deactivates
  • can be activated and deactivated from HA

switch:

  • name: Listerine
      platform: mqtt
      command_topic: ha/dash/listerine
      state_topic: ha/dash/listerine
      payload_on: 'active'
      payload_off: 'inactive'
      retain: false

$[Get Code]4

The switch isn't intended to be used in the HA UI, it should be mapped to a script instead.

To Do

Compile mqtt-dasher with nexe so that nodejs.setcap can't be so easily abused.

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