• Elixir 1.5 & Erlang/OTP 20
• cmake
• Erlang development headers
• NodeJS 6.11 (or later) and npm
• PostgreSQL
• One free GPIO pin

This app is written with a Raspberry Pi in mind. See the Provisioning section below for more information.

To start your Phoenix app:

1. Set up the app with sudo ./app_setup.sh prod (for local development: ./app_setup.sh dev, without sudo - note that GPIO will be disabled)
2. Start Phoenix endpoint with sudo MIX_ENV=prod PORT=4000 mix phoenix.server

Note that sudo and root access is required due to the GPIO interface.

Now you can visit raspberrypi.local:4000 from your browser.

To run the tests, use either mix test or mix test.watch.

The provided Ansible playbook can be used to configure a Raspberry Pi to run Gatekeeper. These instructions assume you are running Raspbian Jesse (Debian 8).

1. Install Ansible: sudo apt-get install ansible
2. Add 127.0.0.1 to the top of /etc/ansible/hosts (works around an old Ansible bug)
3. Run the provisioning script: sudo ansible-playbook -c local -e postgresql_password=SuperSecret provisioning/gatekeeper.yml Make sure to change the PostgreSQL password to something of your choosing

You are now ready to run the app_setup.sh and boot the app.

The application is built to authenticate via Slack. To set up the OAuth connection with Slack, you will need:

• A CLIENT_ID and a CLIENT_SECRET, which can be obtained by registering your app on Slack
• Optional: Your TEAM_ID, if you want to restrict logins to a specific Slack team - find your Slack Team ID here

Make sure you set these environment variables:

• SLACK_CLIENT_ID
• SLACK_CLIENT_SECRET
• SLACK_TEAM_ID (optional)
• GUARDIAN_SECRET_KEY - Set this to a long random string; it is used to ensure the validity of session tokens

The parts listed here are just what I used. Feel free to replace them with equivalents that may be easier or cheaper to acquire.

• Raspberry Pi ($35) - Any model should do
• 12V DC power supply ($8) - recommend at least 2A
• 12V Electric Door Strike ($53)
• 12V-5V DC power regulator ($8) - These circuits are pretty easy to build, but as cheap as they are on Amazon, I opted to purchase this and hack it for my own purposes. It comes with a convenient enclosure and with a mini-USB connector prewired which is great for powering the RPi. Too easy.
• Relay ($4.50) - This one is nice because it includes circuitry allowing it to be driven directly from the TTL-level pins on the Raspberry Pi. Don't try driving a relay directly from the RPi pins without protective circuitry!
• Female-to-Female Breadboard Jumper Wires ($9) - These make it easy and relatively safe to wire the RPi to the relay
• USB RFID Reader ($50) - This includes the reader, the USB adapter, and 2 RFID cards. Additional RFID tags are between $2 and $5 apiece.

Total: $167.50

• Curiosity
• Basic Linux Command Line skills
• Ability to screw and unscrew things
• [Optional] Basic soldering skills if you decide to hack up the 12V-5V DC power regulator