RPi-Computer-Power

Raspberry Pi Remote Computer Startup Device. Works best with Model 2B or better.

Description

Node server for Raspberry Pi that controls a computer's state by remotely pressing the computer's power and reset buttons. Depending on the length of the "press," the computer will either shut down gracefully, hard reset, or start. The node server spawns python scripts that send commands to the RPi GPIO pins. There is also a feature that allows the user to see what power state the computer is in, using the motherboard power led wires.

NOTE: The code makes refrences to a certain keys.json in the root of the server. For each deployment, you will need to specify a keys.json, containing a private key and a password hash for the server. More info on this in the Initial Server Setup section of this readme.

The setup guide in this document demonstrates how to generate a self-signed certificate, which will not satisfy the requirement to have a certificate signed by a certificate authority for any browser to mark the connection as secure without some.

Repo organisation

• comp-power.service - Debian systemd service config file. Set up as described in this StackOverflow post, but use this file and don't create another.
• [repo] - Node server
• repo_public - Contains picures for the README and other md files
• TODO.md - TODO list for this repo

Mechanical configuration

Custom made Y-cables terminated with pin headers split off the power and reset switch wires so they can go to both the computer case and a breadboard. The breadboard has two PC817 optocouplers on it, one for each of power and reset, that on one side are hooked up to the Y-cables and on the other to the GPIO. By applying 5V to the RPI GPIO pins, the optocouplers short the pins together, simulating a keypress.

There is also a Y-cable coming off of the motherdoard power led wires that tells the server if the computer state is on, allowing the user to verify that their computer is in the state that they want it to be in.

Schematic:

Picture of the deployment in my computer: (The dirty side panel window is just an added bonus!)

The pin numbers in the code refer to the physical pin numbers, not the numbers of the GPIO pins on the Raspberry Pi, the gray numbers in this picture:

Raspberry Pi configuration

The Node applicaiton is started and maintained by a systemd service. According to the process documented in this StackOverflow post, configure systemd to use the comp-power.service config file.

OLD:

The Node application is started by a script, mentioned in /etc/rc.local, that runs sudo npm start in the root folder of the server.

Initial Server Setup

There are a set of steps I have found to work for setting the server up for the first time on a Raspberry Pi.

Initial Package and Code Download

• sudo apt update; sudo apt full-upgrade -y
• curl -sL https://deb.nodesource.com/setup_11.x | sudo -E bash -; sudo apt-get install -y nodejs (Link to official nodejs installation guide)
• sudo apt install python-rpi.gpio python3-rpi.gpio libcap2-bin
• git clone https://github.com/neilbalch/RPi-Computer-Power.git
• cd RPi-Computer-Power
• sudo npm install

Generate keys and hashes

Generating Keys and Hashes

A hash can be made by running

• node scripts/hash.js [PASSWORD] [HASH SALT]

Larger numbers for the salt take exponentially longer to compute the hashed string, slowing down the server whenever hash.js is run. (including from the Create new Password Hash feature in the UI.) Preferably choose a number less than 100. Remember the hash salt you just used, you will need it in a couple steps.

A secure secret key can be made by running:

• node -e "console.log('\x1b[32m'+require('crypto').randomBytes(64).toString('hex')+'\x1b[0m')"

The output strings to both will be the bcrypt hash and the secret key respectively.

Configuration

Create keys.json

• vim keys.json

Type both strings along with the hash salt you used into keys.json following this template:

{
  "hash": "BCRYPT_HASH",
  "secret": "SECRET_KEY",
  "hashSalt": "HASH_SALT"
}

Generate Private Keys and Certificates

• mkdir sslcert

Generate private RSA key:

• openssl genrsa 2048 > sslcert/private.key

Create a certificate request:

• openssl req -new -key sslcert/private.key -out sslcert/cert.csr

Generate a signed certificate based on the certificate request:

• openssl x509 -req -in sslcert/cert.csr -signkey sslcert/private.key -out sslcert/certificate.pem

Addressing Default Port Permissions

This needs to be done in order to grant the "safe" pi user permission to access the port 443, which is normally only accessible via the root user. (Stack Overflow, Digital Ocean)

• sudo setcap cap_net_bind_service=+ep /usr/bin/node

Run Server

• Debug Server (Reveals stacktrace to user)

  • npm start OR
  • node bin/www OR
  • nodemon bin/www (Server will automatically restart if it detects that a source file has been changed)

• Production Server (Doesn't reveal stacktrace to user)

  • npm start --production OR
  • node bin/www --production OR
  • nodemon bin/www --production (Server will automatically restart if it detects that a source file has been changed)

Troubleshooting

Permission Errors

• When running scripts you get an error like, Error: Command failed: /bin/sh -c /home/pi/RPi-Computer-Power/routes/../scripts/hash.js 12345678 /bin/sh: 1: /home/pi/RPi-Computer-Power/routes/../scripts/hash.js: Permission denied
  • Run chmod +x * in the scripts directory, as git has caused the permissions to change.
• The server reports an error when trying to start (sudo npm start or sudo nodemon bin/www) regarding a port access issue, i.e. Error: listen EACCES 0.0.0.0:443
  • Make sure that node has access to the default https port (443), that you are running the command with sudo and that another node process (or any other which is bound to the https port 443) isn't running.

Configuration Errors

• When running scripts you get the error /usr/local/bin/node^M: bad interpreter: No such file or directory
  • Run dos2unix [filename], (apt-get) on the file that produced the error.
• The Git Pull Origin Master button doesn't work
  • Reset the timeout for git credentials caching manually, as descrbed here on the GitHub Help and then pull from master on the Raspberry Pi to give git your credentials again.
• The server reports when executing hash.js that it cannot find the module bcrypt
  • Run sudo npm install.
• The server reports the error /bin/sh: 1: /home/pi/RPi-Computer-Power/routes/../scripts/hash.js: not found or similar when running hash.js
  • Edit the first line of scripts/hash.js file to say the correct path to your node installation, (which node) or make a symlink to the correct node path by running ln -s [YOUR_ACTUAL_NODE_PATH] /usr/bin/node, where YOUR_ACTUAL_NODE_PATH refers to the node path.