natechoe.dev has CI now!

Here's the latest natechoe.dev hack, continuous integration with Github Actions!

I have a dockerized node.js container which implements a very simple REST API. Then, whenever I push to Github, Github Actions calls that REST API. The node.js container sees this request and runs a script on the host machine which updates the natechoe.dev container.

The node.js code

const express = require('express')
const bodyParser = require('body-parser')
const app = express()
const port = 3000

app.use(bodyParser.json());

const fs = require('node:fs');
function readfile(file) {
  try {
    return fs.readFileSync(file).toString().trim();
  }
  catch (err) {
    console.error(err);
    process.exit();
  }
}
const apikey = readfile('api-key.txt');

app.post('/gh/*', (req, res, next) => {
  function reject(msg) {
    const body = `{"code":401,"elaboration":"${msg}"}`
    res
      .writeHead(401, {
        'Content-Length': body.length,
        'Content-Type': 'application/json',
      })
      .end(body);
  }
  if (typeof req.headers.authorization === 'undefined') {
    reject("Request is missing Authorization header");
    return;
  }
  headerParts = req.headers.authorization.split(' ');
  if (headerParts.length != 2) {
    reject("Invalid Authorization header");
    return;
  }
  if (headerParts[0].toLowerCase() !== 'bearer') {
    reject("Authorization header doesn't use Bearer authentication");
    return;
  }
  if (headerParts[1] !== apikey) {
    reject("Invalid API key");
    return;
  }
  next();
});

app.post('/gh/update-container', (req, res) => {
  function send(code, msg) {
    const body = `{"code":${code},"elaboration":"${msg}"}`
    res
      .writeHead(code, {
        'Content-Length': body.length,
        'Content-Type': 'application/json',
      })
      .end(body);
  }
  const ip = req.headers["x-real-ip"];
  if (typeof ip !== 'string') {
    send(500, 'Failed to get client IP');
    return;
  }
  const obj = req.body;
  if (typeof obj.repo !== 'string') {
    send(400, "Bad repo value in json");
    return;
  }
  var ret = {
    "ip": ip,
    "repo": obj.repo,
  };
  try {
    fs.writeFileSync('fifo', `${JSON.stringify(ret)}\n`);
    send(200, "We did it reddit");
    return;
  }
  catch {
    send(500, "Failed to send update message");
    return;
  }
});

app.listen(port, () => {
  console.log(`nodejs updater running on port ${port}`)
})

An excerpt from the docker-compose file that runs all of this

nodejs-updater:
  image: natechoe/nodejs-updater
  container_name: nodejs-updater
  volumes:
    - ./nodejs/api-key.txt:/app/api-key.txt
    - /home/nate/cron/update-notify:/app/fifo
  restart: on-failure
  stop_grace_period: 2s

A script facilitating IPC between the container and host machine

#!/bin/sh --
set -e

export XDG_RUNTIME_DIR="$HOME/.tmp"
export DOCKER_HOST=unix://"$XDG_RUNTIME_DIR"/docker.sock

while read line ; do
        printf "%s\n" "$line" >> ~/logs
        IP="$(echo "$line" | jq -r '.ip')"
        REPO="$(echo "$line" | jq -r '.repo')"
        "$HOME"/cron/update-ncd.sh "$REPO" "$IP"
done < <(tail -f $HOME/cron/update-notify)

The script that actually updates the container

#!/bin/sh --
set -e

if [ $# -lt 2 ] ; then
        echo "Usage: $0 [repo] [ip]"
fi

OLDDIR="$(pwd)"

NEWDIR="$(realpath "/home/nate/my-images/natechoe.dev/$1")"

send_email() {
        cat "$3" | sed -e "s/__IP__/$2/g" -e "s/__PATH__/$1/g" | docker exec -i mailserver sendmail nate@natechoe.dev
}

if ! printf "%s\n" "$NEWDIR" | grep -q "^/home/nate/my-images/natechoe.dev/" ; then
        send_email "$1" "$2" /home/nate/cron/malicious.mail
        exit 1
fi
if [ ! -d "$NEWDIR" ] ; then
        send_email "$1" "$2" /home/nate/cron/malicious.mail
        exit 1
fi

send_email "$1" "$2" /home/nate/cron/update.mail
cd "$NEWDIR"
./build.sh
cd /home/nate/http
docker compose up -d natechoe.dev
cd "$OLDDIR"

node.js writes to a file, a script reads that file and calls another script, and that final script updates the container and sends me an email. Neat!

By the way, this blog post is really just an excuse to test this whole system in the wild.