GitHub authentication in ExpressJS app.

GitHubAuthWithExpress.js

const cookieSecret = process.env.COOKIE_SECRET || 'secret'
const cookieName = process.env.COOKIE_NAME || 'GitHubAuthenticated'
const githubHost = process.env.GHE_HOST || 'https://github.com'
const githubApiUrl = process.env.GHE_API_URL || 'https://api.github.com'
const clientId = process.env.CLIENT_ID
const clientSecret = process.env.CLIENT_SECRET
const userAgent = 'My-App'

const express = require('express')
const app = express()
const port = 3000

const cookieParser = require('cookie-parser')
const querystring = require('querystring')
const request = require('request-promise-native')

app.use(cookieParser(cookieSecret))

app.use('/protected', function (req, res, next) {
  const ghAuthCookie = req.signedCookies[cookieName]

  console.log(`Cookie: ${ghAuthCookie}`)

  if (!ghAuthCookie) {
    const authorizeRequest = {
      client_id: clientId,
      redirect_uri: `${req.protocol}://${req.host}:${port}/oauth/callback`,
      state: `${req.protocol}://${req.host}:${port}${req.originalUrl}`
    }
    console.log(`Authorization request: ${JSON.stringify(authorizeRequest)}`)
    res.redirect(`${githubHost}/login/oauth/authorize?${querystring.stringify(authorizeRequest)}`)
  }
  else {
    next()
  }
})

app.get('/oauth/callback', async (req, res) => {
  console.log(`Callback params: ${JSON.stringify(req.query)}`)

  try {
    const code = req.query.code
    const state = req.query.state

    const accessTokenRequest = {
      client_id: clientId,
      client_secret: clientSecret,
      code: code,
      state: state
    }

    const accessToken = await request({
      method: 'POST',
      url: `${githubHost}/login/oauth/access_token`,
      headers: {
        'Accept': 'application/json',
        'User-Agent': userAgent
      },
      form: accessTokenRequest,
      json: true
    })

    console.log(`Access Token: ${JSON.stringify(accessToken)}`)

    const user = await request({
      method: 'GET',
      url: `${githubApiUrl}/user`,
      headers: {
        'Authorization': `token ${accessToken.access_token}`,
        'User-Agent': userAgent
      },
      json: true
    })

    console.log(`User: ${user.login}`)

    res.cookie(cookieName, (new Date()).getTime(), { signed: true })
    res.redirect(state)
  } catch (error) {
    console.log(error)
    res.status(500).send(error)
  }
})

app.get('/', (req, res) => res.send('Hello World!'))
app.get('/protected', (req, res) => res.send('This page is protected by GitHub'))
app.get('/protected/x', (req, res) => res.send('This page is also protected by GitHub'))

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