secure-password-dumb-example.js

const fs = require('fs')
const SecurePassword = require('secure-password')

const pwd = SecurePassword()
const command = process.argv[2]
const inputUsername = process.argv[3]
const inputPassword = Buffer.from(process.argv[4])

if (command === 'createUser') return createUser(inputUsername, inputPassword)
if (command === 'verify') return verify(inputUsername, inputPassword)

function createUser (username, password) {
  pwd.hash(password, (err, hash) => {
    if (err) throw err

    fs.writeFileSync('./users.csv', `${username},${password}`)
    console.log('user created')
  })
}

function verify (username, password) {
  pwd.hash(password, (err, hash) => {
    if (err) throw err

    const userData = fs.readFileSync('./users.csv').toString().split(',')
    const foundUsername = userData[0]
    const foundPassword = Buffer.from(userData[1])

    if (username === foundUsername) {
      return pwd.verify(foundPassword, hash, (err, result) => {
        if (err) throw err

        if (result === SecurePassword.INVALID) return console.log('wrong password')
        if (result === SecurePassword.VALID) return console.log('ACCESS GRANTED')
        if (result === SecurePassword.VALID_NEEDS_REHASH) {
          console.log('making yer pw safer')

          pwd.hash(userPassword, (err, improvedHash) => {
            if (err) console.error('authd but yer pw aint safer')
          })
        }
      })
    }

    return console.log('no user found')
  })
}

$ node index.js createUser axel whatever // "user created"
$ node index.js verify axel whatever // "ACCESS GRANTED"
$ node index.js verify axel notright // "wrong password"
$ node index.js verify whoami whatever // "no user found"