@tremorvideo/blink-cli/src/login/index.js

const ini = require('ini')
const promptly = require('promptly')
const chalk = require('chalk')
const fs = require('fs-extra')
const fsOpts = { encoding: 'utf8' }
const verifyAccess = require('./verify-aws-access')

const printError = (type, value, msg) => {
  console.log(`⚠️  Invalid input for ${type}`)
  console.log(`You entered: ${chalk.red(value)}`)
  throw new Error(msg)
}

const validateId = (value) => {
  const type = 'aws_access_key_id'
  if (value.length !== 20) printError(type, value, `Expecting id to be 20 characters long, yours is ${value.length}`)
  if (/[^\w]/.test(value)) printError(type, value, 'Input should only contain alphanumeric characters')
  return value
}

const validateSecret = (value) => {
  const type = 'aws_secret_access_key'
  if (value.length !== 40) printError(type, value, `Expecting secret to be 40 characters long, yours is ${value.length}`)
  if (/[^\w/+]/.test(value)) printError(type, value, 'Input should only contain numbers, letters, +, and /')
  return value
}

module.exports = async ({ program, env, pkg }) => {
  const credPath = env.filepath
  await fs.ensureFile(credPath)
  const data = await fs.readFile(credPath, fsOpts)
  const config = ini.parse(data)
  if (!config) return Promise.reject(new Error('Parsing the credentials file failed'))
  if (!config.default) config.default = {}
  const id = env.id ? validateId(env.id) : await promptly.prompt('aws_access_key_id:', { validator: validateId })
  const secret = env.secret ? validateSecret(env.secret) : await promptly.prompt('aws_secret_access_key:', { validator: validateSecret })
  config.default.aws_access_key_id = id
  config.default.aws_secret_access_key = secret
  // verify credentials through S3 before writing to file
  await verifyAccess({
    credentials: {
      accessKeyId: id,
      secretAccessKey: secret
    }
  }).catch((err) => {
    // catch S3 access error and return readable error
    return Promise.reject(new Error(`Could not access AWS S3\nCode: ${err.code}\nMessage: ${err.message}`))
  })
  await fs.writeFile(credPath, ini.stringify(config, { whitespace: true }))
}