firebaseCustomToken.js

firebaseCustomTokenLambda.js

'use strict'
const admin = require('firebase-admin')
const jwtDecode = require('jwt-decode')
const serviceAccount = require('path-to-your-firebase-key')

const getCustomToken = async sub => {
  admin.initializeApp({
    credential: admin.credential.cert(serviceAccount)
  })
  const firebaseToken = await admin.auth().createCustomToken(sub)
  return firebaseToken
}

const setCustomTokenFirebase = async (event) => {
  const { headers } = event
  const { Authorization } = headers
  const jtwToken = Authorization.split('Bearer')[1]
  const jwtDecoded = jwtDecode(jtwToken)
  const token = await getCustomToken(jwtDecoded['sub'])
  return { token }
}

module.exports.handler = async (event) => {
  const { token } = await setCustomTokenFirebase(event)
  return { token } 
})