Example Define Auth Challenge Lambda implementing that designates the first and only auth challenge as a CUSTOM_CHALLENGE

CognitoStoresDefineAuthChallenge.js

exports.handler = (event, context, callback) => {
 if (event.request.session.length == 0) {
   event.response.issueTokens = false
   event.response.failAuthentication = false
   event.response.challengeName = 'CUSTOM_CHALLENGE'
 } else if (event.request.session.length == 1 && event.request.session[0].challengeName == 'CUSTOM_CHALLENGE' && event.request.session[0].challengeResult == true) {
   event.response.issueTokens = true
   event.response.failAuthentication = false
 } else {
   event.response.issueTokens = false
   event.response.failAuthentication = true
 }
 callback(null, event)
}