How to execute my nodejs code in block in AWS Lambda - node.js

Question

I am developing a code to validate openssl keys using NodeJs in AWS Lambda. I have a requirement to fetch the public key from the DynamoDB and to validate with the user given private key. As of now, I have two classes, one is to fetch the data from the dynamodb and second is to validate public key and private. But because of asynchronous NodeJS executing my Second class first and is not waiting until my first class gets the data from dynamoDB.
Please help me to execute the code in sequence.
I have tried Promise, bluebird and callback But I'm not able to understand them
const AWS = require('aws-sdk')
const dynamodb = new AWS.DynamoDB();
var promise = require('promise');
exports.handler = async (event) => {
var privatek = '-----BEGIN RSA PRIVATE KEY-----\n'+
'MIICWwIBAAKBgQC2rWURD7fK/3B0W7d36BJnv4ITzSd+K6o+itgHkqe+0EOvoOn2\n'+
'yHK3J11j2c+BkgAcdfwYaBFhH7Gubvyt0TLAKJvxi6cIbD4DVJqoTwJPzgdCczKZ\n'+
'AdhevoYam3t/Q454pW5N7IoF5IzMgPypRbPhi7JnkqcE1/CIXC3hrysMeQIDAQAB\n'+
'AoGANFPlEIcVGdQkDWC8ZF+Y7hkglLV+q5iscq/pA/pRjMoxqVyJyIRQwABJszGQ\n'+
'TEhbOcveQ8uDtvOSPSpTvSKgy4fxmH0/RuypTYcAD/BN76T1DDODSsyn+KuNOdko\n'+
'x6bo30wexmBL/itya9VJMBM49iMMYtYBtOuoJGamMc+vUQECQQDxaWk9alNa37Yb\n'+
'SAfQRGoU7xJvuVQ8qHBY0EgCzYwaMkWuWKkk8GA058PezUxEjwZN8ZRVsYO2YHG1\n'+
'3w3vcF+ZAkEAwbdf1ZVpPEsVyXeftnnu5uPxjN6SGqojV1M1/QXQJaFVd0SFAWMY\n'+
'LE1tqFI6KEfQ1huehvwXhja6HU5z4p+f4QJAce/xRpYvHx2koj2dynLvqk+nYOmU\n'+
'U0igNZqf0grXC+ocLwwTUKbOkUmtjTNRwq3KKPFStBsi8emU4WST/CUKSQJAE2Af\n'+
'AsLl+rTb4gHIBL1fatKjx14/qNEZpdNZ1AvvzMO9Q6ej0gayVUQNUseer4a3WaL7\n'+
'kS7Hv5HbvbCqIKGsoQJAS3LAPW5Wpc2rHFJQDryIGdVnZLW6YdFXGudzMRjHsIB0\n'+
'UMKUywmjRf45ugQMBKJ+iesDwNLmXtOjcB9AdGRz5w==\n'+
'-----END RSA PRIVATE KEY-----';
var publick = '-----BEGIN PUBLIC KEY-----\n'+
'MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC2rWURD7fK/3B0W7d36BJnv4IT\n'+
'zSd+K6o+itgHkqe+0EOvoOn2yHK3J11j2c+BkgAcdfwYaBFhH7Gubvyt0TLAKJvx\n'+
'i6cIbD4DVJqoTwJPzgdCczKZAdhevoYam3t/Q454pW5N7IoF5IzMgPypRbPhi7Jn\n'+
'kqcE1/CIXC3hrysMeQIDAQAB\n'+
'-----END PUBLIC KEY-----';
console.log(event["pk"]);
const table = "MARKETPLACE_USER_RELATED_APPS_TABLE";
var dynamo = new Dynamo(table);
var prik = dynamo.read(dynamo.client());
console.log(prik);
var clientid = '12345'; //event['client_id']
var unique_id = parseInt(Math.random()*10000000000000000).toString();
var time_stamp = new Date();
var Authkey = clientid + ':' + unique_id + ':' + time_stamp;
console.log(Authkey+"Authkey");
console.log(time_stamp + 'time_stamp');
var cryp = new CryptoVerify(publick,privatek, Authkey);
console.log(cryp.hash+'hash key');
console.log(event['pk'])
const response = {
statusCode: 200,
body: cryp.verify(cryp.signature())
};
return response
};
function CryptoVerify(publickey, privatekey, authkey)
{
this.crypto = require ('crypto')
this.hash = this.crypto.createHash('sha256')
.update(authkey)
.digest('base64');
console.log(this.hash+'haskkk');
this.signature = function(){
try{
var signer = this.crypto.createSign('sha1');
signer.update(this.hash);
var sign = signer.sign(privatekey,'base64');
console.log(sign + "Sign")
}
catch(e)
{
var sign = "Private key Errpr: Not matching with the Public
key\nExact " +e;
}
return sign;
}
this.verify = function(sign){
var verifier = this.crypto.createVerify('sha1');
verifier.update(this.hash);
try {
this.ver = verifier.verify(publickey, sign,'base64');
console.log(this.ver);
}
catch (e){
console.log("Private key Error: Not matching with the Public
key/n Exact Error:"+e);
this.ver = e
}
return this.ver;
}
}
function Dynamo(table)
{
this.params = {Key :{"email_id":{S:"testuser#tml.com"},
"app_name":{S:"EDH"}},
TableName: table};
this.op = {};
this.client = function(){
try{
var dynamodb = new AWS.DynamoDB();
}
catch(e){
console.log("Error: Class DynamoDB is not defined");
}
return dynamodb;};
this.read = function(dy){
try{
dy.getItem(this.params, function(err, data){
if(err) console.log(err, err.stack);
else {
this.op = data;
console.log(this.op);
}
});
}
catch(e){
console.log('Please check getIten function to clear the error');
}
return this.op;
};
}
I expect result with the dynamoDB value to be fetched first then Validate class.

Answer 1

Use callback version of lambda handler or when using asyc await wrap all the callback into a promise or promisify the methods using Bluebird's promisify all method.
const AWS = require('aws-sdk')
const dynamodb = new AWS.DynamoDB();
var promise = require('promise');
exports.handler = async (event) => {
var privatek = '-----BEGIN RSA PRIVATE KEY-----\n'+
'MIICWwIBAAKBgQC2rWURD7fK/3B0W7d36BJnv4ITzSd+K6o+itgHkqe+0EOvoOn2\n'+
'yHK3J11j2c+BkgAcdfwYaBFhH7Gubvyt0TLAKJvxi6cIbD4DVJqoTwJPzgdCczKZ\n'+
'AdhevoYam3t/Q454pW5N7IoF5IzMgPypRbPhi7JnkqcE1/CIXC3hrysMeQIDAQAB\n'+
'AoGANFPlEIcVGdQkDWC8ZF+Y7hkglLV+q5iscq/pA/pRjMoxqVyJyIRQwABJszGQ\n'+
'TEhbOcveQ8uDtvOSPSpTvSKgy4fxmH0/RuypTYcAD/BN76T1DDODSsyn+KuNOdko\n'+
'x6bo30wexmBL/itya9VJMBM49iMMYtYBtOuoJGamMc+vUQECQQDxaWk9alNa37Yb\n'+
'SAfQRGoU7xJvuVQ8qHBY0EgCzYwaMkWuWKkk8GA058PezUxEjwZN8ZRVsYO2YHG1\n'+
'3w3vcF+ZAkEAwbdf1ZVpPEsVyXeftnnu5uPxjN6SGqojV1M1/QXQJaFVd0SFAWMY\n'+
'LE1tqFI6KEfQ1huehvwXhja6HU5z4p+f4QJAce/xRpYvHx2koj2dynLvqk+nYOmU\n'+
'U0igNZqf0grXC+ocLwwTUKbOkUmtjTNRwq3KKPFStBsi8emU4WST/CUKSQJAE2Af\n'+
'AsLl+rTb4gHIBL1fatKjx14/qNEZpdNZ1AvvzMO9Q6ej0gayVUQNUseer4a3WaL7\n'+
'kS7Hv5HbvbCqIKGsoQJAS3LAPW5Wpc2rHFJQDryIGdVnZLW6YdFXGudzMRjHsIB0\n'+
'UMKUywmjRf45ugQMBKJ+iesDwNLmXtOjcB9AdGRz5w==\n'+
'-----END RSA PRIVATE KEY-----';
var publick = '-----BEGIN PUBLIC KEY-----\n'+
'MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQC2rWURD7fK/3B0W7d36BJnv4IT\n'+
'zSd+K6o+itgHkqe+0EOvoOn2yHK3J11j2c+BkgAcdfwYaBFhH7Gubvyt0TLAKJvx\n'+
'i6cIbD4DVJqoTwJPzgdCczKZAdhevoYam3t/Q454pW5N7IoF5IzMgPypRbPhi7Jn\n'+
'kqcE1/CIXC3hrysMeQIDAQAB\n'+
'-----END PUBLIC KEY-----';
console.log(event["pk"]);
const table = "MARKETPLACE_USER_RELATED_APPS_TABLE";
var dynamo = new Dynamo(table);
var prik = await dynamo.read(dynamo.client());
console.log(prik);
var clientid = '12345'; //event['client_id']
var unique_id = parseInt(Math.random()*10000000000000000).toString();
var time_stamp = new Date();
var Authkey = clientid + ':' + unique_id + ':' + time_stamp;
console.log(Authkey+"Authkey");
console.log(time_stamp + 'time_stamp');
var cryp = new CryptoVerify(publick,privatek, Authkey);
console.log(cryp.hash+'hash key');
console.log(event['pk'])
const response = {
statusCode: 200,
body: cryp.verify(cryp.signature())
};
return response
};
function CryptoVerify(publickey, privatekey, authkey)
{
this.crypto = require ('crypto')
this.hash = this.crypto.createHash('sha256')
.update(authkey)
.digest('base64');
console.log(this.hash+'haskkk');
this.signature = function(){
try{
var signer = this.crypto.createSign('sha1');
signer.update(this.hash);
var sign = signer.sign(privatekey,'base64');
console.log(sign + "Sign")
}
catch(e)
{
var sign = "Private key Errpr: Not matching with the Public
key\nExact " +e;
}
return sign;
}
this.verify = function(sign){
var verifier = this.crypto.createVerify('sha1');
verifier.update(this.hash);
try {
this.ver = verifier.verify(publickey, sign,'base64');
console.log(this.ver);
}
catch (e){
console.log("Private key Error: Not matching with the Public
key/n Exact Error:"+e);
this.ver = e
}
return this.ver;
}
}
function Dynamo(table)
{
this.params = {Key :{"email_id":{S:"testuser#tml.com"},
"app_name":{S:"EDH"}},
TableName: table};
this.op = {};
this.client = function(){
try{
var dynamodb = new AWS.DynamoDB();
}
catch(e){
console.log("Error: Class DynamoDB is not defined");
}
return dynamodb;};
this.read = function(dy){
return new Promise((resolve, reject) => {
try{
dy.getItem(this.params, function(err, data){
if(err) console.log(err, err.stack);
else {
this.op = data;
console.log(this.op);
return resolve(data);
}
});
}
catch(e){
console.log('Please check getIten function to clear the error');
reject('Error')
}
});
//return this.op;
};
}

Answer 2

Thanks all. I have got the solution to the question by searching more on the internet. AWS itself is providing "Promise" method for every service.
I just included promise function as follows:
dynamodb.getItem(params).promise().then(function(data, err){
if(err)
//do something
else
//do something
});