How to decrypt a value in frontend which is encrypted in the backend (nodejs)? - node.js

Question

Backend developers have encrypted a value in nodejs using crypto module. The code is shown below:
const _encrypt = async function(text){
var cipher = crypto.createCipher('aes-256-cbc','123|a123123123123123#&12')
var crypted = cipher.update(text,'utf8','hex')
crypted += cipher.final('hex');
console.log("in generic function....encrpted val", crypted)
return crypted;
}
I need to decrypt this value in the front end (Angular). So I tried decrypting like below:
let bytes = CryptoJS.AES.decrypt("e0912c26238f29604f5998fa1fbc78f6",'123|a123123123123123#&12');
if(bytes.toString()){
let m = JSON.parse(bytes.toString(CryptoJS.enc.Utf8));
console.log("data ",m);
}
using hardcoded value. But Im getting Error: Malformed UTF-8 data error. Can anybody please tell me how to decrypt this in angular side?

Answer 1

This is a tricky enough one.. the crypto.createCipher function creates a key and IV from the password you provide (See the createCipher documentation for details).
This is implemented using the OpenSSL function EVP_BytesToKey.
A JavaScript implementation is available here: openssl-file.. we'll use this to get a key and IV from the password.
So there are two steps here:
Get a key and IV from your password.
Use these with Crypto.js to decode your encoded string.
Step 1: Get key and IV (Run in Node.js )
const EVP_BytesToKey = require('openssl-file').EVP_BytesToKey;
const result = EVP_BytesToKey(
'123|a123123123123123#&12',
null,
32,
'MD5',
16
);
console.log('key:', result.key.toString('hex'));
console.log('iv:', result.iv.toString('hex'));
Step 2: Decrypt string:
const encryptedValues = ['e0912c26238f29604f5998fa1fbc78f6', '0888e0558c3bce328cd7cda17e045769'];
// The results of putting the password '123|a123123123123123#&12' through EVP_BytesToKey
const key = '18bcd0b950de300fb873788958fde988fec9b478a936a3061575b16f79977d5b';
const IV = '2e11075e7b38fa20e192bc7089ccf32b';
for(let encrypted of encryptedValues) {
const decrypted = CryptoJS.AES.decrypt({ ciphertext: CryptoJS.enc.Hex.parse(encrypted) }, CryptoJS.enc.Hex.parse(key), {
iv: CryptoJS.enc.Hex.parse(IV),
mode: CryptoJS.mode.CBC
});
console.log('Ciphertext:', encrypted);
console.log('Plain text:', decrypted.toString(CryptoJS.enc.Utf8));
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/crypto-js/3.1.9-1/crypto-js.min.js"></script>
Note that if you change the password you need to generate a new key and iv using EVP_BytesToKey.
I should note that createCipher is now deprecated, so use with caution. The same applies to EVP_BytesToKey.