CODEWITHSUNDEEP
node.jsgoencryption
nathanr
nathanr

Reputation: 150

NodeJS AESCFB + pkcs7 padding decryption

I'm trying to port the following Go functions to nodeJS using crypt or crypt-js but i'm having issues trying to figure out what's wrong:

The Go encryption code is available at https://go.dev/play/p/O88Bslwd-qh ( both encrypt and decrypt work)

The current nodejs implementation is:

var decryptKey= "93D87FF936DAB334C2B3CC771C9DC833B517920683C63971AA36EBC3F2A83C24";


const crypto = require('crypto');
const algorithm = 'aes-256-cfb';
const BLOCK_SIZE = 16;

var message = "8a0f6b165236391ac081f5c614265b280f84df882fb6ee14dd8b0f7020962fdd"

function encryptText(keyStr, text) {
  const hash = crypto.createHash('sha256');

  //Decode hex key
  keyStr = Buffer.from(keyStr, "hex")

  hash.update(keyStr);
  const keyBytes = hash.digest();

  const iv = crypto.randomBytes(BLOCK_SIZE);
  const cipher = crypto.createCipheriv(algorithm, keyBytes, iv);
  cipher.setAutoPadding(true);
  let enc = [iv, cipher.update(text,'latin1')];
  enc.push(cipher.final());
  return Buffer.concat(enc).toString('hex');
}

function decryptText(keyStr, text) {
  const hash = crypto.createHash('sha256');
  //Decode hex key
  keyStr = Buffer.from(keyStr, "hex")

  hash.update(keyStr);
  const keyBytes = hash.digest();

  const contents = Buffer.from(text, 'hex');
  const iv = contents.slice(0, BLOCK_SIZE);
  const textBytes = contents.slice(BLOCK_SIZE);
  const decipher = crypto.createDecipheriv(algorithm, keyBytes, iv);
  decipher.setAutoPadding(true);
  let res = decipher.update(textBytes,'latin1');
  res += decipher.final('latin1');
  return res;
}


console.log(message)
result = decryptText(decryptKey,message);
console.log(result);
message = encryptText(decryptKey,'hola').toString();
console.log(message)
result = decryptText(decryptKey,message);
console.log(result);

Any idea why it is not working as expected?

Note: I know that padding is not required with cfb but i can't modify the encryption code, it just for reference.

Upvotes: 1

Views: 767

Answers (1)

robertklep
robertklep

Reputation: 203304

I don't know Go or the specifics of aes.NewCipher(key), but from its documentation it doesn't look like it's hashing the key in any way. The Go code you're linking to also doesn't hash it, so I'm not sure why you're hashing it in the Node.js code.

This should be sufficient:

function encryptText(keyStr, text) {
  const keyBytes = Buffer.from(keyStr, "hex")
  …
}

function decryptText(keyStr, text) {
  const keyBytes = Buffer.from(keyStr, 'hex');
  …
}

As an aside: it looks like you may be encrypting JSON blocks with these functions. If so, I would suggest not using any encoding (like latin1) during the encryption/decryption process, given that JSON text must be encoded using UTF-8.

Upvotes: 1

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