Converting custom message authentication code from Java to JavaScript

Question

This is the java code. I am trying to replicate the same functionality in javascript.

 public String populateHMAC(String app_id, String mobile, String token,
                            String deviceId) {

    String hmac = null;
    try {
        CryptLib cryptLib = new CryptLib();
        String message = app_id + "|" + mobile + "|" + deviceId;
        byte[] tokenBytes = Base64.decode(token, 2);//cryptLib.hexStringToByteArray(token);

        String temp=Base64.encodeToString(cryptLib.SHA256(message),2);

        byte[] tempArr=Base64.decode(temp,2);

        byte[] hmacBytes = cryptLib.encrypt(
                cryptLib.SHA256(message),
                tokenBytes);
        hmac = Base64.encodeToString(hmacBytes, Base64.DEFAULT);
    } catch (Exception e) {
        e.printStackTrace();
    }
    return hmac;
}

These are the functions inside CryptLib

public byte[] SHA256(String paramString) throws Exception {
    MessageDigest md = MessageDigest.getInstance("SHA-256");
    md.update(paramString.getBytes("UTF-8"));
    byte[] digest = md.digest();
    return digest;
}

And the encrypt function

public byte[] encrypt(byte[] data, byte[] key) throws Exception {
    SecretKeySpec keySpec = new SecretKeySpec(key, "AES");
    byte[] iv = new byte[16];
    IvParameterSpec ivSpec = new IvParameterSpec(iv);
    Cipher acipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
    byte[] arrayOfByte1;
    acipher.init(Cipher.ENCRYPT_MODE, keySpec, ivSpec);
    arrayOfByte1 = acipher.doFinal(data);
    return arrayOfByte1;
}

This is the javascript code for the same functionality. I am using the crypto-js library.

var crypto = require('crypto-js');

populateHMAC( app_id,  mobile, token, deviceId){

    var rawStr = token;
    var wordArray = crypto.enc.Utf8.parse(rawStr);
    var base64 = crypto.enc.Base64.stringify(wordArray);

    var enctoken=btoa(token);


    var message= app_id + "|" + mobile + "|" + deviceId;

    var decodedString= atob(enctoken);

    message=encodeURIComponent(message);

    var hash= crypto.SHA256(message);//.toString(crypto.enc.Utf8);

    console.log("params",decodedString,hash.toString(crypto.enc.Hex));


    var iv = crypto.enc.Hex.parse('0000000000000000'); 
    var encryptedString = crypto.AES.encrypt(hash, decodedString, {
                iv:iv,
                mode: crypto.mode.CBC,
                padding: crypto.pad.Pkcs7
            });

    var encodedString= encryptedString.ciphertext.toString(crypto.enc.Base64);


     return encodedString;
}

The two outputs are different and I am unable to figure out why.

The code you've presented here is not HMAC. It has some similarities with CBC-MAC, but that's also not it. Don't call it HMAC. I'd rather throw away this code and implement proper HMAC. Both Java and CryptoJS have native support for actual HMAC. — Artjom B.
– Artjom B., Commented Aug 23, 2016 at 19:54
Yes, It is not hmac. But that's the function that I have to replicate. It is already set in stone so I cannot discard it. — Swaminathan Iyer
– Swaminathan Iyer, Commented Aug 25, 2016 at 7:58

Artjom B. · Accepted Answer · 2016-08-26 18:37:52Z

1

The issues:

I don't see that an equivalent of encodeURIComponent is used in the Java code. You can remove that line.
decodedString is a "binary" string which CryptoJS will treat as a password. You actually want to convert the token to a binary representation that CryptoJS understands:
```
var decodedString = crypto.enc.Base64.parse(token);
```
Remove the other encoding and decoding steps at the beginning of your code.
'0000000000000000' is too short if it is supposed to be a Hex-encoded IV. It must be twice as long to get 16 bytes (32 hexits).

answered Aug 26, 2016 at 18:37

Artjom B.

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