Generate HMAC SHA Algorithm using URI and Key

Question

I wrote a Java program which generates HMAC SHA hash code, But due to some reason I have to write the same code in NodeJs/JavaScript. I tried googling around but did not get anything. In this Java code, I am passing URI and Key as arguments, to generate the hash code, where URI contains Timestamp. The java code is as :

    public static String calcMAC(String data, byte[] key) throws Exception {
    String result=null;
    SecretKeySpec signKey = new SecretKeySpec(key, SecurityConstants.HMAC_SHA1_ALGORITHM);
    Mac mac = Mac.getInstance(SecurityConstants.HMAC_SHA1_ALGORITHM);
    mac.init(signKey);
    byte[] rawHmac;
    try {
        rawHmac = mac.doFinal(data.getBytes("US-ASCII"));
        result = Base64.encodeBase64String(rawHmac);
    } catch (Exception e) {
        e.printStackTrace();
    }
    return result.trim();
}

public static void main(String args[]) {
    String timestamp = args[0];
    String key = "d134hjeefcgkahvg32ajkdbaff84ff180";
    String out = null;
    try {
        out = calcMAC("/req?app_id=47ca34" + timestamp + "=2018-05-22T12:02:15Z", 
                key.getBytes());
        System.out.println(URLEncoder.encode(out, "UTF-8"));
    } catch (Exception e) {
        e.printStackTrace();
    }
}

Is it possible to achieve the same goal in NodeJs/JavaScript?

Note:: I have to call this script from Postman pre-request script.

You can check npm module [npmjs.com/package/hmacsha1] to generate hmac or you can check official nodejs crypto documents [nodejs.org/api/crypto.html#crypto_class_hmac] — Mohammad Raheem
– Mohammad Raheem, Commented Jun 22, 2018 at 10:29

Terry Lennox · Accepted Answer · 2018-06-22 10:56:50Z

2

The crypto module should do this for you, you can substitute the 'data' variable with whatever you want to hash:

const crypto = require('crypto');

const data = 'The fault dear Brutus lies not in our stars';
const key = Buffer.from('d134hjeefcgkahvg32ajkdbaff84ff180', 'utf8');

const hash = crypto.createHmac('sha1', key).update(data).digest('base64');
const uriEncodedHash = encodeURIComponent(hash);
console.log('Hash: ' + uriEncodedHash);

Hashing the data in both Java and Node.js gives me the result (URI Encoded) of:

TJJ3xj93m8bfVpGoucluMQqkB0o%3D

The same Java code would be:

public static void main(String args[]) {
    String data = "The fault dear Brutus lies not in our stars";
    String key = "d134hjeefcgkahvg32ajkdbaff84ff180";
    String out = null;
    try {
        out = calcMAC(data, key.getBytes());
        System.out.println(URLEncoder.encode(out, "UTF-8"));
    } catch (Exception e) {
        e.printStackTrace();
    }
}

Again, we can put anything into 'data' we want.

edited Jun 22, 2018 at 10:56

answered Jun 22, 2018 at 10:51

Terry Lennox

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3 Comments

Terry Lennox Over a year ago

Could you log what data you're getting in the server when you post using postman?

AsthaUndefined Over a year ago

There was an error in evaluating the Pre-request Script: Error: Cannot find module 'crypto'. I am new to Postman.

Terry Lennox Over a year ago

This script will only work on the server side, run by Node.js, if you run it outside this context it won't work!

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