Postman Pre-Request to Generate HMAC256

postman-pre-request-hmacsha256.js

/** Import Required Libraries */
const uuidInstance = require('uuid');
const cryptoJs = require('crypto-js');

/** Get Postman Local Varialbes */
const secretKey = pm.variables.get('secretKey');
const appId = pm.variables.get('appId');
const baseUrl = pm.variables.get('baseUrl');

/** Check if any required variable is missing then throw Error. */
if (!secretKey || !appId || !baseUrl) {
    throw new Error('One of the following variable is missing | secretKey, appId, baseUrl');
}

/** Collect Request Data (Method, Current URI) */
const requestPath = pm.request.url.getPath().toLowerCase();
const requestMethod = pm.request.method.toLowerCase();
const requestUrl = baseUrl + requestPath;

/** Generate UUID and Timestamp */
const nonce = uuidInstance.v4();
const timeStamp = Date.now();

/** Generate Hash and Encode using Base64 */
const hashInBase64 = encryptString(appId, requestMethod, requestUrl, timeStamp, nonce);

/** Create and set Authentication Header */
const authHeader = getAuthorizationHeader(appId, hashInBase64, timeStamp, nonce);
pm.globals.set('authHeader', authHeader);

/** Return Authorization Header */
function getAuthorizationHeader (...params) {
    return params.join(':');
}

/** Encrypt String using HMACSHA256 Algo */
function encryptString (...params) {
    return btoa(cryptoJs.HmacSHA256(params.join(''), secretKey));
}