Node CDNsun URL Signing Token

Readme.md

CDNsun URL Signing Token

This is a Node.js implementation of the CDNsun URL Signing Token function as described here.

It requires on CryptoJs.

signature.js

const CryptoJS = require('crypto-js')

function generateSignedUrl(scheme = "http", cdnResourceUrl, filePath = "/", secretKey, expiryTimestamp = "", clientIp = "") {
    if (scheme === '' || cdnResourceUrl === '') {
        throw new Error('First argument "scheme" and/or second argument "cdnResourceUrl" cannot be empty.');
    }

    // NOTE: We adhere to ngx_secure_link_module hashing strategy
    // Ref: http://nginx.org/en/docs/http/ngx_http_secure_link_module.html#secure_link
    let searchChars = ['+', '/', '='];
    let replaceChars = ['-', '_', ''];

    // 1. Setup Token Key
    // 1.1 Append leading slash if missing
    if (filePath[0] != '/') {
        filePath = `/${filePath}`;
    }
    // 1.2 Extract uri, ignore arguments
    let pos = filePath.indexOf('?')
    if (pos != -1) {
        filePath = $filePath.substring(0, pos);
    }

    // 1.3 Formulate the token key
    tokenKey = expiryTimestamp + filePath + secretKey + clientIp;

    let secureString = CryptoJS.enc.Base64.stringify((CryptoJS.MD5(tokenKey)));
    for (replace in searchChars) {
        secureString = secureString.replace(new RegExp(`\\${searchChars[replace]}`, 'g'), replaceChars[replace])
    }

    // 2. Setup URL
    // 2.1 Append argument - secure (compulsory)
    urlStr = `${scheme}://${cdnResourceUrl}${filePath}?secure=${secureString}`;

    // 2.2 Append argument - expires
    if (expiryTimestamp !== '' && expiryTimestamp !== "0" && expiryTimestamp !== 0) {
        urlStr += `&expires=${expiryTimestamp}`;
    }
    // 2.3 Append argument - ip
    if (clientIp !== '') {
        urlStr += `&ip=${clientIp}`;
    }

    return urlStr;
}