cloudFrontSignUrl.js

const aws = require('aws-sdk');
const cloudFront = aws.CloudFront;

const privateKey = `-----BEGIN RSA PRIVATE KEY-----
YOUR_PRIVATE_KEY_HERE_WITHOUT_ANY_TABULATION_BEFORE
-----END RSA PRIVATE KEY-----`;

const cfSigner = new cloudFront.Signer('YOUR_ACCESS_KEY_ID', privateKey);

const url = `https://randomaddress.cloudfront.net/path/to/file.jpg`;
const expires =  Math.floor((new Date()).getTime() / 1000) + (60 * 60 * 1);

const signedUrl = cfSigner.getSignedUrl({ url, expires });

console.log(singedUrl);