aws v4 signature in modern js (sigv4.js)

gistfile1.txt

'use strict';

const crypto = require('crypto');

module.exports = function (accessKey, secretKey, requestHeaders, httpMethod, path, payload, region, service, timestamp) {
    const signedHeaders = createSignedHeaders(requestHeaders);
    const canonicalRequest = createCanonicalRequest(httpMethod, path, requestHeaders, payload);
    const stringToSign = createStringToSign(timestamp, region, service, canonicalRequest);
    const signature = createSignature(secretKey, timestamp, region, service, stringToSign);
    const authorizationHeader = createAuthorizationHeaders(timestamp, accessKey, region, service, signedHeaders, signature);
    return authorizationHeader;
}

function createAuthorizationHeaders (timestamp, accessKey, region, service, signedHeaders, signature) {
    return `AWS4-HMAC-SHA256 Credential=${accessKey}/${createCredentialScope(timestamp, region, service)} SignedHeaders=${signedHeaders} Signature=${signature}`;
}

function createCanonicalRequest (method, pathname, headers, payload) {
    const payloadJson = JSON.stringify(payload);
    return `${method.toUpperCase()}
${pathname}

${createCanonicalHeaders(headers)}
${createSignedHeaders(headers)}
${hexEncodedHash(payloadJson)}`;
}

function createCanonicalHeaders (headers) {
    return Object.keys(headers)
        .sort()
        .map(name => name.toLowerCase().trim() + ':' + headers[name].toString().trim() + '\n')
        .join('');
}

function createSignedHeaders (headers) {
    return Object.keys(headers)
        .sort()
        .map(name => name.toLowerCase().trim())
        .join(';');
}

function createCredentialScope (time, region, service) {
    return `${toDate(time)}/${region}/${service}/aws4_request`;
}

function createStringToSign (time, region, service, request) {
    return `AWS4-HMAC-SHA256
${toTime(time)}
${createCredentialScope(time, region, service)}
${hexEncodedHash(request)}`;
}

function createSignature (secret, time, region, service, stringToSign) {
    const h1 = hmac(`AWS4${secret}`, toDate(time)).digest(); // date-key
    const h2 = hmac(h1, region).digest(); // region-key
    const h3 = hmac(h2, service).digest(); // service-key
    const h4 = hmac(h3, 'aws4_request').digest(); // signing-key
    return hmac(h4, stringToSign).digest('hex');
}

function toTime(time) {
    return new Date(time).toISOString().replace(/[:\-]|\.\d{3}/g, '');
}

function toDate(time) {
    return toTime(time).substring(0, 8);
}

function hmac(key, data) {
    return crypto.createHmac('sha256', key).update(data);
}

function hexEncodedHash(data) {
    return crypto.createHash('sha256').update(data).digest('hex');
}