Signed AWS requests with node fetch

fetch.js

const nodeFetch = require('node-fetch');
const httpsAgent = require('./httpsAgent');
const handleResponse = require('./handleResponse');

module.exports = async (url, options = {}) => {
  const response = await nodeFetch(url, {
    ...options,
    agent: httpsAgent
  });
  
  return handleResponse(response);
};

handleResponse.js

module.exports = (response) => {
  if (response.ok) {
    const contentType = response.headers.get('content-type');

    if (contentType && contentType.includes('application/json')) {
      return response.json();
    } else {
      return response.text();
    }
  } else {
    throw Error(`Request to ${response.url} responded with a ${response.status}`);
  }
};

httpsAgent.js

const https = require('https');
module.exports = new https.Agent({ keepAlive: true });

index.js

const aws4 = require('aws4');
const { URL } = require('url');
const fetch = require('./fetch');
const resolveCname = require('./resolveCname');

module.exports = async (url, options = {}, credentials = {}) => {
  const parsedURL = new URL(url);

  // Ensure we sign the actual service URL and not a load balancer URL
  const hostname = await resolveCname(parsedURL.host);

  const signedOptions = {
    method: options.method,
    host: hostname,
    path: parsedURL.pathname + parsedURL.search,
    body: options.body,
    headers: options.headers
  };

  aws4.sign(signedOptions, {
    accessKeyId: credentials.awsAccessKey,
    secretAccessKey: credentials.awsSecretAccessKey
  });

  options.headers = signedOptions.headers;

  return fetch(`https://${signedOptions.host}${signedOptions.path}`, options);
};

package.json

{
  "name": "signed-aws-fetch",
  "version": "1.0.0",
  "description": "",
  "engines": {
    "node": ">= 8.0.0"
  },
  "main": "index.js",
  "dependencies": {
    "aws4": "^1.8.0",
    "lru-cache": "^5.1.0",
    "node-fetch": "^2.3.0"
  },
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "Matt Hinchliffe",
  "license": "ISC"
}

resolveCname.js

const dns = require('dns');
const util = require('util');
const LRU = require('lru-cache');

const cache = new LRU({ maxAge: 1000 * 60, stale: true });
const resolveCname = util.promisify(dns.resolveCname);

module.exports = async (domain) => {
  if (/\.amazonaws\.com$/.test(domain)) {
    return domain;
  }

  if (cache.has(domain)) {
    return cache.get(domain);
  }

  const [ resolvedName ] = await resolveCname(domain);

  if (resolvedName) {
    cache.set(domain, resolvedName);
    return resolvedName;
  } else {
    throw Error(`Could not resolve CNAME for ${domain}`);
  }
};