index.js

module.exports = function(options = {}) {
  let security = {}
  security.options = options


  security.setHeaders = function(req, res, next) {
      if(!security.options) options = {}
      else options = security.options


      if (typeof options.CacheControl === 'undefined') {
        options.CacheControl = 'no-cache, no-store, must-revalidate'
      }
      if (options.CacheControl !== false) {
        res.set('Cache-Control', options.CacheControl)
      }

      if (typeof options.Pragma === 'undefined') {
        options.Pragma = 'no-cache'
      }
      if (options.Pragma !== false) {
        res.set('Pragma', options.Pragma)
      }

      if (typeof options.Expires === 'undefined') {
        options.Expires = '0'
      }
      if (options.Expires !== false) {
        res.set('Expires', options.Expires)
      }

      if (typeof options.ContentSecurityPolicy === 'undefined') {
        options.ContentSecurityPolicy = 'default-src \'self\'; frame-ancestors \'none\''
      }
      if (options.ContentSecurityPolicy !== false) {
        res.set('Content-Security-Policy', options.ContentSecurityPolicy )
      }

      if (typeof options.XXSSProtection === 'undefined') {
        options.XXSSProtection = '1; mode=block'
      }
      if (options.XXSSProtection !== false) {
        res.set('X-XSS-Protection', options.XXSSProtection)
      }

      if (typeof options.XDNSPrefetchControl === 'undefined') {
        options.XDNSPrefetchControl = 'off'
      }
      if (options.XDNSPrefetchControl !== false) {
        res.set('X-DNS-Prefetch-Control', options.XDNSPrefetchControl)
      }

      if (typeof options.ExpectCT === 'undefined') {
        options.ExpectCT = 'enforce; max-age=30; report-uri="/_report"'
      }
      if (options.ExpectCT !== false) {
        res.set('Expect-CT', options.ExpectCT)
      }

      if (typeof options.XFrameOptions === 'undefined') {
        options.XFrameOptions = 'deny'
      }
      if (options.XFrameOptions !== false) {
        res.set('X-Frame-Options', options.XFrameOptions)
      }

      if (typeof options.XPoweredBy === 'undefined') {
        options.XPoweredBy = true
      }
      if (options.XPoweredBy !== false) {
        res.removeHeader('X-Powered-By')
      }

      if (typeof options.StrictTransportSecurity === 'undefined') {
        options.StrictTransportSecurity = 'max-age=30'
      }
      if (options.StrictTransportSecurity !== false) {
        res.set('Strict-Transport-Security', options.StrictTransportSecurity)
      }

      if (typeof options.XDownloadOptions === 'undefined') {
        options.XDownloadOptions = 'noopen'
      }
      if (options.XDownloadOptions !== false) {
        res.set('X-Download-Options', options.XDownloadOptions)
      }

      if (typeof options.XContentTypeOptions === 'undefined') {
        options.XContentTypeOptions = 'nosniff'
      }
      if (options.XContentTypeOptions !== false) {
        res.set('X-Content-Type-Options', options.XContentTypeOptions )
      }

      if (typeof options.XPermittedCrossDomainPolicies === 'undefined') {
        options.XPermittedCrossDomainPolicies = 'none'
      }
      if (options.XPermittedCrossDomainPolicies !== false) {
        res.set('X-Permitted-Cross-Domain-Policies', options.XPermittedCrossDomainPolicies)
      }

      if (typeof options.ReferrerPolicy === 'undefined') {
        options.ReferrerPolicy = 'no-referrer'
      }
      if (options.ReferrerPolicy !== false) {
        res.set('Referrer-Policy', options.ReferrerPolicy)
      }


      if (typeof options.allowedMethods === 'undefined') {
        options.allowedMethods = ['GET', 'POST', 'PUT', 'DELETE']
      }
      if (!options.allowedMethods.includes(req.method)) {
        res.status(405).end()
      }

      if (typeof options.onlyDefinedRoutes === 'undefined') {
        options.onlyDefinedRoutes = false
      }
      if (options.onlyDefinedRoutes) {
        if (!options.definedRoutes) {
          options.definedRoutes = []
        }
        let isAllowed = false;
        for (const allowedRoute of options.definedRoutes) {
          if (allowedRoute.startsWith('REGEX:')) {
            let regexString = allowedRoute.split('REGEX:')[1];
            let regexp = new RegExp(regexString);
            if (regexp.test(req.originalUrl)) {
              isAllowed= true;
            }
          } else {
            if (req.originalUrl === allowedRoute) {
              isAllowed = true;
            }
          }
        }
        if (!isAllowed) { 
          res.status(405).end()
        }
      }

      next()
    }

  return security;
}