feat: apply access-control-allow-origin globally

instead of only on some arbitrary routes

configurable via config, please check sample, disabled by default

i still recommend configuring from your own http server (nginx, etc.),
if you want to have a more complex per-routes headers

config.sample.js

@@ -138,14 +138,18 @@ module.exports = {
   /*
     Helmet security headers.
     https://github.com/helmetjs/helmet/tree/v5.0.2#how-it-works
+
+    These headers will be applied to ALL resources, including API endpoints,
+    and files if you serve them with node.
+    If you need to disable some of the headers at certain routes, it's recommended
+    to instead use own http server (nginx, etc.) in front of lolisafe and configure from there.
+
+    NOTE: You may set "helmet" option as an empty object {} to disable Helmet entirely.
+    Setting it as any falsy value will instead apply some default configurations.
   */
   helmet: {
     contentSecurityPolicy: false,
-    /*
+    // Cross-Origin-* headers were enabled by default since Helmet v5.0.0
-      Cross-Origin-* headers were enabled by default since Helmet v5.0.0
-      However, for installations that use own http server for files (nginx, etc.),
-      these headers also need to be configured in there.
-    */
     crossOriginEmbedderPolicy: false,
     crossOriginOpenerPolicy: false,
     crossOriginResourcePolicy: false,
@@ -161,6 +165,21 @@ module.exports = {
     originAgentCluster: false
   },
 
+  /*
+    Access-Control-Allow-Origin
+    https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Access-Control-Allow-Origin
+    These headers will be applied to ALL resources, including API endpoints,
+    and files if you serve them with node.
+
+    If set to true, it will be set as wildcard (*).
+    If set to any falsy value, it will be not set altogether.
+    Otherwise if any string value, it will be set as-is.
+
+    Whether to use this in conjunction with Cross-Origin-* headers depends on your needs.
+    FAQ: https://resourcepolicy.fyi/#acao
+  */
+  accessControlAllowOrigin: false,
+
   /*
     Trust proxy.
     Enable this if you are using proxy such as Cloudflare or Incapsula,

lolisafe.js

@@ -77,6 +77,20 @@ if (config.helmet instanceof Object) {
   safe.use(helmet(defaults))
 }
 
+// Access-Control-Allow-Origin
+if (config.accessControlAllowOrigin) {
+  if (config.accessControlAllowOrigin === true) {
+    config.accessControlAllowOrigin = '*'
+  }
+  safe.use((req, res, next) => {
+    res.set('Access-Control-Allow-Origin', config.accessControlAllowOrigin)
+    if (config.accessControlAllowOrigin !== '*') {
+      res.vary('Origin')
+    }
+    next()
+  })
+}
+
 if (config.trustProxy) {
   safe.set('trust proxy', 1)
 }
@@ -105,9 +119,7 @@ safe.use(bodyParser.urlencoded({ extended: true }))
 safe.use(bodyParser.json())
 
 const cdnPages = [...config.pages]
-let setHeaders = res => {
+let setHeaders
-  res.set('Access-Control-Allow-Origin', '*')
-}
 
 const contentTypes = config.overrideContentTypes && Object.keys(config.overrideContentTypes)
 const overrideContentTypes = (res, path) => {
@@ -187,7 +199,6 @@ if (config.cacheControl) {
   if (config.serveFilesWithNode) {
     initServeStaticUploads({
       setHeaders: (res, path) => {
-        res.set('Access-Control-Allow-Origin', '*')
         // Override Content-Type if necessary
         if (contentTypes && contentTypes.length) {
           overrideContentTypes(res, path)
@@ -205,13 +216,11 @@ if (config.cacheControl) {
   // This requires the assets to use version in their query string,
   // as they will be cached by clients for a very long time.
   setHeaders = res => {
-    res.set('Access-Control-Allow-Origin', '*')
     res.set('Cache-Control', cacheControls.static)
   }
 
   // Consider album ZIPs static as well, since they use version in their query string
   safe.use(['/api/album/zip'], (req, res, next) => {
-    res.set('Access-Control-Allow-Origin', '*')
     const versionString = parseInt(req.query.v)
     if (versionString > 0) {
       res.set('Cache-Control', cacheControls.static)
@@ -223,7 +232,6 @@ if (config.cacheControl) {
 } else if (config.serveFilesWithNode) {
   initServeStaticUploads({
     setHeaders: (res, path) => {
-      res.set('Access-Control-Allow-Origin', '*')
       // Override Content-Type if necessary
       if (contentTypes && contentTypes.length) {
         overrideContentTypes(res, path)