proxyauth: on invalid token, redirect user

https://forum.cloudron.io/topic/6425/403-in-proxyauth-apps-after-server-migration

src/proxyauth.js

@@ -1,7 +1,5 @@
 'use strict';
 
-const blobs = require('./blobs.js');
-
 // heavily inspired from https://gock.net/blog/2020/nginx-subrequest-authentication-server/ and https://github.com/andygock/auth-server
 
 exports = module.exports = {
@@ -12,6 +10,7 @@ exports = module.exports = {
 const apps = require('./apps.js'),
     assert = require('assert'),
     basicAuth = require('basic-auth'),
+    blobs = require('./blobs.js'),
     constants = require('./constants.js'),
     debug = require('debug')('box:proxyAuth'),
     ejs = require('ejs'),
@@ -41,12 +40,12 @@ function jwtVerify(req, res, next) {
 
     jwt.verify(token, gTokenSecret, function (error, decoded) {
         if (error) {
-            debug('jwtVerify: clearing token', error);
-            res.clearCookie('authToken');
-            return next(new HttpError(403, 'Malformed token or bad signature'));
+            debug('jwtVerify: malformed token or bad signature', error.message);
+            req.user = null;
+        } else {
+            req.user = decoded.user || null;
         }
 
-        req.user = decoded.user || null;
         next();
     });
 }
@@ -116,6 +115,7 @@ function isBrowser(req) {
 // called by nginx to authorize any protected route. this route must return only 2xx or 401/403 (http://nginx.org/en/docs/http/ngx_http_auth_request_module.html)
 function auth(req, res, next) {
     if (!req.user) {
+        res.clearCookie('authToken');
         if (isBrowser(req)) return next(new HttpError(401, 'Unauthorized'));
 
         // the header has to be generated here and cannot be set in nginx config - https://forum.nginx.org/read.php?2,171461,171469#msg-171469
@@ -241,7 +241,7 @@ function initializeAuthwallExpressSync() {
         .use(middleware.lastMile());
 
     router.get ('/login',     loginPage);
-    router.get ('/auth',      jwtVerify, basicAuthVerify, auth);
+    router.get ('/auth',      jwtVerify, basicAuthVerify, auth); // called by nginx before accessing protected page
     router.post('/login',     json, passwordAuth, authorize);
     router.get ('/logout',    logoutPage);
     router.post('/logout',    json, logout);