Fix for users getting redirected to the wrong path

frontend/routes/authRoutes.js

@@ -1,24 +1,36 @@
+const crypto = require("crypto");
 const passport = require("passport");
 
 module.exports = (app) => {
-  app.get(
-    "/auth/google",
-    (req, res, next) => {
-      if (req.query.return) {
-        req.session.oauth2return = req.query.return;
+  app.get("/auth/google", (req, res, next) => {
+    crypto.randomBytes(128, (err, buff) => {
+      if (err) {
+        throw err;
       }
-      next();
-    },
-    passport.authenticate("google", { scope: ["email"] }),
-  );
+      const state = buff.toString("hex");
+      app.locals.stateStore.set(state, { returnUrl: req.query.return || "/" });
+      const authenticator = passport.authenticate("google", {
+        scope: ["email"],
+        state,
+      });
+      authenticator(req, res, next);
+    });
+  });
 
   app.get(
     "/auth/google/callback",
     passport.authenticate("google"),
     (req, res) => {
-      const redirect = req.session.oauth2return || "/";
-      delete req.session.oauth2return;
-      res.redirect(redirect);
+      const { state } = req.query;
+      if (app.locals.stateStore.has(state)) {
+        const { redirectUrl } = app.locals.stateStore.get(state).returnUrl;
+        app.locals.stateStore.delete(state);
+        res.redirect(redirectUrl);
+      } else {
+        // If we don't have anything in the state store then treat
+        // the login as invalid
+        res.sendStatus(403);
+      }
     },
   );
 

frontend/webapp.js

@@ -8,6 +8,9 @@
 
 const app = express();
 
+// Initialize the state store
+app.locals.stateStore = new Map();
+
 const corsOptions = {
   origin: [`${config.get("PROJECT")}.appspot.com`, "localhost:5000"],
   allowedHeaders: ["Content-Type"],
@@ -30,8 +33,8 @@
 /* eslint-disable consistent-return */
 const authRequired = function authRequired(req, res, next) {
   if (!req.user) {
-    req.session.oauth2return = req.originalUrl;
-    return res.redirect("/auth/google");
+    const params = new URLSearchParams({ return: req.originalUrl });
+    return res.redirect(`/auth/google?${params.toString()}`);
   }
   next();
 };
@@ -74,5 +77,5 @@
 
 const PORT = process.env.PORT || 8080;
 app.listen(PORT, () => {
   console.log(`Server listening on port ${PORT}...`);
 });