fix(auth): harden session cookie, strip password from req.user, change logout to POST

Fixes #554 - Add httpOnly, Secure, and SameSite=strict to the session cookie
so the token is inaccessible to JavaScript and cannot be sent in cross-origin
requests. The Secure flag is conditioned on NODE_ENV=production to keep
local development functional over HTTP.

Fixes #555 - Pass .select('-password -__v').lean() to deserializeUser so the
bcrypt hash is never attached to req.user. Using .lean() also returns a plain
object instead of a full Mongoose document, preventing accidental exposure of
model methods on the request context.

Fixes #556 - Change the logout endpoint from GET to POST. GET is a safe,
idempotent method that browsers trigger automatically (img src, link prefetch,
CSS url). Any third-party page could embed a zero-pixel image pointing at the
logout URL to silently sign out authenticated users. POST requires an explicit
fetch or form submission, which CORS and SameSite=strict will block from
cross-origin callers. The handler now also calls req.session.destroy() and
clears the cookie to ensure the session is fully invalidated server-side.

Author: anshul23102

backend/config/passportConfig.js

@@ -35,9 +35,12 @@ passport.serializeUser((user, done) => {
 });
 
 // Deserialize user (retrieve user from session)
+// Select only the fields needed for request handling. Excluding password
+// prevents the bcrypt hash from being attached to req.user and accidentally
+// serialized into API responses.
 passport.deserializeUser(async (id, done) => {
     try {
-        const user = await User.findById(id);
+        const user = await User.findById(id).select('-password -__v').lean();
         done(null, user);
     } catch (err) {
         done(err, null);

backend/routes/auth.js

@@ -36,14 +36,23 @@ router.post("/login", validateRequest(loginSchema), passport.authenticate('local
 });
 
 // Logout route
-router.get("/logout", (req, res) => {
+// POST is required here: GET is a safe/idempotent method that browsers trigger
+// automatically (img src, prefetch, etc.), which would allow any third-party
+// page to force-logout authenticated users via a passive CSRF request.
+router.post("/logout", (req, res) => {
 
     req.logout((err) => {
 
         if (err)
             return res.status(500).json({ message: 'Logout failed', error: err.message });
-        else
+
+        req.session.destroy((destroyErr) => {
+            if (destroyErr) {
+                return res.status(500).json({ message: 'Session cleanup failed', error: destroyErr.message });
+            }
+            res.clearCookie('connect.sid');
             res.status(200).json({ message: 'Logged out successfully' });
+        });
     });
 });
 

backend/server.js

@@ -28,10 +28,18 @@ app.use(cors({
 
 // Middleware
 app.use(bodyParser.json());
+const isProduction = process.env.NODE_ENV === 'production';
+
 app.use(session({
     secret: process.env.SESSION_SECRET,
     resave: false,
     saveUninitialized: false,
+    cookie: {
+        httpOnly: true,
+        secure: isProduction,
+        sameSite: 'strict',
+        maxAge: 24 * 60 * 60 * 1000, // 24 hours
+    },
 }));
 app.use(passport.initialize());
 app.use(passport.session());