bug: Security vulnerabilities in external Login API endpoint (#1417)

fix: Fix timing attacks in externalLogin route

src/app/api/admin/services/externalLogin/route.ts

@@ -1,7 +1,13 @@
+import { z } from 'zod';
 import db from '@/db';
 import { NextRequest, NextResponse } from 'next/server';
 import bcrypt from 'bcrypt';
 
+const loginSchema = z.object({
+  email: z.string(),
+  password: z.string(),
+});
+
 export async function POST(req: NextRequest) {
   const authKey = req.headers.get('Auth-Key');
 
@@ -11,46 +17,65 @@ export async function POST(req: NextRequest) {
 
   try {
     const payload = await req.json();
-    const { email, password } = payload;
+
+    const result = loginSchema.safeParse(payload);
+    if (!result.success) {
+      return NextResponse.json(
+        { message: 'Invalid input', errors: result.error.errors },
+        { status: 400 },
+      );
+    }
+
+    const { email, password } = result.data;
+
     const user = await db.user.findFirst({
-      where: {
-        email,
-      },
+      where: { email },
       select: {
         id: true,
         email: true,
         name: true,
         password: true,
       },
     });
-    if (!user) {
-      return NextResponse.json({ message: 'User not found' }, { status: 404 });
+
+    // Perform a dummy bcrypt compare if user doesn't exist to prevent timing attacks
+    if (!user || !user.password) {
+      await bcrypt.compare(password, await bcrypt.hash('dummy', 10));
+      return NextResponse.json(
+        { message: 'Invalid credentials' },
+        { status: 401 },
+      );
     }
 
-    if (
-      user &&
-      user.password &&
-      (await bcrypt.compare(password, user.password))
-    ) {
+    const isPasswordValid = await bcrypt.compare(password, user.password);
+
+    if (isPasswordValid) {
       const courses = await db.course.findMany({
         where: {
           purchasedBy: {
             some: {
-              user: {
-                email,
-              },
+              user: { email },
             },
           },
         },
       });
+
       return NextResponse.json({
         message: 'User found',
         data: {
-          user,
+          user: {
+            id: user.id,
+            email: user.email,
+            name: user.name,
+          },
           courses,
         },
       });
     }
+    return NextResponse.json(
+      { message: 'Invalid credentials' },
+      { status: 401 },
+    );
   } catch (error) {
     return NextResponse.json(
       { message: 'Error fetching user' },