feat: implement full authentication system with CSRF protection and email verification flow

lib/csrf.ts

@@ -0,0 +1,47 @@
+import { NextRequest, NextResponse } from 'next/server';
+import { cookies } from 'next/headers';
+import crypto from 'crypto';
+
+const CSRF_COOKIE_NAME = 'csrf_token';
+const CSRF_HEADER_NAME = 'x-csrf-token';
+
+export async function generateCsrfToken() {
+    const token = crypto.randomBytes(32).toString('hex');
+    const cookieStore = await cookies();
+    
+    cookieStore.set(CSRF_COOKIE_NAME, token, {
+        httpOnly: true,
+        secure: process.env.NODE_ENV === 'production',
+        sameSite: 'lax',
+        path: '/',
+    });
+    
+    return token;
+}
+
+export async function verifyCsrfToken(request: NextRequest) {
+    const cookieStore = await cookies();
+    const cookieToken = cookieStore.get(CSRF_COOKIE_NAME)?.value;
+    const headerToken = request.headers.get(CSRF_HEADER_NAME);
+
+    if (!cookieToken || !headerToken || cookieToken !== headerToken) {
+        return false;
+    }
+
+    return true;
+}
+
+/**
+ * Basic Origin check as an additional layer of defense
+ */
+export function verifyOrigin(request: NextRequest) {
+    const origin = request.headers.get('origin');
+    const host = request.headers.get('host');
+
+    if (!origin || !host) return false;
+
+    // Remove protocol from origin for comparison if host doesn't have it
+    const originHost = origin.replace(/^https?:\/\//, '');
+    
+    return originHost === host || originHost.startsWith(host + ':');
+}