Nextjs authentication

Authentication & Token Management

Priority: P0 (CRITICAL)

Use HttpOnly Cookies for token storage. Never use LocalStorage or sessionStorage.

Implementation Guidelines

• Token Storage: Strictly use HttpOnly, Secure cookies with SameSite: 'Lax' or 'Strict'. Set reasonable maxAge (e.g., 86400). Never store access tokens in localStorage or sessionStorage (XSS-vulnerable). LocalStorage causes hydration issues in Server Components.
• Access Management: Read and verify tokens in Next.js Middleware (middleware.ts) for edge-side redirection and route protection. Use NextRequest to get cookies and NextResponse.redirect for unauthorized users. Use matcher in config for route protection.
• Next.js 15+ Async: Remember that cookies() is a Promise from next/headers and must be awaited: const cookieStore = await cookies();. Access values via (await cookies()).get('token')?.value. Never pass raw token to Client Components.
• Library Selection: Prefer next-auth (Auth.js) or Clerck for social logins and session management. Reach for getServerSession or auth() (Auth.js) to read an encrypted session.
• Data Access: Always use a DAL (Data Access Layer) to validate credentials and verifies cookie presence before rendering.
• CSRF Protection: Guard all Server Actions and Route Handlers by verifying the Origin/Referer headers.
• User Verification: Use await auth() (from Auth.js) or a custom getSession() helper in Server Components. Always validate the session on the backend even if requested via Client Component.

References

• Auth Implementation Examples