Securing Server Actions and Route Handlers in Next.js – Role Checks, Session Validation, and Context Limitations

Server Actions and Security

Server Actions should be protected like public-facing APIs. Always verify that the user is authorized before performing sensitive mutations.

Example: checking user role before proceeding:

// app/lib/actions.ts
'use server'
import { verifySession } from '@/app/lib/dal'

export async function serverAction(formData: FormData) {
  const session = await verifySession()
  const userRole = session?.user?.role

  if (userRole !== 'admin') {
    return null
  }

  // Proceed with the action for authorized users
}

Route Handlers and Access Control

Route Handlers must also verify authentication and authorization. The example below performs a two-tier check:

// app/api/route.ts
import { verifySession } from '@/app/lib/dal'

export async function GET() {
  const session = await verifySession()

  if (!session) {
    return new Response(null, { status: 401 })
  }

  if (session.user.role !== 'admin') {
    return new Response(null, { status: 403 })
  }

  // Continue for authorized users
}

Context Providers and Limitations

Auth context providers work in Client Components, but not in Server Components. Server Components render first and cannot access context values.

// app/layout.tsx
import { ContextProvider } from 'auth-lib'

export default function RootLayout({ children }) {
  return (
    <html lang="en">
      <body>
        <ContextProvider>{children}</ContextProvider>
      </body>
    </html>
  )
}

Client-side usage:

'use client'
import { useSession } from 'auth-lib'

export default function Profile() {
  const { userId } = useSession()
  const { data } = useSWR(`/api/user/${userId}`, fetcher)

  return (
    // ...
  )
}

To prevent exposing sensitive session data, use React’s taintUniqueValue API when needed.

Recommended Libraries

Authentication Libraries:

Auth0
Clerk
NextAuth.js
Supabase
Stytch
Descope
WorkOS

Session Management Libraries:

Iron Session
Jose

Conclusion

In Next.js, Server Actions and Route Handlers must be secured with proper session and role checks. By using verifySession(), enforcing permissions, and understanding context limitations, you can build a secure and scalable authentication system for your application.