authentication

name	authentication
description	Use when adding sign-in/sign-up or session handling to a SaaS app — set up Auth.js (NextAuth) or a hosted provider with secure sessions, OAuth + email, and server-side session checks that protect routes and actions.

Authentication

Overview

Authentication is the gate to everything else, so don't hand-roll it. Use Auth.js (NextAuth) with the Drizzle adapter, or a hosted provider (Clerk/Supabase/WorkOS) if you want MFA and user management out of the box. The non-negotiables: httpOnly session cookies, server-side session resolution, and a single requireSession() helper used by every protected route and action.

When to use

• Adding login, signup, OAuth, or magic-link auth.
• Protecting routes, server actions, or route handlers.
• Resolving "who is the current user/org" on the server.

The pattern (Auth.js)

// src/server/auth/index.ts
import "server-only";
import NextAuth from "next-auth";
import { DrizzleAdapter } from "@auth/drizzle-adapter";
import Google from "next-auth/providers/google";
import { db } from "@/server/db/client";
import { env } from "@/env";

export const { handlers, auth, signIn, signOut } = NextAuth({
  adapter: DrizzleAdapter(db),
  session: { strategy: "database" },
  secret: env.AUTH_SECRET,
  providers: [Google],
});

// src/server/auth/require.ts
import "server-only";
import { redirect } from "next/navigation";
import { auth } from "@/server/auth";

export async function requireSession() {
  const session = await auth();
  if (!session?.user) redirect("/sign-in");
  return session;
}

Use it in a layout to protect a whole route group:

// src/app/(app)/layout.tsx
export default async function AppLayout({ children }) {
  await requireSession();            // server-side, runs before render
  return <>{children}</>;
}

Security essentials

• Sessions in httpOnly, Secure, SameSite=Lax cookies. Never store tokens in localStorage.
• Resolve sessions on the server (auth() in components/actions), not from a client fetch you trust.
• Rotate + expire. Set sensible session max-age; support sign-out everywhere.
• Hash passwords with argon2/bcrypt only if you truly own credentials — prefer OAuth/magic-link.

Pitfalls

• Trusting client-side auth state for authorization — it's a UX hint only; always re-check on the server.
• JWT sessions when you need instant revocation — use the database strategy if "log out all devices" matters.
• Leaking whether an email exists — keep sign-in errors generic (pair with auth-screens UX).
• No CSRF protection on credential posts — Auth.js handles this; don't bypass it with custom forms.
• Protecting only the UI — a route handler without a session check is wide open.

Hand-off

A trustworthy requireSession(). multi-tenancy turns the user into an active org; authorization-rbac checks what that user may do.