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Zhongwei Li
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# Authentication Patterns for Next.js + Supabase
## Common Authentication Patterns
### Pattern 1: Protected Route Groups
Use Next.js route groups to protect multiple routes with a single layout:
```
app/
├── (public)/
│ ├── layout.tsx # Public layout
│ ├── page.tsx # Home page
│ └── about/
│ └── page.tsx # About page
└── (protected)/
├── layout.tsx # Protected layout with requireAuth()
├── dashboard/
│ └── page.tsx
└── settings/
└── page.tsx
```
**Protected layout example:**
```typescript
// app/(protected)/layout.tsx
import { requireAuth } from '@/lib/auth/utils';
export default async function ProtectedLayout({
children,
}: {
children: React.ReactNode;
}) {
await requireAuth();
return <>{children}</>;
}
```
All routes inside `(protected)` automatically require authentication.
### Pattern 2: Conditional UI Based on Auth State
Show different content based on whether user is authenticated:
```typescript
import { getCurrentUser } from '@/lib/auth/utils';
export default async function HomePage() {
const user = await getCurrentUser();
return (
<div>
{user ? (
<div>
<h1>Welcome back, {user.email}!</h1>
<a href="/dashboard">Go to Dashboard</a>
</div>
) : (
<div>
<h1>Welcome to our app</h1>
<a href="/login">Sign in</a>
</div>
)}
</div>
);
}
```
### Pattern 3: Role-Based Access Control
Protect routes based on user roles:
```typescript
// lib/auth/utils.ts - Add role checking
export async function requireRole(allowedRoles: string[]) {
const user = await requireAuth();
const supabase = await createServerClient();
const { data: profile } = await supabase
.from('profiles')
.select('role')
.eq('id', user.id)
.single();
if (!profile || !allowedRoles.includes(profile.role)) {
redirect('/unauthorized');
}
return { user, profile };
}
```
**Usage in admin page:**
```typescript
export default async function AdminPage() {
await requireRole(['admin', 'moderator']);
return <div>Admin Dashboard</div>;
}
```
### Pattern 4: Server Action Authentication
Protect Server Actions that modify data:
```typescript
'use server';
import { requireAuth } from '@/lib/auth/utils';
import { createServerClient } from '@/lib/supabase/server';
import { revalidatePath } from 'next/cache';
export async function createPost(formData: FormData) {
const user = await requireAuth();
const supabase = await createServerClient();
const title = formData.get('title') as string;
const content = formData.get('content') as string;
const { error } = await supabase.from('posts').insert({
title,
content,
author_id: user.id,
});
if (error) throw error;
revalidatePath('/posts');
}
```
### Pattern 5: API Route Authentication
Protect API routes for external access:
```typescript
// app/api/protected/route.ts
import { createServerClient } from '@/lib/supabase/server';
import { NextResponse } from 'next/server';
export async function GET() {
const supabase = await createServerClient();
const {
data: { user },
} = await supabase.auth.getUser();
if (!user) {
return NextResponse.json({ error: 'Unauthorized' }, { status: 401 });
}
// Return protected data
return NextResponse.json({ data: 'Protected data' });
}
```
### Pattern 6: Parallel Data Fetching with Auth
Fetch user and their data in parallel:
```typescript
export default async function ProfilePage() {
const user = await requireAuth();
const supabase = await createServerClient();
// Fetch user profile and posts in parallel
const [{ data: profile }, { data: posts }] = await Promise.all([
supabase.from('profiles').select('*').eq('id', user.id).single(),
supabase.from('posts').select('*').eq('author_id', user.id),
]);
return (
<div>
<h1>{profile?.name}</h1>
<h2>Posts</h2>
{posts?.map((post) => (
<div key={post.id}>{post.title}</div>
))}
</div>
);
}
```
### Pattern 7: Redirect After Login
Preserve intended destination after login:
**Middleware:**
```typescript
export async function middleware(request: NextRequest) {
const { supabaseResponse, user } = await updateSession(request);
if (!user && request.nextUrl.pathname.startsWith('/dashboard')) {
const redirectUrl = new URL('/login', request.url);
// Save the intended destination
redirectUrl.searchParams.set('redirect', request.nextUrl.pathname);
return Response.redirect(redirectUrl);
}
return supabaseResponse;
}
```
**Login page:**
```typescript
export default async function LoginPage({
searchParams,
}: {
searchParams: { redirect?: string };
}) {
// After successful login, redirect to intended page
const redirectTo = searchParams.redirect || '/dashboard';
// Use redirectTo in form action or success handler
}
```
### Pattern 8: Email Verification Check
Require email verification before accessing certain features:
```typescript
export async function requireVerifiedEmail() {
const user = await requireAuth();
if (!user.email_confirmed_at) {
redirect('/verify-email');
}
return user;
}
```
## Best Practices
1. **Use Server Components for Auth Checks**: Leverage Server Components for initial auth checks to avoid client-side flashing
2. **Middleware for Session Refresh**: Always refresh sessions in middleware to keep auth state fresh
3. **Revalidate After Auth Changes**: Use `revalidatePath()` after login/logout to clear cached content
4. **Secure Cookie Configuration**: Ensure cookies use secure, httpOnly, and sameSite settings
5. **Handle Auth Errors Gracefully**: Provide clear error messages and recovery paths
6. **Use TypeScript**: Type your user objects and auth functions for better DX
7. **Test Protected Routes**: Verify both authenticated and unauthenticated access
8. **Implement Proper Redirects**: Always redirect after authentication changes to prevent stale UI
## Anti-Patterns to Avoid
1. **Client-Side Only Auth**: Don't rely solely on client-side auth checks
2. **Checking Auth on Every Component**: Use layouts and route groups instead
3. **Exposing Sensitive Data**: Never send sensitive data to client without auth check
4. **Hardcoded Redirects**: Use dynamic redirects based on user intent
5. **Ignoring Middleware**: Always use middleware for session refresh
6. **Not Handling Loading States**: Show appropriate loading states during auth checks

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# Security Considerations for Supabase Auth
## Cookie Security
### Secure Cookie Configuration
The `@supabase/ssr` package automatically configures secure cookies with these settings:
- **httpOnly**: Prevents client-side JavaScript from accessing cookies
- **secure**: Cookies only sent over HTTPS (except localhost)
- **sameSite**: Prevents CSRF attacks by restricting cross-site cookie sending
- **path**: Limits cookie scope to specific paths
**Do not modify** cookie settings unless you understand the security implications.
### Session Duration
Configure session timeout in Supabase dashboard:
1. Go to Authentication > Settings
2. Adjust "JWT expiry limit" (default: 1 hour)
3. Set "Refresh token expiry" (default: 30 days)
**Recommendations:**
- Short JWT expiry (1 hour) for better security
- Longer refresh token expiry (30 days) for better UX
- Use middleware to automatically refresh sessions
## Row Level Security (RLS)
### Enable RLS on All Tables
Always enable Row Level Security on tables containing user data:
```sql
ALTER TABLE profiles ENABLE ROW LEVEL SECURITY;
```
### Create Restrictive Policies
**Read own data:**
```sql
CREATE POLICY "Users can view own profile"
ON profiles FOR SELECT
USING (auth.uid() = id);
```
**Update own data:**
```sql
CREATE POLICY "Users can update own profile"
ON profiles FOR UPDATE
USING (auth.uid() = id);
```
**Insert on signup:**
```sql
CREATE POLICY "Users can insert own profile"
ON profiles FOR INSERT
WITH CHECK (auth.uid() = id);
```
### Test RLS Policies
Always test policies with different user contexts:
```sql
-- Test as specific user
SET LOCAL ROLE authenticated;
SET LOCAL request.jwt.claims.sub = 'user-uuid-here';
-- Run queries to verify access
SELECT * FROM profiles;
```
## Authentication Best Practices
### 1. Never Trust Client Input
Always validate on server-side:
```typescript
export async function updateProfile(formData: FormData) {
const user = await requireAuth();
// Validate input
const name = formData.get('name') as string;
if (!name || name.length < 2) {
throw new Error('Invalid name');
}
// Only update own profile
const supabase = await createServerClient();
await supabase
.from('profiles')
.update({ name })
.eq('id', user.id); // Ensure user can only update their own data
}
```
### 2. Use Server Components for Sensitive Data
Fetch sensitive data in Server Components, not Client Components:
```typescript
// [OK] Good - Server Component
export default async function ProfilePage() {
const user = await requireAuth();
const supabase = await createServerClient();
const { data: privateData } = await supabase
.from('private_table')
.select('*')
.eq('user_id', user.id);
return <div>{/* Use privateData */}</div>;
}
```
```typescript
// [ERROR] Bad - Client Component exposes API
'use client';
export default function ProfilePage() {
const [data, setData] = useState(null);
useEffect(() => {
// Fetching sensitive data on client
fetch('/api/private-data').then(/* ... */);
}, []);
}
```
### 3. Implement Rate Limiting
Protect authentication endpoints from brute force:
```typescript
// Example using Upstash Rate Limit
import { Ratelimit } from '@upstash/ratelimit';
import { Redis } from '@upstash/redis';
const ratelimit = new Ratelimit({
redis: Redis.fromEnv(),
limiter: Ratelimit.slidingWindow(5, '15 m'), // 5 attempts per 15 minutes
});
export async function signInWithPassword(formData: FormData) {
const email = formData.get('email') as string;
const { success } = await ratelimit.limit(email);
if (!success) {
return { error: 'Too many attempts. Please try again later.' };
}
// Proceed with sign in
}
```
### 4. Validate Email Addresses
Require email verification before granting full access:
```typescript
export async function requireVerifiedEmail() {
const user = await requireAuth();
if (!user.email_confirmed_at) {
redirect('/verify-email');
}
return user;
}
```
Configure in Supabase:
- Authentication > Settings > Enable "Confirm email"
- Customize email templates in Authentication > Email Templates
### 5. Use Environment Variables Correctly
**Public variables** (safe to expose):
- `NEXT_PUBLIC_SUPABASE_URL`
- `NEXT_PUBLIC_SUPABASE_ANON_KEY`
**Private variables** (server-side only):
- `SUPABASE_SERVICE_ROLE_KEY` (never expose to client!)
```typescript
// [OK] Good - Service role only on server
'use server';
import { createClient } from '@supabase/supabase-js';
export async function adminFunction() {
const supabase = createClient(
process.env.NEXT_PUBLIC_SUPABASE_URL!,
process.env.SUPABASE_SERVICE_ROLE_KEY! // Only accessible server-side
);
// Bypasses RLS - use carefully
}
```
## Common Security Mistakes
### 1. Exposing Service Role Key
[ERROR] **Never** use service role key in client-side code:
```typescript
// [ERROR] DANGEROUS - Exposes admin access
const supabase = createClient(
process.env.NEXT_PUBLIC_SUPABASE_URL,
process.env.SUPABASE_SERVICE_ROLE_KEY // Exposed to client!
);
```
### 2. Skipping RLS
[ERROR] **Never** disable RLS or use service role to bypass it unnecessarily:
```sql
-- [ERROR] DANGEROUS - Allows anyone to read all data
ALTER TABLE profiles DISABLE ROW LEVEL SECURITY;
```
### 3. Client-Side Authorization
[ERROR] **Never** rely only on client-side checks:
```typescript
// [ERROR] BAD - Can be bypassed
'use client';
export default function AdminPanel() {
const [user, setUser] = useState(null);
if (user?.role !== 'admin') {
return <div>Unauthorized</div>;
}
return <div>Admin content</div>; // Still rendered in HTML!
}
```
[OK] **Always** enforce on server:
```typescript
// [OK] GOOD - Server-side enforcement
export default async function AdminPanel() {
await requireRole('admin'); // Redirects if not admin
return <div>Admin content</div>;
}
```
### 4. Not Revalidating After Auth Changes
[ERROR] **Never** forget to revalidate after login/logout:
```typescript
// [ERROR] BAD - Stale cached content may show
export async function logout() {
const supabase = await createServerClient();
await supabase.auth.signOut();
redirect('/'); // Missing revalidation!
}
```
[OK] **Always** revalidate:
```typescript
// [OK] GOOD
export async function logout() {
const supabase = await createServerClient();
await supabase.auth.signOut();
revalidatePath('/', 'layout'); // Clears all cached pages
redirect('/');
}
```
## Audit Checklist
Use this checklist when implementing authentication:
- [ ] RLS enabled on all tables with user data
- [ ] RLS policies tested with different user contexts
- [ ] Service role key never exposed to client
- [ ] Email verification required for sensitive actions
- [ ] Rate limiting on authentication endpoints
- [ ] Input validation on all Server Actions
- [ ] Secure cookies configured (httpOnly, secure, sameSite)
- [ ] Middleware refreshes sessions on all requests
- [ ] Sensitive data only fetched in Server Components
- [ ] Authorization checks on server-side, not client-side
- [ ] Proper revalidation after auth state changes
- [ ] Error messages don't leak sensitive information
- [ ] OAuth redirect URLs configured correctly
- [ ] Session timeout appropriate for use case
- [ ] Logout clears all auth state and cookies