Authentication Patterns in v0 Applications

Security

is

paramount in modern

web

applications.Learn

how

to

implement

robust, production - ready

authentication in v0

projects

using Supabase

Auth

and

modern

security

patterns.

#

Authentication

Options

Choose

the

right

authentication

method

based

on

your

application

's needs:

Email/Password: Traditional authentication

with email and

password.Best

for applications where users expect

standard

login

flows.Requires

email

verification

and

password

reset

functionality.

**OAuth

Providers**

: Social login

with Google, GitHub, Twitter, etc. Reduces friction

for users and eliminates password

management.Ideal

for consumer applications.

Magic Links

: Passwordless authentication via email. Users receive a one-time link to sign in. Great

for reducing password fatigue and

improving

security.

**Multi-Factor

Authentication (MFA)**

: Additional security layer

with TOTP, SMS, or authenticator

apps.Essential

for applications handling sensitive data

or

financial

transactions.

#

Supabase

Auth

Integration

Supabase

provides

a

complete

authentication

solution

that

integrates

seamlessly

with v0 applications.

**Setup

Supabase

Auth**

:

```typescript

// lib/supabase/client.ts

import { createBrowserClient } from "@supabase/ssr"

export function createClient() {

return createBrowserClient(process.env.NEXT_PUBLIC_SUPABASE_URL!, process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!)

}

```

```typescript

// lib/supabase/server.ts

import { createServerClient, type CookieOptions } from "@supabase/ssr"

import { cookies } from "next/headers"

export async function createClient() {

const cookieStore = await cookies()

return createServerClient(process.env.NEXT_PUBLIC_SUPABASE_URL!, process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!, {

cookies: {

get(name: string) {

return cookieStore.get(name)?.value

},

set(name: string, value: string, options: CookieOptions) {

cookieStore.set({ name, value, ...options })

},

remove(name: string, options: CookieOptions) {

cookieStore.set({ name, value: "", ...options })

},

},

})

}

```

Email/Password Authentication:

```typescript

// app/actions/auth.ts

'use server'

import { createClient } from "@/lib/supabase/server"

export async function signUp(formData: FormData) {

const supabase = await createClient()

const email = formData.get('email') as string

const password = formData.get('password') as string

const { error } = await supabase.auth.signUp({

email,

password,

options: {

emailRedirectTo: `${process.env.NEXT_PUBLIC_SITE_URL}/auth/callback`,

},

})

if (error) {

return { error: error.message }

}

redirect('/verify-email')

}

export async function signIn(formData: FormData) {

const supabase = await createClient()

const email = formData.get('email') as string

const password = formData.get('password') as string

const { error } = await supabase.auth.signInWithPassword({

email,

password,

})

if (error) {

return { error: error.message }

}

redirect('/dashboard')

}

export async function signOut() {

const supabase = await createClient()

await supabase.auth.signOut()

redirect('/login')

}

```

Login Form Component:

```typescript

// components/auth/login-form.tsx

'use client'

import { signIn } from '@/app/actions/auth'

import { Button } from '@/components/ui/button'

import { Input } from '@/components/ui/input'

import { Label } from '@/components/ui/label'

import { useState } from 'react'

export function LoginForm() {

const [error, setError] = useState<string>()

const [loading, setLoading] = useState(false)

async function handleSubmit(formData: FormData) {

setLoading(true)

setError(undefined)

const result = await signIn(formData)

if (result?.error) {

setError(result.error)

setLoading(false)

}

}

return (

<form action={handleSubmit} className="space-y-4">

<div>

<Label htmlFor="email">Email</Label>

<Input

id="email"

name="email"

type="email"

required

placeholder="you@example.com"

/>

</div>

<div>

<Label htmlFor="password">Password</Label>

<Input

id="password"

name="password"

type="password"

required

placeholder="••••••••"

/>

</div>

{error && (

<div className="text-sm text-destructive">{error}</div>

)}

<Button type="submit" className="w-full" disabled={loading}>

{loading ? 'Signing in...' : 'Sign In'}

</Button>

</form>

)

}

```

OAuth Integration:

```typescript

// components/auth/oauth-buttons.tsx

'use client'

import { createClient } from '@/lib/supabase/client'

import { Button } from '@/components/ui/button'

export function OAuthButtons() {

const supabase = createClient()

async function signInWithProvider(provider: 'google' | 'github') {

await supabase.auth.signInWithOAuth({

provider,

options: {

redirectTo: `${window.location.origin}/auth/callback`,

},

})

}

return (

<div className="space-y-2">

<Button

variant="outline"

className="w-full bg-transparent"

onClick={() => signInWithProvider('google')}

>

Continue with Google

</Button>

<Button

variant="outline"

className="w-full bg-transparent"

onClick={() => signInWithProvider('github')}

>

Continue with GitHub

</Button>

</div>

)

}

```

Protected Routes

Implement route protection to secure your application.

Middleware for Auth:

```typescript

// middleware.ts

import { createServerClient, type CookieOptions } from '@supabase/ssr'

import { NextResponse, type NextRequest } from 'next/server'

export async function middleware(request: NextRequest) {

let response = NextResponse.next({

request: {

headers: request.headers,

},

})

const supabase = createServerClient(

process.env.NEXT_PUBLIC_SUPABASE_URL!,

process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!,

{

cookies: {

get(name: string) {

return request.cookies.get(name)?.value

},

set(name: string, value: string, options: CookieOptions) {

response.cookies.set({

name,

value,

...options,

})

},

remove(name: string, options: CookieOptions) {

response.cookies.set({

name,

value: '',

...options,

})

},

},

}

)

const { data: { user } } = await supabase.auth.getUser()

// Protect dashboard routes

if (request.nextUrl.pathname.startsWith('/dashboard') && !user) {

return NextResponse.redirect(new URL('/login', request.url))

}

// Redirect authenticated users away from auth pages

if ((request.nextUrl.pathname === '/login' || request.nextUrl.pathname === '/signup') && user) {

return NextResponse.redirect(new URL('/dashboard', request.url))

}

return response

}

export const config = {

matcher: ['/dashboard/:path*', '/login', '/signup'],

}

```

Server Component Protection:

```typescript

// app/dashboard/page.tsx

import { createClient } from '@/lib/supabase/server'

import { redirect } from 'next/navigation'

export default async function DashboardPage() {

const supabase = await createClient()

const { data: { user } } = await supabase.auth.getUser()

if (!user) {

redirect('/login')

}

return (

<div>

<h1>Welcome, {user.email}</h1>

{/* Dashboard content */}

</div>

)

}

```

Session Management

Handle sessions securely and efficiently.

Session Refresh:

```typescript

// components/auth/session-provider.tsx

'use client'

import { createClient } from '@/lib/supabase/client'

import { useRouter } from 'next/navigation'

import { useEffect } from 'react'

export function SessionProvider({ children }: { children: React.ReactNode }) {

const router = useRouter()

const supabase = createClient()

useEffect(() => {

const {

data: { subscription },

} = supabase.auth.onAuthStateChange((event, session) => {

if (event === 'SIGNED_IN') {

router.refresh()

}

if (event === 'SIGNED_OUT') {

router.push('/login')

}

if (event === 'TOKEN_REFRESHED') {

router.refresh()

}

})

return () => {

subscription.unsubscribe()

}

}, [router, supabase])

return <>{children}</>

}

```

Role-Based Access Control

Implement RBAC for fine-grained permissions.

Database Schema:

```sql

-- Add role to profiles table

alter table profiles add column role text default 'user';

-- Create enum for roles

create type user_role as enum ('user', 'admin', 'moderator');

alter table profiles alter column role type user_role using role::user_role;

-- RLS policy for admin-only access

create policy "Only admins can view all profiles"

on profiles for select

using (

auth.uid() = id

or

(select role from profiles where id = auth.uid()) = 'admin'

);

```

Permission Checks:

```typescript

// lib/auth/permissions.ts

import { createClient } from '@/lib/supabase/server'

export async function requireAdmin() {

const supabase = await createClient()

const { data: { user } } = await supabase.auth.getUser()

if (!user) {

throw new Error('Not authenticated')

}

const { data: profile } = await supabase

.from('profiles')

.select('role')

.eq('id', user.id)

.single()

if (profile?.role !== 'admin') {

throw new Error('Insufficient permissions')

}

return user

}

```

Security Best Practices

Password Requirements:

- Minimum 8 characters

- At least one uppercase letter

- At least one lowercase letter

- At least one number

- At least one special character

Rate Limiting:

```typescript

// lib/rate-limit.ts

import { Ratelimit } from '@upstash/ratelimit'

import { Redis } from '@upstash/redis'

const ratelimit = new Ratelimit({

redis: Redis.fromEnv(),

limiter: Ratelimit.slidingWindow(5, '15 m'),

})

export async function checkRateLimit(identifier: string) {

const { success, remaining } = await ratelimit.limit(identifier)

if (!success) {

throw new Error('Too many attempts. Please try again later.')

}

return remaining

}

```

CSRF Protection: Next.js provides built-in CSRF protection for Server Actions.

XSS Prevention: Always sanitize user input and use React's built-in XSS protection.

Implementing robust authentication is critical for application security and user trust.