Authentication for ChatGPT Apps

Most useful ChatGPT Apps need to access user-specific data. Authentication makes this possible while keeping data secure.

Why Authentication?

Without auth, your app can only provide generic functionality:

• ❌ "Show MY tasks" (whose tasks?)
• ❌ "Add to MY cart" (whose cart?)
• ❌ "Check MY portfolio" (whose portfolio?)

With auth, you can personalize:

• ✅ User-specific data
• ✅ Saved preferences
• ✅ Secure operations

The OAuth 2.1 Flow

ChatGPT Apps use OAuth 2.1 for authentication:

1. User clicks "Connect" in ChatGPT
    ↓
2. Redirected to your OAuth provider
    ↓
3. User logs in / authorizes
    ↓
4. Redirected back with auth code
    ↓
5. Your server exchanges code for token
    ↓
6. All future requests include token

Implementation with Auth0

We'll use Auth0 as our identity provider:

1. Configure Auth0

• Create an application
• Set callback URLs
• Enable PKCE

2. MCP Server Endpoints

Your server needs:

• GET /authorize — Start OAuth flow
• POST /token — Exchange code for token
• Token validation on every tool call

3. Token Validation

@app.middleware
async def validate_token(request, call_next):
    token = request.headers.get("Authorization")
    user = verify_jwt(token)
    request.state.user = user
    return await call_next(request)

Task Manager Example

Our Task Manager app demonstrates:

• Full OAuth 2.1 flow
• User-scoped data (each user sees only their tasks)
• Secure CRUD operations

Security Best Practices

1. Always use HTTPS — Never transmit tokens over HTTP
2. Validate tokens server-side — Don't trust client claims
3. Use short-lived tokens — Refresh tokens as needed
4. Scope permissions — Request only what you need

Resources

• GitHub: Task Manager App
• MCP Authorization Spec
• Auth0 Documentation