# Starlette OAuth Client

Starlette is a lightweight ASGI framework/toolkit, which is ideal for building high performance asyncio services.

This documentation covers OAuth 1.0, OAuth 2.0 and OpenID Connect Client support for Starlette. Because all the frameworks integrations share the same API, it is best to:

Read Web OAuth Clients at first.

The difference between Starlette and Flask/Django integrations is Starlette is async. We will use `await` for the functions we need to call. But first, let’s create an `OAuth` instance:

    from authlib.integrations.starlette_client import OAuth

    oauth = OAuth()

The common use case for OAuth is authentication, e.g. let your users log in with Twitter, GitHub, Google etc.

## Configuration

Starlette can load configuration from environment; Authlib implementation for Starlette client can use this configuration. Here is an example of how to do it:

    from starlette.config import Config

    config = Config('.env')
    oauth = OAuth(config)

Authlib will load `client_id` and `client_secret` from the configuration, take google as an example:

    oauth.register(name='google', ...)

It will load GOOGLE_CLIENT_ID and GOOGLE_CLIENT_SECRET from the environment.

## Register Remote Apps

`oauth.register` is the same as Web OAuth Clients:

    oauth.register(
        'google',
        client_id='...',
        client_secret='...',
        ...
    )

However, unlike Flask/Django, Starlette OAuth registry is using HTTPX `AsyncOAuth1Client` and `AsyncOAuth2Client` as the OAuth backends. While Flask and Django are using the Requests version of `OAuth1Session` and `OAuth2Session`.

## Enable Session for OAuth 1.0

With OAuth 1.0, we need to use a temporary credential to exchange for an access token. This temporary credential is created before redirecting to the provider (Twitter), and needs to be saved somewhere in order to use it later.

With OAuth 1, the Starlette client will save the request token in sessions. To enable this, we need to add the `SessionMiddleware` middleware to the application, which requires the installation of the `itsdangerous` package:

    from starlette.applications import Starlette
    from starlette.middleware.sessions import SessionMiddleware

    app = Starlette()
    app.add_middleware(SessionMiddleware, secret_key="some-random-string")

However, using the `SessionMiddleware` will store the temporary credential as a secure cookie which will expose your request token to the client.

## Routes for Authorization

Just like the examples in Web OAuth Clients, but Starlette is async, the routes for authorization should look like:

    @app.route('/login/google')
    async def login_via_google(request):
        google = oauth.create_client('google')
        redirect_uri = request.url_for('authorize_google')
        return await google.authorize_redirect(request, redirect_uri)

    @app.route('/auth/google')
    async def authorize_google(request):
        google = oauth.create_client('google')
        token = await google.authorize_access_token(request)
        # do something with the token and userinfo
        return '...'

## Starlette OpenID Connect

An OpenID Connect client is no different than a normal OAuth 2.0 client, just add `openid` scope when `.register`. The built-in Starlette OAuth client will handle everything automatically:

    oauth.register(
        'google',
        ...
        server_metadata_url='https://accounts.google.com/.well-known/openid-configuration',
        client_kwargs={'scope': 'openid profile email'}
    )

When we get the returned token:

    token = await oauth.google.authorize_access_token()

There should be a `id_token` in the response. Authlib has called .parse_id_token automatically, we can get `userinfo` in the `token`:

    userinfo = token['userinfo']

## Examples

We have Starlette demos at https://github.com/authlib/demo-oauth-client

1. OAuth 1.0: Starlette Twitter login

2. OAuth 2.0: Starlette Google login