OAuth 2 Session

Changed in version v0.13: All client related code have been moved into authlib.integrations. For earlier versions of Authlib, check out their own versions documentation.

This documentation covers the common design of a Python OAuth 2.0 client. Authlib provides three implementations of OAuth 2.0 client:

  1. requests_client.OAuth2Session implementation of OAuth for Requests, which is a replacement for requests-oauthlib.

  2. httpx_client.AsyncOAuth2Client implementation of OAuth for HTTPX, which is async OAuth 2.0 client powered by HTTPX.

requests_client.OAuth2Session and httpx_client.AsyncOAuth2Client shares the same API.

There are also frameworks integrations of Flask OAuth Client, Django OAuth Client and Starlette OAuth Client. If you are using these frameworks, you may have interests in their own documentation.

If you are not familiar with OAuth 2.0, it is better to read Introduce OAuth 2.0 now.

OAuth2Session for Authorization Code

There are two steps in OAuth 2 to obtain an access token with authorization code grant type. Initialize the session for reuse:

>>> client_id = 'Your GitHub client ID'
>>> client_secret = 'Your GitHub client secret'
>>> scope = 'user:email'  # we want to fetch user's email
>>>
>>> # using requests implementation
>>> from authlib.integrations.requests_client import OAuth2Session
>>> client = OAuth2Session(client_id, client_secret, scope=scope)
>>>
>>> # using httpx implementation
>>> from authlib.integrations.httpx_client import AsyncOAuth2Client
>>> client = AsyncOAuth2Client(client_id, client_secret, scope=scope)

You can assign a redirect_uri in case you want to specify the callback url.

Redirect to Authorization Endpoint

Unlike OAuth 1, there is no request token. The first step is to jump to the remote authorization server:

>>> authorization_endpoint = 'https://github.com/login/oauth/authorize'
>>> uri, state = client.create_authorization_url(authorization_endpoint)
>>> print(uri)
https://github.com/login/oauth/authorize?response_type=code&client_id=c..id&scope=user%3Aemail&state=d..t

The create_authorization_url returns a tuple of (uri, state), in real project, you should save the state for later use.

Now head over to the generated authorization url, and grant the authorization.

Fetch Token

The authorization server will redirect you back to your site with a code and state arguments:

https://example.com/github?code=42..e9&state=d..t

Use .fetch_token to obtain access token. This method will also verify the state in case of CSRF attack:

>>> authorization_response = 'https://example.com/github?code=42..e9&state=d..t'
>>> token_endpoint = 'https://github.com/login/oauth/access_token'
>>> token = client.fetch_token(token_endpoint, authorization_response=authorization_response)
>>> print(token)
{
    'access_token': 'e..ad',
    'token_type': 'bearer',
    'scope': 'user:email'
}

Save this token to access users’ protected resources.

In real project, this session can not be re-used since you are redirected to another website. You need to create another session yourself:

>>> state = restore_previous_state()
>>>
>>> # using requests
>>> from authlib.integrations.requests_client import OAuth2Session
>>> client = OAuth2Session(client_id, client_secret, state=state)
>>>
>>> # using httpx
>>> from authlib.integrations.httpx_client import AsyncOAuth2Client
>>> client = AsyncOAuth2Client(client_id, client_secret, state=state)
>>>
>>> await client.fetch_token(token_endpoint, authorization_response=authorization_response)

Authlib has a built-in Flask/Django integration. Learn from them.

OAuth2Session for Implicit

OAuth2Session supports implicit grant type. It can fetch the access token with the response_type of token:

>>> uri, state = client.create_authorization_url(authorization_endpoint, response_type='token')
>>> print(uri)
https://some-service.com/oauth/authorize?response_type=token&client_id=be..4d&...

Visit this link, and grant the authorization, the OAuth authoirzation server will redirect back to your redirect_uri, the response url would be something like:

https://example.com/cb#access_token=2..WpA&state=xyz&token_type=bearer&expires_in=3600

Fetch access token from the fragment with .fetch_token method:

>>> token = client.fetch_token(authorization_response=authorization_response)
>>> # if you don't specify access token endpoint, it will fetch from fragment.
>>> print(token)
{'access_token': '2..WpA', 'token_type': 'bearer', 'expires_in': 3600}

Note

GitHub doesn’t support token response type, try with other services.

OAuth2Session for Password

The password grant type is supported since Version 0.5. Use username and password to fetch the access token:

>>> token = client.fetch_token(token_endpoint, username='a-name', password='a-password')

OAuth2Session for Client Credentials

The client_credentials grant type is supported since Version 0.5. If no code or no user info provided, it would be a client_credentials request. But it is suggested that you specify a grant_type for it:

>>> token = client.fetch_token(token_endpoint)
>>> # or with grant_type
>>> token = client.fetch_token(token_endpoint, grant_type='client_credentials')

Client Authentication

When fetching access token, the authorization server will require a client authentication, Authlib provides three default methods defined by RFC7591:

  • client_secret_basic

  • client_secret_post

  • none

The default value is client_secret_basic. You can change the auth method with token_endpoint_auth_method:

>>> client = OAuth2Session(token_endpoint_auth_method='client_secret_post')

If the authorization server requires other means of authentication, you can construct an auth for your own need, and pass it to fetch_token:

>>> auth = YourAuth(...)
>>> token = client.fetch_token(token_endpoint, auth=auth, ...)

It is also possible to extend the client authentication method with .register_client_auth_method. Besides the default three authentication methods, there are more provided by Authlib. e.g.

  • client_secret_jwt

  • private_key_jwt

These two methods are defined by RFC7523 and OpenID Connect. Find more in Using JWTs Client Assertion in OAuth2Session.

There are still cases that developers need to define a custom client authentication method. Take issue#158 as an example, the provider requires us put client_id and client_secret on URL when sending POST request:

POST /oauth/token?grant_type=code&code=...&client_id=...&client_secret=...

Let’s call this weird authentication method client_secret_uri, and this is how we can get our OAuth 2.0 client authenticated:

from authlib.common.urls import add_params_to_uri

def auth_client_secret_uri(client, method, uri, headers, body):
    uri = add_params_to_uri(uri, [
        ('client_id', client.client_id),
        ('client_secret', client.client_secret),
    ])
    uri = uri + '&' + body
    body = ''
    return uri, headers, body

client = OAuth2Session(
    'client_id', 'client_secret',
    token_endpoint_auth_method='client_secret_uri',
    ...
)
client.register_client_auth_method(('client_secret_uri', auth_client_secret_uri))

With client_secret_uri registered, OAuth 2.0 client will authenticate with the signed URI. It is also possible to assign the function to token_endpoint_auth_method directly:

client = OAuth2Session(
    'client_id', 'client_secret',
    token_endpoint_auth_method=auth_client_secret_uri,
)

Access Protected Resources

Now you can access the protected resources. If you re-use the session, you don’t need to do anything:

>>> account_url = 'https://api.github.com/user'
>>> resp = client.get(account_url)
<Response [200]>
>>> resp.json()
{...}

The above is not the real flow, just like what we did in Fetch Token, we need to create another session ourselves:

>>> token = restore_previous_token_from_database()
>>> # token is a dict which must contain ``access_token``, ``token_type``
>>> client = OAuth2Session(client_id, client_secret, token=token)
>>> account_url = 'https://api.github.com/user'
>>> resp = client.get(account_url)

Refresh & Auto Update Token

It is possible that your previously saved token is expired when accessing protected resources. In this case, we can refresh the token manually, or even better, Authlib will refresh the token automatically and update the token for us.

To call refresh_token() manually means we are going to exchange a new “access_token” with “refresh_token”:

>>> token = restore_previous_token_from_database()
>>> new_token = client.refresh_token(token_endpoint, refresh_token=token.refresh_token)

Authlib can also refresh a new token automatically when requesting resources. This is done by passing a update_token function when constructing the client instance:

def update_token(token, refresh_token=None, access_token=None):
    if refresh_token:
        item = OAuth2Token.find(name=name, refresh_token=refresh_token)
    elif access_token:
        item = OAuth2Token.find(name=name, access_token=access_token)
    else:
        return

    # update old token
    item.access_token = token['access_token']
    item.refresh_token = token.get('refresh_token')
    item.expires_at = token['expires_at']
    item.save()

client = OAuth2Session(client_id, client_secret, update_token=update_token)

When sending a request to resources endpoint, if our previously saved token is expired, this client will invoke .refresh_token method itself and call this our defined update_token to save the new token:

token = restore_previous_token_from_database()
client.token = token

# if the token is expired, this GET request will update token
client.get('https://openidconnect.googleapis.com/v1/userinfo')

Revoke and Introspect Token

If the provider support token revocation and introspection, you can revoke and introspect the token with:

token_endpoint = 'https://example.com/oauth/token'

token = get_your_previous_saved_token()
client.revoke_token(token_endpoint, token=token)
client.introspect_token(token_endpoint, token=token)

You can find the available parameters in API docs:

Compliance Fix for non Standard

There are services that claimed they are providing OAuth API, but with a little differences. Some services even return with the wrong Content Type. Compliance hooks are provided to solve those problems:

  • access_token_response: invoked before token parsing.

  • refresh_token_response: invoked before refresh token parsing.

  • protected_request: invoked before making a request.

For instance, Stackoverflow MUST add a site parameter in query string to protect users’ resources. And stackoverflow’s response is not in JSON. Let’s fix it:

from authlib.common.urls import add_params_to_uri, url_decode

def _non_compliant_param_name(url, headers, data):
    params = {'site': 'stackoverflow'}
    url = add_params_to_uri(url, params)
    return url, headers, body

def _fix_token_response(resp):
    data = dict(url_decode(resp.text))
    data['token_type'] = 'Bearer'
    data['expires_in'] = int(data['expires'])
    resp.json = lambda: data
    return resp

session.register_compliance_hook(
    'protected_request', _non_compliant_param_name)
session.register_compliance_hook(
    'access_token_response', _fix_token_response)

If you find a non standard OAuth 2 services, and you can’t fix it. Please report it in GitHub issues.

OAuth 2 OpenID Connect

For services that support OpenID Connect, if a scope of openid is provided, the authorization server will return a value of id_token in response:

>>> client_id = 'Your Google client ID'
>>> client_secret = 'Your Google client secret'
>>> scope = 'openid email profile'
>>> # using requests
>>> client = OAuth2Session(client_id, client_secret, scope=scope)
>>> # using httpx
>>> client = AsyncOAuth2Client(client_id, client_secret, scope=scope)

The remote server may require other parameters for OpenID Connect requests, for instance, it may require a nonce parameter, in this case, you need to generate it yourself, and pass it to create_authorization_url:

>>> from authlib.common.security import generate_token
>>> # remember to save this nonce for verification
>>> nonce = generate_token()
>>> client.create_authorization_url(url, redirect_uri='xxx', nonce=nonce, ...)

At the last step of client.fetch_token, the return value contains a id_token:

>>> resp = session.fetch_token(...)
>>> print(resp['id_token'])

This id_token is a JWT text, it can not be used unless it is parsed. Authlib has provided tools for parsing and validating OpenID Connect id_token:

>>> from authlib.oidc.core import CodeIDToken
>>> from authlib.jose import jwt
>>> # GET keys from https://www.googleapis.com/oauth2/v3/certs
>>> claims = jwt.decode(resp['id_token'], keys, claims_cls=CodeIDToken)
>>> claims.validate()

Get deep inside with JsonWebToken and CodeIDToken. Learn how to validate JWT claims at JSON Web Token (JWT).

AssertionSession

AssertionSession is a Requests Session for Assertion Framework of OAuth 2.0 Authorization Grants. It is also know as service account. A configured AssertionSession with handle token authorization automatically, which means you can just use it.

Take Google Service Account as an example, with the information in your service account JSON configure file:

import json
from authlib.integrations.requests_client import AssertionSession

with open('MyProject-1234.json') as f:
    conf = json.load(f)

token_uri = conf['token_uri']
header = {'alg': 'RS256'}
key_id = conf.get('private_key_id')
if key_id:
    header['kid'] = key_id

# Google puts scope in payload
claims = {'scope': scope}

session = AssertionSession(
    token_endpoint=token_uri,
    issuer=conf['client_email'],
    audience=token_uri,
    claims=claims,
    subject=None,
    key=conf['private_key'],
    header=header,
)
session.get(...)
session.post(...)

There is a ready to use GoogleServiceAccount in loginpass. You can also read these posts: