Register Grants¶

There are four grant types defined by RFC6749, you can also create your own extended grant. Register the supported grant types to the authorization server.

Authorization Code Grant¶

Authorization Code Grant is a very common grant type, it is supported by almost every OAuth 2 providers. It uses an authorization code to exchange access token. In this case, we need a place to store the authorization code. It can be kept in a database or a cache like redis. Here is an example of database AuthorizationCode:

from django.db.models import ForeignKey, CASCADE
from django.contrib.auth.models import User
from authlib.oauth2.rfc6749 import AuthorizationCodeMixin

def now_timestamp():
    return int(time.time())

class AuthorizationCode(Model, AuthorizationCodeMixin):
    user = ForeignKey(User, on_delete=CASCADE)
    client_id = CharField(max_length=48, db_index=True)
    code = CharField(max_length=120, unique=True, null=False)
    redirect_uri = TextField(default='', null=True)
    response_type = TextField(default='')
    scope = TextField(default='', null=True)
    auth_time = IntegerField(null=False, default=now_timestamp)

    def is_expired(self):
        return self.auth_time + 300 < time.time()

    def get_redirect_uri(self):
        return self.redirect_uri

    def get_scope(self):
        return self.scope or ''

    def get_auth_time(self):
        return self.auth_time

Note here, you MUST implement the missing methods of AuthorizationCodeMixin API interface.

Later, you can use this AuthorizationCode database model to handle authorization_code grant type. Here is how:

from authlib.oauth2.rfc6749 import grants
from authlib.common.security import generate_token

class AuthorizationCodeGrant(grants.AuthorizationCodeGrant):
    def save_authorization_code(self, code, request):
        client = request.client
        auth_code = AuthorizationCode(
            code=code,
            client_id=client.client_id,
            redirect_uri=request.redirect_uri,
            response_type=request.response_type,
            scope=request.scope,
            user=request.user,
        )
        auth_code.save()
        return auth_code

    def query_authorization_code(self, code, client):
        try:
            item = AuthorizationCode.objects.get(code=code, client_id=client.client_id)
        except AuthorizationCode.DoesNotExist:
            return None

        if not item.is_expired():
            return item

    def delete_authorization_code(self, authorization_code):
        authorization_code.delete()

    def authenticate_user(self, authorization_code):
        return authorization_code.user

# register it to grant endpoint
server.register_grant(AuthorizationCodeGrant)

Note

AuthorizationCodeGrant is the most complex grant.

Default allowed Client Authentication Methods are:

client_secret_basic
client_secret_post
none

You can change it in the subclass, e.g. remove the none authentication method:

class AuthorizationCodeGrant(grants.AuthorizationCodeGrant):
    TOKEN_ENDPOINT_AUTH_METHODS = ['client_secret_basic', 'client_secret_post']

Note

This is important when you want to support OpenID Connect.

Implicit Grant¶

The implicit grant type is usually used in a browser, when resource owner granted the access, access token is issued in the redirect URI, there is no missing implementation, which means it can be easily registered with:

from authlib.oauth2.rfc6749 import grants

# register it to grant endpoint
server.register_grant(grants.ImplicitGrant)

Implicit Grant is used by public client which has no client_secret. Only allowed Client Authentication Methods: none.

Resource Owner Password Credentials Grant¶

Resource owner uses their username and password to exchange an access token, this grant type should be used only when the client is trustworthy, implement it with a subclass of ResourceOwnerPasswordCredentialsGrant:

from authlib.oauth2.rfc6749 import grants
from django.contrib.auth.models import User

class PasswordGrant(grants.ResourceOwnerPasswordCredentialsGrant):
    def authenticate_user(self, username, password):
        try:
            user = User.objects.get(username=username)
            if user.check_password(password):
                return user
        except User.DoesNotExist:
            return None

# register it to grant endpoint
server.register_grant(PasswordGrant)

Default allowed Client Authentication Methods: client_secret_basic. You can add more in the subclass:

class PasswordGrant(grants.ResourceOwnerPasswordCredentialsGrant):
    TOKEN_ENDPOINT_AUTH_METHODS = [
        'client_secret_basic', 'client_secret_post'
    ]

Client Credentials Grant¶

Client credentials grant type can access public resources and the client’s creator’s resources. It can be easily registered with:

from authlib.oauth2.rfc6749 import grants

# register it to grant endpoint
server.register_grant(grants.ClientCredentialsGrant)

Default allowed Client Authentication Methods: client_secret_basic. You can add more in the subclass:

class ClientCredentialsGrant(grants.ClientCredentialsGrant):
    TOKEN_ENDPOINT_AUTH_METHODS = [
        'client_secret_basic', 'client_secret_post'
    ]

Refresh Token Grant¶

Many OAuth 2 providers haven’t implemented refresh token endpoint. Authlib provides it as a grant type, implement it with a subclass of RefreshTokenGrant:

from authlib.oauth2.rfc6749 import grants

class RefreshTokenGrant(grants.RefreshTokenGrant):
    def authenticate_refresh_token(self, refresh_token):
        try:
            item = OAuth2Token.objects.get(refresh_token=refresh_token)
            if item.is_refresh_token_active():
                return item
        except OAuth2Token.DoesNotExist:
            return None

    def authenticate_user(self, credential):
        return credential.user

    def revoke_old_credential(self, credential):
        credential.revoked = True
        credential.save()

# register it to grant endpoint
server.register_grant(RefreshTokenGrant)

Default allowed Client Authentication Methods: client_secret_basic. You can add more in the subclass:

class RefreshTokenGrant(grants.RefreshTokenGrant):
    TOKEN_ENDPOINT_AUTH_METHODS = [
        'client_secret_basic', 'client_secret_post'
    ]

By default, RefreshTokenGrant will not issue a refresh_token in the token response. Developers can change this behavior with:

class RefreshTokenGrant(grants.RefreshTokenGrant):
    INCLUDE_NEW_REFRESH_TOKEN = True

Custom Grant Types¶

It is also possible to create your own grant types. In Authlib, a Grant supports two endpoints:

Authorization Endpoint: which can handle requests with response_type.
Token Endpoint: which is the endpoint to issue tokens.

Creating a custom grant type with BaseGrant:

from authlib.oauth2.rfc6749.grants import (
    BaseGrant, AuthorizationEndpointMixin, TokenEndpointMixin
)

class MyCustomGrant(BaseGrant, AuthorizationEndpointMixin, TokenEndpointMixin):
    GRANT_TYPE = 'custom-grant-type-name'

    def validate_authorization_request(self):
        # only needed if using AuthorizationEndpointMixin

    def create_authorization_response(self, grant_user):
        # only needed if using AuthorizationEndpointMixin

    def validate_token_request(self):
        # only needed if using TokenEndpointMixin

    def create_token_response(self):
        # only needed if using TokenEndpointMixin

For a better understanding, you can read the source code of the built-in grant types. And there are extended grant types defined by other specs:

Using JWTs as Authorization Grants

Grant Extensions¶

Grant can accept extensions. Developers can pass extensions when registering grant:

server.register_grant(AuthorizationCodeGrant, [extension])

For instance, there is CodeChallenge extension in Authlib:

server.register_grant(AuthorizationCodeGrant, [CodeChallenge(required=False)])

Learn more about CodeChallenge at RFC7636: Proof Key for Code Exchange by OAuth Public Clients.