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 tokens. 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 a SQLAlchemy mixin for AuthorizationCode:

from authlib.integrations.sqla_oauth2 import OAuth2AuthorizationCodeMixin

class AuthorizationCode(db.Model, OAuth2AuthorizationCodeMixin):
    id = db.Column(db.Integer, primary_key=True)
    user_id = db.Column(
        db.Integer, db.ForeignKey('user.id', ondelete='CASCADE')
    )
    user = db.relationship('User')

Implement this grant by subclassing AuthorizationCodeGrant:

from authlib.oauth2.rfc6749 import grants

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,
            scope=request.scope,
            user_id=request.user.id,
        )
        db.session.add(auth_code)
        db.session.commit()
        return auth_code

    def query_authorization_code(self, code, client):
        item = AuthorizationCode.query.filter_by(
            code=code, client_id=client.client_id).first()
        if item and not item.is_expired():
            return item

    def delete_authorization_code(self, authorization_code):
        db.session.delete(authorization_code)
        db.session.commit()

    def authenticate_user(self, authorization_code):
        return User.query.get(authorization_code.user_id)

# 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, an 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 clients which have no client_secret. Default allowed Client Authentication Methods: none.

Resource Owner Password Credentials Grant¶

The resource owner uses its 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

class PasswordGrant(grants.ResourceOwnerPasswordCredentialsGrant):
    def authenticate_user(self, username, password):
        user = User.query.filter_by(username=username).first()
        if user.check_password(password):
            return user

# 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 MAYBE the client’s creator’s resources, depending on how you issue tokens to this grant type. 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 do not implement a 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):
        item = Token.query.filter_by(refresh_token=refresh_token).first()
        # define is_refresh_token_valid by yourself
        # usually, you should check if refresh token is expired and revoked
        if item and item.is_refresh_token_valid():
            return item

    def authenticate_user(self, credential):
        return User.query.get(credential.user_id)

    def revoke_old_credential(self, credential):
        credential.revoked = True
        db.session.add(credential)
        db.session.commit()

# 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.

Changed in version v0.12: Using AuthorizationEndpointMixin and TokenEndpointMixin instead of AUTHORIZATION_ENDPOINT=True and TOKEN_ENDPOINT=True.

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¶

Added in version 0.10.

Grants can accept extensions. Developers can pass extensions when registering grants:

authorization_server.register_grant(AuthorizationCodeGrant, [extension])

For instance, there is the 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.