Flask OIDC Provider¶

OpenID Connect 1.0 is supported since version 0.6. The integrations are built with Custom Grant Types and Grant Extensions. Since OpenID Connect is built on OAuth 2.0 frameworks, you need to read Flask OAuth 2.0 Server at first.

Changed in version v0.12: The Grant system has been redesigned from v0.12. This documentation ONLY works for Authlib >=v0.12.

Looking for OpenID Connect Client? Head over to Flask OAuth Client.

Understand JWT¶

OpenID Connect 1.0 uses JWT a lot. Make sure you have the basic understanding of JOSE Guide.

For OpenID Connect, we need to understand at least four concepts:

alg: Algorithm for JWT
key: Private key for JWT
iss: Issuer value for JWT
exp: JWT expires time

alg¶

The algorithm to sign a JWT. This is the alg value defined in header part of a JWS:

{"alg": "RS256"}

The available algorithms are defined in RFC7518: JSON Web Algorithms, which are:

HS256: HMAC using SHA-256
HS384: HMAC using SHA-384
HS512: HMAC using SHA-512
RS256: RSASSA-PKCS1-v1_5 using SHA-256
RS384: RSASSA-PKCS1-v1_5 using SHA-384
RS512: RSASSA-PKCS1-v1_5 using SHA-512
ES256: ECDSA using P-256 and SHA-256
ES384: ECDSA using P-384 and SHA-384
ES512: ECDSA using P-521 and SHA-512
PS256: RSASSA-PSS using SHA-256 and MGF1 with SHA-256
PS384: RSASSA-PSS using SHA-384 and MGF1 with SHA-384
PS512: RSASSA-PSS using SHA-512 and MGF1 with SHA-512

The HMAC using SHA algorithms are not suggested since you need to share secrets between server and client. Most OpenID Connect services are using RS256.

key¶

A private key is required to generate a JWT. The key that you are going to use dependents on the alg you are using. For instance, the alg is RS256, you need to use an RSA private key. It can be set with:

key = '''-----BEGIN RSA PRIVATE KEY-----\nMIIEog...'''

# or in JWK format
key = {"kty": "RSA", "n": ...}

iss¶

The iss value in the JWT payload. The value can be your website name or URL. For example, Google is using:

{"iss": "https://accounts.google.com"}

Code Flow¶

OpenID Connect authorization code flow relies on the OAuth2 authorization code flow and extends it.

OpenID Connect Code flow is the same as Authorization Code flow, but with extended features. We can apply the OpenIDCode extension to Authorization Code Grant.

First, we need to implement the missing methods for OpenIDCode:

from authlib.oidc.core import grants, UserInfo

class OpenIDCode(grants.OpenIDCode):
    def exists_nonce(self, nonce, request):
        exists = AuthorizationCode.query.filter_by(
            client_id=request.client_id, nonce=nonce
        ).first()
        return bool(exists)

    def get_jwt_config(self, grant):
        return {
            'key': read_private_key_file(key_path),
            'alg': 'RS512',
            'iss': 'https://example.com',
            'exp': 3600
        }

    def generate_user_info(self, user, scope):
        user_info = UserInfo(sub=user.id, name=user.name)
        if 'email' in scope:
            user_info['email'] = user.email
        return user_info

Second, since there is one more nonce value in the AuthorizationCode data, we need to save this value into the database. In this case, we have to update our Authorization Code Grant save_authorization_code method:

class AuthorizationCodeGrant(_AuthorizationCodeGrant):
    def save_authorization_code(self, code, request):
        # openid request MAY have "nonce" parameter
        nonce = request.data.get('nonce')
        auth_code = AuthorizationCode(
            code=code,
            client_id=request.client.client_id,
            redirect_uri=request.redirect_uri,
            scope=request.scope,
            user_id=request.user.id,
            nonce=nonce,
        )
        db.session.add(auth_code)
        db.session.commit()
        return auth_code

    # ...

Finally, you can register AuthorizationCodeGrant with the OpenIDCode extension:

# register it to grant endpoint
server.register_grant(AuthorizationCodeGrant, [OpenIDCode(require_nonce=True)])

The difference between OpenID Code flow and the standard code flow is that OpenID Connect requests have a scope of “openid”:

GET /authorize?
response_type=code
&scope=openid%20profile%20email
&client_id=s6BhdRkqt3
&state=af0ifjsldkj
&redirect_uri=https%3A%2F%2Fclient.example.org%2Fcb HTTP/1.1
Host: server.example.com

With the example above, you will also have to change the scope of your client in your application to something like openid profile email.

Now that you added the openid scope to your application, an OpenID token will be provided to this app whenever a client asks for a token with an openid scope.

Implicit Flow¶

The Implicit Flow is mainly used by Clients implemented in a browser using a scripting language. You need to implement the missing methods of OpenIDImplicitGrant before registering it:

from authlib.oidc.core import grants

class OpenIDImplicitGrant(grants.OpenIDImplicitGrant):
    def exists_nonce(self, nonce, request):
        exists = AuthorizationCode.query.filter_by(
            client_id=request.client_id, nonce=nonce
        ).first()
        return bool(exists)

    def get_jwt_config(self):
        return {
            'key': read_private_key_file(key_path),
            'alg': 'RS512',
            'iss': 'https://example.com',
            'exp': 3600
        }

    def generate_user_info(self, user, scope):
        user_info = UserInfo(sub=user.id, name=user.name)
        if 'email' in scope:
            user_info['email'] = user.email
        return user_info

server.register_grant(OpenIDImplicitGrant)

Hybrid Flow¶

The Hybrid flow is a mix of code flow and implicit flow. You only need to implement the authorization endpoint part, as token endpoint will be handled by Authorization Code Flow.

OpenIDHybridGrant is a subclass of OpenIDImplicitGrant, so the missing methods are the same, except that OpenIDHybridGrant has one more missing method, that is save_authorization_code. You can implement it like this:

from authlib.oidc.core import grants
from authlib.common.security import generate_token

class OpenIDHybridGrant(grants.OpenIDHybridGrant):
    def save_authorization_code(self, code, request):
        nonce = request.data.get('nonce')
        item = AuthorizationCode(
            code=code,
            client_id=request.client.client_id,
            redirect_uri=request.redirect_uri,
            scope=request.scope,
            user_id=request.user.id,
            nonce=nonce,
        )
        db.session.add(item)
        db.session.commit()
        return code

    def exists_nonce(self, nonce, request):
        exists = AuthorizationCode.query.filter_by(
            client_id=request.client_id, nonce=nonce
        ).first()
        return bool(exists)

    def get_jwt_config(self):
        return {
            'key': read_private_key_file(key_path),
            'alg': 'RS512',
            'iss': 'https://example.com',
            'exp': 3600
        }

    def generate_user_info(self, user, scope):
        user_info = UserInfo(sub=user.id, name=user.name)
        if 'email' in scope:
            user_info['email'] = user.email
        return user_info

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

Since all OpenID Connect Flow require exists_nonce, get_jwt_config and generate_user_info methods, you can create shared functions for them.

Find the example of OpenID Connect server.