swh.auth.django: Add parse decoded token to a OIDCUser utility func

Related to T3079

swh/auth/django/utils.py

+# Copyright (C) 2020-2021  The Software Heritage developers
+# See the AUTHORS file at the top-level directory of this distribution
+# License: GNU Affero General Public License version 3, or any later version
+# See top-level LICENSE file for more information
+
+from typing import Any, Dict, Optional
+
+from swh.auth.django.models import OIDCUser
+
+
+def oidc_user_from_decoded_token(
+    decoded_token: Dict[str, Any], client_id: Optional[str] = None
+) -> OIDCUser:
+    """Create an OIDCUser out of a decoded token
+
+    Args:
+        decoded_token: Decoded token Dict
+        client_id: Optional client id of the keycloak client instance used to decode
+            the token. If not provided, the permissions will be empty.
+
+    Returns:
+        The OIDCUser instance
+
+    """
+    # compute an integer user identifier for Django User model
+    # by concatenating all groups of the UUID4 user identifier
+    # generated by Keycloak and converting it from hex to decimal
+    user_id = int("".join(decoded_token["sub"].split("-")), 16)
+
+    # create a Django user that will not be saved to database
+    user = OIDCUser(
+        id=user_id,
+        username=decoded_token["preferred_username"],
+        password="",
+        first_name=decoded_token["given_name"],
+        last_name=decoded_token["family_name"],
+        email=decoded_token["email"],
+    )
+
+    # set is_staff user property based on groups
+    if "groups" in decoded_token:
+        user.is_staff = "/staff" in decoded_token["groups"]
+
+    if client_id:
+        # extract user permissions if any
+        resource_access = decoded_token.get("resource_access", {})
+        client_resource_access = resource_access.get(client_id, {})
+        permissions = client_resource_access.get("roles", [])
+    else:
+        permissions = []
+
+    user.permissions = set(permissions)
+
+    # add user sub to custom User proxy model
+    user.sub = decoded_token["sub"]
+
+    return user

swh/auth/tests/test_utils.py

+# Copyright (C) 2021  The Software Heritage developers
+# See the AUTHORS file at the top-level directory of this distribution
+# License: GNU General Public License version 3, or any later version
+# See top-level LICENSE file for more information
+
+from copy import copy
+
+from swh.auth.django.utils import oidc_user_from_decoded_token
+from swh.auth.tests.sample_data import CLIENT_ID, DECODED_TOKEN
+
+
+def test_oidc_user_from_decoded_token():
+    user = oidc_user_from_decoded_token(DECODED_TOKEN)
+
+    assert user.id == 338521271020811424925120118444075479552
+    assert user.username == "johndoe"
+    assert user.password == ""
+    assert user.first_name == "John"
+    assert user.last_name == "Doe"
+    assert user.email == "john.doe@example.com"
+    assert user.is_staff is False
+    assert user.permissions == set()
+    assert user.sub == "feacd344-b468-4a65-a236-14f61e6b7200"
+
+
+def test_oidc_user_from_decoded_token2():
+    decoded_token = copy(DECODED_TOKEN)
+    decoded_token["groups"] = ["/staff", "api"]
+    decoded_token["resource_access"] = {CLIENT_ID: {"roles": ["read-api"]}}
+
+    user = oidc_user_from_decoded_token(decoded_token, client_id=CLIENT_ID)
+
+    assert user.id == 338521271020811424925120118444075479552
+    assert user.username == "johndoe"
+    assert user.password == ""
+    assert user.first_name == "John"
+    assert user.last_name == "Doe"
+    assert user.email == "john.doe@example.com"
+    assert user.is_staff is True
+    assert user.permissions == {"read-api"}
+    assert user.sub == "feacd344-b468-4a65-a236-14f61e6b7200"