auth: implement OAuth2 flow.oauth2_auth_flow

Add code to implement the OAuth2 flow.

* Add test fixtures for setting up users and OAuth2 clients
* Add tests for token generation with the "Password Grant" flow
* Fix some issues with test due to changes in the database connection's
  row_factory

1 files changed, 18 insertions, 0 deletions

diff --git a/gn3/auth/authentication/oauth2/grants/password_grant.py b/gn3/auth/authentication/oauth2/grants/password_grant.py
new file mode 100644
index 0000000..91fdb7c
--- /dev/null
+++ b/gn3/auth/authentication/oauth2/grants/password_grant.py
@@ -0,0 +1,18 @@
+"""Allows users to authenticate directly."""
+
+from flask import current_app as app
+from authlib.oauth2.rfc6749 import grants
+
+from gn3.auth import db
+from gn3.auth.authentication.users import valid_login, user_by_email
+
+class PasswordGrant(grants.ResourceOwnerPasswordCredentialsGrant):
+    """Implement the 'Password' grant."""
+    TOKEN_ENDPOINT_AUTH_METHODS = ["client_secret_basic", "client_secret_post"]
+
+    def authenticate_user(self, username, password):
+        "Authenticate the user with their username and password."
+        with db.connection(app.config["AUTH_DB"]) as conn:
+            return user_by_email(conn, username).maybe(
+                None,
+                lambda user: valid_login(conn, user, password))