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

3 files changed, 63 insertions, 0 deletions

diff --git a/gn3/auth/authentication/oauth2/grants/__init__.py b/gn3/auth/authentication/oauth2/grants/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/gn3/auth/authentication/oauth2/grants/__init__.py
diff --git a/gn3/auth/authentication/oauth2/grants/authorisation_code_grant.py b/gn3/auth/authentication/oauth2/grants/authorisation_code_grant.py
new file mode 100644
index 0000000..d398192
--- /dev/null
+++ b/gn3/auth/authentication/oauth2/grants/authorisation_code_grant.py
@@ -0,0 +1,45 @@
+"""Classes and function for Authorisation Code flow."""
+import uuid
+from typing import Optional
+
+from flask import current_app as app
+from authlib.oauth2.rfc6749 import grants
+
+from gn3.auth import db
+from gn3.auth.authentication.users import User
+
+class AuthorisationCodeGrant(grants.AuthorizationCodeGrant):
+    """Implement the 'Authorisation Code' grant."""
+    TOKEN_ENDPOINT_AUTH_METHODS = ["client_secret_basic", "client_secret_post"]
+
+    def save_authorization_code(self, code, request):
+        """Persist the authorisation code to database."""
+        raise Exception("NOT IMPLEMENTED!", self, code, request)
+
+    def query_authorization_code(self, code, client):
+        """Retrieve the code from the database."""
+        raise Exception("NOT IMPLEMENTED!", self, code, client)
+
+    def delete_authorization_code(self, authorization_code):# pylint: disable=[no-self-use]
+        """Delete the authorisation code."""
+        with db.connection(app.config["AUTH_DB"]) as conn:
+            with db.cursor(conn) as cursor:
+                cursor.execute(
+                    "DELETE FROM authorisation_code WHERE code_id=?",
+                    (str(authorization_code.code_id),))
+
+    def authenticate_user(self, authorization_code) -> Optional[User]:
+        """Authenticate the user who own the authorisation code."""
+        query = (
+            "SELECT users.* FROM authorisation_code LEFT JOIN users "
+            "ON authorisation_code.user_id=users.user_id "
+            "WHERE authorisation_code.code=?")
+        with db.connection(app.config["AUTH_DB"]) as conn:
+            with db.cursor(conn) as cursor:
+                cursor.execute(query, (str(authorization_code.user_id),))
+                res = cursor.fetchone()
+                if res:
+                    return User(
+                        uuid.UUID(res["user_id"]), res["email"], res["name"])
+
+        return None
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))