auth: Add resource server and /user endpoint

Add a resource server with the validator for the bearer token to protect the
resources endpoints.

Add a protected `/user` endpoint that returns the user details for valid
tokens.

* gn3/auth/authentication/oauth2/resource_server.py: new file
* gn3/auth/authentication/oauth2/views.py: add /user endpoint

1 files changed, 19 insertions, 0 deletions

diff --git a/gn3/auth/authentication/oauth2/resource_server.py b/gn3/auth/authentication/oauth2/resource_server.py
new file mode 100644
index 0000000..885cbd8
--- /dev/null
+++ b/gn3/auth/authentication/oauth2/resource_server.py
@@ -0,0 +1,19 @@
+"""Protect the resources endpoints"""
+
+from flask import current_app as app
+from authlib.oauth2.rfc6750 import BearerTokenValidator as _BearerTokenValidator
+from authlib.integrations.flask_oauth2 import ResourceProtector, current_token
+
+from gn3.auth import db
+from gn3.auth.authentication.oauth2.models.oauth2token import token_by_access_token
+
+class BearerTokenValidator(_BearerTokenValidator):
+    """Extends `authlib.oauth2.rfc6750.BearerTokenValidator`"""
+    def authenticate_token(self, token_string: str):
+        with db.connection(app.config["AUTH_DB"]) as conn:
+            return token_by_access_token(conn, token_string).maybe(
+                None, lambda tok: tok)
+
+require_oauth = ResourceProtector()
+
+require_oauth.register_token_validator(BearerTokenValidator())