change(python): rework session timing

Previously, we were just relying on the cookie expiration
for sessions to expire. We were not cleaning up Session
records either.

Rework timing to depend on an AURREMEMBER cookie which is
now emitted on login during BasicAuthBackend processing.

If the SID does still have a session but it's expired,
we now delete the session record before returning.

Otherwise, we update the session's LastUpdateTS to
the current time.

In addition, stored the unauthenticated result value
in a variable to reduce redundancy.

Signed-off-by: Kevin Morris <kevr@0cost.org>

aurweb/auth/__init__.py

@@ -7,7 +7,6 @@ import fastapi
 
 from fastapi import HTTPException
 from fastapi.responses import RedirectResponse
-from sqlalchemy import and_
 from starlette.authentication import AuthCredentials, AuthenticationBackend
 from starlette.requests import HTTPConnection
 
@@ -97,18 +96,27 @@ class AnonymousUser:
 
 class BasicAuthBackend(AuthenticationBackend):
     async def authenticate(self, conn: HTTPConnection):
+        unauthenticated = (None, AnonymousUser())
         sid = conn.cookies.get("AURSID")
         if not sid:
-            return (None, AnonymousUser())
+            return unauthenticated
 
-        now_ts = datetime.utcnow().timestamp()
-        record = db.query(Session).filter(
-            and_(Session.SessionID == sid,
-                 Session.LastUpdateTS >= now_ts)).first()
+        timeout = aurweb.config.getint("options", "login_timeout")
+        remembered = ("AURREMEMBER" in conn.cookies
+                      and bool(conn.cookies.get("AURREMEMBER")))
+        if remembered:
+            timeout = aurweb.config.getint("options",
+                                           "persistent_cookie_timeout")
 
         # If no session with sid and a LastUpdateTS now or later exists.
+        now_ts = int(datetime.utcnow().timestamp())
+        record = db.query(Session).filter(Session.SessionID == sid).first()
         if not record:
-            return (None, AnonymousUser())
+            return unauthenticated
+        elif record.LastUpdateTS < (now_ts - timeout):
+            with db.begin():
+                db.delete_all([record])
+            return unauthenticated
 
         # At this point, we cannot have an invalid user if the record
         # exists, due to ForeignKey constraints in the schema upheld