Validate internal tool owner attribution

app.py

@@ -224,13 +224,15 @@ if AUTH_ENABLED:
                 _hdr = request.headers.get(INTERNAL_TOOL_HEADER)
                 if _hdr and _hdr == _ITT and _is_trusted_loopback(request):
                     # Impersonation: when the agent's loopback call sets
-                    # X-Odysseus-Owner, attribute the request to that
-                    # user so notes/calendar/etc. land in their account
-                    # instead of being owned by "internal-tool" (which
-                    # made the agent's POSTs invisible to the user that
-                    # asked for them).
+                    # X-Odysseus-Owner, attribute the request to that user only
+                    # if they exist. Authorization checks remain separate; this
+                    # is just owner attribution for notes/calendar/etc.
                     _impersonate = (request.headers.get("X-Odysseus-Owner") or "").strip()
-                    request.state.current_user = _impersonate or "internal-tool"
+                    _auth_mgr = getattr(request.app.state, "auth_manager", None) or auth_manager
+                    if _impersonate and _impersonate in getattr(_auth_mgr, "users", {}):
+                        request.state.current_user = _impersonate
+                    else:
+                        request.state.current_user = "internal-tool"
                     request.state.api_token = False
                     return await call_next(request)
             except Exception:

tests/test_security_regressions.py

@@ -305,6 +305,26 @@ def test_require_admin_allows_when_auth_explicitly_disabled(monkeypatch):
     assert require_admin(_Req()) is None
 
 
+def test_internal_tool_owner_header_logic_requires_known_user():
+    """Pin the owner-attribution branch used by app.AuthMiddleware without
+    booting the full FastAPI app."""
+    users = {
+        "alice": {"is_admin": False},
+        "AdminUser": {"is_admin": True},
+    }
+
+    def resolve_owner(header_value):
+        impersonate = (header_value or "").strip()
+        if impersonate and impersonate in users:
+            return impersonate
+        return "internal-tool"
+
+    assert resolve_owner("alice") == "alice"
+    assert resolve_owner("AdminUser") == "AdminUser"
+    assert resolve_owner("doesnotexist") == "internal-tool"
+    assert resolve_owner("") == "internal-tool"
+
+
 def test_auth_manager_migrates_legacy_admin_role(tmp_path):
     """Old setup.py wrote role='admin'; startup must turn that into is_admin."""
     sys.modules.pop("core.auth", None)