From 8f35b31ab82f5b665460966cec7c1bef323137c1 Mon Sep 17 00:00:00 2001 From: Ben Darnell Date: Sat, 13 May 2023 20:58:52 -0400 Subject: [PATCH] web: Fix an open redirect in StaticFileHandler Under some configurations the default_filename redirect could be exploited to redirect to an attacker-controlled site. This change refuses to redirect to URLs that could be misinterpreted. A test case for the specific vulnerable configuration will follow after the patch has been available. --- tornado/web.py | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/tornado/web.py b/tornado/web.py index 3b676e3c2..565140493 100644 --- a/tornado/web.py +++ b/tornado/web.py @@ -2879,6 +2879,15 @@ class StaticFileHandler(RequestHandler): # but there is some prefix to the path that was already # trimmed by the routing if not self.request.path.endswith("/"): + if self.request.path.startswith("//"): + # A redirect with two initial slashes is a "protocol-relative" URL. + # This means the next path segment is treated as a hostname instead + # of a part of the path, making this effectively an open redirect. + # Reject paths starting with two slashes to prevent this. + # This is only reachable under certain configurations. + raise HTTPError( + 403, "cannot redirect path with two initial slashes" + ) self.redirect(self.request.path + "/", permanent=True) return None absolute_path = os.path.join(absolute_path, self.default_filename) -- 2.47.2