Merge pull request #3267 from bdarnell/branch6.3

Version 6.3.2

docs/releases.rst

@@ -4,6 +4,7 @@ Release notes
 .. toctree::
    :maxdepth: 2
 
+   releases/v6.3.2
    releases/v6.3.1
    releases/v6.3.0
    releases/v6.2.0

docs/releases/v6.3.2.rst

@@ -0,0 +1,11 @@
+What's new in Tornado 6.3.2
+===========================
+
+May 13, 2023
+------------
+
+Security improvements
+~~~~~~~~~~~~~~~~~~~~~
+
+- Fixed an open redirect vulnerability in StaticFileHandler under certain
+  configurations.

tornado/__init__.py

@@ -22,8 +22,8 @@
 # is zero for an official release, positive for a development branch,
 # or negative for a release candidate or beta (after the base version
 # number has been incremented)
-version = "6.3.1"
-version_info = (6, 3, 1, 0)
+version = "6.3.2"
+version_info = (6, 3, 2, 0)
 
 import importlib
 import typing

tornado/web.py

@@ -2879,6 +2879,15 @@ def validate_absolute_path(self, root: str, absolute_path: str) -> Optional[str]
             # 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)