fix: Port CVE-2024-32982 path traversal fix to v3.0 (#3524)

* Backport static files path traversal fix

Author: provinzkraut

litestar/static_files.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import os
 from os.path import commonpath
 from pathlib import Path, PurePath
 from typing import TYPE_CHECKING, Any, Literal, Mapping, Sequence
@@ -83,7 +84,7 @@ def create_static_files_router(
     if file_system is None:
         file_system = BaseLocalFileSystem()
 
-    directories = list(directories)
+    directories = tuple(os.path.normpath(Path(p).resolve() if resolve_symlinks else Path(p)) for p in directories)
 
     _validate_config(path=path, directories=directories, file_system=file_system)
     path = normalize_path(path)
@@ -225,19 +226,26 @@ async def _get_fs_info(
         try:
             joined_path = Path(directory, file_path)
             file_info = await adapter.info(joined_path)
-            if file_info and commonpath([str(directory), file_info["name"], joined_path]) == str(directory):
+            normalized_file_path = os.path.normpath(joined_path)
+            directory_path = str(directory)
+            if (
+                file_info
+                and commonpath([directory_path, file_info["name"], joined_path]) == directory_path
+                and os.path.commonpath([directory, normalized_file_path]) == directory_path
+                and (file_info := await adapter.info(joined_path))
+            ):
                 return joined_path, file_info
         except FileNotFoundError:
             continue
     return None, None
 
 
-def _validate_config(path: str, directories: list[PathType], file_system: Any) -> None:
+def _validate_config(path: str, directories: tuple[PathType, ...], file_system: Any) -> None:
     if not path:
-        raise ImproperlyConfiguredException("path must be a non-zero length string,")
+        raise ImproperlyConfiguredException("path must be a non-zero length string")
 
     if not directories or not any(bool(d) for d in directories):
-        raise ImproperlyConfiguredException("directories must include at least one path.")
+        raise ImproperlyConfiguredException("directories must include at least one path")
 
     if "{" in path:
         raise ImproperlyConfiguredException("path parameters are not supported for static files")

tests/unit/test_static_files/test_file_serving_resolution.py

@@ -9,7 +9,8 @@
 import pytest
 
 from litestar import MediaType, get
-from litestar.static_files import create_static_files_router
+from litestar.file_system import FileSystemAdapter
+from litestar.static_files import _get_fs_info, create_static_files_router
 from litestar.status_codes import HTTP_200_OK
 from litestar.testing import create_test_client
 
@@ -251,3 +252,29 @@ def test_resolve_symlinks(tmp_path: Path, resolve: bool) -> None:
             assert client.get("/test.txt").status_code == 404
         else:
             assert client.get("/test.txt").status_code == 200
+
+
+async def test_staticfiles_get_fs_info_no_access_to_non_static_directory(
+    tmp_path: Path,
+    file_system: FileSystemProtocol,
+) -> None:
+    assets = tmp_path / "assets"
+    assets.mkdir()
+    index = tmp_path / "index.html"
+    index.write_text("content", "utf-8")
+    path, info = await _get_fs_info([assets], "../index.html", adapter=FileSystemAdapter(file_system))
+    assert path is None
+    assert info is None
+
+
+async def test_staticfiles_get_fs_info_no_access_to_non_static_file_with_prefix(
+    tmp_path: Path,
+    file_system: FileSystemProtocol,
+) -> None:
+    static = tmp_path / "static"
+    static.mkdir()
+    private_file = tmp_path / "staticsecrets.env"
+    private_file.write_text("content", "utf-8")
+    path, info = await _get_fs_info([static], "../staticsecrets.env", adapter=FileSystemAdapter(file_system))
+    assert path is None
+    assert info is None

tests/unit/test_static_files/test_static_files_validation.py

@@ -1,5 +1,4 @@
 from pathlib import Path
-from typing import List
 
 import pytest
 
@@ -10,10 +9,9 @@
 from litestar.testing import create_test_client
 
 
-@pytest.mark.parametrize("directories", [[], [""]])
-def test_validation_of_directories(directories: List[str]) -> None:
+def test_validation_of_directories() -> None:
     with pytest.raises(ImproperlyConfiguredException):
-        create_static_files_router(path="/static", directories=directories)
+        create_static_files_router(path="/static", directories=[])
 
 
 def test_validation_of_path(tmpdir: "Path") -> None: