fix(paths): accept filesystem roots in containment checks

litellm/litellm_core_utils/path_utils.py

@@ -33,7 +33,7 @@ def safe_join(base_dir: str, *parts: str) -> str:
             raise ValueError("Path contains null byte")
     base: Final = os.path.realpath(base_dir)
     resolved: Final = os.path.realpath(os.path.join(base, *parts))
-    if not (resolved.startswith(base + os.sep) or resolved == base):
+    if not (resolved.startswith(os.path.join(base, "")) or resolved == base):
         raise ValueError(f"Path {resolved!r} escapes base directory {base!r}")
     return resolved
 
@@ -50,7 +50,7 @@ def is_within(path: str, base_dir: str) -> bool:
     """True when path, with symlinks resolved, is base_dir or sits inside it."""
     base: Final = os.path.realpath(base_dir)
     resolved: Final = os.path.realpath(path)
-    return resolved.startswith(base + os.sep) or resolved == base
+    return resolved.startswith(os.path.join(base, "")) or resolved == base
 
 
 def join_within(base_dir: str, *parts: str) -> str | None:
@@ -65,7 +65,7 @@ def join_within(base_dir: str, *parts: str) -> str | None:
             return None
     base: Final = os.path.normpath(os.path.abspath(base_dir))
     joined: Final = os.path.normpath(os.path.join(base, *parts))
-    if not joined.startswith(base + os.sep):
+    if joined == base or not joined.startswith(os.path.join(base, "")):
         return None
     return joined
 

tests/unit/litellm_core_utils/test_path_utils.py

@@ -1,10 +1,32 @@
 import os
+from collections.abc import Callable
+from pathlib import Path
+from typing import Final
 
 import pytest
 
 from litellm.litellm_core_utils.path_utils import is_within, join_within, safe_filename, safe_join, try_safe_join
 
 
+@pytest.mark.parametrize("join", (safe_join, try_safe_join, join_within))
+def test_join_accepts_filesystem_root(join: Callable[[str, str], str | None], tmp_path: Path) -> None:
+    root: Final = tmp_path.anchor
+    relative: Final = os.path.relpath(str(tmp_path / "file.yaml"), root)
+    assert join(root, relative) == str(tmp_path / "file.yaml")
+
+
+def test_is_within_accepts_filesystem_root(tmp_path: Path) -> None:
+    assert is_within(str(tmp_path / "file.yaml"), tmp_path.anchor)
+    assert is_within(tmp_path.anchor, tmp_path.anchor)
+
+
+@pytest.mark.parametrize("use_root", (True, False))
+@pytest.mark.parametrize("parts", ((), (".",), ("subdir", "..")))
+def test_join_within_rejects_base_itself(tmp_path: Path, use_root: bool, parts: tuple[str, ...]) -> None:
+    base: Final = tmp_path.anchor if use_root else str(tmp_path)
+    assert join_within(base, *parts) is None
+
+
 class TestSafeJoin:
     def test_normal_path(self, tmp_path):
         result = safe_join(str(tmp_path), "subdir", "file.yaml")