fix(security): address Greptile review comments for path traversal protection

- guardrail_endpoints.py: Fix edge case where file named exactly in the
  categories directory could be rejected. Added 'or resolved_path == resolved_categories_dir'
  to the boundary check.

- presidio.py: Add directory boundary check to _validate_recognizer_file_path
  to prevent absolute path attacks. The resolved path must now stay within
  the current working directory, similar to the guardrail_endpoints.py pattern.

These changes address the security review comments from Greptile on PR #20286.

litellm/proxy/guardrails/guardrail_endpoints.py

@@ -766,7 +766,7 @@ async def get_category_yaml(category_name: str):
     # Resolve to absolute path and verify it stays within categories_dir
     resolved_path = os.path.realpath(category_file_path)
     resolved_categories_dir = os.path.realpath(categories_dir)
-    if not resolved_path.startswith(resolved_categories_dir + os.sep):
+    if not (resolved_path.startswith(resolved_categories_dir + os.sep) or resolved_path == resolved_categories_dir):
         raise HTTPException(
             status_code=400, detail="Invalid category name."
         )

litellm/proxy/guardrails/guardrail_hooks/presidio.py

@@ -152,6 +152,7 @@ class _OPTIONAL_PresidioPIIMasking(CustomGuardrail):
         1. No path traversal sequences (../)
         2. File must have .json extension
         3. Path is resolved to absolute and checked
+        4. Path must stay within the current working directory (directory boundary check)
         """
         import os
 
@@ -176,6 +177,14 @@ class _OPTIONAL_PresidioPIIMasking(CustomGuardrail):
                 f"Invalid file path: resolved path must be a .json file. file_path={file_path}"
             )
 
+        # Directory boundary check: ensure the resolved path stays within the
+        # current working directory to prevent absolute path attacks
+        base_dir = os.path.realpath(os.getcwd())
+        if not (resolved_path.startswith(base_dir + os.sep) or resolved_path == base_dir):
+            raise ValueError(
+                f"Invalid file path: path must be within the working directory. file_path={file_path}"
+            )
+
         return resolved_path
 
     def validate_environment(