Check whether path is in appropriate folder.

backend/chainlit/_utils.py

@@ -0,0 +1,8 @@
+"""Util functions which are explicitly not part of the public API."""
+
+from pathlib import Path
+
+
+def is_path_inside(child_path: Path, parent_path: Path) -> bool:
+    """Check if the child path is inside the parent path."""
+    return parent_path.resolve() in child_path.resolve().parents

backend/chainlit/config.py

@@ -24,6 +24,8 @@
 from pydantic.dataclasses import Field, dataclass
 from starlette.datastructures import Headers
 
+from ._utils import is_path_inside
+
 if TYPE_CHECKING:
     from chainlit.action import Action
     from chainlit.element import ElementBased
@@ -353,18 +355,25 @@ def load_translation(self, language: str):
             config_translation_dir, f"{default_language}.json"
         )
 
-        if os.path.exists(translation_lib_file_path):
+        if is_path_inside(
+            Path(translation_lib_file_path), Path(config_translation_dir)
+        ) and os.path.exists(translation_lib_file_path):
             with open(translation_lib_file_path, "r", encoding="utf-8") as f:
                 translation = json.load(f)
-        elif os.path.exists(translation_lib_parent_language_file_path):
+        elif is_path_inside(
+            Path(translation_lib_parent_language_file_path),
+            Path(config_translation_dir),
+        ) and os.path.exists(translation_lib_parent_language_file_path):
             logger.warning(
                 f"Translation file for {language} not found. Using parent translation {parent_language}."
             )
             with open(
                 translation_lib_parent_language_file_path, "r", encoding="utf-8"
             ) as f:
                 translation = json.load(f)
-        elif os.path.exists(default_translation_lib_file_path):
+        elif is_path_inside(
+            Path(default_translation_lib_file_path), Path(config_translation_dir)
+        ) and os.path.exists(default_translation_lib_file_path):
             logger.warning(
                 f"Translation file for {language} not found. Using default translation {default_language}."
             )

backend/chainlit/markdown.py

@@ -1,6 +1,8 @@
 import os
+from pathlib import Path
 
 from chainlit.logger import logger
+from ._utils import is_path_inside
 
 # Default chainlit.md file created if none exists
 DEFAULT_MARKDOWN_STR = """# Welcome to Chainlit! 🚀🤖
@@ -35,7 +37,9 @@ def get_markdown_str(root: str, language: str):
     translated_chainlit_md_path = os.path.join(root, f"chainlit_{language}.md")
     default_chainlit_md_path = os.path.join(root, "chainlit.md")
 
-    if os.path.exists(translated_chainlit_md_path):
+    if is_path_inside(Path(translated_chainlit_md_path), Path(root)) and os.path.exists(
+        translated_chainlit_md_path
+    ):
         chainlit_md_path = translated_chainlit_md_path
     else:
         chainlit_md_path = default_chainlit_md_path

backend/chainlit/server.py

@@ -57,6 +57,8 @@
 from typing_extensions import Annotated
 from watchfiles import awatch
 
+from ._utils import is_path_inside
+
 mimetypes.add_type("application/javascript", ".js")
 mimetypes.add_type("text/css", ".css")
 
@@ -666,6 +668,7 @@ async def project_settings(
     """Return project settings. This is called by the UI before the establishing the websocket connection."""
 
     # Load the markdown file based on the provided language
+
     markdown = get_markdown_str(config.root, language)
 
     profiles = []
@@ -897,8 +900,7 @@ async def serve_file(
     base_path = Path(config.project.local_fs_path).resolve()
     file_path = (base_path / filename).resolve()
 
-    # Check if the base path is a parent of the file path
-    if base_path not in file_path.parents:
+    if not is_path_inside(file_path, base_path):
         raise HTTPException(status_code=400, detail="Invalid filename")
 
     if file_path.is_file():
@@ -941,6 +943,7 @@ async def get_logo(theme: Optional[Theme] = Query(Theme.light)):
 
     if not logo_path:
         raise HTTPException(status_code=404, detail="Missing default logo")
+
     media_type, _ = mimetypes.guess_type(logo_path)
 
     return FileResponse(logo_path, media_type=media_type)
@@ -954,13 +957,19 @@ async def get_avatar(avatar_id: str):
 
     avatar_id = avatar_id.strip().lower().replace(" ", "_")
 
-    avatar_path = os.path.join(APP_ROOT, "public", "avatars", f"{avatar_id}.*")
+    base_path = os.path.join(APP_ROOT, "public", "avatars")
+    avatar_glob = os.path.join(base_path, f"{avatar_id}.*")
 
-    files = glob.glob(avatar_path)
+    files = glob.glob(avatar_glob)
 
     if files:
         avatar_path = files[0]
+
+        if not is_path_inside(Path(avatar_path), Path(base_path)):
+            raise HTTPException(status_code=400, detail="Invalid filename")
+
         media_type, _ = mimetypes.guess_type(avatar_path)
+
         return FileResponse(avatar_path, media_type=media_type)
     else:
         return await get_favicon()