fix(rag): reject unsafe runtime file paths

src/langbot/pkg/rag/service/runtime.py

@@ -1,8 +1,12 @@
 from __future__ import annotations
 
 import posixpath
-from typing import Any
+import re
-from langbot.pkg.core import app
+from typing import TYPE_CHECKING, Any
+from urllib.parse import unquote
+
+if TYPE_CHECKING:
+    from langbot.pkg.core import app
 
 
 class RAGRuntimeService:
@@ -109,8 +113,17 @@ class RAGRuntimeService:
         regardless of the underlying storage provider.
         """
         # Validate storage_path to prevent path traversal
-        normalized = posixpath.normpath(storage_path)
+        decoded_path = unquote(storage_path).replace('\\', '/')
-        if normalized.startswith('/') or '..' in normalized.split('/'):
+        decoded_segments = decoded_path.split('/')
+        normalized = posixpath.normpath(decoded_path)
+        if (
+            not storage_path
+            or '\x00' in decoded_path
+            or normalized.startswith('/')
+            or '..' in decoded_segments
+            or '..' in normalized.split('/')
+            or re.match(r'^[A-Za-z]:/', normalized)
+        ):
             raise ValueError('Invalid storage path')
         content_bytes = await self.ap.storage_mgr.storage_provider.load(normalized)
         return content_bytes if content_bytes else b''

tests/unit_tests/rag/test_runtime_service.py

@@ -0,0 +1,68 @@
+from __future__ import annotations
+
+from types import SimpleNamespace
+
+import pytest
+
+from langbot.pkg.rag.service.runtime import RAGRuntimeService
+
+
+class DummyStorageProvider:
+    def __init__(self, content: bytes | None = b'data'):
+        self.content = content
+        self.loaded_paths: list[str] = []
+
+    async def load(self, path: str):
+        self.loaded_paths.append(path)
+        return self.content
+
+
+def make_service(storage_provider: DummyStorageProvider) -> RAGRuntimeService:
+    return RAGRuntimeService(SimpleNamespace(storage_mgr=SimpleNamespace(storage_provider=storage_provider)))
+
+
+@pytest.mark.asyncio
+async def test_get_file_stream_normalizes_safe_path():
+    storage_provider = DummyStorageProvider()
+    service = make_service(storage_provider)
+
+    content = await service.get_file_stream('safe/./nested/file.pdf')
+
+    assert content == b'data'
+    assert storage_provider.loaded_paths == ['safe/nested/file.pdf']
+
+
+@pytest.mark.asyncio
+@pytest.mark.parametrize(
+    'storage_path',
+    [
+        '',
+        '../secret.txt',
+        '/absolute/path.txt',
+        '..\\secret.txt',
+        'nested\\..\\secret.txt',
+        '%2e%2e/secret.txt',
+        'nested/%2e%2e/secret.txt',
+        'C:\\secret.txt',
+        'safe/\x00file.txt',
+    ],
+)
+async def test_get_file_stream_rejects_unsafe_paths(storage_path: str):
+    storage_provider = DummyStorageProvider()
+    service = make_service(storage_provider)
+
+    with pytest.raises(ValueError, match='Invalid storage path'):
+        await service.get_file_stream(storage_path)
+
+    assert storage_provider.loaded_paths == []
+
+
+@pytest.mark.asyncio
+async def test_get_file_stream_returns_empty_bytes_for_missing_content():
+    storage_provider = DummyStorageProvider(content=None)
+    service = make_service(storage_provider)
+
+    content = await service.get_file_stream('safe/file.pdf')
+
+    assert content == b''
+    assert storage_provider.loaded_paths == ['safe/file.pdf']