fix(feishu): confine downloaded media filenames

tests/channels/test_feishu_media_filename_security.py

@@ -0,0 +1,38 @@
+from pathlib import Path
+from types import SimpleNamespace
+
+import pytest
+
+from nanobot.channels import feishu as feishu_module
+from nanobot.channels.feishu import FeishuChannel
+
+
+@pytest.mark.asyncio
+async def test_feishu_downloaded_media_filename_cannot_escape_media_dir(monkeypatch, tmp_path):
+    media_dir = tmp_path / "media"
+    media_dir.mkdir()
+    outside = tmp_path / "escaped.txt"
+
+    monkeypatch.setattr(feishu_module, "get_media_dir", lambda _channel: media_dir)
+
+    channel = FeishuChannel.__new__(FeishuChannel)
+    channel.logger = SimpleNamespace(
+        debug=lambda *args, **kwargs: None,
+        warning=lambda *args, **kwargs: None,
+    )
+
+    def fake_download(_message_id, _file_key, _resource_type):
+        return b"owned", "../escaped.txt"
+
+    channel._download_file_sync = fake_download
+
+    path_str, content = await channel._download_and_save_media(
+        "file", {"file_key": "fk_123"}, "msg_123"
+    )
+
+    saved_path = Path(path_str)
+    assert not outside.exists()
+    assert saved_path.parent == media_dir
+    assert saved_path.name == "escaped.txt"
+    assert saved_path.read_bytes() == b"owned"
+    assert content == f"[file: {saved_path}]"