perf: enhance file access security in get_file method

Co-authored-by: anka-afk <1350989414@qq.com>

astrbot/dashboard/routes/chat.py

@@ -60,29 +60,26 @@ class ChatRoute(Route):
         if not filename:
             return Response().error("Missing key: filename").__dict__
 
-        # Prevent path traversal attacks by extracting just the basename
-        filename_ = os.path.basename(filename)
-
-        # Check if the filename contains suspicious patterns
-        if (
-            filename_ != filename
-            or ".." in filename
-            or "/" in filename
-            or "\\" in filename
-        ):
-            return Response().error("Invalid filename").__dict__
-
         try:
-            with open(os.path.join(self.imgs_dir, filename_), "rb") as f:
-                if filename_.endswith(".wav"):
+            file_path = os.path.join(self.imgs_dir, os.path.basename(filename))
+            real_file_path = os.path.realpath(file_path)
+            real_imgs_dir = os.path.realpath(self.imgs_dir)
+
+            if not real_file_path.startswith(real_imgs_dir):
+                return Response().error("Invalid file path").__dict__
+
+            with open(real_file_path, "rb") as f:
+                filename_ext = os.path.splitext(filename)[1].lower()
+
+                if filename_ext == ".wav":
                     return QuartResponse(f.read(), mimetype="audio/wav")
-                elif filename_.split(".")[-1] in self.supported_imgs:
+                elif filename_ext[1:] in self.supported_imgs:
                     return QuartResponse(f.read(), mimetype="image/jpeg")
                 else:
                     return QuartResponse(f.read())
 
-        except FileNotFoundError:
-            return Response().error("File not found").__dict__
+        except (FileNotFoundError, OSError):
+            return Response().error("File access error").__dict__
 
     async def post_image(self):
         post_data = await request.files
@@ -138,17 +135,15 @@ class ChatRoute(Route):
 
         self.curr_user_cid[username] = conversation_id
 
-        await web_chat_queue.put(
-            (
-                username,
-                conversation_id,
-                {
-                    "message": message,
-                    "image_url": image_url,  # list
-                    "audio_url": audio_url,
-                },
-            )
-        )
+        await web_chat_queue.put((
+            username,
+            conversation_id,
+            {
+                "message": message,
+                "image_url": image_url,  # list
+                "audio_url": audio_url,
+            },
+        ))
 
         # 持久化
         conversation = self.db.get_conversation_by_user_id(username, conversation_id)