Fix arbitrary file write in /upload and /analyse_m3u_file

/upload stored files under the client-supplied filename (allowing .php
webshells and ../ traversal) and analyse_m3u_file renamed files from
unvalidated filename/id_playlist. Uploads are now always stored as
upload_<uuid>.m3u, id_playlist must be a UUID, and paths go through
safe_join.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server.py

@@ -104,6 +104,18 @@ def safe_join(base_dir, user_filename):
     return candidate
 
 
+UPLOADED_PLAYLIST_RE = re.compile(r'^upload_[0-9a-f]{32}\.m3u$')
+
+
+def validate_id_playlist(value):
+    """Playlist ids are UUIDs; anything else is rejected (they end up in file paths
+    and Mongo collection names)."""
+    try:
+        return str(uuid.UUID(str(value)))
+    except (ValueError, TypeError, AttributeError):
+        raise ValueError('invalid id_playlist')
+
+
 def findInfo(tag, s):
     end = '"'
     if (s.find(tag)>-1):
@@ -451,8 +463,16 @@ async def analyse_m3u_file(request):
     playlist_comment = data.get('comment', '').strip()
     
 
-    new_path_filename = "./" + UPLOAD_PLAYLIST_DIR + '/' + id_playlist + '.m3u'
-    old_path_filename = "./" + UPLOAD_PLAYLIST_DIR + '/' +filename
+    try:
+        id_playlist = validate_id_playlist(id_playlist)
+        if not UPLOADED_PLAYLIST_RE.match(filename or ''):
+            raise ValueError('invalid filename')
+        new_path_filename = safe_join(UPLOAD_PLAYLIST_DIR, id_playlist + '.m3u')
+        old_path_filename = safe_join(UPLOAD_PLAYLIST_DIR, filename)
+    except ValueError as exc:
+        return web.json_response({'error': str(exc)}, status=400)
+    if not os.path.isfile(old_path_filename):
+        return web.json_response({'error': 'uploaded file not found'}, status=400)
     os.rename(old_path_filename,new_path_filename)
     
     collection_channels = get_playlist_collection(id_playlist)
@@ -721,27 +741,36 @@ async def handle_upload(request):
     # Handle both form field and file in one pass
     async for part in reader:
         if part.name == "id_playlist_to_action":
-            id_playlist_data = await part.text()
+            id_playlist_data = (await part.text()).strip()
             if len(id_playlist_data) == 0:
                 print('No playlist to update', flush=True)
                 id_playlist = str(uuid.uuid4())
             else:
-                id_playlist = id_playlist_data
+                try:
+                    id_playlist = validate_id_playlist(id_playlist_data)
+                except ValueError:
+                    if filepath and os.path.exists(filepath):
+                        os.remove(filepath)
+                    return web.Response(text="Invalid id_playlist.", status=400)
                 print('playlist to update :', id_playlist, flush=True)
 
         elif part.name == "file":
-            filename = part.filename
-            if not filename:
+            if not part.filename:
                 return web.Response(text="No file provided.", status=400)
 
-            filepath = os.path.join(UPLOAD_PLAYLIST_DIR, filename)
+            # Never trust the client-supplied filename: always store under a
+            # server-generated .m3u name inside the playlists directory.
+            filename = f"upload_{uuid.uuid4().hex}.m3u"
+            filepath = safe_join(UPLOAD_PLAYLIST_DIR, filename)
 
             with open(filepath, "wb") as f:
                 while chunk := await part.read_chunk():
                     f.write(chunk)
 
     if filepath:
-        return web.json_response({'status': 'ok', 'id_playlist': id_playlist})
+        if id_playlist is None:
+            id_playlist = str(uuid.uuid4())
+        return web.json_response({'status': 'ok', 'id_playlist': id_playlist, 'filename': filename})
 
     return web.Response(text="No file field found in the request.", status=400)