fix(api): force download for HTML previews (#30090)

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

api/controllers/common/file_response.py

@@ -0,0 +1,57 @@
+import os
+from email.message import Message
+from urllib.parse import quote
+
+from flask import Response
+
+HTML_MIME_TYPES = frozenset({"text/html", "application/xhtml+xml"})
+HTML_EXTENSIONS = frozenset({"html", "htm"})
+
+
+def _normalize_mime_type(mime_type: str | None) -> str:
+    if not mime_type:
+        return ""
+    message = Message()
+    message["Content-Type"] = mime_type
+    return message.get_content_type().strip().lower()
+
+
+def _is_html_extension(extension: str | None) -> bool:
+    if not extension:
+        return False
+    return extension.lstrip(".").lower() in HTML_EXTENSIONS
+
+
+def is_html_content(mime_type: str | None, filename: str | None, extension: str | None = None) -> bool:
+    normalized_mime_type = _normalize_mime_type(mime_type)
+    if normalized_mime_type in HTML_MIME_TYPES:
+        return True
+
+    if _is_html_extension(extension):
+        return True
+
+    if filename:
+        return _is_html_extension(os.path.splitext(filename)[1])
+
+    return False
+
+
+def enforce_download_for_html(
+    response: Response,
+    *,
+    mime_type: str | None,
+    filename: str | None,
+    extension: str | None = None,
+) -> bool:
+    if not is_html_content(mime_type, filename, extension):
+        return False
+
+    if filename:
+        encoded_filename = quote(filename)
+        response.headers["Content-Disposition"] = f"attachment; filename*=UTF-8''{encoded_filename}"
+    else:
+        response.headers["Content-Disposition"] = "attachment"
+
+    response.headers["Content-Type"] = "application/octet-stream"
+    response.headers["X-Content-Type-Options"] = "nosniff"
+    return True

api/controllers/files/image_preview.py

@@ -7,6 +7,7 @@ from werkzeug.exceptions import NotFound
 
 import services
 from controllers.common.errors import UnsupportedFileTypeError
+from controllers.common.file_response import enforce_download_for_html
 from controllers.files import files_ns
 from extensions.ext_database import db
 from services.account_service import TenantService
@@ -138,6 +139,13 @@ class FilePreviewApi(Resource):
             response.headers["Content-Disposition"] = f"attachment; filename*=UTF-8''{encoded_filename}"
             response.headers["Content-Type"] = "application/octet-stream"
 
+        enforce_download_for_html(
+            response,
+            mime_type=upload_file.mime_type,
+            filename=upload_file.name,
+            extension=upload_file.extension,
+        )
+
         return response
 
 

api/controllers/files/tool_files.py

@@ -6,6 +6,7 @@ from pydantic import BaseModel, Field
 from werkzeug.exceptions import Forbidden, NotFound
 
 from controllers.common.errors import UnsupportedFileTypeError
+from controllers.common.file_response import enforce_download_for_html
 from controllers.files import files_ns
 from core.tools.signature import verify_tool_file_signature
 from core.tools.tool_file_manager import ToolFileManager
@@ -78,4 +79,11 @@ class ToolFileApi(Resource):
             encoded_filename = quote(tool_file.name)
             response.headers["Content-Disposition"] = f"attachment; filename*=UTF-8''{encoded_filename}"
 
+        enforce_download_for_html(
+            response,
+            mime_type=tool_file.mimetype,
+            filename=tool_file.name,
+            extension=extension,
+        )
+
         return response

api/controllers/service_api/app/file_preview.py

@@ -5,6 +5,7 @@ from flask import Response, request
 from flask_restx import Resource
 from pydantic import BaseModel, Field
 
+from controllers.common.file_response import enforce_download_for_html
 from controllers.common.schema import register_schema_model
 from controllers.service_api import service_api_ns
 from controllers.service_api.app.error import (
@@ -183,6 +184,13 @@ class FilePreviewApi(Resource):
             # Override content-type for downloads to force download
             response.headers["Content-Type"] = "application/octet-stream"
 
+        enforce_download_for_html(
+            response,
+            mime_type=upload_file.mime_type,
+            filename=upload_file.name,
+            extension=upload_file.extension,
+        )
+
         # Add caching headers for performance
         response.headers["Cache-Control"] = "public, max-age=3600"  # Cache for 1 hour