synapse-product/synapse/rest/media/v1/download_resource.py
Denis Kasak 2476d5373c
Mitigate media repo XSSs on IE11. (#10468)
IE11 doesn't support Content-Security-Policy but it has support for
a non-standard X-Content-Security-Policy header, which only supports the
sandbox directive. This prevents script execution, so it at least offers
some protection against media repo-based attacks.

Signed-off-by: Denis Kasak <dkasak@termina.org.uk>
2021-07-27 13:45:10 +02:00

73 lines
2.6 KiB
Python

# Copyright 2014-2016 OpenMarket Ltd
# Copyright 2020-2021 The Matrix.org Foundation C.I.C.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import logging
from typing import TYPE_CHECKING
from twisted.web.server import Request
from synapse.http.server import DirectServeJsonResource, set_cors_headers
from synapse.http.servlet import parse_boolean
from ._base import parse_media_id, respond_404
if TYPE_CHECKING:
from synapse.rest.media.v1.media_repository import MediaRepository
from synapse.server import HomeServer
logger = logging.getLogger(__name__)
class DownloadResource(DirectServeJsonResource):
isLeaf = True
def __init__(self, hs: "HomeServer", media_repo: "MediaRepository"):
super().__init__()
self.media_repo = media_repo
self.server_name = hs.hostname
async def _async_render_GET(self, request: Request) -> None:
set_cors_headers(request)
request.setHeader(
b"Content-Security-Policy",
b"sandbox;"
b" default-src 'none';"
b" script-src 'none';"
b" plugin-types application/pdf;"
b" style-src 'unsafe-inline';"
b" media-src 'self';"
b" object-src 'self';",
)
# Limited non-standard form of CSP for IE11
request.setHeader(b"X-Content-Security-Policy", b"sandbox;")
request.setHeader(
b"Referrer-Policy",
b"no-referrer",
)
server_name, media_id, name = parse_media_id(request)
if server_name == self.server_name:
await self.media_repo.get_local_media(request, media_id, name)
else:
allow_remote = parse_boolean(request, "allow_remote", default=True)
if not allow_remote:
logger.info(
"Rejecting request for remote media %s/%s due to allow_remote",
server_name,
media_id,
)
respond_404(request)
return
await self.media_repo.get_remote_media(request, server_name, media_id, name)