mirror of
https://github.com/element-hq/element-web.git
synced 2024-12-16 03:51:37 +03:00
78 lines
3 KiB
TypeScript
78 lines
3 KiB
TypeScript
/*
|
|
Copyright 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.
|
|
*/
|
|
|
|
// WARNING: We have to be very careful about what mime-types we allow into blobs,
|
|
// as for performance reasons these are now rendered via URL.createObjectURL()
|
|
// rather than by converting into data: URIs.
|
|
//
|
|
// This means that the content is rendered using the origin of the script which
|
|
// called createObjectURL(), and so if the content contains any scripting then it
|
|
// will pose a XSS vulnerability when the browser renders it. This is particularly
|
|
// bad if the user right-clicks the URI and pastes it into a new window or tab,
|
|
// as the blob will then execute with access to Element's full JS environment(!)
|
|
//
|
|
// See https://github.com/matrix-org/matrix-react-sdk/pull/1820#issuecomment-385210647
|
|
// for details.
|
|
//
|
|
// We mitigate this by only allowing mime-types into blobs which we know don't
|
|
// contain any scripting, and instantiate all others as application/octet-stream
|
|
// regardless of what mime-type the event claimed. Even if the payload itself
|
|
// is some malicious HTML, the fact we instantiate it with a media mimetype or
|
|
// application/octet-stream means the browser doesn't try to render it as such.
|
|
//
|
|
// One interesting edge case is image/svg+xml, which empirically *is* rendered
|
|
// correctly if the blob is set to the src attribute of an img tag (for thumbnails)
|
|
// *even if the mimetype is application/octet-stream*. However, empirically JS
|
|
// in the SVG isn't executed in this scenario, so we seem to be okay.
|
|
//
|
|
// Tested on Chrome 65 and Firefox 60
|
|
//
|
|
// The list below is taken mainly from
|
|
// https://developer.mozilla.org/en-US/docs/Web/HTML/Supported_media_formats
|
|
// N.B. Matrix doesn't currently specify which mimetypes are valid in given
|
|
// events, so we pick the ones which HTML5 browsers should be able to display
|
|
//
|
|
// For the record, mime-types which must NEVER enter this list below include:
|
|
// text/html, text/xhtml, image/svg, image/svg+xml, image/pdf, and similar.
|
|
|
|
const ALLOWED_BLOB_MIMETYPES = [
|
|
'image/jpeg',
|
|
'image/gif',
|
|
'image/png',
|
|
|
|
'video/mp4',
|
|
'video/webm',
|
|
'video/ogg',
|
|
|
|
'audio/mp4',
|
|
'audio/webm',
|
|
'audio/aac',
|
|
'audio/mpeg',
|
|
'audio/ogg',
|
|
'audio/wave',
|
|
'audio/wav',
|
|
'audio/x-wav',
|
|
'audio/x-pn-wav',
|
|
'audio/flac',
|
|
'audio/x-flac',
|
|
];
|
|
|
|
export function getBlobSafeMimeType(mimetype: string): string {
|
|
if (!ALLOWED_BLOB_MIMETYPES.includes(mimetype)) {
|
|
return 'application/octet-stream';
|
|
}
|
|
return mimetype;
|
|
}
|