Support sandboxed iframe

[DeepDiver1975]

Describe the Bug

Collabora Online cannot be used inside a sandboxed iframe because collabora tries to access the parent document. See screenshots below for further details

Steps to Reproduce

1. load Collabora in <iframe sandbox="allow-scripts">
2. see it failing

Expected Behavior

Shall load

Actual Behavior

Does not load

Screenshots

Desktop

• Collabora version: image: collabora/code:23.05.5.2.1
• OS and version: Debian 12
• Browser and version: Chromium 124.0.6367.60

Additional Context

ocis docker setup as per https://github.com/owncloud/ocis/tree/master/deployments/examples/ocis_wopi

[meven]

Regarding allow-same-origin, it is required currently for:

• localstorage accessing and reading, user's settings
• localization is loaded using XHtmlRequests

For localization this could be changed. For localstorage, this would require to read and pass to the host window those settings.

Using sandbox="allow-same-origin allow-scripts" is already an isolation improvement, but COOL does not work properly in those conditions. I am looking into it.

[meven]

Regarding allow-same-origin, it is required currently for:

* localstorage accessing and reading, user's settings

* localization is loaded using XHtmlRequests

For localization this could be changed. For localstorage, this would require to read and pass to the host window those settings.

Using sandbox="allow-same-origin allow-scripts" is already an isolation improvement, but COOL does not work properly in those conditions. I am looking into it.

Using allow-scripts allow-same-origin allow-downloads allow-popups for sandbox allows CODE to work properly.

[DeepDiver1975]

Yes - but from a security perspective I don't want to grant an application allow-same-origin.

Under the assumption that the ifamed application is compromised by a vulnerability if can leave the iframe and also attack the parent application. Any interaction between these two applications should happen using Window.postMessage() - see https://developer.mozilla.org/en-US/docs/Web/API/Window/postMessage

[meven]

Yes - but from a security perspective I don't want to grant an application allow-same-origin.

I understand, and Collabora Online could support it with some efforts. allow-same-origin is a lot more restrictive that just communicating with the parent frame.

Collabora Online already uses only postMessage to communicate with the parent frame. But without allow-same-origin, indeed Collabora Online is a potential attack vector.

[meven]

An option on your end, is to host Collabora-online on a host with a different domain (or just port difference). That would restrict access from the iframe to the parent application, making it a cross-domain iframe. That might not be easy to accommodate on your end though.

[mmeeks]

Question is - where are we not using post-message? there is that frame resizing thing; @meven do we have a short list of things to fix that get this wrong ? =)

[meven]

Question is - where are we not using post-message? there is that frame resizing thing; @meven do we have a short list of things to fix that get this wrong ? =)

• localstorage, and how to persist user settings.
• localization data, we use a XHR request to fetch them, that can't work
• the nested iframe to detect resizing, could be replaced with a ResizeObserver

I have a POC branch of Collabora Online with localstorage turned off, localization off and without the resize iframe that runs in Firefox (but not chrome) and firefox has presentation restriction (even with a allow-presentation).

[meven]

The _fileDownloader iframe could also be replaced either with a "<a download" or window.downloads.

[meven]

I have tested the clipboard and it seems affected for complex pasting (but that might another issue).

I have made a branch that has a few features turned off as a baseline to test COOL with sandbox="allow-scripts allow-presentation allow-downloads allow-popups" :

https://github.com/meven/cool-online/tree/meven/iframe-sandboxed

The missing features are the welcome window, l18n, presenting in window is broken and full-screen not-working.

Apart from that, I haven't noticed any problems.

Some compatibility changes are missing (replacing im Map.js the _fileDownloader and _resizeDetector by other means (a download, and ResizeObserver ) that can already be made in master.

[mmeeks]

Getting a new server-side setting storage API implemented is really a larger task if we can't use the browser setting storage; this is a longer term task I think.

[mmeeks]

1. The presentation window is being re-worked to not run JS in a downloaded SVG - which should help there.

2. I believe @vmiklos just re-wrote the clipboard code to do its downloading where necessary server-to-server which should help make those large-inter-document pastes work even in this case.

The welcome window - I believe we can proxy that via online reasonably easily as we currently do for the LOK image; there should be no need for the client to go to a different server for that; so we're making progress :-)

[DeepDiver1975]

Hey - any news on this topic? Anything I can help out? ;-) THX a lot

[mmeeks]

Sure - good to check - a quick update:

• we just merged: https://github.com/CollaboraOnline/online/pull/9442 which has a much stricter set of CSP rules
• that also includes the switch to a more standard 'resize' event instead of this resize-detector iframe.
• Miklos' copy/paste work is merged & shipping, and being bug-fixed.

So; TODO:

• I expect we still need a localization solution that doesn't do this XHR request; not sure we've thought enough about that - probably we could post the local required in the initial post and hard-code the right localization files to load in the served cool.html easily enough - for this specific case if that would help

• configuration: here is where you can help Thomas; we are going to need to store and efficiently serve user configuration data - we have an easy to save registryconfiguration.xcu overlay XML file that we can send you when we shut-down; you can see teh content there in eg. ~/.config/libreoffice/4/user/registrymodifications.xcu on Linux; but we'll want to keep load-time latency down - we could fetch that asynchronously in parallel with document load I guess; from some well-known WOPI URL (per-user, and perhaps per-system - we could stack them) - but that would need some standardization / implementation thought on how that should look. We need 2x well-known-path XML files we can fetch, and one that we can serialize back; that are specific to that user - and (most ideally) we can generate the URLs from trivially and reliably from any WOPI URL - thoughts on that much appreciated ! =) With that in place we can avoid storing any data in the browser.

Thanks!