tbb-dev January 2016

tbb-dev@lists.torproject.org

4 participants
2 discussions

How does Tor Browser treat locally-installed CA cert?
by Linus Nordberg 28 Jan '16

28 Jan '16

Hi, As part of working on the CT Gossip draft [0] I find myself thinking about local trust anchors and how they might change browser behaviours. My understanding is that Tor Browser behaves like Firefox wrt locally added CA certs. If that's correct, do you know if FF treats pinning the way the "What Is HPKP For?" post [1] describes it? Another question that I find interesting is if TB could do better regarding fingerprintability based on what TLS session the browser accepts. [0] https://datatracker.ietf.org/doc/draft-ietf-trans-gossip/ [1] https://noncombatant.org/2015/11/24/what-is-hpkp-for/

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An Electrolysis-based approach for URL-bar domain isolation?
by Arthur D. Edelstein 05 Jan '16

05 Jan '16

Hi, everyone -- Happy New Year! I've been thinking about our work on first-party isolation in Tor Browser and I am wondering if Mozilla's Electrolysis project presents a new opportunity. Currently, we are using a number of isolation patches in Tor Browser: each patch prevents some browser feature (such the HTTP cache or DOM storage) from leaking information between URL bar domains. We're hoping that Mozilla will uplift these patches to mainline Firefox, but it's a very big task [1]. We have also disabled certain stateful features, including SSL Session IDs and TLS session tickets, SPDY, auto form-fill, third-party cookies and third-party HTTP authentication tokens. Disabling these features is straightforward, but somewhat degrades the browsing experience. Meanwhile, Mozilla has been pursuing the Electrolysis (e10s) project, aka Multiprocess Firefox [2]. The first iteration (already implemented and deployed in Aurora) separates the browser into two processes: one process for chrome and one process for all content. The content process is launched by the chrome process; they are both instances of the `firefox` executable. Mozilla says "In future iterations, we expect to have more than one content process." So, I'm thinking: could we use the Electrolysis mechanism to use a separate content process for each URL bar domain? In that case, any information in a given content process not explicitly shared with other processes or written to disk would be automatically isolated to the URL bar domain [3]. For example, there could be a separate in-memory cache in each content process. This approach might have several benefits. It might (a) let us drop most or all of our existing isolation patches (b) permit us to re-enable a number of stateful features, (c) protect against cross-origin tracking attacks we haven't discovered, and (d) allow us to easily implement a "New Identity for this Domain" menu item [4]. I also think Mozilla might find our privacy model easier to adopt if it were implemented this way. Any thoughts on this idea? Thanks, Arthur [1] Things for which we have already written patches for first-party isolation include the HTTP cache, the image cache, blob and media resource URLs, DOM storage, SharedWorkers, OCSP, favicons, and broadcast channels. We may also write further isolation patches for cookies, ServiceWorkers, and HSTS/HPKP, and likely other things. Dave Huseby at Mozilla is currently preparing the ground for attempting to uplift our patches. [2] https://developer.mozilla.org/en-US/Firefox/Multiprocess_Firefox [3] Tor Browser already uses Private Browsing Mode and includes some additional settings and patches to try to prevent anything private from being written to disk. [4] "New Identify for this Domain", the content process would be shut down and re-started, with a new Tor circuit.

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tbb-dev January 2016