On Fri, 10 Nov 2023 at 17:29, Yoav Weiss <yoavwe...@chromium.org> wrote:
> Thanks David! > It's great to see that this will be disabled in modes where we *know* the > machine is shared. > > Fergal - could you address concerns about web developer advice? What > should we tell web developers to do on their logout pages? > Yes, we are in discussion with dev-rel about this. They were already looking at producing advice for auth best practices. We will ensure that this is covered in that, F > > > On Fri, Nov 10, 2023 at 8:37 AM David Dworken <ddwor...@google.com> wrote: > >> Chiming in to say that we discussed the security concerns around this >> proposal quite extensively internally and overall we believe that with the >> short timeout, the security risks are acceptable. The residual security >> risk is for servers that implement purely server-side logouts and is only >> exploitable for a very short period of time (3 minutes). In addition, other >> mitigations like this one >> <https://bugs.chromium.org/p/chromium/issues/detail?id=1468438> further >> reduce the risk such that we believe it is unlikely that this will lead to >> new security issues. >> >> On Friday, October 13, 2023 at 7:14:46 AM UTC-7 vmp...@chromium.org >> wrote: >> >> On Fri, Oct 13, 2023 at 12:00 AM 'Fergal Daly' via blink-dev < >> blin...@chromium.org> wrote: >> >> On Thu, 12 Oct 2023 at 23:05, Yoav Weiss <yoav...@chromium.org> wrote: >> >> >> >> On Thu, Oct 12, 2023 at 3:56 PM Vladimir Levin <vmp...@chromium.org> >> wrote: >> >> Are there any spec changes planned for this feature? I'm not sure if the >> README linked under Specification is meant to make it into WHATWG, maybe to >> close out https://github.com/whatwg/html/issues/7189 >> >> The only spec I could find about CCNS is >> https://www.rfc-editor.org/rfc/rfc9111#section-5.2.1.5, so I'm not sure >> how to reconcile possibly contradicting language in the specs >> >> >> Great questions! Fergal - can you answer that? >> >> >> RFC9111 is about HTTP caches. BFCache is not a HTTP cache, so RFC 9111 >> does not apply. Of course the reality of implementations and expectations >> vs spec is a problem. Some more discussion here >> <https://github.com/fergald/explainer-bfcache-ccns/blob/main/README.md#current-interactions-between-bfcache-and-ccns> >> >> >> I'm not sure I agree with this, or the reasoning in the link. First of >> all, this intent thread is about ignoring CCNS in _some cases_. In other >> cases, CCNS is respected, so it seems like BFCache is de facto subject to >> RFC 9111. >> >> This is, I guess, a bit philosophical but the spec says: >> the cache MUST NOT intentionally store the information in non-volatile >> storage and MUST make a best-effort attempt to remove the information from >> volatile storage as promptly as possible after forwarding it. >> >> Note that the spec here does not make any exceptions for things like >> cookie state not changing or anything else. The document when frozen is >> indeed a volatile storage of the server response, processed and stored in >> some particular format (ie the DOM tree). I admit it's a bit weird to think >> about it this way, since the live document is technically also this cache. >> Whereas I agree that BFCache is not strictly an HTTP Cache, I don't quite >> follow why CCNS should not apply to the BFCache in some cases. >> >> To me, BFCache seems like "a better http cache" which already has >> rendered results, not a completely separate cache that is not subject to >> CCNS. >> >> But I'm late to the game, and I see that the topic of "BFCache is not >> HTTP Cache" has already been discussed a lot. I'm not convinced by existing >> arguments, but I also don't think I'll be able to convince anyone of my >> position. >> >> My problem with the consensus in >> https://github.com/whatwg/html/issues/5744 is the following. People seem >> to agree that we don't want a *new* api that specifically prevents pages >> from entering BFCache. I don't believe it's appropriate to draw a >> conclusion that there is consensus that BFCache should not be subject to >> any *existing* APIs that prevent pages from entering it. This might be true >> independently, but I don't think one follows from the other. To quote this >> comment >> <https://github.com/whatwg/html/issues/5744#issuecomment-811958634>: >> "... And what is the problem with the bank case? I'd expect bank may want >> to ensure its page doesn't enter bfcache, or any other cache, by using >> no-store (and other) header(s) or something ..." >> >> That comment sounds to me like "the status quo is good enough, because >> there are already ways of preventing any cache, including bfcache." If we >> were to claim consensus on doing this work, I'd personally want to see a >> more explicit "let's make it so pages still enter BFCache despite CCNS in >> these cases." The comment from cdumez you quoted is good, but maybe >> following-up there is worthwhile. >> >> >> I concede though that I'm by no means an expert here, so I don't want to >> block moving this forward any longer. I just want to say that it's >> typically easy to be fast if you show stale data, and shifting the blame to >> the site for using CCNS instead of refreshing needed content in script >> doesn't seem appropriate. I personally would not want to be the judge of >> whether CCNS use is appropriate or not since I don't know what >> "appropriate" is in this case. >> >> >> >> >> BFCache and cases where it can/can't be used are specced in the HTML >> standard. We have had very little engagement from other vendors on this >> particular idea but Safari tried to cache all CCNS pages in the past. I am >> hoping that if we demonstrate a way to cache some of them safely, they >> would be on board. Also any browser is free to be *more* conservative than >> the spec while still staying in-spec as BFCaching at all is always optional. >> >> Here <https://github.com/whatwg/html/issues/5744#issuecomment-661997090> >> is cdumez of Safari >> >> Safari / WebKit shipped with all pages going into the bfcache no matter >> what (including cache-control: no-store). The only push back we received >> was the fact that after you log out of a site, you could still go back and >> see a page you should no longer be able to see. We agreed that this >> feedback was valid and our short-term fix was to bypass the bfcache when >> the page uses cache-control: no-store. Sadly, many sites use this and >> their intention is likely not to prevent the bfcache. This is not something >> we like for the long term. >> >> F >> >> >> >> >> Also, Vlad previously asked about the recommended pattern for folks to >> handle credential revocation with BFCache and his concerns with the snippet >> suggested upthread. It'd be great to address that. >> >> >> Thanks! >> vmpstr >> >> On Thu, Oct 12, 2023 at 2:32 AM Yoav Weiss <yoav...@chromium.org> wrote: >> >> I just discussed this with Fergal offline: >> >> - The risky scenario is one where revocation of sensitive info >> (logout, access revoked) happens on the server-side only without a >> client-side update. >> - In such a scenario on a shared computer, someone could back-button >> their way into someone else's sensitive info. >> - It might be interesting to talk to security folks (and maybe >> Project Zero folks) to see if this is not happening already with content >> that's not CCNS decorated. >> - It would be good to run a survey of potentially-sensitive services >> and try to get a signal from them on how many of them are properly doing >> revocation on the client side. >> - I'd love ideas on how we can scale such a survey beyond manual >> inspection of a few known services. >> - It could be interesting to try and ship a version of this with a >> shorter timeout, to minimize the risk of users leaving the machine >> unattended. >> - If we go that route, it'd be good to think through how we'd be >> able to increase that timeout over time, after gaining more confidence >> that >> the risky scenario isn't happening in the wild. >> >> >> >> On Thu, Oct 5, 2023 at 2:36 AM Jason Robbins <jrob...@google.com> wrote: >> >> At this morning's API Owners meeting, they asked me to add all review >> gate types to all of the "web developer facing code change" features that >> are currently under review, including this one. So, I have added Privacy, >> Security, Enterprise, Debuggability, and Testing gates to your feature >> entry. >> >> Please click the gate chips in the "Prepare to ship" stage on your >> feature detail page. For each one, answer survey questions and request >> that of the cross-functional review. You can request them all in >> parallel. In cases where you already have the go/launch >> <https://goto.google.com/launch> bit approved, you can note that in a >> comment on that gate for a potentially faster review. >> >> Thanks, >> jason! >> On Monday, October 2, 2023 at 9:09:18 AM UTC-7 Jason Robbins wrote: >> >> On Friday, September 29, 2023 at 1:01:54 PM UTC-7 Chris Harrelson wrote: >> >> Please also make sure to complete all of the other shipping gate reviews >> <https://groups.google.com/a/chromium.org/g/blink-dev/c/bqvB1oap0Yc/m/YlO8DEHgAQAJ> >> . >> >> >> I think a bug in ChromeStatus may have caused some confusion on this >> feature entry. The feature entry has type "Web developer facing code >> change", so its bilnk-dev thread should have had subject line prefix >> "Web-facing change PSA" rather than "Intent to ship". And, according to >> the launching-features doc >> <https://www.chromium.org/blink/launching-features/#psa-prepare-to-ship>, >> it does not require any approvals, which is why there are no other gates >> offered in the ChromeStatus UI. A fix for that subject-line prefix bug >> should go live today. >> >> Of course, the point of a PSA is to allow concerns to be raised and I see >> that this is a very active thread. So, all that should be worked through. >> Its a mater of the the API Owners prerogative to request any other reviews >> that they think are appropriate, but it is not automatically required by >> the process for this feature type. Also, I see that the launch entry >> <https://launch.corp.google.com/launch/4251651> had some approvals. >> >> Thanks, >> jason! >> >> -- >> You received this message because you are subscribed to the Google Groups >> "blink-dev" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to blink-dev+...@chromium.org. >> To view this discussion on the web visit >> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAL5BFfUszpq%3DS%3DOZ4k_GnopJMRcTnL_trq5iF8J-kAzeYEiqKA%40mail.gmail.com >> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAL5BFfUszpq%3DS%3DOZ4k_GnopJMRcTnL_trq5iF8J-kAzeYEiqKA%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> >> -- >> You received this message because you are subscribed to the Google Groups >> "blink-dev" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to blink-dev+...@chromium.org. >> >> To view this discussion on the web visit >> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAAozHLkA5eFwcvRsTAZhy728KFaBjd5W5EZpP2%3DMmC42ngMUuQ%40mail.gmail.com >> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAAozHLkA5eFwcvRsTAZhy728KFaBjd5W5EZpP2%3DMmC42ngMUuQ%40mail.gmail.com?utm_medium=email&utm_source=footer> >> . >> >> -- You received this message because you are subscribed to the Google Groups "blink-dev" group. 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