On Wed, 6 Dec 2023 at 12:29, Vladimir Levin <vmp...@chromium.org> wrote:
> Thank you for the update! > > This is a good write up. One comment / question below > > From the doc: > > Note that the pageshow event will trigger before the page is rendered > for the first time upon being restored from a back/forward navigation, > which guarantees that your login state check will let you reset the page to > a non sensitive state. > > Correct me if I'm wrong, but I think the viz surface displaying the > persisted contents may be embedded and shown before the page produces a new > frame. So although technically it is correct that this event will fire > before the page produces a rendering and a new frame, a version of the > content may be shown prior to that. > > I'm not sure if I'm being overly pedantic here, or whether my > understanding of this flow is incorrect. > I don't know if that's correct. I didn't think we kept any of the pixels while in BFCache. If you are correct, that sounds like a bug. I've filed https://crbug.com/1508728. Do you know who would know the answer to this? The same issue comes up in discussions of a back-preview (e.g. on mobile when gesturing the go back, we could show a snapshot of the page) and the intention there is to never do this with CCNS pages, F > > Thanks again for the write up > Vlad > > On Tue, Dec 5, 2023, 19:37 'Fergal Daly' via blink-dev < > blink-dev@chromium.org> wrote: > >> We now have a published doc >> <https://web.dev/articles/sign-out-best-practices> that covers best >> practices for BFCache/CCNS (and much more) during logout. Please let us >> know if you have any feedback on it. >> >> We will proceed with cautiously rolling out this change. Thanks everyone, >> >> F >> >> On Thu, 16 Nov 2023 at 13:37, Fergal Daly <fer...@google.com> wrote: >> >>> Thanks everyone. Yes we will keep this thread up to date before >>> releasing this (we'll go to canary/dev very soon so that we start getting >>> stability and impact signals), >>> >>> F >>> >>> On Thu, 16 Nov 2023 at 05:30, Vladimir Levin <vmp...@chromium.org> >>> wrote: >>> >>>> If possible, can you share this document on this thread when it is >>>> available? >>>> >>>> On Wed, Nov 15, 2023 at 12:52 PM Yoav Weiss <yoavwe...@chromium.org> >>>> wrote: >>>> >>>>> LGTM3 with the same condition. >>>>> >>>>> On Wed, Nov 15, 2023 at 6:44 PM Mike Taylor <miketa...@chromium.org> >>>>> wrote: >>>>> >>>>>> +1, thank you. LGTM2 w/ same condition. >>>>>> On 11/15/23 12:39 PM, Daniel Bratell wrote: >>>>>> >>>>>> Thanks for getting the security people to weigh in on this because >>>>>> that was really the main question for me. And it will still be >>>>>> controllable >>>>>> by a finch flag. >>>>>> >>>>>> LGTM1 dependent on there being a published document outlining the >>>>>> options for web developers (i.e. the document you are already working >>>>>> on). >>>>>> >>>>>> /Daniel >>>>>> On 2023-11-10 09:45, Fergal Daly wrote: >>>>>> >>>>>> 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. >>>>> To unsubscribe from this group and stop receiving emails from it, send >>>>> an email to blink-dev+unsubscr...@chromium.org. >>>>> To view this discussion on the web visit >>>>> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAL5BFfXz6RHMEbN4uVKw9pcS7nNyZT-zoQAwf1iSoS6THqAcfw%40mail.gmail.com >>>>> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAL5BFfXz6RHMEbN4uVKw9pcS7nNyZT-zoQAwf1iSoS6THqAcfw%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+unsubscr...@chromium.org. >> To view this discussion on the web visit >> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAAozHLmtJkE1f6GRF3f5NGvYSp%3DZvgU9H2oGxRza9jpeYbr_pQ%40mail.gmail.com >> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAAozHLmtJkE1f6GRF3f5NGvYSp%3DZvgU9H2oGxRza9jpeYbr_pQ%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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