How likely are we to get multiple 3Ps on the page with each using its own issuer?
On Wednesday, November 6, 2024 at 1:19:49 AM UTC+1 Chris Harrelson wrote: > LGTM1 > > On Thu, Oct 31, 2024 at 8:59 AM Ari Chivukula <aric...@chromium.org> > wrote: > >> >>> - In case of the user denies giving consent to X vendors / tech via >>> the CMP (Consent Management Platform), will the token be shared cross >>> site >>> if a wildcard is set anyway? The question also works with the Global >>> privacy control >>> >>> I think this is unrelated to the work here as that's a question about >> how any permissions policy would work with CMP/GPC, and not this specific >> change. >> >> >>> - Is there a way to prevent any adtech to redeem the token to >>> display an ads anywhere outside? (But I think this question is already >>> in >>> the blink discussion) >>> >>> I'm having trouble parsing the question, but if the question is whether >> adtech could redeem a token and then later take action based on past >> redemption the answer is yes as long as it's the same context storage wise >> (otherwise there wouldn't be a way to know a past redemption had occured). >> >> >>> - Not related but somehow related, if the token is considered First >>> party tracking (Potential risk noted in the spec >>> >>> <https://github.com/WICG/trust-token-api/blob/main/README.md#first-party-tracking-potential>) >>> >>> then combined with the wildcard, you have a cross site tracking : How to >>> prevent that? >>> >>> The first-party tracking potential you link to isn't about third-parties >> accessing data but first-parties reading the redemption records (this is >> only available in a top-level frame). The mitigation described in the >> explainer still applies as this change does not impact the availability of >> redemption records. >> >> ~ Ari Chivukula (Their/There/They're) >> >> >> On Thu, Oct 31, 2024 at 7:04 AM Alexandre Nderagakura < >> nderale...@gmail.com> wrote: >> >>> Trying to understand this discussion, the Issue 990 design revue in >>> w3ctag <https://github.com/w3ctag/design-reviews/issues/990> and the >>> privacy side (I put a comment in the Issue 306 >>> <https://github.com/WICG/trust-token-api/pull/306#issuecomment-2449585140> >>> but >>> perhaps talking is here is better) : >>> >>> - In case of the user denies giving consent to X vendors / tech via >>> the CMP (Consent Management Platform), will the token be shared cross >>> site >>> if a wildcard is set anyway? The question also works with the Global >>> privacy control >>> - Is there a way to prevent any adtech to redeem the token to >>> display an ads anywhere outside? (But I think this question is already >>> in >>> the blink discussion) >>> - Not related but somehow related, if the token is considered First >>> party tracking (Potential risk noted in the spec >>> >>> <https://github.com/WICG/trust-token-api/blob/main/README.md#first-party-tracking-potential>) >>> >>> then combined with the wildcard, you have a cross site tracking : How to >>> prevent that? >>> >>> >>> On Wednesday, October 23, 2024 at 1:41:52 AM UTC+2 Jeffrey Yasskin wrote: >>> >>>> This all makes sense to me. I don't personally have a good sense of the >>>> privacy implications of calling this, but that's a question for the >>>> privacy >>>> reviewers, not me. :) I'm torn on the question of when to make it easier >>>> for sites to pick their issuers. The overall TAG sense >>>> <https://github.com/w3ctag/design-reviews/issues/990> was that because >>>> this makes the risk worse, you should add the easier mitigation before >>>> shipping this change. But you have more experience with the particular >>>> users of this API, so it could be that you're right to want to wait for >>>> those users to complain. Is there a good issue for them to comment on if >>>> they run into this problem, so you can notice and fix it quickly? I think >>>> it'd be reasonable for the API owners to let this ship given a good way to >>>> catch if it breaks anything. >>>> >>>> The TAG also requested that you ask the Privacy WG to review the PST >>>> API <https://github.com/w3ctag/design-reviews/issues/990>, to get some >>>> non-Google validation that there aren't any privacy reasons to avoid >>>> loosening the permission policy. I wouldn't expect the API owners to >>>> insist >>>> that shipping wait for the Privacy WG. >>>> >>>> For the thread's information, I also got a request to help PSTs move >>>> into a WG, as the launch process requires we do >>>> <https://www.chromium.org/blink/launching-features/#new-feature-prepare-to-ship:~:text=If%20your%20specification%20is%20still%20in%20an%20incubation%20venue%20and%20not%20a%20working%20group%2C%20propose%20that%20the%20feature%20migrate%20to%20a%20working%20group.>, >>>> >>>> and we're figuring out what shape that should take. >>>> >>>> Jeffrey >>>> >>>> On Thu, Oct 3, 2024 at 11:37 AM Ari Chivukula <ari...@chromium.org> >>>> wrote: >>>> >>>>> Divided Jeffrey's email to separate questions verbatim (italic font). >>>>> Our responses are below the question (bold font). >>>>> >>>>> >>>>> 1. https://github.com/WICG/trust-token-api/issues/106 says that >>>>> adtech services want to redeem tokens without needing to get changes made >>>>> on the top-level site. The request seems to say that it's the adtech >>>>> origin >>>>> that's directly called from the top-level site, but I think this change >>>>> would allow redemptions anywhere down the tree of ad-related frames? >>>>> >>>>> Yes, this change would allow redemptions anywhere down the tree of >>>>> frames regardless of origin unless explicit >>>>> Permissions-Policies/allow-attributes block them (7). >>>>> >>>>> * Is there any risk of an ad redeeming tokens to interfere with >>>>> other ads? >>>>> https://github.com/WICG/trust-token-api?tab=readme-ov-file#private-state-token-exhaustion >>>>> >>>>> says only 1 token is redeemed per top-level page visit, which prevents >>>>> the >>>>> ad from deliberately using up the user's tokens, but it could still race >>>>> to >>>>> prevent any other ad from knowing to trust the user. >>>>> >>>>> Yes, an ad redeeming a token may interfere with other origins' >>>>> capabilities, as that redemption operation associates the issuer with >>>>> the top level origin. And this counts towards the issuer limit. At most 2 >>>>> issuers per top level origin is allowed. See step 4 in algorithm (1). >>>>> Associating an issuer with the top level origin occupies a slot. Once an >>>>> ad >>>>> redeems a token, only one issuer slot is left for all others in the same >>>>> top level page. >>>>> >>>>> Following a successful redemption, a redemption record (3) is stored, >>>>> step 14 in algorithm (2). Redemption records are keyed by (issuer, >>>>> toplevel) origin pair. Any other origin in the page trying to redeem a >>>>> token from the same issuer will get this cached redemption record. >>>>> >>>>> Put another way, ads can’t ‘use up’ tokens that other ads on the page >>>>> want to redeem, because those other ads would just re-use the same >>>>> redemption record. >>>>> >>>>> The explainer text is not in the best shape, created issue #307 >>>>> <https://github.com/WICG/trust-token-api/issues/307> to fix this. >>>>> >>>>> 2. This intent also expands which origins can _issue_ tokens, but I >>>>> don't see the justification for that in the issue. What circumstances >>>>> need >>>>> that? >>>>> >>>>> Yes, you are correct that the particular request cited here is >>>>> pertaining to redemption operations. However, we are aware that many >>>>> anti-fraud vendors are only embedded in 3p contexts, without necessarily >>>>> having script access on the top-level site. Vendors who currently rely on >>>>> third-party cookies to establish and convey trust will need commensurate >>>>> permissions on both redemption and issuance sides. >>>>> >>>>> There's some privacy impact from using this API. The tight default >>>>> permission policy meant that top-level sites had to explicitly ask to >>>>> expose their users to that privacy impact. Without it, shouldn't we >>>>> expect >>>>> lots of embedded resources to try to learn whatever information they can >>>>> using this API? Why is that extra risk good for users overall? >>>>> >>>>> We see this is a key tradeoff that many third-party cookie replacement >>>>> APIs have to contend with. Given the widespread reliance on third-party >>>>> cookies, it may not be practical to have anti-fraud vendors to work with >>>>> every publisher/page to update their permission policy for the frames >>>>> they >>>>> have. Usefulness of the signal depends on its availability. >>>>> >>>>> Further, the extra risk is actually very small: it's not going to >>>>> affect users' privacy if anyone can learn that they've visited 2 >>>>> particular >>>>> issuers and the 6 bits those issuers want to convey about them. In fact, >>>>> the privacy risk is decreased by allowing 3p issuers to send that >>>>> information, because it limits the inference about which sites a user has >>>>> actively visited. >>>>> >>>>> Note that the information embedded resources can learn are constrained >>>>> by limiting information content stored in a token (4) and limiting the >>>>> number of issuers per page (5). Additionally, PST issuers are expected to >>>>> register >>>>> on GitHub >>>>> <https://github.com/GoogleChrome/private-tokens/blob/main/PST-Registration.md> >>>>> >>>>> with some transparency on how they’re using the tokens. >>>>> >>>>> I don't find the "the top-level origin could call hasPrivateToken up >>>>> to twice before any other JavaScript is included" mitigation plausible: >>>>> folks often don't control the order of their Javascript that closely. It >>>>> seems more likely that sites would just explicitly set the permission >>>>> policy to the origins they trust to pick their issuers: is there a reason >>>>> that's not an adequate defense? >>>>> >>>>> Permission policy can certainly be used, but it does not prevent >>>>> third-party scripts embedded on the top-level context from picking their >>>>> own issuers. The hasPrivateToken method overcomes that issue. >>>>> >>>>> For the general case, the JS API method mitigates most cases, but we >>>>> have heard that folks would like a more explicit way of doing this, >>>>> either >>>>> as a meta tag or header that can be sent by the server since the JS >>>>> inclusion order and complexities with single page sites means that this >>>>> is >>>>> a little fragile if it's not the earliest executed JS. >>>>> >>>>> While we could add a new meta-tag/header feature to control issuance >>>>> origins and then change the policy to default to *, given the low usage >>>>> and >>>>> (in our estimation) the low risk of changing the policy default we would >>>>> prefer to pursue this change and follow up if requested by clients. >>>>> >>>>> But then you've still just switched the burden from sites that want to >>>>> delegate use of this API, to sites that need to defend against hostile >>>>> use >>>>> of the API. Can you share any analysis of why you think attacks will be >>>>> much less likely than uses, or some other reason that it's good for users >>>>> and sites to switch that burden? >>>>> >>>>> While it could be viewed as a “burden switch”, the fundamental privacy >>>>> properties of PSTs mentioned above are such that the vast majority of >>>>> sites >>>>> shouldn’t have cause to be concerned. For sites that are looking to >>>>> prevent >>>>> any cross site communication, the permission policy remains available. >>>>> References >>>>> >>>>> 1. >>>>> https://wicg.github.io/trust-token-api/#append-private-state-token-redemption-request-headers >>>>> >>>>> 2. https://wicg.github.io/trust-token-api/#handle-a-redeem-response >>>>> >>>>> 3. https://wicg.github.io/trust-token-api/#redemption-record >>>>> >>>>> 4. https://wicg.github.io/trust-token-api/#limit-encoded-info >>>>> >>>>> 5. https://wicg.github.io/trust-token-api/#per-issuer-limits >>>>> >>>>> 6. https://github.com/WICG/trust-token-api/issues/106 >>>>> >>>>> 7. >>>>> https://developer.mozilla.org/en-US/docs/Web/HTTP/Permissions_Policy#allowlists >>>>> >>>>> 8. https://chromestatus.com/metrics/feature/timeline/popularity/3276 >>>>> >>>>> ~ Ari Chivukula (Their/There/They're) >>>>> >>>>> >>>>> On Wed, Oct 2, 2024 at 4:51 PM Ari Chivukula <ari...@chromium.org> >>>>> wrote: >>>>> >>>>>> These are good questions! Sorry for the delay in replying, now that >>>>>> TPAC has passed we should have something soon. >>>>>> >>>>>> ~ Ari Chivukula (Their/There/They're) >>>>>> >>>>>> >>>>>> On Wed, Sep 11, 2024 at 3:52 PM Jeffrey Yasskin <jyas...@chromium.org> >>>>>> wrote: >>>>>> >>>>>>> This Intent makes me realize that my mental model of Private State >>>>>>> Tokens wasn't correct. I'd been thinking of users going to a site that >>>>>>> trusts them, having that site issue some tokens, and then going to >>>>>>> another >>>>>>> site which would redeem a token to increase its trust. In both cases, >>>>>>> the >>>>>>> sites could rely on third-parties to handle the tokens, but the sites >>>>>>> have >>>>>>> intentional relationships with their service providers and so could >>>>>>> enable >>>>>>> them in the top-level Permission Policy. >>>>>>> >>>>>>> This Intent implies that something else is going on, maybe multiple >>>>>>> things. >>>>>>> >>>>>>> 1. https://github.com/WICG/trust-token-api/issues/106 says that >>>>>>> adtech services want to redeem tokens without needing to get changes >>>>>>> made >>>>>>> on the top-level site. The request seems to say that it's the adtech >>>>>>> origin >>>>>>> that's directly called from the top-level site, but I think this change >>>>>>> would allow redemptions anywhere down the tree of ad-related frames? >>>>>>> * Is there any risk of an ad redeeming tokens to interfere with >>>>>>> other ads? >>>>>>> https://github.com/WICG/trust-token-api?tab=readme-ov-file#private-state-token-exhaustion >>>>>>> >>>>>>> says only 1 token is redeemed per top-level page visit, which prevents >>>>>>> the >>>>>>> ad from deliberately using up the user's tokens, but it could still >>>>>>> race to >>>>>>> prevent any other ad from knowing to trust the user. >>>>>>> 2. This intent also expands which origins can _issue_ tokens, but I >>>>>>> don't see the justification for that in the issue. What circumstances >>>>>>> need >>>>>>> that? >>>>>>> >>>>>>> There's some privacy impact from using this API. The tight default >>>>>>> permission policy meant that top-level sites had to explicitly ask to >>>>>>> expose their users to that privacy impact. Without it, shouldn't we >>>>>>> expect >>>>>>> lots of embedded resources to try to learn whatever information they >>>>>>> can >>>>>>> using this API? Why is that extra risk good for users overall? >>>>>>> >>>>>>> I don't find the "the top-level origin could call hasPrivateToken up >>>>>>> to twice before any other JavaScript is included" mitigation plausible: >>>>>>> folks often don't control the order of their Javascript that closely. >>>>>>> It >>>>>>> seems more likely that sites would just explicitly set the permission >>>>>>> policy to the origins they trust to pick their issuers: is there a >>>>>>> reason >>>>>>> that's not an adequate defense? >>>>>>> >>>>>>> But then you've still just switched the burden from sites that want >>>>>>> to delegate use of this API, to sites that need to defend against >>>>>>> hostile >>>>>>> use of the API. Can you share any analysis of why you think attacks >>>>>>> will be >>>>>>> much less likely than uses, or some other reason that it's good for >>>>>>> users >>>>>>> and sites to switch that burden? >>>>>>> >>>>>>> Thanks, >>>>>>> Jeffrey >>>>>>> >>>>>>> On Mon, Sep 9, 2024 at 5:58 AM Ari Chivukula <ari...@chromium.org> >>>>>>> wrote: >>>>>>> >>>>>>>> Contact emails >>>>>>>> >>>>>>>> ari...@chromium.org, kaust...@chromium.org, sva...@chromium.org, >>>>>>>> ayk...@google.com, nic...@google.com >>>>>>>> >>>>>>>> Specification >>>>>>>> >>>>>>>> https://github.com/WICG/trust-token-api/pull/306 >>>>>>>> >>>>>>>> Summary >>>>>>>> >>>>>>>> Access to the Private State Token API >>>>>>>> <https://wicg.github.io/trust-token-api/> is gated by Permissions >>>>>>>> Policy <https://www.w3.org/TR/permissions-policy/> features. We >>>>>>>> proposed to update the default allowlist >>>>>>>> <https://w3c.github.io/webappsec-permissions-policy/#policy-controlled-feature-default-allowlist> >>>>>>>> >>>>>>>> for both `private-state-token-issuance >>>>>>>> <https://wicg.github.io/trust-token-api/#policy-controlled-feature-private-state-token-issuance>` >>>>>>>> >>>>>>>> and `private-state-token-redemption >>>>>>>> <https://wicg.github.io/trust-token-api/#policy-controlled-feature-private-state-token-redemption>` >>>>>>>> >>>>>>>> features from self to * (wildcard). >>>>>>>> >>>>>>>> >>>>>>>> Blink component >>>>>>>> >>>>>>>> Blink>StorageAccessAPI >>>>>>>> <https://bugs.chromium.org/p/chromium/issues/list?q=component:Blink%3EStorageAccessAPI> >>>>>>>> >>>>>>>> >>>>>>>> Motivation >>>>>>>> >>>>>>>> The Private State Tokens API >>>>>>>> <https://wicg.github.io/trust-token-api/> has received recurring >>>>>>>> feedback from developers >>>>>>>> <https://github.com/WICG/trust-token-api/issues/106> that the >>>>>>>> current requirement to have first-party sites opt-in to allow >>>>>>>> third-parties >>>>>>>> to invoke token issuance and redemption operations is not practical. >>>>>>>> This >>>>>>>> is especially true for use cases where embeds don’t have first-party >>>>>>>> script >>>>>>>> access to either execute the operations directly in first-party >>>>>>>> context, or >>>>>>>> to enable the permission policies on the relevant frames. Current >>>>>>>> default >>>>>>>> requires every site to update permission policy for iframes that embed >>>>>>>> invalid traffic (IVT) detection scripts.Since scale and coverage are >>>>>>>> of >>>>>>>> essence for IVT detection that rely on identifying outlier patterns; >>>>>>>> the >>>>>>>> need for coordination with first-parties places a high cost for >>>>>>>> successful >>>>>>>> adoption. >>>>>>>> >>>>>>>> TAG review >>>>>>>> >>>>>>>> https://github.com/w3ctag/design-reviews/issues/990 >>>>>>>> >>>>>>>> Compatibility >>>>>>>> >>>>>>>> This will not break any existing Private State Token API usage as >>>>>>>> it only increases permissiveness. As usage increases, sites may need >>>>>>>> to >>>>>>>> consider the need to mitigate issuer exhaustion >>>>>>>> <https://wicg.github.io/trust-token-api/#issuer-exhaustion>. >>>>>>>> >>>>>>>> Competing scripts might race to call hasPrivateToken to ensure >>>>>>>> their preferred issuer enters the issuerAssociations >>>>>>>> <https://wicg.github.io/trust-token-api/#issuerassociations> map >>>>>>>> <https://infra.spec.whatwg.org/#ordered-map> before the issuer of >>>>>>>> others given a limit of two per top-level origin >>>>>>>> <https://html.spec.whatwg.org/multipage/webappapis.html#concept-environment-top-level-origin>. >>>>>>>> >>>>>>>> To control this process, the top-level origin >>>>>>>> <https://html.spec.whatwg.org/multipage/webappapis.html#concept-environment-top-level-origin> >>>>>>>> >>>>>>>> could call hasPrivateToken up to twice before any other JavaScript is >>>>>>>> included to ensure their preferred issuers are available. >>>>>>>> >>>>>>>> Few enough websites >>>>>>>> <https://chromestatus.com/metrics/feature/timeline/popularity/3277> >>>>>>>> are using the API that we believe we can broaden the default >>>>>>>> permission set >>>>>>>> and not open any concerning new avenues of attack. >>>>>>>> >>>>>>>> >>>>>>>> Interoperability >>>>>>>> >>>>>>>> Gecko: Position Requested >>>>>>>> <https://github.com/mozilla/standards-positions/issues/1066> >>>>>>>> >>>>>>>> WebKit: Position Requested >>>>>>>> <https://github.com/WebKit/standards-positions/issues/391> >>>>>>>> >>>>>>>> Web developers: Positive >>>>>>>> <https://github.com/WICG/trust-token-api/issues/106> >>>>>>>> >>>>>>>> Debuggability >>>>>>>> >>>>>>>> Storage written can be examined in devtools. >>>>>>>> >>>>>>>> Is this feature fully tested by web-platform-tests? >>>>>>>> >>>>>>>> Yes >>>>>>>> <https://source.chromium.org/chromium/chromium/src/+/main:third_party/blink/web_tests/external/wpt/trust-tokens/> >>>>>>>> >>>>>>>> Tracking bug >>>>>>>> >>>>>>>> https://issues.chromium.org/353738486 >>>>>>>> >>>>>>>> Link to entry on the Chrome Platform Status >>>>>>>> >>>>>>>> https://chromestatus.com/feature/5205548434456576 >>>>>>>> >>>>>>>> -- >>>>>>>> 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/CAGpy5DL2enC2Q1vYBb%2BKA-O3aYW-a3bcvpWnU12NdAvQT6eUcg%40mail.gmail.com >>>>>>>> >>>>>>>> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAGpy5DL2enC2Q1vYBb%2BKA-O3aYW-a3bcvpWnU12NdAvQT6eUcg%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 visit >> https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAGpy5DKLGRyeE9SCYuxyRG0DSLvzzX9qT4%3Dz3MtXW37Ki_9JsA%40mail.gmail.com >> >> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAGpy5DKLGRyeE9SCYuxyRG0DSLvzzX9qT4%3Dz3MtXW37Ki_9JsA%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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