> > > - 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. 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