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. 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/CAOMQ%2Bw-rdkAAy%3DzSeY_a11geRM27WT1Aavpjcy%3Dzv6_0jorAZQ%40mail.gmail.com.
