Explainer for cross-origin trusted signals #1156

morlovich · 2024-04-29T15:04:20Z

Please note that the implementation of this isn't complete yet!

Just documenting the fields for now + section.

dmdabbs · 2024-04-29T15:24:47Z

FLEDGE.md

+}
+```
+
+Seller signals have additional requirements, as the `trustedScoringSignalsURL` is provided by the


This is true in the case where the publisher is invoking runAdAuction and is the top-level seller. But otherwise, sellers are providing & operating the TSS url.

It's still in context of the publisher page, and thus not really having the full trust of the seller's origin though?

FLEDGE.md

dmdabbs · 2024-04-29T15:36:24Z

FLEDGE.md

+   a  [structured headers list of strings](https://www.rfc-editor.org/rfc/rfc8941) describing origins
+   fetching trusted signals from which is permitted. The trusted scoring signals fetch may not begin
+   until this header is received, in order to avoid leaking bid information to a third party.
+   This means using a cross-origin trusted server for seller information may carry a peformance


This means using a cross-origin trusted server for seller information may carry a peformance penalty.

I anticipate that a common seller use case will be a TSS URL that is same-site with the scoring logic URL. Must this case incur the penalty?

question: given that the original cross-origin fetch is CORS-based, how does Access-Control-Max-Age come into play here? In other words, can we provide a mechanism to cache this granting of cross-site access? As @dmdabbs correctly noted, the use case envisioned is a seller using different sub-domains from the same eTLD+1, and to avoid additional performance penalties as a result of this.

Or, better yet, for those "cross-origin" sharing eLTD+1, is there a way to avoid this penalty entirely?

Hmm, I need to figure out who to discuss this with. Your concern is eminently reasonable, but also generally it feels like web platform has been trying to be more origin than eTLD+1 based.

I think Access-Control-Max-Age doesn't come in at all since the signals fetch doesn't need a preflight, though I guess you're suggesting that the script headers sort of play the same role?

I'm trying to better understand if we have pay this penalty on each auction, and if so, how to avoid it -- my comment about CORS was simply that we're borrowing those ACAO concepts.

On today's WICG meeting, it was mentioned that perhaps the pre-connect may still begin, but it's the fetch() itself that is gated -- can we clarify?

Preconnect should still work, only the load is gated, yes. (I should probably test that, though; this is based on staring at the code really hard).

FLEDGE.md

rdgordon-index · 2024-04-29T20:52:46Z

FLEDGE.md

+In case of bidder signals, the following changes occur:
+1. The fetch is a cross-origin CORS fetch with `Origin:` set to the buyer script's origin.
+2. The value is passed to `crossOriginTrustedSignals` parameter, not the `trustedBiddingSignals`
+   parameter, and there is one more level of nesting denoting the server's origin, e.g:


question: Is there a benefit to this level of nesting, rather than simply another parameter indicating the origin / domain of the scoring signals?

It's a bit harder to forget to check? (And also less parameters)

harder to forget to check?

One is already explicitly checking the alternate signals parameter so that should already be priced in, so to speak.

I was thinking in terms of having code do stuff like:

trustedSignals = trustedBiddingSignals || crossOriginTrustedSignals["kv-server.mydomain.com"];

...which simply can't access an unexpected domain.

rdgordon-index · 2024-04-29T20:54:10Z

FLEDGE.md

+}
+```
+
+Note that older version of Chrome did not support cross-origin trusted signals. You can query


question: from a seller's perspective, we won't really have access to an environment where this can be queried before the auctionConfig is returned... so how will we know when to leverage this new behaviour?

I guess it would require whatever script that bootstraps you to pass that in?

I wonder if "give me an entire table of settings" alternative to queryFeatureSupport would be helpful here, though I worry it may eventually get rather large.

Indeed, this is something that we've been floating on the Prebid.js side for precisely this reason.

So I just landed support for queryFeatureSupport('*') which returns a dictionary with all the features that queryFeatureSupport knows about. Explain update (to the feature detection file) is going to come shortly, just in process of going through the comments here...

... And pushed.

patmmccann · 2024-06-05T15:18:42Z

PA_Feature_Detecting.md

+## Getting browser-side detectable features as an object
+Sometimes it's desirable to get status of all features detectable via `queryFeatureSupport` in a
+forward-compatible way. Sufficiently recent versions provide this functionality via
+`queryFeatureSupport('*')`, which returns a dictionary describing state of various features. Since


a feature request in prebid exists to put the results of this in payloads. Are there any assurances this object won't grow beyond some reasonable size, eg 12 items?

I think this list continue to will grow, but, as discussed in a couple of the recent WICG calls, there are various things we can do to limit it's growth. I think one solution was to pass in a Chrome version, which in turn would make the API only inform you of features that are experimentally enabled beyond what that particular version of Chrome Stable supports by default.

FLEDGE.md

PA_Feature_Detecting.md

FLEDGE.md

JensenPaul · 2024-06-26T12:01:52Z

FLEDGE.md

+Seller signals have additional requirements, as the `trustedScoringSignalsURL` is provided by the
+publisher, not the seller:


Suggested change

Seller signals have additional requirements, as the `trustedScoringSignalsURL` is provided by the

publisher, not the seller:

Seller signals have additional requirements, as the `trustedScoringSignalsURL` is provided by a

context that is not required to be same-origin with the seller:

JensenPaul · 2024-06-26T12:02:44Z

FLEDGE.md

+4. The data version is passed in `browserSignals.crossOriginDataVersion`, not
+   `browserSignals.dataVersion`.
+
+Note that older version of Chrome did not support cross-origin trusted signals. You can query


Suggested change

Note that older version of Chrome did not support cross-origin trusted signals. You can query

Note that older versions of Chrome did not support cross-origin trusted signals. You can query

SHA: 38d3b02 Reason: push, by michaelkleber Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Maks Orlovich added 3 commits April 29, 2024 10:06

Start on cross-origin trusted signals explainer.

b10a284

Just documenting the fields for now + section.

The new section, feature detection.

5c7ea5b

Fix links

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rdgordon-index mentioned this pull request Apr 30, 2024

relaxing the same-origin policy to allow for subdomains #813

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Maks Orlovich added 2 commits May 10, 2024 14:35

Feedback + queryFeatureSupport('*')

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Talk about crossOriginDataVersion.

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michaelkleber merged commit 38d3b02 into WICG:main Jul 11, 2024
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Explainer for cross-origin trusted signals (#1156)

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Explainer for cross-origin trusted signals #1156

Explainer for cross-origin trusted signals #1156

morlovich commented Apr 29, 2024

dmdabbs Apr 29, 2024

morlovich Apr 30, 2024

dmdabbs Apr 29, 2024

rdgordon-index Apr 29, 2024

rdgordon-index Apr 30, 2024

morlovich Apr 30, 2024

rdgordon-index May 8, 2024 •

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rdgordon-index May 8, 2024

morlovich May 9, 2024

rdgordon-index Apr 29, 2024

morlovich Apr 30, 2024

dmdabbs Apr 30, 2024

morlovich May 10, 2024

rdgordon-index Apr 29, 2024

morlovich Apr 30, 2024

rdgordon-index May 8, 2024

morlovich May 10, 2024

morlovich May 10, 2024

patmmccann Jun 5, 2024

JensenPaul Jun 17, 2024

JensenPaul Jun 26, 2024

morlovich Jun 26, 2024

JensenPaul Jun 26, 2024

morlovich Jun 26, 2024

		Seller signals have additional requirements, as the `trustedScoringSignalsURL` is provided by the
		publisher, not the seller:

	Note that older version of Chrome did not support cross-origin trusted signals. You can query
	Note that older versions of Chrome did not support cross-origin trusted signals. You can query

Explainer for cross-origin trusted signals #1156

Explainer for cross-origin trusted signals #1156

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morlovich commented Apr 29, 2024

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rdgordon-index May 8, 2024 • edited Loading

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rdgordon-index May 8, 2024 •

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