[blink-dev] Intent to Experiment: Extending Storage Access API (SAA) to non-cookie storage
Ari Chivukula
Contact emails
ari...@chromium.org, wande...@chromium.org, joha...@chromium.org, hel...@google.com
Specification
https://arichiv.github.io/saa-non-cookie-storage/
Feedback
https://github.com/arichiv/saa-non-cookie-storage/issues
Intent to Prototype
https://groups.google.com/a/chromium.org/g/blink-dev/c/inRN8tI49O0
Summary
An origin trial, StorageAccessAPIBeyondCookies, will be made available which enables the proposed extension of the Storage Access API (backwards compatible) to allow access to unpartitioned (cookie and non-cookie) storage in a third-party context. The current API only provides access to cookies, which have different use-cases than non-cookie storage (discussed more in the Motivation section). The API can be used as follows (JS running in an embedded iframe):
// Request a new storage handle via rSA (this should prompt the user)
let handle = await document.requestStorageAccess({all: true});
// Write some 1P context sessionstorage
handle.sessionStorage.setItem("userid", "1234");
// Write some 1P context localstorage
handle.localStorage.setItem("preference", "A");
// Open or create an indexedDB that is shared with the 1P context
let messageDB = handle.indexedDB.open("messages");
// Use locks shared with the 1P context
await handle.locks.request(“example”, …);
The same flow would be used by iframes to get a storage handle when their top-level ancestor successfully called rSAFor, just that in this case the storage-access permission was already granted and thus the rSA call would not require a user gesture or show a prompt, allowing for “hidden” iframes accessing storage.
Beyond calling this additional extension, access to non-cookie storage would match the current requirements for cookie access through the Storage Access API. For example, in Chrome, no prompt is shown when the origins are in the same RWS (Related Website Sets, the new name for First Party Sets). Origins that are not part of the same RWS would be subject to the prompting requirements of the Storage Access API in Chrome.
The origin trial will be available from M120 until M124 (or after Tue, June 11, 2024 in any milestone).
Only Session Storage, Local Storage, Indexed DB, and Web Locks will be available initially, but other storage and communication mechanisms will be added to the Origin Trial in future milestones. These additions will be announced in this thread after each branch cut. Feedback from developers would aid us in prioritizing specific mechanisms for inclusion.
Blink component
Motivation
There has been increasing developer and implementer interest in first-party DOM Storage and Quota Managed Storage being available in third-party contexts the same way that Cookies already can be. In the absence of such a solution, we would in effect be pushing developers to migrate to Cookies from other storage mechanisms. There are tradeoffs between Cookie and non-Cookie storage (size, flexibility, server exposure, network request size, etc.) that could impact user experience from a privacy, security and performance perspective (e.g., cookies are included in HTTP requests and not just available via JavaScript). To prevent sub-optimal use of cookies and to preserve context, we propose a solution for developers to regain 3p access to unpartitioned storage to avoid user-facing breakage in browsers shipping storage partitioning.
TAG review
https://github.com/w3ctag/design-reviews/issues/906
Compatibility
The Storage Access API is already implemented in Safari, Firefox, and Chrome, but the proposed API shape would not change existing behavior without new arguments added.
Interoperability
Gecko: No Position Yet https://github.com/mozilla/standards-positions/issues/898
WebKit: No Position Yet https://github.com/WebKit/standards-positions/issues/262
Web developers: Positive
Debuggability
Storage written can be examined in devtools.
Is this feature fully tested by web-platform-tests?
Tracking bug
Link to entry on the Chrome Platform Status
https://chromestatus.com/feature/5175585823522816
Chris Harrelson
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Ari Chivukula
Rick Byers
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