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Explainer https://github.com/MattMenke2/Explainer---Partition-Network-State/blob/main/README.md Specification https://fetch.spec.whatwg.org/#connections Summary Partition network state by the network partition key (which consists of top frame site and frame site), to protect against cross-site tracking through the use of side channels. "Network State" here includes connections (H1, H2, H3, websocket), the DNS cache, ALPN/H2 support data, TLS/H3 resumption information, Reporting/NEL configuration and uploads, and Expect-CT information. Unpartitioned network state allows for side-channel timing attacks, where one site can figure out if another has been visited recently. For example, if the connection is made quickly, it may be assumed that the socket was warm. It also allows for third parties to track users across first party contexts they are loaded in using a variety of techniques (tracking socket reuse, using per-user alternative service advertisements, etc). Partitioning storage may reduce Chromium’s ability to reuse network resources. We’ve enabled network state partitioning in a 5% experiment on Stable. It slows time to first contentful paint by about 0.5%, and slows cross-site iframe time to first contentful paint by about 5%. These are very rough averages that vary across platforms and users. Explainer: https://github.com/MattMenke2/Explainer---Partition-Network-State/blob/main/README.md Blink component Internals>Network <https://bugs.chromium.org/p/chromium/issues/list?q=component:Internals%3ENetwork> TAG review https://github.com/w3ctag/design-reviews/issues/596 TAG review status Issues addressed Risks Interoperability and Compatibility This proposal partitions the DNS cache and connections, which could result in longer load times when previously reusable resources can no longer be reused. The performance impact will likely be most visible in cross-site iframes. Chromium's implementation partitions state by (top-level site, innermost frame site), unlike the implementation shipped by other browser vendors, which just uses top-level site. This will also potentially increase the number of connections made to sites, both because connections can't be reused as often, and because Chromium is less likely to know in advance if H2 or H3 can be used with a site. When that isn't known, up to six connections are created to a site, instead of one or two. NEL, Reporting, and Expect-CT: Report-To headers tell Chromium how and when to inform a site of certain errors. Partitioning this information means that Chromium potentially won't know where to report errors, particularly the first time it issues a request to a site in a particular context. The latest version of the Reporting API (Reporting V1, to replace Reporting V0) is scoped to frames, anyways, so is already subject to a more restrictive limitation. None of these changes is expected to visibly break sites. Gecko: Shipped/Shipping ( https://bugzilla.mozilla.org/show_bug.cgi?id=1590107) WebKit: Shipped/Shipping ( https://webkit.org/status/#?search=client-side%20storage%20partitioning) Web developers: No signals Other signals: Ergonomics The only risk here is decreased performance, particularly in cross-site iframes. Debuggability DevTools won't display the network partition key, but will continue to display the results of network requests accurately. Is this feature fully tested by web-platform-tests <https://chromium.googlesource.com/chromium/src/+/master/docs/testing/web_platform_tests.md> ? No, though it does have partial coverage. web-platform-tests can't test some features like, e.g., DNS cache partitioning. Flag name SplitHostCacheByNetworkIsolationKey, PartitionConnectionsByNetworkIsolationKey, PartitionHttpServerPropertiesByNetworkIsolationKey, PartitionSSLSessionsByNetworkIsolationKey, PartitionExpectCTStateByNetworkIsolationKey, PartitionNelAndReportingByNetworkIsolationKey Requires code in //chrome? False Tracking bug https://crbug.com/993801 Launch bug https://crbug.com/1166303 Estimated milestones Plan to roll out in M97/M98 over the course of February Link to entry on the Chrome Platform Status https://chromestatus.com/feature/6713488334389248 Links to previous Intent discussionsIntent to prototype: https://groups.google.com/a/chromium.org/g/blink-dev/c/6KKXv1PqPZ0/m/nm2z5I_MBAAJ Intent to Extend Experiment: https://groups.google.com/a/chromium.org/g/blink-dev/c/sLC_W6B8big/m/5sk787RQBAAJ -- 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 on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAEK7mvrYvoXcc%2B28rFrHbb1tEJN6HPf1y%3DHdE%2BcGe3tuJwsAnA%40mail.gmail.com.
