Contact emailsdavid...@chromium.org, dadr...@google.com ExplainerNone
Specificationhttps://datatracker.ietf.org/doc/html/draft-ietf-tls-esni Summary The TLS Encrypted ClientHello (ECH) extension enables clients to encrypt ClientHello messages, which are normally sent in cleartext, under a server’s public key. This allows websites to opt-in to avoid leaking sensitive fields, like the server name, to the network by hosting a special HTTPS RR DNS record. (Earlier iterations of this extension were called Encrypted Server Name Indication, or ESNI.) Blink componentInternals>Network>SSL <https://bugs.chromium.org/p/chromium/issues/list?q=component:Internals%3ENetwork%3ESSL> Search tagsech <https://chromestatus.com/features#tags:ech>, esni <https://chromestatus.com/features#tags:esni>, tls <https://chromestatus.com/features#tags:tls>, ssl <https://chromestatus.com/features#tags:ssl> TAG reviewNot applicable; this is a protocol under IETF TAG review statusNot applicable Risks Interoperability and Compatibility As a networking protocol, interoperability risks look different from a web platform API: This is a draft of a developing protocol, so the final standard will differ from what we ship now. We manage this as in other protocol work: the draft uses different codepoints in the DNS record and ClientHello, set up to not conflict with the final standard. There is also a risk of breaking buggy servers or network middleware. ECH is DNS-gated, so non-ECH servers won't be exposed to ECH itself. We do implement ECH's GREASE mechanism (section 6.2 of the draft), but this should appear as any normal unrecognized extension to non-ECH servers. Servers and network elements that are compliant with RFC 8446, section 9.3, should not be impacted. We will be monitoring for these issues as part of the experiment, comparing error rates and handshake times both for HTTPS servers as a whole, and the subset of those that advertise ECH in DNS. *Gecko*: In development ( https://blog.mozilla.org/security/2021/01/07/encrypted-client-hello-the-future-of-esni-in-firefox ) *WebKit*: No signal *Web developers*: Positive ( https://blog.cloudflare.com/encrypted-client-hello) *Other signals*: Ergonomics ECH is part of TLS, so it is largely abstracted away from web platform APIs themselves. Activation This is a network protocol and thus inherently requires server software changes. It also requires keys deployed in the HTTPS DNS record. At this stage in the process, we do not expect ECH to be deployed beyond a few early adopters. Rather, this experiment is part of real-world testing for the developing protocol. The connection with the DNS record is of particular note. It is possible that, due to DNS caching, etc., that the DNS record we fetch is out of sync with the server instance we talk to. ECH has a built-in recovery mechanism to repair these mismatches. One of the aims of the experiment will be to validate this mechanism. Security See https://datatracker.ietf.org/doc/html/draft-ietf-tls-esni-14#section-10 for security considerations in the specification WebView application risks Does this intent deprecate or change behavior of existing APIs, such that it has potentially high risk for Android WebView-based applications? No WebView-specific risks Goals for experimentation This is a new extension to TLS. As part of the standardization process, we wish to validate the design, and ensure it works, performs well, etc. This is also the first time a TLS extension has been gated on DNS. This introduces a new set of deployment risks. ECH includes mechanisms to mitigate these risks, which we also aim to validate with this experiment. We'll do this by A/B testing clients with and without ECH enabled, and comparing error rates and latency across all TLS connections, and across just connections to hostnames with ECH keys in DNS. We'll also be looking at how often the recovery flow is used. Reason this experiment is being extended n/a Ongoing technical constraints None Debuggability Servers that use ECH are visible in the DevTools security panel. Will this feature be supported on all six Blink platforms (Windows, Mac, Linux, Chrome OS, Android, and Android WebView)?Yes While supported on all platforms, ECH requires keys fetched via DNS in the new HTTPS record. Chrome can currently fetch the HTTPS record over DoH and over our built-in DNS resolver. As of writing, the built-in DNS resolver is not yet enabled on Windows (https://crbug.com/1317948) and Linux ( https://crbug.com/1350321). Is this feature fully tested by web-platform-tests <https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md> ?No (see https://github.com/web-platform-tests/wpt/issues/20159) Flag nameencrypted-client-hello Requires code in //chrome?False Tracking bughttps://crbug.com/1091403 Launch bughttps://crbug.com/1349902 Estimated milestones DevTrial on desktop 105 DevTrial on Android 105 Link to entry on the Chrome Platform Status https://chromestatus.com/feature/6196703843581952 Links to previous Intent discussionsIntent to prototype: https://groups.google.com/a/chromium.org/g/blink-dev/c/YEo4LqB7nWI This intent message was generated by Chrome Platform Status <https://chromestatus.com/>. -- 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/CAF8qwaB488g2%3D1WdmFPnWaAYaXB2pXaVv0-Xe-XXqYFRi5y20A%40mail.gmail.com.
