On 9/11/23 6:34 PM, 'David Adrian' via blink-dev wrote:
Contact emails
david...@chromium.org, dadr...@google.com
Explainer
None
Specification
https://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 component
Internals>Network>SSL
<https://bugs.chromium.org/p/chromium/issues/list?q=component:Internals%3ENetwork%3ESSL>
Search tags
ech <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 review
Not applicable; this is a protocol under IETF
TAG review status
Not 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
Could we please request a signal?
https://github.com/WebKit/standards-positions/issues/new/choose
/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
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.
Is this feature fully tested by web-platform-tests
<https://chromium.googlesource.com/chromium/src/+/main/docs/testing/web_platform_tests.md>?
No
Flag name on chrome://flags
encrypted-client-hello
Finch feature name
None
Non-finch justification
None
Requires code in //chrome?
False
Tracking bug
https://crbug.com/1091403
Launch bug
https://crbug.com/1349902
Availability expectation
Feature is also being launched in Firefox.
Sample links
https://tls-ech.dev
Estimated milestones
Shipping on desktop 117
OriginTrial desktop last 116
OriginTrial desktop first 115
DevTrial on desktop 105
Shipping on Android 117
OriginTrial Android last 116
OriginTrial Android first 115
DevTrial on Android 105
Anticipated spec changes
Open questions about a feature may be a source of future web compat or
interop issues. Please list open issues (e.g. links to known github
issues in the project for the feature specification) whose resolution
may introduce web compat/interop risk (e.g., changing to naming or
structure of the API in a non-backward-compatible way).
n/a
Link to entry on the Chrome Platform Status
https://chromestatus.com/feature/6196703843581952
Links to previous Intent discussions
Intent to prototype:
https://groups.google.com/a/chromium.org/g/blink-dev/c/YEo4LqB7nWI
Intent to Experiment:
https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAF8qwaB488g2%3D1WdmFPnWaAYaXB2pXaVv0-Xe-XXqYFRi5y20A%40mail.gmail.com
This intent message was generated by Chrome Platform Status
<https://chromestatus.com/>.
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