mholt/caddy-l4

Support ECH Split Mode

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#330 opened on Sep 3, 2025

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enhancementhelp wanted

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Description

Hi, I'd like to set up a Caddy-l4 server to accept ECH, and do SNI/QUIC-SNI routing based on the decrypted Inner ClientHello without terminating TLS. I believe this makes Caddy-l4 act as a client-facing server in the Split Mode topology of the draft spec.

I'd like to ask: could it be some day supported in Caddy-L4?

I guess this would probably involve reading SNI matchers for the anonymity set, and remove certs management entirely from Caddy-L4's side. Though I'm not qualified to speak of implementation details

Please let me know if this can be possible, thanks in advance

Further thoughts (just leaving them here if that's okay): redacted because they're rubbish

Contributor guide

Research direction
Research the ECH split mode topology and investigate how to implement Inner ClientHello SNI routing without terminating TLS in Caddy l4.
Tech stack
go
Domain
backendnetworking
Issue type
Feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
4
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
3-5 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Mostly clear
Prerequisites
GoTLSECH
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
20