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Hide ALPN in ECH #383

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Merged
mingyech merged 1 commit into from
Feb 27, 2026
+9 −4
Merged

Hide ALPN in ECH #383

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5 changes: 3 additions & 2 deletions handshake_messages.go
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Original file line number Diff line number Diff line change
Expand Up @@ -242,10 +242,11 @@ func (m *clientHelloMsg) marshalMsgReorderOuterExts(echInner bool, outerExts []u
}
}
if len(m.alpnProtocols) > 0 {
// RFC 7301, Section 3.1
if echInner {
// ALPN extension copy is skipped because in ECH inner, the ALPN might be different
if echInner && false {
echOuterExts = append(echOuterExts, extensionALPN)
} else {
// RFC 7301, Section 3.1
exts.AddUint16(extensionALPN)
exts.AddUint16LengthPrefixed(func(exts *cryptobyte.Builder) {
exts.AddUint16LengthPrefixed(func(exts *cryptobyte.Builder) {
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8 changes: 6 additions & 2 deletions u_tls_extensions.go
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Original file line number Diff line number Diff line change
Expand Up @@ -611,8 +611,12 @@ type ALPNExtension struct {
}

func (e *ALPNExtension) writeToUConn(uc *UConn) error {
uc.config.NextProtos = e.AlpnProtocols
uc.HandshakeState.Hello.AlpnProtocols = e.AlpnProtocols
// Do not overwrite NextProtos in config if Encrypted Client Hello is used.
// Config ALPN will be written to inner Hello
if uc.config.EncryptedClientHelloConfigList == nil {
uc.config.NextProtos = e.AlpnProtocols
uc.HandshakeState.Hello.AlpnProtocols = e.AlpnProtocols
}
return nil
}

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