caddyhttp: create a placeholder for and log ech status (#7328)

Co-authored-by: Francis Lavoie <lavofr@gmail.com>

modules/caddyhttp/app.go

@@ -82,6 +82,7 @@ func init() {
 // `{http.request.tls.proto}` | The negotiated next protocol
 // `{http.request.tls.proto_mutual}` | The negotiated next protocol was advertised by the server
 // `{http.request.tls.server_name}` | The server name requested by the client, if any
+// `{http.request.tls.ech}` | Whether ECH was offered by the client and accepted by the server
 // `{http.request.tls.client.fingerprint}` | The SHA256 checksum of the client certificate
 // `{http.request.tls.client.public_key}` | The public key of the client certificate.
 // `{http.request.tls.client.public_key_sha256}` | The SHA256 checksum of the client's public key.

modules/caddyhttp/marshalers.go

@@ -110,6 +110,7 @@ func (t LoggableTLSConnState) MarshalLogObject(enc zapcore.ObjectEncoder) error
 	enc.AddUint16("cipher_suite", t.CipherSuite)
 	enc.AddString("proto", t.NegotiatedProtocol)
 	enc.AddString("server_name", t.ServerName)
+	enc.AddBool("ech", t.ECHAccepted)
 	if len(t.PeerCertificates) > 0 {
 		enc.AddString("client_common_name", t.PeerCertificates[0].Subject.CommonName)
 		enc.AddString("client_serial", t.PeerCertificates[0].SerialNumber.String())

modules/caddyhttp/replacer.go

@@ -511,6 +511,8 @@ func getReqTLSReplacement(req *http.Request, key string) (any, bool) {
 		return true, true
 	case "server_name":
 		return req.TLS.ServerName, true
+	case "ech":
+		return req.TLS.ECHAccepted, true
 	}
 	return nil, false
 }