trampoline: forwarding, use correct secret for legacy case

electrum/lnpeer.py

@@ -1443,7 +1443,12 @@ class Peer(Logger):
 
         payload = trampoline_onion.hop_data.payload
         payment_hash = htlc.payment_hash
+        payment_data = payload.get('payment_data')
+        if payment_data:  # legacy case
+            payment_secret = payment_data['payment_secret']
+        else:
             payment_secret = os.urandom(32)
+
         try:
             outgoing_node_id = payload["outgoing_node_id"]["outgoing_node_id"]
             amt_to_forward = payload["amt_to_forward"]["amt_to_forward"]

electrum/trampoline.py

@@ -247,7 +247,7 @@ def create_trampoline_onion(*, route, amount_msat, final_cltv, total_msat, payme
         # only for final
         if i == num_hops - 1:
             payload["payment_data"] = {
-                "payment_secret":payment_secret,
+                "payment_secret": payment_secret,
                 "total_msat": total_msat
             }
         # legacy
@@ -255,7 +255,7 @@ def create_trampoline_onion(*, route, amount_msat, final_cltv, total_msat, payme
             payload["invoice_features"] = {"invoice_features":route_edge.invoice_features}
             payload["invoice_routing_info"] = {"invoice_routing_info":route_edge.invoice_routing_info}
             payload["payment_data"] = {
-                "payment_secret":payment_secret,
+                "payment_secret": payment_secret,
                 "total_msat": total_msat
             }
         _logger.info(f'payload {i} {payload}')