lnpeer: better error handling when processing onion packets

electrum/lnonion.py

@@ -484,6 +484,7 @@ class OnionFailureCode(IntEnum):
     FINAL_INCORRECT_HTLC_AMOUNT =             19
     CHANNEL_DISABLED =                        UPDATE | 20
     EXPIRY_TOO_FAR =                          21
+    INVALID_ONION_PAYLOAD =                   PERM | 22
 
 
 # don't use these elsewhere, the names are ambiguous without context

electrum/lnpeer.py

@@ -1149,7 +1149,10 @@ class Peer(Logger):
         if not forwarding_enabled:
             self.logger.info(f"forwarding is disabled. failing htlc.")
             return OnionRoutingFailureMessage(code=OnionFailureCode.PERMANENT_CHANNEL_FAILURE, data=b'')
-        next_chan_scid = processed_onion.hop_data.payload["short_channel_id"]["short_channel_id"]
+        try:
+            next_chan_scid = processed_onion.hop_data.payload["short_channel_id"]["short_channel_id"]
+        except:
+            return OnionRoutingFailureMessage(code=OnionFailureCode.INVALID_ONION_PAYLOAD, data=b'\x00\x00\x00')
         next_chan = self.lnworker.get_channel_by_short_id(next_chan_scid)
         local_height = self.network.get_local_height()
         if next_chan is None:
@@ -1162,7 +1165,10 @@ class Peer(Logger):
                              f"chan state {next_chan.get_state()}, peer state: {next_chan.peer_state}")
             data = outgoing_chan_upd_len + outgoing_chan_upd
             return OnionRoutingFailureMessage(code=OnionFailureCode.TEMPORARY_CHANNEL_FAILURE, data=data)
-        next_cltv_expiry = processed_onion.hop_data.payload["outgoing_cltv_value"]["outgoing_cltv_value"]
+        try:
+            next_cltv_expiry = processed_onion.hop_data.payload["outgoing_cltv_value"]["outgoing_cltv_value"]
+        except:
+            return OnionRoutingFailureMessage(code=OnionFailureCode.INVALID_ONION_PAYLOAD, data=b'\x00\x00\x00')
         if htlc.cltv_expiry - next_cltv_expiry < NBLOCK_OUR_CLTV_EXPIRY_DELTA:
             data = htlc.cltv_expiry.to_bytes(4, byteorder="big") + outgoing_chan_upd_len + outgoing_chan_upd
             return OnionRoutingFailureMessage(code=OnionFailureCode.INCORRECT_CLTV_EXPIRY, data=data)
@@ -1172,7 +1178,10 @@ class Peer(Logger):
             return OnionRoutingFailureMessage(code=OnionFailureCode.EXPIRY_TOO_SOON, data=data)
         if max(htlc.cltv_expiry, next_cltv_expiry) > local_height + lnutil.NBLOCK_CLTV_EXPIRY_TOO_FAR_INTO_FUTURE:
             return OnionRoutingFailureMessage(code=OnionFailureCode.EXPIRY_TOO_FAR, data=b'')
-        next_amount_msat_htlc = processed_onion.hop_data.payload["amt_to_forward"]["amt_to_forward"]
+        try:
+            next_amount_msat_htlc = processed_onion.hop_data.payload["amt_to_forward"]["amt_to_forward"]
+        except:
+            return OnionRoutingFailureMessage(code=OnionFailureCode.INVALID_ONION_PAYLOAD, data=b'\x00\x00\x00')
         forwarding_fees = fee_for_edge_msat(
             forwarded_amount_msat=next_amount_msat_htlc,
             fee_base_msat=lnutil.OUR_FEE_BASE_MSAT,
@@ -1221,12 +1230,20 @@ class Peer(Logger):
         if local_height + MIN_FINAL_CLTV_EXPIRY_ACCEPTED > htlc.cltv_expiry:
             reason = OnionRoutingFailureMessage(code=OnionFailureCode.FINAL_EXPIRY_TOO_SOON, data=b'')
             return False, reason
-        cltv_from_onion = processed_onion.hop_data.payload["outgoing_cltv_value"]["outgoing_cltv_value"]
+        try:
+            cltv_from_onion = processed_onion.hop_data.payload["outgoing_cltv_value"]["outgoing_cltv_value"]
+        except:
+            reason = OnionRoutingFailureMessage(code=OnionFailureCode.INVALID_ONION_PAYLOAD, data=b'\x00\x00\x00')
+            return False, reason
         if cltv_from_onion != htlc.cltv_expiry:
             reason = OnionRoutingFailureMessage(code=OnionFailureCode.FINAL_INCORRECT_CLTV_EXPIRY,
                                                 data=htlc.cltv_expiry.to_bytes(4, byteorder="big"))
             return False, reason
-        amount_from_onion = processed_onion.hop_data.payload["amt_to_forward"]["amt_to_forward"]
+        try:
+            amount_from_onion = processed_onion.hop_data.payload["amt_to_forward"]["amt_to_forward"]
+        except:
+            reason = OnionRoutingFailureMessage(code=OnionFailureCode.INVALID_ONION_PAYLOAD, data=b'\x00\x00\x00')
+            return False, reason
         if amount_from_onion > htlc.amount_msat:
             reason = OnionRoutingFailureMessage(code=OnionFailureCode.FINAL_INCORRECT_HTLC_AMOUNT,
                                                 data=htlc.amount_msat.to_bytes(8, byteorder="big"))
@@ -1463,6 +1480,9 @@ class Peer(Logger):
                         error_reason = OnionRoutingFailureMessage(code=OnionFailureCode.INVALID_ONION_KEY, data=sha256(onion_packet_bytes))
                     except InvalidOnionMac:
                         error_reason = OnionRoutingFailureMessage(code=OnionFailureCode.INVALID_ONION_HMAC, data=sha256(onion_packet_bytes))
+                    except Exception as e:
+                        self.logger.info(f"error processing onion packet: {e!r}")
+                        error_reason = OnionRoutingFailureMessage(code=OnionFailureCode.TEMPORARY_NODE_FAILURE, data=b'')
                     else:
                         if processed_onion.are_we_final:
                             preimage, error_reason = self.maybe_fulfill_htlc(