delete htlc session keys once they are no longer needed.

fixes #8630

Note: maybe we should plan a WalletDB upgrade to cleanup
existing wallets.

electrum/lnchannel.py

@@ -41,7 +41,7 @@ from .bitcoin import redeem_script_to_address
 from .crypto import sha256, sha256d
 from .transaction import Transaction, PartialTransaction, TxInput, Sighash
 from .logging import Logger
-from .lnonion import decode_onion_error, OnionFailureCode, OnionRoutingFailure
+from .lnonion import OnionFailureCode, OnionRoutingFailure
 from . import lnutil
 from .lnutil import (Outpoint, LocalConfig, RemoteConfig, Keypair, OnlyPubkeyKeypair, ChannelConstraints,
                      get_per_commitment_secret_from_seed, secret_to_pubkey, derive_privkey, make_closing_tx,
@@ -704,8 +704,8 @@ class Channel(AbstractChannel):
     def set_onion_key(self, key: int, value: bytes):
         self.onion_keys[key] = value
 
-    def get_onion_key(self, key: int) -> bytes:
+    def pop_onion_key(self, key: int) -> bytes:
-        return self.onion_keys.get(key)
+        return self.onion_keys.pop(key)
 
     def set_data_loss_protect_remote_pcp(self, key, value):
         self.data_loss_protect_remote_pcp[key] = value
@@ -1437,14 +1437,6 @@ class Channel(AbstractChannel):
         htlc = self.hm.get_htlc_by_id(LOCAL, htlc_id)
         return htlc.payment_hash
 
-    def decode_onion_error(self, reason: bytes, route: Sequence['RouteEdge'],
-                           htlc_id: int) -> Tuple[OnionRoutingFailure, int]:
-        failure_msg, sender_idx = decode_onion_error(
-            reason,
-            [x.node_id for x in route],
-            self.onion_keys[htlc_id])
-        return failure_msg, sender_idx
-
     def receive_htlc_settle(self, preimage: bytes, htlc_id: int) -> None:
         """Settle/fulfill a pending offered HTLC.
         Action must be initiated by REMOTE.

electrum/lnworker.py

@@ -68,7 +68,7 @@ from .lnutil import (Outpoint, LNPeerAddr,
                      NoPathFound, InvalidGossipMsg)
 from .lnutil import ln_compare_features, IncompatibleLightningFeatures
 from .transaction import PartialTxOutput, PartialTransaction, PartialTxInput
-from .lnonion import OnionFailureCode, OnionRoutingFailure, OnionPacket
+from .lnonion import decode_onion_error, OnionFailureCode, OnionRoutingFailure, OnionPacket
 from .lnmsg import decode_msg
 from .i18n import _
 from .lnrouter import (RouteEdge, LNPaymentRoute, LNPaymentPath, is_route_sane_to_use,
@@ -2274,6 +2274,7 @@ class LNWallet(LNWorker):
         self._on_maybe_forwarded_htlc_resolved(chan=chan, htlc_id=htlc_id)
         q = None
         if shi := self.sent_htlcs_info.get((payment_hash, chan.short_channel_id, htlc_id)):
+            chan.pop_onion_key(htlc_id)
             payment_key = payment_hash + shi.payment_secret_orig
             paysession = self._paysessions.get(payment_key)
             if paysession:
@@ -2304,6 +2305,7 @@ class LNWallet(LNWorker):
         self._on_maybe_forwarded_htlc_resolved(chan=chan, htlc_id=htlc_id)
         q = None
         if shi := self.sent_htlcs_info.get((payment_hash, chan.short_channel_id, htlc_id)):
+            onion_key = chan.pop_onion_key(htlc_id)
             payment_okey = payment_hash + shi.payment_secret_orig
             paysession = self._paysessions.get(payment_okey)
             if paysession:
@@ -2316,7 +2318,10 @@ class LNWallet(LNWorker):
             if error_bytes:
                 # TODO "decode_onion_error" might raise, catch and maybe blacklist/penalise someone?
                 try:
-                    failure_message, sender_idx = chan.decode_onion_error(error_bytes, route, htlc_id)
+                    failure_message, sender_idx = decode_onion_error(
+                        error_bytes,
+                        [x.node_id for x in route],
+                        onion_key)
                 except Exception as e:
                     sender_idx = None
                     failure_message = OnionRoutingFailure(-1, str(e))