plugin: nwc: unify budget_allows_spend and add_to_budget
What the developer wrote
Authored by f321x
plugin: nwc: unify budget_allows_spend and add_to_budget
There is now only add_to_budget which will return None if the budget
doesn't allow for this spend. It will always add the spend to the
budget, even if the user has no budget so it can be used for display
purposes (and simpler code, only one path).
What changed, and why it matters
This commit is a code cleanup in Electrum's NWC (Nostr Wallet Connect) plugin. It merges two separate budget-checking functions into one. Previously, the code first checked if a payment was within budget, then recorded it. Now it does both in one step. The commit message and diff do not describe any security bug being fixed; it appears to be a simplification/refactoring change. There is no evidence this fixes a known vulnerability.
No immediate security action required. Treat as routine refactoring. If auditing NWC budget enforcement, verify that add_to_budget is called before any payment attempt and that returning None correctly blocks over-budget payments in all code paths.
Security signals we found
Refactoring of budget enforcement logic in NWC plugin
No explicit security fix described in commit message or diff
Behavior change: budget_spends list is now populated even when daily_limit_sat is None
No input validation, cryptographic, or authorization changes visible
Evidence from the diff
The patch refactors NWCServer in electrum/plugins/nwc/nwcserver.py. It removes the standalone budget_allows_spend() method and merges its logic into add_to_budget(). The new add_to_budget() returns None if the requested spend exceeds the configured daily budget, otherwise records the spend and returns the budget item. A side effect is that the spend is now always recorded to budget_spends even when no daily limit is configured, whereas before add_to_budget() was only called after a successful budget check. This is intentional for display/statistics purposes per the commit message. No security weakness is directly addressed by the diff.
Changed components
electrum/plugins/nwc/nwcserver.pyNWCServer.pay_invoice methodNWCServer.add_to_budget methodNWC budget tracking for Nostr Wallet Connect connectionsInspect captured patch +16 / −21
diff --git a/electrum/plugins/nwc/nwcserver.py b/electrum/plugins/nwc/nwcserver.py
index c0682c3..a050746 100644
--- a/electrum/plugins/nwc/nwcserver.py
+++ b/electrum/plugins/nwc/nwcserver.py
@@ -816,9 +816,9 @@ class NWCServer(Logger, EventListener):
elif invoice.get_amount_msat() is None:
invoice.set_amount_msat(amount_msat)
- if not self.budget_allows_spend(request_pub, msat_requested=amount_msat or invoice.get_amount_msat()):
+ budget_item = self.add_to_budget(request_pub, msat_requested=amount_msat or invoice.get_amount_msat())
+ if not budget_item:
return self.get_error_response("QUOTA_EXCEEDED", "Payment exceeds daily limit")
- budget_item = self.add_to_budget(request_pub, amount_msat=amount_msat or invoice.get_amount_msat())
self.wallet.save_invoice(invoice)
success = None
@@ -848,18 +848,6 @@ class NWCServer(Logger, EventListener):
self.logger.info(f"failed to pay invoice request from NWC: {log}")
return response
- def add_to_budget(self, client_pub: str, *, amount_msat: int) -> list[int]:
- """
- If client_pub has a budget, check if the amount is within the budget and add it to the budget.
- Return True if the payment is allowed (within the budget)
- """
- if 'budget_spends' not in self.connections[client_pub]:
- self.connections[client_pub]['budget_spends'] = []
- # tuples don't work because jsondb converts them to lists on reload
- budget_item = [amount_msat, int(time.time())]
- self.connections[client_pub]['budget_spends'].append(budget_item)
- return budget_item
-
def remove_from_budget(self, client_pub: str, budget_item: list[int]) -> None:
assert len(budget_item) == 2, budget_item
budget_spends = self.connections[client_pub].get('budget_spends', [])
@@ -888,14 +876,21 @@ class NWCServer(Logger, EventListener):
continue # could happen if there is a race
return used_budget
- def budget_allows_spend(self, client_pub: str, *, msat_requested: int) -> bool:
+ def add_to_budget(self, client_pub: str, *, msat_requested: int) -> Optional[list[int]]:
+ if 'budget_spends' not in self.connections[client_pub]:
+ self.connections[client_pub]['budget_spends'] = []
+
+ # check if budget allows this spend
client_budget_sat: Optional[int] = self.connections[client_pub].get('daily_limit_sat')
- if client_budget_sat is None:
- return True # unlimited budget
- used_budget_msat: int = self.get_used_budget_msat(client_pub)
- if used_budget_msat + msat_requested > client_budget_sat * 1000:
- return False
- return True
+ if client_budget_sat is not None:
+ used_budget_msat: int = self.get_used_budget_msat(client_pub)
+ if used_budget_msat + msat_requested > client_budget_sat * 1000:
+ return None
+
+ # tuples don't work because jsondb converts them to lists on reload
+ budget_item = [msat_requested, int(time.time())]
+ self.connections[client_pub]['budget_spends'].append(budget_item)
+ return budget_item
async def publish_info_event(self):
"""
Why this scored 27/100
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