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Fix RequestView over-funding reentrancy (do_give double-transfer)

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A follow-up reentrancy sweep of the five remaining money-moving views found
one more instance of the same bug class. The other four (quests, prestige,
fish, shop) verified clean - their underlying do_* functions are idempotent.

RequestView / FundModal (commands/economy_support_commands.py):
- on_submit read self._view.remaining, then awaited do_give, then decremented
  remaining. Because discord.py dispatches each modal submit as its own task
  and do_give is a plain non-idempotent transfer, a funder could open two
  modals and submit both before the first resolved: both read the same
  pre-decrement remaining, both passed the range check, and both transferred
  `amount` - over-funding the request (remaining goes negative) and moving up
  to the funder's whole balance.
- Fix: reserve the amount synchronously (decrement remaining BEFORE the do_give
  await, with no await in between - atomic under asyncio), and roll the
  reservation back if the transfer fails. The second concurrent submit now
  sees the reduced remaining and is rejected. Added a cheap _fund guard
  (remaining<=0 / is_finished) so a click on a funded request doesn't open a
  dead modal.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Rene Arumetsa
2026-08-10 18:49:25 +03:00
parent 968356f925
commit 3b35f82d80
2 changed files with 11 additions and 1 deletions
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11
commands/economy_support_commands.py
View File

@@ -38,15 +38,21 @@ def register_economy_support_commands(
)
return
# Reserve the amount synchronously (no await between the range check
# and the decrement) so two concurrent modal submits can't both fund
# the same request. discord.py runs each submit as its own task and
# do_give is not idempotent, so without this reservation a funder
# could double-submit and transfer `amount` more than once.
self._view.remaining -= amount
res = await economy.do_give(interaction.user.id, self._view.requester.id, amount)
if not res["ok"]:
self._view.remaining += amount # roll back the reservation
data = await economy.get_user(interaction.user.id)
await interaction.response.send_message(
S.ERR["broke"].format(bal=coin(data["balance"])), ephemeral=True
)
return
self._view.remaining -= amount
funded_line = S.REQUEST_UI["funded_line"].format(
name=interaction.user.display_name,
amount=coin(amount),
@@ -84,6 +90,9 @@ def register_economy_support_commands(
self.add_item(self.fund_btn)
async def _fund(self, interaction: discord.Interaction):
if self.remaining <= 0 or self.is_finished():
await interaction.response.send_message(S.ERR["request_closed"], ephemeral=True)
return
if interaction.user.id == self.requester.id:
await interaction.response.send_message(S.ERR["request_self_fund"], ephemeral=True)
return