Submission Details
Severity:
After one day, a player can enter the raffle and automatically win
Description
To end, Snek Raffle needs to last at least 1 day, have one player, and be open. The problem arises if no one plays the raffle and waits for the end of the duration. In such a scenario, a player can directly enter the raffle and call request_raffle_winner to be sure to win.
def request_raffle_winner() -> uint256:
"""Request a random winner from the VRF Coordinator after a raffle has completed."""
is_open: bool = RaffleState.OPEN == self.raffle_state
has_balance: bool = self.balance > 0
assert is_open and time_passed and has_players and has_balance, ERROR_NOT_ENDED
self.raffle_state = RaffleState.CALCULATING
request_id: uint256 = VRF_COORDINATOR.requestRandomWords(
# c gas lane dans chainlink permet de definir du premium
GAS_LANE,
SUBSCRIPTION_ID,
REQUEST_CONFIRMATIONS,
CALLBACK_GAS_LIMIT,
NUM_WORDS
)
return ERC721._total_supply()
Risk
Likelyhood: Low/Medium
After one day without any person participating the raffle.
Impact: High
A player will be sure to win.
Proof of Concept
PoC to add in `snek_raffle_test.py`
def test_instant_win_after_one_day(
raffle_boa, vrf_coordinator_boa, entrance_fee
):
boa.env.time_travel(seconds=INTERVAL + 1)
boa.env.set_balance(USER, STARTING_BALANCE)
with boa.env.prank(USER):
raffle_boa.enter_raffle(value=entrance_fee)
raffle_boa.request_raffle_winner()
vrf_coordinator_boa.fulfillRandomWords(0, raffle_boa.address)
recent_winner = raffle_boa.get_recent_winner()
winner_balance = boa.env.get_balance(recent_winner)
assert recent_winner == USER
assert winner_balance == entrance_fee
Recommended Mitigation
Begin the delay once the first user enters the raffle.
Alternatively, increase the minimum number of players required to end the raffle.
Rewards breakdown
nSLOC
136This contest has a flat reward structure with the following payouts:
100 EXP
20 EXP
2 EXP
Live
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