BattleChain Confidence Pools
Cyfrin
FoundrySolidityLayer 2
7.25 ETH
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Submission Details
Severity: low
Valid

`sweepUnclaimedBonus` does not set `claimsStarted`, understating good-faith bounty

Author Revealed upon completion

Description

  • The moderator may correct the outcome before any claim (claimsStarted == false). Every path that moves accounted value (claimSurvived / claimExpired / claimCorrupted / sweepUnclaimedCorrupted) sets claimsStarted = true on value movement, closing the re-flag window.

  • sweepUnclaimedBonus() moves accounted bonus and reduces totalBonus but intentionally does not set claimsStarted. Recovery can sweep the accounted bonus before the moderator re-flags the outcome to good-faith CORRUPTED, making the later snapshot's bountyEntitlement (= snapshotTotalStaked + snapshotTotalBonus) lower than it should be.

// src/ConfidencePool.sol
function flagOutcome(...) external onlyModerator {
@> if (outcome != PoolStates.Outcome.UNRESOLVED && claimsStarted) revert OutcomeAlreadySet();
...
@> bountyEntitlement = willBeGoodFaithCorrupted ? snapshotTotalStaked + snapshotTotalBonus : 0;
}
​
function sweepUnclaimedBonus() external nonReentrant {
...
if (totalEligibleStake == 0 || riskWindowStart == 0) {
@> totalBonus -= amount <= totalBonus ? amount : totalBonus;
}
// Intentionally does NOT set claimsStarted.
@> stakeToken.safeTransfer(recoveryAddress, amount); // bonus moved, but outcome not latched
}

Risk

Likelihood:

  • The moderator first flags SURVIVED (or EXPIRED) with riskWindowStart == 0, so bonus is not reserved for stakers

  • Recovery (or any caller) calls sweepUnclaimedBonus() before the moderator re-flags to good-faith CORRUPTED

  • The moderator then re-flags to good-faith CORRUPTED naming an attacker, snapshotting the already-swept totalBonus

Impact:

  • The attacker's bountyEntitlement is permanently understated; the swept bonus portion is unrecoverable by the attacker

  • The value split between recovery and attacker is disturbed by a permissionless sweep, diverging from the bounty size the moderator intended when correcting the outcome

Proof of Concept

function testReflagToCorruptedAfterBonusSweepDoesNotOverstateEntitlement() external {
_stake(alice, 100 * ONE);
_contributeBonus(carol, 50 * ONE);
​
attackRegistry.setAgreementState(IAttackRegistry.ContractState.CORRUPTED);
vm.prank(moderator);
pool.flagOutcome(PoolStates.Outcome.SURVIVED, false, address(0));
​
pool.sweepUnclaimedBonus(); // recovery front-runs, gets 50 bonus, claimsStarted still false
​
vm.prank(moderator);
pool.flagOutcome(PoolStates.Outcome.CORRUPTED, true, attacker);
​
assertEq(pool.bountyEntitlement(), 100 * ONE); // should be 150, actually only 100
​
vm.prank(attacker);
pool.claimAttackerBounty();
assertEq(token.balanceOf(attacker), 100 * ONE);
}
forge test --offline --match-test testReflagToCorruptedAfterBonusSweepDoesNotOverstateEntitlement

Recommended Mitigation

if (totalEligibleStake == 0 || riskWindowStart == 0) {
+ uint256 bonusRemoved = amount <= totalBonus ? amount : totalBonus;
totalBonus -= amount <= totalBonus ? amount : totalBonus;
+ if (bonusRemoved > 0 && !claimsStarted) claimsStarted = true;
}
- // Intentionally does NOT set claimsStarted.
stakeToken.safeTransfer(recoveryAddress, amount);
Updates

Lead Judging Commences

inallhonesty Lead Judge 2 days ago
Submission Judgement Published
Validated
Assigned finding tags:

sweepUnclaimedBonus() omits claimsStarted latch, letting a moderator re-flag re-snapshot a drained totalBonus and short the CORRUPTED bounty

Impact – Medium Up to the entire bonus pool can be routed to the wrong party for good, with no on-chain way to unwind it, and in a stakerless pool the effect is total since bountyEntitlement computes to zero and claimAttackerBounty reverts outright. This impact is definitely not High: the pool stays solvent throughout with no principal ever at risk, and the money ends up at the sponsor's own recoveryAddress, which in most pools means a sponsor recovering a bonus they funded themselves. The whitehat's claim on that bonus also only exists because the moderator changed their mind after the fact. Likelihood – Low Four separate things have to coincide: nobody touches the pool for the whole active-risk window (or there are no stakers to begin with), the moderator flags SURVIVED and later reverses to CORRUPTED, that reversal is good-faith with a named attacker, and a sweep lands between the two flags. The first cuts against staker self-interest, since skipping the poke costs them their entire bonus share, and the second asks the moderator to overturn a scope judgement, which is a bigger deal than the typo fix DESIGN.md #4 offers the window for. The sweep itself I'd treat as near-certain once the rest holds, given it's permissionless and the sponsor has an obvious reason to make the call, but assembling the first three in one pool lifecycle is where this stays rare.

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