BattleChain Confidence Pools
Cyfrin
FoundrySolidityLayer 2
7.25 ETH
View all submissions
Previous Next
Submission Details
Impact: medium
Likelihood: low

Accounted bonus can be swept while the outcome-correction window remains open

Author Revealed upon completion

Description

  • The moderator may correct a previously flagged outcome until the first participant relies on it. claimsStarted is intended to close that correction window when value movement makes the old distribution final.

  • In a no-observed-risk SURVIVED outcome, sweepUnclaimedBonus lets any caller transfer the entire accounted totalBonus to recoveryAddress and decrements the live bonus accounting, but deliberately leaves claimsStarted false. The moderator can therefore still correct the outcome to good-faith CORRUPTED, yet the new bounty snapshot excludes bonus that has already left. The named whitehat permanently loses the advertised whole-pool bounty even though the contract still represents the outcome as correctable.

function flagOutcome(PoolStates.Outcome newOutcome, bool goodFaith_, address attacker_)
external
onlyModerator
{
// @> Re-flagging remains available while claimsStarted is false.
if (outcome != PoolStates.Outcome.UNRESOLVED && claimsStarted) {
revert OutcomeAlreadySet();
}
// ...
​
snapshotTotalStaked = totalEligibleStake;
// @> A correction re-snapshots the reduced live totalBonus.
snapshotTotalBonus = totalBonus;
bountyEntitlement =
willBeGoodFaithCorrupted ? snapshotTotalStaked + snapshotTotalBonus : 0;
}
​
function sweepUnclaimedBonus() external nonReentrant {
// ...
uint256 reserved;
if (totalEligibleStake != 0) {
reserved = totalEligibleStake;
// @> With no observed risk, none of totalBonus is reserved.
if (riskWindowStart != 0) {
reserved += snapshotTotalBonus - claimedBonus;
}
}
​
uint256 freeBalance = stakeToken.balanceOf(address(this));
uint256 amount = freeBalance > reserved ? freeBalance - reserved : 0;
​
if (totalEligibleStake == 0 || riskWindowStart == 0) {
// @> Accounted value is removed before the correction window closes.
totalBonus -= amount <= totalBonus ? amount : totalBonus;
}
​
// @> claimsStarted remains false even when amount includes accounted bonus.
stakeToken.safeTransfer(recoveryAddress, amount);
}

Risk

Likelihood: Low

  • The path occurs when a terminal CORRUPTED registry has no locally observed risk window, the moderator initially flags SURVIVED, and a correction to good-faith CORRUPTED is later needed before any staker claim.

  • The initial flag must need correction, making the situation uncommon. During that advertised correction window, however, the sweep is permissionless and requires no special role, capital, or direct economic entitlement.

Impact: Medium

  • The entire accounted bonus can be irreversibly redirected to recoveryAddress before the corrected bounty is snapshotted.

  • The whitehat receives principal only instead of the documented full stake-plus-bonus bounty. Principal remains available, so the loss is limited to the bonus portion.

Proof of Concept

Add the following test to a contract inheriting BaseConfidencePoolTest, or run the existing test at test/poc/ReflagSweepBountyLoss.t.sol:

function testPermissionlessSweepMovesAccountedValueWithoutClosingCorrectionWindow()
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));
​
uint256 recoveryBefore = token.balanceOf(recovery);
vm.prank(dave);
pool.sweepUnclaimedBonus();
​
assertEq(token.balanceOf(recovery) - recoveryBefore, 50 * ONE);
assertFalse(pool.claimsStarted());
​
vm.prank(moderator);
pool.flagOutcome(PoolStates.Outcome.CORRUPTED, true, attacker);
​
// The replacement snapshot sees only the remaining principal.
assertEq(pool.bountyEntitlement(), 100 * ONE);
​
vm.prank(attacker);
pool.claimAttackerBounty();
assertEq(token.balanceOf(attacker), 100 * ONE);
assertEq(token.balanceOf(recovery) - recoveryBefore, 50 * ONE);
}

Run:

forge test --match-contract ReflagSweepBountyLossPoC -vv

Recommended Mitigation

Separate unaccounted donations and dust from accounted totalBonus while correction remains possible. Donation-only value may remain permissionlessly sweepable without creating a 1-wei finality grief, but accounted bonus should stay reserved until either the first claim closes correction or the moderator explicitly finalizes the outcome.

+bool public outcomeFinalized;
+
+function finalizeOutcome() external onlyModerator {
+ if (outcome == PoolStates.Outcome.UNRESOLVED) revert OutcomeNotSet();
+ outcomeFinalized = true;
+}
​
function flagOutcome(...) external onlyModerator {
- if (outcome != PoolStates.Outcome.UNRESOLVED && claimsStarted) {
+ if (
+ outcome != PoolStates.Outcome.UNRESOLVED
+ && (claimsStarted || outcomeFinalized)
+ ) {
revert OutcomeAlreadySet();
}
// ...
}
​
function sweepUnclaimedBonus() external nonReentrant {
uint256 reserved = totalEligibleStake;
+ bool correctionOpen = !claimsStarted && !outcomeFinalized;
+
+ // Preserve accounted value needed by a possible replacement snapshot.
+ if (correctionOpen) {
+ reserved += totalBonus;
+ } else if (totalEligibleStake != 0 && riskWindowStart != 0) {
+ reserved += snapshotTotalBonus - claimedBonus;
+ }
​
uint256 freeBalance = stakeToken.balanceOf(address(this));
uint256 amount = freeBalance > reserved ? freeBalance - reserved : 0;
// ...
}

An alternative is to escrow swept accounted bonus inside the protocol so a later correction can reclaim it. Simply setting claimsStarted during the current sweep is not sufficient: that would let a permissionless caller close the correction window and could make the loss larger by preventing the correction entirely.

Support

FAQs

Can't find an answer? Chat with us on Discord, Twitter or Linkedin.

Give us feedback!