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feat: fix settleAndRefund vulnerability #4

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merged 3 commits into from
Mar 25, 2024
Merged

feat: fix settleAndRefund vulnerability #4

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6a4cb02
feat: update from currency.transfer to mint
ChefMist Mar 22, 2024
7b07b9d
refactor: update logic to be more similar to settle
ChefMist Mar 22, 2024
9461d4c
gas: minor gas tweak - reduce repetitive casting
ChefMist Mar 25, 2024
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2 changes: 1 addition & 1 deletion .forge-snapshots/BinPoolManagerTest#testBurnNativeCurrency.snap
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1 change: 1 addition & 0 deletions .forge-snapshots/VaultTest#testSettleAndMintRefund_WithMint.snap
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1 change: 0 additions & 1 deletion .forge-snapshots/VaultTest#testSettleAndRefund_WithoutErc20Transfer.snap
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12 changes: 6 additions & 6 deletions src/Vault.sol
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Expand Up @@ -126,26 +126,26 @@ contract Vault is IVault, VaultToken, Ownable {
SettlementGuard.accountDelta(msg.sender, currency, -(paid.toInt128()));
}

function settleAndRefund(Currency currency, address to)
function settleAndMintRefund(Currency currency, address to)
external
payable
override
isLocked
returns (uint256 paid, uint256 refund)
{
paid = currency.balanceOfSelf() - reservesOfVault[currency];
int256 currentDelta = SettlementGuard.getCurrencyDelta(msg.sender, currency);
uint256 reservesBefore = reservesOfVault[currency];
reservesOfVault[currency] = currency.balanceOfSelf();
paid = reservesOfVault[currency] - reservesBefore;
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For this part, the function would revert if reservesBefore is larger than the current reserve, since it would mean that the locker did not transfer anything to increase the current balance right?

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@ChefMist ChefMist Mar 25, 2024 •
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if the locker didn't transfer anything, this function shouldn't revert. The behavior should be the same as settle().

Can think of 1 scenario for revert:
1/ might be for rebasing token, where a negative rebase was done which cause the current balance in vault to be lesser than reserveBefore

cc @chefburger or @ChefSnoopy if can add on to more scenarios where revert might happen

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I cant come with other cases either, but i think it's fine to just let it revert if reservesBefore is greater than current.


int256 currentDelta = SettlementGuard.getCurrencyDelta(msg.sender, currency);
if (currentDelta >= 0 && paid > currentDelta.toUint256()) {
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Can cache currentDelta after casting to uint256 so you don't have to keep casting it again, wasting gas.

        if (currentDelta >= 0) {
            uint256 currentDeltaUint256 = currentDelta.toUint256();
            if (paid > currentDeltaUint256 ) {
                // msg.sender owes vault but paid more than whats owed
                refund = paid - currentDeltaUint256;
                paid = currentDeltaUint256;
            }
        }

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Also just to confirm, refund is only done, and paid is only adjusted if currentDelta is positive or zero, never if currentDelta is negative?

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Also just to confirm, refund is only done, and paid is only adjusted if currentDelta is positive or zero, never if currentDelta is negative?

yep. do you think theres a scenario where negative balanceDelta (vault owes caller token) might need to handled?

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Not sure, that's why I'm asking.

// msg.sender owes vault but paid more than than whats owed
refund = paid - currentDelta.toUint256();
paid = currentDelta.toUint256();
}

reservesOfVault[currency] += paid;
SettlementGuard.accountDelta(msg.sender, currency, -(paid.toInt128()));

if (refund > 0) currency.transfer(to, refund);
if (refund > 0) _mint(to, currency, refund);
}

/// @inheritdoc IVault
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10 changes: 7 additions & 3 deletions src/interfaces/IVault.sol
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Expand Up @@ -67,12 +67,16 @@ interface IVault is IVaultToken {
/// @notice Called by the user to pay what is owed
function settle(Currency token) external payable returns (uint256 paid);

/// @notice Called by the user to pay what is owed. If the payment is more than the debt, the surplus is refunded
/// @notice Called by the user to pay what is owed. If the payment is more than the debt, the surplus is refunded by minting
/// @dev To claim the refund, caller must eventually call vault.burn() -> vault.take() to take the ERC20 token from vault
/// @param currency The currency to settle
/// @param to The address to refund the surplus to
/// @param to The address to mint the refund
/// @return paid The amount paid
/// @return refund The amount refunded
function settleAndRefund(Currency currency, address to) external payable returns (uint256 paid, uint256 refund);
function settleAndMintRefund(Currency currency, address to)
external
payable
returns (uint256 paid, uint256 refund);

/// @notice move the delta from target to the msg.sender, only payment delta can be moved
/// @param currency The currency to settle
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8 changes: 4 additions & 4 deletions test/vault/FakePoolManagerRouter.sol
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Expand Up @@ -131,14 +131,14 @@ contract FakePoolManagerRouter {
} else if (data[0] == 0x18) {
// call this method via vault.lock(abi.encodePacked(hex"18", alice));
address to = address(uint160(uint256(bytes32(data[1:0x15]) >> 96)));
vault.settleAndRefund(poolKey.currency0, to);
vault.settleAndRefund(poolKey.currency1, to);
vault.settleAndMintRefund(poolKey.currency0, to);
vault.settleAndMintRefund(poolKey.currency1, to);
} else if (data[0] == 0x19) {
poolManager.mockAccounting(poolKey, 3 ether, -3 ether);
vault.settle(poolKey.currency0);

/// try to call settleAndRefund should not revert
vault.settleAndRefund(poolKey.currency1, address(this));
/// try to call settleAndMintRefund should not revert
vault.settleAndMintRefund(poolKey.currency1, address(this));
vault.take(poolKey.currency1, address(this), 3 ether);
}

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26 changes: 11 additions & 15 deletions test/vault/Vault.t.sol
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Expand Up @@ -173,43 +173,39 @@ contract VaultTest is Test, GasSnapshot {
vault.lock(hex"02");
}

function testSettleAndRefund_WithErc20Transfer() public {
function testSettleAndMintRefund_WithMint() public {
address alice = makeAddr("alice");

// simulate someone transferred token to vault
currency0.transfer(address(vault), 10 ether);
assertEq(IERC20(Currency.unwrap(currency0)).balanceOf(address(fakePoolManagerRouter)), 0 ether);
assertEq(IERC20(Currency.unwrap(currency0)).balanceOf(address(alice)), 0 ether);
assertEq(vault.balanceOf(alice, currency0), 0 ether);

// settle and refund
vm.prank(address(fakePoolManagerRouter));
snapStart("VaultTest#testSettleAndRefund_WithErc20Transfer");
snapStart("VaultTest#testSettleAndMintRefund_WithMint");
vault.lock(abi.encodePacked(hex"18", alice));
snapEnd();

// verify
assertEq(IERC20(Currency.unwrap(currency0)).balanceOf(address(fakePoolManagerRouter)), 0 ether);
assertEq(IERC20(Currency.unwrap(currency0)).balanceOf(address(alice)), 10 ether);
// verify excess currency minted to alice
assertEq(vault.balanceOf(alice, currency0), 10 ether);
}

function testSettleAndRefund_WithoutErc20Transfer() public {
function testSettleAndMintRefund_WithoutMint() public {
address alice = makeAddr("alice");

assertEq(IERC20(Currency.unwrap(currency0)).balanceOf(address(fakePoolManagerRouter)), 0 ether);
assertEq(IERC20(Currency.unwrap(currency0)).balanceOf(address(alice)), 0 ether);
assertEq(vault.balanceOf(alice, currency0), 0 ether);

// settleAndRefund works even if there's no excess currency
vm.prank(address(fakePoolManagerRouter));
snapStart("VaultTest#testSettleAndRefund_WithoutErc20Transfer");
snapStart("VaultTest#testSettleAndMintRefund_WithoutMint");
vault.lock(abi.encodePacked(hex"18", alice));
snapEnd();

// verify
assertEq(IERC20(Currency.unwrap(currency0)).balanceOf(address(fakePoolManagerRouter)), 0 ether);
assertEq(IERC20(Currency.unwrap(currency0)).balanceOf(address(alice)), 0 ether);
// verify no extra token minted
assertEq(vault.balanceOf(alice, currency0), 0 ether);
}

function testSettleAndRefund_NegativeBalanceDelta() public {
function testSettleAndMintRefund_NegativeBalanceDelta() public {
// pre-req: ensure vault has some value in reserveOfVault[] before
currency0.transfer(address(vault), 10 ether);
currency1.transfer(address(vault), 10 ether);
Expand Down
17 changes: 10 additions & 7 deletions test/vault/VaultInvariant.t.sol
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Expand Up @@ -31,7 +31,7 @@ contract VaultPoolManager is Test {
enum ActionType {
Take,
Settle,
SettleAndRefund,
SettleAndMintRefund,
SettleFor,
Mint,
Burn
Expand Down Expand Up @@ -87,7 +87,7 @@ contract VaultPoolManager is Test {

/// @dev In settleAndRefund case, assume user add liquidity and paying to the vault
/// but theres another folk who minted extra token to the vault
function settleAndRefund(uint256 amt0, uint256 amt1, bool sendToVault) public {
function settleAndMintRefund(uint256 amt0, uint256 amt1, bool sendToVault) public {
amt0 = bound(amt0, 0, MAX_TOKEN_BALANCE - 1 ether);
amt1 = bound(amt1, 0, MAX_TOKEN_BALANCE - 1 ether);

Expand All @@ -97,7 +97,7 @@ contract VaultPoolManager is Test {
// mint token to VaultPoolManager, so VaultPoolManager can pay to the vault
token0.mint(address(this), amt0);
token1.mint(address(this), amt1);
vault.lock(abi.encode(Action(ActionType.SettleAndRefund, uint128(amt0), uint128(amt1))));
vault.lock(abi.encode(Action(ActionType.SettleAndMintRefund, uint128(amt0), uint128(amt1))));
}

/// @dev In settleFor case, assume user is paying for hook
Expand Down Expand Up @@ -181,15 +181,18 @@ contract VaultPoolManager is Test {

vault.settle(currency0);
vault.settle(currency1);
} else if (action.actionType == ActionType.SettleAndRefund) {
} else if (action.actionType == ActionType.SettleAndMintRefund) {
BalanceDelta delta = toBalanceDelta(int128(action.amt0), int128(action.amt1));
vault.accountPoolBalanceDelta(poolKey, delta, address(this));

token0.transfer(address(vault), action.amt0);
token1.transfer(address(vault), action.amt1);

vault.settleAndRefund(currency0, address(this));
vault.settleAndRefund(currency1, address(this));
(, uint256 refund0) = vault.settleAndMintRefund(currency0, address(this));
(, uint256 refund1) = vault.settleAndMintRefund(currency1, address(this));

totalMintedCurrency0 += refund0;
totalMintedCurrency1 += refund1;
} else if (action.actionType == ActionType.SettleFor) {
// hook cash out the fee ahead
BalanceDelta delta = toBalanceDelta(int128(action.amt0), int128(action.amt1));
Expand Down Expand Up @@ -244,7 +247,7 @@ contract VaultInvariant is Test, GasSnapshot {
selectors[3] = VaultPoolManager.burn.selector;
selectors[4] = VaultPoolManager.settleFor.selector;
selectors[5] = VaultPoolManager.collectFee.selector;
selectors[6] = VaultPoolManager.settleAndRefund.selector;
selectors[6] = VaultPoolManager.settleAndMintRefund.selector;
targetSelector(FuzzSelector({addr: address(vaultPoolManager), selectors: selectors}));
}

Expand Down
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