veRWA - BenRai's results

Lines of code

https://github.com/code-423n4/2023-08-verwa/blob/a693b4db05b9e202816346a6f9cada94f28a2698/src/VotingEscrow.sol#L326-L349 https://github.com/code-423n4/2023-08-verwa/blob/a693b4db05b9e202816346a6f9cada94f28a2698/src/VotingEscrow.sol#L356-L387

Vulnerability details

Impact

Even though the lock of a user has expired, he cannot withdraw his deposit and needs to lock it for 5 more years to be able to withdraw it in the future.

Proof of Concept

When a user is calling withdraw to withdraw his collateral, it is checked if he is his own delegatee.

require(locked_.delegatee == msg.sender, "Lock delegated");

If not, the user can not withdraw his deposit.

To become his own delegatee he needs to call delegate and delegate his votes to his address. The problem is that it is not possible to delegate his votes to an address that has a shorter locktime than the old delegate.

require(toLocked.end >= fromLocked.end, "Only delegate to longer lock");

Since his locktime is in the past and therefor is smaller than the locktime of his current delegate, the user needs to increase his lock time again. The locktime can only be increased by 5 years resulting in the deposite of the user been locked for 5 more years before he can redeem it again.

Tools Used

Manual review

Recommended Mitigation Steps

Integrate a check in delegate that checks if msg.sender wants to delegate his voting power back to himself. If so allow the transfer of voting power even if the lock time of the msg.sender is smaller than the lock time of the current delegate.

Assessed type

Timing

Lines of code

https://github.com/code-423n4/2023-08-verwa/blob/a693b4db05b9e202816346a6f9cada94f28a2698/src/VotingEscrow.sol#L390-L409

Vulnerability details

Impact

The delegatee of a user decides how long the deposits of the user are locked

Proof of Concept

When calling delegate, users can only delegate their votes to an new address that has a longer or equal locktime than the old one.

require(toLocked.end >= fromLocked.end, "Only delegate to longer lock");

This means that if a user wants to get his votes back from an address he delegated to (current delegate), his lock time must be longer than the log time of the current delegate.

This means that if the current delegatee increases his lock time, the user who wants to delegate his votes back to himself needs to make his locktime bigger than the locktime of the current delegate. Since the deposit can only be withdrawn when the locktime has been passed, the current delegatee indirectly increases the locktime of all users that have delegated votes to him.

Tools Used

Manual review

Recommended Mitigation Steps

Make it possible for a user to get back his voting power without the need to increase his lock time by checking if msg.sender wants to delegate his voting power to himself.

The locking effect can also be mitigated by reducing the variable LOCKTIME to e.g. 1 year. This would make the impact of being forced to increase the own lock time to be able to withdraw the own deposit smaller.

Assessed type

Governance