First Flight #4: Boss Bridge

Summary

The depositTokensToL2 function allows a user to deposit tokens to the vault, which are then locked and emitted as a Deposit event. This event can be picked up by an off-chain service to mint corresponding tokens on L2.

Vulnerability Details

'''solidity
function depositTokensToL2(address from, address l2Recipient, uint256 amount) external whenNotPaused {
if (token.balanceOf(address(vault)) + amount > DEPOSIT_LIMIT) {
revert L1BossBridge__DepositLimitReached();
}
token.safeTransferFrom(from, address(vault), amount);

    // Our off-chain service picks up this event and mints the corresponding tokens on L2
    emit Deposit(from, l2Recipient, amount);
}

'''

Impact

The contract does not check if the from address in depositTokensToL2 has approved the contract to transfer their tokens, which could lead to a failed transaction.

Tools Used

• foundry

Recommendations

The contract must emit events for important state changes like pausing, unpausing, and setting signers. Also the contract must check if the from address in depositTokensToL2 has approved the contract to transfer their tokens,