Cover Protocol is a blockchain-based peer-to-peer coverage market for decentralized finance. The platform allows DeFi users to hedge against risks due to smart contracts' fallacies (especially useful when farming or staking).
The scope of the audit includes the following smart contracts at: https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/CoverRouter.sol https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/Rollover.sol https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/utils/Address.sol https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/utils/Ownable.sol https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/utils/ReentrancyGuard.sol https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/utils/SafeERC20.sol https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/utils/SafeMath.sol https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/interfaces/IBFactory.sol https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/interfaces/IBlacksmith.sol https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/interfaces/IBPool.sol https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/interfaces/ICover.sol https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/interfaces/ICoverERC20.sol https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/interfaces/ICoverRouter.sol https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/interfaces/IERC20.sol https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/interfaces/IProtocol.sol https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/interfaces/IRollover.sol
The audited commit identifier is d5b37e34d47abec3252cdabd46e55e34a72421d4
-
CRITICAL: Bugs leading to Ether or token theft, fund access locking or any other loss of Ether/tokens to be transferred to any party (for example, dividends).
-
MAJOR: Bugs that can trigger a contract failure. Further recovery is possible only by manual modification of the contract state or replacement.
-
WARNINGS: Bugs that can break the intended contract logic or expose it to DoS attacks.
-
COMMENTS: Other issues and recommendations reported to/ acknowledged by the team.
Two auditors independently verified the code.
Stages of the audit were as follows:
- "Blind" manual check of the code and its model
- "Guided" manual code review
- Checking the code compliance with customer requirements
- Discussion of independent audit results
- Report preparation
Not found
1. It is possible to carry out attacks to manipulate pools within one transaction using a flash loan
In contracts https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/CoverRouter.sol and https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/Rollover.sol, any user can exchange tokens with a contract. Any user can add and remove liquidity. An attacker can take a flash loan and perform multiple liquidity manipulations within a single transaction. These manipulations can lead to a loss of funds for other users.
It is recommended to add protection against token manipulation with flash loans. Here's some sample code:
mapping(address => uint256) private _lastSwapBlock;
function some() external {
_preventSameTxOrigin();
....
some logic
...
}
function _preventSameTxOrigin() private {
require(block.number > _lastSwapBlock[tx.origin], "SAME_TX_ORIGIN");
_lastSwapBlock[tx.origin] = block.number;
}Method addCoverAndCreatePools defined at https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/CoverRouter.sol#L128 accepts _protocol and _collateral addresses as arguments, then call _addCover that makes approve for _protocol an unlimited amount of _collateral tokens and call _protocol.addCover. There are no checks of _protocol and _collateral validity, so an attacker can pass malicious _protocol and get unlimited approval of _collateral tokens:
if (_token.allowance(address(this), _spender) < _amount) {
_token.approve(_spender, uint256(-1));
}According to the contract logic in an optimistic flow a contract shouldn't have any tokens in balance, but this invariant not fully checked, e.g. if _protocol.addCover at https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/Rollover.sol#L75 fails and returns false, then the transaction will be executed successfully, but the user's funds will be left on the CoverRouter balance.
We recommend to not use unlimited approve and add particular checks to keep the zero balance invariant.
The variable is assigned to the value of the constructor input parameter. But the parameter is not checked before this. If the value turns out to be zero, then it will be necessary to redeploy the contract since there is no other functionality to set this variable.
- At line https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/CoverRouter.sol#L36 the
protocolFactoryvariable is set to the value of the_protocolFactoryinput parameter. - At line https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/CoverRouter.sol#L37 the
bFactoryvariable is set to the value of the_bFactoryinput parameter.
In all the cases, it is necessary to add a check of the input parameter to zero before initializing the variables.
Since all transactions are visible in the mempool for a little while before being executed, the observers of the network can see and react to an action before it is included in a block. An example of how this can be exploited is with a decentralized exchange where a buy order transaction can be seen, and a second order can be broadcast and executed before the first transaction is included.
At line https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/CoverRouter.sol#L64, any user can execute the rolloverAndAddLiquidityForAccount() function. This function calls other functions and exchanges tokens between the contract and the _account address. Due to the fact that another user completes the transaction earlier, a profitable position in the trade may be lost and the user will lose his profit.
The best remediation is to remove the benefit of Front-Running in your application, mainly by removing the importance of transaction ordering or time. It will be possible to make use of the maximum or minimum acceptable price or amount range for the transaction, thereby limiting the price slippage.
Acknowledged
There is the _transferRem method in the contract. But in some cases, there are no
checks:
- https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/CoverRouter.sol#L45 (
addCoverAndAddLiquidity) - https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/CoverRouter.sol#L115 (
addLiquidity) - https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/CoverRouter.sol#L158 (
createNewPool)
We recommend checking all tokens and transfer remaining balance after every external method of the contract.
At this line _token.approve(_spender, uint256(-1) located at https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/Rollover.sol#L64 we have an unlimited approval access from CoverRouter.
We recommend either to revoke the approval after the execution or to approve only the expected amount.
Basic features for onlyOwner don't emit any events:
- https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/CoverRouter.sol#L179 (
setSwapFee) - https://github.com/CoverProtocol/cover-peripheral/tree/d5b37e34d47abec3252cdabd46e55e34a72421d4/contracts/CoverRouter.sol#L185 (
setCovTokenWeights)
We recommend to create events:SwapFeeUpdate, CovTokenWeightUpdate.
Findings list
| Level | Amount |
|---|---|
| CRITICAL | 0 |
| MAJOR | 2 |
| WARNING | 4 |
| COMMENT | 1 |
Final commit identifier with all fixes: cbf6f30cde5ca6830af0554f3fb5247ae3bdaf06
The audited contract represents an intermediate layer between Cover Protocol core contracts and end-users. The general purpose of the contract is routing requests to target pools, so contract provide a single place to interact with pools and create them (approach is very similar with the Uniswap router model).
Smart contracts were audited and several suspicious places were spotted. Two issues were marked as major since they potentially can break desired contract behavior. The other issues were marked as warnings and comments. After working on the reported findings all issues were fixed by the client’s team or marked as acknowledged. So, the contracts are assumed as secure to use according to our security criteria.