QA Report

[code423n4]

C4-001 : PREVENT DIV BY 0

Impact - LOW

On several locations in the code precautions are taken not to divide by 0, because this will revert the code. However on some locations this isn’t done.

Especially in the claim function div(rewardsDuration) which isn’t checked.

That will cause to revert on the claim function.

Proof of Concept

1. Navigate to the following contract.

https://github.com/code-423n4/2022-02-concur/blob/02d286253cd5570d4e595527618366f77627cdaf/contracts/StakingRewards.sol#L183

    function setRewardsDuration(uint256 _rewardsDuration) external onlyOwner {
        require(
            block.timestamp > periodFinish,
            "Previous rewards period must be complete before changing the duration for the new period"
        );
        rewardsDuration = _rewardsDuration;
        emit RewardsDurationUpdated(rewardsDuration);
    }

https://github.com/code-423n4/2022-02-concur/blob/02d286253cd5570d4e595527618366f77627cdaf/contracts/StakingRewards.sol#L147

Tools Used

None

Recommended Mitigation Steps

Recommend making sure division by 0 won’t occur by checking the variables beforehand and handling this edge case.

C4-002 : Improper Upper Bound Definition on the depositFeeBP

Impact - LOW

The add function does not have any upper or lower bounds. Values that are too large will lead to reversions in several critical functions. User funds will be locked forever.

Proof of Concept

1. Navigate to the following contract.

https://github.com/code-423n4/2022-02-concur/blob/02d286253cd5570d4e595527618366f77627cdaf/contracts/MasterChef.sol#L97

    function add(address _token, uint _allocationPoints, uint16 _depositFee, uint _startBlock) public onlyOwner {
        require(_token != address(0), "zero address");
        uint lastRewardBlock = block.number > _startBlock ? block.number : _startBlock;
        totalAllocPoint = totalAllocPoint.add(_allocationPoints);
        require(pid[_token] == 0, "already registered"); // pid starts from 0
        poolInfo.push(
            PoolInfo({
                depositToken: IERC20(_token),
                allocPoint: _allocationPoints,
                lastRewardBlock: lastRewardBlock,
                accConcurPerShare: 0,
                depositFeeBP: _depositFee
            })
        );
        pid[_token] = poolInfo.length - 1;
    }

Tools Used

None

Recommended Mitigation Steps

Consider to define upper bound on the add function. User can pay %100 fee when the deposit into the pool.

C4-003 : transferOwnership should be two step process

Impact - LOW

"ConvexStakingWrapper.sol", "USDMPegRecovery.sol", "StakingRewards.sol", "MasterChef.sol", "EasySign.sol" inherit OpenZeppelin's OwnableUpgradeable contract which enables the onlyOwner role to transfer ownership to another address. It's possible that the onlyOwner role mistakenly transfers ownership to the wrong address, resulting in a loss of the onlyOwner role. The current ownership transfer process involves the current owner calling Unlock.transferOwnership(). This function checks the new owner is not the zero address and proceeds to write the new owner's address into the owner's state variable. If the nominated EOA account is not a valid account, it is entirely possible the owner may accidentally transfer ownership to an uncontrolled account, breaking all functions with the onlyOwner() modifier. Lack of two-step procedure for critical operations leaves them error-prone
if the address is incorrect, the new address will take on the functionality of the new role immediately

for Ex : -Alice deploys a new version of the whitehack group address. When she invokes the whitehack group address setter to replace the address, she accidentally enters the wrong address. The new address now has access to the role immediately and is too late to revert

Proof of Concept

1. Navigate to "https://github.com/code-423n4/2022-02-concur/blob/main/contracts/ConvexStakingWrapper.sol#L14", "https://github.com/code-423n4/2022-02-concur/blob/main/contracts/EasySign.sol#L8", "https://github.com/code-423n4/2022-02-concur/blob/main/contracts/MasterChef.sol#L13", "https://github.com/code-423n4/2022-02-concur/blob/main/contracts/StakingRewards.sol#L12", "https://github.com/code-423n4/2022-02-concur/blob/main/contracts/USDMPegRecovery.sol#L10".
2. The contracts have many onlyOwner function.
3. The contract is inherited from the Ownable which includes transferOwnership.

Tools Used

None

Recommended Mitigation Steps

Implement zero address check and Consider implementing a two step process where the owner nominates an account and the nominated account needs to call an acceptOwnership() function for the transfer of ownership to fully succeed. This ensures the nominated EOA account is a valid and active account.

C4-004 : Missing zero-address check in constructors and the setter functions

Impact - LOW

Missing checks for zero-addresses may lead to infunctional protocol, if the variable addresses are updated incorrectly.

Proof of Concept

1. Navigate to the following contract functions.

https://github.com/code-423n4/2022-02-concur/blob/main/contracts/USDMPegRecovery.sol#L57

Variables

• kpiOracle

https://github.com/code-423n4/2022-02-concur/blob/main/contracts/ConcurRewardPool.sol#L16

Variables

• rewardNotifier

https://github.com/code-423n4/2022-02-concur/blob/main/contracts/ConvexStakingWrapper.sol#L83

Variables

• treasury
• claimContract

https://github.com/code-423n4/2022-02-concur/blob/02d286253cd5570d4e595527618366f77627cdaf/contracts/StakingRewards.sol#L195

• rewardsDistribution

Tools Used

Code Review

Recommended Mitigation Steps

Consider adding zero-address checks in the discussed constructors:
require(newAddr != address(0));.

C4-005 : Incompatibility With Rebasing/Deflationary/Inflationary tokens

Impact - LOW

BadgerDAO protocol do not appear to support rebasing/deflationary/inflationary tokens whose balance changes during transfers or over time. The necessary checks include at least verifying the amount of tokens transferred to contracts before and after the actual transfer to infer any fees/interest.

Proof of Concept

1. Navigate to the following contract.

https://github.com/code-423n4/2022-02-concur/blob/main/contracts/MasterChef.sol#L206

Tools Used

Manual Code Review

Recommended Mitigation Steps

• Ensure that to check previous balance/after balance equals to amount for any rebasing/inflation/deflation
• Add support in contracts for such tokens before accepting user-supplied tokens
• Consider supporting deflationary / rebasing / etc tokens by extra checking the balances before/after or strictly inform your users not to use such tokens if they don't want to lose them.

C4-006 : Use safeTransfer/safeTransferFrom consistently instead of transfer/transferFrom

Impact - LOW

It is good to add a require() statement that checks the return value of token transfers or to use something like OpenZeppelin’s safeTransfer/safeTransferFrom unless one is sure the given token reverts in case of a failure. Failure to do so will cause silent failures of transfers and affect token accounting in contract.

Reference: This similar medium-severity finding from Consensys Diligence Audit of Fei Protocol: https://consensys.net/diligence/audits/2021/01/fei-protocol/#unchecked-return-value-for-iweth-transfer-call

Proof of Concept

1. Navigate to the following contract.

2. transfer/transferFrom functions are used instead of safe transfer/transferFrom on the following contracts.

https://github.com/code-423n4/2022-02-concur/blob/02d286253cd5570d4e595527618366f77627cdaf/contracts/MasterChef.sol#L206

https://github.com/code-423n4/2022-02-concur/blob/02d286253cd5570d4e595527618366f77627cdaf/contracts/MasterChef.sol#L208

https://github.com/code-423n4/2022-02-concur/blob/02d286253cd5570d4e595527618366f77627cdaf/contracts/ConvexStakingWrapper.sol#L182

https://github.com/code-423n4/2022-02-concur/blob/02d286253cd5570d4e595527618366f77627cdaf/contracts/ConvexStakingWrapper.sol#L179

Tools Used

Code Review

Recommended Mitigation Steps

Consider using safeTransfer/safeTransferFrom or require() consistently.

C4-007 : ERC20 approve method missing return value check

Impact - LOW

The several functions perform an ERC20.approve() call but does not check the success return value. Some tokens do not revert if the approval failed but return false instead.

Proof of Concept

1. The USDMPegRecovery.sol contract functions use an approve method.
2. Tokens that don't actually perform the approve and return false are still counted as a correct approve.

Code Locations

https://github.com/code-423n4/2022-02-concur/blob/02d286253cd5570d4e595527618366f77627cdaf/contracts/USDMPegRecovery.sol#L79
https://github.com/code-423n4/2022-02-concur/blob/02d286253cd5570d4e595527618366f77627cdaf/contracts/USDMPegRecovery.sol#L80

Tools Used

Code Review

Recommended Mitigation Steps

Its recommend to using OpenZeppelin’s SafeERC20 versions with the safeApprove function that handles the return value check as well as non-standard-compliant tokens.

Reference : https://github.com/OpenZeppelin/openzeppelin-contracts/blob/release-v4.1/contracts/token/ERC20/utils/SafeERC20.sol#L74

C4-008 : Use of Block.timestamp

Impact - Non-Critical

Block timestamps have historically been used for a variety of applications, such as entropy for random numbers (see the Entropy Illusion for further details), locking funds for periods of time, and various state-changing conditional statements that are time-dependent. Miners have the ability to adjust timestamps slightly, which can prove to be dangerous if block timestamps are used incorrectly in smart contracts.

Proof of Concept

1. Navigate to the following contract.

https://github.com/code-423n4/2022-02-concur/blob/02d286253cd5570d4e595527618366f77627cdaf/contracts/StakingRewards.sol#L60

https://github.com/code-423n4/2022-02-concur/blob/02d286253cd5570d4e595527618366f77627cdaf/contracts/Shelter.sol#L39

https://github.com/code-423n4/2022-02-concur/blob/02d286253cd5570d4e595527618366f77627cdaf/contracts/ConvexStakingWrapper.sol#L279

Tools Used

Manual Code Review

Recommended Mitigation Steps

Block timestamps should not be used for entropy or generating random numbers—i.e., they should not be the deciding factor (either directly or through some derivation) for winning a game or changing an important state.

Time-sensitive logic is sometimes required; e.g., for unlocking contracts (time-locking), completing an ICO after a few weeks, or enforcing expiry dates. It is sometimes recommended to use block.number and an average block time to estimate times; with a 10 second block time, 1 week equates to approximately, 60480 blocks. Thus, specifying a block number at which to change a contract state can be more secure, as miners are unable to easily manipulate the block number.

C4-009 : Missing Re-entrancy Guard

Impact - Non-Critical

Consider using ReentrancyGuard to protect functions that have external calls and do not follow Checks Effects Interactions pattern. An example of a function that needs to prevent re-entrancy is buy as it calls claim before updating the state and because anyone can add new bounties with no restrictions, it may contain tokens with callbacks on transfer (e.g. erc777) which may call this function again and again.

Proof of Concept

1. Navigate to the following contract function.

https://github.com/code-423n4/2022-02-concur/blob/02d286253cd5570d4e595527618366f77627cdaf/contracts/ConcurRewardPool.sol#L37

2. The functions are missing re-entrancy guard.

Tools Used

Manual Code Review

Recommended Mitigation Steps

Consider implementing re-entrancy guard on the functions. Use the OpenZeppelin ReentrancyGuard.sol on the main functions users will interact with such as buy & claim.(https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/security/ReentrancyGuard.sol)

C4-010 : Missing events for admin only functions that change critical parameters

Impact - Non-Critical

The admin only functions that change critical parameters should emit events. Events allow capturing the changed parameters so that off-chain tools/interfaces can register such changes with timelocks that allow users to evaluate them and consider if they would like to engage/exit based on how they perceive the changes as affecting the trustworthiness of the protocol or profitability of the implemented financial services. The alternative of directly querying on-chain contract state for such changes is not considered practical for most users/usages.

Missing events and timelocks do not promote transparency and if such changes immediately affect users’ perception of fairness or trustworthiness, they could exit the protocol causing a reduction in liquidity which could negatively impact protocol TVL and reputation.

There are owner functions that do not emit any events in the contracts.

Proof of Concept

1. Navigate to the following contract.

https://github.com/code-423n4/2022-02-concur/blob/02d286253cd5570d4e595527618366f77627cdaf/contracts/USDMPegRecovery.sol#L61

https://github.com/code-423n4/2022-02-concur/blob/02d286253cd5570d4e595527618366f77627cdaf/contracts/USDMPegRecovery.sol#L65

https://github.com/code-423n4/2022-02-concur/blob/02d286253cd5570d4e595527618366f77627cdaf/contracts/USDMPegRecovery.sol#L70

https://github.com/code-423n4/2022-02-concur/blob/02d286253cd5570d4e595527618366f77627cdaf/contracts/ConvexStakingWrapper.sol#L83

https://github.com/code-423n4/2022-02-concur/blob/02d286253cd5570d4e595527618366f77627cdaf/contracts/ConvexStakingWrapper.sol#L87

https://github.com/code-423n4/2022-02-concur/blob/02d286253cd5570d4e595527618366f77627cdaf/contracts/MasterChef.sol#L79

https://github.com/code-423n4/2022-02-concur/blob/02d286253cd5570d4e595527618366f77627cdaf/contracts/MasterChef.sol#L83

See similar High-severity H03 finding OpenZeppelin’s Audit of Audius (https://blog.openzeppelin.com/audius-contracts-audit/#high) and Medium-severity M01 finding OpenZeppelin’s Audit of UMA Phase 4 (https://blog.openzeppelin.com/uma-audit-phase-4/)

Tools Used

None

Recommended Mitigation Steps

Add events to all admin/privileged functions that change critical parameters.

C4-011 : Safe Approve Function Is Deprecated

Impact - Non-Critical

safeApprove function is deprecated.

Proof of Concept

1. Navigate to the following contract.

https://github.com/code-423n4/2022-02-concur/blob/02d286253cd5570d4e595527618366f77627cdaf/contracts/ConvexStakingWrapper.sol#L242

https://github.com/code-423n4/2022-02-concur/blob/02d286253cd5570d4e595527618366f77627cdaf/contracts/ConvexStakingWrapper.sol#L244

Tools Used

Code Review

Recommended Mitigation Steps

Consider to enable functions and use safeIncreaseAllowance and safeDecreaseAllowance instead of safeApprove.

C4-012 : Missing Setter Function On The Client Variable

Impact - Non-Critical

Based on the context, client should be able to be updated after deployment. However, there is no function to update it.

Proof of Concept

1. Navigate to the following contract.

https://github.com/code-423n4/2022-02-concur/blob/02d286253cd5570d4e595527618366f77627cdaf/contracts/Shelter.sol#L29

Tools Used

Code Review

Recommended Mitigation Steps

Consider to define function for client variable.

[GalloDaSballo]

C4-001 : PREVENT DIV BY 0
The code is in solidity 0.8.11 so division by zero is checked automatically

C4-002
Dup of #242 Med

C4-003 : transferOwnership should be two step process
Disagree

C4-004 : Missing zero-address check in constructors and the setter functions
Agree

C4-005

Will not consider as blatant copy paste

C4-006 : Use safeTransfer/safeTransferFrom consistently instead of transfer/transferFrom
Agree

C4-007 : ERC20 approve method missing return value check
Disagree because tokens are known and they revert on error

C4-008 : Use of Block.timestamp
Disagree because lacks any detail

C4-009 : Missing Re-entrancy Guard
Agree with the generic reentrancy finding, the warden
Dup of #86 Med

Disagree with all other findings

[GalloDaSballo]

2

[JeeberC4]

@CloudEllie please create new issue for 2 the Med findings above.

[CloudEllie]

Created separate issues for C4-002 and C4-009:

• Improper Upper Bound Definition on the depositFeeBP Improper Upper Bound Definition on the depositFeeBP #274
• Missing Re-entrancy Guard Missing Re-entrancy Guard #275