Unipilot Farming V2 Audit Report

INTRODUCTION

BlockApex (Auditor) was contracted by  VoirStudio  (Client) for the purpose of conducting a Smart Contract Audit/ Code Review. This document presents the findings of our analysis which started from  25th Feb 2022. 

Scope

The git-repository shared was checked for common code violations along with vulnerability-specific probing to detect major issues/vulnerabilities. Some specific checks are as follows:

Project Overview

Unipilot yield farming incentivizes Liquidity Providers to earn $PILOT tokens by staking their Unipilot LP tokens on whitelisted pools.

System Architecture

Unipilot yield farming has 1 main smart contract; UnipilotFarm.sol: which allows Liquidity Providers to earn $PILOT token, an $ALT token, or both by staking their Unipilot LP tokens. UnipilotFarm linearly distributes the $PILOT according to rewardPerBlock and rewardMultiplier.

Methodology & Scope

The codebase was audited in an iterative process. Fixes were applied on the way and updated contracts were examined for more bugs. We used a combination of static analysis tool (slither) and testing framework (hardhat) which indicated some of the critical bugs like reentrancy in the code. We also did manual reviews of the code to find logical bugs, code optimizations, solidity design patterns, code style and the bugs/ issues detected by automated tools.

AUDIT REPORT

Executive Summary

The analysis indicates that the contracts audited are working properly.

Our team performed a technique called “Filtered Audit”, where the contract was separately audited by two individuals. After their thorough and rigorous process of manual testing, an automated review was carried out using Mythril, MythX, and Slither. All the flags raised were manually reviewed and re-tested. 

Our team found: 

Findings

Critical-risk issues

1. First block reward is wrong in Only ALT and Dual Case.

Description: 

If the reward type is changed from only Pilot to only ALT or only Pilot to Dual, the code updates the lastBlockReward variable first for Pilot then for ALT, calculating block difference as 2 instead of 0. Hence, the user gets triple reward for just the first block.

else {
            if (_rewardType == RewardType.Alt) {
                altState.lastRewardBlock = blockNumber;
                updateVaultState(_vault);
            } else {
                altState.lastRewardBlock = blockNumber;
                }
            }
        }
        emit RewardStatus(
            _vault,
            vaultInfo[_vault].reward,
            vaultInfo[_vault].reward = _rewardType,
            _altToken
        );

Remedy:

When updating the reward type lastRewardBlock should be set to the current block number.

else {
            if (_rewardType == RewardType.Alt) {
                altState.lastRewardBlock = blockNumber;
                vaultState.startBlock = blockNumber;
                updateVaultState(_vault);
            } else {
                altState.lastRewardBlock = blockNumber;
                }

Status: 

Fixed as per BlockApex recommendation. 

2. Consecutive change in reward type will disable the stakeLp functionality.

Description: 

If the governance changes reward type from only Pilot to only Alt and then changes it again from only Alt to Dual, no user can stake their LPs.

Scenario: Before staking starts, if the last reward type is changed twice and is finally set to Dual, it causes the last reward block check, inside the stakeLp() function, to break, i.e., to not equal to start block, causing the getGlobalReward() function to be invoked, which in turn causes the mulDiv() error as the value of totalLpLocked never changed from zero.

 function getGlobalReward(
        address _vault,
        uint256 _blockDiff,
        uint256 _multiplier,
        uint256 _lastGlobalReward
    ) private view returns (uint256 _globalReward) {
        if (vaultInfo[_vault].totalLpLocked > 0) {
            _globalReward = FullMath.mulDiv(
                rewardPerBlock,
                _multiplier,
                1e18
            );

            _globalReward = FullMath
                .mulDiv(
                    _blockDiff.mul(_globalReward),
                    1e18,
                    vaultInfo[_vault].totalLpLocked
                )
                .add(_lastGlobalReward);
        } else {
            _globalReward = vaultInfo[_vault].globalReward;
        }
    }

Remedy:

If the totalLpLocked is zero,  the previous state of global reward should return the value of its previous state.  In case zero returns, the function should not calculate the new global reward.

function getGlobalReward(
        address _vault,
        uint256 _blockDiff,
        uint256 _multiplier,
        uint256 _lastGlobalReward
    ) private view returns (uint256 _globalReward) {
        if (vaultWhitelist[_vault]) {
            if (vaultInfo[_vault].totalLpLocked > 0) {
                _globalReward = FullMath.mulDiv(
                    rewardPerBlock,
                    _multiplier,
                    1e18
                );

                _globalReward = FullMath
                    .mulDiv(
                        _blockDiff.mul(_globalReward),
                        1e18,
                        vaultInfo[_vault].totalLpLocked
                    )
                    .add(_lastGlobalReward);
            } else {
                _globalReward = vaultInfo[_vault].globalReward;
            }
        } else {
            _globalReward = vaultInfo[_vault].globalReward;
        }
    }

Status:

Fixed as per BlockApex recommendation.

3. Miscalculation in pilot reward.

Description: 

In an empty farm, if the reward type is changed from only Pilot to only ALT or only Pilot to Dual, the first user who stakes gets a reward of all the empty blocks since the reward type has been updated.

Remedy:

Modify the updateRewardType() function to check if there are no staked LPs in the farm, only then should the start block be updated to set as the current block number.

Status: 

Fixed as per BlockApex recommendation. 

High-risk issues

No issues were found

Medium-risk issues

1. RewardToken validity should be checked.

Description: 

• While calling the initializer() function, if the user sends invalid reward token there is no check to validate whether that token exists in the contract or not. 
• Same problem is confirmed in the UpdateRewardType() function, which also requires a token validity check.

if (!vaultWhitelist[_vaultt[i]] && vaultState.totalLpLocked == 0) {
  insertVault(_vaultt[i], _multipliert [i]);
} else {
  require(!vaultWhitelist[_vault t [i]], "AI");
  if (vaultstate reward == RewardType.Dual) {
    vaultState. LastRewardBlock = blockNum;
    vaultaltState. lastRewardBlock = blockNum;
  } else if (vaultstate reward = RewardType.Alt) {
      vaultAltState. lastRewardBlock = blockNum;
  } else {
      vaultState. LastRewardBlock = blockNum;
  }
}

Remedy:

initializer() and UpdateRewardType() functions should check in the vault contract if the token actually exists by calling the balanceOf() function.

if (!vaultWhitelist[_vault [i]] && vaultstate.totalLpLocked == 0) {
if (
  _rewardType 1 (i) = RewardType. Alt |||
  _rewardType 1 [i] == RewardType.Dual
{
require(
  IERC20(_rewardToken ^ [i]).balanceof(address(this)) > 0,
  "NEB"
);
  vaultAltstate, multiplier = _multipliert[i];
  vaultAltstate.startBlock = blockNum;
  vaultAltState. LastRewardBlock = blockNum;
  vaultAltState. rewardToken = _rewardTokent [i];
}

Status:

Fixed as per BlockApex recommendation.

2. The UpdateRewardPerBlock function will manipulate the last reward for every user.

Description: 

The event in updateRewardPerBlock() function emits the old reward value as well as updating and sending the new reward value, the problem is that this event emits at the start of the function which manipulates the last block reward for every user in the vault.

function updateRewardPerBlock(uint256 _value)
        external
        override
        onlyGovernance
    {
        emit RewardPerBlock(rewardPerBlock, rewardPerBlock = _value);
        require(_value > 0, "IV");

Remedy:

Event should be fired after the calculation at the end of the function. 

function updateRewardPerBlock(uint256 _value)
        external
        override
        onlyGovernance
    {
        require(_value > 0, "IV");
        address[] memory vaults = vaultListed();
        for (uint256 i = 0; i < vaults.length; i++) {
            if (vaultWhitelist[vaults[i]]) {
                if (vaultInfo[vaults[i]].totalLpLocked != 0) {
                    if (vaultInfo[vaults[i]].reward == RewardType.Dual) {
                        updateVaultState(vaults[i]);
                        updateAltState(vaults[i]);
                    } else if (vaultInfo[vaults[i]].reward == RewardType.Alt) {
                        updateAltState(vaults[i]);
                    } else {
                        updateVaultState(vaults[i]);
                    }
                }
            }
        }
        emit RewardPerBlock(rewardPerBlock, rewardPerBlock = _value);
    }

Status:

Fixed as per BlockApex recommendation

3. Should allow Parameters to send Zero to reopen farming

Description: 

There is a check in updateFarmingLimit()  function which does not allow sending zero value in parameter, but it contradicts with the functionality. If the gov sets the farming limit to a specific block and they want to reopen or update the limit they have to send zero value to the updateFarmingLimit() function which will not work if zero value check is placed.

function updateFarmingLimit(uint256 _blockNumber)
        external
        override
        onlyGovernance
    {
       require(_blockNumber > 0, "IV");
        emit UpdateFarmingLimit(
            farmingGrowthBlockLimit,
            farmingGrowthBlockLimit = _blockNumber
        );
        updateLastBlock();
    }

Remedy:

Zero value check should be removed from the function.

function updateFarmingLimit(uint256 _blockNumber)
        external
        override
        onlyGovernance
    {
        emit UpdateFarmingLimit(
            farmingGrowthBlockLimit,
            farmingGrowthBlockLimit = _blockNumber
        );
        updateLastBlock();
    }

Status:

Fixed as per BlockApex recommendation

Low-risk issues

1. RewardToken validity check

Description: 

No zero address check placed for RewardToken while calling the initializer() function.

 function initializer(
        address[] calldata _vault,
        uint256[] calldata _multiplier,
        RewardType[] calldata _rewardType,
        address[] calldata _rewardToken
    ) external override onlyGovernance {
        require(_vault.length == _multiplier.length,"LNS");
        uint256 blockNum = block.number;
        for (uint256 i = 0; i < _vault.length; i++) {

Remedy:

Zero address check should be Placed.

Status:

Fixed as per BlockApex recommendation

2. Necessary checks in updateFarmingLimit() function.

Description: 

If the updateFarmingLimit() function is called with the same value of the block number in which it is going to be executed (or the past block number), the tx will be mined but it will not limit the farming as expected.

function updateFarmingLimit(uint256 _blockNumber)
        external
        override
        onlyGovernance
    {
        emit UpdateFarmingLimit(
            farmingGrowthBlockLimit,
            farmingGrowthBlockLimit = _blockNumber
        );
        updateLastBlock();
    }

Remedy:

A check should be placed in the updateFarmingLimit() function to ensure that block number never equals to current block or past block.

Status:

Fixed as per BlockApex recommendation

3. Emergency exit for users.

Description: 

In event of any mishap with $ALT or $PILOT reward, a user won't be able to withdraw their LP funds. A user calls the unstakeLp()  function, the contract will throw the “Insufficient balance” error.

Remedy:

Contract should have emergency withdraw()  function to withdraw user’s staked LPs 

Status:

Fixed as per BlockApex recommendation

Informatory issues and Optimization

1. Should update Multiplier and RewardType while calling init  function.

Description: 

It's extra work for the governance, for the first time if they want to set a vault for only ALT reward they have to call 3 different functions, this work can be done by calling only one function. 

function initializer(
        address[] calldata _vault,
        uint256[] calldata _multiplier
    ) external override onlyGovernance {
        require(_vault.length == _multiplier.length,"LNS");
        uint256 blockNum = block.number;
        for (uint256 i = 0; i < _vault.length; i++) {
            VaultInfo storage vaultState = vaultInfo[_vault[i]];
            AltInfo storage vaultAltState = vaultAltInfo[_vault[i]];

Remedy:

RewardType and RewardToken should be set by Calling Initializer() function and later it can be handled by individual functions.

function initializer(
        address[] calldata _vault,
        uint256[] calldata _multiplier,
        RewardType[] calldata _rewardType,
        address[] calldata _rewardToken
    ) external override onlyGovernance {

Status:

Fixed as per BlockApex recommendation

DISCLAIMER

The smart contracts provided by the client for audit purposes have been thoroughly analyzed in compliance with the global best practices till date w.r.t cybersecurity vulnerabilities and issues in smart contract code, the details of which are enclosed in this report. 

This report is not an endorsement or indictment of the project or team, and they do not in any way guarantee the security of the particular object in context. This report is not considered, and should not be interpreted as an influence, on the potential economics of the token, its sale or any other aspect of the project. 

Crypto assets/tokens are results of the emerging blockchain technology in the domain of decentralized finance and they carry with them high levels of technical risk and uncertainty. No report provides any warranty or representation to any third-Party in any respect, including regarding the bug-free nature of code, the business model or proprietors of any such business model, and the legal compliance of any such business. No third-party should rely on the reports in any way, including for the purpose of making any decisions to buy or sell any token, product, service or other asset. Specifically, for the avoidance of doubt, this report does not constitute investment advice, is not intended to be relied upon as investment advice, is not an endorsement of this project or team, and it is not a guarantee as to the absolute security of the project.

Smart contracts are deployed and executed on a blockchain. The platform, its programming language, and other software related to the smart contract can have its vulnerabilities that can lead to hacks. The scope of our review is limited to a review of the Solidity code and only the Solidity code we note as being within the scope of our review within this report. The Solidity language itself remains under development and is subject to unknown risks and flaws. The review does not extend to the compiler layer, or any other areas beyond Solidity that could present security risks.

This audit cannot be considered as a sufficient assessment regarding the utility and safety of the code, bug-free status or any other statements of the contract. While we have done our best in conducting the analysis and producing this report, it is important to note that you should not rely on this report only - we recommend proceeding with several independent audits and a public bug bounty program to ensure security of smart contracts.