In this audit report we will highlight the following issues:
Coinsult checked the following privileges:
More owner priviliges are listed later in the report.
This audit report has been prepared by Coinsult’s experts at the request of the client. In this audit, the results of the static analysis and the manual code review will be presented. The purpose of the audit is to see if the functions work as intended, and to identify potential security issues within the smart contract.
The information in this report should be used to understand the risks associated with the smart contract. This report can be used as a guide for the development team on how the contract could possibly be improved by remediating the issues that were identified.
Note that we only audited the code available to us on this URL at the time of the audit. If the URL is not from any block explorer (main net), it may be subject to change. Always check the contract address on this audit report and compare it to the token you are doing research for.
ContractChecker SAFU
Coinsult’s manual smart contract audit is an extensive methodical examination and analysis of the smart contract’s code that is used to interact with the blockchain. This process is conducted to discover errors, issues and security vulnerabilities in the code in order to suggest improvements and ways to fix them.
Coinsult uses software that checks for common vulnerability issues within smart contracts. We use automated tools that scan the contract for security vulnerabilities such as integer-overflow, integer-underflow, out-of-gas-situations, unchecked transfers, etc.
Coinsult’s manual code review involves a human looking at source code, line by line, to find vulnerabilities. Manual code review helps to clarify the context of coding decisions. Automated tools are faster but they cannot take the developer’s intentions and general business logic into consideration.
Coinsult uses certain vulnerability levels, these indicate how bad a certain issue is. The higher the risk, the more strictly it is recommended to correct the error before using the contract.
Coinsult has four statuses that are used for each risk level. Below we explain them briefly.
The Smart Contract Weakness Classification Registry (SWC Registry) is an implementation of the weakness classification scheme proposed in EIP-1470. It is loosely aligned to the terminologies and structure used in the Common Weakness Enumeration (CWE) while overlaying a wide range of weakness variants that are specific to smart contracts.
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Passed
Avoid relying on block.timestamp
block.timestamp can be manipulated by miners.
secondsUntilAutoClaimAvailable = nextClaimTime > block.timestamp ?
nextClaimTime.sub(block.timestamp) :
0;
Recommendation
Do not use block.timestamp
, now
or blockhash
as a source of randomness
Exploit scenario
contract Game {
uint reward_determining_number;
function guessing() external{
reward_determining_number = uint256(block.blockhash(10000)) % 10;
}
}
Eve is a miner. Eve calls guessing
and re-orders the block containing the transaction. As a result, Eve wins the game.
Too many digits
Literals with many digits are difficult to read and review.
function updateGasForProcessing(uint256 newValue) public onlyOwner {
require(newValue >= 200000 && newValue <= 500000, "gasForProcessing must be between 200,000 and 500,000");
require(newValue != gasForProcessing, "Cannot update gasForProcessing to same value");
emit GasForProcessingUpdated(newValue, gasForProcessing);
gasForProcessing = newValue;
}
Recommendation
Use: Ether suffix, Time suffix, or The scientific notation
Exploit scenario
contract MyContract{
uint 1_ether = 10000000000000000000;
}
While 1_ether
looks like 1 ether
, it is 10 ether
. As a result, it’s likely to be used incorrectly.
No zero address validation for some functions
Detect missing zero address validation.
function changeMarketingWallet(address _marketingWallet) external onlyOwner {
require(_marketingWallet != marketingWallet, "Marketing wallet is already that address");
require(!isContract(_marketingWallet), "Marketing wallet cannot be a contract");
marketingWallet = _marketingWallet;
emit MarketingWalletChanged(marketingWallet);
}
Recommendation
Check that the new address is not zero.
Exploit scenario
contract C {
modifier onlyAdmin {
if (msg.sender != owner) throw;
_;
}
function updateOwner(address newOwner) onlyAdmin external {
owner = newOwner;
}
}
Bob calls updateOwner
without specifying the newOwner
, soBob loses ownership of the contract.
Functions that send Ether to arbitrary destinations
Unprotected call to a function sending Ether to an arbitrary address.
function sendBNB(address payable recipient, uint256 amount) internal {
require(address(this).balance >= amount, "Address: insufficient balance");
(bool success, ) = recipient.call{value: amount}("");
require(success, "Address: unable to send value, recipient may have reverted");
}
Recommendation
Ensure that an arbitrary user cannot withdraw unauthorized funds.
Exploit scenario
contract ArbitrarySend{
address destination;
function setDestination(){
destination = msg.sender;
}
function withdraw() public{
destination.transfer(this.balance);
}
}
Bob calls setDestination
and withdraw
. As a result he withdraws the contract’s balance.
Unchecked transfer
The return value of an external transfer/transferFrom call is not checked.
function claimStuckTokens(address token) external onlyOwner {
require(token != address(this), "Owner cannot claim native tokens");
if (token == address(0x0)) {
payable(msg.sender).transfer(address(this).balance);
return;
}
IERC20 ERC20token = IERC20(token);
uint256 balance = ERC20token.balanceOf(address(this));
ERC20token.transfer(msg.sender, balance);
}
Recommendation
Use SafeERC20
, or ensure that the transfer/transferFrom return value is checked.
Exploit scenario
contract Token {
function transferFrom(address _from, address _to, uint256 _value) public returns (bool success);
}
contract MyBank{
mapping(address => uint) balances;
Token token;
function deposit(uint amount) public{
token.transferFrom(msg.sender, address(this), amount);
balances[msg.sender] += amount;
}
}
Several tokens do not revert in case of failure and return false. If one of these tokens is used in MyBank
, deposit
will not revert if the transfer fails, and an attacker can call deposit
for free..
Divide before multiply
Solidity integer division might truncate. As a result, performing multiplication before division can sometimes avoid loss of precision.
uint256 fees = (amount * _totalFees) / 1000;
amount = amount - fees;
if (burnTaxShare > 0)
{
uint256 burnTaxTokens = (fees * burnTaxShare) / _totalFees;
fees -= burnTaxTokens;
super._transfer(from,DEAD,burnTaxTokens);
}
Recommendation
Consider ordering multiplication before division.
Exploit scenario
contract A {
function f(uint n) public {
coins = (oldSupply / n) * interest;
}
}
If n
is greater than oldSupply
, coins
will be zero. For example, with oldSupply = 5; n = 10, interest = 2
, coins will be zero. If (oldSupply * interest / n)
was used, coins
would have been 1
. In general, it’s usually a good idea to re-arrange arithmetic to perform multiplication before division, unless the limit of a smaller type makes this dangerous.
Boolean equality
Detects the comparison to boolean constants.
if (maxWalletLimitEnabled)
{
if (_isExcludedFromMaxWalletLimit[from] == false &&
_isExcludedFromMaxWalletLimit[to] == false &&
to != uniswapV2Pair
) {
uint balance = balanceOf(to);
require(
balance + amount <= maxWalletAmount,
"MaxWallet: Recipient exceeds the maxWalletAmount"
);
}
}
Recommendation
Remove the equality to the boolean constant.
Exploit scenario
contract A {
function f(bool x) public {
// ...
if (x == true) { // bad!
// ...
}
// ...
}
}
Boolean constants can be used directly and do not need to be compare to true
or false
.
Coinsult tests if the owner of the smart contract can set the transfer, buy or sell fee to 25% or more. It is bad practice to set the fees to 25% or more, because owners can prevent healthy trading or even stop trading when the fees are set too high.
Coinsult tests if the owner of the smart contract has the ability to pause the contract. If this is the case, users can no longer interact with the smart contract; users can no longer trade the token.
Coinsult tests if the owner of the smart contract can set the maximum amount of a transaction. If the transaction exceeds this limit, the transaction will revert. Owners could prevent normal transactions to take place if they abuse this function.
Coinsult tests if the owner of the smart contract can exclude addresses from paying tax fees. If the owner of the smart contract can exclude from fees, they could set high tax fees and exclude themselves from fees and benefit from 0% trading fees. However, some smart contracts require this function to exclude routers, dex, cex or other contracts / wallets from fees.
Coinsult tests if the owner of the smart contract can mint new tokens. If the contract contains a mint function, we refer to the token’s total supply as non-fixed, allowing the token owner to “mint” more tokens whenever they want.
A mint function in the smart contract allows minting tokens at a later stage. A method to disable minting can also be added to stop the minting process irreversibly.
Minting tokens is done by sending a transaction that creates new tokens inside of the token smart contract. With the help of the smart contract function, an unlimited number of tokens can be created without spending additional energy or money.
Coinsult tests if the owner of the smart contract needs to manually enable trading before everyone can buy & sell. If the owner needs to manually enable trading, this poses a high centralization risk.
If the owner needs to manually enable trading, make sure to check if the project has a SAFU badge or a trusted KYC badge. Always DYOR when investing in a project that needs to manually enable trading.
Coinsult tests if the owner of the smart contract can blacklist accounts from interacting with the smart contract. Blacklisting methods allow the contract owner to enter wallet addresses which are not allowed to interact with the smart contract.
This method can be abused by token owners to prevent certain / all holders from trading the token. However, blacklists might be good for tokens that want to rule out certain addresses from interacting with a smart contract.
Coinsult lists all important contract methods which the owner can interact with.
⚠ Owner can set max wallet amount
When changing tax fees, multiply the tax fees by 10. So when entering 3%, enter 30 instead of 3. The contract is setup this way.
✅ Max transaction amount sell cannot be lower than current amount
✅ Max wallet percentage cannot be lower than 2%
This is how the constructor of the contract looked at the time of auditing the smart contract.
contract BUSDPay is ERC20, Ownable {
uint256 public rewardFeeOnBuy = 40;
uint256 public marketingFeeOnBuy = 40;
uint256 public liquidityFeeOnBuy = 10;
uint256 public burnTaxFeeOnBuy = 10;
uint256 public rewardFeeOnSell = 80;
uint256 public marketingFeeOnSell = 50;
uint256 public liquidityFeeOnSell = 10;
uint256 public burnTaxFeeOnSell = 10;
uint256 public totalBuyFee = 100;
uint256 public totalSellFee = 150;
uint256 public walletToWalletFee = 0;
address public marketingWallet = 0x3C1619D25837390C55850809fCD9a19875b8Be0B;
address public operator;
IUniswapV2Router02 public uniswapV2Router;
address public uniswapV2Pair;
address private DEAD = 0x000000000000000000000000000000000000dEaD;
bool private swapping;
uint256 public swapTokensAtAmount;
mapping (address => bool) private _isExcludedFromFees;
DividendTracker public dividendTracker;
address public constant rewardToken = 0xe9e7CEA3DedcA5984780Bafc599bD69ADd087D56;//BUSD
uint256 public gasForProcessing = 300000;
event ExcludeFromFees(address indexed account, bool isExcluded);
event FeesBuyUpdated(uint256 rewardFeeOnBuy,uint256 marketingFeeOnBuy,uint256 liquidityFeeOnBuy,uint256 burnTaxFeeOnBuy);
event FeesSellUpdated(uint256 rewardFeeOnSell,uint256 marketingFeeOnSell,uint256 liquidityFeeOnSell,uint256 burnTaxFeeOnSell);
event UpdateWalletToWalletFee(uint256 walletToWalletFee);
event MarketingWalletChanged(address marketingWallet);
event OperatorWalletChanged(address operatorWallet);
event SwapAndLiquify(uint256 tokensSwapped, uint256 bnbReceived, uint256 tokensIntoLiqudity);
event SendMarketing(uint256 bnbSend);
event UpdateDividendTracker(address indexed newAddress, address indexed oldAddress);
event GasForProcessingUpdated(uint256 indexed newValue, uint256 indexed oldValue);
event SendDividends(uint256 amount);
event ProcessedDividendTracker(
uint256 iterations,
uint256 claims,
uint256 lastProcessedIndex,
bool indexed automatic,
uint256 gas,
address indexed processor
);
Coinsult checks the website completely manually and looks for visual, technical and textual errors. We also look at the security, speed and accessibility of the website. In short, a complete check to see if the website meets the current standard of the web development industry.
This audit report has been prepared by Coinsult’s experts at the request of the client. In this audit, the results of the static analysis and the manual code review will be presented. The purpose of the audit is to see if the functions work as intended, and to identify potential security issues within the smart contract.
The information in this report should be used to understand the risks associated with the smart contract. This report can be used as a guide for the development team on how the contract could possibly be improved by remediating the issues that were identified.
Coinsult is not responsible if a project turns out to be a scam, rug-pull or honeypot. We only provide a detailed analysis for your own research.
Coinsult is not responsible for any financial losses. Nothing in this contract audit is financial advice, please do your own research.
The information provided in this audit is for informational purposes only and should not be considered investment advice. Coinsult does not endorse, recommend, support or suggest to invest in any project.
Coinsult can not be held responsible for when a project turns out to be a rug-pull, honeypot or scam.