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Advanced Manual
Smart Contract Audit

June 8, 2022

Audit requested by

Fbox

0xA874A23e4b0C9d1d726ec88ade07850A63432032

Fbox / Security Audit

Table of Contents

1. Audit Summary

1.1 Audit scope

1.2 Tokenomics

1.3 Source Code

2. Disclaimer

3. Global Overview

3.1 Informational issues

3.2 Low-risk issues

3.3 Medium-risk issues

3.4 High-risk issues

4. Vulnerabilities Findings

5. Contract Privileges

5.1 Maximum Fee Limit Check

5.2 Contract Pausability Check

5.3 Max Transaction Amount Check

5.4 Exclude From Fees Check

5.5 Ability to Mint Check

5.6 Ability to Blacklist Check

5.7 Owner Privileges Check

6. Notes

6.1 Notes by Coinsult

6.2 Notes by Fbox

7. Contract Snapshot

8. Website Review

9. Certificate of Proof

Fbox / Security Audit

Audit Summary

Audit Scope

Project Name

Fbox

Blockchain

Binance Smart Chain

Smart Contract Language

Solidity

Contract Address

0xA874A23e4b0C9d1d726ec88ade07850A63432032

Audit Method

Static Analysis, Manual Review

Date of Audit

8 June 2022

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.

Fbox / Security Audit

Tokenomics

Rank Address Quantity (Token) Percentage
1 0x5bb8506fcc5f27307f88ad1d73cce1b94876334c 10,000,000 100.0000%

Source Code

Coinsult was comissioned by Fbox to perform an audit based on the following code:
https://bscscan.com/address/0xA874A23e4b0C9d1d726ec88ade07850A63432032#code

Fbox / Security Audit

Disclaimer

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.

Fbox / Security Audit

Global Overview

Manual Code Review

In this audit report we will highlight the following issues:

Vulnerability Level

Total

Pending

Acknowledged

Resolved

0

0

0

0

7

0

0

0

0

0

0

0

0

0

0

0

Privilege Overview

Coinsult checked the following privileges:

Contract Privilege

Description

Owner can mint?

Owner can blacklist?

Owner can set fees > 25%?

Owner can exclude from fees?

Owner can pause trading?

Owner can set Max TX amount?

More owner priviliges are listed later in the report.

Fbox / Security Audit

Contract contains Reentrancy vulnerabilities

Additional information: This combination increases risk of malicious intent. While it may be justified by some complex mechanics (e.g. rebase, reflections, buyback). 

More information: Slither

				
					function _transfer(
        address sender, address recipient, uint256 amount
    ) internal virtual {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        uint256 senderBalance = _balances[sender];
        require(senderBalance >= amount, "ERC20: transfer amount exceeds balance");
        unchecked {
            _balances[sender] = senderBalance - amount;
        }

        if (!_buyed[recipient] && !isContract(recipient) && recipient != _dead) {
            _buyed[recipient] = true;
            buyUser.push(recipient);
        }

        if (_whites[sender] || _whites[recipient]) {
            _balances[recipient] += amount;
            emit Transfer(sender, recipient, amount);
            return;
        }

        // do fist bonus
        uint256 fists = IERC20(_fist).balanceOf(address(this));
        bool isbonus = false;
        if (fists >= _maxfist && !_swapping && sender != _pair) {
            _swapping = true;
            // fist market 10%
            IERC20(_fist).transfer(_mark, fists / 10);
            // fist bonus  30%
            _doBonusFist(fists * 3 / 10);
            // fist to fbox 40%
            _swapFistForToken(address(this), fists * 4 / 10);
            // fist to ftts 20%
            _swapFistForToken(_ftts, fists * 2 / 10);
            _swapping = false;
            isbonus = true;
        }

        // do fbox burn and liquidity
        uint256 balance = balanceOf(address(this));
        if (!isbonus && balance >= _maxsell && !_swapping && sender != _pair) {
            _swapping = true;

            if (IERC20(_fist).allowance(address(this), _router) <= 10 ** 16
                || allowance(address(this), _router)  0 && fists / 4 > 0) {
                addLiquidityFist(balance / 5, fists / 4);
            }
            _swapping = false;
        }

        // burn 1%
        _balances[_dead] += (amount / 100);
        emit Transfer(sender, _dead, (amount / 100));

        // else 5%
        _balances[address(this)] += (amount * 5 / 100);
        emit Transfer(sender, address(this), (amount * 5 / 100));

        // to user 94%
        amount = amount * 94 / 100;
        _balances[recipient] += amount;
        emit Transfer(sender, recipient, amount);
    }
				
			

Recommendation

Apply the check-effects-interactions pattern.

Exploit scenario

				
					    function withdrawBalance(){
        // send userBalance[msg.sender] Ether to msg.sender
        // if mgs.sender is a contract, it will call its fallback function
        if( ! (msg.sender.call.value(userBalance[msg.sender])() ) ){
            throw;
        }
        userBalance[msg.sender] = 0;
    }
				
			
Bob uses the re-entrancy bug to call withdrawBalance two times, and withdraw more than its initial deposit to the contract.

Fbox / Security Audit

Avoid relying on block.timestamp

block.timestamp can be manipulated by miners.

				
					function _swapFistForToken(address a2, uint256 tokenAmount) private {
        address[] memory path = new address[](2);
        path[0] = _fist;path[1] = a2;
        IPancakeRouter02(_router).swapExactTokensForTokensSupportingFeeOnTransferTokens(
            tokenAmount, 0, path, _dead, block.timestamp);
    }
				
			

Recommendation

Do not use block.timestampnow 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.

Fbox / Security Audit

Too many digits

Literals with many digits are difficult to read and review.

				
					_mint(_main, 10000000 * 10 ** decimals());
				
			

Recommendation

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.

Fbox / Security Audit

No zero address validation for some functions

Detect missing zero address validation.

				
					function setAddrs(address mark, address flow, address wrap) public onlyOwner {
        _mark = mark;
        _flow = flow;
        _wrap = wrap;
    }
				
			

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.

Fbox / Security Audit

Unchecked transfer

The return value of an external transfer/transferFrom call is not checked.

				
					function _transfer(
        address sender, address recipient, uint256 amount
    ) internal virtual {
        require(sender != address(0), "ERC20: transfer from the zero address");
        require(recipient != address(0), "ERC20: transfer to the zero address");

        uint256 senderBalance = _balances[sender];
        require(senderBalance >= amount, "ERC20: transfer amount exceeds balance");
        unchecked {
            _balances[sender] = senderBalance - amount;
        }

        if (!_buyed[recipient] && !isContract(recipient) && recipient != _dead) {
            _buyed[recipient] = true;
            buyUser.push(recipient);
        }

        if (_whites[sender] || _whites[recipient]) {
            _balances[recipient] += amount;
            emit Transfer(sender, recipient, amount);
            return;
        }

        // do fist bonus
        uint256 fists = IERC20(_fist).balanceOf(address(this));
        bool isbonus = false;
        if (fists >= _maxfist && !_swapping && sender != _pair) {
            _swapping = true;
            // fist market 10%
            IERC20(_fist).transfer(_mark, fists / 10);
            // fist bonus  30%
            _doBonusFist(fists * 3 / 10);
            // fist to fbox 40%
            _swapFistForToken(address(this), fists * 4 / 10);
            // fist to ftts 20%
            _swapFistForToken(_ftts, fists * 2 / 10);
            _swapping = false;
            isbonus = true;
        }

        // do fbox burn and liquidity
        uint256 balance = balanceOf(address(this));
        if (!isbonus && balance >= _maxsell && !_swapping && sender != _pair) {
            _swapping = true;

            if (IERC20(_fist).allowance(address(this), _router) <= 10 ** 16
                || allowance(address(this), _router)  0 && fists / 4 > 0) {
                addLiquidityFist(balance / 5, fists / 4);
            }
            _swapping = false;
        }

        // burn 1%
        _balances[_dead] += (amount / 100);
        emit Transfer(sender, _dead, (amount / 100));

        // else 5%
        _balances[address(this)] += (amount * 5 / 100);
        emit Transfer(sender, address(this), (amount * 5 / 100));

        // to user 94%
        amount = amount * 94 / 100;
        _balances[recipient] += amount;
        emit Transfer(sender, recipient, amount);
    }
				
			

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 MyBankdeposit will not revert if the transfer fails, and an attacker can call deposit for free..

Fbox / Security Audit

Missing events arithmetic

Detect missing events for critical arithmetic parameters.

				
					function setMaxsell(uint256 val) public onlyOwner {
        _maxsell = val;
    }
				
			

Recommendation

Emit an event for critical parameter changes.

Exploit scenario

				
					contract C {

  modifier onlyAdmin {
    if (msg.sender != owner) throw;
    _;
  }

  function updateOwner(address newOwner) onlyAdmin external {
    owner = newOwner;
  }
}
				
			

updateOwner() has no event, so it is difficult to track off-chain changes in the buy price.

Fbox / Security Audit

Conformance to Solidity naming conventions

Allow _ at the beginning of the mixed_case match for private variables and unused parameters.

				
					mapping(address => bool) public _buyed;
				
			

Recommendation

Follow the Solidity naming convention.

Rule exceptions

  • Allow constant variable name/symbol/decimals to be lowercase (ERC20).
  • Allow _ at the beginning of the mixed_case match for private variables and unused parameters.

Fbox / Security Audit

Contract Privileges

Maximum Fee Limit Check

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. 

Type of fee

Description

Transfer fee

Buy fee

Sell fee

Type of fee

Description

Max transfer fee

Max buy fee

Max sell fee

Fbox / Security Audit

Contract Pausability Check

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.

Privilege Check

Description

Can owner pause the contract?

Fbox / Security Audit

Max Transaction Amount Check

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.

Privilege Check

Description

Can owner set max tx amount?

Fbox / Security Audit

Exclude From Fees Check

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.

Privilege Check

Description

Can owner exclude from fees?

Fbox / Security Audit

Ability To Mint Check

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.

Privilege Check

Description

Can owner mint?

Fbox / Security Audit

Ability To Blacklist Check

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.

Privilege Check

Description

Can owner blacklist?

Fbox / Security Audit

Other Owner Privileges Check

Coinsult lists all important contract methods which the owner can interact with.

⚠ Owner can set max bonus value

Fbox / Security Audit

Notes

Notes by Fbox

No notes provided by the team.

Notes by Coinsult

✅ No notes provided by Coinsult

Fbox / Security Audit

Contract Snapshot

This is how the constructor of the contract looked at the time of auditing the smart contract.

				
					contract Token is Ownable, IERC20Metadata {
    mapping(address => bool) public _buyed;
    mapping(address => bool) public _whites;
    mapping(address => uint256) private _balances;
    mapping(address => mapping(address => uint256)) private _allowances;

    string  private _name;
    string  private _symbol;
    uint256 private _totalSupply;
    uint256 public  _maxsell;
    uint256 public  _maxfist;
				
			

Fbox / Security Audit

Website Review

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. 

Type of check

Description

Mobile friendly?

Contains jQuery errors?

Is SSL secured?

Contains spelling errors?

Fbox / Security Audit

Certificate of Proof

Fbox

Audited by Coinsult.net

Date: 8 June 2022

Coinsult

coinsult.net

End of report
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