Coinsult

Request your audit at coinsult.net

Advanced Manual
Smart Contract Audit

August 16, 2022

Audit requested by

Crypto Fan Token

0x5BeB1898ae55Fc1e65F65f61DB101Ab8684DF05B

Crypto Fan Token / 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 Crypto Fan Token

7. Contract Snapshot

8. Website Review

9. Certificate of Proof

Crypto Fan Token / Security Audit

Audit Summary

Audit Scope

Project Name

Crypto Fan Token

Blockchain

Binance Smart Chain

Smart Contract Language

Solidity

Contract Address

0x5BeB1898ae55Fc1e65F65f61DB101Ab8684DF05B

Audit Method

Static Analysis, Manual Review

Date of Audit

16 August 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.

Crypto Fan Token / Security Audit

Tokenomics

Rank Address Quantity (Token) Percentage
1 0x7210f2c0c34a80711b67745b7e5d22383410dd0e 1,000,000,000 100.0000%

Source Code

Coinsult was comissioned by Crypto Fan Token to perform an audit based on the following code:
https://bscscan.com/address/0x5BeB1898ae55Fc1e65F65f61DB101Ab8684DF05B#code

Crypto Fan Token / 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.

Crypto Fan Token / 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

2

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.

Crypto Fan Token / Security Audit

No constraints on lock time
				
					    //Locks the contract for owner for the amount of time provided
    function lock(uint256 time) public virtual onlyOwner {
        _previousOwner = _owner;
        _owner = address(0);
        _lockTime = now + time;
        emit OwnershipTransferred(_owner, address(0));
    }
   
				
			

Recommendation

It is recommended to put a require statement to prevent the lock time from exceeding a specific amount. For example, when you try to lock for 1 year, but you make it 10, you lose ownership for 10 years.

Crypto Fan Token / Security Audit

Avoid relying on block.timestamp

block.timestamp can be manipulated by miners.

				
					    //Locks the contract for owner for the amount of time provided
    function lock(uint256 time) public virtual onlyOwner {
        _previousOwner = _owner;
        _owner = address(0);
        _lockTime = now + time;
        emit OwnershipTransferred(_owner, address(0));
    }
    
				
			

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.

Crypto Fan Token / Security Audit

Too many digits

Literals with many digits are difficult to read and review.

				
					    uint256 private _tTotal = 1000000000 * 10**9; // 1 billion
				
			

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.

Crypto Fan Token / Security Audit

Missing events arithmetic

Detect missing events for critical arithmetic parameters.

				
					    function setTaxFeePercent(uint256 taxFee) external onlyOwner() {
        _taxFee = taxFee;
    }
    
    function setLiquidityFeePercent(uint256 liquidityFee) external onlyOwner() {
        _liquidityFee = liquidityFee;
    }

    function setBurnFeePercent(uint256 burnFee) external onlyOwner() {
        _burnFee = burnFee;
    }

    function setMarketingFeePercent(uint256 fee) external onlyOwner() {
        _marketingFee = fee;
    }
				
			

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.

Crypto Fan Token / Security Audit

Costly operations inside a loop

Costly operations inside a loop might waste gas, so optimizations are justified. 

				
					    function includeInReward(address account) external onlyOwner() {
        require(_isExcluded[account], "Account is already excluded");
        for (uint256 i = 0; i < _excluded.length; i++) {
            if (_excluded[i] == account) {
                _excluded[i] = _excluded[_excluded.length - 1];
                _tOwned[account] = 0;
                _isExcluded[account] = false;
                _excluded.pop();
                break;
            }
        }
    }
				
			

Recommendation

Use a local variable to hold the loop computation result.

Exploit scenario

				
					contract CostlyOperationsInLoop{

    function bad() external{
        for (uint i=0; i < loop_count; i++){
            state_variable++;
        }
    }

    function good() external{
      uint local_variable = state_variable;
      for (uint i=0; i < loop_count; i++){
        local_variable++;
      }
      state_variable = local_variable;
    }
}
				
			

Incrementing state_variable in a loop incurs a lot of gas because of expensive SSTOREs, which might lead to an out-of-gas.

Wrong require statement for unlock function (✅ Resolved and fixed)
				
					    //Unlocks the contract for owner when _lockTime is exceeds
    function unlock() public virtual {
        require(_previousOwner == msg.sender, "You don't have permission to unlock");
        require(now &gt; _lockTime , "Contract is locked until 7 days");
        emit OwnershipTransferred(_owner, _previousOwner);
        _owner = _previousOwner;
    }
				
			

Recommendation

‘_lockTime’ is a variable passed through in the ‘lock’ function. It is not set to 7 days by default. This require statement is, therefore, wrong.

Crypto Fan Token / 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

Crypto Fan Token / 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?

Crypto Fan Token / 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?

Crypto Fan Token / 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?

Crypto Fan Token / 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?

Crypto Fan Token / 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?

Crypto Fan Token / Security Audit

Other Owner Privileges Check

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

⚠ Owner can lock the contract, so that he loses ownership of the contract for a specific ‘time’

⚠ Owner can set max wallet percentage

Crypto Fan Token / Security Audit

Notes

Notes by Crypto Fan Token

No notes provided by the team.

Notes by Coinsult

✅ No notes provided by Coinsult

Crypto Fan Token / Security Audit

Contract Snapshot

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

				
					contract CryptoFanToken is Context, IERC20, Ownable {
    using SafeMath for uint256;
    using Address for address;

    mapping (address =&gt; uint256) private _rOwned;
    mapping (address =&gt; uint256) private _tOwned;
    mapping (address =&gt; mapping (address =&gt; uint256)) private _allowances;

    mapping (address =&gt; bool) private _isExcludedFromFee;

    mapping (address =&gt; bool) private _isExcluded;
    address[] private _excluded;
   
    uint256 private constant MAX = ~uint256(0);
    uint256 private _tTotal = 1 * 10**9 * 10**9; // 1 billion
    uint256 private _rTotal = (MAX - (MAX % _tTotal));
    uint256 private _tFeeTotal;

    string private _name = "CryptoFanToken";
    string private _symbol = "CFT";
    uint8 private _decimals = 9;

    uint256 public _burnFee = 0;
    uint256 private _previousBurnFee = _burnFee;

    uint256 public _marketingFee = 6;
    uint256 private _previousMarketingFee = _marketingFee;
    
    uint256 public _taxFee = 1;
    uint256 private _previousTaxFee = _taxFee;
    
    uint256 public _liquidityFee = 2;
    uint256 private _previousLiquidityFee = _liquidityFee;

    address public marketingWallet = 0x7210F2c0C34A80711B67745b7e5d22383410dd0e;

    IUniswapV2Router02 public immutable uniswapV2Router;
    address public immutable uniswapV2Pair;
				
			

Crypto Fan Token / 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?

Crypto Fan Token / Security Audit

Certificate of Proof

Crypto Fan Token

Audited by Coinsult.net

Date: 16 August 2022

Coinsult

coinsult.net

End of report
Smart Contract Audit

Request your smart contract audit / KYC

t.me/coinsult_tg