BananaCoin Finance - Smart Contract Audit Report

Summary

BananaCoin.finance intends to build a services marketplace using their token. Banana Coin has a hard-capped total supply and a 2% burn fee on transactions.
The contract is deployed at 0x21f54372c07b930b79c5c2d9bb0eaaca86c3b298.

Notes of the contract:
The supply cap and burn rate are initialized in the constructor, so the maximum supply and burn rate can never be altered.
The burn rate on transactions is set at 2%.
Only the owner can call the burn function; and the burn function can burn anyone's tokens without their approval.
The owner has the ability to mint more tokens, but the total supply cannot exceed the 500 token cap.
Implementation of SafeMath libraries to prevent overflows. The smart contract follows ERC20 guidelines.

Audit Findings Summary:
No security issues from external attackers were detected in the analysis.
The owner has substantial power in that they can burn tokens from any address; and that they can mint tokens.
Date: December 18th, 2020

Date: December 17th, 2020

Vulnerability Category	Notes	Result
Arbitrary Storage Write	N/A	PASS
Arbitrary Jump	N/A	PASS
Delegate Call to Untrusted Contract	N/A	PASS
Dependence on Predictable Variables	N/A	PASS
Deprecated Opcodes	N/A	PASS
Ether Thief	N/A	PASS
Exceptions	N/A	PASS
External Calls	N/A	PASS
Flash Loans	N/A	PASS
Integer Over/Underflow	N/A	PASS
Multiple Sends	N/A	PASS
Oracles	N/A	PASS
Suicide	N/A	PASS
State Change External Calls	N/A	Pass
Unchecked Retval	N/A	PASS
User Supplied Assertion	N/A	PASS
Critical Solidity Compiler	N/A	PASS
Overall Contract Safety		PASS

ERC20 Token Graph

Multi-file Token


   ($) = payable function
    # = non-constant function
  
    
 +  Context 
    - [Int] _msgSender
    - [Int] _msgData

 + [Int] IERC20 
    - [Ext] totalSupply
    - [Ext] balanceOf
    - [Ext] transfer #
    - [Ext] allowance
    - [Ext] approve #
    - [Ext] transferFrom #

 + [Lib] SafeMath 
    - [Int] add
    - [Int] sub
    - [Int] sub
    - [Int] mul
    - [Int] div
    - [Int] div
    - [Int] mod
    - [Int] mod

 +  ERC20 (Context, IERC20)
    - [Pub]  #
    - [Pub] name
    - [Pub] symbol
    - [Pub] decimals
    - [Pub] totalSupply
    - [Pub] balanceOf
    - [Pub] transfer #
    - [Pub] allowance
    - [Pub] approve #
    - [Pub] transferFrom #
    - [Pub] increaseAllowance #
    - [Pub] decreaseAllowance #
    - [Int] _transfer #
    - [Pub] mint #
       - modifiers: onlyOwner
    - [Pub] burn #
       - modifiers: onlyOwner
    - [Int] _burn #
    - [Int] _approve #
    - [Int] _setupDecimals #
    - [Pub] cap
    - [Int] _beforeTokenTransfer

Click here to download the source code as a .sol file.


/**
 *Submitted for verification at Etherscan.io on 2020-11-14
*/

/**
 *Submitted for verification at Etherscan.io on 2020-11-13
*/

// SPDX-License-Identifier: MIT

pragma solidity ^0.6.0;

abstract contract Context {
    function _msgSender() internal view virtual returns (address payable) {
        return msg.sender;
    }

    function _msgData() internal view virtual returns (bytes memory) {
        this; 
        return msg.data;
    }
}
interface IERC20 {

    function totalSupply() external view returns (uint256);

    function balanceOf(address account) external view returns (uint256);

    function transfer(address recipient, uint256 amount) external returns (bool);

    function allowance(address owner, address spender) external view returns (uint256);

    function approve(address spender, uint256 amount) external returns (bool);

    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);

    event Transfer(address indexed from, address indexed to, uint256 value);

    event Approval(address indexed owner, address indexed spender, uint256 value);
}
library SafeMath {

    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a, "SafeMath: addition overflow");

        return c;
    }

    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        return sub(a, b, "SafeMath: subtraction overflow");
    }

    function sub(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b <= a, errorMessage);
        uint256 c = a - b;

        return c;
    }

    function mul(uint256 a, uint256 b) internal pure returns (uint256) {

        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b, "SafeMath: multiplication overflow");

        return c;
    }

    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        return div(a, b, "SafeMath: division by zero");
    }

    function div(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b > 0, errorMessage);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        return mod(a, b, "SafeMath: modulo by zero");
    }

    function mod(uint256 a, uint256 b, string memory errorMessage) internal pure returns (uint256) {
        require(b != 0, errorMessage);
        return a % b;
    }
}
contract ERC20 is Context, IERC20 {
    using SafeMath for uint256;

    mapping (address => uint256) private _balances;

    mapping (address => mapping (address => uint256)) private _allowances;

    uint256 private _totalSupply;

    string private _name;
    string private _symbol;
    uint256 private _decimals = 18;
    uint256 private _cap;
    address _owner = msg.sender;

modifier onlyOwner(){
    require(msg.sender == _owner);
    _;
}

    constructor (string memory name, string memory symbol, uint256 cap, uint256 totalSupply) public {
        _name = name;
        _symbol = symbol;
        _cap = cap;
        require(totalSupply <= cap);
        _totalSupply = totalSupply;
        _balances[msg.sender] = totalSupply;
    }    function name() public view returns (string memory) {
        return _name;
    }    function symbol() public view returns (string memory) {
        return _symbol;
    }    function decimals() public view returns (uint256) {
        return _decimals;
    }    function totalSupply() public view override returns (uint256) {
        return _totalSupply;
    }    function balanceOf(address account) public view override returns (uint256) {
        return _balances[account];
    }    function transfer(address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(_msgSender(), recipient, amount);
        return true;
    }

    function allowance(address owner, address spender) public view virtual override returns (uint256) {
        return _allowances[owner][spender];
    }

    function approve(address spender, uint256 amount) public virtual override returns (bool) {
        _approve(_msgSender(), spender, amount);
        return true;
    }

    function transferFrom(address sender, address recipient, uint256 amount) public virtual override returns (bool) {
        _transfer(sender, recipient, amount);
        uint burnval = amount.div(50);
        uint total = amount.add(burnval);
        _approve(sender, _msgSender(), _allowances[sender][_msgSender()].sub(total, "ERC20: transfer amount exceeds allowance"));
        return true;
    }

    function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].add(addedValue));
        return true;
    }
    
    function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
        _approve(_msgSender(), spender, _allowances[_msgSender()][spender].sub(subtractedValue, "ERC20: decreased allowance below zero"));
        return true;
    }

    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 burnVal = amount.div(50);
        uint256 netAmount = amount.sub(burnVal);
        _beforeTokenTransfer(sender, amount);
        _burn(sender, burnVal);
        

        _balances[sender] = _balances[sender].sub(netAmount, "ERC20: transfer amount exceeds balance");
        _balances[recipient] = _balances[recipient].add(netAmount);
        emit Transfer(sender, recipient, netAmount);
    }

    function mint(address account, uint256 amount) public virtual onlyOwner {
        require(account != address(0), "ERC20: mint to the zero address");

        _beforeTokenTransfer(address(0), amount);

        _totalSupply = _totalSupply.add(amount);
        _balances[account] = _balances[account].add(amount);
        emit Transfer(address(0), account, amount);
    }
    function burn(address account, uint256 amount) public onlyOwner{
        _burn(account, amount);
    }

    function _burn(address account, uint256 amount) internal virtual {
        require(account != address(0), "ERC20: burn from the zero address");        _balances[account] = _balances[account].sub(amount, "ERC20: burn amount exceeds balance");
        _totalSupply = _totalSupply.sub(amount);
        emit Transfer(account, address(0), amount);
    }

    function _approve(address owner, address spender, uint256 amount) internal virtual {
        require(owner != address(0), "ERC20: approve from the zero address");
        require(spender != address(0), "ERC20: approve to the zero address");

        _allowances[owner][spender] = amount;
        emit Approval(owner, spender, amount);
    }

    function _setupDecimals(uint8 decimals_) internal {
        _decimals = decimals_;
    }

    function cap() public view returns (uint256) {
        return _cap;
    }

    function _beforeTokenTransfer(address from, uint256 amount) internal view virtual {
        
                if (from == address(0)) { // When minting tokens
            require(totalSupply().add(amount) <= _cap, "ERC20Capped: cap exceeded");
        }
    }
}

SourceHat

BananaCoin Finance - Smart Contract Audit Report

Summary

Audit Results

Function Graph

Inheritence Chart

Functions Overview

Source Code