Bigcoin - Smart Contract Audit Report

Audit Summary

Bigcoin Audit Report Bigcoin ($BIG) is a new BEP-20 token on the Binance Smart Chain that pays out static rewards to holders.

We reviewed the CoinToken contract at 0x91CC678f39a86Ec3eB0C4Ae3d21fD771bcbd5c3A on the Binance Smart Chain mainnet.

Audit Findings

Please ensure trust in the team prior to investing as they have substantial control in the ecosystem and currently own 100% of the total supply.
Date: January 15th, 2022.
CoinToken.sol - Finding #1 - Low
Description: The owner can use the lock() function in order to temporarily set ownership to address(0). Ownership is restored after the duration of time determined by the owner has passed and they use the unlock() function.
			
function lock(uint256 time) public virtual onlyOwner {
    _previousOwner = _owner;
    _owner = address(0);
    _lockTime = block.timestamp + time;
    emit OwnershipTransferred(_owner, address(0));
}
function unlock() public virtual {
    require(
        _previousOwner == msg.sender,
        "You don't have permission to unlock"
    );
    emit OwnershipTransferred(_owner, _previousOwner);
    _owner = _previousOwner;  
}
Risk/Impact: The unlock function has the potential to be used after ownership has been set to address(0), which will restore ownership to the original owner that initially created the ownership lock. This can be used in a nefarious way by the project team to restore ownership and change fee structures.
Recommendation: We recommend that the unlock function be modified to set the previous owner variable equal to address(0) at the end of the unlock function to prevent it from being used more than once per lock.

CoinToken.sol - Finding #2 - Gas Optimization
Description: The addLiquidity() function is never called in the contract.
			
function addLiquidity(uint256 tokenAmount, uint256 ethAmount) private {
// approve token transfer to cover all possible scenarios
_approve(address(this), address(uniswapV2Router), tokenAmount);

// add the liquidity
uniswapV2Router.addLiquidityETH{value: ethAmount}(
address(this),
tokenAmount,
0, // slippage is unavoidable
0, // slippage is unavoidable
owner(),
block.timestamp);
}
Recommendation: The project team should remove this function from the contract to optimize deployment costs.

Contract Overview

The total supply of the token is set to 21 million $BIG [21,000,000].
No mint or burn functions are present; though the circulating supply can be reduced by sending tokens to the 0x..dead address if desired.
At the time of writing this report, 65.59% of the total supply belongs to the deployer.
At the time of writing this report, 32.88% of the total supply belongs to a KIPS Locked Wallet.
The next five holders own a cumulative 1.23% of the total supply.

There is a Tax fee, Liquidity fee, Buyback fee, and Marketing fee on all transfers where neither the sender nor the recipient is excluded from fees.
The tokens collected from the Tax fee are removed from the circulating supply; This serves as a frictionless fee redistribution which automatically benefits all token holders at the time of each transaction.
The tokens collected from the Liquidity fee during transfers are stored in the contract address balance. Once the threshold value of tokens (determined by the owner) is met, the tokens are swapped for BNB. A portion of this BNB will be sent to the Liquidity Pool address set by the team. Another portion of the BNB received through this process is sent to the team's Marketing wallet.
On each transfer that occurs while the minimum threshold (determined by the owner) is met, the protocol will spend 1% of its BNB balance toward buying $BIG tokens that are subsequently be burned.
Although the SafeMath library is utilized, the contract is deployed with Solidity v0.8.x which has built-in overflow checks. SafeMath could be safely removed to reduce contract size and deployment costs.
Ownership Controls:
Ownership has not been renounced.
The owner can modify the Tax fee, Buyback fee, and Marketing fee to any percentages at any time. The liquidity fee percentage is the sum of the Buyback fee percentage and Marketing fee percentage. The owner must exercise caution when modifying fees as the Liquidity fee is responsible for funding the BNB for the Liquidity Pool.
The owner can exclude and include accounts from transfer fees and reward distribution.
The owner can set and update a maximum transaction amount at any time, which will impose a limit to the number of tokens that can be transferred during any given transaction.
The owner can enable/disable automatic liquidity adds and the buyback functionality at any time.
The owner can update the threshold number of tokens needed to trigger automatic liquidity adds
The contract includes a Presale() function that allows the owner to set fees to 0, disable automatic liquidity adds, and set the max transaction amount to 100% of the total token supply.
The owner can update the team's Marketing wallet to any address at any time.

External Threat Results

Vulnerability Category	Notes	Result
Arbitrary Storage Write	N/A	PASS
Arbitrary Jump	N/A	PASS
Centralization of Control	The owner can set the Tax fee, Buyback fee, and Marketing fee up to 100%. The team currently owns a large portion of the total supply. The owner can use the lock() function to temporarily set ownership to address(0).	WARNING
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
Integer Over/Underflow	N/A	PASS
Multiple Sends	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

Function Graph

BEP20 Token Graph

Inheritance Chart

Multi-file Token

Functions Overview

												
($) = 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

 + [Lib] Address 
    - [Int] isContract
    - [Int] sendValue #
    - [Int] functionCall #
    - [Int] functionCall #
    - [Int] functionCallWithValue #
    - [Int] functionCallWithValue #
    - [Prv] _functionCallWithValue #

 +  Ownable (Context)
    - [Pub]  #
    - [Pub] owner
    - [Pub] renounceOwnership #
       - modifiers: onlyOwner
    - [Pub] transferOwnership #
       - modifiers: onlyOwner
    - [Pub] getUnlockTime
    - [Pub] getTime
    - [Pub] lock #
       - modifiers: onlyOwner
    - [Pub] unlock #

 + [Int] IUniswapV2Factory 
    - [Ext] feeTo
    - [Ext] feeToSetter
    - [Ext] getPair
    - [Ext] allPairs
    - [Ext] allPairsLength
    - [Ext] createPair #
    - [Ext] setFeeTo #
    - [Ext] setFeeToSetter #

 + [Int] IUniswapV2Pair 
    - [Ext] name
    - [Ext] symbol
    - [Ext] decimals
    - [Ext] totalSupply
    - [Ext] balanceOf
    - [Ext] allowance
    - [Ext] approve #
    - [Ext] transfer #
    - [Ext] transferFrom #
    - [Ext] DOMAIN_SEPARATOR
    - [Ext] PERMIT_TYPEHASH
    - [Ext] nonces
    - [Ext] permit #
    - [Ext] MINIMUM_LIQUIDITY
    - [Ext] factory
    - [Ext] token0
    - [Ext] token1
    - [Ext] getReserves
    - [Ext] price0CumulativeLast
    - [Ext] price1CumulativeLast
    - [Ext] kLast
    - [Ext] burn #
    - [Ext] swap #
    - [Ext] skim #
    - [Ext] sync #
    - [Ext] initialize #

 + [Int] IUniswapV2Router01 
    - [Ext] factory
    - [Ext] WETH
    - [Ext] addLiquidity #
    - [Ext] addLiquidityETH ($)
    - [Ext] removeLiquidity #
    - [Ext] removeLiquidityETH #
    - [Ext] removeLiquidityWithPermit #
    - [Ext] removeLiquidityETHWithPermit #
    - [Ext] swapExactTokensForTokens #
    - [Ext] swapTokensForExactTokens #
    - [Ext] swapExactETHForTokens ($)
    - [Ext] swapTokensForExactETH #
    - [Ext] swapExactTokensForETH #
    - [Ext] swapETHForExactTokens ($)
    - [Ext] quote
    - [Ext] getAmountOut
    - [Ext] getAmountIn
    - [Ext] getAmountsOut
    - [Ext] getAmountsIn

 + [Int] IUniswapV2Router02 (IUniswapV2Router01)
    - [Ext] removeLiquidityETHSupportingFeeOnTransferTokens #
    - [Ext] removeLiquidityETHWithPermitSupportingFeeOnTransferTokens #
    - [Ext] swapExactTokensForTokensSupportingFeeOnTransferTokens #
    - [Ext] swapExactETHForTokensSupportingFeeOnTransferTokens ($)
    - [Ext] swapExactTokensForETHSupportingFeeOnTransferTokens #

 +  CoinToken (Context, IERC20, Ownable)
    - [Pub]  ($)
    - [Pub] name
    - [Pub] symbol
    - [Pub] decimals
    - [Pub] totalSupply
    - [Pub] balanceOf
    - [Pub] transfer #
    - [Pub] allowance
    - [Pub] approve #
    - [Pub] transferFrom #
    - [Pub] increaseAllowance #
    - [Pub] decreaseAllowance #
    - [Pub] isExcludedFromReward
    - [Pub] totalFees
    - [Pub] minimumTokensBeforeSwapAmount
    - [Pub] buyBackUpperLimitAmount
    - [Pub] deliver #
    - [Pub] reflectionFromToken
    - [Pub] tokenFromReflection
    - [Pub] excludeFromReward #
       - modifiers: onlyOwner
    - [Ext] includeInReward #
       - modifiers: onlyOwner
    - [Prv] _approve #
    - [Prv] _transfer #
    - [Prv] swapTokens #
       - modifiers: lockTheSwap
    - [Prv] buyBackTokens #
       - modifiers: lockTheSwap
    - [Prv] swapTokensForEth #
    - [Prv] swapETHForTokens #
    - [Prv] addLiquidity #
    - [Prv] _tokenTransfer #
    - [Prv] _transferStandard #
    - [Prv] _transferToExcluded #
    - [Prv] _transferFromExcluded #
    - [Prv] _transferBothExcluded #
    - [Prv] _reflectFee #
    - [Prv] _getValues
    - [Prv] _getTValues
    - [Prv] _getRValues
    - [Prv] _getRate
    - [Prv] _getCurrentSupply
    - [Prv] _takeLiquidity #
    - [Prv] calculateTaxFee
    - [Prv] calculateLiquidityFee
    - [Prv] removeAllFee #
    - [Prv] restoreAllFee #
    - [Pub] isExcludedFromFee
    - [Pub] excludeFromFee #
       - modifiers: onlyOwner
    - [Pub] includeInFee #
       - modifiers: onlyOwner
    - [Ext] setTaxFee #
       - modifiers: onlyOwner
    - [Ext] setBuybackFee #
       - modifiers: onlyOwner
    - [Ext] setMaxTxAmount #
       - modifiers: onlyOwner
    - [Ext] setMarketingFee #
       - modifiers: onlyOwner
    - [Ext] setNumTokensSellToAddToLiquidity #
       - modifiers: onlyOwner
    - [Ext] setBuybackUpperLimit #
       - modifiers: onlyOwner
    - [Ext] setMarketingAddress #
       - modifiers: onlyOwner
    - [Pub] setSwapAndLiquifyEnabled #
       - modifiers: onlyOwner
    - [Pub] setBuyBackEnabled #
       - modifiers: onlyOwner
    - [Ext] presale #
       - modifiers: onlyOwner
    - [Prv] transferToAddressETH #
    - [Ext]  ($)

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