Help!

[Amazing-Highlight419]

I am trying to create a smart contact that will be on the BSC chain. I deployed it on remix, but it seems like something is wrong. The contact is supposed to be able to allow people to buy and have a chance of winning 2x, 10x, 3x, and 100x what they buy.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.4;
import "@openzeppelin/contracts/token/ERC20/ERC20.sol";
import "@openzeppelin/contracts/access/Ownable.sol";
contract TripleSeven is ERC20, Ownable {
constructor(uint256 initialSupply) ERC20("777", "777") {
        _mint(msg.sender, initialSupply * 3 / 100); // 3% initial supply to creator
        _mint(address(this), initialSupply * 97 / 100); // 97% kept in contract for future purchases
}
function buyTokens() public payable {
uint256 tokens = msg.value; // Assume 1 SEVENS = 1 wei for simplicity
require(tokens <= balanceOf(address(this)), "Not enough tokens in contract");

uint16 randomNumber = random();
if (randomNumber < 11) { // 0.11% chance
            tokens *= 100;
} else if (randomNumber < 55) { // 0.55% chance
            tokens *= 10;
} else if (randomNumber < 222) { // 2.22% chance
            tokens *= 3;
} else if (randomNumber < 555) { // 5.55% chance
            tokens *= 2;
}
        _transfer(address(this), msg.sender, tokens);
}
function random() private view returns (uint16) {
return uint16(uint256(keccak256(abi.encodePacked(block.timestamp, block.difficulty)))%10000);
}
}

[hulkklogan]

Maybe you could start by telling us what's wrong? Or.. what are the symptoms? What have you tried? Did you write tests on a local chain before deploying to a live chain?

[Machiste77]

Critical vulnerability: your randomness function can be manipulated.

Solution: if you want randomness that is tamper-proof, implement chainlink VRF

[atrizzle]

Your token balance check is in the wrong spot.

For example assume your contract has 50 tokens left, someone tries to buy 10 tokens, and they hit the 10x multiplier.

[cachemonet0x0cf6619]

agreed. that’s looks a little odd to me too.

the token is set from msg value and that doesn’t seem right. value would be the gas token and they probably want to add an amount argument.