Solidity&Foundry 安全审计测试 memory滥用

名称：

memory滥用

https://github.com/XuHugo/solidityproject/tree/master/vulnerable-defi

描述：

在合约函数中滥用storage和memory。

memory是一个关键字，用于临时存储执行合约所需的数据。它保存函数的参数数据，并在执行后清除。
storage可以看作是默认的数据存储。它持久地保存数据，消耗更多的gas。

函数updaterewardDebt的功能是，更新UserInfo结构体的rewardDebt值。为了节约gas，我们将变量用关键字memory声明了，这样会导致的问题是，在函数执行结束之后，rewardDebt的值并不会保存下来。因为一旦函数完成执行，内存就会被清除，所做的更改也会丢失。

参考：

Cover protocol hack analysis: Infinite Cover tokens minted via an exploit - Mudit Gupta's Blog

解决方法：

https://mudit.blog/cover-protocol-hack-analysis-tokens-minted-exploit/

proxy合约：

javascript 复制代码

contract Array is Test {
    mapping(address => UserInfo) public userInfo; // storage

    struct UserInfo {
        uint256 amount; // How many tokens got staked by user.
        uint256 rewardDebt; // Reward debt. See Explanation below.
    }

    function updaterewardDebt(uint amount) public {
        UserInfo memory user = userInfo[msg.sender]; // memory, vulnerable point
        user.rewardDebt = amount;
    }

    function fixedupdaterewardDebt(uint amount) public {
        UserInfo storage user = userInfo[msg.sender]; // storage
        user.rewardDebt = amount;
    }
}

foundry测试合约；

javascript 复制代码

// A function to demonstrate the difference between memory and storage data locations in Solidity.
function testDataLocation() public {
    // Simulate dealing 1 ether to Alice and Bob.
    address alice = vm.addr(1);
    address bob = vm.addr(2);
    vm.deal(address(alice), 1 ether);
    vm.deal(address(bob), 1 ether);

    // Create a new instance of the Array contract.
    ArrayContract = new Array();

    // Update the rewardDebt storage variable in the Array contract to 100.
    ArrayContract.updaterewardDebt(100); 

    // Retrieve the userInfo struct for the contract's address and print the rewardDebt variable.
    // Note that the rewardDebt should still be the initial value, as updaterewardDebt operates on a memory variable, not the storage one.
    (uint amount, uint rewardDebt) = ArrayContract.userInfo(address(this));
    console.log("Non-updated rewardDebt", rewardDebt);

    // Print a message.
    console.log("Update rewardDebt with storage");

    // Now use the fixedupdaterewardDebt function, which correctly updates the storage variable.
    ArrayContract.fixedupdaterewardDebt(100);

    // Retrieve the userInfo struct again, and print the rewardDebt variable.
    // This time the rewardDebt should be updated to 100.
    (uint newamount, uint newrewardDebt) = ArrayContract.userInfo(
        address(this)
    );
    console.log("Updated rewardDebt", newrewardDebt);
}