feat: Add front-running and MEV vulnerability detection rule (CP-119)

[Nanle-code]

Overview

Miner/Maximal Extractable Value (MEV) and transaction ordering attacks are among the most underreported vulnerability classes in smart contracts. Contracts that make decisions based on state that can be manipulated between the time a transaction is submitted and when it is mined are vulnerable to front-running. ChainProof needs a dedicated rule to surface these patterns.

Vulnerability Patterns to Detect

1. Commit-Reveal Scheme Absence in Auction/Lottery Contracts

function bid(uint256 amount) external {
    require(amount > highestBid, "too low");
    highestBid = amount;
    highestBidder = msg.sender;
    // Attacker in the mempool sees this tx and front-runs with amount + 1
}

2. Approval Front-Running (ERC-20)

// Standard approve is vulnerable to front-run between approve(100) and approve(50)
// attacker drains the original 100 before the 50 lands
function approve(address spender, uint256 amount) external {
    allowance[msg.sender][spender] = amount;
}

3. Block Timestamp or Block Number Dependence for Randomness

function random() internal view returns (uint256) {
    return uint256(keccak256(abi.encodePacked(block.timestamp, block.difficulty)));
    // Miners can manipulate block.timestamp within ~15 second window
}

4. Sandwich Attack Surface in AMM Interactions

Contracts calling external AMMs with no slippage parameter (amountOutMin == 0).

uniswapRouter.swapExactTokensForTokens(amountIn, 0, path, recipient, deadline);
// amountOutMin = 0 means accept any output — sandwich attacker extracts full slippage

Detection Heuristics

1. Detect block.timestamp or block.difficulty used in keccak256 hash for randomness
2. Detect AMM swap calls with hardcoded 0 for amountOutMin
3. Detect standard ERC-20 approve without increaseAllowance alternative
4. Detect auction/bidding patterns without a commit-reveal structure

Acceptance Criteria

• CP-119 rule in packages/core/src/rules/cp119-frontrunning.ts
• Block timestamp/difficulty randomness detection with High severity
• AMM swap with zero slippage detection with High severity
• ERC-20 approve race condition with Medium severity
• Auction front-running heuristic with Medium severity
• Example vulnerable contracts in examples/contracts/mev/

References

• SWC-120 — Weak Sources of Randomness
• Ethereum Front-Running Overview — ConsenSys
• Flashbots MEV Research

[ZuLu0890]

I would like to work on this issue

[Chigybillionz]

Greetings Maintainer

I would like to work on this issue.

Experience:
I have experience in smart contract security, Solidity static analysis, vulnerability detection, and blockchain security research. I have worked on identifying front-running, MEV-related risks, weak randomness sources, ERC-20 approval race conditions, and unsafe AMM integrations.

Implementation:
I will implement the CP-119 rule to detect front-running and MEV attack surfaces, including weak randomness using block.timestamp/block.difficulty, AMM swaps with zero slippage protection, ERC-20 approval race conditions, and auction patterns lacking commit-reveal mechanisms. I will also add vulnerable example contracts, comprehensive test coverage, and clear severity classifications aligned with the acceptance criteria.

Delivery:
I can complete the implementation, testing, documentation, and example contracts within the required timeframe.

GitHub:
https://github.com/chigybillionz

[dolaoluwa574-source]

I’m excited to contribute to impactful software improvements. My experience includes backend engineering, object-oriented programming, API development, Git collaboration, and building scalable, maintainable applications.