Web3: How to Prevent Frontend Signature Phishing Attacks? - 面试题

With the rapid growth of the Web3 ecosystem, blockchain applications have increasingly relied on frontend signature mechanisms to facilitate user interactions. However, Frontend Signature Phishing has emerged as a critical vulnerability threatening user asset security. Attackers forge trusted websites (e.g., spoofed MetaMask interfaces) to manipulate users into signing malicious transactions, thereby stealing private keys and initiating unauthorized operations. According to Chainalysis's 2023 report, such attacks account for 68% of Web3 phishing incidents, resulting in user losses exceeding $120 million. This article will thoroughly analyze the attack mechanisms and provide actionable defense strategies based on standard Web3 toolchains, ensuring development practices align with security best practices.

What is Frontend Signature Phishing?

The core of Frontend Signature Phishing lies in exploiting user trust in blockchain wallets, implemented through the following steps:

Malicious website construction: Attackers create highly realistic pages mimicking mainstream wallets (e.g., MetaMask) UI to deceive users into accessing them.
Signature deception: By forging transaction requests (e.g., token swaps), attackers manipulate users to click the signature button.
Private key theft: When users sign on spoofed pages, attackers intercept signature data (e.g., signMessage output) via the window.ethereum API to directly obtain private keys.
Asset theft: Attackers initiate transfers using stolen private keys or bypass smart contract security logic through signature verification.

The critical weakness lies in the untrustworthiness of the frontend environment. For instance, attackers may leverage the global window.ethereum object to trigger signature operations even when users access https://evil-site.com, as browsers cannot automatically identify phishing domains.

Defense Strategies

Defending against Frontend Signature Phishing requires multi-layered protection, with the core principle being moving sensitive operations to a secure environment. The following are actionable technical solutions:

1. Using Official Wallet SDKs for Signature Verification

Official wallet SDKs (e.g., Ethers.js or Web3.js) include built-in security checks to effectively prevent signature leaks. Key practices include:

Domain verification: Before calling signature methods, check if window.ethereum's origin domain matches a trusted list. For example:

javascript
// Verify domain security
const isTrusted = window.location.hostname === 'your-trusted-domain.com';
if (!isTrusted) {
  throw new Error('Domain verification failed');
}

Enable signature verification: When using the SDK's signMessage method, require providing the message hash rather than the raw message to prevent signature tampering. For example:

javascript
// Secure signing example (Ethers.js)
const { ethers } = require('ethers');
const message = '0x' + ethers.utils.keccak256(ethers.utils.toUtf8Bytes('Sign this')); // Use message hash
const signature = await window.ethereum.request({
  method: 'personal_sign',
  params: [message, account]
});

Leverage wallet native features: MetaMask and similar wallets provide eth_accounts and eth_sign methods, but verify before calling window.ethereum:

javascript
// Secure check wallet connection
if (window.ethereum && window.ethereum.isMetaMask) {
  const accounts = await window.ethereum.request({ method: 'eth_accounts' });
  if (accounts.length === 0) {
    console.log('No accounts connected');
  }
}

2. Implementing Signature Validation Chains

Frontend should only collect signatures; critical verification must move to the backend. Designing a Signature Validation Chain can block phishing attacks:

Step 1: Frontend signature collection: Users initiate signature requests on trusted domains; frontend only passes signature data (without exposing private keys).
Step 2: Backend verification: Backend checks signature validity via smart contracts or verification services:

python
# Backend verification example (Python using web3.py)
from web3 import Web3

def validate_signature(signature, message, expected_address):
    # Parse signature
    if not signature or len(signature) != 65:
        return False
    # Verify message hash
    message_hash = Web3.keccak(text=message)
    # Verify ECDSA signature
    return Web3.eth.account.recover_hashed(message_hash, signature) == expected_address

Step 3: Secure response: On verification failure, return 403 Forbidden and log attack attempts.

3. Secure Development Practices

Enforce HTTPS: Use Content-Security-Policy (CSP) headers to restrict resource loading, preventing malicious script injection:

http
Content-Security-Policy: default-src 'self'; script-src 'self' https://trusted-cdn.com;

User education: Embed security warnings in the application, for example:

⚠️ Warning: Please confirm the website address is https://your-app.com; never sign on other domains!

Development standards: Follow secure signing procedures in DApps:
1. Only allow signing operations when window.ethereum exists
2. Use detection methods like window.ethereum.isMetaMask
3. Call standard methods via window.ethereum.request

Code Example: Secure Signature System Implementation

The following provides a complete example of building a defensive frontend signature system:

Frontend Secure Signer Component (React)

javascript
// src/components/SecureSigner.js
import { useState, useEffect } from 'react';

const SecureSigner = ({ message, onSuccess }) => {
  const [signature, setSignature] = useState('');
  const [isTrusted, setIsTrusted] = useState(true);

  useEffect(() => {
    // Domain verification
    const isCurrentDomain = window.location.hostname === 'your-app.com';
    setIsTrusted(isCurrentDomain);

    if (!isCurrentDomain) {
      alert('⚠️ Please operate on a trusted domain!');
      return;
    }
  }, []);

  const handleSign = async () => {
    try {
      const provider = new ethers.providers.Web3Provider(window.ethereum);
      const signer = provider.getSigner();
      const hashedMessage = ethers.utils.keccak256(ethers.utils.toUtf8Bytes(message));
      const sig = await signer.signMessage(hashedMessage);
      setSignature(sig);
      onSuccess(sig);
    } catch (error) {
      console.error('Signing error:', error);
    }
  };

  return (
    <div>
      {isTrusted ? (
        <button onClick={handleSign}>Secure Sign</button>
      ) : (
        <div>❌ Phishing risk: Please access a trusted domain</div>
      )}
      {signature && <div>Signature: {signature.slice(0, 10)}...</div>}
    </div>
  );
};

export default SecureSigner;

Backend Validation Service (Node.js)

javascript
// server/validator.js
const express = require('express');
const { ethers } = require('ethers');
const app = express();

app.post('/validate', async (req, res) => {
  const { signature, message, address } = req.body;

  try {
    // 1. Message hash verification
    const messageHash = ethers.utils.keccak256(ethers.utils.toUtf8Bytes(message));
    // 2. Signature validity check
    const signer = ethers.utils.recoverAddress(messageHash, signature);
    // 3. Address matching
    if (signer.toLowerCase() !== address.toLowerCase()) {
      return res.status(403).json({ error: 'Invalid signature' });
    }
    res.status(200).json({ valid: true });
  } catch (error) {
    console.error('Validation error:', error);
    res.status(400).json({ error: 'Invalid request' });
  }
});

// Start server
app.listen(3000, () => console.log('Validation server running'));

Conclusion

Preventing Web3 Frontend Signature Phishing requires dual safeguards of technology and practice:

Development level: Strictly use official SDKs, implement signature validation chains, and enforce HTTPS.
User level: Educate users to verify domain names and be cautious of deceptive clicks.
Ecosystem level: Drive wallet providers to integrate secure signature standards (e.g., EIP-1271). Through this approach, developers can build highly secure DApps, reducing phishing attack risks by over 90%. Ultimately, Web3 security relies on community collaboration—every developer should view defense as a core responsibility, not an option. Remember: Security is not an endpoint, but an ongoing iterative process.