Metamask: Is it possible to validate the Metamask personal_sign in the back end?

I can provide you with an article on validating the personal_sign field in Metamask.

Validate Personal Sign in Metamask Backend

Metamask is a popular Ethereum wallet application that allows users to securely interact with the Ethereum network. One of its features is the ability to sign personal messages, which serves as a form of identification for the user.

In this article, we will discuss how to validate the personal_sign field in Metamask’s backend, ensuring that it accurately represents the user’s identity on the blockchain.

Understanding Personal Sign

The personal_sign field is used to verify the authenticity of messages sent from users. It is generated using a cryptographic algorithm and can be used to confirm that the message was sent by the intended recipient.

However, when Metamask signs personal messages in the client-side JavaScript code, it uses the ethers library, which provides a high-level interface for interacting with Ethereum contracts. Unfortunately, the ethers library does not provide direct access to the underlying blockchain’s metadata, including user identities.

Validating Personal Sign using Blockchain Metadata

To validate the personal_sign field in Metamask’s backend, we need to access the blockchain’s metadata and verify that it matches the expected signature. We can use the following steps to achieve this:

• Get the blockchain metadata: We need to retrieve the blockchain’s metadata, including user identities, from the Ethereum network.

• Verify the personal signature: Once we have the blockchain metadata, we can compare the personal_sign field with the expected signature.

Here is an example of how you can implement this in Metamask’s backend:

const metamask = require('@metamask/client-api');

const ethers = require ( ' ethers ' ) ;


// Get the blockchain metadata

async function getBlockchainMetadata() {

  const provider = await metamask.getProvider();

  const chainId = await provider.getChainId();

  const blockchainMetadata = await provider.getChainIdMetadata(chainId);

  

  // Get user identities from the blockchain metadata

  const userIds = [];

  for ( const id in blockchainMetadata . userIds ) {

    userIds . push ( blockchainMetadata . userIds [ id ] ) ;

  } }

  

  return { userIds };

} }


// Verify the personal sign

async function verifyPersonalSign( userIds , expectedPersonalSign ) { .

  // Get the Ethereum account address of the user

  const accountAddress = await metamask.getAccounts()[0].address;

  

  // Create a new EIP-711 signature object with the user ID and expected personal signature

  const signature = ethers.utils.sigs.Eip712Signature(

    'Personal Sign',

    [ accountAddress , userIds . join ( ' , ' ) ] ,

    expectedStaffSign,

  );

  

  // Verify the signature using Ethereum's EIP-712 library

  if ( await signature . verify ( blockchainMetadata . chainId )) {

    return true ;

  } else {

    return false ;

  } }

} }

Example Use Case

In this example, we can create a new Metamask backend that retrieves the blockchain metadata and verifies the personal sign using the verifyPersonalSign function. We can then use this function to validate user identities on the client-side JavaScript code:

“`javascript

const metamask = require(‘@metamask/client-api’);

const ethers = require ( ‘ ethers ‘ ) ;

// Create a new Metamask backend

async function createBackend() { .

const provider = await metamask.getProvider();

// Get the blockchain metadata

const userIds = await getBlockchainMetadata();

// Verify the personal sign for each user

let isValid = true;

userIds . forEach ( ( userIds , index ) => {

const expectedPersonalSign = ethers.utils.sigs.Eip712Signature(

‘Personal Sign’,

[ userId , userIds . join ( ‘ , ‘ ) ] ,

userId,

);

if (!