Metamask: ReferenceError: Buffer is not defined

Understanding Signed Data Login in MetaMask

As a digital asset enthusiast, you are probably familiar with Metamask, a popular wallet application that allows for seamless interaction between your Ethereum accounts and decentralized applications (dApps). One of the most interesting features of Metamask is its ability to handle signedTypedData logins using Web3.js. However, I would like to take this opportunity to dive into a common issue that can arise when implementing MetaMask Signed Data Login: Undefined error for ‘Buffer’.

Problem

When you try to validate ‘signedTypedData’ using Metamask, it expects a buffer object as the input. This is because the ‘eth.util.signTypedData()’ function returns the hash of the Ethereum transaction in hexadecimal string format (e.g. ‘0x…’).

However, when you work with signed data or other types that do not conform to the buffer interface, such as signedTypedData, metamask throws an error. Specifically, this causes a ReferenceError because the buffer is not defined.

Solution

To fix this issue, you will need to ensure that the input data conforms to the buffer interface. Here are some approaches:

• Define the type of the input data

  : If possible, specify the exact type of signedTypedData in the Buffer object. You can use TypeScript or JavaScript built-in types to specify this.

import * as Web3 from 'web3';
const typedData = {
// data entered here,
type: Buffer.from('your-typed-here'),
value: 'your-value-here',
};
const transactionHash = web3.eth.util.signTypedData(typedData);

• Use a polyfill: If you are working with older browsers or versions of Node.js that do not support TypedArrays, consider using a polyfill such as “typedarray-buffer” or “typedarray-polyfill”. These libraries provide a fallback implementation of the buffer interface.

const { Buffer } = require('buffer');
const typedData = {
type: 'Buffer',
value: Buffer.from('your-typed-here'),
};
const transactionHash = web3.eth.util.signTypedData(typedData);

Conclusion

Implementing MetaMask’s Typed Data sign-in requires some care when working with the entered data. Following the tips above should resolve the “Buffer is undefined” error and successfully validate the “signedTypedData” with your application.

Remember to always check the official documentation for each library or API you use, as their behavior may change over time. Happy coding!