Understanding Login with MetaMask Typed Data
As a digital asset enthusiast, you’re probably familiar with Metamask, a popular wallet app that provides seamless interaction between your Ethereum accounts and decentralized applications (dApps). One of the interesting features of Metamask is its ability to process logins using data typed by MetaMask using Web3.js. However, I would like to take this opportunity to look at a common problem that can occur when implementing a MetaMask input: the undefined Buffer
error.
Problem
When trying to check signedTypedData using Metamask, a Buffer object is expected as input data. This is because the function eth.util.signTypedData()
returns the Ethereum transaction hash in hexadecimal string format (for example, “0x…”).
However, when working with typed data or other types that do not correspond to the Buffer interface, for example, signedTypedData, Metamask throws an error. In particular, a ReferenceError
occurs because the buffer is not defined.
Solution
To solve this problem, you need to make sure that the data you enter corresponds to the buffer interface. Here are some approaches:
- Define the type of typed data: if possible, define the exact type of signedTypedData in the
Buffer
object. You can use built-in TypeScript or JavaScript types to specify it.
`typewriting
import * as Web3 from 'web3';
const typedData = {
// your data is entered here
type: Buffer.from('your-type-here'),
meaning: 'your-meaning-here',
};
const transactionHash = web3.eth.util.signTypedData(typedData);
typedarray-buffer
Use a polyfill: If you're using older browsers or Node.js versions that don't support TypedArrays, consider using a polyfill likeor
typedarray-polyfill. These libraries provide an alternative implementation of the Buffer interface.
javascript
const { Buffer } = require('buffer');
const typedData = {
type: "buffer",
value: Buffer.from('your-type-here'),
};
const transactionHash = web3.eth.util.signTypedData(typedData);
“
Conclusion
Implementing MetaMask login using typed data requires some caution when working with typed data. If you follow the tips above, you should be able to fix the “Buffer not defined” error and successfully test signedTypedData in your application.
Remember to always check the official documentation for each library or API you use, as their behavior may change over time. Happy programming!