_signTypedData result does not match address recovered from signature on the back-end side

Describe the bug When using signer._signTypedData and MetaMask browser extension, the result of the function doesn’t match the recovered signature on the back-end.

Reproduction steps To reproduce this issue:

• create a new provider const provider = new ethers.providers.Web3Provider(window.ethereum)
• create a signer calling const signer = provider.current.getSigner()
• create a signature:

    const signatureResult = await signer._signTypedData(
      domain,
      { types: types.Auth}, // exclude the EIP712Domain type
      message
    );

• sign message via MetaMask;

After that, I make a request to the back-end server to verify the signed data and get JSON with data back, the error described above occurs as the result of this request.

Environment: Front-end:

• ethers.js
• useDapp
• Next.js
• TypeScript

Back-end:

• https://pypi.org/project/web3auth/ (custom open-source framework-agnostic solution for python, uses official ethereum library for python - https://github.com/ethereum/eth-account)
• Ganache
• Truffle

Current solution Currently, I rewrote the code to use the external provider’s sendAsync method like this:

    provider.sendAsync(
      {
        method,
        params: [
          address,
          JSON.stringify({
            domain,
            message,
            primaryType,
            types,
          }),
        ],
      }, (err, result) => ... )

This solved the issue for now. Maybe you could look up to this and propose a possible fix, or provide a better solution to the problem. Thank you in advance.

[skylightxo]

Embarrassing to realize, I completely messed up with types…

    const signatureResult = await signer._signTypedData(
      domain,
      { types: types.Auth}, // <-- the problem was here, 
      message
    );

fixed code

    const signatureResult = await signer._signTypedData(
      domain,
      { Auth: types.Auth}, // <-- works as a charm
      message
    );

@ricmoo thank you for your help, I’m closing the issue.

[skylightxo]

Experiencing this same issue @skylightxo – do you mind explaining why the change from { types: types.Auth} to { Auth: types.Auth} solved this issue?

Hello, @taayyohh. Sure, the problem is that I was passing an argument for types as an object with a ‘types’ key, which is the cause of the issue. So, consider { types: types.Auth } as a variable.

let types = { types: types.Auth }; // <-- not appropriate
let types = { Auth: types.Auth }; // <-- works fine