MetaMask Signature Issues – Resolving Unreadable Signature Request Messages

I was able to figure this out after much debugging. Turns out that the chainid OPCODE is not working correctly in Ganche (if you use their UI - the fix has been released in the ganache-cli project).

The lack of a proper functioning chainid results in the DOMAIN_TYPEHASH being computed incorrectly which prevents ecrecover from generating the correct address from a signature.

You can follow these issues

Chain ID opcode: hardcoded at 1? #1643

istanbul chainId opcode returns bad value #515

Hope this helps others

To resolve the error, remove the EIP712Domain from types object (keep only PermitSingle and PermitDetails there). The domain type is inbuilt in the EIP712 standard and hence TypedDataEncoder so you do not need to specify it in the types. Hence the declared type EIP712Domain was unused and it was causing the error.

Here is a working piece of code:

let result = _TypedDataEncoder.hash(
  {
    name: "Permit2",
    chainId: "1",
    verifyingContract: "0x14a5698aeab8aa3f472c6d0a0061730f45467bd9",
  },
  {
    PermitSingle: [
      { name: "details", type: "PermitDetails" },
      { name: "spender", type: "address" },
      { name: "sigDeadline", type: "uint256" },
    ],
    PermitDetails: [
      { name: "token", type: "address" },
      { name: "amount", type: "uint160" },
      { name: "expiration", type: "uint48" },
      { name: "nonce", type: "uint48" },
    ],
  },
  {
    details: {
      token: "0xc02aaa39b223fe8d0a0e5c4f27ead9083c756cc2",
      amount: "1461501637330902918203684832716283019655932542975",
      expiration: "1690127209",
      nonce: "0",
    },
    spender: "0x49c4f688ade58ad80de1ddd932db3b804fef5cef",
    sigDeadline: "1687537009",
  }
);
console.log(result); 
// 0x3c636bc8d0efd7d4a25e31a001ea1a4743cd000a1148facaf1f60c4c5b327d40