Verifying Metamask Signatures with Web3.js: Troubleshooting

As you use Web3.js to sign transactions and verify them in a smart contract, you may encounter issues with signature verification. This article will help you troubleshoot common issues that you may encounter when using Metamask for signature verification.

Issue 1: Bad Domain Separator (Dadvisor)

Web3.js is incorrectly calculating the “DomainSeparator”. Make sure the following code snippet is correct:

const domainSeparator = ethers.keccak256(
[...,
"0x", // sender address
...// additional addresses, e.g. "0x1234567890abcdef", "0x234567890abcedf", etc.
]
);

The “DomainSeparator” is calculated by combining the sender’s address with other addresses in a specific order. The correct order should be:

• Sender’s address

• Network chain ID (e.g. 4 for Ethereum)

• Contract chain ID (if specified)

Issue 2: Incorrect signature

The signature is not verified because Metamask is not signing it properly. Make sure you use the correct “sign” function and pass the necessary settings:

const tx = {
from: "0x...", // sender's address
to: "0x...", // recipient's address
value: 10n, // transaction value
data: [..., / additional data /], // optional data for the contract
};
const signature = await ethers.sign(
tx,
{ privateKey: "0x..." } // your metamask private key
);

Make sure you specify the correct `privateKey'' option and use thesign'' function provided by Web3.js.

const tx = {
from: "0x...", // sender address
to: "0x...", // recipient address
value: 10n, // transaction value
};
try {
const signature = await ethers.sign(
tx,
{ private Key: "0x..." }
);
console.log("Verification successful:", signature);
} catch (error) {
if (error instance of Error && error.message.includes("insufficient private key")) {
throw new Error(Insufficient private key for verification);
} else {
throw error;
}
}

const tx = {
from: "0x...", // sender address
to: "0x...", // recipient address
value: 10n, // transaction value
};
try {
const signature = await ethers.sign(
tx,
{ private Key: "0x..." }
);
console.log("Verification successful:", signature);
} catch (error) {
if (error instance of Error && error.message.includes(" incorrect chain id")) {
throw new Error(Incorrect chain id for verification`);
} else {
throw error;
}
}

Conclusion

If you follow these troubleshooting steps, you should be able to identify and resolve the issues that are causing Metamask signature verification to fail. Don't forget to check the private key size, chain id, and make sure that all required addresses are included in the 'DomainSeparator' calculation.

If you're still having issues after trying these solutions, feel free to provide more details about your setup, including code snippets, error messages, and any relevant information about Metamask and Web3.js.